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 21, 10:52 am
Poster: Richard Hull

On Dec 21, 10:52 am, Richard Hull wrote:

Jim is correct and also talks of the generalities involved which are many and varied.

Our fusor is ultra simple and for that we trade a lot of stuff off in the quest for quick and cheap.

Think of it this way......

1. We are making deuterons in the simple fusor over the entire volume. Thus, only some very small fraction are are created near the walls where they can accelerate through the full potential and reach fusion energy.

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.

This can be handled mathematically.


2. Not all of the deuterons are hitting head on. With just barely 20KV on a fusor, only head on collisions are going to do fusion. AND THEN...only those at 1/2 fusion energy...or in other words those few that were created at the outer shell volume.

What's more.....

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.

In summary, We are forced to operate at elevated pressures where the density is high to assure ourselves of any fusion at all. Given a volume x of deuterons created/second, we might look at a simple equation

((((x/#at wall)/#surviving to center)/#hitting head-on). Or....a tiny fraction of a tiny fraction of a tiny fraction

What we can do is...

1. use very high voltages.

This assures us that more of the fusor volume will produce, 1/2Ek fusion, deuterions. Now we can have a deuteron hit from the wall area and one from the middle and get fusion too! It is a win, win situation. Also, the cross section improves and thus fusion increases.

2. We can also use higher currents.

This determines the actual number of ionizations and thus the deuterons produced. remember that 1 amp is about 10e19 deuterons/second! The difference between 1 ma and 10ma is ten times the deuteron count and thus 10 times the fusion rate.
A tiny fraction of a tiny fraction of a tiny fraction of 10e19 can still be millions!

But, as Jim notes all this slides slopilly about on an ever shakey mathematical table.

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.

Where does this leave you and the origianl question? There is little math, that will assist you. If you compute the theoretical fusion rate t using the best math, you will find a tremndous shortfall in production. You will have to build it and try, with good instrumentation, to discover the constants for the given system. These operational constants are only found by the doing.

Finally, once you discover the neutron rate, you will also have the rate of production of Tritium gas in your system. For the rate equals the neutron rate.

Richard Hull

The fusor we use will give some small fraction of fusions/ head on collision