Archived - Fusor II

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myID
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Archived - Fusor II

Post by myID » Wed Apr 21, 2010 4:32 pm

Hi-

finally I made my way back to Germany...
Had a little time to set up my new toys- and the pictures show what the setup looks like now.
I call it Fusor II because it is much more then just a small change:

(first picture from left to right)
- new HVPS: Bertan 105, 30kV 33mA, changable polarity
- NIM BIN completed (cabling not finished)
- new pumps: Trivac D4B and Turbovac 50
- new HV Feedthrough (sort of shielded- at least electrocution safe)
- ESP2 with (different) small He3 tube in paintcan

Results (perhaps 1hr run time...):
- no ultimate Vacuum tests so far- how ever- after 40 min P< 10e-5 mbar so at least no big leak
- getting a stable plasma U>25kV is a bit hard...
- fusion: piece of cake with this setup: just introduced some D2 and the ESP started ticking...

Things to do/ come:
- change Oil in the Trivac
- condition the chamber
- Argon purge gas artifice (for glow cleaning and refilling the chamber after use)
- MFC for D2 to be set up
- connect Nim Bin to big He3 Tube (still no SHV cables- btw.: thanks for the efforts Bill and Doug...)
- higher Voltage (connected my homebrew bridge/ driver to my 2 HF HV tanks- NICE arcs so far but still lots of open questions due to strange waveforms.....)
- way to throttle Turbovac (at the moment throttled with inlet filter to decrease pumping speed- also somewhat protects the pump, pump is flanged directly to the chamber on the backside)
- complete shield (lots of lead sheet and paraffin (50kg...) already obtained) (will also act as moderator for activation experiments)
- change Trivac from three phase to one phase

Remarks:
- SHILED YOUR VIEWPORTS: in my setup at U > 25kV LOADS of Xrays....
- also without visible plasma still loads of Xrays
- get a proper power supply- AWESOME investment- worth every cent...
- the pump deal with the Trivac and the Turbovac was GREAT...
- inlet filter is contaminated with the phosphors from TV tube production: nice lightshow

More to come when I have more time because I am super busy with loads of other things still...

And: YES: I spent a fortune- now I am broke and will have to sell some Fusor I stuff

Kind regards
Roman
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Doug Coulter
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Re: Fusor II

Post by Doug Coulter » Wed Apr 21, 2010 6:26 pm

Lookin' good, Roman!

I'd second all those observations myself.
I also shield my viewport from the inside with a clipped in piece of pyrex which is turning brown -- better than than my nice main window/door! We (actually BillF) were very lucky to obtain a nice *thick* lead glass window from a radiology dept and boy do I like that thing for the outside! According to my survey meter, nothing gets through worth worrying about -- it stays very near background level. Due to the higher voltages I'm running, I also wrapped the entire tank in lead -- that one one heck of a job to do, but again, worth it. Safe to stand near it while running now.

People (even CliffS, I think) thought I was nuts to just go buy a really good power supply.
I happen to agree with you -- worth every cent. I love the safety factor and ease of use of a really good one. Just slap it on or off, all nicely current and voltage controlled, interlocked and gee, it just plain works. If there's trouble, it's elsewhere. I'm just having great luck with Spellman supplies, from the new SL2KW (50kv at 40ma but it beats that spec) and used ptv ones too.

I too run into "interesting stability" from time to time and am researching that, as the transition gives me huge bursts of neutrons. Not enough data to make a definitive report yet, but tell ya what -- let a little air or water vapor in there (a percent or so) and it gets much more stable -- which doesn't help neutron output one bit but makes it easier to run. I am also finding effects depending on whether the grid has any sharp edges or not -- seems a little field emission kick starts it a little easier....not necessarily good, but it's definately there.

Gas control is just one tough one. Need good control on both pump speed and gas inlet. Most mass flow controllers don't go low enough to not be wasting a lot of gas. I've made countless tweaks to that part of the system and everything that improves control improves the system as a whole proportionally more than that. It's a really big deal. I'm using needle valves and orifice tubes on inlet and both spinning the pump slower and using a conductance valve on it, and am *almost* there. I've now managed to run half hours once in awhile without touching anything at all....but that's the exception.

Sad you're broke, but hey -- who needs money if you've got the right toys?
Why guess when you can know? Measure!

Richard Hester
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Re: Fusor II

Post by Richard Hester » Wed Apr 21, 2010 7:47 pm

The only thing I really worry about is if the tubo pump will really be happy running in the horizontal position - that may be worth an email to Leybold. I always like to hang mine vertical.

Linda Haile
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Re: Fusor II

Post by Linda Haile » Wed Apr 21, 2010 8:25 pm

Turbos are fine running horizontal Richard. They will even run upside down if required.

A diffusion pump is another matter entirely, though.

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Chris Bradley
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Re: Fusor II

Post by Chris Bradley » Wed Apr 21, 2010 9:15 pm

Lyn Haile wrote:
> Turbos are fine running horizontal Richard. They will even run upside down if required.

Such a blanket comment ("Turbos are fine") is cobblers. Depends on the pump.

These Turbovacs are greased mechanical bearings which I presume are therefore supposedly meant to be 'OK' in horizontal operation but I'd not want to run one unless vertical. I run a Varian with ceramic bearings that handles inverted operation, but horizontal operation is still to be avoided even with those, due to the asymmetric radial loading.

I am sure Roman will take the advice from Richard who has a demonstrated experience of running turbos, rather than from yourself who has none, if he's not already asked the question for himself.

Nice work, Roman. That's quite a few hours of work to make everything look so neat.

Linda Haile
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Re: Fusor II

Post by Linda Haile » Wed Apr 21, 2010 9:33 pm

I beg to differ Chris. I've no experience with mag-lev's, though.

myID
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Re: Fusor II

Post by myID » Wed Apr 21, 2010 10:06 pm

Hi and

thank you for your advise- the manual of the Turbovac says: "come as you are" like Nirvana did- so horizontal mounting is fine. I did not find any information on optimal pressure rise curve when flooding the system....
Further more (I flood REALLY slow) I do not like the sound the pump makes at some RPM (guess hitting some resonance....).
Sooooo.... Flood faster to make the pump stop faster?

Btw.: I will build a "shadow cone shield" like Richard suggested once, and I use a capilarry and needle valve at the moment to control the D2 flow.

Greets

DaveC
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Re: Fusor II

Post by DaveC » Wed Apr 21, 2010 10:12 pm

Roman -

My compliments!.... Very nice setup.

I will second Richard and Chris' caution wrt to turbo orientation. Better safe than sorry.


Dave Cooper

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Chris Bradley
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Re: Fusor II

Post by Chris Bradley » Wed Apr 21, 2010 10:52 pm

Roman, what do you mean, exactly, by "flood the system faster"? I'm not sure I like the sound of that, either!

Linda Haile
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Re: Fusor II

Post by Linda Haile » Wed Apr 21, 2010 11:05 pm

The reason I wouldn't run a mag-lev horizontally is because I'm not sure they are designed to 'crash' in this orientation. Mag-levs have to be scrapped after two crash landings anyway, even in the vertical position.

(Never buy a mag-lev off Ebay!)

It is common practice to run conventional turbo pumps horizontally, as Roman's manual states.

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