Neutron multiplicities as a calorimetric probe of heavy ion-induced fission reactions

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7233170

Cook, L D

A study of neutron multiplicities and angular distribution of fission and complex fragment emission is presented for various heavy ion-induced reactions at low and intermediate energies. These reactions include 7.5 MeV/u [sup 16]O + [sup 208]Pb, [sup 238]U, and 30 MeV/n [sup 14]N + [sup 12]C, [sup 58]Ni, Ag, [sup 144]Sm, [sup 154]Sm, [sup 197]Au, and [sup 238]U. Neutron multiplicities were measured with a recently constructed 4[pi] neutron detector (the TAMU neutron ball) which has a detection efficiency of approximately 85% for [sup 252]Cf neutrons. Fragment angular distributions were measured using an array of [delta]E-E silicon telescopes. Through measurement of the probability for a given number of neutrons emitted per fission event, it is possible to separate the complete and incomplete fusion components. Separating the incomplete fusion component is essential in the study of fission and complex fragment angular distributions and in [gamma]-ray experiments. Total momentum transfer is required before application of a statistical model of fission is possible. Once the complete fusion component was isolated, a comparison with theory was made. Values corresponding to the inertia and temperature of the fissioning systems (K[sub 0] and S[sub 0]) were calculated and compared to the corresponding model. These values provide shape information of the fissioning system. Measured values seem to concur with rotating liquid drop model predictions, but are far from agreement with the statistical scission model. The transition state model inadequately describes the observed results. The measurements indicate that accounting for the presence of incomplete fusion events cannot explain the poor agreement between experimental and statistical model predictions of fission fragment angular distributions in several systems (more specifically, the 120 MeV [sup 16]O + [sup 208]Pb, [sup 238]U, and the 420 MeV [sup 14]N reactions).

• Research Organization: Texas A and M Univ., College Station, TX (United States)
• OSTI ID: 7233170
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702 -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
663450* -- Heavy-Ion-Induced Reactions & Scattering-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
CALORIMETRY
CHARGED-PARTICLE REACTIONS
CHEMISTRY
DISTRIBUTION
EMISSION
FISSION FRAGMENTS
HEAVY ION REACTIONS
MULTIPLICITY
NEUTRON EMISSION
NUCLEAR CHEMISTRY
NUCLEAR FRAGMENTS
NUCLEAR REACTIONS