Development Of Electron Scanning-based Transverse Profile Measurement System Prototype For High Beam Power Accelerators

The High Intensity heavy ion Accelerator Facility(HIAF)was proposed by Institute of Modern Physics,CAS in 2009 and aims to provide beam with higher intensity,higher energy and higher bunch power.Electron Beam Probe(EBP)is dedicated to provide non-interceptive diagnostics for Booster Ring(BRing)in the project.Besides the ability of reconstructing transverse profile of the beam,EBP can also detect beam position,bunch longitudinal distribution,beam neutralization and wakefields.Compared to the traditional diagnostics tools,EBP is non-interceptive,and meanwhile can be used to measure a couple of beam parameters.The aim of which the work will be reached is to develop a prototype of EBP,and realize the profile measurement with a relative error of 10%.Based on the theory of EBP,the paper gives the details of how to build a EBP system by virtue of numerical simulation and beam experiment.In this work,a dedicated electron gun is constructed,and the EBP system is developed.The online measurement result indicates that the EBP system achieves its goal.In this paper,the following work is completed:1,Dedicated numerical simulation algorithm is developed.The algorithm is designed to simulate the motion of electron beam in the space charge field induced by ion beam,as well as the reconstruction of ion beam profile.The deflection of electron beam under coasting beam,3D Gaussian bunch,3D Bi-Gaussian bunch,3D Halo bunch is investigated comprehensively,and profile reconstruction of ion beam is analyzed as well.Especially,we analyzed the influence of the rise time of deflector on the profile reconstruction of 3D bunch.We interpreted the phenomenon of electron beam expansion during the scan in theoretical,and a solution to reduce this is proposed.At last,the reconstruction error is discussed.2,An electron gun is developed.The electron gun is simulated and optimized using CST,SAM and SIMION software,upon which the gun hardware is designed and manufactured.The emittance of the gun is measured using slit+screen method,and the result gives the value 0.5?1 times larger than the simulated one.We proposed a systemic procedure to analyze emittance data,in which an ad hoc-based interpolation is implemented firstly,and then wavelet threshold denoising is performed,finally,the Marching Squares-based edge detection algorithm is adopted.After that,a curve of emittance against threshold is obtained,and the zero-thresholding emittance therefore can be achieved using extrapolation algorithm.The gun fulfills the requirement of EBP,and the goal is achieved.3,EBP offline test.A charged tungsten wire with diameter of 1.5 mm is placed in the pipe to simulate ion beam,and the maximum deflection angle is recorded,which gives a relative deviation of 3% with respect to the theoretical angle.The reconstructed profile of the tungsten wire is analyzed,and the relative deviation is between 8.5% and 0.6%,which verifies that the numerical simulation algorithm is correct and the EBP system is of accuracy in profile reconstruction.4,Build a EBP system and perform online test.An EBP system is built and the first online test is launched in ECR source beam line.The measurement value is compared with wire scanner,and a relative deviation of 0.5% is reached.To evaluate differentiating on noisy discrete data,both of the prior distribution-based least square fit and machine learning-based Kernal Ridge Regression(KRR)algorithm are implemented.5,Random number generation algorithm for five dimensional phase space obeys Maxwell-Boltzmann thermal distribution is developed.Due to the limit of the SIMION software to simulate thermal emission,a random number generation algorithm is developed,which can generate five dimensional random number obeys MaxwellBoltzmann thermal distribution.Importing the random number to SIMION,the thermal emission can be simulated.EBP is the first non-interceptive diagnostics detector based on electron beam scanning technique in China.The electron gun can achieve the beam spot with width of ??0.5mm on the screen with a distance of 1 m from the gun.Online test is consistent with the wire scanner with a relative deviation of 0.5%.In conclusion,the EBP system achieves its goal.