Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

Abstract

Measurements were performed of K-shell ionization cross sections of Ti element by 10∼30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thicktarget method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X-and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation (DWBA) theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.

Experimental study on the Ag L-shell X-ray production cross-sections with thick-target method induced by positrons up to 9 keV

“…with the few experimental data of positron impact (for example, the DWBA values multiplied by 0.67, 0.75 and 0.80, respectively, are consistent with the L-shell experimental data of Ag, In and Sn by Nagashima et al) [5]. To the best of our knowledge, the measurements for atomic inner-shell ionization or X-ray production cross-sections by positron impact near the threshold energy are restricted to the K shell of Ti [6,7], Cu [3] and Ag [2], L shell of Ag [3,4], In and Sn [4], L3 sub-shell of Au [2], M shell of Pb and Bi [8]. In the above experimental studies, the positron beams were all generated by the slow positron beam device based on the 22 Na radioactive source, and except for refs.…”

“…In the above experimental studies, the positron beams were all generated by the slow positron beam device based on the 22 Na radioactive source, and except for refs. [7,8], the positron beam intensities were all acquired by using the off-line method, which assumes the beam current is almost constant [2][3][4][5][6] in the experiment, the beam intensities are all determined at the beginning of the experiment. As we know, the intensity of the positron beam produced from a 22 Na positron source is low, in general, less than 10 6 n/s; as a result, the measurement for each incident energy requires a long time, e.g., 2-3 days [3,6].…”

“…[7,8], the positron beam intensities were all acquired by using the off-line method, which assumes the beam current is almost constant [2][3][4][5][6] in the experiment, the beam intensities are all determined at the beginning of the experiment. As we know, the intensity of the positron beam produced from a 22 Na positron source is low, in general, less than 10 6 n/s; as a result, the measurement for each incident energy requires a long time, e.g., 2-3 days [3,6]. However, the 22 Na radioactive source has a relatively short half-life, i.e., 2.6 years.…”

“…In addition, in the experimental study of atomic inner-shell ionization induced by low-energy positron with the thick-target method, the effects of the multiple scattering of incident positrons, from the bremsstrahlung and annihilation photons, and the other secondary particles on the characteristic X-ray yields, which have been calculated by us, cannot be easily ignored [8]. However, these effects had been neglected in others' experiments [3,4,6]. Besides, we also noticed that the efficiency calibration of the X-ray detector in the others' measurements were determined by using calibrated radioactive sources [3,4] or the whole Monte Carlo simulations [6].…”

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

“…It is of great significance to obtain the accurate characteristic X-ray yields by positron impact ionization in theoretical research, accurate yields can help to understand the mechanism of positron-atom interaction effectively. Besides, characteristic X-ray yields play an important role in various practical fields, such as nuclear fusion, plasma physics, and astrophysics [2][3][4].…”