Talk-Polywell.org

Skipjack wrote: A FRC plasmoid is created at each end of the device. The two plasmoids are accelerated, translated using pulsed magnetic fields until they are colliding in a central burn chamber. The burn chamber is surrounded by a simple cylindrical lithium blanket. All the expensive equipment is at the far ends of the device. I also think that at least Helion expects to get away without superconducting magnets.

Interesting, the very limited exposure I have had to FRC schemes was geared more towards steady state with the reversed plasmoid essentially acting as a tiny spheromak to be pumped with RF or neutral beam heating. Again not really my area.

Pulsing would rule out superconducting coils. I wonder what magnetic field strength they are aiming for; i.e. how much power they will be dumping into copper solenoids. My guess is they are shooting for densities much higher than a typical tokamak to make up for the low confinement time?

It seems that Helion is basically the same concept as General Fusion but with a final compression stage using a theta pinch rather than a physical shockwave.

prestonbarrows wrote: Interesting, the very limited exposure I have had to FRC schemes was geared more towards steady state with the reversed plasmoid essentially acting as a tiny spheromak to be pumped with RF or neutral beam heating. Again not really my area.
Pulsing would rule out superconducting coils. I wonder what magnetic field strength they are aiming for; i.e. how much power they will be dumping into copper solenoids. My guess is they are shooting for densities much higher than a typical tokamak to make up for the low confinement time?.

There was some research at the University of Washington into a steady state FRC fusion reactor design, but that has since been abandoned for lack of funding. There is a Google tech talk by Dr Grossnickle, the researcher behind that one on Youtube, somewhere. IIRC, he even mentions John Slough of MSNW/Helion (who also is at the University of Washington) favorably in his presentation.
In contrast to Grossnickles reactor, MSNWs and TAs reactor designs are pulsed, which is why they are much more viable. From my limited understanding they are quite similar and they seem to benefit from each others work. I have seen John Slough mentioned in at least one text related to Tri Alpha (I cant remember his exact position, I think he was a consulter of sorts on the construction of their test devices, but I might be fantasizing there). On the other hand TA has been doing some interesting experiments regarding neutral beam injection for stabilizing the plasma ( I think the paper was by Michl Binderbauer et al. There are some other tricks that both are using that further improve confinement times and density.
Either way, I think that Slough, Kirtley and the rest of the team at MSNW really have something that could work. Their main problem has been getting the funds for scaling up the their device. They do have a new prototype now, but I don't how close its scale is to the required size. IIRC a lot of the IP on FRCs is in the public domain, making this less interesting for investors, who prefer protected IP.

phrase of the day:
Behavior in Multi-grid Inertial Electrostatic Confinement Fusion
http://www.sppl.umd.edu/projects/02-multigrid.html


syring_289.pdf

I would think that more grids means more grid burn out issues as well as grid losses.
I am no clear on how they think to conquer that unless I have missed something.

I get the part that the aggregate layering improves confinement at the center, but you still have ions zooming around.

EMC2 had magnetic protection of their nubs and still had serious problems with nub heating and consensus of outsiders is that nubs were abandoned. So it is with grids. With modeling I guess these guys think they can find the perfect grid, electron, and ion injection to avoid that. They might do it where so many have failed before, but they aren't claiming to have succeeded. I say good luck to them.

Agreed. I think at any meaningful densities the metal is going to be eaten.

The intent of multiple grids for an IEC device is to form electric lenses that focus ions and electrons into beams, avoiding grid losses. I'm not sure how well that works in reality when you have beam scattering at the device focus.

As for nubs on the WB-6, they weren't well shielded. While they passed through a region of high magnetic field, that field was oriented as a cusp. The current through the nubs was far too small to provide usable shielding.

I would say the current was the same as the coils, however the geometric configuration was not conducive to field concentration, thus they were unprotected.

Recent developments in the field of IEC consist of additional concentric grids to focus the ion beams to limit scattering and thermalization. The result is the multi-grid IEC. Added beam-focusing grids have been shown experimentally to increase ion residence times as well as bunch the ions into resonant packets
http://www.nasa.gov/spacetech/strg/2013_nstrf_chap.html

and this very interesting paper
http://www.google.com/url?sa=t&rct=j&q= ... 5948,d.dmQ
Get that firefly body ready
http://fti.neep.wisc.edu/iec2009/talks/ ... ysedwi.pdf
page six if it holds true.

Awful lot of high energy particles zipping around in there. Seems like an erosion and activation nightmare.

But I guess that is more an engineering problem if the math and sims are true to form.

ladajo wrote:I would say the current was the same as the coils, however the geometric configuration was not conducive to field concentration, thus they were unprotected.

There would be the same current through the connector 'nubs' as any coil assuming they are all in series. However, there would be far fewer amp-turns in the connector since it presumably has only one wire while the coils have on the order of hundreds. So, if you broke the assembly up into components, the coil would have much higher magnetic field strength at the surface of its casing than the straight connector cylinder. I think that is what hanelyp was getting at.

The true field would be a superposition of the contributions of each of the sections. But, the field component from the connector would be relatively very small and almost negligible. This scaling ratio would depend on the number of turns in each coil.

The fields from the coils are essentially pointed radially outward at the location of the connectors. To first order, this would suggest particles riding out on these field-lines would be carried straight into the connectors at almost peak energy leading to considerable losses.

the claim is they have worked around the erosion problem and increased the number of passes by a factor. Two of the guys are currently working for LM.
Just saying

It is a good find for sure.

I remain suspect on the burnoff thing. It appears that this work is more Sim than Live Test.

I understand the intent, but like many things, intent verses action trend apart in the real world.

Agreed, if it was that easy why haven't we done it before.

I liked the idea of heat recovery from the grids (plus cooling) but that still does not answer the mail about activation (proposed coolant & grid material) or embrittlement problems with a bunch of zippy 0n1's screaming about.