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Neutron Scattering

Research Field

The Neutron Scattering group at the Physik-Department of Technische Universität München covers a wide and rather complete spectrum of scientific activities ranging from solid physics to materials research and applied physics. Presently, most efforts concentrate on the investigation of magnetic and superconducting properties of strongly correlated electron systems under extreme conditions and the investigation of materials properties using non-destructive nuclear techniques.

Address/Contact

James-Franck-Str. 1
85748 Garching b. München
+49 89 289 14711
Fax: +49 89 289 14713

Members of the Research Group

Office

Scientists

Other Staff

Teaching

Course with Participations of Group Members

Titel und Modulzuordnung
ArtSWSDozent(en)Termine
Methoden und Experimente in der Neutronenstreuung
Zuordnung zu Modulen:
HS 2 Morkel, C. Mühlbauer, S. Mi, 09:00–10:30, PH 2224
Seminar über Neutronen in Forschung und Industrie
aktuelle Informationen
Zuordnung zu Modulen:
PS 2 Märkisch, B. Morkel, C. Müller-Buschbaum, P.
Mitwirkende: Heiden-Hecht, T.Park, J.
Mo, 14:30–15:45, PH HS3
FOPRA-Versuch 107: Nicht-klassische Physik mit verschränkten Photonen (AEP, KM, QST-EX)
LV-Unterlagen
Zuordnung zu Modulen:
PR 1 Maanwinder Partap Singh Sigl, L.
Leitung/Koordination: Holleitner, A.
Repetitorium zu Methoden und Experimente in der Neutronenstreuung
Zuordnung zu Modulen:
RE 2
Leitung/Koordination: Morkel, C.

Offers for Theses in the Group

Calculation of the electron-positron momentum distribution at lattice defects (ABINIT)

The characterization of lattice defects with respect to their chemical environment is of outmost interest in condensed matter physics and materials science. In coincidence Doppler-broadening spectroscopy (CDBS), both annihilation quanta are detected simultaneously with two high-purity germanium detectors. The resulting background suppression enables the detection of large momenta of core electrons (large Doppler-shifts) in the outer wings of the 511 keV annihilation line. Therefore, CDBS is applied to identify the elements at the annihilation site and hence enables the detection of, e.g., foreign atom-vacancy complexes or precipitates in alloys. Within this thesis CDBS spectra resulting from positron annihilation in point defects will be calculated by using the open-source code ABINIT. This program is based on density functional theory (DFT) and allows the computation of electron and positron densities as well as wave functions in the solid. The calculated  positron lifetimes and positron-electron momentum distributions are compared with experimental results.

The project is carried out within the TUM research group Physics with Positrons.

suitable as
  • Master’s Thesis Condensed Matter Physics
Supervisor: Christoph Pascal Hugenschmidt
Determination of the Atomic Vacancy Concentration in Quenched Tungsten by Doppler-Broadening Spectroscopy of the Positron-Annihilation Line
Doppler-broadening spectroscopy (DBS) of the positron annihilation line with a mono-energetic positron beam is a highly sensitive method to characterize lattice defects within the first few microns of a sample. The creation and behaviour of such defects in tungsten is of outmost interest in nuclear fusion research where tungsten is used as inner wall material of the plasma vessel withstanding the high particle flux and heat loads. A material close to its melting point contains a non-negligible thermal vacancy concentration which can be ’frozen in’ by cooling down a sample very fast from high temperature (quenching). The resulting vacancy concentration, however, is not homogeneously distributed as the mobility of vacancies depends heavily on temperature. The goal of this work is to verify experimentally the vacancy distribution calculated theoretically. Since the probing depth ( ≈ 1.5 µm) of DBS is smaller than the depth beyond which the defect concentration is expected to level out (a few 10 µm), multiple DBS measurements are required with intermittent removal of a surface layer (1 µm to 10 µm). The sample preparation and the quenching procedure will be performed at the labs of the workgroup Ion Beam Analysis and Modification at the MPI for Plasma Physics. The project is carried out within the TUM research group Physics with Positrons.
suitable as
  • Bachelor’s Thesis Physics
Supervisor: Christoph Pascal Hugenschmidt
Determination of the positronium formation on polymer surfaces using a positron beam
Ziel der Bachelorarbeit ist es, die Bildung von Positronium über die 3-gamma-Annihilation an verschiedenen Polymeroberflächen zu beobachten. Hierzu verwenden wir einen monoenergetischen Positronenstrahl, der durch das Anlegen einer (Hoch-)Spannung auf die Probe beschleunigt wird. Die 3-gamma Annihilation lässt sich routinemäßig mit den vorhandenen Ge-Detektoren messen. Auf diese Weise lässt sich tiefenaufgelöst die Positroniumbildungsrate bestimmen. Das Projekt wird in der TUM Forschungsgruppe Physik mit Positronen durchgeführt.
suitable as
  • Bachelor’s Thesis Physics
Supervisor: Christoph Pascal Hugenschmidt
Focusing of a positron beam for depth-resolved defect spectroscopy

Unser Doppler-Verbreiterungsspektrometer ist ein hervorragendes Werkzeug zur Bestimmung der Defektkonzentration in Festkörpern. Hierzu verwenden wir einen monoenergetischen Positronenstrahl, der durch das Anlegen einer (Hoch-)Spannung auf die Probe beschleunigt wird. Die Stahlführung erfolgt durch eine Kombination aus magnetischen und elektrischen Feldern. Ziel der Bachelorarbeit ist es, die Strahlführungsparameter für einen optimalen Strahlfokus speziell im Energiebereich von wenigen eV zu optimieren und erste Messungen zur Positroniumsbildung an Oberflächen durchzuführen.

Das Projekt wird in der TUM Forschungsgruppe Physik mit Positronen durchgeführt.

suitable as
  • Bachelor’s Thesis Physics
Supervisor: Christoph Pascal Hugenschmidt
Measurement of the Age-Momentum Correlation of Positrons in Matter (AMOC)
The positron is a well-established probe to perform defect sensitive spectroscopy on all kind of materials. Typically, one can measure either the lifetime of the positron or the Doppler shift of the annihilation gamma quanta. Both methods give different insights into the concentration, distribution and size of lattice defects in the material. However, it is also possible to record both the energy shift and the time delay of the annihilation radiation simultaneously. The Age-Momentum Correlation (AMOC) technique combines gamma detection with high energy resolution and high time resolution in order to measure the correlation between positron lifetime and momentum. The thesis comprises the construction of a laboratory AMOC setup including the readout system for the detectors and data treatment. Finally, the setup will be benchmarked using an assortment of reference samples and metal alloys. The project is carried out within the TUM research group Physics with Positrons.
suitable as
  • Master’s Thesis Condensed Matter Physics
Supervisor: Christoph Pascal Hugenschmidt
Simulation of positron diffusion with applied electric fields to determine the vacancy concentration in solids (LIMPID)
Positronen können je nach Implantationstiefe im Festkörper zurück an die Oberfläche diffundieren, bevor sie annihilieren. Das resultierende Gammaspektrum – insbesondere die Form der 511 keV Annihilationslinie – ändert sich mit dem Anteil der Positronen die an der Oberfläche annihilieren. Eine Simulation der tiefenaufgelösten Diffusion erlaubt es uns, die Leerstellenkonzentration in der Probe aus bei unterschiedlichen Implantationstiefen gemessenen Daten zu bestimmen. Hauptziel der Masterarbeit ist es, den von uns entwickelten Algorithmus zur numerischen Lösung der Diffusionsgleichung in Python zu erweitern, um zusätzliche Effekte, wie variable Defektverteilungen oder elektrische Felder im Inneren der Probe zu berücksichtigen. Das Projekt wird in der TUM Forschungsgruppe Physik mit Positronen durchgeführt.
suitable as
  • Master’s Thesis Condensed Matter Physics
Supervisor: Christoph Pascal Hugenschmidt

Current and Finished Theses in the Group

Characterization of Metallic Thin-Film Systems by Depth-Dependent Doppler-Broadening Spectroscopy of the Positron Annihilation Line
Abschlussarbeit im Bachelorstudiengang Physik
Themensteller(in): Christoph Pascal Hugenschmidt
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