Recent Advances in QPAD capabilties

QPAD [1] is a unique particle-in-cell (PIC) code that combines the quasi-3D algorithm [2] and quasi-static (QS) approximation to efficiently model plasma-based accelerators (PBAs). The quasi-3D algorithm decomposes the electromagnetic fields and plasma source terms into azimuthal Fourier harmonics on a cylindrical grid, thus reducing the algorithmic complexity to that of a 2D code while still resolving asymmetric 3D physics. In combination with the large time-steps permitted by the quasi-static algorithm, QPAD is orders of magnitude faster than conventional PIC codes and standard 3D QS codes. The code features an azimuthally decomposed ponderomotive guiding center (PGC) algorithm for modeling laser-plasma interactions and support for arbitrarily structured laser (ASTRL) pulses. Recent updates include support for the particle-in-cell modeling interface (PICMI) standard, openPMD standard, and a robust pusher for modeling highly nonlinear wakes. A simulation framework integrating QPAD and OSIRIS to model high brightness beam injection and acceleration in a single PBA stage is presented. Examples of recent QPAD simulations of hosing, beam loading, and staging in the electron arm of an LC are also shown. Comparisons with full-3D PIC codes are presented.

[1] F. Li et al., CPC, 261, 107784 (2021).

[2] A. F. Lifschitz et al., JCP, 228, 1803–1814 (2009).