Recent development in GAMMA 10 experiment

After the attainment of the density doubling due to the potential confinement, GAMMA 10 experiments have been directed to obtain a high-density plasma with potential confinement and also to study the dependence of the confining potential and confinement time on the plasma density. These problems are important to understand the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. GAMMA 10 experiments have advanced greatly after the Sorrento IAEA Conference, where high-density plasma production by using an ICRF heating at a higher harmonic frequency was reported. Recently, a high-density plasma was attained and the reproducibility of high-density plasma production was much improved by adjusting the spacing of the conducting plates installed in the anchor transition regions. In this paper, we report the production of a high-density plasma and the dependence of the confining potential and confinement time on the density up to a density of 4 x 1012 cm-3