Talk-Polywell.org

I think I understand the Ma grid fairly well. I'm not clear how the biased grids worked. Why did they melt whereas the Ma grid does not?

Did Hirsch/Farnsworth ever consider a Ma grid? If so then why not use it?

If they did not consider a magnetic grid then why not?

The inner grid for a Hirsch/Farnsworth (or ETW) does not exist in a Polywell. It is virtual. If it is not there it can not heat. In a fusor, it is heated by oscillating particles and fusion products as it lays near the reaction and target space of the core. (it is actually the target as the ions are pulled to it.)

Almost right. The grid in the ETW (Elmore Tuck Watson) IS the grid in the MaGrid without the Ma. The ETW fusor grid heats because the electrons run into it after <100 transits. The Ma in the MaGrid is the magnetic field that prevents the electrons from running into the grid and allow 1000s (100,000?) transits before impact with the grid.

The hot spots in WB6 & 7 seem to be on the nubs which has less protection. WB7.1 was supposed to modify WB7 to limit/eliminate the problem. Wish we had some data wrt the results thereof.

K?

I thought he was talking about the inner grid only.

But yes, I should have specified the magnetic sheilding (Ma) as well in the construct.

I thought ETW still had two grids.

Indeed, magnetic shielding is key to prevent the anode grid (ETW variation) from being bombarded by high energy electrons (it is high energy ions that bombard the central cathode grid in the conventional Farnsworth Hirsch type fusor).

Also, don't forget that this is only 1/2 of the story. The conformation . placement and strength of the magnetically shielded grids (magrid) leads to the claimed Wiffleball effect. Without this, energy losses would still be ~ 1,000 times or more severe. Even if remarkable recirculation cut down on the electron losses, the density of ions could not be maintained much above the external magrid volume, and due to arcing concerns, the density would be 100's to 1000's times to small for useful fusion rates. Significantly increased volumes for the reactor could compensate for this. But as gain at constant density would scale as r^3 and losses scale at ~ r^2, the size of the machine before breakeven would be very large, probably putting even tokamaks to shame.


Dan Tibbets

I think this alternate IEC fusor design has been discussed here before, but I don't know where. The "hard-coded" wiffleball (in this case a radially-magnetized, hollow, perforated, spherical, permanent magnet "magrid") shown on page 32, Figure 4 is kind of interesting):

Magnetic Core Multi-grid IEC Fusion

(MSimon: sorry for the long link, but the usual aliasing method is not working.)

DeltaV wrote:Magnetic Core Multi-grid IEC Fusion

(MSimon: sorry for the long link, but the usual aliasing method is not working.)

I hadn't noticed. Heh.

The problem is not null fields. It is that the curvature of the fields does not conform to the grid.

Of course considering the conference appears to be 1/2 cranks I'm not surprised.

This would never pass a serious review. Not only that. It appears to have been cribbed in part from a grad school paper by 2 MIT students. Which is explained by the fact that one of the authors of the MIT paper is an author of this paper.

DeltaV wrote:I think this alternate IEC fusor design has been discussed here before, but I don't know where. The "hard-coded" wiffleball (in this case a radially-magnetized, hollow, perforated, spherical, permanent magnet "magrid") shown on page 32, Figure 4 is kind of interesting):

Magnetic Core Multi-grid IEC Fusion

(MSimon: sorry for the long link, but the usual aliasing method is not working.)

That magnetic sphere, magnetized as described, would actually guide ions right to the metal parts of the sphere.

Yup, and I bet it would make a nice expensive lamp as well.

I'm not so sure about charged particles streaming to the exposed poles on the inside of this permanent magnet grid.
On first glance, it looks so, but you need to consider other effects. In single and multiple grided fusors the charged particle beams tend to form into focused channels between the grids- called Star Mode. This apparently increases the effective transparency of the grids to a modest extent, say increasing from ~ 90% transparency to~ 98% transparency. Some have tried to increase this effect through multiple grids. The picture in this article has point cusps at each hole. This might enhance the focusing of the 'Star Mode' beams further. Presumably the charged particles that might follow field lines to the exposed magnetic poles between the holes are in a minority. It would be a compromise between electrostatic effects and some marginal magnetic effects. If only one type of charged particle is considered- eg: pos. ions, the ions that are already mostly focused into a broad beam would glance off the magnetic field lines preferentially towards the holes (if the magnetic polarity is correct) and pass through the holes with greater enthusiasm. There are a lot of permutations possible: numbers of grids, electrical polarity of the grids, direction of the magnetic poles, etc.
I could easily see this as improving the transparency. Sort of a super Star Mode. But, I suspect the improvement would still be far short of what would be required. Gridded fusors (even Hirsch's model) are ~ perhaps 10^5 to 10^8 orders of magnitude short. This technique might eat into this by 1-2 orders of magnidude. This is still way short of break even. But, if might improve thermalization issues and with POPS type effects, who knows...

Additionally, there is no Wiffleball effect, so the density would need to be much less than a Polywell. Unless the focusing/ POPS effects could far exceed those of a working Polywell, the machine size would have to be huge before useful amounts of fusion could be obtained. It might make an excellent neutron source though...

Dan Tibbets

Regarding the nubs that connect the magnets; If the magnets are supported via the flanges don't you still have the supports in the field lines?

MSimon wrote:

DeltaV wrote:Magnetic Core Multi-grid IEC Fusion

(MSimon: sorry for the long link, but the usual aliasing method is not working.)

I hadn't noticed. Heh.

Hmmm... it fixed itself. AI.

WizWom wrote:That magnetic sphere, magnetized as described, would actually guide ions right to the metal parts of the sphere.

I agree with Dan about star-mode operation, which would reduce losses. Still not as good as Polywell, of course.

MSimon wrote:Of course considering the conference appears to be 1/2 cranks I'm not surprised.

This would never pass a serious review. Not only that. It appears to have been cribbed in part from a grad school paper by 2 MIT students. Which is explained by the fact that one of the authors of the MIT paper is an author of this paper.

Agreed on the crank and crib factors. I doubt the MIT guy gave his endorsement. That was the only place I could find that hardware "wiffleball" picture.