The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Domenico Famularo - One of the best experts on this subject based on the ideXlab platform.
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A constrained control strategy for the shape control in Thermonuclear Fusion tokamaks
Automatica, 2013Co-Authors: Massimiliano Mattei, C. Labate, Domenico FamularoAbstract:The paper deals with the application of the so-called Reference (or Command) Governor constrained control strategy to the shape control of plasmas in Thermonuclear Fusion reactors with the main scope of optimizing tokamak operations also in conditions very close to the operating envelope limits. A primal inner loop controlling the plasma-wall distance is first designed; the Reference Governor device is then tuned to modify, whenever necessary, the reference signals to the inner loop, on the basis of constraints due to voltage saturations on the power supply converters, limitations of currents in the active control coils, minimum clearance between the plasma surface and the vacuum chamber wall, maximum induced magnetic fields and forces on coils. As usual in model predictive paradigms, the reference signal modification is accomplished through an on-line optimization procedure which embodies plasma model forecasts computed along a finite time virtual receding horizon. The ITER (International Thermonuclear Experimental Reactor) tokamak is assumed as the case study. Numerical simulations are carried out on a finite elements nonlinear model taking into account induced currents in the passive structures. The proposed application shows how almost a hundred constraints can be managed on-line by the Reference Governor.
Ghulam Murtaza - One of the best experts on this subject based on the ideXlab platform.
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Thermonuclear Fusion in a multicascade liner staged pinch
Laser and Particle Beams, 2001Co-Authors: Zahoor Ahmad, Arshad M. Mirza, N. A. D. Khattak, Ghulam MurtazaAbstract:A theoretical model for a multicascade liner system is proposed with a view to reduce the growth rate of Rayleigh-Taylor (R-T) instability and to calculate the Fusion parameters of a dense 0-pinch plasma. The dynamics of such plasma has been described using the modified snow-plow model for sinusoidal and t 1/3 types of discharge current profiles. Numerical results demonstrate that the Thermonuclear Fusion parameters can be achieved for a dense θ-pinch deuterium-tritium (D-T) fiber plasma for an optimum choice of shell thickness. The relevance of this kind of study is possible use of gas-liner and staged pinches as an alternative source of Thermonuclear Fusion.
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Thermonuclear Fusion with a spinning gas-puff staged pinch
Plasma Physics and Controlled Fusion, 1996Co-Authors: Arshad M. Mirza, N. A. D. Khattak, M. Salahuddin, Ghulam MurtazaAbstract:The implosion dynamics of a high density -pinch plasma driven by a spinning annular gas-puff of negligible thickness is investigated. Numerical results show that spinning the outer Z-pinch plasma alone, though adequate to suppress the growth of RT instability, is not enough to achieve Thermonuclear Fusion conditions with staged pinch. However if, together with the spinning gas-puff, one uses high- Z impurity seeded DT-fibre, then owing to radiative collapse, Thermonuclear Fusion conditions are achievable.
T. Hellsten - One of the best experts on this subject based on the ideXlab platform.
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Status and Prospects of Controlled Thermonuclear Fusion
Hyperfine Interactions, 1993Co-Authors: D.f. Duechs, T. HellstenAbstract:Of all approaches to controlled Thermonuclear Fusion the tokamak experiments have been most successful. Over the last decade particularly three large devices have achieved plasma density,n, temperature,T, and energy confinement time,τ E, in ranges necessary for a Fusion reactor plasma. Such maximum values have, however, been obtained not yet simultaneously but only in separate pulses, although the crucial triple product,nTτ E, has also been improved by several orders of magnitude. The high temperatures sufficient in a Fusion reactor can be produced by injection of neutral atoms or by absorption of radio frequency waves in the ion cyclotron frequency range. The plasma confinement (τ E≈1s) is still not understood and is handled through empirical “scaling laws”. Particle densities have usually been on the low side (n≤5×1019 m−3) because increased fuelling rates can easily lead to violent current disruptions. Progress in obtaining peaked density profiles with pellet injection has led to high density plasmas without disruptions. Serious unsolved problems concern the spoiling of the Fusion rates by (nonhydrogenic) impurities, the plasma parameter control over longer periods of time and indeed the plasma heating by Fusion alpha-particles (“ignition, burning”). The most urgent technological question refers to the lifetime of the first wall which is in direct contact with the plasma. An important step towards ignition has been made by the recent JET/DT experiments in which, for the first time, the actual reactor fuel component tritium has been used to produce neutrons. The “next generation” tokamak ITER is, at present, being planned and designed in a world-wide collaborative effort. It should be operating before the year 2010 and is intended to investigate an ignited plasma burning for several minutes.
G. Schettini - One of the best experts on this subject based on the ideXlab platform.
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Radio-frequency current drive for Thermonuclear Fusion reactors
Scientific Reports, 2018Co-Authors: A. Cardinali, C. Castaldo, R. Cesario, L. Amicucci, A. Galli, F. Napoli, L. Panaccione, C. Riccardi, F. Santini, G. SchettiniAbstract:Principal research on energy from Thermonuclear Fusion uses Deuterium-Tritium plasmas magnetically trapped in toroidal devices. As major scientific problem for an economic (i.e., really feasible) reactor, we must understand how to lead strongly heated plasmas to sustain a high Fusion gain while large fraction of current is self-produced via the presence of strong pressure gradient. To suppress turbulent eddies that impair thermal insulation and pressure tight of the plasma, current drive (CD) is necessary. However, tools envisaged so far in ITER (International Thermonuclear Experiment Rector) are unable accomplishing this task that requires efficiently and flexibly matching the natural current profiles of plasma. Consequently, viability of a Thermonuclear reactor should be problematic. Multi-megawatt radio-frequency (RF) power coupled to plasma would produce the necessary CD, but modelling results based on previous understanding found difficult the extrapolation of this CD concept to reactor conditions of high temperature plasma, and greater flexibility of method would also be required. Here we present new model results based on standard quasilinear (QL) theory that allow establish conditions to drive efficiently and flexibly the RF-driven current at large radii of the plasma column, as necessary for the goal of a reactor.
Massimiliano Mattei - One of the best experts on this subject based on the ideXlab platform.
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A constrained control strategy for the shape control in Thermonuclear Fusion tokamaks
Automatica, 2013Co-Authors: Massimiliano Mattei, C. Labate, Domenico FamularoAbstract:The paper deals with the application of the so-called Reference (or Command) Governor constrained control strategy to the shape control of plasmas in Thermonuclear Fusion reactors with the main scope of optimizing tokamak operations also in conditions very close to the operating envelope limits. A primal inner loop controlling the plasma-wall distance is first designed; the Reference Governor device is then tuned to modify, whenever necessary, the reference signals to the inner loop, on the basis of constraints due to voltage saturations on the power supply converters, limitations of currents in the active control coils, minimum clearance between the plasma surface and the vacuum chamber wall, maximum induced magnetic fields and forces on coils. As usual in model predictive paradigms, the reference signal modification is accomplished through an on-line optimization procedure which embodies plasma model forecasts computed along a finite time virtual receding horizon. The ITER (International Thermonuclear Experimental Reactor) tokamak is assumed as the case study. Numerical simulations are carried out on a finite elements nonlinear model taking into account induced currents in the passive structures. The proposed application shows how almost a hundred constraints can be managed on-line by the Reference Governor.