Answer to Question #3172 Submitted to "Ask the Experts"

There is no simple answer for this question, as it depends on the electronic equipment, shielding of components, their composition (that is, atomic number), gamma energy, and perhaps most importantly, the total dose delivered. Nonetheless, if the manufacturers of the equipment have not tested it, they should be able to provide a component list. NASA (National Aeronautics and Space Administration) is very much involved with this type of research, as such equipment is in the space environment and subject to high radiation fields for prolonged duration. Keep in mind, gamma rays have to interact to deposit energy and cause damage, thus you should examine electron effects. The NASA Web site has a great deal of information, with searchable databases.

In particular, the two paragraphs below are introductions to two areas on this Web site:

"Single Event Effects (SEEs) are caused by a single, energetic particle, and can take on many forms. Single Event Upsets (SEUs) are soft errors, and non-destructive. They normally appear as transient pulses in logic or support circuitry, or as bitflips in memory cells or registers. Several types of hard errors, potentially destructive, can appear: Single Event Latchup (SEL) results in a high operating current, above device specifications, and must be cleared by a power reset. Other hard errors include Burnout of power MOSFETS, Gate Rupture, frozen bits, and noise in CCDs."

"Total Ionizing Dose (TID) Effects. Electronic devices suffer long-term radiation effects, mostly due to electrons and protons. The main sources of these particles are Solar Energetic Particle Events—which usually occur in association with solar flares—and the South Atlantic Anomaly (SAA)—where the Earth's magnetosphere dips closest to the earth, causing more trapped radiation. Cumulative long-term ionizing damage due to protons and electrons can cause devices can suffer threshold shifts, increased device leakage (& power consumption), timing changes, decreased functionality, etc."

David J. Allard, CHP