RFQ linac for heavy ion acceleration

An rf characteristic has been studied on an RFQ model cavity with two kinds of vanes, straight and modulated. The measured resonant frequency is 296.0 MHz for the TE210 mode and well agrees with the calculated value 296.5 MHz by SUPERFISH for the straight vane. The measured one is 293.5 MHz for the modulated vane which has the same cross section as the straight vane at its quadrupole symmetry plane. The measured electric field in the acceleration bore agrees with the calculated one within the statistical error. A sufficient mode separation and uniform field distribution have been obtained with a single loop coupler which matches the cavity to the feeder line. On the basis of the modelling study, a lithium ion test linac LITL has been designed and is in course of construction. It is designed to accelerate heavy ions of 5 keV/u with charge to mass ratio, q/M of 1 approx. 1/7 to the final energy of 138 keV/u in the vane length of 1.22 m. The operating frequency is 100 MHz and the rf power is fed with a single loop coupler. The maximum intervane voltage is 62 kV, which corresponds to 1.8 times the Kilpatrick's limit