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An Office of Science User Facility

X-ray Correlation Spectroscopy (XCS)

XCS Standard Configuration for Run 16

Types of Experiments

With this standard configuration, XCS will be able to support time-resolved wide-angle scattering and x-ray emission measurements for the study of photo-excited molecular dynamics in the solution phase.

A von Hamos spectrometer will be available for the measurement of the following x-ray emission lines: Mn Kß1,3, Kß2,5 and Kα, Fe Kß1,3 and Kß2,5, Co Kß1,3 and Kß2,5, Ni Kß1,3 and Kß2,5, Ti Kß1,3 and Kß2,5 and V Kα.

X-ray and X-Ray Focus

X-ray energy will be fixed at 9.5 keV with the XCS Instrument operating in pink mode with the XCS periscope mirror system or monochromatic with the large offset double crystal monochromator using diamond (111). We expect an average photon flux of 1012/pulse in pink mode and 1010/pulse in monochromatic mode and pulse duration of about 50 fs. Refractive Be lens will be available to deliver a beam size ranging from 2 to 100 um at the sample.

Optical Pump Lasers

Time-resolved experiments employing tunable femtosecond pulses will be supported under this standard configuration. In addition to the 800/400 nm 50 fs Ti:Sapphire fundamental/2nd harmonic wavelengths, an OPA will be available to cover the wavelength range of 480-2400 nm. The optical pump beam will be propagating collinearly with the x-ray beam with about 2 degree crossing angle. The pulse duration will be below 70 fs. We note that the efficiency of the optics and the performance of the laser and the OPA will not be the same for the entire wavelength range. The achievable peak intensity/fluence will be determined by the existing optical system and will not be modified. Contact the XCS scientists to discuss specific needs and to confirm whether they can be achieved in this standard configuration of the laser.

Timing diagnostics

The spectral-encoding based timing tool will be available to provide shot-to-shot jitter measurement. We expect a time resolution of 100 fs considering the pump/probe pulse duration as well as the jitter correction accuracy.

Sample Manipulation and Temperature Control

A helium purged sample chamber will be used to house the liquid jet, with Kapton windows to allow x-ray scattering and emission to be measured by detectors outside the chamber. Liquid jet driven by HPLC pumps will be used to deliver the sample into the interaction point.

Round Jet diameters of the following size are available : 20, 30, 40, 50, 75, 100, 125, 150, 175, 200, 250, 300, 500.

Flat-sheet thicknesses of the following size are available : 19, 25, 38, 50, 75, 100, 125, 175, 188, 250.

Every user group accepted and scheduled to use the XCS standard configuration will be strongly advised to test the injection of their sample at the LCLS Sample Characterization Lab prior to the experiment.

Detectors

A CSPAD-2.3M detector will be mounted downstream of the chamber for the measurement of the forward scattering. The X-ray emission spectra will be measured by a CS140k detector.

XPP Instrument Staff

Matthieu Chollet, Mike Glownia, Roberto Alonso-Mori, Yiping Feng, Takahiro Sato, Matt Seaberg, Sanghoon Song, Diling Zhu

Parameter Table

To be considered for scheduling in this standard configuration, users will be required to include a table in the proposal that lists the specific experimental parameters to ensure compatibility with these configurations. If the experimental parameters are not compatible with the standard configuration or if the table of parameters is incomplete, the proposal will be reviewed and considered for scheduling as general user proposal. Please see the  table of required parameters. No fundamental changes to the standard configurations will occur, but some details of the configuration may be updated in response to inquiries, so users should recheck the website before submitting your proposal to confirm that you have the latest information. Address any questions to the instrument staff.
 
 

LCLS proposals are submitted through the User Portal.

 

 

SLAC SLAC National Accelerator Laboratory, Menlo Park, CA
Operated by Stanford University for the U.S. Dept. of Energy