COMPASS poloidal field power supply system

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 convertors (total power 17MW) are used to maintain the plasma current, to provide vertical (equilibrium) field and to produce the required plasma shapes (eg, 'dee', ellipse). For Pinch operation, a conventional start bank/active crowbar circuit is used to feed a reconfigured winding arrangement. Three high power (250kW) transistor amplifiers are used to energize other machine windings to provide vertical and radial correction fields for fast control of plasma position. Most of the power supply system is now in manufacture and installation has begun; commissioning of the overall system is scheduled for the second half of 1987