Coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

Enrico Brunetti; Xue Yang; Dino A. Jaroszynski

doi:10.1117/12.2523178

24 April 2019 Coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

Enrico Brunetti, Xue Yang, Dino A. Jaroszynski

Proceedings Volume 11036, Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources III; 110360M (2019) https://doi.org/10.1117/12.2523178
Event: SPIE Optics + Optoelectronics, 2019, Prague, Czech Republic

Abstract

Laser-wakefield accelerators generate femtosecond-duration electron bunches with energies from 10s of MeV to several GeV in millimetre distances by exploiting the large accelerating gradients created when a high-intensity laser pulse propagates in an underdense plasma. The process governing the formation of the accelerating structure (bubble") also causes the generation of sub-picosecond duration, 1-2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. We present simulations showing that these wide-angle beams can be used to produce coherent transition radiation in the 0.1-5 THz frequency range with 10s μJ to mJ-level energy if passed through an inserted metal foil, or directly at the plasma-vacuum interface. We investigate how the properties of terahertz radiation change with foil size, position and orientation. The bunch length and size of wide-angle beams increase quickly as the electrons leave the accelerator, causing a shift of the radiation frequency peak from about 1 THz at a distance of 0.1 mm from the accelerator exit to 0.2 THz at 1 mm. If the foil size is reduced, for example to match the typical diameter of the plasma channel formed in a laser-wakefield accelerator, simulating the emission from the plasma-vacuum boundary, the low-frequency side of the spectrum is suppressed. The charge of wide-angle electron beams is expected to increase linearly with the laser intensity, with a corresponding quadratic increase of the terahertz radiation energy, potentially paving the way for mJ-level sources of coherent terahertz radiation.

Conference Presentation

Citation Download Citation

Enrico Brunetti, Xue Yang, and Dino A. Jaroszynski "Coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator", Proc. SPIE 11036, Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources III, 110360M (24 April 2019); https://doi.org/10.1117/12.2523178

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