Neutrons!

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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
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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).
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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
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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.
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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)
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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.)
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

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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
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Garrett Young
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Re: Neutrons!

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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.
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Garrett Young
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Re: Neutrons!

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Added axial magnetic field last night using ceramic magnets at opposing ends. Fairly uniform 200 gauss in the cathode region and 300 gauss at the shaped anodes (which probably improves ionization at the wall, thus increasing average ion energy). Pressure is still 48-58 mTorr during runs. Base pressure has lowered to 3 mTorr (I'm using just a 2-stage rotary pump).
axial-mag.png
Runs are now above 400k n/sec (420k n/sec best run - corroborated with bubble dosimeter). It seems the level of fusion per input power per chamber volume is very high (8.39E+04, n/sec/kW/in^3).

I have my hybrid NIM/Sound Card gamma spectrometer up and running and I'm interested in activating Manganese next.
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Garrett Young
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Re: Neutrons!

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I can't stress enough the importance of conditioning runs with deuterium to ultimately achieve maximum neutron production rates. I know this topic has been addressed, but it's worth another mention. I consistently see a ~3x gain between first few plasmas after the system was brought to atmosphere and the last runs.

Wall loading, system purity, etc. all seem to be contributing factors.

My latest numbers with the mini-linear-fusor configuration (Max Cathode Voltage 28.6kV):
3 mins: 431k n/s, Q 9.84E-10
4 mins: 357k n/s
5 mins: 263k n/s
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Dennis P Brown
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Re: Neutrons!

Post by Dennis P Brown »

Really good scientific work you are performing. You make me realize I should not have abandoned my original fusor that was to based on a 2.75 inch cross. Instead, I decided to use my large surplus chamber and while successful, achieved barely a tenth of the neutron flux you have. I agree with Richard that this approach demonstrates that this design has a lot of advantages; guess it will likely become the "gold" standard for fusor design in the fusor.
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

Garrett, thanks for blowing on the same trumpet I have been tooting on for many years here. It is all about "conditioning the fusor" and the "ability to operate the fusor properly by a skilled hand". The former is seen only after the latter is obtained via the "doing". Fusion in the fusor moves onward and upward through operation and the use and understanding of full and proper instrumentation. The instrumentation need not be calibrated to a high order, but must be capable of showing a run-to-run improvement in performance.

Once the above is attained, calibration can proceed to get a more precise figure on what one is doing and has accomplished. It is a great pity that the rather accurate and final arbiter, the bubble dosimeter, is both rather expensive and sports a limited useful lifetime. I bought them twice. Once in ignorance to prove fusion and get numbers and then 2 years later to calibrate, forever, my 3He detector setup which to this day performs to relative accuracy based on the large amount of data taken during the last lifespan of that second bubble dosimeter. I derived a calibration factor from this data which is now applied to an electronic, timed count in order to obtain my isotropic emission figures.

Keep up the good work and tooting that horn as in your above post. It is a revelation that few will ever see as so many are greedy only for the "win" and never operate their fusor in the manner and never packed the gear to continue on to the realization of what we have seen. I would think that only about 20% on the neutron club list have seen and done what we have done to its full and final realization.

Once you squeeze that last bit of fusion out of your system.....and it will come.....You are in full command of the IEC fusion concept and realize only a redesign or more powerful supply can take the system to greater heights of performance.

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 Dan Knapp »

Garrett, You would be interested in seeing the information on Alex Klein's "MARBLE" reactor (google Alex Klein and MARBLE). He built this device in the dying days of his company and then rode off into the sunset in Malaysia. It is essentially multiple's of your device superimposed to overcome the limitations of space charge at the turning points. It also included an axial magnetic field. He filed a patent on it (application was published) but I've not seen that the patent has ever actually issued. There might be some information from his work that would be helpful to you.
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Garrett Young
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Re: Neutrons!

Post by Garrett Young »

Interesting. Thank you for sharing. I'll have to read more about their device.

Part of choosing the dimensions for my device was making sure child-langmuir space charge didn't limit the ion beam current.
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Garrett Young
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Re: Neutrons!

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Attempted a gamma spec of Indium (background removed). The signal to noise isn't great but that's probably due to the short activation time and low neutron numbers. In addition, it seems the detector is more sensitive to lower energy gammas. Does that make sense for a NaI crystal? Can Theremino MCA be calibrated for this variation in sensitivity using the energy equalizer?
ThereminoMCA_20170403_In.png
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Richard Hull
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Re: Neutrons!

Post by Richard Hull »

The lower end of NaI:Tl xtals are always a noise fest, as the background is a mix of low energy gammas, xrays and weakened cosmic interactions with local matter. The only thing you can background out are terrestrial NORM signals as they are present and rather constant. Random cosmic interactions are not so easy. Depending on the crystal size, low energy stuff, (noise in low energy end), is 100% captured in the xtal and makes a flash. Lots of clutter under 50kev and only a strong source will push out of it enough to be seen easily. Log mode energy display will often assist, but you will never have sharp peaks from and NaI:Tl crystal.

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 »

Acquired a new power supply capable of -60kV and 11mA and have performed several lower power runs and the results are very exciting.

Pressure: 33 mTorr
Cathode Voltage: 44.1 kV
Cathode Current: 10.9 mA

TIER: 1.30 E+6 n/sec (!!)
Q: 3.16 E-9
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Steven Sesselmann
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Re: Neutrons!

Post by Steven Sesselmann »

Garrett,

Congratulations on reaching the mega neutron mark, well done.

My next target..

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
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