Title :
Terrestrial thermal neutrons
Author :
Dirk, LT John D ; Nelson, Martin E. ; Ziegler, James F. ; Thompson, Alan ; Zabel, Theodore H.
Abstract :
The first NIST-traceable measurements of environmental thermal neutrons have been completed. The average sea level flux of thermal neutrons is 4 cm2/hr. This flux changes less than two times over wide varieties of terrain, in all weather conditions and over the solar year. The neutron flux is normalized to 39N-76.5W. This flux scales with geomagnetic Lat/Long and with altitude in a manner similar to the flux of incident energetic cosmic rays. The shielded flux has been measured under 450 g/cm2, with a residual flux of 0.1 times the sea-level value. Preliminary shielding studies inside buildings and under water shows significant variability in the thermal neutron mean attenuation coefficient.
Keywords :
cosmic ray neutrons; geophysical aspects of cosmic rays; neutron flux; radiation hardening (electronics); average sea level flux; environmental thermal neutrons; incident energetic cosmic rays; shielded flux; solar year; terrestrial thermal neutrons; thermal neutron mean attenuation coefficient; weather conditions; Attenuation; Cosmic rays; Geomagnetism; Military computing; Neutrons; Nuclear electronics; Pollution measurement; Rain; Sea level; Sea measurements;
Journal_Title :
Nuclear Science, IEEE Transactions on
DOI :
10.1109/TNS.2003.821587
