Atomic, Molecular, Optical and Plasma Physics Seminar Electron trapping from interactions between laser-driven relativistic plasma waves

Date: Time: 3:30 pm–5:00 pm
Jorgensen Hall Room: Jorgensen Hall Room 145
855 N 16th St
Contact: Physics Department, 472-2770, paoffice@unl.edu
Speaker: Grigory Golovin, Senior Research Associate, Extreme Light Laboratory

Ref.: Phys. Rev. Lett. 121, 104801 (2018)

Controllable injection of electrons into an accelerating plasma wake remains one of the biggest issues of laser and beam-driven wakefield acceleration. Final properties of the accelerated electron beam, such as charge, energy spread, pulse duration, emittance, and stability, are often limited by the injection process. To control and optimize these parameters, electrons have to be placed at a correct phase of the wake with high precision. At Extreme Light
Laboratory we have recently experimentally demonstrated two novel injection mechanisms capable of such precise control: injection via ponderomotive drift and wake-wake interference.

In our experiments, two laser pulses (drive and injector) were propagated through a plasma in crossing directions. The injector pulse of a very high intensity (up to 1.7x10^20 W/cm^2) pushed electrons via its ponderomotive force into the drive-pulse wake, causing their trapping (injection via ponderomotive drift). In addition, it created its own wake, which interfered with the drive-pulse wake, also resulting in electron trapping (injection via wake-wake interference).

The demonstrated injection mechanisms have important features which can lead to novel ways to engineer wakefield-accelerated electron beams and enhance their quality. The injection via ponderomotive drift can occur at any point where the injector laser beam intersects the drive wake. One can, therefore, inject electrons at the optimal location and phase with respect to the wake for maximal accelerator performance and beam quality. Since injection via wake-wake interference occurs periodically, multiple electron bunches, separated by a plasma period, can be injected, forming a bunch train, which is of high interest for numerous applications, including time-resolved pump-probe studies of ultrafast phenomena. In addition, both mechanisms can be used not only in laser-wakefield accelerators, but in beam-driven ones also.

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