PURPOSE: To enable restarting of operation in a short time, and improve the reliability of a whole body of a device by applying a charged particle beam selectively to either a first or a second vacuum duct by an inflector.

CONSTITUTION: An electron beam 1 is radiated into a vacuum duct 21a to go through a transitive track 30a along a stationary circumferential track 22a. A radiation light 28 generated at this time is guided from a radiation light takeout port 14. When a leak occurs by a defective of the vacuum duct 21a during such an operation, it is detected by a vacuum gauge 24a. When the leak is detected, a switching valve 25a is closed, and the electron beam 1 is applied again. At this time, the electron beam 1 is applied by an inflector 31 to a vacuum duct 21b. By adjusting deflection electromagnets 6a-6b and a four- pole electromagnet 7 thereafter, the electron beam 1 is guided from a transitive track 30b to a stationary circumferential track 22b and held.