Abstract
A new helium gas high-pressure cell for X-ray powder diffraction studies up to 0.5 GPa is described. The construction is outlined in particular for standard two-circle diffractometers. Because of the large pressure volume available for the sample and the cylindrical symmetry around the diffractometer axis, it is suitable for recording accurate diffraction patterns even from weakly scattering materials. The performance of the device has been tested by means of a determination of the molecular reorientation with pressure in naphthalene, based on an intensity analysis of the Bragg scattering.