Re: tesla and fusion

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:04 PM 5/6/2007, you wrote:
> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Jim,
>
> I have no problem with using keV.  My text book uses both almost 
> interchangably and I tried to quote the book where ever I could.  It 
> also talks about fusion at almost any average temperature because 
> the temperature of  individual particles have a distribution (a 
> Maxwell distribution, I think I've heard).

A Maxwellian distribution occurs when you "heat" the plasma.  In a 
electrically driven system, though, the distribution can be 
distinctly non-Maxwellian and might even be monochromatic (consider 
an ion gun with a particular accelerating voltage... all the 
deuterons will have the same energy)

> There is a statistical probability that two particles will have the 
> required energy to break the coulumb barrier.  Of course, the lower 
> the average temperature the lower the probability of this occuring.




> I can believe the 40 keV number for deuterium.  The smaller the 
> energy, the smaller the fusion cross section and a more perfect head 
> on collision is required.  My text book (of 33 years ago) says 144 
> keV for hydrogen based particles, but I dont know what cross section 
> that equation is assuming and it will be different for deuterium vs tritium.

There's some  cross section curves on my website (and elsewhere.. I 
didn't do the calcualtions.. there's a huge compedium of these out 
there that you can just punch in the reaction you're interested in 
and it will give you the experimental data and the best curve fit)


> I'm a little confused as to your 100 million K is only 10 keVish 
> statement. It seems like if 11000K = 1 keV, then 100 million K = 
> 9000 keV; and a billion K = 90000 keV

100 million K = 10^8... 10^4 K/eV so 1E8 K approx 1E4 eV = 10keV...




> The easy part, I believe, is to get two particles to fuse.  The hard 
> part is to get this to happen in high numbers.

Got that right...

And, then, if you don't have large numbers, the challenge is in 
detecting that it's happening.  If you get, say, 10,000 
fusions/second, that's kicking out 10,000 neutrons/second, but they 
go in random directions.  If your sensor is, say, 2 cm^2 (2E-4 m^2) 
and a meter away (4*pi m^2 surface area) the you'll not get even one 
neutron per second into the detector.