From SA: “Why Fusion Researchers Are Going Small”

Scientific American

Scientific American

THIS IS A PREVIEW.

David Biello

You can accuse fusion power advocates of being overly optimistic but never of thinking small. Fusion occurs when two elements combine, or “fuse,” together to form a new, third element, converting matter to energy. It is the process that powers the sun, and the fusion world’s marquee projects are accordingly grand.

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This image shows the Sun as viewed by the Soft X-Ray Telescope (SXT) onboard the orbiting Yohkoh satellite.

JAXA ISAS YOKHOH Soft X-ray telescope
JAXA ISAS YOKHOH Soft X-ray telescope

JAXA ISAS YOHKOH satellite
JAXA ISAS YOHKOH satellite

The bright, loop-like structures are hot (millions of degrees) plasma confined by magnetic fields rooted in the solar interior. An image of the sun in visible light would show sunspots at the feet of many of these loops. The halo of gas extending well beyond the sun is called the corona. The darker regions at the North and South poles of the Sun are coronal holes, where the magnetic field lines are open to space and allow particles to escape.

Consider the International Thermonuclear Experimental Reactor (ITER), which a consortium of seven nations is building in France.

ITER Tokamak
ITER tokamak

This $21-billion tokomak reactor will use superconducting magnets to create plasma hot and dense enough to achieve fusion. When finished, ITER will weigh 23,000 metric tons, three times the weight of the Eiffel Tower. The National Ignition Facility (NIF), its main competitor, is equally complex: it fires 192 lasers at a fuel pellet until it is subjected to temperatures of 50 million degrees Celsius and pressures of 150 billion atmospheres.

LLNL NIF
NIF

Despite all this, a working fusion power plant based on ITER or NIF remains decades away. A new crop of researchers are pursuing a different strategy: going small. This year the U.S. Advanced Research Projects Agency–Energy invested nearly $30 million in nine smaller projects aimed at affordable fusion through a program called Accelerating Low-Cost Plasma Heating and Assembly (ALPHA). One representative project, run by Tustin, Calif.–based company Magneto-Inertial Fusion Technologies, is designed to “pinch” a plasma with an electric current until it compresses itself enough induce fusion.

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