Buffer-gas positron traps (BGT) are invaluable for high-resolution matter-antimatter interaction studies, antihydrogen research, and positronium laser spectroscopy. These devices exploit inelastic interactions between positrons and nitrogen molecules to accrue a nonneutral $e^+$ plasma [1]. We present plans to produce short pulses of very low-energy positrons by installing a BGT at the NEPOMUC...
Magnetic dipole traps have demonstrated good confinement properties for both non-neutral and quasi-neutral plasmas, making them highly suitable for the creation and study of low-temperature, long-lived electron-positron pair plasmas. To generate such a plasma, the APEX (A Positron-Electron eXperiment) Collaboration is planning to inject positrons (supplied by the reactor-based beam NEPOMUC,...
Optimization of the shape and intensity of a positron beam requires suitable beam diagnostics. The speed with which a low-energy positron beam can be optimized prior to a measurement is presently limited by available detection techniques, resulting in a sizeable loss of beam time to optimization. In this talk we will present two novel approaches to the detection of the position, shape and...
LIMPID (Layer-wise Investigation of Measurements on Positron Implantation and Diffusion) is a new analysis tool for positron depth profiles generated by variable energy Doppler-broadening spectroscopy. It allows the user to extract positron diffusion lengths by fitting the measured lineshape parameters as a function of implantation energy. The code is written in Python and open source, thereby...
The ultimate goals of the APEX (A Positron Electron eXperiment) Collaboration are the generation and investigation of conned, strongly magnetized, electron-positron plasmas in the laboratory. The mass symmetry of such plasmas simplifies many aspects of their physics, as has been described in more than four decades of theory/simulation predictions.
Our road map to conducting experimental...
The Coincidence Doppler-Broadening (CDB) spectrometer at NEPOMUC has recently been upgraded with six additional HPGe Detectors, bringing the total number of detectors to ten. To take full advantage of the even more capable instrument, a novel data evaluation software package (STACS) is currently under development. The software can already handle and visualize the data generated by Coincidence...
The pulsed positron beams PLEPS and SPM are user facilities at the intense positron source NEPOMUC for defect depth-profiling by means of positron lifetime measurements.
PLEPS uses a monochromatic pulsed positron beam of variable implantation energy and 1 mm diameter. It enables a quantitative and non-destructive characterization of open volume defects, e.g. vacancies, grain boundaries,...
Orthorhombic Barium di-silicide (BaSi2) is an emerging sun light conversion material for thin film solar cells, owing to its suitable bandgap, high light absorption coefficient, and long minority-carrier lifetime. Moreover, Ba and Si are very abundant and environmentally benign materials. The nature of defects in BaSi2 thin films grown by Molecular Beam Epitaxy (MBE), Thermal Evaporation (TE),...
The bright low-energy positron beam provided by the neutron induced positron source in Munich (NEPOMUC) at FRM II is used in a large variety of experiments in materials science, condensed matter and surface physics as well as in fundamental research, e.g., for the creation of a positron-electron pair plasma. Within this contribution, an overview of the current status and developments of the...
Variable energy positron annihilation lifetime measurements and related density functional theory calculations of positron lifetimes are presented and discussed for two emerging thin film photovoltaic materials, the binary semiconductor Sb$_2$Se$_3$ and the halide perovskite MAPbI$_3$. Measurements on a series of Sb$_2$Se$_3$ thin film and single crystal samples are presented. DFT calculations...
