Endurance test of turbo-molecular pump exposed to radiation

In the case of designing the accelerators for high intensity, heavy ion beam for the large scale hadron project and others, it is expected that the level of residual radiation becomes high, therefore together with the research on the reduction of beam loss, the countermeasures for the radiation resistance of the equipments composing an accelerator must be considered. Recently turbomolecular pumps have been used frequently for the vacuum exhaust system for the use requiring high vacuum in radiation environment, such as SOR rings, X-ray analyzers and nuclear fusion devices in addition to accelerators. However, there is restriction in the radiation resistance of the materials of turbomolecular pump components used generally, therefore, it is necessary to ascertain the limit of radiation resistance of turbomolecular pumps. As its part, the verifying test was carried out on a turbomolecular pump which is supported with a permanent magnet and a pivot bearing and is maintenance free (PT-50R made by Mitsubishi Heavy Industries Ltd.). The turbomolecular pump tested, the verifying test by irradiation in National Laboratory for High Energy Physics and so on are reported. (K.I.)