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

{"title":"Simulation of an exploding wire opening switch","authors":"J. Stephens, A. Neuber, M. Kristiansen","doi":"10.1109/MEGAGAUSS.2012.6781418","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781418","url":null,"abstract":"An exploding wire model that accounts for the electric field enhanced conductivity of dense metal plasma is applied to simulate an exploding wire opening switch. In contrast to many z-pinch experiments, operated in vacuum, the experiments here discuss wires vaporized in a high pressure gas environment. In addition to this, these experiments are primarily concerned with sub-eV temperatures, with a specific emphasis on the liquid-vapor phase transition, where significant decreases in conductivity provide the opening switch behavior. It is common that fuses operating within this regime are analyzed using 0-dimensional models, where the resistance is taken to be an experimentally determined function of energy or action. A more accurate 1-dimensional model with added field enhanced conductivity has been developed to better model the fuse dynamics throughout a significantly larger parameter range. The model applies the LANL SESAME database for the equation-of-state, and the conductivity data developed with the Lee-More-Desjarlais (LMD) algorithm. Using conductivity based on conditions of thermal equilibrium accurately predicts fuse opening as well as current re-emergence after a few microseconds dwell time for the case of small electric fields, however, this simple approach fails to capture early fuse restrike if the differential voltage across the wire becomes too large (~few kV/cm for the investigated conditions). It is demonstrated that adding an electric field driven conductivity term to the model will accurately capture the fuse dynamics for the low field as well as the high field case.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126413039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Filamentary modeling of pulsed high-current systems","authors":"B. Novac","doi":"10.1109/MEGAGAUSS.2012.6781437","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781437","url":null,"abstract":"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.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115693667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development and investigation of one-layer quasi-force-free magnets","authors":"G. Shneerson, O. S. Koltunov, A. N. Berezkin, I. Vecherov, S. Krivosheev, A. Nenashev, A. A. Parfentiev","doi":"10.1109/MEGAGAUSS.2012.6781417","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781417","url":null,"abstract":"Numerical calculation and experimental investigation of deformations in the one-layer quasi-force-free magnet placed inside the diamagnetic shield are carried out in this work. The calculations indicated a distinction of the current distribution in the conductor from one calculated without taking into account a presence of gaps and of the finite thickness of conductors. They allowed to estimate appearing additional stresses and indicated a possibility to reduce them by means of filling the slits with a material with comparatively low modulus of elasticity. Experimental study of small deformations indicated compliance of the calculated and experimental data. Possibility of correction of equilibrium state of the quasi-force-free winding with the additional axial current is shown.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121636796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Increasing power of energy preamplifiers for disk magneto-cumulative generators","authors":"V. A. Demidov, S. Kazakov, A. S. Boriskin, Y. Vlasov, V. A. Yanenko","doi":"10.1109/MEGAGAUSS.2012.6781421","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781421","url":null,"abstract":"Nowadays disk magneto-cumulative generators (DMCG) are the most powerful and power-consuming magneto-cumulative generators (MCG). The problem of necessary initial energy supply to the generator circuit is very urgent at creating high-performance disk generators. Preliminary energy amplification in experiments with DMCG is provided with helical MCGs. Along with preset energy supply, the preamplifier should have small characteristic current rise time. It is necessary for decreasing thermal and mechanical supply current effect on elements of the disk generator. This means increasing the output power of the preamplifier and associated with obtaining maximum possible initial energy in the DMCG. Initial inductance and resistance of the DMCG circuit became higher with increase of the DMCG sizes and the number of its elements. This required increasing the power of earlier used preamplifiers. The paper presents experimental results of the MCG-240 characteristics improvement at the expense of turns distribution change and application of more powerful explosive. Other possibilities of the preamplifier power increase are considered in the paper.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134505527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model experiments to adjust the elements of the pulsed power system for ALT-3 assembly","authors":"A. M. Glybin, B. E. Grinevich, P. Duday, V. Dudin, B. Egorychev, V. A. Ivanov, A. Ivanovskiy, A. I. Krayev, V. B. Kudelkin, Yu. I. Mattsev, A. N. Skobelev, A. A. Zimenkov, R. Reinovsky, C. Rousculp","doi":"10.1109/MEGAGAUSS.2012.6781445","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781445","url":null,"abstract":"Electromagnetic implosion of the cylindrical condensed liners is of great interest for the studies of high energy density physics, and in particular for getting pressures of terapascal range and for measuring the Hugoniots of materials under such pressures. The pulsed power systems on the basis of disk explosive magnetic generators (DEMG) provide the highest currents in the liner loads. A device on the basis of a 15-element DEMG Ø 0.4 m with a foil current opening switch and an explosive closing switch connecting the load is being developed to explore a possibility of driving the aluminum liner to a velocity of ~ 20 km/s and using it as an impactor. It is planned to check the operability of this device in the joint VNIIEF-LANL experiment ALT-3. To test the key systems of the ALT-3 assembly, a series of model experiments has been conducted. The model units will be described, the setup of the experiments testing the operability of the explosive current closing switch able to commute the currents of 60 - 70 MA and the system of high-voltage insulation of the line delivering the energy to the liner and able to withstand high voltages will be discussed. The experiment with the system modeling the ALT-3 device to check the scheme of operation of the pulsed power source' elements and the operability of disk elements under the explosive magnetic regime at the initial feeding current of 7.0 - 7.5 MA will be considered.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132132318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Megagauss Institute Award","authors":"P. Turchi","doi":"10.1109/MEGAGAUSS.2012.6781407","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781407","url":null,"abstract":"In 2006, the Board of Directors of the Megagauss Institute established the Megagauss Institute Award for outstanding, career-long contributions to the field of science, technology, and applications of ultra-high magnetic fields. The first award recipient was Professor Fritz Herlach, in 2006. We are pleased to announce that this year's Megagauss Institute Award recipient is Dr. Peter J. Turchi.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129566146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The experimental research on explosively high magnetic field generator","authors":"Z. Gu, Hao Luo, Hengdi Zhang, Shichao Zhao, Xiaosong Tang, Y. Tong, Zhenfei Song, F. Tan, Jianheng Zhao, Chengwei Sun","doi":"10.1109/MEGAGAUSS.2012.6781415","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781415","url":null,"abstract":"The cylindrical isentropic compression by high magnetic field pressure is very useful in high energy density physics. Some primary experimental works on the explosively magnetic flux compression generator had been carried out since 2011 at Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP). A traditional configuration of explosively driven flux generator had been designed and some initial parameters include: the internal diameter of the liner is 97 mm, the initial magnetic field is about 5 Tesla. HE-charge total weight is about 3.7 kg. The movement of liner was recorded optically and its velocity was about 5-6 km/s. Form the photograph results the liner was compressed smoothly and evenly. The magnetic field of over 430 Tesla was measured by magnetic probes.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114154232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flat plate FCG experimental system for material studies","authors":"D. Goerz, D. Reisman, J. Javedani, J. T. Paladichuk, D. Hare, L. Tallerico, G. Earley, R. Kuklo, A. D. White","doi":"10.1109/MEGAGAUSS.2012.6781425","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781425","url":null,"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 μs 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.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127202093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physical evolution of metal surface layers exposed to pulsed megagauss magnetic fields","authors":"P. Turchi","doi":"10.1109/MEGAGAUSS.2012.6781443","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781443","url":null,"abstract":"Metal surfaces exposed to pulsed high magnetic fields in vacuum can experience phase transitions within the metal, vapor over the surface and the development of various dynamic and thermal phenomena that can adversely affect performance. The desired performance may include implosion of a liner without deleterious effects of perturbation growth on the outer surface, or liner compression of buffer magnetic flux surrounding plasma without penetration by high-Z metal vapor. The complexity of interactions and processes has made this a long-standing problem for both theoretical modeling and experimental diagnosis. As a guide for further work, the present paper steps through the physical evolution of the several portions of the surface layer from early heating by skin currents and vapor production, to the possible transition of this vapor into significant plasma. With additional heating, after the onset of nonlinear diffusion, the current density in the metal near the surface becomes roughly uniform and continued resistive heating allows transition from solid to liquid state. As a liquid subject to acceleration, perturbations can grow exponentially. Such growth, however, is restrained for perturbations with wavelengths not small compared to the thickness of the liquid layer. Similar restrained growth of perturbations can occur in the vapor/plasma layer, which may also be thinner than wavelengths of concern (e.g., thickness of region of buffer flux). Experimental attempts to understand the evolution described here suffer due to severe variations of material properties from the metal surface through vapor and plasma, with opportunities for inhomogeneities and nonequilibrium in many forms, and associated uncertainties in transport properties and observed radiation.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127718918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic liner implosion simulations for the ALT-3 experiment","authors":"A. Buyko, S. Garanin, V. Zmushko","doi":"10.1109/MEGAGAUSS.2012.6781435","DOIUrl":"https://doi.org/10.1109/MEGAGAUSS.2012.6781435","url":null,"abstract":"We discuss two-dimensional magnetohydrodynamic simulations of the liner implosion, which model the development of Rayleigh-Taylor-like instability and interaction between the liner and PU glide planes. The simulations were conducted with variations in methodological parameters (random initial perturbations etc.) and in the glide plane shape. We found a glide plane shape that provides reliable electric contact with the liner during implosion and acceptable shape of the liner's front surface before the impact without jets that are dangerous for diagnostics of the liner as an impactor.","PeriodicalId":299352,"journal":{"name":"2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129492331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}