The effect of secondary electrons on the photon energy response of TL and TSEE detectors used for beta and photon dosimetry

For beta dosimetry, thin detectors and thin covering foils are used to indicate H(0.07). The photon energy response of these detectors is affected by the material of the detector, as well as of the dosemeter encapsulation. Experiments have shown that in the photon energy range 20 to 50 keV the relative response RY = R(E)/R(137Cs) for exposure was found to be unexpectedly high (RY = 1.85) for carbon loaded LiF in a finger ring from stainless steel and unexpectedly low (RY = 0.6) for thin TSEE-BeO detectors on a graphite substrate. Secondary electrons, produced in the surrounding materials, contribute significantly to the energy absorption in the thin detector and can be used as the base to optimise photon energy response. The contribution of secondary electrons from different materials in front of the detector was investigated using PE, PTFE, PVC, aluminium, copper and stainless steel. The effect of the dosemeter encapsulation on the photon response depends on the Z value of the material and was found to increase, also for LiF + 1%C, with the mass energy absorption coefficient of the covering material as discussed previously for TSEE-BeO. (author)