Fabrication and Cryogenic Test of a 1.5-M-Long Planar Superconducting Undulator at IHEP

An R&D project aiming to develop superconducting undulators (SCUs) is in progress at the Institute of High Energy Physics (IHEP) in China. The insertion device group has produced a 1.5-m-long NbTi planar superconducting undulator prototype recently. This SCU prototype has a period length of 15 mm and a magnetic gap of 9.5 mm. The SCU was fabricated in a frame to be trained vertically in a Dewar submerged by liquid helium. After dozens of quenches, the maximum current in the superconducting coils reached 450 A. The magnetic field along the axis at different currents were obtained by a measurement system to characterize the local magnetic field distribution. We applied a gap adjustment method to improve the magnetic field quality. A cryostat has been specially designed for this 1.5-m-long SCU prototype. The SCU was installed in the cryostat to be cooled to 4.2 K successfully. A series of cryogenic tests for the SCU prototype in the cryostat are in progress.