Re: Fusion reactors

[BERNARD L COHEN <blc+@PITT.EDU>]

On Mon, 20 Aug 2001 Jacques.Read@eh.doe.gov wrote:



>

> The real promise of fusion energy  is the deuterium burner, where the products

> are He-3 and a proton.  Since everything is charged it all can be magnetically

> contained.  Dick Post (LLNL) had a scheme involving a "pinch machine"

> (essentially an unfolded torus, that leaked at both ends) in which a linear

> accelerator at each end alternately fed in new deuterons and extracted power

> from the plasma by having the He-3 and protons run backwards into them. This

> obviates the need for the lithium blanket to absorb the neutrons and make more

> tritium.

>

> The bad news is that the threshold for D-D is a couple of hundred kilovolts more

> than that for  D-T.



	There is more bad news than that. The cross section for d-d is

much smaller than for d-t at energies of interest. Also d-d releases only

one-fourth as much energy as d-t. Also, when two deuterons collide,

neutrons are produced as frequently as protons; the two reactions with

equal cross section are d + d -> H3 + p and d + d -> He3 + n.

	I believe there is universal agreement that the first fusion

reactors, if there ever are any, will be based on d-t.



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