BeschreibungIn this study, the energy and angular response of the different filtered thermoluminescence (TL) detectors inside the personal radiation protection dosemeter of the Dosimetry Service Seibersdorf is investigated. The single detector element signals are combined for measuring personal dose equivalent, Hp(10), as independent of the incident photon energy and directional distribution as possible. Due to the planned reduction of the dosemeter size and the upcoming approval for the measuring quantity Hp(10), the comparison of measured and computationally calculated response is carried out to provide information about the quality of the results of both methods, experiment and simulation. The main goal of this work is to study the general applicability of the Monte Carlo method for simulating TL based dosemeters. The method is based on a semi-empirical TL efficiency function which relates simulated absorbed dose spectra averaged over the TL detector volume to the measured TL signal. The same mathematical approach of combining experimental and simulated results was already used for developing a new area dosemeter. A close to reality simulation model of the personal dosemeter badge was set-up according to technical drawings using the Monte Carlo N-Particle (MCNP-4C) code. The aluminium dosemeter card inside the plastic badge holds two to four TL detector elements between thin PTFE foils. The special packing foil which encloses the dosemeter card and which protects the TL detectors against environmental influences is also included in the modelling. Similar to the experimental calibration conditions, the simultaneous irradiation of a number dosemeters centred on the front surface of the ISO water slab phantom is simulated for calculating the Hp(10) response. ISO standard 4037 reference photon radiation qualities with mean energies between 24 keV and 1.3 MeV and corresponding conversion coefficients from air kerma to Hp(10) are used for both methods, experiment and simulation. The comparison of the simulated and measured relative Hp(10) energy response results in good agreement within some percent. Only for the metal filtered TL element for photon energies below about 50 keV, an increasing deviation of the simulated response values can be observed. A future revision of the TL efficiency including lower photon energy data is expected to further improve the results and the method for simulating personal dosemeter response.
|11 Apr. 2005 → 15 Apr. 2005
- Biosensor Technologies