Microdosimetric analysis of response of LiF:Mg,Cu,P (MCP-N) TL detectors for alpha-particles and ultra-high doses of gamma-rays

Several models of Radial Dose Distribution predict that in the track core of the heavy ion, at the radial distances closer than 1 nm the local dose can exceed 100 kGy, but this prediction has never been experimentally verified. Within this work MCP-N (LiF:Mg,Cu,P) thermoluminescence (TL) detectors, which show high temperature TL glow peak structure between 350 °C and 500 °C after exposure to doses of gamma-rays as high as 1 MGy, were irradiated with Am-241 α-particles with fluences 107–1011 particles/cm2. For fluences 9 × 109 cm−2 in MCP-N TL glow curves high temperature peaks were observed which confirmed that a fraction of energy of α-particles was transferred with the local doses exceeding 50 kGy. Calculation of dose (fluence) dependent microdosimetric distributions confirmed that at these fluences and target diameters of 80 nm high dose regions do not result from overlapping of tracks. It was estimated that approximately 20% of entire energy of 5.5 MeV α-particle penetrating LiF was deposited with local doses exceeding 50 kGy.