The quasi-static particle-in-cell (PIC) algorithm is extensively utilized to model short-pulse or high-energy charged particle interacting with plasma. Compared to the very computationally intensive full three-dimensional (3D) explicit PIC code, the quasi-static PIC codes are able to speed up the simulations by orders of magnitude, which allows for modeling the physical problems requiring massive computing resource, such as hosing instability and ion motion effect in plasma-based accelerators. In addition to the quasi-static approximation, the Fourier azimuthal decomposition is another effective speedup technique which has been applied into some general-purpose PIC codes. However, none of the existed quasi-static codes have employed this technique. We will present a new PIC code combining the quasi-static approximation and Fourier azimuthal decomposition together. The new code inherited the numerical workflow of our existing quasi-static code QuickPIC but was completely rebuilt based on the Fourier decomposition framework. This algorithm expands the fields, charge and current density into azimuthal harmonics and truncates the expansion. The complex amplitudes of fields are then solved through Maxwell’s equations under quasi-static approximation using the finite difference in conjunction with the multigrid method. The beam and plasma particles are advanced in the cylindrical geometry as well. Benchmark and comparative study against the full 3D explicit PIC code and 3D quasi-static code are also presented.

Authors: Fei Li, Weiming An, Viktor Decyk, Warren Mori

This work is supported by DOE and NSF.

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[2] W. An et al., J. Comp. Phys. 250, 165 (2013).

[3] https://github.com/UCLA-Plasma-Simulation-Group/QuickPIC-OpenSource