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 1 D – 1 T very much because the Bremsstrahlung fraction is low, but it will push the other fuels into regimes where the power density relative to 1 D – 1 T is even lower and the required confinement even more difficult to achieve. For 1 D – 1 D and 1 D – 2 He, Bremsstrahlung losses will be a serious, possibly prohibitive problem. For 2 He – 2 He, p – 3 Li and p – 5 B the Bremsstrahlung losses appear to make a fusion reactor using these fuels with a quasineutral, isotropic plasma impossible. Some ways out of this dilemma have been considered but rejected. This limitation does not apply to non-neutral and anisotropic plasmas ; however, these have their own challenges to contend with.