Experimental Studies of Radio Frequency Waves and Confinement in the Auburn Torsatron. Progress Report, November 15, 1985-November 14, 1986

摘要

During the second year of operation, three master's theses have been completed giving us a basic understanding of the operating parameters of the Auburn Torsatron, and a new vacuum magnetic field diagnostic has been introduced. The first master's thesis, by Randall Tarr, measured the plasma density and temperature profiles with a floating double probe for an ECRH discharge. The probe was swept over the plasma cross section under the control of a computer built specifically for the task. It also recorded the data (voltage, current, coordinates) at which point in its own memory bank. The data was subsequently analyzed on a PC. The second thesis describes the results of plasma injection from a washer stack gun. This method of plasma formation produced higher densities and enabled the plasma lifetime of the plasma to be determined as a function of the magnetic field. The third thesis investigated discharge cleaning methods and tested several ICRF antennas for vacuum breakdown. Because of regularly occurring leaks, only ECRF discharge cleaning was found effective. Attempts to produce plasma directly with rf low frequencies, as commonly done in Uragan-3 were unsucessful, presumably due to insufficient power. Finally, a new method of measuring vacuum magnetic surfaces for stellarators and torsatrons which was pioneered by the Uragon-3 group was tested. Preliminary results show this new method to have great advantages over conventional methods. It appears that not only magnetic surface shapes, but also their quality, may be determined by this method, and this new method is recommended for utilization on ATF. (ERA citation 11:055426)