Nuclear fusion drives the stars, including our sun. But on Earth, despite efforts dating to the 1940s, sustained and controlled fusion for electrical power production has never been realized. Research persists, because few energy sources could be greener. Fusion yields far more energy than any other source per unit of mass; its heavy-hydrogen fuel is plentiful in sea water; burning it produces not a trace of carbon.
There’s more than one scheme for producing fusion power; the two main categories are magnetic confinement and inertial fusion energy. A promising approach to inertial fusion energy, called heavy-ion fusion (HIF), has long been advocated by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).
In inertial fusion, the fuel is a solid target made of frozen isotopes of hydrogen (deuterium, or deuterium and tritium), which is instantly heated to fusion temperature when hit by driver beams of laser light or energetic particles. The heavy-ion fusion approached pursued at Berkeley Lab uses driver beams of ions (atoms lacking one or more electrons) whose atomic mass is generally greater than 100 – cesium or xenon, for example. (For comparison, iron has an atomic mass of 55.85.)
Most controlled-fusion efforts today involve magnetic confinement, however, with the most common reactors being the doughnut-shaped chambers called tokamaks. Tokamaks try to contain, squeeze, and heat a plasma of heavy hydrogen isotopes with magnetic fields, long enough for the nuclei to fuse. Magnetic-confinement research continues, but the inertial fusion energy approach has lately been gaining new attention.
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