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Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Dec 26, 2019 5:43 am
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Dec 26, 2019 1:51 pm
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.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Thu Dec 26, 2019 8:43 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Jan 01, 2020 10:00 am
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Jan 01, 2020 7:22 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Jan 01, 2020 7:48 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Wed Jan 01, 2020 7:59 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 03, 2020 2:26 pm
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)

Jon Rosenstiel

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 03, 2020 3:41 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 03, 2020 5:03 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sat Jan 04, 2020 10:35 am
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sat Jan 04, 2020 9:13 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sun Jan 05, 2020 3:32 am
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sun Jan 05, 2020 3:43 am
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Mon Jan 13, 2020 8:39 pm
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

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Mon Jan 13, 2020 9:11 pm
by Richard Hull
Good Question Jon! I have some 3n6 1/2" rod stock. The alloy sold by many suppliers is to allow for a more machinable product without hampering strength.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Tue Jan 14, 2020 12:42 am
by Jim Kovalchick
Jon, I wouldn't be surprised if it was, but I don't know if the titanium I used was an alloy or not. I bought a small sheet of it at a past HEAS. I think from T.R. Leary.

I'm away from my lab for a while now to check, but I think the sheet had some numbers and/or letters etched on it.



Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 31, 2020 3:57 pm
by Jim Kovalchick
Trying yet another grid. This one is a simple piece of stainless tube. Not a lot of neutrons yet.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 31, 2020 6:23 pm
by Richard Hull
Absolutely lovely!! Too bad about the lagging neutron production. I am glad good old fusor IV is standing by just in case fusor V disappoints me. I have just finished mounting my Turbo, (positioning it and bolting it into place). I hope to test it at its head soon. My fingers are a bit numb in the 35 degree lab. If the turbo disappoints, well, I have the diff pump all cleaned and standing by as well. It is all wait and see while giving the system every opportunity to shine.

Jim, I hope your system climbs over time. Hopefully, some wall effect D2 absorption can work its way into climbing numbers in your system.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 31, 2020 8:12 pm
by Jim Kovalchick
Thanks for the words of encouragement Richard. I'm sure the numbers will come up. Best of luck with your next fusor. Spring and warmer temps are coming soon!

Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Fri Jan 31, 2020 8:52 pm
by Jim Kovalchick
Here is fusor 'outtake '. Arcing from my recent grid while it was conditioning.

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sat Mar 07, 2020 12:39 pm
by Jim Kovalchick
I made a major discovery about why my fusor results were lack luster. A hot connection on my power supply was taking up a lot of the current flow. I corrected the connection and now getting lots of neutrons and my grid heats to red at 6 mA. I did not discover this issue before because I measure my current at my XRT. This picture was taken at 28 kV and 6 mA. Not that I'm happy to see it glow red, but this is more like I expected before. If you zoom in, my phone's picture is very speckled.
Jim K

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sat Mar 07, 2020 1:35 pm
by Richard Hull
Nice picture! I like the red glow. Looks like real power is expended, but that is what fusors do. Too many want power out, but that is not what happens.
I hope to have fusor V on line this spring. I have some ideas that might, just, with some luck, amount to nothing.

Richard Hull

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Sat Mar 07, 2020 1:54 pm
by Mark Rowley
Nice to see it cranking out some good results and am looking forward to seeing your neutron counts.

Fwiw, that's close to the same input numbers I've attained with the 60kV precip supply.

Mark Rowley

Re: Jim Kovalchick -My attempt at smaller fusor

Posted: Mon Mar 09, 2020 1:59 pm
by Jim Kovalchick
An update and a problem.
Update: At 40 kV and 5 mA I am getting roughly 1 million neutrons per second at one end of my cross. Definitely seems neutron readings are stronger at the ends of the electron beams.

Problem: Not a new issue, but as I encounter new voltages, there is initially some arcing until it cleans. With higher voltages, the transients on the system have become more severe. I have fried a couple harbor freight meters and a vacuum gage controller. I also noticed some arcing between hv connections and the shield ends pulled 8 inches back on the ends of the xray cable I am using. I read a paper last night warning about ungrounded ends of shields on xray cables especially where the cable long and coiled. Because xray cable is precious I had been reluctant to cut it. Today I cut 25 feet off it, used only the length I needed, and grounded both ends of the shield pulled 8 inches back from the ends. I did a run in this configuration and found that the few arcs inside the chamber caused less audible noise and my meters recovered quickly until one last arc killed another harbor freight meter. I have this one looking at current by looking at the drop across a 10 ohm power resistor in line with the ground from my XRT. This spot has killed three meters so far. I'm not sure what else I can do.

My power supply is a beefy XRT with a ballast resistor but no cap. The xray cable goes to a voltage divider bucket and then right to my feed through. My terminations are wrapped tight with multiple layers of kapton. I get a slight hiss at the end of the ballast resistor connection at 40 kV but no snapping. My transients start as just grid cleaning arcs that sometimes turn into transients.

My chamber is grounded into a star point which then terminates into a wall box copper ground.

Any ideas are welcome.

Jim K