Electron beam: Simulation and Analysis

Ultrafast Electron Diffraction (UED) is essential for understanding and visualizing structural changes at atomic levels and picosecond time scales, such as the movement of atoms during phase changes. By utilizing femtosecond electron pulses, UED captures snapshots of the phase transition, lattice vibrations, and melting processes with high resolution. The quality of these snapshots depends on beam properties including emittance, space charge, and phase space. Low emittance is essential for achieving tight focusing and coherent diffraction. Space charge introduces repulsion within the electron bunch, degrading beam quality. Phase space analysis provides insight into beam divergence and energy spread indicating how well the electron bunch maintains its direction through lenses. At Brookhaven National Lab (BNL) UED facility, these parameters were investigated through simulation and experimental diagnostics. We compared simulation created with the use of General Particle Tracer (GPT) with actual beam measurements. Results show that increased beam energy reduces space charge effects and preserves emittance. The use of designed and tested solenoids, dipoles, and quadrupole magnets further improved the focusing and beam alignment. These findings are crucial for optimizing UED system performance and allowing for more precise studies of materials used in ultrafast radiation applications.