Measurement Research Of M-Shell Characteristic X-ray Production Cross Section Of Pb And Bi Impacted By Low-energy Electron And Positron

As a basic research in the field of nuclear physics,the measurement of the ionization cross section of the inner shell of atoms induced by positrons and electrons is of great significance both in theoretical research and practical application.In terms of theoretical research,reliable experimental data of the ionization cross sections of the inner shell of atoms induced by positrons and electrons can help people better understand the interaction mechanism between positrons and electrons and substances.In terms of practical application,the ionization cross sections of the inner shell of atoms induced by positrons and electrons have been widely used in many fields,such as perfecting the software database related to nuclear science,materials science,controlled nuclear fusion,radiotherapy and so on.At present,most of the published ionization cross section data of the inner shell of atoms induced by low-energy electrons and positrons are still limited,the experimental data induced by low-energy electron are concentrated in K and L shells,while the experimental data of M shells are scarce;the experimental data induced by low-energy positron are limited in K and L shell of a few elements,and the published papers have shortcomings in experimental techniques and data processing which should be verified.This work have studied and developed experimental technique and data processing in the measurement of ionization cross section of the inner shell of atoms induced by positrons and electrons.In the experiment of ionization cross section of inner shell of atoms induced by electron,the Scanning Electron Microscope is used,and the thin Bi film deposited on self-supporting thin carbon film and the thin Bi film with thick carbon substrate are impacted by electrons below 30 keV,and the correction method of the thick carbon substrate is verified,and then the L? and M?? characteristic X-ray production cross sections of Bi induced by 6-30 keV electrons are acquired.In the experiment of ionization cross section of inner shell of atoms induced by positron,the real-time incident positron's number is acquired by using high-purity germanium detector(HPGe)for recording 511 keV annihilation photon,while the incident positrons' number in others' work is rough estimated by off-time method;the f correction factor,i.e.,the contribution share of the multiple scattering of incident positrons,from the bremsstrahlung and annihilation photons and other secondary particles on the experimental characteristic x-ray yield,were calculated by PENELOPE and adopted in the correction of the experimental characteristic X-ray yield,while the part of contribution is ignored by others;as the Map characteristic peak cannot separated by X-ray spectrometer used in this work,the Map characteristic peak is divided by theoretical integration,and the Tikhonov regularization method was used to deal with the corrected experimental characteristic X-ray yield;use the above methods,the Map characteristic X-ray production cross sections of Pb and Bi induced by 6.25-8.65 keV positrons were obtained.The experimental data were compared with the theoretical predictions by distorted wave Born Approximation theory(DWBA),it indicate that DWBA theory can give a good description of the L and M-shell ionization progress for Bi induced by 6-30 keV electrons and M-shell ionization progress for Pb induced by 6.25-8.75 keV positron and Bi induced by 6.75-8.75 keV positron.In our experimental data,the Map characteristic X-ray production cross sections of Pb and Bi induced by 6.25-8.65 keV positrons is measured in the first time.