Characteristics of plasma discharge in BETA

Summary Form only given, as follows. BETA is a toroidal device with a major radius of 45 cm and minor radius of 15 cm. It has no rotational transform. A conducting limiter provides some equilibrium. Plasma is produced by hot cathode filament discharge. Properties of the discharge have been studied at a toroidal field of 1 kG. As expected, both density and discharge current increase as the electron emission increases. It is seen that as the discharge voltage is increased the floating potential drops from about 70 V to a thermal value of about 15 V while the density appears to increase by a factor of four and discharge current increases only marginally from 0.8 A to 1.0 A. As the operating pressure is increased both discharge current and density fall while floating potential increases. At high discharge voltages, probe characteristics show a Maxwellian nature, whereas at lower discharge voltages deviations from Maxwellian nature are pronounced.<>