## Magnetic mirror machine modification

Discuss how polywell fusion works; share theoretical questions and answers.

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jartsa56
Posts: 4
Joined: Fri Aug 07, 2015 7:08 am

### Magnetic mirror machine modification

Why don't we use a tube to connect one end of a magnetic mirror machine to the other end of said machine?

I mean such a tube that it contains particles magnetically.

If said tube can contain a particle as long as it takes a particle to travel half the length of the tube, then the probability of a partcle in the tube going back into the mirror machine is 50%. So we have reduced the leakage of the mirror machine by about 50%, assuming the ends are the main source of leakage in a magnetic mirror machine.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am

### Re: Magnetic mirror machine modification

I'm not sure the leakage in the tube would be linier, it may be exponential as a function of the distance traveled so knowing the losses at the halfway point may not tel you much. Also, keep in mind that it would be a two way street. In an opposed magnet mirror machine the end magnet point cusp (spindle cusp?) may have losses much less than the equatorial line cusp losses. This is much of the strategy in the Polywell- to significantly reduce the line cusp losses. Recirculating the losses, weather the spindle cusps or the equatorial cusp is attractive for both the Polywell, and the Lockheed Martin Machine. Either reversing and shooting the escaped charged particle (the electron in the Polywell), or looping it entirely around the magnet- as in the Lockeed design or a modified Polywell design may be beneficial. Looping it around several magnets to reenter on the opposite side probably is much more problematic . How do you prevent large losses in this tube that would suffer from various magnetic loss mechanisms such as edge stabilities, balloning instabilities (a type of edge instabilitiy?), ExB diffusion losses, etc. If you are talking about a cylindrical mirror machine where the magnets are not opposed, and you curve it around into a circle it would eliminate the end losses, but now you are in the Tokamak world, with it's own set of challenges.

If you can say that you have 50% of your losses in the first half of the pipe and 50% in the last half, it doesn't mean much. What you need to specify is what the actual losses are. If it is 1 % of the spindle cusp loss, then 99% or 98% of the losses are recovered depending on weather you wish to use 1/2 of total values or the entire path length losses. If you lose 49% of the spindle cusp losses in each 1/2 of the pipe then you are recovering only ~ 2 % of the spindle losses, and this is not worth much. The numbers tell the story.

What you are envisioning may have something comparable to a Field Reversed design. The plasma follows the magnetic field lines on the inside one way then loop around and flow in the opposite direction on the outside to start the journey over again. There are challenges with this design, as with all of the others.

Dan Tibbets
To error is human... and I'm very human.

jartsa56
Posts: 4
Joined: Fri Aug 07, 2015 7:08 am

### Re: Magnetic mirror machine modification

For me this kind of thing is the magnetic mirror machine:
https://en.wikipedia.org/wiki/Magnetic_ ... Mirror.jpg

Admittedly that machine mostly contains particles by another means than reflection.

The two ends are the leaky parts of this machine, they say. Hence the simple minded idea of connecting the ends.

What if we just bend the magnetic mirror machine? Then we have a tokamak with a narrow part. Maybe somehow that would be a good desing.

hanelyp
Posts: 2239
Joined: Fri Oct 26, 2007 8:50 pm

### Re: Magnetic mirror machine modification

A magnetic tube connecting the ends of a magnetic mirror... like a stelerator or https://en.wikipedia.org/wiki/Bumpy_torus? The curvature necessary to close the loop presents stability difficulties.
The daylight is uncomfortably bright for eyes so long in the dark.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am

### Re: Magnetic mirror machine modification

jartsa56 wrote:For me this kind of thing is the magnetic mirror machine:
https://en.wikipedia.org/wiki/Magnetic_ ... Mirror.jpg

Admittedly that machine mostly contains particles by another means than reflection.

The two ends are the leaky parts of this machine, they say. Hence the simple minded idea of connecting the ends.

What if we just bend the magnetic mirror machine? Then we have a tokamak with a narrow part. Maybe somehow that would be a good desing.

That is may appreciation. You essentially eliminate these open end losses. The problem is that other problems result. Things like ballooning instabilities, etc. You trade one set of problems for another. The trick is to pick an choose your problems that make up a compatible whole and try to figure out how to manipulate them so that the final results are acceptable- not perfect or even good, but acceptable.

PS: another solution to the end losses is not to transport the plasma to the other end, but to string it along into another core in a linear string of end to end reaction volumes. With enough nodes the effects would approach that of a totally enclosed system. This has been perused at least theoretically. It was this approach along with POPS effects that Nebel proposed as solution- a string of fusors end to end. This was about 1999, I have not seen any information on the idea since then.

http://newenergyandfuel.com/http:/newen ... rd-effort/

Dan Tibbets
To error is human... and I'm very human.