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FAQ - A new fusor Construction paradigm for 2018

Posted: Sun Dec 10, 2017 4:41 pm
by Richard Hull
"Mine is bigger than yours".....This "old saw" might be headed for the amateur fusion waste bin.

Just a very few years back, would-be fusioneers of limited means began to actually do fusion in smaller conflat tee's and 4 or 6 way crosses. They rarely did much fusion, but they did do fusion. Within the last 2-3 years far more talented and careful amateurs have used the small conflat pre-forms as fusion chambers and, to their great credit, did fabulous and advanced reporting using good instrumentation. We can no longer lord our "big ones" over their "little ones".

I was going to say the evidence is mounting, but with the numerous well done small conflat pre-forms of late hitting near the mega neutron mark, I must now say the The evidence is in! It appears, that for a number of reasons, the smaller fusors under 3 inches in pseudo-diameter, most in the form of 2.75 conflat crosses, can perform amazingly well for their size. This is a marvelous and welcomed advance in the amateur technology of fusion within the Hirsch-Meeks simplified fusor form.

Foremost among the amazing reports are fusor operational pressures in the 50 micron range!! This is 5 times that of most 6" and larger fusor chambers. Also, more fusion is being reported at lower voltages due to this fact. These are theoretically significant facts that fit well with the reports. More fusion fuel per unit volume of the reactor vessel means more fusion. Smaller chamber volumes point to a more efficient use of limited particulate mean free path and a volumetric conservation of deuterium.

This new smallness has several benefits

1. Vastly reduced costs - By using a conflat pre-form (cross), all the connection issues of linking up larger welded spheres and cylinders or lucky e-bay finds with oddball fittings is swept from the field. Now, common attachments can be made at low cost with standard new or surplus juncture fittings.

2. Theoretical issues - As noted above, these might tend to favor the smaller chamber as well. Fusion is best done where there is more fusion fuel in a confined area where the mean free path is almost all within that smaller volume.

3. Less physical construction volume - A fusor can now take up less physical space and require less super structure.

4. A more "physically concentrated" neutron source can be made which can enhance activation experiments. (more flux at the fusor shell.)

5.With careful assembly, using quality parts, smaller vacuum pumps can be used and much faster pump-down times are readily achieved with possibly less chance for major leaks in vacuum system construction.

6. The reduced volume within the device conserves deuterium.

From the above advantages, there are provisos ...............Care in sealing your system is a must if you are looking at advanced operation from a smaller fusor. Among the most terrifying hurdles is, how do you get the needed voltage into such small volumes and not have it arc over to the sharp "high field" junction walls of a cross? Advanced folks here know what the last sentence is all about. Others have done it...Thus, it is doable.

Unknowns to me, as I have not operated such a small device, but it seems obvious... the issue of throttling of the pumped vacuum versus gas flow to maintain the typically much higher deuterium pressures within these small fusors. A new operational art, perhaps. But, this too has been mastered already by very few.

This new paradigm utilizes a term I have coined called The Fusor Criteria....it is an IEC fusor specific form of the "Lawson Criteria"

The Fusor Criteria - Produce the smallest possible containment vessel....Use the highest feasible deuterium pressure. Work at the highest voltage and current obtainable within the arc-over limitation of the construction.

I hope that much more information on this new paradigm might come forth in future through careful construction and scientific reports of operation of value to all future amateur fusion systems. As of this writing Robert Dwyer is doing great work in this area.

It takes a lot to impress this old curmudgeon and I am suitably impressed. New life and new directions at fusor.net

Richard Hull

Re: FAQ - A new fusor Construction paradigm for 2018

Posted: Sun Dec 10, 2017 6:54 pm
by Robert Dwyer
An excellent FAQ as always!

Something I have noticed in my fusor that may be worth mentioning is that the plasma will not light, or stay lit below 50 microns. I have tried many different times to bring the pressure below 50 microns, but it always ends in the plasma flickering out. The system seems to want to stay in the 50-60 microns range. Perhaps this is a characteristic of the grid vs. chamber size ratio? The walls are much closer to the grid in the smaller systems so I am sure that it is affecting the system a great deal. I may try some tests at higher pressure and see what results are gotten.

If devices smaller than 2.75" are to be attempted, something that is going to be a real challenge is protecting the system from arcs from the inner grid to the chamber. I was initially very worried at during construction that I would not be able to push the fusor to higher voltages, because of its small size. I haven't had an arcs from the inner grid, but some serious care would need to be taken in a smaller device to have a grid that can be run at higher powers without melting, but be small enough not to arc.

Re: FAQ - A new fusor Construction paradigm for 2018

Posted: Sun Dec 10, 2017 8:01 pm
by Richard Hull
I corrected David Dwyer to Robert Dwyer in my FAQ... Sorry 'bout that.

I mentioned the arcing issue in the FAQ as possible being 'terrfying". It might limit things a great deal and that is why I also mentioned smaller systems will demand a lot more of builder in the form of critical attention to such things while reducing costs as well.

Richard Hull

Re: FAQ - A new fusor Construction paradigm for 2018

Posted: Mon Jan 21, 2019 12:41 am
by Joe Gayo
Richard,

Looking through the forum it seems that Garrett Young (viewtopic.php?f=18&t=11318) was the first to reach 1M+ n/sec with a small fusor. Is that correct?

Re: FAQ - A new fusor Construction paradigm for 2018

Posted: Mon Jan 21, 2019 2:17 pm
by Richard Hull
Joe, thank you ever so much for your diligence and continued assistance and suggestions. You are helping to make these forums a better place.

I have just added the atta-boy to Garrett Young's neutron club name, giving him credit as being the first one to exceed the mega n/s TIER in a 2.75 conflat cross. I also note he quickly hit 2.75 million n/s TIER.

I might have to try this cross as a Fusor V project. I find that even in a small chamber Garrett also recognized wall stored deuterium improving his successive runs by 3X over is initial pumped down timed runs.

I am so glad I did not proceed with my 10 inch diameter fusor for Fusor IV. I am sad that I had spent all that money obtaining all the parts back in 2006.

Richard Hull

Re: FAQ - A new fusor Construction paradigm for 2018

Posted: Mon Nov 25, 2019 1:23 pm
by Richard Hull
Is Garrett Young still with us???? As noted above by Joe Gayo who graciously supplied the old URL, I see it is now, sadly, missing 100% of his pioneering photos. Garrett can you reload these??
Such a first effort of this type needs its images.

And Garrett was not the first to explore the small cross idea and actually do fusion in a cross. Who was it?

We certainly did not sit up and take significant notice until Garrett cruised over the mega mark and Joe Gayo and a couple of others have shown its unique abilities to the extreme.

Richard Hull