Extraction System Design And Beam Dynamics Study Of The HIAF-BRing

Based on the effective construction and successful operation of the HIRFL（Heavy Ion Research Facility in Lanzhou）,a new plan was proposed to estab-lish the HIAF（High Intensity heavy ion Accelerator Facility）by IMP（Insti-tute of Modern Physics,Chinese Academy of Sciences）in 2009.The HIAF comprises a SECR（Superconducting Electron Cyclotron Resonance）ion source,a superconducting iLinac,a high intensity synchrotron BRing（Booster Ring）,a multi-function high precision synchrotron SRing（Spectrometer Ring）,and a super-conducting radioactive beam line HFRS（HIAF FRagment Separator）to connect the two rings.As the main accelerator of the HIAF complex,the BRing is designed for a maximal momentum rigidity of 34 Tm,it can accelerate the²³⁸U³⁵⁺beam from 17 MeV/u to an extraction energy of 200～835 MeV/u.To fulfill a flexible beam extraction for multi-purpose experiments,both fast and slow extraction systems will be accommodated in the BRing.The two extraction systems are designed to share the same extraction channel for the purpose of saving space and cost.To meet the requirements of the experiments on single-short bunched sec-ondary beams（e.g.,for super-precise mass measurement experiment）,a single-turn fast extraction scheme will be used,and the system mainly consists of two chains of kicker cells.In addition,the effects of the failure and field fluctuation of the kicker cells on beam extraction are also considered.Since the high energy and high current of the BRing,a beam dump system is designed to protect the machine using the kicker cells.Moreover,the detailed design specifications of the fast extraction system are given,and the physical demands of bipolar power supply for the kicker cells are also put forward.To provide quasi-continuous beam in several seconds for material and bio-logical irradiation experiments and some special nuclear physics experiments,a slow extraction scheme will be available,and it comprises chromaticity correc-tion and resonance excitation systems,and both of them can be independently controlled.The code MAD-X is used to simulate the different extraction energy of the²³⁸U³⁵⁺beam using the different and the same extraction lattice.Accord-ing to the simulation results,the solution to realize high extraction efficiency has been proposed under the different extraction parameters of BRing.Meanwhile,the beam extraction trajectories are tracked by the Winagile,and the layout and physical parameters of each element in the slow extraction system has also been presented.Finally,the optical matching parameters at the entrance of the HFRS are calculated by tracking different momenta excited particles.The hardware systems will be able to meet the requirements of the designed fast and slow extraction schemes and engineering demands.The influences of extraction and circulating beam parameters in the BRing on the extracted separatrix is studied based on the new program SESP,and the spill structure is also analyzed by changing the parameters of the RKO.