INVESTIGATION OF BINARY AND TERNARY FISSION IN 238U INDUCED BY MONOENERGETIC NEUTRONS
Department of Physics
(*Department of Chemistry/Physics Radiation Centre)
University of Birmingham, Birmingham B15 2TT, UK
Absolute yields have been determined for 34 binary fission products, representing 29 mass chains created during the fission of 238U with monoenergetic neutrons. The neutron energies used for fission ranged from 1.75 MeV to 5.8 MeV. Neutron fluences were determined with a calibrated fission chamber along with metal foils as secondary flux monitors. Fission product activities were measured with a large, hyperpure Ge detector by direct counting of an irradiated 238U foil. In general, fission yields were determined from several counts at different cooling times, using a least-squares technique to unfold multi-component peaks.
The yields of tritons and long range alpha (LRA) particles in the ternary fission of 238U induced by fast, monoenergetic neutrons were determined with a ΔE-E detector telescope technique. A thin 238U deposit was bombarded with neutrons at energies between 3.6 MeV and 4.12 MeV in a vacuum chamber. Total fission events were monitored with a separate surface barrier detector. A mass versus energy spectrum was obtained of the light fragments using suitable electronics. The resolution of the system decreased with irradiation time due to neutron degradation of the ΔE detector, limiting the number of events that could be detected.
KEYWORDS: fission, mass yields, ternary fission, 238U, monoenergetic neutrons, detector telescope