Robert Dwyer Fusor Progress

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Robert Dwyer
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Robert Dwyer Fusor Progress

Post 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:
20170425_172649.jpg
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.

Overall:

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 fusor.net forums that have inspired a love and passion for science within me!
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Dennis P Brown
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Re: Robert Dwyer Fusor Progress

Post 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.)
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Dennis P Brown
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Re: Robert Dwyer Fusor Progress

Post 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.
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post 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.
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Richard Hull
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Re: Robert Dwyer Fusor Progress

Post 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
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post 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.
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post 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:
20170520_155903.jpg
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.
20170703_220337.jpg
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.
20170703_220414.jpg
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.
20170703_221231.jpg
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.
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post 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
Cut Ceramic Tubes
Niobium Grid
Niobium Grid
Ceramic fed through the flange
Ceramic fed through the flange
Grid in the Chamber
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.
Frame
Frame
Diffusion Pump Mounted into Frame
Diffusion Pump Mounted into Frame
Whole Vacuum System Mounted
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.
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Re: Robert Dwyer Fusor Progress

Post 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.
20170922_222039.jpg
20170922_222047.jpg
20170922_213457.jpg
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
He3 Tube
Tube in the Moderator
Tube in the Moderator
Ludlum 12
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)
HV Diode Stack (rated to 70KV)
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Richard Hull
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Re: Robert Dwyer Fusor Progress

Post by Richard Hull »

With the stuff Carl lent you you are on your way for sure.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

Over the last two days, I fixed a few issues with fusor, including the Ludlum 12 detecting noise, and getting a new power supply.

First with the Ludlum. I figured out that the detector was seeing the noise due to a faulty BNC cable. As soon as the cable was switched and I brought the device back up to about 10kv, no counts were seen.

As for the new power supply, Carl Willis ended up lending me a 50kv 5mA Hipotronics power supply that he had apparently used with one of his old fusors, since I was having issues with the X-ray transformer. In order to use it, I did have to modify some old RG-8 high voltage cable and an Amphenol 259 connector, but that wasn't too difficult to do.

Here are pictures of the supply, and modified cable:
50KV 5mA Power Supply.
50KV 5mA Power Supply.
Inside of the Supply
Inside of the Supply
Modified RG-8
Modified RG-8
As of right now, this is what my whole setup looks like:
Fusor Setup
Fusor Setup

So once I got the HV system up and running, I decided to do tests with no deuterium, just an air plasma. I know that my gas line is a bit leaky after the needle valve, so without opening the Deuterium regulator, I have a controlled air leak. Did a run at about 5 microns going up to 30kv. No plasma was formed at those pressure, and the x-rays coming out of the port were being detected at about 50,000 CPM. The 177 is however, VERY noise susceptible. I ended up moving the pancake probe about 4 feet away from the fusor whilst it was running, and it was still seeing about 10,00cpm. I put it behind the 1/8" lead shielding around the moderator for the He3 tube, and it still saw about the same number of counts. It does tell me that there are x-rays present, but now I know not to any degree of accuracy. The Ludlum 12 However, during this time, barely saw any counts, which is good. This makes me believe that I have fixed the noise issue, and it was really the fault of the cable.

Now, at this point I decided to actually try to maintain a discharge of the air plasma, whilst raising the voltage. This proved to be.... difficult. It was much harder than I expected, I see why operating a fusor is described as an "art." It took a long time with me fiddling with the voltage, and pressure, to finally get above 15kv. After of 3 hours of operation, I finally was getting tired, and decided to call it a night.

This morning was when I decided to try my hand at fusion.

Fusion attempt #1 went as follows:

1.) Turned on the TC gauge.
2.) Started roughing pump.
3.) Waited for the chamber to pump down to about 4 microns.
4.) Turned on ludlum 177 w/ pancake probe
5.) Turned on main power supply, and raised voltage to 20KV. X-rays where seen, but no counts on the ludlum 12. After this, I turned the voltage back down.
6.) Opened ball valve to gas line. The pressure spiked, but quickly pumped down to 5 microns.
7.) Opened Deuterium Bottle, and regulated it down to 10 PSI
8.) Opened needle valve, raised the pressure to about 10 microns.
9.) Raised the voltage on the power supply to about 12kv. Current reading was about 1mA
10.) At this point I began playing with the voltage and pressure to try to (as Richard describe dit) "inch worm" my way up to fusion voltages. No counts were seen during this period until I hit about 20KV @ 1mA
11.) The Ludlum 12 began to click away, but few counts were seen (less than 100CPM), however, as I played with the voltage some more, I began to see higher count rates. The current rise to about 1.5mA but the voltage would drop to 15kv. Here was when I started to see more counts (maybe 500 CPM). Soon, when I started lowering the pressure and getting voltages at about 20-22kv @1mA I started to see significantly larger count rates (1,000-4,000 CPM). I messed with more parameters like pressure and voltage, and I noticed that as the voltage dropped to about 15kv, I was still seeing counts at about 1,000 CPM. At first I thought this was wrong, but I remembered that I do have He3 tube which is fairly sensitive, so I do not believe that it is impossible. Still these are very low neutron counts.

12.) When I started to get the hang of things, and started to hold about 20kv @1mA with a pressure of 15 microns, I saw the highest count rates. The ludlum went off scale, and I had to switch the scale. Here I saw about 10-20,000 CPM, but this was short lived as the pressure would begin to drop and I would have to fiddle witht he pressure, and voltage again. Eventually, I reached a peak voltage of 27kv at about 1.2 mA and here I saw (briefly) about 25-30,000 CPM. A few times the ludlum would, pulse higher, but that was never constant for more than a second.

So that was my first fusion run. Low current, and with that, low neutron counts. However, I definitely think that fusion was occurring. With this I would like to begin the review process for the neutron club. I know that everyone will have questions, and want me to do more runs. After I write this, I am going to do a run without the moderator, but lead shielding. I also am hoping to use a bubble dosimeter to have another form of detection showing that I have neutrons. This is however, very exciting! Over a year I have been working on this, and now the project is finally coming to completion, and hopefully I will be eventually able to do experiments with the neutrons (provided I get better numbers).


Also, I did film a video of myself in the middle of the run. Sadly my phone died so the video cut out before I got the 27kv. Still, I hope this can provide some insight into what was happening within the device. I also apologize if I am repetitive in the video, but I was very excited during the whole thing.

https://www.youtube.com/watch?v=CaHLsl8 ... e=youtu.be
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Dennis P Brown
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Re: Robert Dwyer Fusor Progress

Post by Dennis P Brown »

Your power levels appear rather low for such high counts - I do suspect that your best pressure with a smaller chamber is in the 15 micron range. As such, most likely you are getting some fusion and maybe the detector is also picking up noise and neutrons - now just compare with and without a moderator and you can very likely distinguish between the issues.

Of course, the bubble detector is the gold standard (as long as it isn't over heated - now that must have been depressing for those it happen to.)

You have a 50 kV 5 ma supply, but keep losing the high voltage at 5 microns - you should easily get more current at 20-25 kV; something seems amiss.
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Re: Robert Dwyer Fusor Progress

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Dennis hit the nail on the head here. A rush of high counts is virtually impossible at 20kv and 5 microns and 1.5ma Good counts typically start to occur only around 25 kv @ 6 microns or more and 8-10ma of current. Something is definitely amiss.

I am almost positive the issue envolves a mis-biasing of the corona tube, and or, discrimination issues. Quite possibly, both issues in combination are creating the high counts at such microscopic current levels.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

So I did the test with just lead shielding around the tube, and no moderator, and I did end up seeing noise in the 1,000-5,000 CPM range, with pulses off scale. This made me suspect the counts I was getting even more. I ended up asking if Carl Willis if he could come over and help diagnose my detector issues.

When Carl arrived he began to inspect the tube, he noticed a few things. First, that I was using a cable that was different (longer) than what the tube was calibrated with, and he said that may give false readings. Also, some of the BNC connections were dirty, so we cleaned them out with methanol. He eventually noticed that one of the main BNC connections on the tube was coming off. At 1400V this was causing corona discharge that , unless the connector was at a certain position, cause extremely high counts, without the fusor even being on. However, after fixing the detector to the best we could at the time, and putting it at an (awkward) position, where it wouldn't give any extremely high counts (from the broken BNC connection at least), we began to turn on the fusor once again, and it the counts we saw told a different story than before.

The system was pumped down to about 4 microns, deuterium was added, pressure rose to about 15 microns, and we began to turn up the voltage. After playing with the plasma a bit, we eventually got a stable discharge, along with neutron counts of 200-350 CPM around 15KV 1.5mA and a pressure of about 100 microns. This makes a lot more sense at these low power levels. Carl agreed that it made much more sense than what I was seeing before.

After this, we decided to try running at higher power. A 50W light bulb was being used as ballast, and that is why higher currents were not being seen. Carl and I replaced the bulb with a 20 Amp fuse (making sure to be careful whilst running with that in). However, the run did not produce and fusion. This was due to a solder joint that I had to hold the grid in place. Flux from the solder ended up getting to hot, outgassing, and burned up/spoiled the vacuum. Before this happened, we did get to see a a very beautiful star mode at 4kv. Carl also did say that I eventually will want to get another power supply that will be able to run higher currents, which I agree with.
4KV Nice Star Mode
4KV Nice Star Mode
Progress? Yes. We both believe there neutrons during the second run with 200-350 CPM, but sadly the detector started to succumb to noise during the high power run, and the vacuum feedthrough now needs cleaning. Carl also said he was going to work on repairing the detector connection while I work on cleaning the chamber, And re-orientating the fusor (viewport to the side, and the BeO) feedthrough coming from the bottom. Hopefully within the next week or two I can begin doing runs again, with a less noise susceptible detection system, and (ideally) bubble dosimeter readings.

Attached below are the links to two videos of when Carl Willis came later yesterday afternoon to help. The first is the run with 200-350 CPM, and the second is the high power run attempt. I do apologize for the second one cutting out a lot. My phone was running out of space and started acting weird. I eventually gave up on trying to record, but I hope it may provide some insight.

https://www.youtube.com/watch?v=OoqdWyWb7UU



https://www.youtube.com/watch?v=OoFkHW1g3Gc
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Re: Robert Dwyer Fusor Progress

Post by Richard Hull »

You have the extreme advantage of Carl's direct help. Pay close attention to what he says and does. You will learn a lot. I am sure you will have stable operation soon. All the best, of course, in your continued efforts.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Robert Dwyer Fusor Progress

Post by Dennis P Brown »

Your system pressure for a run was at 100 microns?! Also, one should not have 15 kV and only get 1.5 ma at 100 microns unless your supply x-former is utterly saturated - which isn't very good news for this power supplies' usefulness if you want more current then this at any higher voltage.

I am not aware of anyone running a successful fusor at pressures that high (others may know more.) In any case, I do think your best performance will be in the 15 -20 micron range judging by your chamber size (very small - which has produced good results for some here.) For my x-former, any pressure above 10 - 15 microns results in a runaway current (over 100 ma! which is bad for my x-former.) My ballast resistor helps but isn't meant to handle such a conductive plasma. That is why I run around 5 microns like most do here; but my chamber is rather large.

What is your ballast resistor value?

Also, the color of your star mode appears to be using atm and not deuterium.

Fusor's are noise machines as I discovered and most who use detectors know only too well. Keep at the noise reduction and you will have success - just avoid issues like contamination in the chamber, which just makes running a stable system nearly impossible. Keep at it; progress can be slow and frustrating but once you get a clean signal, all this effort is so worth the trouble.

I am concerned that your overall power levels are very low for fusion - if you can get over 40 kV at 1.5 ma, that should be ok but 20-25 kV at 1.5 ma isn't going to make a significant fusion signal for most detector systems. That is, having a very small neutron signal makes all detection work very difficult; this also ups the requirements a great deal to achieve very low noise levels.

Aside: I discovered that ground loops were causing my detector system issues. So, I went to a battery supply (the detector system floats relative to ground) and this cleared up my last major noise issue relative to the fusor's plasma. This may not be relevant to you but keep it in mind.
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Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

It has been a while since I have posted anything on my fusor, because I have been waiting to get a bubble dosimeter to really show whether or not I had fusion. I knew that noise was being a serious issue for the He3 detector, so I thought a bubble dosimeter was the way to go. While I was waiting for the ones I ordered to come in, Carl Willis contacted me, and let me know he had one I could borrow. The one he lent me is a 20 bubbles/mrem dosimeter.
Bubble Dosimeter before the run
Bubble Dosimeter before the run
Before I did a fusion run, I wanted to make my gas delivery system easier to use, so I added a series of valves to restrict the flow more to add finer control. I added a shutoff valve right after the second ball valve on the regulator, and bellows valve to help throttle the flow before the needle valve.
Valves to be added.
Valves to be added.
New gas admission system
New gas admission system
So after a pump down of the system to about 4 microns, I began admitting the D2 to about 10 microns, and then turned on the power supply. I was using a 20 Amp fuse as a ballast for the supply this time, instead of the 50 watt light bulb, so I had more power, but it also meant I had to be a bit more careful in operation. I placed the bubble detector approximately 6cm away from the inner grid. The total run time was about 20 minutes, and I noticed the first 3 bubbles after about 15 minutes, when my voltage was at 27kv, my pressure at 32 microns, and my current at 4.5mA. In the next five minutes I pushed the voltage up farther to about 32kv @4mA with a pressure of about 25 microns, and saw two more bubbles.
Placement of the Bubble Dosimeter
Placement of the Bubble Dosimeter
Fusion Plasma
Fusion Plasma
Bubble Dosimter after the run
Bubble Dosimter after the run
Bubbles Dosimeter in different lighting
Bubbles Dosimeter in different lighting
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This was extremely exciting to see! I want to do more runs with this detector, but I think this shows that I definately have neutrons. I want to get a bit more data before trying to turn this into a total neutrons/second. With this data I would like to ask to be considered for the neutron club again.
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Dennis P Brown
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Re: Robert Dwyer Fusor Progress

Post by Dennis P Brown »

Glad your efforts are starting to pay off!

I will leave the bubble detector results for those familiar with those types of detectors but certainly, those results look very promising.

Also, your fusor's pressures, voltages and currents sound very good and correct compared to similar systems previously posted - this also demonstrates that your fusor is operating in the proper manner similar to other successful systems!

A side issue: I am concerned that your bubble detector is so close to the fusor's cathode section - do consider a heat shield (a single vertical piece of aluminum foil that is air spaced both sides: i.e. detector-foil- fusor) and be sure cooling air is flowing across the bubble detector to prevent a disaster; that wood block will prevent proper air flow around the detector and also, that wood can insulate the detector in a bad way! Remember, that fusor is going to become very hot over twenty minutes of operation and that detector is sensitive to radiate heat, too.

My main question and I am confused by in your post is: Exactly what is a 20 amp fuse ballast? A fuse has essentially next to no resistance and a ballast for a fusor should, if memory serves, be over 50,000 ohms or so (and be high wattage; this ohm value, as I understand can cover a range.)

Finally, thanks for the pictures and your setup looks very good. Hope the neutron results are conclusive!
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Richard Hull
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Re: Robert Dwyer Fusor Progress

Post by Richard Hull »

The bubbles tell the story and the gear looks capable along with a well documented and progressing back story. I will log your name into the Neutron club. Keep us advised of future efforts with your 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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

Thank you very much! I am honored. It has been a long, but fun journey over the last year and a half of trial-and error, struggling, and most importantly, learning. I will make sure to keep you all updated on further progress I make.

AS for questions on how I am ballasting, right now it is just a screw in 20 Amp fuse in place of the 50W light bulb that was being used as an inductive ballast that kept me from reaching the higher power levels I needed. I can see when I am operating that the device that the current will keep increasing as time goes on, so it it means more care must be taken in operation. It isn't ideal, and I do plan on replacing it soon.
Robert Dwyer
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Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

After about a month, I finally find myself back on the forums ready to report on more progress with my fusor. I have not been able to work too much on it in the last few weeks, because many scholarship application deadlines were due.

After my last post, I had tried a few more runs running at less than 30kv, but none of them yielded too many interesting results. My power supply is capable of 50kv, and I decided that it might be good to invest in some lead shielding to run it at the higher powers.

After the purchasing of the lead shielding, I ran into a major problem trying to run at voltages higher than 35v, arcing. Apparently my insulator bust have been dirty, because arcs were tracking along the ceramic to the vacuum chamber. After cleaning the insulator, I decided to move the fusor so that the HV feedthrough was pointing down, and I could submerge the conductor in oil, to prevent any tracking occurring. It is not exactly the best looking fusor, since It is riddled in lead sheet and duct tape, but it works. Once this was finished, I was ready to try my hand at fusion again.
Latest picture of the fusor
Latest picture of the fusor
The latest run I did was at the following parameters:

Max Voltage: 45kv
Max Current 4.5ma
Pressure: 60-70 microns
Run Time: 12 minutes

I positioned my bubble detector about 7cm from the center of the vacuum chamber. After twelve minutes I had 46 bubbles on my 20 bub/mrem dosimeter. A major improvement. I am hoping to do more runs with my less sensitive dosimeter (easier counting), and try a higher current power supply, to try and increase my fusion numbers.
Bubble dosimeter after latest run
Bubble dosimeter after latest run

I hope to do more runs this weekend, with hopefully better results as I get more experience in operating the device.
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Richard Hull
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Re: Robert Dwyer Fusor Progress

Post by Richard Hull »

Thanks for the report on your latest efforts. Nice work and remember, once you do fusion, practice makes perfect. You do better each time.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
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Joined: Sun Sep 04, 2016 5:34 pm
Real name: Robert Dwyer

Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

Did another run when I got home tonight, but this time using my 13 bubbles/mrem detector, and I reconfigured the lead shielding slightly, so I could place it closer to the source (6cm).

I ran the fusor for 5 minutes, with a max voltage of 48kv and a current of 4.7ma. The result was 33 bubbles.

I believe this means that at 6cm from the source there is about 30mrem/hr of neutron radiation, and that corresponds to about 860,000 n/s! I am much closer to the million n/s mark I am trying to hit!

If I made an error in these calculations, someone please let me know. I am hoping to do another 5 minute run tomorrow to hopefully repeat these values.
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Richard Hull
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Re: Robert Dwyer Fusor Progress

Post by Richard Hull »

Your figures sound about right. However, voltage and current are just part of what you should be reporting. You need to always quote the pressure of the flowing D2. (time of run- precise, pressure- avg., voltage- avg., current- avg.)....Most all fusors working at their maximum will have small voltage and current transients during the run. A few might even see a pressure change. In all cases, good electronic counts and bubble count over the timed period will rather under-estimate your many peak emission rates and over estimate the full run's average emission rate. Regardless, all of this data is better than a poke in the eye with a sharp stick.

With a bubble dosimeter, for calculation purposes, you need to get the fusor more or less near you optimum run point, then put the dosimeter near the fusor at a suitable fixed range, do a timed run and then count your bubbles. Finally, do the math from there to find isotropic neutron emission rate.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Robert Dwyer
Posts: 89
Joined: Sun Sep 04, 2016 5:34 pm
Real name: Robert Dwyer

Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer »

Sorry for forgetting the pressure. That run, the plasma was lite at 60 microns, but my stable pressure was at 55 microns.

I did that second run with the 13 bubble/mrem detector tonight. The parameters were:

Voltage: 49kv
Current 4.5ma
Pressure: 50 microns
Run Time: 3 minutes

Instead of taking the time over the whole run (once the plasma is first lit, and has ended), I decided to get a stable plasma at the 49kv 4.5ma parameters I wanted, uncompressed the detector, and set a timer for three minutes. This way I would get a more accurate n/s.

I got 25 bubbles in a 3 minute period of time, which corresponds to about 1.1e^6 n/s! I finally hit that mega neutron mark! With these numbers I think I am going to start work on a neutron oven so I can do some activation experiments.
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