Archived - better plasma pictures

[Jack Rosky]

Today, scott and I tested our demo fusors after many modifications. Pictures are attached below.
-Jack Rosky and Scott Moroch

[Rich Feldman]

Nice.
Are you still running AC?
Does the lighted section of the lower, thicker wire get longer as you crank up the juice?

[Jack Rosky]

Yes, we are still running AC, but the diodes are at my house and we were at Scotts.
Yes, the line of plasma got longer, but the picture you saw was at full voltage.
Also another question: the stainless steel inner grid turned yellow-ish after we shut it off... we don't know if this was from plasma or heat or something we haven't thought of. If you know of this happening or know why it happened we would be happy to hear.
Thanks
-Jack Rosky

[Richard Hull]

Stainless dis-colors much like steel, based on the heat range it has been subjected to. Yellow or "straw" color is common in tempered metals.

Visually, it appears your vacuum is terrible.

Richard Hull

[Scott Moroch]

This plasma picture was taken when we had a leak in our chamber. The only sealant I had was hot glue, which was not an air tight seal. Today I am going to rip off the hot glue and use an epoxy which will bring a tighter seal. By the end of the run the plasma would melt the hot glue and cause a large leak. How much better plasma could we get with a rectified 6kv NST (which we are using) with a vacuum pressure of about 35 microns?

Thank you,

Scott Moroch

[Richard Hull]

You would get a proper looking discharge as in a real fusor.

Richard Hull

[Scott Moroch]

Today I finished rectifying my NST and will be buying JB weld to get a tight seal. Today during one of my runs the inner grid, which is stainless steel, broke apart. And after it glowed bright orange and white. Since then I have fixed the problem, however, I was wondering how stainless steel wire could have split apart like that. I have attached a few images from the run.

Scott Moroch

[Rich Feldman]

Looks like it melted at the hottest point, then residual bending stress (in cooler sections) pulled the ends apart.
Similar to the result of conducting too much electrical current, except here the conduction current was negligible (with a zero point near the hot spot).

That does not mean you need to upgrade to a refractory metal right away.
See what happens when you get a lower vacuum pressure.
And go easy on that Variac knob.

You are learning to use your eyes as an optical pyrometer.
A filter for gas welding would shift the range in a useful direction.
About $2.50 at hardware store or welding supplier.