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Kinetic energy release in fission of /sup 238/U, /sup 235/U, /sup 232/Th, and /sup 209/Bi by high energy neutrons. [45 and 90 MeV]
John A. Jungerman, S.C. Wright
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Abstract
The ionization produced by single fission fragments are observed in an ionization chamber using electron collection. If fission is induced by 90 MeV neutrons, the distribution of kinetic energy of the fission fragments versus the number of fragments is found to have a single peak in contrast to the double-peaked curve corresponding to the fission made by thermal neutrons. Fission induced by 45 MeV neutrons gives a distribution in which two peaks appear. The dip between the two peaks is about 20 percent of the height of the peaks. The mean kinetic energy is found to be 80 +- 2 MeV for /sup 238/U, 83 +- 1.5 MeV for /sup 235/U, 82 +- 2 MeV for /sup 232/Th, and 71 +- 2 MeV for /sup 209/Bi in the case of fission produced by 90 MeV neutrons. The mean kinetic energy is 79 +- 3 MeV for /sup 238/U and 84 +- 3 MeV for /sup 232/Th if 45 MeV neutrons are used. The most probable kinetic energy of the fragment is 83 MeV for /sup 238/U, 80 MeV for /sup 235/U, 83 MeV for /sup 232/Th, and 75 MeV for /sup 209/Bi in the case of fission produced by 90more » MeV neutrons. The bearing of these observations on the mechanism of fission is discussed.« less