Fission of heavy nuclei induced by energetic pions (original) (raw)
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Radiation Measurements, 2008
The study of pion-induced nuclear reactions are important because pion not only plays the role of a projectile, but also serves as intermediate step particle as in the case of interaction of other projectiles like photon and antiproton. The studies of pion-induced nuclear reaction have important applications, such as in accelerator-driven system (ADS) and in basic nuclear research to probe the nuclear structure. The studies of pion-induced reaction, particularly fission, are as important as the studies of nucleon-induced nuclear reactions, because inter-nuclear cascades in spallation targets are partly propagated by pions. The pion-induced fission has not been as much studied as fission induced by nucleons. The reason is that there is a limited number of facilities available for production of pions, and beam time is scant. Previously, pion-induced fission has been studied using dielectric track-detectors; at present the work has not been carried out using this technique due to non-availability of exposure facilities. So there is a need of computer codes to study cross-section of pion-induced fission, and the proper documentation of existing experimental data. In the present work, fission cross-sections induced by positive pions, for targets 209 Bi, 231 Pa, 232 Th, 238 U and 239 Pu are computed using the cascade-exciton model code CEM95 upto 2500 MeV energy. Also a systematics of positive pion-induced fission is performed on the basis of that performed cross-sections of proton-induced fission. The computed cross-sections of fission using CEM95 have been compared with the available experimental data and with the fission cross-sections obtained using the systematics analysis. A reasonable agreement has been observed.
Mass dependence of positive pion-induced fission
Physical Review C, 1991
Fission cross sections for a range of targets have been measured by solid-state track detectors following 80 and 100 MeV~+ bombardment. Fission probabilities have been inferred by comparison to computed reaction cross sections. Fission probabilities for heavy targets agree with those for other probes of comparable energy and with statistical calculations. Probabilities for lighter targets are much above those previously observed or computed. Ternary fission cross sections and multiplicities of light fragments have also been determined.
Energy dependence of fission probabilities induced by negative pions in Sn, Au and Bi
Nuclear Physics A, 2007
Fission probabilities induced by negative pions in Sn, Au and Bi at different energies using variety of nuclear track detectors have been studied. The target-detector assemblies in 4π-geometric configuration were irradiated at the AGS facility of Brookhaven National Laboratory, USA. After etching the exposed detectors at appropriate etching conditions the detectors have been scanned for the tracks of fission fragments produced as a result of interaction of pions with the target nuclei. Based on the track counts, the values of fission cross sections have been measured and fission probabilities have been calculated using the reaction cross-section calculated with the help of the cascade-exciton model code CEM95. The values of fission probability based on experimental fission cross-sections have been compared with the theoretically calculated values of fission probabilities obtained using the CEM95 code. Theoretical values of fission probability have been computed for incident pion energy up to 2500 MeV in Sn, Au and Bi for comparison to fission data for high energy negative pions at 500, 672, 1068, 1665 MeV and 2300 MeV energies for the same targets. The values of fission probability based on the experimental fission cross section and theoretically calculated values of fission probability have been compared. Reasonable agreement has been observed among the experimentally measured and theoretically computed values of fission probabilities. A saturation of probabilities has been observed for Au and Bi at higher energies, but for Sn an increase of probability with the increase of pion beam momentum up to 1665 MeV has been observed.
Fission induced by nucleons at intermediate energies
Nuclear Physics A 933, 43, 2015
Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Liège Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p, f ) cross sections and used to predict (n, f ) cross sections for the same isotopes. arXiv:1409.4885v1 [nucl-th] 17 Sep 2014 Important applications of intermediate energy fission are energy production with accelerator driven systems [1], radioactive waste transmutation[2]
Preliminary results of fission induced by (1068 MeV) π− in Cu, Sn, Au and Bi using CR-39 detectors
Radiation Measurements, 1999
Fission probabilities in pion induced reactions exhibit characteristic variations with respect to pion energies and target fissility values. At incident energies well above the pionnucleon resonances, the statistical model seems to give good description of the observed data. We have used negative pions of energy 1068 MeV, in order to study fission induced in four target materials with fissility values [(Z-1)2/A] ranging from 12 to 32. All targets were arranged in a single stack in such a way that each target coated on a CR-39 detector was sandwiched by another uncoated CR-39 detector plate. The stack was irradiated at the AGS of Brookhaven National Laboratory (USA). This set-up ensures solid angle coverage of almost 4~z degrees, so that for each fission event one of the fission fragments is expected to be trapped by the forward detector and one by the detector covering backward hemisphere. The effect of pion momentum transfer to the struck nucleus was observed in the form of asymmetry between events counted in the two complementary detectors. The effect of target thickness on the number of tracks revealed in CR-39 has also been noted.
Fission of 209 Bi and 26 Au Nuclei Induced by 30 MeV Protons
Journal of Nuclear Science and Technology, 2001
Thin targets of 209 Bi and 197 Au were bombarded with 30 MeV protons at the Cyclotron Department of Nuclear Research Center for Agriculture and Medicine (NRCAM). Correlated measurements of kinetic energies of fission fragment pairs, and their time-of-flights were made using pair spectrometry. The fission cross sections, fragment mass distributions, and total kinetic energy distributions of the fragments were measured in our experiment. The accurate values of cross sections for fission of 209 Bi and 197 Au nuclei with 30 MeV protons were obtained to be 1,100±100 and 62±5.6 µb, respectively. The cross section of 209 Bi fission with its associated error, through using this method, has not been reported previously. The interpretation in terms of liquid-drop model of fissioning nucleus 210 Po at the excitation energy of 35 MeV was confirmed by the dispersion of the distribution in fragment mass for bismuth fission.
Proton-induced fission of heavy nuclei at intermediate energies
Intermediate energy data of proton-induced fission on 241 Am, 238 U and 237 Np targets were analysed and investigated using the computational simulation code CRISP. Inelastic interactions of protons on heavy nuclei and both symmetric and asymmetric fission are regarded. The fission probabilities are obtained from the CRISP code calculations by means of the Bohr-Wheeler model. The fission cross sections, the fissility and the number of nucleons evaporated by the nuclei, before and after fission, are calculated and compared with experimental data. Some of the model predictions agree completely with the data. We conclude that our two step model of the CRISP code provides a good description of intermediate energy proton-induced fission.
The study of nuclear fission induced by high-energy protons
Revue de Physique Appliquée, 1972
2014 On a étudié les sections efficaces de la fission binaire par la technique des « sandwiches » de mica. Les mesures ont été faites pour les noyaux de l'uranium, du bismuth, du plomb, de l'or et des quelques éléments légers irradiés par des protons de l'énergie entre 0,59 et 23 GeV.
1998
An extended version of the Cascade-Exciton Model (CEM) of nuclear reactions is applied to analyze nucleon-induced fission cross sections for Bi-209 and Pb-208 nuclei in the 45-500 MeV energy range. The available data on linear momentum transfer are analyzed as well. The results are compared with analytical approximations resulting from a comparative critical analysis of all available experimental data. Systematic discrepancies between calculations and experimental data are revealed. A modification of the CEM is proposed, which significantly improves the model predictions for projectile energies above 100 MeV.
Photon and proton induced fission on heavy nuclei at intermediate energies
We present an analysis of fission induced by intermediate energy protons or photons on actinides. The 660 MeV proton induced reactions are on 241 Am, 238 U, and 237 Np targets and the Bremmstrahlung-photons with end-point energies at 50 MeV and 3500 MeV are on 232 Th and 238 U targets. The study was performed by means of the Monte Carlo simulation code CRISP. A multimodal fission extension was added to the code within an approach which accounts for the contribution of symmetric and asymmetric fission. This procedure allowed the investigation of fission cross sections, fissility, number of evaporated nucleons and fission-fragment charge distributions. The comparison with experimental data show a good agreement between calculations and experiments.