Pressure Driven Currents in an ECH Heated, Low Aspect Ratio Torus

Pressure driven currents are observed in an ECH heated, low aspect ratio toroidal plasma in the CDX‐U device. A novel poloidal field configuration is able to provide confinement in the absence of toroidal plasma current. In the initial stages of the discharge, however, field aligned currents flow along open field lines to eliminate the charge separation due to ΔB and curvature drifts and trapped electrons precess toroidally to produce a net toroidal current. The toroidal current of as large as 700 amps was generated with ∼4 kWatts of ECH power. This internally driven current may offer an attractive method to start up and maintain a low aspect ratio tokamak by generating the seed current required for a bootstrap current driven equilibrium.