2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics最新文献

{"title":"Experimental and Theoretical Analyses of Explosively-Formed Fuse (EFF) Opening Switches","authors":"D. Tasker, J. Goforth, H. Oona, Gerald Kiuttu, Matthew Domonkos","doi":"10.1109/MEGAGUSS.2006.4530692","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530692","url":null,"abstract":"The EFF is used at Los Alamos as the primary opening switch for high current applications. It has interrupted currents from ~10 kA to 25 MA, thus diverting the current into low inductance loads. To understand and optimize the performance of full-scale experiments, many parameters were studied in a series of small-scale experiments, including: electrical conduction through the explosive products; current density; explosive initiation; insulator type; conductor thickness; conductor metal; metal temper; and on. The results show a marked inverse correlation of peak EFF resistance with current density. In this paper we postulate and refute a simple extrusion mechanism of EFF operation; demonstrate that the EFF switch has a near-ideal profile for producing flat-topped voltage profiles; and explore possible mechanisms for the degradation of small scale switch performance.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123042705","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 Quest for the Wholly Stable Liner","authors":"W. Atchison, P. Turchi, D. Lemons","doi":"10.1109/MEGAGUSS.2006.4530661","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530661","url":null,"abstract":"For several decades many have studied or conducted experiments to drive magnetic fields into metallic conducting materials. Examples include designs for electrically exploded fuses, exploding wires to generate high energy plasmas, and of course heavy metal liners as kinetic drivers for hydrodynamic experiments. When the material melts the surface can develop highly unstable dynamics. One of the most common results is the onset and growth of spatial perturbations taking on the form of spike and bubble like structures. This is usually identified as Magneto-Raleigh-Taylor (MRT) instability. A clear example is when excessive current is applied to accelerate a near normal density thick metal liner to velocities approaching 1.0 cm/musec or greater. Yet we have observed several experiments where melting of the liner was present but the outside liner surface was observed to remained stable (B-0.5 to 1.3 MG). Analysis of this and other cases compared to MHD simulations enabled us to examine this phenomenon under a variety of conditions. While the majority of the cases still are fundamentally acceleration driven instability of a fluid interface, other phenomenon have been observed to play a significant role such as the effect of liquid/vapor phase change at the surface. Additionally, this suggests there may be drive conditions that can maintain the aluminum at conditions well away from the saturated liquid line until the conditions are well above the triple point in aluminum. There are some indications that this may reduce or delay the MRT like instabilities. However excessive drive that pressurizes the melted layer too much produces unfavorable gradients in the material that grossly aggravate the traditional MRT instabilities. In this talk we will examine in detail the effects of EOS structure, conductivity dependence on state properties (e.g. density and temperature), and the magnitude and time dependence of the driving magnetic field on the evolution of surface conditions. Based on these observations we propose that controlling the surface stability may depend on careful adjustment of time scales associated with the driving waveform and kinetics of the liner in order to control the path in phase space (EOS) the material follows.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122444547","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":"A Bench Top Railgun with Distributed Energy Sources and Diagonostics","authors":"B. McDaniel, J. Mankowski, D. Wetz, B. Mchale, M. Kristiansen","doi":"10.1109/MEGAGUSS.2006.4530677","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530677","url":null,"abstract":"The experimental results of a five stage distributed energy source railgun are presented. The advantages of such a scheme are increased efficiency due to less energy remaining in the railgun inductance and lower rail resistive losses. The design is a bench top 81 cm long solid armature railgun with a 1.27 cm × 1.27 cm bore cross-section separating the 1.27 cm × 2.54 cm copper rails. Multiple capacitive storage banks are connected at different positions along the length of the rails. Each bank is composed of electrolytic capacitors, toroidal inductors, SCRs, and free-wheeling diodes. The primary bank (stage 1) can store 11.6 kJ, and the other stages store 5.8 kJ of energy. The diagnostics include Rogowski coils at each bank, a flux ruler along the entire railgun to monitor the armature's velocity, and B-dots. The switches are controlled by pulsers with fiber optic inputs, which accurately trigger the SCRs. To sequence trigger the storage banks, B-dot sensors provide feedback to the armature's position. Additionally, experimental results are compared to PSPICE simulations.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114835226","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":"Algorithm for Unfolding Current from Faraday Rotation Measurement","authors":"S. E. Mitchell","doi":"10.1109/MEGAGUSS.2006.4530708","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530708","url":null,"abstract":"Various methods are described to translate Faraday rotation measurements into a useful representation of the dynamic current under investigation[1]. For some experiments, simply counting the \"fringes\" up to the turnaround point in the recorded Faraday rotation signal is sufficient in determining the peak current within some allowable fringe uncertainty. For many other experiments, a higher demand for unfolding the entire dynamic current profile is required. In such cases, investigators often rely extensively on user interaction on the Faraday rotation data by visually observing the data and making logical decisions on what appears to be turnaround points and/or inflections in the signal. After determining extrema, inflection points, and locations, a piece-wise, ¿I/¿t, representation of the current may be revealed with the proviso of having a reliable Verdet constant of the Faraday fiber or medium and time location for each occurring fringe. In this paper, a unique software program is reported which automatically decodes the Faraday rotation signal into a time-dependent current representation. System parameters such as the Faraday fiber's Verdet constant and number of loops in the sensor are the only user-interface inputs. The central aspect of the algorithm utilizes a short-time Fourier transform (STFT) which reveals much of the Faraday rotation's hidden detail necessary for unfolding the dynamic current measurement.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134058539","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":"Cooling and Condensation of Hydrogen Isotopes in Isentropic Compression Device","authors":"G. V. Boriskov, A. Bykov, N. Egorov, V. Pavlov","doi":"10.1109/MEGAGUSS.2006.4530718","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530718","url":null,"abstract":"A compression facility that allows isentropically creating multi-megabar pressure in easily compressed substances and studying their thermodynamic and kinetic properties is developed and successfully used nowadays. The mentioned substances are: rare gases and hydrogen isotopes, converted into condensed initial state. An ultra-high magnetic field MC-1 generator is used for ultra-high pressure obtaining on the device, and a cryostat of special design is used for cooling of the studied substance and its transition to a polycrystalline phase. In the paper we present a design and operating principle of the cryogenic device. By the example of deuterium it is shown how it is possible to describe the cooling and crystallization process. Calculation results and analysis of data of laboratory and field experiments show that at cooling it is possible to obtain the samples with the required sizes and initial temperature, and homogeneous enough in density.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132092141","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":"Contribution of Vladimir K. Chernyshev to a Development of Explosive Pulsed Power and Applications","authors":"A. V. Ivanovsky","doi":"10.1109/MEGAGUSS.2006.4530657","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530657","url":null,"abstract":"V.K. Chernyshev proposed and realized (1958) a fast output of energy from the EMG circuit by means of its breaking by the HE charge and also by means of electric explosion. The current opening switches for the DEMG of POTOK family were developed under his leadership.V.K.Chernyshev together with his disciples created a small-size and power-intensive source of energy for a new type of powerful transportable sources of neutrons and together with other VNIIEF scientists they created a new pulsed system as a part of the complex.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117144150","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":"2-D MHD Study of Instabilities During the Compression Phase of an Inverse Z-Pinch MTF System","authors":"P. V. Subhash, S. Madhavan, S. Chaturvedi","doi":"10.1109/MEGAGUSS.2006.4530678","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530678","url":null,"abstract":"Two-dimensional MHD computations have been performed to study the growth of instabilities in an MTF system involving the cylindrical compression of a inverse Z-pinch target plasma by a metallic liner. The growth of modes in the plasma can be divided into two phases. During the first phase, the plasma continues to be Kadomtsev stable. The dominant mode in the liner instability is imposed upon the plasma in the form of a growing perturbation. This mode further transfers part of its energy to its harmonics. During the second phase, however, non-uniform implosion of the liner leads to axial variations in plasma quantities near the liner-plasma interface, such that certain regions of the plasma locally violate the Kadomtsev criteria. Further growth of the plasma modes is then due to plasma instability.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125039128","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":"Time Dependent Inductance Calculation of Magneto-Cumulative Generator During Explosion Using Finite Element Method","authors":"I. Sung, B. Joe, Chun-Yeol You, O. Kwon, Cheon Lee","doi":"10.1109/MEGAGUSS.2006.4530701","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530701","url":null,"abstract":"The time dependent inductance variation is an essential ingredient in the design of magneto-cumulative generator. In most theoretical works, the inductance is modeled by a simple exponential form as a function of time. It is widely accepted that it is proper approximation for the time dependent inductance due to the constant expansion velocity of the liner during the explosion process. In this simple model, however, the magnetic field compression is not correctly treated. Since the inductance is related with the magnetic energy, which is determined by the magnetic flux density, the apposite consideration of the compression of the magnetic field is required. In order to include the effect of the compression of the magnetic field properly, we perform the finite element method calculation for the time dependent inductances in MCG during the explosion process. We find that the time dependent inductance can not be modeled with simple exponential model. Especially, the time derivative of the inductance shows more pronounces difference with the simple exponential model. In order to confirm the calculation results, we design mimic-explosion experiments in order to measure the inductances during the explosion process. It is revealed that the measurement data is well matched with the calculated one.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127101972","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":"Energy Compression Experiments: Simulation of Small-Size MCG to Obtain a Radio Frequency Source","authors":"M. M. Kekez","doi":"10.1109/MEGAGUSS.2006.4530691","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530691","url":null,"abstract":"The electrically driven system was used to simulate the operation of sub-micro-size MCG. Initially, the maximum voltage at the output of the coil is les 6 kV, and the maximum current through the helical coil is < 4 kA. By compressing the energy stored in the coil, the electromagnetic induction voltage reaches up to 700 kV and the induced current is up to 10 kA. The goal of the work is to convert the available gigawatt power pulse into radio frequency (RF) radiations.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"207 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125664077","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":"Single Turn Multi-Megagauss System at the NHMFL-LOS Alamos to study plutonium","authors":"C. Mielke, R. McDonald","doi":"10.1109/MEGAGUSS.2006.4530682","DOIUrl":"https://doi.org/10.1109/MEGAGUSS.2006.4530682","url":null,"abstract":"By utilizing a fast capacitor bank and the single-turn coil technique, a new megagauss system has been commissioned at Los Alamos National Laboratory. The system is specially designed for condensed matter physics experimentation on metallic plutonium and other actinides in extremely high magnetic fields. In addition to special conditions required for handling hazardous samples, the system features 24 synchronous switches at a maximum voltage of 60 kV and a maximum current approaching 4 MA. Peak magnetic fields approaching 300 tesla are predicted for the system. System design and issues related to condensed matter physics experimentation are discussed.","PeriodicalId":338246,"journal":{"name":"2006 IEEE International Conference on Megagauss Magnetic Field Generation and Related Topics","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126944412","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}