NON-DESTRUCTIVE ANALYSIS OF ANCIENT METAL ALLOYS BY IN SITU EDXRF TRANSPORTABLE EQUIPMENT G. E. GIGANTE 1 and R. CESAREO 2 1 Dipartimento di Fisica, UniversitaÁ di Roma, La Sapienza, Piazza A. Moro, 8, Rome, Italy and 2 Istituto di Matematica e Fisica, UniversitaÁ di Sassari, Sassari, Italy AbstractÐThe availability of transportable equipment for in situ non-destructive analysis of works of art is considered to be very important. In situ non-destructive study is typically diagnostic, therefore requiring only qualitative or semiquantitative results. In the case of alloys, quantitative results can also be obtained. In Energy Dispersive X-Ray Fluorescence (EDXRF) analysis, portable instruments can now be assembled. For instance, miniaturised X-ray tubes with air cooling and high resolution semicon- ductor detectors thermoelectrically cooled are now available, allowing the construction of completely transportable apparatus for EDXRF analysis. In this work, aspects regarding methodology of analysis and discussion of the precision obtainable in analysis of ancient metals are presented. # 1998 Elsevier Science Ltd. All rights reserved INTRODUCTION Archaeometry and conservation can be viewed as experimental branches of historical disciplines. In these ®elds, Energy Dispersive X-Ray Fluorescence (EDXRF) has found extensive use because it is a non-invasive technique which makes possible the detection of the elemental pro®le of inorganic materials, such as those constituting objects of art. Among the most signi®cant applications of EDXRF in these ®elds are the quantitative analysis of alloys and the non-destructive study of inorganic pigments in paintings and frescoes. EDXRF is a well known technique in applied ®elds since it oers a number of notable advan- tages, including simplicity. Since the 1980s, trans- portable/portable equipment have been developed using radioisotopic sources and proportional gas counters and scintillators (Cameron and Rhodes, 1961; Cesareo et al., 1972). Unfortunately, use of these was limited by the poor energy resolution of the detectors and problems associated with the transportation of radioisotopic sources. The possi- bility of assembling transportable systems with adequate characteristics has only recently been realised due to (i) the development of cryo- electrically cooled detectors with improved energy resolution (Cesareo et al., 1992; Wang et al., 1993; Huber et al., 1994) and (ii) the realisation of dedi- cated X-ray tubes of small dimensions and adequate stability (Cesareo et al., 1996a,b; Oxford, 1996). There is substantial dierence between a trans- portable and a real portable spectrometer: a porta- ble instrument must be autonomous, i.e. complete with its own battery, and its weight must be su- ciently small that it can be positioned by hand with- out the aid of other support, while a transportable instrument can be brought to the chosen site for measurements. For most applications it is enough to have a transportable rather than a portable system. Indeed, in the case of works of art the problem is really one of not being allowed to take samples, and therefore a spectrometer is required which can be moved in order to analyse desired points on the object. There exist a large number of systems for non- destructive analysis of materials, but only a few have been constructed such that the equipment can be transported to museums or excavation sites, with the advantage of both not needlessly damaging the work of art and of not moving it. To move a work of art is, in fact, very complex for both bureaucratic and security reasons. In particular, the security reasons take into account the two risks that the work of art (i) could be stolen and (ii) could suer damage. In addition, to transfer a work of art is an extremely costly operation. Thus, the use of equip- ment which can be moved can drastically reduce the cost of investigation and favour greater use of such scienti®c methods in the study (including assay before and during restoration) of a work of art. The basic components of the EDXRF apparatus (see Fig. 1) are: (a) an X-ray source; (b) an X-ray detector; (c) an electronic system including data acquisition, storage and data presentation. The transportable EDXRF equipment used in the ®eld of archaeometry and conservation are of two types: 1. for large works of art, such as paintings, frescos, large metal artefacts, large ceramic items, etc. an Radiat. Phys. Chem. Vol. 51, No. 4±6, pp. 689±700, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0969-806X/98 $19.00 + 0.00 PII: S0969-806X(97)00241-7 689