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Articles by J.P. Sephton
Total Records ( 3 ) for J.P. Sephton
  M. Bailey , J.P. Sephton and P.H.G. Sharpe
  The dose rate distribution in a MDS Nordion JS7500 60Co industrial irradiation plant has been calculated using the egspp Monte Carlo code. This code is a development of the established EGSnrc code developed and distributed by National Research Council of Canada.

The coding method is described and absolute dose rates given for each of the dwell positions in the path through the irradiator. These calculated dose rates have been compared with measurements made using a radiation resistant electronic dosimetry system. In addition, the integral dose derived from calculated and measured dose rates has been compared to the value obtained using chemical dosimeters.

  P.H.G. Sharpe , A. Miller , J.P. Sephton , C.A. Gouldstone , M. Bailey and J. Helt-Hansen
  Published data on the effect of irradiation temperature on the response of alanine dosimeters does not extend to the temperatures that may be experienced in high-dose industrial irradiations, particularly in the case of electron beams. We describe here results of the irradiation of alanine dosimeters at temperatures up to 80 °C and doses up to 70 kGy. Data have been obtained for both 60Co and electron beam irradiations and the effect of temperature on the stability of the radiation-induced signal has also been investigated. At temperatures above 50 °C the irradiation temperature coefficient begins to deviate significantly from linearity and shows marked dose dependence. The effect of this behaviour under conditions typically experienced in industrial processing is evaluated and recommendations made concerning the use of alanine dosimeters at high doses and temperatures.
  P.H.G. Sharpe , J.P. Sephton and C.A. Gouldstone
  A cryostat has been constructed to enable irradiations in a MDS Nordion Gammacell 220 irradiator to be carried out at selected temperatures between 100 and 300 K. The principle of operation and the performance of this cryostat are described and results are given of a study into the behaviour of alanine dosimeters at cryogenic temperatures. This work extends previously published data to the region between solid CO2 and liquid N2 temperatures and has demonstrated complex dose-dependent behaviour. A sharp discontinuity in the effect of temperature on alanine dosimeter response has been found in the region between 150 and 180 K, with no further influence of irradiation temperature on response observed below this point.
 
 
 
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