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119 results on '"Dirk Reiser"'

101. Modelling of confinement degradation in the radiative improved mode caused by a strong gas puff

Author

R.R. Weynants, A.M. Messiaen, D. Kalupin, M. Z. Tokar, G. Van Wassenhove, Pierre Dumortier, B. Unterberg, Dirk Reiser, and Sergey Soldatov

Subjects
Materials science, Tokamak, Electron, Plasma, Condensed Matter Physics, Ion, law.invention, Nuclear Energy and Engineering, law, Physics::Plasma Physics, Radiative transfer, Limiter, Dissipative system, ddc:530, Electric current, Atomic physics
Abstract

Confinement deterioration and rollover from the radiative improved (RI) mode to the low (L) confinement mode in plasmas with a strong gas puff in the tokamak TEXTOR-94 are modelled by the one-dimensional transport code RITM (radiation from impurities in the transport model). The anomalous transport coefficients in the plasma core include contributions from the ion temperature gradient and dissipative trapped electron instabilities. This model allows us to reproduce the L-RI bifurcation with impurity seeding in good agreement with experimental observations. Whereas the transport at the plasma edge under the RI-mode conditions might be described by the electrostatic turbulence caused by electric currents in the scrape-off layer of the limiter, the present computations show that the level of the edge transport must be increased by at least a factor of three in order to reproduce the evolution of the plasma density profile and the effective ion charge during RI-to-L back transitions. An increase of this order is in agreement with reflectometer measurements and could tentatively be explained by the effect of neutrals on resistive drift modes.

Published
2001
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102. A Review of 'Agritourism'

Author

Dirk Reiser

Subjects
Economic growth, Geography, Ecotourism, Agricultural diversification, Tourism, Leisure and Hospitality Management, Urbanization, Tourism geography, Geography, Planning and Development, Hospitality management studies, Rural area, Marketing, Tourism
Abstract

In times of growing urbanisation and agricultural diversification, rural areas are increasingly losing residents, but “gaining” short-term visitors. City-dwellers want to visit “the countryside to ...

Published
2009
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103. Density limits in TEXTOR-94 auxiliary heated discharges

Author

P. de Vries, A. Pospieszczyk, A. Krämer-Flecken, M. Z. Tokar, U. Samm, Gennady Sergienko, H. R. Koslowski, Juergen Rapp, Wolfgang Biel, F. C. Schüller, Arkadi Kreter, Dirk Reiser, Michael Lehnen, and Rje Roger Jaspers

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Plasma, Condensed Matter Physics, Instability, Mantle (geology), law.invention, law, Impurity, Phase (matter), Radiative transfer, Limit (mathematics), Atomic physics
Abstract

In a tokamak plasma the maximum achievable density is limited. A too high density will result in a violent end of a discharge. Two types of density limit disruption can be distinguished: (a) impure and moderately heated discharges, if the radiative power exceeds the input power, (b) clean, auxiliary heated discharges, where the Greenwald limit is encountered. It has been found that in TEXTOR-SI these two density limits differ by the radiative instability in the plasma boundary, which preceeds the disruption. A symmetric radiative mantle and a detachment are observed prior to the first type, while the Greenwald limit has a MARFE precursor. Control of the impurity content, edge and recycling properties prevents the growth of the MARFE and makes it possible to exceed the Greenwald limit in TEXTOR-94 by more than a factor of 2. High densities have been obtained by means of normal gas feed. Maximum central densities of n(e)(0) = 1.3 x 10(20) m(-3) have been obtained. The maximum achievable density scales with the input power and plasma current. Non-disruptive discharges, with a stationary (t > 25 tau(E)) density a factor of 1.93 above the Greenwald limit have been produced in L mode. The radiative losses and impurity concentration have been maintained at a relatively low level during the entire high density phase.

Published
1999

104. Limits to Tourism and Recreation in Water Catchments

Author

Malcolm Wells, Dirk Reiser, Alison Dunn, Hughes, Michael, Carlsen, Jack, Malcolm Wells, Dirk Reiser, Alison Dunn, Hughes, Michael, and Carlsen, Jack

Abstract

Increase attention has been focussed on tourism and recreation access to public lands reserved for specific purposes, such as water catchments. Land based activities such as hiking, horse riding, motor and mountain biking, abseiling and off-road driving as well as water based activities (canoeing, fishing, swimming) have all been deemed by water managers as a risk to drinking water quality. Increasing demand has increased pressure for tourism and recreation access to these areas. The question then becomes, what level of risk to drinking water quality is posed by these activities? Also, what is the most appropriate management regime for tourism and recreation in water catchments?This paper is based on a review of the legislative, historical and current framework for managing public water catchment areas and drinking water sources in South Western Australia. The review includes an assessment of catchment management regimes in other states of Australia as well as in the United Kingdom and Canada. Management regimes range from total exclusion (as practiced in Western Australia) to managed tourism and recreation use of water catchments (as in Queensland and Victoria). Management of water catchments requires high levels of co-operation between government agencies responsible for land management, water quality and tourism and recreation and the adoption of integrated catchment management strategies is essential.

Published
2010

105. Rotation dependent ion fluxes in front of resonant magnetic perturbation coils

Author

U. Samm, H. Stoschus, Dirk Reiser, Oliver Schmitz, Michael Lehnen, and B. Unterberg

Subjects
Physics, Nuclear and High Energy Physics, Electron density, Toroid, Field (physics), Physics::Plasma Physics, Modulation, Plasma, Atomic physics, Condensed Matter Physics, Rotation, Magnetic field, Ion
Abstract

Ion fluxes to the first wall of TEXTOR are modulated during application of a fast rotating resonant magnetic perturbation (RMP) field. The modulation in front of the RMP coils matches the magnetic topology modelled in vacuum approximation for low relative rotation of f rel = −0.2 kHz between the RMP field and toroidal plasma rotation. With increasing relative rotation, the ion flux pattern is shifted linearly in counter-B t direction. The shift is correlated to a displacement Δφ = π/2 of the electron density modulation at the outermost resonant flux surface caused by an internal plasma response. This indicates a competition between the near magnetic field of the RMP coils and the net magnetic field at the resonant flux surface.

Published
2012
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106. Modelling of edge localized modes with a current relaxation model on JET and TEXTOR

Author

T. Zhang, Youwen Sun, Yunfeng Liang, C.G. Gimblett, Dirk Reiser, J. Pearson, and Y. Yang

Subjects
Physics, Nuclear and High Energy Physics, Jet (fluid), Tokamak, Safety factor, Relaxation (NMR), Edge (geometry), Condensed Matter Physics, Resonant magnetic perturbations, Computational physics, law.invention, Physics::Plasma Physics, law, Limiter, Atomic physics, Current density
Abstract

The mitigation of edge localized modes (ELMs) has been investigated using external resonant magnetic perturbations (RMPs) on JET. An interesting observation encountered is the formation of resonant structures in the dependence of ELM frequency on the edge safety factor. Using a theory based on an extended Taylor relaxation process, initialized by an external peeling mode, this behaviour is modelled and analysed leading to a prediction of a condition that a low edge current density is required for the resonant nature to be observed. This model is outlined and the results compared with recent experimental observations from JET.The TEXTOR tokamak already has a low edge current density due to its limiter configuration and so is predicted to show the resonant behaviour even without the RMP fields being applied. Similar experiments investigating the effect of the edge safety factor on the ELM frequency are conducted on TEXTOR to validate this prediction. It was found from the model that a case with a low normalized edge current density of 0.01 shows good agreement with observations. For such a case the multi-resonance effect is less well defined than observed on JET due to the appearance of highly detailed structure in the model predictions.

Published
2012
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107. Revisited global drift fluid model for linear devices

Author

Dirk Reiser

Subjects
Physics, Advection, Numerical analysis, Plasma, Mechanics, Condensed Matter Physics, Polarization (waves), Vortex, Magnetic field, Classical mechanics, Vorticity equation, Physics::Plasma Physics, ddc:530, Magnetohydrodynamics
Abstract

The problem of energy conserving global drift fluid simulations is revisited. It is found that for the case of cylindrical plasmas in a homogenous magnetic field, a straightforward reformulation is possible avoiding simplifications leading to energetic inconsistencies. The particular new feature is the rigorous treatment of the polarisation drift by a generalization of the vorticity equation. The resulting set of model equations contains previous formulations as limiting cases and is suitable for efficient numerical techniques. Examples of applications on studies of plasma blobs and its impact on plasma target interaction are presented. The numerical studies focus on the appearance of plasma blobs and intermittent transport and its consequences on the release of sputtered target materials in the plasma. Intermittent expulsion of particles in radial direction can be observed and it is found that although the neutrals released from the target show strong fluctuations in their propagation into the plasma column, the overall effect on time averaged profiles is negligible for the conditions considered. In addition, the numerical simulations are utilised to perform an a-posteriori assessment of the magnitude of energetic inconsistencies in previously used simplified models. It is found that certain popular approximations, in particular by the use of simplified vorticity equations, do not significantly affect energetics. However, popular model simplifications with respect to parallel advection are found to provide significant deterioration of the model consistency. [http://dx.doi.org/10.1063/1.4739765]

Published
2012
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108. Correlation length scaling laws in drift-Alfvén edge turbulence computations

Author

S Konzett, Alexander Kendl, and Dirk Reiser

Subjects
Physics, Density gradient, Plasma parameters, Turbulence, Plasma, Mechanics, Collisionality, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, Physics::Fluid Dynamics, Nuclear Energy and Engineering, Physics::Plasma Physics, Beta (plasma physics), Physics::Space Physics, 0103 physical sciences, 010306 general physics, Shear flow
Abstract

The effect of changes in plasma parameters, that are characteristic near or at an L–H transition in fusion edge plasmas, on fluctuation correlation lengths are analysed by means of drift-Alfven turbulence computations. Scalings by density gradient length, collisionality, plasma beta and by an imposed shear flow are considered. It is found that strongly sheared flows lead to the appearance of long-range correlations in electrostatic potential fluctuations parallel and perpendicular to the magnetic field.

Published
2012
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109. Reduction of the turbulent blob transport in the scrape-off layer by a resonant magnetic perturbation in TEXTOR

Author

K. H. Finken, P. Beyer, Dirk Reiser, B. Unterberg, R. R. Weynants, Y. Xu, M. Mitri, Oliver Schmitz, M. Vergote, M. Lehnen, M. Van Schoor, Textor Team, S. Jachmich, M. W. Jakubowski, and TEXTOR Team

Subjects
Physics, Nuclear and High Energy Physics, Amplitude, Turbulence, Divertor, Outflow, Magnetic perturbation, Mechanics, Atomic physics, Condensed Matter Physics, Reduction (mathematics), Layer (electronics), Interchange instability
Abstract

During the static 6/2 Dynamic Ergodic Divertor experiments in TEXTOR, a significant influence of the edge resonant magnetic perturbation (RMP) on the turbulent blob transport in the scrape-off layer (SOL) has been observed. In ohmic discharges without the RMP, the blobs extend 4–5 cm deep into the SOL with a radially outward moving speed of about 1 km s−1 and hence constitute a strong outflow of mass. With the application of the RMP, the blob amplitudes and their radially moving velocity are both reduced, resulting in a significant reduction of the blob transport in the SOL. The reduction effect of the RMP on blobs is found to be robust to changes in the operational regime and to phasing variations of the RMP as well. The blob dynamics appears to be consistent with the paradigm of the radial motions of the blob structures driven by the interchange instability.

Published
2009
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110. Investigation of geodesic acoustic modes and related zonal flows at TEXTOR

Author

M. Kantor, H. R. Koslowski, A. Krämer-Flecken, Dirk Reiser, and Sergey Soldatov

Subjects
Physics, Shearing (physics), Statistics::Applications, Rational surface, Turbulence, Oscillation, Context (language use), Mechanics, Zonal flow (plasma), Collisionality, Condensed Matter Physics, Ballooning, Statistics::Computation, Classical mechanics, Nuclear Energy and Engineering, Physics::Plasma Physics
Abstract

This paper attempts to give an overview on the study of the geodesic acoustic mode (GAM) and the related velocity oscillation of the zonal flow (ZF) at TEXTOR. The reported results are obtained from poloidal cross correlation reflectometry. The advantages of the diagnostic combined with a multi-antenna set-up, as it is installed at TEXTOR, are shortly reviewed and compared with other diagnostics used in experiments on GAMs.Furthermore, the GAM properties in ohmic discharges are reported as frequency scaling with local temperature, poloidal structure and radial distribution. GAM induced density fluctuations and related velocity oscillations are measured for a large radial range. In the context of the latter the collisionality on the GAMs at the plasma edge is investigated. The measurement of the GAM related velocity fluctuations shows that the ZF occurs in two rings at least, separated by a rational surface. The velocity oscillation allows us to estimate the effect of GAMs on the shearing rate. The influence on the shearing rate is quantitatively investigated. The GAM induced shearing rate is not able to overcome the decorrelation rate of the ambient turbulence (AT).Also the relation between AT and GAMs is analyzed. Therefore the AT is characterized and the turbulence driving the GAMs is discussed. A relation between the density scale length and the pronounced occurrence of GAMs is obtained. This is related to a narrow region of k⊥ρs values, which is characteristic for drift ballooning modes. The spectrum of the AT is analyzed in both ZF rings. A significant change in the shape of the low frequency turbulence is obtained. This may be connected with a transition from drift ballooning modes to ITG modes. The latter seems to drive the GAMs less effectively.

Published
2008
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111. The European turbulence code benchmarking effort: turbulence driven by thermal gradients in magnetically confined plasmas

Author

Tilman Dannert, Ben F. McMillan, V. Grandgirard, Frank Jenko, Anders Nielsen, Maurizio Ottaviani, Alexander Kendl, Paolo Angelino, Dirk Reiser, A. G. Peeters, G. L. Falchetto, Alberto Bottino, Bruce D. Scott, Salomon Janhunen, M. Romanelli, M. J. Pueschel, T. T. Ribeiro, S. Jolliet, and Volker Naulin

Subjects
Physics, Tokamak, Turbulence, Mechanics, Plasma, Collisionality, Condensed Matter Physics, law.invention, Nuclear Energy and Engineering, Physics::Plasma Physics, law, Beta (plasma physics), Statistical physics, Magnetohydrodynamics, Adiabatic process, Scaling
Abstract

A cross-comparison and verification of state-of-the-art European codes describing gradient-driven plasma turbulence in the core and edge regions of tokamaks, carried out within the EFDA Task Force on Integrated Tokamak Modelling, is presented. In the case of core ion temperature gradient (ITG) driven turbulence with adiabatic electrons (neglecting trapped particles), good/reasonable agreement is found between various gyrokinetic/gyrofluid codes. The main physical reasons for some deviations observed in nonlocal simulations are discussed. The edge simulations agree very well on collisionality scaling and acceptably well on beta scaling (below the MHD boundary) for cold-ion cases, also in terms of the non-linear mode structure.

Published
2008
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112. Edge transport barrier formation studies on JET with the JETTO code

Author

Jet-Efda Contributors, Y. Andrew, Denis Kalupin, A. Korotkov, S. Wiesen, Dirk Reiser, J. Spence, M. Z. Tokar, G. Corrigan, and Vassili Parail

Subjects
Physics, Convection, Nuclear and High Energy Physics, Jet (fluid), Tokamak, Plasma, Fusion power, Condensed Matter Physics, Magnetic field, law.invention, High-confinement mode, law, Atomic physics, Scaling
Abstract

The 1.5D transport code JETTO (Cenacchi G. and Taroni A. 1988 Rapporto ENEA RT/TIB (88)5) has been applied to model the transition from the low (L) to the high confinement mode (H-mode) in the JET tokamak. Computed values of the critical power, Pth, required for the L–H transition on JET are directly compared with experiment (Andrew Y. et al 2006 Plasma Phys. Control. Fusion 48 479) across line averaged density and magnetic field scans. Reasonable agreement is found between computations and experiment across all densities considered, including low density discharges, where Pth increases with decreasing density. The minimum of Pth(ne) dependence is explained by the enhanced contribution of the particle convection to heat losses at the edge. Higher convective losses result in lower temperature and its gradient, and therefore more power is required for the L–H transition. Computations performed for JET discharges with varied magnetic field show a rough agreement with the experiment, nonetheless both computed and experimental power thresholds are substantially higher than the inter-machine scaling predictions (ITPA H-mode Power Threshold Database Working Group Presented by Takizuka T. 2004 Plasma Phys. and Control. Fusion 46 A227, Snipes J.A. et al 2002 Proc. 19th Int. Conf. on Fusion Energy 2002 (Lyon, France, 2002)).

Published
2008
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113. The DED at TEXTOR: Transport and Topological Properties of a Helical Divertor

Author

S. Brezinsek, Henning Stoschus, Karl Heinz Finken, Detlev Reiter, Dirk Reiser, Sadrilla S. Abdullaev, M. Clever, Dominik Schega, Michael Lehnen, Oliver Schmitz, U. Samm, J. W. Coenen, M. W. Jakubowski, and B. Unterberg

Subjects
Materials science, Convective heat transfer, Field line, Divertor, Plasma, Edge (geometry), Condensed Matter Physics, Topology, Ion, symbols.namesake, Flux (metallurgy), Physics::Plasma Physics, symbols, Langmuir probe, Atomic physics
Abstract

The topological and transport properties in the edge plasma of the dynamic ergodic divertor is studied to clarify the functionality of this type of helical divertor. The heat and particle fluxes at the DED target plates were measured with Langmuir probes. Peak fluxes are found where field lines end, which penetrate deep into the plasma. The comparison of the measured target profiles to the magnetic topology shows, that heat and particles are mainly transported to the target plates via flux tubes of short connection length. About 65% of the fluxes are found in areas, where field lines with a connection length of 1-2 poloidal turns connect to the target. Analysis of the source distribution shows, that about 40% of the ion sources lie inside the downstream area of the divertor. The high fraction of convective heat flux prevents from establishing high recycling in the divertor for the pulse type discussed here.

Published
2008
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114. Electromagnetic fluid drift turbulence in static ergodic magnetic fields

Author

Bruce D. Scott and Dirk Reiser

Subjects
Electromagnetic field, Physics, Tokamak, Condensed matter physics, Turbulence, Advection, Plasma, Mechanics, Collisionality, Condensed Matter Physics, law.invention, Magnetic field, Physics::Plasma Physics, law, Physics::Space Physics, ddc:530, Magnetohydrodynamics
Abstract

Numerical simulations of three-dimensional nonlinear electromagnetic fluid drift turbulence in a tokamak plasma with externally applied stochastic magnetic-field perturbations are presented. The contributions to the radial particle transport due to nonlinearities arising from ExB advection and magnetic flutter are investigated for perturbation fields of varying strengths in the cases of low and high collisionalities. The perturbation strength is varied to study the physics for Chirikov parameters above 1. In all the cases considered a significant increase of ExB transport is found. A static contribution in the density and velocity perturbations contributes significantly to the total radial ExB transport. For low collisionality, the external perturbation leads to enhanced density and velocity fluctuations over a broad range in the toroidal wave-number spectrum, resulting in an enhanced turbulent flux. For high collisionality, the density fluctuations stay roughly the same and the velocity fluctuations are increased in an intermediate range of the toroidal wave number spectrum, separated from the maximum of the density fluctuations, thus leaving the turbulent flux almost unchanged. (c) 2005 American Institute of Physics.

Published
2005
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115. Self-consistent simulation of supersonic plasma flows in advanced divertors.

Author

Satoshi Togo, Tomonori Takizuka, Dirk Reiser, Mizuki Sakamoto, Naomichi Ezumi, Yuichi Ogawa, Kunpei Nojiri, Kenzo Ibano, Yue Li, and Yousuke Nakashima

Subjects
PLASMA flow, SUPERSONIC flow, FLOW velocity, PLASMA sheaths, SPEED of sound, STANDING waves
Abstract

Advanced divertors gain larger plasma wetted area by poloidal or total flux expansion. Qualitative characteristics of supersonic plasma flows which are generated by the magnetic nozzle effect are studied by using a plasma fluid model incorporating anisotropic ion pressure (AIP model). The AIP model can self-consistently simulate supersonic plasma flows because, unlike the widely-used plasma fluid model (the Braginskii equations), the equation of parallel plasma momentum in it is described as a hyperbolic-type and the plasma flow velocity is solved without using explicit boundary conditions at the sheath entrance in front of divertor plates. In comparisons of plasma profiles between the AIP model and the Braginskii equations, it is observed that the plasma flow velocity in the Braginskii equations is forced to the sound speed at the sheath entrance in conditions of decelerating supersonic plasma flows leading to qualitative deviations with the AIP model. In an application of the AIP model to a scrape-off layer/divertor region incorporating super-X divertors with various flux-expansion ratios, supersonic plasma flows in divertor regions and highly anisotropic ion temperatures are successfully simulated. It is also demonstrated that it becomes easier with the AIP model to explain the mechanisms of generations of supersonic plasma flows and acceleration/deceleration of them (including stationary shock waves) in flux-expanding divertors from the mirror effect point of view. [ABSTRACT FROM AUTHOR]

Published
2019
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119. Deep neural networks for plasma tomography with applications to JET and COMPASS

Author

J. Denis, M. Tardocchi, Kiptily, M. Koubiti, M. Ghate, R. Michling, G. De Masi, T. Tala, M. Bassan, R. McAdams, S. Dowson, Antoine Merle, Seppo Koivuranta, O. J. Kwon, S. Mahesan, P. Sparapani, A. Malaquias, M. Tsalas, Gennady V. Miloshevsky, M. Vecsei, Michal Stano, E. Lerche, Štefan Matejčík, Piergiorgio Sonato, S. D. Pinches, A. Dal Molin, O. McCormack, B. Colling, F. Mink, Ph. Mertens, P. Drewelow, Nuno Cruz, D. Iglesias, Alessandro Zocco, K. Rathod, S. Collins, F. Koechl, James Buchanan, Andrew West, Francesco Maviglia, E. Stefanikova, David Taylor, B. Graham, T. Lunt, S. Meshchaninov, Arturo Buscarino, G. L. Ravera, Maide Bucolo, J. P. Thomas, S. Foley, B. Wakeling, N. Ashikawa, D. W. Robson, N. J. Conway, V. P. Lo Schiavo, Stefan Buller, Sergey Popovichev, M. Saleem, Jorge Luis Rodriguez, M. Wheatley, Gabriele Croci, Hugo Bufferand, J.F. Artaud, R. C. Felton, O. Kovanda, D. Hepple, K. Dylst, Gabor Szepesi, M. Oberkofler, G.J. van Rooij, N. Teplova, Istvan Cziegler, K. K. Kirov, S. Vartanian, Y. Xue, D. Nina, J. Bernardo, Lorenzo Figini, Guglielmo Rubinacci, Peter Lang, R. Scannell, N. C. Hawkes, P. Denner, Istvan Pusztai, D. D. Carvalho, Salvatore Ventre, A. Lescinskis, Afanasev, C. Hamlyn-Harris, Panagiotis Tolias, R. Vale, T. O'Gorman, S. Lesnoj, I.E. Day, Karol Malinowski, D. Carralero, N. Balshaw, Massimo Angelone, Michaele Freisinger, I. Monakhov, Jesús Vega, Jonathan Citrin, Antti Hakola, H. Patten, P. A. Simmons, Y. Austin, Sehyun Kwak, J. Regana, Rohde, T. Eich, A. Alkseev, R. Lawless, C. G. Elsmore, Fusco, S. Hacquin, S. A. Silburn, A. Fernades, Luigi Fortuna, P. Bunting, R. Sartori, Yuji Hatano, D. Borodin, L. Colas, Daniele Marocco, M. Lennholm, Carlo Sozzi, J. J. Rasmussen, P. McCullen, Tommy Ahlgren, A. Kirschner, Thomas Johnson, M. Rack, Göran Ericsson, Hans Nordman, Jakub Bielecki, P. Merriman, M. Cavedon, G. Hermon, Geert Verdoolaege, K. J. Gibson, Daisuke Nishijima, R. Clarkson, Fuchs, M. Tomes, R. Zagórski, Gerald Pintsuk, W. Higginson, Daniel F. Valcarcel, R. Mooney, K. Dawson, A. Tallargio, T.H. Osborne, P. J. Carvalho, M. Gethins, R. Dux, Pierre Dumortier, G. Urbanczyk, Inessa Bolshakova, R. King, B. Tal, Daniel Tegnered, J. W. Coenen, Leena Aho-Mantila, Eva Belonohy, S. Schmuck, Kai Nordlund, Grégoire Hornung, G. Tvalashvili, M. De Bock, Y. Baranov, G. De Tommasi, A. Urban, L. Forsythe, I. Zychor, J. Dobrashian, E. Clark, Paolo Arena, Alessia Santucci, Ivan Lupelli, S. Nowak, M. Curuia, Jonathan Graves, J. C. Hillesheim, Claudio Verona, Zoita, S. Moon, C. Castaldo, A.V. Stephen, Karl Schmid, A. Sahlberg, C. Di Troia, R. Woodley, L. Garzotti, D. Sandiford, Matthew M. Knight, Juho Leppänen, S. Emery, O. G. Pompilian, M. Goniche, C. Luna, M. Mayer, M. Baruzzo, A. Weckmann, M. Kempenaars, S. Hazel, Fabio Pisano, Claudia Corradino, A. G. Meigs, P. Leichauer, S. Potzel, Stéphane Devaux, C. Piron, G. Saibene, David A Rasmussen, Bruce Lipschultz, A. Di Siena, E. Lazzaro, J. Deane, C. Meadowcroft, C. J. Rapson, K.-D. Zastrow, Ph. Duckworth, Tom Wauters, F. Nabais, T. Goerler, D. Brunetti, R. Ellis, David Moulton, L. Jones, E. Delabie, Anna Salmi, Luciano Bertalot, G. Burroughes, B. Kos, Laurent Marot, Daniel Primetzhofer, I Miron, N. Lam, F. Napoli, S. Rowe, E. Pajuste, Choong-Seock Chang, R.P. Doerner, D. Silvagni, C. Guillemaut, S. Warder, A.J. Thornton, Matthew Carr, A. Dempsey, Jorge Morales, Pramit Dutta, J. L. Herfindal, S. Maruyama, P. Camp, X. Lefebvre, Ye. O. Kazakov, Andrea G. Chiariello, Gabriele Manduchi, Andre Neto, T. Powell, J. Griffiths, José Vicente, C. Barcellona, J. Hobirk, F. Clairet, L. Xiang, Dirk Reiser, H. Bergsåker, I. Duran, G. Giacometti, M. Kalsey, David Tskhakaya, A. Martin de Aguilera, T. Dittmar, Edmund Highcock, I. Uytdenhouwen, S. Soare, Giuseppe Prestopino, L. Chôné, W. Davis, G. De Temmerman, Basiuk, G. Learoyd, C. Guerard, A. Klix, M. Incelli, B. Viola, R. J. Robins, A. Burckhart, W. Leysen, Jochen Linke, M. Oberparleiter, A. Murari, M. Sertoli, S. D. Scott, A. Lazaros, R. Dejarnac, P. Buratti, H.R. Strauss, G. T. A. Huijsmans, Hajime Urano, Justine M. Kent, A. Kallenbach, D. Fagan, D. S. Darrow, Benedikt Geiger, A. Wynn, X. Sáez, B. Beckett, Horacio Fernandes, G. Ferro, B. Alper, George Wilkie, A. Uccello, T.C. Luce, S. Zoletnik, Petrzilka, Fulvio Auriemma, D. Guard, A. Ho, R. Henriques, I. T. Chapman, D. Butcher, Ph. Maquet, C. Crapper, S. Murphy, C. Ham, D. Brennan, S. Knott, Krasilnikov, D. Kogut, Cédric Pardanaud, K. Galazka, Nicolò Marconato, Daniele Bonfiglio, M. Sos, E. Militello-Asp, Nesenevich, Sean Conroy, S. Hall, L. F. Ruchko, L. Laguardia, O. Marchuk, F.P. Orsitto, I. S. Nedzelskiy, Eva Macusova, E. Andersson Sundén, C. Ayres, R. Prakash, C. Giroud, M. Parsons, R. Rodionov, M. Marin, A. P. Vadgama, A. Reed, Jacob Eriksson, P. Macheta, R. Neu, J. Orszagh, L. Gil, Riccardo Maggiora, M. Peterka, P. Devynck, M. Price, J. Likonen, Andrew M. Edwards, P. Dalgliesh, I. Vinyar, Andrea Malizia, A. Brett, Jane Johnston, A. Kappatou, P. Blatchford, B. Lloyd, P. Vincenzi, A. Mauriya, A. Garcia-Carrasco, Z. Stancar, D. B. Gin, Gediminas Stankunas, J. Edwards, Giuseppe Ambrosino, A. Goodyear, M. Lungaroni, M. Gardener, R.A. Pitts, Svetlana V. Ratynskaia, E. Ivings, Marek Rubel, L. Calacci, Ivo S. Carvalho, M. Afzal, M. Gherendi, D. Schworer, C. Watts, A. M. Messiaen, E. Safi, P. David, A. Petre, J. Uljanovs, U. von Toussaint, H. Greuner, D. Del Sarto, A.C.A. Figueiredo, D. Gallart, R. Bilato, M. Enachescu, P. Monaghan, M. S. J. Rainford, A. Boboc, M. Reinhart, Hiroyasu Utoh, B. P. Duval, L. Hackett, M. Halitovs, G. De Dominici, B. Lomanowski, P. Cahyna, Aslanyan, T. May-Smith, M. Richiusa, A. Goussarov, M. Okabayashi, R. Howell, T. Tadic, M. E. Manso, J. F. Rivero-Rodriguez, Wayne Arter, Ivan Calvo, U. Losada, H. Weisen, A. Teplukhina, Marica Rebai, R. Andrews, C. H. A. Hogben, M. Klas, A. E. Shevelev, J. McKehon, F. Reimold, Enrico Zilli, R. Maingi, M.F. Stamp, A. Rakha, H. T. Kim, D. 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Subjects
Computer science, Feature extraction, Image processing, Computerized Tomography (CT) and Computed Radiography (CR), Plasma diagnostics - interferometry, spectroscopy and imaging, 01 natural sciences, Convolutional neural network, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, 0302 clinical medicine, Compass, Plasma diagnostics-interferometry, spectroscopy and imaging, 0103 physical sciences, Computer vision, Instrumentation, Mathematical Physics, Jet (fluid), Contextual image classification, 010308 nuclear & particles physics, business.industry, Cognitive neuroscience of visual object recognition, Plasma diagnostics - interferometry spectroscopy and imaging, Tomography, Artificial intelligence, business, plasma diagnostics - interferometry, spectroscopy and imaging
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 the inverse of CNNs, so- called deconvolutional neural networks, can be used for inverse problems such as plasma tomography. In essence, plasma tomography consists in reconstructing the 2D plasma profile on a poloidal cross-section of a fusion device, based on line-integrated measurements from multiple radiation detectors. Since the reconstruction process is computationally intensive, a deconvolutional neural network trained to produce the same results will yield a significant computational speedup, at the expense of a small error which can be assessed using different metrics. In this work, we discuss the design principles behind such networks, including the use of multiple layers, how they can be stacked, and how their dimensions can be tuned according to the number of detectors and the desired tomographic resolution for a given fusion device. We describe the application of such networks at JET and COMPASS, where at JET we use the bolometer system, and at COMPASS we use the soft X-ray diagnostic based on photodiode arrays.

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