skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Stability of elongated cross-section tokamaks to axisymmetric even poloidal mode number deformations

Abstract

A recent paper by Nakayama, Sato and Matsuoka suggests that elliptical cross section tokamaks with aspect ratio R/a = 3.2 and with elongation kappa = 2.6 are unstable to a splitting (m = 2, n = 0) instability for plasma ..beta.. > 5%, and that kappa /> =/ 4.0 plasmas are unstable to splitting for ..beta.. /> =/ 1%. We have tried to reproduce these results using the MHD evolution code TSC, but find these configurations to be stable, not even near a stability boundary. Even a kappa = 3.7 plasma with ..beta.. = 23.0% is stable to the splitting mode. However, the addition of pinching coils at the waist will cause the plasma to split if the current in these coils exceeds a critical value I/sub c/ which decreases with increasing ..beta... 8 refs., 11 figs., 1 tab.

Authors:
; ;
Publication Date:
Research Org.:
Princeton Univ., NJ (USA). Plasma Physics Lab.
OSTI Identifier:
6090264
Report Number(s):
PPPL-2626
ON: DE89013401
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; TOKAMAK TYPE REACTORS; PLASMA INSTABILITY; AXIAL SYMMETRY; MAGNETIC FIELD CONFIGURATIONS; MAGNETIC SURFACES; PLASMA SIMULATION; INSTABILITY; SIMULATION; SYMMETRY; THERMONUCLEAR REACTORS; 700107* - Fusion Energy- Plasma Research- Instabilities

Citation Formats

Weiner, R., Jardin, S.C., and Pomphrey, N. Stability of elongated cross-section tokamaks to axisymmetric even poloidal mode number deformations. United States: N. p., 1989. Web. doi:10.2172/6090264.
Copy to clipboard
Weiner, R., Jardin, S.C., & Pomphrey, N. Stability of elongated cross-section tokamaks to axisymmetric even poloidal mode number deformations. United States. doi:10.2172/6090264.
Copy to clipboard
Weiner, R., Jardin, S.C., and Pomphrey, N. Thu . "Stability of elongated cross-section tokamaks to axisymmetric even poloidal mode number deformations". United States. doi:10.2172/6090264. https://www.osti.gov/servlets/purl/6090264.
Copy to clipboard
@article{osti_6090264,
title = {Stability of elongated cross-section tokamaks to axisymmetric even poloidal mode number deformations},
author = {Weiner, R. and Jardin, S.C. and Pomphrey, N.},
abstractNote = {A recent paper by Nakayama, Sato and Matsuoka suggests that elliptical cross section tokamaks with aspect ratio R/a = 3.2 and with elongation kappa = 2.6 are unstable to a splitting (m = 2, n = 0) instability for plasma ..beta.. > 5%, and that kappa /> =/ 4.0 plasmas are unstable to splitting for ..beta.. /> =/ 1%. We have tried to reproduce these results using the MHD evolution code TSC, but find these configurations to be stable, not even near a stability boundary. Even a kappa = 3.7 plasma with ..beta.. = 23.0% is stable to the splitting mode. However, the addition of pinching coils at the waist will cause the plasma to split if the current in these coils exceeds a critical value I/sub c/ which decreases with increasing ..beta... 8 refs., 11 figs., 1 tab.},
doi = {10.2172/6090264},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 1989},
month = {Thu Jun 01 00:00:00 EDT 1989}
}
Copy to clipboard
Technical Report:
View Technical Report (0.36 MB)
DOI:  10.2172/6090264
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • ; ; - Physics of Fluids B: Plasma Physics; (USA)
    In a recent paper, Nakayama, Sato, and Matsuoka (Phys. Fluids {bold 31}, 630 (1988)) suggested that elliptical cross-section tokamaks with aspect ratio {ital R}/{ital a}=3.2 and with elongation {kappa}=2.6 are unstable to a splitting ({ital m}=2, {ital n}=0) instability for plasma {beta}{gt}5%, and that {kappa}{ge}4.0 plasmas are unstable to a splitting for {beta}{ge}1%. The magnetohydrodynamic evolution code tsc (J. Comput. Phys. {bold 66}, 481 (1986)) indicates, however, that such plasmas are robustly stable with respect to this splitting. In fact, a {kappa}=3.7 plasma with {beta}=23.0% shows no tendency to split. However, the addition of pinching coils at the waist willmore » cause the plasma to split if the current in these coils exceeds a critical value {ital I}{sub {ital c}}, which decreases with increasing beta.« less

  • ;
    Fixed boundary n = 1 MHD instabilities are studied computationally as a function of diamagnetism (..beta../sub pol/) and current profile in elongated toroidal equilibria (1 < b/a less than or equal to 4). It is found that even slightly diamagnetic plasmas with broad current profile and a highly elongated cross section are subject to a ballooning instability for q-values well above unity at the magnetic axis. A peaked current profile in a mildly diamagnetic plasma decreases the elongation of the inner flux surfaces and reduces the marginal q-value by suppressing ballooning modes. The maximum stable volume-averaged beta is achieved withmore » a broad current profile and either a paramagnetic plasma (..beta../sub pol/ < 1) with a highly elongated cross section (b/a > 2) or a diamagnetic plasma (..beta../sub pol/ > 1) with only a mildly elongated cross section (b/a < 2).« less

  • ; ;
    The trapped electron mode can be substantially stabilized on flux surfaces which are sufficiently vertically elongated (especially in high temperature regimes). (Author)

  • ; ;
    The MHD ballooning mode stability limits for tokamak configurations with different cross section shapes but the same total poloidal flux are surprisingly similar. 8 refs., 8 figs.

  • ; ; ; ...
    The stability of high-..beta.. vertically asymmetric tokamak equilibria to rigid displacements is investigated analytically. It is found that vertical stability at large beta poloidal is mainly determined by a coupling between the shape of the plasma surface and the Shafranov shift of the magnetic axis. To the lowest order, symmetric components of the plasma surface shape are found to be the critical destabilizing elements. Asymmetric components have little effect. The inclusion of higher order terms in the high ..beta.. tokamak expansion leads to further destabilization. Qualitative agreement between these analytic results and numerical stability calculations using the PEST code ismore » demonstrated.« less