Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504735
Title: Study of Angular Correlations andDistributions in the SpontaneousFission of 252Cf
Author: Alothman, Miysoon Abdulrahman
ISNI:       0000 0004 0123 3762
Awarding Body: The University of Manchester
Current Institution: University of Manchester
Date of Award: 2008
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Abstract:
The fragment-y angular correlation coefficients, a2, have been measured for the first time using two data sets extracted from experiments using large detector arrays, Euroball and Gammasphere. f-V ACF measurements for v-ray of the 2+ -70+ and 4+ -72+ transitions of even-even fission fragments of isotopes of Ce, Ba, Xe, Te, Mo, Zr, Ru and Pd are performed. The results showed compatibility between the two experiments and consequently validate the analysis techniques used in the two experiments. The results were interpreted using the statistical de-excitation model analysis, which reproduced the experimental angular correlation coefficients a2 and a4, and the intensities of the E2 stretched intraband transitions by evaluating the initial angular momentum of the fission fragments, B. The analysis has revealed the need of a tilting factor in the initial angular distribution in order to achieve a good reproduction of the measured coefficients, which suggests that a considerable proportion ofthe angular momentum generated at scission is oriented parallel to the fission axis, and therefore provides for the first time an evidence that the twisting mode could be active in the fission processes. The v-v correlation between the angles of emission of the 2+ -70+ transitions of complementary fragment pairs in the spontaneous fission of 252Cf are measured for the first time using Gammasphere array. Data are extracted from an experiment that measures the g-factors of excited states. The study shows smaller than expected a2 coefficients (0.013(7)) compared to the value measured in previous study (a2=0.OS7(4)). The attenuation occurring in the angular correlation function (ACF) coefficients a2(2+) is interpreted as due to the perturbation of the ACF as an effect of the magnetic field. Calculations of the amount of dealignment needed to reproduce the measured a2 values suggest a smearing in the Gaussian distribution of the initial angular momentum. That result is consistent with the results obtained from the f-V ACF measurements, which confirms the significant role of the twisting mode in the dynamical processes that occur in the fissioning system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Not available Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.504735  DOI: Not available
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