True, the electric field does't apply for cusp losses, only recirculation and energy balance issues. I'm talking only about the magnetic cusp losses. Imagine the magnetic field lines in these small, diamond shaped cusps. There are four opposing fields, but this is still a corner cusp, not a point cusp. The lines still interesect the casing at the four corners, so there would be unshielded losses there. The question is how it compares to the clasic design.
I think anywhere where the windings form a convex curve towards the cusp, it cannot be a point cusp and so has to have magnetic field lines hitting structure. These cusps are small and presumably have proportionately strong magnetic fields, so perhaps they are more choked and fewer electrons can find them, but the design does not convert all of these cusps to point cusps.
Dan Tibbets
Magrid Vs electrically biased grid
It does make you wonder why Bussard moved away from that style of Magrid. He used it early on for proof of containment for electrons, but then moved away. I wonder if it really did get lost in the shuffle, or he saw something that is not so clear to us. Of course his was simpler in that it was copper tubing, so it acted as an all in one.
Hmmm.
Tom might be able to shed more light on it.
Hmmm.
Tom might be able to shed more light on it.
Not so. Indeed, his last paper indicated a desire to experiment with forms like this. His proposed WB7 was to be a "square plan form" MaGrid like this one without the bowed sides and without the real triangular magnets.ladajo wrote:It does make you wonder why Bussard moved away from that style of Magrid. He used it early on for proof of containment for electrons, but then moved away.
The dodec will be tried if we are a factor of 3 to 5 away from an economical reactor. (break even achieved)
There really is no rush for the dodec. First prove break even. And toroid coil forms (six sides) gives continuity of experiments.
Plumbing etc. will be a nightmare for a working reactor. A dodec will double the points of failure. Why go there if a slightly smaller (you read that right) reactor will get us where we want to go.
There really is no rush for the dodec. First prove break even. And toroid coil forms (six sides) gives continuity of experiments.
Plumbing etc. will be a nightmare for a working reactor. A dodec will double the points of failure. Why go there if a slightly smaller (you read that right) reactor will get us where we want to go.
Engineering is the art of making what you want from what you can get at a profit.
For land based reactors, simple is best, for mobile reactors size and perhaps weight can be a serious issue. Still, first things first, get the thing proven, keep it simple. Optimize later.
One more advantage for a dodec is that for the same size poly, the toroid magnet diameters are smaller so the B field will be higher, so energy density will be higher as a result.
One more advantage for a dodec is that for the same size poly, the toroid magnet diameters are smaller so the B field will be higher, so energy density will be higher as a result.
Counting the days to commercial fusion. It is not that long now.
A trip down memory lane.
I will not cite the previous discussion links on this, we are about due for another round of Magrid Geometry Jeopardy.
Simon: I agree with you but also want to note that Bussard's test plan proposal included a Dodec pre-breakeven to test confinement prior to break even scale. I think the current plan is more or less following the original grand design re-written to address the WB6 epiphany, but will not try a Dodec prior to DEMO. Of course, if we get to DEMO, someone will inevitably try Dodec or Octa or whatever afterwards (probably I think even if DEMO is successful or not...)
I will not cite the previous discussion links on this, we are about due for another round of Magrid Geometry Jeopardy.
Simon: I agree with you but also want to note that Bussard's test plan proposal included a Dodec pre-breakeven to test confinement prior to break even scale. I think the current plan is more or less following the original grand design re-written to address the WB6 epiphany, but will not try a Dodec prior to DEMO. Of course, if we get to DEMO, someone will inevitably try Dodec or Octa or whatever afterwards (probably I think even if DEMO is successful or not...)
Toroids are the simplest to build.ladajo wrote: I agree, but the actual construct of the current series remains as toroids.
IMO, Bussard was convinced the physics had been demonstrated and wanted to build a ruggedized WB6 just to demonstrate it to others. He then wanted to try two diifferent magnet designs before going to WB100/WB-D. They included a "square plan form" magnet version of WB6 and a "higher order polyhedron" which everyone takes to mean a dodec.
Actually, I think some of the root of the path is that Dr. N is not as convinced as Dr. B. was, or else wasn't able to be as convincing as Dr. B. thought he would be to the "expert panel" So instead of trying new magnet forms they are doing larger scale units of the WB6(7) design to get to the same level of confidence that Dr. B. had with WB6.ladajo wrote: The rush to switch the design of WB6 from planned to actual seems to be the root of this path.
Yup, and before the dodec he wanted to try a "square plan form" magnet, i.e., a cubeoctahedron. My "monocoque Magrid" is a cubeocthedron with bowed sides (more spherical I believe) and real-real magnets rather than real-virtual.ladajo wrote: Bussard also wanted to try the dodec, but that also has not yet appeared.