Record Fusion Run for Fusor 2020

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Mark Rowley
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Record Fusion Run for Fusor 2020

Post by Mark Rowley »

I think I may have safely surpassed the mega mark for the first time but I’d like peer review on this before I feel comfortable.

Before I get into specifics, the larger chambered Fusor2020 is a very smooth ride compared to the 2.75” cross Fusor I began with. As of this evening I completed its 4th fusion run since replacing a pinched o-ring. In total, the Fusor has had only 6 runs resulting in neutron production. In the last 3 runs I’ve noticed the conditioning effect that Richard spoke about which netted greater numbers with every subsequent run. Last night I was hitting numbers that appeared to be flirting with the mega mark but I wanted to be sure through repetition.

So this evening I got it running to a level where the Ludlum 2221 / CHM11 neutron detector was registering around 27kcpm/neutrons. To achieve that the input conditions were:

Voltage: 55kV
mA: 3.5
D2 Pressure: 46mTorr

Using a BTI bubble dosimeter, I placed it 17cm from the cathode grid with a total of 0.50” thick lead plate between it and the chamber (necessary for xray shielding). After a 3 minute timed count, the dosimeter registered 46 bubbles. Using the online gammaspectacular TIER calculator, this revealed a total neutron output of 1.18E+6.

Here is a video I made of the 3 minute timed count beginning with a totally fresh BTI dosimeter. If you look closely, at about the 4 second mark, you can see a bubble form as I display the dosimeter from almost 5 feet away! Neutrons are a flyin!

https://youtu.be/lWvRql_tp_I

For a 1 minute speed up version:
https://youtu.be/nfvU6PBSOMU

Mark Rowley
B5DAA0C5-3E74-4969-A4C5-624850CAEE3F.jpeg
Last edited by Mark Rowley on Mon Jul 20, 2020 1:20 pm, edited 1 time in total.
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Richard Hull
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Re: Record Fusion Run for Fusor 2020

Post by Richard Hull »

Great work. Probably a superbly sealed chamber. I am sure you are over the mega mark. Try some neutron activation using silver and a common GM counter. I am glad you are coming on line with this new system. You have a "feel for operation" gained in your first pass cross fusor.

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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Mark Rowley
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Re: Record Fusion Run for Fusor 2020

Post by Mark Rowley »

Thanks Richard
Yesterday evening I got things set up for indium activation using the same arrangement as with the previous Fusor. The best initial activation I could ever get with the old cross Fusor was about 150 counts which quickly decayed to around 50-60 counts during the second minute (LND7311 pancake with a 1.5x1.5” piece of indium foil). Normal background is about 30-35cpm.

-Last nights activation-
After getting about 1.20E+6 TIER neutrons with the new system, I exposed the indium for 2 minutes at a distance of 17cm. First minute of activation registered 768 counts! The second minute it expectedly decayed to 172 counts. An hour later It had decayed to 107 counts and almost 3hrs later (8:45pm) it was at 47 counts.

I can see I’ll have to get my GS1100 set up again for some gamma spec.

Silver foil will be the next activation run.

Mark Rowley
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