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Abstract Indirect Drive Inertial Confinement Fusion Experiments on the National Ignition Facility (NIF) have achieved a burning plasma state with neutron yields exceeding 170 kJ, roughly 3 times the prior record and a necessary stage for igniting plasmas. The results are achieved despite multiple sources of degradations that lead to high variability in performance. Results shown here, for the first time, include an empirical correction factor for mode-2 asymmetry in the burning plasma regime in addition to previously determined corrections for radiative mix and mode-1. Analysis shows that including these three corrections alone accounts for the measured fusion performance variability in the two highest performing experimental campaigns on the NIF to within error. Here we quantify the performance sensitivity to mode-2 symmetry in the burning plasma regime and apply the results, in the form of an empirical correction to a 1D performance model. Furthermore, we find the sensitivity to mode-2 determined through a series of integrated 2D radiation hydrodynamic simulations to be consistent with the experimentally determined sensitivity only when including alpha-heating.

Fusion ignition by inertial confinement requires compression and heating of the fusion fuel to temperatures in excess of 5 keV and densities exceeding hundreds of g/cc. In August 2021, this scientific milestone was surpassed at the National Ignition Facility (NIF), when the Lawson criterion for ignition was exceeded generating 1.37MJ of fusion energy (Abu-Shawareb et al 2022 Phys. Rev. Lett. 129 075001), and then in December 2022 target gain >1 was realized with the production of 3.1MJ of fusion energy from a target driven by 2.0MJ of laser energy (Abu-Shawareb et al 2024 Phys. Rev. Lett. 132 065102). At the NIF, inertial confinement fusion research primarily uses a laser indirect drive in which the fusion capsule is surrounded by a high-Z enclosure (‘hohlraum’) used to convert the directed laser energy into a symmetric x-ray drive on the capsule. Precise measurements of the plasma conditions, x-rays, γ -rays and neutrons produced are key to understanding the pathway to higher performance. This paper discusses the diagnostics and measurement techniques developed to understand these experiments, focusing on three main topics: (1) key diagnostic developments for achieving igniting plasmas, (2) novel signatures related to thermonuclear burn and (3) advances to diagnostic capabilities in the igniting regime with a perspective toward developments for intertial fusion energy.

High-pressure experiments play a critical role in understanding planetary interiors, but are notoriously difficult to carry out. Here, the authors demonstrate a laboratory platform for the controlled exploration of deuterium, with results that challenge existing models of ionization under compression.

A scheme for controlling the polarization of a light wave via its interaction with an auxiliary beam in a nonlinear optical medium is proposed. We first present the linear theory of polarization-dependent wave mixing, where the “probe” beam, whose polarization is to be manipulated, is less intense than the auxiliary beam. Then we show that a simple geometrical arrangement, where the auxiliary and probe are crossing at 90° and the auxiliary is linearly s polarized (orthogonal to the plane of incidence), enables us to control the probe’s polarization even when its intensity exceeds the auxiliary’s intensity. These schemes are of particular interest when the nonlinear optical medium is a plasma, as it might enable dynamic polarization manipulations at ultrafast timescales and far beyond the optics damage threshold of crystal-based photonics devices.

Collisionless shock acceleration of protons and C^{6+} ions has been achieved by the interaction of a 10^{20} W/cm^{2}, 1 μm laser with a near-critical density plasma. Ablation of the initially solid density target by a secondary laser allows for systematic control of the plasma profile. This enables the production of beams with peaked spectra with energies of 10–18 MeV/amu and energy spreads of 10%–20% with up to 3×10^{9} particles within these narrow spectral features. The narrow energy spread and similar velocity of ion species with different charge-to-mass ratios are consistent with acceleration by the moving potential of a shock wave. Particle-in-cell simulations show shock accelerated beams of protons and C^{6+} ions with energy distributions consistent with the experiments. Simulations further indicate the plasma profile determines the trade-off between the beam charge and energy and that with additional target optimization narrow energy spread beams exceeding 100 MeV/amu can be produced using the same laser conditions.