Métodos analíticos não destrutivos para análise de obras de arte

A caracterização de objetos de arte e, ou, arqueológicos, por meio de métodos de análise elementar não destrutiva com feixes iônicos busca a identificação de elementos químicos presentes nas amostras por técnicas nucleares. Os métodos físicos e químicos estão na interface entre a ciência pura e as aplicações diretas para caracterização de bens culturais e é uma área interdisciplinar que demanda uma forte interação, que cresce a cada dia, entre especialistas. Nas pesquisas internacionais o uso destes métodos físicos e químicos, em especial as técnicas atômico-nucleares não destrutivas para o estudo de objetos arqueológicos, de arte e do patrimônio cultural está estabelecido há algumas décadas, mas na América Latina a utilização destas técnicas é relativamente recente, iniciada a partir da década de 1990 [M l]. As técnicas físicas atômico-nucleares podem ser utilizadas em diferentes aplicações como, por exemplo, caracterizar as modificações introduzidas na morfologia e composição elementar pelos processos de corrosão de metais expostos aos efeitos do meio ambiente, bem como para o exame de pinturas, pois a identificação dos elementos presentes nas camadas pictóricas por estas técnicas pode dar indicação dos pigmentos utilizados nas tintas. A aplicação destas técnicas ao estudo de materiais cerâmicos permite identificar elementos traço que podem contribuir para indicar a origem do material utilizado e características dos processos de fabricação de uma obra de arte, e, ou, os elementos presentes nas tintas de uma determinada pinturaThe characterizations of art and/or archaeological objects with non destructive elementary analytical methods with ionic beams explore the identification of the chemical elements presents in the samples using nuclear and atomic techniques. The chemical and physics methods are in the interface between pure science and direct application, in the characterization of the cultural heritage objects. They are also an interdisciplinary area which needs one strong interaction between specialists and increase each day. International researchers frequently use these physics and chemicals methods, principally the non-destructive ones, to analyze archaeological, art and cultural heritage objects and all these techniques were established some years ago. In Latin America the use of these techniques is relatively recently and was initialized in the 90 decade [1-11]. The atomic-nuclear techniques can be used on different applications as for example the characterization of the introduced modification in the morphology and the elementary composition in the metal due to the corrosion process as effect of the environmental exposition. As well as the pictures analysis thought the identification of the elements presents in the different multilayer pigments. The application of these techniques in ceramics analyses allows the identification of trace elements that can be contribute to identify the material origin used to fabricate this art object plus the elements in the pigments present on the ceramic

Decay chain differential equations: Solution through matrix algebra

A matricial method to solve the decay chain differential equations system is presented. The quantity of each nuclide in the chain at a time t may be evaluated by analytical expressions obtained in a simple way using recurrence relations. This method may be applied to problems of radioactive buildup and decay and can be easily implemented computationally. (C) 2009 Elsevier B.V. All rights reserved.CNP

Numerical analysis of an incremented statistical sampling procedure in MCNP

MCNP has stood so far as one of the main Monte Carlo radiation transport codes. Its use, as any other Monte Carlo based code, has increased as computers perform calculations faster and become more affordable along time. However, the use of Monte Carlo method to tally events in volumes which represent a small fraction of the whole system may turn to be unfeasible, if a straight analogue transport procedure (no use of variance reduction techniques) is employed and precise results are demanded. Calculations of reaction rates in activation foils placed in critical systems turn to be one of the mentioned cases. The present work takes advantage of the fixed source representation from MCNP to perform the above mentioned task in a more effective sampling way (characterizing neutron population in the vicinity of the tallying region and using it in a geometric reduced coupled simulation). An extended analysis of source dependent parameters is studied in order to understand their influence on simulation performance and on validity of results. Although discrepant results have been observed for small enveloping regions, the procedure presents itself as very efficient, giving adequate and precise results in shorter times than the standard analogue procedure. (C) 2007 Elsevier Ltd. All rights reserved

Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators

Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748519]FAPESPFAPESPCNPqCNPqCAPESCAPE