In the counter-irradiation, which is one of the fast ignition schemes, higher core energy coupling can be expected when there are two hot electron flows in counter directions. Two plasma mirrors were installed for the counter irradiation at about 180 degrees. The hot electron effective temperatures (T eff ) were measured by using electron energy spectrometers. T eff vs the laser intensity on a foil target followed Wilkes' scaling law. The energy incident on the target could be calculated by estimating the laser intensity on the target from T eff and estimating the focusing radius from the X-ray pinhole camera image. As a result, the reflectivity could be estimated to be 17 ± 3%.
A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 1018 W/cm2, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.
In high energy density physics including inertial fusion energy using high power laser, doping tracer atoms and deuteration of target materials play an important role in diagnosis. For example, the low concentration copper dopant acts as an X-ray source for electron temperature detection while the deuterium dopant acts as a neutron source for fusion reaction detection. However, the simultaneous achievement of Cu doping, deuterated polymer, mechanical toughness and chemical robustness for the fabrication process is not so simple. In this study, we report the successful fabrication of a Cu-doped deuterated target. The obtained samples were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The simultaneous measurements of Cu K-shell X-ray emission and beam fusion neutron were demonstrated using a petawatt laser in Osaka university.
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