Tokamak pump limiters

Conference · Tue May 01 04:00:00 EDT 1984

OSTI ID:6755836

Conn, R W

Recent experiments with a scoop limiter without active internal pumping have been carried out in the PDX tokamak with up to 6MW of auxiliary neutral beam heating. Experiments have also been done with a rotating head pump limiter in the PLT tokamak in conjunction with RF plasma heating. Extensive experiments have been done in the ISX-B tokamak and first experiments have been completed with the ALT-I limiter in TEXTOR. The pump limiter modules in these latter two machines have internal getter pumping. Experiments in ISX-B are with ohmic and auxiliary neutral beam heating. The results in ISX-B and TEXTOR show that active density control and particle removal is achieved with pump limiters. In ISX-B, the boundary layer (or scape-off layer) plasma partially screens the core plasma from gas injection. In both ISX-B and TEXTOR, the pressure internal to the module scales linearly with plasma density but in ISX-B, with neutral beam injection, a nonlinear increase is observed at the highest densities studied. Plasma plugging is the suspected cause. Results from PDX suggest that a region may exist in which core plasma energy confinement improves using a pump limiter during neutral beam injection. Asymmetric radial profiles and an increased edge electron temperature are observed in discharges with improved confinement. The injection of small amounts of neon into ISX-B has more clearly shown an improved electron core energy confinement during neutral beam injection. While carried out with a regular limiter, this Z-mode of operation is ideal for use with pump limiters and should be a way to achieve energy confinement times similar to values for H-mode tokamak plasmas. The implication of all these results for the design of a reactor pump limiter is described.

• Research Organization: California Univ., Los Angeles (USA). Center for Plasma Physics and Fusion Engineering
• DOE Contract Number: AT03-80ER52062
• OSTI ID: 6755836
• Report Number(s): DOE/ER/52062-5; CONF-840520-16; ON: DE84014543
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700209* -- Fusion Power Plant Technology-- Component Development & Materials Testing
BEAM INJECTION
CLOSED PLASMA DEVICES
LIMITERS
NEUTRAL ATOM BEAM INJECTION
PERFORMANCE
PLASMA DENSITY
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
VACUUM SYSTEMS