Robert Dwyer Fusor Progress

For posts specifically relating to fusor design, construction, and operation.
Robert Dwyer
Posts: 44
Joined: Sun Sep 04, 2016 9:34 pm
Real name: Robert Dwyer
Location: New Mexico

Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer » Sun Oct 08, 2017 4:47 pm

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:
20171007_162147.jpg
50KV 5mA Power Supply.
20171007_163953.jpg
Inside of the Supply
20171007_171352.jpg
Modified RG-8
As of right now, this is what my whole setup looks like:
20171007_174654.jpg
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
If we throw more money at it, it will have to work... right?

User avatar
Dennis P Brown
Posts: 1202
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Robert Dwyer Fusor Progress

Post by Dennis P Brown » Sun Oct 08, 2017 7:48 pm

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.

User avatar
Richard Hull
Site Admin
Posts: 10400
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Robert Dwyer Fusor Progress

Post by Richard Hull » Mon Oct 09, 2017 6:19 am

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Robert Dwyer
Posts: 44
Joined: Sun Sep 04, 2016 9:34 pm
Real name: Robert Dwyer
Location: New Mexico

Re: Robert Dwyer Fusor Progress

Post by Robert Dwyer » Tue Oct 10, 2017 2:20 am

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.
Screenshot_2017-10-09-15-44-07.png
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
If we throw more money at it, it will have to work... right?

User avatar
Richard Hull
Site Admin
Posts: 10400
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Robert Dwyer Fusor Progress

Post by Richard Hull » Tue Oct 10, 2017 3:45 am

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

User avatar
Dennis P Brown
Posts: 1202
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Robert Dwyer Fusor Progress

Post by Dennis P Brown » Tue Oct 10, 2017 10:57 am

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.

Post Reply