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The main operations from 1979 to 2000 in the GAMMA 10 tandem-mirror, characterized in terms of the high-potential mode having kV-order plasma-confining potentials and the hot-ion mode yielding fusion neutrons with 10-20 keV bulk-ion temperatures, are summarized and generalized as a result of scalings of the formation and the effects of the potentials. The wide validity of potential-formation physics from Cohen's theory and the validity of the generalized Pastukhov's theory for the effects of thermal-barrier potentials on electron confinement are verified and consolidated through electron-energy balance.

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.

application/pdf, Alfvén-ion-cyclotron modes are generated over a wide range of anisotropy parameter β⊥(T⊥/T∥)2 in ICRF-heated central cell plasmas of the GAMMA 10 tandem mirror. The fluctuations are observed at a small driving force in the convectively unstable region predicted theoretically in an infinite plasma. Before reaching the β limit of β⊥=3.52×(T∥/T⊥)2, above which the absolute instability is predicted, relaxation of pressure anisotropy is observed for the first time by use of an array of diamagnetic loops together with a Faraday cup and secondary-electron emission detectors.

An Ohmic current has been inductively driven in the dc octopole. Resulting flux surfaces are similar to those of a tokamak with poloidal divertors. Quiet and reproducible magnetic-probe traces indicate that the plasma has obtained a stable equilibrium. For the safety factor on the axis less than unity, a current-disruptive instability is observed to redistribute current density from the peak to the wings of the spatial distribution.

Doublet plasma have been produced in Doublet IIA using an active field-shaping coil system. Significant increases in the electron density and energy confinement time have been observed for the doublet configuration relative to elliptic and circular plasmas in Doublet IIA.

A new type of toroidally localized kink instability, which we named the ``slinky mode,'' was observed in a reversed-field\char21{}pinch plasma in the OHTE (Ohmic heating toroidal experiment) device. It is found that the slinky mode is the result of the phase locking of several internal kink modes due to nonlinear coupling and is an effective way to approach the Taylor relaxed state.