Joe Gayo's Fusor - Neutron Detection Upgrade

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Dennis P Brown
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Dennis P Brown »

Amazing setup and really great posts! Your efforts have been really impressive.

One thing you might consider adding is paraffin shielding (and possibly a boron compound added to its outer surface) since you are getting well over (another post) a million neutrons/sec. For longer term operation, this would reduce exposure - while your fusor does not produce a lot of radiation the neutrons are deeply penetrating and have a high impact on tissue compared to most other types of radiation (esp. due to these particles being fast neutrons.) Neutrons are, unlike other forms of radiation, rather long lived (they have a 10 min. half life) and do tend to "hang around" when they are thermalized.
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Joe Gayo
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo »

Added an axial magnetic field (~250 Gauss) to stabilize the discharge and push the power higher.

Pressure: 28mTorr-31mTorr (because the chamber volume is very small and running dozens of 1200W runs the background pressure is effected significantly by the chamber temperature which exceeded 100degC)
Voltage: 52-40kV (drop is based on increasing pressure)
Current: 24mA
TIER: 1,525,000 n/sec
1.5Mnsec-1200W-16Feb2019.png
I repeated this run approximately 30 times with results in the +/- 10% range.
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Rich Feldman
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Rich Feldman »

Nice. Please say more about how you set up the axial magnetic field -- or point to an earlier post if you already told the story. Permanent magnets? Steel yoke?
All models are wrong; some models are useful. -- George Box
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Joe Gayo
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo »

Qty. 2 of 5856K16 (from McMaster Carr) on one opposing pair of sides. The fields are aligned in the same direction. I used FEMM (http://www.femm.info/wiki/HomePage) to calculate the field strength.
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Joe Gayo
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Re: Joe Gayo's Fusor - Neutron Detection Upgrade

Post by Joe Gayo »

For the first few seconds, the count rate is 400/sec when the voltage is 50kV. As the pressure rises and the voltage falls, the count rate finishes at 200/sec. Roughly 100/sec correlates to 500k n/sec, so the rate starts at 2M n/sec and falls to 1M n/sec. If the pressure was dynamically controlled to compensate for the temperature rise, then 2M n/sec would be sustainable.
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