Garchinger Maier-Leibnitz-Kolloquium: Unravelling the Direct Laser Acceleration of electron beams

by Prof. Louise Willingale (University of Michigan, Ann Arbor, USA)

Thursday 8 May 2025, 16:15 → 17:15 Europe/Berlin

Lecture Hall, ground floor (west) (LMU building, Am Coulombwall 1, campus Garching)

The Direct Laser Acceleration (DLA) mechanism is capable of driving high-charge, superponderomotive energy electron beams during relativistically intense laser-plasma interactions. As laser facilities reach multi-petawatt powers, DLA will be increasingly important as the main energy exchange mode between the laser and the plasma. Applications of DLA are for high-charge, high-energy electron beams, bright directional sources of x-rays, or for secondary interactions to create Bremsstrahlung-photons or positrons. The ponderomotive force of the laser pulse acts on the plasma to form a channel containing transverse electric and azimuthal magnetic fields  that enable energy exchange from the laser to the electrons. In this talk I will discuss how the modulation of the effective laser frequency affects the energy exchange process, present experiments performed at the OMEGA EP laser facility and particle-in-cell simulations using the code OSIRIS 4.0. The experimental variables include the plasma density and profile, the laser pulse focusing, energy and pulse duration. Matching the focal spot to the size of the oscillations the electrons perform within the channel is most favourable for achieving the highest energies. Therefore an optimum focal spot size is found to be a function of density and laser pulse power. Additionally, an extended density gradient at the plasma rear created conditions that both improved the channelling of the laser over longer distances to enhance DLA, and inhibited the formation of a sheath field to allow more electrons to escape into the vacuum. Prospects for DLA using multi-petawatt laser drivers will be considered.

Hybrid access via ZOOM:
https://lmu-munich.zoom.us/j/98457332925?pwd=TWc3V1JkSHpyOTBPQVlMelhuNnZ1dz09
Meeting ID: 984 5733 2925
Passcode: 979953

kolloquium-08-05-25.pdf