Restarting Efforts on Demo Fusor II

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Ed Meserve
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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sun Jul 12, 2020 7:29 pm

Thanks for that, Richard.

Based on the pictorial reference, I'd say it's somewhere close to Jon Rosenstiel's "Very Slight Improvement" slide at around 600 mTorr, maybe slightly more diffuse (tough to see with the old webcam).

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2020-06-12 Run: Grid Only Image
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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sat Jul 18, 2020 12:32 pm

Hi all,

I have a question regarding connection for my diffusion pump exhaust. It appears when it was removed from its previous system connection, it was cut off, without a standard connection flange.

How would you suggest I make the connection?

diffusion pump.jpg
Diffusion Pump w/ Valve assembly
diffusion pump exhaust port.jpg
Close-Up of Exhaust port
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Rich Feldman
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Re: Restarting Efforts on Demo Fusor II

Post by Rich Feldman » Sat Jul 18, 2020 1:10 pm

Rubber hose and hose clamp? It's not a high vacuum or even medium vacuum connection.
That might be how it was used before, if there are no signs of a field cut.
For easier disconnection, you could glue on a small KF flange or other fitting.

What's the OD? I have some rubber vacuum hose and spiral-reinforced clear plastic hose that needs to be got rid of.
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Re: Restarting Efforts on Demo Fusor II

Post by Richard Hull » Sat Jul 18, 2020 1:14 pm

I doubt it was cut off unless it was welded. This is actually a very common connection on older diff pumps. It is for a common hose and clamp which will serve very well at mechanical pump vacuum levels. Make sure the hose can take a little heat without out gassing too much. Even so, any out-gassing would be short lived and not generally back stream against the more powerful mechanical pump which would remove it until stabilized. Needless to say, keep the hose very short. ( Place diff pump very close to mechanical pump )

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Ed Meserve
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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sat Jul 18, 2020 2:14 pm

Thanks guys.

The OD is 3/4'. Rich, if you have a length of rubber vacuum hose of that size, I'd be interested in buying some off you. If so, DM me.

Thanks!

Ed
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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sat Sep 12, 2020 9:59 pm

Considering the effort it would take to grind down the surface of the re-purposed MKS valve / Chamber to get a flat surface without the keys, I've decided to abandon it and purchased a 6" conflat tee to use as a chamber.

The three ports will be used as follows:
-On the right will the 6" CF blank for the HV feedthrough,
-Opposite the blank will be the vacuum line; I have a 6" to 2.75" conflat adapter and a 2.75" conflat to NW25.
-The 4.5" CF viewport with a 6" to 4.5" CF adapter will be 90 Degrees to the vacuum line and HV Feedthrough.

I now have most of what I will need to make the switch, only need to purchase copper gaskets, and drill and tap the 6" blank for the new feedthrough.

New Chamber Components.JPG
New Chamber Components
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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sat Sep 12, 2020 10:29 pm

While waiting for chamber components, I've been dusting off the power supply we began building when I was still in the college fusor group. This new power supply is based on Chris Bradley's design he used for one of his projects: viewtopic.php?f=11&t=4887

The timing was right for us; we were ready to build the power supply just as Chris was originally posting about it. We purchased 20-30 of the little high frequency inverters and began building the power supply, but never completed it.
Unfinished PS.JPG
Unfinished Power Supply
I've decided to put a small spin on Chris' original design; Chris mentioned in a previous post that this topology allowed some variability in voltage through individually powering each stage. My small variation is to power one stage with a variable DC source to allow a finer tune for voltage level.

I purchased a small, panel mount 5A adjustable power supply from Amazon.
5A Adjustable PS.jpg
5A Adjustable Power Supply
And setup a simple Greinacher circuit ( which will be used as stages for the new power supply) to test with.
Greinacher Circuit.jpg
Greinacher Circuit
I choose to use one of the inverters I removed the can instead of one with a screw shorting the internal capacitor and soldered directly to it.
Inverter Closeup.JPG
Inverter Closeup
Single Rectified Inverter Test.JPG
Single Rectified Inverter Test
Testing DC supply.JPG
Testing DC Supply
PS Readout.JPG
PS Readout
Measured Voltage.JPG
Measured Voltage (x 1000)

The result was nice granular control from about 150VDC out to around 3kV.

I will setup and test 2 stages to verify the fine control before completing the full power supply.
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Re: Restarting Efforts on Demo Fusor II

Post by Rich Feldman » Sun Sep 13, 2020 7:03 pm

Very cool, Ed.

Back to vacuum gear and foreline connections, I finally dug out the vacuum hoses here.
The ID of spiral-reinforced hose is 1/2 inch, and of thick rubber hose is a little less than 3/8 inch.
Too small for the need you mentioned, but they are free to anyone who wants to pay the postage.

Maybe you can do the job with clear vinyl hose, garden hose, or some kind of corrugated plastic from a hardware store. Or auto parts store, with optional stainless steel braid for hot rod engine look. Must be stiff enough not to collapse when evacuated, even at the hot end next to diffusion pump. Permeation by air is only a problem if it flows enough to make the backing pressure too high.
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Re: Restarting Efforts on Demo Fusor II

Post by John Futter » Sun Sep 13, 2020 7:08 pm

Most farm dairy supply stores carry milking rubber. This is what connects the milking claw to the main vacuum pump and pulsator.
Common sizes are half three quarter and one inch bore sizes --sold by the yard and very suitable for backing lines

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Re: Restarting Efforts on Demo Fusor II

Post by Ed Meserve » Sun Sep 13, 2020 7:21 pm

Thanks Rich.

A little bit of Google-fu turned up this spiral reinforced vacuum hose from Process Hose & Equipment:

https://processhose.com/3-4-in-i-d-kuri ... -foot.html
Vacuum Hose.jpg
Vacuum Hose
Do you think this would suffice for the foreline?

Ed
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