After the attainment of the density doubling due to the potential confinement in 1998, GAMMA 10 experiments have been directed to realization of a high density plasma with potential confinement and also to study dependencies between plasma parameters. These studies are important for understanding of the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. GAMMA 10 experiments have advanced after the last OS2000 Conference where we reported high density plasma production by using an ion cyclotron range of frequency (ICRF) heating at high harmonic frequency and a neutral beam injection in the anchor cell. However, the diamagnetic signal of the high density plasma decreased with application of ECRH. Recently a high density plasma was attained without degradation of the diamagnetic signal, which was attained by adjusting the spacing of the conducting plates installed in the anchor transition regions. Dependencies of particle and energy confinement times and plasma confining potential on the density up to a density of 4×1012 cm−3 are studied for the first time in the high density region.