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Abstract
A tokamak-like plasma has been created and sustained in the CDX device solely by means of an electron beam. The poloidal field structure observed is that of a tokamak and the density and temperatures seen are larger than in previous types of plasmas generated in this device. A plasma current scaling consistent with the helicity balance equation is observed and about 40% of the injected helicity appears in the tokamak plasma. Rapid transport of current from the region of injection to the center produces a peaked current profile. Plasmas with $\beta$ in the neighborhood of the Troyon-Sykes limit may be generated by this technique.
In high-$\beta$ plasmas, a coherent fluctuation is seen which has its largest amplitude in a region of unfavorable curvature. The mode is absent below a certain density and plasma current, corresponding to a threshold $\beta$. When present, the mode has an m = 4 structure and it propagates in the ion diamagnetic direction. These properties identify it as a ballooning mode. A significant radial electric field alters the observed frequency and dispersion of the mode.
