SIMULATION MODELS

The complex physics of laser fusion, means simulation models are critical for designing and interpreting the experiments. Experiments are rarely perfect and real-world differences between a manufactured near-perfect capsule and an ideal capsule need to be understood and managed.  Experiments on laser systems around the work including the National Ignition Facility (NIF) and Omega lasers have shown that current simulation models do not predict the observed experimental behaviour with sufficient accuracy to initiate ignition.

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Experimental implosion data (left) and simulation (right).

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A leading hypothesis for the causes of these inaccuracies are the impact of imperfections in the targets and lasers as well as kinetic laser plasma interaction instabilities (LPIs). These alter the experiments in ways that are very difficult to predict using theoretical descriptions, hard to measure experimentally, and as a result it is not always clear how to calculate them even when using extremely computationally expensive models. Current simulation codes used to design the laser fusion experiments do not resolve of the imperfections in the target and lasers and do not account for all LPI processes. Currently, we cannot predict and the changes they cause.

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A significant component of ongoing UK research combines experiments performed on lasers in the UK, Europe, Asia and USA up to ignition-scale using the NIF. This experimental work informs  extensive computer model developments in the UK. Including UKRI funded multidimensional radiation-hydrodynamics and code, Odin, kinetic particle-in-cell and Vlasov-Fokker-Planck codes EPOCH and Impact.  Developing these computational tools is a key strategy in advancing our  understanding of the many physics questions relevant to direct drive and shock ignition at ignition-scale.

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