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Title: Search for a long lived component in the reaction U+U near the Coulomb barrier

Abstract

We performed an experiment to search for a signature of a long living component in the collision of 238U + 238U between 6.09 and 7.35A MeV. The experiment was performed at GANIL using the spectrometer VAMOS, tuned for observing reactions with kinematics similar to fusion-fission events. Theoretical calculations indicate that if a long living component would exist for this reaction, the most probable fission channel of such a giant system would be via the emission of quasi-lead nuclei. We detected events of such a category in the focal plane of VAMOS. These events present an excitation function growing as a function of the bombarding energy.

Authors:
; ; ; ; ; ; ; ; ; ; ; ;  [1]; ;  [2]; ;  [3]; ;  [4];  [5]
  1. GANIL (IN2P3/CNRS - DSM/CEA) B.P. 55027 14076 Caen Cedex 5 (France)
  2. GSI Planckstr. 1 64291 Darmstadt (Germany)
  3. VEC Center I/AF Bidhan Nagar Kolkata 700064 (India)
  4. SPhN - CEA/DSM/DAPNIA Gif sur Yvette Cedex (France)
  5. SUBATECH, 4 rue Alfred Kastler B.P. 20722 44307 Nantes CEDEX 3 (France) (and others)
Publication Date:
OSTI Identifier:
21056782
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 891; Journal Issue: 1; Conference: 6. Symposium on nuclear physics, Tours (France), 5-8 Sep 2006; Other Information: DOI: 10.1063/1.2713501; (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; COULOMB FIELD; EXCITATION FUNCTIONS; FISSION; GANIL CYCLOTRON; HEAVY ION FUSION REACTIONS; MAGNETIC SPECTROMETERS; MEV RANGE; URANIUM 238 REACTIONS; URANIUM 238 TARGET

Citation Formats

Villari, A. C. C., Golabek, C., Mittig, W., Boilley, D., De France, G., Gaudefroy, L., Marchix, A., Morjean, M., Navin, A., Rejmund, F., Rejmund, M., Roussel-Chomaz, P., Stodel, C., Heinz, S., Winkler, M., Bhattacharyya, S., Mukherjee, G., Dayras, R., Drouart, A., and Giot, L. Search for a long lived component in the reaction U+U near the Coulomb barrier. United States: N. p., 2007. Web. doi:10.1063/1.2713501.
Villari, A. C. C., Golabek, C., Mittig, W., Boilley, D., De France, G., Gaudefroy, L., Marchix, A., Morjean, M., Navin, A., Rejmund, F., Rejmund, M., Roussel-Chomaz, P., Stodel, C., Heinz, S., Winkler, M., Bhattacharyya, S., Mukherjee, G., Dayras, R., Drouart, A., & Giot, L. Search for a long lived component in the reaction U+U near the Coulomb barrier. United States. doi:10.1063/1.2713501.
Villari, A. C. C., Golabek, C., Mittig, W., Boilley, D., De France, G., Gaudefroy, L., Marchix, A., Morjean, M., Navin, A., Rejmund, F., Rejmund, M., Roussel-Chomaz, P., Stodel, C., Heinz, S., Winkler, M., Bhattacharyya, S., Mukherjee, G., Dayras, R., Drouart, A., and Giot, L. Mon . "Search for a long lived component in the reaction U+U near the Coulomb barrier". United States. doi:10.1063/1.2713501.
@article{osti_21056782,
title = {Search for a long lived component in the reaction U+U near the Coulomb barrier},
author = {Villari, A. C. C. and Golabek, C. and Mittig, W. and Boilley, D. and De France, G. and Gaudefroy, L. and Marchix, A. and Morjean, M. and Navin, A. and Rejmund, F. and Rejmund, M. and Roussel-Chomaz, P. and Stodel, C. and Heinz, S. and Winkler, M. and Bhattacharyya, S. and Mukherjee, G. and Dayras, R. and Drouart, A. and Giot, L.},
abstractNote = {We performed an experiment to search for a signature of a long living component in the collision of 238U + 238U between 6.09 and 7.35A MeV. The experiment was performed at GANIL using the spectrometer VAMOS, tuned for observing reactions with kinematics similar to fusion-fission events. Theoretical calculations indicate that if a long living component would exist for this reaction, the most probable fission channel of such a giant system would be via the emission of quasi-lead nuclei. We detected events of such a category in the focal plane of VAMOS. These events present an excitation function growing as a function of the bombarding energy.},
doi = {10.1063/1.2713501},
journal = {AIP Conference Proceedings},
number = 1,
volume = 891,
place = {United States},
year = {Mon Feb 26 00:00:00 EST 2007},
month = {Mon Feb 26 00:00:00 EST 2007}
}
  • A recent measurement of direct {alpha}-particle emission from the {sup 238}U({sup 6}He, fission) reaction is shown to be strongly influenced by the fission trigger.
  • A thick /sup 238/U target has been bombarded with /sup 63//sub,//sup 65/Cu ions at an incident beam energy of 9.6 MeV/nucleon. After radiochemical separations into CdS, HgS, and La-oxalate fractions, a search for evidence of the production of superheavy elements was undertaken using Si surface-barrier detectors and mica foils simultaneously for detection of spontaneous-fission events and high-energy ..cap alpha.. emission. No evidence for the presence of superheavy elements in the samples was found. Upper limits for production cross sections for superheavy elements in each of the three chemical samples, assuming an arbitrary half-life of 100 days and a target thicknessmore » equal to the entire reaction range of the incident ions from initial energy to the reaction barrier, are as follows: (a) CdS (Z = 108--115): 1 x 10/sup -34/ cm/sup 2/; (b) HgS (Z = 112): 6 x 10/sup -35/ cm/sup 2/; (c) La-oxalate (/sup 254/Cf): 8 x 10/sup -35/ cm/sup 2/. (AIP)« less
  • The first results are presented from a new experiment, APEX, designed to study the previously reported sharp lines in sum-energy spectra of positrons and electrons produced in collisions of very heavy ions. Data were collected for {sup 238}U+{sup 181}Ta at 5.95, 6.10, and 6.30 MeV/u and {sup 238}U+{sup 232}Th at 5.95 MeV/u. In none of our analyses is any evidence found for sharp sum-energy lines. For the specific case of the isolated decay of a neutral particle of mass 1.4--2.1 MeV/{ital c}{sup 2}, the upper limits on cross sections obtained from the present data are significantly less than the previouslymore » reported cross sections.« less
  • The fission fragment angular distribution measurements for the {sup 13}C+{sup 235}U system have been carried out to study the entrance channel dependence and spin dependent effects in the fission fragment anisotropies. This particular combination of target and projectile leads to {sup 248}Cf compound nucleus that has been studied earlier using three other entrance channels viz. {sup 11}B+{sup 237}Np, {sup 12}C+{sup 236}U, and {sup 16}O+{sup 232}Th. A comparison of the measured anisotropy data for all the four systems, with the statistical saddle-point model and pre-equilibrium fission (PEF) model, brings out a clear signature of entrance channel dependence in fission anisotropy values,more » characteristic of the PEF model.« less
  • The effective mass spectrum of K..pi.. systems produced in the reaction ..pi../sup -/ U ..-->.. K/sup - +/..pi../sup + -/ +... at 55-GeV/c incident momentum was investigated for the purpose of searching for heavy mesons with a lifetime of 10/sup -12/ to 10/sup -10/ sec. Narrow resonances were not observed in the 1.3--2.3-GeV mass region of the K..pi.. systems. Upper limits for the production cross sections of D/sup 0/ mesons were estimated.