Conceptual design of the radial gamma ray spectrometers system for<i>α</i>particle and runaway electron measurements at ITER

Nocente, M.; Tardocchi, M.; Barnsley, R.; Bertalot, L.; Brichard, B.; Croci, G.; Brolatti, G.; Pace, L. Di; Fernandes, A.; Giacomelli, L.; Lengar, Igor; Moszyński, M.; Krasilnikov, V.; Muraro, A.; Pereira, Rita; Cippo, E. Perelli; Rigamonti, D.; Rebaı̈, M.; Rzadkiewicz, J.; Salewski, M.; Santosh, P.; Sousa, J.; Zychor, I.; Gorini, G.

doi:10.1088/1741-4326/aa6f7d

Cited by 53 publications

(44 citation statements)

References 44 publications

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“…The hard-X-ray radiation emitted by the runaways has been detected by a LaBr 3 (Ce) spectrometer with a counting rate capability up to MHz and high energy resolution (3% at 667keV) [48]. The detector measures gamma-rays, emitted at about 90 degrees with respect to the magnetic field in the core, along a radial line of sight passing through the plasma center.…”

Section: Effect Of Rmps On Hxr Energy Spectrummentioning

confidence: 99%

Runaway electron mitigation by 3D fields in the ASDEX-Upgrade experiment

Gobbin

Liu

et al. 2017

Plasma Phys. Control. Fusion

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Disruption-generated runaway electron (RE) beams represent a severe threat for tokamak plasma-facing components in high current devices like ITER, thus motivating the search of mitigation techniques. The application of 3D fields might aid this purpose and recently was investigated also in the ASDEX Upgrade experiment by using the internal active saddle coils (termed B-coils). Resonant magnetic perturbations (RMPs) with dominant toroidal mode number n = 1 have been applied by the B-coils, in a RE specific scenario, before and during disruptions, which are deliberately created via massive gas injection. The application of RMPs affects the electron temperature profile and seemingly changes the dynamics of the disruption; this results in a significantly reduced current and lifetime of the generated RE beam. A similar effect is observed also in the hard-X-ray (HXR) spectrum, associated to runaway electron emission, characterized by a partial decrease of the energy content below 1MeV when RMPs are applied. The strength of the observed effects strongly depends on the upper-to-lower B-coil phasing, i.e. on the poloidal spectrum of the applied RMPs, which has been reconstructed including the plasma response by the code MARS-F. A crude vacuum approximation fails in the interpretation of the experimental findings: despite the relatively low β (< 0.5%) of these discharges, a modest amplification (factor of 2) of the edge kink response occurs, which has to be considered to explain the observed suppression effects.PACS numbers:

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Section: Effect Of Rmps On Hxr Energy Spectrummentioning

confidence: 99%

Runaway electron mitigation by 3D fields in the ASDEX-Upgrade experiment

Gobbin

Liu

et al. 2017

Plasma Phys. Control. Fusion

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“…They make use of silicon photomultipliers and LaBr 3 as an upgrade of CsI(Tl) and photodiodes. The advantages are an energy resolution comparable to that obtained with photomultiplier tubes, i.e., between 4 and 5% at the 662 keV line (Rigamonti et al 2016), and a significantly faster pulse width of about 100 ns, which opens up to applications in high neutron-yield discharges at MHz counting rates (Nocente et al 2016). The use of a dedicated fully digital acquisition system (Fernandes et al 2014), together with the good energy resolution and time response of the new detectors, make it possible to precisely select only the energy bands associated with the specific fast-ion reactions of interest, as well as to eliminate the interference of neutron-induced events in the spectrum by subtraction of the background in the vicinity of the emission peaks.…”

Section: Neutron Measurementsmentioning

confidence: 98%

Recent progress in fast-ion diagnostics for magnetically confined plasmas

Moseev

Salewski

García-Muñoz

et al. 2018

Rev. Mod. Plasma Phys.

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On the road to a fusion reactor, a thorough control of the fast-ion distribution plays a crucial role. Fusion-born -particles are, indeed, a necessary ingredient of selfsustained burning plasmas. Recent developments in the diagnostic of fast-ion distributions have significantly improved our predictive capabilities towards future devices. Here, we review key diagnostic techniques for confined and lost fast ions in tokamak and stellarator plasmas. We discuss neutron and gamma-ray spectroscopy, fast-ion D-spectroscopy, collective Thomson scattering, neutral particle analyzers, and fast-ion loss detectors. The review covers physical principles of each diagnostic, sensitivities, basic setups, and operational parameters. The review is largely (but not exclusively) based on the contributions from ASDEX Upgrade and JET. Finally, we discuss integrated data analysis of fast-ion diagnostics by velocity-space tomography which allows measurements of 2D velocity distribution functions of confined fast ions.

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“…The sensitivity of ECE at ω < ω c to most of the plasma volume renders such spectra difficult to invert both in real and velocity space, although physically motivated prior information on the electron distribution function, along the lines of [55], might reduce the high dimensionality of the problem. If further input from other diagnostics such as Thomson scattering and X-ray/gamma-ray spectrometry [56] could make an inversion tractable using velocityspace tomography, the results could provide spatial information on the electron velocity distribution (or, perhaps more realistically, simply aid in pinpointing deviations from an assumed distribution function [55]) -independently of measurements in the optically thick regime. This approach could potentially be tested using radiometers operating at ω < ω c in existing fusion devices or using the 55-65 GHz CTS receivers on ITER itself.…”

Section: Diagnostic Implicationsmentioning

confidence: 99%

Modeling the electron cyclotron emission below the fundamental resonance in ITER

Rasmussen

Stejner

Figini

et al. 2019

Plasma Phys. Control. Fusion

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The electron cyclotron emission (ECE) in fusion devices is nontrivial to model in detail at frequencies well below the fundamental resonance where the plasma is optically thin. However, doing so is important for evaluating the background for microwave diagnostics operating in this frequency range.Here we present a general framework for estimating the ECE levels of fusion plasmas at such frequencies using ensemble-averaging of rays traced through many randomized wall reflections. This enables us to account for the overall vacuum vessel geometry, self-consistently include cross-polarization, and quantify the statistical uncertainty on the resulting ECE spectra. Applying this to ITER conditions, we find simulated ECE levels that increase strongly with frequency and plasma temperature in the considered range of 55-75 GHz. At frequencies smaller than 70 GHz, we predict an X-mode ECE level below 100 eV in the ITER baseline plasma scenario, but with corresponding intensities reaching keV levels in the hotter hybrid plasma scenario. Benchmarking against the SPECE raytracing code reveals good agreement under relevant conditions, and the predicted strength of Xmode to O-mode conversion induced by wall reflections is consistent with estimates from existing fusion devices. We discuss possible implications of our findings for ITER microwave diagnostics such as ECE, reflectometry, and collective Thomson scattering.

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Conceptual design of the radial gamma ray spectrometers system forαparticle and runaway electron measurements at ITER

Cited by 53 publications

References 44 publications

Runaway electron mitigation by 3D fields in the ASDEX-Upgrade experiment

Runaway electron mitigation by 3D fields in the ASDEX-Upgrade experiment

Recent progress in fast-ion diagnostics for magnetically confined plasmas

Modeling the electron cyclotron emission below the fundamental resonance in ITER

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