Abstract-Coherent Transition Radiation from Relativistic Beam-Foil Interaction in the Terahertz and Optical Range

W. J. Ding, F. Y. Li, S. M. Weng, P. Bai, Z. M. Sheng

https://arxiv.org/abs/1902.04716

Coherent transition radiation (CTR) from relativistic electron beam interaction with an overdense plasma foil is investigated by making use of two-dimensional particle-in-cell simulations. Well-defined single electron beam either of uniform profile or having substructures is considered for various beam-plasma parameters. The main purpose is to mimic the complicated beam-plasma conditions that is often found, for example, in intense laser plasma interactions. Key properties of the CTR concerning their temporal, angular and spectral profiles are identified. Several saturation effects due to the beam energy, size and foil density are found for the CTR energy, and the dependences vary for different spectral components such as in the Terahertz (THz) and optical range. The detailed substructure of the beam also affects greatly the radiation generation, leading to distinctive high harmonic components. Electrons with kinetic energy from sub MeV to tens of GeV are explored. For few MeV electron beams, the effects of the foil plasma on the beam dynamics and associated CTR generation, resembles closely the CTR from hot electrons produced in intense laser-plasma interactions. These results may find important applications in beam diagnostics either in laser-plasma based acceleration or conventional accelerators. They may also be employed to design novel THz radiation sources using tunable electron beams.

Abstract-Terahertz generation from laser-driven ultrafast current propagation along a wire target

H. B. Zhuo, S. J. Zhang, X. H. Li, H. Y. Zhou, X. Z. Li, D. B. Zou, M. Y. Yu, H. C. Wu, Z. M. Sheng, and C. T. Zhou

Phys. Rev. E 95, 013201 – Published 5 January 2017

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.95.013201

Generation of intense coherent THz radiation by obliquely incidenting an intense laser pulse on a wire target is studied using particle-in-cell simulation. The laser-accelerated fast electrons are confined and guided along the surface of the wire, which then acts like a current-carrying line antenna and under appropriate conditions can emit electromagnetic radiation in the THz regime. For a driving laser intensity ∼3×1018W/cm2 and pulse duration ∼10 fs, a transient current above 10 KA is produced on the wire surface. The emission-cone angle of the resulting ∼0.15 mJ (∼58 GV/m peak electric field) THz radiation is ∼30∘. The conversion efficiency of laser-to-THz energy is ∼0.75%. A simple analytical model that well reproduces the simulated result is presented.

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Abstract-Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses

G. Q. Liao (廖国前), Y. T. Li (李玉同), C. Li (李春), L. N. Su (苏鲁宁), Y. Zheng (郑轶), M. Liu (刘梦), W. M. Wang (王伟民), Z. D. Hu (胡志丹), W. C. Yan (闫文超), J. Dunn, J. Nilsen, J. Hunter, Y. Liu (刘越), X. Wang (王瑄), L. M. Chen (陈黎明), J. L. Ma (马景龙), X. Lu (鲁欣), Z. Jin (金展), R. Kodama (兒玉了祐), Z. M. Sheng (盛政明), and J. Zhang (张杰)

Phys. Rev. Lett. 114, 255001 – Published 23 June 2015

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.255001

Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 100  μJ per steradian in the laser specular direction at an optimal preplasma scale length around 40–50  μm. Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas.

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