Overview of the beam emission spectroscopy diagnostic system on the National Spherical Torus Experiment

Smith, D. R.
Feder, H.
Feder, R.
Fonck, R. J.
Labik, G.
McKee, G. R.
Schoenbeck, N.
Stratton, B. C.
Uzun Kaymak, İlker Ümit
Winz, G.
A beam emission spectroscopy (BES) system has been installed on the National Spherical Torus Experiment (NSTX) to study ion gyroscale fluctuations. The BES system measures D-alpha emission from a deuterium neutral heating beam. The system includes two optical views centered at r/a approximate to 0.45 and 0.85 and aligned to magnetic field pitch angles at the neutral beam. f/1.5 collection optics produce 2-3 cm spot sizes at the neutral beam. The initial channel layout includes radial arrays, poloidal arrays, and two-dimensional grids. Radial arrays provide coverage from r/a approximate to 0.1 to beyond the last-closed flux surface. Photodetectors and digital filters provide high-sensitivity, low-noise measurements at frequencies of up to 1 MHz. The BES system will be a valuable tool for investigating ion gyroscale turbulence and Alfven/energetic particle modes on NSTX. (C) 2010 American Institute of Physics. [doi:10.1063/1.3478660]