A NONLINEAR MAGNETIC HELICITY MODEL OF A TIGHT ASPECT RATIO BOOTSTRAPPED TOKAMAK WITH OSCILLATING FIELD CURRENT DRIVE

Theoretical and computational analyses of bootstrapped tokamaks with o scillating field current drive (OFCD) have been developed using a nonl inear magnetic helicity model. Assuming a rigid current profile, the c onditions for optimal tokamak steady-state operation are derived and a re shown to agree with the results of computer calculations. Generaliz ed limit formulae for the toroidal plasma beta and bootstrap current f raction are also obtained. The results of the analyses indicate that s teady-state bootstrapped tokamak operation with high toroidal plasma b eta can best be achieved in tight aspect ratio A --> 1 reactors with O FCD supplying as much as a quarter of the total toroidal plasma curren t.