Energy resolved fast two-dimensional x-ray imaging for MFE plasmas (invited)

The radiation characteristics of anticipated sample elements, from H through W, in the International Thermonuclear Experimental Reactor (ITER) have been modelled using the diffusion equilibrium model SANCO for the ion concentrations coupled with the spectral signature of the ions, throughout the X-ray and VUV regions (0.1-100 keV), using the Atomic Data and Analysis Structure population code and database, ADAS. The spectral signature varies greatly depending on whether the viewing line-of-sight (LOS) encompasses the divertor and (or) core regions of the plasma volume. Bound-bound transitions required for line profile analyses of nonfuel core ions can locally dominate the continuum spectrum in the 0.1-10 keV region at acceptably low elemental concentrations. While the background continuum is the main source of noise in the line profile analyses, the intensity and features of the continuum when divided into many spectral bands covering 0.1-100 keV are themselves powerful diagnostics of the plasma composition, Z eff and the electron temperature. The spectral signature of the divertor LOSs where 1 < T e < 300 eV is dominated typically and exclusively by lines in the XUV-VUV region, restricted in the case of W to λ > 40 Å. Appropriate instrumentation, relying on imaging Bragg reflectors and diffractors and position-sensitive energy-resolving detectors, is designed to cover the full spatial extent of the core plasma. Estimates of the core signal/noise based on experience with tritium experiments on the Joint European Torus indicates substantial signal levels with tolerable neutron-induced noise and component degradation. The divertor diagnostics make use of a suite of aspheric diffraction grating spectrometers designed to measure impurity ion influxes and are essential for plasma control. The EBIT could be conceived as a neutron-free adjunct facility to the ITER spectroscopic programme. At its simplest level, it provides standards for instrument performance and for the spectroscopic signature of selected ions subjected to electronic and atomic collisions over a wide range of ITER-relevant impacting energies.Résumé : Les caractéristiques anticipées dans ITER d'échantillons allant de H à W ont été modélisées à l'aide du modèle d'équilibre de diffusion SANCO pour les concentrations ioniques, couplé à la signature spectrale des ions, sur l'ensemble des domaines X et VUV (0.1-100 keV), en utilisant le programme de population et la banque de données ADAS. La signature spectrale varie beaucoup, selon que la ligne de visée (LOS) comprend l'écorceur et/ou le coeur du volume de plasma. Les transitions entre états liés, requises pour l'analyse du profil de raie des ions non combustibles du coeur, peuvent dominer largement le spectre continu dans le domaine 0.1-10 keV aux faibles concentrations acceptables des éléments. Alors que le continu du fond est la principale source de bruit dans l'analyse du profil de raie, l'intensité et les caractéristiques du continuum lorsque divisé en plusieurs bandes spectrales couvrant 0.1-100 keV, ...

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“…3 there are ongoing developments in microcalorimeters [16,17] and energy-resolving active pixel array [18,19] technologies.…”

Section: Instrumentation and Broadband Emission-based Diagnosticsmentioning

confidence: 99%

Anticipated X-ray and VUV spectroscopic data from ITERwith appropriate diagnostic instrumentation

Peacock¹,

O’Mullane²,

Barnsley³

et al. 2008

Can. J. Phys.

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“…A 2-D SXR pinhole camera was introduced for the first time as a diagnostic in tokamaks at FTU (ENEA-Frascati) and NSTX (Princeton, U.S.A.) in 2001 [7,8]. It offered a true 2-D direct imaging of the SXR emissions at high sensitivity, noise-free, with energy discrimination [9].Subsequently this kind of detector was installed and currently in-use in KSTAR tokamak (south Korea) [10] and very recently at EAST tokamak (China). A standard GEM foil is made of a Kapton layer (thickness 50 µm) clad on each side with a thin layer of copper and chemically perforated in order to obtain a high density matrix of bi-conical holes.…”

Section: Detector Description 21 Principle Of Operationsmentioning

confidence: 99%

Development and characterization of a new soft x-ray diagnostic concept for tokamaks

Muraro

Claps²,

Croci

et al. 2019

J. Inst.

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A: Diagnosing soft x-ray (SXR) emission from tokamaks represents a unique source of information, since it allows the study of several plasma parameters, such as the electron and ion temperature, the investigation of the ionization equilibrium, particle and impurities transport and the study of MHD fluctuations and disruptions. A new SXR diagnostic system called EXODUS (Enhanced X-ray Optimized Detector for Use in multiple Scenarios) is under development with the aim to obtain energy resolved SXR emission profiles from the plasma with a high time resolution (< 0.1 ms). The system is based on the Gas Electron Multiplier (GEM) technology coupled with the new data acquisition system especially designed for GEM called GEMINI, which gives the possibility to obtain information about the energy deposited in the detector by the incoming radiation using the so called Time-Over-Threshold technique on each detector channel. The information of the deposited energy allows the study of the SXR emission from the plasma resolved in space, energy and time. There are several advantages in the use of GEM based detector in the harsh environment of a tokamak. First of all, it offers very high rate capabilities (up to 1 MHz/mm 2 ), giving the possibility 1Corresponding author.

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“…A quantitative analysis will be developed in the next section showing the capability to distinguish different materials based on energy dependence with a 2D spatial resolution. Energy resolution of this device has been checked with a laboratory source 13 and with a magnetically confined fusion plasma 14 together with 2D imaging detector. 15,16 …”

Section: "Spectral" Radiographymentioning

confidence: 99%

Energy resolved two-dimensional soft x-ray radiography with a micropattern gas detector

Pacella

Bellazzini

Finkenthal

2006

Review of Scientific Instruments

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This article discusses the use of energy resolved two-dimensional soft x-ray imaging (ERXI), in the range of 2–8keV, to study and investigate composition and depth of different materials. This technique represents a new approach in which imaging is merged with multienergy analysis, performed with spectral scans in 25 energy subintervals. The detector used is a micropattern gas detector with gas electron multiplier as amplifying structure, pixel readout board with 144pixels (12×12), and electronics for photon counting for each pixel. As the detector works in a proportional regime, images in adjustable energy windows (independently for each pixel) can be acquired. Energy resolution enhances the contrast and the imaging capability providing more information of the transparencies of the materials under investigations. Contact radiographies have been made with samples of four different materials: CaCl, organic fat matter, aluminum, and thin plastic tape. The resulting data transparency curves for these materials have been derived. These curves demonstrate the value of ERXI at high performances (high efficiency, high dynamics, and high contrast), potentially relevant for many future applications.

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Energy resolved fast two-dimensional x-ray imaging for MFE plasmas (invited)

Cited by 5 publications

References 6 publications

Anticipated X-ray and VUV spectroscopic data from ITERwith appropriate diagnostic instrumentation

Anticipated X-ray and VUV spectroscopic data from ITERwith appropriate diagnostic instrumentation

Development and characterization of a new soft x-ray diagnostic concept for tokamaks

Energy resolved two-dimensional soft x-ray radiography with a micropattern gas detector

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