Run 19 Capabilities

ChemRIXS capabilities for Run 19

The ChemRIXS instrument is a new endstation targeting spectroscopic studies of samples in solution using monochromatic soft x-ray pulses and a tunable optical laser pump.  For rapid x-ray absorption (XAS) measurements and direct beam detection (in the case of transmissive samples), a suite of in-vacuum detectors will be implemented on a rotating arm. The chamber will be equipped with the following:

  • Liquid jet delivery via a microfluidic chip
  • A load-lock chamber that allows chip exchange
  • Catcher for capturing and/or re-circulating sample
  • Viewing and illumination
  • Diagnostic paddle for calibration targets, spatio-temporal overlap, etc.
  • Laser in- and out- coupling
  • Detectors optimized for x-ray absorption and emission spectroscopies
  • Arrival time monitor located ~1.5 m from the interaction point

Performance Parameters for Run 19:

X-ray Parameters 

 

Laser Parameters

Repetition rate (Hz)

Up to 120

 

Repetition rate (Hz)

120 

Energy Range (eV)

250 - 1600

 

Wavelength (nm) 

266*, 400, 800, 480 - 900 (tunable)

Spot Size (um), H x V

10 x 10, min

1000 max

 

Pulse Duration (fs)

<40 @ 800 nm

Energy per pulse (uJ)

>2

 

Fluence (mJ/cm2)

>50

Pulse Duration (fs)

<40

 

Spot size (um)

Min <50 X 50, option for 1:4 aspect ratio with <50 minor axis

*only circular for 266 nm

Beamline Resolving Power 

>2,000

 

Polarization control

Horizontal and vertical, circular at select wavelengths

Temporal resolution (fs)

<60

 

Arrival time monitor precision (fs)

<20

Polarization

Linear horiz.

     

Wavelength scanning

Yes

     

 

The following detectors will be provided to the users:

  • Avalanche PhotoDiodes (APD) and MicroChanel Plate (MCP).  These 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.
  • Andor Newton_SO, 512 X 2048 pixels, 13.5 microns pixel size, capable of full frame read-out at 120Hz when operated in Full Vertical Binning mode.  This CCD detector will be placed outside chemRIXS in the direct beam and will allow for measuring XAS in transmission when using thin sheet jets
  • Portable Varied-Line Spacing (VLS) X-ray Emission Spectrometer (XES).  This is an existing XES spectrometer with resolving power of ~2000, that will nominally be equipped with the abovementioned Andor Newton_SO CCD.  Plans to incorporate a flange mounted MCP assembly, providing a factor ~5-10 increase in horizontal acceptance are underway.  The spectrometer will be mounted in the horizontal plane at 90 degrees with respect to the X-ray beam.

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)
    • TFY mode, using the in-vacuum APD or MCP 
    • Partial Fluorescence Yield (PFY) mode, using the VLS spectrometer
  • Time-resolved XES, using the VLS spectrometer with non-resonant excitation
     

Resonant Inelastic X-ray Scattering (RIXS)measurements, while possible as demonstrated during LCLS-I operation, are expected to remain quite challenging given the similar average flux expected during operation with the Cu linac. Unless a compelling case is made, we discourage users from submitting proposals for experiments targeting time-resolved RIXS, as these will be much more efficient when the superconducting linac is operational. 

Not available for Run 19

The chemRIXS instrument will remain in a configuration suitable for liquid samples throughout the Run.  No condensed matter experiments will be offered in chemRIXS for Run 19.  Users interested in this field are encouraged to contact Georgi Dakovski, dakovski@slac.stanford.edu for more information regarding the Early Science phase of the qRIXS sample chamber in Run 19.