A new neutron moderator for fusor V - a talk in moderation

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Richard Hull
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A new neutron moderator for fusor V - a talk in moderation

Post by Richard Hull » Wed Jul 29, 2020 7:58 pm

What is attached is a PDF file related to the new moderator for fusor V and how I constructed it and a small comparison to water moderation. Also a mention on calibration.
I will add, not included in the paper. The water moderator is the least expensive moderator to build and operate.

Enjoy,

Richard Hull
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Neutron Moderator Fusor V.pdf
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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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Mark Rowley
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Re: A new neutron moderator for fusor V - a talk in moderation

Post by Mark Rowley » Tue Aug 04, 2020 4:13 am

Richard,
Thank you for detailing your moderator arrangement.

I just replicated this setup except for the length. Due to space limitations I had to go 14” but I made it up by adding another sheet on top. Total cost from Tap Plastics was $120.

Compared to the old paraffin moderator, a crude guess would put the HDPE about 25-30% more efficient which is similar to your results. The boron tubes generally have a very low background count at 1 or 2cpm. The HDPE did not change that. However, I did notice a distinct increase in count rate with a weak Po/Be source as well as a typical fusor run.

So, as expected, my calibration is now out of whack. I think my aging BTI’s should still be good enough to get me into the ballpark when I begin calibration runs.

The increased level of thermalized neutrons will be an added benefit to future activation experiments.

Here’s a pic of the arrangement with the lead shielding removed:

CED351B6-86D6-4659-8598-3F7206CB8A68.jpeg
Mark Rowley

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Richard Hull
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Re: A new neutron moderator for fusor V - a talk in moderation

Post by Richard Hull » Tue Aug 04, 2020 9:43 am

Fabulous work Mark! You did a great job. I am glad you got the same boost I did. If you have a BTI you need to hop on that calibration. I am just using qualitative, raw, timed counts to let me know what I am doing.

Wait until you see what I've got cookin' next! Relates to activation. I, too, noticed boost in my little source. Try slipping it in right next to your boron tube, if possible or near it within the moderator. Wow!

More as I do the work needed to bring my idea forth. I already have written and tested the Arduino program that will drive the work. Full details soon.

Again, I am happy that you are happy... As my old Tesla coiling buddy, Bill Richards, in our TCBOR group in the 90's use to say when presented with a new sight to behold........"Nice Stuff!"...or..."That's top drawer stuff, Ace!"

As I write this at 6 AM EST, the current hurricane is centered over Richmond. Lots of rain, not much local wind, however. Now time to go to bed.

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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Richard Hull
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Re: A new neutron moderator for fusor V - a talk in moderation

Post by Richard Hull » Mon Aug 17, 2020 6:39 am

Mark, I do not know the dimensions of your little source, however try slipping it inside the moderator, especially right next to the tube. You will double the count over externally setting it on top of or beside the moderator blocks.

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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