The Study Of Modified Algorithm For Inner-shell Cross Sections Impacted By Positron And Electron With Low Energy By Using Thick Target

The study on the measurement of atomic inner-shell ionization cross sections impacted by electron and positron at low energy is of great significance in lepton-atom interaction modelling and practical applications.In theoretical research,the theoretical models proposed at present need to be tested by accurate ionization cross-section data and then promote the development of theoretical models.In practical application,the inner-shell ionization cross-sections induced by positron and electron is widely used in material science,plasma physics,atmospheric physics and astrophysics and other fields.At present,the experimental ionization cross-sections induced by positron and electron are still fairly scarce,which is due to the lack of experimental techniques.There are thin target-method and thick target-method to obtain the ionization cross sections.The thin-target method has limitations in the preparation of the target sample type,so it is necessary to develop the thick-target method to measure the ionization cross section.When using the thick-target method to obtain ionization cross sections,the scattering effect of positron and electron is serious when colliding with the thick target.And the annihilation photons generated during the positron-atom collision would increase the characteristic X-ray counts.In addition,other secondary particles may also add additional characteristic X-rays.So the contributions of these effects to the characteristic X-ray yields need to be deducted.However,the published cross sections by positron or electron impact using thick-target method have not been corrected.Based on this status quo,the main work carried out in this paper are as follows.Firstly,the ionization cross sections by positron and electron impact in the PENELOPE database based on the ODM optical database were replaced with the corresponding DWBA theoretical prediction values.Secondly,the correction results by positron and electron below 30 keV impacted on the thick target could be calculated by Monte Carlo real simulation in combination with the theoretical integral formula,and the corrected results are used to revise the published data of thick-target method.Thirdly,through the Monte Carlo real simulation,the contributions of primary particles and the above components to the characteristic X-ray yields are obtained during the collision between the particles and the thick target.The conclusions of this work are as follows:The cross sections provided by others have not considered to correct the contributions of secondary particles and the multiple scattering of incident particles to the characteristic X-ray yields,which would result in an inaccurate cross section.When the electron below 30 keV impacting on the thick target,the contribution to the characteristic X-ray yields is mainly derived from the primary incident electrons,and the contribution of secondary electrons and bremsstrahlung photons to the yields could be negligible.In the process of positron collision with pure thick targets(Ti,Ag,Pb and Bi),when the incident positron energy is close to the ionization threshold energy,the contribution to the characteristic X-ray yields is mainly derived from the annihilation photons.As positron energy increases,the contribution of annihilation photons to the yields is gradually reduced,and the contribution of primary positrons to the yields is dominant.