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Robert Dwyer Fusor Progress

Posted: Sun May 07, 2017 1:24 am
by Robert Dwyer
Hello, I have recently made some progress in the construction of my fusor system. A few weeks ago I completed my chamber which so far is able to pull a vacuum of 200 microns. I know that is not very impressive, but I know the fittings that are causing the leaks (up-to-air valve is not vacuum rated), and have replacements that are on the way. I am still however, still trying to find a suitable HV feedthrough (currently I have a temporary flange attached where the feedthrough will eventually go), to make the chamber itself complete.

Here is the most recent picture of my setup:
Now for the plans moving forward:

1.) After having brushed myself up on some electronics knowledge (downloading textbooks on HV engineering, basic electronics, etc...) I began going through the stages of various power supply designs. This went from doing the tedious amount of calculations to see if winding my own HV transformer is worth the effort (it is not), driving a CW multiplier with 60Hz (large and expensive caps), using high frequency power to drive a CW multiplier, and of course the typical and ideal (but expensive) 60Hz x-ray transformer. After drawing up many designs on paper, doing some math, and comparing the costs, I have decide to bite the bullet, save up the money, and to wait for an x-ray transformer to become available.

2.) Once the power supply is finished, I plan on "playing" with the plasma inside the chamber in order to learn about and study how the fusor will operate. My end goal for this stage is to start getting consistent operation in star mode.

3.) My chamber is 2.75" cross that I acquired back in January thinking that I would use it just for my demo fusor, and then have to upgrade to a larger chamber in order to do fusion. However, after the results that were posted by Garrett Young in his fusor, I have to decided that I will experiment with the small chamber size. Neutron detection, I understand, is another large challenge I will have to face, but first, I need to tackle the other obstacles ahead of me.


So far, getting to the point that I have has been challenging, and I expect it to become even more difficult the farther I progress. I have however learned so much, in the span of the last 10 months on not just the theory of many different branches of science through designing a fusor, but also their applications. Moving forward I am very excited to begin moving away from the stage of assembling the vacuum system, and forward into the electrical system. I am greatly looking forward to keeping all of you on this forum updated on the progress I make, and the challenges I face!

I also want to thank all the members for your help, support, and the contribution of everyone's experiences, knowledge, and patience to the forums that have inspired a love and passion for science within me!

Re: Robert Dwyer Fusor Progress

Posted: Mon May 08, 2017 2:22 pm
by Dennis P Brown
And your deuterium source will be?

Also, the pump I see you are using does not appear to be a two stage unit and will not likely work with your diffusion pump.

As for a HV feed thru - I made my own and it works well and cost me little. I used a rod of copper (about 5 mm in diameter and 10 cm long.) Next, I took a rod of machinable ceramic (about 6 centimeters long) and drilled a matching hole through it length wise (however, one could just buy such a cylinder rod.) I used a glass plate and drilled a hole thru it that just cleared the copper rod to pass thru. Glass drills are cheap and available at any large hardware store. I coated part of the road with a high temp epoxy (I used a standard commercial one available at any hardware store - the weld brand epoxy.) And pushed the rod into it leaving two ends epoxy free but filling the center of the ceramic cylinder that also sealed the copper rod to the ceramic cylinder along its internal length. The key is coating a long enough section and have a ceramic cylinder long enough that heat generated by the electrode does not "melt" the epoxy. Five centimeters worked for me. I then epoxied the ceramic/copper rod to the glass plate. My glass plate sits against a O-ring on my chamber. This forms a really good high vac seal.

In the end of the Cu rod I had drilled a smaller diameter vertical hole a centimeter deep and two and a half millimeters wide (before gluing, of course.)

I then bent a steel welding rod into a standard fusor cage (using a bench vice to hold one end of the welding rod) and a handheld vice grip pliers. I used a large piece of old steam pipe to bend the welding rod around - that pipe defined my cage diameter. I formed three complete circles. I removed the steel pipe and reinstalled both ends of the welding rod/circles. I then bent two of the circles into a form that created the fusor "cage" relative to the last one.)

I placed the two ends of the welding rod on the end of my cage into the hole I had drilled into the Cu rod. Using a small steel wood screw, I forced this also into the drilled hole/welding rods creating a strong grip that holds the cage in place.

I have my complete HV feed-thru and fusor electrode.

After discovering that I needed this cage further into the fusor, I simply removed the cage from the existing unit. Then I installed a solid steel bolt (the head cut off) into the end hole of my copper rod (wide enough that the threads griped the copper internally.) Then I put a brass tube that just fit over this thread steel bolt and the brass tube was of a length that put my cage in the correct position for my fusor chamber. I pinched a tight seal between the bolt and brass tube. I then installed the ends of the electrode cage into the other end of this brass tube (again, using a steel wood screw to get a super tight fit between the welding rod ends inside the brass tube.)

Re: Robert Dwyer Fusor Progress

Posted: Mon May 08, 2017 3:09 pm
by Dennis P Brown
An aside: do consider grounding for the fusor and mounting. When you get a real power supply safety is paramount. A good mounting frame for the fusor, proper HV cable and correct fusor/PS grounding is essential to safety. Remember, real fusor power supplies are extremely dangerous and lethal.

Re: Robert Dwyer Fusor Progress

Posted: Mon May 08, 2017 6:19 pm
by Robert Dwyer
Thank you for your reply Dennis.

In regards to the vacuum pump, it is a two stage unit, that I measured 9 microns as an ultimate vacuum at the head, using a CPS vg200 vacrometer. After measuring from the head, I did a test to see what vacuum it would pull using just the diffusion pump as a chamber, and the gauge read 39 microns. Not an ideal foreline pressure, but from what Iknow, it is enough for diffusion pump operation.

As for my gas system, I have a connection at a local university that may be able to supply me a with D2 cylinder. If that does not work out, I may need to look into setting up D2O electrolysis system to supply my D2.

Going into the feedthrough, my first thought was making something similiar to a design I found on Doug Coulter'a website, using fused silica as the insulator. However, I do lack a lathe, and the necessary materials to work with quartz so that got scratched. My next thought was to use ceramic tubes. My largest concern was the epoxy used to hold the conductor on the tube breaking down and causing arcing. However, if that is not as much of a concern as I thought, then I will reconsider the DIY approach to the feedthrough.

As for grounding, I agree, safety is of the upmost importance with this project. A metal cage is in the plan, along with the "star point" grounding system that is recommended within the faqs on this forum. I also welcome any input and criticism regarding safety reccomendations for the fusor.

Re: Robert Dwyer Fusor Progress

Posted: Mon May 08, 2017 9:09 pm
by Richard Hull
Is your diff pump dry in your chamber test? If it has good oil or any old dry residues in it then you might be pumping water in the oil or residues to make that 39 micron reading. In any event 39 microns in the diff pump with your small chamber should be good enough to start the diff pump with good oil in it. You will, of course, have to move your foreline gauge to the chamber or get another gauge for the fusor chamber. It is best to have two gauges.

Richard Hull

Re: Robert Dwyer Fusor Progress

Posted: Tue May 09, 2017 12:03 am
by Robert Dwyer
Yes, the pump is currently dry. I have yet to obtain any oil for it, but I most likely shall within the next month. The CPS gauge is currently attached to the chamber, but I plan on replacing it with the TC gauge I am repairing, and placing the CPS gauge in the foreline.

Re: Robert Dwyer Fusor Progress

Posted: Tue Jul 04, 2017 4:38 am
by Robert Dwyer
Hello, I though I might update everyone here to the progress I have made on my fusor.

I have been fairly busy this summer, so not I haven't gotten too many opportunities to put things together, but I have acquired a few very important parts that will help me moving forward.

I will begin with the x-ray transformer. I have finished testing the transformer, and understanding it to a point where I now know how can use it for the fusor's power supply. After testing which leads go to the HV windings, low voltage windings, etc... I finally (with the help of someone much more experienced with HV and transformers than I), did a few live tests of the transformer by applying a very low voltage to the primary in air. These transformers are no joke! We input 1 volt into the primary and got 350 volts out of one of the HV windings! I believe this transformer will be able to output enough power to run my fusor (700 watts). I am planning to make the power supply out of a few sheets of aluminum by welding them together, wiring the transformer and all the internal circuitry inside, filling it with oil, closing the box and then pulling a vacuum on it to make sure any air bubbles will get out of the transformer's windings. Once I begin construction of the supply I will post more pictures and go more in depth into the circuit for the power supply. HV cable, diodes, resistors, and metering equipment have also been purchased. Here is a picture of the transformer:
As to what is next, Deuterium is acquired!
The stuff wasn't too easy to get, but with some help from some I knew locally that worked for Matheson, I was able to locate a Deuterium lecture bottle.
As for gas delivery, I also got a new MKS mass flow controller and readout, and I believe with the proper adapting, I can get the two to work together. I plan on attaching a fine metering valve after the MFC before the chamber to slowly leak deuterium into the chamber.
I was also lucky enough to come across someone on ebay selling an old He3 Corona tube tried and tested. I believe there has also been some talk of a neutron detection setup this seller was also offering on ebay. I think I may be able to get a ludlum 12 fairly cheap that can work with this tube, so then I will just need to worry about differentiating neutrons from gamma rays.
The main chamber is what I have my attention towards now however. I am currently disassembling the chamber in order to make way for a few feedthroughs on the way, along with a frame I am planning to make out of parts ordered from 80/20 Inc. Overall it appears that, although slowly, I am making progress. Depending on how things go, I am hoping to have the chamber and frame along with the power supply completed by the end of the month, so I can begin to work on getting familiar with my system and maintaining the plasma.

Re: Robert Dwyer Fusor Progress

Posted: Fri Aug 11, 2017 12:53 am
by Robert Dwyer
It has been a bit since my last post, but alas, progress!

The last month I had set out on finishing two specific things, the frame for the fusor, and a high voltage feedthrough.

The high voltage feedthrough is pretty generic. I ordered some ceramic tube from McMaster and cut them to lengths that I needed. The grid is made of pure Niobium wire, which was surprisingly easy to work with compared to the molybdenum wire I had on hand. I simply ran the wire through the tube, then used a 1/2" Swagelok to CF flange adapter, and used a Swagelok end cap to seal the end of the tube, and also provide a a connection to the Niobium wire.
Cut Ceramic Tubes
Niobium Grid
Ceramic fed through the flange
Grid in the Chamber
For the frame, I ordered some parts from 8020. It is simply an 8x12x20" frame, with an aluminum plate supporting the diffusion pump and the chamber. Eventually when I try my hand at fusion, I shall rotate the chamber so the viewport is pointing down at board camera. I also reconstructed the entire vacuum chamber, pulling all of the pieces apart (old gas feedthrough, valve, diffuusion pump christmas tree, etc...) and gave everything a good wipedown with acetone and then methanol (to remove the acetone film). Once everything was wiped down I reassembled the chamber, mounted it, and began to pull a vacuum.
Diffusion Pump Mounted into Frame
Whole Vacuum System Mounted
What did I find? LEAKS! Darn! I was only able to pull a vacuum down to about 1800 microns. that is terrible! It is worse than the previous chamber (previous chamber before reassembly pulled a max of 39 microns after about 25 minutes of pumping. Not great, but not 1800 microns max bad). I went to spraying bits of methonal around the CF flange joints, and sure enough I found a few places where I am going to need to tighten the connections (or get new gaskets, I am re-using the copper gaskets by applying vacuum grease to them).

Work is still needed on the chamber, but it is progress for sure! Also, I have all the components needed for the HV power supply for doing real fusion, but I shall begin work on that, and post that progress after I have my vacuum system at an acceptable point.

Re: Robert Dwyer Fusor Progress

Posted: Sat Sep 23, 2017 6:37 am
by Robert Dwyer
Update on the fusor!

I got finally got all of the fittings in for the new gas system, along with a new feedthrough and neutron moderator (the latter two lent to me by Carl Willis).

First the gas system:

I purchased a surplus lecture bottle regulator, made by Aldrich, from ebay, but it had a CGA 180 fitting, not 170. So I ordered (through Matheson) a new CGA 170 fitting to adapt to the bottle. Once I got that done, I began assembling the gas line. All of the fittings are swagelok 1/4" tubing adapters that clamp into copper tubing. From the regulator, the line goes through a needle valve, to a ball valve, and then to the chamber. Originally I had a MFC in the line, however, I had some difficulties setting it up, and decided to continue to test the MFC later, with a gas less precious (and more inert) than Deuterium. A little work with the foreline valve and the needle valve are neede to get a specific pressure, but it does work.
Two weeks ago I visited Carl Willis' house. During this time he showed me some very interesting materials, and devices, but he also lent me a perfect sized He3 tube, a moderator, and a ludlum 12 unit to read the counts. At his house we calibrated it against an Americium-Beryllium neutron source, and also biased it against a strong gamma source, to get the ludlum to mostly detect the neutrons, and not gamma/x-rays. The moderator he lent me is also covered in lead to help keep any stray/reflected x-rays from begin detected (ideally).
He3 Tube
Tube in the Moderator
Ludlum 12
Carl also lent me an old naval Beryllium-Oxide feedthrough, just like the type Richard Hull described in the FAQ's recently. This now sits on my machine, and after pumping down, my gauge now reads an ultimate pressure of 4 microns (with just a roughing pump and the gas-line's ball valve closed). If the valve were to be opened, the ultimate vacuum is about 9-10 microns.

Still working out some bugs in the electrical system. had my cheap Chinesium HV diode fail on me, so I got a high voltage diode stack (presumably from an old x-ray unit). I am also wrestling with current measurement circuits, and finicky voltage reading issues. When I first began the project, I knew that the electrical system was going to give me the most problems and difficulties however, so I try to view these obstacles as opportunities to learn.
HV Diode Stack (rated to 70KV)

Re: Robert Dwyer Fusor Progress

Posted: Sat Sep 23, 2017 9:07 pm
by Richard Hull
With the stuff Carl lent you you are on your way for sure.

Richard Hull