Gayo 2021 Update

For posts specifically relating to fusor design, construction, and operation.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

@ Frank

Thanks.

I'm well aware neutron flux density changes with the distance squared and therefore the proximity of the activation foil, bubble tube, neutron counter, etc. is critically important for relating measurements to total output.

I want to be very clear, I don't take reporting this result lightly and have performed numerous checks. The 1E+8 number has been confirmed by over 20 runs, all using 1 of 4 bubble tube dosimeters (waiting 30+ minutes after resetting the tube. That's why I have 4, so I can run about every 10 minutes with a new tube). The activation foils were just another check because as Feynman said, the easiest person to fool is yourself. I actually told Jon R. earlier about my results (who has achieved 2E7, only a factor of 6 lower), because I'm very aware of the history here and I respect Jon immensely.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

@Joe B

Thanks for the encouragement!

IMHO, patents are overrated, trade secrets are better (in some cases).

Traditional fusor's are very limited, as Richard has pointed out, but they can be useful and with some modification (still IECF) may be very useful.

What I hope everyone can collaborate on are standard measurement techniques. My top three priorities have become clear, they are diagnostics, diagnostics, and diagnostics. Spectroscopy (optical, mass, gamma), probes (electric and magnetic), thermal, etc. were specifically integrated into my latest design and have revealed new operating modes.

In my opinion, if we want this to advance we need to simulate, design, build, then measure!
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Liam David
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Re: Gayo 2021 Update

Post by Liam David »

Congrats on the 1e8 milestone!

In your screenshot of the fusion rate calculator, I noticed you have 0W for the ion guns box. Are these runs at "standard" fusor pressures with a conventional discharge, or are you using a dual-gunned design?
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Mark Rowley
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Re: Gayo 2021 Update

Post by Mark Rowley »

Amazing numbers Joe! Remarkable achievement.

The phenomenon of good neutron output coupled with higher voltages and subsequent low current draw is exactly what I’ve been seeing here as well.

Mark Rowley
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

@Liam

No. This is a completely new device/approach.

@Mark

Yes. There seems to be a growing trend.
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Jim Kovalchick
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Re: Gayo 2021 Update

Post by Jim Kovalchick »

Joe,
Perhaps you are keeping some details of the new approach close, and I respect that. I am curious though. Does your new approach give more neutrons at lower voltages too, or does it only help in the upper ranges you dwell in now?
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Bob Reite
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Re: Gayo 2021 Update

Post by Bob Reite »

Congrats on keeping 100 KV tamed. Up to around 50 KV, it's not too bad. At 100 KV, everything starts to become a big deal. Corona discharge, field control. Arcs will not take the most direct path but start following weird paths, due to density gradients in the surrounding air. And of course the X-rays.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

@ Jim

I haven't really done much testing bellow 80kV. As with every fusor, not all voltages are accessible or practical (due to pressure and current needs). I don't think my device would perform well at 30kV.

I'm intending on pushing the voltage higher. Every iteration takes longer than expected but I'm hoping to have the next version before the end of the year.

Shielding is becoming a bigger concern. My operator station is a little over 25ft away and a REM ball shows 3 mRem/h of neutrons (every minute run generates 1-2 bubbles in a dosimeter at my control computer).
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Richard Hull
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Re: Gayo 2021 Update

Post by Richard Hull »

Some serious radiations over time at that range, Joe! That I would not like to take over time. At the 7 foot distant control chair from my unshielded system with 43kv applied, kicking out about 1mega neuts TIER, I see about 0.3mrem/hr of X-rays This is so low, I do not shield beyond a small lead shield at the view port.

Your are wise to operate remote at the levels you are getting.

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
JoeBallantyne
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Re: Gayo 2021 Update

Post by JoeBallantyne »

The Phoenix folks had some pictures of their lab setup on their site a few years back.

They were using a stack of the 4'x4' HDPE caged liquid containers full of water for neutron shielding.

Behind that they had a wall of 2'x2'x6' concrete ecology blocks.

One well positioned 4'x4' 275 gallon tote full of water might work wonders for reducing the neutron exposure you are getting.

They aren't very expensive. (Compared to all the other equipment you have invested in...)

Water in southern cal is at least for now still basically free.

Joe.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

I've decided on something similar. A wall of 5 gallon buckets (2 rows staggered) filled with Borax dissolved in water. The wall is placed in front of my lead sheets.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

I've been able to reduce the neutron rate measured at the operator station with water jugs, but as the overall numbers continue to climb, I need a more aggressive approach.

- Moving the operator station another 10ft (35ft total)
- Adding another staggered row of stackable 5gal Jerry cans

My general though has been to place shielding as close to the operator and far from the source as possible.
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Richard Hull
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Re: Gayo 2021 Update

Post by Richard Hull »

This is the best method. I recommended a shadow cone shield years ago and detailed it. By letting everything around you at range get blasted by inverse square law reduced radiation make stopping that much weakened blast easier to shield the operator. The shadow cone was designed to protect an operator at 7 foot ranges by a 18X18 box with an 18X18 sheet of 3/8 inch thick lead plate on exterior of the of the box facing the fusor. Inside the box whose internal interior width is 4 inches, a piece of HDPE sheeting 18x18x1" thick is placed inside the box and the remaining 3" width has borax mixed with molten paraffin is cast in the box.

Jammed up close to the fusor, the lead would limit the x-rays and the interior would absorb and scatter the bulk of the fast neutron flux as thermals. This was for what was then an 85kv fusor design. The cone on the other side of the shield would allow for a 7 foot distant operator to be in the vast shadow cone cast by this shield.

In your case, a bit of both near heavy cone shielding and light distant shielding might be a good idea. X-rays are a major issue, but easily shielded close in by the lead and the paraffin/borax would really kill the bulk of the fast neutrons resulting in heavily scattered thermals, resulting in frontal, rearwards and sideways scattering of the original fast flux. Scatter, close-in, with the shield what is effectively a projected impacting onslaught of fast neuts will turn into a 360 degree sphere of thermal neuts. At distance, within the cone of the close-in shield further shielding should a snap, if an issue at all, due to the inverse square law.

Do your best shielding up close and live in the shadow cone.

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
JoeBallantyne
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Re: Gayo 2021 Update

Post by JoeBallantyne »

I agree with Richard. Shield as close to the source as possible.

When I proposed using a single 275 gallon 4' x 4' tote for neutron shielding, my thought was to place it as close to the fusor as reasonably possible so that the fusor was centered on one face of the cube. Depending on the height of your fusor, centering the tote might very well require raising it a foot or so off the floor. On a short stack of pallets for example.

Then place the operator station as far away as possible on the same line that runs through the center of the fusor and the centerpoint of the face of that cube.

If you want to put even more shielding right in front of the operator station, fine, but I think you will get the most bang for your shielding buck by stopping as many neutrons as close to the fusor as possible.

To be clear, I don't think anyone else on fusor.net needs to be messing around with 275 gallon totes for shielding, but you are in a class by yourself at the moment, and the less irradiated you get, the longer you can keep doing your thing, making even more neutrons. The nasty thing about radiation doses is that they are cumulative, and every dose you get reduces your total remaining radiation handling capacity by that amount. Once your remaining handling capacity hits zero. Game over. No respawn.

Joe.
Last edited by JoeBallantyne on Tue Jul 06, 2021 2:13 am, edited 2 times in total.
JoeBallantyne
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Re: Gayo 2021 Update

Post by JoeBallantyne »

One issue with that kind of neutron shielding up close to the fusor, is that it will likely affect your counts, because some of the neutrons will be reflected back and get counted with the shielding up close. You should probably run some experiments to determine if neutron shielding up close does indeed impact your numbers. I think it will artificially inflate them somewhat depending on the exact geometry of the fusor, shielding, and neutron detection equipment.

Joe.
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

I've been very reluctant to add neutron shielding "close" to the device since I have an array of neutron detectors (at various angles and distances) to better characterize total output and any distribution bias. These detectors have been calibrated with a point source and I don't want excessive moderators changing the distribution of neutrons. In addition, I can't place any detector closer than 100cm or the counts are overwhelming and x-ray pile-up becomes a risk (the latest runs are at 10mA+).
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Joe Gayo
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Re: Gayo 2021 Update

Post by Joe Gayo »

In other news, after a short run I decided to bring my Geiger counter to check to see if I activated any material near the moderated detector tubes. The aluminum plates that electronically shield the detector assembly give about 10k cpm! It fades fairly quickly in agreement with the 2.2min half life of aluminum.
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Richard Hull
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Re: Gayo 2021 Update

Post by Richard Hull »

It's nice to see that the 5 folks who bought my 5 copies of the table of the isotopes at HEAS 31-2020 have been using them. That glorious aid and reference is a must have item for those doing any activation.

Yes, any form of neutron shielding will scatter like a big bear. That is the beauty of the shield!.... To turn any direct fast neutrons heading for a human bag of water, operator into a big sphere of thermals. It does screw with critical neutron counting trying to determine any beaming. Of course wooden structures, building materials, etc., will also send neutrons a-flying in tortured directions if the flux is high enough.

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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