Temperature-field-angle dependent critical current estimation of commercial second generation high temperature superconducting conductor using double hidden layer Bayesian regularized neural network

We estimated the critical current of the second generation (2G) high temperature superconducting (HTS) conductor using neural network fitting methods. The critical current of 2G HTS conductors depends on magnetic field strength and angle as well as on temperature, Ic(T, B, θ). Moreover, the critical current values vary for 2G HTS conductors from different manufacturers. In this study, we addressed three challenging issues in critical current assessment by neural network fitting methods, namely 90-degree asymmetry, a wide range of temperature-field-angle dependence, and different manufacturer conductor differences. Prediction models for three commercial HTS conductors were trained and evaluated by convergence, accuracy, and robustness. The linear regression correlation coefficient R was approximately equal to 1 for the three models. The critical current estimation obtained from the proposed method was compared with the critical current estimation from the interpolation method at different fixed temperatures using a multi-width no-insulation magnet. The model computation speed was also discussed. The proposed model needed only 2.7 s to compute 10 million data sets. Therefore, the convergence, accuracy, reliability, and speed of the proposed method prove that it can be used in a wide range of industrial applications and academic fields.

High-Temperature Superconducting Cable Fault Location Method Based on Improved Time-Frequency Domain Reflection Method and EEMD Noise Reduction

Aiming at the operation and maintenance requirements of the fault location of high-temperature superconducting cables, a fault location method of high-temperature superconducting cables based on the improved time-frequency domain reflection method and EEMD noise reduction is proposed. Considering the cross-term interference problem in the traditional time-frequency domain reflection method, this paper introduces the affine transformation to project the time-frequency distribution of the self-term and the cross term and further highlights the characteristic differences between the two through coordinate transformation, and the particle swarm algorithm is employed to solve the optimal stagger angle of the affine transformation. The unscented particle filter is adopted to separate the cross term, and EEMD noise reduction is introduced to solve the signal noise problem. Finally, two software programs, PSCAD and MATLAB, are employed for joint simulation to build a model of high-temperature superconducting cable. The simulation example shows that the proposed method in this paper can eliminate the cross-term interference of the traditional time-frequency domain reflection method, effectively locate the fault of the high-temperature superconducting cable, and improve the positioning accuracy.

Study on the Applicability of Neutron Radiation Damage Method Used for High-Temperature Superconducting Tape Based on Geant4 and SRIM

High-temperature superconducting material is a promising candidate to fabricate superconducting magnet for magnetic confinement fusion reactors. The DPA number of the 1 µm thick superconducting layer in a high temperature superconducting tape under neutron irradiation needs to be calculated to predict the property changes. The DPA cross sections, which ignore the spatial distribution of vacancies caused by PKAs, are commonly used to obtain the results of the damage energy and DPA. However, for geometric models with the thickness as small as 1 µm, the energy and angular distribution of PKAs reveal that a significant number of PKAs with relatively high energy tend to scatter forward and cross the boundary of model, so the thickness of model has the potential to affect the number of displaced atoms. In this paper, we developed a method based on Geant4 and SRIM to evaluate the deviation of the traditional analytic method caused by the thickness. Geant4 is used to obtain the location, direction, and energy of PKAs, while SRIM is used to track every PKA and obtain damage energy and the number of displaced atoms. The radiation damage calculation of simple thin plate models with different thicknesses and the tape model are conducted with the neutron energies from 1 to 14 MeV. The results show that PKAs need to be tracked continuously for models with thickness less than 10 µm and the deviation of the analytic formulas increases rapidly with the decrease of thickness. For the superconducting layer composed of four different elements in the tape, the deviation also depends on the proportion of each atomic species and the neutron-atom interaction cross sections under different incident neutron energy.