SPOT IL - Slow positron facility in Israel

Abstract

A slow positron facility is being built in Israel, at the Hebrew University, for basic and applied research. It consists of a slow positron beam and a compact Positrons Annihilation Lifetime (PAL) spectrometer. The slow positron beam follows a traditional design, using a 22Na source, of about 40mCi, a Tungsten moderator and a unique grounded target cell, with positrons energy that can vary between 0.03 keV and 30 keV. The detection system will be comprised of High Purity Germanium and BaF2 detectors, facing each other, for low background Doppler Broadening (DB) measurements. The target cell is designed to allow a combined measurement of sample conductivity and DB, with the flexibility to add more detection options in the future. The compact PAL spectrometer includes two fast scintillation detectors read by a fast digitizer (DRS4), with a sampling rate of 5.12 GS/s. A dedicated software package was developed to emulate analogue data acquisition. Lifetime measurements were performed using a ∼25 µCi 22Na source. The time resolution was defined using a 60Co source, to be 180-200ps. First positron lifetime validation measurements of Ti resulted in positrons lifetime of 157 ± 4 ps, consistent with previously published values.