Observation of Terahertz Emission from a Laser-Plasma Accelerated Electron Bunch Crossing a Plasma-Vacuum Boundary

Abstract

Coherent radiation in the 0.3-3 THz range has been generated from femtosecond electron bunches at a plasma-vacuum boundary via transition radiation. The bunches produced by a laser-plasma accelerator contained 1.5 nC of charge. The THz energy per pulse within a limited 30 mrad collection angle was 3-5 nJ and scaled quadratically with bunch charge, consistent with coherent emission. Modeling indicates that this broadband source produces about 0.3 microJ per pulse within a 100 mrad angle, and that increasing the transverse plasma size and electron beam energy could provide more than 100 microJ/pulse.

A multi-beam, multi-terawatt Ti:sapphire laser system for laser wake-field acceleration studies

“…The laser system described in the previous paragraphs has been successfully used in laser driven plasma acceleration experiments both in the single-beam regime for radioisotope production via gamma-neutron activation [3], for intense THz beam generation via laser-plasma accelerated electron bunch crossing a plasma-vacuum boundary [7], and in the multi-beam regime for high quality, quasi-monoenergetic electron beam production from a plasma-channel guided laser wake-field accelerator [8]. Details of these measurements can be found in other reports of the L'OASIS group in this Proceedings.…”

Advances in Laser Driven Accelerator R&D

“…[50] have the potential to resolve fs-bunches. Recently, the generation of coherent radiation from the electron bunches as they exit the plasma was studied experimentally [8,51] and theoretically [9], both as a radiation source and as a diagnostic for measuring the electron bunch properties [36]. The interest in using these bunches for generation of coherent radiation is motivated by two components: (1) extremely dense, sub-ps electron bunches produced with a compact laser-plasma accelerator and (2) the production of coherent transition radiation by these bunches at the boundary between a plasma and vacuum.…”

“…Electron bunches were generated using a single intense laser beam focused on a He-backed gas jet [8]. The total radiated energy was collected in the 0.3-19 THz and in the 0.3-2.9 THz ranges (and hence 2.9-19 THz range).…”

“…Over the years, the quality of these bunches improved, and beams were produced with "smaller" lasers, capable of operating at higher repetition rate. Laser pulse shape effects were studied [3,4], and applications were explored such as radio-isotope production [5,6,7] and THz radiation generation [8,9]. At AAC2002, experiments were reported, in which beams containing electrons with energy up to 200 MeV had been produced, using a 30 TW, 30 fs laser [10].…”

Parameter study of acceleration of externally injected electrons in the linear laser wakefield regime

“…Simulations predict that this length is on the order of a few to ten femtoseconds, 3,[5][6][7] below the current electron bunch length measurement lower limit of 50 fs. 8 The generation of electron bunches with such short duration opens up new applications in fields such as coherent THz generation 9 and compact, femtosecond freeelectron lasers. 10 In addition to having severe requirements on energy, energy spread, bunch duration, and emittance, these applications also require a stable and reliable source of electrons, something current laser wakefield acceleration experiments have not been able to achieve.…”