Propagation of Texas Petawatt laser through high density gas jet targets

We report on a recent experimental campaign funded by LaserNetUS investigating the propagation of the Texas Petawatt laser through high density (~ 10¹⁹ cm^-3) gas jet targets of hydrogen and deuterium in the direct laser acceleration (DLA) regime. Nominal laser parameters are 140 J delivered in 140 fs pulses. Primary objectives of this campaign included investigation of laser propagation instabilities, ion dynamics, electromagnetic pulse production, shock wave generation, plasma heating, optical observation of ion filamentation, and the effects of apodizing the laser beam. Various sizes and geometries of apertures were employed in the laser near field to improve the spatial quality of the laser on target. Diagnostics used included neutron time of flight detectors, an electron spectrometer, radiochromic film, optical probing (shadowgraphy, schlieren, interferometry), bubble detectors, NaI gamma detectors, and electromagnetic pulse detectors. Initial data analysis indicates the existence of an annular electron beam with a divergence of a few degrees surrounding the on axis electron beam. The structure and quality of this annular beam is correlated to the type of aperture used.