Tapering enhanced superradiance with a planar magnetic undulator

Tapering enhanced superradiance (TES) is a novel radiation scheme that significantly improves the energy conversion efficiency in free-electron lasers. The undulator tapering design and optimization are crucial to the success of this efficiency boost and are fairly complicated tasks. Here, we demonstrate how to optimize the linear tapering rate using analytical magnetic field maps derived from pure permanent magnet (PPM) equations. A TES undulator (waveguided tapered undulator) is designed to operate at 0.5 THz at the zero-slippage regime, ensuring phase synchronicity and group velocity match between the electron beam and the radiation field. The superradiance condition is fulfilled by compressing the electron bunch to emit coherently. The results reveal a significant enhancement in energy conversion efficiency for both ideal and realistic beams. The real beam simulations use the ORGAD FEL parameters from the Schlesinger Accelerator Center at Ariel University. This work shows the potential of the TES method to achieve higher radiation energies through careful undulator design and optimized tapering and provides a complete model for this purpose.