Upgrade of a small-angle neutron scattering spectrometer Suanni of China Mianyang Research Reactor

Abstract

The small-angle neutron scattering spectrometer, SANS-Suanni, of the 20 MW China Mianyang Research Reactor (CMRR), was upgraded recently to improve its performance and anti-risk capability. The major modifications include: (i) installing a new mechanical velocity selector consisting of a rotor with helical slots; (ii) a replacement of the front of the detector tank to decrease the minimum sample-to-detector distance; (iii) installing a laser locator and a set of fixed lenses in collimator chamber. After the modifications, firstly, a higher maximum-q (qmax) can be achieved up to 6.3 nm−1. With the help of rotating the detector tank, qmax can be further increased to 10.5 nm−1. Secondly, a higher neutron flux at sample position up to 1.18 ×107 cm−2s−1 (at neutron wavelength of 0.53 nm) is obtained. Thirdly, a convenient and user-friendly beam center finding operation for environmental devices is available. The actual performance after the modifications is demonstrated with the measurements of standard samples.