Volume 3, Issue 4 (April 2006)
The Neutron Spectrum of NBS-1
A proposed set of photonuclear cross sections was used to calculate the neutron spectrum of a RaBe photoneutron source. The calculation used the gamma rays from 226Ra in equilibrium as a driver, transported the gamma rays through the materials of the source, calculated neutron production, and subsequent neutron scattering. The calculation produced 27 % more neutrons than measured, and predicted relatively more low-energy neutrons.