RECENT ADVANCES IN HEAVY-ION BEAM PROBE DIAGNOSTICS

Heavy ion beam probes (HIBPs) have proven to be a unique tool for measuring fluctuations and particle transport in tokamaks. They have been used to measure fluctuations in density, electric potential, and magnetic vector potential. The density and potential fluctuation measurements have determined the particle flux due to electrostatic turbulence in the TEXT and ISX-B tokamaks. In these measurements, the frequency spectra (0-500 kHz) of the phase between density and potential, the wave numbers of the fluctuations, and the fluctuation level are obtained. Three topics are discussed in this paper. We present measurements of magnetic fluctuations during MHD activity using the TEXT HIBP. Analysis of these measurements indicates that the diagnostic is primarily sensitive to the local value of Aφ in the sample volume unless the local A φ is small. In addition, we discuss instrumental effects associated with wave number measurements. We will discuss the effects of sample volume size on the wave number measurements and report the results of experiments in which the sample volume size is reduced by passing the primary beam through an aperture. Finally, a brief description of the new design issues addressed in constructing the 2 MeV HIBP for TEXT-Upgrade and 160 kV ATF HIBP will be presented.