Abstract-Coherent Transition Radiation from Femtosecond Electron Bunches at the Accelerator-based THz Light Source in Thailand

J. Saisut, 

N. Chaisueb, 

C. Thongbai, 

S. Rimjaem

https://www.sciencedirect.com/science/article/pii/S1350449518300392
A THz radiation source based on electron linear accelerator (linac) has been built and commissioned at the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University (CMU) in Thailand since 2005. The accelerator system consists of a thermionic cathode RF electron gun, a magnetic bunch compressor in a form of an alpha-magnet, an S-band travelling-wave linac structure, beam steering and focusing magnets, beam and radiation diagnostic instruments, control system and other support components. Electron bunches with an average kinetic energy of about 8 MeV, a bunch charge of 100 pC, and a bunch length of 300 fs can be produced from the PBP-CMU electron linac system. Coherent THz radiation generated via transition radiation technique is used as a source of the THz spectroscopy and THz imaging applications. The measured power spectrum indicates that the radiation obtained from short electron bunches covers the frequency range of 0.15-1.80 THz or the wavenumber range of 5-60 cm⁻¹. Experimental results reveal that a peak radiation power as high as 0.2 MW per micropulse and an average radiation power of 2.5 mW can be obtained. Generation and characterization of the coherent THz transition radiation as well as some examples of experiments to achieve electron bunch length and radiation power spectrum are reported and discussed in this paper.

Abstract-Coherent terahertz radiation generated from a square-shaped free-electron beam passing through multiple stacked layers with sub-wavelength holes

Yucong Zhou, Yaxin Zhang, Guili Jiang and Zhenhua Wu

http://iopscience.iop.org/0022-3727/48/34/345102/article

zhangyaxin@uestc.edu.cn

Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China 

This paper presents terahertz (THz) coherent radiation from the interaction between a square-shaped electron beam and guiding wave mode in a multiple stacked layers with sub-wavelength holes structure. The simulated results show that such a guiding wave mode enhances the field intensity in the electron beam channel so that the interaction is more efficient than the electron beam-surface wave interaction in traditional grating and bi-grating structures. This electron-beam-driven THz source provides a way with much simpler fabrication processes and a larger square size electron beam rather than sheet beam. Furthermore, such a source can be integrated to construct a 2D source-array structure, which demonstrates a good opportunity to generate high power THz radiation.