Determination of the absorbed dose to water for high-energy photons and electrons by total absorption of electrons in ferrous sulphate solution

Abstract

An arrangement is described for determining the relation between the energy imparted to ferrous sulphate (Fricke) solution by total absorption of 5.6 MeV electrons and the yield of ferric ions produced in the solution. Since the energy imparted is derived from measurements of basic quantities, the method represents an absolute determination of the absorbed dose to water. By means of ampoules filled with calibrated Fricke solution the beam of a cobalt source was measured to serve as a PTB standard for the quantity absorbed dose to water under specified conditions. The total uncertainty of this method of determining the absorbed dose to water for electrons and photons in the energy range above 1 MeV appears to be smaller than that of the calorimetric method, which is also applied in this laboratory for photon radiation.

Photon absorbed dose standards

“…Absorbed dose to water standards for photon and electron beams have been developed based on the calibration of Fricke solutions [70], either by comparison against calorimetry or by total absorption of electron radiation in the Fricke solution [71]. In the former method, absorbed dose (to water or graphite) is measured at a point using calorimetric techniques and used to determine the Fricke detector dose calibration coefficient, 1/(εG) Fe 3+ .…”

“…Feist's [71] original uncertainty analysis led to a 1.02% uncertainty (k = 2) to the absorbed dose at 60 Co derived from the total absorption experiment at 5.6 MeV electrons. The major contributors to this uncertainty are the uncertainty of the primary electron energy (0.2%), the assumption of (εG) Fe 3+ being the same at 5.6 MeV and 60 Co (0.3%) and the uncertainty in the energy loss corrections (0.19%).…”

An Experimental Method for Determining the Heat Defect of Water Using Total Absorption of High-energy Electrons

“…The radiation energy transferred to the absorber is determined as the product of the mean kinetic energy and the number of incident electrons. A similar method of measurement also forms the basis of the realization of the unit of absorbed dose for highenergy photons and electrons [9] by means of the Fricke chemical method.…”

CCRI supplementary comparison of standards for absorbed dose to water in 60Co gamma radiation at radiation processing dose levels

“…The dosimeters were returned immediately to the issuing institutes with information on irradiation temperatures but no information on dose estimates. By January 1999, all irradiating laboratories and both Feist (1982) and Schneider (2002) a No irradiator employed; alanine transfer dosimeters irradiated directly in 60 Co reference field. b Although the IAEA secondary standard ionization chamber is traceable to the BIPM, the high-dose field is traceable to the NPL.…”