To compare the characteristics of imaging systems based on pixel detectors of different thickness, we have measured the respective imaging capabilities, spatial resolution and spectroscopic characteristics. Each system consists of a single photon counting chip, developed in the framework of the Medipix Collaboration, bump bonded to a silicon detector. The detector is a matrix of 64 x 64, square pixels, with 170 mu m pitch and thickness ranging from 300 to 800 mu m. As expected, the intrinsic detection efficiency increases with the detector thickness; nevertheless the spatial resolution can be affected by a charge sharing mechanism between adjacent pixels due to charge diffusion. The aim of the work reported in this paper is to demonstrate that, optimizing the settings of the image systems, we can increase the detection efficiency without losing in spatial resolution. RI Dalla Betta, Gian-Franco/I-1783-201
In this paper, results are reported on the analysis of a fragment of roman fresco, presumably dated from I century A.D. . The analysis of the pigments used in the fresco has been performed using the two complementary techniques of micro-LIBS and micro-Raman spectroscopy. Both the techniques allow for microscopic analysis of the samples: however, while micro-Raman spectroscopy gives information on the surface structure of the pigments and binders used, micro-LIBS gives quantitative information on the elemental composition of them, also allowing for stratigraphic analysis with lateral spatial resolution comparable to the micro-Raman technique. The joint use of i-LIBS and t-Raman spectroscopy allows for a complete characterization of the sample, and is particularly useful in cases when one of the techniques is not able to give by itself a clear information on the nature of the pigment under study.
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