Beam current regulation of DIII-D neutral beam long pulse ion sources

Conference · Wed Nov 01 04:00:00 EST 1989

DOI:https://doi.org/10.1109/FUSION.1989.102383· OSTI ID:5396171

Hong, R.; Kellman, D.; Santamaria, G.; Colleraine, A.; Kim, J.; Lee, R.; Phillips, J.; Wight, J.

An intrinsic characteristic of the neutral beam long pulse ion source installed on the DIII-D tokamak is the slow increase of arc and beam currents during the beam pulse. This ramping is attributed to the heating of the filaments by energetic electrons backstreaming from the accelerator into the arc chamber. The corresponding change in beam perveance causes the beam optics to vary during a beam pulse, often resulting in an overdense condition. A technique which employs the idea of compensating the filament temperature rise by stepping down the voltage applied to the filaments at beam turn-on has proved to be somewhat effective and successful in regulating the beam current. The disadvantage of this technique is that the amount of filament voltage step-down varies from source to source and is dependent on beam energy. A new technique uses a Langmuir probe signal for feedback regulation in the arc power supply. Plasma density within the arc chamber is maintained at a constant value, as is beam current. This arc regulation method also features arc notching'' at beam turn-on to provide perveance matching during initial beam formation, which is crucial to obtaining smooth initial beam extraction, a high perveance beam, and thus higher power beam operation. The beam power achieved with this arc notching and regulation technique is about 10% higher than that obtained previously with the filament voltage step-down method. 2 refs., 12 figs., 1 tab.

• Research Organization: General Atomics, San Diego, CA (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC03-89ER51114
• OSTI ID: 5396171
• Report Number(s): GA-A-19756; CONF-891007--86; ON: DE90002914
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700205* -- Fusion Power Plant Technology-- Fuel
Heating
& Injection Systems
BEAM CURRENTS
BEAM INJECTION
BEAM OPTICS
CONTROL
CURRENTS
DOUBLET REACTORS
ELECTRIC PROBES
ION SOURCES
LANGMUIR PROBE
NEUTRAL ATOM BEAM INJECTION
PROBES
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS
WAVE FORMS