Archived - First Plasma (American University)

[bk8509a]

After starting on this project in novemeber, ordering the parts a month ago, we have assembled the chamber, pumped down to 2.8 mTorr, and created a star mode.

I will show you pictures of the chamber, lowest possible pressure, and pictures of the star mode.

The first picture is the lowest pressure we achieved, 2.8 mTorr.

The second picture shows the completed chamber.

The third picture is of an air plasma, star mode, at 30 mTorr, 2000V. Waiting to get a better grids for a brighter, higher contrast pictures.

We have the ability to pump down lower and the ability to go to -18000 V. The wire gets way to hot, so we are working on making a new grid.

More from us later.

Thanks for all your help,

Brian and Bill

[Doug Coulter]

Looking good! Your wire might be getting hot because of too much gas or the grid shape not matching the outer tank shape -- I tried a sphere grid in my cylinder and it got too hot as well. You probably need higher voltage and lower current to really get something good going on.

We notice here something else -- when we apply volts, and start letting gas in, at the point it lights off, there's too much gas to *run* the thing properly. We can see the time constant of this on a panel meter, it takes about a second (depends on tank volume). You may be running into that one.

[Steven Sesselmann]

Very interesting how the beams in the star form with 60˚ angles between them, even though the grid has 4 wires. Is there something more fundamental going on with the reaction that we should be investigating?

Steven

[Tyler Christensen]

The geometry looks right to me, I think it's just a chance that the camera angle made it look like exactly 60* and there are infact 2 more beams hidden behind two of those beams since there are 8 openings in the grid...

[Steven Sesselmann]

Tyler,

Thanks for clarifying that, easier when you see it in 3D

Steven

[bk8509a]

Steve, the grid does in fact have 3 circles, not two! The angles just poor!