Search results for "Radiation"
showing 10 items of 5298 documents
Dosimetry in mixed gamma–neutron radiation fields and energy compensation filters for CaF2:Tm TL detectors
2008
Abstract Strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) show a relatively small gamma dose. However, for accurate dose estimation, both the neutron as well as the gamma component has to be considered. Different approaches have been studied with various thermoluminescence detectors (TLDs). As a result, CaF2:Tm detectors (TLD-300) are attributed to be most insensitive to thermal neutrons but not tissue-equivalent. In this paper we focus on the measurement of the gamma dose with TLD-300 in mixed irradiation fields. To overcome the disadvantage of being not tissue-equivalent, a study on energy compensation filters was performed. The paper compr…
Image enhancement in photoemission electron microscopy by means of imaging time-of-flight analysis
2004
Abstract Photoemission electron microscopy (PEEM) is widely used in combination with synchrotron sources as a powerful tool to observe chemical and magnetic properties of metal and semiconductor surfaces. Presently, the resolution limit of these instruments using soft-X-ray excitation is limited to about 50 nm, because of the chromatic aberation of the electron optics used. Various sophisticated approaches have thus been reported for enhancing the spatial resolution in photoemission electron microscopy. This work demonstrates the use of a simple imaging energy filter based on electron time-of-flight (ToF) selection. The spatial resolution could be improved dramatically, even though the inst…
EPR of molybdenum-related defect in CdWO4 crystal
1998
Abstract EPR spectra of a molybdenum-related structure defect have been observed at a temperature of 20 K in CdWO 4 scintillator crystal, being as-grown “blue-coloured”. Mo 95 and Mo 97 isotope superhyperfine ( shf ) splittings have been resolved. Further splittings in EPR spectra have been interpreted as arising from shf interactions with W nuclea. In the present model of the defect, the unpaired spin is localised in the Cd-site position and molybdenum replaces one of the neighbouring W atoms.
Quantitative online isolation of 68Ge from 68Ge/68Ga generator eluates for purification and immediate quality control of breakthrough
2013
The breakthrough of ⁶⁸Ge from a ⁶⁸Ge/⁶⁸Ga-generator is one of the most sensitive parameters in the context of the clinical application of ⁶⁸Ga-radiopharmaceuticals. The difficulty in its determination lies in the "spectroscopic invisibility" of ⁶⁸Ge within an excess of ⁶⁸Ga. The introduced method for determining the ⁶⁸Ge content of the ⁶⁸Ge/⁶⁸Ga-generator eluate involves the quantitative separation of ⁶⁸Ga from ⁶⁸Ge, using a cation-exchanger. The eluate contains ⁶⁸Ga free of ⁶⁸Ge, which can be determined immediately, i.e. prior to the application of the ⁶⁸Ga-radiopharmaceutical.
THERP and HEART integrated methodology for human error assessment
2015
Abstract THERP and HEART integrated methodology is proposed to investigate accident scenarios that involve operator errors during high-dose-rate (HDR) treatments. The new approach has been modified on the basis of fuzzy set concept with the aim of prioritizing an exhaustive list of erroneous tasks that can lead to patient radiological overexposures. The results allow for the identification of human errors that are necessary to achieve a better understanding of health hazards in the radiotherapy treatment process, so that it can be properly monitored and appropriately managed.
The energy transfer to the luminescence centers in PbWO4
1998
Abstract The luminescence spectra, rise and decay kinetics and the yield of luminescence in undoped PbWO 4 crystals were studied after pulsed electron beam irradiation. The luminescence intensity rise observed after irradiation pulse showed two mechanisms—excitonic relaxation and electron–hole recombination—were involved in the formation of the excited states of the blue luminescence centers. It is proposed that the excited states of WO 3 and WO 2− 4 luminescence centers were formed from some intermediate metastable state.
Electronic structure of terpene derivatives
1998
Abstract He I photoelectron spectra of terpene derivatives and their preparative intermediates have been measured. The changes of the ionization potentials are discussed in relation to the corresponding variations of the electronic structure. Especially, the effect of methyl and oxygen substitution has been studied.
Numerical expressions for the computation of coincidence-summing correction factors in γ-ray spectrometry with HPGe detectors
2009
Numerical expressions to compute gamma-gamma and gamma-X(K) coincidence summing corrections were deduced by using a suitable computer program and a matrix representation of a decay scheme. For point sources only full-energy peak and total efficiencies are needed. Alternatively, values of peak-to-total ratio can be introduced. For extended sources, the same expressions can be considered with the introduction of "effective efficiencies". Examples of the use of the expressions for point sources and a particulate filter sample measured with a 60% relative efficiency HPGe detector are reported.
TLM Nodes: A New Look at an Old Problem
2015
In this paper, an alternative perspective on the transmission line modeling (TLM) method concepts to unify previous work is presented. The procedure begins by discretizing Maxwell’s equations and proposing TLM equivalent models. Node voltage and mesh current definitions are provided in terms of link line contributions, compatible with stub currents and voltages. They allow obtaining an expression that relates incident and reflected pulses with no other condition required. With this unified approach, modeling of other situations is straightforward. 2-D cases, source implementation, and anisotropic media are described and numerically tested.
Advanced trap spectroscopy using the glow rate technique based on bleaching of color centers
2001
Abstract The glow rate technique (GRT) is the extension of the known heating rate method to the full glow curve. The GRT like the fractional glow technique (FGT) offers a procedure for evaluation of the mean activation energy as a function of temperature in the case of arbitrary thermostimulated relaxation kinetics represented by trap distribution function. The experimental procedure involves at least two subsequent measurements of thermostimulated recombination kinetics at different heating rates. The extension of the GRT to the direct measurements of thermostimulated bleaching of the radiation-induced color centers is presented. The experimental procedure involves measurements of the deca…