S.P. Marsh

University of California, Los Angeles, Los Angeles, California, United States

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Publications (40)42.66 Total impact

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    ABSTRACT: Summary form only given. At Los Alamos, we had previously applied Explosively Formed Fuse (EFF) techniques to large systems, where the EFF has interrupted currents from 19 to 25 MA. More recently we have been investigating the use of the EFF technique to apply high voltages to high impedance loads in compact systems, and have used 43-cm EFF systems to interrupt currents of ~3 MA and produce voltages up to 300 kV. We now report our progress towards producing up to 500 kV, 1-μs duration pulses using 76-cm EFF systems. In compact explosive systems, the interactions of shock and detonation waves with conductors and insulators offers some significant challenges, especially when the local electric fields approach the breakdown strengths of the insulators. The results of computer calculations and experiments of switch performance will be presented
    Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on; 02/1999
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    ABSTRACT: Pulse power systems delivering in excess of 100 MJ represent one of the next major challenges to the community. While laboratory pulse power systems in this energy range are feasible, they represent very substantial investments of both time and resources. Prudence requires that fundamental proof of principle for the contemplated application be established before such massive resources are committed. Explosive pulse power systems using magnetic flux compression provide a direct path to such demonstrations. Furthermore, as energy requirements grow, they may represent the only affordable source of ultra-high energy environments. In this paper we report the results of an experimental test of a first generation disk generator system. Individual disk segments have been tested with framing camera diagnostics to evaluate overall performance dynamics and material, and fabrication failure points. In general no bulk failures were observed in several shots and the critical weld joints were seen to maintain integrity for at least 4 μs after arrival of the detonation front. Single module pulse power experiments have been conducted at reduced initial current (1.5-2.0 MA) with a fixed inductance load of 0.22 nH
    IEEE Transactions on Plasma Science 11/1998; · 0.87 Impact Factor
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    ABSTRACT: At Los Alamos, the authors have primarily applied Explosively Formed Fuse (EFF) techniques to high current systems. In these systems, the EFF has interrupted currents from 19 to 25 MA, thus diverting the current to low inductance loads. The magnitude of transferred current is determined by the ratio of storage inductance to load inductance, and with dynamic loads, the current has ranged from 12 to 20 MA. In a system with 18 MJ stored energy, the switch operates at a power up to 6 TW. The authors are now investigating the use of the EFF technique to apply high voltages to high impedance loads in systems that are more compact. In these systems, they are exploring circuits with EFF lengths from 43 to 100 cm, which have storage inductances large enough to apply 300 to 500 kV across high impedance loads. Experimental results and design considerations are presented. Using cylindrical EFF switches of 10 cm diameter and 43 cm length, currents of approximately 3 MA were interrupted producing {approximately}200 kV. This indicate s the switch had an effective resistance of {approximately}100 m{Omega} where 150--200 m{Omega} was expected. To understand the lower performance, several parameters were studied, including: electrical conduction through the explosive products; current density; explosive initiation; insulator type; conductor thickness; and so on. The results show a number of interesting features, most notably that the primary mechanism of switch operation is mechanical and not electrical fusing of the conductor. Switches opening on a 10 to 10 {micro}s time scale with resistances starting at 50 {micro}{Omega} and increasing to perhaps 1 {Omega} now seem possible to construct, using explosive charges as small as a few pounds.
    10/1998
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    ABSTRACT: Summary form only given, as follows. Explosively formed fuse opening switches have been developed for applications in high-energy explosive pulsed power systems. An explosive charge forces the electrical conductor across a Teflon(R) forming die. The switch thus combines the action of the explosively driven mechanical deformation and electrical fusing of the conductor. Such switches have operated at power levels up to 6 TW in systems with 18 MJ stored energy, allowing currents of up to 20 MA to be delivered to 15 nH loads on time scales of a few μs. These devices were developed to power plasma or solid cylindrical implosion loads. In recent tests we have explored a wider range of parameter space than previously accessed, allowing the consideration of more compact designs with more flexible applications. The combined effects of explosive power and electrical conduction through the explosive products have been studied, and this leads to the choice of better explosives. Experiments conducted in small planar assemblies will be described, and the implications for small diameter cylindrical assemblies. Switches opening on a 1 to 10 μs time scale with resistances starting at 50 μΩ and increasing to perhaps 1 Ω now seem possible to construct, using explosive charges as small as a few pounds: in initial experiments, using cylindrical switches of 10 cm diameter and 43 cm length, the switches interrupted currents of approximately 3 MA producing 200 kV
    Plasma Science, 1998. 25th Anniversary. IEEE Conference Record - Abstracts. 1998 IEEE International on; 07/1998
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    ABSTRACT: Pulse power systems delivering in excess of 100 MJ represent one of the next major challenges to the pulse power community. Explosive pulse power systems using magnetic flux compression provide a direct path to such demonstrations. Furthermore, as energy requirements grow, single use explosive systems may represent the only affordable source of ultra-high energy environments. Currently two flux compressor configurations are under consideration for powering solid liner implosions at currents above 100 MA and at energies above 100 MJ. A simultaneously initiated coaxial flux compressor (Ranchero) is described in a companion paper. A modular, center initiated disk configuration, generally patterned after the DEMG is the other candidate. Either can drive loads directly or can conceptually be connected in parallel with flat plate transmission lines to increase current delivery. Phenomenological models and conceptual designs for DEMG systems have been previously reported. In this paper we report the results of the experimental test of a first generation disk generator system. Individual disk segments have been tested with framing camera diagnostics to evaluate overall performance, dynamics and fabrication failure points. In general no bulk failures were observed in several shots and the critical weld joints maintained their integrity for at least 4 μs after arrival of the detonation front. Single module pulse power experiments have been conducted at reduced initial current (1.5-2.0 MA) with a fixed inductance load of 0.22 nH
    Pulsed Power Conference, 1997. Digest of Technical Papers. 1997 11th IEEE International; 01/1998
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    ABSTRACT: High explosive pulsed power (HEPP) systems are capable of generating very high energies in magnetic fields. Such stored energy is usually developed on time scales of a few tens or hundreds of microseconds. Many applications require shorter pulses and opening switches provide one way to use the large energy available for faster applications. With current flowing in an inductive circuit, introducing resistance produces voltage that can be used to drive current into a load. For an opening switch with a fast rising resistance, the load current rise time is determined by the R/L time constant of the circuit. A significant fraction of the circuit energy must be dissipated in the process, and in applications where very large energies must be dealt with only a few types of switches can be used. Experiments with high explosive driven opening switches have produced a few switches that can carry tens of MA current, and open on the time scale of one or a few μs. We have specialized in a type of switch that we call an explosively formed fuse (EFF), and the use of this switch in the is MJ Procyon system is the subject of this paper. Operation of the EFF switch at levels of ~3 TW for 2 μs has become routine, and we describe its characteristics and give data from a number of tests
    Pulsed Power Conference, 1995. Digest of Technical Papers., Tenth IEEE International; 08/1995
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    ABSTRACT: The Procyon high explosive pulsed power (HEPP) system was designed to drive plasma Z-pinch experiments that produce Megajoule soft X-ray pulses when the plasma stagnates on axis. In the proceedings of the Ninth IEEE Pulsed Power Conference, the authors published results from system development tests. At this time, they have fielded seven tests in which the focus was on either vacuum switching or load physics. Four of the tests concentrated on the performance of a plasma flow switch (PFS) which employed a l/r mass distribution in the PFS barrel. Of the four tests, two had dummy loads and one had an implosion load. In addition, one of the tests broke down near the vacuum dielectric interface, and the result demonstrated what Procyon could deliver to an 18 nH load. The authors summarize PFS results and the 18 nH test which is pertinent to upcoming solid/liquid liner experiments. On their other three tests, they eliminated the PFS switching and powered the Z-pinch directly with the HEPP system. From the best of these direct drive tests, they obtained 1.5 MJ of radiation in a 250 ns pulse, their best radiation pulse to date. They also summarize direct drive test results. More details are given in other papers in this conference for both the PFS and direct drive experiments, and an updated analysis of their opening switch performance is also included. The remainder of this paper describes the parameters and capabilities of their system, and they use the data from several experiments to provide more precise information than previously available
    Pulsed Power Conference, 1995. Digest of Technical Papers., Tenth IEEE International; 08/1995
  • W.J. Carter, S.P. Marsh
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    ABSTRACT: The Hugoniot equations of state of a large number of representative polymers have been obtained. Two aspects of the results are particularly striking: (1) The u{sub s}(u{sub p}) Hugoniots of all the polymers extrapolate to bulk sound velocities higher than the ultrasonic values, an indication of a rapidly varying rate of change of compressibility in this region. This is attributed both to the two-dimensional nature of polymer compression and to the form of the interchain interaction potential. (2) A relatively high pressure transformation (in the range 20-30 GPa), characterized by a change in slope of the u{sub s}(u{sub p}) Hugoniot and sometime by a large volume change as well, is observed for all of the polymers. This transformation is probably associated with pressure-induced cross bonding. In particular, for those polymers which contain rings in their monomer structure and which display the largest volume change at transformation, it is proposed that carbon-carbon covalent bonds along chains are broken and tetragonal bonds between chains are formed in a manner analogous to the graphite-diamond transformation.
    06/1995;
  • W. D. Zerwekh, S. P. Marsh, T.-H. Tan
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    ABSTRACT: Mesa2D hydrocode has been used to model the collapse of 304SS cylinder onto the 6061Al phasing lens, shock in the lines, phase detonation of the PBX 9501 explosive, and Mach disk position. The phase velocity in the system was meausred in microwave-interferometry experiments, and favorably compared with the calculations. The technique allows to accelerate a thin plate intact to above 1 cm/micro-s. (AIP)
    01/1994;
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    ABSTRACT: Not Available
    Pulsed Power Conference, 1993. Digest of Technical Papers. Ninth IEEE International; 07/1993
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    ABSTRACT: Explosive pulse power systems, powered by flux compression generators and including a variety of high current power conditioning components, such as high current opening switches, are attractive for powering fusion physics experiments which require 10's MJ of electrical energy. Such systems are economical when compared to other high energy sources and require little capital investment to enable initial experiments. They are flexible and readily reconfigurable to accommodate changing experimental requirements and can be designed, assembled, and fielded in relatively short periods of time. Several configurations of very high energy flux compressors have been explored at Los Alamos and recently Russian researchers at the All Russian Institute of Experimental Physics (VNIIEF) have reported notable results from modular systems based on disk concepts. A phenomenological model of disk flux compressors is described. The performance predicted by these models is in sufficiently good agreement with the results reported by VNIIEF researchers to allow the model to be applied, in the future, to the design of power conditions systems for use in conjunction with these high performance generators.
    01/1992;
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    ABSTRACT: Los Alamos foil implosion program, Trailmaster, continues with its long-term goal of developing a plasma z-pinch that will produce large quantities of soft x-rays. In addition, we are currently considering ways to increase the scope of our activities utilizing the pulsed power capabilities we have developed. Our program combines a large variety of endeavors, including the development of materials fabrication techniques, explosives systems, computational codes, conventional capacitor banks, explosive pulsed power systems, and plasma diagnostics techniques. In this paper, we will describe how these activities are combined in the framework of three major thrusts that work together to achieve the final goal. We will first note our computational capabilities, and then describe Trailmaster capacitor bank facilities, focusing on recent results and a new facility. Finally, the explosive pulsed power system with which we are currently experimenting will be discussed and we will describe a proposed explosive pulsed power system capable of producing [approximately]5-MJ implosion kinetic energy. Frequently in this paper, we will present the essence of some facet of our program and reference other papers in this conference where more details can be found.
    12/1991
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    ABSTRACT: Not Available
    Pulsed Power Conference, 1991. Digest of Technical Papers. Eighth IEEE International; 07/1991
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    ABSTRACT: Not Available
    Pulsed Power Conference, 1991. Digest of Technical Papers. Eighth IEEE International; 07/1991
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    ABSTRACT: Summary form only given. Soviet scientists have recently reported remarkable advances in explosively driven pulse-power systems based upon magnetic flux compression generators. Combining relatively large, high-gain helical generators with very-high-current disk explosive magnetic generators (DEMGs), two Soviet groups reported experiments in which 100-MJ energies were inductively stored in inductances of 3.2-56 nH at currents of 60 to 25Q MA. Experiments were reported in which the energy delivery time to a load was shortened to approximately 1 μs by the use of electrically exploded metal (copper) fuses. In these power conditioning experiments a DEMG was used to deliver 36-MJ to 20-nH inductive store at 60 MA, and the fuse transferred 35 MA to a 10-nH load at 400 kV. Los Alamos hydrodynamic codes ranging from simple Gurney models (including magnetic pressure) to complete two-dimensional models have been used to characterize the Soviet DEMGs. Models suggest that these energy-rich generator systems, coupled with opening switches such as conventional and explosively formed fuses, can significantly extend the parameter space in which plasma physics experiments can be conducted
    Plasma Science, 1990. IEEE Conference Record - Abstracts., 1990 IEEE International Conference on; 06/1990
  • S. P. Marsh, R. G. McQueen, T. H. Tan
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    ABSTRACT: High-explosive charges were used to accelerate stainless steel plates to velocities of 6 to 7 km/s. A two-stage system was used in which the first stage is a plane-wave detonating system that accelerates the plate down a short barrel. The second stage consists of a hollow cylindrical charge through which the moving plate passes. After an adjustable delay this charge is detonated on the outer circumference of the entry side of the charge. Flash radiographs and witness plates show no breakup in the first stage but bowing and frequent breakup in the second stage.
    08/1989;
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    ABSTRACT: First Page of the Article
    Pulsed Power Conference, 1989. 7th; 02/1989
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    ABSTRACT: The ''disk'' generator was first conceived here as a useful magnetic field source for a class of in situ plasma experiments. Initial current is supplied (from a capacitor bank) to the generator through radial coaxial cables. It enters the top plate, passes through the central post, and exits through the top of the outer cylindrical glide surface, which is insulated from the top plate. The explosive over the top plate is initiated simultaneously over its upper surface at such a time that the top plate starts its downward motion at about peak initial current. Generators of this class were first developed by Chernyshev, Protasov, and Shevtsov who called them ''disk'' generators, the name we have adopted here. Design details of the generator are given in Sec. II. They are based in considerable part on two-dimensional hydrodynamic calculations. Shot results are summarized in Sec. III, together with a discussion of the data obtained. 3 refs., 7 figs.
    01/1989;
  • J.H. Goforth, S.P. Marsh
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    ABSTRACT: Explosive-driven magnetic flux compression generators (explosive generators) provide for the generation of large amounts of energy compactly stored in a magnetic field. Opening switches for use in explosive generator circuits allow the energy to be used for applications requiring higher power than can be developed by the generators themselves. We have developed a type of opening switch that we describe as an explosively formed fuse (EFF). These switches are well suited to explosive generator circuits and provide a considerable enhancement of explosive pulsed-power capability. 10 refs., 14 figs.
    12/1988
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    ABSTRACT: A need is emerging for a class of short-pulse, high-voltage, magnetic flux compression generators (FCGs). It is desirable that these generators be compact, inexpensive and have modest prime power requirements. Toward this end several concepts have been worked on in our Laboratory, one of which is the conical helical generator described in this paper. 5 figs.
    12/1988