Effects of the particle sizes and concentrations on the X-ray absorption by CuO compounds

This work presents a study on the effects of the particle size, material concentration and radiation energy on the X-ray absorption. CuO nanoparticles and microparticles were incorporated separately into a polymeric resin in concentrations of 5%, 10% and 30% relative to the resin mass. X-ray absorption by these materials was analyzed with a CdTe detector. The X-ray absorption is higher for the nanostructured material compared to the microstructured one for low energy X-ray beams for all CuO concentrations. (c) 2011 Elsevier Ltd. All rights reserved

X-ray spectroscopy applied to radiation shielding calculation in mammography

The protective shielding design of a mammography facility requires the knowledge of the scattered radiation by the patient and image receptor components. The shape and intensity of secondary x-ray beams depend on the kVp applied to the x-ray tube, target/filter combination, primary x-ray field size, and scattering angle. Currently, shielding calculations for mammography facilities are performed based on scatter fraction data for Mo/Mo target/filter, even though modern mammography equipment is designed with different anode/filter combinations. In this work we present scatter fraction data evaluated based on the x-ray spectra produced by a Mo/Mo, Mo/Rh and W/Rh target/filter, for 25, 30 and 35 kV tube voltages and scattering angles between 30 and 165 degrees. Three mammography phantoms were irradiated and the scattered radiation was measured with a CdZnTe detector. The primary x-ray spectra were computed with a semiempirical model based on the air kerma and HVL measured with an ionization chamber. The results point out that the scatter fraction values are higher for W/Rh than for Mo/Mo and Mo/Rh, although the primary and scattered air kerma are lower for W/Rh than for Mo/Mo and Mo/Rh target/filter combinations. The scatter fractions computed in this work were applied in a shielding design calculation in order to evaluate shielding requirements for each of these target/filter combinations. Besides, shielding requirements have been evaluated converting the scattered air kerma from mGy/week to mSv/week adopting initially a conversion coefficient from air kerma to effective dose as 1 Sv/Gy and then a mean conversion coefficient specific for the x-ray beam considered. Results show that the thickest barrier should be provided for Mo/Mo target/filter combination. They also point out that the use of the conversion coefficient from air kerma to effective dose as 1 Sv/Gy is conservatively high in the mammography energy range and overestimate the barrier thickness. (c) 2008 American Association of Physicists in Medicine

Spectroscopy of the gamma and X ray leakage radiation from the built-in sources of a Riso TL/OSL reader

In this work we evaluate the intensity and the spectral shape of the leakage radiation from the built-in beta and alpha sources of a Riso TL/OSL reader. LiF (TLD-100), fluorite-based pellets and Al2O3:C detectors were used in order to determine the dose rate delivered to the dosimeters when the sources are closed. the leakage spectra under both alpha and beta sources were registered with a CdTe semiconductor detector. the spectrum measured under the beta source shows the X-ray beam generated by the interaction of the beta particles with the lead used to shield the source. Besides, the 59.4 keV gamma ray from Am-241 was registered under the alpha source. Dose rates from 50 to 100 mu Gy/h were obtained for the dosimeter positions in the turntable under the beta and the alpha sources with the luminescent dosimeters. (C) 2014 Elsevier B.V. All rights reserved.Univ São Paulo, Inst Fis, BR-05508090 São Paulo, BrazilUniversidade Federal de São Paulo, BR-09972270 Diadema, BrazilUniv Estadual Campinas, Fac Engn Eletr & Comp, BR-11050031 Campinas, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, BR-09972270 Diadema, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, BR-04023062 São Paulo, BrazilWeb of Scienc