The Pion Single-Event Latch-Up Cross Section Enhancement: Mechanisms and Consequences for Accelerator Hardness Assurance

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 favor of tests with protons, whose single-event latch-up (SEL) 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 for 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 SEL response are found to vary with the energy under consideration. While a higher pion nuclear reaction rate, that is, probability of interaction, can explain the observed latch-up cross-section enhancement at energies >100 MeV, it is the volume-equivalent linear energy transfer (LET EQ ) of the secondary ions that keeps the pion latch-up response high at lower energies. The higher LET EQ of secondary ions from pion–silicon interactions is 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 fields.