Influence of processing techniques on the VUV transmittance and mechanical properties of magnesium fluoride crystal

The affect of sample position and processing technique on the vacuum ultra-violet transmission and biaxial bending strength of magnesium fluoride crystal specimens has been investigated. It has been established that the transmittance at Lyman alpha for samples cut from the bottom third of a crystal remain reasonably constant but thereafter transmission begins to fall, the lowest transmission being from the top of the crystal. Three sets of samples cut from the same crystal but processed in different ways demonstrated that the processing techniques do not affect the measured transmittance. The results of the strength testing showed no correlation with position in the crystal but the type of processing significantly affected the strength measurements. Average strengths varied from 123 MPa to 167 Mpa depending on the processing technique.