Rf sheaths and impurity generation by ICRF (ion cyclotron range of frequencies) antennas

Technical Report · Tue Nov 01 04:00:00 EST 1988

DOI:https://doi.org/10.2172/6570191· OSTI ID:6570191

Perkins, F W

In general, Faraday screen elements in an ICRF antenna are not aligned precisely along the combined toroidal and poloidal magnetic fields. When plasma of density n > 2epsilon/sub 0/V/eg/sup 2/ /approximately/ 10/sup 9/cm/sup -3/ is present in the gap between elements, electron response to the parallel electric field shorts out the electric field over most of the gap, leaving a narrow sheath of positive space charge and intense electric field. Here V denotes the voltage across the gap and g the gap spacing. This intense electric field accelerates ions up to an appreciable fraction of the gap voltage (/approximately/ 1 kV), sufficient to cause physical sputtering of the screen material. Impurities so generated constitute the principal limitation on power density (kW/cm/sup 2/) for ICRF antennas. ICRF antenna and Faraday screen design principles which minimize sputtering are discussed. 24 refs., 9 figs., 1 tab.

• Research Organization: Princeton Univ., NJ (USA). Plasma Physics Lab.
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 6570191
• Report Number(s): PPPL-2571; ON: DE89004632
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700209 -- Fusion Power Plant Technology-- Component Development & Materials Testing
ANTENNAS
DESIGN
ELECTRICAL EQUIPMENT
EQUIPMENT
HEATING
HIGH-FREQUENCY HEATING
ICR HEATING
IMPURITIES
MAGNETIC FIELDS
PLASMA HEATING
PLASMA SHEATH
RF SYSTEMS
SPUTTERING