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Title: Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

Abstract

A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as βe, ν*e, the MHD α parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and ν*e were relatively low, ballooning parity modes were dominant. As time progressed and both βe and ν*e increased, microtearing became the dominant low-κθ mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-κθ, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job ofmore » predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1]
  1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1182276
Report Number(s):
PPPL-5062
Journal ID: ISSN 1070-664X: PHPAEN
DOE Contract Number:  
DE-AC02-09CH11466
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 8; Related Information: Copyright 2014 AIP Publishing LLC
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Confinement; H-mode Plasma Confinement; Spherical Torus; Spherical Tokamak; Stability, Microinstability; Tokamaks, NSTX; Transport Phenomena

Citation Formats

Kaye, S. M., Guttenfelder, W., Bell, R. E., Gerhardt, S. P., LeBlanc, B. P., and Maingi, R.. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas. United States: N. p., 2014. Web. doi:10.1063/1.4893135.
Kaye, S. M., Guttenfelder, W., Bell, R. E., Gerhardt, S. P., LeBlanc, B. P., & Maingi, R.. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas. United States. doi:10.1063/1.4893135.
Kaye, S. M., Guttenfelder, W., Bell, R. E., Gerhardt, S. P., LeBlanc, B. P., and Maingi, R.. Fri . "Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas". United States. doi:10.1063/1.4893135.
@article{osti_1182276,
title = {Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas},
author = {Kaye, S. M. and Guttenfelder, W. and Bell, R. E. and Gerhardt, S. P. and LeBlanc, B. P. and Maingi, R.},
abstractNote = {A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as βe, ν*e, the MHD α parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and ν*e were relatively low, ballooning parity modes were dominant. As time progressed and both βe and ν*e increased, microtearing became the dominant low-κθ mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-κθ, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.},
doi = {10.1063/1.4893135},
journal = {Physics of Plasmas},
number = 8,
volume = 21,
place = {United States},
year = {Fri Aug 01 00:00:00 EDT 2014},
month = {Fri Aug 01 00:00:00 EDT 2014}
}