Beam Dynamics Study Of Two-plane Painting Multiturn Injection Scheme For The HIAF/BRing

The High Intensity heavy-ion Accelerator Facility?HIAF?is currently under construction in China.Booster Ring?BRing?which is the main accelerator of the HIAF can accelerate the high intensity beams with a wide range of heavy ion species from proton to uranium.The beam intensity is designed up to 1.0×10¹¹ppp(²³⁸U³⁴⁺).In order to reach the high beam intensity,two-plane painting multiturn injection scheme is proposed.Since this scheme can fill both horizontal and vertical phase spaces,it can achieve a higher injection gain,compared with the conventional injection method.However,with the increase of the beam intensity,the space charge effect becomes more serious,which causes many detrimental consequences in the injection.In this paper,detailed studies on the two-plane painting multiturn injection scheme,especially with the space charge effect,are presented.Firstly,the design of the BRing injection system is presented,including the arrangement of injection components,the design of injected and circulating beam orbit,the calculations of injection component's parameters and the matching calculations of the twiss parameters.A set of injection parameters,used as the input of the following optimization,is given.And the primary optimization of injection parameters is performed based on the study of the beam loss mechanisms in the two-plane painting multiturn injection.For further optimization of the injection parameters,the ORBIT code,which is developed for the Spallation Neutron Source?SNS?project and only includes charge-exchange injection module only,is modified.The tilted electrostatic septum?ES?element is added to the ORBIT code to realize the particle tracking in the two-plane painting multiturn injection scheme.The optimization of the two-plane painting multiturn injection scheme,which involves many injection-related parameters,is very complicated.So,the particle swarm optimization?PSO?algorithm is employed.It has the advantages of easy-to-understand algorithm principle,fast search speed and high calculation efficiency.It is difficult to modify the injection parameters in the ORBIT code.A C++code,named TPIS is developed.Via the TPIS code,the further optimization of injection parameters without space charge effect is realized.Then,based on the optimization results,the study on the tune,the injection gain and the final particle distribution under the influence of the space charge effect,is performed with the OBRIT code.The dependence of the injection gain on the injected beam emittance,the injected beam intensity,the tune and the injection gain is also investigated.To reduce the beam loss caused by the space charge effect,the re-optimization of the injection parameters with space charge effect is performed.An injection gain of 85 is reached.This results give possibility to accumulate 1.3×10¹¹particles at the BRing and meets the intensity requirement.The results mentioned above are significant for the design and optimization of the BRing injection system.