U.S. to test powerful explosive in Utah in preps for nuke on iran?, page 2

The only thing is that the only time mettalic hydrogen was made here on Earth it was in 1996, for several miliseconds, and they didn't expect it to happen. It's very difficult to produce, because it requires extreme pressures to create. So while they say it has so much explosive power, it's not something we're likely to see used in bombs for awhile.

"Metallization of hydrogen has been the elusive Holy Grail in high- pressure physics for many years," said Bill Nellis, one of three Livermore researchers involved in the project. "This is a significant contribution to condensed matter physics because a pressure and temperature that actually produce metallization have finally been discovered."

In a paper delivered today at the American Physical Society's annual gathering in St. Louis, and published in the March 11 issue of Physical Review Letters, Livermore researchers Sam Weir, Art Mitchell, and Bill Nellis described the use of a two-stage gas gun at Livermore to create enormous shock pressure on a target containing liquid hydrogen cooled to 20 K (-420 F).

By measuring the electrical conductivity, they found that metallization occurs at pressure equivalent to 1.4 million times Earth's atmospheric pressure, nine times the initial density of hydrogen, and at a temperature of 3000 K (5000 F). Because of the high temperature, the hydrogen was a liquid. The intense pressure lasted less than a microsecond.

Optical evidence of a new phase of hydrogen has been previously reported using an experimental approach that involves crushing microscopic-sized samples of crystalline hydrogen between diamond anvils. However, metallic character has not been established. Metallic character is most directly established by electrical conductivity measurements which are not yet possible in diamond anvil cells at these pressures.

www-phys.llnl.gov...

Our shock compression studies use a 20-meter-long, two-stage light-gas gun built by General Motors in the mid-1960s for ballistic missile studies; the gun has been in operation at the Laboratory since 1972.
The gun consists of a first-stage breech containing up to 3.5 kilograms of gunpowder and a pump tube filled with 60 grams of hydrogen, helium, or nitrogen gas; and a second-stage evacuated barrel for guiding the high-velocity impactor to its target.
Hot gases from the burning gunpowder drive a heavy (4.5- to 6.8-kilograms) piston down the pump tube, compressing the gas. At sufficiently high pressures, the gas eventually breaks a rupture valve and enters the narrow barrel, propelling a 20-gram impactor housed in the barrel toward the target.
When the impactor hits the target, it produces a high-pressure shock wave. In a fraction of a microsecond, the shock wave reverberates through the target. Diagnostic equipment, triggered by the initial wave, measures the properties of the shocked material inside the target during this extremely brief period.
Projectile velocity can range from 1 to 8 kilometers per second (up to 18,000 mph). The preferred velocity is achieved by selecting the appropriate type and amount of gunpowder, driving gas (hydrogen for velocities at or above 4 kilometers per second, helium and nitrogen for lower velocities), pressure required to open the rupture valve, diameter of the barrel, and the metal and mass of the impactor.
The velocity of the shock wave, when combined with the initial conditions (impactor velocity, known densities, equation of state of the projectile and target materials) yields a precise measure of the pressure, density, and energy attained.