Tuning and measurement of inter-electrode voltage for four-rod radio frequency quadrupole accelerator

In order to improve beam transmission efficiency for a four-rod radio frequency quadrupole (RFQ) accelerator, inter-electrode voltage distribution must be tuned and its accurate value need to be measured. Effect of tuning plates on inter-electrode voltage distribution was studied by electromagnetic numerical simulation, as the unflatness of the voltage distribution was caused by unevenly distributed capacitance and tuning plates could change the distributed inductance. The final inter-electrode voltage distribution was tuned to be better than 95%. In beam commissioning, inter-electrode voltage was determined by measuring the energy spectrum of X-ray and multiple energy peaks were studied by beam dynamics simulation. Input power was calibrated with beam commissioning results that 284 kW was needed in order to get 70 kV inter-electrode voltage.