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Marina F Koskinas

Publications and source records attributed to Marina F Koskinas.

10 recordsLinked to original sources
PubMed2006

Application of Monte Carlo simulation to the prediction of extrapolation curves in the coincidence technique.

A technique for simulating all detection processes in a 4pi(beta,e,X)-gamma coincidence system by means of the Monte Carlo technique is described. This procedure yields a more realistic behaviour of the extrapolation curve as compared to the usual polynomial fit. The present paper describes its application to the standardisation of a typical pure beta emitter, namely 35S, by the efficiency tracing technique, and an EC-gamma radionuclide, namely 133Ba. The calculated extrapolations were compared to experimental values obtained at the IPEN.

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PubMed2006

Primary standardization of 72Ga.

The activity of 72Ga sources produced by irradiation at the IEA-R1 reactor have been performed in a 4pibeta-gamma coincidence system by using the extrapolation technique. The measurements were undertaken selecting two windows in the gamma-channel, in order to check the consistency of the results. A Monte Carlo calculation was performed in order to predict the behavior of the observed activity as a function of the 4pibeta detector efficiency and the results were compared to experimental values.

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PubMed2004

Automatic system for ionization chamber current measurements.

The present work describes an automatic system developed for current integration measurements at the Laboratório de Metrologia Nuclear of Instituto de Pesquisas Energéticas e Nucleares. This system includes software (graphic user interface and control) and a module connected to a microcomputer, by means of a commercial data acquisition card. Measurements were performed in order to check the performance and for validating the proposed design.

Journal Article↗
PubMed2003

Standardization of a 204Tl radioactive solution.

The standardization of 204Tl is described. The efficiency tracing technique was applied using 134Cs as tracer. The 4(pi)beta-gamma coincidence system was used for the calibration. The (Laboratorio de Metrologia Nuclear) has participated in this comparison in collaboration with the Laboratório Nacional de Metrologia das Radiações Ionizantes, from Rio de Janeiro. Independent results using different techniques were developed by each of these laboratories and included in the comparison.

Journal Article↗
PubMed2003

Coincidence system for standardization of radionuclides using a 4pi plastic scintillator detector.

A coincidence system using a plastic scintillator detector in 4pi geometry has been developed and applied for the standardization of radionuclides. The scintillator shape and dimensions have been optimized for maximum charge particle detection efficiency, while keeping background low and a nearly constant gamma-ray efficiency for different points from the radioactive source. The gamma-ray events were measured with a NaI(Tl) scintillation counter. The electronic system for processing pulses consisted of logic gates and delay modules feeding a time-to-amplitude converter with output to a multichannel analyzer. The alpha detection efficiency measured with 241Am was around 95% and the beta detection efficiency for 60Co was around 67%. Activity measurements of 241Am and 60Co were performed and the results showed good agreement when compared with a conventional coincidence system employing a 4pi proportional counter.

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PubMedDate not supplied

Developing 152Eu into a standard for detector efficiency calibration.

A gamma-gamma coincidence experiment was performed to check the 152Eu 13-year decay scheme and the placement of the observed gamma-ray transitions. The multi-detector array for residual activity measurement of the Linear Accelerator Laboratory was used. The source activity was 1 MBq, and about 10(9) coincidence events were observed. About 30 gamma's were placed in the decay scheme and four 152Sm levels were added to the previously known set of levels fed in 152Eu 13-year decay.

Calibration↗
PubMedDate not supplied

Standardization of 241Am solution.

The standardization of 241 Am solution has been undertaken using a 4pibeta-gamma coincidence system. The 4pi proportional counter used for alpha detection has a 0.1 mm thick Al window in the outside wall in order to minimize gamma-ray attenuation. The extrapolation technique was applied to determine the activity of the solution. The variation of alpha efficiency has been made using external absorbers and by the electronic discrimination. The results from the two methods were compared and are in agreement within the experimental uncertainty.

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PubMedDate not supplied

Cascade summing corrections for HPGe spectrometers by the Monte Carlo method.

Cascade summing corrections for application in HPGe gamma ray spectrometry have been calculated numerically by the Monte Carlo method. An algorithm has been developed which follows the path in the decay scheme from the starting state at the precursor radionuclide decay level, down to the ground state of the daughter radionuclide. With this procedure, it was possible to calculate the cascade summing correction for all gamma ray transitions present in the decay scheme. Since the cascade correction requires the values of peak and total detection efficiencies, another code has been developed in order to estimate these parameters for point and cylindrical sources. The radionuclides 60Co, 133Ba and 131I were used for testing the procedure. The results were in good agreement with values in the literature.

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PubMedDate not supplied

Disintegration rate measurement of a 152Eu solution.

The procedure followed by the Laboratório de Metrologia Nuclear at the IPEN-CNEN/SP, in São Paulo, for the standardization of 152Eu is described. The disintegration rate of 152Eu has been measured using the 4pi beta-gamma coincidence technique, using a 4pi proportional counter, filled with P-10 gas and operated at 0.1 MPa, coupled to one HPGe detector for the gamma-ray emission. Two discrimination windows were set in the gamma-channel, one related to the beta branch (344 keV) and the other related to the electron capture events (1408.03 keV), in order to determine the counting efficiencies for beta, X-ray and Auger electron events in the proportional counter. The activity of solution was determined by a biparametric extrapolation curve obtained for the two selected gamma-windows.

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