Physics with Positrons 2

This module is the continuation of the module Physics with Positrons I (PH2075) in which the measurement of positron lifetime was last presented. In comparison to this, measurements of electron pulse distributions and element distributions around defects with (coincident) Doppler widening spectroscopy are discussed first. With higher pulse resolution you can determine the electronic structure (Fermi surfaces) of solids by measuring the angular correlation of the annihilation radiation. The advantages of this method, in particular using positron spin, are compared with complementary techniques. Then, highly sensitive positron methods for structure measurement and elemental analysis of surfaces will be presented. Basic experiments on leptonic binding states with positrons and applications in atomic physics will be discussed. Finally, processes for the production of antihydrogen and measurements are explained. Current research results will be discussed and an outlook on future experiments will be given.

After successful participation in this module, the student will be able to

• explain experiments for the detection of crystal defects
• explain how positrons can be used to measure Fermi surfaces
• present experiments on element concentration on surfaces
• explain the basics of positron diffraction on surfaces
• to name the advantages of spin-resolved measurements
• explain the production and measurements with Positronium and the negatively charged Positronium ion
• outline basic experiments with anti-hydrogen

The module is significantly based on previous knowledge from the module Physics with Positrons I (PH2075). Apart from that, no further lectures beyond the admission requirements for the Master's programme are absolutely necessary.

In this lecture, the contents are presented by lecturing the theoretical basics and their experimental implementation, which are explained by illustrative examples. In particular, cross-references and the explanation of complementary measurement methods are used to bridge the gap to various topics. In the lecture, calculations and exemplary estimations are carried out on the basis of examples so that the students can independently explain and apply what they have learned. Great emphasis is put on stimulating interactive discussion with students about what they have just learned. This promotes students' own analytical ability to think through physical problems. The lecture contains hyperlinks and references to the relevant literature, which are intended to promote independent literature research.

Lecture with beamer presentation, blackboard presentation and discussion; lecture notes as pdf-files, supplementary literature

Textbooks in solid state and nuclear physics such as:

• C. Schaefer L. Bergmann. Lehrbuch der Experimentalphysik, Bd. 6: Festkörper. Gruyter, (2005);

• Neil W. Ashcroft and N. David Mermin. Solid State Physics. Saunders College, Fort Worth, (2001);

• G. Schatz and A. Weidinger. Nukleare Festkörperphysik, B. G. Teubner, (1997);

• Theo Mayer-Kuckuk. Kernphysik. Teubner, Stuttgart, (1984);

Positron physics:

• P. Coleman, Positron Beams and Their Applications, World Scientific, (2000).
• References to Reviews will be given during the lecture.

There will be an oral exam of 30 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using comprehension questions, discussions based on sketches and basic formulas.

For example an assignment in the exam might be:

• Describe the setup for the measurement of the angular correlation of the annihilation radiation.
• How can we make spin-resolved measurements?
• How can we produce antihydrogen?