Abstract
Cross-sectional 2D models often represent a computationally efficient alternative to full 3D models, when simulating complex multi-physical magnet systems. However, especially for the case of self-protected, superconducting magnets, where the stored energy has to be dissipated within the magnet coils, the thermal diffusion and the quench development in all three dimensions become key aspects. In order to further improve the simulation of transients in 2D models, a new modelling method for simplified quench development along the direction of the transport current is introduced. The original 2D model is hereby utilized for modelling the thermal domain, and the electrical resistance of each turn is scaled by the estimated time-dependent fraction of quenched conductor. Furthermore, the turn to turn quench propagation following the electrical connections is implemented. The proposed approach allows a very computationally efficient and easy-to-implement calculation since the model is effectively two-dimensional while providing a good approximation of the coil resistance development with sufficient accuracy. In order to illustrate the proposed quench-propagation modelling approach, simulations are compared to experimental results for the case of a self-protected, superconducting Nb-Ti dipole magnet. In general, a very good agreement between measurements and simulations was achieved.
Highlights
S UPERCONDUCTING wires can experience a phenomenon called quench, where parts of the conductor suddenly pass from the superconducting state into the normal state [1]
Federica Murgia was with CERN, CH, 1211 Meyrin, Switzerland
The main limitations of this approximation are twofold: first, the longitudinal temperature gradient is neglected, resulting in an overestimation of the average resistivity of each turn, which is calculated with the 2D model at the point where the quench started; second, the increase of quench propagation velocity due to pre-heating of the parts of the coil still superconducting is neglected
Summary
S UPERCONDUCTING wires can experience a phenomenon called quench, where parts of the conductor suddenly pass from the superconducting state into the normal state [1]. The LEDET model features a simplified electrical magnet circuit, a 2D thermal model including ohmic loss, thermal transients between conductors, and a network reproducing coupling effects and loss between the coil and inter-filament current loops in its conductors. The newly proposed feature introduces an analytical estimation of the time-dependent fraction of quenched conductor in the longitudinal direction, which scales the electrical resistance of the turn The value of this fraction increases linearly with the constant normal-zone propagation velocity [21]–[25]. The main limitations of this approximation are twofold: first, the longitudinal temperature gradient is neglected, resulting in an overestimation of the average resistivity of each turn, which is calculated with the 2D model at the point where the quench started; second, the increase of quench propagation velocity due to pre-heating of the parts of the coil still superconducting is neglected. JANITSCHKE et al.: A SIMPLIFIED APPROACH TO SIMULATE QUENCH DEVELOPMENT IN A SUPERCONDUCTING MAGNET
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