Cryogenic apparatus for scattering and phase equilibrium studies

A cryogenic apparatus has been developed for neutron scattering and phase equilibrium studies on supercritical inert gas mixtures. Scattering and phase equilibrium studies can be performed in the same apparatus; the whole apparatus is transportable to any scattering facility. It centers on a stirred, batch, view cell of unique design. By changing only three parts of simple design (two windows, one sample cylinder) to an appropriate material, this apparatus can be used for studies involving wide or small angle scattering of neutrons or x rays. Its use can also be extended to pure fluids, liquids, and states away from the critical point. It operates within pressure and temperature ranges of 0--13.8 MPa and 20--300 K. To our knowledge this is the first neutron scattering cell with axial fluid mixing and with a temperature gradient of 10 mK or less over a large sample volume (1-cm diameter, 5-cm long). The accuracy and performance of the apparatus was tested on pure neon by reproducing its saturation curve and by performing small angle neutron scattering on some supercritical states