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dc.contributor.authorAlmeida, Gevaldo Lisboa-
dc.contributor.authorSilviani, Maria Ines-
dc.contributor.authorFurieri, Rosanne C. A.-
dc.publisherInstituto de Engenharia Nuclearpt_BR
dc.subjectBeam divergencept_BR
dc.subjectThermal neutron beampt_BR
dc.subjectLine spread functionpt_BR
dc.titleEvaluation of the divergence of a thermal neutron beam using a position sensitive detectorpt_BR
dc.description.resumoThe divergence of the thermal neutron beam available at the main outlet channel of the Argonauta Reactor in the Instituto de Engenharia Nuclear has been measured by using a Position Sensitive Detector. The measurement process addressing a proper beam characterization has been conducted under several geometric arrangements, including attempts to reduce the beam divergence by using a honeycomb-type gadolinium collimator. Since the detector presents finite resolution, each measured position spectrum is a convolution of the true Rocking Curve expressing the beam divergence with the function that describes the detector response. Therefore, those spectra have been submitted to an unfolding process to recover the concealed Rocking Curve. Prior to undertake this task however, the detector Line Spread Function - LSF was determined as required by the unfolding process. This was done by taking the response of the detector to a line source simulated by a narrow slit-collimator placed at several distances from the detector window. After a Lorentzian fitting to the acquired position spectra, the related FWHM were plotted against the source-detector distance. An extrapolation to zero furnishes then the width of the unknown LSF expressed as a normalized Lorentz function, which was then incorporated to a computer program developed to perform the unfolding. The final Rocking Curve emerges then as a normalized Lorentzian function properly defined by its width and a zero offset, showing that the beam diverges about 2.2 cm in 1 meter. The honeycomb collimator could not reduce this divergence due to its low aspect ratio.pt_BR
dc.creator.affiliationInstituto de Engenharia Nuclear-
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