Prof. Dr. rer. nat. habil. Winfried Petry

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

McStas neutron ray tracing calculations of an upgrade of the small-angle scattering instrument SANS-1 with a second detector

The properties of many materials are governed by their structure on the nanoscale (20–2000 Å). This structure can be studied with many methods, with small-angle neutron scattering (SANS) probably being the premier choice if magnetic materials or polymers are involved – or if a process is to be studied in-situ, i.e. one wants to watch the nanoscopic regime while working with the sample (heating, deforming, mixing, external magnetic or electric field, …).

There are several neutron small-angle scattering instruments at the Heinz Maier-Leibnitz Zentrum (MLZ), one of which is the SANS-1, jointly operated by TUM and Helmholtz Zentrum Geestacht (HZG). It is currently equipped with a 1m by 1m neutron detector with a pixel size of 8mm x 8 mm. A second, additional, detector is to be installed at this instrument. It has a smaller pixel size, but is also smaller in overall size. In this thesis project, two scenarios are to be compared:

1. Placing the new detector further away from the sample than the current one. In this setup, even smaller scattering angles can be resolved than at the moment due to the smaller pixel size. Even larger structures than accessible at the moment can be resolved with this arrangement – but how much will be gained exactly?
2. Placing the new detector closer to the sample than the current one. In this case, a wide range of scattering angles can be covered simultaneously, so that many different length scales can be watched at the same time during in-situ measurements. Would it be possible to find instrument settings that yield a usable signal on both detectors at the same time?

The well established Monte Carlo computer simulation program McStas-model of the instrument has to be completed with the two detectors, and then the scattering of some typical samples have to be calculated and compared. The neutron counts have to be histogrammed in bins of the neutron momentum transfer. The work will be performed together with the German Engineering Materials Science team @ MLZ and offers the unique possibility to work at the MLZ, an internationally leading large scale neutron facility.

Contact: Dr. Sebastian Busch, Sebastian.Busch@hzg.de, 089 289 10764

Prof. Dr. Winfried Petry, winfried.petry@frm2.tum.de, 089 289 14704

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geeignet als

• Bachelorarbeit Physik

Themensteller(in): Winfried Petry

McStas neutron ray tracing calculations of the reflectometer REFSANS

McStas neutron ray tracing calculations of the reflectometer REFSANS

A neutron reflectometer can be used to study thin films at interfaces by illuminating the film under a shallow angle with neutrons and counting how many neutrons are reflected specularly. The reflectometer REFSANS at the Heinz Maier-Leibnitz Zentrum (MLZ) is in particular designed to look at the water-air interface. Since this interface cannot be tilted, a complex neutron optic bends the neutron beam onto this horizontal surface in order to realize different shallow angles.

There are currently two separate Monte Carlo McStas simulations of parts of the instrument: The neutron guide from the source to the start of the neutron optics, and the neutron optics itself. The task in this project is to use the output of the neutron guide simulation as input for the neutron optics simulation and to optimize the configuration of the neutron optics in the simulation for bent beams.

The work will be performed together with the German Engineering Materials Science team @ MLZ and offers the unique possibility to work at the MLZ, an internationally leading large scale neutron facility.

Contact: Dr. Sebastian Busch, Sebastian.Busch@hzg.de, 089 289 10764

Prof. Dr. Winfried Petry, winfried.petry@frm2.tum.de, 089 289 14704

geeignet als

• Bachelorarbeit Physik

Themensteller(in): Winfried Petry

Radio frequency neutron spin flipper @ SANS-1: simulation, implementation and characterization

Small-angle neutron scattering (SANS) is a powerful technique to study correlations of condensed matter samples in the range of 20–2000 Å. The new small angle scattering instrument SANS-1 is a joint project of TUM and Helmholtz Zentrum Geestacht (HZG). SANS-1 is located at the end of neutron guide NL4a in the Neutron Guide Hall West of Heinz Maier-Leibnitz Zentrum (MLZ).  SANS-1 is a standard pinhole SANS instrument with both 20 m collimation distance and 20 m sample detector distance, respectively.

For magnetic SANS with polarized neutrons a radio-frequency (RF)-Spin-flipper is required. Recently such a RF flipper has been newly built has to be installed within an air chamber.  This new flipper will undergo different optimization procedures to ensure its performance for the wide wavelength range of SANS-1.  Therefore calculations and measurements will be performed to get optimal results for the final setup.  This task requires both mechanical work, knowledge of electronics and simulations of RF magnetic fields.

The work will be performed together with the SANS-1 team @ MLZ and offers the unique possibility to work at an internationally leading large scale neutron facility like the MLZ.

Contact: Dr. André Heinemann, Andre.Heinemann@hzg.de, 089 289 14534

Prof. Dr. Winfried Petry, winfried.petry@frm2.tum.de, 089 289 14704

geeignet als

• Bachelorarbeit Physik

Themensteller(in): Winfried Petry

TISANE: AC coil setup for kinetic neutron scattering on ferro fluids

Small-angle neutron scattering (SANS) is a powerful technique to study correlations of condensed matter samples in the range of 20–2000 Å. As an extension of a standard SANS setup, TISANE (Time Involved Small Angle Neutron Scattering) is a new neutron scattering technique for time resolved kinetic neutron scattering. TISANE is able to resolve dynamic processes up to microsecond time-scales. The setup is based on two counter-rotating chopper disks installed at a standard small angle neutron scattering beamline.

Such a TISANE setup has recently been installed at the SANS-1 beamline at MLZ, jointly operated by TUM and Helmholtz Zentrum Geesthacht.  The task of this Bachelors thesis is the development, characterization and testing of new, dedicated high frequency AC coils to provide an experimental setup to study the dynamic correlations of ferro fluids (colloidal liquid made of nanoscale ferromagnetic particles in a carrier fluid) by means of time resolved SANS in a range of Hz to kHz. The task requires both mechanical work, knowledge of electronics and simulations of RF magnetic fields.

After characterization and implementation at the instrument SANS-1, the new setup will be used for experiments on ferro fluid samples. Besides the actual experiments, the second stage of the project involves the analysis and fitting of the gathered small angle neutron scattering data and requires a solid background in condensed matter physics and magnetism.

The work will be performed together with the SANS-1 team @ MLZ and offers the unique possibility to work at an internationally leading large scale neutron facility like the MLZ.

Contact: Dr. Sebastian Mühlbauer, sebastian.muehlbauer@frm2.tum.de, 089 289 10784

Prof. Dr. Winfried Petry, winfried.petry@frm2.tum.de, 089 289 14704

geeignet als

• Bachelorarbeit Physik

Themensteller(in): Winfried Petry