Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session UO5: LPI and ICF diagnostics |
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Chair: Gary Grim, Los Alamos National Laboratory Room: 552AB |
Thursday, November 1, 2012 2:00PM - 2:12PM |
UO5.00001: Modeling Cross-Beam Energy Transfer for Polar-Drive Experiments D.H. Edgell, P.B. Radha, V.N. Goncharov, I.V. Igumenshchev, J.A. Marozas, J.F. Myatt, W. Seka, D.H. Froula Direct-drive experiments on the National Ignition Facility require use of the nonspherically symmetric, indirect-drive beam layout. In polar-drive (PD), the power and pointing of the cylindrically symmetric NIF beams are optimized to uniformly implode a capsule. As beams refract in the coronal plasma, cross-beam energy transfer (CBET) can cause laser energy to ``bypass'' the high-absorption region of the plasma near the critical surface. The effect of CBET is modeled for PD implosions on OMEGA and the NIF. Three-dimensional paths and crossings of all beams are calculated using \textit{DRACO}-predicted plasma profiles. CBET is modeled for each of the beam rings. The equatorial third ring suffers the most from CBET, but the reduction in total absorption ($\sim $10{\%}) is similar to the 60-beam symmetric illumination case on OMEGA. Scattered-light measurements and predictions from the CBET modeling show good agreement for PD in OMEGA. This work was supported by the U.S. Department of Energy (DOE) Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 1, 2012 2:12PM - 2:24PM |
UO5.00002: Scattering of Multiple Crossing Laser Beams in Direct-Drive ICF Plasmas A.V. Maximov, J.F. Myatt, R.W. Short, I.V. Igumenshchev, D.H. Edgell, W. Seka In direct-drive inertial confinement fusion (ICF), the nonlinear propagation of multiple crossing laser beams determines the balance between absorption and scattering of laser power. Cross-beam energy transfer (CBET) has been implemented in large-scale hydrodynamic simulations\footnote{I. V. Igumenshchev\textit{ et al.}, Phys. Plasmas \textbf{19}, 056314 (2012).} based on the ray-interaction model and shown to be important for the coupling of laser energy to the target. The full laser--plasma interaction model\footnote{A. V. Maximov \textit{et al.}, Phys. Plasmas \textbf{11}, 2994 (2004).} applied to the scattering of multiple laser beams allowed us to consider the effects of laser speckle intensity distribution and the angular spreading and frequency broadening. The generation of common ion-acoustic waves by multiple laser beams and the light scattering off them has been shown to influence CBET. Modifications to the CBET hydrodynamic model for direct-drive ICF are discussed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 1, 2012 2:24PM - 2:36PM |
UO5.00003: Cross-Beam Energy Transfer (CBET) Effect with Additional Ion Heating Integrated into the 2-D Hydrodynamics Code \textit{DRACO} J.A. Marozas, T.J.B. Collins The cross-beam energy transfer (CBET) effect causes pump and probe beams to exchange energy via stimulated Brillouin scattering.\footnote{ W. L. Kruer, \textit{The Physics of Laser--Plasma Interactions}, Frontiers in Physics, Vol. 73, edited by D. Pines (Addison-Wesley, Redwood City, CA, 1988), p. 45.} The total energy gained does not, in general, equate to the total energy lost; the ion-acoustic wave comprises the residual energy balance, which can decay, resulting in ion heating.\footnote{ E. A. Williams\textit{ et al.}, Phys. Plasmas \textbf{11}, 231 (2004).} The additional ion heating can retune the conditions for CBET affecting the overall energy transfer as a function of time. CBET and the additional ion heating are incorporated into the 2-D hydrodynamics code \textit{DRACO}\footnote{ P. B. Radha\textit{ et al.}, Phys. Plasmas \textbf{12}, 056307 (2005).} as an integral part of the 3-D ray trace where CBET is treated self-consistently within on the hydrodynamic evolution. \textit{DRACO} simulation results employing CBET will be discussed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 1, 2012 2:36PM - 2:48PM |
UO5.00004: A New Platform for Calibrating nTOF Detectors on OMEGA and the NIF using CR39-based Proton Detectors C. Waugh, M. Rosenberg, J. Frenje, F. Seguin, R. Petrasso, V. Glebov, T. Sangster, C. Stoeckl, D. Meyerhofer, J. Knauer, R. Bionta, O. Landen, A. Mackinnon, J. Kilkenny Neutron time of flight (nTOF) detectors routinely measure neutron yields on OMEGA and the NIF. Though originally calibrated using the indium-activation method, an alternative nTOF calibration technique involving CR-39 proton detectors has successfully been developed on OMEGA and verified using the MIT Linear Electrostatic Ion Accelerator (LEIA). Inferring a neutron yield from the CR-39 can be done since the branching ratio for the DDp and DDn channels are known and close to unity. Using DD and D$^{3}$He exploding pushers on OMEGA, excellent calibration of the nTOF detectors was obtained. Data confirm the calibration of nTOF to CR-39 to be 0.95 +/- 0.1 and shows that yield anisotropies are significantly reduced when bang time occurs significantly after the end of the laser pulse. These results indicate that CR-39 detectors can serve as a valuable new platform for calibrating nTOF detectors on OMEGA and the NIF. This work was supported in part by LLE, the NLUF, the FSC, the US DOE, LLNL, and GA. [Preview Abstract] |
Thursday, November 1, 2012 2:48PM - 3:00PM |
UO5.00005: Absolute Ion-Temperature Measurements in D$_{2}$ and DT Implosions on OMEGA V.Yu. Glebov, C. Stoeckl, T.C. Sangster, C. Forrest, R.A. Lerche Measurements of the ion temperature in inertial confinement fusion (ICF) experiments provide valuable information on the state of the compressed fuel to further constrain numerical hydro code simulation models. The neutron-averaged ion temperature in ICF experiments is usually measured by neutron time-of-flight (nTOF) detectors. Accurate measurement of the absolute ion temperature requires an accurate instrument response function (IRF) of the entire nTOF system including the detector, cable, and recording device. The nTOF IRF is typically constructed from measurements and neutron-response simulations. Different methods for measuring nTOF detectors IRF's on OMEGA will be presented. The precision and accuracy of ion-temperature measurements with different nTOF detectors on OMEGA implosions with D$_{2}$ and DT fuels will be discussed. This work is supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 1, 2012 3:00PM - 3:12PM |
UO5.00006: Modeling Cold-Fuel Distributions Inferred from Elastically Scattered Neutrons in Layered Cryogenic-DT Direct-Drive Implosions C. Forrest, V.Yu. Glebov, J.P. Knauer, T.C. Sangster, C. Stoeckl, K.S. Anderson, P.B. Radha, V.N. Goncharov, D.D. Meyehofer, S. Gardner, D. Baldwin High-resolution neutron spectroscopy has been used to probe the areal density of a compressed shell from a cryogenic-DT direct-drive implosion in inertial confinement fusion (ICF) experiments. The two-body kinematics of (n,T) and (n,D) elastic scattering suggest that there should be a correlation between the energy of the neutron and the region of the DT shell probed when using a single line of sight with time-of-flight (TOF) techniques. A finite-source distribution and/or asymmetric compressed-fuel distribution is expected to modify the correlation in the TOF signal significantly. Low-mode perturbation of the DT source/shell have been simulated in a transport code (MCNP) to track neutrons that elastically scatter into a TOF detector. A 3-D plot of the dense-DT-shell scatter locations of the ``detected'' neutrons show that a realistic extended-source distribution probes a much larger region of the fuel shell than a simple point-source distribution. Simulations illustrate that higher \textit{$\rho $R} implosions increase multiple scatterings that further mask the correlation between neutron energy and the sampling area of the dense shell distribution. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 1, 2012 3:12PM - 3:24PM |
UO5.00007: Neutron-induced reactions relevant for Inertial-Cofinement Fusion Experiments Melissa Boswell, Frank Merrill, R. Rundberg, Gary Grim, Carl Wilde, Anna Hayes, Malcom Fowler, Jerry Wilhelmy Measuring the fluencies of both the low- \& high-energy neutrons is a powerful mechanism for studying the implosion process, and the various parameters that drive inertial confinement fusion. We have developed a number of tools to measure the spectral characteristics of the NIF neutron spectrum. Most of these methods rely on exploiting the energy dependence of (n,$\gamma$), (n,2n), (n,3n) and (n,p) reactions on a variety of materials either implicitly present in the NIF implosion or through doping the target capsule or holraum. I will be discussing both prompt activation measurements, and debris activation measurements of these materials currently under development at LANL. Focusing specifically on the development of an {\it{in-situ}} detector to measure short-lived activation products, as well as a low-background counting facility we are developing at the Waste Isolation Pilot Plant (WIPP) to study longer-lived activation products. Furthermore, I will also be discussing several cross section measurements that are important for the interpretation of the data collected from these activation products. [Preview Abstract] |
Thursday, November 1, 2012 3:24PM - 3:36PM |
UO5.00008: Compact DD-neutron spectrometers for studying $\rho $R, $\rho $R symmetry and yield at the NIF and OMEGA F. Seguin, M. Gatu-Johnson, N. Sienian, H. Sio, A. Zylstra, M. Manuel, D. Casey, H. Rinderknecht, M. Rosenberg, J. Frenje, C. Li, R. Petrasso, V. Glebov, J. Knauer, D. Meyerhofer, T. Sangster, C. Stoeckl, R. Bionta, D. Bleuel, S. Hatchett, A. Mackinnon, D. Munro, O. Landen, C. Yeamans, J. Kilkenny R. LEEPER, SNL --- A new and very compact broadband spectrometer for DD neutrons is being tested for diagnosis of $\rho $R and $\rho $R symmetry of implosions at the NIF and OMEGA by measuring direct and down-scattered components at different positions around implosions involving D$^{3}$He or D$_{2}$ fuel. Based on CR-39 nuclear track detectors, C$_{2}$H$_{4}$ neutron-to-proton converters and filters, its 5-cm size enables simultaneous use of multiple modules at different angles. Directionality rejects a large fraction of neutrons scattered from the target chamber. Tests on the MIT linear accelerator provided initial calibration and demonstrated a dynamic range from $\sim $ 10$^{5}$--10$^{8}$ neutrons/cm$^{2}$, while NIF data provided a starting point for testing practical measurements. Results from initial experiments and simulations will be presented. This work was supported in part by the US DOE, LLE, and LLNL. [Preview Abstract] |
Thursday, November 1, 2012 3:36PM - 3:48PM |
UO5.00009: A Streak-Camera based Magnetic Recoil Spectrometer (SCMRS) for measurements of T$_{i}$(t), Y$_{n}$(t), dsr(t) at OMEGA and the NIF J. Frenje, D. Casey, M. Gatu-Johnson, C. Li, F. Seguin, R. Petrasso, R. Bionta, J. Edwards, S. Glenzer, O. Landen, A. Mackinnon, D. Munro, P. Springer, J. Kilkenny, V. Glebov, T. Sangster, C. Stoeckl A Streak-Camera based Magnetic Recoil Spectrometer (SCMRS) for time-resolved, high-resolution measurements of the neutron spectrum is proposed. This is the next-generation neutron spectrometry that has the potential to probe the time evolution of T$_{i}$, fuel $\rho $R, burn history, bang time and kinetic effects. Having time-revolved information about these implosion parameters will be essential for better understanding the issues with the assembly of the hotspot and main fuel. The technique, which is an extension of the MRS technique successfully used on both OMEGA and the NIF, utilizes a combination of a magnetic field and a streak camera to break the dispersion issue for detailed measurements of the neutron spectrum with a time resolution of $\sim $20ps. It is anticipated that SCMRS should work for neutron yields above $\sim $10$^{13}$ and $\sim$5$\times $10$^{14}$ on OMEGA and the NIF, respectively. This work was supported in part by the U.S. DOE, LLNL and LLE. [Preview Abstract] |
Thursday, November 1, 2012 3:48PM - 4:00PM |
UO5.00010: Measurements and interpretation of TT and down-scattered DT neutron spectra at OMEGA and the NIF M. Gatu-Johnson, D.T. Casey, J. Frenje, C. Li, F. S\'eguin, R. Petrasso, V. Glebov, J. Knauer, T.C. Sangster, R. Bionta, J. Edwards, S. Glenzer, S. Hatchett, O. Landen, A. Mackinnon, D. McNabb, D. Munro, J. Pino, S. Sepke, P. Springer, J. Kilkenny The Magnetic Recoil neutron Spectrometers (MRS) on OMEGA and the National Ignition Facility (NIF) have been used to measure inertial confinement fusion (ICF) neutron spectra above $E_{n}\approx $4 MeV from DT and THD implosions with varying fuel composition and areal density ($\rho $R). In the high-$\rho $R DT implosions at the NIF, multiple-neutron scattering in the fuel is observed for the first time. In implosions with high tritium content, the TT neutron spectrum dominates and can be distinguished from other components in the neutron spectrum. In this work, we use an ensemble of measurements with varying conditions to separate the TT and down-scattered DT contributions and to improve our understanding of the shape of the TT spectrum and the source of DT down-scatter. The work motivates the need for high-resolution measurements of the ICF neutron spectrum at low energies ($E_{n}<$5~MeV). This work was supported in part by the U.S. DOE, LLNL and LLE. [Preview Abstract] |
Thursday, November 1, 2012 4:00PM - 4:12PM |
UO5.00011: Developing a D$^{3}$He exploding-pusher platform to study kinetic effects H. Sio, M. Rosenberg, H. Rinderknecht, D. Casey, A. Zylstra, C. Waugh, M. Gatu-Johnson, F. Seguin, C. Li, J. Frenje, R. Petrasso, J. Delettrez, V. Glebov, T. Sangster, C. Stoeckl, V. Goncharov, P. Amendt, C. Bellei, S. Wilks The yield anomalies recently observed in direct-drive and indirect-drive exploding pushers suggests that the shock dynamics in these implosions is not well-described by 1D fluid models. The results suggest that kinetic effects such as species separation, different types of diffusion, and loss of high-energy ions must be accounted for in the modeling of exploding pushers. D$^{3}$He gas-filled exploding pushers are ideal for studying these effects because implosions with varying fuel mixture can be made hydroequivalent, and all D3He reaction products can be measured. In this paper, we discuss the implications of this work as well as steps to develop exploding pusher as a robust platform for study of basic implosion physics in a simple 1D system. This work was supported in part by the U.S. DOE, LLNL and LLE. [Preview Abstract] |
Thursday, November 1, 2012 4:12PM - 4:24PM |
UO5.00012: ABSTRACT WITHDRAWN |
Thursday, November 1, 2012 4:24PM - 4:36PM |
UO5.00013: Detection of D-$^{3}$He Fusion $\gamma $-Rays using Gas Cherenkov Detectors Y. Kim, H.W. Herrmann, J.M. Mack, C. S. Young, G.M. Hale, S.C. Evans, T.J. Sedillo, A. Cahill, C.J. Horsfield, M.S. Rubery, E. Grafil, W. Stoeffl, C. Waugh, H.G. Rinderknecht, J.A. Frenje, R.D. Petrasso, E. Kirk Miller The high-energy $\gamma $-ray from $^{3}$He(d,$\gamma )^{5}$Li reactions has drawn the attention of the nuclear physics and fusion community as a diagnostic signature to study the $^{5}$Li nuclear structure and the D-$^{3}$He fusion reaction. In the past, the D-$^{3}$He $\gamma $-rays have been measured via accelerator-based beam-target experiments and recently in tokamak-based fusion reactors. In this work, we report the detection of D-$^{3}$He fusion $\gamma $-rays generated from inertial confinement fusion (ICF) implosions at the OMEGA laser facility. The $\gamma $-ray signal observed using Gas Cherenkov Detectors (GCD) is proportional to the independently measured 14.7-MeV fusion proton yield and provides a high-bandwidth alternative to fusion protons for D-$^{3}$He burn-history measurements. By comparing $\gamma $-rays from D-$^{3}$He and D-T implosions, we were able to examine (1) similarities in the $\gamma $-ray spectra of D-$^{3}$He and D-T and (2) disparities in the $\gamma $-to-particle branching ratios of D-$^{3}$He and D-T. This experimental work motivates further theoretical investigation of the multichannel $^{5}$Li- and $^{5}$He-system. [Preview Abstract] |
Thursday, November 1, 2012 4:36PM - 4:48PM |
UO5.00014: Refelctivity Loss in Shock Front Velocimetry Peter Celliers, Harry Robey, Thomas Boehly, Stephen Maclaren, Hye-Sook Park, Marilyn Schneider, Klaus Widmann, Gilbert Collins, Otto Landen Velocity interferometry has become an established tool for studying shock timing and drive characterization on NIF ignition scale capsules. The technique is viable as long as a reflection can be captured from the shock front in the sample. Experiments in liquid deuterium are able to track shock fronts up to about 150 km/s velocity beyond which the reflection is extinguished. The reflectivity can be extinguished through a variety of mechanisms most of which involve some form of photoionization of the sample material along the line of sight. Analysis of the case of liquid deuterium suggests that the reflectivity loss is caused by self-emission of radiation from the shock front. Details of this analysis will be described and extended to other cases such as quartz and fused silica to estimate the onset of reflectivity loss in the strong shock limit. [Preview Abstract] |
Thursday, November 1, 2012 4:48PM - 5:00PM |
UO5.00015: Development of UV Two-Frame Imaging Diagnostics for Investigation of Plasma Dynamics in Z Pinches at Stagnation Sara Altemara, Austin Anderson, Daniel Papp, Vladimir Ivanov Two-frame laser diagnostics with high spatial resolution at the wavelength of 266nm were developed for investigation of plasma dynamics in wire arrays at the stagnation stage on the 1 MA Zebra pulsed power generator. UV diagnostics is a significant advance compared to regular diagnostics at 532nm due to smaller adsorption and refraction in dense plasma. UV diagnostics at 266nm allows for unique observations of the internal structure of dense Z pinches hidden by trailing material [1]. Evolution of m=0 necks on the pinch and development of kink instability was observed with two-frame shadowgraphy. Fast plasma motion with a velocity greater than 100km/s was observed in the Z pinch at stagnation. Plasma motion in the stagnated Z pinches may be linked to generation of kinetic energy from magnetic energy. \\[4pt] [1] V. V. Ivanov, J.P. Chittenden, S. D. Altemara et al., Phys. Rev. Lett. 107, 165002 (2011) [Preview Abstract] |
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