Neutrons!

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Garrett Young
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Neutrons!

Post by Garrett Young »

Overall Setup:
IMG_1455.png
Cathode potential: -25,550 (Supply: -29,634 with 393 kohm series resistor)
Cathode current: 10.4 mA

Pressure: 33 mTorr (working to lower this and improve mean free path)

BD-PND (24 bub/mrem):
5 bubbles in 5 min
9.5 cm from cathode
Temp indicator showed 24-28 degC

Placement
IMG_1459.png
Bubbles
IMG_1467.png
(Note: After the 5 min run and the plasma extinguished, the bubble dosimeter was monitored for an additional 10 min and no further bubbles formed)

The BF3 tube/moderator and NIM setup (discussed here: viewtopic.php?f=18&t=11312) averaged 15 cpm above background.

I have many improvements planned over the next few days, but I wanted to share my starting point.
- Garrett
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Garrett, I am glad you look at this as a starting point. You are to be added to the Neutron club. Good work! Too many people look at this success as their last posting.
Keep all of you run data in a log book so that you can sum all the doses for averaging once you get your electronic system going along side the BTI dosimeter and calibrate your
electronics to arrive at a multiplier for future use to indicate a link to neutrons per second.

To all looking at this post. Take a good look at what the bubbles in a good BTI detecting neutrons looks like. Small, obvious, perfect spheres.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Neutrons!

Post by Dennis P Brown »

Congratulations! An excellent setup and experiment.
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

After gaining some operator experience, I achieved 3x the neutrons in the same time period (and same detector location) compared with my previous post.

Running at an average of 27kV@20mA (29kV source with 100kohm series resistor) and 34 mTorr, my bubble detector registered 15 bubbles (only 14 are clearly visible in the picture bellow) in 5 minutes.
IMG_1480.png
- Garrett
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Fabulous work and proof that once you get to fusing, operational skill with your system starts to go through the roof!!! I have harped on this for years and here is another instance that proves it. It is not about the construction all the time or the gear. In the end, it is about operational artistry. We are working at a bleeding edge of this technology operating between a pretty, yet useless glow and a dangerous and destructive arc condition. Wedged in a tiny zone between these two easily achieved extremes, is Fusion!! Only a careful hand can do fusion here and only an experienced hand can do it better.

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
Titanium007
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Re: Neutrons!

Post by Titanium007 »

Where is this neutron bubble detector purchased? Please give me a link, thank you
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

http://bubbletech.ca/product/bd-pnd/

Make sure you check out the FAQs ... lots of good information
- Garrett
John Futter
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Re: Neutrons!

Post by John Futter »

Titanium007
You seem to be short of a few smarts or have a comprehension problem
and have missed the rule of: Only your real name to be used "no handles allowed"
also the rule that stated your first post has to be in the "Please introduce yourself forum"
Please amend these short comings
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

I activated a 2x7 cm piece of 30 gauge pure silver foil tonight during a record 4 minute run of 150k+ n/sec. The neutron oven is a plastic bucket (30cm diameter / 30cm height) filled with water and a sealed tube in the center for housing the activation material. The sample material is 20cm from the cathode.

I used a Fluke Biomedical Geiger Counter and an Eberline Beta Sensitive Scintillation Detector (discriminated to count 1MeV+ betas)

1 min count (within 5 seconds of removal from neutron oven): Fluke 89 / Eberline 17

Foil removed from detectors for background count:
1 min: Fluke 33 / Eberline 3
2 min: Fluke 28 / Eberline 6
3 min: Fluke 32 / Eberline 4
4 min: Fluke 25 / Eberline 4
5 min: Fluke 40 / Eberline 2

Useful calculator: http://www.wise-uranium.org/rnac.html
- Garrett
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Very nice work! Your rather big moderator took advantage of a large intercept cross section. My neutron oven has only 1/4 your cross section I would require about three times the n/s rate to equal your ratio of background to activation level! Again, thanks for sharing. I use water moderation for my 3He tube, but HDPE for my oven.

Richard Hull
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The neutron oven with the 3He water moderator behind it
The neutron oven with the 3He water moderator behind it
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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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Here is a picture of my activation setup. (The string is attached to the sample for quick removal.)
IMG_1491.png
- Garrett
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

During another successful silver activation run, the bubble dosimeter registered 25 bubbles in 210 seconds (at a distance of 12.5 cm). This correlates to 251k n/sec!
IMG_1492.png
I'm not sure what levels have been previously achieved in a small chamber (I'm using a KF50/KF40 reducing tee - 4.7cm inner diameter).
- Garrett
Andrew Seltzman
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Re: Neutrons!

Post by Andrew Seltzman »

That's certainly the highest I've seen from such a small chamber. What was the voltage/current/pressure?
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Cathode Current (Ic, mA), Cathode Voltage (Vc, kV), and Pressure(mTorr) use the left scale
CPM (BF3 tube) and Cathode Power (Pc, W) use the right scale
2300_03102017.png
- Garrett
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

3D CAD (plasma volume 144 cm^3)
Assem-03.pdf
(112.81 KiB) Downloaded 461 times
Mathematica Simulation

https://youtu.be/q5SWm1tc1hM
Last edited by Garrett Young on Sun Mar 12, 2017 2:10 pm, edited 1 time in total.
- Garrett
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Your big win here is the super high D2 pressures you are recording a lot more fuel per unit volume in your system. What you lack in voltage moving you up the D-D cross section, you make up for with fusion fuel density. Wow! Just how tiny can success be in chamber size?? This is certainly one of the finest tiny chamber systems yet, with good instrumentation and data collection technique. It might be the first of its size to offer a second proof of fusion via an unquestionable 2X activation report. I just keeps gettin' better don't it?

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Neutrons!

Post by Andrew Seltzman »

Something looks unusual about the Pc calculation, it's not proportional to Vc*Ic and seems to be min(const*Ic,mTorr).

Nice CAD, some sort of cold cathode ion guns on the end? Looks a lot like the original Farnsworth multipactor guns.
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Andrew,

Pc is absolutely Ic*Vc. I think you are confusing the blue colors of mTorr and Vc.

Edit: These colors are more clear ...
2300_03102017.png
Last edited by Garrett Young on Sat Mar 11, 2017 11:58 pm, edited 1 time in total.
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Re: Neutrons!

Post by Andrew Seltzman »

Ah, ok I see now, that's exactly what I was doing. Wow that's really high pressure. Have you thought of using an axial magnetic field?
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Andrew,

Yes, I have considered an axial magnetic field and plan to try one at some point, but I think the fuel density outweighs the mean free path limitation (as Richard pointed out).

The strategy with this device is to take an ion optics approach to the fusor and that's why the center electrode and end caps are shaped as they are in the drawing.

The end caps support adding cold cathode ions guns in the future. (nice spotting)
- Garrett
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Nice thoughts and ideas. Another way to try and skin th' cat. If your system continues to work better as it is develops, you might just put the old fusor stock construction out of biz and every one with the goods and istrumentation might move over to 2.75 or 4 inch crosses!! I mean it!

I wonder how much the sharper radius joints at the cross arms add to the emission/ionization patterns. I realize the welds are smoothed but still sharper radius than the wall by huge amounts. Just thinking out loud.

We will see how far you can push this puppy.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Richard,

On the onset of this project I performed simulations using FEMM (free here - http://www.femm.info/wiki/HomePage) and custom code in Mathematica to try and optimize the electric field gradient (ion optics approach) and achieve a potential well at the center of the device nearly equal to the applied potential. Many wire grid designs don't effectively "shield" the grounded shell and only have the applied potential near the grid wires (5-10kV less in the center). My electrode design achieves 97% of the applied potential in the center and its shape (along with the contoured end cap inserts) focuses the ions through the center.

At the cross
KF50-40-port.png
Elsewhere
KF50-40-noport.png
(Note: The actual fusor volume is only 8.8 cubic inches.)
- Garrett
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

- Garrett
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

31 Bubbles in 4 minutes (24 bub/mrem dosimeter), 12.5cm distance to cathode, TIER 296K n/sec
IMG_1540.png
- Garrett
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Multiple runs over 300k n/s (344k n/s max)
Activating Indium at ~2x background and Silver ~3.5x background

Code: Select all

Run                      Avg. Background              1 min. Indium Count
In_1800_03162017         36.6                         72
In_1816_03162017         34.3                         80
In_1825_03162017         33.5                         62
In_1833_03162017         33.0                         57

Run                      Avg. Background              1 min. Silver Count
Ag_2252_03172017         40.3                         138
Basically, I never turn the vacuum pump off now and force convection cool the pump to achieve lower base pressure and cleaner system. In addition, I've optimized the deuterium flow rate and pump valve conductance for optimal pressure profile during the run.
- Garrett
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