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Regan SP, Epstein R, Hammel BA, Suter LJ, Scott HA, Barrios MA, Bradley DK, Callahan DA, Cerjan C, Collins GW, Dixit SN, Döppner T, Edwards MJ, Farley DR, Fournier KB, Glenn S, Glenzer SH, Golovkin IE, Haan SW, Hamza A, Hicks DG, Izumi N, Jones OS, Kilkenny JD, Kline JL, Kyrala GA, Landen OL, Ma T, MacFarlane JJ, MacKinnon AJ, Mancini RC, McCrory RL, Meezan NB, Meyerhofer DD, Nikroo A, Park HS, Ralph J, Remington BA, Sangster TC, Smalyuk VA, Springer PT, Town RPJ. Hot-spot mix in ignition-scale inertial confinement fusion targets. PHYSICAL REVIEW LETTERS 2013; 111:045001. [PMID: 23931375 DOI: 10.1103/physrevlett.111.045001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 04/04/2013] [Indexed: 06/02/2023]
Abstract
Mixing of plastic ablator material, doped with Cu and Ge dopants, deep into the hot spot of ignition-scale inertial confinement fusion implosions by hydrodynamic instabilities is diagnosed with x-ray spectroscopy on the National Ignition Facility. The amount of hot-spot mix mass is determined from the absolute brightness of the emergent Cu and Ge K-shell emission. The Cu and Ge dopants placed at different radial locations in the plastic ablator show the ablation-front hydrodynamic instability is primarily responsible for hot-spot mix. Low neutron yields and hot-spot mix mass between 34(-13,+50) ng and 4000(-2970,+17 160) ng are observed.
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Hurricane OA, Smalyuk VA, Raman K, Schilling O, Hansen JF, Langstaff G, Martinez D, Park HS, Remington BA, Robey HF, Greenough JA, Wallace R, Di Stefano CA, Drake RP, Marion D, Krauland CM, Kuranz CC. Validation of a turbulent Kelvin-Helmholtz shear layer model using a high-energy-density OMEGA laser experiment. PHYSICAL REVIEW LETTERS 2012; 109:155004. [PMID: 23102319 DOI: 10.1103/physrevlett.109.155004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Indexed: 06/01/2023]
Abstract
Following the successful demonstration of an OMEGA laser-driven platform for generating and studying nearly two-dimensional unstable plasma shear layers [Hurricane et al., Phys. Plasmas 16, 056305 (2009); Harding et al., Phys. Rev. Lett. 103, 045005 (2009)], this Letter reports on the first quantitative measurement of turbulent mixing in a high-energy-density plasma. As a blast wave moves parallel to an unperturbed interface between a low-density foam and a high-density plastic, baroclinic vorticity is deposited at the interface and a Kelvin-Helmholtz instability-driven turbulent mixing layer is created in the postshock flow due to surface roughness. The spatial scale and density profile of the turbulent layer are diagnosed using x-ray radiography with sufficiently small uncertainty so that the data can be used to ~0.17 μm) in the postshock plasma flow are consistent with an "inertial subrange," within which a Kolmogorov turbulent energy cascade can be active. An illustration of comparing the data set with the predictions of a two-equation turbulence model in the ares radiation hydrodynamics code is also presented.
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Koch JA, Stewart RE, Beiersdorfer P, Shepherd R, Schneider MB, Miles AR, Scott HA, Smalyuk VA, Hsing WW. High-resolution spectroscopy for Doppler-broadening ion temperature measurements of implosions at the National Ignition Facility. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E127. [PMID: 23126948 DOI: 10.1063/1.4731747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Future implosion experiments at the national ignition facility (NIF) will endeavor to simultaneously measure electron and ion temperatures with temporal and spatial resolution in order to explore non-equilibrium temperature distributions and their relaxation toward equilibrium. In anticipation of these experiments, and with understanding of the constraints of the NIF facility environment, we have explored the use of Doppler broadening of mid-Z dopant emission lines, such as krypton He-α at 13 keV, as a diagnostic of time- and potentially space-resolved ion temperature. We have investigated a number of options analytically and with numerical raytracing, and we have identified several promising candidate spectrometer designs that meet the expected requirements of spectral and temporal resolution and data signal-to-noise ratio for gas-filled exploding pusher implosions, while providing maximum flexibility for use on a variety of experiments that potentially include burning plasma.
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Ma T, Izumi N, Tommasini R, Bradley DK, Bell P, Cerjan CJ, Dixit S, Döppner T, Jones O, Kline JL, Kyrala G, Landen OL, LePape S, Mackinnon AJ, Park HS, Patel PK, Prasad RR, Ralph J, Regan SP, Smalyuk VA, Springer PT, Suter L, Town RPJ, Weber SV, Glenzer SH. Imaging of high-energy x-ray emission from cryogenic thermonuclear fuel implosions on the NIF. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E115. [PMID: 23126937 DOI: 10.1063/1.4733313] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide broadband time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered implosions. This diagnostic measures the temperature- and density-sensitive bremsstrahlung emission and provides estimates of hot spot mass, mix mass, and pressure.
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Glenn SM, Benedetti LR, Bradley DK, Hammel BA, Izumi N, Khan SF, Kyrala GA, Ma T, Milovich JL, Pak AE, Smalyuk VA, Tommasini R, Town RP. Extracting core shape from x-ray images at the National Ignition Facility. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E519. [PMID: 23127026 DOI: 10.1063/1.4731743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Measuring the shape of implosions is critical to inertial confinement fusion experiments at the National Ignition Facility. We have developed techniques that have proven successful for extracting shape information from images of x-ray self-emission recorded by a variety of diagnostic instruments for both DT-filled targets and low-yield surrogates. These key results help determine optimal laser and target parameters leading to ignition. We have compensated for instrumental response and have employed a variety of image processing methods to remove artifacts from the images while retaining salient features. The implosion shape has been characterized by decomposing intensity contours into Fourier and Legendre modes for different lines of sight. We also describe procedures we have developed for estimating uncertainties in these measurements.
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Benedetti LR, Bell PM, Bradley DK, Brown CG, Glenn SM, Heeter R, Holder JP, Izumi N, Khan SF, Lacaille G, Simanovskaia N, Smalyuk VA, Thomas R. Crosstalk in x-ray framing cameras: Effect on voltage, gain, and timing (invited). THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:10E135. [PMID: 23126956 DOI: 10.1063/1.4740524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present evidence that electromagnetic crosstalk between independent strips in gated x-ray framing cameras can affect relative gains by up to an order of magnitude and gate arrival times up to tens of picoseconds when strip separation times are less then ∼1 ns. Crosstalk is observed by multiple methods, and it is confirmed by direct measurements of voltage on the active surface of the detector and also by indirect voltage monitors in routine operation. The voltage measurements confirm that crosstalk is produced not only in the active regions of the microchannel plate, but also along the entire input path of the voltage pulses.
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Manuel MJE, Li CK, Séguin FH, Frenje J, Casey DT, Petrasso RD, Hu SX, Betti R, Hager JD, Meyerhofer DD, Smalyuk VA. First measurements of Rayleigh-Taylor-induced magnetic fields in laser-produced plasmas. PHYSICAL REVIEW LETTERS 2012; 108:255006. [PMID: 23004611 DOI: 10.1103/physrevlett.108.255006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Indexed: 06/01/2023]
Abstract
The first experimental demonstration of Rayleigh-Taylor-induced magnetic fields due to the Biermann battery effect has been made. Experiments with laser-irradiated plastic foils were performed to investigate these illusive fields using a monoenergetic proton radiography system. Path-integrated B field strength measurements were inferred from radiographs and found to increase from 10 to 100 T μm during the linear growth phase for 120 μm perturbations. Proton fluence modulations were corrected for Coulomb scattering using measured areal density profiles from x-ray radiographs.
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Hu SX, Fiksel G, Goncharov VN, Skupsky S, Meyerhofer DD, Smalyuk VA. Mitigating laser imprint in direct-drive inertial confinement fusion implosions with high-Z dopants. PHYSICAL REVIEW LETTERS 2012; 108:195003. [PMID: 23003051 DOI: 10.1103/physrevlett.108.195003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Indexed: 06/01/2023]
Abstract
Nonuniformities seeded by both long- and short-wavelength laser perturbations can grow via Rayleigh-Taylor (RT) instability in direct-drive inertial confinement fusion, leading to performance reduction in low-adiabat implosions. To mitigate the effect of laser imprinting on target performance, spherical RT experiments have been performed on OMEGA using Si- or Ge-doped plastic targets in a cone-in-shell configuration. Compared to a pure plastic target, radiation preheating from these high-Z dopants (Si/Ge) increases the ablation velocity and the standoff distance between the ablation front and laser-deposition region, thereby reducing both the imprinting efficiency and the RT growth rate. Experiments showed a factor of 2-3 reduction in the laser-imprinting efficiency and a reduced RT growth rate, leading to significant (3-5 times) reduction in the σ(rms) of shell ρR modulation for Si- or Ge-doped targets. These features are reproduced by radiation-hydrodynamics simulations using the two-dimensional hydrocode DRACO.
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Smalyuk VA, Betti R, Delettrez JA, Glebov VY, Meyerhofer DD, Radha PB, Regan SP, Sangster TC, Sanz J, Seka W, Stoeckl C, Yaakobi B, Frenje JA, Li CK, Petrasso RD, Séguin FH. Implosion experiments using glass ablators for direct-drive inertial confinement fusion. PHYSICAL REVIEW LETTERS 2010; 104:165002. [PMID: 20482057 DOI: 10.1103/physrevlett.104.165002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Indexed: 05/29/2023]
Abstract
Direct-drive implosions with 20-microm-thick glass shells were conducted on the Omega Laser Facility to test the performance of high-Z glass ablators for direct-drive, inertial confinement fusion. The x-ray signal caused by hot electrons generated by two-plasmon-decay instability was reduced by more than approximately 40x and hot-electron temperature by approximately 2x in the glass compared to plastic ablators at ignition-relevant drive intensities of approximately 1x10(15) W/cm2, suggesting reduced target preheat. The measured absorption and compression were close to 1D predictions. The measured soft x-ray production in the spectral range of approximately 2 to 4 keV was approximately 2x to 3x lower than 1D predictions, indicating that the shell preheat caused by soft x-rays is less than predicted. A direct-drive-ignition design based on glass ablators is introduced.
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Smalyuk VA, Hu SX, Hager JD, Delettrez JA, Meyerhofer DD, Sangster TC, Shvarts D. Rayleigh-Taylor growth measurements in the acceleration phase of spherical implosions on OMEGA. PHYSICAL REVIEW LETTERS 2009; 103:105001. [PMID: 19792320 DOI: 10.1103/physrevlett.103.105001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Indexed: 05/28/2023]
Abstract
The Rayleigh-Taylor (RT) growth of 3D broadband nonuniformities was measured using x-ray radiography in spherical plastic shells accelerated by laser light at an intensity of approximately 2 x 10(14) W/cm(2). The 20- and 24-microm-thick spherical shells were imploded with 54 beams on the OMEGA laser system. The shells contained diagnostic openings for backlighter x rays used to image shell modulations. The measured shell trajectories and modulation RT growth were in fair agreement with 2D hydro simulations during the acceleration phase of the implosions with convergence ratios of up to approximately 2.2. Since the ignition designs rely on these simulations, improvements in the numerical codes will be implemented to achieve better agreement with experiments.
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Marshall FJ, McKenty PW, Delettrez JA, Epstein R, Knauer JP, Smalyuk VA, Frenje JA, Li CK, Petrasso RD, Séguin FH, Mancini RC. Plasma-density determination from x-ray radiography of laser-driven spherical implosions. PHYSICAL REVIEW LETTERS 2009; 102:185004. [PMID: 19518881 DOI: 10.1103/physrevlett.102.185004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Indexed: 05/27/2023]
Abstract
The fuel layer density of an imploding laser-driven spherical shell is inferred from framed x-ray radiographs. The density distribution is determined by using Abel inversion to compute the radial distribution of the opacity kappa from the observed optical depth tau. With the additional assumption of the mass of the remaining fuel, the absolute density distribution is determined. This is demonstrated on the OMEGA laser system with two x-ray backlighters of different mean energies that lead to the same inferred density distribution independent of backlighter energy.
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Nagayama T, Mancini RC, Florido R, Tommasini R, Koch JA, Delettrez JA, Regan SP, Smalyuk VA, Welser-Sherrill LA, Golovkin IE. Comparison of genetic-algorithm and emissivity-ratio analyses of image data from OMEGA implosion cores. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:10E921. [PMID: 19044576 DOI: 10.1063/1.2966370] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Detailed analysis of x-ray narrow-band images from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the temperature spatial structure in the core at the collapse of the implosion. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which multiple narrow-band images were recorded with a multimonochromatic x-ray imaging instrument. The temperature spatial structure is investigated by using the sensitivity of the Ly beta/He beta line emissivity ratio to the temperature. Three analysis methods that consider the argon He beta and Ly beta image data are discussed and the results compared. The methods are based on a ratio of image intensities, ratio of Abel-inverted emissivities, and a search and reconstruction technique driven by a Pareto genetic algorithm.
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Florido R, Nagayama T, Mancini RC, Tommasini R, Delettrez JA, Regan SP, Smalyuk VA, Rodríguez R, Gil JM. Analysis of time-resolved argon line spectra from OMEGA direct-drive implosions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:10E310. [PMID: 19044472 DOI: 10.1063/1.2965779] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We discuss the observation and data analysis of argon K-shell line spectra from argon-doped deuterium-filled OMEGA direct-drive implosion cores based on data recorded with two streaked crystal spectrometers. The targets were 870 microm in diameter, 27 microm wall thickness plastic shells filled with 20 atm of deuterium gas, and a tracer amount of argon for diagnostic purposes. The argon K-shell line spectrum is primarily emitted at the collapse of the implosion and its analysis provides a spectroscopic diagnostic of the core implosion conditions. The observed spectra includes the He alpha, Ly alpha, He beta, He gamma, Ly beta, and Ly gamma line emissions and their associated He- and Li-like satellites thus covering a broad photon energy range from 3100 to 4200 eV with a spectral resolution power of approximately 500. The data analysis relies on detailed atomic and spectral models that take into account nonequilibrium collisional-radiative atomic kinetics, Stark-broadened line shapes, and radiation transport calculations.
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Hu SX, Smalyuk VA, Goncharov VN, Skupsky S, Sangster TC, Meyerhofer DD, Shvarts D. Validation of thermal-transport modeling with direct-drive, planar-foil acceleration experiments on OMEGA. PHYSICAL REVIEW LETTERS 2008; 101:055002. [PMID: 18764399 DOI: 10.1103/physrevlett.101.055002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Indexed: 05/26/2023]
Abstract
We present for the first time the experimental validation of the nonlocal thermal-transport model for a National Ignition Facility relevant laser intensity of approximately 10(15) W/cm(2) on OMEGA. The measured thin target trajectories are in good agreement with predictions based on the nonlocal model over the full range of laser intensities from 2 x 10(14) to 10(15) W/cm(2}) The standard local thermal-transport model with a constant flux limiter of 0.06 disagrees with experimental measurements at a high intensity of approximately 10(15) W/cm(2) but agrees at lower intensities. These results show the significance of nonlocal effects for direct-drive ignition designs.
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Smalyuk VA, Hu SX, Goncharov VN, Meyerhofer DD, Sangster TC, Shvarts D, Stoeckl C, Yaakobi B, Frenje JA, Petrasso RD. Rayleigh-Taylor growth stabilization in direct-drive plastic targets at laser intensities of approximately 1 x 10(15) W/cm2. PHYSICAL REVIEW LETTERS 2008; 101:025002. [PMID: 18764186 DOI: 10.1103/physrevlett.101.025002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Indexed: 05/26/2023]
Abstract
Direct-drive, planar-target Rayleigh-Taylor growth experiments were performed for the first time to test fundamental physics in hydrocodes at peak drive intensities of ignition designs. The unstable modulation growth at a drive intensity of approximately 1 x 10(15) W/cm2 was strongly stabilized compared to the growth at an intensity of approximately 5 x 10(14) W/cm2. The experiments demonstrate that standard simulations based on a local model of electron thermal transport break down at peak intensities of ignition designs (although they work well at lower intensities). The preheating effects by nonlocal electron transport and hot electrons were identified as some of the stabilizing mechanisms.
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Landen OL, Bradley DK, Braun DG, Smalyuk VA, Hicks DG, Celliers PM, Prisbrey S, Page R, Boehly TR, Haan SW, Munro DH, Wallace RG, Nikroo A, Hamza A, Biener J, Wild C, Woerner E, Olson RE, Rochau GA, Knudson M, Wilson DC, Robey HF, Collins GW, Ho D, Edwards J, Marinak MM, Hammel BA, Meyerhofer DD, MacGowan BJ. Experimental studies of ICF indirect-drive Be and high density C candidate ablators. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/112/2/022004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li CK, Séguin FH, Rygg JR, Frenje JA, Manuel M, Petrasso RD, Betti R, Delettrez J, Knauer JP, Marshall F, Meyerhofer DD, Shvarts D, Smalyuk VA, Stoeckl C, Landen OL, Town RPJ, Back CA, Kilkenny JD. Monoenergetic-proton-radiography measurements of implosion dynamics in direct-drive inertial-confinement fusion. PHYSICAL REVIEW LETTERS 2008; 100:225001. [PMID: 18643423 DOI: 10.1103/physrevlett.100.225001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Indexed: 05/26/2023]
Abstract
Time-gated, monoenergetic radiography with 15-MeV protons provides unique measurements of implosion dynamics in direct-drive inertial-confinement fusion. Images obtained during acceleration, coasting, deceleration, and stagnation display a comprehensive picture of spherical implosions. Critical information inferred from such images, hitherto unavailable, characterizes the spatial structure and temporal evolution of self-generated fields and plasma areal density. Results include the first observation of a radial electric field inside the imploding capsule. It is initially directed inward (at approximately 10(9) V/m), eventually reverses direction ( approximately 10(8) V/m), and is the probable consequence of the evolution of the electron pressure gradient.
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Hu SX, Smalyuk VA, Goncharov VN, Knauer JP, Radha PB, Igumenshchev IV, Marozas JA, Stoeckl C, Yaakobi B, Shvarts D, Sangster TC, McKenty PW, Meyerhofer DD, Skupsky S, McCrory RL. Studies of plastic-ablator compressibility for direct-drive inertial confinement fusion on OMEGA. PHYSICAL REVIEW LETTERS 2008; 100:185003. [PMID: 18518383 DOI: 10.1103/physrevlett.100.185003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Indexed: 05/26/2023]
Abstract
The compression of planar plastic targets was studied with x-ray radiography in the range of laser intensities of I approximately 0.5 to 1.5x10(15) W/cm2 using square (low-compression) and shaped (high-compression) pulses. Two-dimensional simulations with the radiative hydrocode DRACO show good agreement with measurements at laser intensities up to I approximately 10(15) W/cm2. These results provide the first experimental evidence for low-entropy, adiabatic compression of plastic shells in the laser intensity regime relevant to direct-drive inertial confinement fusion. A density reduction near the end of the drive at a high intensity of I approximately 1.5x10(15) W/cm2 has been correlated with the hard x-ray signal caused by hot electrons from two-plasmon-decay instability.
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Smalyuk VA, Shvarts D, Betti R, Delettrez JA, Edgell DH, Glebov VY, Goncharov VN, McCrory RL, Meyerhofer DD, Radha PB, Regan SP, Sangster TC, Seka W, Skupsky S, Stoeckl C, Yaakobi B, Frenje JA, Li CK, Petrasso RD, Séguin FH. Role of hot-electron preheating in the compression of direct-drive imploding targets with cryogenic D2 ablators. PHYSICAL REVIEW LETTERS 2008; 100:185005. [PMID: 18518385 DOI: 10.1103/physrevlett.100.185005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Indexed: 05/26/2023]
Abstract
The compression of direct-drive, spherical implosions is studied using cryogenic D2 targets on the 60-beam, 351-nm OMEGA laser with intensities ranging from approximately 3x10(14) to approximately 1x10(15) W/cm2. The hard-x-ray signal from hot electrons generated by laser-plasma instabilities increases with laser intensity, while the areal density decreases. Mitigating hot-electron production, by reducing the laser intensity to approximately 3x10(14) W/cm2, results in areal density of the order of approximately 140 mg/cm2, in good agreement with 1D simulations. These results will be considered in future direct-drive-ignition designs.
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Sangster TC, Goncharov VN, Radha PB, Smalyuk VA, Betti R, Craxton RS, Delettrez JA, Edgell DH, Glebov VY, Harding DR, Jacobs-Perkins D, Knauer JP, Marshall FJ, McCrory RL, McKenty PW, Meyerhofer DD, Regan SP, Seka W, Short RW, Skupsky S, Soures JM, Stoeckl C, Yaakobi B, Shvarts D, Frenje JA, Li CK, Petrasso RD, Séguin FH. High-areal-density fuel assembly in direct-drive cryogenic implosions. PHYSICAL REVIEW LETTERS 2008; 100:185006. [PMID: 18518386 DOI: 10.1103/physrevlett.100.185006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Indexed: 05/26/2023]
Abstract
The first observation of ignition-relevant areal-density deuterium from implosions of capsules with cryogenic fuel layers at ignition-relevant adiabats is reported. The experiments were performed on the 60-beam, 30-kJUV OMEGA Laser System [T. R. Boehly, Opt. Commun. 133, 495 (1997)10.1016/S0030-4018(96)00325-2]. Neutron-averaged areal densities of 202+/-7 mg/cm2 and 182+/-7 mg/cm2 (corresponding to estimated peak fuel densities in excess of 100 g/cm3) were inferred using an 18-kJ direct-drive pulse designed to put the converging fuel on an adiabat of 2.5. These areal densities are in good agreement with the predictions of hydrodynamic simulations indicating that the fuel adiabat can be accurately controlled under ignition-relevant conditions.
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Welser-Sherrill L, Mancini RC, Koch JA, Izumi N, Tommasini R, Haan SW, Haynes DA, Golovkin IE, MacFarlane JJ, Delettrez JA, Marshall FJ, Regan SP, Smalyuk VA, Kyrala G. Spectroscopic determination of temperature and density spatial profiles and mix in indirect-drive implosion cores. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:056403. [PMID: 18233772 DOI: 10.1103/physreve.76.056403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 09/25/2007] [Indexed: 05/25/2023]
Abstract
In the field of inertial confinement fusion (ICF), work has been consistently progressing in the past decade toward a more fundamental understanding of the plasma conditions in ICF implosion cores. The research presented here represents a substantial evolution in the ability to diagnose plasma temperatures and densities, along with characteristics of mixing between fuel and shell materials. Mixing is a vital property to study and quantify, since it can significantly affect implosion quality. We employ a number of new spectroscopic techniques that allow us to probe these important quantities. The first technique developed is an emissivity analysis, which uses the emissivity ratio of the optically thin Lybeta and Hebeta lines to spectroscopically extract temperature profiles, followed by the solution of emissivity equations to infer density profiles. The second technique, an intensity analysis, models the radiation transport through the implosion core. The nature of the intensity analysis allows us to use an optically thick line, the Lyalpha, to extract information on mixing near the core edge. With this work, it is now possible to extract directly from experimental data not only detailed temperature and density maps of the core, but also spatial mixing profiles.
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Li CK, Séguin FH, Frenje JA, Rygg JR, Petrasso RD, Town RPJ, Landen OL, Knauer JP, Smalyuk VA. Observation of megagauss-field topology changes due to magnetic reconnection in laser-produced plasmas. PHYSICAL REVIEW LETTERS 2007; 99:055001. [PMID: 17930762 DOI: 10.1103/physrevlett.99.055001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Indexed: 05/25/2023]
Abstract
The spatial structure and temporal evolution of megagauss magnetic fields generated by interactions of up to 4 laser beams with matter were studied with an innovative, time-gated proton radiography method that produces images of unprecedented clarity because it uses an isotropic, truly monoenergetic back-lighter (14.7-MeV protons from D3He nuclear fusion reactions). Quantitative field maps reveal precisely and directly, for the first time, changes in the magnetic topology due to reconnection in a high-energy-density plasma (n(e) approximately 10(20)-10(22) cm(-3), T(e) approximately 1 keV).
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Li CK, Séguin FH, Frenje JA, Rygg JR, Petrasso RD, Town RPJ, Amendt PA, Hatchett SP, Landen OL, Mackinnon AJ, Patel PK, Tabak M, Knauer JP, Sangster TC, Smalyuk VA. Observation of the decay dynamics and instabilities of megagauss field structures in laser-produced plasmas. PHYSICAL REVIEW LETTERS 2007; 99:015001. [PMID: 17678158 DOI: 10.1103/physrevlett.99.015001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Indexed: 05/16/2023]
Abstract
Monoenergetic proton radiography was used to make the first measurements of the long-time-scale dynamics and evolution of megagauss laser-plasma-generated magnetic field structures. While a 1-ns 10(14) W/cm2 laser beam is on, the field structure expands in tandem with a hemispherical plasma bubble, maintaining a rigorous 2D cylindrical symmetry. With the laser off, the bubble continues to expand as the field decays; however, the outer field structure becomes distinctly asymmetric, indicating instability. Similarly, localized asymmetry growth in the bubble interior indicates another kind of instability. 2D LASNEX hydrosimulations qualitatively match the cylindrically averaged post-laser plasma evolution but even then it underpredicts the field dissipation rate and of course completely misses the 3D asymmetry growth.
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Zhou CD, Theobald W, Betti R, Radha PB, Smalyuk VA, Shvarts D, Glebov VY, Stoeckl C, Anderson KS, Meyerhofer DD, Sangster TC, Li CK, Petrasso RD, Frenje JA, Seguin FH. High-rhoR implosions for fast-ignition fuel assembly. PHYSICAL REVIEW LETTERS 2007; 98:025004. [PMID: 17358616 DOI: 10.1103/physrevlett.98.025004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2006] [Indexed: 05/14/2023]
Abstract
Thick, 40 microm plastic shells filled with 25-35 atm of D2 or D3He were imploded on a low-adiabat (alpha approximately 1.3) and with a low-implosion velocity ( approximately 2 x 10(70 cm/s) on the OMEGA laser to generate massive cores of compressed plasma with high areal densities optimal for fast ignition. The targets are driven by 20-kJ relaxation adiabat-shaping laser pulses to keep the inner portion of the shell nearly Fermi degenerate. The measured kinetic energy downshift of proton spectra is in good agreement with the theoretical predictions yielding burn-averaged areal densities of 0.130+/-0.017 g/cm2 and peak rhoR during the burn of about 0.24+/-0.018 g/cm2, the largest rhoR measured on OMEGA to date. The same implosions with empty plastic shells are expected to reach 1.3 g/cm2 across the core (i.e., 2rhoR) enough to stop fast electrons with energies up to 4.5 MeV typical of fast ignition scenarios.
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Li CK, Séguin FH, Frenje JA, Rygg JR, Petrasso RD, Town RPJ, Amendt PA, Hatchett SP, Landen OL, Mackinnon AJ, Patel PK, Smalyuk VA, Sangster TC, Knauer JP. Measuring E and B fields in laser-produced plasmas with monoenergetic proton radiography. PHYSICAL REVIEW LETTERS 2006; 97:135003. [PMID: 17026041 DOI: 10.1103/physrevlett.97.135003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Indexed: 05/12/2023]
Abstract
Electromagnetic (E/B) fields generated by the interaction with plasmas of long-pulse, low-intensity laser beams relevant to inertial confinement fusion have been measured for the first time using novel monoenergetic proton radiography methods. High-resolution, time-gated radiography images of a plastic foil driven by a 10(14) W/cm(2) laser implied B fields of approximately 0.5 MG and E fields of approximately 1.5 x 10(8) V/m. Simulations of these experiments with LASNEX+LSP have been performed and are in overall (though not exact) agreement with the data both for field strengths and for spatial distributions; this is the first direct experimental test of the laser-generated B-field package in LASNEX. The experiments also demonstrated that laser phase plates substantially reduce medium-scale chaotic field structure.
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