1,720,965 research outputs found
Development of automatic systems for the ionising radiation metrology at the ENEA-IRP secondary standard laboratory
No full textThe ENEA IRP Secondary Standard Dosimetry Laboratory of Bologna (Italy) has been operated for more than 30 y as a secondary standard laboratory for X rays, gamma, beta and neutron radiation metrology. For photon radiation, the instruments for radiation protection and clinical dosimetry are calibrated in agreement with the ISO standards, using remotely controlled irradiation units: two 60Co, one 137Cs and three X-ray units (160, 320 and 420 kV, respectively). The calibration procedures, approved by the National Primary Laboratory, have been recently implemented in a software package, which controls the irradiation units and acquires the reference measurements. The system, developed at the laboratory under the LabVIEW programming language, guarantees a constant surveillance of all devices and operations, avoids procedural mistakes and automates the record-keeping and reporting activities. This results in an increase in the reliability of the calibration service
Energy dependence of TLD-300 response from 6 keV up to 1250 keV
No full textThe energy dependence of the response function S(E), of CaF2:Tm (TLD-300) thermoluminescent material (3.2 x 3.2 x 0.90 mm3 ribbons) was measured from 6 keV up to 1250 keV (60Co) using 55Fe, 137Cs and 60Co gamma ray sources as well as X ray ISO reference beams. To the best knowledge of the authors the data for energies below 45 keV are reported for the first time. The S(E) function was also calculated in the energy range from 1 keV up to 20 MeV and compared with the experimental data. relative to the total glow curve. The comparison shows good agreement from 1250 keV down to 40 keV. At lower energy the discrepancy increases. This is interpreted in terms of the X ray attenuation within the thickness of TLD-300. Finally, measurements point out the effects of different reading and annealing treatments on the measured function S(E)
Developing a thermal neutron irradiation system for the calibration of personal dosemeters in terms of Hp(10)
No full textAt the ENEA Radiation Protection Institute in Bologna a thermal neutron irradiation facility is available for the calibration of neutron dosemeters. It consists of a 1 m x 1 m x 1 in polyethylene cube containing three 241 Am-Be sources of about 185 GBq. The cube contains three co-axial cylindrical calibration cavities of different dimension. Due to their limited dimensions, the cavities do not allow the calibration of thermal neutron personal dosemeters in terms of Personal Dose Equivalent Hp(d), that should be carried out on the.30 cm x 30 cm x 15 cm ISO phantom. The study herewith presented was addressed at adapting the facility for external irradiation of personal dosemeters on the ISO phantom. Extensive Monte Carlo studies were carried out to characterise the neutron fluence spatial distribution along the front face of the phantom. A satisfying neutron field homogeneity within the measurement area has been obtained by means of a pyramidal polyethylene fluence flattening filter and the selection of the proper cube to phantom distance. This new irradiation set-up was experimentally tested through measurements with activation foils, according to the spatial mapping array taken from the calculations
Field parameters and dosimetric characteristics of a fast neutron calibration facility: Experimental and Monte Carlo evaluations
No full textAt the ENEA Institute for Radiation Protection (IRP) the fast neutron calibration facility consists of a remote control device which allows locating different sources (Am-Be, Pu-Li, bare and D2O moderated 252Cf) at the reference position, at the desired height from the floor, inside a 10 x 10 x 3 m3 irradiation room. Either the ISO reference sources or the Pu-Li source have been characterised in terms of uncollided H*(10) and neutron fluence according to the ISO calibration procedures. A spectral fluence mapping, carried out with the Monte Carlo Code MCNPô, allowed characterising the calibration point, in scattered field conditions, according to the most recent international recommendations. Moreover, the irradiation of personal dosemeters on the ISO water filled slab phantom was simulated to determine the field homogeneity of the calibration area and the variability of the neutron field (including the backscattered component) along the phantom surface. At the ENEA Institute for Radiation Protection the calibration of neutron area monitors as well as personal dosemeters can now be performed according to the international standards, at the same time guaranteeing suitable conditions for research and qualification purposes in the field of neutron dosimetry
Monte Carlo Calculations of Field Parameters for the ICRU Sphere with Reference Photon Beams
No full textExperimental and Monte Carlo Evaluations of the Dosimetric Characteristics of a Thermal Neutron Calibration Assembly
No full textIn the present report a thermal neutron assembly for calibrating dosimetric instruments at the ENEA Radiation Protection Institute is described. The characterization of such a facility in terms of spectral neutron fluence rate and ambient dose equivalent rate according to the ICRP60 document is shown in detail. The developed study was aimed at characterizing all the components of the field inside the three calibration cavities placed within a polyethylene cube. Besides from the experimental point of view, the assembly was also numerically investigated by means of the Monte Carlo code MCNP. These techniques allowed to calculate, besides the dosimetric quantities to be compared with the experimental results, also the detailed neutron spectra along the cavities. Special variance reduction algorithms developed at ENEA allowed to obtain a satisfactory statistics for each energy group of the spectra
Characterizing a Thermal Neutron Calibration Assembly by Solid State, Nuclear Track Dosemeters and Monte Carlo Technique
No full textIn the present report a thermal neutron assembly consisting of a polyethylene cube for calibrating dosimetric instruments at the ENEA Institute for Radiation Protection is described The characterization of such a facility in terms of the spectral neutron fluence and the ambient dose equivalent rates according to the ICRP60 document is illustrated in detail. The study was aimed at characterizing all the components of the neutron and photon field inside the three calibration cavities placed within the polyethylene cube. This was experimentally investigated by means of solid state and nuclear track detectors and at the same time modelled with the Monte Carlo code MCNP. Besides allowing the experimental results to be compared with the calculated dosimetric quantities, this also permitted the detailed assessment of the neutron spectra along the calibration cavities. Special variance reduction algorithms developed at ENEA allowed satisfactory statistics to be obtained over the whole investigated energy domain
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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