Combined System for Cryogenics and Protection of High-Field Superconducting Magnets

The Paul Scherrer Institute (PSI) is developing an integrated system for cooling and protection of high-field superconducting magnets. Increasing the overall current density of superconducting cables reduces the conductor volume required for high fields but also decreases magnet protectability. To mitigate this, a strategy combining auxiliary coils and electrical discharge has been proposed to generate fast transients in the superconducting coils and enhance protection. For effective coupling, the auxiliary conductor must be located close to the magnet coils; however, in multi-layer configurations, this can reduce magnetic efficiency. Another key challenge in high-field magnets is cryogenic efficiency—both in steady-state cooling and in handling transient losses. To avoid the high costs of helium-bath systems in large magnets, PSI is investigating a conduction-cooling approach using forced-flow pipes embedded between coil layers. Yet, this integration can also impact magnetic performance. To address both protection and cooling challenges simultaneously, PSI proposes a dual-function concept using a hollow electrical conductor that serves as both the protection circuit and the cooling channel. The auxiliary coils are wound from this hollow conductor, which offers suitable electrical properties and enhanced thermal performance through forced-flow cooling. This work applies the proposed strategy to the subscale stress-managed asymmetric common-coil magnet under development at PSI. The study includes multi-physics transient analyses to assess system performance and validate the concept as a compact and efficient approach for superconducting accelerator magnets.