Reducing direct drive preheat with dopants

Preheat in laser-driven experiments can have negative impacts on inertial confinement fusion (ICF) and hydrodynamic experiments. While many groups employ the use of dopants to reduce or block preheat, direct quantification has not previously been explored. We developed a planar platform and a series of ablator targets to measure the electron and x-ray spectra generated by laser-plasma interactions with a direct drive using OMEGA-60. By comparing both thin ablators (75m) and thick ablators (270 m) that were either pure CH, 3% Si doped or 3% I doped, we were able to measure differences in electron and x-ray spectra. In addition, we observed the preheat growth of tracer layers and observed reductions in the growth with different materials. We find that iodine or a thin gold layer is the best at tamping the direct-drive preheat at OMEGA, but that the growth is still significant.