| 摘要 |
An RFQ electrode which can accelerate a large-current ion beam without causing divergence and is used for the accelerating tube, etc., of a high-energy ion implanter is constituted in such a way that the radius R1 of a beam passing space surrounded by four RFQ electrodes ranges from 5 to 9 mm for a resonance frequency as low as about 33 MHz suitable for heavy ions of B, P, As, etc., and that the electrode has a surface on which crests and valleys are repetitively formed in the forward direction of the beam, with each crest having a radius R2 of curvature of 5 to 9 mm in the direction perpendicular to the axial direction, and a height H which is 4 to 6 times as large as the radius R1 (H/R1:4 to 6) from the bottom of the valley to the top of the crest. When the height H of the electrode is lowered, the shunt impedance increases and the power efficiency is improved, though the cooling performance of the electrode becomes insufficient, because the cross section of a cooling water path cannot be made larger. In addition, such a problem that the electrode tends to vibrate due to an insufficient mechanical strength is apt to occur. Therefore, when the RFQ is constituted in the above-mentioned way, the RFQ electrode will have such an optimum configuration as to provide a high power efficiently, an excellent cooling efficiency, a sufficiently strong mechanical strength, and a large beam acceptance.
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