1,720,979 research outputs found
A new system for the simultaneous measurement of δ13C and δ15N by IRMS and radiocarbon by AMS on gaseous samples: Design features and performances of the gas handling interface
No full textWe present the general design features and preliminary performances of a new system for the simultaneous AMS-14C and IRMS δ13C and δ15N measurements on samples with masses in the μg range. The system consists of an elemental analyzer (EA), a gas splitting unit (GSU), a IRMS system, a gas handling interface (GHI) and a sputtering ion source capable of accepting gaseous samples. A detailed description of the system and of the control software supporting unattended operation are presented together with the first performance tests carried out by analyzing samples with masses ranging from 8 μgC to 2.4 mgC. The performances of the system were tested in term of stability of the ion beam extracted from the ion source, precision and accuracy of the results by comparing the measured isotopic ratios with those expected for reference materials
Raman and Photoluminescence spectroscopy of polycarbonate matrices irradiated with different energy 28Si+ ions
No full textThe irradiation of a polycarbonate (PC) matrix with 28Si+ ions has been performed by selecting three different energies: 0.5 MeV, 1.0 MeV and 2.0 MeV. The comparative study of the modifications induced in the polymer as a function of the incident ion beam energy has been carried out in the range of fluences between 5 × 1013 ions cm-2 and 1 × 1015 ions cm-2. The changes induced in the structure of the matrix towards the production of conducting plastics for optoelectronics devices have been evaluated by Raman and Photoluminescence spectroscopy. The carbonization process of the polymer generates a network made of sp2-bonded graphitic clusters embedded in a sp3-bonded matrix. The amount of nanocrystalline-graphite with respect to amorphous-carbon increases as ion energy and fluence increase, in accordance with the increase of the sp2-order arrangement. With 0.5 MeV the modification process is at an initial stage so that the changes, in terms of structure and PL emission, are observed only for the highest fluence, while for 1.0 MeV it has been achieved a higher density of small cluster with an order and homogeneity even better than for 2.0 MeV. The irradiation process with a suitable set of experimental parameters allows tuning the PC emission from ∼510 nm (pristine matrix) up to ∼550-600 nm
Copper ion implantation of polycarbonate matrices: Morphological and structural properties
No full textThe implantation of 1 MeV 63Cu+ ions in polycarbonate (PC) matrices has been carried out in order to evaluate the morphological and structural modifications induced in the polymer as a function of the ion fluence in the range 5 × 1013 ions cm-2 to 1 × 1017 ions cm-2. Atomic Force Microscopy analysis reveals a significant roughness increase of the polymer surface only for fluences higher than 5 × 1016 ions cm-2 with the presence of hillock structures which surface density increases with increasing the ion fluence. X-ray Diffraction measurements of PC implanted with fluences in the range between 5 × 1015 at cm-2 and 5 × 10 16 at cm-2 reveal an increase of the disorder inside the PC matrix, as a consequence of the damaging process induced by the ion irradiation. Evidences about the presence of exotic phase structures ascribed to both cubic Cu2O and cubic Cu have been found
The new gas ion source at CEDAD: Improved performances and first 14C environmental applications
No full textA new sputtering ion source has been installed at CEDAD (Centre for Dating and Diagnostics) at the University of Salento in Lecce, Italy. The installation of the new ion source, capable of accepting both solid and gas samples, required significant modifications of the existing low energy injector of the accelerator mass spectrometry (AMS) system. The new ion source is connected, through an in-house designed gas handling interface, to an elemental analyzer which combusts the samples to carbon dioxide and splits the gas into an IRMS system and also to the gas feed line of the ion source. This arrangement allows the simultaneous measurement of C, N content (in the EA), carbon and nitrogen stable isotopic ratios by IRMS and radiocarbon (14C) by AMS on samples with masses in the microgram range. The results of different tests performed to find optimal operational conditions and to improve the system performances are presented. The performances of the system as a function of the diameter of the glass capillary used to feed the source and the pressure of the gas mixture in the syringe are also presented. The achievable precision and blank levels are discussed together with the results obtained in environmental studie
Measuring stable carbon and nitrogen isotopes by IRMS and14C by AMS on samples with masses in the microgram range: Performances of the system installed at CEDAD-University of Salento
No full textA new experimental set-up dedicated to the simultaneous measurements of stable carbon and nitrogen
isotopic ratios by IRMS (Isotope Ratio Mass Spectrometry) and 14C by AMS (Accelerator Mass Spectrometry)
has been installed at CEDAD (Centre for Dating and Diagnostics)-University of Salento. The new
set-up is formed by different functional blocks: an elemental analyzer, an IRMS spectrometer, a gas handling
unit and a new hybrid sputtering ion source, connected to the AMS system. The general features
of the new system are presented as well as the technical solutions adopted for its integration with the
existing AMS system.
Different tests were performed by analyzing samples of known isotopic composition and of different
masses in order to define optimal operating conditions. In particular it is shown how radiocarbon measurements
with precision of 0.6–0.7% and 1% are possible with the new system on samples of mass of the
order of
∼20 ug and∼10 ug, respectively. Background levels of the order of 10−14 (14C/12C) have been
also demonstrated. The new system has then significantly extended the experimental potential of the
Centre in several research fields where the possibility to date very low mass samples is either a crucial
advantage or mandatory such as in environmental sciences and cultural heritage dating
The new AMS system at CEDAD for the analysis of 10Be, 26Al, 129I and actinides: Set-up and performances
No full textThe Centre for Dating and Diagnostics (CEDAD) at the University of Salento was established in 2001 and became fully operational for routine 14C radiocarbon dating in 2003. The facility has been continuously upgraded over the years with the installation of different beam lines for high energy ion implantation, IBA analyses both in vacuum and in air and nuclear microprobe. In 2011 a second AMS beamline was installed consisting of a dedicated high energy mass spectrometer for the AMS analysis of rare nuclides such as 10Be, 26Al, 129I and actinides. First tests on 10Be allowed to optimize the operating parameters resulting in the proper separation of 10Be from the interfering isobar 10B. In this paper we present the further tests and optimizations which resulted in an enhancement of the overall transmission efficiency, the reduction of the background (in the 10-15 range) and in the possibility to obtain precision levels in routine 10Be/9Be measurements of the order of 0.5%. Furthermore the first results obtained for the analysis of 26Al and 129I are also presented
Solving an historical puzzle. Radiocarbon dating the Capitoline she wolf
No full textThe Capitoline she wolf is a Bronze statue located at the “Capitoline Museums” in Rome, Italy. The extraordinary cultural and symbolic importance of the statue is mainly related to the myth of the Capitoline she wolf and to the legendary origin of the city of Rome. Though traditionally considered an Etruscan bronze, recently a much more recent age was suggested on the base of consideration related to the used casting technique. In this paper we present the results of an AMS radiocarbon dating campaign carried out on the organic residues found in the casting cores recovered from the inner part of the statue. The obtained results firmly anchor the statue to the XI-XII centuries CE, in the Middle Ages
10Be detection at the new AMS beam line at CEDAD: Performance tests and first results
No full textA new AMS (Accelerator Mass Spectrometry) beam line has been recently installed at CEDAD (Centre for Dating and Diagnostics)-university of Salento, Lecce, Italy for the detection by AMS of rare isotopes such as 10Be, 26Al, 129I and actinides. In this paper the performances of the new line for the measurement of 10Be are presented. Different tests were carried out in order to determine proper operating parameters and experimental conditions such as acceleration voltage, selected charge states and silicon nitride degrader thickness. The obtained results allow to assess the good performances of the new spectrometer in terms of boron suppression and background levels
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