A New Way of Generating Load at Cryogenic Temperatures for Neutron Studies

Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly for neutron studies due to the volume of sample required.\footnote{Bailey, I. F. (2003). Z. Kristallogr., 218(2-2003), 84-95.} This challenge has been previously tackled by using a modified Bridgman-seal in a Paris-Edinburgh cell.\footnote{S. Klotz, B. Padmanabhan, J. Philippe, and T. Str\"assle, High Pressure Res. 28, 621 (2008).} We present a novel design of a pressure cell in which load is generated by a bellows driven by helium gas which ensures leak-free operation of the device. The bellows is custom-designed to generate the load of 80~kN at the maximum operational gas pressure of 350~bar. For opposed anvils with 3~mm diameter working surface, for example, this load converts into an average pressure of 11~GPa across the culets. The cell has four large windows for the scattered beam and the setup allows control of pressure in a wide (P,T)-range in which helium is in gas or liquid state. The cell has been used at the WISH beamline of the ISIS Pulsed Neutron Source with sapphire anvils. The device will be presented in detail, along with pressure loading curves and initial experimental data.