Impact of plasma poloidal rotation on resistive wall mode instability in toroidally rotating plasmas

Aiba, N.; Shiraishi, Jun; Tokuda, S.

doi:10.1063/1.3551731

Cited by 13 publications

(15 citation statements)

References 25 publications

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“…where q is the safety factor and F is the toroidal field function [13]. As shown in [3,14], MINERVA(-DI) can treat not only toroidal but also poloidal rotation, and the effects of the Coriolis and centrifugal forces due to these rotations on MHD stability are taken into account. However, the change of MHD equilibrium due to poloidal rotation is assumed to be negligible.…”

Section: Basic Equationmentioning

confidence: 99%

Impact of ion diamagnetic drift on MHD stability at edge pedestal in JT-60U rotating plasmas

2016

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The effect of ion diamagnetic drift on the stability of peeling–ballooning modes in rotating tokamak plasmas has been analyzed numerically. The results show that plasma toroidal rotation can not only destabilize the peeling–ballooning mode but also can reduce the ion diamagnetic drift effect on the mode stability, even though the ion diamagnetic drift effect stabilizes the mode in a static plasma. Plasma poloidal rotation can also destabilize the mode and cancel the ion diamagnetic drift effect, even when the rotation frequency is much smaller than the toroidal one. These impacts of the rotation on the stability can resolve the discrepancy between the result of the numerical stability analysis and the experimental result in type-I ELMy H-mode plasmas in JT-60U. The reduction of the ion diamagnetic drift effect on ELM stability due to plasma rotation is shown to depend on the direction of the rotation, so that the ion diamagnetic drift effect becomes negligible only when the JT-60U plasma rotates in the direction counter to the plasma current.

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Section: Basic Equationmentioning

confidence: 99%

Impact of ion diamagnetic drift on MHD stability at edge pedestal in JT-60U rotating plasmas

2016

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“…The carbon density also appears to be in-out symmetric although there is some indication, at the limit of the measurement accuracy, of higher density at the LFS. In our analysis, we consider these quantities as poloidal flux functions and expect the plasma flows to be structured as described in equation (5). The impact of density asymmetries on the measurement will be assessed a posteriori in section 5.…”

Section: Examples Of Indirect Poloidal Measurementsmentioning

confidence: 99%

“…In fact, the toroidal frequency asymmetries are consistent with a poloidal flow in the electron diamagnetic direction, generating a finitê u(ψ)B t ∼ 10 km s −1 contribution to the toroidal flow, in the co-current direction. The HFS and LFS measurements are now used to calculate the flux functionsω andû that fully characterize the plasma flow through equation (5). First, the HFS and LFS profiles of u t (ψ) are separately fitted with cubic spline curves as shown in figure 3; then equations (15) and (16) are used to computê ω andû(ψ) from the fit curves.…”

Section: Examples Of Indirect Poloidal Measurementsmentioning

confidence: 99%

“…It is, by example, predicted to induce transitions in magnetohydrodynamic (MHD) equilibrium [1,2] and to affect the stability of different types of MHD modes [3][4][5][6]. More generally, poloidal rotation enters the radial force balance equation, which is used to determine experimentally the radial electric field, an essential element in the physics of microinstability and turbulent transport [7].…”

Section: Introductionmentioning

confidence: 99%

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Indirect measurement of poloidal rotation using inboard–outboard asymmetry of toroidal rotation and comparison with neoclassical predictions

et al. 2013

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An alternative experimental spectroscopic measurement of poloidal plasma rotation in toroidally confined plasmas is proven effective in the TCV tokamak. Charge exchange recombination measurements of the toroidal rotation profile over the full mid-plane plasma diameter are used to infer the complete bi-dimensional flow structure of the intrinsic C 6+ impurity, which includes its poloidal component. For divergence free flows, the difference between the toroidal rotation frequency f t = u t /R at the inboard and outboard locations on the same flux surface is proportional to the poloidal rotation. This indirect measurement provides increased accuracy as the measured quantity f t,in − f t,out ≈ 4qu p /R axis (q is the local safety factor) is larger than the intrinsic uncertainties of a direct spectroscopic measurement of poloidal velocity. The method is applied in a variety of TCV ohmic and electron cyclotron heated L-mode plasmas in the banana-plateau collisionality regime (0.2 < ν * ii < 2.4). In the radial range of normalized poloidal flux ρ ψ < 0.8, an impurity poloidal velocity of u p = 0.5-2.5 km s −1 is observed, always in the electron diamagnetic drift direction. The measurements are compared with neoclassical calculations and they agree in magnitude and sign to within <1 km s −1 .

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“…These instabilities exist even after the plasma rotation frequency enters a regime that is stable with respect to RWMs. The plasma stability is analyzed with the linear MHD stability code MINERVA/RWMaC [16,17], MINERVA [18] solves the Frieman-Rotenberg equation [19], including a parallel sound wave damping force Fsd that represents ion Landau damping [1,20]:…”

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confidence: 99%

Excitation of Flow-Stabilized Resistive Wall Mode by Coupling with Stable Eigenmodes in Tokamaks

Aiba

Hirota

2015

Phys. Rev. Lett.

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In a rotating toroidal plasma surrounded by a resistive wall, it is shown that linear MHD instabilities can be excited by couplings between the resistive wall mode (RWM) and stable ideal MHD modes. In particular, it is shown that the RWM can couple not only with stable external kink modes but also with Alfvén eigenmodes that are ordinarily in the stable continuum of a toroidal plasma. The RWM growth rate is shown to peak whenever the Doppler shift caused by the plasma rotation cancels the frequency of an ideal MHD mode, so that the mode appears to have zero frequency in the laboratory frame. At these values of the rotation frequency, the RWM can overcome the stabilizing effects of plasma rotation, continuum damping, and ion Landau damping.

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Impact of plasma poloidal rotation on resistive wall mode instability in toroidally rotating plasmas

Cited by 13 publications

References 25 publications

Impact of ion diamagnetic drift on MHD stability at edge pedestal in JT-60U rotating plasmas

Impact of ion diamagnetic drift on MHD stability at edge pedestal in JT-60U rotating plasmas

Indirect measurement of poloidal rotation using inboard–outboard asymmetry of toroidal rotation and comparison with neoclassical predictions

Excitation of Flow-Stabilized Resistive Wall Mode by Coupling with Stable Eigenmodes in Tokamaks

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