To respond to Franks initial post:
I don’t feel the recent operational fusor audit was meant to exclude anyone, just to get a general feel for how many of us still have operational systems, not just one-and-done fusors that demonstrated neutron output and were subsequently dismantled as people moved on to new hobbies. Neutron activation was just a benchmark of a “reasonable output flux”, and one hour was a “reasonable operational time”. I would personally consider any system that can be turned out and demonstrate neutron flux as an operational fusor.
Scintillator/oscilloscope, BF3 tubes with a removable moderator, He3 tubes, Bubble detectors, activation, beta spectroscopy are ALL acceptable means to prove fusion. Bubble detectors have been chosen by some to demonstrate (especially with lower output fusors) that actual neutron production is occurring, not just noise pickup; their dose integrating nature allows long duration runs at fluxes where a BF3/He3 tube would not provide accurate counting statistics. My first demonstration of fusion was with a bubble detector for just this reason (operating in the ~15kv range), while now with much higher output flux a BF3 tube will easily demonstrate neutron production in my fusor. There is nothing wrong with using one method over another as long is the demonstration of neutron production is clear and the detector and counting statistics are well matched to the neutron flux and signal to noise ratio.
With improved technology, surplus equipment, and understanding of neutron generator technology, the logical urge is to push to higher neutron numbers. Whether by “IECF”, beam on target, pinch, etc... The progress in increasing neutron output continues, as it should. Sure, beam on target is used commercially, but so what, we are an amateur group building neutron generators for fun as a hobby. While IECF was the initial focus of this forum, this was more of a historical occurrence starting with the 1998 Tom Ligon article and Richard Hull’s fusors that kick started armature neutron production as a hobby. Fusors are just more showy as you can see the plasma, though it could just as easily have been a dominantly beam on target hobby but for a flip of a coin on the neutron generation method in that fateful article in 1998.
Absolute flux is a good benchmark. I don’t think separating out into separate beam-on-target, pinch, groups would be productive or necessary. If people can and want to get higher flux with beam-on-target, good on them. Anyone who unambiguously demonstrated “neutron production” (no requirement on flux, just a positive confirmation) should be a member of the neutron club. Likewise, any neutron producing device should, for the purposes of neutron club membership or classification as an “operational fusor”, be accepted. The addition of new and novel designs such as the cube fusor, beam on target, and other designs have pushed the neutron rate to higher levels and fostered technological innovation.
I strongly oppose restricting to, or even implying that, this forum should be IECF based, in the main, because an “IEC fusor” does not have a distinct neutron generation mechanism within the realm of plasma physics. The Hirsch-1967 spatial distribution of fusion neutrons inside the cathode that was originally attributed to virtual electrode formation (poissors) was actually due to beam-on-target effects. The SIGFE experiment at UW Madison demonstrated over a decade ago that the majority of the neutrons produced in the Hirsch-1967 fusor were in fact produced by beam-on-target fusion with the interior surface of the cathode, in addition to beam-on-beam and beam-on-neutral fusion outside the focal point.
https://iec.neep.wisc.edu/usjapan/13th_ ... chalak.pdf
The salient findings were:
- Less than 0.2% of the D-D fusion reactions are from center of SIGFE device
- Virtual potential well structures and other space-charge related physics at the center of the SIGFE cathode are not a significant source of fusion
- D-D and D-3He fusion protons observed from center are consistent with beam-background fusion
- The results of the SIGFE imply that beam-embedded fusion in the cathode lenses is the dominant D-D fusion mechanism in the SIGFE
While generations of multiple virtual electrode formation (Poissors) may exist, they do not exist within the optimum parameter space for highest neutron production of an “IECF” device (eg we operate in star mode rather than Poissor mode), as such, for all intents and purposes, there is no physics basis to claim that "Inertial Electrostatic Confinement Fusion" reaction rates exist to the extent that IEFC is a distinct fusion mechanism for device classification. The term “IEC fusion” is used from historical establishment to describe a spherically convergent gridded electrostatic ion accelerator that is used for neutron production, (our “fusors”), in reality, the dominant neutron production in these devices is NOT due to the originally proposed multiple virtual electrode formation, but rather, beam-on-target, beam-on-neutral, and beam-on-beam effects. Therefore claiming a distinction between “IEF fusors”, beam-on-target, cube fusors, etc does not have a rigorous basis; all these devices generate neutrons by a wide range of mechanisms.