FAQ - A new fusor Construction paradigm for 2018
Posted: Sun Dec 10, 2017 4:41 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 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
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