TSEE RESPONSE OF BEO THIN-FILM DETECTORS IRRADIATED ON ISO ROD PHANTOMS TO PHOTONS AND BETA-RADIATION

Working Group 2 of the International Organization for Standardization (ISO) recommends a cylindrical PMMA (rod) phantom of 19 mm in diameter for the calibration of extremity dosemeters. Exoelectron emitting BeO thin him detectors on graphite substrates, covered with a polypyrrole foil of 6.7 mg.cm(-2), were exposed on this rod phantom to photons an d beta radiation for response assessment. Exposures to photons were ca rried out with heavily filtered X rays of various energies, Cs-137 and Co-60, exposures to beta radiation with Sr-90/Y-90, Tl-204 and Pm-147 . For perpendicular radiation incidence the results are related to mea surements free-in-air. the angular dependence of the response to photo ns is compared with calculated data of H-p(0.07,alpha). For beta radia tion the measured H-p(0.07,alpha) values are, within the margins of me asurement uncertainty, comparable with the corresponding values achiev ed on the commonly used slab phantom. Certain discrepancies at larger angles of radiation incidence are caused by attenuation and scattering effects at the substrate side wall of 0.4 mm height around the TSEE s ensitive plane.