The advanced helical generator

Reisman, D. B.; Javedani, J.B.; Ellsworth, G. F.; Kuklo, R. M.; Goerz, D.A.; White, A. D.; Tallerico, L. J.; Gidding, D. A.; Murphy, Michael J.; Chase, Jay B.

doi:10.1063/1.3309788

Cited by 8 publications

(3 citation statements)

References 9 publications

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“…A capacitor bank was designed and fabricated to produce the initial generator current of 60 kA, 80 kA or 140 kA in our FPG [1], Mini-G [2], and AHG [3] or FFT [4] systems, respectively, and is shown in Fig. 2.…”

Section: B An Explosively Switched Seed Bankmentioning

confidence: 99%

Explosive pulsed power experimental capability at LLNL

White

Milhous

Goerz

et al. 2012

2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)

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Abstract-LLNL has developed a family of advanced magnetic flux compression generators (FCGs) used to perform high energy density physics experiments and material science studies. In recent years we have performed these experiments at explosive test sites in New Mexico and Nevada. In 2011, we re-established an explosive pulsed power test facility closer to Livermore. LLNL's Site 300 is a U.S. DOE-NNSA experimental test site situated on 7000 acres in rural foothills approximately 15 miles southeast of Livermore. It was established in 1955 as a non-nuclear explosives test facility to support LLNL's national security mission. On this site there are numerous facilities for fabricating, storing, assembling, and testing explosive devices. Site 300 is also home to some of DOE's premier facilities for hydrodynamic testing, with sophisticated diagnostics such as high-speed imaging, flash X-ray radiography, and other advanced diagnostics for performing unique experiments such as shock physics experiments, which examine how materials behave under high pressure and temperature. We have converted and upgraded one particular firing bunker at Site 300 (known as Bunker 851) to provide the necessary infrastructure to support high explosive pulsed power (HEPP) experiments. In doing so, we were able to incorporate our established practices for handling grounding, shielding, and isolation of auxiliary systems and diagnostics, in order to effectively manage the large voltages produced by FCGs, and minimize unwanted coupling to diagnostic data. This paper will discuss some of the key attributes of the Bunker 851 facility, including the specialized firesets and isolated initiation systems for multistage explosive systems, a detonator-switched seed bank that operates while isolated from earth and building ground, a fiber-optic based timing, triggering and control system, an EMI Faraday cage that completely encloses diagnostic sensors, cabling and high-resolution digitizers, optical fiber-based velocimetry and current sensor systems, and a flash X-ray radiography system. The photos and experimental results from recent FCG experiments will also be shown and discussed.

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Section: B An Explosively Switched Seed Bankmentioning

confidence: 99%

Explosive pulsed power experimental capability at LLNL

White

Milhous

Goerz

et al. 2012

2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)

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“…LLNL has developed a family of advanced FCGs to be used in our explosively-driven pulsed power experiments. Our high-gain advanced helical generator (AHG) can produce currents of 20 MA and deliver energies of 20 MJ [1]. Our ring-lit coaxial generator (CG), known as the full function test (FFT) device, when coupled with the AHG, can produce currents of 100 MA and deliver energies exceeding 60 MJ [2].…”

Section: Introductionmentioning

confidence: 99%

Flat plate FCG experimental system for material studies

Goerz

Reisman

Javedani

et al. 2012

2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)

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Abstract-Magnetic flux compression generators (FCGs) driven by high explosives can produce extremely high magnetic fields that are useful in accelerating metal liners and sample materials to high velocities to study their properties. For material studies requiring extremely high energy and applied pressures, explosive FCGs can far surpass the typical performance of capacitor based systems. Flat plate generators (FPGs) are useful in many flux compression applications. They are well suited for doing material studies in planar geometries, and they enable the use of certain diagnostic techniques, most notably flash X-ray radiography, which would be difficult if not impossible to utilize in coaxial geometries. Typical flat-plate generators have rather slow-rising output currents. This can cause loads to deform significantly before the highest rate of current gain from the generator can be reached. Shearer et al. at LLNL overcame this handicap by developing a version of FPG that used a flat plate armature and contoured stator. A rectangular block of high explosive (HE) is lit by a row of detonators placed across the width of the HE at a select location along the length of the generator. As the HE burns, the armature takes a characteristic shape determined by the line initiation location. At the appropriate time, the armature first contacts the stator near the input end, then continues to expand into a shape resembling the contoured stator. At late time, the armature contacts the stator at a shallow 1 to 2 degree phasing angle, which rapidly sweeps flux into the load, resulting in a fast current rise time. We have constructed a similar type generator for our present experimental work. It is capable of delivering 20 MA of current with a 2 to 4 s exponential rise time into suitable loads. This paper describes the design of LLNL's flat-plate FCG, along with results of modeling and simulation performed for its development. Experiments have been carried out using the FPG with seed currents ranging from 0.75 to 1.6 MA using capacitor banks, and up to 2 MA using a helical FCG. Accurate measurements of input and output currents have been made and performance agrees remarkably well with MHD simulations. Challenges faced with calibrating diagnostics and fielding these types of experiments will also be discussed.

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“…Thorough descriptions of the design and performance of these generators have been published elsewhere [2] [3] [4], and are beyond the scope of this paper. To briefly summarize these results, we have used a helical generator of our design in series with a coaxial generator of our design to deliver tens of megaamperes and tens of megajoules to low inductance loads.…”

Section: Introductionmentioning

confidence: 99%

Measuring helical FCG voltage with an electric field antenna

White

Anderson

Javedani

et al. 2011

2011 IEEE Pulsed Power Conference

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A method of measuring the voltage produced by a helical explosive flux compression generator using a remote electric field antenna is described in detail. The diagnostic has been successfully implemented on several experiments. Measured data from the diagnostic compare favorably with voltages predicted using the code CAGEN [1], validating our predictive modeling tools. The measured data is important to understanding generator performance, and is measured with a low-risk, minimally intrusive approach.

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The advanced helical generator

Cited by 8 publications

References 9 publications

Explosive pulsed power experimental capability at LLNL

Explosive pulsed power experimental capability at LLNL

Flat plate FCG experimental system for material studies

Measuring helical FCG voltage with an electric field antenna

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