Archived - Frank Sanns Levitated Pit Fusor

[Frank Sanns]

My fusor rebuild contiues forward.

The first picture shows the fusor from the front with a second HV feedthrough added.

Photo #2 is a look straight down into the fusor (ignore my feet and the clutter).

Photo #3 is the levitated pit. A fusor within a fusor if you will. Both grids are isolated from the outer shell and from each other. Two pyrex hemispheres optionally help electrically insulate the 5" (13 cm) outer grid from the outer 10" (25 cm) chamber walls. The upper hemisphere is removed in the photo. Ultimately I will most likely slip cast a ceramic hemisperical insulator if the technology works. The inner grid is 2" (5 cm) but a little hard to see in the photo.

The second feedthrough really increases the versatility of the fusor. It allows for a bias to be on the outer grid. It allows for the center grid to be grounded and the outer grid to be positive HV. It also allows the grids to be oppositely fed with HV. This later case is what I desiging to run. I have two 50 KV supplies of opposite polarity so I will be able to run 100 kv with modest power supplies and feedthroughs. The outer grid will then be positive HV and the inner grid will be negative.

There are a couple of other configurations that will be apparent in the near future but that is the status at the moment.

Frank Sanns

[Steven Sesselmann]

Frank,

I like the look of this....

So I assume the outer grid rests in the pyrex bowl, and your intentions are to have the outer grid positively biased relative to the vacuum chamber.

Will the inner grid (if there is one be held by the electrode?

Steven

[Chris Bradley]

I presume the pyrex hemispheres are not intended to be sealed, but only to slow down the ion losses to the outer grounded shell.

A small gap may be of no issue at all - positive ions that flow outwards from the 'outer grid' would, initially, surely charge the pyrex up, eventually causing the pyrex to be a 'positive sheath' around the whole inner ball assembly. Small physical gaps would not disrupt its e-field significantly.

But I'm not sure what'd happen after that initial stabilisation stage, particularly to electrons running out to the outer grid and on to the pyrex bowl. Some flux balance would have to occur, it'll be interesting to see, and those electrons escaping the gap would ionise some of the outer volume, with the ion products then heading off to the outer grounded shell.

What is your view on the dynamics of this configuration?

[Jon Rosenstiel]

Great idea, Frank. I’m really curious as to what effect (if any) this will have on Bremsstrahlung. Please keep us posted.

Jon R

[Frank Sanns]

Steven,

Outer grid will be biased positve or with RF. Inner grid will be zero or negative.


Chris,

Pyrex bowl should stop recirculation of ions outside of the outer grid. Removing it should alow it. Results should prove interesting.


Jon,

Not sure what the x-rays will do. The only place that will see 100 kv will be the outer grid and there is not much of it so I would say the x rays should be everything you would see with a normal fusor at 50 kv plus the proportion of closed aperature of the outer grid (~12%). This should result in an x-ray flux roughly 70% lower than a 100 kv standard fusor. I don't think the glass will do too much.

Frank S.

[Carl Willis]

Hi Frank,

Nice to see you get back in the game with this innovative upgrade. Sometimes having to rebuild is a blessing in disguise...

My guess may be pessimistic, but I think there will be a lot of electron beam heating that will crack the bowls or melt them and render them locally conducting, with interesting visuals but no real performance advantages.

Having the bipolar grid arrangement is a good idea for sure. You should get some much-improved neutron numbers now that you can effectively double the max accelerating voltage.

-Carl

[Dustinit]

Very interesting setup,
Looking forward to some interesting plasma pix.
Dustin.

[Frank Sanns]

Hi Carl and Dustin,

I agree that electron beams will most likely prematurely take the lives of my $4 each pyrex bowls but they are easily removable and are an interesting addition to the experiment.

The chamber is all buttoned up now and I am plumbing the vacuum so results and photos should start to filter in soon. My biggest hurdle now is another HV lead for the 2nd power supply. Guess I will be putting some connectors on some 9913 coax.

Frank S.

[Richard Hull]

Frank, Good looking rig there with lots of explanation as to your plans. I archived this work. I'll go along with predicting a short life for the bowls in real fusing operation. Glass just doesn't stand a chance when real fusion is going on, again as carl notes, it's the e-beams, (waste electrons), at the higher energy needed for fusion that does in glass.

I had a scary experience in fusor II, (bell jar) as it drifted into my only early attempt to do fusion in a bell jar. I am sure I did fusion but would not claim it as the run was too short and I realized instantly that fusion would not be done in glass on any kind of useful sustained or future experimental basis. Fusor III was quickly cobbled up and did recorded fusion 1 week after first plasma.

I look forward to your effort and reports on the operation. I hope those bowls last long enough to obtain definitive results, what ever that might be.

Richard Hull

[Frank Sanns]

The levitated pit fusor is now exhaling neutrons . During some shakedown and learning runs, the fusor was well behaved and did not melt the pyrex at 60 kv differential and 1 ma current but this is really low power. The plasma is not quite the same as in my normal fusor configuration and I will post some deuterium fusion stars and some neutron vs voltage numbers as I contiune to ramp up power.

Here are some low voltage start up experiment photos that were quite interesting.

Photo #1 Setup for Fusion run. Top supply is negative bottom is set to positive.

Photo #2 Low voltage behavior with outer grid grounded and inner grid at -800 volts.

Photo #3 Low voltage behavior with outer grid electrically floating and inner grid at -800 volts. This shows the effect of the pyrex insulator.

When the inner grid floats and the outer grid is +800 it looks just like photo #3. When the inner grid is grounded, it looks like a hybrid of photo #1 and #2 but as voltage increases as the pressure drops, the behavior looks like photo #2.

More to come.

Frank Sanns

[Mike Beauford]

Hi Frank,

Interesting experiment. Can you tell if the pyrex is heating up alot in any of the sections where it is glowing?

Mike

[MarkS]

Interesting experiments! In photo #2 on the left side of the bowls, is that infrared light, or is there a green light showing on the bowls. In photo #3 what are the glowing specks?

[Frank Sanns]

I should have elaborated on the photographic technique in these pictures but I sometimes erroneously try to keep my posts short.

It is very dark in a fusor except where the plasma is visible or where it illuminates the fusor and from the inside out. This gives pretty blues and reds but is not the best to show the components inside the fusor. It was important to me to show all of the interal elements of the fusor so all of you could understand what you were seeing. For this reaason, I used a small incandescent bulb flashlight to shine into the chamber to provide enough light to illuminate the components but not to much as to overwelm the plasma glow.

What you are seeing is the pyrex bowl getting most of the light on the left side and looking green just like it would sitting on a table. The lattice grid is gold color and gets the light that is also coming from the flashlight. The color temp of my camera was set to 5700 K.

The inside of my chamber has residue on it. I buffed some of it away but I probably should have had it all repolished. You are seeing the remnants of some backstreaming and debris that has deposited on the inside of my fusor after many a varied experiment; most of which have never been posted here. This particular debris is fluorescing from electron beams and/or UV light.

No localized glowing or visible heating of the pyrex has been seen but my maximum power to date is just a little over 60 watts as I get my feet wet with this design. I know many of you are thinking "turn the power up and see what you got" but that is not where the science is done. It is done spending hours making small adjustments of vacuum, voltage, and power in a slightly asymetrical design and studying the effects. I learn more in the slow mode than I ever would by just setting everything up for one maximum run from the start.

Frank Sanns

[Frank Sanns]

Update on the Levitated Pit Fusor .

The Levitated Pit Fusor configuration uses two oppositely charged inner grids and a grounded fusor shell. In this photo, the inner grid was run at -30 KV and the mid size lattice grid was run +30 KV so the fusion energy inside was a full 60 KV at 5 ma.

Outside of the pyrex bowls that are fluorescing green, is very little visible plasma. Also present on the inside of the pyrex bowls and on the aluminum lattice grid are waves and waves of fluorescent pattern that are visible in the runs. No melting of the pyrex yet.

There are a few striking observations that I have made. For one, the x-ray blast through my viewport (without the leaded glass inner shield) was nearly non existant. It seems this configuration is very robust to keep x-rays at a minimum. This is due in part to the pyrex bowls serving to be great x-ray shields due to thier thickness. It is also partly due to the dual polarity electrode configuration which keeps the net potentials at only have the fusion potential.

After running the fusor for quite some time, my neutron counts were well below a normal run for me and well below what I expected at these voltages. The neutron counts were down in the high 10 E 4 range. Even the bubble detector was in slow motion. I thought it was that pyrex has boron in it on the order of 4% so I have effectly placed a neutron absorber around my neutron production zone but boron only shields slow neutrons. It is probably because there is so much surface area from all of the stuff in the fusor that it will take much longer to outgas and condition.

The configuration works really well and I hope to be pushing into 100KV+ territory very soon.

Frank Sanns

[Mike Beauford]

Nice pictures Frank, this is a neat idea. Not sure why your seeing such low numbers either. Even with 4% boron in the glass, it shouldn't be stopping the neutron's that much. I'm wondering if you can do a test and reconfigure without the glass and just run your inner loop to get a set point for a neutron count to help determine if its the cause or not?

Mike

[Frank Sanns]

Mike,

I am going to try a 100 kv run first but then I am going to remove the upper pyrex bowl. This should give some good insight into how the bowl affects ion circulation, insulation to the outer shell.

In addition, leaving only the bottom half of the bowl will alow more visual and metrological information be gained. With the top half of the glass envelope removed, x-ray and neutron data will be available from the top and bottom hemispheres of the fusor durning a single continuous run. This should give really good statistical data on the effects of the bowl.

Frank Sanns

[Chris Bradley]

Frank S. wrote:
> My conclusion is that pyrex has boron in it on the order of 4% so I have effectly placed a neutron absorber around my neutron production zone.

So, do you think there is any chance my earlier posit might explain the lower neutron count? If the initial electrons charge up the pyrex bowl, then perhaps it may reach a potential lower still than the inner electrode (thus will pull viable ions out that get into the region where such e-fields will diverge) rather than in? If this were true, then if you were to wrap some foil around the outside of a bowl (or both) and ground that, then the dielectric fields in the glass (which I don't think will act as a pure insulator with that much electron bombardment anyway) will result in a more favourable field structure within them - namely more positive on the inside and thus directing ions back to the centre.

Just a thought - and possibly the means to test it...

[Starfire]

Great system Frank - my daughter had used Pyrex bowls in her Fusor but found them difficult to seal - she used them for the vacuum chamber with plastic bowls to give some protection.

viewtopic.php?f=18&t=7715#p55674

[Frank Sanns]

Chris,

Interesting theory but I can only tell you what I see. I see waves of patterns on the inside of the pyrex bowls as well as on the mid size outer lattice electrode. This tells me that the electrons are continuously bathing the inside of the conductive and non conductive surfaces and no significant charge is building up on the pyrex bowls. Still, I will keep my eyes open for the phenomenon that you speak. I just wish opening and closing up a fusor were not such an ordeal. It is more than a $10 gasket, as it is a pain to get things back down to fusion conditions once the fusor is opened. Guess we old time fusioneers are getting lazy in our old ages!

Frank Sanns

[Frank Sanns]

Thanks for reminding me John. I had forgotten that you daughter used those. Guess I am late to the game. For my fusor though, I do not seal them as I am observing the fields as they are within the bowls as well as plasma escapes the confinement.

Frank Sanns

[Chris Seyfert]

Frank,

I was recently reading a science forum and this was brought to my attention. Apparently, in 1998, Corning sold its consumer products division, and since then all "Pyrex" brand kitchenware is made of tempered soda lime glass - NOT borosilicate. Pyrex kitchenware made in France and all labware (of course) is still borosilicate.

Speaking of $10 gasket per chamber opening, you may want to look into K.J. Lesker's Viton CF gaskets. They're not cheap, but one put on an access flange pays for itself rapidly - provided you don't need to go above 200 ºC on the chamber