Linear particle accelerator

Quantum mechanics

Beam (structure)

Materials science

Particle accelerator

Nuclear physics

Phase space

Atomic physics

Bunches

Plasma

Classical mechanics

Thermodynamics

Laser

Physics

Plasma acceleration

Ionization

Laser beams

Optics

Astronomy

Laser beam quality

Acceleration

Flattening

Physical Review Letters

Applications of laser-plasma accelerators demand low energy spread beams and high-efficiency operation. Achieving both requires flattening the accelerating fields by controlled beam loading of the plasma wave. Here, we optimize the generation of an electron bunch via localized ionization injection, such that the combination of injected current profile and averaged acceleration dynamics results in optimal beam loading conditions. This enables the reproducible production of 1.2% rms energy spread bunches with 282 MeV and 44 pC at an estimated energy-transfer efficiency of $\ensuremath{\sim}19%$. We correlate shot-to-shot variations to reveal the phase space dynamics and train a neural network that predicts the beam quality as a function of the drive laser.

Optimal Beam Loading in a Laser-Plasma Accelerator