Positron annihilation spectroscopy complex based on Caen digitizers

The PAS complex uses LaBr:Ce or BaF₂ scintillation detectors to measure the PALS spectra. Lifetime measurements using 22Na as a positron source are performed using a 14-bit CAEN waveform digitiser (DT5730S) operating at a 500 MHz sampling rate. Data collection and experiment control are performed using the CoMPASS user programme. Since the constant-fraction discriminator (CFD) is the most suitable method for time estimation, the CFD algorithm is applied to the original signal to obtain a bipolar zero-crossing signal for estimating the timestamp. For coincidence Doppler broadening spectroscopy (CDBS) were used two HPGe detectors (GCD 30185 from BSI, Riga, Latvia) and CAEN dual digital multichannel analyser (DT5780P), which includes two high-voltage power supplies for HPGe detectors and two built-in multichannel analysers with 16,384 channels. The device was again controlled and operated via the COMPASS user programme.