Search

The objective of this work is to discuss the prospects of the formation of cryogenic shock ignition targets based on the FST-layering method (FST—free-standing target) proposed and developed at the Lebedev Physical Institute (LPI). The targets are designed to study alternative fuel ignition schemes at intermediate and megajoule-scale ICF laser facilities. [ABSTRACT FROM AUTHOR]

The Lebedev Physical Institute (LPI) actively develops innovative technologies for creating the HTSC—MAGLEV accelerator for delivering a cryogenic fuel target (CFT) placed in a levitating HTSC-carrier to the ICF chamber for interacting with laser radiation. The LPI approach is based on the phenomenon of HTSC quantum levitation in a gradient magnetic field. Acceleration is provided by a sequence of current-carrying solenoids, and HTSC-carrier levitation occurs due to the use of a magnetic rail, along which the solenoids are placed. A prototype of an elementary block for accelerating an HTSC-carrier is developed and its motion control processes are studied. For this purpose, a special system of operational control of the acceleration block is developed and tested. The HTSC-carrier acceleration up to 1 m/s at the acceleration length La = 20 cm is demonstrated using only one pair of matched solenoids. The results obtained are of practical importance in the area of creating noncontact systems for CFT delivery due to constructing a linear magnetic track by connecting one elementary acceleration unit with many others to achieve a required CFT injection rates from 20 to 200 m/s and higher. [ABSTRACT FROM AUTHOR]

Magnetic levitation technologies are studied as an innovative basis for developing contactless systems for delivering cryogenic targets to the laser focus of an ICF facility or future power plant. A necessary element of such systems is a special target carrier made of high-temperature superconductors (HTSC) with high vortex pinning. It is shown experimentally that an HTSC carrier in the form of an outer coating of the target makes it possible to completely eliminate mechanical friction during target acceleration due to its levitation in gradient magnetic fields. The prospects for further development of this direction in the area of creating HTSC nanostructured films and coatings are discussed. [ABSTRACT FROM AUTHOR]

Fuel magnetization significantly lowers the required radial convergence, enabling cylindrical implosions to become a promising approach for inertial confinement fusion. The Nernst effect on the two-layer single shell magnetized target design applied to a Z-pinch benefits from a gold layer that decreases fuel demagnetization and serves as a magnetothermal insulation layer, preventing magnetothermal losses. The resistive diffusion and Nernst advection of the magnetic field are considered in the radiation magnetohydrodynamic model, which alter the evolution of magnetic flux in the magnetized target and result in plasma demagnetization. The results demonstrate that targets with a wide range of parameters can achieve ignition conditions under a 30 MA driven current. A two-layer single shell magnetized target for lessening the Nernst effect has the potential to achieve ignition conditions. The fusion yield of the optimal target increases by 168% from 0.71 MJ to 1.90 MJ, compared to a one-layer single shell target.

Hybrid fluid-PIC simulations aimed at a better understanding of the implosion physics and the material mixing into the hot spot are described. The application of a hybrid fluid-PIC code is motivated by the difficulty of modeling the material mixing by the commonly used radiation hydrodynamic simulations. Hybrid fluid-PIC techniques, which treat the ions with the traditional particle-in-cell method, and electrons with a massless fluid, are more adaptable to handle the heating of DT fuel through PdV work and the material mixing near the DT ice-gas interface and ablator-fuel interface of a compressed capsule. During implosion shock convergence, significant reactant temperature separation and a noticeable amount of material mixing are observed, both of which have important consequences for estimating neutron yield and the understanding of implosions. Physical explanations for these phenomena are discussed, with the non-equilibrium effect in the hotspot and hydrodynamic instabilities at the interface as the likely explanation, respectively. The hybrid fluid-PIC method would be helpful to test the phenomenological fluid model describing the material mixing in ICF implosion.

The enhancement of fusion reaction rates in a thermonuclear plasma by electron screening of the Coulomb barrier is an important plasma-nuclear effect that is present in stellar models but has not been experimentally observed. Experiments using inertial confinement fusion (ICF) implosions may provide a unique opportunity to observe this important plasma-nuclear effect. Herein, we show that experiments at the National Ignition Facility (NIF) have reached the relevant physical regime, with respect to the density and temperature conditions, but the estimated impacts of plasma screening on nuclear reaction rates are currently too small and need to be increased to lower the expected measurement uncertainty. Detailed radiation hydrodynamics simulations show that practical target changes, like adding readily available high-Z gases, and significantly slowing the inflight implosion velocity, while maintaining inflight kinetic energy, might be able to push these conditions to those where plasma screening effects may be measurable. We also perform synthetic data exercises to help understand where the anticipated experimental uncertainties will become important. But challenges remain, such as the detectability of the reaction products, non-thermal plasma effects, species separation, and impacts of spatial and temporal gradients. This work lays the foundation for future efforts to develop an important platform capable of the first plasma electron screening observation.

The challenge in the field of inertial confinement fusion (ICF) research is related to the study of alternative schemes for fuel ignition on laser systems of medium and megajoule scales. At the moment, it is considered promising to use the method of shock ignition of fuel in a pre-compressed cryogenic target using a focused shock wave (shock- or self-ignition (SI) mode). To confirm the applicability of this scheme to ICF, it is necessary to develop technologies for mass-fabrication of the corresponding targets with a spherically symmetric cryogenic layer (hereinafter referred to as SI-targets). These targets have a low initial aspect ratio Acl (Acl = 3 and Acl = 5) because they are expected to be more hydrodynamically stable during implosion. The paper discusses the preparation of SI-targets for laser experiments using the free-standing target (FST) layering method developed at the Lebedev Physical Institute (LPI). It is shown that, based on FST, it is possible to build a prototype layering module for in-line production of free-standing SI-targets, and the layering time, τform, does not exceed 30 s both for deuterium and deuterium-tritium fuel. Very short values of τform make it possible to obtain layers with a stable isotropic fuel structure to meet the requirements of implosion physics. [ABSTRACT FROM AUTHOR]

Inertial confinement fusion (ICF) experiments create a unique laboratory environment in which thermonuclear fusion reactions occur within a plasma, with conditions comparable to stellar cores and the early universe. In contrast, accelerator-based measurements must compete with bound electron screening effects and beam stopping when measuring fusion cross sections at nucleosynthesis-relevant energies. Therefore, ICF experiments are a natural place to study nuclear reactions relevant to nuclear astrophysics. However, analysis of ICF-based measurements must address its own set of complicating factors. These include: the inherent range of reaction energies, spatial and temporal thermal temperature variation, and kinetic effects such as species separation. In this work we examine these phenomena and develop an analysis to quantify and, when possible, compensate for their effects on our inference. Error propagation in the analyses are studied using synthetic data combined with Markov Chain Monte Carlo (MCMC) machine learning. The novel inference techniques will aid in the extraction of valuable and accurate data from ICF-based nuclear astrophysics experiments.

• A novel design with a grooved aluminum-alloy jacket is proposed to improve the thermal uniformity in a compact fusion target. • The thermal-structural performance at the adhesive interface has been found with significant impact on achieving target thermal uniformity. • Silver-doped adhesive at the arm-jacket interface can improve the robust of circumferential uniformity, as well as a high conductive diagnosis band. • The spherical symmetry of the deuterium-tritium ice layer has been significantly improved under the new design. The roughness of the fuel ice layer at low modes significantly impacts the hydrodynamic instability in inertial confinement fusion experiments with indirect-drive cryogenic targets. It is primarily determined by the thermal uniformity of the capsule. Due to the β-decay heat of tritium, the temperature profiles of targets filled with deuterium-tritium differ from those filled with deuterium-deuterium in a cylindrical hohlraum. The cylindrical shape causes the equator of the capsule to be cooler than the two poles in the steady state without any intervention. Tuning the vertical temperature distribution is essential and requires a high thermal resistance in the target thermal mechanical package. It is very difficult for a compact target which is just half of the National Ignition Facility (NIF) target scale, and is contrary to the previous design of deuterium- deuterium target, which used a high-conductive jacket made from Oxygen-Free Copper (OFC), to provide a relatively uniform thermal field around the capsule. To realize the vertical tuning capability and achieving global thermal uniformity of the capsule, we propose in this paper a novel design featuring a grooved aluminum-alloy jacket, as well as the methods to improve thermal contact reliability and conductivity, including decreasing the width of arm-jacket interface, enhancing the adhesive conductivity by doping silver, and replacing the aluminum diagnosis band with conductive OFC. We further verified this design through experiments. It has reduced the global temperature difference of the capsule by about 70 % and significantly improved the quality of the deuterium-tritium ice layer. [ABSTRACT FROM AUTHOR]

A sustainable burn platform through inertial confinement fusion (ICF) has been an ongoing challenge for over 50 years. Mitigating engineering limitations and improving the current design involves an understanding of the complex coupling of physical processes. While sophisticated simulation codes are used to model ICF implosions, these tools contain necessary numerical approximation but miss physical processes that limit predictive capability. Identification of relationships between controllable design inputs to ICF experiments and measurable outcomes (e.g., neutron yield, neutron velocity, areal density) from performed experiments can help guide the future design of experiments and development of simulation codes, to potentially improve the accuracy of the computational models used to simulate ICF experiments. We use sparse matrix decomposition methods to identify clusters of a few related design variables. Sparse principal component analysis (SPCA) identifies groupings that are related to the physical origin of the variables (laser, hohlraum, and capsule). A variable importance analysis finds that in addition to variables highly correlated with neutron yield, such as picket power and laser energy, variables that represent a dramatic change of the ICF design, such as number of pulse steps, are also very important. The obtained sparse components are then used to train a random forest (RF) regression surrogate for predicting total yield. The RF performance on the training and testing data compares with the performance of the RF trained using all the design variables considered. This work is intended to inform design changes in future ICF experiments by augmenting the expert intuition and simulation results. [ABSTRACT FROM AUTHOR]

Building a sustainable burn platform in inertial confinement fusion (ICF) requires an understanding of the complex coupling of physical processes and the effects that key experimental design changes have on implosion performance. While simulation codes are used to model ICF implosions, incomplete physics and the need for approximations deteriorate their predictive capability. Identification of relationships between controllable design inputs and measurable outcomes can help guide the future design of experiments and development of simulation codes, which can potentially improve the accuracy of the computational models used to simulate ICF implosions. In this article, we leverage developments in machine learning (ML) and methods for ML feature importance/sensitivity analysis to identify complex relationships in ways that are difficult to process using expert judgment alone. We present work using random forest (RF) regression for prediction of yield, velocity, and other experimental outcomes given a suite of design parameters, along with an assessment of important relationships and uncertainties in the prediction model. We show that RF models are capable of learning and predicting on ICF experimental data with high accuracy, and we extract feature importance metrics that provide insight into the physical significance of different controllable design inputs for various ICF design configurations. These results can be used to augment expert intuition and simulation results for optimal design of future ICF experiments. [ABSTRACT FROM AUTHOR]

The development of a system for noncontact positioning and transport of cryogenic fuel targets (CFTs) is an important task in the inertial confinement fusion (ICF) program. In this paper, we investigate the possibility of constructing a levitation system for accelerating the CFT magnetic carrier along a superconducting tape guide made of HTSC materials. [ABSTRACT FROM AUTHOR]

The challenge in the field of inertial confinement fusion (ICF) research is related to the study of alternative schemes for fuel ignition on laser systems of medium and megajoule scales. At the moment, it is considered promising to use the method of shock ignition of fuel in a pre-compressed cryogenic target using a focused shock wave (shock- or self-ignition (SI) mode). To confirm the applicability of this scheme to ICF, it is necessary to develop technologies for mass-fabrication of the corresponding targets with a spherically symmetric cryogenic layer (hereinafter referred to as SI-targets). These targets have a low initial aspect ratio Acl (Acl = 3 and Acl = 5) because they are expected to be more hydrodynamically stable during implosion. The paper discusses the preparation of SI-targets for laser experiments using the free-standing target (FST) layering method developed at the Lebedev Physical Institute (LPI). It is shown that, based on FST, it is possible to build a prototype layering module for in-line production of free-standing SI-targets, and the layering time, τform, does not exceed 30 s both for deuterium and deuterium-tritium fuel. Very short values of τform make it possible to obtain layers with a stable isotropic fuel structure to meet the requirements of implosion physics.

In this article, the activities to fabricate the polystyrene micro-shells by the microencapsulation method for laser fusion targets are presented. To reduce the Rayleigh-Taylor hydrodynamic instabilities in the process of target compression, the target requires a spherical symmetry, excluding any impurity with pre-defined elemental distribution. The polystyrene shells have wall thickness 27±2 µm and diameter 750±50µm, respectively. The transmission holographic Mach-Zehnder interferometer method has been utilized to characterize the micro-shell quality by measurement of the wall thickness and nonuniformity of the micro-shells.

This article is based on my plenary presentation that was associated with my Peter Haas Award, where I overview my 40 years of research and the people with whom I have had the pleasure of working, both domestically and internationally. In 1978, Sandia’s electron beam fusion program emerged from a weapons simulator community that was machine oriented and relied on design principles and J. Charlie Martin (JCM) criteria. The simulation tools were primarily used retrospectively. Fusions’ extraordinary requirements stimulated tremendous innovation in pulsed power, beams, pinches, and simulation tools. I started by developing ion beam deposition and transport models that were integrated into radiation-hydrodynamics codes; validated by experiments on Gamble II and Proto I; and helped initiate Sandia’s light-ion-beam fusion program. Strategic Defense Initiative (SDI) program research led to the development of the Integrated Tiger Series (ITS) suite of electron–photon Monte Carlo codes (1985). A research on Particle Beam Fusion Accelerator I (PBFA-I) and PBFA-II on generating, transporting, and focusing ion beams required developing transport, diagnostic simulation, and analysis tools, which were used in focusing protons to 5 TW/cm2 (1991) and lithium beams to 2 TW/cm2 and heating hohlraums to 65 eV (1996). They also helped identify anode plasma formation by electron heating as the source of diode impedance collapse leading to efforts to include electron–electrode interaction models into particle-in-cell (PIC) codes and initiating hybrid fluid-PIC development (IPROP, LSP). Electrode physics remains a power flow grand challenge for high-yield fusion. In 1999, I led rad-magnetohydrodynamic (MHD) development [arbitrary-Lagrangian–Eulerian general research applications high-energy-density physics (ALEGRA-HEDP)] and oversaw equation of state (EOS) and conductivity model development using quantum molecular dynamics/density function theory (QMD/DFT), resulting in predictive capabilities for dynamic material experiments. Improved z-pinch dynamic hohlraum modeling and experiments resulted in thermonuclear neutrons (2004). 3-D wire array dynamics were modeled and understood. We developed advanced radiographic sources and built a linear transformer driver (LTD) test bed. At the Naval Research Laboratory (NRL), I have overseen advances in modeling and experiments in beams, pinches, pulsed power, and their applications (2009-). My goal throughout has been to develop and validate predictive simulation tools, making pulsed power a Science. [ABSTRACT FROM AUTHOR]

In this article, the story of linear transformer driver (LTD) development is presented, which began in the 1980s when the inductive energy storage (IES) systems with plasma opening switches (POSs) were the focus of pulsed power research all over the world. The accompanying problems of this technology resulted in the development of microsecond LTDs by Boris Kovalchuk, which was the first crucial step toward the development of this new technology. Next came the fast (~100 ns) LTDs, eliminating completely the need for any pulse compression and power amplification. Most recently, the LTD technology was further developed to generate fast rising output pulses with a flat or trapezoidal (rising or falling) top. Such LTD cavities, called Square Pulse LTDs, are better suited for applications such as flash radiography, Z-pinch, high-power microwaves, etc. A number of recent new suggestions important for the viability of LTD technology are also presented. [ABSTRACT FROM AUTHOR]

We investigate and revisit the deployment of a directional time-varying (rotating) driving magnetic field to suppress the magneto-Rayleigh–Taylor (MRT) instability in dynamic Z-pinches. A rotational driving magnetic field is equivalent to two magnetic-field components, $\Theta $ and Z, that alternate in time, referred to as an alternate Theta-Z-pinch configuration. We consider a finitely thick cylindrical liner configuration in this paper. We numerically integrate the perturbation equation to stagnation time based on the optimal background unperturbed trajectories. We assess the cumulative growth of the dominant mode selected by some mechanism at the beginning of an implosion. The maximum e-folding number at the stagnation of the dominant mode of an optimized alternate Theta-Z-pinch is significantly lower than that of the standard Theta- or Z-pinch. The directional rotation of the magnetic field acts to suppress instabilities, independent of the finite thickness of the liner. The finite thickness effect plays a role only when the orientation of the magnetic field varies in time, whereas it does not play a role in the standard Theta- or Z-pinch. The rotating frequency of the magnetic field and the thickness of the liner both have a monotonic effect on suppression. Their synergistic effect can enhance the suppression of the MRT instability. Because the MRT instability can be well suppressed in this way, the alternate Theta-Z-pinch configuration has potential applications in liner inertial fusion that uses a magnetically driven liner to directly compress the fuel target to initiate fusion. [ABSTRACT FROM AUTHOR]

One of the key problems in the ICF program is the development of rapid methods for forming cryogenic fuel targets (CFT) for their feeding to the focus of a high-power laser setup or an ICF reactor. The simulation results on temporal parameters of the formation of reactor-scaled CFTs by the free-standing target (FST) method are presented. The CFT design includes hollow 4-mm-diameter shells of compact and porous polymers, containing solid hydrogen fuel on the inner surface. It is shown that the time of the cryogenic layer formation in the targets does not exceed 30 s, which makes it possible to implement line production of reactor-scaled CFTs based on the FST method. [ABSTRACT FROM AUTHOR]

In inertial confinement fusion, the scientific issues include the generation and transport of driver energy, the pellet design, the uniform target implosion physics, and the realistic nuclear fusion reactor design. In this paper, we present a pellet injection into a power reactor in heavy-ion inertial fusion (HIF). We employ a magnetic correction method to reduce the pellet alignment error in HIF reactor chamber, including the gravity, the reactor gas drag force, and the injection errors. We found that the magnetic correction device proposed in this paper is effective to construct a robust pellet injection system with a sufficiently small pellet alignment error. [ABSTRACT FROM AUTHOR]

The objectives of this tutorial are as follows: 1) to help students and researchers develop a basic understanding of how pulsed-power systems are used to create high-energy-density (HED) matter; 2) to develop a basic understanding of a new, compact, and efficient pulsed-power technology called linear transformer drivers (LTDs); 3) to understand why LTDs are an attractive technology for driving HED physics (HEDP) experiments; 4) to contrast LTDs with the more traditional Marx-generator/pulse-forming-line approach to driving HEDP experiments; and 5) to briefly review the history of LTD technology as well as some of the LTD-driven HEDP research presently underway at universities and research laboratories across the globe. This invited tutorial is part of the Mini-Course on Charged Particle Beams and High-Powered Pulsed Sources, held in conjunction with the 44th International Conference on Plasma Science in May of 2017. [ABSTRACT FROM AUTHOR]

In experimental studies of inertial confinement fusion (ICF), scientific grade charge-coupled device (CCD) cameras are widely used for temporal and spatial investigations of the physical processes that occur during such experiments, such as shock waves. The performance of such a camera is directly related to its accuracy and credibility of measurement, so it is important to calibrate the photoelectric response characteristics of a scientific grade CCD camera before using it. The traditional system and process used for calibration is complex, involving measurement errors that can adversely affect the accuracy and confidence of calibration. This paper proposes a new method that relies on wedge interference is used images captured by the CCD camera to be calibrated and the calculated laser intensity distribution due to interference to obtain the photoelectric response characteristics of the camera via data processing. This method not only ensures realistic and reliable calibration results but also is simple and fast, providing a basis for obtaining accurate data in ICF experiments. [ABSTRACT FROM AUTHOR]

Rayleigh–Taylor (RT) and Richtmyer–Meshkov(RM) instabilities are well-known pathways towards turbulent mixing layers, in many cases characterized by significant mass and species exchange across the mixing layers (Zhou, 2017. Physics Reports , 720–722, 1–136). Mathematically, the pathway to turbulent mixing requires that the initial interface be multimodal, to permit cross-mode coupling leading to turbulence. Practically speaking, it is difficult to experimentally produce a non-multi-mode initial interface. Numerous methods and approaches have been developed to describe the late, multimodal, turbulent stages of RT and RM mixing layers. This paper first presents the initial condition dependence of RT mixing layers, and introduces parameters that are used to evaluate the level of “mixedness” and “mixed mass” within the layers, as well as the dependence on density differences, as well as the characteristic anisotropy of this acceleration-driven flow, emphasizing some of the key differences between the two-dimensional and three-dimensional RT mixing layers. Next, the RM mixing layers are discussed, and differences with the RT mixing layer are elucidated, including the RM mixing layers dependence on the Mach number of the initiating shock. Another key feature of the RM induced flows is its response to a reshock event, as frequently seen in shock-tube experiments as well as inertial confinement events. A number of approaches to modeling the evolution of these mixing layers are then described, in order of increasing complexity. These include simple buoyancy–drag models, Reynolds-averaged Navier–Stokes models of increased complexity, including K – ε , K–L, and K – L – a models, up to full Reynolds-stress models with more than one length-scale. Multifield models and multiphase models have also been implemented. Additional complexities to these flows are examined as well as modifications to the models to understand the effects of these complexities. These complexities include the presence of magnetic fields, compressibility, rotation, stratification and additional instabilities. The complications induced by the presence of converging geometries are also considered. Finally, the unique problems of astrophysical and high-energy-density applications, and efforts to model these are discussed. [ABSTRACT FROM AUTHOR]

After X-ray irradiate a metal cavity, a large number of photoelectrons are emitted into the internal space, thereby producing a very strong system-generated electromagnetic pulse (SGEMP). The X-ray environment inside a laser inertial confinement device is very complex. Even if the diagnostic equipment working inside the target chamber has a good electromagnetic shielding capability, it would still face severe SGEMP interference. In this paper, the X-ray environments inside target chambers of National Ignition Facility, optimized method for estimated guidance accuracy (OMEGA), and Shenguang-III (SG-III) facility were obtained through a survey of the literature. In light of the survey results, the time-biased finite-difference time-domain method and the particle-in-cell method were used to numerically simulate SGEMP inside a 2-D cylindrical cavity model. Besides, the relationships between the SGEMP in the cavity and parameters such as X-ray fluence, energy spectrum, pulsewidth, and spatial size of the model were studied. The fluence and pulsewidth of the X-ray were found to have a more significant effect on the time-domain waveform of the electromagnetic field. Finally, based on the calculation results, the SGEMP of the SG-III facility in the target chamber was calculated to approximately be 0.75 MV/m. [ABSTRACT FROM PUBLISHER]

A deuterated-tritiated polymer was prepared via addition reaction and isotopic exchange between a deuterated polycyclooctene and tritium in the presence of a Pd/BaSO 4 catalyst, free of solvents. After reaction, the gas sample from the vessel was analyzed with mass spectrometer, and compared with the raw T 2 /Ar mixture. It was demonstrated that isotopic exchange as well as hydrogen addition reaction occurred in the tritiation experiment. The abundance of tritium in the deuterated-tritiated polymer was determined to be 17.7%. The deuterated-tritiated polymer dissolved in CDCl 3 was characterized by 2H NMR and 3H NMR spectra. By using the solvent-free tritiation method, the generation of waste radioactive liquids can be avoided, and the deuterated-tritiated polymer can be kept away from the protiums of solvents. [ABSTRACT FROM AUTHOR]

The results of a series of experiments using a piezovibration formation module for producing cryogenic targets with a given fuel layer structure are presented. [ABSTRACT FROM AUTHOR]

Activated Au from a fragmented and dispersed NIF hohlraum is of interest to measure the induced 14.1-MeV Au/Au isotope ratio as an assessment of shot performance. A radiochemical recovery procedure, based on Au complexation by cyanide in NaOH-NaCN solution, was developed to reclaim radiogold (*Au) residues from post-detonation graphite collector foils. The average overall radiochemical yield from grafoils in an equatorial position relative to the hohlraum was 88 %. However, the yield from the identical procedure applied to post-shot grafoils positioned axially (polar) was much decreased. The chemical dependency of explosion reaction products on collector position around an ostensibly symmetric fusion source is currently unexplained. [ABSTRACT FROM AUTHOR]

The Naval Research Laboratory (NRL) was established in 1923 to fulfill Thomas Edison's vision of a government research laboratory that could develop and translate scientific knowledge into effective military systems in times of war. The NRL Plasma Physics Division was established in 1966 to create X-ray simulators for testing the effects of nuclear weapons on materials and components of military hardware, to study the physics and effects of high-altitude nuclear explosions, and to perform nuclear fusion research. This paper traces the development of pulsed power and plasma physics from 1940 to the present day through a set of graphical timeframes that depict both the major geopolitical events and the major pulsed power facilities that were noteworthy in a series of 15–20 year epochs. Pulsed power research began at the U.K. Atomic Weapons Establishment, where it was first used for radiography. Subsequently, Sandia, Los Alamos, and Livermore performed pulsed power research for an expanding set of missions. The earliest facilities consisted mostly of single-module machines that had limited ability to synchronize and pulse shape. The 1983 Strategic Defense Initiative led to the development of technologies for directed energy weapons, railguns, and X-ray lasers. The cessation of nuclear testing in 1992 created an increased need for above ground testing including advanced radiography, nuclear weapons effects simulators, hydrotest facilities, and inertial confinement fusion devices. The Stockpile Stewardship Program, which began in the mid-1990s, saw the construction of several major facilities [e.g., National Ignition Facility, Z, Omega, and DAHRT], with increased power, as well as sophisticated synchronization and pulse shaping capabilities. In 2012, the Department of Defense (DoD) announced a strategic pivot to the joint force of 2020 and a rebalance toward the Asian-Pacific region. Looking to the future, a number of DoD documents describe the need to develop and deploy transformational technologies. For example, the 2012 Naval S&T Strategic Plan emphasizes hypervelocity railguns, DE, the detection and neutralization of weapons of mass destruction, and the ability to retain access in contested environments, especially in space. Future military systems will require pulsed power that is compact, repetitive, efficient, and is thermally managed. Low-temperature plasmas and nonequilibrium plasma chemistry are emerging research areas that could impact DoD missions. Atmospheric plasmas are creating new opportunities in plasma biology and plasma medicine. The research capabilities of the rest of the world, especially China, are rapidly growing, and new ideas and capabilities will increasingly come from outside of the U.S. This paper explores some of the future challenges and opportunities for plasma physics and pulsed power research. [ABSTRACT FROM PUBLISHER]

The Single Pass RF Driver (SPRFD) compacts the beam from the linac without storage rings by manipulations that take advantage of the multiplicity of isotopes (16), the preserved µbunch structure, and increased total linac current. Magnetic switches on a first set of delay lines rearrange the internal structure of the various isotopic beams. A second set of delay lines sets the relative timing of the 16 isotopic beam sections so they will telescope at the pellet, in one of multiple fusion chambers, e.g. 10. Shortening each isotopic beam section uses preservation of the µbunch structure up to the final ~2km drift before final focus. Just before the final drift, differential acceleration of the µbunches in each isotopic beam section (128 total) launches an axial collapse, referred to as the “Slick”. The µbunches interpenetrate as their centers of mass move toward each other and individual µbunches lengthen due to their momentum spread. In longitudinal phase space they slide over one another as they lengthen in time and slim down in instantaneous energy spread. The permissible amount of µbunch lengthening is set by the design pulse shape at the pellet, which varies for different groups of isotopes. In narrow bands of ranges according to the role for each isotope group in the pellet, the ranges extend from 1 to 10g/cm2 to drive the cylinder barrel and thin hemispherical end caps, to heat the ~0.5g/cm2 ρR fast ignition zone, and to improve the quasi-sphericity of the compression of the fast ignition zones at the pellet's ends. Because the µbunch–µbunch momentum differences are correlated, time-ramped beamline transport elements close after the differential accelerator are used to correct the associated shifts of focal point. Beam neutralization is needed after the differential acceleration until adjacent bunches begin to overlap. Concurrent collapse of each isotope and telescoping of the 16 isotopes cause the current in each beamline to rise rapidly during the final microsecond of driver pulse generation. Principal topics discussed are some basic considerations for the final compression processes, benefits for pellet implosion and ignition that may result from new means to shape the power deposition in the pellet in 3D and in time, and immediate needs for investigations. Economics that use HIF's potential for large economies of scale are summarized, to establish the reality of a large fusion energy complex achieving a high share of the overall benefits of fusion: abundance, cleanliness, safety, affordability, and profits. [ABSTRACT FROM AUTHOR]

A modeling approach is proposed to predict the transient and permanent degradation of image sensors in complex radiation environments. The example of the OMEGA facility is used throughout the paper. A first Geant4 simulation allows the modeling of the radiation environment (particles, energies, timing) at various locations in the facility. The image sensor degradation is then calculated for this particular environment. The permanent degradation, i.e. dark current increase, is first calculated using an analytical model from the literature. Additional experimental validations of this model are also presented. The transient degradation, i.e. distribution of perturbed pixels, is finally simulated with Geant4 and validated in comparison with experimental data. [ABSTRACT FROM PUBLISHER]

A hardening method is proposed to enable the use of CMOS image sensors for Fusion by Inertial Confinement Diagnostics. The mitigation technique improves their radiation tolerance using a reset mode implemented in the device. The results obtained evidence a reduction of more than 70% in the number of transient white pixels induced in the pixel array by the mixed neutron and \gamma-ray pulsed radiation environment. [ABSTRACT FROM PUBLISHER]

High current pulsed-power generators efficiently store and deliver magnetic energy to z-pinch targets. We review applications of magnetically driven implosions (MDIs) to inertial confinement fusion. Previous research on MDIs of wire-array z-pinches for radiation-driven indirect-drive target designs is summarized. Indirect-drive designs are compared with new targets that are imploded by direct application of magnetic pressure produced by the pulsed-power current pulse. We describe target design elements such as larger absorbed energy, magnetized and pre-heated fuel, and cryogenic fuel layers that may relax fusion requirements. These elements are embodied in the magnetized liner inertial fusion (MagLIF) concept [Slutz “Pulsed-power-driven cylindrical liner implosions of laser pre-heated fuel magnetized with an axial field,” Phys. Plasmas, 17, 056303 (2010), and Stephen A. Slutz and Roger A. Vesey, “High-Gain Magnetized Inertial Fusion,” Phys. Rev. Lett., 108, 025003 (2012)]. MagLIF is in the class of magneto-inertial fusion targets. In MagLIF, the large drive currents produce an azimuthal magnetic field that compresses cylindrical liners containing pre-heated and axially pre-magnetized fusion fuel. Scientific breakeven may be achievable on the Z facility with this concept. Simulations of MagLIF with deuterium-tritium fuel indicate that the fusion energy yield can exceed the energy invested in heating the fuel at a peak drive current of about 27 MA. Scientific breakeven does not require alpha particle self-heating and is therefore not equivalent to ignition. Capabilities to perform these experiments will be developed on Z starting in 2013. These simulations and predictions must be validated against a series of experiments over the next five years. Near-term experiments are planned at drive currents of 16 MA with D2 fuel. MagLIF increases the efficiency of coupling energy (=target absorbed energy/driver stored energy) to targets by 10–150X relative to indirect-drive targets. MagLIF also increases the absolute energy absorbed by the target by 10-50X relative to indirect-drive targets. These increases could lead to higher fusion gains and yields. Single-shot high yields are of great utility to national security missions. Higher efficiency and higher gains may also translate into more compelling (lower cost and complexity) fusion reactor designs. We will discuss the broad goals of the emerging research on the MagLIF concept and identify some of the challenges. We will also summarize advances in pulsed-power technology and pulsed-power driver architectures that double the efficiency of the driver. [ABSTRACT FROM PUBLISHER]

The National Ignition Facility (NIF), the world's largest and most powerful laser system for inertial confinement fusion (ICF) and experiments studying high-energy-density (HED) science, is now operational at Lawrence Livermore National Laboratory (LLNL). NIF construction was certified by the Department of Energy as complete on March 27, 2009. NIF, a 192-beam Nd:glass laser facility, will ultimately produce 1.8 MJ 500 TW of 351-nm third-harmonic ultraviolet light. On March 10, 2009, a total of 192-beam energy of 1.1 MJ was demonstrated; this is approximately 30 times more energy than ever produced in an ICF laser system. The principal goal of NIF is to achieve ignition of a deuterium--tritium (DT) fuel capsule and provide access to HED physics regimes needed for experiments related to national security, fusion energy, and broader frontier scientific exploration. NIF experiments in support of indirect-drive ignition began in August 2009. These first experiments represent the next phase of the National Ignition Campaign (NIC). The NIC is a national effort to achieve fusion ignition and is coordinated through a detailed execution plan that includes science, technology, and equipment. The equipment required for ignition experiments includes diagnostics, a cryogenic target manipulator, and user optics. Participants in this effort include LLNL, General Atomics, Los Alamos National Laboratory, Sandia National Laboratory, and the University of Rochester Laboratory for Energetics. The primary goal for NIC is to have all of the equipment operational, integrated into the facility, and ready to begin a credible ignition campaign in 2010. With NIF now operational, the long-sought goal of achieving self-sustained nuclear fusion and energy gain in the laboratory is much closer to realization. Successful demonstration of ignition and net energy gain on NIF will be a major step toward demonstrating the feasibility of inertial fusion energy (IFE) and will likely focus the world's attention on the possibility of an ICF energy option. NIF experiments to demonstrate ignition and gain will use central-hot-spot (CHS) ignition, where a spherical fuel capsule is simultaneously compressed and ignited. The scientific basis for CHS has been intensively developed. Achieving ignition with CHS will open the door for other advanced concepts, such as the use of high-yield pulses of visible wavelength rather than ultraviolet and fast-ignition concepts. Moreover, NIF will have important scientific applications in such diverse fields as astrophysics, nuclear physics, and materials science. The NIC will develop the full set of capabilities required to operate NIF as a major national and international user facility. A solicitation for NIF frontier science experiments is planned for summer 2009. This paper summarizes the design, performance, and status of NIF and plans for the NIF ignition experimental program. A brief summary of the overall NIF experimental program is also presented. [ABSTRACT FROM AUTHOR]

Abstract: High-density atomic hydrogen, which is believed to be a quantum liquid, can be formed by heterogeneous catalysis at the surface of hydrogen-transfer metal oxide catalysts. Extensive studies have been made of the hydrogen phase named H(1), with interatomic distance of 150pm found by Coulomb explosion measurements. This bond distance corresponds to a material density of 0.5–0.7kgdm−3. The use of this material as fusion target for inertial confinement fusion (ICF) is proposed in J Fusion Energy 2008;27:296–300. A much denser hydrogen (deuterium) material D(−1) also exists with an interatomic distance of 2.3pm. This material is probably the inverse of metallic D(1), where nuclei and electrons exchange their roles. The ICF process would be greatly simplified if the intended initial multi-laser compression stage was not necessary. The close-packed density of D(−1) is calculated from the bond distance as >130kgcm−3. This is much higher than that required for “fast ignition” laser-driven fusion (>0.3kgcm−3). It may mean that a method already exists to prepare dense hydrogen fuel for small-scale laser-driven fusion. The high energy particles observed experimentally (up to 150keV/atomic mass unit in the peak or 109 K) indicate that high energy processes exist at relatively low laser intensities. [Copyright &y& Elsevier]

The National Ignition Facility (NIF) is a 192-beam Nd:glass laser facility being constructed at the Lawrence Livermore National Laboratory to conduct research in inertial confinement fusion (ICF) and high energy density science. When completed, NIF will produce 1.8 MJ, 500 TW of ultraviolet light, making it the world's largest and highest energy laser system. The NW is poised to become the world's preeminent facility for conducting ICF and fusion energy research and for studying matter at extreme densities and temperatures. [ABSTRACT FROM AUTHOR]

A self-consistent imploding Z-pinch-load model is coupled to a particle-in-cell simulation to study power flow in a recyclable transmission line (RTL) for a Z-pinch-driven inertial fusion energy (IFE) system. The system is driven by a voltage wave appropriate for driving the IFE target implosion when there is no particle emission from the walls of the RTL. Models for both electron and ion emission from the RTL walls are included in the simulations to allow the study of their effects on power coupled to the load. Insight is obtained for designing an efficient IFE system which satisfies system constraints on RTL inductance and driver voltage. [ABSTRACT FROM AUTHOR]

Nano-SiO2 doped polystyrene (SiO2 -d-PS) for inertial confinement fusion (ICF) targets materials were prepared by pretreating the surface of nano-SiO2 using silane coupling agents (A-171 and A-174) and by means of melt-blending technology. Some of the properties of the nano-SiO2 and SiO2-d-PS materials were characterized using dispersibility experiments, X-ray photoelectron spectroscopy (XPS), tensile tests, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The results showed that the dispersibility of nano-SiO2 powder in tetrahydrofuran was significantly enhanced through pretreatment. The surface state of pretreated nano-SiO2 was changed and the content of the —C=O and —C—O groups was increased as determined by XPS. The SiO2-d-PS materials had higher thermal stability compared to virgin PS through TGA. Young's modulus of SiO2-d-PS materials was increased compared with virgin PS. The pretreatment process is an effective way to break the aggregation of nano-TiO2 according to TEM results. [ABSTRACT FROM AUTHOR]

Nano machining based on SPM is a novel, nontraditional advanced manufacturing technique. There are three main machining methods based on SPM, i.e. single atom manipulation, surface modification using physical or chemical actions and mechanical scratching. The current development of this technique is summarized. Based on the analysis of mechanical scratching mechanism, a 5 μm micro inflation hole is fabricated on the surface of inertial confinement fusion (ICF) target. The processing technique is optimized. The machining properties of brittle material, single crystal Ge, are investigated. A micro machining system combining SPM and a high accuracy stage is developed. Some 2D and 3D microstructures are fabricated using the system. This method has broad applications in the field of nano machining. [ABSTRACT FROM AUTHOR]

• A deuterated-tritiated polymer with a tritium ratio of 26.5 % was prepared through solid state catalytic tritiation. • The deuterated-tritiated polymer was characteraized by 2H-NMR and 3H-NMR spectra. • The solid state tritiation free of solvents can avoid the generation of radioactive liquids. Deuterated-tritiated polymers are a type of promising target materials for inertial confinement fusion (ICF). The preparation of a deuterated-tritiated polymer was performed from a deuterated polybutadiene under tritium through solid state catalytic tritiation with 5 wt% Pd/BaSO 4 as a catalyst. After reaction, the gas mixture in the vessel and the raw T 2 /Ar mixture in the flask were analyzed with a gas chromatography, a quadrupole mass spectrometer and a high resolution gas analysis mass spectrometer. The 2H-NMR and 3H-NMR spectra were employed to characterize the deuterated-tritiated polymer. Both isotopic exchange and addition during the reaction were confirmed and the tritium ratio of the deuterated-tritiated polymer was determined to be 26.5 %.The solid state tritiation free of solvents can avoid the generation of high radioactive liquids. [ABSTRACT FROM AUTHOR]