## 10 The HED Instrument
### HED Instrumentation and Capabilities  
The HED instrument is installed at the SASE2 beamline and features an optics hutch (OH) and an experiment hutch (EH). In addition, an X-ray monochromator, focusing devices, a split and delay line optics and a pulse picker are placed inside the preceding tunnel section (see Figure 9). The four-bounce Si-(111) monochromator can reduce the SASE bandwidth to \(\Delta\)E/E \(\sim\)10\({}^{-4}\) at 5-25 keV,while a high-resolution Si-(533) monochromator will allow for a 5 \(\times\) 10\({}^{-6}\) bandwidth at 7.5 keV. Focusing of 5-25 keV X-rays to foci of 1-200 \(\upmu\)m at the sample position is established by several sets of Be compound refractive lenses (CRLs), located in the tunnel section (2\(\times\)) and in OH. A fourth lens set close to the sample position will allow for sub-micron foci. A multilayer-based split-and-delay line has been designed, was constructed by the University of Munster (Germany) and is currently installed at HED [121]. This device allows splitting the X-ray pulse into two with a tunable intensity ratio and to separate them with a maximum delay of 2 ps (at 20 keV) and 23 ps (at 5 keV). A pulse picker will allow selecting X-ray pulses for 10 Hz, 1 Hz or pulse-on-demand operation, thereby synchronizing X-ray and optical laser delivery to the sample. Power slits in OH can tailor the wings of the beam monitored by a beam-imaging unit. Using diamond gratings in first order a fraction of the incident beam can be steered to a single-pulse spectrometer using a bent Si crystal to monitor the incident X-ray spectrum. X-ray beam position and intensity are monitored by two intensity-position monitors, using backscattering from thin foils. Alternatively, real-time intensity monitoring is possible with a scintillator-coupled fast-frame CCD which picks up the other 1 st order diffraction from the diamond grating. The quality of the photon beam can be further improved by cleanup slits for both high and low photon energies, located close to the interaction chamber in EH. The 9 \(\times\) 11 m\({}^{2}\) experiment hutch is enclosed by a heavy concrete wall of thicknesses between 0.5 and 1.0 m to establish radiation shielding for high energetic electrons generated by the relativistic laser-matter interaction processes when focusing the multi-100 TW laser on the sample. In EH two interaction areas IA1 and IA2 have been defined. In IA1, a large vacuum interaction chamber (IC1) with inner dimensions 2.6 \(\times\) 1.7 \(\times\) 1.5 m\({}^{3}\) (LWH) accommodates several configurations for diffraction, imaging or low/high resolution spectroscopy and inelastic X-ray scattering. The IC1 vacuum of \(\sim\)10\({}^{-4}\) mbar is separated from the X-ray optics by differential pumping stage or, above 10 keV, by a diamond window. At IA2 various setups can be interchanged. A second interaction chamber (IC2) with 1 m diameter is dedicated to dynamic diamond anvil cell (DAC) experiments and high-precision dynamic laser compression experiments in a standardized configuration. Alternatively, a goniometer with a pulsed magnetic coil and a cryogenic sample environment shall be placed here. While in IA1 all X-ray and laser beams are available, IA2 has access to the X-ray FEL and the nanosecond laser beams only. X-ray detectors inside IC1 need to be vacuum-compatible with compact dimensions, low weight, modular assembly, and \(>\)10 Hz repetition rate. HED plans to have several detectors installed. Two EPIX100 modules [122] offer a 35 \(\times\) 38 mm\({}^{2}\) chip with 50 \(\upmu\)m pixel pitch and 10\({}^{2}\) dynamic range at  
Figure 9: Schematic outline of the HED scientific instrument at the SASE2 FEL beamline. Shown are major instrumentation items installed in the photon beam transport tunnel, optics hutch and experiment hutch comprising the beam transport, focusing and diagnostic devices as well as the large optical lasers, second interaction area instrumentation and detectors contributed by the HiBEF User Consortium. 8 keV.