The specification of the BL18U1 beamline is listed in Table 1. The energy of 5-18 keV is tunable with an energy resolution of less than 1.8x10-4 at 12.4 keV. The beam size at the sample point was tested to be 9.86 µm (H) x 4.9 µm (V) after careful tuning of the optical elements. The photon flux of the focused beam is 5.81x1011 ph/s at a current of 300 mA, and the divergence of the focused beam is 0.27 (H) x 0.17 (V) mrad2. The divergence does not change with energy and could be further minimized by the slit in front of the focused beam. However, the photon flux also decreases with the minimized divergence.
| Source type | Undulator, U25 25 mm x 80 periods, 6–12 mm gap |
| Toroidal mirror | 800x70x35 mm3, Rh-coated, 3.5 mrad |
| Cylindrical mirror | 1000x85x55 mm3, Rh-coated, 3.5 mrad |
| Monochromator | 1000x85x55 mm3, Rh-coated, 3.5 mrad |
| Energy range (keV) | 5–18 |
| Energy resolution (DE/E) (@12.4 keV) | 2x10-4 |
| Focused beam size (FWHM) (µm2) (Hx V) (@12.4 keV) | <10x7, best 9.86 x 4.9 |
| Divergence (mrad2) (HxV) (@12.4 keV) | <0.27x0.17 |
| Flux (at 12.4 keV, 300 mA) (photons/s) | 5.81x 1011 |
Table 1 The Specifications of BL18U1 Beamline
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