Neutron diffraction at simultaneous high temperatures and pressures, with measurement of temperature by neutron radiography

The commissioning and operation of apparatus for neutron diffraction at simultaneous high temperatures and pressures is reported. The basic design is based on the Paris-Edinburgh cell using opposed anvils, with internal heating. Temperature is measured using neutron radiography. The apparatus has been shown in both on-line and off-line tests to operate to a pressure of 7 GPa and temperature of 1700 degreesC. The apparatus has been used in a neutron diffraction study of the crystal structure of deuterated brucite, and results for 520 degreesC and 5.15 GPa are presented. The diffraction data that can be obtained from the apparatus are of comparable quality to previous high-pressure studies at ambient temperatures, and are clearly good enough for Rietveld refinement analysis to give structural data of reasonable quality.