Experiments have shown that there is a critical threshold energy deposited from an incident ion or proton is needed to trigger a SEE.
For protons, this energy deposition usually takes place through nuclear interactions which result in recoil ions that ionise the impact location’s neighbourhood. Most devices experience SEEs for incident protons of energy 10 MeV and above while recent research points to a 1.5-3 MeV acute sensitivity for modern electronics.
Regarding heavy ions, SEE is triggered via direct ionisation along its path inside the device. In that case, the more convenient energy loss metric is not particle Energy but Linear Energy Transfer (LET) which is the rate of energy loss per unit length on a material. The most common unit used for it is MeV-cm2/mg.
Commercial devices are susceptible to ions of LET as low as a couple of MeV-cm2/mg. More resistant devices present a threshold LET between 15 and 60 MeV-cm2/mg. Last, devices with a LET threshold higher than 150 MeV-cm2/mg are considered SEE-immune and reliable even at the harshest interplanetary environments.
As with the other radiation effects that we discussed, the expected on-orbit rate of SEUs depends on the radiation environment, that is energy flux spectrum of charged particles, and the specific device.
SEUs records during LEO missions such as PROBA-II and SAC-D observe an average error rate ranging from 0.1 to 1 SEU/day for commercial devices. These single event upset rates can decrease by a minimum of five orders of magnitude for radiation hardened counterparts.
As mentioned before in this article, SEEs can be regrouped into two categories: soft errors (non-destructive) and hard errors (destructive):
Copyright 2023 All rights reserved.