Speaker
Description
Electron cloud effects cause beam instabilities and emittance growth in positron storage rings. PyECLOUD, a 2D macro-particle code for simulating electron cloud build-up, currently uses Particle-in-Cell (PIC) algorithms for electric field calculations. PIC methods scale O(N²) in computational complexity and are affected by discrete particle noise.
This work implements the Fast Multipole Method (FMM) combined with the Boundary Element Method (BEM) for electric field calculations in pyECLOUD. FMM reduces computational complexity to O(N) or O(N log N) using multipole expansions and hierarchical spatial decomposition. BEM reduces problem dimensionality by formulating the electrostatic field through boundary integrals on chamber surfaces. The FMM-BEM combination has been applied in various electromagnetic calculations.
The implementation maintains pyECLOUD's modular structure and allows selection between PIC and FMM-BEM solvers. The reduced computational cost enables higher spatial resolution, longer simulation periods, and broader parameter space exploration. The method is applicable to other circular accelerators with electron cloud effects, particularly those with high bunch intensities or complex chamber geometries.
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