Study of the background in the experiments of inner-shell ionization of atoms by positron impact

One of main difficulties in the experiments of inner-shell ionization of atoms by positron impact near threshold energy region is the relatively high low-energy background, which is caused by the deposited part of energy in semi-conductor X-ray detectors of 0.511 MeV gamma rays that are produced by positron annihilations in targets and target chamber. In this paper, by using the Monte Carlo method, we simulated the backgrounds for the X-ray detectors with the sensitive layer thickness of 0.3 mm and 3 mm in the case of 0.511 MeV gamma rays impacting vertically on a Ti plate of 0.2 mm. in thickness, and compared the simulation results with the experimental observations of the other research group and our own. Moreover, we also simulated the backgrounds for a simplified experimental setup in the case of 20 keV positrons impacting. vertically on a thick Ti target and observed that the backgrounds for the X-ray detectors with the sensitive layer thickness of 0.3 mm and S mm, are very similar.