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Title: Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am

Abstract

Average preequilibrium <M{sub n}{sup preeq}> average statistical prescission <M{sub n}{sup stpre}> and postscission <M{sub n}{sup post}> neutron multiplicities as well as average {gamma}-ray multiplicity <M{gamma}>, average energy emitted by {gamma}-rays <E{gamma}> and average energy per one gamma quantum <{epsilon}{gamma}> as a function of mass and total kinetic energy (TKE) of fission fragments were measured in the proton-induced reactions p+232Th{yields}233Pa, p+238U{yields}239Np and p+242Pu{yields}243Am (at proton energy Ep=13, 20, 40 and 55 MeV). The fragment mass and energy distributions (MEDs) have been analyzed in terms of the multimodal fission. The decomposition of the experimental MEDs onto the MEDs of the distinct modes has been fulfilled in the framework of a method that is free from any parameterization of the distinct fission mode mass distribution shapes. The main characteristics for symmetric and asymmetric modes have been studied in their dependence on the compound nucleus composition and proton energy. The manifestation of multimodal fission in average {gamma}-ray multiplicities <M{gamma}> of fission fragments was also studied in this work.

Authors:
; ;  [1];  [2]; ; ; ; ; ; ;  [1];  [3];  [4]; ;  [5];  [6]; ;  [5];  [7]
  1. Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna (Russian Federation)
  2. (Slovakia)
  3. Institut de Recherches Subatomiques, CNRS-IN2P3, Strasbourg (France)
  4. Institute of Physics SASc, Dubravska cesta 9, 84228 Bratislava (Slovakia)
  5. Deparment of Physics, University of Jyvaeskylae, FIN-40351, Jyvaeskylae (Finland)
  6. (Russian Federation)
  7. V.G. Khlopin Radium Institute, St. Petersburg 194021 (Russian Federation)
Publication Date:
OSTI Identifier:
21061820
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 912; Journal Issue: 1; Conference: International symposium on exotic nuclei, Khanty-Mansiysk (Russian Federation), 17-22 Jul 2006; Other Information: DOI: 10.1063/1.2746613; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; AMERICIUM 243 TARGET; ASYMMETRY; COMPOUND NUCLEI; ENERGY SPECTRA; EXCITATION; FISSION; FISSION FRAGMENTS; GAMMA RADIATION; KINETIC ENERGY; MASS DISTRIBUTION; MEV RANGE; MULTIPLICITY; NEPTUNIUM 239 TARGET; NEUTRONS; PROTACTINIUM 233 TARGET; PROTON REACTIONS; PROTON-NUCLEON INTERACTIONS; SCISSION-POINT MODEL

Citation Formats

Beresova, M., Kliman, J., Krupa, L., Institute of Physics SASc, Dubravska cesta 9, 84228 Bratislava, Bogatchev, A. A., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Dorvaux, O., Khlebnikov, S., Lyapin, V., Rubchenia, W., V.G. Khlopin Radium Institute, St.-Petersburg 194021, Stuttge, L., Trzaska, W., and Vakhtin, D.. Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am. United States: N. p., 2007. Web. doi:10.1063/1.2746613.
Beresova, M., Kliman, J., Krupa, L., Institute of Physics SASc, Dubravska cesta 9, 84228 Bratislava, Bogatchev, A. A., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Dorvaux, O., Khlebnikov, S., Lyapin, V., Rubchenia, W., V.G. Khlopin Radium Institute, St.-Petersburg 194021, Stuttge, L., Trzaska, W., & Vakhtin, D.. Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am. United States. doi:10.1063/1.2746613.
Beresova, M., Kliman, J., Krupa, L., Institute of Physics SASc, Dubravska cesta 9, 84228 Bratislava, Bogatchev, A. A., Itkis, I. M., Itkis, M. G., Kniajeva, G. N., Kondratiev, N. A., Kozulin, E. M., Pokrovsky, I. V., Dorvaux, O., Khlebnikov, S., Lyapin, V., Rubchenia, W., V.G. Khlopin Radium Institute, St.-Petersburg 194021, Stuttge, L., Trzaska, W., and Vakhtin, D.. Tue . "Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am". United States. doi:10.1063/1.2746613.
@article{osti_21061820,
title = {Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am},
author = {Beresova, M. and Kliman, J. and Krupa, L. and Institute of Physics SASc, Dubravska cesta 9, 84228 Bratislava and Bogatchev, A. A. and Itkis, I. M. and Itkis, M. G. and Kniajeva, G. N. and Kondratiev, N. A. and Kozulin, E. M. and Pokrovsky, I. V. and Dorvaux, O. and Khlebnikov, S. and Lyapin, V. and Rubchenia, W. and V.G. Khlopin Radium Institute, St.-Petersburg 194021 and Stuttge, L. and Trzaska, W. and Vakhtin, D.},
abstractNote = {Average preequilibrium <M{sub n}{sup preeq}> average statistical prescission <M{sub n}{sup stpre}> and postscission <M{sub n}{sup post}> neutron multiplicities as well as average {gamma}-ray multiplicity <M{gamma}>, average energy emitted by {gamma}-rays <E{gamma}> and average energy per one gamma quantum <{epsilon}{gamma}> as a function of mass and total kinetic energy (TKE) of fission fragments were measured in the proton-induced reactions p+232Th{yields}233Pa, p+238U{yields}239Np and p+242Pu{yields}243Am (at proton energy Ep=13, 20, 40 and 55 MeV). The fragment mass and energy distributions (MEDs) have been analyzed in terms of the multimodal fission. The decomposition of the experimental MEDs onto the MEDs of the distinct modes has been fulfilled in the framework of a method that is free from any parameterization of the distinct fission mode mass distribution shapes. The main characteristics for symmetric and asymmetric modes have been studied in their dependence on the compound nucleus composition and proton energy. The manifestation of multimodal fission in average {gamma}-ray multiplicities <M{gamma}> of fission fragments was also studied in this work.},
doi = {10.1063/1.2746613},
journal = {AIP Conference Proceedings},
number = 1,
volume = 912,
place = {United States},
year = {Tue May 22 00:00:00 EDT 2007},
month = {Tue May 22 00:00:00 EDT 2007}
}
  • Fission product cross sections of intermediate-energy fission of {sup 238}U were used in order to construct the charge and mass yield distributions. Enriched target of {sup 238}U was irradiated by proton beam with energy 660 MeV for several hours at the LNP Phasotron, Joint Institute for Nuclear Research (JINR), Dubna, Russia. The charge distribution of the fission fragments was analyzed for calculation of isobaric cross sections. The mass yield curves were expanded into symmetric and asymmetric components according multimodal fission approach. The fissility values of actinides were calculated at given proton energy. The obtained results have been compared to themore » same data for targets {sup 237}Np and {sup 241}Am.« less
  • Primary and secondary fragment mass and fragment total kinetic energy were measured by the time-of-flight technique in the 12 MeV proton induced fission of {sup 232}Th. The average neutron multiplicity was obtained from the difference of the primary fragment mass and the secondary one as a function of mass and total kinetic energy of fission fragments. Simulation calculations were applied for correction of observed fission data affected by instrumental fluctuations in measurements of flight time and kinetic energies of fragments. Anomalous behaviors of the average neutron multiplicity as a function of total kinetic energy in the mass region of 98-107more » for the lighter fragment and 126-135 for the heavier were observed and they were found to correlate with two fission modes, symmetric and asymmetric fission. The overall trend of the average neutron multiplicity was discussed in terms of the two fission modes. Partition of the total excitation energy between fragment pairs deduced from the neutron multiplicity data was evaluated for each fission mode for the first time.« less
  • The isotopic yields of Rb, In, and Cs from the 40--100 MeV proton-induced fission of /sup 233/U and /sup 235/U, and the isotopic yields of Ga from the 80 and 100 MeV proton-induced fission of /sup 233/U have been measured by on-line mass spectrometry. The yields have been normalized to the independent formation cross sections of selected isotopes measured radiochemically. Total numbers of neutrons emitted per fission event have been deduced from the centroids of the isotopic distributions. The equal charge displacement, minimum potential energy, and unchanged charge distribution mechanisms have been investigated. It is found that the charge-division mechanismmore » is fragment-mass dependent, the minimum potential energy postulate being attributed to asymmetric fission events and the unchanged charge distribution postulate being attributed to near-symmetric fission events.« less
  • Proton-induced fission (E/sub p/ = 190 MeV) has been studied for uranium and selected nuclei, 140< or approx. =A< or approx. =200. Analysis of coincident-fragment energies suggests highly asymmetric fission near A = 140, even in the presence of relatively high fission barriers. The data have been compared with statistical-model fission calculations modified to include precompound nucleon emission. The data can be reproduced using standard fission-barrier and level-density parameters.
  • Fragment-energy and specific-luminescence spectra from the fission of /sup 232/Th and /sup 238/U were measured by a two-dimensional display of coincident signals from a solid state detector and a thin-film organic scintillator detector. Symmetric-to-asymmetric fission ratios and peak-to-valley ratios were determined as a function of bombarding energy. Discontinuities in the ratio curves, observed in some previous experiments but not in others, were mapped out in detail. The major discontinuities were found to occur near fission thresholds.