Abstracts posted for 20th US-Japan IECF Workshop

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Dan Knapp
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Abstracts posted for 20th US-Japan IECF Workshop

Post by Dan Knapp » Mon Oct 08, 2018 2:54 pm

The 20th US-Japan Workshop on Fusion Neutron Sources for Nuclear Assay and Alternate Applications (formerly called workshop on IECF) will be held next week at the University of Maryland. The abstracts for the meeting are now posted at:
https://blog.umd.edu/iecf/posterspresentations/
Of particular interest to this group would be one from the Kyoto University Group (Bakr, Ultra-Compact Neutron Generator based on IEC developed for SNM Interrogation System). In this 17 cm diameter fusor, with 6 cm diameter molybdenum grid, they achieved 8x10e8 neutrons per second at 70 kV/70mA. They achieved a fourfold increase in neutron flux going from a stainless steel to titanium sphere, which they attributed to increased adsorption of deuterium on the anode walls. To operate such a small device at 70 kV required a rather elaborate feedthrough (that is larger than the fusor itself). Although this kind of performance is probably beyond the capabilities of the amateur, it nonetheless shows what is possible in a small device.

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Richard Hull
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Re: Abstracts posted for 20th US-Japan IECF Workshop

Post by Richard Hull » Mon Oct 08, 2018 6:17 pm

What I think this Japanese work shows is my positing about shell absorbed deuterium for the last few years is now a positive direction for our kind of simple fusors.

The kind of "flash in the pan folks" we get here never tap into this possibility. Of course, titanium hemispheres are probably out of reach for even the most advanced folks here. The smaller sized devices with increasing pressures might also be a good place to investigate increasing the numbers.

It is important to realize that the very best hopeful design of a simple fusor will forever remain many orders of magnitude removed from usable fusion energy in the quest for same as an energy source. However, I feel it can be developed to a point of a couple of orders of magnitude improvement through such efforts seen in the work going on in Japan. Of course, costs go up in the fusion biz with such efforts. This is true even with the simple fusor.

To carry on this thread's direction it might be best to start a new one in the advanced discussion forum or the Theory forum.

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: Abstracts posted for 20th US-Japan IECF Workshop

Post by Scott Moroch » Tue Oct 09, 2018 4:21 am

Thanks for the information, Dan. I had absolutely no idea this was happening at my university. I will have to see if it is possible for me to sit in on some of the talks as the conference is a 5 minute walk from where I live. Very interesting abstracts.

Scott
"In the middle of difficulty lies opportunity"
-Albert Einstein

Dan Knapp
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Re: Abstracts posted for 20th US-Japan IECF Workshop

Post by Dan Knapp » Thu Oct 18, 2018 9:34 pm

The meeting was held on Tuesday this week. It was a full day of very interesting presentations. Of possible interest to this group in particular, the Kansai University group reported results from fusors using cubic anodes and cathodes. The cubic shapes are easier to construct than spherical grids. They rotate the cathode 45 degrees with respect to the anode so the openings in the cathode cubic grid are facing anode corners. They stated that this maximizes the beam length increasing the probability of collisions. Their reason for using cubic structures is to make arrays of fusors as planar rather than point sources. Having an anode grid, this shape fusor can be placed in any shape vacuum chamber.

As has been discussed in this forum, there was also considerable discussion of the point that most of the fusion in a fusor seems to be from interactions of fast neutrals with adsorbed deuterium on walls and on the cathode. As stated above, the Kyoto group got significantly improved neutron production by going from a stainless steel to a titanium chamber. A newly participating group from Dresden reported work in collaboration with Khachan's group in Sydney on 3D printed "buckyball" shaped grids, including grids printed in titanium. They concluded that in their experiments, the majority of the fusion is coming from interactions with deuterium bound on the cathode.

Another discussion item which could be useful to the amateur is the use of filament emitted electrons for deuterium ionization vs. discharge ionization. Most fusors are operated in discharge mode, and, as has been extensively discussed here, require considerable skill in achieving stable operation. Filament operation mode is done a lower pressure below the pressure where spontaneous discharge occurs. The Wisconsin group in particular tends to operate in this mode. They showed data where operating at a fixed pressure and cathode voltage, they can continuously vary the fusor current over a wide range by varying the filament emission. They use light bulb filaments. Filament operation requires a filament current supply and another supply to put a negative bias on the filament. The filament is located outside the anode grid, and, in their case, behind another grounded protective mesh. For fusors where the anode is the spherical chamber, filaments can be placed in ports behind a screen attached to the chamber. The additional complexity of the filament and bias power supplies might be more than compensated by simpler operation.

It is my understanding that the presentations will be posted on the meeting web page. When they are, I will post a link.
Last edited by Dan Knapp on Fri Oct 19, 2018 11:47 am, edited 1 time in total.

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Richard Hull
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Re: Abstracts posted for 20th US-Japan IECF Workshop

Post by Richard Hull » Fri Oct 19, 2018 4:29 am

A study of the original Desert cart fusor demo'd before the AEC by Hirsch and Meeks in 1967 utilized a heated filament and ionizer grid outside of the anode grid.

The cubic system takes advantage of the sharp high field emission points.

I have mused over the cross and Tee type small, successful fusors of late here. The multiple sharp, tubulation, weldment points/edges inside a CF cross set as the grounded anode would be high field areas. Interesting.

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.

Dan Knapp
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Re: Abstracts posted for 20th US-Japan IECF Workshop

Post by Dan Knapp » Fri Oct 26, 2018 1:10 pm

The posters and presentations from the meeting are now posted at:
https://blog.umd.edu/iecf/posterspresentations/

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Re: Abstracts posted for 20th US-Japan IECF Workshop

Post by Ben_Barnett » Sun Nov 04, 2018 8:48 pm

Dan, thanks for posting that link.

I am trying to study abroad / intern / research in Japan in Summer 2019 and this thread has me very curious.
Perhaps I will try to reach out to these groups.

Ben

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