Shock compression of liquid helium and helium-hydrogen mixtures : development of a cryogenic capability for shock compression of liquid helium on Z, final report for LDRD Project 141536.

Abstract

This final report on SNL/NM LDRD Project 141536 summarizes progress made toward the development of a cryogenic capability to generate liquid helium (LHe) samples for high accuracy equation-of-state (EOS) measurements on the Z current drive. Accurate data on He properties at Mbar pressures are critical to understanding giant planetary interiors and for validating first principles density functional simulations, but it is difficult to condense LHe samples at very low temperatures (<3.5 K) for experimental studies on gas guns, magnetic and explosive compression devices, and lasers. We have developed a conceptual design for a cryogenic LHe sample system to generate quiescent superfluid LHe samples at 1.5-1.8 K. This cryogenic system adapts the basic elements of a continuously operating, self-regulating 4 He evaporation refrigerator to the constraints of shock compression experiments on Z. To minimize heat load, the sample holder is surrounded by a double layer of thermal radiation shields cooled with LHe to 5 K. Delivery of LHe to the pumped-He evaporator bath is controlled by a flow impedance. The LHe sample holder assembly features modular components and simplified fabrication techniques to reduce cost and complexity to levels required of an expendable device. Prototypes have been fabricated, assembled, and instrumented for initial testing. Cryogenic Capability for LHe Shock Compression on Z ________________________________________________________________________ 4