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The relation between the radial potential profile of the core plasma are examined in the tandem mirror GAMMA 10. It is observed that the radial potential profiles are convex over the cross section ...

Ion distributions in a loss cone are measured in the GAMMA 10 tandem mirror [Phys. Rev. Lett. 55, 939 (1985)]. When Alfven ion cyclotron (AIC) modes are excited in the central cell, enhanced end-loss of ions is observed for a characteristic energy region which agrees well with the resonant ion cyclotron condition with the AIC wave. From measurements of pitch angle distributions of end-loss ions, it is found that the loss cone is filled for this characteristic energy region, indicating an ion diffusion in a velocity space induced by the AIC wave. Magnitude of the observed additional end-loss increases with increase in the amplitude of the AIC modes. In the present experimental parameters in GAMMA 10, the AIC wave effect on the axial ion confinement is not serious.

A gold neutral beam probe system was improved by adopting a multichannel ion detector and adding sweeping functions of beam energy, deflector voltage, and electrode voltage of the analyzer to the system to measure the fluctuations and time evolution of the two-dimensional space potentials with fast resolving time during one shot. Positions of the beam spot on the multichannel detector corresponding to the ionizing points of the beam in the plasma were simulated precisely as a function of the beam energy and the injection angle. A potential derivation formula was determined taking into consideration both the numerical and experimental results, and the reproducibility of the potential profile was checked. Two-dimensional potential profiles were measured in the optimization experiment of the microwave injection angles for formation of the plug potential.

A gentle hump structure on energy distribution function of end-loss ions was observed in the rf-driven tandem mirror plasma by use of an end-loss energy component analyzer. Alfv\'en ion-cyclotron (AIC) fluctuations are excited spontaneously due to anisotropic ion heating in the central cell of the tandem mirror. We observed that the excitation of the AIC waves caused the hump structure on the energy distribution function. The enhancement factor of the end-loss ions is estimated, and the gentle hump structure is discussed from the viewpoint of the heating characteristics of the AIC waves. It is pointed out that the hump structure decreases the ion confinement.