Calculation Of Vacuum Pressure Profiles Of High Intensity Heavy-ion Accelerator Facility

With the requirements of beam lifetime for the high energy nuclear experiments improved,the accelerator vacuum system should be a higher vacuum degree to reduce the interaction between beam and residual gas molecules leading beam lifetime loss.The planned High Intensity Heavy-ion Accelerator Facility（HIAF）,whose vacuum system should be ultra high vacuum or extremely high vacuum,is designated to provided high intensity and high energy heavy ion beams.To estimate the actual pressure of vacuum system,the vacuum bench-marked code VAKTRAK is introduce to calculate pressure profiles and the optimal parameters are selected to achieve the vacuum requirements.VAKTRAK is used to calculate the longitudinal static pressure profiles.Whether its computational results could accurately reflect the operational vacuum pressure is verified by measured pressure data on the current synchrotron HIRFL-CSRm and simulation data of the other code.Therefore the VAKTRAK is applied to study the vacuum system of HIAF.During the vacuum study of HIAF,the representative vacuum systems of Booster Ring（BRing）and HIAF Fragment Separator（HFRS）are taken as the research subject.The BRing,as the main synchrotron of the HIAF project,should be in the range of extremely high vacuum to satisfy the requirements of beam current,beam energy and beam lifetime.Considering the factors of beam transmission and vacuum transition,the vacuum system of HFRS should reach a certain ultra high vacuum.The pressure profiles of the BRing calculated with VAKTRAK is compared with a Monte-Carlo method,so that the advantages and disadvantages VAKTRAK are pointed out.And then,VAKTRAK is used to calculate pressure profiles with different parameters such as conductance,out-gassing rate and pumping speed.The optimal parameters areselected to achieve the required pressure for the BRing.Also the feasibility of the designed HFRS vacuum system are verified by calculations.According to the computational results of the BRing,when the vacuum pipes are mostly occupied by H2,the out-gassing rate of materials is lower than5×10^-11 Pa.L/（s.cm²）and the main pumping speed is 2000L/s,the BRing vacuum system could reach the required vacuum range.The computational results of HFRS proves that the design of vacuum system satisfy the vacuum requirements.