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摘要: CADS注入器Ⅰ试验装置由中国科学院高能物理研究所承建。其10 mA的束流由RFQ结构加速到3.2 MeV，经中能传输段匹配到超导加速结构。为了减小失匹配造成的束流损失，需要测量RFQ出口束流参数，以便调整中能传输段Lattice结构，使束流能匹配进入超导腔。CADS注入器Ⅰ采用丝靶扫四极铁参数的方式测量束流截面并计算RFQ出口Twiss参数。强流加速器在低能段空间电荷力很强，常规的基于矩阵的数据处理方法会带来误差。本文分别用常规的未考虑空间电荷效应的矩阵方法和考虑了空间电荷效应的遗传算法对数据进行处理，得到的结果显示低能强流加速器进行Twiss参数测量时，必须考虑空间电荷效应的影响。Abstract: The test stand of CADS Injector Ⅰ is built at the Institute of High Energy Physics(IHEP). The 3.2 MeV, 10 mA beam from the RFQ will be transported and matched by medium energy transport line (MEBT1) to the superconductive accelerating section. To minimize the beam loss from mismatch, the Twiss parameters at the exit of RFQ should be got. The method of scanning quadrupole strength with wire scanner is used in CADS Injector Ⅰ. As to the data process, the traditional method based on matrix will bring errors for high intensity accelerators, especially at low energy when the space charge force is very strong. This paper introduces the traditional method and the new method considering space charge effect, which is based on MOGA. The result proves that the space charge should be considered when calculating the Twiss parameters for high intensity low energy accelerators.
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Key words:
- wire scanner /
- space charge /
- MOGA /
- high-intensity accelerator
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Table 1. Twiss parameters from traditional method and MOGA
parameter αx αy βx βy εx εy traditional method -1.09 2.15 0.12 0.19 0.19 0.27 MOGA -1.27 1.10 0.16 0.10 0.16 0.24 difference/% 14 96 26 85 18 10 
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[1] Yan F, Geng H, Meng C, et al. Commissioning of the China-ADS Injector-I testing facility[C]//Proceedings of IPAC. 2016: 2048-2051. [2] Wikipedia. Multi-objective optimization[DB/OL]. https://en.wikipedia.org/wiki/Multi-objective_optimization. [3] Uriot D, Pichoff N, Trace Win. CEA Saclay/DSM/Irfu/SACM/LEDA[K]. 2015. [4] Geng H, Pei S, Wang H, el al. Emittance measurement with wire scanners at CADS MEBT1[C]//Proceedings of IPAC. 2014: 3575-3577. -
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