Ormak nears collisionless regime

The Ormak experiment at Oak Ridge National Laboratory has advanced appreciably toward the so‐called collisionless regime in studies that increase the expectation for reaching the “reactor regime” without damaging loss from instabilities. Plasma ions have travelled about five to ten times around the torus before scattering 90 deg, and no new anomalous effects were observed. The result gives increased confidence that no additional empirical components are needed to explain the scaling of ion temperature in this regime, that the same combination of the classical laws of atomic and plasma physics plus empiricism (pseudoclassical scaling) hold true here as in previous experiments. Ormak was able to reach a higher degree of collisionlessness, although the ion temperatures reached did not necessarily exceed temperatures reached in some other experiments, because of its fatdoughnut geometry. These results were described at the March meeting on toroidal plasma confinement in Garching, Germany.