Hotspot ignition using a Z-pinch precursor plasma in a magneto-inertial ICF scheme

NASA Astrophysics Data System (ADS)

Chittenden, J. P.; Vincent, P.; Jennings, C. A.; Ciardi, A.

2006-01-01

Precursor plasma flow is a common feature of wire array Z-pinches. The precursor flow represents a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the Z-pinch then compresses this precursor to substantially higher density. We show that if the same system can be generated with a Deuterium-Tritium plasma then the precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion. The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the pR required for ignition. A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with 50-100 MA currents and a few hundred nanosecond rise-times. This work was partially supported by the U.S. Department of Energy through cooperative agreement DE-FC03-02NA00057.

Implosion dynamics of a megampere wire-array Z-pinch with an inner low-density foam shell at the Angara-5-1 facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V.; Bolkhovitinov, E. A.; Volkov, G. S., E-mail: volkov@triniti.ru

The implosion dynamics of a pinch with a highly inhomogeneous initial axial distribution of the load mass was studied experimentally. A cascade array consisting of a double nested tungsten wire array and a coaxial inner cylindrical shell located symmetrically with respect to the high-voltage electrodes was used as a load of the Angara-5-1 high-current generator. The cylindrical foam shell was half as long as the cathode− anode gap, and its diameter was equal to the diameter of the inner wire array. It is shown experimentally that two stages are typical of the implosion dynamics of such a load: the formationmore » of two separate pinches formed as a result of implosion of the wire array near the cathode and anode and the subsequent implosion of the central part of the load containing the cylindrical foam shell. The conditions are determined at which the implosion of the central part of the pinch with the foam cylinder is preceded by intense irradiation of the foam with the soft X-ray (SXR) emission generated by the near-electrode pinches and converting it into the plasma state. Using such a load, which models the main elements of the scheme of a dynamic hohlraum for inertial confinement fusion, it is possible to increase the efficiency of interaction between the outer accelerated plasma sheath and the inner foam shell by preionizing the foam with the SXR emission of the near-electrode pinches.« less

Implosion dynamics of condensed Z-pinch at the Angara-5-1 facility

NASA Astrophysics Data System (ADS)

Aleksandrov, V. V.; Grabovski, E. V.; Gritsuk, A. N.; Volobuev, I. V.; Kazakov, E. D.; Kalinin, Yu. G.; Korolev, V. D.; Laukhin, Ya. I.; Medovshchikov, S. F.; Mitrofanov, K. N.; Oleinik, G. M.; Pimenov, V. G.; Smirnova, E. A.; Ustroev, G. I.; Frolov, I. N.

2017-08-01

The implosion dynamics of a condensed Z-pinch at load currents of up to 3.5 MA and a current rise time of 100 ns was studied experimentally at the Angara-5-1 facility. To increase the energy density, 1- to 3-mm-diameter cylinders made of a deuterated polyethylene-agar-agar mixture or microporous deuterated polyethylene with a mass density of 0.03-0.5 g/cm3 were installed in the central region of the loads. The plasma spatiotemporal characteristics were studied using the diagnostic complex of the Angara-5-1 facility, including electron-optical streak and frame imaging, time-integrated X-ray imaging, soft X-ray (SXR) measurements, and vacuum UV spectroscopy. Most information on the plasma dynamics was obtained using a ten-frame X-ray camera ( E > 100 eV) with an exposure of 4 ns. SXR pulses were recorded using photoemissive vacuum X-ray detectors. The energy characteristics of neutron emission were measured using the time-offlight method with the help of scintillation detectors arranged along and across the pinch axis. The neutron yield was measured by activation detectors. The experimental results indicate that the plasma dynamics depends weakly on the load density. As a rule, two stages of plasma implosion were observed. The formation of hot plasma spots in the initial stage of plasma expansion from the pinch axis was accompanied by short pulses of SXR and neutron emission. The neutron yield reached (0.4-3) × 1010 neutrons/shot and was almost independent of the load density due to specific features of Z-pinch dynamics.

Z-Pinch Plasma Neutron Sources

DTIC Science & Technology

2006-03-24

deuterium into 9 to 14 keV (around 10 keV), which is well in the fusion energy range we are interested in. To make plasma radiation sources work, we...showing the 1-D dynamics of the pinch plasma implosion, temperature, fusion energy production and deposition for the conditions of shot Z1422. The minimum...histories of ion and electron temperatures, fusion energy production and energy deposition in ID RMHD run modeling deuterium shot Z1422. In our simulations

The effects of insulating coatings and current prepulse on tungsten planar wire array Z-pinches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, M., E-mail: limo@nint.ac.cn; Li, Y.; State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

2015-12-15

This paper presents experimental results on the effects of insulating coatings and current prepulse on tungsten planar wire array Z-pinches on ∼100 ns main current facility. Optical framing images indicated that without a current prepulse the wire ablation process was asymmetrical and the implosion was zippered. The x-ray peak power was ∼320 GW. By using insulating coatings on the wire surface the asymmetry remained, and the processes of ablation and implosion were delayed by ∼30 ns. The x-ray burst was narrow and decreased to ∼200 GW. When current prepulses were used on both standard and insulated wire arrays, implosion symmetry was improved and themore » x-ray burst was improved (to ∼520 GW peak power). In addition, there was a strong emitting precursor column for insulated loads with the current prepulse.« less

A reassessment study of multi-material-shell gas puff z-pinches as a pulsed neutron source on the sandia ZR

NASA Astrophysics Data System (ADS)

Chong, Y. K.; Velikovich, A. L.; Thornhil, J. W.; Giuliani, J. L.; Knapp, P.; Jennings, C.

2013-10-01

Over the last few years, numerous 1D and 2D MHD simulation studies of deuterium (D) based double-shell gas-puff Z-pinch implosions driven by the Sandia ZR accelerator have been carried out to assess the Z-pinch as a pulsed thermal fusion neutron source. In these studies, an ad-hoc time-dependent shunt impedance model was used within the external driving circuit model in order to account for the unresolved current loss in the MITL and the load. In this study, we incorporate an improved ZR circuit model recently formulated based on the recent Sandia argon gas-puff experiment circuit data into the multi-material version of the Mach +DDTCRE RMHD code. We reinvestigate the effects of multidimensional structure and nonuniform gradients as well as the outer- and inner-shell material interaction on the implosion physics and dynamics of both D-on-D and argon-on-D Z-pinch loads using the model. Then, we characterize the neutron production performance of the Z-pinch loads as a function of total mass, mass ratio and/or radius toward their optimization as a pulsed thernonuclear neutron source. Work supported by DOE/NNSA. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's NNSA under contract DE-AC04-94AL85000.

Energy balance in a Z pinch with suppressed Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Baksht, R. B.; Oreshkin, V. I.; Rousskikh, A. G.; Zhigalin, A. S.

2018-03-01

At present Z-pinch has evolved into a powerful plasma source of soft x-ray. This paper considers the energy balance in a radiating metallic gas-puff Z pinch. In this type of Z pinch, a power-law density distribution is realized, promoting suppression of Rayleigh-Taylor (RT) instabilities that occur in the pinch plasma during compression. The energy coupled into the pinch plasma, is determined as the difference between the total energy delivered to the load from the generator and the magnetic energy of the load inductance. A calibrated voltage divider and a Rogowski coil were used to determine the coupled energy and the load inductance. Time-gated optical imaging of the pinch plasma showed its stable compression up to the stagnation phase. The pinch implosion was simulated using a 1D two-temperature radiative magnetohydrodynamic code. Comparison of the experimental and simulation results has shown that the simulation adequately describes the pinch dynamics for conditions in which RT instability is suppressed. It has been found that the proportion of the Ohmic heating in the energy balance of a Z pinch with suppressed RT instability is determined by Spitzer resistance and makes no more than ten percent.

Investigation of magnetic flux transport and shock formation in a staged Z-pinch

NASA Astrophysics Data System (ADS)

Narkis, J.; Rahman, H. U.; Wessel, F. J.; Beg, F. N.

2017-10-01

Target preheating is an integral component of magnetized inertial fusion in reducing convergence ratio. In the staged Z-pinch concept, it is achieved via one or more shocks. Previous work [Narkis et al., Phys. Plasmas 23, 122706 (2016)] found that shock formation in the target occurred earlier in higher-Z liners due to faster flux transport to the target/liner interface. However, a corresponding increase in magnitude of magnetic pressure was not observed, and target implosion velocity (and therefore shock strength) remained unchanged. To investigate other means of increasing the magnitude of transported flux, a Korteweg-de Vries-Burgers equation from the 1-D single-fluid, resistive magnetohydrodynamic equations is obtained. Solutions to the nondispersive (i.e., Burgers) equation depend on nondimensional coefficients, whose dependence on liner density, temperature, etc., suggests an increase in target implosion velocity, and therefore shock strength, can be obtained by tailoring the mass of a single-liner gas puff to a double-liner configuration. In the selected test cases of 1-D simulated implosions of krypton on deuterium, the peak Mach number increased from ˜ 5 to ˜ 8 . While a notable increase was seen, Mach numbers exceeding 10 (implosion velocities exceeding ˜25 cm/μs) are necessary for adequate shock preheating.

Compression of an Applied Bz field by a z-pinch onto a Tamped DT Fiber for Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Nash, Tom

2009-11-01

Simulations of a z-pinch compressing an applied 100 kG Bz field onto an on-axis DT fiber tamped with beryllium show the field reaching over 100 MG in the tamp, sufficient to confine DT alpha particles and to form a thermal barrier. The barrier allows the DT plasma to burn at a rho*r value as low as 0.045 g/cm^2, and at temperatures over 50 keV for a 63 MA drive current. Driving currents between 21 and 63 MA are considered with cryogenic DT fiber diameters between 600 μm and 1.6 mm. Pinch implosion times are 120 ns with a peak implosion velocity of 35 cm/μs. 1D simulations are of a foil pinch, but for improved stability we propose a nested wire-array. Simulated fusion yields with this system scale as the sixth power of the current, with burn fractions scaling as the fourth power of the current. At 63 MA the simulated yield is 521 MJ from 4.2 mg/cm of DT with a 37% burn fraction at a rho*r of only 0.18 g/cm^2.

Efficient Neutron Production from a Novel Configuration of Deuterium Gas-Puff Z-Pinch

NASA Astrophysics Data System (ADS)

Klir, D.; Kubes, P.; Rezac, K.; Cikhardt, J.; Kravarik, J.; Sila, O.; Shishlov, A. V.; Kovalchuk, B. M.; Ratakhin, N. A.; Kokshenev, V. A.; Labetsky, A. Yu.; Cherdizov, R. K.; Fursov, F. I.; Kurmaev, N. E.; Dudkin, G. N.; Nechaev, B. A.; Padalko, V. N.; Orcikova, H.; Turek, K.

2014-03-01

A novel configuration of a deuterium z pinch has been used to generate fusion neutrons. Injecting an outer hollow cylindrical plasma shell around an inner deuterium gas puff, neutron yields from DD reactions reached Yn=(2.9±0.3)×1012 at 700 ns implosion time and 2.7 MA current. Such a neutron yield means a tenfold increase in comparison with previous deuterium gas puff experiments at the same current generator. The increase of beam-target yields was obtained by a larger amount of current assembled on the z-pinch axis, and subsequently by higher induced voltage and higher energies of deuterons. A stack of CR-39 track detectors on the z-pinch axis showed hydrogen ions up to 38 MeV. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial time-of-flight detectors, respectively. The number of DD neutrons per one joule of stored plasma energy approached 5×107. This implies that deuterium gas puff z pinches belong to the most efficient plasma-based sources of DD neutrons.

Effect of the axial magnetic field on a metallic gas-puff pinch implosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousskikh, A. G.; Zhigalin, A. S.; Frolova, V.

2016-06-15

The effect of an axial magnetic field B{sub z} on an imploding metallic gas-puff Z-pinch was studied using 2D time-gated visible self-emission imaging. Experiments were performed on the IMRI-5 generator (450 kA, 450 ns). The ambient field B{sub z} was varied from 0.15 to 1.35 T. It was found that the initial density profile of a metallic gas-puff Z-pinch can be approximated by a power law. Time-gated images showed that the magneto-Rayleigh–Taylor instabilities were suppressed during the run-in phase both without axial magnetic field and with axial magnetic field. Helical instability structures were detected during the stagnation phase for B{sub z} < 1.1 T. For B{submore » z} = 1.35 T, the pinch plasma boundary was observed to be stable in both run-in and stagnation phases. When a magnetic field of 0.3 T was applied to the pinch, the soft x-ray energy was about twice that generated without axial magnetic field, mostly due to longer dwell time at stagnation.« less

Variation of high-power aluminum-wire array Z-pinch dynamics with wire number, load mass, and array radius

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Mock, R. C.; Marder, B. M.; Nash, T. J.; Spielman, R. B.; Peterson, D. L.; Roderick, N. F.; Hammer, J. H.; De Groot, J. S.; Mosher, D.; Whitney, K. G.; Apruzese, J. P.

1997-05-01

A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, (as measured by the radial convergence, the radiated energy, pulse width, and power), increases with wire number. Radiation magnetohydrodynamic (RMHC) xy simulations suggest that the implosion transitions from that of individual wire plasmas to that of a continuous plasma shell when the interwire spacing is reduced below ˜1.4 mm. In this "plasma-shell regime," many of the global radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. In this regime, measured changes in the radiation pulse width with variations in load mass and array radius are consistent with the simulations and are explained by the development of 2D fluid motion in the rz plane. Associated variations in the K-shell yield are qualitatively explained by simple radiation-scaling models.

Review of effects of dielectric coatings on electrical exploding wires and Z pinches

NASA Astrophysics Data System (ADS)

Wu, Jian; Li, Xingwen; Li, Mo; Li, Yang; Qiu, Aici

2017-10-01

As the most powerful x-ray source in the laboratories, the wire array Z pinches have been of great relevance to inertial confinement fusions, laboratory astrophysics, and other high-energy density applications. In order to produce x-ray with greater power and higher efficiency, the dynamics of wire array has been investigated extensively, and various methods have been proposed to improve the implosion quality of the wire array. This review focuses on the experimental and theoretical investigations regarding the effects of the dielectric coatings on electrical exploding wires and Z pinches. Since the early 2000, the electrical wire explosion related to the first stage of the wire array Z pinches has been studied extensively, and the results indicated that the dielectric coatings can significantly increase the joule energy deposition into a wire in the initial stage, and even the corona free explosion of tungsten wires can be achieved. Recently, there is an increasing interest in the dynamics of insulated wire array Z pinches. By applying dielectric coatings, the ablation process is suppressed, the x-ray start time is delayed, and the possibility of multi-peak radiation is decreased. This review is organized by the evolution dynamics of wire array Z pinches, and a broad introduction to relevant scientific concepts and various other applications are presented. According to the current research status, the challenges, opportunities and further developments of Z pinch loads using dielectric coatings are proposed to further promote the researches and their applications.

Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

1999-11-01

The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

Determination of plasma pinch time and effective current radius of double planar wire array implosions from current measurements on a 1-MA linear transformer driver

NASA Astrophysics Data System (ADS)

Steiner, Adam M.; Yager-Elorriaga, David A.; Patel, Sonal G.; Jordan, Nicholas M.; Gilgenbach, Ronald M.; Safronova, Alla S.; Kantsyrev, Victor L.; Shlyaptseva, Veronica V.; Shrestha, Ishor; Schmidt-Petersen, Maximillian T.

2016-10-01

Implosions of planar wire arrays were performed on the Michigan Accelerator for Inductive Z-pinch Experiments, a linear transformer driver (LTD) at the University of Michigan. These experiments were characterized by lower than expected peak currents and significantly longer risetimes compared to studies performed on higher impedance machines. A circuit analysis showed that the load inductance has a significant impact on the current output due to the comparatively low impedance of the driver; the long risetimes were also attributed to high variability in LTD switch closing times. A circuit model accounting for these effects was employed to measure changes in load inductance as a function of time to determine plasma pinch timing and calculate a minimum effective current-carrying radius. These calculations showed good agreement with available shadowgraphy and x-ray diode measurements.

Z pinches as intense x-ray sources for high-energy density physics applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzen, M.K.

1997-05-01

Fast Z-pinch implosions can efficiently convert the stored electrical energy in a pulsed-power accelerator into x rays. These x rays are produced when an imploding cylindrical plasma, driven by the magnetic field pressure associated with very large axial currents, stagnates upon the cylindrical axis of symmetry. On the Saturn pulsed-power accelerator [R. B. Spielman {ital et al.}, in {ital Proceedings of the 2nd International Conference on Dense Z Pinches}, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] at Sandia National Laboratories, for example, currents ofmore » 6{endash}8 MA with a rise time of less than 50 ns are driven through cylindrically symmetric loads, producing implosion velocities as high as 10{sup 8}cm/s and x-ray energies exceeding 400 kJ. Hydromagnetic Rayleigh{endash}Taylor instabilities and cylindrical load symmetry are critical, limiting factors in determining the assembled plasma densities and temperatures, and thus in the x-ray energies and pulse widths that can be produced on these accelerators. In recent experiments on the Saturn accelerator, these implosion nonuniformities have been minimized by using wire arrays with as many as 192 wires. Increasing the wire number produced significant improvements in the pinched plasma quality, reproducibility, and x-ray output power. X-ray pulse widths of less than 5 ns and peak powers of 75{plus_minus}10TW have been achieved with arrays of 120 tungsten wires. Similar loads have recently been fielded on the Particle Beam Fusion Accelerator (PBFA II), producing x-ray energies in excess of 1.8 MJ at powers in excess of 160 TW. These intense x-ray sources offer the potential for performing many new basic physics and fusion-relevant experiments. {copyright} {ital 1997 American Institute of Physics.}« less

Measurement of Radiation Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Hanson, David L.

2001-10-01

The z-pinch driven hohlraum (ZPDH) is a promising approach to high yield inertial confinement fusion currently being characterized in experiments on the Sandia Z accelerator [1]. In this concept [2], x rays are produced by an axial z-pinch in a primary hohlraum at each end of a secondary hohlraum. A fusion capsule in the secondary is imploded by a symmetric x-ray flux distribution, effectively smoothed by wall reemission during transport to the capsule position. Capsule radiation symmetry, a critical issue in the design of such a system, is influenced by hohlraum geometry, wall motion and time-dependent albedo, as well as power balance and pinch timing between the two z-pinch x-ray sources. In initial symmetry studies on Z, we used solid low density burnthrough spheres to diagnose highly asymmetric, single-sided-drive hohlraum geometries. We then applied this technique to the more symmetric double z-pinch geometry [3]. As a result of design improvements, radiation flux symmetry in Z double-pinch wire array experiments now exceeds the measurement sensitivity of this self-backlit foam ball symmetry diagnostic (15% max-min flux asymmetry). To diagnose radiation symmetry at the 2 - 5% level attainable with our present ZPDH designs, we are using high-energy x rays produced by the recently-completed Z-Beamlet laser backlighter for point-projection imaging of thin-wall implosion and symmetry capsules. We will present the results of polar flux symmetry measuremets on Z for several ZPDH capsule geometries together with radiosity and radiation-hydrodynamics simulations for comparison. [1] M. E. Cuneo et al., Phys. Plasmas 8,2257(2001); [2] J. H. Hammer et al., Phys. Plasmas 6,2129(1999); [3] D. L. Hanson et al., Bull. Am. Phys. Soc. 45,360(2000).

Performance of a Liner-on-Target Injector for Staged Z-Pinch Experiments

NASA Astrophysics Data System (ADS)

Conti, F.; Valenzuela, J. C.; Narkis, J.; Krasheninnikov, I.; Beg, F.; Wessel, F. J.; Ruskov, E.; Rahman, H. U.; McGee, E.

2016-10-01

We present the design and characterization of a compact liner-on-target injector, used in the Staged Z-pinch experiments conducted on the UNR-NTF Zebra Facility. Previous experiments and analysis indicate that high-Z gas liners produce a uniform and efficient implosion on a low-Z target plasma. The liner gas shell is produced by an annular solenoid valve and a converging-diverging nozzle designed to achieve a collimated, supersonic, Mach-5 flow. The on-axis target is produced by a coaxial plasma gun, where a high voltage pulse is applied to ionize neutral gas and accelerate the plasma by the J-> × B-> force. Measurements of the liner and target dynamics, resolved by interferometry in space and time, fast imaging, and collection of the emitted light, are presented. The results are compared to the predictions from Computational Fluid Dynamics and MHD simulations that model the injector. Optimization of the design parameters, for upcoming Staged Z-pinch experiments, will be discussed. Advanced Research Projects Agency - Energy, DE-AR0000569.

Diagnostics for Magnetically Driven Implosions on the 1-MA MAIZE Facility

NASA Astrophysics Data System (ADS)

Campbell, Paul; Yager-Elorriaga, David; Miller, Stephanie; Woolstrum, Jeff; Jones, Michael; Jordan, Nicholas; Lau, Y. Y.; Gilgenbach, Ronald; McBride, Ryan

2017-10-01

The Michigan Accelerator for Inductive Z-pinch Experiments (MAIZE) is a 3-m-diameter Linear Transformer Driver (LTD) at the University of Michigan which supplies a fast electrical pulse (0-1 MA in 100 ns, for matched loads) to various experimental configurations. In order to better investigate these loads, new diagnostics are being developed. First, an EUV/XUV micro-channel plate pinhole camera and a UV laser imaging system are being implemented to better observe the instability structures that form during implosions. Second, an x-pinch radiography diagnostic is being developed to probe deeper into the plasma loads. Third, Rogowski coils are being developed for enhanced load current measurements. Finally, a bolometry system and photo-conducting diamond (PCD) detectors will be implemented to measure x-ray power and energy. These new systems, combined with the existing twelve-frame laser shadowgraphy, and b-dot current monitors, will be powerful tools for the investigation of imploding z-pinch experiments. This research was supported by the DOE through award DE-SC0012328, Sandia National Laboratories contract DE-NA0003525, the National Science Foundation, and a Nuclear Regulatory Commission new-faculty development Grant. D.Y.E. was supported by an NSF fello.

Coronal plasma development in wire-array z-pinches made of twisted-pairs

NASA Astrophysics Data System (ADS)

Hoyt, C. L.; Greenly, J. B.; Gourdain, P. A.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Kusse, B. R.

2009-11-01

We have investigated coronal and core plasma development in wire array z-pinches in which single fine wires are replaced by twisted-pairs (``cable'') on the 1 MA, 100 ns rise time COBRA pulsed power generator. X-ray radiography, employed to investigate dense wire core expansion, showed periodic axial nonuniformity and evidence for shock waves developing where the individual wire plasmas collide. Laser shadowgraphy images indicated that the axial instability properties of the coronal plasma are substantially modified from ordinary wire arrays. Cable mass per unit length, material and the twist wavelength were varied in order to study their effects upon the instability wavelength. Implosion uniformity and bright-spot formation, as well as magnetic topology evolution, have also been investigated using self-emission imaging, x-ray diagnostics and small B-dot probes, respectively. Results from the cable-array z-pinches will be compared with results from ordinary wire-array z-pinches. This research was supported by the SSAA program of the National Nuclear Security Administration under DOE Cooperative agreement DE-FC03-02NA00057.

Load Designs For MJ Dense Plasma Foci

NASA Astrophysics Data System (ADS)

Link, A.; Povlius, A.; Anaya, R.; Anderson, M. G.; Angus, J. R.; Cooper, C. M.; Falabella, S.; Goerz, D.; Higginson, D.; Holod, I.; McMahon, M.; Mitrani, J.; Koh, E. S.; Pearson, A.; Podpaly, Y. A.; Prasad, R.; van Lue, D.; Watson, J.; Schmidt, A. E.

2017-10-01

Dense plasma focus (DPF) Z-pinches are compact pulse power driven devices with coaxial electrodes. The discharge of DPF consists of three distinct phases: first generation of a plasma sheath, plasma rail gun phase where the sheath is accelerated down the electrodes and finally an implosion phase where the plasma stagnates into a z-pinch geometry. During the z-pinch phase, DPFs can produce MeV ion beams, x-rays and neutrons. Megaampere class DPFs with deuterium fills have demonstrated neutron yields in the 1012 neutrons/shot range with pulse durations of 10-100 ns. Kinetic simulations using the code Chicago are being used to evaluate various load configurations from initial sheath formation to the final z-pinch phase for DPFs with up to 5 MA and 1 MJ coupled to the load. Results will be presented from the preliminary design simulations. LLNL-ABS-734785 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344 and with support from the Computing Grand Challenge program at LLNL.

Analytic model for the dynamic Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R., E-mail: roberto.piriz@uclm.es; Sun, Y. B.; Tahir, N. A.

2015-06-15

A model is presented for describing the cylindrical implosion of a shock wave driven by an accelerated piston. It is based in the identification of the acceleration of the shocked mass with the acceleration of the piston. The model yields the separate paths of the piston and the shock. In addition, by considering that the shocked region evolves isentropically, the approximate profiles of all the magnitudes in the shocked region are obtained. The application to the dynamic Z-pinch is presented and the results are compared with the well known snowplow and slug models which are also derived as limiting casesmore » of the present model. The snowplow model is seen to yield a trajectory in between those of the shock and the piston. Instead, the neglect of the inertial effects in the slug model is seen to produce a too fast implosion, and the pressure uniformity is shown to lead to an unphysical instantaneous piston stopping when the shock arrives to the axis.« less

Dynamic characteristics of azimuthally correlated structures of axial instability of wire-array Z pinches

NASA Astrophysics Data System (ADS)

Dan, Jia Kun; Huang, Xian Bin; Ren, Xiao Dong; Chen, Guang Hua; Xu, Qiang; Wang, Kun Lun; Ouyang, Kai; Wei, Bing

2017-04-01

Particular attention was placed on observations of dynamic properties of the azimuthally correlated structures of axial instability of wire-array Z pinches, which were conducted at 10-MA (for short circuit load) pulsed power generator-the Primary Test Stand facility. Not well fabricated loads, which were expected to preset bubble or spike in plasma, were used to degrade the implosion symmetry in order to magnify the phenomenon of instability. The side-view sequence of evolution of correlation given by laser shadowgraphy clearly demonstrates the dynamic processes of azimuthal correlation of the bubble and spike. A possible mechanism presented here suggests that it is the substantial current redistribution especially in regions surrounding the bubble/spike resulting from change of inductance due to the presence of the bubble/spike that plays an essential part in establishment of azimuthal correlation of wire array and liner Z pinches.

Controlling Rayleigh-Taylor instabilities in solid liner implosions with rotating magnetic fields

NASA Astrophysics Data System (ADS)

Schmit, P. F.; McBride, R. D.; Robertson, G. K.; Velikovich, A. L.

2016-10-01

We report calculations demonstrating that a remarkable reduction in the growth of the magneto-Rayleigh-Taylor instability (MRTI) in initially solid, cylindrical metal shells can be achieved by applying a magnetic drive with a tilted, dynamic polarization, forming a solid-liner dynamic screw pinch (SLDSP). Using a self-consistent analytic framework, we demonstrate that MRTI growth factors of the most detrimental modes may be reduced by up to two orders of magnitude relative to conventional z-pinch implosions. One key application of this technique is to enable increasingly stable, higher performance liner implosions to achieve fusion. We weigh the potentially dramatic benefits of the SLDSP against the practical tradeoffs required to achieve the desired drive field history and identify promising target designs for future experimental and computational investigations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DoE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion

NASA Astrophysics Data System (ADS)

Calamy, H.; Lassalle, F.; Loyen, A.; Zucchini, F.; Chittenden, J. P.; Hamann, F.; Maury, P.; Georges, A.; Bedoch, J. P.; Morell, A.

2008-01-01

The Sphinx machine [F. Lassalle et al., "Status on the SPHINX machine based on the 1microsecond LTD technology"] based on microsecond linear transformer driver (LTD) technology is used to implode an aluminium wire array with an outer diameter up to 140mm and maximum current from 3.5to5MA. 700to800ns implosion Z-pinch experiments are performed on this driver essentially with aluminium. Best results obtained before the improvement described in this paper were 1-3TW radial total power, 100-300kJ total yield, and 20-30kJ energy above 1keV. An auxiliary generator was added to the Sphinx machine in order to allow a multi microsecond current to be injected through the wire array load before the start of the main current. Amplitude and duration of this current prepulse are adjustable, with maxima ˜10kA and 50μs. This prepulse dramatically changes the ablation phase leading to an improvement of the axial homogeneity of both the implosion and the final radiating column. Total power was multiplied by a factor of 6, total yield by a factor of 2.5 with a reproducible behavior. This paper presents experimental results, magnetohydrodynamic simulations, and analysis of the effect of such a long current prepulse.

Plasma Radiation Source on the Basis of the Gas Puff with Outer Plasma Shell in the Circuit of a Mega-Ampere Load Current Doubler

NASA Astrophysics Data System (ADS)

Kokshenev, V. A.; Labetsky, A. Yu.; Shishlov, A. V.; Kurmaev, N. E.; Fursov, F. I.; Cherdizov, R. K.

2017-12-01

Characteristics of Z-pinch plasma radiation in the form of a double shell neon gas puff with outer plasma shell are investigated in the microsecond implosion mode. Experiments are performed using a GIT-12 mega-joule generator with load current doubler having a ferromagnetic core at implosion currents up to 5 MA. Conditions for matching of the nonlinear load with the mega-ampere current multiplier circuit are determined. The load parameters (plasma shell characteristics and mass and geometry of gas puff shells) are optimized on the energy supplied to the gas puff and n energy characteristics of radiation. It is established that the best modes of K-shell radiation in neon are realized for such radial distribution of the gas-puff material at which the compression velocity of the shell is close to a constant and amounts to 27-30 cm/μs. In these modes, up to 40% of energy supplied to the gas puff is converted into K-shell radiation. The reasons limiting the efficiency of the radiation source with increasing implosion current are analyzed. A modernized version of the energy supply from the current doubler to the Z-pinch is proposed.

Status On Multi-microsecond Prepulse Technique On Sphinx Machine Going From Nested To Single Wire Array For 800 ns Implosion Time Z-pinch

NASA Astrophysics Data System (ADS)

Maury, P.; Calamy, H.; Grunenwald, J.; Lassalle, F.; Zucchini, F.; Loyen, A.; Georges, A.; Morell, A.; Bedoch, J. P.

2009-01-01

The Sphinx machine[1] is a 6 MA, 1 μS driver based on the LTD technology, used for Z-pinch experiments. Important improvements of Sphinx radiation output were recently obtained using a multi-microsecond current prepulse[2]. Total power per unit of length is multiplied by a factor of 6 and FWHM divided by a factor of 2.5. Early breakdown of the wires during the prepulse phase dramatically changes the ablation phase leading to an improvement of axial homogeneity of both the implosion and the final radiating column. As a consequence, the cathode bubble observed on classical shots is definitively removed. The implosion is then centered and zippering effect is reduced, leading to simultaneous x-ray emission of the whole length. A great reproducibility is obtained. Nested arrays were used before to mitigate the Rayleigh-Taylor instabilities during the implosion phase. Further experiments with pre-pulse technique are described here were inner array was removed. The goal of these experiments was to see if long prepulse could give stable enough implosion with single array and at the same time increase the η parameter by reducing the mass of the load. Experimental results of single wire array loads of typical dimension 5 cm in height with implosion time between 700 and 900 ns and diameter varying between 80 and 140 mm are given. Parameters of the loads were varying in term of radius and number of wires. Comparisons with nested wire array loads are done and trends are proposed. Characteristics of both the implosion and the final radiating column are shown. 2D MHD numerical simulations of single wire array become easier as there is no interaction between outer and inner array anymore. A systematic study was done using injection mass model to benchmark simulation with experiments.

Acceleration of Hydrogen Ions up to 30 MeV and Generation of 3 × 1012 Neutrons in Megaampere Deuterium Gas-Puff Z-Pinch

NASA Astrophysics Data System (ADS)

Klir, D.; Cikhardt, J.; Kravarik, J.; Kubes, P.; Rezac, K.; Sila, O.; Shishlov, A.; Cherdizov, R.; Fursov, F.; Kokshenev, V.; Kovalchuk, B.; Kurmaev, N.; Labetsky, A.; Ratakhin, N.; Orcikova, H.; Turek, K.

2013-10-01

Fusion neutrons were produced with a deuterium gas-puff z-pinch on the GIT-12 generator at the Institute of High Current Electronics in Tomsk. The peak neutron yield from DD reactions reached Yn = (2 . 9 +/- 0 . 3) ×1012 at 100 μg/cm linear mass density of deuterium, 700 ns implosion time and 2.7 MA current. Such a neutron yield means that the scaling law of deuterium z-pinches Yn ~I4 was extended to 3 MA currents. The further increase of neutron yields up to (3 . 7 +/- 0 . 4) ×1012 was achieved by placing a deuterated polyethylene catcher onto the axis. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial nToF detectors, respectively. A stack of CR-39 track detectors showed up to 40 MeV deuterons (or 30 MeV protons) on the z-pinch axis. Since the energy input into plasmas was 70 kJ, the number of DD neutrons per one joule of stored plasma energy exceeded the value of 5 ×107 . This value implies that deuterium gas-puff z-pinches belong to the most efficient plasma-based sources of DD neutrons. This work was partially supported by the GACR grant No. P205/12/0454 and by the RFBR research project No. 13-08-00479-a.

Effect of Initial Conditions on Gas-Puff Z-Pinch Dynamics.

NASA Astrophysics Data System (ADS)

Peterson, Gus Gordon

This dissertation concerns the effects initial conditions have on the dynamics of an imploded, annular gas-puff z-pinch. The influence of axial magnetic fields, nozzle size and composition, different gases, pre-ionization, and electrode design on pinch quality and x-ray yield is investigated. The experiment uses a 5-kJ capacitor bank to deliver 0.35 MA to the pinch load in 1.4 mu rm s. This research establishes parameters important to increasing the x-ray yield of dense z-pinches. The initial stage of the implosion is diagnosed with a framing camera that photographs visible light emitted from z-pinch gas breakdown. Data from subsequent stages of the pinch is recorded with a B-dot probe, filtered x-ray diodes, an x-ray filtered pinhole camera, and a nitrogen laser interferometer. Applied axial magnetic fields of ~100 gauss increase average x-ray yield by more than 20%. A substantial increase of K-shell x -ray yield of more than 200% was obtained by increasing the energy delivered to the plasma by enlarging the nozzle diameter from 4 to 5 cm. The use of a Teflon outer-mantle for the nozzle resulted in less uniform gas breakdown as compared to graphite and copper outer-mantles, but x-ray yield and final state uniformity were not reduced. Lower Z gases showed poorer breakdown uniformity. Pre-ionization improved the uniformity of helium and neon breakdown but did not appear to affect subsequent dynamics. X-ray yield was significantly higher using a knife-edge annular anode, as opposed to a flat stainless steel honeycomb anode. Annular anodes with diameters more than a few millimeters different than the nozzle diameter produced low quality pinches with substantially lower x-ray yield.

Advanced Radiation Theory Support Annual Report 2003, Final Report

DTIC Science & Technology

2004-04-19

diameter wires would lose a higher mass fraction. Table 2. Energy Transfers for Ti Loads Dia. & Case H 2 H13 Mass -a-m Z,DE kJ kJ Pg 1000 - Z 428.2...issues covered are (1) issues and directions for future research, (2) zero- and one-dimensional modeling of DQ experiments, (3) enhanced energy ...coupling and x-ray emission in z-pinch implosions, (4) confinement and compression of magnetic flux by plasma shells, and (6) flashover and energy coupling

Multicolor, time-gated, soft x-ray pinhole imaging of wire array and gas puff Z pinches on the Z and Saturn pulsed power generators.

PubMed

Jones, B; Coverdale, C A; Nielsen, D S; Jones, M C; Deeney, C; Serrano, J D; Nielsen-Weber, L B; Meyer, C J; Apruzese, J P; Clark, R W; Coleman, P L

2008-10-01

A multicolor, time-gated, soft x-ray pinhole imaging instrument is fielded as part of the core diagnostic set on the 25 MA Z machine [M. E. Savage et al., in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, New York, 2007), p. 979] for studying intense wire array and gas puff Z-pinch soft x-ray sources. Pinhole images are reflected from a planar multilayer mirror, passing 277 eV photons with <10 eV bandwidth. An adjacent pinhole camera uses filtration alone to view 1-10 keV photons simultaneously. Overlaying these data provides composite images that contain both spectral as well as spatial information, allowing for the study of radiation production in dense Z-pinch plasmas. Cu wire arrays at 20 MA on Z show the implosion of a colder cloud of material onto a hot dense core where K-shell photons are excited. A 528 eV imaging configuration has been developed on the 8 MA Saturn generator [R. B. Spielman et al., and A. I. P. Conf, Proc. 195, 3 (1989)] for imaging a bright Li-like Ar L-shell line. Ar gas puff Z pinches show an intense K-shell emission from a zippering stagnation front with L-shell emission dominating as the plasma cools.

X-pinch dynamics: Neck formation and implosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I.; National Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk 634050; Chaikovsky, S. A.

2014-10-15

We propose a model that describes the neck formation and implosion in an X-pinch. The process is simulated to go in two stages. The first stage is neck formation. This stage begins with an electrical explosion of the wires forming the X-pinch, and at the end of the stage, a micropinch (neck) is formed in the region where the wires are crossed. The second stage is neck implosion. The implosion is accompanied by outflow of matter from the neck region, resulting in the formation of a “hot spot”. Analytical estimates obtained in the study under consideration indicate that these stagesmore » are approximately equal in duration. Having analyzed the neck implosion dynamics, we have verified a scaling which makes it possible to explain the observed dependences of the time of occurrence of an x-ray pulse on the X-pinch current and mass.« less

X-ray Power Increase from Symmetrized Wire-Array z-Pinch Implosions on Saturn.*

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Allshouse, G. O.; Marder, B. M.; Nash, T. J.; Mock, R. C.; Douglas, M. R.; Spielman, R. B.; Seaman, J. F.; McGurn, J. S.; Jobe, D.; Gilliland, T. L.; Vargas, M.; Struve, K. W.; Stygar, W. A.; Hammer, J. H.; Degroot, J. S.; Eddleman, J. L.; Peterson, D. L.; Whitney, K. G.; Thornhill, J. W.; Pulsifer, P. E.; Apruzese, J. P.; Mosher, D.; Maron, Y.

1996-11-01

A systematic experimental study of annular aluminum wire z-pinches on the Saturn accelerator at Sandia National Laboratories shows that, for the first time, many of the measured spatial characteristics and x-ray powers can be correlated to 1D and 2D, radiation-magneto-hydrodynamic code (RMHC) simulations when large numbers of wires are used. Calculations show that the implosion begins to transition from that of individual wire plasmas to that of a continuous plasma shell when the circumferential gap between wires in the array is reduced below 1.4 +1.3/-0.7 mm. This calculated gap coincides with the measured transition of 1.4±0.4 mm between the observed regimes of slow and rapid improvement in power output with decreasing gap. In the plasma-shell regime, x-ray power has been more than tripled over that generated in the wire-plasma regime. In the full paper, measured characteristics in the plasma-shell regime are compared with 2D, 1- and 20-mm axial length simulations of the implosion using a multi-photon-group Lagrangian RMHC^1 and a three-temperature Eulerian RMHC,^2 respectively. ^1J.H. Hammer, et al., Phys. Plasmas 3, 2063 (1996). ^2D.L. Peterson, et al., Phys. Plasmas 3, 368 (1996). Work supported by U.S. DOE Contract No. DE-AC04-94AL85000.

Advanced Design Concepts for Dense Plasma Focus Devices at LLNL

NASA Astrophysics Data System (ADS)

Povilus, Alexander; Podpaly, Yuri; Cooper, Christopher; Shaw, Brian; Chapman, Steve; Mitrani, James; Anderson, Michael; Pearson, Aric; Anaya, Enrique; Koh, Ed; Falabella, Steve; Link, Tony; Schmidt, Andrea

2017-10-01

The dense plasma focus (DPF) is a z-pinch device where a plasma sheath is accelerated down a coaxial railgun and ends in a radial implosion, pinch phase. During the pinch phase, the plasma generates intense, transient electric fields through physical mechanisms, similar to beam instabilities, that can accelerate ions in the plasma sheath to MeV-scale energies on millimeter length scales. Using kinetic modeling techniques developed at LLNL, we have gained insight into the formation of these accelerating fields and are using these observations to optimize the behavior of the generated ion beam for producing neutrons via beam-target interactions for kilojoule to megajoule-scale devices. Using a set of DPF's, both in operation and in development at LLNL, we have explored critical aspects of these devices, including plasma sheath formation behavior, power delivery to the plasma, and instability seeding during the implosion in order to improve the absolute yield and stability of the device. Prepared by LLNL under Contract DE-AC52-07NA27344. Computing support for this work came from the LLNL Institutional Computing Grand Challenge program.

Preliminary experimental results of tungsten wire-array Z-pinches on primary test stand

NASA Astrophysics Data System (ADS)

Huang, Xian-Bin; Zhou, Shao-Tong; Dan, Jia-Kun; Ren, Xiao-Dong; Wang, Kun-Lun; Zhang, Si-Qun; Li, Jing; Xu, Qiang; Cai, Hong-Chun; Duan, Shu-Chao; Ouyang, Kai; Chen, Guang-Hua; Ji, Ce; Wei, Bing; Feng, Shu-Ping; Wang, Meng; Xie, Wei-Ping; Deng, Jian-Jun; Zhou, Xiu-Wen; Yang, Yi

2015-07-01

The Primary Test Stand (PTS) developed at the China Academy of Engineering Physics is a 20 TW pulsed power driver, which can deliver a ˜10 MA, 70 ns rise-time (10%-90%) current to a short-circuit load and has important applications in Z-pinch driven inertial confinement fusion and high energy density physics. Preliminary results of tungsten wire-array Z-pinch experiments on PTS are presented. The load geometries investigated include 15-mm-tall cylindrical single and nested arrays with diameter ranging from 13 mm to 30 mm, consisting of 132-300 tungsten wires with 5-10 μm in diameter. Multiple diagnostics were fielded to characterize the x-ray radiation from wire-array Z pinches. The x-ray peak power (˜50 TW) and total radiated energy (˜500 kJ) were obtained from a single 20-mm-diam array with 80-ns stagnation time. The highest x-ray peak power up to 80 TW with 2.4 ns FWHM was achieved by using a nested array with 20-mm outer diameter, and the total x-ray energy from the nested array is comparable to that of single array. Implosion velocity estimated from the time-resolved image measurement exceeds 30 cm/μs. The detailed experimental results and other findings are presented and discussed.

Investigating the effect of adding an on-axis jet to Ar gas puff Z pinches on Z.

DOE PAGES

Harvey-Thompson, Adam James; Jennings, Christopher Ashley; Jones, Brent M.; ...

2016-10-20

Double-shell Ar gas puff implosions driven by 16.5±0.5 MA on the Z generator at Sandia National Laboratories are very effective emitters of Ar K-shell radiation (photon energy >3 keV), producing yields of 330 ± 9% kJ (B. Jones et al., Phys. Plasmas, 22, 020706, 2015). In addition, previous simulations and experiments have reported dramatic increases in K-shell yields when adding an on-axis jet to double shell gas puffs for some configurations.

Temperature Evolution of a 1 MA Triple-Nozzle Gas-Puff Z-Pinch

NASA Astrophysics Data System (ADS)

de Grouchy, Philip; Banasek, Jacob; Engelbrecht, Joey; Qi, Niansheng; Atoyan, Levon; Byvank, Tom; Cahill, Adam; Moore, Hannah; Potter, William; Ransohoff, Lauren; Hammer, David; Kusse, Bruce; Laboratory of Plasma Studies Team

2015-11-01

Mitigation of the Rayleigh-Taylor instability (RTI) plays a critical role in optimizing x-ray output at high-energy ~ 13 keV using the triple-nozzle Krypton gas-puff at Sandia National Laboratory. RTI mitigation by gas-puff density profiling using a triple-nozzle gas-puff valve has recently been recently demonstrated on the COBRA 1MA z-pinch at Cornell University. In support of this work we investigate the role of shell cooling in the growth of RTI during gas-puff implosions. Temperature measurements within the imploding plasma shell are recorded using a 527 nm, 10 GW Thomson scattering diagnostic for Neon, Argon and Krypton puffs. The mass-density profile is held constant at 22 microgram per centimeter for all three puffs and the temperature evolution of the imploding material is recorded. In the case of Argon puffs we find that the shell ion and electron effective temperatures remain in equilibrium at around 1keV for the majority of the implosion phase. In contrast scattered spectra from Krypton are dominated by of order 10 keV effective ion temperatures. Supported by the NNSA Stewardship Sciences Academic Programs.

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Staged Z-pinch Experiments on Cobra and Zebra

NASA Astrophysics Data System (ADS)

Wessel, Frank J.; Anderson, A.; Banasek, J. T.; Byvank, T.; Conti, F.; Darling, T. W.; Dutra, E.; Glebov, V.; Greenly, J.; Hammer, D. A.; Potter, W. M.; Rocco, S. V.; Ross, M. P.; Ruskov, E.; Valenzuela, J.; Beg, F.; Covington, A.; Narkis, J.; Rahman, H. U.

2017-10-01

A Staged Z-pinch (SZP), configured as a pre-magnetized, high-Z (Ar, or Kr) annular liner imploding onto a low-Z (H, or D) target, was tested on the Cornell University, Cobra Facility and the University of Nevada, Reno, Zebra Facility; each characterized similarly by a nominal 1-MA current and 100-ns risetime while possessing different diagnostic packages. XUV-fast imaging reveals that the SZP implosion dynamics is similar on both machines and that it is more stable with an axial (Bz) magnetic field, a target, or both, than without. On Zebra, where neutron production is possible, reproducible thermonuclear (DD) yields were recorded at levels in excess of 109/shot. Flux compression in the SZP is also expected to produce magnetic field intensities of the order of kilo-Tesla. Thus, the DD reaction produced tritions should also yield secondary DT neutrons. Indeed, secondaries are measured above the noise threshold at levels approaching 106/shot. Funded by the Advanced Research Projects Agency - Energy, under Grant Number DE-AR0000569.

History of HERMES III diode to z-pinch breakthrough and beyond :

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanford, Thomas Williamlou.

HERMES III and Z are two flagship accelerators of Sandias pulsed-power program developed to generate intense -ray fields for the study of nuclear radiation effects, and to explore high energy-density physics (including the production of intense x-ray fields for Inertia Confinement Fusion [ICF]), respectively. A diode at the exit of HERMES III converts its 20-MeV electron beam into -rays. In contrast, at the center of Z, a z-pinch is used to convert its 20-MA current into an intense burst of x-rays. Here the history of how the HERMES III diode emerged from theoretical considerations to actual hardware is discussed. Next,more » the reverse process of how the experimental discovery of wire-array stabilization in a z-pinch, led to a better theory of wirearray implosions and its application to one of the ICF concepts on Z--the DH (Dynamic Hohlraum) is reviewed. Lastly, the report concludes with how the unexpected axial radiation asymmetry measured in the DH is understood. The first discussion illustrates the evolution of physics from theory-to-observationto- refinement. The second two illustrate the reverse process of observationto- theory-to refinement. The histories are discussed through the vehicle of my research at Sandia, illustrating the unique environment Sandia provides for personal growth and development into a scientific leader.« less

Optimization of K-shell emission in aluminum z-pinch implosions: Theory versus experiment

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Thornhill, J. W.; Giuliani, J. L.; Davis, J.; Miles, L. A.; Nolting, E. E.; Kenyon, V. L.; Speicer, W. A.; Draper, J. A.; Parsons, C. R.; Dang, P.; Spielman, R. B.; Nash, T. J.; McGurn, J. S.; Ruggles, L. E.; Deeney, C.; Prasad, R. R.; Warren, L.

1994-09-01

Two sets of z-pinch experiments were recently completed at the Saturn and Phoenix facilities of Sandia National Laboratories and the Naval Surface Warfare Center, respectively, using aluminum wire arrays of different wire and array diameters. Measurements of the total x-ray yield from the K shell of aluminum were made. In this paper, a comparison of these measurements is made to both theoretical predictions and to a similar set of earlier measurements that were made at the Double Eagle facility of Physics International Company. These three sets of yield measurements have points of agreement with predicted yields and with each other, but they also show points of mutual disagreement, whose significance is discussed. The data are analyzed using a slightly revised version of a previously published K-shell yield scaling law, and they support the existence of a reasonably well defined region in (load mass)-(implosion velocity) space in which plasma kinetic energy is efficiently converted into K-shell x rays. Furthermore, a correlation is observed between the inferred conversion efficiencies and the times in which the implosions occur relative to the times when each generator's short-circuit current reaches its peak value. Finally, unlike the Double Eagle experiments, the largest measured yields in the new experiments were observed to occur at the upper velocity boundary of the efficient emission region. Moreover, the observed yields are in fairly good quantitative agreement with an earlier scaling law prediction of the maximum K-shell x-ray yield from aluminum as a function of load mass assuming kinetic energy conversion alone.

One- and two-dimensional modeling of argon K-shell emission from gas-puff Z-pinch plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornhill, J. W.; Chong, Y. K.; Apruzese, J. P.

2007-06-15

In this paper, a theoretical model is described and demonstrated that serves as a useful tool for understanding K-shell radiating Z-pinch plasma behavior. Such understanding requires a self-consistent solution to the complete nonlocal thermodynamic equilibrium kinetics and radiation transport in order to realistically model opacity effects and the high-temperature state of the plasma. For this purpose, we have incorporated into the MACH2 two-dimensional magnetohydrodynamic (MHD) code [R. E. Peterkin et al., J. Comput. Phys. 140, 148 (1998)] an equation of state, called the tabular collisional radiative equilibrium (TCRE) model [J. W. Thornhill et al., Phys. Plasmas 8, 3480 (2001)], thatmore » provides reasonable approximations to the plasma's opacity state. MACH2 with TCRE is applied toward analyzing the multidimensional implosion behavior that occurred in Decade Quad (DQ) [D. Price et al., Proceedings of the 12th IEEE Pulsed Power Conference, Monterey, CA, edited by C. Stallings and H. Kirbie (IEEE, New York, 1999), p. 489] argon gas puff experiments that employed a 12 cm diameter nozzle with and without a central gas jet on axis. Typical peak drive currents and implosion times in these experiments were {approx}6 MA and {approx}230 ns. By using Planar Laser Induced Fluorescence measured initial density profiles as input to the calculations, the effect these profiles have on the ability of the pinch to efficiently produce K-shell emission can be analyzed with this combined radiation-MHD model. The calculated results are in agreement with the experimental result that the DQ central-jet configuration is superior to the no-central-jet experiment in terms of producing more K-shell emission. These theoretical results support the contention that the improved operation of the central-jet nozzle is due to the better suppression of instabilities and the higher-density K-shell radiating conditions that the central-jet configuration promotes. When we applied the model toward projecting argon K-shell yield behavior for Sandia National Laboratories' ZR machine ({approx}25 MA peak drive currents, {approx}100 ns implosion times) [D. McDaniel et al., Proceedings of the 5th International Conference on Dense Z-Pinches, Albuquerque, NM, 2002, edited by J. Davis, C. Deeney, and N. R. Pereira (American Institute of Physics, New York, 2002), Vol. 651, p. 23] for experiments that utilize the 12 cm diameter central-jet nozzle configuration, it predicts over 1 MJ of K-shell emission is attainable.« less

The quest for a z-pinch based fusion energy source—a historical perspective

NASA Astrophysics Data System (ADS)

Sethian, John

1997-05-01

Ever since 1958, when Oscar Anderson observed copious neutrons emanating from a "magnetically self-constricted column of deuterium plasma," scientists have attempted to develop the simple linear pinch into a fusion power source. After all, simple calculations show that if one can pass a current of slightly less than 2 million amperes through a stable D-T plasma, then one could achieve not just thermonuclear break-even, but thermonuclear gain. Moreover, several reactor studies have shown that a simple linear pinch could be the basis for a very attractive fusion system. The problem is, of course, that the seemingly simple act of passing 2 MA through a stable pinch has proven to be quite difficult to accomplish. The pinch tends to disrupt due to instabilities, either by the m=0 (sausage) or m=1 (kink) modes. Curtailing the growth of these instabilities has been the primary thrust of z-pinch fusion research, and over the years a wide variety of formation techniques have been tried. The early pinches were driven by relatively slow capacitive discharges and were formed by imploding a plasma column. The advent of fast pulsed power technology brought on a whole new repertoire of formation techniques, including: fast implosions, laser or field-enhanced breakdown in a uniform volume of gas, a discharge inside a small capillary, a frozen deuterium fiber isolated by vacuum, and staged concepts in which one pinch implodes upon another. And although none of these have yet to be successful, some have come tantalizingly close. This paper will review the history of this four-decade long quest for fusion power.

Symmetric aluminum-wire arrays generate high-quality Z pinches at large array radii

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Mock, R. C.; Spielman, R. B.; Peterson, D. L.; Mosher, D.; Roderick, N. F.

1998-10-01

A Saturn-accelerator study of annular, aluminum-wire array, Z-pinch implosions, in the calculated high-wire-number plasma-shell regime [Phys. Rev. Lett. 77, 5063 (1996)], shows that the radiated x-ray pulse width increases from about 4 nsec to about 7 nsec, when the radius of the array is increased from 8.75 to 20 mm at a fixed array mass of 0.6 mg. Eulerian radiation- magnetohydrodynamic code (E-RMHC) simulations in the r-z plane suggest that this pulse-width increase with radius is due to the faster growth of the shell thickness (that arises from a two-stage development in the magnetic Rayleigh-Taylor instability) relative to the increase in the shell implosion velocity. Over the array radii explored, the measured peak total x-ray power of ˜40 TW and energy of ˜325 kJ show little change outside of a ±15% shot-to-shot fluctuation and are consistent with the E-RMHC simulations. Similarly, the measured peak K-shell (lines plus continuum) power of ˜8 TW and energy of ˜70 kJ show little change with radius. The minimal change in K-shell yield is in agreement with simple K-shell radiation scaling models that assume a fixed radial compression for all initial array radii. These results suggest that the improved uniformity provided by the large number of wires in the initial array reduces the disruptive effects of the Rayleigh-Taylor instability observed in small-wire-number imploding loads.

Dynamics of a Z-pinch x-ray source for heating inertial-confinement-fusion relevant hohlraums to 120-160 eV

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Olson, R. E.; Mock, R. C.; Chandler, G. A.; Leeper, R. J.; Nash, T. J.; Ruggles, L. E.; Simpson, W. W.; Struve, K. W.; Peterson, D. L.; Bowers, R. L.; Matuska, W.

2000-11-01

A Z-pinch radiation source has been developed that generates 60±20 kJ of x rays with a peak power of 13±4 TW through a 4-mm-diam axial aperture on the Z facility. The source has heated National Ignition Facility-scale (6-mm-diam by 7-mm-high) hohlraums to 122±6 eV and reduced-scale (4-mm-diam by 4-mm-high) hohlraums to 155±8 eV—providing environments suitable for indirect-drive inertial confinement fusion studies. Eulerian-RMHC (radiation-magnetohydrodynamics code) simulations that take into account the development of the Rayleigh-Taylor instability in the r-z plane provide integrated calculations of the implosion, x-ray generation, and hohlraum heating, as well as estimates of wall motion and plasma fill within the hohlraums. Lagrangian-RMHC simulations suggest that the addition of a 6 mg/cm3 CH2 fill in the reduced-scale hohlraum decreases hohlraum inner-wall velocity by ˜40% with only a 3%-5% decrease in peak temperature, in agreement with measurements.

The microscopic Z-pinch process of current-carrying rarefied deuterium plasma shell

NASA Astrophysics Data System (ADS)

Ning, Cheng; Feng, Zhixing; Xue, Chuang; Li, Baiwen

2015-02-01

For insight into the microscopic mechanism of Z-pinch dynamic processes, a code of two-dimensional particle-in-cell (PIC) simulation has been developed in cylindrical coordinates. In principle, the Z-pinch of current-carrying rarefied deuterium plasma shell has been simulated by means of this code. Many results related to the microscopic processes of the Z-pinch are obtained. They include the spatio-temporal distributions of electromagnetic field, current density, forces experienced by the ions and electrons, positions and energy distributions of particles, and trailing mass and current. In radial direction, the electric and magnetic forces exerted on the electrons are comparable in magnitude, while the forces exerted on the ions are mainly the electric forces. So in the Z-pinch process, the electrons are first accelerated in Z direction and get higher velocities; then, they are driven inwards to the axis at the same time by the radial magnetic forces (i.e., Lorentz forces) of them. That causes the separations between the electrons and ions because the ion mass is much larger than the electron's, and in turn a strong electrostatic field is produced. The produced electrostatic field attracts the ions to move towards the electrons. When the electrons are driven along the radial direction to arrive at the axis, they shortly move inversely due to the static repellency among them and their tiny mass, while the ions continue to move inertially inwards, and later get into stagnation, and finally scatter outwards. Near the stagnation, the energies of the deuterium ions mostly range from 0.3 to 6 keV, while the electron energies are mostly from 5 to 35 keV. The radial components, which can contribute to the pinched plasma temperature, of the most probable energies of electron and ion at the stagnation are comparable to the Bennett equilibrium temperature (about 1 keV), and also to the highest temperatures of electron and ion obtained in one dimensional radiation magnetohydrodynamic simulation of the plasma shell Z-pinch. The trailing mass is about 20% of the total mass of the shell, and the maximum trailing current is about 7% of the driven current under our trailing definition. Our PIC simulation also demonstrates that the plasma shell first experiences a snow-plow like implosion process, which is relatively stable.

Flux-trapping during the formation of field-reversed configurations

NASA Astrophysics Data System (ADS)

Armstrong, W. T.; Harding, D. G.; Crawford, E. A.; Hoffman, A. L.

1981-10-01

Optimized trapping of bias flux during the early formation phases of a Field Reversed Configuration was studied experimentally on the field reversed theta pinch TRX-1. An annular z-pinch preionizer was employed to permit ionization at high values of initial reverse bias flux. Octopole barrier fields are pulsed during field reversal to minimize plasma/wall contact and associated loss of reverse flux. Also, second half cycle operation was examined in obtaining very high values of reverse flux. Flux loss is generally observed to be governed by resistive diffusion through a current sheath at the plasma boundary, rather than flux convection to the plasma boundary. Trapped reverse flux at the time of field reversal, as well as after the radial implosion, is observed to increase with the applied bias field. This increase is greatest, and in fact nearly linear with bias field, when barrier fields are employed. Barrier fields also appear to broaden the current sheath, which results in some flux loss and a less dynamic radial implosion. A general model and one dimensional simulation of flux loss is described and correlated with experimental results.

Enhanced energy coupling and x-ray emission in Z-pinch plasma implosions

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Thornhill, J. W.; Apruzese, J. P.; Davis, J.; Deeney, C.; Coverdale, C. A.

2004-08-01

Recent experiments conducted on the Saturn pulsed-power generator at Sandia National Laboratories [R. B. Spielman et al., in Proceedings of the Second International Conference on Dense Z Pinches, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] have produced large amounts of x-ray output, which cannot be accounted for in conventional magnetohydrodynamic (MHD) calculations. In these experiments, the Saturn current had a rise time of ~180 ns in contrast to a rise time of ~60 ns in Saturn's earlier mode of operation. In both aluminum and tungsten wire-array Z-pinch implosions, 2-4 times more x-ray output was generated than could be supplied according to one-dimensional (1D) magnetohydrodynamic calculations by the combined action of the j×B acceleration forces and ohmic heating (as described by a classical Braginskii resistivity). In this paper, we reexamine the problem of coupling transmission line circuits to plasma fluid equations and derive expressions for the Z-pinch load circuit resistance and inductance that relate these quantities in a 1D analysis to the surface resistivity of the fluid, and to the magnetic field energy that is stored in the vacuum diode, respectively. Enhanced energy coupling in this analysis, therefore, comes from enhancements to the surface resistivity, and we show that plasma resistivities approximately three orders of magnitude larger than classical are needed in order to achieve energy inputs that are comparable to the Saturn experiment x-ray outputs. Large enhancements of the plasma resistivity increase the rate of magnetic field and current diffusion, significantly modify the qualitative features of the MHD, and raise important questions as to how the plasma fluid dynamics converts enhanced energy inputs into enhanced x-ray outputs. One-dimensional MHD calculations in which resistivity values are adjusted phenomenologically are used to illustrate how various dynamical assumptions influence the way enhanced energy inputs are channeled by the fluid dynamics. Variations in the parameters of the phenomenological model are made in order to determine how sensitively they influence the dynamics and the degree to which the calculated x-ray outputs can be made to replicate the kinds of large variations in the experimental x-ray power data that were observed in three nominally identical aluminum wire shots on Saturn.

Grazing incidence extreme ultraviolet spectrometer fielded with time resolution in a hostile z-pinch environment.

PubMed

Williamson, K M; Kantsyrev, V L; Safronova, A S; Wilcox, P G; Cline, W; Batie, S; LeGalloudec, B; Nalajala, V; Astanovitsky, A

2011-09-01

This recently developed diagnostic was designed to allow for time-gated spectroscopic study of the EUV radiation (4 nm < λ < 15 nm) present during harsh wire array z-pinch implosions. The spectrometer utilizes a 25 μm slit, an array of 3 spherical blazed gratings at grazing incidence, and a microchannel plate (MCP) detector placed in an off-Rowland position. Each grating is positioned such that its diffracted radiation is cast over two of the six total independently timed frames of the MCP. The off-Rowland configuration allows for a much greater spectral density on the imaging plate but only focuses at one wavelength per grating. The focal wavelengths are chosen for their diagnostic significance. Testing was conducted at the Zebra pulsed-power generator (1 MA, 100 ns risetime) at the University of Nevada, Reno on a series of wire array z-pinch loads. Within this harsh z-pinch environment, radiation yields routinely exceed 20 kJ in the EUV and soft x-ray. There are also strong mechanical shocks, high velocity debris, sudden vacuum changes during operation, energic ion beams, and hard x-ray radiation in excess of 50 keV. The spectra obtained from the precursor plasma of an Al double planar wire array contained lines of Al IX and AlX ions indicating a temperature near 60 eV during precursor formation. Detailed results will be presented showing the fielding specifications and the techniques used to extract important plasma parameters using this spectrometer. © 2011 American Institute of Physics

Using a Z-pinch precursor plasma to produce a cylindrical, hotspot ignition, ICF

NASA Astrophysics Data System (ADS)

Chittenden, Jeremy

2005-10-01

We show that if the same precursor plasma that exists in metal wire arrays can be generated with a Deuterium-Tritium plasma then this precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The precursor is generated from a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion. The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the ρR required for ignition. A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with 50-100 MA currents and a few hundred nanosecond rise-times. This work was partially supported by the U.S. Department of Energy through cooperative agreement DE-FC03-02NA00057.

The study of hard x-ray emission and electron beam generation in wire array Z-pinch and X-pinch plasmas at university-scale generators

NASA Astrophysics Data System (ADS)

Shrestha, Ishor Kumar

The studies of hard x-ray (HXR) emission and electron beam generation in Z-pinch plasmas are very important for Inertial Confinement Fusion (ICF) research and HXR emission application for sources of K-shell and L-shell radiation. Energetic electron beams from Z-pinch plasmas are potentially a problem in the development of ICF. The electron beams and the accompanying HXR emission can preheat the fuel of a thermonuclear target, thereby preventing the fuel compression from reaching densities required for the ignition of a fusion reaction. The photons above 3-4 keV radiated from a Z pinch can provide detailed information about the high energy density plasmas produced at stagnation. Hence, the investigation of characteristics of hard x-rays and electron beams produced during implosions of wire array loads on university scale-generators may provide important data for future ICF, sources of K-shell and L-shell radiations and basic plasma research. This dissertation presents the results of experimental studies of HXR and electron beam generation in wire-array and X-pinch on the 1.7 MA, 100-ns current rise time Zebra generator at University of Nevada, Reno and 1-MA 100-ns current rise-time Cornell Beam Research Accelerator (COBRA) at Cornell University. The experimental study of characteristics of HXR produced by multi-planar wire arrays, compact cylindrical wire array (CCWA) and nested cylindrical wire array (NCWA) made from Al, Cu, Mo, Ag, W and Au were analyzed. The dependence of the HXR yield and power on geometry of the load, the wire material, and load mass was observed. The presence of aluminum wires in the load with the main material such as stainless steel, Cu, Mo, Ag, W or Au in combined wire array decreases HXR yield. The comparison of emission characteristics of HXR and generation of electron beams in CCWA and NCWA on both the high impedance Zebra generator and low impedance COBRA generator were investigated. Some of the "cold" K- shell spectral lines (0.7-2.3Á) and cold L-shell spectral lines (1-1.54Á) in the HXR region were observed only during the interaction of electron beam with load material and anode surface. These observations suggest that the mechanism of HXR emission should be associated with non-thermal mechanisms such as the interaction of the electron beam with the load material. In order to estimate the characteristics of the high-energetic electron beam in Z-pinch plasmas, a hard x-ray polarimeter (HXP) has been developed and used in experiments on the Zebra generator. The electron beams (energy more than 30keV) have been investigated with measurements of the polarization state of the emitted bremsstrahlung radiation from plasma. We also analyzed characteristics of energetic electron beams produced by implosions of multi-planar wire arrays, compact cylindrical and nested wire arrays as well as X-pinches. Direct indications of electron beams (electron cutoff energy EB from 42-250 keV) were obtained by using the measured current of a Faraday cup placed above the anode or mechanical damage observed in the anode surface. A comparison of total electron beam energy and the spatial and spectral analysis of the parameters of plasmas were investigated for different wire materials. The dependences of the total electron beam energy (E b) on the wire material and the geometry of the wire array load were studied.

Specific features of implosion of metallized fiber arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitrofanov, K. N., E-mail: mitrofan@triniti.ru; Aleksandrov, V. V.; Gritsuk, A. N.

2017-02-15

Implosion of metallized fiber arrays was studied experimentally at the Angara-5-1 facility. The use of such arrays makes it possible to investigate the production and implosion dynamics of plasmas of various metals (such as tin, indium, and bismuth) that were previously unavailable for such studies. The plasma production rates m-dot (in μg/(cm{sup 2} ns)) for different metals were determined and quantitatively compared. Varying the thickness of the metal layer deposited on kapron fibers (the total linear mass of the metal coating being maintained at the level of 220 μg/cm), the current and velocity of the plasma precursor were studied asmore » functions of the thickness of the metal coating. The strong difference in the rates of plasma production from the metal coating and kapron fibers results in the redistribution of the discharge current between the Z-pinch and the trailing fiber plasma. The outer boundary of the plasma produced from the metal coating is found to be stable against instabilities typical of the final stage of implosion of conventional wire arrays.« less

Hard X-ray and Particle Beams Research on 1.7 MA Z-pinch and Laser Plasma Experiments

NASA Astrophysics Data System (ADS)

Shrestha, Ishor; Kantsyrev, Victor; Safronova, Alla; Esaulov, Andrey; Nishio, Mineyuki; Shlyaptseva, Veronica; Keim, Steven; Weller, Michael; Stafford, Austin; Petkov, Emil; Schultz, Kimberly; Cooper, Matthew; PPDL Team

2013-10-01

Studies of hard x-ray (HXR) emission, electron and ion beam generation in z-pinch and laser plasmas are important for Inertial Confinement Fusion (ICF) and development of HXR sources from K-shell and L-shell radiation. The characteristics of HXR and particle beams produced by implosions of planar wire arrays, nested and single cylindrical wire arrays, and X-pinches were analyzed on 100 ns UNR Zebra generator with current up to 1.7 MA. In addition, the comparison of characteristics of HXR and electron beams on Zebra and 350 fs UNR Leopard laser experiments with foils has been performed. The diagnostics include Faraday cups, HXR diodes, different x-ray spectrometers and imaging systems, and ion mass spectrometer using the technique of Thomson parabola. Future work on HXRs and particle beams in HED plasmas is discussed. This work was supported by the DOE/NNSA Cooperative agreement DE-NA0001984 and in part by DE-FC52-06NA27616. This work was also supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-13-1-0033, to University of Nevada, Reno.

The Pulsed Fission-Fusion (PUFF) Concept for Deep Space Exploration and Terrestrial Power Generation

NASA Technical Reports Server (NTRS)

Adams, Robert; Cassibry, Jason; Schillo, Kevin

2017-01-01

This team is exploring a modified Z-pinch geometry as a propulsion system, imploding a liner of liquid lithium onto a pellet containing both fission and fusion fuel. The plasma resulting from the fission and fusion burn expands against a magnetic nozzle, for propulsion, or a magnetic confinement system, for terrestrial power generation. There is considerable synergy in the concept; the lithium acts as a temporary virtual cathode, and adds reaction mass for propulsion. Further, the lithium acts as a radiation shield against generated neutrons and gamma rays. Finally, the density profile of the column can be tailored using the lithium sheath. Recent theoretical and experimental developments (e.g. tailored density profile in the fuel injection, shear stabilization, and magnetic shear stabilization) have had great success in mitigating instabilities that have plagued previous fusion efforts. This paper will review the work in evaluating the pellet sizes and z-pinch conditions for optimal PuFF propulsion. Trades of pellet size and composition with z-pinch power levels and conditions for the tamper and lithium implosion are evaluated. Current models, both theoretical and computational, show that a z-pinch can ignite a small (1 cm radius) fission-fusion target with significant yield. Comparison is made between pure fission and boosted fission targets. Performance is shown for crewed spacecraft for high speed Mars round trip missions and near interstellar robotic missions. The PuFF concept also offers a solution for terrestrial power production. PuFF can, with recycling of the effluent, achieve near 100% burnup of fission fuel, providing a very attractive power source with minimal waste. The small size of PuFF relative to today's plants enables a more distributed power network and less exposure to natural or man-made disruptions.

A Multiple Z-Pinch Configuration for the Generation of High-Density, Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Tarditi, Alfonso G.

2015-11-01

The z-pinch is arguably the most straightforward and economical approach for the generation and confinement of hot plasmas, with a long history of theoretical investigations and experimental developments. While most of the past studies were focused on countering the natural tendency of z-pinches to develop instabilities, this study attempts to take advantage of those unstable regimes to form a quasi-stable plasma, with higher density and temperature, possibly of interest for a fusion reactor concept. For this purpose, a configuration with four z-pinch discharges, with axis parallel to each other and symmetrically positioned, is considered. Electrodes for the generation of the discharges and magnetic coils are arranged to favor the formation of concave discharge patterns. The mutual attraction from the co-streaming discharge currents enhances this pattern, leading to bent plasma streams, all nearing towards the axis. This configuration is intended to excite and sustain a ``kink'' unstable mode for each z-pinch, eventually producing either plasmoid structures, detached from each discharge, or sustained kink patterns: both these cases appear to lead to plasmas merging in the central region. The feasibility of this approach in creating a higher density, hotter, meta-stable plasma regime is investigated computationally, addressing both the kink excitation phase and the dynamics of the converging plasma columns.

First Experiments with Planar Wire Arrays on U Michigan's Linear Transformer Driver

NASA Astrophysics Data System (ADS)

Safronova, A. S.; Kantsyrev, V. L.; Weller, M. E.; Shrestha, I. K.; Shlyaptseva, V. V.; Cooper, M. C.; Lorance, M.; Stafford, A.; Patel, S. G.; Steiner, A. M.; Yager-Elorriaga, D. A.; Jordan, N. M.; Gilgenbach, R. M.

2014-10-01

For petawatt-class Z-pinch accelerators, a Linear Transformer Driver (LTD)-driven accelerator promises to be (at a given pinch current and implosion time) more efficient than the conventionally used Marx-driven accelerator. Because there exists almost no data on how wire arrays radiate on LTD-based machines in the USA, it is very important to perform radiation and plasma physics studies on this new type of generator. We report on the first outcome of the new partnership with University of Michigan (UM), which resulted in successful UNR-UM experiments on the low-impedance MAIZE generator with planar wire arrays (PWA). PWA is a novel wire array load that was introduced and tested in detail on high-impedance Zebra at UNR during the last years and found to be the most efficient radiator. Implosion of Al Double PWAs of different configurations were achieved on MAIZE, observed with a set of various diagnostics which include x-ray diode detectors, x-ray spectroscopy and imaging, and shadowgraphy. Al and Mg plasmas of more than 450 eV were studied in detail. Research supported by NNSA under DOE Cooperative Agreement DE-NA0001984. S. G. Patel and A. M. Steiner supported by Sandia National Laboratories. D. A. Yager-Elorriaga supported by NSF GF.

Radial and Azimuthal Velocity Profiles in Gas-Puff Z-Pinches

NASA Astrophysics Data System (ADS)

Rocco, Sophia; Engelbrecht, Joseph; Banasek, Jacob; de Grouchy, Philip; Qi, Niansheng; Hammer, David

2016-10-01

The dynamics of neon, argon, and krypton (either singly or in combination) gas puff z-pinch plasmas are studied on Cornell's 1MA, 100-200ns rise-time COBRA pulsed power generator. The triple-nozzle gas puff valve, consisting of two annular gas puffs and a central jet, allows radial tailoring of the gas puff mass-density profile and the use of 1, 2 or 3 different gases at different pressures. Interferometry supplies information on sheath thickness and electron density, variously filtered PCDs and silicon diodes measure hard and soft x-ray production, and multi frame visible and extreme UV imaging systems allow tracking of the morphology of the plasma. A 527nm, 10J Thomson scattering diagnostic system is used to determine radial and azimuthal velocities. Implosion velocities of 170km/s (Kr) and 300km/s (Ne/Ar) are observed. We are investigating the correlations between instability growth, plasma density profile, velocity partitioning as a function of radius, and radiation production. Research supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement No. DE-NA0001836.

Characterization of neutron emission from mega-ampere deuterium gas puff Z-pinch at microsecond implosion times

NASA Astrophysics Data System (ADS)

Klir, D.; Shishlov, A. V.; Kokshenev, V. A.; Kubes, P.; Labetsky, A. Yu; Rezac, K.; Cikhardt, J.; Fursov, F. I.; Kovalchuk, B. M.; Kravarik, J.; Kurmaev, N. E.; Ratakhin, N. A.; Sila, O.; Stodulka, J.

2013-08-01

Experiments with deuterium (D2) triple shell gas puffs were carried out on the GIT-12 generator at a 3 MA current level and microsecond implosion times. The outer, middle and inner nozzle diameters were 160 mm, 80 mm and 30 mm, respectively. The influence of the mass of deuterium shells on neutron emission times, neutron yields and neutron energy spectra was studied. The injected linear mass of deuterium varied between 50 and 255 µg cm-1. Gas puffs imploded onto the axis before the peak of generator current at 700-1100 ns. Most of the neutrons were emitted during the second neutron pulse after the development of instabilities. Despite higher currents, heavier gas puffs produced lower neutron yields. Optimal mass and a short time delay between the valve opening and the generator triggering were more important than the better coincidence of stagnation with peak current. The peak neutron yield from D(d, n)3He reactions reached 3 × 1011 at 2.8 MA current, 90 µg cm-1 injected linear mass and 37 mm anode-cathode gap. In the case of lower mass shots, a large number of 10 MeV neutrons were produced either by secondary DT reactions or by DD reactions of deuterons with energies above 7 MeV. The average neutron yield ratio Y>10 MeV/Y2.5 MeV reached (6 ± 3) × 10-4. Such a result can be explained by a power law distribution for deuterons as \\rmd N_d/\\rmd E_d\\propto E_d^{-3} . The optimization of a D2 gas puff Z-pinch and similarities to a plasma focus and its drive parameter are described.

Staged Z-pinch for the production of high-flux neutrons and net energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wessel, Frank J.; Rahman, Hafiz Ur; Rostoker, Norman

A fusible target is embedded in a high Z liner, ohmically heated and then shock wave heated by implosion of an enveloping high Z liner. The target is adiabatically heated by compression, fusibly ignited and charged-particle heated as it is being ignited. A shock front forms as the liner implodes which shock front detaches from the more slowly moving liner, collides with the outer surface of the target, accelerates inward, rapidly heating the target, adiabatically compressing the target and liner and amplifying the current to converge the liner mass toward a central axis thereby compressing the target to a fusionmore » condition when it begins to ignite and produce charged particles. The charged particles are trapped in a large magnetic field surrounding the target. The energy of the charged particles is deposited into the target to further heat the target to produce an energy gain.« less

The US ICF Ignition Program and the Inertial Fusion Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindl, J D; Hammel, B A; Logan, B G

2003-07-02

There has been rapid progress in inertial fusion in the past few years. This progress spans the construction of ignition facilities, a wide range of target concepts, and the pursuit of integrated programs to develop fusion energy using lasers, ion beams and z-pinches. Two ignition facilities are under construction (NIF in the U.S. and LMJ in France) and both projects are progressing toward an initial experimental capability. The LIL prototype beamline for LMJ and the first 4 beams of NIF will be available for experiments in 2003. The full 192 beam capability of NIF will be available in 2009 andmore » ignition experiments are expected to begin shortly after that time. There is steady progress in the target science and target fabrication in preparation for indirect drive ignition experiments on NIF. Advanced target designs may lead to 5-10 times more yield than initial target designs. There has also been excellent progress on the science of ion beam and z-pinch driven indirect drive targets. Excellent progress on direct-drive targets has been obtained on the Omega laser at the University of Rochester. This includes improved performance of targets with a pulse shape predicted to result in reduced hydrodynamic instability. Rochester has also obtained encouraging results from initial cryogenic implosions. There is widespread interest in the science of fast ignition because of its potential for achieving higher target gain with lower driver energy and relaxed target fabrication requirements. Researchers from Osaka have achieved outstanding implosion and heating results from the Gekko XII Petawatt facility and implosions suitable for fast ignition have been tested on the Omega laser. A broad based program to develop lasers and ions beams for IFE is under way with excellent progress in drivers, chambers, target fabrication and target injection. KrF and Diode Pumped Solid-State lasers (DPSSL) are being developed in conjunction with drywall chambers and direct drive targets. Induction accelerators for heavy ions are being developed in conjunction with thick-liquid protected wall chambers and indirect-drive targets.« less

Development And Characterization Of A Liner-On-Target Injector For Staged Z-Pinch Experiments

NASA Astrophysics Data System (ADS)

Valenzuela, J. C.; Conti, F.; Krasheninnikov, I.; Narkis, J.; Beg, F.; Wessel, F. J.; Rahman, H. U.

2016-10-01

We present the design and optimization of a liner-on-target injector for Staged Z-pinch experiments. The injector is composed of an annular high atomic number (e.g. Ar, Kr) gas-puff and an on-axis plasma gun that delivers the ionized deuterium target. The liner nozzle injector has been carefully studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated 1 cm radius gas profile that satisfies the theoretical requirement for best performance on the 1 MA Zebra current driver. The CFD simulations produce density profiles as a function of the nozzle shape and gas. These profiles are initialized in the MHD MACH2 code to find the optimal liner density for a stable, uniform implosion. We use a simple Snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector. We have performed line-integrated density measurements using a CW He-Ne laser to characterize the liner gas and the plasma gun density as a function of time. The measurements are compared with models and calculations and benchmarked accordingly. Advanced Research Projects Agency - Energy, DE-AR0000569.

Overview of pulsed-power-driven high-energy-density plasma research at the University of Michigan

NASA Astrophysics Data System (ADS)

McBride, R. D.; Campbell, P. C.; Miller, S. M.; Woolstrum, J. M.; Yager-Elorriaga, D. A.; Steiner, A. M.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.; Safronova, A. S.; Kantsyrev, V. L.; Shlyaptseva, V. V.; Shrestha, I. K.; Butcher, C. J.; Laity, G. R.; Leckbee, J. J.; Wisher, M. L.; Slutz, S. A.; Cuneo, M. E.

2017-10-01

The Michigan Accelerator for Inductive Z-pinch Experiments (MAIZE) is a 3-m-diameter, single-cavity Linear Transformer Driver (LTD) at the University of Michigan (UM). MAIZE supplies a fast electrical pulse (0-1 MA in 100 ns for matched loads) to various experimental configurations, including wire-array z-pinches and cylindrical foil loads. This talk will report on projects aimed at upgrading the MAIZE facility (e.g., a new power feed and new diagnostics) as well as various physics campaigns on MAIZE (e.g., radiation source development, power flow, implosion instabilities, and other projects relevant to the MagLIF program at Sandia). In addition to MAIZE, UM is constructing a second, smaller LTD facility consisting of four 1.25-m-diameter cavities. These cavities were previously part of Sandia's 21-cavity Ursa Minor facility. The status of the four Ursa Minor cavities at UM will also be presented. This research was funded in part by the University of Michigan, a Faculty Development Grant from the Nuclear Regulatory Commission, the NNSA under DOE Grant DE-NA0003047 for UNR, and Sandia National Laboratories under DOE-NNSA contract DE-NA0003525.

Advanced Concepts Theory Annual Report 1986.

DTIC Science & Technology

1987-08-12

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Preionization Techniques in a kJ-Scale Dense Plasma Focus

NASA Astrophysics Data System (ADS)

Povilus, Alexander; Shaw, Brian; Chapman, Steve; Podpaly, Yuri; Cooper, Christopher; Falabella, Steve; Prasad, Rahul; Schmidt, Andrea

2016-10-01

A dense plasma focus (DPF) is a type of z-pinch device that uses a high current, coaxial plasma gun with an implosion phase to generate dense plasmas. These devices can accelerate a beam of ions to MeV-scale energies through strong electric fields generated by instabilities during the implosion of the plasma sheath. The formation of these instabilities, however, relies strongly on the history of the plasma sheath in the device, including the evolution of the gas breakdown in the device. In an effort to reduce variability in the performance of the device, we attempt to control the initial gas breakdown in the device by seeding the system with free charges before the main power pulse arrives. We report on the effectiveness of two techniques developed for a kJ-scale DPF at LLNL, a miniature primer spark gap and pulsed, 255nm LED illumination. Prepared by LLNL under Contract DE-AC52-07NA27344.

Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

NASA Astrophysics Data System (ADS)

Klir, D.; Shishlov, A. V.; Kokshenev, V. A.; Kubes, P.; Labetsky, A. Yu; Rezac, K.; Cherdizov, R. K.; Cikhardt, J.; Cikhardtova, B.; Dudkin, G. N.; Fursov, F. I.; Garapatsky, A. A.; Kovalchuk, B. M.; Kravarik, J.; Kurmaev, N. E.; Orcikova, H.; Padalko, V. N.; Ratakhin, N. A.; Sila, O.; Turek, K.; Varlachev, V. A.

2015-04-01

Z-pinch experiments with deuterium gas puffs have been carried out on the GIT-12 generator at 3 MA currents. Recently, a novel configuration of a deuterium gas-puff z-pinch was used to accelerate deuterons and to generate fast neutrons. In order to form a homogeneous, uniformly conducting layer at a large initial radius, an inner deuterium gas puff was surrounded by an outer hollow cylindrical plasma shell. The plasma shell consisting of hydrogen and carbon ions was formed at the diameter of 350 mm by 48 plasma guns. A linear mass of the plasma shell was about 5 µg cm-1 whereas a total linear mass of deuterium gas in single or double shell gas puffs was about 100 µg cm-1. The implosion lasted 700 ns and seemed to be stable up to a 5 mm radius. During stagnation, m = 0 instabilities became more pronounced. When a disruption of necks occurred, the plasma impedance reached 0.4 Ω and high energy (>2 MeV) bremsstrahlung radiation together with high energy deuterons were produced. Maximum neutron energies of 33 MeV were observed by axial time-of-flight detectors. The observed neutron spectra could be explained by a suprathermal distribution of deuterons with a high energy tail f≤ft({{E}\\text{d}}\\right)\\propto E\\text{d}-(1.8+/- 0.2) . Neutron yields reached 3.6 × 1012 at a 2.7 MA current. A high neutron production efficiency of 6 × 107 neutrons per one joule of plasma energy resulted from the generation of high energy deuterons and from their magnetization inside plasmas.

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE PAGES

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.; ...

2016-11-11

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Z-pinch Plasma Temperature and Implosion Velocity from Laboratory Plasma Jets using Thomson Scattering

NASA Astrophysics Data System (ADS)

Banasek, Jacob; Byvank, Tom; Kusse, Bruce; Hammer, David

2016-10-01

We discuss the use of collective Thomson scattering to determine the implosion velocity and other properties of laboratory plasma jets. The plasma jet is created using a 1 MA pulsed power machine with a 15 μm Al radial foil load. The Thomson scattering laser has a maximum energy of 10 J at 526.5 nm with a pulse duration of 3 ns. Using a time gated ICCD camera and spectrometer system we are able to record the scattered spectrum from 9 or 18 regions along the laser path with sub-mm spatial resolution. Collecting scattered radiation from the same area at two different angles simultaneously enables determination of both the radial and azimuthal velocities. The scattered spectrum for non-magnetized jets indicates a radial implosion velocity of 27 km/s into the jets. A determination of ion and electron temperatures from the scattered spectrum is in progress. Comparing results using a laser energy of 10 J and 1 J shows noticeable effects on plasma jet properties when using 10 J. Therefore the lower laser energy must be used to determine the plasma properties. This research is supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0001836.

Observation of >400-eV precursor plasmas from low-wire-number copper arrays at the 1-MA zebra facility.

PubMed

Coverdale, C A; Safronova, A S; Kantsyrev, V L; Ouart, N D; Esaulov, A A; Deeney, C; Williamson, K M; Osborne, G C; Shrestha, I; Ampleford, D J; Jones, B

2009-04-17

Experiments with cylindrical copper wire arrays at the 1-MA Zebra facility show that high temperatures exist in the precursor plasmas formed when ablated wire array material accretes on the axis prior to the stagnation of a z pinch. In these experiments, the precursor radiated approximately 20% of the >1000 eV x-ray output, and time-resolved spectra show substantial emission from Cu L-shell lines. Modeling of the spectra shows an increase in temperature as the precursor forms, up to approximately 450 eV, after which the temperature decreases to approximately 220-320 eV until the main implosion.

Evolution of sausage and helical modes in magnetized thin-foil cylindrical liners driven by a Z-pinch

NASA Astrophysics Data System (ADS)

Yager-Elorriaga, D. A.; Lau, Y. Y.; Zhang, P.; Campbell, P. C.; Steiner, A. M.; Jordan, N. M.; McBride, R. D.; Gilgenbach, R. M.

2018-05-01

In this paper, we present experimental results on axially magnetized (Bz = 0.5 - 2.0 T), thin-foil (400 nm-thick) cylindrical liner-plasmas driven with ˜600 kA by the Michigan Accelerator for Inductive Z-Pinch Experiments, which is a linear transformer driver at the University of Michigan. We show that: (1) the applied axial magnetic field, irrespective of its direction (e.g., parallel or anti-parallel to the flow of current), reduces the instability amplitude for pure magnetohydrodynamic (MHD) modes [defined as modes devoid of the acceleration-driven magneto-Rayleigh-Taylor (MRT) instability]; (2) axially magnetized, imploding liners (where MHD modes couple to MRT) generate m = 1 or m = 2 helical modes that persist from the implosion to the subsequent explosion stage; (3) the merging of instability structures is a mechanism that enables the appearance of an exponential instability growth rate for a longer than expected time-period; and (4) an inverse cascade in both the axial and azimuthal wavenumbers, k and m, may be responsible for the final m = 2 helical structure observed in our experiments. These experiments are particularly relevant to the magnetized liner inertial fusion program pursued at Sandia National Laboratories, where helical instabilities have been observed.

Staged Z-pinch experiments on the Mega-Ampere current driver COBRA

NASA Astrophysics Data System (ADS)

Valenzuela, Julio; Banasek, Jacob; Byvank, Thomas; Conti, Fabio; Greenly, John; Hammer, David; Potter, William; Rocco, Sophia; Ross, Michael; Wessel, Frank; Narkis, Jeff; Rahman, Hafiz; Ruskov, Emil; Beg, Farhat

2017-10-01

Experiments were conducted on the Cornell's 1 MA, 100 ns current driver COBRA with the goal of better understanding the Staged Z-pinch physics and validating MHD codes. We used a gas injector composed of an annular (1.2 cm radius) high atomic number (e.g., Ar or Kr) gas-puff and an on-axis plasma gun that delivers the ionized hydrogen target. Liner implosion velocity and stability were studied using laser shadowgraphy and interferometry as well as XUV imaging. From the data, the signature of the MRT instability and zippering effect can be seen, but time integrated X-ray imaging show a stable target plasma. A key component of the experiment was the use of optical Thomson scattering (TS) diagnostics to characterize the liner and target plasmas. By fitting the experimental scattered spectra with synthetic data, electron and ion temperature as well as density can be obtained. Preliminary analysis shows significant scattered line broadening from the plasma on-axis ( 0.5 mm diameter) which can be explained by either a low temperature H plasma with Te =Ti =75eV, or by a hot plasma with Ti =3keV, Te =350eV if an Ar-H mixture is present with an Ar fraction higher than 10%. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

Beam heated linear theta-pinch device for producing hot plasmas

DOEpatents

Bohachevsky, Ihor O.

1981-01-01

A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

Collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet

NASA Astrophysics Data System (ADS)

Espinosa, G.; Gil, J. M.; Rodriguez, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Suzuki-Vidal, F.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G.; Pickworth, L. A.; Skidmore, J.

2015-12-01

A computational investigation based on collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet is presented. The jet, both in vacuum and in argon ambient gas, was produced on the MAGPIE (Mega Ampere Generator for Plasma Implosion Experiments) generator and is formed by ablation of an aluminum foil driven by a 1.4 MA, 250 ns current pulse in a radial foil Z-pinch configuration. In this work, population kinetics and radiative properties simulations of the jet in different theoretical approximations were performed. In particular, local thermodynamic equilibrium (LTE), non-LTE steady state (SS) and non-LTE time dependent (TD) models have been considered. This study allows us to make a convenient microscopic characterization of the aluminum plasma jet.

Existence of a return direction for plasma escaping from a pinched column in a plasma focus discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubes, P.; Cikhardt, J.; Klir, D.

2015-05-15

The use of multi-frame interferometry used on the PF-1000 device with the deuterium filling showed the existence of a return motion of the top of several lobules of the pinched column formed at the pinched plasma column. This phenomenon was observed in the presence of an over-optimal mass in front of the anode, which depressed the intensity of the implosion and the smooth surface of the pinched plasma column. The observed evolution was explored through the use of closed poloidal currents transmitted outside the pinched plasma. This interpretation complements the scenario of the closed currents flowing within the structures insidemore » the pinched column, which has been published recently on the basis of observations from interferometry, neutron, and magnetic probe diagnostics on this device.« less

Axial magnetic field injection in magnetized liner inertial fusion

NASA Astrophysics Data System (ADS)

Gourdain, P.-A.; Adams, M. B.; Davies, J. R.; Seyler, C. E.

2017-10-01

MagLIF is a fusion concept using a Z-pinch implosion to reach thermonuclear fusion. In current experiments, the implosion is driven by the Z-machine using 19 MA of electrical current with a rise time of 100 ns. MagLIF requires an initial axial magnetic field of 30 T to reduce heat losses to the liner wall during compression and to confine alpha particles during fusion burn. This field is generated well before the current ramp starts and needs to penetrate the transmission lines of the pulsed-power generator, as well as the liner itself. Consequently, the axial field rise time must exceed hundreds of microseconds. Any coil capable of being submitted to such a field for that length of time is inevitably bulky. The space required to fit the coil near the liner, increases the inductance of the load. In turn, the total current delivered to the load decreases since the voltage is limited by driver design. Yet, the large amount of current provided by the Z-machine can be used to produce the required 30 T field by tilting the return current posts surrounding the liner, eliminating the need for a separate coil. However, the problem now is the field penetration time, across the liner wall. This paper discusses why skin effect arguments do not hold in the presence of resistivity gradients. Numerical simulations show that fields larger than 30 T can diffuse across the liner wall in less than 60 ns, demonstrating that external coils can be replaced by return current posts with optimal helicity.

Interferometric analysis of laboratory photoionized plasmas utilizing supersonic gas jet targets.

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2018-06-01

Photoionized plasmas are an important component of active galactic nuclei, x-ray binary systems and other astrophysical objects. Laboratory produced photoionized plasmas have mainly been studied at large scale facilities, due to the need for high intensity broadband x-ray flux. Using supersonic gas jets as targets has allowed university scale pulsed power generators to begin similar research. The two main advantages of this approach with supersonic gas jets include: possibility of a closer location to the x-ray source and no attenuation related to material used for containment and or tamping. Due to these factors, this experimental platform creates a laboratory environment that more closely resembles astrophysical environments. This system was developed at the Nevada Terawatt Facility using the 1 MA pulsed power generator Zebra. Neon, argon, and nitrogen supersonic gas jets are produced approximately 7-8mm from the z-pinch axis. The high intensity broadband x-ray flux produced by the collapse of the z-pinch wire array implosion irradiates the gas jet. Cylindrical wire arrays are made with 4 and 8 gold 10µm thick wire. The z-pinch radiates approximately 12-16kj of x-ray energy, with x-ray photons under 1Kev in energy. The photoionized plasma is measured via x-ray absorption spectroscopy and interferometry. A Mach-Zehnder interferometer is used to the measure neutral density of the jet prior to the zebra shot at a wavelength of 266 nm. A dual channel air-wedge shearing interferometer is used to measure electron density of the ionized gas jet during the shot, at wavelengths of 532nm and 266nm. Using a newly developed interferometric analysis tool, average ionization state maps of the plasma can be calculated. Interferometry for nitrogen and argon show an average ionization state in the range of 3-8. Preliminary x-ray absorption spectroscopy collected show neon absorption lines. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.

Neutron spectra from beam-target reactions in dense Z-pinches

NASA Astrophysics Data System (ADS)

Appelbe, B.; Chittenden, J.

2015-10-01

The energy spectrum of neutrons emitted by a range of deuterium and deuterium-tritium Z-pinch devices is investigated computationally using a hybrid kinetic-MHD model. 3D MHD simulations are used to model the implosion, stagnation, and break-up of dense plasma focus devices at currents of 70 kA, 500 kA, and 2 MA and also a 15 MA gas puff. Instabilities in the MHD simulations generate large electric and magnetic fields, which accelerate ions during the stagnation and break-up phases. A kinetic model is used to calculate the trajectories of these ions and the neutron spectra produced due to the interaction of these ions with the background plasma. It is found that these beam-target neutron spectra are sensitive to the electric and magnetic fields at stagnation resulting in significant differences in the spectra emitted by each device. Most notably, magnetization of the accelerated ions causes the beam-target spectra to be isotropic for the gas puff simulations. It is also shown that beam-target spectra can have a peak intensity located at a lower energy than the peak intensity of a thermonuclear spectrum. A number of other differences in the shapes of beam-target and thermonuclear spectra are also observed for each device. Finally, significant differences between the shapes of beam-target DD and DT neutron spectra, due to differences in the reaction cross-sections, are illustrated.

Current scaling of radiated power for 40-mm diameter single wire arrays on Z

NASA Astrophysics Data System (ADS)

Nash, T. J.; Cuneo, M. E.; Spielman, R. B.; Chandler, G. A.; Leeper, R. J.; Seaman, J. F.; McGurn, J.; Lazier, S.; Torres, J.; Jobe, D.; Gilliland, T.; Nielsen, D.; Hawn, R.; Bailey, J. E.; Lake, P.; Carlson, A. L.; Seamen, H.; Moore, T.; Smelser, R.; Pyle, J.; Wagoner, T. C.; LePell, P. D.; Deeney, C.; Douglas, M. R.; McDaniel, D.; Struve, K.; Mazarakis, M.; Stygar, W. A.

2004-11-01

In order to estimate the radiated power that can be expected from the next-generation Z-pinch driver such as ZR at 28 MA, current-scaling experiments have been conducted on the 20 MA driver Z. We report on the current scaling of single 40 mm diameter tungsten 240 wire arrays with a fixed 110 ns implosion time. The wire diameter is decreased in proportion to the load current. Reducing the charge voltage on the Marx banks reduces the load current. On one shot, firing only three of the four levels of the Z machine further reduced the load current. The radiated energy scaled as the current squared as expected but the radiated power scaled as the current to the 3.52±0.42 power due to increased x-ray pulse width at lower current. As the current is reduced, the rise time of the x-ray pulse increases and at the lowest current value of 10.4 MA, a shoulder appears on the leading edge of the x-ray pulse. In order to determine the nature of the plasma producing the leading edge of the x-ray pulse at low currents further shots were taken with an on-axis aperture to view on-axis precursor plasma. This aperture appeared to perturb the pinch in a favorable manner such that with the aperture in place there was no leading edge to the x-ray pulses at lower currents and the radiated power scaled as the current squared ±0.75. For a full-current shot we will present x-ray images that show precursor plasma emitting on-axis 77 ns before the main x-ray burst.

Wire array Z-pinch insights for enhanced x-ray production

NASA Astrophysics Data System (ADS)

Sanford, T. W. L.; Mock, R. C.; Spielman, R. B.; Haines, M. G.; Chittenden, J. P.; Whitney, K. G.; Apruzese, J. P.; Peterson, D. L.; Greenly, J. B.; Sinars, D. B.; Reisman, D. B.; Mosher, D.

1999-05-01

Comparisons of measured total radiated x-ray power from annular wire-array z-pinches with a variety of models as a function of wire number, array mass, and load radius are reviewed. The data, which are comprehensive, have provided important insights into the features of wire-array dynamics that are critical for high x-ray power generation. Collectively, the comparisons of the data with the model calculations suggest that a number of underlying dynamical mechanisms involving cylindrical asymmetries and plasma instabilities contribute to the measured characteristics. For example, under the general assumption that the measured risetime of the total-radiated-power pulse is related to the thickness of the plasma shell formed on axis, the Heuristic Model [IEEE Trans. Plasma Sci. 26, 1275 (1998)] agrees with the measured risetime under a number of specific assumptions about the way the breakdown of the wires, the wire-plasma expansion, and the Rayleigh-Taylor instability in the r-z plane, develop. Likewise, in the high wire-number regime (where the wires are calculated to form a plasma shell prior to significant radial motion of the shell) the comparisons show that the variation in the power of the radiation generated as a function of load mass and array radius can be simulated by the two-dimensional Eulerian-radiation- magnetohydrodynamics code (E-RMHC) [Phys. Plasmas 3, 368 (1996)], using a single random-density perturbation that seeds the Rayleigh-Taylor instability in the r-z plane. For a given pulse-power generator, the comparisons suggest that (1) the smallest interwire gaps compatible with practical load construction and (2) the minimum implosion time consistent with the optimum required energy coupling of the generator to the load should produce the highest total-radiated-power levels.

Increase in the energy density of the pinch plasma in 3D implosion of quasi-spherical wire arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V., E-mail: alexvv@triniti.ru; Gasilov, V. A.; Grabovski, E. V.

Results are presented from experimental studies of the characteristics of the soft X-ray (SXR) source formed in the implosion of quasi-spherical arrays made of tungsten wires and metalized kapron fibers. The experiments were carried out at the Angara-5-1 facility at currents of up to 3 MA. Analysis of the spatial distribution of hard X-ray emission with photon energies above 20 keV in the pinch images taken during the implosion of quasi-spherical tungsten wire arrays (QTWAs) showed that a compact quasi-spherical plasma object symmetric with respect to the array axis formed in the central region of the array. Using a diffractionmore » grazing incidence spectrograph, spectra of SXR emission with wavelengths of 20–400 Å from the central, axial, and peripheral regions of the emission source were measured with spatial resolutions along the array radius and height in the implosion of QTWAs. It is shown that the emission spectra of the SXR sources formed under the implosion of quasi-spherical and cylindrical tungsten wire arrays at currents of up to 3 MA have a maximum in the wavelength range of 50–150 Å. It is found that, during the implosion of a QTWA with a profiled linear mass, a redistribution of energy in the emission spectrum takes place, which indicates that, during 3D implosion, the energy of longitudinal motion of the array material additionally contributes to the radiation energy. It is also found that, at close masses of the arrays and close values of the current in the range of 2.4{sup −3} MA, the average energy density in the emission source formed during the implosion of a quasi-spherical wire array is larger by a factor of 7 than in the source formed during the implosion of a cylindrical wire array. The experimental data were compared with results of 3D simulations of plasma dynamics and radiation generation during the implosion of quasi-spherical wire arrays with a profiled mass by using the MARPLE-3D radiative magnetohydrodynamic code, developed at the Keldysh Institute of Applied Mathematics, Russian Academy of Sciences.« less

Compression dynamics of quasi-spherical wire arrays with different linear mass profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitrofanov, K. N., E-mail: mitrofan@triniti.ru; Aleksandrov, V. V.; Gritsuk, A. N.

Results of experimental studies of the implosion of quasi-spherical wire (or metalized fiber) arrays are presented. The goal of the experiments was to achieve synchronous three-dimensional compression of the plasma produced in different regions of a quasi-spherical array into its geometrical center. To search for optimal synchronization conditions, quasi-spherical arrays with different initial profiles of the linear mass were used. The following dependences of the linear mass on the poloidal angle were used: m{sub l}(θ) ∝ sin{sup –1}θ and m{sub l}(θ) ∝ sin{sup –2}θ. The compression dynamics of such arrays was compared with that of quasi-spherical arrays without linear massmore » profiling, m{sub l}(θ) = const. To verify the experimental data, the spatiotemporal dynamics of plasma compression in quasi-spherical arrays was studied using various diagnostics. The experiments on three-dimensional implosion of quasi-spherical arrays made it possible to study how the frozen-in magnetic field of the discharge current penetrates into the array. By measuring the magnetic field in the plasma of a quasi-spherical array, information is obtained on the processes of plasma production and formation of plasma flows from the wire/fiber regions with and without an additionally deposited mass. It is found that penetration of the magnetic flux depends on the initial linear mass profile m{sub l}(θ) of the quasi-spherical array. From space-resolved spectral measurements and frame imaging of plasma X-ray emission, information is obtained on the dimensions and shape of the X-ray source formed during the implosion of a quasi-spherical array. The intensity of this source is estimated and compared with that of the Z-pinch formed during the implosion of a cylindrical array.« less

Z-Pinch Fusion for Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

SPIELMAN,RICK B.

2000-01-01

Z pinches, the oldest fusion concept, have recently been revisited in light of significant advances in the fields of plasma physics and pulsed power engineering. The possibility exists for z-pinch fusion to play a role in commercial energy applications. We report on work to develop z-pinch fusion concepts, the result of an extensive literature search, and the output for a congressionally-mandated workshop on fusion energy held in Snowmass, Co July 11-23,1999.

Overview of the Fusion Z-Pinch Experiment FuZE

NASA Astrophysics Data System (ADS)

Weber, T. R.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; UW/LLNL Team

2016-10-01

Previously, the ZaP device, at the University of Washington, demonstrated sheared flow stabilized (SFS) Z-pinch plasmas. Instabilities that have historically plagued Z-pinch plasma confinement were mitigated using sheared flows generated from a coaxial plasma gun of the Marshall type. Based on these results, a new SFS Z-pinch experiment, the Fusion Z-pinch Experiment (FuZE), has been constructed. FuZE is designed to investigate the scaling of SFS Z-pinch plasmas towards fusion conditions. The experiment will be supported by high fidelity physics modeling using kinetic and fluid simulations. Initial plans are in place for a pulsed fusion reactor following the results of FuZE. Notably, the design relies on proven commercial technologies, including a modest discharge current (1.5 MA) and voltage (40 kV), and liquid metal electrodes. Supported by DoE FES, NNSA, and ARPA-E ALPHA.

Neutron generation from Z-pinches

NASA Astrophysics Data System (ADS)

Vikhrev, V. V.; Korolev, V. D.

2007-05-01

Recent advances in both experimental and theoretical studies on neutron generation in various Z-pinch facilities are reviewed. The main methods for enhancing neutron emission from the Z-pinch plasma are described, and the problems of igniting a thermonuclear burn wave in this plasma are discussed.

Characterisation of the current switch mechanism in two-stage wire array Z-pinches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burdiak, G. C.; Lebedev, S. V.; Harvey-Thompson, A. J.

2015-11-15

In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA, 240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inverse wire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wire array, before rapidly switching the majority of the generator current into the load after a 100–150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse is presented. Measurements of the load resistivity and energy deposition suggest significant bulk heating of the array mass occurs. Themore » ∼5 kA pre-pulse delivers ∼0.8 J of energy to the load, leaving it in a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse array begins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicate that the main current switch may evolve in part as a plasma flow switch, driven by the expansion of a magnetic cavity and plasma bubble along the length of the load array. Analysis of implosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, corresponding to a doubling of the generator dI/dt. Potential scaling of the device to higher current machines is discussed.« less

Z-Pinch Fusion Propulsion

NASA Technical Reports Server (NTRS)

Miernik, Janie

2011-01-01

Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Shorter trips are better for humans in the harmful radiation environment of deep space. Nuclear propulsion and power plants can enable high Ispand payload mass fractions because they require less fuel mass. Fusion energy research has characterized the Z-Pinch dense plasma focus method. (1) Lightning is form of pinched plasma electrical discharge phenomena. (2) Wire array Z-Pinch experiments are commonly studied and nuclear power plant configurations have been proposed. (3) Used in the field of Nuclear Weapons Effects (NWE) testing in the defense industry, nuclear weapon x-rays are simulated through Z-Pinch phenomena.

On the Heating of Ions in Noncylindrical Z-Pinches

NASA Astrophysics Data System (ADS)

Svirsky, E. B.

2018-01-01

The method proposed here for analyzing processes in a hot plasma of noncylindrical Z-pinches is based on separation of the group of high-energy ions into a special fraction. Such ions constitute an insignificant fraction ( 10%) of the total volume of the Z-pinch plasma, but these ions contribute the most to the formation of conditions in which the pinch becomes a source of nuclear fusion products and X-ray radiation. The method allows a quite correct approach to obtaining quantitative estimates of the plasma parameters, the nuclear fusion energy yield, and the features of neutron fluxes in experiments with Z-pinches.

Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Vladimir V.

Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics,more » magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated plasma will be studied to estimate its contribution to the Doppler broadening of x-ray lines. Development of “necks” and “hot spots” will be studied with high-resolution UV diagnostics, an x-ray streak camera, and x-ray spectroscopy. Laser initiation of hot spots in Z pinches will be tested. A Faraday rotation diagnostic at 266 nm will be applied to 1-10 MG magnetic fields. For magnetic fields B>20 MG, suggested in micropinches, Cotton-Mouton and cutoff diagnostics will be applied. A picosecond optical Kerr shutter will be tested to increase a sensitivity of UV methods for application at multi-MA Z pinches. The proposal is based on the experimental capability of NTF. The Zebra generator produces 1-1.7 MA Z-pinches with electron plasma density of 10 20-10 21cm -3, electron temperature of 0.5-1 keV, and magnetic fields >10 MG. The Leopard laser was upgraded to energy of 90-J at 0.8 ns. This regime will be used for laser initiation of hot spots. A further upgrade to energy of 250-J is suggested for laser-Z-pinch interaction. A picosecond regime will be used for optical gating. A 10-TW Tomcat laser at NTF is available for the high energy UV laser probing of the Z-pinch. Two graduate students will develop new optical and x-ray diagnostics, carry out experiments, and process experimental data. Other students will be involved in the design and fabrication of loads, supporting regular optical and x-ray diagnostics, and data processing. The new plasma diagnostics may be applied to HEDP experiments at NTF and other multi-MA generators. The feasibility of the research plan is based on the experience of the scientific team in Z-pinch plasma physics, laser physics, development of new plasma diagnostics, and the experimental capability of NTF. The experimental group of Dr. V. V. Ivanov (UNR) collaborates with a group for Z pinch MHD modeling of Dr. J. P. Chittenden (Imperial College, London), and theoretical group of Dr. D. D. Ryutov (LLNL). The suggested research ideas are supported by preliminary experiments.« less

Producing High-Performance, Stable, Sheared-Flow Z-Pinches in the FuZE project

NASA Astrophysics Data System (ADS)

Golingo, R. P.; Shumlak, U.,; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; University of Washington (UW) Collaboration; Lawrence Livermore National Laboratory (LLNL) Collaboration

2017-10-01

The Fusion Z-Pinch Experiment (FuZE) has made significant strides towards generating high-performance, stable Z-pinch plasmas with goals of ne = 1018 cm-3 and T =1 keV. The Z-pinch plasmas are stabilized with a sheared axial flow that is driven by a coaxial accelerator. The new FuZE device has been constructed and reproduces the major scientific achievements the ZaP project at the University of Washington; ne = 1016 cm-3,T = 100 eV, r<1 cm, and tstable >20 μs. These parameters are measured with an array of magnetic field probes, spectroscopy, and fast framing cameras. The plasma parameters are achieved using a small fraction of the maximum energy storage and gas injection capability of the FuZE device. Higher density, ne = 5×1017 cm-3, and temperature, T = 500 eV, Z-pinch plasmas are formed by increasing the pinch current. At the higher voltages and currents, the ionization rates in the accelerator increase. By modifying the neutral gas profile in the accelerator, the plasma flow from the accelerator is maintained, driving the flow shear. Formation and sustainment of the sheared-flow Z-pinch plasma will be discussed. Experimental data demonstrating high performance plasmas in a stable Z-pinches will be shown. This work is supported by an award from US ARPA-E.

Basis set expansion for inverse problems in plasma diagnostic analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, B.; Ruiz, C. L.

A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)] is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20–25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M.more » Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.« less

Basis set expansion for inverse problems in plasma diagnostic analysis

NASA Astrophysics Data System (ADS)

Jones, B.; Ruiz, C. L.

2013-07-01

A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)], 10.1063/1.1482156 is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20-25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.

Observation of fast expansion velocity with insulating tungsten wires on ∼80 kA facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, M.; Li, Y.; State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

2016-07-15

This paper presents experimental results on the effects of insulating coatings on tungsten planar wire array Z-pinches on an 80 kA, 100 ns current facility. Expansion velocity is obviously increased from ∼0.25 km/s to ∼3.5 km/s by using the insulating coatings. It can be inferred that the wire cores are in gaseous state with this fast expansion velocity. An optical framing camera and laser probing images show that the standard wire arrays have typical ablation process which is similar to their behaviors on mega-ampere facilities. The ablation process and precursor plasma are suppressed for dielectric tungsten wires. The wire array implosion might be improvedmore » if these phenomena can be reproduced on Mega-ampere facilities.« less

Core/corona modeling of diode-imploded annular loads

NASA Astrophysics Data System (ADS)

Terry, R. E.; Guillory, J. U.

1980-11-01

The effects of a tenuous exterior plasma corona with anomalous resistivity on the compression and heating of a hollow, collisional aluminum z-pinch plasma are predicted by a one-dimensional code. As the interior ("core") plasma is imploded by its axial current, the energy exchange between core and corona determines the current partition. Under the conditions of rapid core heating and compression, the increase in coronal current provides a trade-off between radial acceleration and compression, which reduces the implosion forces and softens the pitch. Combined with a heuristic account of energy and momentum transport in the strongly coupled core plasma and an approximate radiative loss calculation including Al line, recombination and Bremsstrahlung emission, the current model can provide a reasonably accurate description of imploding annular plasma loads that remain azimuthally symmetric. The implications for optimization of generator load coupling are examined.

X-ray Heating and Electron Temperature of Laboratory Photoionized Plasmas

NASA Astrophysics Data System (ADS)

Mancini, Roberto; Lockard, Tom; Mayes, Daniel C.; Loisel, Guillaume; Bailey, James E.; Rochau, Gregory; Abdallah, J.; Golovkin, I.

2018-06-01

In separate experiments performed at the Z facility of Sandia National Laboratories two different samples were employed to produce and characterize photoionized plasmas. One was a gas cell filled with neon, and the other was a thin silicon layer coated with plastic. Both samples were driven by the broadband x-ray flux produced at the collapse of a wire array z-pinch implosion. Transmission spectroscopy of a narrowband portion of the x-ray flux was used to diagnose the charge state distribution, and the electron temperature was extracted from a Li-like ion level population ratio. To interpret the temperature measurement, we performed Boltzmann kinetics and radiation-hydrodynamic simulations. We found that non-equilibrium atomic physics and the coupling of the radiation flux to the atomic level population kinetics play a critical role in modeling the x-ray heating of photoionized plasmas. In spite of being driven by similar x-ray drives, differences of ionization and charged state distributions in the neon and silicon plasmas are reflected in the plasma heating and observed electron temperatures.This work was sponsored in part by DOE Office of Science Grant DE-SC0014451, and the Z Facility Fundamental Science Program of SNL.

Hohlraum-driven mid-Z (SiO2) double-shell implosions on the omega laser facility and their scaling to NIF.

PubMed

Robey, H F; Amendt, P A; Milovich, J L; Park, H-S; Hamza, A V; Bono, M J

2009-10-02

High-convergence, hohlraum-driven implosions of double-shell capsules using mid-Z (SiO2) inner shells have been performed on the OMEGA laser facility [T. R. Boehly, Opt. Commun. 133, 495 (1997)]. These experiments provide an essential extension of the results of previous low-Z (CH) double-shell implosions [P. A. Amendt, Phys. Rev. Lett. 94, 065004 (2005)] to materials of higher density and atomic number. Analytic modeling, supported by highly resolved 2D numerical simulations, is used to account for the yield degradation due to interfacial atomic mixing. This extended experimental database from OMEGA enables a validation of the mix model, and provides a means for quantitatively assessing the prospects for high-Z double-shell implosions on the National Ignition Facility [Paisner, Laser Focus World 30, 75 (1994)].

Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation.

PubMed

Rochau, Gregory A; Bailey, J E; Macfarlane, J J

2005-12-01

High-power Z pinches on Sandia National Laboratories' Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF2 were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution in each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s-->2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1sigma to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF2 samples is understood within the accuracy of the spectroscopic method.

The electro-thermal stability of tantalum relative to aluminum and titanium in cylindrical liner ablation experiments at 550 kA

NASA Astrophysics Data System (ADS)

Steiner, Adam M.; Campbell, Paul C.; Yager-Elorriaga, David A.; Cochrane, Kyle R.; Mattsson, Thomas R.; Jordan, Nicholas M.; McBride, Ryan D.; Lau, Y. Y.; Gilgenbach, Ronald M.

2018-03-01

Presented are the results from the liner ablation experiments conducted at 550 kA on the Michigan Accelerator for Inductive Z-Pinch Experiments. These experiments were performed to evaluate a hypothesis that the electrothermal instability (ETI) is responsible for the seeding of magnetohydrodynamic instabilities and that the cumulative growth of ETI is primarily dependent on the material-specific ratio of critical temperature to melting temperature. This ratio is lower in refractory metals (e.g., tantalum) than in non-refractory metals (e.g., aluminum or titanium). The experimental observations presented herein reveal that the plasma-vacuum interface is remarkably stable in tantalum liner ablations. This stability is particularly evident when contrasted with the observations from aluminum and titanium experiments. These results are important to various programs in pulsed-power-driven plasma physics that depend on liner implosion stability. Examples include the magnetized liner inertial fusion (MagLIF) program and the cylindrical dynamic material properties program at Sandia National Laboratories, where liner experiments are conducted on the 27-MA Z facility.

ZaP-HD: High Energy Density Z-Pinch Plasmas using Sheared Flow Stabilization

NASA Astrophysics Data System (ADS)

Golingo, R. P.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Hughes, M. C.; Kim, B.; Ross, M. P.; Weed, J. R.

2015-11-01

The ZaP-HD flow Z-pinch project investigates scaling the flow Z-pinch to High Energy Density Plasma, HEDP, conditions by using sheared flow stabilization. ZaP used a single power supply to produce 100 cm long Z-pinches that were quiescent for many radial Alfven times and axial flow-through times. The flow Z-pinch concept provides an approach to achieve HED plasmas, which are dimensionally large and persist for extended durations. The ZaP-HD device replaces the single power supply from ZaP with two separate power supplies to independently control the plasma flow and current in the Z-pinch. Equilibrium is determined by diagnostic measurements of the density with interferometry and digital holography, the plasma flow and temperature with passive spectroscopy, the magnetic field with surface magnetic probes, and plasma emission with optical imaging. The diagnostics fully characterize the plasma from its initiation in the coaxial accelerator, through the pinch, and exhaust from the assembly region. The plasma evolution is modeled with high resolution codes: Mach2, WARPX, and NIMROD. Experimental results and scaling analyses are presented. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

Z-Pinch Pulsed Plasma Propulsion Technology Development

NASA Technical Reports Server (NTRS)

Polsgrove, Tara; Adams, Robert B.; Fabisinski, Leo; Fincher, Sharon; Maples, C. Dauphne; Miernik, Janie; Percy, Tom; Statham, Geoff; Turner, Matt; Cassibry, Jason;

Overview of the FuZE Fusion Z-Pinch Experiment

NASA Astrophysics Data System (ADS)

Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.

2017-10-01

Successful results of the sheared flow stabilized (SFS) Z-pinch from ZaP and ZaP-HD have motivated the new FuZE project to scale the plasma performance to fusion conditions. The SFS Z-pinch is immune to the instabilities that plague the conventional Z-pinch yet maintains the same favorable radial scaling. The plasma density and temperature increase rapidly with decreasing plasma radius, which naturally leads to a compact configuration at fusion conditions. The SFS Z-pinch is being investigated as a novel approach to a compact fusion device in a collaborative ARPA-E ALPHA project with the University of Washington and Lawrence Livermore National Laboratory. The project includes an experimental effort coupled with high-fidelity physics modeling using kinetic and fluid simulations. Along with scaling law analysis, computational and experimental results from the FuZE device are presented. This work is supported by an award from US ARPA-E.

About plasma points' generation in Z-pinch

NASA Astrophysics Data System (ADS)

Afonin, V. I.; Potapov, A. V.; Lazarchuk, V. P.; Murugov, V. M.; Senik, A. V.

1997-05-01

The streak tube study results (at visible and x-ray ranges) of dynamics of fast Z-pinch formed at explosion of metal wire in diode of high current generator are presented. Amplitude of current in the load reached ˜180 kA at increase time ˜50 ns. The results' analysis points to capability of controlling hot plasma points generation process in Z-pinch.

Enhancing the x-ray output of a single-wire explosion with a gas-puff based plasma opening switch

NASA Astrophysics Data System (ADS)

Engelbrecht, Joseph T.; Ouart, Nicholas D.; Qi, Niansheng; de Grouchy, Philip W.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Banasek, Jacob T.; Potter, William M.; Rocco, Sophia V.; Hammer, David A.; Kusse, Bruce R.; Giuliani, John L.

2018-02-01

We present experiments performed on the 1 MA COBRA generator using a low density, annular, gas-puff z-pinch implosion as an opening switch to rapidly transfer a current pulse into a single metal wire on axis. This gas-puff on axial wire configuration was studied for its promise as an opening switch and as a means of enhancing the x-ray output of the wire. We demonstrate that current can be switched from the gas-puff plasma into the wire, and that the timing of the switch can be controlled by the gas-puff plenum backing pressure. X-ray detector measurements indicate that for low plenum pressure Kr or Xe shots with a copper wire, this configuration can offer a significant enhancement in the peak intensity and temporal distribution of radiation in the 1-10 keV range.

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swadling, G. F.; Lebedev, S. V.; Niasse, N.

A series of experiments has been conducted in order to investigate the azimuthal structures formed by the interactions of cylindrically converging plasma flows during the ablation phase of aluminium wire array Z pinch implosions. These experiments were carried out using the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. The main diagnostic used in this study was a two-colour, end-on, Mach-Zehnder imaging interferometer, sensitive to the axially integrated electron density of the plasma. The data collected in these experiments reveal the strongly collisional dynamics of the aluminium ablation streams. The structure of the flows is dominated by amore » dense network of oblique shock fronts, formed by supersonic collisions between adjacent ablation streams. An estimate for the range of the flow Mach number (M = 6.2-9.2) has been made based on an analysis of the observed shock geometry. Combining this measurement with previously published Thomson Scattering measurements of the plasma flow velocity by Harvey-Thompson et al.[Physics of Plasmas 19, 056303 (2012)] allowed us to place limits on the range of the ZT{sub e} of the plasma. The detailed and quantitative nature of the dataset lends itself well as a source for model validation and code verification exercises, as the exact shock geometry is sensitive to many of the plasma parameters. Comparison of electron density data produced through numerical modelling with the Gorgon 3D MHD code demonstrates that the code is able to reproduce the collisional dynamics observed in aluminium arrays reasonably well.« less

Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacFarlane, Joseph John; Rochau, Gregory Alan; Bailey, James E.

2005-06-01

High-power Z pinches on Sandia National Laboratories Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF{sub 2} were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution inmore » each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s {yields} 2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1{sigma} to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF{sub 2} samples is understood within the accuracy of the spectroscopic method.« less

Kinetic Simulations of Dense Plasma Focus Breakdown

NASA Astrophysics Data System (ADS)

Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.

2015-11-01

A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

A 7.2 keV spherical x-ray crystal backlighter for two-frame, two-color backlighting at Sandia's Z Pulsed Power Facility

NASA Astrophysics Data System (ADS)

Schollmeier, M. S.; Knapp, P. F.; Ampleford, D. J.; Harding, E. C.; Jennings, C. A.; Lamppa, D. C.; Loisel, G. P.; Martin, M. R.; Robertson, G. K.; Shores, J. E.; Smith, I. C.; Speas, C. S.; Weis, M. R.; Porter, J. L.; McBride, R. D.

2017-10-01

Many experiments on Sandia National Laboratories' Z Pulsed Power Facility—a 30 MA, 100 ns rise-time, pulsed-power driver—use a monochromatic quartz crystal backlighter system at 1.865 keV (Si He α ) or 6.151 keV (Mn He α ) x-ray energy to radiograph an imploding liner (cylindrical tube) or wire array z-pinch. The x-ray source is generated by the Z-Beamlet laser, which provides two 527-nm, 1 kJ, 1-ns laser pulses. Radiographs of imploding, thick-walled beryllium liners at convergence ratios CR above 15 [ C R = r i ( 0 ) / r i ( t ) ] using the 6.151-keV backlighter system were too opaque to identify the inner radius r i of the liner with high confidence, demonstrating the need for a higher-energy x-ray radiography system. Here, we present a 7.242 keV backlighter system using a Ge(335) spherical crystal with the Co He α resonance line. This system operates at a similar Bragg angle as the existing 1.865 keV and 6.151 keV backlighters, enhancing our capabilities for two-color, two-frame radiography without modifying the system integration at Z. The first data taken at Z include 6.2-keV and 7.2-keV two-color radiographs as well as radiographs of low-convergence (CR about 4-5), high-areal-density liner implosions.

A 7.2 keV spherical x-ray crystal backlighter for two-frame, two-color backlighting at Sandia’s Z Pulsed Power Facility

DOE PAGES

Schollmeier, M. S.; Knapp, P. F.; Ampleford, D. J.; ...

2017-10-10

Many experiments on Sandia National Laboratories’ Z Pulsed Power Facility—a 30 MA, 100 ns rise-time, pulsed-power driver—use a monochromatic quartz crystal backlighter system at 1.865 keV (Si He α) or 6.151 keV (Mn He α) x-ray energy to radiograph an imploding liner (cylindrical tube) or wire array z-pinch. The x-ray source is generated by the Z-Beamlet laser, which provides two 527-nm, 1 kJ, 1-ns laser pulses. Radiographs of imploding, thick-walled beryllium liners at convergence ratios C R above 15 [C R=r i(0)/r i(t)] using the 6.151-keV backlighter system were too opaque to identify the inner radius ri of the linermore » with high confidence, demonstrating the need for a higher-energy x-ray radiography system. Here, we present a 7.242 keV backlighter system using a Ge(335) spherical crystal with the Co He α resonance line. This system operates at a similar Bragg angle as the existing 1.865 keV and 6.151 keV backlighters, enhancing our capabilities for two-color, two-frame radiography without modifying the system integration at Z. The first data taken at Z include 6.2-keV and 7.2-keV two-color radiographs as well as radiographs of low-convergence (C R about 4-5), high-areal-density liner implosions.« less

A 7.2 keV spherical x-ray crystal backlighter for two-frame, two-color backlighting at Sandia’s Z Pulsed Power Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schollmeier, M. S.; Knapp, P. F.; Ampleford, D. J.

Many experiments on Sandia National Laboratories’ Z Pulsed Power Facility—a 30 MA, 100 ns rise-time, pulsed-power driver—use a monochromatic quartz crystal backlighter system at 1.865 keV (Si He α) or 6.151 keV (Mn He α) x-ray energy to radiograph an imploding liner (cylindrical tube) or wire array z-pinch. The x-ray source is generated by the Z-Beamlet laser, which provides two 527-nm, 1 kJ, 1-ns laser pulses. Radiographs of imploding, thick-walled beryllium liners at convergence ratios C R above 15 [C R=r i(0)/r i(t)] using the 6.151-keV backlighter system were too opaque to identify the inner radius ri of the linermore » with high confidence, demonstrating the need for a higher-energy x-ray radiography system. Here, we present a 7.242 keV backlighter system using a Ge(335) spherical crystal with the Co He α resonance line. This system operates at a similar Bragg angle as the existing 1.865 keV and 6.151 keV backlighters, enhancing our capabilities for two-color, two-frame radiography without modifying the system integration at Z. The first data taken at Z include 6.2-keV and 7.2-keV two-color radiographs as well as radiographs of low-convergence (C R about 4-5), high-areal-density liner implosions.« less

Wire-number effects on high-power annular z-pinches and some characteristics at high wire number

DOE Office of Scientific and Technical Information (OSTI.GOV)

SANFORD,THOMAS W. L.

2000-05-23

Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.

Numerical simulation of fiber and wire array Z-pinches with Trac-II

NASA Astrophysics Data System (ADS)

Reisman, David Barton

Trac-II is a two dimensional axisymmetric resistive MHD code. It simulates all three spatial components (r, z, φ) of the magnetic field and fluid velocity vectors, and the plasma is treated as a single fluid with two temperatures (Te,Ti). In addition, it can optionally include a self-consistent external circuit. Recent modifications to the code include the addition of the 3-T radiation model, a 4-phase (solid- liquid-vapor-plasma) equation of state model (QEOS), a 4- phase electrical/thermal conductivity model, and an implicit solution of poloidal (Bz,Br) magnetic field diffusion. These changes permit a detailed study of fiber and wire array Z-pinches. Specifically, Trac-II is used to study the wire array Z-pinch at the PBFA-Z pulse power generator at Sandia National Laboratory. First, in 1-D we examine the behavior of a single wire in the Z-pinch. Then, using these results as initial radial conditions in 2-D, we investigate the dynamics of wire array configurations in the r-z and r-θ plane. In the r- z plane we examine the growth of the m = 0 or ``sausage'' instability in single wires within the array. In the r-θ plane we examine the merging behavior between neighboring wires. Special emphasis is placed on trying to explain how instability growth affects the performance of the Z-pinch. Lastly, we introduce Trac-III, a 3-D MHD code, and illustrate the m = 1 or ``kink'' instability. We also discuss how Trac-III can be modified to simulate the wire array Z-pinch.

Designs and Plans for MAIZE: a 1 MA LTD-Driven Z-Pinch

NASA Astrophysics Data System (ADS)

Gilgenbach, R. M.; Gomez, M. R.; Zier, J.; Tang, W.; French, D. M.; Hoff, B. W.; Jordan, N.; Cruz, E.; Lau, Y. Y.; Fowler-Guzzardo, T.; Meisel, J.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

2007-11-01

We present designs and experimental plans of the first 1 MA z-pinch in the USA to be driven by a Linear Transformer Driver (LTD). The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute for High Current Electronics, utilizing 80 capacitors and 40 spark gap switches to deliver a 1 MA, 100 kV pulse with <100 ns risetime. Designs will be presented of a low-inductance MITL terminated in a wire-array z-pinch. Initial, planned experiments will evaluate the LTD driving time-changing inductance of imploding 4-16 wire-array z-pinches. Wire ablation dynamics, axial-correlations and instability development will be explored. *This work was supported by U. S. DoE through Sandia National Laboratories award number 240985 to the University of Michigan. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

2D Kinetic Particle in Cell Simulations of a Shear-Flow Stabilized Z-Pinch

NASA Astrophysics Data System (ADS)

Tummel, Kurt; Higginson, Drew; Schmidt, Andrea; Link, Anthony; McLean, Harry; Shumlak, Uri; Nelson, Brian; Golingo, Raymond; Claveau, Elliot; Lawrence Livermore National Lab Team; University of Washington Team

2016-10-01

The Z-pinch is a relatively simple and attractive potential fusion reactor design, but attempts to develop such a reactor have consistently struggled to overcome Z-pinch instabilities. The ``sausage'' and ``kink'' modes are among the most robust and prevalent Z-pinch instabilities, but theory and simulations suggest that axial flow-shear, dvz / dr ≠ 0 , can suppress these modes. Experiments have confirmed that Z-pinch plasmas with embedded axial flow-shear display a significantly enhanced resilience to the sausage and kink modes at a demonstration current of 50kAmps. A new experiment is under way to test the concept at higher current, and efforts to model these plasmas are being expanded. The performance and stability of these devices will depend on features like the plasma viscosity, anomalous resistivity, and finite Larmor radius effects, which are most accurately characterized in kinetic models. To predict these features, kinetic simulations using the particle in cell code LSP are now in development, and initial benchmarking and 2D stability analyses of the sausage mode are presented here. These results represent the first kinetic modeling of the flow-shear stabilized Z-pinch. This work is funded by the USDOE/ARPAe Alpha Program. Prepared by LLNL under Contract DE-AC52-07NA27344.

Shock formation in Ne, Ar, Kr, and Xe on deuterium gas puff implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narkis, J.; Rahman, H. U.; Ney, P.

2016-12-29

1- and 2-D simulations of 1-cm radius, gas-puff liners of Ne, Ar, Kr, and Xe imploding onto a deuterium target are conducted using the discharge parameters for the Zebra (1 MA, 130 ns) driver using the resistive MHD code MACH2. This is an implementation of the Staged Z-pinch concept, in which the target is driven to high-energy-density first by shock compression launched by a diffused azimuthal magnetic field (J×B force), and then by the adiabatic compression as the liner converges on axis. During the run-in phase, the initial shock heating preheats the deuterium plasma, with a subsequent stable, adiabatic compressionmore » heating the target to high energy density. Shock compression of the target coincides with the development of a J×B force at the target/liner interface. Stronger B-field transport and earlier shock compression increases with higher-Z liners, which results in an earlier shock arrival on axis. As a result, delayed shock formation in lower-Z liners yields a relative increase in shock heating, however, the 2-D simulations show an increased target isolation from magneto-Rayleigh-Taylor instability penetration, suggesting that an optimal balance between these two effects is reached in an Ar or Kr liner, rather than with Xe.« less

Study of Plasma Flow Modes in Imploding Nested Arrays

NASA Astrophysics Data System (ADS)

Mitrofanov, K. N.; Aleksandrov, V. V.; Gritsuk, A. N.; Branitsky, A. V.; Frolov, I. N.; Grabovski, E. V.; Sasorov, P. V.; Ol'khovskaya, O. G.; Zaitsev, V. I.

2018-02-01

Results from experimental studies of implosion of nested wire and fiber arrays at currents of up to 4 MA at the Angara-5-1 facility are presented. Depending on the ratio between the radii of the inner and outer arrays, different modes of the plasma flow in the space between the inner and outer arrays were implemented: the sub-Alfvénic ( V r < V A ) and super-Alfvénic ( V r > V A ) modes and a mode with the formation of the transition shock wave (SW) region between the cascades. By varying the material of the outer array (tungsten wires or kapron fibers), it is shown that the plasma flow mode between the inner and outer arrays depends on the ratio between the plasma production rates ṁ in / ṁ out in the inner and outer arrays. The obtained experimental results are compared with the results of one-dimensional MHD simulation of the plasma flow between the arrays. Stable implosion of the inner array plasma was observed in experiments with combined nested arrays consisting of a fiber outer array and a tungsten inner array. The growth rates of magnetic Rayleigh-Taylor (MRT) instability in the inner array plasma at different numbers of fibers in the outer array and different ratios between the radii of the inner and outer arrays are compared. Suppression of MRT instability during the implosion of the inner array plasma results in the formation of a stable compact Z-pinch and generation of a soft X-ray pulse. A possible scenario of interaction between the plasmas of the inner and outer arrays is offered. The stability of the inner array plasma in the stage of final compression depends on the character of interaction of plasma jets from the outer array with the magnetic field of the inner array.

Measurements of Hard X-Ray Emission Suggest Absorption Along the Path of the Inner Beams in High Foot Implosion Experiments on the NIF

NASA Astrophysics Data System (ADS)

Ralph, Joseph; Pak, Arthur; Otto, Landen; Kritcher, Andrea; Ma, Tammy; Charles, Jarrott; Callahan, Debra; Hinkel, Denise; Berzak Hopkins, Laura; Moody, John; Khan, Shahab; Doeppner, Tilo; Rygg, Ryan; Hurricane, Omar

2016-10-01

The current high foot hohlraum design fielded on the National Ignition Facility is aimed at providing uniform x-ray drive to provide a spherical implosion by lowering the gas fill from 1.6 to 0.6 mg/cc and increasing the hohlraum width from 5.75 to 6.72 mm while maintaining the same 1.8 mm capsule diameter from previous designs. These changes are intended to improve beam propagation without the need for crossed beam energy transfer. Analysis of the measurements of hard x-ray emission from the gated x-ray detector (GXD) and the static x-ray imager (SXI) looking through the laser entrance hole indicate a significant fraction of the inner beam incident energy is absorbed in the high z blow-off region (either uranium or gold) before reaching the inner wall near the equator. Comparison of inner beam absorption in this region and its effect on the implosion symmetry measurements will be presented. Additionally, the sensitivity of this absorption feature and therefore the implosion symmetry to the pulse shape, hohlraum fill pressure and fraction of energy in beams depositing energy at the hohlraum equator will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Magnetoelectric confinement and stabilization of Z pinch in a soft-x-ray Ar(+8) laser.

PubMed

Szasz, J; Kiss, M; Santa, I; Szatmari, S; Kukhlevsky, S V

2013-05-03

Magnetoelectric confinement and stabilization of the plasma column in a soft-x-ray Ar(+8) laser, which is excited by a capillary Z pinch, via the combined magnetic and electric fields of the gliding surface discharge is experimentally demonstrated. Unlike soft-x-ray lasers excited by the conventional capillary Z pinches, the magnetoelectric confinement and stabilization of plasma do provide the laser operation without using any external preionization circuit.

Astrophysically relevant radiatively cooled hypersonic bow shocks in nested wire arrays

NASA Astrophysics Data System (ADS)

Ampleford, David

2009-11-01

We have performed laboratory experiments which introduce obstructions into hypersonic plasma flows to study the formation of shocks. Astrophysical observations have demonstrated many examples of equivalent radiatively cooled bow shocks, for example the head of protostellar jets or supernova remnants passing through the interstellar medium or between discrete clumps in jets. Wire array z-pinches allow us to study quasi-planar radiatively cooled flows in the laboratory. The early stage of a wire array z-pinch implosion consists of a steady flow of the wire material towards the axis. Given a high rate of radiative cooling, these flows reach high sonic- Mach numbers, typically up to 5. The 2D nature of this configuration allows the insertion of obstacles into the flow, such as a concentric ``inner'' wire array, as has previously been studied for ICF research. Here we study the application of such a nested array to laboratory astrophysics where the inner wires act as obstructions perpendicular to the flow, and induce bow shocks. By varying the wire array material (W/Al), the significance of radiative cooling on these shocks can be controlled, and is shown to change the shock opening angle. As multiple obstructions are present, the experiments show the interaction of multiple bow shocks. It is also possible to introduce a magnetic field around the static object, increasing the opening angle of the shocks. Further experiments can be designed to control the flow density, magnetic field structure and obstruction locations. In collaboration with: S.V. Lebedev, M.E. Cuneo, C.A. Jennings, S.N. Bland, J.P. Chittenden, A. Ciardi, G.N. Hall, S.C. Bott, M. Sherlock, A. Frank, E. Blackman

Pulse Power Compression by Cutting a Dense Z-Pinch with a Laser Beam

NASA Astrophysics Data System (ADS)

Winterberg, F.

1999-07-01

A thin cut made through a z-pinch by an intense laser beam can become a magnetically insulated diode crossed by an intense ion beam. For larger cuts, the gap is crossed by an intense relativistic electron beam, stopped by magnetic bremsstrahlung resulting in a pointlike intense x-ray source. In either case, the impedance of the pinch discharge is increased, with the power delivered rising in the same pro-portion. A magnetically insulated cut is advantageous for three reasons: First, with the ion current com-parable to the Alfvèn ion current, the pinch instabilities are reduced. Second, with the energy deposit-ed into fast ions, a non-Maxwellian velocity distribution is established increasing<σ ν> value for nuclear fusion reactions taking place in the pinch discharge. Third, in a high density z-pinch plasma, the intense ion beam can launch a thermonuclear detonation wave propagating along the pinch discharge channel. For larger cuts the soft x-rays produced by magnetic bremsstrahlung can be used to drive a thermonuclear hohlraum target. Finally, the proposed pulse power compression scheme permits to use a cheap low power d.c. source charging a magnetic storage coil delivering the magnetically stored energy to the pinch discharge load by an exploding wire opening switch.

Simulations of Ar gas-puff Z-pinch radiation sources with double shells and central jets on the Z generator

DOE PAGES

Tangri, V.; Harvey-Thompson, Adam James; Giuliani, J. L.; ...

2016-10-19

Radiation-magnetohydrodynamic simulations using the non-LTE Mach2-TCRE code in (r,z) geometry are performed for two pairs of recent Ar gas-puff Z-pinch experiments on the refurbished Z generator with an 8 cm diameter nozzle. One pair of shots had an outer-to-inner shell mass ratio of 1:1.6 and a second pair had a ratio of 1:1.

First Argon Gas Puff Experiments With 500 ns Implosion Time On Sphinx Driver

NASA Astrophysics Data System (ADS)

Zucchini, F.; Calamy, H.; Lassalle, F.; Loyen, A.; Maury, P.; Grunenwald, J.; Georges, A.; Morell, A.; Bedoch, J.-P.; Ritter, S.; Combes, P.; Smaniotto, O.; Lample, R.; Coleman, P. L.; Krishnan, M.

2009-01-01

Experiments have been performed at the SPHINX driver to study potential of an Argon Gas Puff load designed by AASC. We present here the gas Puff hardware and results of the last shot series. The Argon Gas Puff load used is injected thanks to a 20 cm diameter nozzle. The nozzle has two annuli and a central jet. The pressure and gas type in each of the nozzle plena can be independently adjusted to tailor the initial gaz density distribution. This latter is selected as to obtain an increasing radial density from outer shell towards the pinch axis in order to mitigate the RT instabilities and to increase radiating mass on axis. A flashboard unit produces a high intensity UV source to pre-ionize the Argon gas. Typical dimensions of the load are 200 mm in diameter and 40 mm height. Pressures are adjusted to obtain an implosion time around 550 ns with a peak current of 3.5 MA. With the goal of improving k-shell yield a mass scan of the central jet was performed and implosion time, mainly given by outer and middle plena settings, was kept constant. Tests were also done to reduce the implosion time for two configurations of the central jet. Strong zippering of the radiation production was observed mainly due to the divergence of the central jet over the 40 mm of the load height. Due to that feature k-shell radiation is mainly obtained near cathode. Therefore tests were done to mitigate this effect first by adjusting local pressure of middle and central jet and second by shortening the pinch length. At the end of this series, best shot gave 5 kJ of Ar k-shell yield. PCD detectors showed that k-shell x-ray power was 670 GW with a FWHM of less than 10 ns.

Finite-Larmor-radius effects on z-pinch stability

NASA Astrophysics Data System (ADS)

Scheffel, Jan; Faghihi, Mostafa

1989-06-01

The effect of finite Larmor radius (FLR) on the stability of m = 1 small-axial-wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. We use the incompressible FLR MHD model; a collisionless fluid model that consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD, 2r dp/dr + m2B2/μ0 ≥ 0 predicts instability for internal modes unless the current density is singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the FLR terms are included, a normal-mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall term has a damping (but not absolutely stabilizing) effect - in agreement with earlier work. On specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m = 1 modes are then fully stabilized over the crosssection for wavelengths λ/a ≤ 1, where a denotes the pinch radius. As a general z-pinch result a critical line-density limit Nmax = 5 × 1018 m-1 is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. This limit corresponds to about five Larmor radii along the pinch radius. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 1020 m-1.

Capsule symmetry sensitivity and hohlraum symmetry calculations for the z-pinch driven hohlraum high-yield concept

NASA Astrophysics Data System (ADS)

Vesey, Roger; Cuneo, M. E.; Hanson Porter, D. L., Jr.; Mehlhorn, T. A.; Ruggles, L. E.; Simpson, W. W.; Hammer, J. H.; Landen, O.

2000-10-01

Capsule radiation symmetry is a crucial issue in the design of the z-pinch driven hohlraum approach to high-yield inertial confinement fusion [1]. Capsule symmetry may be influenced by power imbalance of the two z-pinch x-ray sources, and by hohlraum effects (geometry, time-dependent albedo, wall motion). We have conducted two-dimensional radiation-hydrodynamics calculations to estimate the symmetry sensitivity of the 220 eV beryllium ablator capsule that nominally yields 400 MJ in this concept. These estimates then determine the symmetry requirements to be met by the hohlraum design (for even Legendre modes) and by the top-bottom pinch imbalance and mistiming (for odd Legendre modes). We have used a combination of 2- and 3-D radiosity ("viewfactor"), and 2-D radiation-hydrodynamics calculations to identify hohlraum geometries that meet these symmetry requirements for high-yield, and are testing these models against ongoing Z foam ball symmetry experiments. 1. J. H. Hammer et al., Phys. Plas. 6, 2129 (1999).

Experimental study of surface insulated-standard hybrid tungsten planar wire array Z-pinches at "QiangGuang-I" facility

NASA Astrophysics Data System (ADS)

Sheng, Liang; Peng, Bodong; Li, Yang; Yuan, Yuan; Li, Mo; Zhang, Mei; Zhao, Chen; Zhao, Jizhen; Wang, Liangping

2016-01-01

The experimental results of the insulated-standard hybrid wire array Z pinches carried out on "QiangGuang-I" facility at Northwest Institute of Nuclear Technology were presented and discussed. The surface insulating can impose a significant influence on the dynamics and radiation characteristics of the hybrid wire array Z pinches, especially on the early stage (t/timp < 0.6). The expansion of insulated wires at the ablation stage is suppressed, while the streams stripped from the insulated wires move faster than that from the standard wires. The foot radiation of X-ray is enhanced by increment of the number of insulated wires, 19.6 GW, 33.6 GW, and 68.6 GW for shots 14037S, 14028H, and 14039I, respectively. The surface insulation also introduces nonhomogeneity along the single wire—the streams move much faster near the electrodes. The colliding boundary of the hybrid wire array Z pinches is bias to the insulated side approximately 0.6 mm.

Auto-magnetizing liners for magnetized inertial fusion

DOE PAGES

Slutz, S. A.; Jennings, C. A.; Awe, T. J.; ...

2017-01-20

Here, the MagLIF (Magnetized Liner Inertial Fusion) concept has demonstrated fusion-relevant plasma conditions on the Z accelerator using external field coils to magnetize the fuel before compression. We present a novel concept (AutoMag), which uses a composite liner with helical conduction paths separated by insulating material to provide fuel magnetization from the early part of the drive current, which by design rises slowly enough to avoid electrical breakdown of the insulators. Once the magnetization field is established, the drive current rises more quickly, which causes the insulators to break down allowing the drive current to follow an axial path andmore » implode the liner in the conventional z-pinch manner. There are two important advantages to AutoMag over external field coils for the operation of MagLIF. Low inductance magnetically insulated power feeds can be used to increase the drive current, and AutoMag does not interfere with diagnostic access. Also, AutoMag enables a pathway to energy applications for MagLIF, since expensive field coils will not be damaged each shot. Finally, it should be possible to generate Field Reversed Configurations (FRC) by using both external field coils and AutoMag in opposite polarities. This would provide a means to studying FRC liner implosions on the 100 ns time scale.« less

Mode selection of magneto-Rayleigh-Taylor instability from the point of view of Landau phase transition theory

NASA Astrophysics Data System (ADS)

Dan, Jia Kun; Huang, Xian Bin; Ren, Xiao Dong; Wei, Bing

2017-08-01

A theoretical model referring to mode selection of Z-pinch-driven magneto-Rayleigh-Taylor (MRT) instability, which explains the generation of fundamental instability mode and evolution of fundamental wavelength in experiments, is proposed on the basis of the Landau theory of phase transition. The basic idea of this phase transition model lies in that the appearance of MRT instability pattern can be considered as a consequence of the spontaneous generation of interfacial structure like the spontaneous magnetization in a ferromagnetic system. It is demonstrated that the amplitude of instability is responsible for the order parameter in the Landau theory of phase transition and the fundamental wavelength appears to play a role analogous to inverse temperature in thermodynamics. Further analysis indicates that the MRT instability is characterized by first order phase transition and the fundamental wavelength is proportional to the square root of energy entering into the system from the driving source. The theory predicts that the fundamental wavelength grows rapidly and saturates reaching a limiting wavelength of the order of the liner's final outer radius. The results given by this theory show qualitative agreement with the available experimental data of MRT instability of liner implosions conducted on the Sandia Z machine as well as Primary Test Stand facility at the Institute of Fluid Physics.

Polytropic scaling of a flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.; Weed, J. R.

2015-11-01

The ZaP Flow Z-Pinch project investigates the use of velocity shear to mitigate MHD instabilities. The ZaP-HD experiment produces 50 cm long pinches of varying radii. The power to the experiment is split between the plasma formation and acceleration process and the pinch assembly and compression process. Once the pinch is formed, low magnetic fluctuations indicate a quiescent, long-lived pinch. The split power supply allows more control of the pinch current than previous machine iterations, with a designed range from 50 to 150 kA. Radial force balance leads to the Bennett relation which indicates that as the pinch compresses due to increasing currents, the plasma pressure and/or linear density must change. Through ion spectroscopy and digital holographic interferometry coupled with magnetic measurements of the pinch current, the components of the Bennett relation can be fully measured. A scaling relation is then assumed to follow a polytrope as the pinch pressure, initially approximately 250 kPa, increases from an initially formed state to much higher values, approaching 100 MPa. A preliminary analysis of pinch scaling is shown corroborating with other diagnostics on the machine along with extrapolations to required currents for an HEDLP machine. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

Linear Transformer Drivers for Z-pinch Based Propulsion

NASA Technical Reports Server (NTRS)

Adams, Robert; Seidler, William; Giddens, Patrick; Fabisinski, Leo; Cassibry, Jason

2017-01-01

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD's hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept. High-Voltage pulsed power systems used for Z-Pinch experimentation have in the past largely been based on Marx Generators. Marx generators deliver the voltage and current required for the Z-Pinch, but suffer from two significant drawbacks when applied to a flight system: they are very massive, consisting of high-voltage capacitor banks insulated in oil-filled tanks and they do not lend themselves to rapid pulsing. The overall goal of Phase 2 is to demonstrate the construction of a higher voltage stack from a number of cavities each of the design proven in Phase 1 and to characterize and understand the techniques for designing the stack. The overall goal of Phase 3 is to demonstrate the feasibility of constructing a higher energy cavity from a number of smaller LTD stacks, to characterize and understand the way in which the constituent stacks combine, and to extend this demonstration LTD to serve as the basis for a 64 kJ pulse generator for Z-Pinch experiments.

Computational modeling of Krypton gas puffs with tailored mass density profiles on Z

DOE PAGES

Jennings, Christopher A.; Ampleford, David J.; Lamppa, Derek C.; ...

2015-05-18

Large diameter multi-shell gas puffs rapidly imploded by high current (~20 MA, ~100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity Krypton K-shell emission at ~13 keV. Efficiently radiating at these high photon energies is a significant challenge which requires the careful design and optimization of the gas distribution. To facilitate this, we hydrodynamically model the gas flow out of the nozzle and then model its implosion using a 3-dimensional resistive, radiative MHD code (GORGON). This approach enables us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiativemore » output from this combined system. Furthermore, guided by our implosion calculations, we have designed gas profiles that help mitigate disruption from Magneto-Rayleigh–Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission.« less

AN ACCELERATION MECHANISM FOR NEUTRON PRODUCTION IN Z-PINCH DISCHARGES,

DTIC Science & Technology

A model has been developed for the acceleration of deuterons in the tightly compressed column of a z-pinch discharge, in particular that of a plasma ... focus discharge. It was assumed that an annular current distribution undergoes a rapidly contracting transition to an axially peaked distribution, and

Resolving microstructures in Z pinches with intensity interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apruzese, J. P.; Kroupp, E.; Maron, Y.

2014-03-15

Nearly 60 years ago, Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature 178, 1046 (1956)] succeeded in measuring the 30 nrad angular diameter of Sirius using a new type of interferometry that exploited the interference of photons independently emitted from different regions of the stellar disk. Its basis was the measurement of intensity correlations as a function of detector spacing, with no beam splitting or preservation of phase information needed. Applied to Z pinches, X pinches, or laser-produced plasmas, this method could potentially provide spatial resolution under one micron. A quantitative analysis based on the workmore » of Purcell [E. M. Purcell, Nature 178, 1449 (1956)] reveals that obtaining adequate statistics from x-ray interferometry of a Z-pinch microstructure would require using the highest-current generators available. However, using visible light interferometry would reduce the needed photon count and could enable its use on sub-MA machines.« less

A Reactor Development Scenario for the FuZE Sheared-Flow Stabilized Z-pinch

NASA Astrophysics Data System (ADS)

McLean, Harry S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.

2017-10-01

We present a conceptual design, scaling calculations, and development path for a pulsed fusion reactor based on a flow-stabilized Z-pinch. Experiments performed on the ZaP and ZaP-HD devices have largely demonstrated the basic physics of sheared-flow stabilization at pinch currents up to 100 kA. Initial experiments on the FuZE device, a high-power upgrade of ZaP, have achieved 20 usec of stability at pinch current 100-200 kA and pinch diameter few mm for a pinch length of 50 cm. Scaling calculations based on a quasi-steady-state power balance show that extending stable duration to 100 usec at a pinch current of 1.5 MA and pinch length of 50 cm, results in a reactor plant Q 5. Future performance milestones are proposed for pinch currents of: 300 kA, where Te and Ti are calculated to exceed 1-2 keV; 700 kA, where DT fusion power would be expected to exceed pinch input power; and 1 MA, where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPA-E and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-734770.

Pulsed-power-driven cylindrical liner implosions of laser preheated fuel magnetized with an axial field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, S. A.; Herrmann, M. C.; Vesey, R. A.

2010-05-15

The radial convergence required to reach fusion conditions is considerably higher for cylindrical than for spherical implosions since the volume is proportional to r{sup 2} versus r{sup 3}, respectively. Fuel magnetization and preheat significantly lowers the required radial convergence enabling cylindrical implosions to become an attractive path toward generating fusion conditions. Numerical simulations are presented indicating that significant fusion yields may be obtained by pulsed-power-driven implosions of cylindrical metal liners onto magnetized (>10 T) and preheated (100-500 eV) deuterium-tritium (DT) fuel. Yields exceeding 100 kJ could be possible on Z at 25 MA, while yields exceeding 50 MJ could bemore » possible with a more advanced pulsed power machine delivering 60 MA. These implosions occur on a much shorter time scale than previously proposed implosions, about 100 ns as compared to about 10 mus for magnetic target fusion (MTF) [I. R. Lindemuth and R. C. Kirkpatrick, Nucl. Fusion 23, 263 (1983)]. Consequently the optimal initial fuel density (1-5 mg/cc) is considerably higher than for MTF (approx1 mug/cc). Thus the final fuel density is high enough to axially trap most of the alpha-particles for cylinders of approximately 1 cm in length with a purely axial magnetic field, i.e., no closed field configuration is required for ignition. According to the simulations, an initial axial magnetic field is partially frozen into the highly conducting preheated fuel and is compressed to more than 100 MG. This final field is strong enough to inhibit both electron thermal conduction and the escape of alpha-particles in the radial direction. Analytical and numerical calculations indicate that the DT can be heated to 200-500 eV with 5-10 kJ of green laser light, which could be provided by the Z-Beamlet laser. The magneto-Rayleigh-Taylor (MRT) instability poses the greatest threat to this approach to fusion. Two-dimensional Lasnex simulations indicate that the liner walls must have a substantial initial thickness (10-20% of the radius) so that they maintain integrity throughout the implosion. The Z and Z-Beamlet experiments are now being planned to test the various components of this concept, e.g., the laser heating of the fuel and the robustness of liner implosions to the MRT instability.« less

Polar Radiation-Flux Symmetry Measurements in Z-Pinch-Driven Hohlraums with Symmetric Double-Pinch Drive

NASA Astrophysics Data System (ADS)

Hanson, D. L.; Vesey, R. A.; Cuneo Porter, M. E., Jr.; Chandler, G. A.; Ruggles, L. E.; Simpson, W. W.; Seamen, H.; Primm, P.; Torres, J.; McGurn, J.; Gilliland, T. L.; Reynolds, P.; Hebron, D. E.; Dropinski, S. C.; Schroen-Carey, D. G.; Hammer, J. H.; Landen, O.; Koch, J.

2000-10-01

We are currently exploring symmetry requirements of the z-pinch-driven hohlraum concept [1] for high-yield inertial confinement fusion. In experiments on the Z accelerator, the burnthrough of a low-density self-backlit foam ball has been used to diagnose the large time-dependent flux asymmetry of several single-sided-drive hohlraum geometries [2]. We are currently applying this technique to study polar radiation flux symmetry in a symmetric double z-pinch geometry. Wire arrays on opposite ends of the hohlraum, connected in series to a single current drive of 18 MA, implode and stagnate on axis, efficiently radiating about 100 TW of x rays which heat the secondary to 75 eV. Comparisons with 3-D radiosity and 2-D rad-hydro models of hohlraum symmetry performance will be presented. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000. 1 J. H. Hammer et al., Phys. Plasmas 6, 2129 (1999). 2 D. L. Hanson et al., Bull. Am. Phys. Soc. 44, 40 (1999).

Experimental study of surface insulated-standard hybrid tungsten planar wire array Z-pinches at “QiangGuang-I” facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Liang; Peng, Bodong; Yuan, Yuan

The experimental results of the insulated-standard hybrid wire array Z pinches carried out on “QiangGuang-I” facility at Northwest Institute of Nuclear Technology were presented and discussed. The surface insulating can impose a significant influence on the dynamics and radiation characteristics of the hybrid wire array Z pinches, especially on the early stage (t/t{sub imp} < 0.6). The expansion of insulated wires at the ablation stage is suppressed, while the streams stripped from the insulated wires move faster than that from the standard wires. The foot radiation of X-ray is enhanced by increment of the number of insulated wires, 19.6 GW, 33.6 GW, and 68.6 GWmore » for shots 14037S, 14028H, and 14039I, respectively. The surface insulation also introduces nonhomogeneity along the single wire—the streams move much faster near the electrodes. The colliding boundary of the hybrid wire array Z pinches is bias to the insulated side approximately 0.6 mm.« less

Enhanced direct-drive implosions with thin high-Z ablation layers.

PubMed

Mostovych, Andrew N; Colombant, Denis G; Karasik, Max; Knauer, James P; Schmitt, Andrew J; Weaver, James L

2008-02-22

New direct-drive spherical implosion experiments with deuterium filled plastic shells have demonstrated significant and absolute (2x) improvements in neutron yield when the shells are coated with a very thin layer ( approximately 200-400 A) of high-Z material such as palladium. This improvement is interpreted as resulting from increased stability of the imploding shell. These results provide for a possible path to control laser imprint and stability in laser-fusion-energy target designs.

Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas.

PubMed

Ross, M P; Shumlak, U

2016-10-01

The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 μs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 10 20 m -2 with spatial resolution near 10 μm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.

A Reactor Development Scenario for the FUZE Shear-flow Stabilized Z-pinch

NASA Astrophysics Data System (ADS)

McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Golingo, R. P.; Weber, T. R.

2016-10-01

We present a conceptual design, scaling calculations, and a development path for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device have demonstrated stable operation for 40 us at 150 kA total discharge current (with 100 kA in the pinch) for pinches that are 1cm in diameter and 100 cm long. Scaling calculations show that achieving stabilization for a pulse of 100 usec, for discharge current 1.5 MA, in a shortened pinch 50 cm, results in a pinch diameter of 200 um and a reactor plant Q 5 for reasonable assumptions of the various system efficiencies. We propose several key intermediate performance levels in order to justify further development. These include achieving operation at pinch currents of 300 kA, where Te and Ti are calculated to exceed 1 keV, 700 kA where fusion power exceeds pinch input power, and 1 MA where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPAe ALPHA Program and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-697801.

X-ray power and yield measurements at the refurbished Z machine

DOE PAGES

Jones, M. C.; Ampleford, D. J.; Cuneo, M. E.; ...

2014-08-04

Advancements have been made in the diagnostic techniques to measure accurately the total radiated x-ray yield and power from z-pinch loads at the Z Machine with high accuracy. The Z-accelerator is capable of outputting 2MJ and 330 TW of x-ray yield and power, and accurately measuring these quantities is imperative. We will describe work over the past several years which include the development of new diagnostics, improvements to existing diagnostics, and implementation of automated data analysis routines. A set of experiments were conducted on the Z machine where the load and machine configuration were held constant. During this shot series,more » it was observed that total z-pinch x-ray emission power determined from the two common techniques for inferring the x-ray power, Kimfol filtered x-ray diode diagnostic and the Total Power and Energy diagnostic gave 450 TW and 327 TW respectively. Our analysis shows the latter to be the more accurate interpretation. More broadly, the comparison demonstrates the necessity to consider spectral response and field of view when inferring xray powers from z-pinch sources.« less

Observation of emission process in hydrogen-like nitrogen Z-pinch discharge with time integrated soft X-ray spectrum pinhole image

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakai, Y.; Kumai, H.; Nakanishi, Y.

2013-02-15

The emission spectra of hydrogen-like nitrogen Balmer at the wavelength of 13.4 nm in capillary Z-pinch discharge plasma are experimentally examined. Ionization to fully strip nitrogen at the pinch maximum, and subsequent rapid expansion cooling are required to establish the population inversion between the principal quantum number of n = 2 and n = 3. The ionization and recombination processes with estimated plasma parameters are evaluated by utilizing a time integrated spectrum pinhole image containing radial spatial information. A cylindrical capillary plasma is pinched by a triangular pulsed current with peak amplitude of 50 kA and pulse width of 50more » ns.« less

The inverse skin effect in the Z-pinch and plasma focus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usenko, P. L., E-mail: otd4@expd.vniief.ru; Gaganov, V. V.

The inverse skin effect and its influence on the dynamics of high-current Z-pinch and plasma focus discharges in deuterium are analyzed. It is shown that the second compression responsible for the major fraction of the neutron yield can be interpreted as a result of the inverse skin effect resulting in the axial concentration of the longitudinal current density and the appearance of a reversed current in the outer layers of plasma pinches. Possible conditions leading to the enhancement of the inverse skin effect and accessible for experimental verification by modern diagnostics are formulated.

A study of the methods for the production and confinement of high energy plasmas. [injection of dense plasma into long magnetic field

NASA Technical Reports Server (NTRS)

Cheng, D. Y.; Wang, P.

1972-01-01

The injection of dense plasmas into a B sub z long magnetic field from both ends of the field coil was investigated. Deflagration plasma guns and continuous flow Z-pinch are discussed along with the possibility of a continuous flow Z-pinch fusion reactor. The injection experiments are described with emphasis on the synchronization of the two plasma deflagration guns, the collision of the two plasma beams, and the determination of plasma density.

The application of high-speed photography in z-pinch high-temperature plasma diagnostics

NASA Astrophysics Data System (ADS)

Wang, Kui-lu; Qiu, Meng-tong; Hei, Dong-wei

2007-01-01

This invited paper is presented to discuss the application of high speed photography in z-pinch high temperature plasma diagnostics in recent years in Northwest Institute of Nuclear Technology in concentrative mode. The developments and applications of soft x-ray framing camera, soft x-ray curved crystal spectrometer, optical framing camera, ultraviolet four-frame framing camera and ultraviolet-visible spectrometer are introduced.

Coulomb explosion of “hot spot”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Tomsk Polytechnic University, Tomsk; Oreshkin, E. V.

The study presented in this paper has shown that the generation of hard x rays and high-energy ions, which are detected in pinch implosion experiments, may be associated with the Coulomb explosion of the hot spot that is formed due to the outflow of the material from the pinch cross point. During the process of material outflow, the temperature of the hot spot plasma increases, and conditions arise for the plasma electrons to become continuously accelerated. The runaway of electrons from the hot spot region results in the buildup of positive space charge in this region followed by a Coulombmore » explosion. The conditions for the hot spot plasma electrons to become continuously accelerated have been revealed, and the estimates have been obtained for the kinetic energy of the ions generated by the Coulomb explosion.« less

Increasing Plasma Parameters using Sheared Flow Stabilization of a Z-Pinch

NASA Astrophysics Data System (ADS)

Shumlak, Uri

2016-10-01

Recent experiments on the ZaP Flow Z-Pinch at the University of Washington have been successful in compressing the plasma column to smaller radii, producing the predicted increases in plasma density (1018 cm-3), temperature (200 eV), and magnetic fields (4 T), while maintaining plasma stability for many Alfven times (over 40 μs) using sheared plasma flows. These results indicate the suitability of the device as a discovery science platform for astrophysical and high energy density plasma research, and keeps open a possible path to achieving burning plasma conditions in a compact fusion device. Long-lived Z-pinch plasmas have been produced with dimensions of 1 cm radius and 100 cm long that are stabilized by sheared axial flows for over 1000 Alfven radial transit times. The observed plasma stability is coincident with the presence of a sheared flow as measured by time-resolved multi-chord ion Doppler spectroscopy applied to impurity ion radiation. These measurements yield insights into the evolution of the velocity profile and show that the stabilizing behavior of flow shear agrees with theoretical calculations and 2-D MHD computational simulations. The flow shear value, extent, and duration are shown to be consistent with theoretical models of the plasma viscosity, which places a design constraint on the maximum axial length of a sheared flow stabilized Z-pinch. Measurements of the magnetic field topology indicate simultaneous azimuthal symmetry and axial uniformity along the entire 100 cm length of the Z-pinch plasma. Separate control of plasma acceleration and compression have increased the accessible plasma parameters and have generated stable plasmas with radii below 0.5 cm, as measured with a high resolution digital holographic interferometer. This work was supported by Grants from U.S. DOE, NNSA, and ARPA-E.

A conservative MHD scheme on unstructured Lagrangian grids for Z-pinch hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Wu, Fuyuan; Ramis, Rafael; Li, Zhenghong

2018-03-01

A new algorithm to model resistive magnetohydrodynamics (MHD) in Z-pinches has been developed. Two-dimensional axisymmetric geometry with azimuthal magnetic field Bθ is considered. Discretization is carried out using unstructured meshes made up of arbitrarily connected polygons. The algorithm is fully conservative for mass, momentum, and energy. Matter energy and magnetic energy are managed separately. The diffusion of magnetic field is solved using a derivative of the Symmetric-Semi-Implicit scheme, Livne et al. (1985) [23], where unconditional stability is obtained without needing to solve large sparse systems of equations. This MHD package has been integrated into the radiation-hydrodynamics code MULTI-2D, Ramis et al. (2009) [20], that includes hydrodynamics, laser energy deposition, heat conduction, and radiation transport. This setup allows to simulate Z-pinch configurations relevant for Inertial Confinement Fusion.

Electron beam generation in the turbulent plasma of Z-pinch discharges

NASA Astrophysics Data System (ADS)

Vikhrev, Victor V.; Baronova, Elena O.

1997-05-01

Numerical modeling of the process of electron beam generation in z-pinch discharges are presented. The proposed model represents the electron beam generation under turbulent plasma conditions. Strong current distribution inhomogeneity in the plasma column has been accounted for the adequate generation process investigation. Electron beam is generated near the maximum of compression due to run away mechanism and it is not related with the current break effect.

IFE Chamber Technology - Status and Future Challenges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meier, W.R.; Raffray, A.R.; Abdel-Khalik, S.I.

2003-07-15

Significant progress has been made on addressing critical issues for inertial fusion energy (IFE) chambers for heavy-ion, laser and Z-pinch drivers. A variety of chamber concepts are being investigated including drywall (currently favored for laser IFE), wetted-wall (applicable to both laser and ion drivers), and thick-liquid-wall (favored by heavy ion and z-pinch drivers). Recent progress and remaining challenges in developing IFE chambers are reviewed.

Scaling the Shear-flow Stabilized Z-pinch to Reactor Conditions

NASA Astrophysics Data System (ADS)

McLean, H. S.; Schmidt, A.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Cleveau, E.

2015-11-01

We present a conceptual design along with scaling calculations for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device, at the University of Washington, have demonstrated stable operation for durations of 20 usec at ~100kA discharge current for pinches that are ~1 cm in diameter and 100 cm long. The inverse of the pinch diameter and plasma energy density scale strongly with pinch current and calculations show that maintaining stabilization durations of ~7 usec for increased discharge current (~15x) in a shortened pinch (10 cm) results in a pinch diameter of ~200 um and plasma conditions that approach those needed to support significant fusion burn and energy gain (Ti ~ 30keV, density ~ 3e26/m3, ntau ~1.4e20 sec/m3). Compelling features of the concept include operation at modest discharge current (1.5 MA) and voltage (40kV) along with direct adoption of liquid metals for at least one electrode--technological capabilities that have been proven in existing, commercial, pulse power devices such as large ignitrons. LLNL-ABS-674920. This work performed under the auspices of the U.S. Department of Energy ARPAe ALPHA Program by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

P2 Asymmetry of Au's M-band Flux and its smoothing effect due to high-Z ablator dopants

NASA Astrophysics Data System (ADS)

Li, Yongsheng; Zhai, Chuanlei; Ren, Guoli; Gu, Jianfa; Huo, Wenyi; Meng, Xujun; Ye, Wenhua; Lan, Ke; Zhang, Weiyan

2017-10-01

X-ray drive asymmetry is one of the main seeds of low-mode implosion asymmetry that blocks further improvement of the nuclear performance of ``high-foot'' experiments on the National Ignition Facility. More particularly, the P2 asymmetry of Au's M-band flux can also severely influence the implosion performance. Here we study the smoothing effect of mid- and/or high-Z dopants in ablator on M-band flux asymmetries, by modeling and comparing the implosion processes of a Ge-doped and a Si-doped ignition capsule driven by x-ray sources with asymmetric M-band flux. As the results, (1) mid- or high-Z dopants absorb M-band flux and re-emit isotropically, helping to smooth M-band flux arriving at the ablation front, therefore reducing the P2 asymmetries of the imploding shell and hot spot; (2) the smoothing effect of Ge-dopant is more remarkable than Si-dopant due to its higher opacity than the latter in Au's M-band; and (3) placing the doped layer at a larger radius in ablator is more efficient. Applying this effect may not be a main measure to reduce the low-mode implosion asymmetry, but might be of significance in some critical situations such as Inertial Confinement Fusion (ICF) experiments very near the performance cliffs of asymmetric x-ray drives.

Measurements of high-current electron beams from X pinches and wire array Z pinches.

PubMed

Shelkovenko, T A; Pikuz, S A; Blesener, I C; McBride, R D; Bell, K S; Hammer, D A; Agafonov, A V; Romanova, V M; Mingaleev, A R

2008-10-01

Some issues concerning high-current electron beam transport from the X pinch cross point to the diagnostic system and measurements of the beam current by Faraday cups are discussed. Results of computer simulation of electron beam propagation from the pinch to the Faraday cup give limits for the measured current for beams having different energy spreads. The beam is partially neutralized as it propagates from the X pinch to a diagnostic system, but within a Faraday cup diagnostic, space charge effects can be very important. Experimental results show evidence of such effects.

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF

DOE PAGES

Ma, T.; Chen, H.; Patel, P. K.; ...

2016-08-18

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. We describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.Published by AIP Publishing

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF.

PubMed

Ma, T; Chen, H; Patel, P K; Schneider, M B; Barrios, M A; Casey, D T; Chung, H-K; Hammel, B A; Berzak Hopkins, L F; Jarrott, L C; Khan, S F; Lahmann, B; Nora, R; Rosenberg, M J; Pak, A; Regan, S P; Scott, H A; Sio, H; Spears, B K; Weber, C R

2016-11-01

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF

NASA Astrophysics Data System (ADS)

Ma, T.; Chen, H.; Patel, P. K.; Schneider, M. B.; Barrios, M. A.; Casey, D. T.; Chung, H.-K.; Hammel, B. A.; Berzak Hopkins, L. F.; Jarrott, L. C.; Khan, S. F.; Lahmann, B.; Nora, R.; Rosenberg, M. J.; Pak, A.; Regan, S. P.; Scott, H. A.; Sio, H.; Spears, B. K.; Weber, C. R.

2016-11-01

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

Imaging of High-Z doped, Imploded Capsule Cores

NASA Astrophysics Data System (ADS)

Prisbrey, Shon T.; Edwards, M. John; Suter, Larry J.

2006-10-01

The ability to correctly ascertain the shape of imploded fusion capsules is critical to be able to achieve the spherical symmetry needed to maximize the energy yield of proposed fusion experiments for the National Ignition Facility. Implosion of the capsule creates a hot, dense core. The introduction of a high-Z dopant into the gas-filled core of the capsule increases the amount of bremsstrahlung radiation produced in the core and should make the imaging of the imploded core easier. Images of the imploded core can then be analyzed to ascertain the symmetry of the implosion. We calculate that the addition of Ne gas into a deuterium gas core will increase the amount of radiation emission while preserving the surrogacy of the radiation and hydrodynamics in the indirect drive NIF hohlraum in the proposed cryogenic hohlraums. The increased emission will more easily enable measurement of asymmetries and tuning of the implosion.

Multiple shell fusion targets

DOEpatents

Lindl, J.D.; Bangerter, R.O.

1975-10-31

Multiple shell fusion targets for use with electron beam and ion beam implosion systems are described. The multiple shell targets are of the low-power type and use a separate relatively low Z, low density ablator at large radius for the outer shell, which reduces the focusing and power requirements of the implosion system while maintaining reasonable aspect ratios. The targets use a high Z, high density pusher shell placed at a much smaller radius in order to obtain an aspect ratio small enough to protect against fluid instability. Velocity multiplication between these shells further lowers the power requirements. Careful tuning of the power profile and intershell density results in a low entropy implosion which allows breakeven at low powers. For example, with ion beams as a power source, breakeven at 10-20 Terrawatts with 10 MeV alpha particles for imploding a multiple shell target can be accomplished.

Ride-along data LOS 130, 170 & LO330 shots z3139, 3140 and 3141

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loisel, Guillaume Pascal

Each instrument records the x-ray emission from the Z-pinch dynamic hohlraum (ZPDH); LOS 130 TIXTLs instruments record the absorption of the pinch backlighter through an expanding NaF/Mg foil; LOS 170 MLM instruments record monochromatic images at 276 and 528 eV energies near and before ZPDH stagnation time; LOS 330 TREX 6A & B: recoded time resolved absorption spectra from a radiatively heated Ne gas.

Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the “QiangGuang-1" facility

NASA Astrophysics Data System (ADS)

Li, Mo; Wu, Jian; Wang, Liang-Ping; Wu, Gang; Han, Juan-Juan; Guo, Ning; Qiu, Meng-Tong

2012-12-01

Two curved crystal spectrometers are set up on the “QiangGuang-1" generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several “bright spots" indicate electron temperatures between (450 eV ~ 520 eV) ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV ± 30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a ~ 1 MA facility.

Investigating radial wire array Z pinches as a compact x-ray source on the Saturn generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ampleford, David J.; Bland, S. N.; Jennings, Christopher A.

2015-08-27

Radial wire array z pinches, where wires are positioned radially outward from a central cathode to a concentric anode, can act as a compact bright x-ray source that could potentially be used to drive a hohlraum. Experiments were performed on the 7-MA Saturn generator using radial wire arrays. These experiments studied a number of potential risks in scaling radial wire arrays up from the 1-MA level, where they have been shown to be a promising compact X-ray source. Data indicates that at 7 MA, radial wire arrays can radiate ~9 TW with 10-ns full-width at half-maximum from a compact pinch.

High energy density Z-pinch plasmas using flow stabilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shumlak, U., E-mail: shumlak@uw.edu; Golingo, R. P., E-mail: shumlak@uw.edu; Nelson, B. A., E-mail: shumlak@uw.edu

The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes – Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. Amore » sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results and scaling analyses will be presented. In addition to studying fundamental plasma science and high energy density physics, the ZaP and ZaP-HD experiments can be applied to laboratory astrophysics.« less

Wire array K-shell sources on the SPHINX generator

NASA Astrophysics Data System (ADS)

D'Almeida, Thierry; Lassalle, Francis; Grunenwald, Julien; Maury, Patrick; Zucchini, Frédéric; Niasse, Nicolas; Chittenden, Jeremy

2014-10-01

The SPHINX machine is a LTD based Z-pinch driver operated by the CEA Gramat (France) and primarily used for studying K-shell radiation effects. We present the results of experiments carried out with single and nested large diameter aluminium wire array loads driven by a current of ~5 MA in ~800 ns. The dynamic of the implosion is studied with filtered X-UV time-integrated pin-hole cameras. The plasma electron temperature and the characteristics of the sources are estimated with time and spatially dependent spectrographs and PCDs. It is shown that Al K-shell yields (>1 keV) up to 27 kJ are obtained for a total radiation of ~ 230 kJ. These results are compared with simulations performed using the latest implementation of the non-LTE DCA code Spk in the 3D Eulerian MHD framework Gorgon developed at Imperial College. Filtered synthetic bolometers and PCD signals, time-dependent spatially integrated spectra and X-UV images are produced and show a good agreement with the experimental data. The capabilities of a prospective SPHINX II machine (20 MA ~ 800 ns) are also assessed for a wider variety of sources (Ti, Cu and W).

Preliminary investigation on the use of low current pulsed power Z-pinch plasma devices for the study of early stage plasma instabilities

NASA Astrophysics Data System (ADS)

Kaselouris, E.; Dimitriou, V.; Fitilis, I.; Skoulakis, A.; Koundourakis, G.; Clark, E. L.; Chatzakis, J.; Bakarezos, Μ; Nikolos, I. K.; Papadogiannis, N. A.; Tatarakis, M.

2018-01-01

This article addresses key features for the implementation of low current pulsed power plasma devices for the study of matter dynamics from the solid to the plasma phase. The renewed interest in such low current plasma devices lies in the need to investigate methods for the mitigation of prompt seeding mechanisms for the generation of plasma instabilities. The low current when driven into thick wires (skin effect mode) allows for the simultaneous existence of all phases of matter from solid to plasma. Such studies are important for the concept of inertial confinement fusion where the mitigation of the instability seeding mechanisms arising from the very early moments within the target’s heating is of crucial importance. Similarly, in the magnetized liner inertial fusion concept it is an open question as to how much surface non-uniformity correlates with the magneto-Rayleigh-Taylor instability, which develops during the implosion. This study presents experimental and simulation results, which demonstrate that the use of low current pulsed power devices in conjunction with appropriate diagnostics can be important for studying seeding mechanisms for the imminent generation of plasma instabilities in future research.

Assessment of the impact that the capsule fill tube has on implosions conducted with high density carbon ablators

NASA Astrophysics Data System (ADS)

Pak, Arthur; Benedetti, L. R.; Berzak Hopkins, L. F.; Clark, D.; Divol, L.; Dewald, E. L.; Fittinghoff, D.; Izumi, N.; Khan, S. F.; Landen, O.; Lepape, S.; Ma, T.; Marley, E.; Nagel, S.; Volegov, P.; Weber, C.; Bradley, D. K.; Callahan, D.; Grim, G.; Hurricane, O. A.; Patel, P.; Schneider, M. B.; Edwards, M. J.

2017-10-01

In recent inertial confinement implosion experiments conducted at the National Ignition Facility, bright and spatially localized x-ray emission within the hot spot at stagnation has been observed. This emission is associated with higher Z ablator material that is injected into the hot spot by the hydrodynamic perturbation induced by the 5-10 um diameter capsule fill tube. The reactivity of the DT fuel and subsequent yield of the implosion are strongly dependent on the density, temperature, and confinement time achieved throughout the stagnation of the implosion. Radiative losses from higher Z ablator material that mixes into the hot spot as well as non-uniformities in the compression and confinement induced by the fill tube perturbation can degrade the yield of the implosion. This work will examine the impact to conditions at stagnation that results from the fill tube perturbation. This assessment will be based from a pair of experiments conducted with a high density carbon ablator where the only deliberate change was reduction in fill tube diameter from 10 to 5 um. An estimate of the radiative losses and impact on performance from ablator mix injected into the hot spot by the fill tube perturbation will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The Physics of the Dense Z-Pinch in Theory and in Experiment With Application to Fusion Reactor

NASA Astrophysics Data System (ADS)

Haines, M. G.

1982-01-01

A new generation of Z-pinches employing high voltage, high current pulsed lines as power sources produce dense hot plasmas with enhanced stability properties. Three methods of Z-pinch formation are currently in use: (1) cylindrical collapse and compression of a pre-ionised gas; (2) laser initiation and Joule heating of a gas embedded pinch, and (3) hollow gas puff and subsequent collapse to the axis. The first method shows no dynamic bounce and no instability over about ten radial Alfvén transit times. The laser initiated Z-pinch shows benign helical structures, whilst the gas puff experiments are known for their high X-ray energy conversion associated with m = 0 instabilities. The first two experimental conditions are relevant for fusion. A calculation of energy balance for satisfying Lawson conditions with axial and radial energy losses and radiation loss shows that a current I of ~ 106 A and a line density N of 6 × 1018m-1 are required. This leads to two coincidences of physical quantities that are very favourable for controlled fusion. The first is that at this line density and under pressure balance the ratio of the ion Larmor radius to pinch radius is of order 1 so that a marked stabilisation of the configuration is expected. The second coincidence is that the current is only just below the Pease-Braginskii limit; this will permit the possibility of radiative collapse to attain the high density (~ 4 × 1027 m-3) and small radius (~ 20 μm) required for a compact (0.1 m long) discharge. The confining self-magnetic field is 104 T, the confinement time ~ 100 ns, and a matrix of pulsed discharges is envisaged in a moderator and breeding medium which does not have the wall-loading limitations of tokamaks.

High density laser-driven target

DOEpatents

Lindl, John D.

1981-01-01

A high density target for implosion by laser energy composed of a central quantity of fuel surrounded by a high-Z pusher shell with a low-Z ablator-pusher shell spaced therefrom forming a region filled with low-density material.

PINCHED PLASMA REACTOR

DOEpatents

Phillips, J.A.; Suydam, R.; Tuck, J.L.

1961-07-01

BS>A plasma confining and heating reactor is described which has the form of a torus with a B/sub 2/ producing winding on the outside of the torus and a helical winding of insulated overlapping tunns on the inside of the torus. The inner helical winding performs the double function of shielding the plasma from the vitreous container and generating a second B/sub z/ field in the opposite direction to the first B/sub z/ field after the pinch is established.

Laser interferometry of radiation driven gas jets

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2017-06-01

In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)

250 kA compact linear transformer driver for wire array z-pinch loads

NASA Astrophysics Data System (ADS)

Bott, S. C.; Haas, D. M.; Madden, R. E.; Ueda, U.; Eshaq, Y.; Collins, G., IV; Gunasekera, K.; Mariscal, D.; Peebles, J.; Beg, F. N.; Mazarakis, M.; Struve, K.; Sharpe, R.

2011-05-01

We present the application of a short rise (˜150ns) 250 kA linear transformer driver (LTD) to wire array z-pinch loads for the first time. The generator is a modification of a previous driver in which a new conical power feed provides a low inductance coupling to wire loads. Performance of the new design using both short circuit and plasma loads is presented and discussed. The final design delivers ˜200kA to a wire array load which is in good agreement with SCREAMER calculations using a simplified representative circuit. Example results demonstrate successful experiments using cylindrical, conical, and inverse wire arrays as well as previously published work on x-pinch loads.

The Experimental Study of Characterized Noble Gas Puffs Irradiated by Ultra-Short Laser Pulses Compared with X-Pinches as an X-Ray Source

NASA Astrophysics Data System (ADS)

Schultz, Kimberly Ann

The goal of this dissertation is to study the basic physics and X-ray emission (1-10 keV) of two X-ray sources: X-pinch plasmas and a clustered gas-puff irradiated by an ultrashort laser pulse. X-pinches and other typical X-ray sources using solid targets create hot debris that can damage sensitive equipment. Therefore, to perform sensitive backlighting or X-ray effects testing, debris-free sources of radiation must be investigated. In this work, the author presents a broad study of clustered noble gas puffs including characterization measurements and laser heating experiments using several gas nozzles and multiple gases. Ultimately, the goal is to compare the laser-irradiated gas-puff and X-pinch plasmas as X-ray sources. Characterization of the gas puffs is performed at the Radiation Physics Laboratory at the University of Nevada, Reno (UNR) Physics Department using optical interferometry and Rayleigh scattering to determine density and cluster radius. By changing the gas-puff variables control of both the density and cluster size of the gas jets is obtained. Two laser systems provide the high intensities desired for the laser-irradiated gas puff experiments: the UNR Leopard Laser (1-2x1019 W/cm2) and the Lawrence Livermore National Laboratory's Titan Laser (7x1019 W/cm2). X-ray emission is studied as a function of laser pulse parameters, gas target type, gas puff density, and the gas-delay timing between puff initiation and laser interaction with the puff. The tested gases are Ar, Kr, Xe, and four mixtures of the noble gases. Time-resolved X-ray measurements are captured with Silicon diodes and photoconducting diamond detectors. Electron beam detectors include Faraday cups and a high-energy (> 1 MeV) electron spectrometer. Modeling of spectra from X-ray crystal spectrometers provides plasma density and temperature measurement and a molecular dynamics (MD) code describes cluster interactions with the laser pulse. The conversion of laser energy into X rays is also measured. Laser beam transmission through and absorption by the gas puff reveal the complexity of using laser-irradiated gas puffs as X-ray sources. A strong anisotropy of X-ray and electron emissions were observed at both laser facilities. X-pinch plasmas can provide intense hard X rays and strong electron beams originating from small sources with many applications. Recent research has been conducted into four-wire X-pinches at the UNR Zebra machine, a 1-MA pulsed power generator. Two different wire materials are considered in this study, Ag and Mo. We observe a relatively linear correlation between load mass and implosion time for Mo X-pinches; in fact, this relationship also extends to include Ag. Interestingly, X-ray burst features drastically change in shape when the load mass is varied. Advantages of laser-irradiated gas puffs include a lack of damaging debris, high repetition rate, and ease of control. Its disadvantages include its inefficiency at converting electrical energy to X-rays, which is mostly limited by laser efficiency, and relatively low total energy yield. X-pinches, on the other hand, produced kJ of energy in a broad spectral region. However, they create a large amount of debris, have a low repetition rate, and, at 1-MA, have hard-to-predict implosion times.

Effect of Pressure Anisotropy on the m = 1 Small Wavelength Modes in Z-Pinches

NASA Astrophysics Data System (ADS)

Faghihi, M.

1987-05-01

A generalization of Freidberg's perpendicular MHD model is used to investigate the effect of pressure anisotropy on the small wavelength internal kink (m = 1) mode instability in a Z-Pinch. A normal mode analysis of perturbed motion of an incompressible, collisionless and cylindrical plasma is performed. The stability criterion is (rΣB2)' <= 0, where Σ = 1 - (P|| - P⊥)/B2. It cannot be fulfilled without violation of the fire hose stability condition Σ >= 0.

Deconvolution of Stark broadened spectra for multi-point density measurements in a flow Z-pinch

DOE PAGES

Vogman, G. V.; Shumlak, U.

2011-10-13

Stark broadened emission spectra, once separated from other broadening effects, provide a convenient non-perturbing means of making plasma density measurements. A deconvolution technique has been developed to measure plasma densities in the ZaP flow Z-pinch experiment. The ZaP experiment uses sheared flow to mitigate MHD instabilities. The pinches exhibit Stark broadened emission spectra, which are captured at 20 locations using a multi-chord spectroscopic system. Spectra that are time- and chord-integrated are well approximated by a Voigt function. The proposed method simultaneously resolves plasma electron density and ion temperature by deconvolving the spectral Voigt profile into constituent functions: a Gaussian functionmore » associated with instrument effects and Doppler broadening by temperature; and a Lorentzian function associated with Stark broadening by electron density. The method uses analytic Fourier transforms of the constituent functions to fit the Voigt profile in the Fourier domain. The method is discussed and compared to a basic least-squares fit. The Fourier transform fitting routine requires fewer fitting parameters and shows promise in being less susceptible to instrumental noise and to contamination from neighboring spectral lines. The method is evaluated and tested using simulated lines and is applied to experimental data for the 229.69 nm C III line from multiple chords to determine plasma density and temperature across the diameter of the pinch. As a result, these measurements are used to gain a better understanding of Z-pinch equilibria.« less

Deconvolution of Stark broadened spectra for multi-point density measurements in a flow Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogman, G. V.; Shumlak, U.

2011-10-15

Stark broadened emission spectra, once separated from other broadening effects, provide a convenient non-perturbing means of making plasma density measurements. A deconvolution technique has been developed to measure plasma densities in the ZaP flow Z-pinch experiment. The ZaP experiment uses sheared flow to mitigate MHD instabilities. The pinches exhibit Stark broadened emission spectra, which are captured at 20 locations using a multi-chord spectroscopic system. Spectra that are time- and chord-integrated are well approximated by a Voigt function. The proposed method simultaneously resolves plasma electron density and ion temperature by deconvolving the spectral Voigt profile into constituent functions: a Gaussian functionmore » associated with instrument effects and Doppler broadening by temperature; and a Lorentzian function associated with Stark broadening by electron density. The method uses analytic Fourier transforms of the constituent functions to fit the Voigt profile in the Fourier domain. The method is discussed and compared to a basic least-squares fit. The Fourier transform fitting routine requires fewer fitting parameters and shows promise in being less susceptible to instrumental noise and to contamination from neighboring spectral lines. The method is evaluated and tested using simulated lines and is applied to experimental data for the 229.69 nm C III line from multiple chords to determine plasma density and temperature across the diameter of the pinch. These measurements are used to gain a better understanding of Z-pinch equilibria.« less

Parameter scaling toward high-energy density in a quasi-steady flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.

2016-10-01

Sheared axial flows are utilized by the ZaP Flow Z-Pinch Experiment to stabilize MHD instabilities. The pinches formed are 50 cm long with radii ranging from 0.3 to 1.0 cm. The plasma is generated in a coaxial acceleration region, similar to a Marshall gun, which provides a steady supply of plasma for approximately 100 us. The power to the plasma is partially decoupled between the acceleration and pinch assembly regions through the use of separate power supplies. Adiabatic scaling of the Bennett relation gives targets for future devices to reach high-energy density conditions or fusion reactors. The applicability of an adiabatic assumption is explored and work is done experimentally to clarify the plasma compression process, which may be more generally polytropic. The device is capable of a much larger parameter space than previous machine iterations, allowing flexibility in the initial conditions of the compression process to preserve stability. This work is supported by DoE FES and NNSA.

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas

NASA Astrophysics Data System (ADS)

Wallace, M. S.; Haque, S.; Neill, P.; Pereira, N. R.; Presura, R.

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas.

PubMed

Wallace, M S; Haque, S; Neill, P; Pereira, N R; Presura, R

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

A short-pulse mode for the SPHINX LTD Z-pinch driver

NASA Astrophysics Data System (ADS)

D'Almeida, Thierry; Lassalle, Francis; Zucchini, Frederic; Loyen, Arnaud; Morell, Alain; Chuvatin, Alexander

2015-11-01

The SPHINX machine is a 6MA, 1 μs, LTD Z-pinch driver at CEA Gramat (France) and primarily used for studying radiation effects. Different power amplification concepts were examined in order to reduce the current rise time without modifying the generator discharge scheme, including the Dynamic Load Current Multiplier (DLCM) proposed by Chuvatin. A DLCM device, capable of shaping the current pulse without reducing the rise time, was developed at CEA. This device proved valuable for isentropic compression experiments in cylindrical geometry. Recently, we achieved a short pulse operation mode by inserting a vacuum closing switch between the DLCM and the load. The current rise time was reduced to ~300 ns. We explored the use of a reduced-height wire array for the Dynamic Flux Extruder in order to improve the wire array compression rate and increase the efficiency of the current transfer to the load. These developments are presented. Potential benefits of these developments for future Z pinch experiments are discussed.

Conversion of electromagnetic energy in Z-pinch process of single planar wire arrays at 1.5 MA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liangping, Wang; Mo, Li; Juanjuan, Han

The electromagnetic energy conversion in the Z-pinch process of single planar wire arrays was studied on Qiangguang generator (1.5 MA, 100 ns). Electrical diagnostics were established to monitor the voltage of the cathode-anode gap and the load current for calculating the electromagnetic energy. Lumped-element circuit model of wire arrays was employed to analyze the electromagnetic energy conversion. Inductance as well as resistance of a wire array during the Z-pinch process was also investigated. Experimental data indicate that the electromagnetic energy is mainly converted to magnetic energy and kinetic energy and ohmic heating energy can be neglected before the final stagnation. Themore » kinetic energy can be responsible for the x-ray radiation before the peak power. After the stagnation, the electromagnetic energy coupled by the load continues increasing and the resistance of the load achieves its maximum of 0.6–1.0 Ω in about 10–20 ns.« less

A non-LTE kinetic model for quick analysis of K-shell spectra from Z-pinch plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J., E-mail: s.duan@163.com; Huang, X. B., E-mail: s.duan@163.com; Cai, H. C., E-mail: s.duan@163.com

Analyzing and modeling K-shell spectra emitted by low-to moderate-atomic number plasma is a useful and effective way to retrieve temperature density of z-pinch plasmas. In this paper, a non-LTE population kinetic model for quick analysis of K-shell spectra was proposed. The model contains ionization stages from bare nucleus to neutral atoms and includes all the important atomic processes. In the present form of the model, the plasma is assumed to be both optically thin and homogeneous with constant temperature and density, and only steady-state situation is considered. According to the detailed calculations for aluminum plasmas, contours of ratios of certainmore » K-shell lines in electron temperature and density plane as well as typical synthesized spectra were presented and discussed. The usefulness of the model is demonstrated by analyzing the spectrum from a neon gas-puff Z-pinch experiment performed on a 1 MA pulsed-power accelerator.« less

Plasma diagnostics for x-ray driven foils at Z

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heeter, R F; Bailey, J E; Cuneo, M E

We report the development of techniques to diagnose plasmas produced by X-ray photoionization of thin foils placed near the Z-pinch on the Sandia Z Machine. The development of 100+ TW X-ray sources enables access to novel plasma regimes, such as the photoionization equilibrium. To diagnose these plasmas one must simultaneously characterize both the foil and the driving pinch. The desired photoionized plasma equilibrium is only reached transiently for a 2-ns window, placing stringent requirements on diagnostic synchronization. We have adapted existing Sandia diagnostics and fielded an additional gated 3-crystal Johann spectrometer with dual lines of sight to meet these requirements.more » We present sample data from experiments in which 1 cm, 180 eV tungsten pinches photoionized foils composed of 200{angstrom} Fe and 300{angstrom} NaF co-mixed and sandwiched between 1000{angstrom} layers of Lexan (CHO), and discuss the application of this work to benchmarking astrophysical models.« less

Plasma diagnostics for x-ray driven foils at Z

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heeter, R. F.; Bailey, J. E.; Cuneo, M. E.

We report the development of techniques to diagnose plasmas produced by x-ray photoionization of thin foils placed near the Z-pinch on the Sandia Z Machine. The development of 100+ TW x-ray sources enables access to novel plasma regimes, such as the photoionization equilibrium. To diagnose these plasmas one must simultaneously characterize both the foil and the driving pinch. The desired photoionized plasma equilibrium is only reached transiently for a 2-ns window, placing stringent requirements on diagnostic synchronization. We have adapted existing Sandia diagnostics and fielded an additional gated three-crystal Johann spectrometer with dual lines of sight to meet these requirements.more » We present sample data from experiments using 1-cm, 180-eV tungsten pinches to photoionize foils made of 200 Aa Fe and 300 Aa NaF co-mixed and sandwiched between 1000 Aa layers of Lexan (C16H14O3), and discuss the application of this work to benchmarking astrophysical models.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stygar, W.A.; Spielman, R.B.; Allshouse, G.O.

The 36-module Z accelerator was designed to drive z-pinch loads for weapon-physics and inertial-confinement-fusion experiments, and to serve as a testing facility for pulsed-power research required to develop higher-current drivers. The authors have designed and tested a 10-nH 1.5-m-radius vacuum section for the Z accelerator. The vacuum section consists of four vacuum flares, four conical 1.3-m-radius magnetically-insulated transmission lines, a 7.6-cm-radius 12-post double-post-hole convolute which connects the four outer MITLs in parallel, and a 5-cm-long inner MITL which connects the output of the convolute to a z-pinch load. IVORY and ELECTRO calculations were performed to minimize the inductance of themore » vacuum flares with the constraint that there be no significant electron emission from the insulator-stack grading rings. Iterative TLCODE calculations were performed to minimize the inductance of the outer MITLs with the constraint that the MITL electron-flow-current fraction be {le} 7% at peak current. The TLCODE simulations assume a 2.5 cm/{micro}s MITL-cathode-plasma expansion velocity. The design limits the electron dose to the outer-MITL anodes to 50 J/g to prevent the formation of an anode plasma. The TLCODE results were confirmed by SCREAMER, TRIFL, TWOQUICK, IVORY, and LASNEX simulations. For the TLCODE, SCREAMER, and TRIFL calculations, the authors assume that after magnetic insulation is established, the electron-flow current launched in the outer MITLs is lost at the convolute. This assumption has been validated by 3-D QUICKSILVER simulations for load impedances {le} 0.36 ohms. LASNEX calculations suggest that ohmic resistance of the pinch and conduction-current-induced energy loss to the MITL electrodes can be neglected in Z power-flow modeling that is accurate to first order. To date, the Z vacuum section has been tested on 100 shots. They have demonstrated they can deliver a 100-ns rise-time 20-MA current pulse to the baseline z-pinch load.« less

Effect of driver impedance on dense plasma focus Z-pinch neutron yield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sears, Jason, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Link, Anthony, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Schmidt, Andrea, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov

2014-12-15

The Z-pinch phase of a dense plasma focus (DPF) heats the plasma by rapid compression and accelerates ions across its intense electric fields, producing neutrons through both thermonuclear and beam-target fusion. Driver characteristics have empirically been shown to affect performance, as measured by neutron yield per unit of stored energy. We are exploring the effect of driver characteristics on DPF performance using particle-in-cell (PIC) simulations of a kJ scale DPF. In this work, our PIC simulations are fluid for the run-down phase and transition to fully kinetic for the pinch phase, capturing kinetic instabilities, anomalous resistivity, and beam formation duringmore » the pinch. The anode-cathode boundary is driven by a circuit model of the capacitive driver, including system inductance, the load of the railgap switches, the guard resistors, and the coaxial transmission line parameters. It is known that the driver impedance plays an important role in the neutron yield: first, it sets the peak current achieved at pinch time; and second, it affects how much current continues to flow through the pinch when the pinch inductance and resistance suddenly increase. Here we show from fully kinetic simulations how total neutron yield depends on the impedance of the driver and the distributed parameters of the transmission circuit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for neutron source applications.« less

Z-Pinch fusion-based nuclear propulsion

NASA Astrophysics Data System (ADS)

Miernik, J.; Statham, G.; Fabisinski, L.; Maples, C. D.; Adams, R.; Polsgrove, T.; Fincher, S.; Cassibry, J.; Cortez, R.; Turner, M.; Percy, T.

2013-02-01

Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human space flight missions. The Z-Pinch dense plasma focus method is a Magneto-Inertial Fusion (MIF) approach that may potentially lead to a small, low cost fusion reactor/engine assembly [1]. Recent advancements in experimental and theoretical understanding of this concept suggest favorable scaling of fusion power output yield [2]. The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this process can be pulsed over short timescales (10-6 s). This type of plasma formation is widely used in the field of Nuclear Weapons Effects testing in the defense industry, as well as in fusion energy research. A Z-Pinch propulsion concept was designed for a vehicle based on a previous fusion vehicle study called "Human Outer Planet Exploration" (HOPE), which used Magnetized Target Fusion (MTF) [3] propulsion. The reference mission is the transport of crew and cargo to Mars and back, with a reusable vehicle. The analysis of the Z-Pinch MIF propulsion system concludes that a 40-fold increase of Isp over chemical propulsion is predicted. An Isp of 19,436 s and thrust of 3812 N s/pulse, along with nearly doubling the predicted payload mass fraction, warrants further development of enabling technologies.

Studies of the Plasma Triggering Mechanism of Inverse Pinch Switch

DTIC Science & Technology

1993-11-10

plasma - focus driven plasma-puff was also discussed in comparison with the hypocycloidal pinch plasma-puff triggering. The main discharge of inverse pinch switch with plasma - focus driven plasma-puff trigger is found to be more azimuthally uniform than that with hypocycloidal pinch plasma-puff trigger in a gas pressure region between 80 mTorr and 1 Torr. A comparative study of the INPIStron and a spark gap also reveals that the INPIStron with a low impedance Z = 9 ohms can transfer a high voltage pulse with a superior pulse-shape fidelity over that with

Inner-shell radiation from wire array implosions on the Zebra generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ouart, N. D.; Giuliani, J. L.; Dasgupta, A.

2014-03-15

Implosions of brass wire arrays on Zebra have produced L-shell radiation as well as inner-shell Kα and Kβ transitions. The L-shell radiation comes from ionization stages around the Ne-like charge state that is largely populated by a thermal electron energy distribution function, while the K-shell photons are a result of high-energy electrons ionizing or exciting an inner-shell (1s) electron from ionization stages around Ne-like. The K- and L-shell radiations were captured using two time-gated and two axially resolved time-integrated spectrometers. The electron beam was measured using a Faraday cup. A multi-zone non-local thermodynamic equilibrium pinch model with radiation transport ismore » used to model the x-ray emission from experiments for the purpose of obtaining plasma conditions. These plasma conditions are used to discuss some properties of the electron beam generated by runaway electrons. A simple model for runaway electrons is examined to produce the Kα radiation, but it is found to be insufficient.« less

Compression mechanisms in the plasma focus pinch

NASA Astrophysics Data System (ADS)

Lee, S.; Saw, S. H.; Ali, Jalil

2017-03-01

The compression of the plasma focus pinch is a dynamic process, governed by the electrodynamics of pinch elongation and opposed by the negative rate of change of current dI/dt associated with the current dip. The compressibility of the plasma is influenced by the thermodynamics primarily the specific heat ratio; with greater compressibility as the specific heat ratio γ reduces with increasing degree of freedom f of the plasma ensemble due to ionization energy for the higher Z (atomic number) gases. The most drastic compression occurs when the emitted radiation of a high-Z plasma dominates the dynamics leading in extreme cases to radiative collapse which is terminated only when the compressed density is sufficiently high for the inevitable self-absorption of radiation to occur. We discuss the central pinch equation which contains the basic electrodynamic terms with built-in thermodynamic factors and a dQ/dt term; with Q made up of a Joule heat component and absorption-corrected radiative terms. Deuterium is considered as a thermodynamic reference (fully ionized perfect gas with f = 3) as well as a zero-radiation reference (bremsstrahlung only; with radiation power negligible compared with electrodynamic power). Higher Z gases are then considered and regimes of thermodynamic enhancement of compression are systematically identified as are regimes of radiation-enhancement. The code which incorporates all these effects is used to compute pinch radius ratios in various gases as a measure of compression. Systematic numerical experiments reveal increasing severity in radiation-enhancement of compressions as atomic number increases. The work progresses towards a scaling law for radiative collapse and a generalized specific heat ratio incorporating radiation.

Comparison and analysis of the results of direct-driven targets implosion

NASA Astrophysics Data System (ADS)

Demchenko, N. N.; Dolgoleva, G. V.; Gus'kov, S. Yu; Kuchugov, P. A.; Rozanov, V. B.; Stepanov, R. V.; Zmitrenko, N. V.; Yakhin, R. A.

2017-10-01

The article presents calculation results, which were received for the implosion of the typical cryogenic thermonuclear direct-drive targets that are intended for use at the OMEGA facility, NIF and Russian laser facility. The compression and burning characteristics, which were obtained using various numerical codes of different scientific groups, are compared. The data indicate good agreement between the numerical results. Various sources of target irradiation inhomogeneity and their influence on the implosion parameters are considered. The nominal scales of these disturbances for various facilities are close to each other. The main negative effect on the efficiency of compression and burning is due to the accidental offset of the target from the center of the chamber.

Diagnosing x-ray power and energy of tungsten wire array z-pinch with a flat spectral response x-ray diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Kun-lun; Ren, Xiao-dong; Huang, Xian-bin, E-mail: caephxb2003@aliyun.com

2015-11-15

Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter tomore » yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%.« less

Formation, spin-up, and stability of field-reversed configurations

DOE PAGES

Omelchenko, Yuri A.

2015-08-24

Formation, spontaneous spin-up and stability of theta-pinch formed field-reversed configurations are studied self-consistently in three dimensions with a multiscale hybrid model that treats all plasma ions as full-orbit collisional macro-particles and the electrons as a massless quasineutral fluid. The end-to-end hybrid simulations for the first time reveal poloidal profiles of implosion-driven fast toroidal plasma rotation and demonstrate three well-known discharge regimes as a function of experimental parameters: the decaying stable configuration, the tilt unstable configuration and the nonlinear evolution of a fast growing tearing mode.

Measurements of high energy photons in Z-pinch experiments on primary test stand

NASA Astrophysics Data System (ADS)

Si, Fenni; Zhang, Chuanfei; Xu, Rongkun; Yuan, Xi; Huang, Zhanchang; Xu, Zeping; Ye, Fan; Yang, Jianlun; Ning, Jiamin; Hu, Qingyuan; Zhu, Xuebin

2015-08-01

High energy photons are measured for the first time in wire-array Z-pinch experiments on the Primary Test Stand (PTS) which delivers a current up to 8 MA with a rise time of 70 ns. A special designed detecting system composed of three types of detectors is used to measure the average energy, intensity, and pulse waveform of high energy photons. Results from Pb-TLD (thermoluminescence dosimeter) detector indicate that the average energy is 480 keV (±15%). Pulse shape of high energy photons is measured by the photodiode detector consisted of scintillator coupled with a photodiode, and it is correlated with soft x-ray power by the same timing signal. Intensity is measured by both TLD and the photodiode detector, showing good accordance with each other, and it is 1010 cm-2 (±20%) at 2 m in the horizontal direction. Measurement results show that high energy photons are mainly produced in pinch regions due to accelerated electrons. PTS itself also produces high energy photons due to power flow electrons, which is one order smaller in amplitude than those from pinch region.

Measurements of high energy photons in Z-pinch experiments on primary test stand.

PubMed

Si, Fenni; Zhang, Chuanfei; Xu, Rongkun; Yuan, Xi; Huang, Zhanchang; Xu, Zeping; Ye, Fan; Yang, Jianlun; Ning, Jiamin; Hu, Qingyuan; Zhu, Xuebin

2015-08-01

High energy photons are measured for the first time in wire-array Z-pinch experiments on the Primary Test Stand (PTS) which delivers a current up to 8 MA with a rise time of 70 ns. A special designed detecting system composed of three types of detectors is used to measure the average energy, intensity, and pulse waveform of high energy photons. Results from Pb-TLD (thermoluminescence dosimeter) detector indicate that the average energy is 480 keV (±15%). Pulse shape of high energy photons is measured by the photodiode detector consisted of scintillator coupled with a photodiode, and it is correlated with soft x-ray power by the same timing signal. Intensity is measured by both TLD and the photodiode detector, showing good accordance with each other, and it is 10(10) cm(-2) (±20%) at 2 m in the horizontal direction. Measurement results show that high energy photons are mainly produced in pinch regions due to accelerated electrons. PTS itself also produces high energy photons due to power flow electrons, which is one order smaller in amplitude than those from pinch region.

Influence of pinches on magnetic reconnection in turbulent space plasmas

NASA Astrophysics Data System (ADS)

Olshevsky, Vyacheslav; Lapenta, Giovanni; Markidis, Stefano; Divin, Andrey

A generally accepted scenario of magnetic reconnection in space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is widely studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present nitially, and Z-pinches are formed during the simulation. The X-points are relatively stable, and no substantial energy dissipation is associated with them. On contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of approximately 1.5 percent per ion gyro period. Current channels and twisted magnetic fields are ubiquitous in turbulent space plasmas, so pinches can be responsible for the observed high magnetic reconnection rates.

Modeling, measuring, and mitigating instability growth in liner implosions on Z

NASA Astrophysics Data System (ADS)

Peterson, Kyle

2015-11-01

Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. In this talk, we will discuss the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. We present simulations that show electro-thermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent magneto-Rayleigh-Taylor (MRT) instability growth. We discuss measurement results from experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electro-thermal instability growth on well-characterized initially solid aluminum or beryllium rods driven with a 20 MA, 100 ns risetime current pulse. These measurements show good agreement with electro-thermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone. Recent experiments have confirmed simulation predictions of dramatically reduced instability growth in solid metallic rods when thick dielectric coatings are used to mitigate density perturbations arising from the electro-thermal instability. These results provide further evidence that the inherent surface roughness of the target is not the dominant seed for the MRT instability, in contrast with most inertial confinement fusion approaches. These results suggest a new technique for substantially reducing the integral MRT growth in magnetically driven implosions. Indeed, recent results on the Z facility with 100 km/s Al and Be liner implosions show substantially reduced growth. These new results include axially magnetized, CH-coated beryllium liner radiographs in which the inner liner surface is observed to be remarkably straight and uniform at a radius of about 120 microns (convergence ratio ~20). Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusiona)

NASA Astrophysics Data System (ADS)

McBride, R. D.; Martin, M. R.; Lemke, R. W.; Greenly, J. B.; Jennings, C. A.; Rovang, D. C.; Sinars, D. B.; Cuneo, M. E.; Herrmann, M. C.; Slutz, S. A.; Nakhleh, C. W.; Ryutov, D. D.; Davis, J.-P.; Flicker, D. G.; Blue, B. E.; Tomlinson, K.; Schroen, D.; Stamm, R. M.; Smith, G. E.; Moore, J. K.; Rogers, T. J.; Robertson, G. K.; Kamm, R. J.; Smith, I. C.; Savage, M.; Stygar, W. A.; Rochau, G. A.; Jones, M.; Lopez, M. R.; Porter, J. L.; Matzen, M. K.

2013-05-01

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of either 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless ("quasi-isentropic") liner compression. Third, we present "micro-Ḃ" measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density "precursor" plasma to the axis of symmetry.

Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBride, R. D.; Martin, M. R.; Lemke, R. W.

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of eithermore » 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless (“quasi-isentropic”) liner compression. Third, we present “micro-B-dot ” measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density “precursor” plasma to the axis of symmetry.« less

Small-amplitude magnetic Rayleigh-Taylor instability growth in cylindrical liners and Z-pinches imploded in an axial magnetic field

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.

2014-10-01

Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Investigating plasma viscosity with fast framing photography in the ZaP-HD Flow Z-Pinch experiment

NASA Astrophysics Data System (ADS)

Weed, Jonathan Robert

The ZaP-HD Flow Z-Pinch experiment investigates the stabilizing effect of sheared axial flows while scaling toward a high-energy-density laboratory plasma (HEDLP > 100 GPa). Stabilizing flows may persist until viscous forces dissipate a sheared flow profile. Plasma viscosity is investigated by measuring scale lengths in turbulence intentionally introduced in the plasma flow. A boron nitride turbulence-tripping probe excites small scale length turbulence in the plasma, and fast framing optical cameras are used to study time-evolved turbulent structures and viscous dissipation. A Hadland Imacon 790 fast framing camera is modified for digital image capture, but features insufficient resolution to study turbulent structures. A Shimadzu HPV-X camera captures the evolution of turbulent structures with great spatial and temporal resolution, but is unable to resolve the anticipated Kolmogorov scale in ZaP-HD as predicted by a simplified pinch model.

Larger sized wire arrays on 1.5 MA Z-pinch generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safronova, A. S., E-mail: alla@unr.edu; Kantsyrev, V. L., E-mail: alla@unr.edu; Weller, M. E., E-mail: alla@unr.edu

Experiments on the UNR Zebra generator with Load Current Multiplier (LCM) allow for implosions of larger sized wire array loads than at standard current of 1 MA. Advantages of larger sized planar wire array implosions include enhanced energy coupling to plasmas, better diagnostic access to observable plasma regions, and more complex geometries of the wire loads. The experiments with larger sized wire arrays were performed on 1.5 MA Zebra with LCM (the anode-cathode gap was 1 cm, which is half the gap used in the standard mode). In particular, larger sized multi-planar wire arrays had two outer wire planes frommore » mid-atomic-number wires to create a global magnetic field (gmf) and plasma flow between them. A modified central plane with a few Al wires at the edges was put in the middle between outer planes to influence gmf and to create Al plasma flow in the perpendicular direction (to the outer arrays plasma flow). Such modified plane has different number of empty slots: it was increased from 6 up to 10, hence increasing the gap inside the middle plane from 4.9 to 7.7 mm, respectively. Such load configuration allows for more independent study of the flows of L-shell mid-atomic-number plasma (between the outer planes) and K-shell Al plasma (which first fills the gap between the edge wires along the middle plane) and their radiation in space and time. We demonstrate that such configuration produces higher linear radiation yield and electron temperatures as well as advantages of better diagnostics access to observable plasma regions and how the load geometry (size of the gap in the middle plane) influences K-shell Al radiation. In particular, K-shell Al radiation was delayed compared to L-shell mid-atomic-number radiation when the gap in the middle plane was large enough (when the number of empty slots was increased up to ten)« less

Matching an Inductive Accumulator and a System of Acceleration of a Liner with Limitation of the Breaking Voltage,

DTIC Science & Technology

In this work calculations are made of the efficiencies of acceleration of a liner from an inductive accumulator in the mode theta-pinch and Z-pinch...to the speed of the liner . Estimations have been made of the necessary power at the moment of switching the current on the basis of considerations of...the stability of the pinch effect of the liner . The level of energies necessary for the creation of a thermonuclear reactor on the basis of theta

Numerical studies of the use of thin high-Z layers for reducing laser imprint in direct-drive inertial-fusion targets

NASA Astrophysics Data System (ADS)

Bates, Jason; Schmitt, Andrew; Karasik, Max; Obenschain, Steve

2012-10-01

Using the FAST code, we present numerical studies of the effect of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of directly-driven inertial-confinement-fusion (ICF) targets. Previous experimental work on the NIKE Laser Facility at the U.S. Naval Research Laboratory demonstrated that the use of high-Z layers may be efficacious in reducing laser non-uniformities imprinted on the target during the start-up phase of the implosion. Such a reduction is highly desirable in a direct-drive ICF scenario because laser non-uniformities seed hydrodynamic instabilities that can amplify during the implosion process, prevent uniform compression and spoil high gain. One of the main objectives of the present work is to assess the utility of high-Z layers for achieving greater laser uniformity in polar-drive target designs planned for the National Ignition Facility. To address this problem, new numerical routines have recently been incorporated in the FAST code, including an improved radiation-transfer package and a three-dimensional ray-tracing algorithm. We will discuss these topics, and present initial simulation results for high-Z planar-target experiments planned on the NIKE Laser Facility later this year.

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemke, R. W., E-mail: rwlemke@sandia.gov; Dolan, D. H.; Dalton, D. G.

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemke, R. W.; Dolan, D. H.; Dalton, D. G.

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ~1000 GPa is achieved in all cases. Lastly, these experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE PAGES

Lemke, R. W.; Dolan, D. H.; Dalton, D. G.; ...

2016-01-07

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ~1000 GPa is achieved in all cases. Lastly, these experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Scaling of X pinches from 1 MA to 6 MA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bland, Simon Nicholas; McBride, Ryan D.; Wenger, David Franklin

This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parametersmore » at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).« less

Compact hohlraum configuration with parallel planar-wire-array x-ray sources at the 1.7-MA Zebra generator.

PubMed

Kantsyrev, V L; Chuvatin, A S; Rudakov, L I; Velikovich, A L; Shrestha, I K; Esaulov, A A; Safronova, A S; Shlyaptseva, V V; Osborne, G C; Astanovitsky, A L; Weller, M E; Stafford, A; Schultz, K A; Cooper, M C; Cuneo, M E; Jones, B; Vesey, R A

2014-12-01

A compact Z-pinch x-ray hohlraum design with parallel-driven x-ray sources is experimentally demonstrated in a configuration with a central target and tailored shine shields at a 1.7-MA Zebra generator. Driving in parallel two magnetically decoupled compact double-planar-wire Z pinches has demonstrated the generation of synchronized x-ray bursts that correlated well in time with x-ray emission from a central reemission target. Good agreement between simulated and measured hohlraum radiation temperature of the central target is shown. The advantages of compact hohlraum design applications for multi-MA facilities are discussed.

Primary experimental results of wire-array Z-pinches on PTS

NASA Astrophysics Data System (ADS)

Huang, X. B.; Zhou, S. T.; Ren, X. D.; Dan, J. K.; Wang, K. L.; Zhang, S. Q.; Li, J.; Xu, Q.; Cai, H. C.; Duan, S. C.; Ouyang, K.; Chen, G. H.; Ji, C.; Wang, M.; Feng, S. P.; Yang, L. B.; Xie, W. P.; Deng, J. J.

2014-12-01

The Primary Test Stand (PTS) developed at the China Academy of Engineering Physics is a multiterawatt pulsed power driver, which can deliver a ˜10 MA, 70 ns rise-time (10%-90%) current to a short circuit load and has important applications in Z-pinch driven inertial confinement fusion and high energy density physics. In this paper, primary results of tungsten wire-array Z-pinch experiments on PTS are presented. The load geometries investigated include 15-mm-tall cylindrical single and nested arrays with diameter ranging from 14.4-26.4 mm, and consisting of 132˜276 tungsten wires with 5˜10 μm in diameter. Multiple diagnostics were fielded to determine the characteristics of x-ray radiations and to obtain self-emitting images of imploding plasmas. X-ray power up to 80 TW with ˜3 ns FWMH is achieved by using nested wire arrays. The total x-ray energy exceeds 500 kJ and the peak radiation temperature is about 150 eV. Typical velocity of imploding plasmas goes around 3˜5×107 cm/s and the radial convergence ratio is between 10 and 20.

Simulation of K-α Emission from Highly Charged Cu ions for Pinches on ZR

NASA Astrophysics Data System (ADS)

Dasgupta, A.; Giuliani, J. L.; Clark, R. W.; Ouart, N. D.; Jones, B.; Ampleford, D. J.

2012-10-01

Recent spectral data of Cu shots Z1975 and Z2122 from Sandia's ZR machine are believed to show strong K-α emissions. As these K-α lines provide good diagnostics, a detailed spectral model will be developed to investigate these line emissions for analyzing the data. In a Z pinch plasma, K-α emission can occur due to e-beams, hot electrons at the tail of a Maxwellian and also pumping from hot photons emitted near the axis. K-α emission that originates from collisional processes involving hot electrons in the final phase of the pinching plasmas are associated with radiationless electron capture, inner-shell electron collisional excitation and ionization. K-α lines from various ionization stages of various materials such as Fe, Cr, Ni, and Mn were also observed in the ZR data. Contributions from ions with strong K-α transitions will be included for this study which is a preliminary attempt to investigate Cu K-α lines due to hot electrons and photons. Photo-pumped K-α emission from an outer shell is spatially distinguishable from that produced by e-beam on axis.

Obtaining off-Hugoniot equation of state data on solid metals at extreme pressures via pulsed-power driven cylindrical liner implosions

NASA Astrophysics Data System (ADS)

Lemke, Raymond

2015-06-01

The focus of this talk is on magnetically driven, liner implosion experiments on the Z machine (Z) in which a solid, metal tube is shocklessly compressed to multi-megabar pressure. The goal of the experiments is to collect velocimetry data that can be used in conjunction with a new optimization based analysis technique to infer the principal isentrope of the tube material over a range of pressures. For the past decade, shock impact and ramp loading experiments on Z have used planar platforms exclusively. While producing state-of-the-art results for material science, it is difficult to produce drive pressures greater than 6 Mbar in the divergent planar geometry. In contrast, a cylindrical liner implosion is convergent; magnetic drive pressures approaching 50 Mbar are possible with the available current on Z (~ 20 MA). In our cylindrical experiments, the liner comprises an inner tube composed of the sample material (e.g., Ta) of unknown equation of state, and an outer tube composed of aluminum (Al) that serves as the current carrying cathode. Internal to the sample are fielded multiple PDV (Photonic Doppler Velocimetry) probes that measure velocity of the inner free surface of the imploding sample. External to the composite liner, at much larger radius, is an Al tube that is the return current anode. VISAR (velocity interferometry system for any reflector) probes measure free surface velocity of the exploding anode. Using the latter, MHD and optimization codes are employed to solve an inverse problem that yields the current driving the liner implosion. Then, the drive current, PDV velocity, MHD and optimization codes, are used to solve another inverse problem that yields pressure vs. density on approximately the principal isentrope of the sample material. Results for Ta, Re, and Cu compressed to ~ 10 Mbar are presented. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvydky, Alex

This volume of LLE Review, covering October–December 2011, features “Crossed-Beam Energy Transfer in Direct-Drive Implosions” by I. V. Igumenshchev, W. Seka, D. H. Edgell, D. T. Michel, D. H. Froula, R. S. Craxton, R. Follett, J. H. Kelly, T. Z. Kosc, J. F. Myatt, T. C. Sangster, A. Shvydky, S. Skupsky, and C. Stoeckl (LLE); V. N. Goncharov and A. V. Maximov (LLE and Department of Mechanical Engineering, U. of Rochester); L. Divol and P. Michel (LLNL); and R. L. McCrory and D. D. Meyerhofer (LLE and Departments of Mechanical Engineering and Physics, U. of Rochester). In this article (p.more » 1), direct-drive–implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1995)] have shown discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicates the presence of a mechanism that reduces laser coupling efficiency by 10% to 20%. The authors attribute this degradation in laser coupling to crossed-beam energy transfer (CBET)— which is electromagnetically seeded—low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of the incoming light beam to outgoing light, reducing the laser absorption and hydrodynamic efficiency of implosions. One-dimensional hydrodynamic simulations including CBET show good agreement with all observables in implosion experiments on OMEGA. Three strategies to mitigate CBET and improve laser coupling are considered: the use of narrow beams, multicolor lasers, and higher-Z ablators. Experiments on OMEGA using narrow beams have demonstrated improvements in implosion performance.« less

Proton Radiography of Spontaneous Fields, Plasma Flows and Dynamics in X-Ray Driven Inertial-Confinement Fusion Implosions

NASA Astrophysics Data System (ADS)

Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rosenberg, M.; Zylstra, A. B.; Rinderknecht, H. G.; Petrasso, R. D.; Amendt, P. A.; Landen, O. L.; Town, R. P. J.; Betti, R.; Knauer, J. P.; Meyerhofer, D. D.; Back, C. A.; Kilkenny, J. D.; Nikroo, A.

2010-11-01

Backlighting of x-ray-driven implosions in empty hohlraums with mono-energetic protons on the OMEGA laser facility has allowed a number of important phenomena to be observed. Several critical parameters were determined, including plasma flow, three types of spontaneous electric fields and megaGauss magnetic fields. These results provide insight into important issues in indirect-drive ICF. Even though the cavity is effectively a Faraday cage, the strong, local fields inside the hohlraum can affect laser-plasma instabilities, electron distributions and implosion symmetry. They are of fundamental scientific importance for a range of new experiments at the frontiers of high-energy-density physics. Future experiments designed to characterize the field formation and evolution in low-Z gas fill hohlraums will be discussed.

High brightness electrodeless Z-Pinch EUV source for mask inspection tools

NASA Astrophysics Data System (ADS)

Horne, Stephen F.; Partlow, Matthew J.; Gustafson, Deborah S.; Besen, Matthew M.; Smith, Donald K.; Blackborow, Paul A.

2012-03-01

Energetiq Technology has been shipping the EQ-10 Electrodeless Z-pinchTM light source since 1995. The source is currently being used for metrology, mask inspection, and resist development. Energetiq's higher brightness source has been selected as the source for pre-production actinic mask inspection tools. This improved source enables the mask inspection tool suppliers to build prototype tools with capabilities of defect detection and review down to 16nm design rules. In this presentation we will present new source technology being developed at Energetiq to address the critical source brightness issue. The new technology will be shown to be capable of delivering brightness levels sufficient to meet the HVM requirements of AIMS and ABI and potentially API tools. The basis of the source technology is to use the stable pinch of the electrodeless light source and have a brightness of up to 100W/mm(carat)2-sr. We will explain the source design concepts, discuss the expected performance and present the modeling results for the new design.

New developments and applications of intense pulsed radiation sources at Sandia National Laboratories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, D.

In the past thirty-six months, tremendous strides have been made in x-ray production using high-current z-pinches. Today, the x-ray energy (1.9 MJ) and power (200 TW) output of the Z accelerator (formerly PBFA-II) is the largest available in the laboratory. These z-pinch x-ray sources are being developed for research into the physics of high energy density plasmas of interest in weapon behavior and in inertial confinement fusion. Beyond the Z accelerator current of 20 MA, an extrapolation to the X-1 accelerator level of 60 MA may have the potential to drive high-yield ICF reactions at affordable cost if several challengingmore » technical problems can be overcome. New developments have also taken place at Sandia in the area of high current, mm-diameter electron beams for advanced hydrodynamic radiography. On SABRE, x-ray spot diameters were less than 2 mm with a dose of 100 R at 1 meter in a 40 ns pulse.« less

Étude spectrale d'un micro-plasma d'implosion X-pinch

NASA Astrophysics Data System (ADS)

Aranchuk, L. E.

2006-12-01

Le pincement magnétique de type X-pinch permet de réaliser un micro-plasma chaud et dense bien positionné dans l'espace qui présente une applicabilité pour la radiographie X d'objets peu denses de petite taille. Une batterie de diagnostics ayant tous une résolution spectrale a été installée autour d'un X-pinch alimenté par un banc de condensateurs rapide. Les résultats présentés portent sur la taille de la source intégrée en temps, sur la durée d'impulsion et sur le spectre d'émission X. Des exemples de radiographie confortent la détermination de la taille. Des spectres à haute résolution spectrale intégrés en temps (1 à 3 keV) montrent que les ions multichargés présents dans le plasma (Al hydrogénoïde et héliumoïde, Cu et Mo néonoïdes) sont les mêmes que dans les X-pinches alimentés par des générateurs pulsés bien plus puissants. Une spectroscopie large bande à haute résolution temporelle, basée sur des détecteurs innovants, a permis de mettre en évidence une émission dure sub-nanoseconde et de chiffrer la puissance spectrale instantanée et l'énergie X émise entre 20eV et 8keV. La puissance maximale peut dépasser 1GW pendant 0,4-0,7ns. La source émet 10 à 30J pendant 100-150ns en dessous de 400eV.

Ion beam inertial confinement target

DOEpatents

Bangerter, Roger O.; Meeker, Donald J.

1985-01-01

A target for implosion by ion beams composed of a spherical shell of frozen DT surrounded by a low-density, low-Z pusher shell seeded with high-Z material, and a high-density tamper shell. The target has various applications in the inertial confinement technology. For certain applications, if desired, a low-density absorber shell may be positioned intermediate the pusher and tamper shells.

Experimental study of z-pinch driven radiative shocks in low density gases

NASA Astrophysics Data System (ADS)

Skidmore, Jonathan; Lebedev, S. V.; Suzuki-Vidal, F.; Swadling, G.; Bland, S. N.; Burdiak, G.; Chittenden, J. P.; de Grouchy, P.; Hall, G. N.; Pickworth, L.; Suttle, L.; Bennett, M.; Ciardi, A.

2012-10-01

Results of experiments performed on MAGPIE pulsed power facility (1.4MA, 250ns) will be presented. Shocks with velocities of 50-70km/s are driven in Ar, Xe and He gases at density ˜10-5g/cc using radial foil z-pinch configuration [1]. Measurements of the structure of the shocks obtained with laser probing will be presented and observations of the development of instabilities will be discussed. It was found that the structure of the shocks and the development of instabilities strongly depend on the rate of radiative cooling, increasing for gases with higher atomic numbers.[4pt] [1] F. Suzuki-Vidal et al., PoP 19, 022708 (2012)

Particle drift model for Z-pinch-driven magneto-Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Dan, Jia Kun; Xu, Qiang; Wang, Kun Lun; Ren, Xiao Dong; Huang, Xian Bin

2016-09-01

A theoretical model of Z-pinch driven magneto-Rayleigh-Taylor instability is proposed based on the particle drift point of view, which can explain the helical instability structure observed in premagnetized imploding liner experiments. It is demonstrated that all possible drift motions, including polarization drift, gradient drift, and curvature drift, which can lead to charge separations, each will attribute to an effective gravity acceleration. Theoretical predictions given by this model are dramatically different from those given by previous theories which have been readily recovered in the theory presented here as a limiting case. The theory shows qualitative agreement with available experimental data of the pitch angle and provides certain predictions to be verified.

Design of Z-Pinch and Dense Plasma Focus Powered Vehicles

NASA Technical Reports Server (NTRS)

Polsgrove, Tara; Fincher, Sharon; Adams, Robert B.; Cassibry, Jason; Cortez, Ross; Turner, Matthew; Maples, C. Daphne; Miermik, Janie N.; Statham, Geoffrey N.; Fabisinski, Leo;

Development of new platforms for hydrodynamic instability and asymmetry measurements in deceleration phase of indirectly-driven implosions on NIF

NASA Astrophysics Data System (ADS)

Pickworth, Louisa

2017-10-01

Hydrodynamic instabilities and asymmetries are a major obstacle in the quest to achieve ignition as they cause pre-existing capsule perturbations to grow and ultimately quench the fusion burn in experiments at the National Ignition Facility (NIF). This talk will review recent developments of the experimental platforms and techniques to measure high-mode instabilities and low-mode asymmetries in the deceleration phase of implosions. These new platforms provide a natural link between the acceleration-phase experiments and neutron performance of layered deuterium-tritium implosions. In one innovative technique, self-emission from the hot spot was enhanced with argon dopant to ``self-backlight'' the shell in-flight around peak compression. Experiments with pre-imposed 2-D perturbations measured instability growth factors, while experiments with 3-D, ``native-roughness'' perturbations measured shell integrity in the deceleration phase of implosions. In a complimentary technique, the inner surface of the shell, along with its low-mode asymmetries and high-mode perturbations were visualized in implosions using x-ray emission of a high-Z dopant added to the inner surface of the capsule. These new measurements were instrumental in revealing unexpected surprises and providing improved understanding of the role of instabilities and asymmetries on implosion performance. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Symmetry Tuning with Cone Powers for Defect Induced Mix Experiment Implosions

NASA Astrophysics Data System (ADS)

Krasheninnikova, N.; Schmitt, M.; Murphy, T.; Cobble, J.; Tregillis, I.; Kyrala, G.; Bradley, P.; Hakel, P.; Hsu, S.; Kanzleiter, R.; Obrey, K.; Baumgaertel, J.; Batha, S.; DIME Team

2013-10-01

Recent DIME campaigns have demonstrated the effectiveness of cone power tuning to control the implosion symmetry in PDD configuration. DIME aims to assess the effects of mix on thermonuclear burn during a thin-shell capsule implosion. Plastic shell capsules doped with mid-Z material and filled with 5 atm of DD, are ablatively driven in a PDD laser configuration to a CR of ~7. Time-gated, spectrally and spatially resolved, dopant emission images characterize mix and temperature morphology during the implosion, while neutron diagnostics concurrently give the information about burn. Symmetry should be maintained throughout the implosions to achieve high neutron yield and optimum spectroscopic signal. 2D and 3D computer simulations using code HYDRA were performed to validate and optimize implosion symmetry using cone power tuning. In particular, Omega campaign confirmed P2 tunability with cone powers while experiments on NIF demonstrated that by reducing the energy in polar cones P2 was reduced to <1%. However, during NIF campaigns, self-emission images revealed a complex internal structure around the equator, which was not seen in HYDRA simulations and could be attributed to LPI effects. Subsequent DIME campaigns on NIF were able to eliminate this equatorial feature by reducing the laser drive substantiating the LPI hypothesis. Work performed by LANL under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the USDoE.

SOME NEW DATA ON SELF-COMPRESSED DISCHARGES (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kvartskhava, I.F.; Kervalidze, K.N.; Gvaladze, Yu.C.

1962-01-01

The theory of self-constricted discharges, which predicts the possibiiity of the appearance of various types of instabilities, does not reflect fully the multiple phenoniena which are experimentally observed. The models used in the theory evidentiy do not consider the presence of some processes in self- constricted discharges which materially determine the real behavior of the plasma. The experiments showed a number of such processes. Basically, they consist of an unequal heating of the discharge near the walls of the chamber. Thereby the discharge currents fiow along distorted threadlike channels which, in theta - pinches mostly follow either the z-direction ormore » the theta -direction, and in z- pinches they basically follow the theta -direction. In the process of plasma compression the above mentioned thread formations experience unequal accelerations. Having a high conductivity, these formations facilitate the capture of magnetic fieids which obstructs the thermaiization of the kinetic energy of the plasma's radial motion. As a result of this process the plasma is far from thermial equilibrium when in the stage of maximum compression. It is encompassed by a motion of turbulent character. After the maximum compression of the plasma, various kinds of plasma formation are ejected from the surface of the pinch. The magnetic field is more effectively trapped than in zpinches. Consequently, a greater variety of types of instability is observed in theta - pinches than in z-pinches. Highspeed photography of the discharge turned out to be the most practical and fruitful method of studying the processes of formation and the subsequent motion of the plasma. Photographs of the discharges obtained by streak photography and by framing camera are discussed. The results of probe measurements of magnetic and electric fields as well as the results of measurements of currents by means of Rogovsky belts are given. (auth)« less

Radiation magnetohydrodynamic simulation of plasma formed on a surface by a megagauss field.

PubMed

Esaulov, A A; Bauer, B S; Makhin, V; Siemon, R E; Lindemuth, I R; Awe, T J; Reinovsky, R E; Struve, K W; Desjarlais, M P; Mehlhorn, T A

2008-03-01

Radiation magnetohydrodynamic modeling is used to study the plasma formed on the surface of a cylindrical metallic load, driven by megagauss magnetic field at the 1MA Zebra generator (University of Nevada, Reno). An ionized aluminum plasma is used to represent the "core-corona" behavior in which a heterogeneous Z-pinch consists of a hot low-density corona surrounding a dense low-temperature core. The radiation dynamics model included simultaneously a self-consistent treatment of both the opaque and transparent plasma regions in a corona. For the parameters of this experiment, the boundary of the opaque plasma region emits the major radiation power with Planckian black-body spectrum in the extreme ultraviolet corresponding to an equilibrium temperature of 16 eV. The radiation heat transport significantly exceeds the electron and ion kinetic heat transport in the outer layers of the opaque plasma. Electromagnetic field energy is partly radiated (13%) and partly deposited into inner corona and core regions (87%). Surface temperature estimates are sensitive to the radiation effects, but the surface motion in response to pressure and magnetic forces is not. The general results of the present investigation are applicable to the liner compression experiments at multi-MA long-pulse current accelerators such as Atlas and Shiva Star. Also the radiation magnetohydrodynamic model discussed in the paper may be useful for understanding key effects of wire array implosion dynamics.

Dynamics of current sheath in a hollow electrode Z-pinch discharge using slug model

NASA Astrophysics Data System (ADS)

Abd Al-Halim, Mohamed A.; Afify, M. S.

2017-03-01

The hollow electrode Z-pinch (HEZP) experiment is a new construction for the electromagnetic propulsion application in which the plasma is formed by the discharge between a plate and ring electrodes through which the plasma is propelled. The experimental results for 8 kV charging voltage shows that the peak discharge current is about 109 kA, which is in good agreement with the value obtained from the simulation in the slug model that simulates the sheath dynamics in the HEZP. The fitting of the discharge current from the slug model indicates that the total system inductance is 238 nH which is relatively a high static inductance accompanied with a deeper pinch depth indicating that the fitted anomalous resistance would be about 95 mΩ. The current and mass factors vary with the changing the gas pressure and the charging voltage. The current factor is between 0.4 and 0.5 on average which is relatively low value. The mass factor decreases by increasing the gas pressure indicating that the sheath is heavy to be driven by the magnetic pressure, which is also indicated from the decreases of the drive factor, hence the radial sheath velocity decreases. The plasma inductance and temperature increase with the increase of the drive factor while the minimum pinch radius decreases.

Evolution of shock through a void in foam

NASA Astrophysics Data System (ADS)

Kim, Y.; Smidt, J. M.; Murphy, T. J.; Douglass, M. R.; Devolder, B. G.; Fincke, J. R.; Schmidt, D. W.; Cardenas, T.; Newman, S. G.; Hamilton, C. E.; Sedillo, T. J.; Los Alamos, NM 87544 Team

2016-10-01

Marble implosion is an experimental campaign intended to study the effects of heterogeneous mix on fusion burn. A spherical capsule is composed of deuterated plastic foam of controlled pore (or void) size with tritium fill in pores. As capsule implosion evolves, the initially separated deuterium and tritium will mix, producing DT yields. Void evolution during implosion is of interest for the Marble campaign. A shock tube, driven by the laser at Omega, was designed to study the evolution of a shock through a foam-filled ``void'' and subsequent void evolution. Targets were comprised of a 100 mg/cc CH foam tube containing a 200-µm diameter, lower density doped foam sphere. High-quality, radiographic images were obtained from both 2% iodine-doped in plastic foam and 15% tin-doped in aerogel foam. These experiments will be used to inform simulations.

Evidence for an intense solar outburst in prehistory

NASA Astrophysics Data System (ADS)

Peratt, A. L.; Yao, W. F.

2008-04-01

A past intense solar outburst and its effect on Earth was proposed by Gold [3] who based his hypotheses on astronomical and geophysical evidence. The discovery that objects from Neolithic or Early Bronze Ages carry patterns of high-current Z-pinches provides insight into the origin and meaning of these ancient symbols produced by mankind. A comparison of graphical and radiation data from high-current Z-pinches to petroglyphs and megaliths is made [1]. These correspond to mankind's visual observations of ancient aurora if the solar wind had increased at times between one and two orders of magnitude, millennia ago [3]. Reference [2] focused on the source of light and its temporal change from a current-increasing Z-Pinch or dense plasma focus aurora. The orientation and field-of-view (FOV) as surveyed and contributed from 139 countries, the latest data coming from a 300 km survey along the Orinoco River Basin in Venezuela, is given. A reconstruction of the auroral form is shown based on existent geophysical evidence. Shown are relativistic electron flows inward at Earth's south polar axis and hypervelocity proton impacts around the north polar axis. 1. A. L. Peratt, Trans. Plasma Sci., 31, 1192, 2003. 2. A. L. Peratt, Trans. Plasma Sci., 35, 778, 2007. 3. T. Gold, Pontificiae Academiae Scientiarvm Scripta Varia 25, 159, 1962.

Comparative study of INPIStron and spark gap

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Lee, Ja H.

1993-01-01

An inverse pinch plasma switch, INPIStron, was studied in comparison to a conventional spark gap. The INPIStron is under development for high power switching applications. The INPIStron has an inverse pinch dynamics, opposed to Z-pinch dynamics in the spark gap. The electrical, plasma dynamics and radiative properties of the closing plasmas have been studied. Recently the high-voltage pulse transfer capabilities or both the INPIStron and the spark gap were also compared. The INPIStron with a low impedance Z = 9 ohms transfers 87 percent of an input pulse with a halfwidth of 2 mu s. For the same input pulse the spark gap of Z = 100 ohms transfers 68 percent. Fast framing and streak photography, taken with an TRW image converter camera, was used to observe the discharge uniformity and closing plasma speed in both switches. In order to assess the effects of closing plasmas on erosion of electrode material, emission spectra of two switches were studied with a spectrometer-optical multi channel analyzer (OMA) system. The typical emission spectra of the closing plasmas in the INPIStron and the spark gap showed that there were comparatively weak carbon line emission in 658.7 nm and copper (electrode material) line emissions in the INPIStron, indicating low erosion of materials in the INPIStron.

Recent results of the Defect-Induced Mix Experiments (DIME) on NIF

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Bradley, P. A.; Cobble, J. A.; Hakel, P.; Hsu, S. C.; Krasheninnikova, N. S.; Kyrala, G. A.; Murphy, T. J.; Obrey, K. A.; Shah, R. C.; Tregillis, I. L.; Craxton, S. C.; McKenty, P. W.; Mancini, R. C.; Johns, H. M.; Joshi, Tirtha; Mayes, Daniel

2012-10-01

Investigations of directly driven implosions have been performed including experiments on Omega, and more recently NIF, to deduce the extent and uniformity of 4π and defect-induced mix near the shell/gas interface of plastic (CH) capsules filled with 5 atm D2 gas. Imaging diagnostics are used to measure the spatial variation of mix caused by the growth of non-uniformities in both capsule and laser drive characteristics. Thin (2μm) layers containing 1-2% (atomic) mid-Z dopants are imaged spectrally at late time in the implosion using multiple monochromatic imaging of H-like and He-like atomic line emission. Areal image backlighting of the capsules provides both r(t) and the symmetry of the implosion. Recent results will be shown including inferred 4π mix width, laser imprint induced mix, and mix from capsule variations.

Enthalpy generation from mixing in hohlraum-driven targets

NASA Astrophysics Data System (ADS)

Amendt, Peter; Milovich, Jose

2016-10-01

The increase in enthalpy from the physical mixing of two initially separated materials is analytically estimated and applied to ICF implosions and gas-filled hohlraums. Pressure and temperature gradients across a classical interface are shown to be the origin of enthalpy generation from mixing. The amount of enthalpy generation is estimated to be on the order of 100 Joules for a 10 micron-scale annular mixing layer between the solid deuterium-tritium fuel and the undoped high-density carbon ablator of a NIF-scale implosion. A potential resonance is found between the mixing layer thickness and gravitational (Cs2/ g) and temperature-gradient scale lengths, leading to elevated enthalpy generation. These results suggest that if mixing occurs in current capsule designs for the National Ignition Facility, the ignition margin may be appreciably eroded by the associated enthalpy of mixing. The degree of enthalpy generation from mixing of high- Z hohlraum wall material and low- Z gas fills is estimated to be on the order of 100 kJ or more for recent NIF-scale hohlraum experiments, which is consistent with the inferred missing energy based on observed delays in capsule implosion times. Work performed under the auspices of Lawrence Livermore National Security, LLC (LLNS) under Contract No. DE-AC52-07NA27344.

Characterization of fast deuterons involved in the production of fusion neutrons in a dense plasma focus

NASA Astrophysics Data System (ADS)

Kubes, P.; Paduch, M.; Sadowski, M. J.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Munzar, V.; Rezac, K.; Zielinska, E.; Skladnik-Sadowska, E.; Szymaszek, A.; Tomaszewski, K.; Zaloga, D.

2018-01-01

This paper considers regions of a fast deuteron production in a correlation with an evolution of ordered structures inside a pinch column of a mega-ampere plasma focus discharge. Ion pinhole cameras equipped with plastic PM-355 track-detectors recorded fast deuterons escaping in the downstream and other directions (up to 60° to the z-axis). Time-integrated ion images made it possible to estimate sources of the deuteron acceleration at the known magnetic field and deuteron energy values. The images of the fast deuterons emitted in the solid angle ranging from 0° to 4° showed two forms: central spots and circular images. The spots of 1-2 cm in diameter were produced by deuterons from the central pinch regions. The circular-shaped images of a radius above 3 cm (or their parts) were formed by deuterons from the region surrounding the dense pinch column. The ion pinhole cameras placed at angles above 20° to the z-axis recorded the ion spots only, and the ring-images were missing. The central region of the deuteron acceleration could be associated mainly with plasmoids, and the circular images could be connected with ring-shaped regions of the radius corresponding to tops of the plasma lobules outside the dense pinch column. The deuteron tracks forming ring-shaped images of a smaller (0.5-1) cm radius could be produced by deflections of the fast deuterons, which were caused by a magnetic field inside the dense pinch column.

Conceptual Design of a Z-Pinch Fusion Propulsion System

NASA Technical Reports Server (NTRS)

Adams, Robert; Polsgrove, Tara; Fincher, Sharon; Fabinski, Leo; Maples, Charlotte; Miernik, Janie; Stratham, Geoffrey; Cassibry, Jason; Cortez, Ross; Turner, Matthew;

Fully kinetic simulations of dense plasma focus Z-pinch devices.

PubMed

Schmidt, A; Tang, V; Welch, D

2012-11-16

Dense plasma focus Z-pinch devices are sources of copious high energy electrons and ions, x rays, and neutrons. The mechanisms through which these physically simple devices generate such high-energy beams in a relatively short distance are not fully understood. We now have, for the first time, demonstrated a capability to model these plasmas fully kinetically, allowing us to simulate the pinch process at the particle scale. We present here the results of the initial kinetic simulations, which reproduce experimental neutron yields (~10(7)) and high-energy (MeV) beams for the first time. We compare our fluid, hybrid (kinetic ions and fluid electrons), and fully kinetic simulations. Fluid simulations predict no neutrons and do not allow for nonthermal ions, while hybrid simulations underpredict neutron yield by ~100x and exhibit an ion tail that does not exceed 200 keV. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis in a fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency, possibly implicating lower hybrid drift instability as a contributor to anomalous resistivity in the plasma.

A z-pinch photo-pumped pulsed atomic iodine laser

NASA Astrophysics Data System (ADS)

Stone, D. H.; Saunders, D. P.; Clark, M. C.

1984-03-01

A pulsed atomic iodine laser (CF3I) was designed and constructed using a coaxial xenon flash lamp as a pump source. The flash lamp was operated at low pressure to obtain pulse compression via xenon self-pinch. Electrical and optical diagnostics were performed for various xenon and CF3I pressures. Calorimeter data and burn patterns were obtained for the laser. Time-resolved spectroscopic data were taken throughout the CF3I pump band.

High-resolution spectroscopy for Doppler-broadening ion temperature measurements of implosions at the National Ignition Facility.

PubMed

Koch, J A; Stewart, R E; Beiersdorfer, P; Shepherd, R; Schneider, M B; Miles, A R; Scott, H A; Smalyuk, V A; Hsing, W W

2012-10-01

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.

Measurement of inflight shell areal density perturbations in NIF capsule implosions near peak velocity

NASA Astrophysics Data System (ADS)

Hammel, B. A.; Pickworth, L.; Smalyuk, V.; Macphee, A.; Scott, H. A.; Robey, H.; Barrios, M.; Regan, S. P.

2015-11-01

Quantitative measurements of shell-RhoR perturbations in capsules near peak implosion velocity (PV) are challenging. An external backlighter samples both sides of the shell, unless a re-entrant cone is used (potentially perturbing implosion). Emission from the hot core, after shock-stagnation and prior to PV, has been used as a self-backlighter, providing a means to sample one side of the capsule. Adding high-Z gas (~ 1% Ar) to the capsule fill in Symcaps (4He), has produced a continuum backlighter with significant increase in emission at photon energies ~ 8 keV over nominal fills. From images of the transmitted self-emission, above and below the K-edge of an internally doped Cu layer, we infer the growth at PV of imposed perturbations (100 nm amplitude, mode 40). Prepared by LLNL under Contract DE-AC52-07NA27344.

An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

Fusion Propulsion Z-Pinch Engine Concept

NASA Technical Reports Server (NTRS)

Miernik, J.; Statham, G.; Fabisinski, L.; Maples, C. D.; Adams, R.; Polsgrove, T.; Fincher, S.; Cassibry, J.; Cortez, R.; Turner, M.;

Recombination-pumped XUV lasing in capillary discharges and dynamic z-pinches

NASA Astrophysics Data System (ADS)

Pöckl, M.; Hebenstreit, M.; Fertner, R.; Neger, T.; Aumayr, F.

1996-08-01

A fully time-dependent collisional - radiative model is employed to calculate relevant population densities in a recombining carbon/hydrogen z-pinch plasma. In particular, the dependence of the small signal gain G on the maximum electron temperature and cooling rate, as well as the influence of Lyman-0022-3727/29/8/005/img8 reabsorption, are studied. Although in conditions typical for dynamic z-pinches the maximum electron temperature and cooling rates would, in principle, be sufficiently high, gain on the Balmer-0022-3727/29/8/005/img8 transition is strongly reduced by Lyman-0022-3727/29/8/005/img8 reabsorption. In order to investigate vacuum spark capillary discharges, the system of rate equations is coupled with balance equations of the plasma energy and the total number of heavy particles. The resulting set of equations is solved self-consistently. Results are presented that show the systematic dependence of the small signal gain on electrical input power, wall material, and capillary geometry. High gain coefficients 0022-3727/29/8/005/img11 could be achieved by modelling high-voltage discharges with short ringing periods through capillaries containing boron or carbon. While the maximum achievable gain coefficient for lithium is rather poor 0022-3727/29/8/005/img12 the duration of population inversion would be long enough (a few tens of nanoseconds) to make multi-pass operation possible.

Development and demonstration of a water-window soft x-ray microscope using a Z-pinching capillary discharge source

NASA Astrophysics Data System (ADS)

Nawaz, M. F.; Jancarek, Alexandr; Nevrkla, Michal; Duda, Martin Jakub; Pina, Ladislav

2017-05-01

The development and demonstration of a soft X-ray (SXR) microscope, based on a Z-pinching capillary discharge source has been realized. The Z-pinching plasma acts as a source of SXR radiation. A ceramic capacitor bank is pulsed charged up to 80 kV, and discharged through a pre- ionized nitrogen filled ceramic capillary. The discharge current has an amplitude of 25 kA. Working within the water-window spectral region (λ = 2.88 nm), corresponding to the 1s2-1s2p quantum transition of helium-like nitrogen (N5+), the microscope has a potential in exploiting the natural contrast existing between the K-absorption edges of carbon and oxygen as the main constituents of biological materials, and hence imaging them with high spatial resolution. The SXR microscope uses the grazing incidence ellipsoidal condenser mirror for the illumination, and the Fresnel zone plate optics for the imaging of samples onto a BI-CCD camera. The half- pitch spatial resolution of 100 nm [1] was achieved, as demonstrated by the knife-edge test. In order to enhance the photon-flux at the sample plane, a new scheme for focusing the radiation, from multiple capillary sources has been investigated. Details about the source, and the construction of the microscope are presented and discussed.

Plasma expansion dynamics physics: An understanding on ion energy reduction process

NASA Astrophysics Data System (ADS)

Ruzic, David; Srivastava, Shailendra; Thompson, Keith; Spencer, Joshua; Sporre, John

2007-11-01

This paper studies the expanding plasma dynamics of ions produced from a 5J Z-pinch xenon light source used for EUV lithography. Ion energy reduction is essential for the successful implementation of this technology. To aid this investigation, ion energy from a z-pinch DPP plasma source is measured using an ion energy analyzer and effect of introducing a small percentage of low Z material on the ion energy and flux is investigated. Presence of low mass such as H2 or N2, shows a considerable reduction in total flux and in average energy. For example, Xe^+ ion flux at 5 keV are recorded as 425 ± 42 ions/cm^2.eV.pulse at 157 cm and reduced to 125 ± 12 ions/cm^2.eV.pulse when using the low mass into the system at same energy. It is also noticed that such a combination leads to decrease in sputtering without changing the EUV output. Study of the possible mechanism supporting the experimental results is numerically calculated. This computational work indicates that the observed high energies of ions are probably resulting from coulomb explosion initiated by pinch instability. It is postulated that the electrons leave first setting up an electrostatic potential which accelerates the ions. The addition of small mass actually screens the potential and decorates the ions.

Viscosity Control Experiment Feasibility Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, Heidi E.; Bradley, Paul Andrew

Turbulent mix has been invoked to explain many results in Inertial Confinement Fusion (ICF) and High Energy Density (HED) physics, such as reduced yield in capsule implosions. Many ICF capsule implosions exhibit interfacial instabilities seeded by the drive shock, but it is not clear that fully developed turbulence results from this. Many simulations use turbulent mix models to help match simulation results to data, but this is not appropriate if turbulence is not present. It would be useful to have an experiment where turbulent mixing could be turned on or off by design. The use of high-Z dopants to modifymore » viscosity and the resulting influence on turbulence is considered here. A complicating factor is that the plasma in some implosions can become strongly coupled, which makes the Spitzer expression for viscosity invalid. We first consider equations that cover a broad parameter space in temperature and density to address regimes for various experimental applications. Next, a previous shock-tube and other ICF experiments that investigate viscosity or use doping to examine the effects on yield are reviewed. How viscosity and dopants play a role in capsule yield depends on the region and process under consideration. Experiments and simulations have been performed to study the effects of viscosity on both the hot spot and the fuel/ablator mix. Increases in yield have been seen for some designs, but not all. We then discuss the effect of adding krypton dopant to the gas region of a typical OMEGA and a 2-shock NIF implosion to determine approximately the effect of adding dopant on the computed Reynolds number. Recommendations for a path forward for possible experiments using high-Z dopants to affect viscosity and turbulence are made.« less

Suppression of laser nonuniformity imprinting using a thin high-z coating.

PubMed

Karasik, Max; Weaver, J L; Aglitskiy, Y; Oh, J; Obenschain, S P

2015-02-27

Imprinting of laser nonuniformity is a limiting factor in direct-drive inertial confinement fusion experiments, particularly when available laser smoothing is limited. A thin (∼400  Å) high-Z metal coating is found to substantially suppress laser imprint for planar targets driven by pulse shapes and intensities relevant to implosions on the National Ignition Facility while retaining low adiabat target acceleration. A hybrid of indirect and direct drive, this configuration results in initial ablation by x rays from the heated high-Z layer, creating a large standoff for perturbation smoothing.

3D MHD Simulations of Radial Wire Array Z-pinches

NASA Astrophysics Data System (ADS)

Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V.; Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P.

2009-01-01

Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 μs) and SPHINX (4 MA, 700 ns)[1] facilities have shown the relatively high level of scalability of the Radial Wire Array Z-pinches. These configurations where the wires stretch radially outwards from a central cathode offer numerous advantages over standard cylindrical arrays. In particular, imploding in a very stable and compact way, they seem suitable for coupling to small scale hohlraums. Making use of the 3D resistive magneto-hydrodynamic code GORGON[2] developed at Imperial College, the dynamic of the radial wire arrays is investigated. Influence of the cathode hotspots and wires angle on the x-ray emissions is also discussed. Comparison with experiments is offered to validate the numerical studies.

A kind of fast shutter for Z pinch diagnosis device.

PubMed

Wang, Liangping; Zhang, Xinjun; Sun, Tieping; Mao, Wentin

2016-09-01

A kind of fast shutter for protecting the diagnosis devices in Z pinch experiments is introduced in this paper. The shutter is composed of a pulling rod, a magnetic core, and a solenoid. Different from the traditional coils which were used at the voltage of 220 V, the solenoid we used must endure the high voltage of 5-10 kV and the deformation which maybe caused by the 5-10 T intense magnetic field. A creative configuration for the solenoid is developed including the winding guide, insulating sleeve, and stainless-steel sleeve. The experimental results show that the configuration of the solenoid is effective. The velocity of the valve is nearly 19 m/s and the time jitter of the shutdown is within 75 μs.

A kind of fast shutter for Z pinch diagnosis device

NASA Astrophysics Data System (ADS)

Wang, Liangping; Zhang, Xinjun; Sun, Tieping; Mao, Wentin

2016-09-01

A kind of fast shutter for protecting the diagnosis devices in Z pinch experiments is introduced in this paper. The shutter is composed of a pulling rod, a magnetic core, and a solenoid. Different from the traditional coils which were used at the voltage of 220 V, the solenoid we used must endure the high voltage of 5-10 kV and the deformation which maybe caused by the 5-10 T intense magnetic field. A creative configuration for the solenoid is developed including the winding guide, insulating sleeve, and stainless-steel sleeve. The experimental results show that the configuration of the solenoid is effective. The velocity of the valve is nearly 19 m/s and the time jitter of the shutdown is within 75 μs.

Schlieren Cinematography of Current Driven Plasma Jet Dynamics

NASA Astrophysics Data System (ADS)

Loebner, Keith; Underwood, Thomas; Cappelli, Mark

2016-10-01

Schlieren cinematography of a pulsed plasma deflagration jet is presented and analyzed. An ultra-high frame rate CMOS camera coupled to a Z-type laser Schlieren apparatus is used to obtain flow-field refractometry data for the continuous flow Z-pinch formed within the plasma deflagration jet. The 10 MHz frame rate for 256 consecutive frames provides high temporal resolution, enabling turbulent fluctuations and plasma instabilities to be visualized over the course of a single pulse (20 μs). The Schlieren signal is radiometrically calibrated to obtain a two dimensional mapping of the refraction angle of the axisymmetric pinch plasma, and this mapping is then Abel inverted to derive the plasma density distribution as a function radius, axial coordinate, and time. Analyses of previously unknown discharge characteristics and comparisons with prior work are discussed.

MAIZE: a 1 MA LTD-Driven Z-Pinch at The University of Michigan

NASA Astrophysics Data System (ADS)

Gilgenbach, R. M.; Gomez, M. R.; Zier, J. C.; Tang, W. W.; French, D. M.; Lau, Y. Y.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Oliver, B. V.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

2009-01-01

Researchers at The University of Michigan have constructed and tested a 1-MA Linear Transformer Driver (LTD), the first of its type to reach the USA. The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute of High Current Electronics in collaboration with Sandia National Labs and UM. This LTD utilizes 80 capacitors and 40 spark gap switches, arranged in 40 "bricks," to deliver a 1 MA, 100 kV pulse with 100 ns risetime into a matched resistive load. Preliminary resistive-load test results are presented for the LTD facility. Planned experimental research programs at UM include: a) Studies of Magneto-Raleigh-Taylor instability of planar foils, and b) Vacuum convolute studies including cathode and anode plasma.

Z-Pinch Magneto-Inertial Fusion Propulsion Engine Design Concept

NASA Technical Reports Server (NTRS)

Miernik, Janie H.; Statham, Geoffrey; Adams, Robert B.; Polsgrove, Tara; Fincher, Sharon; Fabisinski, Leo; Maples, C. Dauphne; Percy, Thomas K.; Cortez, Ross J.; Cassibry, Jason

2011-01-01

Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human spaceflight missions. Magneto-Inertial Fusion (MIF) is an approach which has been shown to potentially lead to a low cost, small fusion reactor/engine assembly (1). The Z-Pinch dense plasma focus method is an MIF concept in which a column of gas is compressed to thermonuclear conditions by an estimated axial current of approximately 100 MA. Recent advancements in experiments and the theoretical understanding of this concept suggest favorable scaling of fusion power output yield as I(sup 4) (2). The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this is repeated over short timescales (10(exp -6) sec). This plasma formation is widely used in the field of Nuclear Weapons Effects (NWE) testing in the defense industry, as well as in fusion energy research. There is a wealth of literature characterizing Z-Pinch physics and existing models (3-5). In order to be useful in engineering analysis, a simplified Z-Pinch fusion thermodynamic model was developed to determine the quantity of plasma, plasma temperature, rate of expansion, energy production, etc. to calculate the parameters that characterize a propulsion system. The amount of nuclear fuel per pulse, mixture ratio of the D-T and nozzle liner propellant, and assumptions about the efficiency of the engine, enabled the sizing of the propulsion system and resulted in an estimate of the thrust and Isp of a Z-Pinch fusion propulsion system for the concept vehicle. MIF requires a magnetic nozzle to contain and direct the nuclear pulses, as well as a robust structure and radiation shielding. The structure, configuration, and materials of the nozzle must meet many severe requirements. The configuration would focus, in a conical manner, the Deuterium-Tritium (D-T) fuel and Lithium-6/7 liner fluid to meet at a specific point that acts as a cathode so the Li-6 can serve as a current return path to complete the circuit. In addition to serving as a current return path, the Li liner also serves as a radiation shield. The advantage to this configuration is the reaction between neutrons and Li-6 results in the production of additional Tritium, thus adding further fuel to the fusion reaction and boosting the energy output. To understand the applicability of Z-Pinch propulsion to interplanetary travel, it is necessary to design a concept vehicle that uses it. The propulsion system significantly impacts the design of the electrical, thermal control, avionics, radiation shielding, and structural subsystems of a vehicle. The design reference mission is the transport of crew and cargo to Mars and back, with the intention that the vehicle be reused for other missions. Several aspects of this vehicle are based on a previous crewed fusion vehicle study called Human Outer Planet Exploration (HOPE), which employed a Magnetized Target Fusion (MTF) propulsion concept. Analysis of this propulsion system concludes that a 40-fold increase of Isp over chemical propulsion is predicted. This along with a greater than 30% predicted payload mass fraction certainly warrants further development of enabling technologies. The vehicle is designed for multiple interplanetary missions and conceivably may be suited for an automated one-way interstellar voyage.

How Artificial Should the Treatment of a Plasma's Viscosity Be?

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Velikovich, A. L.; Thornhill, J. W.; Davis, J.

1999-11-01

Electron viscosity dominates over ion viscosity and is important in describing the generation of shock fronts in highly ionizable plasmas. The sizes of shock front jumps in electron and ion temperature are determined from the magnitudes of the heat flow vector and pressure tensor, which, in turn, acquire non-negligible nonlinear contributions from the temperature and density gradients when these gradients are large. Thus, a consistent treatment of steep gradient formation in plasmas must come from investigations that include the effects of these nonlinear contributions to heat and momentum transport. Coefficients for each of five nonlinear contributions to the pressure tensor for an (r,z) Z-pinch geometry are presented and discussed in this talk. Hydrodynamic code calculations generally are not designed to provide a testbed for directly evaluating the kinetic energy dissipation that occurs at shock fronts; therefore, the strength of these nonlinear pressure tensor terms will be estimated by post-processing a Z-pinch hydrodynamics calculation and a steady-state planar shock wave calculation.

Hot spot mix in ICF implosions on the NIF

NASA Astrophysics Data System (ADS)

Ma, Tammy

2016-10-01

In the quest to achieve ignition through the inertial confinement fusion scheme, one of the critical challenges is to drive a symmetric implosion at high velocity without hydrodynamic instabilities becoming detrimental. These instabilities, primarily at the ablation front and the fuel-ablator interface, can cause mix of the higher-Z shell into the hot spot, resulting in increased radiation loss and thus reduced temperature and neutron yield. To quantify the level of mix, we developed a model that infers the level of hot spot contamination using the ratio of the enhanced x-ray production relative to the neutron yield. Applying this methodology to the full ensemble of indirect-drive National Ignition Facility (NIF) cryogenically layered DT implosions provides insight on the sensitivity of performance to the level of ablator-hot spot mix. In particular, the improvement seen with the High Foot design can be primarily attributed to a reduction in ablation-front instability mix that enabled the implosions to be pushed to higher velocity and performance. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, Lawrence Livermore National Security, LLC.

Mix Model Comparison of Low Feed-Through Implosions

NASA Astrophysics Data System (ADS)

Pino, Jesse; MacLaren, S.; Greenough, J.; Casey, D.; Dewald, E.; Dittrich, T.; Khan, S.; Ma, T.; Sacks, R.; Salmonson, J.; Smalyuk, V.; Tipton, R.; Kyrala, G.

2016-10-01

The CD Mix campaign previously demonstrated the use of nuclear diagnostics to study the mix of separated reactants in plastic capsule implosions at the NIF. Recently, the separated reactants technique has been applied to the Two Shock (TS) implosion platform, which is designed to minimize this feed-through and isolate local mix at the gas-ablator interface and produce core yields in good agreement with 1D clean simulations. The effects of both inner surface roughness and convergence ratio have been probed. The TT, DT, and DD neutron signals respectively give information about core gas performance, gas-shell atomic mix, and heating of the shell. In this talk, we describe efforts to model these implosions using high-resolution 2D ARES simulations. Various methods of interfacial mix will be considered, including the Reynolds-Averaged Navier Stokes (RANS) KL method as well as and a multicomponent enhanced diffusivity model with species, thermal, and pressure gradient terms. We also give predictions of a upcoming campaign to investigate Mid-Z mixing by adding a Ge dopant to the CD layer. LLNL-ABS-697251 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Preface

NASA Astrophysics Data System (ADS)

Gauthier, Jean-Claude; Hammel, Bruce; Azechi, Hiroshi; Labaune, Christine

2006-06-01

The Fourth International Conference on Inertial Fusion Sciences and Applications (IFSA 2005) was held September 4-9, 2005 at the Bellevue Conference Center in Biarritz, France. The host organizations for this conference were the University of Bordeaux 1, the Centre National de la Recherche Scientifique (CNRS) and the Commissariat a l'Energie Atomique (CEA). The conference objective was to review of the state of the art of research in inertial fusion sciences and applications since the last conference held in Monterey California, USA, in 2003. Altogether 509 abstracts were submitted, 418 accepted, and more than 440 persons from 23 countries attended the conference. These Proceedings contain 249 of the papers presented at IFSA 2005. This collection of papers represents the manuscripts submitted to and passing the peer review process. The IFSA 2005 conference is the first of a new series of three conferences to be organized in France, Japan and the USA and governed under Annex I of the Memorandum of Agreement, signed in June 2004, among the Lawrence Livermore Laboratory operated by the University of California (UC), Osaka University, and Institut Lasers et Plasmas (ILP), operated by CNRS Delegation Aquitaine. The IFSA 2005 continued the strong tradition of the three previous conferences in Bordeaux, Kyoto and Monterey. It was the largest IFSA yet with a substantial participation from countries such as China and Russia. With a goal of achieving inertial fusion ignition and burn propagation in the laboratory, there continues to be significant progress in the international inertial fusion community. At IFSA 2005, researchers presented the exciting advances in traditional hot spot ignition approach, including results from the early experiments from the NIF laser. A particularly emphasis of the meeting was the rapid and exciting progress in the fast ignition scheme. Integrated and basic physics experiments on GekkoXII, Vulcan, and other laser-matter interaction facilities have shown promising results. A lot of new results of experiments and numerical simulations in ultra-intense laser interactions have also been presented. The Megajoule Laser (LMJ), as one of two facilities being built to achieve target ignition, was a key attraction of IFSA 2005. About 200 participants toured the LMJ construction site and the LIL laser prototype during the conference. Before the tour, a special Facility Focus session examined progress on inertial fusion facilities around the world, including the soon-to-be-completed OMEGA-EP upgrade at Rochester, USA, and FIREX I, at Osaka, Japan. Recent progresses in hohlraum physics continue to give confidence in the ultimate achievement of ignition on the NIF Laser and the Megajoule Laser. The USA are pursuing a very focused program on ICF under the National Ignition Campaign (NIC). In China, a national project has been launched, the goal of which is fusion ignition and plasma burning in about 2020. Progress in direct drive has been notable over the past few years with the cryogenic implosions at LLE, polar direct-drive that may enable to switch rapidly from an indirect- to a direct-drive laser configuration, adiabat shaping of laser pulses, and even "Saturn targets", a short circuit topic from ICF to laboratory astrophysics. About this last topic, radiative shocks and plasma jets were among the most studied subjects. There were also sessions on the technologies of al1 types of drivers, including KrF and DPSSL lasers, particle beams, and Z-pinches. Advances in Z-pinch included double-hohlraum irradiation symmetry and the construction of a PW laser beam for the Z-facility. Advance in plasma diagnostics were dominated by proton imaging from ultra-intense interactions and precise imaging spectroscopy of core implosions. Of special interest, advanced target physics and reactor design studies have started to be more present during this IFSA edition. These Proceedings start with special chapters on the keynote speeches and the Teller lectures. The keynotes give an overview of progress in inertial fusion in North America, Europe and Asia. The Teller lectures show the contributions of this year's two winners: Joe Kilkenny of General Atomics and Max Tabak of LLNL. The remainder of the Proceedings is divided into three parts. Part A covers the physics of inertial fusion; Part B covers facilities, lasers, particle beams, Z-pinches, target fabrication and reactor design; Part C covers fundamental high-energy density science and other applications of inertial fusion VI technology such as plasma diagnostics, atomic physics and X-ray sources, laboratory astrophysics and laser particle acceleration. The readers should be aware that for some of the papers, only a short version is presented in this book: the extended version will be published in a topical issue of the European Physical Journal. The IFSA International Organizing Committee and Scientific Advisory Board appreciate the efforts of inertial fusion researchers worldwide in making IFSA 2005 an extremely successful conference. Jean-Claude Gauthier, technical committee co-chair Bruce Hammel, technical committee co-chair Hiroshi Azechi, technical committee co-chair Christine Labaune, proceedings co-editor

Staged Z-pinch Experiments at the 1MA Zebra pulsed-power generator: Neutron measurements

NASA Astrophysics Data System (ADS)

Ruskov, Emil; Darling, T.; Glebov, V.; Wessel, F. J.; Anderson, A.; Beg, F.; Conti, F.; Covington, A.; Dutra, E.; Narkis, J.; Rahman, H.; Ross, M.; Valenzuela, J.

2017-10-01

We report on neutron measurements from the latest Staged Z-pinch experiments at the 1MA Zebra pulsed-power generator. In these experiments a hollow shell of argon or krypton gas liner, injected between the 1 cm anode-cathode gap, compresses a deuterium plasma target of varying density. Axial magnetic field Bz <= 2 kGs, applied throughout the pinch region, stabilizes the Rayleigh-Taylor instability. The standard silver activation diagnostics and 4 plastic scintillator neutron Time of Flight (nTOF) detectors are augmented with a large area ( 1400 cm2) liquid scintillator detector to which fast gatedPhotek photomultipliers are attached. Sample data from these neutron diagnostics systems is presented. Consistently high neutron yields YDD >109 are measured, with highest yield of 2.6 ×109 . A pair of horizontally and vertically placed plastic scintillator nTOFs suggest isotropic i.e. thermonuclear origin of the neutrons produced. nTOF data from the liquid scintillator detector was cross-calibrated with the silver activation detector, and can be used for accurate calculation of the neutron yield. Funded by the Advanced Research Projects Agency - Energy, under Grant Number DE-AR0000569.

Neutron Activation Diagnostics in Deuterium Gas-Puff Experiments on the 3 MA GIT-12 Z-Pinch

NASA Astrophysics Data System (ADS)

Cikhardt, J.; Klir, D.; Rezac, K.; Cikhardtova, B.; Kravarik, J.; Kubes, P.; Sila, O.; Shishlov, A. V.; Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.; Turek, K.

2016-10-01

The experiments with a deuterium z-pinch on the GIT-12 generator at IHCE in Tomsk were performed in the frame of the Czech-Russian agreement. A set of neutron diagnostics included scintillation time-of-flight detectors, bubble detectors, and several kinds of threshold nuclear activation detectors in the order to obtain information about the yield, anisotropy, and spectrum of the neutrons produced by a deuterium gas-puff. The average neutron yield in these experiments was of the order of 1012 neutrons per a single shot. The energy spectrum of the produced neutrons was evaluated using neutron time-of-flight detectors and a set of neutron activation detectors. Because the deuterons in the pinch achieve multi-MeV energies, non-DD neutrons are produced by nuclear reactions of deuterons with a stainless steel vacuum chamber and aluminum components of diagnostics inside the chamber. An estimated number of the non-DD was of the order of 1011. GACR (Grant No. 16-07036S), CME (Grant Nos. LD14089, LG13029, and LH13283), MESRF (Grant No. RFMEFI59114X0001), IAEA (Grant No. RC17088), CTU (Grant No. SGS 16/223/OHK3/3T/13).

Use of vacuum arc plasma guns for a metal puff Z-pinch system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousskikh, A. G.; Zhigalin, A. S.; Oreshkin, V. I.

The performance of a metal puff Z-pinch system has been studied experimentally. In this type of system, the initial cylindrical shell 4 cm in diameter was produced by ten plasma guns. Each gun initiates a vacuum arc operating between magnesium electrodes. The net current of the guns was 80 kA. The arc-produced plasma shell was compressed by using a 450-kA, 450-ns driver, and as a result, a plasma column 0.3 cm in diameter was formed. The electron temperature of the plasma reached 400 eV at an average ion concentration of 1.85 {center_dot} 10{sup 18} cm{sup -3}. The power of themore » Mg K-line radiation emitted by the plasma for 15-30 ns was 300 MW/cm.« less

Plasma-puff initiation of high Coulomb transfer switches

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Venable, Demetrius D.; Lee, Ja H.; Choi, Eun H.; Kim, Y. K.; Kim, J. H.; Nguyen, D. X.

1993-01-01

The plasma-puff triggering mechanism based on a hypocycloidal pinch geometry was investigated to determine the optimal operating conditions for an azimuthally uniform surface flashover which initiates plasma-puff under wide ranges of fill gas pressures of Ar, He and N2. The optimal fill gas pressures for the azimuthally uniform plasma-puff were about 120 mTorr less than P(sub opt) less than 450 Torr for He and N2. For Argon 20 mTorr is less than P(sub opt) is less than 5 Torr. The inverse pinch switch was triggered with the plasma-puff and the switching capability under various electrical parameters and working gas pressures of Ar, He and N2 was determined. It was also shown that the azimuthally uniform switching discharges were dependent on the type of fill gas and its fill pressure. A new concept of plasma-focus driven plasma-puff was also discussed in comparison with hypocycloidal pinch plasma-puff triggering. The main discharge of the inverse pinch switch with the plasma-focus driven plasma-puff trigger is found to be more azimuthally uniform than that with the hypocycloidal pinch plasma-puff trigger in a gas pressure region between 80 mTorr and 1 Torr. In order to assess the effects of plasma current density on material erosion of electrodes, emissions from both an inverse-pinch plasma switch (INPIStron) and from a spark gap switch under test were studied with an optical multichannel analyzer (OMA). The color temperature of the argon plasma was approximately 4,000 K which corresponded with the peak continuum emission near 750 nm. There are the strong line emissions of argon in the 650 - 800 nm range and a lack of line emissions of copper and other solid material used in the switch. This indicates that the plasma current density during closing is low and the hot spot or hot filament in the switch is negligible. This result also indicates considerable reduction of line emission with the INPIStron switch over that of a spark-gap switch. However, a strong carbon line emission exists due to vaporization of the plastic insulator used. In order to reduce the vaporization of the insulator, the plexiglass insulating material of INPIStron was replaced with Z-9 material. A comparative study of the INPIStron and a spark gap also reveals that the INPIStron, with a low impedance of Z = 9 ohms, can transfer a high voltage pulse with a superior pulse-shape fidelity over that of a spark gap with Z = 100 ohms.

Plasma-puff initiation of high Coulomb transfer switches

NASA Technical Reports Server (NTRS)

Venable, D. D.; Han, K. S.

1993-01-01

The plasma-puff triggering mechanism based on a hypocycloidal pinch geometry was investigated to determine the optimal operating conditions for an azimuthally uniform surface flashover which initiates plasma-puff under wide ranges of fill gas pressures of Ar, He and N2. The optimal fill gas pressures for the azimuthally uniform plasma-puff were about 120 mTorr less than P(opt) less than 450 Torr for He and N2. For Argon 120 mTorr less than P(opt) less than 5 Torr for argon. The inverse pinch switch was triggered with the plasma-puff and the switching capability under various electrical parameters and working gas pressures of Ar, He and N2 was determined. It was also shown that the azimuthally uniform switching discharges were dependent on the type of fill gas and its fill pressure. A new concept of plasma-focus driven plasma-puff was also discussed in comparison with hypocycloidal pinch plasma-puff triggering. The main discharge of the inverse pinch switch with the plasma-focus driven plasma-puff trigger is found to be more azimuthally uniform than that with the hypocycloidal pinch plasma-puff trigger in a gas pressure region between 80 mTorr and 1 Torr. In order to assess the effects of plasma current density on material erosion of electrodes, emissions from both an inverse-pinch plasma switch (INPIStron) and from a spark gap switch under test were studied with an optical multichannel analyzer (OMA). The color temperature of the argon plasma was approximately 4,000 K which corresponded with the peak continuum emission near 750 nm. There are the strong line emissions of argon in the 650 - 800 nm range and a lack of line emissions of copper and other solid material used in the switch. This indicates that the plasma current density during closing is low and the hot spot or hot filament in the switch is negligible. This result also indicates considerable reduction of line emission with the INPIStron switch over that of a spark-gap switch. However, a strong carbon line emission exists due to vaporization of the plastic insulator used. In order to reduce the vaporization of the insulator, the plexiglass insulating material of INPIStron was replaced with Z-9 material. A comparative study of the INPIStron and a spark gap also reveals that the INPIStron, with a low impedance of Z equals 9 ohms, can transfer a high voltage pulse with a superior pulse-shape fidelity over that of a spark gap with Z equals 100 ohms.

An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

Magnetic Inertial Confinement Fusion (MICF)

NASA Astrophysics Data System (ADS)

Miao, Feng; Zheng, Xianjun; Deng, Baiquan; Liu, Wei; Ou, Wei; Huang, Yi

2016-11-01

Based on the similarity in models of the early Sun and the 3-D common focal region of the micro-pinch in X-pinch experiments, a novel hybrid fusion configuration by continuous focusing of multiple Z-pinched plasma beams on spatially symmetric plasma is proposed. By replacing gravity with Lorentz force with subsequent centripetal spherical pinch, the beam-target fusion reactivity is enhanced in a quasi-spherical converging region, thus achieving MICF. An assessment, presented here, suggests that a practical fusion power source could be achieved using deuterium alone. Plasma instabilities can be suppressed by fast rotation resulting from an asymmetric tangential torsion in the spherical focal region of this configuration. Mathematical equivalence with the Sun allows the development of appropriate equations for the focal region of MICF, which are solved numerically to provide density, temperature and pressure distributions that produce net fusion energy output. An analysis of MICF physics and a preliminary experimental demonstration of a single beam are also carried out. supported by National Natural Science Foundation of China (Nos. 11374217 and 11176020)

Interaction of infectious spleen and kidney necrosis virus ORF119L with PINCH leads to dominant-negative inhibition of integrin-linked kinase and cardiovascular defects in zebrafish.

PubMed

Yuan, Ji-Min; He, Bai-Liang; Yang, Lu-Yun; Guo, Chang-Jun; Weng, Shao-Ping; Li, Shengwen Calvin; He, Jian-Guo

2015-01-01

Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the Megalocytivirus genus, Iridoviridae family, causing a severe systemic disease with high mortality in mandarin fish (Siniperca chuatsi) in China and Southeast Asia. At present, the pathogenesis of ISKNV infection is still not fully understood. Based on a genome-wide bioinformatics analysis of ISKNV-encoded proteins, we found that ISKNV open reading frame 119L (ORF119L) is predicted to encode a three-ankyrin-repeat (3ANK)-domain-containing protein, which shows high similarity to the dominant negative form of integrin-linked kinase (ILK); i.e., viral ORF119L lacks the ILK kinase domain. Thus, we speculated that viral ORF119L might affect the host ILK complex. Here, we demonstrated that viral ORF119L directly interacts with particularly interesting Cys-His-rich protein (PINCH) and affects the host ILK-PINCH interaction in vitro in fathead minnow (FHM) cells. In vivo ORF119L overexpression in zebrafish (Danio rerio) embryos resulted in myocardial dysfunctions with disintegration of the sarcomeric Z disk. Importantly, ORF119L overexpression in zebrafish highly resembles the phenotype of endogenous ILK inhibition, either by overexpressing a dominant negative form of ILK or by injecting an ILK antisense morpholino oligonucleotide. Intriguingly, ISKNV-infected mandarin fish develop disorganized sarcomeric Z disks in cardiomyocytes. Furthermore, phosphorylation of AKT, a downstream effector of ILK, was remarkably decreased in ORF119L-overexpressing zebrafish embryos. With these results, we show that ISKNV ORF119L acts as a domain-negative inhibitor of the host ILK, providing a novel mechanism for the megalocytivirus pathogenesis. Our work is the first to show the role of a dominant negative inhibitor of the host ILK from ISKNV (an iridovirus). Mechanistically, the viral ORF119L directly binds to the host PINCH, attenuates the host PINCH-ILK interaction, and thus impairs ILK signaling. Intriguingly, ORF119L-overexpressing zebrafish embryos and ISKNV-infected mandarin fish develop similar disordered sarcomeric Z disks in cardiomyocytes. These findings provide a novel mechanism for megalocytivirus pathogenesis. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Phase velocity enhancement of linear explosive shock tubes

NASA Astrophysics Data System (ADS)

Loiseau, Jason; Serge, Matthew; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent

2011-06-01

Strong, high density shocks can be generated by sequentially detonating a hollow cylinder of explosives surrounding a thin-walled, pressurized tube. Implosion of the tube results in a pinch that travels at the detonation velocity of the explosive and acts like a piston to drive a shock into the gas ahead of it. In order to increase the maximum shock velocities that can be obtained, a phase velocity generator can be used to drag an oblique detonation wave along the gas tube at a velocity much higher than the base detonation velocity of the explosive. Since yielding and failure of the gas tube is the primary limitation of these devices, it is desirable to retain the dynamic confinement effects of a heavy-walled tamper without interfering with operation of the phase velocity generator. This was accomplished by cutting a slit into the tamper and introducing a phased detonation wave such that it asymmetrically wraps around the gas tube. This type of configuration has been previously experimentally verified to produce very strong shocks but the post-shock pressure and shock velocity limits have not been investigated. This study measured the shock trajectory for various fill pressures and phase velocities to ascertain the limiting effects of tube yield, detonation obliquity and pinch aspect ratio.

Comparison of high-density carbon implosions in unlined uranium versus gold hohlraums

NASA Astrophysics Data System (ADS)

Dewald, Eduard; Meezan, Nathan; Tommasini, Riccardo; Khan, Shahab; MacKinnon, Andrew; Berzak Hopkins, Laura; Divol, Laurent; Lepape, Sebastien; Moore, Alastair; Schneider, Marilyn; Pak, Arthur; Nikroo, Abbas; Landen, Otto

2016-10-01

In Inertial Confinement Fusion (ICF) implosions, laser energy is converted to x-ray radiation in hohlraums with High-Z walls. At radiation temperatures near 300 eV relevant for ICF experiments, the radiative losses in heating the wall are lower for U than for Au hohlraums. Furthermore, the intensity of the ``M-band'' x-rays with photon energies h ν >1.8 keV is lower for uranium, allowing for reduced capsule dopant concentrations employed to minimize inner ablator preheat and hence keep favorable fuel/ablator interface Atwood numbers. This in turn improves the ablator rocket efficiency and reduces the risk of polluting the hot-spot with emissive dopant material. The first uranium vacuum hohlraum experiments on the National Ignition Facility (NIF) with undoped high-density carbon (HDC, or diamond) capsules have demonstrated 30% lower ``M-band'' intensity relative to Au, resulting in lower inflight ablator thickness due to reduced preheat. In addition, fusion neutron yields are 2x higher in U than in Au hohlraums for D2-gas filled capsule implosions at ICF relevant velocities of 380 +/-20 km/s. These results have led the NIF ICF implosions to routinely employ U hohlraums. Prepared by LLNL under Contract DE-AC52-07NA27344.

Impedance Dynamics in the Self-Magnetic Pinch (SMP) Diode on the RITS-6 Accelerator

NASA Astrophysics Data System (ADS)

Renk, Timothy; Johnston, Mark; Leckbee, Joshua; Webb, Timothy; Mazarakis, Michael; Kiefer, Mark; Bennett, Nichelle

2014-10-01

The RITS-6 inductive voltage adder (IVA) accelerator (3.5-8.5 MeV) at Sandia National Laboratories produces high-power (TW) focused electron beams (<3 mm diameter) for flash x-ray radiography applications. The Self-Magnetic Pinch (SMP) diode utilizes a hollowed metal cathode to produce a pinched focus onto a high Z metal converter. The electron flow from the IVA driver into the load region complicates understanding of diode evolution. There is growing evidence that reducing cathode size below some ``optimum'' value in order to achieve desired spot size reduction results in pinch instabilities leading to either reduced dose-rate, early radiation power termination, or both. We are studying evolving pinch dynamics with current and x-ray monitors, optical diagnostics, and spectroscopy, as well as with LSP [1] code simulations. We are also planning changes to anode-cathode materials as well as changes to the diode aspect ratio in an attempt to mitigate the above trends and improve pinch stability while achieving simultaneous spot size reduction. Experiments are ongoing, and latest results will be reported [1]. LSP is a software product of ATK Mission Research, Albuquerque, NM. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Adminis-tration under Contract DE-AC04-94AL85000.

Triangle singularities and XYZ quarkonium peaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szczepaniak, Adam P.

2015-06-01

We discuss analytical properties of partial waves derived from projection of a 4-legged amplitude with crossed-channel exchanges in the kinematic region of the direct channel that corresponds to the XYZ peaks in charmonium and bottomonium. We show that in general partial waves can develop anomalous branch points in the vicinity of the direct channel physical region. In a specific case, when these branch points lie on the opposite side of the unitary cut they pinch the integration contour in a dispersion relation and if the pinch happens close to threshold, the normal threshold cusp is enhanced. We show that this effect only occurs if masses of resonances in the crossed channel are in a specific, narrow range. We estimate the size of threshold enhancements originating from these anomalous singularities in reactions where themore » $$Z_c(3900)$$ and the $$Z_b(10610)$$ peaks have been observed.« less

Experimental research of neutron yield and spectrum from deuterium gas-puff z-pinch on the GIT-12 generator at current above 2 MA

NASA Astrophysics Data System (ADS)

Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Shishlov, A. V.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.

2017-05-01

The Z-pinch experiments with deuterium gas-puff surrounded by an outer plasma shell were carried out on the GIT-12 generator (Tomsk, Russia) at currents of 2 MA. The plasma shell consisting of hydrogen and carbon ions was formed by 48 plasma guns. The deuterium gas-puff was created by a fast electromagnetic valve. This configuration provides an efficient mode of the neutron production in DD reaction, and the neutron yield reaches a value above 1012 neutrons per shot. Neutron diagnostics included scintillation TOF detectors for determination of the neutron energy spectrum, bubble detectors BD-PND, a silver activation detector, and several activation samples for determination of the neutron yield analysed by a Sodium Iodide (NaI) and a high-purity Germanium (HPGe) detectors. Using this neutron diagnostic complex, we measured the total neutron yield and amount of high-energy neutrons.

X-ray absorption spectroscopy of aluminum z-pinch plasma with tungsten backlighter planar wire array source.

PubMed

Osborne, G C; Kantsyrev, V L; Safronova, A S; Esaulov, A A; Weller, M E; Shrestha, I; Shlyaptseva, V V; Ouart, N D

2012-10-01

Absorption features from K-shell aluminum z-pinch plasmas have recently been studied on Zebra, the 1.7 MA pulse power generator at the Nevada Terawatt Facility. In particular, tungsten plasma has been used as a semi-backlighter source in the generation of aluminum K-shell absorption spectra by placing a single Al wire at or near the end of a single planar W array. All spectroscopic experimental results were recorded using a time-integrated, spatially resolved convex potassium hydrogen phthalate (KAP) crystal spectrometer. Other diagnostics used to study these plasmas included x-ray detectors, optical imaging, laser shadowgraphy, and time-gated and time-integrated x-ray pinhole imagers. Through comparisons with previous publications, Al K-shell absorption lines are shown to be from much lower electron temperature (∼10-40 eV) plasmas than emission spectra (∼350-500 eV).

Magneto-Rayleigh-Taylor instability driven by a rotating magnetic field

NASA Astrophysics Data System (ADS)

Duan, Shuchao; Xie, Weiping; Cao, Jintao; Li, Ding

2018-04-01

In this paper, we analyze theoretically the magneto-Rayleigh-Taylor instability driven by a rotating magnetic field. Slab configurations of finite thickness are treated both with and without using the Wenzel-Kramers-Brillouin approximation. Regardless of the slab thickness, the directional rotation of the driving magnetic field contributes to suppressing these instabilities. The two factors of the finite thickness and directional rotation of the magnetic field cooperate to enhance suppression, with the finite thickness playing a role only when the orientation of the magnetic field is time varying. The suppression becomes stronger as the driving magnetic field rotates faster, and all modes are suppressed, in contrast to the case of a non-rotating magnetic field, for which the vertical mode cannot be suppressed. This implies that the dynamically alternate configuration of a Theta-pinch and a Z-pinch may be applicable to the concept of Theta-Z liner inertial fusion.

Fusion neutron detector for time-of-flight measurements in z-pinch and plasma focus experiments.

PubMed

Klir, D; Kravarik, J; Kubes, P; Rezac, K; Litseva, E; Tomaszewski, K; Karpinski, L; Paduch, M; Scholz, M

2011-03-01

We have developed and tested sensitive neutron detectors for neutron time-of-flight measurements in z-pinch and plasma focus experiments with neutron emission times in tens of nanoseconds and with neutron yields between 10(6) and 10(12) per one shot. The neutron detectors are composed of a BC-408 fast plastic scintillator and Hamamatsu H1949-51 photomultiplier tube (PMT). During the calibration procedure, a PMT delay was determined for various operating voltages. The temporal resolution of the neutron detector was measured for the most commonly used PMT voltage of 1.4 kV. At the PF-1000 plasma focus, a novel method of the acquisition of a pulse height distribution has been used. This pulse height analysis enabled to determine the single neutron sensitivity for various neutron energies and to calibrate the neutron detector for absolute neutron yields at about 2.45 MeV.

Plasma-based EUV light source

DOEpatents

Shumlak, Uri; Golingo, Raymond; Nelson, Brian A.

2010-11-02

Various mechanisms are provided relating to plasma-based light source that may be used for lithography as well as other applications. For example, a device is disclosed for producing extreme ultraviolet (EUV) light based on a sheared plasma flow. The device can produce a plasma pinch that can last several orders of magnitude longer than what is typically sustained in a Z-pinch, thus enabling the device to provide more power output than what has been hitherto predicted in theory or attained in practice. Such power output may be used in a lithography system for manufacturing integrated circuits, enabling the use of EUV wavelengths on the order of about 13.5 nm. Lastly, the process of manufacturing such a plasma pinch is discussed, where the process includes providing a sheared flow of plasma in order to stabilize it for long periods of time.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoup, R.W.; Long, F.; Martin, T.H.

Sandia has developed PBFA-Z, a 20-MA driver for z-pinch experiments by replacing the water lines, insulator stack. and MITLs on PBFA II with hardware of a new design. The PBFA-Z accelerator was designed to deliver 20 MA to a 15-mg z-pinch load in 100 ns. The accelerator was modeled using circuit codes to determine the time-dependent voltage and current waveforms at the input and output of the water lines, the insulator stack, and the MITLs. The design of the vacuum insulator stack was dictated by the drive voltage, the electric field stress and grading requirements, the water line and MITLmore » interface requirements, and the machine operations and maintenance requirements. The insulator stack consists of four separate modules, each of a different design because of different voltage drive and hardware interface requirements. The shape of the components in each module, i.e., grading rings, insulator rings, flux excluders, anode and cathode conductors, and the design of the water line and MITL interfaces, were optimized by using the electrostatic analysis codes, ELECTRO and JASON. The time-dependent performance of the insulator stacks was evaluated using IVORY, a 2-D PIC code. This paper will describe the insulator stack design, present the results of the ELECTRO and IVORY analyses, and show the results of the stack measurements.« less

Multiple Monochromatic Imaging (MMI) Status and Plans for LANL Campaigns on Omega and NIF

NASA Astrophysics Data System (ADS)

Wysocki, F. J.; Hsu, S. C.; Tregillis, I. L.; Schmitt, M. J.; Kyrala, G. A.; Martinson, D. D.; Murphy, T. J.; Mancini, R. C.; Nagayama, T.

2011-10-01

LANL's DIME (Defect Implosion Experiment) campaigns on Omega and NIF are aimed at obtaining improved understanding of defect-induced mix via experiments and simulations of directly driven high-Z doped plastic capsules with DD or DT gas fill. To this end, the MMI diagnostic has been identified as a key diagnostic for providing space and time-resolved density, temperature, and mix profiles. The high Z shell dopants used on Omega are Ti and V, and to be used on NIF are Ge and Se. This poster will discuss the following four areas of MMI-related work at LANL, in collaboration with UNR: (1) data and preliminary analysis of MMI data from FY11 Omega campaigns, (2) development of a capability to generate simulated MMI data from radiation- hydrodynamic simulations of ICF implosions, (3) design of an MMI instrument for NIF that will cover the photon energy range 9.5-16.9 keV which includes the Ge/Se, H- like/He-like, α/ β lines, and (4) the development of MMI data post- processing and spectroscopic analysis tools. Supported by DOE NNSA.

Measurement of the hot spot electron temperature in NIF ICF implosions using Krypton x-ray emission spectroscopy

NASA Astrophysics Data System (ADS)

Ma, T.; Chen, H.; Patel, P. K.; Schneider, M.; Barrios, M.; Berzak Hopkins, L.; Casey, D.; Chung, H.-K.; Hammel, B.; Jarrott, C.; Nora, R.; Pak, A.; Scott, H.; Spears, B.; Weber, C.

2015-11-01

The inference of ion temperature from neutron spectral measurements in indirect-drive ICF implosions is known to be sensitive to non-thermal velocity distributions in the fuel. The electron temperature (Te) inferred from dopant line ratios should not be sensitive to these bulk motions and hence may be a better measure of the thermal temperature of the hot spot. Here we describe a series of experiments to be conducted on the NIF where a small concentration of a mid-Z dopant (Krypton) is added to the fuel gas. The x-ray spectra is measured and the electron temperature is inferred from Kr line ratios. We also quantify the level of radiative cooling in the hot spot due to this mid-Z dopant. These experiments represent the first direct measurement of hot spot Te using spectroscopy, and we will describe the considerations for applying x-ray spectroscopy in such dense and non-uniform hot spots. This work performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

A non-LTE analysis of high energy density Kr plasmas on Z and NIF

DOE PAGES

Dasgupta, A.; Clark, R. W.; Ouart, N.; ...

2016-10-20

We report that multi-keV X-ray radiation sources have a wide range of applications, from biomedical studies and research on thermonuclear fusion to materials science and astrophysics. The refurbished Z pulsed power machine at the Sandia National Laboratories produces intense multi-keV X-rays from argon Z-pinches, but for a krypton Z-pinch, the yield decreases much faster with atomic number Z A than similar sources on the National Ignition Facility (NIF) laser at the Lawrence Livermore National Laboratory. To investigate whether fundamental energy deposition differences between pulsed power and lasers could account for the yield differences, we consider the Kr plasma on themore » two machines. The analysis assumes the plasma not in local thermodynamic equilibrium, with a detailed coupling between the hydrodynamics, the radiation field, and the ionization physics. While for the plasma parameters of interest the details of krypton’s M-shell are not crucial, both the L-shell and the K-shell must be modeled in reasonable detail, including the state-specific dielectronic recombination processes that significantly affect Kr’s ionization balance and the resulting X-ray spectrum. We present a detailed description of the atomic model, provide synthetic K- and L-shell spectra, and compare these with the available experimental data from the Z-machine and from NIF to show that the K-shell yield behavior versus Z A is indeed related to the energy input characteristics. In conclusion, this work aims at understanding the probable causes that might explain the differences in the X-ray conversion efficiencies of several radiation sources on Z and« less

A non-LTE analysis of high energy density Kr plasmas on Z and NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dasgupta, A.; Clark, R. W.; Ouart, N.

We report that multi-keV X-ray radiation sources have a wide range of applications, from biomedical studies and research on thermonuclear fusion to materials science and astrophysics. The refurbished Z pulsed power machine at the Sandia National Laboratories produces intense multi-keV X-rays from argon Z-pinches, but for a krypton Z-pinch, the yield decreases much faster with atomic number Z A than similar sources on the National Ignition Facility (NIF) laser at the Lawrence Livermore National Laboratory. To investigate whether fundamental energy deposition differences between pulsed power and lasers could account for the yield differences, we consider the Kr plasma on themore » two machines. The analysis assumes the plasma not in local thermodynamic equilibrium, with a detailed coupling between the hydrodynamics, the radiation field, and the ionization physics. While for the plasma parameters of interest the details of krypton’s M-shell are not crucial, both the L-shell and the K-shell must be modeled in reasonable detail, including the state-specific dielectronic recombination processes that significantly affect Kr’s ionization balance and the resulting X-ray spectrum. We present a detailed description of the atomic model, provide synthetic K- and L-shell spectra, and compare these with the available experimental data from the Z-machine and from NIF to show that the K-shell yield behavior versus Z A is indeed related to the energy input characteristics. In conclusion, this work aims at understanding the probable causes that might explain the differences in the X-ray conversion efficiencies of several radiation sources on Z and« less

Formation of a dual-stage pinch-accelerator in a Z-pinch (plasma focus) device

NASA Astrophysics Data System (ADS)

Behbahani, R. A.; Hirose, A.; Xiao, C.

2018-01-01

A novel dense plasma focus configuration with two separate concentric current sheet run-down regions has been demonstrated to produce several consecutive plasma focusing events. In a proof-of-principle experiment on a low-energy plasma focus device, the measured tube voltages and discharge current have been explained by using circuit analyses of the device. Based on the calculated plasma voltages the occurrence of flash-over phase, axial phase, and compression phase has been discussed. The electrical signals along with the calculated plasma voltages suggest the occurrence of several focusing events in the new structure.

Effects of smartphone overuse on hand function, pinch strength, and the median nerve.

PubMed

İnal, Esra Erkol; Demİrcİ, kadİr; Çetİntürk, Azİze; Akgönül, Mehmet; Savaş, Serpİl

2015-08-01

In this study we investigated the flexor pollicis longus (FPL) tendon and median nerve in smartphone users by ultrasonography to assess the effects of smartphone addiction on the clinical and functional status of the hands. One hundred two students were divided into 3 groups: non-users, and high or low smartphone users. Smartphone Addiction Scale (SAS) scores and grip and pinch strengths were recorded. Pain in thumb movement and rest and hand function were evaluated on the visual analog scale (VAS) and the Duruöz Hand Index (DHI), respectively. The cross-sectional areas (CSAs) of the median nerve and the FPL tendon were calculated bilaterally using ultrasonography. Significantly higher median nerve CSAs were observed in the dominant hands of the high smartphone users than in the non-dominant hands (P<0.001). SAS scores correlated with VAS pain for movement and rest, DHI scores, and pinch strength (P<0.05; r=0.345, 0.272, 0.245, and 0.281, respectively). Smartphone overuse enlarges the median nerve, causes pain in the thumb, and decreases pinch strength and hand functions. © 2015 Wiley Periodicals, Inc.

A numerical study of neutral-plasma interaction in magnetically confined plasmas

NASA Astrophysics Data System (ADS)

Taheri, S.; Shumlak, U.; King, J. R.

2017-10-01

Interactions between plasma and neutral species can have a large effect on the dynamic behavior of magnetically confined plasma devices, such as the edge region of tokamaks and the plasma formation of Z-pinches. The presence of neutrals can affect the stability of the pinch and change the dynamics of the pinch collapse, and they can lead to deposition of high energy particles on the first wall. However, plasma-neutral interactions can also have beneficial effects such as quenching the disruptions in tokamaks. In this research a reacting plasma-neutral model, which combines a magnetohydrodynamic (MHD) plasma model with a gas dynamic neutral fluid model, is used to study the interaction between plasma and neutral gas. Incorporating this model into NIMROD allows the study of electron-impact ionization, radiative recombination, and resonant charge-exchange in plasma-neutral systems. An accelerated plasma moving through a neutral gas background is modeled in both a parallel plate and a coaxial electrode configuration to explore the effect of neutral gas in pinch-like devices. This work is supported by a Grant from US DOE.

Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garanin, S. G.; Ivanovskiy, A. V., E-mail: ivanovsky@elph.vniief.ru

2015-12-15

The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

NASA Astrophysics Data System (ADS)

Garanin, S. G.; Ivanovskiy, A. V.

2015-12-01

The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

Testing low-mode symmetry control with low-adiabat, extended pulse-lengths in BigFoot implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hohenberger, Matthias; Casey, D. T.; Thomas, C. A.; Baker, K. L.; Spears, B. K.; Khan, S. F.; Hurricane, O. A.; Callahan, D.

2017-10-01

The Bigfoot approach to indirect-drive inertial confinement fusion (ICF) has been developed as a compromise trading high-convergence and areal densities for high implosion velocities, large adiabats and hydrodynamic stability. Shape control and predictability are maintained by using relatively short laser pulses and merging the shocks within the DT-ice layer. These design choices ultimately limit the theoretically achievable performance, and one strategy to increase the 1-D performance is to reduce the shell adiabat by extending the pulse shape. However, this can result in loss of low-mode symmetry control, as the hohlraum ``bubble,'' the high-Z material launched by the outer-cone beams during the early part of the laser pulse, has more time to expand and will eventually intercept inner-cone beams preventing them from reaching the hohlraum waist, thus losing equatorial capsule drive. We report on experimental results exploring shape control and predictability with extended pulse shapes in BigFoot implosions. Prepared by LLNL under Contract DE-AC52-07NA27344.

A Numerical Model for Two-Plasmon-Decay Hot-Electron Production and Mitigation in Direct-Drive Implosions

NASA Astrophysics Data System (ADS)

Myatt, J. F.; Shaw, J. G.; Solodov, A. A.; Maximov, A. V.; Short, R. W.; Seka, W.; Follett, R. K.; Edgell, D. H.; Froula, D. H.; Goncharov, V. N.

2015-11-01

Hot-electron preheat, caused by laser-plasma instabilities, can impair the performance of inertial confinement fusion implosions. It is therefore imperative to understand processes that can generate hot electrons and to design mitigation strategies should preheat be found to be excessive at the ignition scale (laser-plasma interactions do not follow hydrodynamic scaling). For this purpose, a new 3-D model [laser-plasma simulation environment (LPSE)] has been constructed that computes hot-electron generation in direct-drive plasmas based on the assumption that two-plasmon decay is the dominant, hot-electron-producing instability. It uses an established model of TPD-driven turbulence together with a new GPU based hybrid particle method of hot-electron production. The time-dependent hot-electron power, total energy, and energy spectrum are computed and compared with data from recent OMEGA implosion experiments that have sought to mitigate TPD by the use of multilayered (mid- Z) ablators. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

A non-LTE analysis of high energy density Kr plasmas on Z and NIF

NASA Astrophysics Data System (ADS)

Dasgupta, A.; Clark, R. W.; Ouart, N.; Giuliani, J.; Velikovich, A.; Ampleford, D. J.; Hansen, S. B.; Jennings, C.; Harvey-Thompson, A. J.; Jones, B.; Flanagan, T. M.; Bell, K. S.; Apruzese, J. P.; Fournier, K. B.; Scott, H. A.; May, M. J.; Barrios, M. A.; Colvin, J. D.; Kemp, G. E.

2016-10-01

Multi-keV X-ray radiation sources have a wide range of applications, from biomedical studies and research on thermonuclear fusion to materials science and astrophysics. The refurbished Z pulsed power machine at the Sandia National Laboratories produces intense multi-keV X-rays from argon Z-pinches, but for a krypton Z-pinch, the yield decreases much faster with atomic number ZA than similar sources on the National Ignition Facility (NIF) laser at the Lawrence Livermore National Laboratory. To investigate whether fundamental energy deposition differences between pulsed power and lasers could account for the yield differences, we consider the Kr plasma on the two machines. The analysis assumes the plasma not in local thermodynamic equilibrium, with a detailed coupling between the hydrodynamics, the radiation field, and the ionization physics. While for the plasma parameters of interest the details of krypton's M-shell are not crucial, both the L-shell and the K-shell must be modeled in reasonable detail, including the state-specific dielectronic recombination processes that significantly affect Kr's ionization balance and the resulting X-ray spectrum. We present a detailed description of the atomic model, provide synthetic K- and L-shell spectra, and compare these with the available experimental data from the Z-machine and from NIF to show that the K-shell yield behavior versus ZA is indeed related to the energy input characteristics. This work aims at understanding the probable causes that might explain the differences in the X-ray conversion efficiencies of several radiation sources on Z and NIF.

Competing effects of collisional ionization and radiative cooling in inertially confined plasmas

NASA Astrophysics Data System (ADS)

Woolsey, N. C.; Hammel, B. A.; Keane, C. J.; Back, C. A.; Moreno, J. C.; Nash, J. K.; Calisti, A.; Mossé, C.; Stamm, R.; Talin, B.; Asfaw, A.; Klein, L. S.; Lee, R. W.

1998-04-01

We describe an experimental investigation, a detailed analysis of the Ar XVII 1s2 1S-1s3p 1P (Heβ) line shape formed in a high-energy-density implosion, and report on one-dimensional radiation-hydrodynamics simulation of the implosion. In this experiment trace quantities of argon are doped into a lower-Z gas-filled core of a plastic microsphere. The dopant level is controlled to ensure that the Heβ transition is optically thin and easily observable. Then the observed line shape is used to derive electron temperatures (Te) and electron densities (ne). The high-energy density plasma, with Te approaching 1 keV and ne=1024 cm-3, is created by placing the microsphere in a gold cylindrical enclosure, the interior of which is directly irradiated by a high-energy laser; the x rays produced by this laser-gold interaction indirectly implode the microsphere. Central to the interpretation of the hydrodynamics of the implosions is the characterization and understanding of the formation of these plasmas. To develop an understanding of the plasma and its temporal evolution, time-resolved Te and ne measurements are extracted using techniques that are independent of the plasma hydrodynamics. Comparing spectroscopic diagnostics with measurements derived from other diagnostic methods, we find the spectroscopic measurements to be reliable and further we find that the experiment-to-experiment comparison shows that these implosions are reproducible.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornhill, Tom Finley, III; Reinhart, William Dodd; Lawrence, Raymond Jeffery Jr.

Kill assessment continues to be a major problem for the nation's missile defense program. A potential approach for addressing this issue involves spectral and temporal analysis of the short-time impact flash that occurs when a kill vehicle intercepts and engages a target missile. This can provide identification of the materials involved in the impact event, which will, in turn, yield the data necessary for target identification, engagement analysis, and kill assessment. This report describes the first phases of a project under which we are providing laboratory demonstrations of the feasibility and effectiveness of this approach. We are using two majormore » Sandia facilities, the Z-Pinch accelerator, and the two- and three-stage gas guns at the Shock Thermodynamics and Applied Research (STAR) facility. We have looked at the spectral content of impact flash at velocities up to 25 km/s on the Z-Pinch machine to establish the capability for spectroscopy for these types of events, and are looking at similar experiments at velocities from 6 to 11 km/s on the gas guns to demonstrate a similar capability for a variety of research-oriented and applied materials. The present report describes only the work performed on the Z machine.« less

Progress Toward Ignition on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kauffman, R L

2011-10-17

The principal approach to ignition on the National Ignition Facility (NIF) is indirect drive. A schematic of an ignition target is shown in Figure 1. The laser beams are focused through laser entrance holes at each end of a high-Z cylindrical case, or hohlraum. The lasers irradiate the hohlraum walls producing x-rays that ablate and compress the fuel capsule in the center of the hohlraum. The hohlraum is made of Au, U, or other high-Z material. For ignition targets, the hohlraum is {approx}0.5 cm diameter by {approx}1 cm in length. The hohlraum absorbs the incident laser energy producing x-rays formore » symmetrically imploding the capsule. The fuel capsule is a {approx}2-mm-diameter spherical shell of CH, Be, or C filled with DT fuel. The DT fuel is in the form of a cryogenic layer on the inside of the capsule. X-rays ablate the outside of the capsule, producing a spherical implosion. The imploding shell stagnates in the center, igniting the DT fuel. NIC has overseen installation of all of the hardware for performing ignition experiments, including commissioning of approximately 50 diagnostic systems in NIF. The diagnostics measure scattered optical light, x-rays from the hohlraum over the energy range from 100 eV to 500 keV, and x-rays, neutrons, and charged particles from the implosion. An example of a diagnostic is the Magnetic Recoil Spectrometer (MRS) built by a collaboration of scientists from MIT, UR-LLE, and LLNL shown in Figure 2. MRS measures the neutron spectrum from the implosion, providing information on the neutron yield and areal density that are metrics of the quality of the implosion. Experiments on NIF extend ICF research to unexplored regimes in target physics. NIF can produce more than 50 times the laser energy and more than 20 times the power of any previous ICF facility. Ignition scale hohlraum targets are three to four times larger than targets used at smaller facilities, and the ignition drive pulses are two to five times longer. The larger targets and longer pulse lengths produce unique plasma conditions for laser-plasma instabilities that could reduce hohlraum coupling efficiency. Initial experiments have demonstrated efficient coupling of laser energy to x-rays. X-ray drive greater than 300 eV has been measured in gas-filled ignition hohlraum and shows the expected scaling with laser energy and hohlraum scale size. Experiments are now optimizing capsule implosions for ignition. Ignition conditions require assembling the fuel with sufficient density and temperature for thermonuclear burn. X-rays ablate the outside of the capsule, accelerating and spherically compressing the capsule for assembling the fuel. The implosion stagnates, heating the central core and producing a hot spot that ignites and burns the surrounding fuel. The four main characteristics of the implosion are shell velocity, central hot spot shape, fuel adiabat, and mix. Experiments studying these four characteristics of implosions are used to optimize the implosion. Integrated experiments using cryogenic fuel layer experiments demonstrate the quality of the implosion as the optimization experiments progress. The final compressed fuel conditions are diagnosed by measuring the x-ray emission from the hot core and the neutrons and charged particles produced in the fusion reactions. Metrics of the quality of the implosion are the neutron yield and the shell areal density, as well as the size and shape of the core. The yield depends on the amount of fuel in the hot core and its temperature and is a gauge of the energy coupling to the fuel. The areal density, the density of the fuel times its thickness, diagnoses the fuel assembly, which is measured using the fraction of neutrons that are down scattered passing through the dense shell. The yield and fraction of down scattered neutrons, or shell rho-r, from the cryogenic layered implosions are shown in Figure 3. The different sets of data represent results after a series of implosion optimization experiments. Both yield and areal density show significant increases as a result of the optimization. The experimental Ignition Threshold Factor (ITFX) is a measure of the progress toward ignition. ITFX is analogous to the Lawson Criterion in Magnetic Fusion. Implosions have improved by over a factor of 50 since the first cryogenic layered experiments were done in September 2010. This increase is a measure of the progress made toward the ignition goal in the past year. Optimization experiments are planned in the coming year for continued improvement in implosion performance to achieve the ignition goal. In summary, NIF has made significant progress toward ignition in the 30 months since project completion. Diagnostics and all of the supporting equipment are in place for ignition experiments. The Ignition Campaign is under way as a national collaborative effort of all the National Nuclear Security Administration (NNSA) science laboratories as well as international partners.« less

Non-LTE modeling for the National Ignition Facility (and beyond)

NASA Astrophysics Data System (ADS)

Scott, H. A.; Hammel, B. A.; Hansen, S. B.

2012-05-01

Considerable progress has been made in the last year in the study of laser-driven inertial confinement fusion at the National Ignition Facility (NIF). Experiments have demonstrated symmetric capsule implosions with plasma conditions approaching those required for ignition. Improvements in computational models - in large part due to advances in non-LTE modeling - have resulted in simulations that match experimental results quite well for the X-ray drive, implosion symmetry and total wall emission [1]. Non-LTE modeling is a key part of the NIF simulation effort, affecting several aspects of experimental design and diagnostics. The X-rays that drive the capsule arise from high-Z material ablated off the hohlraum wall. Current capsule designs avoid excessive preheat from high-energy X-rays by shielding the fuel with a mid-Z dopant, which affects the capsule dynamics. The dopant also mixes into the hot spot through hydrodynamic instabilities, providing diagnostic possibilities but potentially impacting the energy balance of the capsule [2]. Looking beyond the NIF, a proposed design for a fusion reactor chamber depends on lowdensity high-Z gas absorbing X-rays and particles to protect the first wall [3]. These situations encompass a large range of temperatures, densities and spatial scales. They each emphasize different aspects of atomic physics and present a variety of challenges for non-LTE modeling. We discuss the relevant issues and summarize the current state of the modeling effort for these applications.

Evidence for an intense solar outburst in prehistory

NASA Astrophysics Data System (ADS)

Peratt, A. L.; Yao, W. F.

2008-10-01

A past intense solar outburst and its effect on Earth was proposed by Gold (1962 Pontificiae Acad. Sci. Scr. Varia 25 159) who, along with others, based his hypotheses on strong astronomical and geophysical evidence. The discovery that objects from the Neolithic or Early Bronze Age carry patterns associated with high-current Z-pinches, as would result from an intense plasma impinging Earth, provides a possible insight into the origin and meaning of these ancient symbols produced by humans. Peratt (2003 Trans. Plasma Sci. 31 1192) dealt with the comparison of graphical and radiation data from high-current Z-pinches to petroglyphs, geoglyphs and megaliths. Peratt (2007 Trans. Plasma Sci. 35 778) focused primarily, but not exclusively, on petroglyphs of some 84 different morphologies; pictures found in laboratory experiments and carved on rock. These corresponded to mankind's visual observations of ancient aurora as might be produced if the solar wind had increased at times between one and two orders of magnitude, millennia ago (Gold 1962 Pontificiae Acad. Sci. Scr. Varia 25 159). In Peratt (2007 Trans. Plasma Sci. 35 778), the data were given on the source of light and its temporal change from a current-increasing Z-pinch or dense plasma focus aurora. Orientation and field-of-view data are given as surveyed and contributed from 139 countries, from sites and fields containing several millions of these objects, the latest data coming from a 300 km survey along the Orinoco river basin in Venezuela. In this paper, we include additional petroglyph figures derivable from experiment and computer. This information allows a reconstruction of the auroral form presumably associated with extreme geomagnetic storms and shows, based on existent geophysical evidence, relativistic electron flow inward at Earth's south polar axis and hypervelocity proton impacts around the north polar axis.

A Compact Soft X-Ray Microscope using an Electrode-less Z-Pinch Source.

PubMed

Horne, S F; Silterra, J; Holber, W

2009-01-01

Soft X-rays (< 1Kev) are of medical interest both for imaging and microdosimetry applications. X-ray sources at this low energy present a technological challenge. Synchrotrons, while very powerful and flexible, are enormously expensive national research facilities. Conventional X-ray sources based on electron bombardment can be compact and inexpensive, but low x-ray production efficiencies at low electron energies restrict this approach to very low power applications. Laser-based sources tend to be expensive and unreliable. Energetiq Technology, Inc. (Woburn, MA, USA) markets a 92 eV, 10W(2pi sr) electrode-less Z-pinch source developed for advanced semiconductor lithography. A modified version of this commercial product has produced 400 mW at 430 eV (2pi sr), appropriate for water window soft X-ray microscopy. The US NIH has funded Energetiq to design and construct a demonstration microscope using this source, coupled to a condenser optic, as the illumination system. The design of the condenser optic matches the unique characteristics of the source to the illumination requirements of the microscope, which is otherwise a conventional design. A separate program is underway to develop a microbeam system, in conjunction with the RARAF facility at Columbia University, NY, USA. The objective is to develop a focused, sub-micron beam capable of delivering > 1 Gy/second to the nucleus of a living cell. While most facilities of this type are coupled to a large and expensive particle accelerator, the Z-pinch X-ray source enables a compact, stand-alone design suitable to a small laboratory. The major technical issues in this system involve development of suitable focusing X-ray optics. Current status of these programs will be reported.

A Compact Soft X-Ray Microscope using an Electrode-less Z-Pinch Source

PubMed Central

Silterra, J; Holber, W

2009-01-01

Soft X-rays (< 1Kev) are of medical interest both for imaging and microdosimetry applications. X-ray sources at this low energy present a technological challenge. Synchrotrons, while very powerful and flexible, are enormously expensive national research facilities. Conventional X-ray sources based on electron bombardment can be compact and inexpensive, but low x-ray production efficiencies at low electron energies restrict this approach to very low power applications. Laser-based sources tend to be expensive and unreliable. Energetiq Technology, Inc. (Woburn, MA, USA) markets a 92 eV, 10W(2pi sr) electrode-less Z-pinch source developed for advanced semiconductor lithography. A modified version of this commercial product has produced 400 mW at 430 eV (2pi sr), appropriate for water window soft X-ray microscopy. The US NIH has funded Energetiq to design and construct a demonstration microscope using this source, coupled to a condenser optic, as the illumination system. The design of the condenser optic matches the unique characteristics of the source to the illumination requirements of the microscope, which is otherwise a conventional design. A separate program is underway to develop a microbeam system, in conjunction with the RARAF facility at Columbia University, NY, USA. The objective is to develop a focused, sub-micron beam capable of delivering > 1 Gy/second to the nucleus of a living cell. While most facilities of this type are coupled to a large and expensive particle accelerator, the Z-pinch X-ray source enables a compact, stand-alone design suitable to a small laboratory. The major technical issues in this system involve development of suitable focusing X-ray optics. Current status of these programs will be reported. PMID:20198115

Neutron production in deuterium gas-puff z-pinch with outer plasma shell at current of 3 MA

NASA Astrophysics Data System (ADS)

Cikhardt, J.; Klir, D.; Rezac, K.; Cikhardtova, B.; Kravarik, J.; Kubes, P.; Sila, O.; Shishlov, A. V.; Cherdizov, R. K.; Frusov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu.; Ratakhin, N. A.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.; Turek, K.; Krasa, J.

2015-11-01

Z-pinch experiments at the current of about 3 MA were carried out on the GIT-12 generator. The outer plasma shell of deuterium gas-puff was generated by the system of 48 plasma guns. This configuration exhibits a high efficiency of the production of DD fusion neutrons with the yield of above 1012 neutrons produced in a single shot with the duration of about 20 ns. The maximum energy of the neutrons produced in this pulse exceeded 30 MeV. The neutron radiation was measured using scintillation TOF detectors, CR-39 nuclear track detectors, bubble detectors BD-PND and BDS-10000 and by several types of nuclear activation detectors. These diagnostic tools were used to measure the anisotropy of neutron fluence and neutron energy spectra. It allows us to estimate the total number of DD neutrons, the contribution of other nuclear reactions, the amount of scattered neutrons, and other parameters of neutron production. This work was supported by the MSMT grants LH13283, LD14089.

EQ-10 electrodeless Z-pinch EUV source for metrology applications

NASA Astrophysics Data System (ADS)

Gustafson, Deborah; Horne, Stephen F.; Partlow, Matthew J.; Besen, Matthew M.; Smith, Donald K.; Blackborow, Paul A.

2011-11-01

With EUV Lithography systems shipping, the requirements for highly reliable EUV sources for mask inspection and resist outgassing are becoming better defined, and more urgent. The sources needed for metrology applications are very different than that needed for lithography; brightness (not power) is the key requirement. Suppliers for HVM EUV sources have all resources working on high power and have not entered the smaller market for metrology. Energetiq Technology has been shipping the EQ-10 Electrodeless Z-pinchTM light source since 19951. The source is currently being used for metrology, mask inspection, and resist development2-4. These applications require especially stable performance in both output power and plasma size and position. Over the last 6 years Energetiq has made many source modifications which have included better thermal management to increase the brightness and power of the source. We now have introduced a new source that will meet requirements of some of the mask metrology first generation tools; this source will be reviewed.

Evaluation of Turner relaxed state as a model of long-lived ion-trapping structures in plasma focus and Z-pinches

NASA Astrophysics Data System (ADS)

Auluck, S. K. H.

2011-03-01

Relatively long-lived spheroidal structures coincident with the neutron emission phase have been observed in frozen deuterium fiber Z-pinch and some plasma focus devices. Existence of energetic ion-trapping mechanism in plasma focus has also been inferred from experimental data. It has been conjectured that these are related phenomena. This paper applies Turner's theory [L. Turner, IEEE Trans. Plasma Sci. 14, 849 (1986)] of relaxation of a Hall magnetofluid to construct a model of these structures and ion-trapping mechanism. Turner's solution modified for a finite-length plasma is used to obtain expressions for the magnetic field, velocity, and equilibrium pressure fields and is shown to represent an entity which is simultaneously a fluid vortex, a force-free magnetic field, a confined finite-pressure plasma, a charged object, and a trapped energetic ion beam. Characteristic features expected from diagnostic experiments are evaluated and shown to resemble experimental observations.

Spectroscopic Study of Neon Z-Pinch Plasma for Sodium-Neon Photopumping Experiments

DTIC Science & Technology

1992-01-06

enhancement of the 11-A radiation from the n=4 level of neon when the sodium pump was present. For the 25-GV pump power, theoretical calculations predict...when the neon plasma is photopumped. Extensive theoretical analysis has been devoted to establishing the appropriate conditions for these plasmas. 5 ,44...producing thermonuclear neutrons. 63-65 Extensive theoretical modeling of the stability of these plasmas has guided this work.66 An imploding-liner Z

Atomic kinetics of a neon photoionized plasma experiment at Z

NASA Astrophysics Data System (ADS)

Mayes, D. C.; Mancini, R. C.; Schoenfeld, R. P.; Bailey, J. E.; Loisel, G. P.; Rochau, G. A.; ZAPP Collaboration

2017-10-01

We discuss an experimental effort to study the atomic kinetics in neon photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted at the collapse of a Z-pinch to heat and backlight a photoionized plasma contained within a cm-scale gas cell placed at various distances from the Z-pinch and filled with neon gas pressures in the range from 3.5 to 120 Torr. The experimental platform affords an order of magnitude range in the ionization parameter characterizing the photoionized plasma from about 5 to 80 erg*cm/s. Thus, the experiment allows for the study of trends in ionization distribution as a function of the ionization parameter. An x-ray crystal spectrometer capable of collecting both time-integrated and time-gated data is used to collect absorption spectra. The spectra show line absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. Analysis of these spectra yields ion areal-densities and charge state distributions, which can be compared with results from atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of nearby energy levels in Li- and Be-like ions, which can be used to test heating models of photoionized plasmas. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451, and the Z Facility Fundamental Science Program of SNL.

Mission and Objectives for the X-1 Advanced Radiation Source*

NASA Astrophysics Data System (ADS)

Rochau, Gary E.; Ramirez, Juan J.; Raglin, Paul S.

1998-11-01

Sandia National Laboratories PO Box 5800, MS-1178, Albuquerque, NM 87185 The X-1 Advanced Radiation Source represents a next step in providing the U.S. Department of Energy's Stockpile Stewardship Program with the high-energy, large volume, laboratory x-ray source for the Radiation Effects Science and Simulation, Inertial Confinement Fusion, and Weapon Physics Programs. Advances in fast pulsed power technology and in z-pinch hohlraums on Sandia National Laboratories' Z Accelerator provide sufficient basis for pursuing the development of X-1. The X-1 plan follows a strategy based on scaling the 2 MJ x-ray output on Z via a 3-fold increase in z-pinch load current. The large volume (>5 cm3), high temperature (>150 eV), temporally long (>10 ns) hohlraums are unique outside of underground nuclear weapon testing. Analytical scaling arguments and hydrodynamic simulations indicate that these hohlraums at temperatures of 230-300 eV will ignite thermonuclear fuel and drive the reaction to a yield of 200 to 1,200 MJ in the laboratory. Non-ignition sources will provide cold x-ray environments (<15 keV) and high yield fusion burn sources will provide high fidelity warm x-ray environments (15 keV-80 keV). This paper will introduce the X-1 Advanced Radiation Source Facility Project, describe the project mission, objective, and preliminary schedule.

Linear Stability of Self-Similar Flow: 1. Isothermal Cylindrical Implosion and Expansion.

DTIC Science & Technology

1978-03-01

Attn: J. Tachon N. Trocheris C. Z4ercier R. B. Paris 3. Centro di Studio sui Gas lonizzati Univereita di Pe4ova 6/a Via Gre.denigo 35100 Padova, Italia...fur Plasma Physics 8046 Garching bet ?~rncben West Germany Attn: D. Biskamp K. Von Hagenow Horst Pacher chodura V. Schneider D. Pfirsch 10. Siberian

Beams 92: Proceedings. Volume 1: Invited papers, pulsed power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mosher, D.; Cooperstein, G.

1993-12-31

This report contains papers on the following topics: Ion beam papers; electron beam, bremsstrahlung, and diagnostics papers; radiating Z- pinch papers; microwave papers; electron laser papers; advanced accelerator papers; beam and pulsed power applications papers; pulsed power papers; and these papers have been indexed separately elsewhere.

Diagnosing magnetized liner inertial fusion experiments on Z

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Stephanie B.; Gomez, Matthew R.; Sefkow, Adam B.

The Magnetized Liner Inertial Fusion experiments performed at Sandia's Z facility have demonstrated significant thermonuclear fusion neutron yields (~10 12 DD neutrons) from multi-keV deuterium plasmasinertially confined by slow (~10 cm/μs), stable, cylindrical implosions. Moreover, effective magnetic confinement of charged fusion reactants and products is signaled by high secondary DT neutron yields above 10 10. Further analysis of extensive power, imaging, and spectroscopicx-ray measurements provides a detailed picture of ~3 keV temperatures, 0.3 g/cm 3 densities, gradients, and mix in the fuel and liner over the 1–2 ns stagnation duration.

Diagnosing magnetized liner inertial fusion experiments on Z

DOE PAGES

Hansen, Stephanie B.; Gomez, Matthew R.; Sefkow, Adam B.; ...

2015-05-14

The Magnetized Liner Inertial Fusion experiments performed at Sandia's Z facility have demonstrated significant thermonuclear fusion neutron yields (~10 12 DD neutrons) from multi-keV deuterium plasmasinertially confined by slow (~10 cm/μs), stable, cylindrical implosions. Moreover, effective magnetic confinement of charged fusion reactants and products is signaled by high secondary DT neutron yields above 10 10. Further analysis of extensive power, imaging, and spectroscopicx-ray measurements provides a detailed picture of ~3 keV temperatures, 0.3 g/cm 3 densities, gradients, and mix in the fuel and liner over the 1–2 ns stagnation duration.

Atomic kinetics of a neon photoionized plasma experiment at Z

NASA Astrophysics Data System (ADS)

Mayes, Daniel C.; Mancini, Roberto; Bailey, James E.; Loisel, Guillaume; Rochau, Gregory; ZAPP Collaboration

2018-06-01

We discuss an experimental effort to study the atomic kinetics in astrophysically relevant photoionized plasmas via K-shell line absorption spectroscopy. The experiment employs the intense x-ray flux emitted at the collapse of a Z-pinch to heat and backlight a photoionized plasma contained within a cm-scale gas cell placed at a variable distance from the Z-pinch and filled with neon gas pressures in the range from 3.5 to 30 Torr. The experimental platform affords an order of magnitude range in the ionization parameter characterizing the photoionized plasma at the peak of the x-ray drive from about 5 to 80 erg*cm/s. Thus, the experiment allows for the study of trends in ionization distribution as a function of the ionization parameter. An x-ray crystal spectrometer capable of time-integrated and/or time-gated configurations is used to collect absorption spectra. The spectra show line absorption by several ionization stages of neon, including Be-, Li-, He-, and H-like ions. Analysis of these spectra yields ion areal densities and charge state distributions, which can be compared with simulation results from atomic kinetics codes. In addition, the electron temperature is extracted from level population ratios of nearby energy levels in Li- and Be-like ions, which can be used to test heating models of photoionized plasmas.

Final Report: Radiation-magnetohydrodynamic evolution and instability of conductors driven by megagauss magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Bruno, S.; Siemon, Richard, E.

2008-10-22

We are pleased to report important progress in experimentally characterizing and numerically modeling the transformation into plasma of walls subjected to pulsed megagauss magnetic fields. Understanding this is important to Magnetized Target Fusion (MTF) because an important limitation to the metal liner approach to MTF comes from the strong eddy current heating on the surface of the metal liner. This has intriguing non-linear aspects when the magnetic field is in the megagauss regime as needed for MTF, and may limit the magnetic field in an MTF implosion. Many faculty, students, and staff have contributed to this work, and, implicitly ormore » explicitly, to this report. Contributors include, in addition to the PIs, Andrey Esaulov, Stephan Fuelling, Irvin Lindemuth, Volodymyr Makhin, Ioana Paraschiv, Milena Angelova, Tom Awe, Tasha Goodrich, Arunkumar Prasadam, Andrew Oxner, Bruno Le Galloudec, Radu Presura, and Vladimir Ivanov. Highlights of the progress made during the grant include: • 12 articles published, and 44 conference and workshop presentations made, on a broad range of issues related to this project; • An ongoing experiment that uses the 1 MA, 100-ns Zebra z-pinch at UNR to apply 2 5 megagauss to a variety of metal surfaces, examining plasma formation and evolution; • Numerical simulation studies of the 1-MA Zebra, and potential Shiva Star and Atlas experiments that include realistic equations of state and radiation effects, using a variety of tables. • Collaboration with other groups doing simulations of this experiment at LANL, VNIIEF, SNL, and NumerEx leading to a successful international workshop at UNR in the spring of 2008.« less

A Solvable Self-Similar Model of the Sausage Instability in a Resistive Z-Pinch

DTIC Science & Technology

1989-09-20

Ithaca, NY 14853 Dr. V. Nardi Dr. John C. Riordan Stevens Institute of Technology Physics International Co. Hoboken, NJ 07803 2700 Merced Street Dr...92122 Dr. Rick B. Spielman Dr. Frank C. Young Sandia National Laboratories Naval Research Laboratory P.O. Box 5800 Code 4770.1 Albuquerque, NM 87115

Thomas Gold's Intense Solar Wind; It's evidence in prehistoric petroglyphs recorded along rivers in North and South America

NASA Astrophysics Data System (ADS)

Peratt, A. L.

2008-11-01

A past intense solar outburst and its effect on Earth circa 8,000 BCE was proposed by Gold who based his hypotheses on astronomical and geophysical evidence [1]. The discovery of high-current Z-pinch patterns in Neolithic petroglyphs provides evidence for this occurrence and insight into the origin and meaning of these ancient symbols produced by mankind. These correspond to mankind's visual observations of ancient aurora if the solar wind had increased between one and two orders of magnitude millennia ago [2]. Our data show identical MHD patterns from surveys along 300 km of the Orinoco River (Venezuela), the Chuluut River (Mongolia), the Columbia River (USA), Red Gorge (South Australia) and the Urubamba River (Peru). Three-dimensional, high-fidelity PIC simulations of intense Z-pinches replicate the carved data [3]. 1. T. Gold, Pontificiae Academiae Scientiarvm Scripta Varia, 25, 159, 1962. 2. A. L. Peratt. Trans. Plasma Sci. 35. 778. 2007. 3. A. L. Peratt and W. F. Yao, Physica Scripta, T130, August 2008.

Diagnosing magnetized liner inertial fusion experiments on Z

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, S. B., E-mail: sbhanse@sandia.gov; Gomez, M. R.; Sefkow, A. B.

Magnetized Liner Inertial Fusion experiments performed at Sandia's Z facility have demonstrated significant thermonuclear fusion neutron yields (∼10{sup 12} DD neutrons) from multi-keV deuterium plasmas inertially confined by slow (∼10 cm/μs), stable, cylindrical implosions. Effective magnetic confinement of charged fusion reactants and products is signaled by high secondary DT neutron yields above 10{sup 10}. Analysis of extensive power, imaging, and spectroscopic x-ray measurements provides a detailed picture of ∼3 keV temperatures, 0.3 g/cm{sup 3} densities, gradients, and mix in the fuel and liner over the 1–2 ns stagnation duration.

The microjetting behavior from single laser-induced bubbles generated above a solid boundary with a through hole

NASA Astrophysics Data System (ADS)

Abboud, Jack E.; Oweis, Ghanem F.

2013-01-01

An inertial bubble collapsing near a solid boundary generates a fast impulsive microjet directed toward the boundary. The jet impacts the solid boundary at a high velocity, and this effect has been taken advantage of in industrial cleaning such as when tiny bubbles are driven ultrasonically to cavitate around machined parts to produce jets that are believed to induce the cleaning effect. In this experimental investigation, we are interested in the jetting from single cavities near a boundary. By introducing a through hole in the boundary beneath a laser-induced bubble, it is hypothesized that the forming jet, upon bubble implosion, will proceed to penetrate through the hole to the other side and that it may be utilized in useful applications such as precise surgeries. It was found that the growth of the bubble induced a fast flow through the hole and lead to the formation of secondary hydrodynamic cavitation. The experiments also showed the formation of a counter jet directed away from the hole and into the bubble. During the growth phase of the bubble, and near the point of maximum expansion, the bubble wall bulged out toward the hole in a `bulb' like formation, which sometimes resulted in the pinching-off of a secondary small bubble. This was ensued by the inward recoiling of the primary bubble wall near the pinch-off spot, which developed into a counter jet seen to move away from the hole and inward into the bubble.

The microjetting behavior from single laser-induced bubbles generated above a solid boundary with a through hole

NASA Astrophysics Data System (ADS)

Abboud, Jack E.; Oweis, Ghanem F.

2012-12-01

An inertial bubble collapsing near a solid boundary generates a fast impulsive microjet directed toward the boundary. The jet impacts the solid boundary at a high velocity, and this effect has been taken advantage of in industrial cleaning such as when tiny bubbles are driven ultrasonically to cavitate around machined parts to produce jets that are believed to induce the cleaning effect. In this experimental investigation, we are interested in the jetting from single cavities near a boundary. By introducing a through hole in the boundary beneath a laser-induced bubble, it is hypothesized that the forming jet, upon bubble implosion, will proceed to penetrate through the hole to the other side and that it may be utilized in useful applications such as precise surgeries. It was found that the growth of the bubble induced a fast flow through the hole and lead to the formation of secondary hydrodynamic cavitation. The experiments also showed the formation of a counter jet directed away from the hole and into the bubble. During the growth phase of the bubble, and near the point of maximum expansion, the bubble wall bulged out toward the hole in a `bulb' like formation, which sometimes resulted in the pinching-off of a secondary small bubble. This was ensued by the inward recoiling of the primary bubble wall near the pinch-off spot, which developed into a counter jet seen to move away from the hole and inward into the bubble.

Simulations of Ar gas-puff Z-pinch radiation sources with double shells and central jets on the Z generator

NASA Astrophysics Data System (ADS)

Tangri, V.; Harvey-Thompson, A. J.; Giuliani, J. L.; Thornhill, J. W.; Velikovich, A. L.; Apruzese, J. P.; Ouart, N. D.; Dasgupta, A.; Jones, B.; Jennings, C. A.

2016-10-01

Radiation-magnetohydrodynamic simulations using the non-local thermodynamic equilibrium Mach2-Tabular Collisional-Radiative Equilibrium code in (r, z) geometry are performed for two pairs of recent Ar gas-puff Z-pinch experiments on the refurbished Z generator with an 8 cm diameter nozzle. One pair of shots had an outer-to-inner shell mass ratio of 1:1.6 and a second pair had a ratio of 1:1. In each pair, one of the shots had a central jet. The experimental trends in the Ar K-shell yield and power are reproduced in the calculations. However, the K-shell yield and power are significantly lower than the other three shots for the case of a double-shell puff of 1:1 mass ratio and no central jet configuration. Further simulations of a hypothetical experiment with the same relative density profile of this configuration, but higher total mass, show that the coupled energy from the generator and the K-shell yield can be increased to levels achieved in the other three configurations, but not the K-shell power. Based on various measures of effective plasma radius, the compression in the 1:1 mass ratio and no central jet case is found to be less because the plasma inside the magnetic piston is hotter and of lower density. Because of the reduced density, and the reduced radiation cooling (which is proportional to the square of the density), the core plasma is hotter. Consequently, for the 1:1 outer-to-inner shell mass ratio, the load mass controls the yield and the center jet controls the power.

Defect-induced mix experiment for NIF

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Bradley, P. A.; Cobble, J. A.; Hsu, S. C.; Krasheninnikova, N. S.; Kyrala, G. A.; Magelssen, G. R.; Murphy, T. J.; Obrey, K. A.; Tregillis, I. L.; Wysocki, F. J.; Finnegan, S. M.

2013-11-01

The Defect Induced Mix Experiment (DIME-II) will measure the implosion and mix characteristics of CH capsules filled with 5 atmospheres of DT by incorporating mid-Z dopant layers of Ge and Ga. This polar direct drive (PDD) experiment also will demonstrate the filling of a CH capsule at target chamber center using a fill tube. Diagnostics for these experiments include areal x-ray backlighting to obtain early time images of the implosion trajectory and a multiple-monochromatic imager (MMI) to collect spectrally-resolved images of the capsule dopant line emission near bangtime. The inclusion of two (or more) thin dopant layers at separate depths within the capsule shell facilitates spatial correlation of mix between the layers and the hot gas core on a single shot. The dopant layers are typically 2 μm thick and contain dopant concentrations of 1.5%. Three dimensional Hydra simulations have been performed to assess the effects of PDD asymmetry on capsule performance.

Hohlraum-Driven Ignition-Like Double-Shell Implosion Experiments on Omega: Analysis and Interpretation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amendt, P; Robey, H F; Park, H-S

2003-08-22

An experimental campaign to study hohlraum-driven ignition-like double-shell target performance using the Omega laser facility has begun. These targets are intended to incorporate as many ignition-like properties of the proposed National Ignition Facility (NIF) double-shell ignition design [1,2] as possible, given the energy constraints of the Omega laser. In particular, this latest generation of Omega double-shells is nominally predicted to produce over 99% of the (clean) DD neutron yield from the compressional or stagnation phase of the implosion as required in the NIF ignition design. By contrast, previous double-shell experience on Omega [3] was restricted to cases where a significantmore » fraction of the observed neutron yield was produced during the earlier shock convergence phase where the effects of mix are deemed negligibly small. These new targets are specifically designed to have optimized fall-line behavior for mitigating the effects of pusher-fuel mix after deceleration onset and, thereby, providing maximum neutron yield from the stagnation phase. Experimental results from this recent Omega ignition-like double-shell implosion campaign show favorable agreement with two-dimensional integrated hohlraum simulation studies when enhanced (gold) hohlraum M-band (2-5 keV) radiation is included at a level consistent with observations.« less

Inductively Driven, 3D Liner Compression of a Magnetized Plasma to Megabar Energy Densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slough, John

To take advantage of the smaller scale, higher density regime of fusion an efficient method for achieving the compressional heating required to reach fusion gain conditions must be found. What is proposed is a more flexible metallic liner compression scheme that minimizes the kinetic energy required to reach fusion. It is believed that it is possible to accomplish this at sub-megajoule energies. This however will require operation at very small scale. To have a realistic hope of inexpensive, repetitive operation, it is essential to have the liner kinetic energy under a megajoule which allows for the survivability of the vacuummore » and power systems. At small scale the implosion speed must be reasonably fast to maintain the magnetized plasma (FRC) equilibrium during compression. For limited liner kinetic energy, it becomes clear that the thinnest liner imploded to the smallest radius consistent with the requirements for FRC equilibrium lifetime is desired. The proposed work is directed toward accomplishing this goal. Typically an axial (Z) current is employed for liner compression. There are however several advantages to using a θ-pinch coil. With the θ-pinch the liner currents are inductively driven which greatly simplifies the apparatus and vacuum system, and avoids difficulties with the post implosion vacuum integrity. With fractional flux leakage, the foil liner automatically provides for the seed axial compression field. To achieve it with optimal switching techniques, and at an accelerated pace however will require additional funding. This extra expense is well justified as the compression technique that will be enabled by this funding is unique in the ability to implode individual segments of the liner at different times. This is highly advantageous as the liner can be imploded in a manner that maximizes the energy transfer to the FRC. Production of shaped liner implosions for additional axial compression can thus be readily accomplished with the modified power modules. The additional energy and switching capability proposed will thus provide for optimal utilization of the liner energy. The following tasks were outlined for the three year effort: (1) Design and assemble the foil liner compression test structure and chamber including the compression bank and test foils [Year 1]. (2) Perform foil liner compression experiments and obtain performance data over a range on liner dimensions and bank parameters [Year 2]. (3) Carry out compression experiments of the FRC plasma to Megagauss fields and measure key fusion parameters [Year 3]. (4) Develop numerical codes and analyze experimental results, and determine the physics and scaling for future work [Year 1-3]. The principle task of the project was to design and assemble the foil liner FRC formation chamber, the full compression test structure and chamber including the compression bank. This task was completed successfully. The second task was to test foils in the test facility constructed in year one and characterize the performance obtained from liner compression. These experimental measurements were then compared with analytical predictions, and numerical code results. The liner testing was completed and compared with both the analytical results as well as the code work performed with the 3D structural dynamics package of ANSYS Metaphysics®. This code is capable of modeling the dynamic behavior of materials well into the non-linear regime (e.g. a bullet hit plate glass). The liner dynamic behavior was found to be remarkably close to that predicted by the 3D structural dynamics results. Incorporating a code that can also include the magnetics and plasma physics has also made significant progress at the UW. The remaining test bed construction and assembly task is was completed, and the FRC formation and merging experiments were carried out as planned. The liner compression of the FRC to Megagauss fields was not performed due to not obtaining a sufficiently long lived FRC during the final year of the grant. Modifications planned to correct this deficiency included a larger FRC source as well as a much larger liner driver energy storage system. Due to discontinuation of the grant neither of these improvements were carried out.« less

Cinematic Characterization of Convected Coherent Structures Within an Continuous Flow Z-Pinch

NASA Astrophysics Data System (ADS)

Underwood, Thomas; Rodriguez, Jesse; Loebner, Keith; Cappelli, Mark

2017-10-01

In this study, two separate diagnostics are applied to a plasma jet produced from a coaxial accelerator with characteristic velocities exceeding 105 m/s and timescales of 10 μs. In the first of these, an ultra-high frame rate CMOS camera coupled to a Z-type laser Schlieren apparatus is used to obtain flow-field refractometry data for the continuous flow Z-pinch formed within the plasma deflagration jet. The 10 MHz frame rate for 256 consecutive frames provides high temporal resolution, enabling turbulent fluctuations and plasma instabilities to be visualized over the course of a single pulse. The unique advantage of this diagnostic is its ability to simultaneously resolve both structural and temporal evolution of instabilities and density gradients within the flow. To allow for a more meaningful statistical analysis of the resulting wave motion, a multiple B-dot probe array was constructed and calibrated to operate over a broadband frequency range up to 100 MHz. The resulting probe measurements are incorporated into a wavelet analysis to uncover the dispersion relation of recorded wave motion and furthermore uncover instability growth rates. Finally these results are compared with theoretical growth rate estimates to identify underlying physics. This work is supported by the U.S. Department of Energy Stewardship Science Academic Program in addition to the National Defense Science Engineering Graduate Fellowship.

Stability of short-axial-wavelength internal kink modes of an anisotropic plasma

NASA Astrophysics Data System (ADS)

Faghihi, M.; Scheffel, J.

1987-12-01

The double adiabatic equations are used to study the stability of a cylindrical Z-pinch with respect to small axial wavelength, internal kink (m ≥ 1) modes. It is found that marginally (ideally) unstable, isotropic equilibria are stabilized. Also, constant-current-density equilibria can be stabilized for P > P and large β

Experimental demonstration of the stabilizing effect of dielectric coatings on magnetically accelerated imploding metallic liners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awe, Thomas James; Peterson, Kyle J.; Yu, Edmund P.

Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70 μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=R in,0/R in(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. Lastly, the inner-wall radius R in(z,t) displayed unprecedented uniformity, varying from 95 to 130 μm over the 4.0 mm axial height captured by the radiograph.

Experimental demonstration of the stabilizing effect of dielectric coatings on magnetically accelerated imploding metallic liners

DOE PAGES

Awe, Thomas James; Peterson, Kyle J.; Yu, Edmund P.; ...

2016-02-10

Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70 μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=R in,0/R in(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. Lastly, the inner-wall radius R in(z,t) displayed unprecedented uniformity, varying from 95 to 130 μm over the 4.0 mm axial height captured by the radiograph.

Mass density slope of elliptical galaxies from strong lensing and resolved stellar kinematics

NASA Astrophysics Data System (ADS)

Lyskova, N.; Churazov, E.; Naab, T.

2018-04-01

We discuss constraints on the mass density distribution (parametrized as ρ ∝ r-γ) in early-type galaxies provided by strong lensing and stellar kinematics data. The constraints come from mass measurements at two `pinch' radii. One `pinch' radius r1 = 2.2REinst is defined such that the Einstein (i.e. aperture) mass can be converted into the spherical mass almost independently of the mass-model. Another `pinch' radius r2 = Ropt is chosen so that the dynamical mass, derived from the line-of-sight velocity dispersion, is least sensitive to the anisotropy of stellar orbits. We verified the performance of this approach on a sample of simulated elliptical galaxies and on a sample of 15 SLACS lens galaxies at 0.01 ≤ z ≤ 0.35, which have already been analysed in Barnabè et al. by the self-consistent joint lensing and kinematic code. For massive simulated galaxies, the density slope γ is recovered with an accuracy of ˜13 per cent, unless r1 and r2 happen to be close to each other. For SLACS galaxies, we found good overall agreement with the results of Barnabè et al. with a sample-averaged slope γ = 2.1 ± 0.05. Although the two-pinch-radii approach has larger statistical uncertainties, it is much simpler and uses only few arithmetic operations with directly observable quantities.

Design and initial results from a kilojoule level Dense Plasma Focus with hollow anode and cylindrically symmetric gas puff.

PubMed

Ellsworth, J L; Falabella, S; Tang, V; Schmidt, A; Guethlein, G; Hawkins, S; Rusnak, B

2014-01-01

We have designed and built a Dense Plasma Focus (DPF) Z-pinch device using a kJ-level capacitor bank and a hollow anode, and fueled by a cylindrically symmetric gas puff. Using this device, we have measured peak deuteron beam energies of up to 400 keV at 0.8 kJ capacitor bank energy and pinch lengths of ∼6 mm, indicating accelerating fields greater than 50 MV/m. Neutron yields of on the order of 10(7) per shot were measured during deuterium operation. The cylindrical gas puff system permitted simultaneous operation of DPF with a radiofrequency quadrupole accelerator for beam-into-plasma experiments. This paper describes the machine design, the diagnostic systems, and our first results.

Policy and science in children's health and environment: recommendations from the PINCHE project.

PubMed

van den Hazel, Peter; Zuurbier, Moniek; Bistrup, Marie Louise; Busby, Chris; Fucic, Aleksandra; Koppe, Janna G; Lundqvist, Christofer; Ronchetti, Roberto; ten Tusscher, Gavin

2006-10-01

Policy recommendations result from the discussions and analysis of the present situation in environment and health. Such analysis was performed in PINCHE. This led to recommendations based on the scientific literature. In the field of children's environmental health the policy process will follow more or less fixed rules, but this process is still at an early level of development. The link between science and policy still faces many challenges. Scientific assessment of environmental risk must recognize and tackle the problems of data sets, variability of human and environmental systems, the range, spatial and temporal diffusion of potential health effects and many biases and confounding factors. The PINCHE network recommends a general improvement of the supporting scientific fields in environment and health. Assessments from epidemiology or toxicology should play a key role in influencing science-policy decisions in programmes that are intended to inform the public policy process. Scientific committees at a local level could play a role. The relation between health and environment needs to be better incorporated in training and education. There is a need for harmonization of data production and use. The priorities in PINCHE focus on the most important issues. A classification of low, medium or high priority for action was used to describe a range of different environmental stressors. PINCHE provided recommendations to reduce exposure for children. Exposure reduction is not always linked to improved health in the short term, but it will reduce the body burden of accumulating chemicals in children. A strategic choice is reduction of exposure of children to compounds by changing production techniques or by increasing the distance of child specific settings to sources. The contribution of all players in the production, distribution and use of scientific knowledge in the field of children's environmental health is necessary.

On the Evolution From Micrometer-Scale Inhomogeneity to Global Overheated Structure During the Intense Joule Heating of a z-Pinch Rod

DOE PAGES

Awe, T. J.; Yu, E. P.; Yates, K. C.; ...

2017-02-21

Ultrafast optical microscopy of metal z-pinch rods pulsed with megaampere current is contributing new data and critical insight into what provides the fundamental seed for the magneto-Rayleigh-Taylor (MRT) instability. A two-frame near infrared/visible intensified-charge-coupled device gated imager with 2-ns temporal resolution and 3-μm spatial resolution captured emissions from the nonuniformly Joule heated surfaces of ultrasmooth aluminum (Al) rods. Nonuniform surface emissions are consistently first observed from discrete, 10-μm scale, subelectronvolt spots. Aluminum 6061 alloy, with micrometer-scale nonmetallic resistive inclusions, forms several times more spots than 99.999% pure Al 5N; 5-10 ns later, azimuthally stretched elliptical spots and distinct strata (40-100more » μm wide by 10 μm tall) are observed on Al 6061, but not on Al 5N. In such overheat strata, aligned parallel to the magnetic field, we find that they are highly effective seeds for MRT instability growth. Our data give credence to the hypothesis that early nonuniform Joule heating, such as the electrothermal instability, may provide the dominant seed for MRT.« less

Construction and Initial Tests of MAIZE: 1 MA LTD-Driven Z-Pinch *

NASA Astrophysics Data System (ADS)

Gilgenbach, R. M.; Gomez, M. R.; Zier, J. C.; Tang, W.; French, D. M.; Lau, Y. Y.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Oliver, B. V.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

2008-11-01

We report construction and initial testing of a 1-MA Linear Transformer Driver (LTD), The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE). This machine, the first of its type to reach the USA, is based on the joint HCEI, Sandia Laboratories, and UM development effort. The compact LTD uses 80 capacitors and 40 spark gap switches, in 40 ``bricks'', to deliver 1 MA, 100 kV pulses with 70 ns risetime into a matched resistive load. Test results will be presented for a single brick and the full LTD. Design and construction will be presented of a low-inductance MITL. Experimental research programs under design and construction at UM include: a) Studies of Magneto-Raleigh-Taylor Instability of planar foils, and b) Vacuum convolute studies including cathode and anode plasma. Theory and simulation results will be presented for these planned experiments. Initial experimental designs and moderate-current feasibility experiments will be discussed. *Research supported by U. S. DoE through Sandia National Laboratories award document numbers 240985, 768225, 790791 and 805234 to the UM. MRG supported by NNSA Fellowship and JCZ supported by NPSC Fellowship / Sandia National Labs.

High-Energy Space Propulsion Based on Magnetized Target Fusion

NASA Technical Reports Server (NTRS)

Thio, Y. C. F.; Landrum, D. B.; Freeze, B.; Kirkpatrick, R. C.; Gerrish, H.; Schmidt, G. R.

1999-01-01

Magnetized target fusion is an approach in which a magnetized target plasma is compressed inertially by an imploding material wall. A high energy plasma liner may be used to produce the required implosion. The plasma liner is formed by the merging of a number of high momentum plasma jets converging towards the center of a sphere where two compact toroids have been introduced. Preliminary 3-D hydrodynamics modeling results using the SPHINX code of Los Alamos National Laboratory have been very encouraging and confirm earlier theoretical expectations. The concept appears ready for experimental exploration and plans for doing so are being pursued. In this talk, we explore conceptually how this innovative fusion approach could be packaged for space propulsion for interplanetary travel. We discuss the generally generic components of a baseline propulsion concept including the fusion engine, high velocity plasma accelerators, generators of compact toroids using conical theta pinches, magnetic nozzle, neutron absorption blanket, tritium reprocessing system, shock absorber, magnetohydrodynamic generator, capacitor pulsed power system, thermal management system, and micrometeorite shields.

New Regimes of Implosions of Larger Sized Wire Arrays With and Without Modified Central Plane at 1.5-1.7 MA Zebra

NASA Astrophysics Data System (ADS)

Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Weller, M. E.; Shrestha, I.; Shlyaptseva, V. V.; Stafford, A.; Keim, S. F.; Petkov, E. E.; Lorance, M.; Chuvatin, A. S.; Coverdale, C. A.; Jones, B.

2013-10-01

The recent experiments at 1.5-1.7 MA on Zebra at UNR with larger sized planar wires arrays (compared to the wire loads at 1 MA current) have demonstrated higher linear radiation yield and electron temperatures as well as advantages of better diagnostics access to observable plasma regions. Such multi-planar wire arrays had two outer wire planes from mid-Z material to create a global magnetic field (gmf) and mid-Z plasma flow between them. Also, they included a modified central plane with a few Al wires at the edges to influence gmf and to create Al plasma flow in the perpendicular direction. The stationary shock waves which existed over tens of ns on shadow images and the early x-ray emissions before the PCD peak on time-gated spectra were observed. The most recent experiments with similar loads but without the central wires demonstrated a very different regime of implosion with asymmetrical jets and no precursor formation. This work was supported by NNSA under DOE Cooperative Agreement DE-NA0001984 and in part by DE-FC52-06NA27616. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Relationship between patient-reported and objective measurements of hand function in patients with rheumatoid arthritis.

PubMed

Günay, S M; Tuna, Z; Oskay, D

2016-12-31

Rheumatoid arthritis (RA) often results in impairments in upper extremities, especially in the small joints of hand. Involvement of hand brings limitations in activities of daily living. However, it is commonly observed that patient-reported functional status of hand does not always corresponds to their actual physical performance in the clinical setting. The aim of this pilot study is to investigate the relationship between patient self-reported and objectively measured hand functions in patients with RA. Twenty-six patients (51±13 years) with RA diagnosis participated in the study. Hand grip and pinch (lateral, bipod, tripod) strengths were measured and Jebsen Hand Function Test (JHFT) was performed for objective functional performance. Duruöz Hand Index and Beck Depression Inventory - Turkish version were completed by patients. Grip and all three-pinch strength results significantly correlated with Duruöz Hand Index scores (p<0.05). JHFT results except the sentence writing also correlated with the Duruöz scores (p<0.05). Our results showed that self-reported outcome scales might be used for determining functional level of hand in patients with RA in rheumatology practice. Objective quantitative functional tests are the best methods in evaluating functional level of hand, but require valid and reliable equipment with accurate calibration. Therefore, in case of unavailability of objective assessment tools, patient-reported scales may also reflect the real status of hand functions.

Implosive accretion and outbursts of active galactic nuclei

NASA Technical Reports Server (NTRS)

Lovelace, R. V. E.; Romanova, M. M.; Newman, W. I.

1994-01-01

A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

Progress Toward Fabrication of Machined Metal Shells for the First Double-Shell Implosions at the National Ignition Facility

DOE PAGES

Cardenas, Tana; Schmidt, Derek W.; Loomis, Eric N.; ...

2018-01-25

The double-shell platform fielded at the National Ignition Facility requires developments in new machining techniques and robotic assembly stations to meet the experimental specifications. Current double-shell target designs use a dense high-Z inner shell, a foam cushion, and a low-Z outer shell. The design requires that the inner shell be gas filled using a fill tube. This tube impacts the entire machining and assembly design. Other intermediate physics designs have to be fielded to answer physics questions and advance the technology to be able to fabricate the full point design in the near future. One of these intermediate designs ismore » a mid-Z imaging design. The methods of designing, fabricating, and characterizing each of the major components of an imaging double shell are discussed with an emphasis on the fabrication of the machined outer metal shell.« less

Progress Toward Fabrication of Machined Metal Shells for the First Double-Shell Implosions at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardenas, Tana; Schmidt, Derek W.; Loomis, Eric N.

The double-shell platform fielded at the National Ignition Facility requires developments in new machining techniques and robotic assembly stations to meet the experimental specifications. Current double-shell target designs use a dense high-Z inner shell, a foam cushion, and a low-Z outer shell. The design requires that the inner shell be gas filled using a fill tube. This tube impacts the entire machining and assembly design. Other intermediate physics designs have to be fielded to answer physics questions and advance the technology to be able to fabricate the full point design in the near future. One of these intermediate designs ismore » a mid-Z imaging design. The methods of designing, fabricating, and characterizing each of the major components of an imaging double shell are discussed with an emphasis on the fabrication of the machined outer metal shell.« less

CONTROLLED NUCLEAR FUSION REACTOR

DOEpatents

Tuck, J.L.; Kruskal, M.; Colgate, S.A.; Rosenbluth, M.N.

1962-01-01

A plasma generating and heating device is described which comprises a ceramic torus with exterior layers of a thick metal membrane and a metallic coil. In operation, the coil generates a B/sub z/ field prior to the formation of an enclosing plasma sheath. Diffusion of the trapped magnetic field outward through the plasma sheath causes enhanced heating, particularly after the sheath has been pinched. (D.L.C.)

Impact of High-Z Coatings on the Ablation Pressure of Laser Driven Targets.

NASA Astrophysics Data System (ADS)

Mostovych, Andrew; Oh, Jaechul; Schmitt, Andrew; Weaver, James

2007-11-01

Recent hydrodynamic experiments [1] with planar high-Z coated targets at the Naval Research Laboratory and spherical implosion experiments with high-Z coated shell targets [2] at the Omega facility all show significant improvement in target stability as a result of the high-Z coatings. For better understanding of the hydrodynamic processes it is important to know the changes in ablation pressure as a result of the high-Z layers. Using the Nike Laser, we have conducted new experiments to measure the change in shock speed of planar CH targets that are irradiated with and without the presence of a 200 Ang. gold high-Z coating. The evolution of shock propagation inside the targets is diagnosed with VISAR probing while average shock velocities are also measured by shock breakout detection from the stepped rear surface of the targets. We find that the high-Z layers produce a time dependent ablation pressure which is detected via the observation of non-steady shocks in the targets. Experimental results and comparisons to hydrodynamic simulations will be presented. Work supported by U. S. Department of Energy. [1] S.P. Obenschain et al., Phys. Plasmas 9, 2234 (2002). [2] A.N. Mostovych et al., APS Abstracts DPPFO3002M, (2005).

Diagnostics of deuterium gas-puff z-pinch experiments on the GIT-12 generator

NASA Astrophysics Data System (ADS)

Cikhardt, J.; Klir, D.; Rezac, K.; Kubes, P.; Kravarik, J.; Batobolotova, B.; Sila, O.; Turek, K.; Shishlov, A.; Labetsky, A.; Kokshenev, V.; Chedizov, R.; Ratakhin, N.; Varlachev, V.; Garapatsky, A.; Dudkin, G.; Padalko, V.; GIT-12 Team

2014-10-01

Z-pinch experiments with a deuterium gas-puff and an outer plasma shell generated by plasma guns were carried out on the GIT-12 generator at the IHCE in Tomsk. Using this novel configuration of the load, the neutron yields from the DD reaction were significantly increased from 2×1011 up to 3×1012 neutrons per shot at the current level of about 3 MA. In addition to recent experiments, the threshold activation detectors were used in order to get the information about the energy spectrum of the generated neutrons. The copper, indium, and lead samples were irradiated by the pulse of the neutrons generated during the experimental shot. The decay radiation of the products from the reactions 63Cu(n,2n)62Cu, 115In(n, γ) 116 mIn and 206Pb (n,3n)204mPb was observed using gamma spectrometer. According to the used neutron ToF scintillation detectors, the energy of neutrons reaches up to 20 MeV. The work was supported by the MSMT of the Czech Republic research Programs No. ME090871, No. LG13029, by the GACR Grant No. P205/12/0454, Grant CRA IAEA No. 17088 and RFBR research Project No. 13-08-00479-a.

Numerical simulations of Z-Pinch experiments to create supersonic differentially-rotating plasma flows

NASA Astrophysics Data System (ADS)

Bochi, Matteo; Ummels, Sebastiaan; Chittenden, Jeremy; Lebedev, Sergey

2011-10-01

Recently, it was proposed that a small number of plasma jets produced by lasers could be used to generate a plasma configuration relevant to some features of astrophysical accretion disc physics. We propose complementary experimental configurations which employ converging flows generated in a cylindrical wire array Z-pinch modified to produce a rotating plasma. In this paper we present 3D MHD simulations using the code GORGON which show how this approach can be implemented at the MAGPIE facility at Imperial College, London. We will present the general scenario and the results of a parametric study relating the parameters of the array with the features of the resulting plasma. In particular, we will show how a rotating plasma cylinder or ring, with typical rotation velocity 30 Km/s and Mach number 8 is formed, and how, after about 1-2 revolutions, the material of the plasma ring is ejected in a pair of thermally driven, conical outflows propagating along the rotation axis. We will discuss to what aspects of the physics of accretion discs, the results of such experiments could be relevant. We will also consider the effects of different magnetic configurations, which further expand the possibility to relate the experiments with the astrophysical discs. Experimental implementation of some of these setups is currently in progress on MAGPIE.

Flux-trapping during the formation of field-reversed configurations

NASA Astrophysics Data System (ADS)

Armstrong, W. T.; Harding, D. G.; Crawford, E. A.; Hoffman, A. L.

1982-11-01

Flux-trapping during the early formation phases of a field-reversed configuration has been studied experimentally on the field-reversed theta-pinch TRX-1. An annular z-pinch preionizer was employed to permit ionization at high values of reverse-bias flux. Contrary to previous analysis, the rate of flux loss was not governed exclusively by inertially limited plasma convection to the tube walls. At high reverse flux levels, a pressure bearing sheath was observed to form at the tube walls and the flux loss was restricted by resistive diffusion across this sheath. The characteristic time for flux loss was 0.08rt (cm) μsec, independent of the bias field and independent of the fill pressure for fill pressures above 15 mTorr D2. Octopole barrier fields were found to be effective in limiting the inertially governed flux loss at very early times before the wall sheath formed.

Nuclear Fusion Within Extremely Dense Plasma Enhanced by Quantum Particle Waves

NASA Astrophysics Data System (ADS)

Miao, Feng; Zheng, Xianjun; Deng, Baiquan

2015-05-01

Quantum effects play an enhancement role in p-p chain reactions occurring within stars. Such an enhancement is quantified by a wave penetration factor that is proportional to the density of the participating fuel particles. This leads to an innovative theory for dense plasma, and its result shows good agreement with independent data derived from the solar energy output. An analysis of the first Z-pinch machine in mankind's history exhibiting neutron emission leads to a derived deuterium plasma beam density greater than that of water, with plasma velocities exceeding 10000 km/s. Fusion power could be achieved by the intersection of four such pinched plasma beams with powerful head-on collisions in their common focal region due to the beam and target enhanced reaction. supported by the Fund for the Construction of Graduate Degree of China (No. 2014XWD-S0805)

The Effect of Interchanging the Polarity of the Dense Plasma Focus on Neutron Yield

NASA Astrophysics Data System (ADS)

Jiang, Sheng; Higginson, Drew; Link, Anthony; Schmidt, Andrea

2017-10-01

The dense plasma focus (DPF) Z-pinch devices can serve as portable neutron sources when deuterium is used as the filling gas. DPF devices are normally operated with the inner electrode as the anode. It has been found that interchanging the polarity of the electrodes can cause orders of magnitude decrease in the neutron yield. Here we use the particle-in-cell (PIC) code LSP to model a DPF with both polarities. We have found the difference in the shape of the sheath, the voltage and current traces, and the electric and magnetic fields in the pinch region due to different polarities. A detailed comparison will be presented. Prepared by LLNL under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (15-ERD-034) at LLNL. Computing support for this work came from the LLNL Institutional Computing Grand Challenge program.

An university-scale pulsed-power system using a bipolar Marx generator

NASA Astrophysics Data System (ADS)

Chang, Po-Yu; Yang, Sheng-Hua; Huang, Mei-Feng; Isaps, Natl Cheng Kung Univ Team

2017-10-01

A bipolar Marx generator is being built for x-ray sources or laboratory astrophysics and space research for university-scale laboratory. The system consists of ten stages. In each stage, two 1 μF capacitors connected in series are charged to +/- 30 kV storing 9 kJ of total energy. It delivers a current of 200 kA to the load with a 200 ns rise time during the discharge. It will be used for following three purposes: (1) gas-puff z pinches generating soft x-ray for bio-medical research in the future; (2) generating plasma jets to study interactions between plasma flows and unmagnetized/magnetized obstacles analogous to the interactions between solar winds and planetary magnetic fields or unmagnetized planets; and (3) studying the pinch in a dense plasma focus device. The results of current measurements and circuit characteristics are shown.

Laser imprint reduction for the critical-density foam buffered target driven by a relatively strong foot pulse at early stage of laser implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J. W., E-mail: li-jiwei@iapcm.ac.cn; He, X. T.; Institute of Applied Physics and Computational Mathematics, P. O. Box 8009, Beijing 100094

In order to reduce the effect of laser imprint in direct-drive ignition scheme a low-density foam buffered target has been proposed. This target is driven by a laser pulse with a low-intensity foot at the early stage of implosion, which heats the foam and elongates the thermal conduction zone between the laser absorption region and ablation front, increasing the thermal smoothing effect. In this paper, a relatively strong foot pulse is adopted to irradiate the critical-density foam buffered target. The stronger foot, near 1 × 10{sup 14 }W/cm{sup 2}, is able to drive a radiative shock in the low-density foam, which helps smoothmore » the shock and further reduce the effect of laser imprint. The radiative shock also forms a double ablation front structure between the two ablation fronts to further stabilize the hydrodynamics, achieving the similar results to a target with a high-Z dopant in the ablator. 2D analysis shows that for the critical-density foam buffered target irradiated by the strong foot pulse, the laser imprint can be reduced due to the radiative shock in the foam and an increased thermal smoothing effect. It seems viable for the critical-density foam buffered target to be driven by a relatively strong foot pulse with the goal of reducing the laser imprint and achieving better implosion symmetry in the direct-drive laser fusion.« less

Benefits of Moderate-Z Ablators for Direct-Drive Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Lafon, M.; Betti, R.; Anderson, K. S.; Collins, T. J. B.; Skupsky, S.; McKenty, P. W.

2014-10-01

Control of hydrodynamic instabilities and DT-fuel preheating by hot electrons produced by laser-plasma interaction is crucial in inertial confinement fusion. Moderate- Z ablators have been shown to reduce the laser imprinting on target and suppress the generation of hot electrons from the two-plasmon-decay instability. These results have motivated the use of ablators of higher- Z than pure plastic in direct-drive-ignition target designs for the National Ignition Facility (NIF). Two-dimensional radiation-hydrodynamic simulations assess the robustness of these ignition designs to laser imprint and capsule nonuniformities. The complex behavior of the hydrodynamic stability of mid- Z ablators is investigated through single and multimode simulations. A polar-drive configuration is developed within the NIF Laser System specifications for each ablator material. The use of multilayer ablators is also investigated to enhance the hydrodynamic stability. Results indicate that ignition target designs using mid- Z ablators exhibit good hydrodynamic properties, leading to high target gain for direct-drive implosions on the NIF. 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.

Laser targets compensate for limitations in inertial confinement fusion drivers

NASA Astrophysics Data System (ADS)

Kilkenny, J. D.; Alexander, N. B.; Nikroo, A.; Steinman, D. A.; Nobile, A.; Bernat, T.; Cook, R.; Letts, S.; Takagi, M.; Harding, D.

2005-10-01

Success in inertial confinement fusion (ICF) requires sophisticated, characterized targets. The increasing fidelity of three-dimensional (3D), radiation hydrodynamic computer codes has made it possible to design targets for ICF which can compensate for limitations in the existing single shot laser and Z pinch ICF drivers. Developments in ICF target fabrication technology allow more esoteric target designs to be fabricated. At present, requirements require new deterministic nano-material fabrication on micro scale.

Design of a line-VISAR interferometer system for the Sandia Z Machine

NASA Astrophysics Data System (ADS)

Galbraith, J.; Austin, K.; Baker, J.; Bettencourt, R.; Bliss, E.; Celeste, J.; Clancy, T.; Cohen, S.; Crosley, M.; Datte, P.; Fratanduono, D.; Frieders, G.; Hammer, J.; Jackson, J.; Johnson, D.; Jones, M.; Koen, D.; Lusk, J.; Martinez, A.; Massey, W.; McCarville, T.; McLean, H.; Raman, K.; Rodriguez, S.; Spencer, D.; Springer, P.; Wong, J.

2017-08-01

A joint team comprised of Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratory (SNL) personnel is designing a line-VISAR (Velocity Interferometer System for Any Reflector) for the Sandia Z Machine, Z Line-VISAR. The diagnostic utilizes interferometry to assess current delivery as a function of radius during a magnetically-driven implosion. The Z Line-VISAR system is comprised of the following: a two-leg line-VISAR interferometer, an eight-channel Gated Optical Imager (GOI), and a fifty-meter transport beampath to/from the target of interest. The Z Machine presents unique optomechanical design challenges. The machine utilizes magnetically driven pulsed power to drive a target to elevated temperatures and pressures useful for high energy density science. Shock accelerations exceeding 30g and a strong electromagnetic pulse (EMP) are generated during the shot event as the machine discharges currents of over 25 million amps. Sensitive optical components must be protected from shock loading, and electrical equipment must be adequately shielded from the EMP. The optical design must accommodate temperature and humidity fluctuations in the facility as well as airborne hydrocarbons from the pulsed power components. We will describe the engineering design and concept of operations of the Z Line-VISAR system. Focus will be on optomechanical design.

Comparison of the Three NIF Ablators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kritcher, A. L.; Clark, D. S.; Haan, S. W.

Indirect drive implosion experiments on NIF have now been performed using three different ablator materials: glow discharge polymer (GDP) or CH, high density carbon (HDC, which we also refer to as diamond), and sputtered beryllium (Be). It has been appreciated for some time that each of these materials has specific advantages and disadvantages as an ICF ablator.[1-4] In light of experiments conducted on NIF in the last few years, how do these ablators compare? Given current understanding, is any ablator more or less likely to reach ignition on NIF? Has the understanding of their respective strengths and weaknesses changed sincemore » NIF experiments began? How are those strengths and weaknesses highlighted by implosion designs currently being tested or planned for testing soon? This document aims to address these questions by combining modern simulation results with a survey of the current experimental data base. More particularly, this document is meant to fulfill an L2 Milestone for FY17 to “Document our understanding of the relative advantages and disadvantages of CH, HDC, and Be designs.” Note that this document does not aim to recommend a down-selection of the current three ablator choices. It is intended only to gather and document the current understanding of the differences between these ablators and thereby inform the choices made in planning future implosion experiments. This document has two themes: (i) We report on a reanalysis project in which post-shot simulations were done on a common basis for layered shots using each ablator. This included data from keyholes, 2D ConA, and so forth, from each campaign, leading up to the layered shots. (“Keyholes” are shots dedicated to measuring the shock timing in a NIF target, as described in Ref. 5. “2DConAs” are backlit implosions in which the symmetry of the implosion is measured between about half and full convergence, as described in Ref. 6.) This set of common-basis postshot simulations is compared to the respective shots. Each was then scaled to a “full NIF” experiment that could be done using the respective ablators at full NIF power and/or energy, and these scaled-up designs were simulated in detail. (ii) The report also contains a general survey of experimental and simulated results as pertinent to comparing and evaluating the three ablators.« less

In-Situ Anode Heating and Its Effects on Atomic Constituents in the A-K Gap in Self-Magnetic Pinch (SMP) Experiments

NASA Astrophysics Data System (ADS)

Simpson, Sean; Renk, Timothy; Johnston, Mark; Mazarakis, Mike; Patel, Sonal

2015-11-01

The RITS-6 inductive voltage adder (IVA) accelerator (3.5-8.5 MeV) at Sandia National Laboratories produces high-power (TW) focused electron beams (<3mm diameter) for flash x-ray radiography applications. The Self-Magnetic Pinch (SMP) diode utilizes a hollowed metal cathode to produce a pinched focus onto a high-Z metal anode converter. There is not a clear understanding as to the effects various contaminants such as C, CO, H, H2O, HmCn, O2, and N2, on the anode surface or in the bulk may have on impedance dynamics, beam stability, beam spot size, and reproducibility. Heating pure Ta anodes with and without a thin Al coating have been investigated using temperatures ranging from 400 °C to 1000 °C. Initial experiments indicate a significant reduction in H and C as seen in high-speed spectral analysis of plasmas at the converter and a reduction in the back-streaming proton current. Experiments are ongoing, and latest results will be reported. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Exploring the limits of case-to-capsule ratio, pulse length, and picket energy for symmetric hohlraum drive on the National Ignition Facility Laser

NASA Astrophysics Data System (ADS)

Callahan, D. A.; Hurricane, O. A.; Ralph, J. E.; Thomas, C. A.; Baker, K. L.; Benedetti, L. R.; Berzak Hopkins, L. F.; Casey, D. T.; Chapman, T.; Czajka, C. E.; Dewald, E. L.; Divol, L.; Döppner, T.; Hinkel, D. E.; Hohenberger, M.; Jarrott, L. C.; Khan, S. F.; Kritcher, A. L.; Landen, O. L.; LePape, S.; MacLaren, S. A.; Masse, L. P.; Meezan, N. B.; Pak, A. E.; Salmonson, J. D.; Woods, D. T.; Izumi, N.; Ma, T.; Mariscal, D. A.; Nagel, S. R.; Kline, J. L.; Kyrala, G. A.; Loomis, E. N.; Yi, S. A.; Zylstra, A. B.; Batha, S. H.

2018-05-01

We present a data-based model for low mode asymmetry in low gas-fill hohlraum experiments on the National Ignition Facility {NIF [Moses et al., Fusion Sci. Technol. 69, 1 (2016)]} laser. This model is based on the hypothesis that the asymmetry in these low fill hohlraums is dominated by the hydrodynamics of the expanding, low density, high-Z (gold or uranium) "bubble," which occurs where the intense outer cone laser beams hit the high-Z hohlraum wall. We developed a simple model which states that the implosion symmetry becomes more oblate as the high-Z bubble size becomes large compared to the hohlraum radius or the capsule size becomes large compared to the hohlraum radius. This simple model captures the trends that we see in data that span much of the parameter space of interest for NIF ignition experiments. We are now using this model as a constraint on new designs for experiments on the NIF.

Visualizing density perturbations in the capsule shell in NIF implosions near peak velocity

NASA Astrophysics Data System (ADS)

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; Macphee, A.; Scott, H. A.; Robey, H. F.; Field, J.; Barrios, M.; Regan, S. P.

2016-10-01

Engineering features on the capsule (surface roughness, support structures, etc.) can introduce outer surface perturbations that are ultimately detrimental to the performance of the capsule. Recent experiments have assessed minimal support structures and alternate pulse shapes using a re-entrant cone and back lighter that is perturbing to the implosion below radii of 500 μ m. Emission from the hot core, after shock-stagnation and prior to peak velocity (PV), has been used as a self-backlighter, providing a means to sample one side of the capsule at smaller radii. Adding high-Z gas ( 1 % Ar) to the capsule fill in Symcaps (4He), has produced a continuum backlighter with significant increase in emission at hv 8 keV over nominal fills. High-resolution imaging diagnostics with photon energy selectivity form 2D images of the transmitted self-emission, above and below the K-edge of an internally doped Cu layer. We can infer from these images the growth at PV of outer surface perturbations. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-697620.

Radiation characteristics of Al wire arrays on Z*

NASA Astrophysics Data System (ADS)

Coverdale, C. A.; Ampleford, D. J.; Jones, B.; Cuneo, M. E.; Hansen, S.; Jennings, C. A.; Moore, N.; Jones, S. C.; Deeney, C.

2011-10-01

Analysis of mixed material nested wire array experiments at Z have shown that the inner wire array dominates the hottest regions of the stagnated z pinch. In those experiments, substantial free-bound continuum radiation was observed when Al was fielded on the inner wire array. Experiments with Al (5% Mg) on both wire arrays have also been fielded, with variations in the free-bound continuum observed. These variations appear to be tied to the initial mass and diameter of the wire array. The results presented here will investigate the trends in the measured emission (Al and Mg K-shell and free-bound continuum) and will compare the measured output to more recent Al wire array experimental results on the refurbished Z accelerator. *Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. +current address: NNSA/DOE Headquarters, Washington D.C.

Charger 1: A New Facility for Z-Pinch Research

NASA Technical Reports Server (NTRS)

Taylor, Brian; Cassibry, Jason; Cortez, Ross; Doughty, Glen; Adams, Robert; DeCicco, Anthony

2017-01-01

Charger 1 is a multipurpose pulsed power laboratory located on Redstone Arsenal, with a focus on fusion propulsion relevant experiments involving testing z-pinch diodes, pulsed magnetic nozzle and other related physics experiments. UAH and its team of pulsed power researchers are investigating ways to increase and optimize fusion production from Charger 1. Currently the team has reached high-power testing. Due to the unique safety issues related to high power operations the UAH/MSFC team has slowed repair efforts to develop safety and operations protocols. The facility is expected to be operational by the time DZP 2017 convenes. Charger 1 began life as the Decade Module 2, an experimental prototype built to prove the Decade Quad pinch configuration. The system was donated to UAH by the Defense Threat Reduction Agency (DRTA) in 2012. For the past 5 years a UAH/MSFC/Boeing team has worked to refurbish, assemble and test the system. With completion of high power testing in summer 2017 Charger 1 will become operational for experimentation. Charger 1 utilizes a Marx Bank of 72 100-kV capacitors that are charged in parallel and discharged in series. The Marx output is compressed to a pulse width of approximately 200 ns via a pulse forming network of 32 coaxial stainless steel tubes using water as a dielectric. After pulse compression a set of SF6 switches are triggered, allowing the wave front to propagate through the output line to the load. Charger 1 is capable of storing 572-kJ of energy and time compressing discharge to less than 250 ns discharge time producing a discharge of about 1 TW of discharge with 1 MV and 1 MA peak voltage and current, respectively. This capability will be used to study energy yield scaling and physics from solid density target as applied to advanced propulsion research.

New compact hohlraum configuration research at the 1.7 MA Z-pinch generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kantsyrev, V. L., E-mail: victor@unr.edu; Shrestha, I. K.; Esaulov, A. A.

A new compact Z-pinch x-ray hohlraum design with parallel-driven x-ray sources was experimentally demonstrated in a full configuration with a central target and tailored shine shields (to provide a symmetric temperature distribution on the target) at the 1.7 MA Zebra generator. This presentation reports on the joint success of two independent lines of research. One of these was the development of new sources – planar wire arrays (PWAs). PWAs turned out to be a prolific radiator. Another success was the drastic improvement in energy efficiency of pulsed-power systems, such as the Load Current Multiplier (LCM). The Zebra/LCM generator almost doubledmore » the plasma load current to 1.7 MA. The two above-mentioned innovative approaches were used in combination to produce a new compact hohlraum design for ICF, as jointly proposed by SNL and UNR. Good agreement between simulated and measured radiation temperature of the central target is shown. Experimental comparison of PWAs with planar foil liners (PFL) - another viable alternative to wire array loads at multi-MA generators show promising data. Results of research at the University of Nevada Reno allowed for the study of hohlraum coupling physics at University-scale generators. The advantages of new hohlraum design applications for multi-MA facilities with W or Au double PWAs or PFL x-ray sources are discussed.« less

Axial plasma jet characterization on a microsecond x-pinch

NASA Astrophysics Data System (ADS)

Jaar, G. S.; Appartaim, R. K.

2018-06-01

The jets produced on a microsecond x-pinch (quarter period T1/4 ˜ 1 μs, dI/dt ˜ 0.35 kA/ns) have been studied through light-field schlieren imaging and optical framing photographs across 4 different materials: Al, Ti, Mo, and W. The axial velocity of the jets was measured and exhibited no dependence on atomic number (Z) of the wire material. There may be a dependence on another factor(s), namely, the current rise rate. The average axial jet velocity across all four materials was measured to be 2.9 ± 0.5 × 106 cm/s. The average jet diameter and the average radial jet expansion rate displayed inverse relationships with Z, which may be attributed to radiative cooling and inertia. Asymmetry between the anode and cathode jet behavior was observed and is thought to be caused by electron beam activity. The mean divergence angle of the jet was found to vary with wire material and correlated inversely with the thermal conductivity of the cold wire. Optical images indicated a two-layer structure in Al jets which may be caused by standing shocks and resemble phenomena observed in astrophysical jet formation and collimation. Kinks in the jets have also been observed which may be caused by m = 1 MHD instability modes or by the interaction of the jet with the electrode plasma.

Simulations of Radiation-Driven Shock Wave Experiments

NASA Astrophysics Data System (ADS)

Dukart, R. J.; Asay, J. R.; Porter, J. L.; Matzen, M. K.

1997-07-01

For inertial confinement fusion (I.C.F.) target design, we need to understand material properties between 1- and 150-Mbar pressure. In this presentation we will show that we can use radiatively-driven ablation to generate high pressures in a wide variety of materials. PBFA-Z is being developed to generate centimeter scale hohlraums with temperatures from 80 to 150 eV. 1-D radiation/hydrodynamic simulations using these hohlraums predict the generation 1- to 15-Mbar pressures in a wide variety of materials through direct ablation. Through the use of thick ablators, we can obtain 4.5- to 25-Mbar pressures in Aluminum. This pressure regime can be extended to 40 Mbar for 200-eV hohlraums predicted for the X1, next generation, Z-pinch driver.

Improvements in the EQ-10 electrodeless Z-pinch EUV source for metrology applications

NASA Astrophysics Data System (ADS)

Horne, Stephen F.; Gustafson, Deborah; Partlow, Matthew J.; Besen, Matthew M.; Smith, Donald K.; Blackborow, Paul A.

2011-04-01

Now that EUV lithography systems are beginning to ship into the fabs for next generation chips it is more critical that the EUV infrastructure developments are keeping pace. Energetiq Technology has been shipping the EQ-10 Electrodeless Z-pinch™ light source since 2005. The source is currently being used for metrology, mask inspection, and resist development. These applications require especially stable performance in both power and source size. Over the last 5 years Energetiq has made many source modifications which have included better thermal management as well as high pulse rate operation6. Recently we have further increased the system power handling and electrical pulse reproducibility. The impact of these modifications on source performance will be reported.

Controlling dynamics of imploded core plasma for fast ignition

NASA Astrophysics Data System (ADS)

Nagatomo, H.; Johzaki, T.; Sunahara, A.; Shiraga, H.; Sakagami, H.; Cai, H.; Mima, K.

2010-08-01

In the Fast ignition, formation of highly compressed core plasma is one of critical issue. In this work, the effect hydrodynamic instability in cone-guided shell implosion is studied. Two-dimensional radiation hydrodynamic simulations are carried out where realistic seeds of Rayleigh-Taylor instability are imposed. Preliminary results suggest that the instability reduces implosion performance, such as implosion velocity, areal density, and maximum density. In perturbed target implosion, the break-up time of the tip of the cone is earlier than that of ideal unperturbed target implosion case. This is crucial matter for the Fast ignition because the pass for the heating laser is filled with plasma before the shot of heating laser. A sophisticated implosion design of stable and low in-flight aspect ratio is necessary for cone-guided shell implosion.

On the importance of minimizing "coast-time" in x-ray driven inertially confined fusion implosions

NASA Astrophysics Data System (ADS)

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.; Landen, O.; Patel, P. K.; Springer, P. T.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Hinkel, D. E.; Berzak Hopkins, L. F.; Kline, J.; Le Pape, S.; Ma, T.; MacPhee, A. G.; Moore, A.; Pak, A.; Park, H.-S.; Ralph, J.; Salmonson, J. D.; Widmann, K.

2017-09-01

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400 × , making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, toff, well before bang-time, tBT, for a coast-time of t coast = t B T - t o f f > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnation pressure and fusion yield. Herein we show that the ablation pressure, pabl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing tcoast boosts pabl by as much as ˜ 2 × prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after toff to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ˜ 15 % higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small ( ˜ 5 % - 10 %) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ˜ 2 × as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Finally, we show how the high-foot implosion data is consistent with the above mentioned picture.

On the importance of minimizing “coast-time” in x-ray driven inertially confined fusion implosions

DOE PAGES

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.; ...

2017-09-01

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400×, making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, t off, well before bang-time, t BT, for a coast-time of t coast = t BT – t off > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnationmore » pressure and fusion yield. Herein we show that the ablation pressure, p abl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing t coast boosts p abl by as much as ~2× prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after t off to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ~15% higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small (~5%–10%) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ~2× as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Lastly, we show how the high-foot implosion data is consistent with the above mentioned picture.« less

On the importance of minimizing “coast-time” in x-ray driven inertially confined fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400×, making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, t off, well before bang-time, t BT, for a coast-time of t coast = t BT – t off > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnationmore » pressure and fusion yield. Herein we show that the ablation pressure, p abl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing t coast boosts p abl by as much as ~2× prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after t off to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ~15% higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small (~5%–10%) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ~2× as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Lastly, we show how the high-foot implosion data is consistent with the above mentioned picture.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A.; Kline, J. L.; Meezan, N.

The current high-foot and related implosions have adequate CR and implosion velocity to ignite, but require improved finesse particularly in, but not limited to, implosion symmetry. This is being pursued. The challenge of controlling drive symmetry is also motivating lower convergence ratio designs. These require higher velocity implosions and are also being pursued.

NIF Double Shell outer/inner shell collision experiments

NASA Astrophysics Data System (ADS)

Merritt, E. C.; Loomis, E. N.; Wilson, D. C.; Cardenas, T.; Montgomery, D. S.; Daughton, W. S.; Dodd, E. S.; Desjardins, T.; Renner, D. B.; Palaniyappan, S.; Batha, S. H.; Khan, S. F.; Smalyuk, V.; Ping, Y.; Amendt, P.; Schoff, M.; Hoppe, M.

2017-10-01

Double shell capsules are a potential low convergence path to substantial alpha-heating and ignition on NIF, since they are predicted to ignite and burn at relatively low temperatures via volume ignition. Current LANL NIF double shell designs consist of a low-Z ablator, low-density foam cushion, and high-Z inner shell with liquid DT fill. Central to the Double Shell concept is kinetic energy transfer from the outer to inner shell via collision. The collision determines maximum energy available for compression and implosion shape of the fuel. We present results of a NIF shape-transfer study: two experiments comparing shape and trajectory of the outer and inner shells at post-collision times. An outer-shell-only target shot measured the no-impact shell conditions, while an `imaging' double shell shot measured shell conditions with impact. The `imaging' target uses a low-Z inner shell and is designed to perform in similar collision physics space to a high-Z double shell but can be radiographed at 16keV, near the viable 2DConA BL energy limit. Work conducted under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396.

Laser Imprint Reduction with a Short Shaping Laser Pulse Incident Upon a Foam-Plastic Target

DTIC Science & Technology

2002-12-01

Corporation, McLean, VA 22150, and Physics Department, Nuclear Research Center Negev , P. O. Box 9001, Beer Sheva, Israel Alexander L. Velikovich and...plasma oscillate rather than grow. Density tailoring seems to improve radiative performance of Z-pinch plasma radiation sources: For example, the cross...efficiency of the density profile shaping described above for laser imprint mitigation. We now use the the FAST2D hydrocode in a 2-D mode. The radiation

X-Ray Laser Program Report for FY 1989

DTIC Science & Technology

1990-05-24

theoretical photopumped x-ray laser program also involves the use of a neon lasant plasma. However, that is the only similarity to the Na/Ne scheme described...K-shell neon Z pinch photons of energy hv > 900 eV, photoionize inner K-shell electrons from the neutral neon, leading to Auger decay from Ne II to...is generated by electrons which are produced in the photoionization of Ne I. For example, ionization by the Ly-a line produces 150-eV photoelectrons

In-flight observations of low-mode ρR asymmetries in NIF implosions

DOE PAGES

Zylstra, A. B.; Frenje, J. A.; Seguin, F. H.; ...

2015-05-01

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D 3He gas-filled implosions at the National Ignition Facility produce energetic protons via D+ 3He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3-5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%,more » which are interpreted as l=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.« less

In-flight observations of low-mode ρR asymmetries in NIF implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B., E-mail: zylstra@mit.edu; Frenje, J. A.; Séguin, F. H.

2015-05-15

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D{sup 3}He gas-filled implosions at the National Ignition Facility produce energetic protons via D+{sup 3}He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3–5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%,more » which are interpreted as ℓ=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.« less

The One-Dimensional Cryogenic Implosion Campaign on OMEGA: Modeling, Experiments, and a Statistical Approach to Predict and Understand Direct-Drive Implosions

NASA Astrophysics Data System (ADS)

Betti, R.

2017-10-01

The 1-D campaign on OMEGA is aimed at validating a novel approach to design cryogenic implosion experiments and provide valuable data to improve the accuracy of 1-D physics models. This new design methodology is being tested first on low-convergence, high-adiabat (α 6 to 7) implosions and will subsequently be applied to implosions with increasing convergence up to the level required for a hydro-equivalent demonstration of ignition. This design procedure assumes that the hydrodynamic codes used in implosion designs lack the necessary physics and that measurements of implosion properties are imperfect. It also assumes that while the measurements may have significant systematic errors, the shot-to-shot variations are small and that cryogenic implosion data are reproducible as observed on OMEGA. One of the goals of the 1-D campaign is to find a mapping of the data to the code results and use the mapping relations to design future implosions. In the 1-D campaign, this predictive methodology was used to design eight implosions using a simple two-shock pulse design, leading to pre-shot predictions of yields within 5% and ion temperatures within 4% of the experimental values. These implosions have also produced the highest neutron yield of 1014 in OMEGA cryogenic implosion experiments with an areal density of 100 mg/cm2. Furthermore, the results from this campaign have been used to test the validity of the 1-D physics models used in the radiation-hydrodynamics codes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DENA0001944 and LLNL under Contract DE-AC52-07NA27344. * In collaboration with J.P. Knauer, V. Gopalaswamy, D. Patel, K.M. Woo, K.S. Anderson, A. Bose, A.R. Christopherson, V.Yu. Glebov, F.J. Marshall, S.P. Regan, P.B. Radha, C. Stoeckl, and E.M. Campbell.

Influence of argon impurities on the elastic scattering of x-rays from imploding beryllium capsules

DOE PAGES

Saunders, A. M.; Chapman, D. A.; Kritcher, A. L.; ...

2018-03-01

Here, we investigate the effect of argon impurities on the elastic component of x-ray scattering spectra taken from directly driven beryllium capsule implosions at the OMEGA laser. The plasma conditions were obtained in a previous analysis [18] by fitting the inelastic scattering component. We show that the known argon impurity in the beryllium modifies the elastic scattering due to the larger number of bound electrons. We indeed find significant deviations in the elastic scattering from roughly 1 at.% argon contained in the beryllium. With knowledge of the argon impurity fraction, we use the elastic scattering component to determine the chargemore » state of the compressed beryllium, as the fits are rather insensitive to the argon charge state. Lastly, we discuss how doping small fractions of mid- or high-Z elements into low-Z materials could allow ionization balance studies in dense plasmas.« less

Enhanced electron/fuel-ion equilibration through impurity ions: Studies applicable to NIF and Omega

NASA Astrophysics Data System (ADS)

Petrasso, R. D.; Sio, H.; Kabadi, N.; Lahmann, B.; Simpson, R.; Parker, C.; Frenje, J.; Gatu Johnson, M.; Li, C. K.; Seguin, F. H.; Rinderknecht, H.; Casey, D.; Grabowski, P.; Graziani, F.; Taitano, W.; Le, A.; Chacon, L.; Hoffman, N.; Kagan, G.; Simakov, A.; Zylstra, A.; Rosenberg, M.; Betti, R.; Srinivasan, B.; Mancini, R.

2017-10-01

In shock-driven exploding-pushers, a platform used extensively to study multi-species and kinetic effects, electrons and fuel ions are far out of equilibrium, as reflected by very different temperatures. However, impurity ions, even in small quantities, can couple effectively to the electrons, because of a Z2 dependence, and in turn, impurity ions can then strongly couple to the fuel ions. Through this mechanism, electrons and fuel-ions can equilibrate much faster than they otherwise would. This is a quantitative issue, depending upon the amount and Z of the impurity. For NIF and Omega, we consider the role of this process. Coupled non-linear equations, reflecting the temperatures of the three species, are solved for a range of conditions. Consideration is also given to ablatively driven implosions, since impurities can similarly affect the equilibration. This work was supported in part by DOE/NNSA DE-NA0002949 and DE-NA0002726.

Influence of argon impurities on the elastic scattering of x-rays from imploding beryllium capsules

NASA Astrophysics Data System (ADS)

Saunders, A. M.; Chapman, D. A.; Kritcher, A. L.; Schoff, M.; Shuldberg, C.; Landen, O. L.; Glenzer, S. H.; Falcone, R. W.; Gericke, D. O.; Döppner, T.

2018-03-01

We investigate the effect of argon impurities on the elastic component of x-ray scattering spectra taken from directly driven beryllium capsule implosions at the OMEGA laser. The plasma conditions were obtained in a previous analysis [18] by fitting the inelastic scattering component. We show that the known argon impurity in the beryllium modifies the elastic scattering due to the larger number of bound electrons. We indeed find significant deviations in the elastic scattering from roughly 1 at.% argon contained in the beryllium. With knowledge of the argon impurity fraction, we use the elastic scattering component to determine the charge state of the compressed beryllium, as the fits are rather insensitive to the argon charge state. Finally, we discuss how doping small fractions of mid- or high-Z elements into low-Z materials could allow ionization balance studies in dense plasmas.

Compact submicrosecond, high current generator for wire explosion experiments

NASA Astrophysics Data System (ADS)

Aranchuk, L. E.; Chuvatin, A. S.; Larour, J.

2004-01-01

The PIAF generator was designed for low total energy and high energy density experiments with liners, X-pinch or fiber Z-pinch loads. These studies are of interest for such applications as surface and material science, microscopy of biological specimens, lithography of x-ray sensitive resists, and x-ray backlighting of pulsed-power plasmas. The generator is based on an RLC circuit that includes six NWL 180 nF-50 kV capacitors that store up to 1.3 kJ. The capacitors are connected in parallel to a single multispark switch designed to operate at atmospheric pressure. The switch allows reaching a time delay between the trigger pulse and the current pulse of less than 80 ns and has jitter of 6 ns. The total inductance without a load compartment was optimized to be as low as 16 nH, which leads to extremely low impedance of ˜0.12 Ω. A 40 kV initial voltage provides 250 kA maximum current in a 6 nH inductive load with a 180 ns current rise time. PIAF has dimensions of 660×660×490 mm and weight of less than 100 kg, thus manifesting itself as robust, simple to operate, and cost effective. A description of the PIAF generator and the initial experimental results on PIAF with an X-pinch type load are reported. The generator was demonstrated to operate successfully with an X-pinch type load. The experiments first started with investigation of the previously unexplored X-pinch conduction time range, 100 ns-1 μs. A single short radiation pulse was obtained that came from a small, point-like plasma. The following x-ray source characteristics were achieved: typical hot spot size of 50-100 μm, radiation pulse duration of 1.5-2 ns, and radiation yield of about 250-500 mJ in the softer spectral range (hν⩾700 eV) and 50-100 mJ in the harder one (hν⩾1 keV). These results provide the potential for further application of this source, such as use as a backlight diagnostic tool.

Design and testing of a magnetically driven implosion peak current diagnostic

NASA Astrophysics Data System (ADS)

Hess, M. H.; Peterson, K. J.; Ampleford, D. J.; Hutsel, B. T.; Jennings, C. A.; Gomez, M. R.; Dolan, D. H.; Robertson, G. K.; Payne, S. L.; Stygar, W. A.; Martin, M. R.; Sinars, D. B.

2018-04-01

A critical component of the magnetically driven implosion experiments at Sandia National Laboratories is the delivery of high-current, 10s of MA, from the Z pulsed power facility to a target. In order to assess the performance of the experiment, it is necessary to measure the current delivered to the target. Recent Magnetized Liner Inertial Fusion (MagLIF) experiments have included velocimetry diagnostics, such as PDV (Photonic Doppler Velocimetry) or Velocity Interferometer System for Any Reflector, in the final power feed section in order to infer the load current as a function of time. However, due to the nonlinear volumetrically distributed magnetic force within a velocimetry flyer, a complete time-dependent load current unfold is typically a time-intensive process and the uncertainties in the unfold can be difficult to assess. In this paper, we discuss how a PDV diagnostic can be simplified to obtain a peak current by sufficiently increasing the thickness of the flyer. This effectively keeps the magnetic force localized to the flyer surface, resulting in fast and highly accurate measurements of the peak load current. In addition, we show the results of experimental peak load current measurements from the PDV diagnostic in recent MagLIF experiments.

Reconstruction of Axial Energy Deposition in Magnetic Liner Inertial Fusion Based on PECOS Shadowgraph Unfolds Using the AMR Code FLASH

NASA Astrophysics Data System (ADS)

Adams, Marissa; Jennings, Christopher; Slutz, Stephen; Peterson, Kyle; Gourdain, Pierre; U. Rochester-Sandia Collaboration

2017-10-01

Magnetic Liner Inertial Fusion (MagLIF) experiments incorporate a laser to preheat a deuterium filled capsule before compression via a magnetically imploding liner. In this work, we focus on the blast wave formed in the fuel during the laser preheat component of MagLIF, where approximately 1kJ of energy is deposited in 3ns into the capsule axially before implosion. To model blast waves directly relevant to experiments such as MagLIF, we inferred deposited energy from shadowgraphy of laser-only experiments preformed at the PECOS target chamber using the Z-Beamlet laser. These energy profiles were used to initialize 2-dimensional simulations using by the adaptive mesh refinement code FLASH. Gradients or asymmetries in the energy deposition may seed instabilities that alter the fuel's distribution, or promote mix, as the blast wave interacts with the liner wall. The AMR capabilities of FLASH allow us to study the development and dynamics of these instabilities within the fuel and their effect on the liner before implosion. Sandia Natl Labs is managed by NTES of Sandia, LLC., a subsidiary of Honeywell International, Inc, for the U.S. DOEs NNSA under contract DE-NA0003525.

Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma.

PubMed

Marshall, F J; Radha, P B

2014-11-01

A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

X-ray Spectropolarimetry of Z-pinch Plasmas with a Single-Crystal Technique

NASA Astrophysics Data System (ADS)

Wallace, Matt; Haque, Showera; Neill, Paul; Pereira, Nino; Presura, Radu

2017-10-01

When directed beams of energetic electrons exist in a plasma the resulting x-rays emitted by the plasma can be partially polarized. This makes plasma x-ray polarization spectroscopy, spectropolarimetry, useful for revealing information about the anisotropy of the electron velocity distribution. X-ray spectropolarimetry has indeed been used for this in both space and laboratory plasmas. X-ray polarization measurements are typically performed employing two crystals, both at a 45° Bragg angle. A single-crystal spectropolarimeter can replace two crystal schemes by utilizing two matching sets of internal planes for polarization-splitting. The polarization-splitting planes diffract the incident x-rays into two directions that are perpendicular to each other and the incident beam as well, so the two sets of diffracted x-rays are linearly polarized perpendicularly to each other. An X-cut quartz crystal with surface along the [11-20] planes and a paired set of [10-10] planes in polarization-splitting orientation is now being used on aluminum z-pinches at the University of Nevada, Reno. Past x-ray polarization measurements have been reserved for point-like sources. Recently a slotted collimating aperture has been used to maintain the required geometry for polarization-splitting enabling the spectropolarimetry of extended sources. The design of a single-crystal x-ray spectropolarimeter and experimental results will be presented. Work was supported by U.S. DOE, NNSA Grant DE-NA0001834 and cooperative agreement DE-FC52-06NA27616.

Nonlinear ideal magnetohydrodynamics instabilities

NASA Astrophysics Data System (ADS)

Pfirsch, D.; Sudan, R. N.

1993-07-01

Explosive phenomena such as internal disruptions in toroidal discharges and solar flares are difficult to explain in terms of linear instabilities. A plasma approaching a linear stability limit can, however, become nonlinearly and explosively unstable, with noninfinitesimal perturbations even before the marginal state is reached. For such investigations, a nonlinear extension of the usual MHD (magnetohydrodynamic) energy principle is helpful. (This was obtained by Merkel and Schlüter, Sitzungsberichted. Bayer. Akad. Wiss., Munich, 1976, No. 7, for Cartesian coordinate systems.) A coordinate system independent Eulerian formulation for the Lagrangian allowing for equilibria with flow and with built-in conservation laws for mass, magnetic flux, and entropy is developed in this paper which is similar to Newcomb's Lagrangian method of 1962 [Nucl. Fusion, Suppl., Pt. II, 452 (1962)]. For static equilibria nonlinear stability is completely determined by the potential energy. For a potential energy which contains second- and nth order or some more general contributions only, it is shown in full generality that linearly unstable and marginally stable systems are explosively unstable even for infinitesimal perturbations; linearly absolutely stable systems require finite initial perturbations. For equilibria with Abelian symmetries symmetry breaking initial perturbations are needed, which should be observed in numerical simulations. Nonlinear stability is proved for two simple examples, m=0 perturbations of a Bennet Z-pinch and z-independent perturbations of a θ pinch. The algebra for treating these cases reduces considerably if symmetries are taken into account from the outset, as suggested by M. N. Rosenbluth (private communication, 1992).

Capsule Performance Optimization for the National Ignition Facility

NASA Astrophysics Data System (ADS)

Landen, Otto

2009-11-01

The overall goal of the capsule performance optimization campaign is to maximize the probability of ignition by experimentally correcting for likely residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models before proceeding to cryogenic-layered implosions and ignition attempts. This will be accomplished using a variety of targets that will set key laser, hohlraum and capsule parameters to maximize ignition capsule implosion velocity, while minimizing fuel adiabat, core shape asymmetry and ablator-fuel mix. The targets include high Z re-emission spheres setting foot symmetry through foot cone power balance [1], liquid Deuterium-filled ``keyhole'' targets setting shock speed and timing through the laser power profile [2], symmetry capsules setting peak cone power balance and hohlraum length [3], and streaked x-ray backlit imploding capsules setting ablator thickness [4]. We will show how results from successful tuning technique demonstration shots performed at the Omega facility under scaled hohlraum and capsule conditions relevant to the ignition design meet the required sensitivity and accuracy. We will also present estimates of all expected random and systematic uncertainties in setting the key ignition laser and target parameters due to residual measurement, calibration, cross-coupling, surrogacy, and scale-up errors, and show that these get reduced after a number of shots and iterations to meet an acceptable level of residual uncertainty. Finally, we will present results from upcoming tuning technique validation shots performed at NIF at near full-scale. Prepared by LLNL under Contract DE-AC52-07NA27344. [4pt] [1] E. Dewald, et. al. Rev. Sci. Instrum. 79 (2008) 10E903. [0pt] [2] T.R. Boehly, et. al., Phys. Plasmas 16 (2009) 056302. [0pt] [3] G. Kyrala, et. al., BAPS 53 (2008) 247. [0pt] [4] D. Hicks, et. al., BAPS 53 (2008) 2.

Using multiple secondary fusion products to evaluate fuel ρR, electron temperature, and mix in deuterium-filled implosions at the NIF

DOE PAGES

Rinderknecht, H. G.; Rosenberg, M. J.; Zylstra, A. B.; ...

2015-08-25

In deuterium-filled inertial confinement fusion implosions, the secondary fusion processes D( 3He,p) 4He and D(T,n) 4He occur, as the primary fusion products 3He and T react in flight with thermal deuterons. In implosions with moderate fuel areal density (~ 5–100 mg/cm 2), the secondary D- 3He reaction saturates, while the D-T reaction does not, and the combined information from these secondary products is used to constrain both the areal density and either the plasma electron temperature or changes in the composition due to mix of shell material into the fuel. The underlying theory of this technique is developed and appliedmore » to three classes of implosions on the National Ignition Facility: direct-drive exploding pushers, indirect-drive 1-shock and 2-shock implosions,and polar direct-drive implosions. In the 1- and 2-shock implosions, the electron temperature is inferred to be 0.65 x and 0.33 x the burn-averaged ion temperature, respectively. The inferred mixed mass in the polar direct-drive implosions is in agreement with measurements using alternative techniques.« less

Two-dimensional implosion simulations with a kinetic particle code [2D implosion simulations with a kinetic particle code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagert, Irina; Even, Wesley Paul; Strother, Terrance Timothy

Here, we perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focusmore » on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.« less

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

NASA Astrophysics Data System (ADS)

Hansen, E. C.; Barnak, D. H.; Betti, R.; Campbell, E. M.; Chang, P.-Y.; Davies, J. R.; Glebov, V. Yu; Knauer, J. P.; Peebles, J.; Regan, S. P.; Sefkow, A. B.

2018-05-01

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1D code LILAC was used to model the central region of the implosion, and results were compared to 2D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysis shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.

Subscale HDC implosions driven at high radiation temperature using advanced hohlraums

NASA Astrophysics Data System (ADS)

Ho, D.; Amendt, P.; Jones, O.; Berzak Hopkins, L.; Le Pape, S.

2017-10-01

Implosions using HDC ablators have received increased attention because of shorter pulse length and can access higher implosion velocity than CH ablators. Recent HDC midscale (979 m radius) implosion experiments have achieved DT neutron yields of 1.5e16. Our 2D simulations show that subscale (890 m radius) HDC capsules can achieve robust high-yield performance if driven at high enough radiation temperature 330 eV, because the penalty for less fuel mass can be offset by higher implosion velocity. To achieve 330 eV will likely require the use of innovative hohlraum concepts, e.g., subscale rugby-shaped hohlraum using 1.3 MJ of laser energy without incurring a risk of high laser backscatter. Radiation symmetry is currently under study. Confidence in our modeling of HDC implosions is high in part because our 2D modeling of recent HDC implosions experiments show good agreement with data. Work performed under auspices of U.S. DOE by LLNL under 15-ERD-058.

Two-dimensional implosion simulations with a kinetic particle code [2D implosion simulations with a kinetic particle code

DOE PAGES

Sagert, Irina; Even, Wesley Paul; Strother, Terrance Timothy

2017-05-17

Here, we perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focusmore » on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.« less

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE PAGES

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho; ...

2017-05-23

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Fire suppression as a thermal implosion

NASA Astrophysics Data System (ADS)

Novozhilov, Vasily

2017-01-01

The present paper discusses the possibility of the thermal implosion scenario. This process would be a reverse of the well known thermal explosion (autoignition) phenomenon. The mechanism for thermal implosion scenario is proposed which involves quick suppression of the turbulent diffusion flame. Classical concept of the thermal explosion is discussed first. Then a possible scenario for the reverse process (thermal implosion) is discussed and illustrated by a relevant mathematical model. Based on the arguments presented in the paper, thermal implosion may be observed as an unstable equilibrium point on the generalized Semenov diagram for turbulent flame, however this hypothesis requires ultimate experimental confirmation.

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Wellbottom fluid implosion treatment system

DOEpatents

Brieger, Emmet F.

2001-01-01

A system for inducing implosion shock forces on perforation traversing earth formations with fluid pressure where an implosion tool is selected relative to a shut in well pressure and a tubing pressure to have a large and small area piston relationship in a well tool so that at a predetermined tubing pressure the pistons move a sufficient distance to open an implosion valve which permits a sudden release of well fluid pressure into the tubing string and produces an implosion force on the perforations. A pressure gauge on the well tool records tubing pressure and well pressure as a function of time.

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Weber, C. R.; Milovich, J. L.

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This study describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Finally, for both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Weber, C. R.; Milovich, J. L.

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This paper describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. For both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE PAGES

Clark, D. S.; Weber, C. R.; Milovich, J. L.; ...

2016-03-14

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This study describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Finally, for both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

Hybrid strategy for increasing fusion performance and stagnation pressure in x-ray driven inertially confined fusion implosions on the NIF

NASA Astrophysics Data System (ADS)

Hurricane, O. A.; Callahan, D. A.; Edwards, M. J.; Casey, D.; Doeppner, T.; Hohenberger, M.; Hinkel, D.; Berzak Hopkins, L.; Le Pape, S.; MacLaren, S.; Masse, L.; Thomas, C.; Zylstra, A.

2017-10-01

Post NIC (2012), more stable and lower convergence implosions were developed and used as part of a `basecamp' strategy to identify obstacles to further performance. From 2013-2015 by probing away from a conservative working implosion in-steps towards conditions of higher velocity and compression, `Fuel Gain' and alpha-heating were obtained. In the process, performance cliffs unrelated to `mix' were identified the most impactful of which were symmetry control of the implosion and hydro seeded by engineering features. From 2015-2017 we focused on mitigating poor symmetry control and engineering improvements on fill-tubes and capsule mounting techniques. The results were more efficient implosions that can obtain the same performance levels as the earlier implosions, but with less laser energy. Presently, the best of these implosions is poised to step into a burning plasma state. Here, we describe the next step in our strategy that involves using the data we've acquired across parameter space to make a step to the largest symmetric implosions that can be fielded on NIF with the energy available. We describe the key principles that form the foundation of this approach. Performed under the auspices of U.S. Dept. of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

In-flight observations of low-mode ρR asymmetries in NIF implosionsa)

NASA Astrophysics Data System (ADS)

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; Rygg, J. R.; Kritcher, A.; Rosenberg, M. J.; Rinderknecht, H. G.; Hicks, D. G.; Friedrich, S.; Bionta, R.; Meezan, N. B.; Olson, R.; Atherton, J.; Barrios, M.; Bell, P.; Benedetti, R.; Berzak Hopkins, L.; Betti, R.; Bradley, D.; Callahan, D.; Casey, D.; Collins, G.; Dewald, E. L.; Dixit, S.; Döppner, T.; Edwards, M. J.; Gatu Johnson, M.; Glenn, S.; Grim, G.; Hatchett, S.; Jones, O.; Khan, S.; Kilkenny, J.; Kline, J.; Knauer, J.; Kyrala, G.; Landen, O.; LePape, S.; Li, C. K.; Lindl, J.; Ma, T.; Mackinnon, A.; Manuel, M. J.-E.; Meyerhofer, D.; Moses, E.; Nagel, S. R.; Nikroo, A.; Parham, T.; Pak, A.; Petrasso, R. D.; Prasad, R.; Ralph, J.; Robey, H. F.; Ross, J. S.; Sangster, T. C.; Sepke, S.; Sinenian, N.; Sio, H. W.; Spears, B.; Tommasini, R.; Town, R.; Weber, S.; Wilson, D.; Yeamans, C.; Zacharias, R.

2015-05-01

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D3He gas-filled implosions at the National Ignition Facility produce energetic protons via D+3He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3-5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳ 10 % , which are interpreted as ℓ = 2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained ("no-coast"), implying a significant time-dependent asymmetry in peak drive.

Dose-current discharge correlation analysis in a Mather type Plasma Focus device for medical applications

NASA Astrophysics Data System (ADS)

Sumini, M.; Mostacci, D.; Tartari, A.; Mazza, A.; Cucchi, G.; Isolan, L.; Buontempo, F.; Zironi, I.; Castellani, G.

2017-11-01

In a Plasma Focus device the plasma collapses into the pinch where it reaches thermonuclear conditions for a few tens of nanoseconds, becoming a multi-radiation source. The nature of the radiation generated depends on the gas filling the chamber and the device working parameters. The self-collimated electron beam generated in the backward direction with respect to the plasma motion is one of the main radiation sources of interest also for medical applications. The electron beam may be guided against a high Z material target to produce an X-ray beam. This technique offers an ultra-high dose rate source of X-rays, able to deliver during the pinch a massive dose (up to 1 Gy per discharge for the PFMA-3 test device), as measured with EBT3 GafchromicⒸfilm tissue equivalent dosimeters. Given the stochastic behavior of the discharge process, a reliable on-line estimate of the dose-delivered is a very challenging task, in some way preventing a systematic application as a potentially interesting therapy device. This work presents an approach to linking the dose registered by the EBT3 GafchromicⒸfilms with the information contained in the signal recorded during the current discharge process. Processing the signal with the Wigner-Ville distribution, a spectrogram was obtained, displaying the information on intensity at various frequency scales, identifying the band of frequencies representative of the pinch events and define some patterns correlated with the dose.

Particle-In-Cell Modeling For MJ Dense Plasma Focus with Varied Anode Shape

NASA Astrophysics Data System (ADS)

Link, A.; Halvorson, C.; Schmidt, A.; Hagen, E. C.; Rose, D.; Welch, D.

2014-10-01

Megajoule scale dense plasma focus (DPF) Z-pinches with deuterium gas fill are compact devices capable of producing 1012 neutrons per shot but past predictive models of large-scale DPF have not included kinetic effects such as ion beam formation or anomalous resistivity. We report on progress of developing a predictive DPF model by extending our 2D axisymmetric collisional kinetic particle-in-cell (PIC) simulations to the 1 MJ, 2 MA Gemini DPF using the PIC code LSP. These new simulations incorporate electrodes, an external pulsed-power driver circuit, and model the plasma from insulator lift-off through the pinch phase. The simulations were performed using a new hybrid fluid-to-kinetic model transitioning from a fluid description to a fully kinetic PIC description during the run-in phase. Simulations are advanced through the final pinch phase using an adaptive variable time-step to capture the fs and sub-mm scales of the kinetic instabilities involved in the ion beam formation and neutron production. Results will be present on the predicted effects of different anode configurations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (11-ERD-063) and the Computing Grand Challenge program at LLNL. This work supported by Office of Defense Nuclear Nonproliferation Research and Development within U.S. Department of Energy's National Nuclear Security Administration.

Numerical simulations of Z-Pinch experiments to create supersonic differentially-rotating plasma flows

NASA Astrophysics Data System (ADS)

Bocchi, M.; Ummels, B.; Chittenden, J. P.; Lebedev, S. V.

2012-02-01

In the context of high energy density laboratory astrophysics, we aim to produce and study a rotating plasma relevant to accretion discs physics. We devised an experimental setup based on a modified cylindrical wire array and we studied it numerically with the three-dimensional, resistive magneto-hydrodynamic code GORGON. The simulations show that a rotating plasma cylinder is formed, with typical rotation velocity ~35 km/s and Mach number ~5. In addition, the plasma ring is differentially rotating and strongly radiatively cooled. The introduction of external magnetic fields is discussed.

Noise and sensitivity of x-ray framing cameras at Nike (abstract)

NASA Astrophysics Data System (ADS)

Pawley, C. J.; Deniz, A. V.; Lehecka, T.

1999-01-01

X-ray framing cameras are the most widely used tool for radiographing density distributions in laser and Z-pinch driven experiments. The x-ray framing cameras that were developed specifically for experiments on the Nike laser system are described. One of these cameras has been coupled to a CCD camera and was tested for resolution and image noise using both electrons and x rays. The largest source of noise in the images was found to be due to low quantum detection efficiency of x-ray photons.

X-Ray Laser Program Final Report for FY91

DTIC Science & Technology

1992-09-16

from a Na z pinch is used to photoionize Ne to the He-like ground state and radiation from the Na 1 s 2-1 s2p 1P1 transition is used to resonantly...creating photopumped x-ray lasers2 , imploding inertial confinement fusion capsules, 3 and studying the photoionization kinetics of plasmas in intense...has received extensive theoretical study, 5 -8 employs radiation from the 1s2 -1s2p 1P1 transition at 11.0027 A in He-like Na to resonantly photoexcite

Isochoric Implosions for Fast Ignition

NASA Astrophysics Data System (ADS)

Clark, Daniel; Tabak, Max

2006-10-01

Various gain models have shown the potentially great advantages of Fast Ignition (FI) Inertial Confinement Fusion (ICF) over its conventional hotspot ignition counterpart. These gain models, however, all assume nearly uniform-density fuel assemblies. By contrast, typical ICF implosions yield hollowed fuel assemblies with a high-density shell of fuel surrounding a low-density, high-pressure hotspot. To realize fully the advantages of FI, then, an alternative implosion design must be found which yields nearly isochoric fuel assemblies without substantial hotspots. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley [Luftfahrtforschung 19, 302 (1942)] may be employed to yield precisely such quasi-isochoric imploded states. The difficulty remains, however, of accessing these self-similarly imploding configurations from initial conditions representing an actual ICF target, namely a uniform, solid-density shell at rest. Furthermore, these specialized implosions must be realized for practicable drive parameters, i.e., accessible peak pressures, shell aspect ratios, etc. An implosion scheme is presented which meets all of these requirements, suggesting the possibility of genuinely isochoric implosions for FI.

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, E. C.; Barnak, D. H.; Betti, R.

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE PAGES

Hansen, E. C.; Barnak, D. H.; Betti, R.; ...

2018-04-04

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A., E-mail: abos@lle.rochester.edu; Woo, K. M.; Betti, R.

2015-07-15

The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of χ{sub Ω} ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Woo, K. M.; Nora, R.

2015-07-02

The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of ΧΩ ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

A novel feedback algorithm for simulating controlled dynamics and confinement in the advanced reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahlin, J.-E.; Scheffel, J.

2005-06-15

In the advanced reversed-field pinch (RFP), the current density profile is externally controlled to diminish tearing instabilities. Thus the scaling of energy confinement time with plasma current and density is improved substantially as compared to the conventional RFP. This may be numerically simulated by introducing an ad hoc electric field, adjusted to generate a tearing mode stable parallel current density profile. In the present work a current profile control algorithm, based on feedback of the fluctuating electric field in Ohm's law, is introduced into the resistive magnetohydrodynamic code DEBSP [D. D. Schnack and D. C. Baxter, J. Comput. Phys. 55,more » 485 (1984); D. D. Schnack, D. C. Barnes, Z. Mikic, D. S. Marneal, E. J. Caramana, and R. A. Nebel, Comput. Phys. Commun. 43, 17 (1986)]. The resulting radial magnetic field is decreased considerably, causing an increase in energy confinement time and poloidal {beta}. It is found that the parallel current density profile spontaneously becomes hollow, and that a formation, being related to persisting resistive g modes, appears close to the reversal surface.« less

Time resolved EUV spectra from Zpinching capillary discharge plasma

NASA Astrophysics Data System (ADS)

Jancarek, Alexandr; Nevrkla, Michal; Nawaz, Fahad

2015-09-01

We developed symmetrically charged driver to obtain high voltage, high current Z-pinching capillary discharge. Plasma is created by up to 70 kA, 29 ns risetime current pulse passing through a 5 mm inner diameter, 224 mm long capillary filled with gas to initial pressure in the range of 1 kPa. Due to the low inductance design of the driver, the pinch is observable directly from the measured current curve. Time-integrated and time-resolved spectra of discharge plasma radiation are recorded together with the capillary current and analyzed. The most encouraging spectra were captured in the wavelength range 8.3 ÷ 14 nm. This spectral region contains nitrogen Balmer series lines including potentially lasing NVII 2 - 3 transition. Spectral lines are identified in the NIST database using the FLY kinetic code. The line of 13.38 nm wavelength, transition NVII 2 - 3, was observed in gated, and also in time-integrated spectra for currents >60 kA. This work has been supported by the Ministry of Education, Youth and Sports of the Czech Republic grants LG13029.

A simple method to prevent hard X-ray-induced preheating effects inside the cone tip in indirect-drive fast ignition implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Dongxiao; Shan, Lianqiang; Zhou, Weimin

During fast-ignition implosions, preheating of inside the cone tip caused by hard X-rays can strongly affect the generation and transport of hot electrons in the cone. Although indirect-drive implosions have a higher implosion symmetry, they cause stronger preheating effects than direct-drive implosions. To control the preheating of the cone tip, we propose the use of indirect-drive fast-ignition targets with thicker tips. Experiments carried out at the ShenGuang-III prototype laser facility confirmed that thicker tips are effective for controlling preheating. Moreover, these results were consistent with those of 1D radiation hydrodynamic simulations.

Developing one-dimensional implosions for inertial confinement fusion science

DOE PAGES

Kline, John L.; Yi, Sunghwan A.; Simakov, Andrei Nikolaevich; ...

2016-12-12

Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains. To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where 1D means measured yield overmore » the 1D clean calculation. A high adiabat, low convergence platform is being developed using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However, double shell targets have a different set of trade-off versus advantages. As a result, details for each of these approaches are described.« less

High-resolution, detailed simulations of low foot and high foot implosion experiments on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Clark, Daniel

2015-11-01

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensional (3-D) character of the flow, accurately modeling NIF implosions remains at the edge of current radiation hydrodynamics simulation capabilities. This talk describes the current state of progress of 3-D, high-resolution, capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Most importantly, it is found that a single, standard simulation methodology appears adequate to model both implosion types and gives confidence that such a model can be used to guide future implosion designs toward ignition. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Characterization of laser-cut copper foil X-pinches

NASA Astrophysics Data System (ADS)

Collins, G. W.; Valenzuela, J. C.; Hansen, S. B.; Wei, M. S.; Reed, C. T.; Forsman, A. C.; Beg, F. N.

2016-10-01

Quantitative data analyses of laser-cut Cu foil X-pinch experiments on the 150 ns quarter-period, ˜250 kA GenASIS driver are presented. Three different foil designs are tested to determine the effects of initial structure on pinch outcome. Foil X-pinch data are also presented alongside the results from wire X-pinches with comparable mass. The X-ray flux and temporal profile of the emission from foil X-pinches differed significantly from that of wire X-pinches, with all emission from the foil X-pinches confined to a ˜3 ns period as opposed to the delayed, long-lasting electron beam emission common in wire X-pinches. Spectroscopic data show K-shell as well as significant L-shell emission from both foil and wire X-pinches. Fits to synthetic spectra using the SCRAM code suggest that pinching foil X's produced a ˜1 keV, ne ≥ 1023 cm-3 plasma. The spectral data combined with the improved reliability of the source timing, flux, and location indicate that foil X-pinches generate a reproducible, K-shell point-projection radiography source that can be easily modified and tailored to suit backlighting needs across a variety of applications.

Inertial confinement fusion ablator physics experiments on Saturn and Nova

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, R.E.; Porter, J.L.; Chandler, G.A.

1997-05-01

The Saturn pulsed power accelerator [R. B. Spielman {ital et al.}, in {ital Proceedings of the 2nd International Conference on Dense} Z-{ital pinches}, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] at Sandia National Laboratories (SNL) and the Nova laser [J. T. Hunt and D. R. Speck, Opt. Eng. {bold 28}, 461 (1989)] at Lawrence Livermore National Laboratory (LLNL) have been used to explore techniques for studying the behavior of ablator material in x-ray radiation environments comparable in magnitude, spectrum, and duration to those thatmore » would be experienced in National Ignition Facility (NIF) hohlraums [J. D. Lindl, Phys. Plasmas {bold 2}, 3933 (1995)]. The large x-ray outputs available from the Saturn pulsed-power-driven z pinch have enabled us to drive hohlraums of full NIF ignition scale size at radiation temperatures and time scales comparable to those required for the low-power foot pulse of an ignition capsule. The high-intensity drives available in the Nova laser have allowed us to study capsule ablator physics in smaller-scale hohlraums at radiation temperatures and time scales relevant to the peak power pulse for an ignition capsule. Taken together, these experiments have pointed the way to possible techniques for testing radiation-hydrodynamics code predictions of radiation flow, opacity, equation of state, and ablator shock velocity over the range of radiation environments that will be encountered in a NIF hohlraum. {copyright} {ital 1997 American Institute of Physics.}« less

Nonlinear ideal magnetohydrodynamics instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfirsch, D.; Sudan, R.N.

1993-07-01

Explosive phenomena such as internal disruptions in toroidal discharges and solar flares are difficult to explain in terms of linear instabilities. A plasma approaching a linear stability limit can, however, become nonlinearly and explosively unstable, with noninfinitesimal perturbations even before the marginal state is reached. For such investigations, a nonlinear extension of the usual MHD (magnetohydrodynamic) energy principle is helpful. (This was obtained by Merkel and Schlueter, Sitzungsberichted. Bayer. Akad. Wiss., Munich, 1976, No. 7, for Cartesian coordinate systems.) A coordinate system independent Eulerian formulation for the Lagrangian allowing for equilibria with flow and with built-in conservation laws for mass,more » magnetic flux, and entropy is developed in this paper which is similar to Newcomb's Lagrangian method of 1962 [Nucl. Fusion, Suppl., Pt. II, 452 (1962)]. For static equilibria nonlinear stability is completely determined by the potential energy. For a potential energy which contains second- and [ital n]th order or some more general contributions only, it is shown in full generality that linearly unstable and marginally stable systems are explosively unstable even for infinitesimal perturbations; linearly absolutely stable systems require finite initial perturbations. For equilibria with Abelian symmetries symmetry breaking initial perturbations are needed, which should be observed in numerical simulations. Nonlinear stability is proved for two simple examples, [ital m]=0 perturbations of a Bennet Z-pinch and [ital z]-independent perturbations of a [theta] pinch. The algebra for treating these cases reduces considerably if symmetries are taken into account from the outset, as suggested by M. N. Rosenbluth (private communication, 1992).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awe, T. J., E-mail: tjawe@sandia.gov; Jennings, C. A.; McBride, R. D.

Recent experiments at the Sandia National Laboratories Z Facility have, for the first time, studied the implosion dynamics of magnetized liner inertial fusion (MagLIF) style liners that were pre-imposed with a uniform axial magnetic field. As reported [T. J. Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] when premagnetized with a 7 or 10 T axial field, these liners developed 3D-helix-like hydrodynamic instabilities; such instabilities starkly contrast with the azimuthally correlated magneto-Rayleigh-Taylor (MRT) instabilities that have been consistently observed in many earlier non-premagnetized experiments. The helical structure persisted throughout the implosion, even though the azimuthal drive field greatly exceeded themore » expected axial field at the liner's outer wall for all but the earliest stages of the experiment. Whether this modified instability structure has practical importance for magneto-inertial fusion concepts depends primarily on whether the modified instability structure is more stable than standard azimuthally correlated MRT instabilities. In this manuscript, we discuss the evolution of the helix-like instability observed on premagnetized liners. While a first principles explanation of this observation remains elusive, recent 3D simulations suggest that if a small amplitude helical perturbation can be seeded on the liner's outer surface, no further influence from the axial field is required for the instability to grow.« less

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

DOE PAGES

Smalyuk, V. A.; Robey, H. F.; Döppner, T.; ...

2015-08-27

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.

A near one-dimensional indirectly driven implosion at convergence ratio 30

NASA Astrophysics Data System (ADS)

MacLaren, S. A.; Masse, L. P.; Czajka, C. E.; Khan, S. F.; Kyrala, G. A.; Ma, T.; Ralph, J. E.; Salmonson, J. D.; Bachmann, B.; Benedetti, L. R.; Bhandarkar, S. D.; Bradley, P. A.; Hatarik, R.; Herrmann, H. W.; Mariscal, D. A.; Millot, M.; Patel, P. K.; Pino, J. E.; Ratledge, M.; Rice, N. G.; Tipton, R. E.; Tommasini, R.; Yeamans, C. B.

2018-05-01

Inertial confinement fusion cryogenic-layered implosions at the National Ignition Facility, while successfully demonstrating self-heating due to alpha-particle deposition, have fallen short of the performance predicted by one-dimensional (1D) multi-physics implosion simulations. The current understanding, from experimental evidence as well as simulations, suggests that engineering features such as the capsule tent and fill tube, as well as time-dependent low-mode asymmetry, are to blame for the lack of agreement. A short series of experiments designed specifically to avoid these degradations to the implosion are described here in order to understand if, once they are removed, a high-convergence cryogenic-layered deuterium-tritium implosion can achieve the 1D simulated performance. The result is a cryogenic layered implosion, round at stagnation, that matches closely the performance predicted by 1D simulations. This agreement can then be exploited to examine the sensitivity of approximations in the model to the constraints imposed by the data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A., E-mail: hurricane1@llnl.gov; Callahan, D. A.; Casey, D. T.

The “High-Foot” platform manipulates the laser pulse-shape coming from the National Ignition Facility laser to create an indirect drive 3-shock implosion that is significantly more robust against instability growth involving the ablator and also modestly reduces implosion convergence ratio. This strategy gives up on theoretical high-gain in an inertial confinement fusion implosion in order to obtain better control of the implosion and bring experimental performance in-line with calculated performance, yet keeps the absolute capsule performance relatively high. In this paper, we will cover the various experimental and theoretical motivations for the high-foot drive as well as cover the experimental resultsmore » that have come out of the high-foot experimental campaign. At the time of this writing, the high-foot implosion has demonstrated record total deuterium-tritium yields (9.3×10{sup 15}) with low levels of inferred mix, excellent agreement with implosion simulations, fuel energy gains exceeding unity, and evidence for the “bootstrapping” associated with alpha-particle self-heating.« less

Progress of LMJ-relevant implosions experiments on OMEGA

NASA Astrophysics Data System (ADS)

Casner, A.; Philippe, F.; Tassin, V.; Seytor, P.; Monteil, M.-C.; Gauthier, P.; Park, H. S.; Robey, H.; Ross, J.; Amendt, P.; Girard, F.; Villette, B.; Reverdin, C.; Loiseau, P.; Caillaud, T.; Landoas, O.; Li, C. K.; Petrasso, R.; Seguin, F.; Rosenberg, M.; Renaudin, P.

2013-11-01

In preparation of the first ignition attempts on the Laser Mégajoule (LMJ), an experimental program is being pursued on OMEGA to investigate LMJ-relevant hohlraums. First, radiation temperature levels close to 300 eV were recently achieved in reduced-scale hohlraums with modest backscatter losses. Regarding the baseline target design for fusion experiments on LMJ, an extensive experimental database has also been collected for scaled implosions experiments in both empty and gas-filled rugby-shaped hohlraums. We acquired a full picture of hohlraum energetics and implosion dynamics. Not only did the rugby hohlraums show significantly higher x-ray drive energy over the cylindrical hohlraums, but symmetry control by power balance was demonstrated, as well as high-performance D2 implosions enabling the use of a complete suite of neutrons diagnostics. Charged particle diagnostics provide complementary insights into the physics of these x-ray driven implosions. An overview of these results demonstrates our ability to control the key parameters driving the implosion, lending more confidence in extrapolations to ignition-scale targets.

Progress in detailed modelling of low foot and high foot implosion experiments on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Clark, D. S.; Weber, C. R.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Kritcher, A. L.; Marinak, M. M.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.

2016-05-01

Several dozen high convergence inertial confinement fusion ignition experiments have now been completed on the National Ignition Facility (NIF). These include both “low foot” experiments from the National Ignition Campaign (NIC) and more recent “high foot” experiments. At the time of the NIC, there were large discrepancies between simulated implosion performance and experimental data. In particular, simulations over predicted neutron yields by up to an order of magnitude, and some experiments showed clear evidence of mixing of ablator material deep into the hot spot that could not be explained at the time. While the agreement between data and simulation improved for high foot implosion experiments, discrepancies nevertheless remain. This paper describes the state of detailed modelling of both low foot and high foot implosions using 1-D, 2-D, and 3-D radiation hydrodynamics simulations with HYDRA. The simulations include a range of effects, in particular, the impact of the plastic membrane used to support the capsule in the hohlraum, as well as low-mode radiation asymmetries tuned to match radiography measurements. The same simulation methodology is applied to low foot NIC implosion experiments and high foot implosions, and shows a qualitatively similar level of agreement for both types of implosions. While comparison with the experimental data remains imperfect, a reasonable level of agreement is emerging and shows a growing understanding of the high-convergence implosions being performed on NIF.

Double shell planar experiments on OMEGA

NASA Astrophysics Data System (ADS)

Dodd, E. S.; Merritt, E. C.; Palaniyappan, S.; Montgomery, D. S.; Daughton, W. S.; Schmidt, D. W.; Cardenas, T.; Wilson, D. C.; Loomis, E. N.; Batha, S. H.; Ping, Y.; Smalyuk, V. A.; Amendt, P. A.

2017-10-01

The double shell project is aimed at fielding neutron-producing capsules at the National Ignition Facility (NIF), in which an outer low-Z ablator collides with an inner high-Z shell to compress the fuel. However, understanding these targets experimentally can be challenging when compared with conventional single shell targets. Halfraum-driven planar targets at OMEGA are being used to study physics issues important to double shell implosions outside of a convergent geometry. Both VISAR and radiography through a tube have advantages over imaging through the hohlraum and double-shell capsule at NIF. A number physics issues are being studied with this platform that include 1-d and higher dimensional effects such as defect-driven hydrodynamic instabilities from engineering features. Additionally, the use of novel materials with controlled density gradients require study in easily diagnosed 1-d systems. This work ultimately feeds back into the NIF capsule platform through manufacturing tolerances set using data from OMEGA. Supported under the US DOE by the LANS, LLC under contract DE-AC52-06NA25396. LA-UR-17-25386.

Spectroscopy of Al wire array stagnation on Z

NASA Astrophysics Data System (ADS)

Jones, B.; Jennings, C. A.; Hansen, S. B.; Bailey, J. E.; Rochau, G. A.; Coverdale, C. A.; Yu, E. P.; Ampleford, D. J.; Cuneo, M. E.; Maron, Y.; Fisher, V. I.; Bernshtam, V.; Starobinets, A.; Weingarten, L.; Pinhas, S.

2011-10-01

In this work, we present analysis of time-gated spectra of ~2 keV K-shell emissions from Al (5% Mg) wire arrays on Z to provide details of the plasma conditions and dynamics at the onset of stagnation. The plasma is modeled as concentric radial zones, and collisional-radiative modeling with self-consistent radiation transport is used to constrain the temperatures and densities in these regions. A hot ~2 keV plasma core bearing a few percent of the total mass forms at the foot of the x-ray pulse, with participating mass increasing toward peak x-ray power as material arrives on axis with ~50 cm/ μs implosion velocity. The atomic modeling accounts for K-shell line opacity and Doppler effects, and is compared to 3D MHD simulations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE National Nuclear Security Administration under contract DE-AC04-94AL85000.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanagawa, T.; Sakagami, H.; Nagatomo, H.

In inertial confinement fusion, the implosion process is important in forming a high-density plasma core. In the case of a fast ignition scheme using a cone-guided target, the fuel target is imploded with a cone inserted. This scheme is advantageous for efficiently heating the imploded fuel core; however, asymmetric implosion is essentially inevitable. Moreover, the effect of cone position and opening angle on implosion also becomes critical. Focusing on these problems, the effect of the asymmetric implosion, the initial position, and the opening angle on the compression rate of the fuel is investigated using a three-dimensional pure hydrodynamic code.

On krypton-doped capsule implosion experiments at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Chen, Hui; Ma, T.; Nora, R.; Barrios, M. A.; Scott, H. A.; Schneider, M. B.; Berzak Hopkins, L.; Casey, D. T.; Hammel, B. A.; Jarrott, L. C.; Landen, O. L.; Patel, P. K.; Rosenberg, M. J.; Spears, B. K.

2017-07-01

This paper presents the spectroscopic aspects of using Krypton as a dopant in NIF capsule implosions through simulation studies and the first set of NIF experiments. Using a combination of 2D hohlraum and 1D capsule simulations with comprehensive spectroscopic modeling, the calculations focused on the effect of dopant concentration on the implosion, and the impact of gradients in the electron density and temperature to the Kr line features and plasma opacity. Experimental data were obtained from three NIF Kr-dopant experiments, performed with varying Kr dopant concentrations between 0.01% and 0.03%. The implosion performance, hotspot images, and detailed Kr spectral analysis are summarized relative to the predictions. Data show that fuel-dopant spectroscopy can serve as a powerful and viable diagnostic for inertial confinement fusion implosions.

Effect of the implosion and demolition of a hospital building on the concentration of fungi in the air.

PubMed

Barreiros, Gloria; Akiti, Tiyomi; Magalhães, Ana Cristina Gouveia; Nouér, Simone A; Nucci, Marcio

2015-12-01

Building renovations increase the concentration of Aspergillus conidia in the air. In 2010, one wing of the hospital building was imploded due to structural problems. To evaluate the impact of building implosion on the concentration of fungi in the air, the demolition was performed in two phases: mechanical demolition of 30 m of the building, followed by implosion of the wing. Patients at high risk for aspergillosis were placed in protected wards. Air sampling was performed during mechanical demolition, on the day of implosion and after implosion. Total and specific fungal concentrations were compared in the different areas and periods of sampling, using the anova test. The incidence of IA in the year before and after implosion was calculated. The mean concentration of Aspergillus increased during mechanical demolition and on the day of implosion. However, in the most protected areas, there was no significant difference in the concentration of fungi. The incidence of invasive aspergillosis (cases per 1000 admissions) was 0.9 in the 12 months before, 0.4 during, and 0.5 in the 12 months after mechanical demolition (P > 0.05). Continuous monitoring of the quality of air and effective infection control measures are important to minimize the impact of building demolition. © 2015 Blackwell Verlag GmbH.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoup, R.W.; Long, F.; Martin, T.H.

Sandia is developing PBFA-Z, a 20-MA driver for z-pinch experiments by replacing the water lines, insulator stack, and MITLs on PBFA II with new hardware. The design of the vacuum insulator stack was dictated by the drive voltage, the electric field stress and grading requirements, the water line and MITL interface requirements, and the machine operations and maintenance requirements. The insulator stack will consist of four separate modules, each of a different design because of different voltage drive and hardware interface requirements. The shape of the components in each module, i.e., grading rings, insulator rings, flux excluders, anode and cathodemore » conductors, and the design of the water line and MITL interfaces, were optimized by using the electrostatic analysis codes, ELECTRO and JASON. The time dependent performance of the insulator stack was evaluated using IVORY, a 2-D PIC code. This paper will describe the insulator stack design and present the results of the ELECTRO and IVORY analyses.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singledecker, Steven John

The purpose of this document is to describe the waste stream from Z-Pinch Residual Waste Project that due to worker safety concerns and operational efficiency is a candidate for blending Transuranic and low level waste together and can be safely packaged as low-level waste consistent with DOE Order 435.1 requirements and NRC guidance 10 CFR 61.42. This waste stream consists of the Pu-ICE post-shot containment systems, including plutonium targets, generated from the Z Machine experiments requested by LANL and conducted by SNL/NM. In the past, this TRU waste was shipped back to LANL after Sandia sends the TRU data packagemore » to LANL to certify the characterization (by CCP), transport and disposition at WIPP (CBFO) per LANL MOU-0066. The Low Level Waste is managed, characterized, shipped and disposed of at NNSS by SNL/NM per Sandia MOU # 11-S-560.« less

The effect of dopants on laser imprint mitigation

NASA Astrophysics Data System (ADS)

Phillips, Lee; Gardner, John H.; Bodner, Stephen E.; Colombant, Denis; Dahlburg, Jill

1999-11-01

An intact implosion of a pellet for direct-drive ICF requires that the perturbations imprinted by the laser be kept below some threshold. We report on simulations of targets that incorporate very small concentrations of a high-Z dopant in the ablator, to increase the electron density in the ablating plasma, causing the laser to be absorbed far enough from the solid ablator to achieve a substantial degree of thermal smoothing. These calculations were performed using NRL's FAST radiation hydrodynamics code(J.H. Gardner, A.J. Schmitt, et al., Phys. Plasmas) 5, 1935 (1998), incorporating the flux-corrected transport algorithm and opacities generated by an STA code, with non-LTE radiation transport based on the Busquet method.

Time-resolved hard x-ray spectrometer

NASA Astrophysics Data System (ADS)

Moy, Kenneth; Cuneo, Michael; McKenna, Ian; Keenan, Thomas; Sanford, Thomas; Mock, Ray

2006-08-01

Wired array studies are being conducted at the SNL Z accelerator to maximize the x-ray generation for inertial confinement fusion targets and high energy density physics experiments. An integral component of these studies is the characterization of the time-resolved spectral content of the x-rays. Due to potential spatial anisotropy in the emitted radiation, it is also critical to diagnose the time-evolved spectral content in a space-resolved manner. To accomplish these two measurement goals, we developed an x-ray spectrometer using a set of high-speed detectors (silicon PIN diodes) with a collimated field-of-view that converged on a 1-cm-diameter spot at the pinch axis. Spectral discrimination is achieved by placing high Z absorbers in front of these detectors. We built two spectrometers to permit simultaneous different angular views of the emitted radiation. Spectral data have been acquired from recent Z shots for the radial and axial (polar) views. UNSPEC 1 has been adapted to analyze and unfold the measured data to reconstruct the x-ray spectrum. The unfold operator code, UFO2, is being adapted for a more comprehensive spectral unfolding treatment.

Deformation of periodic nanovoid structures in Mg single crystals

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing; Zare Chavoshi, Saeed

2018-01-01

Large scale molecular dynamics (MD) simulations in Mg single crystal containing periodic cylindrical voids subject to uniaxial tension along the z direction are carried out. Models with different initial void sizes and crystallographic orientations are explored using two interatomic potentials. It is found that (i) a larger initial void always leads to a lower yield stress, in agreement with an analytic prediction; (ii) in the model with x[\\bar{1}100]-y[0001]-z[11\\bar{2}0] orientations, the two potentials predict different types of tension twins and phase transformation; (iii) in the model with x[0001]-y[11\\bar{2}0]-z[\\bar{1}100] orientations, the two potentials identically predict the nucleation of edge dislocations on the prismatic plane, which then glide away from the void, resulting in extrusions at the void surface; in the case of the smallest initial void, these surface extrusions pinch the void into two voids. Besides bringing new physical understanding of the nanovoid structures, our work highlights the variability and uncertainty in MD simulations arising from the interatomic potential, an issue relatively lightly addressed in the literature to date.

Magnetic curvature effects on plasma interchange turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, B., E-mail: bli@pku.edu.cn; Liao, X.; Sun, C. K.

2016-06-15

The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.

Neutron Energy and Flux Distributions from a Crossed-Field Acceleration Model of Plasma Focus and Z-Pinch Discharges.

DTIC Science & Technology

plasma focus . A generalized beam-target model is assumed where (1) high-energy deuterons have angular distributions consistent with a crossed-field acceleration mechanism, and (2) these energetic deuterons undergo fusion collisions primarily with stationary target ions. Energy distributions of ions proportional to 1/(E sub d) cubed in the range from 50 to as high as 600 keV give computed results agreeing with many experimental observations at laboratory angles of 0, 90, and 180 deg. These ion-energy distributions can account for a 50- to 100-fold increase in neutron yeild

MHD Stability of Axisymmetric Plasmas In Closed Line Magnetic Fields

NASA Astrophysics Data System (ADS)

Simakov, Andrei N.; Catto, Peter J.; Ramos, Jesus J.; Hastie, R. J.

2003-04-01

The stability of axisymmetric plasmas confined by closed poloidal magnetic field lines is considered. The results are relevant to plasmas in the dipolar fields of stars and planets, as well as the Levitated Dipole Experiment, multipoles, Z pinches and field reversed configurations. The ideal MHD energy principle is employed to study stability of pressure driven Alfvén modes. A point dipole is considered in detail to demonstrate that equilibria exist, which are MHD stable for arbitrary beta. Effects of sound waves and plasma resistivity are investigated next for point dipole equilibria by means of resistive MHD theory.

Quantification of hand function by power grip and pinch strength force measurements in ulnar nerve lesion simulated by ulnar nerve block.

PubMed

Wachter, Nikolaus Johannes; Mentzel, Martin; Krischak, Gert D; Gülke, Joachim

2017-06-24

In the assessment of hand and upper limb function, grip strength is of the major importance. The measurement by dynamometers has been established. In this study, the effect of a simulated ulnar nerve lesion on different grip force measurements was evaluated. In 25 healthy volunteers, grip force measurement was done by the JAMAR dynamometer (Fabrication Enterprises Inc, Irvington, NY) for power grip and by a pinch strength dynamometer for tip pinch strength, tripod grip, and key pinch strength. A within-subject research design was used in this prospective study. Each subject served as the control by preinjection measurements of grip and pinch strength. Subsequent measurements after ulnar nerve block were used to examine within-subject change. In power grip, there was a significant reduction of maximum grip force of 26.9% with ulnar nerve block compared with grip force without block (P < .0001). Larger reductions in pinch strength were observed with block: 57.5% in tip pinch strength (P < .0001), 61.0% in tripod grip (P < .0001), and 58.3% in key pinch strength (P < .0001). The effect of the distal ulnar nerve block on grip and pinch force could be confirmed. However, the assessment of other dimensions of hand strength as tip pinch, tripod pinch and key pinch had more relevance in demonstrating hand strength changes resulting from an distal ulnar nerve lesion. The measurement of tip pinch, tripod grip and key pinch can improve the follow-up in hand rehabilitation. II. Copyright © 2017 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Laser-driven magnetized liner inertial fusion

DOE PAGES

Davies, J. R.

2017-06-05

A laser-driven, magnetized liner inertial fusion (MagLIF) experiment is designed in this paper for the OMEGA Laser System by scaling down the Z point design to provide the first experimental data on MagLIF scaling. OMEGA delivers roughly 1000× less energy than Z, so target linear dimensions are reduced by factors of ~10. Magneto-inertial fusion electrical discharge system could provide an axial magnetic field of 10 T. Two-dimensional hydrocode modeling indicates that a single OMEGA beam can preheat the fuel to a mean temperature of ~200 eV, limited by mix caused by heat flow into the wall. One-dimensional magnetohydrodynamic (MHD) modelingmore » is used to determine the pulse duration and fuel density that optimize neutron yield at a fuel convergence ratio of roughly 25 or less, matching the Z point design, for a range of shell thicknesses. A relatively thinner shell, giving a higher implosion velocity, is required to give adequate fuel heating on OMEGA compared to Z because of the increase in thermal losses in smaller targets. Two-dimensional MHD modeling of the point design gives roughly a 50% reduction in compressed density, temperature, and magnetic field from 1-D because of end losses. Finally, scaling up the OMEGA point design to the MJ laser energy available on the National Ignition Facility gives a 500-fold increase in neutron yield in 1-D modeling.« less

Laser-driven magnetized liner inertial fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, J. R.

A laser-driven, magnetized liner inertial fusion (MagLIF) experiment is designed in this paper for the OMEGA Laser System by scaling down the Z point design to provide the first experimental data on MagLIF scaling. OMEGA delivers roughly 1000× less energy than Z, so target linear dimensions are reduced by factors of ~10. Magneto-inertial fusion electrical discharge system could provide an axial magnetic field of 10 T. Two-dimensional hydrocode modeling indicates that a single OMEGA beam can preheat the fuel to a mean temperature of ~200 eV, limited by mix caused by heat flow into the wall. One-dimensional magnetohydrodynamic (MHD) modelingmore » is used to determine the pulse duration and fuel density that optimize neutron yield at a fuel convergence ratio of roughly 25 or less, matching the Z point design, for a range of shell thicknesses. A relatively thinner shell, giving a higher implosion velocity, is required to give adequate fuel heating on OMEGA compared to Z because of the increase in thermal losses in smaller targets. Two-dimensional MHD modeling of the point design gives roughly a 50% reduction in compressed density, temperature, and magnetic field from 1-D because of end losses. Finally, scaling up the OMEGA point design to the MJ laser energy available on the National Ignition Facility gives a 500-fold increase in neutron yield in 1-D modeling.« less

A Comparison of Implosive Therapy and Systematic Desensitization in the Treatment of Test Anxiety

ERIC Educational Resources Information Center

Smith, Ronald E.; Nye, S. Lee

1973-01-01

Both Desensitization and implosive therapy resulted in significant decreases in scores on Sarason's Test Anxiety Scale. However, the desensitization group also demonstrated a significant reduction in state anxiety assessed during simulated testing sessions and a significant increase in grade point average, while the implosive therapy group showed…

New and improved CH implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Doeppner, T.; Kritcher, A. L.; Ralph, J. E.; Jarrott, L. C.; Albert, F.; Benedetti, L. R.; Field, J. E.; Goyon, C. S.; Hohenberger, M.; Izumi, N.; Milovich, J. L.; Bachmann, B.; Casey, D. T.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

2017-10-01

Improvements to the hohlraum for CH implosions have resulted in near-record hot spot pressures, 225 Gbar. Implosion symmetry and laser energy coupling are improved by using a hohlraum that, compared to the previous high gas-fill hohlraum, is longer, larger, at lower gas fill density, and is fielded at zero wavelength separation to minimize cross-beam energy transfer. With a capsule at 90% of its original size in this hohlraum, implosion symmetry changes from oblate to prolate, at 33% cone fraction. Simulations highlight improved inner beam propagation as the cause of this symmetry change. These implosions have produced the highest yield for CH ablators at modest power and energy, i.e., 360 TW and 1.4 MJ. Upcoming experiments focus on continued improvement in shape as well as an increase in implosion velocity. Further, results and future plans on an increase in capsule size to improve margin will also be presented. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Ultra High Mode Mix in NIF NIC Implosions

NASA Astrophysics Data System (ADS)

Scott, Robbie; Garbett, Warren

2017-10-01

This work re-examines a sub-set of the low adiabat implosions from the National Ignition Campaign in an effort to better understand potential phenomenological sources of `excess' mix observed experimentally. An extensive effort has been made to match both shock-timing and backlit radiography (Con-A) implosion data in an effort to reproduce the experimental conditions as accurately as possible. Notably a 30% reduction in ablation pressure at peak drive is required to match the experimental data. The reduced ablation pressure required to match the experimental data allows the ablator to decompress, in turn causing the DT ice-ablator interface to go Rayleigh-Taylor unstable early in the implosion acceleration phase. Post-processing the runs with various mix models indicates high-mode mix from the DT ice-ablator interface may penetrate deep into the hotspot. This work offers a potential explanation of why these low-adiabat implosions exhibited significantly higher levels of mix than expected from high-fidelity multi-dimensional simulations. Through this new understanding, a possible route forward for low-adiabat implosions on NIF is suggested.

Addressing Common Technical challenges in Inertial Confinement Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, Donald A.

2016-09-22

The implosion phase for Inertial Confinement Fusion (ICF) occurs from initiation of the drive until just before stagnation. Evolution of the shell and fusion fuel during the implosion phase is affected by the initial conditions of the target, the drive history. Poor performing implosions are a result of the behavior that occurs during the implosion phase such as low mode asymmetries, mixing of the ablator into the fuel, and the hydrodynamic evolution of initial target features and defects such as the shell mounting hardware. The ultimate results of these effects can only be measured at stagnation. However, studying the implosionmore » phase can be effective for understanding and mitigating these effects and for of ultimately improving the performance of ICF implosions. As the ICF program moves towards the 2020 milestone to “determine the efficacy of ignition”, it will be important to understand the physics that occurs during the implosion phase. This will require both focused and integrated experiments. Focused experiments will provide the understanding and the evidence needed to support any determination concerning the efficacy of ignition.« less

Contribution of flexor pollicis longus to pinch strength: an in vivo study.

PubMed

Goetz, Thomas J; Costa, Joseph A; Slobogean, Gerard; Patel, Satyam; Mulpuri, Kishore; Travlos, Andrew

2012-11-01

To estimate the contribution of the flexor pollicis longus (FPL) to key pinch strength. Secondary outcomes include tip pinch, 3-point chuck pinch, and grip strength. Eleven healthy volunteers consented to participate in the study. We recorded baseline measures for key, 3-point chuck, and tip pinch and for grip strength. In order to control for instability of the interphalangeal (IP) joint after FPL paralysis, pinch measurements were repeated after immobilizing the thumb IP joint. Measures were repeated after subjects underwent electromyography-guided lidocaine blockade of the FPL muscle. Nerve conduction studies and clinical examinations were used to confirm FPL blockade and to rule out median nerve blockade. Paired t-tests were used to compare pre- and postblock means for both unsplinted and splinted measures. The difference in means was used to estimate the contribution of FPL to pinch strength. All 3 types of pinch strength showed a significant decrease between pre- and postblock measurements. The relative contribution of FPL for each pinch type was 56%, 44%, and 43% for key, chuck, and tip pinch, respectively. Mean grip strength did not decrease significantly. Splinting of the IP joint had no significant effect on pinch measurements. FPL paralysis resulted in a statistically significant decrease in pinch strength. IP joint immobilization to simulate IP joint fusion did not affect results. Reconstruction after acute or chronic loss of FPL function should be considered when restoration of pinch strength is important. Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Zonal flow generation in inertial confinement fusion implosions

DOE PAGES

Peterson, J. L.; Humbird, K. D.; Field, J. E.; ...

2017-03-06

A supervised machine learning algorithm trained on a multi-petabyte dataset of inertial confinement fusion simulations has identified a class of implosions that robustly achieve high yield, even in the presence of drive variations and hydrodynamic perturbations. These implosions are purposefully driven with a time-varying asymmetry, such that coherent flow generation during hotspot stagnation forces the capsule to self-organize into an ovoid, a shape that appears to be more resilient to shell perturbations than spherical designs. Here this new class of implosions, whose configurations are reminiscent of zonal flows in magnetic fusion devices, may offer a path to robust inertial fusion.

Zonal flow generation in inertial confinement fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, J. L.; Humbird, K. D.; Field, J. E.

A supervised machine learning algorithm trained on a multi-petabyte dataset of inertial confinement fusion simulations has identified a class of implosions that robustly achieve high yield, even in the presence of drive variations and hydrodynamic perturbations. These implosions are purposefully driven with a time-varying asymmetry, such that coherent flow generation during hotspot stagnation forces the capsule to self-organize into an ovoid, a shape that appears to be more resilient to shell perturbations than spherical designs. Here this new class of implosions, whose configurations are reminiscent of zonal flows in magnetic fusion devices, may offer a path to robust inertial fusion.

Functional sensibility assessment. Part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release.

PubMed

Hsu, Hsiu-Yun; Kuo, Li-Chieh; Chiu, Haw-Yen; Jou, I-Ming; Su, Fong-Chin

2009-11-01

Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom-designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity. Based on these tests, five force-related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes-Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

NASA Astrophysics Data System (ADS)

Bose, A.; Betti, R.; Mangino, D.; Woo, K. M.; Patel, D.; Christopherson, A. R.; Gopalaswamy, V.; Mannion, O. M.; Regan, S. P.; Goncharov, V. N.; Edgell, D. H.; Forrest, C. J.; Frenje, J. A.; Gatu Johnson, M.; Yu Glebov, V.; Igumenshchev, I. V.; Knauer, J. P.; Marshall, F. J.; Radha, P. B.; Shah, R.; Stoeckl, C.; Theobald, W.; Sangster, T. C.; Shvarts, D.; Campbell, E. M.

2018-06-01

This paper describes a technique for identifying trends in performance degradation for inertial confinement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA which achieved inferred hot-spot pressures ≈56 ± 7 Gbar [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid-modes. This suggests that in addition to low modes, which can cause a degradation of the stagnation pressure, mid-modes are present which reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. It is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase in the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [Bose et al., Phys. Rev. E 94, 011201(R) (2016)].

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

DOE PAGES

Bose, A.; Betti, R.; Mangino, D.; ...

2018-05-29

This paper describes a technique for identifying trends in performance degradation for inertial con finement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA that achieved inferred hot-spot pressures ≈56 ± 7 Gbar [S. Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid modes. This suggests that in addition to low modes, that can cause amore » degradation of the stagnation pressure, mid modes are present that reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. Finally, it is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase of the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [A. Bose et al., Phys. Rev. E 94, 011201(R) (2016)].« less

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Betti, R.; Mangino, D.

This paper describes a technique for identifying trends in performance degradation for inertial con finement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA that achieved inferred hot-spot pressures ≈56 ± 7 Gbar [S. Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid modes. This suggests that in addition to low modes, that can cause amore » degradation of the stagnation pressure, mid modes are present that reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. Finally, it is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase of the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [A. Bose et al., Phys. Rev. E 94, 011201(R) (2016)].« less

Improving cryogenic deuterium–tritium implosion performance on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangster, T. C.; Goncharov, V. N.; Betti, R.

2013-05-15

A flexible direct-drive target platform is used to implode cryogenic deuterium–tritium (DT) capsules on the OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)]. The goal of these experiments is to demonstrate ignition hydrodynamically equivalent performance where the laser drive intensity, the implosion velocity, the fuel adiabat, and the in-flight aspect ratio (IFAR) are the same as those for a 1.5-MJ target [Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)] designed to ignite on the National Ignition Facility [Hogan et al., Nucl. Fusion 41, 567 (2001)]. The results from a series of 29 cryogenic DT implosions are presented.more » The implosions were designed to span a broad region of design space to study target performance as a function of shell stability (adiabat) and implosion velocity. Ablation-front perturbation growth appears to limit target performance at high implosion velocities. Target outer-surface defects associated with contaminant gases in the DT fuel are identified as the dominant perturbation source at the ablation surface; performance degradation is confirmed by 2D hydrodynamic simulations that include these defects. A trend in the value of the Lawson criterion [Betti et al., Phys. Plasmas 17, 058102 (2010)] for each of the implosions in adiabat–IFAR space suggests the existence of a stability boundary that leads to ablator mixing into the hot spot for the most ignition-equivalent designs.« less

Improving cryogenic deuterium tritium implosion performance on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangster, T. C.; Goncharov, V. N.; Betti, R.

2013-01-01

A flexible direct-drive target platform is used to implode cryogenic deuterium–tritium (DT) capsules on the OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)]. The goal of these experiments is to demonstrate ignition hydrodynamically equivalent performance where the laser drive intensity, the implosion velocity, the fuel adiabat, and the in-flight aspect ratio (IFAR) are the same as those for a 1.5-MJ target [Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)] designed to ignite on the National Ignition Facility [Hogan et al., Nucl. Fusion 41, 567 (2001)]. The results from a series of 29 cryogenic DT implosions are presented.more » The implosions were designed to span a broad region of design space to study target performance as a function of shell stability (adiabat) and implosion velocity. Ablation-front perturbation growth appears to limit target performance at high implosion velocities. Target outer-surface defects associated with contaminant gases in the DT fuel are identified as the dominant perturbation source at the ablation surface; performance degradation is confirmed by 2D hydrodynamic simulations that include these defects. A trend in the value of the Lawson criterion [Betti et al., Phys. Plasmas 17, 058102 (2010)] for each of the implosions in adiabat–IFAR space suggests the existence of a stability boundary that leads to ablator mixing into the hot spot for the most ignition-equivalent designs.« less

Particularly interesting Cys-His-rich protein is highly expressed in human intracranial aneurysms and resists aneurysmal rupture

PubMed Central

Peng, Yu-Tao; Shi, Xiang-En; Li, Zhi-Qiang; He, Xin; Sun, Yu-Ming

2016-01-01

Particularly interesting Cys-His-rich protein (PINCH) has several biological functions in cancer development, invasion and metastasis in malignant cells, and the expression of PINCH is upregulated in several cancer types, including breast cancer, gastric adenocarcinoma and rectal cancer. However, the contribution of PINCH to human cerebral aneurysms remains largely unknown. Therefore, the significance of PINCH expression in cerebral aneurysm growth and rupture was examined in the present study. The protein expression levels of alpha-smooth muscle actin, osteopontin (OPN), matrix metalloproteinase (MMP) 9 and PINCH were evaluated using immunohistochemistry and western blot analyses. The results demonstrate that the protein expression levels of OPN, MMP9 and PINCH in the unruptured intracranial aneurysm (UA) and ruptured intracranial aneurysm (RA) groups were markedly higher than those of the control group, whereas OPN and PINCH expression levels were decreased in the RA group compared to those of the UA group. In addition, there was a strong correlation between PINCH and tumor size (r=0.650 and P=0.0026), as well as between PINCH and OPN (r=0.639 and P=0.0033) in the unruptured cerebral aneurysms. However, the correlation between PINCH and tumor size (r=0.450 and P=0.1393) and between PINCH and OPN (r=0.366 and P=0.2426) revealed no obvious difference in the ruptured cerebral aneurysms. In conclusion, PINCH was highly expressed in the UAs, which may be a critical factor for preventing aneurysmal rupture. Moreover, PINCH may facilitate intracranial aneurysm progression, at least partially, through the activation of extracellular signal-regulated kinase signaling and the suppression of c-Jun N-terminal kinase signaling. PMID:28101173

Particularly interesting Cys-His-rich protein is highly expressed in human intracranial aneurysms and resists aneurysmal rupture.

PubMed

Peng, Yu-Tao; Shi, Xiang-En; Li, Zhi-Qiang; He, Xin; Sun, Yu-Ming

2016-12-01

Particularly interesting Cys-His-rich protein (PINCH) has several biological functions in cancer development, invasion and metastasis in malignant cells, and the expression of PINCH is upregulated in several cancer types, including breast cancer, gastric adenocarcinoma and rectal cancer. However, the contribution of PINCH to human cerebral aneurysms remains largely unknown. Therefore, the significance of PINCH expression in cerebral aneurysm growth and rupture was examined in the present study. The protein expression levels of alpha-smooth muscle actin, osteopontin (OPN), matrix metalloproteinase (MMP) 9 and PINCH were evaluated using immunohistochemistry and western blot analyses. The results demonstrate that the protein expression levels of OPN, MMP9 and PINCH in the unruptured intracranial aneurysm (UA) and ruptured intracranial aneurysm (RA) groups were markedly higher than those of the control group, whereas OPN and PINCH expression levels were decreased in the RA group compared to those of the UA group. In addition, there was a strong correlation between PINCH and tumor size ( r =0.650 and P=0.0026), as well as between PINCH and OPN ( r =0.639 and P=0.0033) in the unruptured cerebral aneurysms. However, the correlation between PINCH and tumor size ( r =0.450 and P=0.1393) and between PINCH and OPN ( r =0.366 and P=0.2426) revealed no obvious difference in the ruptured cerebral aneurysms. In conclusion, PINCH was highly expressed in the UAs, which may be a critical factor for preventing aneurysmal rupture. Moreover, PINCH may facilitate intracranial aneurysm progression, at least partially, through the activation of extracellular signal-regulated kinase signaling and the suppression of c-Jun N-terminal kinase signaling.

The High-Foot Implosion Campaign on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hurricane, Omar

2013-10-01

The `High-Foot' platform manipulates the laser pulse-shape coming from the National Ignition Facility (NIF) laser to create an indirect drive 3-shock implosion that is significantly more robust against instability growth involving the ablator and also modestly reduces implosion convergence ratio. This tactic gives up on theoretical high-gain in an inertial confinement fusion implosion in order to obtain better control of the implosion and bring experimental performance in-line with calculated performance, yet keeps the absolute capsule performance relatively high. This approach is generally consistent with the philosophy laid out in a recent international workshop on the topic of ignition science on NIF [``Workshop on the Science of Fusion Ignition on NIF,'' Lawrence Livermore National Laboratory Report, LLNL-TR-570412 (2012). Op cit. V. Gocharov and O.A. Hurricane, ``Panel 3 Report: Implosion Hydrodynamics,'' LLNL-TR-562104 (2012)]. Side benefits our the High-Foot pulse-shape modification appear to be improvements in hohlraum behavior--less wall motion achieved through higher pressure He gas fill and improved inner cone laser beam propagation. Another consequence of the `High-Foot' is a higher fuel adiabat, so there is some relation to direct-drive experiments performed at the Laboratory for Laser Energetics (LLE). In this talk, we will cover the various experimental and theoretical motivations for the High-Foot drive as well as cover the experimental results that have come out of the High-Foot experimental campaign. Most notably, at the time of this writing record DT layer implosion performance with record low levels of inferred mix and excellent agreement with one-dimensional implosion models without the aid of mix models. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

DOE PAGES

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; ...

2014-11-03

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

Core conditions for alpha heating attained in direct-drive inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Woo, K. M.; Betti, R.

It is shown that direct-drive implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA implosion [Regan et al., Phys. Rev. Lett. 117,more » 025001 (2016)] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF implosions.« less

Core conditions for alpha heating attained in direct-drive inertial confinement fusion

DOE PAGES

Bose, A.; Woo, K. M.; Betti, R.; ...

2016-07-07

It is shown that direct-drive implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA implosion [Regan et al., Phys. Rev. Lett. 117,more » 025001 (2016)] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF implosions.« less

Beryllium implosion experiments at high case-to-capsule ratio on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Zylstra, Alex; Yi, Austin; Kline, John; Kyrala, George; Loomis, Eric; Perry, Ted; Shah, Rahul; Batha, Steve; MacLaren, Steve; Ralph, Joe; Salmonson, Jay; Masse, Laurent; Nikroo, Abbas; Stadermann, Michael; Callahan, Debbie; Hurricane, Omar; Rice, Neal; Huang, Haibo; Kong, Casey

2017-10-01

Using beryllium as an ablator material has several potential advantages for inertial fusion because of its low opacity and thus higher ablation rate. This could enable novel designs taking advantage of the reduced ablation-front growth rate, or operating at lower radiation temperature. To investigate the integrated performance of beryllium implosions, we conducted a tuning campaign leading into DT layered implosions using a 900um radius capsule in a 6.72mm diameter hohlraum (case-to-capsule ratio CCR=3.7); the large CCR enables direct study of the 1-D implosion performance. The tuning campaign shots demonstrate excellent control over the shock timing and implosion symmetry at this CCR. Performance data from the DT experiments will also be discussed. This work was performed under the auspices of the U.S. DoE by LANL under contract DE-AC52-06NA52396.

Core conditions for alpha heating attained in direct-drive inertial confinement fusion.

PubMed

Bose, A; Woo, K M; Betti, R; Campbell, E M; Mangino, D; Christopherson, A R; McCrory, R L; Nora, R; Regan, S P; Goncharov, V N; Sangster, T C; Forrest, C J; Frenje, J; Gatu Johnson, M; Glebov, V Yu; Knauer, J P; Marshall, F J; Stoeckl, C; Theobald, W

2016-07-01

It is shown that direct-drive implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)10.1103/PhysRevLett.117.025001] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF implosions.

Acute and repeated activation of male sexual behavior by tail pinch: opioid and dopaminergic mechanisms.

PubMed

Leyton, M; Stewart, J

1996-07-01

We studied the effect of tail pinch on male sexual behavior and its neurochemical basis. Male rats were gonadectomized and maintained on low doses of testosterone propionate (20.0 micrograms/day). Tail pinch significantly increased the percentage of males that mounted, intromitted, and ejaculated within a 30-min test, and these increases were attenuated by both pimozide (1.0 mg/kg, i.p.) and by naloxone (0.5, 1.0, and 2.0 mg/kg, s.c.). Moreover, tail pinch in the presence of an estrous female led to significantly increased female-directed behavior 48 h later during a test without tail pinch. Repeated tail pinch tests led to progressively more sexual activity, and the development of this behavioral sensitization was prevented by naloxone. These findings suggest that tail pinch increases the salience of the incentive characteristics of the female. Furthermore, during subsequent tests, with or without tail pinch, the increased salience of the female remains, as measured by the continued increases in sexual activity. These acute and sensitized behavioral increases might result from tail pinch-induced activation of the midbrain dopamine system via an opioid mechanism; either preventing tail pinch-induced dopamine activation (by an opioid antagonist) or blocking the effects of dopamine activation (by a dopamine antagonist) attenuated the long-term facilitation of sexual behavior seen after pairing the female with tail pinch.

[Contrast of Z-Pinch X-Ray Yield Measure Technique].

PubMed

Li, Mo; Wang, Liang-ping; Sheng, Liang; Lu, Yi

2015-03-01

Resistive bolometer and scintillant detection system are two mainly Z-pinch X-ray yield measure techniques which are based on different diagnostic principles. Contrasting the results from two methods can help with increasing precision of X-ray yield measurement. Experiments with different load material and shape were carried out on the "QiangGuang-I" facility. For Al wire arrays, X-ray yields measured by the two techniques were largely consistent. However, for insulating coating W wire arrays, X-ray yields taken from bolometer changed with load parameters while data from scintillant detection system hardly changed. Simulation and analysis draw conclusions as follows: (1) Scintillant detection system is much more sensitive to X-ray photons with low energy and its spectral response is wider than the resistive bolometer. Thus, results from the former method are always larger than the latter. (2) The responses of the two systems are both flat to Al plasma radiation. Thus, their results are consistent for Al wire array loads. (3) Radiation form planar W wire arrays is mainly composed of sub-keV soft X-ray. X-ray yields measured by the bolometer is supposed to be accurate because of the nickel foil can absorb almost all the soft X-ray. (4) By contrast, using planar W wire arrays, data from scintillant detection system hardly change with load parameters. A possible explanation is that while the distance between wires increases, plasma temperature at stagnation reduces and spectra moves toward the soft X-ray region. Scintillator is much more sensitive to the soft X-ray below 200 eV. Thus, although the total X-ray yield reduces with large diameter load, signal from the scintillant detection system is almost the same. (5) Both Techniques affected by electron beams produced by the loads.

Age-Related and Sex-Related Differences in Hand and Pinch Grip Strength in Adults

ERIC Educational Resources Information Center

Puh, Urska

2010-01-01

The purpose of the study was to quantify age-related changes in hand grip strength and three types of pinch grip strength (key pinch, tip pinch, and palmar pinch) among male and female participants. The study included 199 healthy participants (100 females, 99 males) aged 20-79 years, who were divided into four age groups. The Baseline Hydraulic…

Investigation on the pinch point position in heat exchangers

NASA Astrophysics Data System (ADS)

Pan, Lisheng; Shi, Weixiu

2016-06-01

The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the iterative method in all conditions rather than taking for granted.

Three-dimensional hydrodynamic simulations of OMEGA implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; Campbell, E. M.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Marshall, F. J.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Stoeckl, C.; Schmitt, A. J.; Obenschain, S.

2017-05-01

The effects of large-scale (with Legendre modes ≲ 10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets ( ˜10 to 20 μm), beam-power imbalance ( σrms˜10 %), and variations ( ˜5 %) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosion targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ˜1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh-Taylor growth.

Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, M. J., E-mail: mrosenbe@mit.edu; Zylstra, A. B.; Séguin, F. H.

Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D{sub 2} and D{sup 3}He gas-filled “exploding-pusher” inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to themore » predictions of 2D DRACO hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.« less

Pressure signature and evaluation of hammer pulses during underwater implosion in confining environments.

PubMed

Gupta, Sachin; Matos, Helio; Shukla, Arun; LeBlanc, James M

2016-08-01

The fluid structure interaction phenomenon occurring in confined implosions is investigated using high-speed three-dimensional digital image correlation (DIC) experiments. Aluminum tubular specimens are placed inside a confining cylindrical structure that is partially open to a pressurized environment. These specimens are hydrostatically loaded until they naturally implode. The implosion event is viewed, and recorded, through an acrylic window on the confining structure. The velocities captured through DIC are synchronized with the pressure histories to understand the effects of confining environment on the implosion process. Experiments show that collapse of the implodable volume inside the confining tube leads to strong oscillating water hammer waves. The study also reveals that the increasing collapse pressure leads to faster implosions. Both peak and average structural velocities increase linearly with increasing collapse pressure. The effects of the confining environment are better seen in relatively lower collapse pressure implosion experiments in which a long deceleration phase is observed following the peak velocity until wall contact initiates. Additionally, the behavior of the confining environment can be viewed and understood through classical water hammer theory. A one-degree-of-freedom theoretical model was created to predict the impulse pressure history for the particular problem studied.

Higher velocity, high-foot implosions on the National Ignition Facility laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.

By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.« less

Higher velocity, high-foot implosions on the National Ignition Facility laser

DOE PAGES

Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.; ...

2015-05-15

By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.« less

Robust spherical direct-drive design for NI

NASA Astrophysics Data System (ADS)

Masse, Laurent; Hurricane, O.; Michel, P.; Nora, R.; Tabak, M.; Lawrence Livermore Natl Lab Team

2016-10-01

Achieving ignition in a direct-drive or indirect-drive cryogenic implosion is a tremendous challenge. Both approaches need to deal with physic and technologic issues. During the past years, the indirect drive effort on the National Ignition Facility (NIF) has revealed unpredicted lost of performances that force to think to more robust designs and to dig into detailed physics aspects. Encouraging results have been obtained using a strong first shock during the implosion of CH ablator ignition capsules. These ``high-foot'' implosion results in a significantly lower ablation Rayleigh-Taylor instability growth than that of the NIC point design capsule. The trade-off with this design is a higher fuel adiabat that limits both fuel compression and theoretical capsule yield. The purpose of designing this capsule is to recover a more ideal one-dimensional implosion that is in closer agreement to simulation predictions. In the same spirit of spending energy on margin, at the coast of decreased performance, we are presenting here a study on ``robust'' spherical direct drive design for NIF. This 2-Shock direct drive pulse shape results in a high adiabat (>3) and low convergence (<17) implosion designed to produce a near 1D-like implosion. We take a particular attention to design a robust implosion with respect to long-wavelength non uniformity seeded by power imbalance and target offset. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

Mitigation of hot electrons from laser-plasma instabilities in high-Z, highly ionized plasmas

DOE PAGES

Fein, J. R.; Holloway, J. P.; Trantham, M. R.; ...

2017-03-20

Intense lasers interacting with under-dense plasma can drive laser-plasma instabilities (LPIs) that generate largeamplitude electron plasma waves (EPWs). Suprathermal or “hot” electrons produced in the EPWs are detrimental to inertial confinement fusion (ICF), by reducing capsule implosion efficiency through preheat, and also present an unwanted source of background on x-ray diagnostics. Mitigation of hot electrons was demonstrated in the past by altering plasma conditions near the quarter-critical density, n c/4, with the interpretation of reduced growth of the twoplasmon decay (TPD) instability. Here, we present measurements of hot electrons generated in laser-irradiated planar foils of material ranging from low- tomore » high-Z, where the fraction of laser energy converted to hot electrons, fhot was reduced by a factor of 10 3 going from CH to Au. This correlates with steepening density gradient length-scales that were also measured. Radiation hydrodynamic simulations produced electron density profiles in reasonable agreement with our measurements. According to the simulations, both multi-beam TPD and stimulated Raman scattering were predicted to be above threshold with linear threshold parameters that decreased with increasing Z due to steepening length-scales, as well as enhanced laser absorption and increased EPW collisional and Landau damping.« less

Mitigation of hot electrons from laser-plasma instabilities in high-Z, highly ionized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fein, J. R.; Holloway, J. P.; Trantham, M. R.

Intense lasers interacting with under-dense plasma can drive laser-plasma instabilities (LPIs) that generate largeamplitude electron plasma waves (EPWs). Suprathermal or “hot” electrons produced in the EPWs are detrimental to inertial confinement fusion (ICF), by reducing capsule implosion efficiency through preheat, and also present an unwanted source of background on x-ray diagnostics. Mitigation of hot electrons was demonstrated in the past by altering plasma conditions near the quarter-critical density, n c/4, with the interpretation of reduced growth of the twoplasmon decay (TPD) instability. Here, we present measurements of hot electrons generated in laser-irradiated planar foils of material ranging from low- tomore » high-Z, where the fraction of laser energy converted to hot electrons, fhot was reduced by a factor of 10 3 going from CH to Au. This correlates with steepening density gradient length-scales that were also measured. Radiation hydrodynamic simulations produced electron density profiles in reasonable agreement with our measurements. According to the simulations, both multi-beam TPD and stimulated Raman scattering were predicted to be above threshold with linear threshold parameters that decreased with increasing Z due to steepening length-scales, as well as enhanced laser absorption and increased EPW collisional and Landau damping.« less

Particle-in-cell modeling for MJ scale dense plasma focus with varied anode shape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Link, A., E-mail: link6@llnl.gov; Halvorson, C., E-mail: link6@llnl.gov; Schmidt, A.

2014-12-15

Megajoule scale dense plasma focus (DPF) Z-pinches with deuterium gas fill are compact devices capable of producing 10{sup 12} neutrons per shot but past predictive models of large-scale DPF have not included kinetic effects such as ion beam formation or anomalous resistivity. We report on progress of developing a predictive DPF model by extending our 2D axisymmetric collisional kinetic particle-in-cell (PIC) simulations from the 4 kJ, 200 kA LLNL DPF to 1 MJ, 2 MA Gemini DPF using the PIC code LSP. These new simulations incorporate electrodes, an external pulsed-power driver circuit, and model the plasma from insulator lift-off throughmore » the pinch phase. To accommodate the vast range of relevant spatial and temporal scales involved in the Gemini DPF within the available computational resources, the simulations were performed using a new hybrid fluid-to-kinetic model. This new approach allows single simulations to begin in an electron/ion fluid mode from insulator lift-off through the 5-6 μs run-down of the 50+ cm anode, then transition to a fully kinetic PIC description during the run-in phase, when the current sheath is 2-3 mm from the central axis of the anode. Simulations are advanced through the final pinch phase using an adaptive variable time-step to capture the fs and sub-mm scales of the kinetic instabilities involved in the ion beam formation and neutron production. Validation assessments are being performed using a variety of different anode shapes, comparing against experimental measurements of neutron yield, neutron anisotropy and ion beam production.« less

Pin-Ching Maness | NREL

Science.gov Websites

Pin-Ching Maness Photo of Pin-Ching Maness Pin-Ching Maness Group Research Manager III-Molecular University, 1974 Professional Experience Principal Group Manager, Photobiology Group, National Renewable in Rubrivivax gelatinosus," PLOS ONE (2014) Illustration of a model of carbon monoxide and

Comparison of grip and pinch strength in young women with and without hyperkyphosis: A cross-sectional study.

PubMed

Yoosefinejad, Amin Kordi; Ghaffarinejad, Farahnaz; Hemati, Mahbubeh; Jamshidi, Narges

2018-05-21

Hyperkyphosis is a common postural defect with high prevalence in the 20 to 50 year old population. It appears to compromise proximal scapular stability. Grip and pinch strength are used to evaluate general upper extremity function. The aim of this study was to compare pinch and grip strength between young women with and without hyperkyphosis. Thirty young women (18-40 years old) with hyperkyphosis and 30 healthy women matched for age and body mass index participated in the study. Hyperkyphosis was confirmed by measuring the kyphosis angle with a flexible ruler. Grip strength was measured with the Waisa method and a dynamometer. Pinch strength was assessed with a pinch meter. Grip (P= 0.03) and pinch strength (P= 0.04) were significantly lower in women with hyperkyphosis compared to the control group. Kyphosis angle correlated weakly with grip (r= 0.26) and pinch strength (r= 0.23). Hyperkyphotic posture has led to decreased grip and pinch strength compared to people without hyperkyphosis.

Comparison between initial Magnetized Liner Inertial Fusion experiments and integrated simulations

NASA Astrophysics Data System (ADS)

Sefkow, A. B.; Gomez, M. R.; Geissel, M.; Hahn, K. D.; Hansen, S. B.; Harding, E. C.; Peterson, K. J.; Slutz, S. A.; Koning, J. M.; Marinak, M. M.

2014-10-01

The Magnetized Liner Inertial Fusion (MagLIF) approach to ICF has obtained thermonuclear fusion yields using the Z facility. Integrated magnetohydrodynamic simulations provided the design for the first neutron-producing experiments using capabilities that presently exist, and the initial experiments measured stagnation radii rstag < 75 μm, temperatures around 3 keV, and isotropic neutron yields up to YnDD = 2 ×1012 from imploded liners reaching peak velocities around 70 km/s over an implosion time of about 60 ns. We present comparisons between the experimental observables and post-shot degraded integrated simulations. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration under Contract DE-AC04-94AL85000.

A broadband proton backlighting platform to probe shock propagation in low-density systems

DOE PAGES

Sio, H.; Hua, R.; Ping, Y.; ...

2017-01-17

A proton backlighting platform has been developed for the study of strong shock propagation in low-density systems in planar geometry. Electric fields at the converging shock front in inertial confinement fusion implosions have been previously observed, demonstrating the presence of—and the need to understand—strong electric fields not modeled in standard radiation-hydrodynamic simulations. In this planar configuration, long-pulse ultraviolet lasers are used to drive a strong shock into a gas-cell target, while a short-pulse proton backlighter side-on radiographs the shock propagation. Finally, the capabilities of the platform are presented here. Future experiments will vary shock strength and gas fill, to probemore » shock conditions at different Z and T e.« less

Simulations of fill tube effects on the implosion of high-foot NIF ignition capsules

NASA Astrophysics Data System (ADS)

Dittrich, T. R.; Hurricane, O. A.; Berzak-Hopkins, L. F.; Callahan, D. A.; Casey, D. T.; Clark, D.; Dewald, E. L.; Doeppner, T.; Haan, S. W.; Hammel, B. A.; Harte, J. A.; Hinkel, D. E.; Kozioziemski, B. J.; Kritcher, A. L.; Ma, T.; Nikroo, A.; Pak, A. E.; Parham, T. G.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Salmonson, J. D.; Springer, P. T.; Weber, C. R.; Zimmerman, G. B.; Kline, J. L.

2016-05-01

Encouraging results have been obtained using a strong first shock during the implosion of carbon-based ablator ignition capsules. These “high-foot” implosion results show that capsule performance deviates from 1D expectations as laser power and energy are increased. A possible cause of this deviation is the disruption of the hot spot by jets originating in the capsule fill tube. Nominally, a 10 μm outside diameter glass (SiO2) fill tube is used in these implosions. Simulations indicate that a thin coating of Au on this glass tube may lessen the hotspot disruption. These results and other mitigation strategies will be presented.

Scaling laws for ignition at the National Ignition Facility from first principles.

PubMed

Cheng, Baolian; Kwan, Thomas J T; Wang, Yi-Ming; Batha, Steven H

2013-10-01

We have developed an analytical physics model from fundamental physics principles and used the reduced one-dimensional model to derive a thermonuclear ignition criterion and implosion energy scaling laws applicable to inertial confinement fusion capsules. The scaling laws relate the fuel pressure and the minimum implosion energy required for ignition to the peak implosion velocity and the equation of state of the pusher and the hot fuel. When a specific low-entropy adiabat path is used for the cold fuel, our scaling laws recover the ignition threshold factor dependence on the implosion velocity, but when a high-entropy adiabat path is chosen, the model agrees with recent measurements.

Capsule Ablator Inflight Performance Measurements Via Streaked Radiography Of ICF Implosions On The NIF*

NASA Astrophysics Data System (ADS)

Dewald, E. L.; Tommasini, R.; Mackinnon, A.; MacPhee, A.; Meezan, N.; Olson, R.; Hicks, D.; LePape, S.; Izumi, N.; Fournier, K.; Barrios, M. A.; Ross, S.; Pak, A.; Döppner, T.; Kalantar, D.; Opachich, K.; Rygg, R.; Bradley, D.; Bell, P.; Hamza, A.; Dzenitis, B.; Landen, O. L.; MacGowan, B.; LaFortune, K.; Widmayer, C.; Van Wonterghem, B.; Kilkenny, J.; Edwards, M. J.; Atherton, J.; Moses, E. I.

2016-03-01

Streaked 1-dimensional (slit imaging) radiography of 1.1 mm radius capsules in ignition hohlraums was recently introduced on the National Ignition Facility (NIF) and gives an inflight continuous record of capsule ablator implosion velocities, shell thickness and remaining mass in the last 3-5 ns before peak implosion time. The high quality data delivers good accuracy in implosion metrics that meets our requirements for ignition and agrees with recently introduced 2-dimensional pinhole radiography. Calculations match measured trajectory across various capsule designs and laser drives when the peak laser power is reduced by 20%. Furthermore, calculations matching measured trajectories give also good agreement in ablator shell thickness and remaining mass.

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility

DOE PAGES

Olson, R. E.; Leeper, R. J.; Kline, J. L.; ...

2016-12-07

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D 2 and DT layer Inertial Confinement Fusion (ICF) implosions that can access low-to-moderate hot spot convergence ratio (1230) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CR’s of 12-17, and the hot spot formation is well understood, demonstratedmore » by good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.« less

The Defect Induced Mix Experiment (DIME) for NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmitt, Mark J; Bradley, Paul A; Cobble, James A

2012-06-18

LANL will perform two Defect Induced Mix Experiment (DIME) implosion campaigns on NIF in July and September, 2012. This presentation describes the goals for these shots and the experimental configuration and diagnostic set up to collect the appropriate data. The first two-shot campaign will focus on executing polar direct drive (PDD) implosions of plastic CH capsules filled with deuterium gas. Gas filling will be performed through a fill tube at target chamber center. A vanadium backligher foil will provide x-rays to radiograph the last half of the implosion to compare the implosion trajectory with modeling predictions. An equatorial groove inmore » one of the capsules will be present to determine its effect on implosion dynamics. The second DIME campaign will commission and use a spectral imager (MMI) to examine the evolution of thin capsule layers doped with either Ge or Ga at 1.85%. Spectral line emission from these layers will quantify the mix width at the inner shell radius and near an equatorial groove feature.« less

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Olson, R. E.; Leeper, R. J.; Kline, J. L.; Zylstra, A. B.; Yi, S. A.; Biener, J.; Braun, T.; Kozioziemski, B. J.; Sater, J. D.; Bradley, P. A.; Peterson, R. R.; Haines, B. M.; Yin, L.; Berzak Hopkins, L. F.; Meezan, N. B.; Walters, C.; Biener, M. M.; Kong, C.; Crippen, J. W.; Kyrala, G. A.; Shah, R. C.; Herrmann, H. W.; Wilson, D. C.; Hamza, A. V.; Nikroo, A.; Batha, S. H.

2016-12-01

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D2 and DT layer inertial confinement fusion (ICF) implosions that can access a low-to-moderate hot-spot convergence ratio (12 30 ) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CRs of 12-17, and the hot-spot formation is well understood, demonstrated by a good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Berzak Hopkins, L. F.; Ma, T.; Ralph, J. E.; Albert, F.; Benedetti, L. R.; Celliers, P. M.; Döppner, T.; Goyon, C. S.; Izumi, N.; Jarrott, L. C.; Khan, S. F.; Kline, J. L.; Kritcher, A. L.; Kyrala, G. A.; Nagel, S. R.; Pak, A. E.; Patel, P.; Rosen, M. D.; Rygg, J. R.; Schneider, M. B.; Turnbull, D. P.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

2016-11-01

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4 ×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robey, H. F.; Smalyuk, V. A.; Milovich, J. L.

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 inmore » 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.« less

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

DOE PAGES

Robey, H. F.; Smalyuk, V. A.; Milovich, J. L.; ...

2016-04-01

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 & fuel adiabat, separately and controllably. Two principal conclusions are drawn from this study: 1) It is shown that an increase in laser picket energy reduces ablation-front instability growth in low-foot implosions resulting in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. 2.) It is shown that a decrease inmore » laser trough power reduces the fuel adiabat in high-foot implosions results in a significant (36%) increase in fuel compression together with no reduction in neutron yield. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results.« less

2D Implosion Simulations with a Kinetic Particle Code

NASA Astrophysics Data System (ADS)

Sagert, Irina; Even, Wesley; Strother, Terrance

2017-10-01

Many problems in laboratory and plasma physics are subject to flows that move between the continuum and the kinetic regime. We discuss two-dimensional (2D) implosion simulations that were performed using a Monte Carlo kinetic particle code. The application of kinetic transport theory is motivated, in part, by the occurrence of non-equilibrium effects in inertial confinement fusion (ICF) capsule implosions, which cannot be fully captured by hydrodynamics simulations. Kinetic methods, on the other hand, are able to describe both, continuum and rarefied flows. We perform simple 2D disk implosion simulations using one particle species and compare the results to simulations with the hydrodynamics code RAGE. The impact of the particle mean-free-path on the implosion is also explored. In a second study, we focus on the formation of fluid instabilities from induced perturbations. I.S. acknowledges support through the Director's fellowship from Los Alamos National Laboratory. This research used resources provided by the LANL Institutional Computing Program.

Fuel gain exceeding unity in an inertially confined fusion implosion.

PubMed

Hurricane, O A; Callahan, D A; Casey, D T; Celliers, P M; Cerjan, C; Dewald, E L; Dittrich, T R; Döppner, T; Hinkel, D E; Berzak Hopkins, L F; Kline, J L; Le Pape, S; Ma, T; MacPhee, A G; Milovich, J L; Pak, A; Park, H-S; Patel, P K; Remington, B A; Salmonson, J D; Springer, P T; Tommasini, R

2014-02-20

Ignition is needed to make fusion energy a viable alternative energy source, but has yet to be achieved. A key step on the way to ignition is to have the energy generated through fusion reactions in an inertially confined fusion plasma exceed the amount of energy deposited into the deuterium-tritium fusion fuel and hotspot during the implosion process, resulting in a fuel gain greater than unity. Here we report the achievement of fusion fuel gains exceeding unity on the US National Ignition Facility using a 'high-foot' implosion method, which is a manipulation of the laser pulse shape in a way that reduces instability in the implosion. These experiments show an order-of-magnitude improvement in yield performance over past deuterium-tritium implosion experiments. We also see a significant contribution to the yield from α-particle self-heating and evidence for the 'bootstrapping' required to accelerate the deuterium-tritium fusion burn to eventually 'run away' and ignite.

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility.

PubMed

Olson, R E; Leeper, R J; Kline, J L; Zylstra, A B; Yi, S A; Biener, J; Braun, T; Kozioziemski, B J; Sater, J D; Bradley, P A; Peterson, R R; Haines, B M; Yin, L; Berzak Hopkins, L F; Meezan, N B; Walters, C; Biener, M M; Kong, C; Crippen, J W; Kyrala, G A; Shah, R C; Herrmann, H W; Wilson, D C; Hamza, A V; Nikroo, A; Batha, S H

2016-12-09

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D_{2} and DT layer inertial confinement fusion (ICF) implosions that can access a low-to-moderate hot-spot convergence ratio (1230) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CRs of 12-17, and the hot-spot formation is well understood, demonstrated by a good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility.

PubMed

Hinkel, D E; Berzak Hopkins, L F; Ma, T; Ralph, J E; Albert, F; Benedetti, L R; Celliers, P M; Döppner, T; Goyon, C S; Izumi, N; Jarrott, L C; Khan, S F; Kline, J L; Kritcher, A L; Kyrala, G A; Nagel, S R; Pak, A E; Patel, P; Rosen, M D; Rygg, J R; Schneider, M B; Turnbull, D P; Yeamans, C B; Callahan, D A; Hurricane, O A

2016-11-25

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

Theory of hydro-equivalent ignition for inertial fusion and its applications to OMEGA and the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nora, R.; Betti, R.; Bose, A.

The theory of ignition for inertial confinement fusion capsules [R. Betti et al., Phys. Plasmas 17, 058102 (2010)] is used to assess the performance requirements for cryogenic implosion experiments on the Omega Laser Facility. The theory of hydrodynamic similarity is developed in both one and two dimensions and tested using multimode hydrodynamic simulations with the hydrocode DRACO [P. B. Radha et al., Phys. Plasmas 12, 032702 (2005)] of hydro-equivalent implosions (implosions with the same implosion velocity, adiabat, and laser intensity). The theory is used to scale the performance of direct-drive OMEGA implosions to the National Ignition Facility (NIF) energy scalesmore » and determine the requirements for demonstrating hydro-equivalent ignition on OMEGA. Hydro-equivalent ignition on OMEGA is represented by a cryogenic implosion that would scale to ignition on the NIF at 1.8 MJ of laser energy symmetrically illuminating the target. It is found that a reasonable combination of neutron yield and areal density for OMEGA hydro-equivalent ignition is 3 to 6 × 10{sup 13} and ∼0.3 g/cm{sup 2}, respectively, depending on the level of laser imprinting. This performance has not yet been achieved on OMEGA.« less

Three-Dimensional Hydrodynamic Simulations of the Effects of Laser Imprint in OMEGA Implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Campbell, E. M.; Goncharov, V. N.; Regan, S. P.; Shvydky, A.; Schmitt, A. J.

2017-10-01

Illumination of direct-drive implosion targets by the OMEGA laser introduces large-amplitude broadband modulations in the absorbed energy from the largest (target size 900- μm) to smallest (speckle size 2- μm) spatial scales. These modulations ``imprint'' perturbations into a target that are amplified because of the secular and Rayleigh-Taylor growths during acceleration and deceleration of the target. The degradation of performance of room-temperature and cryogenic OMEGA implosions caused by these perturbations were simulated in three dimensions using the code ASTER. The highest-resolution simulations resolve perturbation modes as high as l 200 . The high modes l 50to 100 dominate in the perturbation spectrum during the linear growth, while the late-time nonlinear evolution results in domination of modes with l 30to 50 . Smoothing by spectral dispersion reduces the linear-phase mode amplitudes by a factor of 4 and results in substantial improvements in implosion performance that is in good agreement with measurements. The effects of imprint on implosion performance are compared with the effects of other implosion asymmetries, such as those induced because of laser beam imbalance, mistiming and mispointing, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Effects of local defect growth in direct-drive cryogenic implosions on OMEGA

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Goncharov, V. N.; Shmayda, W. T.; Harding, D. R.; Sangster, T. C.; Meyerhofer, D. D.

2013-08-01

Spherically symmetric, low-adiabat (adiabat α ≲ 3) cryogenic direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1995)] yield less than 10% of the neutrons predicted in one-dimensional hydrodynamic simulations. Two-dimensional hydrodynamic simulations suggest that this performance degradation can be explained assuming perturbations from isolated defects of submicron to tens-of-micron scale on the outer surface or inside the shell of implosion targets. These defects develop during the cryogenic filling process and typically number from several tens up to hundreds for each target covering from about 0.2% to 1% of its surface. The simulations predict that such defects can significantly perturb the implosion and result in the injection of about 1 to 2 μg of the hot ablator (carbon-deuterium) and fuel (deuterium-tritium) materials from the ablation surface into the targets. Both the hot mass injection and perturbations of the shell reduce the final shell convergence ratio and implosion performance. The injected carbon ions radiatively cool the hot spot, reducing the fuel temperature, and further reducing the neutron yield. The negative effect of local defects can be minimized by decreasing the number and size of these defects and/or using more hydrodynamically stable implosion designs with higher shell adiabat.

Wavelength Detuning Cross-Beam Energy Transfer Mitigation Scheme for Direct-Drive: Modeling and Evidence from National Ignition Facility Implosions

NASA Astrophysics Data System (ADS)

Marozas, J. A.

2017-10-01

Cross-beam energy transfer (CBET) has been shown to significantly reduce the laser absorption and implosion speed in direct-drive implosion experiments on OMEGA and the National Ignition Facility (NIF). Mitigating CBET assists in achieving ignition-relevant hot-spot pressures in deuterium-tritium cryogenic OMEGA implosions. In addition, reducing CBET permits lower, more hydrodynamically stable, in-flight aspect ratio ignition designs with smaller nonuniformity growth during the acceleration phase. Detuning the wavelengths of the crossing beams is one of several techniques under investigation at the University of Rochester to mitigate CBET. This talk will describe these techniques with an emphasis on wavelength detuning. Recent experiments designed and predicted using multidimensional hydrodynamic simulations including CBET on the NIF have exploited the wavelength arrangement of the NIF beam geometry to demonstrate CBET mitigation through wavelength detuning in polar-direct-drive (PDD) implosions. Shapes and trajectories inferred from time-resolved x-ray radiography of the imploding shell, scattered-light spectra, and hard x-ray spectra generated by suprathermal electrons all indicate a reduction in CBET. These results and their implications for direct-drive ignition will be presented and discussed. In addition, hydrodynamically scaled ignition-relevant designs for OMEGA implosions exploiting wavelength detuning will be presented. Changes required to the OMEGA laser to permit wavelength detuning will be discussed. Future plans for PDD on the NIF including more-uniform implosions with CBET mitigation will be explored. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Experimental demonstration of fusion-relevant conditions in magnetized liner inertial fusion

DOE PAGES

Gomez, Matthew R.; Slutz, Stephen A..; Sefkow, Adam B.; ...

2014-10-06

This Letter presents results from the first fully integrated experiments testing the magnetized liner inertial fusion concept [S.A. Slutz et al., Phys. Plasmas 17, 056303 (2010)], in which a cylinder of deuterium gas with a preimposed axial magnetic field of 10 T is heated by Z beamlet, a 2.5 kJ, 1 TW laser, and magnetically imploded by a 19 MA current with 100 ns rise time on the Z facility. Despite a predicted peak implosion velocity of only 70 km/s, the fuel reaches a stagnation temperature of approximately 3 keV, with T e ≈ T i, and produces up tomore » 2e12 thermonuclear DD neutrons. In this study, X-ray emission indicates a hot fuel region with full width at half maximum ranging from 60 to 120 μm over a 6 mm height and lasting approximately 2 ns. The number of secondary deuterium-tritium neutrons observed was greater than 10 10, indicating significant fuel magnetization given that the estimated radial areal density of the plasma is only 2 mg/cm 2.« less

X-ray continuum as a measure of pressure and fuel–shell mix in compressed isobaric hydrogen implosion cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Epstein, R.; Goncharov, V. N.; Marshall, F. J.

Pressure, by definition, characterizes the conditions within an isobaric implosion core at peak compression [Gus'kov et al., Nucl. Fusion 16, 957 (1976); Betti et al., Phys. Plasmas 8, 5257 (2001)] and is a key parameter in quantifying its near-ignition performance [Lawson, Proc. Phys. Soc. London, B 70, 6 (1957); Betti et al., Phys. Plasmas 17, 058102 (2010); Goncharov et al., Phys. Plasmas 21, 056315 (2014); and Glenzer et al., Phys. Plasmas 19, 056318 (2012)]. At high spectral energy, where the x-ray emission from an imploded hydrogen core is optically thin, the emissivity profile can be inferred from the spatially resolvedmore » core emission. This emissivity, which can be modeled accurately under hot-core conditions, is dependent almost entirely on the pressure when measured within a restricted spectral range matched to the temperature range anticipated for the emitting volume. In this way, the hot core pressure at the time of peak emission can be inferred from the measured free-free emissivity profile. The pressure and temperature dependences of the x-ray emissivity and the neutron-production rate explain a simple scaling of the total filtered x-ray emission as a constant power of the total neutron yield for implosions of targets of similar design over a broad range of shell implosion isentropes. This scaling behavior has been seen in implosion simulations and is confirmed by measurements of high-isentrope implosions [Sangster et al., Phys. Plasmas 20, 056317 (2013)] on the OMEGA laser system [Boehly et al., Opt. Commun. 133, 495 (1997)]. Attributing the excess emission from less-stable, low-isentrope implosions, above the level expected from this neutron-yield scaling, to the higher emissivity of shell carbon mixed into the implosion's central hot spot, the hot-spot “fuel–shell” mix mass can be inferred.« less

Functional sensibility assessment. Part I: develop a reliable apparatus to assess momentary pinch force control.

PubMed

Chiu, Haw-Yen; Hsu, Hsiu-Yun; Kuo, Li-Chieh; Chang, Jer-Hao; Su, Fong-Chin

2009-08-01

A precise magnitude and timing control of pinch performance is based on accurate feed-forward and feedback control mechanisms. Ratio of peak pinch force and maximum load force during a functional performance is a sensitive parameter to reflect the ability to scale pinch force output according to actual loads. A pinch apparatus was constructed to detect momentary pinch force modulation of 20 subjects with normal hand sensation. The results indicated high intra-class correlation coefficient and small coefficient of variation of the detected force ratio among three repeated tests, which represented that the stability test of the measured response confirmed the feasibility of this apparatus. The force ratio for a 480 g object with a steel surface ranged between 1.77 and 1.98. Normal subjects were able to scale and contribute pinch force precisely to a pinch-holding-up test. This study may provide clinicians a reliable apparatus and method to analyze the recovery of functional sensibility in patients with nerve injuries. Copyright 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Self-pinched lithium beam transport experiments on SABRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, D.L.; Olson, C.L.; Poukey, J.W.

Self-pinched transport of ion beams has many advantages for ion-driven ICF applications involving high yield and energy production. The authors are currently preparing for a self-pinched lithium beam transport experiment on the SABRE accelerator. There are three transport elements that must eventually be demonstrated: (1) efficient lithium beam generation and ballistic transport to a focus at the self-pinched transport channel entrance; (2) self-pinched transport in the channel, requiring optimized injection conditions and gas breakdown; and (3) self-pinched transport of the equilibrated beam from the channel into free space, with associated aiming and stability considerations. In the present experiment, a hollowmore » annular lithium beam from an applied-B extraction ion diode will be focused to small radius (r {le} 2 cm) in a 60 cm long ballistic focus section containing argon gas at a pressure of a few Torr. The self-pinched transport channel will contain a low pressure background gas of 10--40 mTorr argon to allow sufficient net current to confine the beam for long distance transport. IPROP simulations are in progress to optimize the design of the ballistic and self-pinched transport sections. Progress on preparation of this lithium self-pinched transport experiment, including a discussion of transport system design, important gas breakdown issues, and diagnostics, will be presented.« less

Systematic Fuel Cavity Asymmetries in Directly Driven Inertial Confinement Fusion Implosions

DOE PAGES

Shah, Rahul C.; Haines, Brian Michael; Wysocki, Frederick Joseph; ...

2017-03-30

Here, we present narrow-band self-emission x-ray images from a titanium tracer layer placed at the fuel-shell interface in 60-laser-beam implosion experiments at the OMEGA facility. The images are acquired during deceleration with inferred convergences of ~9-14. Novel here is that a systematically observed asymmetry of the emission is linked, using full sphere 3D implosion modeling, to performance-limiting low mode asymmetry of the drive.