Monte Carlo_Based Beam Dynamics Study of a Compact Linear Accelerator for Localized X_ray Generation
Compact electron linear accelerators are being increasingly investigated as enabling platforms for localized X-ray generation and energy-controlled irradiation, due to the demand for a reduced footprint and improved beam control. In this work, a conceptual compact LINAC architecture with a fixed total length of 0.5 m is investigated through comprehensive Monte Carlo beam dynamics simulations, focusing on the comparative performance of two operating modes delivering electron beams at 60 keV and 300 keV, respectively. The study aims to isolate energy-dependent beam transport effects within an identical lattice configuration, emphasizing transverse and longitudinal phase-space evolution, emittance growth, beam envelope stability, and target spot formation. Particle tracking is performed using a statistical Monte Carlo framework incorporating RF cavity acceleration, simplified quadrupole focusing, and space-charge-induced diffusion effects. Transverse and longitudinal phase spaces are analyzed at multiple locations along the accelerator, and key beam quality metrics are extracted at the exit. The results demonstrate that low-energy operation at 60 keV is strongly influenced by collective effects, leading to pronounced emittance growth and halo formation, whereas the 300 keV mode exhibits significantly enhanced beam rigidity, improved phase space preservation, and a compact beam spot at the target.