Doppler shift anisotropy in small angle neutron scattering

The two-dimensional patterns in our small angle neutron scattering (SANS) e xperiments from rapidly moving aerosols are anisotropic. To test the kinema tic theory of two-body scattering that describes the anisotropy, we conduct ed SANS experiments using a constant source of D2O aerosol with droplets mo ving at similar to 440 m/s, and varied the neutron velocity from 267 to 800 m/s. The theoretically predicted anisotropy of the laboratory scattering i ntensities agrees well with the experimental results. Based on an analysis of the scattering intensity in the Guinier region, we also determined the p article velocity. The results are in very good agreement with independent v elocity estimates based on supersonic flow measurements. [S1063-651X(99)023 10-7].