Extraction of High Power Microwave from GHz-Repetition Rate Relativistic Short Electron Pulses

• Main Authors: Huang, Cheng-Wei, 黃正瑋
• Other Authors: 柳克強
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/85773500824688243206

碩士 === 國立清華大學 === 先進光源科技學位學程 === 99 === RF linacs are able to provide stable ultra-relativistic electron beams with excellent beam quality. Such beams can be used to produce high power microwaves by extracting the wave power from a specially designed rf structure in which wake-fields are excited by the electron beam and are stored in the structure. The power level of this type of high power microwave source can be as high as a few hundred megawatts and can be used to drive high gradient linear accelerator as well as microwave undulator for free electron lasers. A compact design of X-ray free electron laser using short-period microwave undulator is under discussion at National Synchrotron Radiation Research Center (NSRRC) in the high brightness injector research team. In this study, we tentatively designed a 12 GHz, 2??3 mode disk-loaded periodic waveguide structure such that 100 MW of microwave power can be extracted from a 3 GHz repetition-rate electron beam of 5 nC bunch charge. The geometry of this structure (including upstream and downstream output couplers) has been set by extensive electromagnetic wave and wake-field calculations by HFSS and CST particle studio. We also built a prototype structure for characterization of microwave properties at low power level. We have identified that a 2??3 mode has be excited in the structure with resonant frequency and group velocity close to their design values. R/Q has been obtained by means of bead-pull measurement that agrees very well with the designed value.