Direct Measurement of the Vacancies Produced in Sodium Chloride by Fast Reactor Neutrons

Abstract

When unstrained NaCl single crystals are irradiated with gamma rays, reproducible curves of color-center, especially $F$-center, concentration vs dose can be obtained. At doses of approximately ${10}^7$ R it appears that all of the negative-ion vacancies in the crystal have been converted into $F$ centers and that they are stable at room temperature. When crystals which have been previously colored with gamma rays to this extent are bombarded with fast neutrons, and then the gamma-ray irradiations are resumed, there is an increase in $F$ center, i.e., vacancy concentration, which is proportional to the total fast neutron flux. The number of vacancies induced by the fast neutron bombardment, determined in this way, is in agreement with the theoretical treatments of Kinchin and Pease, and Seitz and Koehler.