arXiv subjects

You-He Zhou

Publications and source records attributed to You-He Zhou.

3 recordsLinked to original sources

arXiv2025

Complete suppression of flux instabilities in ramped superconducting magnets with synchronous temperature-modulated Jc

Nonlinear multi-field coupling as an intrinsic property of complex physical systems often leads to abrupt and undesired instabilities. For current-ramped high-field Nb3Sn magnets, frequent flux jumps are observed, which easily causes premature quenches and requires prolonged and resource-intensive magnet training process. In this study, we propose a paradigm-shifting methodology framework that achieves complete suppression of thermomagnetic instabilities through synchronized temperature-modulated critical current density (Jc). Through numerical simulations of flux jumps in multifilamentary Nb3Sn wires at various temperatures, we construct thermomagnetic stability diagram in the Ha-T plane. The simulated results are in good agreement with experiments, confirming that the synchronized temperature ramp-down can fully eliminate flux jumps. We reveal the underlying mechanism of enhancing the thermomagnetic stability arises from that synchronized temperature ramp-down can continuously tune both Jc and its slope. Furthermore, we explore the thermomagnetic instabilities of current-ramped superconducting magnets through large-scale GPU-optimized algorithm. The flux jump and quench diagram in the Ia-T plane are obtained. It indicates that the temperature ramp-down can completely suppress flux jumps without compromising Jc at high magnetic fields. Importantly, this method does not require modifications to the superconducting microstructures or fabrication process, offering a practical and broadly applicable solution. The findings not only provide a robust method for stabilizing various superconducting magnet systems, including high-temperature superconducting magnets wound with second-generated (2G) coated tapes, but also suggest a generalizable strategy for controlling instability in other nonlinear non-equilibrium physical systems.

cond-mat.supr-con↗

arXiv2024

Intertwined effects of elastic deformation and damage on vortex pinning and Jc degradation in polycrystalline superconductors

The damage and the critical current density (Jc) degradation of polycrystalline superconductors induced by strain dramatically influence their performance in applications. Unfortunately, the state-of-the-art experimental techniques are unable to detect the damage of internal polycrystalline structures and the microscopic superconductivity in the presence of strain. We propose a groundbreaking multi-scale theoretical framework aimed at revealing the underlying physical mechanisms of the reversible and irreversible Jc degradation induced by the strain through tackling the complex intertwined effects of elastic deformation and damage on the superconductivity of grain boundaries and the associated vortex pinning. The results are well validated by experimental measurements. Utilizing the benchmarked physical model, we demonstrate that the damage evolutions of polycrystalline superconductors in the presence of strain can be approximately estimated by means of the electromagnetic experiments on Jc. Furthermore, we also discuss the characteristics of damage and Jc degradation of polycrystalline superconductors subjected to biaxial mechanical loads. The findings will pave the way to investigate the tunable vortex pinning and Jc of superconductors by strain, and to develop a brand new electromagnetic method to manifest the damage of polycrystalline superconductors.

cond-mat.supr-con↗

arXiv2017

A high-precision method for general nonlinear initial-boundary value problems

A high precision, and space time fully decoupled, wavelet formulation numerical method is developed for a class of nonlinear initial boundary value problems. This method is established based on a proposed Coiflet based approximation scheme with an adjustable high order for a square integrable function over a bounded interval, which allows expansion coefficients to be explicitly expressed by function values at a series of single points. In applying the solution method, the nonlinear initial boundary value problems are first spatially discretized into a nonlinear initial value problem by combining the proposed wavelet approximation scheme and the conventional Galerkin method. A novel high order step by step time integrating approach is then developed for the resulting nonlinear initial value problem using the same function approximation scheme based on wavelet theory. The solution method is shown to have Nth-order accuracy, as long as the Coiflet with [0, 3N-1] compact support is adopted, where N can be any positive even number. In addition, the stability property of the method is analyzed, and the stable domain is determined. Numerical examples are considered to justify both the accuracy and efficiency of the method. Results show that the proposed solution method has better accuracy and efficiency than most other methods.

math.NA↗