Linearity studies of HD-810 dosimeters by light ion beams

Radiochromic films (RCF), also called GafChromic™ films, represent a performant material for accurate quantitative radiation dosimetry. Their compositions allow high dose sensitivity and fewer environmental dependence, giving a good feedback to the absorbed dose value and to the active media absorption, turning color upon being irradiated. The RCF take into account their reduced response near the Bragg peak due to a high linear energy transfer (LET). HD-810 GafChromic™ films are tissue-equivalent, have easy optical readings and can be employed for ion dosimetry in radio diagnostic and therapy and for industrial applications. Such dosimeters were employed at Tandetron-Nuclear Physics Institute (Řež, Czech Republic) to study the responses of helium, proton and carbon beams, commonly employed in radiotherapy and microelectronics. The sensitivity of the detector is low enough to measure multiple-beam exposures. The induced effects by the ions in the energy range of 600 keV to 2.0 MeV were investigated in terms of optical absorbance, measured in the irradiated active region of the polymer. The employed ion dose range was between 40 Gy and 2.5 kGy. The experimental results show that the absorbance increases with the irradiation time (i.e. with the absorbed dose). The absorbance induced in the radio chromic film was measured at 673 nm, at which is observed the highest sensitivity of the films. Such data, together with the dose linearity and the dependence on the ion stopping power will be presented and discussed.