PLT reaches high temperature in a collisionless plasma

New experimental results at the Princeton Large Torus have shown that a low‐density tokamak plasma can be heated to a record‐breaking temperature for tokamaks without any serious instabilities occurring. Many plasma theorists had anticipated that at higher temperatures and lower densities trapped‐particle modes would limit the temperature rise in the PLT experiment, in what was considered a worst‐case situation—a collisionless plasma. Because such trapped‐particle instabilities have not shown up, many fusion physicists feel encouraged that a power‐producing tokamak reactor need not be nearly as large as some had feared. But the full implications on reactor size are not known.