Investigating the $\beta $ limit on MST with pellet injection and NBI

Pellet injection into improved confinement ohmically-heated MST plasmas has resulted in a density exceeding substantially the empirical Greenwald Limit and a total $\beta $, normalizing to the magnetic pressure at the plasma boundary, of 26{\%}. Although tearing mode amplitudes are larger at higher $\beta $, a clear $\beta $ limit has not been observed. The addition of a 1 MW heating neutral beam on MST will provide additional heating which will be utilized to further probe for a $\beta $ limit. The fast ion confinement is measured to be several times greater than the thermal particle confinement time, but the thermalization time tends to be long for low density improved confinement plasmas. The high density, low temperature pellet fueled plasmas should provide an ideal target for deposition of the beam power to the plasma. Work Supported by USDOE.