Power Test of the Ladder IH-RFQ Accelerator at Peking University

A 104-MHz ladder interdigital-H radio frequency quadrupole accelerator (T-IH-RFQ) is developed for applying RFQs to heavy ion implantation and accelerator-based mass spectroscopy in recent years at the Institute of Heavy Ion Physics, Peking University. It could accelerate ions with a mass-to-charge ratio of less than 14, from 2.9 keV/u to 35.7 keV/u within a length of 1.1 m. The T-IH-RFQ cavity operating at H₂₁₍₀₎ mode was constructed successfully. Based on a well designed rf power feeding system, the cavity was cold measured and tested with high rf power. In the case of cold measurement, the rf properties were obtained using a vector network analyzer with the help of a perturbation capacitor. During a high power test, the inter−electrode voltage was derived from the energy spectrum of x-rays measured by a high purity Ge detector. The results show that the specific shunt impedance of the T-IH-RFQ cavity reaches 178 kΩm, which could meet the requirements of beam dynamics design.