High confinement high temperature plasmas in MST

With inductive modification of the current profile and reduction of magnetic fluctuations, the energy confinement time in MST had previously been increased ten-fold, to about 10 ms. However, this result was achieved at relatively low plasma current, 0.2 MA, and relatively low temperature, Te = 0.6 keV and Ti = 0.2 keV. We have now extended improved confinement to the upper range of MST's plasma-current capability, around 0.5 MA. Here, the ohmically heated electrons reach 2 keV, and ions are heated to well above 1 keV by magnetic reconnection occurring prior to improved confinement. The global energy confinement time in these plasmas is about 12 ms, a modest improvement over the confinement at low current. This corresponds to a global thermal diffusivity of about 5 m$^2$/s. Total beta (volume-averaged pressure/total field pressure at the plasma boundary) is about 10 percent. Supported by USDOE and NSF.