Drift Waves in the GAMMA-10 and Kinetically Stabilized Tandem Mirror

The tandem mirror remains an attractive magnetic confinement geometry. The absence of toroidal curvature and internal plasma parallel current gives the system strongly favorable stability and transport properties. Additionally, GAMMA-10 experimental results demonstrate that sheared rotation can suppress turbulent radial losses. We analyze electrostatic drift wave eigenmodes for two machines: the GAMMA-10 (Cho, \it et al.\rm, Nuclear Fusion 45 (12), 2005) and the Kinetically Stabilized Tandem Mirror reactor (Post \it et al.\rm, Fusion Science and Technology, 47 (49) 2005). We compare results with experimental data from the GAMMA-10. Recent achievements of this machine include 3 keV ion confinement potentials and $T_e > 500 $ eV. The implications of drift waves results on radial confinement times developed using Bohm, gyro-Bohm, and electron temperature gradient (ETG) scalings in Pratt and Horton (Phys. Plasmas (13), 2006) are discussed. The plug mirrors create an ambipolar potential that controls end losses; radial losses are driven by drift wave turbulence that controls the electron temperature profile through radial transport. Total energy confinement times for the GAMMA-10 experiment are significantly larger than corresponding empirical confinement times in toroidal devices. We conclude that the tandem mirror has a qualitatively different form of drift wave radial transport from that in toroidal devices. *Work supported by the Department of Energy Grant DE-FG02-04ER5474.