Abstract
A THz coherent undulator radiation (THz-CUR) source has been developed at the Institute of Advanced Energy, Kyoto University. A photocathode Radio-Frequency (RF) gun and a bunch compressor chicane are used for generating short-bunch electron beams. When the electron beam energy is low, the space-charge effect strongly degrades the beam quality, such as the bunch length and the energy spread at the high bunch charge condition at around 160 pC, and results in the reduction of the highest frequency and the maximum radiated power of the THz-CUR. To mitigate the space charge effect, we have investigated the dependence of the electron beam quality on the laser distribution in transverse and longitudinal directions by using a numerical simulation code, General Particle Tracer GPT. The manipulation of the laser distribution has potential for improving the performance of the THz-CUR source. The electron bunch was effectively compressed with the chicane magnet when the laser transverse distribution was the truncated Gaussian profile, illuminating a cathode. Moreover, the compressed electron bunch was shortened by enlarging the laser pulse width. Consequently, an enhancement of the radiated power of the THz-CUR has been indicated.
Highlights
Thanks to the rapid evolution of ultrashort pulse laser technology based on solid-state lasers, intense THz pulses are widely available [1,2,3]
The accelerator-based THz sources such as free electron lasers (FELs) [7,8], which can generate intense quasi-monochromatic THz pulses, are good candidates to be used for nonlinear THz spectroscopy
In addition to FELs, nowadays, coherent radiations directly generated from an ultrashort high-energy electron bunch are attracting interest for their potential to generate intense quasi-monochromatic THz pulses via coherent undulator radiation (CUR) source and superradiance THz FELs [9,10]
Summary
Thanks to the rapid evolution of ultrashort pulse laser technology based on solid-state lasers, intense THz pulses are widely available [1,2,3]. 2. The schematic of the THz-CUR system square of the number of radiating electrons per bunch, N shaping the laser distribution in order to reduce the space-charge effect causing emittance has been is shownin inmany. To eliminate the problem addressed above, it is necessary of electron beam energy can reduce the space-charge force and be helpful to enhance the radiated to studyHowever, how the our laser shapehas is asignificant thepower, bunch and compression and the impact obtaininga power. Section is dedicated to the the dependence of the electron beam quality on the operating conditions, such as the parameters results of compressed bunch length, radiated power, and the improvement in source of the laser, including laser pulse width and transverse size, have been investigated and are shown performance aftermanipulation manipulatingof thethe laser distributions. The investigation of the longitudinal phase space is presented as follows
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