Current State and Item Lists - Any advice?

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Jack Puntawong
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Re: Current State and Item Lists - Any advice?

Post by Jack Puntawong » Tue Jan 29, 2013 5:05 pm

Another advice is to start small with a feedthrough. I wouldn't buy anything bigger than 4.5" feedthrough. 2.75" feedthrough is the norm for most guys here. The price range of a 2.75" 30kv is anywhere between $130-200. For 4.5" CF 45 kV, the price is between $350- 500. Just a reminder, don't forget to ground you chamber and pump. I think you've got one of the biggest chamber around here and there's lots of room for upgrades.

felyza
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Re: Current State and Item Lists - Any advice?

Post by felyza » Tue Jan 29, 2013 7:41 pm

What I'm hoping to achieve, if my friend at a metal shop doesn't kill the blank in the process, is convert one of the 8" blanks to a 4.5" reducer, then take the 4.5" and make a feedthrough of copper core with quartz insulation. I really want to try for both high-end amateur fusion as well as low-end, and I'm hoping this chamber will do 'normal voltages' and leave room to grow.

Dave Coultier's videos show a much, much larger chamber. I know he also works a bit with the high end of things, as he's who warned me about streamers that don't make sense at very high voltages.

If I can make it myself, I'm looking at $50 in parts + cost of torch. If I have to buy one, I will not be getting a secondary pump and gauge... basically what it boils down to.

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Carl Willis
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Re: Current State and Item Lists - Any advice?

Post by Carl Willis » Tue Jan 29, 2013 9:01 pm

The fellow you're talking about is named Doug Coulter.

His feedthrough is a complicated variation on a simple theme that has been tried and used successfully before. You could start out with the simple version (a single alumina or glass tube held in compression fittings) and see how far it takes you, and THEN, if necessary, worry about making ring seals in quartz. Doug's intention with those ring seals is evidently to build up a thicker wall out of material that is sold in a limited range of standard wall thicknesses. I understand the motivation to do that, but I do wonder how much of an breakdown upgrade it really achieves with the resulting air gap figured in. Could you do the same thing with a single thickness of alumina or Pyrex or Teflon and avoid the hassle of ring-sealing quartz? Personally, I'd be willing to bet that you could. In any case, the compression fittings wouldn't have to be changed and probably neither would the center conductor.

Quartz is a nuisance and you will spend a lot more than $50 to set up for it. You need special eyewear beyond didymium glassblowing eyewear to protect your eyes from UV. You need stainless torch fittings (okay, I've seen people use brass or even regular copper brazing tips, but they won't last long and stand to contaminate your work with metal). You need industrial gases to run the torch. The quartz must be cleaned (sulfuric acid + hydrogen peroxide, followed by dilute HF and then DI water) or you will have nasty devitrification. You cannot touch it or your fingerprints will be permanently burned into the quartz surface as white devit patterns (I can show you photos of my fingerprints on quartz tubing). Similarly, all the graphite tools commonly found on a glass workbench are no-nos, because carbon reduces silica and nucleates devitrification. Finally, those ring seals require some technique. They have to retain the right diameter to fit through the compression fitting and the tubes have to be registered coaxially. You might get lucky and turn out some good seals right away. Or, more likely, you will go through quite a few hours and lots of supplies to get your fixturing and technique in the bag. You'd be embarking on a tangential adventure. Nothing wrong with adventures...unless you're getting into it thinking it's cheap and easy.

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JakeJHecla
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Re: Current State and Item Lists - Any advice?

Post by JakeJHecla » Wed Jan 30, 2013 1:47 am

If you're looking for a cheap way to make a tubing feedthrough, take a look at this one I built a few weeks back. It's cheap, easy and it has survived quite well so far. In lieu of quartz, I am using borosillicate glass, and I have yet to see any major issues. While I have next to no experience in HV electronics besides what the fusor has afforded me, experimental evidence suggests the feedthrough will do well until sputtering kills it. Mr. Willis, Mr. Hull or other sage experimenters may have some suggestions on how to improve it, or whether the design is sound (which I would take a look at before replicating my efforts)

download_thread.php?site=fusor&bn=fusor ... 1357713788

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Richard Hull
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Re: Current State and Item Lists - Any advice?

Post by Richard Hull » Wed Jan 30, 2013 2:49 pm

Jake appears to have solved his problems related to a feed-thru insulator.

As part of any construction of a feed-thru, it is very important to put your feed-thru on a stock conflat of some sort. Most use the 2.75-inch conflat, but larger insulator situations may demand a larger conflat.

Regardless of your brilliant attempts at a feed-thru, what ever they may be, as voltages climb and first stabs fail, any redo will not involve a major rework of the chamber, but only a rather inexpensive, new conflat blank to accept you latest brilliant solution. Custom fitting and sealing your first pass brilliance to your chamber, directly, using a kludged fitting on the chamber will usually end in tears and a costly and tedious re-work on the second pass.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

felyza
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Re: Current State and Item Lists - Any advice?

Post by felyza » Wed Jan 30, 2013 9:10 pm

Yeah, no matter what I do for the feedthrough (looking over Hecla's material now), it is going on a flange. I have a spare 8" and a spare 6", and an industrial drill press... so should be something I can accomplish. I do agree it would be a LOT cheaper to replace a copper gasket to change the feedthrough than to retool a chamber wall.

The closest I'm going to get to heavy modifications to parts is building the feedthrough itself, and building the deuterium supply itself. The chamber will only see any modifications if, once I have everything here to hook up the vacuum pump, I find leaks. Then, I'm going to correct leaks using the least invasive means I can (will depend on what leaks where).

Really want to reuse everything in future experiments once I get past proof-on-concept and into real science. Really really hoping to tangent off into two realms, ultra low power fusion (looking at things, it should be doable < 10kV, though you won't be breaking any neutron records) and very high power fusion (still want to see what happens >100KV).

Before a naysayer says 10kV fusion is impossible, yes, with my current proof-of-concept setup it will be, for the most part. For a second or third generation, I'm wanting to try and achieve fusion in a 1.33" cube. Someone else has ~12kV working in a 2.75" chamber. Scientific experimentation will come after I achieve viable neutron production.

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