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Beam dynamics simulation of HEBT for the SSC-linac injector-1


CPC(HEP & NP), 2012, 36(11): 1126–1131

Chinese Physics C

Vol. 36, No. 11, Nov., 2012

Beam dynamics simulation of HEBT for the SSC-linac injector *
LI Xiao-Ni( HE Yuan(
1

)1;1) )1

YUAN You-Jin( )1,2

)1

XIAO Chen(

)1,2 )1

WANG Zhi-Jun(

SHENG Li-Na(

Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China 2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Abstract: The SSC-linac (a new injector for the Separated Sector Cyclotron) is being designed in the HIRFL (Heavy Ion Research Facility in Lanzhou) system to accelerate 238 U34+ from 3.72 keV/u to 1.008 MeV/u. As a part of the SSC-linac injector, the HEBT (high energy beam transport) has been designed by using the TRACE-3D code and simulated by the 3D PIC (particle-in-cell) Track code. The total length of the HEBT is about 12 meters and a beam line of about 6 meters are shared with the exiting beam line of the HIRFL system. The simulation results show that the particles can be delivered e?ciently in the HEBT and the particles at the exit of the HEBT well match the acceptance of the SSC for further acceleration. The dispersion is eliminated absolutely in the HEBT. The space-charge e?ect calculated by the Track code is inconspicuous. According to the simulation, more than 60 percent of the particles from the ion source can be transported into the acceptance of the SSC. Key words: SSC-linac, HEBT, dispersion, space-charge e?ect, acceptance PACS: 29.20.Ej DOI: 10.1088/1674-1137/36/11/016

1

Introduction

The SSC (Separated Sector Cyclotron) is the main accelerator of the HIRFL (Heavy Ion Research Facility in Lanzhou) system. Presently, higher beam intensity and quality are required to perform higher level experiments. The existing SSC injector [1], the Sector Focused Cyclotron, can only supply 0.1 p?A heavy ion beam with energy 5–6 MeV/u. It limits the beam intensity of the SSC. Therefore, a new SSClinac injector is designed to add to the HIRFL system to supply middle and heavy ion beams, such as a 1 p?A heavy ion beam with energy 5–6 MeV/u for super heavy elements experiments [2] and a high intensity heavy ion beam with energy of about 10 MeV/u for the cooler store ring. The HEBT is designed to transport the heavy ion beam and provide a good match between the SSClinac injector and the SSC. Presently, the HEBT has been designed and extensively simulated by using the TRACE-3D code [3] and the Track code [4], which

is a new program for the dynamics simulation of linear accelerators and was developed based on the PIC (particle-in-cell) method.

2

The arrangement of the HEBT

The SSC-linac injector is designed to accelerate heavy ion beam with the q/A=1/7. Therefore, the HEBT simulation primarily focuses on the uranium beam, 238 U34+ . The HEBT layout is shown in Fig. 1. The three quadrupole magnets following the DTL are used to convert an asymmetric beam distribution at the entrance of the HEBT. In the following two dipoles and three quadrupole magnets, the beam is bent and the dispersion is eliminated absolutely. A beam waist is produced by the ?rst ?ve quadrupole magnets in the HEBT and a buncher located at this point focuses the beam to match the longitudinal acceptance of the SSC. The following quadrupole magnets are used to change the transverse phase spaces to match the transverse acceptances of the SSC.

Received 17 February 2012 * Supported by National Natural Science Foundation of China (10635090) 1) E-mail: lixn@impcas.ac.cn ?2012 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd


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