Conveners
Positrons: Positrons I
- Christoph Hugenschmidt
Positrons: Positrons II
- Christoph Hugenschmidt
Positrons: Positrons III
- Christoph Hugenschmidt
Buffer-gas traps (BGT) can efficiently accumulate positrons from a continuous source into a dense, low-energy nonneutral plasma. Inelastic collisions between positrons and nitrogen molecules promote capture of the former in the electric potential minimum created by a series of cylindrical electrodes in a uniform magnetic field. Usually, the positron source is a neon-moderated radioisotope of...
Predicting helium retention in tungsten is of relevance for future nuclear fusion reactors as it influences tritium uptake and transport, the latter effects being a critical question to achieve tritium self-sufficiency.
While the macroscopic effects of helium agglomeration in tungsten are known it is still an open topic of discussion what the underlying processes on a microscopic scale are....
Positron annihilation lifetime spectroscopy (PALS) is a powerful tool for defect detection and characterization in material science. To investigate inhomogeneous defect distributions, e.g. close to fatigue cracks or dispersive alloy, with PALS a monochromatic pulsed positron beam of variable energy with a diameter in the range of 1 µm and a pulse width of 150 ps FWHM is needed. To this aim the...
We developed a new analysis tool for positron depth profiles generated by variable energy Doppler-broadening spectroscopy. It allows users to extract positron diffusion lengths by fits to the S parameter measured as a function of implantation energy. The code written in Python is easily accessible and adaptable. In this talk we present the theoretical background of the algorithm implemented,...
To form an electron-positron plasma in the 10L volume of a levitated dipole, large numbers of low-energy positrons are needed. The APEX (A Positron Electron eXperiment) collaboration plans to use a combination of multiple Penning-Malmberg traps for the accumulation of such large numbers, which will be installed at the NEPOMUC facility.
In this contribution we introduce the high-field...
A Positron-Electron eXperiment (APEX) aims to produce a magnetically confined, low temperature positron-electron plasma in order to test predictions that such a system with equal mass but oppositely charged species, in contrast to nearly all laboratory and astrophysical plasma, is remarkably stable and exhibits other unique plasma characteristics. The magnetic trap consists of a levitated...
Gallium nitride (GaN) and related alloys [(AlGaIn)N] are promising materials for next generation power electronics. For GaN, for example, because of its wide bandgap, high saturation electron velocity, sufficient thermal conductivity, and high breakdown voltage, it yields a higher figure of merit compared with that of other semiconductors for power devices such as Si and SiC. The presence of...
The Pulsed Low-Energy Positron System PLEPS [1] is a user facility for defect depth-profiling by means of positron lifetime measurements with a monochromatic pulsed positron beam of variable energy ranging from 0.5-21 keV at the intense positron source NEPOMUC at the MLZ in Garching [2].
To further extend the scope of defect characterization of PLEPS various possibilities of in-situ...
Low-energy positron beams can only be handled inside of high vacuum chambers. As ordinary electronic construction relies on a suite of materials which is not compatible with ultra-high vacuum it is necessary for conventional electronics to be installed on the outside of experimental chambers and beamlines. In this talk we'll showcase our most recent endeavors in overcoming this limitation by...
