Analysis of an m = 1 electrostatic barrier scrape-off layer as a technique for reducing and controlling the particle and energy losses on the large major radius edge of tokamak

Technical Report · Thu Dec 01 00:00:00 EST 1988

DOI:https://doi.org/10.2172/6392444· OSTI ID:6392444

LaBombard, B; Conn, R W

It is observed in many tokamaks that particle and heat fluxes from the core region are poloidally asymmetric, favoring higher cross field transport on the large major radius edge of the torus. We propose a novel technique that may allow one to control this asymmetric flux into the tokamak boundary plasma. The scheme principally involves the formation of a mobility limited transport layer or 'electrostatic barrier' to inhibit the flow of plasma into the boundary layer at large major radii, forcing plasma to exit on the small major radius side of the torus instead. At the same time, the technique produces an 'ExB divertor' effect, efficiently exhausting plasma and impurities within the boundary layer. The implications of such a scheme are potentially important. By forcing plasma to exit on the inside half of the torus where the intrinsic cross-field transport is lower, the overall confinement characteristics of the central plasma may be improved. Furthermore, scrape-off plasma fluxes, subsequent recycling conditions, and their asymmetries at limiter, divertor, and wall structures can be actively controlled. An important feature of the technique is that it may be employed in both limiter and divertor configurations. The first-order response of the scrape-off layer plasma to the applied bias is estimated in this report using a simple two fluid transport model which includes cross-field diffusion and mobility. It is shown that the influence of an applied bias on the scrape-of layer density e-folding length depends only on the relative magnitudes of cross-field ion and electron mobilities. 17 refs., 6 figs.

• Research Organization: California Univ., Los Angeles (USA). Inst. for Plasma and Fusion Research
• DOE Contract Number: FG03-86ER52134
• OSTI ID: 6392444
• Report Number(s): UCLA-PPG-1186; ON: DE89007770
• Resource Relation: Other Information: Portions of this document are illegible in microfiche products
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
PLASMA SCRAPE-OFF LAYER
TRANSPORT THEORY
BOUNDARY LAYERS
DIVERTORS
ELECTRON MOBILITY
ENERGY LOSSES
EQUATIONS OF MOTION
LIMITERS
PLASMA CONFINEMENT
TOKAMAK DEVICES
CLOSED PLASMA DEVICES
CONFINEMENT
DIFFERENTIAL EQUATIONS
EQUATIONS
LAYERS
LOSSES
MOBILITY
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE MOBILITY
THERMONUCLEAR DEVICES
700103* - Fusion Energy- Plasma Research- Kinetics