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midmoe 21st January 2013 03:12 AM

diamond cathode tubes
to whom it may concern....check out the october 1992 scientific american, page 89. It is the last page of an article by Michael Geis and John C. Agnus, titled "Diamond Film Semiconductors". The article is intresting enough till the last page which states that a diamond film on a metal substrate will naturally emit electrons in a vaccuum ! By this, the implication of building tubes that essentially last forever and can outperform normal tubes is suggested, along with superiority of doped diamond over silicon....of course being a tube man, my intrest is in starting a project to build diamond cathoded tubes, beginng with simple removal of the filament/cathode structures of normal 6L6's and re-inserting a diamond coated copper cylinder....with a low cost vaccuum chamber, and finding someone with access to a research grade diamond film apparatus, the job should be doable. I understand there are places in Russia growing diamonds from methane gas...anyone intrested or has knowledge, please respond. Thanks, midmoe.

Pano 21st January 2013 03:20 AM

Yeah, I remember this stuff from the early 90's. There was talk about micro-tubes too.
Whatever became of it all?

midmoe 22nd January 2013 02:26 PM

yes, seemingly nothing has become of an intresting and potentially lucrative market for "diamond tubes". I'd sure be buying them if they were on the market....a diy'ers dream....imagine the re-tubeing market, the oem market....the energy saved by not having to power up the filaments.....I've been asking these questions since I first read the article in '92.....seems too good to be true to some folks, I guess....I'd sure like to form an exploratory committee to check out patents and other legal aspects, once the underlying physics can be verified...the article states, as I recall, the main work was done at MIT...I will re-read this and attempt to contact the principals involved with the research, to see if follow-up is possible. Any patent lawyers out there who'd like to get involved? Anyone intrested in the project, go to Scientific American, for Oct, 1992. I imagine the article about diamond semiconductors is available online....and then you'll know as much as I do......midmoe

smoking-amp 22nd January 2013 04:00 PM

I suspect that the diamond film emitters mentioned are field emitters (which depend on point defects and HV for emission), but I will have to read the Sci. Am. article.

Back in 2000, another (and much easier to produce) technique was found for making low temperature emitters. (and further improvements have been made since then too.)

From an old post:
"Its possible to build multi-ampere low voltage tubes nowadays. Have a look at these journals: Physics World, October 2000, page 25 to 26 or Physical Review Letters 2000 Vol. 85 page 864.. Two scientists, Vu Thien Binh and Christophe Adessi, have solved the problem of a room temperature thermionic emitter 50 years too late. They use a 50 nm film of Titanium oxide on a nickel plate as a cathode. It has a mere 0.1 electron volt thermal barrier which is satisfied by just room temperature. The technique is robustly stable in the normal vacuum tube environment against adsorbed surface contaminants as well as ion bombardment. (the field emitter techniques, like the nanotubes, diamond film etc, are not) It also has good current emission density."

You can make these early films by using simple electrolysis. Later (higher performing, lower temp.) films require CVD. You will of course need a high vacuum system for making tubes. I am quite familiar with high vacuum equipment if you need any info. Turbomolecular and diffusion pump systems here. Ebay is your hunting ground for vacuum equipment. Still quite expensive stuff though.

Moderation Team 22nd January 2013 04:25 PM

:cop: Trollish and OT post deleted. Let's keep it respectful and on topic.

Wavebourn 22nd January 2013 04:56 PM

I don't think 6L6 deserves diamond cathodes, but some nice planar tube can be definitely made!
Diamond cathode, gold-patted mesh for a grid, and nickel alloy anode with fins.

But such expensive tube mush have the way to replace filament! :-)

midmoe 22nd January 2013 05:18 PM

thank you smoking amp for the tips about the newer technology of using titanium oxide as emmisson stimulant....I will check this out....could someone already be making such devices ? .....midmoe.....

Wavebourn 22nd January 2013 06:14 PM


Originally Posted by midmoe (
thank you smoking amp for the tips about the newer technology of using titanium oxide as emmisson stimulant....I will check this out....could someone already be making such devices ? .....midmoe.....


midmoe 7th February 2013 05:29 PM

any further intrest in diamond cathoded or titanium cathoded room temperature tubes should be submitted to my other thread "medium power OTL circlotron amplifier". I would be very much intrested in persuing a business venture aimed at small scale manufacturing/sales of such items, should it prove feasable. Thank you...midmoe.

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