Speaker
Description
Laser wakefield acceleration is currently considered as one of the most promising mechanisms to potentially reduce the size and cost of future electron accelerators. In this technique, plasma electrons are injected into a plasma wave (wakefield), generated and dragged by an ultra-short, ultra-intense laser beam in optically transparent plasma. Such electrons gain relativistic energy within a few millimeters, which is three orders of magnitude lower than the contemporary more expensive technology. The electron injection process is one of the most crucial attributes that determine the final properties of the electron bunch in laser wakefield accelerators. So-called self-injection is unquestionably the least experimentally demanding and the most commonly used mechanism. However, bunches generated by this process are either low-charged or non-localized and it is difficult to tune their parameters. Laser beams with a Gaussian intensity profile are typically used in such experiments. Here, a new injection method triggered by using the super-Gaussian laser beam instead of the Gaussian beam is proposed. Such a beam undergoes rapid variations in its intensity distribution due to the special diffraction properties. If this diffraction occurs in plasma, consequent alterations in the wakefield structure activate a localized injection process. The research was carried out by numerical particle-in-cell simulations for standard parameters feasible with current sub-100 TW laser systems. In the simulations, remarkably high charge (> 100 pC) and short duration (< 2 fs) of the bunch are observed simultaneously. Such short bunches produce coherent X-ray pulses of the equivalent duration, which are interesting in the terms of applications, e.g., high-quality phase-contrast imaging of biological samples. Furthermore, the ultrashort duration of the bunch and radiation pulses enables the studying of ultra-fast processes on atomic scales.
