New Generation of Arc and Arc Filament Power Supplies for Pulsed Neutral Beams

摘要

The new Tandem Mirror Experiment (TMX) facility at LLL requires that neutral beams operate for pulse lengths between 25 and 100 ms. The inevitable increase in cost over the present 12-ms pulse length capability dictated that a more economical alternative to the pulse forming networks and the transformer-type arc filament power supplies currently in use be found. A study of the various alternatives and design requirements revealed that battery banks are the most economical alternative. The thermionic arc filaments have relatively simple power-supply requirements in terms of control and regulation. The battery arc filament power supply controls and electromechanical hardware heat the filaments to provide the electrons which produce the plasma. Component testing revealed problems that must be addressed in the finished production design. The battery arc power supply poses a difficult set of requirements for current control. The TMX requires current control accuracy of +-1.0 percent and rise/fall times of 50 mu s. These requirements are met with a novel thyristor switching circuit. The features of the four-section battery bank design, capable of a total of 4000 A at 58 V dc, are detailed. Control hardware compatible with the current generation of pulse-forming network hardware has been developed. The cost effectiveness of the battery power supplies also is discussed. (ERA citation 03:020705)