Shiva laser

The basic idea of any ICF device is to rapidly heat the outer layers of a "target", normally a small plastic sphere containing a few milligrams of fusion fuel, typically a mix of deuterium and tritium.

Due to Newton's Third Law, the remaining portion of the target is driven inwards, eventually collapsing into a small point of very high density.

Prior to firing, the laser glass of the Shiva was "pumped" with light from a series of xenon flash lamps fed power from a large capacitor bank.

Some of this light is absorbed by the neodymium atoms in the glass, raising them to an excited state and leading to a population inversion which readies the lasing medium for amplification of a laser beam.

A small amount of laser light, generated externally, was then fed into the beamlines, passing through the glass and becoming amplified through the process of stimulated emission.

After each amplifier module there was a spatial filter, which was used to smooth the beam by removing any nonuniformity or power anisotropy which had accumulated due to nonlinear focusing effects of intense light passage through air and glass.

Studies of the causes of the lower than expected compression led to the realization that the laser was coupling strongly with the hot electrons (~50 keV) in the plasma which formed when the outer layers of the target were heated, via stimulated raman scattering.

John Holzrichter, director of the ICF program at the time, said: The laser beam generates a dense plasma where it impinges on the target material.

ICF research turned to using an "optical frequency multiplier" to convert the incoming IR light into the ultraviolet at about 351 nm, a technique that was well known at the time but was not efficient enough to be worthwhile.

On January 24, 1980, a 5.8 Mw  earthquake (the first in a doublet) shook Livermore and the facility enough to shear fist-sized bolts off Shiva; repairs were made and the laser was subsequently put back online a month later.