Search results for "Cluster decay"
showing 10 items of 41 documents
Theoretical and experimental studies of the neutron rich fission product yields at intermediate energies
2012
A new method to measure the fission product independent yields employing the ion guide technique and a Penning trap as a precision mass filter, which allows an unambiguous identification of the nuclides is presented. The method was used to determine the independent yields in the proton-induced fission of 232 Th and 238 U at 25 MeV. The data were analyzed with the consistent model for description of the fission product formation cross section at the projectile energies up to 100 MeV. Pre-compound nucleon emission is described with the two-component exciton model using Monte Carlo method. Decay of excited compound nuclei is treated within time-dependent statistical model with inclusion of the…
Mass-asymmetric fission in the 40ca+142Nd reaction
2016
Shell effects play a major role in fission. Mass-asymmetric fission observed in the spontaneous and low energy fission of actinide nuclei was explained by incorporating the fragment shell properties in liquid drop model. Asymmetric fission has also been observed in the low energy fission of neutron-deficient 180 Hg nuclei in recent β -delayed fission experiments. This low-energy β -delayed fission has been explained in terms of strong shell effects in pre-scission configurations associated with the system after capture. Calculations predicted asymmetric fission for heavier Hg isotopes as well, at compound nuclear excitation energy as high as 40 MeV. To explore the evolution of fission fragm…
Measurements of isomeric yield ratios of fission products from proton-induced fission on natU and 232Th via direct ion counting
2017
Independent isomeric yield ratios (IYR) of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyväskylä. A direct ion counting measurement of the isomeric fission yield ratios was accomplished for the first time, registering the fission products in less than a second after their production. In addition, the IYRs of natU were measured by means of γ-spectroscopy in order to verify the consistency of the recently upgraded experimental setup. From the obtained results, indications of a dependence of the production rate …
Delayed-neutrons from arsenic isotopes 84As, 85As and 86As
1973
Abstract Short-lived arsenic isotopes were produced by thermal-neutron fission of 235U and isolated within 2·5 sec by volatilization of arsenic hydride. The existence of a strong delayed-neutron precursor of 2·05±0·05 sec half-life among the arsenic isotopes is confirmed and its assignment to 85As ascertained by milking of the daughter product 33 sec 85Se and 3·1 min 84Se, which is the final nucleus in the neutron decay branch of 85As. A delayed-neutron yield of 7·8 ± 1·2 neutrons/104 fissions was obtained for 85As. A new isotope, 0·9 ± 0·2 sec 86As, was detected by delayed-neutron counting and by following the decay of its most prominent γ-ray. The mass assignment was verified by milking o…
Advanced model for the prediction of the neutron-rich fission product yields
2013
The consistent models for the description of the independent fission product formation cross sections in the spontaneous fission and in the neutron and proton induced fission at the energies up to 100 MeV is developed. This model is a combination of new version of the two-component exciton model and a time-dependent statistical model for fusion-fission process with inclusion of dynamical effects for accurate calculations of nucleon composition and excitation energy of the fissioning nucleus at the scission point. For each member of the compound nucleus ensemble at the scission point, the primary fission fragment characteristics: kinetic and excitation energies and their yields are calculate…
CORRELATIONS IN TERNARY FISSION
2000
An experiment investigating correlations in ternary fission of233U induced by cold polarized neutrons was performed at the high flux reactor of the ILL in Grenoble (France). With the experimental setup, Left—Right and time reversal symmetry violating and conserving correlations between neutron spin\(\hat \sigma \), neutron momentum\(\hat p_n \), momenta of fission fragments\(\hat p_f \) and ternary particles\(\hat p_t \) could be investigated.
Independent yields of neutron-rich nuclei in charged-particle induced fission
1997
Abstract Yields of fission products have been studied at the recently upgraded IGISOL facility in Jyvaskyla using 50 MeV H2+ beam (Ep = 25 MeV) and thin natTh and natU targets. The independent yields of fission products in the mass regions A = 99−112 (elements Y, Nb and Tc) and A = 127−134 (elements Sn, Sb and Te) have been obtained. Comparisons of the experimental isotopic distributions with theoretical ones are presented. Enhancement of the production rate of the doubly magic 132Sn is observed in the experimental yield curve.
Fission product yields at intermediate energy
1998
The results of experimental and theoretical studies of fission product yields in proton-induced fission of 238U are presented. The yields of neutron-rich Ni, Cu, Zn, Ga and Ge—isotopes were measured by 25 MeV protons and the ion guide-based isotope separator technique. The pre-neutron emission fragment mass distributions were measured by protons at energies Ep=20, 35, 50 and 60 MeV using time-of-flight method. The results indicate enhancement for superasymmetric mass division at intermediate excitation energy of the fissioning nucleus. A model calculation of fission products yields for fission of 238U by protons and neutrons is presented which predicts the formation cross sections for neutr…
Mass and charge distributions in the very asymmetric thermal neutron induced fission of the odd-Z nucleus 242mAm
1999
Yields of light fission products (A = 68, 70-84, 87, 88, 94, 96, 98, 102 and 106-108), their kinetic energies and nuclear charge distributions (A = 71-84, 87 and 88) in the thermal neutron induced fission of the odd-Z nucleus Am-242m(Z = 95) were measured using the mass-separator Lohengrin at the Institute Laue-Langevin in Grenoble (France). The mass yield curve shows a fine structure at A = 70, probably due to shell and/or odd-even effects affecting also the nuclear charge distribution. The analysis of isotopic chain yields gives evidence for a very low excitation energy of the lightest fission fragments observed. A preferential formation of fragments with even Z is found for this odd-Z co…
Fragment mass distribution in superasymmetric region in proton-induced fission of U and Th
1998
Fission fragment mass distributions down to super-asymmetric mass region and both pre- and post-scission neutron multiplicity for238U(p,fission) reaction atEp = 20, 35, 50, 60 MeV and for232Th(p, fission) reaction atEp = 50, 60 MeV were measured using HENDES set-up. The results indicate enhancement for super-asymmetric mass division at intermediate excitation energies.