| 摘要 |
An electron beam detecting device detects a state of an electron beam radiated by an electron beam radiation device. A plurality of wire electrodes 46, which are conductors, are disposed corresponding to a plurality of filaments 25, the wire electrodes being electrically insulated from each other, in the area in which the electron beams are radiated. The electrical current flowing through each of the wire electrodes 46 is measured by an electric current measuring instrument (measuring unit) 48. A CPU (determining unit) 49 determines the radiation level of the electron beams by receiving a signal output by the electric current measuring instrument 48. The CPU 49 judges that when the measuring instrument 48 measures a decrease of the current value, an abnormal condition exists in the filament 25 corresponding to the conductor with the lower current value. |
