Every time the plasma physicists at Sandia National Laboratories in Albuquerque, New Mexico, fire a shot on their fusion reactor, a big chunk of the hardware goes up in smoke. Their Z machine contains banks of capacitors that fill up with more electrical energy than a thousand lightning bolts. With the flip of a switch, 20 million amps surge toward a fuel-filled cylinder the size of a pencil eraser. The electrical current induces an overwhelming magnetic field, which pinches the tube so fast and furiously that hydrogen atoms inside fuse into helium, releasing a blast of high-energy neutrons and helium nuclei (known as a particles). The blast vaporizes the intricate hardware that holds the tiny tube—10 kilograms of solid metal. "We're basically delivering three sticks of dynamite worth of energy," says Mike Cuneo, a manager on the project. "After, there's a crater a foot wide."
The physicists are now preparing to make even bigger bangs by adding a precious fuel, used in thermonuclear weapons, that carries both risks and rewards. Calculations, simulations, and experimental results published in recent years suggest that Sandia's machine could offer a quicker and cheaper path to self-sustaining fusion than other approaches that blast the fuel with lasers or trap it in reactors called tokamaks. But so far the Z machine has unleashed its fury mainly on deuterium (a hydrogen with one neutron in its nucleus), which releases limited amounts of fusion energy. In August, however, researchers added a dash of tritium—hydrogen with two neutrons. Over the next 5 years, the tests will gradually ramp up to a 50-50 blend of deuterium and tritium (DT).
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