In an effort to understand why I am seeing contamination of the anode (left in attached photo) but not the cathodes (right) in a Penning trap, I turned up a very old paper that explains these deposits as carbon formed by electron bombardment of organic surface contaminants (e.g. pump oil vapor). This is a likely source of the "chamber wall rainbows" in fusors.
Insulating contaminant layers create problems in ion optical systems when the surfaces charge up. An old preventive was to coat electrode surfaces with colloidal graphite (Aquadag). If these electron induced contaminant layers are elemental carbon and therefore conductive, it may be that they aren't problematic in regard to surface charging and might even be helpful.
Chamber wall rainbows
Re: Chamber wall rainbows
- Attachments
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- electron induced contamination2.pdf
- electron induced contamination paper
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