Completion of Demo Fusor

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Boris Said
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Completion of Demo Fusor

Post by Boris Said » Sun Oct 09, 2016 12:53 am

I have finally completed my demo fusor. Here is a video of it: https://www.youtube.com/watch?v=HBM2nXsdxbA
Something interesting I noticed, and don't know what caused it the tube. My assumption is that the plasma in the tube is caused by the wire reinforced tubing being electrified some way. Anyways, I will describe the components I used now.

Vacuum:
I used an alactel mechanical vacuum pump. I connected it to the chamber with wire reinforced tubing. For the chamber I used 1/2 inch thick pyrex between two aluminum base plates. I created a gasket out of Viton rubber and vacuum grease. All ports to the vacuum chamber where made with swagelok fittings. To measure the vacuum pressure I used a thermocouple gauge. Unfortunately, the thermocouple only worked on time. It was the second test when the gauge finally showed movement. At around 10 microns, it stopped. I have tried turning the thermocouple gauge while the vacuum chamber is opened and it still doesn't work. Help with the gauge would be very nice.

High voltage:
For my power I used a 15KV neon sign transformer. I rectified it with two hv diodes. I measured it with a large hvstuff resistor and a smaller resistor. I used a multimeter to try and measure the voltage. The values the multimeter return fluctuate rapidly and show no resemblance to the voltage the transformer should be outputting. I grounded the vacuum chamber and high voltage meter circuitry with a welder ground. I fed the power to the NST with a variac. For a high voltage port I used a spark plug and a Viton o-ring.

Inner grid: I used molybdenum wire in a 1 inch circle brazed together. I know that this is overkill for a simple demo fusor, but I wanted practice manipulating molybdenum. So far, the grid has held up very well.

The fusor is housed on a table and placed on rubber for insulation purposes.

Thanks for reading my post. Also, any help with my thermocouple gauge or hv gauge would be very nice. Thank you.

John Futter
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Re: Completion of Demo Fusor

Post by John Futter » Sun Oct 09, 2016 4:12 am

Boris
there appears to be no earth on your chamber ( high voltage return path) available to the high voltage power supply

this is dangerous as the plasma is making its own path to earth through the plastic tube to your vacuum pump.

I have had up to 30 yards of plastic 1/4" tubing light up like this with an earth failure on the plasma chamber

all very bad karma

Boris Said
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Re: Completion of Demo Fusor

Post by Boris Said » Sun Oct 09, 2016 2:49 pm

So would I connect the ground screw to the fusor chamber to do this? Thanks for your help.

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Werner Engel
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Re: Completion of Demo Fusor

Post by Werner Engel » Sun Oct 09, 2016 3:36 pm

yes, the outside of the fusor has to be grounded as well as he pump.
additionally you can put a metall mesh between the fusor and the tube -and also ground it. this should also prevent Plasma from igniting between the fusor and the pump.

Boris Said
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Re: Completion of Demo Fusor

Post by Boris Said » Sun Oct 09, 2016 5:48 pm

Would the ground the vacuum pump already has be sufficient or do you recommend running a separate cable to the ground screw.

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Werner Engel
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Re: Completion of Demo Fusor

Post by Werner Engel » Sun Oct 09, 2016 7:11 pm

Gronud should always have one common Point. And from there you go to every Thing you want to ground - in the shape of a star.
There are some FAQs regarding these issues ...

BR,
Wener

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Dennis P Brown
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Re: Completion of Demo Fusor

Post by Dennis P Brown » Sun Oct 09, 2016 8:16 pm

Your fusor (the chamber) should always have a true ground; then all components such as vacuum pumps, turbo/diffusion, gauges, and even the support stand should have a ground, as well. The star method is commonly used so read the FAQ on this and follow it. A NST allows some mistakes but a real fusor power supply will not - those will kill if you come into contact with them in any manner. Have fun doing this work (I do) but be careful - high voltage is dangerous and real fusors are lethal. Grounding a fusor chamber is not always easy since some x-formers have issues when reading current. Read the FAQ's on this subject when you cross that bridge.

My fusor has two independent grounds as does my fusor power supply; all my support equipment is also grounded using the star mode. I take as few risks as possible. It is a good idea to confirm your house's (or where ever your lab is set up) has a good and valid center pin ground - not just the neutral working. Any large hardware store sells an inexpensive plug in device that will tell you if the center ground is valid as well as if neutral/hot have the correct polarity. Safety is your responsibility.

Boris Said
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Re: Completion of Demo Fusor

Post by Boris Said » Tue Oct 11, 2016 2:11 pm

Thank you for informing me about these modifications. I changed my fusor to be this way, and there is no glow in the tube. Thank you, again.

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