Single event upset rates on 1 Mbit and 256 Kbit memories: CRUX experiment on APEX

This paper presents the results from the CRUX experiment on the Air Force APEX satellite. The experiment monitors single event upsets on screened commercial 256 Kbit and 1 Mbit SRAMs. It is shown that trapped protons dominate the single event upset rates, as evidenced by correlation with measured proton flux peaks and with flux contours calculated with the AP8 model. Pitfalls of using generic ground test data are made clearly evident.