Global gyrokinetic study of shaping effects on electromagnetic modes at NSTX aspect ratio with ad hoc parallel magnetic perturbation effects

Sharma, A. Y. ; Cole, M. D. J. ; Görler, T.; Chen, Y.; Hatch, D. R.; Guttenfelder, W. ; Hager, R. ; Sturdevant, B. J. ; Ku, S. ; Mishchenko, A. ; Chang, C. S.
Issue date: 2022
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Sharma, A. Y., Cole, M. D. J., Görler, T., Chen, Y., Hatch, D. R., Guttenfelder, W., Hager, R., Sturdevant, B. J., Ku, S., Mishchenko, A., & Chang, C. S. (2022). Global gyrokinetic study of shaping effects on electromagnetic modes at NSTX aspect ratio with ad hoc parallel magnetic perturbation effects [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.34770/415v-8p16
@electronic{sharma_a_y_2022,
  author      = {Sharma, A. Y. and
                Cole, M. D. J. and
                Görler, T. and
                Chen, Y. and
                Hatch, D. R. and
                Guttenfelder, W. and
                Hager, R. and
                Sturdevant, B. J. and
                Ku, S. and
                Mishchenko, A. and
                Chang, C. S.},
  title       = {{Global gyrokinetic study of shaping effe
                cts on electromagnetic modes at NSTX asp
                ect ratio with ad hoc parallel magnetic
                perturbation effects}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2022,
  url         = {https://doi.org/10.34770/415v-8p16}
}
Description:

Plasma shaping may have a stronger effect on global turbulence in tight-aspect-ratio tokamaks than in conventional-aspect-ratio tokamaks due to the higher toroidicity and more acute poloidal asymmetry in the magnetic field. In addition, previous local gyrokinetic studies have shown that it is necessary to include parallel magnetic field perturbations in order to accurately compute growth rates of electromagnetic modes in tight-aspect-ratio tokamaks. In this work, the effects of elongation and triangularity on global, ion-scale, linear electromagnetic modes are studied at NSTX aspect ratio and high plasma beta using the global gyrokinetic particle-in-cell code XGC. The effects of compressional magnetic perturbations are approximated via a well-known modification to the particle drifts that was developed for flux-tube simulations [N. Joiner et al., Phys. Plasmas 17, 072104 (2010)], without proof of its validity in a global simulation. Magnetic equilibria are re-constructed for each distinct plasma profile that is used. Coulomb collision effects are not considered. Within the limitations imposed by the present study, it is found that linear growth rates of electromagnetic modes (collisionless microtearing modes and kinetic ballooning modes) are significantly reduced by NSTX-like shaping. For example, growth rates of kinetic ballooning modes at high beta are reduced to the level of that of collisionless trapped electron modes.

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