Measurement of prompt gamma-ray energy distribution and multiplicity of U-235 following thermal fission using STEFF

  • Elizabeth Murray

Student thesis: Phd


More accurate knowledge of gamma-ray heating in nuclear reactors has beenlisted as a high priority request by the NEA [23]. In response to this the SpecTrometerfor Exotic Fission Fragments (STEFF), a 2-velocity, 2-energy spectrometer assembledby the Manchester Fission Group has been used to take measurements ofprompt gamma-rays from thermal fission of U-235. Through the procedures discussed,the average total gamma-ray energy and average multiplicity were determined to be8.40 +/- 0.26 MeV and 7.74 +/- 0.12, respectively. The single energy spectrum for eachindividual detector has been determined as well as the total energy distribution.A new parallel plate avalanche counter has been tested for its potential to improvethe timing resolution of the current STEFF stop detector. The timing resolution ofthe new detector is found to be 337 ps, an improvement of 75 % on the previous stopdetector.The pulse shapes created by a fission fragment in an ionisation chamber havebeen investigated. The relationship with fragment atomic number has been tested byemploying the Lohengrin spectrometer to separate fragments by mass so that theirindividual pulse shapes can be studied.Evaluation work has been performed at the NNL, Cumbria, under the supervisionof Dr Robert Mills. Experimental data determined from the spontaneous fission ofCf-252 has been extracted and evaluation techniques performed upon it so that thedata can be considered for inclusion within an evaluated nuclear database.
Date of Award1 Aug 2015
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorAlastair Smith (Supervisor) & Robert Mills (Supervisor)


  • Thermal-fission, U-235, 235U, STEFF, multiplicity, NaI, fission
  • energy, timing, fragments, gamma-ray

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