Theoretical Research On The Production Rates Of Cosmogenic Nuclei

High energy nucleon induced reactions often occur in cosmic ray related disci-plines.When cosmic ray nuclei travel in galaxy,the nuclei will interact with extrater-restrial bodies and cosmogenic nuclei will be produced by these reactions.The cross sections for high energy reactions between proton/neutron and heavier nuclei are key parameters used to interpret experimental data.However,in many cases the cross sections for proton induced reactions do not exist.This situation is much poorer for neutron induced reactions,since the neutron is radioactive and uncharged.On the other hand,nucleon induced reactions have been described by the two-step model proposed in 1947 by Serber.In recent years,this model has been developed rapidly.The Liege Intra Nuclear Cascade model(INCL model)has been considered as one of the most ac-curate tools to simulate spallation reactions.Thus,one purpose of this work is mainly to test the validity of INCL model in calculating the cross sections of proton-induced reactions for cosmogenic nuclei using the newly compiled database of proton cross sections.In Section 2,we select 3He,10Be and 26Al as research objects.The model calculations of 3He display the rising tendency of cross sections with the increase of energy,in accordance with the experimental data.Meanwhile,the differences between the theoretical results and experimental data of production cross sections(10Be and 26 Al)are generally within a factor of 3,meaning that the INCL model works quite well for the proton-induced reactions.Based on the good agreement,we predict the pro?duction cross sections of 26Al from reactions n+27Al,n+28Si and n+40Ca,and those of 10Be from reactions n+16O and n+28Si.The results also show a good agreement with a posteriori excitation functions.On the basis of testing the validity of INCL model in calculating the proton and neutron cross sections,a physical model based on the open-source toolkit Geant4 for production rates of cosmogenic nuclei on the lunar surface is proposed and calibrated in Section 3.The fluxes of proton and neutron beneath the lunar surface are obtained by simulating the physical processes between the cosmic-ray particles and the lunar surface material.By combining the experimental proton cross sections and the a pos-teriori neutron cross sections,together with some neutron cross sections calculated by INCL model,we calculate the depth profiles of long-lived nuclei(10Be,14C,26Al,36C1,and 53Mn).Through comparing experimental and theoretical data for these nuclei,we find that for all the selected nuclei,experimental and theoretical production rate depth profiles agree well with each other by introducing a single normalization factor.It means that the physical model based on Geant4 can also reproduce the depth profiles of cosmogenic nuclei.In addition,we predict the production rates of three stable nu-clei(21Ne,22Ne and 38 Ar).According to the depth profiles of the production rates,we can also find that the neutron production rate is predominant with the depth increasing,indicating the importance of the neutron cross sections.