Hot pressing of germanium monochromator crystals

The method and parameters for vacuum hot pressing of single-crystal germanium, suitable for a large-area double-focusing neutron monochromator, are presented. The square virgin crystals have a mosaic that is less than 0.01° and isotropic. After appropriate pressing at high temperature (1073 K at a pressure of 10.7 MPa) the mosaic becomes anisotropic, about 0.5° in one direction and 0.2° in the other. The distribution of the mosaic widths of the crystals in the two directions are given, together with their composite values.