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With the addition of recent PW shots, the propagation of short-pulse laser generated electron beams have been studied using laser pulse energies from 30 J to 300 J, generating currents up to ∼15 MA in solid Al:Cu targets. This is ∼5% of the current that will be required in an ignition pulse. To this level, the current appears to simply scale with laser power, the propagation spread not change at all. The resistance of the aluminum does not seem to play a role in the propagation characteristics, though it might in setting the current starting parameters. We do find that at the highest currents parts of these targets reach temperatures high enough to modify the Cu-K$_{\alpha }$emission spectrum rendering our Bragg imaging mirrors ineffective; spectrometers will be needed to collect data at these higher temperatures.

We present the results of some recent experiments performed at the LULI laboratory using the 100 TW laser facility concerning the study of the propagation of fast electrons in gas targets. Novel diagnostics have been implemented including chirped shadowgraphy and proton radiography. Proton radiography images did show the presence of very strong fields in the gas probably produced by charge separation. In turn, these imply a slowing down of the fast electron cloud as it penetrates in the gas, and a strong inhibition of propagation. Indeed chirped shadowgraphy images show a strong reduction of the electron cloud velocity from the initial value close to a fraction of c.

One of the main issues of the fast ignitor scheme is the role of fast electron transport in the solid fuel heating. Recent experiments used a new target scheme based on the use of cone to guide the PW laser and enhance the electron production. In this context it is fundamental to understand the physics underlying this new target scheme. We report here recent and preliminary results of ultra-intense laser pulse interaction with three layer targets in presence of the cone or without. Experiments have been performed at LULI with the 100 TW laser facility, at intensities up to 3 1019W/cm2. Several diagnostics have been implemented (2D Kαimaging, Kαspectroscopy and rear side imaging, protons emission) to quantify the cone effect.

The control of parametric instabilities in large plasmas remains a challenge for the ICF program. Clearly, kinetic effects play an important role in the saturation mechanisms. Sub-picosecond Thomson analysis associated with short pulse interaction permits to explore these topics. A set of experiments have been performed in preformed, He plasmas using the 100-TW laser facility at LULI. The spectra of the electrostatic waves driven by stimulated Raman and Brillouin backscatterings generated in the 1.5 ps, ${\rm \omega} $laser interaction have been measured with 0.3 ps time-resolution by using a short Thomson probe. Additionally, space-resolved and k-resolved spectra have been obtained. The experiments show that the fastest instability -B-SRS- first develops in the rising part of the pump. The B-SBS-driven IAW grows more slowly. B-SRS then abruptly vanishes around the maximum of the pump, while the IAW can be detected tens of picoseconds after the pump, allowing direct measurement of the IAW damping. The EPW k-spectra show that the EPW dispersion relation significantly deviates from the standard one. They exhibit a k-feature which could be related to the presence of a hot electron population produced in the B-SRS saturation process.