Recent biasing experiments on tokamaks have been very successful in improving the global particle (H-mode-like) confinement resulting from the setup of an outward-pointing radial electric field at the edge. These experiments have been extended to the current-free Advanced Toroidal Facility (ATF), and initial biasing experiments have been carried out in electron-cyclotron-heated (ECH) plasmas. ATF has a torsatron configuration with {ell} = 2, 12 field periods (M = 12), a major radius R{sub 0} = 2.1 m, and an average plasma radius a = 0.27 m. The current-free magnetic configuration of ATF that is produced by external means has moderate shear; the rotational transform ({chi} = 1/q, where q is the safety factor) at the last closed flux surface (LCFS) is {chi} {approx} 1, which is about a factor of 3 higher than the central value. ECH plasmas are created at a magnetic field B = 0.95 T using a 53-GHz gyrotron source with heating power up to P {approximately} 400 kW. In these ECH plasmas, a representative line-averaged plasma density is {bar n}{sub e} {approximately} 5 {times} 10{sup 12} cm{sup {minus}3}, and the plasma stored energy W{sub p} {approx} 2 kJ. A pair of rail limiters, which are normally floating, one at the top and one at the bottom of the device, are biased at positive and negative potentials with respect to the vessel. 7 refs., 5 figs
