Energy response of an aluminium oxide detector in kilovoltage and megavoltage photon beams: An EGSnrc Monte Carlo simulation study

A Monte Carlo study of the energy response of an aluminium oxide (Al2O3) detector in kilovoltage and megavoltage photon beams relative to Co-60 gamma rays has been performed using EGSnrc Monte Carlo simulations. The sensitive volume of the Al2O3 detector was simulated as a disc of diameter 2.85 mm and thickness 1 mm. The phantom material was water and the irradiation depth chosen was 2.0 cm in kilovoltage photon beams and 5.0 cm in megavoltage photon beams. The results show that the energy response of the Al2O3 detector is constant within 3% for photon beam energies in the energy range of Co-60 gamma rays to 25 MV X rays. However, the Al2O3 detector shows an enhanced energy response for kilovoltage photon beams, which in the case of 50 kV X rays is 3.2 times higher than that for Co-60 gamma rays. There is essentially no difference in the energy responses of LiF and Al2O3 detectors irradiated in megavoltage photon beams when these Al2O3 results are compared with literature data for LiF thermoluminescence detectors. However, the Al2O3 detector has a much higher enhanced response compared with LiF detectors in kilovoltage X-ray beams, more than twice as much for the case of 50 kV X rays.