Cube fusor build

For posts specifically relating to fusor design, construction, and operation.
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

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
User avatar
Joe Gayo
Posts: 404
Joined: Sun Jan 06, 2019 9:34 pm
Real name: Joe Gayo
Location: USA

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.
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

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
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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
JonR
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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 11814 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
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

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
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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.

JonR
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

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
User avatar
Finn Hammer
Posts: 298
Joined: Sat Mar 05, 2016 7:21 am
Real name: Finn Hammer
Contact:

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
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

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
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

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
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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.

Jon Rosenstiel
Attachments
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)
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

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.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

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
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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.

Jon Rosenstiel
Attachments
Data
Data
8, 10, 12mm Hornyak buttons with PMT
8, 10, 12mm Hornyak buttons with PMT
The setup
The setup
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

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!

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
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

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.

Jim K
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

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.

Jim K
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

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.
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
User avatar
Mark Rowley
Posts: 909
Joined: Sun Dec 29, 2002 12:20 am
Real name: Mark Rowley
Location: Sacramento California
Contact:

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?

Mark Rowley
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

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.

Jon Rosenstiel
Attachments
Chart_02.png
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

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.
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
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

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.

Jim K
JoeBallantyne
Posts: 326
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

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.

Joe.
JoeBallantyne
Posts: 326
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

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.
Post Reply

Return to “Fusor Construction & Operation (& FAQs)”