AC Loss Analysis On Central Solenoid Model Coil And Its Current Leads For Fusion Test Reactor

The central solenoid(CS)coil is an important component of the China Fusion Engineering Test Reactor(CFETR).It is used to produce and stabilize the plasma in the superconducting tokamak and guarantee that the magnet and fusion device work in a safe and stable environment.The CS model coil(CSMC)has the same scientific goals and physical parameters as that in the CS prototype coil of CFETR system,which is the basis of the research of the CS prototype coil.The AC loss of CSMC is the most important factor in terms of its stability and efficiency because it works at extremely high current and magnetic field.The CSMC system contains the model coil itself,high temperature superconducting current lead(HTSCL),etc.A study of the HTS tapes and HTS stacks is the first step of the analysis of the HTS current lead.Research on the magnetic field configuration and AC loss of the model coil,HTS tapes,HTS stacks and HTS current lead is the foundation of the Research and Development(R&D)of the CFETR CS model coil.In this dissertation,the AC loss of the CS model coil is analyzed theoretically and experimentally.In addition,the AC loss of the HTS current lead is studied based on the theory of HTS tapes and HTS stacks.An AC loss calculation model of the CSMC based on actual operating conditions is established.The irregular transport current of the CSMC is divided into several time segments based on the piecewise linear method and the magnetic field and field rate of change are solved according to the Ampere Circuital Theorem.The AC loss can be finally obtained by using magnetic field and field rate of change.The hysteresis loss and coupling loss of the CSMC at real operating current is calculated with different kinds of(cable-in-conduit conductors)CICCs,providing the foundation for CICC selection for the CS model coil in the near future.An experimental method for transport loss measurement of the CSMC in practical operated conditions is proposed.An adjustable capacitor box and compensation coil are used as a double compensation system and a Hall Effect sensor is utilized to calibrate the transport current.The transport loss of the superconducting coil is measured using non-sinusoidal current to verify the feasibility of the test system.The reasonableness of the result shows that the test system can measure the transport loss of superconducting coils carrying non-sinusoidal current.Furthermore,the potential measurement errors of the proposed system are analyzed and several countermeasures are proposed.A magnetization loss test system for HTS tape based on the calibration-free method is proposed and test platform is built.The magnetization loss of the HTS tape is measured and the frequency dependence,magnetic field amplitude dependence of themagnetization loss is analyzed.In addition,the transport loss of the HTS tape with non-sinusoidal current is measured at same time.Using the H-formulation finite element method(FEM),the magnetization and transport loss of the HTS tape are calculated and compared with the test results.The effect of the shielding of the magnetic field at metal stabilizer layers in proximity to the HTS tape on the magnetization loss is considered and analyzed.The relationship of the shielding effect and the gap between the HTS tape and copper stabilizer tape is analyzed.The effect of this shielding effect of HTS tape and Roebel cable on the AC loss is also analyzed and compared.The concept of the effective penetration field of the HTS tape is proposed and calculation models of the effective penetration field and the dynamic resistance of HTS tape are developed.The magnetization losses of HTS stacks and Roebel cables are measured using the calibration-free method.The field amplitude dependence,field angular dependence and field frequency dependence of the magnetic field are measured and compared with the FEM results.The relationship between the magnetization loss of HTS stacks and Roebel cable at different field amplitude range is deduced and analyzed.According to this relation,the magnetization loss of the HTS stack and Roebel cable are deduced each other at the high field amplitude range.In addition,the transport loss of the HTS stack at non-sinusoidal current is measured and compared with the FEM results,providing a good foundation for AC loss analysis of HTS current leads.Two kinds of structures,rectangular and hexagonal of HTS current leads with high transport current are designed.The AC losses of these two HTS structures are calculated based on H-formulation FEM.A test system for measuring the AC loss of HTS current leads is built and the losses with non-sinusoidal transport current are measured.The result shows that the loss of the hexagonal structure current lead with good symmetry is smaller than that of the rectangular structure current lead in the same conditions,which providing a good reference design for the current lead for the CSMC.