Scanning Microscopy


Proton-induced x-ray emission (PIXE) spectrometry is fast developing a reputation as a powerful analytical tool in the study of a range of ancient materials, including bronze, iron, gold, glass, faience, and smelting slag. PIXE data allows determination of the primary constituents which would indicate their recipe of production and determine their bulk physical properties (e.g., color of a glass, brittleness in a metal), and of a wide range of trace elements which may indicate the source of raw material s from which an artifact was constituted. Over the past seven years, PIXE spectrometry's primary advantage over other recognized methods now being applied in archaeological research (particularly, xrf spectrometry and SEM/EDAX) - -that protons induce very little bremsstrahlung and therefore contribute very little to spectrum background during analysis has been much enhanced through the use of various kinds of selective filters in the detection system that heavily suppress the x-ray signal of dominant element(s) in the artifact's matrix (Cu in bronze, Si and Ca in glass, etc.). PIXE detection limits are kept exceptionally low (usually in the 10 ppm to 100 ppm range), because the selective filters almost entirely eliminate secondary background effects arising from response inertia in the detection system's electronics. Archaeological applications of the PIXE method, as reviewed here, now cover both the Old World, the New World, ancient Asia and Polynesia, and a time-span of the 5th millennium B.C. through to the 19th century A.D.

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