2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)最新文献

{"title":"Variational formulation of particle algorithms for kinetic electromagnetic plasma simulations","authors":"A. Stamm, B. Shadwick, E. Evstatiev","doi":"10.1109/PLASMA.2013.6635213","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635213","url":null,"abstract":"Summary form given only. A rigorous variational methodology was used to derive a selfconsistent set of discrete macro-particle kinetic plasma equations from a discretized Lagrangian. Discretization of the Lagrangian was performed by reduction of the phase-space distribution function to a collection of finite-sized macroparticles of arbitrary shape, and subsequent discretization of the field onto a spatial grid. The equations of motion were then obtained by demanding the action be stationary upon variation of the particles and field quantities. This yields a finite-degree of freedom description of the particle-field system which is inherently self-consistent. This project extends the work of Evstatiev et al.1 from a simplified electrostatic formulation to the full electromagnetic case. The primary advantage of variational approaches relative to the more common Particle-In-Cell (PIC) formulation is that they preserve the symmetry of the Lagrangian, which in our case leads to energy conservation and avoids difficulties with grid heating. Additional benefits originate from the decoupling of particle size from grid spacing and a relaxation of the restrictions on particle shape, which leads to a decrease in numerical noise. The variational approach also guarantees a consistent level of approximation, and is amiable to higherorder approximations in both space and time. For many configurations of interest to laser-driven plasma accelerators, it is computationally efficient to use a coordinate system co-moving with the laser pulse. Since we are using a Lagrangian formulation, we can easily transform to moving window coordinates yielding a particle algorithm explicitly formulated in the moving window. Thus we, for the first time, demonstrate an energy conserving set of discrete equations in moving window coordinates rigorously derived from a discretized electromagnetic Lagrangian. Example simulations conducted with the new equations of motion demonstrate the desired energy conservation.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"21 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90932670","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":"Nonstationary oscillations of gyrotron backward wave oscillators","authors":"Shih-Hung Chen, Liu Chen","doi":"10.1109/PLASMA.2013.6635119","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635119","url":null,"abstract":"Summary form only given. The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) was studied by the steady-state analysis and the time-dependent simulation. The steady-state analysis gives the equilibrium states of the gyro-BWO, which stabilities can be examined by the time-dependent simulation. Comparisons of the numerical results show that the gyro-BWO becomes nonstationary while the trailing field structure completely forms due to the dephasing energetic electrons. The radiated wave in the trailing field structure is backward propagating to interfere with the main internal feedback loop of the gyro-BWO. Therefore, the frequency discrepancy between the radiated wave from the trailing field structure and the oscillation in the contracted field structure causes the alternative appearance of the field contraction and expansion, which forms the nonstationary oscillation of the gyro-BWO. The frequency separation from the central resonant frequency of the gyro-BWO and sidebands is scaled with the field amplitude of the contracted field structure, which shows that the nonstationary oscillation of the gyro-BWO is essentially different from the self-modulation of the gyromonotron.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"21 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91273223","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":"Study of implosion dynamics and radiative mechanisms of planar foil liners in comparison with planar wire arrays at 1.7 MA UNR zebra generator","authors":"V. Kantsyrev, A. Safronova, A. Esaulov, I. Shrestha, H. Zunino, V. Shlyaptseva, M. Weller, G. Osborne, A. Stafford, S. Keim, A. Chuvatin, L. Rudakov, L. Velikovich","doi":"10.1109/PLASMA.2013.6633175","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6633175","url":null,"abstract":"Summary form only given. Planar foil liners are alternative loads to wire arrays at multi-mega ampere generators as well as a promising object for the investigation of the magnetic energy dissipation mechanisms in Z-pinch plasmas. Experimental comparison of implosion dynamics and radiative mechanisms of Al planar foils and single planar wire arrays (SPWAs) of the same width and linear mass was performed for the 0.9-1.6-MA current region. Foils radiate approximately 80-90% of the total yield and power of SPWAs. The non-LTE code was applied to estimate the average electron temperature in Al planar foils that was found to be 20% higher, than that in SPWAs, and the average electron density in foils that was an order of magnitude lower than for SPWAs. Also, the foils are characterized by smaller axial gradient of electron temperature and density than SPWAs. In addition, anisotropic emission from Al planar foils was observed to be similar to Al SPWAs: the total yield registered orthogonally to the foil plane was 1.3 times higher than that along the plane (compared to 1.5 for SPWAs). The anomalous MHD resistivity consideration suggests that a significant part of foil radiation could be due to formation of strongly-inhomogeneous plasma through instabilities appearing on shadowgraphic images of a symmetric foil as a result of initial sharp edges inhomogeneity. This idea was tested in the recent experiments with modified foils where one edge was initially sharp and the other was folded with smaller initial inhomogeneity. The yield from a foil with a folded edge was 13-15% lower than that with both sharp edges as predicted by MHD modeling. Presented results on radiation from foils suggest them as potentially useful x-ray sources for various HEDP applications due to simpler load foil preparations compared to wire arrays. Preliminary results of the research we started on radiation from double foils in comparison with double planar wire arrays (DPWAs) are also discussed.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"24 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90422400","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":"Mixing efficiency estimation by probe discharge spectroscopy","authors":"S. Leonov, A. Firsov, M. Shurupov, D. Yarantsev","doi":"10.2514/6.2013-2765","DOIUrl":"https://doi.org/10.2514/6.2013-2765","url":null,"abstract":"Summary form is given. This work considers the dynamics of long filamentary pulse discharge generated along the contact zone of two co-flown gases [1], basically: hydrocarbon fuel and oxidizer. The effect of the mixing actuation in compressible flow is observed because of the gas dynamic instability arisen after the discharge generation. The mixing efficiency is examined qualitatively by means of Probe Discharge Breakdown Spectroscopy. An adequate measurement of the mixing efficiency is principally important for this study. The best way for that is to know the concentrations of main components and their spatial distribution. The idea is to realize breakdown of the so-called “probe” discharge that has much less power than the main one at some delay after the main breakdown and to analyze the spectrum of this probe discharge. The temporal resolution of this method is equal to the duration of probe discharge luminescence - <; 1 us - it is reasonably small. The spatial resolution is determined by the collecting optical system and can be no more than lxd=3x1mm. It is a little bit worse than spatial resolution of the LBF [2] method but it still seems satisfactory for mixing efficiency estimation. Spectroscopic observations were carried out by means of high luminosity monochromator combined with ANDOR DU420 spectroscopic camera. Dispersion of this system is 0.5 Å/pixel and spectral resolution is about 2.5 Å. Spectrum of the main discharge (E1=1.5J) contains high intensity continuous emission that arises due to high temperature within the main discharge channel. Power release in probe discharge is measured as low as E2=0.03J per pulse. Probe discharge spectrum was measured at variation of the delay time between main and probe discharge and the probe discharge location. It was found that spectrum of the probe discharge doesn't contain CN at all without preceding breakdown of the main discharge. If main discharge isapplied for mixing, the CN emission arises in spectrum of the probe discharge. Its intensity grows with growth of the probe discharge delay that means increasing of the CO2 concentration. It is also seen that intensity of the N2 bands tends to reduce, when disturbances reach the measurements region.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"4 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88479549","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":"Fast pulsed cluster jet","authors":"R. Madden, P. Coleman, M. Krishnan","doi":"10.1109/PLASMA.2013.6635128","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635128","url":null,"abstract":"Summary form only given. Short burst, ultrafast laser pulses interact intensely with matter to generate beams of secondary radiation such as coherent x-rays via high harmonic generation, electron bunches via laser wakefield acceleration, and protons via laser-driven ion acceleration. These secondary radiation sources have applications in biological imaging, medical diagnostics and treatment, and nondestructive evaluation. The emerging field of laser-plasma acceleration (LPA) has demonstrated electron accelerators with unprecedented electric field gradients. Supersonic, highly collimated gas jets and gas-filled capillary discharge waveguides are two primary targets of choice for LPA. A new LPA accelerated beam energy record of >2 GeV has been recorded using the Texas Petawatt laser (150 J) focused into a 7 cm He gas cell. The electron beams were highly-collimated (<;1 mrad divergence), containing high charge (>1 nC), and had a broad energy spectrum (peaked at ~2 GeV, with electrons up to 2.4 GeV). A fast opening and closing gas valve is essential to a LPA. This paper describes a fast valve (developed under a DOE SBIR grant) that opens in <;100μs, closes in <;400μs and can run (in cooled mode) at ~10Hz rep-rates at pressures as high as 1000psia. Recently we have designed advanced versions of the nozzle to create ~10-15mm long supersonic gas jets with tailored density gradients to test the concept of phase locking in an LPA. Dense gas jets with high concentrations of clusters are also of interest for such ultra-fast laser interactions. Development of a dense cluster jet using our ultra-fast opening/closing valve is also described.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"49 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73539838","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":"Nonuniform 2D Mott-Gurney law","authors":"Y. Zhu, L. Ang","doi":"10.1109/PLASMA.2013.6634947","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6634947","url":null,"abstract":"For high charge injection into a solid dielectric, the 1D current density is described by the classical Mott-Gurney (MG) law for trap-free solid and Mark-Helfrich (HF) law for trap-filled solid. Recently, due to the development of nanotechnology, the geometry current enhancement is observed in many experiment, such as electron transport in nanowire. In this paper, we develop a numerical method to solved the 2D space charge limited current problem.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"82 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76630091","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":"Repetitive x-ray source using triboluminescence","authors":"S. Furuya","doi":"10.1109/PLASMA.2013.6635143","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635143","url":null,"abstract":"Triboluminescence is a luminous phenomenon resulted from friction; for example, peeling scotch tape, breaking rock sugar with a hammer, peeling mica and so on. Triboluminescence is well known over 50 years but in 2008 UCLA group reported the radiation of x-ray region by triboluminescence in vacuum for the first time1. UCLA group made an automatic machine which peels scotch tape. With a view to practical application of triboluminescence to roentgen diagnosis we made an automatic peeling machine similar to that of UCLA group. An x-ray tube for conventional roentgen diagnosis needs a high voltage power supply. In contrast, triboluminescence does not need it. So it is very useful for roentgen diagnosis to replace a conventional x-ray tube with triboluminescence. Thus far, we have attempted to confirm the x-ray generation from triboluminescence using a filtered phosphor screen when the parameters such as the followings are changed; peeling speed, atmospheric pressure, variety of scotch tape, emission angle etc. Then in a similar way we have also attempted to measure x-ray dose from triboluminescence using a potable dosemeter. It was found that the x-ray generation has a directional property. Because the method to peel scotch tapes does not enable to operate continuously, new method without scotch tapes has been proposed2-3. The new method repeatedly contacts silicone with epoxy to produce x-ray. In this conference, we have reported the x-ray dose of triboluminescence x-ray source when the following conditions are changed; combinations of contact materials, contact methods, contact frequency and so on.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"96 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76848778","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 study of aluminum x-pinch assembly through x-ray abosrption spectroscopy","authors":"A. Cahill, C. Hoyt, S. Pikuz, T. Shelkovenko, D. Hammer","doi":"10.1109/PLASMA.2013.6635023","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635023","url":null,"abstract":"Summary form only given. Previous studies of plasma pinches, such as x-pinches or hybrid pinches, have thoroughly characterized the radiating hot spot formed at the center of the plasma in terms of size, temperature, and density. However, much of the plasma volume surrounding the hot spot has remained relatively unstudied. While point projection imaging and interferometry can be used to probe the density of this surrounding plasma, these diagnostics cannot provide measurements of plasma temperature. Emission spectroscopy can reveal temperatures, but the intensity of the hot spot outshines the surrounding plasma making spectral studies of nearby regions exceptionally challenging. We propose that a study of the surrounding plasma can be accomplished by means of absorption spectroscopy in spite of the high brightness of the x-pinch. Such an experiment has been designed for the XP pulser at Cornell University. The XP pulser, which is capable of delivering 500 kA of current in 100 ns, is used to drive an x-pinch as a source of continuum radiation. This radiation is dispersed by an astigmatic mica crystal before interacting with another x-pinch serving as the object plasma. The astigmatism of the crystal allows focusing to occur both at the sample location as well as at the detector for increased luminosity. To date, the experimental design for the study of plasma in an aluminum x-pinch has been completed. The object plasma under study will be Al 5056, an Al alloy containing 5% Mg. The H-like and He-like resonance and satellite lines in the spectrum from the Mg will be used as the basis for plasma diagnosis. The back lighting source will be tantalum due to its relatively flat continuum spectrum between the wavelengths of 8.2 and 9.5 angstroms. Preliminary results from this experiment will be presented.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"29 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78144550","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":"Electron-orbit control using a postdiode magnetic-field structure","authors":"S. Swanekamp, G. Cooperstein, D. Hinshelwood, D. Mosher, P. Ottinger, J. Schumer, B. Weber, J. Zier","doi":"10.1109/PLASMA.2013.6634904","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6634904","url":null,"abstract":"For many applications, control and manipulation of the electron orbits in a high-current electron beam is desirable. This is especially true when a weakly-self-pinched, multi-MV electron-beam is used to make bremsstrahlung radiation. In this case, the radiation pattern is highly peaked along the direction that the electron beam makes when it strikes the x-ray target. Therefore, to maximize the number of photons in the forward direction, it is desirable that the electrons strike the x-ray target as close to normal with as little spread in the beam angles as possible. In this paper, a method for controlling the macroscopic angle of a high-power electron beam using a post-diode magnetic-field structure is presented. The idea is to extract the electron beam into a vacuum cavity through a thin, low-mass foil where a portion of the return-current flows through a central post. The amount of current that flows through the central post and therefore the amount of beam straightening is controlled by inductively splitting the return current so that a portion of it returns through the central post and a portion returns outside the beam. By adjusting the balance between these two currents one can alter the electron orbits and achieve a wide range of angles that the electron beam makes with the target without the need for plasma or an external pulser.1 Particle-in-cell simulations have been performed to determine the parameters required to straighten an 8-MV, 200-kA, 23-cm-diameter hollow electron beam with an inward 20° macroscopic (average) angle so that it approaches the x-ray target at normal incidence. The simulations show an increase in the forward photon spectrum by up to a factor of 3. Experiments with similar beam parameters using the Mercury Inductive-Voltage Adder at the Naval Research Laboratory have shown an increase of a factor of two in the forward dose using this technique and are in good qualitative agreement with the simulations. Additional simulations and experiments are planned to optimize the forward dose and will be reported on during this talk.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"7 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78278691","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":"Ion acceleration in the divergent gas-puff Z-pinch plasma","authors":"K. Takasugi, Mineyuki Nishio","doi":"10.1109/PLASMA.2013.6635134","DOIUrl":"https://doi.org/10.1109/PLASMA.2013.6635134","url":null,"abstract":"Summary form only given. The divergent gas-puff z pinch is a non-uniform system in the axial direction. The degree of non-uniformity can be controlled by the angle of gas-puffing. High-energy ions around 1 MeV have been observed in the divergent gas-puff z-pinch experiment. As the ion acceleration has also been observed in the current reversal experiment, the acceleration has been attributed to some mechanism independent of the current direction. The result indicates that the acceleration mechanism is not the electromagnetic induction, and the further understanding of the mechanism is desired. Here the experiment was carried out to examine the relationship between the non-uniformity and the ion acceleration in the axial direction. The experiment was carried out on the SHOTGUN-III z-pinch device in which divergent gas nozzle was installed. Three divergent gas nozzles (10, 20 and 30 degrees) were prepared. The high-speed gas valve was filled with 5 atm argon gas. The device is equipped with a capacitor bank of 12 μF, which can be charged either positively or negatively. Typical discharge current is 150 kA at the charged voltage of 25 kV. A Thomson parabola energy analyzer was used for the ion analysis in the axial direction. Track detector (BaryotrakP) was used for observing the ions. Singly to triply ionized argon ions were observed in the series of experiment, and the maximum energy was about 1MeV. The preliminary result showed that ions with higher energy were observed at the smaller gas angle. The tendency supports the ion acceleration model of multiple reflections by the magnetic wall.","PeriodicalId":6313,"journal":{"name":"2013 Abstracts IEEE International Conference on Plasma Science (ICOPS)","volume":"21 1","pages":"1-1"},"PeriodicalIF":0.0,"publicationDate":"2013-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75017576","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}