Fusor inside of tokamak

[fucion_cro]

Let's say that we have tokamak, so we put maybe 4 fusor grid inside. Fusor vacuum chamber is actually tokamak.
1. start vacuum pump, like in normal fusor/tokamak reactor
2. start fusor fusion proces, grid is inside tokamak
3. when we got our fusion and plasma on fusor grids, tokamak magnetic fields are turning on
4. grids are moved somewhere to not disturb plasma flow inside tokamak


What do you think about that?

[Dan Tibbets]

I'm guessing you are considering that the fusor grids could somehow boost the tokamac to ignition conditions, then be sidelined. The problem is that the fusor (with its grids is perhaps a million times worse at confinement and has only reached ~ 1/10-100 millionth of Q=1, while the tokamac has already reached ~ 0.8 to 1 Q (depending on how strict you wish to be). Also, the tokamac plasma density (which along with temperature and volume) determines the fusion rate, and this would benefit none of these conditions. The tokamac (tokamak) already has challenges with macroinstabilities and diverter challenges. It doesn't need any more disruptions of the plasma containment.

Fusors are better at heating plasmas to higher temperatures, but it is at heart a monoenergetic beam machine. This is already a part of how energy is fed into a tokamac- through neutral particle beams. This would not be changed with an internal fusor- it would only get in the way. I'm not certain why a tokamac has a much harder time reaching higher temperatures, except that they are forced to be large and thus have large surface areas to radiate away the heat you are trying to pump into it.. If you could decrease the size (perhaps through higher Beta operation) while maintaining the confinement, the heating would be less demanding.

Having said that, there may be some electrostatic inputs that might be employed to help instabilities- something like what Tri Alpha may be doing with their FRC.

Dan Tibbets

[David Geer]

Shouldn't be too much of an engineering feat to scale down the size of a tokamak to that of a fusor. Since I'm already looking into uses of strong earth magnets like the NIBs, I could try designing a tokamak-fusor chamber. Plenty of people already use the halo-ish magrids anyways, why not attach electromagnetic NIB curved panels onto the magrids to see how containment fairs. Though, ICF-wise, I'd only go with outer grid NIB containment with a standard tungsten-based inner magrid. This would allow a bigger "push" to the core area without having to over-complicate the design.

Perhaps, with the smaller scale the instabilities would remain within tolerance and one could achieve longer fusion runtimes for the same amount of fuel and power consumption.

[Dan Tibbets]

There is a reason Tokamaks are so large. The requirements to contain the fuel long enough requires the size to be large due to ExB type of transport across magnetic fields to the walls of the chamber. The further the ions have to travel, the longer they are effectively contained. IEC designs can contain either ions or electrons mildly well, but not both. Physical grids within the plasma space will always be an intolerable source of losses. Except, if the grids are magnetically shielded. This might solve the losses, but it would be extremely difficult, because the containment would have to be as long as in tTkamaks (hundreds of seconds). The only way to overcome this is to increase the density of the plasma so that the fusion rate increases rapidly and the required effective confinement times go down considerably.
So, for an IEC scheme to improve on the Tokamak, you need three things- excellent magnetic shielding of the grid/grids, significantly increased density, and some method to overcome the ExB transport losses of ions. The ability to reach higher effective temperatures does not hurt either.
The best example of this effort is the Polywell. Through magnetic shielding of an Elmore Tuck Watson type of fusor they improved confinement (or transparency of the grids) by a factor of ~ 10,000 or more. This is still not good enough, but claimed additional effects (recirculation) makes up the difference. The density is a seemingly insurmountable problem, but due to what is called the Wiffleball effect this absolutely critical density limit is overcome. The Wiffleball effect also is critical to achieving the claimed confinement improvements. The ExB constraints are overcome through using an excess of electrons in the system so that a vertual (no wire) cathode and potential well is formed that results in the ions being electrostatically confined, so the ExB drift problem is overcome (electrons do not require nearly as much space as ions in order for ExB drift losses to be tolorable.
Even then there are a few other tricks that the Polywell needs for it to work. This convoluted scheme, if it works, is only applicable to a near spherical configuration. It is not compatable with and will not work or contribute to a torus (Tokamak) type approach. The physics are not compatable. The Polywell utilizes a non magnetic plasma, while the Tokamak and other purely magnetic confinment schemes result in a magnetized plasma. I believe the same applies to other simple fusors. Certainly magnetic schemes are used in other schemes than the Polywell, that might result in magnatized plasmas- eg: some of the ideas from Miley at the Univ. of Illinois at Urbana(?).

Where electrostatic forces might help in a torus or FRC type system is in controlling macro- instabilities. These forces applied from outside the plasma might help stabilize the plasma. It would be a complicated sensing and local electrostatic and/ or magnetic force application process to control these problems. Perhaps somewhat analogous to controlling an aerodynamically unstable fighter aircraft .
None of this would decrease the size of a Tokamak. There is apparently a version of the Tokamak which used a higher Beta condition that presumably increase the density somewhat and thus decrease the required size. My impression is that if this version (or indead any version) of the Tokamak works, the gains would be small compared to a Polywell .

In short, forget about putting a fusor inside a Tokamak. Some other functions might lend themselves to a fusor approach. Eg: a fusor might serve as a better neutral plasma beam injector into a Tokamak, perhaps allowing higher temperatures and/ or less reliance on other means of heating the plasma.

Dan Tibbbets