Chamber wall rainbows

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Dan Knapp
Posts: 402
Joined: Wed Aug 06, 2008 8:34 am
Real name: Dan Knapp

Re: Chamber wall rainbows

Post by Dan Knapp »

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.
Attachments
electron induced contamination2.pdf
electron induced contamination paper
(1.85 MiB) Downloaded 308 times
photo of Penning trap anode contamination.
photo of Penning trap anode contamination.
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