## 2 Typical Performance  
Table 1 shows basic radiation characteristics for the first XFEL beamline, BL3. The unique injector system combines an e-gun using a thermionic cathode and a multi-stage bunch compression system, instead of an RF-photo cathode system. This configuration can produce high peak power with an X-ray pulse duration shorter than 10 fs under normal operating conditions. Such a short pulse duration assures analysis with a \"diffraction-before-destruction\" scheme and potentially facilitate ultrafast experiments. The beamline provides hard X-ray FEL with a high photon energy, greater than \(\sim\)15 keV, even with a moderate beam energy of 8 GeV. This distinct capability is possible due to the in-vacuum short-period undulator, a core device adopted for our compact XFEL machine. Furthermore, shorter wavelength X-rays can be produced while fixing the electron beam energy by decreasing the magnetic field by opening a gap between the undulator magnets. This variable-gap design enables the production of two-color XFEL pulses with a wavelength separation above 30% using a simple split undulator technique, where the undulator gaps between the upstream and downstream sections are changed [38]. In the autumn of 2016, the first user experiment to use the maximum repetition rate of 60 Hz took place. The standard repetition rate in daily operations has increased steadily and will be 60 Hz during the latter half of 2017. Figure 1 shows a typical trend graph of pulse energy for user experiments. The constant output with a small fluctuation of 16% in root mean square (rms) demonstrates the high stability of operations, another important feature of SACLA operations. The mean fault interval in 2016 was more than 1 h at a repetition rate of 30 Hz. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Typical Value** \\ \hline Pulse energy & \(\sim\)0.5 mJ at 10 keV \\ Pulse duration & \(<\)10 fs \\ Peak power & \(>\)50 GW \\ Photon energy (Wavelength) & 4.0–20 keV 1 (0.062–0.31 nm) \\ Bandwidth & 0.5\% (FWHM 2) \\ Repetition rate & 60 Hz maximum \\ \hline \hline \end{tabular}  
* 4.0–15 keV in daily operation. 2 Full width at half maximum.  
\end{table} 
Table 1: Typical characteristics for the X-ray Free Electron Laser (XFEL) light of beamline 3 (BL3). Figure 2 shows the current schema for BL3. In the original design, the beamline had only basic functions, such as beam transport, monochromatization, focusing, and monitoring of fundamental beam parameters [5]. The beam-transport optical system basically consists of two sets of double plane mirrors and a double crystal monochromator (DCM). One of the mirror sets or DCM is selected to deliver a beam that is pink or monochromatic, respectively. The double mirror systems with different glancing angles (2 and 4 mrad) reflect X-rays below cutoff energies and attenuates the higher order harmonics above them. The DCM with Si (111) crystals delivers a monochromatic beam with a bandwidth of \(\sim\)10\({}^{-4}\) (\(\Delta E/E\)). The standard focusing optical device is a Kirkpatrick-Baez mirror pair, which is stationed at an experimental hutch to provide a 1 \(\upmu\)m X-ray spot [30]. In the upgraded beamline, new functions have been added to support broader and more advanced applications. The following major upgrades have been applied:  
Beam-transport and 1 \(\upmu\)m focusing mirrors were replaced with longer ones to increase acceptable beam sizes, especially in the lower photon energy ranges with a larger beam size [39]. Transmission ratios from the source to the sample position were improved from 30% to 55% at 5.5 keV, from 46% to 61% at 7.0 keV, and from 59% to 65% at 10 keV. * Transmission gratings working as beam splitters were installed in an optics hutch (OH2). The gratings are used for simultaneous diagnostics of timing [36] and/or spectrum [29] at the first experimental hutch EH1 with user experiments performed at another experimental hutch [37]. * A diamond phase retarder was stationed in OH2 for the polarization control of XFEL light [40].