Ground level upsets have been observed in computer systems containing large amounts of random access memory fRAM).A~osphcric neutrons are most llkcly the major cause of the upscts based on measured data using the Weapons Neutron Rescarch (WNR) neutron beam.

Abstruct-The occurrence of single-event upset (SEU) in aircraft electronics has evolved from a series of interesting anecdotal incidents to accepted fact. A study completed in 1992 demonstrated that SEU's are real, that the measured in-flight rates correlate with the atmospheric neutron flux, and that the rates can be calculated using laboratory SEU data. Once avionics SEU was shown to be an actual effect, it had to be dealt with in avionics designs. The major concern is in random access memories (RAM's), both static (SRAM's) and dynamic (DRAM'S), because these microelectronic devices contain the largest number of bits, but other parts, such as microprocessors, are also potentially susceptible to upset. In addition, other singleevent effects (SEE's), specifically latch-up and burnout, can also be induced by atmospheric neutrons.

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