Transfer Learning of High-Fidelity Opacity Spectra in Autoencoders and Surrogate Models

Simulations of high energy density physics are expensive, largely in part for the need to produce nonlocal thermodynamic equilibrium opacities. High-fidelity spectra may reveal new physics in the simulations not seen with low-fidelity spectra, but the cost of these simulations also scale with the level of fidelity of the opacities being used. Neural networks are capable of reproducing these spectra, but neural networks need data to to train them which limits the level of fidelity of the training data. This paper demonstrates that it is possible to reproduce high-fidelity spectra with median errors in the realm of 3% to 4% using as few as 50 samples of high-fidelity Krypton data by performing transfer learning on a neural network trained on many times more low-fidelity data. K. D. Humbird is with Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA, 94550 USA, email: humbird1@llnl.gov. In this case, higher fidelity opacity calculations are necessary Inertial confinement fusion (ICF) is currently to capture important physical processes accurately one of the experimental approaches to controlled [4], [5]. In this work, we focus on improving the nuclear fusion.