future fusor part collection: vacuum gauge

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randy baron
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future fusor part collection: vacuum gauge

Post by randy baron »

hi,
I keep my eye out for parts that would be useful for eventually building a fusor and/or telescope mirror coating vacuum chamber.
I just came across a like-new used vacuum gauge for quite a good price but am not sure it would be appropriate.
Can anyone comment on the utility of a Testo 552?
https://www.testo.com/en-US/testo-552/p/0560-5522

Some specs from the above URL:

Measuring range
0 to 0.39 psi / / 0 to 26.66 mbar /
0 to 20000 micron

Accuracy
±(10 micron + 10 % of mv) (100 to 1000 micron)

Resolution
1 micron (0 to 1000 micron) /
10 micron (1000 to 2000 micron) /
100 micron (2000 to 5000 micron) /
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Richard Hull
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Re: future fusor part collection: vacuum gauge

Post by Richard Hull »

Looks to be no more accurate than a thermocouple gauge, which is used by many of us on our foreline pumps. Seems OK

Richard Hull
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Re: future fusor part collection: vacuum gauge

Post by Paul_Schatzkin »

This is a test.
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television - http://farnovision.com/book.html
"Fusion is not 20 years in the future; it is 50 years in the past and we missed it."
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Re: future fusor part collection: vacuum gauge

Post by John Futter »

hello test
aka Paul
Jerry Biehler
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Re: future fusor part collection: vacuum gauge

Post by Jerry Biehler »

If you plan on doing coating you need an ion gauge of some sort. You really want to be in the -6 range for coating.
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Re: future fusor part collection: vacuum gauge

Post by Paul_Schatzkin »

Hmm... I thought I'd deleted this after it went through.
John Futter wrote: Mon Oct 31, 2022 12:32 am hello test
aka Paul
Thanks John. I posted that last night after discovering that I'd inadvertently filled up the storage on the other side of the server divide between fusor.net and my other websites (I've been setting up some new ones). I wanted to make sure that little oopsie hadn't disturbed anything here, which, apparently, it hasn't. So, yay. The work that The Coalman did to relocate the site, is paying off.

I don't anticipate any problems but if there are any wrinkles rest assured I'm getting out in front of them.

Thanks,

--P
Paul Schatzkin, aka "The Perfesser" – Founder and Host of Fusor.net
Author of The Boy Who Invented Television - http://farnovision.com/book.html
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Dennis P Brown
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Re: future fusor part collection: vacuum gauge

Post by Dennis P Brown »

I've done a lot of metal coating (Al, Cu, Ni and Ge) and even a telescope mirror for myself (also repolished and then recoated a mirror diagonal). Besides needing 10^-6 torr, one needs a high current power supply (welder level) to melt/vaporize the aluminum. Also, a a turbo pump or a diffusion pump (in which case a trap is essential for coating but need not be cooled) besides the ability to measure that vacuum level. But your premise is correct - those vacuum items are needed for a fusor.

Unless you are coating very small mirrors a coating chamber is also essential (height is important to get uniform coatings) and can be a difficult item - read expensive - to obtain, unlike a fusor chamber.

Considering the cost of an aluminizing system, a fusor is far less expensive. Sputtering is far cheaper (no high vacuum) and easier but cannot be used to coat aluminum.
randy baron
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Re: future fusor part collection: vacuum gauge

Post by randy baron »

Thanks a lot for the replies.
Richard Hull wrote: Sun Oct 30, 2022 11:18 am Looks to be no more accurate than a thermocouple gauge, which is used by many of us on our foreline pumps. Seems OK
Richard Hull
If I can get this Testo gauge for $80-90 would it make sense, or should get some other more appropriate gauge that costs the same or less? I do also have a 901P Loadlock.
Jerry Biehler wrote: Mon Oct 31, 2022 4:22 am If you plan on doing coating you need an ion gauge of some sort. You really want to be in the -6 range for coating.
I guess you mean 10^-6 Torr (or mbar...basically the same)?
Dennis P Brown wrote: Tue Nov 01, 2022 7:35 am I've done a lot of metal coating (Al, Cu, Ni and Ge) and even a telescope mirror for myself (also repolished and then recoated a mirror diagonal). Besides needing 10^-6 Torr, one needs a high current power supply (welder level) to melt/vaporize the aluminum. Also, a a turbo pump or a diffusion pump (in which case a trap is essential for coating but need not be cooled) besides the ability to measure that vacuum level. But your premise is correct - those vacuum items are needed for a fusor.

Unless you are coating very small mirrors a coating chamber is also essential (height is important to get uniform coatings) and can be a difficult item - read expensive - to obtain, unlike a fusor chamber.

Considering the cost of an aluminizing system, a fusor is far less expensive. Sputtering is far cheaper (no high vacuum) and easier but cannot be used to coat aluminum.
I do have a rough idea of the parts I still need for mirror coating. This guy, luciano jorge ritchie, does a really nice overview of his simple but functional mirror coating vacuum system:
https://www.youtube.com/watch?v=75AoWl3jhcQ&t

So far I've salvaged a Leybold rotary vane Trivac D8B to do the roughing. I have been keeping my eyes open for an affordable turbo pump.
I don't know about the power supply yet. I do have a stick welder...maybe I can use that? I also have an 8-10A@230V Variac. Not sure that's enough but the wall socket only supplies 10A, so...make do, do without? I also got a 901P Loadlock Vacuum pressure transducer from ebay a while ago (about $40) but haven't figure out how to use it yet. I think it should go well with the D8B pump since the pump's final pressure is should to be 10^-4 Torr and the gauge should read 1000 to 10^-5 Torr. So say their respective manuals at least.

Maybe I should add this next remark as a new post, but, what is your quick opinion on using this 92cm high 68cm inside diameter stainless steel container as a vacuum chamber, perhaps stick-welding 3-4 rings or maybe longitudinal ribs to the outside of the cylinder as anti-implosion insurance? I could get it for around $30. I don't know the wall thickness yet but the seller said something like "pretty thick." I have a (very) small shop and can do basic metal working and other techniques.

...it looks like I can't add an image, so I put it temporarily on an image sharing site:
https://ibb.co/pZzfgx0
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Re: future fusor part collection: vacuum gauge

Post by Jerry Biehler »

Yes, -6 torr but at that point torr or mbar is close enough.

Interesting video and setup. Though I would not use an acrylic dome, it's too brittle. But it's not much of a risk with a diff pump, you won't kill anything if it shatters. Though that dome shattering could cause serious injury.

I actually have considered a welder as a filament power supply. You dont need more than about 3 to 6v but you need a lot of current 50-200 amps for most boats or filaments. You could get on of the cheap Chinese inverter welders and that would probably work pretty well.

That container might actually work. Wall thickness is going to be the concern and how it was constructed. It should be welded on the inside to prevent virtual leaks.

I have a couple systems I am working on for coating. Project log for them here: https://hackaday.io/project/190-vacuum- ... deposition

Just moved so still getting things somewhat organized. I put the roughing pump and roots blower in a shed on the other side of the wall and need to plumb it though as well as get power through still.
randy baron
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Re: future fusor part collection: vacuum gauge

Post by randy baron »

Hadn't heard of 'virtual leaks' but I see what it is now. Maybe I could braze over any seams if they were on the inside and unwelded. Or weld them I suppose. I've never welded stainless but it looks like you mainly need the right stick type.

>Chinese inverter welders
I have a Stanley stick welder that does 5-160A. Maybe that would work? Although it has some anti-stick feature that reduces current when it senses that you got the electrode stuck to the workpiece...that might make it unusable as a filament supply.

>Project log for them here: https://hackaday.io/project/190-vacuum- ... deposition
wow, that looks like a really nice set up.
That one pic shows some device with the label "Dymaxion" on it. Do you know there was a funny 1933 concept car called that https://en.wikipedia.org/wiki/Dymaxion_car?
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Bob Reite
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Re: future fusor part collection: vacuum gauge

Post by Bob Reite »

Welding stainless is best done using a TIG rig with stainless filler rod.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
randy baron
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Re: future fusor part collection: vacuum gauge

Post by randy baron »

I will have to do the TIG welding in my dreams. :) Stick welder only at the moment. And mini oxy-gas welder that I don't know how to use yet.
Anyway, in the meantime, somebody else bought the big stainless container. It's too bad. Based on scouring the classifieds the past 7yrs or so, I probably won't see such a deal again for a long time.
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