Contact

Porträt Dr. Schmidt, Konrad; FWKK

Dr. Konrad Schmidt

Staff scientist
HZDR High-Potential Fellow
Nuclear Physics
konrad.schmidtAthzdr.de
Phone: +49 351 260 3581
+49 351 260 3900

Eye catcher

Konrad Schmidt

Staff scientist
HZDR-High-Potential Fellow

Experimental Nuclear Astrophysics


Im Inneren des Felsenkeller Beschleunigers ©Copyright: Dr. Schmidt, Konrad

Konrad Schmidt inside the particle accelerator at the underground laboratory Dresden Felsenkeller

Foto: Konrad Schmidt

About me

I am staff scientist in the Nuclear Astrophysics group, in the Division of Nuclear Physics, at the Institute of Radiation Physics at HZDR. In addition, I am affiliated with the Joint Institute for Nuclear Astrophysics - Center for the Evolution of the Elements (JINA-CEE), USA, and member of the extended core team of the ChETEC (Chemical Elements as Tracers of the Evolution of the Cosmos) COST Action.

My research focuses on experiments understanding the processes forming the elements. In particular I am interested in nuclear reactions inside the sun and heavier stars, after the Big Bang, and related to exploding stars, as Supernovae, X-ray bursts and other scenarios. My field is experimental nuclear astrophysics where I investigate reaction probabilities with low-energy nuclear physics experiments.


Research

Big Bang related

Beschleuniger im Felsenkeller ©Copyright: HZDR/André Wirsig

Underground accelerator laboratory Dresden Felsenkeller

Foto: HZDR/André Wirsig

In the first three minutes of our Universe, the first three chemical elements were formed: hydrogen, helium and lithium. The main driver for this to happen were fusion reactions, as the nuclear reaction of hellium-3 and helium-4 to beryllium-7. In order to measure reaction probabilities, we operate a new particle accelerator in the underground laboratory Dresden Felsenkeller (see figure on the right). With its help, helium ions can be accelerated to astrophysically interesting energies. These ions then hit on other helium atoms, which are (i) implanted in a small tantalum disc, (ii) shot as a gas jet perpendicular to the ion beam, or (iii) located in a windowless gas reservoir. I'm interested in reaction probabilities which are needed for reaction network calculations, in which Big Bang nucleosynthesis standards for the abundances of the first chemical element are predicted. These abundances then can be compared well with other predictions e.g. from measurements of the cosmic microwave background or from the spectral lines of very old stars.

Sun related

The fusion of helium-3 and helium-4 to beryllium-7 is an important reaction also in the inner regions of our Sun. There, mainly hydrogen burning within the proton-proton chains and tinily (about 0.8%) the CNO-cycle contribute to Sun's energy production. With the help of the new underground particle accelerator Dresden Felsenkeller a wide range of nuclear reactions can be studied. This will result in important abundances from the lightest elements up to carbon (C), nitrogen (N) and oxygen (O). Threrby, I am intersted in neutrino-producing reactions, since detectors as e.g. Borexino are able to measure the flux of those solar CNO-neutrinos. Hence, next to helioseismology and the analysis of the solar spectral lines, neutrinos created by nuclear reactions deep inside are another method to observe our Sun.

Supernova related

Hubble’s view of supernova explosion Cassiopeia A ©Copyright: © NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

Hubble’s view of supernova explosion Cassiopeia A

Foto: © NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

Titanium-44 is a radioactive isotope of the 22nd element in the periodic table. It is created in supernovae and can be detected in their remnants, as e.g. Cassiopeia A (see figure on the left). With the help of satellite-based gamma-ray spectrometers, titanium can be observed together with radioactive iron, silicon, magnesium and more.

With a titanium-44 half-life of about 60 years and a supernova rate in our Galaxy between two and three per century, several supernova remnants are expected to show signatures of titanium. However, much to the surprise of astrophysicists, so far radiation from the decay of titanium-44 has been observed only for one supernova remnant in the Milky Way, Cassiopeia A. Several other remnants of recently studied supernovae did not show the expected emission. This contradiction leads to an exciting question in astrophysics.

In order to examine whether the currently accepted supernova models are correct nuclear reaction rates need to be determined. Dedicated sensitivity studies have shown that the reaction rate of helium-4 with calcium-40 is one of the most important parameters of these models.

In this context,  am interested to study individual resonances in this reaction with stable, high intensity, low energy ion beams provided by the 3-MV Tandetron at the Ion Beam Center (IBC) on the main campus of HZDR, by the platform AIFIRA (Applications Interdisciplinaires des Faisceaux d’Ions en Région Aquitaine) at the Centre Etudes Nucléaires de Bordeaux Gradignan (CENBG), France, and at the new shallow-underground accelerator laboratory Dresden Felsenkeller. Thin calcium targets have been fabricated at the GSI target laboratory and at the Institute for Nuclear Research (ATOMKI, Hungarian Academy of Sciences (MTA) to determine the resonance strengths with methods of gamma spectroscopy, firstly by the measurement of propt gamma rays emitted when the helium ion beam hit the calcium target and secondly by counting the decays of the produced titanium-44 nuclei at ultra-low background detectors at Dresden Felsenkeller. The latter will be supplemented with accelerator mass spectrometry, prospectively.

X-ray burst related

JENSA Targetkammer mit Düse und Gasfänger umgeben von Silizium-Detektoren am NSCL/MSU ©Copyright: Dr. Schmidt, Konrad

JENSA JENSA target chamber with nozzle and receiver surrrounded by silicon detector arrays at NSCL/MSU

Foto: Konrad Schmidt

When a neutron star accretes the outer layers of its binary companion, material, mostly hydrogen and helium, accumulates on the neutron star surface resulting eventually in a thermonuclear ignition and runaway. The explosive buring of the accreted layer is observed as an X-ray burst. The burst disrupts the accretion disk but leaves the neutron star relatively unscathed, such that the process can repeat itself on the order of weeks, days, or even hours.

During the thermonuclear explosion, temperatures of more than one billion Kelvin can be achieved, triggering several reaction chains, as the triple-alpha process, the Hot CNO cycle that breaks out into the alpha-proton process that in turn leads to the rapid proton capture process.

Related, previously inaccessible reactions can be studied with the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target at the National Superconducting Cyclotron Laboratory (NSCL) on the campus of Michigan State University (MSU). JENSA is a multi-institutional collaboration led by Oak Ridge National Laboratory (ORNL).

In a stand-alone mode, JENSA enables to study reactions emitting charged particles as alpha-proton reactions. Further, JENSA is planned to be the main target of the Separator for Capture Reactions (SECAR) at the Facility for Rare Isotope Beams (FRIB). In this configuration, JENSA will enable to study proton and alpha capture reactions and hence aiming at understanding X-ray bursts.


Teaching

Summer term 2020

Winter term 2019/20

Summer term 2019

Winter term 2018/19

Summer term 2013

Summer term 2012

Summer term 2011

Winter term 2007/08


Contact me

  Dr. Konrad Schmidt
Division of Nuclear Physics
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
Bautzner Landstr. 400
01328 Dresden, Germany

+49 351 260 3581 (Rossendorf)
+49 351 260 3900 (Felsenkeller)

konrad.schmidthzdr.de

Contact

Dr. Konrad Schmidt

Staff scientist
HZDR High-Potential Fellow
Nuclear Physics
konrad.schmidtAthzdr.de
Phone: +49 351 260 3581
+49 351 260 3900