Electrostatic end plugging accompanied by a central-cell density increase in an axisymmetric tandem mirror

Journal Article · Tue Sep 01 04:00:00 EDT 1987 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.866050· OSTI ID:6283440

Ferron, J R; Goulding, R; Nelson, B A; Intrator, T; Wang, E Y; Severn, G; Hershkowitz, N; Brouchous, D; Pew, J; Breun, R A; others, and

Electrostatic end plugging is observed in a completely axisymmetric, three cell tandem mirror under conditions where the central-cell plasma density is always larger than the end-cell density. A factor of 4 increase in the central-cell density, to a maximum of 1.2 x 10 T cm T with simultaneous plasma beta of 13%, occurs upon application of the end plugging potential. Ion confining potentials of 25 V and 80 V at the two ends of the device, respectively, result in a factor of 2.5 increase in the axial confinement time for T/sub i//sub c/ = 40 eV in agreement with the collisional flow model for ion confinement. The non-Boltzmann ion confining potential is caused by electron heating in the end cells by rf near the ion-cyclotron frequency. The initial central-cell density rise is caused by an increase in the ionization rate that occurs because of an increase in the electron temperature. The density remains high throughout the end-cell heating pulse as a result of increased particle confinement time. There is no nonambipolar radial ion loss in the core plasma (rless than or equal to16 cm) but inward radial transport of ions is observed at a rate consistent with ion--neutral collisions and a radial electric field in the negative radial direction. Steady-state thermal-barrier-like potential dips that are in agreement with the Boltzmann model for potentials are observed in the transitions between the central cell and the end cells.

• Research Organization: University of Wisconsin, Madison, Wisconsin 53706
• OSTI ID: 6283440
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 30:9; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
CONFINEMENT
COULOMB FIELD
ELECTRIC FIELDS
MAGNETIC MIRRORS
OPEN PLASMA DEVICES
PLASMA CONFINEMENT
PLASMA DENSITY
TANDEM MIRRORS
THERMONUCLEAR DEVICES