The characterization of ejecta particle size distributions from shock-loaded metals has significant interest to National Laboratories. Traditional measurement techniques have employed holography, Mie scattering, and low-energy X-ray imaging. Recent advancements in optical diagnostics have demonstrated that dark-field (Schlieren) imaging enhances the contrast of ejecta images by emphasizing high-frequency spatial information, thereby improving particle detection and size distribution measurements. To achieve simultaneous light-field and dark-field imaging, an optical system has been designed to split the ejecta motions onto two independent cameras. This configuration enables the concurrent recording of both conventional light-field images and dark-field images, facilitating a comprehensive analysis of ejecta dynamics. High-speed imaging sequences will be utilized to capture the temporal evolution of ejecta dispersal, providing critical insight into the underlying physical mechanisms. Dark-field imaging is particularly advantageous in that it suppresses coherent laser artifacts, such as mode structures and speckle, which can obscure fine-scale features in recorded images. The imaging system is configured such that the ejecta volume is illuminated by a high-intensity laser source. A Fourier optical relay system introduces a well-defined spatial stop, where incident laser light is focused onto an absorbing element, preventing direct illumination from reaching the imaging sensor. As a result, the camera records only scattered light, enhancing contrast and enabling improved particle size discrimination. A 50/50 beam splitter directs a portion of the light to a secondary camera, allowing for the simultaneous acquisition of light-field images. n additional benefit to using dark field imaging occurs when optimizing the alignment of complex optical imaging systems. Alignment set up time is greatly reduced. However, this approach necessitates direct access to the Fourier plane stop position. Analyzing the astigmatism of an optical imaging system is much easier in dark field imaging mode.

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.

Abstract Proppant selection, and the resulting dimensionless fracture conductivity, impacts well performance. Proppant quality standards were developed to quantify proppant performance using dimensionless fracture conductivity, correlating the flow potential of the propped fracture relative to the formation. Since 2018, there has been a near complete switch to in-basin sand (IBS) for completing oil and gas wells in the Permian Basin. The switch to IBS has primarily been based on the idea that overall well and field economics are improved because: 1) capital costs are lowered by sourcing sand locally reducing costs and logistics, and 2) well results using IBS were "good enough" in terms of well performance justifying the use of inferior proppants. Little regard is given to the long-term production impacts, field development value and cumulative free cash flow over a five-to-ten-year horizon. Rystad Energy (2022) evaluated 850 wells from seven operators in both the Midland and Delaware basins and provided clear evidence that the perceived benefits of using IBS to complete Wolfcamp A (WCA) wells in the Permian is not accurate. The Rystad Energy studies will be reviewed in detail. This manuscript presents extensive hydraulic fracture modeling and production simulations of the WCA formation for both the Delaware and Midland basins using 100- and 40/70-mesh to identify the conductivity difference between IBS and NWS to provide an engineering basis for the Rystad Energy results. Conductivity differences for each mesh and sand type ultimately allowed a comparison of well production and net cash flow for P50 wells. The WCA production forecast cases were calibrated to the published Rystad Energy data, where possible, and EUR values. The payout, cumulative production differences and net cash flow are presented comparing IBS and NWS materials. Comparing results between NWS and IBS provides an engineering basis that NWS characteristics drive superior well performance in the Permian basin. As fracture conductivity increases, either from using NWS material or larger mesh sizes, the well production also increases over time. This is also the general conclusion from the Rystad study. This work demonstrates that NWS, while more expensive upfront, performs better throughout the well life, and is almost always the better economic choice and shows a long-term benefit using NWS. Utilizing IBS in the Permian basin results in suboptimal cashflow and reduced long-term profitability. The well performance using IBS is expected to progressively worsen over time. This work demonstrates fractures in the Permian basin are conductivity limited and using IBS negatively affects cash flow and long term well deliverability. NWS is a superior product to IBS and generates enhanced fracture conductivity and production in the Delaware and Midland basins.

Four large zoom lens systems are currently being built for x-ray sources. Radiographic imaging needs require 270 mm x 270 mm square scintillators and the capability to use both 92 x 92 mm and 62 x 62 mm CCD cameras. Each zoom lens system incorporates 11 elements and is designed to be almost telecentric in both image and object space. Each zoom lens system images a thick scintillator emitting light peaking at 435 nm, so special glass types are required for the lens elements. Much larger elliptical pellicles are needed to deflect the scintillator light out of the x-ray path into the zoom lens system. The optical axis of the imaging system must be colinear with the x-ray axis. Two scintillators are positioned on each of two x-ray axes, for a total of four scintillators and four zoom lens systems. An optional configuration will be shown, enabling two lens systems imaging opposite sides of a single scintillator, for a total of four lenses and two scintillators. Although this configuration has advantages, it could suffer from crosstalk. Care must be taken to analyze the anti-reflection coatings applied to all the elements in the imaging chain, including the CCD array and its vacuum window. Design of two-color counter-propagating laser alignment systems will be demonstrated, which shows how the best possible resolution can be achieved. Flip mirrors are used to allow six alignment lasers to have access to the optical axis. Monitoring all retro-reflections at two different wavelengths simplify optical alignment. The evolution of our x-ray radiographic systems over the last two decades will be discussed.

This work explores quick predictive methods for calculating potentially risky stresses and deflections in cemented doublets experiencing temperature change that agree well with finite element analysis. There are three failure modes of interest: cohesive failure of the adhesive, delamination (surface bond failure or debonding), and glass fracture. Adhesive theory, confirmed by finite element analysis, predicts stress singularities that complicate interpretation of the stress calculations. The presence of a stress singularity indicates the breakdown of linear elastic assumptions, but damage initiation and stress singularities are related. The authors find that geometry details near a bond edge can exacerbate or minimize damage initiation and stress concentrations. Because the interpretation of the stress results is complicated, the authors investigated predicted stresses in doublets that have been successfully tested between -40 degrees C and 85 degrees C. This study found that the thermal strain (Delta TDelta(alpha)) should be less than 189 ppm, where Delta T is the temperature excursion and Delta(alpha) is the difference in the two glass coefficients of thermal expansion. If the thermal strain is equal to or greater than 189 ppm, further analysis and testing is warranted. But the authors also show that the fabrication process can significantly influence stress failure, particularly with large diameter doublets.

Direct evidence of inertially confined fusion ignition appears in the abrupt temperature increase and consequent rapid increase in the thermonuclear burn rate as seen in the reaction history. The Gamma Reaction History (GRH) and Gas Cherenkov Detector (GCD) diagnostics are γ-based Cherenkov detectors that provide high quality measurements of deuterium–tritium fusion γ ray production and are, thus, capable of monitoring the thermonuclear burn rate. Temporal shifts in both peak burn time and burn width have been observed during recent high-yield shots (yields greater than 1017 neutrons) and are essential diagnostic signatures of the ignition process. While the current GRH and GCD detectors are fast enough to sense the changes of reaction history due to alpha heating, they do not have enough dynamic range to capture the onset of alpha heating. The next generation of instrumentation, GRH-15m, is proposed to increase the yield-rate coverage to measure the onset of alpha-heating.

The NNSS has been at the forefront of custom high-fidelity x-ray/gamma radiographic imaging solutions that serve our national security for over five decades. Our radiography team utilizes expertise in physics modeling and analysis, along with optical, mechanical, and electrical design, in close collaboration with our customers, to develop imaging methods and capabilities that go beyond their needs. Conceptual designs are developed through R&D efforts to provide solutions for the specific problem at hand. Field systems are designed and built in-house, then qualified utilizing a range of facilities across the National Security Enterprise. Radiographic imaging systems are deployed by our team in the most challenging environments. The NNSS has a strong math and programming team that provides novel on-site image analysis methods that extract crucial information from data returned in field tests.

Cygnus is a dual beam high-energy radiographic x-ray source. Ten years ago, three large zoom lenses were assembled to collect images from 200 mm x 200 mm square scintillators. The zoom capability allows zooming down to a 60 mm x 60 mm picture from the scintillator. Current radiographic imaging needs now require larger 270 mm x 270 mm square scintillators and the capability to use both 92 mm x 92 mm and 62 mm x 62 mm CCD cameras, and a new lens design to meet these needs. This zoom lens incorporates 11 elements and is designed to be telecentric. It images a scintillator emitting light peaking at 435 nm, so special glass types are required for the lens elements. Much larger elliptical pellicles are needed to deflect the scintillator light out of the x-ray path into the lens. The optical axis of the imaging system must be colinear with the x-ray axis. Two scintillators are positioned in each of two Cygnus x-ray axes, for a total of four scintillators and four lens systems. An optional configuration will be shown, enabling two lens systems imaging opposite sides of a single scintillator, for a total of four lenses and two scintillators. Although this configuration has advantages, it suffers from crosstalk. Care must be taken to analyze the anti-reflection coatings applied to all the elements in the imaging chain, including the CCD array and its vacuum window. The evolution of our Cygnus radiographic systems over the last two decades will be discussed.

Presentation to be presented during the first annual Prompt Radiation Detection and Imaging Workshop, hosted by the NNSS Dynamic Instruments Team, April 25–28, 2022, at NLV C-01 Auditorium and via Webex.

Certain companies particularly those with strong design and optical manufacturing units keep strict but private statistical records regarding optical manufacturing and also use the data for design purposes. Design houses without manufacturing sectors are at a disadvantage. However, there is a small but growing public body of knowledge regarding these statistics. In this work, we develop a process to go from gathering raw manufacturing data to using the data for lens system tolerancing. We will describe a tolerancing practice using CODE V and our existing data with the goal of improving our ability to predict manufacturing outcomes. We present reasonable parameter values for the truncated normal and other distributions for variables such as wedge. In some cases, we will link the parameter values to standard tolerance categories that many manufacturers give: commercial, precision, and high precision. The tolerancing method will use established CODE V practice as well as macros with parameter values derived from data as one of the inputs. An example of how to use these techniques on a lens design will be given. We also provide an appendix that classifies glass type by manufacturability. The data provided in the appendix can be used in the tolerancing process.

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.

Interrogating ejecta particles launched from target materials that are undergoing dynamic shock can be done with both xray imaging and visible shadowgraph imaging. Our dynamic testing must be done inside a containment vessel with limited access ports available. We designed an imaging system to relay both types of imaging systems through a single port using the same optical relay and then splitting the images onto three separate high-speed imaging cameras outside the containment vessel. X-ray imaging provides ejecta density measurements. Shadowgraph imaging that is done at two wavelengths (blue and red) constrains ejecta particle size distributions and provides areal density measurements of the ejecta cloud. The ejecta particles are positioned 225 mm before the x-ray scintillators; this arrangement permits a folded mirror system to allow the shadowgraph data to bypass the x-ray scintillators. This configuration results in spatial separations between the intermediate image planes of the x-ray and shadowgraph images along the optical axis. At the position of the x-ray intermediate image plane, mirrors are positioned such that the shadowgraph images are kicked out and their images are sent on to different cameras. Positioning of the large doublet relay lenses keeps shrapnel from impacting the vessel containment windows.

Prototype zoom lenses should be designed with flexibility. One never knows what the future use of a prototype as-build lens will be. In a prior design of a large-image-format zoom lens used for proton radiography, extra back focal distance was constrained in the design to allow for future insertion of extra lenses. These added lenses can change the magnification to a different camera system, having a smaller image size. Three single commercial lens elements were mounted into a commercial variable-length housing barrel that was attached to the back of the zoom lens using a 3Dprinted flange. This new design has been adapted to support neutron radiography; the new configuration collects light from a thick, blue-light-emitting scintillator. After the initial request was made, it took us only three weeks to design, assemble, and conduct imaging tests. The scintillator’s light travels 24 inches before entering into the zoom lens. A large pellicle is inserted into the optical path to keep the zoom lens and camera out of the neutron flux. Because of reduced resolution from the volume scintillator, a five-axis self-leveling alignment laser was sufficient to adjust the tilting of the scintillator, pellicle, zoom lens, and camera. The design process for picking suitable COTS lens elements will be discussed.

The Aerogel Cherenkov Detector for Cygnus (ACD/C) is a time-dependent, x-ray spectral detector that uses SiO2 aerogels spanning an index of refraction (n = 1.02-1.07) corresponding to a 1.1-2.3 MeV x-ray energy threshold. The ACD/C was developed for pulsed power x-ray sources like Cygnus located at the Nevada National Site and Mercury located at the Naval Research Laboratory (NRL). Aerogels sit between the measurement capabilities of gas (>2 MeV) and solids such as fused silica (>0.3 MeV). The detector uses an aluminum converter to Compton scatter incoming x-rays and create relativistic electrons, which produce Cherenkov light in an aerogel or a fused silica medium. The ACD/C was fielded at the NRL when Mercury was tuned to produce up to 4.8 MeV endpoint bremsstrahlung. Despite a high radiation and electromagnetic interference background, the ACD/C was able to achieve high signal over noise across five aerogel densities and fused silica, including a signal to noise for a 1.1 MeV aerogel threshold. Previous experiments at Cygnus observed a signal that was comparable to the noise (1×) at the same threshold. The ACD/C observed time-resolved rise and fall times for different energy thresholds of the photon spectrum. Monte Carlo simulations of the ACD/C's aerogel response curves were folded with a simulation of Mercury's photon energy spectrum and agree within the error to the observed result.

Fusion reaction history and ablator areal density measurements for Inertial Confinement Fusion experiments at the National Ignition Facility are currently conducted using the Gamma Reaction History diagnostic (GRH_6m). Future Gas Cherenkov Detectors (GCDs) will ultimately provide ∼100x more sensitivity, reduce the effective temporal response from ∼100 to ∼10 ps, and lower the energy threshold from 2.9 to 1.8 MeV, relative to GRH_6m. The first phase toward next generation GCDs consisted of inserting the existing coaxial GCD-3 detector into a reentrant well which puts it within 4 m of the implosion. Reaction history and ablator gamma measurement results from this Phase I are discussed here. These results demonstrate viability for the follow-on Phases of (II) the use of a revolutionary new pulse-dilation photomultiplier tube to improve the effective measurement bandwidth by >10x relative to current PMT technology; and (III) the design of a NIF-specific "Super" GCD which will be informed by the assessment of the radiation background environment within the well described here.

The Cherenkov mechanism used in Gas Cherenkov Detectors (GCDs) is exceptionally fast. However, the temporal resolution of GCDs, such as the Gamma Reaction History diagnostic at the National Ignition Facility (NIF), has been limited by the current state-of-the-art photomultiplier tube technology to ∼100 ps. The soon-to-be deployed Pulse Dilation Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolution comparable to that of the gas cell or ∼10 ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through precision measurements of reaction history and ablator areal density (ρR) history, leading to better constrained models. Features such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes may become visible for the first time. Test measurements of the PD-PMT at Atomic Weapons Establishment confirmed that design goals have been met. The PD-PMT provides dilation factors of 2 to 40× in 6 increments. The GCD-3 recently deployed at the NIF has been modified for coupling to a PD-PMT and will soon be making ultrafast measurements.

A zoom lens has been designed for proton radiography applications. Radiographic images are recorded at the end of an accelerator, where protons exit an aluminum vacuum window producing a shadowgraph image onto an LYSO (lutetium yttrium orthosilicate) scintillator. Emission from this 5-inch-square scintillator reflects off a pellicle and is then collected by a zoom lens located 24 inches away. Proton radiography can make high-speed, multi-frame radiographs or radiographic movies. This zoom lens provides 2X magnification for viewing different object sizes. The zoom lens incorporates eleven lenses, including a moving doublet that changes the magnification. Refocus of the camera is required when zooming. Only one moving doublet lens is required to change magnification. The stop was anchored to the moving doublet and its diameter is unchanged throughout magnification changes. The entire lens system is housed in a cylindrical tube. This lens will be used with a 10-frame camera with a 44 × 44 mm square image format and 1100 × 1100 pixel resolution. Stray light suppression is most important in this lens system. Radial compensation is controlled by two locking micrometers on element 9, which relaxes the mechanical tolerancing. A helical cam barrel using a linear rail controls the movement of the doublet. Alignment of the mechanical gears will be discussed.