Liam David Fusor Update

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Liam David
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Real name: Liam David
Location: Arizona

Re: Liam David Fusor Update

Post by Liam David » Sat Jun 06, 2015 1:31 am

It's been a while since I last posted. I have bought a 6 way 2.75" conflat cross to serve as a new main chamber. It will get here next week. Also, when I'm roughing the chamber out, the pressure drops to ~55 mtorr (still leaks) and then starts to slowly rise to 56 and then 57 as the pump starts to warm up. I disassembled and cleaned the pump, including one of the rotary vane stages, and got the chamber down to 55 mtorr, a 20mtorr improvement from before the cleaning. The rise in pressure still happens. Any idea what could be causing this?

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Richard Hull
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Re: Liam David Fusor Update

Post by Richard Hull » Sun Jun 07, 2015 7:22 am

What can the pump do at the head? Put a gauge directly at the pump inlet.

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.

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Liam David
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Location: Arizona

Re: Liam David Fusor Update

Post by Liam David » Thu Jun 11, 2015 1:15 am

At the moment, I am unable to deadhead the gauge. I got my new chamber in the mail today- it's a 6 way 2.75" conflat cross. Here is it assembled with used copper gaskets just for reference.
Image

Image

On a separate note, my school is building a 1MeV cyclotron starting next year. The project will be guided by Tim Koeth from UMD, and I had the pleasure of talking to him briefly after the school interest meeting for the cyclotron was over. Hopefully I will be fully involved in the project over the next few years- I am probably one of the more vacuum and high voltage knowledgeable students at my school currently (though I'm mostly still a newb), and I am sure that my "experience" building a fusor will help earn me a spot on the team.
-Liam

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Nick Peskosky
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Re: Liam David Fusor Update

Post by Nick Peskosky » Thu Jun 11, 2015 4:03 am

Just a quick note: I see that you're using some type of NPT threaded elbow adapter to connect the VCR flange on the 275 Mini, you did use a metal gasket seal between the VCR flange and the VCR->NPT coupling? These connections require silver plated SS crush discs which must be seated (and ideally centered) between the Male/Female VCR connections. I had a minor leak on my gas line which was affecting my ultimate pressure with the turbo on and the fix was as simple as utilizing vice grips and a wrench to tighten each VCR connection. Try placing ~90% isopropyl alcohol (denatured) or acetone on the flange seams and if you see the pressure climb even further than you've found your leak.

Just some food for thought.
Nick Peskosky
NPeskosky@gmail.com

"The whole of science is nothing more than the refinement of everyday thinking." - Albert Einstein

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Liam David
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Re: Liam David Fusor Update

Post by Liam David » Thu Jun 11, 2015 10:41 am

Yeah, it's not the right fitting. I used it earlier by brazing a washer to the end to act as a rudimentary seal surface along with a cast solder gasket. It undoubtedly leaked and I'm replacing it with a VCR to KF adapter soon. It's just in the picture for "show". Do I need silver plated SS gaskets or can I use copper?

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Richard Hull
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Re: Liam David Fusor Update

Post by Richard Hull » Fri Jun 12, 2015 12:02 am

It think the gaskets are typically AG plated copper. The VCR fitting is a close relative of the old, much larger, Curvovac fittings that tried to work around the old conflat patents. I have some old 2.75 curvovac stuff hanging around the lab. In many ways, to my mind, it seemed like it would be better than conflats, but is just not seen now.

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.

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Liam David
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Location: Arizona

Re: Liam David Fusor Update

Post by Liam David » Fri Jun 12, 2015 12:09 am

Hmm. I guess LDS vacuum sells only plain VCR copper gaskets, which I assume will work fine.

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Richard Hull
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Re: Liam David Fusor Update

Post by Richard Hull » Fri Jun 12, 2015 12:21 am

Sure, they will do just fine. Just make sure to really tighten the fitting down good and firm. They make centering rings for those gaskets.

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.

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Liam David
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Location: Arizona

Re: Liam David Fusor Update

Post by Liam David » Wed Oct 21, 2015 11:13 pm

It's been a while since I last shared my progress. I finally found a turbo pump! It's a Pfeiffer TPU 040 pump with TCP 040 controller, which was described as not working. Opening it up revealed a loose relay, and a quick atmosphere test confirmed that it was the problem. I now have a fully functional turbo system, and it only cost $150. All things considered, I made out like a bandit. Once a KF-40 to KF-16 adapter gets here, I'll test the pump on the chamber.
I'll post progress on my HV transformer soon.

-Liam David

Image

Image

Image

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Liam David
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Real name: Liam David
Location: Arizona

Re: Liam David Fusor Update

Post by Liam David » Fri Oct 23, 2015 4:06 pm

Anyone know if I can run the TPU-040 pump horizontally, or will it destroy the pump? I have been unsuccessful in finding a manual.

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