Alvra specializes in measuring the ultrafast dynamics of photochemical and photobiological systems in solution, suspension, or crystals, using a variety of X-ray scattering and spectroscopic techniques. Alvra consists of two instruments: Alvra Prime and Alvra Flex. Prime is a helium/low vacuum atmosphere chamber designed to perform a range of techniques, including serial femtosecond crystallography (SFX), X-ray scattering (XDS), and X-ray absorption and emission spectroscopy (XAS, XES, and RIXS) over the full SwissFEL hard X-ray photon energy range of 2-13 keV. Flex is a versatile instrument designed to accommodate user experiments with an X-ray spectrometer that can be used for many different types of measurements, including inelastic X-ray scattering (IXS) and high energy resolution off-resonant spectroscopy (HEROS), as well as host user-provided setups. An overview of the Alvra design parameters can be found here and on the SwissFEL facility here. A user laboratory, to support chemistry and biology experiments is also available on-site. The summary of the lab infrastructure and equipment can be found here.
Alvra is currently in full-user operation mode, with both the Prime and Flex instruments commissioned at 100 Hz. A summary of the experimental station parameters follows
Alvra Prime
The Alvra Prime chamber is used for the majority of experiments at the Alvra Endstation.
Alvra Prime is a compact chamber which is usually operated under a low-vacuum Helium environment. The main door provides access to the XYZ stage and chamber interior. Several additional through-put ports are available for experimental setups.
The specifics of the chamber and its adjoining components are detailed in the table below.
| Photon energy range | 2 – 13 keV (full SwissFEL Aramis photon energy range) |
| Beam profile | Measured focus 20 µm (FWHM) at 2 and 4.5 keV (defocussed beam also possible) Measured focus 1.5 µm (FWHM) at 12 keV (defocussed beam also possible) Unfocused beam: 500 µm to 1 mm (FWHM) energy dependent Flexible KB mirrors can also provide an asymmetric focus |
| Bandwidth | SASE 0.25% (pink beam), large bandwith availabe upon request (up to 2%) Monochromatic: Si(111), Si(311) and InSb(111) |
| Sample Environment | From vacuum (5 x 10-4 mbar) up to 800 mbar pressure (He or N2) |
| Sample delivery systems | Liquid jet for chemistry:
LCP viscous injector (50-100 µm) GDVN injectors tested in chamber (user provided) Solid samples upon request |
| Detectors and Spectrometers | 16M Jungfrau forward scattering detector at 10 cm distance (<1 Å resolution at 12.4 keV) |
| 4M Jungfrau forward scattering detector at 10 cm distance (1.5 Å resolution at 12.4 keV) | |
| 2 x 2 crystal von Hamos dispersive X-ray emission spectrometer (1-12.4 keV) | |
| APD and PIPS diodes for x-ray absorption measurements |
Alvra Flex
Alvra Flex is, as its name suggests, a flexible experimental area where users can build up their required setup.
At a basic level, Alvra Flex is a large table with an XYZ stage sitting downstream of the Alvra Prime chamber. Various motors and stages are installed and can be used for a variety of setups. A 1M JUNGFRAU detector is also permanently mounted and available for use.
The details of Alvra Flex and its adjoining components are detailed in the table below.
| Photon energy range | 6 – 13 keV |
| Beam profile | Flexible focus from 10 to >100 µm (FWHM) |
| Unfocused beam: ~1 x 1 mm2 (FWHM) energy dependent | |
| Bandwidth | SASE 0.5% (pink beam) |
| Monochromatic: Si(111), Si(311) and InSb(111) | |
| Sample Environment | Atmospheric conditions (in-air setup) |
| Sample delivery systems | Liquid jet for chemistry: |
| - Flat jet (100, 200 and 300 µm) with gear or peristaltic pump | |
| - Round jet (20-100 µm) with HPLC pump | |
| LCP viscous injector (50-100 µm) | |
| Solid samples | |
| Detectors and Spectrometers | 3 crystal von Hamos dispersive X-ray emission spectrometer with 1M Jungfrau detector |
| Diodes for x-ray absorption measurements |
Optical Pump Laser
The majority of experiments at the Alvra Endstation make use of the optical pump laser.
The system is developed and maintained by Philip Johnson from the Pump Laser Group.
| Primary pump source | 800 nm, 35 fs FWHM, 10 mJ (Ti:Sapphire) |
|---|---|
| Secondary pump sources | 240 nm – 2.5 micron (OPA with additional nonlinear conversion options). At present pulse energies at the sample location for 240-400 nm have been measured in the range of 10-30 µJ. We expect pulse energies of 150-500 µJ between 400 nm and 780 nm; 150-500 µJ between 1 µm and 2.5 µm. Pulse durations are expected to be approximately 50 fs fwhm. |
| Timing diagnostics | Alvra currently has two spectral encoding time-tools available, one pre and one post-interaction region. This approach has been demonstrated at several other facilities and works well for experiments that use the full SASE pulses at the full X-ray range of the endstation (2-12 keV) and for monochromatic experiments at the higher x-ray energies (>6 keV). |
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