Machine modification for active MHD control in RFX

Sonato, P.; Chitarin, G.; Zaccaria, P.; Gnesotto, F.; Ortolani, S.; Buffa, A.; Bagatin, M.; Baker, William R.; Bello, S. Dal; Fiorentin, P.; Grando, L.; Marchiori, G.; Marcuzzi, D.; Masiello, A.; Peruzzo, S.; Pomaro, N.; Serianni, G.

doi:10.1016/s0920-3796(03)00177-7

Cited by 205 publications

(150 citation statements)

References 13 publications

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“…QSH states have been observed in several RFP devices 5,16,17 and predicted in numerical simulations 18 . They are an intermediate state between the multiple-helicity and the theoretical single-helicity ones, because the secondary modes are still present.Here, we present experimental findings obtained in the RFXmod device 19 that show a clear evolution of the plasma towards the single-helicity state. This has been made possible by the exploration of a wide range of plasma current levels, which for the first time in a RFP have reached values higher than 1 MA, and by the control of the radial magnetic field at the plasma boundary through an advanced feedback system 20 .…”

mentioning

confidence: 91%

Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas

Lorenzini¹,

Martines²,

Piovesan³

et al. 2009

Nature Phys

253

304

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In the quest for new energy sources, the research on controlled thermonuclear fusion 1 has been boosted by the start of the construction phase of the International Thermonuclear Experimental Reactor (ITER). ITER is based on the tokamak magnetic configuration 3, which is the best performing one in terms of energy confinement. Alternative concepts are however actively researched, which in the long term could be considered for a second generation of reactors. Here, we show results concerning one of these configurations, the reversed-field pinch 4,5 (RFP). By increasing the plasma current, a spontaneous transition to a helical equilibrium occurs, with a change of magnetic topology. Partially conserved magnetic flux surfaces emerge within residual magnetic chaos, resulting in the onset of a transport barrier. This is a structural change and sheds new light on the potential of the RFP as the basis for a low-magnetic-field ohmic fusion reactor.The main magnetic field configurations studied for the confinement of toroidal fusion-relevant plasmas are the tokamak 3 , the stellarator 6 and the reversed-field pinch 4,5 (RFP). In the tokamak, a strong magnetic field is produced in the toroidal direction by a set of coils approximating a toroidal solenoid, and the poloidal field generated by a toroidal current flowing into the plasma gives the field lines a weak helical twist. This is the configuration that has been most studied and has achieved the best levels of energy confinement time. Thus, it is the natural choice for the International Thermonuclear Experimental Reactor, which has the mission of demonstrating the scientific and technical feasibility of controlled fusion with magnetic confinement.The RFP, like the tokamak, is axisymmetric and exploits the pinch effect due to a current flowing in a plasma embedded in a toroidal magnetic field. The main difference is that, for a given plasma current, the toroidal magnetic field in a RFP is one order of magnitude smaller than in a tokamak, and is mainly generated by currents flowing in the plasma itself. This feature is underlying the main potential advantage of the RFP as a reactor concept, namely the capability of achieving fusion conditions with ohmic heating only in a much simpler and compact device. In the past, this positive feature was overcome by the poorer stability properties, which led to the growth and saturation of several magnetohydrodynamic (MHD) instabilities, eventually downgrading the confinement performance. These instabilities, represented by Fourier modes in the poloidal and toroidal angles θ and φ as exp [i(mθ − nφ) were considered as an unavoidable ingredient of the dynamo self-organization process 4,8,9 , necessary for the sustainment of the configuration in time. The occurrence of several MHD modes resonating on different plasma layers gives rise to overlapping magnetic islands, which result in a chaotic region, extending over most of the plasma volume 10 , where the magnetic surfaces are destroyed and the confinement level is modest. This conditi...

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mentioning

confidence: 91%

Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas

Lorenzini¹,

Martines²,

Piovesan³

et al. 2009

Nature Phys

253

304

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“…Equilibria closely modelling the RFP device RFX [31] is used. Circular plasma cross-section is taken with major radius R 0 = 2.0 m and aspect ratio ε = 0.23.…”

Section: Equilibriummentioning

confidence: 99%

“…In this work numerical studies of the effect of kinetic resonances on the RWM stability are performed for reversed-field pinch (RFP) configuration. Particularly, parameters corresponding to the RFX device [31] is used. In RFP the values of poloidal and toroidal components are of the same order of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Effects of kinetic resonances on the stability of resistive wall modes in reversed field pinch

Yadykin¹,

Liu²,

Paccagnella³

2011

Plasma Phys. Control. Fusion

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The kinetic effects, due to the mode resonance with thermal particle drift motions in the reversed field pinch (RFP) plasmas, are numerically investigated for the stability of the resistive wall mode, using a non-perturbative MHDkinetic hybrid formulation. The kinetic effects are generally found to be too weak to substantially change the mode growth rate, or the stability margin, reenforcing the fact that the ideal MHD model is rather adequate for describing the RWM physics in RFP experiments.

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“…The enhancement is a joint proposal by four Associations, IPP, FZJ, KTH, and Consorzio RFX, which in particular contributes with its experience in the field of MHD modes control on Reversed Field Pinch [2] and with direct responsibility in the development of the Conceptual Design of the Power Supply System. MHD instabilities considerably limit the performance of thermonuclear fusion experiments; their control is needed to explore high beta regimes beyond currently achieved parameters.…”

Section: Introductionmentioning

confidence: 99%

Conceptual design of the power supply system for the in-vessel saddle coils for MHD control in ASDEX Upgrade

Gaio¹,

Zamengo²,

Toigo³

et al. 2011

Fusion Engineering and Design

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In the frame of an ASDEX Upgrade enhancement, a system of active in-vessel coils (of two types, dubbed "A" and "B") and conducting wall for MagnetoHydroDynamic (MHD) stabilization is being designed and implemented.The conceptual design of the Power Supply (PS) system has been worked out and extensive analyses have been performed to verify that the identified basic modules, based on a cascade topology with two IGBT (Isolated Gate Bipolar Transistor) H-bridges in series for the A units and one H-bridge for the B ones, were able to fulfill all the requirements, well within semiconductors safety operating limits. The paper summarizes the work which led to the definition of the PS requirements, describes the topologies of the selected basic units and of the overall scheme, discusses the design choices and reports the results of the numerical simulations carried out to check the overall performance.

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Machine modification for active MHD control in RFX

Cited by 205 publications

References 13 publications

Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas

Self-organized helical equilibria as a new paradigm for ohmically heated fusion plasmas

Effects of kinetic resonances on the stability of resistive wall modes in reversed field pinch

Conceptual design of the power supply system for the in-vessel saddle coils for MHD control in ASDEX Upgrade

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