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Manipulation of Laser Distribution to Mitigate the Space-Charge Effect for Improving the Performance of a THz Coherent Undulator Radiation Source
摘要： 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 pro?le, 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.
关键词： manipulation of laser distribution,performance,coherent undulator radiation (CUR),space charge effect
更新于2025-09-16 10:30:52
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Microbunch Rotation and Coherent Undulator Radiation from a Kicked Electron Beam
摘要： Coherent emission from a microbunched electron beam is the driving force behind the revolution in light sources, enabling x-ray free-electron lasers (FELs) to emit pulses 9 orders of magnitude brighter than previous sources. Microbunches form perpendicular to the electron travel direction, and the conventional understanding is that they shear rather than rotate in response to a transverse kick, locking FEL facilities into a single-user operating mode. In this paper, we show that microbunches rotate toward the new direction of travel if the electron beam is kicked and defocused. We provide evidence that microbunch rotation explains the unexpectedly large amount of off-axis radiation observed during experiments at the Linac Coherent Light Source. We demonstrate that LCLS can be multiplexed into at least three separate beams using this principle. Finally, we propose using a magnetic triplet to rotate microbunches through significantly larger angles without microbunch degradation. This new understanding of microbunch dynamics can lead to significantly improved multiplexing at FEL facilities, microbunch preservation through a bend, and x-ray pulses with a pulse-front tilt.
关键词： electron beam,Linac Coherent Light Source,coherent undulator radiation,x-ray free-electron lasers,microbunch rotation
更新于2025-09-09 09:28:46