Electronic Reliability and the Environmental Thermal Neutron Flux

Abstract

Abstract : Boron, which is used in the manufacturing process of manufacturing, is highly sensitive to thermal neutrons. When ambient thermal neutrons originating from cosmic rays interact with the nucleus of boron, ionizing radiation is produced that can change the logic state of a cell on a microchip. This phenomenon is known as a Single Event Upset or Soft Error and is an important problem facing computer manufacturers. The goal of this project is to characterize the environmental thermal neutron flux with respect to electronic reliability by performing measurements of the thermal neutron flux in various locations at the United States Naval Academy and in surrounding sites. The measurements were based on the use of two He(sup 3) gas-proportional counters, one detector was bare while the other was shrouded with boron-impregnated rubber that shielded it from thermal neutrons. The different in the response between the two detectors yielded the thermal flux. The detectors were calibrated at the National Institute of Standards and Technology (NIST) and the Armed Forces Radiobiology Research Institute (AFRRI). This project produced a portable, NIST traceable, accurately calibrated thermal neutron detection system. Measurements with that system showed a relatively constant thermal neutron flux from cosmic rays at sea level.