A spatial detector array for measuring plasma turbulence with the heavy ion beam probe

Abstract

The heavy ion beam probe (HIBP) has become a valuable diagnostic for measuring the plasma space potential and electron density in high-temperature plasmas. However, due to the limitations placed on the design of the HIBP by the size and complexity of the electrostatic energy analyzer, only limited information can be extracted from the HIBP’s fluctuation measurements. By extending the range and number of sample volumes simultaneously recorded by the beam probe, a better understanding of the turbulence distribution, S(k,ω), can be achieved. This can be accomplished by installing an array of secondary particle detectors close to the plasma edge. InterScience, Inc. has developed a particle detector capable of measuring the small signal levels required by the HIBP in the high background environment associated with operating near the plasma edge. In addition, this detector has been incorporated into the design of a 20-element, spatial array for the 2 MeV HIBP on TEXT. A flexible design has been developed such that the array can make measurements that are nearly poloidally or radially aligned. With the use of spatial Fourier transform, this will allow the HIBP to better determine S(k,ω). Details of the design of the detector array and initial experimental results will be presented.