Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry

This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX 1076 phenols with and without low content (5\% by weight) of gadolinium oxide (Gd_2O_3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10^11 cm^-2 to 10^14 cm^-2}. Linearity of EPR response was found and the signal was compared with that of commercial alanine films. Our analysis showed that gadolinium oxide (5% by weight) can enhance the thermal neutron sensitivity more than 18 times. Irradiated dosimetric films of phenolic compound exhibited EPR signal fading of about 4% after ten days from irradiation.