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Re: Wait, what? Tiny fusors? Not for me!

Posted: Wed Dec 27, 2017 5:34 am
by Finn Hammer
When the voltage in a circuit exceeds 20 - 30kV, field control becomes a game changer, and the key word here is radius of curvature.
Why is that?
The object is to avoid flash over in the form of arcs, or discharges into the surrounding air in the form of corona.
These things appear in the reverse order, without corona, there are no arcs. So fight corona and you will contain your charge.

One good way to control the field gradient of an electrical connection is with the use of toroids, below is the way I suggest it should be done, at least it is how I intend to do it when I get so far.
Dual toroidal field controll
Dual toroidal field controll
Cheers, Finn Hammer

Re: Wait, what? Tiny fusors? Not for me!

Posted: Wed Dec 27, 2017 7:10 pm
by Richard Hull
Field control is the answer and I have written extensively on this in the past. I purchased a nice hand spun 4" diameter, copper toroid from John Freau at the 2012 HEAS. I purchased another aluminum 4" toroid from John at this past HEAS gathering in October. I currently use a 2" ball on fusor IV but will probably use the 4" toroid on fusor V, if it ever gets built. I kill corona at the 2.75: conflat bolts just below the insulator terminal with silicone HV putty wadded over the cap head screws. My past 1990's decade of Tesla coiling experience taught me all about "practical" field control.

See the image attached on how to not arc along a 12 tall coil with 50 kv at one end and 1.2 megavolts at the other....in air!!

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Wed Dec 27, 2017 10:11 pm
by ian_krase
Can you tell me more about these balls? Is anything inside them? Do they enclose the connector, or get drilled for a banana plug?


Has anybody pulled off fully insulated HV connections?

Re: Wait, what? Tiny fusors? Not for me!

Posted: Wed Dec 27, 2017 11:45 pm
by Richard Hull
The ball on fusor IV is just a hollow chrome ball with an internal banana jack. My HV cable is not shielded at all but is a 50kv rated silicone HV wire with a banana plug on the end. This just pushes through a concaved hole in the ball and into the banana jack. No corona at 50kv. A ball is never as good as a toroid but 50kv is a rather low voltage and as long as there is no corona or sharp grounded components within 3 inches and the ball is kept meticulously clean of dust and grime, there is little chance of a DC arc.

There are many images of fusor IV in images du jour.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Thu Dec 28, 2017 6:00 am
by Dennis P Brown
When you ask:
Has anybody pulled off fully insulated HV connections?
I assume you mean a near zero corona, fully insulated connection? If so, I have done this for all internal connections for my fusor power supply by building all diodes and ballast resistors/connections under oil. Simple, cheap and easy. This method also eliminates humidity problems. A minor advantage - I can use normal wire and connectors to assemble some components since, when under oil, they are fully insulated. Saves me money and lost power from the x-former.

As for 'messy', I've had no issues in this regards because I allow these devices to drain overnight; if in a hurry, I just rinse with 90% alcohol and use lint free rags. The oil (synthetic motor oil; anti-corrosion additives improve the oils dielectric properties further so they are actually better) is very cheap (compared to most x-former oils) and easy to obtain just about anywhere. Do not use regular motor oil.

There is a link to the photo of the insides of my full wave diode bridge and return current resistor for the x-former system (oil not yet added to diodes.)

download/file.php?id=10789&mode=view

Here is the complete assembly, with oil and covered. The small oil pan item on the left is my main output ballast resistor with its main power cable connection all under its own oil bath:

download/file.php?id=10788&mode=view

This system has performed without issue for some time now. I get zero corona issues and no flash over problems (a good idea to prevent this from happening to your HV diodes. Also, really keeps diodes cool which is very important - esp. for the ballast resistor to dissipate heat during long and/or heavy current operation.)

For a large vertical insulator column, wouldn't be too difficult to add a cup for oil if one does not want to deal with machining or buying sphere's or other or shaped brass/copper adapters; and these metal items can still have issues on very humid days. Nor is dust then an issue. Also, provides a nice and almost fool proof physical reminder barrier to the HV terminal.

While I just bury my main fusor connector (just 32 kV) in a ceramic case, for really high voltage (over 50 kV), whenever I deal with those levels I always go with oil since, again, eliminates humidity and flash over problems and creates a safer system.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Thu Dec 28, 2017 7:44 am
by Jim Kovalchick
As far as the ticking I was experiencing, it went away after I peeled the shielding on my hv x-ray machine cabling a few more inches back. I also rewrapped my insulation tighter and thicker with polyimide tape. I use polyimide on all my exposed conductor points. I have tested this on my new fusor under load to 40 kV with no corona hiss to speak of.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 01, 2018 2:55 pm
by Jim Kovalchick
A few updates for my fusor:

1. I did some runs with deuterium, but even at elevated voltage the neutron numbers were dubious at best.
2. With deuterium versus air in addition to neutrons I was expecting a plasma color change from air and higher pressure Paschen points. For a given voltage the Paschen point was only a few milltorr higher than air. The color was more blue than the pink I was hoping for.
3. All of the observations pointed toward an air leak polluting my plasma. Reluctantly, I broke vacuum and connected my helium leak detector. My home made feedthrough has developed a leak at the stem. My guess is that heating impacted the stem seal. I will need to make a repair.
4. I've been using the neutron detector I demo'd at HEAS. I had it tuned for the SK-1 clicker such that it would only sound on neutrons. Here in my lab I have it connected to NIM components, and I have the ability to adjust its threshold. I noticed that my detector, which uses the LiI element out of a NeutronRAE, easily sees x-rays above 28 kV. So for folks using NeutronRAEs for neutron detection you will need to demonstrate x-ray discrimination before claiming fusion. I am using the 59 keV gammas out of Am 241 to set my threshold.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 01, 2018 6:17 pm
by Richard Hull
Jim, Thanks for passing on the x-ray issue with the neutronRAE detection system. Fortunately the detections of same can be discriminated out of the data

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sat Jan 06, 2018 1:23 pm
by Jim Kovalchick
I'm still having trouble getting neutrons out of my fusor. I'm troubleshooting my detector, but I decided to also do a little glow cleaning. Here is a pretty picture of some liow voltage deuterium plasma 4000 V and 10 mA.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sat Jan 06, 2018 3:43 pm
by Richard Hull
Just from what I see, you are basically clean and it is just a matter of a bit more operation and hitting the higher voltages of 30kv with a pressure as low as 5-6 microns and 8ma and you had better be counting. The real rock and roll will be obvious at that pink glow with 35kv or more at 10 microns and 10ma. (kind of a 500k n/s zone). All the best in moving upward. To hit the mega mark on fusor IV, I must be over 40kv applied, 12+ microns, 12 + ma. At this point, most the rays are gone or very faint.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sat Jan 06, 2018 7:55 pm
by Jim Kovalchick
-38 kV, 8 mA, 6 millitorr

I'm convinced my neutron indication is the issue. Our PNC-1 is on the blink, but I think I can connect its BF3 tube to a scaler.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sun Jan 07, 2018 11:25 am
by Richard Hull
That is a little Nancy Woods tube, but BF3 is a the best detector of neutrons after the 3He tube of the same size. The PNC-1 uses a good paraffin moderator. Good luck.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sun Jan 07, 2018 12:40 pm
by Jim Kovalchick
This morning I finally confirmed neutrons from this latest fusor. I used the BF3 from our PNC-1 and the standard PNC cad covered parafin block moderator, but connected to an old Ludlum 2200. At 38 kV, 8 mA, and 5.9 mtorr I measured 300 cpm well over a foot from the fusor center. The moderator pull test passed with flying colors because the bare tube placed directed on the shell of the chamber went down to near zero cpm. The ultimate proof was activation of a thin piece of silver solder to 40 percent over background. Im sure I will get better activation numbers in future runs with better material and geometry.

My estimate of neutron production is rough at best, but right now I think at least 750,000 per minute. The same tube measured 400 cpm on Richards fusor running at a million a few years ago at a HEAS. I could get closer to Richard's poisser, but the electronics are different this time.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sun Jan 07, 2018 8:44 pm
by Jim Kovalchick
An evening run of my fusor at 39 kV and 8.5 mA yielded 400 cpm on my BF3 tube. Given the distance from the chamber and comparison reading of the same tube at Richard's I am estimating that my fusor has passed the 1 million neutron mark.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 08, 2018 9:35 am
by Richard Hull
Great work!

The little BF3 tube did yeoman duty once hooked to the Ludlum. I have stored away in my lab, somewhere, a rather large BF3 tube that I bought in the late 90's from Don Orie of O.E. Technologies when he offered an attractive little box of assorted color quarks in his printed catalog. We all miss Don's surplus mecca. To my knowledge he was the only source of fully warranted surplus neutron detection tubes. With e-bay it is always a pig in a poke.

This big BF3 tube is about 2.5-inches in diameter and well over 2 feet long! I obtained my 3He tube so soon after the BF3 that I just tucked it away. (somewhere...Or I might have even sold it at a long ago HEAS gathering and forgot).

Continued best wishes on what will surely be improved operation. I am sure you can hit the two mega mark in future.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 08, 2018 10:54 am
by Jim Kovalchick
Thanks Richard. At this point achieving big numbers isnt among my primary goals, but they will help. I am particularly interested in doing some activation and fiddling with alternate neutron detection methods.

Next steps - not necessarily in order of priority
1. Shielding - I am at the point where the xrays are disfunctional and will become hazardous. I will be looking into some shielding that will make my lab safe without limiting easy access to controls. I believe my xrf, feedthrough, and chamber can do some more volts if I add the right amount of lead. I also believe that good shielding is much better than electronic discrimination when it comes to sorting neutrons from photons.
2. Improve my installed neutron indication. The geometry and thermalization I'm using are not optimal.
3. Improve the dimensions and geometry of my neutron oven.
4. Spend a little less time in the lab and more with my spouse. The holiday push to the mega mark caused some understandable grumbling.
5. Improve my gas control. I am currently using an old variable leak valve that experienced some corrosion in a former life. It has beautiful fine control except there is a spot in its span that seems to pass extra flow causing me to juggle both it and the main vacuum valve as I pass through it.
6. Rebuild the grid. I have managed to avoid sputtering my tungsten all over the chamber, but I'm afraid I wont always be so lucky if I stick with my current conductor. I have procured some stranded tungsten from the orphan bin at tungsten.com for this purpose.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sat Jan 20, 2018 7:22 pm
by Jim Kovalchick
I was able to fix my variable leak valve. Turns out that if the screw drive is slightly misaligned it can momentarily reverse act. A simple adjustment fixed the issue.

Now that I have smoother gas control to walk up my voltage I toyed with some longer 40 kV operation. Tonight I sandwiched a one ounce silver coin in some hdpe and stuck it next to of the base of my chamber for about 10 minutes at 40 kV and 8 mA. After shutting off the power and closing the gas, the coin still was more than three times background on a pancake Geiger. This makes me happy.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sat Jan 20, 2018 11:41 pm
by Richard Hull
That kind of activation is typical of what I get at 750,000 n/s + +. You are fusing big time! More, from this point, will be easy.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Sun Jan 28, 2018 7:01 pm
by Jim Kovalchick
My current grid gets a little thermionically unstable at the high end of my operating range. I would like a little more current and voltage so I am pondering a new grid. I haven't installed it yet, but this one uses heavy braided tungsten instead of single strand. This also only has two loops because the heavy nature of it makes my crimp construction more than awkward. Opinions welcome.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 29, 2018 12:36 am
by Richard Hull
I have used a simple two loop tungsten grid for 4 years. It looks like your grid in the photo. We all know I can and have done good work with this simple grid. A complex geodesic sphere looks really nice and gives off many star rays, but I doubt it will do much better than a well done two loop grid.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Jan 29, 2018 7:15 am
by Jim Kovalchick
A few more notes on the grid construction techniques I am using:

1. I wasn't sure at first how I was going to cut the braided tungsten. I have a hard enough time getting good cuts on single strand tungsten. You can't use cheap wire cutters because it will chunk your cutting edge. To my pleasure, I was able to buzz through the braided stuff with a 1-1/2 inch Dremel EZ lock cutoff wheel for metal. It goes through in seconds. No expensive diamond wheel needed.

2. I make my own crimps for the grid wires and stem connection using a segment of steel tubing. I cut it off with the same cutoff wheel. I make a double segmented crimp by a perpendicular cut about two thirds through and then a cut along the full length of the crimp. This allow me to fasten the grid wires at the base independently of the stem. I cut one end of each loop a little shorter than the other so it extends only through the first segment of the crimp. The other ends will extend through both segments of the crimp so they make up with the stem when I tighten the crimp.

If you use my crimp technique, be sure to clean all burrs and edges before you use them in your fusor. Otherwise, you will spend a long time trying to burn them off with frustrating sparks and arcs.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Mon Feb 12, 2018 3:25 pm
by Jim Kovalchick
Tried to break in my new grid today. Still a little noisy nearing 40 kV but starting to settle below that. Neutron numbers are improving with this grid's ability to take current. At 38 kV and 12 mA my BF3 tube was around 700 cpm. My rough estimate is 1.7+ million neutrons/sec.

Re: Wait, what? Tiny fusors? Not for me!

Posted: Tue Feb 13, 2018 2:10 am
by Richard Hull
Jim what was the pressure? Real good reporting will always supply: voltage, current and pressure of the D2.
Voltage tells where you are in cross section.
Current tells how many ionizations, (hopefully deuterons), you have.
Pressure tells how much fusion fuel you have in the chamber.

Richard Hull

Re: Wait, what? Tiny fusors? Not for me!

Posted: Tue Feb 13, 2018 5:42 am
by Jim Kovalchick
Richard, I dont watch pressure much during runs because I don't control by it. I recall around 7 mtorr when I was done. That number is uncorrected for deuterium.