Advanced particle acceleration and radiation source research supported by Long-Wave IR lasers

A multi-terawatt, picosecond long-wave infrared (LWIR) 9-µm laser at the Accelerator Test Facility supports a broad user program in strong-field and plasma physics. The LWIR wavelength offers higher photon number per joule, stronger ponderomotive force, and lower critical plasma density than near-IR lasers. These features enable new regimes in laser wakefield acceleration at low plasma densities (~10¹⁶ cm⁻³), with large trapping volumes and potential for compact accelerators with low emittance and energy spread. The co-located high-brightness linac enables precise injection studies and wakefield mapping. LWIR laser also drives ion acceleration in gas jets, producing quasi-monoenergetic MeV-class proton beams. In inverse Compton scattering (ICS), LWIR laser combined with nC-level electron beam enable single-shot imaging and nonlinear ICS to high harmonics. LWIR radiation further supports efficient THz generation via optical rectification and plasma transition radiation. Future upgrades to few-cycle, multi-TW operation will open new frontiers in generating high-quality beams and ultrafast X-ray sources for scientific, biomedical, and industrial applications.