Download or read book The Angular Distribution of Fission Fragments from the Fast Neutron induced Fission of U 234 written by Richard W. Lamphere and published by . This book was released on 1962 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Angular Distribution of Fission Fragments from the Fast Neutron Induced Fission of U 234 thesis written by and published by . This book was released on 1962 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Submitted to Univ. of Tennessee, Knoxville. The fast neutron-induced fission cross section of U/sup 234/ was measured from threshold to 4-Mev neutron energy. A maximum of 1.26 barns was found at 850 kev followed by a minimum of 1.10 barns at 8050 kev. The angular ani-sotropy of the fragment distribution was measured for neutron energies from 400 kev to 4 Mev. Extrema in the ratio sigma /sub f//(sigma /sub f(90 deg) were found at 500, 850, and 1050 kev; the distribution at 500 kev showing a maximum in the direction normal to the beam (side-wise peaking) while that at 850 kev showed a maximum along the beam direction. The distribution at 8050 kev showed forward peaking but to a lesser extent than for energies immediately higher or lower. The behavior was analyzed according to the theories of Bohr and Wheeler. The dip in cross section between 850 and 1050 kev is consistent with the suggestion of Wheeler that neutron competition in the decay of the compound nucleus enters with increased strength in this area. Vibration-rotational levels in U/sup 234/ beginning at 790 kev are known to exist and inelastic neutron scattering to these levels serves to depress the fission cross section. The changes in fragment angular distribution are shown to be explainable in terms of the theory of Bohr which states that fission occurs through distinct channels composed of a K-band structure analogous to that observed at low excitations in heavy deformed nuclei. More detailed angular distribution measurements were carried out at 850 and 1050 kev. The overall picture is consistent with a K-band structure in U/sup 235/* near the saddle point deformation of K equals 1/2+, 3/2--, 1/2-- in that order, the bands being separated from each other by a few hundred kilovolts. (auth).
Download or read book Fission Fragment Angular Distribution and Fission Cross Section Validation written by Lou Sai Leong and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present knowledge of angular distributions of neutron-induced fission is limited to a maximal energy of 15 MeV, with large discrepancies around 14 MeV. Only 238U and 232Th have been investigated up to 100 MeV in a single experiment. The n_TOF Collaboration performed the fission cross section measurement of several actinides (232Th, 235U, 238U, 234U, 237Np) at the n_TOF facility using an experimental set-up made of Parallel Plate Avalanche Counters (PPAC), extending the energy domain of the incident neutron above hundreds of MeV. The method based on the detection of the 2 fragments in coincidence allowed to clearly disentangle the fission reactions among other types of reactions occurring in the spallation domain. I will show the methods we used to reconstruct the full angular resolution by the tracking of fission fragments. Below 10 MeV our results are consistent with existing data. For example in the case of 232Th, below 10 MeV the results show clearly the variation occurring at the first (1 MeV) and second (7 MeV) chance fission, corresponding to transition states of given J and K (total spin and its projection on the fission axis), and a much more accurate energy dependence at the 3rd chance threshold (14 MeV) has been obtained. In the spallation domain, above 30 MeV we confirm the high anisotropy revealed in 232Th by the single existing data set. I'll discuss the implications of this finding, related to the low anisotropy exhibited in proton-induced fission. I also explore the critical experiments which is valuable checks of nuclear data. The 237Np neutron-induced fission cross section has recently been measured in a large energy range (from eV to GeV) at the n TOF facility at CERN. When compared to previous measurements, the n TOF fission cross section appears to be higher by 5-7 % beyond the fission threshold. To check the relevance of n TOF data, we simulate a criticality experiment performed at Los Alamos with a 6 kg sphere of 237Np. This sphere was surrounded by enriched uranium 235U so as to approach criticality with fast neutrons. The simulation predicts a multiplication factor keff in better agreement with the experiment (the deviation of 750 pcm is reduced to 250 pcm) when we replace the ENDF/B- VII.0 evaluation of the 237Np fission cross section by the n TOF data. We also explore the hypothesis of deficiencies of the inelastic cross section in 235U which has been invoked by some authors to explain the deviation of 750 pcm. The large distortion that should be applied to the inelastic cross sections in order to reconcile the critical experiment with its simulation is incompatible with existing measurements. Also we show that the nubar of 237Np can hardly be incriminated because of the high accuracy of the existing data. Fission rate ratios or averaged fission cross sections measured in several fast neutron fields seem to give contradictory results on the validation of the 237Np cross section but at least one of the benchmark experiments, where the active deposits have been well calibrated for the number of atoms, favors the n TOF data set. These outcomes support the hypothesis of a higher fission cross section of 237Np.
Download or read book Fission Fragment Angular Distribution Measurements of 235U and 238U at CERN N TOF Facility written by Esther Leal Cidoncha and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron-induced fission cross sections of 238U and 235U are used as standards in the fast neutron region up to 200 MeV. A high accuracy of the standards is relevant to experimentally determine other neutron reaction cross sections. Therefore, the detection effciency should be corrected by using the angular distribution of the fission fragments (FFAD), which are barely known above 20 MeV. In addition, the angular distribution of the fragments produced in the fission of highly excited and deformed nuclei is an important observable to investigate the nuclear fission process. In order to measure the FFAD of neutron-induced reactions, a fission detection setup based on parallel-plate avalanche counters (PPACs) has been developed and successfully used at the CERN-n_TOF facility. In this work, we present the preliminary results on the analysis of new 235U(n,f) and 238U(n,f) data in the extended energy range up to 200 MeV compared to the existing experimental data.
Download or read book Energy Distribution of the Fragments Resulting from the Fission of U235 and Th232 by Slow and Fast Neutrons written by Joseph L. Fowler and published by . This book was released on 1947 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Angular Distribution of Fragments from 14 mev Neutron induced Fission of Uranium written by Kenneth Gen Wah Inn and published by . This book was released on 1971 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fission Fragment Mass Distributions and Total Kinetic Energy Release of 235 Uranium and 238 Uranium in Neutron Induced Fission at Intermediate and Fast Neutron Energies written by and published by . This book was released on 2015 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Ph. D. dissertation describes a measurement of the change in mass distributions and average total kinetic energy (TKE) release with increasing incident neutron energy for fission of 235U and 238U. Although fission was discovered over seventy-five years ago, open questions remain about the physics of the fission process. The energy of the incident neutron, En, changes the division of energy release in the resulting fission fragments, however, the details of energy partitioning remain ambiguous because the nucleus is a many-body quantum system. Creating a full theoretical model is difficult and experimental data to validate existing models are lacking. Additional fission measurements will lead to higher-quality models of the fission process, therefore improving applications such as the development of next-generation nuclear reactors and defense. This work also paves the way for precision experiments such as the Time Projection Chamber (TPC) for fission cross section measurements and the Spectrometer for Ion Determination in Fission (SPIDER) for precision mass yields.
Download or read book Fission Fragment Mass Distributions and Total Kinetic Energy Release of 235 uranium and 238 uranium in Neutron induced Fission at Intermediate and Fast Neutron Energies LA UR 15 28829 written by Dana L. Duke and published by . This book was released on 2015 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fragment Angular Distributions from Neutron and Alpha particle Induced Fission written by Leroy Norman Blumberg and published by . This book was released on 1962 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Keywords Index to U S Government Technical Reports written by United States. Department of Commerce. Office of Technical Services and published by . This book was released on 1962 with total page 990 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Keywords Index to U S Government Technical Reports permuted Title Index written by United States. Department of Commerce. Office of Technical Services and published by . This book was released on 1962 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Publications Announcements with Indexes written by United States. National Aeronautics and Space Administration and published by . This book was released on 1962 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book WASH written by and published by . This book was released on 1959 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Division Annual Progress Report for Period Ending written by Oak Ridge National Laboratory. Physics Division and published by . This book was released on 1963 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1978 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A CONF 15 P written by and published by . This book was released on 1958 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
