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Adiabat-shaping in indirect drive inertial confinement fusion (2015)

K. L. Baker, H. F. Robey, J. L. Milovich, O. S. Jones, V. A. Smalyuk, D. T. Casey, A. G. Mac; Phee, A. Pak, P. M. Celliers, D. S. Clark, O. L. Landen, J. L. Peterson, L. F. Berzak-Hopkins, C. R. Weber, S. W. Haan, T. D. Döppner, S. Dixit, E. Giraldez, A. V. Hamza, K. S. Jancaitis, J. J. Kroll, K. N. Lafortune, B. J. Mac; Gowan, J. D. Moody, A. Nikroo and C. C. Widmayer

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2015-05-06

Description: Adiabat-shaping techniques were investigated in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator. This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. These experiments were conducted using the keyhole experimental platform for both three and four shock laser pulses. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses. This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. This approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.

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Design of indirectly driven, high-compression Inertial Confinement Fusion implosions with improved hydrodynamic stability using a 4-shock adiabat-shaped drive (2015)

J. L. Milovich, H. F. Robey, D. S. Clark, K. L. Baker, D. T. Casey, C. Cerjan, J. Field, A. G. Mac; Phee, A. Pak, P. K. Patel, J. L. Peterson, V. A. Smalyuk and C. R. Weber

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2015-12-11

Description: Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al ., Phys. Plasmas 20 , 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm 2 , but with significantly lower total neutron yields (between 1.5 × 10 14 and 5.5 × 10 14 ) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the “high-foot” experiments [O. A. Hurricane et al ., Nature 506 , 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3–10× improvement in the neutron yield (〉40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of 〉1 g/cm 2 . Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.

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Performance of indirectly driven capsule implosions on the National Ignition Facility using adiabat-shaping (2016)

H. F. Robey, V. A. Smalyuk, J. L. Milovich, T. Döppner, D. T. Casey, K. L. Baker, J. L. Peterson, B. Bachmann, L. F. Berzak Hopkins, E. Bond, J. A. Caggiano, D. A. Callahan, P. M. Celliers, C. Cerjan, D. S. Clark, S. N. Dixit, M. J. Edwards, N. Gharibyan, S. W. Haan, B. A. Hammel, A. V. Hamza, R. Hatarik, O. A. Hurricane, K. S. Jancaitis, O. S. Jones, G. D. Kerbel, J. J. Kroll, K. N. Lafortune, O. L. Landen, T. Ma, M. M. Marinak, B. J. Mac; Gowan, A. G. Mac; Phee, A. Pak, M. Patel, P. K. Patel, L. J. Perkins, D. B. Sayre, S. M. Sepke, B. K. Spears, R. Tommasini, C. R. Weber, C. C. Widmayer, C. Yeamans, E. Giraldez, D. Hoover, A. Nikroo, M. Hohenberger and M. Gatu Johnson

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2016-04-02

Description: A series of indirectly driven capsule implosions has been performed on the National Ignition Facility to assess the relative contributions of ablation-front instability growth vs. fuel compression on implosion performance. Laser pulse shapes for both low and high-foot pulses were modified to vary ablation-front growth and fuel adiabat, separately and controllably. Three principal conclusions are drawn from this study: (1) It is shown that reducing ablation-front instability growth in low-foot implosions results in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. (2) It is shown that reducing the fuel adiabat in high-foot implosions results in a significant (36%) increase in fuel compression together with a small (10%) increase in neutron yield. (3) Increased electron preheat at higher laser power in high-foot implosions, however, appears to offset the gain in compression achieved by adiabat-shaping at lower power. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results.

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First results of radiation-driven, layered deuterium-tritium implosions with a 3-shock adiabat-shaped drive at the National Ignition Facility (2015)

V. A. Smalyuk, H. F. Robey, T. Döppner, O. S. Jones, J. L. Milovich, B. Bachmann, K. L. Baker, L. F. Berzak Hopkins, E. Bond, D. A. Callahan, D. T. Casey, P. M. Celliers, C. Cerjan, D. S. Clark, S. N. Dixit, M. J. Edwards, E. Giraldez, S. W. Haan, A. V. Hamza, M. Hohenberger, D. Hoover, O. A. Hurricane, K. S. Jancaitis, J. J. Kroll, K. N. Lafortune, O. L. Landen, B. J. Mac; Gowan, A. G. Mac; Phee, A. Nikroo, A. Pak, P. K. Patel, J. L. Peterson, C. R. Weber, C. C. Widmayer and C. Yeamans

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2015-08-28

Description: Radiation-driven, layered deuterium-tritium plastic capsule implosions were carried out using a new, 3-shock “adiabat-shaped” drive on the National Ignition Facility. The purpose of adiabat shaping is to use a stronger first shock, reducing hydrodynamic instability growth in the ablator. The shock can decay before reaching the deuterium-tritium fuel leaving it on a low adiabat and allowing higher fuel compression. The fuel areal density was improved by ∼25% with this new drive compared to similar “high-foot” implosions, while neutron yield was improved by more than 4 times, compared to “low-foot” implosions driven at the same compression and implosion velocity.

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Electron plasma dynamics during autoresonant excitation of the diocotron mode (2015)

C. J. Baker, J. R. Danielson, N. C. Hurst and C. M. Surko

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2015-02-04

Description: Chirped-frequency autoresonant excitation of the diocotron mode is used to move electron plasmas confined in a Penning-Malmberg trap across the magnetic field for advanced plasma and antimatter applications. Plasmas of 10 8 electrons, with radii small compared to that of the confining electrodes, can be moved from the magnetic axis to ≥90% of the electrode radius with near unit efficiency and reliable angular positioning. Translations of ≥70% of the wall radius are possible for a wider range of plasma parameters. Details of this process, including phase and displacement oscillations in the plasma response and plasma expansion, are discussed, as well as possible extensions of the technique.

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Competing single-particle and collective behavior in ^{71}Se (2012)

A. R. Howe, R. A. Haring-Kaye, J. Döring, N. R. Baker, S. J. Kuhn, S. L. Tabor, S. R. Arora, J. K. Bruckman, and C. R. Hoffman

American Physical Society (APS)

In: Physical Review C

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Publication Date: 2012-07-31

Description: Author(s): A. R. Howe, R. A. Haring-Kaye, J. Döring, N. R. Baker, S. J. Kuhn, S. L. Tabor, S. R. Arora, J. K. Bruckman, and C. R. Hoffman The high-spin decay of 71 Se was studied using the 54 Fe( 23 Na, α p n ) reaction at 80 MeV and the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. Based on prompt γ - γ coincidences measured in the experiment, the known level schem... [Phys. Rev. C 86, 014328] Published Mon Jul 30, 2012

Keywords: Nuclear Structure

Print ISSN: 0556-2813

Electronic ISSN: 1089-490X

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Transition strengths and the role of the f_{7/2} orbital in ^{71} As (2011)

R. A. Kaye, C. J. Drover, S. L. Tabor, J. Döring, Y.-C. Yang, Y. Sun, S. R. Arora, N. R. Baker, J. K. Bruckman, T. A. Hinners, C. R. Hoffman, and S. Lee

American Physical Society (APS)

In: Physical Review C

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Publication Date: 2011-04-26

Description: Author(s): R. A. Kaye, C. J. Drover, S. L. Tabor, J. Döring, Y.-C. Yang, Y. Sun, S. R. Arora, N. R. Baker, J. K. Bruckman, T. A. Hinners, C. R. Hoffman, and S. Lee High-spin states in ^{71} As were studied using the ^{54} Fe(^{23} Na,α2p) reaction at 80 MeV. Prompt γ-γ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. The existing high-spin level... [Phys. Rev. C 83, 044316] Published Mon Apr 25, 2011

Keywords: Nuclear Structure

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Single-neutron excitations in ^{18}N (2013)

C. R. Hoffman, M. Albers, M. Alcorta, S. Almaraz-Calderon, B. B. Back, S. I. Baker, S. Bedoor, P. F. Bertone, B. P. Kay, J. C. Lighthall, T. Palchan, R. C. Pardo, G. Perdikakis, K. E. Rehm, A. M. Rogers, D. Santiago-Gonzalez, Cenxi Yuan, and J. P. Schiffer

American Physical Society (APS)

In: Physical Review C

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Publication Date: 2013-10-16

Description: Author(s): C. R. Hoffman, M. Albers, M. Alcorta, S. Almaraz-Calderon, B. B. Back, S. I. Baker, S. Bedoor, P. F. Bertone, B. P. Kay, J. C. Lighthall, T. Palchan, R. C. Pardo, G. Perdikakis, K. E. Rehm, A. M. Rogers, D. Santiago-Gonzalez, Cenxi Yuan, and J. P. Schiffer States in 18 N have been populated in the neutron-adding ( d , p ) reaction on the short-lived 17 N beam. Previously observed levels, found in this work at excitation energies of 0.12(1) MeV and 0.74(1) MeV, have been identified as those expected from a proton 0 p 1/2 hole coupled to the 19 O 5/2 + ground sta... [Phys. Rev. C 88, 044317] Published Tue Oct 15, 2013

Keywords: Nuclear Structure

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Single-neutron energies outside ^{136}Xe (2011)

B. P. Kay, J. P. Schiffer, S. J. Freeman, C. R. Hoffman, B. B. Back, S. I. Baker, S. Bedoor, T. Bloxham, J. A. Clark, C. M. Deibel, A. M. Howard, J. C. Lighthall, S. T. Marley, K. E. Rehm, D. K. Sharp, D. V. Shetty, J. S. Thomas, and A. H. Wuosmaa

American Physical Society (APS)

In: Physical Review C

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Publication Date: 2011-08-30

Description: Author(s): B. P. Kay, J. P. Schiffer, S. J. Freeman, C. R. Hoffman, B. B. Back, S. I. Baker, S. Bedoor, T. Bloxham, J. A. Clark, C. M. Deibel, A. M. Howard, J. C. Lighthall, S. T. Marley, K. E. Rehm, D. K. Sharp, D. V. Shetty, J. S. Thomas, and A. H. Wuosmaa The single-neutron properties of the N =83 nucleus 137 Xe have been studied using the 136 Xe( d , p ) reaction in inverse kinematics at a beam energy of 10 MeV/u. The helical-orbit spectrometer, HELIOS, at Argonne National Laboratory was used to analyze the outgoing protons, achieving an excitation-energy ... [Phys. Rev. C 84, 024325] Published Mon Aug 29, 2011

Keywords: Nuclear Structure

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Early time implosion symmetry from two-axis shock-timing measurements on indirect drive NIF experiments (2014)

J. D. Moody, H. F. Robey, P. M. Celliers, D. H. Munro, D. A. Barker, K. L. Baker, T. Döppner, N. L. Hash, L. Berzak Hopkins, K. La; Fortune, O. L. Landen, S. Le; Pape, B. J. Mac; Gowan, J. E. Ralph, J. S. Ross, C. Widmayer, A. Nikroo, E. Giraldez and T. Boehly

American Institute of Physics (AIP)

In: Physics of Plasmas

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Publication Date: 2014-09-04

Description: An innovative technique has been developed and used to measure the shock propagation speed along two orthogonal axes in an inertial confinement fusion indirect drive implosion target. This development builds on an existing target and diagnostic platform for measuring the shock propagation along a single axis. A 0.4 mm square aluminum mirror is installed in the ablator capsule which adds a second orthogonal view of the x-ray-driven shock speeds. The new technique adds capability for symmetry control along two directions of the shocks launched in the ablator by the laser-generated hohlraum x-ray flux. Laser power adjustments in four different azimuthal cones based on the results of this measurement can reduce time-dependent symmetry swings during the implosion. Analysis of a large data set provides experimental sensitivities of the shock parameters to the overall laser delivery and in some cases shows the effects of laser asymmetries on the pole and equator shock measurements.

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