Liquid helium-cooled high-purity copper coil for generation of long pulsed magnetic fields.

The article focuses on the development and evaluation of a pulsed magnet system using a high-purity (99.9999%) copper coil cooled by liquid helium or nitrogen to generate long-duration pulsed magnetic fields with low energy consumption. The coil exhibits a very low residual resistance ratio of 1140, significantly reducing Joule heating and enabling the generation of magnetic fields up to 19.8 tesla with pulse durations exceeding one second, roughly twice the field strength achievable with liquid nitrogen cooling. The system employs an electric-double-layer-capacitor (EDLC) bank for energization and compares thyristor- and insulated gate bipolar transistor (IGBT)-based discharge circuits, highlighting the IGBT circuit's ability to stop pulses on demand and improve energy efficiency. Numerical analyses confirm that operating the high-purity copper coil at low temperatures is more effective for achieving high peak fields and long pulse durations than increasing voltage or coil mass alone, underscoring the advantages of high-purity materials and cryogenic cooling in pulsed magnet technology.