How stuff works: Sandia Z-Machine

Today we're not going to talk about lightning of the natural variety, and instead talk about lightning of the man-made variety. Specifically, we're going to talk about the Z-Machine, an enormous X-ray generator at Sandia National Laboratory.

How enormous? This enormous:

(You can click on the picture for a bigger version. Believe me, it's worth it.)

What you see here is the Z-Machine after it has just fired. Essentially, it's a gigantic electrical discharge fed into a very small space, and directed at a tiny target made of a cylinder of hair-fine tungsten wires.

But let's back up a little first.

The Z-Machine was originally designed to test theories about atomic explosions. It used extreme heat and pressure confined to a very, very small space to study the behavior of materials at very high temperatures–the kinds of temperatures you'd get in the center of a nuclear bomb blast.

The way it works is surprisingly simple, really. Power is fed into several Marx generators, which store the electricity. Marx generators are banks of capacitors arranged in such a way that they are discharged in series, multiplying the voltage that was used to charge them considerably.

The Z-machine uses a series of huge Marx generators arranged in a circle. Each of these is charged from ordinary household-level current for a while. When they're all charged, several laser triggers fire, discharging the Marx generators through several massive copper wires, each about five feet across, arranged like spokes in a wheel. The wires conduct the electricity to the target, which is promptly, and vigorously, annihilated.

The total amount of electrical power that's used to zap the target is huge–about 290 trillion watts, or roughly eighty times the total output of all the power generating plants in the world. This electrical surge is very short; it only lasts for a few billionths of a second. The power instantly vaporizes the tungsten target, by heating it to nearly two million degrees. The ultrahot tungsten is turned into plasma, which quickly implodes under the tremendous magnetic field generated by this huge surge of electricity. The plasma crushes the target within the cylinder of tungsten wires using forces and temperatures comparable to what you'd find at the surface of the sun.

Originally, this was done to help design more efficient nuclear weapons. By studying the density and flow of energy inside a nuclear blast, scientists could design nuclear bombs that operated more efficiently. Today, the Z-Machine is used to research nuclear fusion–a hypothetical power source that can produce virtually limitless amounts of energy from ordinary seawater, without radioactive waste.

The electrical discharge you see all over the place in the photograph above isn't electricity from the Marx generators themselves. It's electricity induced in any nearby metal objects, such as ladders and support structures, just by the electromagnetic pulse produced from the collapsing plasma inside the target chamber in the middle of the ring. The ring itself is filled with deionized water, to help buffer and cool the enormous cables that bring the electricity from the Marx generators to the target in the center.