Development of a Short REBCO Undulator Magnet With Resistive Joints

Abstract

Recently, the rare earth barium copper oxide (REBCO) second generation high temperature superconducting coated conductors were applied in the development of undulator magnets. Due to the advantage of REBCO superconductor such as higher operating temperature and higher engineering current densities than low-temperature superconductors, undulators with REBCO winding may achieve better performance. In this study, a three-period undulator magnet prototype with a period length of 13 mm was fabricated with REBCO conductor. The width of the REBCO tapes is 3.3 mm. The thickness of the REBCO tape is 0.07 mm with the stabilizing copper layer. Each coil pack has 25 turns. Windings in adjacent grooves were connected with resistive joints. The joints of special shape were fabricated with soldering temperature below 200 °C and have a low resistance of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> Ω. One heater and voltage taps were arranged in the winding. The heater was used for triggering a coil quench. The voltage taps, which were inserted in different layers of coil windings, recorded the coil voltages during the quench process. The short undulator magnet was tested in liquid nitrogen bath. The critical current of the magnet was measured. The quench behavior of the magnet was analyzed and discussed.