Plasma-turbulence suppression and transport-barrier formation by externally driven radiofrequency waves in spherical tokamaks

Komoshvili, K.; Cuperman, S.; Bruma, C.

doi:10.1017/s0022377801001015

Cited by 3 publications

(3 citation statements)

References 3 publications

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“…Relevant specific topics are considered, e.g. [7] (non-inductive current drive); [8] (RF heating); [9,10] (suppression of turbulence using sheared electric fields generated by externally driven RF waves); see also results of applications of these theories in [11][12][13][14][15][16]. The importance of the Alfvén waves, in particular the Alfvén eigenmodes, lies also in their potential destabilization by fast ions (see, e.g.…”

Section: Introductionmentioning

confidence: 99%

The combined toroidicity, ellipticity and triangularity effects on the energy deposition of Alfvén modes in pre-heated, low aspect ratio tokamaks

2007

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Section: Introductionmentioning

confidence: 99%

The combined toroidicity, ellipticity and triangularity effects on the energy deposition of Alfvén modes in pre-heated, low aspect ratio tokamaks

2007

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“…To ensure the steady-state of a ST, some additional (auxiliary) non-inductive current drive is required (see, e.g., [8]; also [9,10,11,12,13,14]). One suitable option for this is the use of e.m. waves launched from an externally located antenna; in particular, for the pre-heated stage, low frequency (Alfvén) waves are quite appropriate (see, e.g., [15,16,17,18,19,20,21,22]).…”

Section: Introductionmentioning

confidence: 99%

Effects of an Anomalous Resistivity on the Power Deposition by Alfvén Waves in Pre-Heated Spherical Tokamaks

Bruma¹,

Cuperman²,

Komoshvili³

2005

Phys. Scr.

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We derive a lower bound for the mass of the spacetime in axion-dilaton gravity with U(1) gauge fields. It is an analogue of the Bogomolnyi bound. This bound can be expressed in terms of generalized total magnetic and electric charges of U(1) fields. PACS number: 0450The first proof of the positive mass theorem was given by Schoen and Yau [1]. Shortly afterwards Witten conceived the very elegant proof that the ADM mass of an asymptotically flat spacetime containing matter satisfying the dominant energy condition is non-negative and vanishes only in the case of flat spacetime [2]. Nester [3] treated the problem of the positive mass theorem in a fully covariant way, avoiding technical difficulties in taking the three-dimensional truncation of the four-dimensional divergence theorem. Israel and Nester [4] extended this formulation to the case of the Bondi mass, which is associated with asymptotically null 3-surfaces and gives the mass not yet radiated away by a certain retarded time. The Bondi mass decreases with the passage of retarded time and cannot exceed the ADM mass.Gibbons and Hull [5] have proved a version of the positive-mass theorem for Einstein-Maxwell theory. They derived a lower bound for the mass of spacetime in terms of its electric and magnetic charges-an analogue of the Bogomolnyi bound for the magnetic monopole [6]. It also turned out that the positive mass theorem can be generalized to hold for extended gauged supergravity theories [5,7].Gibbons et al [8] extended the Witten proof and show that the mass is positive for initial data on an asymptotically flat spatial hypersurface which is regular outside an apparent horizon. In the case of a black hole with an electromagnetic charge, its mass is greater than the modulus of the charge. These results are also valid for the Bondi mass at null infinity.Recently Penrose et al [9] developed a new technique, based on casual structure and focusing, for proving the positive mass theorem. Their results were extended by Gibbons and Wells [10] in dilaton gravity.The subject of the Bogomolnyi bound was investigated in the case of stringy black holes [11,12]. Gibbons et al [13] showed that inclusion of various interactions, i.e. Yang-Mills fields, Yang-Mills-Higgs, dilaton interactions, implies that the self-gravitating solitons saturate a gravitational version of the Bogomolnyi bound on the energy of an arbitrary field configuration. †

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“…This work represents a significant extension of previous works in which we considered the simpler one-dimensional (cylindrically symmetric) case in the presence of a 2%concentric antenna and simulating the LFS equilibrium profiles of a START-like device [3]- [8].…”

Section: Introductionmentioning

confidence: 99%

On the Generation of Transport Suppression Barriers by Externally Driven Alfvén Waves in D-Shaped, Low Aspect Ratio Tokamaks

2003

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We investigate quantitatively the possibility of turbulence suppression through the generation of transport barriers in pre-heated low aspect ratio tokamaks (LARTs) by the sheared electric fields generated by externally driven rf waves in the frequency range ωA ≃ ω < ωci (ωA and ωci are, respectively, the Alfvén and ion cyclotron frequencies). To this aim the following sequential steps are followed: (1) Solutions of the resistive two-fluid model full wave equation for a realistic LART configuration (D-shape cross-section and aspect ratio, R/a ≳ 1, as well as suitably located low field side, LFS, antenna) upon using a quite general dielectric tensor operator; (2) Calculation of the ponderomotive forces and their magnetic surface averages; (3) Solution of a strongly non-linear differential equation for the quasi-stationary radial electric field, including the particle orbit squeezing effects, based on the results of steps (1) and (2); and (4) Calculation of the radial flow shear, S⊥ , for both banana and potato collisional regimes.

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Plasma-turbulence suppression and transport-barrier formation by externally driven radiofrequency waves in spherical tokamaks

Cited by 3 publications

References 3 publications

The combined toroidicity, ellipticity and triangularity effects on the energy deposition of Alfvén modes in pre-heated, low aspect ratio tokamaks

The combined toroidicity, ellipticity and triangularity effects on the energy deposition of Alfvén modes in pre-heated, low aspect ratio tokamaks

Effects of an Anomalous Resistivity on the Power Deposition by Alfvén Waves in Pre-Heated Spherical Tokamaks

On the Generation of Transport Suppression Barriers by Externally Driven Alfvén Waves in D-Shaped, Low Aspect Ratio Tokamaks

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