MEASUREMENT OF THE FISSION THRESHOLDS OF Pu$sup 230$, U$sup 233$, U$sup 238$ USING THE (d,p) REACTION

Journal Article · Tue Sep 01 00:00:00 EDT 1959 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.115.1277· OSTI ID:4226534

Northrop, J A; Stokes, R H; Boyer, K

An experiment is described which measures the fission thresholds of thermally fissionable nuclides. In contrast to fission induced by neutron capture, use of the (d,p) reaction allows compound nuclei to be produced with excitations less than the binding energy of the last neutron. Measurements of the energy spectra of protons in coincidence with fission, normalized by the energy spectra of all emitted protons, allowed the thresholds of Pu/sup 239/, U/ sup 233/, and U/sup 235/ to be observed. It should be emphasized that the compound nucleus is stable against neutron emission in the region of these fission thresholds, thus avoiding distortions by this competing reaction. The threshold of U/sup 238/ was obtained for comparison with neutron data. In the case of the even-even compound nuclei, the observed step structure of the fission threshold is a clear indication of a multiple fission barrier. This multiple barrier is predicted by the collective model of fission and is correlated with the experimental data. The equivalent neutron energies at the center of the first threshold are as follows: for Pu/sup 239/, -1.61 Mev; for U/sup 233/, -1.47 Mev; and for U/sup 235/, -0.60 Mev. The second thresholds observable are: for Pu/ sup 239/, -0.72 Mev, and for U/sup 233/, -0.72 Mev. The threshold of U/sup 238/ agrees well with the data from neutron excitation. In each case the fission probability decreases in the region of positive neutron energies. This would result either if neutron emission were to compete with fission or if there were a significant contribution to the proton spectrum from the electric breakup of the deuteron. (auth)

• Research Organization: Los Alamos Scientific Lab., N. Mex.
• NSA Number: NSA-14-003037
• OSTI ID: 4226534
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Vol. Vol: 115; Other Information: Orig. Receipt Date: 31-DEC-60
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

PHYSICS
BINDING ENERGY- COMPOUND NUCLEI- DEUTERON BEAMS- EXCITATION- FISSION- NEUTRONS- NUCLEAR REACTIONS- NUCLEI- PROTONS
COINCIDENCE METHODS- DEUTERON BEAMS- ENERGY- FISSION- MEASURED VALUES- NUCLEAR REACTIONS- PLUTONIUM 239- PROTONS- SPECTRA- URANIUM 233- URANIUM 235- - URANIUM 238
COMPOUND NUCLEI- EMISSION- EXCITATION- FISSION- NEUTRONS- NUCLEI- STABILITY
FISSION- NUCLEAR MODELS