Cube fusor build

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Richard Hull
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Re: Cube fusor build

Post by Richard Hull »

If I remember correctly, from my old readings, fusion of D-D via tunneling is perfectly isotropic and cares not a whit about the field conditions or original collisional directions. Anisotropy is more a function of reflection and scattering after the totally isotropic fusion event, itself. This makes sense as the original directions of the deuterons or fast neutrals are under 50kev. The reaction zone at the instant of fusion produces a net energy on the order of several meV. This swamps out any lower energy directional momentum plus any electric field conditions as far as the neutrons are concerned. The neutrons go wherever they want to and that nets out to isotropic emission.

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Re: Cube fusor build

Post by Jon Rosenstiel »

Richard,

The reaction may be isotropic in nature, but the neutrons coming out of the cube are definitely not. Both Joe and I have confirmed that the cube's neutron "output" or "flux" is about four times stronger in line with the plasma beam than at right angles to the beam.

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Re: Cube fusor build

Post by Richard Hull »

If this is true then it points to the ion streamlines impacting possible buried deuterium on the end plugs. (A form of beam on target where the source of the reaction is not within the grid and perhaps not even in the ion streamlines.) Two fusion emission points. Worth looking into.

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
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Re: Cube fusor build

Post by Jon Rosenstiel »

Titanium cathode testing. One of titanium's downsides is outgassing when it becomes red-hot.
Ti cathode_640_jpg.jpg
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Re: Cube fusor build

Post by Richard Hull »

Get yer red hots, right here!! The old call from vendors at ball games is apropos here. That is one hot Ti electrode.

Jon, guide me here with some of your long working wisdom and your current efforts and opinions with the cross/cube. I look at them as being one and the same.

How are the neutron numbers coming, Jon? Are they tough to get compared to your spherical system? I am about to take down fusor IV to monkey with the small CF cross idea. In your honest opinion, is it worth it for those who need neutrons? You are a solid guy with the good gear like only a few of us possess. Talk candidly here as I do not seek a new path for the sake of newness, nor am I just looking for a first pass win like so many newbies. I like neutrons and not fusion. Unfortunately, fusion is a route to obtaining those neuts. Do you think it is a good idea to cast off the old working system in favor of the cross if neutrons are the criteria?

While the cross can be an easy in for doing fusion and proving it at the newbie level, is it a real good neutron producer.

If a mega mark is tough for you to reach in the small system, I will still dismantle fusor IV and totally revamp the system to a much needed upgrade from the old 2004 original build. For the foreseeable future, I am voltage limited to 45kv max with 40kv more likely to be my limit. As you know, I struggle to get, but regularly do get, 10e6 neutrons or a bit more with luck and several days of "run in".

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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
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Re: Cube fusor build

Post by Jon Rosenstiel »

Richard,

I'll have some answers for you in a few days, I'm still trying to digest results I'm seeing from the titanium cathode.

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Re: Cube fusor build

Post by Richard Hull »

One has to be also concerned about the anisotropy that you noticed in the previous post related to the cylinder electrode which seems more beam on target related. The BC-720 neutron detector is about the smallest rather directional neutron detector one might employ to look for signs of anisotropy. Unfortunately you have to have a rather rich source of neutrons to rely on its typical 0.5% efficiency.

My very first fusion was detected back in 1999 using a BC-720 I paid a small fortune for from Bicron. I might have to pull it out of storage in future for use with big neutron numbers.

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
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Re: Cube fusor build

Post by Jon Rosenstiel »

Richard,

Joe Gayo found an interesting paper on isotropy / anisotropy.

Link to Joe's post...
viewtopic.php?f=6&t=12149&start=30

Link to the paper... (See pages 18 & 19)
https://ir.library.dc-uoit.ca/bitstream ... Leslie.pdf

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Re: Cube fusor build

Post by Richard Hull »

I can now see how your system as made here can be more neutron directed that our classic fusor being a loose form of beam on target due to the low energies we tend to use. This being the case, why aren't the more focused directional neutron number you get far above those of the spherical more isotropic system?

Oops I re-read some of the old posts regarding the poor numbers and understand you will be running and reporting on loading with the new titanium cylinder, which you have not reported on yet. Sorry, you advised me to wait a while as you will be doing this next. Memory, ain't what it used to be.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
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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 Jim Kovalchick »

Jon,
You are making good efforts trying to understand the neutron emission spatial characterization.
I'm far from expert, but I sense that emissions in your latest device are too complex to understand with conventional detectors. CR-39 plastic placed at various orientations might shed some light.

I think Monte Carlo in the right hands might be the answer.

Getting down to it, I'm not sure I would care if I were you. For me, it would be more about does this configuration let me get an activation sample in a higher flux because that is what I want to do with my neutrons. Even if fusion rates are smaller, the geometry may let you get samples closer to the point of neutron birth. Maybe you can compare activation to your original fusor. Another side benefit could be that new one uses less D. Who knows, but those questions' answers maybe more important than total numbers.
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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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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.

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
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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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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
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
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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

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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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Fusion is the energy of the future....and it always will be
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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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304 SS, 400 W.jpg
304 SS_1.jpg
304 SS_2.jpg
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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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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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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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