Electron cyclotron heating and current drive: Present experiments to ITER

Electron cyclotron (EC) power has technological and physics advantages for heating and current drive in a tokamak reactor, and advances in source development make it credible for applications in ITER. Strong single pass absorption makes heating to ignition particularly simple. The optimized EC current drive (ECCD) efficiency (IR/P) shows a linear temperature scaling at temperatures up to ∼15 keV. For temperatures above 30 keV, the efficiency saturates at approximately 0.3·1020 A/(m2W) for a frequency of 220 GHz in an ITER target plasma with toroidal field of 6 T, due primarily to harmonic overlap and to a lesser extent due to limitations arising from relativistic effects. The same efficiency can also be obtained at 170 GHz for the same plasma equilibrium except that the magnetic field is reduced to (170/200) x 6 T = 4.6 T. The ECCD efficiencies are obtained with the comprehensive 3D, bounce-averaged Fokker-Planck CQL3D codes and BANDIT3D