Study On The High-gain And Adjustable Standing-wave Resonant Conditioning System For High-power Coupler

As an essential part of the radio-frequency system in particle accelerator,the high-power coupler is fragile.Prior to its online operation integrated with the resonator in the tunnel,the coupler must be conditioned off-line for testing and improving its operational stability and reliability.For the large-scale accelerator,the off-line conditioning of a large number of the couplers using the traditional conditioning technique needs a huge amount of the microwave sources,which is costly.Therefore,to make the couplers be conditioned thoroughly and cost-effectively,there is a need to reduce the requirement of the output power of each microwave source.About 150 high-power couplers will be equipped for the China initiative Accelerator Driven System(Ci ADS),hence the thoroughness and cost-effectiveness of its coupler-conditioning systems are also of importance.The conditioning system in resonant mode has been routinely used to reduce the output power of the power source needed for the coupler conditioning in the industry.However,the existing resonant conditioning schemes have their limitations,mainly including the following two aspects: 1)the power gain of the system is low,hence the output power of the power source required for the conditioning can not be greatly reduced;2)the field distribution inside the couplers under conditioning is not adjustable,therefore,the coupler can not be conditioned thoroughly by sweeping the peak field on the whole inner surface of the coupler.This thesis reports a new standing-wave resonant conditioning system with high power gain and adjustable field distribution inside the couplers under conditioning.The power gain of the new system was analyzed theoretically based on the equivalent circuit model.In light of the power gain analysis,the conceptual design and simulation of the system were performed,where the number of half-wavelengths of the resonant cavity and the antenna structure of the feeding coupler were determined.Finally,the proof-of-principle of the system was built.The cold test and power test indicate: 1)the system can condition the coupler thoroughly by shifting the standing-wave resonant field inside the coupler;2)a high power gain ranging from 50 to 94 was achieved,which corresponds to the equivalent traveling-wave power gain ranging from 200 to 376.The consistency of the power gain between the cold test and power test was also verified.Two types of the multipacitng inside the couplers under conditioning were observed during the power test,and the mechanism of their influences on the power gain was clarified.