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My first plasma

Posted: Sat Sep 08, 2018 5:09 pm
by Eduardo_Machado
Hello everybody,

With the help of the many FAQs on this forum, today I finished my first demo fusor, and I would like to join the Plasma Club.

On my first try the vacuum wasn't good enough and I couldn't achieve plasma, as you can see in the picture bellow.
photo1.jpg
After that, we adjusted the vacuum pump and put more grease in the rubber, and finally we achieved plasma.
photo2.jpg
photo3.jpg
And then we had a problem. I don't know why, an arc opened between the grid and the glass. Anyone can help me explain that?
photo4.jpg

Re: My first plasma

Posted: Sat Sep 08, 2018 7:31 pm
by Cristiano_Machado
Well done! Now we are going to the next level: real fusion.

Re: My first plasma

Posted: Sun Sep 09, 2018 12:07 am
by ian_krase
Not sure what you mean by an "arc from the grid to the glass" -- may need better pictures.

Your glass looks too clear for sputtering to be a big problem. Is there a hot spot?

Re: My first plasma

Posted: Mon Sep 10, 2018 7:25 am
by Eduardo_Machado
Hello Ian,

Thank you for your help. The glass was very hot in general.

In this picture you can see that the glass melted just in the point were this arc formed. I assume there was some speck in the glass which may caused that.
IMG_1425.JPG

Re: My first plasma

Posted: Mon Sep 10, 2018 3:06 pm
by Richard Hull
There was no speck in the glass. You were probably seconds or minutes away from a glass implosion event. You had an ion/electron beam focused on the glass and this area is now dangerously stressed and weakened. The central white lozenge at the core is the impact point and the toned area around the hit area is deposition of grid material. It seems that the beam came from the tip end of the spiral grid. (high field area)

This is the problem with glass demo fusors that are over driven. While running fusor II in an attempt to do fusion, back in 1998, my bell jar was hit by a jet for a period that caused the tiny area to heat to a yellow white heat. Within seconds a glass shard poped out into the interior of the chamber. I never operated fusor II, ever again!!

I immediately realized that even boro-silicate glass (pyrex and Kimax) is dangerous to use in any form of fusion effort and immediately got to work on fusor III, an all Stainless steel fusor. Regular junk soda and lime glass is even worse in this regard.

Take from this, what you will.....

Richard Hull

Re: My first plasma

Posted: Mon Sep 10, 2018 9:08 pm
by Cristiano_Machado
Dear Mr. Hull,

I am the father of Eduardo, I help and monitor his project. Thank you for your experience and advise, I was very concerned when I saw the beam, it was coming exactly from the tip end from the grid. At that moment we shuted everything down.

We are planning to buy a new glass, improve the mesurements and traing more with vaccum, without tension. Untill we get an inox vacuum chamber and setup a real fusor.

Re: My first plasma

Posted: Tue Sep 11, 2018 1:14 am
by Richard Hull
Sir, I am glad Eduardo has a watchful parent at hand. Glass makes a fine demo device, but the tendency to over drive it is a powerful one. The demo fusor is more to allow the study of plasma and how they react as voltage and current are varied. The visual observations are of importance. The most interesting is to see the ion/electron beams exit the inner grid as the vacuum increases or decreases at varying voltages and currents.

However, an intense beam hitting the glass can certainly be observed, but only for a few seconds. Local heating of the glass can be intense at beam contact. The spiral grid is fine, but a closed grid with no sharp points will tend to issue many beams of moderate intensity rather than one intense one.

The deeper the vacuum just short of extinction of the visible glow the more likely that multiple beams will develop. (note my avatar image)
This was seen at a vacuum level of 10 microns in my old fusor III and photographed through a 1" view port window on the stainless steel vessel.

The beams are a sign and symbolic of a good usable vacuum in a fusor. In a real fusion situation the beams grow more needle like and more faint.

I attach a couple of good images of a real fusion star and then a demo fusor star.

Richard Hull

Re: My first plasma

Posted: Tue Sep 11, 2018 6:45 am
by Dennis P Brown
I agree with Richard, the glass chamber is just too dangerous to use if one is driving the plasma enough to get those results. I would never allow that to occur in my chamber against my window - it is a disaster in the making.

As for fusion, you had better build a proper metal chamber because a glass chamber will not withstand the plasma of a real fusion power supply for very long.

Of course, always wear safety glasses and and ALWAYS surround any glass vacuum chamber that is under vacuum with a grounded wire screen/cage!

At the very least one should have a "ball" end piece on any wire end to prevent a focused high voltage point from developing just as it did in your system. I do, in fact, terminate all my high voltage wires and bolts using metal 'balls" in this very manner so corona issues do not develop.

Re: My first plasma

Posted: Tue Sep 11, 2018 3:46 pm
by ian_krase
One thing that might be tried is to have separate beam blocks and structural vacuum chamber. The former can be made of cheap thin glass.

Re: My first plasma

Posted: Tue Sep 11, 2018 7:32 pm
by Rich Feldman
What if the chamber were lined with a non-structural metal screen that you can see through?
For example, fine woven wire cloth like that in fuel filters. Or perforated sheet metal like in microwave oven doors.

If the holes are small enough, and/or optical transparency low enough, ion beams and e-beams won't hit the glass so hard.
You can subdue the room lights to get a better view inside the screen.

Or have a nonstructural metal sheet between the central grid and the glass.
It would have a hole to look through, which can be covered with an unstressed, sacrificial glass window as others have suggested.

Re: My first plasma

Posted: Wed Sep 12, 2018 4:59 pm
by Dennis P Brown
The best course to take is throw away that glass chamber, buy a low cost Stainless Steel (SS) four way cross (50 mm dia.) and make that your chamber. Installing a decent window (1 cm thick glass) and a high voltage feed thru is very easy - that leaves a place to add a vacuum exhaust and gas feed line. This SS 4-way will not just make a vastly safer way to do fusion but relax's the voltage/current required to do detectable fusion, too!

See fairly recent examples of people using 20 - 25 kV and around 10 ma or so in a 50 mm 4-way and getting strong fusion neutron counts. Aside: I assume you have deuterium gas, a proper power supply, and neutron detection system since you indicated your next step is fusion.)

Re: My first plasma

Posted: Wed Sep 12, 2018 5:25 pm
by Richard Hull
I have given instruction on how to avoid direct hot beam contact with a viewport window in an all stainless chamber.

In short, mount you grid so that the north or south pole is viewed "dead on in the window. You may lose the pretty core image but the rays and beams will be seen well. There is zero chance a beam with emit from the juncture of the north/south wire bundle in the grid. Note: Your window will still slowly be occluded with deposition, but not be burned or stressed.

Fusor IV image attached in faux colors due to deposition on the window over long operational periods. This is normal and the reason a color camera is of no real value on a fusor that is, or has been, operated unopened or serviced, internally, over many months or years of use.

Richard Hull

Re: My first plasma

Posted: Thu Sep 13, 2018 8:28 pm
by Eduardo_Machado
Hello,

Thank you all for advise and suggestions. We don't have a new chamber yet, but we are looking for a stainless steel one. For sure I will share my progress with you.

Regards,

Eduardo

Re: My first plasma

Posted: Sun Oct 27, 2019 7:29 pm
by Eduardo_Machado
After more than a year, we finally got neutrons! See my other post.

Eduardo