Abstract
At present, the Tokamak has become a mainstream form of the magnetic confinement fusion device. The toroidal field (TF) magnet in the Tokamak system is required to generate a high-steady field to confine and shape the high temperature plasma. To secure high current density and high thermal stability, the no-insulation (NI) winding technique is used in the fabrication of the TF magnet. During plasma operation, heat is generated in the TF magnet caused by the interaction with central solenoid (CS) coils, poloidal field (PF) coils, and the plasma current. The heat generated in NI coils is complex owing to the existence of current flow between adjacent turns. Thus, it is necessary to calculate the thermal problems. Taking into consideration the effect of turn-to-turn contact resistance, this paper presents the thermal behavior of a NI toroidal magnet under different operating conditions. The NI toroidal magnet is composed of 10 double-pancake (DP) coils wound with BSCCO tapes. The analysis procedure combines the finite element method (FEM) with an equivalent circuit model. This analysis has applicability and practical directive to the design of cryogenic cooling system for NI toroidal magnet.
Highlights
The magnet system is a crucial part of Tokamak machine
According to a previous study performed by the authors, the NI toroidal magnet possesses excellent magnetic field stability benefited from the RC in the radial direction, characterizing the typical electromagnetic behavior of an RL parallel circuit in time-varying conditions
This study aims to describe the analysis procedure considering the influence of poloidal field (PF) magnetic field
Summary
The magnet system is a crucial part of Tokamak machine. It consists of toroidal field (TF) coils, central solenoid (CS) coils, and poloidal field (PF) coils. In the process of plasma discharge, one of the essential issues is the operational stability of the magnet system. The TF coils provide a steady toroidal magnetic field to confine the plasma movement, while CS and PF coils operate in pulse mode to control the plasma current. During plasma discharge, the TF coils are operating under steady state in a variant magnetic field. The nuclear fusion device contains very strict requirements for the intensity and stability of the toroidal magnetic field. In order to keep the plasma confined and stable, the intensity of the magnetic field requires reaching the Tesla level. When a plasma current exists, the current fluctuation of the constant direct current (DC) power supply requires it to be less than 1% to ensure the stability of the magnetic field
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