Center For Isotopic Research On Cultural And Environmental Heritage Research Articles

Measurement of the 7Be(p, γ)8B reaction cross section with the recoil mass separator ERNA

The cross section of 7Be(p,γ)8B represents one of the most important nuclear inputs for the prediction of the high energy component of solar neutrinos and it has also a direct impact on the 7Li abundance after the Big Bang Nucleosynthesis. The importance of this reaction triggered an intense experimental work over the last decades, where discrepancies were observed between the results of different measurements. In addition, a question remains about possible common systematic effects, considering that all measurements share the same experimental approach, i.e. an intense proton beam impinging on a 7Be radioactive target. Inverse kinematics, i.e. a 7Be ion beam and a hydrogen target, with the direct measurement of the total reaction cross section by means of the detection of the 8B recoils, can shed light on such systematic effects. Efforts attempted so far were limited by the low 7Be beam intensity. We present here the results of a new measurement at Ecm = 376 to 819 keV using a high intensity 7Be beam in combination with a windowless gas target and the recoil mass separator ERNA (European Recoil mass separator for Nuclear Astrophysics) at CIRCE (Center for Isotopic Research on Cultural and Environmental heritage), Caserta, Italy. Our results, including the systematic error, are compatible with previous measurements that yields lower value of S17(0) and are compatible with the currently accepted value from [1] only at a 2-σ level.

Test measurement of 7Be(p, $\gamma$ γ )8B with the recoil mass separator ERNA

7Be(p, $\gamma$ )8B has an important role in nuclear astrophysics, having a direct impact on both the high energy component of solar neutrinos and the 7Li abundance after the Big Bang Nucleosynthesis. All direct measurements providing useful information on this reaction so far used the same approach, i.e. a proton beam on a radioactive 7Be target. The overall precision and accuracy of the estimate of the astrophysical rate of this reaction are limited by the discrepancy between the results of existing measurements, possibly due to the complicated stoichiometry and beam induced deterioration of the radioactive targets. The ERNA (European Recoil separator for Nuclear Astrophysics) collaboration planned a new experiment in inverse kinematics exploiting the intense 7Be beam available at CIRCE (Center for Isotopic Research on Cultural and Environmental heritage), Caserta, Italy. The 8B recoils are produced in a windowless hydrogen gas target and detected after the efficient mass separation provided by ERNA. Here we present the commissioning of the experimental setup and a first cross section measurement at $E_{\mathrm{cm}}\approx 812$ keV.

Measurements of δ 11 B in water by use of a mass spectrometer with accelerator

Abstract This study describes the tests carried out to measure the isotopic composition of Boron (B) in water samples by use of the magnetic spectrometer and accelerator of the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) of Italy. B was extracted from water samples to obtain Boric acid (B(OH)3), which was then analyzed. We quantified the precision of our experimental system and the variability introduced by the chemical extraction measuring chemically untreated and treated pure B(OH)3 samples. We found an instrumental precision around 10‰ (1σ), but, by increasing the number of replicates (>30), we obtained a standard deviation of the mean (σerr) around 3‰ or lower. We also tested whether the chemical extraction caused isotopic fractionation and found a small fractionation (e = 5 ± 4‰) of treated samples normalized against untreated ones, compatible with zero at 2σ. In order to avoid δ11B biases, we decided to normalize unknown treated samples with treated standards. Finally, we measured δ11B of seawater and groundwater samples to test the analytical method, and obtained values of 30 ± 6‰ and −4 ± 4‰ respectively. We conclude that our experimental system is only suitable when remarkable (>10‰) δ11B differences exist among water samples, but cannot be used to measure natural differences (

AMS 14C dating at CIRCE: The Major Temple in Cumae (NA – Italy)

We present here one recent CIRCE (Centre for Isotopic Research on Cultural and Environmental Heritage) – Caserta (Italy) project on cultural heritage field, analysing several mice bones, discovered in the Major Temple on the acropolis of Cumae (Napoli, Southern Italy). The bones were found in a vase linked to the holy context. In order to know their dating and formulate an hypothesis on their presence on the site, if it was an accidental rodent inclusion (believed on the base of archaeological context to have occurred during building abandonment periods (IV–V or XIII centuries AD)) or an intentional and ritual remain, the bones were 14C dated by AMS at CIRCE. The results indicate that the mice bones date to the IV century BC and are contemporaneous with building construction. This dating seems to exclude an accidental rodent presence and it supports the hypothesis of Apollo veneration in the temple, based on the already known link between mice and Apollo worship rituals.

Mass and abundance 236U sensitivities at CIRCE

The actinides (e.g. 236U and xPu isotopes) are present in environmental samples at the ultra trace level since atmospheric tests of NWs (Nuclear Weapons) performed in the past, deliberate dumping of nuclear waste, nuclear fuel reprocessing, on a large scale and operation of NPPs (Nuclear Power Plants) on a small scale have led to the release of a wide range of radioactive nuclides in the environment. Their detection requires the most sensitive AMS (Accelerator Mass Spectrometry) techniques and at the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy, an upgraded actinide AMS system, based on a 3-MV pelletron tandem accelerator, has been operated.In this paper the progress made in order to push the 236U mass sensitivity and 236U/238U isotopic ratio down to the natural levels is reported. A uranium contamination mass of about 0.05μg and a 236U/238U isotopic ratio sensitivities at the level of 3.2×10−13 are presently achievable.

Uranium beam characterization at CIRCE for background and contamination determinations

The Accelerator Mass Spectrometry (AMS) is the most sensitive technique, compared either to the Inductively Coupled Plasma (ICP-MS) or Thermal Ionization (TI-MS) mass spectrometer, for the actinide (e.g. 236U, xPu isotopes) measurements. They are present in environmental samples at the ultra trace level since atmospheric tests of Nuclear Weapons (NWs) performed in the past, deliberate dumping of nuclear waste, nuclear fuel reprocessing, on a large scale, and operation of Nuclear Power Plants (NPPs), on a small scale, have led to the release of a wide range of radioactive nuclides in the environment.At the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy, an upgraded actinide AMS system, based on a 3-MV pelletron tandem accelerator, has been developed and routinely operated. At CIRCE a charge state distribution as a function of terminal voltage, the beam emittance, measured in the 20° actinides dedicated beam line, as well as the energy and position validation of the U ions were performed in order to determine the best measurement conditions. A 236U/238U isotopic ratio background level of about 5×10−12 or 3×10−13, depending on the Time of Flight-Energy (TOF-E) configurations, as well as the spatial distribution of the 235U, 238U interferences ions and a 236U contamination mass of about 0.5fg have been determined.

AMS radiocarbon dating of mortar: The case study of the medieval UNESCO site of Modena

The carbon dioxide contributing to binder formation during the set of a lime mortar reflects the atmospheric 14C content at the time of construction of a building. For this reason, the 14C dating of mortars is used with increasing frequencies in archaeological and architectural research. Mortars, however, may also contain carbonaceous contaminants potentially affecting radiocarbon dating. The Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) of the Second University of Naples (SUN) has recently obtained some promising results in mortar radiocarbon dating thanks to the development of a procedure (i.e. CryoSoniC/Cryo2SoniC) aiming to eliminate exogenous C contamination that may occur in a mortar.The construction history of the UNESCO World Heritage Site of Modena (Italy) is still controversial and represents a challenging case study for the application of absolute dating methodologies for different reasons. From the point of view of 14C dating, for example, given the high percentage of carbonate aggregates composing these samples, Modena mortars represent an experimental test particularly indicative of exogenous carbon sources suppression ensuring methodology accuracy.In this paper several AMS Radiocarbon dates were carried out on lime lumps with the aim to: (i) verify procedure accuracy by a comparison of the results obtainable from lime lumps dated after different treatments (i.e. bulk lime lumps vs. CryoSoniC purified lime lumps); (ii) compare different building phases absolute chronology for the medieval UNESCO site of Modena, with that assumed by historical sources in order to assess preliminary the 14C dating feasibility for of the site.Historical temporal constraints and mortar clustering, based on petrography, have been applied to define a temporal framework of the analyzed structure. Moreover, a detailed petrographic characterization of mortars was used both as a preliminary tool for the choice of samples and to infer about the lack of accuracy (when verified) of the applied mortar 14C dating procedure.

Study of236U/238U ratio at CIRCE using a 16-strip silicon detector with a TOF system

Accelerator Mass Spectrometry (AMS) is presently the most sensitive technique for the measurement of long-lived actinides, e.g. 236 U and x Pu isotopes. A new actinide AMS system, based on a 3-MV pelletron tandem accelerator, is operated at the Center for Isotopic Research on Cultural and Environmental Heritage (CIRCE) in Caserta, Italy. In this paper we report on the procedure adopted to increase the 236 U abundance sensitivity as low as possible. The energy and position determinations of the 236 U ions, using a 16-strip silicon detector have been obtained. A 236 U/ 238 U isotopic ratio background level of about 2.9×10 −11 was obtained, summing over all the strips, using a Time of Flight-Energy (TOF-E) system with a 16-strip silicon detector (4.9×10 −12 just with one strip).

Biomass Growth Rate of Trees from Cameroon Based on 14C Analysis and Growth Models

The question of whether the rise in CO2 levels observed during the industrial era has influenced the rates of tree biomass growth represents one of the main unsolved questions in the field of climate change science. In this framework, the African tropical forest represents one of the most important carbon (C) sinks, but detailed knowledge of its response to elevated CO2 is still lacking, especially regarding tree growth rate estimations. A major limitation to determining growth rates in the African tropical region is that many trees lack seasonality in cambial activity determining annual growth rings. In this study, several species of trees characterizing the African tropical forest have been investigated to estimate their biomass growth rate by means of a procedure based on 14C and growth models. A total of 71 subsamples were analyzed for a Entandrophragma cylindricum (sapele) tree, and 38 and 25 wood subsamples for Erythrophleum suaveolens (tali) and Triplochiton scleroxylon (ayous) trees, respectively, using radiocarbon measurements at the Centre for Isotopic Research on Cultural and Environmental Heritage (CIRCE). All measured modern samples were in agreement with the Southern Hemisphere (SH) 14C bomb-spike curve. Observed preliminary results indicate a decrease in the growth rate of the sapele tree (∼350 yr old) in the industrial period compared to the pre-industrial era. Growth rates for trees of the other 2 species were higher than sapele, with ayous being the fastest-growing species.

Accelerator mass spectrometry 14C dating of lime mortars: Methodological aspects and field study applications at CIRCE (Italy)

Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) has, recently, obtained some promising results in testing the feasibility of mortar radiocarbon dating by means of an ad hoc developed purification procedure (CryoSoniC: Cryobraking, Sonication, Centrifugation) applied to a series of laboratory mortars. Observed results encouraged CryoSoniC accuracy evaluation on genuine mortars sampled from archeological sites of known or independently constrained age (i.e., other 14C dates on different materials).In this study, some 14C measurements performed on genuine mortars will be discussed and compared with independently estimated (i.e., radiocarbon/archaeometrical dating) absolute chronologies of two Spanish sites. Observed results confirm the agreement of the CryoSoniC mortar dates with the archaeological expectations for both examined cases.Several authors reported the possibility of obtaining accurate radiocarbon dates of mortar matrices by analyzing lime lumps: binder-related particles of different sizes exclusively composed of calcium carbonate.In this paper, preliminary data for the absolute chronology reconstruction of the Basilica of the cemetery complex of Ponte della Lama (Canosa di Puglia, Italy) based on lime lumps will also be discussed. Dating accuracy will be quantified by comparing 14C data on mortar lime lumps from a funerary inscription of known age found near the Basilica, in the same study site. For this site, a comparison between absolute chronologies performed by bulk and CryoSoniC purified lime lumps, and charcoal incased in mortars (when found) will also be discussed.Observed results for this site provide evidence of how bulk lime lump dating may introduce systematic overestimations of the analyzed sample while CryoSoniC purification allows accurate dating.

Actinides AMS at CIRCE and 236U and Pu measurements of structural and environmental samples from in and around a mothballed nuclear power plant

Accelerator mass spectrometry (AMS) is presently the most sensitive technique for the measurement of long-lived actinides, e.g. 236U and 239Pu. A new actinide line is in operation at the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy. Using the actinide line a uranium mass sensitivity of around 4μg has been reached measuring with a 16-strip silicon detector, and a 239Pu background level of below 0.1fg has been obtained.In this work we also discuss preliminary results for environmental and structural samples from in and around the Garigliano nuclear power plant (GNPP), presently in the decommissioning phase. Measurements on environmental samples from the vicinity of the plant allow the assessment of contamination, if any, over the years. Measurements of structural samples from the plant are relevant to the optimization of the decommissioning program for the GNPP.

Preliminary Radiocarbon Analyses of Contemporaneous and Archaeological Wood from the Ansanto Valley (Southern Italy)

The Ansanto Valley (southern Italy) is characterized by hydrothermal phenomena, with volcanic gas emissions arising from some vents. In the 1 st millennium BC, a sanctuary dedicated to the goddess Mephitis was built but later destroyed by landslides in the valley. During archaeological excavations in the 1950s, many items were found including wooden artifacts, preserved thanks to the imbibition and subsequent mineralization of the wood tissues due to the gas emissions. Radiocarbon dating of these objects is underway at CIRCE (Centre for Isotopic Research on Cultural and Environmental Heritage), in Caserta, Italy. Unfortunately, 2 main problems arise in dating these materials. The first is possible fossil dilution caused by the CO2 emitted from the nearby volcanic vents, which could affect the trees of the valley and also the archaeological materials. In order to determine the magnitude of the fossil dilution in the area, 14C measurements were performed on contemporaneous wood cored from 2 oak trees growing near the vents. 14C values measured in these samples confirmed the presence of a strong fossil dilution in the Ansanto Valley. The second problem is the restoration that the objects underwent during the last century (mostly by using modern organic substances). To investigate suitable pretreatment procedures for removing the restoration materials from the archaeological findings, contemporaneous wood was also analyzed. The wood of trees from the Ansanto Valley and from a distant village (unaffected by the Ansanto fossil dilution) were submitted to the same restoration process applied to the archaeological artifacts, followed by an “artificial weathering” process. Some archaeological materials were also tested for the removal of restoration materials. We subjected the artificially aged trees and the archaeological samples to different chemical processes. Here, we present the results of these processes. Almost all methods turned out to be suitable for the contemporaneous wood, while the results for the archaeological samples remain uncertain. For this reason, more tests are needed, concerning the “artificial weathering,” the restoration, and the chemical procedure for removing the consolidation materials.

Dating mortars: three medieval Spanish architectures

One of the major issues in building archaeology is finding the age of elements and structures discovered. Mortars represent a class of material basically constituted by a mixture of different phases (i.e. binder, aggregates, water) and are widely used for constructive uses and artworks. Current scientific literature regarding the possibility of accurate radiocarbon dating for mortars reports different and still contradictory results. In this study, a new protocol for radiocarbon dating of mortar developed at the Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) is used to perform 14 C measurements on archaeological mortars coming from three medieval architectures of northern Spain (two churches and the walls of a castle). Results observed will be discussed and compared with independent age estimations (i.e. radiocarbon dating performed on organic materials found in the same study site, archaeological analyses) in order to frame experimental observations in the actual site knowledge by means of a multidisciplinary approach.

Forensic applications of 14C at CIRCE

The decreasing trend of the radiocarbon pulse produced during the atmospheric tests of nuclear weapons (bomb-carbon) coupled with high sensitivity accelerator mass spectrometry (AMS) measurements, drastically increased the precision of radiocarbon age determinations since the second part of the sixties, allowing the application of radiocarbon AMS to a wide range of studies previously not directly involving conventional radiocarbon dating (i.e. food authenticity, forensic, biochemistry). In the framework of authenticity evaluation of artworks, high precision radiocarbon ( 14C) AMS measurements (Δ R/ R < 0.3%) reduce the conventional uncertainty of the dating to few decades, allowing precise age estimation of materials containing carbon (C). The Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) during its activity on AMS 14C dating achieved high precision measurements opening the opportunity to these kinds of applications. This paper presents the main results obtained from radiocarbon measurements on a set of bone samples analyzed for the determination of the post-mortem interval in the framework of an unsolved case investigated by the Rome prosecutor office. The chronological characterization of the wooden support of the “Acerenza portrait” is also presented with the aim to evaluate its age and to further investigate the possibility to attribute this artwork to Leonardo da Vinci. Bomb- 14C dating on the lipid and collagen fractions of bones allows the evaluation of the year of the death of the individuals by means of ad hoc calibration data sheet with the typical few years precision and difference between collagen apparent age and the year of death appeared in agreement with the age of one individual estimated by dating of tooth collagen. Conventional radiocarbon dating on both wood and wood extracted cellulose leads to an estimation of the portrait wood board age (2σ) of 1459–1524 AD (57% relative probability), 1571–1631 AD interval (42% relative probability).and 1559–1563 AD (1% relative probability). These results attribute with the highest relative probability an age comprised within the life span of Leonardo (1452–1519) to the support.

A new AMS facility in Caserta/Italy

A new AMS system has been installed at Center for Isotopic Research on Cultural and Environmental Heritage (CIRCE) in Caserta/Italy. It was built by National Electrostatics Corp. Middleton, WI/USA, and arrived at CIRCE in the middle of January 2005; the installation and the acceptance tests were completed at the end of February 2005. At first, the system is intended for Radiocarbon AMS; for future Al and Be AMS only minor upgrades are needed and the magnets are designed to bend heavy isotopes like Uranium. Concerning Radiocarbon AMS, the first measurements of unknown samples, prepared in the internal preparation laboratory, already yielded results of high precision and 14C dating is in full swing.