Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Abstract

Characteristics of axial plasma confinement in recent high-density mode of GAMMA 10/PDX tandem mirror is reported in this paper. The parameter of the end-loss ion flux is an important issue in the divertor simulation studies in GAMMA 10/PDX. With an ICRF heating in the anchor-cells of the machine, large increase in the electron line-density in the central-cell (NLCC) and the end-loss particle flux were observed. The behavior of the electron line density, plasma temperature and the amount of end-loss ion flux during the experiments suggested that the mechanism of the axial ion loss was changed due to the increase of ion collision frequency. In contrast with the standard operations of GAMMA 10/PDX, plasma parameters in recent high-density operations stays in the range of high collision frequency. In such collisional plasma, the end-loss ion particle flux show linear dependence on the plasma density instead of the parabolic dependence expected in plasmas of low collisionfrequency. In the high collision frequency plasma, it is notable that plasma potential φ largely changes the dependence of the particle flux on the plasma density.

Effect of the Potential of Confined Plasma on End-Loss Ion in GAMMA 10/PDX

“…Therefore, it is necessary to increase the density by increasing the particle flux of the end-loss plasma. In previous experiments, ion cyclotron range of frequency (ICRF) heating in the anchor cells has been performed for increasing of the end-loss ion flux [8][9][10][11]. A significant increase of the ion flux has been observed with the increase of the plasma potential.…”