Showing papers by "Boris Breizman published in 2019"
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135 citations
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TL;DR: In this article, a detailed review of the physics basis for the DTE2 operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of DTE plasmas (thermal and particle transport, high confinement mode, Be and W erosion, fuel recovery, etc).
Abstract: For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des.
82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T,
leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the
first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this
purpose, a concerted physics and technology programme was launched with a view to prepare
the D–T campaign (DTE2). This paper addresses the key elements developed by the JET
programme directly contributing to the D–T preparation. This intense preparation includes
the review of the physics basis for the D–T operational scenarios, including the fusion power
predictions through first principle and integrated modelling, and the impact of isotopes in the
operation and physics of D–T plasmas (thermal and particle transport, high confinement mode
(H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving
several aspects of plasma operation for DTE2, such as real time control schemes, heat load
control, disruption avoidance and a mitigation system (including the installation of a new
shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the threeions
scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode
antennas, neutral gauges, radiation hard imaging systems…) and the calibration of the JET
neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation
of JET for the 2020 D–T campaign provides an incomparable source of information and a
basis for the future D–T operation of ITER, and it is also foreseen that a large number of key
physics issues will be addressed in support of burning plasmas.
79 citations
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TL;DR: In this paper, the injection of cryogenic pellets into a magnetically confined plasma is shown to be accompanied by a considerable transfer of thermal energy from the electrons in the background plasma to the ions.
Abstract: The injection of cryogenic pellets into a magnetically confined plasma is shown to be accompanied by a considerable transfer of thermal energy from the electrons in the background plasma to the ions. The resulting ion heating can be significant, particularly in plasmas with disparate electron and ion temperatures, and can affect the energy balance of the plasma. In recent Wendelstein 7-X experiments, this mechanism can account for a substantial fraction of the ion heating power during pellet injection.
16 citations
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TL;DR: In this paper, a power-balance model, with radiation losses from impurities and neutrals, gives a unified description of the density limit (DL) of the stellarator, the L-mode tokamak, and the reversed field pinch.
Abstract: A power-balance model, with radiation losses from impurities and neutrals, gives a unified description of the density limit (DL) of the stellarator, the L-mode tokamak, and the reversed field pinch ...
12 citations
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TL;DR: In this article, an overview of the potential of ion cyclotron resonance heating (ICRH) or radio frequency heating (RF) for the DEMO machine is presented. But it is not discussed in detail.
Abstract: The present paper offers an overview of the potential of ion cyclotron resonance heating (ICRH) or radio frequency heating for the DEMO machine. It is found that various suitable heating schemes ar ...
12 citations
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TL;DR: Tritium distributions on tungsten (W)-coated tiles used in the third ITER-like wall campaign (2015-2016) of the Joint European Torus (JET) were examined by means of an imaging plate technique and beta-ray induced x-ray spectrometry, and they were compared with the distributions after the second (2013-2014) campaign as discussed by the authors.
Abstract: Tritium (T) distributions on tungsten (W)-coated plasma-facing tiles used in the third ITER-like wall campaign (2015-2016) of the Joint European Torus (JET) were examined by means of an imaging plate technique and beta-ray induced x-ray spectrometry, and they were compared with the distributions after the second (2013-2014) campaign. Strong enrichment of T in beryllium (Be) deposition layers was observed after the second campaign. In contrast, T distributions after the third campaign was more uniform though Be deposition layers were visually recognized. The one of the possible explanations is enhanced desorption of T from Be deposition layers due to higher tile temperatures caused by higher energy input in the third campaign.
9 citations
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TL;DR: In this article, an improved neutron activation method for the evaluation of neutron fluence at fusion devices has been developed, where activation assemblies similar to those used at JET were irradiated under 14 MeV neutrons at the Frascati Neutron Generator (FNG) reference neutron field.
8 citations
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TL;DR: This work has shown that convolutional neural networks, which have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition, are good candidates for machine learning.
Abstract: Convolutional neural networks (CNNs) have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition. It has also been shown that th ...
6 citations
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TL;DR: Alfven eigenmodes driven by energetic particles are routinely observed in tokamak plasmas as mentioned in this paper, which consist of poloidal harmonics of shear Alfven waves coupled by inhomogeneity in the magnetic field.
Abstract: Alfven eigenmodes driven by energetic particles are routinely observed in tokamak plasmas. These modes consist of poloidal harmonics of shear Alfven waves coupled by inhomogeneity in the magnetic f ...
5 citations
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TL;DR: In this paper, a simple image processing algorithm is developed to analyze the behavior of the hot spots in the outer divertor tiles of JET, isolates areas of bright pixels in the camera image and compares them to previously identified hot spots.
3 citations
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TL;DR: In this article, a theoretical framework has been developed for an NBI scenario to model the hard nonlinear evolution of Global Alfven Eigenmodes (GAEs) where the adiabatic motion of phase-space sturctures (holes and clumps), associated with the frequency chirping, occurs in generalized phase space of slowing down energetic particles.
Abstract: A theoretical framework has been developed for an NBI scenario to model the hard nonlinear evolution of Global Alfven Eigenmodes (GAEs) where the adiabatic motion of phase-space sturctures (holes and clumps), associated with the frequency chirping, occurs in generalized phase-space of slowing down energetic particles. The radial profile of the GAE is expanded using finite elements which allows update of the mode structure as the mode frequency chirps. Constants of motion are introduced to track the dynamics of energetic particles during frequency chirping by implementing proper Action-Angle variables and canonical transformations which reduce the dynamics essentially to 1D. Consequently, we specify whether the particles are drifting inward/outward as the frequency deviates from the initial MHD eigenfrequency. Using the principle of least action, we have derived the nonlinear equation describing the evolution of the radial profile by varying the total Lagrangian of the system with respect to the weights of finite elements. For the choice of parameters in this work, it is shown that the peak of the radial profile is shifted and also broadens due to frequency chirping. The time rate of frequency change is also calculated using the energy balance and we show that the adiabatic condition remains valid once it is satisfied. This model clearly illustrates the theoretical treatment to study the long range adiabatic frequency sweeping events observed for Alfven gap modes in real experiments.
01 Jan 2019
TL;DR: In this article, the authors consider electron cooling in a collisionless plasma slab between two cold and freely emitting walls and show that the cooling rate slows down and eventually stops, leaving the system with a significant fraction of its initial thermal energy.
Abstract: We consider electron cooling in a collisionless plasma slab between two cold and freely emitting walls. Numerical calculations suggest a counterintuitive behavior of this system: the cooling rate slows down and eventually stops, leaving the system with a significant fraction of its initial thermal energy. Analytical treatment within the Vlasov–Poisson model reveals a set of steady-states with a two-component distribution of electrons: the primary electrons trapped within the potential wells and the secondary electrons forming the counterstreaming beams. We show that such steady-states are linearly stable with respect to one-dimensional perturbations. Establishment of a particular steady-state depends on initial conditions.