Measurements of plasma fluctuations with a heavy-ion beam probe

A heavy-ion beam probe can provide simultaneous, spatially resolved measurements of φ̃ and (ñσeff) in magnetically confined plasmas. Capabilities have been demonstrated on TMX, RENTOR, and ISX-B using single detector systems, which permit the evaluation of the frequency spectra out to several hundred kilohertz. The cross correlation and phase difference between ñ and φ̃ are also obtained by assuming T̃e fluctuations to be negligible. Present development effort is focused on the use of multiple detectors and multiple ion species. These should allow the determination of both the frequency and wave number spectra for ñ, φ̃, and T̃e. The resolution and limitation of these techniques and their application to studying fluctuation-induced transport will be discussed.