FAQ - A new fusor Construction paradigm for 2018

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Richard Hull
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FAQ - A new fusor Construction paradigm for 2018

Post by Richard Hull » Sun Dec 10, 2017 9:41 pm

"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 and beyond 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 equal and, in some cases, outclass 6" and larger spheres and cylinders of the early days of this forum. 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.

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.

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
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.

Robert Dwyer
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Re: FAQ - A new fusor Construction paradigm for 2018

Post by Robert Dwyer » Sun Dec 10, 2017 11:54 pm

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.
If we throw more money at it, it will have to work... right?

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Re: FAQ - A new fusor Construction paradigm for 2018

Post by Richard Hull » Mon Dec 11, 2017 1:01 am

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
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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