Frequency Tunable 4-rod RFQ

Yoshihisa Iwashita and Hiroshi Fujisawa* Accelerator Laboratory, Nuclear Science Facility Institute for Chemical Research, Kyoto University Gokanosho, Uji-shi, Kyoto-fu 611 Japan *R&D Division, Nissin Electric Co.,Ltd. 575 Kuze Tonoshiro-cho, Minami-ku, Kyoto-shi, Kyoto-fu 601 Japan

Abstract

The frequency tunability of the 4-rod RFQ is investigated. The experimental results show that the resonant frequency can be varied almost twofold by moving the shorting electrodes between the posts, which support the 4-rod electrodes from the base. In that configuration the shunt impedance is found to be low at higher frequency region. An additional ON-OFF posts-shorting electrode above the electrodes can overcome this draw back. It raises the resonant frequency without lowering the shunt impedance too much and when used with the moving shorting-plates it expands practically available resonant frequency range. Because the ON-OFF shorting electrode requires no sliding rf contact, this device is simple and easy to fabricate. The effect of the proposed ON-OFF shorting electrode is studied by MAFIA.
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