Rebuilding my fusor.

[William_Estlick]

Safty first.
I will be running a 20 amp 240v circut for the 30kv transformer. I will have a solid ground for the chamber then.

The new transformer arrived.

It looks like someone hastily potted some of the components, but the iron core seems to be intact.

[Rich Gorski]

William,
I agree with Joe's suggestion of leaving the anode and cathodes as they are now and just ground the chamber and the center tap (case) of both NSTs. If I understand your NST and bridge circuit correctly grounding both the anode, chamber and NST center tap will cut the potential difference between cathodes and anode in half. However I see no reason why you can't do this as a test to see how the plasma behaves. The third (round) prong of a standard outlet will (or should) provide a good earth ground connection. If you want to go more secure use a cold water pipe for Earth ground with a screw down pipe connector or use a metal hose clamp and use a good heavy size copper wire.

I had an interesting issue that had to do with grounding my chamber a while ago when I was experimenting with high energy, 5k Joule, 100 usec pulses from a capacitor bank going into the vacuum chamber. After I ran a few pulses and then go up stairs from my basement lab I noticed a LED light (standard home lighting 120VAC LED bulb) or two would no longer work. At first I thought it was just a coincidence but after it happened a few more occasions after working in the lab I concluded that my high energy pulses were the cause. I had the chamber grounded with thick 4 AWG copper cable to a cold water pipe but somehow I figured a transient HV spike was getting into the house ground and blowing up LED bulbs. After several weeks of looking into this I finally found the problem. My house earth ground connection was faulty where the breaker box ground wire was attached to the incoming cold water pipe. The problem was that the ground clamp on the cold water pipe was very corroded and just not making a good connection to Earth. The LED problem disappeared after I installed a new clamp.

Rich G.

[William_Estlick]

Thanks Rich.
A solid ground and well bonded water pipes are super important.
Also, if you have an outdoor meter socket, make sure the nutral is not corroded as well.
Grounds and nutrals should be solidly bonded together in the panel because if you lose the nutral, you can send 240 volts through your 120 volt circuts and bad things can happen.

My plan is to try grounding the chamber and see what happens. If it causes a problem, I may use the lead shielding (I have yet to build) as a faraday cage and still isolate the chamber.

[Dennis P Brown]

The primary house ground supplied by the utility is a good ground. Yes, I also use the well water piping as an auxiliary ground. What I refuse to do is depend on the std neutral (some old homes do not have a center plug ground - mine was like that but I had all of them replaced.) One needs the independent ground on a three connector plug (and know that is connected to the main ground provided by the utility in the main breaker panel.) Getting a testing plug in device (any major hardware store) can check the plug is properly wired and the ground is valid. But if one has access to the water pipe (metal) that is an excellent aux. (and added safety) ground point.

[William_Estlick]

Waterpipe is a very good ground if it is metal all the way out to the street.
But be careful, even though the house has copper pipe, sometimes the line on the street side of the water meter is plastic "Pex", if so, do not use it as a ground.

[Dennis P Brown]

Your more knowledgeable on the subject but at a hundred and up volts, water in the pipe is a good conductor, no? The walls of the tube in the house must be metal but the outside pipe can be plastic, I thought. Again, appreciate your input to people here do not make a dangerous mistake.

[Richard Hull]

Water flowing in a copper tube will pick up Cu ions as water is an ionic medium. However Cu ions in water are not conductive in plastic pipe to carry ground currents. The chemical, copper sulfate, in solution in lengths of plastic tubing if often used as a high watt resistor! Mostly in high voltage systems of some size. These chemical resistors have often been used in charging circuits of giant high voltage capacitors in the megajoule range in high impulse systems.

Copper ions in drinking water picked up in copper plumbing is a super high ohm resistor when running in plastic plumbing, thus, not a good current carrying ground.

Richard Hull

[William_Estlick]

First, I need to turn my vacuum guage around because my lead shielding is only 12" high.

New vacuum guage.

[William_Estlick]

And something like this for the deuterium.

[William_Estlick]

Cool new avatar.

[Dennis P Brown]

That plasma indicates that you appear to have a better vacuum.

[William_Estlick]

Its the same vacuum I have always had, I am just getting better images.

If I draw too much of a vacuum, the ions don't cluster around the cathodes, the plasma simply reverts back into a difuse arc.

There is a sweet spot.

[William_Estlick]

What I am interested in is what is happening in between the cathodes.

There seems to be distinct and coherent regions in the plasma with the top and bottom plasmas mirroring each other.
But the white plasma is presumably the hottest part of the plasma.
The top white plasma has a convex face and the bottom face is concave.

As the vacuum is reduced, the white plasma fills the space between the cathodes until finally it forms a ball.

[Dennis P Brown]

You can use google to get papers on the subject of simple plasma's generated at various pressures & gasses vs. voltage.

[William_Estlick]

Unfortunatly, I have not found any reference of 2 negative glow discharges interacting.

[William_Estlick]

1/16" thick lead sheet for shielding.

[William_Estlick]

These are parts for the 120/240volt 20amp power management system.
The momentary switch with lockout is to both add safty and to limit the time the fusor is on.

[Dennis P Brown]

Good idea for the x-ray shielding. Getting enough plugs is always a good idea in one's "lab" area. Be certain to test them for proper polarity and grounding after install. Make sure the neutral system and ground systems in the secondary box are correctly wired so they follow code! Since that is not the primary junction box means those two circuits must be kept separate. It is essential for safety that any secondary junction box must follow code.

[William_Estlick]

Will do, thank you.

[William_Estlick]

Working the lead around a form was easier than I thought it was going to be; I thought, I was going to have to solder a lip around the edge.

The lip helps make the lead more ridged, plus it will help prevent any leaks.

[William_Estlick]

And this is how I will get into the chamber, as you can see I will need to insulate the hv connections from the grounded shielding.

So, this is it.

I have a 4"×6" mirror on the way and will make a lead shield for it. Then I will cut the hole in the lid for the viewing port when I determine exactly what size it needs to be.

[Rich Gorski]

William,

Nice lead shielding. Looks like you will be well protected from X-rays.

Thinking about your electrode configuration, I have a few thoughts.

1. Since both cathodes are at the same negative potential, ionization is created by the potential difference between the two cathodes and the anode wire placed near the wall of the chamber. I think that means if you were to use a thin connecting wire between the two cathodes the plasma would still form the same way. The plasma, once ignited will act as a conductor so its already acting as a wire.

2. Positive ions will be accelerated from the anode wire towards the cathode and electrons the other way. There may be some focusing going on near the cathodes but you would need to run a computer simulation to really know what's going on with the trajectory paths.

3. The plasma kinda reminds me of the primer fields videos I saw on Youtube.

It would be nice to know what voltage you are running the cathodes at. Since you are using two full wave rectified NSTs with little or no capacitance I assume your HV output is pulsed DC. Do you have the NST outputs tied together and then connected to the cathodes or is each cathode connected to its own NST?

Thanks,
Rich G.

[William_Estlick]

Yes, it does look a bit like the primer field. But it does appear that external magnetic fields disturb the coherint structure of plasma when combined with electric fields as you can see in tokamaks.

I wanted to try out the new digital vacuum guage, but of course found leak, I think it might be the old guage and so I plan on removing it.

I will also need to dismantel and refit much of the fusor to be able to handle the 30kv power supply.

Do you use microns as a unit of measurement?

[Dennis P Brown]

Yes, microns are preferred here but certainly not mandatory. A voltage of 30 K can produce serious x-rays. So check with your x-ray detector, and avoid looking over the shield into the device. You had better have a ballast resistor and a current meter so as not to overload and damage the transformer. Also, be careful on overheating the system for long operation (depends on the supply's power.)
Tokamaks do not work at all like your system.

[William_Estlick]

Thank you, Dennis,
My plan is to install a mirror at a 45 degree angle with a lead shield. That way I can view the plasma indirectly with a camera and never be in direct line of site of the plasma.

I will use a spark gap switch a limiter to protect the transformer.

And my reference to a Tokamak was only to compare it to the Primer field experiment as they both rely on eletric current and an external magnetic field.

I am sure my fusor does generate its own magnetic field as it has both moving charged particles and electrons.

I do really do apreacate this forum and all your input, Dennis. There are not a lot of places out there where you can talk about nuclear physics.
Thanks again.