DISCOVERY OF ELECTRIC PULSATION IN A TOROIDAL HELICAL PLASMA

A pulsating behavior of the electrostatic potential has been discovere d in a low-density, high-electron-temperature plasma of the CHS heliot ron/torsatron. The potential profiles were observed to swing repeatedl y between two distinctive states in a constant external magnetic field under a continuous supply of particles and energy. The change of the potential profile, which occurs on a much faster time scale (microseco nds) than the diffusive time scale (milliseconds), is accompanied by c hanges in density and temperature. This discovery clearly demonstrates that even in a low beta regime a toroidal helical plasma can produce a self-sustaining dynamic steady state, like the sawtooth oscillation in tokamaks.