Dense monoenergetic proton beams from chirped laser-plasma interaction

Proton sheet crossing in thin relativistic plasma irradiated by a femtosecond petawatt laser pulse

Leveraging on analyses of Hamiltonian dynamics to examine the ion motion, we explicitly demonstrate that the proton sheet crossing and plateau-type energy spectrum are two intrinsic features of the effectively accelerated proton beams driven by a drift quasistatic longitudinal electric field. Via two-dimensional particle-in-cell simulations, we show the emergence of proton sheet crossing in a relativistically transparent plasma foil irradiated by a linearly polarized short pulse with the power of one petawatt. Instead of successively blowing the whole foil forward, the incident laser pulse readily penetrates through the plasma bulk, where the proton sheet crossing takes place and the merged self-generated longitudinal electric field traps and reflects the protons to yield a group of protons with plateau-type energy spectrum.

Chirped-Standing-Wave Acceleration of Ions with Intense Lasers

We propose a novel mechanism for ion acceleration based on the guided motion of electrons from a thin layer. The electron motion is locked to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the layer. This provides a stable longitudinal field of charge separation, thus giving rise to chirped-standing-wave acceleration of the residual ions of the layer. We demonstrate, both analytically and numerically, that stable proton beams, with energy spectra peaked around 100 MeV, are feasible for pulse energies at the level of 10 J. Moreover, a scaling law for higher laser intensities and layer densities is presented, indicating stable GeV-level energy gains of dense ion bunches, for soon-to-be-available laser intensities.

Polarization-tunable terahertz radiation in the high-field regime

Polarization control of terahertz (THz) pulses in the high-field regime is a challenging subject. Here we propose and numerically demonstrate an all-optical scheme to generate a polarization-tunable high-field THz source based on relativistic laser plasma interactions. By adjusting the polarization state of the driving laser, collective oscillation of the plasmas can be steered. Phase difference between the laser field components is inherited in the plasma dynamics, as well as in the resulting THz generation process. Single-cycle extremely intense THz pulses with field strength ∼  GV/cm can be generated. The THz polarization state can be tuned from linear through elliptical to circular by changing the polarization state of the driving laser.

Generating high-energy highly charged ion beams from petawatt-class laser interactions with compound targets

A new method of generation of high-energy highly charged ion beams is proposed. The method is based on the interaction of petawatt circularly polarized laser pulses with high-Z compound targets consisting of two species of different charge-to-mass ratio. It is shown that highly charged ions produced by field ionization can be accelerated up to tens of MeV/u with ion (actually with Z ≤ 25) beam parameters like density and total charge inaccessible in conventional accelerators. A possibility of further ionization of the accelerated ion bunches in foil is also discussed.