Single shot CBET gain curve measurements with Fourth generation Laser for Ultrabroadband eXperiments (FLUX) first light

Mitigation of laser-plasma instabilities has been a long-time goal of the ICF community, as this would facilitate higher ablation pressures and improved symmetry. Spectral bandwidth has been proposed as a practical technique to mitigate a large number of instabilities such as CBET, TPD, and SBS. The FLUX beam capable of producing 1.5% bandwidth at 351nm has achieved first light and was used to demonstrate a novel plasma diagnostic that can measure spatially localized plasma conditions. The FLUX beam with 1nm of continuous bandwidth was focused to a ∼ 100 μm diameter spot in a nitrogen/hydrogen plasma that was pre-heated by several OMEGA beams. The FLUX beam was crossed by a narrowband 351 nm OMEGA beam focused to a ∼ 200 μm diameter spot. In the overlapped volume, ion-acoustic waves where excited by the broadband electromagnetic beatwave, which mediated the transfer of energy between the beams (CBET). The ratio of the transmitted to incident spectral power as a function of wavelength, over the entire gain curve, was measured in a single laser shot. The locations and width of the resonant peaks in the gain provide a measure of the electron and ion temperature, with the magnitude of transfer can be used to determine plasma density.