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Extraction Electrode for a 100-kV, 40-A, 10-s Ion Source

Hiroshi Horiike, Masato Akiba, Masanori Araki, Masaaki Kuriyama, Shinzaburo Matsuda, Mamoru Matsuoka, Yoshihiro Ohara, Yoshikazu Okumura, Kiyoshi Shibanuma, Shigeru Tanaka

Fusion Science and Technology

Volume 7 / Number 2 / March 1985 / Pages 171-179


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Countermeasures against mechanical warpage of the extraction electrode for the JT-60 ion source were studied experimentally. A conventional plasma electrode, consisting of a single thin plate, exhibited unacceptably large deflections during long-pulse operation at extraction power levels exceeding 75 kV, 35 A. To measure the deflection characteristics of this electrode, hot water was circulated in the electrode cooling channels. Results from this test showed that an unacceptably large warpage occurs at temperatures moderately below the operation temperature. To suppress warpage, two modified electrodes were fabricated and tested. In the first design, the electrode was stiffened by adding material at the edges of the aperture area. In the second design, constraints on the thermal expansion of the aperture area were released by segmenting the aperture area and joining them to the stiff electrode frame through a bellows. Both designs successfully reduced electrode deflection and were used to extract 100-kV, 40-A, 10-s beams. These tests provided a measure of the permissible deflection level of the plasma electrode.

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