| 摘要 |
PURPOSE:To obtain a device for certainly shielding an output to a high voltage cable at the time of removing a high voltage cable from an electron gun by providing a shielding device which shields the power supply input to the electron gun with a vacuum pressure increase signal. CONSTITUTION:A control circuit (a) of a shielding device MX is connected with a limit switch 16 and a vacuum gauge 4' connected in series thereto. An electron gun 1 is generally sealed and placed under the vacuum condition. When a high voltage cable 5 and a box nut are removed, the interior of electron gun 1 is exposed to the atmospheric condition through the clearance 15 of connector 7 and the vacuum condition in the electron gun 1 is broken. When a vacuum pressure increases exceeding the predetermined constant value, the vacuum gauge 4' sends a signal to the shielding device MX. With such signal, the shielding device MX shields the 3-phase AC input (b) to a high voltage transformer 18 and thereby no input is applied to the electron gun 1 from the high voltage cable 5.
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