Adapting a triple-axis spectrometer for small angle neutron scattering measurements

Area of Science:

• Materials Science
• Condensed Matter Physics
• Neutron Scattering Techniques

Background:

• Standard small-angle neutron scattering (SANS) instruments utilize cold neutrons and collimated beams to achieve scattering vector (q) ranges typically from 0.001 to 0.6 A(-1).
• The Canadian Neutron Beam Centre (CNBC) lacked a cold source, necessitating alternative methods for SANS measurements.

Purpose of the Study:

• To adapt a triple-axis spectrometer for SANS measurements at the CNBC.
• To extend SANS capabilities to lower q values despite the absence of a cold neutron source.

Main Methods:

• Modification of a triple-axis spectrometer by employing multiple converging incident beams to increase neutron flux by a factor of 20.
• Implementation of horizontal Soller collimators to mitigate smearing effects caused by vertical divergence.
• Achieving a minimum measurable scattering vector (q(min)) of approximately 0.006 A(-1).

Main Results:

• The modified triple-axis spectrometer successfully performed SANS measurements.
• The technique allowed for SANS analysis down to a q(min) of approximately 0.006 A(-1).
• Data acquired using the modified spectrometer showed good agreement with results from the established NG3-SANS instrument at NIST.

Conclusions:

• A triple-axis spectrometer can be effectively adapted for SANS measurements, even without a dedicated cold neutron source.
• This adaptation significantly enhances neutron flux and reduces smearing effects, enabling measurements at lower q values.
• The developed method provides a viable alternative for SANS research in facilities lacking cold neutron sources.