Computational methods in the Warp code framework for kinetic simulations of particle beams and plasmas

Summary form only given. The Warp code (and its framework of associated tools) was initially developed for Particle-in-Cell simulations of space-charge-dominated ion beams in accelerators, for heavy-ion-driven inertial fusion energy and related experiments. It has found a broad range of applications, including non-neutral plasmas in traps, stray “electron-clouds” in accelerators, laser-based acceleration, and the capture and focusing of ion beams produced when short-pulse lasers irradiate foil targets. We present an overview of the novel methods that have been developed and implemented in Warp. These include a time-stepping formalism conducive to diagnosis and particle injection; an interactive Python/Fortran/C structure that enables scripted and interactive user “steering” of runs; a variety of geometries (3-D; 2-D r,z; 2-D x,y); electrostatic and electromagnetic field solvers using direct and iterative methods, including MPI parallelization; a Shortley-Weller cut-cell representation for internal boundaries (no restriction to “Lego bricks”); the use of “warped” coordinates for bent beam lines; Adaptive Mesh Refinement, including the capability of simulating time-dependent space-charge-limited flow from curved surfaces; models for accelerator “lattice elements” (magnetic or electrostatic quadrupole lenses, solenoids, accelerating gaps, etc.) at user-selectable levels of detail; models for particle interactions with gas and walls; moment/envelope models that support sophisticated particle loading; a “drift-Lorentz” mover for rapid tracking of species that traverse regions of strong and weak magnetic field; a Lorentz-boosted frame formulation with a Lorentz-invariant modification of the Boris mover; and an electromagnetic solver with tunable dispersion and stride-based digital filtering. Use of Warp, together with the fast 1-D code ASP, to design LBNL's new NDCX-II facility is also presented.