Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Grid Losses
Date: Nov 25, 09:46 am
Poster: Richard Hull

On Nov 25, 09:46 am, Richard Hull wrote:

>Please define "Grid Losses" as all the fusor "hype" never seems to mention them.


You are correct. You would have to be a deep insider or actually have played with the fusor to realize why the losses occur.

The device is electrostatic in nature and the confinement of the ions are based on this principle as well as collisional processes due to electrostatic accelertion.

The inner grid is where the losses occur. This is the also the grid which has all the fusion processes locked within it. (although some researchers believe that some occurs just outside)

The incoming ions bound for collision enter this confinement area at the urging of the electrostatic field setp up by the grid. The grid wires actually block part of the volume and shield it against some small percentage of the incoming ions. In low pressure fusors, the bombardment of the grid by ions can be so great that it can melt or even vaporize. This represents loss to the system. Most simple fusors have inner grids with a "transparency" of 97% so far as the geometry is concerned. That is, only 3% of the spherical surface area of the inner grid's outer area is metal which can block ion penetration.

There is another concern as well which causes a greater loss than the grid wires themselves. That is the electron exit beams. These beams are centered within the open areas of the geodesic grid openings. They are moderately broad, round beams. These will intercept and react with the incoming ions as well. A myriad of reactions can occur here, none of them will be fusion! This exodus of electrons from within the grid is due to temperature considerations within the poissor itself. Both ions and electrons are ejected or pass right through the reaction zone in the center. This new hassle might accont for another 5-8% of loss. Finally, in the zone where there are no grid wires and no exiting beam, the electrostatic field is not particularly linear or smooth and a certain percentage of the incoming charged ions are deflected from ideal hits in the center.

At higher exhaustions this process is much less active and losses fall dramatically, but so does fusion due to the reduced gas load to form ions.

It is a tradeoff which can work and do fusion over a wide range, but never allow for sustained ignition in its current embodiment.

Well engineered grid transparency figures are in the 90% range.

I hope this helped.

Richard Hull