成像法在电磁叠加型光阴极注入器中的应用

范培亮; 王科; 何小中; 杨柳; 魏涛; 江孝国; 杨治勇; 杨兴林

doi:10.11884/HPLPB202234.220112

成像法在电磁叠加型光阴极注入器中的应用

doi: 10.11884/HPLPB202234.220112

中国工程物理研究院流体物理研究所，四川绵阳 621900

基金项目: 国家自然科学基金项目(11805191, 12035012，11875242)

详细信息

作者简介:
范培亮，fanpeiliang@163.com

通讯作者:
王　科，caepacc@sina.com

中图分类号: O59
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- 文章访问数: 542
- HTML全文浏览量: 244
- PDF下载量: 66
- 被引次数: 0
出版历程
- 收稿日期: 2022-04-18
- 修回日期: 2022-05-31
- 网络出版日期: 2022-06-11
- 刊出日期: 2022-08-22

Application of imaging method in overlapping field type photoinjector

Institute of Fluid Physics, CAEP, Mianyang 621900, China

摘要

摘要: 光阴极注入器为X射线自由电子激光提供高品质电子束团，其中，阴极面上电子发射的均匀性在很大程度上影响着电子束团的束流品质，实验中常通过测量光阴极量子效率分布来评估电子发射的均匀性。成像法测量光阴极量子效率分布时具有实时、高分辨的特点，目前，此方法只在电磁分离型光阴极注入器中有所应用。探索成像法在电磁叠加型光阴极注入器中应用的可行性，采用理论分析结合数值模拟的方法，研究结果显示成像法适用于电磁叠加型光阴极注入器，且由此获得的量子效率分布具有阴极面中心位置处分辨率优于外层的特点。此外，针对成像法在初始束团横向动量分布测量中的应用进行模拟计算分析，并在此基础上提出一种判断阴极面剩余磁场是否为零的方法。
- 量子效率 /
- 成像法 /
- 叠加场 /
- 注入器
Abstract: The photoinjectors are promising high quality electron sources for X-ray free electron laser (XFEL). The uniformity of the electron emission from the photocathode has big influence on the electron beam quality. Usually, the quantum efficiency (QE) mapping is used to evaluate the uniformity in experiments. The QE mapping imaging method used to measure the QE mapping has high resolution and it can be used in real-time measurement, so far it is only used in separated type photoinjectors. In our photoinjector, the electric field and magnetic field are overlapping in the cathode vicinity, according to theoretical analysis and simulations, we analyze the application of this method in overlapping field. Finally, we demonstrate that the imaging method is suitable for this overlapping field, and the results show that the QE mapping has higher resolution in the center of the photocathode than the outer part. We also analyze the imaging method used to measure the transverse momentum distribution, and one way is proposed to judge whether the rest magnetic field on the cathode is zero or not.
- quantum efficiency /
- imaging method /
- overlapping field /
- injector

HTML全文

图 1 阴极附近电磁场分布

Figure 1. Electric and magnetic fields distribution in the cathode vicinity

下载: 全尺寸图片幻灯片

图 2 粒子在z=0与z = 2.0 m处的横向分布

Figure 2. Transverse distribution at z = 0.0 m and z =2.0 m

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图 3 分辨率$ {\delta _x} $随螺线管磁场的变化

Figure 3. Resolution $ {\delta _x} $ versus solenoid magnetic field

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图 4 不同半径情况下的$ {\delta _x} $ (图中R为初始束团分布的最大半径)

Figure 4. $ {\delta _x} $ with different radius (R is the maximum radius of the initial particle distribution)

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图 5 初始动量分布与z=2.0 m处的横向粒子分布

Figure 5. Transverse momentum distribution and particle distribution at z=2.0 m

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图 6 束斑尺寸$ {\sigma _x} $随副线圈电流$ {I_{\text{b}}} $的变化， $ {I_{\text{b}}} $=200 A时阴极表面磁场为零

Figure 6. $ {\sigma _x} $ as a function of the bucking solenoid current $ {I_{\text{b}}} $, $ {B_{{\text{res}}}}{\text{ = }}0 $ when $ {I_{\text{b}}} $=200 A

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