用于激光驱动质子束测量的腔式束流位置探测器模拟研究

李成财; 朱昆; 林晨; 朱军高; 吴旻剑; 李东彧; 徐筱菡; 颜学庆

doi:10.11884/HPLPB201931.190020

用于激光驱动质子束测量的腔式束流位置探测器模拟研究

doi: 10.11884/HPLPB201931.190020

北京大学核物理与核技术国家重点实验室, 北京 100871

基金项目:

国家重大科学仪器设备开发专项 2012YQ030142

详细信息

作者简介:
李成财(1993-), 男，硕士研究生，从事激光加速器方面研究；1601210146@pku.edu.cn

通讯作者:
朱昆(1977-)，男，高级工程师，从事加速器技术及应用方面研究；zhukun@pku.edu.cn

林晨(1982-)，女，研究员，从事激光加速器方面研究；lc0812@pku.edu.cn

中图分类号: TL506
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出版历程
- 收稿日期: 2019-01-18
- 修回日期: 2019-03-26
- 刊出日期: 2019-07-15

Cavity beam position monitor in laser-driven proton accelerator

State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China

摘要

摘要: 根据激光驱动质子束流低发射度、短脉冲、单束团低电量的性质，研究腔式束流位置探测器(BPM)测量激光加速器产生的质子束团横向位置的可行性问题。针对质子束团的大横向分布和发散角问题，推导了其通过腔式BPM的输出信号，结果表明该信号与集中从束团对称中心、倾斜一定角度通过的束流产生的输出信号相同。依据上述原理，使用CST软件进行了腔式BPM的设计和仿真，确定了矩形谐振腔波导耦合的方案。讨论了该方案的腔式BPM对于激光加速束流的适用性和不同激光驱动质子束流参数的分辨率，并针对PW级激光加速系统进行了分辨率估算。
- 腔式BPM /
- 激光驱动质子 /
- 大横向分布 /
- 发散角
Abstract: According to low-emittance, short-pulse and low-charge-in-single-bunch properties of laser-driven proton beam, we study the feasibility of cavity beam position monitor (BPM) to measure the transverse position of proton beam generated by laser accelerator. In view of the large transverse distribution and divergence angle of proton beam, we derive the output signal when it goes through the cavity BPM, and the result shows that the output signal is identical to that generated by the beam passing through the symmetry center of the transverse distribution and at a certain angle of inclination. Based on the above principle, we use CST software to design and simulate cavity BPM, and determine the scheme of rectangular cavity with coupling waveguide. We discuss the applicability of this scheme for laser-accelerated beam and the resolution of different laser-driven proton beam parameters, and estimate the resolution of PW laser acceleration system.
- cavity BPM /
- laser-driven proton /
- large transverse distribution /
- divergence angle

HTML全文

图 1 (a) RCF测得约25%能散束流横向分布，(b)闪烁体测得约4%能散束流横向分布，(c)MCP测得约1%能散束流横向分布

Figure 1. Experimental results: (a) beams' transverse distribution with about 25% energy dispersion on RCF, (b) beams' transverse distribution with about 4% energy dispersion on scintillator, and (c) beams' transverse distribution with about 1% energy dispersion on MCP

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图 2 束团倾斜入射进腔式BPM的轨迹在x-z平面的投影

Figure 2. Projection of the trajectory of the beam into the cavity BPM in the x-z plane

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图 3 偶极模磁场(a)TM210模，(b)TM120模

Figure 3. H-field of dipole mode(a)TM210 mode, (b)TM120 mode

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图 4 TM210模(a)和TM120模(b)在x=1, 0.5, 0.2 mm的R/Q₀

Figure 4. R/Q₀ of TM210 mode. (a) and TM120 mode(b) at x=1, 0.5, 0.2 mm

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图 5 (a) 脉宽分布，(b) R/Q₀分布

Figure 5. Estimated results: (a) distribution of pulse time, (b) distribution of R/Q₀

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表 1 腔式BPM优化尺寸

Table 1. Optimum geometry of cavity BPM

a /mm	b/mm	L/mm	D/mm	waveguide length X/mm	waveguide position X/mm	waveguide length Y/mm	waveguide position Y/mm
241.6	210	75	80	250	90.5	280	76

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表 2 腔式BPM理论参数

Table 2. Theoretical parameters of cavity BPM

f₁₁₀/GHz	(R/Q₀)₁₁₀/Ω	f₂₁₀/GHz	(Q_ext)₂₁₀	(R/Q₀)₂₁₀/Ω	f₁₂₀/GHz	(Q_ext)₁₂₀	(R/Q₀)₁₂₀/Ω
0.9167	224.5	1.320	1955	0.1088	1.420	2103	0.1328

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表 3 分辨率估计

Table 3. Resolution estimation

E/MeV	σ_t/ps	q/pC	(R/Q₀)₂₁₀/Ω	resolution/mm
30	273	500	0.039 2	0.6
50	208	150	0.050 7	0.8
100	142	50	0.093 2	1

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参考文献(12)

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