TY - CONF TI - Radiation phenomena and particle fluxes in the X-event in JET AB - 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. AU - "Jaeckel, H J" AU - "Bartlett, D V" AU - "Falter, H" AU - "Lingertat, J" AU - "Reichle, R [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking]" KW - "70 PLASMA PHYSICS AND FUSION" KW - "PLASMA MACROINSTABILITIES" KW - "RADIATION FLUX" KW - "DIVERTORS" KW - "H-MODE PLASMA CONFINEMENT" KW - "HIGH-FREQUENCY DISCHARGES" KW - "JET TOKAMAK" KW - "PLASMA DISRUPTION" KW - "PLASMA IMPURITIES" KW - "WALL EFFECTS" DO - https://doi.org/ UR - https://www.osti.gov/etdeweb/servlets/purl/456196 PB - CY - France PY - 1994 DA - 1994-07-01 LA - English J2 - [] VL - C1 - Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking C2 - C3 - JET-P-94-29; CONF-9406270- C4 - C5 - INIS; OSTI as DE97621358 L3 - 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. ER -