Ultraviolet (UV) and visible impurity spectra (200～750 nm) are commonly used to study plasma and wall interactions in magnetic fusion plasmas. Two optical multi-channel analysis (OMA) systems have been installed for the UV-visible spectrum measurement on EAST. These two OMA systems are both equipped with the Czerny-Turner (C-T) type spectrometer. The upper vacuum vessel and inner divertor baffle can be viewed simultaneously through two optical lenses. The OMA1 system is mainly used for multi-impurity lines radiation measurement. A 280 nm wavelength range can be covered by a 300 mm focal length spectrometer equipped with a 300 grooves/mm grating. The Dα/Hα line shapes can be resolved by the OMA2 system. The focal length is 750 mm. The spectral resolution can be up to 0.01 nm using a 1800 grooves/mm grating. The impurity behaviour and hydrogen ratio evolution after boroniztion, lithium coating, and siliconization are compared. Lithium coating has shown beneficial effects on the reduction of edge recycling and low Z impurity (C,O) influx. The impurity expelling effect of the divertor configuration is also briefly discussed through multi-channels observation of OMA1 system.
FU JiaLI YingyingSHI YuejiangWANG FudiZHANG WeiLV BoHUANG JuanWAN BaonianZHOU Qian
The spectra of HeI(587.6 nm),H_α(656.28 nm) and Dα(656.1 nm) of the helium discharges as well as the normal deuterium discharges have been measured with two optical spectroscopic multi-channel analysis(OMA) systems on the experimental advanced superconducting tokamak(EAST).The influx ratio of the sum of H and D to He spectral lines and the influx ratio of H to D are given.In this way the ratio of hydrogen/deuterium ion(S/X B)H/D to(S/X B)He as well as(S/X B)H/D is not very sensitive to the variation in the edge density and temperature. The low-density helium discharges are operated in order to reduce the recycling hydrogen fluxes; however,the effect is not obvious.The possible reason is that the number of helium discharges is not enough and the content of hydrogen in the wall is still very abundant,which is caused by frequent wall conditionings and the vacuum leakage.The H/(H+D) ratio decreases quickly after one lithium coating and reduces to less than 10%using several accumulated lithium wall conditioning.It is found that the deposited He atoms on the carbon wall will remain at a low level after several D2 discharges.
An attempt was made to improve the spatio-temporal resolution of the tangen- tial X-ray crystal spectrometer (XCS) on the Experimental Advanced Superconducting Tokamak (EAST) by evaluating experimentally the applicability of a novel X-ray photon detection tech- nology for measuring the satellite spectra of Ar XVII with a high counting rate. High-resolution experimental data on the profiles of ion temperature and plasma rotation velocity facilitate the studies of the mechanisms underlining important physical phenomena, such as plasma heating, L-H transition and momentum transport. Based on silicon diode array and single-photon counting technology, a relatively small area (83.8×33.5 mm 2 ) two-dimensional detector was successfully in- stalled and tested in the recent EAST campaign. X-ray photon counting rate higher than 20 MHz was observed for the first time, and high quality satellite spectra were recorded for ion temperature and plasma rotation measurement, indicating that the new technology is suitable for the next-step high-resolution XCS on EAST, and the deployment of a detector array with a much larger X-ray sensing area is planned for better plasma coverage.
吕波石跃江王福地万宝年Manfred BITTERKenneth W. HILLSang-gon LEE李颖颖符佳张继宗徐经翠沈永才
