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

Small angle neutron scattering (SANS) instruments typically cover a q (scattering vector) range from 0.001 to 0.6 A(-1). This range in q is achieved through a combination of cold neutrons (lambda>4 A) and a highly collimated beam. However, as a direct result of the unavailability of a cold source at the Canadian Neutron Beam Centre (CNBC), we have resorted to adapting a triple-axis spectrometer to perform SANS measurements. This is achieved through the use of multiple converging incident beams which enhance the neutron flux on the sample by a factor of 20, compared to a single beam of the same spot size. Furthermore, smearing effects due to vertical divergence from the slit geometry are reduced through the use of horizontal Soller collimators. As a result, this modified triple-axis spectrometer enables SANS measurements to a minimum q value (q(min)) of approximately 0.006 A(-1). Data obtained from the modified triple-axis spectrometer are in good agreement with those data from the 30 m NG3-SANS instrument located at the National Institute of Standards and Technology (Gaithersburg, MD, USA).