Custom Fusor Power Supply

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Wed Mar 17, 2021 3:58 am

Over the past three days I’ve literally thrown the kitchen sink at the supply and have had no reportable performance issues. Collectively, it’s now got about two hours of run time and has incurred two 30 minute non-stop operational runs.

Tonight I decided to “destroy” the supply by running it full tilt (saturation point of the rewound MOT which supplies the driver). Well, it wouldn’t fail, just kept going and the neutron numbers just kept climbing. The maximum raw CPM/N on the Ludlum 2221 was over 23,000. Based on this fusors ability to load, I’d suspect tomorrow’s run will be in the mid 30k range.

So far the value of the multiplier caps are remaining true to their specs. But tbh, I really don’t care if one blows out at this point. Each capacitor is about 50 cents, so if I have to replace one every now and then it’s no big deal. Additionally, it’s modular design makes for a 10 minute process to replace. The performance to capacitor replacement ratio is well worth it...providing its ultimately required.

Now the real difficult stuff begins, getting the gamma spec system up and running. We built a new computer a month ago and the sound card isn’t working well with the MCA software. The ultimate goal is to activate Molybdenum and detect Technetium via the MCA, so that’s now priority.

Here’s the latest run with the flyback supply. Please excuse the clutter, I know it’s a mess:

https://youtu.be/arbNemCBjho

Mark Rowley

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Richard Hull
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Re: Custom Fusor Power Supply

Post by Richard Hull » Wed Mar 17, 2021 4:07 am

Great work and a great supply. Nice video. You continued removal of the 3He tube from the moderator is great. All newbies need to take special notice of this wonderful proof of fusion with a thermal neutron detector as "running proof" that you are fusing. It looks like you have a super supply that is fully capable. Again, great work.

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.

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Dennis P Brown
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Re: Custom Fusor Power Supply

Post by Dennis P Brown » Thu Apr 08, 2021 8:19 pm

A really impressive feat on the PS. Good pics. Also, could you supply a schematic of your power supply?

A pic of the fusor and overall system would be nice, too.

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Fri Apr 09, 2021 1:26 am

Thanks Dennis
The fusor hasn’t changed at all. It’s the same as listed in the original threads.

viewtopic.php?t=13503

viewtopic.php?t=13536

Regarding the schematic, I really dont have one as it’s assembly is extremely basic. On page one, you can see the basic outline of the components which almost by itself is a perfect schematic.

In a nutshell, it’s just 4 custom AC flybacks being run in parallel. The outputs are individually fed into separate single stage multipliers. The outputs of the multipliers are placed in series providing the 60kV.

As Richard correctly pointed out, the ceramic capacitors do tend to loose some value after lengthy run times. However, nothing to the point where performance was compromised, at least to a noticeable level.

Twice now, I’ve intentionally pushed this design to the point of destruction. The last failure occurred at ~89kV / 5mA. A arcover condition occurred in the #4 multiplier causing a surge that took out half the diodes. Zero damage to the flybacks, ZVS driver, or caps. The diodes were rated at 20kV (which is ok for the multiplier circuit) but the almost 90kV arcing over made the diodes easy pickins. Being that I designed this to be a 60kV supply, the failure is actually a success. A success that under harsh conditions the flybacks survived as well as the driver. Replacing the diodes only took about 30 minutes and it was good as new. I’m fairly pleased as it’s proven to be a very stable design for 60kV.

I’m currently in the process of making a couple design changes that may or may not make a difference. First, each multiplier will be changed from half wave to full wave. And secondly, I’m replacing the ceramic caps with 2nF 30kV poly/foil types. As with the ceramics, I’ll be periodically checking the values for any signs of degradation.

Once reassembled I’ll update.

Mark Rowley

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Bob Reite
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Re: Custom Fusor Power Supply

Post by Bob Reite » Sat Apr 17, 2021 9:41 pm

You might be able to get away with smaller capacitors if you switch to full wave, as the ripple frequency will now be doubled.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Mon Apr 26, 2021 6:44 am

Finally got around to building the multiplier module with the new axial poly caps. As before it’s a very basic arrangement except that this version is full wave and a bit bigger due to the larger caps.

597B8658-D664-40EA-A0F4-F77427C1606B.jpeg

FC29DAE2-4F84-49C6-B279-EFF6774829BE.jpeg


Had just enough time to conduct a brief 10 minute test run with the fusor. Operationally I didn’t notice much difference but it does seem to have a slightly higher voltage ceiling. Over the next few weeks I’ll focus more on long term sustained runs as opposed to pushing it to the point of failure.

Mark Rowley

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Dennis P Brown
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Re: Custom Fusor Power Supply

Post by Dennis P Brown » Mon Apr 26, 2021 10:53 am

Very impressive build and I really like the clear box for the VM system and x-formers.

One suggestion for the future (well, two.) Use balled solder joints for joining wires and do away with sharp corner metal nuts where ever possible (I use plastic hardware.) Even under oil these issues can lead to problems for long term high voltage operation.

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Mon Apr 26, 2021 6:02 pm

Thanks Dennis
Those clear containers are actually medical radioisotope lock boxes. Very thick plastic and 100% leakproof (as mandated by hospital regs). By sheer luck the size was perfect and the need for modifications was minimal.

Another mod on this go-around was the addition of fused quartz insulator sleeves between the primary windings and the cores. I also elected to rewind flyback #4 while saturating the wire in Alumalite epoxy resin. Very little air (if any) is within the windings. Expectedly, this mod alone almost doubled the output of the flyback. As stated earlier I wanted to avoid that type of arrangement as it makes coil repair almost impossible. I used a different method of winding this time which may allow for repair... hopefully such a repair won’t be necessary. The flybacks have actually held up nicely unless I push them way beyond what I designed them for.

If I end up doing major surgery again I’ll try the blob method on the solder joints. There are only two areas where this could be mostly beneficial.

Mark Rowley

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Tue Apr 27, 2021 2:53 am

Conducted a sustained 30 minute run this afternoon at roughly 1.5E+6 n/s TIER. No signs of problems so this just may be the final iteration for awhile.

This is a video of it powering the fusor during the aforementioned run. The noise in the background is the Ludlum 2221 counting the moderated neutrons.

https://youtu.be/gGG1GeDi3nw

I have some larger ferrite cores I may try this upcoming summer but for now I’m fairly pleased with its performance.

Mark Rowley

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Mark Rowley
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Re: Custom Fusor Power Supply

Post by Mark Rowley » Wed Jun 09, 2021 3:55 pm

It’s been about 6 weeks and roughly 20 runs since the last update. No problems with performance and the poly caps are holding up perfect with no change in value.

In the meantime I’ve been experimenting with some different flyback cores as well as epoxy encasement. Initially, epoxy was off the table as it eliminated the possibility of any repair to the windings. However, since the supply has been tested under adverse conditions which would normally obliterate a commercial precipitator unit, it’s concluded the larger gauge windings and stronger diodes removed most of that concern. For comparison, I wound an identical flyback but this time encased the windings in Alumalite brand clear epoxy. By doing so it almost tripled the voltage and current capacity over a non-resin flyback which only used mineral oil as an insulator.

This opens the possibility of completely removing the multiplier circuits and running four rectified ~20kV custom flybacks with the outputs directly in series. In theory, this should greatly increase the current capabilities of the supply.

Mark Rowley

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