CONVERSION COEFFICIENTS FROM AIR KERMA TO DIRECTIONAL DOSE EQUIVALENT H′(0.07) FOR PHOTONS

Abstract New conversion coefficients from air kerma free-in-air, Ka, to directional dose equivalent at 0.07mm depth, H′(0.07), are provided for monoenergetic values and for the spectra of the radiation qualities defined in ISO 4037-1. The interpolation procedure of the monoenergetic conversion coefficients from ICRU Report 57 was improved compared to former publications. The values resulting from the new interpolation procedure describe the energy dependence of the conversion coefficients more accurately and differ by up to 5% between 50keV and 100keV from former values. Due to an additional change of the extrapolation to low energies, the values for angles of radiation incidence above 60° and energies below 40keV changed by up to 50%. The influence on the spectrum weighted conversion coefficients is similar to the changes of the monoenergetic values.

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INFLUENCE OF NEW MASS ENERGY-ABSORPTION COEFFICIENTS FROM ICRU REPORT NO. 90 ON AIR KERMA TO DOSE EQUIVALENT CONVERSION COEFFICIENTS

Radiation Protection Dosimetry ◽

10.1093/rpd/ncy213 ◽

2018 ◽

Vol 185 (1) ◽

pp. 27-33

Author(s):

Katharina Bairlein ◽

Oliver Hupe

Keyword(s):

Energy Absorption ◽

Radiation Protection ◽

Cross Sections ◽

Mass Energy ◽

Dose Equivalent ◽

Absorption Coefficients ◽

X Ray ◽

Air Kerma ◽

Conversion Coefficients ◽

Operational Quantities

Abstract In Report No. 90 of the International Commission on Radiation Units and Measurements (ICRU), new mass energy-absorption coefficients are listed which are based on renormalized Scofield photoeffect cross-sections. The mass energy-absorption coefficients are the basis for the conversion coefficients from air kerma to the operational quantities listed in ISO 4037-3. Although ICRU does not give a recommendation if these new mass energy-absorption coefficients should be applied instead of the values used so far, an examination of the possible consequences for radiation protection quantities is necessary. We calculated the conversion coefficients for the X-ray qualities specified in ISO 4037-1 with the new mass energy-absorption coefficients and with the mass energy-absorption coefficients used so far to determine the deviations. Our calculations show that the change of the conversion coefficients due to the new values from ICRU Report No. 90 is negligible.

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DEVELOPMENT OF A NEW SECONDARY STANDARD FOR H*(10)

Radiation Protection Dosimetry ◽

10.1093/rpd/ncz296 ◽

2020 ◽

Vol 188 (3) ◽

pp. 378-382

Author(s):

K Bairlein ◽

B Behnke ◽

O Hupe

Keyword(s):

Ionization Chamber ◽

Secondary Standard ◽

Dose Equivalent ◽

Air Kerma ◽

Radiation Fields ◽

Ambient Dose Equivalent ◽

Conversion Coefficients ◽

Aluminium Coating ◽

Pulsed Fields ◽

Ambient Dose

Abstract A secondary standard for ambient dose equivalent, H*(10), is necessary for the dissemination of the unit Sievert (Sv), but there is no such standard commercially available currently. Furthermore, the measurement of H*(10) instead of calculating H*(10) from air kerma and conversion coefficients is needed for unknown radiation fields. We developed a prototype of a new secondary standard for H*(10) based on a spherical 1 l ionization chamber for air kerma. This chamber was modified with copper wires at the inner surface to adjust the response of the chamber according to H*(10). Additionally, a Makrolon shell and an aluminium coating were added to optimize the response at energies below 50 keV. The prototype fulfils the requirements given in ISO 4037-2 in the energy range from 12 keV to 7 MeV. In combination with an electrometer, it can be used as area dosemeter, suitable for pulsed fields and for low energy radiation.

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