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Achievement of acceleration voltage of 500 kV in dc photocathode electron gun for next-generation light-sourcesMar. 10, 2010A high-voltage dc photocathode electron gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 h was demonstrated at an acceleration voltage of 500 kV. The dc photocathode electron gun is designed for future light sources based on energy-recovery linac and consists of a Cockcroft–Walton generator, a segmented cylindrical ceramic insulator, guard-ring electrodes, a support-rod electrode, a vacuum chamber, and a pressurized insulating gas tank. The segmented cylindrical ceramic insulator and the guard-ring electrodes were utilized to prevent any damage to the insulator from electrons emitted by the support-rod electrode. The research was conducted by collaboration of Japan Atomic Energy Agency (JAEA), High Energy Accelerator Research Organization (KEK), Hiroshima University and Nagoya University. The applied voltage satisfies the requirement of future ERL light sources for x-ray and γ-ray radiation. A key to the successful high-voltage operation is the especially designed ceramic insulator and guard-ring electrodes. The segmented cylindrical ceramic insulator covered with the guard-ring electrodes effectively prevents breakdown of high voltage and fatal damage to the ceramic, which are triggered by electrons emitted by the support-rod electrode. The successful result obtained with the chemically polished titanium electrodes in the 500-kV gun will be a good starting point to study electrode material and surface treatment suitable for vacuum high voltage insulation at a large gap. This work was partially supported by the MEXT Quantum Beam Technology Program. This work will be published online in "Review of Scientific Instruments" on March 10, 2010.  |
