ARAMIS Experimental Station A (ESA)
Experimental Station A (ESA) is designed as a pump-probe experimental station, which will focus on investigating photochemical and photobiological systems using some combination of X-ray spectroscopy and X-ray scattering from 2 to 12.4 keV. This station has been introduced in detail in the ESA Conceptual Design Report, which is publically available.
- ESA Prime: an experimental chamber located at the X-ray focus (~1 μm) capable of operating in neutral environments (He or N2) or vacuum, coupled to a 2D 16M Jungfrau detector [1-3] and an X-ray emission spectrometer located in vacuum using a dispersive von Hamos geometry  targeting the 2-5 keV energy range.
- ESA Flex: an in-air experimental setup capable of handling a variety of user-supplied chambers in combination with a flexible multi-crystal von Hamos geometry X-ray emission spectrometer  that can be operated at a range of scattering angles, and in a vertical or horizontal scattering geometry.
Both stations will have access to the amplified femtosecond laser system for sample photoexcitation with a range of wavelengths (200 nm to 10 μm). A timing tool  will allow X-ray/laser jitter measurements of <50 fs, providing excellent time resolution for pump-probe measurements. A range of PSI detectors will be available, including a vacuum-compatible 16M Jungfrau adaptive-gain pixel detector for scattering measurements. [1-3]
X-ray OpticsThe X-ray delivery system to the experiment is shown below. The Aramis 1 branch to ESA consists of two horizontally-deflecting offset mirrors, followed by a fixed-exit monochromator + two vertical deflecting mirrors which can be removed from the beam to allow for non-monochromatic experiments. The final element will be a set of two Kirkpatrick-Baez mirrors, capable of focusing the beam to ~1 μm at the ESA Prime sample position and some tens of μm at the ESA Flex sample position. The beam height in the experimental hutch is 1.4 m.
|Specifications DCM||Specifications KB Mirror System|
|Fixed offset (20 mm) and variable offset (4 – 42 mm)||Full energy range 1.7 – 12.4 keV|
|3 crystal pairs, Si (111), Si (311), InSb (111)||Variable spot size|
|Common Bragg axis 5 – 80 deg||Two working distances|
|1800 eV – 20000 eV||Mean mirror radii 500 m ... flat|
|Pink / Monochromatic mode||Mirror optical length 500 mm|
Photon DiagnosticsThe photon beam will be characterized by a variety of tools along its path from the Front-End through the experiment. These include a Gas Monitor, for pulse energy characterization, a Single-Shot Spectrometer , for photon spectrum characterization, Backscattering Monitors[8,9], for pulse intensity and position characterization, Screens, for beam position and spot size information, and a Timing Tool [5,10], for measurement of the timing jitter between the X-ray and optical laser pulses.
Experimental HutchThe experimental hutch is 9 x 15 x 3 m with climate control to <1°C. The hutch has a ceiling-mounted crane capable of lifting up to 1.6 T. The current layout and a recent hutch picture are shown below.
Segmented von Hamos CrystalsWe will take advantage of the ability developed at PSI to manufacture segmented crystals from thin Si wafers for dispersive X-ray spectrometers. Both ESA Prime and ESA Flex will use the same crystals types to allow for interchange between the setups. The specifications for these crystals are: 1 mm stripes, 25 cm radius of curvature, 50 x 100 mm substrate area. The crystal cuts available are Si(100), Si(110), Si(111), Si(310), Si(311), Si(331), Si(531). A figure covering the von Hamos geometry and some details on the crystals and their energy resolution is below.
Sample InjectorsBoth ESA Prime and ESA Flex will use various sample injectors including standard Kyburz liquid sheet jets (100, 200 and 300 mm thickness)[12,13]. For serial femtosecond crystallography we are currently working on integrating a lipidic cubic phase (LCP) injector purchased from Arizona State University into the ESA Prime chamber. The group of Joerg Standfuss in the BIO Department at PSI has used this injector successfully for experiments at LCLS, ESRF and the the Swiss Light Source. The injector cross-section (top) and the setup as used at ESRF (bottom) are shown below.
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