Resumo de eventos cient??ficos
CaSO4:Dy and CaSO4:Ce,Eu intrinsic efficiencies dependence on ionizing radiation type and quality
Autor
NUNES, M.G.
VILLANI, D.
RODRIGUES, L.L. de C.
INTERNATIONAL CONFERENCE ON APPLICATIONS OF RADIATION SCIENCE AND TECHNOLOGY
Resumen
The dependence of a thermoluminescent (TL) dosimeter response to the type and quality
of radiation is a key issue that is being tackled worldwide by the development of new
dosimetric materials associated with this technique. In this context, the aim of the present
work is to evaluate the intrinsic efficiency of CaSO4:Dy, considered as the standard material,
and CaSO4:Ce,Eu, a newly developed TL material, for different ionizing radiation types
and energies. To do so, a batch of 55 dosimeters of each material was selected according
to their non-irradiated TL readout and intrinsic efficiency to the 60Co
-radiation on air
and electronic equilibrium conditions and then divided into eleven sets of five dosimeters,
one of the sets being kept as the control set to evaluate the non-irradiated TL signal while
the ten remaining sets were irradiated, again in air and electronic equilibrium conditions,
with doses ranging from 0:1 mGy to 10 Gy in secondary standards 60Co and 137Cs
-
radiation sources, RQR, RQA and RQT ISO/IEC 61267 series and N ISO 4037 series X-ray
beams, always including the reference quality for the radiation beam series, and tertiary
standard collimated electron beams with effective energies from 4 MeV to 20 MeV. AThermo
(Harshaw) 3500 thermoluminescent reader was used to evaluate TL readouts 24 h after
the irradiation and the obtained glow curves were exported in the ASC format through
WinREMS TL reader controller associated software. Individual peak intensity, integrated
response, peak to peak intensity ratio, calibration curves and intrinsic efficiency, provided
that all dosimeters are 0:8 mm thick pellets of 6:0 mm of diameter containing 16:67 mg of
TL material, were calculated with the aid of SciLab 5.5.2 software, also used to graphically
explore the behaviour of CaSO4:Dy and CaSO4:Ce,Eu intrinsic efficiencies with the radiation
type or the radiation quality. As expected from literature, CaSO4:Dy intrinsic efficiency
presented a dependence of up to 30% with radiation type or quality while CaSO4:Ce,Eu
intrinsic efficiency varied by 200% with radiation quality. Despite this huge dependence,
the CaSO4:Ce,Eu peak I to peak II intensity ratio remains stable with the radiation type and
varies by 5% from one radiation type to another, so that this newly developed TL material
can be used as a dosimeter capable of determining, in non-mixed radiation fields and after
an adequate and rigorous calibration, both radiation type and quality besides the dose.