A Quick Question - What Would You Guess This Is?

For posts specifically relating to fusor design, construction, and operation.
Jackson Oswalt
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A Quick Question - What Would You Guess This Is?

Post by Jackson Oswalt » Thu Jan 25, 2018 3:09 am

What would you suggest this is:
image.png
Counts
You can see at the start of the 2 minute mark I added the deuterium. At the 4 minute mark I added a small bit more, but I quickly shut the deuterium valve not realizing I was getting counts.
This is at:
14-20 microns. This is mainly deuterium gas, but there is certainly a few microns of regular air due to my crappy diffusion pump cooling system.
40kv @ 7ma
~ 25 seconds of runtime
Neutron Detector:
image.png
Setup
SNM-10 detector
2.5” of HDPE moderator
1500 volts
Trigger set to -30mv
Background levels were 2-6cpm.
These values were confirmed by the person who makes and sells the neutron detector setup I have: https://www.ebay.com/itm/Turn-Key-Heliu ... SwiHpaDgTG

Unfortunately, I don't have any pictures of deuterium plasma, but I can confirm it was the purpleish pinkish color described. Also, plasma would not ignite until I added deuterium as per the fusor operation FAQ.
Larger post coming soon.

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Dennis P Brown
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Re: A Quick Question - What Would You Guess This Is?

Post by Dennis P Brown » Fri Jan 26, 2018 11:19 am

Right off hand, you may or may not have real neutron counts.

A few issues: First, you need to better document your run with details like the voltage and current. An image of your setup is generally required (unless you have previously document this in past posts.) Obviously, a pic of the plasma would be helpful.

Second, since the plasma will create noise in a detector, you need to make a plasma run with no moderator (or just use air and no deuterium) and see what the detector count rate is with the plasma/x-former running (ground loops and RF pick up from electrical wiring can be an issue for detector electronics near a plasma like a fusor) - this is a rather important test on the detector system.

Finally, after getting your noise floor defined, you then must make a few runs with and without the modulator (this is the gold standard test.) The counts should be your noise floor without the moderator and you should get significant (statistically speaking) counts with the moderator.

So far, you have demonstrated a possible neutron signal but until you do the previous tests, this is only a possible signal.

Jackson Oswalt
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Re: A Quick Question - What Would You Guess This Is?

Post by Jackson Oswalt » Fri Jan 26, 2018 1:16 pm

Thanks for the feedback. this post wasn’t intended as an application, but rather a test to see if it would even be worth applying for neutron club. What you've suggested is very likely. Are you supposing I would just subtract the noise floor from my total counts once it's been measured to get my neutrons? Just to be clear, I should run the fusor with air plasma and with no moderator, and the counts I get from that will be my noise floor? Thanks!

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Dennis P Brown
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Re: A Quick Question - What Would You Guess This Is?

Post by Dennis P Brown » Fri Jan 26, 2018 9:34 pm

As to that last question, yes, that is what defines the noise level for your detector system (i.e. no moderator and using air; one could use dueterium but that isn't the point here.)

So, a fusor plasma creates a lot of electric noise; some detector systems are very well shielded and some are not. As such, until you know how well your detector operates relative to just a plasma, you won't know its noise floor. This can be done with a deuterium plasma but you can't have any moderator around. Or can be done with air if ones does not want to waste deuterium (then leaving the moderator in place is fine.) It is possible that you get near zero counts for your noise floor - that is fine. It means your detector system is well shielded.

Aside: don't try to shield your system without understanding how to do that - that is a very difficult issue to address. First, defining the noise level is critical; even if the counts from the noise are fairly high, that may not be an issue as long as it does not overwhelm your neutron count. If it does create a problem, then that issue is best to discuss here before trying fixes unless you know that subject well.

Once that noise level count number is determined (and one run is fine), then yes, that is used to subtract from the neutron run values (the the plural.) Of course, you have to use deuterium gas for all neutron tests.Then measure your counts with and without a moderator screening your detector. The runs without a moderator, after noise subtraction, will roughly equal zero (yes, some could go a little negative, just round them to zero since experiments have variation.)

The runs with the moderator, after subtraction of the "noise count', is your likely neutron signal. I say likely because it may only differ by a small number. In which case one does many runs with and without a moderator to get a statistically significant signal form the 'noise'.

If, on the other-hand, one gets many more counts with a moderator after noise subtraction, there is little doubt that is your neutron signal. If you are unsure if the data is clean, this subject is carefully defined (i.e. signal to noise relative to data sets) in any good experimental physics lab book. But the simplest method is to just post here and let the community (i.e., really Richard) determine if your results pass muster.

Jackson Oswalt
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Re: A Quick Question - What Would You Guess This Is?

Post by Jackson Oswalt » Sat Jan 27, 2018 1:44 am

image.jpeg
Air plasma
I just got done with testing. Here are my results:

The neutron detector background is on average 5cpm.

The neutron detector with reactor running on air: 15, 32, 22, 32, 15. Average: 23.2

Reactor was operated at full 50kv and at 17-20 microns for exactly 30 seconds.

If you subtract the averaged noise floor along with the background counts with my fusion run you get 92cpm

Is it worth applying for neutron club?

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Richard Hull
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Re: A Quick Question - What Would You Guess This Is?

Post by Richard Hull » Sat Jan 27, 2018 5:23 am

If those colors are correct, that doesn't look like a deuterium plasma.

Run the fusor full tilt with what you think is fusion for five minutes without the moderator near or around the detector tube. Record that count. That is your noise level background. Next, do the same thing again with the tube inside its moderator. The difference between the two runs, if significant, is the neutron count.

No normal neutron detector tube will count any neutrons out side a moderator. To detect neutrons it must be in a moderator.

The best of all worlds.........you have your tube in a moderator, running the fusor and it is clicking way producing 40,50, 200 or 755 clicks a minute.....Pull the tube out of the moderator and the counts magically stop. When it was clicking away inside the moderator, you now have confirmed and know those were true neutron counts.

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.

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Dennis P Brown
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Re: A Quick Question - What Would You Guess This Is?

Post by Dennis P Brown » Sat Jan 27, 2018 10:48 am

A few questions and some advice:

You give counts with air but none with deuterium (in the last post here) - isn't the point here is to do a deuterium run with and without the moderator? I assume you are referencing the previous work? If so, why? Redoing runs to get more results following the methodology outlined is both important and instructive to prove your neutron count. A single run isn't necessarily proof (for a host of reasons that really, aren't worth discussing now). Also, your previous data run did not include a no moderator experiment. One needs to do that as both Richard and I have mentioned.

Are you short of deuterium gas?

When providing power supply information, include both the current as well as voltage.

The color issue for the plasma needs to be addressed as per Richard's questions - is the color we see in the picture the color you are seeing?

You mention the deuterium in the fusor might not be pure due to the diffusion pump? It is critical that the gas in the fusor be nearly pure deuterium. Even a trace of water vapor (converts to hydrogen) can prevent detectable fusion as I understand from Richard's post's on this subject.

Keep at it. Your setup looks good and the noise level from the detector appears low (assuming your neutron signal is well above this. Which if the singular run you made is accurate, it certainly appears it is.) Getting a fusor to work can take a number of runs/fixes before neutrons are detected.

Jackson Oswalt
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Re: A Quick Question - What Would You Guess This Is?

Post by Jackson Oswalt » Sat Jan 27, 2018 2:03 pm

Richard: The picture above is not of a deuterium plasma. As it says in the caption below, it's an air plasma. The results I posted yesterday (the 23.3 average) was my established noise floor. I ran five tests with just air and averaged them together. Later today I am doing another fusion run in which I will remove the tube from the moderator mid operation and see what results I get.

Dennis: Again, the caption says air plasma. I will I supply a deuterium plasma pic later today after I finish my run. As I mentioned above, I will be doing a no moderator run in this next test. I have a nearly full 10L bottle of deuterium. The power supply is 50kv @ 7ma.

Thank you both for your assistance in this endeavor. I will post my results from my deuterium run later today. Thanks!

Jackson Oswalt
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Re: A Quick Question - What Would You Guess This Is?

Post by Jackson Oswalt » Sat Jan 27, 2018 10:30 pm

I haven't done a full fusion run yet, but here is a picture of a deuterium plasma:
image.png
This is at 100mTorr. Once I properly cool my diff. Pump I'll be able to replace all air with 10 microns of deuterium.

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Dennis P Brown
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Re: A Quick Question - What Would You Guess This Is?

Post by Dennis P Brown » Sun Jan 28, 2018 3:10 pm

Is your DP water cooled and you haven't hooked up the water yet and that is why your runs are so short and infrequent? If so, do avoid using it until the water issue is resolved. Burning the oil in a DP is ugly and no fun to clean nor will your system be very clean, either.

When you can make runs, be sure to run long enough to get a good count level for the runs - at least a few minutes each (assuming your first run is mostly neutrons.) That is, do a moderator run and no moderator run and do this at least three times. Besides giving better statistics, it will more fully clarify the signal and leave no doubt about your neutron signal.

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