The ''ring killer'' experiment: Electron confinement in the ELMO Bumpy Torus without the influence of hot-electron rings

Technical Report · Sat Nov 01 04:00:00 EST 1986

OSTI ID:7006313

Hillis, D L; Wilgen, J B; Cobble, J A; Davis, W A; Hiroe, S; Rasmussen, D A; Richards, R K; Uckan, T; Jaeger, E F; Hankins, O E

The ELMO Bumpy Torus (EBT) (Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1975), Vol. II, p. 141) normally has an energetic electron ring in each of its 24 mirror sectors. The original intention of using this hot-electron population was to provide an average local minimum in the magnetic field (through its diamagnetism) to stabilize the simple interchange and flute modes, which otherwise are theoretically inherent in a closed-field-line bumpy torus. To study the confinement properties of a bumpy torus without the influence of hot-electron rings, a water-cooled stainless steel limiter in each mirror sector was extended into the plasma to the ring location; this eliminated the hot-electron ring population. These limiters were aptly named ''ring killers.'' Electron temperature, density, space potential, and plasma fluctuations have been measured during the ring killer experiment and are compared to standard EBT operation. The results of these experiments indicate that the hot-electron rings in EBT do enhance the core plasma properties of EBT and do, in fact, reduce plasma fluctuations; however, these improvements are not large in magnitude. These measurements and recent theoretical models suggest that simple interchange/flute modes are stabilized, or fluctuation levels reduced, well before that condition is obtained for average minimum-B stabilization. Several possible mechanisms for this stabilization are discussed.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7006313
• Report Number(s): ORNL/TM-9475; ON: DE87005270
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
BUMPY TORI
CONFINEMENT
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELMO BUMPY TORUS
ELMO DEVICES
LIMITERS
MAGNETIC MIRRORS
OPEN PLASMA DEVICES
OSCILLATIONS
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
THERMONUCLEAR DEVICES