A5025147335- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- High-pressure geophysics and materials
- Radiation Detection and Scintillator Technologies
- Shape Memory Alloy Transformations
- Microstructure and Mechanical Properties of Steels
- NMR spectroscopy and applications
- Particle Detector Development and Performance
- Nuclear reactor physics and engineering
- Thermal properties of materials
- Magnetic Properties and Applications
- Solid-state spectroscopy and crystallography
- Force Microscopy Techniques and Applications
- Rare-earth and actinide compounds
- Radiation Therapy and Dosimetry
- Microstructure and mechanical properties
- Quantum, superfluid, helium dynamics
- Advanced machining processes and optimization
- Particle physics theoretical and experimental studies
- Radiation Effects in Electronics
- Scientific Measurement and Uncertainty Evaluation
- Heusler alloys: electronic and magnetic properties
- Advanced Chemical Physics Studies
- Titanium Alloys Microstructure and Properties
- Radioactive Decay and Measurement Techniques
Philipps University of Marburg
2020
European Spallation Source
2020
Technical University of Munich
2001-2019
Heinz Maier-Leibnitz Zentrum
2007-2019
University of Iowa
2010-2017
Oerlikon (Liechtenstein)
2004
The phonon dispersions of the bcc and fcc phases pure iron ($\ensuremath{\alpha}$-Fe, $\ensuremath{\gamma}$-Fe, $\ensuremath{\delta}$-Fe) at ambient pressure were investigated close to respective phase transition temperatures. In open structure transverse phonons along T${}_{1}[\ensuremath{\xi}\ensuremath{\xi}0]$ T${}_{1}[\ensuremath{\xi}\ensuremath{\xi}2\ensuremath{\xi}]$ are particularly low energy. eigenvectors these correspond displacements needed for transformation $\ensuremath{\gamma}$...
We obtain phonon lifetimes in aluminium by inelastic neutron scattering experiments, ab initio molecular dynamics, and perturbation theory. At elevated temperatures significant discrepancies are found between experiment theory, which disappear when using dynamics due to the inclusion of full anharmonicity correct treatment multiphonon background. show that multiple-site interactions small local pairwise dominates phonon-phonon interactions, permits an efficient computation lifetimes.
We report on the structural instability of ${\text{Ni}}_{2}\text{MnAl}$ from calorimetry measurements and inelastic neutron scattering. The acoustic optical phonon dispersions along high-symmetry $[\ensuremath{\xi}00]$, $[\ensuremath{\xi}\ensuremath{\xi}0]$, $[\ensuremath{\xi}\ensuremath{\xi}\ensuremath{\xi}]$ directions have been interpolated normal modes vibration using Born--von K\'arm\'an model. tendency to undergo a martensitic transformation shows up in anomalous softening particular...
We report on the vibrational properties of ferromagnetic shape memory alloy system Ni-Mn-Ga in its stoichiometric Ni${}_{2}$MnGa and off-stoichiometric Ni${}_{49}$Mn${}_{32}$Ga${}_{19}$ compositions. Elastic inelastic neutron scattering measurements at different temperatures are presented with a focus austenite phase compared to first-principles calculations. The overall behavior full phonon dispersion is similar for both compositions remarkable exceptions...
Different diffusive motions in liquid C(32)H(66) on a picosecond time scale could be disentangled by resolution resolved quasielastic time-of-flight neutron spectroscopy (QENS). It is demonstrated that at all observation times, the dominating motion causes Q(2) proportionality of QENS signal, which indicates Fickian diffusion mechanism. The observed can characterized an dependent apparent coefficient D(a)(t(o)), up to one order magnitude larger than molecular self-diffusion D(s). By...
The radiation hardness of specific scintillating materials used in particle physics experiments is one the main focuses research detector development. This report summarizes preparation methods, light yield characterization and damage tests a plastic scintillator with polysiloxane base pTP bis-MSB dopants. shown to be promising candidate for detectors its intense output around 400 nm very little scintillation or transmission loss after proton irradiation 4 × 105 Gy.
The TOFTOF spectrometer is a disc chopper, time-of-flight and positioned in the neutron guide hall of FRM-II, some 60 m away from reactor core. All instruments hall, including spectrometer, are powered with neutrons cold source operating liquid D2 at 25 K. remote position combination an elaborate shielding concept s-shaped curved primary guide, which acts as velocity filter, results excellent signal-to-background ratio (see next). equipped system seven high-speed carbon fiber chopper discs...
Studying the phonon dispersion of ferromagnetic shape memory alloy system Ni–Mn–Ga gives insight into mechanism martensite transition and forces driving transition. Transformation austenite single crystals under uniaxial stress results in coexistence two martensitic variants with perpendicular modulation vector. Here we report on inelastic neutron scattering studies off-stoichiometric compositions, varying from non-modulated (NM) to five- (5M) seven- (7M) layer modulated phases. Both 5M 7M...
The borosilica, a very common PMT window and envelope material, contains 5% Boron (1% 10B). high cross section for 10B capturing thermal neutrons (3980 barn), is concern LHC experiments using borosilica PMTs. This study investigates the rate size of signals generated by neutron boron interaction in PMTs; Hamamatsu R7525-HA R7600U-200-M4. Although virtually all incident on borosilicate glass are absorbed, probability generating signal was measured to be 3 × 10−4 10−6 R7600U-200-M4 PMTs,...
The quasi-two dimensional Coulomb interaction potential in transition metal dichalcogenides is determined using the Kohn-Sham wave functions obtained fromab initiocalculations. An effective form factor derived that accounts for finite extension of direction perpendicular to material layer. resulting matrix elements are used microscopic calculations based on Dirac Bloch equations yielding an efficient method calculate band gap and opto-electronic properties different environments under...
Science with neutrons has a longstanding tradition in Germany, since its foundation 1957, by Heinz Maier-Leibnitz, when the first neutron source Forschungsreaktor München (FRM) started operation. With this nuclear reactor widely spread range of applications from scattering to irradiations and medical cancer treatment was envisaged beginning. Following motto “Do some thing new,” development instrumentation played an important part activities at FRM. High precision measurements length thermal...
The quartz plate calorimeters are considered as hadronic calorimeter options for upgrading Large Hadron Collider experiments. Previous studies have shown that can resist up to 12 MGy of proton irradiation. Using uniformly distributed wavelength shifting fibers embedded the plates solve problem low visible light production on Cherenkov process. Here, we report performance tests a 20-layer prototype, which is constructed with this approach. prototype was tested at CERN H2 area in and...
We investigate liquid ${\mathrm{GeO}}_{2}$ with inelastic neutron scattering at temperatures up to two times the glass transition temperature ${T}_{g}.$ Structural relaxation is still too slow be resolved by instrumental resolution. The spectra reveal a pronounced peak 3 meV. position of maximum shows no dispersion in wave number q. Over full-energy range scale Bose occupation as expected for harmonic vibrations. For energies below $\ensuremath{\simeq}2 \mathrm{meV}$ dynamic susceptibility...