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Journal articlePérez-Callejo G, Wark JS, Rose SJ, 2019,
Radiation transfer in cylindrical, toroidal and hemi-ellipsoidal plasmas
, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol: 235, Pages: 24-30, ISSN: 0022-4073We present solutions of the radiative transfer equation for cylinders, hollow hemi-ellipsoidal shells and tori for a uniform plasma of fixed geometry. The radiative transfer equation is explicitly solved for two directions of emission, parallel and perpendicular to the axis of symmetry. The ratio between the fluxes in these two directions is also calculated and its use in measuring the frequency resolved opacity of the plasma is discussed. We find that the optimal geometry to use this ratio as an opacity measurement is a planar geometry.
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Journal articleWeller ME, Beiersdorfer P, Lockard TE, et al., 2019,
Observation of He-like satellite lines of the H-like potassium K XIX emission
, Astrophysical Journal, Vol: 881, ISSN: 0004-637XWe present measurements of the H-like potassium (K XIX) X-ray spectrum and its Helike (K XVIII) satellite lines, which are situated in the wavelength region between 3.34 and 3.39Å, which has been of interest for the detection of dark matter. The measurements were takenwith a high-resolution X-ray spectrometer from targets irradiated by a long-pulse (2 ns) beamfrom the Orion laser facility. We obtain experimental wavelength values of dielectronicrecombination satellite lines and show that the ratio of the Lyα lines and their dielectronicsatellite lines can be used to estimate the electron temperature, which in our case was about1.5±0.3 keV.
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Working paperHare JD, MacDonald J, Bland SN, et al., 2019,
Two-colour interferometry and Thomson scattering measurements of a plasma gun
, Publisher: IOP PUBLISHING LTD- Author Web Link
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- Citations: 14
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Journal articleHare JD, MacDonald J, Bland S, et al., 2019,
Two-colour interferometry and Thomson scattering measurements of a plasma gun
, Plasma Physics and Controlled Fusion, Vol: 61, ISSN: 0741-3335We present experimental measurements of a pulsed plasma gun, using two-colour imaging laser interferometry and spatially resolved Thomson scattering. Interferometry measurements give an electron density ne ≈ 2.7 × 1017 cm−3 at the centre of the plasma plume, at 5 mm from the plasma gun nozzle. The Thomson scattered light is collected from two probing angles allowed us to simultaneously measure the collective and non-collective spectrum of the electron feature from the same spatial locations. The inferred electron densities from the location of the electron plasma waves is in agreement with interferometry. The electron temperatures inferred from the two spectra are not consistent, with Te ≈ 10 eV for non-collective scattering and Te ≈ 30 eV for collective scattering. We discuss various broadening mechanisms such as finite aperture effects, density gradients within the collective volume and collisional broadening to account for some of this discrepancy. We also note the significant red/blue asymmetry of the electron plasma waves in the collective scattering spectra, which could relate to kinetic effects distorting the distribution function of the electrons.
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Journal articleOta TA, Amott R, Carlson CA, et al., 2019,
Comparison of Simultaneous Shock Temperature Measurements from Three Different Pyrometry Systems
, Journal of Dynamic Behavior of Materials, ISSN: 2199-7446 -
Journal articleHoarty DJ, Morton J, Jeffery M, et al., 2019,
A proposal to measure iron opacity at conditions close to the solar convective zone-radiative zone boundary
, High Energy Density Physics, Vol: 32, Pages: 70-76, ISSN: 1574-1818A major problem in stellar modelling is the discrepancy between solar models and helioseismology data in the position of the convective zone-radiative zone boundary in the sun. This could be explained by a large uncertainty in the calculated opacity data and recent experimental data on iron using the Sandia National Laboratory Z facility have shown large differences, up to a factor of 4, between measurement and prediction at plasma conditions close to the convective zone-radiative zone boundary. This paper describes a proposal for a radiative burn-through experiment to be fielded on NIF to observe if a radiation wave transit through a Fe2O3 sample is consistent with the factor of 2-4 change in the iron opacity seen in the Z experiments. A target design and the diagnostic method are described. A detailed radiation-hydrodynamic model has been used to generate synthetic results and explore the sensitivities and experimental accuracy needed for the proposed measurement.
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Journal articleCohen A, Levi-Hevroni D, Fridman P, et al., 2019,
In-situ radiography of a split-Hopkinson bar dynamically loaded materials
, JOURNAL OF INSTRUMENTATION, Vol: 14, ISSN: 1748-0221 -
Journal articlePerez-Callejo G, Jarrott LC, Liedahl DA, et al., 2019,
Laboratory measurements of geometrical effects in the x-ray emission of optically thick lines for ICF diagnostics
, Physics of Plasmas, Vol: 26, ISSN: 1070-664XUnderstanding the effects of radiative transfer in High Energy Density Physics experiments is critical for the characterization of the thermodynamic properties of highly ionized matter, in particular in Inertial Confinement Fusion (ICF). We report on non-Local Thermodynamic Equilibrium experiments on cylindrical targets carried out at the Omega Laser Facility at the Laboratory for Laser Energetics, Rochester NY, which aim to characterize these effects. In these experiments, a 50/50 mixture of iron and vanadium, with a thickness of 2000 Å and a diameter of 250 μm, is contained within a beryllium tamper, with a thickness of 10 μm and a diameter of 1000 μm. Each side of the beryllium tamper is then irradiated using 18 of the 60 Omega beams with an intensity of roughly 3 × 1014 W cm−2 per side, over a duration of 3 ns. Spectroscopic measurements show that a plasma temperature on the order of 2 keV was produced. Imaging data show that the plasma remains cylindrical, with geometrical aspect ratios (quotient between the height and the radius of the cylinder) from 0.4 to 2.0. The temperatures in this experiment were kept sufficiently low (∼1–2 keV) so that the optically thin Li-like satellite emission could be used for temperature diagnosis. This allowed for the characterization of optical-depth-dependent geometric effects in the vanadium line emission. Simulations present good agreement with the data, which allows this study to benchmark these effects in order to take them into account to deduce temperature and density in future ICF experiments, such as those performed at the National Ignition Facility.
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Conference paperNguyen TT, Masouros S, 2019,
Penetration of Blast Fragments to the Thorax
, International Research Council On Biomechanics Of Injury -
Conference paperNguyen TT, Masouros S, 2019,
Penetration of Blast Fragments to the Thorax
, International Research Council On Biomechanics Of Injury 2019 -
Journal articleHatfield P, Rose S, Scott R, 2019,
The blind implosion-maker: Automated inertial confinement fusion experiment design
, Physics of Plasmas, Vol: 26, ISSN: 1070-664XThe design of inertial confinement fusion (ICF) experiments, alongside improving the development of energy density physics theory and experimental methods, is one of the key challenges in the quest for nuclear fusion as a viable energy source [O. A. Hurricane, J. Phys.: Conf. Ser. 717, 012005 (2016)]. Recent challenges in achieving a high-yield implosion at the National Ignition Facility (NIF) have led to new interest in considering a much wider design parameter space than normally studied [J. L. Peterson et al., Phys. Plasmas 24, 032702 (2017)]. Here, we report an algorithmic approach that can produce reasonable ICF designs with minimal assumptions. In particular, we use the genetic algorithm metaheuristic, in which “populations” of implosions are simulated, the design of the capsule is described by a “genome,” natural selection removes poor designs, high quality designs are “mated” with each other based on their yield, and designs undergo “mutations” to introduce new ideas. We show that it takes ∼5 × 104 simulations for the algorithm to find an original NIF design. We also link this method to other parts of the design process and look toward a completely automated ICF experiment design process—changing ICF from an experiment design problem to an algorithm design problem.
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Conference paperNguyen TT, Meek G, Masouros S, 2019,
Blast Fragment Protection for The Extremities
, Light Weight Armour for Defense & Security 2019 -
Journal articleDerrick JG, Rutherford ME, Chapman DJ, et al., 2019,
Investigating shock processes in bimodal powder compaction through modelling and experiment at the mesoscale
, International Journal of Solids and Structures, Vol: 163, Pages: 211-219, ISSN: 0020-7683Impact-driven compaction is a proposed mechanism for the lithification of primordial bimodal granular mixtures from which many meteorites derive. We present a numerical-experimental mesoscale study that investigates the fundamental processes in shock compaction of this heterogeneous matter, using analog materials. Experiments were performed at the European Synchrotron Radiation Facility generating real-time, in-situ, X-ray radiographs of the shock's passage in representative granular systems. Mesoscale simulations were performed using a shock physics code and set-ups that were geometrically identical to the experiments. We considered two scenarios: pure matrix, and matrix with a single chondrule. Good agreement was found between experiments and models in terms of shock position and post-shock compaction in the pure powder setup. When considering a single grain embedded in matrix we observed a spatial porosity anisotropy in its vicinity; the compaction was greater in the region immediately shockward of the grain, and less in its lee. We introduced the porosity vector, C, which points in the direction of lowest compaction across a chondrule. This direction-dependent observation may present a new way to decode the magnitude, and direction, of a single shock wave experienced by a meteorite in the past.
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Journal articleYanuka D, Rososhek A, Theocharous S, et al., 2019,
X-ray radiography of the overheating instability in underwater electrical explosions of wires
, Physics of Plasmas, Vol: 26, ISSN: 1070-664XWe present the measurements of the development of striation like instabilities during the electrical driven explosions of wires in a waterbath. In vacuum based wire explosion experiments, such instabilities have long been known. However, in spite of intense research into theexplosion of wires in liquids, the development of these instabilities has either not been observed or has been assumed to play a minor role inthe parameters of the exploding wire due to the tamping of the wire’s explosion. Using synchrotron based multiframe radiography, we haveseen the development of platelike density structures along an exploding copper wire. Our measurements were compared to a 2Dmagnetohydrodynamics simulation, showing similar striation formation. These observed instabilities could affect the measurements of theconductivity of the wire material in the gas-plasma state—an important parameter in the warm dense matter community. The striationscould also act as a seed for other instabilities later in time if the wire is in a dense flow of material or experiences a shock from an adjacentwire—as it would do in experiments with arrays of wires.
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Journal articleGould O, Mangles S, Rajantie A, et al., 2019,
Observing thermal Schwinger pair production
, Physical Review A, Vol: 99, ISSN: 1050-2947We study the possibility of observing Schwinger pair production enhanced by a thermal bath of photons. We consider the full range of temperatures and electric field intensities from pure Schwinger production to pure thermal production, and identify the most promising and interesting regimes. In particular, we identify temperatures of ∼ 20 keV/kB and field intensities of ∼ 10²³ W cm¯² where pair production would be observable. In this case, the thermal enhancement over the Schwinger rate is exponentially large and due to effects which are not visible at any finite order in the loop expansion. Pair production in this regime can thus be described as more nonperturbative than the usual Schwinger process, which appears at one loop. Unfortunately, such high temperatures appear to be out of reach of foreseeable technologies, though nonthermal photon distributions with comparable energy densities are possible. We suggest the possibility that similar nonperturbative enhancements may extend out of equilibrium and propose an experimental scheme to test this.
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Journal articleSeidel JV, Castaneda-Uribe OA, Arevalo S, et al., 2019,
Relative permittivity estimation of wheat starch: A critical property for Check for understanding electrostatic hazards
, JOURNAL OF HAZARDOUS MATERIALS, Vol: 368, Pages: 228-233, ISSN: 0304-3894- Author Web Link
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- Citations: 8
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Journal articleYanuka D, Theocharous S, Efimov S, et al., 2019,
Synchrotron based X-ray radiography of convergent shock waves driven by underwater electrical explosion of a cylindrical wire array
, Journal of Applied Physics, Vol: 125, ISSN: 0021-8979We present X-ray radiography images showing the propagation of shock waves generated by electrical explosion of a cylindrical arrangement of wires in water driven by pulsed power. In previous experiments [S. N. Bland et al., Phys. Plasmas 24, 082702 (2017)], the merger of shock waves from adjacent wires has produced a highly symmetrical, cylindrical shock wave converging on the axis, where it is expected to produce a high density, strongly coupled plasma ideal for warm dense matter research. However, diagnostic limitations have meant that much of the dynamics of the system has been inferred from the position of the front of the cylindrical shock and timing/spectra of light emitted from the axis. Here, we present a synchrotron-based radiography of such experiments—providing direct quantitative measurements on the formation of the convergent shock wave, the increased density of water on the axis caused by its arrival, and its “bounce” after arrival on the axis. The obtained images are compared with two-dimensional hydrodynamic simulations, which reproduce the observed dynamics with a satisfactory agreement in density values.
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Journal articlePissarenko A, Yang W, Quan H, et al., 2019,
Tensile behavior and structural characterization of pig dermis
, ACTA BIOMATERIALIA, Vol: 86, Pages: 77-95, ISSN: 1742-7061- Author Web Link
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- Citations: 46
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Journal articlePerez-Callejo G, Liedahl DA, Schneider MB, et al., 2019,
The use of geometric effects in diagnosing ion density in ICF-related dot spectroscopy experiments
, High Energy Density Physics, Vol: 30, Pages: 45-51, ISSN: 1574-1818We describe a method to calculate the ion density of High Energy Density (HED) cylindrical plasmas used in dot spectroscopy experiments. This method requires only spectroscopic measurements of the Heα region obtained from two views (Face-on and Side-on). We make use of the fact that the geometry of the plasma affects the observed flux of optically thick lines. The ion density can be derived from the aspect ratio (height-to-radius) of the cylinder and the optical depth of the Heα-y line (1s2p 3P1 → 1s2 1S0). The aspect ratio and the optical depth of the y line are obtained from the spectra using ratios measured from the two directions of emission of the optically thick Heα-w line (1s2p 1P1 → 1s2 1S0) and the ratio of the optically thick to thin lines. The method can be applied to mid-Z elements at ion densities of 1019– and temperatures of a the order of keV, which is a relevant regime for Inertial Confinement Fusion (ICF) experiments.
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Journal articleNguyen T-T, Pearce AP, Carpanen D, et al., 2019,
Experimental platforms to study blast injury
, Journal of the Royal Army Medical Corps, Vol: 165, Pages: 33-37, ISSN: 2052-0468Injuries sustained due to attacks from explosive weapons are multiple in number, complex in nature, and not well characterised. Blast may cause damage to the human body by the direct effect of overpressure, penetration by highly energised fragments, and blunt trauma by violent displacements of the body. The ability to reproduce the injuries of such insults in a well-controlled fashion is essential in order to understand fully the unique mechanism by which they occur, and design better treatment and protection strategies to alleviate the resulting poor long-term outcomes. This paper reports a range of experimental platforms that have been developed for different blast injury models, their working mechanism, and main applications. These platforms include the shock tube, split-Hopkinson bars, the gas gun, drop towers and bespoke underbody blast simulators.
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Journal articleTheocharous SP, Bland SN, Yanuka D, et al., 2019,
Use of synchrotron-based radiography to diagnose pulsed power driven wire explosion experiments
, Review of Scientific Instruments, Vol: 90, ISSN: 0034-6748We describe the first use of synchrotron radiation to probe pulsed power driven high energy density physics experiments. Multi-frame x-ray radiography with interframe spacing of 704 ns and temporal resolution of <100 ps was used to diagnose the electrical explosion of different wire configurations in water including single copper and tungsten wires, parallel copper wire pairs, and copper x-pinches. Such experiments are of great interest to a variety of areas including equation of state studies and high pressure materials research, but the optical diagnostics that are usually employed in these experiments are unable to probe the areas behind the shock wave generated in the water, as well as the internal structure of the exploding material. The x-ray radiography presented here, performed at beamline ID19 at European Synchrotron Radiation Facility (ESRF), was able to image both sides of the shock to a resolution of up to 8 μm, and phase contrast imaging allowed fine details of the wire structure during the current driven explosion and the shock waves to be clearly observed. These results demonstrate the feasibility of pulsed power operated in conjunction with synchrotron facilities, as well as an effective technique in the study of shock waves and wire explosion dynamics.
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Journal articleRutherford ME, Derrick JG, Chapman DJ, et al., 2019,
Insights into local shockwave behavior and thermodynamics in granular materials from tomography-initialized mesoscale simulations
, Journal of Applied Physics, Vol: 125, ISSN: 0021-8979Interpreting and tailoring the dynamic mechanical response of granular systems relies upon understanding how the initial arrangement of grains influences the compaction kinetics and thermodynamics. In this article, the influence of initial granular arrangement on the dynamic compaction response of a bimodal powder system (soda-lime distributed throughout a porous, fused silica matrix) was investigated through continuum-level and mesoscale simulations incorporating real, as-tested microstructures measured with X-ray tomography. By accounting for heterogeneities in the real powder composition, continuum-level simulations were brought into significantly better agreement with previously reported experimental data. Mesoscale simulations reproduced much of the previously unexplained experimental data scatter, gave further evidence of low-impedance mixture components dominating shock velocity dispersion, and crucially predicted the unexpectedly high velocities observed experimentally during the early stages of compaction. Moreover, only when the real microstructure was accounted for did simulations predict that small fractions of the fused silica matrix material would be driven into the β-quartz region of phase space. These results suggest that using real microstructures in mesoscale simulations is a critical step in understanding the full range of shock states achieved during dynamic granular compaction and interpreting solid phase distributions found in real planetary bodies.
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Journal articleShelkovenko TA, Pikuz SA, Tilikin IN, et al., 2018,
Evolution of X-pinch loads for pulsed power generators with current from 50 to 5000 kA
, Matter and Radiation at Extremes, Vol: 3, Pages: 267-277, ISSN: 2468-080XA review of X-pinches of various configurations and of different materials as an X-ray source for various applications is presented. The advantages and disadvantages of different designs of X-pinches as a load for generators with a wide range of output parameters and as a source of X-ray radiation for X-ray point-projection imaging were analyzed.
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Journal articleMcBride RD, Stygar WA, Cuneo ME, et al., 2018,
A primer on pulsed power and linear transformer drivers for high energy density physics applications
, IEEE Transactions on Plasma Science, Vol: 46, Pages: 3928-3967, ISSN: 0093-3813The 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.
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Journal articleYanuka D, Rososhek A, Theocharous S, et al., 2018,
Multi frame synchrotron radiography of pulsed power driven underwater single wire explosions
, Journal of Applied Physics, Vol: 124, ISSN: 0021-8979We present the first use of synchrotron-based phase contrast radiography to study pulsed-power driven high energy density physics experiments. Underwater electrical wire explosions have become of interest to the wider physics community due to their ability to study material properties at extreme conditions and efficiently couple stored electrical energy into intense shock waves in water. The latter can be shaped to provide convergent implosions, resulting in very high pressures (1-10 Mbar) produced on relatively small pulsed power facilities (100s of kA-MA). Multiple experiments have explored single-wire explosions in water, hoping to understand the underlying physics and better optimize this energy transfer process; however, diagnostics can be limited. Optical imaging diagnostics are usually obscured by the shock wave itself; and until now, diode-based X-ray radiography has been of relatively low resolution and rather a broad x-ray energy spectrum. Utilising phase contrast imaging capabilities of the ID19 beamline at the European Synchrotron Radiation Facility, we were able to image both the exploding wire and the shock wave. Probing radiation of 20-50 keV radiographed 200 μm tungsten and copper wires, in ∼2-cm diameter water cylinders with resolutions of 8 μm and 32 μm. The wires were exploded by a ∼30-kA, 500-ns compact pulser, and 128 radiographs, each with a 100-ps X-ray pulse exposure, spaced at 704 ns apart were taken in each experiment. Abel inversion was used to obtain the density profile of the wires, and the results are compared to two dimensional hydrodynamic and one dimensional magnetohydrodynamic simulations.
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Journal articleMagnus D, Khan MA, Proud WG, 2018,
Epidemiology of civilian blast injuries inflicted by terrorist bombings from 1970-2016
, DEFENCE TECHNOLOGY, Vol: 14, Pages: 469-476, ISSN: 2096-3459- Author Web Link
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- Citations: 22
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Conference paperNguyen TT, Carpanen D, Tear G, et al., 2018,
Fragment Penetrating Injury to the tibia
, Personal Armour Systems Symposia 2018 -
Journal articleZhang X, Wang G, Luo B, et al., 2018,
Refractive index and polarizability of polystyrene under shock compression
, JOURNAL OF MATERIALS SCIENCE, Vol: 53, Pages: 12628-12640, ISSN: 0022-2461 -
Conference paperButler BJ, Williams A, Tucker AW, et al., 2018,
Comparative quasi-static mechanical characterization of fresh and stored porcine trachea specimens
, 12th International Conference of the European-Association-for-the-Promotion-of-Research-into-the-Dynamic-Behaviour-of-Materials-and-its-Applications (DYMAT-Association), Publisher: SPRINGER HEIDELBERG, Pages: 55-60, ISSN: 1951-6355- Author Web Link
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- Citations: 2
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Journal articleShelkovenko TA, Pikuz SA, Tilikin IN, et al., 2018,
X-pinch X-ray emission on a portable low-current, fast rise-time generator
, Journal of Applied Physics, Vol: 124, ISSN: 0021-8979We report on experiments exploring X-ray emission from an X-pinch driven by a small Marx-waterline generator supplying 50 kA with a risetime of 50 ns and a peak voltage of ∼250 kV. Both standard crossed wire loads and hybrid loads utilizing conical metal electrodes with a single short wire in between them were studied, and in both cases reliable modes of operation were obtained for X-ray radiography. Soft (few keV) and Hard (>5 keV) X-ray emission characteristics were observed. With standard X-pinches, soft radiation emanated from a small hot spot about 3 μm in size, along with hard radiation from a ∼200 μm region close to this hot spot. With hybrid X-pinches, the hot spot was <7 μm in size. There was a clear correlation between the soft and hard X-ray emission—pinches that produced intense soft X-ray emission from a small hot spot also produced the most intense, localized hard X-ray emission.
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