Precision Lattice Parameter Determination at Liquid Helium Temperatures by Double-Scanning Diffractometry

Abstract

Abstract The back-reflect ion double-scanning diffractometer method, by which lattice parameters can be measured with a reproducibility of one part in 150,000 has been applied at liquid helium temperatures. A cryostat attachment is described which enables diffraction profiles to be scanned on both sides of the primary X-ray beam up to 163°, 2 θ . Alignment errors may, thus, be eliminated by measuring the included angle 4 θ between respective Bragg reflections. The method is illustrated by measuring the lattice parameters of the I.U.Cr. standard specimens of silicon and tungsten at various cryogenic temperatures.