Usable Chamber?

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Miles Hawley
Posts: 14
Joined: Sun May 13, 2018 7:32 pm
Real name: Miles Hawley

Usable Chamber?

Post by Miles Hawley » Tue May 15, 2018 5:52 am

Hello, after searching around for what type of vacuum chamber to use I finally decided to go with a pre-made one. I was originally planning to use 2 304 SS 6" diameter, .120" thick hemispheres, that would be welded together. However I was wondering if these would be easier to work with: https://www.ebay.com/itm/MDC-Stainless- ... SwIzBazVzy or https://www.ebay.com/itm/2-3-4-OD-UHV-C ... SwCGVX7tSE or https://www.ebay.com/i/273173224305?chn=ps

This is for real fusion, so I need a pressure line, gas line (Deuterium) , high voltage line, viewing line, and a vacuum line. Would these chambers be able to work with real fusion. Any suggestions are welcomed.

-Miles

Michael Bretti
Posts: 115
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

Re: Usable Chamber?

Post by Michael Bretti » Tue May 15, 2018 3:12 pm

Miles,

Yes, the 2.75" conflat 5-way and 4-way crosses will work. There are several members on here who have produced a working neutron-producing fusor with 2.75" conflat crosses. I myself am also working on a system based on this hardware, for both beam on target and pulsed fusor systems. My goal is to develop a highly engineered and modular solution with very tight experimental control at a professional research level, but still using resources and constraints present to the general hobbyist. I actually purchased my 5-way cross for the main chamber from the second link you listed on ebay from surplusvacuum. The cross was in flawless condition when it arrived.

If you want to see the type of system I am designing with this type of hardware, as an example utilizing this size chamber, you can see all of the calculations, cad modeling, design choices, and specifications here:

http://appliedionsystems.com/portfolio/ ... v4-design/

For a detailed design walkthrough going over the engineering design choices, you can find the table of contents here:

http://appliedionsystems.com/high-vacuu ... roduction/

Also the full discussion on the design is posted here on the forums:

viewtopic.php?f=10&t=12114

There are obviously benefits and trade-offs associated between the design and running a fusor between a very large chamber and a small chamber. It depends also on your objectives, constraints, and system planning to account for the variables and challenges you will encounter. Both a four way and five way cross provides enough inputs for pumping, viewing, gas injection, and high voltage. I would strongly recommend going through the above resources, as well as other resources on this site, and doing as thorough research and as much planning as possible.

Miles Hawley
Posts: 14
Joined: Sun May 13, 2018 7:32 pm
Real name: Miles Hawley

Re: Usable Chamber?

Post by Miles Hawley » Tue May 15, 2018 5:08 pm

Thank you for replying so fast. I appreciate the information. I'll be ordering from the same link soon.

prestonbarrows
Posts: 201
Joined: Sun Jun 24, 2012 5:27 am
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Re: Usable Chamber?

Post by prestonbarrows » Sat May 19, 2018 5:27 am

In general, Conflat flanges are the way to go for vacuum cleanliness and repeatability.

A 2.75" conflat cross is just about the minimum practical size. The physical distance between your grid and feedthru stalk (at HV) and the chamber wall (at ground) will set a nominal electric field (volts per distance). This electric field when the internal grid is held at fusion relavent potentials (>10's kV) needs to be on the correct side of the Paschen curve for fusion relavent pressures (`10's mTorr). On the wrong side of this curve, you will just make an expensive 'neon' light bulb with little fusion.

A larger distance between your grid and chamber means you can crank up the grid potential (needed for fusion) while maintaining a low e-field WRT ground (needed to prevent glow discharge).

So, in general, a larger chamber will be more forgiving to getting the settings dialed in. A 2.75" CF can be made to work, but getting the largest chamber you can will make things easier to control. The problem is cost scales quickly with diameter.

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