Experimental Study On Plasma Temperature Measurement With Two-crystal X-ray Spectrometers On EAST

X-ray Imaging crystal spectrometer is one of the important methods for diagnosing and measuring tokamak plasma temperature and rotation velocities.It is one of the conventional methods equipped on the main Tokamak at home and abroad,it is also a diagnostic device for future planning fusion reactor.In recent years,the problem of narrow range of parameters measurement based on single X-ray Imaging crystal spectrometer had become more and more obvious.For this challenge,the upgrade of the X-ray two-crystal Spectrometer system on EAST had been early start at home and abroad,in order to measure the plasma parameters at low temperature and high temperature respectively,and the measurement of plasma parameters under higher plasma temperature was satisfied.Firstly,the upgrading of the two-crystal spectrometer was summarized in this paper.The tangential X-ray crystal spectrometer installed a two-crystal structure,complete high quality Ar XVII and Ar XVIII spectra had been obtained using Ar XVII and Ar XVIII as the diagnostic ions and quartz 110 and quartz 102 as the crystals.The poloidal X-ray crystal spectrometer also installed a two-crystal structure obtained complete high quality Ar XVII and Fe XXV spectra using Ar XVII and Fe XXV as the diagnostic ions and quartz 110and Ge 422 as the crystals.According to the obtained two-crystal spectral line,the plasma parameters are in good agreement and can measurement of plasma temperature in the range of 10 keV ^ Te≥ 0.5keV.As the complexity of the assembly of the two-crystal increased,the wavelength range of the diagnostic ions increased,metal impurities may be introduced into the plasma during high-parameter experiments,like Mo,Fe,W and Cu,etc.So that the spectral lines of some impurity with wavelengths in the range of Ar XVII and Ar XVIII ions were also captured by the detector,overlap with the spectral,resulting in spectral contamination.The wavelength of each impurity peak was calibrated by the two-crystal spectral line,and the tungsten ions and its wavelengths as the high intensity impurity peak located next to the z line of the Ar XVII spectrum line was identified.And all impurity types and wavelengths in the wavelength range of Ar XVII and Ar XVIII ions were summarized according to the NIST atomic spectrum database,including first-order diffracted molybdenum ions and second-order diffracted iron ions.The appearance of these impurity peaks challenges the measurement of plasma parameters with a two-crystal spectrometer,because the impurity spectral line caused the spectrum pollution,the measurement results of ion temperature and electron temperature had a large deviation and the error increased.This paper provided a new way to measure the plasma parameters by using the two-crystal spectrometer.