LH launcher Arcs Formation and Detection on JET

Journal Article · Fri Dec 23 00:00:00 EST 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3664918· OSTI ID:21612470

Baranov, Yu F; Challis, C D; Kirov, K; Mailloux, J; Monakhov, I ^[1]; Ekedahl, A; Goniche, M ^[2]

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1. Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)
2. CEA, IRFM, F-13108 Saint Paul-lez-Durance (France)

Mechanisms of arc formation have been analyzed and the critical electric fields for the multipactor effect calculated, compared to the experimental values and found to be within the normal operational space of the LH system on JET. It has been shown that the characteristic electron energy (20-1000)eV for the highest multipactor resonances (N = 4-9) are within the limits of secondary electron yield above 1 required for multipactoring. Electrons with these energies provide the highest gas desorption efficiency when hitting the waveguide walls. The effect of higher waveguide modes and magnetic field on the multipactor was also considered. The distribution function for electrons accelerated by LH waves in front of the launcher has been calculated. The field emission currents have been estimated and found to be small. It is proposed that emission of Fel5, 16 lines, which can be obtained with improved diagnostics, could be used to detect arcs that are missed by a protection system based on the reflected power. The reliability and time response of these signals are discussed. A similar technique based on the observation of the emission of low ionized atoms can be used for a fast detection of other undesirable events to avoid sputtering or melting of the plasma facing components such as RF antenna. These techniques are especially powerful if they are based on emission uniquely associated with specific locations and components.

• OSTI ID: 21612470
• Journal Information: AIP Conference Proceedings, Vol. 1406, Issue 1; Conference: 9. topical conference on radio frequency power in plasmas, Newport (United States), 1-3 Jun 2011; Other Information: DOI: 10.1063/1.3664918; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
BOLOMETERS
DESORPTION
DISTRIBUTION FUNCTIONS
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTRONS
EV RANGE
FIELD EMISSION
FIRST WALL
JET TOKAMAK
LOWER HYBRID CURRENT DRIVE
LOWER HYBRID HEATING
MAGNETIC FIELDS
RELIABILITY
RESONANCE
CLOSED PLASMA DEVICES
CURRENTS
ELECTRICAL EQUIPMENT
ELEMENTARY PARTICLES
EMISSION
ENERGY RANGE
EQUIPMENT
FERMIONS
FUNCTIONS
HEATING
HIGH-FREQUENCY HEATING
LEPTONS
MEASURING INSTRUMENTS
NON-INDUCTIVE CURRENT DRIVE
PLASMA HEATING
SORPTION
THERMONUCLEAR DEVICES
THERMONUCLEAR REACTOR WALLS
TOKAMAK DEVICES