Gyrokinetic Simulations of Short-Wavelength ITG Instability in the Presence of a Static Magnetic Island

Hilscher, Paul P.; Imadera, Kenji; Li, Jiquan; Kishimoto, Y.

doi:10.1585/pfr.8.2403040

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…q Li > 1:0) can provide a possible channel of electron transport. [28][29][30][31][32] Here, we conduct an analysis on the effect of impurity ions on the SWITG mode. For comparison, two cases of density gradient R=L n ¼ 3 and 10 are considered.…”

Section: B L Ez Effectmentioning

confidence: 99%

“…[23][24][25][26][27] It is found that the impurity ions with inwardly (outwardly) peaked density profiles have stabilizing (destabilizing) effects on the conventional long-wavelength ITG modes in circular plasmas. Recently, a shortwavelength ITG (SWITG) instability was found to exist in sheared slab geometry [28][29][30] as well as in toroidal geometry. 31 It was shown that the linear growth rate of the SWITG mode is comparable to the conventional ITG, but its contribution to the heat flux in the nonlinear regime is relatively low.…”

Section: Introductionmentioning

confidence: 99%

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Impurity effects on short wavelength ion temperature gradient mode in elongated tokamak plasmas

Wang

Dong

2015

Physics of Plasmas

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The effects of impurity ions on the short wavelength ion temperature gradient (SWITG) driven instability in elongated tokamak plasmas are numerically investigated with the gyrokinetic integral eigenmode equation. It is found that for a moderate electron density gradient, the SWITG mode is first destabilized and then stabilized with increasing elongation j, which is different from the conventional long wavelength ITG mode. For a large electron density gradient, the elongation can effectively stabilize the SWITG mode. Moreover, the low Z impurity ions with inwardly (outwardly) peaked density profiles have stabilizing (destabilizing) effects on the SWITG modes in elongated plasmas. Interestingly, the high Z tungsten impurity ions with inwardly peaked density profiles play a stronger stabilizing role in the SWITG modes than the low Z impurity ions (such as carbon and oxygen) do. In particular, the high Z tungsten impurity ions with a weakly outwardly peaked density profile still have a stabilizing effect. Finally, the critical threshold of impurity density gradient scale length for exciting impurity mode is also numerically obtained, indicating that the impurity mode is harder to be excited in elongated plasmas than in circular ones. V C 2015 AIP Publishing LLC. [http://dx.

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Section: B L Ez Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impurity effects on short wavelength ion temperature gradient mode in elongated tokamak plasmas

Wang

Dong

2015

Physics of Plasmas

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Short wavelength ion temperature gradient mode in tokamak plasmas with hollow density profiles

Dong

Liu

et al. 2020

Physics of Plasmas

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By the gyrokinetic integral eigenmode equation, we numerically investigate the short-wavelength ion-temperature-gradient (SWITG) mode in tokamak plasmas with hollow density profiles. This paper finds that the critical ion temperature gradient (ITG) R/LTiC exists for the hollow density profile. Over such a gradient, the SWITG mode is unstable. The R/LTiC for a hollow density profile is slightly lower than that for a peaked density profile, though far away from the threshold, the mode in the latter case is more unstable. Furthermore, the scaling of the ITG threshold increasing with ion-to-electron temperature ratio Ti/Te has been calculated, suggesting that the SWITG mode is more difficult to excite in hot ion plasmas as compared with that in hot electron plasmas. For the slightly hollow density profiles, it is shown that in the case of flat (peaked) electron temperature profiles, the SWITG modes are destabilized (stabilized) by the trapped electrons. For the steep hollow density profiles, however, the trapped electrons reduce the growth rate substantially, and thus, the SWITG stability threshold is raised significantly. In addition, the dependence of the threshold on local plasma parameters is analyzed in detail. It is found that the SWITG modes become more unstable for the high safety factor, small Larmor radius, weak magnetic shear, and high electron-to-ion temperature ratio.

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Gyrokinetic Simulations of Short-Wavelength ITG Instability in the Presence of a Static Magnetic Island

Cited by 2 publications

References 8 publications

Impurity effects on short wavelength ion temperature gradient mode in elongated tokamak plasmas

Impurity effects on short wavelength ion temperature gradient mode in elongated tokamak plasmas

Short wavelength ion temperature gradient mode in tokamak plasmas with hollow density profiles

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