The effect of high intensity laser propagation instabilities on channel formation in underdense plasmas

International audienceExperiments have been performed using high power laser pulses (up to 50 TW) focused into underdense helium plasmas (ne ⩽ 5×10^19 cm^−3). Using shadowgraphy, it is observed that the laser pulse can produce irregular density channels, which exhibit features such as long wavelength hosing and “sausage-like” self-focusing instabilities. This phenomenon is a high intensity effect and the characteristic period of oscillation of these instabilities is typically found to correspond to the time required for ions to move radially out of the region of highest intensity

Energetic heavy-ion and proton generation from ultraintense laser-plasma interactions with solids

The ultraintense laser plasma interaction experiments have produced observations of new phenomenon such as: the acceleration of electrons to high energies; production of intense proton beams; and the generation of magnetic fields. Observations of proton emission indicate significant structure in the energy spectrum and angular emission profile which varies with energy. The two different components of ion emission observed are a high energy component and a low energy component

Observation of a hot high-current electron beam from a selfmodulated laser wake field accelerator

International audienceA highly relativistic electron beam produced by a 50 TW laser-plasma accelerator has been characterized by photonuclear techniques. The beam has large divergence that increases with plasma density. The electron yield also increases with plasma density and reaches up to 4×10^11 electrons ( >10MeV), with beam current approaching the Alfvén limit. Effective electron temperatures exceeding 8 MeV are found, leading to an order of magnitude higher photonuclear activation yield than in solid target experiments with the same laser system

Diagnosis of peak laser intensity from high energy ion measurements during intense laser interactions with underdense plasmas

International audienceExperiments were performed using high-power laser pulses (greater than 50 TW) focused into underdense helium, neon, or deuterium plasmas (ne [less-than-or-equal] 5 × 1019 cm−3). Ions having energies greater than 300 keV were measured to be produced primarily at 90° to the axis of laser propagation. Ion energies greater than 6 MeV were recorded from interactions with neon. Spatially resolved pinhole images of the ion emission were also obtained and were used to estimate the intensity of the focused radiation in the interaction region

Measurements of energetic proton transport through magnetized plasma from intense laser interactions with solids

Protons with energies up to 18 MeV have been measured from high density laser-plasma interactions at incident laser intensities of 5 × 1019 W/cm2. Up to 1012 protons with energies greater than 2 MeV were observed to propagate through a 125 μm thick aluminum target and measurements of their angular deflection were made. It is likely that the protons originate from the front surface of the target and are bent by large magnetic fields which exist in the target interior. To agree with our measurements these fields would be in excess of 30 MG and would be generated by the beam of fast electrons which is also observed