A $5,000 Mistake

23 11 2010

All photos.

Last night I made a $5,000 mistake.

Do you see the problem?

I disassembled this butterfly valve a month ago for cleaning. Apparently when I put it back together I alligned the indicator perpendicular to the flap when it should have been parallel.

Last night I was doing a vacuum check with the clean chamber:

I set the butterfly valve to what I thought was full open (but was actually full closed!)

Do you know what happens next???

I turn on the vacuum pump. The turbopump goes to full speed.

Now the butterfly valve is actually closed. Which means the vacuum can’t get to the chamber.

Which means the chamber is at atmospheric pressure.

Then I turn the butterfly valve….

TTHHHHHWWWWOOOMMMMMPPPPPPP

Apmospheric air slams into the full speed turbopump, and it makes a bad sound.

Then I smell smoke..

And now the turbopump won’t spin up all.  I likely ruined the turbopump’s rotor – the most expensive part of the pump. Likely repair:

Worst case $5,000.

Likely case $3,000.

Best case $1200.

When I opened the valve I instantly knew what was happening, but it was too late.

I can’t believe I broke the pump AGAIN. Really heartbreaking, especially because I knew to avoid this specific condition.

The repair will likely take a month. I’m going to ship the pump out and…

I’ll be traveling in december.

I imagine the cheapest way out is to buy a used turbopump like mine to scavenge it’s rotor. Here it is:





Possible Polywells

15 11 2010

All photos.

This diagram shows the possible coil configurations of the superconducting tape. Going from minor radius 2 mm at top to minor radius  7 mm at bottom.

I used the very cool XRVG to generate SVG diagrams from ruby.





Electron Gun Mounted

12 11 2010

All photos.

I have locked down a final configuration for the electron gun:

The electron gun is aimed through the face and out the corner:





Coil Formers Installed!

10 11 2010

All photos .

The has been a major uphill battle… but I’ve finally installed the coil formers. This was really challenging and I fumbled every step of the way.

But looks at this beauty:





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:





Electron Gun

4 11 2010

Looking at photos of Joe Khachan’s electron gun, it is clear that my electron gun is producing much more coronal discharge:

My electron gun.

Joe's electron gun.

I emailed Joe to get his thoughts on the matter. He replied:

Two reason for the difference with yours could possibly be the following: we operate in hydrogen and we work below 10 mTorr. We have a large chamber which helps in breakdown at lower pressure. Since your chamber is smaller, you may need to operate at a higher pressure but this will reduce the depth of the virtual cathode that can be established. You may be able to reduce the pressure by using electron emission from a light bulb tungsten filament. You’ll need to extract the electrons from the filament by applying a potential difference between the filament and, say, a wire mesh as the anode. The electrons will go through the anode and produce enough ionization to enable you to start the discharge at lower pressure. The lower pressure also produces deeper virtual cathodes within the polywell.
Perhaps we could run this experiment with NO gas… only electrons from a hot cathode? See Vacuum Arc.
-
Joe adds:
Yes, just using an electron gun would be the better way to do this. We are making electrons guns based on a hot filament in order to do this. It is possible to get quite a large current from a filament of about an amp. A gun is needed in order to direct the electrons into the polywell because it is made of teflon. Bussard did it with filaments and used the voltage bias on WB6 to draw the electrons into it, so the WB6 is part of the electron gun.
And indeed I think this is the approach I’ll take.




New Polywell Simulations

3 11 2010

Joel Rogers has published new Polywell simulations. Get it while it’s hot:

http://www.plasma.ee.kansai-u.ac.jp/iec2010/pdf/pdf_slides_posters/Rogers2.pdf





Coil Former Installation

2 11 2010

All photos.

Finally coming to a game plan for mounting the coil formers:

The standoffs have 20cm threaded holes, and they will need to be cut down for final fitting.

The electron gun will mount through the conflat’s center hole.





Neodymium Magnet

2 11 2010

All photos.

I received a neodymium ring magnet today with an eye towards a permanent magnet magrid.

This thing is wicked strong!





Projects I Dig

1 11 2010

I’ve come across some projects I really dig. Though I’d share:

ChemHacker is building an open source scanning tunneling microscope: http://www.chemhacker.com/topics/stm/

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Ivan Bozovic has fabricated a nanometer scale superconductor at Brookhaven National Laboratory:

http://www.sciencedaily.com/releases/2010/06/100614092602.htm

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Junior has hacked together an incredible SLA style DIY 3D printer:

http://3dhomemade.blogspot.com/

This project has sparked my interest in the amazing Digital Light Processing technology.

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Kenneth V. Noren shows genetic algorithms can design electronic circuits!

http://www.mrc.uidaho.edu/mrc/people/knoren/GAs/B-159_paper.PDF








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