The dose given to a polythene energy absorber in the radiation field from a 14 MeV neutron generator has been measured calorimetrically. The calorimeter was calibrated by giving the energy absorber a known dose of gamma -rays. The dose measured in this way was compared with that determined with a polythene-ethylene ionization chamber, and the two results agreed to better than 1, though the estimated uncertainties on the calorimeter and ionization chamber results were each about 4. This result can be used to determine a value of the ratio Wn/We, for 14 MeV neutrons in ethylene, where Wnis the W value for the charged particles generated in the neutron field in ethylene, and Weis the W value for electrons in the same gas. The measured value of Wn/Wewas found to be 1.07+or-3.9. The significance of the 'thermal defect' in polythene is discussed.
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