Modeling ambipolar potential formation due to ICRF heating effects on electrons

Technical Report · Thu Aug 01 00:00:00 EDT 1985

OSTI ID:5086161

Johnson, J W; Callen, J D; Hershkowitz, N

A mechanism for the potential bump observed near the region of ICRF heating in the endplugs of the Phaedrus tandem mirror experiment is investigated by numerical simulation of electron orbits in a simple mirror geometry. Given initial magnetic and ambipolar potential wells that trap the electrons, the ''near field'' parallel electric field E-tilde/sub z/e/sup -i..omega..t/, which is localized near and due to the ICRF heating, tends to eject electrons from the region where E-tilde/sub z/ is nonzero. This depletion of the local electron population causes a local increase in the ambipolar potential. The rate at which the electrons are ejected, (dn/dt), is calculated from the electron orbit computation for a given potential well depth. The rate at which passing particles ''fill in'' the potential well can also be calculated. An estimate of how large the bump in the ambipolar potential becomes is obtained by finding the well depth at which (dn/dt) approximately equals the ''filling'' rate. For Phaedrus parameters (n/sub 0/ approx. = 4.0 x 10/sup 12/ cm/sup -3/, T/sub e/ = 20 eV, E-tilde/sub z/ approx. = 1.0 V/cm) the electron pumping rate balances the ''filling'' rate at a potential well depth of approximately 40 V, consistent with experimental results.

• Research Organization: Wisconsin Univ., Madison (USA). Dept. of Nuclear Engineering
• DOE Contract Number: AC02-80ER53104
• OSTI ID: 5086161
• Report Number(s): DOE/ER/53104-T4; UWPR-85-4; ON: DE85018047
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TANDEM MIRRORS
ELECTRIC FIELDS
ICR HEATING
MAGNETIC FIELDS
MATHEMATICAL MODELS
PLUGGING
SIMULATION
HEATING
HIGH-FREQUENCY HEATING
MAGNETIC MIRRORS
OPEN PLASMA DEVICES
PLASMA HEATING
THERMONUCLEAR DEVICES
700202* - Fusion Power Plant Technology- Magnet Coils & Fields