Study of Coherent Radiation from an Electron Beam Prebunched at the Photocathode

Controlling the longitudinal distribution in an electron beam traveling through an accelerator can enhance system performance in various ways. Prebunching an electron beam in an accelerator can lead to enhanced radiation production from various emitters. Smoothing the shape of the electron beam pulse may suppress instabilities that result in beam breakup. This work, a collaboration between the University of Maryland and the Source Development Laboratory at Brookhaven National Laboratory, uses a Ti:Sapphire drive laser modulated at terahertz frequencies to extract a prebunched beam directly from the photocathode prior to acceleration in a linear RF accelerator. We have demonstrated that prebunched terahertz structure can be maintained after leaving the photocathode and through acceleration to high energy. Through the use of simulation and experiment, this work further explores the characteristics of an electron beam produced in this manner and examines the possibility of using this technology to develop a compact, powerful, narrowband terahertz emitter.