Wait, what? Tiny fusors? Not for me!

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

Post by Richard Hull »

That might be one of the best looking chambers to be presented here in years!! Keep us up to date on your progress. I am fairly sure that there is a significant UV component in a fusor. Vacuum UV can only be found in such systems. Any dangerous UV would never leave the system, of course, without a Quartz window.

All the best in getting this plus-ultra system on line.

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

Post by Silviu Tamasdan »

Well _some_ UV is bound to escape, depending on intensity and wavelength. Glass is to UV what lead is to gammas, they get attenuated but not completely absorbed. That's the problem with photons, you can never get rid of them completely.
There _is_ madness to my method.
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Dennis P Brown
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Re: Wait, what? Tiny fusors? Not for me!

Post by Dennis P Brown »

Regular plate glass cuts off essentially all hard UV (UV-B) and one need not worry about that spectrum at all (say about 330 nm and shorter.) That said, do be aware that both UV-A even to Blue-Green ... say down to 450 nm can be harmful to the eyes (apparently, the new very white LED's street lights can damage the eyes); however, little of those wavelengths are usually produced via a plasma in a fusor. If one is using a Hg source, plate glass is rather effective cutting off most the harmful wavelengths.
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Jim Kovalchick
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Re: Wait, what? Tiny fusors? Not for me!

Post by Jim Kovalchick »

Final holiday update
I used a helium leak detector to locate some CF torquing issues, but a fairly bad leak remained. I never thought to pass a little helium over a KF 40 bellows hose I was using to connect to my turbo. When I finally hit it, it was a huge hit on the leak detector. I have temporarily replaced it with hard pipe. I was able to remove the leak detector and roughed the chamber to less than 10 mllitorr in five minutes. Isolated, the chamber rises less than a milltorr a minute. This is all before any bake out. I think my chamber is ready for plasma.

Next steps after the holiday - clean up the construction mess to make the lab safe, get my power supply ready, and get some current and HV indicators attached.
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Dennis P Brown
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Re: Wait, what? Tiny fusors? Not for me!

Post by Dennis P Brown »

Yes, bellows can be a tricky issue since they are easy to overlook; while sorry to hear that, still, I am glad you have a tight system now - the bake out will certainly and dramatically lower the out gassing rate. I use dry air to purge my accelerator to better enable it to get into the low vacuum range more quickly; that or argon might be useful for your chamber if you decide to go ultra high (below 10^-6 torr.)
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Richard Hull
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Re: Wait, what? Tiny fusors? Not for me!

Post by Richard Hull »

Great work and what a beauty. That is a system to be proud of. I'll bet it will kick butt and easily hit the mega mark with ease in the 35-45 kv range.

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

Post by Jim Kovalchick »

First light for this chamber.

1. Started at -8 kV with air.

2. Walked voltage to - 17.8 kV holding about 8 mA.

3. Need to rework HV cable because I heard some ticking from the cable near tbe feed through at peak voltage. Probably dont have the shield stripped far enough back.

4. One of my grid wires shifted a little when it warmed, but otherwise there was only minor and brief arcing as I stepped voltage.

5. I don't think this is a surprise to anyone but the uranium glass marble did glow a little. The glow doesnt show up well in the photo.
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Dennis P Brown
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Re: Wait, what? Tiny fusors? Not for me!

Post by Dennis P Brown »

I discovered the hard way that 30 kV will go a long way along an insulated cable and reach the shielding strap (and I had carefully cleaned the cable after striping away the shielding); a good four inches was needed, so I ended up removing 8". In the HV cabinet, I even placed the cable end under oil for the ballast resistor connection to play it safe.
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Re: Wait, what? Tiny fusors? Not for me!

Post by Jim Kovalchick »

Dennis,
I just atripped back about 8 inches where there was only 4 before. This seemed to do the trick up to -40 kV. This is the highest voltage I've ever spent any time at. It made a nice tight spot of plasma.
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ian_krase
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Re: Wait, what? Tiny fusors? Not for me!

Post by ian_krase »

Allegedly, folding back the shield, possibly over an O-ring or similar, rather than just cutting it can also help. That is what I did, and while I had corona I never had arcover at 50kV just from the end of my cable.
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Finn Hammer
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Re: Wait, what? Tiny fusors? Not for me!

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

Post 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
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Magnifer 10E  real field control 50kv to 1.2 Mev 1 foot separation!!
Magnifer 10E real field control 50kv to 1.2 Mev 1 foot separation!!
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: Wait, what? Tiny fusors? Not for me!

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

Post 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
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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Dennis P Brown
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Re: Wait, what? Tiny fusors? Not for me!

Post 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.
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Jim Kovalchick
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Re: Wait, what? Tiny fusors? Not for me!

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

Post 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.
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Richard Hull
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Re: Wait, what? Tiny fusors? Not for me!

Post 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

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

Post 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.
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Richard Hull
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Re: Wait, what? Tiny fusors? Not for me!

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

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

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

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

Post 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.
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Richard Hull
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Re: Wait, what? Tiny fusors? Not for me!

Post 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
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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