Current drive by fast magnetosonic waves near the lower hybrid frequency in the JIPP T-IIU tokamak.

Current drive by fast magnetosonic waves is successfully performed in the JIPP T-IIU tokamak by means of a four-element dipole antenna array with a Faraday shield. A plasma current of about 50 kA is sustained by an rf power of about 80 kW in a low-density plasma (3 ×{} 10¹² cm^-3) with an efficiency comparable to that of slow-wave current drive. A density limit for fast magnetosonic current drive is observed, contrary to theoretical expectations based on linear wave propagation.