Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Proton therapy of pediatric rhabdomyosarcoma: Same tumor control as photon therapy, with less adverse effects / Protonentherapie von Rhabdomyosarkompatienten im Kindesalter: Gleiche lokale Tumorkontrolle wie bei Photonentherapie mit weniger Nebenwirkungen

Gurtner, K.; Baumann, M.

there is no abstract

Publ.-Id: 23162

Comprehensive analysis of signal transduction in three-dimensional ECM-based tumor cell cultures.

Eke, I.; Hehlgans, S.; Zong, Y.; Cordes, N.

Analysis of signal transduction and protein phosphorylation is fundamental to understanding physiological and pathological cell behavior and identifying novel therapeutic targets. Despite the fact that the use of physiological three-dimensional cell culture assays is increasing, 3D proteomics and phosphoproteomics remain challenging due to difficulties with easy, robust and reproducible sample preparation. Here, we present an easy-to-perform, reliable and time-efficient method for the production of 3D cell lysates that does not compromise cell adhesion before cell lysis. The samples can be used for western blotting as well as phosphoproteome array technology. This technique will be of interest for researchers working in all fields of biology and drug development.

Keywords: 3D cell culture; extracellular matrix; phosphoproteomics; protein analysis; signaling

Publ.-Id: 23161

Cell-ECM interactions control DDR

Dickreuter, E.; Cordes, N.

there ist no abstract

Keywords: DNA repair; cell-ecm interactions; integrins

  • Open Access Logo Oncoscience 2(2015)8, 679-680

Publ.-Id: 23160

Hyperfractionated accelerated radiation therapy (HART) of 70.6 Gy with concurrent 5-FU/Mitomycin C is superior to HART of 77.6 Gy alone in locally advanced head and neck cancer: long-term results of the ARO 95-06 randomized phase III trial.

Budach, V.; Stromberger, C.; Poettgen, C.; Baumann, M.; Budach, W.; Grabenbauer, G.; Marnitz, S.; Olze, H.; Wernecke, K. D.; Ghadjar, P.


To report the long-term results of the ARO 95-06 randomized trial comparing hyperfractionated accelerated chemoradiation with mitomycin C/5-fluorouracil (C-HART) with hyperfractionated accelerated radiation therapy (HART) alone in locally advanced head and neck cancer.

The primary endpoint was locoregional control (LRC). Three hundred eighty-four patients with stage III (6%) and IV (94%) oropharyngeal (59.4%), hypopharyngeal (32.3%), and oral cavity (8.3%) cancer were randomly assigned to 30 Gy/2 Gy daily followed by twice-daily 1.4 Gy to a total of 70.6 Gy concurrently with mitomycin C/5-FU (C-HART) or 16 Gy/2 Gy daily followed by twice-daily 1.4 Gy to a total dose of 77.6 Gy alone (HART). Statistical analyses were done with the log-rank test and univariate and multivariate Cox regression analyses.

The median follow-up time was 8.7 years (95% confidence interval [CI]: 7.8-9.7 years). At 10 years, the LRC rates were 38.0% (C-HART) versus 26.0% (HART, P=.002). The cancer-specific survival and overall survival rates were 39% and 10% (C-HART) versus 30.0% and 9% (HART, P=.042 and P=.049), respectively. According to multivariate Cox regression analysis, the combined treatment was associated with improved LRC (hazard ratio [HR]: 0.6 [95% CI: 0.5-0.8; P=.002]). The association between combined treatment arm and increased LRC appeared to be limited to oropharyngeal cancer (P=.003) as compared with hypopharyngeal or oral cavity cancer (P=.264).

C-HART remains superior to HART in terms of LRC. However, this effect may be limited to oropharyngeal cancer patients.

Publ.-Id: 23159

Quantifying the Kelvin-Helmholtz instability in interstellar jets with radiation observable on Earth

Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Widera, R.; Bussmann, M.

We present a new diagnostic method to both identify the presence of the Kelvin-Helmholtz instability (KHI) in interstellar plasma jets and determine its growth rate by measuring the emitted radiation.

Based on the electron dynamics inside the KHI vortices, we derive the emitted radiation power and polarization and show their correlation to the magnetic field evolution, driving the instability. These correlations are verified against simulations of the relativistic KHI using the 3D3V particle-in-cell code PIConGPU. It determines the angularly resolved radiation spectra for billions of electrons using generally valid Liénard-Wiechert potentials. The simulation shows that the growth rate correlation between radiation power and magnetic field agrees over orders of magnitude for the entire linear phase of the KHI while the polarization signature allows a clear identification of this phase.

The method presented can resolve the question whether the KHI occurs in astro-physical particle jets and furthermore provides quantitative insides to the jet dynamics by analyzing the radiation observable on Earth.

Keywords: KHI; radiation; PIConGPU; spectra; polarization; interstellar jets

  • Lecture (Conference)
    DPG-Frühjahrstagung, 29.02.-04.03.2016, Hamburg, Deutschland

Publ.-Id: 23158

Expanding global access to radiotherapy

Atun, R.; Jaffray, D. A.; Barton, M. B.; Bray, F.; Baumann, M.; Vikram, B.; Hanna, T. P.; Knaul, F. M.; Lievens, Y.; Lui, T. Y.; Milosevic, M.; O'Sullivan, B.; Rodin, D. L.; Rosenblatt, E.; van Dyk, J.; Yap, M. L.; Zubizarreta, E.; Gospodarowicz, M.

Radiotherapy is a critical and inseparable component of comprehensive cancer treatment and care. For many of the most common cancers in low-income and middle-income countries, radiotherapy is essential for effective treatment. In high-income countries, radiotherapy is used in more than half of all cases of cancer to cure localised disease, palliate symptoms, and control disease in incurable cancers. Yet, in planning and building treatment capacity for cancer, radiotherapy is frequently the last resource to be considered. Consequently, worldwide access to radiotherapy is unacceptably low. We present a new body of evidence that quantifies the worldwide coverage of radiotherapy services by country. We show the shortfall in access to radiotherapy by country and globally for 2015-35 based on current and projected need, and show substantial health and economic benefits to investing in radiotherapy. The cost of scaling up radiotherapy in the nominal model in 2015-35 is US$26·6 billion in low-income countries, $62·6 billion in lower-middle-income countries, and $94·8 billion in upper-middle-income countries, which amounts to $184·0 billion across all low-income and middle-income countries. In the efficiency model the costs were lower: $14·1 billion in low-income, $33·3 billion in lower-middle-income, and $49·4 billion in upper-middle-income countries-a total of $96·8 billion. Scale-up of radiotherapy capacity in 2015-35 from current levels could lead to saving of 26·9 million life-years in low-income and middle-income countries over the lifetime of the patients who received treatment. The economic benefits of investment in radiotherapy are very substantial. Using the nominal cost model could produce a net benefit of $278·1 billion in 2015-35 ($265·2 million in low-income countries, $38·5 billion in lower-middle-income countries, and $239·3 billion in upper-middle-income countries). Investment in the efficiency model would produce in the same period an even greater total benefit of $365·4 billion ($12·8 billion in low-income countries, $67·7 billion in lower-middle-income countries, and $284·7 billion in upper-middle-income countries). The returns, by the human-capital approach, are projected to be less with the nominal cost model, amounting to $16·9 billion in 2015-35 (-$14·9 billion in low-income countries; -$18·7 billion in lower-middle-income countries, and $50·5 billion in upper-middle-income countries). The returns with the efficiency model were projected to be greater, however, amounting to $104·2 billion (-$2·4 billion in low-income countries, $10·7 billion in lower-middle-income countries, and $95·9 billion in upper-middle-income countries). Our results provide compelling evidence that investment in radiotherapy not only enables treatment of large numbers of cancer cases to save lives, but also brings positive economic benefits.

Publ.-Id: 23157

First beam characterization of SRF gun II at ELBE with a Cu photocathode

Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.

An improved SRF gun has been installed and commissioned at HZDR since 2014. This new gun replaces the first SRF gun at the superconducting linear accelerator ELBE which had been in operation since 2007. The new SRF gun II has an improved 3.5-cell niobium cavity and a superconducting solenoid inside the gun cryostat. The gun has been tested first with a Cu photocathode. Using the standard high repetition rate laser system, this allows low bunch charge beams of a few pC only. The beam parameters for these low charges have been measured, and the first beam has been guided into the ELBE accelerator. Since 2015 the photocathode transfer system is installed for future use of Cs2Te photocathodes with high quantum efficiency photocathodes.

Keywords: electron source; photo injector; photo cathode; superconducting RF

  • Invited lecture (Conferences)
    Workshop on Energy Recovery Linacs (ERL2015), 07.-12.06.2015, Stony Brook, USA
  • Open Access Logo Contribution to proceedings
    Workshop on Energy Recovery Linacs (ERL2015), 07.-12.06.2015, Stony Brook, USA
    Proceedings of the ERL 2015: Jacow

Publ.-Id: 23156

Synthetic radiation diagnostics in PIConGPU - integrating spectral detectors into particle-in-cell codes

Pausch, R.; Debus, A.; Burau, H.; Huebl, A.; Steiniger, K.; Widera, R.; Bussmann, M.

We present the in-situ far field radiation diagnostics in the particle-in-cell code PIConGPU. It was developed to close the gap between simulated plasma dynamics and radiation observed in laser plasma experiments. Its predictive capabilities, both qualitative and quantitative, have been tested against analytical models. Now, we apply this synthetic spectral diagnostics to investigate plasma dynamics in laser wakefield acceleration, laser foil irradiation and plasma instabilities.

Our method is based on the far field approximation of the Liénard-Wiechert potential and allows predicting both coherent and incoherent radiation spectrally from infrared to x-rays. Its capability to resolve the radiation polarization and to determine the temporal and spatial origin of the radiation enables us to correlate specific spectral signatures with characteristic dynamics in the plasma. Furthermore, its direct integration into the highly-scalable GPU framework of PIConGPU allows computing radiation spectra for thousands of frequencies, hundreds of detector positions and billions of particles efficiently.

In this talk we will demonstrate these capabilities on resent simulations of laser wakefield acceleration (LWFA) and high harmonics generation during target normal sheath acceleration (TNSA).

Keywords: PIConGPU; radiation; LWFA; TNSA; HHG; synthetic diagnostics; spectra

  • Lecture (Conference)
    DPG-Frühjahrstagung, 14.-18.03.2016, Darmstadt, Deutschland

Publ.-Id: 23155

Laser Cooling of Relativistic Ion Beams at FAIR. From ESR to SIS100 and HESR

Bussmann, M.; Löser, M.; Seltmann, M.; Siebold, M.; Schramm, U.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Sanchez-Alarcon, R.; Ullmann, J.; Lochmann, M.; Nörtershäuser, W.; Eidam, L.; Boine-Frankenheim, O.; Winters, D.; Kozhuharov, C.; Sanjari, S.; Litvinov, Y.; Giacomini, T.; Steck, M.; Dimopoulou, C.; Nolden, F.; Shevelko, S.; Stöhlker, T.; Spiller, P.; Wen, W.; Yang, J.; Zhang, D.; Ma, X.; Hannen, V.

We present recent results and future perspectives on laser cooling of relativistic storage beams

Keywords: laser cooling; storage ring; relativistic; ion beam

  • Invited lecture (Conferences)
    Kick-off Meeting für APPA-Verbundforschung, 14.-15.01.2016, Darmstadt, Deutschland

Publ.-Id: 23154

The Power of Performant Code Abstraction in Real World HPC Applications

Bussmann, M.; Eckert, C.; Huebl, A.; Jung, F.; Widera, R.; Zacharias, M.; Zenker, E.

Many-core architectures are going to stay for a while. Thus, scaling real world applications on HPC systems with thousands of nodes and hybrid architectures will be important to application developers. We present two real world applications, plasma simulations and high repetition rate data analysis, that strongly benefit from speed ups seen with accelerator hardware. From our viewpoint as users with real-world problems we discuss our path towards scalable, hardware-independent, performant application codes. Our focus is not to reinvent the wheel, but to make full use of the power of existing C++ codes by fully abstracting all parts of a code that require optimization, separating concepts used in the code from their optimized implementation. We do this by providing light-weight, single-purpose, zero-overhead interfaces to central code components. In the talk I will discuss our experiences with this approach, the reusable interfaces that have come out of this and the vision behind putting everything together.

Keywords: many core; picongpu; simulation; hpc

  • Invited lecture (Conferences)
    SPPEXA Annual Plenary Meeting, 25.-27.01.2016, Garching b. München, Deutschland

Publ.-Id: 23153

The fastest code in the field of laser-plasma physics

Döring, C

Ultra fast, scalable and free of charge – what began as a “youth conducts research” project, is today one of the most powerful programme codes for calculations in the field of astrophysics and plasma physics.

Keywords: picongpu; laser plasma; cancer therapy; acceleration

Publ.-Id: 23152

Laser focus Simulations explore how a tumor-killing laser’s high-energy fields can rip matter apart.

Bussmann, M.

Laser physicists are tantalizingly close to building a device that delivers highly focused beams of tumor-killing ionized particles and packing it in a compact unit that would fit in a doctor’s office. OncoRay, a research center in Dresden, Germany, is designing what would be the first prototype compact particle therapy units.

Keywords: cancer therapy; laser; simulation; picongpu

Publ.-Id: 23151

Hot electron currents in ultra-intense laser-solid interactions

Kluge, T.

The generation and propagation of strong currents of laser-accelerated hot electrons in solid density foils is of importance in many applications such as resistive heating, generation of resistive magnetic fields and ion acceleration. We present results from particle-in-cell simulations for the scaling of hot electron currents in solids and demonstrate the importance of a full description of the currents with respect to its spectral distribution and spatio-temporal structure. Taking them into account, we derive analytic scalings from first principle conservation laws that as an input to models for heating, magnetic field generation or ion acceleration prove to be consistent with the simulations in contrast to simple expressions such as j=\gamma n_c.

  • Lecture (Conference)
    2nd European Advanced Accelerator Concepts Workshop, 13.-19.09.2015, La Biodola, Italien

Publ.-Id: 23150

High Current LMIS for Ion Implanters and Single-ended Accelerators

Laufer, P.; Bock, D.; Pilz, W.; Bischoff, L.; Tajmar, M.

An ion source module based on high current Liquid Metal Ion Sources (LMIS) will be presented for optional use of mon - or polyatomic ion currents of metallic or semiconducting elements [1, 2, 3]. Total emitted ion currents in the order of 100 µA can be reached which are formed to a nearly parallel ion beam of 2 mm diameter using an asymmetric ion-optical Einzel lens. fractions are in the range of per mil up to a few percent dependent on the emitted elements. A mass separation system (Wien filter) selects the desired ions while a quadrupole is used for beam adjustment. Few-atomic cluster ions are of interest to be implanted for an effective surface modification [4]. High cluster ion currents enable the formation of different nanostructures or even smooth surfaces over an area in cm2-range. The LMIS preparation and the performance of the ion beam module at certain experiments will be presented and discussed.
[1] M. Tajmar, et al., Ultramicroscopy 111 (2010) 1
[2] D. Bock, et. al., DPG Conference Dresden (2014) DS 17.6
[3] P. Laufer, et al., DPG Conference Berlin (2015) DS 19.9
[4] L. Bischoff, et al., Nucl. Instr. and Meth. B 272 (2012) 198

Keywords: Liquid Metal Ion Source; cluster ions; mass separation

  • Lecture (Conference)
    DPG Frühjahrstagung, 07.-11.03.2016, Regensburg, Deutschland

Publ.-Id: 23149

Nanometer-scale characterization of laser-driven plasmas, compression, shocks and phase transitions, by coherent small angle x-ray scattering

Kluge, T.

Combining ultra-intense short-pulse and high-energy long-pulse lasers, with brilliant coherent hard X-ray FELs, such as the Helmholtz International Beamline for Extreme Fields (HIBEF) [1] under construction at the HED Instrument of European XFEL [2], or MEC at LCLS [3], holds the promise to revolutionize our understanding of many High Energy Density Physics phenomena. Examples include the relativistic electron generation, transport, and bulk plasma response [4], and ionization dynamics and heating [5] in relativistic laser-matter interactions, or the dynamics of laser-driven shocks, quasi-isentropic compression, and the kinetics of phase transitions at high pressure [3,6]. A particularly promising new technique is the use of coherent X-ray diffraction to characterize electron density correlations [4], and by resonant scattering to characterize the distribution of specific charge-state ions [5], either on the ultrafast time scale of the laser interaction, or associated with hydrodynamic motion. As well one can image slight density changes arising from phase transitions inside of shock-compressed high pressure matter. The feasibility of coherent diffraction techniques in laser-driven matter will be discussed. including recent results from demonstration experiments at MEC. Among other things, very sharp density changes from laser-driven compression are observed, having an effective step width of 10 nm or smaller. This compares to a resolution of several hundred
nm achieved previously [6] with phase contrast imaging.
[3] B. Nagler et al., J. Synchrotron Rad. 22, 520 (2015).
[4] T. Kluge et al, Phys. Plasmas 21, 033110 (2014).
[5] T. Kluge et al.,
[6] A. Schropp et al., Sci. Rep. 3, 1633 (2013).

Author T. Kluge on behalf of HIBEF User Consortium, for the Helmholtz International Beamline for Extreme Fields at the European XFEL.

  • Invited lecture (Conferences)
    57th Annual Meeting of the APS Division of Plasma Physics, 16.-20.11.2015, Savannah, GA, USA

Publ.-Id: 23148

Nanometer-scale characterization of laser-driven compression, shocks and phase transitions, by coherent x-ray diffraction

Kluge, T.; Rödel, C.; Rödel, M.; Pelka, A.; Mcbride, E.; Galtier, E.; Fletcher, L. B.; Lee, H. J.; Nagler, B.; Gutt, C.; Garcia, L.; Zeil, K.; Metzkes, J.; Obst, L.; Chung, H.-K.; Schropp, A.; Schroer, C.; Glenzer, S. H.; Schramm, U.; Cowan, T. E.

Concept of solid plasma diagnostics with Small Angle X-ray Scattering, experimental feasibility of SAXS at femtosecond and nanosecond laser driven solid material, and beyond electron-electron correlations: Resonant SAXS for ion distribution measurements

  • Poster
    European XFEL User Meeting, 27.-29.01.2016, Hamburg, Deutschland

Publ.-Id: 23147

Proton and electron Irradiation in oxynitrided gate 4H-SiC MOSFET: A recent open issue

Michel, P.; Florentin, M.; Alexandru, M.; Constant, A.; Monserrat, J.; Millan, J.; Godignon, P.

Long-term degradation of MOS devices has to be avoided in different harsh irradiated environments, especially for aerospace or military applications. In this paper, an overview of the irradiation experiments recently performed on 4H-SiC MOSFETs having an oxynitrided gate oxide is given, with a special focus on the threshold voltage and the effective channel mobility drifts. The general mechanisms taking place during irradiation and post-annealing treatments are described. Finally, new open issues recently observed by performing the temperature measurement on irradiated MOSFETs are introduced and discussed.

Keywords: Charge trapping; Electron; Irradiation; Mobility; Proton; SiC MOSFET; SiO2/SiC interface; Threshold voltage; Time bias stress instability

  • Contribution to proceedings
    European Conference on Silicon Carbide and Related Materials, ECSCRM 2014, Grenoble, France 21-25 September 2014, 21.-25.09.2014, Grenoble, France
    Materials Science Forum, Volume 821-823, 667-672
    DOI: 10.4028/

Publ.-Id: 23146

PET imaging for the monitoring of particle therapy: from GSI experience to new developments

Rohling, H.

History and current challenges of PET for particle therapy with the focus on GSI experiences.

  • Invited lecture (Conferences)
    Arbeitstreffen Kernphysik, 19.-26.02.2015, Schleching / Oberbayern, Deutschland

Publ.-Id: 23145

Aqueous chemistry of tetravalent cerium (Ce(IV)): Characterisation of polymer and cluster complexes formed via hydrolysis

Ikeda-Ohno, A.

Because of their high charge density, the aqueous chemistry of f-elements with lower valences (i.e. tri- and tetravalent) is predominantly controlled by strong hydrolysis producing a variety of hydroxide species. Interestingly enough, this strong hydrolysis often induces the intrinsic formation of polymer and nano-sized cluster complexes which are stable even in aqueous solutions. This talk will provide a recent overview of the hydrolysis-induced polymer/cluster formation of tetravalent f-elements, with a special focus on tetravalent cerium (Ce(IV)), primarily from the viewpoint of structural chemistry, as well as the associated characterisation techniques (e.g. X-ray absorption spectroscopy or X-ray scattering).

Keywords: Actinides; lanthanides; f-elements; tetravalent; aqueous chemistry; hydrolysis; characterisation; X-ray; synchrotron

  • Invited lecture (Conferences)
    Internal Scientific Seminar at Joint Research Centre - Institute for Transuranium Elements, 02.02.2016, JRC-ITU, Karlsruhe, Germany

Publ.-Id: 23144

Broadband(UV-VIS), Single-shot spectometer for fs electron bunches

Zarini, O.; Debus, A.; Köhler, A.; Couperus, J. P.; Seidel, W.; Irman, A.; Schramm, U.

Broadband(UV-VIS), Single-shot spectometer for fs electron bunches is presented.

Keywords: Broadband(UV-VIS); Single-shot spectometer; electron bunch

  • Lecture (Conference)
    The 4.annual meeting of the LAOLA collaboration, 23.-24.06.2015, Wismer, Deutschland

Publ.-Id: 23143

Broadband (UV - mid-IR) spectrometer for single-shot femtosecond electron bunch duration measurement

Zarini, O.; Debus, A.; Couperus, J. P.; Köhler, A.; Jochmann, A.; Seidel, W.; Irman, A.; Schramm, U.

Measurement of coherent transition radiation (CTR) spectra of ultrashort electron bunches from LWFA by using a high-resolution, broadband spectrometer for single-shot bunch duration measurements.

Keywords: broadband spectrometer; Single-shot bunch length measurement; coherent transition radiation; absolute calibration

  • Poster
    3rd ARD ST3 workshop, 15.-17.07.2015, Karlsruhe, Deutschland

Publ.-Id: 23142

Studies of a Proton Phase Beam Monitor for Range Verification in Proton Therapy

Werner, T.; Dreyer, A.; Golnik, C.; Hueso-Gonzalez, F.; Enghardt, W.; Straessner, A.; Petzoldt, J.; Roemer, K.; Pausch, G.; Kormoll, T.

A primary subject of the present research in particle therapy is to ensure the precise irradiation of the target volume. The prompt gamma timing (PGT) method provides one possibility for in vivo range verification during the irradiation of patients. Prompt gamma rays with high energies are emitted promptly due to nuclear reactions of protons with tissue. The arrival time of these gammas to the detector reflects the stopping process of the primary protons in tissue and are directly correlated to the range. Due to the time resolution of the detector and the proton bunch time spread, as well as drifts of the bunch phase with respect to the accelerator frequency, timing spectra are smeared out and compromise the accuracy of range information intended for future clinical applications. Nevertheless, counteracting this limitation and recovering range information from the PGT measured spectra, corrections using a phase beam monitor can be performed. A first prototype of phase beam monitor was tested at GSI Darmstadt, where measurements of the energy profile of the ion bunches were performed. At the ELBE accelerator Helmholtz-Zentrum Dresden-Rossendorf (HZDR), set up to provide bremsstrahlung photons in very short pulses, a constant fraction algorithm for the incoming digital signals was evaluated, which is for optimizing the time resolution. Studies of scattering experiments with different thin targets and detector positions are accomplished at Oncoray Dresden, where a clinical proton beam is available. These experiments allow a basic characterization of the proton bunch structure and the detected yield.

Keywords: Range Verification; Proton Therapy

  • Lecture (Conference)
    ANIMMA 2015, 20.-24.04.2015, Lisboa, Portugal

Publ.-Id: 23141

Measurements of the Time Spread of Proton Pencil Beams at a Clinical Therapy Facility

Petzoldt, J.; Roemer, K. E.; Kormoll, T.; Enghardt, W.; Fiedler, F.; Helmbrecht, S.; Hueso-González, F.; Golnik, C.; Rohling, H.; Werner, T.; Pausch, G.

In proton therapy, high dose conformality and the finite range of the projectiles are exploited to reduce the dosage to healthy tissue while increasing the dose inside the tumor volume compared to conventional radiotherapy. However, those benefits can be diminished by range uncertainties. An online range verification and in-vivo dosimetry is therefore highly desired.
The prompt gamma ray timing (PGT) method utilizes the detection time of high energetic photons emitted during treatment. The time distribution of the gamma rays contains essential information about the range of the protons. However, PGT spectra are smeared by the time spread of the proton bunches. Knowledge about this time spread would help to disentangle the PGT data and to give better input parameters to simulation procedures.
At the UniversitaetsProtonenTherapieDresden (Dresden, Germany), a dedicated experiment was realized to measure the time spread of a clinical proton pencil beam created by a Cyclone 230 fixed energy cyclotron from Ion Beam Applications. Two phoswich detectors each made out of plastic scintillator and BGO were placed under 90 degrees to detect coincident protons originating from elastic pp-scattering at a thin slice of PMMA. The time spread was measured for incident proton energies between 70 MeV and 225 MeV as well as for several positions of the momentum limiting slits of the energy selection system. Additionally, the absolute transmission of protons from point of extraction to beam exit was determined.
Summarizing, the measured data will help to create reasonable range verification procedures using the PGT method in clinical routine.

Keywords: proton therapy; prompt gamma ray timing

  • Lecture (Conference)
    2015 IEEE Nuclear Science Symposium & Medical Imaging Conference, 31.10.-07.11.2015, San Diego, USA

Publ.-Id: 23140

Pair production by Schwinger and Breit-Wheeler processes in bi-frequent fields

Otto, A.; Nousch, T.; Seipt, D.; Kämpfer, B.; Blaschke, D.; Panferov, A. D.; Smolyansky, S. A.; Titov, A. I.

Counter-propagating and suitably polarized light (laser) beams can provide conditions for pair production. Here, we consider in more detail the following two situations: (i) In the homogeneity regions of anti-nodes of linearly polarized ultra-high intensity laser beams, the Schwinger process is dynamically assisted by a second high-frequency field, e.g. by a XFEL beam. (ii) A high-energy probe photon beam colliding with a superposition of co-propagating intense laser and XFEL beams gives rise to the laser assisted Breit-Wheeler process. Prospects of such bi-frequent field constellations with respect to the feasibility of conversion of light into matter are discussed.

Publ.-Id: 23139

Determination of the carrier envelope phase for short, circularly polarized laser pulses

Titov, A. I.; Kämpfer, B.; Hosaka, A.; Nousch, T.; Seipt, D.

We analyze the impact of the carrier envelope phase on the differential cross sections of the Breit-Wheeler and the generalized Compton scattering in the interaction of a charged electron (positron) with an intensive ultra-short electromagnetic (laser) pulse. The differential cross sections as a function of the azimuthal angle of the outgoing electron have a clear bump structure, where the bump position coincides with the value of the carrier phase. This effect can be used for the carrier envelope phase determination.


Publ.-Id: 23138

Quantum processes in short and intensive electromagnetic fields

Titov, A. I.; Kämpfer, B.; Hosaka, A.; Takabe, H.

This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field or generalized Breit-Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is non-linear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields.

Publ.-Id: 23137

Strange hadron production at SIS energies: an update from HADES

Lorenz, M.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcy, G.; Kornakov, G.; Kotte, R.; Krasa, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim8, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.

We present and discuss recent experimental activities of the HADES collaboration on open and hidden strangeness production close or below the elementary NN threshold. Special emphasis is put on the feed-down from φ mesons to antikaons, the presence of the Ξ- excess in cold nuclear matter and the comparison of statistical model rates to elementary p+p data. The implications for the interpretation of heavy-ion data are discussed as well.

Publ.-Id: 23136

RF-bunching of relativistic 12 C 3+ ion beam for laser cooling experiment at the CSRe

Wang, H. B.; Wen, W. Q.; Ma, X.; Huang, Z. K.; Zhang, D. C.; Bussmann, M.; Winters, D. F. A.; Yuan, Y. J.; Zhu, X. L.; Zhao, D. M.; Mao, R. S.; Li, J.; Mao, L. J.; Yang, J. C.; Zhao, H. W.; Xu, H. S.; Xiao, G. Q.; Xia, J. W.

To prepare the upcoming experiment of laser cooling of relativistic 12 C 3+ ion beams at the experimental cooler storage ring (CSRe), a test experiment was performed with 12 C 3+ ion beams at an energy of 122 MeV/u on the CSRe, at the Institute of Modern Physics, Lanzhou, China. In this experiment, the main storage ring of CSRm was employed to accumulate and accelerate the ion beam which was injected into the CSRe for the experiments. The number of 12 C 3+ ions at the CSRe reached 5×10 8 for every injection, which satisfied the experimental requirement. To fulfil the laser cooling experiment, the 12 C 3+ ion beams were bunched by sinusoidal waveforms with fixed and sweeping frequencies, respectively. A resonant Schottky pick-up was employed to record the Schottky spectra of these ion beams. The test experimental results demonstrated that the RF-buncher and diagnostic systems at the CSRe worked well and the CSRe was very stable with 12 C 3+ ion beams, hereby the CSRe is suitable for laser cooling experiment.

Keywords: rf bunching; relativistic; ion beam; storage ring; dynamics

Publ.-Id: 23135

Broadband(UV- mid-IR) spectrometer for single-shot femtosecond electron bunch measurement first experiment @ HZDR

Zarini, O.; Debus, A.; Couperus, J. P.; Köhler, A.; Jochmann, A.; Irman, A.; Schramm, U.

Laser-wakefield accelerators (LWFA) feature electron bunch durations ranging from several fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top Xray light-sources and remains a big challenge due to the resolution limit of existing diagnostic techniques.
Measurement of broadband coherent and incoherent transition radiation produced when LWFA electron bunches pass a metal foil is a promising way to analyze longitudinal characteristics of these bunches.
Because of the limited reproducibility due to the nonlinear nature of the electron source this characterization requires single-shot capability.
Our ultra-broadband spectrometer combines the TR spectrum in UV/VIS (200-1000nm), NIR (0.9-1.7µm) and mid-IR (1.6-12µm). A high spectral sensitivity, dynamic bandwidth and spectral resolution are realized by three optimized dispersion and detection systems to a single-shot spectrometer.
A complete characterization and calibration of the spectrometer has been done with regard to wavelengths, relative spectral sensitivities and absolute photometric sensitivity, also taking into account for the light polarization.
Our spectrometer is able to characterize electron bunches with charges as low as 1 pC and resolve time-scales from 0.7 to 40 fs.

Keywords: Broadband spectrometer; coherent transition radiation; electron bunch duration; longitudinal profile; absolute calibration

  • Lecture (Conference)
    2nd European Advanced Accelerator Concepts Workshop (EAAC), 13.-19.09.2015, La Biodola, Isola d'Elba, Italien
  • Lecture (Conference)
    DoKDoK 2015, 10.-15.10.2015, Eisenach, Deutschland

Publ.-Id: 23134


Bechmann, N.; Kniess, T.; Pietzsch, J.; König, J.; Köckerling, M.

kein Abstract verfügbar

Keywords: crystal structure; d-chlorobutyl; phenyl ketone; hyrogen bonding

Publ.-Id: 23133

Dynamics of bulk electron heating and ionization in solid plasmas driven by ultra-short relativistic laser pulses

Huang, L. G.; Kluge, T.; Bussmann, M.; Chung, H. K.; Cowan, T. E.

We investigate the dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses. During laser-plasma interactions, the solid plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A part of the electrons with high kinetic energy travels through the solid plasma and transfers energy into bulk electrons, which results in bulk electron heating by return current. The bulk electron temperatures in the interest of bulk region agrees very well with the theory based on Ohmic heating mechanism by treating the return current correctly. The bulk electron heating is finally translated into bulk ionization dynamics, which is modeled by Thomas-Fermi ionization mechanism in our studies.

Keywords: bulk heating; ionization; high power laser; solid plasmas

  • Poster
    Novel Light Sources from Laser-Plasma Interactions, 20.-24.04.2015, Dresden, Germany

Publ.-Id: 23131

Scintillator-Based High-Throughput Fast Timing Spectroscopy for Real-Time Range Verification in Particle Therapy

Pausch, G.; Petzoldt, J.; Berthel, M.; Enghardt, W.; Fiedler, F.; Golnik, C.; Hueso-González, F.; Lentering, R.; Römer, K.; Ruhnau, K.; Stein, J.; Wolf, A.; Kormoll, T.

Range verification of particle beams in real time is considered a key for tapping the full potential of radiooncological particle therapies. The novel technique of prompt gamma-ray timing (PGT), recently proposed and explored in first proof-of-principle experiments, promises range assessment at reasonable expense but challenges detectors, electronics, and data acquisition. Energy-selected time distributions have to be measured at very high throughput rates to obtain the statistics necessary for range verification with single pencil beam spots. Clinically applicable systems should provide a time resolution of about 200 ps, to be obtained with large (about 2” diameter) scintillators, detector loads in the few-Mcps range, and data acquisition rates around 1 Mcps, if possible with compact and inexpensive systems. Such requirements can be met best with CeBr3 scintillators read out with conventional photomultiplier tubes, coupled to commercial but customized electronics featuring high-resolution pulse digitization and fast digital signal processing. The paper deduces design parameters from the constraints given by typical treatment conditions, and presents first results obtained with prototype detectors and electronics developed in accordance with the derived specifications.

Keywords: Hadron therapy; proton beams; range monitoring; gamma rays; gamma-ray spectroscopy; gamma ray detectors; fast timing; inorganic scintillators; cerium bromide; photomultipliers; digital signal processing; medical applications

  • IEEE Transactions on Nuclear Science 63(2016)2, 664-672
    DOI: 10.1109/TNS.2016.2527822
  • Lecture (Conference)
    13th International Conference on Scintillators and their Applications (SCINT), 07.-12.06.2015, Berkeley, USA

Publ.-Id: 23130

Review and present status of preparation of thin layer lead photocathodes for e- injectors of superconducting RF linacs

Lorkiewicz, J.; Nietubyc, R.; Sekutowicz, J.; Barlak, M.; Kostin, D.; Kosinska, A.; Barday, R.; Xiang, R.; Mirowski, R.; Grabowski, W.; Witkowski, J.

Results are reported on using evaporation and UHV arc lead deposition to create thin-layer superconducting Pb photocathodes on niobium wall of electron gun. Evaporated photocathodes were prepared and tested for the first time in 2014. A complete XFEL-type photo-injector with an evaporated photocathode underwent successful quality check at DESY - an acceptable working point was reached. On the other hand poor adhesion to niobium proved to be the most serious shortcoming of the evaporated Pb layers. UHV arc deposition seems to be much more promising in this context as it allows energetic coating. Filtered arc coating lead to creation of uniform, 2 μm thick lead layers with casual spherical extrusions which enhance locally electric field and leads to high dark current. Conditioning in electric field is needed to reduce the field emission effects from these layers to acceptably low value. Using non-filtered UHV lead deposition enabled fast coating up to a thickness above 10 μm. Pb films obtained in this way require further post-processing in pulsed plasma ion beams in a rod plasma injector. In order to reach a sufficiently planar film surface the pulsed heat flow through a lead layer on niobium was modeled and computed.

Keywords: Superconductors; Coating; Niobium; Plasmas; Electrons; Ion beams

  • Contribution to proceedings
    XXXVI Symposium on Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments, 25.05.2015, Wilga, Poland
    Proceedings of SPIE - The International Society for Optical Engineering, Wilga, 966233
    DOI: 10.1117/12.2205443

Publ.-Id: 23129

Optische Synchronisation am CW-Beschleuniger ELBE

Kuntzsch, M.

Moderne Experimente in der Kurzzeitphysik erfordern eine hochpräzise Synchronisation der beteiligten Strahlungsquellen, um dynamische Prozesse und atomare Strukturen aufzulösen. Die Komplexität und räumliche Ausdehnung einer linearbeschleuniger-getriebenen Strahlungsquelle wie ELBE verlangt nach neuen Konzepten, um die anspruchsvollen Anforderungen zu erfüllen.
Kernbestandteile der vorliegenden Arbeit sind die Konzeption, der Aufbau und die Inbetriebnahme eines gepulsten optischen Synchronisationssystems zur Verteilung eines Phasenreferenzsignals. Dieses System bildet eine wesentliche Grundvoraussetzung für wissenschaftliche Experimente mit einer Auflösung im Bereich von wenigen zehn Femtosekunden.
Darüber hinaus wurde der Prototyp eines Ankunftszeitmonitors am ELBE-Beschleuniger entwickelt und charakterisiert. Mit diesem Diagnoseelement wurden erstmals Messungen der Elektronenpulsankunftszeit mit einer Auflösung von wenigen Femtosekunden am ELBE-Strahl möglich. Die implementierte Datenanalyse erlaubt einzelpulsaufgelöste Messzyklen mit bisher unerreichter spektraler Bandbreite am kontinuierlichen (CW) Elektronenstrahl. Ferner wurde eine Methode zur Datenerfassung entwickelt, die unter Verwendung der Lockin-Technik besonders rauscharme Messungen hervorbringen kann.
Abschließend wurde der ELBE-Beschleuniger hinsichtlich Ankunftszeit und Energiestabilität umfassend untersucht. Dabei wurden die erweiterten Möglichkeiten, die ELBE als CW-Beschleuniger bietet, ausgeschöpft. Der Fokus lag besonders auf der spektralen Analyse der Störungen bei verschiedenen Kompressionszuständen der Elektronenpulse. Diese methodische Untersuchung wurde sowohl für den thermionischen Injektor als auch für die supraleitende Fotoelektronenquelle durchgeführt.
Die präsentierten Messergebnisse ermöglichen ein erweitertes Verständnis für die wirkenden Störmechanismen während der Elektronenpulspropagation und stellen den Ausgangspunkt für systematische Verbesserungen der Strahlqualität dar. Ein beschriebener Grundlagenversuch belegt, wie der ELBE-Elektronenstrahl in Zukunft aktiv stabilisiert werden kann, um die erforderliche Zeitauflösung zu erreichen. Intrinsische Strahlinstabilitäten können dadurch signifikant reduziert werden.

Experiments in ultra-fast science require a precise synchronization of the interacting light sources to resolve dynamic processes and structures on an atomic scale. The complexity and spatial dimension of an accelerator-driven radiation source need novel concepts to fulfill these requirements.
The main focus of this thesis lies on the conceptual design, realization and commissioning of a pulsed optical synchronization system to distribute phase-stable reference signals. It is a basic prerequisite for scientific experiments with a temporal resolution in the ten femtosecond range.
Based on the synchronization system a prototype of a bunch arrival time monitor has been developed and characterized at ELBE. It enables measurements with few femtosecond accuracy which were done for the first time at ELBE. The implemented data processing scheme allows single pulse resolution measurements at the continuous wave (CW) electron beam at an unprecedented spectral range. A second method based on lockin-amplifier technique has been developed which has the potential for very low noise measurements.
Finally comprehensive energy and timing jitter studies have been performed at ELBE using the unique properties offered by a CW-accelerator. The investigation was mainly focused on spectral analysis of noise components at varying compression states of the electron bunches. This examination has been done for both the thermionic injector and the superconducting photo electron source.
The results presented in this thesis created an extended comprehension of how noise sources are affecting the beam propagating along the accelerator and lead to further improvements of the beam quality. A proof of concept experiment demonstrates how a future feedback scheme can be used to reduce the residual jitter and to achieve the desired temporal resolution. Intrinsic beam instabilities can be lowered significantly by using this technique.

Keywords: Synchronisation; synchronization; ELBE; CW; continous wave; Beschleuniger; accelerator

  • Doctoral thesis
    TU Dresden, 2015
    Mentor: Prof. Dr. Thomas Cowan
    0156 Seiten

Publ.-Id: 23128

Positron Annihilation Study of Vacancy-Type Defects in Al Single Crystal Foils with the Tweed Structures Across the Surface

Kuznetsov, P.; Cizek, J.; Hruska, P.; Anwand, W.; Bordulev, Y.; Lider, A.; Laptev, R.; Mironov, Y.

The vacancy-type defects in the aluminum single crystal foils after a series of the cyclic tensions were studied using positron annihilation. Two components were identified in the positron lifetime spectra associated with the annihilation of free positrons and positrons trapped by dislocations. With increasing number of cycles the dislocation density firstly increases and reaches a maximum value at N = 10 000 cycles but then it gradually decreases and at N = 70 000 cycles falls down to the level typical for the virgin samples. The direct evidence on the formation of a two-phase system “defective near-surface layer/base Al crystal” in aluminum foils at cyclic tension was obtained using a positron beam with the variable energy.

Keywords: Al single crystal foils; tweed structures; cyclic tension; positron annihilation

Publ.-Id: 23127

TOPFLOW-Experiments on Direct Condensation and Bubble Entrainment

Seidel, T.; Lucas, D.; Beyer, M.

Direct Contact Condensation between steam and water as well as bubble entrainment below the water surface play an important role in different accident scenarios for light water reactors. One example is the emergency core cooling water injection into a two-phase mixture. It has to be considered for example to evaluate potential pressurized thermal shock phenomena.
This report documents experiments conducted in flat basin inside the TOPFLOW pressure chamber aiming on the generation of a database useful for CFD model development and validation. It comprises 3 different setups: condensation at a stratified flow of sub-cooled water, condensation at a sub-cooled water jet and a combination of both phenomena with steam bubble entrainment. The documentation includes all details on the experimental set up, on experimental conditions (experimental matrices), on the conduction of the experiments, on measuring techniques used and on data evaluation procedures. In addition, selected results are presented.

Keywords: experiment; CFD; two-phase flow; condensation; bubble entrainment

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-066 2016
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 23126

Nuclear and optical dual-labelled imaging agents: Design and challenges

Singh, G.; Gott, M.; Pietzsch, H.-J.; Stephan, H.

Over the last two decades, molecular imaging has been established as a valuable technology, aiming at visualization and characterization of biochemical processes on a molecular level in isolated cells, tissues and higher organisms. Within the wide scope of the various imaging techniques, dual-labelled modalities for nuclear (PET, SPECT) and near-infrared fluorescence (NIRF) imaging show promise owing to their comparable detection sensitivity. Novel materials offer excellent prospects for the development of new non-invasive strategies of early diagnosis and efficient monitoring of therapeutic treatments. In the field of cancer medicine, the combination of different imaging techniques such as PET/SPECT and OI for tracking down tumours and metastases, and subsequent image-guided surgery for tumour resection is particularly attractive.
This review focuses on the development of promising dual-labelled agents to be applied in bimodal nuclear/optical imaging, combining radionuclides and fluorescent dyes. The discussion encompasses modular ligands as well as nanoscale systems, including antibodies and their fragments.

  • Open Access Logo Nuklearmedizin 55(2016)2, 41-50


Publ.-Id: 23125

Correlation of electron and laser beam parameters on the spectral shape and bandwidth of laser-Thomson backscattering x-ray beams

Irman, A.; Jochmann, A.; Couperus, J. P.; Bussmann, M.; Debus, A.; Pausch, R.; Schlenvoigt, H.-P.; Kuntzsch, M.; Lehnert, U.; Wagner, A.; Seipt, D.; Sauerbrey, R.; Ledingham, K.; Stöhlker, T.; Thorn, D.; Trotsenko, S.; Cowan, T.; Schramm, U.

  • Lecture (Conference)
    Novel Light Sources from Laser-Plasma Interactions Workshop, 20.-24.04.2015, Dresden, Germany

Publ.-Id: 23124

Commissioning of LWFA and Laser-Thomson scattering experiments at HZDR

Irman, A.; Couperus, J. P.; Köhler, A.; Zarini, O.; Krämer, J.; Jochmann, A.; Lehnert, U.; Schramm, U.

Commissioning of laser wakefield acceleration and laser-Thomson backscattering experiments at HZDR is presented.

  • Invited lecture (Conferences)
    Laboratory for Laser- and beam-driven plasma Acceleration Workshop, 23.-24.06.2015, Wismar, Germany

Publ.-Id: 23123

Towards laser wakefield acceleration with external injection at HZDR: current status

Irman, A.

Progress towards laser wakefield acceleration with external injection is presented.

  • Invited lecture (Conferences)
    2nd EuCARD-2 Annual Meeting, 21.-24.04.2015, Barcelona, Spain

Publ.-Id: 23121

Laser cooling of relativistic heavy-ion beams for FAIR

Winters, D.; Beck, T.; Birkl, G.; Dimopoulou, C.; Hannen, V.; Rühl, T.; Lochmann, M.; Löser, M.; Ma, X.; Nolden, F.; Nörtershäuser, W.; Rein, B.; Sanchez, R.; Schramm, U.; Siebold, M.; Stiller, P.; Steck, M.; Stöhlker, T.; Ullmann, J.; Walther, T.; Wen, W.; Yang, J.; Zhang, D.; Bussmann, M.

Laser cooling is a powerful technique to reduce the longitudinal momentum spread of stored relativistic ion beams. Based on successful experiments at the experimental storage ring at GSI in Darmstadt, of which we show some important results in this paper, we present our plans for laser cooling of relativistic ion beams in the future heavy-ion synchrotron SIS100 at the Facility for Antiproton and Ion Research in Darmstadt.

Keywords: laser cooling; storage ring; heavy ion; relativistic; bion beam; sis100; fair

Publ.-Id: 23120

Progress of laser cooling of 12 C 3+ ions at the CSRe

Wang, H. B.; Ma, X.; Wen, W. Q.; Huang, Z. K.; Zhang, D. C.; Hai, B.; Zhu, X. L.; Zhao, D. M.; Li, J.; Ma, X. M.; Yan, T. L.; Mao, R. S.; Zhao, T. C.; Wu, J. X.; Yang, J. C.; Yuan, Y. J.; Xia, J. W.; Loeser, M.; Siebold, M.; Schramm, U.; Boine-Frankenheim, O.; Eidam, L.; Winters, D.; Birkl, G.; Rein, B.; Walther, T.; Bussmann, M.

We have performed a test run for laser cooling experiments with 12 C 3+ ion beams at an energy of 122 MeV/u at the CSRe with a pulsed laser. During this beamtime a lot of progress have been made. This was the first time we could successfully separate the 12 C 3+ ions and 16 O 4+ ions in the Schottky spectrum with the help of electron cooling. And our newly installed CPM detector worked well during the experiment. We tried to see effects from the interaction of the pulsed laser light with the stored 12 C 3+ ion beams, but no cooling effects could yet be observed.

Keywords: rf bunching; ion beam; storage ring; relativistic

Publ.-Id: 23119

Optimized small animal tumor model for the radiobiological characterization of low-energy laser accelerated protons

Beyreuther, E.; Brüchner, K.; Baumann, M.; Krause, M.; Leßmann, E.; Schmidt, M.; Pawelke, J.

The long-term aim of developing laser based particle acceleration (protons, heavier ions) towards clinical radiotherapy application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra-short and ultra-intensive particle beam pulses. Already obtained in vitro data reveal similar effects of laser accelerated versus conventional proton beams on clonogenic cell survival and DNA double-strand breaks. To proceed in the translational chain, these effects have to be further verified by radiobiological experiments in vivo. However, as the proton energies currently available by laser driven acceleration are still too low to penetrate standard tumor models on mouse legs, a small animal tumor model allowing the delivery of a homogeneous 3D dose distribution with low energy protons (<30 MeV) was established. In the present work, the optimization of this small animal model towards its applicability in a full scale radiobiological experiment at a laser driven proton accelerator will be shown.

  • Contribution to proceedings
    25. Symposium „Experimentelle Strahlentherapie und klinische Strahlenbiologie, 12.-13.02.2016, Dresden, Deutschland
    Proceeedings zum 25. Symposium „Experimentelle Strahlentherapie und klinische Strahlenbiologie
  • Poster
    25. Symposium „Experimentelle Strahlentherapie und klinische Strahlenbiologie, 12.-13.02.2016, Dresden, Deutschland

Publ.-Id: 23118

Radiosynthese von [F-18]NS10746- ein neuer Radioligand des α7-nikotinischen Acetylcholin-Rezeptors (α7-nAChR)

Fischer, S.; Sarasamkan, J.; Ludwig, F. A.; Peters, D.; Steinbach, J.; Brust, P.

Ziel: α7-nAChR-Liganden sind für das Neuroimaging degenerativer und inflammatorischer Prozesse von Interesse. Wir erarbeiteten die Herstellung von 4-[5-(2-[F-18]fluor-phenyl)-[1,3,4]oxadiazol-2-yl]-1,4-diaza-bicyclo[3.2.2]nonane ([F-18]NS10746), einem selektiven α7-nAChR-Radioliganden mit höherer Affinität als [F-18]NS10743.
Methodik: Entwicklung einer Synthese basierend auf der nukleophilen Substitution eines NO2-Präkursors durch [F-18]Fluorid und Übertragung auf eine automatisierte Herstellung.
Ergebnisse: Der NO2-Präkusor (NS14559, 2mg) wurde mit K[F-18]F-K222-K2CO3 in DMF bzw. DMSO (0,75; 1,0ml) bei erhöhten Temperaturen (145 bzw. 155°C) mit Ausbeuten von 12- 20% bzw. 15- 21% (n=7,7) umgesetzt. Parallel zum Zielprodukt wurde, vor allem in DMF, ein F-18- markiertes Folgeprodukt detektiert, welches durch Reaktion von 12-16 min in DMSO ausreichend minimiert werden konnte. Versuche zur Mikrowellen-unterstützten Reaktionsführung (n=15) erbrachten keine Erhöhung der Ausbeute. Die Isolierung von [F-18]NS10746 erfolgte mittels semi-präparativer Gradienten-HPLC (NH4OAcaq /MeCN an RP-Säule, z. B. ReproSil-Pur C18-AQ). Die Zielfraktion wurde auf eine Kartusche (SEP-PAK LIGHT C18) aufgetragen, mit EtOH eluiert und als sterile 10% EtOH/0,9% NaCl-Lösung formuliert. Die Herstellungsprozedur konnte auf das Synthesemodul TRACERlab FX N übertragen werden (RCY: 13-15%, 65- 70 min, n= 5). Das Produkt wurde mit hoher chemischer und radiochemische Reinheit (jeweils > 95%) sowie hoher spez. Aktivität (150- 320 GBq/μmol) erhalten.
Schlussfolgerungen: Es konnte ein Verfahren zur Herstellung von [F-18]NS10746 erarbeitet werden, wobei die Markierungsausbeute geringer war als die von [F-18]NS10743 (p-Fluor-Substitution; 40- 55%). Der Radioligand [F-18]NS10746 wird für laufende In-vitro- und In-vivo- Validierungen bereitgestellt.

  • Poster
    NuklearMedizin2016, 54. Jahrestagung der DGN, 20.-23.04.2016, Dresden, Deutschland

Publ.-Id: 23117

Development update of the PENELOPE laser system

Albach, D.; Siebold, M.; Loeser, M.; Roeser, F.; Schramm, U.

We present the development status of the PENELOPE laser system currently being under construction at the Helmholtz-Zentrum Dresden-Rossendorf. We will present experimental data for the first amplification stages as well as results for the stretcher-compressor setup. The focus will be set on the main amplifying stages designed to boost the output energy after compression above 150J.

Keywords: laser; diode pumping; DPSSL; amplification; Ytterbium; Penelope

  • Lecture (Conference)
    The 4th Advanced Lasers and Photon Sources, 22.-24.04.2015, Yokohama, Japan

Publ.-Id: 23116

Rectifying filamentary resistive switching in ion-exfoliated LiNbO3 thin films

Pan, X.; Shuai, Y.; Wu, C.; Luo, W.; Sun, X.; Zeng, H.; Zhou, S.; Böttger, R.; Ou, X.; Mikolajick, T.; Zhang, W.; Schmidt, H.

In this letter, we report the resistive switching properties of ion-exfoliated LiNbO3thin films. After annealing in Ar or in vacuum, electro-forming has been observed on the thin films, and the oxygen gas bubbles can be eliminated by tuning the annealing conditions in order to prevent the destruction of top electrodes. The thin films show rectifying filamentary resistive switching after forming, which is interpreted by a simplified model that the local filament does not penetrate throughout the LiNbO3thin film, resulting in asymmetric contact barriers at the two interfaces. The well controlled electro-forming step and the highly reproducible switching properties are attributed to the more homogeneous distribution of defects in single crystalline materials and the specific geometry of filament.

Keywords: gold; electrodes; mangetization reversal; single crystals; crystal structure

Publ.-Id: 23115

Synthesis, characterization and in vivo evaluation of radiolabeled anti-inflammatory dendritic polyglycerol: A structure – pharmacokinetics relationship

Pant, K.; Gröger, D.; Bergmann, R.; Pietzsch, J.; Stephan, H.; Haag, R.

Dendritic polyglycerols (dPGs) represent highly biocompatible scaffolds with narrow polydispersity, multivalency and ease of synthesis. The sulfate derivatives (dPGS) in particular, are potent candidates for, e.g., in the development of anti-inflammatory drugs due to their ability to inhibit the L & P selectins. In order to understand the physiological fate of these nano-objects, it is crucial to understand their behavior especially with respect to their absorption, distribution, metabolism and excretion (ADME). Herein, we present the in vivo distribution pattern of the neutral (dPG) as well as the therapeutically active polymer scaffolds using radiolabeling strategies. A novel 3H radiolabeling strategy has been established for these nano-objects which enable to study longer biochemical processes via radio imaging. In parallel, isothiocyanate and/or maleimide-functionalized TACN based CuII-chelating ligands were attached to dPGS derivatives with terminal amine or mercapto groups to allow for performing positron emission tomography (PET) studies using 64Cu (t1/2 = 12.5 h). 1H NMR, DLS and zeta potential measurements have been performed in order to achieve information about the number of chelators, size and charge of the dPGS derivatives. A new titration assay was established to determine the copper loading capacity and to obtain exact numbers of CuII chelators for the dPG derivatives. The 64Cu - conjugates are resistant to transchelation in vitro as well as in vivo. Independent studies in rats & mice show different routes of excretion for neutral dPGs in contrast to their polysulfated analogs. Furthermore, to derive an insight on the pharmacokinetics, effect of size, charge and surface groups have been studied in a range of scaffolds. Uptake mechanism in the cells, protein adsorption profile and cytotoxicity will be discussed. The results from these studies show that these polyglycerols are highly promising candidates for theranostic applications and drug targeting.

  • Poster
    PACIFICHEM 2016, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23114

Polyglycerol based Nanoparticles as an EGFR specific multimodal imaging agent

Pant, K.; Zarschler, K.; Neuber, C.; Pufe, J.; Pietzsch, J.; Spiccia, L.; Graham, B.; Stephan, H.

Purpose: Dendritic polyglycerols (dPG) are globular, highly biocompatible macromolecular scaffold which can be synthesized with a broad range of molecular weights and sizes for their desired application.[1] They show a size dependent blood circulation, no protein interactions and a very fast renal clearance.[2] The multiple peripheral groups gives them an advantage of multivalent interactions and thus, multiple moieties for e.g. for PET imaging or optical imaging can be integrated on a single probe for an enhanced resolution leading to an early diagnosis. The purpose of the work was to use these polyglycerols based nanoparticles to attach 64Cu based PET tracer, a dye to the scaffold. For a receptor mediated targeting, a camelid single domain antibody (SdAb) was used which is known to bind to the epidermal growth factor receptors (EGFR).
Experimental description: Dendritic polyglycerol with peripheral hydroxyl groups of a size of 10 kDa and a hydrodynamic volume of 6.5 ± 1.5 nm was prepared in a one pot reaction using ROMBP. Amine groups (9.5%) were introduced to the scaffold for further functionalization. For synthesizing the multimodal agent, the dPG was thiolated using iminothiolane. To the thiolated dPG in a one pot reaction, a maleimide containing DMPTACN based 64Cu chelator, a maleimide containing Cy3 (in vitro) or Cy7 (in vivo) dye were added in a slow monomer type addition. For the targeting unit, the SdAb was attached to the polyglycerol via a maleimide containing PEG linker.
Results: Purification was done using dialysis and several chromatographic techniques. The conjugates were then characterized by UV-Vis, radiometric titrations and microscopy experiments. Radiolabeling was done using 64CuCl2 at physiological conditions with a 99% RCY. Uptake and binding studies were done using A431 and FaDu cell lines using 64Cu labeled conjugate. Confocal scanning laser microscopy was performed for colocalization and internalization studies. In vivo PET and bio distribution studies were done on an A431-tumor mouse model. To confirm receptor specific binding, in vitro as well as in vivo blocking studies were done. The results show a pronounced affinity and active targeting of the dPG multimodal conjugate.
Conclusions: Soft matter nanoparticles based on dendritic polyglycerols are a promising platform for multimodal imaging and theranostics.

Acknowledgements: This study is part of a research initiative “Technologie und Medizin – Multimodale Bildgebung zur Aufklärung des in-vivo Verhaltens von polymeren Biomaterialien” of the Helmholtz-Portfoliothema. Financial support by the Helmholtz Virtual Institute NanoTracking (Agreement Number VH-VI-421) is gratefully acknowledged.

References :
[1] H.Frey, R. Haag; Rev.Mol. Biotechn. 2002, 90, 257-67.
[2] K. Pant, D. Gröger, R. Bergmann, J. Pietzsch, J. Steinbach, B. Graham, L. Spiccia, F. Berthon, B. Czarny, L. Devel, V. Dive, H. Stephan, R. Haag; Bioconjugate Chem. 2015, 26, 906-18

Keywords: Polyglycerols; PET imaging; Nanoparticles; Optical imaging; Antibodies; Multimodality

  • Poster
    2nd International Symposium on Nanoparticles/Nanomaterials and Applications (ISN2A 2016), 18.-21.01.2016, Lisbon, Portugal

Publ.-Id: 23113

Dendritic polyglycerols as dual modal imaging agent for EGF-receptor mediated tumor targeting

Pant, K.; Zarschler, K.; Bergmann, R.; Pietzsch, J.; Stephan, H.

Dendritic polymers represent a powerful, multifunctional nanoscalic platform for imaging and therapeutic applications. To overcome specific limitations in imaging, having multiple modalities on a single carrier molecule is preferred and also obviates the need to administer several compounds with different pharmacokinetics. In this regard, dendritic polyglycerols (dPG) are globular macromolecules with a narrow size distribution, high degree of branching and high end group functionalities. The great versatility of the dendritic polymers allows to fine tune physico-chemical parameters such as particle size, water solubility, surface charge, chemical functionalities, etc., that are relevant for the successful preparation of theranostic systems. Lower molecular weights (LMW) uncharged dPGs' (2-20kDa) however are known to show no/minimum uptake by the cells and thus represent ideal candidates for receptor mediated targeting. The present work here deals with the development of a dendritic polyglycerol derivative (10kDa,10% NH2 groups) as a dual modal agent for epidermal growth factor receptor (EGFR) specific tumor targeting. In this respect, in a one pot reaction, simultaneously maleimido- bearing fluorescent labels (dye) and macrocyclic chelators for 64Cu (PET tracer) were attached to thiol anchoring groups of the polymeric scaffold. For an EGFR specific targeting, a small camelid single-domain antibody (sdAb) representing a potential recognition agent for EGFR was attached via a PEG linker. Purification of the bioconjugates was achieved using size exclusion chromatography. 64Cu radiolabeling was done under ambient temperature and physiological pH. Binding and uptake studies were performed using A431 and FaDu cell lines using 64Cu-labeled bioconjugates. Confocal laser scanning microscopy was used to study the receptor mediated cellular uptake. The results obtained unveil the potential of dendritic polyglycerols as multimodal platforms for theranostic applications.

  • Lecture (Conference)
    PACIFICHEM 2015, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23112

Polyoxometalates with potent inhibitory activity at P2X receptors

Spanier, C.; Abdelrahman, A.; Tang, J.; Hausmann, R.; Kortz, U.; Schmalzin, G.; Stephan, H.; Wang, W.; Müller, C. E.

P2X receptors are trimeric ligand-gated ion channels activated by ATP and permeable for cations such as Na+, K+ and Ca2+. Seven different subunits exist, assembled as homo- or heterotrimers of various stoichiometry.1 Polyoxometalates (POMs) are polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+). This class of inorganic metal cluster compounds exhibits great variability with respect to shape, size, charge and composition.2 POMs bear several negative charges and in this respect resemble ATP, which binds to P2X receptors in its negatively charged state. We previously found that certain POMs can inhibit ATP-hydrolyzing ectonucleotidases.2-4 In the present study we investigated whether tungsten-containing POMs can interact with P2X receptors. A series of POMs was investigated for their ability to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X receptor subtypes. Several POMs were found to be highly potent inhibitors of P2X receptors exhibiting low nanomolar potency. PEGylation of POMs to increase their metabolic stability was tolerated by the receptors. Structure-activity relationships at P2X receptor subtypes differed from those observed for ecto¬nucleotidases. The majority of POMs were found to be non-cytotoxic at pharmacologically active concentrations.

(1) Coddou, C., Yan, Z., Obsil, T., Huidobro-Toro, J.P., Stojilkovic, S.S. Activation and regulation of purinergic P2X receptor channels. Pharmacol Rev, 2011, 63:641-683
(2) Stephan, H., Kubeil, M., Emmerling, F., Müller, C.E. Polyoxometalates as versatile enzyme inhibitors. Eur. J. Inorg. Chem., 2013, 1585-1594
(3) Müller, C.E., Iqbal, J., Baqi, Y., Zimmermann, H., Röllich, A., Stephan, H. Polyoxometalates – a new class of potent ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) inhibitors. Bioorg Med Chem Lett, 2006, 16:5943-5947
(4) Lee, S., Fiene, A., Li, W., Hanck, T., Brylev, K.A., Fedorov, V.E., Lecka, J., Haider, A., Pietzsch, H.J., Zimmermann, H., Sévigny, J., Kortz, U., Stephan, H., Müller, C.E. Polyoxometalates – potent and selective ecto-nucleotidase inhibitors. Biochem Pharmacol, 2015, 93:171-181

  • Poster
    Purinergic Signaling Symposium, 24.-28.01.2016, Vancouver, Canada

Publ.-Id: 23110

Target development for LWFA experiments at HZDR: Supersonic gas jets and plasma waveguides

Köhler, A.; Messmer, M.; Couperus, J. P.; Zarini, O.; Jochmann, A.; Wolterink, T.; Bastiaens, B.; Boller, K.; Irman, A.; Schramm, U.

Laser wakefield acceleration (LWFA) has emerged as a promising concept for the next generation of high energy electron accelerators. To attain highest possible particle energies in this acceleration scheme, high intensity laser beam must be maintained over distances much longer that the Rayleigh length. Therefore laser guiding is necessary to counteract the diffraction induced divergence of the beam.
For this, a plasma channel is created inside a capillary via the concept of slow capillary discharge and characterized using an interferometric method. It is shown that the plasma channel has a refractive index profile suitable for laser guiding. As the first step, the pressure range and the time window in which guiding can occur are determined by guidance of a He-Ne laser. With the gained knowledge, laser guiding capabilities of a pulse Ti:Sa laser are evaluated.
The results show a broad, easy to realize parameter window for pressure and time in which high laser transmission of above 75% are achieved.

  • Lecture (Conference)
    Laser Plasma Targetry Workshop, 20.-22.04.2015, Paris, Frankreich

Publ.-Id: 23109

Cyclam propionates: Stable copper(II) chelates for radiopharmaceutical application

Kubeil, M.; Zarschler, K.; Pietzsch, J.; Stephan, H.; Comba, P.

Due to their ability to form thermodynamically stable complexes with copper(II), ligands based on 1,4,8,11-tetraazacyclotetradecane (cyclam) are important for radiopharmaceutical applications [1]. Of particular interest are ligands that enable the simultaneous introduction of targeting molecules, e.g. peptides and/or fluorescence units, to construct effective radiopharmaceuticals for diagnostic and therapeutic purposes. In this context, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetracetic acid (TETA) is widely used for the development of copper-based target-specific radiopharmaceuticals.

Herein, we present a comprehensive study of CuII-cyclam complexes with propionic acid arms [2]. The influence of the number of pendant arms on structural features of CuII complexes formed as well as the radiopharmacologic properties of 64Cu-complexes are investigated and compared to CuII-TETA. Quite a few parameters (e.g. charge, configuration, lipophilicity) influence the kinetic inertness of the radiocopper complexes and thus may impair the pharmacokinetic properties.
All experiments point to a decrease of complex and in vivo stability with an increasing number of N-substituted propionic acid groups. Altogether, the cyclam mono- and dipropionic acids TE1P and trans-TE2P are ideally suited as chelating agents for 64CuII due to their fast complexation kinetics, their high kinetic inertness in the presence of superoxide dismutase (SOD) and human serum as well as their excellent biodistribution behavior. trans-TE2P has the possibility to use the non-chelating second propionate to introduce additional functions, such as solubilizing, fluorescent and targeting units.

1. T. J. Wadas, E. H. Wong, G. R. Weisman, C. J. Anderson, Chem. Rev. 110, 2858 (2010).
2. P. Comba, F. Emmerling, M. Jakob, W. Kraus, M. Kubeil, M. Morgen, J. Pietzsch, H. Stephan, Dalton Trans. 42, 6142 (2013).

  • Lecture (Conference)
    PACHIFICHEM 2015, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23108

High intensity laser guiding in plasma waveguides created by slow capillary discharge

Messmer, M.; Köhler, A.; Couperus, J. P.; Jochmann, A.; Irman, A.; Schramm, U.

Laser wakefield acceleration (LWFA) has emerged as a promising concept for the next generation of high energy electron accelerators. To attain highest possible particle energies in this acceleration scheme, high intensity laser beam must be maintained over distances much longer that the Rayleigh length. Therefore laser guiding is necessary to counteract the diffraction induced divergence of the beam.
For this, a plasma channel is created inside a capillary via the concept of slow capillary discharge and characterized using an interferometric method. It is shown that the plasma channel has a refractive index profile suitable for laser guiding. As the first step, the pressure range and the time window in which guiding can occur are determined by guidance of a He-Ne laser. With the gained knowledge, laser guiding capabilities of a pulse Ti:Sa laser are evaluated.
The results show a broad, easy to realize parameter window for pressure and time in which high laser transmission of above 75% are achieved.

  • Lecture (Conference)
    DPG-Frühjahrstagung Wuppertal, 09.-13.03.2015, Wuppertal, Deutschland

Publ.-Id: 23107

Investigation of betatron radiation from laser-wakefield accelerators

Köhler, A.; Couperus, J. P.; Zarini, O.; Debus, A.; Jochmann, A.; Irman, A.; Schramm, U.

Betatron radiation emitted by accelerated electrons in laser-wakefield accelerators can be used as a diagnostic tool to investigate electron dynamics during the acceleration process. Utilizing a 2D x-ray imaging spectroscopy technique we analyse the spectral dependence of the emitted Betatron pattern which basically represents certain electron beam parameters inside the plasma cavity.
The experiments are carried out with the Draco Ti:Sapphire laser system at HZDR.

Keywords: LWFA; Laser-wakefield acceleration; Betatron radiation

  • Lecture (Conference)
    DoKDoK, 11.-15.10.2015, Eisenach, Deutschland

Publ.-Id: 23106

Molecular imaging of cancer using bispidine ligands

Stephan, H.; Comba, P.

The development of multi-functional complexing agents for radiometal nuclides with a view of nuclear medical application represents a field of research that is intensively dealt with and has rapidly been developing. In this context, ligands that form highly stable metal complexes and additionally possess several different functional groups are of particular interest. This enables the simultaneous introduction of targeting, solubilizing and, for example, fluorescent units into the relevant metal complexes.

Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable coordination compounds, in particular with CuII. Due to the formation of thermodynamically and kinetically stable CuII complexes, bispidine ligands are well suited for in vivo application in cancer imaging (64CuII) and radiotherapy (64CuII, 67CuII). Since they are also relatively easy to functionalize with multiple modalities, they are ideal chelators for the design of novel multimodal imaging agents. The bispidine scaffold has a number of options for derivatization that permit the introduction of additional functions such as biological vectors and fluorescence molecules.

Here, the important properties of 64CuII-labeled bispidine complexes, e. g. stabilities, ligand exchange kinetics, serum stability, partition coefficients (n-octanol/water) and biodistribution data will be reported. It can be concluded that 64CuII-labeled bispidine derivatives with fluorescent tags have considerable potential for targeted dual imaging using positron emission tomography (PET) and fluorescence imaging.

  • Lecture (Conference)
    PACIFICHEM 2015, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23105

Radiopharmaceutical Evaluation of Peptide Nucleic Acid Bioconjugates as Complementary System for Tumor Targeting

Stephan, H.

The search for novel strategies for the diagnosis and therapy of cancer is currently a field of active research. A promising option is the use of a pretargeting approach with the non-natural DNA/RNA analogues Peptide Nucleic Acids (PNAs) as in vivo recognition units. Such a concept overcomes major drawbacks present when conventional monoclonal antibodies (mAbs) are employed as tumor-targeting agents by decoupling the delivery of a tumor-specific mAb from the delivery of the diagnostic or therapeutic radionuclide. In this multistep process an unlabeled, highly specific antibody-PNA conjugate has sufficient time to target the tumor before administering a small, fast-clearing radiolabeled complementary PNA that hybridizes with the antibody-PNA conjugate at the tumor side. Rapid clearance of the radiolabeled PNA significantly reduces radiation exposure of non-target tissues and its small size permits speedy delivery to the tumor, creating excellent tumor/non-tumor ratios. These appealing characteristics allow the rational application of the pretargeting approach for diagnosis as well as therapy of cancer.

Herein a successful tumor pretargeting approach using PNA radiolabeled with clinically available 99mTc and complementary PNA linked to the antibody Cetuximab in murine xenografts will be presented. Importantly, no metabolization and a high specific tumor accumulation of the PNA conjugate were observed.

The results presented in this work are promising in the view of further preclinical studies including internal radiotherapeutic treatment.

  • Lecture (Conference)
    PACIFICHEM 2015, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23104

Ultrasmall nanomaterials for biomedical applications

Stephan, H.

The field of nanomedicine offers excellent prospects for the development of new non-invasive strategies for the diagnosis and therapy of cancer [1, 2]. A major advantage of nanomaterials (NMs) is their potential to be used as non-invasive diagnostic tools. By combining multiple modalities into a single probe, higher sensitivity can be achieved, leading to deeper insights into different in vitro and in vivo processes. Despite the significant progress that has been made in the field of NMbased cancer diagnostics, our overall understanding of their pharmacokinetics (adsorption, uptake, distribution, metabolism and excretion) is still limited. Detailed investigations of the physicochemical properties and physiological behavior of NMs in biological environments are required to be better able to understand, predict and control their biodistribution.
We are aiming to develop targeted nanomaterials capable of imaging cancer by a combination of positron emission tomography PET, fluorescence optical imaging (OI) and/or magnetic resonance imaging (MRI) to provide a deeper understanding of their interactions in vitro and in in vivo. For the development of any functional nanomaterial to be applied for cancer imaging, it is of utmost importance to evade capture by the mononuclear phagocyte system and to circulate in vivo until reaching the target. It is now well recognized that ultrasmall (< 6 nm), renally-excretable particles are the most appropriate from this point of view, provided that they can be coupled to an efficient targeting vector.
Prototypes of highly-defined narrow-sized NPs have been developed and characterized, e.g. 2 - 4 nm-sized silicon NPs with reactive surface moieties, such as amino and carboxylic acid groups. Ultrasmall superparamagnetic iron oxide (USPIOs), upconverting nanophosphors and dendritic polyglycerol derivatives (< 10 nm) are also available as defined platforms. New assembly strategies, resulting in well-defined surface-attached radiochelates, fluorophores and targeting vectors will be presented. This includes in particular the engineering of zwitterionic-coated “stealth” NPs, leaving only targeting groups directly exposed to the surrounding biological milieu. [3] A small camelid single-domain antibody (sdAb) was chosen as targeting vector of the epidermal growth factor receptor (EGFR) which is overexpressed in a variety of solid tumors. [4]

[1] Ferrari, M. Cancer nanotechnology: opportunities and challenges. Nat. Rev. Cancer 5 (2005) 161-71.
[2] Kim, B. Y.; Rutka, J. T.; Chan, W. C. Nanomedicine. N. Engl. J. Med. 363 (2010) 2434-43.
[3] Pombo García, K.; Zarschler, K.; Barbaro, L.; Barreto, J. A.; O'Malley, W.; Spiccia, L.; Stephan, H.; Graham, B. Zwitterionic-coated "stealth" nanoparticles for biomedical applications: recent advances in countering
biomolecular corona formation and uptake by the mononuclear phagocyte system. Small 10 (2014) 2516-2529.
[4] Zarschler, K.; Prapainop, K.; Mahon, E.; Rocks, L.; Kelly, P. M.; Bramini, M.; Stephan, H.; Dawson, K. A. Diagnostic nanoparticle targeting of the EGF-receptor in complex biological conditions using single-domain antibodies.
Nanoscale 6 (2014) 6046-6056.

  • Invited lecture (Conferences)
    1st International Caparica Christmas Congress on Translational Chemistry, 07.-10.12.2015, Lisbon, Portugal

Publ.-Id: 23103

The influence of microorganisms on the immobilization of radionuclide in subsurface crystalline rock environments

Krawczyk-Bärsch, E.

In the underground rock characterization facility tunnel ONKALO in Finland, and in the Äspö Hard Rock Laboratory (HRL) in Sweden massive 5–10-mm thick biofilms were observed attached to tunnel walls where groundwater was seeping from bedrock fractures. The main goal of the study was to evaluate the relevance of microbial processes for the immobilization of radionuclides in a deep crystalline repository for high-level radioactive waste. In laboratory experiments the effect of uranium on biofilms was studied on site in the ONKALO tunnel by adding uranium to the fracture water in a self constructed flow cell by using detached biofilm samples. Biofilm specimens collected for transmission electron microscopy studies indicated that uranium in the biofilm was immobilized intracellularly in microorganisms as needle-shaped uranyl phosphate minerals, similar to meta-Autunite (Ca[UO2]2[PO4]2•10-12H2O).
Gallionella ferruginea dominated biofilms associated with bacteriogenic iron oxides (BIOS) from the Äspö HRL were used for laboratory experiments, in which uranium and neptunium, respectively, were added to the BIOS biofilms. The biofilms were submerged in Äspö groundwater in a flow cell under aerobic conditions. The results showed a substantial decrease of uranium and neptunium in the groundwater of approximately 85% and 95%, respectively. Thermodynamic calculation of the theoretical predominant fields of uranium species showed that the formation of an aqueous uranium carbonate species Ca2UO2(CO3)3 was predicted due to the high concentration of carbonate in the groundwater. Under the given pH conditions the uptake of uranium and neptunium in the BIOS biofilm depends predominantly on the high amount of ferrihydrite, which precipitated onto the ferrous iron-oxidizing and stalk-forming bacterium Gallionella ferruginea. Consequently, the combination of the biological material and iron oxides created an abundant surface area for bioaccumulation and adsorption of radionuclides.

Keywords: biofilm; uranium; neptunium; nuclear waste repository

  • Invited lecture (Conferences)
    Teaching module: Interactions of heavy metals with bacteria for bioremediation purposes., 16.06.2015, Granada, Spain

Publ.-Id: 23102

Topological Spin Textures as Emitters for Multidimensional Spin Wave Modes

Sluka, V.; Weigand, M.; Kakay, A.; Schultheiss, K.; Erbe, A.; Tyberkevych, V.; Slavin, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.; Wintz, S.

The investigation of propagating spin waves is a key topic of magnetism research. For the excitation of spin waves with short wavelengths, it was typically necessary to either use transducers with sizes on the order of the desired wavelengths (striplines or point-contacts) or to generate those spin waves parametrically by a double-frequency spa- tially uniform microwave signal. Only recently, a novel mechanism for the local excitation of spin waves has been discovered, which over- comes the wavelength limit given by the minimum patterning size. This method utilizes the translation of natural topological defects, namely the gyration of spin vortex cores. In the present contribution we will show that in a vortex pair system with uniaxial magnetic anisotropy, spin waves of even different symmetries and dimensionalities can be excited.

Keywords: spin wave; multilayers; dipole-exchange; non-reciprocity

  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion kondensierte Materie, 06.-11.03.2016, Regensburg, Deutschland

Publ.-Id: 23101

Relaxation of excited surface states of thin Ge-implanted silica films probed by OSEE spectroscopy

Zatsepin, A. F.; Buntov, E. A.; Mikhailovich, A. P.; Slesarev, A. I.; Schmidt, B.; von Czarnowski, A.; Fitting, H. J.

As an example of thin silica films, 30 nm SiO2-Si heterostructures implanted with Ge+ ions (10(16) cm(-2) fluence) and rapid thermally annealed (RTA) at 950 degrees C are studied by means of optically stimulated electron emission (OSEE) in the spectral region of optical transparency for bulk silica. Quartz glass samples were used as references. Experimental data revealed a strong dependence between electron emission spectral features and RTA annealing time. The spectral contributions of both surface band tail states and interband transitions were clearly distinguished. The application of emission Urbach rule as well as Kane and Passler equations allowed to analyze the OSEE spectra at different optical excitation energy ranges and to retrieve the important microstructural and energy parameters. The observed correlations between parameter values of Urbach- and Kane-related models suggest the implantation-induced conversion of both the vibrational subsystem and energy band of surface and interface electronic states.

Keywords: Surface states; Relaxation; Thin films; Ion implantation; Electron emission; Energy structure

Publ.-Id: 23100

Novel implementation of memristive systems for data encryption and obfuscation

Du, N.; Manjunath, N.; Shuai, Y.; Buerger, D.; Skorupa, I.; Schueffny, R.; Mayr, C.; Basov, D.; Di Ventra, M.; Schmidt, O. G.; Schmidt, H.

With the rise of big data handling, new solutions are required to drive cryptographic algorithms for maintaining data security. Here, we exploit the nonvolatile, nonlinear resistance change in BiFeO3 memristors [Shuai et al., J. Appl. Phys. 109, 124117 (2011)] by applying a voltage for the generation of second and higher harmonics and develop a new memristor-based encoding system from it to encrypt and obfuscate data. It is found that a BiFeO3 memristor in high and low resistance state can be used to generate two clearly distinguishable sets of second and higher harmonics as recently predicted theoretically [Cohen et al., Appl. Phys. Lett. 100, 133109 (2012)]. The computed autocorrelation of encrypted data using higher harmonics generated by a BiFeO3 memristor shows that the encoded data distribute randomly.

Keywords: analog resistive switch; flexible barrier height; BiFeO3; fast and energy-efficient resistive swiching

Publ.-Id: 23099

Electric-field-induced insulator to Coulomb glass transition via oxygen vacancy migration in Ca-doped BiFeO3

Lim, J. S.; Lee, J. H.; Ikeda-Ohno, A.; Ohkochi, T.; Kim, K.-S.; Seidel, J.; Yang, C.-H.

The BiFeO3 (BFO) is an interesting playground to explore correlated electronic conduction. It is found that a non-rigid polaronic band is created by hole doping as a result of a strong electron-lattice coupling. We also show strong evidence for the disorder-driven formation of a Coulomb glass state. These results can be harmonized in a framework of the spatial inhomogeneity of polaronic charge density, suggesting a unique electronic conduction mechanism applicable to systems with coexistence of strong electron correlation, electron-lattice interaction, and randomness.

Keywords: Material science; insulator; synchrotron; PEEM; XAS; XPS; XRD; characterisation


Publ.-Id: 23097

Spin-glass behavior of Fe doped InAs prepared by ion implantation and pulsed laser annealing

Yuan, Y.; Cai, H.; Helm, M.; Zhou, S.

Dilute magnetic semiconductors (DMSs) attracted great interests in the last several decades because of their potential for spintronic device [1]. III-V compounds especially GaAs based DMS has recently emerged as the most popular material for this new technology. However, that the low mobility of holes in p-type DMS limits the potential application in semiconductor spintronic devices. Therefore, the searching for n-type DMS is of interest.
The doping of Fe in InAs is attracting research attentions due to the possibility to fabricate n-type diluted magnetic semiconductors [2, 3]. However, the low solubility of Fe in InAs is the most difficulty to achieve InFeAs DMS. In this work, we obtain Fe doped InAs layers by ion implantation and pulsed laser annealing. This approach has shown success for preparing other III-V based DMSs [4, 5]. The formed InFeAs layers are proved to be epitaxial-like on InAs substrates. The prepared InFeAs layers reveal similar magnetic properties independent of their conductivity types. While the samples are lacking of charactersistics of DMS, they appear to be spin-glass like, revealing such as time-dependent magnetiszation measurements reveal aging and memory effects.
1. T. Dietl et al., Science 287, 1019-1022 (2000)
2. M. Kobayashi et al., Appl. Phys. Lett., 105, 032403(2014)
3. P. Nam Hai et al., Appl. Phys. Lett., 101, 182403 (2012)
4. D. Bürger et al., Phys. Rev. B, 81, 115202 (2010)
5. M. Khalid et al., Phys. Rev. B, 89, 121301(R) (2014)

  • Poster
    ICM 2015, 05.-10.07.2015, Barcelona, Spain

Publ.-Id: 23096

What defines the quantum regime of the free-electron laser?

Kling, P.; Giese, E.; Endrich, R.; Preiss, P.; Sauerbrey, R.; Schleich, W. P.

The quantum regime of the free-electron laser (FEL) emerges when the discreteness of the momentum of the electron plays a dominant role in the interaction with the laser and the wiggler field. Motivated by a heuristic phase space approach we pursue two different routes to define the transition from the classical FEL to the quantum domain: (i) standard perturbation theory and (ii) the method of averaging. Moreover, we discuss the experimental requirements for realizing a Quantum FEL and connect them to today's capabilities.

Keywords: free-electron laser; quantum regime; Quantum FEL

Publ.-Id: 23094

Quantum theory for the dynamic micro-structure in correlated two-component systems far from equilibrium -- application to x-ray scattering

Vorberger, J.; Chapman, D. A.

We present a quantum theory for the dynamic structure factors in non-equilibrium, correlated, two-component systems like plasmas or warm dense matter. On this basis, expressions for the local field corrections in non-equilibrium could be determined as well. The polarization function, needed as input for the calculation of the structure factors, is calculated in non-equilibrium based on a perturbation expansion in the interaction strength. To make our theory applicable for x-ray scattering, a generalized Chihara decomposition for the total electron structure factor in non-equilibrium is derived. Examples are given for the special case of equilibrium and for a bump-on-hot-tail distribution as often encountered during laser heating of materials.

Keywords: Plasma kinetic equations; Thermodynamics of plasmas; Strongly-coupled plasmas; Perturbative methods; X-ray and γ-ray measurements; Dielectric properties; Scattering theory (quantum mechanics)

Publ.-Id: 23093

Multiphase CFD activities at Helmholtz–Zentrum Dresden – Rossendorf

Lucas, D.

Multiphase flows are frequently applied in industrial processes as e.g. in chemical engineering, oil industries or power plants. Reliable predictions of the flow characteristics such as local concentration of species, interfacial area density or heat transfer in gas-liquid flows can contribute to an optimization of the design of corresponding apparatuses and processes. While Computational Fluid Dynamics (CFD) is frequently used for industrial problems in case of single phase flows, it is not yet mature for two-phase flows. The reason is the complex gas-liquid interface. For medium and large scale flow domains it is not feasible to resolve all details of this interface. Averaging procedures have to be applied and in most cases the so-called two- or multi-fluid approach is used. It assumes interpenetrating phases and the information on the interface gets lost by these averaging procedures. This information has to be added to the basic balance equations by so-called closure models. The development and validation of general frameworks as well as closure models is done at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) to obtain tools for reliable predictions of multiphase flow characteristics in medium and large industrial scales.
In this talk the HZDR-strategy for the CFD-model development and validation for multiphase flows with focus on gas-liquid flows is presented.

Keywords: CFD; two-fluid model; iMUSIG; GENTOP

  • Invited lecture (Conferences)
    EVT/Virtuhcon-Seminar, 15.01.2016, Freiberg, Deutschland

Publ.-Id: 23092

Single pairing spike-timing dependent plasticity inBiFeO3 memristors with a time window of 25ms to 125µs

Du, N.; Kiani, M.; Mayr, C. G.; You, T.; Buerger, D.; Skorupa, I.; Schmidt, O. G.; Schmidt, H.

Memristive devices are popular among neuromorphic engineers for their ability to emulate forms of spike-driven synaptic plasticity by applying specific voltage and current waveforms at their two terminals. In this paper, we investigate spike-timing dependent plasticity(STDP) with a single pairing of one presynaptic voltage spike and one post-synaptic voltage spike in a BiFeO3 memristive device. In most memristive materials the learning window is primarily a function of the material characteristics and not of the applied waveform. In contrast, we show that the analog resistive switching of the developed artificial synapses allows to adjust the learning time constant of the STDP function from 25ms to 125μs via the duration of applied voltage spikes. Also, as the induced weight Change may degrade, we investigate the remanence of the resistance change for several hours after analog resistive switching, thus emulating the processes expected in biological synapses. As the power consumption is a major constraint in neuromorphic circuits, we show methods to reduce the consumed energy per setting pulse to only 4.5 pJ in the developed artificial synapses.

Keywords: BiFeO3 memristor; artificial synapse; single Pairing STDP; memory consolidation; learning window; low-power device

Publ.-Id: 23091

An Energy-Efficient, BiFeO3-Coated Capacitive Switch with Integrated Memory and Demodulation Functions

You, T.; Selvaraj, L. P.; Zeng, H.; Luo, W.; Du, N.; Buerger, D.; Skorupa, I.; Prucnal, S.; Lawerenz, A.; Mikolajick, T.; Schmidt, O. G.; Schmidt, H.

A capacitive switching behavior is observed in a Si 3 N 4 /p-Si-based metal–insulator–semiconductor (MIS) structure due to the electron tunneling at the Si 3 N 4 /p-Si interface. A BiFeO 3 (BFO) layer is deposited on Si 3 N 4 /p-Si by pulsed laser deposition technique to obtain the memcapacitive effect as the distribution of positive charges in the Si 3 N 4 layer can be stabilized by the polarization charge of the ferroelectric BFO coating layer. The capacitive switching behavior of the Al/BFO/Si 3 N 4 /p-Si/Au MIS structure is also sensitive to both intensity and wavelength of the illumination, which offers the possibility to create a photodetector for both intensity and color detection. Thus, the presented device has the potential application for future information storage and visible light communications. As an example, a photocapacitive demodulator with capability of decoding both wavelength and intensity information of the incident light is demonstrated.

Keywords: analog resistive switch; flexible barrier height; BiFeO3; fast and energy-efficient resistive switching

Publ.-Id: 23089

Sorption of trivalent lanthanides and actinides onto montmorillonite: Macroscopic, thermodynamic and structural evidence for ternary hydroxo and carbonato surface complexes on multiple sorption sites

Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.

The credibility of long-term safety assessments of radioactive waste repositories may be greatly enhanced by a molecular level understanding of the sorption processes onto individual minerals present in the near- and far-field. In this study we couple extensive macroscopic sorption experiments to surface complexation modelling and spectroscopic tools including extended X-ray absorption fine structure (EXAFS) and time-resolved laser fluorescence spectroscopies (TRLFS), in order to elucidate the uptake mechanism of trivalent actinides and lanthanides (Ln/AnIII) on montmorillonite in the absence and presence of dissolved carbonate. Based on the experimental sorption isotherms, the previously developed 2SPNE SC/CE sorption model needed to be complemented with an additional surface complexation reaction on to a weak site (ºSWOEu2+) for the carbonate-free system. In the presence of carbonate, the previously published model required refinement by reducing the strong-site capacity and by adding the formation of Ln/AnIII-carbonato complexes both on strong and weak sites. EXAFS spectra collected of selected Am sorption samples and TRLFS spectra of selected Cm sorption samples corroborate the model assumptions by showing the existence of different surface complexation sites and evidencing the formation of Ln/AnIII carbonate surface complexes. In the absence of carbonate and at low loadings, Ln/AnIII form strong innersphere sorption complexes through binding to three Al(O,OH)6 octahedra, most likely by occupying vacant sites in the octahedral layers of montmorillonite, which are exposed on {010} and {110} edge faces. At higher loadings, Ln/AnIII bind to only one Al octahedron, forming a weaker, edge-sharing sorption complex. In the presence of carbonate, we identified a ternary mono-carbonato Ln/AnIII complex binding directly to one Al(O,OH)6 octahedron, thereby revealing that type-A ternary complexes form with one or two carbonato groups pointing away from the surface into the solution phase; these complexes form on weak sites only at the observable concentration range, in line with the small amount of strong-site complexes suggested by the complexation model. When the solubility of carbonates was exceeded, formation of an Am carbonate hydroxide could be identified. The excellent agreement between the thermodynamic model parameters developed by fitting a large set of macroscopic data, and the spectroscopically identified mechanisms, demonstrates the mature state of the 2SPNE SC/CE model for predicting and quantifying the retention of Ln/AnIII elements by montmorillonite-rich clay rocks.

Keywords: Americium; Sorption; clay rocks; montmorillonite; TRLFS; EXAFS; surface complexation modeling

Publ.-Id: 23088

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

Wang, Z.; Qureshi, N.; Yasin, S.; Mukhin, A.; Ressouche, E.; Zherlitsyn, S.; Skourski, Y.; Geshev, J.; Ivanov, V.; Gospodinov, M.; Skumryev, V.

Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of ≈50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions.

Publ.-Id: 23086

Room temperature deposition of highly dense TiO2 thin films by Filtered Cathodic Vacuum Arc

Guillen, E.; Heras, I.; Rincon Llorente, G.; Lungwitz, F.; Alcon-Camas, M.; Escobar-Galindo, R.

A systematic study of TiO2 films deposited by dc filtered cathodic vacuum arc (FCVA) was carried out by varying the deposition parameters in a reactive oxygen atmosphere. The influence of the oxygen partial pressure on film properties is analyzed. Composition was obtained by Rutherford backscattering spectroscopy (RBS) measurements, which also allow us to obtain the density of the films. Morphology of the samples was studied by scanning electron microscopy (SEM) and their optical properties by ellipsometry. Transparent, very dense and stoichiometric TiO2 films were obtained by FCVA at room temperature.

  • Contribution to proceedings
    SPIE Optics + Photonics 2015, 09.-13.08.2015, San Diego, USA
    Proceedings of SPIE 9558
    DOI: 10.1117/12.2189503


Publ.-Id: 23085

Cyclotron Resonance in InAs/AlSb Quantum Wells in Magnetic Fields up to 45 T

Spirin, K. E.; Krishtopenko, S. S.; Sadofyev, Y. G.; Drachenko, O.; Helm, M.; Teppe, F.; Knap, W.; Gavrilenko, V. I.

Electron cyclotron resonance in InAs/AlSb heterostructures with quantum wells of various widths in pulsed magnetic fields up to 45 T are investigated. Our experimental cyclotron energies are in satisfactory agreement with the results of theoretical calculations performed using the eight-band kp Hamiltonian. The shift of the cyclotron resonance (CR) line, which corresponds to the transition from the lowest Landau Level to the low magnetic-field region, is found upon varying the electron concentration due to the negative persistent photoconductivity effect. It is shown that the observed shift of the CR lines is associated with the finite width of the density of states at the Landau levels.

Keywords: cyclotron resonance; quantum wells

Publ.-Id: 23083

Magnetic anisotropy and reduced neodymium magnetic moments in Nd3Ru4Al12

Gorbunov, D.; Henriques, M. S.; Andreev, A. V.; Eigner, V.; Gukasov, A.; Fabrèges, X.; Skourski, Y.; Petricek, V.; Wosnitza, J.

This paper addresses the electronic properties of Nd3Ru4Al123Ru4Al12.We performed magnetization measurements on a single crystal in static and pulsed magnetic fields as well as neutron-diffraction experiments. Nd3Ru4Al12 is a strongly anisotropic uniaxial ferromagnet with a Curie temperature of 39 K. The magnetic moments are aligned collinearly along the [001] axis. The magnetic structure of Nd3Ru4Al12 has orthorhombic symmetry for which the crystallographic Nd site is split into two magnetically inequivalent positions, Nd1 and Nd2. The Nd1 and Nd2 atoms exhibit reduced magnetic moments, 0.95 and 2.66 μB, as compared to the free Nd3+-ion value (3.28 μB). We discuss this finding in terms of crystal-field effects and competing exchange and anisotropy interactions. Since the single-ion mechanism in Nd3Ru4Al12 leads to uniaxial anisotropy and the two-ion mechanism of the actinide analog U3Ru4Al12 is known to lead to planar anisotropy, this paper demonstrates the decisive influence of these different mechanisms on the magnetic anisotropy.

Publ.-Id: 23082

Structural stability study of the mixed La0.7-xLuxEu0.3PO4 solid solutions by Extended X-ray Absorption Spectroscopy

Lozano-Rodriguez, M. J.; Arinicheva, Y.; Holthausen, J.; Neumeier, S.; Scheinost, A. C.

Monazite and related solid solutions are considered as potential candidates for the immobilization of actinides for the disposal of high-level nuclear waste. Because of their low solubility, high resistance to radiation damage and high chemical flexibility, phosphate materials are matter of study 1. Recently many efforts have been putting to find effective ways to synthesis and characterize lanthanide phosphates through diverse methods3. However, a deeper understanding on structural determinations concerning the local atomic arrangement of surrogate elements, i.e., europium, in phosphates matrices is still in progress. In order to correlate the high chemical flexibility of monazite/xenotime structures with local atomic ordering, mixed La0.7-xLuxEu0.3PO4 solid solutions (x=0, 0.35, 0.5, 0.7) have been study by Extended X-ray Absorption Spectroscopy. La L1, Eu L3 and Lu L3-edges were measured for each phosphate solid solution series. It has been found that for each measured element, the local atomic environment has tendency to adopt an environment closer to monazite or xenotime depending strongly to the x loading. The results obtained by XRPD, XANES and EXAFS are discussed with respect to its chemical flexibility in potential host matrix for sequestering long-lived radionuclides.

Keywords: EXAFS; phosphate solid solutions; monazite; lanthanides

  • Invited lecture (Conferences)
    Scientific Basis for Nuclear Waste Management XXXIX, 02.-06.11.2015, Montpellier, France

Publ.-Id: 23081

Determination of local structure in mixed lanthanoid phosphate solid solutions by X-ray absorption spectroscopy

Lozano-Rodriguez, M. J.; Arinicheva, Y.; Heuser, J.; Kvashnina, K.; Neumeier, S.; Scheinost, A. C.

In the 21st century, scientific challenges are required for the disposal of high-level nuclear waste in deep geological formations. Ceramic waste forms like monazite and xenotime, are natural lanthanoid phosphate minerals containing U and Th. When light lanthanoids are involved the monazite structure forms; when heavy lanthanoids are present, the xenotime structure predominates. X-ray absorption spectroscopy was carried out to elucidate the structural changes induced by different lanthanoids when mixed lanthanoids phosphates are formed. EXAFS measurements for La1-xEuxPO4 solid solutions around La and Eu, show the flexibility of the monazite structure when two light lanthanoids are hosted. The La-O distances in the first coordination shell and the first metal-metal distances decrease with increasing Eu content; while the Eu-O local coordination remains unchanged. Additionally, HR-XANES shows an increase on the white line in the absorption coefficient with increasing Eu content, suggesting a change in the valence electron distribution. However, EXAFS measurements of Sm1-xTbxPO4 solid solutions around the Sm, show significant differences between low and high Tb content.

Keywords: EXAFS; phosphate solid solutions; lanthanoids

  • Lecture (Conference)
    E-MRS 2015 Spring Meeting, 11.-15.05.2015, Lille, France

Publ.-Id: 23080

Modern Approaches in Ion Beam Analysis - Challenges and ongoing Developments

Heller, R.

The general trend in technology and science to create, process and analyze small structures on a nm scale or even on an atomic scale leads to new challenges in modern ion beam analysis (IBA). This is accompanied by higher demands on the lateral resolution as well as by the demand on high precision determination of elemental compositions on an atomic depth scale. Further the complexity of processing materials in micro and nano electronics is increasing continuously. Thus elemental analysis is no longer limited to the determination of a few particular atomic species and a division of measurement tasks into „light element in a heavy matrix“ or vise versa becomes obsolete in this way. 

Thinner but more complex layer structures are closely related to an increased sensitivity on external impacts. Even the transport of a sample to the place of analysis under ambient conditions can lead to unwanted (chemical) modifications at the surface. Thus IBA under in-situ conditions has developed into an established method within recent years. Furthermore in technological developments not only the state of a system after processing but the process itself may be of particular interest. “Online” IBA under process conditions is thus more and more desired.

Analysis methods of classical IBA like RBS (Rutherford Backscattering Spectrometry), ERD (Elastic Recoil Detection Analysis), PIXE (Particle Induced X-Ray Emission) or PIGE (Particle Induced Gamma Emission), either applied as broad beam or in terms of a micro probe, can therefore rapidly reach their limits. Even the use of modern magnetic spectrometers with depth resolution of a few nano-meters may in particular situations not be sufficient.

Searching for approaches to all these modern measurement tasks often brings IBA to the physical limits and thus complicates quantitative analysis. This for instance may manifest in energy depended charge fractions of the projectile, deviations from classical Rutherford cross-sections, the modification of the sample by the probing beam, etc. All these effects have to be carefully taken into consideration when interpreting analysis results.

The present contribution will give an overview on the demands and difficulties resulting from the described demands on modern IBA. Ongoing development of new IBA techniques and approaches at the Ion Beam Center at HZDR will be presented and discussed. Those are covering

- the realization of IBA within a Helium ion microscope,
- the unification of different IBA techniques in complex experimental chambers including in-situ capabilities,
- the increase of efficiency of lateral resolved PIXE measurements,
- the controlled implantation of single ions into surfaces with nm precision, as well as
- concepts for a new low-energy ion laboratory.

Keywords: Ion Beam Analysis; IBA; TBS; ERD; PIXE; lateral resolved IBA

  • Invited lecture (Conferences)
    50th Zakopane School of Physics, 18.-23.05.2015, Zakopane, Polen

Publ.-Id: 23079

Carbon:nickel nanocomposite templates - predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

Melkhanova, S.; Kunze, T.; Haluska, M.; Hübner, R.; Keller, A.; Abrasonis, G.; Gemming, S.; Krause, M.

Carbon: nickel (C:Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD). Two NCT types of 2 nm thickness were prepared by ion beam co-sputtering without (type I) or with assisting Ar+ ion irradiation (type II). NCT type I comprised Ni-rich nanoparticles (NPs) with defined diameter in an amorphous carbon matrix, while NCT type II was a homogenous C:Ni film. Based on the Raman spectra of more than 600 individual SWCNTs, the diameter distribution obtained from both types of NCT was determined. SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I. About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm. In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution are obtained from NCT type II. From both catalyst templates predominantly separated as-grown SWCNTs are obtained. They are free of solvents or surfactants, exhibit a low degree of bundling and contain negligible amounts of MWCNTs. The study demonstrates the advantage of predefined catalysts for diameter-controlled SWCNT synthesis in comparison to in situ formed catalysts.

Keywords: Nanocomposites; single-walled carbon nanotubes; diameter selective growth; predifined stable catalyst templates

Publ.-Id: 23078

Comprehensive real time characterization of AlTiO(x)N(y) thin films at high temperatures

Heras, I.; Guillén, E.; Krause, M.; Wenisch, R.; Lungwitz, F.; Escobar-Galindo, R.

AlTiN, AlTiO, and AlTiO(x)N(y) thin films were investigated in order to understand the influence of the oxygen to nitrogen ratio on the failure mechanisms at high temperatures. The thin films were deposited by cathodic vacuum arc and characterized in-situ following the methodology proposed for comprehensive environmental testing of optical properties in thin films using the HZDR cluster tool [1].
This multi-chamber material processing and analysis system enables the detailed analysis of the temperature dependence of composition, chemical bonding, and optical properties of thin films. The methodology combines the sequential study of the optical constants by spectroscopic ellipsometry, compositional analysis using ion beam analysis techniques and structure analysis by Raman spectroscopy. All characterizations of AlTiO(x)N(y) thin films were carried out in situ without sample exposure to undefined atmospheres. The samples were heated in vacuum from room temperature to 800°C inside the different chambers and in parallel, to elucidate the influence of the ambience on the degradation process. Moreover, ex-situ annealing in air was performed. Ellipsometry, Raman and ERDA results show the influence of the initial oxygen content in the sample with the inward diffusion of oxygen into the coating and the oxidation resistance at high temperatures.

[1] I. Heras, E. Guillén, R. Wenisch, M. Krause, R. Escobar Galindo, J.L. Endrino - Comprehensive environmental testing of optical properties in thin films. Procedia CIRP. 22 (2014) 271–276

Keywords: In situ analysis; cluster tool; new energy materials; solar-selective coatings

  • Lecture (Conference)
    78th IUVSTA Workshop, 05.-09.10.2015, Braga, Portugal

Publ.-Id: 23077

New energy materials - concepts, structure formation and in situ analysis

Krause, M.

An overview on the current activities on new energy materials is given. It includes concepts, structure formation, and in situ analysis of nanocomposite materials for solar energy applications.

Keywords: New energy materials; in situ analysis; nanocomposites

  • Lecture (Conference)
    Ehrenkolloquium für Prof. Hans Kuzmany, 10.09.2015, Wien, Österreich

Publ.-Id: 23076

Solar selective coatings based on carbon:transition metal nanocomposites

Heras, I.; Guillén, E.; Krause, M.; Pardo, A.; Endrino, J.-L.; Escobar, R.

The design of efficient and stable solar selective coatings for Concentrating Solar Power (CSP) central receivers requires a comprehensive knowledge about the incorporated materials. In this work solar selective coatings were grown by filtered cathodic vacuum arc (FCVA) deposition. The complete stacks consist of an infrared reflection layer, an absorber layer of C:ZrC nanocomposites and an antireflection layer. The Carbon-transition metal nanocomposites were studied as absorber materials because they show appropriate optical properties, i.e. high absorption in the solar region and low thermal emittance. Furthermore metal carbides are thermally and mechanically stabile in air at high temperatures. In order to optimize the absorber layer, the metal content was controlled by adjusting the pulse ratio between the two arc sources. The elemental composition of the absorber layers was determined by Ion Beam Analysis. X-Ray diffraction (XRD) measurements show the formation of metal carbides when the metal content is high enough. The optical properties of the deposited coatings were characterized by spectroscopic ellipsometry (SE). The reflectance spectra of the complete selective coating were simulated with the optical software CODE. Bruggeman effective medium approximation (EMA) was employed to average the dielectric functions of the two components which compose the nanocomposite in the absorber layer. Good agreement was found between simulated and measured reflectance spectra of the solar selective multilayer.

Keywords: Solar selective coatings; carbide thin films; high temperature applications; cathodic arc deposition; simulation of optical properties

  • Lecture (Conference)
    SPIE: Optics + Photonics 2015, 09.-13.08.2015, San Diego, United States
  • Contribution to proceedings
    SPIE Optics + Photonics for Sustainable Energy, 09.-13.08.2015, San Diego, USA
    Proceedings Volume 9559, High and Low Concentrator Systems for Solar Energy Applications X
    DOI: 10.1117/12.2189515


Publ.-Id: 23075

Effect of hydrogen on magnetic properties of Fe60Al40 alloy thin films

Ehrler, J.; Bali, R.; Otalora, C.; Yildirim, O.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Cornelius, S.; Böttger, R.; Heller, R.; Potzger, K.

The influence of hydrogen on magnetic properties and defects of metallic thin films based on FeAl alloys was investigated. Therefore, hydrogen ions have been implanted with different fluences into disordered Fe60Al40 thin films. Magneto-optical Kerr effect showed an increase of coercivity with increasing ion fluence. The treatment of paramagnetic Fe60Al40 thin films in a climate chamber, on the other hand, led to an establishment of ferromagnetism. Elastic Recoil Detection Analysis showed no hydrogen in the implanted and climate chamber treated samples. However, positron annihilation measurements suggest storage of hydrogen in vacancies. The origin of ferromagnetism was investigated with further methods.

Keywords: Hydrogen; Defects; Implantation; Climate Chamber; FeAl; MOKE; VSM; RBS; ERD; PAS

  • Poster
    PSI Summer School 2015, 15.-21.08.2015, Zuoz, Schweiz

Publ.-Id: 23074

Magnetohydrodynamic effects in liquid metal batteries

Stefani, F.; Galindo, V.; Kasprzyk, C.; Landgraf, S.; Seilmayer, M.; Starace, M.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) consist of two liquid metal electrodes and a molten salt ionic conductor sandwiched between them. The density ratios allow for a stable stratification of the three layers. LMBs were already considered as part of energy conversion systems in the 1960s and have recently received renewed interest for economical large-scale energy storage. In this paper, we concentrate on the magnetohydrodynamic aspects of this cell type with special focus on electro-vortex flows and possible effects of the Tayler instability.

  • Contribution to proceedings
    Liquid Metal Processing & Casting Conference 2015, 20.-24.09.2015, Leoben, Austria
    LMPC 2015 - Proceedings of the 2015 International Symposium on Liquid Metal Processing and Casting, Leoben: ASMET, 978-3-901384-63-9, 347-354
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 143(2016), 012024
    DOI: 10.1088/1757-899X/143/1/012024

Publ.-Id: 23073

Contactless inductive flow tomography: basic principles and first applications in the experimental modelling of continuous casting

Stefani, F.; Eckert, S.; Ratajczak, M.; Timmel, K.; Wondrak, T.

Contactless inductive flow tomography (CIFT) aims at reconstructing the flow structure of a liquid metal from the magnetic fields measured at various positions outside the fluid body which are induced by the flow under the influence of one or multiple applied magnetic fields. We recap the basic mathematical principles of CIFT and the results of an experiment in which the propeller-driven three-dimensional flow in a cylindrical had been reconstructed. We also summarize the recent activities to utilize CIFT in various problems connected with the experimental simulation of the continuous casting process. These include flow reconstructions in single-phase and two-phase flow problems in the Mini-LIMMCAST model of slab-casting, studies of the specific effects of an electromagnetic stirrer attached to the Submerged Entry Nozzle (SEN), as well as first successful applications of CIFT on the background of a strong electromagnetic brake field. We conclude by discussing some remaining obstacles for the deployment of CIFT in a real caster.

  • Contribution to proceedings
    Liquid Metal Processing & Casting Conference 2015, 20.-24.09.2015, Leoben, Austria
    LMPC 2015 - Proceedings of the 2015 International Symposium on Liquid Metal Processing and Casting, Leoben: ASMET, 978-3-901384-63-9, 339-346
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 143(2016), 012023
    DOI: 10.1088/1757-899X/143/1/012023

Publ.-Id: 23072

Evolution of Crystal Structure During the Initial Stages of ZnO Atomic Layer Deposition

Boichot, R.; Tian, L.; Richard, M.-I.; Crisci, A.; Chaker, A.; Cantelli, V.; Coindeau, S.; Lay, S.; Ouled, T.; Guichet, C.; Chu, M. H.; Aubert, N.; Ciatto, G.; Blanquet, E.; Thomas, O.; Deschanvres, J.-L.; Fong, D. D.; Renevier, H.

A complementary suite of in situ synchrotron X-ray techniques is used to investigate both structural and chemical evolution during ZnO growth by atomic layer deposition. Focusing on the first 10 cycles of growth, we observe that the structure formed during the coalescence stage largely determines the overall microstructure of the film. Furthermore, by comparing ZnO growth on silicon with a native oxide with that on Al2O3(001), we find that even with lattice-mismatched substrates and low deposition temperatures, the crystalline texture of the films is dependent strongly on the nature of the interfacial bonds.

Keywords: ALD; ZnO; in-situ X-ray scattering

Publ.-Id: 23071

Nickel-Enhanced Graphitic Ordering of Carbon Ad-Atoms During Physical Vapor Deposition

Wenisch, R.; Hübner, R.; Munnik, F.; Gemming, S.; Abrasonis, G.; Krause, M.

The mechanism of graphitic ordering of atomic C on Ni was investigated at temperatures ranging from room temperature to 550°C. The C/Ni films were prepared by ion beam sputtering. Their structure has been determined by Rutherford backscattering spectrometry/nuclear reaction analysis, X-ray photoelectron spectroscopy, Raman spectroscopy and cross-sectional transmission electron microscopy. A temperature-induced and a Ni-induced enhancement of graphitic ordering is demonstrated. The Ni-effect is responsible for the formation of a bi-layer structure of the C films at higher deposition temperatures. In the bi-layers, C forms graphenic planes parallel to the Ni surface within a thickness range of 1-2 nm. Further deposited C grows preferentially perpendicular to the surface. The results are discussed on the basis of hyperthermal atom deposition, surface diffusion, metal-induced crystallization and dissolution-precipitation. Our findings point to a dominating role of surface diffusion-assisted crystallization in the carbon ordering process.

Publ.-Id: 23070

Quantitative detection of microscopic lithium distributions with neutrons

Neri, G.; Gernhäuser, R.; Lichtinger, J.; Winkler, S.; Seiler, D.; Bendel, M.; Kunze-Liebhäuser, J.; Brumbarov, J.; Portenkirchner, E.; Renno, A. D.; Rugel, G.

The importance of lithium in the modern industrial society is continuously increasing. Spatially resolved detection of tritium particles from 6Li(n,α)3H nuclear reactions is used to reconstruct microscopic lithium distributions. Samples are exposed to a flux of cold neutrons. Emitted charged particles are detected with a PSD. Introducing a pinhole aperture between target and detector, the experimental setup works like a “camera obscura”, allowing to perform spatially resolved measurements. Tritium detection analysis was successfully used to reconstruct the lithium content in self-organized TiO2-x-C and Si/TiO2-x-C nanotubes electrochemically lithiated, for the first time. Titanium dioxide nanotubes are a candidate for a safe anode material in lithium-ion batteries. Also lithium distributions in geological samples, so called “pathfinder-minerals” containing lithium, like lepidolite from a pegmatite, were analyzed. With this development we present a new precision method using nuclear physics for material science.
Supported by the DFG (GE 2296/1-1).

Keywords: microscopic lithium distribution; PNAA

  • Lecture (Conference)
    DPG-Frühjahrstagung des Fachverbandes Physik der Hadronen und Kerne (HK), 14.-18.03.2016, Darmstadt, Deutschland

Publ.-Id: 23069

Multiphase Flow Measurement and Visualization for Fluid Dynamics Research at Helmholtz-Zentrum Dresden-Rossendorf

Schleicher, E.

The presentation will give a short overview on our research activities in the field of multiphase flow investigations and focus on advanced measurement techniques developed in-house.
The content can be summarized to:
- introduction of HZDR:
o Who we are?
o Where we come from?
o Basic structure of German research organization.
- Institute of fluid dynamics: structure and research topics
- Advanced measurement techniques to create CFG grate data for multiphase flow experiments,
functional principle and application examples of:
o wire-mesh sensors,
o gamma-ray computed tomography,
o ultra-fast X-ray tomography.

  • Lecture (others)
    Institutsseminar bei CSIRO, Melbourne, 17.11.2015, Melbourne, Australien

Publ.-Id: 23068

An algorithm for refined reconstruction of the phase interface for two-phase gas/liquid annular flows using wire-mesh data

Aydin, T. B.; Brito, R.; Schleicher, E.; Pereyra, E.; Sarica, C.

Wire-Mesh sensors (WMS) are used to measure the instantaneous distributions of the phases with high temporal and spatial resolutions with conducting and non-conducting fluids. The experimental data acquired from WMS can be used in a variety of ways to obtain detailed information on the two-phase flow topology including the quantitative visualization of the phase interface.

The current study explores the applicability of a phase interface identification algorithm for two-phase annular flows. The experimental data used in the development of the algorithm is acquired by a WMS with a 16×16 wires for water/air two-phase annular flow at Tulsa University Horizontal Well Artificial Lift Projects (TUHWALP) in 0.05 m (2-in.), 1° upward inclined pipe. The superficial gas and liquid velocities are set to 26 m/s and 0.075 m/s, respectively.

Initially, the WMS data is transformed from a Cartesian coordinate system (with a mesh size of 16×16) onto a polar coordinate system with a mesh size of (MRF×16)×(MRF×16) using a weighted average interpolation, where MRF is the mesh refinement factor. The interpolated data (defined in the polar coordinate system) enables the identification of the phase interface based on the local liquid holdup profile along the radial direction at a given tangential position using the centre of mass concept.

The data interpolation scheme conserves the liquid mass within the pipe cross-section as the mesh refinement factor is increased. However, large values of the refinement factor yield in outliers in the phase interface coordinates. The significance of these outliers is more pronounced if the WMS measurements are affected by the end effects such as in capacitance based measurements. The current algorithm is also capable of producing satisfactory results under stratified flow conditions.

Keywords: Phase interface reconstruction; two-phase; annular flow; wire-mesh

  • Contribution to proceedings
    7th International Symposium on Process Tomography, 01.-03.09.2015, Dresden, Deutschland
    Proceedings of the 7th International Symposium on Process Tomography
  • Poster
    7th International Symposium on Process Tomography, 01.-03.09.2015, Dresden, Deutschland

Publ.-Id: 23067

Preparation and characterization of high purity Ti thin films by high power impulse magnetron sputtering deposition

Meško, M.; Munnik, F.; Heller, R.; Grenzer, J.; Hübner, R.; Krause, M.

The increased ion-to-atom ratio in high power impulse magnetron sputtering (HiPIMS) allows directional deposition and film densification by the bombarding ions [1]. Recently, Andersson et al. showed HiPIMS gasless self-sputtering operation and proposed this method for the synthesis of ultraclean metal coatings through self-ion-assisted deposition [2]. In the present work we investigated Ti thin films prepared by direct current magnetron sputtering (dcMS) and HiPIMS with respect to their element composition, surface roughness, and microstructure. Ti films were deposited on Si/SiO2 substrates at room temperature. The base pressure prior to the two hours depositions was 5x10-5 Pa. The film thicknesses were determined by profilometry after the deposition and are 800 nm and 200 nm for dcMS and HiPIMS respectively. It is shown that Ti thin films prepared by HiPIMS do not suffer from bulk contamination like dcMS films (Fig. 1). In particular, the impurity levels for O, N and C are below the detection limit (0.3 – 0.5 at.%) of elastic recoil detection analysis (ERDA) and the hydrogen content was measured to 0.5 at.% for the HiPIMS case. Compared to the dcMS films, we observed an element specific reduction of impurities by a factor 3- 4 for N and H; and a factor of 20 for O. This suggests the presence of at least two sources of impurities. Unlike in [2], the HiPIMS self-sputtering regime was sustained in Ar gas. The high purity of Ti films can be partly explained by gas rarefaction and the cleaning effect of the bombarding ions. Moreover, densification effects presumably suppress post-deposition oxidation. The compositional effects are correlated with differences in the film microstructure revealed by SEM, XRD and TEM analysis. A more sensitive analytical method is needed to evaluate the actual impurity levels of O, N, and C in the deposited HiPIMS films.
[1] U. Helmersson, M. Lattemann, J. Bohlmark, A. P. Ehiasarian, J. T. Gudmundsson “Ionized physical vapor deposition (IPVD): A review of technology and applications” (2006) Thin Solid Films 513, 1–24
[2] J. Andersson and A. Anders “Gasless sputtering: Opportunities for ultraclean metallization, coatings in space, and propulsion” (2008) Appl. Phys. Lett. 92, 221503

Keywords: HiPIMS; self-sputtering; impurity level; Ti thin films

  • Poster
    6th International Conference on HIPIMS 2015, 10.-11.06.2015, Braunschweig, Deutschland

Publ.-Id: 23066

Carbide Formation and Optical Properties in Carbon: Transition Metal Nanocomposites Thin Films

Heras, I.; Guillen, E.; Krause, M.; Pardo, A.; Endrino, J. L.; Escobar Galindo, R.

Transition metals with carbon deposited by physical vapor deposition techniques, lead the formation of metal nano-clusters or nanocrystalline metallic carbides embedded in a carbon matrix. Interstitial carbides are stable at high temperature, have high melting points and possess a high reflectivity. In contrast, the resulting carbon: transition metal nanocomposites show optical selective properties such as good absorptance in the visible with high reflectance in the infrared. These properties make them very attractive for applications where high temperature resistant materials with selective optical properties are required.
In this study, carbon: transition metal nanocomposites were grown using a physical vapor deposition system incorporating two pulsed filtered cathodic arc sources, one provided with a graphite cathode and the other with a metallic cathode (Zr, V or Mo). The metal content in the composite was controlled by adjusting the pulse ratio between the two sources, and determined by Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). Comprehensive structure characterization was carried out using a combination of X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). Optical characterization has been done using both ellipsometry and spectrophotometer measurements in order to obtain the optical constants and the reflectance spectra of the samples.
Together with experimental characterization, a computer program is used to simulate the reflectance spectra of different carbon: transition metal films. Bruggeman effective medium theory was used to average the dielectric functions of the two components which compose the film. According to our simulations, the resulting reflectance of the nanocomposite films is strongly affected by the metal content, independently if it results in metallic nano-clusters or nanocrystalline metallic carbides. Simulated spectra were compared with the measured reflectance of the deposited films obtaining good agreement between simulations and experimental results.

Keywords: Nanocomposites; Optical properties; Carbon

  • Lecture (Conference)
    2015 MRS Spring Meeting & Exhibit, 06.-10.04.2015, San Francisco, United States

Publ.-Id: 23065

Subcritical excitation of the current-driven Tayler instability by super-rotation

Rüdiger, G.; Schultz, M.; Gellert, M.; Stefani, F.

It is known that in a hydrodynamic Taylor-Couette system, uniform rotation or a rotation law with positive shear (“super-rotation”) is linearly stable. It is also known that a conducting fluid under the presence of a sufficiently strong axial electric-current becomes unstable against nonaxisymmetric disturbances. It is thus suggestive that a cylindrical pinch formed by a homogeneous axial electric-current is stabilized by rotation laws with dOmega/dR ≥ 0. For magnetic Prandtl number Pm not equal 1 and for slow rotation, however, rigid rotation and super-rotation support the instability by lowering the critical Hartmann numbers. This double-diffusive instability of superrotation even exists for toroidal magnetic fields with rather arbitrary radial profiles, the current-free profile B_phi∝1/R included. The sign of the azimuthal drift of the nonaxisymmetric hydromagnetic instability pattern strongly depends on the magnetic Prandtl number. The pattern counterrotates with the flow for Pm ≪ 1 and it corotates for Pm ≫ 1 while for rotation laws with negative shear, the instability pattern migrates in the direction of the basic rotation for all Pm. An axial electric-current of minimal 3.6 kA flowing inside or outside the inner cylinder suffices to realize the double-diffusive instability for super-rotation in experiments using liquid sodium as the conducting fluid between the rotating cylinders. The limit is 11 kA if a gallium alloy is used

Publ.-Id: 23064

Ferromagnetism of nonstoichiometric manganese monosilicides at room temperature

Semisalova, A. S.; Chernoglazov, K. Y.; Perov, N. S.; Gan'Shina, E. A.; Granovsky, A. B.; Zenkevich, A. V.; Zhou, S.; Rylkov, V. V.

Ferromagnetic Si-Mn alloys attract increasing interest due to their interesting properties - recently it was found that these alloys prepared by PLD method exhibit unusual magnetic characteristics which cannot be adequately interpreted within the framework of available theoretical models. Curie temperature TC in nonstoichiometric Si1-xMnx alloys slightly enriched in Mn (x ~ 0.52-0.55) was shown to be on order of magnitude higher (TC ~ 300 K) in comparison to the stoichiometric MnSi (TC ~ 30 K). The mechanism of high-temperature ferromagnetism is still not clear. The ferromagnetic exchange is associated with the formation of defects with localized magnetic moments coupled via spin fluctuations of itinerant electrons in the host. Also we suppose that structural defects have a strong influence on the formation of metastable phases with enhanced ferromagnetic response. In this contribution the recent experimental results on ferromagnetism of PLD deposited SiMn alloys are summarized.

  • Poster
    DPG Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), 17.-20.03.2015, Berlin, Germany

Publ.-Id: 23063

Correlations of RBM, G line, and D line frequencies of individual SWCNTs grown from carbon:nickel nanocomposite templates

Melkhanova, S.; Kunze, T.; Haluska, M.; Hübner, R.; Keller, A.; Gemming, S.; Krause, M.

Carbon:nickel nanocomposite templates were used for CVD growth of separated, individual single-walled carbon nanotubes (SWCNTs) free of solvents or surfactants. The as-grown carbon nanotubes were characterized by laser-energy dependent Raman spectroscopy and atomic force microscopy. Raman spectra showing a single radial breathing mode (RBM) line were analyzed with respect to correlations of RBM, G+ line and D line frequencies for SWCNT diameters covering the range of 0.8 nm to 1.6 nm. Opposite line shifts were found for RBM and G+ lines of the individual SWCNTs. However, the line shifts of the G+ line are smaller than the standard deviation of the G+ position for SWCNTs with almost the same RBM frequency, i.e. 1 1/cm compared to ± 1 1/cm for the whole diameter range. The D line often shows a complex shape including up to three components, which makes the identification of correlations with RBM frequencies possible only in selected cases.

Keywords: Nanocomposites; thin films; carbon nanotubes; Raman spectroscopy

  • Poster
    29th International Winterschool for Electronic Properties of Novel Materials, 07.-14.03.2015, Kirchberg, Austria

Publ.-Id: 23062

Maldistribution susceptibility of monolith reactors: Case study of glucose hydrogenation performance

Schubert, M.; Haase, S.; Lange, R.; Kost, S.; Salmi, T.; Hampel, U.

In this work an ultrafast electron beam modality was applied for the first time to characterise the gas-liquid Taylor flow inside each channel of an opaque honeycomb monolith structure (65 cpsi) for u_(G,S)=0.1…0.5 m/s and u_(L,S)=0.2 m/s. Significant spatial and temporal deviations in the phase holdup as well as in the gas bubble and liquid slug lengths were found. In order to evaluate the impact of Taylor flow maldistribution on the reactor performance, the data of more than 125,000 unit cells were used to simulate the reactor productivity in the hydrogenation of glucose. The results verify that a monolith reactor solely designed by using superficial velocities and empirical correlations for gas bubble and liquid slug lengths fails significantly in achieving high product selectivity and the desired conversion. The developed methods are a solid base to design and select proper distributors ensuring the favourable flow configurations for specific chemical processes.

Keywords: monolith reactor; Taylor flow; X-ray tomography; reactor modelling; glucose hydrogenation

Publ.-Id: 23061

Controlled immobilization of His-tagged proteins for protein-ligand interaction experiments using Ni2+-NTA layer on glass surfaces

Cherkouk, C.; Rebohle, L.; Lenk, J.; Keller, A.; Ou, X.; Laubec, M.; Neuber, C.; Haase-Kohn, C.; Pietzsch, J.; Skorupa, W.

Gold surfaces functionalized with nickel-nitrilotriacetic acid (Ni2+-NTA) as self-assembled monolayers (SAM) to immobilize histidine (His)-tagged biomolecules are broadly reported in the literature. However, the increasing demand of using microfluidic systems and biosensors takes more and more advantage on silicon technology which provides dedicated glass surfaces and substantially allows cost and resource savings. Here we present a novel method for the controlled oriented immobilization of His-tagged proteins on glass surfaces functionalized with a Ni2+-NTA layer. Exemplarily, the protein pattern morphology after immobilization on the Ni2+-NTA layer of His6-tagged soluble receptor for advanced glycation endproducts (sRAGE) was investigated and compared to non-oriented immobilization of sRAGE on amino SAM by using scanning electron microscopy (SEM). Moreover, we demonstrated interaction of immobilized sRAGE with three structurally different ligands, S100A12, S100A4, and glycated low density lipoproteins (glycLDL), by means of peak-force tapping atomic force microscopy (PF-AFM). We showed a clear discrimination of different protein-ligand orientations by differential height measurements.

Keywords: His-tagged proteins; glycated low density lipoproteins; microfluidic systems and biosensors; S100 proteins; self-assembled monolayers; soluble receptor for advanced glycation endproducts

Publ.-Id: 23060

Quantitative observation of tracer transport with high-resolution PET

Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J.

Transport processes in natural porous media are typically heterogeneous over various scales. This heterogeneity is caused by the complexity of pore geometry and molecular processes. Heterogeneous processes, like diffusive transport, conservative advective transport, mixing and reactive transport, can be observed and quantified with quantitative tomography of tracer transport patterns. Positron Emission Tomography (PET) is by far the most sensitive method and perfectly selective for positron-emitting radiotracers, therefore it is suited as reference method for spatiotemporal tracer transport observations.
The number of such PET-applications is steadily increasing. However, many aplications are afflicted by the low spatial resolution (3 - 5 mm) of the clinical scanners from cooperating nuclear medical departments. This resolution is low in relation to typical sample dimensions of 10 cm, which are restricted by the mass attenuation of the material. In contrast, our GeoPET-method applies a high-resolution scanner with a resolution of 1 mm, which is the physical limit of the method and which is more appropriate for samples of the size of soil columns or drill cores. This higher resolution is achieved at the cost of a more elaborate image reconstruction procedure, especially considering the effects of Compton scatter. The result of the quantitative image reconstruction procedure is a suite of frames of the quantitative tracer distribution with adjustable frame rates from minutes to months. The voxel size has to be considered as reference volume of the tracer concentration. This continuous variable includes contributions from structures far below the spatial resolution, as far as a detection threshold, in the pico-molar range, is exceeded.
Exemples from a period of almost 10 years (Kulenkampff et al. 2008a, Kulenkampff et al. 2008b) of development and application of quantitative GeoPET-process tomography are shown. Theses examples include differnt transport processes, like conservative flow, reactive transport, and diffusion (Kulenkampff et al, 2015). Such experimental data are complementary to the outcome of model simulations based upon structural µCT-images. The PET-data can be evaluated with respect to specific process parameters, like effective volume and flow velocity distribution. They can further serve as a basis for establishing intermediate-scale simulation models which directly incorporate the observed specific response functions, without requiring modeling on the pore scale at the highest possible spatial resolution.
Kulenkampff, J., Gründig, M., Richter, M., Wolf, M., Dietzel, O.: First applications of a small-animal-PET scanner for process monitoring in rocks and soils. Geophysical Research Abstracts, Vol. 10, EGU2008-A-03727, 2008a.
Kulenkampff, J., Gründig, M., Richter, M., and Enzmann, F.: Evaluation of positron emission tomography for visualisation of migration processes in geomaterials, Physics and Chemistry of the Earth, 33, 937-942, 2008b.
Kulenkampff, J., Gruendig, M., Zakhnini, A., Gerasch, R., and Lippmann-Pipke, J.: Process tomography of diffusion with PET for evaluation anisotropy and heterogeneity, Clay Minerals, accepted 2015, 2015.

  • Lecture (Conference)
    European Geosciences Union General Assembly 2016 (EGU 2016), 17.-22.04.2016, Wien, Österreich

Publ.-Id: 23058

MHD effects in continuous casting and liquid metal batteries

Stefani, F.

This invited talk gives an overview about the recent activities of the Magnetohydrodynamics Department at HZDR related to continuous casting and liquid metal batteries. Particular focus is laid on the development and first experimental tests of the contactless inductive flow tomography (CIFT) for the continuous casting of steel, and the simulation of various MHD phenomena in liquid metal batteries.

  • Invited lecture (Conferences)
    Liquid metal processing and casting conference, LMPC 2015, 20.-24.09.2015, Leoben, Austria

Publ.-Id: 23057

The DRESDYN project: Theoretical background and planned experiments

Stefani, F.

The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is a platform for large scale experiments related to geo- and astrophysics as well as to various industrial liquid metal applications. The most ambitious parts of DRESDYN are a homogeneous hydromagnetic dynamo driven solely by precession, and a large Tayler-Couette type experiment for the combined investigation of the magnetorotational instability (MRI) and the Tayler instability (TI). We present recent numerical results on precession driven flows in cylinders and their dynamo action. We also discuss some new theoretical results on various versions of the magnetorotational instability and the Tayler instability, including magnetically triggered instabilities of rotating flows with positive shear. The progress of the construction of the DRESDYN building and of the design of the various experiments is delineated.

  • Invited lecture (Conferences)
    The Dynamo Effect in Astrophysical and Laboratory Plasmas, 07.-09.12.2015, Princeton, USA

Publ.-Id: 23056

Liquid metal experiments on dynamo action, magnetorotational instability and current-driven instabilities

Stefani, F.

Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, cosmic magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both effects, i.e. hydromagnetic dynamo action and magnetically triggered flow instabilities, have been the subject of purely theoretical investigations. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe [1,2]. Since 2006, the VKS dynamo experiment in Cadarache has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability (MRI) was observed in the PROMISE experiment in Dresden-Rossendorf [3]. More recently, the azimuthal MRI was found at the same facility [4]. First evidence of the current-driven Tayler instability in a liquid metal was obtained, too [5].
The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities. It concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project [6].

1. Gailitis, A., Lielausis, O., Platacis, E., Gerbeth, G., Stefani, F., Rev. Mod. Phys. 74 (2002), 973-990
2. Stefani, F., Gailitis, A., Gerbeth, G., ZAMM - Z. Angew. Math. Mech. 88 (2008), 930-954
3. Stefani, F. et al., Phys. Rev. Lett. 97 (2006), 184502
4. Seilmayer, M. et al., Phys. Rev. Lett. 113 (2014), 024505
5. Seilmayer, M. et al., Phys. Rev. Lett. 108 (2012), 244501
6. Stefani, F. et al, Magnetohydrodynamics 48 (2012), 103-113

  • Invited lecture (Conferences)
    Russian Conference on Magnetohydrodynamics, 22.-25.06.2015, Perm, Russia

Publ.-Id: 23055

The present status of the DRESDYN project, and some recent theoretical results

Stefani, F.

Magnetic fields of planets, stars and galaxies are produced by self-excitation in moving electrically conducting fluids. Once produced, cosmic magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, hydromagnetic dynamo action and magnetically triggered flow instabilities, have been the subject of purely theoretical investigations. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the VKS dynamo experiment in Cadarache has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability (MRI) was observed in the PROMISE experiment in Dresden-Rossendorf. More recently, the azimuthal MRI was found at the same facility. First evidence of the current-driven Tayler instability in a liquid metal was obtained, too.
The lecture gives a short overview about liquid metal experiments on dynamo action and magnetically triggered instabilities. The main part is devoted to future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project at HZDR.

  • Lecture (Conference)
    GdR Dynamo 2015, 08.-12.06.2015, Bangalore, India

Publ.-Id: 23054

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