The impedance of energy efficiency of a coaxial magnetized plasma source used for spheromak formation and sustainment

Conference · Sun Jan 01 04:00:00 EST 1989

DOI:https://doi.org/10.1063/1.859459· OSTI ID:5175365

Barnes, C W; Jarboe, T R; Marklin, G J; Knox, S O; Henins, I

Electrostatic (dc) helicity injection has previously been shown to successfully sustain the magnetic fields of spheromaks and tokamaks. The magnitude of the injected magnetic helicity balances (within experimental error) the flux lost be resistive decay of the toroidal equilibrium. The problem of optimizing this current drive scheme hence involves maximizing the injected helicity (the voltage-connecting-flux product) while minimizing the current (which multiplied by the voltage represents the energy input and also possible damage to the electrodes). The impedance (voltage-to-current ratio) and energy efficiency of a dc helicity injection experiment are studied on the CTX spheromak. Over several years changes were made in the physical geometry of the coaxial magnetized plasmas source as well as changes in the external electrical circuit. The source could be operated over a wide range of external charging voltage (and hence current), applied axial flux, and source gas flow rate. A database of resulting voltage, helicity injection, efficiency, electron density, and rotation has been created. These experimental results are compared to an ideal magnetohydrodynamic theory of magnetic flux flow. The theory is parameterized by the dimensionless Hall parameter, the ratio of electric to mass current. For a constant Hall parameter the theory explains why the voltage depends quadratically on the current at constant flux. The theory also explains the approximately linear dependence of the impedance-to-current ratio on the current-to-flux ratio of the source. 9 refs., 6 figs.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5175365
• Report Number(s): LA-UR-89-3720; CONF-8911130--5; ON: DE90003220
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
CLOSED PLASMA DEVICES
CONFINEMENT
CTX SPHEROMAK
EFFICIENCY
ELECTRIC IMPEDANCE
ELECTRON GUNS
FLOW MODELS
HALL EFFECT
IMPEDANCE
MAGNETIC FIELDS
MATHEMATICAL MODELS
PLASMA CONFINEMENT
SPHEROMAK DEVICES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES