Research output: Contribution to journal › Conference article › peer-review

**Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold.** / Imada, K.; Wilson, H. R.; Connor, J. W.; Dudkovskaia, A. V.; Hill, P.

Research output: Contribution to journal › Conference article › peer-review

Imada, K, Wilson, HR, Connor, JW, Dudkovskaia, AV & Hill, P 2018, 'Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold', *Journal of Physics: Conference Series*, vol. 1125, no. 1, 012013. https://doi.org/10.1088/1742-6596/1125/1/012013

Imada, K., Wilson, H. R., Connor, J. W., Dudkovskaia, A. V., & Hill, P. (2018). Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold. *Journal of Physics: Conference Series*, *1125*(1), [012013]. https://doi.org/10.1088/1742-6596/1125/1/012013

Imada K, Wilson HR, Connor JW, Dudkovskaia AV, Hill P. Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold. Journal of Physics: Conference Series. 2018 Nov 23;1125(1). 012013. https://doi.org/10.1088/1742-6596/1125/1/012013

@article{46ed13e725ae47c79a6329dd22fdeb54,

title = "Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold",

abstract = " Controlling neoclassical tearing modes (NTMs) is vital for future tokamaks, such as ITER. An NTM control system relies on the magnetic island threshold physics. In this paper, new results for the ion response to the island perturbation and its influence on the island evolution are presented. Considering a small island, w ≪ r, where r is the minor radius, but crucially retaining the ordering ρ bi ∼ w (relevant for threshold) to capture the finite orbit width effect, we determine the ion response using the drift kinetic equation. Momentum conservation and quasineutrality are taken into account, which are crucial for determining the current perturbations. The results show that the finite particle orbit effects are significant even for a moderately small ratio of ρ θ i /w (ρ θ i is the ion poloidal Larmor radius; ρ b i ∼ 1/2 ρ θ i ). When w ∼ ρ θ i , the flattening of the pressure gradient across the island is substantially restored, implying that the bootstrap current drive for the island growth is suppressed. Moreover, we find that for a sufficiently small island, w ≪ ρ θ i , the contribution can be negative, meaning that it can stabilize small seed islands, providing a threshold. This will have significant impact on our understanding of the NTM threshold physics. ",

author = "K. Imada and Wilson, {H. R.} and Connor, {J. W.} and Dudkovskaia, {A. V.} and P. Hill",

note = "{\textcopyright} 2018, IOP Publishing Ltd. ; 2018 Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas ; Conference date: 27-08-2018 Through 31-08-2018",

year = "2018",

month = nov,

day = "23",

doi = "10.1088/1742-6596/1125/1/012013",

language = "English",

volume = "1125",

journal = "Journal of Physics: Conference Series",

issn = "1742-6588",

publisher = "IOP Publishing Ltd.",

number = "1",

}

TY - JOUR

T1 - Drift kinetic response of ions to magnetic island perturbation and effects on NTM threshold

AU - Imada, K.

AU - Wilson, H. R.

AU - Connor, J. W.

AU - Dudkovskaia, A. V.

AU - Hill, P.

N1 - © 2018, IOP Publishing Ltd.

PY - 2018/11/23

Y1 - 2018/11/23

N2 - Controlling neoclassical tearing modes (NTMs) is vital for future tokamaks, such as ITER. An NTM control system relies on the magnetic island threshold physics. In this paper, new results for the ion response to the island perturbation and its influence on the island evolution are presented. Considering a small island, w ≪ r, where r is the minor radius, but crucially retaining the ordering ρ bi ∼ w (relevant for threshold) to capture the finite orbit width effect, we determine the ion response using the drift kinetic equation. Momentum conservation and quasineutrality are taken into account, which are crucial for determining the current perturbations. The results show that the finite particle orbit effects are significant even for a moderately small ratio of ρ θ i /w (ρ θ i is the ion poloidal Larmor radius; ρ b i ∼ 1/2 ρ θ i ). When w ∼ ρ θ i , the flattening of the pressure gradient across the island is substantially restored, implying that the bootstrap current drive for the island growth is suppressed. Moreover, we find that for a sufficiently small island, w ≪ ρ θ i , the contribution can be negative, meaning that it can stabilize small seed islands, providing a threshold. This will have significant impact on our understanding of the NTM threshold physics.

AB - Controlling neoclassical tearing modes (NTMs) is vital for future tokamaks, such as ITER. An NTM control system relies on the magnetic island threshold physics. In this paper, new results for the ion response to the island perturbation and its influence on the island evolution are presented. Considering a small island, w ≪ r, where r is the minor radius, but crucially retaining the ordering ρ bi ∼ w (relevant for threshold) to capture the finite orbit width effect, we determine the ion response using the drift kinetic equation. Momentum conservation and quasineutrality are taken into account, which are crucial for determining the current perturbations. The results show that the finite particle orbit effects are significant even for a moderately small ratio of ρ θ i /w (ρ θ i is the ion poloidal Larmor radius; ρ b i ∼ 1/2 ρ θ i ). When w ∼ ρ θ i , the flattening of the pressure gradient across the island is substantially restored, implying that the bootstrap current drive for the island growth is suppressed. Moreover, we find that for a sufficiently small island, w ≪ ρ θ i , the contribution can be negative, meaning that it can stabilize small seed islands, providing a threshold. This will have significant impact on our understanding of the NTM threshold physics.

UR - http://www.scopus.com/inward/record.url?scp=85058337905&partnerID=8YFLogxK

U2 - 10.1088/1742-6596/1125/1/012013

DO - 10.1088/1742-6596/1125/1/012013

M3 - Conference article

AN - SCOPUS:85058337905

VL - 1125

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

SN - 1742-6588

IS - 1

M1 - 012013

T2 - 2018 Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas

Y2 - 27 August 2018 through 31 August 2018

ER -