<Tr> <Td> p - 6 3Li </Td> <Td> 800 </Td> <Td> 0.21 </Td> </Tr> <Tr> <Td> p - 11 5B </Td> <Td> 300 </Td> <Td> 0.57 </Td> </Tr> <P> The actual ratios of fusion to Bremsstrahlung power will likely be significantly lower for several reasons . For one, the calculation assumes that the energy of the fusion products is transmitted completely to the fuel ions, which then lose energy to the electrons by collisions, which in turn lose energy by Bremsstrahlung . However, because the fusion products move much faster than the fuel ions, they will give up a significant fraction of their energy directly to the electrons . Secondly, the ions in the plasma are assumed to be purely fuel ions . In practice, there will be a significant proportion of impurity ions, which will then lower the ratio . In particular, the fusion products themselves must remain in the plasma until they have given up their energy, and will remain some time after that in any proposed confinement scheme . Finally, all channels of energy loss other than Bremsstrahlung have been neglected . The last two factors are related . On theoretical and experimental grounds, particle and energy confinement seem to be closely related . In a confinement scheme that does a good job of retaining energy, fusion products will build up . If the fusion products are efficiently ejected, then energy confinement will be poor, too . </P> <P> The temperatures maximizing the fusion power compared to the Bremsstrahlung are in every case higher than the temperature that maximizes the power density and minimizes the required value of the fusion triple product . This will not change the optimum operating point for 2 - 3 very much because the Bremsstrahlung fraction is low, but it will push the other fuels into regimes where the power density relative to 2 - 3 is even lower and the required confinement even more difficult to achieve . For 2 - 2 and 2 - 3 2He, Bremsstrahlung losses will be a serious, possibly prohibitive problem . For 3 2He - 3 2He, p - 6 3Li and p - 11 5B the Bremsstrahlung losses appear to make a fusion reactor using these fuels with a quasineutral, isotropic plasma impossible . Some ways out of this dilemma are considered--and rejected--in fundamental limitations on plasma fusion systems not in thermodynamic equilibrium . This limitation does not apply to non-neutral and anisotropic plasmas; however, these have their own challenges to contend with . </P>

The fusion equations show the production of atoms