High energy neutrons are produced in nuclear cascade showers created by nuclear spallation reactions between cosmic rays(mainly protons)and atmospheric nuclei(nitrogen and oxygen).Atmospheric neutrons have been identified as the main cause of single-event-effects(SEE)at elevated altitudes.Avionics are vulnerable to atmospheric neutrons,which can easily produce SEE in High energy neutrons are produced in nuclear cascade showers created by nuclear spallation reactions between cosmic rays (mainly protons) and atmospheric nuclei (nitrogen and oxygen). Atmospheric neutrons have been identified as the main cause of single-event-effects (SEE) at elevated altitudes.Avionics are vulnerable to atmospheric neutrons, which can easily produce SEE in