Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session JO5: ICF/HEDP Diagnostics |
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Chair: Gary Grim, Los Alamos National Laboratory Room: Governor's Square 10 |
Tuesday, November 12, 2013 2:00PM - 2:12PM |
JO5.00001: A New Neutron Time-of-Flight Detector for Fuel Areal-Density Measurements on OMEGA V.Yu. Glebov, C.J. Forrest, K.L. Marshall, A. Pruyne, M. Romanofsky, T.C. Sangster, M.J. Shoup III, C. Stoeckl A new neutron time-of-flight (nTOF) detector for fuel areal-density measurements in cryogenic DT implosions on the OMEGA Laser System was designed, manufactured, and tested. The nTOF detector has a cylindrical thin-wall stainless steel 8-in.-diam, 4-in.-thick cavity filled with an oxygenated xylene scintillator. Four gated photomultiplier tubes (PMT's) with different gains are designed to measure primary DT neutrons, downscattered neutrons, and tertiary neutrons. The nTOF detector is located 13.85 m from the target chamber center in a collimated line of sight. The design details of the nTOF detector, PMT optimization, and test results on OMEGA will be presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Tuesday, November 12, 2013 2:12PM - 2:24PM |
JO5.00002: T(t,2n)$^{4}$He Neutron Spectrum from Inertial Confinement Implosions Dennis McNabb, Andy Bacher, Carl Brune, Jac Caggiano, Maria Gatu-Johnson, Dan Sayre Measurements of the T(t,2n)$^{4}$He reaction (TT) have been conducted using high-purity tritium, gas-filled capsules in ICF implosions at the NIF and OMEGA facilities. Neutron spectra were measured using two instruments: the neutron-time-of-flight (nTOF) and the Magnetic Recoil Spectrometer. The nTOF spectra represent a significant improvement in energy resolution and statistics over previous measurements, and afford the first definitive observation of a small, narrow peak starting at the 9.44 MeV endpoint resulting from sequential decay through the ground state of $^{5}$He at low reaction energies E$_{\mathrm{cm}}$\textless\ 100 keV. However, most of the TT reaction produces a broad neutron spectrum from 0-9.5 MeV. To describe the spectrum, an R-matrix model that accounts for interferences from fermion symmetry and intermediate states has been developed. This model can describe the entire spectrum via sequential decay through l$=$1 states in $^{5}$He, which differs from previous interpretations. Work is in collaboration with V. Yu Glebov,~R. Hatarik, D. L. Bleuel, D. T. Casey, C. J. Cerjan, M. J. Eckart, R. J. Fortner, J. A. Frenje, G. P. Grim, C. Hagmann, J. P. Knauer, J. L. Kline, J. M. McNaney, J. M. Mintz, M. J. Moran, A. Nikroo, T. Phillips, J. E. Pino, B. A. Remington, D. P. Rowley, D. H. Schneider, V. A. Smalyuk, W. Stoeffl, R. E. Tipton, S. V. Weber, C. B. Yeamans, C. K. Li, M. J.-E. Manuel, D. D. Meyerhofer, R. D. Petrasso,~ P. B. Radha, T. C. Sangster, N. Sinenian, F. H. Seguin, and A. B. Zylstra. [Preview Abstract] |
Tuesday, November 12, 2013 2:24PM - 2:36PM |
JO5.00003: D-D proton spectra and emission imaging for diagnosing imploded capsules on Shenguang III laser prototype facility Jian Teng, Tiankui Zhang, Yudong Pu, Bo Wu, Wei Hong, Bin Zhu, Weihua He, Feng Lu, Lianqiang Shan, Xianlun Wen, Weimin Zhou, Leifeng Cao, Shaoen Jiang, Yuqiu Gu Understanding and controlling implosion dynamics are critical for progress in inertial confinement fusion (ICF). Primary D-D protons spectra and emission imaging is used for diagnosing areal density and implosion asymmetries on Shenguang III laser prototype facility with low neutron yields for the first time. An accurately calibrated charged particle spectrometer (CPS) is used with CR39 detector for the measurement of the proton spectra. The properties of the noise and proton signal on the CR39 are characterized, and the spectra of the implosion proton are obtained by excluding the noise. For the investigation of the implosion asymmetries, a new method of directly imaging of primary DD protons in the implosion region by miniature magnetic quadrupole lenses is proposed. The imaging properties such as spatial resolution and focus length are investigated by simulation and calibration experiment. [Preview Abstract] |
Tuesday, November 12, 2013 2:36PM - 2:48PM |
JO5.00004: X-ray Spectroscopy of High-Z Elements on Nike Y. Aglitskiy, J.L. Weaver, M. Karasik, V. Serlin, S.P. Obenschain, Yu. Ralchenko Survey X-ray spectrometer covering a spectral range from 0.5 to 19.5 angstroms has been added to the spectroscopic suite of Nike diagnostics. That allows simultaneous observation of both M- and N- spectra of W, Ta and Au with high spectral resolution. Low energy test shots confirmed strong presence of 3-4 transitions of Ni-like W, Ta and Au with X-ray energies as high as 3.5 keV when above mentioned elements were used as the targets. In our continuous effort to support DOE-NNSA's inertial fusion program, the future campaign will cover a wide range of plasma conditions that result in relatively energetic X-ray production. Eventually, absolutely calibrated spectrometers of similar geometry will be fielded at NIF in cooperation with NIF diagnostic group. [Preview Abstract] |
Tuesday, November 12, 2013 2:48PM - 3:00PM |
JO5.00005: Dynamic Granularity for X-Ray Imaging Systems Matthias Geissel, Verle H. Bigman, Aaron D. Edens, Marius Schollmeier, Ian C. Smith, Jonathon E. Shores, John L. Porter Dynamic range and spatial resolution are correlated, because imaging units such as pixels or film grains can cover a wider dynamic range if they are larger, so that they can contain more electrons in a well or fluorescence centers in a grain. However, for systems that are subject to low photon flux, statistical noise influences the spatial resolution. Statistical noise is important for many experiments that rely on single shot X-ray imaging diagnostics. Detectors face a limited photon flux and often also a limited detection probability, where photons of higher energy may just penetrate the detector. The effective spatial resolution depends on detector efficiency, incident photon flux, detector cell size (grain/pixel), and the detector's inherent noise. We describe the combined influences with a ``dynamic granularity'' function, based on measurements of the grain size dependent distinguishability of grey levels. The dynamic granularity is unique to each imaging system, but allows us to quantify the performance of different detectors in a system. We have characterized a fast microchannel plate imaging detector and imaging plate with respect to dynamic granularity on the 6.151 keV crystal imaging system at the Z-Beamlet laser. [Preview Abstract] |
Tuesday, November 12, 2013 3:00PM - 3:12PM |
JO5.00006: 2D x-ray imaging spectroscopic diagnostics using convex bent crystal Daniel Papp, Radu Presura, Matt Wallace, Billy Largent, Showera Haque, Angel Arias, Vijay Khanal, Vladimir Ivanov A new 2-dimensional time-integrated x-ray spectroscopic diagnostics technique was developed to create multi-monochromatic images of high-energy density Al plasmas. 2-dimensional is an advanced spectroscopic tool, providing a way to determine the spatial dependence of plasma temperature and density ($T_{e}$ and $n_{e})$ in hot plasmas. The new technique uses the strong source broadening of convex cylindrically bent KAP crystal spectrometers, which contains spatial information along the dispersive direction. The perpendicular direction is imaged using a slit. The spatial resolution of the method is improved by the deconvolution of the source broadened line profiles from the lineshapes (recorded by the convex crystal spectrometer) with lineshapes of minimum instrumental broadening. The latter spectra were recorded with a concave cylindrically bent KAP crystal spectrometer, based on the Johann geometry. Spectroscopic model of the plasma x-ray emission was developed using the PrismSPECT code. The identification of suitable spectral features allows deriving $T_{e}$ and $n_{e}$ from line intensities. We applied this model to get temperature and density distribution maps for wire array z-pinch plasmas. [Preview Abstract] |
Tuesday, November 12, 2013 3:12PM - 3:24PM |
JO5.00007: Characterization of a quartz crystal for X-ray spectropolarimetric plasma diagnostics Matt Wallace, Nino Pereira, Alan Kastengren, Radu Presura The x-rays emitted by the plasma an electron beam passes through can be polarized. Information about the anisotropy of the electron energy distribution can be reveled by the x-ray spectrum's polarization. A promising way of performing spectropolarimetry uses one crystal containing two sets of planes that, for the appropriate wavelength and incidence angle, diffract the incident x-rays in two directions that are perpendicular to each other and to the incident beam.\footnote{E O Baronova and M M Stepanenko, ``A novel x-ray polarimeter based on hexagonal crystal, for application to thermonuclear fusion experiments,'' Plasma Phys. Control. Fusion 45 1113(2003)} The diffracted x-rays are linearly polarized perpendicularly to each other. Polarization splitting quartz crystals were tested with the linearly polarized x-rays from the Advanced Photon Source. A crystal with surface cut [10-10] that splits polarization with [11-20] planes at 3.5 keV was among those tested. This can be used for plasma containing Cl, Ar, or K. The crystal characteristics and requirements for its use to diagnose electron beams in z-pinch plasmas will be presented. [Preview Abstract] |
Tuesday, November 12, 2013 3:24PM - 3:36PM |
JO5.00008: Imaging of hard X-rays from implosions of CH shells at Omega Daniel Lemieux, Gary Grim, Brad Barber, Robert Aragonez, David Clark, Chris Danly Making use of the recently designed gamma ray imaging system prototype made for the National Ignition Facility, images of hard X-rays produced in implosions of plastic shells using the Omega laser are presented. Preheating from hot-electrons produced by two-plasmon-decay is a concern for direct drive implosions as it increases the adiabat of the fuel assembly. The hot-electrons undergo bremsstrahlung scattering in the CH material, producing X-rays ranging from a few keV to a few hundred keV. These X-rays are produced in implosions of 875 micron CH shells, filled with $^{3}$He, and are imaged using a 200 micron pinhole onto an LYSO scintillator system. Copper is used as a high-pass filter of the signal. A description of the gamma ray imaging diagnostic will be presented along with images of the hard X-rays. [Preview Abstract] |
Tuesday, November 12, 2013 3:36PM - 3:48PM |
JO5.00009: Soft X-Ray Backlighting of Cryogenic Implosions Using a Narrowband Crystal Imaging System C. Stoeckl, R. Epstein, G. Fiksel, D. Guy, V.N. Goncharov, R.K. Jungquist, C. Mileham, P.M. Nilson, T.C. Sangster, M.J. Shoup III, W. Theobald X-ray backlighting of high-energy-density matter is widely used for imaging high-energy-density plasmas in hydrodynamic experiments. High-energy petawatt (HEPW) lasers such as OMEGA EP promise significantly improved backlighting capability by producing enhanced x-ray power and shorter emission times. A narrowband x-ray imager with an astigmatism-corrected, aspherically bent, quartz crystal for the Si He$_{\alpha }$ line at $\sim $1.86 keV has been used to record backlit images of cryogenic direct-drive implosions. A time-gated recording system was used to minimize the self-emission of the imploding target. With backlighter laser energies of $\sim $1.25 kJ at a 10-ps pulse duration, the radiographic images show a high signal-to-background ratio of \textgreater~100:1 and a spatial resolution of better than 15 $\mu $m. The backlit images will be used to assess the symmetry of the implosions close to stagnation. This material is based upon work supported by the Department of Energy National Nuclear Security Administration DE-NA0001944 and the Office of Science under DE-FC02-04ER54789. [Preview Abstract] |
Tuesday, November 12, 2013 3:48PM - 4:00PM |
JO5.00010: Ultraviolet Thomson Scattering from Direct-Drive Coronal Plasmas R.J. Henchen, V.N. Goncharov, D.T. Michel, R.K. Follett, J. Katz, D.H. Froula Ultraviolet ($\lambda_{4\omega} =$ 263 nm) Thomson scattering (TS) was used to probe ion-acoustic waves (IAW's) and electron plasma waves (EPW's) from direct-drive coronal plasmas. Fifty-nine drive beams ($\lambda_{3\omega} =$ 351 nm) illuminate a spherical target with a radius of $\sim $860 $\mu $m. Advances in the ultraviolet (UV) TS diagnostic at the Omega Laser Facility provide the ability to detect deep UV photons ($\sim $190 nm) and allow access to scattered light from EPW's propagating near the 3$\omega $ quarter-critical surface ($\sim $2.5 $\times $ 10$^{\mathrm{21}}$ cm$^{-3})$. A series of experiments studied the effects of ablator materials on coronal plasma conditions. Electron temperatures and densities were measured from 150 $\mu $m to 400 $\mu $m from the initial target surface. Standard CH shells were compared to three-layered shells consisting of Si doped CH, Si, and Be. Early analysis indicates that these multilayered targets have less hot-electron energy as a result of higher electron temperature in the coronal plasma. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Tuesday, November 12, 2013 4:00PM - 4:12PM |
JO5.00011: Effect of Ion Temperature on Spectroscopic Electron Temperature Diagnosis J.P. Apruzese, J.L. Giuliani, J.W. Thornhill, B. Jones, S.B. Hansen, C.A. Jennings, D.J. Ampleford, A.J. Harvey-Thompson, M.E. Cuneo Ratios of lines from different ionization stages are often used to diagnose electron temperature in Z pinches. Populations of the various stages can be influenced by photoexcitation to excited states, from which ionization proceeds very rapidly. The ion temperature affects the line width, opacity, and the photoexcitation rate, therefore the line ratios, and the inferred electron temperature. We discuss a practical example where this effect is important: Ar gas-puff shot Z2382. [Preview Abstract] |
Tuesday, November 12, 2013 4:12PM - 4:24PM |
JO5.00012: ICF Gamma-Ray measurements on the NIF Hans Herrmann, Y. Kim, N.M. Hoffman, S.H. Batha, W. Stoeffl, J.A. Church, D.B. Sayre, J.A. Liebman, C.J. Cerjan, A.C. Carpenter, E.M. Grafil, H.Y. Khater, C.J. Horsfield, M. Rubery The primary objective of the NIF Gamma Reaction History (GRH) diagnostic is to provide bang time and burn width information in order to constrain implosion simulation parameters such as shell velocity and confinement time. This is accomplished by measuring DT fusion gamma-rays with energy-thresholded Gas Cherenkov detectors that convert MeV gamma-rays into UV/visible photons for high-bandwidth optical detection. Burn-weighted CH ablator areal density is also inferred based on measurement of the 12C(n,n') gammas emitted at 4.44 MeV from DT neutrons inelastically scattering off carbon nuclei as they pass through the plastic ablator. This requires that the four independent GRH gas cells be set to differing Cherenkov thresholds (e.g., 2.9, 4.5, 8 {\&} 10 MeV) in order to be able to unfold the primary spectral components predicted to be in the gamma ray energy spectrum (i.e., DT$\gamma $; $^{27}$Al {\&} $^{28}$Si (n,n') $\gamma $ from the thermo-mechanical package (TMP); and $^{12}$C(n,n') $\gamma $ from the ablator). The GRH response to $^{12}$C(n,n') $\gamma $ is calibrated in-situ by placing a known areal density of carbon in the form of a puck placed $\sim$6 cm from a DT exploding pusher implosion. Comparisons between inferred gamma fluences and simulations based on the nuclear cross sections databases will be presented. [Preview Abstract] |
Tuesday, November 12, 2013 4:24PM - 4:36PM |
JO5.00013: A Kirkpatrick-Baez Microscope for Core Implosion Imaging at NIF Louisa Pickworth, David Bradley, Tommaso Pardini, Vladimir Smalyuk, Nobuhiko Izumi, Michael Pivovaroff, Julia Vogel, Christopher Walton, Paul Mirkarimi, Perry Bell, Todd Decker, Thomas McCarville, Marion Ayers, Joseph Kilkenny ICF experiments have typical core diameters raging from $50\mu m$, in layered implosions, to $100\mu m$ in SymCaps. The emission spectrum is peaked between 8 and 10keV. Current X-ray imaging at NIF uses time resolved pinhole cameras with 10-20$\mu m$ pinholes that limit resolution and throughput to the detector. Selection of observed photon energy requires filtering that further reduces transmission. Low resolution, in combination with poor signal to noise ratio, limits the observable features during the later stages of capsule implosion. Using grazing incidence mirrors in a Kirkpatrick-Baez (KB) configuration, a focusing x-ray microscope is in design for NIF. The system will have x12 magnification, detector limited resolution and x10 higher throughput in comparison to pinhole systems. A KB microscope for imaging ICF experiments will be described, utilizing multilayer mirrors to enhance reflectivity for the core emission. Optimization of the multilayer coating allows observation of extended sources and high reflectivity in a selected energy band $>0.2$keV. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-640864 [Preview Abstract] |
Tuesday, November 12, 2013 4:36PM - 4:48PM |
JO5.00014: Talbot-Lau X-ray Moir\'{e} deflectometry Diagnostic for High Energy Density Plasmas Maria Pia Valdivia Leiva, Dan Stutman, Michael Finkenthal A Talbot-Lau (TL) x-ray interferometer measures beam angular deviations due to refraction index gradients within objects along its path. By tilting one of the gratings in the interferometer by small angles, Moir\'{e} patterns which enable the detection of density gradients in low-Z matter are obtained. In addition to the detection of both sharp and smooth density gradients this technique makes also possible the identification of micro structures within an object. The sensitivity and spatial resolution is adequate to characterize High Energy Density Laboratory Plasmas (HEDLP). The technique allows for the simultaneous acquisition of x-ray attenuation, refraction, and scatter information from a single x-ray image. Experimental and simulated results acquired show a clear advantage of the TL Moir\'{e} single image based phase-retrieval technique over the attenuation and propagation methods. Additionally, the method makes use of extended, polychromatic, incoherent, line and continuum x-ray sources, thus allowing for less demanding backlighters than those typically used in HEDLP radiography. [Preview Abstract] |
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