Comparison of the standards for absorbed dose to water of the NPL, United Kingdom and the BIPM for⁶⁰Co γ rays

Abstract

A comparison of the standards for absorbed dose to water of the National Physical Laboratory (NPL), United Kingdom and of the Bureau International des Poids et Mesures (BIPM) has been made in 60 Co gamma radiation under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result, based on the calibration coefficients for two transfer standards and expressed as a ratio of the NPL and the BIPM standards for absorbed dose to water, is 0.9980 (0.0064). The degrees of equivalence for the NPL and the other participants in this comparison have been calculated and the results are given in the form of a table for the eleven national metrology institutes (NMIs) that have taken part in the ongoing comparison for absorbed dose to water. A graphical presentation is also given.

New standards of absorbed dose to water under reference conditions by graphite calorimetry for60Co and high-energy x-rays at LNE-LNHB

“…A recent review of the different methods to measure photon absorbed dose can be found in the literature [1]. Some of the NMIs use water calorimetry (METAS-Switzerland, NIST-USA, NRCC-Canada, PTB-Germany, VSL-Netherlands [2][3][4][5][6][7][8][9][10]) and others use graphite calorimetry (BIPM, ARPANSA-Australia, BEV-Austria, ENEA-INMRI-Italy, NMIJ-Japan, NPL-United Kingdom, VNIIFTRI-Russia [11][12][13][14][15][16][17][18][19][20][21][22][23][24]).…”

Temperature dependence of cavity ionization chamber response

“…Considering that the uncertainty level is greater than 2 parts in 10 3 for the primary standards of air kerma and absorbed dose [23][24][25], the standard uncertainty of the temperature coefficients is minor and is essentially negligible as it is combined to obtain the overall uncertainty in the key comparison measurements with those chambers among the national metrology institutes. The present value of the graphite chamber is in agreement with that of Mayo and Gottschalk within the measurement uncertainty [7].…”