The <SUP>241</SUP>Am photofission and photoneutron cross section, the mean number of prompt neutrons per fission υ* and the delayed neutron yield have been measured between 5 and 10 MeV. The photofission cross section has been measured over a wider range and with better resolution than any previous data. The photoneutron cross section, υ* and the delayed neutron yield had not been measured before. The experiment was peformed using bremsstrahlung radiation produced by the 136 MeV Harwell electron linac HELIOS. Fission neutrons and photoneutrons from the <SUP>241</SUP>Am target were detected by an oil-moderated tank containing fifty-six <SUP>10</SUP>BF<SUB>3</SUB> proportional counters arranged in five concentric rings. For each run, the events associated with each beam burst were recorded as a multiplicity distribution. The end-point energy was cycled between two neighbouring energy points during the run to give difference yields in order to minimise the effects of energy drifting. The data were corrected, fitted and bremsstrahlung unfolded to give both the photofission and photoneutron cross sections as well as υ* and an upper limit for the delayed neutron yield. The results were then compared with other data. An attempt was made to try to explain the structure seen at 6.0 MeV in the photofission cross section of ^241Am in terms of a sub-barrier resonance by fitting a theoretically calculated cross section to the data. Calculations show that there is the possibiity of a resonance in this region, though this would require damping to be less than contemporary theory would suggest. Cross sections were also calculated for the other actinides studied at Harwell with this set-up, namely ^232Th and ^238U.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663542 |
| Date | January 1990 |
| Creators | Watson, S. J. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11519 |
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