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 Reactions
Date: Aug 01, 1:38 pm
Poster: Richard Hull

On Aug 01, 1:38 pm, Richard Hull wrote:

>The reaction rates (in a percentage of the ions present that fuse in a given time interval sense) for a fusor is MUCH higher than the sun.
>Richard's getting, say, 1E5 n/sec, in a 8" fusor (4 liters) at 1 micron pressure (roughly 1E-6 atmospheres) (i.e. around 1E17 atoms in the sphere)... so he is reacting 1E-12 of the atoms every second. (He'll burn em all up in about 31,000 years)
>The sun, on the other hand, should burn for about 10 billion years (easily), or roughly 315E15 seconds.. The fractional reaction rate is, then, around 3E-18.. or about a millionth of what you do in a fusor.
>All these calculations are very back of the envelope and may be off by orders of magnitude. But, you should get the general idea... slow reaction rates (small cross sections) don't hurt you if you have billions of tons of reactants...


Thanks for all the back of envelope calcs. They help put a lot of fusion data in perspective for the new guys and re-familiarize the old hands.

As you note, the sun ain't all that efficient at fusion but it is lit and burnin' thankfully, at a terrible efficiency. When one further considers that planet wide, we intercept a cone of only a fraction of a billionth of its output, this being further grossly attenuated by the atmosphere, etc., it is stunning what a really large grossly inefficient fusion reactor can do. I never thought of my little simple fusor as working at a million times the efficiency of the Sun per unit volume. I'll have to quote that.

Richard Hull