Joe Gayo's Fusor - Neutron Detection Upgrade

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Richard Hull
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Richard Hull » Sat Jan 19, 2019 5:35 am

My First fusion was with a mechanical pump that could hit 5 microns, backed by a micromaze that bottomed my TC gauge. (actual vacuum unknown). The best I ever did with fusor III was 250kn/s but I never got above 32 kv. Now that we are into the wall loading concept, day to day operation will see a bit of improvement. In addition, when fusor III was in operation I have far less knowledge and much reduced neutron detection (Eberline PNC-1) a good counter, but with a small Nancy Wood BF3 tube in it.

A word of advice. When you have your bubble detector fix forever your neutron tube and moderator or mark its position well. Calibrate your counter using the bubble detector. over many days and many runs recording all data counts during a run and the number of bubbles per run. Do this as many times as you can over the life of the bubble detector. I have many, many pages of such data. In the end, Based on the bubble detector's rmem dose back figure to the digital counters run total counts, you will arrive at a multiplication factor for future total counts that you can use in future long after the bubble detector is dead to arrive at a total isotropic emission per second of neutrons from your fusor. The accuracy of the multiplier will rely highly on the number of data samples taken over time. More samples, obviously the better the statistics and the resultant multiplier.

My multiplier turned out to be 21.6. I backed it off to an easy and conservative 20.0.

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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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo » Sat Jan 19, 2019 4:06 pm

Will do with the bubble detector!

I assume when you say micromaze you are referring to a sorption pump?

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo » Sat Jan 19, 2019 9:41 pm

The following is for those who are looking for the lowest financial bar for a neutron producing fusor:

If you have reasonable strong electronics knowledge, then a sub $1000 fusor is possible maybe even sub $500.

** Use a high quality two-stage rotary vacuum pump (Edwards, Pfiffer, Precision Vacuum, etc.) - no diffusion or turbo pump required. A base pressure bellow 7mTorr seems sufficient. This also means you only need a thermocouple vacuum gauge.

** KF 40 cross makes an excellent chamber. KF fittings are cheap and simple to assemble / disassemble.

** Purchase NIM BIN equipment even if it's not guaranteed to work. Schematics are readily available in the manuals. The common failure points are cold solder joints, failed output BJTs, and tantalum capacitors. (I fixed/refurbished my NIMs and preamp)

** Purchase the OEM models of Spellman or Glassman power supplies, or better yet, units with just the multiplier stack (viewtopic.php?f=11&t=12625)

** Spark plug high voltage feedthrough - https://www.ebay.com/itm/Metric-M14-x-1 ... 2480729252 with a Champion J99 599 industrial spark plug. As long as the air side is sufficiently insulated you should be able to reack 20kV+.

My fusor was around $720.

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Richard Hull » Sun Jan 20, 2019 5:03 am

The micromase was pushed by Lesker for a few years and is no longer available. It was great and could warrant about one order of magnitude below a good mechanical pump that could go under 10 microns on its own. It had its own internal heater to purge bad stuff out and clean itself up. It was found by me that a full one hour pumping, heated purge of the micromaze and gas ballasting for each days run of the fusor. This hassle might have been the complaints around their micromaze and its demise. I did not mind it in those early days.

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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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo » Tue Jan 22, 2019 3:12 am

Bubble detectors arrived (55 and 54 bub/mrem)!

Did a quick 30 second run at near full power 45kV, 15mA, and 28mTorr.
Dosimeter has a holder that places it 22.4 cm from the center of the chamber.

5 bubbles ... 545,000 n/s TIER
IMG_1050_sm.jpg
Obviously I have more runs planned, but I couldn't wait to post.

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Dennis P Brown » Tue Jan 22, 2019 1:20 pm

Very nice results; Bubble detectors are useful and the gold standard.

I too checked mine with a 22 bubbles/rem - turns out my neutron detector wasn't too far off (around 170 k neutrons/sec.) I did two chamber sizes with two bubble measurements to show that halving the fusor volume nearly doubled the neutron count (gas pressure and voltage all the same.) Was hoping someone else would look into that question and do more definitive experiments - one experimental run is not exactly proof.

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Cristiano_Machado » Tue Jan 22, 2019 1:37 pm

Hello Joe,

Nice work and I am happy the BD have arrived earlier than expected.

I am trying to send you a private massage about the BD, but I don't know why the messages can't go out of my outbox. Can you contact me about our deal? Fell free to email me directly (c_machado@yahoo.com).

Regards,

Cristiano

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Pablo Llaguno » Tue Jan 22, 2019 10:24 pm

Great work Joe!

I am curious as to how you set up your vacuum and D2 system. Does your setup use any valve between the pump and chamber? If not, how do you manage to not waste so much D2?

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo » Wed Jan 23, 2019 1:59 am

I do have an isolation valve but I do flow the D2 and waste a decent amount at this point. My runs are fairly short.

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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo » Wed Jan 23, 2019 5:58 am

Good statistical run...

98 bubbles in 180 seconds, 12.5 cm distance

554,000 n/sec TIER

45kV 16mA

28mTorr
42B17938-41F7-44CF-91FD-AB00978F44F7.jpeg

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