The current, which created pressures in materials millions of times greater than normal, was part of an experiment to better understand nuclear weapons.

The experiment was conducted on Wednesday at the test site's Atlas Pulsed Power Facility by scientists from Los Alamos National Laboratory in New Mexico, along with staff from the test site and contractor Bechtel Nevada.

19 million amps

During the few millionths of a second that it operated, the 650-ton Atlas pulsed-power generator discharged nearly 19 million amps of current through an aluminum cylindrical shell about the size of a tuna can, the National Nuclear Security Administration said.

Atlas, which works as a giant power multiplier, was designed as part of an Energy Department programme to determine the readiness of the nation's nuclear stockpile without underground testing.

It was built at Los Alamos and recently moved to the Nevada Test Site, a proving ground just north of Las Vegas.