NG-7 30-METER SMALL ANGLE NEUTRON SCATTERING INSTRUMENT

The 30 m small angle neutron scattering (SANS) instrument on neutron guide NG-7 is sponsored by NIST, the Exxon Research and Engineering Co., the University of Minnesota, and Texaco R&D. As an instrument developed by a participating research team (PRT), 75% of the beam time is used by the members of the PRT and the remaining 25% is available through the CNRF proposal system.

The layout of the instrument is shown in the figure below. A number of improvements were made to this instrument in 1994. Chief among these were modifications to the sample chamber and post-sample flight path to allow the instrument's area detector to be positioned as close as 1.2 m from the sample thus increasing the maximum Q limit to 6 nm-1. The total Q-range accessible extends from 0.015 to 6 nm-1. This instrument is now functionally identical to the newer CHRNS 30 m SANS instrument on guide NG-3 (see description on previous page). The following tables summarize the characteristics of the instrument and the types of sample environment equipment that are available for use on either 30 m machine.

Contact:
Charles J. Glinka, (301) 975-6242; cglinka@nist.gov
John Barker, (301) 975-6732; barker@enh.nist.gov

Sample Environment Equipment

• Computer Controlled Sample Changers
• 9 position, ambient temperature
• 7 position heating stage (up to 250 C with 0.5 C accuracy)
• 7 position cooling/heating stage (-10 to 100 C with 0.1 C accuracy)
• 10 position cooling/heating stage (-10 to 100 C with 0.01 C accuracy)
• 2 position high precision heating stage (up to 250 C with 0.05 C accuracy)
• 5 position stage for horizontal electromagnet (up to 18 Kgauss accuracy)
• Magnets
• Horizontal Field Electromagnets
  (up to 1.8 Tesla, H perp. to ki, up to 0.5 Tesla, H para. to ki)
• Superconducting magnet (up to 7 Tesla) with insert cryostat
  (from 1.2 K to 300 K) for measurements with H perp. or para. to ki
• Couette flow shear cell (0 to 10,000 Hz shear rate)
• Sliding plate oscillatory shear cell for soft solids
  (up to 20 hz) with temperature control (up to 250 C)
• Pressure cell (up to 1 kbar) with temperature control (up to 200 C)
• Cryostats and closed cycle helium displex refrigerators for low temperature experiments (4 to 350 K)

Instrument Characteristics and Performance

• Source: neutron guide (NG-7), 50 cm x 50 cm
• Monochromator: mechanical velocity selector with variable speed and pitch
• Wavelength Range: 0.5 to 2.0 nm
• Wavelength Resolution: 9% to 30% del lambda/lambda (FWHM)
• Source-to-Sample Distance: 4 m to 16 m in 1.5 m steps via insertion of guide sections
• Sample-to-Detector Distance: 1.2 to 15 m continuously variable
• Collimation: circular pinhole collimation
• Sample Size: 5 to 25 mm diam
• Q-range: 0.015 to 6.0 nm-1
• Size Regime: 1 to 500 nm
• Detector: 650mm x 650 mm 3He position-sensitive proportional counter (10 mm x 10 mm resolution)

Neutrons on Sample vs. Qmin

Qmin(nm**-1) (10**5 n/sec)
0.015----------0.2
0.020----------0.6
0.040----------9.0
0.100----------50.

measured for 1.5 cm diam sample, del lambda/lambda= 0.15,

Last modified 18-October-2001