An HTS Magnet With Individually Controllable Coil Currents Energized by a Single Power Source

Abstract

This paper reports a feasibility study of a high temperature superconductor (HTS) magnet with individually controllable coil currents energized by a single power source. An HTS magnet, a stack of four double pancake (DP) coils, was designed, constructed, and tested. We fabricated four DP coils using no-insulation winding technique and then connected them in parallel to build the HTS magnet. Each DP coil has two current leads, inlet and outlet, and they are electrically soldered to two HTS current leads connected to a single power source in series. The joints between HTS current leads and each coil's current lead, to be named "control resistors," are used to measure and control coil currents in a passive way. A charge-discharge test was performed with the HTS magnet in a liquid nitrogen bath at 77 K. We investigated the electromagnetic behaviors of the HTS magnet by measuring currents, voltages, and magnetic fields. The measurements were described with a numerical simulation using an equivalent circuit model. Two advantages of the HTS magnet were demonstrated: 1) the controllability of coil currents by using "control resistor"; and 2) the improvement of the central magnetic field performance by sharing coil currents.