Abstract
Based on particle-in-cell simulations, we propose to generate sub-nanosecond pulses of narrowband terahertz radiation with tens of MW power using unique properties of kiloampere relativistic (2 MeV) electron beams produced by linear induction accelerators. Due to small emittance of such beams, they can be focused into millimeter and sub-millimeter spots comparable in sizes with the wavelength of THz radiation. If such a beam is injected into a plasma, it becomes unstable against the two-stream instability and excites plasma oscillations that can be converted to electromagnetic waves at the plasma frequency and its harmonics. It is shown that several radiation mechanisms with high efficiency of power conversion (∼1%) come into play when the radial size of the beam–plasma system becomes comparable with the wavelength of the emitted waves.
Highlights
In recent years, the efforts of many scientific groups have been aimed at creating radiation sources in the terahertz (THz) frequency range (0.3–10 THz)
At the early stages, when the ion density perturbation can be considered as a small one, its presence should enhance the radiation at the second harmonic, since each beam-driven wave is able to radiate by the additional mechanism of the plasma antenna [26,27,38]
Recent studies have shown that a thin beam–plasma system can convert a significant fraction of the injected beams power into radiation power at harmonics of the plasma frequency due to the mechanisms of the plasma antenna and head-on collision of plasma waves with different potential profiles
Summary
The efforts of many scientific groups have been aimed at creating radiation sources in the terahertz (THz) frequency range (0.3–10 THz). A promising way in the development of powerful narrowband THz radiation sources is the use of kiloampere electron beams The power of such beams reaches several gigawatts; conversion into radiation of even a percent of this power makes it possible to produce electromagnetic (EM) emission at the level of hundreds of MW. In this paper, using particle-in-cell (PIC) simulations, we study the possibility to generate high-power THz radiation in plasma by the counterstreaming electron beams with a few kA currents and relativistic energies ∼2 MeV typical to the linear induction accelerators [32].
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