SXR Standard Configurations

SXR Standard Configuration #1 for Run 17

Types of Experiments

With this new standard configuration, SXR will be able to support various time-resolved pump-probe X-ray absorption and small angle scattering experiments studying ultrafast dynamics of thin solid-state films in a transmission geometry.

X-ray and X-ray Focus

X-ray transmission is measured by dividing in two and focusing the x-ray beam with a diffractive optic. The transmitted beam is placed in one of the two beams while with no sample in the other beam.   Both beams diverge and illuminate a pnCCD detector that is 2.5 m downstream of the diffractive optic.  The transmission is measured on each shot by comparing the signal on the detector for the beam transmitted though the sample with the reference beam.  This method can measure transmission with a sensitivity of 1% per shot and is compatible with 120 Hz operation. The available diffractive optic can operate between 475 and 600 eV. However, additional energy ranges may be possible—for feasibility please contact us (srd-sxd@slac.stanford.edu) before submitting the proposal.   

The SXR monochromator has a resolving power (E/ΔE) of 1000-2000 depending on the photon energy and will be available as part of the standard configuration. X-ray polarization control over a limited energy range is offered via Delta undulation. The Delta offers X-ray polarizations of linear horizontal, linear vertical and right and left circular polarization, together with the fast switching of polarization during the experiment (~1 minute). Soft X-ray self-seeding, XLEAP, two-color FEL, and two-pulse operations are NOT part of the standard configuration. 

Optical Pump Lasers

Time-resolved experiments employing tunable femtosecond pulses will be supported under this standard configuration.  The fundamental and harmonics (800, 400 and 267 nm) of the SXR, ~50 fs Ti:Sapphire laser will be available, delivered to the sample 5 degrees off axis with respect to the x-ray beam. The configuration can also be used with a TOPAS-Prime Optical Parametric Amplifier (OPA) capable of 480-2400 nm wavelengths. Again, 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 SXR scientists to discuss specific needs and to confirm whether they can be achieved in this standard configuration of the laser. The expected performance of the OPA is shown below.

Timing Diagnostics

The SXR transmission sample system time-tool will be available to record single shot arrival times (t<100 fs) that can be post-sorted assuming sufficient FEL pulse energy (>1 mJ).  Coarse temporal overlap (t<20 ps) can be obtained via photoelectric effect monitoring on an SMA wire.

Sample Manipulation System

Sample translation is supported via in-vacuum three-axis sample stages shown in the photo below.  The stages are Newport MFA-CCV6.  The reference system and the diffractive optic have identical motion stages.

To control the spot size on the sample it can be moved 130 to 155 mm downstream of the diffractive optic.  The intensity on the sample is typically less than 1μJ/cm² but at the focus could reach 1kJ/cm².  It is difficult to measure the exact spot size at the sample and thus the exact intensity. 

The separation of the two beams at the sample position is roughly 2-3 mm as illustrated in the Plan experimental setup below.  Therefore, samples must be located within 1.5 mm of the edge their substrate.   The setup can accommodate four 3 mm TEM grid type samples.   Other sample geometries are possible for a user provided sample holder. Contact us (srd-sxd@slac.stanford.edu) for interface specifications.   

Sample Environment

The sample holder can accommodate for some temperature control ~200 K to 400 K.   Or an electromagnet can be used to control the magnetic field on the sample. 

Samples can only be measured in transmission and must be UHV compatible.  Sample exchanges may be possible but will take at least one hour.

Detector

The pnCCD offers full 120 Hz readout of the reference and sample transmission from the diffractive optic.   It is isolated from the sample area and pump laser via a 200 nm thick Al foil.  The location of the pnCCD is fixed for this experiment. There direct beam transmitted through the pnCCD terminates on a beamstop.  

SXR Instrument Staff

Bill Schlotter, Alex Reid, Joshua J. Turner, Giacomo Coslovich, and Michael P. Minitti

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.

SXR Standard Configuration #2 for Run 17

The RSXS End Station in SXR

Types of Experiments

With this standard configuration, SXR will be able to support various time-resolved pump-probe resonant soft x-ray scattering (diffraction), and RIXS measurements studying the temporal dynamics of charge/spin/orbital orders in solid state materials. Additionally, X-ray absorption (XAS) measurements may also be performed by measuring total fluorescence yield.

X-ray and X-ray Focus

X-ray energies ranging from 390 to 2000 eV will be available (700 to 1200 eV for use with DELTA undulator). The SXR monochromator has a resolving power (E/ΔE) of 1000-2000 depending on the photon energy and will be available as part of the standard configuration.  The setup will also permit use the x-ray polarization control via the DELTA undulator as well as the high-power fixed linear polarizations available from the LCLS normal operation. Additionally, zeroth order, full SASE beam will be available.

SXR’s KB focusing system can provide foci up to 2 micron (FWHM) and is adjustable in size up to several 100s of microns FWHM.

Optical Pump Lasers

Time-resolved experiments employing tunable femtosecond pulses will be supported under this standard configuration. The fundamental (800 nm) of the SXR, ~100 fs Ti:Sapphire laser will be available, delivered to the sample collinearly with the x-rays, with in-coupling ~800 mm upstream of the sample and with the focusing lens ~1000-1200 mm away from the sample. The system can also be used with an HE-TOPAS Optical Parametric Amplifier (OPA) capable of 1150-2400 nm and 4000-17000 nm wavelengths. Again, 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 fluence will be determined by the existing optical system and will not be modified. Contact the SXR scientists to discuss specific needs and to confirm whether they can be achieved in this standard configuration of the laser.

Timing Diagnostics

The SXR transmission sample system time-tool will be available to record single shot arrival times (t<100 fs) that can be post-sorted. Coarse temporal overlap (t<20 ps) can be obtained via photoelectric effect monitoring on an SMA wire. For some pump wavelengths, finer time zero determination (<300 fs) at the sample can be obtained using an SXR-supplied target to measure the index of refraction change (in reflection) induced by the x-ray beam.

RSXS Mechanical System

There is total six degrees of freedom for the sample: three translational (x, y, z from manipulator) and three rotational degrees of freedom (Θ,χ,Φ) with a differentially pumped rotary seal.

Detectors

The RSXS end station has two avalanche photodiodes and a multi-channel plate (MCP) detector. These detectors are mounted on a fully motorized in-vacuum detector stage, allowing detector manipulation in both horizontal (360 degrees) & vertical (90 degrees) scattering planes.

A varied line-space plane grating spectrometer, optimized to operate from 250 eV to 2000 eV with an expected resolving power of 1500 to as high as 3000 at lower energies will be offered as well, enabling FEL based RIXS studies.  The spectrometer can operate outside of the optimized energy range with compromised performance. The spectrum is detected with an in-vacuum CCD binned along the spectral energy direction to enable 120 Hz readout.   In this standard configuration the spectrometer is mounted 90° to the x-ray beam in the horizontal plane.

SXR Instrument Staff

Joshua J. Turner, Bill Schlotter, Alex Reid, Giacomo Coslovich, and Michael P. Minitti

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.