摘要
Results on diagnoses of laser-driven, shock-heated foam plasma with time-resolved Al 1s-2p absorption spectroscopy are reported. Experiments were carried out to produce a platform for the study of relativistic electron transport. In cone-guided Fast Ignition (FI), relativistic electrons generated by a high-intensity, short-pulse igniter beam must be transported through a cone tip to an imploded core. Transport of the energetic electrons could be significantly affected by the temperature-dependent resistivity of background plasmas. The experiment was conducted using four UV beams of the OMEGA EP laser at the Laboratory For Laser Energetics. One UV beam (1.2xA0;kJ, 3.5xA0;ns square) was used to launch a shock wave into a foam package target, consisting of 200xA0;mg/cm3 CH foam with aluminum dopant and a solid plastic container surrounding the foam layer. The other three UV beams with the total energy of 3.2xA0;kJ in 2.5xA0;ns pulse duration were tightly focused onto a Sm dot target to produce a point X-ray source in the energy range of 1.4-1.6xA0;keV. The quasi-continuous X ray signal was transmitted through the shock-heated Al-doped, foam layer and recorded with an X-ray streak camera. The measured 1s-2p Al absorption features were analyzed using an atomic physics code FLYCHK. Electron temperature of 40xA0;eV inferred from the spectral analysis is consistent with 2-D DRACO Radiation-hydrodynamic simulations.