Self-injection Of Plasma Electrons Research Articles

Plasma bubble evolution in laser wakefield acceleration in a petawatt regime

The bubble regime of the laser wakefield acceleration is one of the most recent and promising mechanisms for generating quasi-monoenergetic electron beams. In this work, we propose to study the dynamics of bubble (a wake structure devoid of electrons created in underdense plasma by a highly-intense ultrashort laser pulse) in a petawatt regime. The dependence of the electron beam energy and the quality of the electron beam on the shape of the bubble is the main motivation behind this work. The bubble length as well as bubble shape have been investigated using two-dimensional particle-in-cell simulations. The evolution of the bubble with time, and the correlation of bubble length (longitudinal and transverse radius) with the intensity of laser pulse have been revealed in this study. The change of bubble dimensions can be estimated by various determining factors such as the laser pulse focusing, the beam loading, the residual electrons, and the bubble velocity. It has also been confirmed that the shape of the bubble cannot be predicted using fixed shape models as spherical or elliptical. Simulations unveil that as the bubble traverses in plasma, it evolves from spherical shape to the highly elliptical shape. And, as it approaches the dephasing length, the eccentricity decreases further. Consequently, the self-injection of plasma electrons in the bubble is seriously affected by the bubble evolution. Comparison of the electron energy gain at different intensities of laser pulse has also been provided. Various scaling laws for electron beam energy estimations are predicted in this investigation. High quality electron beam can be obtained by controlling the bubble evolution, which may have significant applications in future coherent light sources, biomedical, condensed matter physics, and x-ray generation by table-top FEL.

Laser-pulse-induced generation of attosecond electron bunches on crossing the vacuum–plasma boundary

A physical mechanism responsible for the self-injection of plasma electrons and the formation of ultrashort electron bunches in the wake wave generated by laser pulse crossing the boundary of inhomogeneous plasma has been studied.

Reproducibility of electron beams from laser wakefield acceleration in capillary tubes

The stability of accelerated electron beams produced by self-injection of plasma electrons into the wakefield driven by a laser pulse guided inside capillary tubes is analyzed statistically in relation to laser and plasma parameters, and compared to results obtained in a gas jet. The analysis shows that reproducible electron beams are achieved with a charge of 66pC ±11%, a FWHM beam divergence of 9mrad ±14%, a maximum energy of 120MeV ±10% and pointing fluctuations of 2.3mrad using 10mm long, 178μm diameter capillary tubes at an electron density of (10.0±1.5)×1018cm−3. Active stabilization of the laser pointing was used and laser parameters were recorded on each shot. Although the shot-to-shot laser energy fluctuations can account for a fraction of the electrons fluctuations, gas density fluctuations are suspected to be a more important source of instability.

Effects of density gradient on short-bunch injection by wave breaking in the laser wake field acceleration

Effects of density gradient on the self-injection of plasma electrons in the phase of laser pulse wake for further acceleration, is studied for moderate laser intensities, a0⩽3. It is shown that transverse wave breaking can shorten the length of accelerated electrons, whereas effective longitudinal wave breaking requiring steep plasma density interface increases their total charge. For the considered range of laser intensities, the total charge of electrons injected by wave breaking rises exponentially with a0.

Effect of self-injection on ultraintense laser wake-field acceleration.

The self-injection of plasma electrons which have been accelerated to relativistic energies by a laser pulse moving with a group velocity less than the speed of light with I lambda(2)>5 x 10(19) W microm(2)/cm(2) is found via particle-in-cell simulation to be efficient for laser wake-field acceleration. When the matching condition a(0)> or =(2(1/4)omega/omega(pl))(2/3) is met, the self-injection, along with wave breaking, dominates monoenergetic electron acceleration yielding up to 100 MeV energies by a 100 TW, 20 fs laser pulse. In contrast to the injection due to wave-breaking processes, self-injection allows suppression of production of a Maxwell distribution of accelerated particles and the extraction of a beam-quality bunch of energetic electrons.