Laser-wakefield acceleration offers the promise of a compact electron accelerator for generating a multi-GeV electron beam using the huge field gradient induced by an intense laser pulse, compared to conventional rf accelerators. However, the energy and quality of the electron beam from the laser-wakefield accelerator have been limited by the power of the driving laser pulses and interaction properties in the target medium. Recent progress in laser technology has resulted in the realization of a petawatt (PW) femtosecond laser, which offers new capabilities for research on laser-wakefield acceleration. Here, we present a significant increase in laser-driven electron energy to the multi-GeV level by utilizing a 30-fs, 1-PW laser system. In particular, a dual-stage laser-wakefield acceleration scheme (injector and accelerator scheme) was applied to boost electron energies to over 3 GeV with a single PW laser pulse. Three-dimensional particle-in-cell simulations corroborate the multi-GeV electron generation from the dual-stage laser-wakefield accelerator driven by PW laser pulses.

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Nanostructured thin plastic foils have been used to enhance the mechanism of laser-driven proton beam acceleration. In particular, the presence of a monolayer of polystyrene nanospheres on the target front side has drastically enhanced the absorption of the incident 100 TW laser beam, leading to a consequent increase in the maximum proton energy and beam charge. The cutoff energy increased by about 60% for the optimal spheres’ diameter of 535 nm in comparison to the planar foil. The total number of protons with energies higher than 1 MeV was increased approximately 5 times. To our knowledge this is the first experimental demonstration of such advanced target geometry. Experimental results are interpreted and discussed by means of $2\frac{1}{2}$-dimensional particle-in-cell simulations.

We report on the generation of $1.0\mathrm{PW}$, $30\mathrm{fs}$ laser pulses at a $0.1\mathrm{Hz}$ repetition rate from a chirped-pulse amplification Ti:sapphire laser system. The energy of the laser pulses is amplified up to $47\mathrm{J}$ in a final three-pass booster amplifier having $96\mathrm{J}$ pump energy. To the best of our knowledge, this is the first petawatt Ti:sapphire laser system at a $0.1\mathrm{Hz}$ repetition rate. The shot-to-shot energy fluctuation of the laser pulses is as low as 0.53% in rms value, and the laser pulses have homogeneous flattop spatial beam profiles.

Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton and/or ion acceleration in the intensity range of $5\times {10}^{19}$ to $3.3\times {10}^{20}\mathrm{W}/{\mathrm{cm}}^2$ by irradiating linearly polarized, 30-fs laser pulses on 10-to 100-nm-thick polymer targets. The proton energy scaling with respect to the intensity and target thickness is examined, and a maximum proton energy of 45 MeV is obtained when a 10-nm-thick target is irradiated by a laser intensity of $3.3\times {10}^{20}\mathrm{W}/{\mathrm{cm}}^2$. The proton acceleration is explained by a hybrid acceleration mechanism including target normal sheath acceleration, radiation pressure acceleration, and Coulomb explosion assisted-free expansion. The transition of proton energy scaling from $I^{1/2}$ to $I$ is observed as a consequence of the hybrid acceleration mechanism. The experimental results are supported by two- and three-dimensional particle-in-cell simulations.