Intermittent turbulent potential fluctuations in ion-cyclotron wave heated plasmas and effects of their suppression due to strongly sheared plasma rotation with electron-cyclotron heating (ECH) for potential formation are observed in GAMMA 10. Such a shear effect on the central-cell potential data is demonstrated by the use of a heavy ion beam probe (HIBP) for the first time in GAMMA 10. The HIBP system with a gold neutral beam is employed for measuring profiles of radially formed potential as well as the associated radially sheared E r in the central cell. During the application of ECH, the produced stronger E r shear results in reduction of the turbulent fluctuations. The results are consistent with reported X-ray tomography data on the effect of E r shear on turbulence suppression.

In the tandem mirror GAMMA 10, plasma confinement is achieved by not only a magnetic mirror configuration but also high potentials in both end regions. Before plug electron cyclotron resonance heating (P-ECH) was applied, drift-type fluctuations were observed in potential and density measurements. Potential and density fluctuation suppression during potential formation by the application of P-ECH was clearly observed using a gold neutral beam probe (GNBP) system. We study the relationship between the suppression levels of potential fluctuations and the effects of the produced potentials by varying the applied ECH power. Moreover, the particleflux-related values obtained by the phase difference between the potential and density fluctuations are measured using the GNBP. We can clearly show that radial anomalous transport induces radial particle transport, which decreases the plasma stored energy.

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Advances in potential formation have led to remarkable discoveries on the effects of radial electric field distribution on turbulence suppression and transverse loss reduction. In order to study the improvement in plasma confinement because of the formation of plasma confinement potential, we constructed a multi-channel microwave interferometer system that can measure the density and density fluctuation radial profiles in a single plasma shot. We obtained clear density fluctuation suppression by the formation of the plasma confinement potential. Therefore, we have a powerful diagnostic tool with which to study the improvement in plasma confinement.

A correlation between drift-type fluctuations and anomalous radial transport was observed in GAMMA 10, and these fluctuations were suppressed by the electron-cyclotron-heating-driven radial electric field. We developed new diagnostics to conduct these studies: a simultaneous two-point-measurement gold neutral beam probe (GNBP) for the radial electric field and potential fluctuations, and a high-speed end-plate potential fluctuation measurement system. The electric field and its fluctuations were successfully obtained in a single plasma shot for the first time. Coherence between the drift-type potential fluctuations measured in the core plasma by the GNBP and those obtained by end-plate measurements was clearly observed. These potential and electric field fluctuations were clearly suppressed by the positive electric fields measured by two-point potential measurements using the GNBP and the end-plate system. We can obtain a powerful tool for probing the radial electric field and potential fluctuations in the core plasma because the end-plate potential fluctuation is the same as that in the core plasma measured using the new GNBP.