Poloidal beam emission spectroscopy system for the measurement of density fluctuations in Large Helical Device

Oishi, T.; Kado, S.; Ida, K.; Yoshinuma, M.; Nakano, H.; Yamazaki, K.
October 2010
Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D719
Academic Journal
A system of beam emission spectroscopy (BES) for density fluctuation measurements having the sightlines passing through the plasma in the poloidal direction was developed in the Large Helical Device (LHD). Even though the angle between the beam and the sightline is slightly larger than a right angle, Doppler-shifted beam emission can be distinguished from background emission because of the high energy (120-170 keV) of the neutral beam for heating with negative ion sources. Spatial resolution is about 0.1-0.2 in the normalized radius. Compared with the prototype BES system with toroidal sightlines, the BES system with poloidal sightlines showed improved spatial resolution.


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