Radiation damage study of thin YAG:Ce scintillator using low-energy protons

摘要

Radiation hardness of a 50 μm thin YAG:Ce scintillator in a form of dependence of a signal efficiency on 3.1 MeV proton fluence was measured and analysed using X-ray beam. The signal efficiency is a ratio of signals given by a CCD chip after and before radiation damage. The CCD chip was placed outside the primary beam because of its protection from damage which could be caused by radiation. Using simplified assumptions, the 3.1MeV proton fluences were recalculated to: ? 150 MeV proton fluences with intention to estimate radiation damage of this sample under conditions at proton therapy centres during medical treatment, ? 150 MeV proton doses with intention to give a chance to compare radiation hardness of the studied sample with radiation hardness of other detectors used in medical physics, ? 1 MeVneutron equivalent fluences with intention to compare radiation hardness of the studied sample with properties of position sensitive silicon and diamond detectors used in nuclear and particle physics. The following results of our research were obtained. The signal efficiency of the studied sample varies slightly (±3%) up to 3.1 MeV proton fluence of c. (4 - 8) × 10~(14) cm~(-2). This limit is equivalent to 150 MeV proton fluence of (5 - 9) × 10~(16) cm~(-2), 150 MeV proton dose of (350 - 600) kGy and 1 MeV neutron fluence of (1 - 2) × 10~(16) cm~(-2). Beyond the limit, the signal efficiency goes gradually down. Fifty percent decrease in the signal efficiency is reached around 3.1 MeV fluence of (1 - 2) × 10~(16) cm~(-2) which is equivalent to 150 MeV proton fluence of around 2 × 10~(18) cm~(-2), 150 MeV proton dose of around 15MGy and 1 MeV neutron equivalent fluence of (4 - 8) × 10~(17) cm~(-2). In contrast with position sensitive silicon and diamond radiation detectors, the studied sample has at least two order of magnitude greater radiation resistance. Therefore, YAG:Ce scintillator is a suitable material for monitoring of primary beams of particles of ionizing radiation.