Analysis on components of characteristic X-ray yield of pure thick targets by positron impact near threshold energy

• Published in: Europhysics letters Vol. 133; no. 4; p. 43001
• Main Authors: Ke, Z. X., Wu, Y., Pan, M., Liang, S., Xu, M. X., Zhao, Z., Wang, B. Y., Zhang, P.
• Format: Journal Article
• Language: English
• Published: Les Ulis IOP Publishing 01-02-2021
• Subjects: Atoms & subatomic particles; Backscattering; Characteristic X rays; Electromagnetic fields; Electrons; Impact analysis; Monte Carlo simulation; Photons; Positrons
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/133/43001

Abstract
In the process of low-energy positron impact with pure thick target, the atomic inner-shell ionization is induced by not only the incident positrons whose energy is completely deposited in the target but also the other particles produced during positron-target collision, namely, the backscattered positrons that deposited part of their energy before escaping the target, the annihilation photons and the secondary electrons. In this paper, the W-M
characteristic X-ray yields of two pure thick targets with different diameters impacted by a positron accelerated by the negative high voltage to 5–9 keV have been measured. The contributions from annihilation photons, secondary electrons, backscattered positrons, and the non-uniform electromagnetic field in the target chamber to the characteristic X-ray yields have been evaluated by the realistic Monte Carlo simulation. Besides, Nagashima
et al
. (
Phys. Rev. Lett.
,
92
(2004) 223201) neglected the contribution from annihilation photons, secondary electrons and backscattered positrons to the yields when calculating the cross-section by the characteristic X-ray yields of thick target impacted by a positron. Here we also caculated the contribution share of the above particles to the Cu-K and the Ag-L characteristic X-ray yields of pure thick target impact by positrons below 30 keV. The results show that the contributions from the above components are non-negligible. Hence, it is necessary to modify the experimental yields for obtaining the accurate yields of pure thick targets by non-backscattered positron impact.