Deformation luminescence of X-irradiated KCl:Eu2+ by bending test

It is well known that luminescence occurs during plastic deformation of X-irradiated alkali halide crystals. Luminescence pattern of KCl single crystals doped with europium has been observed during bending tests by using a CCD camera. Luminescence begins on both the fulcrum contact and opposite sides of a crystal at the beginning of plastic deformation. Several luminescence lines run along slip bands toward neutral axis from the outside of a sample in the direction of 45 degrees. Flash sometimes occurs both in the tension area and in the compression one. As deformation proceeds the luminescence lines are confused and right triangle-like luminescence pattern appears symmetrically on both sides of a central fulcrum in the compression area as well as in the tension one for three point bending tests. Strong flash has taken place in the triangle-like area just at fracture. But relatively homogeneous luminescence between two inner fulcrums has been observed for four point bending tests.