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Title: High n ballooning modes in highly elongated tokamaks

Abstract

An analytic study of stability against high n ballooning modes in highly elongated axisymmetric plasmas is presented and compared with computational results. From the equation for the marginal pressure gradient, it is found that the local shear plays an important role on the stability of elongated and shifted plasma, and that high elongation deteriorates the stability by decreasing the stabilizing effects of field line bending and local shear. The net contribution of the local shear to stability decreases with elongation and shift for strongly ballooning modes (eigenfunctions strongly localized near the outer edge of the toroidal flux surfaces) but increases for interchange modes (eigenfunctions more uniform along the flux surfaces). The computational study of high n ballooning modes in a highly elongated plasma reveals that lowering the aspect ratio and broadening the pressure profile enhance the marginal beta for ..beta../sub p/ less than unity but severely reduce the marginal beta for ..beta../sub p/ larger than unity.

Authors:
;
Publication Date:
Research Org.:
Oak Ridge National Lab., TN (USA)
OSTI Identifier:
5501356
Report Number(s):
ORNL/TM-7074
TRN: 80-005461
DOE Contract Number:
W-7405-ENG-26
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; ANALYTICAL SOLUTION; TOKAMAK DEVICES; ASPECT RATIO; BETA RATIO; MAGNETIC FIELD CONFIGURATIONS; SHEAR; STABILIZATION; CLOSED PLASMA DEVICES; INSTABILITY; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; THERMONUCLEAR DEVICES; 700107* - Fusion Energy- Plasma Research- Instabilities

Citation Formats

An, C.H., and Bateman, G. High n ballooning modes in highly elongated tokamaks. United States: N. p., 1980. Web. doi:10.2172/5501356.
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An, C.H., & Bateman, G. High n ballooning modes in highly elongated tokamaks. United States. doi:10.2172/5501356.
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An, C.H., and Bateman, G. Fri . "High n ballooning modes in highly elongated tokamaks". United States. doi:10.2172/5501356. https://www.osti.gov/servlets/purl/5501356.
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@article{osti_5501356,
title = {High n ballooning modes in highly elongated tokamaks},
author = {An, C.H. and Bateman, G.},
abstractNote = {An analytic study of stability against high n ballooning modes in highly elongated axisymmetric plasmas is presented and compared with computational results. From the equation for the marginal pressure gradient, it is found that the local shear plays an important role on the stability of elongated and shifted plasma, and that high elongation deteriorates the stability by decreasing the stabilizing effects of field line bending and local shear. The net contribution of the local shear to stability decreases with elongation and shift for strongly ballooning modes (eigenfunctions strongly localized near the outer edge of the toroidal flux surfaces) but increases for interchange modes (eigenfunctions more uniform along the flux surfaces). The computational study of high n ballooning modes in a highly elongated plasma reveals that lowering the aspect ratio and broadening the pressure profile enhance the marginal beta for ..beta../sub p/ less than unity but severely reduce the marginal beta for ..beta../sub p/ larger than unity.},
doi = {10.2172/5501356},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Feb 01 00:00:00 EST 1980},
month = {Fri Feb 01 00:00:00 EST 1980}
}
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Technical Report:
View Technical Report (1.36 MB)
DOI:  10.2172/5501356
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