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Air kerma calibration factors and chamber correction values for PTW soft x-ray, NACP and Roos ionization chambers at very low x-ray energies.

Ipe, N E*; Rosser, K E; Moretti, C J; Manning, J W; Palmer, M J (2001) Air kerma calibration factors and chamber correction values for PTW soft x-ray, NACP and Roos ionization chambers at very low x-ray energies. Phys. Med. Biol., 46. pp. 2107-2117.

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Abstract

This paper evaluates the characteristics of ionization chambers for the measurement of absorbed dose due to water using very low-energy x-rays. The values of the chamber correction factor, kch, used in the IPEMB 1996 code of practice for the UK secondary standard ionization chambers (PTW type M23342 and PTW type M23344), the Roos (PTW type 34001) and NACP electron chambers are derived.
The responses in air of the small and large soft x-ray chambers (PTW type M23342 and PTW type M23344) and NACP and Roos electron ionization chambers were compared. Besides the soft x-ray chambers, the NACP and Roos chambers can be used for very low-energy x-ray dosimetry provided that they are used in the restricted energy range for which their response does not change by more than 5%.
The chamber correction factor was founded by comparing the absorbed dose to water determination using the dosimetry protocol recommended for low-energy x-rays with that for very low-energy x-rays. The overlap energy range was extended using data from Grosswendt and Knight. Chamber correction factors given in this paper are chamber dependent, varying form 1.037 to 1.066 for PTW type 23344 chamber, which is very different from the value of unity given in the IPEMB code. However, the values of kch determined in this paper agree with those given in the DIN standard within experimental uncertainty. The authors recommend that the very low-energy section of the IPEMB code is amended to include the most up-to-date values of kch.

Item Type: Article
Subjects: Ionising Radiation
Ionising Radiation > Dosimetry
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/2206

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