SAXS Beamline Technical Specifications

This page details the technical specifications and development of the SAXS beamline. For information about running samples please refer to the Beamline Wiki.

SAXS_beamline_21Sept09_nm_002.jpg

Endstation of the SAXS / WAXS beamline.

Commissioning of the beamline optics was completed in 2009 and the full range of energies and camera lengths is available with the beamline running a full operations program since mid-2009. Development of the endstation has provided rapid & reliable methods for video camera based sample alignment and a flexible sample stage allows straightforward sample mounting. Sample mounting is continuing to be developed on the beamline with a focus on improved efficiency and higher sample throughput. SAXS, WAXS, GISAXS and anomalous scattering experiments are all possible with a fully functional endstation. Two Pilatus detectors are in operation for SAXS (1M detector) and WAXS (200k detector) and may be run concurrently with excellent dynamic range, low noise and short exposures with up to 30 and 150 frames per second. A MAR-165 CCD (165 mm diameter) is also available for SAXS data collection. 

Beamline_Schematic_500pix.JPG

Schematic Diagram of the SAXS /WAXS Beamline

Index to sections below

Technical Specifications

Q-range & SAXS Camera Lengths

Instrument Background

Beamline Flux

Detector Specifications

 

Technical Specifications  

Source In-vacuum undulator, 22mm period, 3m length, Kmax 1.56
Energy range 5 - 21 KeV. Optimised for 8.15 KeV and 11.00 KeV.
Energy resolution 10-4 from cryo-cooled Si(111) double crystal monochromator.
Mirrors

Horizontal and vertical focussing mirrors for monochromatic beam with variable focus for different camera lengths.

3 mirror stripes (Si, Rh, Pt) allow full coverage of energy range rejecting higher energy harmonics.

Mirrors may be removed for speciality experiments.

Maximum flux at sample

 2 x 1013 photons per second.

10 KeV, Si-111 DCM, 200 mA ring current.

Beam size at sample (sample position focus)

250 µm horizontal × 150 µm vertical (FWHM)

Smaller beam size achievable by slitting down.

Beam divergence at sample position 140-260 µrad horizontal; 30 - 60 µrad vertical depending on focal position.
q-range

SAXS - 0.0015 - 1.1 Å-1 (using multiple camera lengths)

WAXS - 0.5 - 10 Å-1 (using multiple detector angles)
 Instrument background  Minimum < 0.02 cm-1 @0.01 Å-1

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Q-range & SAXS Camera Lengths

Q-ranges are calculated for a 12 KeV beam (1.0322 Å wavelength). These scattering angle ranges may be further adjusted by selecting different beam energies (5.2 - 21 KeV) or by slightly modifying the camera length by attaching longer or shorter nosecones as in the interactive q calculator for different SAXS camera setups. The Q-range and camera setup required for an experiment must be included in applications for beamtime; if additional information is required please contact beamline staff.

Camera length (mm) Q-range (Å-1) D spacing range (Å)
500 0.02 - 1.1 6 - 300
650 0.015 - 0.95 7 - 400
900 0.010 - 0.7 9 - 550
1600 0.006 - 0.4 17 - 1000
3300 0.003 - 0.18 35 - 2000
7000 0.0015 - 0.09 75 - 4500

camera_1f.png

Diagram of the different camera lengths available on the SAXS / WAXS beamline.

 

 

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Instrument Background

The beamline is well suited to analysing weakly scattering samples due to high flux and low parastic scattering. An in vacuum sample holder is in development for particularly weak scatternig samples, however it is not currently available. How weak a scatterer can be analysed?

Below is the measured background intensity at two main camera lengths calibrated into absolute intensity units (assuming a 1.5mm sample thickness). Above approx 0.01 Å-1 the background is controlled by air scattering, or for solutions by water scattering (note water = 0.016cm -1).  Below ~ 0.01 Å-1 the background is controlled mostly by the instrument itself - assuming the sample mount (capillaries, substrates, etc...) produce no scattering. There is a good chance of getting usable data if the net scattering (sample minus background) is a few percent above the instrument background. If you have a reasonable idea of your sample structure, concentrations, etc., it is worth doing some planning calculations to check whether the scattering is likely to be observable.

Inst_Background_500pix.JPG

Calibrated for a 1.5mm water path length. The 1.6m data were collected with a 10mm longer air path with air scattering, although low, dominating the background above 0.01 Å-1.

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Beamline Flux

The beamline is capable of utilising x-rays in the range of 5.2 - 20 KeV with the optics optimised for the 8 - 12 KeV range. The flux delivered at the sample position is dependent upon the undulator harmonic selected as shown below for the 5th and 7th harmonics. The 3rd, 5th, 7th, 9th and 11th harmonics may be selected to cover the full energy range with somewhat lower flux delivered for higher harmonics and higher energies.

Beamline_Flux_500pix.JPG

Flux at the sample position for 5th and 7th undulator harmonics.

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Detector Specifications

 The SAXS beamline primarily uses two Pilatus detectors for SAXS (1M, 170 mm x 170 mm) and WAXS (200k, 33 mm x 170 mm) data collection although a MAR-165 CCD (165 mm diameter) is also available where there is a good technical case for its use. The Pilatus detectors provide excellent 2D data collection for SAXS and some limited 2D WAXS collection allowing better particle statistics and sensitivity than a 1-D detector. However, the beamline is not optimised for full 2D WAXS data collection. Time-resolved data collection is also well supported as the Pilatus detectors are capable of collection at 30 Hz (1M) and 150 Hz (200K). For greater detail on the detectors please refer to the SAXS / WAXS Detectors page (under construction).

Detector Specifications
Dectris - Pilatus 1M
  •  Technology: bumpbonded hybrid-pixel
  •  Photon counting detector
  •  Multi-module (10 modules in 2 x 5 array with 7 x 17 pixel gap between each)
  •  Size: 169 x 179 mm; 981 x 1043 pixels (8.4% = intermodule gap)
  •  Mounted on X-Y stages to pautomatically produce gap-free images from 3 raw frames
  •  Pixel size: 172 x 172 micron
  •  Dynamic range: 6 orders of magnitude
  •  Frame rate: 10 Hz
  •  Readout time: 30 ms
  •  Threshold range: 2 - 20 KeV
Dectris - Pilatus 200K
  •  Technology: bumpbonded hybrid-pixel
  •  Photon counting detector
  •  Multi-modules (2 modules in 2 x 1 array with 7 pixel gap)
  •  Size: 169 x 33 mm; 981 x 195 pixels (0.7% = intermodule gap)
  •  Pixel size: 172 x 172 micron
  •  Dynamic range: 6 orders of magnitude
  •  Frame rate: 50 Hz
  •  Readout time: 10 ms
  •  Threshold range: 2 - 20 KeV
MAR-165
  •  Technology: CCD
  •  Integrating detector
  •  Single module, i.e. no gaps in active area
  •  Size: 165mm diameter; 2048 x 2048 pixels
  •  Pixel size: 79 x 79 micron
  •  Dynamic range: 3.5 - 4 orders of magnitude
  •  Frame rate: 1 Hz, less when readout time is considered
  •  Readout time: 4 seconds
  •  Threshold range: N/A

In  the majority of experiments the Pilatus 1M detector is used for SAXS data collection because the detector offers very low noise, a large dynamic range and rapid data collection over a large active area. Dead space due to intermodule gaps is overcome by radial integration with the detector slightly offset. The dynamic range and single photon resolution of the Pilatus 1M detector allow a full range of scattering information to be collected in a single exposure, as shown below, by resolving data that would otherwise be lost due to the background. However, at the cost of higher background and slower data collection the MAR-165 detector provides superior data resolution due to a smaller pixel size. If the MAR-165 detector is likely to be required for your experiment please contact beamline staff and include this in the experimental section of your applications for beamtime.

Example_Data2_500pix.JPG

R. Haverkamp, et. al., July 2009. SAXS data collected using the Pilatus 1M detector.

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