Comparison of the Proton and Neutron SEE Cross Sections for Devices With High-LET Thresholds

It is widely recognized that the proton and neutron single-event effect (SEE) cross sections are nearly equal above 50 MeV. The purpose of this article is to explore whether this conclusion holds true for devices with high linear energy transfer (LET) thresholds, which is interesting and important. We predict the proton and neutron single-event latchup (SEL) cross sections of two static random access memories (SRAMs) with LET threshold greater than 15 MeV<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>cm2/mg in the 20 MeV to 10 GeV region. Their proton and neutron SEL cross sections are dominated by the p+W and n+W reactions, respectively. We find that the neutron SEL cross sections are much lower than the proton ones even at 1 GeV, which breaks the widely accepted conclusion. The difference between them has nothing to do with whether there is a Coulomb barrier between the incident particles and tungsten. The proton and neutron SEL cross sections are mainly contributed by the fission fragments from the fission reactions triggered by protons and neutrons in tungsten. Consequently, the W(p,f) and W(n,f) cross sections determine the trend of the proton and neutron SEL cross sections with energy and determine the difference between them. The difference between the W(p,f) and W(n,f) cross sections results from that between the fission probabilities of the composite nuclei Re and W. Our study on another SRAM indicates that the widely accepted conclusion holds true for devices with low-LET thresholds, whose proton and neutron SEE cross sections are dominated by the p+Si and n+Si reactions, respectively.