摘要
The spectral broadening of motional Stark effect(MSE)is simulated in the HL-2A tokamak,which is in good agreement with the experimental observation.The divergence angle of the neutral beam,finite lens size and beam energy dissociation are the main broadening factors,while the lens size is the most important one.The experimental spectra fitted by multiple Gaussian distributions reveal that the Stark splitting and its full width at half maximum(FWHM)are~0.07 nm and~0.19 nm,respectively.Therefore,theπandσcomponents of the MSE will overlap since the Stark splitting is much smaller than its spectral broadening.A narrowband filter with the FWHM of about 0.16 nm is good enough to isolate the two components for providing the polarization fraction over 50%,which guarantees reasonable measurement precision for magnetic field pitch angle.
基金
Supported by the National Magnetic Confinement Fusion Science Program of China under grant No 2010GB101001
the National Natural Science Foundation of China under Grant Nos 11075046 and 10935004
the China-Korean Joint Foundation under Grant No 2012DFG02230.
