We show that x-rays from a recently demonstrated table top source of bright, ultrafast, coherent synchrotron radiation [Kneip et al., Nat. Phys. 6, 980 (2010)] can be applied to phase contrast imaging of biological specimens. Our scheme is based on focusing a high power short pulse laser in a tenuous gas jet, setting up a plasma wakefield accelerator that accelerates and wiggles electrons analogously to a conventional synchrotron, but on the centimeter rather than tens of meter scale. We use the scheme to record absorption and phase contrast images of a tetra fish, damselfly and yellow jacket, in particular highlighting the contrast enhancement achievable with the simple propagation technique of phase contrast imaging. Coherence and ultrafast pulse duration will allow for the study of various aspects of biomechanics.

Stimulated Raman side scattering of an ultrashort high power laser pulse is studied in experiments on laser wakefield acceleration. Experiments and simulations reveal that stimulated Raman side scattering occurs at the beginning of the interaction, that it contributes to the evolution of the pulse prior to wakefield formation, and also that it affects the quality of electron beams generated. The relativistic shift of the plasma frequency is measured.

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Measurements of silver K-shell and bremsstrahlung emission from thin-foil laser targets as a function of laser prepulse energy are presented. The silver targets were chosen as a potential 22 keV backlighter source for the National Ignition Facility Experiments. The targets were irradiated by the Titan laser with an intensity of 8 × 1017 W/cm2 with 40 ps pulse length. A secondary nanosecond timescale laser pulse with controlled, variable energy was used to emulate the laser prepulse. Results show a decrease in both Kα and bremsstrahlung yield with increasing artificial prepulse. Radiation hydrodynamic modeling of the prepulse interaction determined that the preplasma and intact target fraction were different in the three prepulse energies investigated. Interaction of the short pulse laser with the resulting preplasma and target was then modeled using a particle-in-cell code PSC which explained the experimental results. The relevance of this work to future Advanced Radiographic Capability laser x-ray backlighter sources is discussed.

We report the implementation of a tunable, narrow-spectral-bandwidth, pulsed, four-pass dye-laser amplifier with strongly reduced amplified spontaneous emission. We present temporal pulse profiles, pulse spectra, and gain measurements of the amplifier output for the case of Coumarin 307 dye as the gain medium, seeded at wavelengths of approximately 508 nm and pumped at 355 nm.

Articles you may be interested inAbstract. Electron density bubbles generated in plasma of density n e ~ 10 19 /cm 3 are shown to reshape copropagating probe pulses into optical "bullets." The bullets, reconstructed by frequency-domain interferometric techniques, are used to visualize bubble formation independently of relativistic electron generation.

Experiments with a solid Cu foam ($1.3 g/cm 3) sphere coated by a 20 lm CH ablator are performed on the GEKKO-LFEX laser facility to study the effect of hot electron preheat on the implosion performance. When the target is imploded by the GEKKO lasers ($1.2 Â 10 15 W/cm 2 in peak intensity), plenty of hot electrons are measured through the induced Cu Ka emission, indicating that the target could suffer strong preheat. This suffering of preheat is confirmed by the temporal evolution of the target self-emission, which is well reproduced by a 2D cylindrically symmetric radiative hydrodynamic code (FLASH) when a module handling the hot electron preheat is coupled. The results given by this benchmarked code indicate that, in the typical experiments with a small ($200 lm in diameter) solid sphere target conducted on the GEKKO-LFEX laser facility, the hot electron preheat greatly degrades the implosion performance, reducing the peak areal densities of a Cu foam sphere and a CD sphere by $20%

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