In our recent experiment RB1120146 we obtained exciting new results on neutron scattering from the liquid helium surface. At 2.3K there was no difference in reflectivity between pure 4He and isotopic mixtures. However, at 0.4K a significant difference was observed, suggesting the presence of a substantial number of 3He atoms close to the surface as predicted theoretically by Andreev almost half a century ago. Unfortunately we cannot fit the data using the neutron reflection model available at ISIS due to optical distortion caused by liquid helium meniscus. We propose to repeat our latest Crisp experiment on the neutron reflectometer Polref, which has a much higher flux and better neutron beam configuration flexibility. The main aim of the experiment is to obtain reflectivity density profiles by quantitative analysing of non-distorted experimental data.