ATTEMPT TO DETECT AN (n,2n) REACTION IN DEUTERIUM

Abstract

A detailed account is given of experiments carried out to detect an (n,2n) reaction in deuterium. A Po-α-Be neutron source was surrounded by a hollow aluminum sphere 30 cm. in diameter, which could be filled with heavy water. The sphere was surrounded by an effectively infinite medium of paraffin oil. The neutron density distribution outside the sphere was measured with a small boron trifluoride chamber (6 mm. diameter × 20 mm. long). The total integrated densities of neutrons were determined both with the sphere empty and filled with heavy water. After correcting for absorption of thermal neutrons by the heavy water, the aluminum sphere, and the source, and of fast neutrons by the oxygen of the heavy water, it is shown that the fraction of neutrons giving an (n,2n) effect is 0.1 ± 2.7%. This indicates that the effect is less than both that predicted by Höcker's theory (~ 10%) and that reported from an earlier experiment by Halban and coworkers (18%). However it is in good agreement with measurements made by Fenning and Knowles (1.4 ± 5%).