Inductively Coupled (RF Heated) Plasma Extraction

A simple Inductively Coupled Ion Source can be made by using a negative bias on an extractor cone or electrode to attract the positive ions and can later be focused into a beam with magnets. Such a source is suitable at high powers as a Deuteron source for an IEC fusor or for processes such as ion beam deposition or directional plasma cleaning. As seen in Patent #4,793,961, these architectures have been proven for exceptional use as hydrogen or deuterium ion sources.

The ICP coil is placed on a quartz tube mounted via a Kovar KF40 flange to the vacuum chamber and an antenna tuner (matching network) is used to couple the RF energy from 10 meter Ham radio transmitter to the coil. A Multi-cusp Magnetic assembly could be used as shown below to keep energetic electrons from being lost into the ion source walls, confine their motion, and reduce the occurrence of electron-ion recombination.


(Click on image to enlarge)

A high (low) negative voltage (usually between -400v and -2kv) is used on the extractor electrode. If this design was implemented in an IEC fusor, the extractor could be grounded because the fusor grid is held at a negative potential.

Fluorescence was observed in the quartz tube during these experiments due to electron bombardment. While the chamber was pumped down and MFCs setup, a DC copper sputtering environment was created for testing purposes as well as a controlled and isolated anode glow region of an incomplete glow discharge which forms a spherical region above the copper plate (anode) and could be used for uniform plasma cleaning.

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