The Cyber Security Transparency Centre in Brussels

Original text published in German: Christoph Hugenschmidt, Wie Huawei Cybersecurity praktiziert und wie transparent das wirklich ist - Ein Besuch im Cyber Security Transparency centre in Brüssel, in Marc Furrer (Ed.), Selbstbestimmt. Sind Souveräne Kommunikationsnetze in der Schweiz möglich?, Stämpfli Verlag, Bern, 2022, 89-95. Published in English with permission of the publisher

CDBS: Coincident Doppler-broadening spectrometer

The CDBS, operated by the Technische Universität München, located at NEPOMUC, allows the detection of open volume defects and their chemical surrounding. Defect distributions can be imaged in 3D by lateral scanning with the energy variable positron beam

PAES: Positron annihilation induced Auger electron spectrometer

Positron annihilation induced Auger electron spectroscopy (PAES) is a newly developed application for surface studies with high elemental selectivity and exceptional surface sensitivity. The instrument is operated by the Technische Universität München and is located at NEPOMUC

NEPOMUC: Neutron induced positron source Munich

NEPOMUC, operated by the Technische Universität München and the Universität der Bundeswehr München, provides a high-intensity low-energy positron beam for applications in solid state and surface physics as well as for fundamental research in nuclear and atomic physics. The intensity amounts to > 109 moderated positrons per second at a beam energy of E = 1 keV

Absolute fraction of emitted Ps determined by GEANT4 supported analysis of gamma spectra

The fraction of positronium (Ps) emitted from a surface of a germanium single crystal at high temperature is usually assumed to approach unity at zero positron implantation energy. In the experiment, however, the determination of the absolute Ps fraction is not straight forward since recording a reference spectrum with $100\,\%$ Ps formation remains demanding. We use GEANT4-simulated detector responses to $2\gamma$ and $3\gamma$ radiation sources mimicking positron and Ps annihilation inside the (coincidence) Doppler-broadening spectrometer at NEPOMUC, FRM II, in order to derive a reliable value for the Ps fraction reemitted from a Ge(100) target heated close to its melting point. Analysis of the measured spectra by fitting the simulated spectra shows an absolute value of $(72\,\pm{4})\,\%$ maximum Ps formation, contradicting the $100\,\%$ assumption