Heavy ion beam probe development

Summary form only given. We are conducting experiments with the ultimate goal of developing a non-perturbing diagnostic technique for measuring RF field and density fluctuations in fusion plasmas. In order to develop this technique, a helicon plasma with a heavy ion beam probe (HIBP) diagnostic is being constructed. The helicon plasma has a magnetic field of up to 1.5 kG produced by a set of circular coils. A 1 kW, 13.56 MHz RF generator will be used to drive helicon waves in the plasma. Diagnostic apparatus utilizes a 60 keV HIBP diagnostic beam and detector that were previously used on the Tokamak de Varenne. The detection electronics is being modified to operate at higher frequencies. Present status of the experiment as well as key issues in extending HIBP measurements to higher frequencies will be discussed. The HIBP proposed for LDX, based on the old EBT/TARA system, is intended to study convective cells in a simple magnetic dipole field, similar to that found in planetary magnetospheres. Both potential structures and the impact of flows around them as observed in fluctuation measurements can be characterized with such a system. An HIBP system has also been proposed for NSTX, based on the 500 kV TEXT HIBP. There is presently no plan for the 2 MeV TEXT Upgrade system.