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Title: ELM-related fluctuations in PBX-M H-modes

Abstract

Edge Localized Modes, or ELMs, are at the same time both disadvantageous and advantageous features of H-modes. ELMs can cause energy and particle losses from the plasma, with instantaneous energy losses reaching 40% of the total stored energy in the case of large-amplitude ELMs. The energy loss from these ELMs, or closely spaced smaller ELMs, may result in what is known as a beta-collapse, an event in which energy is lost over a substantial duration of the discharge. On the other hand, if controlled, the ELM related energy and, especially, impurity losses can lead to near steady-state discharge conditions with relatively low radiative power losses. The importance of ELMs in the development of the H-phase has led to numerous studies which attempt to uncover their nature. The purpose of the present work is to present additional observations of, most notably, high frequency magnetic fluctuations associated with ELMS. There are some observations here that are consistent with previously reported ones, namely the appearance of high frequency ({ge}250 kHz) activity prior to the D{sub {alpha}} increase, suggesting again that the rise in D{sub {alpha}} is some delayed response to an instability occurring farther inside the plasma edge. While this high frequency activitymore » is global, with high coherence for all coil pairs both on the inside and outside midplane, there is no identifiable mode structure. Reported here for the first time are observations of a very intense outward ballooning feature that appears simultaneously with the D{sub {alpha}} increase and lasts for about 5 msec. The toroidal mode structure of this feature is clearly identifiable, consisting of a series of toroidal harmonics from n=3 to 8, at frequencies given by f{sub n}=f{sub 0}+n{Delta}f, with f{sub 0}=30 to 50 kHz and A{Delta}=20 to 30 kHz.« less

Authors:
; ; ; ; ;  [1]; ;  [2]
  1. Princeton Univ., NJ (United States). Plasma Physics Lab.
  2. Oak Ridge National Lab., TN (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10162666
Report Number(s):
PPPL-2967
ON: DE94014517; TRN: 94:013120
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Apr 1994
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EDGE LOCALIZED MODES; FLUCTUATIONS; PBX DEVICES; H-MODE PLASMA CONFINEMENT; PARTICLE LOSSES; 700310; PLASMA CONFINEMENT

Citation Formats

Kaye, S M, Hahm, T S, Sesnic, S, Tang, W, Roney, P, Davis, W, Dunlap, J L, and Harris, J H. ELM-related fluctuations in PBX-M H-modes. United States: N. p., 1994. Web. doi:10.2172/10162666.
Kaye, S M, Hahm, T S, Sesnic, S, Tang, W, Roney, P, Davis, W, Dunlap, J L, & Harris, J H. ELM-related fluctuations in PBX-M H-modes. United States. https://doi.org/10.2172/10162666
Kaye, S M, Hahm, T S, Sesnic, S, Tang, W, Roney, P, Davis, W, Dunlap, J L, and Harris, J H. 1994. "ELM-related fluctuations in PBX-M H-modes". United States. https://doi.org/10.2172/10162666. https://www.osti.gov/servlets/purl/10162666.
@article{osti_10162666,
title = {ELM-related fluctuations in PBX-M H-modes},
author = {Kaye, S M and Hahm, T S and Sesnic, S and Tang, W and Roney, P and Davis, W and Dunlap, J L and Harris, J H},
abstractNote = {Edge Localized Modes, or ELMs, are at the same time both disadvantageous and advantageous features of H-modes. ELMs can cause energy and particle losses from the plasma, with instantaneous energy losses reaching 40% of the total stored energy in the case of large-amplitude ELMs. The energy loss from these ELMs, or closely spaced smaller ELMs, may result in what is known as a beta-collapse, an event in which energy is lost over a substantial duration of the discharge. On the other hand, if controlled, the ELM related energy and, especially, impurity losses can lead to near steady-state discharge conditions with relatively low radiative power losses. The importance of ELMs in the development of the H-phase has led to numerous studies which attempt to uncover their nature. The purpose of the present work is to present additional observations of, most notably, high frequency magnetic fluctuations associated with ELMS. There are some observations here that are consistent with previously reported ones, namely the appearance of high frequency ({ge}250 kHz) activity prior to the D{sub {alpha}} increase, suggesting again that the rise in D{sub {alpha}} is some delayed response to an instability occurring farther inside the plasma edge. While this high frequency activity is global, with high coherence for all coil pairs both on the inside and outside midplane, there is no identifiable mode structure. Reported here for the first time are observations of a very intense outward ballooning feature that appears simultaneously with the D{sub {alpha}} increase and lasts for about 5 msec. The toroidal mode structure of this feature is clearly identifiable, consisting of a series of toroidal harmonics from n=3 to 8, at frequencies given by f{sub n}=f{sub 0}+n{Delta}f, with f{sub 0}=30 to 50 kHz and A{Delta}=20 to 30 kHz.},
doi = {10.2172/10162666},
url = {https://www.osti.gov/biblio/10162666}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 01 00:00:00 EST 1994},
month = {Fri Apr 01 00:00:00 EST 1994}
}