Construction and analysis of guiding center distributions for tokamak plasmas with ambient radial electric field
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2024
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| author | Bierwage, Andreas Lauber, Philipp Nakajima, Noriyoshi Shinohara, Kouji Brochard, Guillaume Ghim, Young-chul Lee, Wonjun Matsuyama, Akinobu Sumida, Shuhei Yang, Hao Yagi, Masatoshi |
| author_facet | Bierwage, Andreas Lauber, Philipp Nakajima, Noriyoshi Shinohara, Kouji Brochard, Guillaume Ghim, Young-chul Lee, Wonjun Matsuyama, Akinobu Sumida, Shuhei Yang, Hao Yagi, Masatoshi |
| contents | The contribution of a time-independent toroidally-symmetric radial electric field $E_r$ is implemented in VisualStart [Comp. Phys. Comm. 275 (2022) 108305; arXiv:2111.08224], a code whose purposes include the construction of guiding center (GC) drift orbit databases for the study of plasma instabilities in tokamaks. $E_r$ is important for the thermal part of the velocity distribution and for fast particle resonances in the kHz frequency range. KSTAR, JT-60U and ITER tokamak cases are used as working examples to test our methods and discuss practical issues connected with $E_r$. Two points are worth noting: First, the GC orbit space is sampled in the magnetic midplane as before, and we find that in the presence of $E_r$, midplane-based coordinates are not only equivalent but superior to conventional constants of motion, allowing to attain high numerical accuracy and efficiency with a relatively simple mesh. Second, the periodic parallel acceleration and deceleration of GCs via the mirror force is modulated by $E_r$. Although this parallel electric acceleration averages to zero during a poloidal transit (or bounce) period, it has important consequences, one being the known shift of the trapped-passing boundary. Another consequence is that electric frequency shifts depend on the chosen reference point, so that some care is required when evaluating the $E_r$-dependence of transit frequencies for resonance analyses. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2411_19288 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Construction and analysis of guiding center distributions for tokamak plasmas with ambient radial electric field Bierwage, Andreas Lauber, Philipp Nakajima, Noriyoshi Shinohara, Kouji Brochard, Guillaume Ghim, Young-chul Lee, Wonjun Matsuyama, Akinobu Sumida, Shuhei Yang, Hao Yagi, Masatoshi Plasma Physics The contribution of a time-independent toroidally-symmetric radial electric field $E_r$ is implemented in VisualStart [Comp. Phys. Comm. 275 (2022) 108305; arXiv:2111.08224], a code whose purposes include the construction of guiding center (GC) drift orbit databases for the study of plasma instabilities in tokamaks. $E_r$ is important for the thermal part of the velocity distribution and for fast particle resonances in the kHz frequency range. KSTAR, JT-60U and ITER tokamak cases are used as working examples to test our methods and discuss practical issues connected with $E_r$. Two points are worth noting: First, the GC orbit space is sampled in the magnetic midplane as before, and we find that in the presence of $E_r$, midplane-based coordinates are not only equivalent but superior to conventional constants of motion, allowing to attain high numerical accuracy and efficiency with a relatively simple mesh. Second, the periodic parallel acceleration and deceleration of GCs via the mirror force is modulated by $E_r$. Although this parallel electric acceleration averages to zero during a poloidal transit (or bounce) period, it has important consequences, one being the known shift of the trapped-passing boundary. Another consequence is that electric frequency shifts depend on the chosen reference point, so that some care is required when evaluating the $E_r$-dependence of transit frequencies for resonance analyses. |
| title | Construction and analysis of guiding center distributions for tokamak plasmas with ambient radial electric field |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2411.19288 |