用于C波段光阴极微波电子枪的发射度测量仪设计

陈伟文; 姜世民; 刘仁洪; 杨涛; 黄蔚玲; 杨仁俊; 李晓

doi:10.11884/HPLPB202537.250038

用于C波段光阴极微波电子枪的发射度测量仪设计

doi: 10.11884/HPLPB202537.250038

陈伟文^{1, 2, 3,},
姜世民^{1, 3},
刘仁洪^{1, 3},
杨涛^{1, 3},
黄蔚玲^{1, 2, 3},
杨仁俊^{1, 2, 3, ,},
李晓^{1, 2, 3}

1.
中国科学院高能物理研究所，北京 100049
2.
中国科学院大学，北京 100049
3.
散裂中子源科学中心，广东东莞 523803

基金项目: 广东省基础与应用基础研究基金项目（2022A1515140179）；中国科学院高能物理研究所基金谢家麟基金项目（E4546JU2）

详细信息

作者简介:
陈伟文，chenww@ihep.ac.cn

通讯作者:
杨仁俊，yangrenjun@ihep.ac.cn。

中图分类号: O572.21
计量
- 文章访问数: 40
- HTML全文浏览量: 8
- PDF下载量: 1
- 被引次数: 0
出版历程
- 收稿日期: 2025-02-27
- 修回日期: 2025-08-05
- 录用日期: 2025-07-18
- 网络出版日期: 2025-09-25

Design of an emittance measurement device for the C-band photocathode RF gun

Chen Weiwen^{1, 2, 3
,},
Jiang Shimin^{1, 3},
Liu Renhong^{1, 3},
Yang Tao^{1, 3},
Huang Weiling^{1, 2, 3},
Yang Renjun^{1, 2, 3
, ,},
Li Xiao^{1, 2, 3}

1.
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2.
University of Chinese Academy of Sciences, Beijing 100049, China
3.
Spallation Neutron Source Science Center, Dongguan 523803, China

摘要

摘要: 束团电荷量100 pC条件下，C波段光阴极微波电子枪出口的束流归一化发射度预计低于0.2 mm.mrad。为实现对极小束流发射度的准确测量，设计了一套基于单狭缝扫描法的发射度测量仪，并利用数值模拟对发射度仪的狭缝结构和子束团漂移距离等核心参数进行了优化。考虑动态误差的数值模拟表明：采用宽度5 μm、厚度1 mm的狭缝和0.11 m的子束团漂移距离时，95%发射度的测量偏差低于5%。
- C波段光阴极微波电子枪 /
- 高品质束流 /
- 归一化发射度 /
- 发射度测量仪 /
- 单狭缝扫描法
Abstract: Background
To enhance the performance of the next-generation X-ray free electron laser (XFEL), a photocathode RF gun capable of providing the required high-quality electron beam with a small emittance has been a significant research objective. In comparison to the conventional L-band or S-band RF gun, the C-band RF gun features a higher acceleration gradient above 150 MV/m and the ability to generate a small-emittance beam. Low-emittance electron beams are critical for enhancing XFEL coherence and brightness, driving demand for advanced RF gun designs. For a bunch charge of 100 pC, a normalized emittance of less than 0.2 mm.mrad has been expected at the gun exit.
Purpose
This paper presents the design of an emittance measurement device, which can accurately measure such a small emittance at the C-band RF gun exit to ensure beam quality for XFEL applications.
Methods
To achieve the desired accuracy, the primary parameters —slit width, slit thickness, and beamlet-drift length—have been systematically optimized through numerical simulations using Astra and Python based on the single-slit-scan method. Dynamic errors, including motor displacement and imaging resolution, were quantified to ensure measurement reliability.
Results
The evaluations indicate that the measurement error of 95% emittance is less than 5%, employing a slit width of 5 μm, a slit thickness of 1 mm, and a beamlet-drift length of 0.11 m under dynamic conditions.
Conclusions
This optimized emittance measurement device supports precise beam quality characterization for XFELs, offering potential for further advancements in electron beam diagnostics.
- C-band RF gun /
- beam with high quality /
- normalized beam emittance /
- emittance measurement device /
- single-slit-scan method

HTML全文

图 1 C波段光阴极微波电子枪测试平台布局图

Figure 1. Layout of the C-band photocathode RF gun test platform

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图 2 采用单狭缝扫描法的发射度仪主要参数

Figure 2. The main parameters of the emittancemeter using the single-slit scanning method

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图 3 不同束团电荷量下，狭缝出口处的子束团${R_{sc}}$值评估

Figure 3. Assessed ${R_{sc}}$ for the beamlets at the slit exit under different beam charge

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图 4 束团电荷量100 pC时，粒子损失与狭缝宽度和厚度的关系

Figure 4. Particle loss versus slit width and thickness for a bunch charge of 100 pC

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图 5 对于理想完全阻挡材料和钨材料靶，下游剖面探测器处的子束团分布

Figure 5. Horizontal beamlet distribution at the downstream profile monitor for ideal complete blocking materials and tungsten material targets

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图 6 束团电荷量100 pC时，考虑与不考虑空间电荷力的重建发射度与狭缝宽度的关系

Figure 6. Evaluations of the reconstructed emittance as a function of slit width with and without space charge effects for a bunch charge of 100 pC

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图 7 狭缝宽度为10 μm和5 μm时，100%发射度和95%发射度的测量偏差与子束团漂移距离的关系

Figure 7. Measurement error of 100% emittance and 95% emittance versus beamlet drift length for the slit widths of 10 μm and 5 μm

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图 8 驱动电机的单向位移精度测量

Figure 8. The measured displacement error of the driven motor

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图 9 基于单狭缝扫描法的发射度测量仪结构

Figure 9. A schematic layout of the single-slit-scan based emittancemeter

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图 10 采用Sugitoh TS-93022镜头的USAF1951分辨率板成像

Figure 10. Image of the USAF1951 resolution board by the Sugitoh TS-93022 len

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图 11 考虑动态误差时，100%发射度和95%发射度测量偏差与子束团漂移距离的关系

Figure 11. Measurement errors of 100% emittance and 95% emittance as a function of beamlet drift length in the presence of dynamic errors

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图 12 初始和重建的相空间分布

Figure 12. The initial and the reconstructed phase-space distributions

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表 1 C波段光阴极微波电子枪的主要束流参数 (设计值)

Table 1. Major beam parameters of the C-band photocathode RF gun (design values)

Charge (pC)	Energy (MeV)	$100{\text{%}} {\varepsilon _n}$ (mm·mrad)	$95{\text{%}} {\varepsilon _n}$ (mm·mrad)
100	7.26	0.175	0.111
300	7.25	0.323	0.215
500	7.24	0.463	0.304

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表 2 多缝法和单缝扫描法在光阴极注入器上的应用^[27-33]

Table 2. The application of multi-slit and single-slit scan measurement on photoinjectors

facility name	method	beam energy /MeV	charge/pC	slit width/μm	Normalize emittance/(mm.mrad)
SITF	Single-slit-scan	7	100	20	0.46
PITZ	Single-slit-scan	4.6	100	10	0.26
ELBE	Single-slit-scan	4.45	100	100	2.84
DC-SRF-II	Single-slit-scan	2.42	100	30	0.54
ORGAD	Multi-slit	6.5	30	40	3
LEReC	Multi-slit	2.6	75	150	1.6

下载: 导出CSV

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