The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
D Chandra - One of the best experts on this subject based on the ideXlab platform.
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Plasma Currents induced by resonant magnetic field perturbations in tokamaks
Physics of Plasmas, 2009Co-Authors: D Reiser, D ChandraAbstract:The Plasma response on externally applied resonant magnetic field perturbations is studied by means of numerical simulations. It is shown that dependent on collisionality and perturbation strength, Plasma Currents build up which can compensate the external field. These Plasma Currents are accompanied by out-of-phase Currents and poloidal flows at the resonant surfaces. With an increasing perturbation field the screening of the externally applied field decreases and at a certain level, the vacuum field approximation holds for the total magnetic field.
Gabriele Neretti - One of the best experts on this subject based on the ideXlab platform.
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High-Voltage High-Frequency Arbitrary Waveform Multilevel Generator for DBD Plasma Actuators
IEEE Transactions on Industry Applications, 2015Co-Authors: Filopimin A. Dragonas, Gabriele Neretti, Padmanaban Sanjeevikumar, Gabriele GrandiAbstract:A high-voltage high-frequency single-phase arbitrary waveform voltage generator able to supply a wide range of Plasma reactors is proposed in this paper. The generator structure is based on the cascaded H-bridge multilevel (ML) topology, including 24 H-bridge basic modules with the capability of 49 output voltage levels. The individual H-bridge dc supply (600 V) is provided by a flyback converter fed by a low-voltage (12 V) dc battery. This way, the input isolation of the ±14.4 kV maximum output voltage is realized in a simple and effective manner, and a portable device is obtained. The ML generator has been tested by supplying a dielectric barrier discharge (DBD) fluid-dynamic Plasma actuator with different voltage waveforms, pointing out a wide and interesting set of results in terms of output Plasma Currents, and a first comparison has been carried out with respect to a conventional ac sinusoidal generator. A simplified circuit model has been introduced for the DBD Plasma actuator, and the whole system has been numerically implemented by Simulink of MATLAB. The simulation results are in good agreement with the experiments.
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High-voltage high-frequency arbitrary waveform multilevel generator for dielectric barrier discharge
2014 International Symposium on Power Electronics Electrical Drives Automation and Motion, 2014Co-Authors: Filopimin A. Dragonas, Gabriele Grandi, Gabriele NerettiAbstract:A high-voltage high-frequency arbitrary waveform voltage generator able to supply a wide range of Plasma reactors is proposed in this paper. The generator structure is based on the cascaded H-bridge multilevel topology, including 24 H-bridge basic modules with the capability of 49 output voltage levels. The individual H-bridge dc supply (600V) is provided by a flyback converter fed by a low-voltage (12V) dc battery. In this way, the input isolation of the ±15kV maximum output voltage is realized in a simple and effective manner, and a portable device is obtained. The generator has been tested by supplying a DBD Plasma actuator with different voltage waveforms, up to 20 kHz, pointing out a wide and interesting set of results in terms of output Plasma Currents.
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charge distribution on the surface of a dielectric barrier discharge actuator for the fluid dynamic control
Journal of Applied Physics, 2013Co-Authors: Andrea Cristofolini, C A Borghi, Gabriele NerettiAbstract:The electric potential distribution induced on the surface of an aerodynamic Plasma actuator, operating by means of a surface dielectric barrier discharge (DBD), has been studied both numerically and experimentally. Three actuators made with three different dielectric materials (Teflon, Plexiglas, and glass) have been used. The geometric configuration of the three actuators is the same one. An electrode pair separated by a 2 mm thick dielectric sheet constitutes the DBD actuator. The exposed high voltage electrode has been fed by a 5 kHz a.c. electrical signal. Voltage values between 7.5 and 15 kVp have been used. Measurements of the distribution of the electrical potential in the dielectric surface, generated by the charge deposited on it, have been done. Numerical simulations allowed to evaluating the charge distribution on the dielectric surface. The discharge has been switched off after positive and negative Plasma Currents. The measurements have been carried out after both phases. The potential distr...
A Sykes - One of the best experts on this subject based on the ideXlab platform.
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Results from the MAST spherical tokamak
Proceedings of the 19th IEEE IPSS Symposium on Fusion Engineering. 19th SOFE (Cat. No.02CH37231), 2002Co-Authors: A Sykes, R.j. Akers, E. Arends, K. Axon, R.j. Buttery, C. Byrom, P.g. Carolan, D. Ciric, N.j. Conway, G.f. CounsellAbstract:The MAST (Mega-Amp Spherical Tokamak) experiment has been operational since Jan 2000. Results from MAST are important both in evaluating the potential of future ST fusion devices, and in developing understanding of processes relevant to conventional aspect ratio tokamaks. In this paper methods of initiating, ramping up, and sustaining the high Plasma Currents associated with ST fusion devices are discussed. New physics results, including the effectiveness of inboard gas puffing, the threshold power required for the L-H transition, and the 'natural' divertor configuration are given. Plans for improvements during 2002 are outlined.
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the spherical tokamak programme at culham
Nuclear Fusion, 1999Co-Authors: A SykesAbstract:The spherical tokamak (ST) is the low aspect ratio limit of the conventional tokamak and appears to offer attractive physics properties in a simpler device. The START (Small Tight Aspect Ratio Tokamak) experiment provided the world's first demonstration of the properties of hot Plasmas in an ST configuration and was operational at Culham from January 1991 to March 1998, obtaining Plasma Currents of up to 300 kA and pulse durations of ~50 ms. Its successor, MAST, is nearing completion and is a purpose built, high vacuum machine designed to have a tenfold increase in Plasma volume with Plasma Currents of up to 2 MA. Current drive and heating will be by a combination of induction-compression as on START, a high performance central solenoid, with 1.5 MW ECRH and 5 MW of NBI. The promising results from START are reviewed, and the many challenges posed for the next generation of purpose built STs (such as MAST) are described.
A Runov - One of the best experts on this subject based on the ideXlab platform.
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on the confinement of passing alpha particles in a tokamak reactor with resonant magnetic field perturbations shielded by Plasma Currents
Nuclear Fusion, 2012Co-Authors: M F Heyn, Ivan Borisovich Ivanov, S V Kasilov, Winfried Kernbichler, A Loarte, V V Nemov, A RunovAbstract:Alpha-particle losses due to the resonant magnetic field perturbations (RMPs) created by the coil system for edge-localized mode mitigation in ITER are studied numerically. If shielding of RMPs by the Plasma is not taken into account, passing α-particles are the main loss channel which, together with the trapped particle contribution leads to a loss of more than 5% of fusion alpha particle power. Shielding of RMPs practically eliminates this channel so that the overall losses are reduced to about 1%.
D Reiser - One of the best experts on this subject based on the ideXlab platform.
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Plasma Currents induced by resonant magnetic field perturbations in tokamaks
Physics of Plasmas, 2009Co-Authors: D Reiser, D ChandraAbstract:The Plasma response on externally applied resonant magnetic field perturbations is studied by means of numerical simulations. It is shown that dependent on collisionality and perturbation strength, Plasma Currents build up which can compensate the external field. These Plasma Currents are accompanied by out-of-phase Currents and poloidal flows at the resonant surfaces. With an increasing perturbation field the screening of the externally applied field decreases and at a certain level, the vacuum field approximation holds for the total magnetic field.