Bell and whistles diffusion pump based vacuum system.

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Richard Hull
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull » Sun Dec 27, 2020 4:31 am

I have always recommended running with old oil in a pump, (provided a small drained cup full is not just dark gummy soup). The old oil, if it has covered things up well should be run for over an hour until the pump is hot. In this manner all the seals and walls will have a chance to circulate and get any crud and glop off the walls and partially polish the vanes and their springs. If what comes out is nasty then you have done good and will not totally waste a first run of clean oil. If what comes out is relatively dark but clean then so much the better.

Your first run with old oil from storage was really quite good! Fresh oil may win you a clean and nice running pump. Great work on the foreline pump setup.

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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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski » Mon Dec 28, 2020 9:54 pm

Today I’ve made some minor improvements to the system - I’m hoping to test the diffusion pump tomorrow. But for today I’ve celebrated by making a little bit of plasma:


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“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland

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Richard Hull
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull » Tue Dec 29, 2020 6:15 am

Please run the plasma again. Report the voltage, the pressure and the current and you will be the first human being to make the new plasma club!! The rules say to must report those three variables. You have already supplied the required images. Fabulous images!

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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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski » Tue Dec 29, 2020 11:28 am

Richard! I don’t think it’s worth the plasma club - I’ve done it mainly to test the micrometric valve I’ve rebuilt some time ago. Ad as I had In hand a random feed through and a power supply from an ancient photocopier (5kV and very current limited due to selenium rectifier stack based voltage doubler) I just put a soft soldered “grid” inside to make nice plasma photos.
I’m building much more serious power supply based on the breakdown tester transformer. Then I’m going to do some experiments with electron current measurements.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland

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Maciek Szymanski
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Those damn switches

Post by Maciek Szymanski » Tue Dec 29, 2020 8:52 pm

For controlling the solenoid valves I’ve used old Russian ТП1-2 rocker switches. They are rated 2 amps. But apparently the transient currents of those big electromagnets overloaded them, and two has failed. Today I’ve replaced the three switches with standard Chinese ones - 10 amps rated. Two failed immediately. Third failed after one successful switching.
I hope that the 5A rated Russian switches will be reliable enough...
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland

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Richard Hull
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull » Tue Dec 29, 2020 11:10 pm

Whatever you think is right for you Maciek. I am still looking for a first in the Plasma club. I am glad we strengthened the requirement to exclude DIY mason jar demon system, "quick dabbles". Strong wins here means a stronger cadre of contributors.

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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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski » Wed Feb 03, 2021 8:52 pm

I’ve finally replaced the faulty switches with the 5A old stock Russian ones. And today I’ve started the diffusion pump for the first time. It worked seamlessly pumping the chamber (the gate valve body blanked with a 100mm flange and a viewport) down below 1 micron in less than minute. But I was surprised how quickly the coolant heats up. I have a 20 liter plastic tank filled with the -35°C rated car antifreeze diluted 1:1 with water. After 40 minutes of operation the tank was significantly warmer. I’ve to put a thermometer into the tank and monitor the temperature.
The ionization gauge has measured 1.5e-7 Torr, but I do not trust this figure. The calibration potentiometers seems to be dirty, making the adjustments a bit sloppy and I’ve to recheck the base voltage and current of the gauge. For other hand I trust my pirani gauge, so the it was surely below 1 micron.


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The pump system with the diffusion pump working. The dark liquid in the tank is the diluted car antifreeze. For circulation I’m using a sunkable 24V camper faucet pump.


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The glass Bayard–Alpert ionization sensor with KF25 flange.


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The diffusion pump illuminated by the Bayard–Alpert glowing filament.


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The low and high vacuum gauges. The top unit is PN21 double pirani showing clearly pressure below 1e-3 Torr. The lower unit is PW11 ionization gauge set in the logarithmic range, showing suspectable 1.5e-7 Torr.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland

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Nikodem Czechowski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Nikodem Czechowski » Thu Feb 04, 2021 1:40 pm

Nice results, although indeed the 1.5e-7 seems to be suspiciously low. Do you have fresh oil the diff pump?

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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski » Thu Feb 04, 2021 6:18 pm

The oil is fresh DC704 and the whole system is cleaned and overhauled. I don’t believe this ultimate pressure, it seem to me as gauge fault. I’m using very similar system at work (same pumps and valves) and it routinely pumps down to 1e-6 mBar (7.5e-7 Torr) but it takes a bit longer.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland

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Finn Hammer
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Finn Hammer » Fri Apr 09, 2021 12:28 pm

Maciek,

This is a good thread, which I have just read from start to finish.
Very usefull for me.
During the testing of my vacuum station, I had already noticed that a turbo takes forever to come to a halt at E-3 Torr, and bringing it down faster by increasing the pressure is, although possible, inelegant.
Your design with the many valves, and in particular the vacuum holding vessel in the foreline is better, I will copy it.
Back to the drawing board.
Thanks!

Cheers, Finn Hammer

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