START plasma overcomes large-scale instabilities

Increasing the plasma confinement time is one of the critical challenges in the drive to produce energy by thermonuclear fusion. The relationship between the confinement time and the size or, more precisely, "aspect ratio" of the plasma is relatively well understood, but experiments on a small-aspect-ratio plasma have now produced confinement times twice as long as expected (A Sykes el al. Plasma Phys. Control. Fusion (1993) 35 1051). These results could have significant implications for the projected size and costs of a future fusion reactor.