A small-angle neutron scattering cell for the study of supercritical fluids at elevated pressure and high temperature: A study of heavy water

The main characteristics of a cell optimized for small-angle neutron scatte ring experiments on supercritical fluids are presented. The cell operates s atisfactorily at pressures up to 300 bar at 400 degrees C and 750 bar at 90 degrees C. It has large apertures sealed by thick synthetic sapphire windo ws. The maximum forward scattering angle is 16 degrees and the sample path length is 5.1 mm. It has been used to study scattering from supercritical h eavy water close to its critical point at wave number transfers up to 0.34 Angstrom(-1). (C) 1999 American Institute of Physics. [S0034-6748(99)01510- 5].