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Title: A prototype double Bragg detector for fission yield measurements
Author: Frost, Robert
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2017
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This work details the commissioning and further development of a double gridded Bragg detector (DGBD), for the purpose of investigating the energies, masses and angular distributions fission fragments. The process of charge collection in ionisation chamber is also investigated, as is the efficacy of using the DGBD to perform measurements in fast neutron fluxes. Optimal operating conditions for the DGBD were determined using a ²⁵²Cf(sf) source and two different fill gases are compared. Digital signal processing algorithms were developed to perform the necessary correction to the recorded pulse traces and further analysis was performed to correct the mass distributions obtained for the effects of pulse- high-deficit and neutron-evaporation. Investigation into signal generation was performed using a segmented anode; and study of the background rates experienced in fast neutron fluxes was performed using 2.5 MeV and 14.2 MeV neutrons at the LPSC, Grenoble and by Monte Carlo simulation. The DGBD was found to operate to a high standard but that the fission fragment source used in the present study results in energy losses of ~ 10% in both detector regions. It was found that Frisch grid inefficiency of < 1 % can be achieved without compromising charge collection on the anode, that iso-butane fill gas sees large ~ 15% charge-recombination, whereas as P-10 appears to see higher diffusion than iso-butane. It is concluded that fast neutron-induced fission studies are not feasible with isotropic neutron sources due to neutron-induced charge-particle emmission from the fill gas; and that the current induced on a segmented anode can be reliably simulated using analytical methods to obtain the Shockley-Ramo weighting potentials.
Supervisor: Smith, Alastair Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: 252Cf ; Bragg detector ; segmented anode ; Skockley-Ramo theorm ; spontaneous fisson