Building a Radio Frequency Plasma Source for DIII-D Neutral Beam Applications

The Miniature Arc Chamber Experiment (MACE) is a tabletop scale device used to emulate the filament driven arc chamber of the ion source of the Neutral Beams system at DIII-D. It was developed to study arcing and component failures of the ion source under normal conditions and particularly for helium operations. Now with a view to enhancing the capabilities of DIII-D, attention has turned to increasing neutral beam power. To achieve greater NBI power a higher density plasma source needs to be developed. To this end, The MACE device has been converted to an RF inductively coupled plasma (ICP) source. Here we present an account of the project to convert the MACE device. The control software was modified using python so that it could interface to the required components. A matching network was built using variable capacitors to match the 50 ohm impedance output of the amplifier. Argon plasma was created and verified through spectroscopy and Langmuir probe data. The purpose of the device is to gain knowledge of RF ICP operation and inform the design of a new ion source for DIII-D.