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Registered Member #2004
Joined: Sat Feb 28 2009, 11:43PM
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Posts: 39
wrote ... Just throw your foil in a blender filled with water (to prevent flash fires) and run it a while. Odds are you won't be able to say you don't have any aluminum powder after ten minutes of blending.
It might work, but I'd think the aluminum would oxidize rather quickly in this scenario. It is pretty reactive, right?
Registered Member #1917
Joined: Fri Jan 09 2009, 02:38AM
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Posts: 62
I've just finished testing my updated ETG rig, and it outperforms the one before it by a huge margin. In fact, I believe that it has now exceeded 5%. Using only 300J (at about 6kV), I obtained results nearly identical to what the old setup would produce at 1350J. All of this was made possible simply by reducing the chamber volume from 2cc to about 20mm^3 and redoing the connectors (changed them to shiny new 2 gauge copper cable). I'll be updating my ETG development thread soon with more results of that test.
Just a month ago, rp181 was warning me against using powder, saying that foil or thin wire was far superior . So which do you think it is? If this idea is correct, then good old fireworks grade dark aluminum may be the way to go - loads of surface area and very fine particles. If you could test this, I'd love to see the results, but foil isn't necessarily that bad. After all, it is less than one mil thick in most cases.
_Fnord's switch-in-the-chamber idea is roughly similar to something I've already thought of. If the switching losses aren't losses at all, quite a bit of overall efficiency could be gained. If I can get use of a decent machine shop at some point, I'll almost certainly try it (right after I build a working barrel sealer valve, which has eluded me so far).
Registered Member #1917
Joined: Fri Jan 09 2009, 02:38AM
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When emailing me, you said that the Al powder in the ETCG design I posted on Spudfiles should be replaced with foil.
Yes, the tests tonight were done with a pulse cap (7.5kV, 16uF). Or, at least I think it's a pulse cap. There is some possibility that it's a metalized film construction, but the volume and mass of the thing in relation to its stored energy inclines me to believe that it's a foil cap.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
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hmm, do not remember that. A good way to see if its pulse: if you can, measure ESR or ESL If you have nothing, compare the terminals to other capacitor's.
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ETG gun theoretical efficiencies
. So which do you think it is? If this idea is correct, then good old fireworks grade dark aluminum may be the way to go - loads of surface area and very fine particles. If you could test this, I'd love to see the results, but foil isn't necessarily that bad. After all, it is less than one mil thick in most cases.