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(Left) EPEC air-blast sensor peak overpressure values from Table II scaled to the full-scale dimensions for a 1 KT reference free air burst, and the expected peak air blast dynamic overpressure values from Kinney and Graham 7 for 1 KT nuclear (cyan, solid) and chemical high explosive (HE) (red, dashed). The arrow linking the filled to open symbol represents the correction factor for a "contact burst." (Right) Reproduction of Figure 3 from Grun 6 with the older NRL data and the EPEC data on a logarithmic scale.
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The energy partitioning energy coupling experiments at the National Ignition Facility (NIF) have been designed to measure simultaneously the coupling of energy from a laser-driven target into both ground shock and air blast overpressure to nearby media. The source target for the experiment is positioned at a known height above the ground-surface si...
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Citations
... where A is a numerical constant of for a given γ and S is the scaled range parameter. In Fig. 4.21, the data from NRL experiment and NIF laser with 10 kJ irradiations are plotted with orange and green solid circles in (P, S) diagram [26]. For comparison to another type of blast wave, those produced by high-explosive and nuclear explosion are also shown with red dashed and solid blue lines. ...
... 26 Self-similar solutions of density, pressure, and velocity of the ejector-dominant blast wave of a typical Type Ia supernova remnant. The radius r = R c is the contact surface. ...
Strong shock waves are used to compress and heat any matters in the laboratory. The ablation pressure by intense laser is used to compress even solid matters. In plane geometry, it is easier to design multi-shocks to compress the matters, while it is more beneficial to use the spherical compression. No simple solutions are available to know the trajectories of shocks in one-dimensional spherical symmetry. Here we see several analytical solutions with the self-similar method. The method is to find new governing solution of ordinary differential equation from partial differential fluid equations. The self-similar method is known before the birth of computer.
The blast wave is the most famous one. Here, we review the basic method to derive several self-similar solutions allowing the spherical implosion, useful to laser driven implosion. The isobaric solution provides uniform pressure and spark-main fuel structure, and isochoric solution gives us uniform density profile at the maximum compression. It is shown that even including thermal conduction, it is possible to find a solution of ablation structure. This is an extended solution more appropriate compared to the steady state solutions shown in the previous chapter.
The blast waves are widely used from laser experiments to supernova remnants (SNRs). SNRs are blast waves driven by the matters exploding by supernova explosion. A self-similar solution with forward and reverse shock waves is found to explain many observation data of SNRs. A numerical simulation shows that the solution of ejecta-driven shock changes from Chevalier’s self-similar solution to the other Sedov-Taylor one. The self-similarity is one of the key physics controlling nonlinear hydrodynamic equations.
... The combination of the continuing demonstrations of the importance of CBET produced plasma optics cells in controlling the power deposition profiles in ICF experiments [43][44][45][46][47][48] and the emergence of experimentally validated models of CBET that prove quite accurate under certain conditions 49,53,57,[74][75][76]78 have motivated the first design and test of a stand-alone plasma optic based on CBET 59,60,78 for use in a specific application requiring high fluence in a beam. 58 The device, a beam-combiner, has combined much of the energy of up to 20, f/20 pump beams into a single output beam of 1 ns duration as described in recent publications studying up to eight pump beams 59,60 and a forthcoming publications that describes the results with 20 pump in more detail. 61 The maximum pumping studied so far has resulted in a 10Â amplification of a low power seed which provides a > 3Â increase in single beam power and energy available in a 1 ns pulse at the NIF facility. ...
Optical components for laser beams with high peak and averaged powers are being developed worldwide using stimulated plasma scattering that occurs when plasmas interact with intense, coherent light. After decades of pursuit of pulse compressors, mirrors, and other plasma based components that can be created by stimulated scattering from electron density perturbations forming on ultra-short time scales (e.g., via Stimulated Raman Scattering), more recent work has produced optical components on longer time scales allowing ion motion as well [via Stimulated Brillouin Scattering (SBS)]. In the most recent work, ion wave plasma optics have had success in producing pulses of focusable coherent light with high energy and fluence by operating on ns time scales and now promise to enable numerous applications. Experiments have further shown that in some parameter regimes, even simple plasma response models can describe the output of such optics with sufficient accuracy that they can be used as engineering tools to design plasma optics for future applications, as is already being done to control power deposition in fusion targets. In addition, the development of more sophisticated models promises to enable still higher performance from SBS driven plasma optical components under a wider range of conditions. The present status and most promising directions for future development of ion wave plasma optic techniques are discussed here.
... Numerical experiments using material models trained on observations of chemical explosions could be used to predict the effects of large nuclear explosions (Chipman, 2011). And high energy density laser experiments could fill in experimental gaps between chemical and nuclear explosions (Fournier et al., 2014). ...
Forensic capabilities to understand chemical and nuclear explosions are greatly aided by an accurate estimate of explosive yield with uncertainty. The relationship between explosive size and geophysical observations of seismic, acoustic, and optical waves can be exploited to provide an estimate of yield. Any near‐surface yield estimate is complicated by the surface interaction, so an estimate for the explosion height‐of‐burst is necessarily included in the relationship. The relationship dictates a trade‐off between estimates of yield and height‐of‐burst. Fortunately, the surface interaction for each type of observation is different, which breaks the trade‐off, and the inclusion of height‐of‐burst with multiple data types improves yield estimation. We define simple parametric forward models to relate seismoäcoustoöptic observations from a data set of known explosive yields and height‐of‐bursts. The parameters of the models and a prediction for the yield and height‐of‐burst of a new event can then be estimated given new observations via Bayesian inference. We report posterior distribution estimates of the parametric models using a Markov chain Monte Carlo sampling technique. These models are then used to predict the yield and height‐of‐burst of SUGAR, a historical near‐surface nuclear explosion, using its reported historical observations. The reported yield of 1.2 ktonne Trinitrotoluene (TNT)‐equivalent (Department of Energy, 2015) is within the estimated posterior. Yield uncertainty can be estimated from the spread of the posterior, which is between 0.9 and 2.1 ktonne TNT‐equivalent. The posterior for height‐of‐burst has a wider range between 10 m below and 8 m above ground that includes the true height‐of‐burst of 1 m.
... We further describe the initial tests of this combiner using only 8 pumping beams to produce resonant amplification of a single beam. 31 The output of this plasma beam combiner is optimized for application in future experiments on nuclear weapons effects at the NIF, 32 and should also find other high energy density physics (HEDP) applications, such as bright x-ray backlighters, and advanced hohlraums 33 or potentially as a driver for a second stage of plasma amplification or compression of a beam with a much shorter pulse. 34 The technique represents one of the first uses of the self-generated plasma optics developed for fusion energy experiments 4 to create optical devices made from plasmas that can withstand fluences and intensities orders of magnitude higher than conventional solid state optics. ...
... The resonant pump quads cross the seed at polar angles ranging from 14.5 to 20.9 giving a beam crossing geometry in the target that is shown schematically in Fig. 2 where the dimensions are given by the NIF beam focal spots size in their standard configuration (i.e.; using standard phase plates and spot sizes). The non-resonant pump beams used are also shown in Figs. 1 and 2, and where chosen from beams in the same (bottom) hemisphere of the NIF chamber so that in eventual applications of the beam combiner there would be a > 2p sr of solid angle which could be occupied by the target to which the amplified beam would be delivered (see for example Ref. 32). Next, the plasma material and density was chosen to fill the region that the pumps and seed intersect in, as also indicated in Fig. 2. Because efficient depletion of the pumps will require that CBET is maintained close to its resonant value over as much of the intersection volume as possible, and because of the difficulty in maintaining a high degree of uniformity in the plasma conditions affecting the resonance, a broad resonance is desirable. ...
Combining laser beams in a plasma is enabled by seeded stimulated Brillouin scattering which allows cross-beam energy transfer (CBET) to occur and re-distributes the energy between beams that cross with different incident angles and small differences in wavelength [Kirkwood et al. Phys. Plasmas 4, 1800 (1997)]. Indirect-drive implosions at the National Ignition Facility (NIF) [Haynam et al. Appl. Opt. 46, 3276–3303 (2007)] have controlled drive symmetry by using plasma amplifiers to transfer energy between beams [Kirkwood et al., Plasma Phys. Controlled Fusion 55, 103001 (2013); Lindl et al., Phys. Plasmas 21, 020501 (2014); and Hurricane et al. Nature 506, 343–348 (2014)]. In this work, we show that the existing models are well enough validated by experiments to allow a design of a plasma beam combiner that, once optimized, is expected to produce a pulse of light in a single beam with the energy greatly enhanced over existing sources. The scheme combines up to 61 NIF beams with 120 kJ of available energy into a single f/20 beam with a 1 ns pulse duration and a 351 nm wavelength by both resonant and off-resonance CBET. Initial experiments are also described that have already succeeded in producing a 4 kJ, 1 ns pulse in a single beam by combination of up to eight incident pump beams containing <1.1 kJ/beam, which are maintained near resonance for CBET in a plasma that is formed by 60 pre-heating beams [Kirkwood et al., Nat. Phys. 14, 80 (2018)].
... CBET produces the highest energy 1 ns pulse of ultraviolet light available at the NIF and is directly scalable to larger numbers of beams to produce a still higher single-beam fluence, radiance and energy. Such a beam combiner holds promise to advance a range of HEDP applications that require high energy and fluence in collimated beams to access the interior of complex targets 31 Figure 1 | Beam combiner target. a,b, The gas-filled balloon target (10 mm in major diameter) shown in a is used to create a uniform plasma to amplify a single seed beam (red) by combination of eight pumping beams (yellow), each with the incident power shown in b, via seeded SBS forward scatter. ...
Extreme optical fluences, much beyond the damage threshold of conventional optics, are of interest for a range of high-energy-density physics applications. Nonlinear interactions of multiple beams in plasmas have the potential to produce optics that operate at much higher intensity and fluence than is possible in solids. In inertial confinement fusion experiments indirectly driven with lasers, many beams overlap in the plasma inside a hohlraum, and cross-beam energy transfer by Brillouin scattering has been employed to redistribute energy between laser beams within the target. Here, we show that in a hot, under-dense plasma the energy of many input beams can be combined into a single well-collimated beam. The emerging beam has an energy of 4 kJ (over 1 ns) that is more than triple that of any incident beam, and a fluence that is more than double. Because the optic produced is plasma, and is diffractive, it is inherently capable of generating higher fluences in a single beam than solid-state refractive or reflective optics.
Nuclear security is one of the defining challenges of our time. Nuclear threats range from deliberate dispersal of radioactive material to contaminate the vital infrastructure to diversion and smuggling of special nuclear material for clandestine nuclear programs and nuclear terrorism, respectively. There is an associated need to develop and sustain nuclear forensics capabilities, which can be aided by good understanding of complex processes that occur in plasmas containing nuclear materials. The area of nuclear safety has seen a resurgence of public interest, and there is a concomitant need to safely store used nuclear fuel and to detect structural material failure in nuclear power systems, especially in innovative reactor designs envisioned for future adoption. Laser-produced plasmas are complicated extreme environments that can generate intense and rich, highly specific signatures of nuclear and radiological materials, which can then be explored for applications. They include interdiction and rapid detection of nuclear materials, including their isotopic composition, detection over long distances, laboratory simulation of weapons effects, monitoring the condition of structural materials in dry cask storage containers, and novel instrumentation for nuclear power systems. We present a compilation of recent representative examples of the application of laser spectroscopy, and laser-induced breakdown spectroscopy in particular, to nuclear safety and security problems. A case is made that spectroscopic techniques based on laser-produced plasmas offer complementary, and sometimes unique, capabilities that motivate continued exploration of their efficient production and broader understanding of the signatures they produce.
Consequences of an explosion inside an air-filled cavity under the earth's surface are partly duplicated in a laboratory experiment on spatial scales 1000 smaller. The experiment measures shock pressures coupled into a block of material by an explosion inside a gas-filled cavity therein. The explosion is generated by suddenly heating a thin foil that is located near the cavity center with a short laser pulse, which turns the foil into expanding plasma, most of whose energy drives a blast wave in the cavity gas. Variables in the experiment are the cavity radius and explosion energy. Measurements and GEODYN code simulations show that shock pressuresmeasured in the block exhibit a weak dependence on scaled cavity radius up to ∼25 m/kt1/3, above which they decrease rapidly. Possible mechanisms giving rise to this behavior are described. The applicability of this work to validating codes used to simulate full-scale cavityexplosions is discussed.
