Simulation and measurement of the response of the blowfish detector to low-energy neutrons
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Blowfish is a highly segmented neutron detector array consisting of 88 cells filled with BC-505 liquid scintillator. The cells make up a spherical shape that covers approximately one quarter of the total solid angle of 4 pi steradians. A high-priority measurement for Blowfish is the low energy contribution to the Gerasimov-Drell-Hearn (GDH) sum rule on the deuteron, which uses circularly polarized gamma rays. The experimental data that needs to be collected are the absolute cross-sections when the gamma ray helicity and target polarization are parallel and anti-parallel. To extract absolute cross-sections from the data, it will be necessary to have characterized the efficiency of the detector.Another measurement that would benefit from the efficiency calibration is the photodistegration of deuterium, which has already been performed. This measurement used linearly-polarized gamma rays at energies of 2.6, 3.5, 4.0 and 6.0 MeV. The relative cross-sections from this measurement provide much useful information, but to extract the absolute cross-sections the Blowfish efficiency calibration is needed. This thesis presents this efficiency calibration. The efficiency calibration was done using a 252Cf source in a parallel plate ionization chamber over the energy range of 0 to 6 MeV. To determine the absolute scale of the extracted efficiency curves, an efficiency analysis and simulation of a previously characterized BC-519 liquid scintillator cell needed to be performed along with a simulation of the Blowfish detector array. The measured efficiencies were consistent with those predicted by the simulation over the desired energy range.
DegreeMaster of Science (M.Sc.)
DepartmentPhysics and Engineering Physics
ProgramPhysics and Engineering Physics
SupervisorKolb, Norman R.
CommitteeUrquhart, Stephen G.; Steele, Tom G.; Smolyakov, Andrei I.; Pywell, Robert E.; Xiao, Chijin
Copyright DateAugust 2003