Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31828 Publications
An attempt to enrich holmium ions in a flow system by inhomogeneous magnetic fields.
Kolczyk, K.; Wojnicki, M.; Zabinski, P.; Yang, X.; Mutschke, G.;
Recent experimental results regarding an attempt to enrich holmium ions in a flow system by inhomogeneous magnetic fields
are presented.
Keywords: magnetic field, magnetic separation
  • Invited lecture (Conferences)
    International Workshop ECMAG - Magnetic Field Effects on Aqueous Solutions, 20.-21.04.2017, Dresden, Deutschland

Publ.-Id: 26763 - Permalink


Magnetic e-skins enabled somatic and touch-less interactive devices
Jin, G.; Xu, W.; Gilbert Santiago, C. B.; Jürgen, F.; Denys, M.;
Humans skin provide perceptions of the temperature of objects, strain and pressure on skin, friction for holding objects, which help humans interact with unstructured surroundings very precisely. Electronic skins [1,2] allow for the realization of similar sensing functions and also having the possibility of integrating other sensing functions beyond humans. Very recently we demonstrated magnetosensitive e-skins, which is an important step towards the realization of artificial magnetoception for humans [3,4].
Here, we present a magnetic e-skin that not only is sensitive to mechanical forces and deformation, but also has the ability to detect the position and movement of magnetic objects in a touch-less manner. The magnetic skin is a stack of a wrinkled magnetic sensor layer and a pyramid-structured magnetic foil. The GMR sensor enables the sensing of the movement of the remote magnetic objects (touch-less interaction). Furthermore, the distance change between the sensor and the magnetic foil make the magnetic skin sensitive to pressure, stretch and flexion (somatic interaction). This magnetic e-skin will hold great promise for the realization of humanoid robots, biomedical prostheses, and surgical electronic gloves.

1. Z. Ma et al. Science 333, 830 (2011).
2. Z. Bao et al. Adv. Mater. 25, 5997 (2013).
3. M. Melzer et al, Nat. Commun. 6, 6080 (2015).
4. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
Keywords: e-skin, pressure sensor, magnetoresistance, artificial skin, GMR sensor
  • Lecture (Conference)
    DPG Spring Meeting 2017, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 26762 - Permalink


Multiplexing of imperceptible temperature sensor arrays for on-skin applications
Voitsekhivska, T.; Fassbender, J.; Makarov, D.;
Beside the direct temperature measurement resembling the standard health indicator, the access to the body core temperature and its temporal variations provides the information, which is absolutely crucial to assess the psycho-physiological conditions of the patient, e.g. level of stress. To measure spatial and temporal temperature gradients, multiple temperature sensors have to be attached and processed on the human body surface [1, 2].
Here, we introduce a thermal characterization technology for real - time monitoring the human body temperature using arrays of highly compliant on-skin temperature sensors, realized on 6-micrometer-thick polymeric foils, which are haptically not perceived when worn on the skin. Beside the realization of the arrays of imperceptible temperature sensors, we put strong emphasis on the integration of a multiplexing unit on flexible foils in order to achieve measurements with mapping capabilities.
[1] R. Chad Webb et al., Nature Materials 12, pp. 938-944 (2013).
[2] Tomoyuki Yokota et al., PNAS 112, pp. 14533-14538 (2015).
Keywords: multiplexing, temperature sensor arrays
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 26761 - Permalink


Mesoscale Dzyaloshinskii-Moriya interaction
Volkov, O.; Sheka, D.; Makarov, D.; Fassbender, J.; Kravchuk, V.; Gaididei, Y.;
A broken chiral symmetry in a magnetic system leads to the appearance of both periodical and localized magnetization structures. Intrinsic to the crystal spin-orbit driven Dzyaloshinskii-Moriya interaction (DMI) is the origin of all those magnetic textures [1]. Recently, we reported [2,3] that geometrically broken symmetry in curvilinear magnetic systems also leads to the appearance of shape-induced effective DMI.
The combined intrinsic and shape-induced DMI can be reffered to as a mesoscale DMI, whose symmetry and strength depend on the geometrical and material parameters. The mesoscale DMI determines chiral properties of 3D curved systems. We derive the general expression for the mesoscopic DMI terms and determined the conditions for periodical magnetisation structures to appear in one-dimensional ferromagnetic helix wires.
[1] A. Soumyanarayanan et. al., Nature 539, 509-517 (2016).
[2] Y. Gaididei et. al, Phys. Rev. Lett. 112, 257203 (2014).
[3] D. D. Sheka et. al., J. Phys. A: Math. Theor. 48, 125202 (2015).
Keywords: Dzyaloshinskii-Moriya interaction, curved geometry, helical wire, magnetochirality, mesoscale
  • Lecture (Conference)
    DPG Spring Meeting 2017, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 26760 - Permalink


Programmed Magnetically-Triggered Ultrathin Soft Robots with Fast Actuation Speed
Wang, X.; Ge, J.; Canon Bermudez, G. S.; Fassbender, J.; Makarov, D.;
Soft robots have been designed and developed to fulfil the demands of better deformability and adaptability to changing environment [1-2]. These soft robots could be made of various stimuli responsive materials that can be actuated by magnetic field [3], light [4], temperature [5], electric fields [6], chemicals [7], pressure [8], etc. In contrast to other actuation mechanisms, magnetic fields are appealing for numerous application scenarios (e.g. environmental, biological, medical), where the benefits stem from their long range penetration, easy accessibility and controllability [2]. There are already impressive demonstrations of magnetically triggered actuators performing as walkers, swimmers and grippers [9]. However, most of these robots are bulky (0.2 mm thick) [11], reveal low actuation speed (2.7 s deflection time) [11] and not sufficiently soft to demonstrate reversible large scale actuation amplitude (less than 1 micron) [12]. Furthermore, they require rather large magnetic fields (42 mT) [13] for actuation, which limits their application potential.

Here, we present an ultrathin and lightweight soft robot that can be actuated in a tiny magnetic field of 0.2 mT reaching full actuation amplitude with reaction times of 10 ms only. The Young’s modulus of the developed magnetic elastomer (NdFeB particles are dispersed into a PDMS host) goes down to remarkable 5 MPa while still maintaining stretchability levels of 50%. The weight of the magnetic foil is 4 mg/cm2 and it can provide 0.16 mN/mg. By programming the foils into different geometries, these soft robots are readily used for different applications, such as quick gripper that can pick, transport and release objects in a controllable manner.

[1] D. Rus et al., Nature 521, 467 (2015)
[2] M. Sitti et al., Adv. Mater. 29, 13 (2017)
[3] S. Kwon et al., Nature materials 10, 747 (2011)
[4] S.H Peng et al., J. Am. Chem. Soc. 138, 225 (2016)
[5] M. Takata et al., Nature Materials 14, 1002 (2015)
[6] J. D. W. Madden et al., Materials Today, 10, 30 (2007)
[7] J.Y. Yuan et al., Nature communications 5 (2014).
[8] G. M. Whitesides et al., Science, 337, 828 (2012)
[9] O. Sandre et al., Chem. Soc. Rev., 42, 7099 (2013).
[10] R. V. Ramanujan et al., Adv Mater., 24, 4041-54 (2012).
[11] H. Z. Liu. et al., ACS Appl. Mater. Interfaces, 8, 14182 (2016)
[12] M. Sitti et al., Nature Communications 5, 3124 (2014)
[13] D. Fragouli et al., ACS Appl. Mater. Interfaces 7, 19112 (2015).
Keywords: soft robot, magnetic field, human-mimic motion, ultra-fast actuation, super durable
  • Lecture (Conference)
    2017 MRS Fall Meeting, 26.11.-01.12.2017, Boston, USA

Publ.-Id: 26759 - Permalink


Multifunctional Highly Compliant Implants for Cancer
Kruv, A.; Canon Bermudez, G. S.; Voitsekhivska, T.; Lebanov, A.; Fassbender, J.; Yevsa, T.; Makarov, D.;
Cancer is one of the main death reasons worldwide [1]. Radio- and chemotherapies, which are the most common approaches to combat this disease, cause severe side effects due to their non-selective nature [2]. As an alternative paradigm, a targeted cancer therapy has recently emerged. This method aims to affect only cancer cells thus spare the healthy tissues [3].
The large fraction of the targeted therapies relay on drug delivery in nanovectors (e.g. micelles, dendrimers) to the tumour site via vascular system followed by the drug release in response to binding to a certain molecule, local environment (e.g. pH) or externally provided heat [4]. These methods suffer from delivery complexity (e.g. due to multiple physiological barriers), non-reliability of the release mechanism, difficulty in organising the feedback for precise control over the process as well as toxicity and stability concerns [4,5].
In order to overcome these limitations, we propose an alternative approach to the targeted cancer treatment (liver cancer is used as a case study) which relies on the implantation at the tumour site of an ultra-thin flexible device comprising a resistive heater and temperature sensor. The devices are prepared on a 6 micrometer thick PET foil. This foil thickness was found to be optimal as it provides the best compliancy to the very soft liver tissue and does not mechanically damage the tissue. The heater can heat the tissue to a pre-defined temperature of up to 55 °C even when the driving current is in the range of 10 mA. The integrated temperature sensor provides a real-time feedback about the on-site thermal impact. We demonstrate a proof-of-the-concept prototype together with the evaluation of its electrical and mechanical performance and the results of the first clinical trials on mice models.
This device allows realizing several negative for tumour interactions including thermal impact all the way up to burning the tissue, highly localized drug release, enhancement of immune response and drug uptake [6]. In addition, it raises the possibility to establish precise control over temperature and potentially evaluate the treatment effects which are of fundamental importance for the development of the new models for cancer research especially in the case of such a severe one as liver cancer.

[1] A. Jemal et al., CA: a cancer journal for clinicians, 61(2), 69-90 (2011).
[2] Padma, V. V. (2015). An overview of targeted cancer therapy. BioMedicine, 5(4), 19-19.
[3] A. A. Alexander-Bryant et al., Advances in cancer research, 118, 1 (2012).
[4] J. Shi et al., Nature Reviews Cancer, 17, 20 (2017).
[5] M. Ferrari, Nature Reviews Cancer 5, 161 (2005).
[6] K. F. Chu et al., Nature Reviews Cancer 14, 199 (2014).
Keywords: cancer threatment,ultra-thin flexible heater
  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Publ.-Id: 26758 - Permalink


Mesoscale Dzyaloshinskii-Moriya interaction in curved geometry
Volkov, O.; Sheka, D.; Kravchuk, V.; Makarov, D.; Fassbender, J.; Gaididei, Y.;
A broken chiral symmetry in magnetic systems manifests itself at the appearance of either periodical (e.g. helical or cycloid modulations) or localized magnetization structures (e.g. chiral domain walls and skyrmions) [1,2]. The origin of these magnetic textures is spin-orbit driven Dzyaloshinskii-Moriya interaction (DMI), which is intrinsic to the crystal or layer stack. Recently, it was reported that geometrically broken symmetry in curvilinear systems leads to the appearance of exchange-driven DMI-like chiral term in energy functional [3,4]. This term is determined by the sample geometry (it is linear with respect to curvature and torsion) and is therefore extrinsic to the crystal or layer stack. The magnetic properties of curvilinear magnets with intrinsic DMI will be necessarily determined by the interplay between two types of chiral interactions. Hence, the resulting chiral term in such type of objects is referred to as a vector of mesoscale DMI, which is the vector sum of the intrinsic and extrinsic DMI vectors. The symmetry and strength of this term are determined by the geometrical and material properties of the curvilinear magnet. Here we study the properties of the mesoscale DMI using a one-dimensional helical wire as a case of study. The clear cut comparison with the straight wire with intrinsic DMI reveals: (i) a single vector of magnetochirality, which is referred to as vector of the mesoscale DMI, originates from the vector sum of the intrinsic and extrinsic DMI vectors; (ii) a symmetry and period of the chiral modulated structures are determined by the strength and direction of the mesoscale DMI vector; (iii) a phase transition between homogeneous and chiral modulated states in the case of mesoscale DMI is a complex second-order phase transition with the intermediate conical state.

References

[1] U. K. Rößler, A. N. Bogdanov, C. Pfleiderer, Nature 442, 797801 (2006)
[2] N. Nagaosa, Y. Tokura, Nature Nanotechnology 8, 899-911 (2013)
[3] Y. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett. 112, 257203 (2014)
[4] O. V. Pylypovskyi, V. P. Kravchuk, D. D. Sheka, D. Makarov, O. G. Schmidt, Y. Gaididei, Phys. Rev. Lett. 114, 197204 (2015)
Keywords: Dzyaloshinskii-Moriya interaction, curved geometry, helical wire, magnetochirality, mesoscale
  • Poster
    633. Wilhelm und Else Heraeus-Seminar, Spin Orbit Dynamics, 04.-06.01.2017, Physikzentrum Bad Honnef, Germany

Publ.-Id: 26757 - Permalink


Compliant on-skin compass for artificial magnetoception and interactive devices
Cañón Bermúdez, G. S.; Makarov, D.;
Flexible electronics has inspired novel concepts like electronic skins [1] equipped with e.g. pressure and temperature sensing capabilities, which could replicate the 5 empirical senses of humans. Very recently, magnetosensitive skins enabled by shapeable magnetoelectronics [2] were reported providing humans with perception of magnetic fields, which is beyond the senses developed during the evolution.
Here, we present a technology platform to realize a functional on-skin compass system. The highly compliant compasses are prepared on 6-μm-thick polymeric foils and rely on the anisotropic magnetoresistance effect. The response of these sensors is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole configuration and Wheatstone bridge arrangement.
We envision that these on-skin compasses can enable humans to electronically emulate the magnetoceptive sense which some mammals possess naturally. This feat could open new possibilities to support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.
REFERENCES:
1. M. L. Hammock, A. Chortos, B. C.-K. Tee, J. B.-H. Tok, Z. Bao. The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress. Adv. Mater. 25, 5997 (2013).
2. D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt. Shapeable Magnetoelectronics. Appl. Phys. Rev. 3, 011101 (2016).
Keywords: Magnetic properties, Performance/Functionality/sensor, Composition & Microstructure/Material Type/polymer.
  • Lecture (Conference)
    NanoBioSensor Conference, 04.-05.09.2017, Dresden, Germany

Publ.-Id: 26756 - Permalink


Simplified expression and production of small metal binding peptides for biosorptive materials
Braun, R.ORC; Schönberger, N.; Jain, R.ORC; Matys, S.ORC; Lederer, F.; Pollmann, K.
Phage display for discovery of specific binding peptides is nowadays widely used in the pharmaceutical industry and in many biotechnological applications. Using state-of-the-art cloning techniques we developed an easy-to-use cloning and expression system, allowing the fast production of identified peptides while avoiding proteolysis.
Keywords: protein expression, metal binding, peptide, biosorption, phage display, molecular genetics, gibson assembly, metal interaction, biomaterials
  • Poster
    HZDR Doktorandenseminar 2017, 16.-18.10.2017, Seiffen, Deutschland

Publ.-Id: 26755 - Permalink


A 3D geometrical and geometallurgical model of a chromite mine
Menzel, P.; Bachmann, K.; Prior-Arche, A.; Tolosana-Delgado, R.; van den Boogaart, K. G.; Gutzmer, J.;
This contribution introduces a 3D geometallurgical model that has been developed to assess the resource potential of PGE (+Ni and Cu) recovery at the Thaba chromite mine, South Africa. The Thaba Mine is located on the northwestern limb of the Bushveld Complex and is operated by Cronimet SA. The geometallurgical model is based on a structural model and geostatistical interpolation of primary geometallurgical properties, obtained from mineral liberation analysis (MLA) and geochemical exploration data.

More than 250 MLA samples and 750 geochemical measurements cover four target seams (lower group chromitite seams: LG 6 and LG6a; middle group chromitite seams: MG1 and MG2). The data provides information about chemistry, modal mineralogy and micro-fabric from the platinum group minerals and associated base metal sulfides.
The 3D model is based on the geometry and lithological interpretations of 300 drill cores and the known main faults in the study area and covers all stratigraphic units. The MLA measurements are linked to the 3D geometry of the target seams by the sampling positions in the associated boreholes. This allows to interpolate the information based on the MLA measurements over the horizontal extension of the target seams. The model can be enhanced with further information, e.g the distance to a volume of alterated silicate host rock. The final step is to transfer the geometallurgical model to a block model, that allows to predict for each block the parameters for an optimized processing.
Our approach shows how the different ore types are spatially related to geological features and that a separate extraction of different geometallurgical ore types would be sensible.
Keywords: Geometallurgy, geological model, geometallurgical model, geostatistics
  • Lecture (Conference)
    Resources for Future Generations - RFG 2018, 16.-21.06.2018, Vancouver, Canada

Publ.-Id: 26754 - Permalink


Compliant on-skin compass for artificial magnetoception
Cañon Bermúdez, G. S.; Makarov, D.; Fassbender, J.;
Flexible electronics has inspired novel concepts like electronic skins[1] and more recently, magnetosensitive skins[2], i. e., artificial skins which allow humans to perceive magnetic fields. This ability to detect and respond to magnetic fields, commonly referred to as magnetoception, has sparked several legends since the old sailing times. Back then, it was believed that compass rose tattoos would allow sailors to always find the way home. Here, we present a flexible electronics platform to turn this ancient belief into a functional on-skin compass system.
The highly compliant compass is prepared on 6-micron-thick polymeric foils and relies on the anisotropic magnetoresistance (AMR) effect in magnetic thin film sensors. Its response is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole scheme, which forces the current in the sensor to flow 45 degrees skewed with respect to the easy axis of the AMR stripes. We envision that this on-skin compass could support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.
[1] D. H. Kim et al., Science 333, 838 (2011).
[2] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
Keywords: Functional Materials (Actuators, catalysts, energy storage, energy conversion, filters, sensors, shape memory)
  • Lecture (Conference)
    DPG Spring Meeting, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 26753 - Permalink


Electronic On-skin Compass for Magnetoception and Interactive Devices
Cañón Bermúdez, G. S.; Makarov, D.; Fassbender, J.;
Flexible electronics has inspired novel concepts like electronic skins [1-3] equipped with e.g. pressure [4] and temperature [5] sensing capabilities, which could potentially replicate the 5 empirical senses of humans. Very recently, magnetosensitive skins [6-8] enabled by shapeable magnetoelectronics [9] were reported, allowing humans to perceive magnetic fields, which is beyond the senses developed during the evolution.

Magnetoception for humans, i.e., the ability to detect and respond to magnetic fields, has been a subject of debate and dreams since the early days of navigation when sailors used compasses to orient themselves with respect to earth’s magnetic field. Sailors of old times often had compass rose tattoos to “enable” magnetoception, assuring success and luck in their trips [10,11].

Here, we present a technology platform to turn these dreams into a functional on-skin compass system. The highly compliant compasses are prepared on 6-µm-thick polymeric foils and rely on the anisotropic magnetoresistance (AMR) effect in magnetic thin film sensors. The response of these sensors is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole [12] configuration and preconditioned via a Wheatstone bridge arrangement. In a barber pole configuration, conductive slabs with a 45 degrees tilt are fabricated on top of Permalloy sensing stripes to force the current to flow skewed with respect to the easy axis of the stripes. By defining the tilt angle and properly adjusting the inter-slab separation, the magnetic field dependence of the AMR on the stripes becomes even and linear around zero.

We envision that this on-skin compass can enable humans to electronically emulate the magnetoceptive sense which some mammals possess naturally [13]. Thereby, allowing us to orient ourselves with respect to earth’s magnetic field ubiquitously. This feat could open new possibilities to support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.

[1] T. Someya et al., Proc. Natl. Acad. Sci. U. S. A. 101, 9966 (2004).
[2] D. H. Kim et al., Science 333, 838 (2011).
[3] S. Bauer et al., Adv. Mater. 26 149 (2014)
[4] S. Lee et al., Nature Nanotechnology 11, 472 (2016).
[5] X. Ren et al., Adv. Mater. 28, 4832 (2016).
[6] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
[7] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[8] N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
[9] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[10] F. Fahlander et al., The skin I live in. The materiality of body imagery, (2015).
[11] Taylor, E.G.R. Journal of Navigation, 4, 351 (1951).
[12] Phillips Semicond., Electronic Compass Design using KMZ51 and KMZ52, (2000).
[13] W. Wiltschko et al., J. Comp. Physiol. A 191, 675 (2005).
Keywords: Properties, Magnetic, magnetic properties, Performance, Functionality/sensor, Composition & Microstructure/Material Type/polymer
  • Lecture (Conference)
    2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, Arizona, USA

Publ.-Id: 26752 - Permalink


On-site Multiplexing of Mechanically Imperceptible Sensor Arrays
Voitsekhivska, T.; Cañon Bermúdez, G. S.; Lebanov, A.; Kruv, A.; Fassbender, J.; Makarov, D.;
Flexible electronics is a rapidly growing research field which enables a wide range of applications, as for consumer electronics, healthcare, environmental monitoring and a smart skins [1-3]. There are already impressive demonstrations of different types of sensors developments prepared on flexible or elastomeric support [4-9]. However, to mimic the human skin sensory ability will require the combination of multiple, distributed sensor arrays (i.e. temperature, tactile, strain) integrated on a flexible substrate. One of the challenges here is to connect each sensor with the read-out electronics. For example, if 10 sensors are to be connected, one would require at least 20 wires, which would increase the overall complexity of whole system, make it bulky and diminish its flexibility. In electrical engineering the standard approach to solve this issue is to use a multiplexing unit to minimize the amount of wires to be addressed. Yet, as there are no flexible multiplexers available, the integration of their rigid counterparts into flexible wearable systems becomes crucial [10]. Therefore, it is key point is to have a small size yet high performance multiplexer which improves the conformability and integration level of the system. As an improvement over the smallest commercially available CMOS multiplexer (32 to 1 multiplexer, overall size 7 mm x 7 mm) we have developed a monolithic CMOS analog multiplexer comprised of 96 CMOS transfer gates arranged as 3 x 32:1 multiplexers. It allows addressing up to 32 sensors simultaneously usingby 9 wires going outside and has having a footprint of just 1 mm x 4 mm.

Here, we applied the developed multiplexer for interfacing ultra-thin and mechanically imperceptible resistive temperature sensor arrays realized on imperceptible 6-µm-thick polymeric foils. As a case study, we used temperature sensor arrays. The multiplexer was integrated on a flexible printed circuit board connectedand coupled to the ultrathin sensors part by using of Z-conductive tape ora novel combination of soldering and encapsulation processes to establish reliable contacts. Using this method, we could perform real time measurements on distributed arrays of on-skin sensors. By placing these arrays on the fingers of a human hand, wWe demonstrated their use ability of this sensor array to capture and quantify the temperature information of cold/hot objects as approached by a test subject. This concept is promising for robotics, rehabilitation and, human-machine interfaces, where precise determination of local variables (e.g. temperature, pressure) is of high importance.
[1] Y. Zhang et al., Adv. Healthcare Mater. 5, (2016).
[2] W. Gao et al., Nature 529, (2016).
[3] G. Schwartz et al., Nature Communication 4, 1859 (2013).
[4] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[5] X. Wang et al., Advanced Materials 26, pp. 1336–1342 (2014).
[6] M. Melzer, D. Makarov et al., Nature Communication 6, 6080 (2015).
[7] M. Drack et al., Advanced Materials, 27, pp. 34-40 (2015).
[8] R. Chad Webb et al., Nature Materials, 12, pp. 938–944 (2013).
[9] T. Yokota et al., PNAS, 112, pp. 14533–14538 (2015).
[10] J. Viventi et al., Nature Neuroscience 14, pp. 1599–1605 (2011).
Keywords: Flexible electronics, multiplexing, soft matter, polymer
  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Publ.-Id: 26751 - Permalink


Touchless Omnidirectional Magnetosensitive Skins for Interactive Electronics
Cañón Bermúdez, G. S.; Fassbender, J.; Makarov, D.;
The widespread permeation of electronic devices into our daily life has increased the importance ofseamless interaction schemes that simplify the user’s experience. Electronic skins [1-3] contribute naturally to this development by combining sensor [4,5] and actuator elements in a compliant and mechanically imperceptible [6] format, thus eliminating the need for rigid interfaces. To advance beyond the conventional tactile interactions, we have recently proposed magnetosensitive skins [7-10] as a novel way to interact with objects in a touchless manner. This vision implies that basic building blocks of any interaction like pressing (proximity sensing) or turning (direction sensing) have to be replicated in a touchless format. In order to do so, our methodology utilizes magnetic fields as external stimuli to magnetosensitive circuits which provide a 3D reconstruction of motion in space. Moreover, to expand the breadth of applications, these interactive devices should operate over the whole range of typically available magnetic fields, spanning from the geomagnetic field of 40 μT up to regular permanent magnet fields of ~10 mT.
Here, we introduce a technology platform that addresses this vision to extend the potential of magnetosensitive skins. At its core, the platform utilizes metallic thin films as magnetoresistive (MR) and Hall-effect sensor elements, which are prepared on 6-μm-thick polymeric foils. This combination of out-of-plane (Hall) and in-plane (MR) sensors allows omnidirectional sensing on a single substrate. In addition, by using geometrical modifications like barber poles [11] or measurement schemes like zero-offset anomalous Hall magnetometry [12,13], the output sensitivity and offset can be optimized for a wide variety of applications.
We foresee that these highly compliant magnetic skins could be used to digitize fine motion, e.g. fingers with respect to the palm. This feat could enable the integration of usually rigid magnetic detection systems into on-skin, textilebased or Internet of Things (IoT) applications. A successful implementation could lead to a new class of virtual or augmented reality systems and interactive input devices which extract information from their surroundings through magnetic tags.
[1] T. Someya et al., Proc. Natl. Acad. Sci. U. S. A. 101, 9966 (2004).
[2] D. H. Kim et al., Science 333, 838 (2011).
[3] S. Bauer et al., Adv. Mater. 26 149 (2014)
[4] S. Lee et al., Nature Nanotechnology 11, 472 (2016).
[5] X. Ren et al., Adv. Mater. 28, 4832 (2016).
[6] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[7] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
[8] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[9] N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
[10] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[11] Phillips Semicond., Electronic Compass Design using KMZ51 and KMZ52, (2000).
[12] T. Kosub et al. Phys. Rev. Lett. 115, 097201 (2015).
[13] T. Kosub et al., Nat. Commun. 8, 13985 (2017).
Keywords: Properties/Magnetic/magnetic properties, Performance/Functionality/sensor, Composition & Microstructure/Material Type/polymer
  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Publ.-Id: 26750 - Permalink


A novel method for the measurement of flotation recovery by means of 4D particle tracking velocimetry
Sommer, A.-E.ORC; Nikpay, M.; Heitkam, S.ORC; Rudolph, M.ORC; Eckert, K.ORC
This work focuses on the analysis of the collection process in flotation by a simultaneous time-resolved measurement of particle and bubble trajectories. We introduced a new method that determined the probability of collision and attachment by a 3D particle tracking method with high temporal (1000 fps) and spatial (0.03 mm/pixel) resolution in the dense particle flow (5000 particles/ml). A tomographic particle image velocimetry device with three high-speed cameras recorded the three-phase flow in a rectangular bubble column (bubble chain). Particles made of fluorescent polystyrene were employed so that particles appeared bright and bubbles dark on the captured images. An attachment occurred if the trajectory of a particle coincided with that of a bubble. The recovery was calculated based on the number of particles attached to a bubble compared to the total particles density. With this method, the true flotation depending on the particle diameter (30 µm - 100 µm) was investigated and compared the results with an existing model of the bubble-particle collection microprocess.
Keywords: Collection zone recovery, Particle tracking velocimetry, Polystyrene flotation, Bubble-particle interaction
  • Minerals Engineering 124(2018), 116-122
    DOI: 10.1016/j.mineng.2018.05.006
  • Lecture (Conference)
    Flotation '17, 13.-16.11.2017, Cape Town, South Africa
  • Lecture (Conference)
    89th GAMM Annual Meeting, 19.-23.03.2018, München, Deutschland

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Publ.-Id: 26749 - Permalink


Geostatistics for Geometallurgical Property Prediction
van den Boogaart, K. G.; Menzel, P.; Bachmann, K.; Krupko, N.; Prior, A.; Tolosana Delgado, R.; Gutzmer, J.;
Geometallurgy distinguishes primary and secondary ore properties. Primary properties are describing the analytically observable properties of the ore, such as chemical composition, modal mineralogy or microstructure. Secondary properties describe the properties observable in processing experiments, like milling energy consumption, recovery and concentrate grade and thus finally monetary return as a function of processing decisions. While only the primary properties can be obtained in a sufficiently dense spatial grid at reasonable costs, the secondary properties determine processing decisions and the ultimate value.

The standard approach is to estimate two things: A geostatistical block model of primary properties based on a spatial dataset and a regression model mapping the observable primary properties to experimental secondary properties on a smaller dataset. This regression model is then applied to the predicted primary properties. Due to the nonlinearity of the dependence and due to the difference in covariance structure between observed and predicted primary properties this is however misleading and will lead to suboptimal processing decisions and a loss in resource and energy efficiency.

We solve this problem by defining intermediate properties, which can be computed directly from automated mineralogy data, on which processing properties depend approximately linearily. In this approach each particle observed is separated, remilled and circulated in virtual plants according to their observed microstructures. Nonlinear effects like the influence of the microstructure on the recovery are handled in this transformation. In this way most value relevant properties (recovery, dillution and mass pull, etc.) become a linear function of the virtual distribution of microstructures. This multivariate dataset of intermediate values is then predicted by standard geostatistical techniques.

The methodology will be exemplified with a 2D case study from a chromite mine based on local geological knowledge and automated mineralogy data acquired on a suite of samples from known locations. The resultant model readily illustrates domains of differing processing characteristics
Keywords: Geometallurgy, Particle based modelling, Geostatistics, Secondary Properties
  • Lecture (Conference)
    IAMG2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-08.09.2018, Olomouc, Česká republika

Publ.-Id: 26748 - Permalink


Analysis of the defect clusters in the congruent lithium tantalate
Vyalikh, A.; Zschornak, M.; Köhler, T.; Nentwich, M.; Weigel, T.; Hanzig, J.; Zaripov, R.; Vavilova, E.; Gemming, S.; Brendler, E.; Meyer, D. C.;
A wide range of technological applications of lithium tantalate LiTaO3 (LT) is closely related to the defect chemistry. Several cation substitution defect models have been considered in literature since decades. Here we report a combinational approach based on DFT calculations of electric field gradients (EFG) and solid-state NMR in order to reveal the defect structure in congruent lithium tantalate. Using this approach, we were able to identify the cation substitution structure attributed to the Empty site defect model in one of two congruent LT crystals studied in our work. This observation is supported by the calculation of the energy for defect formation as well as by evaluation of the defect models based on the structural refinements and chemical reasonability reported in literature. After thermal treatment, hydrogen out diffusion and homogenation of other defects in lithium tantalate have been observed by electron spin resonance (ESR), NMR and FTIR spectroscopies. Identification of the defect structure in the second LT sample seems to be more challenging, as the extrinsic defects for balancing other impurities and/or an inhomogeneous defect distribution have to be taken into account. We have found that, although grown by the same method; the two congruent LT samples provided by two manufacturers show rather different defect structures, which is manifested not only in the distribution of EFGs at 7Li, but also in the FTIR and ESR spectra and in the 7Li spin-lattice relaxation behaviour. This observation has to be taken into account when attempting to favour one specific defect model within the scientific community and when studying the physical – particularly, magneto-optical – phenomena in the systems where lithium tantalate is used as a substrate.
Keywords: Lithium tantalate, defect models, cation substitution, DFT, solid-state 7Li NMR, spin-lattice relaxation, ESR , ferroic

Publ.-Id: 26747 - Permalink


A comparative biocompatibility study of graded TiC/a-C coatings prepared by dcMS and chopped-HiPIMS
Meško, M.; Gotzmann, G.; Bohovičová, J.; Zacková, P.; Čaplovič, Ľ.; Munnik, F.; Čaplovičová, M.; Vančo, Ľ.; Skákalová, V.; Krause, M.;
Differences in the structural and biocompatibility properties of graded TiC/a-C coatings prepared by direct current magnetron sputtering (dcMS) and chopped -high power impulse magnetron sputtering (c-HiPIMS) were studied. The higher ID/IG ratio in c-HiPIMS a-C films is due to the clustering of the sp2 phase as indicated by Raman spectroscopy. C-HiPIMS a-C films are more hydrophobic with contact angle difference of about 9 % in comparison to the dcMS films at average power of 250W. The metabolic activity of human fibroblast cells cultivated on the samples grown by c-HiPIMS is of about 20 % higher than that of the samples deposited by dcMS. The increased metabolic activity is due to a confluent cell layer on these surfaces. The investigation of the cell morphology revealed no negative influence on biocompatibility for both deposition methods.
  • Contribution to proceedings
    The Fourteenth International Symposium on Sputtering and Plasma Processes (ISSP 2017), 05.-07.07.2017, Kanazawa, Japan, ISSN 2187-7637, 256-259
  • Poster
    The Fourteenth International Symposium on Sputtering and Plasma Processes (ISSP 2017), 05.-07.07.2017, Kanazawa, Japan

Publ.-Id: 26745 - Permalink


Beneficiation potential of complex Sn deposits in the Erzgebirge
Kern, M.;
Presentation for the 15th Freiberger Short Course on Economic Geology (2017)
  • Invited lecture (Conferences)
    15th Freiberger Short Course on Economic Geology, 03.-06.12.2017, Freiberg, Germany

Publ.-Id: 26744 - Permalink


Electrical characterization of Si nanocrystal devices suitable for RT-SET operation
Belli, M.; Alia, M.; Xu, X.; Laviron, C.; Gharbi, A.; Rommel, M.; Stumpf, F.; Prüfer, T.; Wolf, D.; Bischoff, L.; Hübner, R.; Hlawacek, G.; Facsko, S.; Heinig, K.-H.; von Borany, J.; Fanciulli, M.;
The contribution addresses two needs of the current micro/nanoelectronics field: the creation of low-power consumption devices, together with the compatibility with CMOS technology. Both can be potentially fulfilled adopting single electron transistors (SETs), prepared by opportune methods, to be inserted into hybrid SET-CMOS devices.
Here we focus on the electrical characterization of structures whose preparation method is suited for large-scale production of SET devices, potentially operative at room temperature: the device core is represented by few-nanometer size nanocrystals embedded in a SiO2 matrix, and is produced by ion beam mixing and subsequent thermal annealing. The preparation starts with a Si/SiO2/Si stack characterized by a few nm-size inner SiO2 layer. Ion bombardment induces atom displacements between the layers, which can be partly recovered by thermal annealing. Thanks to the joint use of process simulations and experiment, it is possible to find an opportune thermal annealing process to yield few nm-size silicon crystals embedded in the middle of the SiO2 layer. The small crystal size (< 5 nm) and the extremely narrow SiO2 bridges (~ 2 nm) between the nanocrystals and the electrical contacts are designed to ensure high tunneling probability towards the Si quantum dot and room temperature operation. The production method should allow fast transfer to industrial processes, being scalable to standard full wafer-size processing. Results on the electrical characterization in the 5 K – 350 K range of preliminary structures will be presented, in view of the realization of SET and hybrid SET-CMOS devices.
The authors acknowledge support from H2020 project “IONS4SET”, contract number 688072.
  • Lecture (Conference)
    EUROMAT 2017, 17.-22.09.2017, Thessaloniki, Greece

Publ.-Id: 26743 - Permalink


Challenges of digitalizing the circular economy: Assessment of the state-of-the-art of metallurgical carrier metal platform for lead and its associated technology elements
van Schalkwyk, R. F.; Reuter, M. A.; Gutzmer, J.; Stelter, M.;
The circular economy (CE) paradigm in its broadest sense is key to our survival as a species. Due to this critical importance, understanding its fundamental limitations is thus of significant importance. Especially understanding the losses to Nature are key as these represent the true limitation to circularity. This requires at the minimum an understand of the thermodynamics and entropy of the losses. Most CE work as well as the many depictions to date neglect to address this in detail, the many losses are brushed aside. Many texts in CE do not use the words entropy, thermodynamics, mass and heat transfer, technology etc. which all ultimately fundamentally affect both the circularity as well as economic viability of the system. Using lead as carrier for the narrative of this paper, the state-of-the art from technology to the thermodynamics as well as heat and mass transfer, product design, modularity, environmental impact, system simulation etc. will be critically discussed. This will reveal what key knowledge and data is presently missing to the achieve the economically viable circularity of materials and products This paper goes further to offer pointers what should be researched and developed to “close” the circular economy system. It thus provides a “ground zero” or baseline for the evaluation of the true economic viability of the CE paradigm relative to what we are presently achieving in our linear economy paradigm.
Keywords: Circular Economy, Lead, Technology Elements, Process metallurgy, Resource efficiency, Sustainability

Publ.-Id: 26742 - Permalink


Chancen und Grenzen der Circular Economy: Wie recycelbar sind Mobiltelefone?
Reuter, M. A.; Weigl, A.;
Um Ressourcen verantwortungsvoll und effizient zu nutzen, ist eine fortschrittliche Circular Economy (CE ─ Kreislaufwirtschaft), in der Recycling ein Kernelement ist, der vielversprechendste Ansatz. Auf der politischen Agenda Europas ist die CE ganz oben angekommen. Circular Economy und Recycling sollten, so fordert zum Beispiel der französische Premierminister, Emmanuel Macron, eine wichtige Säule bei der Rohstoffsicherung für die heimische Industrie bilden (1). Auch verhandeln derzeit die EU-Mitgliedstaaten über ein europäisches Kreislaufwirtschaftspaket (2).
Wieviel Recycling ist aber angesichts von immer komplexeren elektronischen Geräten und anderen Hochtechnologieanwendungen derzeit überhaupt möglich? Eine aktuelle Recyclingstudie zeigt am Beispiel eines Mobiltelefons die Chancen und Grenzen der Circular Economy auf.
Keywords: Circular Economy, Kreislaufwirtschaft, CE, Recycling, Recyclingstudie, Mobiltelefon, Rohstoffe, Recycelbarkeit, Metallurgie
  • ACAMONTA - Zeitschrift für Freunde und Förderer der TU Bergakademie Freiberg 24(2017), 65-68

Publ.-Id: 26740 - Permalink


Property-based Modelling and Simulation of Mechanical Separation Processes using Dynamic Binning and Neural Networks
Hannula, J.; Kern, M.; Luukkanen, S.; Roine, A.; van den Boogaart, K. G.; Reuter, M. A.;
To fully understand the limits of the Circular Economy (CE), a comprehensive model taking into account its different stages (product design, mechanical pre-processing, metallurgy, etc.) is required. A crucial aspect is to understand the inevitable losses at different stages of recycling. The complexity of the material streams in mechanical separation processes requires a detailed description of particles and their properties to successfully simulate unit processes. This paper presents a new approach that connects measurement-based particle properties to statistical modelling and simulation of mechanical separation processes. The proposed approach combines particle tracking with the generalization ability of neural networks. Above all it advances the present particle binning and tracking methods utilizing property-based binning rather than liberation-based binning for modelling purposes of complex systems. In order to demonstrate the new approach, this paper uses Mineral Liberation Analysis (MLA) data from magnetic and gravity separation processes of a complex ore and shows the benefits of property based binning over for example liberation based binning. The proposed approach can be integrated into present simulation platforms such as HSC Sim.
Keywords: Particle Tracking, Particle-based model, Modelling, Simulation, Circular Economy
  • Minerals Engineering 126(2018), 52-63
    DOI: 10.1016/j.mineng.2018.06.017
  • Lecture (Conference)
    Sustainable Minerals '18, 15.06.2018, Windhoek, Namibia

Publ.-Id: 26739 - Permalink


Central receiver coatings for high-temperature concentrated solar power studied by in situ RBS, Raman spectroscopy and spectroscopic ellipsometry
Lungwitz, F.; Heras, I.; Janke, D.; Wenisch, R.; Schumann, E.; Guillén Rodriguez, E.; Escobar Galindo, R.; Gemming, S.; Krause, M.;
The development of solar-selective CSP receiver coatings with high-temperature and environmental stability requires new concepts of design and in operando monitoring. Solar receiver tubes are a key component of solar thermal power plants. The increase of their operation temperature from today’s maximum of 550°C to about 800°C could increase the CSP efficiency by approximately 15 to 20% and improve the competiveness of this technology compared to other ones of carbon-free electricity generation. Potential alternatives to fast degrading state-of-the-art pigment paint receiver tube coatings are based on refractive metal carbides, nitrides, and oxides because of their high thermal stability and oxidation resistance.
New types of solar-selective coatings were studied in situ at temperatures of up to 830°C by Rutherford backscattering spectrometry, Raman spectroscopy, and spectroscopic ellipsometry within a cluster tool. High-temperature stability in high-vacuum is demonstrated for carbon-metal- and oxynitride-absorber-based multilayers as well as for a solar-selective transmitter based on a transparent conductive oxide.
Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.
Keywords: Solar selective coatings, Oxynitrides, Thermosolar energy, Optical simulation, in situ analysis
  • Poster
    X Iberian Vacuum Conference, RIVA, 04.-06.10.2017, Bilbao, Espana

Publ.-Id: 26738 - Permalink


An update on possibilities of metals recovery from Polish copperores by biotechnology. Project Ecometals
Szubert, A.; Guezennec, A.-G.; Bodénan, F.; Dirlich, S.; Pawłowska, A.; Grotowski, A.; Sadowski, Z.; Witecki, K.;
The possibilities of metals recovery from copper ores with the biotechnological methods are widely known. The methods consist in bioleaching of copper ores, copper concentrates and byproducts of their production, as well as metals recovery from leaching solutions. Biohydrometallurgical methods were tested for years to be applied at KGHM Polska Miedź S.A., in order to improve efficiency of copper production. Several different research units worked on the topic, and the most significant and wide range initiatives in this area are mentioned in this article. One of the initiatives is an ongoing German and French Ecometals project. KGHM Polska Miedź S.A. and KGHM Cuprum Ltd. Research and Development Centre are this project Partners. In the frame of the project different metals bearing materials (ores, concentrates and tailings) are tested. Among them three lithological types of the copper ore from Rudna mine and the copper concentrate from Lubin concentrator are used for studies. The article gives a general overview of these activities, with the main focus on results of bioleaching studies of selected materials, conducted by KGHM Cuprum. In these studies sandstone and shale, as well as so called “shale concentrate” (containing 39% of the shale) were used for experiments, and possibilities of their bioleaching were evaluated.
Keywords: Biohydrometallurgie; biohydrometallurgy; Biolaugung; bioleaching, Kupfer; copper
  • Open Access LogoContribution to proceedings
    Mineral Engineering Conference MEC2017, 20.-23.09.2017, Wisła, Polska
    E3S Web of Conferences 18 , 01015
    DOI: 10.1051/e3sconf/201712301015

Publ.-Id: 26736 - Permalink


Bewertung - zwischen Vollständigkeit und Praxisnähe
Dirlich, S.;
Der Buchbeitrag beschäftigt sich mit der Bewertung von Handlungsoptionen in verschiedenen Themenfelder der Siedlungsentwicklung, die in einem Projekt im BMBF-Förderprogramm "Nachhaltiges Landmanagement" entwickelt wurde. Eine Bewertung der vorgeschlagenen Handlungsoptionen ist erforderlich, um deren Wirkungen aus Sicht der Ressourceneffizienz und Emissionsarmut einzuschätzen und miteinander zu vergleichen. Aufgrund der Bandbreite der Themenfelder von der Abfallwirtschaft bis hin zur Siedlungsentwicklung und der transdisziplinären Herangehensweise ist ein projektspezifischer angepasster Ansatz nötig, der sowohl den Erfordenissen der Wissenschaft nach Vollständigkeit und Vergleichbarkeit gerecht wird, als auch den Anforderungen der beteiligten Akteure entspricht.
Keywords: nachhaltiges Landmanagement; sustainable land management; Bewertung; assessment; Siedlungsentwicklung; settlement development
  • Open Access LogoBook chapter
    Schiller, Georg: Wege zur Umsetzung von Ressourceneffizienzstrategien in der Siedlungs- und Infrastrukturplanung IÖR Schriften Band 74, Berlin: RHOMBOS-Verlag, 2017, 978-3-944101-74-3

Publ.-Id: 26735 - Permalink


Relativistic Effects in Laser Plasmas -Plasma Birefringence and Generation of Mega-Tesla Magnetic Field-
Arefiev, A.; Stark, D. J.; Toncian, T.; Murakami, M.;
と呼ばれる物理現象は,高強度レーザーとプラズマとの相互作用に対する近年の当該領 域の研究の中でもパラダイムシフトとも言うべき極めて興味深いものである.超高強度レーザーの照射によりプ ラズマ中の電子温度が急速に相対論領域(!500 keV)にまで上昇すると,たとえ非相対論領域においてレーザー が完全反射されるほどの高密度のプラズマでも,レーザー光はプラズマの奥深く浸透することが可能となり,こ の特性は「相対論的透明性」と呼ばれる.本章では,相対論的透明性が顕著に見られる2つの集団現象にスポッ トを当てることにより,レーザーと物質との相互作用において同特性が演じる重要な役割を俯瞰する.第一の現 象は,相対論領域におけるプラズマ中で見られる複屈折である.この相対論的複屈折では超高強度レーザー照射 によってプラズマが非等方性を持ち,結果としてその光学特性がレーザーの偏光に強く依存する.第二の現象は, 高密度プラズマと超高強度レーザーとの(極小幅を持つ境界面ではなく奥行きを持った有限空間に分布する)体 積的相互作用により誘起される超高強度の準静磁場の生成である.このような相対論的高エネルギー密度領域で は MeV オーダーの
Keywords: relativistic transparency, laser-matter interaction, megatesta magnetic field, plasma birefringence
  • Open Access LogoJournal of Plasma and Fusion Research 93(2017)11, 535-544

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Publ.-Id: 26734 - Permalink


Integration of mineralogical and hyperspectral data for drill-core characterization
Tusa, L.; Andreani, L.; Contreras, C. I.; Ivascanu, P.; Gloaguen, R.; Gutzmer, J.;
Mineral exploration and resource definition require extensive drilling campaigns that are generally done with tight deadlines and often rely only on visual qualitative evaluation of the rock characteristics (core logging) and limited chemical analyses. The aim of these campaigns is to understand the genesis and zonality of mineral deposits. The ore, in many cases, is closely related to the distribution of hydrothermal alterations and their associated structures. Therefore, the host characteristics are analysed in order to build a distribution model of the mineralization. However, traditional techniques such as core logging can present limitations in the identification of often subtle and therefore similar mineral assemblages and the acquired data are only qualitative. Additionally, the identification and quantification of other textural and structural features, such as veins, is slow, laborious and frequently limited by the subjectivity of the observer.
Our aim is to develop new methods which respond to the need for rapid, automated and precise extraction of mineralogical, textural and structural information from cores. We propose to process hyperspectral VNIR/SWIR data from core scanners, using innovative image segmentation and classification techniques in order to quickly extract precise numerical parameters of both mineralogical and structural information. We use scanning electron microscopy (SEM)-based analyses on selected samples to train the classifier and validate the results. SEM shows great potential in the identification of the main alteration assemblages as well as of the main hydrothermal events they are associated with. Even though it requires extensive sample preparation and the measurements are time consuming, by analysing representative samples for different alteration types, SEM-based analyses provide control information for the interpretation and classification of hyperspectral data. Hyperspectral data allow the identification of the main alteration phases and the distribution of specific mineral assemblages as each vein type displays a specific signature in the VNIR-SWIR region of the electromagnetic spectrum. Image segmentation techniques allow us to extract veins and additional parameters such as orientations and densities. The interest of this approach is that it (1) allows the combined analysis of compositional and structural features, (2) provides a very rapid and validated mapping of the cores that is based on (3) the upscaling of SEM data.
The proposed methodology has been tested on selected core samples from the Bolcana copper-gold porphyry system (Romania). This site is located in the Golden Quadrilateral (Apuseni Mountains) where extensive drilling has been performed by Eldorado Gold using state of art methodology that includes thorough chemical analyses, detailed logging and spectral characterization of assay pulps. The mineralization in Bolcana is hosted in Neogene subvolcanic dioritic intrusions and associated magmatic-hydrothermal breccias that intruded in a shallow volcanic environment. The system is characterized by complex transitions on lithological and alteration assemblages. The porphyry mineralization is also overprinted by later epithermal events that lead to different alteration patterns than those usually encountered in porphyry systems.
The analyses of the cores collected from the Bolcana site have shown a preferential association of specific alteration assemblages with different vein generations such as white mica dominant assemblages for late stage pyrite veins, a chlorite-epidote dominant assemblage on early chalcopyrite veins and low intensity white mica dominant assemblage associated with early quartz veins. At core scale a preferential orientation of these veins was additionally observed.
The integration of this new approach with traditional logging methods performed by site geologists as well as with structural data (Reflex IQ-logger) provided by Eldorado Gold gives us an insight on the spatial and directional distribution of the main vein types and their characteristic alteration assemblages in the Bolcana site. The integration of such new methodologies in the exploration campaign allows for better and faster exploration targeting based on key mineral assemblages and structural features, as well as a more comprehensive preliminary ore evaluation and resource modelling. This would be achieved by the implementation of on-site drill-core scanning.
  • Poster
    Applied Geological Remote Sensing, 12.-15.12.2017, Lisbon, Portugal

Publ.-Id: 26731 - Permalink


Distribution of lead- and zinc-bearing minerals in the gossan of the Gamsberg Zn deposit, South Africa
Tusa, L.; Moeckel, R.; Gutzmer, J.;
The giant Gamsberg massive sulphide deposit is currently being developed by Vedanta Resources. During mine development, the massive gossan zone is stripped in order to expose the sulphide orebody. During a field visit In September 2016, a suite of samples was collected from the gossan in the developing open pit. Three lithologically distinct zones were recognized. The topmost zone is a goethitic hard cap that is also well exposed at the present-day land surface (Rozendaal, 1986). The goethitic hard cap grades down into an iron oxide-poor zone that comprises of very friable siliceous material. The latter is cross-cut by fractures filled by hematite. The third zone of the gossan is marked by an abundance of fine-grained earthy hematite intergrown with semi-friable silica. Vugs are commonly lined by chalcedony. A detailed study revealed the presence of a complex suite of secondary lead and zinc minerals. Zinc is most abundant in the goethite cap – apparently related to the occurrence iron-rich smectite group minerals. Minor amounts of Pb-rich minerals, such as anglesite and members of the corkite-beaudantite were also identified. Most abundant, however, is lead below the goethitic cap where anglesite and members of the mimetite- pyromorphite and corkite-beaudantite series are very common. The lowermost gossan zone consists of mainly fine grained silica and hematite. Lead- and zinc-bearing minerals are conspicuously absent. The results obtained are consistent with observations by Rozendaal (1986) – and the apparent enrichment of lead-bearing secondary minerals in the gossan - relative to scarce nature of galena in the sulphide orebody. This apparent enrichment is attributed to the greater mobility of zinc – relative to lead - in the supergene environment.
  • Poster
    Geology of Ore Deposits, 08.-11.03.2017, Hannover, Germany

Publ.-Id: 26730 - Permalink


3D Si-SiO2 nano-networks formed by diode laser-induced liquid- and solid-state decomposition of SiOx
Schumann, E.; Hübner, R.; Carcelen, V.; Grenzer, J.; Heinig, K.-H.; Gemming, S.; Krause, M.;
Thin films of nano-structured crystalline silicon (nc-Si) are potential absorber and supporting layers for next-generation Si solar cells. As one candidate, Si-SiO2 nanocomposites with percolated nc-Si have been fabricated by rapid thermal annealing (RTA) of sputter-deposited SiOx films (x≈1). A percolated silicon network has been formed by solid state phase separation into nc-Si and SiO2 [1, 2].
In the present study, SiO0.6 layers of ~500nm thickness are grown on quartz by ion beam sputter (IBS) as well as by reactive magnetron sputter (RMS) deposition. Formation of percolated Si-SiO2 nanocomposites is achieved by two different modes of thermal treatment: (i) Furnace annealing at 950°C and (ii) scanning laser processing. In case (ii), a diode laser with dwell times in the ms range, power densities of ~30 kW/cm², a wavelength of λ= 808nm and a line focus of 100µm x 11mm is applied. This process is ~106 times faster than isothermal treatment and ~103 times faster than RTA. Another advantage of this method is the usability of temperature sensitive substrates and maintaining homogeneous processing.
Rutherford backscattering spectra of as-deposited and processed SiO0.6 reveals a compositional change in thin surface and interface layers, but no significant change in the bulk composition. Raman spectroscopy and X-ray diffraction show that the crystallinity of the nc-Si is higher for the laser-treated sample.
High resolution- and energy-filtered transmission electron microscopy (HTEM, EFTEM) show additionally, that in both cases the as-deposited SiO0.6 is transformed into a percolated nanocomposite consisting of amorphous SiO2 and nc-Si.
In more detail, laser processing of IBS-deposited layers leads to isotropic morphologies self-similar to furnace-annealed samples, but scaled up by a factor of ~5. This is explained by a phase separation in the liquid state and the solid state, respectively, which cause diffusion coefficients differing by several orders of magnitude.
During the deposition by RMS, phase separated filament-like morphologies form. Here, furnace annealing leads to enhanced phase separation accompanied by crystallization. In contrast laser processing erases the as-deposited filaments and produces isotropic morphologies similar to IBS-deposited and laser-processed samples

[1] Friedrich, D. et al. Sponge-like Si-SiO2 nanocomposite - Morphology studies of spinodally decomposed silicon-rich oxide. Appl. Phys. Lett. 103, 131911 (2013).
[2] Ilday, S. et al. Multiscale Self-Assembly of Silicon Quantum Dots into an Anisotropic Three-Dimensional Random Network. Nano Lett. 16, 1942–1948 (2016).
  • Lecture (Conference)
    2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, USA

Publ.-Id: 26728 - Permalink


Design of high-temperature solar-selective coatings based on aluminium titanium oxynitrides AlyTi1-y(OxN1-x). Part 1: Advanced microstructural characterisation and optical simulation
Heras, I.; Guillén, E.; Lungwitz, F.; Rincón-Llorente, G.; Munnik, F.; Schumann, E.; Azkona, I.; Krause, M.; Escobar-Galindo, R.;
Aluminium titanium oxynitrides were studied as candidate materials for high temperature absorbers in solar selective coatings due to their excellent stability and their tuneable optical behaviour. A set of individual AlyTi1-y(OxN1-x) layers with different oxygen content was prepared by cathodic vacuum arc (CVA) deposition. The composition, morphology, phase structure and microstructure of the films were characterized by elastic recoil detection (ERD), scanning and transmission electron microscopy and X-ray diffraction. An fcc phase structure is found in a broad compositional range of AlyTi1-y(OxN1-x). Simultaneously, sample microstructure and morphology undergo systematic changes from a columnar growth to the development of a heterogeneous structure with spherical nanoparticle inclusions when the oxygen concentration is increased. The optical properties were determined by spectroscopic ellipsometry and UV–Vis–NIR and FTIR spectrophotometry. A comprehensive analysis of the film properties allowed an accurate modelling of the optical constants of the AlyTi1-y(OxN1-x) in the whole wavelength range of solar interest (from 190 nm to 25 µm). It points to a transition from metallic to dielectric behaviour with increasing oxygen content. Consequently, it is demonstrated that the optical properties of these AlyTi1-y(OxN1-x) deposited films can be controlled in a wide range from metallic to dielectric character by adjusting the oxygen concentration, opening a huge range of possibilities for the design of solar selective coatings (SSC) based on this material. Complete SSC, including a TiN layer as IR reflector, were designed by applying optical simulations, obtaining excellent optical selective properties of α=94.0% and εRT = 4.8%.
Keywords: Solar selective coatings, Oxynitrides, Thermosolar energy, Optical simulation

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Publ.-Id: 26727 - Permalink


Phase Transitions in C:Ni Nanocomposite Templates during Diameter-Selective CVD Synthesis of SWCNTs
Krause, M.; Melkhanova, S.; Hübner, R.; Haluska, M.; Gemming, S.;
Phase transitions in carbon: nickel nanocomposite templates during diameter-selective CVD synthesis of SWCNTs were studied. While almost conserving their pre-defined diameter distribution, as-deposited Ni3C nanoparticles transform into fcc-NiO during activation in low-pressure air atmosphere, and are reduced to a mixture of fcc-Ni and Ni3C under nanotube growth conditions. The first phase transition leads to a substitutional replacement of the protective carbon matrix by a protective oxide layer. The second one reflects competing reduction processes of NiO. A mechanism for the complementary roles of carbon matrix and Ni species in the three-step CVD synthesis is proposed that includes nanoparticle immobilization, carbon delivery and catalysis of nanotube growth.
Keywords: nanocomposites, single-walled carbon nanotubes, catalysis, transmission electron microscopy, Raman spectroscopy

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Publ.-Id: 26726 - Permalink


On the synchronizability of Tayler–Spruit and Babcock–Leighton type dynamos
Stefani, F.; Giesecke, A.; Weber, N.; Weier, T.;
The solar cycle appears to be remarkably synchronized with the gravitational torques exerted by the tidally dominant planets Venus, Earth and Jupiter. Recently, a possible synchronization mechanism was proposed that relies on the intrinsic helicity oscillation of the current-driven Tayler instability which can be stoked by tidal-like perturbations with a period of 11.07 years. Inserted into a simple alpha-Omega dynamo model these resonantly excited helicity oscillations led to a 22.14 years dynamo cycle. Here, we assess various alternative mechanisms of synchronization. Specifically we study a simple time-delay model of Babcock–Leighton type dynamos and ask whether periodic changes of either the minimal amplitude for rising toroidal flux tubes or the Omega effect could eventually lead to synchronization. In contrast to the easy and robust synchronizability of Tayler–Spruit dynamo models, our answer for those Babcock–Leighton type models is less propitious.

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Publ.-Id: 26725 - Permalink


Metallurgie und Recycling im HIF - Gegenwart und Zukunft
Kelly, N.; Scharf, C.;
  • Lecture (others)
    Topictreffen „Ressourcentechnologie“, 03.-04.07.2017, Freiberg, Deutschland

Publ.-Id: 26724 - Permalink


FWGM - Division METALLURGY & RECYCLING - Helmholtz Institute Freiberg for Resource Technology
Kelly, N.; Scharf, C.;
  • Lecture (others)
    Meeting VITO - FWGM, 26.-27.01.2017, Freiberg, Deutschland

Publ.-Id: 26723 - Permalink


FWGM - Division METALLURGY & RECYCLING - Helmholtz Institute Freiberg for Resource Technology
Kelly, N.; Scharf, C.;
  • Lecture (others)
    Meeting IWKS - FWGM, 13.02.2017, Freiberg, Deutschland

Publ.-Id: 26722 - Permalink


Current Projects and Objectives at Helmholtz Institute Freiberg – Department of Metallurgy and Recycling
Kelly, N.; Scharf, C.;
Current Projects and Objectives at Helmholtz Institute Freiberg – Department of Metallurgy and Recycling
  • Poster
    International Workshop ECMAG - Magnetic Field Effects on Aqueous Solutions, 20.-21.04.2017, Dresden-Rossendorf, Deutschland

Publ.-Id: 26721 - Permalink


Screening the potential of Halophilic bacteria for Pyrite bio depression
Luque Consuegra, G.; Kutschke, S.; Rudolph, M.; Pollmann, K.;
The separation of minerals has been a pressing issue in the last decades. One of the most common techniques to separate useful minerals from gangue minerals is Froth Flotation. Flotation is a relatively cheap and efficient process but the use of harmful chemicals and continuous decrease in ore quality due to the scarcity of high grade ores has motivated researchers to find alternative solutions to the standard flotation reagent scheme in order to make the process more efficient and environmentally friendly. Bioflotation has the potential of making the beneficiation of minerals more efficient and environmentally friendlier. Different bacteria and bacterial products have demonstrated to have prospective applications in bio flotation of different minerals (Behera and Mulaba-Bafubiandi, 2016). Halophilic bacteria are adapted to high salinity environments and other extreme conditions. Halophilic bacteria produce Extracellular Polymeric Substances (EPS) that aid them in the formation of biofilms and resist abrupt changes in salinity, pH, temperature and pressure. These EPS could have potential applications in flotation operations performed in sea water, such as the Copper-Molybdenum flotation operations in Chile. To date, there are no reports of halophilic bacteria been used in bio flotation experiments.
Halomonas boliviensis, Marinobacter spp, Halobacillus sp, Marinococcus sp and Halomonas eurihalina were studied to examine their potential as pyrite bio depressants, a gangue mineral common in Cu-Mo flotation. Micro flotation experiments using Hallimond tubes as well as flocculation, adsorption and Zeta potential experiments were performed in order to report the potential of these bacteria in the flotation process. In this study we will show the first results of using halophilic bacteria as Pyrite bio depressants, as well as an initial characterisation of the Extracellular Polymeric Substances excreted by these bacteria that could have an influence on the adsorption and mechanism by which these bacteria alter the surface of Pyrite.
Keywords: Biodepression, Halophilic bacteria, Pyrite
  • Poster
    Tagung 2017 Aufbereitung und Recycling, 08.-09.11.2017, Freiberg, Deutschland

Publ.-Id: 26720 - Permalink


Whole exome sequencing identifies mTOR and KEAP1 as potential targets for radiosensitization of HNSCC cells refractory to EGFR and β1 integrin inhibition
Klapproth, E.; Dickreuter, E.; Zakrzewski, F.; Seifert, M.; Petzold, A.; Dahl, A.; Schröck, E.; Klink, B.; Cordes, N.;
Intrinsic and acquired resistances are major obstacles in cancer therapy. Genetic characterization is commonly used to identify predictive or prognostic biomarker signatures and potential cancer targets in samples from therapy-naïve patients. By far less common are such investigations to identify specific, predictive and/or prognostic gene signatures in patients or cancer cells refractory to a specific molecular-targeted intervention. This, however, might have a great value to foster the development of tailored, personalized cancer therapy. Based on our identification of a differential radiosensitization by single and combined β1 integrin (AIIB2) and EGFR (Cetuximab) targeting in more physiological, three-dimensional head and neck squamous cell carcinoma (HNSCC) cell cultures, we performed comparative whole exome sequencing, phosphoproteome analyses and RNAi knockdown screens in responder and non-responder cell lines. We found a higher rate of gene mutations with putative protein-changing characteristics in non-responders and different mutational profiles of responders and non-responders. These profiles allow stratification of HNSCC patients and identification of potential targets to address treatment resistance. Consecutively, pharmacological inhibition of mTOR and KEAP1 effectively diminished non-responder insusceptibility to β1 integrin and EGFR targeting for radiosensitization. Our data pinpoint the added value of genetic biomarker identification after selection for cancer subgroup responsiveness to targeted therapies.
Keywords: β1 integrin, EGFR, Exome, ionizing radiation, HNSCC

Publ.-Id: 26719 - Permalink


Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements
Mechernich, S.; Dunai, T. J.; Binnie, S. A.; Goral, T.; Heinze, S.; Dewald, A.; Schimmelpfennig, I.; Keddadouche, K.; Aumaître, G.; Bourlès, D.; Marrero, S. M.; Wilcken, K.; Simon, K.; Fink, D.; Phillips, F. M.; Caffee, M. W.; Gregory, L. C.; Phillips, R.; Freeman, S. P. H. T.; Shanks, R. P.; Sarıkaya, M. A.; Pavetich, S.; Rugel, G.; Merchel, S.; Akçar, N.; Yesiyurt, S.; Ivy-Ochs, S.; Vockenhuber, C.;
Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-feldspar from a Namibian pegmatite. The sample preparation took place at the University of Cologne and a rotating splitter was used to obtain homogeneous splits of both ICMs. Forty-five measurements of CoCal-N (between 1 and 16 per facility) and forty-four measurements of CoFsp-N (between 2 and 20 per facility) have been undertaken by ten target preparation laboratories measured by seven different AMS facilities. The internal laboratory scatter of the 36Cl concentrations indicate no overdispersion for half of the laboratories and 3.9 to 7.3% (1σ) overdispersion for the others. We show that the CoCal-N and CoFsp-N splits are homogeneous regarding their 36Cl and Clnat concentrations. The grand average (average calculated from the average of each laboratory) yields initial consensus 36Cl concentrations of (3.74 ± 0.10) x 106 at 36Cl/g (CoCal-N) and (2.93 ± 0.07) x 106 at 36Cl/g (CoFsp-N) at 95% confidence intervals. The coefficient of variation is 5.1% and 4.2% for CoCal-N and CoFsp-N, respectively. The Clnat concentration corresponds to the lower and intermediate range of typical rock samples with 0.73 ± 0.18 μg/g in CoCal-N and 73.9 ± 6.8 μg/g in CoFsp-N. We discuss the most relevant points of the sample preparation and measurement and the chlorine concentration calculation to further approach intra-laboratory comparability. We propose to use continuous measurements of the ICMs to provide a valuable quality control for future determination of 36Cl and Clnat concentrations.
Keywords: Accelerator mass spectrometry, Terrestrial cosmogenic nuclides (TCN), Round Robin, Intercomparison material (ICM), Consensus values

Publ.-Id: 26718 - Permalink


Optimization of an SRF Gun for High Bunch Charge Applications at ELBE
Lu, P.;
As a cutting-edge type of photoinjectors, SRF gun is expected to provide a CW electron beam with high bunch charge and low emittance, which is highly demanded by the development of future FELs, ERLs and 4th/5th generation light sources. However, existing researches have not explored the full potential of SRF gun predicted by theory.
Keywords: photo injector, superconducting RF, SRF gun, ELBE facility, electron beam transport, simulation
  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Dr. Jochen Teichert
    134 Seiten

Publ.-Id: 26717 - Permalink


Operation of the SRF Gun with Mg Photocathodes for Production of Neutrons and THz Radiation at ELBE
Teichert, J.;
Status Report on Superconducting Rf Photoinjector application at ELBE
Keywords: SRF gun, photo injector, ELBE
  • Lecture (Conference)
    PITZ Collaboration Meeting, 05.-06.12.2017, Zeuthen, Germany

Publ.-Id: 26716 - Permalink


The Superconducting RF Photoinjector and its Present and Future Use at the ELBE Accelerator
Teichert, J.;
The Superconducting RF Photoinjector and its Present and Future Use at the ELBE Accelerator
Keywords: SRF Gun, ELBE facility, superconducting RF, photocathodes, Nb resonator
  • Lecture (others)
    Seminar talk, 06.-10.11.2017, Chengdu, China

Publ.-Id: 26715 - Permalink


Operational Aspects of Photocathodes for SRF Guns
Teichert, J.; Xiang, R.;
The talk reports on operational aspects and experiences of photocathodes for the superconducting Rf photo injector at the ELBE accelerator
Keywords: photocathode, SRF gun, photo injector, cathode handling
  • Invited lecture (Conferences)
    EWPAA workshop, 20.-22.09.2017, Berlin, Germany

Publ.-Id: 26714 - Permalink


Using the Mineral Liberation Analyzer for mineralogical studies of a carbonaceous apatite ore
Hoang, D. H.ORC; Leißner, T.ORC; Haser, S.; Rudolph, M.ORC; Peuker, U. A.ORC
Liberation analysis on grinding products is a very important subject for application in respect of both mineralogical characteristics and beneficiation process relevant parameters. The Mineral Liberation Analyzer (MLA) combines a large specimen chamber automated Scanning Electron Microscope (SEM), multiple Energy Dispersive X-ray detectors (EDX) with automated quantitative mineralogy software. SEM-based automated mineralogy tools are essential in measuring parameters, such as modal mineralogy, mineral locking, mineral association, theoretical grade - recovery and mineral liberation.
Such quantitative information is fundamental to investigate and evaluate the mineral processing of ores. In this study carbonaceous apatite ore samples from Lao Cai deposit (Vietnam) was used. The petrographic, mineralogical and mineral liberation observations showed that the ore sample is quite
complex, containing carbonate impurities (dolomite and calcite) and having very fine intergrown texture. The separation of carbonate from apatite has been recognized as one of the most difficult subjects in mineral processing due to the similarities in their physiochemical properties.
Keywords: Mineral Liberation Analyzer; automated mineralogy; carbonaceous apatite; flotation.
  • Contribution to proceedings
    International Conferences on Earth Sciences and Sustainable Geo-Resources Development, 12.-15.11.2016, Hanoi, Vietnam
    Proceedings of the ESASGD 2016, Hanoi, Vietnam: Transport Publishing House, 978-604-76-1171-3, 42-51

Publ.-Id: 26713 - Permalink


Diagnostics of ELBE SRF Gun - Status and Future Design
Lu, P. N.; Arnold, A.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.;
Report on the Diagnostics for Beam Characterization of the ELBE SRF-Gun
Keywords: SRF gun, photo injector, transverse emittance, beam charactetization
  • Poster
    IBIC 2017 - International Beam Instrumentation Conference, 20.-24.08.2017, Grand Rapids, USA
  • Open Access LogoContribution to proceedings
    IBIC 2017 - International Beam Instrumentation Conference, 20.-24.08.2017, Grand Rapids, USA
    Proceedings of IBIC 2017, Genf: JACoW, 53-56

Publ.-Id: 26712 - Permalink


Optimization of ELBE SRF Gun II for high-bunch-charge applications
Lu, P.; Arnold, A.; Vennekate, H.; Murcek, P.; Teichert, J.; Xiang, R.;
Report on the beam transport simulation of the ELBE accelerator for injection with the SRF gun for THz, neutron and CBS applications.
Keywords: SRF gun, electron source, superconducting acceleerator
  • Poster
    The 3rd annual meeting of Matter and Technologies, 31.01.-02.02.2017, Darmstadt, Germany

Publ.-Id: 26711 - Permalink


Metal and Semiconductor Photocathodes in the HZDR SRF Gun
Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.;
The superconducting RF photoelectron gun at the ELBE accelerator facility is a high-repetition rate electron injector for CW operation and can provide high average current and high brightness electron beams. During commissioning and operating time different types of photocathodes, metallic (Cu, Mg) and semiconductors (Cs2Te), have been used. We present the preparation processes, properties as well as performance and operational experience of the cathodes in the SRF gun. Furthermore, specific issues like cathode cooling, multipacting, and dark current will be discussed.
Keywords: SRF gun, electron source, photocathode, Mg, Cu, Cs2Te
  • Invited lecture (Conferences)
    ERL 17 - The 59th ICFA Advanced Beam Dynamics Workshop on Energy recovery Linacs, 18.-23.06.2017, Geneva, Switzerland

Publ.-Id: 26710 - Permalink


RF Performance and Beam Parameter Measurement of the 2nd 3.5 cell SRF Gun for ELBE
Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.;
In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In our contribution we will report on the commissioning of the SRF gun by presenting a full set of RF performance results as well as detailed beam parameter measurements up to a bunch charge of 300 pC. Additionally, we will present the results of the first two user experiments (neutron and THz generation) that demonstrated the reliability of this gun concept.
Keywords: SRF gun, electron source, superconducting accelerator, ELBE, beam parameter
  • Poster
    ERL 17 The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 18.-23.06.2017, Geneva, Switzerland

Publ.-Id: 26709 - Permalink


Application status of SRF gun II as the injector for the ELBE radiation center
Xiang, R.; Arnold, A.; Lehnert, U.; Lu, P.; Michel, P.; Murcek, P.; Teichert, J.; Vennekate, H.;
An improved SRF gun (ELBE SRF Gun II) has been installed at the ELBE radiation center as an additional electron source since 2014. This new gun is able to produce up to 300 pC bunch charges in CW mode. This poster summarizes the latest results of user application with SRF Gun II
Keywords: SRF Gun, photo injector, ELBE, CW mode
  • Poster
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Publ.-Id: 26708 - Permalink


Beam Transport Optimization for Applying an SRF Gun at the ELBE Center
Lu, P. N.; Arnold, A.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.;
An SRF gun at the ELBE center has been operated with a magnesium cathode. Electron beams were produced with a maximum bunch charge of 200 pC and an emittance of 7.7 μm. Simulations have been conducted with ASTRA and Elegant for applying the SRF gun to ELBE user experiments, including neutron beam generation, positron beam generation, THz radiation and Compton backscattering experiment. Beam transport has been optimized to solve the best beam performance for these user stations at the bunch charge of 200 pC. Simulation results indicate that the SRF gun is potential to benefit the high bunch charge applications at ELBE.
Keywords: SRF gun, photo injector, electron source, ELBE, simulation, electron accelerator
  • Poster
    IPAC 2017- 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
  • Open Access LogoContribution to proceedings
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
    Proceedings of the 8th International Particle Accelerator Conference, G: JACoW

Publ.-Id: 26707 - Permalink


Pre-production and quality assurance of the Mu2e calorimeter Silicon Photomultipliers
Cordelli, M.; Cervelli, F.; Diociaiuti, E.; Donati, S.; Donghia, R.; Di Falco, S.; Ferrari, A.; Giovannella, S.; Happacher, F.; Martini, M.; Morescalchi, L.; Miscetti, S.; Mueller, S.; Pedreschi, E.; Pezzullo, G.; Sarra, I.; Spinella, F.;
The Mu2e electromagnetic calorimeter has to provide precise information on energy, time and position for ~100 MeV electrons. It is composed of 1348 un-doped CsI crystals, each coupled to two large area Silicon Photomultipliers (SiPMs). A modular and custom SiPM layout consisting of a 3 x 2 array of 6 x 6 mm UV-extended monolithic SiPMs has been developed to fulfill the Mu2e calorimeter requirements and a pre-production of 150 prototypes has been procured by three international firms (Hamamatsu, SensL and Advansid). A detailed quality assurance process has been carried out on this first batch of photosensors: the breakdown voltage, the gain, the quenching time, the dark current and the Photon Detection Efficiency (PDE) have been determined for each monolithic cell of each SiPMs array. One sample for each vendor has been exposed to a neutron fluency up to ~8.5 x 10^11 1 MeV (Si) eq. n/cm2 and a linear increase of the dark current up to tens of mA has been observed. Others 5 samples for each vendor have undergone an accelerated aging in order to verify a Mean Time To Failure (MTTF) higher than ~10^6 h.
Keywords: Calorimeter Silicon Photomultiplier Quality assurance Radiation damage

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  • Secondary publication expected from 21.12.2019

Publ.-Id: 26706 - Permalink


The neutron transmission of natFe, 197Au and natW
Beyer, R.ORC; Junghans, A. R.; Schillebeeckx, P.; Sirakov, I.; Song, T.-Y.; Bemmerer, D.; Capote, R.; Ferrari, A.; Hartmann, A.; Hannaske, R.; Heyse, J.; Kim, H. I.; Kim, J. W.; Kögler, T.; Lee, C. W.; Lee, Y.-O.; Massarczyk, R.; Müller, S. E.; Reinhardt, T. P.; Röder, M.; Schmidt, K.; Schwengner, R.; Szücs, T.; Takacs, M. P.; Wagner, A.; Wagner, L.; Yang, S.-C.
Neutron total cross sections of natFe, 197Au and natW have been measured at the nELBE neutron time-of-flight facility in the energy range from 0.2 - 8 MeV with an uncertainty due to counting statistics of up to 2 % and a total uncertainty due to systematic effects of 1 %. The neutrons are produced with the superconducting electron accelerator ELBE using a liquid lead circuit as photo-neutron target. By periodical sample-in-sample-out measurements the transmission of the sample materials has been determined using a low-threshold plastic scintillation detector. The resulting effective total cross sections show good agreement with previously measured data that cover only part of the energy range available at nELBE. The results have also been compared to evaluated library files and recent calculations based on a dispersive coupled channel optical model potential.
Keywords: nELBE, fast neutrons, total cross section, transmission, iron, gold, tungsten

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Publ.-Id: 26704 - Permalink


Phage surface display derived short peptides for the development of new biosorbents for the recovery of valuable elements from primary and secondary sources
Matys, S.; Lederer, F.; Schönberger, N.; Braun, R.; Pollmann, K.;
In the course of evolution, nature has developed diverse strategies to avoid toxic effects of metals in the surrounding environment. Many organisms are able to bind metals to their surface via a variety of structurally diverse biomolecules carrying different functional groups. Because of the need for green and sustainable economic solutions, innovative biotechnological processes using biomolecules have become increasingly important.Biomolecules as sorbents are not only attractive for bioremediation, but also for the recovery of elements from recycling or mining. Currently, we are focusing on the development of new biosorbents based on short peptides for the selective recovery of valuable or toxic elements in complex process water streams such as Co, Ni, Ga or As and microparticles containing rare earth elements from fluorescent lamp powder. To select and identify these peptides we recently established Phage Surface Display Technology (PSD) as novel biotechnological platform in our group. Different adapted experimental setups for the peptide selection of each respective target material could be established and will be presented in detail. Specific and selectively metal binding peptides for particulate materials as well as for ionic species could be identified from commercially available phage libraries. These libraries contain a pool of genetically engineered phage of up to 10^9 different peptide motifs presented at their surface, which will be reduced in variability in an iterative biopanning process to capture the best binders. This contribution will give an insight into current research activities in our group focusing on PSD, introducing suitable spectroscopic techniques to characterize the metal-peptide complexes and discuss strategies for technical applications.
Keywords: peptides, metal binding, phage surface display, metal peptide complexes
  • Lecture (Conference)
    Jahrestagung der Vereinigung für Allgemeine und Angewandte Mikrobiologie, 15.-18.04.2018, Wolfsburg, Deutschland

Publ.-Id: 26703 - Permalink


In situ RBS and Raman spectroscopy study of nickel-catalyzed amorphous carbon graphitization
Janke, D.; Hulman, M.; Wenisch, R.; Munnik, F.; Gemming, S.; Rafaja, D.; Krause, M.;
Session: Thin films type of contribution: Poster
Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of the energy of the scattered ions for both layers respectively and proving the combination of the observed graphitization process with LE during annealing. The thickness of the synthesized crystalline graphitic layer is controlled by the finite carbon source – the deposited a-C film, which is a decisive advantage of this process compared to CVD. It is demonstrated that the structure and the crystallite size of the metallic catalyst layer has a strong influence on the crystallite size and the quality of the graphitic film.
LE is potentially interesting for industrial applications, as it allows the formation of polycrystalline thin films of G14E at much lower temperatures - than during thermal annealing without the metallic catalyst. Depending on the initial stacking sequence, the crystalline graphitic film can be deposited on a suitable device-ready substrate or transferred to another substrate after the dissolution of the transition metal catalyst.
  • Poster
    Iberian Vacuum Conference, RIVA-X, 04.-05.10.2017, Bilbao, Spanien

Publ.-Id: 26702 - Permalink


Development in the application of contactless inductive flow tomography
Ratajczak, M.ORC; Wondrak, T.ORC; Timmel, K.; Stefani, F.; Eckert, S.
The contactless inductive flow tomography (CIFT) allows for reconstructing the mean flow structure of liquid metals by measuring the flow induced perturbations of one or more applied magnetic fields. These measurements are utilized to infer the flow field by solving a linear inverse problem using an appropriate regularization technique. We will give an overview of the application of CIFT to three models of continuous casting available at the Helmholtz-Zentrum Dresden – Rossendorf. These include a 1:8 and a 1:2 model of a slab casting mould as well as a 1:3 model of a cylindrical mould.
Keywords: Slab casting, round billet casting, flow measurement, contactless inductive flow tomography, electromagnetic brake
  • Lecture (Conference)
    9th ECCC European Continuous Casting Conference – ECCC 2017, 29.06.2017, Wien, Österreich
  • Contribution to proceedings
    9th ECCC European Continuous Casting Conference – ECCC 2017, 29.06.2017, Wien, Österreich

Publ.-Id: 26701 - Permalink


Computation of the forward problem of the contactless inductive flow tomography
Jacobs, R. T.; Wondrak, T.; Stefani, F.;
The Contactless Inductive Flow Tomography is a procedure that enables the reconstruction of the global three-dimensional flow structure of an electrically conducting fluid by measuring the flow induced magnetic flux density outside the melt and by subsequently solving the associated linear inverse problem. The accurate computation of the forward problem which is essential for the inversion represents the focal point of this investigation. The tomography procedure is described by a system of coupled integral equations where the integrals contain a singularity when a source point coincides with a field point. The contribution of a singular point to the value of the surface and volume integrals in the system is considered in detail. A significant improvement of the accuracy is achieved by applying higher order elements and by attributing special attention to the singularities inherent in the integral equations. The treatment of the singularities described in this investigation is similar to the procedure applied in the boundary element method. It represents a novelty in the Contactless Inductive Flow Tomography.
Keywords: contactless inductive flow tomography, magnetohydrodynamics, integral equations, inverse problems
  • Lecture (Conference)
    International Symposium on Theoretical Electrical Engineering (ISTET), 16.-19.07.2017, Ilmenau, Deutschland

Publ.-Id: 26700 - Permalink


Geological mapping for mineral exploration using ground-based hyperspectral imaging in the thermal infrared
Lorenz, S.; Kirsch, M.; Gloaguen, R.; Zimmermann, R.; Jackisch, R.; Tusa, L.; Herrmann, E.; Unger, G.;
Geological mapping for mineral exploration using ground-based hyperspectral imaging in the thermal infrared
  • Lecture (Conference)
    Telops 13th Annual Workshop on Hyperspectral Imaging, 16.-17.10.2017, München, Deutschland

Publ.-Id: 26699 - Permalink


Numerical and experimental study on vorticity measurement in liquid metal using local Lorentz force velocimetry
Hernández, D.; Marangoni, R.; Schleichert, J.; Karcher, C.; Fröhlich, T.; Wondrak, T.;
Local Lorentz force velocimetry (local LFV) is a contactless velocity measurement technique for liquid metals. Due to the relative movement between an electrically conductive fluid and a static applied magnetic field, eddy currents and a flow-braking Lorentz force are generated inside the metal melt. This force is proportional to the flow rate or to the local velocity, depending on the volume subset of the flow spanned by the magnetic field. By using small-size magnets, a localized magnetic field distribution is achieved allowing a local velocity assessment in the region adjacent to the wall. In the present study, we describe a numerical model of our experiments at a continuous caster model where the working fluid is GaInSn in eutectic composition. Our main goal is to demonstrate that this electromagnetic technique can be applied to measure vorticity distributions, i.e. to resolve velocity gradients as well. Our results show that by using a cross-shaped magnet system, the magnitude of the torque perpendicular to the surface of the mold significantly increases improving its measurement in a liquid metal flow. According to our numerical model, this torque correlates with the vorticity of the velocity in this direction. Before validating our numerical predictions, an electromagnetic dry calibration of the measurement system composed of a multicomponent force and torque sensor and a cross-shaped magnet was done using a rotating disk made of aluminum. The sensor is able to measure simultaneously all three components of force and torque, respectively. This calibration step cannot be avoided and it is used for an accurate definition of the center of the magnet with respect to the sensor’s coordinate system for torque measurements. Finally, we present the results of the experiments at the mini-LIMMCAST facility showing a good agreement with the numerical model.
Keywords: liquid metals, magnetohydrodynamics, Lorentz force, flow measurement, multicomponent force/torque measurement

Publ.-Id: 26698 - Permalink


Numerical and experimental study of the effect of the induced electric potential in Lorentz force velocimetry
Hernández, D.; Böck, T.; Karcher, C.; Wondrak, T.;
Lorentz force velocimetry (LFV) is a contactless velocity measurement technique for electrically conducting fluids. When a liquid metal or a molten glass flows through an externally applied magnetic field, eddy currents and a flow-braking force are generated inside the liquid. This force is proportional to the velocity or flow rate of the fluid and, due to Newton's third law, a force of the same magnitude but in opposite direction acts on the source of the applied magnetic field which in our case are permanent magnets. According to Ohm's law for moving conductors at low magnetic Reynolds numbers, an electric potential is induced which ensures charge conservation. In this paper, we analyze the contribution of the induced electric potential to the total Lorentz force by considering two different scenarios: conducting walls of finite thickness and aspect ratio variation of the cross-section of the flow. In both the cases, the force component generated by the electric potential is always in the opposite direction to the total Lorentz force. This force component is sensitive to the electric boundary conditions of the flow of which insulating and perfectly conducting walls are the two limiting cases. In the latter case, the overall electric resistance of the system is minimized, resulting in a considerable increase in the measured Lorentz force. Additionally, this force originating from the electric potential also decays when the aspect ratio of the cross-section of the flow is changed. Hence, the sensitivity of the measurement technique is enhanced by either increasing wall conductivity or optimizing the aspect ratio of the cross-section of the flow.
Keywords: flow measurement, conducting walls, liquid metals, Lorentz force, magnetohydrodynamics

Publ.-Id: 26695 - Permalink


UHV Photocathode Plug Transfer Chain for the BERLinPro SRF-Photoinjector
Kühn, J.; Borninkhof, J.; Bürger, M.; Frahm, A.; Jankowiak, A.; Kamps, T.; Schmeißer, M. A. H.; Schuster, M.; Murcek, P.; Teichert, J.; Xiang, R.;
A dedicated particle free UHV photocathode plug transfer chain from the preparation system to the SRF-Photoinjector was set up and commissioned at HZB for the bERLinPro project. The plug handling system was designed in collaboration with the ELBE team at HZDR, where the same transfer chain is in commissioning phase. In the future the exchange of photocathodes between the laboratories offers the possibility to test different types of photocathodes in different SRF-photoinjectors.
Keywords: photocathode SRF-photoinjector, electron source, plug transfer
  • Poster
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
  • Open Access LogoContribution to proceedings
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
    Proceedings of the 8th International Particle Accelerator Conference, Genf: JACoW

Publ.-Id: 26694 - Permalink


Improvement of the Photoemission Efficiency of Magnesium Photocathodes
Xiang, R.; Arnold, A.; Lu, P. N.; Michel, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Patra, P.;
To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensity laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
Keywords: photocathode, photo-injector, electron source, magnesium, quantum efficiency
  • Poster
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
  • Open Access LogoContribution to proceedings
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
    Proceedings of the 8th International Particle Accelerator Conference, Genf: JACoW

Publ.-Id: 26693 - Permalink


Synchrotron X-ray diffraction on ensemble and individual GaAs/InxGa1-xAs core/shell nanowires at beamline P08 – PETRA III (DESY)
Bussone, G.; Grifone, R.; Balaghi, L.; Dimakis, E.;
Chemical composition, strain, structural polytypism and stacking faults in semiconductor nanostructures can be described quantitatively by high-resolution X-ray diffraction. It is a non-destructive technique that is suitable for the characterization of epitaxial nanostructures on their original substrates. The extracted information can be a valuable contribution to the understanding of the growth and strain relaxation mechanisms, which in turn are essential elements for tailoring the electronic properties in functional devices. Beamline P08 at PETRA III, Hamburg, offers a well-functioning high-resolution X-ray diffraction setup for the characterization of nanowire ensembles. Moreover, a newly developed configuration with a nano-focused beam is operational and can be used for the investigation of individual nanostructures.
The strengths of our setup have been tested in the characterization of GaAs/InxGa1-xAs core/shell nanowires. The nanowires were grown vertically on Si(111) substrates by molecular beam epitaxy (at HZDR). A set of samples with different shell thicknesses (5-80 nm) but the same In concentration (x≈0.20) and the same core diameter (25 nm) has been characterized. The measured in-plane and out-of-plane lattice constants as a function of the shell thickness suggest that the shell grew coherently around the core even for the thickest shell, the thickness of which is well beyond the critical value for planar In0.2Ga0.8As layers on GaAs. Furthermore, the tensile strain of the core due to the lattice mismatch with the shell increases with increasing the shell thickness up to 40nm, whereas the corresponding compressive strain of the shell decreases gradually to zero. All aforementioned results demonstrate the unique possibilities for strain engineering in core/shell nanowires.
Keywords: high-resolution X-ray diffraction, core/shell nanowires, structural characterization
  • Poster
    Nanowire Week 2017, 29.05.-02.06.2017, Lund, Sweden

Publ.-Id: 26692 - Permalink


Ground- and Boat-based hyperspectral imaging in Central-West Greenland
Zimmermann, R.;
Summary of the work done in 2016 and 2017 in Central-West Greenland and discussion of the results with the Karrat Zinc project team.
  • Lecture (others)
    Karrat Zinc - Project meeting 2018, 08.-09.01.2018, København, Danmark

Publ.-Id: 26691 - Permalink


Taking profit from molecular sensitivity on the macro scale: application of PET for investigating transport processes in barrier material
Kulenkampff, J.;
Positron emission tomography (PET) is an ideal method for tracing smallest amounts of radiolabelled substances propagating through widely impermeable material. It provides a means for experimental crossing of scales from molecular dimensions to the macroscale in particular in tight, heterogeneous, and complex materials. Characterization of transport properties of barrier material with this method benefits from its
- extremely high sensitivity („picomolar“),
- reasonable spatial resolution (around 1 mm),
- stability (up to years),
- direct comparability with and input for geochemical modelling.
These features are accomplished with high-resolution PET scanners, actually dedicated for biomedical research, in combination with a radionuclide laboratory for producing PET-tracers. Such a facility is available at the Leipzig research site of the HZDR, where we developed and applied the GeoPET-method since about 15 years. GeoPET provides a suite of quantitative tomograms of the concentration of the propagating PET-tracer during transport processes, i.e., reactive flow and diffusion. Subsequently, such flow field data are parameterized with the aid of time-resolved-image processing methods and inverse modelling.
In order to illustrate the high potential of the method, we present examples from measurements on barrier rocks (granite, salt rock, clay), that yield spatially resolved flow and diffusion parameters on macroscopic samples.
Keywords: PET nuclear waste disposal barrier rock transport experiments
  • Poster
    European Geosciences Union General Assembly 2018, 11.-13.04.2018, Wien, Österreich

Publ.-Id: 26690 - Permalink


Low-temperature intracenter relaxation times of shallow donors in germanium
Zhukavin, R. K.; Kovalevskii, K. A.; Sergeev, S. M.; Choporova, Y. Y.; Gerasimov, V. V.; Tsyplenkov, V. V.; Knyazev, B. A.; Abrosimov, N. V.; Pavlov, S. G.; Shastin, V. N.; Schneider, H.; Deßmann, N.; Shevchenko, O. A.; Vinokurov, N. A.; Kulipanov, G. N.; Hübers, H.-W.;
The relaxation times of localized states of antimony donors in unstrained and strained germanium uniaxially compressed along the [111] crystallographic direction are measured at cryogenic temperatures. The measurements are carried out in a single-wavelength pump–probe setup using radiation from the Novosibirsk free electron laser (NovoFEL). The relaxation times in unstrained crystals depend on the temperature and excitation photon energy. Measurements in strained crystals are carried out under stress bar, in which case the ground-state wavefunction is formed by states belonging to a single valley in the germanium conduction band. It is shown that the application of uniaxial strain leads to an increase in the relaxation time, which is explained by a decrease in the number of relaxation channels.
Keywords: free-electron laser, shallow impurities, germanium, terahertz pump-probe

Downloads:

Publ.-Id: 26689 - Permalink


Radiometric Correction and 3D Integration of Long-Range Ground-based Hyperspectral Imagery for Mineral Exploration of Vertical Outcrops
Lorenz, S.; Salehi, S.; Kirsch, M.; Zimmermann, R.; Unger, G.; Sørensen, E. V.; Gloaguen, R.;
Recently, ground-based hyperspectral imaging has come to the fore, supporting the arduous task of mapping near-vertical, difficult-to-access geological outcrops. The application of outcrop sensing within a range of one to several hundred meters, including geometric corrections and integration with accurate terrestrial laser scanning models, is already developing rapidly. However, there are only very few studies dealing with ground-based imaging of distant (i.e., in the range of several kilometres) targets such as mountain ridges, cliffs, and pit walls. In particular the extreme influence of atmospheric effects and topography-induced illumination differences have remained an unmet challenge on the spectral data. Those effects cannot be corrected by means of common correction tools for nadir satellite- or airborne data. Thus, this article presents an adapted workflow to overcome the challenges of long-range outcrop sensing, including straightforward atmospheric and topographic corrections. Using two datasets with different characteristics, we demonstrate the application of the workflow and highlight the importance of the presented corrections for a reliable geological interpretation. The achieved spectral mapping products are integrated with 3D photogrammetric data to create large-scale now-called “hyperclouds”, i.e. geometrically correct representations of the hyperspectral datacube. The presented workflow opens up a new range of application possibilities of hyperspectral imagery by significantly enlarging the scale of ground-based measurements.
Keywords: hyperspectral, topographic correction, atmospheric correction, radiometric correction, long-range, long-distance, Structure from Motion (SfM), photogrammetry, mineral mapping, Minimum Wavelength mapping, Maarmorilik, Riotinto
  • Open Access LogoRemote Sensing 10(2018)2, 176
    DOI: 10.3390/rs10020176
  • Lecture (Conference)
    Whispers Conference 9th Workshop on Hyperspectral Image and Signal Processing, 23.-26.09.2018, Amsterdam, Nederland

Publ.-Id: 26688 - Permalink


FLUKA simulations of the neutron flux in the Dresden Felsenkeller
Grieger, M.; Bemmerer, D.; Hensel, T.; Müller, S. E.; Zuber, K.;
The Dresden Felsenkeller ist a shallow-underground site featuring a rock overburden of 47 m which hosts a 5 MV Pelletron accelerator in tunnels VIII and IX. Using previous measurements in the lowbackground 𝛾-couting facility in tunnel IV as a benchmark, a FLUKA simulation has been developed to predict the neutron flux in tunnels VIII and IX. The simulation results provide insight into local neutron field inhomogenities caused by the measurement environment itself.
  • Lecture (Conference)
    DPG Frühjahrstagung, 26.02.-02.03.2018, Bochum, Deutschland

Publ.-Id: 26687 - Permalink


Long-Wave Hyperspectral Imaging For Lithological Mapping: A Case Study
Lorenz, S.; Kirsch, M.; Zimmermann, R.; Tusa, L.; Möckel, R.; Chamberland, M.; Gloaguen, R.;
Hyperspectral long-wave infrared imaging (LWIR HSI) adds a promising complement to visible, near infrared, and shortwave infrared (VNIR and SWIR) HSI data in the field of mineral mapping. It enables characterization of rock- forming minerals such as silicates and carbonates, which show no detectable or extremely weak features in VNIR and SWIR. In the last decades, there has been a steady increase of publications on satellite, aerial, and laboratory LWIR data. However, the application of LWIR HIS for ground- based, close-range remote sensing of vertical geological outcrops is sparsely researched and will be the focus of the current study. We present a workflow for acquisition, mosaicking, and radiometric correction of LWIR HSI data. We demonstrate the applicability of this workflow using a case study from a gravel quarry in Germany. Library spectra are used for spectral unmixing and mapping of the main lithological units, which are validated using sample X-ray diffraction (XRD) and thin section analysis as well as FTIR point spectrometer data.
Keywords: long wave infrared, thermal infrared, mineral mapping, hyperspectral
  • Contribution to proceedings
    International Geoscience and Remote Sensing Symposium, IGARSS 2018, 23.-27.07.2018, Valencia, España

Publ.-Id: 26686 - Permalink


FLUKA simulations of neutron transport in the Dresden Felsenkeller
Grieger, M.; Bemmerer, D.; Müller, S. E.; Szücs, T.; Zuber, K.;
A new underground ion accelerator with 5 MV acceleration potential is currently being readied for installation in the Dresden Felsenkeller. The Felsenkeller site consists of altogether nine mutually connected tunnels. It is shielded from cosmic radiation by a 45 m thick rock overburden, enabling uniquely sensitive experiments. In order to exclude any possible effect by the new accelerator in tunnel VIII on the existing low-background gamma-counting facility in tunnel IV, Monte Carlo simulations of neutron transport are being performed. A realistic neutron source field is developed, and the resulting additional neutron flux at the gamma-counting facility is modeled by FLUKA simulations. – Supported by NAVI (HGF VH-VI-417).
  • Lecture (Conference)
    DPG Frühjahrstagung, 23.-27.03.2015, Heidelberg, Deutschland

Publ.-Id: 26685 - Permalink


Strahlenschutzrechnungen für den Untertage-Ionenbeschleuniger am Standort Felsenkeller
Grieger, M.;
Geringe natürliche Hintergrundstrahlung ist für die Untersuchung von Brennprozessen in Sternen von hoher Bedeutung. Für mehrere Szenarien wurden detaillierte FLUKA durchgeführt um die zusätzliche Strahlungserzeugung durch den neuen 5 MV Pelletron Beschleuniger zu studieren - mit dem Ziel die benötigte Abschirmung zu optimieren.
  • Poster
    Lange Nacht der Wissenschaften Dresden, 16.06.2017, Dresden, Deutschland

Publ.-Id: 26684 - Permalink


Flue dust from the copper converter process - Recovery of Cu and In by solvent extraction
Rädecker, P.; Scharf, C.; Zürner, P.; Frisch, G.; Pieplow, G.; Lindner, D.; Koch, J.;
Flue dusts from copper metallurgy are resources for base metals such as copper, zinc, tin or lead. However, there is also a potential for the recovery of strategic elements like indium. At the moment flue dusts are recirculated within the copper process, but residues are available from historic produc-tion processes.
Hydrometallurgical processes seem to be a promising method to recover the base and strategic met-als from these fine-grained flue dusts. In preparation for further processing, the secondary material was characterized by mineral liberation analysis (MLA) and electron probe micro analysis (EPMA). An iron- and zinc-rich spinel phase (Zn,Fe,Mn)(Fe,Mn)2O4 was detected as the main phase (76 wt.-%) in the flue dust. The chemical composition of the flue dust was analysed by X-ray fluo-rescence spectroscopy (XRF spectroscopy). Leaching by sulfuric acid leads to precipitation of lead sulphate and calcium sulphate, which remain in the residue. The level of some impurities in the solu-tion can be controlled.
This work focuses on the selective recovery of copper and indium by solvent extraction from the leaching solution. Preliminary synthetic solutions of copper, iron(III), zinc, indium and mixtures of them were used for the investigations. The influence of pH value, concentration of acidic extract-ants, extraction time, and phase ratio on the extraction of copper, iron(III), zinc, and indium were studied. The results of the selective extraction of copper in the presence of iron(III) will be present-ed.
  • Contribution to proceedings
    European Metallurgical Conference EMC2017, 25.-28.06.2017, Leipzig, Deutschland
    Proceedings of the EMC2017, Clausthal-Zellerfeld: GDMB Verlag GmbH, 978-3-940276-74-2, 1121-1132
  • Lecture (Conference)
    European Metallurgical Conference EMC 2017, 25.-28.06.2017, Leipzig, Deustchland

Publ.-Id: 26682 - Permalink


The Natural Neutron Background Underground: Measurement Using Moderated ³He Counters in Felsenkeller
Grieger, M.;
A FLUKA simulation has been made to analyse the propagation of neutrons from the future Felsenkeller accelerator throughout the tunnel system of Felsenkeller. A neutron flux measurement with detectors loaned by the BELEN-collaboration has been performed to put the accelerator induced neutron flux into perspective with the natural neutron background. To deduce the neutron flux from the counting rates, FLUKA has been used to simulate the detector responses. The three measured locations in the existing γ-measurement facility in tunnel IV show different traits in their neutron spectra. Their cause has been analysed and the results had an impact on the construction planning of the new Felsenkeller laboratory in tunnels VIII and IX.
  • Poster
    Felsenkeller Workshop, 26.-28.06.2017, Dresden, Deutschland
  • Poster
    NDRA 2016, 29.06.-02.07.2016, Riva del Garda, Italia
  • Lecture (Conference)
    DPG Frühjahrstagung, 14.-18.03.2016, Darmstadt, Deutschland
  • Master thesis
    TU Dresden, 2016
    Mentor: PD Dr. Daniel Bemmerer

Publ.-Id: 26681 - Permalink


Fakultät für Werkstoffwissenschaft und Werkstofftechnologie an der TU Bergakademie Freiberg
Rädecker, P.;
Vorstellung der Studiengänge der Fakultät 5 der TU Bergakademie Freiberg.
  • Lecture (others)
    Studieninformationstag am BSZ Konrad Zuse, 14.11.2017, Hoyerswerda, Deutschland

Publ.-Id: 26680 - Permalink


Construction and setup of a KÜHNI column in pilot scale
Rädecker, P.; Scharf, C.; Zürner, P.; Frisch, G.; Pieplow, G.; Lindner, D.; Koch, J.;
Die Trennung von Kupfer und Eisen durch Solventextraktion ist in der Metallurgie, speziell bei der Verarbeitung von Lösungen aus dem Laugungsprozess oxidischer Kupfererze, ein vielfältig untersuchtes Verfahren. Es wurden die Reaktionsisotherme für Kupfer, die Zeit- und Konzentrationsabhängigkeiten sowie die Trennung von Kupfer und Eisen bestimmt. Die ermittelten optimalen Parameter werden angewendet, um den Prozess auf eine gerührte 32-mm KÜHNI-Extraktionskolonne (bereitgestellt durch SULZER Chemtech AG) zu übertragen. Die Einbauten sind aus korrosionsfestem Kunststoff und die wässrige Phase wird als disperse Phase gefahren.
Keywords: KÜHNI-Kolonne, Solventextraktion, Kupfer, LIX984
  • Poster
    Neue Verfahren und Materialien für Energie- und Umwelttechnik, 09.11.2017, Zwickau, Deutschland

Publ.-Id: 26679 - Permalink


FLUKA Radiation Safety Calculations for the Underground Accelerator Laboratory Felsenkeller/Dresden
Grieger, M.; Bemmerer, D.;
The study of stable stellar burning reactions in nuclear astrophysics requires the use of ion accelerators in a low-background setting underground. Currently, there is only one such laboratory, the LUNA 0.4 MV accelerator deep underground in Gran Sasso/Italy. Several higher-energy underground accelerators are under development worldwide, including a 5 MV Pelletron to be placed in the Felsenkeller underground laboratory in Dresden/Germany. The shielding requirements for underground accelerators, where the paramount concern is the background in neighbouring rare-event searches is reviewed. Detailed FLUKA simulations have been carried out to study several different operating scenarios of the new 5 MV Felsenkeller accelerator, with a focus on the side effects on an existing γ-counting facility in the same tunnel system. The results of the simulations and practical implications will be discussed.
  • Poster
    Felsenkeller Workshop, 26.-28.06.2017, Dresden, Deutschland

Publ.-Id: 26678 - Permalink


FLUKA shielding calculations for the underground accelerator laboratory Felsenkeller/Dresden
Grieger, M.;
The study of stable stellar burning reactions in nuclear astrophysics requires the use of ion accelerators in a low-background setting underground. Currently, there is only one such laboratory, the LUNA 0.4 MV accelerator deep underground in Gran Sasso/Italy. Several higher-energy underground accelerators are under development worldwide, including a 5 MV Pelletron to be placed in the Felsenkeller underground laboratory in Dresden/Germany. The shielding requirements for underground accelerators, where the paramount concern is the background in neighbouring rare-event searches is reviewed. Detailed FLUKA simulations have been carried out to study several different operating scenarios of the new 5 MV Felsenkeller accelerator, with a focus on the side effects on an existing γ-counting facility in the same tunnel system. The results of the simulations and practical implications will be discussed.
  • Poster
    SATIF-13, 10.-12.10.2016, Dresden, Deutschland

Publ.-Id: 26677 - Permalink


XPS spectra, electronic structure, and magnetic properties of RFe5Al7 intermetallics
Finkelstein, L. D.; Efremov, A. V.; Korotin, M. A.; Andreev, A. V.; Gorbunov, D. I.; Mushnikov, N. V.; Zhidkov, I. S.; Kikharenko, A. I.; Cholakh, S. O.; Kurmaev, E. Z.;
The results of X-ray photoelectron spectroscopy measurements (core levels and valence bands) of RFe5Al7 (R = Lu, Tm, Er, Ho, Dy, Tb, Gd) single crystals are presented in comparison with the results of bulk magnetization studies and electronic structure calculations. It is shown that the increase of the Curie temperature in RFe5Al7 from Tm to Gd is associated with an increase of the indirect R 4f - Fe 3d exchange interaction at the expense of the multiplicity 2S + 1 (statistical weight) in the ground state 2S + 1LJ of R3+ ions. The nonmonotonic behavior of the ferrimagnetic compensation temperature, Tcomp, as well as the values of the spontaneous magnetic moment, Ms, and formation energy, Eform, of the 4fn levels in R metals in a series from ErFe5Al7 to GdFe5Al7 are explained by the difference in the quantum numbers L, J and S of the ground state of R3+ ions, leading to a maximum value of Tcomp, Ms and Eform for the Dycontaining compound. The electronic structure of Gd/LuFe5Alsub>7 is calculated using the GGA+U approach, on the basis of which the physical mechanism and relative strength of the interatomic R-Fe and Al-Fe interactions are considered, and also the difference in the magnetic moments of iron atoms in different structural positions is explained.

Publ.-Id: 26676 - Permalink


Process Simulation of Si Dot Fabrication for SETs by Ion Beam Mixing and Phase Separation in Nanopillars
Prüfer, T.; Heinig, K. H.; Möller, W.; Xu, X.; Hlawacek, G.; Facsko, S.; Hübner, R.; Wolf, D.; Bischoff, L.; von Borany, J.;
The single electron transistor (SET) is considered a promising candidate to continue the revolution of information technology due to its very low energy consumption (~100 times less then common FET). The big challenge is the manufacturability of SETs working at room temperature (RT). This requires the fabrication of much smaller structures (<5nm) than present-day and even future (multi-E-beam or EUV) lithography can provide.

Here we propose an ion-beam-assisted, CMOS compatible fabrication process of SETs. To realize the controlled tunneling of single electrons we propose a nanopillar of a Si/SiO2/Si stack with a single Si quantum dot embedded in SiO2 and connected by tunnel junctions to Si electrodes, which makes the drain and source. For RT operation the quantum dot has to be smaller than 5nm and requires tunnel distances lower than 2nm. The size of this pillar needs to be in the range of 10-20nm.

In this presentation we show the simulation of a CMOS compatible process to fabricate this quantum dot by using ion beam mixing and self-assembly. Earlier projects proved already the reliability of dot formations using ion beam mixing technologies. Starting with a layerstack of Si/SiO2/Si, the ion beam irradiation by high energy Si+ ions causes mixing of the two Si/SiO2 interfaces what transforms the SiO2 layer into metastable SiOx (Figure 1). During subsequent heat treatment the mixed region of SiOx (<10nm2) separates into Si and SiO2, what leads to the formation of one single Si nanodot in the SiO2 layer (Figure 2). The irradiation simulations are done by TRIDYN and TRI3DYN program codes and the annealing by a self-developed Kinetic Monte Carlo program. We will present, how this process can be controlled using the ion beam irradiation values, geometrical sizes and the heat treatment parameters, so that it is yielding suitable conditions for application in hybrid SET-CMOS devices operating at RT.

This part of the work is being funded by the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 688072 (Project IONS4SET).
Keywords: SET, CMOS, Phase Separation, Ion Beam Mixing
  • Lecture (Conference)
    Electron, Ion, and Photon Beam Technology and Nanofabrication, 30.05.-02.06.2017, Orlando, USA

Publ.-Id: 26675 - Permalink


Determining antiferromagnetic domain patterns electrically
Kosub, T.; Hübner, R.; Appel, P.; Shields, B.; Maletinsky, P.; Kopte, M.; Schmidt, O. G.; Faßbender, J.; Makarov, D.;
Extrinsic effects on Cr2O3 thin films are shown. Also a statistical method to evaluate AF domain pattern in an electric way is demonstrated.
  • Poster
    AF Spintronics Workshop, 25.10.2017, Grenoble, France

Publ.-Id: 26672 - Permalink


Purely Antiferromagnetic Magnetoelectric RAM
Kosub, T.; Kopte, M.; Appel, P.; Shields, B.; Maletinsky, P.; Hübner, R.; Fassbender, J.; Schmidt, O. G.; Makarov, D.;
MERAM based on Cr2O3/Pt is presented
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.03.2017, Dresden, Germany
  • Invited lecture (Conferences)
    CIMTEC Ceramics Congress, 18.-22.06.2018, Perugia, Italien
  • Invited lecture (Conferences)
    MMM Pittsburgh, 13.-17.11.2017, Pittsburgh, USA
  • Invited lecture (Conferences)
    EMN Meeting, 16.-20.07.2018, Berlin, Deutschland

Publ.-Id: 26671 - Permalink


Purely Antiferromagnetic MERAM
Kosub, T.; Kopte, M.; Appel, P.; Shields, B.; Maletinsky, P.; Hübner, R.; Schmidt, O. G.; Faßbender, J.; Makarov, D.;
Magnetoelectric and purely antiferromagnetic RAM is shown based on Cr2O3/Pt
  • Lecture (Conference)
    IEEE Dublin, 24.04.2017, Dublin, Ireland

Publ.-Id: 26669 - Permalink


Unconventional spin dynamics in the honeycomb-lattice material α-RuCl3: High-field electron spin resonance studies
Ponomaryov, A. N.; Schulze, E.; Wosnitza, J.; Lampen-Kelley, P.; Banerjee, A.; Yan, J.-Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Kolezhuk, A. K.; Zvyagin, S. A.;
We present high-field electron spin resonance (ESR) studies of the honeycomb-lattice material α-RuCl3, a prime candidate to exhibit Kitaev physics. Two modes of antiferromagnetic resonance were detected in the zigzag ordered phase, with magnetic field applied in the ab plane. A very rich excitation spectrum was observed in the field-induced quantum paramagnetic phase. The obtained data are compared with the results of recent numerical calculations, strongly suggesting a very unconventional multiparticle character of the spin dynamics in α-RuCl3. The frequency-field diagram of the lowest-energy ESR mode is found consistent with the behavior of the field-induced energy gap, revealed by thermodynamic measurements.

Publ.-Id: 26668 - Permalink


Optimized Synthesis of the Bismuth Subiodides BimI4 (m = 4, 14, 16, 18) and the Electronic Properties of Bi14I4 and Bi18I4
Weiz, A.; Le Anh, M.; Kaiser, M.; Rasche, B.; Herrmannsdörfer, T.; Doert, T.; Ruck, M.;
We optimized the syntheses of α- and β-Bi4I4 and transferred the method to the very bismuth-rich iodides Bi14I4, Bi16I4, and Bi18I. Phase-pure, microcrystalline powders of BimI4 (m = 4, 14, 18) can now by synthesized on a multigram scale. Conditions for the growth of single crystals of Bi16I4 and Bi18I4 were determined. The redetermination of the crystal structure of Bi16I4 hints at a stacking disorder or the presence of 1͚[BimI4] ribbons with m = 14 and 18 among the dominant type along with m = 16. The electronic band structures for m = 14, 16, and 18 were calculated including spin-orbit coupling. They vary markedly with m and show numerous bands crossing the Fermi level, predicting a 3D-metallic behavior. Measurements of the electrical resistivity of a polycrystalline sample of Bi14I4 as well as polycrystalline and single-crystalline samples of Bi18I4 confirmed their metallic nature over the temperature range 300 K to 2 K. For BiI4, a positive and strictly linear magnetoresistance at 2 K in static magnetic fields up to 14 T was observed, which could indicate a topologically nontrivial electronic state.

Publ.-Id: 26667 - Permalink


Flat Bands, Indirect Gaps, and Unconventional Spin-Wave Behavior Induced by a Periodic Dzyaloshinskii-Moriya Interaction
Gallardo, R. A.ORC; Cortés-Ortuno, D.; Schneider, T.; Roldán-Molina, A.; Ma, F.; Lenz, K.ORC; Fangohr, H.; Lindner, J.; Landeros, P.ORC
Periodically patterned metamaterials are known for exhibiting wave properties similar to the ones observed in electronic band structures in crystal lattices. In particular, periodic ferromagnetic (FM) materials, also known as magnonic crystals (MCs), are characterized by the presence of bands and bandgaps (BGs) at tunable frequencies in their spin-wave (SW) spectrum. While those frequencies typically cover the GHz-range, no fundamental reason prevents one from extending this range towards THz-frequencies, a regime of high importance in communication technologies. Recently, the fabrication of magnets hosting Dzyaloshinskii-Moriya interactions (DMIs) has been pursued with high interest since properties such as the stabilization of chiral spin textures and nonreciprocal SW propagation originate from this antisymmetric exchange interaction. In this context, to further engineer the band structure of MCs, we propose the implementation of MCs with periodic DMIs, which can be obtained, for instance, patterning periodic arrays of heavy metals (HMs) on top of an ultrathin FM film. We demonstrate through theoretical calculations and micromagnetic simulations that such systems exhibit a unique evolution of the standing SWs around the BGs in areas of the FM film that are in contact with the HM wires. We also predict the emergence of at SW bands and indirect magnonic gaps, and we show that these effects depend on the strength of the DMI. This study opens further pathways towards engineered metamaterials for SW-based devices.
Keywords: chiral, magnonics, spin waves, DMI, Dzyaloshinskii-Moriya Interaction, magnonic crystals, metamaterials, micromagnetic simulations, ferromagnetic resonance, FMR

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Publ.-Id: 26666 - Permalink


Transglutaminase 2 as a target for functional tumour imaging: From substrates to inhibitors to radiotracers
Löser, R.;
The talk is covering the efforts of our group in the development of inhibitor-based radiotracers for the imaging of tumour-associated transglutaminase 2. After introducing the biological function of transglutaminase 2, the development of substrates for fluorimetric activity assays will be lined out. Major emphasis will be put on the synthesis, kinetic characterisation and in vitro pharmacokinetic profiling of acrylamide-based irreversible inhibitors. Finally, labelling of these compounds with fluorine-18 and initial results towards their radiopharmacological evaluation will be discussed.
  • Lecture (others)
    Pharmazeutisches Kolloquium, 03.11.2017, Bonn, Deutschland

Publ.-Id: 26665 - Permalink


Metallic Photocathodes for Superconducting RF Photo Guns
Teichert, J.; Xiang, R.;
Report on results and status of photocathode development and measurement in the EC project EuCARD2.
Keywords: photocathode, quantum efficiency, magnesium, lead, niobium
  • Lecture (Conference)
    EuCARD2 WP11 Annual Meeting, 14.-15.03.2017, Warsaw/Swierk, Poland

Publ.-Id: 26664 - Permalink


Structural characterization of (Sm,Tb)PO4 solid solutions and pressure-induced phase transitions
Heuser, J. M.; Palomares, R. I.; Bauer, J. D.; Lozano Rodriguez, M. J.; Cooper, J.; Lang, M.; Scheinost, A. C.; Schlenz, H.; Winkler, B.; Bosbach, D.; Neumeier, S.; Deissmann, G.;
Sm1-xTbxPO4 solid solutions were synthesized and extensively characterized by powder X-ray diffraction, vibrational spectroscopy, and X-ray absorption spectroscopy. At ambient conditions solid solutions up to x = 0.75 crystallize in the monazite structure, whereas TbPO4 is isostructural to xenotime. For x = 0.8 a mixture of both polymorphs was obtained. Moreover, a phase with anhydrite structure was observed coexisting with xenotime, which was formed due to mechanical stress. Selected solid solutions were investigated at pressures up to 40 GPa using in situ high pressure synchrotron X-ray diffraction and in situ high pressure Raman spectroscopy. SmPO4 and Sm0.5Tb0.5PO4 monazites are (meta)stable up to the highest pressures studied here. TbPO4 xenotime was found to transform into the monazite structure at a pressure of about 10 GPa. The transformation of Sm0.2Tb0.8PO4 xenotime into the monazite polymorph commences already at about 3 GPa. This study describes the reversibility of the pressure-induced (Sm,Tb)PO4 xenotime-monazite transformation.
Keywords: monazite, xenotime, anhydrite, solid solutions, phase transformation

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  • Secondary publication expected

Publ.-Id: 26663 - Permalink


MoS₂ quantum dots as an efficient catalyst material for oxygen evolution reaction
Mohanty, B.; Ghorbani-Asl, M.ORC; Kretschmer, S.ORC; Ghosh, A.; U. Guha, P.; Panda, S. K.; Jena, B.; Krasheninnikov, A. V.ORC; Jena, B. K.
The development of an active, earth-abundant and inexpensive catalyst for oxygen evolution reaction (OER) is highly desirable but remains a great challenge. Here, by combining experiments and first-principles calculations, we demonstrate that MoS₂ quantum dots (MSQDs) are an efficient material for OER. We use a simple route for the synthesis of MSQDs from a single precursor in aqueous medium avoiding the formation of unwanted carbon quantum dots (CQDs). The as-synthesized MSQDs exhibit higher OER activity with the lower Tafel slope as compared to that for the state-of-the-art catalyst IrO₂/C. The potential cycling of the MSQDs activates the surface and improves the OER catalytic properties. The density functional theory calculations reveal that MSQD vertices are reactive and the vacancies at the edges also promote the reaction, which indicates that the small flakes with defects at the edges are efficient for OER. The presence of CQDs affects the adsorption of reaction intermediates and dramatically suppresses the OER performance of the MSQDs. Our theoretical and experimental findings provide important insights into the synthesis process of MSQDs and their catalytic properties and suggest promising routes to tailoring the performance of the catalysts for OER applications.
Keywords: MoS₂, Quantum Dots, Electrocatalysis, Oxygen Evolution Reaction, First-Principles Calculations, Defects

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Publ.-Id: 26662 - Permalink


Si amorphization by focused ion beam milling: Point defect model with dynamic BCA simulation and experimental validation
Huang, J.; Loeffler, M.; Muehle, U.; Moeller, W.; Mulders, J. J. L.; Kwakman, L. F. T.; van Dorp, W. F.; Zschech, E.;
A Ga focused ion beam (FIB) is often used in transmission electron microscopy (TEM) analysis sample preparation. In case of a crystalline Si sample, an amorphous near-surface layer is formed by the FIB process. In order to optimize the FIB recipe by minimizing the amorphization, it is important to predict the amorphous layer thickness from simulation. Molecular Dynamics (MD) simulation has been used to describe the amorphization, however, it is limited by computational power for a realistic FIB process simulation. On the other hand, Binary Collision Approximation (BCA) simulation is able and has been used to simulate ion-solid interaction process at a realistic scale. In this study, a Point Defect Density approach is introduced to a dynamic BCA simulation, considering dynamic ion-solid interactions. We used this method to predict the c-Si amorphization caused by FIB milling on Si. To validate the method, dedicated TEM studies are performed. It shows that the amorphous layer thickness predicted by the numerical simulation is consistent with the experimental data. In summary, the thickness of the near-surface Si amorphization layer caused by FIB milling can be well predicted using the Point Defect Density approach within the dynamic BCA model.
Keywords: Amorphization, Beam plasma interactions, Computational chemistry, Defect density, Focused ion beams,High resolution transmission electron microscopy, Ion beams, IonsMilling (machining), Molecular dynamics, Point defects, Silicon, Surface defects, Transmission electron microscopy

Publ.-Id: 26661 - Permalink


Addendum: Ion beam irradiation of nanostructures: sputtering, dopant incorporation, and dynamic annealing
Holland-Moritz, H.; Johannes, A.; Möller, W.; Ronning, C.;
A previously published formalism to derive nanosphere sputtering yields is corrected and refined.
Keywords: Ion Irradiation, Nanostructures, Sputtering

Publ.-Id: 26660 - Permalink


Relative biological effectiveness in proton beam therapy – current knowledge and future challenges
Lühr, A.; von Neubeck, C.; Krause, M.; Troost, E. G. C.;
This review summarizes recent abstracts to international meetings and international peer-reviewed publications on the potential variation of the RBE and its possible side-effects, and compares these with past publication on photon beam irradiation. Moreover, recent literature on how to deal with potential RBE variations and the resulting uncertainty during treatment planning as well as solutions to correlate dose and LET distributions to subsequent (magnetic resonance) imaging changes are presented. Finally, the current status on RBE measured in vitro and in vivo is reviewed and input given on how to bridge the existing gap between lab and clinic.
Keywords: RBE, relative biological effectiveness, clinical side-effects, in vitro and in vivo models, MRI, dose recalculation

Publ.-Id: 26658 - Permalink


Prognostic Value of Head and Neck Tumor Proliferative Sphericity From 3’-Deoxy-3’-[18F] Fluorothymidine Positron Emission Tomography
Majdoub, M.; Hoeben, B.; Troost, E. G. C.; Oyen, W.; Kaanders, J.; Le Rest, C.; Visser, E.; Visvikis, D.; Hatt, M.;
Background: Enhanced proliferative activity in head and neck squamous cell carcinoma (HNSCC) adversely affects outcome after (chemo)radiotherapy. 3’-deoxy-3’-[18F] fluorothymidine (18F-FLT) positron emission tomography (PET) can be used for quantifying tumour proliferation and its changes during therapy. In this study, we investigated the complementary prognostic value of sphericity and standard metrics in 18F-FLT PET images before and during (chemo)radiotherapy regarding 4-year disease-free survival (DFS).
Methods: 48 HNSCC patients treated with radiotherapy (n=32) or chemoradiotherapy (n=16) with curative intent, underwent 18F-FLT PET-CT scans before and in the second week of treatment. Patients were followed for a median of 52 months. Primary tumours were delineated using the Fuzzy Locally Adaptive Bayesian algorithm. The proliferative volumes were further characterized by extracting SUV, volume and sphericity. Prognostic value for disease-free survival (DFS) of features was assessed using Kaplan-Meier survival analysis.
Results: In univariate analysis, the per-treatment sphericity (p=0.02, HR=4.2 [1.3– 13.9]) and SUVmean (p=0.03, HR=4.1 [1.2 – 14.2]) were prognostic factors, whereas none of the pre-treatment features were significant. Reduction in SUVmax (p=0.04, HR=4 [1.1 – 15.1]) was also a prognostic factor, but reduction of proliferative tumour volume did not reach statistical significance. The best stratification of patients for DFS was achieved with the combination of the two per-treatment features SUVmean and sphericity (p<0.001, HR=6.7 [1.8 – 25]).
Conclusion: High sphericity combined with low mean 18F-FLT SUV during treatment were associated with better DFS. These results suggest the potential prognostic value of advanced tumour proliferative volume characterization from 18F-FLT PET in HNSCC that may be further explored in larger cohorts.

Publ.-Id: 26657 - Permalink


Strain distribution in GaAs/InxGa1-xAs core/shell nanowires grown by molecular beam epitaxy on Si(111) substrates
Balaghi, L.; Hübner, R.; Bussone, G.; Grifone, R.; Hlawacek, G.; Grenzer, J.; Schneider, H.; Helm, M.; Dimakis, E.;
Strain distribution in GaAs/InxGa1-xAs core/shell nanowires grown by molecular beam epitaxy on Si(111) substrates
  • Lecture (Conference)
    Workshop on Surface and Interface Diffraction in Condensed Matter Physics and Chemistry (CMPC), 09.-10.03.2017, DESY, Hamburg, Germany

Publ.-Id: 26656 - Permalink


Strain distribution in highly mismatched GaAs/(In,Ga)As core/shell nanowires
Balaghi, L.; Hübner, R.; Bussone, G.; Grifone, R.; Ghorbani, M.; Krasheninnikov, A.; Hlawacek, G.; Grenzer, J.; Schneider, H.; Helm, M.; Dimakis, E.;
The core/shell nanowire (NW) geometry is suitable for the pseudomorphic growth of highly mismatched semiconductor heterostructures, where the shell thickness can exceed significantly the critical thickness in equivalent planar heterostructures. We have investigated the accommodation of misfit strain in self-catalyzed GaAs/(In,Ga)As core/shell NWs grown on Si (111) substrates by molecular beam epitaxy. The NWs have their axis along the [111] crystallographic direction, six {11 ̅0} sidewalls, and their crystal structure is predominantly zinc blende. For strain analysis, we used Raman scattering spectroscopy, transmission electron microscopy, X-ray diffraction and photoluminescence spectroscopy. Within a certain range of core/shell dimensions and shell composition, our findings reveal that the elastic energy in NWs without misfit dislocations can be confined exclusively inside the core, allowing for the shell to be strain-free. The experimental results are also compared with theoretical simulations of the strain (continuum elasticity theory) and phonon energy (density functional theory).
  • Lecture (Conference)
    DPG Spring Meeting 2017, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 26655 - Permalink


Nanoscale surface patterning by non-equilibrium self-assembly of ion-induced vacancies and ad-atoms
Facsko, S.; Ou, X.; Engler, M.; Erb, D.; Skeren, T.; Bradley, R. M.;
Various self-organized nanoscale surface patterns can be produced by low- and medium-energy ion beam irradiation [1], depending on the irradiation conditions. Hexagonally ordered dot or pit patterns, checkerboard patterns, as well as periodic ripple patterns oriented perpendicular or parallel to the ion beam direction are formed spontaneously during the continuous surface erosion by ion sputtering. On amorphous surfaces, the formation of these patterns results from an interplay of different roughening mechanisms, e.g. curvature dependent sputtering, ballistic mass redistribution, or altered surface stoichiometry on binary materials, and smoothing mechanisms, e.g. surface diffusion or surface viscous flow.

An additional surface instability arises above the recrystallization temperature of the material. In this case, ion induced bulk defects are dynamically annealed and amorphization is prevented. The diffusion of ion-induced vacancies and ad-atoms on the crystalline surface is now affected by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier to cross terrace steps. Vacancies and ad-atoms are trapped on terraces and can nucleate to form new extended pits or terraces, respectively [2].

For the mathematical description of the pattern formation and evolution in the reverse epitaxy regime, a continuum equation can be used which combines the ballistic effects of ion irradiation and effective diffusion currents due to the ES barrier on the crystalline surface. By comparison with experimental studies of pattern formation on Ge and GaAs surfaces at different angles and temperatures, we will show that the pattern evolution is determined by the surface instability due to the ES barrier, surface diffusion, and ballistic effects of ion irradiation.

[1] A. Keller and S. Facsko, Materials 3, 4811 (2010).
[2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).
Keywords: ion beam irradiation, surface patterning, reverse epitaxy
  • Invited lecture (Conferences)
    20th International Conference on Surface Modification of Materials by Ion Beams, 09.-14.07.2017, Lisbon, Portugal

Publ.-Id: 26654 - Permalink


Ion-induced patterning of Ge surfaces above the recrystallization temperature
Facsko, S.; Ou, X.; Engler, M.; Erb, D.; Skeren, T.; Bradley, R. M.;
Low- and medium-energy ion beam irradiation can lead to various self-organized nanoscale surface patterns depending on the irradiation conditions [1]. If the sample temperature is below the material recrystallization temperature, the ion bombardment results in amorphization of the surface. On such amorphous surfaces, the formation of nanoscale patterns is driven by the interplay of different ion beam induced roughening and smoothing mechanisms: curvature dependent sputtering, ballistic mass redistribution or altered surface stoichiometry (on binary materials) are roughening the surface, while surface diffusion or surface viscous flow are smoothing it.

An additional surface instability arises above the recrystallization temperature of the material, when the surface remains crystalline during ion irradiation. In this case, the diffusion of ion-induced vacancies and ad-atoms on the crystalline surface is affected by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier to cross terrace steps. Vacancies and ad-atoms are thereby trapped on terraces and nucleate to form new extended pits or islands, respectively [2]. In molecular beam epitaxy mounds with different facets are formed due to the ES barrier. In ion-induced reverse epitaxy the additionally diffusing vacancies lead to different morphologies, like inverse pyramid and checkerboard patterns.

However, on Ge (001) surfaces irradiated at incidence angles greater than 50° mound patterns are formed and for angles greater than 75° the pattern turns into ripples. This transition from checkerboard over mound to ripple patterns in the reverse epitaxy regime can be described by a continuum equation which combines the ballistic effects of ion irradiation and the effective diffusion currents due to the ES barrier on the crystalline surface.

[1] A. Keller and S. Facsko, Materials 3, 4811 (2010).
[2] X. Ou, A. Keller, M. Helm, J. Fassbender, and S. Facsko, Phys. Rev. Lett. 111, 016101 (2013).
Keywords: ion beam irradiation, surface patterning, reverse epitaxy
  • Lecture (Conference)
    Nanopatterning 2017, 26.-28.06.2017, Helsinki, Finland

Publ.-Id: 26652 - Permalink


REE by-product potential at Catalão I: a geometallurgical assessment
Birtel, S.; Pereira, L.; Silva, A. C.; Gutzmer, J.;
A geometallurgical study of the rare earth mineralogy and microfabric relations was undertaken at the Catalão I deposit, Chapadão mine, Goiás/Brazil. At Catalão I a carbonatite and its lateritic cap have been exploited for more than 40 years; being the world’s second largest niobium deposit and producer. The study was undertaken to assess the technical possibility and feasibility to recover rare earth minerals as a by-product of niobium production. For this purpose, nine samples were collected from different stages of the beneficiation process in the so-called Tailings Plant. Mineral Liberation Analyzer (MLA), X-ray powder diffraction and bulk rock chemistry were used to characterize these samples for their processing properties. The recovery of REE in each of the tailing streams was quantified by mass balance. The results were used to identify the most suitable approach to recover REE as a by-product – without placing constraints on niobium production.

Monazite is the dominant REE mineral in the feed to the Tailings Plant; this feed heralds from the exploitation of lateritic weathering residues. Quartz, FeTi-oxides and phosphate minerals are the main gangue minerals. The highest REE contents are reported in the final flotation tailings stream (1.75 wt.% TREO), with monazite-bearing particles in a size range suitable for further processing (10-120 µm size range). Yet, liberation of monazite in this particle size fraction is rather poor. By seeking an analogy to the Brown's Range deposit in Australia, a tentative economic assessment is attempted for REE production at Chapadão. For this purpose, parameters derived from MLA were used to model possible monazite recovery and concentrate grades. This assessment illustrates that a marketable REE concentrate may be obtained as a by-product at Chapadão even at current REE prices.
Keywords: REE production, by product, geometallurgy
  • Lecture (Conference)
    Resources for Future Generations, 16.-21.06.2018, Vancouver, Canada

Publ.-Id: 26651 - Permalink


Extremely lattice mismatched GaAs/InxGa1-xAs core/shell nanowires: coherent growth and strain distribution
Balaghi, L.; Hübner, R.; Bussone, G.; Grifone, R.; Grenzer, J.; Ghorbani Asl, M.; Krasheninnikov, A.; Hlawacek, G.; Schneider, H.; Helm, M.; Dimakis, E.;
Compound semiconductors are versatile materials due to the possibility to tailor their (opto)electronic properties by selecting their composition appropriately. When grown heteroepitaxially, though, this possibility is constrained by the lattice mismatch with the substrate. InxGa1-xAs is a good example because it can have, depending on x, a suitable direct optical band gap for optoelectronic applications in the infrared (e.g. telecommunication wavelengths) or high electron mobility for high-speed transistors. However, the practical choices of x are limited by the available substrates, typically GaAs for low x or InP for x≈0.53.
Nanowires are a promising alternative for the realization of epitaxial heterostructures with high lattice mismatch due to their unique geometry and high surface-to-volume ratio. In addition, the possibility of monolithic integration in Si-CMOS platforms adds to their technological significance. In this work, we have investigated the growth of free-standing GaAs/InxGa1-xAs core/shell nanowires on Si(111) substrates by molecular beam epitaxy and the accommodation of lattice mismatch therein. Specifically, we have concentrated on highly lattice mismatched heterostructures (x=0.20-0.80) and very thin cores (diameter < 25 nm).
Self-catalyzed growth of very thin GaAs core nanowires with a sufficiently low number density (to avoid beam shadowing during the shell growth) was possible on native-oxide/Si(111) substrates, after an in situ treatment of the latter with Ga droplets. This resulted in zinc blende nanowires with their axis along the [111] crystallographic direction and six {1-10} sidewalls. Subsequently, conformal overgrowth of the InxGa1-xAs shell was obtained only under kinetically limited growth conditions that suppressed mismatch-induced bending phenomena. The strain in the core and the shell was studied systematically as a function of the shell composition and thickness. To that end, we used Raman scattering spectroscopy, transmission electron microscopy and (synchrotron/lab source) X-ray diffraction, and compared the results with theoretical predictions based on continuum elasticity and density functional theories. All findings point to the existence of anisotropic tensile strain in the core that increases (as quantified by Raman measurements) with increasing the shell thickness, whereas the corresponding compressive strain in the shell decreases to zero. Our work demonstrates the opportunity to grow not only relaxed InxGa1-xAs shells with high structural quality (as adopted from the GaAs core) in a wide, if not the whole, compositional range, but also highly strained (tensile) GaAs cores with (opto)electronic properties that remain to be explored.
Keywords: core/shell nanowire, strained core, relaxed shell
  • Poster
    Nanowire Week 2017, 29.05.-02.06.2017, Lund, Sweden

Publ.-Id: 26650 - Permalink


Nanoscale surface patterning of crystalline semiconductor surfaces by broad ion beam irradiation
Facsko, S.; Ou, X.; Engler, M.; Erb, D.; Skeren, T.; Bradley, R. M.;
arious self-organized nanoscale surface patterns can be produced by low- and medium-energy ion beam irradiation [1], depending on the irradiation conditions. Hexagonally ordered dot or pit patterns, checkerboard patterns, as well as periodic ripple patterns oriented perpendicular or parallel to the ion beam direction are formed spontaneously during the continuous surface erosion by ion sputtering. On amorphous surfaces, the formation of these patterns results from an interplay of different roughening mechanisms, e.g. curvature dependent sputtering, ballistic mass redistribution, or altered surface stoichiometry on binary materials, and smoothing mechanisms, e.g. surface diffusion or surface viscous flow.
An additional surface instability arises above the recrystallization temperature of the material. In this case, ion induced bulk defects are dynamically annealed and amorphization is prevented. The diffusion of ion-induced vacancies and ad-atoms on the crystalline surface is now affected by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier to cross terrace steps. Vacancies and ad-atoms are trapped on terraces and can nucleate to form new extended pits or terraces, respectively [2].
For the description of the pattern formation and evolution in the reverse epitaxy regime, a continuum equation can be used which combines the ballistic effects of ion irradiation and effective diffusion currents due to the ES barrier on the crystalline surface. By comparison with experimental studies of pattern formation on Ge and GaAs surfaces at different angles and temperatures, we will show that the pattern evolution is determined by the combined action of surface instability due to the ES barrier, surface diffusion, and ballistic effects of ion irradiation.
[1] A. Keller and S. Facsko, Materials 3, 4811 (2010).
[2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).
Keywords: ion irradiation, surface patterning, reverse epitaxy
  • Invited lecture (Conferences)
    MRS Fall Meeting, 26.11.-1.12.2017, Boston, USA

Publ.-Id: 26648 - Permalink


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