Discharge initiation experiments in the Tokapole II tokamak

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5726922

Shepard, D A

Experiments in the Tokapole II tokamak demonstrate the benefits of high density (n/sub e//n/sub o/ greater than or equal to 0.01) preionization by reducing four quantities at startup: necessary toroidal loop voltage (V/sub 1/) (50%), volt-second consumption (40-50%), impurity radiation (25-50%), and runaway electron production (approx. 80-100%). A zero-dimensional code models the loop voltage reduction dependence on preionization density and predicts a similar result for reactor scale devices. The code shows low initial resistivity and a high resistivity time derivative contribute to loop voltage reduction. Microwaves at the electron cyclotron resonance (ECR) frequency and plasma gun injection produce high density preionization, which reduces the initial V/sub 1/, volt-second consumption, and runaways. The ECR preionization also reduces impurity radiation by shortening the time from voltage application to current channel formation. This, evidently, reduces the total plasma-wall interaction at startup. The power balance of the ECR plasma in a toroidal-field-only case was studied using Langmuir probes and impurity doping. The vertical electric field and current, which result from curvature drift, were measured as approx. 10 V/cm and 50 amps, respectively, and exceeded expected values for the bulk electron temperature (approx. 10 eV).

• Research Organization: Wisconsin Univ., Madison (USA)
• OSTI ID: 5726922
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
BEAM INJECTION
CLOSED PLASMA DEVICES
ECR HEATING
ELECTRIC DISCHARGES
ENERGY BALANCE
HEATING
HIGH-FREQUENCY HEATING
INTERNAL RING DEVICES
IONIZATION
PLASMA HEATING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TOKAPOLE DEVICES