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

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

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

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

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

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

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

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

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

Posted: Mon Sep 28, 2020 8:46 pm
by Richard Hull
Remember tinker toys, Erector sets, Lincoln logs? Maybe not for the younger crowd. I just ordered 4 long strips of HDPE. 2 strips 1 X 1-inch, 8 foot long and 2 strips 1.5 X 1-inch, 8 foot long. with these in hand, I can make up a number of moderator blocks of varying length to make up and test experimental moderators and neutron ovens. These can include sources, foils, detectors or all three. I will have a moderator builder's kit, in effect. Stack 'em and build 'em. Total cost, with tax, is $96 bucks. I figure on 16 4-inch long pieces of 1X1 and 16 4-inch long pieces of 1.5X1 I'll then stock the two 32-inch long stubs plus the two remaining full 96-inch length pieces of 1X1 and 1.5X1 for future cuts in my moderator kit of neutron slowing, nuclear toy blocks.

Naturally, my current fusor V moderator remains un-touched.

Richard Hull