COMPASS electrical systems and commissioning

The COMPASS experiment is designed to operate in both pinch and tokamak modes, the latter with both circular and shaped plasma cross sections. In tokamak mode, the primary windings are used as an inductive store with a two-stage opening switch system to transfer the energy to the plasma loop. Three thyristor converters (total power 17 MW) are used to maintain the plasma current to provide vertical equilibrium field, and to produce the required plasma shapes (e.g. dee, ellipse, etc.). For pinch operation, a conventional start-bank/active-crowbar circuit is used to feed a reconfigured winding arrangement. Three high-power (each 250 kW) transistor amplifiers are used to energize other machine windings to provide vertical and radial correction fields for fast control of plasma position. A thyristor rectifier (40 MVA) is used to supply the toroidal-field system (92 kA/turn for a maximum field of 2.1 T). The control system uses programmable controllers controlled by a central computer. The operating interface is through touch-sensitive color monitors