Seminar of Dr Sam Webb

Dr Sam Webb is beamline scientist at the SSRL (Stanford Synchrotron Research Laboratory, Stanford University)

Abstract

ynchrotron based techniques are widely used for the analysis of complex materials, in part due to the high brilliance of the x-ray source and the ability to tune the x-ray energy.  While these characteristics often provide superior performance over traditional lab-based sources, it may also create problems with respect to the high photon flux and potential modification of the sample, which presents unique challenges to the stakeholders of cultural heritage experiments.
 
Paintings and paint pigments have been well studied by synchrotron-based techniques. While a wealth of information can be obtained through x-ray analysis, one must also be aware of radiation damage.  Of particular interest in this work is the chemistry of S moieties in lapis based ultramarine pigments, and As in emerald green pigments.  Results from earlier work show that the x-ray beam can alter these compounds under some experimental conditions.  Calculation of the doses applied and absorbed allows a kinetic analysis of the reactions, allowing an assessment on the acceptable amount of radiation exposure.  Multi-modal approaches utilize the power of multiple, complimentary techniques to better characterize samples as well as having the potential to elucidate mechanisms.  The difficulty in such approaches lies within the need to combine data sets from distinct experiments for a holistic analysis. This work will show some recent advances on how data registration and integration can be performed and highlight some example applications of multi-modal data analysis.