Methods of Generation and Detailed Characterization of Millimeter-Scale Plasmas Using a Gasbag Target

Gasbag targets are useful for the research of laser-plasma interactions in inertial confinement fusion, especially in the laser overlapping regime. We report that on the Shengguang-II laser facility, millimeter−scale plasmas are successfully generated by four 0.35 µm laser beams using a gasbag target. Multiple diagnostics are applied to characterize the millimeter−scale plasmas in detail. The images from the x-ray pinhole cameras confirm that millimeter-scale plasmas are indeed created. An optical Thomson scattering system diagnoses the electron temperature of the CH filling plasmas by probing the thermal ion-acoustic fluctuations, which indicates that the electron temperature has a 600 eV flat roof in 0.7–1.3 ns. Another key parameter, i.e. the electron density of the millimeter-scale plasmas, is inferred by the spectrum of the back stimulated Raman scattering of an additional 0.53 µm laser beam. The inferred electron density keeps stable at 0.1n_c in early time consistent with the controlled filling pressure and splits into a higher density in late time, which is attributed to the blast wave entering into the SRS interaction region.