DD and DT nuclear fusion optimization algorithm

An optimization algorithm for pairwise nuclear fusion algorithms with arbitrarily weighted macro-particles is proposed and demonstrated in particle-in-cell (PIC) simulations. Faster computation of the Coulomb collision operator is achieved compared to the classical nuclear fusion algorithm, which can be implemented into the PIC simulation code with marginal efforts. The algorithm is benchmarked in situations with like-particles, D(d,n)3He, unlike-particles, D(t,n)4He, thermonuclear fusion, and the beam-target fusion. It is demonstrated that the CPU time can be significantly reduced without reduction in the simulation accuracy.