Fast electron studies in the ZT-40M edge plasma

Conference · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6503407

Ingraham, J C; Ellis, R F; Downing, J N; Miller, G; Munson, C P; Pickrell, M M; Schoenberg, K F; Weber, P G; Wurden, G A

Measurements of the edge plasma on the ZT-40M Reversed Field Pinch (RFP) show the presence of a dilute (1 to 10 per cent of the edge density), fast (T{sub H} {approx equal} (2 {minus} 3)T{sub {epsilon}0}) electron tail with a nearly unidirectional flow along B in a toroidal sense that is against the external applied electric field force. These studies have been extended over a wide range of operating conditions including high density and krypton-injected radiation-dominated (P{sub RAD} {approx equal} 0.9 P{sub IN}) discharges. In all cases the current density of the fast electrons is sufficient to account for the current density required to maintain the RFP. For low current 60 kA discharges this result has been confirmed in to a depth 20 mm inside of the reversal surface suggesting that the source of the fast electrons is the core of the discharge. The fast electrons also carry a large power flux parallel to B (several hundreds of MW/m{sup 2}, typically), and radial transport measurements of the fast electrons in the shadow of a movable limiter for 120 kA standard discharges indicate that the fast electrons are the primary electron energy loss channel. The fast electrons are a significant energy loss channel for a broad range of other cases as well. The collisionality of the fast electrons varies widely over the range of cases studied and it is noted that a small backflowing component of fast electrons increases in relative size as the collisionality increases. An estimate of the magnetic field stochastic diffusivity at the edge is made from the fast electron limiter shadow measurements and shows that the stochasticity of the magnetic field is low at the edge relative to the core, in agreement with magnetic fluctuation diffusivity measurements and MHD simulations. 35 refs., 10 figs.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6503407
• Report Number(s): LA-UR-90-3456; CONF-9010230-4; ON: DE91002323; TRN: 90-035701
• Resource Relation: Conference: International school of plasma physics, Varenna (Italy), 15-19 Oct 1990
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ZT-40 DEVICES
CURRENT DENSITY
DIFFUSION
ELECTRON TEMPERATURE
ELECTRON-ION COLLISIONS
ELECTRONS
ENERGY TRANSPORT
MAGNETIC FIELDS
MHD EQUILIBRIUM
PLASMA SCRAPE-OFF LAYER
POWER LOSSES
BOUNDARY LAYERS
COLLISIONS
ELECTRON COLLISIONS
ELEMENTARY PARTICLES
ENERGY LOSSES
EQUILIBRIUM
FERMIONS
ION COLLISIONS
LAYERS
LEPTONS
LOSSES
700103* - Fusion Energy- Plasma Research- Kinetics