GAMMA RAYS IN U$sup 238$ FISSION BY 2.8 AND 14.7 Mev NEUTRONS

The energies of rays emitted in U/sup 238/ fission by fast neutrons was determined by comparison with the y spectra from U/sup 235/ thermal fission. The quanta were recorded by a scintillation counter with NaI(Tl) crystal working in coincidence with a single-layer dividing chamber for fission recordings. Targets of U/sup 235/ and U/sup 238/ similar in diameter to the mean density of 1.8 and 2.2 mg/cm/sup 2/ respectively, were used. The amplitude distributions of quantum pulses in U/sup 235/ fission by thermal neutrons and U/sup 238/ fission by 2.8 and 14.7 Mev fast neutrons are plotted. The data show that the mean total -ray energy for U/sup 238/ fission by fast neutrons is identical, within 15%, to that of U/sup 235/ fission by thermal neutrons. Also, it was found that the mean quantum energy value per fission event for U/sup 235/, U/sup 238/, and Cf/sup 252/ is very similar and that the quantum energy does not before the fission. (R.V.J.)