Electromagnetic, Structural and Thermal Analyses of the Vacuum Vessel

Abstract

This chapter deals with the electromagnetic (EM), structural, and thermal analyses of the vacuum vessel (VV) of Tokamaks. First, the structure, the basic functions, and operation circumstance of VV are introduced. The VV, which is one of the key components, will have to withstand not only the EM force due to the plasma disruption and the Halo current, but also the pressure of shielding fluid and the thermal stress due to baking. In this chapter, as a typical EM load, the induced current, and resulting EM forces on the VV during a major disruption are studied in detail by analytical and numerical methods. According to the principle of EM induction, by simplifying the VV double-shell structure to several dozens of circular coils, distribution of the induced current and its effects on the background magnetic field are analyzed, and the resulting EM forces are simulated with Fortran software codes. Finite element methods are used to analyze the eddy current, the EM force, and the stress on VV during MD more accurately. Prior to operation, the VV is to be baked out and discharge cleaned at a higher temperature in order to get an ultra-high vacuum and a clean environment for plasma operation. During baking out the nonuniformity of temperature distribution on the VV will also bring about serious thermal stress that may damage the vessel. The temperature field and thermal stress of the VV during baking is analyzed detailed.