## This content will become publicly available on August 13, 2020

# Reversal of turbulent gyroBohm isotope scaling due to nonadiabatic electron drive

## Abstract

Here, the influence of kinetic electrons on the isotope scaling of gyrokinetic turbulent energy flux is assessed. A simple framework is used to study the transition from ion-dominated turbulence regimes to regimes where electron and ion transport levels are comparable. In the ion-dominated regime, the turbulent ion energy flux increases as the ion mass increases, in agreement with simple gyroBohm scaling arguments. Conversely, in the latter regime for which the influence of electrons is significant, a strong reversal from the gyroBohm scaling is observed which cannot be captured by mixing length estimates. In this reversed regime, the turbulent ion energy flux decreases as ion mass increases. The reversal is controlled by finite electron-to-ion mass-ratio dependence of the nonadiabatic electron response. This mass-ratio dependence is dominated by the parallel motion terms in the electron gyrokinetic equation, and provides a correction to the bounce-averaged electron limit which is independent of mass ratio. The finite-mass correction is larger for light ions and explains the observed gyroBohm reversal for hydrogen plasmas. Lastly, an implication is that isotope scaling may not be properly described by simplified fluid or bounce-averaged electron equations.

- Authors:

- General Atomics, San Diego, CA (United States)

- Publication Date:

- Research Org.:
- Dept. of Energy (DOE), Washington DC (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

- OSTI Identifier:
- 1559134

- Grant/Contract Number:
- FC02-04ER54698; FG02-95ER54309; FC02-06ER54873; SC0017992

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physics of Plasmas

- Additional Journal Information:
- Journal Volume: 26; Journal Issue: 8; Journal ID: ISSN 1070-664X

- Publisher:
- American Institute of Physics (AIP)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

### Citation Formats

```
Belli, E. A., Candy, J., and Waltz, R. E. Reversal of turbulent gyroBohm isotope scaling due to nonadiabatic electron drive. United States: N. p., 2019.
Web. doi:10.1063/1.5110401.
```

```
Belli, E. A., Candy, J., & Waltz, R. E. Reversal of turbulent gyroBohm isotope scaling due to nonadiabatic electron drive. United States. doi:10.1063/1.5110401.
```

```
Belli, E. A., Candy, J., and Waltz, R. E. Tue .
"Reversal of turbulent gyroBohm isotope scaling due to nonadiabatic electron drive". United States. doi:10.1063/1.5110401.
```

```
@article{osti_1559134,
```

title = {Reversal of turbulent gyroBohm isotope scaling due to nonadiabatic electron drive},

author = {Belli, E. A. and Candy, J. and Waltz, R. E.},

abstractNote = {Here, the influence of kinetic electrons on the isotope scaling of gyrokinetic turbulent energy flux is assessed. A simple framework is used to study the transition from ion-dominated turbulence regimes to regimes where electron and ion transport levels are comparable. In the ion-dominated regime, the turbulent ion energy flux increases as the ion mass increases, in agreement with simple gyroBohm scaling arguments. Conversely, in the latter regime for which the influence of electrons is significant, a strong reversal from the gyroBohm scaling is observed which cannot be captured by mixing length estimates. In this reversed regime, the turbulent ion energy flux decreases as ion mass increases. The reversal is controlled by finite electron-to-ion mass-ratio dependence of the nonadiabatic electron response. This mass-ratio dependence is dominated by the parallel motion terms in the electron gyrokinetic equation, and provides a correction to the bounce-averaged electron limit which is independent of mass ratio. The finite-mass correction is larger for light ions and explains the observed gyroBohm reversal for hydrogen plasmas. Lastly, an implication is that isotope scaling may not be properly described by simplified fluid or bounce-averaged electron equations.},

doi = {10.1063/1.5110401},

journal = {Physics of Plasmas},

number = 8,

volume = 26,

place = {United States},

year = {2019},

month = {8}

}

Works referenced in this record:

##
Dependence of L mode confinement on plasma ion species in JET

journal, September 1993

- Tibone, F.; Balet, B.; Bures, M.
- Nuclear Fusion, Vol. 33, Issue 9

##
Isotope Effects on Trapped-Electron-Mode Driven Turbulence and Zonal Flows in Helical and Tokamak Plasmas

journal, April 2017

- Nakata, Motoki; Nunami, Masanori; Sugama, Hideo
- Physical Review Letters, Vol. 118, Issue 16

##
Collisionality dependence of density peaking in quasilinear gyrokinetic calculations

journal, November 2005

- Angioni, C.; Peeters, A. G.; Jenko, F.
- Physics of Plasmas, Vol. 12, Issue 11

##
Linearized model collision operators for multiple ion species plasmas and gyrokinetic entropy balance equations

journal, November 2009

- Sugama, H.; Watanabe, T. -H.; Nunami, M.
- Physics of Plasmas, Vol. 16, Issue 11

##
An Eulerian gyrokinetic-Maxwell solver

journal, April 2003

- Candy, J.; Waltz, R. E.
- Journal of Computational Physics, Vol. 186, Issue 2

##
Isotope scaling and η _{ i } mode with impurities in tokamak plasmas

journal, November 1994

- Dong, J. Q.; Horton, W.; Dorland, W.
- Physics of Plasmas, Vol. 1, Issue 11

##
Implications of advanced collision operators for gyrokinetic simulation

journal, February 2017

- Belli, E. A.; Candy, J.
- Plasma Physics and Controlled Fusion, Vol. 59, Issue 4

##
Isotope effects on L-H threshold and confinement in tokamak plasmas

journal, November 2017

- Maggi, C. F.; Weisen, H.; Hillesheim, J. C.
- Plasma Physics and Controlled Fusion, Vol. 60, Issue 1

##
Toroidal semicollisional microinstabilities and anomalous electron and ion transport

journal, April 1990

- Romanelli, F.; Briguglio, S.
- Physics of Fluids B: Plasma Physics, Vol. 2, Issue 4

##
Bounce averaged trapped electron fluid equations for plasma turbulence

journal, November 1996

- Beer, M. A.; Hammett, G. W.
- Physics of Plasmas, Vol. 3, Issue 11

##
Isotopic scaling of confinement in deuterium–tritium plasmas

journal, June 1995

- Scott, S. D.; Zarnstorff, M. C.; Barnes, Cris W.
- Physics of Plasmas, Vol. 2, Issue 6

##
Theory of the ubiquitous mode

journal, October 1977

- Coppi, B.; Pegoraro, F.
- Nuclear Fusion, Vol. 17, Issue 5

##
Isotope effects of trapped electron modes in the presence of impurities in tokamak plasmas

journal, March 2016

- Shen, Yong; Dong, J. Q.; Sun, A. P.
- Plasma Physics and Controlled Fusion, Vol. 58, Issue 4

##
Hydrogen isotope effects on ITG scale length, pedestal and confinement in JT-60 H-mode plasmas

journal, July 2013

- Urano, H.; Takizuka, T.; Aiba, N.
- Nuclear Fusion, Vol. 53, Issue 8

##
Deuterium–tritium high confinement (H‐mode) studies in the Tokamak Fusion Test Reactor

journal, June 1995

- Bush, C. E.; Sabbagh, S. A.; Zweben, S. J.
- Physics of Plasmas, Vol. 2, Issue 6

##
A fluid–kinetic hybrid electron model for electromagnetic simulations

journal, May 2001

- Lin, Zhihong; Chen, Liu
- Physics of Plasmas, Vol. 8, Issue 5

##
A high-accuracy Eulerian gyrokinetic solver for collisional plasmas

journal, November 2016

- Candy, J.; Belli, E. A.; Bravenec, R. V.
- Journal of Computational Physics, Vol. 324

##
Critical gradient formula for toroidal electron temperature gradient modes

journal, September 2001

- Jenko, F.; Dorland, W.; Hammett, G. W.
- Physics of Plasmas, Vol. 8, Issue 9

##
Progress towards a predictive model for pedestal height in DIII-D

journal, July 2009

- Groebner, R. J.; Leonard, A. W.; Snyder, P. B.
- Nuclear Fusion, Vol. 49, Issue 8

##
Gyro-Landau fluid equations for trapped and passing particles

journal, October 2005

- Staebler, G. M.; Kinsey, J. E.; Waltz, R. E.
- Physics of Plasmas, Vol. 12, Issue 10

##
Diffusive particle and heat pinch effects in toroidal plasmas

journal, October 1989

- Weiland, J.; Jarmén, A. B.; Nordman, H.
- Nuclear Fusion, Vol. 29, Issue 10

##
Density gradient driven microinstabilities and turbulence in ASDEX Upgrade pellet fuelled plasmas

journal, August 2017

- Angioni, C.; Lang, P. T.; Manas, P.
- Nuclear Fusion, Vol. 57, Issue 11

##
Gyrokinetic simulations of ion and impurity transport

journal, February 2005

- Estrada-Mila, C.; Candy, J.; Waltz, R. E.
- Physics of Plasmas, Vol. 12, Issue 2

##
Reduced equations for electromagnetic turbulence in tokamaks

journal, January 2003

- Hinton, F. L.; Rosenbluth, M. N.; Waltz, R. E.
- Physics of Plasmas, Vol. 10, Issue 1

##
Dynamics of axisymmetric and poloidal flows in tokamaks

journal, January 1999

- Hinton, F. L.; Rosenbluth, M. N.
- Plasma Physics and Controlled Fusion, Vol. 41, Issue 3A

##
Chapter 2: Plasma confinement and transport

journal, December 1999

- Transport, ITER Physics Expert Group on Confin; Database, ITER Physics Expert Group on Confin; Editors, ITER Physics Basis
- Nuclear Fusion, Vol. 39, Issue 12

##
Microturbulence study of the isotope effect

journal, January 2015

- Bustos, A.; Bañón Navarro, A.; Görler, T.
- Physics of Plasmas, Vol. 22, Issue 1

##
A nonlinear bounce‐kinetic equation for trapped electrons

journal, December 1990

- Gang, F. Y.; Diamond, P. H.
- Physics of Fluids B: Plasma Physics, Vol. 2, Issue 12

##
The isotope effect in ASDEX

journal, August 1993

- Bessenrodt-Weberpals, M.; Wagner, F.; Gehre, O.
- Nuclear Fusion, Vol. 33, Issue 8

##
Gyrokinetic nonlinear isotope effects in tokamak plasmas

journal, December 2016

- Garcia, J.; Görler, T.; Jenko, F.
- Nuclear Fusion, Vol. 57, Issue 1

##
Verification of long wavelength electromagnetic modes with a gyrokinetic-fluid hybrid model in the XGC code

journal, May 2017

- Hager, Robert; Lang, Jianying; Chang, C. S.
- Physics of Plasmas, Vol. 24, Issue 5

##
Noncircular, finite aspect ratio, local equilibrium model

journal, April 1998

- Miller, R. L.; Chu, M. S.; Greene, J. M.
- Physics of Plasmas, Vol. 5, Issue 4

##
Spectral treatment of gyrokinetic shear flow

journal, March 2018

- Candy, J.; Belli, E. A.
- Journal of Computational Physics, Vol. 356

##
A gyro-Landau-fluid transport model

journal, July 1997

- Waltz, R. E.; Staebler, G. M.; Dorland, W.
- Physics of Plasmas, Vol. 4, Issue 7

##
Plasma confinement in JET H mode plasmas with H, D, DT and T isotopes

journal, March 1999

- Cordey, J. G.; Balet, B.; Bartlett, D. V.
- Nuclear Fusion, Vol. 39, Issue 3

##
Isotope and fast ions turbulence suppression effects: Consequences for high-β ITER plasmas

journal, May 2018

- Garcia, J.; Görler, T.; Jenko, F.
- Physics of Plasmas, Vol. 25, Issue 5

##
Isotope mass and charge effects in tokamak plasmas

journal, December 2011

- Pusztai, I.; Candy, J.; Gohil, P.
- Physics of Plasmas, Vol. 18, Issue 12

##
A gyrokinetic ion zero electron inertia fluid electron model for turbulence simulations

journal, February 2001

- Chen, Yang; Parker, Scott
- Physics of Plasmas, Vol. 8, Issue 2