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Magnetic flux compression

Description: Magnetic Flux Compression, as treated in this paper, is accomplished by high explosives. Flux is first captured in a closed conducting circuit, of which some or all of the conducting elements are overlaid with high explosives. Upon detonation of the explosives, these elements are driven in such a fashion as to compress the flux into regions of smaller areas or, in engineering terminology, into regions of lower inductance. The magnetic energy associated with the flux is increased by the flux compression. The additional energy is ultimately supplied by the explosive as it drives the conductors against the magnetic field pressure, which in some cases may be in the megabar range. Various names in common use for flux compression devices are flux compression generators (FCG), magneto-cumulative generators (MCG), particularly in the USSR, or simply, flux compressors. FCGs are generally used in two broadly defined categories: as compact, high-power sources to drive various loads: and as generators of very large magnetic fields. In this talk, general principles of flux compression are first discussed. This is followed by a description of several applications in which different types of FCGs are used to supply pulsed power to various devices. The talk closes with a discussion of results obtained from a number of experiments done to explore the properties of materials in very large magnetic fields or under nearly isentropic compression. As requested, the work reported here surveys the Los Alamos program. However, sources cited in the bibliography contain much of the extensive literature in the field. Individual papers cited have been selected partly to highlight other groups that have been active in the field. 25 refs., 15 figs.
Date: January 1, 1989
Creator: Fowler, C.M.
Partner: UNT Libraries Government Documents Department

Generator powered plasma focus

Description: An earlier set of experiments will be described briefly, in which plate flux compression generators were used to power a Plasma Focus. Currents, voltages and 'rundown times' obtained in these experiments are shown to agree well with a simple model. This same model is then used to show how dramatic operational improvements could be obtained with use of an appropriate fuse, provided the model remained valid.
Date: January 1, 2002
Creator: Fowler, C. M.
Partner: UNT Libraries Government Documents Department

Spherical compression of a magnetic field

Description: In an interesting paper, Rutkevich obtained the electromagnetic wave solution for the compression of a magnetic field contained by an imploding, perfectly conducting cylindrical shell or liner. The magnetic and electric susceptibilities were taken as constant. The solution was obtained by Laplace transforms. In his paper, he also considered the corresponding plane problem when driving together two perfectly conducting, parallel plates that confine a magnetic field. He compared the method of solution obtained by Laplace transforms with that obtained by the method of characteristics which was used to obtain the original solution. He concluded his paper by noting that the transform method is more versatile that the characteristic method. Somewhat later, Bodulinskii and Medvedev obtained a solution for the wave structure generated when an initial magnetic field is compressed by the implosion of a conducting spherical liner. Again, the solution was obtained by transform methods. In this paper, we outline the solution to the spherical problem using the method of characteristics. The utility of this method is described for some other situations.
Date: September 1, 1996
Creator: Fowler, C.M.
Partner: UNT Libraries Government Documents Department

Four decades in the megagauss world

Description: This paper contains a short history of the generation of megagauss magnetic fields obtained by explosive flux compression at Los Alamos over the last four decades, a brief description of the high field systems most commonly used for solid state research, and a survey of selected physics experiments performed using these systems as high magnetic field sources.
Date: November 1, 1997
Creator: Fowler, C.M.
Partner: UNT Libraries Government Documents Department

Rail gun powered by an integral explosive generator

Description: We propose the use of a rail gun powered by an explosive magnetic flux compression generator built into the rail gun itself in which the rails of the gun are driven together behind the projectile by explosives. The magnetic field established between the rails by an initial current supplied by an external source at the breech of the gun is trapped and compressed by the collapsing rails to accelerate the projectile down the bore of the gun.
Date: January 1, 1979
Creator: Peterson, D.R. & Fowler, C.M.
Partner: UNT Libraries Government Documents Department

Perturbation analysis of rail guns powered by explosive magnetic flux compression

Description: Perturbation methods are used to predict the performance of rail guns powered by explosive magnetic flux compression, and the results are compared with experimental data. The problem of designing explosive magnetic flux compression generators for optimum rail gun performance is also discussed.
Date: January 1, 1980
Creator: Peterson, D.R. & Fowler, C.M.
Partner: UNT Libraries Government Documents Department

Conceptual design for a short-pulse explosive-driven generator

Description: A design is described for a short-pulse explosive-driven generator. The initial flux is provided by a side-fed one-turn coil that is crow-barred at peak field. This field is then compressed by the axially uniform expansion of a cylindrical armature inside the coil. A multistrand helical coil is used to convert the changing flux to voltage at the coaxial output. The circuit is completed by the impact of the armsture against contact rings connected to the helical coil and output. An approximate circuit model is derived. The analysis indicates that several megajoules can be delivered to an inductive load in 0.5 to 5.0 ..mu..s.
Date: January 1, 1986
Creator: Caird, R.S. & Fowler, C.M.
Partner: UNT Libraries Government Documents Department

The Mark IX generator

Description: A large, explosive helical generator (the Mark IX) is described. The stator ID is 35.6 cm and the armature OD is 17.3 cm. The overall length is 112 cm. This generator delivered 11, 23.5, and 30 MA to 120-, 56-, 35-nH loads, respectively. A Marxing technique is used that enables us to employ over 1 MJ of capacitor bank energy for the initial current without destroying the generator prematurely by magnetic forces. The shot data were analyzed by first computing the generator inductance vs. time curve and then deriving the resistance vs. time curve from the data. This approach yields a useful characterization of the generator. 5 refs., 7 figs., 1 tab.
Date: January 1, 1989
Creator: Fowler, C.M. & Caird, R.S.
Partner: UNT Libraries Government Documents Department

Evolution of some Los Alamos flux compression programs

Description: When we were approached to give a general discussion of some aspects of the Los Alamos flux compression program, we decided to present historical backgrounds of a few topics that have some relevance to programs that we very much In the forefront of activities going on today. Of some thirty abstracts collected at Los Alamos for this conference, ten of them dealt with electromagnetic acceleration of materials, notably the compression of heavy liners, and five dealt with plasma compression. Both of these topics have been under investigation, off and on, from the time a formal flux compression program was organized at Los Alamos. We decided that a short overview of work done In these areas would be of some interest. Some of the work described below has been discussed in Laboratory reports that, while referenced and available, are not readily accessible. For completeness, some previously published, accessible work Is also discussed but much more briefly. Perhaps the most striking thing about the early work In these two areas is how primitive much of it was when compared to the far more sophisticated, related activities of today. Another feature of these programs, actually for most programs, Is their cyclic nature. Their relevance and/or funding seems to come land go. Eventually, many of the older programs come back into favor. Activities Involving the dense plasma focus (DPF), about which some discussions will be given later, furnish a classic example of this kind, coming Into and then out of periods of heightened interest. We devote the next two sections of this paper to a review of our work In magnetic acceleration of solids and of plasma compression. A final section gives a survey of our work In which thin foils are imploded to produce intense quantities of son x-rays. The authors are well ...
Date: December 31, 1996
Creator: Fowler, C.M. & Goforth, J.H.
Partner: UNT Libraries Government Documents Department

Projectile oscillations in augmented rail guns

Description: The projectile in an inductive store-powered rail gun, augmented by an external magnetic field, will oscillate under certain conditions. This behavior is easily understood when there is no resistance in the circuit comprising the storage coil, rails and armature. In this case, the flux in the complete circuit is conserved. However, as the projectile moves down the rails, more flux from the augmenting field is picked up. This must be accompanied by a decrease in current in the system to conserve the total flux. At a certain distance down the rails, the current must reverse to conserve the flux, and thus the force on the projectile reverses. This mechanism leads to oscillation of the projectile. An analytic solution is given for the case in which the resistance is zero.
Date: January 1, 1986
Creator: Hodgdon, M.L.; Fowler, C.M. & Homan, C.G.
Partner: UNT Libraries Government Documents Department

Disk generator with nearly shockless accelerated driver plate

Description: 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.
Date: January 1, 1989
Creator: Fowler, C.M.; Hoeberling, R.F. & Marsh, S.P.
Partner: UNT Libraries Government Documents Department

Megagauss technology and pulsed power applications

Description: This is the final report of a 3-year LDRD project at LANL. Because of recent changes in Russia, there are opportunities to acquire and evaluate technologies for ultrahigh-magnetic-field flux compressors and ultrahigh-energy, ultrahigh-current pulsed-power generators that could provide inexpensive access to various extreme matter conditions and high-energy-density physics regimes. Systems developed by the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) at Arzamas-16 (Sarova) have the potential of creating new thrusts in several areas of high-magnetic-field and high-energy-density R&D, including high-field and high-temperature superconductivity, Faraday effect, cyclotron resonance, isentropic compression, magneto-optical properties, plasma physics, astrophysics, energy research, etc. Through a formal collaboration supported and encouraged by high-ranking DOE officials and senior laboratory management, we have gained access to unique Russian technology, which substantially exceeds US capabilities in several areas, at a small fraction of the cost which would be incurred in an intensive and lengthy US development program.
Date: September 1996
Creator: Lindemuth, I. R.; Reinovsky, R. E. & Fowler, C. M.
Partner: UNT Libraries Government Documents Department

The Russian-American high magnetic field collaboration

Description: We report here on a joint experimental shot series with teams from Russia and the United States. The program was based largely upon the MC-1 generator, a high magnetic field explosive flux compressor, developed by the Pavlovskii group at Arzamas-16. The series was of historical interest in that it was carried out in a Los Alamos security area, the first time for such a collaboration. We discuss a number of technical issues involved in matching Russian hardware with Los Alamos explosives, initiation systems and the seed field energy source, as well as comparison of field measuring diagnostics fumished by the two teams. We conclude with a discussion of an investigation of the high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO), employing these generators. The low temperature critical magnetic field of this material was found to be 340+40 T, as determined from a 94 GHz microwave interferometer developed for this purpose.
Date: July 1, 1995
Creator: Fowler, C.M.; Christian, J.M. & Freeman, B.L.
Partner: UNT Libraries Government Documents Department

Explosive generation of high magnetic fields in large volumes and solid state applications

Description: Various methods of producing ultra-high magnetic fields by explosive flux compression are described. A survey is made of the kinds of high magnetic field solid state data obtained in such fields by various groups. Preliminary results are given for the magnetic phase boundary that separates the spin-flop and paramagnetic regions of MnF/sub 2/.
Date: January 1, 1980
Creator: Fowler, C.M.; Caird, R.S.; Erickson, D.J.; Freeman, B.L. & Garn, W.B.
Partner: UNT Libraries Government Documents Department

Circuit model for the explosive-driven plate generator

Description: It is useful to model explosive-driven generators as lumped-parameter circuit elements in order to estimate performance in new applications and to optimize the design of experiments. The plate generator is essentially a parallel or tilted-plate transmission line in which the current-carrying flat-plate conductors are driven by plane-wave explosive systems. We have developed a simple model for the time-varying inductance of this system. First, an analytic expression is used to predict the plate motion. Then, the inductance is expressed as a function of plate separation to give the computational model. Time-dependent flux losses are accounted for by an increasing waste inductance. Model predictions are compared with the available shot data.
Date: January 1, 1983
Creator: Caird, R.S.; Erickson, D.J.; Fowler, C.M.; Freeman, B.L. & Goforth, J.H.
Partner: UNT Libraries Government Documents Department

Survey of recent work on explosive-driven magnetic flux compression generators

Description: There are five widely-used classes of explosive-driven flux compression generators. They are the spiral, coaxial, strip, plate and cylindrical implosion systems. The configurations are described and the characteristics of the various types are compared. There are a number of techniques for sharpening or impedance-matching the output pulse of the generators. The use of switching, fuses and transformers are discussed. Some of the areas of application of the generators are outlined briefly. Much of the recent work at Los Alamos has been directed toward the development of the plate generator. This type consists essentially of a transmission line with explosive slabs on the flat surfaces. These plates may be parallel or at an angle with respect to each other. A plane detonation front in the explosive allows a large area of conductor to be driven simultaneously. As a result, the power and current outputs are very high - many megamperes at the terawatt level. This generator is particularly well suited to driving low impedance plasma devices. The results of the plate generator tests are discussed.
Date: January 1, 1978
Creator: Caird, R.S.; Fowler, C.M.; Erickson, D.J.; Freeman, B.L. & Garn, W.B.
Partner: UNT Libraries Government Documents Department

A battery-powered flux compression generator system

Description: Flux compression generators (FCGs) are primarily used as energy amplifiers. While a FCG can be made small, typically the ''seed'' energy that the FCG amplifies comes from a capacitator bank much larger and heavier than the FCG. If seed energy was supplied by a compact device, FCGs could be used as portable power supplies. One application of interest is to combine a compact seed source with a FCG and transformer. The result would be a self-contained power supply capable of producing a microsecond long, megavolt pulse. The objective of the work described in this paper was to make a seed source capable of energizing a standard Los Alamos plate FCG. The power supply was to be relatively small, light weight, and able to deliver at least 100-kJ to a 280-nH inductive load, e.g., plate FCG. 4 figs., 2 tabs.
Date: January 1, 1989
Creator: Vorthman, J.E.; Fowler, C.M.; Hoeberling, R.F. & Fazio, M.V.
Partner: UNT Libraries Government Documents Department

Design of the Mark 101 magnetic flux compression generator

Description: The Mark 101 explosive flux compression generator was designed to generate high voltages into external loads. The stators are helically wound but the armature explosive is simultaneously initiated along its axis. Thus, the generator can possess the large inductance of conventional helical generators, but the burntime is substantially reduced. This leads to large generator impedances that lead to high voltage generation. The armature wall-thickness is varied in such a fashion that it leaves the load output aperture open as the armature starts contact with the stator. Calculations are given for a number of designs in which both the number of stator turns and load inductances are varied. It is also noted that flux losses in the generator skin can be significant.
Date: January 1, 1986
Creator: Fowler, C.M.; Caird, R.S.; Freeman, B.L. & Marsh, S.P.
Partner: UNT Libraries Government Documents Department

Results of railgun experiments

Description: During the 1979 Megagauss II conference the hypervelocity potential of railguns and the pulsed power technology needed to power them were discussed. Since then, many laboratories have initiated railgun R and D projects for a variety of potential applications. Los Alamos and Lawrence Livermore National Laboratories initiated a collaborative experimental railgun project which resulted in several successes in accelerating projectiles to high velocities, emphasized the limits on railgun operation, and indicated that the numerical modeling of railgun operation was in good agreement with the experiments.
Date: April 1, 1983
Creator: Hawke, R.S.; Brooks, A.L.; Fowler, C.M. & Peterson, D.R.
Partner: UNT Libraries Government Documents Department