Using directly driven beryllium spheres to study heat transport

Heat transport in integrated experiments can be difficult to study due to the complex interplay between radiation transport, laser-plasma interactions, and heat conduction. Self-generated magnetic fields, nonlocality, and micro-instabilities all alter the underlying heat flux. Here, we report experimental results of directly driven beryllium spheres at the Omega laser facility. Low Z beryllium reduces power emitted as x-rays to a small percentage of incident laser power. Incident laser intensity of $10^{14}$ W/cm$^2$ results in $\sim 96\%$ of laser energy coupled to the target, in agreement with radiation-hydrodynamics simulations which neglect cross-beam energy transfer (CBET). At $2.5\times10^{14}$ W/cm$^2$, coupled laser energy drops to $~87\%$ and it is believed that CBET results in a loss of $\sim10\%$ of the incident energy. Comparisons are made between measured densities and temperatures using Thomson scattering and 2D simulations which include Thomson self-heating from the probe beam. At drive intensity of $10^{14}$ W/cm$^2$, Thomson self-heating has roughly a $10\%$ effect on measured temperature. The impact of self-generated fields on heat transport in the 2D simulation is assessed.