| 摘要 |
PROBLEM TO BE SOLVED: To provide an insulation protector for a coaxial cable used for an electron gun capable of effectively preventing dielectric breakdown by eliminating the attenuation pulsation in discharge. SOLUTION: This electron gun 10 is provided with a cathode 12, an accelerating electrode 14 and a target electrode 16. In an isolation transformer 18A, a coaxial cable is used, a core wire is a secondary-coil 18a, and a sheath line is used as a primary-coil 18b. In the electron gun 10, an insulation protector 32a comprising a diode group 34 of a plurality of diodes connected in series is provided. The protector 32a is for protecting the insulation of the isolation transformer 18 comprising the coaxial cable, one end of the diode group 34 is grounded and the other end is connected with a connection node of the coaxial cable 26 and the cathode 12. If arc discharge occurs and the potential of the core wire of the coaxial cable 26 is high to exceed a specified value, the one end of the diode group 34 of the protective device 32a is higher than the grounding potential and part of a surge current in discharge flows into the grounding side through the diode group 34. COPYRIGHT: (C)2004,JPO
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