Capabilities

chemRIXS/qRIXS Capabilities for Run 22

chemRIXS Capabilities

chemRIXS Capabilities for Run 22

The ChemRIXS instrument within the NEH 2.2 hutch is designed to support cutting edge experiments in the fields of chemistry using soft X-rays of the LCLS-II superconducting linac. The hutch features two interaction points (IPs). NEH 2.2  is coupled to the LCLS soft x-ray undulators, which offer a variable gap, providing horizontally polarized x-rays in the photon energy range from 250 eV to 1100 eV. The two interaction points house the chemRIXS instrument (IP1) for investigations of ultrafast photochemistry in solutions phase by time-resolved soft X-ray spectroscopy and the qRIXS instrument (IP2) for material science experiments.

During run 22, the chemRIXS endstation will be for the first time available for standard user experiments following commissioning with the LCLS-II superconducting linac and an Early Science program to demonstrate readiness of all components. Due to the ongoing commissioning efforts, the available capabilities are evolving. The following tables summarize the expected x-ray and laser capabilities for the SC accelerator and OPCPA laser system. If you plan to submit a proposal, please contact the instrument scientist Kristjan Kunnus for the most up-to-date information.

The Early Science program at chemRIXS will make use of the existing instrument in combination with a new OPCPA laser system and will focus on commissioning and demonstrating transient X-ray absorption and/or RIXS spectroscopy experiments in liquid jets.

 

Guidelines and Performance Parameters for Run 22

Run 22 will be the first opportunity to make use of the new superconducting LCLS-II accelerator for regular user experiments which will eventually operate at repetition rates up to 1 MHz. During run 22 the repetition rate will be limited to 100 kHz with the following x-ray performance parameters. Please direct any questions on X-ray parameters to Kristjan Kunnus.

Performance Parameters:

 

X-ray Parameters 

Repetition rate (Hz)

Up to 100 kHz

Energy Range (eV)

250 - 1100

Pulse Duration (fs)

20 fs (nominal)

Energy per pulse (downstream of mono)

>100 nJ

Beamline Resolving Power

>2000

Spot Size, FWHM (range)

10 - 1000

(um) diameter

Polarization Linear, Horizontal

The new OPCPA laser system should offer short (< 25 fs) 800 nm laser pulses. Harmonics of these pulses can be generated (400/266 nm). 

Laser Parameters
Repetition rate (Hz) Synchronized up to 33 kHz
Wavelength 800 nm 400 nm 266 nm
Pulse Duration < 25 fs < 50 fs < 50 fs

Energy per pulse

(on target)

300 μJ > 30 μJ ~ 3 μJ

 

Spot Size, FWHM

(800 nm)

50 to 100 μm
Polarization Variable: linear, circular
Angle ~0.5 deg angle with x-ray beam

Arrival Time

Monitor

< 20 fs accuracy in x-ray/laser arrival time tagging should be available. Overall temporal resolution will be dependent on machine and instrument configuration.

The following detectors will be provided to the users:

  • 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.

  • 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 path of 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 be equipped with the above mentioned Andor Newton_SO CCD.  The spectrometer will be mounted in the horizontal plane at 45 degrees with respect to the X-ray beam. The spectrometer can be used simultanaeously with the TFY APDs and the direct beam Andor CCD.

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 spectrometer
  • Time-resolved XES, using the VLS spectrometer with non-resonant excitation
  • Time-resolved RIXS, using the VLS spectrometer

 

 

qRIXS Capabilities

qRIXS Early Science Capabilities for Run 22

The qRIXS Instrument is a large-scale x-ray emission spectrometer, designed for cutting-edge time-resolved resonant inelastic x-ray scattering experiments on condensed matter systems.  It consists of the Sample Chamber and a 6-meter long Spectrometer arm. The Chamber is also suitable for experiments focusing on X-ray Diffraction/Resonant Elastic X-ray Scattering, X-ray reflectivity, and X-ray Absorption Spectroscopy.  The following capabilities will be provided:

  • Sample positioning on an in-vacuum diffractometer, 6 degrees of freedom, sphere of confusion <50 microns
  • At the moment only bulk samples and thin films on substrates will be considered
  • A load-lock chamber  
  • Sample cooling, ~ 25 K
  • Diagnostic paddle for calibration targets, spatio-temporal overlap, etc.
  • Laser in- and out- coupling (in co-linear configuration)
  • Detectors optimized for x-ray absorption and diffraction
  • Arrival time monitor located ~1.5 m from the interaction point
  • For this Run the qRIXS spectrometer will remain at a fixed scattering angle of 150 degrees

qRIXS operations in Run 22 will be restricted to commissioning and Early Science with the LCLS-II superconducting linac. As a result, there will not be time available for standard user experiments. The Early Science program will be led by the LCLS Materials Sciences Department. If you have interest in participating in the Early Science Program please consider sending a letter of intent to the Materials  Sciences department head Apurva Mehta (mehta@slac.stanford.edu) who will coordinate this effort. The department head will work with the user community to develop an LCLS-led Early Science campaign. In preparation for these efforts the following tables summarize the expected x-ray and laser capabilities for the SC accelerator and OPCPA laser system. The development team(s) will try to provide the largest array of possible capabilities. Please use these tables to guide your thinking on possible Early Science experiments.

Performance Parameters for Run 22

X-ray Parameters 

 

Laser Parameters

Repetition rate (kHz)

33

 

Repetition rate (kHz)

33

Energy Range (eV)

250 - 1100

 

Wavelength (nm) 

800

Spot Size (um), H x V

10 x 10, min

1000 max

 

Pulse Duration (fs)

<40 @ 800 nm

Energy per pulse (nJ)

>10

 

Energy per pulse (μJ)

300

Pulse Duration (fs)

<200

 

Spot size (μm)

50 min

Beamline Resolving Power 

>20,000

 

Polarization control

Horizontal and vertical, circular

Combined Spectrometer resolving power

10,000 @ 931 eV

 

Arrival time monitor precision (fs)

<20

Polarization

Linear horiz.

     

The following detectors will be provided to the users:

  • Avalanche PhotoDiodes (APD) and Large area photodiodes.  The APDs are single-photon sensitive fast detectors suitable for X-ray Absorption Spectroscopy (XAS) in Total Fluorescence Yield (TFY) mode, and for X-ray Diffraction.  These detectors will be mounted on an in-vacuum rotatable stage (2-theta arm) and can be placed in the horizontal scattering plane.
  • Depending on timely delivery, an in-vacuum 2D detector will be offered as well, with the following characteristics:
    • 512 X 512 pixels
    • 50 um pixel size
    • 5 kHz full frame readout
      This detector will also be mounted on the 2-theta arm


Users are encouraged to contact Apurva Mehta, mehta@slac.stanford.edu and Georgi Dakovski, dakovski@slac.stanford.edu for more information.