Search for instantaneous radiation near the instant of break momentum of various fissioning nuclear systems at low excitation energies

Journal Article · Thu Dec 15 00:00:00 EST 2011 · Crystallography Reports

DOI:https://doi.org/10.1134/S1063774511070352· OSTI ID:22054206

Val'ski, G V; Gagarskii, A M; Guseva, I S; Petrov, G A; Petrova, V I; Serebrin, A Yu; Sokolov, V E; Shcherbakov, O A ^[1]

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1. Russian Academy of Sciences, St. Petersburg Nuclear Physics Institute (Russian Federation)

The main results of studying the properties of 'instantaneous' neutrons and {gamma} photons during the fission of {sup 233,235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f) nuclei and spontaneous fission of {sup 252}Cf, which were performed on the WWR-M reactor at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences, are presented. Along with obtaining the main characteristics of the instantaneous radiation from fission fragments, these studies were also aimed at gaining deeper insight into such exotic processes as the emission of break neutrons and {gamma} photons from a fissioning nucleus near the break point. These investigations were performed on different experimental setups using different analytical methods. This approach allowed us not only to find but also to reduce to minimum possible systematic effects. The yields of break neutrons were found to be about (5-7) Multiplication-Sign 10{sup -2} of the total number of neutrons per {sup 233,235}U(n, f) fission event and approximately twice as much for {sup 239}Pu(n, f) and {sup 252}Cf. The coefficient of T-odd asymmetry for {gamma} photons is in agreement with the estimate obtained on the assumption that the observed effect is mainly related to the {gamma} photons emitted by excited fragments with highly oriented angular momenta. This fact gave grounds to conclude that the desired break {gamma} photons cannot be reliably selected (within the obtained experimental accuracy) against the much larger background of {gamma} photons from fission fragments.

• OSTI ID: 22054206
• Journal Information: Crystallography Reports, Vol. 56, Issue 7; Other Information: Copyright (c) 2011 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACCURACY
ANGULAR MOMENTUM
ASYMMETRY
CALIFORNIUM 252 TARGET
EMISSION
EXCITATION
FISSION FRAGMENTS
PHOTONS
PLUTONIUM 239 TARGET
SPONTANEOUS FISSION
THERMAL NEUTRONS
URANIUM 233 TARGET
URANIUM 235 TARGET