The pion single-event latch-up cross-section enhancement : mechanisms and consequences for accelerator hardness assurance

Abstract

Pions make up a large part of the hadronic environment typical of accelerator mixed-fields. Characterizing device cross-sections against pions is usually disregarded in favour of tests with protons, whose single-event latch-up cross-section is, nonetheless, experimentally found to be lower than that of pions for all energies below 250 MeV. While Monte-Carlo simulations are capable of reproducing such behavior, the reason of the observed pion cross-section enhancement can only be explained by a deeper analysis of the underlying mechanisms dominating proton-silicon and pion-silicon reactions. The mechanisms dominating the single-event latchup response are found to vary with the energy under consideration. While a higher pion nuclear reaction rate, i.e., probability of interaction, can explain the observed latchup cross-section enhancement at energies > 100 MeV, it is the volume-equivalent linear energy transfer (LETEQ) of the secondary ions that keeps the pion latchup response high at lower energies. The higher LETEQ of secondary ions from pion-silicon interactions are caused by the pion absorption mechanism, which is highly exothermic. In spite of the observed higher cross-section for pions, the high-energy hadron approximation is found to still provide reliable estimations of the latch-up response of a device in mixed-field.