RF test on the unmodulated prototype RFQ at IUAC

The 48.5MHz RFQ is designed to accelerate ions with A/q of 7 from 8keV/A to 180 keV/A. The RFQ structure is 4m long and the vane shaped rods are supported by vane posts. An initial unmodulated 1.17m prototype of 48.5MHz RFQ is designed, constructed and installed at Inter University Accelerator Centre (IUAC) and studied to determine the final specifications for modulated RFQ accelerator. Precise measurement of quality factor Q, and resonant frequency of the RFQ cavity using complex transmission coefficient data as a function of frequency has been done. The asymmetry in the electric field distribution in the four gaps, in the longitudinal direction and transverse plane is measured. A comprehensive analysis of the experimental results obtained by perturbation method using fully automated bead puller system which uses stepping motors to position the bead, and network analyser and self exciting loop (SEL) to measure the resulting frequency shifts, are presented in this paper. A comparison between the experimental results and the theoretical model is also reported. (author)