Study of a Relativistic-Electron-Beam Driven Superradiant Terahertz Undulator Radiation Source

ShanYou Teng^1,2*, Wai-Keung Lau², An-Ping Lee², Ming-Chang Chou²

¹Phsics, National Central University, Taoyuan, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:ShanYou Teng, email:awdrgy012311@gmail.com

Accelerator-based intense THz radiation sources are useful for studying nonlinear and non-equilibrium states of matter in their spectral range. In National Synchrotron Radiation Research Center (NSRRC) [1], we built a photoinjector system to generate a few tens MeV electron beams of sub-picosecond bunch length[2]. Tunable super-radiant THz radiation of MW-level peak power can be generated from electron beams while passing through gap-variable undulators. However, beam energy spread is unavoidably introduced into the system that may deteriorate coherent THz undulator radiations during rf bunch compression in the booster linac of the photoinjector. In this study, we established a three-dimensional particle tracking code to analyze electron beam dynamics under the actions of the undulator and external laser fields. Multi-particle dynamics in the system are tracked using 4th-order Runge-Kutta method. Instantaneous radiation fields from electrons are simultaneously calculated using Lienard-Weichert potential [3]. Furthermore, the effects of beam properties such as beam size, bunch length, and energy spread on radiation field are also investigated. Simulation results agree well with the experimental measurement in the context of large energy spread.
Key words: superradiance, undulator radiation, time-domain simulation

[1] M.C. Chou et al., “Experimental Study of Coherent THz Sources Driven by the NSRRC High Brightness Photoinjector”,Proceedings of IPAC 2018 (2018) THPMK017.
[2] H. Wiedemann, “Particle Accelerator Physics – Basic Principles and Linear Beam Dynamics”, Springer-Verlag, New York (1993) 317-320.
[3] J.D. Jackson, “Classical Electrodynamics”, 3rd edition, John Wieley & Sons Inc., New York (1999) 661-707.
[4] L. Serafini and M. Ferrario,” Velocity Bunching in Photo-Injectors”, in Physics of, and Science with, the X-ray Free-Electron Laser, AIP Conf. Proc. 2001, No. 581.

Keywords: super-radiance, Undulator radiation, Time-domain simulation