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![[Figure 1]](ay5631fig1mag.jpg)
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Figure 1
An overview of the experimental setup of the cavity-based X-ray free-electron laser (CBXFEL) project, which consists of an electron beam source, a cascade of undulators and two chicanes, and a rectangular X-ray cavity. The X-ray cavity consists of four diamond crystal mirrors (C1–C4), reflecting X-rays in the 400 Bragg reflection at exactly 45° with a photon energy of 9.831 keV, and two X-ray lenses (L1, L2). Diamond crystal C1 has a drumhead crystal structure (Kolodziej et al., 2016  ) with a ∼20 µm-thick membrane to outcouple X-rays (Kim et al., 2008; Kim & Shvyd'ko, 2009; Shvyd'ko, 2019) to diagnostics station G in the X-ray pump–probe (XPP) LCLS experimental hutch, which is located ∼250 m downstream of the undulators (Chollet et al., 2015). In station G, Si channel-cut monochromator crystals (CC) will be used to monochromatize the broadband X-rays to a narrow band centered on 9.831 keV for further diagnostics. A thin diamond Cx in the 440 exact Bragg backscattering is used for precise energy calibration and C1 angular alignment. The long-arm length L of the rectangle is 32.10 m and the short-arm length W is 0.65 m. A diamond grating (Li et al., 2020) downstream of C2 will also be used for alternative output coupling for X-ray diagnostics in station E. The upper-left inset (a) shows the total reflectivity of the four diamond crystals and transmissivity of the drumhead crystal C1, with a drumhead membrane thickness of (left) 20 µm and (right) 15 µm. |
![[Figure 1]](ay5631fig1.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
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