NUKLEONIKA 2012, 57(4):507-512

 


APPLICATIONS OF LiF:Mg,Cu,P (MCP-N) THERMOLUMINESCENT DETECTORS (TLD) FOR EXPERIMENTAL VERIFICATION OF RADIAL DOSE DISTRIBUTION MODELS



Wojciech Gieszczyk, Paweł Olko, Paweł Bilski, Leszek Grzanka, Barbara Obryk,
Tomasz Horwacik

The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN),
152 Radzikowskiego Str., 31-342 Kraków, Poland

In track structure theory, the radial distribution of dose, D(r), around an ion track plays a fundamental role in predicting the response of biological systems and physical detectors after a dose (or fluence) of ions. According to the formulations of i>D(r), the local dose at radial distances below 1 nm can reach values as high as 106 Gy. We propose a new method of verifying experimentally the radial dose distribution around alpha-particle tracks, using LiF:Mg,Cu,P (MCP-N) thermoluminescent detectors (TLD) which are able to measure gamma-ray doses in the kGy range via evaluation of their high-temperature TL glow peak structure over the temperature range of 350–550°C. MCP-N detectors were irradiated with Am-241 alpha-particles at fluences ranging from 107 to 1011 particles/cm2, and by Co-60 gamma-ray doses ranging from several Gy up to the MGy. A number N of individual high-temperature TL peaks were analysed in the obtained glow curves by deconvolution, using the GlowFit code. For each of these peaks, an equation relating the intensity, A, of the TL signal obtained after alpha-particle irradiation and after gamma-ray doses, via the dose-frequency function, falpha(D), was written in the form: Aalphai = Aalphai(D.falpha(DdD, i = 1, ..., N. Using this set of N equations, where Aalphai and Agammai(D) were known (measured), the single unknown function falpha(D) was unfolded and converted to D(r). Parametric unfolding and the SAND-II iterative code were applied. While we were able to confirm the 1/r2 dependence of D(r) in agreement with D(r) expressions, we were unable to conclusively evaluate the dependence of D(r)) at intermediate ranges of radial distance r. This preliminary result of our unique experimental approach to determine the radial dose distribution around the path of heavy charged particles in LiF detectors, requires further development.

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