High-quality GeV electron beams from an all-optical plasma waveguide

Laser-plasma accelerators produce and operate extremely strong electric fields, which may allow challenging the conventional kilometers-long particle accelerators. Despite this promise and after decades of development, this technology still lacks a solution to deliver simultaneously high energy, high stability, and good beam quality.

A team of scientists from LOA’s UPX group and the Weizmann Institute of Science found one such solution based on a laser-generated plasma waveguide in a density-shaped gas target enabling controlled injection of electrons into the accelerating wakefield.

Figure | Schematic view of the experiment and main diagnostics. The laser is split into three separate beams: P1 - the acceleration driver, P2 - the pulse that generates the waveguide, and P3 - the probe beam. The two main beams, P1 and P2, are focused in a 15 mm long rectangular gas jet. The generation beam, P2, is focused in the target, 2 ns before P1, by an f/4 axiparabola. The main beam, P1, is focused by an f/18 spherical mirror. It ac-celerates electron bunches whose energy is then analyzed with a spectrometer consisting of a dipole magnet, a LANEX scintillating screen and a 16 bits camera (a). It is eventually attenuated to image its focal spot after interaction (b). The probe beam, P3, crosses the plasma transversely, just after P1 (c). It is then sent to a wavefront sensor to measure the transverse density profile.

This simple and versatile scheme has allowed production of electron beams at the GeV level, with unprecedented quality and efficiency. Since this accelerator is immune to optical damage, it can be used with arbitrarily high laser energies and repetition rates, opening new avenues for the realization of ultra-compact high-energy accelerators.

Figure | Acceleration of high-quality electron beams. a, Ten angularly resolved elec-tron spectra sorted by charge. b, Two examples of angularly-integrated spectra correspond-ing to spectra marked by blue and green lines in (a).