On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. As recently reported, a burning plasma state, where the alpha-heating in the plasma is the primary source of heating, was achieved in laboratory experiments. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin ``burn propagation'' into surrounding cold fuel, enabling the possibility of high energy gain. While ``scientific breakeven'' (i.e. unity target gain) has not yet been achieved, this talk reports the first controlled fusion experiment on the National Ignition Facility to produce capsule gain greater than unity (here 5.8) and reach ignition by many different formulations of the Lawson criterion. In the talk, we will discuss some key basic physics inertial confinement fusion (ICF) principles behind the burning plasma and ignition results as well as discuss future challenges.

The advanced radiographic capability located at the National Ignition Facility (NIF) uses high intensity, short pulse lasers to create bright photon sources for diagnosing high energy density experiments. There are radiographic needs for a multi-frame time-resolved MeV gamma diagnostic for experiments on the NIF with sub-nanosecond resolution. A series of experiments demonstrated measurements of MeV x-ray spectra resolved with a time separation of a few nanoseconds through the use of gas Cherenkov detectors. A two-pulse radiographic experiment found a 30% reduction in > 2.8 MeV photon flux compared to the first frame exposure.

The advanced radiographic capability (ARC) laser system, part of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ∼1-38ps in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. These simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 1018W/cm2.

Compound parabolic concentrator (CPC) cone targets have been shown to produce increased MeV photons on the NIF-ARC by 10× over flat targets. Multiple x-ray frames can potentially be generated by firing the NIF-ARC's beamlets into distinct cone targets at few nanosecond relative delays. This requires that the cone targets with delayed beams are not degraded by their proximity to previous targets. One concern is that the spatial wings of a beam fired into one target can fall on neighboring targets, producing a preformed plasma that may interfere with laser light reaching the tip of the cone. In this work, 3D hydra simulations of realistic targets and beam parameters show that hundreds of micrometer scale length preplasmas are produced in cones within 1 mm of the laser spot. 2D particle-in-cell simulations of the intense main pulse in this preplasma indicate a density threshold for the onset of relativistic filamentation in our conditions. Applying our modeling approach to a NIF-ARC shot with an intentional 15 J prepulse yields good agreement with experimental results.

The Precision Diagnostic System (PDS) is an advanced set of laser diagnostic tools installed within the National Ignition Facility (NIF). It is capable of picking off a single, full aperture, 1053nm (1 omega) beamline before the beam propagates to the target chamber and directing it to a suite of precision laser diagnostics. It was instrumental in validating the performance of the final optics 3 omega frequency conversion system design when NIF was built. The PDS has recently been recommissioned after more than a decade of non-use and enhanced to better understand laser performance limitations' and to characterize underperforming beams. In addition to recommissioning existing diagnostics for calorimetry, power, wavefront, near-field and far-field imaging, new diagnostics have been added: two types of time-resolved near field imaging systems; higher resolution wavefront imaging; and a 1 omega spectrometer. Additionally, the beam transport system was upgraded to allow PDS to select among four different 1 omega beamlines to enable improved understanding of beam-to-beam variations. Two of these four beams are top hemisphere beams, while two are bottom-hemisphere, with known performance variations. The results from NIF Shots with the new and recommissioned PDS diagnostic (spatial resolution, dynamic range, time gating, etc..) will be reviewed and data up to 14 kJ, 3.2 TW will be presented.

The National Ignition Facility (NIF) laser produces 192 pulsed beams with transverse dimensions 40 cm x 40 cm and a diversity of temporal shapes with typical durations ranging from 1 to 30 ns and a total energy on target up to 2.1 MJ in the UV.(1) Standard diagnostics include near-field cameras that record the spatial dependence of the time-integrated pulse fluence, as well as sensors that record the spatially integrated pulse power versus time. While these diagnostics are indispensable, beamlines and the pulses they transport may be better characterized with a diagnostic that reveals more of the spatio-temporal pulse structure, i.e., the local irradiance, especially in the presence of nonlinear optical effects. Recently, the time-resolving capability of the Icarus camera has been leveraged in the Precision Diagnostic System (PDS) at the NIF. The Icarus is a gated CMOS sensor designed to capture X-ray images in various experimental settings.(2,3) However, its sensitivity in the near-IR is sufficient for capturing time-gated images of NIF beams, thus opening the door to better characterization than is possible with standard space- and/or time-integrated diagnostics. In this work, we present the first time-gated beam profiles measured in PDS at the NIF during high-energy and high-peak-power experiments, and discuss their implications in terms of past, present, and future laser performance.

ARC is a kilojoule petawatt-class laser system which generates high energy x-ray and particle sources for radiography of experiments on the National Ignition Facility. We present recent progress on laser performance measurements and system modeling.

The National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory, is the world's largest and highest-energy laser system. NIF's 192 intense laser beams can deliver more energy than any previous laser system with a design point of 1.8 MJ of UV and 500 TW peak power. Efforts are currently underway to better understand the NIF performance and its limitations(1). One goal of recent and future campaigns is to better understand the accumulation of B-integral within the NIF laser using existing diagnostics, as well as the Precision Diagnostic System (PDS). Among these diagnostics, the Shack-Hartmann (SH) sensor in the Output Sensor Package (OSP), a standard NIF diagnostic, and the dedicated PDS Radial Shearing Interferometer (RSI) both measure the wavefront of the beam. Using these diagnostics in concert with the NIF Programmable Spatial Shaper (PSS), which is used to tailor arbitrary spatial beam profiles, we have performed integrated experiments to study the B-Integral induced wavefront through the entire NIF main laser. We propagated a probe beam with a slowly varying spatial intensity profile through the NIF laser to produce a spatially varying B-Integral induced wavefront at the laser output, from which we obtained the magnitude of the B-Integral of the system. We present these direct measurements of the spatially resolved B-Integral induced wavefront scaled for the first time from a table-top experiment(2) to a fusion-class laser chain These measurements are compared to results of current simulations using Virtual Beamline (VBL) software(3).

Beamlines at the National Ignition Facility (NIF) use large neodymium-doped glass slabs for amplification of pulsed beams with various temporal shapes and transverse dimensions _40 cm _ 40 cm. Currently, the Virtual Beam Line (VBL) simulator1 computes saturable amplification according to the approach of Frantz and Nodvik, modified to include drain of the lasing transition's lower level. Linearly chirped pulses are amplified by gain media parameterized by an emission cross section value referenced to the instantaneous beam wavelength. Expanding the capabilities of VBL to a family of waveforms that is more diverse in terms of spectral amplitude and phase calls for the adoption of an approach that is fundamentally dispersive. In this work, we describe an approach to computing broadband amplification in the time domain according to coupled equations that describe evolution of the population inversion and the associated resonant polarization. Considering the diversity of glass species with respect to various gain inhomogeneities, we explore various model extensions for capturing the non-Lorentzian emission cross section in the small-signal regime and how the underlying resonant susceptibility is deformed by gain saturation. The polarization envelope acts as transverse-spatial sources to (3+1)D spectral envelope propagation that fully accounts for linear-optical diffraction and dispersion in the host glass, and includes the usual instantaneous non-resonant third-order electronic response (optical Kerr effect).

Filamentation during simultaneous space-time focusing in bulk fused silica is investigated numerically. We model the use of a pair of concentric gratings to transform a common femtosecond laser pulse with a Gaussian spatial profile into a radially chirped, annular beam shape that is focused into the bulk of silica by a lens. By varying the energy and/or time-chirp of the incident pulse, we capture the pulse dynamics and material response that yields material modification and damage in the nonlinear focus. The results show rich pulse dynamics, enhanced damage/modification site localization, and suggest novel approaches to laser machining of solids. (C) 2016 Optical Society of America

Control of the time duration of a laser pulse as it focuses spatially in a material provides a means for delaying the onset of nonlinear effects during propagation. We investigate simultaneous space-time focusing (SSTF) of femtosecond radially-chirped annular pulses in Kerr dielectrics. The energy and temporal chirp of pulses incident upon a grating-grating-lens system are varied in simulations that solve the unidirectional pulse propagation equation. This system is modeled by inserting transformations that act on the electric field obtained from propagation from one component to the next. The propagation is coupled to the time evolution of the free charge density as a function of space. The resulting "ionization tracks" are taken as a metric for predicting material modification and/or damage in bulk fused silica. As expected from linear-optical considerations, the temporal pre-chirp determines the overall pulse duration as the focusing annulus closes. We find in addition that, for a given pulse energy, the temporal pre-chirp also determines the on-axis intensity distribution as energy collapses onto the propagation axis. This effect determines how the local ionization-induced decrease in refractive index shifts energy in time relative to energy arriving on-axis from the spatially collapsing beam. The magnitude of the pre-chirp can thus control the spatial structure of ionization that may lead to material modification and/or damage.

We describe simulations of nonlinear space-time focusing of femtosecond annular beams in silica. Adjusting the chirp of µJ pulses traversing a pair of concentric gratings leads to pronounced plasma blue-shift, and enhanced material modification localization.

In calculations of ultrafast laser-induced ionization the treatment of fundamental mechanisms such as photoionization and the Kerr effect are treated in isolation using monochromatic perturbative approaches. Such approaches are often questionable for pulses of ultrashort duration and multi-chromatic spectra. In this work we address this issue by solving the quantum optical Bloch equations in a 3D quasi-momentum space and show how to couple this model to ultrashort pulse propagation in dielectrics. This approach self-consistently couples a quantum calculation of the photoionization yield, the photoionization current, and the current from free-carriers with the traditional Kerr effect (self-focusing and self phase modulation) without resort to a perturbative treatment. The material band structure is taken in the tight binding limit and is periodic in the crystal momentum space. As this model makes no assumption about the pulse spectrum, we examine the laser-material interaction of strongly chirped pulses and multi-color multi-pulse schemes of laser-induced material modification. These results are compared to those predicted by standard treatments, such as the Keldysh model of photoionization, for pulses of ultrashort duration.

The use of femtosecond lasers in industrial, biomedical, and defense related applications during the last 15 years has necessitated a detailed understanding of pulse propagation coupled with ultrafast laser-material interactions. Current models of ultrashort pulse propagation in solids describe the pulse evolution of fields with broad spectra and are typically coupled to models of ionization and laser-plasma interaction that assume monochromatic laser fields. In this work we address some of the errors introduced by combining these inconsistent descriptions. In particular, we show that recently published experiments and simulations demonstrate how this contradiction can produce order-of-magnitude errors in calculating the ionization yield, and that this effect leads to altered dimensions and severity of optical breakdown and laser-induced modifications to dielectric solids. We introduce a comprehensive treatment of multi-chromatic non-equilibrium laser-material interaction in condensed matter and successfully couple this model to a unidirectional (frequency-resolved) pulse propagation equation for the field evolution. This approach, while more computationally intensive than the traditional single rate equation for the free electron density, reduces the number of adjustable phenomenological parameters typically used in current models. Our simulation results suggest that intentionally multi-chromatic fields (i.e. strongly chirped pulses or co-propagating pulses of different frequencies) can be arranged to control ionization yields and hence ultrafast laser induced material modifications.

A comprehensive model of ultrafast laser-induced plasma generation intended for coupling with pulse propagation simulations in transparent solids is introduced. It simultaneously accounts for the changing spectrum of a propagating ultrashort laser pulse while coupling to the evolution of the energy-resolved nonequilibrium free-carrier distribution. The presented results indicate that strong pulse chirps lead to ionization dynamics that are not captured by the standard monochromatic treatment of laser-induced plasma formation. These results have strong implications for ultrafast laser-solid applications that depend on ionization in a strong nonlinear focus.

The geochemistry and petrography of a stalagmite from Wanxiang Cave in central China provide a paleodimate record of the Penultimate Glacial Maximum (PGM) suggesting unexpectedly abundant non-monsoonal atmospheric precipitation at the nadir of the PGM. Eleven U-Th(Th-230) ages from 149 to 140 ka BP place the stalagmite in Marine Isotope Stage 6b, coincident with the greatest benthic marine delta O-18(calcite) values of MIS 6. Carbon and oxygen stable isotope data, measurements of layer-specific width, positions of surfaces of non-deposition or dissolution, changes in the character and thickness of seemingly annual layers, changes in concentration of organic acids within the stalagmite's calcite, and patterns in the Mg concentration of that calcite all combine to give a coherent paleodimate record. These data suggest that the stalagmite represents a wetter period than before or after its growth, with the wettest and coldest phase at 145 to 144 ka BP. This extreme in climate yields a striking correlation with the LRO4 stack of oxygen isotope records from marine benthic forams, if the latter is subjected to a 4500-year chronological adjustment previously suggested by U-Th data from corals. The timing of the Wudu stalagmite's deposition combines with findings elsewhere to suggest that the PGM was the most extreme of later Pleistocene glacial maxima.Petrography and U-Th age determinations suggest dramatic changes in climate during the PGM. At the beginning (149-146 ka BP) and end (143-140 ka BP) of the stalagmite's growth, abrupt (century-scale) drying caused lengthy hiatuses as dripwater to the stalagmite diminished. On the other hand, delivery of water to the stalagmite during the wettest phase (145-144 ka BP) caused dissolution of previous layers of the stalagmite. Enhanced atmospheric precipitation during the cold of a glacial maximum is unexpected because, within the spectrum of Holocene climate, cooler conditions lessen the impact of the East Asian monsoon. Changes in the character of stalagmite layers indeed suggest weakened to negligible influence of the East Asian monsoon during the nadir of the PGM. However, data from the stalagmite are compatible with atmospheric precipitation from westerly winds that today reach only northwestern China but that may have been deflected southward in the PGM by southward migration of the Siberian High. This unexpected significance of the Westerlies during the PGM may be a result of the hypothesized extreme nature of the PGM relative to other glacial maxima of the later Pleistocene. (C) 2013 Elsevier B.V. All rights reserved.

Plasmonic materials that strongly interact with light are ideal candidates for designing subwavelength photonic devices. We report on direct coupling of terahertz waves in metallic nanorods by observing the resonant transmission of surface plasmon polariton waves through lithographically patterned films of silver nanorod (100 nm in diameter) micro-hole arrays. The best enhancement in surface plasmon resonant transmission is obtained when the nanorods are perfectly aligned with the electric field direction of the linearly polarized terahertz wave. This unique polarization-dependent propagation of surface plasmons in structures fabricated from nanorod films offers promising device applications. We conclude that the anisotropy of nanoscale metallic rod arrays imparts a material anisotropy relevant at the microscale that may be utilized for the fabrication of plasmonic and metamaterial based devices for operation at terahertz frequencies.