Characteristics of regular discharges in Uragan-3M torsatron

The Uragan-3M device is equipped with two antennas which are fed by RF power with the frequency below ion cyclotron. The frame antenna was used for pre-ionization and the three-half turn antenna makes plasma heating. In this experimental series, the radial profiles of C III, O V and C V optical line intensity and the second cyclotron harmonic emission are measured using a pulse-by-pulse technique. The results of these measurements and Biot-Savart calculations of the Uragan-3M magnetic configuration could be explained by the existence of a small central area with relatively high electron temperature and good plasma confinement surrounded by a zone where the electron temperature and confinement are worse. The relatively low average electron temperature and high RF power needed to sustain plasma are the consequences.