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Träfflista för sökning "WFRF:(Murari Andrea) "

Sökning: WFRF:(Murari Andrea)

  • Resultat 1-8 av 8
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1.
  • Gatu Johnson, Maria, 1978-, et al. (författare)
  • Modeling and TOFOR measurements of scattered neutrons at JET
  • Annan publikation (övrigt vetenskapligt)abstract
    • In this paper, the scattered and direct neutron fluxes in the line-of-sight of the TOFOR neutron spectrometer at JET are simulated and the simulations compared with measurement results. The Monte Carlo code MCNPX is used in the simulations, with a vessel material composition obtained from the JET drawing office and neutron emission profiles calculated from TRANSP simulations of beam ion density profiles. The MCNPX simulations show that the material composition of the scattering wall has a large effect on the shape of the scattered neutron spectrum. Neutron source profile shapes as well as radial and vertical source displacements in the TOFOR line-of-sight are shown to only marginally affect the scatter, while having a larger impact on the direct neutron flux. A matrix of simulated scatter spectra for mono-energetic source neutrons is created which is folded with an approximation of the source spectrum for each JET pulse studied to obtain a scatter component for use in the data analysis. The scatter components thus obtained are shown to describe the measured data. It is also demonstrated that the scattered flux is approximately constant relative to the total neutron yield as measured with the JET fission chambers, while there is a larger spread in the direct flux, consistent with simulations. The simulated effect on the integrated scattered/direct ratio of an increase with movements outward along the radial direction and a drop at higher values of the vertical plasma position is also reproduced in the measurements. Finally, the quantitative agreement found in scatter/direct ratios between simulations (0.185±0.005) and measurements (0.187±0.050) serves as a solid benchmark of the MCNPX model used.
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  • Gatu Johnson, Maria, 1978-, et al. (författare)
  • The TOFOR neutron spectrometer and its first use at JET
  • 2006
  • Ingår i: Review of Scientific Instruments. - American Institute of Physics. - 0034-6748 .- 1089-7623. ; 77:10E702, s. 1-3, s. 840-
  • Tidskriftsartikel (refereegranskat)abstract
    • A time-of-flight neutron spectrometer (TOFOR) has been developed to measure the 2.45  MeV  d+d3He+n neutron emission from D plasmas. The TOFOR design features the capability to operate at high rates in the 100  kHz range, data collection with fast time digitizing and storing, and monitoring of the signals from the scintillation detectors used. This article describes the principles of the instrument and its installation at JET and presents preliminary data to illustrate the TOFOR performance as a neutron emission spectroscopy diagnostic.
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  • Murari, Andrea, et al. (författare)
  • Detection of Causal Relations in Time Series Affected by Noise in Tokamaks Using Geodesic Distance on Gaussian Manifolds
  • 2017
  • Ingår i: Entropy. - : MDPI. - 1099-4300 .- 1099-4300. ; 19:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Modern experiments in Magnetic Confinement Nuclear Fusion can produce Gigabytes of data, mainly in form of time series. The acquired signals, composing massive databases, are typically affected by significant levels of noise. The interpretation of the time series can therefore become quite involved, particularly when tenuous causal relations have to be investigated. In the last years, synchronization experiments, to control potentially dangerous instabilities, have become a subject of intensive research. Their interpretation requires quite delicate causality analysis. In this paper, the approach of Information Geometry is applied to the problem of assessing the effectiveness of synchronization experiments on JET (Joint European Torus). In particular, the use of the Geodesic Distance on Gaussian Manifolds is shown to improve the results of advanced techniques such as Recurrent Plots and Complex Networks, when the noise level is not negligible. In cases affected by particularly high levels of noise, compromising the traditional treatments, the use of the Geodesic Distance on Gaussian Manifolds allows deriving quite encouraging results. In addition to consolidating conclusions previously quite uncertain, it has been demonstrated that the proposed approach permit to successfully analyze signals of discharges which were otherwise unusable, therefore salvaging the interpretation of those experiments.
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  • Murari, Andrea, et al. (författare)
  • On the Use of Transfer Entropy to Investigate the Time Horizon of Causal Influences between Signals
  • 2018
  • Ingår i: Entropy. - : MDPI. - 1099-4300 .- 1099-4300. ; 20:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding the details of the correlation between time series is an essential step on the route to assessing the causal relation between systems. Traditional statistical indicators, such as the Pearson correlation coefficient and the mutual information, have some significant limitations. More recently, transfer entropy has been proposed as a powerful tool to understand the flow of information between signals. In this paper, the comparative advantages of transfer entropy, for determining the time horizon of causal influence, are illustrated with the help of synthetic data. The technique has been specifically revised for the analysis of synchronization experiments. The investigation of experimental data from thermonuclear plasma diagnostics proves the potential and limitations of the developed approach.
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7.
  • Romanelli, Francesco, et al. (författare)
  • The role of JET for the preparation of the ITER exploitation
  • 2011
  • Ingår i: Fusion engineering and design. - 0920-3796 .- 1873-7196. ; 86:6-8, s. 459-464
  • Tidskriftsartikel (refereegranskat)abstract
    • The JET programme is devoted to the consolidation of ITER design choices and the qualification of ITER integrated regimes of operation. During the experimental campaigns carried out in 2008 and 2009 attention focussed on the test of the ITER-like ICRH antenna, the ITER scenario preparation, the verification of the adequacy of the ITER poloidal field coil design and the test of disruption mitigation methods such as massive gas injection. From 2011 the new ITER-like wall with all beryllium and tungsten plasma facing components, the neutral beam power upgrade and the enhanced control and diagnostic capability will allow key questions on plasma-wall interactions, fuel retention and plasma impurity control with the foreseen ITER wall materials to be addressed. Finally, feasibility studies have confirmed the option of installing an ITER-technology based 170 GHz/10 MW electron cyclotron resonance heating system for the control of MHD activity and the development of advanced tokamak scenarios, and 32 in-vessel coils for ELM control capable of producing magnetic perturbation spectra with a Chirikov parameter above unity for plasma currents up to 5 MA. During the ITER construction phase, JET will be the only device of its class in operation and will therefore play a key role in the preparation of ITER operations - saving time and reducing risk from the ITER programme.
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  • Resultat 1-8 av 8

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