Development Of Beam Emission Spectroscopy Diagnostics On EAST

Plasma density fluctuation is a very important physical parameter in L-H transition,particle transition and others plasma research,especially the 2D plasma density fluctuation which can give out the turbUFence structure directly.BES(Beam Emission Spectroscopy)is one of the 2D plasma density fluctuation with high spatial and temporal resolution.The author takes part in the BES development on EAST including the optical system design,key elements chosen,system construction,some structures checking,space calibration and some experimental results.And some advanced research of joint diagnostics between BES and UF-CXRS.The main contents of this paper are summarized as follows:BES diagnostics relys on NBI(Neutral Beam Injection),the Doppler shifted effective signal of BES comes from the interaction between NBI and the main plasma.Firstly,some briefly introduction of NBI production,interaction between NBI and main plasma,especially the calculation process of BES effective signal.Then we turn to the BES system optical design mainly from diagnosing window chosen,Lighting system,signal detection part and key elements.And finished the construction of the hardware structure.EAST-BES detects the Doppler red shifted Da signal in 659nm,spatial and temporal resolution are 1-3cm and lus,respectively.The diagnostic has 128 detection channels in 16 × 8(poloidal x radial),which 2D viewing area is movable in p = 0-1.2.The system is written in IDL program.All entry Settings and other control commands are written in a one-to-one manner and we can control the system from a GUI panel.This BES adopts the transmission type optical path design,and when the system is set up,the important components in the optical path are tested and the space calibration of the diagnostics system is necessary.Effective signal of BES as the characteristic spectral line,the performance of the filter directly decides the signal-to-noise ratio(SNR)of the signal.The diagnosis system of light path closure also plays a key role in the quality of the signal at the same time,light-leaking checking is necessary.In order to determine the spatial position and horizontal vertical condition of 2D viewing area,the system was calibrated by hardware calibration and software calibration.The hardware calibration is tedious.When the system is maintained,it needs to be calibrated again,but the calibration results are high reliable.The software calibration process is simple and can be carried out at any time.The accuracy of coordinates of reference points has great influence on the calibration results.Therefore,both types of calibration have advantages and disadvantages.During the EAST physical experiment,we make sure the BES signal is only from NBI when there are other auxiliary heating.And the response of BES system to the NBI is real time.The 2D plasma density fluctuation shows some turbulence.Some results of advanced research of BES and UF-CXRS joint diagnostics are still given.