The Design of a Horizontal Testing Cryostat for the Superconducting curved magnets of Compact Synchrotron

Abstract A superconducting heavy ion therapy device is developing in Lanzhou, which gantry and synchrotron require curved superconducting magnets to reduce size. To cool and test the performance of superconducting magnets by horizontal placement, a horizontal testing cryostat was designed for the curved superconducting magnet of the heavy ion therapy device. With the maximum operating current reaching 369 A, 6 pairs of 500 A High-temperature superconductivity (HTS) current leads are required to be powered. For the testing needs of 45-degree superconducting magnets and other curved superconducting magnets in the future, the horizontal testing cryostat is designed with eccentric flanges and different bases to accommodate superconducting magnets with a deflection angle of 30-60 degrees and a deflection radius of 1000-2500 mm. In addition, the design of the eccentric flange can be adapted to different diameters of warm bore tubes by replacing the flange with different inner diameters. To facilitate superconducting magnet installation, the horizontal testing cryostat is designed with slide rails for superconducting magnet support and installation, supported by three support posts. The static heat load of the horizontal testing cryostat is about 2.49 [email protected] K, 141.26 W@50 K. In the process of rapid excitation, there is AC loss in the superconducting coils and the metal parts such as radiation screen, and the dynamic heat load is about 6.96 [email protected] K, 132.8 W@50 K. In order to conduct cooling and maintain the low temperature of 4.2 K for superconducting magnets and 50 K for radiation screen, six two-stage GM cryocoolers with 1.8 [email protected] K and 35 W@50 K cooling capacity are required. For the 45-degree curved superconducting magnet with a cold mass of about 1000 kg, it takes 6 days to theoretically cool down to 4.2 K, and the rewarming time after quench is about 5.5 hours. The horizontal testing cryostat has be processed and assembled, and the relevant design parameters will be further verified by experiments.