Different transport regimes by flow control in a magnetized off-axis heated plasma*

Results of a basic heat transport experiment at LAPD involving an off-axis heat source are presented. A ring-shaped electron beam source injects low energy electrons (below ionization energy) along a strong magnetic field into a pre-existing, large and cold plasma, resulting in a long, hollow, cylindrical region of elevated plasma pressure. Azimuthal sheared flows and axial flows are present as a consequence of the boundary conditions at the ring-source. Previously, two regimes were identified: 1) a regime dominated by avalanches, consisting of sudden intermittent rearrangements of the pressure profile triggered by the rapid growth of drift-Alfven waves. 2) A late-stage state dominated by sustained drift-Alfven wave activity following a global collapse of the density profile. Recently, a new ring-source configuration has been implemented that allows active control of the plasma flows. The experiment now offers control over the size and the frequency of the avalanches, including their full suppression. Another regime has been found that under certain flow conditions generates a single frequency, maser-like mode, that causes enhanced transport.