تقرير
Influence of collisions on trapped-electron modes in tokamaks and low-shear stellarators
| العنوان: | Influence of collisions on trapped-electron modes in tokamaks and low-shear stellarators |
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| المؤلفون: | Morren, M. C. L., Proll, J. H. E., van Dijk, J., Pueschel, M. J. |
| سنة النشر: | 2024 |
| المجموعة: | Physics (Other) |
| مصطلحات موضوعية: | Physics - Plasma Physics |
| الوصف: | The influence of collisions on the growth rate of trapped-electron modes (TEMs) in core plasmas is assessed through both analytical linear gyrokinetics and linear gyrokinetic simulations. Both methods are applied to the magnetic geometry of the DIII-D tokamak, as well as the Helically Symmetric eXperiment (HSX) and Wendelstein 7-X (W7-X) stellarators, in the absence of temperature gradients. Here we analytically investigate the influence of collisions on the TEM eigenmode frequency by a perturbative approach in the response of trapped particles to the mode, using an energy-dependent Krook operator to model collisions. Although the resulting growth rates exceed perturbative thresholds, they reveal important qualitative dependencies: a geometry-dependent stabilization rate occurs for all wavenumbers at high collisionality, while at low collisionality, a geometry-sensitive mixture of collisionless, resonantly driven, and collisionally destabilized modes is found. Additionally, linear gyrokinetic simulations have been performed with a rigorous pitch-angle scattering operator for the same geometries. In the case of DIII-D and large wavenumber modes in HSX, the trends predicted by analytical theory are reproduced. Dissimilarities are, however, obtained in W7-X geometry and for low wavenumber modes in HSX, which are shown to be due to a collision-induced transition to the Universal Instability as the dominant instability at marginal collisionality. Comment: 24 pages, 46 figures |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1063/5.0199265 |
| URL الوصول: | http://arxiv.org/abs/2401.11937 |
| رقم الأكسشن: | edsarx.2401.11937 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1063/5.0199265 |
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