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First Plasma - Daniel Fajardo

Posted: Wed Sep 27, 2017 5:45 pm
by Daniel Fajardo
In this post I want to share pictures and some data about the first run of my demo fusor. Plasma was formed, and I was hoping to get in the plasma club.

I constructed all the chamber myself, in aluminum. I used an old small mechanical pump, measuring the pressure with a Pirani gauge. These pictures were taken at 92 mtorr, which I know is above the ideal levels (below 20 mtorr). However, I have a more robust mechanical pump and even a turbomolecular pump (which I think would be overkill, because with the big mechanical pump I got to 14 mtorr in a test I did without applying voltage) available here at my university. I applied ~3 kV, though I'm working on a better power source which I hope would get to around 12 kV.

I believe I will be posting better results soon.

Thank you for your attention, and please make as many comments and sugestions as possible.

Daniel Fajardo
Medellin, Colombia

Re: First Plasma - Daniel Fajardo

Posted: Wed Sep 27, 2017 11:17 pm
by Richard Hull

A very impressive beginning effort. I have placed your name in the Plasma Club listing.

Richard Hull

Re: First Plasma - Daniel Fajardo

Posted: Thu Sep 28, 2017 10:19 am
by Dennis P Brown
Second Richard's "Very impressive." Making your own chamber and using such good vacuum systems is a very good start.

Guess your next focus after increasing the voltage to a NST level will be to obtain a proper power supply for fusion. Since you have access to a University, maybe they will allow you to borrow such a supply? Same for deuterium , maybe.

As for your vacuum being just 97 mTorr that could be due to out gassing from the surfaces. Keep the system under vacuum (don't open it) and run the vacuum pump and plasma a few times over a week and see if the system gets down to under 5 mTorr. If not, a leak is possible. Maybe a photo of your electrical feed-thru would be helpful - if not commercial, they can be a common leak source.

Do not know if your pump has an anti-oil vapor back-flow restrictor? If not, making one is very easy considering your skills with machining metal. Preventing oil from the pump back streaming into the system is important; if one has a main valve, of course, this isn't important since when the pump is running, the oil vapors do not significantly back stream. However, without such a valve, really can't leave the system under vacuum without the pump running.

One thing to do for your system before increasing voltage is that you should consider building a proper ground system - it is a good idea to use a default ground arrangement; that is, one for the chamber and another for the metal stand (I feel any metal stand for a fusor should have its own ground - not necessary, of course but I feel that is a good safety practice.) Of course, the standard star system with the fusor is always the best approach.

A minor point - consider using washers on your nuts and bolt heads. Besides protecting the flange surfaces, it makes for a more uniform pressure on the flanges making a tighter and more critically, a more uniform seal - both important for proper long term operation.

And welcome to the plasma club. I started their too before joining the neutron club.

Re: First Plasma - Daniel Fajardo

Posted: Fri Sep 29, 2017 2:07 pm
by Dennis P Brown
Forgot to add; you will need either a diffusion pump or if able, a turbo if you decide to attempt to build a fusor. As such, you should keep this in mind for the design and future growth of your chamber.