The effect of limiter biasing on the plasma edge rotation and MHD activities

2014 ◽  
Vol 32 ◽  
pp. 1460332
Author(s):  
A. Lahazi ◽  
P. Khorshid ◽  
M. Ghoranneviss
Keyword(s):  
Electric Field ◽  
Oscillation Amplitude ◽  
Sharp Decrease ◽  
Rotation Frequency ◽  
Radial Electric Field ◽  
Dominant Mode ◽  
Floating Potential ◽  
Plasma Edge ◽  
Magnetic Island ◽  
Toroidal Rotation

Plasma edge rotations and magnetohydrodynamic behaviors have been studied during radial electric field variations in IR-T1 tokamak. An external positive limiter bias has been used as an external radial electric field. The profiles of radial electric field, floating potential, poloidal and toroidal rotation velocities and MHD activities have been studied during positive limiter bias. The poloidal and toroidal velocities reduced when the bias was applied and their fluctuations on the plasma edge became smoother furthermore. A significant excitation in dominant mode (4, 1) oscillation amplitude and a sharp decrease in magnetic island rotation frequency have been seen.

scholarly journals Investigation of turbulence rotation and radial electric field in the island divertor and plasma edge at W7-X

2019 ◽  
Vol 61 (5) ◽  
pp. 054003 ◽  
Author(s):  
A Krämer-Flecken ◽  
X Han ◽  
T Windisch ◽  
J Cosfeld ◽  
P Drews ◽  
...  
Keyword(s):  
Electric Field ◽  
Radial Electric Field ◽  
Plasma Edge

scholarly journals Bootstrap current and parallel ion velocity in imperfectly optimized stellarators

2020 ◽  
Vol 86 (1) ◽  
Author(s):  
Peter J. Catto ◽  
Per Helander
Keyword(s):  
Magnetic Field ◽  
Kinetic Equation ◽  
Electric Field ◽  
Flow Velocity ◽  
Collision Frequency ◽  
Rotation Frequency ◽  
Radial Electric Field ◽  
Local Form ◽  
Bootstrap Current ◽  
Ion Velocity

A novel derivation of the parallel ion velocity, and the bootstrap and Pfirsch–Schlüter currents in an imperfectly optimized (that is, almost omnigenous) stellarator magnetic field, $\boldsymbol{B}$ , is presented that somewhat more generally recovers expressions completely consistent with previous analytic results. However, it is also shown that, when the conventional radially local form of the drift kinetic equation is employed, the flow velocity and the bootstrap current acquire a spurious contribution proportional to $\unicode[STIX]{x1D714}/\unicode[STIX]{x1D708}$ , where $\unicode[STIX]{x1D714}$ denotes the $\boldsymbol{E}\times \boldsymbol{B}$ rotation frequency (due to the radial electric field $\boldsymbol{E}$ ) and $\unicode[STIX]{x1D708}$ the collision frequency. This contribution is particularly large in the $\sqrt{\unicode[STIX]{x1D708}}$ regime and at smaller collisionalities, where $\unicode[STIX]{x1D714}/\unicode[STIX]{x1D708}\gtrsim 1$ , and is presumably present in most numerical calculations, but it disappears if a more accurate drift kinetic equation is used.

On the Origin of Steep and Localized Radial Electric Field in the Transport Barrier at Plasma Edge

2016 ◽  
Vol 56 (6-8) ◽  
pp. 522-527 ◽  
Author(s):  
K. Itoh ◽  
S.-I. Itoh ◽  
T. Kobayashi ◽  
K. Kamiya ◽  
T. Ido ◽  
...  
Keyword(s):  
Electric Field ◽  
Radial Electric Field ◽  
Plasma Edge ◽  
Transport Barrier

scholarly journals Generation of the sheared radial electric field by a magnetic island structure

2004 ◽  
Vol 3 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Ana Mancic ◽  
Aleksandra Maluckov ◽  
Yokoyama Masayoshi ◽  
Okamoto Masao
Keyword(s):  
Electric Field ◽  
Local Treatment ◽  
Radial Electric Field ◽  
Model Parameters ◽  
Field Region ◽  
Field Profile ◽  
Magnetic Island ◽  
Island Structure ◽  
Non Local ◽  
Electric Field Profile

The effect of the presence of a magnetic island structure on the am bipolar radial electric field is studied in the context of the belt island model. It is shown that the sheared radial electric field region exists on the island position. Depending on the model parameters, the single (ion root) or multiple (one ion and two electron roots) solutions for the radial electric field are obtained at different radial positions. The radially non-local treatment is developed proposing the steady-state plasma conditions. The numerical calculations show that the diffusion of the radial electric field is significant only near the island boundaries. As a result the discontinuities in the am bipolar electric field profile are smoothed.

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