Coherent collective amplification of terahertz microbunching seeded by laser frequency beating in relativistic electron beams
Abstract
High-power, continuously tunable terahertz sources based on free-electron lasers require precise control of electron-beam microstructures. Quantitative prediction of the modulation amplitude across a broad frequency range remains challenging because the laser-induced distribution and its collective evolution must be treated together. To describe this coupled evolution, a nonlinear model is developed for microbunching seeded by a frequency-beating laser heater. The non-Gaussian heater-exit distribution is obtained by optical phase averaging and propagated through multistage compression in six-dimensional phase space. Source-induced correlations are retained, with space charge, coherent synchrotron radiation, and radio-frequency wakefields evaluated self-consistently. The wavelength-dependent bunching response is thereby connected to the laser beat frequency, laser power, and compression partition. The short-wavelength double peak is found to be governed mainly by longitudinal space charge, while bunching near a selected wavelength can be enhanced by redistributing compression at fixed total compression. The predicted source modulation and downstream response are benchmarked against Elegant and IMPACT-Z, respectively. Experimental measurements of the wavelength-dependent bunching factor at different laser pulse energies are found to agree well with the trends predicted by theory and simulation. The resulting framework provides a computationally efficient and predictive route to optimizing electron-beam microbunching for tunable, high-power terahertz generation at free-electron-laser facilities.
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BibTeX
@misc{cheng2026coherent,
title = {{Coherent collective amplification of terahertz microbunching seeded by laser frequency beating in relativistic electron beams}},
author = {Wencai Cheng and Yin Kang and Kaiqing Zhang and Zhen Wang and Duan Gu and Guangling Chen and Chao Feng and Haixiao Deng},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18725},
eprint = {2609.18725},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18725},
}
RIS
TY - UNPB
TI - Coherent collective amplification of terahertz microbunching seeded by laser frequency beating in relativistic electron beams
AU - Wencai Cheng
AU - Yin Kang
AU - Kaiqing Zhang
AU - Zhen Wang
AU - Duan Gu
AU - Guangling Chen
AU - Chao Feng
AU - Haixiao Deng
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18725
UR - https://arxiv.org/abs/2609.18725
AB - High-power, continuously tunable terahertz sources based on free-electron lasers require precise control of electron-beam microstructures. Quantitative prediction of the modulation amplitude across a broad frequency range remains challenging because the laser-induced distribution and its collective evolution must be treated together. To describe this coupled evolution, a nonlinear model is developed for microbunching seeded by a frequency-beating laser heater. The non-Gaussian heater-exit distribution is obtained by optical phase averaging and propagated through multistage compression in six-dimensional phase space. Source-induced correlations are retained, with space charge, coherent synchrotron radiation, and radio-frequency wakefields evaluated self-consistently. The wavelength-dependent bunching response is thereby connected to the laser beat frequency, laser power, and compression partition. The short-wavelength double peak is found to be governed mainly by longitudinal space charge, while bunching near a selected wavelength can be enhanced by redistributing compression at fixed total compression. The predicted source modulation and downstream response are benchmarked against Elegant and IMPACT-Z, respectively. Experimental measurements of the wavelength-dependent bunching factor at different laser pulse energies are found to agree well with the trends predicted by theory and simulation. The resulting framework provides a computationally efficient and predictive route to optimizing electron-beam microbunching for tunable, high-power terahertz generation at free-electron-laser facilities.
ER -