Tecniche nucleari di analisi e datazione dei beni culturali con l’acceleratore tandetron del CEDAD
10.6092/issn.1973-9494/4743
SummaryThe Accelerator Mass Spectrometry technique for measuring carbon isotopes anddating artifacts, together with nuclear techniques of ion beam analysis are widely used in the field of cultural heritage owing to the great advantage of their being non-destructive. In Italy, CEDAD - CEntro Di DAtazione e Diagnostica of the University of Salento, with its tandetron accelerator of 3MV, has played a major role for over ten years, in studying materials of cultural assets requiring the determination of their elemental composition and determination of absolute chronology using radiocarbon. This study describes the Accelerator Mass Spectrometry technique used with the accelerator at CEDAD to determine age by means of radiocarbon and PIXE-PIGE techniques, and to determine elements, even in traces, present in materials. Some case studies carried out at CEDAD are reported, including those on the Riace Bronzes and Capitoline Wolf. The latter has been definitively dated to the Middle Ages, 17 centuries later than the previously attributed dating by historians. In addition, an important technical innovation is described, achieved within the framework of the IT@CHA Project enabling organic materials to be dated using only 10 μg of carbon. RésuméLa technique de la spectrométrie de masse avec accélérateur est largement utilisée pour la mesure des isotopes du carbone et pour la datation des biens culturels, car elle a le grand avantage de ne pas être destructrice. Il en est de même pour les analyses par faisceaux d’ions. En Italie, depuis plus d’une décennie, le Centre de datation et de diagnostic de l’Università del Salento (CEDAD – CEntro di DAtazione e Diagnostica dell’Università del Salento), avec son accélérateur Tandetron de 3 mV, joue un rôle fondamental dans le domaine des études des biens culturels pour lesquels il est important de connaître la composition élémentaire des pièces et d’établir leur chronologie absolue par la méthode du radiocarbone. Sont ici décrits la technique de la spectrométrie de masse avec accélérateur que nous utilisons au CEDAD pour la datation avec la méthode du radiocarbone, ainsi que les techniques PIXE-PIGE pour la détermination des éléments présents dans les matériaux, également en traces. Sont également présentées des études réalisées au CEDAD, dont celle sur les Bronzes de Riace et sur la Louve du Capitole. Celle-ci a été définitivement datée au Moyen Âge, et est donc plus récente de dix-sept siècles par rapport à sa datation traditionnelle dans l’histoire de l’art. Il est également présentéune nouveauté technologique importante, réalisée dans le cadre du projet IT@CHA, qui permet de dater les matières organiques avec 10 μg de carbone seulement. ZusammenfassungDie Technik der Beschleuniger-Massenspektrometrie zur Messung der Kohlenstoffisotope und zur Datierung von Kulturgütern, sowie die atomaren Analysemethoden mittels Ionenstrahlen finden breiten Einsatz bei Kulturgütern, weil sie den großen Vorteil haben, dass sie nicht destruktiv sind. In Italien spielt das CEDAD – CEntro di DAtazione e Diagnostica (Datierungs- und Diagnosezentrum) der Università del Salento mit seinem 3MV Tandetron-Beschleuniger seit über 10 Jahren eine wesentliche Rolle bei der Analysevon Materialien aus Kulturgütern, die eine Bestimmung der elementaren Zusammensetzung der Manufakte sowie die absolute Radiokarbondatierung erfordern. In diesem Werk wird die Technik der von CEDAD zur Altersbestimmung mittels Radiokarbondatierung angewandten Beschleuniger-Massenspektrometrie, sowie die PIXE-PIGE-Methode zur Bestimmung der auch nur spurenweise in den Materialien vorhandenen Elemente beschrieben. Es werden einige Studien erläutert, die bei CEDAD durchgeführt wurden. Dazu gehören diejenigen der Bronzestatuen von Riace und die der Kapitolinischen Wölfin. Letztere wurde endgültig auf das Mittelalter datiert, d. h. sieist 17 Jahrhunderte jünger, als ihr bisher von der Kunstgeschichte zugeschrieben wurde. Darüber hinaus wird eine bedeutende technische Innovation beschrieben, die im Rahmen des Projekts IT@CHA realisiert wurde und es gestattet, organische Materialien mit nur 10 μg Kohlenstoff zu datieren. ResumenLa técnica de la espectrometría de masas con acelerador para medir los isótoposdel carbono y datar bienes culturales, y las técnicas nucleares de análisis por haces de iones gozan de una amplia aplicación en el ámbito del patrimonio cultural, pues ofrecen la gran ventaja de no ser técnicas destructivas. En Italia, el CEDAD (centro de datación y diagnóstico perteneciente a la universidad del Salento), con su acelerador Tandetron de 3 MV, desempeña desde hace más de diez años un papel fundamental en los estudios sobre materiales de interés para el patrimonio cultural. Esta clase de estudios requieren que se determine la composición elemental de los objetos y una cronología absoluta mediante radiocarbono. En este trabajo se describe la técnica de espectometría de masas con acelerador empleada en el CEDAD para establecer la datación por radiocarbono y las técnicas PIXE-PIGE para determinar los elementos contenidos en los materiales, aun cuando se trate de meras trazas. Se ilustran algunos estudios efectuados por el CEDAD, entre ellos, los correspondientes a los Bronces de Riace y la Loba Capitolina. Esta última ha sido datada definitivamente en la Edad Media, es decir, diecisiete siglos antes de loque la Historia del Arte había señalado hasta ahora. Además, se describe una importante innovación tecnológica aplicada en el marco del proyecto IT@CHA que permite datar material orgánico empleando solo 10 μg de carbono. 简介凭借无损检测的优势，用于测量碳的同位素、推测文物年代的加速器质谱检测技术和核离子束技术分析法在文物研究领域发挥了巨大的作用。在意大利， Salento大学–CEDAD年代分析和诊断中心，凭借着3 MV 的Tandetron加速器，十多年来，在确定制成品成分和放射性碳测定方面绝对年份方面，即文物材料研究领域，起到非常重要的作用。这份研究中描述了CEDAD使用加速器质谱检测器，以放射性碳年代测定法确定年代，以及使用PIXE-PIGE技术确定材料中的元素，包括微量存在元素。其中选择了一下有CEDAD进行的研究进行说明，包括对Riace(里亚切)青铜像和罗马母狼铜像的研究。后者年代最终被确定在中世纪，这要比迄今为止艺术史中提及的年代晚了17个世纪。此外，研究中还包括了一份非常重要的在IT@CHA合作领域内的科技创新发明，凭借这个发明仅使用10μg碳 即可确定一份材料组织的年代。 РезюмеМетод масс-спектрометрии с использованием ускорителя для измерения изо-топов углерода и датировки культурных памятников, а также ядерные методы ионно-пучкового анализа материалов широко применяются при работе с предме-тами культурного наследия, так как они являются неразрушающими методами. В Италии Центр датировки и диагностики CEDAD при университете Саленто, осна-щенный ускорителем Tandetron на 3 МВ, уже 10 лет играет первостепенную роль в изучении материалов, связанных с предметами культурного наследия, когда нужно определить поэлементный состав объектов, а также определить их абсо-лютный возраст методом радиоуглеродного датирования. В этой работе описан метод масс-спектрометрии с использованием ускорите-ля, который применяется центром CEDAD для радиоуглеродного датирования, а также описаны методы анализа PIXE-PIGE для определения элементов, при-сутствующих даже в остаточных количествах в материалах. Кроме того, в работе представлены некоторые исследования, выполненные CEDAD, в том числе на статуях Воинов из Риаче и на Капитолийской волчице. Последний монумент был окончательно датирован Средними веками, то есть, он оказался на 17 веков мо-ложе, чем предполагали до сих пор искусствоведы. Кроме того, в работе описано важное нововведение, выполненное в рамках проекта IT@CHA, позволяющее датировать органические материалы при помощи всего лишь 10 мкг углерода.
application/pdf
1973-9494
4743
en
Lucio Calcagnile
Conservation Science in Cultural Heritage
Riace Bronzes
Nuclear techniques for the analysis and dating of cultural heritage with the tandetron accelerator at the CEDAD
Text.Serial.Journal
https://conservation-science.unibo.it/
14
Articles
2014-12-20
2015-02-25
2014-12-20
2015-11-02
99-112
CSCH
Lucio Calcagnile
2014/12/20
10.6092/issn.1973-9494/4743
99
1973-9494
Riace Bronzes
en
112
BARTOLONI G., 2010, La Lupa Capitolina – Nuove prospettive di studio, L’Erma di Bretschneider. Roma.
Nuclear techniques for the analysis and dating of cultural heritage with the tandetron accelerator at the CEDAD
https://conservation-science.unibo.it/article/download/4743/4222
14
N       UCLEAR TECHNIQUES FOR THE ANALYSIS AND DAT-
        ING OF CULTURAL HERITAGE WITH THE TANDETRON
        ACCELERATOR AT THE CEDAD



   Lucio Calcagnile•
   CEDAD - Centro di Datazione e Diagnostica
   Dipartimento di Ingegneria dell’Innovazione
   Università del Salento, Italy

   Keywords: radiocarbon dating, accelerator mass spectrometry, ion beam analysis,
   Capitoline She-Wolf, Riace Bronzes


   1.     Introduction

   Nuclear techniques for the analysis and dating of cultural heritage have received
considerable interest in recent years due to the characteristic of being practically non-
destructive. In the field of determining absolute dating chronology by radiocarbon, it
was in 2001 that Italy finally bridged the technological gap with Australia, France, Ger-
many, Switzerland, the United Kingdom, the United States and other countries that
have had laboratories equipped with particle accelerators for dating cultural heritage
since the 80s.
   Abroad, some of these laboratories are able to perform either materials analy-
sis or just dating using the Accelerator Mass Spectrometry technique. In Italy, the




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
University of Salento (formerly Lecce University) has set up the CEDAD - CEnter
for DAting and Diagnostics, the first Research Center and service for radiocarbon
dating and ion beam analysis using a 3MV particle accelerator. Over the years the
CEDAD has significantly increased its technological potential becoming a point of
reference both in Italy and abroad for studies related to Archaeology, Art History,
Materials Science, Geological and Earth Sciences and Forensic Sciences. Hun-
dreds of archaeological sites have been studied and tens of thousands of samples
have been dated so far using the Tandetron accelerator at CEDAD.
   In this paper we will discuss the advantages of nuclear techniques used in the CEDAD
laboratories to establish the absolute chronology of cultural heritage and to determine the
composition of archaeological and artistic artifacts. In addition, thanks to the IT@CHA pro-
ject, an important technological innovation carried out by researchers at the CEDAD will be
described which allows us to date a material with only 10 μg of organic material.

   2.     The CEDAD – Center for DAting and Diagnostics –University of Salento

  In 2001, the University of Lecce set up the CEDAD – Center for DAting and Diag-
nostics, a multidisciplinary Center for dating by AMS (Accelerator Mass Spectrometry)
and for the study of cultural heritage using IBA (Ion Beam Analysis) techniques [1- 4].

• Corresponding author: lucio.calcagnile@unisalento.it

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                                                                                                                                   The main facility at the CEDAD is the Tandetron, a 3MV ion accelerator connected to
                                                                                                                                   six experimental beamlines (Fig. 1) that enable:
                                                                                                                                      a)    AMS radiocarbon dating up to 50,000 years;
                                                                                                                                      b)    dating and isotopic analysis of 10Be, 26Al; 129I and actinides;
L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                      c)    materials analysis by Rutherford Backscattering Spectrometry;
                                                                                                                                      d)    elemental analysis by PIXE- PIGE in the air;
                                                                                                                                      e)    proton microbeam analysis;
                                                                                                                                      f)    high energy ion implantation.

                                                                                                                                     The Centre also has laboratories for the chemical preparation of a wide range of
                                                                                                                                   samples for radiocarbon dating [5].




                                                                                                                                   Figure 1. The AMS-IBA system at the CEDAD - University of Salento. 6 beamlines and 4 ion
                                                                                                                                   sources are connected to the Tandetron accelerator for radiocarbon dating and compositional
                                                                                                                                   analysis of materials




                                                                                                                                      3.    Radiocarbon dating by Accelerator Mass Spectrometry

                                                                                                                                       Radiocarbon age determination of an organic sample (bones, charcoals, fragments
                                                                                                                                   of wood, clothes, etc.) requires the measurement of the residual concentration of 14C in
                                                                                                                                   the sample. The method was developed after World War II by W. Libby and has become
                                                                                                                                   over the years an important tool of investigation in many fields of research [6]. Radio-
                                                                                                                                   carbon produced in the upper atmosphere as a result of the interaction of cosmic rays
                                                                                                                                   with 14N, is oxidized to form carbon dioxide 14CO2, together with the two stable forms of
                                                                                                                                   carbon dioxide (12CO2 and 13CO2) in the different carbon reservoirs of our planet (atmos-
                                                                                                                                   phere, oceans, biosphere and lithosphere). In every living organism, the concentration
                                                                                                                                   of radiocarbon remains constant and equal, in a first approximation, to the value present
                                                                                                                                   in its reservoir of radiocarbon because of the onset of a condition of dynamic balance

                                                                                                                             100
for which the 14C that decays radioactively or that is released outwards due to the effect
of biological processes, is offset by the 14C absorbed through diet or, for plants, through
photosynthesis. With the death of the organism, this condition of dynamic equilibrium
no longer exists and the concentration of radiocarbon begins to decrease exponentially.
Therefore the measurement of the residual concentration of radiocarbon in a sample al-
lows us to determine the time that has elapsed since the death of the organism.
    This determination can be carried out by measuring the radioactivity of the sample,
i.e. by counting the β- particles emitted during the decay. This is the so called “Radio-
metric or Conventional” technique developed by Libby in the 50s and for which he was
awarded the Nobel Prize for Chemistry in 1960.
    At the CEDAD, however, the determination of absolute chronology is performed
using accelerator mass spectrometry (AMS), introduced at the end of the 70s [7].This
technique is based on the direct measurement of radiocarbon by a particle accelerator.
The AMS technique has an efficiency which is a million times higher than the radio-
metric technique and thus allows dating using less than one milligram of carbon with
results obtained in just a few tens of minutes.
    The main advantages of this technique are to reduce both the sample mass required
for dating and the measurement time. Some laboratories for AMS radiocarbon dating
are able to measure bulk samples of the order of 0.1-1 mg, with uncertainty about age
ranging from 20-30 years, in just 10-15 minutes of measurement with the accelerator.
In paragraph 7, a major technological innovation will be described achieved through
the project IT@CHA at the CEDAD which allows us to date materials of interest of cul-
tural heritage with a few tens of micrograms of carbon, i.e. a hundred times less than
the amount currently used in similar laboratories abroad.
    The AMS system consists of an ion source, a low energy mass spectrometer, a 3MV
Tandetron accelerator and a high energy mass spectrometer for the separation and
analysis of carbon isotopes. In the ion source, an ion beam is extracted from the graph-




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
ite sample prepared in chemical laboratories, accelerated to an energy of 35 keV and
sent to the low energy system where the separation of the components of the beam
occurs according to the energy/charge and mass/charge ratios, prior to injection into
the acceleration system. In the central part of the accelerator (stripper) the particles
collide with argon gas of low density losing electrons, thus allowing the dissociation of
carbon isobars. In the high-energy spectrometer the separation and analysis in mass
and energy take place together with the measurement of the isotopes 12C, 13C and 14C.

   4.    Ion Beam Analysis techniques at the CEDAD

   Determination of the composition of elements in materials is carried out at the CE-
DAD with Ion Beam Analysis (IBA) techniques with the same accelerator used for
determining the absolute chronology of organic materials. The Group of Applied Phys-
ics of the Department of Engineering for Innovation was among the first to follow the
IBA-AMS integrated approach for the determination of the chronology and composition
of materials of cultural heritage interest using the same facility. IBA techniques are
essentially based on the study of interaction processes, atomic and nuclear, between
MeV charged particles and the surface of the sample.
   The main analytical IBA techniques, which find applications in the field of cultural
heritage, are the PIXE (Particle Induced X-ray Emission) and PIGE techniques (Particle
Induced Gamma Ray Emission,) and RBS ( Rutherford Backscattering Spectrometry).

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                                                                                                                                       Figure 2 shows the experimental set-up for IBA in the air developed at the CEDAD.
                                                                                                                                   A particle beam, typically protons or α particles, accelerated to energies of 2-4 MeV
                                                                                                                                   is focused onto the surface of the sample to be analyzed by inducing the emission of
                                                                                                                                   characteristic radiation (x-rays and gamma) and the backscattering of incident parti-
L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                   cles. The simultaneous detection and analysis of the energy of x-rays, gamma rays
                                                                                                                                   and backscattered particles is used to determine, both qualitatively and quantitatively,
                                                                                                                                   the elemental composition of the material analyzed.
                                                                                                                                       The ability to detect and analyze simultaneously, and not destructively, the various
                                                                                                                                   products of the interaction of the incident beam with the sample, allows PIXE, PIGE
                                                                                                                                   and RBS measurements to be carried out at the same time, providing additional infor-
                                                                                                                                   mation in terms of detectable elements, depth of analysis and sensitivity.
                                                                                                                                       Although IBA techniques are applied in numerous fields of research such as Materi-
                                                                                                                                   als Science, Biology, Science of the Earth, and environmental monitoring, they have
                                                                                                                                   become, especially in recent years, an analytical tool used in the field of cultural herit-
                                                                                                                                   age diagnostics. In this field, in fact, the possibility of compositional analysis of both
                                                                                                                                   major and trace elements, without the need for sampling, represents the fundamental
                                                                                                                                   advantage of these analytical techniques as witnessed by the numerous applications
                                                                                                                                   in the analysis of Renaissance paintings, manuscripts, miniatures, ceramics, glass,
                                                                                                                                   jewelry and textiles, to name just a few examples.

                                                                                                                                      5.    PIXE (Particle Induced X-Ray Emission)




                                                                                                                                              Figure 2. The PIXE-PIGE external beamline for cultural heritage at the
                                                                                                                                              CEDAD. A: Switching magnet; Riv1: 30 mm2 Si(Li) X-ray detector; Riv.2:
                                                                                                                                              80 mm2 Si(Li) X-ray detector; Riv3: Gamma Ray Ge detector; B: external
                                                                                                                                              window; C: TV camera; D:sample x-y stage

                                                                                                                             102
    The PIXE technique is based on the detection and analysis of the characteristic
x-ray energies emitted by a material when subjected to bombardment with particle
beams with (typically protons) energy of the order of MeV [4 ]. The interaction of the in-
cident proton with an electron of one of the atomic inner shells, has a certain probability
it will be ejected, leaving the atom in an ionized state. The vacancy left by the electron
in the inner shell is “filled” by the transition of an electron from an outer shell, which
corresponds to the emission of a photon by the atom of energy equal to the difference
between the two shells. Since the energies of the electrons in the various shells are
characteristic of each atomic species, so are the differences between them, and thus
the energy of the emitted photon x is too. In the field of cultural heritage diagnostics,
the PIXE technique has the following advantages:
    a)     Multi-element analysis: this technique makes it possible to determine at the
same time, in a single measurement, all elements with an atomic number greater than
that of sodium.
    b)     Analysis in air: this technique has the considerable advantage of being used
either in air or in a helium atmosphere thanks to the reduced loss of energy in air of the
protons exiting the accelerator.
    c)      High sensitivity: the use of appropriate energy of the incident beam, of suit-
able geometry detection and experimental set-up enables detection of both the major
elements in the sample (for example, the matrix elements) and the trace elements, with
sensitivity in the order of parts per million (ppm).
    d)     Non-destructiveness and reduced measurement times: the high value of the
ionization cross section allows the use of reduced currents in the ion beam probe and
therefore, leads to a reduction in measurement times (typically a few minutes), and
damage caused to the material.
    e)     Complementarity with other IBA analysis techniques: the interaction of the
incident proton beam causes not only the emission of x-rays from the material but also




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
gamma rays and the backscattering of protons. The detection of x-rays occurring at the
same time as the analysis of these additional products of interaction is used to detect
elements lighter than sodium which cannot be determined with PIXE. In particular,
the detection of gamma rays is used to determine elements such as fluorine, sodium,
magnesium and aluminum, while the analysis of the backscattered protons allows the
detection of carbon, oxygen and nitrogen.

   6.    Application of IBA-AMS techniques to Cultural Heritage

   6.a   Detail of the statue of St. Francis

   As part of the collaboration between the CEDAD and the Department of Arts and
History at the University of Salento several parts of various sculptures which under-
went analysis were dated by radiocarbon method and analyzed using the IBA tech-
niques at the CEDAD. As an example, the study reports on a detail of the statue of St.
Francis of unknown author which is preserved in the Church of Santa Chiara in Lecce.
The purpose of the analysis was to obtain information on the elemental composition
of the original painting pigments and on the layer beneath the original pigments and
to determine the time of realization. Two analyses were performed on the hand of the
statue of St. Francis (Fig. 3) which is characterized by the presence of stigmata.



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L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                                              Figure 3. Detail of St. Francis’s hand.




                                                                                                                                      A first analysis was carried out on the inside of the stigmata to obtain information
                                                                                                                                   on the pigment used to reproduce the blood. In addition to the lines of lead, the X-ray
                                                                                                                                   spectrum shows those of mercury, a chemical element found in cinnabar red (Fig. 4a).
                                                                                                                                   Furthermore, in a particularly abraded area, one point of the analysis shows the pres-
                                                                                                                                   ence of white lead, used for the flesh tones (Fig. 4b).




                                                                                                                                                 Figure 4. Hand of the St. Francis statue: (a) blood, (b) flesh tones




                                                                                                                             104
    Investigations carried out on various parts of the hand made it possible to acquire in-
formation about the elements used for the pigments in the original paint layer (especially
lead white, and cinnabar for the reds and flesh tones). In the abraded areas, elements
such as titanium and zinc were detected, probably attributable to modern restoration
and the use of titanium dioxide, and zinc oxide for the white. The presence of emission
lines x for calcium may indicate the use of a gypsum for restoration. In the case of the
analyzed samples, finally, given the high intensities of the lines of lead (and the overlap
of line Mα1 of lead at 2.345 keV with line Kα of sulfur at 2.307 keV) it was not possible
to discriminate unequivocally the presence of sulfur and obtain, therefore, unique and
conclusive information about the existence of an original plaster-based preparation. Ra-
diocarbon dating was carried out by taking some tiny fragments of wood from the statue
of St. Francis of Assisi. By using the AMS dating technique the amount of wood taken
was reduced to 10-20 mg, minimizing the destructiveness of the analysis. Dating results
are shown in Figure 5.




                                                                                                      CONSERVATION SCIENCE IN CULTURAL HERITAGE

                 Figure 5. Results of radiocarbon dating of St. Francis’s hand



   6.b   Radiocarbon dating the Capitoline She-Wolf

    The Capitoline Wolf is a bronze statue known throughout the world as the symbol of
Rome and preserved in the Capitoline Museums of Rome in Italy. Historically, it has been
attributed to the Etruscan age (5th century B.C.). It has a significant symbolic and cultural
value because its creation can be traced back to the legendary foundation of Rome. The
statue represents the Capitoline Wolf suckling the twins Romulus and Remus, the sons
of Rhea Silvia and the god Mars. Legend tells that the twins were abandoned on the
Tiber river and were then saved and suckled by the wolf. The twins placed beneath the
Capitoline Wolf were added in the fifteenth century, perhaps by Pollaiuolo


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L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                                Figure 6. The Capitoline She-Wolf during investigations by the
                                                                                                                                                CEDAD team




                                                                                                                                       Doubts about the realization of the bronze statue during the Etruscan era were
                                                                                                                                   also advanced in the nineteenth century by various researchers. The restoration of
                                                                                                                                   1997-2000 commissioned by the direction of the Capitoline Museums was given to
                                                                                                                                   Anna Maria Carruba [9]. The Capitoline She-Wolf was made with the technique of
                                                                                                                                   lost-wax casting. The casting contains numerous plant remains which were added
                                                                                                                                   to give firmness to the mixture and to facilitate the expulsion of fumes during its
                                                                                                                                   treatment with high temperature. There have been numerous debates and study
                                                                                                                                   days over the years on the Capitoline Wolf, organized to refute Anna Maria Car-
                                                                                                                                   ruba’s thesis about the Carolingian origin of the she-wolf [10].
                                                                                                                                       Researchers at the CEDAD were contacted directly by the direction of the Cap-
                                                                                                                                   itoline Museums, and carried out a systematic study to determine the absolute
                                                                                                                                   chronology of the she-wolf by using the Tandetron accelerator. The organic materi-
                                                                                                                                   als taken from the wolf were dated making it possible to establish the time of its
                                                                                                                                   realization. The study lasted almost five years and was held in two phases. In the
                                                                                                                                   first phase, the organic materials collected during the restoration were dated. In the
                                                                                                                                   second phase, the Group of Applied Physics of the University of Salento removed
                                                                                                                                   further samples using an endoscope inserted through the center hole below the
                                                                                                                                   statue (Fig. 7) with specifically designed equipment.




                                                                                                                             106
                 Figure 7. The phases of sampling from the casting through the hole
                 under the belly of the Capitoline She-Wolf




   The plant remains found in the Capitoline Wolf belong to the category of C3 plants,
that is, during photosynthesis carbon atoms form chains of three atoms. Paleobotanical
investigations carried out at the University of Rome “La Sapienza” by Dr. Alessandra
Celant have determined the presence of caryopses and wheat straw (Figures 8a and b).




                                                                                                     CONSERVATION SCIENCE IN CULTURAL HERITAGE




                        Figure 8. (a) caryopses, (b) plant remains




    Putting aside the controversy that sought to obscure the results of the CEDAD research-
ers, the radiocarbon dating using the AMS technique enabled us to establish definitively
that the Capitoline She-Wolf was made in the Middle Ages. In particular, the resulting aver-
age of the 28 datings made on internal parts, from the head to the tail, led to establishing
the absolute chronology of the she-wolf between 1021 and 1153 with a confidence level
of 95.4%. Therefore the realization of the wolf is about 17 centuries later than the wrongly
attributed dating based on historical and stylistic considerations.


                                                                                               107
                                                                                                                                     6.c    AMS-IBA investigations on the Riace Bronzes

                                                                                                                                      The Riace bronzes are two famous masterpieces of great importance for the his-
                                                                                                                                   tory of art. They were found off the coast of Riace in Calabria in 1972. The dating of
L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                   the “elder” is attributed archaeologically to between 470 and 460 BC, while the second
                                                                                                                                   statue, the “youth”, is archaeologically dated to between 440 and 430 BC.




                                                                                                                                                     Figure 9. The Riace Bronzes, (a) the youth, (b) the elder




                                                                                                                                       After the discovery of the Riace Bronzes, they were restored first in Florence and
                                                                                                                                   then in Rome at the Central Institute for Restoration. In order to carry out the absolute
                                                                                                                                   determination of the bronzes using the radiocarbon method, with the CEDAD accelera-
                                                                                                                                   tor AMS technique, numerous organic samples were extracted from the casting core
                                                                                                                                   of the two bronzes - fragments of wood, plant remains, charcoal and animal hairs were
                                                                                                                                   found inside the casting cores of the Bronzes (Fig. 10).




                                                                                                                                                     Figure 10. Organic materials found in the casting core of
                                                                                                                                                     the Riace Bronzes



                                                                                                                             108
   13 samples were dated for statue A and 12 for statue B. The combined dating results
made it possible to attribute statue A to 512-398 and statue B to 510-400 BC, an age
calibrated in years with a confidence interval of 95.4%. The radiocarbon dating results are
therefore consistent with expected archaeological methods.
   9 samples from statue A and 13 from B were also analyzed with the IBA techniques at
the CEDAD. We found various elements Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, As, Rb, Sr, Y, Zr, Pb
with PIXE and F, Na, Al, Si with the PIGE technique. The concentration of SiO2, Sr, and
S is shown in Figure 11 from which it was possible to confirm the hypothesis that the right
arm of statue B has been restored or replaced, as evidenced by the significant composition
with respect to its casting cores.




                                                                                                       CONSERVATION SCIENCE IN CULTURAL HERITAGE
           Figure 11. Three-dimensional plot of Sr, S and SiO2. The different
           composition of the casting cores from statue A and B and the arm of
           statue B is clearly shown



   7.    IT@CHA Project: Italian Technologies for Advanced applications in Cul-
   tural Heritage Assets

    An important innovation is in progress at the CEDAD thanks to the IT@CHA Project (Ital-
ian Technologies for Advanced applications in Cultural Heritage Assets). It is an industrial
research project for the development of innovative Italian technologies in support of cultural
heritage. The CETMA Consortium coordinates the project with the participation of the Univer-
sity of Salento and the CEDAD, Palermo University, and the University of Calabria together
with many industrial partners. In relation to radiocarbon dating by accelerator mass spec-
trometry, the CEDAD, is currently working on a gas ion source capable of the direct dating of
gaseous samples. AMS dating is usually performed once the sample has undergone various
physical and chemical treatments on samples of graphite. An extremely small quantity of
material is then taken from the object which is then treated until production of CO2 occurs by
acidification or combustion. The sample is subsequently reduced to a graphite, pressed and
inserted in the accelerator for the measurement. At the CEDAD the dating of organic materi-
als can be done with just one milligram of carbon in the graphite for routine measurements.


                                                                                                 109
                                                                                                                                       The CEDAD Group of Applied Physics within the framework of the IT@CHA project
                                                                                                                                   has designed a new ion source capable of injecting the CO2 produced from the sample
                                                                                                                                   directly into the accelerator. This will result in a considerable reduction in the quantity of
                                                                                                                                   material necessary for dating. Preliminary measurements have brought the amount of
L. Calcagnile - Nuclear techniques for the analysis and dating of cultural Heritage with the tandetron accelerator at the CEDAD




                                                                                                                                   carbon necessary for dating from 1 mg to 10 μg, i.e. with a quantity one hundred times
                                                                                                                                   lower than that usually used for dating with an accelerator.
                                                                                                                                       The new gas source connected to the TANDETRON accelerator is interfaced with
                                                                                                                                   an IRMS spectrometer (Isotope Ratio Mass Spectrometry) capable of measuring the
                                                                                                                                   stable isotopes of carbon, 12C and 13C, directly on the same gases. In fact, the sample
                                                                                                                                   is first loaded into an elemental analyzer, burned, and sent to the IRMS spectrometer
                                                                                                                                   connected to the gas source of the accelerator. The IRMS spectrometer measures the
                                                                                                                                   effects of the natural isotopic fractionation and is therefore also able to check the status
                                                                                                                                   of residual contamination, if any by measuring the δ13C.
                                                                                                                                       In the gas ion source, the CO2 is injected through a syringe and a capillary on a target of
                                                                                                                                   Al provided with an insert of Ti. On the latter a complicated chemical-physical phenomenon
                                                                                                                                   takes place leading to the formation of carbon by sputtering with Cs ions on the surface of
                                                                                                                                   the Ti. Figure 12a shows the block diagram of the gas ion source interfaced with the IRMS
                                                                                                                                   spectrometer and the diagram (Fig. 12b) of the system of gas injection and trapping in the
                                                                                                                                   accelerator. Some details of the interior of the new source are shown in Figure 13.




                                                                                                                                   Figure 12. (a) Diagram of the source gas connected to the IRMS spectrometer and the elemental
                                                                                                                                   analyzer EA, and (b) diagram of the gas injection system using a syringe in a sputtering source


                                                                                                                             110
                 Figure 13. Details of the injection system for the gas ion source


      Acknowledgements

   I would like to thank Marisa D’Elia and Gianluca Quarta at the University of Salento
for the radiocarbon datings and sample preparation and Raffaele Casciaro for provid-
ing the detail of the statue of St. Francis.


      References

[1]     CALCAGNILE L., QUARTA G., D’ELIA M., RIZZO A., GOTTDANG A., KLEIN M.,
        MOUS D.J.W., 2004, A new accelerator mass spectrometry facility in Lecce, Italy
        in “Nuclear Instruments and Methods in Physics Research B”, Vol 223-224C pp
        16-20.
[2]     CALCAGNILE L., QUARTA G., D’ELIA M., MUSCOGIURI D., MARUCCIO L.,




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
        BUTALAG K., GIANFRATE G., SANAPO C., TOMA U., 2005a, Instrumental de-
        velopments at the IBA-AMS at the University of Lecce in “Nuclear Instruments
        and Methods in Physics Research B”, Vol. 240, pp 22-25.
[3]     CALCAGNILE L., QUARTA G., D’ELIA M., 2005b, High resolution accelerator-
        based mass spectrometry: precision accuracy and background in “Applied Ra-
        diation and Isotopes”, Vol 62/4 pp 623-629.
[4]     JOHANSSON S.A., CAMPBELL J.L., 1988, PIXE a Novel Technique for Elemen-
        tal Analysis, John Wiley and Sons Ltd.
[5]     D’ELIA M., CALCAGNILE L., QUARTA G., RIZZO A., SANAPO C., LAUDISA M.,
        TOMA U., 2004, Sample preparation and blank values at the AMS radiocarbon
        facility of the University of Lecce in “Nuclear Instruments and Methods in Physics
        Research B”, Vol 223-224C pp 278-283.
[6]     LIBBY W. F., 1955, Radiocarbon dating, 2nd Edition, Chicago, University of Chi-
        cago Press.
[7]     LITHERLAND A.E., 1984, Accelerator mass spectrometry in “Nuclear Instru-
        ments and Methods in Physics Research B5” pp. 100-108.
[8]     REIMER P.J., BAILLIE M., BARD E., BAYLISS A. A., BECK J.W., BERTRAND
        C., BLACKWELL P.G., BUCK C.E., BURR G.G., CUTLER K.B., DAMON P.E.,
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                                                                                                                                        F.W., VAN DER PLICHT J., WEYHENMEYER C.E., 2004,Terrestrial Radiocar-
                                                                                                                                        bon Age Calibration, 0–26 Cal KyrBP in “Radiocarbon” 46, pp. 1029-1058.
                                                                                                                                   [9] CARRUBA A.M., 2006, La Lupa Capitolina – Un bronzo medievale, De Luca
                                                                                                                                        Editori D’Arte, Roma.
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                                                                                                                                   [10] BARTOLONI G., 2010, La Lupa Capitolina – Nuove prospettive di studio, L’Erma
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                                                                                                                                     Biographical Notes

                                                                                                                                      Lucio Calcagnile has been Full Professor of Applied Physics at the University of
                                                                                                                                   Salento, Department of Engineering for Innovation, since 2005. His research activity
                                                                                                                                   concerns the study of ion-matter interactions, the development and applications of nu-
                                                                                                                                   clear techniques for non-destructive analysis and dating of materials, accelerator mass
                                                                                                                                   spectrometry, applications of cosmogenic isotopes in Archaeology, Geology, Environ-
                                                                                                                                   mental science, Forensic science. He has conducted research at Legnaro National
                                                                                                                                   Laboratories of Nuclear Physics, at the FOM Institute for Atomic and Molecular Phys-
                                                                                                                                   ics in Amsterdam, the Tandetron Laboratory Gif sur Ivette the AGLAE-CNR Laboratory
                                                                                                                                   in Paris, and the Leibniz Labor in Kiel. In 1999 he created the CEDAD – CEnter for
                                                                                                                                   DAting and Diagnostics, the first Italian center for research and service using radiocar-
                                                                                                                                   bon dating, which he currently heads.
                                                                                                                                      He has given numerous talks at schools and conferences in Italy, France, Belgium,
                                                                                                                                   Malta, Egypt, Holland, Australia and the USA. He has been Chairman of international
                                                                                                                                   workshops and co-chairman of the 11th International Conference on Accelerator Mass
                                                                                                                                   Spectrometry held in Rome from 14th to 19th September 2008. He is a member of Ad-
                                                                                                                                   visory Committees of international conferences, including Radiocarbon and AMS Con-
                                                                                                                                   ferences. He is author and co-author of over 100 publications in international journals.




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