Investigation of neutron field in an asymmetric pocket inside hydrogenous moderator of photoneutrons

The results of experimental investigation of thermal, resonance and fast neutron flux density distribution in a large (up to 3500 cm3) asymmetric cavity inside a polyethylene moderator of photoneutrons generated in a lead converter under the effect of bremsstrahlung of electrons from 30 MeV microtron are discussed. It is shown that the field of thermal and resonance neutrons is almost homogenous with accuracy up to 10 % even in such large cavity. The mean flux density in the cavity decreases approximately with the factor of 1.5 when the height of the cavity 15 cm in-diameter is increased from 2 up to 20 cm. The efficiency of such moderator application for neutron activation analysis of oil and its reprocessing products, large samples of rocks and ores, impurities in liquid and aggressive substances, content of noble gases in electronic plates and their components is experimentally proved