| Plasma electron temperature is one of the most important parameters in the magnetic confinement fusion research.As the most common 2D diagnostic of electron temperature profile and fluctuation in the current magnetic confinement fusion device,electron cyclotron emission imaging(ECEI)diagnostic has played an important role in the study of macro MHD(magnetohydrodynamics)instability and turbulence of tokamak plasma in the past 20 years.This paper foucus on the quasi optical design,the electronics platform test and system installation of ECEI on J-TEXT tokamak,as well as the preliminary physical experiment based on ECEI diagnostic.As the basis of two-dimensional measurement,quasi optical design is critical for the imaging quality of ECEI diagnostic.In this paper,the design and test of imaging optics and local oscillator optics are carried out.The J-TEXT ECEI imaging optics adopts a dual array structure covering W-band(75-110 GHz)and F-band(90-140 GHz).The imaging optics has enough aperture and good robustness.The dual array can not only adjust the focus observation of all the radial positions of the plasma independently through the Focus lens,but also realize the poloidal zoom function by moving the Zoom lens group.The poloidal coverage zoom ratio is 1.13-1.9,the maximum field curvature is 7.3 mm,and the maximum Rayleigh length is 503 mm.All of the optical parameters are completely decoupled in the case of the narrow poloidal zoom.And the design performance of the imaging optics has reached the leading level in the world.Another main content of quasi optical design is the design of local oscillator optics.According to the requirements of the limited space and the feed beam collimation,two different types of the local oscillator optics are adopted,which are the traditional spherical lens and the new hyperbolic lens.The local oscillator optics with spherical lens is more robust,which is convenient for installation and long-term stable work.The innovative design of the local oscillator optics of the 3-lens hyperbolic lens can produce more uniform linear distribution feed power and greater poloidal power coverage on the antenna,and the introduction of beam expanding lens improves the robustness of hyperbolic lens local oscillator optics compared with the two lenses option.In order to verify the design performance,the ECEI quasi optical system is tested on the platform.The test contents include anti-interference testing,stability testing,refractive index testing,and optical performance testing for the validation of optical design.The test results show that the performance of the quasi optical system is in good agreement with the design parameters,and some abnormal results are analyzed and discussed.After the quasi optical design and platform test of ECEI,the platform test of J-TEXT ECEI electronics system is also carried out,including the voltage output testing of the power supply box to verify the working stability of the electronic system,the functional consistency testing to verify the performance of the electronic design and the signal quality testing.The test results show the test parameters of the electronic system are consistent with the design values,and the electronic system can operate stably in all parameters except for a few signal interferences.Based on the excellent performance of platform test,the installation of J-TEXT ECEI diagnostic system is finally completed,and the preliminary physical experiment observation is carried out.Through the observation of two-dimensional temperature distribution evolution in the process of sawtooth collapse on J-TEXT device by ECEI,it is found that the process is quite consistent with Kadomtsev's complete reconnection model.And in the experiment of mode coupling phenomenon,the mode coupling images of m/n= 2/1 and m/n= 3/1 at high and low field sides are given,and the three stages of mode coupling process are shown.These results show that the development of J-TEXT ECEI diagnostic has good performance and can provide strong support for physical research. |
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