Experimental Station 4-2

 Beam line 4-2 is a small-angle scattering/diffraction station dedicated to structural biology studies primarily on non-crystalline systems. The instrument features a pin-hole geometry SAXS camera, which can be semi-automatically configured to have one of seven sample-to-detector distances between 0.25m and 3.5m. This allows to tune and optimize the instrument to the experimental needs. A Pilatus3 X 1M is the primary detector used at the beamline. It features a large active area, photon counting x-ray detection and a 500Hz maximum frame rate which also allows fast Time-resolved studies at BL4-2. A large area gap-less Rayonix225HE ccd-detector is also available for experiments that require smaller pixel sizes and a detection area without gaps. The facility provides a large selection of specialized sample handling devices, such as a stopped-flow rapid mixer, a high-throughput automated sample changer for solution scattering, a size-exclusion chromatography coupled solution SAXS setup among others.

Supported Techniques
Biological Small-angle X-ray Scattering (BioSAXS)
Fiber diffraction
Lipid membrane diffraction
Small-angle single crystal diffraction
Time-resolved biological SAXS
Main Scientific Disciplines
Biomedical Sciences
Structural Molecular Biology
Beam Line Specifications


20-pole, 2.0-Tesla Wiggler ID End Station

  Energy Range Resolution ΔE/E Spot Size Flux (ph/sec)
6000-17000 eV 5 x 10-4 0.2 x 1mm2 3 x 1012
8000-12000 eV 3 x 10-2 0.2 x 1mm2 1 x 1014



M0 mirror: bent cylinder

15.4m vertical radius (adjustable) and 57 mm horizontal radius

Rh-coated silicon (cutoff energy 17.5 keV)

mean angle of incidence: 3.8 mrad

Magnification 1.0, upward reflecting 

Monochromator(s): liquid N2 cooled Si(111) and Mo/B4C multilayer




Detectors: Pilatus3 X 1M, Rayonix225HE, Vortex detector

Intensity monitor: photodiode in beamstop for transmitted intensity, APD for incident intensity

Slits: JJ-Xray beam defining and guard slits, Xenocs scatterless guard slit in front of sample

Other: mirror pitch feedback for beam stability, variable filters, fast shutter, variable length flight path

Angular range (at 11 keV, 4 mm beamstop):

Distance(m) Typical q -Range (Å-1)
0.25 0.045 - 3.6
0.45 0.024 - 2.2
0.65 0.017 - 1.6
1.10 0.010 - 1.0
1.65 0.0068 - 0.67
2.40 0.0045 - 0.46
3.40 0.0034 - 0.33

Please refer to http://ssrl.slac.stanford.edu/~saxs

Sample Environment

Autosampler (automated liquid sample loader):

Sample volume: 10 ul – 30 ul

Temperature range: 5 C – 40 C

Manual loading (flow) cell:

Sample volume: 10 ul – 30 ul

Temperature range: 5 C – 40 C

Stopped-flow mixer (for fast time-resolved solution SAXS) :

Sample volume: 30 ul – 100 ul (per shot)

Temperature range: 5 C – 70 C

Mixing deadtime: ~1 ms

Humidity Chamber (for lipid diffraction and GiSAXS) :

Sample temperature range: 10 C – 50 C

rH range: 30% - 100%

Data Acquisition and Analysis

Data acquisition: Blu-ice
Data analysis: SAXSPipe, SECPipe, SasTool, GraphIt, ATSAS, Raw, FoXS 

see: http://www-ssrl.slac.stanford.edu/~saxs/daq/daq.htm 

X-ray Data Booklet

Beam Line Phone
650-926-5242. On-site Users: Contact the Duty Operator at 9-926-4040
Beam Line Contact

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