Hello,
This might be old news....
This Dr. in England built a fusor. He made a film about it. It is a pretty good movie....
http://topdocumentaryfilms.com/fusioneer/
30 minute film about Jonathan Howard building a fusor
Interesting video, but there are some innacuracies. He implies that the melting grid is the limiting factor, without pointing out tha tthe ion impacts is what is doing the heating and that this is a transfer of energy from the ions to the grid and thus a (huge) containment loss mechanism. The best gridded fusors may allow for an ion oh make ~ 10-20 passes/ orbits before it hits the grid. This is a simple ratio of the wire surface area verses the surface area of a sphere (or column) with a radius of the wire grid. There have been multiple efforts to improve this with multiple gridded systems that focus the ions between the grid wires. Non have performed as well as the researchers hoped for. Bussard pointed out that in his estimates the ions would have to make at least ~ 10,000 passes before breakeven was possible
The videos claim of 1/100,000 Q obtained by fusors is actually off by a factor of 1-10 thousand. Q closer to ~1/billion is the norm.
Another point not mentioned is the electron current which has no containment. Elmore Tuck and Watson tried to address the electron loss issue by using a peripheral grid to accelerate the electrons towards the center. But, ignoring the wire impact issues, this just reversed the the electron and ion loss paths.
The Polywell claims to avoid the incompatibility between electrostatic ion AND electron confinement by using magnetic forces to confinement one species and the associated induced electrostatic forces to confine the other species. This is nice, but doesn't necessary resolve the loss- gain issues. The wire grid issues have to be addressed, as do the cross field magnetic field diffusion issues. Bussard solved the latter issue by using electrons to generate the electrostatic field, which contains the ions. The electrons have the huge benefit in terms of magnetic containment because of their much smaller mass/ momentum, so that their magnetic field penetrating diffusion is ~ 60 times slower. This allows for smaller volumes with greater densities without the ExB diffusion limiting the magnetic confinement. The system does have cusps and these do leak relatively profusely but the obtainable fusion generating density obtainable exceeds these cusp loss issues (triple product issues). At least they are claimed to do so once recirculation improves electron confinement by a factor of about 10 or possibly more. That and of course the essential Wiffleball effects. Other possible benefits of mono energetic characteristics and confluence (central focus) are icing on the cake for D-D or D-T fusion and possibly for D-He3 fusion (allowing for annealing claims). Electron dynamics in the machine (fast on the edge, slow in the center) and Bremsstruhlung minimizing through dilution with excess protons compared to the boron are additional processes that may allow for P-B11 profitable fusion.
A gridded fusor with some magnetic shielding of the wire grids may help some, but by itself does not change the electron losses to the wall (or ion). I'm guessing that performances approaching ~1/millionth of the Polywell might be obtainable. This is a ~ 1 thousand fold improvement over conventional gridded fusors. The Polywell uses the Wiffleball effect and recirculation to make up the rest of the difference.
Even this wordy reply is a simplified view that does not address some issues but it does outline my understanding of why the Polywell overcomes the known short comings of typical wire grid fusors, or even purely magnetic confinement schemes like Tokamaks. I have read that Tri Alpha is using electrostic forces to help overcome some of the magnetic confinement short comings of their FRC approach. This may imply that arrangements that can segregate ions and electrons and their respective responses to magnetic and electrostatic fields is a key to small scale (not behemoth sized Tokamaks) Fusion reactors. And, don't forget DPF General Fusions's approaches. LCF seems not better than the Tokamak approach from an economic viewpoint.
Dan Tibbets
The videos claim of 1/100,000 Q obtained by fusors is actually off by a factor of 1-10 thousand. Q closer to ~1/billion is the norm.
Another point not mentioned is the electron current which has no containment. Elmore Tuck and Watson tried to address the electron loss issue by using a peripheral grid to accelerate the electrons towards the center. But, ignoring the wire impact issues, this just reversed the the electron and ion loss paths.
The Polywell claims to avoid the incompatibility between electrostatic ion AND electron confinement by using magnetic forces to confinement one species and the associated induced electrostatic forces to confine the other species. This is nice, but doesn't necessary resolve the loss- gain issues. The wire grid issues have to be addressed, as do the cross field magnetic field diffusion issues. Bussard solved the latter issue by using electrons to generate the electrostatic field, which contains the ions. The electrons have the huge benefit in terms of magnetic containment because of their much smaller mass/ momentum, so that their magnetic field penetrating diffusion is ~ 60 times slower. This allows for smaller volumes with greater densities without the ExB diffusion limiting the magnetic confinement. The system does have cusps and these do leak relatively profusely but the obtainable fusion generating density obtainable exceeds these cusp loss issues (triple product issues). At least they are claimed to do so once recirculation improves electron confinement by a factor of about 10 or possibly more. That and of course the essential Wiffleball effects. Other possible benefits of mono energetic characteristics and confluence (central focus) are icing on the cake for D-D or D-T fusion and possibly for D-He3 fusion (allowing for annealing claims). Electron dynamics in the machine (fast on the edge, slow in the center) and Bremsstruhlung minimizing through dilution with excess protons compared to the boron are additional processes that may allow for P-B11 profitable fusion.
A gridded fusor with some magnetic shielding of the wire grids may help some, but by itself does not change the electron losses to the wall (or ion). I'm guessing that performances approaching ~1/millionth of the Polywell might be obtainable. This is a ~ 1 thousand fold improvement over conventional gridded fusors. The Polywell uses the Wiffleball effect and recirculation to make up the rest of the difference.
Even this wordy reply is a simplified view that does not address some issues but it does outline my understanding of why the Polywell overcomes the known short comings of typical wire grid fusors, or even purely magnetic confinement schemes like Tokamaks. I have read that Tri Alpha is using electrostic forces to help overcome some of the magnetic confinement short comings of their FRC approach. This may imply that arrangements that can segregate ions and electrons and their respective responses to magnetic and electrostatic fields is a key to small scale (not behemoth sized Tokamaks) Fusion reactors. And, don't forget DPF General Fusions's approaches. LCF seems not better than the Tokamak approach from an economic viewpoint.
Dan Tibbets
To error is human... and I'm very human.