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. This is not a particularly efficient process; in total, around ~1% of the electricity used to feed the lamps ends up amplifying the beam on most Nd:glass lasers.