Research of influential factors on pulsed μSR spectra using Monte Carlo simulations

Abstract

The quality of pulsed μSR spectra are affected by several factors, namely beam time structure, the time width of detector signals, signal processing methods. A Monte Carlo simulation code—“MuSS” (Musr Signal Simulation) has been developed to investigate the influences of all these factors. Simulations show that both beam time width and external transverse field decrease the observable asymmetry. The asymmetry reduces quickly with larger beam time width under strong filed (> 100 Gauss). The deadtime calculated by leading-edge or constant fraction discrimination method shows no big differences. Bias voltage setup in the constant fraction discriminator should be small (in the range (−10, 10) mV). A figure of merit is used to quantify the maximum tolerable event rate of μSR detectors. Using a proper pole-zero circuit, the deadtime of the Chinese μSR detector can be reduced from ∼ 14 to ∼ 7 ns. Therefore the maximum tolerable event rate can be increased from 8 to 12 events/frame/detector.