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Waldrop, M.M., 2020. News Feature: Small-scale fusion tackles energy, space applications. Proceedings of the National Academy of Sciences 117, 1824.

http://www.pnas.org/content/117/4/1824.abstract Efforts are underway to exploit a strategy that could generate fusion with relative ease. On July 14, 2015, nine years and five billion kilometers after liftoff, NASA's New Horizons spacecraft passed the dwarf planet Pluto and its outsized moon Charon at almost 14 kilometers per second - roughly 20 times faster than a rifle bullet. The images and data that New Horizons painstakingly radioed back to Earth in the weeks that followed revealed a pair of worlds that were far more varied and geologically active than anyone had thought possible. The revelations were breathtaking - and yet tinged with melancholy, because New Horizons was almost certain to be both the first and the last spacecraft to visit this fascinating world in our lifetimes. Unless, that is, Samuel Cohen succeeds with the offbeat fusion reactor that he's developing at the Princeton Plasma Physics Laboratory in New Jersey. Cohen's current prototype is a clear plastic cylinder that sits in the middle of his lab amidst a dense mass of cables, magnets, and power supplies, emitting a violet pulse of light every two seconds like a two-meter-long strobe light. 'We're only using hydrogen right now,' Cohen explains, referring to the ionized plasma inside the tube that's emitting the flashes. So there are no actual fusion reactions taking place; that's not in his research plan until the mid-2020s, when he hopes to be working with a more advanced prototype at least three times larger than this one. If that hope pans out and his future machine does indeed produce more greenhouse gas - free fusion energy than it consumes, Cohen and his team will have beaten the standard timetable for fusion by about a decade - using a reactor that's just a tiny fraction of the size and cost of the huge, donut- shaped 'tokamak' devices that have long devoured most of the research funding in this field. The flagship of this tokamak approach, the International Thermonuclear Experimental Reactor (ITER) now under construction in France, will be twice as large as any fusion reactor before it, will cost at least $20 billion to build, and isn't expected to start producing fusion energy until the mid-2030s. If and when Cohen does reach his fusion energy milestone, he will likely have company. His device is just one of a family of small, alternative reactor projects designed to exploit a phenomenon known as the field-reversed configuration (FRC): a dense mass of ionized plasma that holds itself together something like a smoke ring and that could allow researchers to achieve fusion conditions with comparatively little effort. Among the members of this family are some of the best-known fusion upstarts: firms such as TAE Technologies (formerly TriAlpha Energy) in Foothill Ranch, California, and Helion Energy in Redmond, Washington. 'There's been a rejuvenation in that whole area' of FRCs, says Stephen Dean, a nuclear engineer who has championed fusion energy for more than 50 years. 'All of the projects have good ideas, all of them are doing good work.' But even if some or all of them do end up producing fusion energy in the lab at some point in the