Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session NO8: ICF/HED Diagnostics |
Hide Abstracts |
Chair: Laura Berzak, Lawrence Livermore National Laboratory Room: 212 CD |
Wednesday, November 2, 2016 9:30AM - 9:42AM |
NO8.00001: Neutron Measurements in Small MagLIF Experiments on OMEGA V.Yu. Glebov, D.H. Barnak, J.R. Davies, J.P. Knauer, R. Betti, S.P. Regan, T.C. Sangster, E.M. Campbell The Laboratory for Laser Energetics (LLE) is participating in laser-driven magnetized linear inertial fusion (MagLIF) research on the OMEGA Laser System in partnership with Sandia as part of ARPA-E's ALPHA Program. In the current OMEGA setup, a CH cylindrical tube filled with D$_{\mathrm{2}}$ gas is compressed by 40 laser beams, preheated by one of the beams, and an axial magnetic field is applied to limit electron heat loss. Two copper coils provide 10-T magnetic fields. A neutron time-of-flight (nTOF) detector has been designed, fabricated, and calibrated to diagnose primary D--D fusion neutron yield in the range of 1 \texttimes 10$^{\mathrm{7}}$ to 5 \texttimes 10$^{\mathrm{9}}$ and ion temperature from 2 to 8 keV. The design details and calibration results of these nTOF detectors will be presented together with neutron measurement results from recent laser-driven MagLIF experiments on OMEGA. The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000568, and the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, November 2, 2016 9:42AM - 9:54AM |
NO8.00002: Inferences of Shell Asymmetry in ICF Implosions using Fluence Compensated Neutron Images at the NIF D. Casey, D. Fittinghoff, R. Bionta, V. Smalyuk, G. Grim, D. Munro, B. Spears, K. Raman, D. Clark, A. Kritcher, D. Hinkel, O. Hurricane, D. Callahan, T. Döppner, O. Landen, T. Ma, S. Le Pape, S. Ross, N. Meezan, A. Pak, H.-S. Park, P. Volegov, F. Merill In ICF experiments, a dense shell is imploded and used to compress and heat a hotspot of DT fuel. Controlling the symmetry of this process is both important and challenging. It is therefore important to observe the symmetry of the stagnated shell assembly. The Neutron Imaging System at the NIF is used to observe the primary 14 MeV neutrons from the hotspot and the down-scattered neutrons (6-12 MeV), from the assembled shell but with a strong imprint from the primary-neutron fluence. Using a characteristic scattering angle approximation, we have compensated the image for this fluence effect, revealing information about shell asymmetry that is otherwise difficult to extract without models. Preliminary observations with NIF data show asymmetries in imploded shell, which will be compared with other nuclear diagnostics and postshot simulations. [Preview Abstract] |
Wednesday, November 2, 2016 9:54AM - 10:06AM |
NO8.00003: Modeling down-scattered neutron images from cryogenic fuel implosions at the National Ignition Facility Kumar Raman, Dan Casey, Debra Callahan, Dan Clark, David Fittinghoff, Gary Grim, Steve Hatchett, Denise Hinkel, Ogden Jones, Andrea Kritcher, Scott Seek, Larry Suter, Frank Merrill, Doug Wilson In experiments with cryogenic deuterium-tritium (DT) fuel layers at the National Ignition Facility (NIF), an important technique for visualizing the stagnated fuel assembly is to image the 6-12 MeV neutrons created by scatters of the 14 MeV hotspot neutrons in the surrounding cold fuel. However, such down-scattered neutron images are difficult to interpret without a model of the fuel assembly, because of the nontrivial neutron kinematics involved in forming the images. For example, the dominant scattering modes are at angles other than forward scattering and the 14 MeV neutron fluence is not uniform. Therefore, the intensity patterns in these images usually do not correspond in a simple way to patterns in the fuel distribution, even for simple fuel distributions. We describe our efforts to model synthetic images from ICF design simulations with data from the National Ignition Campaign and after. We discuss the insight this gives, both to understand how well the models are predicting fuel asymmetries and to inform how to optimize the diagnostic for the types of fuel distributions being predicted. [Preview Abstract] |
Wednesday, November 2, 2016 10:06AM - 10:18AM |
NO8.00004: Advanced Scintillator Detectors for Neutron Imaging in Inertial Confinement Fusion Verena Geppert-Kleinrath, Christopher Danly, Frank Merrill, Raspberry Simpson, Petr Volegov, Carl Wilde The neutron imaging team at Los Alamos National Laboratory (LANL) has been providing two-dimensional neutron imaging of the inertial confinement fusion process at the National Ignition Facility (NIF) for over five years. Neutron imaging is a powerful tool in which position-sensitive detectors register neutrons emitted in the fusion reactions, producing a picture of the burning fuel. Recent images have revealed possible multi-dimensional asymmetries, calling for additional views to facilitate three-dimensional imaging. These will be along shorter lines of sight to stay within the existing facility at NIF. In order to field imaging capabilities equivalent to the existing system several technological challenges have to be met: high spatial resolution, high light output, and fast scintillator response to capture lower-energy neutrons, which have scattered from non-burning regions of fuel. Deuterated scintillators are a promising candidate to achieve the timing and resolution required; a systematic study of deuterated and non-deuterated polystyrene and liquid samples is currently ongoing. A test stand has been implemented to measure the response function, and preliminary data on resolution and light output have been obtained at the LANL Weapons Neutrons Research facility. [Preview Abstract] |
Wednesday, November 2, 2016 10:18AM - 10:30AM |
NO8.00005: Gas Cherenkov Detectors For Gamma Ray Measurements At The National Ignition Facility (NIF) Hans W. Herrmann, Y.H. Kim, A.B. Zylstra, F.E. Lopez, J. Griego, V. E. Fatherley, J. A. Oertel, S. H. Batha, A. Carpenter, H. Khater, J.E. Hernandez, M.S. Rubery, C.J. Horsfield, S. Gales, A. Leatherland, T. Hilsabeck, J.D. Kilkenny, R.M. Malone, J.D. Hares, J. Milnes, W. T. Shmayda New requirements to improve reaction history and ablator areal density measurements at the NIF necessitate diagnostic capability improvements in sensitivity, temporal and spectral response relative to the existing Gamma Reaction History diagnostic (GRH-6m) located 6 meters from target chamber center (TCC). Relative to GRH-6m, a new DIM-based ``Super'' Gas Cherenkov Detector (GCD) will ultimately provide \textasciitilde 200x more sensitivity to DT fusion gamma rays, reduce the effective temporal resolution from \textasciitilde 100 to \textasciitilde 10 ps and lower the energy threshold from 2.9 to 1.8 MeV. Initially, the existing GCD-3 will be placed into a reentrant well, putting it within 4 meters of TCC. This diagnostic platform will allow assessment of the x-ray radiation background environment within the well which will be fed into the shielding design for the follow-on ``Super'' GCD. It will also enable use of a pulse-dilation PMT (PD-PMT) which has the potential to improve the effective measurement bandwidth by\textasciitilde 10x relative to current PMT technology. Initial measurements of both GCD-3 on NIF and a PD-PMT prototype on ORION will be discussed. [Preview Abstract] |
Wednesday, November 2, 2016 10:30AM - 10:42AM |
NO8.00006: Quantitative Analysis of X-ray Self Emission in ICF Implosions Using Orthogonal Images Laura Robin Benedetti, S. R. Nagel, N. Izumi, S. F. Khan, T. Ma, A. Pak, G. A. Kyrala, P. Patel, D. K. Bradley Laser-driven experiments can create implosion cores that are hot and dense enough for inertially-confined fusion. This implosion method is inherently three-dimensional, where loss of symmetry often indicates reduced performance. However, the symmetry of the core at stagnation is typically only diagnosed by images of x-ray self emission along two orthogonal lines of sight. We report on a method to use x-ray self-emission images along multiple lines of sight to infer quantitative properties of the implosion. Specifically we find that we can use absolute x-ray yields to quantify variations in the compressed fuel and shell that surrounds the core. In addition, we can use the spatial variations in x-ray brightness to estimate volumes of very asymmetric hotspots that are otherwise not well described by spherical or ellipsoidal approximations. [Preview Abstract] |
Wednesday, November 2, 2016 10:42AM - 10:54AM |
NO8.00007: Conduction-Zone Measurements Using X-Ray Self-Emission Images A.K. Davis, D.T. Michel, R. Epstein, S.X. Hu, J.P. Knauer, D.H. Froula Time-gated soft x-ray self-emission images of directly driven implosions were used to measure the hydrodynamic conditions between the critical-density surface and the ablation front of a CH target (conduction zone) at the beginning of a laser pulse. These images were calibrated using the time-resolved broadband soft x-ray spectrometer Dante, azimuthally averaged to reduce the noise, and Abel-inverted to determine the emissivity at each point in the plasma. The electron temperature was determined using co-timed images taken with three different filters to obtain a coarse measurement of the emission spectrum at each point. With the temperature determined, the density profile in the corona was determined from the emissivity profile. This measurement is critical for inertial confinement fusion since it governs the length of time that the plasma is too small to provide substantial beam smoothing through thermal conduction, determining the laser imprint efficiency. This region has previously proven challenging to probe because the density is too high for optical diagnostics and the temperature is too high for x-ray radiography. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, November 2, 2016 10:54AM - 11:06AM |
NO8.00008: A 7.2 keV spherical crystal backlighter system for Sandia's Z Pulsed Power Facility M. Schollmeier, P.F. Knapp, D.J. Ampleford, G.P. Loisel, G. Robertson, J.E. Shores, I.C. Smith, C.S. Speas, J.L. Porter, R.D. McBride Many experiments on Sandia's Z facility, a 30 MA, 100 ns rise-time, pulsed-power driver, use a monochromatic Quartz crystal imaging backlighter system at 1.865\,keV (Si He$_\alpha$) or 6.151\,keV (Mn He$_\alpha$) x-ray energy to radiograph an imploding liner (cylindrical tube) or wire array. The x-ray source is generated by the Z-Beamlet Laser (ZBL), which provides up to 4.5 kJ at 527 nm during a 6 ns window. Radiographs of an imploding thick-walled Beryllium liner at a convergence ratio of about 20 $[$CR $ = R_{in.}(0)/R_{in.}(t)]$ were too opaque to identify the inner surface of the liner with high confidence, demonstrating the need for a higher-energy x-ray backlighter between 6 and 10 keV. We present the design, test and first application of a Ge\,(335) spherical crystal x-ray backlighter system using the 7.242\,keV Co He$_\alpha$ resonance line. The system operates at an almost identical Bragg angle as the existing 1.865 and 6.151\,keV backlighters, enhancing our capabilities such as two-color, two-frame radiography, without changing detector shielding hardware.\\ SAND No: SAND2016-6724 A. [Preview Abstract] |
Wednesday, November 2, 2016 11:06AM - 11:18AM |
NO8.00009: Development of a High Resolution X-Ray Spectrometer for the National Ignition Facility (NIF) K. W. Hill, M. Bitter, L. Delgado-Aparicio, P.C. Efthimion, R. Ellis, L. Gao, J. Maddox, N.A. Pablant, M.B. Schneider, H. Chen, S. Ayers, R.L. Kauffman, A.G. MacPhee, P. Beiersdorfer, T. Ma, R.C. Nora, H.A. Scott, D.B. Thorn, J.D. Kilkenny, D. Nelson, M. Shoup III, Y. Maron A high resolution (E/$\Delta $E \textasciitilde 2000) Bragg crystal x-ray spectrometer is being developed to measure plasma parameters in NIF experiments. The instrument will be a positioner insertable cassette designed to infer electron density in compressed capsules from Stark broadening of the helium-$\beta $ (1s$^{\mathrm{2}}$-1s3p) lines of krypton, and electron temperature from the relative intensities of dielectronic satellites. Two conically shaped crystals will diffract and sagittally focus (1) the Kr He$\beta $ complex and (2) the He$\alpha $ and Ly$\alpha $ complexes onto a streak camera photocathode for time resolved measurement. A third cylindrical crystal will focus the full He$\alpha $ to He$\beta $ spectrum onto an image plate for a time integrated calibration spectrum. Performance estimates and design status will be presented. [Preview Abstract] |
Wednesday, November 2, 2016 11:18AM - 11:30AM |
NO8.00010: High-Resolving-Power, Streaked X-Ray Spectroscopy on the OMEGA EP Laser System P.M. Nilson, F. Ehrne, C. Mileham, D. Mastrosimone, R.K. Jungquist, C. Taylor, R. Boni, J. Hassett, C.R. Stillman, S.T. Ivancic, D.J. Lonobile, R.W. Kidder, M.J. Shoup III, A.A. Solodov, C. Stoeckl, W. Theobald, D.H. Froula, K.W. Hill, L. Gao, M. Bitter, P. Efthimion, D.D. Meyerhofer A high-resolving-power, streaked x-ray spectrometer is being developed and tested on the OMEGA EP Laser System to study temperature-equilibration dynamics in rapidly heated solid matter. Temporal spectral shifts of the Cu K$_{\alpha }$ line in isochorically heated solid targets provide a fairly simple system where the spectrometer performance will be validated. The goal is to achieve a resolving power of several thousand and $\sim 2\mbox{-ps}$ temporal resolution. A time-integrating survey spectrometer has been developed and deployed on OMEGA EP to evaluate the throughput, focusing fidelity, and spectral resolution of two different crystal geometries. The results from these measurements will be presented and used to justify the down-selected time-resolved spectrometer design. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, November 2, 2016 11:30AM - 11:42AM |
NO8.00011: Single crystal X-ray spectropolarimeter for HED plasmas and its use on wire array z-pinches Matt Wallace, Showera Haque, Paul Neill, Alan Kastengren, Nino Pereira, Radu Presura When energetic electrons in a plasma have a preferred direction the resulting X-rays can be polarized. This makes plasma X-ray polarization spectroscopy, spectropolarimetry, useful for revealing information about the anisotropy of the electron velocity distribution, and X-ray spectropolarimetry has indeed been used for this in both space and laboratory plasmas. For pulsed plasmas the spectrum's polarization is typically measured by obtaining each component of polarization separately, with two crystals both at a 45 degree Bragg angle or one on successive shots. However, obtaining the two orthogonal polarizations can be done using one crystal. Crystals with hexagonal symmetry present pairs of internal planes that diffract incident X-rays in two directions that are perpendicular to each other and the incident ray. The polarization splitting properties of quartz crystals were confirmed with linearly polarized X-rays from the APS. An X-cut crystal with (10-10) planes in polarization splitting orientation is now being used on wire array z-pinches at UNR. The design of a single crystal X-ray polarimeter, and what data obtained so far indicate about the anisotropy of wire array z-pinch plasmas will be presented. [Preview Abstract] |
Wednesday, November 2, 2016 11:42AM - 11:54AM |
NO8.00012: Schlieren Cinematography of Current Driven Plasma Jet Dynamics Keith Loebner, Thomas Underwood, Mark Cappelli Schlieren cinematography of a pulsed plasma deflagration jet is presented and analyzed. An ultra-high frame rate CMOS camera coupled to a Z-type laser Schlieren apparatus is used to obtain flow-field refractometry data for the continuous flow Z-pinch formed within the plasma deflagration jet. The 10 MHz frame rate for 256 consecutive frames provides high temporal resolution, enabling turbulent fluctuations and plasma instabilities to be visualized over the course of a single pulse (20 $\mu$s). The Schlieren signal is radiometrically calibrated to obtain a two dimensional mapping of the refraction angle of the axisymmetric pinch plasma, and this mapping is then Abel inverted to derive the plasma density distribution as a function radius, axial coordinate, and time. Analyses of previously unknown discharge characteristics and comparisons with prior work are discussed. [Preview Abstract] |
Wednesday, November 2, 2016 11:54AM - 12:06PM |
NO8.00013: Plasma Jet Interaction with Thomson Scattering Probe Laser Tom Byvank, Jacob Banasek, William Potter, Bruce Kusse Thomson scattering systems can diagnose plasma temperatures and velocities. When probing a plasma jet with the Thomson scattering laser, we observe a laser-plasma interaction that inputs energy into the plasma jet. The absorbed energy causes a bubble of low density (\textasciitilde 5*10\textasciicircum 17 cm\textasciicircum -2) in the jet (unperturbed \textasciitilde 10\textasciicircum 18 cm\textasciicircum -2). A pulsed power machine (1 MA peak current, 100 ns rise time) with a radial foil (15 $\mu $m thick Al) configuration generates the plasma jet. We compare the effects of using 10 J and 1 J laser energies, for which the 10 J laser is a larger perturbation. We discuss how the interaction affects the Thomson scattering temperature and velocity measurements. [Preview Abstract] |
Wednesday, November 2, 2016 12:06PM - 12:18PM |
NO8.00014: Initial Tests of a Plasma Beam Combiner at NIF R. K. Kirkwood, D. P. Turnbull, T. D. Chapman, S. C. Wilks, R. A. London, R. L. Berger, P. A. Michel, L. Divol, W. H. Dunlop, B. J. MacGowan, K. B. Fournier, B. E. Blue The seeded forward SBS process that is known to effectively amplify beams in ignition targets [1] has recently been used to design and test a target to combine the power and energy of many beams of the NIF facility into a single beam by intersecting them in an ionized gas [2]. The demand for high-power beams for a variety of applications at NIF makes a demonstration of this process attractive. We will describe experiments using a gas-filled balloon heated by 10 quads of beams, and pumped by additional frequency-tuned quads to amplify a single beam. The beam energy is indicated by gated x-ray images of both the spots produced by the transmitted pump and probe beams and the spot produced by a non-interacting quad of beams when they terminate on a foil. The first experiment produced a high brightness seed beam with significant reductions in brightness of the pumping beams, consistent with their depletion by energy transfer to the seed. Additional experiments studying spot brightness with varying pump power to determine total delivered seed beam energy and power will be discussed as available. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 [1] R. K. Kirkwood et al PLASMA PHYSICS AND CONTROLLED FUSION~~55, 10, 103001 (2013) [2] R. K. Kirkwood et al Bull. Am. Phys. Soc. 60, 19, UP12.00021 (2015), ibid . 57, 12, CP8.00089 (2012) [Preview Abstract] |
Wednesday, November 2, 2016 12:18PM - 12:30PM |
NO8.00015: ABSTRACT WITHDRAWN |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700