Nuclear Physics for Cultural Heritage
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NUCLEAR PHYSICS FOR CULTURAL HERITAGE A TOPICAL REVIEW BY the Nuclear Physics Division of the European Physical Society EDITED BY Anna Macková, Douglas MacGregor, Faiçal Azaiez, Johan Nyberg, and Eli Piasetzky INTRODUCTION BY Walter Kutschera NUCLEAR PHYSICS FOR CULTURAL HERITAGE PUBLISHED BY Nuclear Physics Division of the European Physical Society, October 2016 EDITED BY Anna Macková, Douglas MacGregor, Faiçal Azaiez, Johan Nyberg, and Eli Piasetzky COPYRIGHT ©2016 The Authors. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/ by-nc-nd/4.0/). DOI: 10.1071/978-2-7598-2091-7 ISBN: 978-2-7598-2091-7 COVER PICTURE Early example of an external proton-beam PIXE set-up at the Ion Beam Center, Helmholtz Zentrum, Dresden - Rossendorf, Germany to study the color composition of the panel Die vierzehn Nothelfer by Lucas Cranach the Elder (1472-1553). Figure from C. Neelmeijer, W. Wagner, H.-P. Schramm, Diagnose von Kunstwerken am Teilchenbeschleuniger, Restauro 5 (1995) 326-329. TABLE OF CONTENTS FOREWORD 01 1. IMPORTANCE OF NUCLEAR PHYSICS FOR CULTURAL HERITAGE STUDY AND PRESERVATION 02 1.1. INVESTIGATION OF CULTURAL HERITAGE OBJECTS 02 1.2. PRESERVATION OF CULTURAL HERITAGE OBJECTS 03 1.3. PRESERVE THE OLD, BUT KNOW THE NEW 03 2. ION BEAM ANALYTICAL METHODS 05 2.1. BASIC PRINCIPLES OF ION BEAM ANALYSIS (IBA) 05 2.2. INSTRUMENTATION OF IBA 08 2.3. APPLICATIONS OF IBA 10 3. NEUTRON BEAM ANALYTICAL METHODS 23 3.1. BASIC PRINCIPLES OF NEUTRON BEAM ANALYSIS 23 3.2. INSTRUMENTATION OF NEUTRON BEAMS 26 3.3. APPLICATIONS OF NEUTRON BEAMS 27 4. DATING METHODS - LUMINESCENT DATING AND ACCELERATOR MASS SPECTROMETRY 30 4.1. BASIC PRINCIPLES OF DATING METHODS 30 4.2. INSTRUMENTATION OF DATING METHODS 31 4.3. APPLICATIONS OF DATING METHODS 33 TABLE OF CONTENTS 5. COMPLEMENTARY METHODS: γ-BEAM TECHNIQUES, X-RAY FLUORESCENCE (XRF) AND NUCLEAR MAGNETIC RESONANCE (NMR) 37 5.1. BASIC PRINCIPLES 37 5.2. INSTRUMENTATION OF COMPLEMENTARY METHODS 40 5.3. APPLICATIONS OF COMPLEMENTARY METHODS 42 6. PRESERVATION OF CULTURAL HERITAGE 54 6.1. BASIC PRINCIPLES 54 6.2. INSTRUMENTATION OF NUCLEAR PRESERVATION METHODS 55 6.3. APPLICATIONS OF NUCLEAR PRESERVATION METHODS 55 7. CONCLUSION 58 APPENDIX A: EUROPEAN FACILITIES USING NUCLEAR TECHNIQUES TO STUDY CULTURAL HERITAGE 59 APPENDIX B: GLOSSARY OF TERMS 63 APPENDIX C: EXPERTISE OF AUTHORS 65 REFERENCES 68 NUCLEAR PHYSICS FOR CULTURAL HERITAGE foreword I.J. DOUGLAS MACGREGOR, VICE-CHAIR NUCLEAR PHYSICS DIVISION, EUROPEAN PHYSICAL SOCIETY TABLE OF FOREWORD CONTENTS uclear physics applications in medicine and authoritative account we have invited contributions from energy are well known and widely reported. See, leading experts across Europe, and this publication is Nfor example, the recent report “Nuclear Physics for the combined result of their work. We are grateful to all Medicine”, published by the European Science Foundation our contributors for sharing their specialist knowledge [1] or “Energy for the Future: the Nuclear Option”, written with you. by scientists at the European Physical Society (EPS)[2]. Of course there are previous reviews of work in this field Less well known are the many important nuclear and which are aimed at experts. See for instance, “Nuclear related techniques used for the study, characterisation, Techniques for Cultural Heritage Research”, published by assessment and preservation of cultural heritage. There the International Atomic Energy Agency [3]. We do not seek has been enormous progress in this field in recent years to duplicate this work, but rather to present an overview and the current review aims to provide the public with a for the more general reader. The review is extensively popular and accessible account of this work. illustrated with important discoveries and examples The Nuclear Physics Division of the EPS represents from archaeology, pre-history, history, geography, culture, scientists from all branches of nuclear physics across religion and curation, which underline the breadth and Europe. One of its aims is the dissemination of knowledge importance of this field. The large number of groups and about nuclear physics and its applications. Not only is laboratories working in the study and preservation of the Division motivated to promote understanding of cultural heritage across Europe (see appendix on European nuclear issues, it is in a unique position to do this. This Facilities) indicate the enormous effort and importance review is led by Division board member Anna Macková, attached by society to this activity. Head of the Tandetron Laboratory at the Nuclear Physics We are grateful to Prof. Walter Kutschera for writing Institute, Řež, in the Czech Republic, and the review the introduction to our review. His expertise makes him committee includes four other members of the nuclear ideally suited to describe the range of techniques, scope physics board interested in this area: Faiçal Azaiez, of investigation and the degree of innovation which has Johan Nyberg, Eli Piasetzky and myself. To create a truly made this such an important field of study. WWW.EPS.ORG 01 1. Importance OF nuclear physics for cultural heritage NUCLEAR PHYSICS FOR CULTURAL HERITAGE W. KUTSCHERA 1. IMPORTANCE OF NUCLEAR PHYSICS FOR CULTURAL HERITAGE STUDY AND PRESERVATION he importance of cultural heritage for mankind objects of cultural significance. This is due to the flexibility was once well expressed by the Austrian artist of ion beams, where the beam species (protons, alphas, TFriedensreich Hundertwasser (1928-2000) when heavy ions), the energy, the intensity, and the diameter he said: “If we do not honour our past we lose our future. of the beam (sub-millimeter to sub-micron size) can If we destroy our roots we cannot grow.” This statement be varied in a suitable way. In addition, the efficiency refers almost directly to the two pillars of this review: and resolution of detector systems for X-rays, γ-rays, Investigation and preservation of our cultural treasures. and charged particles have greatly improved over the The various contributions summarised in the current years. An important aspect for ion beam analyses of art review demonstrate that the methods inherent to nuclear objects is the use of an external beam, because often physics are capable of following Hundertwasser’s vision. these objects cannot be brought inside the accelerator The basic concept is to use nuclear radiations of various vacuum system (as an example, see the cover picture of kinds (X-rays, γ-rays, electrons, neutrons and ion beams) this report). A multitude of different ion beam techniques to analyse the elemental and/or isotopic composition is now available: NRA (Nuclear Reaction Analysis), PIXE of an object, or to preserve it by irradiation processes. (Proton Induced X-Ray Emission), PIGE (Proton Induced γ-ray Emission), RBS (Rutherford Back-Scattering), ERDA 1.1. InvestIgatIon (Elastic Recoil Detection Analysis). All of these are of cultural herItage objects discussed in this review. It is clear that precious cultural heritage objects should 1.1.2. X-ray and γ-ray beams remain unaltered after they are exposed to analytical investigation. Therefore non-destructive methods are of Since the birth of nuclear physics around 1900, X-rays have crucial importance for investigations. This simply means been available from the bremsstrahlung radiation emitted that the (unavoidable) side-effects of an irradiation must by energetic electrons as they pass through materials, and not be noticeable on the object of interest, now or in from X-rays emitted when an electron vacancy is filled in the future. an atomic orbit (characteristic X-rays). The most common This can be primarily achieved by reducing the method for cultural heritage investigation is XRF (X-ray intensity of the irradiation to very low levels. In order to Fluorescence). Due to its different depth-sensitivity it is obtain meaningful analytical information, the low primary complementary to PIXE, and is sometimes combined irradiation has to be balanced by a correspondingly with it. Portable instruments make XRF a very valuable high detection efficiency of the secondary signal one method for studying objects which cannot be moved to wants to analyse. Great strides in this direction have an accelerator. The invention of polycapillary focusing been undertaking in recent times, opening up many lenses for X-rays led to the development of Micro-XRF, possibilities to analyse valuable pieces of art. which improved the spatial resolution and thus the versatility of analysing distributions of trace elements. 1.1.1. Ion beams Such developments are being further advanced by utilising the very powerful X-rays from electron synchrotrons which Although ion beam analysis developed later than other are pushing Micro-XRF into the nanometer spatial regime. methods – simply because suitable accelerators only High-energy X-rays from free-electron laser facilities will became available in the second half of the 20th century, likely add another dimension to the quest for ever more it is now the most versatile technique for investigating detailed X-ray studies of culture heritage objects. 2 WWW.EPS.ORG NUCLEAR PHYSICS FOR CULTURAL HERITAGE 1. Importance OF nuclear physics for cultural heritage The European initiative for Extreme Light Infrastructure years. The determination of an absolute age from the (ELI) laboratories at ELI-NP in Romania, will provide measured 14C content requires a calibration curve, which tunable γ-rays from inverse Compton scattering of is updated about every five years by an international laser light on a high-energy electron beam. This will collaboration committee. allow Nuclear Resonance Fluorescence (NRF) studies An unusual help to uncover recent art forgery comes of isotope-specific trace element distributions to be from the so-called 14C bombpeak, an abrupt doubling performed with unprecedented sensitivity. of the atmospheric 14C content around 1960 due to the intense atmospheric nuclear weapons testing period. 14 1.1.3. neutron actIvatIon analysIs (NAA) Finding this C excess in an object of supposedly pre- nuclear origin is an unambiguous proof of forgery.