The larger ASDEX tokamak succeeding Pulsator was equipped with auxiliary heating methods, viz. neutral-particle and high-frequency heating, along with the plasma current.
Instead of having a material limiter, as in Pulsator, the ASDEX plasma was limited to the outside with an auxiliary magnetic field. This divertor, as it is called, directed the boundary layer of the plasma into side chambers, where the plasma particles along with impurities were pumped off. As with all tokamaks worldwide, a major problem cropped up: The thermal insulation of the plasma dropped as soon as the temperature was raised by external heating. Despite strong heating ignition conditions were still not approached.
The remedy was found in 1982 with the discovery of the “H-regime” (high-confinement regime) in ASDEX. In this favourable plasma state thermal insulation was doubled. Divertor operation and the H-regime became the basis of modern tokamaks, right up to the ITER international test reactor, now being built.
ASDEX was shut down in 1990. Five years later, the device was passed on to Southwestern Institute of Plasma Physics in Leshan, People’s Republic of China. Since 2002 ASDEX has continued under its new name, HL-2A.