Laser acceleration in argon clusters and gas media

Abstract

We experimentally investigated the generation of high-energy electron beams from laserdriven wakefield acceleration in argon gas jets by using tens of terawatt 30 fs ultrafast laser pulses that were focused to a relatively large-spot size, unmatched with the laser-plasma parameters. In this interaction, and depending on the Ar gas jet density, we could distinguish two different regimes for electron acceleration in the argon medium. In the high-density argon gas jet where argon clusters are formed, upon interaction with the laser electron beams having as high a charge as 3nC are generated. However, the energy spectra of those electron beams were continuous. On the other hand, high-quality quasi-mono-energetic electron beams with a modest charge of tens of pC are observed at much lower argon gas jet densities. The generation of such a high-quality electron beam is attributed to the ionization injection mechanism in which the electron injection takes place over only a few hundred micrometers of the laser-plasma interaction length, leading to the generation of high-quality electron beams.

Laser wakefield acceleration with active feedback at 5 Hz

“…The mean charge measured on the electron spectrometer was 55 pC, with a standard deviation of 19 pC. The energy spectrum was continuous, as has been previously observed with cluster gas targets [30], but it also featured a peak of variable size and energy. By averaging over a burst of 50 shots, the quality of the data could be improved enough to be used with the optimization algorithm.…”

“…However, the clusters make this extremely difficult, because they introduce physics on a length scale much smaller than the laser wavelength. We cannot neglect the clusters, as it has previously been shown that they substantially increase the amount of charge accelerated [22,30,43]. As such, these simulations are beyond the scope of this work.…”

Controlled electron injection facilitated by nanoparticles for laser wakefield acceleration

“…The nanoparticle insertion method for LWFA looks similar with the cluster target 31 , 32 where nano-scaled solids are mixed with a background gas. However, the acceleration mechanism is entirely different, where the either the dominant mechanism for acceleration is direct acceleration or the injection mechanism in LWFA is ionization injection.…”

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).…”