J.M. Gómez Ros

On the peculiarities of peak 4 in LiF TLD-100

Abstract A detailed study of the different glow curves that can be obtained from LiF TLD-100 is presented. This study has been made measuring glow curves after different preparation and readout conditions, and using computerized glow curve analysis to resolve individual glow peaks. In particular, the evolution of peak 4 has been carefully followed. This peak is detected with very different intensity, shape and temperature position depending on the characteristics of the cooling stage of the preparation thermal treatment, and also on the readout heating rate. After very fast cooling and also for fast readout, peak 4 is the most intense peak in the TLD-100 glow curve. The unique behaviour of peak 4 is discussed in the light of the current models for thermoluminescent processes.

Effects of simultaneous release of trapped carriers and pair production on fading in thermoluminescent materials during storage in radiation fields

A calculation of fading effects on the trapped charge population in a TL trap is presented when radiation-induced pair production and thermal raising of trapped charges occurs simultaneously. For the calculation, different time-intensity irradiation profiles have been employed, selected with reference to practical situations in radiation dosimetry. Different sets of TL trapping parameters have been employed to investigate the influence of the kinetic parameters (trap activation energy, frequency factor and retrapping-recombination cross-section ratio) on the stability of the trapped charges. The calculations presented here, which exclusively concern fading effects in a variety of practical situations, would help clarify the respective role of trap and charge effects in the stability of practical TL materials.

MCNPX CALCULATIONS OF SPECIFIC ABSORBED FRACTIONS IN SOME ORGANS OF THE HUMAN BODY DUE TO APPLICATION OF 133Xe, 99mTc and 81mKr RADIONUCLIDES

Monte Carlo simulations were performed to evaluate treatment doses with wide spread used radionuclides 133Xe, 99mTc and 81mKr. These different radionuclides are used in perfusion or ventilation examinations in nuclear medicine and as indicators for cardiovascular and pulmonary diseases. The objective of this work was to estimate the specific absorbed fractions in surrounding organs and tissues, when these radionuclides are incorporated in the lungs. For this purpose a voxel thorax model has been developed and compared with the ORNL phantom. All calculations and simulations were performed by means of the MCNP5/X code.