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1

Dynamics of a high-power aluminum-wire array Z-pinch implosion  

SciTech Connect

Annular Al-wire Z-pinch implosions on the Saturn accelerator [D. D. Bloomquist {ital et al.}, {ital Proceedings, 6th Pulsed Power Conference} (Institute of Electrical and Electronics Engineers, New York, 1987), p. 310] that have high azimuthal symmetry exhibit both a strong first and weaker second x-ray burst that correlate with strong and weaker radial compressions, respectively. Measurements suggest that the observed magnetic Rayleigh{endash}Taylor (RT) instability prior to the first compression seeds an m=0 instability observed later. Analyses of axially averaged spectral data imply that, during the first compression, the plasma is composed of a hot core surrounded by a cooler plasma halo. Two-dimensional (2-D) radiation magnetohydrodynamic computer simulations show that a RT instability grows to the classic bubble and spike structure during the course of the implosion. The main radiation pulse begins when the bubble reaches the axis and ends when the spike finishes stagnating on axis and the first compression ends. These simulations agree qualitatively with the measured characteristics of the first x-ray pulse and the overall energetics, and they provide a 2-D view into the plasma hydrodynamics of the implosion.

Sanford, T.W.; Nash, T.J.; Mock, R.C.; Spielman, R.B.; Struve, K.W. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Hammer, J.H.; De Groot, J.S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Whitney, K.G.; Apruzese, J.P. [Naval Research Laboratory, Radiation Hydrodynamics Branch, Washington, D.C. 20375 (United States)] [Naval Research Laboratory, Radiation Hydrodynamics Branch, Washington, D.C. 20375 (United States)

1997-06-01

2

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

SciTech Connect

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 {approximately} 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.

Sanford, T.W.L.; Mock, R.C.; Marder, B.M. [and others

1997-12-01

3

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

SciTech Connect

A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, including the radiated power, increases with wire number. Radiation magnetohydrodynamic (RMEC) 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 {approximately} 1.4 mm. In the plasma-shell regime, the experimental implosions exhibit 1D- and 2D-code characteristics as evidenced by the presence of a strong first and a weak second radiation pulse that correlates with a strong and weak radial convergence. In this regime, many of the radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. Moreover, measured changes in the radiation pulse width with variations in array mass and 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 K-shell radiation scaling models.

Sanford, T.W.L.; Mock, R.C.; Marder, B.M. [and others

1997-06-01

4

Experimental astrophysics with high power lasers and Z pinches  

SciTech Connect

With the advent of high energy density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, mm-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors; equations of state relevant to planetary interiors; strong shock driven nonlinear hydrodynamics and radiative dynamics, relevant to supernova explosions and subsequent evolution; protostellar jets and high Mach-number flows; radiatively driven molecular clouds and nonlinear photoevaporation front dynamics; and photoionized plasmas relevant to accretion disks around compact objects, such as black holes and neutron stars.

Remington, B A; Drake, R P; Ryutov, D D

2004-12-10

5

Structure of stagnated plasma in aluminum wire array Z pinches  

SciTech Connect

Experiments with aluminum wire array Z pinches have been carried out on the mega-ampere generator for plasma implosion experiments (MAGPIE) at Imperial College London [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]. It has been shown that in these arrays, there are two intense sources of radiation during stagnation; Al XII line emission from a precursor-sized object, and both continuum and Al XIII radiation from bright spots of either significantly higher temperature or density randomly distributed around this object so as to produce a hollow emission profile. Spatially resolved spectra produced by spherically bent crystals were recorded, both time-integrated and time-resolved, and were used to show that these two sources of radiation peak at the same time.

Hall, G. N.; Pikuz, S. A.; Shelkovenko, T. A.; Bland, S. N.; Lebedev, S. V.; Ampleford, D. J.; Palmer, J. B. A.; Bott, S. C.; Rapley, J.; Chittenden, J. P.; Apruzese, J. P. [Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States); Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2006-08-15

6

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

SciTech Connect

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.

SANFORD,THOMAS W. L.

2000-05-23

7

Use of the Pegasus Z pinch machine to study inertial instabilities in aluminum: a preliminary report  

SciTech Connect

We have designed a target to probe the use of the Pegasus Z-Pinch machine to image inertial instabilities that develop on cylindrical- convergent material interfaces. The Z-pinch is tailored so that the target, soft Al 1100-O, remains solid; instabilities and inertial effects are seeded by wire inclusions of different densities. We present here the first images and preliminary results from this experiment.

Chandler, E.; Egan, P.; Winer, K.; Stokes, J.; Fulton, R.D.; King, N.S.P.; Morgan, D.V.; Obst, A.W.; Oro, D.W.

1997-06-13

8

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

SciTech Connect

A Saturn-accelerator study of annular, aluminum-wire array, Z-pinch implosions, in the calculated high-wire-number plasma-shell regime [Phys. Rev. Lett. {bold 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{endash}Taylor instability) relative to the increase in the shell implosion velocity. Over the array radii explored, the measured peak total x-ray power of {approximately}40 TW and energy of {approximately}325 kJ show little change outside of a {plus_minus}15{percent} shot-to-shot fluctuation and are consistent with the E-RMHC simulations. Similarly, the measured peak {ital K}-shell (lines plus continuum) power of {approximately}8 TW and energy of {approximately}70 kJ show little change with radius. The minimal change in {ital K}-shell yield is in agreement with simple {ital 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{endash}Taylor instability observed in small-wire-number imploding loads. {copyright} {ital 1998 American Institute of Physics.}

Sanford, T.W.; Mock, R.C.; Spielman, R.B. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Peterson, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545-0010 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545-0010 (United States); Mosher, D. [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States)] [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States); Roderick, N.F. [University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [University of New Mexico, Albuquerque, New Mexico 87131 (United States)

1998-10-01

9

Analyzing time-resolved spectroscopic data from an azimuthally symmetric, aluminum-wire array, z-pinch implosion  

SciTech Connect

A 90-wire, aluminum, z-pinch experiment was conducted on the Saturn accelerator at the Sandia National Laboratories that exhibited azimuthally symmetric implosions and two x-ray bursts, a main burst and a subsidiary one. These bursts correlated with two consecutive radial implosions and are consistent with predicted magnetohydrodynamics behavior. A variety of time-resolved, accurately timed, spectroscopic measurements were made in this experiment and are described in this paper. These measurements include (1) the pinch implosion time, (2) time-resolved pinhole pictures that give sizes of the K-shell emission region, (3) time-resolved K-series spectra that give the relative amounts of hydrogenlike to heliumlike to continuum emission, (4) the total and the K-shell x-ray power outputs, and (5) time-resolved photoconducting diode measurements from which continuum slopes and time-resolved electron temperatures can be inferred. Time-resolved Ly-{alpha} and Ly-{beta} linewidths are obtained from the spectra and inferences about time-resolved ion temperatures are also made. All of these data correlate well with one another. A method is then presented of analyzing this data that relies on the complete set of time-resolved measurements. This analysis utilizes one-dimensional radiative magnetohydrodynamic simulations of the experiments, which drive z-pinch implosions using the measured Saturn circuit parameters. These simulations are used to calculate the same x-ray quantities as were measured. Then, comparisons of the measured and calculated data are shown to define a process by which different dynamical assumptions can be invoked or rejected in an attempt to reproduce the ensemble of data. This process depends on the full data set and provides insight into the structure of the radial temperature and density gradients of the on-axis pinch. (Abstract Truncated)

Whitney, K.G.; Thornhill, J.W.; Pulsifer, P.E.; Apruzese, J.P. [Radiation Hydrodynamics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)] [Radiation Hydrodynamics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Sanford, T.W.; Nash, T.J.; Mock, R.C.; Spielman, R.B. [Sandia National Laboratories P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)

1997-09-01

10

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

SciTech Connect

Two sets of [ital 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 [ital 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 [ital 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 [ital 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 [ital K]-shell x-ray yield from aluminum as a function of load mass assuming kinetic energy conversion alone.

Whitney, K.G.; Thornhill, J.W.; Giuliani, J.L. Jr.; Davis, J. (Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)); Miles, L.A.; Nolting, E.E.; Kenyon, V.L.; Speicer, W.A.; Draper, J.A.; Parsons, C.R.; Dang, P. (Naval Surface Warfare Center, White Oak, Silver Spring, Maryland 20903 (United States)); Spielman, R.B.; Nash, T.J.; McGurn, J.S.; Ruggles, L.E. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)); Deeney, C.; Prasad, R.R.; Warren, L. (Physics International Co., San Leandro, California 94577 (United States))

1994-09-01

11

A comparison of aluminum and nickel wire array z-pinches and aluminium exploding single wires  

Microsoft Academic Search

Summary form only given. An extensive aluminum wire array experiment has been performed. Wire arrays of 6-25-mm diameter have been imploded on the 6-TW Double-EAGLE generator. With the masses adjusted so that the implosion time was between 85 and 95 ns, an optimum aluminum K-shell yield of 30 kJ was obtained with an array diameter of 12.5 mm. Analyses were

C. Deeney; T. Nash; P. D. LePell; R. R. Prasad; M. Krishnan; K. G. Whitney; J. W. Thornhill; M. C. Coulter; J. Giuliani

1990-01-01

12

Driver coupling to quasistatic Z-pinches  

Microsoft Academic Search

Quasistatic Z-pinches formed ``on axis'' and magnetically confined by a current layer larger than a critical current (>1.5 MA for deuterium) are supposed to undergo radiative collapse providing high energy density thermal plasmas. Z-pinches created from solid fibers do not well couple to the necessarily high power drivers due to lacking initial conductivity and compressibility resulting in fast global plasma

G. Decker; W. Kies; S. Stein

1997-01-01

13

X-ray backlighting density measurements of tungsten and aluminum wire and wire array Z-pinches  

Microsoft Academic Search

Summary form only given. Calibrated density measurements in both the coronal plasmas and dense cores of exploding W wire and wire array Z-pinches, powered by the ~450 kA, 100 ns XP-pulser at Cornell University, have been made using two-frame X-ray backlighting in conjunction with known thickness W step wedges. The backlighting images are made by Mo wire X-pinch radiation filtered

D. A. Hammer; S. A. Pikuz; T. A. Shelkovenko; J. B. Greenly; D. B. Sinars; A. R. Mingaleev

1999-01-01

14

Dense Z-pinch plasmas  

SciTech Connect

Early researchers recogniZed the desirable features of the linear Z-pinch configuration as a magnetic fusion scheme. In particular, a Z-pinch reactor might not require auxiliary heating or external field coils, and could constitute an uncomplicated, high plasma ..beta.. geometry. The simple Z pinch, however, exhibited gross MHD instabilities that disrupted the plasma, and the linear Z pinch was abandoned in favor of more stable configurations. Recent advances in pulsed-power technology and an appreciation of the dynamic behavior of an ohmically heated Z pinch have led to a reexamination of the Z pinch as a workable fusion concept.

Shlachter, J.S.; Hammel, J.E.; Scudder, D.W.

1985-07-12

15

Explosive Z Pinch  

E-print Network

We propose an explanation for the recently observed powerful contained explosion in a Z pinch experiment performed at Sandia National Laboratories. Our arguments are based on the assumption that a pure SU(2) Yang-Mills theory of scale $\\sim 0.5 $MeV is responsible for the emergence of the electron and its neutrino.

Francesco Giacosa; Ralf Hofmann; Markus Schwarz

2006-04-20

16

Characteristics of implosion and radiation for aluminum planar wire array z-pinch at 1.5 MA  

NASA Astrophysics Data System (ADS)

Planar wire arrays Z pinches were carried out on Qiangguang generator (1.5 MA, 100 ns). Loads with varied row widths (6-24 mm) and wire numbers (10-34) were employed in the experiments. The implosion dynamics of planar wire arrays has been studied. Meanwhile, the changes of the implosion time, radiation yield and power with array mass, inter-wire gap, and array width were investigated. The images of a soft X-ray camera exhibit that the trailing mass, precursor column, and R-T instability exist during the implosion phase, and when m = 0 maybe accompanied with m = 1, instability will rapidly develop after stagnation. The implosion trajectories show that loads will implode by the snowplow mode and about 50% of total initial array mass will participate in the final implosion. The maximum total X-ray energy is 22 kJ with a power of 630 GW, while the maximum K-shell yield is 3.9 kJ with a power of 158 GW. Experiments with different planar wire arrays show that the value of mPD02 (the product of line mass and squared width) is the critical factor which affects the implosion time and the X-ray products of the wire arrays. The optimum value of mPD02 should be in the range of 200-400 ?gcm and the inter-wire gap should be less than 1 mm.

Liangping, Wang; Jian, Wu; Mo, Li; Juanjuan, Han; Ning, Guo; Gang, Wu; Aici, Qiu

2012-12-01

17

X-ray backlighting density measurements of tungsten and aluminum wire and wire array z-pinches  

SciTech Connect

Calibrated density measurements in both the coronal plasmas and dense cores of exploding W wire and wire array Z-pinches, powered by the {approximately}450 kA, 100 ns XP-pulser at Cornell University, have been made using two-frame x-ray backlighting in conjunction with known thickness W step wedges. The backlighting images are made by Mo wire X-pinch radiation filtered by 12.5 {micro}m Ti impinging upon a sandwich of films (Micrat VR, Kodak GWL, Kodak DEF) which have different sensitivities to increase the dynamic range of the method. A W step wedge filter is placed in front of the films, giving absolute line density calibration of each exposure with estimated errors ranging from 20 to 50%. Assuming x-ray absorption by the W plasma is the same as for the solid material, the authors are able to measure W areal densities from 3.2 x 10{sup 19} to 2 x 10{sup 17}/cm{sup 2}. These can be converted to number density assuming azimuthal symmetry. For example, for an exploded 7.5 {micro}m wire with a 15--20 {micro}m diameter dense core and a 1 mm corona diameter, the implied W volume density ranges from 2x10{sup 18} to over 10{sup 22}/cm{sup 3}. Integration of the line density gives an estimate of the fraction of the wire mass in the corona and core. For example, with 100 kA peak current in a single 7.5 {micro}m W wire, {approximately}70% (>90%) of the W mass is in the corona after 53 ns (61 ns). The authors also observe that the corona has large, roughly axisymmetric axial nonuniformity both in radius and in mass density. In addition, the coronal plasma contains more of the W mass, expands faster and is more uniform when the wire is surface-cleaned by preheating. In arrays of 2--8 wires with the same 100 kA total current, detectable coronal plasma appears after 25--35 ns, and much of it is swept toward the center of the array, forming a dense channel. The portion of the initial wire mass in the coronal plasma increases with smaller wire diameter and decreases with greater wire number: 15% for 4 x 13.5 {micro}m, 35% for 4 x 7.5 {micro}m, and 25% for 8 x 7.5 {micro}m, at 46--48 ns (unheated). Similar measurements are now being made with Al wires and an Al step wedge. Results will be presented.

Hammer, D.A.; Pikuz, S.A.; Shelkovenko, T.A.; Greenly, J.B.; Sinars, D.B.; Mingaleev, A.R.

1999-07-01

18

Systematic trends in x-ray emission characteristics of variable-wire-number, fixed-mass, aluminum-array, Z-pinch implosions  

SciTech Connect

Increasing the number of wires an order of magnitude from 10 to almost 200 while simultaneously fixing the total wire mass in annular aluminum-wire-array Z-pinch implosions on the 20 TW Saturn generator [{ital Proceedings of the 6th International IEEE Pulsed Power Conference} (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1987), p. 310] demonstrates two separate power-law trends in the measured x-ray characteristics as a function of the initial interwire gap ({ital g}). These trends are approximately independent of the array radius. When {ital g} decreases from {approximately}6 to 0.4 mm, the peak total radiated power increases by a factor of 20 and the total energy by a factor of 2. There is a more rapid increase in peak power and energy radiated as {ital g} decreases for gaps greater than {approximately}2 mm. This increase is related to a measured decrease in precursor plasma and to a calculated decreased sensitivity of the implosion to azimuthal asymmetries that occurs when individual wire plasmas begin to merge following their vaporization. The substantial increase in power arises from an inferred increase in plasma compression and can be correlated with an almost linear reduction in the calculated effective thickness of the plasma annulus near stagnation as {ital g} decreases. {copyright} {ital 1999 American Institute of Physics.}

Sanford, T.W.; Mock, R.C.; Nash, T.J. [Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185 (United States); Whitney, K.G.; Pulsifer, P.E.; Apruzese, J.P. [Naval Research Laboratory, Radiation Hydrodynamics Branch, Washington, DC 20375 (United States)] [Naval Research Laboratory, Radiation Hydrodynamics Branch, Washington, DC 20375 (United States); Mosher, D. [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States)] [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States); Peterson, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Haines, M.G. [Imperial College, The Blackett Laboratory, London SW7 2BZ (United Kingdom)] [Imperial College, The Blackett Laboratory, London SW7 2BZ (United Kingdom)

1999-04-01

19

Increased x-ray power generated from low-mass large-number aluminum-wire-array Z-pinch implosions  

SciTech Connect

A Saturn accelerator study of annular, aluminum-wire-array, Z-pinch implosions in the calculated high-wire-number plasma-shell regime [Phys. Rev. Lett. {bold 77}, 5063 (1996)] shows that a factor of 2 decrease in pulse width and an associated doubling of the total radiated x-ray power occurs when the mass of 12 mm radius, 2 cm long array is reduced from above 1.9 mg to below 1.3 mg. The study utilized extensive time- and space-resolved measurements to characterize the implosion over the mass range 0.42{endash}3.4 mg. Eulerian radiation-magnetohydrodynamic-code simulations in the r-z plane agree qualitatively with the measurements. They suggest that the pulse-width decrease with mass is due to the faster implosion velocity of the plasma shell relative to the growth of the shell thickness that arises from a two-stage development of the magnetic Rayleigh{endash}Taylor instability. Over the bulk of the mass-range explored, the variation in {ital K}-shell (lines plus free-bound continuum) yield is in qualitative agreement with simple {ital K}-shell radiation-scaling models. These models indicate that the doubling of the measured {ital K}-shell yield, which also occurs for masses below 1.3 mg relative to masses above 1.9 mg, arises from increased plasma temperature. {copyright} {ital 1998 American Institute of Physics.}

Sanford, T.W.; Mock, R.C.; Spielman, R.B. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Peterson, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Mosher, D. [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States)] [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States); Roderick, N.F. [University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [University of New Mexico, Albuquerque, New Mexico 87131 (United States)

1998-10-01

20

Multi-dimensional z-pinch calculations with ALEGRA  

SciTech Connect

Two and three-dimensional modeling of exploding z-pinch wires as well as the imploding z-pinch wire array is important to provide insight into the relevant issues for designing high-power z-pinch configurations. The authors present several calculations done with the MHD modeling capability available within the ALEGRA framework for parallel shock-physics computations. A set of wire explosion calculations illustrates the extreme sensitivity of these configurations to mesh resolution. Use of the ALE capability in ALEGRA will be illustrated. An additional set of calculations investigating the run in and stagnation of an initial merged-wire sheath configuration will be compared with previous calculations and experimental results.

Robinson, A.C.; Garasi, C.J.; Haill, T.A.; Morse, R.L.; Stolz, P.H.

1999-07-01

21

Z-Pinch Experiments with Styrofoam Fibres and Plasmajets  

Microsoft Academic Search

Z-pinch plasmas created from fibres are less prone to macroscopic instabilities than predicted by ideal MHD theory. However, solid fibre experiments at the pulseline KALIF (2 MV, 900 kA) gave disappointing results with respect to driver-load coupling and pinch plasma confinement. High power discharges led to current leaks and plasma expansion presumably due to lacking initial conductivity and compressibility. Therefore

S. Stein; G. Decker; W. Kies; P. Rwekamp; G. Ziethen; K. Baumung; H. Bluhm; W. Ratajczak; D. Rusch; J. M. Bayley

1994-01-01

22

Plasma formation in metallic wire Z pinches  

SciTech Connect

Plasma formation in metallic wire Z pinches is modeled using a two-dimensional resistive magnetohydrodynamics code. Modified Thomas-Fermi equations of state and dense plasma transport coefficients allow the phase transitions from solid to plasma to be approximated. Results indicate the persistence of a two-component structure with a cold, dense core embedded within a much hotter, low density, m=0 unstable corona. Extensive benchmark testing against data from a number of single-wire experiments is presented. Artificial laser schlieren and x-ray back-lighting images generated from the code data are compared directly to experimental results. The results were found to be insensitive to inaccuracies in the equations of state and transport coefficients. Simulations of individual wires in a wire array show different behavior to that observed experimentally due to the absence of three-dimensional effects. Simulations with similar conditions to wires in an array show a general trend in the plasma structure at start of implosion from discrete wires with large m=0 perturbation amplitudes to partially merged wires with smaller perturbation amplitudes as the number of wires is increased. Results for a wire number scan with aluminum wire arrays on the SATURN generator suggest that the observed sharp transition to high x-ray power at around 40 wires corresponds to a sharp decrease in m=0 perturbation amplitude and hence a sharp decrease in the seed perturbation for the Rayleigh-Taylor instability. (c) 2000 The American Physical Society.

Chittenden, J. P. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Lebedev, S. V. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Ruiz-Camacho, J. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Beg, F. N. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Bland, S. N. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Jennings, C. A. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Bell, A. R. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Haines, M. G. [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom); Pikuz, S. A. [P. N. Lebedev Physical Institute, Moscow 121433, Russia (Russian Federation)] [P. N. Lebedev Physical Institute, Moscow 121433, Russia (Russian Federation); Shelkovenko, T. A. [P. N. Lebedev Physical Institute, Moscow 121433, Russia (Russian Federation)] [P. N. Lebedev Physical Institute, Moscow 121433, Russia (Russian Federation)

2000-04-01

23

Implosion and stagnation of wire array Z pinches  

SciTech Connect

Detailed measurements of the dynamics of aluminum wire array Z pinches from immediately prior to implosion until stagnation and dissipation on axis are presented. Before implosion, the {approx}0.5 mm axial modulation seen in earlier laser probing images is observed as ablation on the surface of the wire cores facing away from the array axis. This results in the complete ablation of sections of the wire cores and a redistribution of current at the start of implosion. The dynamics of implosion are then strongly influenced by the number of wires in the array. With only eight wires, discrete snowplough bubbles expand from each wire toward the precursor. There is little, if any, correlation between the bubbles from adjacent wires, and a large temporal spread over which the bubbles arrive at the precursor is observed, along with a long rise time, low power soft x-ray pulse. With 32 or more wires, bubbles from adjacent wires merge close to the array edge to form an imploding sheath. The front edge of the sheath is well defined with a small spatial spread, and upon reaching the precursor, the start of a fast rising high power soft-x-ray pulse is seen. As x-ray emission increases, the stagnating column on axis starts to decrease in diameter, reaching a minimum at peak x-ray emission, which also coincides with the time when the rear edge of the snowplough reaches the column. Thereafter, the stagnated column is seen to go unstable, and trailing mass left behind during the implosion is accelerated toward the axis. Intense x-ray emission ends as this mass becomes cleared out.

Bland, S. N.; Lebedev, S. V.; Chittenden, J. P.; Hall, G. N.; Suzuki-Vidal, F.; Ampleford, D. J.; Bott, S. C.; Palmer, J. B. A.; Pikuz, S. A.; Shelkovenko, T. A. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); AWE plc, Aldemaston, Reading RG7 4PR (United Kingdom); Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States)

2007-05-15

24

K-shell radiation physics in low- to moderate-atomic-number z-pinch plasmas on the Z accelerator  

Microsoft Academic Search

Dense z-pinches produced by 100ns implosions of wire arrays or gas puffs produce substantial soft X-ray power. One class of z-pinch radiation sources includes low- to moderate-atomic-number K-shell radiators, such as aluminum and iron. These loads are designed for 110keV K-shell X-ray generation, and offer opportunities for crystal spectroscopy that can reveal fundamental properties of the plasma when studied using

B. Jones; C. Deeney; C. A. Coverdale; P. D. LePell; J. L. McKenney; J. P. Apruzese; J. W. Thornhill; K. G. Whitney; R. W. Clark; A. L. Velikovich; J. Davis; Y. Maron; V. Kantsyrev; A. Safronova; V. I. Oreshkin

2006-01-01

25

Spectroscopic study in Z-pinch discharge  

SciTech Connect

The temporal variation of the emitted line intensity has been investigated, and thus an important information about the dynamic ionization stages in the Z-pinch discharge has been studied. Also the electron temperature Te, has been deduced by using a spectroscopic technique.

Garamoon, A.A.; Saudy, A.H.; Shark, W. [Al-Azhar Univ., Cairo (Egypt)] [and others

1995-12-31

26

The conical z-pinch plasma gun  

Microsoft Academic Search

An investigation of a conical z-pinch plasma gun, using a high speed camera and magnetic probes, has shown that a conical current sheet implodes to form a highly luminous axial pinch. The plasma and the current sheet at the muzzle of the gun are always symmetrical about the axis. The interaction between the azimuthal magnetic field and the current sheet

D. G. Fearn; E. R. Wooding

1967-01-01

27

Use of Z-pinch sources for high-pressure shock wave studies  

SciTech Connect

In this paper, we will discuss the use of z-pinch sources for shock wave studies at multi-Mbar pressures. Experimental plans to use the technique for absolute shock Hugoniot measurements are discussed. Recent developments have demonstrated the use of pulsed power techniques for producing intense radiation sources (Z pinches) for driving planar shock waves in samples with spatial dimensions significantly larger than possible with other radiation sources. Initial indications are that using Z pinch sources for producing Planckian radiation sources in secondary hohlraums can be used to drive shock waves in samples with diameters to a few millimeters and thickness approaching one millimeter in thickness. These dimensions provides the opportunity to measure both shock velocity and the particle velocity behind the shock front with accuracy comparable to that obtained with gun launchers. In addition, the peak hohlraum temperatures of nearly 150 eV that are now possible with Z pinch sources result in shock wave pressures approaching 45 Mbar in high impedance materials such as tungsten and 10-15 Mbar in low impedance materials such as aluminum and plastics. In this paper, we discuss the use of Z pinch sources for making accurate absolute EOS measurements in the megabar pressure range.

Konrad, C.H.; Asay, J.R.; Hall, C.A. [and others

1998-01-01

28

Development of the Axial Instability in Low Wire Number Wire Array Z-Pinches  

Microsoft Academic Search

We investigate the growth of the axial instability in wire-array Z-pinches. In these experiments we image individual wires in aluminum wire arrays using laser shadowgraphy and XUV framing cameras at times ranging from 0 to 100 ns after the start of a 1 MA, 100 ns rise time current pulse. We document the radial growth of the coronal plasma around

Patrick Knapp; John Greenly; Pierre Gourdain; Cad Hoyt; Matthew Martin; Sergei Pikuz; Tania Shelkovenko; David Hammer; Bruce Kusse

2009-01-01

29

Z-Pinch Driven Isentropic Compression for Inertial Fusion  

SciTech Connect

The achievement of high gain with inertial fusion requires the compression of hydrogen isotopes to high density and temperatures. High densities can be achieved most efficiently by isentropic compression. This requires relatively slow pressure pulses on the order of 10-20 nanoseconds; however, the pressure profile must have the appropriate time. We present 1-D numerical simulations that indicate such a pressure profile can be generated by using pulsed power driven z pinches. Although high compression is calculated, the initial temperature is too low for ignition. Ignition could be achieved by heating a small portion of this compressed fuel with a short (-10 ps) high power laser pulse as previously described. Our 1-D calculations indicate that the existing Z-accelerator could provide the driving current (-20 MA) necessary to compress fuel to roughly 1500 times solid density. At this density the required laser energy is approximately 10 kJ. Multidimensional effects such as the Rayleigh-Taylor were not addressed in this brief numerical study. These effects will undoubtedly lower fuel compression for a given chive current. Therefore it is necessary to perform z-pinch driven compression experiments. Finally, we present preliminary experimental data from the Z-accelerator indicating that current can be efficiently delivered to appropriately small loads (- 5 mm radius) and that VISAR can be used measure high pressure during isentropic compression.

Asay, J.R.; Hall, C.A.; Holland, K.G.; Slutz, S.A.; Spielman, R.B.; Stygar, W.A.

1999-02-01

30

Axial Instability Growth in Tungsten Wire Array Z-Pinches  

NASA Astrophysics Data System (ADS)

The individual exploding wires in wire array z-pinches have been shown to suffer from axially non-uniformity beginning from the moment of plasma formation. This non-uniformity grows in amplitude and wavelength until it reaches what appears to be a material dependent wavelength at the time array implosion begins. Previous work by Knapp et al. [1] studied the temporal evolution of this instability in aluminum wire arrays. We have extended that work to include the evolution of tungsten wire array instabilities. Time gated laser shadowgraphy is used to track wavelength and amplitude over a series of shots to develop a record of the instability's growth. We attempt to identify array parameters which significantly contribute to the growth of this instability. [4pt] [1] Knapp, P. F., J. B. Greenly, P. A. Gourdain, C. L. Hoyt, M. R. Martin, S. A. Pikuz, C. E. Seyler, T. A. Shelkovenko, and D. A. Hammer. ``Growth and Saturation of the Axial Instability in Low Wire Number Wire Array Z Pinches.'' Physics of Plasmas 17 (2010). Web.

Cahill, Adam; Knapp, Patrick; Greenly, John; Pikuz, Sergei; Shelkovenko, Tania; Hammer, David

2010-11-01

31

Z-pinch plasma neutron sources  

Microsoft Academic Search

A deuterium gas-puff load imploded by a multi-MA current driver from a large initial diameter could be a powerful source of fusion neutrons, a plasma neutron source (PNS). Unlike the beam-target neutrons produced in Z-pinch plasmas in the 1950s and deuterium-fiber experiments in the 1980s, the neutrons generated in deuterium gas-puffs with current levels achieved in recent experiments on the

A. L. Velikovich; R. W. Clark; J. Davis; Y. K. Chong; C. Deeney; C. A. Coverdale; C. L. Ruiz; G. W. Cooper; A. J. Nelson; J. Franklin; L. I. Rudakov

2007-01-01

32

X-ray laser research using Z pinches  

Microsoft Academic Search

The Z-pinch offers both significant advantages and disadvantages when considered as an x-ray laser source. To date, three demonstrations of x-ray fluorescence using resonant photopumping, including one population inversion, have been reported in experiments conducted with Z pinches. Thus far, it has not been possible to demonstrate the robust Ne-like laser on a Z pinch, probably due in part to

J. P. Apruzese

1995-01-01

33

Radiation Losses In Z-pinch Plasma  

SciTech Connect

We have estimated the rate of total radiation losses from argon Z-pinches. Radiation losses due to excitation, dielectronic recombination, bremsstrahlung, radiative recombination and also ionization are considered. Ions in each ionization stage are analyzed, and the effects of finite density is taken into account. Our pinch dynamics includes Joule heating, anomalous plasma resistance, plasma outflow in the z-direction, electron beam generation, magnetic field pressure and radiation losses. For discharge current 1MA, the main radiation losses are associated with excitation. The effect of turbulent magnetic field is found essential in the later stage of the pinch.

Baronova, E. O.; Vikhrev, V. V.; Fujimoto, T. [RRC Kurchatov Institute, Moscow (Russian Federation); Kyoto University (Japan)

2006-01-15

34

Staged Z pinch for controlled fusion  

NASA Astrophysics Data System (ADS)

A staged Z pinch is considered in which an annular plasma shell made of a high Z material like Kr implodes onto a coaxial plasma target made of a low Z material like deuterium or a deuterium-tritium mixture. The target plasma could be made either by exploding a cryogenically extruded fiber or by filling the annular shell with a gas puff or a plasma puff. Modeling is performed with a two-dimensional (2D) radiation-MHD (magnetohydrodynamic) code. A parameter study is made to determine the sensitivity of this configuration to initial conditions of the shell and the target plasmas. An axial magnetic field is essential for a stable implosion and efficient energy coupling to the final load. Using a 50-50 mixture of deuterium-tritium as a target plasma, the fusion energy gain is optimized by adjusting the initial parameters. The calculations are based on the parameters of the University of California Irvine Z-pinch facility which has a maximum energy storage of 50 kJ.

Ney, P.; Rahman, H. U.; Wessel, F. J.; Rostoker, N.

2001-02-01

35

Fusion Propulsion Z-Pinch Engine Concept  

NASA Technical Reports Server (NTRS)

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. 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 assembly1. 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(exp -6 sec). 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 Decade Module 2 (DM2), approx.500 KJ pulsed-power is coming to the RSA Aerophysics Lab managed by UAHuntsville in January, 2012. 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.

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

2011-01-01

36

Investigation of plasma instabilities in the stagnated Z pinch  

NASA Astrophysics Data System (ADS)

High-resolution laser probing diagnostics at a wavelength of 266 nm allow observation of the internal structure and instabilities in dense stagnated Z pinches, typically hidden by trailing material. The internal structure of the 1-MA Z pinch includes strong kink and sausage instabilities, loops, flares, and disruptions. Mid- and small-scale density perturbations develop in the precursor and main pinch. The three-dimensional shape and dynamics of the wire-array Z pinch are predetermined by the initial configuration of the wire array. Cylindrical, linear, and star wire-array Z pinches present different sets of instabilities seeded to the pinch at the implosion stage. Prolonged implosion of trailing mass can enhance x-ray production in wire arrays. Fast plasma motion with a velocity >100 km/s was observed in the Z pinch at stagnation with two-frame shadowgraphy. Development of instabilities in wire arrays is in agreement with three-dimensional magnetohydrodynamic simulations.

Ivanov, V. V.; Chittenden, J. P.; Mancini, R. C.; Papp, D.; Niasse, N.; Altemara, S. D.; Anderson, A. A.

2012-10-01

37

Z-pinch plasma neutron sources  

NASA Astrophysics Data System (ADS)

A deuterium gas-puff load imploded by a multi-MA current driver from a large initial diameter could be a powerful source of fusion neutrons, a plasma neutron source (PNS). Unlike the beam-target neutrons produced in Z-pinch plasmas in the 1950s and deuterium-fiber experiments in the 1980s, the neutrons generated in deuterium gas-puffs with current levels achieved in recent experiments on the Z facility at Sandia National Laboratories could contain a substantial fraction of thermonuclear origin. For recent deuterium gas-puff shots on Z, our analytic estimates and one- and two-dimensional simulations predict thermal neutron yields 31013, in fair agreement with the yields recently measured on Z [C. A. Coverdale et al., Phys. Plasmas (to be published)]. It is demonstrated that the hypothesis of a beam-target origin of the observed fusion neutrons implies a very high Z-pinch-driver-to-fast-ions energy transfer efficiency, 5 to 10%, which would make a multi-MA deuterium Z-pinch the most efficient light-ion accelerator. No matter what mechanism is eventually determined to be responsible for generating fusion neutrons in deuterium gas-puff shots on Z, the deuterium neutron yield is shown to scale as YnIm4, where Im is the peak current of the pinch. Theoretical estimates and numerical modeling of deuterium gas-puff implosions demonstrate that the yields of thermonuclear fusion neutrons that can be produced on ZR and the next-generation machines are sufficiently high to make PNS the most powerful, cost- and energy-efficient laboratory sources of 2.5-14MeV fusion neutrons, just like plasma radiation sources are the most powerful sources of soft and keV x rays. In particular, the predicted deuterium-tritium thermal neutron-producing capability of PNS driven by the next-generation ZR and ZX accelerators is 51016 and 1018, respectively.

Velikovich, A. L.; Clark, R. W.; Davis, J.; Chong, Y. K.; Deeney, C.; Coverdale, C. A.; Ruiz, C. L.; Cooper, G. W.; Nelson, A. J.; Franklin, J.; Rudakov, L. I.

2007-02-01

38

Buoyant magnetic flux tubes enhance radiation in Z pinches  

PubMed

In numerous experiments, magnetic energy coupled to strongly radiating Z-pinch plasmas exceeds the thermalized kinetic energy, sometimes by a factor of 2-3. We demonstrate that the enhanced energy coupling may be due to the buoyancy rise of toroidal magnetic flux tubes converging to the axis through the unstable pinch plasma. We derive an explicit formula for the enhanced dissipation rate and apply this formula to reconsider an old problem of power balance in a steady-state Z pinch, and then to analyze a new challenge of producing K-shell 3 to 10 keV radiation in long-pulse Z-pinch implosions. PMID:11019081

Rudakov; Velikovich; Davis; Thornhill; Giuliani; Deeney

2000-04-10

39

Implosion dynamics of a radiative composite Z-pinch  

Microsoft Academic Search

2D simulation of a composite Z-pinch was performed by the complete radiative magnetohydrodynamic code ZETA including detailed calculation of EOS, spectral properties of materials and radiation transport in non-LTE multicharged ions plasma.

R. Benattar; P. Ney; A. Nikitin; S. V. Zakharov; A. A. Otochin; A. N. Starostin; A. E. Stepanov; V. K. Roerich; A. F. Nikiforov; V. G. Novikov; A. D. Solomyannaya; V. A. Gasilov; A. Yu. Krukovskii

1997-01-01

40

Implosion dynamics of a radiative composite Z-pinch  

SciTech Connect

2D simulation of a composite Z-pinch was performed by the complete radiative magnetohydrodynamic code ZETA including detailed calculation of EOS, spectral properties of materials and radiation transport in non-LTE multicharged ions plasma.

Benattar, R.; Ney, P.; Nikitin, A.; Zakharov, S. V.; Otochin, A. A.; Starostin, A. N.; Stepanov, A. E.; Roerich, V. K.; Nikiforov, A. F.; Novikov, V. G.; Solomyannaya, A. D.; Gasilov, V. A.; Krukovskii, A. Yu. [LPMI, Ecole Polytechnique (France); Troitsk Institute for Innovation and Thermonuclear Investigation (TRINITI) (Russian Federation); Keldysh Institute for Applied Mathematics (Russian Federation); Institute for Mathematical Modeling (Russian Federation)

1997-05-05

41

Implosion dynamics of a radiative composite Z-pinch  

Microsoft Academic Search

Two-dimensional simulation of a composite Z-pinch was performed by the complete radiative magnetohydrodynamic (MHD) code ZETA including detailed calculation of equations of state, spectral properties of materials, and radiation transport in non-local thermodynamic equilibrium multicharged ions plasma. The initial geometry, the substance components, and the electric current through the Z-pinch were similar to the joint experiment set up JEX-94 at

R. Benattar; P. Ney; A. Nikitin; S. V. Zakharov; A. A. Otochin; A. N. Starostin; A. E. Stepanov; V. K. Roerich; A. F. Nikiforov; V. G. Novikov; A. D. Solomyannaya; V. A. Gasilov; A. Yu. Krukovskii

1998-01-01

42

Faraday Rotation Measurements on Z-Pinches Final Report  

SciTech Connect

The Campus Executive Program sponsored this research at Cornell University. The research was directed toward the implementation of laser-based diagnostics for wire-array Z-pinches. Under this contract we were able to carry out all the necessary preparations to setup the laser diagnostics to complement our x-ray backlighting measurements of the early phase of exploding wire z-pinch plasma formation.

Greenley, J.B.

1998-10-01

43

Self-Organized Structures In Z-Pinch Devices  

SciTech Connect

In several z-pinch devices there has been observation of regular structures, which appear systematically when repeating the experiments. The fact that very identifiable, recurrent, geometrical structures appear in z-pinches, which are relatively long lived, has motivated the analysis of the experimental data from the point of view of self-organization: there is an input of energy in the form of Joule heating, and densely magnetized plasma is formed, stabilized by several MHD effects and the expulsion of entropy.

Ortiz-Tapia, Arturo [Mexican Petroleum Institute, Eje Central Lazaro Cardenas no. 152, Col. Sn. Bartolo Atepehuacan, 07730, Mexico, D.F. (Mexico)

2006-12-04

44

Z-Pinch Experiments with Styrofoam Fibres and Plasmajets  

NASA Astrophysics Data System (ADS)

Z-pinch plasmas created from fibres are less prone to macroscopic instabilities than predicted by ideal MHD theory. However, solid fibre experiments at the pulseline KALIF (2 MV, 900 kA) gave disappointing results with respect to driver-load coupling and pinch plasma confinement. High power discharges led to current leaks and plasma expansion presumably due to lacking initial conductivity and compressibility. Therefore two alternative schemes have been investigated: Solid fibres were replaced by styrofoam fibres with about 1 % solid density and plasmajets of a deuterium-argon mixture. Analyses of the experimental results showed no major differences between styrofoam and solid fibres. However, the plasmajet experiments resulted in significant improvements with respect to the initial discharge behaviour. Unfortunately, severe pinch disruptions about 40 ns after discharge initiation prevented pinch formation and confinement. The high electric field of the pulseline KALIF and the low density of the jet plasma (E/n > 10-15 Vm2) resulted in runaway electrons and plasma erosion rather than in magnetic confinement to the pinch.

Stein, S.; Decker, G.; Kies, W.; Rwekamp, P.; Ziethen, G.; Baumung, K.; Bluhm, H.; Ratajczak, W.; Rusch, D.; Bayley, J. M.

1994-03-01

45

The ZaP Flow Z-Pinch Project  

SciTech Connect

The results from the ZaP experiment are consistent with the theoretical predictions of sheared flow stabilization. Z pinches with a sheared flow are generated in the ZaP experiment using a coaxial accelerator coupled to an assembly region. The current sheet in the accelerator initially acts as a snowplow. As the Z pinch forms, plasma formation in the accelerator transits to a deflagration process. The plasma exits the accelerator and maintains the flow in the Z pinch. During the quiescent period in the magnetic mode activity at z=0 cm, a stable Z pinch is seen on the axis of the assembly region. The evolution of the axial velocity profile shows a large velocity shear is measured at the edge of the Z pinch during the quiescent period. The velocity shear is above the theoretical threshold. As the velocity shear decreases towards 0.1kV{sub A}, the predicted stability threshold, the quiescent period ends. The present understanding of the ZaP experiment shows that it may be possible for the Z pinch to operate in a steady state if the deflagration process can be maintained by constantly supplying neutral gas or plasma to the accelerator.

Shumlak, U.; Nelson, B. A.

2005-09-01

46

Progress in Z-pinch inertial fusion energy.  

SciTech Connect

The goal of z-pinch inertial fusion energy (IFE) is to extend the single-shot z-pinch inertial confinement fusion (ICF) results on Z to a repetitive-shot z-pinch power plant concept for the economical production of electricity. Z produces up to 1.8 MJ of x-rays at powers as high as 230 TW. Recent target experiments on Z have demonstrated capsule implosion convergence ratios of 14-21 with a double-pinch driven target, and DD neutron yields up to 8x10exp10 with a dynamic hohlraum target. For z-pinch IFE, a power plant concept is discussed that uses high-yield IFE targets (3 GJ) with a low rep-rate per chamber (0.1 Hz). The concept includes a repetitive driver at 0.1 Hz, a Recyclable Transmission Line (RTL) to connect the driver to the target, high-yield targets, and a thick-liquid wall chamber. Recent funding by a U.S. Congressional initiative for $4M for FY04 is supporting research on RTLs, repetitive pulsed power drivers, shock mitigation, full RTL cycle planned experiments, high-yield IFE targets, and z-pinch power plant technologies. Recent results of research in all of these areas are discussed, and a Road Map for Z-Pinch IFE is presented.

Weed, John Woodruff

2010-03-01

47

Wire array initiation at 1MA z-pinch ZEBRA  

NASA Astrophysics Data System (ADS)

The initial stage of W and Al wire array explosions on the 1MA z-pinch installation ZEBRA was investigated. Data from breakdown light emission, B-dot and axial/peripheral V-dots were obtained. Observation of the resistive voltage and the moment of corona generation allow calculation of the condition of the wire core after breakdown. With a current prepulse of 300ns duration, we observed plasma formation at 200ns before the main current. At this moment a first light emission and V-dot signals was observed. During the next 5-10 ns fast plasma components arrive at the center of the wire array and shunt the axial V-dot. After shunting, the axial V-dot shows signals correlated to axial current. Analyzing mass-velocity ratios, we determined that for the Al wire array hydrogen plasma arrived first at the center with velocity 666km/s, followed by carbon plasma with velocity 200km/s and later, the aluminum plasma with velocity 130km/s. Hence, before the main current starts the internal volume of the array is filled by low-density plasma. The axial V-dot signal indicates that the main current initially flows though the entire wire array cross-section, but it is rapidly rejected to the periphery. During the compression stage we observed that the current again flows through the center of the wire array.

Sarkisov, G. S.; Ivanov, V. V.; Cowan, T. E.; Rosenthal, S. E.; Struve, K. W.; Morozov, A.; Haboub, A.; Astanovitskiy, A.; La Galloudec, B.

2006-10-01

48

Z-Pinch Pulsed Plasma Propulsion Technology Development  

NASA Technical Reports Server (NTRS)

Fusion-based propulsion can enable fast interplanetary transportation. Magneto-inertial fusion (MIF) is an approach which has been shown to potentially lead to a low cost, small reactor for fusion break even. The Z-Pinch/dense plasma focus method is an MIF concept in which a column of gas is compressed to thermonuclear conditions by an axial current (I approximates 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). This document presents a conceptual design of a Z-Pinch fusion propulsion system and a vehicle for human exploration. The purpose of this study is to apply Z-Pinch fusion principles to the design of a propulsion system for an interplanetary spacecraft. This study took four steps in service of that objective; these steps are identified below. 1. Z-Pinch Modeling and Analysis: There is a wealth of literature characterizing Z-Pinch physics and existing Z-Pinch physics models. In order to be useful in engineering analysis, simplified Z-Pinch fusion thermodynamic models are required to give propulsion engineers the quantity of plasma, plasma temperature, rate of expansion, etc. The study team developed these models in this study. 2. Propulsion Modeling and Analysis: While the Z-Pinch models characterize the fusion process itself, propulsion models calculate the parameters that characterize the propulsion system (thrust, specific impulse, etc.) The study team developed a Z-Pinch propulsion model and used it to determine the best values for pulse rate, amount of propellant per pulse, and mixture ratio of the D-T and liner materials as well as the resulting thrust and specific impulse of the system. 3. Mission Analysis: Several potential missions were studied. Trajectory analysis using data from the propulsion model was used to determine the duration of the propulsion burns, the amount of propellant expended to complete each mission considered. 4. Vehicle Design: 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 and structural subsystems of a vehicle. The study team developed a conceptual design of an interplanetary vehicle that transports crew and cargo to Mars and back and can be reused for other missions. Several aspects of this vehicle are based on a previous crewed fusion vehicle study -- the Human Outer Planet Exploration (HOPE) Magnetized Target Fusion (MTF) vehicle. Portions of the vehicle design were used outright and others were modified from the MTF design in order to maintain comparability.

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

2010-01-01

49

Applications of high-power diode lasers for aluminum welding  

NASA Astrophysics Data System (ADS)

Industries worldwide are confronted with the need for an increased use of aluminum alloys in various applications. Therefore the requirements result in the necessity for a multitude of joining and welding innovations. Applications of modern aluminum alloys are not constricted to common components anymore. In fact, they are used in ever more complex lightweight structures. However, this complexity has to be fulfilled by a higher geometric flexibility in laser welding and represents a major challenge for new approaches in working lightweight structures. The present work includes the welding of aluminum utilizing Bifocal Hybrid Laser Welding (BHLW) and a 6 kW high power diode laser (HPDL) for welding. The welding setups allow for welded butt- and fillet-welds of tubes under consideration of the hardly fusion weldable alloy AA6060. Welded joints of AA6060 are investigated metallographically in regard to the influence of process parameters like intensity and the interconnected penetration. The weldability is characterized by qualitative investigations of the microstructure as well as the mechanical behavior under quasistatic loading. The investigations result in an adequate welding process for AA6060.

Huber, Sonja; Merzkirch, Matthias; Zaeh, Michael F.; Schulze, Volker

2009-02-01

50

Diagnostics for studying the dynamics of wire array Z pinches  

SciTech Connect

The evolution of a wire array Z pinch encompasses a huge range of conditions--with spatial dimensions varying from micrometers to centimeters, densities from solid metal through plasmas of 10{sup 15}-10{sup 22} e{sup -} cm{sup -3}, and temperatures from sub-eV to many 100 eV. We present a summary of the diagnostics developed and used at the Imperial College MAGPIE facility to study the formation and dynamics of plasma in wire array Z pinches, describing the plasma conditions for which they are useful, their various limitations, and some of the novel diagnostic techniques applied.

Bland, S. N.; Bott, S. C.; Hall, G. N.; Lebedev, S. V.; Suzuki, F.; Ampleford, D. J.; Palmer, J. B. A.; Pikuz, S. A.; Shelkovenko, T. A. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); AWE Plc., Aldermaston, Reading RG7 4PR (United Kingdom); Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States)

2006-10-15

51

Seeded Perturbations in Wire Array Z-Pinches  

SciTech Connect

Controlled seeding of perturbations is employed to study the evolution of wire array z-pinch implosion instabilities which strongly impact x-ray production when the 3D plasma stagnates on axis. Wires modulated in radius exhibit locally enhanced magnetic field and imploding bubble formation at discontinuities in wire radius due to the perturbed current path. Wires coated with localized spectroscopic dopants are used to track turbulent material flow. Experiments and MHD modeling offer insight into the behavior of z-pinch instabilities.

Jones, B.; Deeney, C.; McKenney, J.L.; Garasi, C.J.; Mehlhorn, T.A.; Robinson, A.C.; Wunsch, S.E.; Coverdale, C.A. [Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185 (United States); LePell, P.D. [Ktech Corp., Albuquerque, NM 87123 (United States); Bland, S.N.; Lebedev, S.V.; Chittenden, J.P.; Bott, S.C.; Ampleford, D.J.; Palmer, J.B.A.; Hall, G.N.; Rapley, J. [Blackett Laboratory, Imperial College, London, SW7 2BZ (United Kingdom); Oliver, B.V. [Mission Research Corp., Albuquerque, NM 87110 (United States); Safronova, A.S.; Kantsyrev, V. [Department of Physics, University of Nevada, Reno, NV 89557 (United States)] (and others)

2006-01-05

52

Polycrystalline diamond based detector for Z-pinch plasma diagnosis  

SciTech Connect

A detector setup based on polycrystalline chemical-vapor-deposition diamond film is developed with great characteristics: low dark current (lower than 60 pA within 3 V/{mu}m), fast pulsed response time (rise time: 2-3 ns), flat spectral response (3-5 keV), easy acquisition, low cost, and relative large sensitive area. The characterizing data on Qiangguang-I accelerator show that this detector can satisfy the practical requirements in Z-pinch plasma diagnosis very well, which offers a promising prototype for the x-ray detection in Z-pinch diagnosis.

Liu Linyue; Zhao Jizhen; Chen Liang [Northwest Institute of Nuclear Technology, P.O. Box 69-9, Xi'an 710024 (China); Ouyang Xiaoping [Northwest Institute of Nuclear Technology, P.O. Box 69-9, Xi'an 710024 (China); School of Nuclear Science and Technology, Xi'an Jiaotong University, Xi'an 710049 (China); Wang Lan [Northwest Institute of Nuclear Technology, P.O. Box 69-9, Xi'an 710024 (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2010-08-15

53

MHD simulation studies of z-pinch shear flow stabilization  

NASA Astrophysics Data System (ADS)

The development of the m=0 instability in a z-pinch in the presence of sheared plasma flows is investigated with the aid of a two-dimensional magnetohydrodynamic (MHD) simulation code (MHRDR). The linear growth rates are compared to the results obtained by solving the ideal MHD linearized equations [1] and to the results obtained using a 3D hybrid simulation code [2]. The instability development is followed into the nonlinear regime where its growth and saturation are examined. [1] V.I. Sotnikov, I. Paraschiv, V. Makhin, B.S. Bauer, J.-N. Leboeuf, and J.M. Dawson, "Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid mode", Phys. Plasmas 9, 913 (2002). [2] V.I. Sotnikov, V. Makhin, B.S. Bauer, P. Hellinger, P. Travnicek, V. Fiala, J.-N. Leboeuf, "Hybrid Simulations of Current-Carrying Instabilities in Z-pinch Plasmas with Sheared Axial Flow", AIP Conference Proceedings, Volume 651, Dense Z-Pinches: 5th International Conference on Dense Z-Pinches, edited by J. Davis et al., page 396, June 2002.

Paraschiv, I.; Bauer, B. S.; Sotnikov, V. I.; Makhin, V.; Siemon, R. E.

2003-10-01

54

An Inertial-Fusion Z-Pinch Power Plant Concept  

SciTech Connect

With the promising new results of fast z-pinch technology developed at Sandia National Laboratories, we are investigating using z-pinch driven high-yield Inertial Confinement Fusion (ICF) as a fusion power plant energy source. These investigations have led to a novel fusion system concept based on an attempt to separate many of the difficult fusion engineering issues and a strict reliance on existing technology, or a reasonable extrapolation of existing technology, wherever possible. In this paper, we describe the main components of such a system with a focus on the fusion chamber dynamics. The concept works with all of the electrically-coupled ICF proposed fusion designs. It is proposed that a z-pinch driven ICF power system can be feasibly operated at high yields (1 to 30 GJ) with a relatively low pulse rate (0.01-0.1 Hz). To deliver the required current from the rep-rated pulse power driver to the z-pinch diode, a Recyclable Transmission Line (RTL) and the integrated target hardware are fabricated, vacuum pumped, and aligned prior to loading for each power pulse. In this z-pinch driven system, no laser or ion beams propagate in the chamber such that the portion of the chamber outside the RTL does not need to be under vacuum. Additionally, by utilizing a graded-density solid lithium or fluorine/lithium/beryllium eutectic (FLiBe) blanket between the source and the first-wall the system can breed its own fuel absorb a large majority of the fusion energy released from each capsule and shield the first-wall from a damaging neutron flux. This neutron shielding significantly reduces the neutron energy fluence at the first-wall such that radiation damage should be minimal and will not limit the first-wall lifetime. Assuming a 4 m radius, 8 m tall cylindrical chamber design with an 80 cm thick spherical FLiBe blanket, our calculations suggest that a 20 cm thick 6061-T6 Al chamber wall will reach the equivalent uranium ore radioactivity level within 100 years after a 30 year plant operation. The implication of this low radioactivity is that a z-pinch driven power plant may not require deep geologic waste storage.

DERZON,MARK S.; ROCHAU,GARY E.; DEGROOT,J.; OLSON,CRAIG L.; PETERSON,P.; PETERSON,R.R.; SLUTZ,STEPHEN A.; ZAMORA,ANTONIO J.

2000-12-15

55

Wire array z-pinch insights for high x-ray power generation  

SciTech Connect

The discovery that the use of very large numbers of wires enables high x-ray power to be generated from wire-array z-pinches represents a breakthrough in load design for large pulsed power generators, and has permitted high temperatures to be generated in radiation cavities on Saturn. In this paper, changes in x-ray emission characteristics as a function of wire number, array mass, and load radius, for 20-mm-long aluminum arrays on Saturn that led to these breakthrough hohlraum results, are discussed and compared with a few related emission characteristics of high-wire-number aluminum and tungsten arrays on Z. X=ray measurement comparisons with analytic models and 2-D radiation-magnetohydrodynamic (RMHC) code simulations in the x-y and r-z planes provide confidence in the ability of the models and codes to predict future x-ray performance with very-large-number wire arrays.

Sanford, T.W.L.; Mock, R.C.; Nash, T.J. [and others

1998-08-01

56

Wire array z-pinch insights for high x-ray power generation  

SciTech Connect

The discovery that the use of very large numbers of wires enables high x-ray power to be generated from wire-array z-pinches represents a breakthrough in load design for large pulsed power generators, and has permitted high temperatures to be generated in radiation cavities on Saturn and Z. In this paper, changes in x-ray emission characteristics as a function of wire number, array mass, and load radius, for 20-mm-long aluminum arrays on Saturn that led to these breakthrough hohlraum results, are discussed and compared with a few related emission characteristics of high-wire-number aluminum and tungsten arrays on Z. X-ray measurement comparisons with analytic models and 2-D radiation-magnetohydrodynamic (RMHC) code simulations in the x-y and r-z planes provide confidence in the ability of the models and codes to predict future x-ray performance with very-large-number wire arrays.

Sanford, T.W.L.; Mock, R.C.; Marder, B.M. [and others

1997-12-31

57

Wire array z-pinch insights for high X-ray power generation  

SciTech Connect

The discovery that the use of very large numbers of wires enables high x-ray power to be generated from wire-array z-pinches represents a breakthrough in load design for large pulsed power generators, and has permitted high temperatures to be generated in radiation cavities on Saturn and Z. In this paper, changes in x-ray emission characteristics as a function of wire number, array mass, and load radius, for 20-mm-long aluminum arrays on Saturn that led to these breakthrough hohlraum results, are discussed and compared with a few related emission characteristics of high-wire-number aluminum and tungsten arrays on Z. X-ray measurement comparisons with analytic models and 2-D radiation-magnetohydrodynamic (RMHC) code simulations in the x-y and r-z planes provide confidence in the ability of the models and codes to predict future x-ray performance with very-large-number wire arrays.

Sanford, T.W.L.; Marder, B.M.; Desjarlais, M.P. [and others

1998-12-31

58

Growth and saturation of the axial instability in low wire number wire array Z pinches  

SciTech Connect

The growth of the axial instability in low wire number wire array Z pinches using a 100 ns rise time, 1 MA pulsed power accelerator is examined. The axial instability manifests itself as a quasiperiodic variation of the radius of the coronal plasma along each wire and a consequent modulation of the rate of ablation of material from the dense wire core. The dominant wavelength of the modulation becomes constant late in time. In this work laser shadowgraphy is used to measure the growth of the wavelength and amplitude of the instability as well as the size of the coronal plasma in aluminum wire arrays from the time of plasma formation to the time the wavelength seen late in time is reached. Using magnetic probes, the distribution of current and magnetic topology are also investigated. It is found that a distinct change in magnetic field topology associated with the onset of advection of current to the array axis by the streaming wire-ablation plasma appears to be responsible for ending the growth of the axial instability and initiating the quasisteady state ablation phase of the wire array Z pinch.

Knapp, P. F.; Greenly, J. B.; Gourdain, P.-A.; Hoyt, C. L.; Martin, M. R.; Pikuz, S. A.; Seyler, C. E.; Shelkovenko, T. A.; Hammer, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2010-01-15

59

Growth and saturation of the axial instability in low wire number wire array Z pinches  

NASA Astrophysics Data System (ADS)

The growth of the axial instability in low wire number wire array Z pinches using a 100 ns rise time, 1 MA pulsed power accelerator is examined. The axial instability manifests itself as a quasiperiodic variation of the radius of the coronal plasma along each wire and a consequent modulation of the rate of ablation of material from the dense wire core. The dominant wavelength of the modulation becomes constant late in time. In this work laser shadowgraphy is used to measure the growth of the wavelength and amplitude of the instability as well as the size of the coronal plasma in aluminum wire arrays from the time of plasma formation to the time the wavelength seen late in time is reached. Using magnetic probes, the distribution of current and magnetic topology are also investigated. It is found that a distinct change in magnetic field topology associated with the onset of advection of current to the array axis by the streaming wire-ablation plasma appears to be responsible for ending the growth of the axial instability and initiating the quasisteady state ablation phase of the wire array Z pinch.

Knapp, P. F.; Greenly, J. B.; Gourdain, P.-A.; Hoyt, C. L.; Martin, M. R.; Pikuz, S. A.; Seyler, C. E.; Shelkovenko, T. A.; Hammer, D. A.

2010-01-01

60

Seeded perturbations in wire array z-pinches.  

SciTech Connect

The impact of 3D structure on wire array z-pinch dynamics is a topic of current interest, and has been studied by the controlled seeding of wire perturbations. First, Al wires were etched at Sandia, creating 20% radial perturbations with variable axial wavelength. Observations of magnetic bubble formation in the etched regions during experiments on the MAGPIE accelerator are discussed and compared to 3D MHD modeling. Second, thin NaF coatings of 1 mm axial extent were deposited on Al wires and fielded on the Zebra accelerator. Little or no axial transport of the NaF spectroscopic dopant was observed in spatially resolved K-shell spectra, which places constraints on particle diffusivity in dense z-pinch plasmas. Finally, technology development for seeding perturbations is discussed.

Robinson, Allen Conrad; Kantsyrev, Victor Leonidovich (University of Nevada, Reno, NV); Wunsch, Scott Edward; Oliver, Bryan Velten (Mission Research Corporation, Albuquerque, NM); Lebedev, Sergey V. (Imperial College, London, UK); Safronova, Alla S. (University of Nevada, Reno, NV); Maxwell, J. (Los Alamos National Laboratory, Los Alamos, NM); McKenney, John Lee; Ampleford, David J. (Imperial College, London, UK); Rapley, J. (Imperial College, London, UK); Bott, S. C. (Imperial College, London, UK); Palmer, J. B. A. (Imperial College, London, UK); Bland, Simon Nicholas (Imperial College, London, UK); Jones, Brent Manley; Chittenden, Jeremy Paul (Imperial College, London, UK); Garasi, Christopher Joseph; Hall, Gareth Neville (Imperial College, London, UK); Mehlhorn, Thomas Alan; Deeney, Christopher

2004-11-01

61

Radiating Shock Measurements in the Z-Pinch Dynamic Hohlraum  

Microsoft Academic Search

The Z-pinch dynamic hohlraum is an x-ray source for high energy-density physics studies that is heated by a radiating shock to radiation temperatures >200eV. The time-dependent 300 400 eV electron temperature and 15 35mg\\/cc density of this shock have been measured for the first time using space-resolved Si tracer spectroscopy. The shock x-ray emission is inferred from these measurements to

G. A. Rochau; J. E. Bailey; Y. Maron; G. A. Chandler; G. S. Dunham; D. V. Fisher; V. I. Fisher; R. W. Lemke; J. J. Macfarlane; K. J. Peterson; D. G. Schroen; S. A. Slutz; E. Stambulchik

2008-01-01

62

Dynamics of conical wire array Z-pinch implosions  

NASA Astrophysics Data System (ADS)

A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generatorsthe MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.

Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Jennings, C. A.; Kantsyrev, V. L.; Safronova, A. S.; Ivanov, V. V.; Fedin, D. A.; Laca, P. J.; Yilmaz, M. F.; Nalajala, V.; Shrestha, I.; Williamson, K.; Osborne, G.; Haboub, A.; Ciardi, A.

2007-10-01

63

X-ray power increase from symmetrized wire-array z-pinch implosions  

SciTech Connect

A systematic experimental study of annular aluminum-wire z-pinches on the Saturn accelerator shows that, for the first time, the measured spatial characteristics and x-ray powers can approach those of two-dimensional, radiation-magneto-hydrodynamic simulations when large numbers of wires are used. Calculations show that the implosion begins to transition from that of individual plasma wires 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 powers in excess of a factor of three over that generated in the plasma-wire region are measured.

Sanford, T.W.L.; Allshouse, G.O.; Marder, B.M. [and others

1996-08-01

64

The ZaP Flow Z-Pinch Project: Investigations of Flow Shear on MHD Stability  

Microsoft Academic Search

The ZaP Flow Z-Pinch observes gross stability of a Z-pinch while a sheared axial flow is present.(U. Shumlak et al.), Phys. Rev. Lett. 87 (20), p. 205005-1, 2001 The Z-pinch is maintained more than 700 times the predicted kink instability growth time of a static pinch. The stable time is correlated with measurements of a sheared axial flow, and instability

B. A. Nelson; U. Shumlak; R. P. Golingo; S. L. Jackson; J. Bright; D. J. den Hartog

2002-01-01

65

SPEED2 Driven A Gas Embedded Z-Pinch Preliminary Results  

SciTech Connect

Preliminary results in a gas embedded Z-pinch driven by the SPEED2 generators are presented. A 0-D model for a quasi static z-pinch with variable line density has been applied to determined the initial conditions to produce a gas embedded z-pinch to be driven by SPEED2 generator. Initial conditions to produce a gas embedded z-pinch with enhanced stability by means resistive effects and by finite Larmor radius effects were obtained. Using these results the electrodes were designed and constructed.

Soto, Leopoldo; Moreno, Jose; Sylvester, Gustavo; Silva, Patricio; Zambra, Marcelo [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Pavez, Cristian [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Universidad de Concepcion (Chile)

2006-01-05

66

Fast Z - Pinch Study in Russia and Related Problems  

NASA Astrophysics Data System (ADS)

The fast Z pinches are considered as a perspective source of powerful soft x-ray emission for the ICF pellet ignition. The physical phenomena which take place in process fast of Z-pinch implosion are under investigation in the TRINITI (Troisk), in the RSC Kurchatov Institute (KI, Moscow) and the HCEI (Tomsk). In the KI the possibility of terawatt electrical power transfer in small volume hohlraum during nanosecond time duration is studied. In the TRINITI the physics of multi wire arrays implosion, the rate of plasma production in current-driven wire arrays, the conversion of pulsed power energy into x-ray emission are studied. In the HCEI (Tomsk) the stability of double gas puff implosion and the influence of gas puff regime and current pulse duration on the implosion and emitted x-ray spectrum are under investigation. The HCEI develops the new components of pulse power multi spark switches and the generators of impulse currents (LTD) with duration of an energy supply less than 100 ns. As available way to get the pulsed power generator with multi tens megaampere current the joint team of scientists from the laboratories of the TRINITI, the Efremov Institute, RFNC VNIITF (Snezinsk) have developed the concept of the Baikal facility. The KI designs, creates and tests the plasma erosion switches for the module of the Baikal facility. The inductive storage, the systems of magnetic field compression and the explosive open switches are developed in the TRINITI and the Efremov Institute. The development of new design of the pulse power generators and physics of fast Z-pinch implosion aims to create next advanced generation of powerful driver for ICF.

Grabovskii, E. V.

2002-12-01

67

Z-Pinch fusion-based nuclear propulsion  

NASA Astrophysics Data System (ADS)

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.

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

68

Nonlinear Rayleigh-Taylor instabilities in fast Z pinches  

SciTech Connect

A simplified analytic model is presented to describe the implosion of a plasma column by an azimuthal magnetic field of sufficient magnitude to drive a strong shock wave into the plasma. This model is employed together with buoyancy-drag-based models of nonlinear single-mode and turbulent multimode Rayleigh-Taylor growth to investigate the mixing process in such fast Z pinches. These models give predictions that characterize limitations the instability can impose on the implosion in terms of maximum convergence ratios attainable for an axially coherent pinch. Both the implosion and instability models are validated with results from high-resolution numerical simulations.

Miles, Aaron R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2009-03-15

69

Nonlinear Rayleigh-Taylor instabilities in fast z-pinches  

SciTech Connect

A simplified analytic model is presented to describe the implosion of a plasma column by an azimuthal magnetic field of sufficient magnitude to drive a strong shock wave into the plasma. This model is employed together with buoyancy-drag-based models of nonlinear single-mode and turbulent multimode Rayleigh-Taylor (RT) growth to investigate the mixing process in such fast z-pinches. These models give predictions that characterize limitations the instability can impose on the implosion in terms of maximum convergence ratios (CR) attainable for an axially coherent pinch. Both the implosion and instability models are validated with results from high-resolution numerical simulations.

Miles, A R

2008-09-16

70

Azimuthally correlated ablation between z-pinch wire cores  

SciTech Connect

Azimuthally correlated wire core ablation was compared for closely spaced versus widely spaced wires in a 1 MA Z-pinch. X-ray point-projection diagnostics revealed that 240 {mu}m spaced wires exhibited a correlation coefficient approaching unity in both real space and in k-space. This correlated ablation between wires at a fixed axial location is believed to occur due to an enhanced, localized Joule heating. Wires separated by 2.47 mm or greater were uncorrelated in real space, but correlated in k-space, indicating the ablation structure between wires was shifted in phase.

Zier, J. C.; Gilgenbach, R. M.; Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Douglass, J. D.; Blesener, I. C.; Blesener, K. S.; Chalenski, D. A.; Greenly, J. B.; Hammer, D. A.; Knapp, P. F.; Kusse, B. R.; McBride, R. D.; Syed, W. [Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States); Yu, E. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2009-10-15

71

A time-resolved spectroscopic diagnostic based on fast scintillator and optical fiber array for z-pinch plasmas  

NASA Astrophysics Data System (ADS)

We report a specially designed type of temporal resolved x-ray spectroscopic diagnostic using a spherically bent quartz crystal for z-pinch plasmas. Registration of time-resolved spectra was accomplished by coupling fast plastic scintillator, an optical fiber array, an optical streak camera, and a charge coupled device as the recording medium of this diagnostic. The diagnostic has been tested in imploding wire array experiments on S-300 pulsed power facility. Time-resolved K-shell lines were successfully obtained for aluminum wire array implosion plasmas.

Ye, Fan; Qin, Yi; Jiang, Shuqing; Xue, Feibiao; Li, Zhenghong; Yang, Jianlun; Xu, Rongkun; Anan'ev, S. S.; Dan'ko, S. A.; Kalinin, Yu. G.

2009-10-01

72

A time-resolved spectroscopic diagnostic based on fast scintillator and optical fiber array for z-pinch plasmas  

SciTech Connect

We report a specially designed type of temporal resolved x-ray spectroscopic diagnostic using a spherically bent quartz crystal for z-pinch plasmas. Registration of time-resolved spectra was accomplished by coupling fast plastic scintillator, an optical fiber array, an optical streak camera, and a charge coupled device as the recording medium of this diagnostic. The diagnostic has been tested in imploding wire array experiments on S-300 pulsed power facility. Time-resolved K-shell lines were successfully obtained for aluminum wire array implosion plasmas.

Ye Fan [Institute of Nuclear Physics and Chemistry, P.O. Box 919-212, Mianyang 621900 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Beijing 100084 (China); Qin Yi; Jiang Shuqing; Xue Feibiao; Li Zhenghong; Yang Jianlun; Xu Rongkun [Institute of Nuclear Physics and Chemistry, P.O. Box 919-212, Mianyang 621900 (China); Anan'ev, S. S.; Dan'ko, S. A.; Kalinin, Yu. G. [RRC Kurchatov Institute, Moscow 123182 (Russian Federation)

2009-10-15

73

A time-resolved spectroscopic diagnostic based on fast scintillator and optical fiber array for z-pinch plasmas.  

PubMed

We report a specially designed type of temporal resolved x-ray spectroscopic diagnostic using a spherically bent quartz crystal for z-pinch plasmas. Registration of time-resolved spectra was accomplished by coupling fast plastic scintillator, an optical fiber array, an optical streak camera, and a charge coupled device as the recording medium of this diagnostic. The diagnostic has been tested in imploding wire array experiments on S-300 pulsed power facility. Time-resolved K-shell lines were successfully obtained for aluminum wire array implosion plasmas. PMID:19895094

Ye, Fan; Qin, Yi; Jiang, Shuqing; Xue, Feibiao; Li, Zhenghong; Yang, Jianlun; Xu, Rongkun; Anan'ev, S S; Dan'ko, S A; Kalinin, Yu G

2009-10-01

74

High Power Selective Laser Melting (HP SLM) of Aluminum Parts  

NASA Astrophysics Data System (ADS)

Selective Laser Melting (SLM) is one of the Additive Manufacturing (AM) technologies that enables the production of light weight structured components with series identical mechanical properties without the need for part specific tooling or downstream sintering processes, etc. Especially aluminum is suited for such eco-designed components due to its low weight and superior mechanical and chemical properties. However, SLM's state-of-the-art process and cost efficiency is not yet suited for series-production. In order to improve this efficiency it is indispensable to increase the build rate significantly. Thus, aluminum is qualified for high build rate applications using a new prototype machine tool including a 1 kW laser and a multi-beam system.

Buchbinder, D.; Schleifenbaum, H.; Heidrich, S.; Meiners, W.; Bltmann, J.

75

High Power Selective Laser Melting (HP SLM) of Aluminum Parts  

Microsoft Academic Search

Selective Laser Melting (SLM) is one of the Additive Manufacturing (AM) technologies that enables the production of light weight structured components with series identical mechanical properties without the need for part specific tooling or downstream sintering processes, etc. Especially aluminum is suited for such eco-designed components due to its low weight and superior mechanical and chemical properties. However, SLM's state-of-the-art

D. Buchbinder; H. Schleifenbaum; S. Heidrich; W. Meiners; J. Bltmann

2011-01-01

76

D-D fusion experiments using fast Z pinches  

SciTech Connect

The development of high current (I > 10 MA) drivers provides the authors with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I{sup 2} and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast (<100 ns) implosions are more stable to the usual MHD instabilities that plagued the traditional slower implosions. The authors describe experiments in which deuterium gas puffs or CD{sub 2} fiber arrays were imploded in a fast z-pinch configuration on Sandia`s Saturn facility generating up to 3 {times} 10{sup 12} D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, the authors intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices.

Spielman, R.B.; Baldwin, G.T.; Cooper, G. [and others

1998-03-01

77

D-D fusion experiments using fast z pinches  

SciTech Connect

The development of high current (I > 10 MA) drivers provides us with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I{sup 2} and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast (< 100 ns) implosions are more stable to the usual MHD instabilities that plagued the traditional slower implosions. We describe experiments in which deuterium gas puffs or CD{sub 2} fiber arrays were imploded in a fast z-pinch configuration on Sandia`s Saturn facility generating up to 3 {times} 10{sup 12} D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, we intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices.

Spielman, R.B.; Baldwin, G.T.; Cooper, G. [and others

1994-04-01

78

Optical diagnostics on dense Z-pinch plasmas  

SciTech Connect

A novel point-diffraction'' interferometer has been implemented on the Los Alamos Solid Fiber Z-Pinch experiment. The laser beam is split into two legs after passing through the plasma. The reference leg is filtered with a pin-hole aperture and recombined with the other leg to form an interferogram. This allows compact mounting of the optics and relative ease of alignment. The Z-Pinch experiment employs a pulsed-power generator that delivers up to 700 KA with a 100ns rise-time through a fiber of deuterium or deuterated polyethylene (CD{sub s}) that is 5-cm long and initially solid with radius r{approx}15{mu}m. The interferometer, using a {triangle}t{approx}200ps pulse from a Nd:YAG laser frequency doubled to {lambda}=532nm, measures the electron line density and, assuming azimuthal symmetry, the density as a function of radial and axial position. Calculations predict Faraday rotations of order {pi}/2 for plasma and current densities that this experiment was designed to produce. The resulting periodic loss of fringes would provide the current density distribution.

Riley, R.A. Jr.; Lovberg, R.H.; Shlachter, J.S.; Scudder, D.W.

1992-01-01

79

Optical diagnostics on dense Z-pinch plasmas  

SciTech Connect

A novel ``point-diffraction`` interferometer has been implemented on the Los Alamos Solid Fiber Z-Pinch experiment. The laser beam is split into two legs after passing through the plasma. The reference leg is filtered with a pin-hole aperture and recombined with the other leg to form an interferogram. This allows compact mounting of the optics and relative ease of alignment. The Z-Pinch experiment employs a pulsed-power generator that delivers up to 700 KA with a 100ns rise-time through a fiber of deuterium or deuterated polyethylene (CD{sub s}) that is 5-cm long and initially solid with radius r{approx}15{mu}m. The interferometer, using a {triangle}t{approx}200ps pulse from a Nd:YAG laser frequency doubled to {lambda}=532nm, measures the electron line density and, assuming azimuthal symmetry, the density as a function of radial and axial position. Calculations predict Faraday rotations of order {pi}/2 for plasma and current densities that this experiment was designed to produce. The resulting periodic loss of fringes would provide the current density distribution.

Riley, R.A. Jr.; Lovberg, R.H.; Shlachter, J.S.; Scudder, D.W.

1992-05-01

80

Time-Resolved 1-D X-ray Imaging Technique for Z-Pinch Plasma Diagnosis  

SciTech Connect

A sensitive time-resolved 1-D x-ray imaging system with linear energy response to 100eV-2keV x-rays is developed and applied in Z-Pinch experiments to investigate time dependent x-ray distribution with one-dimensional(1-D) spatial resolution of 0.1mm{approx}0.4mm and temporal resolution of 3ns. A slit in the system relays the 1-D image of the pinch plasma to a plastic scintillator foil with a thickness of 0.2mm which converts x-ray to visible and near-infrared light and has linear response to x-ray energy. With an optical fiber array consisting of 40 linearly arranged individual fibers behind the scintillator foil, it is capable of transmitting the 1-D image out from within the vacuum chamber. The optical fiber array is subsequently coupled to a streak camera via optical fiber bundle consisting of 40 individual 30-meter-long fibers to allow the investigation of time-resolved 1D x-ray distribution. To avoid viewing the plasma-generated visible light and covering aluminum foil on the scintillator, both the scintillator foil and the fiber array are tilted at an angle of 45 degrees from the line of sight. This diagnostic system has been successfully applied in gas-puff and tungsten wire-array Z-Pinch experiments carried out on Qiang-Guang-1, S-300, and Angara-5-1 facilities for time-resolved measurement of x-ray power distribution along the axis or radius of the imploding plasma. In these experiments, the current is in the range of 1-3MA and the x-ray radiation energy is in the order of 10-50kJ. Some experimental results will be presented in this paper.

Yang, J.L.; Li, Z.H.; Xu, R.K.; Li, L.B.; Ning, J.M.; Guo, C.; Song, F.J.; Xu, Z.P.; Xia, G.X. [Institute of Nuclear Physics and Chemistry, P.O.Box 919-212, Mianyang 621900 (China)

2006-01-05

81

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics  

NASA Astrophysics Data System (ADS)

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1?s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-? simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J. P.; Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.

2006-01-01

82

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics  

SciTech Connect

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J.P.; Chittenden, J.P.; Lebedev, S.V.; Jennings, C.A.; Bland, S.N. [Centre d'Etudes de Gramat, BP 80200, 46500 Gramat (France) and Blackett Laboratory, Imperial College, London, SW7 2BW (United Kingdom)

2006-01-05

83

2D r-z Analysis of Hohlraum Experiments on Sphinx Machine using Axial Radiation from a Wire Array Z-pinch  

Microsoft Academic Search

Axial radiation flux from an aluminum Z-pinch on SPHINX machine is used to drive 5 mm diameter, 7 mm height hohlraums. 2006 results demonstrated that >200 GW power in 10 ns could be achieved creating >35 eV radiation temperatures. A 20-30 ns delay between the axial power starting time and the temperature rise had, however, to be explained. In this

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

2007-01-01

84

A review of the dense Z-pinch  

NASA Astrophysics Data System (ADS)

The Z-pinch, perhaps the oldest subject in plasma physics, has achieved a remarkable renaissance in recent years, following a few decades of neglect due to its basically unstable MHD character. Using wire arrays, a significant transition at high wire number led to a great improvement in both compression and uniformity of the Z-pinch. Resulting from this the Z-accelerator at Sandia at 20 MA in 100 ns has produced a powerful, short pulse, soft x-ray source >230 TW for 4.5 ns) at a high efficiency of ~15%. This has applications to inertial confinement fusion. Several hohlraum designs have been tested. The vacuum hohlraum has demonstrated the control of symmetry of irradiation on a capsule, while the dynamic hohlraum at a higher radiation temperature of 230 eV has compressed a capsule from 2 mm to 0.8 mm diameter with a neutron yield >3 1011 thermal DD neutrons, a record for any capsule implosion. World record ion temperatures of >200 keV have recently been measured in a stainless-steel plasma designed for K? emission at stagnation, due, it was predicted, to ion-viscous heating associated with the dissipation of fast-growing short wavelength nonlinear MHD instabilities. Direct fusion experiments using deuterium gas-puffs have yielded 3.9 1013 neutrons with only 5% asymmetry, suggesting for the first time a mainly thermal source. The physics of wire-array implosions is a dominant theme. It is concerned with the transformation of wires to liquid-vapour expanding cores; then the generation of a surrounding plasma corona which carries most of the current, with inward flowing low magnetic Reynolds number jets correlated with axial instabilities on each wire; later an almost constant velocity, snowplough-like implosion occurs during which gaps appear in the cores, leading to stagnation on the axis, and the production of the main soft-x-ray pulse. These studies have been pursued also with smaller facilities in other laboratories around the world. At Imperial College, conical and radial wire arrays have led to highly collimated tungsten plasma jets with a Mach number of >20, allowing laboratory astrophysics experiments to be undertaken. These highlights will be underpinned in this review with the basic physics of Z-pinches including stability, kinetic effects, and finally its applications.

Haines, M. G.

2011-09-01

85

Extreme ultraviolet imaging of wire array z-pinch experiments  

NASA Astrophysics Data System (ADS)

A multi-frame extreme ultraviolet imaging system based on four pinhole cameras, each backed by a gated microchannel plate (MCP) detector, was used to analyze plasma formation and dynamics in wire array z-pinch experiments on the MAGPIE generator (1 MA, 240 ns) at Imperial College (London). The use of pinhole size, object, and image distances, and MCP sensitivity to determine the spatial and spectral response of the diagnostic is discussed. A high magnification, high resolution version of the diagnostic has produced important information on wire initiation and plasma ablation in various materials. A low magnification version has allowed direct study of the snowplough sheath during array implosion, and of plasma instabilities during stagnation.

Bland, S. N.; Ampleford, D. J.; Bott, S. C.; Lebedev, S. V.; Palmer, J. B. A.; Pikuz, S. A.; Shelkovenko, T. A.

2004-10-01

86

Plasma dynamics in an inverse wire array z-pinch  

NASA Astrophysics Data System (ADS)

We describe experiments on the MAGPIE facility (1MA, 250ns) with inverse wire array z-pinches, in which the wires act as a return current cage placed around a central current conductor. In this configuration the plasma ablated from the wires is pushed by the JxB force in the radially outward direction and expands into the region free of the magnetic field. The parameters of the coronal plasma were measured using laser interferometry, X-ray and XUV imaging. The experimental set-up also allows addition of axial and radial magnetic fields, and we study the effects of these fields on the plasma dynamics and the ablation rate. The complete ablation of the wires triggers radial ``explosion'' of the plasma which proceeds through formation of gaps in the wire cores, similar to the dynamics of standard wire arrays. The opening of the current path in the final stages could potentially be used as a plasma opening switch.

Lebedev, Sergey; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Hall, G. N.; Suzuki, F. A.; Ciardi, A.; Palmer, J. B. A.

2006-10-01

87

Implosion dynamics in double planar wire array Z pinches  

NASA Astrophysics Data System (ADS)

The double planar wire array (DPWA) Z pinch is a highly efficient radiation source with unique implosion dynamics and precursor formations. The inductively divided current successively ablates the wires and injects the material to the interior of the array. Three uniquely imploding DPWA load types were identified and classified according to the critical load parameter: low, intermediate, or high aspect ratio. Radiation pulse shaping was obtained from secondary precursors: off-axis mass carrying high current densities during the implosion phase. Time-gated EUV spectroscopy of off-axis mass accumulations is used to assess a 60 eV electron temperature prior to the implosion phase. These structures are shown to form by a different mechanism than the secondary precursors. High yields, compact size, and shaped radiation pulses merit further consideration of the DPWA as a candidate for inertial confinement fusion research.

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

2010-11-01

88

Implosion dynamics in double planar wire array Z pinches  

SciTech Connect

The double planar wire array (DPWA) Z pinch is a highly efficient radiation source with unique implosion dynamics and precursor formations. The inductively divided current successively ablates the wires and injects the material to the interior of the array. Three uniquely imploding DPWA load types were identified and classified according to the critical load parameter: low, intermediate, or high aspect ratio. Radiation pulse shaping was obtained from secondary precursors: off-axis mass carrying high current densities during the implosion phase. Time-gated EUV spectroscopy of off-axis mass accumulations is used to assess a 60 eV electron temperature prior to the implosion phase. These structures are shown to form by a different mechanism than the secondary precursors. High yields, compact size, and shaped radiation pulses merit further consideration of the DPWA as a candidate for inertial confinement fusion research.

Williamson, K. M.; Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Cox, P.; Shrestha, I.; Osborne, G. C.; Weller, M. E.; Ouart, N. D.; Shlyaptseva, V. V. [Department of Physics, University of Nevada Reno, 1664 N. Virginia St. MS220 Reno, Nevada 89557 (United States)

2010-11-15

89

The stability of the High-Density Z-Pinch  

SciTech Connect

Fiber-initiated High Density Z-Pinches at Los Alamos, NRL, and Karlsruhe have shown anomalously good stability. Kink modes are never seen, and sausage modes are at least delayed until late in the discharge. The success of these devices in reaching fusion conditions may depend on maintaining and understanding this anomalous stability. We have developed two numerical methods to study the stability in the regime where fluid theory is valid. While our methods are applicable to all modes, we will describe them only for the m = 0 sausage mode. The appearance of sausage modes late in the discharge and the total absence of kink modes suggest that an understanding of sausage modes is more urgent, and it is also simpler. 14 refs., 8 figs.

Glasser, A.H.; Nebel, R.A.

1989-01-01

90

Fusion burn dynamics in dense Z-pinches (DZP)  

SciTech Connect

The fusion burn dynamics and energy yield of the dense Z-pinch (DZP) are examined using a profile-averaged, zero-dimensional time-dependent model. A range of conditions (fuel, line density, voltage, fusion-product heating, enthalpy endless, density and temperature profiles, current rise rate, electrode impurities) are examined. Magneto-hydrodynamic stability is assumed, and initial conditions are based on those ideally existing after the melting and ionization of a solid fiber of fusion fuel. Plasma-conditions required of neutron sources for materials testing ({dot S}{sub n} {ge} 10{sup 19} n/s) and for possible commercial power production are examined. 25 refs., 9 figs.

Krakowski, R.A.; Miller, R.L.; Bathke, C.G.; Werley, K.A.; Hagenson, R.L. (Los Alamos National Lab., NM (USA); Phillips Petroleum Co., Bartlesville, OK (USA))

1989-01-01

91

Instability heating of solid-fiber Z pinches  

SciTech Connect

The Los Alamos High Density Z Pinch-II (HDZP-II) facility is used to study the dynamics of z-pinch plasmas generated from solid fibers of deuterated polyethylene CD{sub 2} with a range in radii of 3--60 {mu}m. HDZP-II is a pulsed-power generator that delivers a current that rises to 700 kA in 100 ns through an inductive load. A multiframe circular schlieren records the evolution of the shape and size of the plasma on seven images taken at 10-ns intervals. These circular-schlieren images show very strong m=0 instability at the onset of current and a rapid radial expansion of the plasma. No higher-order instabilities are observed. An interferometer is used to infer the electron density and electron line density, giving a measure of the fraction of plasma contained within the outline of the circular-schlieren image at one time during the multiframe sequence. A three-channel x-ray crystal-reflection spectrometer provides the time-resolved, spatially-averaged electron temperature. The magnitude of the x-ray emission at these energies also gives qualitative information about the electron temperature and density at late times. A lower bound on the ion temperature is inferred from the particle pressure needed to balance the magnetic field pressure. The ion temperature rose above that of the electrons, strongly suggesting an additional heating term that puts energy directly into the ions. An ion heating term is proposed to explain the observed rapid radial expansion and elevated ion temperatures. This heating term is based on the assumption that the observed m=0 instabilities reconnect, enclosing magnetic flux which degenerates into turbulence in the plasma. A 0-D simulation is developed to investigate the relevance of different physical models to the data presented.

Riley, R.A. Jr.

1994-02-01

92

Progress in symmetric ICF capsule implosions and wire-array z-pinch source physics for double z-pinch driven hohlraums.  

SciTech Connect

Over the last several years, rapid progress has been made evaluating the double-z-pinch indirect-drive, inertial confinement fusion (ICF) high-yield target concept (Hammer et al 1999 Phys. Plasmas 6 2129). We have demonstrated efficient coupling of radiation from two wire-array-driven primary hohlraums to a secondary hohlraum that is large enough to drive a high yield ICF capsule. The secondary hohlraum is irradiated from two sides by z-pinches to produce low odd-mode radiation asymmetry. This double-pinch source is driven from a single electrical power feed (Cuneo et al 2002 Phys. Rev. Lett. 88 215004) on the 20 MA Z accelerator. The double z-pinch has imploded ICF capsules with even-mode radiation symmetry of 3.1 {+-} 1.4% and to high capsule radial convergence ratios of 14-21 (Bennett et al 2002 Phys. Rev. Lett. 89 245002; Bennett et al 2003 Phys. Plasmas 10 3717; Vesey et al 2003 Phys. Plasmas 10 1854). Advances in wire-array physics at 20 MA are improving our understanding of z-pinch power scaling with increasing drive current. Techniques for shaping the z-pinch radiation pulse necessary for low adiabat capsule compression have also been demonstrated.

Bliss, David Emery; Vesey, Roger Alan; Rambo, Patrick K.; Lebedev, Sergey V. (Blackett Laboratory, Imperial College, London, UK); Hanson, David L.; Nash, Thomas J.; Yu, Edmund P.; Matzen, Maurice Keith; Afeyan, Bedros B. (Polymath Research, Inc., Pleasanton, CA); Smith, Ian Craig; Stygar, William A.; Porter, John Larry, Jr.; Cuneo, Michael Edward; Bennett, Guy R.; Campbell, Robert B.; Sinars, Daniel Brian; Chittenden, Jeremy Paul (Blackett Laboratory, Imperial College, London, UK); Waisman, Eduardo Mario; Mehlhorn, Thomas Alan

2005-07-01

93

X-Ray Imaging Measurements of Capsule Implosions Driven by a Z-Pinch Dynamic Hohlraum  

Microsoft Academic Search

The radiation and shock generated by impact of an annular tungsten Z-pinch plasma on a 10-mm diam 5-mg\\/cc CH2 foam are diagnosed with x-ray imaging and power measurements. The radiative shock was virtually unaffected by Z-pinch plasma instabilities. The 5-ns-duration ~135-eV radiation field imploded a 2.1-mm-diam CH capsule. The measured radiation temperature, shock radius, and capsule radius agreed well with

J. E. Bailey; G. A. Chandler; S. A. Slutz; G. R. Bennett; G. Cooper; J. S. Lash; S. Lazier; R. Lemke; T. J. Nash; D. S. Nielsen; T. C. Moore; C. L. Ruiz; D. G. Schroen; R. Smelser; J. Torres; R. A. Vesey

2002-01-01

94

Implosion and stagnation dynamics of wire array z-pinches  

NASA Astrophysics Data System (ADS)

We present detailed measurements of the implosion and stagnation phases of wire array z-pinch experiments on the MAGPIE generator (1MA, 240ns). The implosion of the array, which consists of an accelerating snowplough of current traveling towards the axis, critically depends upon the redistribution of mass ablated from the wires prior to implosion. Array configurations that alter the ablation of plasma from the wires of the array (e.g. by varying B?, introducing Bz and Br and/or by reversing the direction of Er) are used to explore the dependence of implosion on this process. The initiation of the implosion phase and formation of the snowplough sheath is investigated. The width of the sheath colliding with a precursor plasma column on axis is consistent with the rise time of the X-ray pulse observed in the experiments; and whilst the level of emission increases, the stagnated body of plasma on axis compresses, and axial electron beams are observed. After peak emission, the stagnated plasma shows large scale instabilities that then cause discontinuities. This research was sponsored by Sandia National Laboratories Albuquerque, the SSAA program of NNSA under DOE Cooperative Agreement DE-FC03-02NA00057

Bland, S. N.; Hammer, D. A.; Mitchell, I. H.

2005-10-01

95

Implosion dynamics of long-pulse wire array Z pinches  

SciTech Connect

Recent improvements in Z-pinch wire array load design at Sandia National Laboratories have led to a substantial increase in pinch performance as measured by radiated powers of up to 280 TW in 4 ns and 1.8 MJ of total radiated energy. Next generation, higher-current machines will allow for larger mass arrays and comparable or higher velocity implosions to be reached, possibly extending these results. As the current is pushed above 20 MA, a conventional machine design based on a 100 ns implosion time results in higher voltages, hence higher cost and power flow risk. Another approach, which shifts the risk to the load configuration, is to increase the implosion time to minimize the voltage. This approach is being investigated in a series of experimental campaigns on the Saturn [C. Deeney et al., Phys. Plasmas 6, 3576 (1999)] and Z [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] machines. In this paper, both experimental and two-dimensional computational modeling of the first long implosion time Z experiments will be presented. The experimental data shows broader pulses, lower powers, and larger pinch diameters compared to the corresponding short pulse data. By employing a nested array configuration, the pinch diameter was reduced by 50% with a corresponding increase in power of >30%. Numerical simulations suggest that load velocity is the dominating mechanism behind these results. (c) 2000 American Institute of Physics.

Douglas, M. R. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Deeney, C. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Spielman, R. B. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Coverdale, C. A. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Roderick, N. F. [University of New Mexico, Albuquerque, New Mexico 87102 (United States)] [University of New Mexico, Albuquerque, New Mexico 87102 (United States); Peterson, D. L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-05-01

96

The physics of the high density Z-pinch  

SciTech Connect

The fiber-initiated High-Density Z-Pinch (HDZP) is a novel concept in which fusion plasma could be produced by applying 2 MV along a thin filament of frozen deuterium, 20-30 ..mu..m in diameter, 5-10 cm long. The megamp-range currents that result would ohmically heat the fiber to fusion temperatures in 100 ns while maintaining nearly constant radius. The plasma pressure would be held stably by the self-magnetic field for many radial sound transit times during the current-rise phase while, in the case of D-T, a significant fraction of the fiber undergoes thermonuclear fusion. This paper presents results of Los Alamos HDZP studies. Existing and new experiments are described. A succession of theoretical studies, including 1D self-similar and numerical studies of the hot plasma phase, 1D and 2D numerical studies of the cold startup phase, and 3D numerical studies of stability in the hot regime, are then presented. 9 refs., 4 figs.

Glasser, A.H.; Hammel, J.E.; Lewis, H.R.; Lindemuth, I.R.; McCall, G.H.; Nebel, R.A.; Scudder, D.W.; Schlachter, J.S.; Lovberg, R.H.; Rosenau, P.; Sheehey, P.T.

1988-01-01

97

Electromagnetic wave propagation through the ZR Z-pinch accelerator.  

SciTech Connect

A fully three-dimensional electromagnetic model of the major pulsed power components of the 26-MA ZR accelerator is presented. This large-scale simulation model tracks the evolution of electromagnetic waves through the intermediate storage capacitors, laser-triggered gas switches, pulse-forming lines, water switches, tri-plate transmission lines, and water convolute to the vacuum insulator stack. The plates at the insulator stack are coupled to a transmission line circuit model of the four-level magnetically-insulated transmission line section and post-hole convolutes. The vacuum section circuit model is terminated by either a short-circuit load or dynamic models of imploding z-pinch loads. The simulations results are compared with electrical measurements made throughout the ZR accelerator and good agreement is found, especially for times before and up to peak load power. This modeling effort represents new opportunities for modeling existing and future large-scale pulsed power systems used in a variety of high energy density physics and radiographic applications.

Welch, Dale Robert (Voss Scientific, LLC, Albuquerque, NM); Clark, R. E. (Voss Scientific, LLC, Albuquerque, NM); Rose, David Vincent (Voss Scientific, LLC, Albuquerque, NM); Madrid, Elizabeth Ann (Voss Scientific, LLC, Albuquerque, NM); Corcoran, P. A. (L-3 Communications, San Leandro, CA); Struve, Kenneth William; Stygar, William A.; Miller, C. L. (Voss Scientific, LLC, Albuquerque, New Mexico); Whitney, B. (L-3 Communications, San Leandro, CA)

2008-08-01

98

Soldered Contact and Current Risetime Effects on Negative Polarity Wire Array Z-pinches  

SciTech Connect

The Cornell University COBRA pulser is a nominal 1 MA machine, capable of driving up to 32 wire cylindrical Z-pinch arrays. COBRA can operate with variable current risetimes ranging from 100 ns to 200 ns (short and long pulse, respectively). Wires are typically strung with a 'press' contact to the electrode hardware, where the wire is loosely pulled against the hardware and held there to establish electrical contact. The machine is normally negative, but a bolt-on convolute can be used to modify the current path and effectively produce positive polarity operation at the load.Previous research with single wires on a 1-5 kA pulser has shown that soldering the wire, thereby improving the wire/electrode contact, and operating in positive polarity can improve the energy deposition into the wire and enhance wire core expansion. Negative polarity showed no difference. Previous experiments on the negative polarity, 20 MA, 100 ns Z accelerator have shown that improving the contact improved the x-ray yield.Cornell data were collected on 16-wire Aluminum Z-pinch arrays in negative polarity. Experiments were conducted with both short and long current pulses with soldered and no-soldered wire/electrode contacts. The initiation, ablation, implosion and stagnation phases were compared for these four conditions. Time dependent x-ray signals were measured using diodes and diamond detectors. An inductive voltage monitor was used to infer minimum current radius achieved, as defined by a uniform shell of current moving radially inward, producing a time dependent inductance. Total energy data were collected with a metal-strip bolometer. Self-emission data were collected by an XUV 4-frame camera and an optical streak camera.In negative polarity and with short pulses, soldering appeared to produce a smaller radius pinch and decrease variations in the x-ray pulse shape. The bolometer, laser backlighter, 4-frame and streak cameras showed negligible differences in the initiation ablation and implosion phases. X-ray yield was increased with soldered arrays in negative polarity with long pulses. The bolometer also showed a 50% increase in radial power emitted for soldered arrays. 4-frame images showed soldered arrays have a more pronounced 'Christmas Tree' effect originating from the cathode. The inductive voltage monitor showed, with both long and short pulses, that soldered and no-solder arrays reached the same minimum current radius at the same time. However, with long pulses soldered arrays radiate x-rays at the time of minimum current radius while no-solder array x-ray output is delayed by {approx}20 ns, resulting in decreased x-ray yield.

Chalenski, D. A.; Kusse, B. R.; Greenly, J. B.; Blesener, I. C.; McBride, R. D.; Hammer, D. A.; Knapp, P. F. [Cornell University Laboratory of Plasma Studies, 439 Rhodes Hall, Ithaca, NY 14853 (United States)

2009-01-21

99

Development of the Axial Instability in Low Wire Number Wire Array Z-Pinches  

NASA Astrophysics Data System (ADS)

We investigate the growth of the axial instability in wire-array Z-pinches. In these experiments we image individual wires in aluminum wire arrays using laser shadowgraphy and XUV framing cameras at times ranging from 0 to 100 ns after the start of a 1 MA, 100 ns rise time current pulse. We document the radial growth of the coronal plasma around each wire and the development of the wavelength and amplitude of the instability from the time of plasma formation until the instability stops growing. The ratio of the dominant instability wavelength to the coronal plasma radius is 1 during this time. The magnetic field topology is also probed using small B-dot probes inside the array. The change in topology from local- to global- field dominated near an exploding wire correlates well in time with the moment that the instability stops growing. In addition, preliminary experiments show that perturbations seeded in the coronal plasma using twisted wires grow at the twist wavelength and evolve to much larger amplitude than in the unseeded case. This research was supported by the SSAA program of the National Nuclear Security Administration under DOE Cooperative agreement DE-FC03-02NA00057.

Knapp, Patrick; Greenly, John; Gourdain, Pierre; Hoyt, Cad; Martin, Matthew; Pikuz, Sergei; Shelkovenko, Tania; Hammer, David; Kusse, Bruce

2009-11-01

100

Fusion burn dynamics in dense Z-pinch (DZP)  

SciTech Connect

The fusion burn dynamics and energy yield of the dense Z-pinch (DZP) are examined using a profile-averaged, zero-dimensional, time dependent model. A range of conditions (fuel, line density, voltage, fusion-product heating, enthalpy endloss, density and temperature profiles, current rise rate, electrode impurities) are examined. Magneto-hydrodynamic stability is assumed, and initial conditions are based on those ideally existing after the melting and ionization of a solid fiber of fusion fuel. Plasma conditions required of neutron sources for materials testing ({dot S}{sub n} {ge} 10{sup 19} n/s) and for possible commercial power production (ratio of fusion energy yield to energy input, Q{sub p} {approx equal} 15, lower values if reversible recovery of a fraction of the magnetic energy is possible) are described. If f{sub B} {approx gt} 0.8 fractional fuel burnup is possible in a nominal 800-ns DT discharge (200-ns current-rise phase at 20 MV/m followed by a 500-ns constant-current crowbarred phase), reactor-relevant values of Q{sub p} may be possible. For the simpler (and shorter) constant-voltage discharge (e.g., no voltage crowbar) the value of Q{sub p} is in the range 5--10 for discharges below 200-ns duration. Smaller levels of fuel burnup, shorter discharges, or generally lower levels of Q{sub p} will require a reversible energy transfer system to meet reactor energy-balance requirements. Imposition of a plasma current rise-time constraint that may be needed for stable plasma operation (e.g., I > 10{sup 12} A/s) will burnup, Q{sub p} and discharge time to an extent where reversible energy/transfer system will be required to meet reactor energy- balance requirements. 25 refs.

Krakowski, R.A.

1990-04-01

101

Axial x-ray backlighting of wire-array Z-pinches using X pinches  

SciTech Connect

For the first time, a geometry has been developed to allow for an axial imaging system for wire-array Z-pinch experiments that produce high-resolution x-ray images. The new geometry required a significant redesign of the electrode hardware. Calibrated areal density measurements of the Z-pinch plasma including wire cores, coronal plasma, streaming plasma, and the precursor were obtained. The system used eight-wire molybdenum (Mo) X pinches in series with and directly below the Z-pinch axis to provide micron-scale x-rays sources for point-projection radiography. The images formed on the x-ray sensitive film had a 15 mm diameter field of view at the center height of the array and a magnification of about 7.5:1. Titanium (Ti) filters in front of the film transmitted radiation in the spectral range of 3-5 keV. For calibration, a separate film with the same thickness Ti filter was placed the same distance from the X pinch. This film had an unobstructed path that bypasses the Z-pinch but included step wedges for calibration of the Z-pinch plasma. The step wedges had thicknesses of tungsten (W) ranging from 0.015 to 1.1 {mu}m to obtain areal density measurements of the W plasma from the wire-array. Images had subnanosecond temporal resolution and about 10 {mu}m spatial resolution.

Blesener, I. C.; Greenly, J. B.; Pikuz, S. A.; Shelkovenko, T. A.; Vishniakou, S.; Hammer, D. A.; Kusse, B. R. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2009-12-15

102

The ZaP Flow Z-Pinch Project: Investigations of Flow Shear on MHD Stability  

NASA Astrophysics Data System (ADS)

The ZaP Flow Z-Pinch observes gross stability of a Z-pinch while a sheared axial flow is present.(U. Shumlak et al.), Phys. Rev. Lett. 87 (20), p. 205005-1, 2001 The Z-pinch is maintained more than 700 times the predicted kink instability growth time of a static pinch. The stable time is correlated with measurements of a sheared axial flow, and instability of the pinch is correlated with measurements of lower velocities with little or no shear. The sheared-flow Z-pinch is created by coaxial electrodes accelerating an annular plasma into a Z-pinch assembly region. Diagnostics include axial and azimuthal surface magnetic probe arrays, internal magnetic field probes, an azimuthal Rogowski array, a gridded energy analyzer, a bolometer, fast framing photography and diode arrays using spectral filters, ruby laser holographic interferometry, a CCD survey spectrometer, and a high-resolution gateable 20-channel ICCD spectrometer system. Recent modifications include a solid ``bullet-nose'' inner electrode, an opening in the outer electrode end wall, and the replacement of two outer electrode gas puff valves by eight faster valves.

Nelson, B. A.; Shumlak, U.; Golingo, R. P.; Jackson, S. L.; Bright, J.; den Hartog, D. J.

2002-11-01

103

Theory of wire number scaling in wire-array Z pinches  

SciTech Connect

Pulsed-power-driven Z pinches, produced by imploding cylindrical arrays of many wires, have generated very high x-ray radiation powers ({gt}200 TW) and energies (2 MJ). Experiments have revealed a steady improvement in Z-pinch performance with increasing wire number at fixed total mass and array radius. The dominant mechanism acting to limit the performance of these devices is believed to be the Rayleigh-Taylor instability which broadens the radially imploding plasma sheath and consequently reduces the peak radiation power. A model is presented which describes an amplification over the two-dimensional Rayleigh-Taylor growth rate brought about by kink-like forces on the individual wires. This amplification factor goes to zero as the number of wires approaches infinity. This model gives results which are in good agreement with the experimental data and provides a scaling for wire-array Z pinches. {copyright} {ital 1999 American Institute of Physics.}

Desjarlais, M.P.; Marder, B.M. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

1999-05-01

104

The Imaging of Z-Pinches Using X-Pinch Backlighting  

SciTech Connect

Imaging using X-pinch backlighters has been implemented on the COBRA accelerator at Cornell University to study the early stages of wire-array Z-pinches. Two of four return-current posts in the wire-array load region are replaced by X pinches so that two images of one wire in an eight-wire z-pinch are obtained from different angles and at different times. High resolution images have been obtained that show the evolution of wire structure and instabilities. X-pinch wire diameter and other parameters were varied in order to shift the timing of the X pinches relative to the start of the z-pinch current pulse. It was found that XPBL wire diameter (mass per unit length) has the strongest influence on radiation timing.

Douglass, J.D.; Greenly, J.B.; Hammer, D.A.; McBride, R.D.; Pikuz, S.A.; Shelkovenko, T.A. [Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States)

2006-01-05

105

Characteristics of the Z-pinch Implosion Plasmas on Low Current Generators  

SciTech Connect

The primary physical images of the low driven current (<7MA) Z-pinch experiments on the three facilities, including the Angara-5-1 and S-300 in Russia, and the Qiangguang-I in China, were analyzed and summarized. The wire-array Z-pinch implosion processes were simulated by using a zero-dimensional model and an one-dimensional radial-magneto-hydrodynamic code. It is found that in the different pulse power driver, even if there are the same peak currents, the process of the wire-array plasma implosion and the compression state can be quite different due to the different rising-time of the current. Moreover, it is also found that not total mass of the wire-array takes part in the implosion process in the Z-pinch experiment.

Ding Ning; Yang Zhenhua; Ning Cheng; Wu Jiming; Liu Quan; Fan Wenbin; Zhang Yang [Institute of Applied Physics and Computational Mathematics, P. O. Box 8009-11, Beijing 100088 (China)

2006-01-05

106

Measurement of Temperature, Density, and Particle Transport with Localized Dopants in Wire-Array Z Pinches  

NASA Astrophysics Data System (ADS)

Axially localized NaF dopants are coated onto Al cylindrical wire arrays in order to act as spectroscopic tracers in the stagnated z-pinch plasma. Non-local-thermodynamic-equilibrium kinetic models fit to Na K-shell lines provide an independent measurement of the density and temperature that is consistent with spectroscopic analysis of K-shell emissions from Al and an alloyed Mg dopant. Axial transport of the Na dopant is observed, enabling quantitative study of instabilities in dense z-pinch plasmas.

Jones, B.; Deeney, C.; McKenney, J. L.; Ampleford, D. J.; Coverdale, C. A.; Lepell, P. D.; Shelton, K. P.; Safronova, A. S.; Kantsyrev, V. L.; Osborne, G.; Sotnikov, V. I.; Ivanov, V. V.; Fedin, D.; Nalajala, V.; Yilmaz, F.; Shrestha, I.

2008-03-01

107

Control of initial mass on metal vapor puff z-pinch  

NASA Astrophysics Data System (ADS)

The high energy density z-pinch plasma created by injecting metal vapor between the electrodes has been examined experimentally. In the metal vapor puff z-pinch, an initial mass of metal vapor greatly affects the pinch characteristics. To control the metal vapor spatial distribution and the puffed vapor velocity, a discharge current with a square wave is employed to produce the metal vapor. We have constructed the LC ladder discharge circuit which can generate the current pulse with 10 microsecs in pulse width. Ag metal vapor is ejected by the discharge through a small hole drilled at the center of the electrode.

Furuya, Seizo; Arai, Kenji; Goto, Eiji; Ishii, Shozo

1994-06-01

108

Measurement of Temperature, Density, and Particle Transport with Localized Dopants in Wire-Array Z Pinches  

SciTech Connect

Axially localized NaF dopants are coated onto Al cylindrical wire arrays in order to act as spectroscopic tracers in the stagnated z-pinch plasma. Non-local-thermodynamic-equilibrium kinetic models fit to Na K-shell lines provide an independent measurement of the density and temperature that is consistent with spectroscopic analysis of K-shell emissions from Al and an alloyed Mg dopant. Axial transport of the Na dopant is observed, enabling quantitative study of instabilities in dense z-pinch plasmas.

Jones, B.; Deeney, C.; McKenney, J. L.; Ampleford, D. J.; Coverdale, C. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); LePell, P. D.; Shelton, K. P. [Ktech Corp., Albuquerque, New Mexico 87123 (United States); Safronova, A. S.; Kantsyrev, V. L.; Osborne, G.; Sotnikov, V. I.; Ivanov, V. V.; Fedin, D.; Nalajala, V.; Yilmaz, F.; Shrestha, I. [University of Nevada, Reno, Nevada 89557 (United States)

2008-03-14

109

Design, simulation, and application of quasi-spherical z-pinch implosions driven by tens of mega-amperes.  

SciTech Connect

A quasi-spherical z-pinch may directly compress foam or deuterium and tritium in three dimensions as opposed to a cylindrical z-pinch, which compresses an internal load in two dimensions only. Because of compression in three dimensions the quasi-spherical z-pinch is more efficient at doing pdV work on an internal fluid than a cylindrical pinch. Designs of quasi-spherical z-pinch loads for the 28 MA 100 ns driver ZR, results from zero-dimensional (0D) circuit models of quasi-spherical implosions, and results from 1D hydrodynamic simulations of quasi-spherical implosions heating internal fluids will be presented. Applications of the quasi-spherical z-pinch implosions include a high radiation temperature source for radiation driven experiments, a source of neutrons for treating radioactive waste, and a source of fusion energy for a power generator.

Struve, Kenneth William; Deeney, Christopher D.; Leeper, Ramon Joe; McDaniel, Dillon Heirman; Nash, Thomas J.; DeGroot, John Stacey; Sanford, Thomas W. L.

2004-08-01

110

UV Laser Diagnostics of the 1-MA Z-pinch Plasmas  

SciTech Connect

The 532 nm laser diagnostic set at the Zebra generator shows the details of the ablation and stagnation phases in cylindrical, planar, and star-like wire arrays but it cannot show the structure of the stagnated z-pinch and the implosion in small diameter loads, 1-3 mm in diameter. The absorption increment and the refraction angle of the 532 nm laser, when passing through the plasma, are too great to obtain quality images. An ultraviolet probing beam at the wavelength of 266 nm was developed to study small-diameter loads and to investigate the structure of the 1-MA z-pinch. The UV radiation has a much smaller absorption increment and refraction angles in plasmas than the 532 nm light and allows for better imaging of the z-pinch plasmas. Estimates showed that UV probing would be able to probe the high-density z-pinch plasma in experiments on the Zebra generator, and the early results of UV probing on the Zebra generator have shown promise.

Altemara, S. D.; Ivanov, V. V.; Astanovitskiy, A. L.; Haboub, A. [University of Nevada, Reno, NV 89557 (United States)

2009-01-21

111

Dust and debris transport modeling for experimental z-pinch driven inertial fusion systems  

NASA Astrophysics Data System (ADS)

A model using the TEXAS-NCV computer code is presented for the transport of dust and debris in a z-pinch driven explosive propagation of gas into vacuum. First, TEXAS-NC was improved, updated, and benchmarked against several experiments for quasi-one-dimensional shock propagation applications involving multi-component, multi-phase systems. Second, a vacuum transport model was developed and incorporated into TEXAS and benchmarked for adiabatic expansions and wall pressure histories at various dimensionless distances. This model eliminates the severe problem usually encountered with vacuum transport in Eulerian hydrodynamics codes, and gives TEXAS a rare set of capabilities that is not known to exist before. Third, TEXAS-NCV was used to model dust and debris transport in z-pinch driven experiments designed for application to the U.S. inertial fusion energy program. Results showed that if radioactive dust and debris is to be completely contained within the Z experiment chamber, explosive closures placed at the ends of the MITLs must complete the closure process in less than 1 ms. Substantially faster closure times will be required if the valves are to be placed closer to the center of the Z-pinch convolute or if magnetic effects during the z-pinch have already accelerated debris.

Utschig, Tristan Thomas

112

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

SciTech Connect

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.

Chittenden, J.P.; Vincent, P.; Jennings, C.A.; Ciardi, A. [Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom)

2006-01-05

113

Convective Cell Formation in a Z-Pinch Plasma Science and Fusion Center  

E-print Network

Convective Cell Formation in a Z-Pinch J. Kesner Plasma Science and Fusion Center Massachusetts systems can develop convective cells when the MHD inter- change stability criterion is violated. Using the system may develop large-scale convective cells which can lead to nonlocal transport [6, 7, 8, 9, 10

114

Radiation science using Z-pinch x raysa... J. E. Bailey,1,b)  

E-print Network

Radiation science using Z-pinch x raysa... J. E. Bailey,1,b) G. A. Chandler,1 D. Cohen,2 M. E 200 TW peak power, 5­10 ns duration x-ray bursts that provide new possibilities to advance radiation away from the pinch, where it is heated to 10­100 eV temperatures by the pinch radiation

Cohen, David

115

Radio-Frequency-Preionized Xenon Z Pinch Source for Extreme Ultraviolet Lithography  

Microsoft Academic Search

Intense amplified spontaneous emission is generated in generally axial directions in a recombining uniform Z pinch. This effect allows the generation of highly efficient soft x-ray beams, including the intense xenon-band emission at 134 , of interest for extreme ultraviolet lithography. We discuss the characteristics of this source, including optimization of the xenon helium mix and measurements of source size,

Malcolm McGeoch

1998-01-01

116

Efficient neutron production from a novel configuration of deuterium gas-puff z-pinch.  

PubMed

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 Y(n)=(2.9 0.3) 10(12) 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 10(7). This implies that deuterium gas puff z pinches belong to the most efficient plasma-based sources of DD neutrons. PMID:24655260

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

117

Magnetic Rayleigh-Taylor instability mitigation in large-diameter gas puff Z-pinch implosions  

SciTech Connect

Recently, a new approach for efficiently generating K-shell x-rays in large-diameter, long-implosion time, structured argon gas Z-pinches has been demonstrated based on a 'pusher-stabilizer-radiator' model. In this paper, direct observations of the Rayleigh-Taylor instability mitigation of a 12-cm diameter, 200-ns implosion time argon Z-pinch using a laser shearing interferometer (LSI) and a laser wavefront analyzer (LWA) are presented. Using a zero-dimensional snowplow model, the imploding plasma trajectories are calculated with the driver current waveforms and the initial mass distributions measured using the planar laser induced fluorescence method. From the LSI and LWA images, the plasma density and trajectory during the implosion are measured. The measured trajectory agrees with the snowplow calculations. The suppression of hydromagnetic instabilities in the ''pusher-stabilizer-radiator'' structured loads, leading to a high-compression ratio, high-yield Z-pinch, is discussed. For comparison, the LSI and LWA images of an alternative load (without stabilizer) show the evolution of a highly unstable Z-pinch.

Qi, N.; Sze, H.; Failor, B. H.; Banister, J.; Levine, J. S.; Riordan, J. C.; Steen, P.; Sincerny, P. [L-3 Communications Pulse Sciences, San Leandro, California 94577 (United States); Lojewski, D. [Defense Threat Reduction Agency, Albuquerque, New Mexico 87117 (United States)

2008-02-15

118

Plasma channel and Z-pinch dynamics for heavy ion transport  

SciTech Connect

A self stabilized, free standing, z-pinch plasma channel has been proposed to deliver the high intensity heavy ion beam from the end of a driver to the fuel target in a heavy ion inertial fusion power plant. The z-pinch relaxes emittance and energy spread requirements requiring a lower cost driver. A z-pinch transport would reduce the number of beam entry port holes to the target chamber from over a hundred to four as compared to neutralized ballistic focusing thus reducing the driver hardware exposure to neutron flux. Experiments where a double pulse discharge technique is used, z-pinch plasma channels with enhanced stability are achieved. Typical parameters are 7 kV pre-pulse discharge and 30 kV main bank discharge with 50 kA of channel current in a 7 torr background gas atmosphere. This work is an experimental study of these plasma channels examining the relevant physics necessary to understand and model such plasmas. Laser diagnostics measured the dynamical properties of neutrals and plasma. Schlieren and phase contrast techniques probe the pre-pulse gas dynamics and infrared interferometry and faraday effect polarimetry are used on the z-pinch to study its electron density and current distribution. Stability and repeatability of the z-pinch depend on the initial conditions set by the pre-pulse. Results show that the z-pinch channel is wall stabilized by an on-axis gas density depression created by the pre-pulse through hydrodynamic expansion where the ratio of the initial gas density to the final gas density is > 10/1. The low on-axis density favors avalanching along the desired path for the main bank discharge. Pinch time is around 2 s from the main bank discharge initiation with a FWHM of {approx} 2 cm. Results also show that typical main bank discharge plasma densities reach 10{sup 17} cm{sup -3} peak on axis for a 30 kV, 7 torr gas nitrogen discharge. Current rise time is limited by the circuit-channel inductance with the highest contribution to the impedance due to the plasma. There is no direct evidence of surface currents due to high frequency skin effects and magnetic field experiments indicate that > 70% of the current carried by the channel is enclosed within FWHM of the channel. Code-experiment benchmark comparisons show that simulations capture the main mechanisms of the channel evolution, but complete atomic models need to be incorporated.

Ponce-Marquez, David

2002-07-09

119

Examination of resistivity issues in solid liner Z-pinches  

Microsoft Academic Search

Summary form only given. Experiments being conducted at the Los Alamos National Lab Pegasus facility are examining driving an aluminum liner with a pulsed magnetic field. The Pegasus facility provides a current of 5 to 8 Mega-amps to compress a cylindrical liner. Liners of various size thickness are used, and depending on the specific experimental objectives. In several of these

W. L. Atchison; R. J. Faehl; R. E. Reinovsky

1999-01-01

120

Effect of soft metal gasket contacts on contact resistance, energy deposition, and plasma expansion profile in a wire array Z pinch  

NASA Astrophysics Data System (ADS)

Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire and the electrode in an aluminum wire Z pinch by more than an order of magnitude over the best weighted contact case. Clamping a gasket over a Z-pinch wire compresses the wire to the electrode with a greater normal force than possible with wire weights. Average contact resistance was reduced from the range of 100-3000 ? (depending on wire weight mass) to 1-10 ? with soft metal gaskets. Single wire experiments (13 ?m Al 5056) on a 16 kA, 100 kV Marx bank showed an increase in light emission (97%) and emission volume (100%) of the plasma for the reduced contact resistance cases. The measured increases in plasma volume and light emission indicate greater energy deposition in the ablated wire. Additionally, dual-wire experiments showed plasma edge effects were significantly decreased in the soft metal gasket contact case. The average height of the edge effects was reduced by 51% and the width of the edge effects was increased by 40%, thus the gasket contact case provided greater axial uniformity in the plasma expansion profile of an individual wire.

Gomez, M. R.; Zier, J. C.; Gilgenbach, R. M.; French, D. M.; Tang, W.; Lau, Y. Y.

2008-09-01

121

Effect of soft metal gasket contacts on contact resistance, energy deposition, and plasma expansion profile in a wire array Z pinch  

SciTech Connect

Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire and the electrode in an aluminum wire Z pinch by more than an order of magnitude over the best weighted contact case. Clamping a gasket over a Z-pinch wire compresses the wire to the electrode with a greater normal force than possible with wire weights. Average contact resistance was reduced from the range of 100-3000 {omega} (depending on wire weight mass) to 1-10 {omega} with soft metal gaskets. Single wire experiments (13 {mu}m Al 5056) on a 16 kA, 100 kV Marx bank showed an increase in light emission (97%) and emission volume (100%) of the plasma for the reduced contact resistance cases. The measured increases in plasma volume and light emission indicate greater energy deposition in the ablated wire. Additionally, dual-wire experiments showed plasma edge effects were significantly decreased in the soft metal gasket contact case. The average height of the edge effects was reduced by 51% and the width of the edge effects was increased by 40%, thus the gasket contact case provided greater axial uniformity in the plasma expansion profile of an individual wire.

Gomez, M. R.; Zier, J. C.; Gilgenbach, R. M.; French, D. M.; Tang, W.; Lau, Y. Y. [Plasma, Pulsed Power, and Microwave Laboratory, Nuclear Engineering and Radiological Sciences Department, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States)

2008-09-15

122

History of HERMES III diode to z-pinch breakthrough and beyond : learning about pulsed power and z-pinch ICF.  

SciTech Connect

HERMES III and Z are two flagship accelerators of Sandia's 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, 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.

Sanford, Thomas W. L.

2013-04-01

123

Z-Pinch Driven Inertial Confinement Fusion Target Physics Research at Sandia National Laboratories  

SciTech Connect

Three hohlraum concepts are being pursued at Sandia National Laboratories (SNL) to investigate the possibility of using pulsed power driven magnetic implosions (z-pinches) to drive high gain targets capable of yields in the range of 200-1000 MJ. This research is being conducted on SNL'S.Z facility that is capable of driving peak currents of 20 MA in z-pinch loads producing implosion velocities as high as 7.5X 107 cm/s, x-ray energies approaching 2 MJ, and x-ray powers exceeding 200 TW. This paper will discuss each of these hohlraum concepts and will overview the experiments that have been conducted on these systems to date.

Alberts, T.E.; Asay, J.R.; Baca, P.M.; Baker, K.L.; Breeze, S.P.; Chandler, G.A.; Cook, D.L.; Cooper, G.W.; Deeney, C.; Derzon, M.S.; Douglas, M.R.; Fehl, D.L.; Gilliland, T.; Hebron, D.E.; Hurst, M.J.; Jobe, D.O.; Kellogg, J.W.; Lash, J.S.; Lazier, S.E.; Leeper, R.J.; Matzen, M.K.; McDaniel, D.H.; McGurn, J.S.; Mehlhorn, T.A.; Moats, A.R.; Mock, R.C.; Muron, D.J.; Nash, T.J.; Olson, R.E.; Porter, J.L.; Quintenz, J.P.; Reyers, P.V.; Ruggles, L.E.; Ruiz, C.L.; Sandford, T.W.L.; Schmidlapp, F.A.; Seamen, J.F.; Spielman, R.B.; Stark, M.A.; Struve, K.W.; Stygar, W.A.; Tibbetts-Russell, D.R.; Torres, J.A.; Vargas, M.; Wagoner, T.C.; Wakefield, C.

1998-10-27

124

Magnetic Field Measurements in Wire-Array Z-Pinches and X Pinches  

SciTech Connect

We are investigating several techniques to obtain time-dependent magnetic field measurements in wire-array Z-pinches and X-pinches. One general approach is to use 'remote sensing' methods whereby a very small sensor material is placed in the plasma and then is investigated to extract useful information. Faraday rotation of polarized laser light traversing a small area through thin film waveguides coupled to a fine optical fiber is a possibility. While these films may not survive for long in a dense Z-pinch, they may provide useful information for a significant fraction of the current pulse. We also discuss results of experiments conducted using magnetic CoPt thin films to obtain the maximum magnetic field seen by the film near the end of the load current pulse.

Syed, W. [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Hammer, D.A. [Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Lipson, M. [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Van Dover, R.B. [Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853 (United States)

2006-01-05

125

Determination of the inductance of imploding wire array Z-pinches using measurements of load voltage  

NASA Astrophysics Data System (ADS)

The inductance of imploding cylindrical wire array z-pinches has been determined from measurements of load voltage and current. A thorough analysis method is presented that explains how the load voltage of interest is found from raw signals obtained using a resistive voltage divider. This method is applied to voltage data obtained during z-pinch experiments carried out on the MAGPIE facility (1.4 MA, 240 ns rise-time) in order to calculate the load inductance and thereafter the radial trajectory of the effective current sheath during the snowplough implosion. Voltage and current are monitored very close to the load, allowing these calculations to be carried out without the need for circuit modelling. Measurements give a convergence ratio for the current of between 3.1 and 5.7 at stagnation of the pinch.

Burdiak, G. C.; Lebedev, S. V.; Hall, G. N.; Harvey-Thompson, A. J.; Suzuki-Vidal, F.; Swadling, G. F.; Khoory, E.; Pickworth, L.; Bland, S. N.; de Grouchy, P.; Skidmore, J.

2013-03-01

126

X-ray backlighting of two-wire Z-pinch plasma using X-pinch  

NASA Astrophysics Data System (ADS)

Two 50-?m Mo wires in parallel used as a Z-pinch load are electrically exploded with a pulsed current rising to 275 kA in 125 ns and their explosion processes are backlighted using an X-pinch as an x-ray source. The backlighting images show clearly the processes similar to those occurring in the initial stages of a cylindrical wire-array Z-pinch, including the electric explosion of single wires characterised by the dense wire cores surrounded by a low-density coronal plasma, the expansion of the exploding wire, the sausage instability (m = 0) in the coronal plasma around each wire, the motion of the coronal plasma as well as the wire core toward the current centroid, the formation of the precursor plasma column with a twist structure something like that of higher mode instability, especially the kink instability (m = 1).

Zhao, Tong; Zou, Xiao-Bing; Zhang, Ran; Wang, Xin-Xin

2010-07-01

127

Progress in Z-pinch research driven by the mega-ampere device SPEED2  

SciTech Connect

Several pinch configurations have being studied at the Chilean Nuclear Energy Commission using the SPEED2 generator: plasma focus, gas embedded z-pinch and wire arrays. SPEED2 is a generator based on Marx technology (4.1 {mu}F equivalent Marx generator capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns rise time, dI/dt{approx}10{sup 13} A/s). Currently the device is being operated at 70kJ stored energy producing a peak current of 2.4 MA in short circuit. In this work results related to studies in gas embedded z-pinch in deuterium and studies in wire arrays are presented.

Pavez, Cristian; Soto, Leopoldo; Moreno, Jose [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Center for Research and Applications in Plasma Physics and Pulsed Power, P4 (Chile); Tarifeno, Ariel [Center for Research and Applications in Plasma Physics and Pulsed Power, P4 (Chile); Universidad de Concepcion (Chile); Sylvester, Gustavo [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile)

2008-04-07

128

Advances in experimental spectroscopy of Z-pinch plasmas and applications  

NASA Astrophysics Data System (ADS)

Recent advances in experimental work on plasma spectroscopy of Z-pinches are presented. The results of experiments on the 1.7 MA Z-pinch Zebra generator at UNR with wire arrays of various configurations and X-pinches are overviewed. A full x-ray and EUV diagnostic set for detailed spatial and temporal monitoring of such plasmas together with theoretical support from relativistic atomic structure and non-LTE kinetic codes used in the analysis are discussed. The use of a variety of wire materials in a broad range from Al to W provided an excellent opportunity to observe and study specific atomic and plasma spectroscopy features. In addition, the applications of such features to fusion and astrophysics will be considered.

Kantsyrev, V. L.; Safronova, A. S.; Safronova, U. I.; Shrestha, I.; Weller, M. E.; Osborne, G. C.; Shlyaptseva, V. V.; Wilcox, P. G.; Stafford, A.

2012-06-01

129

MHD simulation of wire ablation and implosion in wire-array Z-pinch  

Microsoft Academic Search

We present magnetohydrodynamic (MHD) simulation of ablated tungsten wire in the wire-array Z-pinch on MAGPIE using the GORGON code. The simulation is incorporated with theoretical models of equation-of-state and electrical conductivities for nonideal plasmas in addition to an astrophysical model for radiation cooling effects. The dynamic behaviors of exploding wire plasma are demonstrated in a two-dimensional domain during the early

Deok-Kyu Kim; Jeremy P. Chittenden; Sergey V. Lebedev; A. Marocchino; F. Suzuki-Vidal

2010-01-01

130

Time Gated Imaging of Cylindrical Wire Array Z-Pinches Using X-Pinch Backlighting  

Microsoft Academic Search

X-Pinch radiography has been used routinely at Cornell for more than 10 years to produce high quality x-ray images with excellent spatial and temporal resolution [T.A. Shelkovenko et al., Phys. Plasmas 8, 1305-1318 (2001).]. This imaging technique is being used on the COBRA accelerator at Cornell to study the early stages of wire-array Z-pinches. The configuration is similar to those

Jon Douglass

2005-01-01

131

Wire-array holder critical in high wire-number z-pinch implosions  

Microsoft Academic Search

The quality of high wire-number z-pinch implosions on Z using a dynamic-hohlraum configuration is significantly affected by the method of holding the wires. The two arrangements discussed here have led to differences of a factor of 1.60.2 in radial x-ray power, where the higher power is produced by the holder with the superior current contact at the cathode. In support

T. W. L. Sanford; R. C. Mock; T. L. Gilliland; J. F. Seamen; R. J. Leeper; R. G. Watt; R. E. Chrien; G. C. Idzorek; D. L. Peterson; P. U. Duselis

2003-01-01

132

An intense auroral z-pinch recorded in antiquity on southwestern artifacts  

Microsoft Academic Search

Summary form only given. A direct correlation of several tens of morphologies of Z-pinch instabilities to archaic petroglyphs, thought to date to 5000-4000 BCE, has been made. The accuracy of the petroglyphs in depicting MHD instabilities suggests the influx to Earth of intense plasma visible as highly collimated synchrotron light from sub-gigaampere currents. Here we analyze an ancient Mixtec ceremonial

A. H. Qoyawayma; A. L. Peratt

2006-01-01

133

Influence of the Hall effect on a neck development in the Z-pinch discharges  

Microsoft Academic Search

The detailed analysis of the z-pinch neck formation is presented. The two-dimensional MHD modeling is carring out with special attention to the magnetic field transfer by the electron component (the so called Hall effect). Shown, that the neck development may be nonsimmetrical with respect to the current direction, when the linear density N becomes less than 1017 cm-1. There are

Victor Vikhrev; Oleg Zabaidullin

1997-01-01

134

Hybrid Simulations of Current-Carrying Instabilities in Z-Pinch Plasmas with Sheared Axial Flow  

NASA Astrophysics Data System (ADS)

The development of instabilities in z-pinch plasmas has been studied with three-dimensional (3D) hybrid simulations. Plasma equilibria without and with sheared axial flow have been considered. Results from the linear phase of the hybrid simulations compare well with linear Hall magnetohydrodynamics (MHD) calculations for sausage modes. The hybrid simulations show that sheared axial flow has a stabilizing effect on the development of both sausage and kink modes.

Sotnikov, Vladimir I.; Makhin, Volodymyr; Bauer, Bruno S.; Hellinger, Petr; Travnicek, Pavel; Fiala, Vladimir; Leboeuf, Jean-Noel

2002-12-01

135

3D MHD Simulations of Radial Wire Array Z-pinches  

Microsoft Academic Search

Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 mus) 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

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

2009-01-01

136

Shock Mitigation using Compressible Two-Phase Jets for Z-Pinch IFE Reactor Applications  

Microsoft Academic Search

Compressible liquid\\/gas jets offer the opportunity to limit and mitigate the mechanical consequences of rapid heating\\/evaporation of the protective jets in a high-yield, low repetition rate Inertial Fusion Energy (IFE) system such as the Z-Pinch IFE reactor. In this investigation, experiments have been conducted to quantify the extent by which a two-phase jet can attenuate a shock wave. The experiments

C. C. Lascar; D. L. Sadowski; S. I. Abdel-Khalik

2005-01-01

137

Characteristics for the occurrence of a high-current, Z-pinch aurora as recorded in antiquity  

Microsoft Academic Search

The discovery that objects from the Neolithic or Early Bronze Age carry patterns associated with high-current Z-pinches provides a possible insight into the origin and meaning of these ancient symbols produced by man. This paper directly compares the graphical and radiation data from high-current Z-pinches to these patterns. The paper focuses primarily, but not exclusively, on petroglyphs. It is found

Anthony L. Peratt

2003-01-01

138

The influence of temperature gradients on the distribution of axial current in a large current Z-pinch implosion  

Microsoft Academic Search

General algebraic expressions for the tensor electrical conductivity and heat conductivity are presented that are needed in one-dimensional (1-D) magnetohydrodynamic modeling of Z-pinch implosions. The expressions contain both the ionization state and the magnetic field dependence of these quantities and generalize Braginskii's results. The ionization dependence is important in any description of a Z-pinch's implosion dynamics, since substantial ionization occurs

K. G. Whitney; J. W. Thornhill

1998-01-01

139

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

Microsoft Academic Search

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

M G Haines

1982-01-01

140

Formation of copper vapors at the initial stage of electrical conductor explosion in vacuum - Z-pinch  

Microsoft Academic Search

The conditions giving rise to Z-pinch during the electrical explosion of conductors in vacuum are discussed. It is shown that, at the initial stage of the electrical explosion, Z-pinch leads to the pulsed ejection of plasma from the discharge channel. The duration of plasma ejection is not more than 1 microsecond; the rate of plasma expansion is 10-100 km\\/s. By

S. V. Baranov; S. S. Sulakshin

1987-01-01

141

Aluminum-doped lithium nickel cobalt oxide electrodes for high-power lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Non-doped and aluminum-doped LiNi 0.8Co 0.2O 2 cathodes from three industrial developers coupled with graphite anodes were made into lithium-ion cells for high-power applications. The powder morphology of the active cathode materials was examined by a scanning electron microscope. The electrochemical performance of these cells was investigated by hybrid pulse power characterization (HPPC) testing, accelerated aging, and AC impedance measurement of symmetric cells. Although all of the fresh cells are found to meet and exceed the power requirements set by PNGV, the power capability of those cells with non-doped LiNi 0.8Co 0.2O 2 cathodes fades rapidly due to the rise of the cell impedance. Al-doping is found very effective to suppress the cell impedance rise by stabilizing the charge-transfer impedance on the cathode side. The stabilization mechanism may be related to the low average oxidation state of nickel ions in the cathode. The powder morphology also plays a secondary role in determining the impedance stabilization.

Chen, C. H.; Liu, J.; Stoll, M. E.; Henriksen, G.; Vissers, D. R.; Amine, K.

142

Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches  

SciTech Connect

The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Stafford, A.; Shlyaptseva, V. V. [Physics Department, University of Nevada, Reno, Nevada 89557 (United States); Velikovich, A. L. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Rudakov, L. I. [Icarus Research Inc., Bethesda, Maryland 20824 (United States); Williamson, K. M. [Physics Department, University of Nevada, Reno, Nevada 89557 (United States); Plasma Engineering Research Laboratory, Texas A and M University, Corpus Christi, TX 78412 (United States)

2011-10-15

143

Study of micro-pinches in wire-array Z pinches  

SciTech Connect

Bright and hot areas with a high plasma density and temperature are observed in all kinds of Z pinches. We studied bright radiating spots produced by micro-pinches in cylindrical and planar wire-arrays at the 1 MA Zebra pulsed power generator using an x-ray streak camera synchronized with laser diagnostics, x-ray time-gated pinhole camera, and spectroscopy. Hot spots with extremely dense and relatively hot plasma arise during the collapse of the micro-pinches. These hot spots radiate a continuum spectrum with energy >2.5 keV. Typical micro-pinches in Al wire arrays generate x-ray bursts with durations of 0.41 ns in the soft x-ray range and 0.10.4 ns in the keV range. UV two-frame shadowgraphy shows spatial correlation of hot spots with the collapse and explosion of micro-pinches. Micro-pinches typically occur at the necks of the Z pinch, but can demonstrate a variety of parameters and different dynamics. An analysis of x-ray streak images shows that micro-pinches can generate >20% of the x-ray energy in some types of wire-array Z pinches.

Ivanov, V. V.; Papp, D.; Anderson, A. A.; Talbot, B. R.; Astanovitskiy, A. L.; Nalajala, V.; Dmitriev, O. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)] [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Chittenden, J. P.; Niasse, N. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)] [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Pikuz, S. A.; Shelkovenko, T. A. [P.N. Lebedev Physical Institute, Moscow 119991 (Russian Federation)] [P.N. Lebedev Physical Institute, Moscow 119991 (Russian Federation)

2013-11-15

144

Application of 2-D simulations to hollow z-pinch implosions  

SciTech Connect

The application of simulations of z-pinch implosions should have at least two goals: first, to properly model the most important physical processes occurring in the pinch allowing for a better understanding of the experiments and second, provide a design capability for future experiments. Beginning with experiments fielded at Los Alamos on the Pegasus 1 and Pegasus 2 capacitor banks, the authors have developed a methodology for simulating hollow z-pinches in two dimensions which has reproduced important features of the measured experimental current drive, spectrum, radiation pulse shape, peak power and total radiated energy. This methodology employs essentially one free parameter, the initial level of the random density perturbations imposed at the beginning of the 2-D simulation, but in general no adjustments to other parameters are required. Currently the authors are applying this capability to the analysis of recent Saturn and PBFA-Z experiments. The code results provide insight into the nature of the pinch plasma prior to arrival on-axis, during thermalization and development after peak pinch time. Among other things, the simulation results provide an explanation for the production of larger amounts of radiated energy than would be expected from a simple slug-model kinetic energy analysis and the appearance of multiple peaks in the radiation power. The 2-D modeling has also been applied to the analysis of Saturn dynamic hohlraum experiments and is being used in the design of this and other Z-Pinch applications on PBFA-Z.

Peterson, D.L.; Bowers, R.L.; Brownell, J.H. [and others

1997-12-01

145

Study of micro-pinches in wire-array Z pinches  

NASA Astrophysics Data System (ADS)

Bright and hot areas with a high plasma density and temperature are observed in all kinds of Z pinches. We studied bright radiating spots produced by micro-pinches in cylindrical and planar wire-arrays at the 1 MA Zebra pulsed power generator using an x-ray streak camera synchronized with laser diagnostics, x-ray time-gated pinhole camera, and spectroscopy. Hot spots with extremely dense and relatively hot plasma arise during the collapse of the micro-pinches. These hot spots radiate a continuum spectrum with energy >2.5 keV. Typical micro-pinches in Al wire arrays generate x-ray bursts with durations of 0.4-1 ns in the soft x-ray range and 0.1-0.4 ns in the keV range. UV two-frame shadowgraphy shows spatial correlation of hot spots with the collapse and explosion of micro-pinches. Micro-pinches typically occur at the necks of the Z pinch, but can demonstrate a variety of parameters and different dynamics. An analysis of x-ray streak images shows that micro-pinches can generate >20% of the x-ray energy in some types of wire-array Z pinches.

Ivanov, V. V.; Papp, D.; Anderson, A. A.; Talbot, B. R.; Astanovitskiy, A. L.; Nalajala, V.; Dmitriev, O.; Chittenden, J. P.; Niasse, N.; Pikuz, S. A.; Shelkovenko, T. A.

2013-11-01

146

Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches  

NASA Astrophysics Data System (ADS)

The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev , Phys. PlasmasPHPAEN1070-664X10.1063/1.2896577 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Velikovich, A. L.; Rudakov, L. I.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Williamson, K. M.; Stafford, A.; Shlyaptseva, V. V.

2011-10-01

147

Radiative signatures of Z-pinch plasmas at UNR: from X-pinches to wire arrays  

NASA Astrophysics Data System (ADS)

University-scale Z-pinch generators are able to produce High Energy Density (HED) plasmas in a broad range of plasma parameters under well-controlled and monitored experimental conditions suitable for radiation studies. The implosion of X-pinch and wire array loads at a 1 MA generator yields short (1-20 nsec) x-ray bursts from one or several bright plasma spots near the wire cross point (for X-pinches) or along and near Z-pinch axis (for wire arrays). Such X- and Z-pinch HED plasma with scales from a few m to several mm in size emits radiation in a broad range of energies from 10 eV to 0.5 MeV and is subject of our studies during the last ten years. In particular, the substantial number of experiments with very different wire loads was performed on the 1 MA Zebra generator and analyzed: X-pinch, cylindrical, nested, and various types of the novel load, Planar Wire Arrays (PWA). Also, the experiments at an enhanced current of 1.5-1.7 MA on Zebra using Load Current Multiplier (LCM) were performed. This paper highlights radiative signatures of X-pinches and Single and Double PWAs which are illustrated using the new results with combined wire loads from two different materials.

Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Safronova, U. I.; Shlyaptseva, V. V.; Shrestha, I.; Osborne, G. C.; Weller, M. E.; Stafford, A.; Lorance, M.; Chuvatin, A. S.

2014-08-01

148

Increasing the K-shell yield of line radiation in Z-pinch implosions using alloyed Al/Mg wire-arrays  

NASA Astrophysics Data System (ADS)

The variation of the K-shell yield of pure aluminum wire-array Z-pinch implosions with load parameters is discussed. The mechanism and the efficiency of increasing the K-shell yield using alloyed Al/Mg wire-arrays are numerically investigated. It has been shown that the maximum K-shell yield from a pure aluminum wire-array Z-pinch implosion can be obtained at an optimal load mass for a given generator and at a fixed initial wire-array radius. This optimal load mass is determined by the load energy coupling with the generator, the capability of Z-pinch plasmas to emit the K-shell radiation, and the self absorption of K-shell lines. For different generators, the optimal load mass increases as the drive current increases, and the line absorption limits the further increase of K-shell radiation. The coupled energy per ion is likely decreasing with increased mass, so the plasma might not be able to ionize into the K-shell. Also, the ability of the plasma to radiatively cool can increase with mass, thus, making it difficult for the plasma to ionize into and remain in the K-shell during the stagnation phase of the implosion. Alloyed Al/Mg wire-arrays were thus suggested to be used to decrease the opacity of K-shell lines and to increase the overall K-shell yield. In this paper, we show that using alloyed Al/Mg wire-arrays will decrease the opacity and increase the K-shell yield remarkably if the plasma is optically thick. We will also show that the efficiency of increasing the K-shell yield with alloyed Al/Mg wire-arrays cannot increase indefinitely. The ratio of K-shell yield from an alloyed Al/Mg wire-array to that from a pure aluminum wire-array reaches a limit. For example, we show that when the mass share of magnesium is 10% then this limit is 1.2, and for a 50% mass share, the limit is 1.3.

Delong, Xiao; Ning, Ding; Chuang, Xue; Jun, Huang; Yang, Zhang; Cheng, Ning; Shunkai, Sun

2013-01-01

149

Development of UV Laser Probing Diagnostics for the Investigation of DenseZ Pinch Plasmas  

NASA Astrophysics Data System (ADS)

UV, 266-nm wavelength, laser probing diagnostics were developed for the investigation of the dense plasma on the 1-MA pulsed power generator, Zebra, located at the University of Nevada, Reno. These new diagnostics complemented the 532-nm laser probing diagnostics, which were not highly applicable for a z-pinch with an electron density higher than 1019 cm -3, due to strong absorption and refraction of the beam as it passes through the plasma. The UV laser diagnostics, shadowgraphy and interferometry, have been successfully tested at the ablation, implosion, stagnation, and dissipation phases of wire-array z-pinches. Probing simultaneously with 266-nm and 532-nm light has shown that the UV laser probes deeper into the z-pinch plasma, with higher resolution. The UV laser probe enjoys a significant advantage over the 532-nm laser probe, because the inverse bremsstrahlung absorption increment and refraction in the plasma column is proportional to the wavelength squared. For interferometry, the phase shift of the laser beam is proportional to the wavelength. UV interferometry was employed to measure the plasma density profile up to an electron density of 12x1020 cm -3. A high resolution laser probing channel was developed for further study of the dense z-pinch plasma. Specially designed anode and cathode plates allowed installation of the objective lens inside of the vacuum chamber. A spatial resolution of 4 microns was achieved with UV. Instabilities in the dense plasma pinch were directly observed. The micro-structure of the dense pinch was unfolded for the first time. Micro-pinches, small-scale and mid-scale instabilities, large kink and sausage instabilities, and breaks in the plasma column were studied with UV high resolution shadowgraphy and interferometry. To investigate the dynamics of the dense plasma, a second, time-delayed, frame was developed for the UV laser diagnostics. Large velocities, greater than 100 km/s, were measured. These demonstrate the generation of kinetic energy in the stagnation phase of the z-pinch.

Altemara, Sara D.

150

Absorption coefficient of aluminum near the critical point and the consequences on high-power nanosecond laser ablation  

SciTech Connect

During nanosecond laser ablation, the absorption coefficient determines the laser energy deposition in the target, the accurate knowledge of which near the material critical point is crucial for understanding the fundamental physics of high-power nanosecond laser ablation. In this letter, the absorption coefficient of aluminum near the critical point is calculated through the Drude model based on the measured electrical conductivity data, and its effect on laser ablation is investigated numerically using a heat transfer model. The result supports the experimental observations that phase explosion occurs for the ablation of aluminum by sufficiently intense laser pulses, and the model predicted phase explosion threshold is consistent with experimental measurements.

Wu Benxin; Shin, Yung C. [Center for Laser-based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2006-09-11

151

The importance of EBIT data for Z-pinch plasma diagnostics  

SciTech Connect

The results from the last six years of x-ray spectroscopy and spectropolarimetry of high energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory (LLNL) are presented. The two topics discussed are the development of M-shell x-ray W spectroscopic diagnostics and K-shell Ti spectropolarimetry of Z-pinch plasmas. The main focus is on radiation from a specific load configuration called an 'X-pinch'. X-pinches are excellent sources for testing new spectral diagnostics and for atomic modelling because of the high density and temperature of the pinch plasmas, which scale from a few {micro}m to several mm in size. They offer a variety of load configurations, which differ in wire connections, number of wires, and wire materials. In this work the study of X-pinches with tungsten wires combined with wires from other, lower-Z materials is reported. Utilizing data produced with the LLNL EBIT at different energies of the electron beam the theoretical prediction of line positions and intensity of M-shell W spectra were tested and calibrated. Polarization-sensitive X-pinch experiments at the University of Nevada, Reno (UNR) provide experimental evidence for the existence of strong electron beams in Ti and Mo X-pinch plasmas and motivate the development of x-ray spectropolarimetry of Z-pinch plasmas. This diagnostic is based on the measurement of spectra recorded simultaneously by two spectrometers with different sensitivity to the linear polarization of the observed lines and compared with theoretical models of polarization-dependent spectra. Polarization-dependent K-shell spectra from Ti X-pinches are presented and compared with model calculations and with spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap.

Safronova, A S; Kantsyrev, V L; Neill, P; Safronova, U I; Fedin, D A; Ouart, N D; Yilmaz, M F; Osborne, G; Shrestha, I; Williamson, K; Hoppe, T; Harris, C; Beiersdorfer, P; Hansen, S

2007-04-04

152

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

SciTech Connect

This recently developed diagnostic was designed to allow for time-gated spectroscopic study of the EUV radiation (4 nm < {lambda} < 15 nm) present during harsh wire array z-pinch implosions. The spectrometer utilizes a 25 {mu}m 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 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.

Williamson, K. M.; Kantsyrev, V. L.; Safronova, A. S.; Wilcox, P. G.; Cline, W.; Batie, S.; LeGalloudec, B.; Nalajala, V.; Astanovitsky, A. [Plasma Physics and Diagnostics Laboratory, Physics Department, University of Nevada, Reno, Nevada 89557 (United States)

2011-09-15

153

Z-Pinch Generated X-Rays Demonstrate Indirect-Drive ICF Potential  

SciTech Connect

Hohlraums (measuring 6-mm in diameter by 7-mm in height) have been heated by x-rays from a z-pinch. Over measured x-ray input powers P of 0.7 to 13 TW, the hohlraum radiation temperature T increases from {approximately}55 to {approximately}130 eV, and is in agreement with the Planckian relation P-T{sup 4}. The results suggest that indirect-drive ICF studies involving NIF relevant pulse shapes and <2-mm diameter capsules can he studied using this arrangement.

Bowers, R.L.; Chandler, G.A.; Derzon, M.S.; Hebron, D.E.; Leeper, R.J.; Matzen, M.K.; Mock, R.C.; Nash, T.J.; Olson, R.E.; Peterson, D.L.; Ruggles, L.E.; Sanford, T.W.L.; Simpson, W.W.; Struve, K.W.; Vesey, R.A.

1999-06-16

154

Shock model description of the interaction radiation pulse in nested wire array z-pinches  

NASA Astrophysics Data System (ADS)

Bow shock structures are observed in a nested wire array z-pinch as ablation streams from the outer array pass the inner array. The jump in plasma conditions across these shocks results in an enhancement of snowplow emission from the imploding plasma piston. Results from a snowplow model modified to account for the shock jumps are discussed and compared to experimental data from MAGPIE. Magnetohydrodynamic simulations indicate that this is the primary heating mechanism responsible for the interaction pulse recorded on the Z generator, which is required for pulse shaping for inertial confinement fusion.

Ampleford, D. J.; Jennings, C. A.; Lebedev, S. V.; Bland, S. N.; Cuneo, M. E.; Sinars, D. B.; Bott, S. C.; Hall, G. N.; Suzuki-Vidal, F.; Palmer, J. B. A.; Chittenden, J. P.

2012-12-01

155

Structure of Stagnated Plasma in Aluminium Wire Array Z-pinches  

SciTech Connect

Experiments with aluminium wire array Z-pinches have been carried out on the MAGPIE generator (1MA, 240ns) at Imperial College London. It has been shown that in these arrays there are two intense sources of radiation during stagnation: line emission from a precursor-sized object and continuum radiation from bright-spots of significantly higher temperature randomly distributed around this object such as to produce a hollow emission profile. Spatially resolved spectra produced by spherically-bent crystals were recorded, both time-integrated and time-resolved, and were used to show that these two sources of radiation peak at the same time.

Hall, G.N.; Bland, S.N.; Lebedev, S.V.; Ampleford, D.J.; Palmer, J.B.A.; Bott, S.C.; Rapley, J.; Chittenden, J.P. [Blackett Laboratory, Imperial College, London, SW7 2BW (United Kingdom); Pikuz, S.A.; Shelkovenko, T.A. [Laboratory of plasma studies, Cornell University, Ithaca NY (United States)

2006-01-05

156

Radiation Energetics of ICF-Relevant Wire-Array Z Pinches  

NASA Astrophysics Data System (ADS)

Short-implosion-time 20-mm diameter, 300-wire tungsten arrays maintain high peak x-ray powers despite a reduction in peak current from 19 to 13 MA. The main radiation pulse on tests with a 1-mm on-axis rod may be explained by the observable j?B? work done during the implosion, but bare-axis tests require sub-mm convergence of the magnetic field not seen except perhaps in >1 keV emission. The data include the first measurement of the imploding mass density profile of a wire-array Z pinch that further constrains simulation models.

Sinars, D. B.; Lemke, R. W.; Cuneo, M. E.; Lebedev, S. V.; Waisman, E. M.; Stygar, W. A.; Jones, B.; Jones, M. C.; Yu, E. P.; Porter, J. L.; Wenger, D. F.

2008-04-01

157

Flow-through Z-pinch study for radiation generation and fusion energy production  

SciTech Connect

We discuss a high-density fusion reactor which utilizes a flow-through Z pinch magnetic confinement configuration. Assessment of this reactor system is motivated by simplicity and small unit size (few hundred MWe) and immunity to plasma contamination made possible at high density. The type reactor discussed here would employ a liquid Li vortex as the first wall/blanket to capture fusion neutrons with minimum induced radioactivity and to achieve high wall loading and a power density of 200 w/cm{sup 3}.

Hartman, C.W.; Eddleman, J.L.; Moir, R. [Lawrence Livermore National Lab., CA (United States); Shumlak, U. [Phillips Lab., Kirtland AFB, NM (United States)

1994-06-20

158

Modeling nonlinear Rayleigh-Tayor instabilities in fast z-pinches  

SciTech Connect

A simplified analytic model is presented to describe the implosion of a plasma column by an azimuthal magnetic field of sufficient magnitude to drive a strong shock wave into the plasma. This model is employed together with turbulent multimode Rayleigh-Taylor growth to investigate the mixing process in such fast z-pinches. These models give predictions that characterize limitations the instability can impose on the implosion in terms of maximum convergence ratios attainable for an axially coherent pinch. Both the implosion and instability models are validated with results from high-resolution numerical simulations.

Miles, A R

2008-09-16

159

Steady-state radiation ablation in the wire-array Z pinch  

SciTech Connect

The mass ablation phase of a wire-array Z pinch is investigated using steady-state (r,{theta}) simulations. By identifying the dominant physical mechanisms governing the ablation process, a simple scaling relation is derived for the mass ablation rate m with drive current I, in the case where radiation is the primary energy transport mechanism to the wire core. In order to investigate the dependence of m on wire core size, a simplified analytical model is developed involving a wire core placed in a heat bath and ablating due to radiation. Results of the model, simulation, and experiment are compared.

Yu, Edmund P.; Oliver, B. V.; Sinars, D. B.; Mehlhorn, T. A.; Cuneo, M. E.; Sasorov, P. V.; Haines, M. G.; Lebedev, S. V. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1193 (United States); Institute of Theoretical and Experimental Physics, Moscow 117218, Russia (Russian Federation); Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom)

2007-02-15

160

On the possibility of neutron generation in an imploding TiD{sub 2} puff Z pinch  

SciTech Connect

Simulation of implosion of a TiD{sub 2} puff Z pinch is reported. The Z pinch is supposed to be produced by the plasma flow generated by a vacuum arc, as described by Rousskikh et al.[Phys. Plasmas 18, 092707 (2011)]. To simulate the implosion, a one-dimensional two-temperature radiative magnetohydrodynamics code was used. The simulation has shown that neutrons are generated during the implosion of a TiD{sub 2} puff Z pinch due to thermalization of the pinch plasma stagnated on axis. It has been shown that the necessary condition for neutron generation is that the ion temperature must be substantially higher than the electron temperature. For a pinch current of 1 MA, the predicted yield of 'thermal' neutrons is 2.5 10{sup 9} neutrons/shot.

Baksht, Rina B. [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation) [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation); Tel-Aviv University, Tel Aviv (Israel); Oreshkin, Vladimir I. [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation) [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation); Tomsk Polytechnic University, Tomsk (Russian Federation); Rousskikh, Alexander G. [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation)] [Institutes of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation)

2013-08-15

161

PBFA II-Z: A 20-MA driver for z-pinch experiments  

SciTech Connect

Sandia is modifying the PBFA II accelerator into a dual use facility. While maintaining the present ion-beam capability, we are developing a long-pulse, high-current operating mode for magnetically-driven implosions. This option, called PBFA II-Z, will require new water transmission lines, a new insulator stack, and new magnetically-insulated transmission lines (MITLs). Each of the existing 36, coaxial water pulse-forming sections will couple to a 4.5-{Omega}, bi-plate water-transmission line. The water transmission lines then feed a four-level insulator stack. The insulators are expected to operate at a maximum, spatially-averaged electric field of {approximately}l00 kV/cm. The MITL design is based on the successful biconic Saturn design. The four ``disk`` feeds will each have a vacuum impedance of {approximately}2.0 {Omega}. The disk feeds are added in parallel using a double post-hole convolute at a diameter of 15 cm. We predict that the accelerator will deliver 20 MA to a 15-mg z-pinch load in 100 ns, making PBFA II-Z the most powerful z-pinch driver in the world providing a pulsed power and load physics scaling testbed for future 40-80-MA drivers.

NONE

1995-12-01

162

An alternative scaling model for neutron production in Z-pinch devices  

SciTech Connect

The DD neutron yield (Y{sub n}) from z-pinches, either dense plasma foci or fast radial pinches, has been fitted for decades to the scaling model Y{sub n} {approx} {alpha}(I{sub max}){sup {delta}}, where {alpha} is a numerical scaling coefficient, I{sub max} the peak current, and 3 < {delta} < 5. The data from 12 000 pulses analyzed from eight different z-pinches presented in this paper show that Y{sub n} varies by as much as {+-}15 000% about the best fit value of the conventional scaling model with {delta} = 4. A revised scaling model derived from the reaction rate equation and a circuit model that includes the time derivative of the current dI/dt (normalized to its initial value) reduces the scatter in data from {+-}15 000% to {+-}100%. For the special case of very high normalized dI/dt, the standard deviation between the revised scaling prediction and the measured neutron yields is reduced to just {+-}30%. Implications of this revised scaling for higher current pinches are discussed.

Bures, Brian L.; Krishnan, Mahadevan [Alameda Applied Sciences Corporation, 3077 Teagarden St., San Leandro, California 94577 (United States)

2012-11-15

163

Modeling of Radiative Properties of the Wire Array Z-Pinches  

NASA Astrophysics Data System (ADS)

Recent experiments show that the wire-array z-pinch plasmas are strongly inhomogeneous at small scales. The inhomogeneities are not shot-to-shot reproducible while the arrays provide extremely reproducible x-ray pulses and generate mega-joules of radiation at implosion. This is possible if small-scale structures are averaged in the implosion dynamics and if the energy balance and radiation production are mainly determined by the macroscopic, space-averaged plasma properties. We suggest that the basic physics of radiating wire array implosions could be modeled within a quasi-1D large-scale description. We show that such a quasi-1D hydro model reproduces basic radiative properties of the wire-array z-pinches if the Spitzer resistivity is enhanced by a factor, proportional to ?2, where ? = ?e?e is the Hall parameter. It becomes possible to explain the radiation pulse shapes and high experimental efficiency of magnetic energy conversion into radiation in the most powerful laboratory x-ray sources. Our results also reproduce some recently discovered properties of these x-ray sources, such as trailing mass during the implosion and radiation beginning before arrival of the entire imploding mass onto the axis.

Chuvatin, A. S.; Rudakov, L. I.; Velikovich, A. L.

2006-01-01

164

Modeling of Radiative Properties of the Wire Array Z-Pinches  

SciTech Connect

Recent experiments show that the wire-array z-pinch plasmas are strongly inhomogeneous at small scales. The inhomogeneities are not shot-to-shot reproducible while the arrays provide extremely reproducible x-ray pulses and generate mega-joules of radiation at implosion. This is possible if small-scale structures are averaged in the implosion dynamics and if the energy balance and radiation production are mainly determined by the macroscopic, space-averaged plasma properties. We suggest that the basic physics of radiating wire array implosions could be modeled within a quasi-1D large-scale description. We show that such a quasi-1D hydro model reproduces basic radiative properties of the wire-array z-pinches if the Spitzer resistivity is enhanced by a factor, proportional to {beta}2, where {beta} {omega}e{tau}e is the Hall parameter. It becomes possible to explain the radiation pulse shapes and high experimental efficiency of magnetic energy conversion into radiation in the most powerful laboratory x-ray sources. Our results also reproduce some recently discovered properties of these x-ray sources, such as trailing mass during the implosion and radiation beginning before arrival of the entire imploding mass onto the axis.

Chuvatin, A.S. [Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, 91128 Palaiseau (France); Rudakov, L.I. [Icarus Research, Inc., P.O. Box 30780, Bethesda, MD 20824-0780 (United States); Velikovich, A.L. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2006-01-05

165

Development of a Non-LTE model for Z-pinch simulations  

NASA Astrophysics Data System (ADS)

Predicting the energetic and spectral characteristics of Z-pinch sources is a delicate task. It requires solving the Atomic Physics equations for plasmas in a wide range of conditions. In addition, the increasing optical depth of the plasma at stagnation can have a strong influence on its own dynamics, suggesting that simultaneous solution of both the magneto-hydrodynamic and radiative response is required. This constraint places a special emphasis on code optimization. We introduce a simple atomic model that can be run inline with the three dimensional resistive Eulerian MHD code GORGON developed at Imperial College. Based on a Screened-Hydrogenic Model (SHM) with nl splitting and making use of an inexpensive modification of the SAHA equation, this code has demonstrated a good ability to mimic Non-LTE plasma conditions. Preliminary results obtained with the standalone version of the model have shown good agreement with commercial packages (PrismSpect). Comparisons of predictions produced by the inline version with data from High Energy Density Plasma Physics (HEDP) experiments at Imperial College, Sandia National Laboratory and Centre d'tudes de Gramat are presented. Synthetic Z-pinch XUV images and time dependant spectra are produced.

Niasse, Nicolas; Chittenden, Jeremy

2010-11-01

166

Analysis of spatially resolved Z-pinch spectra to investigate the nature of ``bright spots''  

NASA Astrophysics Data System (ADS)

Localized, intensely radiating regions are often observed in Z pinches. High resolution images of such areas have been recorded at least as far back as the 1970s. However, there is as yet no widely accepted consensus on the nature of these "bright spots" or how they are formed. This phenomenon has also been referred to "hot spots" or "micropinches." To shed further light on this issue, we have analyzed axially resolved K-shell spectra from 4 Z pinches driven by the refurbished Z generator ("ZR") at Sandia National Laboratories, and the previous version of the Z machine ("Z"). The atomic numbers of the loads varied from 13 to 29. We find that higher spatial K-shell intensity in the Al pinch correlates with density. The K-shell intensity within a copper shot taken on ZR correlates strongly with increased electron temperature, but another, somewhat less well-diagnosed copper shot from Z shows correlation with density. The bright spots in a Ti pinch correlate with neither density nor temperature, but do correlate with the product of density and diameter (proportional to opacity). This opacity correlation is also observed in the other 3 pinches.

Apruzese, J. P.; Giuliani, J. L.; Thornhill, J. W.; Coverdale, C. A.; Jones, B.; Ampleford, D. J.

2013-02-01

167

Ion Beam Driven Shock Device Using Accelerated High Density Plasmoid by Phased Z-Pinch  

NASA Astrophysics Data System (ADS)

Different from three methods to generate high shock pressure by acceleration of high density plasma or particles (intense ion beams, plasma gun and rail gun) having their intrinsic deficiencies, new frontier is proposed to propel the shock physics and chemistry by using the high density plasma. In the present paper, new scheduled Z-pinch method is developed as a new device to generate high shock pressure. In the present method, plasma density can be compressed to the order of 10^18 to 10^19 cm-3, and high density plasma can be accelerated by zippering together with axial shock pressure, resulting in high-velocity launching of flyer. In the present paper, systematic experimental works are performed to demonstrate that high energy plasma flow can be electro-magnetically driven by the scheduled capillary Z-pinch, and to characterize the ion velocity and its current density. The estimated value of ion speed from the plasma-measurement reaches to 7 x 10^7 cm/s corresponding to 70 to 100 KeV for Ar. Copper flyer can be shot with the velocity range from 1km/s to 3km/s in the standard condition.

Horioka, Kazuhiko; Aizawa, Tatsuhiko; Tsuchida, Minoru

1997-07-01

168

Calibrated areal density measurements of cable-array Z-pinch plasmas at 1 MA  

NASA Astrophysics Data System (ADS)

We present areal density measurements of multi-wire cable-array Z-pinch plasmas obtained using X-pinch x-ray backlighter radiographs. The elements of a cable array are made by twisting 2 - 4 wires into a cable with a twist wavelength ranging from 0.5mm to 4mm. In experiments on the 1 MA COBRA pulsed power generator, the radiographs of the cables displayed density structure not observed in standard wire-array z-pinches, including sharp density gradients in the form of spirals that follow the twisting wires and small scale striations that are the result of an undetermined mechanism. The X-ray radiographs were produced using the 3-5 keV spectral band of Mo X-pinches, which was obtained using 12.5 micron Ti filters. Ag, Ni, Cu and W cable-arrays have been tested, and film exposure was converted to plasma areal density using calibrated step wedges of the test material that were deposited on the Ti filter. X-pinch timing was monitored with 12.5 micron Ti filtered silicon diodes. Laser shadowgraphy and XUV self-emission diagnostics were also employed. This research is supported by the NNSA SSAA program under DOE Cooperative Agreement DE-FC03-02NA00057.

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

2010-11-01

169

Analysis of spatially resolved Z-pinch spectra to investigate the nature of 'bright spots'  

SciTech Connect

Localized, intensely radiating regions are often observed in Z pinches. High resolution images of such areas have been recorded at least as far back as the 1970s. However, there is as yet no widely accepted consensus on the nature of these 'bright spots' or how they are formed. This phenomenon has also been referred to 'hot spots' or 'micropinches.' To shed further light on this issue, we have analyzed axially resolved K-shell spectra from 4 Z pinches driven by the refurbished Z generator ('ZR') at Sandia National Laboratories, and the previous version of the Z machine ('Z'). The atomic numbers of the loads varied from 13 to 29. We find that higher spatial K-shell intensity in the Al pinch correlates with density. The K-shell intensity within a copper shot taken on ZR correlates strongly with increased electron temperature, but another, somewhat less well-diagnosed copper shot from Z shows correlation with density. The bright spots in a Ti pinch correlate with neither density nor temperature, but do correlate with the product of density and diameter (proportional to opacity). This opacity correlation is also observed in the other 3 pinches.

Apruzese, J. P.; Giuliani, J. L.; Thornhill, J. W. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Coverdale, C. A.; Jones, B.; Ampleford, D. J. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-02-15

170

Design of the PST: A Diagnostic for 1-D Imaging of Fast Z-Pinch Power Emissions  

SciTech Connect

Fast Z-pinch technology developed on the Z machine at Sandia National Laboratories can produce up to 230 TW of thermal x-ray power for applications in inertial confinement fusion (ICF) and weapons physics experiments. During implosion, these Z-pinches develop Rayleigh-Taylor (R-T) instabilities which are very difficult to diagnose and which functionally diminish the overall pinch quality. The Power-Space-Time (PST) instrument is a newly configured diagnostic for measuring the pinch power as a function of both space and time in a Z-pinch. Placing the diagnostic at 90 degrees from the Z-pinch axis, the PST provides a new capability in collecting experimental data on R-T characteristics for making meaningful comparisons to magneto-hydrodynamic computer models. This paper is a summary of the PST diagnostic design. By slit-imaging the Z-pinch x-ray emissions onto a linear scintillator/fiber-optic array coupled to a streak camera system, the PST can achieve {approximately}100 {micro}m spatial resolution and {approximately}1.3 ns time resolution. Calculations indicate that a 20 {micro}m thick scintillating detection element filtered by 1,000 {angstrom} of Al is theoretically linear in response to Plankian x-ray distributions corresponding to plasma temperatures from 40 eV to 150 eV, By calibrating this detection element to x-ray energies up to 5,000 eV, the PST can provide pinch power as a function of height and time in a Z-pinch for temperatures ranging from {approximately}40 eV to {approximately}400 eV. With these system pm-meters, the PST can provide data for an experimental determination of the R-T mode number, amplitude, and growth rate during the late-time pinch implosion.

ROCHAU,GREGORY A.; DERZON,MARK S.; CHANDLER,GORDON A.; LAZIER,STEVEN EARL

2000-08-03

171

Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator  

SciTech Connect

Experimental results are presented that characterize the implosion dynamics and radiation output of wire-array Z pinches on the 1-MA, 100-ns rise-time Cornell Beam Research Accelerator (COBRA) [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)]. The load geometries investigated include 20-mm-tall cylindrical arrays ranging from 4 to 16 mm in diameter, and consisting of 8, 16, or 32 wires of either tungsten, aluminum, or Invar (64% iron, 36% nickel). Diagnostics fielded include an optical streak camera, a time-gated extreme-ultraviolet framing camera, a laser shadowgraph system, time-integrated pinhole cameras, an x-ray wide-band focusing spectrograph with spatial resolution, an x-ray streak camera, a load voltage monitor, a Faraday cup, a bolometer, silicon diodes, and diamond photoconducting detectors. The data produced by the entire suite of diagnostics are analyzed and presented to provide a detailed picture of the overall implosion process and resulting radiation output on COBRA. The highest x-ray peak powers (300-500 GW) and total energy yields (6-10 kJ) were obtained using 4-mm-diameter arrays that stagnated before peak current. Additional findings include a decrease in soft x-ray radiation prior to stagnation as the initial wire spacing was changed from 1.6 mm to 785 {mu}m, and a timing correlation between the onset of energetic electrons, hard x-ray generation, and the arrival of trailing current on axis - a correlation that is likely due to the formation of micropinches. The details of these and other findings are presented and discussed.

McBride, R. D.; Shelkovenko, T. A.; Pikuz, S. A.; Hammer, D. A.; Greenly, J. B.; Kusse, B. R.; Douglass, J. D.; Knapp, P. F.; Bell, K. S.; Blesener, I. C.; Chalenski, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2009-01-15

172

Characterization of plasma expansion dynamics in a high power diode with a carbon-fiber-aluminum cathode  

NASA Astrophysics Data System (ADS)

Thermal plasma expansion is characterised during the operation of a high power diode with an explosive emission carbon-fiber-aluminum cathode driven by a 250 kV, 150 ns accelerating pulse. It is found that a quasi-stationary state of plasma expansion is obtained during the main part of the accelerating pulse and the whole plasma expansion exhibits an "U"-shape velocity evolution. A theoretical model describing the dynamics of plasma expansion is developed, which indicates that the plasma expansion velocity is determined by equilibrium between the diode current density and plasma thermal electron current density.

Ju, J.-C.; Liu, L.; Cai, D.

2014-06-01

173

Theoretical and Experimental Studies of Radiation from Z-Pinch Complex Wire Arrays and Applications  

NASA Astrophysics Data System (ADS)

In the research area of high energy density plasmas an ever increasing goal is searching for higher efficient radiators, particularly in z-pinch plasmas, and their applications. This goal is a major focus of this dissertation and implements both theoretical and experimental tools in the process. The theoretical tools involve the Wire Ablation Dynamics Model (WADM) to infer z-pinch implosion characteristics and various non-local thermodynamic equilibrium (LTE) kinetic models to understand the radiative properties of plasmas, including a new model for L-shell Ag. The experimental tools includes an advanced set of diagnostics, in particular a newly developed time-gated hard x-ray spectrometer to gain an understanding as to how these plasmas radiate in time, particularly in the 0.7 - 4.4 A range. The experiments predominately took place on the 1.7 MA Zebra generator at the Nevada Terawatt Facility (NTF) at the University of Nevada, Reno (UNR). Traditional nested cylindrical wire arrays with mixed materials (brass and Al, Mo and Al) were tested to understand how the inner and outer arrays implode and radiate. Novel planar wire arrays, which have been shown to be very powerful radiation sources, arranged in single, double, and triple wire array configurations were tested with Mo and Ag materials, which have both been shown to be powerful radiators, and also mixed with Al to understand opacity effects and how a mixture of two different plasmas radiate. Radiation from the extreme ultraviolet (EUV) range has also been of recent interest due the substantial contribution into total radiation yields. Therefore EUV radiation of M-shell Cu was modeled and benchmarked with spheromak and laser-produced plasma data. Lastly, lasing gain from L-shell Ag is calculated as an application of the aforementioned model to evaluate whether lasing might be occurring in wire array z-pinches. In connection to creating a uniform plasma column to measure lasing lines, the split double planar wire array is introduced and preliminary results discussed.

Weller, Michael Eugene

174

Linear analysis and 3D hybrid simulation study of z-pinch instabilities in the presence of nonideal MHD effects  

Microsoft Academic Search

The development of z-pinch instabilities in the presence of the Hall term, finite Larmor radius effects (FLR), and axial magnetic field is being investigated. The linear stage of instability development is studied with linearized magnetohydrodynamic (MHD) equations based on the Hall fluid model. Results for linear growth rates as a function of axial sheared flow, axial magnetic field, and the

V. I. Sotnikov; L. Wanes; B. S. Bauer; I. Paraschiv; J. N. Leboeuf; P. Hellinger; P. Travnicek; V. Fiala

2003-01-01

175

Influence of Non-Ideal MHD Effects on the Development of Instabilities in Z-pinch Plasmas  

Microsoft Academic Search

The development of z-pinch instabilities in the presence of the Hall term, finite Larmor radius effects (FLR), and axial magnetic field is being investigated via 3D hybrid (particle ions, fluid electrons) simulations. The hybrid simulations serve the dual purpose of comparing with linear Hall MHD theory and of investigating the nonlinear stage of instability. Simulations have been carried out in

Vladimir Sotnikov; Bruno Bauer; Jean-Noel Leboeuf; Petr Hellinger; Pavel Travnicek; Vladimir Fiala

2002-01-01

176

2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches  

SciTech Connect

Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.

Hammer, J.H.; Eddleman, J.L.; Springer, P.T. [and others

1995-11-06

177

Role of Z-pinches in magnetic reconnection in space plasmas  

NASA Astrophysics Data System (ADS)

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 initially, and Z-pinches are formed during the simulation. The X-points are relatively stable, and no substantial energy dissipation is associated with them. On the contrary, turbulent magnetic reconnection driven by kinking of the pinches causes the magnetic energy to decay at a rate of 1.5% 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.

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

2014-06-01

178

Investigation of a 5 kJ conical Z-pinch discharge  

NASA Astrophysics Data System (ADS)

A conical 5 kJ Z-pinch experiment with 35 ?s discharge time was constructed and operated. Preliminary results showed that the total circuit parameters are 287 nH inductance and 13 m? total resistance. The cone plasma inductance has its maximum value at the pinch. It has been determined that the pinching time is inversely proportional to the deposited energy. Moreover, a calculated delay time of about 2.1 ?s is required for the pinch to occur and the calculated sheath velocity ranges between 1 and 11.5 cm/ ?s. Erosion of the pin electrode could potentially explain the difference between the mass of helium gas inside the cone and the calculated swept mass. The main product of the ionization process is a singly-ionized helium atom.

Abdel-kader, Mohamed E.; Abd Al-Halim, Mohamed A.; Shagar, Azza M.; Saudy, Ali H.

2014-06-01

179

Dense Plasma Focus Z-pinches for High Gradient Particle Acceleration  

SciTech Connect

The final Z-pinch stage of a Dense Plasma Focus (DPF) could be used as a simple, compact, and potentially rugged plasma-based high-gradient accelerator with fields at the 100 MV/m level. In this paper we review previously published experimental beam data that indicate the feasibility of such an DPF-based accelerator, qualitatively discuss the physical acceleration processes in terms of the induced voltages, and as a starting point examine the DPF acceleration potential by numerically applying a self-consistent DPF system model that includes the induced voltage from both macroscopic and instability driven plasma dynamics. Applications to the remote detection of high explosives and a multi-staged acceleration concept are briefly discussed.

Tang, V; Adams, M L; Rusnak, B

2009-07-24

180

3D MHD Simulations of Radial Wire Array Z-pinches  

NASA Astrophysics Data System (ADS)

Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 ?s) 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.

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

181

Design of Z-Pinch and Dense Plasma Focus Powered Vehicles  

NASA Technical Reports Server (NTRS)

Z-pinch and Dense Plasma Focus (DPF) are two promising techniques for bringing fusion power to the field of in-space propulsion. A design team comprising of engineers and scientists from UAHuntsville, NASA's George C. Marshall Space Flight Center and the University of Wisconsin developed concept vehicles for a crewed round trip mission to Mars and an interstellar precursor mission. Outlined in this paper are vehicle concepts, complete with conceptual analysis of the mission profile, operations, structural and thermal analysis and power/avionics design. Additionally engineering design of the thruster itself is included. The design efforts adds greatly to the fidelity of estimates for power density (alpha) and overall performance for these thruster concepts

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

2011-01-01

182

X-ray spectroscopy of Cu impurities on NSTX and comparison with Z-pinch plasmas  

SciTech Connect

X-ray spectroscopy of mid-Z metal impurities is important in the study of tokamak plasmas and may reveal potential problems if their contribution to the radiated power becomes substantial. The analysis of the data from a high-resolution x-ray and extreme ultraviolet grating spectrometer, XEUS, installed on NSTX, was performed focused on a detailed study of x-ray spectra in the range 7-18 A. These spectra include not only commonly seen iron spectra but also copper spectra not yet employed as an NSTX plasma impurity diagnostic. In particular, the L-shell Cu spectra were modeled and predictions were made for identifying contributions from various Cu ions in different spectral bands. Also, similar spectra, but from much denser Cu plasmas produced on the UNR Z-pinch facility and collected using the convex-crystal spectrometer, were analyzed and compared with NSTX results.

Safronova, A. S.; Ouart, N. D.; Kantsyrev, V. L.; Cox, P. G.; Shlyaptseva, V.; Williamson, K. M. [University of Nevada, Reno, Nevada 89557 (United States); Lepson, J. K. [Space Sciences Laboratory, Berkeley, California 94720 (United States); Beiersdorfer, P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Stratton, B.; Bitter, M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2010-10-15

183

Dynamics of quasi-spherical Z-pinch implosions with mass redistribution and displacement modification  

NASA Astrophysics Data System (ADS)

Implosions of (quasi-)spherical loads with mass redistribution and displacement modification are investigated numerically. Both methods can theoretically counterbalance the nonuniformity of magnetic pressure along the load surface and realize quasi-spherical Z-pinch implosions. Mass redistribution is feasible for spherical loads with large radius and weight, while the displacement modification is more suitable for light loads, such as those composed of wire arrays. Simulation results suggest that, for mass redistributed spherical loads, wall instabilities induced by polar mass flows will deform the imploding shell. For prolate spherical loads, in which the wall instability cannot develop, the kinetic energy distribution is disturbed at high latitude. These passive behaviors and their possible mitigation methods, such as reshaping the electrode, are investigated numerically in this paper.

Zhang, Yang; Ding, Ning; Li, Zheng-Hong; Sun, Shun-Kai; Xue, Chuang; Ning, Cheng; Xiao, De-Long; Huang, Jun

2012-12-01

184

Plasma density measurements in tungsten wire-array Z-pinches  

SciTech Connect

Measurements of the plasma density profile near the exploding wires in 1 MA tungsten (W) wire-array Z-pinches have been made using calibrated x-ray absorption. As many as 5 x-ray images per pulse were obtained between 65 and 160 ns after the start of the 100 ns rise time current pulse. Measured W ion densities range from above 10{sup 19}/cm{sup 3} close to the wire to {approx}10{sup 17}/cm{sup 3} about 1 mm away from the wire in the plasma stream. After accurate geometrical registration of the individual wires in each successive image in a pulse using the Genetic Algorithm, the temporal evolution of the axial modulation wavelength distribution of the ablation rate from the wires in each array and the global mass-ablation rate as a function of time are presented.

Douglass, J. D.; Hammer, D. A.; Pikuz, S. A.; Shelkovenko, T. A.; Blesener, K. S. [Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States)

2012-07-15

185

Plasma density measurements in tungsten wire-array Z-pinches  

NASA Astrophysics Data System (ADS)

Measurements of the plasma density profile near the exploding wires in 1 MA tungsten (W) wire-array Z-pinches have been made using calibrated x-ray absorption. As many as 5 x-ray images per pulse were obtained between 65 and 160 ns after the start of the 100 ns rise time current pulse. Measured W ion densities range from above 1019/cm3 close to the wire to 1017/cm3 about 1 mm away from the wire in the plasma stream. After accurate geometrical registration of the individual wires in each successive image in a pulse using the Genetic Algorithm, the temporal evolution of the axial modulation wavelength distribution of the ablation rate from the wires in each array and the global mass-ablation rate as a function of time are presented.

Douglass, J. D.; Hammer, D. A.; Pikuz, S. A.; Shelkovenko, T. A.; Blesener, K. S.

2012-07-01

186

3D MHD Simulations of Radial Wire Array Z-pinches  

SciTech Connect

Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 {mu}s) 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.

Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V. [Blackett Laboratory, Imperial College, London, SW7 2BW (United Kingdom); Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P. [Centre d'Etudes de Gramat, Gramat (France)

2009-01-21

187

Exact self-similar solutions for the magnetized Noh Z pinch problem  

SciTech Connect

A self-similar solution is derived for a radially imploding cylindrical plasma with an embedded, azimuthal magnetic field. The plasma stagnates through a strong, outward propagating shock wave of constant velocity. This analysis is an extension of the classic Noh gasdynamics problem to its ideal magnetohydrodynamics (MHD) counterpart. The present exact solution is especially suitable as a test for MHD codes designed to simulate linear Z pinches. To demonstrate the application of the new solution to code verification, simulation results from the cylindrical R-Z version of Mach2 and the 3D Cartesian code Athena are compared against the analytic solution. Alternative routines from the default ones in Athena lead to significant improvement of the results, thereby demonstrating the utility of the self-similar solution for verification.

Velikovich, A. L.; Giuliani, J. L.; Thornhill, J. W. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Zalesak, S. T. [Berkeley Research Associates, Beltsville, Maryland 20705 (United States); Gardiner, T. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2012-01-15

188

Theoretical Investigation of Radiation Characteristics of Silver Z-pinch Arrays with Applications  

NASA Astrophysics Data System (ADS)

Experiments of Ag planar wire array z-pinches have been carried out on the 1.7 MA Zebra generator at UNR and produced L-shell plasmas with electron temperatures exceeding 1.8 keV and total radiated energy upwards of 30 kJ, which is of interest for radiation physics studies. Recently, an important question about such Ag plasmas is whether lasing occurs in the Na-like and Ne-like soft x-ray range, and if so, at what gains was considered. To this end, level populations were used from modified SCRAM to calculate theoretical lasing gains for Ne-like Ag. In addition, HELIOS-CR from PRISM was utilized for 1D MHD calculations for simple cylindrical Ag configurations. The importance of the study of Ag planar wire arrays is discussed.

Weller, M. E.; Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Shrestha, I.; Osborne, G. C.; Shlyaptseva, V. V.; Keim, S. F.; Stafford, A.; Petkov, E. E.; Chuvatin, A. S.; Apruzese, J. P.; Golovkin, I. E.; Macfarlane, J. J.

2012-10-01

189

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

SciTech Connect

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.

Gilgenbach, R. M.; Gomez, M. R.; Zier, J. C.; Tang, W. W.; French, D. M.; Lau, Y. Y. [Plasma, Pulsed Power and Microwave Lab, University of Michigan, Ann Arbor, MI 48109-2104 (United States); Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Oliver, B. V.; Mehlhorn, T. A. [Sandia National Laboratories, Albuquerque, NM (United States); Kim, A. A.; Sinebryukhov, V. A. [Institute of High Current Electronics Tomsk (Russian Federation)

2009-01-21

190

Experimental r-? density profiles of wire-array and cylindrical foil Z-pinches on COBRA  

NASA Astrophysics Data System (ADS)

Calibrated r-? ion density profiles from wire-array and cylindrical foil experiments on the 1-MA COBRA machine will be presented. Profiles are axially averaged over the 1-cm height of the array. The data was gathered using an axial X pinch backlighter.ootnotetextI.C. Blesener et al., ``Axial x-ray backlighting of wire-array Z-pinches using X pinches'', Rev. Sci. Instrum. 80, 123505 (2009). Images have better than 5-micron resolution with calibrated ion densities from 10^18 to 10^20 cm-3. The latest data will be presented, comparing the timing and development of ablation streams and precursor formation between wire-arrays and cylindrical foils. Experimental data will also be compared to simulation results.

Blesener, Isaac; Greenly, John; Pikuz, Sergey; Shelkovenko, Tatiana; Kusse, Bruce; Seyler, Charles

2010-11-01

191

A compact soft X-ray microscope using an electrode-less Z-pinch source  

NASA Astrophysics Data System (ADS)

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. (Supported by NIH grants 5R44RR022488-03 and 5R44RR023753-03)

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

2009-09-01

192

Magnetohydrodynamic simulation of solid-deuterium-initiated Z-pinch experiments  

SciTech Connect

Solid-deuterium-initiated Z-pinch experiments are numerically simulated using a two-dimensional resistive magnetohydrodynamic model, which includes many important experimental details, such as ``cold-start`` initial conditions, thermal conduction, radiative energy loss, actual discharge current vs. time, and grids of sufficient size and resolution to allow realistic development of the plasma. The alternating-direction-implicit numerical technique used meets the substantial demands presented by such a computational task. Simulations of fiber-initiated experiments show that when the fiber becomes fully ionized rapidly developing m=0 instabilities, which originated in the coronal plasma generated from the ablating fiber, drive intense non-uniform heating and rapid expansion of the plasma column. The possibility that inclusion of additional physical effects would improve stability is explored. Finite-Larmor-radius-ordered Hall and diamagnetic pressure terms in the magnetic field evolution equation, corresponding energy equation terms, and separate ion and electron energy equations are included; these do not change the basic results. Model diagnostics, such as shadowgrams and interferograms, generated from simulation results, are in good agreement with experiment. Two alternative experimental approaches are explored: high-current magnetic implosion of hollow cylindrical deuterium shells, and ``plasma-on-wire`` (POW) implosion of low-density plasma onto a central deuterium fiber. By minimizing instability problems, these techniques may allow attainment of higher temperatures and densities than possible with bare fiber-initiated Z-pinches. Conditions for significant D-D or D-T fusion neutron production may be realizable with these implosion-based approaches.

Sheehey, P.T.

1994-02-01

193

High-power electron beam deposition studies on aluminum and graphite  

Microsoft Academic Search

The deposition phenomena produced by a 25-135-MW electron beam have been studied experimentally on aluminum and graphite targets. Large concentrations of multicharged ions of Al and C were produced. The parameters which were obtained quantitatively included momentum transferred to the target by the blow-off material, total mass loss, species velocities, radiation losses, and enthalpy rise in the target materials. From

Milton Farber; James E. Robin; R. D. Srivastava

1972-01-01

194

Properties of the Best Ar K-Shell Radiators: Two Decades of Data Analysis from Seven Z-Pinch Drivers  

SciTech Connect

Z Pinches formed from Ar gas puffs have been investigated for more than two decades. Experiments have been performed on many generators; a frequent objective has been maximization of the yield in the K-shell lines. The increase in available current during that time, from 2 to 15 MA, has resulted in a remarkable enhancement in yield from a few kJ on PITHON to {approx}300 kJ on Sandia's Z generator. We have analyzed spectroscopic and other radiation data from seven Z-pinch drivers, some dating back to 1991, in an effort to determine what properties of the pinches correlate with high K-shell yield. The strongest correlation is with the amount of mass that is heated to K-shell emitting temperatures. Those temperatures, effective at emitting Ar K-shell x rays, exhibit a range of {approx}1 to 2.4 keV.

Apruzese, J. P.; Commisso, R. J.; Weber, B. V.; Thornhill, J. W.; Giuliani, J. L. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Mosher, D.; Young, F. C. [L-3 Communications/Titan Group, Reston VA 20190 (United States); Levine, J. S.; Failor, B. H.; Sze, H.; Qi, N.; Banister, J. W. [L-3 Communications/Pulse Sciences, San Leandro CA 94577 (United States); Coleman, P. L. [Alameda Applied Sciences Corporation, San Leandro CA 94577 (United States); Coverdale, C. A.; Deeney, C. [Sandia National Laboratories, Albuquerque NM 87545 (United States)

2009-01-21

195

Structure of the dense cores and ablation plasmas in the initiation phase of tungsten wire-array Z pinches  

Microsoft Academic Search

The early stages of tungsten (W) wire-array Z-pinch implosions have been studied using two-frame point projection x-ray backlighting on the 1 MA COBRA pulsed power generator [J. D. Douglass, J. B. Greenly, D. A. Hammer, and B. R. Kusse, in Proceedings of the 15th IEEE International Pulsed Power Conference, Monterey, 2005 (to be published)]. X-pinch backlighter images with subnanosecond time

J. D. Douglass; S. A. Pikuz; T. A. Shelkovenko; D. A. Hammer; S. N. Bland; R. D. McBride

2007-01-01

196

Development of the axial instability and magnetic field topology in low wire number wire array Z-pinches  

Microsoft Academic Search

Summary form only given. We are investigating the development of the axial instability that occurs on each exploding wire in wire-array Z-pinches. The axial instability is a growing modulation of the size of the coronal plasma around individual wires of the array that results in non-uniform ablation of material from the cold wire core. It has long been known that

P. F. Knapp; K. S. Bell; I. C. Blesener; D. A. Chalenski; J. B. Greenly; C. L. Hoyt; M. R. Martin; R. D. McBride; S. Pikuz; T. A. Shelkovenko; D. A. Hammer; B. R. Kusse

2009-01-01

197

Development of novel techniques to study the magnetic field evolution in wire array Z-pinches and X pinches  

Microsoft Academic Search

Understanding the magnetic field topology in wire-array Z-pinches is of great significance for their ultimate application to stockpile stewardship and inertial confinement fusion. We have developed and tested several novel techniques involving material-based sensors to measure magnetic fields as a function of space and time in high energy density plasmas on pulsed power machines. We first briefly introduce a technique

Wasif Syed

2010-01-01

198

Demonstration of Radiation Pulse Shaping with Nested-Tungsten-Wire-Array Z Pinches for High-Yield Inertial Confinement Fusion  

Microsoft Academic Search

Nested wire-array Z pinches are shown to generate soft x-ray radiation pulse shapes required for three-shock isentropic compression and hot-spot ignition of high-yield inertial confinement fusion capsules. We demonstrate a reproducible and tunable foot pulse (first shock) produced by interaction of the outer and inner arrays. A first-step pulse (second shock) is produced by inner array collision with a central

M. E. Cuneo; R. A. Vesey; D. B. Sinars; E. M. Waisman; R. W. Lemke; D. E. Bliss; W. A. Stygar; J. L. Porter; M. G. Mazarakis; G. A. Chandler; T. A. Mehlhorn; J. P. Chittenden; S. V. Lebedev; D. G. Schroen

2005-01-01

199

Magnetic Rayleigh-Taylor instability mitigation and efficient radiation production in gas puff Z-pinch implosions  

Microsoft Academic Search

Large radius Z-pinches are inherently susceptible to the magnetic Rayleigh-Taylor (RT) instability because of their relatively long acceleration path. This has been reflected in a significant reduction of the argon K-shell yield as was observed when the diameter of the load was increased from 2.5 to >4 cm. Recently, an approach was demonstrated to overcome the challenge with a structured

H. Sze; J. S. Levine; J. Banister; B. H. Failor; N. Qi; P. Steen; A. L. Velikovich; J. Davis; A. Wilson

2007-01-01

200

Design of Z-pinch based, jet-target collision experiments for laboratory astrophysics using 3D MHD modelling  

Microsoft Academic Search

Summary form only given. The ablating plasma and precursor plasma flow obtained in conical wire array Z-pinches on the 1MA, 240ns rise-time MAGPIE facility provides a mechanism for generating radiatively cooled plasma jets with velocities of several hundred km\\/sec which can be sustained for several hundred nano-seconds. Such laboratory jets have been shown to provide a directly scalable representation of

J. P. Chittenden; M. Bocchi; S. V. Lebedev; F. Suzuki-Vidal; G. N. Hall; A. Ciardi

2010-01-01

201

X-ray emission from z pinches at 107 A: Current scaling, gap closure, and shot-to-shot fluctuations  

Microsoft Academic Search

We have measured the x-ray power and energy radiated by a tungsten-wire-array z pinch as a function of the peak pinch current and the width of the anode-cathode gap at the base of the pinch. The measurements were performed at 13- and 19-MA currents and 1-, 2-, 3-, and 4-mm gaps. The wire material, number of wires, wire-array diameter, wire-array

W. A. Stygar; H. C. Ives; D. L. Fehl; M. E. Cuneo; M. G. Mazarakis; J. E. Bailey; G. R. Bennett; D. E. Bliss; G. A. Chandler; R. J. Leeper; M. K. Matzen; D. H. McDaniel; J. S. McGurn; J. L. McKenney; L. P. Mix; D. J. Muron; J. L. Porter; J. J. Ramirez; L. E. Ruggles; J. F. Seamen; W. W. Simpson; C. S. Speas; R. B. Spielman; K. W. Struve; J. A. Torres; R. A. Vesey; T. C. Wagoner; T. L. Gilliland; M. L. Horry; D. O. Jobe; S. E. Lazier; J. A. Mills; T. D. Mulville; J. H. Pyle; T. M. Romero; J. J. Seamen; R. M. Smelser

2004-01-01

202

One, two-, and three-dimensional modeling of the different phases of wire array Z-pinch evolution  

Microsoft Academic Search

A series of one-, two-, and three-dimensional (1-D, 2-D, and 3-D) resistive magnetohydrodynamic models are used to build up a composite model of the different phases of wire array Z-pinch implosions. 1-D(r) and 2-D(r,z) ``cold-start'' simulations of single wire experiments are used to illustrate some of the important processes in the plasma formation phase of wire arrays. Detailed comparison of

J. P. Chittenden; S. V. Lebedev; S. N. Bland; F. N. Beg; M. G. Haines

2001-01-01

203

One, two-, and three-dimensional modeling of the different phases of wire array Z-pinch evolution  

Microsoft Academic Search

A series of one-, two-, and three-dimensional (1-D, 2-D, and 3-D) resistive magnetohydrodynamic models are used to build up a composite model of the different phases of wire array Z-pinch implosions. 1-D(r) and 2-D(r,z) cold-start simulations of single wire experiments are used to illustrate some of the important processes in the plasma formation phase of wire arrays. Detailed comparison of

J. P. Chittenden; S. V. Lebedev; S. N. Bland; F. N. Beg; M. G. Haines

2001-01-01

204

COBRA-STAR, a five frame point-projection x-ray imaging system for 1 MA scale wire-array Z pinches  

Microsoft Academic Search

A new imaging system for 1 MA scale wire-array Z-pinch experiments that produces up to five high-resolution x-ray images per experimental pulse has been developed. Calibrated areal density measurements of the Z-pinch plasma can be obtained from each pulse. The system substitutes five molybdenum (Mo) X pinches for the normal copper return-current conductors to provide point sources of x-rays for

J. D. Douglass; D. A. Hammer

2008-01-01

205

Recent experimental results on ICF target implosions by Z-pinch radiation sources and their relevance to ICF ignition studies.  

SciTech Connect

Inertial confinement fusion capsule implosions absorbing up to 35 kJ of x-rays from a {approx}220 eV dynamic hohlraum on the Z accelerator at Sandia National Laboratories have produced thermonuclear D-D neutron yields of (2.6 {+-} 1.3) x 10{sup 10}. Argon spectra confirm a hot fuel with Te {approx} 1 keV and n{sub e} {approx} (1-2) x 10{sup 23} cm{sup -3}. Higher performance implosions will require radiation symmetry control improvements. Capsule implosions in a {approx}70 eV double-Z-pinch-driven secondary hohlraum have been radiographed by 6.7 keV x-rays produced by the Z-beamlet laser (ZBL), demonstrating a drive symmetry of about 3% and control of P{sub 2} radiation asymmetries to {+-}2%. Hemispherical capsule implosions have also been radiographed in Z in preparation for future experiments in fast ignition physics. Z-pinch-driven inertial fusion energy concepts are being developed. The refurbished Z machine (ZR) will begin providing scaling information on capsule and Z-pinch in 2006. The addition of a short pulse capability to ZBL will enable research into fast ignition physics in the combination of ZR and ZBL-petawatt. ZR could provide a test bed to study NIF-relevant double-shell ignition concepts using dynamic hohlraums and advanced symmetry control techniques in the double-pinch hohlraum backlit by ZBL.

Bailey, James E.; Chandler, Gordon Andrew; Vesey, Roger Alan; Hanson, David Lester; Olson, Craig Lee; Nash, Thomas J.; Matzen, Maurice Keith; Ruiz, Carlos L.; Porter, John Larry, Jr.; Cuneo, Michael Edward; Varnum, William S.; Bennett, Guy R. (K-tech Corporation, Albuquerque, NM); Cooper, Gary Wayne; Schroen, Diana Grace (Schafer Gorp., Livermore, CA); Slutz, Stephen A.; MacFarlane, Joseph John (Prism Computational Sciences, Madison, WI); Leeper, Ramon Joe; Golovkin, I. E. (Prism Computational Sciences, Madison, WI); Mehlhorn, Thomas Alan; Mancini, Roberto Claudio (University of Nevada, Reno, NV)

2003-07-01

206

The Role of Strong Coupling in Z-Pinch-Driven Approaches to High Yield Inertial Confinement Fusion  

SciTech Connect

Peak x-ray powers as high as 280 {+-} 40 TW have been generated from the implosion of tungsten wire arrays on the Z Accelerator at Sandia National Laboratories. The high x-ray powers radiated by these z-pinches provide an attractive new driver option for high yield inertial confinement fusion (ICF). The high x-ray powers appear to be a result of using a large number of wires in the array which decreases the perturbation seed to the magnetic Rayleigh-Taylor (MRT) instability and diminishes other 3-D effects. Simulations to confirm this hypothesis require a 3-D MHD code capability, and associated databases, to follow the evolution of the wires from cold solid through melt, vaporization, ionization, and finally to dense imploded plasma. Strong coupling plays a role in this process, the importance of which depends on the wire material and the current time history of the pulsed power driver. Strong coupling regimes are involved in the plasmas in the convolute and transmission line of the powerflow system. Strong coupling can also play a role in the physics of the z-pinch-driven high yield ICF target. Finally, strong coupling can occur in certain z-pinch-driven application experiments.

MEHLHORN,THOMAS A.; DESJARLAIS,MICHAEL P.; HAILL,THOMAS A.; LASH,JOEL S.; ROSENTHAL,STEPHEN E.; SLUTZ,STEPHEN A.; STOLTZ,PETER H.; VESEY,ROGER A.; OLIVER,B.

1999-11-08

207

Numerical studies of the effects of precursor plasma on the performance of wire-array Z-pinches  

NASA Astrophysics Data System (ADS)

This paper is to numerically investigate, in one dimension, the effects of precursor plasma resulted from wire-array ablation on the performance of its following implosion after the ablation. The wire-array ablation is described by an analytic model, which consists of a rocket model or Sasorov's expression of wire-array mass ablation rate, the evolution equation of magnetic field, and several roughly reasonable assumptions. The following implosion is governed by the radiation magnetohydrodynamics. The implosion processes of wire-array Z-pinch from plasma shells prefilled and un-prefilled by the low-density plasma inside them are studied, and that from the wire-array ablations, which may be changed through varying the ablation time, ablation rate, and ablation velocity Vabl, are also simulated. The obtained results reveal that the prefilled low-density plasma and the precursor plasma from the wire-array ablation help to enhance the plasma shell pinch and the final implosion of the wire array, respectively, compared to the pinch of un-prefilled plasma shell. With the same plasma masses, which are distributed in the interior of the array and the shell, and modified Spitzer resistivity, the implosions that start from the wire ablation develop faster than that from the plasma shell with the prefill. If more substance ablates from the wire array before the start of its implosion, the final Z-pinch performance could be better. The Z-pinch plasma is highly magnetized with driven current more than 3 MA.

Ning, Cheng; Sun, Shun-Kai; Xiao, De-Long; Zhang, Yang; Ding, Ning; Huang, Jun; Xue, Chuang; Shu, Xiao-Jian

2010-06-01

208

NUMERICAL SIMULATIONS OF Z-PINCH EXPERIMENTS TO CREATE SUPERSONIC DIFFERENTIALLY ROTATING PLASMA FLOWS  

SciTech Connect

The physics of accretion disks is of fundamental importance for understanding of a wide variety of astrophysical sources that includes protostars, X-ray binaries, and active galactic nuclei. The interplay between hydrodynamic flows and magnetic fields and the potential for turbulence-producing instabilities is a topic of active research that would benefit from the support of dedicated experimental studies. Such efforts are in their infancy, but in an effort to push the enterprise forward we propose an experimental configuration which employs a modified cylindrical wire array Z-pinch to produce a rotating plasma flow relevant to accretion disks. We present three-dimensional resistive magnetohydrodynamic simulations which show how this approach can be implemented. In the simulations, a rotating plasma cylinder or ring is formed, with typical rotation velocity {approx}30 km s{sup -1}, Mach number {approx}4, and Reynolds number in excess of 10{sup 7}. The plasma is also differentially rotating. Implementation of different external magnetic field configurations is discussed. It is found that a modest uniform vertical field of 1 T can affect the dynamics of the system and could be used to study magnetic field entrainment and amplification through differential rotation. A dipolar field potentially relevant to the study of accretion columns is also considered.

Bocchi, M.; Ummels, B.; Chittenden, J. P.; Lebedev, S. V. [Plasma Physics, Imperial College, London SW7 2BW (United Kingdom)] [Plasma Physics, Imperial College, London SW7 2BW (United Kingdom); Frank, A.; Blackman, E. G., E-mail: mbocchi@imperial.ac.uk [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States)

2013-04-10

209

Nitrogen Recombination X-Ray Laser Scheme in a Capillary Discharge Z-Pinch  

NASA Astrophysics Data System (ADS)

A recombination based X-Ray laser has a preferred energy scaling compared to collisional ionization scheme [1-3]. The difficulty in realizing this scheme lies in the required plasma cooling rate [4,5]. Implementing a nitrogen recombination laser at ?13.4 nm, requires initially Te140eV and Ne10^20cm-3, and than cooling to Te<60eV, at a time scale shorter than the 3-body recombination time scale of 3-6ns. An experimental setup has been built to achieve these conditions in a capillary discharge. A 90mm long capillary with 3-6mm inner diameter was filled with 0.5-3 Torr N2 and coupled to a generator supplying a peak current of 60-70 KA at 70 ns. The radiation from N^5+ and N^6+ was measured with XRD and appropriate filters. The results show that the cooling time of the plasma is shorter than 5 ns, indicationg that the recombination scheme may be feasible. The experimental measurements will be used in search for the optimal initial conditions for lasing. [1] Elton R. C.: X-Ray Lasers, Academic Press, New York, 1990. [2] Rocca J.J. et. al., PRL 73, 2192, (1994). [3] Ben-Kish A. et. al., PRL 87, 015002, (2001) [4] Lee K., Kim J. H., Kim D., Phys. of plasmas 9, 4749, (2002). [5] Vrba P., et. al., 6th Intl. Conf. on Dense Z-Pinches, 2005

Be'Ery, I.; Kampel, N.; Rikanati, A.; Avni, U.; Ben-Kish, A.; Fisher, A.; Ron, A.

2006-10-01

210

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

NASA Astrophysics Data System (ADS)

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 50?s. 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.

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

211

Radiatively cooled supersonic plasma jets generated in wire array Z-pinches  

NASA Astrophysics Data System (ADS)

We will present experiments on the generation of a highly supersonic plasma jet by a convergent plasma flow, produced by electrodynamic acceleration of plasma in a conical array of fine metallic wires (a modification of the wire array Z-pinch [1]). Stagnation of the plasma flow on the axis of symmetry forms a standing conical shock, which effectively collimates the flow in the axial direction. This scenario is essentially similar to that discussed by Cant et al. [2] as a possible, purely hydrodynamic mechanism of jet formation in young stellar objects. Experiments using different materials (Al, Fe and W) show that a highly supersonic (M 20) and a well-collimated jet is generated when the radiative cooling rate of the plasma is significant. The interaction of this jet with a plasma target could be used for scaled [3] laboratory astrophysical experiments on hydrodynamic instabilities in decelerated plasma flow. [1] M.K. Matzen, Phys. Plasmas v.4, 1519 (1997) [2] J. Cant, et. al. Astron. Astrophys. v.192, 287 (1994). [3] D. Ryutov et al., ApJ, v.518, 821 (1999)

Bland, Simon; Lebedev, Sergey; Chittenden, Jerry; Beg, F. N.; Ciardi, A.; Haines, M. G.

2000-10-01

212

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

PubMed

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. PMID:23215497

Schmidt, A; Tang, V; Welch, D

2012-11-16

213

Numerical investigation on the implosion dynamics of wire-array Z-pinches in (r, ?) geometry  

NASA Astrophysics Data System (ADS)

The implosion dynamics of wire-array Z-pinches are investigated numerically in 2D (r, ?) geometry by using a resistive MHD code. It is assumed that the wires have expanded to plasmas with diameter d0, which is used as the initial condition for the consequent implosion process. In fact, the explosion process of individual wires is not included. By changing d0, the effects of the wire expansion degree on the implosion dynamics are analyzed. When d0 is larger, the current density is more concentrated at the outer side of the wires and the fraction of current flow around the wire plasmas is nearly in proportion to d0. As a result, the ablation rate of wires is increased and the implosion phase starts earlier. This conclusion agrees with the simulation works of other authors [Chittenden et al., Phys. Plasmas 11(3), 1118 (2004)]. When the array radius and initial wire plasma diameter are fixed, the increase of wire number leads to the azimuthal merge of wires during implosion. When the wires number exceed a critical value, which is related to d0, wire plasmas can merge to a continuous shell with an azimuthal perturbation in density, which depends on the initial wires number.

Huang, Jun; Ding, Ning; Ning, Cheng; Sun, Shun-Kai; Zhang, Yang; Xiao, De-Long; Xue, Chuang

2012-06-01

214

Dynamics of cylindrically converging precursor plasma flow in wire-array Z-pinch experiments  

SciTech Connect

This paper summarizes the present understanding of the processes leading to precursor column formation in cylindrical wire arrays on the 1 MA MAGPIE generator at Imperial College London. Direct experimental measurements of the diameter variation during the collapse and formation phase of the precursor column are presented, along with soft x-ray emission, and quantitative radiography. In addition, data from twisted cylindrical arrays are presented which give additional information on the behavior of coronal plasma generated in wire array z pinches. Three stages in precursor column formation are identifiable from the data: broad initial density profile, rapid contraction to small diameter, and slow expansion after formation. The correlation of emission to column diameter variation indicates the contraction phase is a nonlinear collapse resulting from the increasing on-axis density and radiative cooling rate. The variation in the minimum diameter is measured for several array materials, and data show good agreement with a pressure balance model. Comparison of column expansion rates to analytical models allows an estimate of column temperature variation, and estimates of the current in the column are also made. Formation data are in good agreement with both fluid and kinetic modeling, but highlight the need to include collisionless flow in the early time behavior.

Bott, S. C.; Lebedev, S. V.; Bland, S. N.; Chittenden, J. P.; Ciardi, A.; Haines, M. G.; Sherlock, M.; Hall, G.; Rapley, J. [Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); Ampleford, D. J.; Jennings, C. [Sandia National Laboratory, Albuquerque, NM (United States); Beg, F. N. [Department of Mechanical and Aerospace Engineering, University of California San Diego, California (United States); Palmer, J. [AWE Plc., Aldermaston, RG7 4PR (United Kingdom)

2006-10-15

215

Long implosion time tungsten wire array Z pinches on the Saturn generator  

SciTech Connect

Recent success on the Saturn [C. Deeney et al., Phys. Rev. E 56, 5945 (1997)] and Z [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] accelerators at Sandia National Laboratories have demonstrated the ability to scale Z-pinch parameters to increasingly larger current pulsed power facilities. Next generation machines will require even larger currents (>20 MA), placing further demands on pulsed power technology. To this end, experiments have been carried out on Saturn operating in a long pulse mode, investigating the potential of lower voltages and longer implosion times while still maintaining pinch fidelity. High wire number, 25 mm diam tungsten arrays were imploded with implosion times ranging from 130 to 240 ns. The results were comparable to those observed in the Saturn short pulse mode, with rise times on the order of 4.5-6.5 ns. Experimental data will be presented, along with two-dimensional radiation magnetohydrodynamic simulations used to explain and reproduce the experiment. (c) 2000 American Institute of Physics.

Douglas, M. R. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Deeney, C. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Spielman, R. B. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Coverdale, C. A. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Roderick, N. F. [University of New Mexico, Albuquerque, New Mexico 87102 (United States)] [University of New Mexico, Albuquerque, New Mexico 87102 (United States); Haines, M. G. [The Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)] [The Blackett Laboratory, Imperial College, London SW7 2BZ, (United Kingdom)

2000-07-01

216

The Physics of Long-Pulse Wire Array Z-Pinch Implosions  

SciTech Connect

Recent improvements in z-pinch wire array load design at Sandia National Laboratories have led to a substantial increase in pinch performance as measured by radiated powers of up to 280 TW in 4 ns and 1.8 MJ of total radiated energy. Next generation, higher current machines will allow for larger mass arrays and comparable or higher velocity implosions to be reached, possibly extending these result.dis the current is pushed above 20 MA, conventional machine design based on a 100 ns implosion time results in higher voltages, hence higher cost and power flow risk. Another approach, which shifts the risk to the load configuration, is to increase the implosion time to minimize the voltage. This approach is being investigated in a series of experimental campaigns on the Saturn and Z machines. In this paper, both experimental and two dimensional computational modeling of the fist long implosion Z experiments will be presented. The experimental data shows broader pulses, lower powers, and larger pinch diameters compared to the corresponding short pulse data. By employing a nested array configuration, the pinch diameter was reduced by 50% with a corresponding increase in power of > 30%. Numerical simulations suggest load velocity is the dominating mechanism behind these results.

DOUGLAS,MELISSA R.; DEENEY,CHRISTOPHER; SPIELMAN,RICK B.; COVERDALE,CHRISTINE A.; RODERICK,N.F.; PETERSON,D.L.

1999-12-14

217

Experimental Study of an Inverse Wire Array Z-Pinch Operating as a Current Switch  

NASA Astrophysics Data System (ADS)

We will present experiments on the MAGPIE facility (1.5MA, 250ns) in which an inverse wire array [1] (with the wires acting as a return current cage placed around a central current conductor) operated as a fast current switch. This allowed to significantly reduce the rise-time of the current pulse (<100ns) delivered to a separate, standard imploding wire array z-pinch load. Experimental studies of the operation of this arrangement as a current switch will be discussed and new measurements of current switching into the load array will be presented. We will also discuss how pre-conditioning of the load array wires by the current pre-pulse [2] depends on wire materials (Al, Cu, W) used in the load and the exploding wire arrays. [4pt] [1] A. Harvey-Thompson, S.V. Lebedev, S.N. Bland et al., PoP 16, 022701 (2009).[0pt] [2] A. Harvey-Thompson, S.V. Lebedev, G. Burdiak, et al., PRL 106, 205002 (2011)

Lebedev, Sergey; Harvey-Thomson, A.; Hall, G. N.; Waisman, E. M.; Khoory, E.; Burdiak, G.; Chittenden, J. P.; de Grouchy, P.; Suzuki-Vidal, F. A.; Swadling, G.; Bland, S. N.; Pickworth, L.; Skidmore, J.; Suttle, L.

2011-11-01

218

Tungsten wire-array Z-pinch experiments at 200 TW and 2 MJ  

SciTech Connect

Here Z, a 60 TW/5 MJ electrical accelerator located at Sandia National Laboratories, has been used to implode tungsten wire-array Z pinches. These arrays consisted of large numbers of tungsten wires (120{endash}300) with wire diameters of 7.5 to 15 {mu}m placed in a symmetric cylindrical array. The experiments used array diameters ranging from 1.75 to 4 cm and lengths from 1 to 2 cm. A 2 cm long, 4 cm diam tungsten array consisting of 240, 7.5 {mu}m diam wires (4.1 mg mass) achieved an x-ray power of {approximately}200TW and an x-ray energy of nearly 2 MJ. Spectral data suggest an optically thick, Planckian-like radiator below 1000 eV. One surprising experimental result was the observation that the total radiated x-ray energies and x-ray powers were nearly independent of pinch length. These data are compared with two-dimensional radiation magnetohydrodynamic code calculations. {copyright} {ital 1998 American Institute of Physics.}

Spielman, R.B.; Deeney, C.; Chandler, G.A.; Douglas, M.R.; Fehl, D.L.; Matzen, M.K.; McDaniel, D.H.; Nash, T.J.; Porter, J.L.; Sanford, T.W.; Seamen, J.F.; Stygar, W.A.; Struve, K.W.; Breeze, S.P.; McGurn, J.S.; Torres, J.A.; Zagar, D.M.; Gilliland, T.L.; Jobe, D.O.; McKenney, J.L.; Mock, R.C.; Vargas, M.; Wagoner, T. [Sandia National Laboratories, Albuquerque, New Mexico87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico87185 (United States); Peterson, D.L. [Los Alamos National Laboratories, Los Alamos, New Mexico87545 (United States)] [Los Alamos National Laboratories, Los Alamos, New Mexico87545 (United States)

1998-05-01

219

Manufacturing Concepts for an IFE Power Plant Using Z-Pinch Technology  

SciTech Connect

The Z-Pinch Power Plant (ZP3) uses the results from Sandia National Laboratories' Z accelerator in a power plant application to generate energy pulses using inertial confinement fusion. A collaborative project has been initiated by Sandia to investigate the scientific principles of a power generation system. Research is underway to investigate the use of recyclable transmission lines to directly connect the wire array and the hohlraum to the pulsed power driver. The resulting power plant will require an intense on-site manufacturing system to rebuild the transmission lines, wire arrays and hohlraums at a rate of 0.1 Hz per power unit. By recycling virtually all of the materials, the system is expected to be economically competitive with other power generation technologies. Current research is investigating the available approaches to manufacturing and determining the cost effectiveness of the alternatives. This paper examines the various options available for manufacturing and development requirements leading to a Proof-of-Principle experiment to demonstrate the technology.

Cipiti, B.B.; Rochau, G.E. [Sandia National Laboratories (United States)

2005-04-15

220

The role of Z-pinches and related configurations in magnetized target fusion  

SciTech Connect

The use of a magnetic field within a fusion target is now known as Magnetized Target Fusion in the US and as MAGO (Magnitnoye Obzhatiye, or magnetic compression) in Russia. In contrast to direct, hydrodynamic compression of initially ambient-temperature fuel (e.g., ICF), MTF involves two steps: (a) formation of a warm, magnetized, wall-confined plasma of intermediate density within a fusion target prior to implosion; (b) subsequent quasi-adiabatic compression and heating of the plasma by imploding the confining wall, or pusher. In many ways, MTF can be considered a marriage between the more mature MFE and ICF approaches, and this marriage potentially eliminates some of the hurdles encountered in the other approaches. When compared to ICF, MTF requires lower implosion velocity, lower initial density, significantly lower radial convergence, and larger targets, all of which lead to substantially reduced driver intensity, power, and symmetry requirements. When compared to MFE, MTF does not require a vacuum separating the plasma from the wall, and, in fact, complete magnetic confinement, even if possible, may not be desirable. The higher density of MTF and much shorter confinement times should make magnetized plasma formation a much less difficult step than in MFE. The substantially lower driver requirements and implosion velocity of MTF make z-pinch magnetically driven liners, magnetically imploded by existing modern pulsed power electrical current sources, a leading candidate for the target pusher of an MTF system.

Lindemuth, I.R.

1997-07-10

221

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

222

Optimal welding parameters for very high power ultrasonic additive manufacturing of smart structures with aluminum 6061 matrix  

NASA Astrophysics Data System (ADS)

Ultrasonic additive manufacturing (UAM) is a recent solid state manufacturing process that combines ad- ditive joining of thin metal tapes with subtractive milling operations to generate near net shape metallic parts. Due to the minimal heating during the process, UAM is a proven method of embedding Ni-Ti, Fe-Ga, and PVDF to create active metal matrix composites. Recently, advances in the UAM process utilizing 9 kW very high power (VHP) welding has improved bonding properties, enabling joining of high strength materials previously unweldable with 1 kW low power UAM. Consequently, a design of experiments study was conducted to optimize welding conditions for aluminum 6061 components. This understanding is critical in the design of UAM parts containing smart materials. Build parameters, including weld force, weld speed, amplitude, and temperature were varied based on a Taguchi experimental design matrix and tested for me- chanical strength. Optimal weld parameters were identi ed with statistical methods including a generalized linear model for analysis of variance (ANOVA), mean e ects plots, and interaction e ects plots.

Wolcott, Paul J.; Hehr, Adam; Dapino, Marcelo J.

2014-03-01

223

Shock waves in a Z-pinch and the formation of high energy density plasma  

SciTech Connect

A Z-pinch liner, imploding onto a target plasma, evolves in a step-wise manner, producing a stable, magneto-inertial, high-energy-density plasma compression. The typical configuration is a cylindrical, high-atomic-number liner imploding onto a low-atomic-number target. The parameters for a terawatt-class machine (e.g., Zebra at the University of Nevada, Reno, Nevada Terawatt Facility) have been simulated. The 2-1/2 D MHD code, MACH2, was used to study this configuration. The requirements are for an initial radius of a few mm for stable implosion; the material densities properly distributed, so that the target is effectively heated initially by shock heating and finally by adiabatic compression; and the liner's thickness adjusted to promote radial current transport and subsequent current amplification in the target. Since the shock velocity is smaller in the liner, than in the target, a stable-shock forms at the interface, allowing the central load to accelerate magnetically and inertially, producing a magneto-inertial implosion and high-energy density plasma. Comparing the implosion dynamics of a low-Z target with those of a high-Z target demonstrates the role of shock waves in terms of compression and heating. In the case of a high-Z target, the shock wave does not play a significant heating role. The shock waves carry current and transport the magnetic field, producing a high density on-axis, at relatively low temperature. Whereas, in the case of a low-Z target, the fast moving shock wave preheats the target during the initial implosion phase, and the later adiabatic compression further heats the target to very high energy density. As a result, the compression ratio required for heating the low-Z plasma to very high energy densities is greatly reduced.

Rahman, H. U. [Magneto-Inertial Fusion Technologies Inc. (MIFTI), Irvine, California 92612 (United States) and Department of Physics, University of California Irvine, Irvine, California 92697 (United States); Wessel, F. J. [Department of Physics, University of California Irvine, Irvine California 92697 (United States); Ney, P. [Mount San Jacinto College, Menifee, California 92584 (United States); Presura, R. [University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0208 (United States); Ellahi, Rahmat [Department of Mathematics and Statistics, FBAS, IIU, Islamabad (Pakistan) and Department of Mechanical Engineering, University of California Riverside, Riverside, California 92521 (United States); Shukla, P. K. [Department of Mechanical and Aerospace Engineering and Center for Energy Research, University of California San Diego, La Jolla, California 92093 (United States)

2012-12-15

224

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

NASA Astrophysics Data System (ADS)

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 a 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 ZTe 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.

Swadling, G. F.; Lebedev, S. V.; Niasse, N.; Chittenden, J. P.; Hall, G. N.; Suzuki-Vidal, F.; Burdiak, G.; Harvey-Thompson, A. J.; Bland, S. N.; De Grouchy, P.; Khoory, E.; Pickworth, L.; Skidmore, J.; Suttle, L.

2013-02-01

225

Wire Array Z-Pinch Insights for Enhanced X-Ray Production  

SciTech Connect

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, interact. 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 2-D 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.

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

1999-01-04

226

Mass profile and instability growth measurements for 300-wire z-pinch implosions driven by 14-18, MA.  

SciTech Connect

We present the first comprehensive study of high wire-number, wire-array Z-pinch dynamics at 14-18 MA using x-ray backlighting and optical shadowgraphy diagnostics. The cylindrical arrays retain slowly expanding, dense wire cores at the initial position up to 60% of the total implosion time. Azimuthally correlated instabilities at the array edge appear during this stage which continue to grow in amplitude and wavelength after the start of bulk motion, resulting in measurable trailing mass that does not arrive on axis before peak x-ray emission.

Cuneo, Michael Edward; Yu, Edmund P.; Nash, Thomas J.; Bliss, David Emery; Porter, John Larry, Jr.; Sinars, Daniel Brian

2004-07-01

227

Development of novel techniques to study the magnetic field evolution in wire array Z-pinches and X pinches  

NASA Astrophysics Data System (ADS)

Understanding the magnetic field topology in wire-array Z-pinches is of great significance for their ultimate application to stockpile stewardship and inertial confinement fusion. We have developed and tested several novel techniques involving material-based sensors to measure magnetic fields as a function of space and time in high energy density plasmas on pulsed power machines. We first briefly introduce a technique that was used to measure a lower limit of the maximum magnetic field of a sub-microsecond duration pulse using magnetic reversal in CoPt thin films. The time-varying magnetic field was generated by an exploding wire array plasma called an X pinch produced on the 0.5 MA, 100 ns pulse duration, XP pulsed power generator. We then introduce a technique based on Faraday rotation that was used to measure magnetic fields in wire-array Z-pinches produced on the 1 MA, 100 ns rise time, COBRA pulsed power generator as well as on the XP generator. This technique measures magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide, multicomponent terbium borate glass, placed adjacent to, or within, the wire array. We have measured fields > 10 T with 100 ns rise times outside of a wire-array Z-pinch for the entire duration (250 ns) of the current pulse and as much as 2 T inside a wire-array for 40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using the terbium borate glass. The third method, also based on Faraday rotation of SLM laser light utilized an integrated optical fiber sensor (a fiber-sensor-fiber assembly) on the XP pulsed power generator that also yielded a measurement of the magnetic field of a wire-array Z-pinch for part of the current pulse. Finally, we repeated the third method by fabricating a "thin film waveguide" of terbium borate glass to increase the spatial resolution of the measurement. The thin film waveguide was then coupled to an optical fiber system. Although we successfully fabricated thin film nanowaveguides of terbium borate glass, the first time such waveguides have been made, due to poor coupling efficiency of light between components, preliminary Faraday rotation measurements were unsuccessful. The technique developed in this dissertation is potentially viable for magnetic field measurements in high current pulsed power systems if the device is protected from intimate interaction with the high energy density plasma during the time that a magnetic field measurement is to be made.

Syed, Wasif

228

Dense Z-pinch (DZP) as a fusion power reactor: preliminary scaling calculations and sysems energy balance  

SciTech Connect

A conceptual DT fusion reactor concept is described that is based upon the dense Z-pinch (DZP). This study emphasizes plasma modeling and the parametric assessment of the reactor energy balance. To this end simple analytic and numerical models have been developed and evaluated. The resulting optimal reactor operating point promises a high-Q, low-yield system of a scale that may allow the use of conventional high-voltage Marx/water-line technology to drive a potentially very small reactor system.

Hagenson, R.L.; Tai, A.S.; Krakowski, R.A.; Moses, R.W.

1980-01-01

229

Enhanced keV peak power and yield using twisted pair 'cables' in a z-pinch  

SciTech Connect

Individual wires in a z-pinch were replaced with twisted pair 'cables' of similar linear mass on the COBRA pulsed power generator, resulting in peak power and yield increases in radiation above 1 keV. A cable is defined here as two or more fine wires twisted together to form a continuous strand with a wavelength ({lambda}{sub t}) dependent on the twists per unit length. The magnitude of {lambda}{sub t} appears to play a strong role in these increases, with the largest gains found for a {lambda}{sub t} of Almost-Equal-To 0.75 mm.

Hoyt, C. L.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Cahill, A. D.; Gourdain, P.-A.; Greenly, J. B.; Kusse, B. R.; Hammer, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2012-06-11

230

Enhanced keV peak power and yield using twisted pair ``cables'' in a z-pinch  

NASA Astrophysics Data System (ADS)

Individual wires in a z-pinch were replaced with twisted pair "cables" of similar linear mass on the COBRA pulsed power generator, resulting in peak power and yield increases in radiation above 1 keV. A cable is defined here as two or more fine wires twisted together to form a continuous strand with a wavelength (?t) dependent on the twists per unit length. The magnitude of ?t appears to play a strong role in these increases, with the largest gains found for a ?t of ?0.75 mm.

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

2012-06-01

231

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

NASA Astrophysics Data System (ADS)

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 function 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.

Vogman, G. V.; Shumlak, U.

2011-10-01

232

Study of the effect of preliminary wire explosion on X-ray generation during wire array Z-pinch implosion  

NASA Astrophysics Data System (ADS)

Results are presented from experimental studies and numerical simulations of the effect of preliminary wire explosion on the parameters of X-ray emission generated during wire array Z-pinch implosion. The wire array implosion was driven by a current pulse with an amplitude of 0.5 MA and a rise time of 0.5 ?s, while the preliminary wire explosion was produced by a current pulse with an amplitude of 0.5-1 kA per wire, a rise time of 100 ns, and a full width at half maximum of 200 ns. The experiments showed that the current prepulse significantly impaired the parameters of X-ray pulses. In particular, along with a decrease in the amplitude and an increase in the duration of the X-ray pulse, its spiky structure became more pronounced. The results of numerical simulations with the use of a one-dimensional radiative MHD code are in good agreement with the parameters of Z-pinch emission in experiments with and without a current prepulse.

Repin, P. B.; Selemir, V. D.; Selyavski?, V. T.; Savchenko, R. V.; Orlov, A. P.; Repin, B. G.; Ibragimov, M. Sh.

2009-01-01

233

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

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 function 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.

Vogman, G. V. [Univ. of California, Berkeley, CA (United States); Shumlak, U. [Univ. of Washington, Seattle, WA (United States)

2011-10-13

234

A novel extreme ultraviolet four channels normal incidence imaging system for plasma diagnostics of Z-pinch facility  

NASA Astrophysics Data System (ADS)

A novel EUV four channels normal incidence imaging system for plasma diagnostics of Z-pinch facility was presented in this paper, which consists of four concave mirrors and one convex mirror used for focusing an object onto four different positions with about 30 ?m resolution on the same image plane. In addition, this imaging system can work at the energies of 50 eV, 95 eV, 150 eV, and broadband of 50-100 eV by using different multilayer films deposited on the concave and convex mirrors. This instrument, combined with framing camera, can achieve the power of two-dimensional spatial and temporal resolution, as well as the ability to imaging the plasma at the specific temperature. In the paper, the four channels microscope centering at multi-energies was developed.

Wang, Xin; Mu, Baozhong; Zhu, Jingtao; Wang, Ling; Yi, Shengzhen; Li, Wenbin; Wang, Zhanshan; Qin, Yi; Xu, Zeping; Xu, Rongkun; Li, Zhenghong

2013-07-01

235

Physics of Multi-Planar and Compact Cylindrical Wire Arrays Implosions on University-Scale Z-pinch Generators  

SciTech Connect

The presented research focuses on investigation of Z-pinch plasma formation, implosion, and radiation characteristics as a function of the load configuration. The single planar and multi-planar wire arrays as well as compact cylindrical wire arrays were studied on the 1.3 MA UNR Zebra and 1 MA Cornell COBRA generators. The largest yields and powers were found for W and Mo double planar and compact wire arrays. A possibility of radiation pulse shaping was demonstrated. Two types of bright spots were observed in plasmas. A comparison of Mo double planar and compact wire array data indicates the possibility that the same heating mechanism operates during the final implosion and stagnation stages.

Kantsyrev, V. L.; Safronova, A. S.; Esaulov, A. A.; Williamson, K. M.; Shrestha, I.; Ouart, N. D.; Yilmaz, M. F.; Wilcox, P. G.; Osborne, G. C.; Weller, M. E.; Shlyaptseva, V. V. [Physics Department, University of Nevada, Reno, NV 89557 (United States); Chuvatin, A. S. [Ecole Polytechnique, 91128 Palaiseau (France); Rudakov, L. I. [Icarus Research Inc., Bethesda, MD 20824-0780 (United States); Greenly, J. B.; McBride, R. D.; Knapp, P. F.; Blessener, I. C.; Bell, K. S.; Chalenski, D. A.; Hammer, D. A. [Laboratory of Plasma Studies Cornell University, Ihaca, NY 14853 (United States)] (and others)

2009-01-21

236

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

NASA Astrophysics Data System (ADS)

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 106 and 1012 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.

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

2011-03-01

237

Structure of the dense cores and ablation plasmas in the initiation phase of tungsten wire-array Z pinches  

NASA Astrophysics Data System (ADS)

The early stages of tungsten (W) wire-array Z-pinch implosions have been studied using two-frame point projection x-ray backlighting on the 1MA COBRA pulsed power generator [J. D. Douglass, J. B. Greenly, D. A. Hammer, and B. R. Kusse, in Proceedings of the 15th IEEE International Pulsed Power Conference, Monterey, 2005 (to be published)]. X-pinch backlighter images with subnanosecond time resolution and 4-10?m spatial resolution have been obtained of individual W exploding wires in 8-wire arrays that show evolution of wire-core and coronal plasma structures. The timing of the X-pinch x-ray bursts relative to the Z-pinch initiation time was adjusted over a 50ns time interval by varying the X-pinch mass per unit length. Wire-cores seen in two images separated in view by 120 show that the expansion is remarkably azimuthally symmetric. A strong correlation is observed between the structure on the dense exploding wire-cores and the structure of the ?1018/cm3 ablation plasma being drawn from radial prominences. Plasma ablation velocity was estimated to have a lower bound of 24km/s. The wire-core expansion rate was found to be approximately constant with time over the interval 50-100ns after the start of the current pulse. Finally, micron-scale axial gaps, seen as early as 70ns into the current pulse and persisting from that time, were observed along the wire-core.

Douglass, J. D.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Bland, S. N.; Bott, S. C.; McBride, R. D.

2007-01-01

238

Structure of the dense cores and ablation plasmas in the initiation phase of tungsten wire-array Z pinches  

SciTech Connect

The early stages of tungsten (W) wire-array Z-pinch implosions have been studied using two-frame point projection x-ray backlighting on the 1 MA COBRA pulsed power generator [J. D. Douglass, J. B. Greenly, D. A. Hammer, and B. R. Kusse, in Proceedings of the 15th IEEE International Pulsed Power Conference, Monterey, 2005 (to be published)]. X-pinch backlighter images with subnanosecond time resolution and 4-10 {mu}m spatial resolution have been obtained of individual W exploding wires in 8-wire arrays that show evolution of wire-core and coronal plasma structures. The timing of the X-pinch x-ray bursts relative to the Z-pinch initiation time was adjusted over a 50 ns time interval by varying the X-pinch mass per unit length. Wire-cores seen in two images separated in view by 120 deg. show that the expansion is remarkably azimuthally symmetric. A strong correlation is observed between the structure on the dense exploding wire-cores and the structure of the {>=}10{sup 18}/cm{sup 3} ablation plasma being drawn from radial prominences. Plasma ablation velocity was estimated to have a lower bound of 24 km/s. The wire-core expansion rate was found to be approximately constant with time over the interval 50-100 ns after the start of the current pulse. Finally, micron-scale axial gaps, seen as early as 70 ns into the current pulse and persisting from that time, were observed along the wire-core.

Douglass, J. D.; Hammer, D. A.; McBride, R. D. [Laboratory of Plasma Studies, 439 Rhodes Hall, Cornell University, Ithaca, New York 14853 (United States); Pikuz, S. A.; Shelkovenko, T. A. [Laboratory of Plasma Studies, 439 Rhodes Hall, Cornell University, Ithaca, New York 14853 (United States); P. N. Lebedev Physical Institute, Leninsky Prospect 53, Moscow 117924 (Russian Federation); Bland, S. N.; Bott, S. C. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2007-01-15

239

A model for ablated-plasma distribution and width for wire-array Z-pinch implosions  

SciTech Connect

A one-dimensional radial magnetohydrodynamic model of the plasma ablated from a multi-MA wire-array Z pinch is developed. The model is used to compute the mass weighted-density width {delta} of the plasma at the end of the ablation phase. The wire-array cores are represented as a prescribed source of plasma injection. The plasma, beyond a thin boundary layer, is approximated as a perfect conductor experiencing only magnetic forces and negligible pressure gradients. Assuming that the current driving the Z-pinch implosion increases linearly with time t during the ablation phase, and that the mass-ablation rate varies as t{sup {nu}}, it is shown that the density width {delta} is a function of the dimensionless parameter {lambda}=u{sub a}(t{sub a})t{sub a}/r{sub 0}, where u{sub a} is the ablation velocity, t{sub a} is the total ablation time, and r{sub 0} is the initial wire-array radius. The velocity u{sub a} is defined such that its product with the mass-ablation rate equals the magnetic force at r{sub 0}, which is assumed to be the mass injection point. A solution is obtained for the plasma flow in semianalytical form when the current is an exponential function of time, and u{sub a} is constant. The ablated plasma density width {delta} obtained under these two sets of conditions is compared. In addition, assuming that the plasma sheath at stagnation is proportional to the width {delta}, scaling relationships for the peak x-ray power radiated when the pinch stagnates on axis are suggested.

Waisman, Eduardo M.; Cuneo, M.E.; Stygar, W.A.; Sasorov, P.; Yu, E.P. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1194 (United States); Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1194 (United States)

2006-06-15

240

Magnetic Rayleigh-Taylor instability mitigation and efficient radiation production in gas puff Z-pinch implosions  

SciTech Connect

Large radius Z-pinches are inherently susceptible to the magnetic Rayleigh-Taylor (RT) instability because of their relatively long acceleration path. This has been reflected in a significant reduction of the argon K-shell yield as was observed when the diameter of the load was increased from 2.5 to >4 cm. Recently, an approach was demonstrated to overcome the challenge with a structured gas puff load that mitigates the RT instability, enhances the energy coupling, and leads to a high compression, high yield Z-pinch. The novel load consists of a 'pusher', outer region plasma that carries the current and couples energy from the driver, a 'stabilizer', inner region plasma that mitigates the RT growth, and a ''radiator,'' high-density center jet plasma that is heated and compressed to radiate. In 3.5-MA, 200-ns, 12-cm initial diameter implosions, the Ar K-shell yield has increased by a factor of 2, to 21 kJ, matching the yields obtained on the same accelerator with 100-ns, 2.5-cm-diam implosions. Further tests of such structured Ar gas load on {approx}6 MA, 200-ns accelerators have achieved >80 kJ. From laser diagnostics and measurements of the K-shell and extreme ultraviolet emission, initial gas distribution and implosion trajectories were obtained, illustrating the RT suppression and stabilization of the imploding plasma, and identifying the radiation source region in a structured gas puff load. Magnetohydrodynamic simulations, started from actual initial density profiles, reproduce many features of the measurements both qualitatively and quantitatively.

Sze, H.; Levine, J. S.; Banister, J.; Failor, B. H.; Qi, N.; Steen, P.; Velikovich, A. L.; Davis, J.; Wilson, A. [L-3 Pulse Sciences, San Leandro, California 94577 (United States); Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Avonia Inc., San Diego, California 92130 (United States)

2007-05-15

241

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

NASA Astrophysics Data System (ADS)

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)], that 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 12cm diameter nozzle with and without a central gas jet on axis. Typical peak drive currents and implosion times in these experiments were 6MA and 230ns. 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 (25MA peak drive currents, 100ns 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 12cm diameter central-jet nozzle configuration, it predicts over 1MJ of K-shell emission is attainable.

Thornhill, J. W.; Chong, Y. K.; Apruzese, J. P.; Davis, J.; Clark, R. W.; Giuliani, J. L.; Terry, R. E.; Velikovich, A. L.; Commisso, R. J.; Whitney, K. G.; Frese, M. H.; Frese, S. D.; Levine, J. S.; Qi, N.; Sze, H.; Failor, B. H.; Banister, J. W.; Coleman, P. L.; Coverdale, C. A.; Jones, B.; Deeney, C.

2007-06-01

242

Modifying Wire-Array Z-Pinch Ablation Structure Using Coiled Arrays  

SciTech Connect

A new wire-array configuration has been used to control the modulation of ablated plasma flow for the first time. Cylindrical aluminum coiled arrays, in which each straight wire is replaced with a single helix, were driven by a 1 MA, 240 ns current pulse. Ablated plasma is directed away from the coiled wire cores in a manner that can be understood in terms of Lorentz forces that arise from a complex current path modeled by 3D magnetohydrodynamic simulations. Outside the diameter of the helix, the flow of ablated plasma is axially modulated at the wavelength of the coil.

Hall, G. N.; Chittenden, J. P.; Bland, S. N.; Lebedev, S. V.; Bott, S. C.; Jennings, C.; Palmer, J. B. A.; Suzuki-Vidal, F. [Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom)

2008-02-15

243

A discontinuous Galerkin method for the two-fluid plasma system and its application to the Z-pinch  

NASA Astrophysics Data System (ADS)

An algorithm for simulation of 5 moment two-fluid plasma dynamics using the discontinuous Galerkin method is presented. The algorithm is developed in multiple dimensions arbitrary geometries and on parallel platforms. The explicit algorithm uses a second or third order spatial discretization with 3rd or 4th order time discretizations. Numerical issues associated with the two-fluid plasma system are discussed. The algorithm is validated with simulations of an electron acoustic pulse, an MHD shock and the GEM challenge magnetic reconnection problem. Full two-fluid simulations of a Z-pinch are also presented along with the identification of a fast growing instability that is accompanied by ion shock waves. The algorithm can be used as a basis for fully electromagnetic PIC, hybrid or higher moment fluid plasma codes. Though the algorithm is written for the full two-fluid system, the same technique can easily be applied to simpler plasma fluid models including two-fluid MHD, Hall MHD and MHD.

Loverich, John

244

Measurements of Ion Beam Production and Neutron Yields in the LLNL High Gradient Z-Pinch Experiment  

NASA Astrophysics Data System (ADS)

Dense plasma focus (DPF) z-pinch plasmas are known to produce abundant neutrons and particle beams, but the mechanisms behind the high gradient fields in DPFs are not well understood. We have a 4 MeV deuteron beam that can be used to probe the electric field gradients produced by the DPF experiment at LLNL. This information can be used in conjunction with fully kinetic simulations of DPF plasmas to further our understanding of the mechanisms that produce these beams. This knowledge allows us to optimize the gradients in the DPF for next generation compact accelerators. The beam and neutron output from the LLNL DPF have been characterized. We present measurements of beam and neutron production for a variety of pinch currents. Acceleration gradients greater than 0.5 MV/cm have been achieved, a record for sub-kJ DPFs. Our upgraded gun design allows a probe beam to pass through the plasma, allowing for the first-ever measurements of DPF gradients. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (11-ERD-063) at LLNL.

Ellsworth, J. L.; Falabella, S.; Rusnak, B.; Schmidt, A.; Tang, V.

2012-10-01

245

Numerical investigation on the implosion dynamics of wire-array Z-pinches in (r, {theta}) geometry  

SciTech Connect

The implosion dynamics of wire-array Z-pinches are investigated numerically in 2D (r, {theta}) geometry by using a resistive MHD code. It is assumed that the wires have expanded to plasmas with diameter d{sub 0}, which is used as the initial condition for the consequent implosion process. In fact, the explosion process of individual wires is not included. By changing d{sub 0}, the effects of the wire expansion degree on the implosion dynamics are analyzed. When d{sub 0} is larger, the current density is more concentrated at the outer side of the wires and the fraction of current flow around the wire plasmas is nearly in proportion to d{sub 0}. As a result, the ablation rate of wires is increased and the implosion phase starts earlier. This conclusion agrees with the simulation works of other authors [Chittenden et al., Phys. Plasmas 11(3), 1118 (2004)]. When the array radius and initial wire plasma diameter are fixed, the increase of wire number leads to the azimuthal merge of wires during implosion. When the wires number exceed a critical value, which is related to d{sub 0}, wire plasmas can merge to a continuous shell with an azimuthal perturbation in density, which depends on the initial wires number.

Huang Jun; Ding Ning; Ning Cheng; Sun Shunkai; Zhang Yang; Xiao Delong; Xue Chuang [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2012-06-15

246

Initial magnetic field compression studies using gas-puff Z-pinches and thin liners on COBRA  

NASA Astrophysics Data System (ADS)

This magnetic compression of cylindrical liners filled with DT gas has promise as an efficient way to achieve fusion burn using pulsed-power machines. However, to avoid rapid cooling of the fuel by transfer of heat to the liner an axial magnetic field is required. This field has to be compressed during the implosion since the thermal insulation is more demanding as the compressed DT plasma becomes hotter and its volume smaller. This compression of the magnetic field is driven both by the imploding liner and plasma. To highlight how this magnetic field compression by the plasma and liner evolves we have separately studied Z-pinch implosions generated by gas puff and liner loads. The masses of the gas puff and liner loads were adjusted to match COBRA's current rise times. Our results have shown that Ne gas-puff implosions are well described by a snowplow model where electrical currents are predominately localized to the outer surface of the imploding plasma and the magnetic field is external to the imploding plasma. Liner implosions are dominated by the plasma ablation process on the inside surface of the liner and the electrical currents and magnetic fields are advected into the inner plasma volume; the sharp radial gradient associated with the snowplow process is not present.

Gourdain, P.-A.; Concepcion, R. J.; Evans, M. T.; Greenly, J. B.; Hammer, D. A.; Hoyt, C. L.; Kroupp, E.; Kusse, B. R.; Maron, Y.; Novick, A. S.; Pikuz, S. A.; Qi, N.; Rondeau, G.; Rosenberg, E.; Schrafel, P. C.; Seyler, C. E.; Shelkovenko, T. C.

2013-08-01

247

Beryllium liner z-pinches for Magneto-Rayleigh--Taylor studies on Z.  

SciTech Connect

Magnetic Liner Inertial Fusion (MagLIF) [S. A. Slutz, et al., Phys. Plasmas 17 056303 (2010)] is a promising new concept for achieving >100 kJ of fusion yield on Z. The greatest threat to this concept is the Magneto-Rayleigh-Taylor (MRT) instability. Thus an experimental campaign has been initiated to study MRT growth in fast-imploding (<100 ns) cylindrical liners. The first sets of experiments studied aluminum liner implosions with prescribed sinusoidal perturbations (see talk by D. Sinars). By contrast, this poster presents results from the latest sets of experiments that used unperturbed beryllium (Be) liners. The purpose for using Be is that we are able to radiograph 'through' the liner using the 6-keV photons produced by the Z-Beamlet backlighting system. This has enabled us to obtain time-resolved measurements of the imploding liner's density as a function of both axial and radial location throughout the field of view. This data is allowing us to evaluate the integrity of the inside (fuel-confining) surface of the imploding liner as it approaches stagnation.

McBride, Ryan D.; Martin, Matthew Ryan; Vesey, Roger Alan; Lemke, Raymond William; Sinars, Daniel Brian; Herrmann, Mark C.; Jennings, Christopher A.; Cuneo, Michael Edward; Slutz, Stephen A.

2010-12-01

248

Neutron emission generated during wire array Z-pinch implosion onto deuterated fiber  

SciTech Connect

The implosion of both cylindrical and conical wire arrays onto a deuterated polyethylene fiber was studied on the S-300 pulsed power generator [A. S. Chernenko et al., Proceedings of the 11th International Conference on High Power Particle Beams (Academy of Science of Czech Republic, Prague, 1996), p. 154]. Neutron measurements were used to obtain information about acceleration of fast deuterons. An average neutron yield approached 10{sup 9} on the current level of 2 MA. In the case of conical wire arrays, side-on neutron energy spectra peaked at 2.48{+-}0.05 MeV with 450{+-}100 keV full width at half-maximum. In the downstream direction, the peak neutron energy and the width of a neutron spectrum were 2.65{+-}0.10 MeV and 350{+-}100 keV, respectively. The total number of fast deuterons was 10{sup 15} and their average kinetic energy was about 150 keV. Most of the deuterons were directed toward the cathode. The broad width of neutron spectra in the side-on direction implied a high radial component of deuteron velocity. With regard to the emission time, neutron pulses temporally correlated with hard x rays and also with measured voltage. The neutron emission lasted on average 30{+-}5 ns and it was observed during the stagnation and at the beginning of the expansion of a plasma column. At this moment, the plasma impedance reached 0.2-0.4 {omega}. In the post-stagnation phase, this value was formed significantly by enhanced plasma resistance. Similar experimental results were observed also with cylindrical wire arrays imploding onto a deuterated fiber.

Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K. [Czech Technical University, Faculty of Electrical Engineering, Department of Physics, Technicka 2, 166 27 Prague 6 (Czech Republic); Anan'ev, S. S.; Bakshaev, Yu. L.; Blinov, P. I.; Chernenko, A. S.; Kazakov, E. D.; Korolev, V. D.; Meshcherov, B. R.; Ustroev, G. I. [Russian Research Center, Kurchatov Institute, 1 Kurchatov Sq., 123182 Moscow (Russian Federation); Juha, L.; Krasa, J.; Velyhan, A. [Institute of Physics, Na Slovance 2, 182 21 Prague 8 (Czech Republic)

2008-03-15

249

Observed Multi-Decade DD and DT Z-Pinch Fusion Rate Scaling in 5 Dense Plasma Focus Fusion Machines  

SciTech Connect

Dense Plasma Focus (DPF) machines are in use worldwide or a wide variety of applications; one of these is to produce intense, short bursts of fusion via r-Z pinch heating and compression of a working gas. We have designed and constructed a series of these, ranging from portable to a maximum energy storage capacity of 2 MJ. Fusion rates from 5 DPF pulsed fusion generators have been measured in a single laboratory using calibrated activation detectors. Measured rates range from ~ 1015 to more than 1019 fusions per second have been measured. Fusion rates from the intense short (20 50 ns) periods of production were inferred from measurement of neutron production using both calibrated activation detectors and scintillator-PMT neutron time of flight (NTOF) detectors. The NTOF detectors are arranged to measure neutrons versus time over flight paths of 30 Meters. Fusion rate scaling versus energy and current will be discussed. Data showing observed fusion cutoff at D-D fusion yield levels of approximately 1?1012, and corresponding tube currents of ~ 3 MA will be shown. Energy asymmetry of product neutrons will also be discussed. Data from the NTOF lines of sight have been used to measure energy asymmetries of the fusion neutrons. From this, center of mass energies for the D(d,n)3He reaction are inferred. A novel re-entrant chamber that allows extremely high single pulse neutron doses (> 109 neutrons/cm2 in 50 ns) to be supplied to samples will be described. Machine characteristics and detector types will be discussed.

Hagen, E. C. [National Security Technologies, LLC; Lowe, D. R. [National Security Technologies, LLC; O'Brien, R. [University of Nevada, Las Vegas; Meehan, B. T. [National Security Technologies, LLC

2013-06-18

250

Evidence and mechanisms of axial-radiation asymmetry in dynamic hohlraums driven by wire-array Z pinches  

SciTech Connect

Dynamic hohlraums driven by arrays consisting of large numbers of tungsten wires in Z pinches exhibit differences in radiation emitted from REHs (radiation exit holes) symmetrically located at either end of the hohlraum [Sanford et al., Phys. Plasmas 10, 1187 (2003)]. Significantly greater peak power is radiated from the top (anode) REH relative to the bottom (cathode) REH. Spectral measurements of tungsten M-shell emission (2-2.4 keV) indicate the peak radiated power from either REH anticorrelates with the fraction of wire-array tungsten plasma inferred to sweep across (or into the field of view of) the REH near the time of peak axial emission. In all cases, greater M-shell emission relative to the total emission in the band 1.4-4 keV is measured at the bottom REH in comparison to the top REH. The decrease in peak power radiated from the bottom REH relative to the top appears to be due, in part, to an increase in localized opacity arising from the presence of increased wire-array tungsten plasma near the bottom REH. The asymmetry in both peak axial power and pulse shape is largely removed by adding two thin annular pedestals extending 3 mm into the anode-cathode gap from either electrode, just radially outboard of the REHs. The pedestals are designed to prevent the radial flow of tungsten plasma from prematurely crossing the REHs. A polarity effect [Sarkisov et al., Phys. Rev. E 66, 046413(6) (2002)] during wire initiation may offer one possible explanation for the underlying cause of such a tungsten-related axial power asymmetry.

Sanford, T.W.L.; Nash, T.J.; Mock, R.C.; Peterson, D.L.; Watt, R.G.; Chrien, R.E.; Apruzese, J.P.; Clark, R.W.; Roderick, N.F.; Sarkisov, G.S.; Haines, M.G. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Naval Research Laboratory, Washington, DC 20375 (United States); University of New Mexico, Albuquerque, New Mexico 87131 (United States); Ktech Corporation, Albuquerque, 1030 Eubank Boulevard, Albuquerque, New Mexico 87123 (United States); Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2005-02-01

251

THE WIRE ARRAY Z-PINCH: AN EFFICIENT X-RAY SOURCE FOR ICF AND A NEW ION HEATING MECHANISM  

SciTech Connect

The Z-pinch provides an efficient x-ray source for driving a hohlraum for inertial confinement fusion. The basic physics of wire-array implosions is reviewed. It can be understood in several sequential stages. First, the wires heat and form a surrounding vapor which ionizes, causing the current to transfer to this lower resistance. The JxB global force leads to ejection of this plasma towards the axis to form a precursor plasma. The wire cores continue to ablate due to the heat flux from the Joule-heated nearby plasma. The cooling of this plasma by the wire-cores leads to a low magnetic Reynolds number so that the precursor plasma carries little or no current. When gaps appear in the liquid/vapor cores the plasma temperature and Reynolds' number rise and this plasma accelerates in towards the axis carrying the current. This is the main implosion, and it sweeps up earlier ablated plasma, which acts to reduce Rayleigh-Taylor growth. At stagnation the ion kinetic energy is thermalised and equipartition heats the electrons, which then radiate in a 5 ns pulse. In some conditions the energy radiated as soft x-rays exceeds the ion kinetic energy by a factor of 3 or 4. A theory has been developed to explain this in which fine-scale, fast growing m = 0 MHD instabilities grow to saturation, viscous dissipation of which leads to ion heating, followed by equipartition. World record ion temperatures of 2 to 3 billion Kelvin were predicted, and measured at Sandia National Laboratory. Lastly progress in capsule implosions and in application to inertial fusion energy is reported.

Haines, M. G. [Blackett Laboratory, Imperial College, London SW7 2BZ United Kingdom (United Kingdom)

2009-07-26

252

The high-density Z-pinch as a pulsed fusion neutron source for fusion nuclear technology and materials testing  

SciTech Connect

The dense Z-pinch (DZP) is one of the earliest and simplest plasma heating and confinement schemes. Recent experimental advances based on plasma initiation from hair-like (10s ..mu..m in radius) solid hydrogen filaments have so far not encountered the usually devastating MHD instabilities that plagued early DZP experiments. These encouraging results along with debt of a number of proof-of principle, high-current (1--2 MA in 10--100 ns) experiments have prompted consideration of the DZP as a pulsed source of DT fusion neutrons of sufficient strength (/dot S//sub N/ greater than or equal to 10/sup 19/ n/s) to provide uncollided neutron fluxes in excess of I/sub ..omega../ = 5--10 MW/m/sup 2/ over test volumes of 10--30 litre or greater. While this neutron source would be pulsed (100s ns pulse widths, 10--100 Hz pulse rate), giving flux time compressions in the range 10/sup 5/--10/sup 6/, its simplicity, near-time feasibility, low cost, high-Q operation, and relevance to fusion systems that may provide a pulsed commercial end-product (e.g., inertial confinement or the DZP itself) together create the impetus for preliminary considerations as a neutron source for fusion nuclear technology and materials testings. The results of a preliminary parametric systems study (focusing primarily on physics issues), conceptual design, and cost versus performance analyses are presented. The DZP promises an expensive and efficient means to provide pulsed DT neutrons at an average rate in excess of 10/sup 19/ n/s, with neutron currents I/sub ..omega../ /approx lt/ 10 MW/m/sup 2/ over volumes V/sub exp/ greater than or equal to 30 litre using single-pulse technologies that differ little from those being used in present-day experiments. 34 refs., 17 figs., 6 tabs.

Krakowski, R.A.; Sethian, J.D.; Hagenson, R.L.

1989-01-01

253

Z-Pinch Generated X-Rays in Static-Wall Hohlraum Geometry Demonstrate Potential for Indirect-Drive ICF Studies  

SciTech Connect

Hohlraums of full ignition scale (6-mm diameter by 7-mm length) have been heated by x-rays from a z-pinch magnet on Z to a variety of temperatures and pulse shapes which can be used to simulate the early phases of the National Ignition Facility (NIF) temperature drive. The pulse shape is varied by changing the on-axis target of the z pinch in a static-wall-hohlraum geometry. A 2-{micro}m-thick walled Cu cylindrical target of 8-mm diameter filled with 10 mg/cm{sup 3} CH, for example, produces foot-pulse conditions of {approx}85 eV for a duration of {approx}10 ns, while a solid cylindrical target of 5-mm diameter and 14-mg/cm{sup 3} CH generates first-step-pulse conditions of {approx}122 eV for a duration of a few ns. Alternatively, reducing the hohlraum size (to 4-mm diameter by 4-mm length) with the latter target has increased the peak temperature to {approx}150 eV, which is characteristic of a second-step-pulse temperature. In general, the temperature T of these x-ray driven hohlraums is in agreement with the Planckian relation T{approx}(P/A){sup 1/4}. P is the measured x-ray input power and A is the surface area of the hohlraum. Fully-integrated 2-D radiation-hydrodynamic simulations of the z pinch and subsequent hohlraum heating show plasma densities within the useful volume of the hohlraums to be on the order of air or less.

BOWERS,RICHARD; CHANDLER,GORDON A.; HEBRON,DAVID E.; LEEPER,RAMON J.; MATUSLKA,WALTER; MOCK,RAYMOND CECIL; NASH,THOMAS J.; OLSON,CRAIG L.; PETERSON,BOB; PETERSON,DARRELL; RUGGLES,LAURENCE E.; SANFORD,THOMAS W. L.; SIMPSON,WALTER W.; STRUVE,KENNETH W.; VESEY,ROGER A.

1999-11-01

254

Studying Radiation from Z-pinch Wire Array and X-Pinch Plasmas: K-shell Mg to M-shell Mo  

SciTech Connect

University-scale Z-pinch generators are able to produce plasmas with a broad range of temperatures, densities, and opacity properties depending on the type, size, and mass of wire-array loads and wire materials. Experiments with very different Z-pinch loads were performed on the 1 MA Zebra generator at UNR and analyzed during the last five years including Single and Nested Cylindrical, Conical, and various types of Planar Wire Arrays. It is shown that such wire arrays are good sources of x-rays and that they produce significant radiation yield (up to 25 kJ) on a ns time scale, and generate bright spots of sub-mm size. They can be used for studying radiative properties of moderate density (between 10{sup 18} cm{sup -3} and 5x10{sup 21} cm{sup -3}) and temperature (<=1.5 keV) plasmas. In addition, X-pinches generated higher density (>10{sup 22} cm{sup -3}) and temperature (>2 keV) plasmas on scales as small as a few mum to several mm in size. Wire materials with a broad range of nuclear charge Z were used, ranging from low-Z, such as alloyed Al wires with varying concentrations of Mg, to mid-Z, such as Stainless steel, Cu, Brass, and Mo. Uniform (made from one wire material) as well as combined (made from two wire materials with almost equal wire masses) wire arrays were considered. Uniform, combined, symmetric and asymmetric X-pinches (some of which included a small fraction of tracer Al wires) were also considered. Non-LTE kinetic models to account for K- and L-shell radiation were employed to understand radiative properties of Z-pinch and X-pinch plasmas. Implosion characteristics of such loads are discussed using the wire dynamics and MHD models. Opacity effects of Z-pinch plasmas are studied and benefits of using alloyed and tracer wires are highlighted.

Safronova, A. S.; Kantsyrev, V. L.; Safronova, U. I.; Esaulov, A. A.; Yilmaz, M. F.; Ouart, N. D.; Shrestha, I.; Williamson, K. W.; Osborne, G. C.; Wilcox, P. G.; Weller, M. E.; Shlyaptseva, V. [University of Nevada, Reno, NV 89557 (United States); Coverdale, C. A.; Jones, B.; Ampleford, D. J. [Sandia National Laboratories Albuquerque, NM 87185 (United States); LePell, P. D. [KTech Corporation, Albuquerque, NM 87123 (United States); Deeney, C. [NNSA/DOE, Headquarters, Washington, DC 20585 (United States)

2009-09-10

255

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

SciTech Connect

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 50 ns.

Sakai, Y.; Kumai, H.; Nakanishi, Y.; Ishizuka, Y.; Takahashi, S.; Komatsu, T.; Xiao, Y.; Bin, H.; Quishi, Z.; Hayashi, Y.; Song, I.; Kawamura, T.; Watanabe, M.; Hotta, E. [Department of Energy Sciences, Tokyo Institute of Technology, Nagatsuta, Midoriku, Yokohama, Kanagawa 226-8502 (Japan); Rosenzweig, J. [Department of Physics and Astronomy, University of California Los Angeles, 405 Hilgard Ave., Los Angeles, California 90095 (United States)

2013-02-15

256

Measurements of the mass distribution and instability growth for wire-array Z-pinch implosions driven by 14-20 MA  

SciTech Connect

The mass distribution and axial instability growth of wire-array Z-pinch implosions driven by 14-20 MA has been studied using high-resolution, monochromatic x-ray backlighting diagnostics. A delayed implosion is consistently observed in which persistent, dense wire cores continuously ablate plasma until they dissipate and the main implosion begins. In arrays with small interwire gaps, azimuthally correlated axial instabilities appear during the wire ablation stage and subsequently seed the early growth of magneto-Rayleigh-Taylor instabilities. The instabilities create a distributed implosion front with trailing mass that may limit the peak radiation power.

Sinars, D.B.; Cuneo, M.E.; Jones, B.; Coverdale, C.A.; Nash, T.J.; Mazarakis, M.G.; Porter, J.L.; Deeney, C.; Wenger, D.F.; Adams, R.G.; Yu, E.P.; Bliss, D.E.; Sarkisov, G.S. [Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185 (United States)

2005-05-15

257

Pulsed current wave shaping with a transmission line by utilizing superposition of a forward and a backward voltage wave for fast capillary Z-pinch discharge.  

PubMed

By using a water transmission line, current wave shaping was demonstrated for a fast capillary Z-pinch discharge recombination soft x-ray laser study. The pulsed power system consists of a water capacitor, a gap switch, a transmission line, and a capillary plasma load. A voltage wave initiated at the water capacitor propagates toward the capillary load through the transmission line. Control of the pulse delay that occurred in the transmission line provides the superposition of the forward and the backward voltage waves effectively in order to perform current wave shaping with higher current amplitude and rapid current decay. PMID:20441338

Sakai, Y; Takahashi, S; Watanabe, M; Kim, G-H; Hotta, E

2010-04-01

258

Observations of modified three-dimensional instability structure for imploding z-pinch liners that are premagnetized with an axial field.  

PubMed

Novel experimental data are reported that reveal helical instability formation on imploding z-pinch liners that are premagnetized with an axial field. Such instabilities differ dramatically from the mostly azimuthally symmetric instabilities that form on unmagnetized liners. The helical structure persists at nearly constant pitch as the liner implodes. This is surprising since, at the liner surface, the azimuthal drive field presumably dwarfs the axial field for all but the earliest stages of the experiment. These fundamentally 3D results provide a unique and challenging test for 3D-magnetohydrodynamics simulations. PMID:24476283

Awe, T J; McBride, R D; Jennings, C A; Lamppa, D C; Martin, M R; Rovang, D C; Slutz, S A; Cuneo, M E; Owen, A C; Sinars, D B; Tomlinson, K; Gomez, M R; Hansen, S B; Herrmann, M C; McKenney, J L; Nakhleh, C; Robertson, G K; Rochau, G A; Savage, M E; Schroen, D G; Stygar, W A

2013-12-01

259

Anisotropy of energy losses in high-current Z-pinches produced by the implosion of cylindrical tungsten wire arrays  

NASA Astrophysics Data System (ADS)

Results are presented from measurements of the anisotropy of energy losses in high-current Z-pinches produced by the implosion of wire arrays at the ANGARA-5-1 facility at load currents of up to 4MA. The energy losses were measured in the radial direction and along the pinch axis from the anode side. The main diagnostics were time-integrated thermocouple calorimeters, nanosecond X-ray diodes (XRDs) with different filters, and a foil radiation calorimeter with a time resolution of 2 ?s. The azimuthal anisotropy of energy losses was measured for different wire array configurations and different shapes of the high-voltage electrode. The presence of strong initial azimuthal inhomogeneity of the wire mass distribution (sectioned arrays), as well as the use of conical electrodes instead of plane ones, does not increase the azimuthal inhomogeneity of the total energy losses. For cylindrical wire arrays, energy losses in the radial direction are compared with those along the pinch axis. According to XRD and calorimetric measurements, the radiation yield per unit solid angle along the pinch axis is two to three times lower than that in the radial direction. In the axial direction, the energy flux density of the expanding plasma is two to three times lower than the radiation intensity. The measured radiation yield across the pinch is 2.5-5 kJ/sr, while that along the pinch axis is 1-2 kJ/sr. The results obtained by means of XRDs agree to within measurement errors with those obtained using the radiation calorimeter. It is found that the energy per unit solid angle carried by the expanding plasma in the radial direction does not exceed 10% of the soft X-ray yield. Analysis of the structure of time-integrated pinhole images and signals from the radial and axial XRDs shows that radiation emitted in the radial direction from the hot central region of the pinch is partially screened by the less dense surrounding plasma halo, whereas radiation emitted in the axial direction is a superposition of the emissions from the hot dense central region of the pinch and the colder less dense peripheral plasma.

Aleksandrov, V. V.; Volkov, G. S.; Grabovski, E. V.; Gritsuk, A. N.; Lakhtyushko, N. I.; Medovshchikov, S. F.; Oleinik, G. M.; Svetlov, E. V.

2014-02-01

260

Comparison of Deuterium-Deuterium-Deuterium and Neon-Deuterium-Deuterium Triple Shell Gas-Puff Z-pinch on the Level of 3 MA  

NASA Astrophysics Data System (ADS)

The experiments of a triple shell gas-puff Z-pinch were carried out on the GIT-12 generator at IHCE in Tomsk during the April-May-June campaign in 2012. We diagnosed 17 Z-pinch shots where the triple D2-D2-D2 (with the linear mass in the range of 50 - 255 ?g/cm) and Ne-D2-D2 (with the linear mass in the range of 110 - 285 ?g/cm) gas-puffs with diameter of 160 mm / 80 mm / 30 mm were mostly used as loads. This contribution is focused on the comparison of the results obtained by X-ray and neutron diagnostics, especially to the difference in reconstructed neutron energy spectra and obtained neutron yields (with the maximum of 3.3 x10^11 neutrons/shot on a current level of 2.5 MA). The time correlations with other diagnostics such as electrical characteristics, a visible streak camera and MCP frames are also presented.

Rezac, K.; Klir, Daniel; Kubes, P.; Kravarik, J.; Shishlov, A.; Labetsky, A.; Ratakhin, N.

2012-10-01

261

Simulation and mitigation of the magneto-Rayleigh-Taylor instabilities in Z-pinch gas discharge extreme ultraviolet plasma radiation sources  

SciTech Connect

The development and use of a single-fluid two-temperature approximated 2-D Magneto-Hydrodynamics code is reported. Z-pinch dynamics and the evolution of Magneto-Rayleigh-Taylor (MRT) instabilities in a gas jet type Extreme Ultraviolet (EUV) source are investigated with this code. The implosion and stagnation processes of the Z-pinch dynamics and the influence of initial perturbations (single mode, multi- mode, and random seeds) on MRT instability are discussed in detail. In the case of single mode seeds, the simulation shows that the growth rates for mm-scale wavelengths up to 4 mm are between 0.05 and 0.065 ns{sup ?1}. For multi-mode seeds, the mode coupling effect leads to a series of other harmonics, and complicates MRT instability evolution. For perturbation by random seeds, the modes evolve to longer wavelengths and finally converge to a mm-scale wavelength approximately 1 mm. MRT instabilities can also alter the pinch stagnation state and lead to temperature and density fluctuations along the Z axis, which eventually affects the homogeneity of the EUV radiation output. Finally, the simulation results are related to experimental results to discuss the mitigations of MRT instability.

Huang, B.; Tomizuka, T.; Xie, B.; Sakai, Y.; Zhu, Q.; Song, I.; Okino, A.; Xiao, F.; Watanabe, M.; Hotta, E. [Department of Energy Sciences, Tokyo Institute of Technology, 4259 J2-35 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)] [Department of Energy Sciences, Tokyo Institute of Technology, 4259 J2-35 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

2013-11-15

262

Use of X-pinches of diagnose behavior of low density CH foams on axis of wire array Z-pinches  

SciTech Connect

X-pinch radiography was used to analyze the interaction between streams of coronal plasma and on-axis foam targets in wire array z-pinch experiments on the MAGPIE generator (1 MA,240 ns). The implosion of the x-pinch, used in place of a current return conductor to the load, provided a short (<2 s) small ({approx}5 {mu}m) intense burst of soft x-rays, ideal for point projection backlighting. Timimg of the x-pinch was adjusted via the mass of its wires, allowing us to study the evolution of the foam during the experiment. Choice of the x-pinch materials, filters, and recording film determined the probing radiation, and hence the plasma/foam densities were resolved. Quantitative results will be discussed.

Bott, S.C.; Palmer, J.B.A.; Ampleford, D.J.; Bland, S.N.; Chittenden, J.P.; Lebedev, S.V. [Blackett Laboratory, Imperial College, London, SW7 2BZ, United Kingdom and AWE Plc., Aldermaston, RG7 4PR (United Kingdom)

2004-10-01

263

COBRA-STAR, a five frame point-projection x-ray imaging system for 1 MA scale wire-array Z pinches.  

PubMed

A new imaging system for 1 MA scale wire-array Z-pinch experiments that produces up to five high-resolution x-ray images per experimental pulse has been developed. Calibrated areal density measurements of the Z-pinch plasma can be obtained from each pulse. The system substitutes five molybdenum (Mo) X pinches for the normal copper return-current conductors to provide point sources of x-rays for point-projection radiography. Each backlighting X pinch consists of four Mo wires, the x-ray burst timing of which was controlled by varying the wire diameter (mass) from 10.2 to 30 microm in the five X pinches. Typical images have a 16x8 mm2 field of view at the wire array and a magnification of about 6.5:1 on the x-ray-sensitive film. Titanium (Ti) filters in front of the films transmit continuum radiation in the spectral range of 3-5 keV. Inclusion on the Ti of a step wedge having known thickness increments of the same material as the wires enables the calibrated areal density measurements to be made of the exploding wire plasmas. Here, we used tungsten (W) step wedges with step thicknesses ranging from 0.015 to 1.1 microm to obtain accurate (+/-10%) areal density measurements of W plasmas from the spatial profile of film exposure. When imaging arrays that produce intense radiation pulses, a plastic monofilament "quencher" is placed on axis to avoid film saturation. Images have subnanosecond temporal resolution and about 7 microm spatial resolution. PMID:18377006

Douglass, J D; Hammer, D A

2008-03-01

264

COBRA-STAR, a five frame point-projection x-ray imaging system for 1 MA scale wire-array Z pinches  

NASA Astrophysics Data System (ADS)

A new imaging system for 1MA scale wire-array Z-pinch experiments that produces up to five high-resolution x-ray images per experimental pulse has been developed. Calibrated areal density measurements of the Z-pinch plasma can be obtained from each pulse. The system substitutes five molybdenum (Mo) X pinches for the normal copper return-current conductors to provide point sources of x-rays for point-projection radiography. Each backlighting X pinch consists of four Mo wires, the x-ray burst timing of which was controlled by varying the wire diameter (mass) from 10.2to30?m in the five X pinches. Typical images have a 168mm2 field of view at the wire array and a magnification of about 6.5:1 on the x-ray-sensitive film. Titanium (Ti) filters in front of the films transmit continuum radiation in the spectral range of 3-5keV. Inclusion on the Ti of a step wedge having known thickness increments of the same material as the wires enables the calibrated areal density measurements to be made of the exploding wire plasmas. Here, we used tungsten (W) step wedges with step thicknesses ranging from 0.015to1.1?m to obtain accurate (10%) areal density measurements of W plasmas from the spatial profile of film exposure. When imaging arrays that produce intense radiation pulses, a plastic monofilament "quencher" is placed on axis to avoid film saturation. Images have subnanosecond temporal resolution and about 7?m spatial resolution.

Douglass, J. D.; Hammer, D. A.

2008-03-01

265

COBRA-STAR, a five frame point-projection x-ray imaging system for 1 MA scale wire-array Z pinches  

SciTech Connect

A new imaging system for 1 MA scale wire-array Z-pinch experiments that produces up to five high-resolution x-ray images per experimental pulse has been developed. Calibrated areal density measurements of the Z-pinch plasma can be obtained from each pulse. The system substitutes five molybdenum (Mo) X pinches for the normal copper return-current conductors to provide point sources of x-rays for point-projection radiography. Each backlighting X pinch consists of four Mo wires, the x-ray burst timing of which was controlled by varying the wire diameter (mass) from 10.2 to 30 {mu}m in the five X pinches. Typical images have a 16x8 mm{sup 2} field of view at the wire array and a magnification of about 6.5:1 on the x-ray-sensitive film. Titanium (Ti) filters in front of the films transmit continuum radiation in the spectral range of 3-5 keV. Inclusion on the Ti of a step wedge having known thickness increments of the same material as the wires enables the calibrated areal density measurements to be made of the exploding wire plasmas. Here, we used tungsten (W) step wedges with step thicknesses ranging from 0.015 to 1.1 {mu}m to obtain accurate ({+-}10%) areal density measurements of W plasmas from the spatial profile of film exposure. When imaging arrays that produce intense radiation pulses, a plastic monofilament ''quencher'' is placed on axis to avoid film saturation. Images have subnanosecond temporal resolution and about 7 {mu}m spatial resolution.

Douglass, J. D.; Hammer, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2008-03-15

266

New X-ray backlighting results on small-scale structure formation, including liquid-vapor foam-like appearance, in exploding wire Z-pinches and X-pinches  

Microsoft Academic Search

Summary form only given. Exploding wire and wire array experiments have been carried out in Z-pinch and X-pinch geometry using low current (4.5 kA amplitude, 1.4 ps period damped sinusoid) and high current (up to 225 kA, 100 ns) drivers. X-ray backlighter images have been obtained using Mg, Al, Ti, Fe, Ni, NiCr, Cu, brass, Mo, Pd, Ag, Ta, W,

S. A. Pikuz; T. A. Shelkovenko; D. A. Hammer; D. B. Sinars; Y. S. Dimant; J. B. Greenly

1999-01-01

267

Bow shocks in ablated plasma streams for nested wire array z-pinches: A laboratory astrophysics testbed for radiatively cooled shocks  

NASA Astrophysics Data System (ADS)

Astrophysical observations have demonstrated many examples of bow shocks, for example, the head of protostellar jets or supernova remnants passing through the interstellar medium or between discrete clumps in jets. For such systems where supersonic and super-Alfvnic flows and radiative cooling are all important, carefully scaled laboratory experiments can add insight into the physical processes involved. The early stage of a wire array z-pinch implosion consists of the steady ablation of material from fine metallic wires. Ablated material is accelerated toward the array axis by the JB force. This flow is highly supersonic (M>5) and becomes super-Alfvnic (MA>2). Radiative cooling is significant in this flow and can be controlled by varying the material in the ablated plasma. The introduction of wires as obstructions in this steady flow leads to the formation of bow shocks, which can be used as a laboratory testbed for astrophysical bow shocks. The magnetic field associated with this obstruction wire can be controlled by varying the current through it. Differences in the shock for different cooling rates and different magnetic fields associated with the obstruction will be discussed, along with comparisons of dimensionless parameters in the experiments to astrophysical systems.

Ampleford, D. J.; Jennings, C. A.; Hall, G. N.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Suzuki-Vidal, F.; Palmer, J. B. A.; Chittenden, J. P.; Cuneo, M. E.; Frank, A.; Blackman, E. G.; Ciardi, A.

2010-05-01

268

Bow shocks in ablated plasma streams for nested wire array z-pinches: A laboratory astrophysics testbed for radiatively cooled shocks  

SciTech Connect

Astrophysical observations have demonstrated many examples of bow shocks, for example, the head of protostellar jets or supernova remnants passing through the interstellar medium or between discrete clumps in jets. For such systems where supersonic and super-Alfvenic flows and radiative cooling are all important, carefully scaled laboratory experiments can add insight into the physical processes involved. The early stage of a wire array z-pinch implosion consists of the steady ablation of material from fine metallic wires. Ablated material is accelerated toward the array axis by the JxB force. This flow is highly supersonic (M>5) and becomes super-Alfvenic (M{sub A}>2). Radiative cooling is significant in this flow and can be controlled by varying the material in the ablated plasma. The introduction of wires as obstructions in this steady flow leads to the formation of bow shocks, which can be used as a laboratory testbed for astrophysical bow shocks. The magnetic field associated with this obstruction wire can be controlled by varying the current through it. Differences in the shock for different cooling rates and different magnetic fields associated with the obstruction will be discussed, along with comparisons of dimensionless parameters in the experiments to astrophysical systems.

Ampleford, D. J.; Jennings, C. A.; Cuneo, M. E. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1106 (United States); Hall, G. N.; Lebedev, S. V.; Bland, S. N.; Suzuki-Vidal, F.; Palmer, J. B. A.; Chittenden, J. P. [Blackett Laboratory, Imperial College, London SW7 2BW (United Kingdom); Bott, S. C. [Center for Energy Research, University of California, San Diego, La Jolla, California 92093 (United States); Frank, A.; Blackman, E. G. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States) and Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627 (United States); Ciardi, A. [LERMA, Universite Pierre et Marie Curie, Observatoire de Paris, 5 Place Jules Janssen, Meudon 92195 (France)

2010-05-15

269

K-shell and extreme ultraviolet spectroscopic signatures of structured Ar puff Z-pinch loads with high K-shell x-ray yield  

SciTech Connect

Structured 12-cm-diam Ar gas-puff loads have recently produced Z-pinch implosions with reduced Rayleigh-Taylor instability growth and increased K-shell x-ray yield [H. Sze, J. Banister, B. H. Failor, J. S. Levine, N. Qi, A. L. Velikovich, J. Davis, D. Lojewski, and P. Sincerny, Phys. Rev. Lett. 95, 105001 (2005)]. To better understand the dynamics of these loads, we have measured the extreme ultraviolet (XUV) emission resolved radially, spectrally, and axially. Radial measurements indicated a compressed diameter of {approx_equal}3 mm, consistent with the observed load inductance change and an imploded-mass consisting of a {approx_equal}1.5-mm-diam, hot, K-shell-emitting core and a cooler surrounding blanket. Spectral measurements indicate that, if the load is insufficiently heated, then radiation from the core will rapidly photoheat the outer blanket, producing a strong increase in XUV emission. Also, adding a massive center jet ({>=}20% of load mass) increases the rise and fall times of the XUV emission to {>=}40 ns, consistent with a more adiabatic compression and heating of the load. Axial measurements show that, despite differences in the XUV and K-shell emission time histories, the K-shell x-ray yield is insensitive to axial variations in load mass.

Failor, B. H.; Sze, H. M.; Banister, J. W.; Levine, J. S.; Qi, N.; Apruzese, J. P.; Lojewski, D. Y. [L-3 Communications/Pulse Sciences, San Leandro, California 94577 (United States); Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Defense Threat Reduction Agency, Albuquerque, New Mexico 87117 (United States)

2007-02-15

270

Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.  

SciTech Connect

Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot z-pinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO{sub 2} production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber. Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-of-Principle) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is demonstrated at the SNL Z-IFE LTD laboratory with rep-rates up to 10.3 seconds between shots (this is essentially at the goal of 10 seconds for Z-IFE). (7) A single LTD switch at Tomsk was fired repetitively every 12 seconds for 36,000 shots with no failures. (8) Five 1.0 MA, 100 kV, 100 ns, LTD cavities have been combined into a voltage adder configuration with a test load to successfully study the system operation. (9) The combination of multiple LTD coaxial lines into a tri-plate transmission line is examined. The 3D Quicksilver code is used to study the electron flow losses produced near the magnetic nulls that occur where coax LTD lines are added together. (10) Circuit model codes are used to model the complete power flow circuit with an inductive isolator cavity. (11) LTD architectures are presented for drivers for Z-IFE and high yield. A 60 MA LTD driver and a 90 MA LTD driver are proposed. Present results from all of these power flow studies validate the whole LTD/RTL concept for single-shot ICF high yield, and for repetitive-shot IFE.

Sharpe, Robin Arthur; Kingsep, Alexander S. (Kurchatov Institute, Moscow, Russia); Smith, David Lewis; Olson, Craig Lee; Ottinger, Paul F. (Naval Research Laboratory, Washington, DC); Schumer, Joseph Wade (Naval Research Laboratory, Washington, DC); Welch, Dale Robert (Voss Scientific, Albuquerque, NM); Kim, Alexander (High Currents Institute, Tomsk, Russia); Kulcinski, Gerald L. (University of Wisconsin, Madison, WI); Kammer, Daniel C. (University of Wisconsin, Madison, WI); Rose, David Vincent (Voss Scientific, Albuquerque, NM); Nedoseev, Sergei L. (Kurchatov Institute, Moscow, Russia); Pointon, Timothy David; Smirnov, Valentin P. (Kurchatov Institute, Moscow, Russia); Turgeon, Matthew C.; Kalinin, Yuri G. (Kurchatov Institute, Moscow, Russia); Bruner, Nichelle "Nicki" (Voss Scientific, Albuquerque, NM); Barkey, Mark E. (University of Alabama, Tuscaloosa, AL); Guthrie, Michael (University of Wisconsin, Madison, WI); Thoma, Carsten (Voss Scientific, Albuquerque, NM); Genoni, Tom C. (Voss Scientific, Albuquerque, NM); Langston, William L.; Fowler, William E.; Mazarakis, Michael Gerrassimos

2007-01-01

271

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)

The Sphinx machine[1] is a 6 MA, 1 ?S 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 ? 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.

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

2009-01-01

272

High power fiber lasers  

Microsoft Academic Search

We discuss fundamental aspects of high-power fiber lasers and describe their recent dramatic advances and prospects including our up-to-date experimental results with particular attention to kilowatt-class, refined power amplifier regimes.

Y. Jeong; J. Nilsson; J. K. Sahu; P. Dupriez; C. A. Codemard; D. B. S. Soh; C. Farrell; J. Kim; D. J. Richardson; D. N. Payne

2005-01-01

273

Influence of insulating coating on aluminum wire explosions  

NASA Astrophysics Data System (ADS)

Single wire explosions are widely used in understanding the early stages of z-pinch experiments. This paper presents a serial of experiments conducted on the pulse power generator with 1 kA peak current and 10 ns rising time in Xi'an Jiao Tong University. Polyimide coated aluminum wires and uncoated ones were tested under three different voltages to analyze the effect of insulating coating. Experimental results showed that insulating coating can increase the energy deposition 10%30% in aluminum wires by delaying the voltage collapse and raising the maximum load resistance. The substantial energy deposition resulted in about 20% faster expansion rates for coated wires. Experimental evidence that plasma channel shunts the current from the wire core was observed by streak camera and schlieren graphs. This paper also briefly discussed the influence of nonuniform coating on the morphology of wire expansion.

Li, Yang; Sheng, Liang; Wu, Jian; Li, Xingwen; Zhao, Jizhen; Zhang, Mei; Yuan, Yuan; Peng, Bodong

2014-10-01

274

High Power Hall Thrusters  

NASA Technical Reports Server (NTRS)

The development of Hall thrusters with powers ranging from tens of kilowatts to in excess of one hundred kilowatts is considered based on renewed interest in high power. high thrust electric propulsion applications. An approach to develop such thrusters based on previous experience is discussed. It is shown that the previous experimental data taken with thrusters of 10 kW input power and less can be used. Potential mass savings due to the design of high power Hall thrusters are discussed. Both xenon and alternate thruster propellant are considered, as are technological issues that will challenge the design of high power Hall thrusters. Finally, the implications of such a development effort with regard to ground testing and spacecraft intecrati'on issues are discussed.

Jankovsky, Robert; Tverdokhlebov, Sergery; Manzella, David

1999-01-01

275

High power density targets  

NASA Astrophysics Data System (ADS)

In the context of new generation rare isotope beam facilities based on high-power heavy-ion accelerators and in-flight separation of the reaction products, the design of the rare isotope production targets is a major challenge. In order to provide high-purity beams for science, high resolution is required in the rare isotope separation. This demands a small beam spot on the production target which, together with the short range of heavy ions in matter, leads to very high power densities inside the target material. This paper gives an overview of the challenges associated with this high power density, discusses radiation damage issues in targets exposed to heavy ion beams, and presents recent developments to meet some of these challenges through different projects: FAIR, RIBF and FRIB which is the most challenging. Extensive use of Finite Element Analysis (FEA) has been made at all facilities to specify critical target parameters and R&D work at FRIB successfully retired two major risks related to high-power density and heavy-ion induced radiation damage.

Pellemoine, Frederique

2013-12-01

276

New x-ray backlighting results on small-scale structure formation, including liquid-vapor foam-like appearance, in exploding wire Z-pinches and X-pinches  

SciTech Connect

Exploding wire and wire array experiments have been carried out in Z-pinch and X-pinch geometry using low current (4.5kA amplitude, 1.4 {micro}s period damped sinusoid) and high current (up to 225 kA, 100 ns) drivers, X-ray backlighter images have been obtained using Mg, Al, Ti, Fe, Ni, NiCr, Cu, brass, Mo, Pd, Ag, Ta, W, Pt, Au, and Ni-coated Ti wires with initial diameters ranging from 7.5 {micro}m (W) to 46 {micro}m (Mg). There were typically two Mo X-pinch x-ray backlighters which generated pulses of <0.5 ns duration from sources small enough to allow resolution of {approximately}1 {micro}m scale structure in the resulting images. In the high current experiments, images of dense cores within coronal plasmas are obtained with higher Z materials including Ni, Cu, Mo, Pd, Ta, W, Pt and Au; with lower Z materials, only the dense cores are visible in the backlighter images. In all cases a fine structure in the interior of the dense cores, and/or surface instabilities are observed. some of the dense cores show a shock-wave-like structure and others show gaps that open up more rapidly than the wire cores are expanding. The wire interiors develop a foam-like liquid-vapor mix, with some of the bubbles breaching the surface and spewing vapor out of the dense core. The low current experiments follow the same general behavior but require several {mu}s to complete the process instead of 50--100ns. With W and Al wire explosions, step wedges have been used to permit calibrated density measurements to be made of the core (W and Al) and coronal (W) plasmas. The two X-pinches have also been used to radiograph each other, yielding high resolution images of the on-axis collapsing z-pinch and minidiode formation at the X-pinch cross point very close to the time of x-ray burst emission.

Pikuz, S.A.; Shelkovenko, T.A.; Hammer, D.A.; Sinars, D.B.; Dimant, Y.S.; Greenly, J.B.

1999-07-01

277

Progress in symmetric ICF capsule implosions and wire-array z-pinch source physics for double-pinch-driven hohlraumsThis paper is based on an invited talk given by M K Matzen at the 32nd EPS Conference on Plasma Physics (Tarragona, Spain, 2005)  

Microsoft Academic Search

Over the last several years, rapid progress has been made evaluating the double-z-pinch indirect-drive, inertial confinement fusion (ICF) high-yield target concept (Hammer et al 1999 Phys. Plasmas6 2129). We have demonstrated efficient coupling of radiation from two wire-array-driven primary hohlraums to a secondary hohlraum that is large enough to drive a high yield ICF capsule. The secondary hohlraum is irradiated

M E Cuneo; R A Vesey; G R Bennett; D B Sinars; W A Stygar; E M Waisman; J L Porter; P K Rambo; I C Smith; S V Lebedev; J P Chittenden; D E Bliss; T J Nash; G A Chandler; B B Afeyan; E P Yu; R B Campbell; R G Adams; D L Hanson; T A Mehlhorn; M K Matzen

2006-01-01

278

High power pulsed lasers  

Microsoft Academic Search

Pulsed high power lasers can deliver sufficient energy on inertial fusion time scales (0.110 ns) to heat and compress DT fuel to fusion reaction conditions. Several laser systems have been examined for application to the fusion problem. Examples are Nd:glass, CO2, KrF, and I2, etc. A great deal of developmental effort has been applied to the Nd:glass laser and the

J. F. Holzrichter; D. Elimerl; E. V. George; J. B. Trenholme; W. W. Silnmons; J. T. Hunt

1982-01-01

279

High-power red VCSEL arrays  

NASA Astrophysics Data System (ADS)

High-power red laser sources are used in many applications such as cosmetics, cancer photodynamic therapy, and DNA sequencing in the medical field, laser-based RGB projection display, and bar-code scanning to name a few. Verticalcavity surface-emitting lasers (VCSELs) can be used as high-power laser sources, as efficient single devices can be configured into high-power two-dimensional arrays and scaled into modules of arrays. VCSELs emit in a circular, uniform beam which can greatly reduce the complexity and cost of optics. Other advantages include a narrow and stable emission spectrum, low speckle of the far-field emission, and good reliability. However, developing efficient red VCSEL sources presents some challenges because of the reduced quantum-well carrier confinement and the increased Aluminum content (to avoid absorption) which increases thermal impedance, and also decreases the DBR index contrast resulting in increased penetration length and cavity losses. We have recently developed VCSEL devices lasing in the visible 6xx nm wavelength band, and reaching 30% power conversion efficiency. We fabricated high-power 2D arrays by removing the GaAs substrate entirely and soldered the chips on high thermal conductivity submounts. Such arrays have demonstrated several Watts of output power at room temperature, in continuous-wave (CW) operation. Several tens of Watts are obtained in QCW operation. Results and challenges of these high-power visible VCSEL arrays will be discussed.

Seurin, Jean-Francois; Khalfin, Viktor; Xu, Guoyang; Miglo, Alexander; Li, Daizong; Zhou, Delai; Sundaresh, Mukta; Zou, Wei-Xiong; Lu, Chien-Yao; Wynn, James D.; Ghosh, Chuni

2013-03-01

280

K-shell emission x-ray imaging of z-pinch plasmas with a pinhole and a logarithmic spiral crystal  

SciTech Connect

An in-chamber, mini x-ray imaging instrument employs a pinhole and a logarithmic spiral crystal has been developed for obtaining K-shell line images of the imploding aluminum wire array on the ''Yang'' accelerator. The logarithmic spiral crystal acts as a monochromator and a non-dispersive mirror that reflects the pinhole image to a x-ray film detector with a very narrow photon energy bandwidth (<1 eV, mainly determined by the width of rocking curve of the crystal). Two imaging configurations with the use of Quartz (1010) crystal and Mica (002) crystal are designed, respectively, to image the Al Ly{sub {alpha}2} line (1727.7 eV) emission and Al He{sub {alpha}} intercombination line (1588.3 eV) emission. The primary experimental data corresponding to these two configurations are presented and discussed.

Yang Qingguo; Li Zeren; Peng Qixian; Yang Libing; Chen Guanhua; Ye Yan; Huang Xianbin; Cai Hongchun; Li Jing [Institute of Fluid Physics, CAEP, Mianyang, Sichuan 621900 (China); Xiao Shali [Key Laboratory of Optic-electronic Technology and System, Ministry of Education, Chongqing University, Chongqing 400044 (China)

2011-09-15

281

High power microwave generator  

DOEpatents

A device (10) for producing high-powered and coherent microwaves is described. The device comprises an evacuated, cylindrical, and hollow real cathode (20) that is driven to inwardly field emit relativistic electrons. The electrons pass through an internally disposed cylindrical and substantially electron-transparent cylindrical anode (24), proceed toward a cylindrical electron collector electrode (26), and form a cylindrical virtual cathode (32). Microwaves are produced by spatial and temporal oscillations of the cylindrical virtual cathode (32), and by electrons that reflex back and forth between the cylindrical virtual cathode (32) and the cylindrical real cathode (20).

Minich, Roger W. (Patterson, CA)

1988-01-01

282

VUV absorption spectroscopy measurements of the role of fast neutral atoms in high-power gap breakdown  

SciTech Connect

The maximum power achieved in a wide variety of high-power devices, including electron and ion diodes, z pinches, and microwave generators, is presently limited by anode-cathode gap breakdown. A frequently-discussed hypothesis for this effect is ionization of fast neutral atoms injected throughout the anode-cathode gap during the power pulse. The authors describe a newly-developed diagnostic tool that provides the first direct test of this hypothesis. Time-resolved vacuum-ultraviolet absorption spectroscopy is used to directly probe fast neutral atoms with 1 mm spatial resolution in the 10 mm anode-cathode gap of the SABRE 5 MV, 1 TW applied-B ion diode. Absorption spectra collected during Ar RF glow discharges and with CO{sub 2} gas fills confirm the reliability of the diagnostic technique. Throughout the 50--100 ns ion diode pulses no measurable neutral absorption is seen, setting upper limits of 0.12--1.5 x 10{sup 14} cm{sup {minus}3} for ground state fast neutral atom densities of H, C, N, O, F. The absence of molecular absorption bands also sets upper limits of 0.16--1.2 x 10{sup 15} cm{sup {minus}3} for common simple molecules. These limits are low enough to rule out ionization throughout the gap as a breakdown mechanism. This technique can now be applied to quantify the role of neutral atoms in other high-power devices.

FILUK,A.B.; BAILEY,JAMES E.; CUNEO,MICHAEL E.; LAKE,PATRICK WAYNE; NASH,THOMAS J.; NOACK,DONALD D.; MARON,Y.

2000-03-20

283

Silver based batteries for high power applications  

NASA Astrophysics Data System (ADS)

The present status of silver oxide-zinc technology and applications has been described by Karpinski et al. [A.P. Karpinski, B. Makovetski, S.J. Russell, J.R. Serenyi, D.C. Williams, Silver-Zinc: status of technology and applications, Journal of Power Sources, 80 (1999) 53-60], where the silver-zinc couple is still the preferred choice where high specific energy/energy density, coupled with high specific power/power density are important for high-rate, weight or size/configuration sensitive applications. Perhaps the silver oxide cathode can be considered one of the most versatile electrode materials. When coupled with other anodes and corresponding electrolyte management system, the silver electrode provides for a wide array of electrochemical systems that can be tailored to meet the most demanding, high power requirements. Besides zinc, the most notable include cadmium, iron, metal hydride, and hydrogen electrode for secondary systems, while primary systems include lithium and aluminum. Alloys including silver are also available, such as silver chloride, which when coupled with magnesium or aluminum are primarily used in many seawater applications. The selection and use of these couples is normally the result of a trade-off of many factors. These include performance, safety, risk, reliability, and cost. When high power is required, silver oxide-zinc, silver oxide-aluminum, and silver oxide-lithium are the most energetic. For moderate performance (i.e., lower power), silver oxide-zinc or silver-cadmium would be the system of choice. This paper summarizes the suitability of the silver-based couples, with an emphasis on the silver-zinc system, as primary or rechargeable power sources for high energy/power applications.

Karpinski, A. P.; Russell, S. J.; Serenyi, J. R.; Murphy, J. P.

284

Multidimensional z-pinch calculations with ALEGRA  

Microsoft Academic Search

Summary form only given. ALEGRA is one of the principal computer codes being used at Sandia National Laboratories for simulating the dynamic material response of complex configurations. It solves coupled physics problems in two or three spatial dimensions using Lagrangian, Eulerian, and\\/or ALE coordinates. The code runs on massively parallel computers, and contains a large variety of physics options including

T. A. Haill; T. A. Brunner; K. G. Budge; R. B. Campbell; N. I. Desjarlais; C. J. Garasi; R. J. Lawrence; R. W. Lemke; T. A. Mehlhorn; A. C. Robinson; K. Cochrane; B. V. Oliver

2001-01-01

285

Fabrication Processes for Surface-Emitting via External 45-DEGREE Reflectors, High-Power via Arrayed Ridge - Single-Mode Phase-Locked Aluminum Gallium Arsenide/gallium Arsenide Semiconductor Laser Sources.  

NASA Astrophysics Data System (ADS)

The fabrication of monolithically integrated configurations of semiconductor lasers incorporating multiple functions is still an open issue today in engineering. A useful set of functions to integrate are: surface-emitting, high -power, phase-locked, single-mode, and collimated laser beam output. In this work new materials and advanced fabrication processes are developed for integrating the first four of the five functions listed. The interest in semiconductor lasers is due to their greater than 90% internal quantum efficiency in converting current-flux to photon-flux, their small size and weight, and their wavelength range from 400 to 1,550 nm. Multitudes of applications are possible for semiconductor laser sources ranging from the low-volume market of satellite-based communications systems to the high-volume market of image display screens. Semimetallic amorphous carbon (SMAC) thin film is introduced as an etch mask for chemically assisted ion beam etching (CAIBE) resulting in smooth etched facets in AlGaAs/GaAs at normal- and 45-degrees- incidence angles. A self-aligned etch technique is introduced using 4 separate photoresist selector-masks on top of a fixed SMAC master -mask on top of the AlGaAs/GaAs substrate to perform 4 separate CAIBE etches at 3 different angles and to 3 different depths to create self-aligned 3-dimensional microstructures of 1.3-?m deep ridge waveguides (RWG), 6-?m deep laser facets, and 11- ?m long back-to-back 45-degree reflectors arranged in 3 by 100 arrays. Trenches on topside and underside of laser facets are introduced to deflect current away from laser facets. Silicon-rich nitro-oxide thin film is introduced as triple-use encapsulation to provide chemical passivation of AlGaAs/GaAs, optical anti-reflection coating by being refractive-index matched to AlGaAs/GaAs, and electrical insulation. A pincer-action sample-holder for CAIBE is introduced allowing samples to heat up by ion beam heating. Various surface preparations procedures are used to precede either deposition or etching of materials. Carbon thin film is used as adhesion mediator between photoresist and AlGaAs/GaAs. A complete fabrication process sequence is demonstrated. Operations are demonstrated of spontaneous emission output and of the surface-emitting function.

Porkolab, Gyorgy Arpad

286

Alpha high-power chemical laser program  

NASA Astrophysics Data System (ADS)

Alpha is a megawatt-class hydrogen fluoride, continuous wave, space based chemical laser brassboard which demonstrates and validates technology for space-based applications. It consists of a cylindrical gain generator that exhausts radially outward through circumferential nozzles forming an annular lasing media and an annular ring resonator, which extracts the laser energy. Technical innovations first demonstrated on Alpha include: (1) use of extruded aluminum components, (2) diamond turned, annular optics made of molybdenum, (3) uncooled silicon mirrors, (4) light weight optical benches, and (5) active alignment. Alpha first lased in 1989, and has repeatably demonstrated megawatt-class power and excellent beam quality. Using Alpha, TRW has demonstrated the use of low weight uncooled mirrors in very high power lasers to reduce system jitter. They have performed flawlessly and beam jitter levels were significantly reduced.

Ackerman, Richard A.; Callahan, David; Cordi, Anthony J.; Lurie, Henry; Thomson, Matthew

1995-03-01

287

Instabilities, Strength and Material Failure in Cylindrically Shocked and Imploded Aluminum  

NASA Astrophysics Data System (ADS)

We have used the LANL PEGASUS Z-pinch facility driving a thin cylindrically convergent Al liner to 3 km/s to launch 300 kbar shocks in a 3-mm thick 10-mm-i.d. aluminum cylinder whose interior is filled with 1 atm Xe gas. The subsequent material motion of the metal and gas is diagnosed with both radial and axial flash x-rays and with optical framing cameras . Instabilities are seeded by implanting wires of assorted higher density metal parallel to the cylinder axis. We have done two shots, varying the target from Al 1100-O to Al 6061-T6 to explore the effect of changing material strength. The images show the spallation failure of the metal-gas interface on shock release and the effect of the seeded instabilities.

Egan, P.; Chandler, E. A.; Winer, K.; Stokes, J.; Fulton, R. D.; King, N.; Morgan, D.; Obst, A.; Oona, H.; Oro, D.; Platts, D.

1998-03-01

288

High power ferrite microwave switch  

NASA Technical Reports Server (NTRS)

A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out short-slot 3 db quadrature coupler, a dual driver electronic circuit, and input logic interface circuitry. The basic mode of operation of the high power ferrite microwave switch is identical to that of a four-port, differential phase shift, switchable circulator. By appropriately designing the phase shifters and electronic driver circuits to operate in the flux-transfer magnetization mode, power and temperature insensitive operation was achieved. A list of the realized characteristics of the developed units is given.

Bardash, I.; Roschak, N. K.

1975-01-01

289

High Power Thulium Fiber Lasers  

NASA Astrophysics Data System (ADS)

Recent years have seen a phenomenal rise in the capabilities of high power fibers lasers. 10 kW is now achievable in single-mode fiber and the race is on to break the 100 kW mark. This has been enabled with the development of high power 976 nm pump diodes, ideally matched for efficiently exciting the ~1030-1080 nm transition in Yb-doped silica fibers. In the shadow of this remarkable development we are now witnessing a similar growth pattern for a sister to this laser, the 2 ?m thulium fiber laser. This laser possesses rather unique characteristics. Pumped by 790 nm diodes, the excitation scheme uses a cross-relaxation process that results in two-for-one photon generation with slope efficiencies approaching 70%. Powers approaching the kW level are now achievable. This talk summarizes the development of this unique laser source in the MIR, and speculates on its future applications in the medical, manufacturing and defense arenas. In particular we describe new experiments where we exploit the broad >200 nm spectral bandwidth, and the advantages this laser brings to operating in the pulsed regime. We characterize the capabilities of conventional gratings, fiber Bragg gratings, volume Bragg gratings and guided mode resonant filters to lock the linewidth to as small as 50 pm, within the range from ~1950 nm to ~2150 nm. This spectral region covers many sharp atmospheric absorption lines in the atmosphere. We describe the first long range (1 km) atmospheric transmission tests with a tunable high power (200 W) thulium fiber laser. The capability to lock a number of these lasers to specific wavelengths each with <100 pm linewidths opens the option of spectrally combining many lasers within the overall spectral bandwidth. We examine the benefits of this approach to reaching 100 kW power levels. In the pulse regime we describe the generation of nanosecond, picosecond and femtosecond pulses in oscillator and MOPA configurations.

Shah, Lawrence; McComb, Timothy S.; Sims, R. Andrew; Willis, Christina C. C.; Kadwani, Pankaj; Sudesh, Vikas; Richardson, Martin

2010-10-01

290

High-power pulsed lasers  

SciTech Connect

The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization.

Holzrichter, J.F.

1980-04-02

291

Aluminum-air batteries for military applications  

Microsoft Academic Search

The authors review the basic characteristics of aluminum-air batteries, describe some of the recent advances involving aluminum anodes and air cathodes, aluminum-air batteries and demonstrate certain potential military applications. They can be transported as lightweight, collapsible batteries and can be filled with water at the site of operation. The alkaline Al\\/air battery is advantageous when a high power is desired.

B. M. L. Rao; R. Cook; W. Kobasz; G. D. Deuchars

1992-01-01

292

Thermal transients during processing of materials by very high power ultrasonic additive manufacturing  

Microsoft Academic Search

Dynamic recrystallisation at interfaces has been suggested as the bonding mechanism in the joining of metallic tapes, during very high power ultrasonic additive manufacturing. To understand the reasons for such occurrence of dynamic recrystallization, thermal transients from the interface regions were recorded during processing of aluminum alloy (3003 and 6061 series) and 11000 copper tapes under similar conditions. Measurements in

M. R. Sriraman; Matt Gonser; Hiromichi T. Fujii; S. S. Babu; Matt Bloss

2011-01-01

293

High Power UV LED Industrial Curing Systems  

Microsoft Academic Search

UV curing is a green technology that is largely underutilized because UV radiation sources like Hg Lamps are unreliable and difficult to use. High Power UV LEDs are now efficient enough to replace Hg Lamps, and offer significantly improved performance relative to Hg Lamps. In this study, a modular, scalable high power UV LED curing system was designed and tested,

Karlicek; F. Robert; Robert Sargent

2012-01-01

294

High power rechargeable batteries Paul V. Braun  

E-print Network

High power rechargeable batteries Paul V. Braun , Jiung Cho, James H. Pikul, William P. King storage Secondary batteries High energy density High power density Lithium ion battery 3D battery of rechargeable (second- ary) batteries, as this is critical for most applications. As the penetration

Braun, Paul

295

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

296

NASA GRC High Power Electromagnetic Thruster Program  

NASA Technical Reports Server (NTRS)

High-power electromagnetic thrusters have been proposed as primary in-space propulsion options for several bold new interplanetary and deep-space missions. As the lead center for electric propulsion, the NASA Glenn Research Center designs, develops, and tests high-power electromagnetic technologies to meet these demanding mission requirements. Two high-power thruster concepts currently under investigation by Glenn are the magnetoplasmadynamic (MPD) thruster and the Pulsed Inductive Thruster (PIT). This paper describes the MPD thruster and the test facility.

LaPointe, Michael R.; Pensil, Eric J.

2004-01-01

297

Characterization of High-Power Lasers  

E-print Network

This paper discusses methods for characterization of high power lasers. Specifically, these methods have been developed for the High Energy Laser Joint Technology Office and used for independent, government-sponsored testing ...

Edwards, Brian E.

298

High power millimeter wave source development program  

NASA Technical Reports Server (NTRS)

High power millimeter wave sources for fusion program; ECH source development program strategy; and 1 MW, 140 GHz gyrotron experiment design philosophy are briefly outlined. This presentation is represented by viewgraphs only.

George, T. V.

1989-01-01

299

Coupling output of multichannel high power microwaves  

SciTech Connect

The coupling output of multichannel high power microwaves is a promising technique for the development of high power microwave technologies, as it can enhance the output capacities of presently studied devices. According to the investigations on the spatial filtering method and waveguide filtering method, the hybrid filtering method is proposed for the coupling output of multichannel high power microwaves. As an example, a specific structure is designed for the coupling output of S/X/X band three-channel high power microwaves and investigated with the hybrid filtering method. In the experiments, a pulse of 4 GW X band beat waves and a pulse of 1.8 GW S band microwave are obtained.

Li Guolin; Shu Ting; Yuan Chengwei; Zhang Jun; Yang Jianhua; Jin Zhenxing; Yin Yi; Wu Dapeng; Zhu Jun; Ren Heming; Yang Jie [College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2010-12-15

300

Test facilities for high power electric propulsion  

NASA Technical Reports Server (NTRS)

Electric propulsion has applications for orbit raising, maneuvering of large space systems, and interplanetary missions. These missions involve propulsion power levels from tenths to tens of megawatts, depending upon the application. General facility requirements for testing high power electric propulsion at the component and thrust systems level are defined. The characteristics and pumping capabilities of many large vacuum chambers in the United States are reviewed and compared with the requirements for high power electric propulsion testing.

Sovey, James S.; Vetrone, Robert H.; Grisnik, Stanley P.; Myers, Roger M.; Parkes, James E.

1991-01-01

301

High-power microwave pulse generator  

Microsoft Academic Search

An inexpensive alternative to commercial high-power microwave pulse generators is described. The present high-power microwave pulse generator utilizes a surplus MIT model 3 Mark II hard tube modulator and 2J51 magnetron. The basic design and technical details of the pulse generator are presented. The pulse generator is designed to produce 8.59.6 GHz pulses with pulse lengths ranging from 2 to

G. O. White; L. Chen; C. E. Patton; R. L. Tinkoff

1992-01-01

302

High-power microwave pulse generator  

Microsoft Academic Search

An inexpensive alternative to commercial high-power microwave-pulse generators is described. The present high-power microwave-pulse generator utilizes a surplus MIT model-3 Mark-II hard-tube modulator and 2J51 magnetron. The basic design and technical details of the pulse generator are presented. The pulse generator is designed to produce 8.5-9.6 GHz pulses with pulse lengths ranging from 2 to 4 microns with a nominal

G. O. White; L. Chen; C. E. Patton; R. L. Tinkoff

1992-01-01

303

Very High Power THz Radiation Sources  

SciTech Connect

We report the production of high power (20 watts average, {approx}1 Megawatt peak) broadband THz light based on coherent emission from relativistic electrons. Such sources are ideal for imaging, for high power damage studies and for studies of non-linear phenomena in this spectral range. We describe the source, presenting theoretical calculations and their experimental verification. For clarity, we compare this sources with one based on ultrafast laser techniques.

G.L. Carr; Michael C. Martin; Wayne R. McKinney; Kevin Jordan; George R. Neil; Gwyn P. Williams

2002-10-01

304

Very high power THz radiation sources  

SciTech Connect

We report the production of high power (20 watts average, {approx} 1 Megawatt peak) broadband THz light based on coherent emission from relativistic electrons. Such sources are ideal for imaging, for high power damage studies and for studies of non-linear phenomena in this spectral range. We describe the source, presenting theoretical calculations and their experimental verification. For clarity we compare this source to one based on ultrafast laser techniques.

Carr, G.L.; Martin, Michael C.; McKinney, Wayne R.; Jordan, K.; Neil, George R.; Williams, G.P.

2002-10-31

305

Thin film circuit fabrication on diamond substrates for high power applications  

SciTech Connect

Sandia Laboratories has developed a thin film diamond substrate technology to meet the requirements for high power and high density circuits. Processes were developed to metallize, photopattern, laser process, and, package diamond thin film networks which were later assembled into high power multichip modules (MCMS) to test for effectiveness at removing heat. Diamond clearly demonstrated improvement in heat transfer during 20 Watt, strip heating experiments with junction-to-ambient temperature increases of less than 24 C compared to 126 C and 265 C for the aluminum nitride and ceramic versions, respectively.

Norwood, D.; Worobey, W.; Peterson, D.; Sweet, J.; Johnson, D.; Miller, D. [Sandia National Labs., Albuquerque, NM (United States); Andaleon, D. [Sandia National Labs., Livermore, CA (United States)

1995-05-01

306

High Power Co-Axial Coupler  

SciTech Connect

A very high power Coax RF Coupler (MW-Level) is very desirable for a number of accelerator and commercial applications. For example, the development of such a coupler operating at 1.5 GHz may permit the construction of a higher-luminosity version of the Electron-Ion Collider (EIC) being planned at JLab. Muons, Inc. is currently funded by a DOE STTR grant to develop a 1.5-GHz high-power doublewindowcoax coupler with JLab (about 150 kW). Excellent progress has been made on this R&D project, so we propose an extension of this development to build a very high power coax coupler (MW level peak power and a max duty factor of about 4%). The dimensions of the current coax coupler will be scaled up to provide higher power capability.

Neubauer, M. [Muons, Inc.; Dudas, A. [Muons, Inc.; Rimmer, Robert A. [JLAB; Guo, Jiquan [JLAB; Williams, R. Scott [JLAB

2013-12-01

307

High-power and high-brightness laser diode structures using Al-free active region  

Microsoft Academic Search

High bit-rate, WDM, networks are reliant on Er or Er\\/Yb doped fiber amplifiers. Reliable, high power laser diodes at 980nm and 1480nm are key devices for pumping these amplifiers. We have developed several 980 nm laser diode structures at 980 nm, using an Aluminum free active region and standard AR\\/HR coatings on the facets. Our laser show low optical losses,

Sophie-Charlotte Auzanneau; Michel M. Krakowski; Francois Berlie; Michel Calligaro; Yannick Robert; Olivier Parillaud; Michel Lecomte; B. Boulant; Thierry Fillardet

2003-01-01

308

BEAM INSTRUMENTATION FOR HIGH POWER HADRON BEAMS  

SciTech Connect

This presentation will describe developments in the beam diagnostics which support the understanding and operation of high power hadron accelerators. These include the measurement of large dynamic range transverse and longitudinal beam profiles, beam loss detection, and non-interceptive diagnostics.

Aleksandrov, Alexander V [ORNL] [ORNL

2013-01-01

309

High Power Hg Target Conceptual Design Review  

E-print Network

High Power Hg Target Conceptual Design Review Hg Jet Nozzle Analysis M. W. Wendel Oak Ridge LABORATORY U. S. DEPARTMENT OF ENERGY Conceptual Design Review 7-8 Feb 05 Cavitation in the nozzle the chamber pressure · Ultimately the nozzle design needs to be tested. #12;14 OAK RIDGE NATIONAL LABORATORY U

McDonald, Kirk

310

Development of high power QFN package  

Microsoft Academic Search

Leadframe CSP package had been well known to be a superior choice for high-speed application where high thermal performance is desired. With the advancement in technology trend, there is more increasing demand for higher thermal performance in miniature package to dissipate heat and improve the device performances. This paper describes the cost-effective development and material characterisation of high power quad

Francis Poh KS; Tan Hien Boon; Krishnamoorthi Sivalingam; Lim Beng Kuan; A. Y. S. Sun; Rahamat Bidin

2004-01-01

311

The high-power iodine laser  

SciTech Connect

This book covers the design and operation of pulsed high-power iodine lasers. Also examined are a large range of laser-produced plasma, beam quality and losses, the ASTERIX III system and the scalability and prospects of the iodine laser.

Brederlow, G.E.F.; Witte, K.J.

1983-01-01

312

Automated System Tests High-Power MOSFET's  

NASA Technical Reports Server (NTRS)

Computer-controlled system tests metal-oxide/semiconductor field-effect transistors (MOSFET's) at high voltages and currents. Measures seven parameters characterizing performance of MOSFET, with view toward obtaining early indication MOSFET defective. Use of test system prior to installation of power MOSFET in high-power circuit saves time and money.

Huston, Steven W.; Wendt, Isabel O.

1994-01-01

313

Very High Power IGCT PEBB technology  

Microsoft Academic Search

In the field of power electronics the power electronics building block (PEBB) is a key functional component. With regard to the applications, it is of outmost importance that the PEBB technology used is compact, cost-effective and reliable. The IGCT is at the forefront of technology in high power, medium-voltage applications. For further improvement in size and costs a new ANPC

P. K. Steimer; O. Apeldoorn; B. Odegard; S. Bernet; T. Bruckner

2005-01-01

314

Use of high power microwave weapons  

Microsoft Academic Search

The destructive power of high power microwave (HPM) generators allow them to be used as effective weapons by both law enforcement and criminal organizations. Now, with the desperate need for cash by some developing nations, devices such as relativistic magnetrons, capable of producing multi-megawatts and for use in weapons, have been offered for sale to other nations, groups, and individuals.

E. Van Keuren; J. Knighten

1995-01-01

315

Targets for high power neutral beams  

SciTech Connect

Stopping high-power, long-pulse beams is fast becoming an engineering challenge, particularly in neutral beam injectors for heating magnetically confined plasmas. A brief review of neutral beam target technology is presented along with heat transfer calculations for some selected target designs.

Kim, J.

1980-01-01

316

Ablation dynamics in coiled wire-array Z-pinches  

NASA Astrophysics Data System (ADS)

Experiments to study the ablation dynamics of coiled wire arrays were performed on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and on the COBRA generator at Cornell University's Laboratory of Plasma Studies (1 MA, 100 ns). The MAGPIE generator was used to drive coiled wires in an inverse array configuration to study the distribution of ablated plasma. Using interferometry to study the plasma distribution during the ablation phase, absolute quantitative measurements of electron line density demonstrated very high density contrasts between coiled ablation streams and inter-stream regions many millimetres from the wire. The measured density contrasts for a coiled array were many times greater than that observed for a conventional array with straight wires, indicating that a much greater axial modulation of the ablated plasma may be responsible for the unique implosion dynamics of coiled arrays. Experiments on the COBRA generator were used to study the complex redirection of plasma around a coiled wire that gives rise to the ablation structure exhibited by coiled arrays. Observations of this complex 3D plasma structure were used to validate the current model of coiled array ablation dynamics [Hall et al., Phys. Rev. Lett. 100, 065003 (2008)], demonstrating irrefutably that plasma flow from the wires behaves as predicted. Coiled wires were observed to ablate and implode in the same manner on both machines, indicating that current rise time should not be an issue for the scaling of coiled arrays to larger machines with fast current rise times.

Hall, G. N.; Lebedev, S. V.; Suzuki-Vidal, F.; Swadling, G.; Chittenden, J. P.; Bland, S. N.; Harvey-Thompson, A.; Knapp, P. F.; Blesener, I. C.; McBride, R. D.; Chalenski, D. A.; Blesener, K. S.; Greenly, J. B.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Kusse, B. R.

2013-02-01

317

3D Resistive, Radiative MHD Modeling of Z-pinches  

SciTech Connect

We present results from GORGON, a three dimensional, parallel, radiative, resistive MHD code which we use to study the evolution of various wire array configurations. We describe the implosion of cylindrical wire arrays and the interaction of nested wire arrays on the MAGPIE generator of Imperial College. In addition to cylindrical arrays we describe results from the modeling of novel array configurations such as radial, conical and spherical wire arrays, which are of interest in laboratory astrophysics, and the understanding of basic array physics. For spherical array implosions we demonstrate a precursor flow convergence that is not entirely spherical. We show that jet formation on axis, and compression from precursor streams generates a roughly cylindrical precursor, which at late times becomes unstable. Final implosion is dominated by two magnetic cavities that expand axially to collide at the array center.This research supported by the NNSA under Department of Energy cooperative agreement DE-F03-02NA00057.

Jennings, C.A.; Chittenden, J.P.; Ciardi, A.; Sherlock, M.; Lebedev, S.V.; Ampleford, D.J.; Bland, S.N.; Bott, S.C.; Hall, G.; Rapley, J. [Blackett Laboratory, Imperial College, London, SW7 2BZ (United Kingdom); AWE Plc., Aldermaston, RG7 4PR (United Kingdom)

2006-01-05

318

Axial and temporal gradients in Mo wire array Z pinches  

SciTech Connect

Three nested molybdenum wire arrays with initial outer diameters of 45, 50, and 55 mm were imploded by the {approx}20 MA, 90 ns rise-time current pulse of Sandia's Z accelerator. The implosions generated Mo plasmas with {approx_equal}10% of the array's initial mass reaching Ne-like and nearby ionization stages. These ions emitted 2-4 keV L-shell x rays with radiative powers approaching 10 TW. Mo L-shell spectra with axial and temporal resolution were captured and have been analyzed using a collisional-radiative model. The measured spectra indicate significant axial variation in the electron density, which increases from a few times 10{sup 20} cm{sup -3} at the cathode up to {approx}3x10{sup 21} cm{sup -3} near the middle of the 20 mm plasma column (8 mm from the anode). Time-resolved spectra indicate that the peak electron density is reached before the peak of the L-shell emission and decreases with time, while the electron temperature remains within 10% of 1.7 keV over the 20-30 ns L-shell radiation pulse. Finally, while the total yield, peak total power, and peak L-shell power all tended to decrease with increasing initial wire array diameters, the L-shell yield and the average plasma conditions varied little with the initial wire array diameter.

LePell, P.D.; Hansen, S.B.; Shlyaptseva, A.S.; Coverdale, C.; Deeney, C.; Apruzese, J.P.; Fournier, K.B.; Safronova, U.I. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Physics Department/220, University of Nevada Reno, Reno, Nevada 89557 and Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Physics Department/220, University of Nevada Reno, Reno, Nevada 89557 (United States); Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Radiation Hydrodynamics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); University of Notre Dame, Notre Dame, Indiana 46566 (United States)

2005-03-01

319

Azimuthal clumping instabilities in a Z-pinch wire array  

SciTech Connect

A simple model is constructed to evaluate the temporal evolution of azimuthal clumping instabilities in a cylindrical array of current-carrying wires. An analytic scaling law is derived, which shows that randomly seeded perturbations evolve at the rate of the fastest unstable mode, almost from the start. This instability is entirely analogous to the Jeans instability in a self-gravitating disk, where the mutual attraction of gravity is replaced by the mutual attraction among the current-carrying wires.

Strickler, Trevor; Lau, Y.Y.; Gilgenbach, R.M.; Cuneo, M.E.; Mehlhorn, T.A. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States)

2005-05-15

320

Implosion Dynamics in Conical Wire Array Z-pinches  

SciTech Connect

We present initial results from imploding conical wire array experiments performed on both the MAGPIE generator (1MA, 240ns) at Imperial College London and the Nevada Terawatt Facility's Zebra generator (1MA, 100ns) at University of Nevada, Reno. This paper will discuss the implosion dynamics of conical wire arrays, including initial implosion of the cathode end of the array and the formation of a magnetic bubble.

Ampleford, D.J.; Lebedev, S.V.; Chittenden, J.P.; Bland, S.N.; Bott, S.C.; Hall, G.N.; Palmer, J.B.A.; Rapley, J. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Kantsyrev, V.L.; Safronova, A.S.; Ivanov, V.V.; Fedin, D.A.; Laca, P.J.; Sotnikov, V.I.; Yilmaz, F.; Ouart, N.; Nalajala, V.; Shrestha, I.; Pokala, S. [Physics Department, University of Nevada, Reno, NV 89557 (United States); Jones, B. [Sandia National Laboratories, Albuquerque, NM 87185 (United States)] (and others)

2006-01-05

321

A Faraday rotation diagnostic for Z pinch experiments  

NASA Astrophysics Data System (ADS)

The MagLIF experiment is an approach to Magneto Inertial Fusion (MIF) that will compress a laser preheated magnetized plasma inside a small sub cm size beryllium capsule and the magnetic field inside. A good measurement of the compressed magnetic field will help us understand how the compression proceeds, and the time scale over which field diffuses out. We are working on a first step to the direct measurement of vacuum magnetic field (expected to be mostly Bz) compression time history, potentially space-resolved, without a plasma fill. A small magneto-active section of optical fiber can measure magnetic fields in the 1-1000 Tesla range. Directly measured vacuum Bz is an initial but important step towards validating the codes supporting MagLIF. The technology will use a Terbium doped optical fiber as a Faraday rotation medium. The optical path and hardware is simple, inexpensive, and small enough to fit inside a MagLIF capsule, and can be radiation hardened. Low noise, optically coupled magnetic field measurements will be possible for vacuum MagLIF shots.

Gao, K. W.; Intrator, T. P.; Weber, T. E.; Yoo, C. B.; Klarenbeek, J.

2012-10-01

322

Instability Control in a Staged Z-pinch  

SciTech Connect

A \\Staged Z-Pinch? is a fusion-energy concept in which stored-electric energy is first converted into plasma-liner-kinetic energy, and then transferred to a coaxialtarget plasma [H. U. Rahman, F. J. Wessel, and N. Rostoker, Phys. Rev. Lett. 74, p. 714(1996)]. Proper choice of the liner and target materials, and their initial radii and mass densities, leads to dynamic stabilization, current amplification, and shock heating of the target. Simulations suggest that this configuration has merit as a alternative inertial-confinement-fusion concept, and may provide an energy release exceeding thermonuclear break-even, if tested on one of many newer pulsed power systems, for example those located at Sandia National Laboratories.

Frank J. WESSEL

2011-04-22

323

Status of Z-Pinch Research Fusion Power Associates  

E-print Network

Plunger Flibe Jets Chamber Molten Flibe Pool Transmission Lines To Linear Transformer Pulsed Power Driver 20 Torr Inert Gas Inert Gas Flow for Contamination Control Cartridge Large Particulate Collections IFE driver architectures 3. Shock mitigation Theory/simulations Experiments: water ring

324

High Power Disk Loaded Guide Load  

SciTech Connect

A method to design a matching section from a smooth guide to a disk-loaded guide, using a variation of broadband matching, [1, 2] is described. Using this method, we show how to design high power loads. The load consists of a disk-loaded coaxial guide operating in the TE{sub 01}-mode. We use this mode because it has no electric field terminating on a conductor, has no axial currents, and has no current at the cylinder-disk interface. A high power load design that has -35 dB reflection and a 200 MHz, -20 dB bandwidth, is presented. It is expected that it will carry the 600 MW output peak power of the pulse compression network. We use coaxial geometry and stainless steel material to increase the attenuation per cell.

Farkas, Z.D.; /SLAC

2006-02-22

325

High Power Picosecond Laser Pulse Recirculation  

SciTech Connect

We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

2010-04-12

326

High-power, high-efficiency FELs  

SciTech Connect

High power, high efficiency FELs require tapering, as the particles loose energy, so as to maintain resonance between the electromagnetic wave and the particles. They also require focusing of the particles (usually done with curved pole faces) and focusing of the electromagnetic wave (i.e. optical guiding). In addition, one must avoid transverse beam instabilities (primarily resistive wall) and longitudinal instabilities (i.e sidebands). 18 refs., 7 figs., 3 tabs.

Sessler, A.M.

1989-04-01

327

High-Power -Doped Phosphate Fiber Amplifier  

Microsoft Academic Search

We report on the development of novel high-power light sources utilizing a Yb3+-doped phosphate fiber as the gain element. This host presents several key benefits over silica, particularly much higher Yb2 O3 concentrations (up to 26 wt%), a 50% weaker stimulated Brillouin scattering (SBS) gain cross section, and the absence of observable photodarkening even at high population inversion. These properties

Yin-Wen Lee; Michel J. F. Digonnet; Supriyo Sinha; Karel E. Urbanek; Robert L. Byer; Shibin Jiang

2009-01-01

328

Advanced characterization techniques for high power VCSELs  

NASA Astrophysics Data System (ADS)

The performance of high power VCSELs in a specific application depends on the geometrical and thermal design as well as on the quality of the epitaxially grown material. Due to the relatively high heat load in densely packed high power arrays the temperature in the active zone and the DBR mirrors changes significantly with the applied current and the traditional characterization methods become less meaningful than for low power devices. This paper presents a method to measure temperature independent power curves with the help of short pulse techniques and data mapping at different heat sink temperatures. In addition the internal quantum efficiency, the transparency current and the gain coefficient are measured by a novel method which operates the VCSEL material as an edge emitter and applies a cut-back technique. The optical losses in the DBR mirrors are determined using external feedback. In summary all relevant parameters which determine the quality of an epitaxial design are measured independently and can be directly compared with modeling and help to optimize the high power VCSEL performance.

Moench, Holger; Baier, Johannes; Gronenborn, Stephan; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Schemmann, Marcel; Valster, Adriaan

2010-02-01

329

High Power UV LED Industrial Curing Systems  

SciTech Connect

UV curing is a green technology that is largely underutilized because UV radiation sources like Hg Lamps are unreliable and difficult to use. High Power UV LEDs are now efficient enough to replace Hg Lamps, and offer significantly improved performance relative to Hg Lamps. In this study, a modular, scalable high power UV LED curing system was designed and tested, performing well in industrial coating evaluations. In order to achieve mechanical form factors similar to commercial Hg Lamp systems, a new patent pending design was employed enabling high irradiance at long working distances. While high power UV LEDs are currently only available at longer UVA wavelengths, rapid progress on UVC LEDs and the development of new formulations designed specifically for use with UV LED sources will converge to drive more rapid adoption of UV curing technology. An assessment of the environmental impact of replacing Hg Lamp systems with UV LED systems was performed. Since UV curing is used in only a small portion of the industrial printing, painting and coating markets, the ease of use of UV LED systems should increase the use of UV curing technology. Even a small penetration of the significant number of industrial applications still using oven curing and drying will lead to significant reductions in energy consumption and reductions in the emission of green house gases and solvent emissions.

Karlicek, Robert, F., Jr; Sargent, Robert

2012-05-14

330

High Temperature, High Power Piezoelectric Composite Transducers  

PubMed Central

Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, StewarT.

2014-01-01

331

Aluminum Analysis.  

ERIC Educational Resources Information Center

Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

Sumrall, William J.

1998-01-01

332

Hardening and welding with high-power diode lasers  

NASA Astrophysics Data System (ADS)

Commercially available high power diode lasers (HPDLs) with output powers of up to 6 kW have been recognized as an interesting tool for industrial applications. In certain fields of application they offer many advantages over Nd:YAG and CO2 lasers because of their low maintenance, compact design and low capital costs. Examples of successful industrial implementation of HPDLs include plastic welding, surface hardening and heat conduction welding of stainless steel and aluminum. The joining of plastics with an HPDL offers the advantages of producing a weld seam with high strength, high consistency and superior appearance. One example is the keyless entry system introduced with the Mercedes E-class where the microelectronic circuits are embedded in a plastic housing. Other applications include instrument panels, cell phones, headlights and tail lights. Applications in the field of surface treatment of metals profit from the HPDL's inherent line-shaped focus and the homogeneous intensity distribution across this focus. An HPDL system is used within the industry to harden rails for coordinate measurement machines. This system contains a customized zoom optic to focus the laser light onto the rails. With the addition of a temperature control, even complex shapes can be hardened with a constant depth and minimum distortion.

Ehlers, Bodo; Herfurth, Hans-Joachim; Heinemann, Stefan

2000-03-01

333

High-power LEDs for plant cultivation  

NASA Astrophysics Data System (ADS)

We report on high-power solid-state lighting facility for cultivation of greenhouse vegetables and on the results of the study of control of photosynthetic activity and growth morphology of radish and lettuce imposed by variation of the spectral composition of illumination. Experimental lighting modules (useful area of 0.22 m2) were designed based on 4 types of high-power light-emitting diodes (LEDs) with emission peaked in red at the wavelengths of 660 nm and 640 nm (predominantly absorbed by chlorophyll a and b for photosynthesis, respectively), in blue at 455 nm (phototropic function), and in far-red at 735 nm (important for photomorphology). Morphological characteristics, chlorophyll and phytohormone concentrations in radish and lettuce grown in phytotron chambers under lighting with different spectral composition of the LED-based illuminator and under illumination by high pressure sodium lamps with an equivalent photosynthetic photon flux density were compared. A well-balanced solid-state lighting was found to enhance production of green mass and to ensure healthy morphogenesis of plants compared to those grown using conventional lighting. We observed that the plant morphology and concentrations of morphologically active phytohormones is strongly affected by the spectral composition of light in the red region. Commercial application of the LED-based illumination for large-scale plant cultivation is discussed. This technology is favorable from the point of view of energy consumption, controllable growth, and food safety but is hindered by high cost of the LEDs. Large scale manufacturing of high-power red AlInGaP-based LEDs emitting at 650 nm and a further decrease of the photon price for the LEDs emitting in the vicinity of the absorption peak of chlorophylls have to be achieved to promote horticulture applications.

Tamulaitis, Gintautas; Duchovskis, Pavelas; Bliznikas, Zenius; Breive, Kestutis; Ulinskaite, Raimonda; Brazaityte, Ausra; Novickovas, Algirdas; Zukauskas, Arturas; Shur, Michael S.

2004-10-01

334

Operation of high power converters in parallel  

NASA Technical Reports Server (NTRS)

High power converters that are used in space power subsystems are limited in power handling capability due to component and thermal limitations. For applications, such as Space Station Freedom, where multi-kilowatts of power must be delivered to user loads, parallel operation of converters becomes an attractive option when considering overall power subsystem topologies. TRW developed three different unequal power sharing approaches for parallel operation of converters. These approaches, known as droop, master-slave, and proportional adjustment, are discussed and test results are presented.

Decker, D. K.; Inouye, L. Y.

1993-01-01

335

High power holographic masks for beam shaping  

NASA Astrophysics Data System (ADS)

A new class of optically generated holographic projection masks is reported that shapes a high power laser beam into any number of image forming sub-beams. Unlike computer generated holograms or TIR volume holography approaches, the work reported here involves a phase only transmission in-line optical hologram to shape beams and image patterns on a workpiece. By combining the functions of beam homogenizer, mask and projection lens into a single in-line optical element, this approach yields a highly efficient but greatly simplified lithography system for ablation patterning. A lower cost ablation process tool with throughput 10-100 times that of existing tools is one result. This report examines the use of high power holographic projection masks to replace traditional reflective photomasks and the associated projection imaging optics currently used in laser ablation systems. A holographic projection mask also exhibits image redundancy, reducing the need for beam homogenization and increasing its resistance to print defects produced by contamination or damage.

Parker, William

2007-09-01

336

Aluminum as anode for energy storage and conversion: a review  

NASA Astrophysics Data System (ADS)

Aluminum has long attracted attention as a potential battery anode because of its high theoretical voltage and specific energy. The protective oxide layer on the aluminum surface is however detrimental to the battery performance, contributing to failure to achieve the reversible potential and causing the delayed activation of the anode. By developing aluminum alloys as anodes and solution additives to electrolytes, a variety of aluminum batteries have been extensively investigated for various applications. From molten salt and other non-aqueous electrolytes, aluminum can be electrodeposited and therefore be suitable for developing rechargable batteries. Considerable efforts have been made to develop secondary aluminum batteries of high power density. In the present paper, these research activities are reviewed, including aqueous electrolyte primary batteries, aluminum-air batteries and molten salt secondary batteries.

Li, Qingfeng; Bjerrum, Niels J.

337

Conversion of aluminum chlorohydrate to aluminum hydroxide  

Microsoft Academic Search

aluminum hydroxide. X-ray, IR, and 27A1 NMR spectroscopic data indicate that aluminum chlorohydrate is composed of a central aluminum in tetrahedral configuration surrounded by 12 aluminums each in octahedral configuration. This highly .charged complex is neutralized by 7 chloride counterions. In contrast, aluminum hydroxide has a polymer-like structure whose basic unit is a ring of six aluminums in octahedral configuration

DIRK L. TEAGARDEN; STANLEY L. HEM

338

Feedthrough terminal for high-power cell  

DOEpatents

A feedthrough terminal for a high power electrochemical storage cell providing low resistance coupling to the conductive elements therein while isolating the terminal electrode from the highly corrosive environment within the cell is disclosed. A large diameter, cylindrical copper electrode is enclosed in a stainless steel tube with a BN powder feedthrough seal maintained around the stainless steel tube by means of facing insulative bushings and an outer sleeve. One end of the copper conductor is silver-brazed directly to a flat, butterfly bus bar within the cell, with the adjacent end of the surrounding outer feedthrough sleeve welded to the bus bar. A threaded seal is fixedly positioned on a distal portion of the stainless steel tube immediately adjacent the distal insulative bushing so as to compress the feedthrough seal in tight fitting relation around the stainless steel tube in providing a rugged, leak-proof electrical feedthrough terminal for the power cell.

Kaun, T.D.

1982-05-28

339

High-Power Options for LANSCE  

SciTech Connect

The LANSCE linear accelerator at Los Alamos National Laboratory has a long history of successful beam operations at 800 kW. We have recently studied options for restoration of high-power operations including approaches for increasing the performance to multi-MW levels. In this paper we will discuss the results of this study including the present limitations of the existing accelerating structures at LANSCE, and the high-voltage and RF systems that drive them. Several options will be discussed and a preferred option will be presented that will enable the first in a new generation of scientific facilities for the materials community. The emphasis of this new facility is 'Matter-Radiation Interactions in Extremes' (MaRIE) which will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges.

Garnett, Robert W. [Los Alamos National Laboratory

2011-01-01

340

Diamond shines in high-power devices  

NASA Astrophysics Data System (ADS)

The 20-W S-band power amplifiers aboard the GOES E and F spacecraft exemplify the problems that type-IIa diamond heat sinks have been developed to solve, including the requirement for junction temperatures to be kept below 125 C. Diamond heat sinks allow high power S-band semiconductors to operate at a flange temperature of 70 C without exceeding the stipulated maximum junction temperature. Type-IIA diamond, which is an excellent electrical insulator, possesses a thermal conductivity four times better than pure copper at 100 C, and outperforms BeO by an even greater margin. Higher costs are offset by high reliability. Attention is presently given to the results of tests conducted by the NASA Goddard Space Flight Center.

Line, L.

1984-07-01

341

Efficient, monochromatic, high-power microwave generator  

SciTech Connect

Microwave generation by electron beams in virtual cathode configurations can achieve significant power levels. However, most designs inherently have two competing mechanisms generating microwaves; namely the oscillating virtual cathode and the reflexing electrons. These two mechanisms tend to interfere destructively with each other. Specifically, the reflexing electrons subject the electron beam to two-stream instability, causing considerable heating of the electron beam. In addition, the space-charge of the reflexing electrons can cause the diode independence to fluctuate, resulting in oscillations of the electron beam energy. We have investigated a novel idea to remove these undesirable effects and we found that high-power, narrow-band, and monochromatic microwaves could be generated with efficiency of 10 to 20%. 16 refs., 7 figs.

Kwan, T.J.T.; Snell, C.M.

1986-01-01

342

Hydrodynamic Penetration of High Power Particle Beams  

NASA Astrophysics Data System (ADS)

A high power particle beam that dwells on a target can produce hydrodynamic effects if the energy deposition exceeds a threshold needed to vaporize the target (typically a few kJ/g). If lateral hydrodynamic expansion causes decompression during the pulse, the beam can penetrate much farther than expected. By combining the MARS energy deposition code with 2- and 3-D hydrodynamic codes (MESA and SPHINX) we have calculated the effects of high power beams in abnormal situations. A 20 TeV proton beam with ?_x=?_y=2 mm, 410^14 ppp, 290?s,which strikes the face of a 47800 cm graphite block, simulating a beam dump, creates a hole that expands laterally at 0.02cm/?s and longitudinally at 10cm/?s . If the beam is scanned across the face of the block at >=1mm/?s the beam moves into fresh material fast enough that there is no additional penetration beyond the static range. Proton interactions with a scraper were simulated with a ?_x=?_y=0.2 mm beam propagating 1 or 2? from a steel slab. A low density groove propagates parallel to the beam in the steel at about 60cm/?s, creating temperatures of 7000^circC and pressures of 25 kbar. Simulation of a superconducting magnet section produces similar temperatures and densities in the blowoff. Energy deposition in the superconducting coils reaches 25 J/g by 6?s and the beam tube reaches 1500^circC. These calculations illucidate abnormal scenarios to be avoided in accelerator design.

Wilson, D. C.; Goldstein, J. C.; Wingate, C. A.; Godwin, R. P.; Mokhov, N. V.

1998-04-01

343

Interaction of a High-Power Laser Beam with Metal Sheets  

SciTech Connect

Experiments with a high-power laser beam directed onto thin aluminum sheets, with a large spot size, demonstrate that airflow produces a strong enhancement of the interaction. The enhancement is explained in terms of aerodynamic effects. As laser heating softens the material, the airflow-induced pressure difference between front and rear faces causes the metal to bulge into the beam. The resulting shear stresses rupture the material and remove it at temperatures well below the melting point. The material heating is shown to conform to an elementary model. We present an analytic model of elastic bulging. Scaling with respect to spot size, wind speed, and material parameters is determined.

Boley, C D; Cutter, K P; Fochs, S N; Pax, P H; Rotter, M D; Rubenchik, A M; Yamamoto, R M

2009-06-24

344

Interaction of a high-power laser beam with metal sheets  

SciTech Connect

Experiments with a high-power laser beam directed onto thin aluminum sheets, with a large spot size, demonstrate that airflow produces a strong enhancement of the interaction. The enhancement is explained in terms of aerodynamic effects. As laser heating softens the material, the airflow-induced pressure difference between front and rear faces causes the metal to bulge into the beam. The resulting shear stresses rupture the material and remove it at temperatures well below the melting point. The material heating is shown to conform to an elementary model. We present an analytic model of elastic bulging. Scaling with respect to spot size, wind speed, and material parameters is determined.

Boley, C. D.; Cutter, K. P.; Fochs, S. N.; Pax, P. H.; Rotter, M. D.; Rubenchik, A. M.; Yamamoto, R. M. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2010-02-15

345

Measuring temperature profiles in high-power optical fiber components  

E-print Network

in temperature distribution caused by coupling a high-power laser beam into an optical fiber and by splicing two by coupling a high-power laser into an optical fiber. A uniform fiber Bragg grating was written at the end-coherence spectral interferometry. A large temperature change is found owing to coupling of a high-power laser

Horowitz, Moshe

346

Functionally strain-graded nanoscoops for high power Li-ion battery anodes.  

PubMed

Lithium-ion batteries show poor performance for high power applications involving ultrafast charging/discharging rates. Here we report a functionally strain-graded carbon-aluminum-silicon anode architecture that overcomes this drawback. It consists of an array of nanostructures each comprising an amorphous carbon nanorod with an intermediate layer of aluminum that is finally capped by a silicon nanoscoop on the very top. The gradation in strain arises from graded levels of volumetric expansion in these three materials on alloying with lithium. The introduction of aluminum as an intermediate layer enables the gradual transition of strain from carbon to silicon, thereby minimizing the mismatch at interfaces between differentially strained materials and enabling stable operation of the electrode under high-rate charge/discharge conditions. At an accelerated current density of ?51.2 A/g (i.e., charge/discharge rate of ?40C), the strain-graded carbon-aluminum-silicon nanoscoop anode provides average capacities of ?412 mAh/g with a power output of ?100 kW/kg(electrode) continuously over 100 charge/discharge cycles. PMID:21192713

Krishnan, Rahul; Lu, Toh-Ming; Koratkar, Nikhil

2011-02-01

347

Surface alloying of silicon into aluminum substrate.  

SciTech Connect

Aluminum alloys that are easily castable tend to have lower silicon content and hence lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:YAG laser with fiberoptic beam delivery was used to carry out the laser surface treatment to enhance the silicon content. Process parameters were varied to minimize the surface roughness from overlap of the laser beam treatment. The surface-alloyed layer was characterized and the silicon content was determined.

Xu, Z.

1998-10-28

348

Aluminum chlorohydrate III: Conversion to aluminum hydroxide.  

PubMed

Bayerite, an aluminum hydroxide polymorph, readily forms when the hydroxyl to aluminum ratio of aluminum chlorohydrate is raised to 3 by titration with sodium hydroxide. Dilution of aluminum chlorhydrate solutions with water leads to the formation of gibbsite, another aluminum hydroxide polymorph. The mechanism of conversion in each instance is related to the structure of the Al13O4(OH)24(H2O)7+(12) complex. PMID:7264935

Teagarden, D L; White, J L; Hem, S L

1981-07-01

349

High frequency, high power capacitor development  

NASA Astrophysics Data System (ADS)

A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

White, C. W.; Hoffman, P. S.

1983-03-01

350

Improved Collectors for High Power Gyrotrons  

SciTech Connect

High power gyrotrons are used for electron cyclotron heating, current drive and parasitic mode suppression in tokamaks for fusion energy research. These devices are crucial for successful operation of many research programs around the world, including the ITER program currently being constructed in France. Recent gyrotron failures resulted from cyclic fatigue of the copper material used to fabricated the collectors. The techniques used to collect the spent beam power is common in many gyrotrons produced around the world. There is serious concern that these tubes may also be at risk from cyclic fatigue. This program addresses the cause of the collector failure. The Phase I program successfully demonstrated feasibility of a mode of operation that eliminates the cyclic operation that caused the failure. It also demonstrated that new material can provide increased lifetime under cyclic operation that could increase the lifetime by more than on order of magnitude. The Phase II program will complete that research and develop a collector that eliminates the fatigue failures. Such a design would find application around the world.

R. Lawrence Ives, Amarjit Singh, Michael Read, Philipp Borchard, Jeff Neilson

2009-05-20

351

High Power Experiments in VX-10  

NASA Astrophysics Data System (ADS)

In the Advanced Space Propulsion Laboratory VASIMR experiment (VX-10) we have measured a plasma flux to input gas rate ratio near 100power levels up to 10 kW. The plasma source is being developed to supply a dense target with a high degree of ionization for ICRF acceleration of the flow in an expanding magnetic field. An upgrade to 20 kW helicon operations is underway. Recent results at Oak Ridge National Laboratory show enhanced efficiency operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter, so comparable power densities will be achieved in VX-10. We have operated with a Boswell double-saddle antenna design with a magnetic cusp just upstream of the antenna. Recently we have converted to a double-helix half-turn antenna. ICRF experiments have been performed as 1.5 kW that show significant plasma flow acceleration, doubling the flow velocity. A 10 kW ICRF upgrade is underway. Results from high total power ( 30 kW) experiments with this new helicon antenna and ICRF acceleration are presented.

Squire, Jared; Chang-Diaz, Franklin; Araya-Chacon, Gonzalo; Jacobson, Verlin; Glover, Tim; McCaskill, Greg; Vera, Jerry; Baity, Wally; Carter, Mark; Goulding, Rick

2004-11-01

352

High power diode laser remelting of metals  

NASA Astrophysics Data System (ADS)

This article is focused on the laser surface remelting of the steel samples with predefined overlapping of the laser spots. The goal of our experimental work was to evaluate microstructure and hardness both in overlapped zone and single pass ones for three kinds of ferrous metals with different content of carbon, cast iron, non-alloy structural steel and tool steel. High power fibre coupled diode laser Laserline LDF 3600-100 was used with robotic guided processing head equipped by the laser beam homogenizer that creates rectangular beam shape with uniform intensity distribution. Each sample was treated with identical process parameters - laser power, beam diameter, focus position, speed of motion and 40% spot overlap. Dimensions and structures of the remelted zone, zone of the partial melting, heat affected zone and base material were detected and measured by means of laser scanning and optical microscopes. Hardness progress in the vertical axis of the overlapped zone from remelted surface layer to base material was measured and compared with the hardness of the single spots. The most hardness growth was found for cast iron, the least for structural steel. Experiment results will be used to processing parameters optimization for each tested material separately.

Chmelickova, H.; Tomastik, J.; Ctvrtlik, R.; Supik, J.; Nemecek, S.; Misek, M.

2014-04-01

353

High-power LED package requirements  

NASA Astrophysics Data System (ADS)

Power LEDs have evolved from simple indicators into illumination devices. For general lighting applications, where the objective is to light up an area, white LED arrays have been utilized to serve that function. Cost constraints will soon drive the industry to provide a discrete lighting solution. Early on, that will mean increasing the power densities while quantum efficiencies are addressed. For applications such as automotive headlamps & projection, where light needs to be tightly collimated, or controlled, arrays of die or LEDs will not be able to satisfy the requirements & limitations defined by etendue. Ultimately, whether a luminaire requires a small source with high luminance, or light spread over a general area, economics will force the evolution of the illumination LED into a compact discrete high power package. How the customer interfaces with this new package should be an important element considered early on in the design cycle. If an LED footprint of adequate size is not provided, it may prove impossible for the customer, or end user, to get rid of the heat in a manner sufficient to prevent premature LED light output degradation. Therefore it is critical, for maintaining expected LED lifetime & light output, that thermal performance parameters be defined, by design, at the system level, which includes heat sinking methods & interface materials or methdology.

Wall, Frank; Martin, Paul S.; Harbers, Gerard

2004-01-01

354

High frequency, high power capacitor development  

NASA Technical Reports Server (NTRS)

A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

White, C. W.; Hoffman, P. S.

1983-01-01

355

Innovations in high power fiber laser applications  

NASA Astrophysics Data System (ADS)

Diffraction-limited high power lasers represent a new generation of lasers for materials processing, characteristic traits of which are: smaller, cost-effective and processing "on the fly". Of utmost importance is the high beam quality of fiber lasers which enables us to reduce the size of the focusing head incl. scanning mirrors. The excellent beam quality of the fiber laser offers a lot of new applications. In the field of remote cutting and welding the beam quality is the key parameter. By reducing the size of the focusing head including the scanning mirrors we can reach scanning frequencies up to 1.5 kHz and in special configurations up to 4 kHz. By using these frequencies very thin and deep welding seams can be generated experienced so far with electron beam welding only. The excellent beam quality of the fiber laser offers a high potential for developing new applications from deep penetration welding to high speed cutting. Highly dynamic cutting systems with maximum speeds up to 300 m/min and accelerations up to 4 g reduce the cutting time for cutting complex 2D parts. However, due to the inertia of such systems the effective cutting speed is reduced in real applications. This is especially true if complex shapes or contours are cut. With the introduction of scanner-based remote cutting systems in the kilowatt range, the effective cutting speed on the contour can be dramatically increased. The presentation explains remote cutting of metal foils and sheets using high brightness single mode fiber lasers. The presentation will also show the effect of optical feedback during cutting and welding with the fiber laser, how those feedbacks could be reduced and how they have to be used to optimize the cutting or welding process.

Beyer, Eckhard; Mahrle, Achim; Ltke, Matthias; Standfuss, Jens; Brckner, Frank

2012-02-01

356

Breakdown phenomena in high power klystrons  

SciTech Connect

In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a renewed interest in breakdown phenomena for nanosecond pulse, multi-megavolt per centimeter fields has been sparked by recent R and D work in the area of gigawatt RF sources. The most important regions of electrical breakdown are in the output cavity gap area, the RF ceramic windows, and the gun ceramic insulator. The details of the observed breakdown in these regions, experiments performed to understand the phenomena and solutions found to alleviate the problems will be discussed. Recently experiments have been performed on a new prototype R and D klystron. Peak electric fields across the output cavity gaps of this klystron exceed 2 MV/cm. The effect of peak field duration (i.e. pulse width) on the onset of breakdown have been measured. The pulse widths varied from tens of nanoseconds to microseconds. Results from these experiments will be presented. The failure of ceramic RF windows due to multipactor and puncturing was an important problem to overcome in order that our high power klystrons would have a useful life expectancy. Consequently many studies and tests were made to understand and alleviate window breakdown phenomena. Some of the results in this area, especially the effects of surface coatings, window materials and processing techniques and their effects on breakdown will be discussed. Another important source of klystron failure in the recent past at SLAC has been the puncturing of the high voltage ceramic insulator in the gun region. A way of alleviating this problem has been found although the actual cause of the puncturing is not yet clear. The ''practical'' solution to this breakdown process will be described and a possible mechanism for the puncturing will be presented. 9 refs., 5 figs., 3 tabs.

Vlieks, A.E.; Allen, M.A.; Callin, R.S.; Fowkes, W.R.; Hoyt, E.W.; Lebacqz, J.V.; Lee, T.G.

1988-03-01

357

The Jefferson Lab High Power Light Source  

SciTech Connect

Jefferson Lab has designed, built and operated two high average power free-electron lasers (FEL) using superconducting RF (SRF) technology and energy recovery techniques. Between 1999-2001 Jefferson Lab operated the IR Demo FEL. This device produced over 2 kW in the mid-infrared, in addition to producing world record average powers in the visible (50 W), ultraviolet (10 W) and terahertz range (50 W) for tunable, short-pulse (< ps) light. This FEL was the first high power demonstration of an accelerator configuration that is being exploited for a number of new accelerator-driven light source facilities that are currently under design or construction. The driver accelerator for the IR Demo FEL uses an Energy Recovered Linac (ERL) configuration that improves the energy efficiency and lowers both the capital and operating cost of such devices by recovering most of the power in the spent electron beam after optical power is extracted from the beam. The IR Demo FEL was de-commissioned in late 2001 for an upgraded FEL for extending the IR power to over 10 kW and the ultraviolet power to over 1 kW. The FEL Upgrade achieved 10 kW of average power in the mid-IR (6 microns) in July of 2004, and its IR operation currently is being extended down to 1 micron. In addition, we have demonstrated the capability of on/off cycling and recovering over a megawatt of electron beam power without diminishing machine performance. A complementary UV FEL will come on-line within the next year. This paper presents a summary of the FEL characteristics, user community accomplishments with the IR Demo, and planned user experiments.

James R. Boyce

2006-01-01

358

High Power Amplifier and Power Supply  

NASA Technical Reports Server (NTRS)

A document discusses the creation of a high-voltage power supply (HVPS) that is able to contain voltages up to -20 kV, keep electrical field strengths to below 200 V/mil (approximately equal to 7.87 kV/mm), and can provide a 200-nanosecond rise/fall time focus modulator swinging between cathode potential of 16.3 kV and -19.3 kV. This HVPS can protect the 95-GHz, pulsed extended interaction klystron (EIK) from arcs/discharges from all sources, including those from within the EIK fs vacuum envelope. This innovation has a multi-winding pulse transformer design, which uses new winding techniques to provide the same delays and rise/fall times (less than 10 nanoseconds) at different potential levels ranging from -20 kV to -16 kV. Another feature involves a high-voltage printed-wiring board that was corona-free at -20 kV DC with a 3- kV AC swing. The corona-free multilayer high-voltage board is used to simulate fields of less than 200 V/mil (approximately equal to 7.87 kV/mm) at 20 kV DC. Drive techniques for the modulator FETs (field-effect transistors) (four to 10 in a series) were created to change states (3,000-V swing) without abrupt steps, while still maintaining required delays and transition times. The packing scheme includes a potting mold to house a ten-stage modulator in the space that, in the past, only housed a four-stage modulator. Problems keeping heat down were solved using aluminum oxide substrate in the high-voltage section to limit temperature rise to less than 10 while withstanding -20 kV DC voltage and remaining corona-free.

Duong, Johnny; Stride, Scot; Harvey, Wayne; Haque, Inam; Packard, Newton; Ng, Quintin; Ispirian, Julie Y.; Waian, Christopher; Janes, Drew

2008-01-01

359

High power infrared QCLs: advances and applications  

NASA Astrophysics Data System (ADS)

QCLs are becoming the most important sources of laser radiation in the midwave infrared (MWIR) and longwave infrared (LWIR) regions because of their size, weight, power and reliability advantages over other laser sources in the same spectral regions. The availability of multiwatt RT operation QCLs from 3.5 ?m to >16 ?m with wall plug efficiency of 10% or higher is hastening the replacement of traditional sources such as OPOs and OPSELs in many applications. QCLs can replace CO2 lasers in many low power applications. Of the two leading groups in improvements in QCL performance, Pranalytica is the commercial organization that has been supplying the highest performance QCLs to various customers for over four year. Using a new QCL design concept, the non-resonant extraction [1], we have achieved CW/RT power of >4.7 W and WPE of >17% in the 4.4 ?m - 5.0 ?m region. In the LWIR region, we have recently demonstrated QCLs with CW/RT power exceeding 1 W with WPE of nearly 10 % in the 7.0 ?m-10.0 ?m region. In general, the high power CW/RT operation requires use of TECs to maintain QCLs at appropriate operating temperatures. However, TECs consume additional electrical power, which is not desirable for handheld, battery-operated applications, where system power conversion efficiency is more important than just the QCL chip level power conversion efficiency. In high duty cycle pulsed (quasi-CW) mode, the QCLs can be operated without TECs and have produced nearly the same average power as that available in CW mode with TECs. Multiwatt average powers are obtained even in ambient T>70C, with true efficiency of electrical power-to-optical power conversion being above 10%. Because of the availability of QCLs with multiwatt power outputs and wavelength range covering a spectral region from ~3.5 ?m to >16 ?m, the QCLs have found instantaneous acceptance for insertion into multitude of defense and homeland security applications, including laser sources for infrared countermeasures for protecting aircraft from MANPADS, testing of infrared countermeasures, MWIR and LWIR lasers for identify-friend-or-foe (IFF) personnel beacons, infrared target illuminators and designators and tunable QCL applications including in-situ and standoff detection of chemical warfare agents (CWAs) and explosives. The last of these applications addresses a very important and timely need for detection of improvised explosive devices (IEDs) in combat environments like Iraq and Afghanistan.

Patel, C. Kumar N.

2012-01-01

360

High Power Flex-Propellant Arcjet Performance  

NASA Technical Reports Server (NTRS)

A MW-class electrothermal arcjet based on a water-cooled, wall-stabilized, constricted arc discharge configuration was subjected to extensive performance testing using hydrogen and simulated ammonia propellants with the deliberate aim of advancing technology readiness level for potential space propulsion applications. The breadboard design incorporates alternating conductor/insulator wafers to form a discharge barrel enclosure with a 2.5-cm internal bore diameter and an overall length of approximately 1 meter. Swirling propellant flow is introduced into the barrel, and a DC arc discharge mode is established between a backplate tungsten cathode button and a downstream ringanode/ spin-coil assembly. The arc-heated propellant then enters a short mixing plenum and is accelerated through a converging-diverging graphite nozzle. This innovative design configuration differs substantially from conventional arcjet thrusters, in which the throat functions as constrictor and the expansion nozzle serves as the anode, and permits the attainment of an equilibrium sonic throat (EST) condition. During the test program, applied electrical input power was varied between 0.5-1 MW with hydrogen and simulated ammonia flow rates in the range of 4-12 g/s and 15-35 g/s, respectively. The ranges of investigated specific input energy therefore fell between 50-250 MJ/kg for hydrogen and 10-60 MJ/kg for ammonia. In both cases, observed arc efficiencies were between 40-60 percent as determined via a simple heat balance method based on electrical input power and coolant water calorimeter measurements. These experimental results were found to be in excellent agreement with theoretical chemical equilibrium predictions, thereby validating the EST assumption and enabling the utilization of standard TDK nozzle expansion analyses to reliably infer baseline thruster performance characteristics. Inferred specific impulse performance accounting for recombination kinetics during the expansion process implied nearly frozen flow in the nozzle and yielded performance ranges of 800-1100 sec for hydrogen and 400-600 sec for ammonia. Inferred thrust-to-power ratios were in the range of 30-10 lbf/MWe for hydrogen and 60-20 lbf/MWe for ammonia. Successful completion of this test series represents a fundamental milestone in the progression of high power arcjet technology, and it is hoped that the results may serve as a reliable touchstone for the future development of MW-class regeneratively-cooled flex-propellant plasma rockets.

Litchford, Ron J.

2011-01-01

361

High-power semiconductor separate-confinement double heterostructure lasers  

SciTech Connect

The review is devoted to high-power semiconductor lasers. Historical reference is presented, physical and technological foundations are considered, and the concept of high-power semiconductor lasers is formulated. Fundamental and technological reasons limiting the optical power of a semiconductor laser are determined. The results of investigations of cw and pulsed high-power semiconductor lasers are presented. Main attention is paid to inspection of the results of experimental studies of single high-power semiconductor lasers. The review is mainly based on the data obtained in the laboratory of semiconductor luminescence and injection emitters at the A.F. Ioffe Physicotechnical Institute. (review)

Tarasov, I S [A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg (Russian Federation)

2010-10-15

362

Technology trend and challenges in high power semiconductor laser packaging  

Microsoft Academic Search

High power semiconductor lasers have found increased applications in pumping of solid state laser systems for industrial, military and medical applications as well as direct material processing applications such as welding, cutting, and surface treatment. Driven by low cost, longer lifetime and new applications, the requirements of high power semiconductor lasers have been changed and the demand for new products

Xingsheng Liu; Wei Zhao

2009-01-01

363

Practical medium voltage converter topologies for high power applications  

Microsoft Academic Search

Multilevel power conversion has been receiving increasing attention in the past few years for high power applications. Numerous topologies and modulation strategies have been introduced and studied extensively for utility and drive applications in the recent literature. These converters are suitable in high voltage and high power applications due to their ability to synthesize waveforms with better harmonic spectrum and

Peter K. Steimer; Madhav D. Manjrekar

2001-01-01

364

Dual Robust Controller Design for High Power AC Servo Drive  

Microsoft Academic Search

High power AC motors have a highly interacting multivariable control structure, and it is difficult to design high dynamic performance AC drive with traditional PID-like controller for high power AC servo motor. This paper presents analysis, design and simulation of velocity loop dual robust controller for 11 kw permanent magnetic synchronous motor (PMSM) in the AC servo system. By combining

Stone Cheng; Yuan-Yong Huang; Hsin-Hung Chou

2008-01-01

365

Aluminum/sulfur battery discharge in the high current domain  

SciTech Connect

The search for contemporary batteries with the requisite high power and energy densities for electric propulsion of vehicles has blurred the conventional distinctions of electrochemical storage systems. The author previously introduced an aqueous aluminum/sulfur battery with separate anode and cathode compartments (separated by an ion-selective membrane). The high-capacity cathode compartment contained aqueous polysulfide electrolyte, while the anode compartment contained concentrated alkali, but no polysulfide, electrolyte to prevent chemical attack of the aluminum by solution-phase zero-valent sulfur. The author reports here that concentrated dissolved sulfur, rather than attacking the aluminum anode, permits facile efficient aluminum oxidation. Therefore, a cell configuration without a resistive limiting membrane is feasible. An aluminum/sulfur battery is demonstrated to be capable of sustained current densities of 1 A/cm{sup 2}. High efficiency and current density are important for electric vehicle applications.

Licht, S. [Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Chemistry

1997-06-01

366

OPERATIONAL ASPECTS OF HIGH POWER ENERGY RECOVERY LINACS  

SciTech Connect

We have been operating a high-power energy-recovery linac (ERL) at Jefferson Lab for several years. In the process we have learned quite a bit about both technical and physics limitations in high power ERLs. Several groups are now considering new ERLs that greatly increase either the energy, the current or both. We will present some of our findings on what to consider when designing, building, and operating a high power ERL. Our remarks for this paper are limited to lattice design and setup, magnets, vacuum chamber design, diagnostics, and beam stability.

Stephen Benson; David Douglas; Pavel Evtushenko; Kevin Jordan; George Neil; Paul Powers

2006-08-21

367

8. HIGH POWER SPRAY IN MEN'S PACK ROOM. Hot ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. HIGH POWER SPRAY IN MEN'S PACK ROOM. - Hot Springs National Park Bathhouse Row, Maurice Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

368

9. HIGH POWER SPRAY IN MEN'S STEAM ROOM. Hot ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. HIGH POWER SPRAY IN MEN'S STEAM ROOM. - Hot Springs National Park, Bathhouse Row, Fordyce Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

369

Innovative fuel designs for high power density pressurized water reactor  

E-print Network

One of the ways to lower the cost of nuclear energy is to increase the power density of the reactor core. Features of fuel design that enhance the potential for high power density are derived based on characteristics of ...

Feng, Dandong, Ph. D. Massachusetts Institute of Technology

2006-01-01

370

Design of annular fuel for high power density BWRs  

E-print Network

Enabling high power density in the core of Boiling Water Reactors (BWRs) is economically profitable for existing or new reactors. In this work, we examine the potential for increasing the power density in BWR plants by ...

Morra, Paolo

2005-01-01

371

Analysis of delamination and darkening in high power LED packaging  

Microsoft Academic Search

Luminous emittance declination due to interfacial delamination and darkening is a fatal defect for the GaN-based high power light-emitting diodes (LEDs) under a long time service. This letter brought forward an accelerated aging test under 350 mA forward current, 25degC, 54% RH, 256 hours to testify and analysis the abnormal dark stain on the die surface of high power blue

Longzao Zhou; Bing An; Yiping Wu; Shunhong Liul

2009-01-01

372

Design and technology of compact high-power converters  

Microsoft Academic Search

New material technologies such as silicon carbide (SiC) are promising in the development of compact high-power converters for next-generation power electronics applications. This paper presents an optimized converter design approach that takes into consideration nonlinear interactions among various converter components, source and load. It is shown that with the development of high-temperature, high-power SiC power module technology, magnetic components and

Krishna Shenai; Philip G. Neudeck; G. Schwarze

2000-01-01

373

Beam-path conditioning for high-power laser systems  

SciTech Connect

Heating of mirrors and windows by high-power radiation from a laser transmitter produces turbulent density gradients in the gas near the optical surfaces. If the gradients are left uncontrolled, the resulting phase errors reduce the intensity on the target and degrade the signal returned to a receiver. Beam path conditioning maximizes the efficiency of the optical system by alleviating thermal turbulence within the beam path. Keywords: High power radiation, Beam path, Optical surface, Laser beams, Reprints. (JHD)

Stephens, T.; Johnson, D.; Languirand, M.

1990-01-01

374

Arc-Free High-Power dc Switch  

NASA Technical Reports Server (NTRS)

Hybrid switch allows high-power direct current to be turned on and off without arcing or erosion. Switch consists of bank of transistors in parallel with mechanical contacts. Transistor bank makes and breaks switched circuit; contacts carry current only during steady-state "on" condition. Designed for Space Shuttle orbiter, hybrid switch can be used also in high-power control circuits in aircraft, electric autos, industrial furnaces, and solar-cell arrays.

Miller, W. N.; Gray, O. E.

1982-01-01

375

A three-phase soft-switched high power density DC\\/DC converter for high power applications  

Microsoft Academic Search

The authors present three DC\\/DC converter topologies suitable for high-power-density high-power applications. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is seen to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high frequency

R. W. De Doncker; D. M. Divan; M. H. Kheraluwala

1988-01-01

376

A three-phase soft-switched high-power-density DC\\/DC converter for high-power applications  

Microsoft Academic Search

Three DC\\/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode.

Rik W. A. A. De Doncker; Deepakraj M. Divan; Mustansir H. Kheraluwala

1991-01-01

377

High-power visible laser effect on a Boston Micromachines' MEMS deformable mirror  

NASA Astrophysics Data System (ADS)

Continuous-facesheet and segmented Boston Micromachines Corporations' (BMC) Micro-Electrical Mechanical Systems (MEMS) Deformable Mirrors (DM) have been tested for their response to high-power visible-wavelength laser light. The deformable mirrors, coated with either protected silver or bare aluminum, were subjected to a maximum of 2 Watt laser-light at a wavelength of 532 nanometers. The laser light was incident on a ~ 3.53.5 cm area for time periods from minutes to 7 continuous hours. Spot heating from the laser-light is measured to induce a local bulge in the surface of each DM. For the aluminum-coated continuous facesheet DM, the induced spot heating changes the surface figure by 16 nm rms. The silver-coated continuous-facesheet and segmented (spatial light modulator) DMs experience a 6 and 8 nm surface rms change in surface quality with the laser at 2 Watts. For spatial frequencies less than the actuator spacing (300 mm), the laser induced surface bulge is shown to be removable, as the DMs continued to be fully functional during and after their exposure. Over the full 10 mm aperture one could expect the same results with a 15 Watt laser guide star (LGS). These results are very promising for use of the MEMS DM to pre-correct the outgoing laser light in the Laboratory for Adaptive Optics' (LAO) laser uplink application.

Norton, Andrew; Gavel, Donald; Dillon, Daren; Cornelissen, Steven

2010-07-01

378

Aluminum and Young Artists.  

ERIC Educational Resources Information Center

The author suggests a variety of ways in which aluminum and aluminum foil can be used in elementary and junior high art classes: relief drawing and rubbing; printing; repousse; sculpture; mobiles; foil sculpture; and three dimensional design. Sources of aluminum supplies are suggested. (SJL)

Anderson, Thomas

1980-01-01

379

Output spectrum of high-power CW fiber amplifier  

NASA Astrophysics Data System (ADS)

A generation spectrum of a high-power Yb-doped fiber amplifier (YDFA) becomes broader with increasing power in the master oscillator power amplifier (MOPA) configuration, which degenerating the coherence of the laser. In this work, a spectral model had been proposed for the high-power YDFA in Continuous Wave (CW) region. A fiber amplifier was built at the 600W level and experiments were conducted for its output spectral characteristics based on this model. Through this model, the output spectrum of high-power YDFA in CW region could be calculated. Though the theoretical spectra were in little different from the measured ones, the predictions of the theory were still in excellent quantitative agreement with the experimental results.

Liu, Wei; Xiao, Hu; Wang, Xiaolin; Zhou, Pu

2013-09-01

380

Stretchers and compressors for ultra-high power laser systems  

NASA Astrophysics Data System (ADS)

This review is concerned with pulse stretchers and compressors as key components of ultra-high power laser facilities that take advantage of chirped-pulse amplification. The potentialities, characteristics, configurations and methods for the matching and alignment of these devices are examined, with particular attention to the history of the optics of ultra-short, ultra-intense pulses before and after 1985, when the chirped-pulse amplification method was proposed, which drastically changed the view of the feasibility of creating ultra-high power laser sources. The review is intended primarily for young scientists and experts who begin to address the amplification and compression of chirped pulses, experts in laser optics and all who are interested in scientific achievements in the field of ultra-high power laser systems.

Yakovlev, I. V.

2014-05-01

381

High-power lead-acid batteries for different applications  

NASA Astrophysics Data System (ADS)

High-power lead-acid batteries have been used for a rather long time in various applications, especially for uninterruptible power supplies (UPSs) and starting of automobiles. Future automotive service requires, in addition to cold-cranking performance, the combination of high-power capability, a very good charge-acceptance, and an excellent cycle-life. Such applications include stop-start, regenerative braking, and soft, mild and full hybrid vehicles. For UPS, there has been a clear tendency to shorter discharge times and higher discharge rates. During the past decades, the specific power of lead-acid batteries has been raised steadily and there is still, room for further improvement. This paper gives an overview of the progress made in the development of high-power lead-acid batteries and focuses on stationary and automotive applications.

Wagner, Rainer

382

Ultra high vacuum broad band high power microwave window  

DOEpatents

An improved high vacuum microwave window has been developed that utilizes high density polyethylene coated on two sides with SiOx, SiNx, or a combination of the two. The resultant low dielectric and low loss tangent window creates a low outgassing, low permeation seal through which broad band, high power microwave energy may be passed. No matching device is necessary and the sealing technique is simple. The features of the window are broad band transmission, ultra-high vacuum compatibility with a simple sealing technique, low voltage standing wave ratio, high power transmission and low cost.

Nguyen-Tuong, Viet (Seaford, VA); Dylla, III, Henry Frederick (Yorktown, VA)

1997-01-01

383

High power density direct formic acid fuel cells  

NASA Astrophysics Data System (ADS)

A demonstration of direct formic acid fuel cells (DFAFCs) generating relatively high power density at ambient temperature is reported. The performance of Nafion 112-based DFAFCs with different concentrations of formic acid at different temperatures has been evaluated. DFAFCs operated with dry air and zero back-pressure can generate power densities of 110 and 84 mW cm -2 at 30 and 18 C, respectively, which are considerably higher than direct methanol fuel cells (DMFCs) operated under the same conditions. The DFAFCs are especially suited to power portable devices used at ambient temperature because the significant high power density can be achieved with highly concentrated formic acid.

Zhu, Yimin; Ha, Su Y.; Masel, Richard I.

384

High power ytterbium-doped fiber lasers fundamentals and applications  

NASA Astrophysics Data System (ADS)

In this paper, we summarize the fundamental properties and review the latest developments in high power ytterbium-doped fiber (YDF) lasers. The review is focused primarily on the main fiber laser configurations and the related cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancements observed in high power fiber lasers. The review also includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, modal instabilities and photodarkening. The paper summarizes the power evolution in continuous-wave (CW) and pulsed YDF lasers and their impact on material processing and other industrial applications.

Zervas, Michalis N.

2014-03-01

385

Electronic protection of high-power rectifiers from current overloads  

Microsoft Academic Search

This paper describes a fast-acting and economical circuit for protecting high-power lines from current overloads; the circuit can operate into any load and has a turn-off time less than one half-cycle of the line voltage.

I. Y. Butov; A. N. Kuzyutin

1985-01-01

386

The asterix III pulsed high-power iodine laser  

Microsoft Academic Search

A system description and first results of the Asterix III high-power iodine laser built at IPP Garching are given. This laser is designed to yield an output energy of 1 kJ in about 1 ns. Until now pulses with output energies up to 300 J and pulse lengths ranging from 1 to 3 ns have been obtained.

G. Brederlow; K. J. Witte; E. Fill; K. Hohla; R. Volk

1976-01-01

387

On the film density using high power impulse magnetron sputtering  

Microsoft Academic Search

The influence on thin film density using high power impulse magnetron sputtering (HiPIMS) has been investigated for eight different target materials (Al, Ti, Cr, Cu, Zr, Ag, Ta, and Pt). The density values as well as deposition rates have been compared to results obtained from thin films grown by direct current magnetron sputtering (DCMS) under the same experimental conditions. Overall,

Mattias Samuelsson; Daniel Lundin; Jens Jensen; Michael A. Raadu; Jon Tomas Gudmundsson; Ulf Helmersson

2010-01-01

388

Using a Balun Transformer Combiner for High Power Microwave Experiments  

SciTech Connect

A novel coaxial power combiner design has been duplicated that has distinct advantages over other combiner geometries that can handle high power. This design is being applied to combine four 3 kW power supplies to obtain a 10 kW, 5 MHz system for an ICRF antenna on HSX. In the past, Wilkinson type combiners have had limited application to high power systems because of the lack of non-inductive, high power, 100 Omega balance loads. With this new design, standard 50 Omega dummy loads can be used instead for the balance load. The cost is considerably lower than lumped element combiner designs which are dominated by capacitor costs. At such a relatively low frequency, a 3-dB quarter-wave coupled-line coupler becomes impractically long, and a conventional branch-line hybrid requires 35 Omega-line, which is commercially unavailable. The balun combiner uses less transmission line than a ring hybrid and has good bandwidth characteristics even away from its best line impedance. Theoretical calculations and modeling were performed for line impedances from 65 Omega to 75 Omega. Measurements from a low-power test device show excellent agreement with theory, and construction of the high power system is underway.

Kaufman, Michael C [ORNL; Pesavento, Philip V [ORNL

2011-01-01

389

A control method for high power UPSs in parallel operation  

Microsoft Academic Search

The parallel operation of static inverters is, in a large number of cases, the appropriate solution to achieve the high power required by some applications or to improve system reliability. To higher the power in a lot of industrial applications is equivalent to adding a new UPS unit to an already existing one. In UPS systems there are situations where

A. P. Martins; A. S. Carvalho; A. S. Araujo

1995-01-01

390

Energetics of Propellant Options for High-Power Hall Thrusters  

E-print Network

Energetics of Propellant Options for High-Power Hall Thrusters Alex Kieckhafer and Lyon B. King propellants such as krypton and cadmium are favorable for high-Isp, low-thrust applications, whereas heavier propellants such as mercury and bismuth are preferable for low-Isp, high-thrust missions. Calculations

King, Lyon B.

391

Novel SBS suppression scheme for high-power fiber amplifiers  

Microsoft Academic Search

A new scheme for suppression of Stimulated Brillouin Scattering (SBS) in high power fiber amplifiers is proposed where the fiber core diameter varies along the fiber length. The fiber has an ultra-large core diameter at most locations to suppress SBS, while at certain locations the core is relatively small to reduce bending sensitivity. A numerical model based on SBS rate

Anping Liu

2006-01-01

392

Very high Power THz radiation from Relativistic Electrons  

SciTech Connect

We report the production of high power (20 watts average, {approx}1 Megawatt peak) broadband THz light based on coherent emission from relativistic electrons. We describe the source, presenting theoretical calculations and their experimental verification. For clarity we compare this source with one based on ultrafast laser techniques.

G.L. Carr; Michael C. Martin; Wayne R. McKinney; Kevin Jordan; George R. Neil; Gwyn P. Williams

2002-08-01

393

High-power UV LED array for curing photoadhesives  

Microsoft Academic Search

A high power UV LED array operating at 396nm with an output greater than 1 Watt has been developed. Performance characteristics of the device are presented. It is also shown that the device is as effective as traditional arc lamps in curing acrylic adhesives as demonstrated through microhardness and DSC testing.

Manfred Hubert; Chris F. Dimas; Paul Orava; Joyce Koo

2003-01-01

394

IGCTs: High-Power Technology for power electronics applications  

Microsoft Academic Search

This paper focuses on the most recent technical developments in integrated gate commutated thyristors. Improved safe operating area (SOA) of a new IGCT chip set based on ABB's high power technology (HPT) platform with a rated voltage of 10 kV is presented. A matching 10 kV freewheeling diode is also reported. Combined, these developments open the door to new applications

I. Nistor; T. Wikstrom; M. Scheinert

2009-01-01

395

Resonance tracking and vibration stablilization for high power ultrasonic transducers.  

PubMed

Resonant frequency shift and electrical impedance variation are common phenomena in the application of high power ultrasonic transducers, e.g. in focused ultrasound surgery and in cutting. They result in low power efficiency and unstable vibration amplitude. To solve this problem, a driving and measurement system has been developed to track the resonance of high power transducers and to stabilise their vibration velocity. This has the ability to monitor the operating and performance parameters of the ultrasonic transducers in real time. The configuration of the system, with its control algorithm implemented in LabVIEW (National Instruments, Newbury, UK), ensures flexibility to suit different transducers and load conditions. In addition, with different programs, it can be utilised as a high power impedance analyser or an instantaneous electrical power measurement system for frequencies in the MHz range. The effectiveness of this system has been demonstrated in detailed studies. With it, high transducer performance at high power can be achieved and monitored in real time. PMID:23928264

Kuang, Y; Jin, Y; Cochran, S; Huang, Z

2014-01-01

396

Damping and resonance in a high power switching circuit  

Microsoft Academic Search

Switching circuits with thyristor controlled reactors are used in high power systems for static VAR control and flexible AC transmission. These circuits can exhibit highly nonlinear behavior because the thyristor switch off time depends on the circuit state. This paper shows how to understand and predict damping and resonance in a basic thyristor controlled reactor circuit used for static VAR

Ian Dobson; Sasan Jalali; Rajesh Rajaraman

1995-01-01

397

Active beam integrator for high-power coherent lasers  

Microsoft Academic Search

In laser materials processing applications it is often necessary to work with uniform intensity distributions. This goal is quite difficult to achieve when dealing with high power laser beams, and becomes critical for a successful application involving surface heat treatment of non-metallic materials. We have designed and tested a very simple beam shaper for transforming the initial intensity distribution of

Ferran Laguarta; J. Armengol; Fidel Vega; Nuria B. Lupon

1996-01-01

398

Power MOSFETs Paralleling Operation for High Power High Density Converters  

Microsoft Academic Search

In high power high density converters, the power MOSFETs can be used in parallel as the main switch to meet the current rating requirement, increase the switching frequency, and reduce the power loss. This paper investigates the possible benefits and problems associated with the power MOSFETs paralleling operation for higher power high frequency applications. The conduction state current sharing and

Hongfang Wang; Fred Wang

2006-01-01

399

Modal Interactions in High-Power Ultrasonic Processing Transducers  

NASA Astrophysics Data System (ADS)

High-power ultrasonic processing is based on the exploitation of nonlinear phenomena linked to large amplitude ultrasonic waves and includes a wide range of processes. Such processes require the development of specific devices for the right generation of the high-intensities needed. Stepped-plate transducers, piezoelectrically driven, represent a new efficient power ultrasonic technology for applications in fluids and multiphase media. Such devices are multimode systems which operate in one single selected mode at high power and low ultrasonic frequencies. However, nonlinearity gives rise to a series of phenomena which are not present under linear excitation. In particular, the appearance of harmonics, fractional harmonics, combination resonances, etc., as well as the interaction among different modes represent important limitations for the use of high-power ultrasonic transducers. Energy exchange among the modes may generate high-amplitude vibration of non-tuned modes causing heating, noise and even component failures. This paper deals with the experimental evidence of the production of undesired vibration modes and their interaction in high-power stepped-plate ultrasonic transducers and suggests some practical procedures in the design and use of such devices to avoid or to palliate such important practical problem.

Gallego-Jurez, J. A.; Riera, E.; Acosta-Aparicio, V. M.

2008-06-01

400

Transmutation and energy-production with high power accelerators  

SciTech Connect

Accelerator-driven transmutation offers attractive new solutions to complex nuclear problems. This paper outlines the basics of the technology, summarizes the key application areas, and discusses designs of and performance issues for the high-power proton accelerators that are required.

Lawrence, G.P.

1995-07-01

401

High-Power Target System for Radioisotope Production.  

National Technical Information Service (NTIS)

To utilize the powerful external beams, available from H sup - cyclotrons, a high-power, target system was designed by The Cyclotron Corp. of Berkeley, CA and further developed at TRIUMF. The system consists of two target stations served by beam lines fro...

J. J. Burgerjon, Z. Gelbart, G. O. Hendry, J. C. Lofvendahl, L. McIlwraith

1986-01-01

402

Device for wavefront correction in an ultra high power laser  

DOEpatents

A system for wavefront correction in an ultra high power laser. As the laser medium flows past the optical excitation source and the fluid warms its index of refraction changes creating an optical wedge. A system is provided for correcting the thermally induced optical phase errors.

Ault, Earl R. (Livermore, CA); Comaskey, Brian J. (Walnut Creek, CA); Kuklo, Thomas C. (Oakdale, CA)

2002-01-01

403

Solidly mounted resonators under high power study for reliability assessment  

Microsoft Academic Search

This work deals with BAW SMR reliability at high power levels. Experimental methods easy to set up in common RF laboratories are presented and validated. Experimental results concerning frequency shifts versus the dissipated power and the harmonics generation are reported. The main origins of these effects are discussed physically and conclusions in light of the obtained results about the characterization

Nizar Ben Hassine; Denis Mercier; Philippe Renaux

2009-01-01

404

Optical simulation analysis of high power LED package structure  

Microsoft Academic Search

The single LED package structure determines the light intensity distribution and the well-designed package structure will be conductive to light emitting and improve its external quantum efficiency. This paper based on the optical package structure of high power LED, in order to analyze the influence of the structure of LED package on optical performance and the feasibility of the packaging

Yinong Liu; Yiping Wu; Bing An

2011-01-01

405

High power factor rectifier with reduced conduction and commutation losses  

Microsoft Academic Search

This paper presents a high power factor rectifier with reduced conduction and commutation losses for telecommunication applications. The reduced conduction losses are obtained through the use of a single converter, instead of the conventional configuration, composed of a four-diode front-end rectifier followed by a boost converter. A nondissipative snubber is responsible for the reduction in the commutation losses. A prototype

Alexandre Ferrari de Souza; Ivo Barbi

1999-01-01

406

High power density, high frequency, and high voltage pulse transformer  

Microsoft Academic Search

Summary form only given, as follows. In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power

S. C. Kim; S. H. Nam; D. T. Kim

2001-01-01

407

High power density, high frequency, and high voltage pulse transformer  

Microsoft Academic Search

In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power supply. However, a step-up ratio of

S. C. Kim; S. H. Nam; S. H. Kim; D. T. Kim; S. H. Jeong

2001-01-01

408

High Power Electric Propulsion for Deep Space Missions  

NASA Technical Reports Server (NTRS)

Slide presentation reviews: (1) An Electric Propulsion Primer (2) The Flexible Path and the Electric Path (2a) A New Plan for Human Exploration (2b)The Role of Electric Propulsion (3) High Power Electric Thrusters (3a)Hall Thrusters (3b) Magnetoplasmadynamic Thrusters (4)Challenges for the Next Generation of Advanced Propulsion Technologist

Polk, Jay

2011-01-01

409

Aluminum: Recycling of Aluminum Dross/Saltcake  

SciTech Connect

As this NICE3 publication details, the objective of this project is to commercialize the process technology to eliminate all landfill waste associated with black dross and saltcake generated from aluminum recycling in the United States.

Blazek, S.

1999-01-29

410

High power light emitting diode based setup for photobleaching fluorescent impurities  

E-print Network

High power light emitting diode based setup for photobleaching fluorescent impurities Tobias K be photobleached before final sample preparation. The instrument consists of high power light emitting diodes

Kaufman, Laura

411

Pinch me - I'm fusing! Fusion Power - what is it? What is a z pinch? And why are z-pinches a promising fusion power technology?  

Microsoft Academic Search

The process of combining nuclei (the protons and neutrons inside an atomic nucleus) together with a release of kinetic energy is called fusion. This process powers the Sun, it contributes to the world stockpile of weapons of mass destruction and may one day generate safe, clean electrical power. Understanding the intricacies of fusion power, promised for 50 years, is sometimes

MARK S

2000-01-01

412

Aspects of aluminum toxicity  

SciTech Connect

Aluminum is the most abundant metal in the earth's crust. The widespread occurrence of aluminum, both in the environment and in foodstuffs, makes it virtually impossible for man to avoid exposure to this metal ion. Attention was first drawn to the potential role of aluminum as a toxic metal over 50 years ago, but was dismissed as a toxic agent as recently as 15 years ago. The accumulation of aluminum, in some patients with chronic renal failure, is associated with the development of toxic phenomena; dialysis encephalopathy, osteomalacic dialysis osteodystrophy, and an anemia. Aluminum accumulation also occurs in patients who are not on dialysis, predominantly infants and children with immature or impaired renal function. Aluminum has also been implicated as a toxic agent in the etiology of Alzheimer's disease, Guamiam amyotrophic lateral sclerosis, and parkinsonism-dementia. 119 references.

Hewitt, C.D.; Savory, J.; Wills, M.R. (Univ. of Virginia Health Sciences Center, Charlottesville (USA))

1990-06-01

413

Observation of exothermic reaction during laser-assisted iron oxide coating on aluminum alloy  

Microsoft Academic Search

Aluminum and Fe3O4 reacts readily in what is known as thermite reaction to produce large amount of heat. Attempts were made to coat Fe-oxide on A319 cast aluminum alloy employing a high power laser to exploit this reaction. High-speed, high-resolution infrared thermography was employed to study the thermal conditions during the laser treatment. Parallel experiment using a less exothermic oxide

S. Nayak; Hsin Wang; Edward A. Kenik; Ian M. Anderson; Narendra B. Dahotre

2005-01-01

414

Aluminum\\/sulfur battery discharge in the high current domain  

Microsoft Academic Search

The search for contemporary batteries with the requisite high power and energy densities for electric propulsion of vehicles has blurred the conventional distinctions of electrochemical storage systems. The author previously introduced an aqueous aluminum\\/sulfur battery with separate anode and cathode compartments (separated by an ion-selective membrane). The high-capacity cathode compartment contained aqueous polysulfide electrolyte, while the anode compartment contained concentrated

Stuart Licht

1997-01-01

415

An innovative demonstration of high power density in a compact MHD (magnetohydrodynamic) generator  

SciTech Connect

The present program was conducted by the University of Tennessee Space Institute (UTSI). It was by its nature a high risk experimental program to demonstrate the feasibility of high power density operation in a laboratory scale combustion driven MHD generator. Maximization of specific energy was not a consideration for the present program, but the results have implications in this regard by virtue of high energy fuel used. The power density is the ratio of the electrical energy output to the internal volume of the generator channel. The MHD process is a volumetric process and the power density is therefore a direct measure of the compactness of the system. Specific energy, is the ratio of the electrical energy output to consumable energy used for its production. The two parameters are conceptually interrelated. To achieve high power density and implied commensurate low system volume and weight, it was necessary to use an energetic fuel. The high energy fuel of choice was a mixture of powdered aluminum and carbon seeded with potassium carbonate and burned with gaseous oxygen. The solid fuel was burned in a hybrid combustion scheme wherein the fuel was cast within a cylindrical combustor in analogy with a solid propellant rocket motor. Experimental data is limited to gross channel output current and voltage, magnetic field strength, fuel and oxidizer flow rates, flow train external temperatures and combustor pressure. Similarly, while instantaneous oxidizer flow rates were measured, only average fuel consumption based on pre and post test component weights and dimensions was possible. 4 refs., 60 figs., 9 tabs.

Schmidt, H.J.; Lineberry, J.T.; Chapman, J.N.

1990-06-01

416

Test Results From a High Power Linear Alternator Test Rig  

NASA Technical Reports Server (NTRS)

Stirling cycle power conversion is an enabling technology that provides high thermodynamic efficiency but also presents unique challenges with regard to electrical power generation, management, and distribution. The High Power Linear Alternator Test Rig (HPLATR) located at the NASA Glenn Research Center (GRC) in Cleveland, Ohio is a demonstration test bed that simulates electrical power generation from a Stirling engine driven alternator. It implements the high power electronics necessary to provide a well regulated DC user load bus. These power electronics use a novel design solution that includes active rectification and power factor control, active ripple suppression, along with a unique building block approach that permits the use of high voltage or high current alternator designs. This report describes the HPLATR, the test program, and the operational results.

Birchenough, Arthur G.; Hervol, David S.; Gardner, Brent G.

2010-01-01

417

High power microwave components for space communications satellite  

NASA Technical Reports Server (NTRS)

Analyzed, developed, and tested were high power microwave components for communications satellites systems. Included were waveguide and flange configurations with venting, a harmonic filter, forward and reverse power monitors, electrical fault sensors, and a diplexer for two channel simultaneous transmission. The assembly of 8.36 GHz components was bench tested, and then operated for 60 hours at 3.5 kW CW in a high vacuum. The diplexer was omitted from this test pending a modification of its end irises. An RF leakage test showed only that care is required at flange junctions; all other components were RF tight. Designs were extrapolated for 12 GHz and 2.64 GHz high power satellite systems.

Jankowski, H.; Geia, A.

1972-01-01

418

Gate Drive For High Speed, High Power IGBTs  

SciTech Connect

A new gate drive for high-voltage, high-power IGBTs has been developed for the SLAC NLC (Next Linear Collider) Solid State Induction Modulator. This paper describes the design and implementation of a driver that allows an IGBT module rated at 800A/3300V to switch up to 3000A at 2200V in 3{micro}S with a rate of current rise of more than 10000A/{micro}S, while still being short circuit protected. Issues regarding fast turn on, high de-saturation voltage detection, and low short circuit peak current will be presented. A novel approach is also used to counter the effect of unequal current sharing between parallel chips inside most high-power IGBT modules. It effectively reduces the collector-emitter peak current, and thus protects the IGBT from being destroyed during soft short circuit conditions at high di/dt.

Nguyen, M.N.; Cassel, R.L.; de Lamare, J.E.; Pappas, G.C.; /SLAC

2007-06-18

419

A Lemon Cell Battery for High-Power Applications  

NASA Astrophysics Data System (ADS)

This article discusses the development of a lemon cell battery for high-power applications. The target application is the power source of a dc electric motor for a model car constructed by first-year engineering students as part of their introductory course design project and competition. The battery is composed of a series of lemon juice cells made from UV vis cuvets that use a magnesium anode and copper cathode. Dilution of the lemon juice to reduce the rate of corrosion of the magnesium anode and the addition of table salt to reduce the internal resistance of the cell are examined. Although our specific interest is the use of this lemon cell battery to run an electric dc motor, high-power applications such as radios, portable cassette or CD players, and other battery-powered toys are equally appropriate for demonstration and laboratory purposes using this battery.

Muske, Kenneth R.; Nigh, Christopher W.; Weinstein, Randy D.

2007-04-01

420

Modelling of a reflective waveplate for high-power lasers  

NASA Astrophysics Data System (ADS)

The polarization state of a laser has a huge bearing on the physics of laser-plasma interactions and it is often desirable to change between linear and circular. For short pulse high power lasers large beam apertures are necessary for transportation. However, in these extreme conditions transmissive birefringent polarization optics become impractical due to their delicacy and their dispersion of the laser bandwidth which will increase the pulse length, which along with large B-integrals, which arises from the transmission of the high-power beams through optics, can be detrimental to the intensity of the laser. It is therefore necessary to consider reflective optics in order to change the polarization. Modelling has been performed at the Central Laser Facility on a design of a large aperture broadband reflective waveplate suitable for short pulse laser systems.

Heathcote, Robert I.; Buck, Samuel; Clarke, Robert J.; Green, James S.

2014-09-01

421

Designing high power targets with computational fluid dynamics (CFD)  

SciTech Connect

High power liquid hydrogen (LH2) targets, up to 850 W, have been widely used at Jefferson Lab for the 6 GeV physics program. The typical luminosity loss of a 20 cm long LH2 target was 20% for a beam current of 100 {micro}A rastered on a square of side 2 mm on the target. The 35 cm long, 2500 W LH2 target for the Qweak experiment had a luminosity loss of 0.8% at 180 {micro}A beam rastered on a square of side 4 mm at the target. The Qweak target was the highest power liquid hydrogen target in the world and with the lowest noise figure. The Qweak target was the first one designed with CFD at Jefferson Lab. A CFD facility is being established at Jefferson Lab to design, build and test a new generation of low noise high power targets.

Covrig, Silviu D. [JLAB

2013-11-01

422

Review of high-power microwave source research  

Microsoft Academic Search

This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of

Steven H. Gold; Gregory S. Nusinovich

1997-01-01

423

Design considerations for high power high frequency transformers  

Microsoft Academic Search

Various design considerations for high-power (multikilowatt), high-frequency transformers for DC-DC power converters are investigated. Although Ferrite (PC40) is lossier than Permalloy80 (0.5 mil) at the frequencies of interest (25-50 kHz) the use of the former is justified on the basis of cost, weight, and wide ranges of shapes. The influence of the leakage flux distribution in the window region on

M. H. Kheraluwala; D. W. Novotny; D. M. Divan

1990-01-01

424

Modeling of high power LED illumination distribution using ANN  

Microsoft Academic Search

High power light emitting diodes (HP-LEDs) are more suitable for energy saving applications and have becoming replacing traditional fluorescent and incandescent bulbs for its energy efficient. Therefore, HP-LED lighting has been regarded in the next-generation lighting. In this study, illumination distribution of white color HP-LED was examined and modeled by artificial neural network (ANN) to use at the different lighting

I. Kiyak; V. Topuz; B. Oral

2009-01-01

425

High power wide bandwidth plasma-beam amplifier  

Microsoft Academic Search

High power broad-band stationary-regime microwave amplifier has been developed by authors. This beam-plasma-filled microwave amplifier (plasma TWT) based on hybrid slow-wave structure (SWS) has been developed by the authors as a non-relativistic gas-plasma-filled Coupled Cavity Traveling-Wave Tube (CC TWT) designed as a sealed tube, is characterized by a combination of unique high electron efficiency 35%, pass-band width up to 25%,

V. Perevodchikov; P. Borovikov; S. Gusev; J. Kuznetsov; V. Martynov; A. Shapiro; E. Shlifer; P. Tyuryukanov; M. Zavjalov

2000-01-01

426

High power pulsed magnetron sputtering of transparent conducting oxides  

Microsoft Academic Search

High power pulsed magnetron sputtering (HPPMS) has been used in order to study the deposition of transparent conducting oxides. We summarize the studies carried out on different materials (indium tin oxide-ITO and aluminium-doped zinc oxide-AZO) using rather different technological approaches, namely sputtering of ceramic targets and reactive sputtering.For the deposition of AZO reactive HPPMS for metallic targets has been used.

V. Sittinger; F. Ruske; W. Werner; C. Jacobs; B. Szyszka; D. J. Christie

2008-01-01

427

Optical fiber instrumentation of a high power generator and turbine  

NASA Astrophysics Data System (ADS)

The instrumentation of a high power generator and its complementary systems including the turbine bearings is presented and discussed. The generator consists of a 175MW hydroelectric generator installed in the Salto Osrio power plant in the southern region of Brazil. Results show good agreement with the already existing instrumentation and demonstrate the technology potential for a full optical fiber sensing system to monitor these large machines.

da Silva, Erlon Vagner; Dreyer, Uilian Jos; de Morais Sousa, Kleiton; Babinski, Valderi Junot; Somenzi, Jonas; Mezzadri, Felipe; de Loureno Junior, Ivo; Martelli, Cicero; Cardozo da Silva, Jean Carlos

2013-05-01

428

High power operational experience with the LANSCE Linac  

SciTech Connect

The heart of the Los Alamos Neutron Science Center (LANSCE) is a pulsed linear accelerator that is used to simultaneously provide H+ and H- beams to several user facilities. This accelerator contains two Cockcroft-Walton style injectors, a 100-MeV drift tube linac and an 800-MeV coupled cavity linac. This presentation will touch on various aspects of the high power operation including performance, tune-up strategy, beam losses and machine protection.

Rybarcyk, Lawrence J [Los Alamos National Laboratory

2008-01-01

429

Novel approach using tapers for high power FET chips characterization  

Microsoft Academic Search

This paper introduces a novel approach for the characterization of high power devices of total gate periphery (GP) around 20 mm. Electrical models of two power FET chip devices (GP=4.8 mm and 12.6 mm) are obtained from scattering parameters measurements based on broadband impedance transformers and from DC pulsed measurements. A small scaling factor applied on these electrical models allows

M. Zoyo; C. Galy; A. Darbandi; L. Lapierre; J. F. Sautereau

1995-01-01

430

High-power laser diodes at various wavelengths  

SciTech Connect

High power laser diodes at various wavelengths are described. First, performance and reliability of an optimized large transverse mode diode structure at 808 and 941 nm are presented. Next, data are presented on a 9.5 kW peak power array at 900 nm having a narrow emission bandwidth suitable for pumping Yb:S-FAP laser materials. Finally, results on a fiber-coupled laser diode array at {approx}730 nm are presented.

Emanuel, M.A.

1997-02-19

431

Optical design of a high power fiber optic coupler  

SciTech Connect

Fiber optic beam delivery systems are replacing conventional mirror delivery systems for many reasons (e.g., system flexibility and redundancy, stability, and ease of alignment). Commercial products are available that use of fiber optic delivery for laser surgery and materials processing. Also, pump light of dye lasers can be delivered by optical fibers. Many laser wavelengths have been transported via optical fibers; high power delivery has been reported for argon, Nd:YAG, and excimer. We have been developing fiber optic beam delivery systems for copper vapor laser light; many of the fundamental properties of these systems are applicable to other high power delivery applications. A key element of fiber optic beam delivery systems is the coupling of laser light into the optical fiber. For our application this optical coupler must be robust to a range of operating parameters and laser characteristics. We have access to a high power copper vapor laser beam that is generated by a master oscillator/power amplifier (MOPA) chain comprised of three amplifiers. The light has a pulse width of 40--50 nsec with a repetition rate of about 4 kHz. The average power (nominal) to be injected into a fiber is 200 W. (We will refer to average power in this paper.) In practice, the laser beam's direction and collimation change with time. These characteristics plus other mechanical and operational constraints make it difficult for our coupler to be opto-mechanically referenced to the laser beam. We describe specifications, design, and operation of an optical system that couples a high-power copper vapor laser beam into a large core, multimode fiber. The approach used and observations reported are applicable to fiber optic delivery applications. 6 refs., 6 figs.

English, R.E. Jr.; Halpin, J.M.; House, F.A.; Paris, R.D.

1991-06-19

432

Improved output performance of high-power VCSELs  

Microsoft Academic Search

The intention of this paper is to report on state-of-the-art high-power vertical-cavity surface-emitting laser diodes (VCSELs), single devices as well as two-dimensional (2-D) arrays. Both approaches are studied in terms of electrooptical characteristics, beam performance, and scaling behavior. The maximum continuous wave (CW) output power at room temperature of large-area bottom-emitting devices with ac