Cube fusor build

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Jon Rosenstiel
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Re: Cube fusor build

Post by Jon Rosenstiel »

Richard,

The cube’s neutron numbers at 40 kV, 10 mA with the original, aluminum cathode, ID= 0.5”, OD= 1.0”, L= 0.7” was around 5.5E+05 n/s (TIER), about one-half that of my fully conditioned spherical fusor. (1.0E+06 n/s) Note that unless otherwise specified 40 kV, 10 mA was used for all testing.

Neutron numbers from my latest two test cathodes (304 SS and titanium, both with ID= 0.65”, OD= 0.75”, L= 0.75”) was around 2.8E+06 n/s, nearly a 3-times increase over my spherical fusor! (And a 5x increase over the original aluminum cathode) At 40 kV, 15 mA both cathodes produced around 3.6E+06 n/s. As to evidence of wall loading from the titanium cathode, nothing yet.

The numbers come very quickly. First run with the Ti cathode gave 1.8E+06 n/s, second run 2.4E+06 n/s. By the third run (run times: 5 to 10-minutes) the cathode reached its maximum of 2.8E+06 n/s. I remember my spherical fusor taking weeks (or more) to reach its final, best neutron output.

So, if you’re after the numbers it seems that a cross or cube is a must-have.

My simplistic take (from my simplistic mind) on how these devices get their high numbers is that they’ve taken the spherical fusor’s multiple star-mode “rays or beams” and condensed (consolidated, combined) them into two beams. Basically, the same amount of fusion stuffed into a smaller space.

Now, about TIER. TIER doesn’t really work with these devices as they do not emit neutrons isotropically. So how can we fairly compare the traditional spherical fusor’s neutron output to a cross or cube? Or can it not be done?

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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

I'm with Jim. Let Activation tell the tale for those of us looking for quick usable activation. It sounds like I will give the cross a shot, just to go on an adventure. I can see real advantages in the two beam system as the end plugs are easily and cheaply exchanged for experiment (beam on target). Lots of ideas and materials in mind.

Thanks for the highly detailed exposition given above. Helped out a lot.

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Re: Cube fusor build

Post by Jon Rosenstiel »

Jim, Richard...

Right you are, it's the activation that matters. To that end, I just attempted to duplicate (as best I could) Richard Hull's HEAS silver activation experiment. A 2" diameter piece of silver 0.007" thick was placed between two 4" x 4" x 2" thick PE blocks nestled up against one of the cube's endcaps. Activation was for 5-minutes at 40 kV, 10 mA. (2.5 to 2.8E+06 n/s) At the start of the 5-minute run pressure was 22.2 mTorr, chamber temperature was 25 C. At run's end pressure was 25.7 mTorr, chamber temp was 53 C. It took about 6-seconds to transfer the silver from fusor to detector. Initial count-rate on a 2" pancake tube was over 5000 cpm. Yikes!

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Jim Kovalchick
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Re: Cube fusor build

Post by Jim Kovalchick »

Jon,
Wow! I was hoping you would have these results. Maybe my next fusor is one like this. Activation is really on of the best amateur uses of fusion. Thanks for the careful reporting.

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Re: Cube fusor build

Post by Richard Hull »

I can't better Jim's comments, and hold with my original statement in this thread.. Jon's work is first rate,and he knows how to report to those of us who know fusion in the fusor. He knows all the key variables and what the gaining fusioneer hungers for in such reports of new ways of getting to key goals. Thanks so much Jon!

Looks like I may find myself on the cross, but hopefully, not be suffering there.

Richard Hull
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Re: Cube fusor build

Post by Jon Rosenstiel »

Guys, appreciate the kind words, glad I could help out in some way.

Below is a TIER comparison between my spherical fusor and the new cube.
fusor vs fusor.png
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Re: Cube fusor build

Post by Richard Hull »

Nice graph! At my limit, 40kv, it appears to represent an increase of over 2.5 times in the cube/cross with cylindrical cathode. Sweet.

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Re: Cube fusor build

Post by Rex Allers »

Jon,

A few basic questions:
1) Your neutron numbers are a good bit higher with the SS and Ti cathodes vs the original aluminum, but the cathode dimensions on the newer ones also changed. Do you have any notion if the material is much of a factor vs the dimensions?

2) In one of your earlier pics you showed the two end plates after operation. The beams left a pattern on them. They seem to have a somewhat linear shape. The dimensions of the chamber and cathode are circularly symmetric. Do you have any thoughts why those patterns seem to have a linear component vs just circular.

3) Joe had originally planned to use magnets to focus the beams. Do you know if that has been done and did it have any affect?

4) Possibly dumb question: On pics of your HV feedthru there are two red rings around porcelain grooves. Do they serve some purpose like making arcing less likely or some other reason?
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Re: Cube fusor build

Post by Jon Rosenstiel »

Rex,

Cathode construction: From what I’ve found neutron production is strongly related to cathode dimensions, and only weakly related (if at all) to cathode material.

End cap patterns: One of the reasons I posted the endcap pix was I was hoping someone would tell me about the patterns. Anyway, my take is that the dark, linear shaped patterns are where the electron “beam” strikes the endcap. (The dark material has to be aluminum from the cathode) I have no idea why the pattern is shaped as it is. I think the fainter, circular patterns may be from D2 ions. The circular patterns also seem to somewhat define the outer limits of the “neutron cone”.

Edit: Remember, I'm mainly guessing here... every time I look at those images I change my mind about what's what. With it's present SS cathode the cube has been settling down and running smoother and smoother. Perhaps in a few weeks I'll pull off the endcaps to see what they look like. Should be interesting.

Magnets: (Edited 11-10-19) Depending upon positioning, the magnets either did nothing or reduced neutron output.

HV feedthrough red-rings: Rex, those are silicone o-rings, McMaster-Carr # 1283N263. The idea came from Joe Gayo. Bore the ID of a piece of 1.25” PVC pipe out to 1.5”, slide the pipe over the o-rings and fill with mineral oil. Increases the 30 kV feedthrough’s air-side stand-off voltage two to three times. (I’ve run mine up to 70 kV and I think Joe has run his up to over 90 kV)

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Re: Cube fusor build

Post by Jon Rosenstiel »

304 SS cathode images.

Removed after about two weeks of runtime, the majority of that time at 400 W input power. (40 kV, 10 mA, 2.4E+06 n/s) There are two things I find interesting, the narrow ring around the cathode's internal circumference and the whiskers it grew. My guess is the ring is where the current flows into the plasma. As to why it's sporting the stubble, I just don't know.

Top image: Running at 400 W.
Bottom two images: Two different views of the cathode.

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Re: Cube fusor build

Post by Frank Sanns »

Great work again Jon! Nice to see your latest evolution. My comments that follow are not a critique of your work but rather a quest for answers.

More and more of these anisotropy conclusions seem to be coming up. I am still skeptical of the conclusion because I have yet to see the separation between direction and location of neutron output.

Consider a black box cube. You cannot see in and you have no idea what is going on inside. You take a neutron measurement and find that neutron count is higher when you measure or activated at one of the faces. Does this imply that neutrons are directional or that they are being formed closer to the face? Any one experiment cannot distinguish. A minimum of two and preferably at least three measurements must be made to identify what is occurring.

Measurements can be done with coincidence counting, directional arrays, activation arrays, non directional sensor arrays to name a few.

One technique that I have used time and time again is the inverse square relationship. This occurred to me one day that Carl Willis and I were U ore prospecting. There was much radioactive sand in the area so there were many hot spots that we had to dig. Thinking that there must be a better way, I started taking measurements at various heights above the soil level. The inverse square law must be in effect so I took a reading then raised the probe until only one quarter the number of counts were seen. This distance then would be how far the source must have been from my probe. Of course this excludes the shielding effects of the ground but you get the idea. Found some great ore specimens those days with minimal wasted digging for diffuse radioactive sand.

The point is that the inverse square law is a powerful tool to not only see directionality but distance to the source. In the case of Jon's cube, a measurement or activation at 90 degrees to the suspected spot of neutron formation would be necessary to prove location of formation. Then backing off the two measuring or activation devices by double the distance should give one quarter the neutron numbers of both. If not, then the neutrons are indeed coming off in a shower in one direction over another.

I would really like to see this one resolved as it is an important result. I personally do not believe that the neutrons are coming of directionally but rather are being formed in a region that is deceptively giving higher neutron counts only because of closer proximity to the measuring device.

I may move this post to another forum so I do not contaminate Jon's excellent work but I feel it is relevant in this thread for the discussions already occurring.
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Re: Cube fusor build

Post by Mark Rowley »

Amazing work Jon. I may end up trying the cylindrical grid as well after a couple other mods are put in place.

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Re: Cube fusor build

Post by Jon Rosenstiel »

Frank, great idea that may help us get to the bottom of this conundrum, much appreciated. I’ve worked on this just enough to realize that the detector clamped in a lab stand is not going to cut it, takes too long to reposition the detector and is not very accurate. I’m in the process of upgrading my setup, but the bronchitis I contracted over the holidays isn’t helping one bit.

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Re: Cube fusor build

Post by Jon Rosenstiel »

Sorry for the long delay Frank. Feedthrough puncture issues, other projects, a water-cooling mod and on and on.

All data runs were done at 8 mA, 44 kV, ~23.5 mTorr. Two detectors were used, a moveable fast neutron detector (2” BC-720 replica coupled to a pmt) and a stationary 1”x 22” He3 tube in a paraffin moderator that was used to monitor the fusor’s neutron output. The outputs of both detectors were displayed on an Ortec 778 dual counter. Run times were 60-seconds.

For the on-axis (0-degrees) inverse square measurement the detector’s initial position was 3.5” from the cube’s center. The detector was moved away until its count-rate was one-fourth the initial count-rate. When the one-fourth count-rate position was attained the detector had been moved 2.75”. If I have this correct that’s telling us that the neutron formation area (spot?) is 0.75” from the cube’s center. (Cylindrical grid is 0.75” in diameter and 0.75” in length, so the neutron formation area would be 0.375” from the end of the cylinder) The inverse square measurements were repeated two more times… results were nearly the same each time.

For the off-axis (90-degree) inverse square measurement the detector’s initial position was 3.5” from the cube’s centerline with the center of the detector in line with the previously determined neutron formation spot. As before, the detector was moved away until its count-rate was one-quarter that of the initial rate. When the one-quarter count-rate position was attained the detector had been moved 4.625”. The diameter of the cube’s bore is 1.875”. Subtracting 4.625” from the detector’s initial position of 3.5” to centerline places the neutron formation area 3/16” past the bore’s far wall inside of the cube’s aluminum body. I should note that with the detector at 3.5” the count-rate at 0-degrees (136.2 cps) was nearly three times the count-rate at 90-degrees. (46.1 cps)

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Cube anisotropy. Fast neutron flux measured every 10 degrees through a 90 degree arc. 90-degree segments combined to show a 360-degree chart.
Cube anisotropy. Fast neutron flux measured every 10 degrees through a 90 degree arc. 90-degree segments combined to show a 360-degree chart.
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

Fabulous work Jon! This tells the tale. I was stunned at the location of fusion production. Could it be we are looking at fusion due to a combo of opposing high speed deuterons colliding in a high energy zone or high speed deuterons from wall launch at near the full potential colliding with fast neutrals? The walls are out and the grid is out as a maximized fusion center. As in the movie the King and I...."is a puzzlement".

This sort of backs up the U of W findings of years ago that fusion is not taking place to a maximized degree in the grid, but in the gas volume of the device. Kind of makes sense as that is where the bulk of the fusion fuel is located.

Continued first rate experimental results.

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Re: Cube fusor build

Post by Frank Sanns »

Great work again Jon! Your follow through is always most excellent!

At first I thought I was looking at a Smith chart!

I think though that you may have just proven that the neutron production is completely isotropic. Only your precise measurements make this interpretation possible. If you don't mind, I have super imposed my explanation overtop of your photo for clarity.

The mechanism that I propose is that along the axis of the bore of your cube Fusor, there is fusion occurring. Each point along that axis is generating isotropic neutrons. They are escaping the cube. The ones perpendicular to the cube are being measured as they form and leave by the short route.

The isotropic neutrons that just happen to be traveling in the direction of the axis, continue on until they exit the end caps. The thing is, ALL of the other isotropic neutrons produced along the longitudinal axis are doing the same. I believe you are measuring the additive artifact effect of this. Think LASER without the mirrors or stimulated emission. Of course the light would be brighter looking down the bore of the tube than it would be looking in the side even when zero lasing is taking place. The calculation for this should be the integral from 0 to L for the r^2 of the fall off with distance.

The conclusions is that I think you have proven complete isotropy of neutron production.

You have also proven that it is not beam on target that is creating most of the neutrons. Had this been the case, you would have had a spherical dumbbell shape source of neutrons at the end caps which you do not.

Most excellent!
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Re: Cube fusor build

Post by Jon Rosenstiel »

Wow, very interesting hypothesis Frank, and great analogy, think laser without the mirrors. I had a great time doing the experiment. And that BC-720 replica I made nearly twenty years ago finally found a purpose.

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Re: Cube fusor build

Post by Dennis P Brown »

Very good experimental work. Creating high quality measurements and setups is essential and you did that.

Your results make a lot of sense and certainly provide support that fusion is dominated by direct collisions/capture between free ions.

Certainly just a professional demonstration of outstanding work by people here.

My orginal work almost two years ago showing that smaller fusors led to greater fusion rate only due to more fuel, rather then any special geometry or electric field effects, supports both Frank's conclusions and your data results.
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Re: Cube fusor build

Post by Joe Gayo »

Frank,

I don't think the laser cavity analogy really holds. Isotropic sources would resemble a candle or filament and obey the 1/r^2 law. The only definitive proof would be if Jon performed the experiment with the detector at a much greater distance so the line source would be approximated as a point and the readings would be isotropic.
LineIsoDist.PNG
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Re: Cube fusor build

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I agree with Joe. The laser bit is not really applicable with matter particles. The only reason you are strongly isotropic is this is a dual beam on target system this isn't working well. (But well enough!) The grid "form", as a cylinder, is the beam-line determining implement. The target is rather unloaded due to the focused beam current intensity. All, or the bulk of the deuteron velocities, are beam-line axially centric, thus, the axial emission.

I have believed the Washington State group's findings of years ago that the spherical fusor has anisotropic nodes. Most likely, this is a form of beam on target over a much larger volume due to the star rays impacting the shell. Maybe, the increased number of rays from a complex geodesic grid can improve the spherical emission?

My avatar shows thirteen beams! this was in fusor III, the first fusion in the amateur "fusor" world was done in this fusor. (circa 1998). The fusion results were poor due to my limited power supply in use at that time, and having to work with a less than ideal neutron counting arrangement long before fusor IV. (circa 2004) We no longer construct complex grids in any of the mega fusor reports and no one has done extended modern runs in the mega-fusion range with a complex geodesic grid in a spherical fusor. We dropped it for the simpler three loop grid long ago. and the three loop can have 6 beam lines only.

For a given fusion current, the more beam lines might be more friendly to local wall loading/storage of neutral deuterium due to less localized heating at impact points (parallel circuit theory), as the beam lines are part of a plasmic/ionic circuit. Would this be akin to distributing the target load? You would still have a form of beam on target but much more spherically distributed.

Just thinking it out.

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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

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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.
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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.

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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.
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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.
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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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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.
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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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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.

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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!
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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.
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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
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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 6244 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.

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0 / 90 chart
0 / 90 chart
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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.

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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.
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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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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.

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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

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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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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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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.

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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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Re: Cube fusor build

Post by Richard Hull »

Great data and presentation! Seems reasonable as the focus is very beam on target. I was rather stunned there was so much off axis neutron detection. Scattering might explain that, but so might some isotropic production in velocity space or maybe simple Maxwellian neutral-fast fusion. As always, follow the beaming where it exists. I am more tempted to go with scattering.

Great work with the homemade hornyak neutron detectors!

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Re: Cube fusor build

Post by Jim Kovalchick »

As always Jon, you work is mastery.
.
I wonder if your work means that everyone who thinks they know their tier numbers needs to rethink it. I have speculated on this in the past when people have parked bubble detectors right next to their fusors and then over simplified an impossibly complex geometry by using point source calculation.

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Re: Cube fusor build

Post by Jim Kovalchick »

As always Jon, your work is mastery.
.
I wonder if your work means that everyone who thinks they know their tier numbers needs to rethink it. I have speculated on this in the past when people have parked bubble detectors right next to their fusors and then over simplified an impossibly complex geometry by using point source calculation.

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Re: Cube fusor build

Post by Frank Sanns »

I was out your way for a few days last week Jon but could not get the time to get over to see you. Seems traffic has picked back up since the pandemic is winding down and we are becoming immobile again due to antiquated single person transportation systems.

My fusor does not get run for the multiple hours at a time on multiple consecutive days that many of you do. When I am done with a run, I bring the pressure part way back up with a bit of deuterium before letting it sit until I get back to it. It seems to accelerate the restart up to good neutron numbers again.

A 50 KeV deuteron alone is not going to change the direction of a 2.4 MeV neutron just based on collisional vectors. O-P is something else of course.

At first I was wondering why there was a discontinuity of the function (top three points on your graph) as you neared the top of the peak but I guess that is due to the diameter of the detector and the neutron production areas not being point sources. Still, it tells something of the production. Can you do a cure fit and find the equation for the curve for all but the top three points? Does it follow the inverse square law? If you post the data we can do it. Guess I could pick it off the graph but you may have already done it.

Great work! I really wish I would have had more time last week. Alway enjoy the visits.
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Re: Cube fusor build

Post by Mark Rowley »

DIY efforts like this are the best. Another outstanding presentation Jon.

Aside from the stellar work of casting your own buttons, the efforts you put into establishing a very stable and consistent neutron output are notable. Regarding chamber cooling, I’ve noticed here that 18 Celsius seems to be the magic number for stability. Anything below seems to be inconsequential and above the numbers begin to vary a bit more. What is the optimal temp for your chamber?

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Re: Cube fusor build

Post by Jon Rosenstiel »

Frank, too bad we couldn’t get together, hopefully you’ll have a little more time next time you're out here.

Best fit was with an exponential trendline. I have to wonder if the shape of the curve is affected by the geometry of the Hornyak button vs. the angle in which the neutrons interact with the button. For example, with the button centered on the endcap neutrons are most likely interacting fully with the button’s 8mm diameter and 5/8” depth, but as the button is moved towards the cube’s edge the neutrons are more and more interacting with the button from the side. (Hope this makes sense)

Mark,
For these runs with the A/C blowing through the radiator the chamber temp was around 28~29 C, lowest I’ve ever run. One of these days I need to try adding ice to the cooling H2O, try and get a handle on the "how low can you go" point.

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Re: Cube fusor build

Post by Frank Sanns »

If there is a beam line of anisotropy, then why is it following the inverse square law? Pulling out of a beam (using the term loosely) should give a quick drop when starting to remove the detector. Once out of the beam, the drop would then fall off quickly.

I know most of you are convinced that there is more out of the ends but I still am not convinced it is due to neutron direction from fusion itself. I still think it is a geometric artifact on where the fusion is occurring. I know that ALL of the evidence does not exactly support that but some of it does like this most recent experiment. Still pondering.
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Re: Cube fusor build

Post by Jim Kovalchick »

Frank,
I am with you on this one. This is why I have been harping on geometry of detection. You can't put detectors right up against shells when we have said there is a lot of fusion happening on the walls. All this variance proves is that the fusion isn't happening on the walls uniformly. Why would we assume otherwise when Jon's fusor has a single center line beam?

To understand if there is direction to the neutrons, we need to back out our detectors. I don't believe we are making directional neutron beams.

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Re: Cube fusor build

Post by JoeBallantyne »

Jon, very outstanding work!

One thing you might try if you are worried the angular orientation of the beam relative to your detector might be having an impact, is to simply do a run where you leave the detector centered on the end cap where the total measured neutron flux is the highest, and then rotate your detector 90 degrees in the horizontal plane while maintaining it centered on the beamline. Start with the detector exactly in line with the beam, and end up with the detector at exactly perpendicular to the beam. You could rotate it in both directions (right and left), although I suspect there should not be much difference in the response between the two rotations. You will need to shift the detector slightly in order to keep the beamline centered on the horniak button as you rotate it.

If there is some detector sensitivity to angle, you should see a change in measured output.

You could then use that data to factor out any detector angular sensitivity from your measured neutron output based on side to side displacement of the detector.

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Re: Cube fusor build

Post by JoeBallantyne »

Another experiment you could do, would be to figure out the exact location on the endcap that the beam is hitting. Make that the center of a circle of sufficient diameter that you can sweep your detector in a quarter circle around that point, always keeping the detector exactly aligned on a line passing through the center of that point, and so when the detector is at 90 degrees to the beamline, it doesn't hit your chamber. ie: make the radius big enough that your detector can sweep continuously around that point without impacting the chamber at any point.

So the front of the detector will be on the circle, and the angle of the body of the detector with the beamline will be zero degrees initially, and will end up at 90 degrees to the beamline. ie: the detector is always exactly aligned with a ray that goes through the center of the beam impact point on the end cap of your chamber.

If a large percentage of fusions are happening in the wall at that point where the beamline hits, and you maintain a constant distance from that point, and those fusions result in isotropic output, then there should be no difference in detected neutron output from that portion of the neutron signal if you move your detector as described.

Since the distance to the point where the fusions are happening is constant, and the horniak button will always be exactly perpendicular to the line that intersects with that point.

If most of the fusions are happening in the end cap point where the beam hits, then the amount of variation you get from this measurement should be significantly less than the one you get from the side to side sweep.

Joe.
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Re: Cube fusor build

Post by Richard Hull »

I am beginning to see this device as a BOT system fusor! Backing off my position many posts back in this thread. This thing (cube) as long as the ends are kept cool might just implant D in the end caps and at the same time does a good bit of fusion there as all real evidence so well presented here seems to point out. I am also sure fusion is happening in velocity space as well and I'll bet there are good counts to be had from the tube arm walls, just nothing like Jon is getting on the beam line which is obviously where the action is. Of course, in activation work all this beaming will just slow and scatter in the moderator if it does its true job. However, it is nice to concentrate the neutrons at the moderator. That is where beaming comes in real handy. I like it.

Make no mistake, beaming or not, this is still a fusor!....A simple two electrode amateur fusor that is really cookin'! Jon is a master at setting up experiment and relaying great data and results of his efforts. This may be a long thread but a really valuable one that teaches and inspires thoughtful comment and is another way to skin the cat in amateur fusion.

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Re: Cube fusor build

Post by Jon Rosenstiel »

Frank,
I’ve found that the inverse square law does not hold up well at small source to detector distances. I ran some tests using a 2” x 2” NaI(Tl) detector and a 10 uCi Cs-137 source and found that in order to get good data the source to detector distance should be no less than 4”. What I’m trying to say is, we probably should not put too much faith in close-in measurements.

As to the anisotropy, take a look at pages 18 thru 20 in the attached paper. (Characterization of Neutron Fields Around an Intense Neutron Generator) I believe this applies to our case, but not really sure. (Dammit Frank, I’m a mechanic, not a physicist) Anyway, I would like to hear your thoughts on this.

Joe,
Nice to hear from you! Thanks for the good ideas, I’ll keep them in mind for future reference.

Richard,
I’ve finally come to the same conclusion; the cube is a BOT device.

Pic of a Monte Carlo neutron flux simulation for a BOT device. Looks quite familiar, huh? Link to complete paper below. (Didn’t attach the paper as it’s nearly 18 MB is size)
https://escholarship.org/content/qt6z74 ... ee762b.pdf

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Re: Cube fusor build

Post by Frank Sanns »

Jon,

Good paper. Nice compilation of lots of information that we have been discussing.

Some conclusions.

1. We agree that close measurements are not good because neither the neutron producing area nor the detector are points. That is why I asked you to throw the top 3 points away on your original curve. I could see they were corrupted because of the near distance. The minimum distance for a good measurement will depend upon the size of the detector. Smaller detectors look more like point detectors at closer distances.

2. Deuterium is a unique beast in that it is such a simple atom, that minor shift between the center of mass of the atom and its charge location (a neutron and a proton), have meaning in the real world. The nucleus is neutral at one end and positively charged at the other. The inverse square at play so and impact from the neutron side is slightly more desirable since there is just a little less repelling charge at that end. By tritium, this effect is much less and the heavier atoms is probably non existent.

3. There is no neutron beam coming out of the ends of fusor. There is a higher probability of of productive collisions when the deuteron is aligned in an electric field that in a random field.

4. The paper also points out that the polarization of the neutrons are also anisotropic. Good luck with that portion of the experiment. Although, it is interesting to think about that as keeping your detector in place and rotating it 90 degrees should also show a difference. Want to handle some cadmium with slots cut in it for the front of your detectors. lol. I AM KIDDING. DON'T EVEN THINK ABOUT IT. Gadolinium is probably not a whole lot better. Maybe Boron Carbide pieces arranged into slats. Just thinking.

5. Your results are most excellent Jon. The effect is not a huge one but you are detecting it. It is important to point out that the confidence in your numbers is in your technique and setup but the repetition of measurements along multiple changes gives the confidence in the numbers. I single reading close and at another distance for a total of two points cannot tell the story. Multiple data points in good agreement gives a good confidence interval to evaluate the data.
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Re: Cube fusor build

Post by Jon Rosenstiel »

Frank, you were correct in your skepticism, allow me to explain.

The following 0-degree/90-degree fast neutron-rate comparisons are based on the assumption that the neutron formation area (NFA) of the cube fusor is centered on (or very close to) the endcap surface. Detector for this test was a 2” diameter by 0.6” thick Hornyak button coupled to a Thorn/EMI 9258KB03 PMT. NIM electronics consisted of the following: Ortec 4001M minibin, Canberra 3102D hv supply, Ortec 113 preamp, Ortec 572 amp, Ortec 550 SCA, Tennelec 534 counter/timer. Both amp and SCA outputs were monitored on an oscilloscope.

My initial plan was to run a 0/90-degree comparison at 3” and 13” to the NFA. (13” is the maximum my setup would allow) At 3” to the NFA the 0-degree position count-rate was about 22% higher than that at 90 degrees. At 13” I expected to find a smaller difference in count-rate between the 0/90-degree positions, maybe somewhere around 15%. I was quite surprised when the 0/90 difference increased to 37%. Additional data points at 5.5”, 8”, and 10.5” did nothing to change things.

At this point I was somewhat baffled so I made a simple drawing of the cube. First thing I noticed was that at 0-degrees there is 0.375” of aluminum between the NFA and the detector vs. 2” of aluminum at 90-degrees. Seems so simple, but something that I had, up to this point, failed to recognize.

Ok, with the above in mind I placed a block of aluminum 1.625” in thickness between the detector and the endcap at the 0-degree position to mimic the 2” of aluminum at the 90-degree position. (Endcap + Al block = 2.0”)

With the 1.625” Al block in place a rerun of the 0/90-degree comparison at 3” and 13” resulted in the following.
At 3” to NFA: 0-deg measurement was 2.3% higher than at 90-deg.
At 13” to NFA: 90-deg measurement was 2.7% higher than at 0-deg.

So, what this is telling me is that the previously measured anisotropy was nothing more than neutron absorption/moderation/scattering in the cube’s aluminum walls. The following Richard Feynman quote comes to mind: “The first principle is that you must not fool yourself – and you are the easiest person to fool”.

Jon Rosenstiel
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Detector at 90-degree position, 3" from NFA. Shaded areas are 6061 aluminum.
Detector at 90-degree position, 3" from NFA. Shaded areas are 6061 aluminum.
Long-tailed pulse from the ZnS(Ag) loaded scintillator & data pulse from the SCA.
Long-tailed pulse from the ZnS(Ag) loaded scintillator & data pulse from the SCA.
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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

Great report and observation, Jon. You are giving a lot of good information based on interesting experiment in detection and sorting out anisotropy. Sure, fooling oneself is easy.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.
Frank Sanns
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Re: Cube fusor build

Post by Frank Sanns »

More great work Jon,

It may just be the physical distance measurement that is giving the effect. If you measured from the outer surface of your Fusor, then you started closer and that would explain the higher numbers that almost met the perpendicular readings as the distance increased. At greater distance, the measurement error on starting distance would be less of contribution.

I am not sure attenuation of neutrons by aluminum is much of a factor. It has a very low cross section so it should not be intercepting many neutrons.

Thanks again for posting the data. Good stuff!
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