First Measurements of the Facet Coherent Terahertz Radiation Source

The Facility for Accelerator science and Experimental Tests (FACET) at SLAC provides a high charge, high peak current, sub-picosecond bunched electron beam that is ideal for 0.1 to 2 THz radiation generation via coherent transition radiation. This paper presents preliminary characterization of the terahertz pulses generated by the FACET electron beam. The measured THz frequency content spans from 0.25 THz to 2.3 THz and peaks at around 0.5 THz. The radiation has been focused down to a 4.4 x 4.8 mm2 transverse spot with 0.69 mJ collected total energy per pulse. Fitting the energy to the spatiotemporal profile of the THz pulse yields peak efield amplitude of 1.5 MV/cm.