An equilibrium model for RFP plasmas in the presence of resonant tearing modes

Zanca, P.; Sattin, F.

doi:10.1088/0741-3335/45/1/301

Cited by 21 publications

(15 citation statements)

References 46 publications

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“…The plasma cross section is shrunk and enlarged in two wide toroidal regions of about 100 toroidal degrees located, respectively, at toroidal angles lower and higher than φ lock . Besides modifying the LCFS radius, the locking in phase of m = 0 modes is believed to change also the topology of the magnetic surfaces in the region external to the reversal radius: according to the reconstruction of the flux surfaces presented in [12] the bulging region is characterized by large magnetic islands, whose amplitude is reduced in the shrunk region.…”

Section: Introductionmentioning

confidence: 99%

Toroidally asymmetric particle transport caused by phase-locking of MHD modes in RFX-mod

et al. 2007

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The particle and energy transport in reversed field pinch experiments is affected by the locking in phase of the tearing modes, also dubbed dynamo modes, that sustain the magnetic configuration. In standard RFP pulses many m = 1 and m = 0 resonant modes have a relatively large amplitude (a spectrum dubbed MH for multiple helicity). The locking in phase of m = 1 tearing modes produces a helical deformation (locked mode (LM)) of the magnetic surfaces in a region of approximately 40 toroidal degrees. The region of the LM is characterized by a strong plasma–wall interaction and by high losses of energy and particles that account for a significant fraction of the input power and of the total particle outflux. The locking in phase of m = 0 modes modifies the plasma radius, shrinking and enlarging the plasma cross section in two wide toroidal regions of about 100°. The purpose of this paper is to investigate to what extent the locking in phase of m = 0 modes introduces toroidal asymmetries in the transport properties of the plasma. This study has been carried out investigating the shape of the density profile in the RFX-mod experiment. The analyses show that the profile exhibits a dependence on the toroidal angle, which is related to the deformation of the plasma column due to the locking in phase of m = 0 modes: the least steep density gradients at the edge are found in the region where the plasma column is shrunk, entailing that in this region the particle transport is enhanced. An analogous asymmetry also characterizes the density and magnetic fluctuations at the edge, which are enhanced in the same toroidal region where the particle transport also is enhanced. This result can be considered the first experimental evidence of an instability localized where the plasma column is shrunk.

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Section: Introductionmentioning

confidence: 99%

Toroidally asymmetric particle transport caused by phase-locking of MHD modes in RFX-mod

et al. 2007

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“…Note that the core magnetic perturbation amplitudes, in particular, the m 1, are theoretically and experimentally found to be proportional to such signals [16,17]. The line-averaged electron density profile n e is measured by a two chords (located at r=a 0 and 0.69) interferometer [18] and the line-integrated alpha line emission D of the working gas (deuterium) is measured by a toroidal array of 17 monochromators looking at the plasma core [19].…”

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confidence: 95%

Improved Particle Confinement in Transition from Multiple-Helicity to Quasi-Single-Helicity Regimes of a Reversed-Field Pinch

et al. 2006

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The quasi-single-helicity (QSH) state of a reversed-field pinch (RFP) plasma is a regime in which the RFP configuration can be sustained by a dynamo produced mainly by a single tearing mode and in which a helical structure with well-defined magnetic flux surfaces arises. In this Letter, we show that spontaneous transitions to the QSH regime enhance the particle confinement. This improvement is originated by the simultaneous and cooperative action of the increase of the magnetic island and the reduction of the magnetic stochasticity.

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“…0 is the aspect ratio. Without energetic ions, equation(9) reduces to equation (17) in[14]. Next, to obtain the expression of δ p h , it is necessary to solve the perturbed distribution of energetic ions.…”

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confidence: 99%

Influence of energetic ions on tearing modes in a reversed field pinch

Cai

Lin

Ding

et al. 2015

Plasma Phys. Control. Fusion

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Tearing mode stability analysis in the presence of circulating energetic ions (CEI) is studied in the reversed field pinch (RFP) magnetic configuration. In contrast to the minimal effect of precessional drift of CEI on tearing modes in tokamaks, the effect of precessional drift of CEI on tearing modes is important in the RFP. It is found that the effects of CEI on tearing modes in RFP depend on their toroidal circulating direction, and have a strong relation to the pressure gradient of CEI. For co-CEI, tearing modes can be stabilized if the pressure gradient of energetic ions is sufficiently large, which is qualitatively consistent with experimental results in the Madison Symmetric Torus.

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An equilibrium model for RFP plasmas in the presence of resonant tearing modes

Cited by 21 publications

References 46 publications

Toroidally asymmetric particle transport caused by phase-locking of MHD modes in RFX-mod

Toroidally asymmetric particle transport caused by phase-locking of MHD modes in RFX-mod

Improved Particle Confinement in Transition from Multiple-Helicity to Quasi-Single-Helicity Regimes of a Reversed-Field Pinch

Influence of energetic ions on tearing modes in a reversed field pinch

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