Electromagnetic-structural Analysis And Thermal Analysis Of The Resonant Magnetic Perturbation Coils On J-TEXT Tokamak

J-TEXT tokamak belongs to Huazhong University of Science and Technology. Sincethe first realizing of150kA plasma current in2007, its peripheral equipment andfundamental diagnostic instruments have been building and improving. So series ofphysical experiments are carrying on, centering in plasma transport and turbulence andMHD instabilities. The external resonant magnetic perturbation coils produce a rotatinghelical magnetic field in the vacuum vessel, which has a mutual influence with the plasmaand makes an effect on its MHD instabilities. Both theory and experiment prove thatexternal helical perturbation magnetic field with enough strength and certain mode canpenetrate J-TEXT’s error field and carry experiments about mode locking, plasma transportand edge located modes.Based on J-TEXT tokamak’s structural characters, a set of4in-vessel saddle coils willbe placed, uniformly located along the toroidal vacuum vessel. Each set of coils composesof3individual ones. They will be mounted in the low field side and the up and downwindows of the vacuum vessel through welding. The coils will be fed with alternatingcurrents up to10kA at frequencies up to10kHz and are made up of inner copper conductor,protective stainless steel pipe, strengthening parts and insulation materials. What are mainlyconsidered when designing the coils include three parts: First, the coils should not get intouch with other in-vessel components and be able to withstand the huge electromagneticforces caused by the currents flowing in them; Second, the coils must be capable ofundertaking the instant huge electromagnetic forces caused by the induced currents due toplasma disruption; Lastly, the thermal environment in the vacuum vessel is very complex,plasma radiation and joule heat both contribute to the temperature rise of the coils.Successive operation leads to heat accumulation and shortens the coils’ lives.This paper summarizes the design and usage of external perturbation coils in tokamakes. The electromagnetic-structural analysis and thermal analysis are carried onusing finite element method software ANSYS during the designing and verifying process.Through this work we get the magnetic field distribution of J-TEXT, the resistance andinductance of the coil, the stress distribution, intrinsic frequencies and the thermaldistribution. At present, one down coil for testing has been installed and tested in DCcurrent up to7.5kA/50ms. Results show that the coil is stable in structure and thermalenvironment and is ready for experiments.