chemRIXS Standard Configurations

chemRIXS Liquid Standard Configuration

The chemRIXS endstation provides a liquid standard configuration for time-resolved pump-probe XAS and/or RIXS/XES experiments on liquids/solution. This configuration operates with monochromatized X-ray beam with DE/E ~ 2000. In-vacuum liquid jets used for sample delivery. Sample recirculation capability is part of the standard setup. The endstation provides a high throughput RIXS spectrometer (RP~2000). In-vacuum APDs are available for fluorescence detection and downstream beam intensity detector(s) can be utilized for transmission experiments. Typical pump-probe time-resolution is on the order of 100 fs. Tables below summarize the X-ray and laser capabilities for Run 26 (120 Hz CuRF beam) and Run 25 (SCRF beam up to 33 kHz). 

chemRIXS FZP Standard Configuration

For Run 26 (120 Hz) the chemRIXS endstation will provide a standard configuration that allows dispersive detection of X-rays with an in-line transmission Fresnel Zone Plate (FZP) spectrometer. Typical experiment envisioned for this configuration will utilize unmonochromatized X-rays (SASE or attosecond XLEAP beam) which are transmitted trough a sheet jet in chemRIXS. The X-ray spectrum is subsequently detected shot-by-shot using the downstream FZP spectrometer.

Please contact the instrument scientist Kristjan Kunnus for any questions regarding the standard configurations or any other questions (e.g. non-standard experiments with solid samples and/or advanced X-ray modes). 

Guidelines and Performance Parameters for Run 26

Run 26 will make use of the LCLS-I accelerator which will operate at the 120 Hz repetition rate. The OPCPA laser system with 800 nm fundamental will be synchronized to the X-rays and available for pump-probe experiments.
The community is encouraged to propose experiments focusing on the following techniques:

• Time-resolved XAS, which can be implemented in three modes:
  • Direct transmission (for samples delivered in the form of a thin sheet jet)
  • TFY mode, using the in-vacuum APD
  • Partial Fluorescence Yield (PFY) mode, using the VLS or SVLS spectrometer
• Unmonochromatized experiments
  • Utilizing advanced XLEAP modes (attasecond single or double pulses).
  • Dispersive detection with in-line FZP spectrometer downstream of chemRIXS IP.

Due to incident flux limitations, time-resolved RIXS experiments are discouraged.

Guidelines and Performance Parameters for Run 25

Run 25 will make use of the new superconducting LCLS-II accelerator which will operate at repetition rates up to 33 kHz. The OPCPA laser system with 800 nm fundamental will be synchronized to the X-rays and available for pump-probe experiments.
The community is encouraged to propose experiments focusing on the following techniques:

• Time-resolved RIXS/XES
• Time-resolved XAS, which can be implemented in three modes:
  • Direct transmission (for samples delivered in the form of a thin sheet jet)
  • TFY mode, using the in-vacuum APD
  • Partial Fluorescence Yield (PFY) mode, using the VLS or SVLS spectrometer

Performance Parameters 

The new OPCPA laser system will offer short (< 25 fs) 800 nm laser pulses. Harmonics of these pulses can be generated (400/266 nm) and  Vis-OPA providing 480 - 900 nm is available.

chemRIXS detection techniques

• Variable-Line Spacing (VLS) Spectrometer.  This is an existing spectrometer with resolving power of ~1300 that is equipped with the Andor Newton_SO CCD (512 X 2048 pixels, 13.5 microns pixel size).  The CCD will integrate over many X-ray shots, with read-out rates up to 100 Hz in full-vertical-binning mode or up to 1 Hz in image mode. The spectrometer will be mounted in the horizontal plane at 45 degrees with respect to the X-ray beam.
• High-throughput Spherical Variable-Line Spacing (SVLS) Spectrometer.  This is a new spectrometer with nominal resolving power of 2000 that is equipped with the AXIS-SXR-60 CMOS detector (6144 X 6144 pixels, 10 microns pixel size).  The CMOS will integrate over many X-ray shots, with read-out rates up to 100 Hz in cropped image mode. The spectrometer will be mounted in the horizontal plane at 90 degrees with respect to the X-ray beam. The spectrometer is currently under installation/commissioning.
• Avalanche PhotoDiodes (APD).  The APDs are single-photon sensitive fast detectors suitable for X-ray Absorption Spectroscopy (XAS) in Total Fluorescence Yield (TFY) mode.  These detectors will be mounted on an in-vacuum rotatable stage and can be placed in the horizontal scattering plane. APDs are single shot detectors and can be read-out at 33 kHz.
• Transmission-XAS detectors for measuring transmitted beam intensity downstream of ChemRIXS when using thin sheet jets.
  • Andor Newton_SO, 512 X 2048 pixels, 13.5 microns pixel size, capable of read-out up to 100 Hz in full-vertical-binning mode and 1 Hz in full image mode. Will be used in integrating mode with high rep.-rate beam, i.e. accumulating signal over many X-ray shots. This is an existing CCD camera used before with 120 Hz beam.
  • ePixM, 384 X 764 pixels, 50 microns pixel size, capable of full image read-out up to 5 kHz. This detector is currently in the testing phase.
  • Single-shot APD for indirect detection of transmitted beam by a fluorescence from a target.

The RIXS/XES spectrometers can be used simultaneously with the TFY APDs and the transmission detectors.