Energy of High-Velocity Neutrons by the Photographic Method

Abstract

FOR many years it has been known that after the development of certain types of photographic plates, the tracks of any heavy ionizing particles which have passed through the emulsion are represented by a succession of developed grains. Several investigators have examined the question of the precision with which the length of the track can be taken as a measure of the energy of the particle. Opinion on the question has been divided^1,2,3, and the method has not come into general use for nuclear problems though several investigators are using it for work on the cosmic rays. If the method could be made precise, it would have great advantages over expansion chamber technique in dealing with certain types of nuclear problem. Recently, having made experiments with Dr. Heitler on the heavy particles in the cosmic radiation by this method, we decided to re-examine the question of its precision in detail. In view of the importance of developing more powerful methods of measuring neutron and gammaray energies, the results seem to us to suggest that the method merits the serious consideration of those engaged in nuclear research.