Discovery of Electric Pulsation in a Toroidal Helical Plasma

A pulsating behavior of the electrostatic potential has been discovered in a low-density, high-electron-temperature plasma of the CHS heliotron/torsatron. The potential profiles were observed to swing repeatedly 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 (microseconds) than the diffusive time scale (milliseconds), is accompanied by changes 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.