Role of turbulence regime on determining the local density gradient
Abstract
In this study we show that the local density gradient in the plasma core depends on the calculated modefrequency of the most unstable linear mode and reaches a maximum when this frequency is close to zero. Previous theoretical and experimental work on AUG has shown that the ratio of electron to ion temperature, and as such the frequency of the dominant linear gyrokinetic mode, affects the local density gradient close to ρ = 0.3 [1, 2]. On DIIID we find that by adding Electron Cyclotron Heating (ECH), we modify the dominant unstable linear gyro kinetic mode from an Ion Temperature Gradient (ITG) mode to a Trapped Electron Mode (TEM), which means that the frequency of the dominant mode changes sign (from the ion to the electron direction). Local density peaking around midradius increases by 50% right around the crossover between the ITG and TEM regimes. By comparing how the particle flux changes, through the derivative of the electron density, n _{e}, with respect to time, ∂n _{e}/∂t, we find that the particle flux also exhibits the same trend versus mode frequency. As a result, we find that the changes in local particle transport are inversely proportional to the changes inmore »
 Authors:
 College of William and Mary, Williamsburg, VA (United States)
 Univ. of California, Los Angeles, CA (United States)
 General Atomics, San Diego, CA (United States)
 Publication Date:
 Research Org.:
 General Atomics, San Diego, CA (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1420327
 Grant/Contract Number:
 FC0204ER54698
 Resource Type:
 Journal Article: Accepted Manuscript
 Journal Name:
 Nuclear Fusion
 Additional Journal Information:
 Journal Volume: 58; Journal Issue: 1; Journal ID: ISSN 00295515
 Publisher:
 IOP Science
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; transport; turbulence; tokamak
Citation Formats
Wang, X., Mordijck, Saskia, Doyle, E. J., Zeng, L., Staebler, Gary M., Meneghini, Orso, and Smith, Sterling P. Role of turbulence regime on determining the local density gradient. United States: N. p., 2017.
Web. doi:10.1088/17414326/aa92a0.
Wang, X., Mordijck, Saskia, Doyle, E. J., Zeng, L., Staebler, Gary M., Meneghini, Orso, & Smith, Sterling P. Role of turbulence regime on determining the local density gradient. United States. doi:10.1088/17414326/aa92a0.
Wang, X., Mordijck, Saskia, Doyle, E. J., Zeng, L., Staebler, Gary M., Meneghini, Orso, and Smith, Sterling P. 2017.
"Role of turbulence regime on determining the local density gradient". United States.
doi:10.1088/17414326/aa92a0.
@article{osti_1420327,
title = {Role of turbulence regime on determining the local density gradient},
author = {Wang, X. and Mordijck, Saskia and Doyle, E. J. and Zeng, L. and Staebler, Gary M. and Meneghini, Orso and Smith, Sterling P.},
abstractNote = {In this study we show that the local density gradient in the plasma core depends on the calculated modefrequency of the most unstable linear mode and reaches a maximum when this frequency is close to zero. Previous theoretical and experimental work on AUG has shown that the ratio of electron to ion temperature, and as such the frequency of the dominant linear gyrokinetic mode, affects the local density gradient close to ρ = 0.3 [1, 2]. On DIIID we find that by adding Electron Cyclotron Heating (ECH), we modify the dominant unstable linear gyro kinetic mode from an Ion Temperature Gradient (ITG) mode to a Trapped Electron Mode (TEM), which means that the frequency of the dominant mode changes sign (from the ion to the electron direction). Local density peaking around midradius increases by 50% right around the crossover between the ITG and TEM regimes. By comparing how the particle flux changes, through the derivative of the electron density, ne, with respect to time, ∂ne/∂t, we find that the particle flux also exhibits the same trend versus mode frequency. As a result, we find that the changes in local particle transport are inversely proportional to the changes in electron density, indicating that the changes are driven by a change in thermodiffusive pinch.},
doi = {10.1088/17414326/aa92a0},
journal = {Nuclear Fusion},
number = 1,
volume = 58,
place = {United States},
year = 2017,
month =
}

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