Ω-type jitter-free static magnetic compressor for sub-50-fs 200-keV electron pulses

Ultrafast electron diffraction and microscopy (UED/UEM) require not only short probe pulses but also long-term timing stability at the sample. In most compression schemes, radio-frequency (RF) phase jitter and laser-RF synchronization errors translate directly into arrival-time fluctuations, limiting the effective temporal resolution. Here we propose and numerically investigate a jitter-free Ω-type static magnetic compressor that performs longitudinal phase-space rotation using only static magnetic fields, thereby removing RF-related timing jitter and eliminating any requirement for laser-RF synchronization. The compressor employs a symmetric large-angle sector-bend arrangement to generate deterministic energy-dependent path-length differences (effective R₅₆) and enables temporal focusing at the sample plane through dispersion matching with the downstream drift. Three-dimensional particle-tracking simulations show that 200-keV electron pulses can be reproducibly compressed to <50 fs (rms) at the sample plane for femtocoulomb-level charges while maintaining transverse beam parameters compatible with UED/UEM operation. We further show that energy-selective filtering in the high-dispersion region suppresses nonlinear space-charge wings and can push the pulse duration toward the ∼20 fs (rms) regime at reduced transmitted charge. With a compact, collinear geometry and millimeter-scale alignment tolerance, the proposed Ω-type compressor provides a practical, jitter-free upgrade path for existing 100-300 keV ultrafast electron instruments.