Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session BO4: Compression and Burn I |
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Chair: Debra Callahan, Lawrence Livermore National Laboratory Room: Salon E |
Monday, October 27, 2014 9:30AM - 9:42AM |
BO4.00001: Measures of Alpha Heating in Inertial Confinement Fusion R. Betti, A.R. Christopherson Assessing the degree to which fusion alpha particles contribute to the fusion yield is essential to the understanding of the onset of the thermal runaway process of thermonuclear ignition. It is shown that in inertial confinement fusion, the yield enhancement resulting from alpha particle heating (before ignition occurs) depends on the fractional alpha energy or, equivalently, on the generalized Lawson criterion. Both the fractional alpha energy and the generalized Lawson criterion can be inferred from experimental observables. This result can be used to assess the performance of current ignition experiments at the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786. [Preview Abstract] |
Monday, October 27, 2014 9:42AM - 9:54AM |
BO4.00002: Alpha-Heating and a Burning Plasma State O.A. Hurricane, D.A. Callahan, D.T. Casey, E.L. Dewald, T.R. Dittrich, T. Doeppner, M.A. Barrios Garcia, S. Haan, D.E. Hinkel, L.F. Berzak Hopkins, O. Jones, A.L. Kritcher, S. Le Pape, T. Ma, A. MacPhee, J. Milovich, J. Moody, A. Pak, H.-S. Park, P.K. Patel, B.A. Remington, H.F. Robey, J. Salmonson, P.T. Springer, R. Tommasini L. R. BENEDETTI, D. BRADLEY, D. FITTINGHOFF, N. IZUMI, S. KHAN, R. TOWN (LLNL) G. GRIM, N. GULER, G. KYRALA, F. MERRILL, C. WILDE, P. VOLEGOV (LANL) High-foot implosions show net fuel gains and significant alpha-heating [Hurricane et al., \textit{Nature}, \textbf{506}, (2014)] using a per shot analysis of NIF data with a static reconstruction of the implosion energetics [e.g. Cerjan et al., \textit{PoP}, \textbf{20}, (2013)]. Inference of the alpha-heating contribution to the yield is made using a simulation database of DT implosions and the one-to-one correspondence of yield amplification and normalized Lawson criteria [Patel et al., APS-DPP, (2013); Patel et al. this conf.]. A dynamic semi-analytic model for the DT self-heating rate can be constructed that can more directly be used, with data, to determine the degree of bootstrapping occuring in implosions. Here we propose that the suite of high-foot data demonstrate a scaling of fusion yield performance versus energy absorbed that provides an alternate proof of significant alpha-particle self-heating. This analysis shows that recent high-foot implosions are alpha-heating dominated and thus have achieved a 'burning-plasma' state. [Preview Abstract] |
Monday, October 27, 2014 9:54AM - 10:06AM |
BO4.00003: Thin Shell, High Velocity, High-Foot ICF Implosions on the National Ignition Facility T. Ma, O.A. Hurricane, D.A. Callahan, M.A. Barrios, D.T. Casey, E.L. Dewald, T.R. Dittrich, T. Doeppner, D.E. Hinkel, L.F. Berzak Hopkins, S. Le Pape, A.G. MacPhee, A. Pak, H-S. Park, P.K. Patel, H.F. Robey, B.A. Remington, J.D. Salmonson, P.T. Springer, R. Tommasini Experiments have recently been conducted at the National Ignition Facility utilizing ICF capsule ablators that are 175 $\mu$m in thickness, 10\% thinner than the nominal thickness capsule used throughout the High-Foot and most of the National Ignition Campaigns. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Early results have shown good repeatability, with little to no hydrodynamic mix into the DT hot-spot, and $>$ 1/2 the yield coming from $\alpha$-particle self-heating. [Preview Abstract] |
Monday, October 27, 2014 10:06AM - 10:18AM |
BO4.00004: High-Performance Layered DT Capsule Implosions in Depleted Uranium Hohlraums on the NIF Tilo Doeppner, O.A. Hurricane, D.A. Callahan, D. Casey, T. Ma, H.-S. Park, L. Benedetti, E.L. Dewald, T.R. Dittrich, D. Fittinghoff, S. Haan, D. Hinkel, L. Berzak Hopkins, N. Izumi, A. Kritcher, S. Le Pape, A. Pak, P. Patel, H. Robey, B. Remington, J. Salmonson, P. Springer, K. Widmann, F. Merrill, C. Wilde We report on the first layered DT capsule implosions in depleted uranium (DU) hohlraums driven with a high-foot pulse shape. High-foot implosions have demonstrated improved resistance to hydrodynamic instabilities. [Hurricane et al., Nature {\bf 506}, 343 (2014)]. DU hohlraums provide a higher albedo and thus an increased drive equivalent to 25 TW extra laser power at the peak of the drive compared to Au hohlraums. Additionally, we observe an improved implosion shape closer to round which indicates enhanced drive from the waist. As a result, these first high-foot DU experiments achieved total neutron yields approaching 10$^{16}$ neutrons where more than 50\% of the yield was due to additional heating of alpha particles stopping in the DT fuel. [Preview Abstract] |
Monday, October 27, 2014 10:18AM - 10:30AM |
BO4.00005: Hot spot conditions achieved in DT implosions on the NIF P.K. Patel, D.A. Callahan, C. Cerjan, D.S. Clark, T.R. Dittrich, T. Doeppner, M.J. Edwards, S. Haan, D.E. Hinkel, L.F. Berzak Hopkins, O.A. Hurricane, A.L. Kritcher, J.D. Lindl, T. Ma, A.G. MacPhee, A.E. Pak, H.S. Park, H.F. Robey, J.D. Salmonson, B. Spears, P.T. Springer, N. Izumi, S. Khan We describe a 1D model that uses experimentally measured data to derive the thermodynamic conditions at stagnation of the hot spot, dense fuel, and ablator, in deuterium-tritium (DT) layered implosions on the National Ignition Facility (NIF). Neutron measurements---spectrally, spatially and temporally resolved---are used to infer the hot spot burn-averaged pressure, density, areal density, ion temperature, volume, and internal energy. X-ray spectral measurements are used to infer electron temperature, radiative energy loss, and the presence of ablator mix in the hot spot. In addition, we can calculate the fraction of alpha-particle energy trapped in the hot spot and, hence, estimate the degree of self-heating. Recent DT layered implosions using the high-foot design [Hurricane et al., Nature 506, 343 (2014)] have achieved areal densities and temperatures in the hot spot whereby a significant fraction of the internal energy at stagnation can be attributed to alpha-particle self-heating. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, October 27, 2014 10:30AM - 10:42AM |
BO4.00006: Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums N.B. Meezan, L.F. Berzak Hopkins, S. Le Pape, S.F. Khan, A.E. Pak, L. Divol, D.D. Ho, T. Ma, T. Doeppner, J.R. Rygg, J.E. Field, O.S. Jones, J.L. Milovich, B.J. Kozioziemski, A.V. Hamza, A.J. MacKinnon, W.W. Hsing, M.J. Edwards High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations $< 10$ ns. A series of experiments in 2013 on the National Ignition Facility culminated in a DT layered implosion driven by a 6.5 ns, 2-shock laser pulse. This talk describes these experiments and comparisons with the design code HYDRA. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape; however, other diagnostics suggested an asymmetric compressed fuel layer. The streak camera-based SPIDER diagnostic showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of a low-temperature hot spot. Changes to the laser pulse-shape and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot-spot and a thermonuclear yield of $1.8 \times 10^{15}$ neutrons. [Preview Abstract] |
Monday, October 27, 2014 10:42AM - 10:54AM |
BO4.00007: Cryogenic Implosion Performance Using High-Purity Deuterium--Tritium Fuel T.C. Sangster, V.N. Goncharov, P.B. Radha, R. Earley, R. Epstein, C.J. Forrest, D.H. Froula, V.Yu. Glebov, S.X. Hu, I.V. Igumenshchev, F.J. Marshall, P.W. McKenty, W.T. Shmayda, M.J. Shoup III, D.T. Michel, C. Stoeckl, W. Seka, J.A. Frenje, M. Gatu Johnson Demonstrating hydrodynamic equivalence between symmetric implosions on OMEGA and National Ignition Facility ignition designs will require a number of facility enhancements that include dynamic bandwidth reduction, a set of higher-order super-Gaussian phase plates, high-spatial-resolution gated-core imaging, high-bandwidth neutron burnwidth measurements, improved power balance, and contaminant-free deuterium--tritium (DT) fuel. The historic DT fuel supply was contaminated with $\sim 6\mbox{\thinspace atm}\% $ of $^{\mathrm{1}}$H, leading to significant fractionation of the fuel during the layering process (the triple points of H:D and H:T are significantly colder than DD, DT, and TT). The fractionation leads to a drop in the potential yield because the D and T number densities are lower in the void than they would be with a pure-DT mixture). An isotope separation system has been developed to remove the $^{\mathrm{1}}$H from the DT fuel supply. This talk will discuss the first results with the purified fuel, conclusions from recent implosions to test cross-beam energy transfer mitigation, and the status of the remaining facility enhancements. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Monday, October 27, 2014 10:54AM - 11:06AM |
BO4.00008: Early time hot electron generation and deposition at the capsule in indirect drive ICF implosions on the National Ignition Facility Eduard Dewald, Arthur Pak, Jose Milovich, Benjamin Bachmann, Matthias Hohenberger, Felicie Albert, Harry Robey, Cliff Thomas, Laurent Divol, Tilo Doeppner, Andrew Mackinnon, Nathan Meezan, Debbie Callahan, Denise Hinkel, Omar Hurricane, Otto Landen, John Edwards In indirect drive ICF experiments [1] on the National Ignition Facility (NIF), hot electrons generated by laser plasma instabilities can preheat the deuterium-tritium (DT) capsule, compromising ignition. While below detection limit, the early time (picket) allowable hot electrons in low adiabat implosions [1] are $\sim$ 1J in electrons with \textgreater 170 keV energy compared to 1000 J during the late time peak laser power [2]. At the same time, High Foot implosions [3] that demonstrated fuel-ablator mix mitigation and improved yield, have also shown picket hot electrons that can be comparable to allowable threshold. High Foot Re-emit experiments for tuning the picket radiation symmetry also infer the fraction and uniformity of hot electrons reaching the capsule by hard x-ray (50 keV) imaging combined with 40-300 keV spectra [2]. Their scalings with laser and plasma conditions are discussed. \\[4pt] [1] M. J. Edwards et al, \textit{Phys.} \textit{Plasmas} \textbf{20}, 070501 (2013).\\[0pt] [2] E.L. Dewald, \textit{et. al.,} \textit{Rev. Sci. Instrum.} \textbf{81}, 10D938 (2010).\\[0pt] [3] O. Hurricane, \textit{et. al,} \textit{Nature} \textbf{506, }343 (2014). [Preview Abstract] |
(Author Not Attending)
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BO4.00009: The measurement of cold fuel adiabat from neutron images of ICF experiments at NIF Frank Merrill, Baolian Cheng, Christopher Danly, Nevzat Guler, Carl Wilde, Petr Volegov, David Fittinghoff Dozens of laser driven inertially confined fusion (ICF) experiments have been performed at NIF over the past several years to investigate the potential for ignition in indirect ablative compression of plastic (CH) capsules containing DT ice layers, initially filled with DT gas. In these experiments, the gas inside of the DT ice layer is compressed and heated by the convergent implosion to reach temperatures of $\sim$ 5 keV. This hot-spot is surrounded by the colder fuel that was initially in the DT ice layer. Fusion in the hot spot generates 10$^{14}$-10$^{15}$ 14 MeV neutrons and $\sim$ 5{\%} of these are scattered in the surrounding cold fuel to energies of 6-12 MeV. Images are formed with 14 MeV neutrons and 6-12 MeV neutrons, providing a measure of the hot-spot and cold fuel size and shape, respectively. One dimensional analytic models of these implosions [2] show that the ratio of the hotspot diameter to the cold fuel diameter provides a measure of the adiabat on which the cold fuel is compressed. The most recent neutron imaging data, which has been analyzed to extract this information, will be presented to show relative changes of the fuel compression adiabat from ICF experiments performed at NIF. \\[4pt] [1] F. E. Merrill, et al., Rev. Sci. Instrum.~\textbf{83}, 10D317\\[0pt] [2] B. Cheng, et al., Phys. Rev. E~\textbf{88}, 041101 [Preview Abstract] |
Monday, October 27, 2014 11:18AM - 11:30AM |
BO4.00010: Direct measurement of the effect of early time hot electron preheat on a deuterium-tritium cryogenic ice layer James Ross, Harry Robey, John Moody, Peter Celliers, Laurent Divol, Laura Berzak-Hopkins, Sebastien Le Pape, Matthias Hohenberger, Joe Ralph, Otto Landen, John Edwards The direct effect of early time supra-thermal electron preheat on a deuterium-tritium (DT) cryogenic ice layer has been measured for the first time in indirect drive inertial confinement fusion experiments on the National Ignition Facility. Controlled changes in the early-time laser power are used to vary the hot electron (E $>$ 170 keV) energy over the range of $<$1 J to 27 J. At the 27 J energy level the DT ice layer was measured to expand from the initial thickness of 71.5 $\mu$m to a thickness of 82.4 $\mu$m prior to the breakout of the first laser generated shock using the layered keyhole platform. There was no measurable expansion of the DT ice layer when the hot electron level was 5 J or less. Hot electron levels $>$5 J increase the entropy of the fuel and can significantly degrade the quality of the implosion. The experimental results are compared to post shot simulations. [Preview Abstract] |
Monday, October 27, 2014 11:30AM - 11:42AM |
BO4.00011: A model for degradation of indirectly driven ICF implosions by supra-thermal electron preheat H.F. Robey, M.D. Rosen, D.S. Clark, E.L. Dewald, S.W. Haan, A.L. Kritcher, W. Kruer, J.D. Lindl, M.M. Marinak, J.D. Moody, M. Patel, P.K. Patel, J.S. Ross, J.D. Salmonson, P.T. Springer, C.R. Weber, D. Shvarts, M. Hohenberger, B. Afeyan, D.S. Montgomery In recent years, significant progress has been made in the performance of indirectly driven inertial confinement fusion (ICF) implosions performed on the National Ignition Facility (NIF). Experimental results to date, however, have fallen short of the predicted neutron yield, the expected compression of the deuterium-tritium (DT) fuel layer, and the pressure and density achieved in the central hot spot. A numerical model is presented for the degradation of implosion performance due to preheat of the DT fuel layer by supra-thermal electrons. The model is benchmarked by comparison with focused experiments, which directly measure the expansion of a DT ice layer caused by preheat from a controlled, well-characterized flux of supra-thermal electrons. The same model applied to ignition implosions shows improved agreement with a wide range of experimental observables, and may help to provide an explanation for many of the features observed in ignition implosions on the NIF. [Preview Abstract] |
Monday, October 27, 2014 11:42AM - 11:54AM |
BO4.00012: Antipodal neutron time of flight (nToF) detectors more than double their diagnostic value Joseph Kilkenny, James Knauer, Joseph Caggiano, Mark Eckart, Robert Hatarik, David Munro, Daniel Sayre, Brian Spears Moments of the neutron-velocity distribution give unique insights to the quality of an inertial confinement fusion (ICF) implosion. The three, 20m distance nToF detectors on the NIF are being augmented by adding an antipodal detector to each of them. Antipodal pairs of detectors increase the sampling of imploded DT ice but also allow an accurate measurement of the areal density of the odd modes of the compressed ice from the un-scattered yield ratio, and with the two measurements distinguishing center of mass drift velocity from the thermodynamic ion temperature. [Preview Abstract] |
Monday, October 27, 2014 11:54AM - 12:06PM |
BO4.00013: Angular Distribution of Ion-Temperature Measurements for Non-Stagnating Inertial Confinement Fusion Implosions J.P. Knauer, J.A. Caggiano, R. Hatarik, D. Munro, D.B. Sayre, B.K. Spears, M. Gatu Johnson, J.A. Frenje Moments of the neutron-velocity distribution give unique insights to the quality of an inertial confinement fusion (ICF) implosion. The second moment (width) has been used to measure the ion temperature of an ICF core. An analysis is presented that shows how the velocity distribution of an ICF core that does not stagnate changes the measured width with angle. Neutron data from implosions at the National Ignition Facility provide five DT peak width and three DD peak width measurements. These data are used to determine thermal temperatures for DD and DT fusion and the direction and magnitude of a ``shear''-like motion in the core. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Monday, October 27, 2014 12:06PM - 12:18PM |
BO4.00014: ABSTRACT WITHDRAWN |
Monday, October 27, 2014 12:18PM - 12:30PM |
BO4.00015: Inference of total DT fusion neutron yield from prompt gamma-ray measurements at the National Ignition Facility J.A. Church, H.W. Herrmann, W. Stoeffl, J.A. Caggiano, C. Cerjan, D. Sayre Prompt D-T fusion gamma-rays measured at the National Ignition Facility (NIF) with the Gamma-ray Reaction History detector (GRH) have been used recently to infer the total DT fusion neutron yield of inertial confinement fusion (ICF) implosions. DT fusion produces energetic gamma-rays (16.75 MeV) with a small branching ratio of approximately (4.2 $+$/- 2.0)e-5 $\gamma $/n. While the large error bar precludes use of the branching ratio for an accurate yield determination, the gamma-rays themselves provide the most unperturbed measure of fusion burn and can be used for such a purpose. A cross-calibration for the DT fusion gamma-ray to neutron signal is obtained via low areal density exploding pusher implosions which have mostly unperturbed neutron and gamma-ray signals. The calibration is then used to infer total DT neutron yield from gamma-ray measurements on high areal-density, cryogenically layered implosions in which neutrons are heavily down-scattered (up to 30{\%}). Furthermore, the difference between the gamma-ray inferred total DT yield and the primary neutron yield (unscattered neutrons) can be used to estimate the total down-scatter fraction. Error analysis and comparison of yield values will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, LLNL-ABS-657694. [Preview Abstract] |
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