The application of an Heavy Ion Beam Probe for measurements on a helicon discharge

A Heavy Ion Bema Probe, HIBP, has been installed on an helicon discharge and initial operation has started. The helicon discharge is driven at 13.56MHz with up to 1kW of forward power from the supply. The helicon uses a Nagoya type III antenna. There are 6 magnetic field coils providing an axial field of up to 1.7kG. The HIBP can be operated with Li+ or Na+ ions in the 4 - 20KV energy range. Both the helicon discharge and the HIBP have been installed and have been operated independently. Initial combined runs are scheduled for the summer of 2001 and results will be presented. The HIBP detector electronics have been modified to have a 15MHz bandwidth with the intension of measuring the plasma parameters at the RF drive frequency. The goal is to demonstrate the HIBP capability to make measurements at ICRF frequencies. Measuring the fluctuations of the plasma electric potential and magnetic potential at the drive frequency will lead to a better understanding of the heating deposition and plasma wave physics. The measurements, which represent an order of magnitude increase in frequency response over previous HIBP systems, are complicated by the relatively slow ion transit time across the plasma compared to one period of the RF oscillation. Additional modeling is necessary to address this issue. Initial results of which will be presented. Work supported by the U.S. Department of Energy Grant number DE-FG02-99ER5452985.