Toward Accessing the Solid Metallic State of Hydrogen via Ramp Compression of Solid parahydrogen

Producing solid metallic hydrogen in a laboratory has been recognized as one of the grand challenges of physics¹. Theoretical work suggests that crystalline metallic hydrogen possesses a number of remarkable properties such as room-temperature superconductivity. The investigation of this material is also of fundamental interest for planetary science since metallic hydrogen is the primary constituent of gas giants.

Recent studies² at the National Ignition Facility observed an insulator–metal transition during ramp compression of liquid hydrogen. To extend these experiments into the crystalline metallic regime, similar experiments with solid parahydrogen were conducted. With an initial temperature of 10 K, this target has minimal initial entropy, limiting the temperature increase during compression. The drive, consisting of an initial picket and a ramp, was tailored to a near-isentropic compression using the hydrocode HYADES. Pressure and density of the target were reconstructed from VISAR data³, while the temperature was measured using streaked optical pyrometry. Experimental results of a recent pilot study will be discussed.