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Radiation phenomena and particle fluxes in the X-event in JET

Abstract

The radiation build-up and the particle fluxes in the phase, immediately preceding the X-event, has been studied bolometrically and using spectroscopy. The results show that the H-mode phase in high performance discharges tends to collapse irreversibly. The (calculated) target temperature just before the X-event amounts to about 1400 C. Any deterioration of confinement at this temperature leads to run-away conditions of the target temperature and a final fall-back into L-mode. Possible causes of the confinement deterioration are: MHD activities can cause a fast plasma loss and, hence, a power flash, dumped on the divertor target, leading to a temperature jump of up to 1000 C; enhanced recycling, due to thermal release of trapped deuterium from the graphite target plates causes an effective plasma edge cooling; loose graphite on the target tiles with virtually no thermal coupling to the target bulk can be sublimated and ejected into the main plasma with even small power levels. An active cooling, keeping the bulk target at ambient temperature could make the discharge more resilient against even medium MHD instabilities, as e.g. giant ELMs. 5 refs., 4 figs.
Authors:
Jaeckel, H J; Bartlett, D V; Falter, H; Lingertat, J; Reichle, R [1] 
  1. Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking
Publication Date:
Jul 01, 1994
Product Type:
Conference
Report Number:
JET-P-94-29; CONF-9406270-
Reference Number:
SCA: 700340; PA: AIX-28:032703; EDB-97:058939; SN: 97001766276
Resource Relation:
Conference: 21. EPS conference on controlled fusion and plasma physics, Montpellier (France), 27 Jun - 1 Jul 1994; Other Information: PBD: Jul 1994; Related Information: Is Part Of Controlled fusion and plasma physics; PB: 240 p.
Subject:
70 PLASMA PHYSICS AND FUSION; PLASMA MACROINSTABILITIES; RADIATION FLUX; DIVERTORS; H-MODE PLASMA CONFINEMENT; HIGH-FREQUENCY DISCHARGES; JET TOKAMAK; PLASMA DISRUPTION; PLASMA IMPURITIES; WALL EFFECTS
OSTI ID:
456196
Research Organizations:
Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking
Country of Origin:
France
Language:
English
Other Identifying Numbers:
Other: ON: DE97621358; TRN: FR9701776032703
Availability:
INIS; OSTI as DE97621358
Submitting Site:
FRN
Size:
pp. 151-156
Announcement Date:

Citation Formats

Jaeckel, H J, Bartlett, D V, Falter, H, Lingertat, J, and Reichle, R. Radiation phenomena and particle fluxes in the X-event in JET. France: N. p., 1994. Web.
Jaeckel, H J, Bartlett, D V, Falter, H, Lingertat, J, & Reichle, R. Radiation phenomena and particle fluxes in the X-event in JET. France.
Jaeckel, H J, Bartlett, D V, Falter, H, Lingertat, J, and Reichle, R. 1994. "Radiation phenomena and particle fluxes in the X-event in JET." France.
@misc{etde_456196,
title = {Radiation phenomena and particle fluxes in the X-event in JET}
author = {Jaeckel, H J, Bartlett, D V, Falter, H, Lingertat, J, and Reichle, R}
abstractNote = {The radiation build-up and the particle fluxes in the phase, immediately preceding the X-event, has been studied bolometrically and using spectroscopy. The results show that the H-mode phase in high performance discharges tends to collapse irreversibly. The (calculated) target temperature just before the X-event amounts to about 1400 C. Any deterioration of confinement at this temperature leads to run-away conditions of the target temperature and a final fall-back into L-mode. Possible causes of the confinement deterioration are: MHD activities can cause a fast plasma loss and, hence, a power flash, dumped on the divertor target, leading to a temperature jump of up to 1000 C; enhanced recycling, due to thermal release of trapped deuterium from the graphite target plates causes an effective plasma edge cooling; loose graphite on the target tiles with virtually no thermal coupling to the target bulk can be sublimated and ejected into the main plasma with even small power levels. An active cooling, keeping the bulk target at ambient temperature could make the discharge more resilient against even medium MHD instabilities, as e.g. giant ELMs. 5 refs., 4 figs.}
place = {France}
year = {1994}
month = {Jul}
}