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  • Conference paper
    Proud WG, O'Brien S, Wilson MA, 2020,

    Elicitation of knowledge from a defence expert

    , ISSN: 1742-6588

    The aim of this work is to understand the way that a defence expert defines the concept of importance in relation to the ideas contained in a scientific document. The expert's views on the importance of the concepts in this document were elicited in two phases. In the first phase, the expert was asked to summarise an eight-page document on the effects of electromagnetic fields on propellant combustion. Completion of this task generated a series of 'key points'. Phase two of the methodology was a sit-down interview with the expert. This interview comprised three parts: asking the expert to talk through why each of the key points were important, asking the expert to sort the key points into categories according to how important they are and then asking the expert to generate categories of why the points are important. The techniques used for expert elicitation proved highly successful in relation to this domain of knowledge. Not only were the procedures able to extract the underlying categories through which the expert structured their understanding of the field, but the results indicated reliability in the content of knowledge extracted through different methods. Subsequent papers in this project compare this work to parallel analysis conducted using Natural Language Processing tools.

  • Journal article
    Nguyen TT, Meek G, Breeze J, Masouros Set al., 2020,

    Gelatine backing affects the performance of single-layer ballistic-resistant materials against blast fragments

    , Frontiers in Bioengineering and Biotechnology, Vol: 8, Pages: 1-10, ISSN: 2296-4185

    Penetrating trauma by energized fragments is the most common injury from explosive devices, the main threat in the contemporary battlefield. Such devices produce projectiles dependent upon their design, including preformed fragments, casings, glass, or stones; these are subsequently energized to high velocities and cause serious injuries to the body. Current body armor focuses on the essential coverage, which is mainly the thoracic and abdominal area, and can be heavy and cumbersome. In addition, there may be coverage gaps that can benefit from the additional protection provided by one or more layers of lightweight ballistic fabrics. This study assessed the performance of single layers of commercially available ballistic protective fabrics such as Kevlar®, Twaron®, and Dyneema®, in both woven and knitted configurations. Experiments were carried out using a custom-built gas-gun system, with a 0.78-g cylindrical steel fragment simulating projectile (FSP) as the impactor, and ballistic gelatine as the backing material. FSP velocity at 50% risk of material perforation, gelatine penetration, and high-risk wounding to soft tissue, as well as the depth of penetration (DoP) against impact velocity and the normalized energy absorption were used as metrics to rank the performance of the materials tested. Additional tests were performed to investigate the effect of not including a soft-tissue simulant backing material on the performance of the fabrics. The results show that a thin layer of ballistic material may offer meaningful protection against the penetration of this FSP. Additionally, it is essential to ensure a biofidelic boundary condition as the protective efficacy of fabrics was markedly altered by a gelatine backing.

  • Journal article
    Felten M, Fries M, Pullen A, Proud WG, Jung Aet al., 2020,

    Investigation of Strain-Rate Effects in Ni/PU Hybrid Foams under Low-Impact Velocities

    , ADVANCED ENGINEERING MATERIALS, Vol: 22, ISSN: 1438-1656
  • Journal article
    Miller SM, Slutz SA, Bland SN, Klein SR, Campbell PC, Woolstrum JM, Kuranz CC, Gomez MR, Jordan NM, McBride RDet al., 2020,

    A pulsed-power implementation of “Laser Gate” for increasing laser energy coupling and fusion yield in magnetized liner inertial fusion (MagLIF)

    , Review of Scientific Instruments, Vol: 91, Pages: 1-9, ISSN: 0034-6748

    Magnetized Liner Inertial Fusion (MagLIF) at Sandia National Laboratories involves a laser preheating stage where a few-ns laser pulse passes through a few-micron-thick plastic window to preheat gaseous fusion fuel contained within the MagLIF target. Interactions with this window reduce heating efficiency and mix window and target materials into the fuel. A recently proposed idea called “Laser Gate” involves removing the window well before the preheating laser is applied. In this article, we present experimental proof-of-principle results for a pulsed-power implementation of Laser Gate, where a thin current-carrying wire weakens the perimeter of the window, allowing the fuel pressure to push the window open and away from the preheating laser path. For this effort, transparent targets were fabricated and a test facility capable of studying this version of Laser Gate was developed. A 12-frame bright-field laser schlieren/shadowgraphy imaging system captured the window opening dynamics on microsecond timescales. The images reveal that the window remains largely intact as it opens and detaches from the target. A column of escaping pressurized gas appears to prevent the detached window from inadvertently moving into the preheating laser path.

  • Journal article
    McLean KW, Rose SJ, 2020,

    Corrections to weighted opacities and energy exchange rate in 3-T radiation-hydrodynamics

    , High Energy Density Physics, Vol: 35, Pages: 1-5, ISSN: 1574-1818

    It is often the case that high energy density systems can be well described and simulated in the 3T approximation, where electrons, ions and the radiation field are defined at unique temperatures given by Te, Ti, Tr. The difference in temperature between the electrons and radiation field is important when calculating weighted opacities and electron-radiation energy exchange rates. Often, it is assumed that Tr ≈ Te, meaning the quantities can be calculated as functions of Te only. This paper explores the consequences that arise when one uses this assumption in regions where Tr ≠ Te. Mutliplicative correction factors are derived for the Rosseland and Planckian mean opacities (κR and κP) and for the electron-radiation energy exchange rate. We find that there exists a very small region of parameter space where the corrections are negligible. However, for the majority of parameter space explored, numerical corrections vary from factors of 2 to multiple orders of magnitude.

  • Journal article
    Behm K, Hussein AE, Zhao TZ, Baggott RA, Cole JM, Hill E, Krushelnick K, Maksimchuk A, Nees J, Rose SJ, Thomas AGR, Watt R, Wood JC, Yanovsky V, Mangles SPDet al., 2020,

    Demonstration of femtosecond broadband X-rays from laser wakefield acceleration as a source for pump-probe X-ray absorption studies

    , High Energy Density Physics, Vol: 35, Pages: 1-5, ISSN: 1574-1818

    We present X-ray absorption measurements near the K-edge of laser heated aluminum in a pump-probe configuration using X-rays generated in a laser wakefield accelerator. A 30 fs duration laser pulse from the Herculeslaser system was split into two beamlines, with one used to heat a 4 µm thickness Al foil and the second to drive a laser wakefield accelerator. The laser-heated plasma was probed at various pump-probe delays using the femtosecond duration X-rays generated by betatron oscillations of the electrons in the wakefield. We observe an apparent blue-shift of the K-edge occurring on a sub-picosecond timescale in the transmission spectra.

  • Journal article
    Hobbs LMR, Burridge D, Hill MP, Hoarty DJ, Brown CRD, Charles R, Cooper G, James SF, Wilson LA, Babbage W, Hatfield PW, Beiersdorfer P, Nilsen J, Scott H, Rose SJet al., 2020,

    X-ray-line coincidence photopumping in a potassium-chlorine mixed plasma

    , Physical Review A, Vol: 101, Pages: 053431-1-053431-8, ISSN: 2469-9926

    Exploiting the multiple long pulse capability and suite of x-ray diagnostics of the Orion laser, we have set out to explore line coincidence photopuming—the enhancement in population of an atomic level brought on by resonant absorption of x rays from a different emitting ion. Unlike previous work, the two ions are in the same plasma and so the experiment is an x-ray analog of the well-known Bowen resonance fluorescence mechanism that operates in astrophysical situations in the optical region. Our measurements have shown enhanced fluorescence in a chlorine plasma, attributable to line coincident photopumping from co-mixed potassium ions. To detect this relatively low signal-to-noise phenomenon, the data from multiple shots are combined, and the statistical method of bootstrapping is used to assign a confidence value to the measured enhancement, resulting in an estimate of the enhancement of 39±1618% compared to the null case, where no pumping occurs. The experimental results have been compared to coupled radiation-transport and radiation hydrodynamics simulations using the cretin code together with the nym radiation hydrodynamics model and agreement has been found, with the simulations also predicting modest enhancement.

  • Journal article
    Escauriza EM, Duarte JP, Chapman DJ, Rutherford ME, Farbaniec L, Jonsson JC, Smith LC, Olbinado MP, Skidmore J, Foster P, Ringrose T, Rack A, Eakins DEet al., 2020,

    Collapse dynamics of spherical cavities in a solid under shock loading

    , SCIENTIFIC REPORTS, Vol: 10, ISSN: 2045-2322
  • Conference paper
    Nilsen J, Burridge D, Hobbs LMR, Hoarty D, Beiersdorfer P, Brown GV, Hell N, Panchenko D, Gu MF, Saunders AM, Scott HA, Hatfield P, Hill MP, Wilson L, Charles R, Brown CRD, Rose Set al., 2020,

    Enhanced fluorescence from X-Ray line coincidence pumping

    , 16th International Conference on X-ray Lasers, Publisher: Springer International Publishing, Pages: 29-35, ISSN: 0930-8989

    Many resonant photo-pumped X-ray laser schemes that use a strong pump line such as Ly-α or He-α to populate the upper laser state of a separate lasing material have been proposed over the last four decades but none have been demonstrated. As a first step to creating a photo-pumped X-ray laser we have decided to reinvestigate some of these schemes at the Orion laser facility with the goal to show enhanced fluorescence. In particular we look at using the Ly-α or He-α K lines to pump the 1s–3p and 4p transitions in H-like Cl and see fluorescence on the 4f–3d line at 65 Å and the 3d–2p line at 23 Å. Preliminary experiments are presented that show a modest enhancement. As an alternative we also look at enhancing the 2p–2s line in Ne-like Ge at 65 Å using the Ly-α Mg line to photo-pump the 2s–3p line of Ne-like Ge. Calculations are presented that suggest modest enhancements of 2.5.

  • Journal article
    Nguyen TT, Carpanen D, Stinner D, Rankin I, Ramasamy A, Breeze J, Proud W, Clasper J, Masouros Set al., 2020,

    The risk of fracture to the tibia from a fragment simulating projectile

    , Journal of The Mechanical Behavior of Biomedical Materials, Vol: 102, ISSN: 1751-6161

    Penetrating injuries due to fragments energised by an explosive event are life threatening and are associated with poor clinical and functional outcomes. The tibia is the long bone most affected in survivors of explosive events, yet the risk of penetrating injury to it has not been quantified. In this study, an injury-risk assessment of penetrating injury to the tibia was conducted using a gas-gun system with a 0.78-g cylindrical fragment simulating projectile. An ovine tibia model was used to generate the injury-risk curves and human cadaveric tests were conducted to validate and scale the results of the ovine model. The impact velocity at 50% risk (±95% confidence intervals) for EF1+, EF2+, EF3+, and EF4+ fractures to the human tibia – using the modified Winquist-Hansen classification – was 271 ± 30, 363 ± 46, 459 ± 102, and 936 ± 182 m/s, respectively. The scaling factor for the impact velocity from cadaveric ovine to human was 2.5. These findings define the protection thresholds to improve the injury outcomes for fragment penetrating injury to the tibia.

  • Journal article
    Bailie D, Hyland C, Singh R, White S, Sarri G, Keenan F, Riley D, Rose S, Hill E, Wang F, Yuan D, Zhao G, Wei H, Han B, Zhu B, Zhu J, Yang Pet al., 2020,

    An investigation of the L-shell X-ray conversion efficiency for laser-irradiated tin foils

    , Plasma Science and Technology, Vol: 22, Pages: 1-7, ISSN: 1009-0630

    We have used the Shenguang II laser in third harmonic (351 nm) to investigate the emission ofL-shell radiation in the 3.3 to 4.4 keV range generated using thin foils of Sn coated onto a parylenesubstrate with irradiation of order 1015 Wcm−2 and nanosecond pulse duration. In our experiment,we have concentrated on assessing the emission on the non-laser irradiated side as this allows anexperimental geometry relevant to experiments on photo-ionised plasmas where a secondary targetmust be placed close to the source, to achieve X-ray fluxes appropriate to astrophysical objects.Overall L-shell conversion efficiencies are estimated to be of order 1%, with little dependence onSn thickness between 400 and 800 nm.

  • Conference paper
    Tear GR, Proud WG, 2020,

    Experimental Methodology for Characterising Microwave Damaged Concrete

    , 21st Biennial American-Physical-Society -Topical-Group Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Journal article
    Hatfield P, Rose S, Scott R, Almosallam I, Roberts S, Jarvis Met al., 2020,

    Using sparse Gaussian processes for predicting robust inertial confinement fusion implosion yields

    , IEEE Transactions on Plasma Science, Vol: 48, Pages: 14-21, ISSN: 0093-3813

    Here, we present the application of an advanced sparse Gaussian process-based machine learning algorithm to the challenge of predicting the yields of inertial confinement fusion (ICF) experiments. The algorithm is used to investigate the parameter space of an extremely robust ICF design for the National Ignition Facility, the ``Simplest Design''; deuterium-tritium gas in a plastic ablator with a Gaussian, Planckian drive. In particular, we show that: 1) GPz has the potential to decompose uncertainty on predictions into uncertainty from lack of data and shot-to-shot variation; 2) it permits the incorporation of science-goal-specific cost-sensitive learning (CSL), e.g., focusing on the high-yield parts of parameter space; and 3) it is very fast and effective in high dimensions.

  • Conference paper
    Jonsson JC, Farbaniec L, Escauriza EM, Smith LC, Chapman DJ, Eakins DEet al., 2020,

    Effect of Texture on Elastic Precursor Decay in Magnesium Alloy AZ31B

    , 21st Biennial American-Physical-Society -Topical-Group Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Conference paper
    Proud WG, Martin E, Tear GR, Sory DRet al., 2020,

    The Effect of Temperature on the Failure of a Simple Perspex Structure

    , 21st Biennial American-Physical-Society -Topical-Group Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Conference paper
    Lee JJ, Sory DR, Proud WG, 2020,

    Simulation of Two-gauge Measurement Method on the SHPB for Testing Soft Materials

    , 21st Biennial American-Physical-Society -Topical-Group Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Conference paper
    Magnus D, Sory DR, Lee J, Khan MA, Proud WGet al., 2020,

    Study of Soft Material Blast Mitigation Effects Using a Shock Tube

    , 21st Biennial American-Physical-Society -Topical-Group Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • Journal article
    Kettle B, Gerstmayr E, Streeter MJV, Albert F, Baggott RA, Bourgeois N, Cole JM, Dann S, Falk K, Gallardo González I, Hussein AE, Lemos N, Lopes NC, Lundh O, Ma Y, Rose SJ, Spindloe C, Symes DR, Šmíd M, Thomas AGR, Watt R, Mangles SPDet al., 2019,

    Single-shot multi-keV X-ray absorption spectroscopy using an ultrashort laser-wakefield accelerator source

    , Physical Review Letters, Vol: 123, Pages: 254801-1-254801-6, ISSN: 0031-9007

    Single-shot absorption measurements have been performed using the multi-keV x rays generated by a laser-wakefield accelerator. A 200 TW laser was used to drive a laser-wakefield accelerator in a mode which produced broadband electron beams with a maximum energy above 1 GeV and a broad divergence of ≈15  mrad FWHM. Betatron oscillations of these electrons generated 1.2±0.2×106  photons/eV in the 5 keV region, with a signal-to-noise ratio of approximately 300∶1. This was sufficient to allow high-resolution x-ray absorption near-edge structure measurements at the K edge of a titanium sample in a single shot. We demonstrate that this source is capable of single-shot, simultaneous measurements of both the electron and ion distributions in matter heated to eV temperatures by comparison with density functional theory simulations. The unique combination of a high-flux, large bandwidth, few femtosecond duration x-ray pulse synchronized to a high-power laser will enable key advances in the study of ultrafast energetic processes such as electron-ion equilibration.

  • Journal article
    Yanuka D, Theocharous S, Bland SN, 2019,

    Pulsed power driven cylindrical wire array explosions in different media

    , PHYSICS OF PLASMAS, Vol: 26, Pages: 1-7, ISSN: 1070-664X

    Cylindrical copper wire array explosions were carried out in de-ionized water, sodium polytungstate solution, nitromethane, and polyester in order to obtain high energy density conditions in the vicinity of implosion using the generated converging shock waves. The use of different materials in which the array is immersed can contribute to this goal with higher density resulting in higher shock velocities and possible combustion. The generated shock waves were captured by a framing and a streak camera, and shock velocities were calculated and compared. The pressure behind the shock front was calculated using the known hydrodynamic relations (for water, polytungstate, and polyester) and compared to two-dimensional hydrodynamic simulations coupled with the equations of state (for water and polyester). It was shown that despite lower shock wave velocity in polytungstate solution than in water, the pressures generated are similar in both materials. In polyester, both shock velocities and generated pressures are 2–4 times higher than in water. It was also shown that it is possible to carry out these explosions in a solid which has several advantages compared to liquids, such as not relying on waterproof systems and easier transportation.

  • Journal article
    Beesley JJ, Rose SJ, 2019,

    Free electron relativistic correction factors to collisional excitation and ionisation rates in a plasma

    , High Energy Density Physics, Vol: 33, ISSN: 1574-1818

    This paper presents approximate correction factors to collisional excitation and ionisation rates which account for special relativity in the free electron motion as a function of free electron temperature and the threshold energy of the reaction. These are calculated by taking the ratio of collisional rates derived from simple empirical cross sections using relativistic and non-relativistic mechanics. These results are extended to de-excitation and three body recombination rates using detailed balance. It is found that the relativistic correction is significant in regimes potentially important to galactic intracluster media and diagnostic dopants in burning ICF plasmas.

  • Journal article
    Rankin IA, Thuy-Tien N, Carpanen D, Clasper JC, Masouros SDet al., 2019,

    Restricting lower limb flail is key to preventing fatal pelvic blast injury

    , Annals of Biomedical Engineering, Vol: 47, Pages: 2232-2240, ISSN: 0090-6964

    Pelvic vascular injury in the casualty of an explosive insult is a principal risk factor for increased mortality. The mechanism of injury has not previously been investigated in a physical model. In this study, a small-animal model of pelvic blast injury with a shock-tube mediated blast wave was utilised and showed that lower limb flail is necessary for an unstable pelvic fracture with vascular injury to occur. One hundred and seventy-three cadaveric mice underwent shock-tube blast testing and subsequent injury analysis. Increasingly displaced pelvic fractures and an increase in the incidence of pelvic vascular injury were seen with increasing lower limb flail; the 50% risk of vascular injury was 66° of lower limb flail out from the midline (95% confidence intervals 59°–75°). Pre-blast surgical amputation at the hip or knee showed the thigh was essential to result in pelvic displacement whilst the leg was not. These findings, corroborated by clinical data, bring a paradigm shift in our understanding of the mechanism of blast injury. Restriction of lower limb flail in the human, through personal protective equipment, has the potential to mitigate the effects of pelvic blast injury.

  • Conference paper
    Nilsen J, Burridge D, Hobbs LMR, Hoarty D, Beiersdorfer P, Brown GV, Hell N, Panchenko D, Gu MF, Saunders AM, Scott HA, London RA, Hatfield P, Hill MP, Wilson L, Charles R, Brown CRD, Rose Set al., 2019,

    Enhanced fluorescence from x-ray line coincidence pumping of K-pumped Cl and Mg-pumped Ge plasmas

    , X-Ray Lasers and Coherent X-Ray Sources: Development and Applications XIII, Publisher: SPIE, Pages: 1111105-1-1111105-6

    Many resonant photo-pumped X-ray laser schemes that use a strong pump line such as Ly-α or He-α to populate the upper laser state of a separate lasing material have been proposed over the last four decades but none have been demonstrated. As a first step to creating a photo-pumped X-ray laser we decided to reinvestigate some of these schemes at the Orion laser facility with the goal to demonstrate enhanced fluorescence as a first step toward creating a laser. In particular we look at using the Ly-α or He-α K lines to pump the 1s – 3p and 4p transitions in H-like Cl and see fluorescence on the 4f -3d line at 65 Å and the 3d – 2p line at 23 Å. Preliminary experiments are presented that show a modest enhancement of 40% on the 3d-2p line. As an alternative we also look at enhancing the 2p – 2s line in Ne-like Ge at 65Å using the Ly-α Mg line to photo-pump the 2s – 3p line of Ne-like Ge. Calculations are presented that suggest modest enhancements of 2.5 and recent experiments will be presented that show emission from a Ge plasma pumped by the Ly-α Mg line.

  • Journal article
    Pérez-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: 0022-4073

    We 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.

  • Journal article
    Weller ME, Beiersdorfer P, Lockard TE, Brown GV, McKelvey A, Nilsen J, Shepherd R, Soukhanovskii VA, Hill MP, Hobbs LMR, Burridge D, Hoarty DJ, Morton J, Wilson L, Rose SJ, Hatfield Pet al., 2019,

    Observation of He-like satellite lines of the H-like potassium K XIX emission

    , Astrophysical Journal, Vol: 881, ISSN: 0004-637X

    We 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.

  • Journal article
    Hare JD, MacDonald J, Bland S, Dranczewski J, Halliday J, Lebedev S, Suttle L, Tubman E, Rozmus Wet al., 2019,

    Two-colour interferometry and Thomson scattering measurements of a plasma gun

    , Plasma Physics and Controlled Fusion, Vol: 61, ISSN: 0741-3335

    We 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.

  • Working paper
    Hare JD, MacDonald J, Bland SN, Dranczewski J, Halliday JWD, Lebedev S, Suttle LG, Tubman ER, Rozmus Wet al., 2019,

    Two-colour interferometry and Thomson scattering measurements of a plasma gun

    , Publisher: IOP PUBLISHING LTD
  • Journal article
    Ota TA, Amott R, Carlson CA, Chapman DJ, Collinson MA, Corrow RB, Eakins DE, Graves TE, Hartsfield TM, Holtkamp DB, Iverson AJ, Richley JC, Stone JBet al., 2019,

    Comparison of Simultaneous Shock Temperature Measurements from Three Different Pyrometry Systems

    , Journal of Dynamic Behavior of Materials, ISSN: 2199-7446
  • Journal article
    Hoarty DJ, Morton J, Jeffery M, Pattison LK, Wardlow A, Mangles SPD, Rose SJ, Iglesias C, Opachich K, Heeter RF, Perry TSet 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: 1574-1818

    A 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.

  • Journal article
    Cohen A, Levi-Hevroni D, Fridman P, Chapman D, Rack A, Olbinado MP, Yosef-Hai A, Eakins Det al., 2019,

    In-situ radiography of a split-Hopkinson bar dynamically loaded materials

    , JOURNAL OF INSTRUMENTATION, Vol: 14, ISSN: 1748-0221
  • Journal article
    Perez-Callejo G, Jarrott LC, Liedahl DA, Marley EV, Kemp GE, Heeter RF, Emig JA, Foord ME, Widmann K, Jaquez J, Huang H, Rose S, Wark JS, Schneidner MBet 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: 1070-664X

    Understanding 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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