Beam Emission Diagnostic for Estimating Neutral Beam Attenuation

Neutral beam attenuation has been investigated by the beam emission diagnostic system at LHD which consists of a quartz optical fiber, leading to a spectrometer and an ICCD detector. The spectral resolution and the reciprocal dispersion are 0.21 nm and 1.4 nm/mm, respectively. The behavior of the beam-stopping cross-section derived from the beam emission is consistent with that of the cross-section from the Atomic Data and Analysis Structure (ADAS) database. The intensity of the beam emission decreases with increasing stopping cross-section from the use of heavy ions in a discharge. We have also observed that the measured cross-section of the hydrogen is larger than that of the ADAS calculation.