RGA Baseline

25 02 2011

All photos.

I’ve decided to adjust my research by taking smaller steps more frequently.

Yesterday I installed the RGA to get a clean baseline for the vacuum system.

It didn’t detect much! Which is good news:

I also spent HOURS organizing the lab. Getting wires off the floor, shelving, etc:

And got a stethoscope for future vacuum diagnostics:

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Deep Vacuum

18 02 2011

Let the pump run all night.

The chamber with blanks got down to 98 nanotorr:

Pretty great actually.

Now we have a baseline best case performance for the vacuum system.





FIXED

17 02 2011

All photos.

I found the fucking leak. It was the glass viewport. The passivation ate the metal between the glass and the steel:

For the record: do not passivate glass viewports.

I found the leak by listening. Late last night the building was quiet enough to hear the leak. I didn’t hear a hissing so much as I heard the sound of the pump emanating from the surface of the glass.

NOW THE EXPERIMENT CAN PROCEED!!

I will let the pump run overnight to see how deep a vacuum we can get with just blanks.





Pump was never broken!

16 02 2011

All photos.

Previously I though I had broken my pump.

So the pump is back from repairs. But the strange thing is when Pfeiffer received it, they said it was working fine! Although I did manage to knock the rotor out of balance and it needed fresh oil.  Here is the pump capped with a blank conflat running at full speed. GOOD.

But the problem was never the pump! The problem is a gross leak in the vacuum chamber.

Once I attach the pump to the chamber, the pump won’t spin up… indicating a gross vacuum leak.

The copper gaskets are all new, and I even got the torque wrench out to make sure the conflats were tight enough.

I can’t hear any hissing.

How do I troubleshoot this…

Here is a good overview on leak detection.

 

UPDATE:

I though I head a hiss near the bellows. So I tested just the bellows and it’s working fine. So the leak is somewhere in the chamber.





Turbo Molecular Pump Teardown

21 12 2010

All photos.

Yesterday I did a tear down of an old unused turbo molecular pump I’ve had laying around. Very instructive to see the insides. Here it is to begin with:

To assist disassembly, the pump has pry screws to push off the top case (Stuart’s tip):

Once you remove the outer shell you see this:

Sliding out the stators allows the removal of each pancake.

The rotor appears to be in perfect condition. It is machined from a single solid piece of metal. The stators are flimsy and largely bent out of shape.

At this point we still haven’t figured out how to remove the main rotor.





Bellows Holder

9 11 2010

All photos.

I’ve been meaning to make a little bracket to keep this bellows feedthrough from moving around

So today I designed this bellows holder in Sketchup. I’m waiting on a quote for 3D metal printing:





Vacuum Check

20 10 2010

All photos.

Just out of curiosity I wanted to see how deep a vacuum I could reach with just the ion gauge connected to the pump.

I tested the pump’s bake-out heater:

Heater switch.

Heater collar.

I let the pump and heater run all afternoon and I got as low as 25 nano torr:

It was still dropping slowly when I finished.

 

I also played around with the Hornet’s RS485 digital interface and Labview, but didn’t get too far.

 








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