Pulsed Power Hydrodynamics: A Discipline Offering High Precision Data for Motivating and Validating Physics Models

Summary form only given. Pulsed power hydrodynamics is a new application of pulsed high magnetic fields to explore advanced hydrodynamics, instabilities, fluid turbulences, and material properties in a highly precise, controllable environment at the extremes of pressure and material velocity. The Atlas facility designed and built by Los Alamos is the world's first and only laboratory pulsed power system designed specifically to explore this relatively new family of pulsed power applications. Constructed in 2000 and commissioned in August 2001, Atlas is a 24-MJ high-performance capacitor bank delivering up to 30-megamperes with a current risetime of 5-6-musec. The high-precision, cylindrical, imploding liner is the tool most frequently used to convert electromagnetic energy into the hydrodynamic (particle kinetic) energy needed to drive the experiments. For typical liner parameters with an initial radius of 5-cm, the peak current of 30-MA delivered by Atlas results in magnetic fields just over 1-MG outside the liner prior to implosion. During the 5 to 10-musec implosion, the field outside the liner rises to several MG in typical situations. At these fields the rear surface of the liner is melted and it is subject to a variety of complex behaviors including: diffusion dominated and/or melt wave field penetration and heating; magneto Rayleigh-Taylor sausage mode behavior at the liner/field interface; and azimuthal asymmetry due to perturbations in current drive. The first Atlas liner implosion experiments were conducted in September 2001 and 16 experiments were conducted in the first year of operation. Immediate applications of the new pulsed power hydrodynamics techniques include material property topics such as: exploration of material strength at high rates of strain, material failure including fracture and spall, and-interfacial dynamics at high relative velocities and high interfacial pressures. A variety of complex hydrodynamic geometries will be explored and experiments will be designed to explore unstable perturbation growth and transition to turbulence. Longer term applications include the study of the hydrodynamics and properties of strongly coupled plasmas and equation of state of materials at pressures above 10 Mbar. This paper will provide an overview of the Atlas system and of the range of problems to which pulsed power hydrodynamics can be applied and the issues associated with these techniques

Over the last few years a new application for high performance pulsed power technology has joined the family of traditional radiation source applications. This new application uses the magnetic fields from large current pulses to implode near-solid density cylindrical liners, with very high precision, for the study of material properties and hydrodynamics in complex geometries. The 24-MJ Atlas pulsed power system, operated since September 2001 in Los Alamos, has employed high-precision liners driven with currents up to 25 MA to conduct a variety of experiments involving the production of moderate to strong shocks to study material failure and the dynamic behavior of an interface at high relative velocities and high normal pressures and the compression of targets in complex geometries to validate sophisticated hydrodynamic simulations. This paper will describe the behavior of the initial liner implosions evaluating the physical cause for the perturbation growth and will describe the later, more uniform, implosions. The paper will attempt to address the physical behaviors that lead to different behaviors in each case.

Recently, pulsed power technologies, including pulsed electric fields (PEFs) and time-modulated plasmas, are starting to be applied actively in agriculture and food processing. In the applications, compact pulsed power generators with moderate peak power and repetitive operation are developed for controlling discharge plasmas and electric field distribution. These applications are mainly based on the biological effects of a spatially distributed electric field and the chemically active species in the plasma. The PEFs are caused by applying pulse voltage between the electrodes and contribute to form pores on the cell membrane or to change conformation of protein. When the applied voltage exceeds the discharge onset criterion, plasmas are generated through the avalanche process of electron accelerated with intense electric field in a gas or liquids medium. The plasmas produce chemically active species, UV radiation, an intense electric field in the vicinity of discharge channel and shock waves, which also have different biological effects. The agricultural applications of pulsed power can be categorized as two phases: pre-harvest and post-harvest phases. The pre-harvest phase consists of seed germination, seedling growth, plant growth and growth mode change from vegetative to reproductive. Pulsed power technologies are used to promotion of seed germination, plant growth enhancement through direct stimulation or indirect effect such as inactivation of bacteria in soil and liquid hydroponic media, and promotion of mushroom fruit body formation. The post-harvest phase consists of harvesting the agricultural produce, storing the products, transporting the products to consumers and food processing such as drying, pasteurization (sterilization of bacteria), permeabilization and fermentation. The pulsed power technologies are also used to keep freshness of agricultural produce through decontaminating airborne, inactivating bacteria and decomposition of plant hormone in the storage containers. The poration of cell membrane by PEF contributes improvement of extraction of juice, nutritional agents, and antioxidant metabolites such as polyphenols from agricultural products. In this review, at first, a basis of pulsed power system for agricultural applications and bio-effect by high-electric field exposure is outlined. After that, pre-harvest and post-harvest agricultural applications are described. The utilization of pulsed power technologies to contribute efficient food processing and improve food safety and quality is also described.

Anisakis is a parasite that is found in many marine products and can cause anisakiasis when present in fish consumed raw. The most common way to prevent anisakiasis is to freeze the fish, but this causes a noticeable decrease in the quality of the fish when eaten as sashimi. Although no practical method of killing anisakis other than freezing has been found, we have now succeeded in inactivating anisakis inside the fish meat by repeatedly and instantaneously applying electric current to the fish meat using pulsed power technology. The fish meat was placed in buffer saltwater, and pulsed power was applied multiple times. The immobilization rate was highest when the buffer saltwater was 5 mS/cm. The immobility ratio increased as the number of shots increased. Sensory evaluation of the fish meat after the pulse treatment confirmed that it retained its quality as sashimi. Breaking tests and color measurements were also conducted. We believe that this pulsed power treatment is a useful alternative to freezing as a method for killing anisakis.

In this introduction to the Special Issue on pulsed power and its applications, background information is provided for the nonspecialist to better understand the many challenges in designing pulsed power systems, and the wide diversity of applications that are now emerging. The approach to providing a tutorial on pulsed power technology is to make available to the reader the paper written by J. C. Martin which appeared in a Special Section of the Proceedings of the IEEE on pulsed power technology in June 1992. That paper is supplemented in this introduction with additional information that complements many of the invited papers composing this Special Issue.

This paper describes a new recycling method for metal-coated plastics. Pulsed power technology was used to remove a metal layer (aluminum) from CD-ROM. The progress of removal and the state of discharge were investigated in detail. In addition, the shadow picture method including a digital image processing was used to estimate removal amount. A pulsed power generator using magnetic pulse compression (MPC-PPG) with maximum storage energy of 40 J/pulse was used. Pulsed power was applied to concentric ring electrodes placed on the CD-ROM. Separation between electrodes was about 35 mm. Results show that almost all of the metal layer was removed under application of about 30 shots of pulse power. A strong correlation between the removed area measured by the shadow picture method and the removed mass was obtained, allowing the removed area and mass to be measured instantly by the shadow picture method. Furthermore, it was revealed that the discharge onset voltage increases with gap length between the electrodes and the aluminum layer left on the surface. Due to the surface flashover voltage between ring electrodes of about 80 kV, a pulsed power source output voltage larger than 80 kV is required.

Pulsed power technology provides a platform for investigating plasmas in strong magnetic fields using a university-scale machine. Presented here are methods for generating and measuring the 1–4-MG magnetic fields developed for the 1-MA Zebra pulsed power generator at the University of Nevada, Reno. A laser coupled with the Zebra generator produces a magnetized plasma, and experiments investigate how a megagauss magnetic field affects the two-plasmon decay and the expansion of the laser-produced plasma in both transverse and longitudinal magnetic fields.

Agricultural and food processing applications of pulsed power and plasma technologies are described in this paper. Repetitively operated compact pulsed power generators with a moderate peak power are developed for the agricultural and the food processing applications. These applications are mainly based on biological effects and can be categorized as germination control of plants such as Basidiomycota and arabidopsis; inactivation of bacteria in soil and liquid medium of hydroponics; extraction of juice from fruits and vegetables; decontamination of air and liquid, etc. Types of pulsed power that have biological effects are caused with gas discharges, water discharges, and electromagnetic fields. The discharges yield free radicals, UV radiation, intense electric field, and shock waves. Biologically based applications of pulsed power and plasma are performed by selecting the type that gives the target objects the adequate result from among these agents or byproducts. For instance, intense electric fields form pores on the cell membrane, which is called electroporation, or influence the nuclei. This paper mainly describes the application of the pulsed power for the germination control of Basidiomycota i.e. mushroom, inactivation of fungi in the soil and the liquid medium in hydroponics, and extraction of polyphenol from skins of grape.

The University of Texas at Austin is constructing a spacious facility for research in pulse power technology at the Balcones Research Center, located in north Austin. The arrangement and capacity of the facility are intended to support high-current experiments. The laboratory power supply being designed consists of six homopolar generators, each capable of delivering ten megajoules of energy. The output bus is configured such that various series, parallel, and series-parallel circuits of homopolar generators are possible. Both resistive and inductive loads can be driven from the power supplies. Research programs will be supported with a wide range of physical facilities, including materials handling, machine shop, data acquisition and analysis, engineering and operating personnel, chemical analysis and metallurgical laboratories, and an information center. These facilities will be available to the U. S. technical community through several types of arrangements with The University through the Center for Electromechanics. Each of the six homopolar generators is designed to deliver 1 MA at 100 V, with a maximum repetition rate of a discharge every five minutes. In addition to EM launch research and applications, other intended uses of the power supply include welding of large cross-sections of metal (up to 650 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> or 100 in. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of steel), generation of high magnetic fields in low-impedance magnets, and testing of high-current opening switches. Status of major elements of the project is reported.

Innovative triggering method demonstrates reduced jitter and improved reliability for high repetition rate pulsed power sources.

Existing and future pulse power technology is a major engineering challenge for any particle accelerator. It is employed at Daresbury Laboratory on the existing synchrotron radiation source (SRS) for injecting and extracting electron beams and on the energy recovery linac prototype (ERLP) for thermionic valve protection. The proposed new 4th generation light source (4GLS) has a conceptual design that requires significant advances on the current pulse power technology operating at Daresbury Laboratory. The international Muon ionisation cooling experiment at Rutherford Appleton Laboratory is in its design phase and requires pulsed applications for the RF system and target actuator motor amplifier.

Filamentary modeling, also termed the network mesh or mesh-matrix method, has a long history and the first to use this method of analyzing electric circuits was J.C. Maxwell. In pulsed power technology, the most intensive users of this numerical modeling were those designing electromagnetic launchers and homopolar generators. The filamentary technique has been successfully applied at Loughborough along the years in a wide range of pulsed power, high-current applications, including pulsed magnetic field coils, explosively driven magnetic flux-compression generators, various electromagnetic launchers, ultrahigh magnetic field generation by single-turn coils and electromagnetic implosions and the design of various types of high-voltage air-core pulsed transformers. After an introduction into the filamentary technique, most of these applications will be detailed.

Pulsed power technology is gradually forming a development trend of civil-military integration, which puts forward more requirements for pulsed power generators. This paper takes magnetic switches (MSs) as the starting point and reviews recent advancements in pulse generators based on MSs. First, the working mechanism of the MS "rapid inductance drop after magnetic core saturation" is analyzed. Second, the basic uses of MSs are introduced with specific examples, namely, magnetic compression unit, saturated pulse transformer, and magnetic delay switches. Then, the typical topologies of pulse generators based on MSs are discussed, including transmission line, Marx, Fitch, linear transformer driver, and semiconductor opening switch pumping circuits. These circuits' technical characteristics and parameter levels are highlighted. Finally, the existing problems and future development trends of MS-based solid-state pulse generators are discussed.

When an instructor creates an educational content with narration on Microsoft PowerPoint, it is the easiest method that he/she uses one's built-in feature of recording narration because there is no need to install any other software. We constructed the content authoring system for e-Learning, named Kumamoto Universal and Multipurpose Authoring (KUMA) system, which is based on cloud computing. Using the system, an instructor only has to upload the slide with narration created on PowerPoint to the system, and then he/she can publish a Windows Media streaming video and a PDF slide. The application of the system is the website of streaming video lectures contributed by researchers in the field of pulsed power, which we call "Streaming Book on Pulsed Power Engineering". Another application of it is the website of video lectures for graduate students as a part of blended learning. To deliver streaming videos to more than 100 students simultaneously, we need to configure quality of encoding streaming videos and estimate the amount of transferring data and the network traffic load. The purpose of this study is to examine the traffic load for streaming e-Learning content in applications of KUMA system. In this work, we use Windows Media Load Simulator to simulate the connections from more than 100 students.

A conceptual design of an angular multiplexed 50 kJ KrF laser module for Inertial Confinement Fusion is presented. Optical designs for encoding, beam packing and beam transfer between amplifier stages are developed; emphasis is placed on reducing prepulse problems and achieving acceptable optical quality. An axisymmetric optical design is identified as optimum in terms of simplicity, optical quality, cost and alignment. A kinetic code model was developed for the KrF amplifier and was used to derive scaling maps for the 50 kJ module. Attention was given to reducing parasitics, achieving acceptable extraction efficiency and accounting for amplified spontaneous emission effects. The size of the module is constrained by parasitic suppression and damage thresholds; the power gain is constrained by demanding 40% extraction efficiency in a double pass extraction geometry; and, the run time is constrained by the pulsed power technology (PFN or PFL) and acceptable values of g/sub 0/L. The bounds imposed on the design by the pulsed power technology were examined. Both PFLs and PFNs were considered along with their associated diode, hibachi and guide field requirements. A base line design for a 50 kJ module including amplifier staging, layout and overall size is discussed. Cost analysis and scaling for optical components, pulsed power technology and the guide field are also presented.