STATION 2.1
X-ray scattering of non-crystalline materials

Description

Station 2.1 belongs to the SRS stations managed by the Biology & Medicine College. It provides a time resolved small angle scattering / fibre diffraction facility operating at a fixed wavelength of 1.54 Å . X-rays are focused in both horizontal and vertical directions by means of a triangular monochromator and plane mirror, respectively. The camera length is variable between 1 and 8.25 m, providing spacial resolutions ranging from 8 to 1500 Å. Data can be collected in the millisecond time regime. The detector and data acquisition system allows measurements in one- and two-dimensional manner.

Functional Description

2.1 is a fixed wavelength, X-ray scattering station. The station has been optimised for low angle scattering studies, but is also capable of some wide angle diffraction (e.g. with image plate at 20-50cm distance from sample). It is used largely by scientists working in the fields of biological and materials sciences to obtain size and shape information both in static and dynamic manner. Depending on sample properties and experimental set-up the station can operate down to microsecond data collection times.

Technical Description

Station 2.1 is a fixed wavelength station (λ = 1.54 Å) with tangent-point demagnification in the range 3:1 to 1:1. The conventional mirror-monochromator arrangement has been reversed which results in a reduced heat loading on the mirror, thus producing a highly stable focal spot. This camera is able to produce a focal spot with mean dimensions of approximately 0.3 mm x 2.5 mm and a beam cross section of 1 mm x 5mm at the specimen position. At the maximum camera length of 8.25m Bragg spacings as large as 1500 Å can be resolved.

Benchmark

With the SRS operating at 250 mA, 7.5 mrad horizontal aperture beam and all slits open, a reading of ca. 800 mV on an ion chamber situated immediately at the exit window of the beamline can be measured.
Ion chamber operating conditions:1500 V, 3 mm aperture and an amplification gain of 107. For a focus at 6 m, the beam size at the sample position will be ca. 0.75 mm vertically and 5 mm horizontally.

On average 2 hours are needed for a standard experimental set-up. However, it can take somewhat longer, depending on the complexity of the user requirements and sample environment.

News

Progress report on RAPID move »
SAXS/WAXS setup and other developments »

Development

• According to the phased closure
  (www.srs.ac.uk/srs/station_plan/proposed_station_closure_plan.htm) of experimental SRS stations, 2.1 will be operational until September 2008 which is the end of SRS operations.
  
  
• From the 17^th of July 2006 (beginning of AP46) the 2D Multiwire Proportional Gas Counter will be replaced with the RAPID 2-D detector system, currently the fastest photon-counting detector in the world (for specifications see Detector section) (2.1_detectors.html). The Rapid detector system has been operating successfully for a number of years on station 16.1. The previously used gas detectors (area and quadrant will still be available upon request).
  
  
• From AP46 the Generic Data Acquisition (GDA) (www.gda.ac.uk/) system will be installed allowing for the integration of the various sample environments, beamline controls and data acquisition.
  
  
• Due to the closure of station 16.1 (Time Resolved X-ray Scattering from Non-Crystalline Materials) it is envisaged that SAXS/WAXS experiments will be relocated to station 2.1. This involves limited modification of the station camera layout and the incorporation of the HOTWAXS (*2.1_HOTWAXS.pdf) detector which has been preliminary tested on 16.1 and 9.3. The SAXS/WAXS capability should be available to users by AP47 (December2006)
  *HOTWAXS slides from G. Derbyshire. SRI APS Meeting Dec. 2005

Technical References

• Station 2.1 :
  "Time-resolved x-ray diffraction station: X-ray optics, detectors and data acquisition"
  E. Towns-Andrews, A. Berry, J. Bordas, G.R.Mant, P.K.Murray, K. Roberts, I. Sumner, J.S.Worgan and R. Lewis (1989), Rev. Sci. Instrum. 60 (7) 2346-2349 (2.1_reference.pdf)
  
  "Shape Determination of Biomolecules in Solution form Synchrotron X-ray Scattering"
  J.G. Grossman from Scattering and Inverse Scattering in Pure and Applied Science Edit . R. Pike and P Sabatier, Academic Press, 2002.
  
  
• RAPID2 detector system :
  "The Rapid2 X-ray detection system"
  Berry A., Helsby W.I., Parker B.T., Hall C.J., Buksh P.A., Hill A., Clague N., Hillon M., Corbett G., Clifford P., Tidbury A., Lewis R.A., Cernik  R.J., Barnes P., Derbyshire G.E., Nuc. Instr. and Meth. in Phys. Res. A (2003), 513, 260-263. (2.1_Rapid.pdf)
  
  "The RAPID2 interpolating system"
  Helsby W.I., Berry A., Buksh P.A., Hall C.J., Lewis R.A., Nuc. Instr. and Meth. in Phys. Res. A (2003), 510, 138-144. (2.1_Rapid_2.pdf)
  
  
• Multiwire Gas Proportional Counter :
  "Multiwire Gas Proportional Counters" Decrepit Antiques or Classic Performers? "
  R. Lewis J. Synchrotron Rad. (1994) 1 43-53 (2.1_gas detector.pdf)