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In recent years, global investment in magnetic resonance imaging (MRI) has surged, with 3 T MRI technology overtaking 1.5 T as the standard in hospitals gradually. A combination of linear programming, genetic algorithms, and nonlinear programming was employed to design an actively shielded 3 T superconducting MRI magnet system. This magnet consists of seven main coils and two shielding coils, achieving a magnetic field with a peak-to-peak inhomogeneity of 10 ppm within a 50-cm-diameter spherical volume (DSV). To address the risk of quench in superconducting magnets, which can lead to damage due to excessive temperature, voltage, and stress, a quench protection system is crucial. The designed system segments the coils for protection, using diode pairs and shunt resistors to manage the quench. Initial simulations indicated that temperature rises and voltages were within safe limits, but some coils were slow to quench or did not quench at all, risking burnout. To mitigate this, quench propagation heating plates were added to increase the quench speed. Updated simulations showed rapid quench across all coils and a significant reduction in hot spot temperatures and peak voltages. [ABSTRACT FROM AUTHOR]

The magnetic dam (MD) is a promising passive protection method for high-temperature superconducting (HTS) magnets. Urgent problems remain to be resolved in order to put it into practice. This article deals with the deformation problem of the magnetic dam in the background magnet quench. A novel copper–steel composite structure was proposed, which could improve the MD's mechanical properties. As a comparison criterion, the electromagnetic stress and deformation of the magnetic dam during the background field magnet quench are simulated and analyzed. The effect of different thicknesses of stainless steel on the strength and the protection performance of the magnetic dam is also discussed. The results revealed that the original copper magnetic dam does not possess sufficient strength to survive from the low-temperature superconducting (LTS) magnet quench in the HTS/LTS magnetic system. The composite structure is more apt to be used as a passive protection method for the insert HTS magnets. [ABSTRACT FROM AUTHOR]

The application of resistive-type superconducting fault current limiters (RSFCLs) in electrical networks is very attractive due to their relative compactness, light weight, and good performance. However, this technology still has drawbacks: asymmetrical quench, uncertain limiting velocity, passive action and incapability of enlarging capacity. Here, we present an active quenching technique which can potentially solve these problems. The quenching process is triggered using high-frequency (HF) AC fields, which are generated by two coupled copper coils attached on both sides of the YBCO sample. Our experiments show that this approach is effective in guaranteeing uniform quench and therefore is expected to be able to significantly extend the service life of the device. Moreover, the quench speed can be considerably increased by the HF field. We find that the performance of acceleration is positively correlated to the transport current, intensity and frequency of the AC field. In addition, a DC magnetic field is added around the sample holder simultaneously with the AC field, to study the field-angular-frequency dependence of the quench time t(BACfACBDC휃DC). Experimental results prove that the DC magnetic field can cooperate with the HF AC field to accelerate quench, which means better performance can be produced with lower costs with the two fields acting together. In all, this technique showed outstanding performance regarding quench acceleration and tape protection. We believe the HF-assisted quenching technology has a promising future in current-limiting devices and hope our findings could be helpful for its potential applications. [ABSTRACT FROM AUTHOR]