Development of a split coaxial RFQ at INS

A split coaxial RFQ with modulated vanes is being developed at INS for acceleration of the unstable and stable nuclei with a charge-to-mass ratio larger than 1/60. In order to make it easy to install the modulated vanes in a split coaxial resonator, a multimodule cavity structure has been employed. A feature of this structure is that it is able to support the electrodes not only at one point but at several points. The rf characteristics of this structure have been investigated experimentally by means of a cold model with flat vanes and theoretically by using an equivalent circuit analysis. Based on these studies, a proton-accelerating model working at a frequency of 50 MHz has been constructed to evaluate the overall performance of this split coaxial RFQ. Through the beam test it is confirmed that the accelerating performance of the RFQ approximately agrees with the expected one. (orig.)