Laser wakefield acceleration with active feedback at 5 Hz

Abstract

We describe the use of a genetic algorithm to apply active feedback to a laser wakefield accelerator at a higher power (10 TW) and a lower repetition rate (5 Hz) than previous work. The temporal shape of the drive laser pulse was adjusted automatically to optimize the properties of the electron beam. By changing the software configuration, different properties could be improved. This included the total accelerated charge per bunch, which was doubled, and the average electron energy, which was increased from 22 to 27 MeV. Using experimental measurements directly to provide feedback allows the system to work even when the underlying acceleration mechanisms are not fully understood, and, in fact, studying the optimized pulse shape might reveal new insights into the physical processes responsible. Our work suggests that this technique, which has already been applied with low-power lasers, can be extended to work with petawattclass laser systems.

The data-driven future of high-energy-density physics

“…an evolutionary approach (i.e. genetic algorithms 41,113,114 ), a numerical minimisation method (e.g. Nelder-Mead 114 ) or by Bayesian optimisation using a machine learned surrogate model 115116 .…”

Automation and control of laser wakefield accelerators using Bayesian optimization

“…Machine learning techniques are ideal for this kind of problem and have been demonstrated in other plasma physics, accelerator science and light source applications 12 – 15 . Genetic algorithms have been applied to laser-plasma sources including; using the spatial phase of the laser to optimize a keV electron source 16 , and subsequently using both spectral and spatial phase (although not simultaneously) to optimize a MeV-electron source 17 . In both cases, only the laser parameters were controlled preventing full optimization of the LWFA which relies on the complex interplay between the laser and the plasma.…”

Nonlinear wakefields and electron injection in cluster plasma

“…Experimental campaigns have looked at accelerated electrons from clustering gas targets (using methane and argon) discovering an impact on electron beam features due to the presence of clusters. These experiments observed a broader energy spectrum of the accelerated electron beam [43][44][45][46][47][48], increased amounts of accelerated charge [45,46], higher peak energies [45,46], and better reproducibility [47] using cluster targets. Researchers argued ( [43,45]) that a significant part of the acceleration of cluster electrons is due to direct laser acceleration (DLA).…”