Development of beam profile monitor using Kirkpatrick Baez mirrors
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摘要: 为了对衍射极限储存环的束流横向截面尺寸及发射度进行测量，设计了一套Kirkpatrick-Baez(KB)反射镜聚焦成像系统，并在上海光源(SSRF)储存环进行预制研究。该系统主体由两面垂直放置的KB反射镜组成，分别在水平及垂直方向对弯转磁铁光源点进行成像，系统工作在硬X射线波段，聚焦光斑被闪烁体X射线相机采集。对影响系统成像质量的像差和点扩散函数进行了计算。目前，实现了对束流的实时成像，可精确测量束流横向截面尺寸为75.9 μm(水平方向)和20.2 μm(垂直方向)，系统稳定性(RMS)小于0.1 μm。Abstract: A Kirkpatrick Baez mirror imaging system has been designed and installed to measure the beam transverse profile and emittance of SSRF storage ring. The new system could be interchangeable with the original X-pinhole system. Two orthogonal cylindrical mirrors are used to image the dipole source point in the horizontal and vertical directions. Hard X-ray with peak energy of 20.5 keV will be focused at the X-ray scintillator camera. Aberration and point spread function which would cause image blur are evaluated. The system commissioning and optimization have been done. The electron transverse beam size has been measured precisely with horizontal 75.9 μm and vertical 20.2 μm. The system stability is less than 0.1 μm.
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Key words:
- KB mirror /
- beam size measurement /
- beam diagnostic /
- emittance /
- synchrotron radiation
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图 2 经过Al窗口与入射狭缝、VFM镜、HFM镜后的同步辐射光谱
Figure 2. Spectrum of the synchrotron radiation filtered by Al window, entrance slits, vertical focusing mirror (VFM) and horizontal focusing mirror (HFM)
表 1 KB镜参数
Table 1. Design parameters of KB mirrors
mirror VFM HFM shape cylindrical cylindrical radius of curvature/km 2.57 2.57 grazing angle/mrad 3 3 substrate silicon silicon coating Rh Rh acceptance angle/μrad 122 117 size L×W×H 320 mm×40 mm×40 mm 320 mm×40 mm×40 mm clear aperture L×W 300 mm×10 mm 300 mm×10 mm roughness RMS/nm < 0.2 < 0.2 slope error RMS/μrad < 0.3 < 0.3 distance to source/m 7.36 7.72 distance to image/m 8.08 7.72 magnification 1.1 1 heat load hitting 1.083 W@absorbed 0.832 W hitting 0.251 W@absorbed 0.058 W 
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表 2 光源点理论参数
Table 2. Theoretical electron parameters of source point
βx/m βy/m ηx/m ηy/m σe 0.794 0 12.65 0.048 7 0 0.985 3×10-3
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