EXPERIMENTAL DIVERTOR PHYSICS

The physics of diverters in tokamaks is reviewed, primarily from an ex perimental point of view, although where possible simple analytic mode lling is included. The paper covers the four main subject areas at iss ue in divertor research: (1) the wide dispersal of plasma power exhaus ted from the main plasma, (2) the production of sufficiently high gas pressures in the vicinity of pump ducts to enable the removal of fuel and helium ('ash') gas from the system, (3) the elimination or reducti on of impurity production and (4) the screening of impurities produced , or intentionally added, at the plasma boundary from the plasma core. A simple analytic model, the 'two-point' model, is introduced early i n the paper and provides a framework for comparison of the experimenta l results, drawn from many machines, with simply derived expectations. Conclusions regarding the direction of future research priorities are made.