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Title: Investigation of the effect of resistive MHD modes on spherical torus performance in CDX-U

Abstract

Resistive MHD modes and associated effects on spherical torus performance are investigated in the CDX-U device for Ip {le} 100 kA. Presently, the growth of resistive MHD modes (n=1/m=3 or n=1/m=2) as the edge q[q(a)] is lowered toward 3.5 appears to limit the maximum current achievable in CDX-U. For low q(a) discharges, a prominent rotating hot spot can be seen with the soft x-ray array, indicative of a magnetic island associated with a n=1/m=1 mode. The edge mode, which is n=1/m=3 or n=1/m=2, can be seen by the soft x-ray and edge magnetic pick up coil array. The growth of those modes in space and amplitude eventually leads to an Internal Reconnection Event (IRE). Prior to the IRE, strong mode-mixing takes place suggesting magnetic island overlap. The IRE causes a rapid heat loss from the core causing a strong plasma elongation and current spike due to the plasma inductance drop. With an appropriate discharge control, a MHD quiescent high confinement regime with over twice the central electron temperature relative to the MHD active regime has been found. To assess the halo-induced effects during the MHD events, a pair of segmented Rogowski coils were installed on the center stack. The observedmore » halo-induced current fraction is generally small (less than 5% of the total plasma current) even for the case of forced disruption.« less

Authors:
;  [1];  [2]
  1. Princeton Univ., NJ (United States). Princeton Plasma Physics Lab.
  2. Korean Advanced Inst. for Science and Technology (Korea, Republic of); and others
Publication Date:
Research Org.:
Princeton Univ., Princeton Plasma Physics Lab., NJ (United States)
Sponsoring Org.:
USDOE Office of Energy Research, Washington, DC (United States)
OSTI Identifier:
304212
Report Number(s):
PPPL-3225
ON: DE97051506; TRN: 99:002015
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jan 1997
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; TOKAMAK DEVICES; PLASMA INSTABILITY; INSTABILITY GROWTH RATES; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; PLASMA DISRUPTION; CONFINEMENT; ENERGY LOSSES

Citation Formats

Ono, M, Stutman, D, and Hwang, Y S. Investigation of the effect of resistive MHD modes on spherical torus performance in CDX-U. United States: N. p., 1997. Web. doi:10.2172/304212.
Ono, M, Stutman, D, & Hwang, Y S. Investigation of the effect of resistive MHD modes on spherical torus performance in CDX-U. United States. https://doi.org/10.2172/304212
Ono, M, Stutman, D, and Hwang, Y S. 1997. "Investigation of the effect of resistive MHD modes on spherical torus performance in CDX-U". United States. https://doi.org/10.2172/304212. https://www.osti.gov/servlets/purl/304212.
@article{osti_304212,
title = {Investigation of the effect of resistive MHD modes on spherical torus performance in CDX-U},
author = {Ono, M and Stutman, D and Hwang, Y S},
abstractNote = {Resistive MHD modes and associated effects on spherical torus performance are investigated in the CDX-U device for Ip {le} 100 kA. Presently, the growth of resistive MHD modes (n=1/m=3 or n=1/m=2) as the edge q[q(a)] is lowered toward 3.5 appears to limit the maximum current achievable in CDX-U. For low q(a) discharges, a prominent rotating hot spot can be seen with the soft x-ray array, indicative of a magnetic island associated with a n=1/m=1 mode. The edge mode, which is n=1/m=3 or n=1/m=2, can be seen by the soft x-ray and edge magnetic pick up coil array. The growth of those modes in space and amplitude eventually leads to an Internal Reconnection Event (IRE). Prior to the IRE, strong mode-mixing takes place suggesting magnetic island overlap. The IRE causes a rapid heat loss from the core causing a strong plasma elongation and current spike due to the plasma inductance drop. With an appropriate discharge control, a MHD quiescent high confinement regime with over twice the central electron temperature relative to the MHD active regime has been found. To assess the halo-induced effects during the MHD events, a pair of segmented Rogowski coils were installed on the center stack. The observed halo-induced current fraction is generally small (less than 5% of the total plasma current) even for the case of forced disruption.},
doi = {10.2172/304212},
url = {https://www.osti.gov/biblio/304212}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1997},
month = {Wed Jan 01 00:00:00 EST 1997}
}