Jim Kovalchick -My attempt at smaller fusor

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Jim Kovalchick
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Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Holiday's for me mean leaving my apartment in Atlanta and getting back to my permanent home with my wife in South Carolina. That's also where my lab is. So, after a long absence I'm back at it.

I've been inspired by all the success with small fusors, so I'm going to give it a try too. Back when my son Mike was just in middle school (he's a PhD candidate now), he and I scrounged ebay for parts for his triboelectric xray generator. We found a working turbo and controller with a lot of misc vacuum parts sold as a lot. The turbo still sees use, but I wasn't sure we would ever use a CF 6 way cross in the pile. So here it is 2019 and the cross is looking pretty good.

I haven't made a grid yet, but I like the single electron axis pipe grids I'm seeing on the forum. The feedthrough is good to at least 30 kV because that's what Mike ran it too. He wrapped the post with several layers of Kapton, and I'm pretty sure it will do 40 that way.

I hope to get it under vacuum by the end of the weekend with Hope's for Christmas neutrons when I'm home next.

Cheers,

Jim K
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Richard Hull
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

As Jimmy Durante used to say when other actors appeared to out shine him or appeared out of no where........"Everybody wants ta' get into da' act!"

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Richard,
Well, ink-a dink-a doo.

I love neutrons and when I see Jon R pounding silver to 5000 cpm I want to be all about that even if it means copying.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

As you can see from my recent post in construction, I am on my way there slowly with my 6 way cross.

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

I pulled first vacuum on the chamber this morning. A roughing pump that hasn't run since last winter brought vacuum down into uncalibrated single millitorr in less than 15 minutes. Small chambers are fun. I will eventually put it on a helium leak detector but will wait for all the rest of the connections and valves before I do it.
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Even though the current forum problems will probably result in this post disappearing into the ether, I thought I would share my new fusor's first light achieved this morning. My grid is a piece of sheet stock titanium that I formed by beating it around a steel tube. I left a narrow tail on it when I sheared it so I could crimp it to my feedthrough stem. I am not using alumina on the stem because I have found from past experience that it leads to prolonged arcing.

After pumping down the chamber, I set the voltage to -7000 to start and was able to slowly raise air pressure on my chamber using a variable leak valve. Current started nice and low, and I was able to slowly work up the current as arcing subsided. After 10 minutes most arcing was gone.

This was done with air, and I dont expect to use deuterium for some time because most of my swagelok fittings are still MIA from the move.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jon Rosenstiel »

Lookin' good Jim. Hurry up and find those Swagelok fittings and gaskets.

Jon Rosenstiel
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

Great work Jim! You've got guts for posting this, for as you note, it could be gone at any moment.

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Okay I'm a little puzzled over this one. My cylinder grid is throwing off beams in more than the axis of the grid openings. Here is a picture of -13 kV and 10 mA with party balloon helium as the feed gas. You can see the obvious at each pipe end but notice the beam coming towards the view port and the other directing orthogonally to the left. Has anyone else seen this with the pipe grids?

The beam coming toward the view port is fluorescing the glass.
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

Very bizarre. You don't think you have some micro holes in the sheet metal, do you? The near fields in so small a device can get pretty intense. If that keeps up, you will deposit in the center of the view port. What about local heating of the glass? I would watch out for that. If no holes are in the grid it is an amazing thing that one would not expect off a smooth cylinder.

Screen wire placed inside the arm just at the view port would keep the deposition and local heating down I would think .

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Richard,
The two extra beams I am seeing want to run down the center of the arms. Weird.
I am also concerned about the view port glass, but at this voltage and current the view port did not seem hot to the touch even though the chamber was too hot to touch.

I don't think that the electrons are penetrating micro holes, but I suppose it's possible. The titanium is not glowing red at all, even at the origin points of the beams.

I may try higher voltages or a different gas to see if things change.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Maciek Szymanski »

Personally I’d suspect that due to tight packing and quite complex space geometry the e-field is very anisotropic, so you get some focusing of the ions, and the secondary electrons get accelerated so much, that can’t be deflected toward the anode, fall into the cross arm working like a kind of a drift tube and hit the glass. You can easily check the charge sign with a deflecting magnet.

The secondary discharge looks for me like a typical glow discharge with cathode glow and positive column.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Thanks Maciek. The secondary beams remind me of stuff I've seen in higher pressure plasma. I am very curious what it will look like when I take it up the tail of the Paschen curve.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

I did my first d runs last night and this morning.

The plasma in my first run was very blue and was likely influenced by liberation of the party balloon helium from the grid and chamber walls. See blue picture.

The second run plasma was more lavender. I ran for an extended period of time between 26 and 29 -kV and around 4 to 6 mA. There is absolutely no sign of grid heating issues, but I did experience a fair amount of arcing that is gradually subsiding. The arcs played havoc with my instrumentation, and it looks like I may have fried a vacuum gauge controller :(.
At these voltages, xrays were not a big problem except out the view port as expected.

As others have also reported, the chamber pressure is high compared to the same electrical conditions in larger fusors. Much higher and I will be concerned about the turbo. Maybe a diff pump is a better fit.

My neutron indication is not reliable with all the arcing. I do not have a silver foil, but a silver foil did not measurably activate over background.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Third d run tonight.

32 kg and 10 mA. Arcs mostly gone. Neutrons confirmed with moderator removal test. Estimate roughly 200 to 300 thousand per second.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

A couple other notes about the latest run...

Pressure at 32 kV and 10 mA was about 30 mtorr uncorrected.

Also, the fluorescence on my view port is back but no signs of heating. Blowing up a picture of the spot also shows rad speckles on my camera.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

Great pix and great work. I am pacing myself, allowing all the pioneers get the arrows in their backs. I have already been on the first wagon train out to fusion land years ago. Pioneering the small chambers by trusted old boys teaches well. Plus, the unheated lab is no place to while-away the hours. Mechanical pump oil is like paving tar at 20 degrees. I actually burned out a motor's starting winding a few years back trying to force the issue of starting a freezing cold pump. If desperate, I will put a forced air heater on the pump body for an hour. From what I hear, I might just keep the already mounted and functional diff pump. We will see.

Jon and Jim, thanks for the intro to this work. I am sure I will see the twinkling sparks just as I did in 1997 as junk and micro projections burn off the grid, and in these close quarters, probably the sharp arm joints of the cross.

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jon Rosenstiel »

Nice going Jim, and congrats on first neutrons. The cube's pressure while running at 30 kV, 10 mA is around 27 mTorr... quite similar to your setup. And I noticed that the plasma beam coming from the left-hand end of your cathode looks a little thready, may be due to not having the cathode perfectly square (concentric) within your device's bore. (These things seem kind of touchy that way)

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Jon,
My beam is oriented vertically, but unless you open the image by clicking on it, the web page displays it 90 degrees off. Either way, I see the beam you are talking about. It looks like the intensity across the beam makes it look like a double beam. Perhaps you are right that my sloppy set up is affecting the beam. I'm going to leave it for now and see if my neutron numbers improve with more run time.
Thanks

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jon Rosenstiel »

Jim,

It'll be interesting to see what the neutron numbers do with increased runtime. With my cube the neutron numbers changed very little (if any) with increased runtime.

Jon
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Some interesting and bothersome results. At 38 kV and 10 mA I recorded roughly 750,000 neutrons/sec. I noticed that it appears that my neutron probe saw significantly more neutrons at the lower end of my chamber corresponding to one end of the beam. There were some on the opposite end but not as much.

I also noticed my chamber outgases a lot as it heats up. I think maybe it's my titanium grid.

I did a second run at 38 to 40 kV later today and neutron numbers were way down. Even pictures I took were noticeably less speckled. I moved my gas to throttle ratio to flow more d with no improvement. Hmmm.

I have an idea for a new grid design that does not involve titanium and has only one opening...a cup grid. This will have to wait because it's back to the grindstone for me.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

With poor results from my last grid I decided on another approach. This time I used a coil of tungsten braided wire. This grid does not make a tight beam, but I'm happy with the proof of concept. Some minor design modifications should fix it.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull »

Did you get that twin braided W wire from the "orphan pile" at Midwest Tungsten? I picked up 20 strands a few years back of that double twist wire and it has been the grid in fusor IV for about 5 years. Works great!
I enjoy your reports on your project and the issues with the system. It will help me a lot.

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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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick »

Richard,
Yes, from the orphan pile. Sadly, it appears that the orphan pile web page is gone. I gave some of my pieces away and still have a few. They are perfect for our work.

Jim K
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jon Rosenstiel »

Jim,

As to outgassing, was your titanium cathode pure Ti or an alloy? (The one I made was an alloy, 6Al-4V)

Jon R
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