## Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges

## Abstract

A reduced transport model for microtearing modes is developed for use in integrated predictive modeling studies, employing a unified fluid/kinetic approach to derive the nonlinear dispersion relation. This approach advances the kinetic description and allows the inclusion of nonlinear effects due to magnetic fluctuations. In this numerical study, the dependence of the microtearing mode real frequency and growth rate on plasma parameters and on DIII-D like L-mode and H-mode plasma profiles is examined. The magnetic fluctuation strength as well as electron thermal diffusivity due to microtearing modes is computed. The saturated amplitude of the magnetic fluctuations is calculated utilizing numerically determined microtearing mode eigenvalues in the nonlinear microtearing modes envelope equation. It is found that the electron temperature gradient in the presence of moderate collision frequency is required for the microtearing mode to become unstable. The effects of small and large collisionality and small and large wavenumbers on microtearing modes are found to be stabilizing, while the effects of density gradient, plasma beta, low current density, and large magnetic shear are found to be destabilizing. The microtearing mode growth rate, magnetic fluctuation strength, as well as electron thermal diffusivity is found to be larger in the H-mode plasma than inmore »

- Authors:

- Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
- Chalmers University of Technology and EURATOM-VR Association, Gothenburg, Sweden
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA

- Publication Date:

- Research Org.:
- Lehigh Univ., Bethlehem, PA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1540138

- Alternate Identifier(s):
- OSTI ID: 1416079

- Grant/Contract Number:
- FG02-92ER54141; SC0013977

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physics of Plasmas

- Additional Journal Information:
- Journal Volume: 25; Journal Issue: 1; Journal ID: ISSN 1070-664X

- Publisher:
- American Institute of Physics (AIP)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- Physics

### Citation Formats

```
Rafiq, T., Kritz, A. H., Weiland, J., Luo, L., and Schuster, E. Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges. United States: N. p., 2018.
Web. doi:10.1063/1.5009105.
```

```
Rafiq, T., Kritz, A. H., Weiland, J., Luo, L., & Schuster, E. Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges. United States. doi:10.1063/1.5009105.
```

```
Rafiq, T., Kritz, A. H., Weiland, J., Luo, L., and Schuster, E. Mon .
"Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges". United States. doi:10.1063/1.5009105. https://www.osti.gov/servlets/purl/1540138.
```

```
@article{osti_1540138,
```

title = {Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges},

author = {Rafiq, T. and Kritz, A. H. and Weiland, J. and Luo, L. and Schuster, E.},

abstractNote = {A reduced transport model for microtearing modes is developed for use in integrated predictive modeling studies, employing a unified fluid/kinetic approach to derive the nonlinear dispersion relation. This approach advances the kinetic description and allows the inclusion of nonlinear effects due to magnetic fluctuations. In this numerical study, the dependence of the microtearing mode real frequency and growth rate on plasma parameters and on DIII-D like L-mode and H-mode plasma profiles is examined. The magnetic fluctuation strength as well as electron thermal diffusivity due to microtearing modes is computed. The saturated amplitude of the magnetic fluctuations is calculated utilizing numerically determined microtearing mode eigenvalues in the nonlinear microtearing modes envelope equation. It is found that the electron temperature gradient in the presence of moderate collision frequency is required for the microtearing mode to become unstable. The effects of small and large collisionality and small and large wavenumbers on microtearing modes are found to be stabilizing, while the effects of density gradient, plasma beta, low current density, and large magnetic shear are found to be destabilizing. The microtearing mode growth rate, magnetic fluctuation strength, as well as electron thermal diffusivity is found to be larger in the H-mode plasma than in the L-mode plasma.},

doi = {10.1063/1.5009105},

journal = {Physics of Plasmas},

number = 1,

volume = 25,

place = {United States},

year = {2018},

month = {1}

}