Development of Cu mosaic monochromator for neutron spectrometer (1)

The Cu single crystal in order to use monochromator was grown by Czochralski method in Pusan National Univ. Crystal Bank. The axis of crystal measured to use for FCD(Four Circle Diffractometer). After axes determination, the large size crystal was cut into the slab shape and seed by using electric discharge machining. The seed was used for making high quality single crystal. We were measured that the mosaic spread of slab depended on pressure in order to increase effective mosaicity. Also, the mosaic spread to depend on pressure was delicately made at Liquid Nitrogen(LN) temperature. The transformation of Cu single crystals depended on impurity in identical case, because the impurity in Cu single crystals had different amount and modification. The large Cu slabs were made the sizes (70x30x5mm3). We have carried out a series of experiments in which imperfections were introduced into the mosaic crystals at various pressures. We obtained the optimum condition of pressure to increase effective mosaicity (11min) for a mosaic Cu monochromator. We also evaluated the resolution of Cu monochromator to use for standard sample, Fe, and Cu slabs at ST1 test station