Generation of frequency-chirped density modulation electron beam for producing ultrashort THz radiation pulse

Haoran Zhang,Qika Jia,Chen Li,Zhigang He,Shimin Jiang,Wenxing Wang,Lin Wang,Duohui He

doi:10.1103/physrevaccelbeams.23.020704

Abstract

A new scheme is proposed to generate electron beams with a frequency-chirped density modulation for producing ultrashort THz radiation pulse in an optimally tapered undulator. In this scheme, an energy chirped electron beam is sequentially modulated in two modulators by interacting with two laser pulses with the same central frequency but different chirp rates, practically one laser pulse is linearly chirped and the other is chirpfree. Two dispersion sections are applied to transfer the energy modulation formed in the modulators to the desired density modulation. The central frequency of the density modulation of the electron beam can be continuously tuned by changing the compression coefficients of the dispersion sections, and the chirp rate of the final modulation frequency can also be tuned by either varying the compression coefficients or the linear chirp rates of the modulation laser pulses. The generation of ultrashort and broadband THz radiation pulses is also briefly discussed.

Highlights

Terahertz (THz) radiation is finding its use in an increasingly wide variety of applications
THz undulator radiation sources are widely studied in the accelerator community [10,11,12,13,14,15,16,17], and there is continuous interest to produce radiation pulses with shorter duration [18,19,20]
To meet the demands of ultrashort THz radiation pulses, a scheme is proposed to generate quasi-halfcycle THz pulses, which is emitted from a frequencychirped electron bunch train traversing an optimally tapered undulator [21,22]

Summary

INTRODUCTION

Terahertz (THz) radiation is finding its use in an increasingly wide variety of applications. We propose a new scheme with two same centralfrequency laser pulses for modulating the electron bunch to obtain such a desired microbunched beam, leading to the generation of an ultrashort THz pulse in an optimally tapered undulator. This scheme is similar to that of using two laser pulses with the same frequency to modulate the electron beam for generating an spaced microbunched beam [25], but we replace the conventional laser with a frequency-chirped laser.

LASER-ELECTRON INTERACTION SCHEME AND MODULATION THEORY

SIMULATION RESULTS OF ELECTRON BEAM MODULATION

GENERATION OF ULTRASHORT AND BROADBAND THZ RADIATION

CONCLUSION