ENERGY DISTRIBUTION OF FRAGMENTS FROM A TRIPLE FISSION OF URANIUM NUCLEI UNDER THE ACTION OF NEUTRONS

One triple flssion event was observed per 350 events of U/sup 235/ double fission. The energy distribution of alpha particles was continuous with the maximum near 15 Mev. Maximum alpha energy was 28 Mev. The most probable angle between alpha particle emission and the light fragment direction is 80 deg . A double ionization chamber surrounded with an alpha chamber for eliminating the angular correlation was used in the investigation. The thicknesses were 20 mu g/cm/sup 2/ for U/sup 235/5 and 10 mu g/cm/sup 2/ for U/ sup 23 The effective solid angle of the alpha chamber in relation to the target was 12.5% at 4 pi . A 63 channel amplitude analyzer with an electron memory device was used for recording pulse amplitude spectra. Accidental coincidences between double fission fragments and background alpha chamber pulses was about 2% of the total number of coincidences. The triple fission fragment spectra from the U/sup 235/ layer was plotted with consideration for ionization. The corrections were equal to 2.5 Mev. Comparisons of double and triple fission fragment spectra for U/sup 235/5 show that they are analogous in form, but a noticeable shift of peaks is observed toward lower energies. The energy peakmore » shift DELTA E/sub 1/ = 9.5 Mev and DELTA E/sub h/ = 7.5 Mev. Dune to eliminnted effects of angular correlation of fragments and alpha particles, the results of the experiments with U/sup 235/ show higher peaks for light fragment than for the heavy ones. The measured parameters of U/sup 233/ double and triple fission fragment energy distributions correspond to those of U/sup 235/. The total kinetic energy for U/sup 235/ and U/sup 233/ triple fission fragments is l7 Mev less than the corresponding total for double fission. With the probable triple fission combined with emission of 15 Mev alpha particle, the triple fission total kinetic energy is equal to the binary fission. (R.V.J.)« less