Lighea Pappalardo

Macro and Micro Full Field X-Ray Fluorescence with an X-Ray Pinhole Camera Presenting High Energy and High Spatial Resolution

This work describes a tabletop (50 cm × 25 cm × 25 cm) full field X-ray pinhole camera (FF-XPC) presenting high energy- and high spatial-resolution. The FF-XPC consists of a conventional charge-coupled device (CCD) detector coupled, in a coaxial geometry, to a pinhole collimator of small diameter. The X-ray fluorescence (XRF) is induced on the samples with an external low-power X-ray tube. The use of the CCD as an energy dispersive X-ray detector was obtained by adopting a multi-image acquisition in single photon counting and by developing a processing algorithm to be applied in real-time to each of the acquired image-frames. This approach allowed the measurement of X-ray spectra with an energy resolution down to 133 eV at the reference value of 5.9 keV. The detection of the X-ray fluorescence through the pinhole-collimator allowed the two-dimensional elemental mapping of the irradiated samples. Two magnifications (M), determined by the relative sample-pinhole-CCD distances, are used in the present setup. A low value of M (equal to 0.35×) allows the macro-FF-XRF of large area samples (up to 4 × 4 cm(2)) with a spatial resolution down to 140 μm; a large magnification (M equal to 6×) is used for the micro-FF-XRF of small area samples (2.5 × 2.5 mm(2)) with a spatial resolution down to 30 μm.

Real-time elemental imaging of large dimension paintings with a novel mobile macro X-ray fluorescence (MA-XRF) scanning technique

A novel mobile macro-XRF (MA-XRF) scanning technique allowing real-time elemental imaging is presented for the investigation of macroscopic paintings. The instrument is based on a microfocus X-ray tube focused with a polycapillary and two SDD detectors operated simultaneously in a time-list event mode. The scanner is based on a three-axis system covering a dimension of 110 × 70 × 20 cm3. MA-XRF scanning is generally performed by positioning samples out of the polycapillary focus with the primary X-ray beam presenting a spot size in the range of hundreds of microns. However, a lateral resolution of up to 25 μm can be achieved at the focus position, allowing complementary use of the scanner for both micro-XRF and macro-XRF mapping. Scanning of artworks is performed with a maximum continuous speed of 100 mm s−1. The full area is covered in 4.3 h in the case of final images presenting a 500 μm pixel size (i.e., corresponding to a dwell time per pixel of 5 ms). The system is controlled with a custom developed control unit (CU) including a graphical user interface (GUI) programmed in Labview for real-time control of all sensors in the scanner and for real-time elaboration of X-ray data. X-ray spectra are processed during the scanning by the least square fast fitting procedure developed in PyMCa and integrated in the system. Up to 7000 fitted spectra per second are possible. A number of editing, processing and mathematical tools are available to users in the GUI and can be applied in a live mode to the forming elemental images. The sum spectrum and maximum pixel spectrum are continuously updated. Final images are available at the end of the scanning and, in most of the cases, they are ready for the interpretation.

The Polychromy of Nasca Pottery: A Nondestructive Analytical Approach for Compositional and Mineralogical Investigation of Pigments

Some new considerations about the characterization of pigments on polychromatic Nasca pottery by the use of PIXE-alpha and XRD nondestructive and in situ techniques are presented. The investigation, in particular, is focused on the compositional study of painted surfaces on selected archaeological Nasca fragments coming from the ceremonial center of Cahuachi in Southern Peru. Quantitative data are also discussed, with the aim of identifying the raw materials. A review of the nondestructive instruments and methods developed at the Laboratori Nazionali del Sud (LNS) of the Istituto Nazionale di Fisica Nucleare (INFN) and at the Istituto per i Beni Archeologici e Monumentali (IBAM) of Consiglio Nazionale delle Ricerche (CNR) is given. In particular, this article revisits the PIXE-alpha (Particle Induced X-ray Emission) system, based on the use of a 210Po radioactive-source-emitting alpha particles, the XRF (X-ray Fluorescence), and the micro XRF and XRD portable spectrometers. It also describes an analytical protocol for fully quantitative data, based on the combined use of the portable PIXE-alpha and XRD nondestructive techniques.

FF-XRF, XRD, and PIXE for the Nondestructive Investigation of Archaeological Pigments

This chapter discusses the integration of particle-induced X-ray emission (PIXE), full-field X-ray fluorescence (FF-XRF), and X-ray diffraction (XRD) for the analysis of archaeological pigments. It summarizes the research activity performed for developing these innovative, custom-built, and portable instruments. A novel analytical protocol has been developed by combining these techniques with the aim of performing an in situ quantitative characterization of painted materials. The potentiality of using this approach is demonstrated for manganese black used in archaeological pottery manufactured over time by different cultures.

Salerno Exultet: its characterization by Raman and PIXE-α analyses

Two non-destructive techniques, Raman spectroscopy and particle induced x-ray emission spectrometry, were used for a compete connotation of the Salerno Exultet, an illuminated parchment dated back to 13th century. The Salerno Exultet exhibits several areas which have underdone restoration treatments during the years. The complete connotation of this masterpiece was necessary in order to identify and to distinguish the original and the added pigments. Owing to its dimensions, it has been impossible to analyze the Salerno Exultet directly under the microscope of our Micro- Raman spectrometer. We have therefore used optical fibers connected to a three axis micro-positioned measurement head mounted on a large metal frame. PIXE analysis was performed using the portable instrumentation set up by the INFN-LANDIS Laboratory, Catania, Italy. The combination of these two complementary techniques allowed us to reveal a palette formed by lapis-lazuli, cinnabar, verdigris, earths organic lakes and chalk.