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ABSTRACT: To provide substantial reduction in the size and energy of high-energy-density experiments, we have designed, built, and operated a liner implosion system that is driven by a multiturn-primary, single-turn-secondary, current step-up toroidal transformer. The Precision High Energy-density Liner Implosion eXperiment (PHELIX) pulsed-power driver, which is currently under development at Los Alamos National Laboratory, Los Alamos, NM, can provide >;400 kJ of capacitively stored energy and peak load currents of >;5 MA to implode centimeter-size liners in 10-20 μs, attaining speeds of 1-4 km/s. Diagnosis of scaled-down liner implosion experiments will be performed with the 800-MeV proton radiographic (pRad) system at Los Alamos Neutron Science Center (LANSCE); therefore, PHELIX is designed to be portable with a footprint of only 8 ×25 ft<sup>2</sup>. The multiframe, high-resolution imaging capability of pRad will be used to study hydrodynamic and material phenomena. Experiments with scaled-down electromagnetic railguns, pulsed high-field magnets, and magnetic flux compression are also under consideration. This paper discusses the overall PHELIX design concept and layout, and details of the electromechanical design needed to ensure repeatable operation.
IEEE Transactions on Plasma Science 11/2011; · 1.17 Impact Factor
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James H Goforth,
Henn Oona,
Dennis H Herrera,
David T Torres,
D. G. Tasker,
R. K. Meyer,
W. L. Atchison,
C. L. Rousculp,
R. E. Reinovsky,
M. Sheppard, P. J. Turchi,
R. G. Watt
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ABSTRACT: In 1980, Los Alamos formed the 'Megajoule Committee' with the expressed goal of developing a one Megajoule plasma radiation source. The ensuing research and development has given rise to a wide variety of high explosive pulsed power accomplishments, and there is a continuous stream of work that continues to the present. A variety of flux compression generators (FCGs or generators) have been designed and tested, and a number of pulse shortening schemes have been investigated. Supporting computational tools have been developed in parallel with experiments. No fewer that six unique systems have been developed and used for experiments. This paper attempts to pull together the technical details, achievements, and wisdom amassed during the intervening thirty years, and notes how we would push for increased performance in the future.
10/2010
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ABSTRACT: Plasma guns offer opportunities to generate and direct plasma flows at high energy density. Typically, such guns comprise coaxial electrodes that are connected to high-current sources (e.g., capacitor banks, pulse lines, inductive stores, or magnetic-flux-compression generators). The basic interactions include ionization of materials such as injected gas or preinstalled wires/foils, acceleration of these materials by the Lorentz force, and expulsion of the resulting plasma flows. We review the use of a particular arrangement in the form of a plasma flow switch that acts as a multimegampere commutator, but it can also provide a magnetized-plasma target for compression by an imploding liner. In a quite separate concept, a plurality of quasi-steady plasma guns in a spherical array provides converging, collimated jets to compress plasma with stand-off from the plasma generators and chamber walls. Such stand-off in a repetitively pulsed system can be crucial for the development of fusion power reactors at megagauss energy densities.
IEEE Transactions on Plasma Science 09/2010; · 1.17 Impact Factor
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ABSTRACT: The Precision, High-Energy Density, Liner Implosion eXperiment (PHELIX) pulsed power driver is currently under development at Los Alamos National Laboratory. When operational PHELIX will provide 5-10 MAmps of peak current with pulse rise-time of ~5-10 ms. Crucial to the performance of PHELIX is a multi-turn primary, single-turn secondary, current step-up toroidal transformer, R<sub>major</sub> ~ 30 cm, R<sub>minor</sub> ~ 10 cm. The transformer lifetime should exceed 100 shots. Therefore it is essential that the design be robust enough to survive the magnetic stresses produced by high currents. In order to evaluate our design, two methods have been utilized. First, an analytical evaluation has been performed. By identifying the magnetic forces as J<sub>1</sub> <sup>2</sup>/2 ¿L<sub>1</sub> + J<sub>1</sub>J<sub>2</sub>¿M<sub>12</sub>, where J<sub>1</sub> and J<sub>2</sub> are currents in two circuits, coupled by mutual inductance M<sub>12</sub> and L<sub>1</sub> is the self-inductance of the circuit carrying current J<sub>1</sub>, analytical estimates of stress can be obtained. These results are then compared to a computational MHD model of the same system and to a full finite-element, electromagnetic simulation.
Pulsed Power Conference, 2009. PPC '09. IEEE; 08/2009
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Conference Proceeding:
PHELIX
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ABSTRACT: The Precision, High-Energy density, Liner Implosion eXperiment (PHELIX) pulsed power driver is currently under development at Los Alamos National Laboratory. When operational PHELIX will provide 0.5-1.0 MJ of capacitively stored energy into cm size liners that will reach implosion velocities of 1-4 km/s with approximately 10-20 microsecond implosion time. Peak load currents will be in the 5-10 megamp range. To do this the machine will employ a reusable, multi-turn primary, single-turn secondary transformer to couple the 100-120 kV Marx capacitor system to the load. The transformer has been designed toward a coupling coefficient of 0.9. PHELIX is designed to be portable with only an 8 Ã 25 ft<sup>2</sup> footprint. This will allow the machine to be taken to the experiment designer's diagnostic of choice. The first such diagnostic will the LANL proton-radiography facility. There the multi-frame, high-resolution, imaging capability will be used to study hydrodynamic and material phenomena.
Pulsed Power Conference, 2009. PPC '09. IEEE; 08/2009
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P.J. Turchi
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ABSTRACT: Several plasma targets have been proposed for compression by imploding liners, ranging from magnetically-confined to wall-supported concepts. In all cases, a critical issue remains one of preventing the high atomic-number material of the liner from penetrating the plasma and countering the gain in plasma temperature sought by compression. Two factors foster development of such deleterious penetration: the creation of a liquid/vapor layer at the liner surface at high magnetic fields, and disruption of this layer by Rayleigh-Taylor instability in the final stages of plasma compression. Within a general consideration of issues of liner compression of plasma, we discuss reactor cost optimization by use of plasma at pressures intermediate between the values of conventional magnetically-or inertially-confined fusion concepts. We also describe the development of an equilibrium layer of vapor adjacent to the liner surface at high magnetic fields, the instability of such a thin layer, and the consequences of liner deceleration and rebound for reactor concepts and research progress.
IEEE Transactions on Plasma Science 03/2008; · 1.17 Impact Factor
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J.H. Degnan,
D.J. Amdahl,
A. Brown,
T. Cavazos,
S.K. Coffey,
M.T. Domonkos,
M.H. Frese,
S.D. Frese,
D.G. Gale,
T.C. Grabowski, [......],
J.D. Letterio,
J.V. Parker,
R.E. Peterkin,
N.F. Roderick,
E.L. Ruden,
R.E. Siemon,
W. Sommars,
W. Tucker, P.J. Turchi,
G.A. Wurden
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ABSTRACT: Magnetized target fusion (MTF) is a means to compress plasmas to fusion conditions that uses magnetic fields to greatly reduce electron thermal conduction, thereby greatly reducing compression power density requirements. The compression is achieved by imploding the boundary, a metal shell. This effort pursues formation of the field-reversed configuration (FRC) type of magnetized plasma, and implosion of the metal shell by means of magnetic pressure from a high current flowing through the shell. We reported previously on experiments demonstrating that we can use magnetic pressure from high current capacitor discharges to implode long cylindrical metal shells (liners) with size, symmetry, implosion velocity, and overall performance suitable for compression of FRCs. We also presented considerations of using deformable liner-electrode contacts of Z-pinch geometry liners or theta pinch-driven liners, in order to have axial access to inject FRCs and to have axial diagnostic access. Since then, we have experimentally implemented the Z-pinch discharge driven deformable liner-electrode contact, obtained full axial coverage radiography of such a liner implosion, and obtained 2frac12 dimensional MHD simulations for a variety of profiled thickness long cylindrical liners. The radiographic results indicate that at least 16 times radial compression of the inner surface of a 0.11-cm-thick Al liner was achieved, with a symmetric implosion, free of instability growth in the plane of the symmetry axis. We have also made progress in combining 2frac12-D MHD simulations of FRC formation with imploding liner compression of FRCs. These indicate that capture of the injected FRC by the imploding liner can be achieved with suitable relative timing of the FRC formation and liner implosion discharges.
IEEE Transactions on Plasma Science 03/2008; · 1.17 Impact Factor
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ABSTRACT: Pulsed-power hydrodynamics (PPH) is an evolving application of low-impedance pulsed-power technology. PPH is particularly useful for the study of problems in advanced hydrodynamics, instabilities, turbulence, and material properties. PPH techniques provide a precisely characterized controllable environment at the currently achievable extremes of pressure and material velocity. The Atlas facility, which is designed and built by Los Alamos National Laboratory, is the world's first, and only, laboratory pulsed-power system designed specifically for this relatively new family of pulsed-power applications. Atlas joins a family of low-impedance high-current drivers around the world, which is advancing the field of PPH. The high-precision cylindrical magnetically imploded liner is the tool most frequently used to convert electromagnetic energy into the hydrodynamic (particle kinetic) energy needed to drive strong shocks, quasi-isentropic compression, or large-volume adiabatic compression for the experiments. At typical parameters, a 30-g 1-mm-thick liner with an initial radius of 5 cm and a moderate current of 20 MA can be accelerated to 7.5 km/s, producing megabar shocks in medium density targets. Velocities of up to 20 km/s and pressures of > 20 Mbar in high-density targets are possible. The first Atlas liner implosion experiments were conducted in Los Alamos in September 2001. Sixteen experiments were conducted in the first year of operation before Atlas was disassembled, moved to the Nevada Test Site (NTS), and recommissioned in 2005. The experimental program resumed at the NTS in July 2005. The first Atlas experiments at the NTS included two implosion dynamics experiments, two experiments exploring damage and material failure, a new advanced hydrodynamics series aimed at studying the behavior of particles of damaged material ejected from a free surface into a gas, and a series exploring friction at sliding interfaces under conditions of high normal pressure and h-
igh relative velocities. Longer term applications of PPH and the Atlas system include the study of material interfaces subjected to multimegagauss magnetic fields, material strength at high strain rate, the properties of strongly coupled plasmas, and the equation of state of materials at pressures approaching 10 Mbar.
IEEE Transactions on Plasma Science 03/2008; · 1.17 Impact Factor
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ABSTRACT: Preparation of the target plasma represents a critical issue in liner compression techniques to achieve fusion conditions. We consider the use of an ultrahigh speed plasma flow from a special coaxial-gun arrangement known as the plasma flow switch. Experiments have demonstrated that this arrangement can provide plasma flows with speeds in excess of 2000 km/s. Stagnation of such a plasma flow results in fully stripped aluminum plasma with electron temperatures of 30 keV. Substitution of deuterium or a deuterium-tritium mixture could provide target plasma at kilovolt temperatures within an imploding liner. Such temperatures suggest that, even if substantial heat loss occurred during liner compression, fusion-level temperatures would be possible. The concatenation of events to generate the ultrahigh speed flow, to direct it into the implosion chamber, and to arrange liner dynamics for effective compression demands numerical simulation, which is based on initial analytical estimates. Both types of calculation for exploring this concept are discussed.
IEEE Transactions on Plasma Science 03/2008; · 1.17 Impact Factor
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R. E. Siemon,
B. S. Bauer,
T. J. Awe,
M. A. Angelova,
S. Fuelling,
T. Goodrich,
I. R. Lindemuth,
V. Makhin,
W. L. Atchison,
R. J. Faehl,
R. E. Reinovsky, P. J. Turchi,
J. H. Degnan,
E. L. Ruden,
M. H. Frese,
S. F. Garanin,
V. N. Mokhov
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ABSTRACT: A method is described for choosing experimental parameters in studies of high-energy-density (HED) physics relevant to fusion
energy, as well as other applications. An important HED issue for magneto-inertial fusion (MIF) is the interaction of metal
pusher materials with megagauss (MG) magnetic fields during liner compression of magnetic flux and fusion fuel. The experimental
approach described here is to study a stationary conductor when a pulsed current generates MG fields at the surface, instead
of studying the inner surface of a moving liner. This places less demand upon the pulsed power system, and significantly improves
diagnostic access. Thus the deceptively simple geometry chosen for this work is that of a z pinch composed of a metal cylinder
carrying large current. Consideration of well known stability issues for the z pinch shows that for given peak current and
rise time from a particular power supply, there is a minimum radius and thus maximum B field that can be created without disruption
of the conductor before peak current. The reasons are reviewed why MG levels of magnetic field, as required for MIF, result
in high temperatures and plasma formation at the surface of the metal in response to Ohmic heating. The distinction is noted
between the liner regime obtained with cylindrical rods, which have a skin depth small compared to the conductor radius, and
the exploding thin-wire regime, which has skin depth larger than the wire radius. A means of diagnostic development is described
using a small facility (DPM15) built at the University of Nevada, Reno. It is argued that surface plasma temperature measurements
in the 10-eV range are feasible based on the intensity of visible light emission.
Journal of Fusion Energy 01/2008; 27(4):235-240. · 0.52 Impact Factor
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R.E. Siemon,
B.S. Bauer,
T.J. Awe,
M.A. Angelova,
S. Fuelling,
T. Goodrich,
I.R. Lindemuth,
V. Makhin,
V. Ivanov,
R. Presura,
W.L. Atchison,
R.J. Faehl,
R.E. Reinovsky,
D.W. Scudder, P.J. Turchi,
J.H. Degnan,
E.L. Ruden,
M.H. Frese,
S.F. Garanin,
V.N. Mokhov
[show abstract]
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ABSTRACT: Experiments suitable for a variety of pulsed power facilities are being developed to study plasma formation and stability on the surface of typical liner materials in the megagauss (MG) regime. Understanding the plasma properties near the surface is likely to be critical for the design of Magnetized Target Fusion experiments, where the plasma density in the region near the wall can play an important role in setting the transport from hot fuel to the cold boundary. From the perspective of diagnostic access and simplicity, the surface of a stationary conductor with large enough current to generate MG surface field offers advantages compared with studying the surface of a moving liner. This paper reports on recent experiments at UNR that have generated magnetic fields in the range of about 0.2 to 3 MG, which confirm the viability of future experiments planned at Atlas and/or Shiva Star. Diagnostics reported here involve electrical measurements, streak camera photography, and surface luminosity. Additional diagnostic measurements and numerical modeling will be reported in the future.
Megagauss magnetic field generation and related topics, 2006 ieee international conference on; 12/2006
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S. Fuelling,
T.J. Awe,
B.S. Bauer,
T. Goodrich,
V. Makhin,
V.V. Ivanov,
R. Presura,
R.E. Siemon,
R.E. Reinovsky, P.J. Turchi,
J.H. Degnan,
E.L. Ruden
[show abstract]
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ABSTRACT: Load hardware and diagnostics have been developed to study metal vapor and plasma formed from aluminum surfaces by pulsed MG fields on Zebra. Radiation MHD modeling indicates plasma formation should occur between 3-5 MG, but such modeling depends on assumed material properties, which are a topic of ongoing research. The experiment is designed to learn about this interesting threshold for plasma formation. A current of 1 MA is pulsed along a stationary, central wire, to generate magnetic fields of 3-5 MG. The goal is to observe and diagnose the formation of metal vapor and plasma in the vicinity of the wire. The simple geometry enables easy access by diagnostics, which include magnetic sensors, filtered photodiode measurements, optical imaging, and laser schlieren, shadowgraphy, interferomerry and Faraday rotation. From these measurements the magnetic field, the density and temperature of the surface metal plasma, the radiation field, and the growth of instabilities will be inferred. Predictions of experimental data will be calculated from numerical simulations and compared with experimental results. The diagnostics are time resolved, so as to examine individually the distinct phases of compression, plasma formation, radiation-magnetohydrodynamic evolution, and instability. Diagnostics have being developed using a small HV pulser.
Megagauss magnetic field generation and related topics, 2006 ieee international conference on; 12/2006
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[show abstract]
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ABSTRACT: For several decades many have studied or conducted experiments to drive magnetic fields into metallic conducting materials. Examples include designs for electrically exploded fuses, exploding wires to generate high energy plasmas, and of course heavy metal liners as kinetic drivers for hydrodynamic experiments. When the material melts the surface can develop highly unstable dynamics. One of the most common results is the onset and growth of spatial perturbations taking on the form of spike and bubble like structures. This is usually identified as Magneto-Raleigh-Taylor (MRT) instability. A clear example is when excessive current is applied to accelerate a near normal density thick metal liner to velocities approaching 1.0 cm/musec or greater. Yet we have observed several experiments where melting of the liner was present but the outside liner surface was observed to remained stable (B-0.5 to 1.3 MG). Analysis of this and other cases compared to MHD simulations enabled us to examine this phenomenon under a variety of conditions. While the majority of the cases still are fundamentally acceleration driven instability of a fluid interface, other phenomenon have been observed to play a significant role such as the effect of liquid/vapor phase change at the surface. Additionally, this suggests there may be drive conditions that can maintain the aluminum at conditions well away from the saturated liquid line until the conditions are well above the triple point in aluminum. There are some indications that this may reduce or delay the MRT like instabilities. However excessive drive that pressurizes the melted layer too much produces unfavorable gradients in the material that grossly aggravate the traditional MRT instabilities. In this talk we will examine in detail the effects of EOS structure, conductivity dependence on state properties (e.g. density and temperature), and the magnitude and time dependence of the driving magnetic field on the evolution of surface conditions.-
Based on these observations we propose that controlling the surface stability may depend on careful adjustment of time scales associated with the driving waveform and kinetics of the liner in order to control the path in phase space (EOS) the material follows.
Megagauss magnetic field generation and related topics, 2006 ieee international conference on; 12/2006
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P.J. Turchi
[show abstract]
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ABSTRACT: For several decades, the notion of compression of plasma to fusion conditions by liner implosion has been pursued by several groups. This quest has often achieved success with some form of liner implosion technology, but not in the actual compression of plasma. Several plasma targets have been proposed, ranging from plasma magnetized to reduce heat transfer, but mechanically-supported by the liner, to plasmas confined and supported by magnetic field, in some configuration of open and closed field-lines. In all cases, the principal issue remains one of preventing the high atomic-number material of the liner from penetrating the plasma and countering the gain in plasma temperature sought by compression. Two factors foster development of such deleterious penetration: the creation of a liquid/vapor layer at the liner surface at high magnetic fields, and disruption of this layer by Rayleigh-Taylor instability in the final stages of plasma compression. The latter factor, of course, depends on the desired efficiency of energy transfer from liner kinetic energy to the plasma. In reactor concepts, the efficiency needs to be high in order to reduce the total system energy and size to attractive values. Within a general review of issues of liner compression of plasma, we discuss reactor cost optimization by use of plasma at pressures intermediate between the values of conventional magnetically- or inertially-confined fusion concepts. We also describe the development of an equilibrium layer of vapor adjacent to the liner surface at high magnetic fields, and the consequences of liner deceleration and rebound for reactor concepts and research progress.
Magagauss Magnetic Field Generation and Related Topics, 2006 IEEE International Conference on; 12/2006
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J.H. Degnan,
A.N. Brown,
T. Cavazos,
S.K. Coffey,
M. Domonkos,
M.H. Frese,
S.D. Frese,
D. Gale,
C. Gilman,
C. Grabowski, [......],
J.V. Parker,
R.E. Peterkin,
N.F. Roderick,
E.L. Ruden,
R.E. Siemon,
W. Sommars,
W. Tucker, P.J. Turchi,
G.A. Wurden,
Y C.F. Thio
[show abstract]
[hide abstract]
ABSTRACT: Magnetized Target Fusion (MTF) is a means to compress plasmas to fusion conditions that uses magnetic fields to greatly reduce electron thermal conduction, thereby greatly reducing compression power density requirements (1,2). The compression is achieved by imploding the boundary, a metal shell. This effort pursues formation of the Field Reversed Configuration (FRC) type of magnetized plasma, and implosion of the metal shell by means of magnetic pressure from a high current flowing through the shell. We reported at Megagauss 9 that we had shown experimentally (3) that we can use magnetic pressure from high current capacitor discharges to implode long cylindrical metal shells (liners) with size, symmetry, implosion velocity, and overall performance that is suitable for compression of Field Reversed Configurations (FRC's). We also presented considerations of using deformable liner ¿ electrode contacts of Z-pinch geometry liners or theta pinch driven liners, in order to have axial access to inject FRC's and to have axial diagnostic access. Since then, we have experimentally implemented the Z-pinch discharge driven deformable liner ¿ electrode contact, obtained full axial coverage radiography of such a liner implosion, and obtained 2D-MHD simulations for a variety of profiled thickness long cylindrical liners. The radiographic results indicate that at least 16 times radial compression of the inner surface of a 0.11 cm thick Al liner was achieved, with a symmetric implosion free of instability growth. We have also made progress in combining 2D-MHD simulations of FRC formation with imploding liner compression of FRC's.
Megagauss magnetic field generation and related topics, 2006 ieee international conference on; 12/2006
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J.H. Degnan,
D. Amdahl,
A. Brown,
T. Cavazos,
S.K. Coffey,
G.G. Craddock,
M.H. Frese,
S.D. Frese,
D. Gale,
T.C. Grabowski, [......],
F.M. Lehr,
J.D. Letterio,
R.E. Peterkin,
N.F. Roderick,
E.L. Ruden,
R.E. Siemond,
W. Sommarsb,
Y.F.C. Thioe,
W. Tucker, P.J. Turchi
[show abstract]
[hide abstract]
ABSTRACT: We obtained full axial coverage radiography of a deformable contact imploding liner. This radiographic data indicates the feasibility of using a varying thickness in a long cylindrical solid liner, driven as a 12 megamp Z-pinch, to achieve factor- 16 cylindrical convergence, while using 8 cm diameter aperture electrodes. The Al liner was 30 cm long, with 9.78 cm inner diameter for its full length, 10.0 cm outer diameter for the central 18 cm of its length and outer diameter increased linearly to 10.2 cm at 1 cm from either electrode, and to 11 cm at electrode contacts. The electrode apertures allow injection of Field Reversed Configurations in proposed future experiments on magnetized target fusion.
Pulsed Power Conference, 2005 IEEE; 07/2005
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ABSTRACT: The design of compact pulsed power systems involves the trade between size, pulse length and pulse shape. A stacked Blumlein line with high dielectric constant material can deliver a voltage flattop to a matched load with an energy density similar to capacitor banks. By imbedding nano-scale titanate particles in an epoxy matrix, a composite material with a relative permittivity in the range of 30 to 60 may be realized without the drastic loss in dielectric strength associated with large area ceramics. So called ceramic loaded polymer dielectric employed in a Blumlein line facilitates the fabrication of a compact pulse forming line potentially suitable for driving loads of several tens of Ohms in the GW power range for greater than 100 ns. This paper describes the initial efforts to fabricate and test a parallel plate Blumlein incorporating ceramic loaded polymer dielectric. Two single-stage parallel plate Blumlein lines were fabricated with different ceramic loading. The lines were designed to yield a 50 ns pulse into a 6.25 Omega load. The Blumlein lines were designed to be charged to 62.5 kV, and both fabricated units held the charge voltage in static tests. A small railgap switch was fabricated for use with the Blumlein lines. A mid-plane knife-edge electrode was used to trigger the switch. The results of the tests are presented along with projections for the future development of this technology.
Pulsed Power Conference, 2005 IEEE; 07/2005
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P.J. Turchi,
K. Alvey,
C. Adams,
B. Anderson,
H.D. Anderson,
W.E. Anderson,
E. Armijo,
W.L. Atchison,
J. Bartos,
R.L. Bowers, [......],
G. Rodriguez,
D. Sandoval,
G. Sandoval,
M.A. Salazar,
W. Sommars,
W. Steckle,
J.L. Stokes,
J. Studebaker,
L. Tabaka,
A.J. Taylor
[show abstract]
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ABSTRACT: We discuss the design, fabrication, and operation of a liner implosion system at peak currents of 16 MA. Liners of 1100 aluminum, with initial length, radius, and thickness of 4 cm, 5 cm, and 1 mm, respectively, implode under the action of an axial current, rising in 8 μs. Fields on conductor surfaces exceed 0.6 MG. Design and fabrication issues that were successfully addressed include: Pulsed Power-especially current joints at high magnetic fields and the possibility of electrical breakdown at connection of liner cassette insulator to bank insulation; Liner Physics-including the angle needed to maintain current contact between liner and glide-plane/electrode without jetting or buckling; Diagnostics-X-radiography through cassette insulator and outer conductor without shrapnel damage to film.
IEEE Transactions on Plasma Science 11/2002; · 1.17 Impact Factor
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ABSTRACT: As part of ongoing hydrodynamic code verification and validation efforts, a series of near-term liner experiments (NTLX) was designed for the Shiva Star capacitor bank at the Air Force Research Laboratory . An aluminum liner that is magnetically imploded onto a central target by self-induced Lorentz forces drove the experiments. Target design utilized the adaptive mesh refinement Eulerian hydrodynamics code radiative adaptive grid eulerian (RAGE) in twoand three-dimensions. One-dimensional simulations of the liner driver utilizing the lagrangian magnetohydrodynamics code RAVEN are used to set the initial temperature and density profiles as well as liner velocity at impact time. During liner/target impact, a convergent shock is generated in the target that drives subsequent hydrodynamics experiments. In concentric targets, a cylindrically symmetric shock will converge on axis. The degree of shock symmetry observed characterizes the liner symmetry at impact. By shifting the target center away from the liner driver axis, variations in shock propagation velocity generate off-center shock convergence. Results indicate that RAVEN and RAGE are in excellent agreement for the calculated shock trajectory. However, a small but significant discrepancy does occur during the last few millimeters of run-in when convergence effects are greatest. The codes predict shock arrival times that are approximately 100 ns faster than those observed experimentally.
IEEE Transactions on Plasma Science 11/2002; · 1.17 Impact Factor
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Y. C. F. Thio,
R. Eskridge,
M Lee,
A Martin,
J Smith,
J. T. Cassibry,
S. T. Wu,
R.C. Kirkpatrick,
C. E. Knapp, P.J. Turchi,
Stephen L. Rodgers
[show abstract]
[hide abstract]
ABSTRACT: The current research effort at NASA Marshall Space Flight Center (MSFC) in MTF is directed towards exploring the critical physics issues of potential embodiments of MTF for propulsion, especially standoff drivers involving plasma liners for MTF. There are several possible approaches for forming plasma liners. One approach consists of using a spherical array of plasma jets to form a spherical plasma shell imploding towards the center of a magnetized plasma, a compact toroid. Current experimental plan and status to explore the physics of forming a 2-D plasma liner (shell) by merging plasma jets are described. A first-generation coaxial plasma guns (Mark-1) to launch the required plasma jets have been built and tested. Plasma jets have been launched reproducibly with a low jitter, and velocities in excess of 50 km/s for the leading edge of the plasma jet. Some further refinements are being explored for the plasma gun, Successful completion of these single-gun tests will be followed by an experimental exploration of the problems of launching a multiple number of these jets simultaneously to form a cylindrical plasma liner.
02/2002;
