A grid design idea

For Farnsworth type designs.

Re: A grid design idea

Postby William A Washburn » Wed Jan 19, 2011 1:10 pm

Congrats Doug on the finer definition you observed and sorry about the leak. I''m sure if the beam is better defined the
graphite must have done something for your system. Is this the first diamagnetic material you have used for a grid?
I understand the H effects between para and dia are small but is this a possible reason for your success?
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Re: A grid design idea

Postby Doug Coulter » Wed Jan 19, 2011 1:29 pm

I believe it's merely that it's more accurate than any other I've put in there, simple as that -- the trend is fairly well established on that one. As to the effect of the ceramic, unknown at the moment, and the obvious thing to do is try it both ways -- the design makes that easy (not by accident). The smaller overall size of this new one may be contributing something...but having not noticed huge differences with minor size changes so far, I doubt it's a big deal. I should make a couple more in different sizes to try as well, I suppose -- now that I have a good degreeing setup for the machine so I won't mess them up anymore - the raw material isn't real cheap here. Next time I order ceramics, I suppose I should try and find some that have larger ID so I can make composite ones the same size as the plain graphite ones. Lots more to do, and yeah, leaks are a pain, at least I have a way to find them quick. I'd never have guessed that last one -- it's been trouble free and therefore untouched for a long time, this is an unusual event. I may take the opportunity to rethink how I mount that on the tank, and alter where I let the gas in anyway, but it's just at a bad time to do a major tear-down and refit...For the moment, it's just going to be band-aids till the next bunch of demos I have scheduled is done with. I don't want to risk people showing up and me not have something that works!

Right now, the ions from that source have to travel about 2+ inches to get inside the main tank, down a skinny pipe, as I have tubing coupler on a 1.33" flange, which is bolted into another 8" flange. Getting the glow closer in should be a pretty big deal....I might contrive some way to get a good bit closer, and improve my ion extractor on the next go around.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: A grid design idea

Postby William A Washburn » Wed Jan 19, 2011 9:45 pm

Speaking of leak repair have you ever used Apeizon hard stick wax? I used this on my all glass vacuum system 40 years back
to make pyrex/metal vacuum feed throughs. I had the torches but not the correct metals and know-how. The wax is hard but not brittle.
It also has a vapor pressure of 10e-9 and never leaked (much, as far as I know). Had no idea how expensive it must have been until
looking at this site:

http://www.strongholdwax.com/Qstore/p000055.htm
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Re: A grid design idea

Postby Doug Coulter » Wed Jan 19, 2011 10:06 pm

Yes, I bought a pound of "W" early on, and sometimes give it out to my pals (minimum purchase size is now over $100 at the vendors and is a more than lifetime supply). It won't work here though, it gets pretty hot there and it would melt -- if I could even get it in there at all. Sadly, my glyptal congealed, so I'm going to have to get more of that -- it works pretty good in heat and even thermo-sets. But gluing a removable fitting probably isn't the way I want to go here -- I'll just tear it apart, find the problem, and fix it. It will take all day, and make me crack the system again, but...last time it lasted over a year. I need to get in there anyway to replace or remove the end ceramic on that grid, which has a flaw that prevents me from getting to voltage with the new grid anyway. Sigh. Hopefully the system will work OK with the big metal screen not in place -- it's a two man job to replace that once removed (at least).

I'm even thinking of blanking that flange and just getting another tubing coupler and welding it straight into a tank wall -- helps with the long distance issue, or coming up with another quartz/tank seal design that has even less depth. That was the motivation for trying to design and build another version of the source, which I failed to build -- brazing thin SS to thick brass didn't work out with a no Cd type of silver solder and a torch. I might pull it off in a furnace where temp control is better.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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