Eletromagnetic Shielding Optimization Research Of ECE Imaging Diagnostic On EAST

Electron Cyclotron Emission Imaging (ECEI) diagnostic system is an advanced diagnostics on tokamak, the system is used to detect nw magnitude plasma radiation signals, measuring the electron temperature profile of a small section of the tokamak.384channels ECEI diagnostic system has been installed on EAST tokamak. The main advantages of ECEI technique are the high spatial andtemporal resolutions and the two dimensional diagnostics ability, and the main advance in the384-channel ECEI system is the much larger radial coverage. What’s more, the EAST tokamak device has been equipped with4MW ICRF system,4MW LHCD system and NBI system.This paper mainly describe384channels ECEI system on the EAST tokamak.We have obtained some meaningful data in core plasma. The main subject of this part is about the quasi-optics, the antenna array, the wide-band inter-mediate frequency (IF) electronics of the ECEI system, Secondly, the paper introduces the operation of the384channels ECEI system in2012:we obtained the first successful commissioning, and we have obtained some meaningful data in core plasma, such as, calculating the surface of Q=1when observing the sawtooth oscillation. However, sometimes the power supply of IF electronics is unstable.ECEI diagnostic system on EAST tokamak was heavily interfered by the Lower Hybrid Current Drive. The mesh is helpful for shielding EM noise wave according to shielding principle. The shielding performance will be improved by increasing mesh density or number of layers. Building2.45GHz sources as interference, the antenna array and the power supply have been interferenced. Finally we determine to use copper mesh as the shield. The optimization of the electromagnetic shielding is presented, which help to reduce the interference to40dB. Appropriate copper mesh shield and the correct ground connection are the key solutions. The comparison of the ECEI raw signals before and after the optimization clearly show that the shielding performance is greatly improved.The EAST experiment in2014has ensured the feasibility of the shielding. In order to improve the "robust" of shielding performance, we design a new shielding box, designing groove to reducing electromagnetic leakage, using L>10W waveguide window to meet the needs of the ventilation, using conductive rubber gasket to fix the high-pass filtering plate. Finally, we set up the test platform with2-18GHz frequency synthesizer source, microwave probes and horn to test shielding performance of the box, the shielding effectiveness of the box is50dB at least.