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# Study of up–down poloidal density asymmetry of high- $$\mathrm{Z}$$ impurities with the new impurity version of XGCa

## Abstract

Addition of multispecies impurity ions to the total-f gyrokinetic particle-in-cell code XGCa is reported, including a cross-verification of neoclassical physics against the NEO code. This new version of the neoclassical gyrokinetic code XGCa is used to benchmark and confirm the previous reduced-equation-based prediction that high- $$\mathrm{Z}$$ impurity particles in the Pfirsch–Schlüter regime can exhibit a significant level of up–down poloidal asymmetry, through the large parallel friction force, and thus influence the radial plasma transport significantly. The study is performed in a plasma with weak toroidal rotation. In comparison, when the impurity particles are in the plateau regime, the up–down poloidal asymmetry becomes weak, with the parallel friction force becoming weaker than the parallel viscous force. It is also found that the linearization of the perturbed distribution function, based on the small poloidal asymmetry assumption, can become invalid. Finally, using the numerical data from XGCa, each term in the parallel fluid force-balance equation have been analysed to find that both the main ions and the electrons respond to the poloidal potential variation adiabatically when the high- $$\mathrm{Z}$$ tungsten possesses large poloidal variation.

- Authors:

- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Max-Planck-Inst. für Plasmaphysik, Greifswald (Germany)
- Ulsan National Inst. of Science and Technology, Ulsan (Korea, Republic of)

- Publication Date:

- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1573501

- Grant/Contract Number:
- AC02-05CH11231; AC02-09CH11466

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Plasma Physics

- Additional Journal Information:
- Journal Volume: 85; Journal Issue: 5; Journal ID: ISSN 0022-3778

- Publisher:
- Cambridge University Press

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; fusion plasma; plasma simulation

### Citation Formats

```
Dominski, J., Chang, C. S., Hager, R., Helander, P., Ku, S., and Yoon, E. S. Study of up–down poloidal density asymmetry of high- $\mathrm{Z}$ impurities with the new impurity version of XGCa. United States: N. p., 2019.
Web. doi:10.1017/S0022377819000722.
```

```
Dominski, J., Chang, C. S., Hager, R., Helander, P., Ku, S., & Yoon, E. S. Study of up–down poloidal density asymmetry of high- $\mathrm{Z}$ impurities with the new impurity version of XGCa. United States. doi:10.1017/S0022377819000722.
```

```
Dominski, J., Chang, C. S., Hager, R., Helander, P., Ku, S., and Yoon, E. S. Thu .
"Study of up–down poloidal density asymmetry of high- $\mathrm{Z}$ impurities with the new impurity version of XGCa". United States. doi:10.1017/S0022377819000722.
```

```
@article{osti_1573501,
```

title = {Study of up–down poloidal density asymmetry of high- $\mathrm{Z}$ impurities with the new impurity version of XGCa},

author = {Dominski, J. and Chang, C. S. and Hager, R. and Helander, P. and Ku, S. and Yoon, E. S.},

abstractNote = {Addition of multispecies impurity ions to the total-f gyrokinetic particle-in-cell code XGCa is reported, including a cross-verification of neoclassical physics against the NEO code. This new version of the neoclassical gyrokinetic code XGCa is used to benchmark and confirm the previous reduced-equation-based prediction that high- $\mathrm{Z}$ impurity particles in the Pfirsch–Schlüter regime can exhibit a significant level of up–down poloidal asymmetry, through the large parallel friction force, and thus influence the radial plasma transport significantly. The study is performed in a plasma with weak toroidal rotation. In comparison, when the impurity particles are in the plateau regime, the up–down poloidal asymmetry becomes weak, with the parallel friction force becoming weaker than the parallel viscous force. It is also found that the linearization of the perturbed distribution function, based on the small poloidal asymmetry assumption, can become invalid. Finally, using the numerical data from XGCa, each term in the parallel fluid force-balance equation have been analysed to find that both the main ions and the electrons respond to the poloidal potential variation adiabatically when the high- $\mathrm{Z}$ tungsten possesses large poloidal variation.},

doi = {10.1017/S0022377819000722},

journal = {Journal of Plasma Physics},

number = 5,

volume = 85,

place = {United States},

year = {2019},

month = {10}

}

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