Development of the radiation-hardened Magnetically Suspended Compound Molecular Pump

The Magnetically Suspended Compound Molecule Pump is used for the vacuum pumping system in the 3 GeV Rapid Cycle Synchrotron (3 GeV-RCS) at Japan Proton Accelerator Research Complex (J-PARC). Due to the radiation environment it is used under, the pump must be resistant to at least 10 MGy of radiation. The standard Magnetically Suspended Compound Molecular Pump is only capable of withstanding up to 3.5 MGy under the radiation environment. For this reason, the radiation-hardened Magnetically Suspended Compound Molecular Pump was developed based on the gamma-ray irradiation examination results for the standard Magnetically Suspended Compound Molecular Pump, and an irradiation test was performed. The radiation-hardened Magnetically Suspended Compound Molecular Pump got a sensor tuning error when the accumulative radiation dose reached to 73.8 MGy. As a result of a disassembly check, cause of the failure was determined to be a decreased movement of the shaft due to the deformation of epoxy resin for the mandrel. However, all other parts such as the position sensor, the electromagnet and the motor, were no problem.