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: Fusion reaction rates
Date: Dec 22, 2:34 am
Poster: Richard Hull

On Dec 22, 2:34 am, Richard Hull wrote:

>This is something I think is a pretty serious problem. How much energy are we wasting this way?

About 99.999999999% wasted! We are doing fusion though. RH


I'm looking at a couple of ideas for plasma generators that work primarily at the edges of the chamber and at higher vacuums. This will allow me to effectively decouple current and voltage -- I can set the current by setting the plasma generation rate. One design that I've thought of (and would all those more experienced than I please comment!) consisting of two grids at the edge and a number of electron filaments. The outer of these two grids would be grounded and the inner held at a positive potential just above the ionization potential for deuterons. The filaments would be located on the outer grid. In operation, this would cause a flow of electrons from the outer to the inner grid, where they would ionize deuterons. Careful setting of the inner grid voltage would cause most of the ionization to occur in a narrow shell near that grid. They would then be accelerated in the normal fashion.


Your idea is clever and has merit, but the 70s Hirsch-Meeks patent achieves the same result with less hardware. Single extra grid. Electrons shot out by a filament almost touching the shell race towards a grid real close to the shell ionizing the D2 gas to make deuterons which accelerate through the bulk of the potential drop to achieve fusion energy. RH
>>We might look at the fusor as a layered shell of deuteron energies. If we supply ever more voltage, then more of the chamber volume from the wall inward can now support generation of potentially fusion energetic deuterons.
>That just seems so wasteful of energy.


It is, but we are doing MORE fusion. Wall outlet power is so cheap! Besides, few on this list will ever even do the ultra-simple fusor! For those micro few that do, my tips still hold. RH


>>3. Our mean free path is just about the radius of the chamber (3-4 inches) so, in theory, only half of the these perfectly created deuterons will make it to the center and then only a tiny fraction of those will hit head on... and then only a tiny fraction of those will hit another deuteron of equal energy (remember, they can hit head on with a deuteron created in the middle of the chamber and nothing will happen.
>Which seems to me to be a call for higher vacuum, tighter ion optics, and higher voltages. With those kinds of losses, grid losses are the least of your concerns!


Correct! again, but how many here will ever use the higher vacuum.... almost none; tighten up their ion optics..... ZERO; use higher voltages... a few. Doing fusion on th' cheap demands a simple fusor. You are talking orders of magnitude more bother, precision and mainly expense. Leaving virtually every other person on this list out of the ballpark. Let's get 'em demoing first (glowing), fusin' second, and refining third. RH

>>Also a key thing which Jim pointed out...Remember, you won't detect but a tiny fraction of the neutrons with any counter and thus you must be intimate with the neutron detector. As I have noted before many times, neutron counting is a black art.
>This is a kicker -- I don't know the black art. I may end up on your doorstep Richard, begging for a dispensation of neutron clue.

Always willing to dispense what I have learned.

I am no neutron counting expert. That admission is the first step in the path to becoming one. The mere full understanding of the scope of trying to effectively count particles by happenstance secondary events and realize that you have to have a hail of thousands a second being produced inches from the detector to rise above the noise floor is down right humbling.

It is a matter of event counting, obtaining accurate background counts, culling out the false counts, and knowing you specific detector's efficiency at a given neutron energy.

On my system, which is pretty good, 1 count a minute over back ground at a range of 8 inches from the source will mean over 1000 neutrons per second are streaming out!!!! With a background count of 5-10/minute, one extra plus or minus is noise.

Richard Hull