Preliminary considerations for the gasdynamic precompression of solid molecular hydrogen

A preliminary examination of the feasibility of quasi-isentropically compressing solid or liquid molecular hydrogen to multi-megabar pressures by means of a gas-cushioned projectile impact experiment is presented. The primary purpose for using a gas-cushioned projectile is to prevent large temperature increases in the sample. Initial experimental design concepts, and a series of one-dimensional Lagrangian computations that demonstrate the feasibility of the experimental concepts are presented. The expected temperature rises in the hydrogen sample undergoing continuous compression are briefly discussed and contrasted with the temperature rises expected in direct shock loading. This experimental procedure will allow the acquisition of very high pressure data which are beyond the range of diamond-anvil cell technology. Since the estimated peak presusres of the experiment are within theoretical predictions of the metal-insulator transition in molecular hydrogen, the proposed experiment will directly probe the existence of this transition. The molecular-to-metallic transition in hydrogen is a subject of current importance in solid-state physics.