Real-Time Equilibrium Reconstruction in a Tokamak

This paper deals with the numerical reconstruction of the plasma current density in a Tokamak and of its equilibrium. The problem consists in the identification of a non-linear source in the 2D Grad-Shafranov equation, which governs the axisymmetric equilibrium of a plasma in a Tokamak. The experimental measurements that enable this identification are the magnetics on the vacuum vessel, but also polarimetric and interferometric measures on several chords, as well as motional Stark effect or pressure measurements. The reconstruction can be obtained in real-time using a finite element method, a non-linear fixed-point algorithm and a least-square optimization procedure

YAP scintillators for resonant detection of epithermal neutrons at pulsed neutron sources

Recent studies indicate the resonance detector (RD) technique as an interesting approach for neutron spectroscopy in the electron volt energy region. This work summarizes the results of a series of experiments where RD consisting of YAlO3 (YAP) scintillators were used to detect scattered neutrons with energy in the range 1-200 eV. The response of YAP scintillators to radiative capture gamma emission from a U-238 analyzer foil was characterized in a series of experiments performed on the VESUVIO spectrometer at the ISIS pulsed neutron source. In these experiments a biparametric data acquisition allowed the simultaneous measurements of both neutron time-of-flight and gamma pulse height (energy) spectra. The analysis of the gamma pulse height and neutron time of flight spectra permitted to identify and distinguish the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the pulse height at about 600 keV equivalent photon energy. Present results strongly indicate YAP scintillators as the ideal candidate for neutron scattering studies with epithermal neutrons at both very low (<5degrees) and intermediate scattering angles. (C) 2004 American Institute of Physics

A new modular structural system for tall buildings based on tetrahedral configuration

Inspired by the high mechanical performance of diagrid structures, the minimization of material consumption on braced tubes and the expressive potency of tensegrity modular structures, this work proposes an innovative three-dimensional system for tall buildings. A new modular structural system generated from the assembly of tetrahedral units is investigated. The paper integrates insights on the architectural implications and mechanical performance of the reticular system arranged in repetitive triangular-based modules. The impact of different geometric configurations of the structural members on the economic design is also discussed and recommendations for the optimal topology are made. Guidelines for the design and analytical formula for accessing preliminary member sizes are proposed on the basis of stiffness requirements

Facility for fast neutron irradiation tests of electronics at the ISIS spallation neutron source

The VESUVIO beam line at the ISIS spallation neutron source was set up for neutron irradiation tests in the neutron energy range above 10 MeV. The neutron flux and energy spectrum were shown, in benchmark activation measurements, to provide a neutron spectrum similar to the ambient one at sea level, but with an enhancement in intensity of a factor of 107. Such conditions are suitable for accelerated testing of electronic components, as was demonstrated here by measurements of soft error rates in recent technology field programable gate arrays

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

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

Study of archaeological samples via neutron techniques

The discovery of ancient artefacts and artworks usually raises a variety of questions such as the correct determination of their historical and cultural timeframe, the place and method of production, the choice of treatments and conditions for restoration and preservation. In the field of archaeometry, new perspectives are opened up by the use of neutron techniques. Results on a selection of archaeological samples, Etruscan bronzes coming from the Museo Nazionale di Villa Giulia and Roman marbles from Villa Adriana (Tivoli, Rome), are presented. ANCIENT CHARM project aims to develop a quantitative 3D imaging technique. This work presents some of results on a series of experimental investigation performed on test samples called “Black Boxes”. Elements’ and compounds’ identification on the internal features of the boxes are obtained by the combined use of different neutron analysis methods. The presented studies successfully showed the high potential of neutron techniques in the study of ancient archaeological artefacts

Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus

Neutron spectroscopy measurements with a single crystal diamond detector have been carried out at JET, for the first time in an experiment aimed at accelerating deuterons to MeV energies with radio frequency heating at the third harmonic. Data are interpreted by means of the expected response function of the detector and are used to extract parameters of the highly non-Maxwellian distribution function generated in this scenario. A comparison with observations using a time of flight and liquid scintillator neutron spectrometers is also presented. The results demonstrate the capability of diamond detectors to contribute to fast ion physics studies at JET and are of more general relevance in view of the application of such detectors for spectroscopy measurements in the neutron camera of next step tokamak devices.EURATOM 63305

a telescope proton recoil spectrometer for fast neutron beam lines

A telescope proton recoil spectrometer for fast neutron beam-lines C. Cazzaniga1,3,∗, M. Rebai2,3, M. Tardocchi3, G. Croci2,3, M. Nocente2,3, S. Ansell1, C. D. Frost1, and G. Gorini2,3 1ISIS Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK 2Universita degli Studi di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, Milano, Italy 3Istituto di Fisica del Plasma "P. Caldirola", Associazione EURATOM-ENEA/CNR, Via Cozzi 53, Milano, Italy ∗E-mail: [email protected]

The very low angle detector for high-energy inelastic neutron scattering on the VESUVIO spectrometer

The Very Low Angle Detector (VLAD) bank has been installed on the VESUVIO spectrometer at the ISIS spallation neutron source. The new device allows for high-energy inelastic neutron scattering measurements, at energies above 1 eV, maintaining the wave vector transfer lower than 10 A^- 1. This opens a still unexplored region of the kinematical (q,w) space, enabling new and challenging experimental investigations in condensed matter. This paper describes the main instrumental features of the VLAD device, including instrument design, detector response, and calibration procedure