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Description
A Solid State High Frequency (HF) 1MHz, 40kW source is intended for plasma formation in neutral beam source by inductive coupling of RF power. An important design feature of such a HF source is its ability to sustain large transient swings of load(due to impedance transition in microseconds time scale). A 40kW High Frequency Power Supply( HFPS) has been configured with multiple Class-D H-Bridge inverters modules by using latest generation switching semiconductors; each capable of delivering 3kW Power, magnetic combiners, LC tuning network to provide 1 MHz sinusoidal output at 50 Ω standard Load. The developed prototype power supply has been coupled to a single driver RF ion source test bed ROBIN in IPR to characterize the system with actual load conditions.
In recent experimental campaign, tuning of matching network parameters helped to strike and sustain plasma over the range of 1Pa to 0.42 Pa pressure with forward power of 37kW to 22kW. Additional impedance matching network was implemented to map the power supply impedance(50Ω) with impedance offered from source(>90Ω seen at PS end). Configurable frequency with resolution(~1kHz) helped to achieve Power factor close to unity. Experiments helped to study the behavior of power supply in scenarios of dynamic (plasma) impedance. Auto tunable frequency for matching the varying load is being implemented in the HF power supply.
Summary
This paper describes the topology, design and operational experiences of 40kW Solid State HF power supply with plasma load.
