Archived - Brush Inner Grids

[Frank Sanns]

Early on in my fusor I ran an RF souce to a piece of SS mesh and used it an an ion source. It gave a cool discharge and I have long wondered how it would work and an inner or outer grid to help form more ions. Here are some photos of the brush discharge as an inner grid. Sorry for the not so good photos but I did not have my good camera with me.

First picture is an air plasma showing the mesh ball. It was deliberately chosen to be chaotic and it is placed about and 4 cm off center high in my fusor.

The second picture is D2 and you can see a nice jet. A little surprising in that there is not much symetry to this grid and many edges that potentially could have had streamers emanating from them. This was not the case. In fact, the jet comes pretty much from the center of mass of the inner brush grid.

The third picture is of a fusion run with ~40 KV and 6 ma. Notice that the hot area is in the convergence center of mass and not in the outer wires and definately not in the center of the chamber.

The fusion numbers though are the worst ever. Almost non existant neutrons. They were there but at least a couple of order of magnitude less than a normal wire grid.

Frank S.

[Jon Rosenstiel]

Pretty interesting, Frank. I've put steel wool in the microwave, but never a Brillo pad in my fusor. -;)

I'm surprised the wire mesh didn't vaporize at 240 Watts input. About how large was the chunk of mesh?

Jon Rosenstiel

[UG!]

thats very interesting.

i wonder if a compleatly random homogonious lump of stuff was used, weather the ion beams would melt out paths. would be interesting to see what geomitery it formed.

[Richard Hull]

Oliver has a point there! Nature does things by laws our calculus can't follow due to complexities we can't enter data to discover. A tin or bismuth ball might be a good target here.

I figure it would wind up with a field image negative of the inside of your fusor. In a perfect sphere the tin/bismuth should melt and displace evenly down to a smaller sphere. complications due to the input HV stalk, viewing windows and ports would foul this symmetry.

Of course, as the melted material driped away and gravitationally ran towards the bottom of the ball, its geometry and field system would change.

Richard Hull

[Frank Sanns]

The grid actually did melt or at least relax and change dimensions as the run went along. It started out as a stainless steel scruby that was pretty beefy and not fine like steel wool. Original length was on the order of 3 cm and it finished with wires sticking out giving more like 5 cm overal length.

A hole was made in the center of the grid like a magnifiying glass were focused on one point and then it was rotated through the better part of ~270 degrees. It was more impressive in person looking through the leaded glas than with the photos.

As for using a low melting alloy, I think a subliming conductive material would be better or maybe a reactive one. Even carbon fiber mesh would turn to methane where the deuterium strikes. I still think the result would be as I saw; focusing of all o the energy on convergence point near the center of mass of the inner electrode and ablation of that material until there is a clear shot for many of the impacting ions.

Frank S.

[DaveC]

I think Frank's experiment, establishes the point that the ion beams converge at some place which is the electrostatic center of the electrode structure. This fact is actually evident in almost every picture showing a convergence region inside an inner grid.

Very clever, Frank... And nice photos, particularly the second one.

Dave Cooper