Progress in 3D particle-in-cell modeling of heavy ion beam transport in quadrupole focusing channels

Summary Form only given, as follows. The authors discuss the use of discrete-particle simulations to model beam transport during the pulse-compression stage of a heavy-ion fusion accelerator. Recent efforts have concentrated on the development and application of an emittance diagnostic. They do not directly calculate the x-x´ emittance of all particles which cross a particular axial plane during the current step. Instead, they work with all particles within any of several comoving windows in z. The emittance calculated for any finite-length window is erroneously large, but it is (to a good approximation) linear in the window length, for short windows that do not span the edge of a lens. Thus, the authors use overlapping windows of different lengths, and by extrapolating to zero window length, they obtain a true local x-x´ (or y-y´) emittance with good statistics. The authors have also developed a formalism for modeling a bent beam using a time-dependent simulation algorithm that differs only minimally from that used for a straight beam.<>