Demo Fusor Progress

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Jim Enright
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Demo Fusor Progress

Post by Jim Enright » Sun Nov 10, 2019 6:28 pm

Hello everyone! I hope I'm posting to the proper forum, but if not, please let me know!

As some of you may recall from previous posts, I am a high school special education and STEM teacher, as well as an advisor for the High Energy Physics club at the high school where I work. We considered several demo fusors but decided on the Make Magazine version for now due to relative ease of construction and cost (I am funding the club myself). Although this particular demo fusor is not even close to the scope of a research grade demo fusor, I wanted to take small steps in the process so that the science of the process would not be lost. I also felt it important that we research IEC and build a prototype of the demo fusor to understand the construction and how it would work. The pictures are of the finished prototype. The vacuum pump and OBIT are only for a visual for the students so they could see how it all connected and was powered. The gauge at the top is also only for visual purposes - it is actually a gauge from an old welding unit! For the actual unit, we will be using a 1-HP, 2-stage vacuum pump, and a 15kV NST connected to a 140V variac. The inner grid in the prototype is just soldered paper clips! The actual inner grid (in the 3rd picture) is 1mm stainless steel TIG welded. We will begin construction of the actual demo fusor after Thanksgiving break. Our goal is to eventually move to a stainless steel cross to house the grid.

The primary goal of this project is for the students in the club to understand how IEC works to produce fusion. Being a STEM project, I felt it important for the students to first become familiar with the components, evaluate the design plans, then build a prototype. We have access to a full welding and woodworking shop in our school so all components are constructed by students. Once the actual demo fusor is built, we will consult with an electrician regarding safety (he is a certified electrician with children in our school district so he is always willing to help us, as he did when we built CRT's from glass bottles this past Spring). Since we are not adding any gas (nor will we ever add gas to this demo fusor since it is not even close to having the necessary beefy components), we will not have any neutron detection devices, although I will have our Geiger counter next to the unit so students understand the importance of proper detection. We will also operate the demo fusor for only short stretches of time (minutes, at most), and behind a shield to ensure safety from implosion.

The kids are loving this project, and enjoying the learning process! We are hoping to achieve plasma and I would like my posts to serve as documentation of our efforts. We have learned a tremendous amount from this site, so thank you all for the input along the way!
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“Whether you think you can, or you think you can't – you're right." Henry Ford

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Richard Hull
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Re: Demo Fusor Progress

Post by Richard Hull » Sun Nov 10, 2019 10:40 pm

Yes, you posted in the correct forum. It looks like a nice little project and am glad that the students are finding it interesting. Just wait until first light. If the vacuum is deep enough you and they will be pleased. All the best on that first run.

One Question: I assume you have two diodes in that PVC TEE. If so, have you grounded the Transformer's metal case and taken its case lead to the fusors base? There are two ways to rectify the Transformer's output. The proper and safe way is full wave. Two diodes one hooked to each transformer knob then the other leads are then joined together. This juncture is the high voltage and goes to the main input terminal and grid on the fusor.

The case of the transformer is a center tap point for the two ends of the high voltage out of the transformer and it must be grounded and this ground will be connected the metal base of the fusor. Without the metal transformer case grounded to both electrical ground at the wall outlet and to the fusor base plate, the transformer case can be a lethal hazard.

I could not see a wire going to the black metal transformer case from ground or the base metal plate of the fusor.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jim Enright
Posts: 21
Joined: Sun Aug 04, 2019 11:12 pm
Real name: Jim Enright

Re: Demo Fusor Progress

Post by Jim Enright » Mon Nov 11, 2019 1:11 am

Richard, thank you for the encouragement and feedback! You are correct that there are 2 diodes in the PVC Tee. The 2 diodes are soldered together with the white bands away from each other. A 16-gauge wire is soldered to each end of the soldered diodes (leading to the sides of the Tee), and a third wire is soldered where the diodes are soldered together (leading to the top of the Tee). The ends of the Tee connect to the HV terminals on the transformer. The top of the Tee connects to the HV feed-through. The wire leading from the top of the demo fusor will be wired to the ground of the transformer. The pictures are misleading in that the two wires coming off of the sides of the Tee are only hooked on to the 2 poles of the OBIT, and the wire leading from the top of the unit is not connected to anything as of right now. We had that vacuum pump and OBIT from a CRT project that we made in the Spring, and I used those items as a way of facilitating the discussion about high voltages and vacuum with the students. Does the set-up I described sound like it will address the issue you raised as far as the transformer case being dangerous?

The kids are very excited as we build the project, I can’t even imagine how excited they will be if we are able to see the light! I know that there will need to be adjustments to the system, but that is just one of the components that I am trying to instill in the students – design, building a prototype, considering changes, problem solving, reflection, etc.
“Whether you think you can, or you think you can't – you're right." Henry Ford

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Richard Hull
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Re: Demo Fusor Progress

Post by Richard Hull » Mon Nov 11, 2019 3:09 pm

Great! I just wanted to make sure that the metal case of the transformer would be grounded as that is your return path for the high voltage and the winding's center tap.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jim Enright
Posts: 21
Joined: Sun Aug 04, 2019 11:12 pm
Real name: Jim Enright

Re: Demo Fusor Progress

Post by Jim Enright » Mon Nov 11, 2019 5:06 pm

Thanks Richard!

Thinking ahead, at some point we would like to convert the housing to a stainless steel chamber, and I'm thinking that a stainless cross would be best. Can we use the same set up but use the stainless cross in lieu of the borosilicate glass and aluminum disks? If that is possible, where would I connect the wire leading from the transformer ground to the demo fusor housing? Would one of the flange bolts be an appropriate location?

In the longer term, I would like to construct a full research grade demo fusor that could eventually be set up to run the deuterium through it. The deuterium lines is much longer term, but I am trying to take steps along the way to advance our learning and knowledge as we progress. This is the reason that we would like to convert the glass and aluminum set-up to a stainless steel housing.
“Whether you think you can, or you think you can't – you're right." Henry Ford

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