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Fusion magnets generate significant AC loss during the processes of excitation and demagnetization. The electrical measurement was predominantly employed as the method for estimating the AC loss. However, the phase-locked amplifier method and integral method (IM) can access the average power across one or multiple current cycles but leave the instantaneous power value unrecorded. In this study, the AC loss of two types of high-temperature superconducting (HTS) stacked conductors composed of REBCO and Bi-2223 were measured. An AC loss analysis method based on parameter identification method is employed to study AC loss in REBCO and Bi-2223 stacked conductors by identifying their instantaneous inductance and instantaneous resistance. Unlike the integral method, the AC loss analysis method based on parameter identification method can analyze the average power, and also the instantaneous power at any given time using a fixed forgetting factor which can affect the accuracy of the calculation. The experimental data suggest that, under identical frequency and current, the AC loss of the REBCO stacked conductor is approximately three times that of the Bi-2223 stacked conductor. [ABSTRACT FROM AUTHOR]

Compared with traditional insulated High Temperature Superconducting (HTS) coil, no-insulation (NI) HTS coil has higher thermal stability and self-protection capability, so that is considered as an important way to generate high steady-state magnetic field. This paper focuses on the experimental phenomena that mechanical damage always occurs in NI coils during quench with high background field. A multi-physics quench simulation model is established for NI insert coils, which contains a 2-d axisymmetric partial element equivalent circuit (PEEC) model for electromagnetic calculation and two axisymmetric finite element models for thermal and mechanical analysis. Based on these models, we analyzed the electromagnetic, thermal and mechanical phenomena of insert coils during quench propagation and recovery. The simulation results show that mechanical damage may occur in the outer superconducting zone near the normal zone in no-insulation coils during quench, and thermal strain caused by temperature rise during quench may exacerbate mechanical damage. Meanwhile, quench at different single-pancake coils has different effects on the mechanical performance of the entire insert coils. Based on the electromagnetic simulation results, we also analyzed the time delay of the traditional terminal voltage quench detection method and its causes. This study analyzed the multi-physics quench phenomenon of no-insulation HTS insert coils. And the results imply that hoop strain will increase to the critical strain due to high magnetic field and current redistribution caused by radial current shunt during quench, resulting in mechanical damage. Additionally, radial current shunt and induced voltage will retard quench propagation velocity, resulting in the time delay in terminal voltage quench detection. [ABSTRACT FROM AUTHOR]

• The design scheme and stress analysis of an HTS insert coil. • The stress problem caused by screening current effect. • The stress-strain distribution of the HTS insert coil. An 8 T no-insulation (NI) high temperature superconducting (HTS) insert has been designed using a 12 T low temperature superconducting (LTS) magnet to build a 20 T magnet. This paper focuses on the electromagnetic design and stress analysis of the 8 T HTS insert coil. The preserve elitist genetic algorithm was adopted to design a coil with the least cost in conjunction with the finite element program. The pre-stress during the winding, the thermal stress during the cooling down, and the electromagnetic stress considering screening current effect during the charging of the HTS insert coil were analyzed and discussed in this paper. [ABSTRACT FROM AUTHOR]