The Research Of Self-supporting Thin Grid Target On The Measurement Of W Element L And M-shell X-ray Production Cross Sections Impacted By 5-30 KeV Electrons

Atomic inner-shell ionization cross sections caused by low energy electron and positron play an important role in the field of atomic physics.In one side,the measured data could provide a sound proof to the accuracy of the theoretical models.In another side,the cross sections data help us to explore the interaction mechanism of electron or positron with atoms.For the measurements of inner-shell ionization cross sections impacted by low energy electron are mainly distributed in K and L-shell,and there are only a few elements can be found for M-shell.Discrepancies still exist in the data which are presented by different authors.As we know,the targets which have been used in the inner-shell ionization cross sections measurements can be summarized as four kinds: thin film deposited on self-supporting thin film target,thin film deposited on thick substrate target,the pure thick target and gasses target.Using the thin film deposited on self-supporting thin film target could get more accurate data,but it is hard to prepare and transport.Because the effect of the target substrate,the thin film deposited on thick substrate target and the pure thick target will bring some correction errors.For the gasses target,it can reduce the effects of the multiple scattering of the incident electrons but it can only be prepared for some special elements.In order to resolve the above issue,we propose a new kind of target named thin film deposited on self-supporting thin carbon grid target.This kind of target is prepared by depositing thin film?few nanometers thick?on self-supporting thin carbon grid?20 ?g/cm² thick?.The self-supporting thin carbon grid is made of high strength super-aligned carbon nanotube arrays.Besides,because of the thickness of thin carbon grid substrate,the corrections caused by the substrate could be ignored,and it is more convenient to preserve and transport than the target of thin film deposited on self-supporting C film.In this paper we mainly undertook the following work.Firstly,three kinds of thin film deposited on self-supporting thin carbon grid target?thin film deposited on thin carbon grid target with a layer of monoatomic carbon between the film and the grid substrate,thin film deposited on thin dense carbon grid target and the thin film deposited on thin sparse carbon grid target?are prepared to measure the L_?,L_? and M_?? X-ray production cross sections of W element induced by 5-30 keV electron and compare our measured results with the DWBA theoretical predictions.Secondly,we also measured the L_? and L_? X-ray production cross sections of W element induced by 5-30 keV electron on the equal experimental setting by using the thin film with thick carbon target.The effect of directional and energy spreads of the incident electron beam within the films and the characteristic X-ray enhancement due to backscattered electrons and bremsstrahlung photons generated from the substrates are corrected by the Penmain subroutine package in the PENELOPE code.We compared the experimental results measured by the two different kinds of targets.Thirdly,for the three different kinds of self-supporting carbon grid target,The DWBA predictions are in good agreement with the experimental results for the thin film deposited on thin carbon grid target with a layer of monoatomic carbon between the film and the grid substrate and the thin film deposited on thin dense carbon grid target.So the first two kinds of targets are fit for the measurements on atomic inner shell ionization impacted by low energy electrons.For thin film deposited on thin dense carbon grid target,the gaps with the DWBA predictions are fairly big and it is not fit for the measurements on atomic inner shell ionization impacted by low energy electrons.For the thin film with thick carbon target,the L_? and L_? experimental data are consistent with the first two kinds of self-supporting carbon grid targets.Besides,we firstly present the M_?? X-ray production cross sections of W element by 5³0 keV electron impact in this paper.