Siyuan Chen

The axially stacked pulsed magnet exhibits distinct advantages in reducing energy demands and mitigating electromagnetic coupling, but comprehensive investigations into its electromagnetic characteristics and subsequent design optimization remain insufficient. To address this, a 2D axisymmetric finite-difference time-domain computational method is developed for multi-physics analysis. This method accurately simulates axial and radial magnetic field penetration within conductor cross-sections, while accounting for eddy-current and magnetoresistance effects during discharge. Consequently, transient 2D electromagnetic and thermal characteristics can be rapidly calculated for each individual conductor layer. Numerical validation against FEM results in COMSOL demonstrates that the proposed method significantly accelerates computation without compromising accuracy. Using this tool, parametric studies show that higher secondary coil segmentation enhances coupling but degrades efficiency, while its geometric configuration strongly influences temperature rise and energy requirements. Based on these findings, an optimized 101 T magnet design is achieved, meeting all electromagnetic-thermal and mechanical criteria. The method serves as a reliable, balanced tool for the rapid preliminary design and subsequent optimization of pulsed magnets.

Pulsed magnets producing 45-100 T magnetic fields with millisecond pulse durations are essential tools for advanced research in condensed matter physics and materials science. Conventional radially nested multi-coil systems, however, suffer from high inductance, strong electromagnetic coupling, and excessive energy consumption, which limit the achievable magnetic field. To overcome these limitations, a novel axially stacked pulsed magnet configuration is proposed. Investigating its electromagnetic and thermal responses requires an efficient multi-physics computational framework. Existing rapid-computation tools, such as PMDS, which assume coaxial and parallel coils, are unsuitable for this topology, while commercial finite-element software often involves long computation times and convergence issues. To address these challenges, a dedicated numerical framework is developed, integrating circuit equations, magnetic-field diffusion, and heat conduction, while accounting for magnetoresistance and eddy-current effects. A MATLAB-based code is validated against COMSOL simulations, demonstrating deviations below 2%. In a 95 T case study, the axially stacked design reduces self and mutual inductances by over 60%, decreases energy demand by 60%, and shortens pulse width by 36%. The proposed axially stacked topology offers a new pathway toward realizing ultra-high-field pulsed magnets exceeding 100 T

The development of pulsed magnets capable of generating magnetic fields exceeding 100 Tesla has been recognized as a crucial pursuit for advancing the scientific research on high magnetic fields. However, the operation of magnets at ultra-high magnetic fields often leads to accidental failures at their ends, necessitating a comprehensive exploration of the underlying mechanisms. To this end, this study investigates, for the first time, the mechanical behaviors of Zylon fiber-reinforced polymers (ZFRPs) within pulsed magnets from a composite perspective. The study begins with mechanical testing of ZFRPs, followed by the development of its constitutive model, which incorporates the plasticity and progressive damage. Subsequently, in-depth analyses are performed on a 95-T double-coil prototype that experienced a failure. The outcomes reveal a notable reduction of approximately 45% in both the radial and axial stiffness of ZFRPs, and the primary reason for the failure is traced to the damage incurred by the end ZFRPs of the inner magnet. The projected failure field closely aligns with the experiment. Additionally, two other magnet systems, achieving 90.6 T and 94.88 T, are analyzed. Finally, the discussion delves into the impact of transverse mechanical strength of the reinforcement and axial Lorentz forces on the structural performance of magnets.

Accurate structural analyses of continuous fiber-reinforced polymers (FRPs) are imperative for diverse engineering applications, demanding efficient material constitutive models. Nonetheless, the constitutive modeling of FRPs is complicated by the nonlinear behavior resulting from internal damages and the inherent plasticity. Consequently, this study presents an innovative anisotropic constitutive model for FRPs, designed to adeptly capture both the damage evolution and plasticity. All requisite parameters can be easily obtained through fundamental mechanical tests, rendering the model practical and user-friendly. The model utilizes the three-dimensional Puck criteria to determine damages, initiating the evolution process through a combination of continuum damage mechanics and linear stiffness attenuation methods. This evolution is coupled with a one-parameter plastic model. Subsequently, the numerical implementation method, integrated into ANSYS, is detailed. This emphasizes the Cauchy stress and consistent tangent stiffness solution strategy. Finally, the effectiveness of the developed model is demonstrated through comprehensive verification, encompassing existing biaxial tension and open-hole-tension tests conducted on carbon and glass FRP laminates. The simulation results exhibit a remarkable correspondence with the experimental data, validating the reliability and accuracy of the proposed model.

The Zylon fiber-reinforced polymer (ZFRP) reinforcements of pulsed magnets often manifest transverse and shearing failure modes under ultrahigh magnetic fields, resulting in unintended disruptions of the magnet system. Nevertheless, the transverse tensile, compression, and in-plane shear behaviors of ZFRP remain insufficiently understood, impeding efforts to elucidate the underlying failure mechanisms and enhance magnet performance. To address this knowledge gap, this paper undertook a comprehensive mechanical tests of ZFRP. Specimen were fabricated using the autoclave-forming technique, followed by transverse tensile, compression and in-plane shear tests conducted at 213 K, 243 K, and 296 K. The elastic modulus and stress-strain response were both characterized, and the influence of the fiber-filling factor were also discussed.

A triple-coil pulsed magnet aiming at 100 T (Tesla) was designed and tested at the Wuhan National High Magnetic Field Center. The magnet was powered by a 100 MJ pulse generator, a battery bank, and 25 kV capacitor banks in combination. The magnet failed at 83 T, while the whole structure remained intact. The failure process was analyzed by using the recorded waveforms of the voltage and the current, as well as disassembling and dismantling the failed magnet. It shows that the inner coil broke down first, and then the electrical breakdown occurred between the middle and outer coils. The possible reasons were also discussed. The buckling analysis results show that the inner and middle coils would buckle at 71 T and 83 T, respectively, which were consistent with the experimental results. The cross-ply reinforcement method is proposed to enhance the structural stability of high field magnets.

A triple-coil pulsed magnet aiming at 100 T (Tesla) was developed and tested at the Wuhan National High Magnetic Field Center (WHMFC). The outer coil was powered by a 100 MJ pulse generator and a battery bank connected in series. The middle and inner coils were energized by 25 kV capacitor banks. The magnet failed at 83 T, while the whole structure remained intact. The failure process is analyzed by using the recorded waveforms of the voltage and the current, as well as disassembling and dismantling the failed magnet. It shows that the electrical breakdown occurred between the middle and outer coils as well as within the inner coil, and the inner coil broke down before the middle and outer coils. Based on the previous analysis, the time line of the failure process is given. Additionally, the possible reasons for the failure are also discussed. The results show that the buckling and fiber fracture of the inner coil might cause the accident.

The aim of traditional designs of pulsed magnets is to keep the von-Mises stress on the midplane less than the ultimate tensile strength of materials. However, recently failed high-field experiments showed that some short circuits occurred at the magnet end, which is most possibly caused by the axial displacement of wires. This indicates that the former design is inadequate and accurate axial mechanical analysis of magnets is necessary. In this paper, a finite element model of pulsed magnets considering interface characteristics is proposed. Both the contact status and interfacial friction between the conductor layers and reinforcements can be accounted for Simulations are conducted with a failed 95 T dual-coil prototype, which was originally designed with the self-developed Pulsed Magnet Design Software (PMDS) software. The simulation results show that all the originally expected separations calculated by the PMDS software disappear due to the compression. This makes the calculated maximal von-Mises stress of the inner four reinforcement layers about 600 MPa less than the former designs. The influence of the interfacial friction is also presented. Besides, the simulations show that the maximum axial displacement at the magnet end is up to 8 mm at the designed peak field, which is deadly to the insulations. Hence, we suggest that the axial displacement at the magnet end should also be one design objective of pulsed magnets. At last, the factors affecting the axial displacement are analyzed.

The 65 T pulsed magnetic field with 10 ms flat-top has been achieved at the Wuhan National High Magnetic Field Center (WHMFC). This is an upgrade based on the 41 T with 6 ms flat-top system. Both the magnet and the coupling transformer were newly designed and fabricated. The magnet circuit and the auxiliary circuit were driven by ten and two 1 MJ capacitor bank modules, respectively. At the voltage of 19.1 kV for the magnet circuit and 8.5 kV for the auxiliary circuit, peak field of 64 T with 10 ms flat-top and 0.3% flatness was obtained. The primary specific heat measurement of sample CeRhln5 was successfully performed.