Prompt gamma activation studies on archaeological objects at a pulsed neutron source

The potential of Prompt Gamma Activation Analysis (PGAA) for non-destructive quantitative investigation of archaeological objects at a pulsed neutron spallation source was studied. Experiments were performed on the ROTAX time-of-flight diffractometer of the ISIS neutron source on a chalcolithic copper axe, a limestone sample from the ancient Quarry of Masarah (Egypt), a Roman bronze fibula and two fragments of glass from the Roman Villa Adriana. For reference and comparison, measurements were also performed at the PGAA station of the Budapest research reactor. It is found that the performance of a PGAA analysis at a pulsed source, with a make-shift set-up on an instrument designed for diffraction studies, cannot match the achievable results at a dedicated PGAA facility at a reactor source. However, the possibility of performing different investigations, e.g., neutron diffraction for structure analysis and PGAA for elemental analysis, at a single facility on one and the same object remains attractive and offers useful applications in the field of cultural heritage

Neutron-induced prompt gamma activation analysis (PGAA) of metalsand non-metals in ocean floor geothermal vent-generated samples

Neutron-induced prompt gamma activation analysis (PGAA) hasbeen used to analyze ocean floor geothermal vent-generated samples thatare composed of mixed metal sulfides, silicates, and aluminosilicates.The modern application of the PGAA technique is discussed, and elementalanalytical results are given for 25 elements observed in the samples. Theelemental analysis of the samples is consistent with the expectedmineralogical compositions, and very consistent results are obtained forcomparable samples. Special sensitivity to trace quantities of hydrogen,boron, cadmium, dysprosium, gadolinium, and samarium isdiscussed

Polished stone axes from Varna/Nössingbühel and Castelrotto/Grondlboden, South Tyrol (Italy)

A collection of polished stone axes from a late Neolithic site and an Early Bronze Age hill fort in South Tyrol (Italy) have been analysed through a multi-analytical approach, mainly based on non-destructive techniques (i.e. Raman spectroscopy, X-ray fluorescence and prompt gamma activation analysis) to identify the raw materials used in the same area during different periods and compare them with those in use in the surrounding territories. The analytical results suggest raw material exploitation strategies based on local or close sedimentary, metamorphic and magmatic rocks. Most of the artefacts are made from antigoritic serpentinite, whose origin is probably from Hohe Tauern (Austria) or related secondary deposits. These data confirm the importance of such raw material for the production of polished stone axes during recent prehistory and integrate the present knowledge about the distribution of antigoritic artefacts in north-eastern Italy and neighbouring countries

Combined prompt gamma activation and neutron diffraction analyses of historic metal objects and limestone samples

Two non-destructive neutron techniques have been used for the analysis of archaeological objects, among them English monumental brass plates, Dutch tin-lead spoons, a Roman leaded bronze fibula and several limestone samples. Prompt Gamma Activation Analysis (PGAA) is a non-destructive method for determination of the major and trace element compositions of various archaeological materials. Time-Of-Flight Neutron Diffraction (TOF-ND), on the other hand, is a non-invasive diagnostic tool for obtaining structural information from ceramic and metal objects. The element information (PGAA) holds the key information for addressing questions of provenance and authentication, whereas the structure information (TOF-ND) addresses questions of ancient materials and making techniques. Here we present data from those two complementary neutron methods, applied to different types of materials and artefacts, in order to highlight commonalities and differences

Nuclear physics for cultural heritage

We report about the expert review, published by the Nuclear Physics Division of the European Physical Society (NPD EPS), which aims to provide the public with a popular and accessible account of the latest developments in the field of nuclear physics application for cultural heritage. The contributions from a range of leading specialists explain how applied atomic and nuclear techniques can be used to obtain information that can help us to understand the way of life in ancient times and how they can be used to conserve cultural heritage treasures. This topical review draws heavily on European work and is extensively illustrated with important discoveries and examples from archaeology, pre-history, history, geography, culture, religion and curation. It outlines key advances in a wide range of cross-disciplinary techniques and has been written with the minimum of technical detail so as to be accessible by as wide as possible audience. The large number of groups and laboratories working in the study and preservation of cultural heritage using mainly nuclear physics methods across Europe indicates the enormous effort and importance paid by society to this activity

A new PGAI-NT setup at the NIPS facility of the Budapest Research Reactor

Prompt gamma activation analysis (PGAA) is a well known tool for non-destructive bulk elemental analysis of objects. The measured concentrations are only representative of the whole sample if it is homogenous; otherwise it provides only a sort of average composition of the irradiated part. In this latter case one has to scan the sample to obtain the spatial distribution of the elements. To test this idea we have constructed a prompt gamma activation imaging – neutron tomograph (PGAI-NT) setup at the NIPS station of the Budapest Research Reactor, consisting of a high-resolution neutron tomograph and a germanium gamma-spectrometer. The samples are positioned relative to the intersection of the collimated neutron beam and the projection of the gamma-collimator (isocenter) by using an xyzω-moving table

A multi-analytical study of Bronze Age pottery from the UNESCO site of Al-Khutm (Bat, Oman)

The extensive investigation carried out in recent years at the UNESCO site of Al-Khutm (Ibri, Oman) has allowed to uncover the monumental remains of a tower dated back to the third millennium BC and to collect an abundant ceramic assemblage from the associated soil deposits. Eighteen selected pottery samples have been investigated using a multi-analytical approach including microfocus X-ray computed tomography, X-ray diffraction, optical microscopy and prompt gamma activation analysis to analyse the vessel-forming technique and to characterise their micro-structure, mineralogical and chemical composition to recognise possible local vs. non-local raw materials. The results provided new insights on ancient manufacturing processes and revealed that most of the vessels were locally produced exploiting raw materials from the surroundings of the site with the exception of a fragment of a black slipped jar. The chemical results suggest that the latter was imported from the Indus area in nowadays Pakistan. This evidence integrates our knowledge about the presence of this type of vessels in Oman and confirms the involvement of inland centres like Bat and Al-Khutm into a large-scale exchange system

A new prompt gamma-ray database for cold and thermal neutron capture

Comprehensive prompt neutron capture gamma-ray data are important for basic nuclear structure studies, reaction mechanisms, sorr-process nucleosynthesis, and applications like Prompt Gamma Ray Activation Analysis (PGAA). The only readily available prompt neutron capture gamma ray library is the compilation by Lone et al1. These data are elemental measurements without anyisotopic assignments reported. They were measured with early, small Ge(Li) detectors and have numerous contaminant peaks, missing transitions, and limited uncertainty information. The Evaluated Nuclear Structure Data File (ENSDF)2 has more up-to-date information and is organized by isotope. The ENSDF neutron capture intensities are not normalized to absolute cross sections, but instead to per 100 decays of the parent. These normalizations are seldom more precise than +-10% and are not useful for applications like PGAA. Until now no completely satisfactory library of prompt neutron gamma rays has been produced. New prompt gamma-ray data have emerged from a series of experiments at the 10-MW Budapest Research Reactor. Accurate gamma-ray energies and production cross sections have been measured for nearly all elements from hydrogen to uranium. The measurements were performed with natural targets using a subthermal guided neutron beam and a Compton-suppressed HPGespectrometer. Energies were measured with respect to well-known 35Cl neutron-capture gamma rays. Gamma-ray production cross sections were determined with respect to the 1H capture cross section using internal standards, mostly stoichiometric compounds, to avoid corrections for neutron absorption and scattering. Precision of a few percent was attained for the strongest gamma rays from most elements. The Budapest data is precise, but the complexity of elemental measurements often makes it difficult to resolve weak transitions. To remedy this situation we are combining the isotopic data from ENSDF with the Budapest elemental data as part of an International Atomic Energy Agency Coordinated Research Project. The ENSDF file often contains precise energies and relative transition intensities that were measured with separated isotope targets. We are using ENSDF to assign the gamma rays in the Budapest datasets to the correct isotopes and place them in the level scheme. The level energies are then least-squares fit to the gamma-ray energies todetermine the self-consistency of the data. Outliers are a possible indication of unrecognized multiplets or errors in the level schemes. The ENSDF gamma-ray intensities are then renormalized to the identical scale as the Budapest intensities. The two datasets are then averaged and discrepancies are noted and corrected. The resulting prompt gamma-ray neutron capture database will be more completeand self-consistent then either of the component databases. In special cases additional corrections for non-unity Westcott g-factors will be provided.A first pass through the Budapest data has been completed, and we have assigned gamma rays for each element to the level schemefor the appropriate isotope based on ENSDF. This provides a database for identifying impurities in the spectra. We have also compared the observed cross section yields, based on the level scheme or the decay gamma rays, with those compiled by Mughabghabet al3. Although our values should be less than or equal to the compiled values, depending on the completeness of the level scheme, we found that many values differed well beyond the error bars. The final analysis of the prompt gamma-ray neutron capture database is in progress and we will report on our results in this paper in this presentation