The conversion coefficients from air kerma to ICRU operational dose equivalent quantities for
ENEA’s realization of the X-radiation qualities L10-L35 of the ISO “Low Air Kerma rate” series
(L), N10-N40 of the ISO “Narrow spectrum” series (N) and H10-H60 of the ISO “High Air-kerma
rate” (H) series and two beams at 5 kV and 7.5 kV were determined by utilising X-ray spectrum
measurements.
The pulse-height spectra were measured using a planar high-purity germanium spectrometer
(HPGe) and unfolded to fluence spectra using a stripping procedure then validate with using Monte
Carlo generated data of the spectrometer response.
HPGe portable detector has a diameter of 8.5 mm and a thickness of 5 mm. The entrance window of
the crystal is collimated by a 0.5 mm thick Aluminum ring to an open diameter of 6.5 mm. The
crystal is mounted at a distance of 5 mm from the Berillium window (thickness 25.4 micron).
The Monte Carlo method (MCNP-4C) was used to calculate the efficiency, escape and Compton
curves of a planar high-purity germanium detector (HPGe) in the 5-60 keV energy. These curves
were used for the determination of photon spectra produced by the X-ray machine SEIFERT
ISOVOLT 160 kV in order to allow a precise characterization of photon beams in the low energy
range, according to the ISO 4037. The detector was modelled with the MCNP computer code and
validated with experimental data.
To verify the measuring and the stripping procedure, the first and the second half-value layers and
the air kerma rate were calculated from the counts spectra and compared with the values measured
using an a free-air ionization chamber. For each radiation quality, the spectrum was characterized
by the parameters given in ISO 4037-1. The conversion coefficients from the air kerma to the ICRU
operational quantities Hp(10), Hp(0.07), H’(0.07) and H*(10) were calculated using monoenergetic
conversion coefficients. The results are discussed with respect to ISO 4037-4, and compared with
published results for low-energy X-ray spectra.
The main motivation for this work was the lack of a treatment of the low photon energy region
(from a few keV up to about 60 keV).
| Identifer | oai:union.ndltd.org:unibo.it/oai:amsdottorato.cib.unibo.it:884 |
| Date | 19 June 2008 |
| Creators | Mariotti, Francesca <1976> |
| Contributors | Fantuzzi, Elena |
| Publisher | Alma Mater Studiorum - Università di Bologna |
| Source Sets | Università di Bologna |
| Language | Italian |
| Detected Language | English |
| Type | Doctoral Thesis, PeerReviewed |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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