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.

 





Muriatic Acid

18 10 2010

Finally scored some muriatic acid in Brooklyn at True Value on 558 Metropolitan Avenue.

 

I’ll be using an 18% solution to clean or “pickle” all the parts going into the vacuum chamber.

 

 





Passivation Success

12 10 2010

All photos.

The vacuum chamber and parts are back from their passivation. Look how shiny and new:

The glass viewport survived the acid:





Operation Passivation

6 10 2010

All photos.

I decided to passivate all the vacuum equipment. This entails completely disassembling the fusor:

Look at the extreme deposition on the ceramic standoff:

Clearly the deposit is going from negative to ground judging from the super clean inner grid (negative) and the very dirty outter grid (ground):

You can see where the electron beams touched the walls of the chamber:





Passivation

30 09 2010

Just got a quote from a vendor down the street to clean and passivate my vacuum chamber and all conflat fittings: ~$225.00

Currently I would describe my chamber as filthy. Passivating it would restore all vacuum parts to a factory new condition.

Would my ceramic feedthroughs and glass viewports be damaged by the strong acids used in the passivation process? I’m guessing so.





Vacuum Pump Fixed!

3 06 2010

All photos.

The vacuum pump is back online!

Although Pfeiffer sent the wrong o-ring:

I was able to re-use the previous o-ring:

I’ll upgrade the o-ring to the new one when I get it from Pfeiffer.

Here is the removed broken vent valve:

The vent plug installed:





Heat Shield

1 12 2009

The red hot fusor grid reminds me  – I must address thermal issues from plasma, xrays and neutrons for polywell fusion without boiling the superconductor’s liquid nitrogen.

I asked for help with thermal modeling on the polywell talk forum. Good feedback.

Here is a rough draft of the superconducting magrid with a vacuum separated heat shield:

The trick is, the shield must have a gap so that you can weld the lid to the chassis. The welded magrid would have a gap in the shield along the midplane of the torus.

This gap would bring the vacuum between the heat shield and the inner superconductor holder. Well actually it would be  ~10 mToor of ionized deuterium.

This design does not include liquid water cooling. Although it’s easy to add cooling channels with the Arcam process, the real challenge is connecting fluid channels when you weld the lids onto the chassis.








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