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By extending the concept of thin film compression [Mourou et al., Eur. Phys. J. Spec. Top. 223(6), 1181 (2014)] to a thin plate, nonlinear post-compression from 24 fs to 13 fs of sub-petawatt laser pulses is demonstrated experimentally using a 1 mm-thick silica plate and chirped mirrors with a total anomalous dispersion of −50 fs2. The measurements were implemented with a specially designed dispersionless vacuum frequency-resolved optical gating, which is based on second harmonic generation of tested pulses in a 10 μm β-barium borate crystal glued on a 1 mm fused silica substrate. The used compression scheme is implemented in a geometry compatible with high power on-target experiment realization. [ABSTRACT FROM AUTHOR]

Using a laser plasma accelerator, experiments with a 80 TW and 30 fs laser pulse demonstrated quasi-monoenergetic electron spectra with maximum energy over 0.4 GeV. This is achieved using a supersonic He gas jet and a sharp density ramp generated by a high intensity laser crossing pre-pulse focused 3 ns before the main laser pulse. By adjusting this crossing pre-pulse position inside the gas jet, among the laser shots with electron injection, more than 40% can produce quasi-monoenergetic spectra. This could become a relatively straight forward technique to control laser wakefield electron beams parameters. [ABSTRACT FROM AUTHOR]

X-ray computed tomography of plants requires a high number of X-ray photons, good source stability, and a large field of view. We show that we can optimize a laser-based synchrotron X-ray source for this application. The X-ray beam is produced during electron acceleration by laser wakefield. These results were obtained using 160 TW on-target laser peak power, 4.6×1019Wcm-2 laser pulse intensity, and nitrogen gas target. We measured a critical energy ∼ 15 keV, enough X-ray photons to realize an image with one single laser shot, more than 50 mrad divergence, a good shot to shot stability and spatial distribution homogeneity required for tomography imaging. The gas jet target pressure is low enough to use the laser system at the laser nominal repetition rate (2.5 Hz). We produced a micrometer X-ray source size that allows high resolution (< 20 μm) and phase contrast imaging. [ABSTRACT FROM AUTHOR]

The generation of an electron beam through longitudinal field acceleration from a tightly focused radially polarized (TM01) laser mode is reported. The longitudinal field is generated by focusing a TM01 few-cycle laser pulse (1.8 μm, 550 μJ, 15 fs) with a high numerical aperture parabola. The created longitudinal field in the focal region is intense enough to ionize atoms and accelerate electrons to 23 keV of energy from a low density oxygen gas. The characteristics of the electron beam are presented. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration of 500 MeV to 1 GeV electron bunches has been demonstrated using ionization injection in mixtures of 4% to 10% of CO2 in He. 80 TW laser pulses were propagated through 5 mm gas jet targets at electron densities of 0.4-1.5×1019cm-3. Ionization injection led to lower density thresholds, a higher total electron charge, and an increased probability of producing electrons above 500 MeV in energy compared to self-injection in He gas alone. Electrons with GeV energies were also observed on a few shots and indicative of an additional energy enhancement mechanism. [ABSTRACT FROM AUTHOR]