X-Ray Study on the Radiation Damage in LiF Crystals

Abstract

The reflection intensity of x-rays was measured as a function of the distance from the irradiated outer surface to the measured location in a neutron irradiated LiF crystal; the distance was converted to thermal neutron dose. The measurements showed that the reflection intensity monotonically increased with increasing neutron dose. Rocking curves were obtained for LiF specimens, taking the irradiation conditions as parameters. The curves showed that the rocking curve broadened as irradiation proceeded, indicating that the coherent domain bocame small when neutron irradiated unless the recovery of crystalline defects actively worked.
From the above results, the extinction coefficient of LiF crystal for x-rays is concluded to decrease with neutron irradiation. The decrease of extinction is suggested to be caused by the complex color centers consisting of a cluster of defects. The clustered defects and small dislocation loops, both of which are introduced by heavy neutron irradiation, also work to make the coherent domain in LiF crystals smaller.