  The start-up and sustainment of a stochastic wave non-inductive current on a
spherical torus was experimentally demonstrated for the first time using only
electron cyclotron waves. The plasma current is insensitive to the injection
angle of ECWs and approximately linearly correlated with the slope of the X-ray
spectrum. Its direction is determined by the vertical magnetic field (BV). The
temporal development in the number of X-ray bremsstrahlung photons with a
specified energy is consistent with the stochastic heating model. Moreover, the
ratio of Amps to Watts of the ECW is generally >1 kA/kW under normal conditions
(maximum plasma current: 150 kA, ECW: 140 kW). The experimental results are
explained using the stochastic heating model of the asymmetric electron
velocity distribution in stochastic electromagnetic waves.
