In our recent experiment RB1120146 we have obtained new exciting results on neutron scattering on liquid He surface. At 1.5 and 2.3K there was no difference in reflectivity between pure 4He and the mixtures. However, at 0.4K significant difference was observed which suggests the presence of a substantial number of 3He atoms close to the surface. However there is one unexplainable deviation from the expected reflectivity curve which is present on all dependences and this significantly complicates the data analysis. In order to investigate this effect we need reflection measurements on D2O in the original cell at 300K and on He surface at 1.5K, but with CRISP multi-detector. If we can explain the reason of the deviation it will allow us to resolve the data analysis problem which is currently the main obstacle, preventing us from publishing important results in high profile journal.