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

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2010-10-01
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]