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Proposed specification for a primary standard of air kerma for 60Co, 137Cs and 192Ir -ray sources.

Angliss, R F; Moretti, C J; Nutbrown, R F (2001) Proposed specification for a primary standard of air kerma for 60Co, 137Cs and 192Ir -ray sources. NPL Report. CIRM 53

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Abstract

The three cavity chambers, the mean response of which constitutes the primary standard of sir kerma for 60Co and 137Cs -rays in the United Kingdom, have been in continuous, almost daily, use at the National Physical Laboratory (NPL) since 1956.
These chambers were initially designed for use with 2 MV X-rays at therapy level air kerma rates. However since 1978 that have also been used for protection level air kerma rates, initially, with X-rays generated at 1 MV and 2 MV and more recently with 60Co and 137Cs -rays. They have been used for therapy level air kerma calibrations with 60Co -rays since 1997 following the demise of the NPL 2 MV Van de Graaff generator.
This report describes the proposals for a new primary standard and methods that will be used to give better performance than the present standard when used with air kerma rates from as high as 1 Gy min-1 down to 10 mGy hr-1. The design will also seek to ensure that the standard will be capable of providing traceably calibration for 192Ir high doserate brachytherapy sources.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CIRM 53
Keywords: primary standard, cavity chambers, air kerma, protection levels, therapy levels, radiology, brachytherapy, ionisation chamber, dosimetry
Subjects: Ionising Radiation
Ionising Radiation > Dosimetry
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/2410

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