Adapt FFTPoissonSolver to 2D
Adapt FFTPoissonSolver to support a Hockney-Eastwood Poisson solve on a 2D grid.
This is part of adding "2.5D" solver to IPPL where the space charge potentials from a bunch which is long compared with its transverse size is computed. In a 2.5D solver the bunch is divided into 2D slices, the 2D potential from each slice is computed and applied to the particles. A 1D space charge potential is computed based on the longitudinal line density of the bunch and applied to the particles resulting in an energy/longitudinal momentum kick.
More details here: 20230712_review_presentation.pdf
Edited by carl_j