Bulletin of the American Physical Society
2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005; Denver, Colorado
Session QO3: ICF Target Fabrication/Diagnostics |
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Chair: Craig Sangster, University of Rochester Room: Adam's Mark Hotel Governor's Square 15 |
Thursday, October 27, 2005 9:30AM - 9:42AM |
QO3.00001: Measurements of absolute infrared absorption on condensed deuterium-tritide from 2400-3400 cm$^{-1}$ J.D. Sater, D.N. Bittner, J.W. Pipes The current point design for the indirect drive hohlraum target requires a smooth DT ice layer at 1.5 K below the triple point. Previous experiments have shown that the DT ice roughness increases with lower temperature due to cracking of the ice and facet formation. Infrared enhanced layering has been shown to effectively suppress the increase in surface roughening as the temperature lowers well below the triple point. Infrared laser power absorption occurs in both the DT ice as well as the surrounding shell. The best choice for IR laser frequency is the one giving the maximum absorption in the ice and the minimum absorption in the shell. Accurate knowledge of the absolute absorption spectrum of D-T in the 2.5-4.0 $\mu$m region is essential for choosing the best frequency. Previous work has accurately determined the positions but not the magnitude of the major lines [P. C. Souers, 1986]. We will present absorption measurements made on condensed D-T with a Fourier transform infrared spectrometer. Implications of the measured results on the choice of capsule materials and fundamental limits of enhanced layering will be discussed. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48 and by Schafer Corporation under contract number DE-AC03-01SF2260. [Preview Abstract] |
Thursday, October 27, 2005 9:42AM - 9:54AM |
QO3.00002: Demonstration Of DT Fuel Fill, Layer Formation And Thermal Shimming In A Cryogenic NIF Hohlraum Target.$^{1}$ J.J. Sanchez, B. Kozioziemski, J.D. Moody, J. Sater, D. Bittner Targets for the National Ignition Facility (NIF) require thick $>$80$\mu $m deuterium-tritium (DT) fuel layers that are spherically symmetric for ignition. We describe experiments using a NIF scale indirect drive hohlraum target which demonstrate capsule DT fill through a 5 micron ID fill tube, using a self-contained low pressure fuel reservoir. We also describe the subsequent formation of uniform solid DT layers on the inside of the target capsule. A slow-growth technique was used to insure smooth layers. Thermal shimming was used to control the lowest modes in the ice. The target consists of a capsule mounted in the center of a gold hohlraum fitted with side windows. A 5 $\mu $m ID fill tube at the capsule, attaches to a 1 cc reservoir filled with 50 psia of DT. In operation the capsule is filled with DT to a level that can be controlled by setting the temperature of the fill reservoir. Once the capsule fills to the desired level, the hohlraum temperature is lowered to freeze the DT within the fill tube and begin the process of layer formation. We will show results for fast frozen layers and layers slowly grown from single crystal seeds as well as the effects of thermal shimming to produce spherically symmetric layers. $^{1}$Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. [Preview Abstract] |
Thursday, October 27, 2005 9:54AM - 10:06AM |
QO3.00003: Deuterium-tritium solid layer formation and characterization in a beryllium shell Bernard Kozioziemski, David Montgomery, Cort Gautier, James Sater, John Moody, Jorge Sanchez Copper-doped beryllium ablators are part of the current baseline design for indirect drive hohlraum targets for use at the National Ignition Facility. Recent advances in phase-contrast enhanced x-ray imaging have made it possible to characterize solid deuterium-tritium layers inside of the optically opaque beryllium shells. The imaging system used for characterization will be described. We will report results of experiments to produce smooth D-T layers inside of a beryllium shell. We find that the D-T layer RMS roughness of modes 4-128 increases from 0.9 $\mu$m at 19.4 K to 1.3 $\mu$m at 18.3 K. We observe the layer to become smoother with time when held at 18.3 K. [Preview Abstract] |
Thursday, October 27, 2005 10:06AM - 10:18AM |
QO3.00004: Temperature control and sensitivity of low ice modes in a NIF scale hohlraum J.D. Moody, J.J. Sanchez, B.J. Kozioziemski, R.A. London, J.D. Sater Direct and indirect drive ignition schemes require smooth Deuterium-Tritium (DT) ice layers on the inner surface of the fuel shell. These ice layers are grown slowly from liquid into a solid shell with an outer radius of about 0.9 mm and thickness of about 0.1 mm. The inner surface ice roughness is characterized in terms of a spatial power spectrum from which the RMS amplitude for any scalelength of roughness can be obtained. Short scalelength ice roughness is determined mainly by hydrogen crystal properties and long scalelength roughness primarily by the surrounding thermal environment. The shell is placed in the center of a gold cylinder or hohlraum in the indirect drive scheme. Active heating (called thermal shimming) is applied to the hohlraum surface to create spherical isotherms at the inner ice surface. It is important to determine that active heating can control the ice low mode roughness with sufficient accuracy. We describe experiments and modeling which investigate the control of long scalelength ice modes in the fuel ice layer of an indirect drive target with imposed thermal perturbations on the hohlraum wall. Work performed under the auspicies of the U.S. DOE by UC, LLNL contract number W--7405--ENG--48 [Preview Abstract] |
Thursday, October 27, 2005 10:18AM - 10:30AM |
QO3.00005: Heating of Cryogenic Indirect Drive ICF Targets Upon Shroud Removal Richard London, John Moody, Jorge Sanchez, James Sater, Donald Bittner Cryogenic inertial confinement fusion targets at the National Ignition Facility and the Laser Megajoule will be protected from thermal infrared radiation by a cold shroud. As the shroud is removed before the laser shot, radiation will heat and possibly degrade the symmetry of the deuterium-tritium fuel layer. A lumped component mathematical model has been constructed to calculate how long an indirect drive target can be exposed to thermal radiation before the fuel layer degrades. The model predicts that the maximum exposure time is $\approx $ 0.17 s for plastic capsules in hohlraums with transparent laser entrance holes. By covering the laser entrance holes with a partially reflective coating, and/or by using beryllium capsules, the exposure time can be increased to 1-2 s. Several other design concepts could increase the exposure time even further. The allowed exposure time sets the maximum shroud removal time and therefore has important implications for the design of the cryogenic shroud systems. Lengthening the exposure time to 1 s could allow a significant cost savings. [Preview Abstract] |
Thursday, October 27, 2005 10:30AM - 10:42AM |
QO3.00006: Status of the Development of Beryllium-Copper Alloy Ignition Capsules by Precision Machining Arthur Nobile, Jason Cooley, David Alexander, Robert Hackenberg, Robert Field, Robert Day, Gerald Rivera, Ann Kelly, Pallas Papin Cu-doped Be capsules are being developed for ignition on the National Ignition Facility (NIF). The fabrication approach being pursued at Los Alamos is based on bonding of cylindrical parts containing precision machined hemispherical cavities, followed by machining the external contour to produce a spherical capsule. While we have demonstrated this approach, there are several key issues that need to be resolved before a capsule meeting NIF specifications can be produced. These issues are synthesis of high purity small grain size Be-Cu alloy, formation of a hemishell bond strong enough to allow the capsule to be machined after the hemishells are bonded, precision machining and polishing of the capsule to meet stringent specifications for surface finish and spherical quality, and filling with DT. In this paper we report on the progress that has been made on these issues. \textit{This work is performed at Los Alamos National Laboratory and supported by U.S. Department of Energy under contract number W7405-ENG36} [Preview Abstract] |
Thursday, October 27, 2005 10:42AM - 10:54AM |
QO3.00007: A Compact, Multiangle Electron Spectrometer for Ultra-Intense Laser--Plasma Interaction Experiments O.V. Gotchev, D.D. Meyerhofer, C. Stoeckl In the fast ignitor scheme for inertial confinement fusion, one of the main challenges is the efficient coupling of the ignitor laser pulse into kinetic energy of forward-going electrons and the transport of these from the critical surface to the compressed core. Experiments on LLE's multiterawatt (MTW) laser will study the effect of the focal-spot shape on the forward acceleration and collimation of electrons. A compact electron spectrometer has been developed to simultaneously record the energy spectra of electrons ejected from the intersection of the laser focus with various targets at multiple angular locations. A modular system with replaceable magnets, the spectrometer provides an adjustable energy band that is currently 0.2 to 5 MeV. The detector is an array of imaging plates and is designed to operate in the high-noise MTW environment (bremsstrahlung and Compton x rays, gamma rays, scattered electrons), while being compact enough to fit in the diagnostic space of the target chamber. The detector geometry and shielding were optimized with the particle/radiation transport code GEANT4. The required dynamic range, sensitivity, and resolution are satisfied with this detector choice. This work was supported by the U.S. Department of Energy under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Thursday, October 27, 2005 10:54AM - 11:06AM |
QO3.00008: Proton radiography of electromagnetic fields generated by laser-driven plastic foils C.K. Li, F.H. Seguin, J.R. Rygg, J.A. Frenje, R.D. Petrasso, T.C. Sangster, V.A. Smalyuk, J.A. Delettrez, J.P. Knauer, S.P. Regan, J. Soures, F.J. Marshall, P.W. McKenty, D.D. Meyerhofer, C. Stoeckl, R.P. Town, P. Patel, A.J. Mackinnon, P. Amendt, N. Izumi, O. Landen We are conducting the first experiments using proton radiography to study electromagnetic fields generated by OMEGA laser-driven plastic foils. Transient E and B fields will be probed using proton deflectometry. Monoenergetic DD and D$^{3}$He protons are generated from direct-drive implosions of D$^{3}$He-filled glass micro-balloons. Using various mesh grids, both face-on and side-on proton images are recorded on CR-39 track detectors. The magnitude and shape of proton deflections will provide quantitative information about these fields as well as laser-solid interactions. The details of these experiments will be reported and discussed. This work was supported in part by LLE, LLNL, the U.S. DoE, the Univ. of Rochester, and the N.Y.State Energy Research and Development Authority. [Preview Abstract] |
Thursday, October 27, 2005 11:06AM - 11:18AM |
QO3.00009: Neutron Detection with Bubble Chambers M.C. Ghilea, D.D. Meyerhofer, T.C. Sangster, R.A. Lerche, L. Disdier To improve neutron imaging resolution, we have developed a general imaging design tool for inertial confinement fusion facilities that can simulate aperture errors, generate arbitrary neutron source distributions, simulate arbitrary aperture shapes, calculate point-spread functions using ray tracing, and reconstruct source images using a variety of filter functions. Predicted system performance can be compared to various concepts before construction. This software design tool is being developed for the UR/LLE OMEGA laser and the NIF as part of a process to design and build an imaging system based on a bubble chamber detector\footnote{R. A. Lerche\textit{ et al.}, Rev. Sci. Instrum. \textbf{74}, 1709 (2003).} for the UR/LLE OMEGA laser. This talk will present the latest results on aperture contributions to system performance and review the conceptual design of the bubble chamber-based imaging system, its conceptual design being reviewed in the second part of the presentation. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Thursday, October 27, 2005 11:18AM - 11:30AM |
QO3.00010: A magnetic recoil spectrometer (MRS) for $\rho $R, yield and T$_{i}$ measurements of implosions at OMEGA and the NIF J.A. Frenje, D.T. Casey, C.K. Li, J.R. Rygg, F.H. Seguin, S. Volkmer, R.D. Petrasso, V.Yu. Glebov, D.D. Meyerhofer, T.C. Sangster, C. Stoeckl, S. Haan, S. Hatchett, P. Amendt, D. Eder, N. Izumi, O. Landen, D. Lerche, D.C. Wilson, G. Kyrala, R. Leeper, R. Olson Charged-particle diagnostics have been extensively used for determining $\rho $R of several types of implosions, but they will fail for $\rho $R$>$200 mg/cm$^{2}$ and not work for the $\sim $300 mg/cm$^{2}$ expected in upcoming OMEGA cryogenic DT implosions or the 700-2000 mg/cm$^{2 }$expected in NIF implosions. We are therefore currently developing a neutron spectrometer for measurements of down-scattered neutrons from which $\rho $R in the 100 to 2000 mg/cm$^{2}$ can be inferred. The spectrometer is a Magnetic Recoil Spectrometer (MRS) that covers the energy range 6 to 32 MeV, which enables simultaneous measurements of down-scattered, primary and tertiary neutrons. Due to the MRS principle, measurements of these different neutrons are spatially separated, which is critical for successful $\rho $R measurements. This work was supported in part by UR-LLE, LLNL, the U.S. DoE, and the N.Y. State Energy Research and Development Authority$. $ [Preview Abstract] |
Thursday, October 27, 2005 11:30AM - 11:42AM |
QO3.00011: Three-Dimensional Density Measurement by Time-Gated Neutron Imaging of Imploded ICF Capsules Michael Moran, Jeffrey Koch, Carlos Barrera, Edward Morse Recent neutron imaging systems$^{1}$ have produced a sequence of improving images of the spatial distribution of neutron emission from confinement fusion capsules with neutron yields less that 10$^{14}$. Higher neutron yields at the National Ignition Facility and LMJ raise the prospect of neutron imaging methods that probe the physics of the burning capsule. For example, a set of three time-gated images that select different portions of the 14-MeV spectral peak can produce spatial temperature maps of a burning target.$^{2}$ Simultaneous images of temperature and neutron emission can be combined to infer the source density distribution by using Abel inversion, a method that has been used in x-ray imaging.$^{3}$ A test of this method, based on Gaussian radial temperature and density profiles, indicates that uncertainty in the inferred density varies linearly with uncertainties in the temperature and emission measurements. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. References: [1] L. Disdier, et. Al., Rev. Sci. Instrum. \underline {75}, 2134 (2004) [2] D.C. Wilson et.al., Rev. Sci. Inst. \underline {74}, p. 1705 (2003). [3] J.A. Koch, et.al., J. Quantit. Spectros. {\&} Rad. Trans. \underline {88}, p. 433 (2004). [Preview Abstract] |
Thursday, October 27, 2005 11:42AM - 11:54AM |
QO3.00012: WITHDRAWN--Core Temperature and Density Maps of Direct Drive Implosions using Multispectral X-ray Imaging R. Tommasini, J.A. Koch, L.A. Welser, R.C. Mancini, J. Delettrez, S.P. Regan, V. Smalyuk We report on the experiments to obtain core temperature and density maps in direct drive implosions performed at the OMEGA laser facility using a multi-monochromatic X-ray imager, consisting of an array of pinholes and a flat multilayer mirror, providing unique multi-spectral images distributed over a wide spectral range. Employing Ar as a dopant in the DD-filled plastic shells produces emission images in the Ar He-$\beta $ and Ly-$\beta $ spectral regions. These images allow the retrieval of temperature and density maps of the imploding core. Using three identical imagers in a quasi-orthogonal line-of-sight geometry we obtain three-dimensional profiles and images of the cores in different temporal intervals. Temperature and density profiles will be presented and compared with earlier works on direct- and indirect-drive. [UCRL-ABS-213695] [Preview Abstract] |
Thursday, October 27, 2005 11:54AM - 12:06PM |
QO3.00013: Analysis methods for slit-imaged line spectra from argon-doped implosion cores at Z R. Mancini, J. Bailey, G. Rochau, G. Dunham, G. Chandler, D. Sinars, P. Lake, K. Peterson, S. Slutz, T. Mehlhorn, T. Burris-Mog, I. Golovkin, J. MacFarlane The availability of time-resolved slit-imaged X-ray line spectra from argon-doped deuterium-filled implosion cores driven by z-pinch dynamic-hohlraums at the Z facility, creates an opportunity for developing new spectroscopic diagnostics of the core. The combination of broad-range X-ray line spectra with high-spectral-resolution, and spatial- and time-resolution provides information for unfolding the temperature and density spatial-structure of the core. Analysis methods are discussed based on using spatially-resolved spectral lineouts that correspond to a spatial-integration over core slices. Alternatively, a set of narrow-spectral-band slit-image intensity spatial-profiles can also be used for analysis. Results are illustrated for argon K-shell spectra recorded with framed crystal spectrometers equipped with space-resolving slits that afforded up to 0.3 ns of time- and 50 $\mu $m of space-resolution, and covered the He$\alpha $ to Ly$\gamma $ lines spectral range with a spectral resolution power of 1000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Dept. of Energy. [Preview Abstract] |
Thursday, October 27, 2005 12:06PM - 12:18PM |
QO3.00014: Update on the Rochester Optical Streak System P.A. Jaanimagi, R. Boni, D.D. Meyerhofer The Rochester Optical Streak System (ROSS) is a modern, self-calibrating, remotely controlled streak camera platform capable of accepting a variety of different streak tubes. The optical calibration module (OCM) for the ROSS camera has been completed and integrated with the main streak tube housing. The OCM incorporates an achromatic Offner triplet that allows fiber-delivered input and free-space propagated signals to be simultaneously relayed to the photocathode. It also encloses of the light sources and reticles required to accomplish a full suite of system calibrations including: autofocus of the input and electron optics, geometric distortion and flat-field correction, time base, system gain, and linearity. We will present data illustrating the system capabilities and our latest results comparing the dynamic performance of the P510 and P820 streak tubes. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
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