Cube fusor build

For posts specifically relating to fusor design, construction, and operation.
Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

Joe, I don't know if you consider 20-inches a "much greater distance", but that's the limit of my setup.

Ratio of 0-degree to 90-degree count-rates at different distances.
At 3.5-inches = 3.0:1
At 10-inches = 2.0:1
At 20-inches = 1.7:1

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Re: Cube fusor build

Post by Frank Sanns »

I am a little surprised at the statements here. Isotropic is isotropic be it particle or photon. Of course in the case of a photon, orders of magnitude more are being emitted from a tube of plasma. It is still a statistical game be it emission of a photon or a neutron.

My drawing is a series of several isotropic emitters in a row. In reality, there is a near infinite number of emitters along the axis. Only by integrating the sum of their effects in both the axial and the transverse direction can the results be tabulated.

Then there is the detector. it is not a point source. Not even close. Knowing Jon, I am sure he consistently used a measurement. It matters not if it is the center of the detector to the center of the axis or if it is the edge to the edge or some other combination. It is important that the measurement procedure and geometry be the same for all measurements.

For those of you beam on target fans, please explain why there is not a dumbbell shape to the neutron emissions. Should not the end caps be the target and a spherical emission should emanate from the point of impact on each target end? Why no such result?

I am still not convinced that there is even a significant amount of beam on target fusion going on in the best of our fusors. The numbers just don't seem to be there. In the case of the cube fusor, an ion is formed on one side of the hollow tube grid. It is accelerated toward the tube and enters it. It is driving inside with no change in velocity because there is no electric field inside of the hollow conductor. The ion emerges on the other side and is slowed down by the same potential that accelerated it in the first place. It therefore must lose a significant amount of energy before impinging upon the far wall of the end cap. If the fusion cross section for impinging 40 KeV deuterons is not the greatest, how is a much lesser energy deuteron cross section to a stationary wall target?


Assuming there is a lot of deuterium in the walls, maybe on the order of 0.25 mole percent, what are the chances that a fast ion will find a deuterium atom in the sea of stainless steel atoms and have sufficient energy to overcome all of those nuclei and fuse? A fusor is not even close to looking like a beam on target machine. Not the 40kv applied voltage, not the SS end cap, not the pressure, not many things.

I do not want to derail Jon's excellent work but I see no evidence in the numbers of beam on target fusion.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

I fully stated the cube fusor here is a failed example of beam on target in my post. I assume it was never built as such. (first line of my post) Yet it still does fusion and not beam on target to any useful extent as beam on target. Jon's work showed no source of fusion on the end caps, just neutron emission strongly pouring out of them. The fusion is in the beam line! and even localized within it or around it. It fails as beam on target due to the very intense beam currents not allowing long term accumulation of any fuel material to make the ends a target! Simple really based on Jon's superb report.

Wall loading in a spherical fusor may not occur at the multiple ray impact points, (a guess), but more in the walls where the rays do not strike. The important point regarding spherical loading is fusion never ever occurs at the loaded wall... never has and never will!!... no fusion energy there just buried deuterium from fast neutral collisions and recoiling deuterons. What does occur is fast neutrals buried over the large spherical surface of a sphere can also pop out deuterons from the impact of electrons and other fast neutrals, boosting the deuteron population once the walls are loaded be it to a greater of lesser degree.

Jon's device seems to being doing fusion in or near the beam-line forcing some directionality by normal quantum tunneling just like every other fusor does fusion, but just in a different modality due to the grid form and the geometry of the cube.

It is sad, but just the way it works out that Jon can't get but so far away from his device as Joe suggested, but as amateurs, we are often space limited. Still, Jon's farthest measurement still showed anisotropic emission which militates for beam line emission.

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: Cube fusor build

Post by Frank Sanns »

Richard, apologies if it appeared that I was dissing your post. Not my intent. I don’t have a horse in this race. Just looking for some answers. Hope others ponder this and give there thoughts.

As for the loading of deuterium in the walls, I am going to suggest another possible mechanism for why a long running fusor runs better. Could it just be that all of that implantation just knocks other gasses from the interstices of the Stainless steel and eventually leads to a purer deuterium? Void of energy intercepting impurities will give more number of productive fusions.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Joe Gayo
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Re: Cube fusor build

Post by Joe Gayo »

Jon,

Mathematically 20 inches is far enough. Thanks for confirming the measurements I took when I started 2 years ago (although my cathode was different, I still had the single beamline).

Frank,

The red is Jon's measurements and the dashed line is a line source of isotropic emitters with infinite points.
Iso v Ani.PNG
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Jim Kovalchick
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Re: Cube fusor build

Post by Jim Kovalchick »

Frank,
I am curious about your postulation that a finite supply non D is knocked off the walls and poisons the plasma early in chamber conditioning as an explanation for what others perceive as wall loading for target fusion events.
I personally think that loading happens on the grid and is why grid material makes a difference in numbers.
I haven't quite resolved in my mind why chamber temp seems to flatten the neutron curve for me and others. I'm not sure it isnt about chambers getting leaky when they get hot. Or could it be just the grid getting hotter and not holding as much D?
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Jim Kovalchick
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Re: Cube fusor build

Post by Jim Kovalchick »

Someone needs to spend the gazillion dollars to buy a neutron camera to 'see' the tomography.
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Re: Cube fusor build

Post by Frank Sanns »

Jon, thanks for the measurements. Joe, thanks for the graph.

I did the first terms by hand and came up with a 2.3 to 1 estimate for an isotropic radiator and that is right on your plot Joe. Of course it needs to be 1 far away and the theoretical plot does show that.

I really need to get good math program as once my old Maple software went dark a decade ago, I have not had cause to pay for a new subscription based software. Then there is the syntax subtleties that makes an equation solve or give an error. I have even given up on my graphing calculator for the same reason. Use it for complex math so infrequently that the pencil and paper comes out before it does.

Back to the problem at hand. So there will be an APPARENT anisotropy of 2.3 to 1 for an isotropic radiator. Jon's measurement is showing an anisotropy of 3 to 1.7. A troublesome conundrum for sure.

What can account for this particular rate of drop? Should the near measurement be around 3.9? What is the theoretical ratio if it is both end caps? What if it is in the beam line? What if it is in the center where the grid is? Systematic measurement error? I will have to ponder that as a good solution does not seem to pop out.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Dennis P Brown
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Re: Cube fusor build

Post by Dennis P Brown »

In many neutron measurement systems, a serious problem is the lifetime of neutrons (15 minutes!) and their ability to be cooled by many common substances. As such, one can build up a lot of stray neutrons in a local area that then do not appear to come from the source at all. This has bitten many experimenters in the field making their measurements.
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Joe Gayo
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Re: Cube fusor build

Post by Joe Gayo »

Frank,

If you look at the image below you'll notice I altered the axis00 equation to have preferential emission 1.6x that of axis90. I would say within the error of measurement and only evaluating 2 angles this closely approximates Jon's data.

Joe
Iso v Ani - 2.PNG
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Re: Cube fusor build

Post by Frank Sanns »

Ok, so I think I have it. In an earlier post in this thread I mentioned the distance of the detector from the source. It is important because a detector is not a point. It is a volume. Most importantly it has a thickness.

For a far field measurement, a half an inch difference between the face of the detector and the center of the detector is negligible to the overall distance. The near measurement though, it becomes more and more important. At the 3.5' close measurement, having the center of measuring scintillator being a 0.5" inch farther away (not sure of Jon's exact detector dimensions) thank its face, will give a significantly lower reading with the inverse square law at play. It is my belief that that is why the curve that Joe made matches it well but I think accounting for the thickness error in the scintillator distance would tie up the accounting error.

We have to realize that even with the measurements given, they are around +/- 30% of theory. This includes operating a fusor consistently during the time of the experiment and measuring those ephemeral neutrons. All in all, I would say outstanding work to Jon!
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Joe Gayo
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Re: Cube fusor build

Post by Joe Gayo »

All that I've trying to show, in a general sense, is that the measurements that Jon took are best described by an anisotropy volume source, not an isotropic volume source.
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Re: Cube fusor build

Post by Frank Sanns »

Either I am not understanding the original data chart or I do not understand the interpretation. I looked through everything again and I am just not getting something here. How can it be anisotropic if measured around the fusor or is it? Is this a two dimensional x,y plot or a one dimensional linear plot? How can a count be 90 dI am not sure why I am so confused by the results. My interpretation was the graph was a perimeter measurement of the output of the fusor; a 2 D plot.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

Frank,
I sat on that graph for quite a while because something didn't seem quite right about it, but I never could put my finger on what it was.

Here is a similar chart from the attached paper.
Screenshot 2019-12-19 15.24.59.png
DD Anisotropic neutron emission.pdf
(1.99 MiB) Downloaded 598 times
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Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

Detector position for the 90-degree data in an earlier post was in-line with the neutron formation area (0.75” off center) not the cube's centerline.

Below find close-up 0-degree/90-degree data taken with the detector on the cube's centerline at both 0-degrees and 90-degrees.
data_1.jpg
data_1.jpg (22.12 KiB) Viewed 11811 times
Each distance data-point consisted of four 60-second runs in an alternating order. (0-deg, 90-deg, 0-deg, 90-deg) Total run time, including a warm-up, recording results, repositioning the detector, and a quick bathroom break was 58-minutes. Cube temperature was 37.6 C at the beginning and 39.3 C at the 58-munute mark. Wow, water cooling to the rescue! Input power was set to 8 mA, 44 kV. At the end of the 58-minute run the current had dropped to 7 mA and the voltage had increased to 46 kV. Chamber pressure was in the 22.5 t o23.5 mTorr range. The 1” x 22” He3 detector that I used as a control was positioned 36” from the fusor. It’s highest count-rate (406 cps) occurred during the 3.75” run. It’s lowest count-rate (392 cps) occurred at the very end of the 6.25" run. Wow again, seems impossible, doesn't it? I didn’t measure the cube’s TIER, but based on previous runs it was probably around 2.0E+06 n/s.

Plotting the 0 / 90 data in Excel: Best fit (r^2 value of 0.97) was obtained with a power trendline. At this point I’m not really sure if what I’m doing is kosher, and I know it’s dangerous to extend a trendline too far out (thinking about a Corona-virus chart from our government that showed the virus gone by the end of May) but anyway, here it is.

Jon Rosenstiel
0 / 90 chart
0 / 90 chart
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

I believe and assume from Jon's report that the movable device that made the measurements was the 2" diameter BC-720 work-alike on a PMT which detects only fast neutrons, not needing a moderator with only about .1% efficiency for the scintillator. You need a hot source to make it sing. (low CPM readings) I also assume it read face on, thus a very narrow frontal volume of detection exposure. The scintillator is a 2"- dia. X ~1" thick detector. I do not think or assume his ratios were not done using the larger volume of the moderated 3He system. At least this is what I read back on page #4. Correct me if I am wrong Jon.

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
Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

Except for the detector’s thickness (it’s 5/8” thick) you’ve got it right, Richard.

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Re: Cube fusor build

Post by Frank Sanns »

Jim,

I have have waited to evaluate Jon's data before I answered your question. It would seem that loading to displace gas from the shell and to provide more fuel when hit by a collision or just something coming out of the interstices of the metal then I can by into that. It seems a much harder stretch to believe there is much beam on target going on there compared to what is happening at the cathode. After all, the highest energy deuterons (with no circulation present) is at front grid surface. Any collisions there would have the best chance of having enough energy for fusion. It is also the smallest surface area and the higher current density in the fusor so it should load the fastest. And as you said, can unload the fastest at high temperatures.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Finn Hammer
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Re: Cube fusor build

Post by Finn Hammer »

Jon, all
As you will see in another post, your cube fusor has my full attention, and I have been puzzeled by this picture for a while:
https://fusor.net/board/download/file. ... mode=view
My focus is on the coloring on the outside surface. There is a blue band at each end, and in the middle, the metal has turned brown. The coloring of a metal is a natural result of heat treatment, and a desirable measure of the level of annealing attained after a hardening process, but the sharp border between blue and brown is difficult to explain, at least within the limited framework of my experience in the fusor atmosphere. Is there a known mechanism behind the 2 blue bands?

Cheers, Finn Hammer
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Jim Kovalchick
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Re: Cube fusor build

Post by Jim Kovalchick »

Finn,
I also use tube grids and have seen these color patterns. I believe that the variations are from different deposition patterns that correspond to field variations.

Good luck with your cube build. I know it will be great.

Jim K
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

I agree 100% with Jim. Deposition related to high field points on the cylinder. You can the it on the stalk in the photo. There is a rather even deposit due to uniform field about the smooth high field stalk

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
Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

I think Jim may have hit upon what's going on here.

Below images are of a brand new, freshly machined aluminum (6061-T6) cathode. I believe the greenish plasma is related to the “burning off” of aluminum oxide and/or other contaminates.

As a side note, neutron production rate of this cathode was about one-fourth that of its similarly dimensioned stainless-steel counterpart.

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9-minutes into initial conditioning run. (20 kV, 15 mA, 14.3 mTorr)
9-minutes into initial conditioning run. (20 kV, 15 mA, 14.3 mTorr)
16-minutes into initial conditioning run. (20 kV, 15 mA, 24.9 mTorr)
16-minutes into initial conditioning run. (20 kV, 15 mA, 24.9 mTorr)
2 ~ 3-hours of runtime and several runs later. (20 kV, 15 mA)
2 ~ 3-hours of runtime and several runs later. (20 kV, 15 mA)
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Jim Kovalchick
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Re: Cube fusor build

Post by Jim Kovalchick »

I actually posted an inquiry about the color bands before and posted some of my own pictures. viewtopic.php?f=18&t=13077&p=87033#p87033

I didn't understand them either. I have since come to the conclusion that the only things that could be making uniform and distinct color transitions are fields.
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

I have yapped about fields for years here and a full understanding of them in the assembly of our super high voltage systems is key to avoid arcing internal or external to the system and naturally to deposition. Most of my knowledge and respect for high field conditions grew from the 12 years spent in Tesla coiling. The beautiful diamond lozenge images in the inner spherical shell of fusor III and IV due to the geodesic grid photographed 15 years ago, spoke to the field causal distribution of material via the multi-beaming ports. This is a form of incidental electrostatic focusing, deposition and heating.

For most every person in electronics 100 DC volts is considered high voltage for we fusion folks, 10,000 volts DC is considered far too low a voltage of any genuine value. Tesla coilers work in the million plus volt range albeit at RF frequencies. Field control is far more important in preventing arcing and huge electrical losses due to corona, (which can foster arcing). However it can also affect and control deposition in high voltage components in a vacuum system. I have grown so use to such depositions over these many years, I just do not give such things a second thought beyond being an indicator of high field regions, which are to be avoided or looked at as a possible danger point in the system. It also indicates a point of lost energy in the system or, conversely, a point of successful deposition where desired.

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: Characterizing the cube fusor’s neutron flux

Post by Jon Rosenstiel »

Previous work with a 2” BC-720 replica fast neutron detector showed that the cube fusor’s neutron emissions were anisotropic in nature. viewtopic.php?f=6&t=12954&hilit=anisotropic&start=30

In order to “see” this in more detail I used a Hornyak button 8mm in diameter by 5/8” thick coupled to a Hamamatsu R6095 28mm PMT. This detector was then swept across the cube’s left end from edge to edge (100mm, 4”) using a linear stage. Data was recorded every 5mm. (One turn of the stage’s crank handle)

As I had no idea of the sensitivity of such a small Hornyak button I decided to cast three buttons of 8, 10, and 12mm in diameter. The buttons consisted of a mixture of ZnS(Ag) and casting resin. Mixing ratio was 5.7% by weight. The buttons, once hardened, were centered in HDPE molds 28mm in diameter and back-filled with clear resin. After hardening, the ends of buttons were machined flat, wet sanded, and then polished on a buffing wheel.

The 28mm Hamamatsu PMT and its housing are SAIC surplus. I have a few of these on hand courtesy of George Schmermund, but they are also often found on eBay. The machined aluminum endcap was my doing.

The SAIC units have a plus/minus 5V powered preamp attached to the PMT’s base, but the output is a 1-micorsecond wide pulse that doesn’t play well with spectroscopy electronics. I ended up taking the output off of the anode’s coupling capacitor and feeding it into an Ortec 113 preamp.

NIM electronics were comprised of a Canberra 3102D hv supply, an Ortec 572 spec amp, Ortec 550 SCA, Ortec 773 timer/counter and an Ortec 778 dual counter.

The “control” fast detector used to monitor NPR was a 2” diameter by 0.45” thick Hornyak button coupled to an EMI 9266 PMT. Electronics consisted of a Ortec 113 preamp, Ortec 571 spec amp, Ortec 550 SCA, and a Canberra 3102D hv supply. SCA output was fed into the 778 dual counter.

As each data run took around 30-minutes to complete, stable operation of the fusor was critical. Some of the steps taken to ensure stability. 1) Using another fast detector to monitor NPR. 2) Running at low power, 50 kV, 6 mA, 300 W, TIER of about 2.4E+06 n/s. 3) Directing the outlet of a portable A/C unit into the cube’s water-cooling radiator. 4) Running early afternoon when my lab’s temperature was most stable. 5) Long warm-up/conditioning period.

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Data
Data
8, 10, 12mm Hornyak buttons with PMT
8, 10, 12mm Hornyak buttons with PMT
The setup
The setup
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