S.J. Fleming

Selective filtering in PIXE spectrometry

Abstract The Bartol Research Institutes PIXE facility has made extensive use of selective filters in the study of compositional patterns in archaeological artifacts. The purpose of such filtering is to reduce the intensity of the primary X-rays by up to two orders of magnitude. This allows for an equivalent increase in the beam current and a corresponding reduction in the detection limits for the higher Z trace elements. In this report we bring together all the filter combinations we currently use and discuss their purpose and effectiveness.

PIXE spectrometry in Archaeometry: The development of a system with high spatial resolution

Abstract A new PIXE facility has been constructed at the Bartol Foundation with a tightly-focused proton beam (typically 50 μm across) that allows a variety of inhomogeneous archaeological artifacts to be studied in spatial detail. This paper discusses the practical need for micro-PIXE research in archaeology — applications could include the analysis of metal residues in smelting slag, the solder joins of Classical jewelry, sound metal in corroded bronzes and individual color bands on core-formed glass vessels — and summarizes the role of the various components that comprise the facility itself.

Recent applications of PIXE spectrometry in archaeology I. Characterization of bronzes with special consideration of the influence of corrosion processes on data reliability

Abstract Long-term burial of bronze invariably results in a number of complex chemical processes through which the superficial layers of the metal are converted into cuprite and various kinds of copper chlorides and/or carbonates. Dependent upon the environmental conditions under which such conversions are achieved, minor and trace elements in the bronze are leached out of the bulk metal with varying degrees of efficiency, thereafter tending to accumulate among the corrosion products. We discuss the practicalities and problems involved in the PIXE analysis of ancient bronzes in a nondestructive way, with particular reference to artifacts from ancient Mesopotamia.

Roman mosaic glass: a study of production processes, using PIXE spectrometry

The most attractive Roman glass produced during the early part of the 1st century A.D. was mosaic ware ‐ bowls and dishes molded from arrays of multi-colored canes that created abstract floral and geometric designs. Yet ancient literature tells us little about the organization of the glassworking industry in which such wares were produced. We have focused upon two kinds of mosaic decoration that include a component of white glass in their cane construction and have purple glass as their matrix. A consistent pattern in the minor levels of lead in each kind of glass suggests that they were the products of two separate workshops, each with separate sources of supply for their glass stock. ” 1999 Elsevier Science B.V. All rights reserved.

Color additives and trace elements in ancient glasses: Specialized studies using PIXE spectrometry

Abstract This paper discusses the physical processes of proton induced X-ray emission (PIXE) spectrometry that underlie its general advantages as an analytical tool in the study of ancient glasses, and reviews the practical limitations met in the routine determination of certain elements (e.g., titanium in a calcium-rich matrix, arsenic and tin in an lead-rich matrix). Detection limits are given for 19 elements (minor and trace) that might characterize the source of raw materials used in the making of an ancient glass. Emphasis is laid upon how a controlled variation of the proton beams energy, together with the use of a wide variety of selective filters, allows certain background effects from the X-ray output of dominant matrix elements to be appreciably reduced. Applications include the study of brown and blue decorated glass vessels from the ancient Greek settlement site of Cyrene, in Libya.

The Bartol PIXE microprobe facility: Recent applications in archaeology

Abstract The first part of this paper describes some of the novel features of the Bartol PIXE facility that have made it such an effective analytical tool for the study of a diverse range of ancient materials, including the recent development of a microprobe arrangement with a tightly-focused proton beam of 50 μm spot size. The second part summarizes the use of this arrangement in the study of (i) multi-colored banding on glass beads and vessels, (ii) metal residues entrapped in smelting slags, and (iii) the variability in the composition of painted decoration on pottery.

Recent applications of PIXE spectrometry in archaeology II. Characterization of Chinese pottery exported to the Islamic world

Abstract The early 9th century a.d. trade links between Chinas Tang dynasty and the Western world, by land along the caravan routes of the Silk Road and by sea via India and the Gulf, encouraged a taste for many kinds of Chinese ceramics among the affluent societies of the Islamic empire. Using PIXE analysis to determine the primary composition and minor element patterns of the clay fabrics of a wide range of pottery recovered from the Islamic city of Siraf (in southern Iran), we have established clear differences between Chinese wares imported to that region and a variety of imitative wares of local origin. Parallels and contrasts are drawn between our data and those obtained by Chinese scholars in recent years for the products of various Tang kiln sites, particularly for a series of distinctive stonewares from Tongguan (Hunan province).

Recent applications of PIXE spectrometry in archaeology part I Observations on the early development of copper metallurgy in the Old World

Abstract The early development of copper metallurgy can be characterized by three steps of innovation: i) exploitation of native copper resources for simple tool-making as early as the 7th millennium B.C. in the Near East; ii) the recovery of copper metal from minerals such as malachite, by smelting, during the 5th millennium B.C., both in the Near East and in eastern Europe; and iii) the deliberate alloying of copper and tin, to make bronze, circa 2800 B.C. in Mesopotamia (modern Iraq). This paper reviews the technological aspects associated the first two of these steps, comparing compositional patterns (as determined by PIXE spectrometry) for the copper metallurgy of various regions including the Middle Danube basin, the Tigris basin and the Iranian Plateau.

The Late Bronze Egyptian Garrison at Beth Shan: glass and faience production and importation in the late New Kingdom

Beth Shan, strategically located at the juncture of the Jordan and Jezreel Valleys where major trade routes intersected, was architecturally restructured in the 13th century B. C. E. as one of the most important late New Kingdom Egyptian bases in Palestine. The archaeological and technological evidence from the site provides a unique perspective on how a deliberate imperialistic policy can affect local ceramic traditions, including the pottery and silicate industries. The Egyptians appear to have controlled the silicate industry at its most basic level, including the preparation and supply of raw materials. The Palestinian ceramic specialists, whether voluntarily or as a forced response, then adapted their techniques and were most likely responsible for technological and stylistic innovations. The silicate manufacture at the site, however, was limited to small artifacts, such as beads and pendants. Larger artifacts, in particular glass and faience vessels, were imported from Egypt. Chemical analyses support this interpretation, although a specific site where the vessels were manufactured in the late New Kingdom is yet to be determined.

New directions in the Bartol PIXE system for studies in archaeometry

Abstract This paper describes, firstly, the physical processes of PIXE that underly its advantages as an analytical tool and the practical limitation met in the compositional patterning of ancient bronzes, irons and glasses. Controlled variation of the energy of the proton beam and the use of selective filters in the X-ray detection system allows certain background effects from the X-ray output of the dominant elements to be significantly reduced. Secondly, plans for a new beam line for the Bartol PIXE facility are described. This system will provide for a beam diameter as small as 20 μm with a laser-based optical system that will allow for the precise location of the proton beam on the artifacts surface. This system will enable one to study inhomogeneous materials, such as metal residues trapped in smelted slag, solder joints in classical jewelry and islands of metal in heavily corroded artifacts.