This is the Saturn pulsed power accelerator at Sandia National Labs in New Mexico. In just a few billionths of a second, this machine generates X-rays containing as much energy as the entire output of the U.S. electrical grid, fifty times over.
A pulsed power accelerator can pump out absolutely staggering amounts of power. It manages to do this without dimming lights around the world by not operating continuously; instead, it charges up for a few hours, and then unleashes all of its stored energy all at once in a very short, very massive pulse.
Sandia's Saturn accelerator is specifically designed to convert as much electrical power as it can into X-rays, in order to simulate what happens during a nuclear detonation. To do this, the accelerator channels its output pulse through a tiny cylinder made of very thin tungsten wires. As each wire essentially gets hit by its own lightning bolt, it gets turned into a plasma, which is instantly driven inward by the intense electromagnetic field. This implosion releases hundreds of thousands of joules of X-ray energy, which is as close as we can get to seeing what happens when a nuke goes off without actually, you know, setting off a nuke.
This picture above shows Saturn during a "shot," as it's called. The little cylinder of metal wires that generates the X-ray pulse is at the very center of the machine, and the electrical energy is fed in from the outside. The electrical components are submerged in water which functions as an insulator, but the charges are so powerful that lightning arcs around the accelerator anyway. The photographer is Randy Montoya, and here's one more pic of Saturn in operation: