The NRC Canadian Neutron Beam Centre is operated on a continuous proposal basis. Proposals for experiments may be submitted at any time. Experiments are given beam time on the basis of peer review.
All the details are available on line: http://neutron.nrc.gc.ca/beamtime_e.html
The laboratory currently operates six thermal neutron
spectrometers:
C2, High Resolution Powder Diffractometer
C5, Polarized Beam Triple-Axis Spectrometer
D3, Neutron Reflectometer
E3, Materials Science and
Triple Axis Spectrometer
L3, Strain-Scanning Diffractometer
N5, Triple-Axis Spectrometer
New Reflectometer
The D3 Neutron Reflectometer is the latest addition Operating in the horizontal scattering plane, D3 is a thermal instrument using a fixed wavelength, l = 2.37Å. At this energy range, using thermal neutrons (instead of cold neutrons) it is a facility of international calibre thanks to several unique features.
It has a pyrolytic graphite monochromator that is 300 mm tall and vertically-focused, creating an intense image of the source 45 mm high at the sample position. The collimator between the source and the monochromator is tapered oppositely in two directions: diverging vertically (needed to illuminate the tall monochromator) and converging horizontally (to keep the fast-neutron background down to an absolute minimum). This feature alone leads to a factor of 6 improvement in the signal-to-background ratio compared to the C5 setup. A sapphire filter, placed as far up the beam line as possible, rejects fast-neutrons at the earliest opportunity. Space is reserved if this filter needs to be thickened in the future in order to improve signal-to-background further. A slit with vertical adjustment allows the reduction of the monochromator height if a particular experiment requires a smaller vertical divergence of the beam.
Immediately downstream from the monochromator (hence furthest away from the sample in this leg) the beam passes through a pyrolytic graphite filter for l/2 and l/3 rejection, another feature that reduces unwanted neutrons as early as possible. All the slits downstream from the monochromator are driven by high-precision translation stages, with the critical ones having 2 micron accuracy.
Neutrons reflected off the sample are captured by a 300 mm tall 3He detector, consisting of individually recorded 32 signal wires. Although not part of the original proposal, a high-resolution area detector will be implemented in the near future. Another feature that will be implemented shortly is the polarized neutron capability using magnetized super-mirrors. In additions to these features, this "full-time" reflectometer will maintain alignment and calibration, ensuring reliability and repeatability of data over prolonged research campaigns requiring multiple measurement sessions, say, over the duration of research for a Ph.D. candidate.
Alastair McIvor
Strategic Planning and
Marketing | Agent de planification stratégique et de promotion.
National
Research Council | Canadian Neutron Beam Centre
Conseil national de
recherches Canada | Centre canadien de faisceaux de neutrons
http://neutron.nrc-cnrc.gc.ca/
tel
(613) 584 8298 | fax (613) 584 4040
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