Measurements of Neutron Radiation Around Medical Electron Accelerators by Means of 235U Fission Chamber and Indium Foil Activation

1 June 1988

journal article
Published by Oxford University Press (OUP) in Radiation Protection Dosimetry

Vol. 23 (1-4) , 345-348
https://doi.org/10.1093/oxfordjournals.rpd.a080194

Abstract

Measurements of neutron radiation inside and outside the 16-50 MV photon beams from medical electron accelerators in Sweden were performed using a ²³⁵U fission chamber and an indium foil activation method. The fast neutron fluences measured at the isocentre varied between 2.5 x 10⁷ and 0.7 x 10⁷ cm^-2.Gy^-1 for low and high energy treatment units, respectively. The results of the thermal neutron fluence for the photon beams of energies 18 - 50 MV ranged from 3.3 x 10⁶ to 0.2 x 10⁶ cm^-2.Gy^-1. The differences between the results obtained by both methods, presented for the 21 MV microtron and the 42 MV Siemens betatron, were less than 15% and smaller than the estimated absolute error of 20% for each of the methods separately. The greatest advantages of the measurements with the ²³⁵U fission chamber are the high sensitivity and the possibility of getting on-line results.

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