Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

Abstract

Abstract. The Helmholtz-Zentrum Dresden-Rossendorf operates a superconducting linear accelerator for electrons with energies up to 35 MeV and average beam currents up to 1.6 mA. The electron beam is employed for production of several secondary beams including X-rays from bremsstrahlung production, neutrons, and positrons. The secondary positron beam after moderation feeds the Monoenergetic Positron Source (MePS) where positron annihilation lifetime (PALS) and positron annihilation Doppler-broadening experiments in materials science are performed in parallel. The adjustable repetition rate of the continuous-wave electron beams allows matching of the pulse separation to the positron lifetime in the sample under study. The energy of the positron beam can be set between 0.5 keV and 20 keV to perform depth resolved defect spectroscopy and porosity studies especially for thin films.

Zinc Oxide Defect Microstructure and Surface Chemistry Derived from Oxidation of Metallic Zinc: Thin‐Film Transistor and Sensor Behavior of ZnO Films and Rods

“…The positron lifetime investigations were performed at the Monoenergetic Positron Spectroscopy (MePS) beamline, which is the end station of the radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) at HZDR, Germany. [68] A digital lifetime CrBr 3 scintillator detector with homemade software operating on SPDevices ADQ14DC-2X hardware with 14-bit vertical resolution, 2GSs À1 horizontal resolution, and with at ime-resolution function down to about 230 ps was utilized. All spectra contained at least 5 10 6 counts.…”

Vacancy-Hydrogen Interaction in Niobium during Low-Temperature Baking

“…Measurements in the presented work were taken in a collaborative effort using four different setups, which were used to cross-check individual measurements but also complemented each other. Depth resolved VEPAS studies of sub-surface region were carried out at the Helmholtz Zentrum Dresden-Rossendorf on a continuous slow positron beam 'SPONSOR' 45 and ' AIDA' 46 employing DB spectroscopy (DB-VEPAS) as well as on a pulsed positron beam MePS 47,48 of the ELBE facility employing positron lifetime measurement (VEPALS). The spot size diameter of the positron beams were in the order of 3-5 mm and the energy of incident positrons was variable in the range 0.03-36 keV for DB-VEPAS (it corresponds to the mean positron penetration depth into Nb from 0.02 to 1380 nm) and 1-10 keV for VEPALS (it corresponds to the mean positron penetration depth into Nb from 4.7 to 394 nm).…”

Defects in Thin Layers of High Entropy Alloy HfNbTaTiZr

“…The positron annihilation lifetime spectroscopy (PALS) measurements were performed at the monoenergetic positron spectroscopy (MePS) beamline [10] at the ELBE (Electron Linac for beams with high Brilliance and low Emittance) facility at the Helmholtz-Zentrum Dresden-Rossendorf. Positron lifetime spectra were measured using a digital spectrometer with the time resolution of 250 ps (FWHM of resolution function).…”