Bifurcated states of ohmically heated tokamak plasmas

Experiments in the Rijnhuizen Tokamak Project are reported which show bifurcated states of plasmas in the linear Ohmic confinement regime. One branch is the usual Ohmic state. The second, newly discovered, state features a much broader temperature profile, while the density has a very pronounced gradient near the half radius. The bifurcated states form after off-axis electron cyclotron heating is switched off. The new state contradicts theoretical models which predict improved confinement for peaked density profiles or high collisionality. [S0031-9007(98)08046-6].