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Proceedings Paper

Coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator
Author(s): Enrico Brunetti; Xue Yang; Dino A. Jaroszynski
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Paper 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.

Paper Details

Date Published: 24 April 2019
PDF: 7 pages
Proc. SPIE 11036, Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources III, 110360M (24 April 2019); doi: 10.1117/12.2523178
Show Author Affiliations
Enrico Brunetti, Univ. of Strathclyde (United Kingdom)
Xue Yang, Capital Normal Univ. (China)
Dino A. Jaroszynski, Univ. of Strathclyde (United Kingdom)

Published in SPIE Proceedings Vol. 11036:
Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources III
Dino A. Jaroszynski; MinSup Hur, Editor(s)

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