Theoretical And Experimental Study On Bunched Ion Beam Cooling And Pulsed Electron Beam Cooling

With the development of the high energy heavy ion accelerators and electron-ion colliders,beam cooling,an important mean to increase the performance of these machines,is moving toward to high energy and some new technologies are under development.Among them,the cooling of bunched ion beam with bunched electron beam is an inevitable direction for the future.In the paper,a simulation code is developed for the studies on beam cooling and pulsed electron beam cooling,which is based on the theoretical model and the experimental results of low energy electron cooling.Based on the simulation code and the experiments that carried out on the HIRFL-CSR,the bunched ion beam cooling and pulsed electron beam cooling are investigated.In the paper,the details about electron cooling theory,beam phase space theory,beam temperature,cooling force and heating effects are introduced.The corresponding mathematical model is estimated and the simulation code is developed.A simulation code based on multi-particle tracking is developed to calculated the bunched ion beam cooling process,in which the electron cooling,intra-beam scattering,ion beam space charge field,transverse and synchrotron motion are considered.The performance of each module of the code is benchmarked by the experiments on CSR.The bunched ion beam cooling is studied on HIRFL-CSRm,in which the bunch is compressed during the cooling process.The dependence of the cold bunch length on the RF voltage and particle number is also investigated.Base on the simulation and experiment result,the effect of IBS and space charge on the bunch shape is analyzed and we established an analytical model to describe the limitation of the bunch length of the cooled ion beam.It is observed that the IBS effect is dominant for low intensity beam and the space charge effect is much more important for high intensity beams.The experimental results in CSRm show a good agreement with the analytical model in IBS dominated regime.The simulation work offers us comparable results to those from the analytical model both in IBS dominated and space charge dominated regimes.The pulsed electron beam cooling experiment on HIRFL-CSR is an exploratory experiment for the purpose of the future development of high energy electron cooling.It is the first time in the world to generate the pulsed electron beam with adjustable pulse width and repetition frequency.In the experiment,the ion beam was cooled by the pulsed electron beam.Moreover,some new phenomena were also observed,such as the“grouping effect”and the sidebands in schottky spectrum.According to the simulation results and analytical model,it demonstrates that the barrier voltage that created by the pulsed electron beam space charge field has a critical effect on the cooling process.It is also the first time to combine the electron cooling and barrier bucket theory into together,which provides a new direction for the application of high energy pulsed electron beam in the future.