Design Of Beam Diagnosis System For Terahertz Near-field High-flux Material Property Testing System

There is an electronic linear accelerator(Linac)with a length of about 3 m in the National Synchrotron Radiation Laboratory(NSRL)"THz Hertz High-flux Material Physical Property Testing System" project.According to the related technical requirements of the electronic Linac,a beam diagnostic system with functions such as beam position measurement,beam energy and energy spread measurement,bunch length measurement,and beam current measurement needs to be designed.Therefore,the relevant research is carried out.The beam position measurement system is designed.At the front and back of the undulator in the electronic Linac,there are two beam position monitors(BPM).Due to the high cost performance of the stripline BPM,it is finally selected.Before the undulator,a stripline BPM under a cylindrical vacuum chamber with orthogonal symmetry is used.In order to solve the problem that the non-orthogonal symmetry of the undulator exit in the NSRL "THz Hertz High-flux Material Physical Property Testing System" project,two stripline BPMs under the rectangular vacuum chamber and the racetrack vacuum chamber are designed.The modeling and simulation are based on the boundary element method via Matlab.The energy and energy spread of the beam is one of the key parameters of the accelerator.In the project,the main device is a Linac,which requires the resolution of energy and energy spread to be better than 10 KeV.Compared with various measurement methods,an energy spectrum analysis system is finally choosed.In the project,the resolution of the bunch length measurement is required to be better than 50 fs.Based on the RF zero phasing method,combined with the transverse deflecting cavity method,a multi-phase method is proposed.In the practical application of the multi-phase method,the low level radiation frequency control system is used to determine the reference phase,and then the phase is measured.The energy spectrum analysis system is used to measure the corresponding energy spread.In the beam current measurement system,according to the characteristics of the bunch length,a non-interceptive BCM of which core is an ICT is selected.Finally,the ICT from Bergoz is used to be detector.The BCM-IHR is choosed to be electronics equipment.The Keysight's oscilloscope is employed for data acquisition and display.Finally,the entire system is summarized.The significance and disadvantages of each system are discussed,and the corresponding improvement plan is proposed.