Amateur polywell?

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emanroga
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Amateur polywell?

Post by emanroga » Fri Nov 07, 2008 7:24 am

Hi everyone. I've been a lurker here for a while - I probably visited after discovering UW's program back early in the decade, but got really into fusors after watching Dr. Bussard's talk (several times). I'm just finishing grad school and my life is starting to settle to the point where I'd like to get hands on and start tinkering with my own in the next year or so.

I've seen a lot of fusors being built on this forum, but mainly with grids. Have any of the amateurs attempted a polywell? This piques my curiosity, and is a bit different.

My bachelor's is in EE, although I never really used it for anything but hobbies. My masters will be Aerospace. My hobbies go more towards wooden crafts, but I have a basic machine shop at my work that I can use on weekends and I have a good amount of experience on drill presses, saws, and oxyacetylene torches. In other words, I know there are plenty of gaps in my experience, but I think I can do this.

I have a basic conceptual design worked out - to keep it simple, I've decided to go with the continuous pipe approach that EMC2 used in the MG machine. My goal for this version is plasma, I don't expect fusion.

I'll probably make the first magrid from stainless, to allow me to run it on easier-to-find power supplies, and so that it will take a heating and a beating from what will no doubt be lots of bending, power surges, and good ol' fashin rasslin' into place. I won't cool it at first, but it will be possible with this setup to cool it with water. Not sure where to go for a good low voltage PS, but I've seen a few threads on that in these forums and we've got a good surplus store in town, so I'll start there.

I'm thinking I'll just do a Lexan dome for the vacuum chamber, and use a resin injection pump, which should be able to get it well under 1 mbar.

The area that I have no idea about is the electron source. Can I use the gun from a CRT or is this a bad place to start? Remember I'm just looking to make a fuzzy glowing ball at this point - the hope being I'll learn enough about everything to make fusion next time.

My questions -

I'm sure there's at least one "is he crazy?" statement in there. So please feel free to point it out with colorful language.

I'm at a point right now where I think the next move is to build something, but I want to avoid wasting money as much as possible (see above re: grad student). I get enough calculating at work and school, and I'd like to make this as empirical as possible - but what can I absolutely not get away with fudging here? Meaning, what kinds of things have cost people months and hundreds to thousands of dollars on a forehead-slapper after they finally did calculate something and realized it would never work?

I did a search and didn't find anything - has any of you attempted a polywell design before? I see mostly double-screen designs in this forum.

Thanks everyone!

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Re: Amateur polywell?

Post by Nanos » Fri Nov 07, 2008 7:36 am

I'd like to have a go myself after I get a fusor working.(My particular interest is in permanent magnets and whether they can play a useful role or not.) I don't know if your aware, but you might find this forum particularly useful in that direction:

http://www.talk-polywell.org/bb/index.php


Progess for me is slow due to lack of time and funds, but I have noticed so far that the more money you have, the less time you need

Having plenty of space to build is a good thing, and as many friends with skills to help wouldn't go amiss either.

And spending litterly months reading all the previous forum posts and making notes will help a lot more than you might think.

Ebay can be a useful source for parts.

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Chris Bradley
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Re: Amateur polywell?

Post by Chris Bradley » Fri Nov 07, 2008 10:02 am

What is your motivation for doing a 'demo' Polywell? The issue is that you WILL get a plasma if you zap a big enough ion/electron gun into just about any micron-evacuated device, whether or not you've scattered magnets around inside it, randomly or otherwise. So you will need to identify your 'end-point', that is, how will you know if your experiment is 'Polywell-ing' and confining electrons?

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Re: Amateur polywell?

Post by Hector » Fri Nov 07, 2008 5:12 pm

Dude, what kind of question is that? The guy wants to do it because it's COOL, yeah....!!

Because it gives him bragging rights. Who knows, who cares, just let people do what they do in their time with their money. At least it's better than making a model plastic airplane.

My friends at the University of Illinois IEC program used to ask the same question about the Fusor forum people, they thought our time would be better spend making liquid rocket engines and I told them the same thing I'm telling all of you, we do it because it's COOL and Fun.

No other reason needed, but feel free to add your own.


Peace.

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Chris Bradley
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Re: Amateur polywell?

Post by Chris Bradley » Fri Nov 07, 2008 5:56 pm

...because I'd like to see him have bragging rights over something more than just a bright light if he's going to put that much effort into something. Just a bit of experimental and instrumentation planning on day one may help, with a little bit of upfront discussion!

I could get a plasma-ball-toy from the shop and put a half-dozen magnets around it to make it look like a Polywell. That hardly means I've done anything of merit towards an amateur Polywell, does it? I understand the point of posting here *prior* to a proposed experiment is to encourage some dialogue to progress the idea. If there is no discussion wanted, then just do the experiment and *then* post with results!

Bragging rights come with posting results. But bragging rights aren't like 'futures', you can't claim them now then cash them in later. Speculative forward-bragging doesn't get much respect here, but it may generate a 'healthy' discussion!

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Re: Amateur polywell?

Post by Hector » Fri Nov 07, 2008 6:35 pm

Hey I'm all for that, just don't bring the guy down, that was my point.

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Chris Bradley
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Re: Amateur polywell?

Post by Chris Bradley » Fri Nov 07, 2008 6:54 pm

Sorry. I seem to be coming across in 'hardball' mode these days.

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Re: Amateur polywell?

Post by Hector » Fri Nov 07, 2008 7:03 pm

It's cool. It happens to all of us.

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Carl Willis
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Re: Amateur polywell?

Post by Carl Willis » Fri Nov 07, 2008 7:13 pm

Welcome.

No, there are no amateur Polywell builders to date.

I suspect this has a lot to do with the fact that the Polywell concept remains, for all practical purposes, unproven for doing measurable and significant fusion. In the hobby world where personal money is dear, time is more valuable, and we're often a little insecure in our own levels of competence with fabrication techniques or theoretical preparation, it's not surprising that most of us gravitate toward relatively safe and incremental improvements on well-established technology--namely, the Hirsch-type gridded fusors you see everyone building around here. They're simple, and they do fusion with a degree of reliability that is appealing. Even if one of us were to build a Polywell device, chances are we would approach it only after cutting our teeth for a long while on simple fusors.

From what you wrote about your intended approach to the project, I can foresee some sticking points. The devil is really in the details.

>I'll probably make the first magrid from stainless, to allow me to run it on easier-to-find power supplies

I don't understand what this means. Will stainless steel be used to carry any current? These magnets need to be strong (lots of amp-turns)! They will generate an awful lot of heat if made out of copper, and stainless steel is just flat-out off the table as regards being part of the magnet winding. By the way, if this Polywell is destined for continuous operation, it absolutely must be cooled by forced convection of a liquid. As you probably know, vacuum is a superlative thermal insulator. Even a few watts will cause temperatures to go through the roof unless coolant is actually brought into and out of the part. EMC2's machines have all been pulsed, I'd guess in no small part because of the magnet cooling problem. Not only do you need forced cooling, but the coolant must traverse the electric gradient in the machine (the magrid would be at high voltage) and the coolant plumbing must traverse vacuum also. That's a headache even to professionals.

You also mention a vacuum system that is likely to be inadequate for this project (Lexan chamber, 1 mbar from a resin pump). Trapped electrons won't last very long, and plasma around them at low vacuum will shield out the potential well that is supposed to form and confine ions. You'll get a glow all right, but it would just be a normal glow (Paschen breakdown) or arc. You need to plan on a hardcore vacuum system here.

-Carl
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Richard Hull
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Re: Amateur polywell?

Post by Richard Hull » Fri Nov 07, 2008 8:15 pm

Carl said it all, pretty much, and at a level the aspiring amateur can understand.

You asked about the electron gun. As Carl noted you will need a class one high vac system if you plan on using an electron gun of the normal vintage where electrons is all you want. Higher pressures will not allow the gun to perform as advertised. Instead, you will get electrons and ions floating about in the glow and a minute life span on the e-gun filament.

Richrad 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.

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