Design and Fabrication of Iron-Dominated Magnets and Cryomodule Magnetic Shielding for the Re-Accelerator Project at MSU

Abstract

The National Superconducting Cyclotron Laboratory at Michigan State University is constructing a rare isotope beam re-accelerator facility, called “ReA.” The compact facility will provide unique reaccelerated low-energy rare isotope beams produced by in-flight nuclear reactions and then stopped by interaction with matter. The ReA3 linac beam transport system comprises of room-temperature dipoles, quadrupoles, solenoids, and corrector magnets. The accelerating system of the linac is composed of cryomodules each containing niobium resonators and superconducting solenoids. The performance of the cavity is sensitive to magnetic fields coming mainly from the solenoid fringe field and the residual Earth's field. The 9-T solenoid is shielded with both a return yoke and bucking coils to reduce the magnetic field in the neighboring SRF cavities. The cavities are also equipped with a shield made up of commercially available high permeable material to further reduce the magnetic field on the cavities. Two of the cryomodules are in operation and have demonstrated effective shielding, eliminating the requirement of hysteresis cycling. This paper presents the results of the design of the magnets, fabrication, and status. In addition to the design of the magnetic shield, results of the survey of magnetic field in the cavities are presented.