NASA Astrophysics Data System (ADS)
Robinson, A. P. L.; Schmitz, H.; Fox, T. E.; Pasley, J.; Symes, D. R.
2015-03-01
When strong shocks interact with transverse density gradients, it is well known that vorticity deposition occurs. When two non-planar blast waves interact, a strong shock will propagate through the internal structure of each blast wave where the shock encounters such density gradients. There is therefore the potential for the resulting vorticity to produce pronounced density structures long after the passage of these shocks. If the two blast waves have evolved to the self-similar (Sedov) phase this is not a likely prospect, but for blast waves at a relatively early stage of their evolution this remains possible. We show, using 2D numerical simulations, that the interactions of two 'marginally young' blast waves can lead to strong vorticity deposition which leads to the generation of a strong protrusion and vortex ring as mass is driven into the internal structure of the weaker blast wave.
Interaction of Atmospheric Plasma Vortices
NASA Astrophysics Data System (ADS)
Izhovkina, N. I.; Artekha, S. N.; Erokhin, N. S.; Mikhailovskaya, L. A.
2016-08-01
Atmospheric electric fields, connected with the ionization of particles and plasma processes, occur in the fields of pressure gradients of mosaic mesh topology. Atmospheric aerosol particles play a significant role in the vortex generation. The Coriolis force and the motion of charged particles in the geomagnetic field lead to gyrotropy of the atmosphere and ionosphere. Occurrence of plasma vortices is stochastically determined for such an inhomogeneous gyrotropic medium. The geomagnetic field influences the change of structures of inhomogeneous media in the process of excitation of plasma vortices and their interaction. If colliding vortices are centered on the one geomagnetic line, the merge of vortices and the generation of a joint powerful vortex are possible. If a collision of vortices with centers at different geomagnetic field lines occurs, then the emergence of areas of heating and jet streams and the generation of new vortices are possible.
Recent developments in DBD plasma flow control
NASA Astrophysics Data System (ADS)
Wang, Jin-Jun; Choi, Kwing-So; Feng, Li-Hao; Jukes, Timothy N.; Whalley, Richard D.
2013-10-01
Flow control using DBD (dielectric-barrier-discharge) plasma actuators is a relatively new, but rapidly expanding area of research. There are a number of review papers available on this subject, but few discuss on their latest developments. The purpose of the present article is to “fill the gap” by reviewing the recent trend of plasma actuator design and to summarise aerodynamic control techniques. Here, we review new plasma actuators, such as plasma synthetic jet actuators, plasma spark jet actuators, three-dimensional plasma actuators and plasma vortex generators, which can induce three-dimensional flows away from the wall. We also review the starting vortex that leads to formation of a plasma wall jet. This is an important subject not only for a better understanding of the flow induced by DBD plasma actuators, but also as a database that can be used to calibrate the numerical models for plasma flow control. Design of DBD plasma actuators to obtain turbulent skin-friction reduction is shown and the modifications to near-wall turbulence structures are summarised. Novel applications of DBD plasma actuators for aerodynamic control are then discussed, including pitch and roll control, plasma jet vectoring, circulation control and plasma flap, showing a potential of DBD plasma actuators for replacing movable, aircraft control surfaces. Finally, vortex shedding control techniques by a number of different plasma actuators are surveyed.
Vorticity in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Deng, Wei-Tian; Huang, Xu-Guang
2016-06-01
We study the event-by-event generation of flow vorticity in the BNL Relativistic Heavy Ion Collider Au +Au collisions and CERN Large Hadron Collider Pb +Pb collisions by using the hijing model. Different definitions of the vorticity field and velocity field are considered. A variety of properties of the vorticity are explored, including the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction, and the time evolution. In addition, the spatial distribution of the flow helicity is also studied.
Shock Generation and Control Using DBD Plasma Actuators
NASA Technical Reports Server (NTRS)
Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.
2012-01-01
spanwise actuators in series and at a voltage of 75 kVp-p could fully suppress the flow separation downstream of the shock. The simulation results from case c showed that the streamwise plasma actuators are highly effective in creating pairs of counter-rotating vortices, much like the mechanical vortex generators, and could also potentially have beneficial effects for SBLI control. However, to achieve these effects, the positioning and the quantity of the DBD actuators used must be optimized. The wind tunnel experiments mapped the baseline flow with good agreement to the numerical simulations. The experimental results were conducted with spanwise actuators for cases a and b, but were limited by the inability to generate a sufficiently high voltage due to arcing in the wind-tunnel test-section. The static pressure in the tunnel was lower than the static pressure in an inlet at flight conditions, promoting arching and degrading the actuator performance.
Simulation of Flow Around Cylinder Actuated by DBD Plasma
NASA Astrophysics Data System (ADS)
Wang, Yuling; Gao, Chao; Wu, Bin; Hu, Xu
2016-07-01
The electric-static body force model is obtained by solving Maxwell's electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge (DBD) plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry (PIV) experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around the cylinder.
Chattopadhyay, S.
1994-11-01
The motivation, feasibility and potential for two unconventional collider concepts - the Gamma-Gamma Collider and the Muon Collider - are described. The importance of the development of associated technologies such as high average power, high repetition rate lasers and ultrafast phase-space techniques are outlined.
NASA Astrophysics Data System (ADS)
Yamamoto, Akira; Yokoya, Kaoru
2015-02-01
An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.
NASA Astrophysics Data System (ADS)
Yamamoto, Akira; Yokoya, Kaoru
An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.
Investigation of DBD for Fabrics Depending on Experimental Parameters
NASA Astrophysics Data System (ADS)
Korkmaz, Sunduz; Oksuz, Lutfi; Goktepe, Fatma; Helhel, Selcuk; Kati, Evren
2004-09-01
The presence of scale on a wool and cotton fiber surface introduces a number of problems such as felting and a surface barrier to dyestuffs in the wool and cotton industry. In the past, chemical methods were the major treatment for eliminating those problems. However, the effluents generated from wool and cotton dyeing and finishing processes are seriously contaminated with different kinds of chemicals, e.g. chlora-organic compounds from the anti-felt process. With the increasing of ecological and economical restrictions imposed on the textile industry, the industries were required to find environmentally favorable alternatives in wool and cotton treatment processes. Dielectric barrier discharge (DBD) is one of the treatment methods. The results of the surface treatment, using an atmospheric pressure dielectric barrier discharge (DBD), of wool and cotton in order to establish the most suitable conditions for textile treatments, are presented. Surface treatments will be performed with different applied voltages, different gap sizes, different thicknesses of dielectric at atmospheric pressure of air conditions. Scanning Electron Microscope (SEM) will be used to detect the physical surface changes on the samples. Surface luster, wet ability, dye ability of specimens will be presented. Breaking extension for cotton is increased by about 21% in length from 14.4mm to 17.47mm by DBD and about 27% in length from 14.4 to 18.254 by ECR. ECR modified samples are more strength than DBD applied. Hydrofility for cotton is also increased.
DBD-Corona Discharge for Degradation of Toxic Gases
NASA Astrophysics Data System (ADS)
Pacheco-Pacheco, M.; Pacheco-Sotelo, J.; Moreno-Saavedra, H.; A. Diaz-Gomez, J.; Mercado-Cabrera, A.; Yousfi, M.
2007-12-01
The non-thermal plasma technology is a promising technique to treat SO2 and NOx. Chemical radicals produced with this technology can remove several pollutants at atmospheric pressure in a very short period of time simultaneously. Both theoretical and experimental study on SO2 and NOx removal, by a dielectric barrier discharge (DBD) with corona effect, is presented.
Executive Function Deficits in Preschool Children with ADHD and DBD
ERIC Educational Resources Information Center
Schoemaker, Kim; Bunte, Tessa; Wiebe, Sandra A.; Espy, Kimberly Andrews; Dekovic, Maja; Matthys, Walter
2012-01-01
Background: Impairments in executive functions (EF) are consistently associated with attention deficit hyperactivity disorder (ADHD) and to a lesser extent, with disruptive behavior disorder (DBD), that is, oppositional defiant disorder or conduct disorder, in school-aged children. Recently, larger numbers of children with these disorders are…
Palmer, R.B. |; Sessler, A.; Skrinsky, A.
1996-01-01
Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should thus be regarded as complementary. Parameters are given of 4 TeV and 0.5 TeV high luminosity {micro}{sup +}{micro}{sup {minus}}colliders, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders, starting from the proton accelerator needed to generate the muons and proceeding through muon cooling, acceleration and storage in a collider ring. Problems of detector background are also discussed.
Removal of paper microbial contamination by atmospheric pressure DBD discharge
NASA Astrophysics Data System (ADS)
Vrajova, J.; Chalupova, L.; Novotny, O.; Cech, J.; Krcma, F.; Stahel, P.
2009-08-01
In this paper the removal of the microbial contamination from paper material using the plasma treatment at atmospheric pressure is investigated. The Aspergillus niger has been chosen as a bio-indicator enabling to evaluate the effect of plasma assisted microbial inactivation. Dielectric barrier discharge (DBD) operated at atmospheric pressure was used for the paper sterilization. The working gas (nitrogen, argon and helium), plasma exposition time and the plasma power density were varied in order to see the effect of the plasma treatment on the fungi removal. After the treatment, the microbial abatement was evaluated by the standard plate count method. This proved a positive effect of the DBD plasma treatment on fungi removal. Morphological and colorimetric changes of paper substrate after plasma treatment were also investigated.
Fischer, W.
2011-12-01
Ion colliders are research tools for high-energy nuclear physics, and are used to test the theory of Quantum Chromo Dynamics (QCD). The collisions of fully stripped high-energy ions create matter of a temperature and density that existed only microseconds after the Big Bang. Ion colliders can reach higher densities and temperatures than fixed target experiments although at a much lower luminosity. The first ion collider was the CERN Intersecting Storage Ring (ISR), which collided light ions [77Asb1, 81Bou1]. The BNL Relativistic Heavy Ion Collider (RHIC) is in operation since 2000 and has collided a number of species at numerous energies. The CERN Large Hadron Collider (LHC) started the heavy ion program in 2010. Table 1 shows all previous and the currently planned running modes for ISR, RHIC, and LHC. All three machines also collide protons, which are spin-polarized in RHIC. Ion colliders differ from proton or antiproton colliders in a number of ways: the preparation of the ions in the source and the pre-injector chain is limited by other effects than for protons; frequent changes in the collision energy and particle species, including asymmetric species, are typical; and the interaction of ions with each other and accelerator components is different from protons, which has implications for collision products, collimation, the beam dump, and intercepting instrumentation devices such a profile monitors. In the preparation for the collider use the charge state Z of the ions is successively increased to minimize the effects of space charge, intrabeam scattering (IBS), charge change effects (electron capture and stripping), and ion-impact desorption after beam loss. Low charge states reduce space charge, intrabeam scattering, and electron capture effects. High charge states reduce electron stripping, and make bending and acceleration more effective. Electron stripping at higher energies is generally more efficient. Table 2 shows the charge states and energies in the
NASA Astrophysics Data System (ADS)
Mineev, V. P.
2013-10-01
Unlike to superfluid 4He the superfluid 3He-A support the existence of vortices with half-quantum of circulation as well as single quantum vortices. The singular single quanta vortices as well as nonsingular vortices with 2 quanta of circulation have been revealed in rotating 3He-A. However, the half-quantum vortices in open geometry always possess an extra energy due to spin-orbit coupling leading to formation of domain wall at distances larger than dipole length ˜10-3 cm from the vortex axis. Fortunately the same magnetic dipole-dipole interaction does not prevent the existence of half-quantum vortices in the polar phase of superfluid 3He recently discovered in peculiar porous media "nematically ordered" aerogel. Here we discuss this exotic possibility. The discoveries of half-quantum vortices in triplet pairing superconductor Sr2RuO4 as well in the exciton-polariton condensates are the other parts of the story about half-quantum vortices also described in the paper.
The effect of jet and DBD plasma on NCI-78 blood cancer cells
NASA Astrophysics Data System (ADS)
Kaushik, Nagendra K.; Kaushik, Neha; Choi, Eun Ha
2013-06-01
In this study we describe the effects of a nonthermal jet and dielectric barrier discharge (DBD) plasma on the T98G brain cancer cell line. The results of this study reveal that the jet and DBD plasma inhibits NCI-78 blood cancer cells growth efficiently with the loss of metabolic viability of cells. The main goal of this study is to induce cell death in NCI-78 blood cancer cells by the toxic effect of jet and DBD plasma.
NASA Technical Reports Server (NTRS)
Holmes, Bruce J. (Inventor); Carraway, Debra L. (Inventor); Holmes, Harlan K. (Inventor); Moore, Thomas C. (Inventor)
1988-01-01
A crossflow vorticity sensor for the detection of crossflow vorticity characteristics is described. The sensor is comprised of crossflow sensors which are noninvasively adhered to a swept wing laminar surface either singularly, in multi-element strips, in polar patterns, or in orthogonal patterns. These crossflow sensors are comprised of hot-film sensor elements which operate as a constant temperature anemometer circuit to detect heat transfer rate changes. Accordingly, crossflow vorticity characteristics are determined via cross-correlation. In addition, the crossflow sensors have a thickness which does not exceed a maximum value h in order to avoid contamination of downstream crossflow sensors.
The distribution of vorticity in a large vortical motion
NASA Technical Reports Server (NTRS)
Disimile, Peter J.
1988-01-01
An experimental investigation into the distribution of vorticity in the large scale vortical motions which are found in free shear layers was undertaken. Using hot-wire anemometry, both quasi-instantaneous and phase averaged transverse vorticity were acquired. These results appear to indicate that the transverse vorticity in a large scale vortical motion is distributed in a marble cake manner and not in laminated sheets spooled up into a coil or helical spring. Also, levels of vorticity were found to vary by as much as an order of magnitude in these concentrated vortical cores.
Palmer, R.
2009-10-19
Parameters are given of muon colliders with center of mass energies of 1.5 and 3 TeV. Pion production is from protons on a mercury target. Capture, decay, and phase rotation yields bunch trains of both muon signs. Six dimensional cooling reduces the emittances until the trains are merged into single bunches, one of each sign. Further cooling in 6 dimensions is then applied, followed by final transverse cooling in 50 T solenoids. After acceleration the muons enter the collider ring. Ongoing R&D is discussed.
Reichhardt, Charles
2008-01-01
When a sufficiently strong magnetic field is applied to a superconductor, some of the field can pierce it through the generation of magnetic vortices, each of which contains a quantized amount of magnetic flux. Although the superconducting state of the material outside each vortex is maintained (and destroyed within each vortex), the interaction of vortices with a current passing through the material can cause them to move, dissipating energy and thereby generating a source of electrical resistance. The ability to manipulate an individual superconducting vortex represents a powerful tool for studying the dynamics of vortices and the superconductors that support them. It could also lead to the development of a new class of fluxon-based electronics.
NASA Astrophysics Data System (ADS)
Vaupel, M.; Weiss, C. O.
1995-05-01
Using a photorefractive oscillator, we show experimental optical patterns whose principal features are optical vortices moving around an optical axis on circles. These patterns can be interpreted as simultaneous emission of helical fields with high-charge phase singularities and other rotationally symmetric fields. Patterns with up to nine circling vortices are shown, as well as patterns with two concentric ``wheels'' of vortices. Mode locking in these rotating patterns corresponds to a stopping of the rotation. An intermediate case between free rotation and locking, in which the pattern ``jumps'' between certain angular positions, is demonstrated, showing that phase locking of these modes, which is not possible for an isotropic resonator, can come about by small anisotropies.
Relaminarization under stationary vortices
NASA Astrophysics Data System (ADS)
Breidenthal, Robert
2005-11-01
Flow visualization reveals that a turbulent boundary layer is relaminarized when stationary streamwise vortices are introduced. Following a suggestion of Balle, the vortices are stabilized by large streamwise ``Karman'' grooves in a wavy wall. In a water tunnel, upstream vortex generators place a large streamwise vortex in the middle of each groove, at the stationary point where Prandtl's vortex force vanishes. According to a theory by Cotel, the wall fluxes of a turbulent boundary layer should decline to laminar values under such ``persistent'' vortices. The observed relaminarization is consistent with this theory and with previous measurements of heat transfer by Touel and Balle. However, the structure of the transverse flow resembles the cats-eye pattern of a temporal shear layer rather than the anticipated von Karman wake. The cats-eye pattern corresponds to the forced shear layers of Oster-Wygnanski and Roberts, who found that the Reynolds stresses and mixing rate also decline to laminar values.
Olson Reichhardt, C J; Hastings, M B
2004-04-16
We propose an experiment for directly constructing and locally probing topologically entangled states of superconducting vortices which can be performed with present-day technology. Calculations using an elastic string vortex model indicate that as the pitch (the winding angle divided by the vertical distance) increases, the vortices approach each other. At values of the pitch higher than a maximum value the entangled state becomes unstable to collapse via a singularity of the model. We provide predicted experimental signatures for both vortex entanglement and vortex cutting. The local probe we propose can also be used to explore a wide range of other quantities.
NASA Astrophysics Data System (ADS)
Olson Reichhardt, C. J.; Hastings, M. B.
2004-04-01
We propose an experiment for directly constructing and locally probing topologically entangled states of superconducting vortices which can be performed with present-day technology. Calculations using an elastic string vortex model indicate that as the pitch (the winding angle divided by the vertical distance) increases, the vortices approach each other. At values of the pitch higher than a maximum value the entangled state becomes unstable to collapse via a singularity of the model. We provide predicted experimental signatures for both vortex entanglement and vortex cutting. The local probe we propose can also be used to explore a wide range of other quantities.
Effect of Water Vapor on Toluene Removal in Catalysis-DBD Plasma Reactors
NASA Astrophysics Data System (ADS)
Wang, Jingting; Cao, Xu; Zhang, Renxi; Gong, Ting; Hou, Huiqi; Chen, Shanping; Zhang, Ruina
2016-04-01
The experiment was carried out in a cylindrical dielectric barrier discharge (DBD) reactor assisted with a catalyst to decompose toluene under different humidity. In order to explore the synergistic effect on removing toluene in the catalysis-DBD reactor, this paper investigated the decomposition efficiency and the energy consumption in the catalysis-DBD and the non-catalyst DBD reactors under different humidity. The results showed that the catalysis-DBD reactor had a better performance than the non-catalysis one at the humidity ratio of 0.4%, and the removal efficiency of toluene could reach 88.6% in the catalysis-DBD reactor, while it was only 59.9% in the non-catalytic reactor. However, there was no significant difference in the removal efficiency of toluene between the two reactors when the humidities were 1.2% and 2.4%. Additionally, the degradation products were also analyzed in order to gain a better understanding of the mechanism of decomposing toluene in a catalysis-DBD reactor. supported by the Key Project which is sponsored by the Science and Technology Commission of Shanghai Municipality (No. 13231201903), the Key Programs for Science and Technology Development sponsored by the Science and Technology Commission of Shanghai Municipality (Nos. 13231201901 and 14DZ1208401), and the Key Project sponsored by the State-owned Assets Supervision and Administration Commission of Shanghai, China (No. 2013019)
Not Available
1991-01-01
This past year our group participated in both the D0 experiment at Fermilab and the SDC experiment at the SSC. Most of our effort was concentrated on the D0 project, where we contributed as much manpower as possible to the commissioning of the detector in preparation for the coming collider run. Our SDC work consisted of the investigation of one of the candidate technologies for the forward calorimeter. On the D0 experiment, our primary responsibilities have been in the areas of electronics commissioning and in the establishment of triggers for the coming collider run. We have also actively participated in the physics studies and have contributed to the upgrade effort as much as time has permitted. Our group has also participated in the cosmic ray run and in the D0 test beam. In view of our contributions, James White was selected as a member of the D0 Trigger board, and Jay Wightman is being trained as one of the global experts'' who are responsible for keeping the detector operational during the run. In addition, Amber Boehnlein has played a major role in the Level-2 trigger commissioning. A more detailed description of these activities is given in this paper.
Black pepper powder microbiological quality improvement using DBD systems in atmospheric pressure
NASA Astrophysics Data System (ADS)
Grabowski, Maciej; Hołub, Marcin; Balcerak, Michał; Kalisiak, Stanisław; Dąbrowski, Waldemar
2015-07-01
Preliminary results are given regarding black pepper powder decontamination using dielectric barrier discharge (DBD) plasma in atmospheric pressure. Three different DBD reactor constructions were investigated, both packaged and unpackaged material was treated. Due to potential, industrial applications, in addition to microbiological results, water activity, loss of mass and the properties of packaging material, regarding barrier properties were investigated. Argon based treatment of packed pepper with DBD reactor configuration is proposed and satisfactory results are presented for treatment time of 5 min or less. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark
Toward modeling wingtip vortices
NASA Technical Reports Server (NTRS)
Zeman, O.
1993-01-01
Wingtip vortices are generated by lifting airfoils; their salient features are compactness and relatively slow rate of decay. The principal motivation for studying the far field evolution of wingtip vortices is the need to understand and predict the extent of the vortex influence during aircraft take-off or landing. On submarines a wingtip vortex ingested into a propeller can be a source of undesirable noise. The main objectives of this research are (1) to establish theoretical understanding of the principal mechanisms that govern the later (diffusive) stages of a turbulent vortex, (2) to develop a turbulence closure model representing the basic physical mechanisms that control the vortex diffusive stage, and further (3) to investigate coupling between the near and far field evolutions; in other words, to study the effect of initial conditions on the vortex lifetime and the ultimate state.
NASA Astrophysics Data System (ADS)
Cropp, Bethan; Liberati, Stefano; Turcati, Rodrigo
2016-06-01
In the analog gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in curved space-time. This description is possible only when the fluid under consideration is barotropic, inviscid, and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric that depends algebrically on the local speed of sound, density, and the background flow velocity, the latter assumed to be vorticity-free. In this work we provide a straightforward extension in order to go beyond the irrotational constraint. Using a charged—relativistic and nonrelativistic—Bose-Einstein condensate as a physical system, we show that in the low-momentum limit and performing the eikonal approximation we can derive a d’Alembertian equation of motion for the charged phonons where the emergent acoustic metric depends on flow velocity in the presence of vorticity.
Axisymmetric Vortices with Swirl
NASA Astrophysics Data System (ADS)
Elcrat, A.
2007-11-01
This talk is concerned with finding solutions of the Euler equations by solving elliptic boundary value problems for the Bragg-Hawthorne equation L u= -urr -(1/r)ur - = r^2f (u) + h(u). Theoretical results have been given for previously (Elcrat and Miller, Differential and Integral Equations 16(4) 2003, 949-968) for problems with swirl and general classes of profile functions f, h by iterating Lu(n+1)= rf(u)n)) + h(u(n)), and showing u(n) converges montonically to a solution. The solutions obtained depend on the initial guess, which can be thought of as prescribing level sets of the vortex. When a computational program was attempted these monotone iterations turned out to be numerically unstable, and a stable computation was acheived by fixing the moment of the cross section of a vortex in the merideanal plane. (This generalizes previous computational results in Elcrat, Fornberg and Miller, JFM 433 2001, (315-328) We obtain famillies of vortices related to vortex rings with swirl, Moffatt's generalization of Hill's vortex and tubes of vorticity with swirl wrapped around the symmetry axis. The vortices are embedded in either an irrotational flow or a flow with shear, and we deal with the transition form no swirl in the vortex to flow with only swirl, a Beltrami flow.
Degradation of Dye Wastewater by ns-Pulse DBD Plasma
NASA Astrophysics Data System (ADS)
Gao, Jin; Gu, Pingdao; Yuan, Li; Zhong, Fangchuan
2013-09-01
Two plasma reactors have been developed and used to degrade dye wastewater agents. The configuration of one plasma reactor is a comb-like extendable unit module consisting of 5 electrodes covered with a quartz tube and the other one is an array reactor which is extended from the unit module. The decomposition of wastewater by ns pulse dielectric barrier discharge (DBD) plasma have been carried out by atomizing the dyeing solutions into the reactors. During experiments, the indigo carmine has been treated as the waste agent. The measurements of UV-VIS absorption spectroscopy and the chemical oxygen demand (COD) are carried out to demonstrate the decomposition effect on the wastewater. It shows that the decoloration rate of 99% and the COD degradation rate of 65% are achieved with 15 min treatment in the unit reactor. The effect of electrical parameters on degradation has been studied in detail. Results from the array reactor indicate that it has a better degradation effect than the unit one. It can not only totally remove the chromogenic bond of the indigo carmine solution, but also effectively degrade unsaturated bonds. The decoloration rate reaches 99% after 10 min treatment, the decomposition rate of the unsaturated bond reaches 83% after 60 min treatment, and the COD degradation rate is nearly 74%.
Nitrogen oxide removal dynamic process through 15 Ns DBD technique
NASA Astrophysics Data System (ADS)
Wang, Xiaojun; Zhang, Lianshui; Lai, Weidong; Liu, Fengliang
2015-05-01
Nitrogen oxides exhaust gas assumes the important responsibility on air pollution by forming acid rain. This paper discusses the NO removal mechanism in 15 ns pulse dielectric barrier discharge (DBD) plasma through experimental and simulating method. Emission spectra collected from plasma are evaluated as sourced from N+ and O(3P). The corresponding zero-dimensional model is established and verified through comparing the simulated concentration evolution and the experimental time-resolved spectra of N+. The electron impact ionization plays major role on NO removal and the produced NO+ are further decomposed into N+ and O(3P) through electron impact dissociative excitation rather than the usual reported dissociative recombination process. Simulation also indicates that the removal process can be accelerated by NO inputted at lower initial concentration or electrons streamed at higher concentration, due to the heightened electron impact probability on NO molecules. The repetitive pulse discharge is a benefit for improving the NO removal efficiency by effectively utilizing the radicals generated from the previous pulse under the condition that the pulse period should be shorter enough to ignore the spatial diffusion of radicals. Finally, slight attenuation on NO removal has been experimentally and simulatively observed after N2 mixed, due to the competitive consumption of electrons.
NASA Astrophysics Data System (ADS)
Palmer, R. B.; Gallardo, J. C.
INTRODUCTION PHYSICS CONSIDERATIONS GENERAL REQUIRED LUMINOSITY FOR LEPTON COLLIDERS THE EFFECTIVE PHYSICS ENERGIES OF HADRON COLLIDERS HADRON-HADRON MACHINES LUMINOSITY SIZE AND COST CIRCULAR e^{+}e^- MACHINES LUMINOSITY SIZE AND COST e^{+}e^- LINEAR COLLIDERS LUMINOSITY CONVENTIONAL RF SUPERCONDUCTING RF AT HIGHER ENERGIES γ - γ COLLIDERS μ ^{+} μ^- COLLIDERS ADVANTAGES AND DISADVANTAGES DESIGN STUDIES STATUS AND REQUIRED R AND D COMPARISION OF MACHINES CONCLUSIONS DISCUSSION
Defining and Computing Vortices Objectively from the Vorticity
NASA Astrophysics Data System (ADS)
Haller, George; Hadjighasem, Alireza; Farazmand, Mohammad; Huhn, Florian
2015-11-01
We introduce the notion of rotationally coherent Lagrangian vortices as tubular material surfaces in which fluid elements complete equal bulk material rotation relative to the mean rotation of the fluid. We find that initial positions of such tubes coincide with tubular level surfaces of the Lagrangian-Averaged Vorticity Deviation (LAVD), the trajectory integral of the normed difference of the vorticity from its spatial mean. LAVD-based vortices turn out to be objective, i.e., invariant under time-dependent rotations and translations of the reference frame. In the limit of vanishing Rossby numbers in geostrophic flows, cyclonic LAVD vortex centers can be proven to coincide with the observed attractors for light particles. A similar result holds for heavy particles in anticyclonic LAVD vortices. We also discuss a relationship between rotationally coherent Lagrangian vortices and their instantaneous Eulerian counterparts. The latter are formed by tubular surfaces of equal material rotation rate, objectively measured by the Instantaneous Vorticity Deviation (IVD). We show how the LAVD and the IVD detect rotationally coherent Lagrangian and Eulerian vortices objectively in analytic flow models and numerical flow data.
Commercial aircraft wake vortices
NASA Astrophysics Data System (ADS)
Gerz, Thomas; Holzäpfel, Frank; Darracq, Denis
2002-04-01
This paper discusses the problem of wake vortices shed by commercial aircraft. It presents a consolidated European view on the current status of knowledge of the nature and characteristics of aircraft wakes and of technical and operational procedures of minimizing and predicting the vortex strength and avoiding wake encounters. Methodological aspects of data evaluation and interpretation, like the description of wake ages, the characterization of wake vortices, and the proper evaluation of wake data from measurement and simulation, are addressed in the first part. In the second part an inventory of our knowledge is given on vortex characterization and control, prediction and monitoring of vortex decay, vortex detection and warning, vortex encounter models, and wake-vortex safety assessment. Each section is concluded by a list of questions and required actions which may help to guide further research activities. The primary objective of the joint international efforts in wake-vortex research is to avoid potentially hazardous wake encounters for aircraft. Shortened aircraft separations under appropriate meteorological conditions, whilst keeping or even increasing the safety level, is the ultimate goal. Reduced time delays on the tactical side and increased airport capacities on the strategic side will be the benefits of these ambitious ventures for the air transportation industry and services.
NASA Technical Reports Server (NTRS)
Greenblatt, David
2005-01-01
A wind tunnel investigation was carried out on a semi-span wing model to assess the feasibility of controlling vortices emanating from outboard flaps and tip-flaps by actively varying the degree of boundary layer separation. Separation was varied by means of perturbations produced from segmented zero-efflux oscillatory blowing slots, while estimates of span loadings and vortex sheet strengths were obtained by integrating wing surface pressures. These estimates were used as input to inviscid rollup relations as a means of predicting changes to the vortex characteristics resulting from the perturbations. Surveys of flow in the wake of the outboard and tip-flaps were made using a seven-hole probe, from which the vortex characteristics were directly deduced. Varying the degree of separation had a marked effect on vortex location, strength, tangential velocity, axial velocity and size for both outboard and tip-flaps. Qualitative changes in vortex characteristics were well predicted by the inviscid rollup relations, while the failure to account for viscosity was presumed to be the main reason for observed discrepancies. Introducing perturbations near the outboard flap-edges or on the tip-flap exerted significant control over vortices while producing negligible lift excursions.
Stability of streamwise vortices
NASA Technical Reports Server (NTRS)
Khorrami, M. K.; Grosch, C. E.; Ash, R. L.
1987-01-01
A brief overview of some theoretical and computational studies of the stability of streamwise vortices is given. The local induction model and classical hydrodynamic vortex stability theories are discussed in some detail. The importance of the three-dimensionality of the mean velocity profile to the results of stability calculations is discussed briefly. The mean velocity profile is provided by employing the similarity solution of Donaldson and Sullivan. The global method of Bridges and Morris was chosen for the spatial stability calculations for the nonlinear eigenvalue problem. In order to test the numerical method, a second order accurate central difference scheme was used to obtain the coefficient matrices. It was shown that a second order finite difference method lacks the required accuracy for global eigenvalue calculations. Finally the problem was formulated using spectral methods and a truncated Chebyshev series.
Decanini, Yves; Folacci, Antoine
2003-04-01
By using the complex angular momentum method, we provide a semiclassical analysis of electron scattering by a magnetic vortex of Aharonov-Bohm type. Regge poles of the S matrix are associated with surface waves orbiting around the vortex and supported by a magnetic field discontinuity. Rapid variations of sharp characteristic shapes can be observed on scattering cross sections. They correspond to quasibound states which are Breit-Wigner-type resonances associated with surface waves and which can be considered as quantum analogues of acoustic whispering-gallery modes. Such a resonant magnetic vortex could provide a different kind of artificial atom while the semiclassical approach developed here could be profitably extended in various areas of the physics of vortices.
NASA Astrophysics Data System (ADS)
Dong, Xiaoyu; Yuan, Yulian; Tang, Qian; Dou, Shaohua; Di, Lanbo; Zhang, Xiuling
2014-01-01
In this study, Saccharomyces cerevisiae (S. cerevisiae) was exposed to dielectric barrier discharge plasma (DBD) to improve its ethanol production capacity during fermentation. Response surface methodology (RSM) was used to optimize the discharge-associated parameters of DBD for the purpose of maximizing the ethanol yield achieved by DBD-treated S. cerevisiae. According to single factor experiments, a mathematical model was established using Box-Behnken central composite experiment design, with plasma exposure time, power supply voltage, and exposed-sample volume as impact factors and ethanol yield as the response. This was followed by response surface analysis. Optimal experimental parameters for plasma discharge-induced enhancement in ethanol yield were plasma exposure time of 1 min, power voltage of 26 V, and an exposed sample volume of 9 mL. Under these conditions, the resulting yield of ethanol was 0.48 g/g, representing an increase of 33% over control.
Characterization of a DBD-Based Plasma Jet Using a Variable Pulse Width Nanosecond Pulser
NASA Astrophysics Data System (ADS)
Ziemba, Timothy; Picard, Julian; Prager, James; Miller, Kenneth; Carscadden, John
2015-11-01
Most high voltage pulsers used to drive dielectric barrier discharges (DBDs), produce a single pulse shape (width and voltage), thus making it challenging to assess the effect of pulse shape on the production of different chemical species during a discharge. Eagle Harbor Technologies, Inc. (EHT) has developed a high voltage nanosecond pulser that enables independent control of the output voltage, pulse width, and pulse repetition frequency. This pulser has been specifically designed to drive dielectric barrier discharges (DBD). EHT has used this pulser to conduct a parametric investigation of a DBD-based jet utilizing spectroscopic diagnostics. A better understanding of this parameter dependency can allow for more targeted and effective application of plasma in medical, environmental, industrial, and other applications. Results comparing DBD voltage and current waveforms with plasma spectrographic measurements will be presented.
Motion of multiple helical vortices
NASA Astrophysics Data System (ADS)
Velasco Fuentes, Oscar
2015-11-01
In 1912 Joukowsky deduced that in an unbounded ideal fluid a set of helical vortices--when these are equal, coaxial and symmetrically arranged--would translate and rotate steadily while the vortices preserve their form and relative position. Each vortex is an infinite tube whose cross-section is circular (with radius a) and whose centerline is a helix of pitch L and radius R. The motion is thus determined by three non-dimensional parameters only: the number of vortices N, the vortex radius α = a / R and the vortex pitch τ = L / 2 πR . Here, we express the linear and angular velocities of the vortices as the sum of the mutually induced velocities found by Okulov (2004) and the self-induced velocities found by Velasco Fuentes (2015). We verified that our results are accurate over the whole range of values of the vortices' pitch and radius by numerically computing the vortex motion with two smoothed versions of the Biot-Savart law. It was found that the translation velocity U grows with the number of vortices (N) but decreases as the vortices' radius and pitch (a and τ, respectively) increase; in contrast, the rotation velocity Ω grows with N and a but has a local minimum around τ = 1 for fixed values of N and a.
NASA Technical Reports Server (NTRS)
Rossow, Vernon J.
2011-01-01
As part of an ongoing effort to find ways to make vortex flow fields decompose more quickly, photographs and observations are presented of vortex flow fields that indicate the presence of multiple layers of fluid rotating about a common axis. A survey of the literature indicates that multiple-layered vortices form in waterspouts, tornadoes and lift-generated vortices of aircraft. An explanation for the appearance of multiple-layered structures in vortices is suggested. The observations and data presented are intended to improve the understanding of the formation and persistence of vortex flow fields.
Photon collider Higgs factories
NASA Astrophysics Data System (ADS)
Telnov, V. I.
2014-09-01
The discovery of the Higgs boson (and still nothing else) have triggered appearance of many proposals of Higgs factories for precision measurement of the Higgs properties. Among them there are several projects of photon colliders (PC) without e+e- in addition to PLC based on e+e- linear colliders ILC and CLIC. In this paper, following a brief discussion of Higgs factories physics program I give an overview of photon colliders based on linear colliders ILC and CLIC, and of the recently proposed photon-collider Higgs factories with no e+e- collision option based on recirculation linacs in ring tunnels.
Kim, K.J.; Sessler, A.
1996-06-01
Gamma-gamma colliders make intense beams of gamma rays and have them collide so as to make elementary particles. The authors show, in this article, that constructing a gamma-gamma collider as an add-on to an electron-positron linear collider is possible with present technology and that it does not require much additional cost. Furthermore, they show that the resulting capability is very interesting from a particle physics point of view. An overview of a linear collider, with a second interaction region devoted to {gamma}{gamma} collisions is shown.
Longitudinal vortices beneath breaking waves
NASA Astrophysics Data System (ADS)
Nepf, H. M.; Cowen, E. A.; Kimmel, S. J.; Monismith, S. G.
1995-08-01
The formation of longitudinal vortices has been observed in a wavy channel flow and appears to be linked to spilling breaking and/or to vertical vorticity generated by a wave instability at the wave maker. Both conditions were present when the wave slope, ak exceeded 0.25. The wave instability produced velocity jets beneath and just downstream of the plunger that could provide the initial perturbation for the CL2 instability mechanism (Faller and Caponi, 1978). The breaker activity could also contribute to the CL2 production mechanism by eliminating the negative, stabilizing shear observed within the wave maker wake and by providing seed perturbations to the vorticity field. As the cells evolved downstream, they were maintained through interaction with the bottom boundary layer. When the vortices were present, both vertical mixing and turbulent kinetic energy were enhanced. Despite some differences in scale these results suggest that Langmuir circulation may produce similar changes in the mixed layer.
On the Potential Vorticity Dynamics of Tropical Instability Vortices
NASA Astrophysics Data System (ADS)
Holmes, R.; Thomas, L. N.; Thompson, L.; Darr, D.
2012-12-01
Tropical Instability Vortices (TIVs) in the Eastern Equatorial Pacific contain numerous energetic submesoscale features (sharp fronts and vortices) that can have a significant influence on the broader scale circulation by driving lateral mixing and vertical exchange between the ocean surface and interior. We use a set of nested high-resolution simulations of the Equatorial Pacific, with a finest grid size of 3km, to show that the spatial and temporal distribution of the Ertel potential vorticity (PV), which determines the balanced dynamics of the TIVs, is influenced by submesoscale processes. The TIV cores are characterized by vortically low PV water: the relative vorticity is anticyclonic with magnitude similar to the local Coriolis parameter. A study of the variation of PV and other scalars along Lagrangian fluid parcel tracks entering the TIVs shows that the low PV water in their cores is a mix of Equatorial Undercurrent water and North Equatorial Counter Current water. As these water masses enter the TIVs, Lagrangian changes in temperature, salinity, and PV occur that are largest near the submesoscale fronts in the cold cusps on the western flanks of the vortices. The leading order force balance at these fronts is geostrophy with a secondary contribution from the centrifugal force. However, frontogenetic and frontolytic strain disrupt the geostrophic balance and drive vertical motions and subduction. These results emphasize the role of submesoscale processes in altering the properties and transport of water masses in the Equatorial Pacific, with implications for the large-scale circulation.(Bottom) Model SST and temperature-PV diagram for Lagrangian floats inside a TIV. (Top) Model SST and temperature-PV diagram for the same Lagrangian floats 75 days earlier. The floats are shaded with latitude. Water from the Equatorial Undercurrent and the North Equatorial Counter Current combine experiencing significant Lagrangian changes in temperature and PV to form the
How rotational vortices enhance transfers
NASA Astrophysics Data System (ADS)
Griffani, D.; Rognon, P.; Metzger, B.; Einav, I.
2013-09-01
Inspired by recent observations of granular flow, we examine how rotational vortices contribute to heat or mass transfer enhancement in a fluid. We use a tracer method to simulate both diffusion and advection in systems of differing intrinsic diffusivities D0, vortex sizes R, vortex rotation frequencies f, and vortex lifetimes ℓ. The results reveal that these systems exhibit an effective diffusive behavior, characterized by an effective diffusivity Deff. A striking finding is the existence of two regimes, dichotomised by the Péclet number Pe = R2f/D0. When the Péclet number is less than one, there is no transfer enhancement, Deff = D0. For higher values, vortices produce some transfer enhancement with a corresponding power law Deff/D0 ≈ Pen. The power n ranges from a lower bound of 0.5 for stationary vortices of lifetime infinity, to an upper bound of 1 for vortices of lifetimes shorter than half a rotation. This difference is attributed to two different internal mechanisms involving the coupling of diffusion and advection. These results could provide new insights on the transfer properties of fluid systems comprising rotational vortices, such as granular materials, suspensions, foams, and emulsions, as well as low Reynolds number stirred flows.
Filamentation with nonlinear Bessel vortices.
Jukna, V; Milián, C; Xie, C; Itina, T; Dudley, J; Courvoisier, F; Couairon, A
2014-10-20
We present a new type of ring-shaped filaments featured by stationary nonlinear high-order Bessel solutions to the laser beam propagation equation. Two different regimes are identified by direct numerical simulations of the nonlinear propagation of axicon focused Gaussian beams carrying helicity in a Kerr medium with multiphoton absorption: the stable nonlinear propagation regime corresponds to a slow beam reshaping into one of the stationary nonlinear high-order Bessel solutions, called nonlinear Bessel vortices. The region of existence of nonlinear Bessel vortices is found semi-analytically. The influence of the Kerr nonlinearity and nonlinear losses on the beam shape is presented. Direct numerical simulations highlight the role of attractors played by nonlinear Bessel vortices in the stable propagation regime. Large input powers or small cone angles lead to the unstable propagation regime where nonlinear Bessel vortices break up into an helical multiple filament pattern or a more irregular structure. Nonlinear Bessel vortices are shown to be sufficiently intense to generate a ring-shaped filamentary ionized channel in the medium which is foreseen as opening the way to novel applications in laser material processing of transparent dielectrics. PMID:25401574
NASA Astrophysics Data System (ADS)
Myers, Stephen
The Large Hadron Collider (LHC) was first suggested (in a documented way) in 1983 [1] as a possible future hadron collider to be installed in the 27 km "LEP" tunnel. More than thirty years later the collider has been operated successfully with beam for three years with spectacular performance and has discovered the long-sought-after Higgs boson. The LHC is the world's largest and most energetic particle collider. It took many years to plan and build this large complex machine which promises exciting, new physics results for many years to come...
Sessler, A.M.
1997-03-01
During the period of the 50`s and the 60`s colliders were developed. Prior to that time there were no colliders, and by 1965 a number of small devices had worked, good understanding had been achieved, and one could speculate, as Gersh Budker did, that in a few years 20% of high energy physics would come from colliders. His estimate was an under-estimate, for now essentially all of high energy physics comes from colliders. The author presents a brief review of that history: sketching the development of the concepts, the experiments, and the technological advances which made it all possible.
Superconducting vortices in semilocal models.
Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S
2006-02-01
It is shown that the SU(2) semilocal model--the Abelian Higgs model with two complex scalars--admits a new class of stationary, straight string solutions carrying a persistent current and having finite energy per unit length. In the plane orthogonal to their direction they correspond to a nontrivial deformation of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by the current flowing through them. The new solutions bifurcate with the ANO vortices in the limit of vanishing current. They can be either static or stationary. In the stationary case, the relative phase of the two scalars rotates at constant velocity, giving rise to an electric field and angular momentum, while the energy remains finite. The new static vortex solutions have lower energy than the ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings).
Superconducting Vortices in Semilocal Models
NASA Astrophysics Data System (ADS)
Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S.
2006-02-01
It is shown that the SU(2) semilocal model—the Abelian Higgs model with two complex scalars—admits a new class of stationary, straight string solutions carrying a persistent current and having finite energy per unit length. In the plane orthogonal to their direction they correspond to a nontrivial deformation of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by the current flowing through them. The new solutions bifurcate with the ANO vortices in the limit of vanishing current. They can be either static or stationary. In the stationary case, the relative phase of the two scalars rotates at constant velocity, giving rise to an electric field and angular momentum, while the energy remains finite. The new static vortex solutions have lower energy than the ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings).
Hairpin Vortices: Autogeneration and Interaction
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; Maharjan, Rijan; Sanders, Andrew
2013-11-01
The regeneration of hairpin vortices is examined in a free-surface water channel where vortices are artificially generated by means of injection in a laminar boundary layer. The process is visualized with dye and hydrogen bubble-wire techniques. The strength of an isolated hairpin required to begin the autogeneration process is established by means of PIV measurements on the symmetry plane. Because hairpins are in close proximity in a fully-turbulent boundary layer, two hairpins are generated at different streamwise locations and allowed to interact at different stages of development. The relative position, strength and maturity of the interacting hairpins that generate secondary vortices are examined. The morphology of the generation process and of the resulting secondary hairpin for both the isolated and interacting cases are discussed and compared to previous work. Supported by the National Science Foundation under Grant CBET-1040236.
Spinning gas clouds - without vorticity
NASA Astrophysics Data System (ADS)
Gaffet, B.
2000-06-01
Ovsiannikov and Dyson have considered an ordinary differential reduction of the gas-dynamical equations for an ideal gas which is adiabatically expanding and rotating. Gaffet has shown, based on its Painlevé property, the complete integrability of that ellipsoidal gas cloud model, when there is neither rotation nor vorticity and the gas is monatomic (γ = 5/3), and has conjectured that the integrability might persist in more general cases including rotation. In this paper we show that the presence of vorticity in general destroys the integrability property, but the conjecture is otherwise verified, under the simplifying assumption of rotation around a fixed axis. In a future work we hope to extend the present result to Dyson's most general spinning gas cloud without vorticity.
Superconducting vortices in semilocal models.
Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S
2006-02-01
It is shown that the SU(2) semilocal model--the Abelian Higgs model with two complex scalars--admits a new class of stationary, straight string solutions carrying a persistent current and having finite energy per unit length. In the plane orthogonal to their direction they correspond to a nontrivial deformation of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by the current flowing through them. The new solutions bifurcate with the ANO vortices in the limit of vanishing current. They can be either static or stationary. In the stationary case, the relative phase of the two scalars rotates at constant velocity, giving rise to an electric field and angular momentum, while the energy remains finite. The new static vortex solutions have lower energy than the ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings). PMID:16486806
Vortices in Spatially Inhomogeneous Superfluids
NASA Astrophysics Data System (ADS)
Sheehy, Daniel E.; Radzihovsky, Leo
2004-03-01
Trapped degenerate Bose gases exhibit superfluidity with spatially nonuniform superfluid density. We study the vortex distribution in such rotating nonuniform superfluids, focusing particularly on deviations from a uniform distribution corresponding to an average rigid-body rotation. The origin of such deviations is the discrete way in which vortices impart angular momentum to the superfluid. This effect favors highest vortex density in regions where the superfluid density is most uniform, i.e., at the center of a trap, while tending to decrease the overall number of vortices. Supported by NSF DMR-0321848 and the Packard Foundation.
Richter, B.
1985-12-01
A report is given on the goals and progress of the SLAC Linear Collider. The status of the machine and the detectors are discussed and an overview is given of the physics which can be done at this new facility. Some ideas on how (and why) large linear colliders of the future should be built are given.
What Causes Mars' Annular Polar Vortices?
NASA Astrophysics Data System (ADS)
Toigo, A. D.; Waugh, D. W.; Guzewich, S. D.
2016-09-01
Martian polar vortices exhibit annuli of high potential vorticity, unlike the Earth, likely due to the effect of latent heating of carbon dioxide condensation in polar regions, which does not occur for Earth's most abundant atmospheric species.
Stochastic Vorticity and Associated Filtering Theory
Amirdjanova, A.; Kallianpur, G.
2002-12-19
The focus of this work is on a two-dimensional stochastic vorticity equation for an incompressible homogeneous viscous fluid. We consider a signed measure-valued stochastic partial differential equation for a vorticity process based on the Skorohod-Ito evolution of a system of N randomly moving point vortices. A nonlinear filtering problem associated with the evolution of the vorticity is considered and a corresponding Fujisaki-Kallianpur-Kunita stochastic differential equation for the optimal filter is derived.
Combustor with multistage internal vortices
Shang, Jer Yu; Harrington, R.E.
1987-05-01
A fluidized bed combustor is provided with a multistage arrangement of vortex generators in the freeboard area. The vortex generators are provided by nozzle means which extend into the interior of the freeboard for forming vortices within the freeboard areas to enhance the combustion of particulate material entrained in product gases ascending into the freeboard from the fluidized bed. Each of the nozzles are radially inwardly spaced from the combustor walls defining the freeboard to provide for the formation of an essentially vortex-free, vertically extending annulus about the vortices whereby the particulate material centrifuged from the vortices against the inner walls of the combustor is returned through the annulus to the fluidized bed. By adjusting the vortex pattern within the freeboard, a significant portion of the full cross-sectional area of the freeboard except for the peripheral annulus can be contacted with the turbulent vortical flow for removing the particulate material from the gaseous products and also for enhancing the combustion thereof within the freeboard. 2 figs.
Combustor with multistage internal vortices
Shang, Jer Y.; Harrington, Richard E.
1989-01-01
A fluidized bed combustor is provided with a multistage arrangement of vortex generators in the freeboard area. The vortex generators are provided by nozzle means which extend into the interior of the freeboard for forming vortices within the freeboard area to enhance the combustion of particulate material entrained in product gases ascending into the freeboard from the fluidized bed. Each of the nozzles are radially inwardly spaced from the combustor walls defining the freeboard to provide for the formation of an essentially vortex-free, vertically extending annulus about the vortices whereby the particulate material centrifuged from the vortices against the inner walls of the combustor is returned through the annulus to the fluidized bed. By adjusting the vortex pattern within the freeboard, a significant portion of the full cross-sectional area of the freeboard except for the peripheral annulus can be contacted with the turbulent vortical flow for removing the particulate material from the gaseous products and also for enhancing the combustion thereof within the freeboard.
Discharge characteristics of dielectric barrier discharge (DBD) based VUV/UV sources
NASA Astrophysics Data System (ADS)
Pal, U. N.; Kumar, M.; Khatun, H.; Sharma, A. K.
2008-05-01
Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using coaxial and planar geometry of DBD (gas gap: 1-3 mm) made of quartz with N2/Ar/Xe gas at different pressures. A proper ultra high vacuum system and gas filing system has been made for the processing & characterization of DBD tubes. A RF generator (20-100 kHz, 0-2.4 kV peak) is used for discharges in DBD tube. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. The discharge characteristics have been analyzed by V-I characteristics & Lissajous figure and found that the spatial discharge processes varies strongly according to the applied voltage waveform, pressure of filled gas and geometry of tube.
NASA Astrophysics Data System (ADS)
Tamura, Keishiro; Kameshima, Seigo; Ishibashi, Yutaro; Mizukami, Ryo; Yamazaki, Takumi; Nozaki, Tomohiro
2015-09-01
Pulsed dry methane reforming in DBD-catalyst hybrid reaction was investigated. Optical emission spectroscopy was also employed for the better understanding of reaction mechanism for enhanced CH4 and CO2 conversion as well as carbon removal reaction. Strong emission from C2 high pressure Swan system was uniquely observed when the Boudouard reaction dominates the surface reaction: C2 molecules were selectively produced via vibrationally excited CO which is originated from the adsorbed carbon on the catalysts. Time dependent change in gas composition and optical emission profiles of CO Ångström and C2 high pressure Swan systems were correlated in a systematic and consistent manner, leading to the deep insight into the CH4 and CO2 activation mechanisms over solid catalysts. Moreover, individual contribution of radical injection and heat generated by DBD were investigated. The result clearly showed that the CH4 and CO2 conversion rates were increased essentially by the radical injection, not the thermal effect of DBD.
Towards future circular colliders
NASA Astrophysics Data System (ADS)
Benedikt, Michael; Zimmermann, Frank
2016-09-01
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) presently provides proton-proton collisions at a center-of-mass (c.m.) energy of 13 TeV. The LHC design was started more than 30 years ago, and its physics program will extend through the second half of the 2030's. The global Future Circular Collider (FCC) study is now preparing for a post-LHC project. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh) in a new ˜100 km tunnel. It also includes the design of a high-luminosity electron-positron collider (FCCee) as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3 S n superconductor, for the FCC-hh hadron collider, and a highly-efficient superconducting radiofrequency system for the FCC-ee lepton collider. Following the FCC concept, the Institute of High Energy Physics (IHEP) in Beijing has initiated a parallel design study for an e + e - Higgs factory in China (CEPC), which is to be succeeded by a high-energy hadron collider (SPPC). At present a tunnel circumference of 54 km and a hadron collider c.m. energy of about 70 TeV are being considered. After a brief look at the LHC, this article reports the motivation and the present status of the FCC study, some of the primary design challenges and R&D subjects, as well as the emerging global collaboration.
Wiedemann, H.
1981-11-01
Since no linear colliders have been built yet it is difficult to know at what energy the linear cost scaling of linear colliders drops below the quadratic scaling of storage rings. There is, however, no doubt that a linear collider facility for a center of mass energy above say 500 GeV is significantly cheaper than an equivalent storage ring. In order to make the linear collider principle feasible at very high energies a number of problems have to be solved. There are two kinds of problems: one which is related to the feasibility of the principle and the other kind of problems is associated with minimizing the cost of constructing and operating such a facility. This lecture series describes the problems and possible solutions. Since the real test of a principle requires the construction of a prototype I will in the last chapter describe the SLC project at the Stanford Linear Accelerator Center.
Mechanical Control of Individual Superconducting Vortices
2016-01-01
Manipulating individual vortices in a deterministic way is challenging; ideally, manipulation should be effective, local, and tunable in strength and location. Here, we show that vortices respond to local mechanical stress applied in the vicinity of the vortex. We utilized this interaction to move individual vortices in thin superconducting films via local mechanical contact without magnetic field or current. We used a scanning superconducting quantum interference device to image vortices and to apply local vertical stress with the tip of our sensor. Vortices were attracted to the contact point, relocated, and were stable at their new location. We show that vortices move only after contact and that more effective manipulation is achieved with stronger force and longer contact time. Mechanical manipulation of vortices provides a local view of the interaction between strain and nanomagnetic objects as well as controllable, effective, and reproducible manipulation technique. PMID:26836018
Palmer, R.; Peoples, J.; Ankenbrandt, C.
1982-01-01
The objective of this group was to make a rough assessment of the characteristics of a hadron-hadron collider which could make it possible to study the 1 TeV mass scale. Since there is very little theoretical guidance for the type of experimental measurements which could illuminate this mass scale, we chose to extend the types of experiments which have been done at the ISR, and which are in progress at the SPS collider to these higher energies.
NASA Astrophysics Data System (ADS)
Telnov, Valery
2001-10-01
High energy photon colliders ( γγ, γe) based on backward Compton scattering of laser light is a very natural addition to e +e - linear colliders. In this report, we consider this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case, the γγ luminosity in the high energy part of spectrum can reach about (1/3) Le +e -. Typical cross-sections of interesting processes in γγ collisions are higher than those in e +e - collisions by about one order of magnitude, so the number of events in γγ collisions will be more than that in e +e - collisions. Photon colliders can, certainly, give additional information and they are the best for the study of many phenomena. The main question is now the technical feasibility. The key new element in photon colliders is a very powerful laser system. An external optical cavity is a promising approach for the TESLA project. A free electron laser is another option. However, a more straightforward solution is "an optical storage ring (optical trap)" with a diode pumped solid state laser injector which is today technically feasible. This paper briefly reviews the status of a photon collider based on the linear collider TESLA, its possible parameters and existing problems.
NASA Astrophysics Data System (ADS)
Mattner, Trent; Chong, Min; Joubert, Peter
2000-11-01
Vortical flow past a sphere in a constant diameter pipe was studied experimentally in a guide vane apparatus similar to those used in fundamental experimental studies of vortex breakdown. The initial effect of swirl was to shorten the downstream separation bubble. For a small range of the swirl intensity, an almost stagnant upstream separation bubble formed. As the swirl intensity was increased, the bubble became unstable and an unsteady spiral formed. At high swirl intensity there was a mean recirculation region which penetrated far upstream while the flow on the downstream hemisphere was attached. Measurements of the velocity field were obtained using laser Doppler velocimetry. Analysis of these results suggests that the onset of upstream separation is associated with the formation of a negative azimuthal vorticity component which slows the axial flow near the axis of symmetry. This is consistent with inviscid distortion of the vortex filaments in the diverging flow approaching the sphere.
Breathers on quantized superfluid vortices.
Salman, Hayder
2013-10-18
We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings. PMID:24182275
Breathers on Quantized Superfluid Vortices
NASA Astrophysics Data System (ADS)
Salman, Hayder
2013-10-01
We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings.
Sessler, Andrew M.
1996-01-01
Since the seminal work by Ginsburg, et al., the subject of giving the Next Linear Collider photon-photon capability, as well as electron-positron capability, has drawn much attention [1]. A 1990 article by V.I. Telnov describes the situation at that time [2]. In March 1994, the first workshop on this subject was held [3]. This report briefly reviews the physics that can be achieved through the photon-photon channel and then focuses on the means of achieving such a collider. Also reviewed is the spectrum of backscattered Compton photons—the best way of obtaining photons. We emphasize the spectrum actually obtained in a collider with both polarized electrons and photons (peaked at high energy and very different from a Compton spectrum). Luminosity is estimated for the presently considered colliders, and interaction and conversion-point geometries are described. Also specified are laser requirements (such as wavelength, peak power, and average power) and the lasers that might be employed. These include conventional and free-electron lasers. Finally, we describe the R&D necessary to make either of these approaches viable and explore the use of the SLC as a test bed for a photon-photon collider of very high energy.
Sessler, A.M.
1995-04-01
Since the seminal work by Ginsburg, et at., the subject of giving the Next Linear Collider photon-photon capability, as well as electron-positron capability, has drawn much attention. A 1990 article by V.I. Teinov describes the situation at that time. In March 1994, the first workshop on this subject was held. This report briefly reviews the physics that can be achieved through the photon-photon channel and then focuses on the means of achieving such a collider. Also reviewed is the spectrum of backscattered Compton photons -- the best way of obtaining photons. We emphasize the spectrum actually obtained in a collider with both polarized electrons and photons (peaked at high energy and very different from a Compton spectrum). Luminosity is estimated for the presently considered colliders, and interaction and conversion-point geometries are described. Also specified are laser requirements (such as wavelength, peak power, and average power) and the lasers that might be employed. These include conventional and free-electron lasers. Finally, we describe the R&D necessary to make either of these approaches viable and explore the use of the SLC as a test bed for a photon-photon collider of very high energy.
Executive functions in preschool children with ADHD and DBD: an 18-month longitudinal study.
Schoemaker, Kim; Bunte, Tessa; Espy, Kimberly Andrews; Deković, Maja; Matthys, Walter
2014-01-01
In this longitudinal study, we examined the stability of the association between executive functions and externalizing behavior problems, and the developmental change of executive functions in a predominately clinically diagnosed preschool sample (N = 200). Inhibition and working memory performance were assessed three times in 18 months. Across time, poorer inhibition performance in young children was associated with attention deficit hyperactivity disorder (ADHD) and disruptive behavior disorders (DBD), and poorer working memory performance was associated with ADHD. Inhibition and working memory performance increased over time, especially in the early preschool period. The improvement of inhibition performance was more pronounced in the clinically diagnosed children compared to the TD children.
Swarming of active colloidal Janus particles: Polar waves and vortices
NASA Astrophysics Data System (ADS)
Xu, Cong; Yan, Jing; Han, Ming; Luijten, Erik; Granick, Steve
2015-03-01
The synthesis of artificial ``swarming'' particles with tunable interaction represents a strong interest of the soft active matter community. Here, we demonstrate a straightforward design of swarming Janus colloids that exhibit transient mutual alignment within a certain frequency range of an applied AC electric field. In a dense two-dimensional suspension of these Janus colloids, we observe that coherent polar waves emerge at first, which then collide and merge into stable discrete vortices. Based upon a careful analysis of the pair interaction, we propose a simple mechanism that explains the formation of the polar waves, with agreement between experiment and simulation. A rich spectrum of phenomena, including dimer swarming, chain formation, and particle clustering, can be further achieved by changing the frequency of the AC electric field. Currently working as a postdoctoral researcher in Princeton University.
Plane mixing layer vortical structure kinematics
NASA Technical Reports Server (NTRS)
Leboeuf, Richard L.
1993-01-01
The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.
Vortical sources of aerodynamic force and moment
NASA Technical Reports Server (NTRS)
Wu, J. Z.; Wu, J. M.
1989-01-01
It is shown that the aerodynamic force and moment can be expressed in terms of vorticity distribution (and entropy variation for compressible flow) on near wake plane, or in terms of boundary vorticity flux on the body surface. Thus the vortical sources of lift and drag are clearly identified, which is the real physical basis of optimal aerodynamic design. Moreover, these sources are highly compact, hence allowing one to concentrate on key local regions of the configuration, which have dominating effect to the lift and drag. A detail knowledge of the vortical low requires measuring or calculating the vorticity and dilatation field, which is however still a challenging task. Nevertheless, this type of formulation has some unique advantages; and how to set up a well-posed problem, in particular how to establish vorticity-dilatation boundary conditions, is addressed.
Evans, Lyndon
2012-02-28
The construction of the Large Hadron Collider (LHC) has been a massive endeavour spanning almost 30 years from conception to commissioning. Building the machine with the highest possible energy (7 TeV) in the existing large electron-positron (LEP) collider tunnel of 27 km circumference and with a tunnel diameter of only 3.8 m has required considerable innovation. The first was the development of a two-in-one magnet, where the two rings are integrated into a single magnetic structure. This compact two-in-one structure was essential for the LHC owing to the limited space available in the existing LEP collider tunnel and the cost. The second was a bold move to the use of superfluid helium cooling on a massive scale, which was imposed by the need to achieve a high (8.3 T) magnetic field using an affordable Nb-Ti superconductor.
Moduli Space of Non-Abelian Vortices
NASA Astrophysics Data System (ADS)
Eto, Minoru; Isozumi, Youichi; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke
2006-04-01
We completely determine the moduli space MN,k of k vortices in U(N) gauge theory with N Higgs fields in the fundamental representation. Its open subset for separated vortices is found as the symmetric product (C×CPN-1)k/Sk. Orbifold singularities of this space correspond to coincident vortices and are resolved resulting in a smooth moduli manifold. The relation to Kähler quotient construction is discussed.
Two applications of potential vorticity thinking
NASA Technical Reports Server (NTRS)
Robinson, Walter A.
1987-01-01
The phenomena of dissipative destabilization of external Rossby waves and the acceleration of the zonal mean jet during baroclinic life cycles are described in terms of potential vorticity. The main principle of the potential temperature variations at rigid boundaries have the same effect on the interior flow as do sheets of potential vorticity located just within the boundaries. It is noted that the potential vorticity theory is useful for understanding the dynamical behavior of meterological phenomena.
Separation vortices and pattern formation
NASA Astrophysics Data System (ADS)
Andersen, Anders; Bohr, Tomas; Schnipper, Teis
2010-03-01
In this paper examples are given of the importance of flow separation for fluid patterns at moderate Reynolds numbers—both in the stationary and in the time-dependent domain. In the case of circular hydraulic jumps, it has been shown recently that it is possible to generalise the Prandtl-Kármán-Pohlhausen approach to stationary boundary layers with free surfaces going through separation, and thus obtain a quantitative theory of the simplest type of hydraulic jump, where a single separation vortex is present outside the jump. A second type of jump, where an additional roller appears at the surface, cannot be captured by this approach and has not been given an adequate theoretical description. Such a model is needed to describe “polygonal” hydraulic jumps, which occur by spontaneous symmetry breaking of the latter state. Time-dependent separation is of importance in the formation of sand ripples under oscillatory flow, where the separation vortices become very strong. In this case no simple theory exists for the determination of the location and strengths of separation vortices over a wavy bottom of arbitrary profile. We have, however, recently suggested an amplitude equation describing the long-time evolution of the sand ripple pattern, which has the surprising features that it breaks the local sand conservation and has long-range interaction, features that can be underpinned by experiments. Very similar vortex dynamics takes place around oscillating structures such as wings and fins. Here, we present results for the vortex patterns behind a flapping foil in a flowing soap film, which shows the interaction and competition between the vortices shed from the round leading edge (like the von Kármán vortex street) and those created at the sharp trailing edge.
Zisman, Michael S
2010-05-17
We describe the scientific motivation for a new type of accelerator, the muon collider. This accelerator would permit an energy-frontier scientific program and yet would fit on the site of an existing laboratory. Such a device is quite challenging, and requires a substantial R&D program. After describing the ingredients of the facility, the ongoing R&D activities of the Muon Accelerator Program are discussed. A possible U.S. scenario that could lead to a muon collider at Fermilab is briefly mentioned.
Zisman, Michael S.
2011-01-05
We describe the scientific motivation for a new type of accelerator, the muon collider. This accelerator would permit an energy-frontier scientific program and yet would fit on the site of an existing laboratory. Such a device is quite challenging, and requires a substantial R&D program. After describing the ingredients of the facility, the ongoing R&D activities of the Muon Accelerator Program are discussed. A possible U.S. scenario that could lead to a muon collider at Fermilab is briefly mentioned.
NASA Astrophysics Data System (ADS)
Brüning, O.; Burkhardt, H.; Myers, S.
2012-07-01
The Large Hadron Collider (LHC) is the world’s largest and most energetic particle collider. It took many years to plan and build this large complex machine which promises exciting, new physics results for many years to come. We describe and review the machine design and parameters, with emphasis on subjects like luminosity and beam conditions which are relevant for the large community of physicists involved in the experiments at the LHC. First collisions in the LHC were achieved at the end of 2009 and followed by a period of a rapid performance increase. We discuss what has been learned so far and what can be expected for the future.
Palmer, R. |; Sessler, A.; Skrinsky, A.
1996-03-01
The possibility of muon colliders was introduced by Skrinsky et al., Neuffer, and others. More recently, several workshops and collaboration meetings have greatly increased the level of discussion. In this paper we present scenarios for 4 TeV and 0.5 TeV colliders based on an optimally designed proton source, and for a lower luminosity 0.5 TeV demonstration based on an upgraded version of the AGS. It is assumed that a demonstration version based on upgrades of the FERMILAB machines would also be possible. 53 refs., 25 figs., 8 tabs.
Making sound vortices by metasurfaces
NASA Astrophysics Data System (ADS)
Ye, Liping; Qiu, Chunyin; Lu, Jiuyang; Tang, Kun; Jia, Han; Ke, Manzhu; Peng, Shasha; Liu, Zhengyou
2016-08-01
Based on the Huygens-Fresnel principle, a metasurface structure is designed to generate a sound vortex beam in airborne environment. The metasurface is constructed by a thin planar plate perforated with a circular array of deep subwavelength resonators with desired phase and amplitude responses. The metasurface approach in making sound vortices is validated well by full-wave simulations and experimental measurements. Potential applications of such artificial spiral beams can be anticipated, as exemplified experimentally by the torque effect exerting on an absorbing disk.
Decontamination Efficiency of a DBD Lamp Containing an UV-C Emitting Phosphor.
Caillier, Bruno; Caiut, José Maurício Almeida; Muja, Cristina; Demoucron, Julien; Mauricot, Robert; Dexpert-Ghys, Jeanette; Guillot, Philippe
2015-01-01
Among different physical and chemical agents, the UV radiation appears to be an important route for inactivation of resistant microorganisms. The present study introduces a new mercury-free Dielectric Barrier Discharge (DBD) flat lamp, where the biocide action comes from the UV emission produced by rare-earth phosphor obtained by spray pyrolysis, following plasma excitation. In this study, the emission intensity of the prototype lamp is tuned by controlling gas pressure and electrical power, 500 mbar and 15 W, corresponding to optimal conditions. In order to characterize the prototype lamp, the energetic output, temperature increase following lamp ignition and ozone production of the source were measured. The bactericidal experiments carried out showed excellent results for several gram-positive and gram-negative bacterial strains, thus demonstrating the high decontamination efficiency of the DBD flat lamp. Finally, the study of the external morphology of the microorganisms after the exposure to the UV emission suggested that other mechanisms than the bacterial DNA damage could be involved in the inactivation process. PMID:25626463
Selective cytotoxic effect of non-thermal micro-DBD plasma.
Kwon, Byung-Su; Choi, Eun Ha; Chang, Boksoon; Choi, Jeong-Hyun; Kim, Kyung Sook; Park, Hun-Kuk
2016-01-01
Non-thermal plasma has been extensively researched as a new cancer treatment technology. We investigated the selective cytotoxic effects of non-thermal micro-dielectric barrier discharge (micro-DBD) plasma in cervical cancer cells. Two human cervical cancer cell lines (HeLa and SiHa) and one human fibroblast (HFB) cell line were treated with micro-DBD plasma. All cells underwent apoptotic death induced by plasma in a dose-dependent manner. The plasma showed selective inhibition of cell proliferation in cervical cancer cells compared to HFBs. The selective effects of the plasma were also observed between the different cervical cancer cell lines. Plasma treatment significantly inhibited the proliferation of SiHa cells in comparison to HeLa cells. The changes in gene expression were significant in the cervical cancer cells in comparison to HFBs. Among the cancer cells, apoptosis-related genes were significantly enriched in SiHa cells. These changes were consistent with the differential cytotoxic effects observed in different cell lines. PMID:27603748
Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process.
Guo, Yufang; Liao, Xiaobin; Fu, Mingli; Huang, Haibao; Ye, Daiqi
2015-02-01
Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.
Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process.
Guo, Yufang; Liao, Xiaobin; Fu, Mingli; Huang, Haibao; Ye, Daiqi
2015-02-01
Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression. PMID:25662254
Selective cytotoxic effect of non-thermal micro-DBD plasma
NASA Astrophysics Data System (ADS)
Kwon, Byung-Su; Choi, Eun Ha; Chang, Boksoon; Choi, Jeong-Hyun; Kim, Kyung Sook; Park, Hun-Kuk
2016-10-01
Non-thermal plasma has been extensively researched as a new cancer treatment technology. We investigated the selective cytotoxic effects of non-thermal micro-dielectric barrier discharge (micro-DBD) plasma in cervical cancer cells. Two human cervical cancer cell lines (HeLa and SiHa) and one human fibroblast (HFB) cell line were treated with micro-DBD plasma. All cells underwent apoptotic death induced by plasma in a dose-dependent manner. The plasma showed selective inhibition of cell proliferation in cervical cancer cells compared to HFBs. The selective effects of the plasma were also observed between the different cervical cancer cell lines. Plasma treatment significantly inhibited the proliferation of SiHa cells in comparison to HeLa cells. The changes in gene expression were significant in the cervical cancer cells in comparison to HFBs. Among the cancer cells, apoptosis-related genes were significantly enriched in SiHa cells. These changes were consistent with the differential cytotoxic effects observed in different cell lines.
Decontamination Efficiency of a DBD Lamp Containing an UV-C Emitting Phosphor.
Caillier, Bruno; Caiut, José Maurício Almeida; Muja, Cristina; Demoucron, Julien; Mauricot, Robert; Dexpert-Ghys, Jeanette; Guillot, Philippe
2015-01-01
Among different physical and chemical agents, the UV radiation appears to be an important route for inactivation of resistant microorganisms. The present study introduces a new mercury-free Dielectric Barrier Discharge (DBD) flat lamp, where the biocide action comes from the UV emission produced by rare-earth phosphor obtained by spray pyrolysis, following plasma excitation. In this study, the emission intensity of the prototype lamp is tuned by controlling gas pressure and electrical power, 500 mbar and 15 W, corresponding to optimal conditions. In order to characterize the prototype lamp, the energetic output, temperature increase following lamp ignition and ozone production of the source were measured. The bactericidal experiments carried out showed excellent results for several gram-positive and gram-negative bacterial strains, thus demonstrating the high decontamination efficiency of the DBD flat lamp. Finally, the study of the external morphology of the microorganisms after the exposure to the UV emission suggested that other mechanisms than the bacterial DNA damage could be involved in the inactivation process.
Vortices in spatially inhomogeneous superfluids
NASA Astrophysics Data System (ADS)
Sheehy, Daniel E.; Radzihovsky, Leo
2004-12-01
We study vortices in a radially inhomogeneous superfluid, as realized by a trapped degenerate Bose gas in a uniaxially symmetric potential. We show that, in contrast to a homogeneous superfluid, an off-axis vortex corresponds to an anisotropic superflow whose profile strongly depends on the distance to the trap axis. One consequence of this superflow anisotropy is vortex precession about the trap axis in the absence of an imposed rotation. In the complementary regime of a finite prescribed rotation, we compute the minimum-energy vortex density, showing that in the rapid-rotation limit it is extremely uniform, despite a strongly inhomogeneous (nearly) Thomas-Fermi condensate density ρs(r) . The weak radially dependent contribution [∝∇2lnρs(r)] to the vortex distribution, that vanishes with the number of vortices Nv as 1/Nv , arises from the interplay between vortex quantum discreteness (namely their inability to faithfully support the imposed rigid-body rotation) and the inhomogeneous superfluid density. This leads to an enhancement of the vortex density at the center of a typical concave trap, a prediction that is in quantitative agreement with recent experiments. One striking consequence of the inhomogeneous vortex distribution is an azimuthally directed, radially shearing superflow.
Rees, J.R.
1989-10-01
April, 1989, the first Z zero particle was observed at the Stanford Linear Collider (SLC). The SLC collides high-energy beams of electrons and positrons into each other. In break with tradition the SLC aims two linear beams at each other. Strong motives impelled the Stanford team to choose the route of innovation. One reason being that linear colliders promise to be less expensive to build and operate than storage ring colliders. An equally powerful motive was the desire to build an Z zero factory, a facility at which the Z zero particle can be studied in detail. More than 200 Z zero particles have been detected at the SLC and more continue to be churned out regularly. It is in measuring the properties of the Z zero that the SLC has a seminal contribution to make. One of the primary goals of the SLC experimental program is to determine the mass of the Z zero as precisely as possible.In the end, the SLC's greatest significance will be in having proved a new accelerator technology. 7 figs.
Palmer, R.B.; Gallardo, J.C.
1997-02-01
The authors consider the high energy physics advantages, disadvantages and luminosity requirements of hadron (pp, p{anti p}), lepton (e{sup +}e{sup {minus}}, {mu}{sup +}{mu}{sup {minus}}) and photon-photon colliders. Technical problems in obtaining increased energy in each type of machine are presented. The machines relative size are also discussed.
High luminosity muon collider design
Palmer, R.; Gallardo, J.
1996-10-01
Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should be regarded as complementary. Parameters are given of 4 TeV high luminosity {mu}{sup +}{mu}{sup {minus}} collider, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders.
On generating counter-rotating streamwise vortices
NASA Astrophysics Data System (ADS)
Winoto, S. H.; Mitsudharmadi, H.; Budiman, A. C.; Hasheminejad, S. M.; Nadesan, T.; Tandiono; Low, H. T.; Lee, T. S.
2015-09-01
Counter-rotating streamwise vortices are known to enhance the heat transfer rate from a surface and also to improve the aerodynamic performance of an aerofoil. In this paper, some methods to generate such counter-rotating vortices using different methods or physical conditions will be briefly considered and discussed.
Nonquasineutral electron vortices in nonuniform plasmas
Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W.; Ottinger, P. F.
2014-11-15
Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds V{sub ϕ} close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λ{sub B}=|B|/4πen and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λ{sub B}. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.
Flute vortices in nonuniform magnetic fields
Yu, M.Y.; Shukla, P.K.; Varma, R.K.
1985-09-01
Localized double vortices associated with the flute modes are shown to exist. Special emphasis is given to the effect of the convective variation of the fluid magnetic moment. It is shown that the latter effect considerably modifies the existence regions of the vortices.
Vortices in normal part of proximity system
Kogan, V. G.
2015-05-26
It is shown that the order parameter Δ induced in the normal part of superconductor-normal-superconductor proximity system is modulated in the magnetic field differently from vortices in bulk superconductors. Whereas Δ turns zero at vortex centers, the magnetic structure of these vortices differs from that of Abrikosov's.
Vorticity generation by contoured wall injectors
NASA Technical Reports Server (NTRS)
Waitz, Ian A.; Marble, Frank E.; Zukoski, Edward E.
1992-01-01
A class of contoured wall fuel injectors was designed to enable shock-enhancement of hypervelocity mixing for supersonic combustion ramjet applications. Previous studies of these geometries left unresolved questions concerning the relative importance of various axial vorticity sources in mixing the injectant with the freestream. The present study is a numerical simulation of two generic fuel injectors which is aimed at elucidating the relative roles of axial vorticity sources including: baroclinic torque through shock-impingement, cross-stream shear, turning of boundary layer vorticity, shock curvature, and diffusive flux. Both the magnitude of the circulation, and the location of vorticity with respect to the mixing interface were considered. Baroclinic torque and cross-stream shear were found to be most important in convectively mixing the injectant with the freestream, with the former providing for deposition of vorticity directly on the fuel/air interface.
Relative equilibria of vortices in two dimensions.
Palmore, J I
1982-01-01
An old problem of the evolution of finitely many interacting point vortices in the plane is shown to be amenable to investigation by critical point theory in a way that is identical to the study of the planar n-body problem of celestial mechanics. For any choice of positive circulations of the vortices it is shown by critical point theory applied to Kirchhoff's function that there are many relative equilibria configurations. Each of these configurations gives rise to a stationary configuration of the vortices in a suitably chosen rotating coordinate system. A sharp lower bound on the number of stationary vortex configurations for the problem of point vortices interacting in the plane is given. The problem of point vortices in a circular disk is defined and it is shown that these estimates hold for stationary configurations of small size. PMID:16593155
Vorticity generation by contoured wall injectors
Waitz, I.A.; Marble, F.E.; Zukoski, E.E. California Institute of Technology, Pasadena )
1992-07-01
A class of contoured wall fuel injectors was designed to enable shock-enhancement of hypervelocity mixing for supersonic combustion ramjet applications. Previous studies of these geometries left unresolved questions concerning the relative importance of various axial vorticity sources in mixing the injectant with the freestream. The present study is a numerical simulation of two generic fuel injectors which is aimed at elucidating the relative roles of axial vorticity sources including: baroclinic torque through shock-impingement, cross-stream shear, turning of boundary layer vorticity, shock curvature, and diffusive flux. Both the magnitude of the circulation, and the location of vorticity with respect to the mixing interface were considered. Baroclinic torque and cross-stream shear were found to be most important in convectively mixing the injectant with the freestream, with the former providing for deposition of vorticity directly on the fuel/air interface. 19 refs.
Relative equilibria of vortices in two dimensions.
Palmore, J I
1982-01-01
An old problem of the evolution of finitely many interacting point vortices in the plane is shown to be amenable to investigation by critical point theory in a way that is identical to the study of the planar n-body problem of celestial mechanics. For any choice of positive circulations of the vortices it is shown by critical point theory applied to Kirchhoff's function that there are many relative equilibria configurations. Each of these configurations gives rise to a stationary configuration of the vortices in a suitably chosen rotating coordinate system. A sharp lower bound on the number of stationary vortex configurations for the problem of point vortices interacting in the plane is given. The problem of point vortices in a circular disk is defined and it is shown that these estimates hold for stationary configurations of small size.
Composite vortices in nonlinear circular waveguide arrays
NASA Astrophysics Data System (ADS)
Leykam, Daniel; Malomed, Boris; Desyatnikov, Anton S.
2013-04-01
It is known that, in continuous media, composite solitons with hidden vorticity, which are built of two mutually symmetric vortical components whose total angular momentum is zero, may be stable while their counterparts with explicit vorticity and nonzero total angular momentum are unstable. In this work, we demonstrate that the opposite occurs in discrete media: hidden vortex states in relatively small ring chains become unstable with the increase of the total power, while explicit vortices are stable, provided that the corresponding scalar vortex state is also stable. There are also stable mixed states, in which the components are vortices with different topological charges. Additionally, degeneracies in families of composite vortex modes lead to the existence of long-lived breather states which can exhibit vortex-charge flipping in one or both components.
Electroweak Vortices and Gauge Equivalence
NASA Astrophysics Data System (ADS)
MacDowell, Samuel W.; Törnkvist, Ola
Vortex configurations in the electroweak gauge theory are investigated. Two gauge-inequivalent solutions of the field equations, the Z and W vortices, have previously been found. They correspond to embeddings of the Abelian Nielsen-Olesen vortex solution into a U(1) subgroup of SU(2)×U(1). It is shown here that any electroweak vortex solution can be mapped into a solution of the same energy with a vanishing upper component of the Higgs field. The correspondence is a gauge equivalence for all vortex solutions except those for which the winding numbers of the upper and lower Higgs components add to zero. This class of solutions, which includes the W vortex, corresponds to a singular solution in the one-component gauge. The results, combined with numerical investigations, provide an argument against the existence of other vortex solutions in the gauge-Higgs sector of the Standard Model.
Ferroelectric vortices from atomistic simulations
NASA Astrophysics Data System (ADS)
Bellaiche, Laurent
2011-03-01
In 2004, the use of a first-principles-based effective Hamiltonian led to the prediction of a novel structure in zero-dimensional ferroelectrics, in which the electric dipoles organize themselves to form a vortex. Such structure exhibits the so-called spontaneous toroidal moment, rather than the spontaneous polarization, as its order parameter. Subsequently, various original phenomena, all related to vortices, were predicted in ferroelectric nanostructures. Examples of such phenomena are: (i) the existence of a new order parameter, denoted as the hypertoroidal moment, that is associated with many complex dipolar structures (such as double-vortex states); (ii) the possible control of single and double vortex states by electric fields, via the formation of original intermediate states [4-8]; (iii) the discovery of a new class of quantum materials (denoted as incipient ferrotoroidics), for which zero-point vibrations wash out the vortex state and yield a complex local structure; (iv) the existence of chiral patterns of oxygen octahedral tiltings that originate from the coupling of these tiltings with the ferroelectric vortices. The purpose of this talk is to discuss some of these striking phenomena, as well as, to reveal others (if time allows). These studies are done in collaboration with A.R. Akbarzadeh, H. Fu, I. Kornev, I. Naumov, I. Ponomareva, S. Prosandeev, Wei Ren and D. Sichuga. These works are supported by the NSF grants DMR 0701558 and DMR-0080054 (C-SPIN), DOE grant DE-SC0002220, and ONR grants N00014-08-1-0915 and N00014-07-1-0825 (DURIP).
NASA Astrophysics Data System (ADS)
Zhang, Haibao; Li, Hua; Fang, Ming; Wang, Zhengduo; Sang, Lijun; Yang, Lizhen; Chen, Qiang
2016-12-01
In this paper the roll-to-roll atmospheric dielectric barrier discharge (DBD) was used to pre-treat polyethylene (PE) web surface before the conventional thermal evaporation aluminum (Al) was performed as a barrier layer. We emphasized the plasma environment effect based on the inlet three kinds of reactive monomers. The cross hatch test was employed to assess the Al coating adhesion; and the oxygen transmission rate (OTR) was used to evaluate gas barrier property. The results showed that after roll-to-roll DBD plasma treatment all Al coatings adhered strongly on PE films and were free from pinhole defects with mirror morphology. The OTR was reduced from 2673 cm3/m2 day for Al-coated original PE to 138 cm3/m2 day for Al-coated allyamine (C3H7N) modified PE. To well understand the mechanism the chemical compositions of the untreated and DBD plasma pretreated PE films were analyzed by X-ray photoelectron spectroscopy (XPS). The surface topography was characterized by atomic force microscopy (AFM). For the property of surface energy the water contact angle measurement was also carried out in the DBD plasma treated samples with deionized water.
Generation and Growth of Single Hairpin Vortices
NASA Astrophysics Data System (ADS)
Haji-Haidari, Ahmad
The behavior of selectively generated single hairpin vortices are examined within a laminar boundary layer environment over a range of Reynolds numbers, the hairpin vortices are experimentally generated by means of controlled fluid injection from a streamwise slot. Flow visualization using both dye and hydrogen bubble wire is employed in conjunction with hot film anemometry to investigate the growth characteristics and evolution of these single hairpin vortices. Qualitatively, it is established that hairpin vortices form by local destabilization at the interface between the low-speed fluid introduced through the slot and the higher speed boundary layer flow. Kinematical considerations of the hairpin vortex are established. It is observed that a hairpin vortex generally displays visualization and velocity signatures characteristic of those observed for a turbulent boundary layer. Hydrogen-bubble wire visualization results specifically indicate that hairpin vortices generate two purely turbulent-like flow patterns. The first is a low-speed streak pattern developing immediately adjacent to the surface due to surface interaction by the counter -rotating legs of the hairpin vortex; the second pattern is a turbulent pocket-like pattern farther removed from the surface. It is determined from the visualization data that hairpin vortices manifest the necessary flow characteristics which give rise to the regenerative and sustained process required for maintenance of turbulence. The regeneration and the growth process takes place through the formation of similar hairpin-like vortices by one of two means. The first is an inviscid lateral propagation of the initial disturbance which gives rise to outboard (subsidiary), vortices which cause the lateral spreading of the structure. A more complicated and eruptive process occurs by means of viscous-inviscid interactions which give rise to trailing vortices (secondary), which cause the streamwise elongation of the disturbance. A
Lehners, Jean-Luc
2007-11-20
In a braneworld description of our universe, we must allow for the possibility of having dynamical branes around the time of the big bang. Some properties of such domain walls in motion are discussed here, for example the ability of negative-tension domain walls to bounce off spacetime singularities and the consequences for cosmological perturbations. In this context, we will also review a colliding branes solution of heterotic M-theory that has been proposed as a model for early universe cosmology.
Muon Collider Progress: Accelerators
Zisman, Michael S.
2011-09-10
A muon collider would be a powerful tool for exploring the energy-frontier with leptons, and would complement the studies now under way at the LHC. Such a device would offer several important benefits. Muons, like electrons, are point particles so the full center-of-mass energy is available for particle production. Moreover, on account of their higher mass, muons give rise to very little synchrotron radiation and produce very little beamstrahlung. The first feature permits the use of a circular collider that can make efficient use of the expensive rf system and whose footprint is compatible with an existing laboratory site. The second feature leads to a relatively narrow energy spread at the collision point. Designing an accelerator complex for a muon collider is a challenging task. Firstly, the muons are produced as a tertiary beam, so a high-power proton beam and a target that can withstand it are needed to provide the required luminosity of ~1 × 10{sup 34} cm{sup –2}s{sup –1}. Secondly, the beam is initially produced with a large 6D phase space, which necessitates a scheme for reducing the muon beam emittance (“cooling”). Finally, the muon has a short lifetime so all beam manipulations must be done very rapidly. The Muon Accelerator Program, led by Fermilab and including a number of U.S. national laboratories and universities, has undertaken design and R&D activities aimed toward the eventual construction of a muon collider. Design features of such a facility and the supporting R&D program are described.
DBD in burst mode: solution for more efficient CO2 conversion?
NASA Astrophysics Data System (ADS)
Ozkan, A.; Dufour, T.; Silva, T.; Britun, N.; Snyders, R.; Reniers, F.; Bogaerts, A.
2016-10-01
CO2 conversion into value-added products has gained significant interest over the few last years, as the greenhouse gas concentrations constantly increase due to anthropogenic activities. Here we report on experiments for CO2 conversion by means of a cold atmospheric plasma using a cylindrical flowing dielectric barrier discharge (DBD) reactor. A detailed comparison of this DBD ignited in a so-called burst mode (i.e. where an AC voltage is applied during a limited amount of time) and pure AC mode is carried out to evaluate their effect on the conversion of CO2 as well as on the energy efficiency. Decreasing the duty cycle in the burst mode from 100% (i.e. corresponding to pure AC mode) to 40% leads to a rise in the conversion from 16-26% and to a rise in the energy efficiency from 15 to 23%. Based on a detailed electrical analysis, we show that the conversion correlates with the features of the microfilaments. Moreover, the root-mean-square voltage in the burst mode remains constant as a function of the process time for the duty cycles <70%, while a higher duty cycle or the usual pure AC mode leads to a clear voltage decay by more than 500 V, over approximately 90 s, before reaching a steady state regime. The higher plasma voltage in the burst mode yields a higher electric field. This causes the increasing the electron energy, and therefore their involvement in the CO2 dissociation process, which is an additional explanation for the higher CO2 conversion and energy efficiency in the burst mode.
Alekseev, Oleg; Donovan, Kelly; Limonnik, Vladimir; Azizkhan-Clifford, Jane
2014-01-01
Purpose Herpes keratitis (HK) is the leading cause of cornea-derived and infection-associated blindness in the developed world. Despite the availability of effective antivirals, some patients develop refractory disease, drug-resistant infection, and topical toxicity. A nonpharmaceutical treatment modality may offer a unique advantage in the management of such cases. This study investigated the antiviral effect of nonthermal dielectric barrier discharge (DBD) plasma, a partially ionized gas that can be applied to organic substances to produce various biological effects. Methods Human corneal epithelial cells and explanted corneas were infected with herpes simplex virus type 1 (HSV-1) and exposed to culture medium treated with nonthermal DBD plasma. The extent of infection was measured by plaque assay, quantitative PCR, and Western blot. Corneal toxicity assessment was performed with fluorescein staining, histologic examination, and 8-OHdG detection. Results Application of DBD plasma–treated medium to human corneal epithelial cells and explanted corneas produced a dose-dependent reduction of the cytopathic effect, viral genome replication, and the overall production of infectious viral progeny. Toxicity studies showed lack of detrimental effects in explanted human corneas. Conclusions Nonthermal DBD plasma substantially suppresses corneal HSV-1 infection in vitro and ex vivo without causing pronounced toxicity. Translational Relevance Nonthermal plasma is a versatile tool that holds great biomedical potential for ophthalmology, where it is being investigated for wound healing and sterilization and is already in use for ocular microsurgery. The anti-HSV-1 activity of DBD plasma demonstrated here could be directly translated to the clinic for use against drug-resistant herpes keratitis. PMID:24757592
Merging of co-rotating vortices
NASA Astrophysics Data System (ADS)
Cerretelli, C.; Williamson, C. H. K.
2001-11-01
We present results from an experimental study on the interaction of two co-rotating trailing vortices. The flow is generated by towing a biplane wing system through a tank of water. The vortex dynamics, as a function of the Reynolds number (Re), are analyzed by means of DPIV. We find that vortex merging is essentially a 3-stage process. Initially, the vortices undergo a diffusive growth until the cores reach a critical size. This diffusion process can be either viscous (when Re < 530) or turbulent (when Re > 530). The second (convective) stage in vortex merging, involves a breaking of the initial symmetry of the vorticity field. At this point, the convective stage occurs, with a strong deformation of the vortex cores which start moving towards each other. The decomposition of the vorticity and velocity fields into symmetric and antisymmetric components shows that the antisymmetric vorticity pushes the vortices together, and causes the phenomenon of merging. The merging velocity can be measured from the antisymmetric velocity field, and agrees very well with direct measurement of the rate at which the centroids approach each other. The third stage of vortex merger is again a diffusive stage, whereby the final merging of the two vortices into one axisymmetric structure is achieved only by diffusion.
Measurement of vorticity diffusion by NMR microscopy.
Brown, Jennifer R; Callaghan, Paul T
2010-05-01
In a Newtonian fluid, vorticity diffuses at a rate determined by the kinematic viscosity. Here we use rapid NMR velocimetry, based on a RARE sequence, to image the time-dependent velocity field on startup of a fluid-filled cylinder and therefore measure the diffusion of vorticity. The results are consistent with the solution to the vorticity diffusion equation where the angular velocity on the outside surface of the fluid, at the cylinder's rotating wall, is fixed. This method is a means of measuring kinematic viscosity for low viscosity fluids without the need to measure stress. PMID:20189854
Vortices and turbulence in trapped atomic condensates
White, Angela C.; Anderson, Brian P.; Bagnato, Vanderlei S.
2014-01-01
After more than a decade of experiments generating and studying the physics of quantized vortices in atomic gas Bose–Einstein condensates, research is beginning to focus on the roles of vortices in quantum turbulence, as well as other measures of quantum turbulence in atomic condensates. Such research directions have the potential to uncover new insights into quantum turbulence, vortices, and superfluidity and also explore the similarities and differences between quantum and classical turbulence in entirely new settings. Here we present a critical assessment of theoretical and experimental studies in this emerging field of quantum turbulence in atomic condensates. PMID:24704880
Vortices in magnetically coupled superconducting layered systems
Mints, Roman G.; Kogan, Vladimir G.; Clem, John R.
2000-01-01
Pancake vortices in stacks of thin superconducting films or layers are considered. It is stressed that in the absence of Josephson coupling topological restrictions upon possible configurations of vortices are removed and various examples of structures forbidden in bulk superconductors are given. In particular, it is shown that vortices may skip surface layers in samples of less than a certain size R{sub c} which might be macroscopic. The Josephson coupling suppresses R{sub c} estimates. (c) 2000 The American Physical Society.
Hollow vortices in weakly compressible flows
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikas; Crowdy, Darren
2015-11-01
In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.
Atmospheric Vortices near Guadalupe Island
NASA Technical Reports Server (NTRS)
2000-01-01
These MISR images from June 11, 2000 (Terra orbit 2569) demonstrate a turbulent atmospheric flow pattern known as the von Karman vortex street. This phenomenon is named after aerodynamicist Theodore von Karman, who theoretically derived the conditions under which it occurs. The alternating double row of vortices can form in the wake of an obstacle, in this instance the eastern Pacific island of Guadalupe. The rugged terrain of this volcanic Mexican island reaches a maximum elevation of 1.3 kilometers. The island is about 35 kilometers long and is located 260 kilometers west of Baja California.
The vortex pattern is made visible by the marine stratocumulus clouds around Guadalupe Island. The upper image is a color view obtained by MISR's vertical-viewing (nadir) camera. North is toward the left. The orientation of the vortex street indicates that the wind direction is from lower left to upper right (northwest to southeast). The areas within the vortex centers tend to be clear because the rotating motions induce a vertical wind component that can break up the cloud deck.
The lower view is a stereo picture generated from data acquired by MISR's fore- and aft-viewing 70-degree cameras. A 3-D effect is obtained by viewing the image with red/blue glasses and placing the red filter over your left eye. Note how the downwelling atmospheric motion (change in elevation from high to low) is accompanied by a clearing in the center of the first vortex. As the vortices propagate downstream, their rotational velocities weaken. As a consequence, the induced vertical motion and cloud-clearing effect weakens as well.
Theodore von Karman was a Professor of Aeronautics at Caltech and Director of Caltech's Guggenheim Aeronautical Laboratory from 1930-1949. He was one of the principal founders of the Jet Propulsion Laboratory.
MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra
Balzer, Julian; Heuer, Kiara; Demir, Erhan; Hoffmanns, Martin A; Baldus, Sabrina; Fuchs, Paul C; Awakowicz, Peter; Suschek, Christoph V; Opländer, Christian
2015-01-01
The proliferation of fibroblasts and myofibroblast differentiation are crucial in wound healing and wound closure. Impaired wound healing is often correlated with chronic bacterial contamination of the wound area. A new promising approach to overcome wound contamination, particularly infection with antibiotic-resistant pathogens, is the topical treatment with non-thermal "cold" atmospheric plasma (CAP). Dielectric barrier discharge (DBD) devices generate CAP containing active and reactive species, which have antibacterial effects but also may affect treated tissue/cells. Moreover, DBD treatment acidifies wound fluids and leads to an accumulation of hydrogen peroxide (H2O2) and nitric oxide products, such as nitrite and nitrate, in the wound. Thus, in this paper, we addressed the question of whether DBD-induced chemical changes may interfere with wound healing-relevant cell parameters such as viability, proliferation and myofibroblast differentiation of primary human fibroblasts. DBD treatment of 250 μl buffered saline (PBS) led to a treatment time-dependent acidification (pH 6.7; 300 s) and coincidently accumulation of nitrite (~300 μM), nitrate (~1 mM) and H2O2 (~200 μM). Fibroblast viability was reduced by single DBD treatments (60-300 s; ~77-66%) or exposure to freshly DBD-treated PBS (60-300 s; ~75-55%), accompanied by prolonged proliferation inhibition of the remaining cells. In addition, the total number of myofibroblasts was reduced, whereas in contrast, the myofibroblast frequency was significantly increased 12 days after DBD treatment or exposure to DBD-treated PBS. Control experiments mimicking DBD treatment indicate that plasma-generated H2O2 was mainly responsible for the decreased proliferation and differentiation, but not for DBD-induced toxicity. In conclusion, apart from antibacterial effects, DBD/CAP may mediate biological processes, for example, wound healing by accumulation of H2O2. Therefore, a clinical DBD treatment must be well-balanced in
Demir, Erhan; Hoffmanns, Martin A.; Baldus, Sabrina; Fuchs, Paul C.; Awakowicz, Peter; Suschek, Christoph V.; Opländer, Christian
2015-01-01
The proliferation of fibroblasts and myofibroblast differentiation are crucial in wound healing and wound closure. Impaired wound healing is often correlated with chronic bacterial contamination of the wound area. A new promising approach to overcome wound contamination, particularly infection with antibiotic-resistant pathogens, is the topical treatment with non-thermal “cold” atmospheric plasma (CAP). Dielectric barrier discharge (DBD) devices generate CAP containing active and reactive species, which have antibacterial effects but also may affect treated tissue/cells. Moreover, DBD treatment acidifies wound fluids and leads to an accumulation of hydrogen peroxide (H2O2) and nitric oxide products, such as nitrite and nitrate, in the wound. Thus, in this paper, we addressed the question of whether DBD-induced chemical changes may interfere with wound healing-relevant cell parameters such as viability, proliferation and myofibroblast differentiation of primary human fibroblasts. DBD treatment of 250 μl buffered saline (PBS) led to a treatment time-dependent acidification (pH 6.7; 300 s) and coincidently accumulation of nitrite (~300 μM), nitrate (~1 mM) and H2O2 (~200 μM). Fibroblast viability was reduced by single DBD treatments (60–300 s; ~77–66%) or exposure to freshly DBD-treated PBS (60–300 s; ~75–55%), accompanied by prolonged proliferation inhibition of the remaining cells. In addition, the total number of myofibroblasts was reduced, whereas in contrast, the myofibroblast frequency was significantly increased 12 days after DBD treatment or exposure to DBD-treated PBS. Control experiments mimicking DBD treatment indicate that plasma-generated H2O2 was mainly responsible for the decreased proliferation and differentiation, but not for DBD-induced toxicity. In conclusion, apart from antibacterial effects, DBD/CAP may mediate biological processes, for example, wound healing by accumulation of H2O2. Therefore, a clinical DBD treatment must be well
Balzer, Julian; Heuer, Kiara; Demir, Erhan; Hoffmanns, Martin A; Baldus, Sabrina; Fuchs, Paul C; Awakowicz, Peter; Suschek, Christoph V; Opländer, Christian
2015-01-01
The proliferation of fibroblasts and myofibroblast differentiation are crucial in wound healing and wound closure. Impaired wound healing is often correlated with chronic bacterial contamination of the wound area. A new promising approach to overcome wound contamination, particularly infection with antibiotic-resistant pathogens, is the topical treatment with non-thermal "cold" atmospheric plasma (CAP). Dielectric barrier discharge (DBD) devices generate CAP containing active and reactive species, which have antibacterial effects but also may affect treated tissue/cells. Moreover, DBD treatment acidifies wound fluids and leads to an accumulation of hydrogen peroxide (H2O2) and nitric oxide products, such as nitrite and nitrate, in the wound. Thus, in this paper, we addressed the question of whether DBD-induced chemical changes may interfere with wound healing-relevant cell parameters such as viability, proliferation and myofibroblast differentiation of primary human fibroblasts. DBD treatment of 250 μl buffered saline (PBS) led to a treatment time-dependent acidification (pH 6.7; 300 s) and coincidently accumulation of nitrite (~300 μM), nitrate (~1 mM) and H2O2 (~200 μM). Fibroblast viability was reduced by single DBD treatments (60-300 s; ~77-66%) or exposure to freshly DBD-treated PBS (60-300 s; ~75-55%), accompanied by prolonged proliferation inhibition of the remaining cells. In addition, the total number of myofibroblasts was reduced, whereas in contrast, the myofibroblast frequency was significantly increased 12 days after DBD treatment or exposure to DBD-treated PBS. Control experiments mimicking DBD treatment indicate that plasma-generated H2O2 was mainly responsible for the decreased proliferation and differentiation, but not for DBD-induced toxicity. In conclusion, apart from antibacterial effects, DBD/CAP may mediate biological processes, for example, wound healing by accumulation of H2O2. Therefore, a clinical DBD treatment must be well-balanced in
Vorticity matching in superfluid helium
NASA Astrophysics Data System (ADS)
Samuels, David C.
1991-12-01
Recent experiments have rekindled interest in high Reynolds number flows using superfluid helium. In a continuing series of experiments, the flow of helium II through various devices (smooth pipes, corrugated pipes, valves, venturies, turbine flowmeters, and coanda flowmeters for example) was investigated. In all cases, the measured values (typically, mass flow rates and pressure drops) were found to be well described by classical relations for high Reynolds flows. This is unexpected since helium II consists of two interpenetrating fluids; one fluid with nonzero viscosity (the normal fluid) and one with zero viscosity (the superfluid). Only the normal fluid component should directly obey classical relations. Since the experiments listed above only measure the external behavior of the flow (i.e., pressure drops over devices), there is a great deal of room for interpretation of their results. One possible interpretation is that in turbulent flows the normal fluid and the superfluid velocity fields are somehow 'locked' together, presumably by the mutual friction force between the superfluid vortex filaments and the normal fluid. We refer to this locking together of the two fluids as 'vorticity matching.'
Combustion enhancement by axial vortices
NASA Astrophysics Data System (ADS)
Gutmark, E.; Schadow, K. C.; Parr, T. P.; Parr, D. M.; Wilson, K. J.
1987-06-01
A tapered slot jet was studied experimentally in nonreacting and reacting tests using hot-wire anemometry, water-tunnel flow visualization, and Planar Laser Induced Fluorescence (PLIF). The tapered slot jet is a modified elliptic jet which has a conical contraction leading to its outlet. The added contraction changes the entire flow field. The jet spread in the major axis plane is larger than in the minor axis plane, which is the opposite behavior of an elliptic jet. Consequently, no axes switching, typical to an elliptic jet, is observed. The turbulence amplification in the jet core is higher than in circular and elliptic jets. The different behavior is attributed to the change in flow direction, inside the nozzle, from the conical section to the slot outlet. During this transition, the flow acquires angular momentum thereby generating axial vorticity. The influence of the contraction angle and the outlet aspect ratio were investigated. The effect of the augmented turbulence on reactive flow was tested in a premixed flame. The combustion rate was augmented in both the core and edges of the flame relative to a circular burner.
Tornadoes and other atmospheric vortices
NASA Technical Reports Server (NTRS)
Deissler, R. G.
1976-01-01
The growth of random vortices in an atmosphere with buoyant instability and vertical wind shear is studied along with the velocities in a single gravity-driven vortex; a frictionless adiabatic model which is supported by laboratory experiments is first considered. The effects of axial drag, heat transfer, and precipitation-induced downdrafts are then calculated. Heat transfer and axial drag tend to have stabilizing effects; they reduce the downdrafts of updrafts due to buoyancy. It is found that downdrafts or tornadic magnitude might occur in negatively-buoyant columns. The radial-inflow velocity required to maintain a given maximum tangential velocity in a tornado is determined by using a turbulent vortex model. Conditions under which radial-inflow velocities become sufficiently large to produce tangential velocities of tornadic magnitude are determined. The radial velocities in the outer regions, as well as the tangential velocities in the inner regions may be large enough to cause damage. The surface boundary layer, which is a region where large radial inflows can occur, is studied, and the thickness of the radial-inflow friction layer is estimated. A tornado model which involves a rotating parent cloud, as well as buoyancy and precipitation effects, is discussed.
Hussein, M.S.; Pato, M.P. )
1992-05-20
In this paper, the authors suggest a revised version of the Superconducting Super Collider (SSC) that employs the planned SSC first stage machine as an injector of 0.5 TeV protons into a power laser accelerator. The recently developed Non-linear Amplification of Inverse Bremsstrahlung Acceleration (NAIBA) concept dictates the scenario of the next stage of acceleration. Post Star Wars lasers, available at several laboratories, can be used for the purpose. The 40 TeV CM energy, a target of the SSC, can be obtained with a new machine which can be 20 times smaller than the planned SSC.
Month, M.; Weng, W.T.
1983-06-21
The objective is to investigate whether existing technology might be extrapolated to provide the conceptual framework for a major hadron-hadron collider facility for high energy physics experimentation for the remainder of this century. One contribution to this large effort is to formalize the methods and mathematical tools necessary. In this report, the main purpose is to introduce the student to basic design procedures. From these follow the fundamental characteristics of the facility: its performance capability, its size, and the nature and operating requirements on the accelerator components, and with this knowledge, we can determine the technology and resources needed to build the new facility.
Muon Colliders and Neutrino Factories *
NASA Astrophysics Data System (ADS)
Geer, Steve
2009-11-01
Over the past decade, there has been significant progress in developing the concepts and technologies needed to produce, capture, and accelerate O(1021) muons per year. These developments have paved the way for a new type of neutrino source (neutrino factory) and a new type of very high energy lepton-antilepton collider (muon collider). This article reviews the motivation, design, and research and development for future neutrino factories and muon colliders.
Muon Colliders and Neutrino Factories
Geer, Steve; /Fermilab
2009-11-01
Over the past decade, there has been significant progress in developing the concepts and technologies needed to produce, capture, and accelerate {Omicron}(10{sup 21}) muons per year. These developments have paved the way for a new type of neutrino source (neutrino factory) and a new type of very high energy lepton-antilepton collider (muon collider). This article reviews the motivation, design, and research and development for future neutrino factories and muon colliders.
Muon colliders and neutrino factories
Geer, S.; /Fermilab
2010-09-01
Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture and accelerate {Omicron}(10{sup 21}) muons/year. This development prepares the way for a new type of neutrino source (Neutrino Factory) and a new type of very high energy lepton-antilepton collider (Muon Collider). This article reviews the motivation, design and R&D for Neutrino Factories and Muon Colliders.
Linear collider development at SLAC
Irwin, J.
1993-08-01
Linear collider R&D at SLAC comprises work on the present Stanford Linear Collider (SLC) and work toward the next linear collider (NLC). Recent SLC developments are summarized. NLC studies are divided into hardware-based and theoretical. We report on the status of the NLC Test Accelerator (NLCTA) and the final focus test beam (FFTB), describe plans for ASSET, an installation to measure accelerator structure wakefields, and mention IR design developments. Finally we review recent NLC theoretical studies, ending with the author`s view of next linear collider parameter sets.
Pondrom, L.G. )
1990-12-14
The present status of hadron collider physics is reviewed. The total cross section for {bar p} + p has been measured at 1.8 TeV: {sigma}{sub tot} = 72.1 {plus minus} 3.3 mb. New data confirm the UA2 observation of W/Z {yields} {bar q}q. Precision measurements of M{sub W} by UA2 and CDF give an average value M{sub W} = 80.13 {plus minus} 0.30 GeV/c{sup 2}. When combined with measurements of M{sub Z} from LEP and SLC this number gives sin{sup 2}{theta}{sub W} = 0.227 {plus minus} 0.006, or m{sub top} = 130{sub {minus}60}{sup +40} GeV/c{sup 2} from the EWK radiative correction term {Delta}r. Evidence for hadron colliders as practical sources of b quarks has been strengthened, while searches for t quarks have pushed the mass above M{sub W}: m{sub top} > 89 GeV/c{sup 2} 95% cl (CDF Preliminary). Searches beyond the standard model based on the missing E{sub T} signature have not yet produced any positive results. Future prospects for the discovery of the top quark in the range m{sub top} < 200 GeV/c{sup 2} look promising. 80 refs., 35 figs., 7 tabs.
NASA Astrophysics Data System (ADS)
Boekema, B. K. H. L.; Vlig, M.; Guijt, D.; Hijnen, K.; Hofmann, S.; Smits, P.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P.; Middelkoop, E.
2016-02-01
Cold plasma has been shown to provide a promising alternative antimicrobial treatment for wound healing. We developed and tested a flexible surface dielectric barrier discharge (DBD) and compared it to an argon gas based plasma jet operated remotely with a distance between plasma plume and sample of 8 mm. Tests were conducted using different models: on cultured cells, on ex vivo human skin and on bacteria (Pseudomonas aeruginosa) (on agar, in suspension, in collagen/elastin matrix or on ex vivo human skin), allowing us to directly compare bactericidal with safety aspects under identical conditions. Both plasma devices were highly efficient when used on bacteria in non-buffered solutions, but DBD was faster in reaching the maximum bacterial reduction. Treatment of bacteria on intact skin with DBD resulted in up to 6 log reductions in 3 min. The jet was far less efficient on intact skin. Even after 8 min treatment no more than 2 log reductions were obtained with the jet. Treatment of bacteria in burn wound models with DBD for 6 min resulted in a 4.5 log reduction. Even when using DBD for 6 min on infected burn wound models with colonizing or biofilm phase bacteria, the log reductions were 3.8 or 3.2 respectively. DBD plasma treatment for 6 min did not affect fibroblast viability, whereas a treatment for 8 min was detrimental. Similarly, treatment with DBD or plasma jet for 6 min did also not affect the metabolic activity of skin biopsies. After treatment for 8 min with DBD or plasma jet, 78% or 60% of activity in skin biopsies remained, respectively. Multiple treatments of in vitro burn wound models with surface DBD for 6 min or with plasma jet for 8 min did not affect re-epithelialization. With the flexible surface DBD plasma strip we were able to quickly inactivate large numbers of bacteria on and in skin. Under the same conditions, viability of skin cells or re-epithelialization was not affected. The DBD source has potential for treating
Gaseous Vortices in Barred Spiral Galaxies
NASA Technical Reports Server (NTRS)
England, Martin N.; Hunter, James H., Jr.
1995-01-01
During the course of examining many two-dimensional, as well as a smaller sample of three-dimensional, models of gas flows in barred spiral galaxies, we have been impressed by the ubiquitous presence fo vortex pairs, oriented roughly perpendicular to their bars, with one vortex on each side. The vortices are obvious only when viewed in the bar frame, and the centers of their velocity fields usually are near Lagrangian points L(sub 4,5). In all models that we have studied, the vortices form on essentially the same time scale as that for the development of gaseous spiral arms, typically two bar rotations. Usually the corotation radius, r(sub c), lies slightly beyond the end of the bar. Depending upon the mass distributions of the various components, gas spirals either into, or out of, the vortices: In the former case, the vortices become regions of high density, whereas the opposite is true if the gas spirals out of a vortex. The models described in this paper have low-density vortices, as do most of the models we have studied. Moreover, usually the vortex centers lie approximately within +/- 15 deg of L(sub 4,5). In the stellar dynamic limit, when pressure and viscous forces are absent, short-period orbits exist, centered on L(sub 4,5). These orbits need not cross and therefore their morphology is that of gas streamlines, that is, vortices. We believe that the gas vortices in our models are hydrodynamic analogues of closed, short-period, libration orbits centered on L(sub 4,5).
Initial Circulation and Peak Vorticity Behavior of Vortices Shed from Airfoil Vortex Generators
NASA Technical Reports Server (NTRS)
Wendt, Bruce J.; Biesiadny, Tom (Technical Monitor)
2001-01-01
An extensive parametric study of vortices shed from airfoil vortex generators has been conducted to determine the dependence of initial vortex circulation and peak vorticity on elements of the airfoil geometry and impinging flow conditions. These elements include the airfoil angle of attack, chord length, span, aspect ratio, local boundary layer thickness, and free stream Mach number. In addition, the influence of airfoil-to-airfoil spacing on the circulation and peak vorticity has been examined for pairs of co-rotating and counter-rotating vortices. The vortex generators were symmetric airfoils having a NACA-0012 cross-sectional profile. These airfoils were mounted either in isolation, or in pairs, on the surface of a straight pipe. The turbulent boundary layer thickness to pipe radius ratio was about 17 percent. The circulation and peak vorticity data were derived from cross-plane velocity measurements acquired with a seven-hole probe at one chord-length downstream of the airfoil trailing edge location. The circulation is observed to be proportional to the free-stream Mach number, the angle-of-attack, and the span-to-boundary layer thickness ratio. With these parameters held constant, the circulation is observed to fall off in monotonic fashion with increasing airfoil aspect ratio. The peak vorticity is also observed to be proportional to the free-stream Mach number, the airfoil angle-of-attack, and the span-to-boundary layer thickness ratio. Unlike circulation, however, the peak vorticity is observed to increase with increasing aspect ratio, reaching a peak value at an aspect ratio of about 2.0 before falling off again at higher values of aspect ratio. Co-rotating vortices shed from closely spaced pairs of airfoils have values of circulation and peak vorticity under those values found for vortices shed from isolated airfoils of the same geometry. Conversely, counter-rotating vortices show enhanced values of circulation and peak vorticity when compared to values
Positrons for linear colliders
Ecklund, S.
1987-11-01
The requirements of a positron source for a linear collider are briefly reviewed, followed by methods of positron production and production of photons by electromagnetic cascade showers. Cross sections for the electromagnetic cascade shower processes of positron-electron pair production and Compton scattering are compared. A program used for Monte Carlo analysis of electromagnetic cascades is briefly discussed, and positron distributions obtained from several runs of the program are discussed. Photons from synchrotron radiation and from channeling are also mentioned briefly, as well as positron collection, transverse focusing techniques, and longitudinal capture. Computer ray tracing is then briefly discussed, followed by space-charge effects and thermal heating and stress due to showers. (LEW)
Collider Signal I :. Resonance
NASA Astrophysics Data System (ADS)
Tait, Tim M. P.
2010-08-01
These TASI lectures were part of the summer school in 2008 and cover the collider signal associated with resonances in models of physics beyond the Standard Model. I begin with a review of the Z boson, one of the best-studied resonances in particle physics, and review how the Breit-Wigner form of the propagator emerges in perturbation theory and discuss the narrow width approximation. I review how the LEP and SLAC experiments could use the kinematics of Z events to learn about fermion couplings to the Z. I then make a brief survey of models of physics beyond the Standard Model which predict resonances, and discuss some of the LHC observables which we can use to discover and identify the nature of the BSM physics. I finish up with a discussion of the linear moose that one can use for an effective theory description of a massive color octet vector particle.
NASA Astrophysics Data System (ADS)
Mimasu, Ken; Sanz, Verónica
2015-06-01
New pseudo-scalars, often called axion-like particles (ALPs), abound in model-building and are often associated with the breaking of a new symmetry. Traditional searches and indirect bounds are limited to light axions, typically in or below the KeV range for ALPs coupled to photons. We present collider bounds on ALPs from mono-γ, tri-γ and mono-jet searches in a model independent fashion, as well as the prospects for the LHC and future machines. We find that they are complementary to existing searches, as they are sensitive to heavier ALPs and have the capability to cover an otherwise inaccessible region of parameter space. We also show that, assuming certain model dependent correlations between the ALP coupling to photons and gluons as well as considering the validity of the effective description of ALP interactions, mono-jet searches are in fact more suitable and effective in indirectly constraining ALP scenarios.
Alexahin, Y.; /Fermilab
2010-09-01
Muon Collider (MC) - proposed by G.I. Budker and A.N. Skrinsky a few decades ago - is now considered as the most exciting option for the energy frontier machine in the post-LHC era. A national Muon Accelerator Program (MAP) is being formed in the USA with the ultimate goal of building a MC at the Fermilab site with c.o.m. energy in the range 1.5-3 TeV and luminosity of {approx} 1.5 {center_dot} 10{sup 34} cm{sup -2} s{sup -1}. As the first step on the way to MC it envisages construction of a Neutrino Factory (NF) for high-precision neutrino experiments. The baseline scheme of the NF-MC complex is presented and possible options for its main components are discussed.
NASA Astrophysics Data System (ADS)
Mora, E. Y.; Sarmiento, A.; Vera, E.
2016-02-01
In this work was studied the CO2 carbon dioxide treatment, which is a pollutant gas and the main cause of global warming. For this aim, plasma was generated, through dielectric barrier discharges DBD, using hydrogen H2 together with the CO2 as reaction gases. There were used as dielectrics, alumina and quartz tubes of identical geometry. It was studied the CO2 conversion in function of mixture composition CO2+H2, of the electrical power and the operation frequency, for three different gas flows. In all cases it was achieved better conversion levels with the alumina; this is because the alumina has a relative dielectric permittivity coefficient higher than the quartz. As products of CO2 conversion in the chemical reactions, water H2O and methane gas CH4 were identified. The CO2 conversion percentage to fixed work conditions was higher with the decrease the quantity of this gas in the mixture, with increase the active electrical power, and with decrease the operation electrical frequency.
In-Flight Infrared Measurements for Quantification of Transition Delay with DBD Plasma Actuators
NASA Astrophysics Data System (ADS)
Simon, Bernhard; Grundmann, Sven
2014-11-01
Active flow control with a single DBD plasma actuator is performed in flight on wing of a motorized in order to delay laminar-turbulent transition at Rec = 3 .106 . While earlier experiments measured transition delay with point wise sensors such as microphones or surface hot wires, these dynamic sensors are now simultaneously applied with the infrared measurement technique. This allows a more accurate spatial quantification of the flow control impact. The miniature high resolution IR camera is mounted below the wing as the experiments are conducted on the pressure side. Two control strategies, boundary layer stabilization and active wave cancelation of Tollmien Schlichting (TS) waves, are performed in flight experiments, showing significant advantages of the IR measurement technique. Spanwise and streamwise effects on the transition delay are measured and evaluated with novel post processing strategies. This allows a detailed view on the correlation of TS wave damping and transition delay for different plasma actuator operation modes and flight conditions. This project is founded by the German Research Foundation DFG (GR 3524/4-1).
An experimental study of atmospheric pressure dielectric barrier discharge (DBD) in argon
Subedi, D. P.; Tyata, R. B.; Shrestha, R.; Wong, C. S.
2014-03-05
In this paper, experimental results on atmospheric pressure argon dielectric barrier discharge (DBD) have been presented. The discharge was generated using a high voltage (0 to 20 kV) power supply operating at frequency of 10 to 30 kHz and was studied by means of electrical and optical measurements. A homogeneous and steady discharge was observed between the electrodes with gap spacing from 1 mm to 3 mm and with a dielectric barrier of thickness 1.5 mm while argon gas is fed at a controlled flow rate of 2liter per min. The electron temperature (T{sub e}) and electron density (n{sub e}) of the plasma have been determined by means of optical emission spectroscopy. Our results show that the electron density is of the order of 10{sup 16} cm{sup −3} while the electron temperature is estimated to be ∼ 1 eV. The homogeneity and non-thermal nature of the discharge were utilized in the investigation of the change in wettabilty of a polymer sample subjected to the treatment by the discharge. Contact angle analysis showed that the discharge was effective in improving the wettability of low density Polyethylene (LDPE) polymer sample after the treatment.
Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators
NASA Technical Reports Server (NTRS)
Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.
2012-01-01
The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.
Jiang, Liying; Zhu, Runye; Mao, Yubo; Chen, Jianmeng; Zhang, Liang
2015-01-01
The combination of chemical oxidation methods with biotechnology to removal recalcitrant VOCs is a promising technology. In this paper, the aim was to identify the role of key process parameters and biodegradability of the degradation products using a dielectric barrier discharge (DBD) reactor, which provided the fundamental data to evaluate the possibilities of the combined system. Effects of various technologic parameters like initial concentration of mixtures, residence time and relative humidity on the decomposition and the degradation products were examined and discussed. It was found that the removal efficiency of mixed VOCs decreased with increasing initial concentration. The removal efficiency reached the maximum value as relative humidity was approximately 40%–60%. Increasing the residence time resulted in increasing the removal efficiency and the order of destruction efficiency of VOCs followed the order styrene > o-xylene. Compared with the single compounds, the removal efficiency of styrene and o-xylene in the mixtures of VOCs decreased significantly and o-xylene decreased more rapidly. The degradation products were analyzed by gas chromatography and gas chromatography-mass spectrometry, and the main compounds detected were O3, COx and benzene ring derivatives. The biodegradability of mixed VOCs was improved and the products had positive effect on biomass during plasma application, and furthermore typical results indicated that the biodegradability and biotoxicity of gaseous pollutant were quite depending on the specific input energy (SIE). PMID:25629961
NASA Astrophysics Data System (ADS)
Coulombe, Sylvain; Diaz Gomez Maqueo, Pablo; Evans, Mathew; Sainct, Florent; Bergthorson, Jeff
2015-09-01
This contribution discusses the development and characteristics of a coaxial dielectric barrier discharge (DBD) using a methane-oxygen mixture at atmospheric conditions of temperature and pressure. A sinusoidal voltage waveform of 12 kVp-p at 20 kHz produces discharges in a 1.15 mm gap. Power is estimated using a Lissajous figure method while optical emission spectroscopy (OES) is used to estimate the rotational and vibrational temperatures of the gas. Obtained OES spectra are similar, differing mainly on the intensity of their CH and OH bands, tending towards a more intense OH band as oxygen availability increased. CH bands show the strongest emission intensities of which, CH(C-X) seems to be the most intense of all, followed by CH(A-X) and lastly by CH(B-X). The spectra of CH(A-X) and CH(C-X) were uploaded into a simulation software to estimate the plasma temperatures. For the CH(A-X) bands, a simulation with a Trot = 600 K and a Tvib = 6000 K matched the experimental spectra. In the case of the CH(C-X) band, a Trot = 800 K and a Tvib = 4000 K were determined. The vibrational temperatures are especially high, a result which is particularly important for the development of a plasma-catalysis reactor. The authors acknowledge the financial support provided by NSERC, FRQNT as well as McGill University through the McGill Engineering Doctoral Award program.
N-doped TiO2 Prepared by RF DBD Plasma
NASA Astrophysics Data System (ADS)
Sun, Zhi-Guang; Liu, Jing-Lin; Li, Xiao-Song; Zhai, Zhao-Jun; Zhu, Ai-Min; Laboratory of Plasma Physical Chemistry Team
2014-10-01
TiO2 is the most promising photocatalyst because of its chemical stable, nontoxic, low cost, high photocatalytic activity and other attractive properties. Anatase has the highest photocatalytic activity among the three crystal form of TiO2. However, the 3.2 eV bandgap of anatase TiO2 makes it can only utilize the ultraviolet part of solar spectrum. Nitrogen doping is an effective method to extend the absorption range of anatase to visible light. N-doped TiO2 preparation methods, such as heat treatment under NH3 flow, the hydrolytic precipitation and the sol-gel process, have been reported. In this work, preparation of N-doped TiO2 was explored by radio-frequency (RF) dielectric barrier discharge (DBD) plasma using Ar as discharge gas. TiCl4, O2 and N2 were used as Ti, O and N precursors, respectively. In addition, H2 was added to the plasma. X-ray photoelectron spectra (XPS) showed nitrogen was successfully doped into the as-prepared TiO2. Further investigations on structure, composition and optical property of the as-prepared TiO2 samples were conducted by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and UV-Vis absorption spectra techniques.
Jiang, Liying; Zhu, Runye; Mao, Yubo; Chen, Jianmeng; Zhang, Liang
2015-02-01
The combination of chemical oxidation methods with biotechnology to removal recalcitrant VOCs is a promising technology. In this paper, the aim was to identify the role of key process parameters and biodegradability of the degradation products using a dielectric barrier discharge (DBD) reactor, which provided the fundamental data to evaluate the possibilities of the combined system. Effects of various technologic parameters like initial concentration of mixtures, residence time and relative humidity on the decomposition and the degradation products were examined and discussed. It was found that the removal efficiency of mixed VOCs decreased with increasing initial concentration. The removal efficiency reached the maximum value as relative humidity was approximately 40%-60%. Increasing the residence time resulted in increasing the removal efficiency and the order of destruction efficiency of VOCs followed the order styrene > o-xylene. Compared with the single compounds, the removal efficiency of styrene and o-xylene in the mixtures of VOCs decreased significantly and o-xylene decreased more rapidly. The degradation products were analyzed by gas chromatography and gas chromatography-mass spectrometry, and the main compounds detected were O3, COx and benzene ring derivatives. The biodegradability of mixed VOCs was improved and the products had positive effect on biomass during plasma application, and furthermore typical results indicated that the biodegradability and biotoxicity of gaseous pollutant were quite depending on the specific input energy (SIE). PMID:25629961
Measurements of Supersonic Wing Tip Vortices
NASA Technical Reports Server (NTRS)
Smart, Michael K.; Kalkhoran, Iraj M.; Benston, James
1994-01-01
An experimental survey of supersonic wing tip vortices has been conducted at Mach 2.5 using small performed 2.25 chords down-stream of a semi-span rectangular wing at angle of attack of 5 and 10 degrees. The main objective of the experiments was to determine the Mach number, flow angularity and total pressure distribution in the core region of supersonic wing tip vortices. A secondary aim was to demonstrate the feasibility of using cone probes calibrated with a numerical flow solver to measure flow characteristics at supersonic speeds. Results showed that the numerically generated calibration curves can be used for 4-hole cone probes, but were not sufficiently accurate for conventional 5-hole probes due to nose bluntness effects. Combination of 4-hole cone probe measurements with independent pitot pressure measurements indicated a significant Mach number and total pressure deficit in the core regions of supersonic wing tip vortices, combined with an asymmetric 'Burger like' swirl distribution.
Vorticity, defects and correlations in active turbulence
Thampi, Sumesh P.; Golestanian, Ramin; Yeomans, Julia M.
2014-01-01
We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion constant, on the order parameter and flow fields. Defects and distortions in the director field act as sources of vorticity, and thus vorticity is strongly correlated to the director field. In particular, the characteristic length of decay of vorticity and order parameter correlations is controlled by the defect density. By contrast, the decay of velocity correlations is determined by a balance between activity and dissipation. We highlight the role of microscopic flow generation mechanisms in determining the flow patterns and characteristic scales of active turbulence and contrast the behaviour of extensile and contractile active nematics. PMID:25332382
Droplet Vorticity Alignment in Model Polymer Blends
NASA Astrophysics Data System (ADS)
Migler, Kalman
2000-03-01
The shear induced deformation of polymeric droplets in an immiscible polymeric matrix is studied using a transparent rotating plate-plate device. We consider the case where the viscosity ratio of the two phases is near unity, but the elasticity ratio of the droplet to the matrix is of order 10^2. This is achieved by using a matrix of PDMS and a droplet of a PIB based Boger fluid. In the limit of weak shear and small droplets, the droplet alignment is along the shear direction, whereas for strong shear and large droplets, the alignment is along the vorticity direction. There is a range of conditions for which alignment can be along either axis. For droplets aligned along the vorticity axis, the distribution of aspect ratios is broad. The transformation from flow alignment to vorticity alignment upon commencement of shear flow has been observed and correlates with the time scale for development of normal forces in the Boger fluid.
Possible dust devils - Vortices on Mars
NASA Technical Reports Server (NTRS)
Ryan, J. A.; Lucich, R. D.
1983-01-01
This paper presents the results of a study of local vortices, and dust devils, on Mars as observed by Viking Landers 1 and 2. It is found that these vortices are most common during Martian spring and summer, as occurs on earth. Seven of the vortices involve wind speeds that may raise dust from the Martian surface. There is no indication that these possible dust devils contribute to the planet-wide spread of major dust storms. However, it appears that they may help in maintaining the atmospheric dust content. The data indicate that there is no preference in rotation direction, at least to core diameters of 300 m (corresponding to a region of influence of about 3 km diameter).
Vorticity and Divergence in the Solar Photosphere
NASA Astrophysics Data System (ADS)
Wang, Yi; Noyes, Robert W.; Tarbell, Theodore D.; Title, Alan M.
1995-07-01
We have studied an outstanding sequence of continuum images of the solar granulation from Pic du Midi Observatory. We have calculated the horizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar fields: the vertical component of the curl, the horizontal divergence, and the horizontal flow speed. The divergence field has substantially longer coherence time and more power than does the curl field. Statistically, curl is better correlated with regions of negative divergence that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranular lanes. The average value of the divergence is largest (i.e., outflow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general convection also shows similar statistical differences between curl and divergence. Some individual small bright points in the granulation pattern show large local vorticities.
A Note on Trapping Moving Vortices
NASA Technical Reports Server (NTRS)
Kao, Hsiao C.
2000-01-01
The topic of stationary configurations of point vortices, also known as vortex equilibrium, has received considerable attention in recent years. By observing numerical results, it is found that a "counterpart" of this system also exists, in which moving vortices may be "trapped" by an inlet-like device to form a stationary pattern with no translational motion. After an intuitive explanation for the process, vortex trajectory maps based on numerical results are presented. These maps exhibit two stationary points under the present conditions, which are the focal points of vortex trajectories. A vortex upstream of these points, if within a certain offset range, will move towards these points spontaneously and be captured there. This proposed device is also capable of trapping spinning vortex pairs and triads. It is possible to impose a uniform stream at infinity, as long as the flow field is still dominated by the moving vortices.
Moduli of Vortices and Grassmann Manifolds
NASA Astrophysics Data System (ADS)
Biswas, Indranil; Romão, Nuno M.
2013-05-01
We use the framework of Quot schemes to give a novel description of the moduli spaces of stable n-pairs, also interpreted as gauged vortices on a closed Riemann surface Σ with target {Mat_{r × n}({C})}, where n ≥ r. We then show that these moduli spaces embed canonically into certain Grassmann manifolds, and thus obtain natural Kähler metrics of Fubini-Study type. These spaces are smooth at least in the local case r = n. For abelian local vortices we prove that, if a certain "quantization" condition is satisfied, the embedding can be chosen in such a way that the induced Fubini-Study structure realizes the Kähler class of the usual L 2 metric of gauged vortices.
Vorticity and divergence in the solar photosphere
NASA Technical Reports Server (NTRS)
Wang, YI; Noyes, Robert W.; Tarbell, Theodore D.; Title, Alan M.
1995-01-01
We have studied an outstanding sequence of continuum images of the solar granulation from Pic du Midi Observatory. We have calculated the horizontal vector flow field using a correlation tracking algorithm, and from this determined three scalar field: the vertical component of the curl; the horizontal divergence; and the horizontal flow speed. The divergence field has substantially longer coherence time and more power than does the curl field. Statistically, curl is better correlated with regions of negative divergence - that is, the vertical vorticity is higher in downflow regions, suggesting excess vorticity in intergranular lanes. The average value of the divergence is largest (i.e., outflow is largest) where the horizontal speed is large; we associate these regions with exploding granules. A numerical simulation of general convection also shows similar statistical differences between curl and divergence. Some individual small bright points in the granulation pattern show large local vorticities.
Identification of vortices in complex flows
NASA Astrophysics Data System (ADS)
Chakraborty, P.; Balachandar, S.; Adrian, R. J.
2007-12-01
Dating back to Leonardo da Vinci's famous sketches of vortices in turbulent flows, fluid dynamicists for over five centuries have continued to visualize and interpret complex flows in terms of motion of vortices. Nevertheless, much debate surrounds the question of how to unambiguously define vortices in complex flows. This debate has resulted in the availability of many vortex identification criteria---mathematical statements of what constitutes a vortex. Here we review the popularly used local or point- wise vortex identification criteria. Based on local flow kinematics, we describe a unified framework to interpret the similarities and differences in the usage of these criteria. We discuss the limitations on the applicability of these criteria when there is a significant component of vortex interactions. Finally, we provide guidelines for applying these criteria to geophysical flows.
Characterization of reconnecting vortices in superfluid helium
Bewley, Gregory P.; Paoletti, Matthew S.; Sreenivasan, Katepalli R.; Lathrop, Daniel P.
2008-01-01
When two vortices cross, each of them breaks into two parts and exchanges part of itself for part of the other. This process, called vortex reconnection, occurs in classical and superfluids, and in magnetized plasmas and superconductors. We present the first experimental observations of reconnection between quantized vortices in superfluid helium. We do so by imaging micrometer-sized solid hydrogen particles trapped on quantized vortex cores and by inferring the occurrence of reconnection from the motions of groups of recoiling particles. We show that the distance separating particles on the just-reconnected vortex lines grows as a power law in time. The average value of the scaling exponent is approximately ½, consistent with the self-similar evolution of the vortices. PMID:18768790
Quantum-beamsstrahlung laser collider
Tajima, T.; Chattopadyay, S.; Xie, M.
1997-11-01
An e{sup +}e{sup {minus}} linear collider at energies beyond a TeV runs into a problem of severe beamsstrahlung, characterized by {Upsilon} on the order of unity (and beyond). In the regime of extremely high {Upsilon} the beamsstrahlung may be largely suppressed due to the quantum effect. In the design of an e{sup +}e{sup {minus}} collider there are two ways to satisfy the collider physics constraints. One is to decrease the number of particles per bunch (and thus to increase the repetition rate) and the other is to decrease the longitudinal bunch length. The former approach can limit {Upsilon}, while the latter boosts it. (It may be useful to reevaluate the future collider parameters in view of this.) The laser wakefield driver for a collider in comparison with the microwave driver naturally offers a very short bunch length, which is appropriate for the latter collider option. The authors show that this choice of collider design with a short bunch length and high {Upsilon} has advantages and provide sample design parameters at 5 TeV. Such sample design parameters challenge them in a number of fronts, such as the preservation of high quality bunches, efficient high repetition rate lasers, etc. The collision point physics simulated by the CAIN code shows a surprisingly well preserved luminosity spectrum.
Aerodynamics and vortical structures in hovering fruitflies
NASA Astrophysics Data System (ADS)
Meng, Xue Guang; Sun, Mao
2015-03-01
We measure the wing kinematics and morphological parameters of seven freely hovering fruitflies and numerically compute the flows of the flapping wings. The computed mean lift approximately equals to the measured weight and the mean horizontal force is approximately zero, validating the computational model. Because of the very small relative velocity of the wing, the mean lift coefficient required to support the weight is rather large, around 1.8, and the Reynolds number of the wing is low, around 100. How such a large lift is produced at such a low Reynolds number is explained by combining the wing motion data, the computed vortical structures, and the theory of vorticity dynamics. It has been shown that two unsteady mechanisms are responsible for the high lift. One is referred as to "fast pitching-up rotation": at the start of an up- or downstroke when the wing has very small speed, it fast pitches down to a small angle of attack, and then, when its speed is higher, it fast pitches up to the angle it normally uses. When the wing pitches up while moving forward, large vorticity is produced and sheds at the trailing edge, and vorticity of opposite sign is produced near the leading edge and on the upper surface, resulting in a large time rate of change of the first moment of vorticity (or fluid impulse), hence a large aerodynamic force. The other is the well known "delayed stall" mechanism: in the mid-portion of the up- or downstroke the wing moves at large angle of attack (about 45 deg) and the leading-edge-vortex (LEV) moves with the wing; thus, the vortex ring, formed by the LEV, the tip vortices, and the starting vortex, expands in size continuously, producing a large time rate of change of fluid impulse or a large aerodynamic force.
Martian polar vortices: Comparison of reanalyses
NASA Astrophysics Data System (ADS)
Waugh, D. W.; Toigo, A. D.; Guzewich, S. D.; Greybush, S. J.; Wilson, R. J.; Montabone, L.
2016-09-01
The structure and evolution of the Martian polar vortices is examined using two recently available reanalysis systems: version 1.0 of the Mars Analysis Correction Data Assimilation (MACDA) and a preliminary version of the Ensemble Mars Atmosphere Reanalysis System (EMARS). There is quantitative agreement between the reanalyses in the lower atmosphere, where Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data are assimilated, but there are differences at higher altitudes reflecting differences in the free-running general circulation model simulations used in the two reanalyses. The reanalyses show similar potential vorticity (PV) structure of the vortices: There is near-uniform small PV equatorward of the core of the westerly jet, steep meridional PV gradients on the polar side of the jet core, and a maximum of PV located off of the pole. In maps of 30 sol mean PV, there is a near-continuous elliptical ring of high PV with roughly constant shape and longitudinal orientation from fall to spring. However, the shape and orientation of the vortex varies on daily time scales, and there is not a continuous ring of PV but rather a series of smaller scale coherent regions of high PV. The PV structure of the Martian polar vortices is, as has been reported before, very different from that of Earth's stratospheric polar vortices, but there are similarities with Earth's tropospheric vortices which also occur at the edge of the Hadley Cell, and have near-uniform small PV equatorward of the jet, and a large increase of PV poleward of the jet due to increased stratification.
Up-sliding Slantwise Vorticity Development and the complete vorticity equation with mass forcing
NASA Astrophysics Data System (ADS)
Cui, Xiaopeng; Gao, Shouting; Wu, Guoxiong
2003-09-01
The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development (USVD) is proposed based on the theory of Slantwise Vorticity Development (SVD). When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity will develop, and the steeper the isentropic surface is, the more violent the development will be. From the definition of MPV and the MPV equation produced here in, a complete vorticity equation is then put forward with mass forcing, which explicitly includes the effects of both internal forcings, such as variations of stability, baroclinicity, and vertical shear of horizontal wind, and external forcings, such as diabatic heating, friction, and mass forcing. When isentropic surfaces are flat, the complete vorticity equation matches its traditional counterpart. The physical interpretations of some of the items which are included in the complete vorticity equation but not in the traditional one are studied with a simplified model of the Changjiang-Huaihe Meiyu front. A 60-h simulation is then performed to reproduce a torrential rain event in the Changjiang-Huaihe region and the output of the model is studied qualitatively based on the theory of USVD. The result shows that the conditions of the theory of USVD are easily satisfied immediately in front of mesoscale rainstorms in the downwind direction, that is, the theory of USVD is important to the development and movement of these kinds of systems.
Vorticity Confinement Applied to Turbulent Wing Tip Vortices for Wake-Integral Drag Prediction
NASA Astrophysics Data System (ADS)
Pierson, Kristopher; Povitsky, Alex
2013-11-01
In the current study the vorticity confinement (VC) approach was applied to tip vortices shed by edges of stationary wings in order to predict induced drag by far-field integration in Trefftz plane. The VC parameter was evaluated first by application to convection of vortices in 2-D uniform flow and then to tip vortices shed in 3-D simulation of finite-aspect ratio rectangular wing in subsonic flight. Dependence of VC parameter on the flight Mach number and the angle of attack was evaluated. The aerodynamic drag results with application of VC to prevent numerical diffusion are much closer to analytic lifting line theory compared to integration over surface of wing while the viscous profile drag is more accurately evaluated by surface integration. To apply VC to viscous and turbulent flows, it is shown that VC does not affect the physical rate of dissipation of vortices in viscous/turbulent flows at time scales corresponding to convection of vortices from the wing to Trefftz plane of integration. To account for turbulent effects on tip vortices, VC was applied in combination with Spalart-Allmaras, k- ɛ, and six Reynolds stresses models of turbulence. The results are compared to experiments to validate the physical dissipation of tip vortex. This research was supported by The Dayton Area Graduate Studies Institute (DAGSI) and US Air Force Research Laboratory (AFRL) grants in 2009-2013, US Army Research Office (ARO) in 2012-2013 and ASEE/AFRL summer faculty grant.
Lattices of quantized vortices in polariton superfluids
NASA Astrophysics Data System (ADS)
Boulier, Thomas; Cancellieri, Emiliano; Sangouard, Nicolas D.; Hivet, Romain; Glorieux, Quentin; Giacobino, Élisabeth; Bramati, Alberto
2016-10-01
In this review, we will focus on the description of the recent studies conducted in the quest for the observation of lattices of quantized vortices in resonantly injected polariton superfluids. In particular, we will show how the implementation of optical traps for polaritons allows for the realization of vortex-antivortex lattices in confined geometries and how the development of a flexible method to inject a controlled orbital angular momentum (OAM) in such systems results in the observation of patterns of same-sign vortices.
Noise from two-dimensional vortices
NASA Technical Reports Server (NTRS)
Sanders, N. D.; Stockman, N. O.
1972-01-01
The fluctuating flow in an idealized model of a turbulent shear layer composed of many discrete vortices is analyzed. Computer solutions reveal irregular motions which are similar in many respects to observed flows in turbulent three-dimensional layers. The model is further simplified to a pair of equal co-rotating vortices and the noise generation is analyzed in terms of equivalent quadrupole oscillations. Results of the analysis in a uniform medium are consistent with Lighthill's results. New results are obtained for the effects of mean velocity gradients, compressibility, temperature inhomogenities, and gradients of the mean Mach number.
Spatially-partitioned many-body vortices
NASA Astrophysics Data System (ADS)
Klaiman, S.; Alon, O. E.
2016-02-01
A vortex in Bose-Einstein condensates is a localized object which looks much like a tiny tornado storm. It is well described by mean-field theory. In the present work we go beyond the current paradigm and introduce many-body vortices. These are made of spatially- partitioned clouds, carry definite total angular momentum, and are fragmented rather than condensed objects which can only be described beyond mean-field theory. A phase diagram based on a mean-field model assists in predicting the parameters where many-body vortices occur. Implications are briefly discussed.
Vortices and the related principles of hydrodynamics
NASA Technical Reports Server (NTRS)
Betz, A
1921-01-01
Here, conceptions concerning vortices are illustrated by the simplest possible examples. Mathematical formulas and similar means of presentation, which, for the most part, do not help the understanding of persons not versed therein, have been avoided as much as possible. Instead, the author has endeavored to demonstrate the phenomena by means of simple geometrical and mechanical illustrations. For the sake of clarity, the author chiefly considers currents in one plane only, a situation that can be readily represented by diagrams. Some of the peculiarities of vortices in three dimensional flow are briefly discussed.
Linear phase distribution of acoustical vortices
Gao, Lu; Zheng, Haixiang; Ma, Qingyu; Tu, Juan; Zhang, Dong
2014-07-14
Linear phase distribution of phase-coded acoustical vortices was theoretically investigated based on the radiation theory of point source, and then confirmed by experimental measurements. With the proposed criterion of positive phase slope, the possibility of constructing linear circular phase distributions is demonstrated to be determined by source parameters. Improved phase linearity can be achieved at larger source number, lower frequency, smaller vortex radius, and/or longer axial distance. Good agreements are observed between numerical simulations and measurement results for circular phase distributions. The favorable results confirm the feasibility of precise phase control for acoustical vortices and suggest potential applications in particle manipulation.
Hadron collider physics at UCR
Kernan, A.; Shen, B.C.
1997-07-01
This paper describes the research work in high energy physics by the group at the University of California, Riverside. Work has been divided between hadron collider physics and e{sup +}-e{sup {minus}} collider physics, and theoretical work. The hadron effort has been heavily involved in the startup activities of the D-Zero detector, commissioning and ongoing redesign. The lepton collider work has included work on TPC/2{gamma} at PEP and the OPAL detector at LEP, as well as efforts on hadron machines.
Vanilla technicolor at linear colliders
NASA Astrophysics Data System (ADS)
Frandsen, Mads T.; Järvinen, Matti; Sannino, Francesco
2011-08-01
We analyze the reach of linear colliders for models of dynamical electroweak symmetry breaking. We show that linear colliders can efficiently test the compositeness scale, identified with the mass of the new spin-one resonances, until the maximum energy in the center of mass of the colliding leptons. In particular we analyze the Drell-Yan processes involving spin-one intermediate heavy bosons decaying either leptonically or into two standard model gauge bosons. We also analyze the light Higgs production in association with a standard model gauge boson stemming also from an intermediate spin-one heavy vector.
NASA Technical Reports Server (NTRS)
Baker, John
2010-01-01
Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.
NASA Technical Reports Server (NTRS)
Ashpis, David E.; Laun, Matthew C.
2014-01-01
We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a large diameter, grounded, metal sleeve.
A factor involved in efficient breakdown of supersonic streamwise vortices
NASA Astrophysics Data System (ADS)
Hiejima, Toshihiko
2015-03-01
Spatially developing processes in supersonic streamwise vortices were numerically simulated at Mach number 5.0. The vortex evolution largely depended on the azimuthal vorticity thickness of the vortices, which governs the negative helicity profile. Large vorticity thickness greatly enhanced the centrifugal instability, with consequent development of perturbations with competing wavenumbers outside the vortex core. During the transition process, supersonic streamwise vortices could generate large-scale spiral structures and a number of hairpin like vortices. Remarkably, the transition caused a dramatic increase in the total fluctuation energy of hypersonic flows, because the negative helicity profile destabilizes the flows due to helicity instability. Unstable growth might also relate to the correlation length between the axial and azimuthal vorticities of the streamwise vortices. The knowledge gained in this study is important for realizing effective fuel-oxidizer mixing in supersonic combustion engines.
Evolution of a barotropic shear layer into elliptical vortices.
Guha, Anirban; Rahmani, Mona; Lawrence, Gregory A
2013-01-01
When a barotropic shear layer becomes unstable, it produces the well-known Kelvin-Helmholtz instability (KHI). The nonlinear manifestation of the KHI is usually in the form of spiral billows. However, a piecewise linear shear layer produces a different type of KHI characterized by elliptical vortices of constant vorticity connected via thin braids. Using direct numerical simulation and contour dynamics, we show that the interaction between two counterpropagating vorticity waves is solely responsible for this KHI formation. We investigate the oscillation of the vorticity wave amplitude, the rotation and nutation of the elliptical vortex, and straining of the braids. Our analysis also provides a possible explanation for the formation and evolution of elliptical vortices appearing in geophysical and astrophysical flows, e.g., meddies, stratospheric polar vortices, Jovian vortices, Neptune's Great Dark Spot, and coherent vortices in the wind belts of Uranus. PMID:23410439
Evolution of a barotropic shear layer into elliptical vortices.
Guha, Anirban; Rahmani, Mona; Lawrence, Gregory A
2013-01-01
When a barotropic shear layer becomes unstable, it produces the well-known Kelvin-Helmholtz instability (KHI). The nonlinear manifestation of the KHI is usually in the form of spiral billows. However, a piecewise linear shear layer produces a different type of KHI characterized by elliptical vortices of constant vorticity connected via thin braids. Using direct numerical simulation and contour dynamics, we show that the interaction between two counterpropagating vorticity waves is solely responsible for this KHI formation. We investigate the oscillation of the vorticity wave amplitude, the rotation and nutation of the elliptical vortex, and straining of the braids. Our analysis also provides a possible explanation for the formation and evolution of elliptical vortices appearing in geophysical and astrophysical flows, e.g., meddies, stratospheric polar vortices, Jovian vortices, Neptune's Great Dark Spot, and coherent vortices in the wind belts of Uranus.
Collider Physics an Experimental Introduction
NASA Astrophysics Data System (ADS)
Elvezio Pagliarone, Carmine
2011-04-01
This paper reviews shortly a small part of the contents of a set of lectures, presented at the XIV International School of Particles and Fields in Morelia, state of Michoacán, Mexico, during November 2010. The main goal of those lectures was to introduce students to some of the basic ideas and tools required for experimental and phenomenological analysis of collider data. In particular, after an introduction to the scientific motivations, that drives the construction of powerful accelerator complexes, and the need of reaching high center of mass energies and luminosities, some basic concept about collider particle detectors will be discussed. A status about the present running colliders and collider experiments as well as future plans and research and development is also given.
Beam collimation at hadron colliders
Nikolai V. Mokhov
2003-08-12
Operational and accidental beam losses in hadron colliders can have a serious impact on machine and detector performance, resulting in effects ranging from minor to catastrophic. Principles and realization are described for a reliable beam collimation system required to sustain favorable background conditions in the collider detectors, provide quench stability of superconducting magnets, minimize irradiation of accelerator equipment, maintain operational reliability over the life of the machine, and reduce the impact of radiation on personnel and the environment. Based on detailed Monte-Carlo simulations, such a system has been designed and incorporated in the Tevatron collider. Its performance, comparison to measurements and possible ways to further improve the collimation efficiency are described in detail. Specifics of the collimation systems designed for the SSC, LHC, VLHC, and HERA colliders are discussed.
Beam Rounders for Circular Colliders
A. Burov; S. Nagaitsev; Ya. Derbenev
2001-07-01
By means of linear optics, an arbitrary uncoupled beam can be locally transformed into a round (rotation-invariant) state and then back. This provides an efficient way to round beams in the interaction region of circular colliders.
Beam rounders for circular colliders
A. Burov and S. Nagaitsev
2002-12-10
By means of linear optics, an arbitrary uncoupled beam can be locally transformed into a round (rotation-invariant) state and then back. This provides an efficient way to round beams in the interaction region of circular colliders.
Physicists dream of supersized collider
NASA Astrophysics Data System (ADS)
Hao, Cindy
2015-12-01
Particle physicists in China are hopeful that the Chinese government will allocate 1 billion yuan (about £104m) to design what would be the world's largest particle accelerator - the Circular Electron Positron Collider (CEPC).
Polarized Electrons for Linear Colliders
NASA Astrophysics Data System (ADS)
Clendenin, J. E.; Brachmann, A.; Garwin, E. L.; Kirby, R. E.; Luh, D.-A.; Maruyama, T.; Prescott, C. Y.; Sheppard, J. C.; Turner, J.; Prepost, R.
2005-08-01
Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting RF structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a DC-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%.
Polarized Electrons for Linear Colliders
Clendenin, J.
2004-11-19
Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting rf structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a dc-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%.
Cyclones and attractive streaming generated by acoustical vortices.
Riaud, Antoine; Baudoin, Michael; Thomas, Jean-Louis; Bou Matar, Olivier
2014-07-01
Acoustical and optical vortices have attracted great interest due to their ability to capture and manipulate particles with the use of radiation pressure. Here we show that acoustical vortices can also induce axial vortical flow reminiscent of cyclones, whose topology can be controlled by adjusting the properties of the acoustical beam. In confined geometry, the phase singularity enables generating "attractive streaming" with the flow directed toward the transducer. This opens perspectives for contactless vortical flow control.
Crosswind Shear Gradient Affect on Wake Vortices
NASA Technical Reports Server (NTRS)
Proctor, Fred H.; Ahmad, Nashat N.
2011-01-01
Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.
Cosmological perturbations: Vorticity, isocurvature and magnetic fields
NASA Astrophysics Data System (ADS)
Christopherson, Adam J.
2014-10-01
In this paper, I review some recent, interlinked, work undertaken using cosmological perturbation theory — a powerful technique for modeling inhomogeneities in the universe. The common theme which underpins these pieces of work is the presence of nonadiabatic pressure, or entropy, perturbations. After a brief introduction covering the standard techniques of describing inhomogeneities in both Newtonian and relativistic cosmology, I discuss the generation of vorticity. As in classical fluid mechanics, vorticity is not present in linearized perturbation theory (unless included as an initial condition). Allowing for entropy perturbations, and working to second order in perturbation theory, I show that vorticity is generated, even in the absence of vector perturbations, by purely scalar perturbations, the source term being quadratic in the gradients of first order energy density and isocurvature, or nonadiabatic pressure perturbations. This generalizes Crocco's theorem to a cosmological setting. I then introduce isocurvature perturbations in different models, focusing on the entropy perturbation in standard, concordance cosmology, and in inflationary models involving two scalar fields. As the final topic, I investigate magnetic fields, which are a potential observational consequence of vorticity in the early universe. I briefly review some recent work on including magnetic fields in perturbation theory in a consistent way. I show, using solely analytical techniques, that magnetic fields can be generated by higher order perturbations, albeit too small to provide the entire primordial seed field, in agreement with some numerical studies. I close this paper with a summary and some potential extensions of this work.
Long Term Changes in the Polar Vortices
NASA Astrophysics Data System (ADS)
Braathen, Geir O.
2016-04-01
As the amount of halogens in the stratosphere is slowly declining and the ozone layer slowly recovers it is of interest to see how the meteorological conditions in the vortex develop over the long term since such changes might alter the foreseen ozone recovery. In conjunction with the publication of the WMO Antarctic and Arctic Ozone Bulletins, WMO has acquired the ERA Interim global reanalysis data set for several meteorological parameters. This data set goes from 1979 - present. These long time series of data can be used for several useful studies of the long term development of the polar vortices. Several "environmental indicators" for vortex change have been calculated, and a climatology, as well as trends, for these parameters will be presented. These indicators can act as yardsticks and will be useful for understanding past and future changes in the polar vortices and how these changes affect polar ozone depletion. Examples of indicators are: vortex mean temperature, vortex minimum temperature, vortex mean PV, vortex "importance" (PV*area), vortex break-up time, mean and maximum wind speed. Data for both the north and south polar vortices have been analysed at several isentropic levels from 350 to 850 K. A possible link between changes in PV and sudden stratospheric warmings will be investigated, and the results presented. The unusual meteorological conditions of the 2015 south polar vortex and the 2010/11 and 2015/16 north polar vortices will be compared to other recent years.
Physics at Future Circular Colliders
NASA Astrophysics Data System (ADS)
Kotwal, Ashutosh
2016-03-01
The Large Hadron Collider has been a grand success with the discovery of the Higgs boson, with bright prospects for additional discoveries since the recent increase in collider energy and the anticipated large datasets. Big open questions such as the nature of dark matter, the origin of the matter-antimatter asymmetry in the Universe, and the theoretical puzzle of the finely-tuned parameters in the Higgs sector, demand new physics principles that extend the established Standard Model paradigm. Future circular colliders in a substantially larger tunnel can house both a high luminosity electron-positron collider for precision measurements of Higgs and electroweak parameters, as well as a very high energy proton-proton collider which can directly manifest particles associated with these new physics principles. We discuss the physics goals of these future circular colliders, and the prospects for elucidating fundamental new laws of nature that will significantly extend our understanding of the Universe. Detailed studies of the discovery potential in specific benchmark models will be presented, with implications for detector design.
Muon muon collider: Feasibility study
1996-06-18
A feasibility study is presented of a 2 + 2 TeV muon collider with a luminosity of L = 10{sup 35} cm{sup {minus}2} s{sup {minus}1}. The resulting design is not optimized for performance, and certainly not for cost; however, it does suffice--the authors believe--to allow them to make a credible case, that a muon collider is a serious possibility for particle physics and, therefore, worthy of R and D support so that the reality of, and interest in, a muon collider can be better assayed. The goal of this support would be to completely assess the physics potential and to evaluate the cost and development of the necessary technology. The muon collider complex consists of components which first produce copious pions, then capture the pions and the resulting muons from their decay; this is followed by an ionization cooling channel to reduce the longitudinal and transverse emittance of the muon beam. The next stage is to accelerate the muons and, finally, inject them into a collider ring which has a small beta function at the colliding point. This is the first attempt at a point design and it will require further study and optimization. Experimental work will be needed to verify the validity of diverse crucial elements in the design.
Controlled Manipulation of Individual Vortices in a Superconductor
Straver, E.W.J.
2010-04-05
We report controlled local manipulation of single vortices by low temperature magnetic force microscope (MFM) in a thin film of superconducting Nb. We are able to position the vortices in arbitrary configurations and to measure the distribution of local depinning forces. This technique opens up new possibilities for the characterization and use of vortices in superconductors.
An eddy closure for potential vorticity
Ringler, Todd D
2009-01-01
The Gent-McWilliams (GM) parameterization is extended to include a direct influence in the momentum equation. The extension is carried out in two stages; an analysis of the inviscid system is followed by an analysis of the viscous system. In the inviscid analysis the momentum equation is modified such that potential vorticity is conserved along particle trajectories following a transport velocity that includes the Bolus velocity in a manner exactly analogous to the continuity and tracer equations. In addition (and in contrast to traditional GM closures), the new formulation of the inviscid momentum equation results in a conservative exchange between potential and kinetic forms of energy. The inviscid form of the eddy closure conserves total energy to within an error proportional to the time derivative of the Bolus velocity. The hypothesis that the viscous term in the momentum equation should give rise to potential vorticity being diffused along isopycnals in a manner analogous to other tracers is examined in detail. While the form of the momentum closure that follows from a strict adherence to this hypothesis is not immediately interpretable within the constructs of traditional momentum closures, three approximations to this hypothesis results in a form of dissipation that is consistent with traditional Laplacian diffusion. The first two approximations are that relative vorticity, not potential vorticity, is diffused along isopyncals and that the flow is in approximate geostrophic balance. An additional approximation to the Jacobian term is required when the dissipation coefficient varies in space. More importantly, the critique of this hypothesis results in the conclusion that the viscosity parameter in the momentum equation should be identical to the tradition GM closure parameter {Kappa}. Overall, we deem the viscous form of the eddy closure for potential vorticity as a viable closure for use in ocean circulation models.
Bilinear relative equilibria of identical point vortices
NASA Astrophysics Data System (ADS)
Aref, Hassan; Beelen, Peter; Brøns, Morten
2011-11-01
A new class of bilinear relative equilibria of identical point vortices in which the vortices are constrained to be on two perpendicular lines, taken to be the x- and y-axes of a cartesian coordinate system, is introduced and studied. In general we have m vortices on the y-axis and n on the x- axis. We define generating polynomials q (z) and p (z) , respectively, for each set of vortices. A second order, linear ODE for p (z) given q (z) is derived. Several results relating the general solution of the ODE to relative equilibrium configurations are established. Our strongest result, obtained using Sturm's comparison theorem, is that if p (z) satisfies the ODE for a given q (z) with its imaginary zeros symmetric relative to the x-axis, then it must have at least n - m + 2 simple, real zeros. For m = 2 this provides a complete characterization of all zeros, and we study this case in some detail. In particular, we show that given q (z) =z2 +η2 , where η is real, there is a unique p (z) of degree n, and a unique value of η2 =An , such that the zeros of q (z) and p (z) form a relative equilibrium of n + 2 point vortices. We show that An ~2/3 n +1/2 , as n --> ∞ , where the coefficient of n is determined analytically, the next order term numerically. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.
Prometheus Induced Vorticity in Saturn's F Ring
NASA Astrophysics Data System (ADS)
Sutton, Phil J.; Kusmartsev, Feo V.
2016-09-01
Saturn's rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non-zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of great interest to planet and planetesimals in proto-planetary disks where vortices and turbulence are suspected of having a significant role in their formation and migrations. Additionally, it is found that the immediate channel edges created by the close passage of Prometheus actually show high radial dispersions in the order ~20-50 cm/s, up to a maximum of 1 m/s. This is much greater than the value required by Toomre for a disk to be unstable to the growth of axisymmetric oscillations. However, an area a few hundred km away from the edge shows a more promising location for the growth of coherent objects.
A Photon Collider Experiment based on SLC
Gronberg, J
2003-11-01
Technology for a photon collider experiment at a future TeV-scale linear collider has been under development for many years. The laser and optics technology has reached the point where a GeV-scale photon collider experiment is now feasible. We report on the photon-photon luminosities that would be achievable at a photon collider experiment based on a refurbished Stanford Linear Collider.
Water Content Effect on Oxides Yield in Gas and Liquid Phase Using DBD Arrays in Mist Spray
NASA Astrophysics Data System (ADS)
Chen, Bingyan; Zhu, Changping; Fei, Juntao; He, Xiang; Yin, Cheng; Wang, Yuan; Jiang, Yongfeng; Chen, Longwei; Gao, Yuan; Han, Qingbang
2016-01-01
Electric discharge in and in contact with water can accompany ultraviolet (UV) radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals (OH), oxygen radical (O), ozone (O3) and hydrogen peroxide (H2O2). In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge (DBD) arrays in water mist spray. The relationship between droplet size and water content was examined, and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O3 and nitrogen dioxide (NO2) in DBD room decreased with increasing water content. Moreover, the concentrations of H2O2, O3 and nitrogen oxides (NOx) in treated water decreased with increasing water content, and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last, the water containing phenol was tested in this system for the concentration from 100 mg/L to 9.8 mg/L in a period of 35 min. supported by National Natural Science Foundation of China (Nos. 11274092, 51107033, 11404092, 11274091), the Nantong Science and Technology Project, China (No. BK2014024), the Open Project of Jiangsu Province Key Laboratory of Environmental Engineering, China (No. KF2014001), and the Fundamental Research Funds for the Central Universities, China (No. 2014B11414)
Ji, Sang-Hye; Choi, Ki-Hong; Pengkit, Anchalee; Im, Jun Sup; Kim, Ju Sung; Kim, Yong Hee; Park, Yeunsoo; Hong, Eun Jeong; Jung, Sun Kyung; Choi, Eun-Ha; Park, Gyungsoon
2016-09-01
In this study, we analyzed seed germination, seedling growth, and physiological aspects after treatment with high voltage nanosecond pulsed plasma and micro DBD plasma in spinach (Spinacia oleracea L.), a green leafy vegetable known to have low germination rate. Both germination and dry weight of seedlings increased after high voltage pulse shots were applied to spinach seeds. However seeds treated with many shots (10 shots) showed a decrease in germination rate and seedling growth. Seeds treated with air DBD plasma exhibited slightly higher germination and subsequent seedling growth than those treated with N2 plasma. Seed surface was degenerated after treated with high voltage pulsed plasma and micro DBD plasma but no significant difference in the degree of degeneration was observed among micro DBD plasma treatment time. Level of GA3 hormone and mRNA expression of an amylolytic enzyme-related gene in seeds were elevated 1 day after treatment with high voltage pulsed plasma. The relative amount of chlorophyll and total polyphenols in spinach seedlings grown from seeds treated with air DBD plasma was increased in 30 s, 1 min, and 3 min treatments. Taken together, our results suggest a possibility that plasma can enhance seed germination by triggering biochemical processes in seeds. PMID:26944552
Ji, Sang-Hye; Choi, Ki-Hong; Pengkit, Anchalee; Im, Jun Sup; Kim, Ju Sung; Kim, Yong Hee; Park, Yeunsoo; Hong, Eun Jeong; Jung, Sun Kyung; Choi, Eun-Ha; Park, Gyungsoon
2016-09-01
In this study, we analyzed seed germination, seedling growth, and physiological aspects after treatment with high voltage nanosecond pulsed plasma and micro DBD plasma in spinach (Spinacia oleracea L.), a green leafy vegetable known to have low germination rate. Both germination and dry weight of seedlings increased after high voltage pulse shots were applied to spinach seeds. However seeds treated with many shots (10 shots) showed a decrease in germination rate and seedling growth. Seeds treated with air DBD plasma exhibited slightly higher germination and subsequent seedling growth than those treated with N2 plasma. Seed surface was degenerated after treated with high voltage pulsed plasma and micro DBD plasma but no significant difference in the degree of degeneration was observed among micro DBD plasma treatment time. Level of GA3 hormone and mRNA expression of an amylolytic enzyme-related gene in seeds were elevated 1 day after treatment with high voltage pulsed plasma. The relative amount of chlorophyll and total polyphenols in spinach seedlings grown from seeds treated with air DBD plasma was increased in 30 s, 1 min, and 3 min treatments. Taken together, our results suggest a possibility that plasma can enhance seed germination by triggering biochemical processes in seeds.
Measuring vortical flows in the solar interior
NASA Astrophysics Data System (ADS)
Langfellner, Jan
2015-09-01
This thesis focuses on observations of the effects of rotation on solar convection at the length scales of supergranulation and larger (>30 Mm). Rotation drives vortical flows through the Coriolis force and causes anisotropic velocity correlations that are believed to influence the large-scale solar dynamics. We obtain horizontal flows using photospheric Doppler velocity and continuum intensity images from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) spacecraft via the techniques of time-distance helioseismology (TD) and local correlation tracking (LCT) of granules. In time-distance helioseismology, the local vertical vorticity can be measured by taking the difference between wave travel times measured in the anti-clockwise and clockwise directions along a closed contour. The agreement between the TD and LCT methods is excellent up to Â±60Â° latitude, provided that a center-to-limb correction is applied. Averaging over longitude, one finds that there is a small but significant correlation between the horizontal divergence and the vertical vorticity component of supergranular flows away from the solar equator. By comparison to a noise model, we find that the TD technique can be used to probe the vertical vorticity of flows on spatial scales larger than about 15 Mm, thus including supergranules and also giant cells. We also find that the vertical vorticity signal is much easier to measure using SDO/HMI observations than previous observations. The impact of the Sun's rotation on supergranulation is studied in detail by making spatial maps of the vertical vorticity of the flows associated with the average supergranule. The average supergranule is constructed by co-aligning thousands of individual supergranules in a given latitude band. For the first time, we are able to spatially resolve vorticity associated with inflows and outflow regions. In the northern hemisphere, outflows are on average associated with a clockwise
Chiral magnetic and vortical effects in high-energy nuclear collisions-A status report
NASA Astrophysics Data System (ADS)
Kharzeev, D. E.; Liao, J.; Voloshin, S. A.; Wang, G.
2016-05-01
The interplay of quantum anomalies with magnetic field and vorticity results in a variety of novel non-dissipative transport phenomena in systems with chiral fermions, including the quark-gluon plasma. Among them is the Chiral Magnetic Effect (CME)-the generation of electric current along an external magnetic field induced by chirality imbalance. Because the chirality imbalance is related to the global topology of gauge fields, the CME current is topologically protected and hence non-dissipative even in the presence of strong interactions. As a result, the CME and related quantum phenomena affect the hydrodynamical and transport behavior of strongly coupled quark-gluon plasma, and can be studied in relativistic heavy ion collisions where strong magnetic fields are created by the colliding ions. Evidence for the CME and related phenomena has been reported by the STAR Collaboration at Relativistic Heavy Ion Collider at BNL, and by the ALICE Collaboration at the Large Hadron Collider at CERN. The goal of the present review is to provide an elementary introduction into the physics of anomalous chiral effects, to describe the current status of experimental studies in heavy ion physics, and to outline the future work, both in experiment and theory, needed to eliminate the existing uncertainties in the interpretation of the data.
Vortical versus skyrmionic states in mesoscopic p -wave superconductors
NASA Astrophysics Data System (ADS)
Fernández Becerra, V.; Sardella, E.; Peeters, F. M.; Milošević, M. V.
2016-01-01
We investigate the superconducting states that arise as a consequence of mesoscopic confinement and a multicomponent order parameter in the Ginzburg-Landau model for p -wave superconductivity. Conventional vortices, but also half-quantum vortices and skyrmions, are found as the applied magnetic field and the anisotropy parameters of the Fermi surface are varied. The solutions are well differentiated by a topological charge that for skyrmions is given by the Hopf invariant and for vortices by the circulation of the superconducting velocity. We revealed several unique states combining vortices and skyrmions, their possible reconfiguration with varied magnetic field, as well as temporal and field-induced transitions between vortical and skyrmionic states.
Recovering the vorticity of a light beam after scattering
Salla, Gangi Reddy Perumangattu, Chithrabhanu; Anwar, Ali; Prabhakar, Shashi; Singh, Ravindra P.
2015-07-13
We generate optical vortices and scatter them through a rough surface. However, the scattered light passing through a lens shows the same vorticity when probed at the Fourier plane. The vorticity is measured using a nonseparable state of polarization and orbital angular momentum of light as it cannot be confirmed by the standard interferometric technique. The observed vorticity is found to be independent of the amount of scattered light collected. Therefore, vortices can be used as information carriers even in the presence of scattering media. The experimental results are well supported by the theoretical results.
Challenges in future linear colliders
Swapan Chattopadhyay; Kaoru Yokoya
2002-09-02
For decades, electron-positron colliders have been complementing proton-proton colliders. But the circular LEP, the largest e-e+ collider, represented an energy limit beyond which energy losses to synchrotron radiation necessitate moving to e-e+ linear colliders (LCs), thereby raising new challenges for accelerator builders. Japanese-American, German, and European collaborations have presented options for the Future Linear Collider (FLC). Key accelerator issues for any FLC option are the achievement of high enough energy and luminosity. Damping rings, taking advantage of the phenomenon of synchrotron radiation, have been developed as the means for decreasing beam size, which is crucial for ensuring a sufficiently high rate of particle-particle collisions. Related challenges are alignment and stability in an environment where even minute ground motion can disrupt performance, and the ability to monitor beam size. The technical challenges exist within a wider context of socioeconomic and political challenges, likely necessitating continued development of international collaboration among parties involved in accelerator-based physics.
Wilson, P.B.
1987-05-01
The next generation of linear collider after the SLC (Stanford Linear Collider) will probably have an energy in the range 300 GeV-1 TeV per linac. A number of exotic accelerating schemes, such as laser and plasma acceleration, have been proposed for linear colliders of the far future. However, the technology which is most mature and which could lead to a collider in the above energy range in the relatively near future is the rf-driven linac, in which externally produced rf is fed into a more or less conventional metallic accelerating structure. Two basic technologies have been proposed for producing the required high peak rf power: discrete microwave power sources, and various two-beam acceleration schemes in which the rf is produced by a high current driving beam running parallel to the main accelerator. The current status of experimental and analytic work on both the discrete source and the two-beam methods for producing rf is discussed. The implications of beam-beam related effects (luminosity, disruption and beamstrahlung) for the design of rf-driven colliders are also considered.
Intensity of vortices: from soap bubbles to hurricanes
Meuel, T.; Xiong, Y. L.; Fischer, P.; Bruneau, C. H.; Bessafi, M.; Kellay, H.
2013-01-01
By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones. PMID:24336410
Development and Interaction of Artificially Generated Hairpin Vortices
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; McKenna, Christopher
2012-11-01
The development and interaction of hairpin vortices are examined and categorized to better understand their role in fully turbulent boundary layers. Hairpin vortices are generated within an otherwise laminar boundary layer using a free surface water channel. Direct injection is the primary generation method and the behavior of the vortices is first examined using flow visualization. Hydrogen bubble wire is combined with dye injection to help clarify the role of the vorticity in the fluid immediately surrounding the hairpin vortex. PIV data is also used to classify the development and maturity of the vortices for a range of free stream and injection conditions. The interactions of two hairpin vortices of varying maturity are characterized to investigate the potential mechanisms for the formation of hairpin packets beyond autogeneration. Finally, the behavior of hairpin vortices generated with a new technique that uses a transient hemispherical protrusion is also examined. Supported by the National Science Foundation under Grant CBET-1040236.
Intensity of vortices: from soap bubbles to hurricanes.
Meuel, T; Xiong, Y L; Fischer, P; Bruneau, C H; Bessafi, M; Kellay, H
2013-01-01
By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones. PMID:24336410
Intensity of vortices: from soap bubbles to hurricanes.
Meuel, T; Xiong, Y L; Fischer, P; Bruneau, C H; Bessafi, M; Kellay, H
2013-01-01
By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones.
Emergent vortices in populations of colloidal rollers.
Bricard, Antoine; Caussin, Jean-Baptiste; Das, Debasish; Savoie, Charles; Chikkadi, Vijayakumar; Shitara, Kyohei; Chepizhko, Oleksandr; Peruani, Fernando; Saintillan, David; Bartolo, Denis
2015-01-01
Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and structure of this pattern remains lacking. Here we report the self-organization of motile colloids into a macroscopic steadily rotating vortex. Combining physical experiments and numerical simulations, we elucidate this collective behaviour. We demonstrate that the emergent-vortex structure lives on the verge of a phase separation, and single out the very constituents responsible for this state of polar active matter. Building on this observation, we establish a continuum theory and lay out a strong foundation for the description of vortical collective motion in a broad class of motile populations constrained by geometrical boundaries. PMID:26088835
Emergent vortices in populations of colloidal rollers
Bricard, Antoine; Caussin, Jean-Baptiste; Das, Debasish; Savoie, Charles; Chikkadi, Vijayakumar; Shitara, Kyohei; Chepizhko, Oleksandr; Peruani, Fernando; Saintillan, David; Bartolo, Denis
2015-01-01
Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and structure of this pattern remains lacking. Here we report the self-organization of motile colloids into a macroscopic steadily rotating vortex. Combining physical experiments and numerical simulations, we elucidate this collective behaviour. We demonstrate that the emergent-vortex structure lives on the verge of a phase separation, and single out the very constituents responsible for this state of polar active matter. Building on this observation, we establish a continuum theory and lay out a strong foundation for the description of vortical collective motion in a broad class of motile populations constrained by geometrical boundaries. PMID:26088835
Numerical prediction of flow in slender vortices
NASA Technical Reports Server (NTRS)
Reyna, Luis G.; Menne, Stefan
1988-01-01
The slender vortex approximation was investigated using the Navier-Stokes equations written in cylindrical coordinates. It is shown that, for free vortices without external pressure gradient, the breakdown length is proportional to the Reynolds number. For free vortices with adverse pressure gradients, the breakdown length is inversely proportional to the value of its gradient. For low Reynolds numbers, the predictions of the simplified system agreed well with the ones obtained from solutions of the full Navier-Stokes equations, whereas for high Reynolds numbers, the flow became quite sensitive to pressure fluctuations; it was found that the failure of the slender vortex equations corresponded to the critical condition as identified by Benjamin (1962) for inviscid flows. The predictions obtained from the approximating system were compared with available experimental results. For low swirl, a good agreement was obtained; for high swirl, on the other hand, upstream effects on the pressure gradient produced by the breakdown bubble caused poor agreement.
Dynamics and nucleation of vorticity in superfluids
NASA Astrophysics Data System (ADS)
Freire, Jose Arruda De Oliveira
1997-11-01
This thesis contains numerical studies on vortex dynamics and on quantum nucleation of vorticity in superfluids at zero temperature. In both cases the superfluid was described by the Gross-Pitaevskii model. In the first part of the thesis, the vortex mass problem is analyzed by a numerical integration of the condensate equation of motion, the nonlinear Schrodinger equation. We were able to extract, from the observed vortex dynamics in a time-dependent superflow, the frequency dependence of the vortex effective mass. In the second part, the problem of quantum nucleation of vorticity in superflows past obstacles, in both one and two dimensions, is studied by the application of the bounce formalism of Coleman (12) to the coherent state action of the Gross-Pitaevskii model. We obtained bounce solutions and tunneling rates by directly solving the field equations for the condensate in imaginary time.
Motion of vortices outside a cylinder
NASA Astrophysics Data System (ADS)
Tulu, Serdar; Yilmaz, Oguz
2010-12-01
The problem of motion of the vortices around an oscillating cylinder in the presence of a uniform flow is considered. The Hamiltonian for vortex motion for the case with no uniform flow and stationary cylinder is constructed, reduced, and constant Hamiltonian (energy) curves are plotted when the system is shown to be integrable according to Liouville. By adding uniform flow to the system and by allowing the cylinder to vibrate, we model the natural vibration of the cylinder in the flow field, which has applications in ocean engineering involving tethers or pipelines in a flow field. We conclude that in the chaotic case forces on the cylinder may be considerably larger than those on the integrable case depending on the initial positions of vortices and that complex phenomena such as chaotic capture and escape occur when the initial positions lie in a certain region.
Numerical Investigations of Reconnection of Quantized Vortices
NASA Astrophysics Data System (ADS)
Rorai, Cecilia; Fisher, Michael E.; Lathrop, Daniel P.; Sreenivasan, Katepalli R.; Kerr, Robert M.
2011-11-01
Reconnection of quantized vortices in superfluid helium was conjectured by Feynman in 1955, and first observed experimentally by Bewley et al. (PNAS 105, 13708, 2007). The nature of this phenomenon is quantum mechanical, involving atomically thin vortex cores. At the same time, this phenomenon influences the large scale dynamics, since a tangle of vortices can change topology through reconnection and evolve in time. Numerically, the Gross-Pitaevskii (GP) equation allows detailed predictions of vortex reconnection as first shown by Koplik and Levine (1993). We have undertaken further calculations to characterize the dynamics of isolated reconnection events. Initial conditions have been analyzed carefully, different geometries have been considered and a new approach has been proposed. This approach consists in using the diffusion equation associated to the GP equation to set minimum energy initial vortex profiles. The underlying questions we wish to answer are the universality of vortex reconnection and its effect on energy dissipation to the phonon field.
Shear-Layer Effects on Trailing Vortices
NASA Technical Reports Server (NTRS)
Zheng, Z. C.; Baek, K.
1998-01-01
Crosswind shear can influence the trailing vortex trajectories significantly, according to both field measurement and numerical simulations. Point vortex models are used in this paper to study the fluid dynamic mechanism in the interactions between trailing vortex pair and shear layers. It has been shown that the shear-layer deformation causes the vortex descent history difference in the two vortices of the vortex pair. When a shear layer is below the vortex pair with the same sign as the left vortex, the right vortex descends less than the left vortex. When the same shear layer is above the vortex pair, the right vortex descends more. The descent altitudes of the two vortices are the same when they go through a constant, non-deformed shear layer. Those trends are in agreement with Navier-Stokes simulations.
Electric generation of vortices in polariton superfluids
NASA Astrophysics Data System (ADS)
Flayac, H.; Pavlovic, G.; Kaliteevski, M. A.; Shelykh, I. A.
2012-02-01
We have theoretically demonstrated the on-demand electric generation of vortices in an exciton-polariton superfluid. Electric pulses applied to a horseshoe-shaped metallic mesa, deposited on top of the microcavity, generate a noncylindrically symmetric solitonic wave in the system. Breakdown of its wave front at focal points leads to the formation of vortex-antivortex pairs, which subsequently propagate in the superfluid. The trajectory of these vortex dipoles can be controlled by applying a voltage to additional electrodes. They can be confined within channels formed by metallic stripes and unbound by a wedged mesa giving birth to grey solitons. Finally, single static vortices can be generated using a single metallic plate configuration.
Control of boundary layer separation and the wake of an airfoil using ns-DBD plasma actuators
NASA Astrophysics Data System (ADS)
Ashcraft, Timothy
The efficacy of nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators for boundary layer separation and wake control is investigated experimentally. A single ns-DBD plasma actuator is placed at the leading edge of a NACA 0012 airfoil model. Both baseline and controlled flow fields are studied using static pressure measurements, Particle Image Velocimetry (PIV) and Constant Temperature Anemometry (CTA). Experiments are primarily performed at Re = 0.74 x 106 and alpha = 18°. CP, PIV and CTA data show that a forcing frequency of F+ = 1.14 is optimal for separation control. CTA surveys of the wake at x/c = 7 indicate three approximate regimes of behavior. Forcing in the range 0.92< F+ < 1.52 results in the best conditions for separation control over the airfoil, but has no dominant signature in the wake at x/c = 7. Excitation in the range of 0.23 < F+ < 0.92 produces a single dominant frequency in the wake while F+ < 0.23 shows behavior representing a possible impulse response or nonlinear effects. PIV data confirm these observations in all three regimes. Cross-correlations of CTA data are also employed to evaluate the two-dimensionality of the excited wake. The initial results presented here are part of an ongoing effort to use active flow control (AFC), in the form of ns-DBDs, as an enabling technology for the study of unsteady aerodynamics and vortex-body interactions.
NASA Astrophysics Data System (ADS)
Nozaki, Tomohiro; Tsukijihara, Hiroyuki; Fukui, Wataru; Okazaki, Ken
2006-10-01
Although huge amounts of biogas, which consists of 20-60% of CH4 in CO2/N2, can be obtained from landfills, coal mines, and agricultural residues, most of them are simply flared and wasted: because global warming potential of biogas is 5-15 times as potent as CO2. Poor combustibility of such biogas makes it difficult to utilize in conventional energy system. The purpose of this project is to promote the profitable recovery of methane from poor biogas via non-thermal plasma technology. We propose low-temperature steam reforming of biogas using DBD generated in catalyst beds. Methane is partially converted into hydrogen, and then fed into internal combustion engines for improved ignition stability as well as efficient operation. Low-temperature steam reforming is beneficial because exhaust gas from an engine can be used to activate catalyst beds. Space velocity (3600-15000 hr-1), reaction temperature (300-650^oC), and energy cost (30-150 kJ per mol CH4) have been investigated with simulated biogas (20-60% CH4 in mixtures of CO2/N2). The DBD enhances reaction rate of CH4 by a factor of ten at given catalyst temperatures, which is a rate-determining step of methane steam reforming, while species concentration of upgraded biogas was governed by thermodynamic equilibrium in the presence of catalyst.
Efficient synthesis of ammonia from N2 and H2 alone in a ferroelectric packed-bed DBD reactor
NASA Astrophysics Data System (ADS)
Gómez-Ramírez, A.; Cotrino, J.; Lambert, R. M.; González-Elipe, A. R.
2015-12-01
A detailed study of ammonia synthesis from hydrogen and nitrogen in a planar dielectric barrier discharge (DBD) reactor was carried out. Electrical parameters were systematically varied, including applied voltage and frequency, electrode gap, and type of ferroelectric material (BaTiO3 versus PZT). For selected operating conditions, power consumption and plasma electron density were estimated from Lissajous diagrams and by application of the Bolsig + model, respectively. Optical emission spectroscopy was used to follow the evolution of plasma species (\\text{N}{{\\text{H}}*},{{\\text{N}}*},~{N}2+~\\text{and} ~{N}2* ) as a function of applied voltage with both types of ferroelectric material. PZT gave both greater energy efficiency and higher ammonia yield than BaTiO3: 0.9 g NH3 kWh-1 and 2.7% single pass N2 conversion, respectively. This performance is substantially superior to previously published findings on DBD synthesis of NH3 from N2 and H2 alone. The influence of electrical working parameters, the beneficial effect of PZT and the importance of controlling reactant residence time are rationalized in a reaction model that takes account of the principal process variables
NASA Astrophysics Data System (ADS)
Ohtsubo, Tetsuya; Ono, Reoto; Hayashi, Nobuya
2015-09-01
Little has been reported on action mechanism of active species produced by plasmas affecting living cells. In this study, active species in culture medium generated by torch type DBD and variations of animal cells are attempted to be clarified. Animal cells are irradiated by DBD plasma through various media such as DMEM, PBS and distilled water. Irradiation period is 1 to 15 min. The distance between the lower tip of plasma touch and the surface of the medium is 10 mm. Concentrations of NO2 -, O2 in liquid are measured. After the irradiation, the cells were cultivated in culture medium and their modifications are observed by microscope and some chemical reagents. Concentration of NO2 - and H2 O2 in all media increased with discharge period. Increase rate of NO2 -concentration is much higher than that of hydrogen peroxide. After plasma irradiation for 15 min, concentrations of NO2 were 80 mg/L in DMEM, 30 mg/L in PBS and 15 mg/L in distilled water. Also, the concentration of H2 O2 became 3mg/L in DMEM, 6.5 mg/L in PBS and 6.5mg/L in distilled water. The significant inactivation of cells was observed in the PBS. Above results indicate that, in this experiment, H2 O2 or OH radicals would affect animal cells in culture media.
NASA Astrophysics Data System (ADS)
Suzuki, S.; Itoh, H.
2015-10-01
We have investigated the effect of the surface roughness of a dielectric electrode for dielectric barrier discharge (DBD). We prepared three alumina plates made from the same material with different surface roughnesses for use as electrodes. During the repeated breakdown from the first breakdown to the stationary state, we observed gradual increases in the secondary ionization coefficient and the charge accumulated on the alumina electrodes under the application of a sinusoidal voltage in argon up to a pressure of 105 Torr. A strong correlation was also observed between them, similarly to in a previous paper on CaO film electrodes. The results suggest that increasing the surface roughness of an alumina electrode results in a larger secondary ionization coefficient and greater charge accumulation on the electrode. Moreover, it is concluded that the charges that accumulate on the alumina can be liberated from the surface as initial electrons when it acts as a cathode, depending on the polarity of the alternating gap voltage. These electrons induce the formation of an atmospheric-pressure Townsend discharge. Finally, we discuss the effect of the secondary ionization coefficient in DBD.
Use of the DBD-FISH technique for detecting DNA breakage in response to high doses of X-rays.
Cortés-Gutiérrez, Elva I; Dávila-Rodríguez, Martha I; Cerda-Flores, Ricardo M; Fernández, José Luis; López-Fernández, Carmen; Gosálvez, Jaime
2014-11-01
The aim of this study was to generate a dose-response curve using the DNA breakage detection-fluorescent in situ hybridization (DBD-FISH) test as a biomarker of initial genetic effects induced by high doses of X-rays. A dose-response curve was obtained by measuring the ex vivo responses to increasing doses (0-50 Gy) of X-rays in the peripheral blood lymphocytes of ten healthy donors. The overall dose-response curve was constructed using integrated density (ID; area × fluorescence intensity) as a measure of genetic damage induced by irradiation. The correlation coefficient was high (r = 0.934, b(0) = 10.408, and b(1) = 0.094). One-way ANOVA with the Student-Newman-Keuls test for multiple comparisons showed significant differences among the average ln ID values according to dose. Our results suggest the usefulness of the DBD-FISH technique for measuring intrinsic individual cellular radio sensitivity ex vivo.
Generation of optical vortices by fractional derivative
NASA Astrophysics Data System (ADS)
Preda, L.
2014-03-01
This paper presents a new method of vortex generation using two-dimensional fractional derivative. The characteristics of vortices obtained using this method from Gaussian and Hermite-Gauss distributions are presented. Changing the parameters of fractional derivative such as the fractional order, r, and the direction, θ, the positions of the vortex centers can be changed. The method can be used to design a filter for vortex generation. The analysis of an experimental vortex pattern using fractional derivative is also demonstrated.
Vorticity, Stokes' Theorem and the Gauss's Theorem
NASA Astrophysics Data System (ADS)
Narayanan, M.
2004-12-01
Vorticity is a property of the flow of any fluid and moving fluids acquire properties that allow an engineer to describe that particular flow in greater detail. It is important to recognize that mere motion alone does not guarantee that the air or any fluid has vorticity. Vorticity is one of four important quantities that define the kinematic properties of any fluid flow. The Navier-Stokes equations are the foundation of fluid mechanics, and Stokes' theorem is used in nearly every branch of mechanics as well as electromagnetics. Stokes' Theorem also plays a vital role in many secondary theorems such as those pertaining to vorticity and circulation. However, the divergence theorem is a mathematical statement of the physical fact that, in the absence of the creation or destruction of matter, the density within a region of space can change only by having it flow into, or away from the region through its boundary. This is also known as Gauss's Theorem. It should also be noted that there are many useful extensions of Gauss's Theorem, including the extension to include surfaces of discontinuity in V. Mathematically expressed, Stokes' theorem can be expressed by considering a surface S having a bounding curve C. Here, V is any sufficiently smooth vector field defined on the surface and its bounding curve C. Integral (Surface) [(DEL X V)] . dS = Integral (Contour) [V . dx] In this paper, the author outlines and stresses the importance of studying and teaching these mathematical techniques while developing a course in Hydrology and Fluid Mechanics. References Arfken, G. "Gauss's Theorem." 1.11 in Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 57-61, 1985. Morse, P. M. and Feshbach, H. "Gauss's Theorem." In Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 37-38, 1953. Eric W. Weisstein. "Divergence Theorem." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/DivergenceTheorem.html
Admissible upstream conditions for slender compressible vortices
NASA Technical Reports Server (NTRS)
Liu, C. H.; Krause, E.; Menne, S.
1986-01-01
The influence of the compressibility on the flow in slender vortices is being studied. The dependence of the breakdown of the slender-vortex approximation on the upstream conditions is demonstrated for various Reynolds numbers and Mach numbers. Compatibility conditions, which have to be satisfied if the vortex is to remain slender, are discussed in detail. The general discussions are supplemented by several sample calculations.
Vortices in rotating superfluid 3He.
Lounasmaa, O V; Thuneberg, E
1999-07-01
In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe.
Anomalous Energetics and Dynamics of Moving Vortices.
Radzihovsky, Leo
2015-12-11
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely suspended smectic-C films, I study the deformation, energetics, and dynamics of moving vortices in an overdamped XY model and show that their properties are significantly and qualitatively modified by the motion. PMID:26705656
Anomalous Energetics and Dynamics of Moving Vortices
NASA Astrophysics Data System (ADS)
Radzihovsky, Leo
2015-12-01
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely suspended smectic-C films, I study the deformation, energetics, and dynamics of moving vortices in an overdamped X Y model and show that their properties are significantly and qualitatively modified by the motion.
Anomalous energetics and dynamics of moving vortices
NASA Astrophysics Data System (ADS)
Radzihovsky, Leo
Motivated by the general problem of moving topological defects in an otherwise ordered state and specifically, by the anomalous dynamics observed in vortex-antivortex annihilation and coarsening experiments in freely-suspended smectic-C films, I study the deformation, energetics and dynamics of moving vortices in an overdamped xy-model and show that their properties are significantly and qualitatively modified by the motion. Supported by NSF through DMR-1001240, MRSEC DMR-0820579, and by Simons Investigator award from Simons Foundation.
Chiral Self-Gravitating Cosmic Vortices
Rybakov, Yu.P.
2005-06-01
In the framework of general relativity, an exact axisymmetric (vortex) solution of the equations of motion is obtained for the SU(2) symmetric sigma model. This solution is characterized by the topological charge (winding number) and angular deficit. In the linearized approximation, the Lyapunov stability of vortices is proved and the deflection angle of a light ray in the gravitational field of the vortex (gravitational lens effect) is calculated.
Surface Signature of Subsurface-Intensified Vortices
NASA Astrophysics Data System (ADS)
Ciani, D.; Carton, X. J.; Chapron, B.; Bashmachnikov, I.
2014-12-01
The ocean at mesoscale (20-200 km) and submesoscale (0.5-20km) is highly populated by vortices. These recirculating structures are more energetic than the mean flow, they trap water masses from their origin areas and advect them across the ocean, with consequent impact on the 3D distribution of heat and tracers. Mesoscale and submesoscale structures characterize the ocean dynamics both at the sea surface and at intrathermocline depths (0-1500m), and are presently investigated by means of model outputs, in-situ and satellite (surface) data, the latest being the only way to get high resolution and synoptic observations at planetary scale (e.g., thermal-band observations, future altimetric observations given by the SWOT satellite mission). The scientific question arising from this context is related to the role of the ocean surface for inferring informations on mesoscale and submesoscale vortices at depth. This study has also been motivated by the recent detection of subsurface eddies east of the Arabian Peninsula (PHYSINDIEN experiment - 2011).Using analytical models in the frame of the QG theory, we could describe the theoretical altimetric signature of non-drifting and of drifting subsurface eddies. Numerical experiments, using both coupled QG-SQG and primitive equations models, allowed us to investigate the surface expression of intrathermocline eddies interacting with baroclinic currents or evolving under planetary beta-effect. The eddy characteristics (radius, depth, thickness, velocity) were varied, to represent various oceanic examples (Meddies, Swoddies, Reddies, Peddies, Leddies). Idealized simulations with the ROMS model, confirming theoretical estimates, showed that drifting subsurface-intensified vortices can induce dipolar sea level anomalies, up to 3 cm. This result, compatibly with future SWOT measurement accuracies (about 2 cm), is a first step towards systematic and synoptic detection of subsurface vortices.
Vortices in rotating superfluid 3He.
Lounasmaa, O V; Thuneberg, E
1999-07-01
In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895
Muon Collider Task Force Report
Ankenbrandt, C.; Alexahin, Y.; Balbekov, V.; Barzi, E.; Bhat, C.; Broemmelsiek, D.; Bross, A.; Burov, A.; Drozhdin, A.; Finley, D.; Geer, S.; /Fermilab /Argonne /Brookhaven /Jefferson Lab /LBL, Berkeley /MUONS Inc., Batavia /UCLA /UC, Riverside /Mississippi U.
2007-12-01
Muon Colliders offer a possible long term path to lepton-lepton collisions at center-of-mass energies {radical}s {ge} 1 TeV. In October 2006 the Muon Collider Task Force (MCTF) proposed a program of advanced accelerator R&D aimed at developing the Muon Collider concept. The proposed R&D program was motivated by progress on Muon Collider design in general, and in particular, by new ideas that have emerged on muon cooling channel design. The scope of the proposed MCTF R&D program includes muon collider design studies, helical cooling channel design and simulation, high temperature superconducting solenoid studies, an experimental program using beams to test cooling channel RF cavities and a 6D cooling demonstration channel. The first year of MCTF activities are summarized in this report together with a brief description of the anticipated FY08 R&D activities. In its first year the MCTF has made progress on (1) Muon Collider ring studies, (2) 6D cooling channel design and simulation studies with an emphasis on the HCC scheme, (3) beam preparations for the first HPRF cavity beam test, (4) preparations for an HCC four-coil test, (5) further development of the MANX experiment ideas and studies of the muon beam possibilities at Fermilab, (6) studies of how to integrate RF into an HCC in preparation for a component development program, and (7) HTS conductor and magnet studies to prepare for an evaluation of the prospects for of an HTS high-field solenoid build for a muon cooling channel.
Model flocks in a steady vortical flow.
Baggaley, A W
2015-05-01
We modify the standard Vicsek model to clearly distinguish between intrinsic noise due to imperfect alignment between organisms and extrinsic noise due to fluid motion. We then consider the effect of a steady vortical flow, the Taylor-Green vortex, on the dynamics of the flock, for various flow speeds, with a fixed intrinsic particle speed. We pay particular attention to the morphology of the flow, and quantify its filamentarity. Strikingly, above a critical flow speed there is a pronounced increase in the filamentarity of the flock, when compared to the zero-flow case. This is due to the fact that particles appear confined to areas of low vorticity; a familiar phenomena, commonly seen in the clustering of inertial particles in vortical flows. Hence, the cooperative motion of the particles gives them an effective inertia, which is seen to have a profound effect on the morphology of the flock, in the presence of external fluid motion. Finally, we investigate the angle between the flow and the particles direction of movement and find it follows a power-law distribution. PMID:26066260
Thermally Activated Decay of Magnetic Vortices
NASA Astrophysics Data System (ADS)
Burgess, Jacob; Grombacher, Denys; Fortin, David; Davis, John; Freeman, Mark
2010-03-01
We experimentally probe thermally activated decay of magnetic vortices, by observing annihilations within an array of Ni80Fe20 discs through hysteresis measurements. Specifically, the statistics of vortex annihilation are mapped as a function of the magnitude of, and the dwell time at, the peak fields applied during hysteresis scans. Magnetic vortices in micro- and nano-scale thin film ferromagnetic elements exhibit interesting and complex behavior. Demagnetization interactions make understanding processes like the annihilation of a vortex during magnetic switching challenging. Recent work has shown that the annihilation process can take place over an extended period of timefootnotetextZ. Liu, R.D. Sydora and M.R. Freeman, PRB 77, 174410 (2008). implying that there is a characteristic decay process, likely thermally governed. Through application of an Arrhenius model we extract information about the energy barrier preventing decay, and hence information about the energetic contributions of the demagnetization effects. We anticipate that this information will be useful in extending analytical models of magnetic vortices.
Long term changes in the polar vortices
NASA Astrophysics Data System (ADS)
Braathen, Geir O.
2015-04-01
As the amount of halogens in the stratosphere is slowly declining and the ozone layer slowly recovers it is of interest to see how the meteorological conditions in the vortex develop over the long term since such changes might alter the foreseen ozone recovery. In conjunction with the publication of the WMO Antarctic and Arctic Ozone Bulletins, WMO has acquired the ERA Interim global reanalysis data set for several meteorological parameters. This data set goes from 1979 - present. These long time series of data can be used for several useful studies of the long term development of the polar vortices. Several "environmental indicators" for vortex change have been calculated, and a climatology, as well as trends, for these parameters will be presented. These indicators can act as yardsticks and will be useful for understanding past and future changes in the polar vortices and how these changes affect polar ozone depletion. Examples of indicators are: vortex mean temperature, vortex minimum temperature, vortex mean PV, vortex "importance" (PV*area), vortex break-up time, mean and maximum wind speed. Data for both the north and south polar vortices have been analysed at several isentropic levels from 350 to 850 K. A possible link between changes in PV and sudden stratospheric warmings will be investigated, and the results presented.
Merging of co-rotating trailing vortices
NASA Astrophysics Data System (ADS)
Cerretelli, C.; Leweke, T.; Williamson, C. H. K.
1999-11-01
The merging of co-rotating vortices is an important physical phenomenon in aerodynamics as well as in fundamental turbulent flows. Merging plays a role in the aerodynamics of airplane wing wakes, where it can accelerate the development of the Crow instability (Crouch 1997). Although vortex merger has been extensively studied, most numerical investigations concern the case of the two dimensional inviscid interactions. On the other hand, the dynamics of three dimensional viscous vortices, which spin around each other in an helical path, is not yet fully understood, and this is the focus of the present experimental investigation. Previous work by Chen, Jacob and Savas (1999) shows that merging of co-rotating vortices, from a flapped wing, occurs at approximately 0.8 of an orbit period after formation, independently of the circulation Reynolds number Re_Γ. In the present work, merging is studied by using a biplane wing system, as well as the DPIV technique. In our investigation, we find that the time taken for merging, measured in orbit periods, is a function not only of the experimental geometry, but is also a function of the circulation Reynolds number.
Self-Similar Compressible Free Vortices
NASA Technical Reports Server (NTRS)
vonEllenrieder, Karl
1998-01-01
Lie group methods are used to find both exact and numerical similarity solutions for compressible perturbations to all incompressible, two-dimensional, axisymmetric vortex reference flow. The reference flow vorticity satisfies an eigenvalue problem for which the solutions are a set of two-dimensional, self-similar, incompressible vortices. These solutions are augmented by deriving a conserved quantity for each eigenvalue, and identifying a Lie group which leaves the reference flow equations invariant. The partial differential equations governing the compressible perturbations to these reference flows are also invariant under the action of the same group. The similarity variables found with this group are used to determine the decay rates of the velocities and thermodynamic variables in the self-similar flows, and to reduce the governing partial differential equations to a set of ordinary differential equations. The ODE's are solved analytically and numerically for a Taylor vortex reference flow, and numerically for an Oseen vortex reference flow. The solutions are used to examine the dependencies of the temperature, density, entropy, dissipation and radial velocity on the Prandtl number. Also, experimental data on compressible free vortex flow are compared to the analytical results, the evolution of vortices from initial states which are not self-similar is discussed, and the energy transfer in a slightly-compressible vortex is considered.
Managing Flap Vortices via Separation Control
NASA Technical Reports Server (NTRS)
Greenblatt, David
2006-01-01
A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management by means of boundary layer separation control. Passive control was achieved using a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressures, was used to predict vortex characteristics based on inviscid rollup relations and vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over either outboard or inboard edge vortices while producing small lift and moment excursions. Unsteady surface pressures indicated that dynamic separation and attachment control can be exploited to perturb vortices at wavelengths shorter than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.
Two-particle vortices in graphene
NASA Astrophysics Data System (ADS)
Portnoi, Mikhail; Downing, Charles
We show that a pair of two-dimensional massless Dirac-Weyl fermions can form a bound state independently on the sign of the inter-particle interaction potential, as long as this potential decays at large distances faster than Kepler's inverse distance law. The coupling occurs only at the Dirac point, when the charge carriers lose their chirality. These bipartite states must have a non-zero internal angular momentum, meaning that they only exist as stationary vortices. This leads to the emergence of a new type of energetically-favorable quasiparticles: double-charged zero-energy vortices. Their bosonic nature allows condensation and gives rise to Majorana physics without invoking a superconductor. The presence of dark-matter-like silent immobile vortices explains a range of poorly understood experiments in gated graphene structures at low doping. This work was supported by EU H2020 RISE project CoExAN, EU FP7 ITN NOTEDEV and FP7 IRSES project InterNoM.
Recent results from hadron colliders
Frisch, H.J. )
1990-12-10
This is a summary of some of the many recent results from the CERN and Fermilab colliders, presented for an audience of nuclear, medium-energy, and elementary particle physicists. The topics are jets and QCD at very high energies, precision measurements of electroweak parameters, the remarkably heavy top quark, and new results on the detection of the large flux of B mesons produced at these machines. A summary and some comments on the bright prospects for the future of hadron colliders conclude the talk. 39 refs., 44 figs., 3 tabs.
Muon Muon Collider: Feasibility Study
Gallardo, J.C.; Palmer, R.B.; Tollestrup, A.V.; Sessler, A.M.; Skrinsky, A.N.; Ankenbrandt, C.; Geer, S.; Griffin, J.; Johnstone, C.; Lebrun, P.; McInturff, A.; Mills, Frederick E.; Mokhov, N.; Moretti, A.; Neuffer, D.; Ng, K.Y.; Noble, R.; Novitski, I.; Popovic, M.; Qian, C.; Van Ginneken, A. /Fermilab /Brookhaven /Wisconsin U., Madison /Tel Aviv U. /Indiana U. /UCLA /LBL, Berkeley /SLAC /Argonne /Sobolev IM, Novosibirsk /UC, Davis /Munich, Tech. U. /Virginia U. /KEK, Tsukuba /DESY /Novosibirsk, IYF /Jefferson Lab /Mississippi U. /SUNY, Stony Brook /MIT /Columbia U. /Fairfield U. /UC, Berkeley
2012-04-05
A feasibility study is presented of a 2 + 2 TeV muon collider with a luminosity of L = 10{sup 35} cm{sup -2}s{sup -1}. The resulting design is not optimized for performance, and certainly not for cost; however, it does suffice - we believe - to allow us to make a credible case, that a muon collider is a serious possibility for particle physics and, therefore, worthy of R and D support so that the reality of, and interest in, a muon collider can be better assayed. The goal of this support would be to completely assess the physics potential and to evaluate the cost and development of the necessary technology. The muon collider complex consists of components which first produce copious pions, then capture the pions and the resulting muons from their decay; this is followed by an ionization cooling channel to reduce the longitudinal and transverse emittance of the muon beam. The next stage is to accelerate the muons and, finally, inject them into a collider ring wich has a small beta function at the colliding point. This is the first attempt at a point design and it will require further study and optimization. Experimental work will be needed to verify the validity of diverse crucial elements in the design. Muons because of their large mass compared to an electron, do not produce significant synchrotron radiation. As a result there is negligible beamstrahlung and high energy collisions are not limited by this phenomena. In addition, muons can be accelerated in circular devices which will be considerably smaller than two full-energy linacs as required in an e{sup +} - e{sup -} collider. A hadron collider would require a CM energy 5 to 10 times higher than 4 TeV to have an equivalent energy reach. Since the accelerator size is limited by the strength of bending magnets, the hadron collider for the same physics reach would have to be much larger than the muon collider. In addition, muon collisions should be cleaner than hadron collisions. There are many detailed particle
Theoretical studies in mesoscale jets and vortices
NASA Astrophysics Data System (ADS)
Radko, Timour
1997-11-01
Mesoscale vortices in the mid-ocean are known to move large distances without loss of coherence, preserving their speed and (usually westward) direction. Still open are the questions of how an eddy is able to preserve its structure during many turnaround times and what is the role in this process of the specific perturbations of the circular basic state. To investigate the effect of the rectilinear motion of the isolated eddies, we construct several analytical steady state models and examine the realizability in time of those solutions using the initial-value numerical calculations. To gain a preliminary understanding of the process, we first consider the barotropic f-plane model. It is demonstrated using linearized (about the circular basic state) calculations that for almost any eddy with compact basic velocity we can find a small amplitude disturbance of the first azimuthal harmonic (m=1 mode) that results in the rectilinear motion of an eddy. If such a disturbance is sufficiently small, the vortex can propagate many diameters away from its origin, as shown by a weak non-linear theory. This conclusion is confirmed by the spectral calculations using the full two dimensional vorticity equation. A more realistic representation of the ocean eddies is given by the equivalent-barotropic model, which includes effects of the passive lower layer and the ambient potential vorticity gradient (the beta-effect). Analytical theory is developed to construct a wide class of stable quasi-monopolar vortecies propagating in the westward direction with the supercritical (U<{-}beta Rsbsp{d}{2}) velocities. A remarkable similarity is found between the structure of the solutions in barotropic and equivalent-barotropic models for all values of the propagation velocity. The numerical spectral calculations, initiated by our analytical solutions, indicate that the (supercritical) vortices initially move with the predicted velocity, but later slow down to the speed of the long planetary
Waves and vortices in rotating stratified turbulence
NASA Astrophysics Data System (ADS)
Pouquet, Annick; Herbert, Corentin; Marino, Raffaele; Rosenberg, Duane
2015-04-01
The interactions between vortices and waves is a long-standing problem in fluid turbulence. It can lead to a self-sustaining process that is dominant, for example in pipe flows, and to the prediction of large-scale coherent structures such as baroclinic jets in planetary atmospheres, and it can also be used as a control tool for the onset of turbulence. Similarly, the dynamics of the atmosphere and the ocean is dominated by complex interactions between nonlinear eddies and waves due to a combination of rotation and stratification (characterized respectively by frequencies f and N), as well as shear layers. The waves are faster at large scales, and this leads to a quasi-geostrophic quasi-linear regime in which there is a balance between pressure gradient and the Coriolis and gravity forces. The range of scales in these geophysical flows before dissipation prevails is such that other regimes can arise in which turbulence comes into play, with the eddy turn-over time becoming comparable to the wave period, and for which isotropy recovers for sufficiently high Reynolds numbers. One may decompose the flow-- observational, experimental or numerical, in terms of the normal modes that it supports, i.e. the inertia-gravity waves and the (slow, zero frequency) vortical modes carrying the potential vorticity, thanks to the existence of a small parameter, as for example the fluctuation around a mean flow or the ratio of the wave period to the eddy turn-over time. In this context an ensemble of data sets of rotating stratified turbulence will be analyzed, stemming from accurate direct numerical simulations of the Boussinesq equations at high resolution, up to 40963 grid points, using high-performance computing. These flows all support a constant-flux bi-directional cascade of energy towards both the large scales and the small scales. The parameter space includes the Reynolds number, the Prandtl number(s), and the Rossby and Froude numbers, and a universal response to a variety
Large Deviation Statistics of Vorticity Stretching in Isotropic Turbulence
NASA Astrophysics Data System (ADS)
Johnson, Perry; Meneveau, Charles
2015-11-01
A key feature of 3D fluid turbulence is the stretching/re-alignment of vorticity by the action of the strain-rate. It is shown using the cumulant-generating function that cumulative vorticity stretching along a Lagrangian path in isotropic turbulence behaves statistically like a sum of i.i.d. variables. The Cramer function for vorticity stretching is computed from the JHTDB isotropic DNS (Reλ = 430) and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain-rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramer functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of largest FTLE. A model Fokker-Planck equation is constructed by approximating the viscous destruction of vorticity with a deterministic non-linear relaxation law matching conditional statistics, while the fluctuations in vorticity stretching are modelled by stochastic noise matching the statistics encoded in the Cramer function. The model predicts a stretched-exponential tail for the vorticity magnitude PDF, with good agreement for the exponent but significant error (30-40%) in the pre-factor. Supported by NSF Graduate Fellowship (DGE-1232825) and NSF Grant CMMI-0941530.
Surfzone vorticity in the presence of extreme bathymetric variability
NASA Astrophysics Data System (ADS)
Clark, D.; Elgar, S.; Raubenheimer, B.
2014-12-01
Surfzone vorticity was measured at Duck, NC using a novel 5-m diameter vorticity sensor deployed in 1.75 m water depth. During the 4-week deployment the initially alongshore uniform bathymetry developed 200-m long mega-cusps with alongshore vertical changes of 1.5 m or more. When waves were small and the vorticity sensor was seaward of the surfzone, vorticity variance and mean vorticity varied with the tidally modulated water depth, consistent with a net seaward flux of surfzone-generated vorticity. Vorticity variance increased with incident wave heights up to 2-m. However, vorticity variance remained relatively constant for incident wave heights above 2-m, and suggests that eddy energy may become saturated in the inner surfzone during large wave events. In the presence of mega-cusps the mean vorticity (shear) is often large and generated by bathymetrically controlled rip currents, while vorticity variance remains strongly correlated with the incident wave height. Funded by NSF, ASD(R&E), and WHOI Coastal Ocean Institute.
Tevatron Collider Status and Prospects
Moore, Ronald S.
2009-10-01
The Tevatron proton-antiproton collider at Fermilab continues operation as the world's highest energy particle accelerator by delivering luminosity at a center-of-mass energy of 1.96 TeV. We review recent performance and plans for the remainder of Run 2.
CERN's Large Hadron Collider project
NASA Astrophysics Data System (ADS)
Fearnley, Tom A.
1997-03-01
The paper gives a brief overview of CERN's Large Hadron Collider (LHC) project. After an outline of the physics motivation, we describe the LHC machine, interaction rates, experimental challenges, and some important physics channels to be studied. Finally we discuss the four experiments planned at the LHC: ATLAS, CMS, ALICE and LHC-B.
Butler, J.N.; /Fermilab
2005-09-01
This paper discusses the physics opportunity and challenges for doing high precision B physics experiments at hadron colliders. It describes how these challenges have been addressed by the two currently operating experiments, CDF and D0, and how they are addressed by three experiments, ATLAS, CMS, and LHCb, at the LHC.
Muon Colliders: The Next Frontier
Tourun, Yagmur [Illinois Institute of Technology, Chicago, Illinois, United States
2016-07-12
Muon Colliders provide a path to the energy frontier in particle physics but have been regarded to be "at least 20 years away" for 20 years. I will review recent progress in design studies and hardware R&D and show that a Muon Collider can be established as a real option for the post-LHC era if the current vigorous R&D effort revitalized by the Muon Collider Task Force at Fermilab can be supported to its conclusion. All critical technologies are being addressed and no show-stoppers have emerged. Detector backgrounds have been studied in detail and appear to be manageable and the physics can be done with existing detector technology. A muon facility can be built through a staged scenario starting from a low-energy muon source with unprecedented intensity for exquisite reach for rare processes, followed by a Neutrino Factory with ultrapure neutrino beams with unparalleled sensitivity for disentangling neutrino mixing, leading to an energy frontier Muon Collider with excellent energy resolution.
Muon Colliders: The Next Frontier
Tourun, Yagmur
2009-07-29
Muon Colliders provide a path to the energy frontier in particle physics but have been regarded to be 'at least 20 years away' for 20 years. I will review recent progress in design studies and hardware R&D and show that a Muon Collider can be established as a real option for the post-LHC era if the current vigorous R&D effort revitalized by the Muon Collider Task Force at Fermilab can be supported to its conclusion. All critical technologies are being addressed and no show-stoppers have emerged. Detector backgrounds have been studied in detail and appear to be manageable and the physics can be done with existing detector technology. A muon facility can be built through a staged scenario starting from a low-energy muon source with unprecedented intensity for exquisite reach for rare processes, followed by a Neutrino Factory with ultrapure neutrino beams with unparalleled sensitivity for disentangling neutrino mixing, leading to an energy frontier Muon Collider with excellent energy resolution.
Muon Colliders: The Next Frontier
Tourun, Yagmur
2009-07-29
Muon Colliders provide a path to the energy frontier in particle physics but have been regarded to be "at least 20 years away" for 20 years. I will review recent progress in design studies and hardware R&D and show that a Muon Collider can be established as a real option for the post-LHC era if the current vigorous R&D effort revitalized by the Muon Collider Task Force at Fermilab can be supported to its conclusion. All critical technologies are being addressed and no show-stoppers have emerged. Detector backgrounds have been studied in detail and appear to be manageable and the physics can be done with existing detector technology. A muon facility can be built through a staged scenario starting from a low-energy muon source with unprecedented intensity for exquisite reach for rare processes, followed by a Neutrino Factory with ultrapure neutrino beams with unparalleled sensitivity for disentangling neutrino mixing, leading to an energy frontier Muon Collider with excellent energy resolution.
Feedback Systems for Linear Colliders
1999-04-12
Feedback systems are essential for stable operation of a linear collider, providing a cost-effective method for relaxing tight tolerances. In the Stanford Linear Collider (SLC), feedback controls beam parameters such as trajectory, energy, and intensity throughout the accelerator. A novel dithering optimization system which adjusts final focus parameters to maximize luminosity contributed to achieving record performance in the 1997-98 run. Performance limitations of the steering feedback have been investigated, and improvements have been made. For the Next Linear Collider (NLC), extensive feedback systems are planned as an integral part of the design. Feedback requirements for JLC (the Japanese Linear Collider) are essentially identical to NLC; some of the TESLA requirements are similar but there are significant differences. For NLC, algorithms which incorporate improvements upon the SLC implementation are being prototyped. Specialized systems for the damping rings, rf and interaction point will operate at high bandwidth and fast response. To correct for the motion of individual bunches within a train, both feedforward and feedback systems are planned. SLC experience has shown that feedback systems are an invaluable operational tool for decoupling systems, allowing precision tuning, and providing pulse-to-pulse diagnostics. Feedback systems for the NLC will incorporate the key SLC features and the benefits of advancing technologies.
Physics at hadron colliders: Experimental view
Siegrist, J.L.
1987-08-01
The physics of the hadron-hadron collider experiment is considered from an experimental point of view. The problems encountered in determination of how well the standard model describes collider results are discussed. 53 refs., 58 figs.
Demarteau, M.
1992-04-01
A brief introduction to {bar p}p collider physics is given. Selected results from the collider experiments at the CERN S{bar p}pS and the Tevatron collider are described. The emphasis is on experimental aspects of {bar p}p collisions. Minimum bias physics and the production of jets, Intermediate Vector Bosons and heavy flavors is reviewed. The outlook for physics at hadron colliders for the near future is briefly discussed.
From Neutrino Factory to Muon Collider
Geer, S.; /Fermilab
2010-01-01
Both Muon Colliders and Neutrino Factories require a muon source capable of producing and capturing {Omicron}(10{sup 21}) muons/year. This paper reviews the similarities and differences between Neutrino Factory and Muon Collider accelerator complexes, the ongoing R&D needed for a Muon Collider that goes beyond Neutrino Factory R&D, and some thoughts about how a Neutrino Factory on the CERN site might eventually be upgraded to a Muon Collider.
Numerical studies of the margin of vortices with decaying cores
NASA Technical Reports Server (NTRS)
Liu, G. C.; Ting, L.
1986-01-01
The merging of vortices to a single one is a canonical incompressible viscous flow problem. The merging process begins when the core sizes or the vortices are comparable to their distances and ends when the contour lines of constant vorticity lines are circularized around one center. Approximate solutions to this problem are constructed by adapting the asymptotic solutions for distinct vortices. For the early stage of merging, the next-order terms in the asymptotic solutions are added to the leading term. For the later stage of merging, the vorticity distribution is reinitialized by vortices with overlapping core structures guided by the 'rule of merging' and the velocity of the 'vortex centers' are then defined by a minimum principle. To show the accuracy of the approximate solution, it is compared with the finite-difference solution.
Zombie Vortices: Angular Momentum Transport and Planetesimal Formation
NASA Astrophysics Data System (ADS)
Barranco, Joseph; Marcus, Philip; Pei, Suyang; Jiang, Chung-Hsiang; Hassanzadeh, Pedram; Lecoanet, Daniel
2014-11-01
Zombie vortices may fill the dead zones of protoplanetary disks, where they may play important roles in star and planet formation. We will investigate this new, purely hydrodynamic instability and explore the conditions necessary to resurrect the dead zone and fill it with large amplitude vortices that may transport angular momentum and allow mass to accrete onto the protostar. One unresolved issue is whether angular momentum transport is mediated via asymmetries in the vortices, vortex-vortex interactions, or acoustic waves launched by the vortices. Vortices may also play a crucial role in the formation of planetesimals, the building blocks of planets. It is still an open question how grains grow to kilometer-size. We will investigate the interactions of dust with vortices generated via our new hydrodynamic instability, and bridge the gap between micron-sized grains and kilometer-sized planetesimals. Supported by NSF AST-1010052.
HIGH ENERGY PHYSICS POTENTIAL AT MUON COLLIDERS
PARSA,Z.
2000-04-07
In this paper, high energy physics possibilities and future colliders are discussed. The {mu}{sup +} {mu}{sup {minus}} collider and experiments with high intensity muon beams as the stepping phase towards building Higher Energy Muon Colliders (HEMC) are briefly reviewed and encouraged.
NASA Astrophysics Data System (ADS)
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to
X-ray phase vortices: theory and experiment
NASA Astrophysics Data System (ADS)
Peele, Andrew G.; Nugent, Keith A.; Mancuso, Adrian P.; Paterson, David; McNulty, Ian; Hayes, Jason P.
2004-08-01
We review the current work on x-ray phase vortices. We explain the role of an x-ray vortex in phase recovery and speculate on its possible applications in other fields of x-ray optical research. We present our theoretical understanding of the structure of phase vortices and test these predictions against experiment. We present experimental observations of phase vortices with charge greater than 3 and observe that their propagation appears to be consistent with our theoretical models.
On relation between scalar interfaces and vorticity in inviscid flows
NASA Astrophysics Data System (ADS)
Ramesh, O. N.; Patwardhan, Saurabh
2013-11-01
A great variety of applications like pollutant mixing in the atmosphere, mixing of reactants in combustion highlight the importance of passive scalar dynamics in fluid flows. The other dynamically important variable in the study of fluid flow is the vorticity. Vorticity though, unlike a passive scalar, does affect the fluid motion. The dynamics of scalar (linear) and vorticity (non-linear) are governed by the equations which inherently have different characteristics. This paper addresses the question of the faithfulness of representation of vorticity by scalar marker and the motivation for this comes from the experiment of Head and Bandyopadhyay (1981) which showed the existence of coherent vortices by using smoke flow visualization in a turbulent boundary layer. We will show analytically in regions where the molecular diffusion effects are negligible, the vorticity and scalar gradients are orthogonal to each other. The iso- surface of scalar follows the vorticity in an inviscid situation. Also, we will demonstrate that in the case of unsteady burgers vortex and vortex shedding behind a finite circular cylinder, the scalar gradient is orthogonal to vorticity and inner product of vorticity and scalar gradients is zero in regions away from the wall.
Gluon propagators and center vortices in gluon plasma
Chernodub, M. N.; Nakagawa, Y.; Nakamura, A.; Saito, T.; Zakharov, V. I.
2011-06-01
We study electric and magnetic components of the gluon propagators in quark-gluon plasma in terms of center vortices by using a quenched simulation of SU(2) lattice theory. In the Landau gauge, the magnetic components of the propagators are strongly affected in the infrared region by removal of the center vortices, while the electric components are almost unchanged by this procedure. In the Coulomb gauge, the time-time correlators, including an instantaneous interaction, also have an essential contribution from the center vortices. As a result, one finds that magnetic degrees of freedom in the infrared region couple strongly to the center vortices in the deconfinement phase.
Dynamics of vortices and drift waves: a point vortex model
NASA Astrophysics Data System (ADS)
Leoncini, Xavier; Verga, Alberto
2013-03-01
The complex interactions of localized vortices with waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.
Drift waves and vortices: a dynamical point vortex model
NASA Astrophysics Data System (ADS)
Leoncini, Xavier; Verga, Alberto
2013-10-01
Interactions of localized vortices with drift waves are investigated using a model of point vortices in the presence of a transverse or longitudinal wave. This simple model shows a rich dynamical behavior including oscillations of a dipole, splitting and merging of two like-circulation vortices, and chaos. The analytical and numerical results of this model have been found to predict under certain conditions, the behavior of more complex systems, such as the vortices of the Charney-Hasegawa-Mima equation, where the presence of waves strongly affects the evolution of large coherent structures.
Observations of Electron Vorticity in the Inner Plasma Sheet
NASA Technical Reports Server (NTRS)
Gurgiolo, C.; Goldstein, M. L.; Vinas, A. F.; Matthaeus, W. H.; Fazakerley, A. N.
2011-01-01
From a limited number of observations it appears that vorticity is a common feature in the inner plasma sheet. With the four Cluster spacecraft and the four PEACE instruments positioned in a tetrahedral configuration, for the first time it is possible to directly estimate the electron fluid vorticity in a space plasma. We show examples of electron fluid vorticity from multiple plasma sheet crossings. These include three time periods when Cluster passed through a reconnection ion diffusion region. Enhancements in vorticity are seen in association with each crossing of the ion diffusion region.
Vorticity, gyroscopic precession, and spin-curvature force
NASA Astrophysics Data System (ADS)
Liang, Wei Chieh; Lee, Si Chen
2013-02-01
In investigating the relationship between vorticity and gyroscopic precession, we calculate the vorticity vector in Godel, Kerr, Lewis, Schwarzschild, and Minkowski metrics and find that the vorticity vector of the specific observers is the angular velocity of the gyroscopic precession. Furthermore, when space-time torsion is included, the vorticity and spin-curvature force change sign. This result is very similar to the behavior of the positive and negative helicities of quantum spin in the Stern-Gerlach force. It implies that the inclusion of torsion will lead to an analogous property of quantum spin even in classical treatment.
Inviscid to turbulent transition of trailing vortices
NASA Technical Reports Server (NTRS)
Iversen, J. D.
1974-01-01
The characteristics of the plateau region in the vortex system which trails from a lifting wing are discussed. The decay of the vortex due to viscous or turbulent shear is very slow in the plateau so that the maximum tangential speed in the vortices remains nearly constant for some distance downstream of roll-up and then begins to decrease, becoming inversely proportional to the square root of the distance downstream. Mathematical models are developed to analyze the structure of the plateau area. Solutions are obtained for both constant and variable eddy viscosity models.
A geometric approach to quantum vortices
NASA Astrophysics Data System (ADS)
Penna, Vittorio; Spera, Mauro
1989-12-01
In this paper a geometrical description is given of the theory of quantum vortices first developed by Rasetti and Regge [Physica A 80, 217 (1975)] relying on the symplectic techniques of Marsden and Weinstein [J. Phys. D 7, 305 (1983)], and Kirillov-Kostant-Souriau geometric quantization. The RR-current algebra is interpreted as the natural Hamiltonian algebra associated to a certain coadjoint orbit of the group G=SDiff(R3), the KKS prequantization condition of which is related to the Feynman-Onsager relation. This orbit is also shown to possess a G-invariant Kaehler structure, whence, in principle, it is possible to quantize it in a natural way.
Nonlinear Generation of Vorticity by Surface Waves.
Filatov, S V; Parfenyev, V M; Vergeles, S S; Brazhnikov, M Yu; Levchenko, A A; Lebedev, V V
2016-02-01
We demonstrate that waves excited on a fluid surface produce local surface rotation owing to hydrodynamic nonlinearity. We examine theoretically the effect and obtain an explicit formula for the vertical vorticity in terms of the surface elevation. Our theoretical predictions are confirmed by measurements of surface motion in a cell with water where surface waves are excited by vertical and harmonic shaking the cell. The experimental data are in good agreement with the theoretical predictions. We discuss physical consequences of the effect. PMID:26894714
Effect of Trapping on Vortices in Plasma
NASA Astrophysics Data System (ADS)
Siddiqui, H.; Shah, H. A.; Tsintsadze, N. L.
2008-09-01
Microscopic trapping of electrons is considered in one- and two-dimensional potential wells (shallow and deep) and its effect on vortex formation is investigated by deriving modified Hasegawa Mima (HM) equations. Inhomogenieties in the number density and magnetic field are taken into account. The modified HM equations are analysed by considering bounce frequencies of the trapped particles. Solitary vortices are obtained via Kortweg deVries (KdV) type of equations and both exact and Sagdeev potential solutions are obtained. In general it is observed that trapping produces stronger non-linearities and this leads to the modification of the original HM equation.
Future Electron-Hadron Colliders
Litvinenko, V.
2010-05-23
Outstanding research potential of electron-hadron colliders (EHC) was clearly demonstrated by first - and the only - electron-proton collider HERA (DESY, Germany). Physics data from HERA revealed new previously unknown facets of Quantum Chromo-Dynamics (QCD). EHC is an ultimate microscope probing QCD in its natural environment, i.e. inside the hadrons. In contrast with hadrons, electrons are elementary particles with known initial state. Hence, scattering electrons from hadrons provides a clearest pass to their secrets. It turns EHC into an ultimate machine for high precision QCD studies and opens access to rich physics with a great discovery potential: solving proton spin puzzle, observing gluon saturation or physics beyond standard model. Access to this physics requires high-energy high-luminosity EHCs and a wide reach in the center-of-mass (CM) energies. This paper gives a brief overview of four proposed electron-hadron colliders: ENC at GSI (Darmstadt, Germany), ELIC/MEIC at TJNAF (Newport News, VA, USA), eRHIC at BNL (Upton, NY, USA) and LHeC at CERN (Geneva, Switzerland). Future electron-hadron colliders promise to deliver very rich physics not only in the quantity but also in the precision. They are aiming at very high luminosity two-to-four orders of magnitude beyond the luminosity demonstrated by the very successful HERA. While ENC and LHeC are on opposite side of the energy spectrum, eRHIC and ELIC are competing for becoming an electron-ion collider (EIC) in the U.S. Administrations of BNL and Jlab, in concert with US DoE office of Nuclear Physics, work on the strategy for down-selecting between eRHIC and ELIC. The ENC, EIC and LHeC QCD physics programs to a large degree are complimentary to each other and to the LHC physics. In last decade, an Electron Ion Collider (EIC) collaboration held about 25 collaboration meetings to develop physics program for EIC with CM energy {approx}100 GeV. One of these meetings was held at GSI, where ENC topic was in the
On vortex loops and filaments: three examples of numerical predictions of flows containing vortices.
Krause, Egon
2003-01-01
Vortex motion plays a dominant role in many flow problems. This article aims at demonstrating some of the characteristic features of vortices with the aid of numerical solutions of the governing equations of fluid mechanics, the Navier-Stokes equations. Their discretized forms will first be reviewed briefly. Thereafter three problems of fluid flow involving vortex loops and filaments are discussed. In the first, the time-dependent motion and the mutual interaction of two colliding vortex rings are discussed, predicted in good agreement with experimental observations. The second example shows how vortex rings are generated, move, and interact with each other during the suction stroke in the cylinder of an automotive engine. The numerical results, validated with experimental data, suggest that vortex rings can be used to influence the spreading of the fuel droplets prior to ignition and reduce the fuel consumption. In the third example, it is shown that vortices can also occur in aerodynamic flows over delta wings at angle of attack as well as pipe flows: of particular interest for technical applications of these flows is the situation in which the vortex cores are destroyed, usually referred to as vortex breakdown or bursting. Although reliable breakdown criteria could not be established as yet, the numerical predictions obtained so far are found to agree well with the few experimental data available in the recent literature.
Temporal evolution of vorticity staircases in randomly strained two-dimensional vortices
NASA Astrophysics Data System (ADS)
Turner, M. R.
2014-11-01
The evolution of a Gaussian vortex subject to a weak-external-random n-fold multipolar strain field is examined using fully nonlinear simulations. The simulations show that at large Reynolds numbers, fine scale steps form at the periphery of the vortex, before merging, generally leaving one large step, which acts as a barrier between the vorticity within the coherent core and the surrounding, well mixed, "surf zone." It is shown for n = 2 that the width and the number of fine scale steps which initially form at the periphery of the vortex is dependent on the strain parameters, but that the range of radial values for which steps initially occur is only dependent on n and the amplitude of the strain field. A criteria is developed which can predict this range of radial values using the linear stability results of Le Dizès ["Non-axisymmetric vortices in two-dimensional flows," J. Fluid Mech. 406, 175 (2000)]. This criteria is based upon the perturbation vorticity needing to be larger than some fraction of the vorticity gradient to flatten the vortex profile. For n = 3 and 4, the radial step range is again predicted, and it is observed that for these higher wavenumbers the long lasting steps are narrower than the n = 2 case. For n = 4 the steps which form are so narrow that they do not persist very long before they are destroyed by the strain field and viscosity.
Theoretical and experimental study of the acoustic spectrum of a DBD-driven planar KrCl excilamp
NASA Astrophysics Data System (ADS)
Sosnin, Eduard A.; Panarin, Victor A.; Pikulev, Aleksei A.; Tarasenko, Victor F.
2013-01-01
Experiments and theoretical simulation were performed to study the acoustic characteristics of a planar KrCl excilamp driven by a dielectric barrier discharge (DBD) with a mixture ratio of Kr:Cl2 = 400:1 at a pressure of 20 kPa. The acoustic spectrum of the excilamp bulb was measured and resonances at 4.96, 5.36, 9.92, 10.8, and 21.6 kHz were detected. The natural frequency of the bulb walls and the acoustic frequency of the gas were calculated. The acoustic energy of the gas was determined depending on the vibration frequency of the bulb walls. Comparison of the experimental and simulation data shows that in the frequency range >10 kHz, acoustic peaks occur at natural frequencies of the gas in the excilamp bulb.
Zhang, Ruo-Bing; Wu, Yan; Li, Guo-Feng; Wang, Ning-Hui; Li, Jie
2004-01-01
Degradation of the Indigo Carmine (IC) by the bipolar pulsed DBD in water-air mixture was studied. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetitive rate and ect., on color removal efficiency of dying wastewater were investigated. Concentrations of gas phase o3 and aqueous phase H2O2 under various conditions were measured. Experimental results showed that air bubbling facilitates the breakdown of water and promotes generation of chemically active species. Color removal efficiency of IC solution can be greatly improved by the air aeration under various solution conductivities. Decolorization efficiency increases with the increase of the gas flow rate, and decreases with the increase of the initial solution conductivity. A higher pulse repetitive rate and a larger pulse capacitor C(p) are favorable for the decolorization process. Ozone and hydrogen peroxide formed decreases with the increase of initial solution conductivity. In addition, preliminary analysis of the decolorization mechanisms is given.
Surucu, Seda; Turkoglu Sasmazel, Hilal
2016-01-01
This paper reported a study related to atmospheric pressure dielectric barrier discharge (DBD) Ar + O2 and Ar + N2 plasma modifications to alter surface properties of 3D PCL/Chitosan/PCL layer-by-layer hybrid scaffolds and to improve mouse fibroblast (L929 ATCC CCL-1) cell attachment, proliferation, and growth. The scaffolds were fabricated using electrospinning technique and each layer was electrospun sequentially on top of the other. The surface modifications were performed with an atmospheric pressure DBD plasma under different gas flow rates (50, 60, 70, 80, 90, and 100 sccm) and for different modification times (0.5-7 min), and then the chemical and topographical characterizations of the modified samples were done by contact angle (CA) measurements, scanning electron microscopy (SEM), atomic force microscopy, and X-ray photoelectron spectroscopy. The samples modified with Ar + O2 plasma for 1 min under 70 cm(3)/min O2 flow rate (71.077° ± 3.578) showed a 18.83% decrease compare to unmodified samples' CA value (84.463° ± 3.864). Comparing with unmodified samples, the average fiber diameter values for plasma-modified samples by Ar + O2 (1 min 70 sccm) and Ar + N2 (40 s 70 sccm) increased 40.756 and 54.295%, respectively. Additionally, the average inter-fiber pore size values exhibited decrease of 37.699 and 48.463% for the same Ar + O2 and Ar + N2 plasma-modified samples, respectively, compare to unmodified samples. Biocompatibility performance was determined with MTT assay, fluorescence, Giemsa, and confocal imaging as well as SEM. The results showed that Ar + O2-based plasma modification increased the hydrophilicity and oxygen functionality of the surface, thus affecting the cell viability and proliferation on/within scaffolds. PMID:26494511
Crab Cavities for Linear Colliders
Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; Shulte, D.; Jones, Roger M.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC
2011-11-08
Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.
COLLIDE: Collisions into Dust Experiment
NASA Technical Reports Server (NTRS)
Colwell, Joshua E.
1999-01-01
The Collisions Into Dust Experiment (COLLIDE) was completed and flew on STS-90 in April and May of 1998. After the experiment was returned to Earth, the data and experiment were analyzed. Some anomalies occurred during the flight which prevented a complete set of data from being obtained. However, the experiment did meet its criteria for scientific success and returned surprising results on the outcomes of very low energy collisions into powder. The attached publication, "Low Velocity Microgravity Impact Experiments into Simulated Regolith," describes in detail the scientific background, engineering, and scientific results of COLLIDE. Our scientific conclusions, along with a summary of the anomalies which occurred during flight, are contained in that publication. We offer it as our final report on this grant.
SLC: The first linear collider
NASA Astrophysics Data System (ADS)
Phinney, Nan
The Stanford Linear Collider (SLC) was built in the 1980s at the Stanford Linear Accelerator Center (SLAC) in California. Like LEP, it was designed to study the properties of the Z boson at a center-of-mass energy of about 91 GeV. The SLC was also a prototype for an entirely new approach to electron-positron colliders. The development of a new technology was motivated by the fact that in an electron storage ring, the electrons radiate synchrotron radiation as they are bent around the ring. To avoid excessive energy loss from this radiation, the circumference of the ring has to increase as the square of the desired energy, making very high energy rings prohibitively large and expensive. With a linear accelerator, the electrons do not need to bend and the tunnel length only grows linearly with energy...
NASA Astrophysics Data System (ADS)
Gu, Mingyao; Feltham, Graham; Ekmekci, Alis
2014-11-01
When oncoming streams of weak vorticity aligned with the axle axis of a two-wheel landing gear impinge near the forward stagnation point of the wheels, a mechanism for vorticity collection, growth, amplification into discrete large-scale vortices, and shedding was formerly shown to exist. In the current study, the impinging vorticity streams are perpendicular to the axle axis, i.e. in a vertical orientation as opposed to the horizontal orientation before. Experiments are conducted in a recirculating water channel using hydrogen bubble visualization and particle image velocimetry at a Reynolds number of 32,500 (based on the wheel diameter). As with the horizontal orientation, vorticity collection and amplification are observed, but the large-scale vortices thus formed are stretched around the wheel circumference in contrast to being stretched around the wheel sides, as observed for the horizontal orientation. This flow behavior varies with the impingement location of the vorticity streams across the wheel width. Maximum vorticity amplification occurs at a critical impingement location and drastically alters the flow separation along the wheel circumference. In addition, the instantaneous vortical structures are identified and tracked using a Galilean-invariant criterion.
Luminosity limitations for Electron-Ion Collider
Valeri Lebedev
2000-09-01
The major limitations on reaching the maximum luminosity for an electron ion collider are discussed in application to the ring-ring and linac-ring colliders. It is shown that with intensive electron cooling the luminosity of 10{sup 33} cm{sup -2} s{sup -1} is feasible for both schemes for the center-of-mass collider energy above approximately 15 GeV. Each scheme has its own pros and cons. The ring-ring collider is better supported by the current accelerator technology while the linac-ring collider suggests unique features for spin manipulations of the electron beam. The article addresses a general approach to a choice of collider scheme and parameters leaving details for other conference publications dedicated to particular aspects of the ring-ring and linac-ring colliders.
The effect of entrainment on starting vortices
NASA Astrophysics Data System (ADS)
Rosi, Giuseppe; Rival, David
2015-11-01
Recent work shows that vortex detachment behind accelerating plates coincides with when streamlines enclosing the starting vortex (SV) form a full saddle. In the case of a linearly accelerating plate, it can be shown that vorticity-containing mass, and thus the SV's development scale with only dimensionless towed distance, while the SV's circulation scales with the acceleration rate. This results in shear-layer instabilities whose structure is Reynold-number independent, but whose strength scale with Reynolds number. It is hypothesized that the increased strength of the instabilities promotes entrainment, which causes the formation of the full saddle and thereby detachment to occur at an earlier dimensionless towed distance. To test this hypothesis, a circular plate is linearly accelerated from rest to pinch-off with chord-based Reynolds numbers of 103, 104, and 105 at the midpoint of the motion. Planar PIV data is acquired, from which FTLE and enstrophy fields are calculated. Vortex detachment is identified from the dynamics of the FTLE saddles, while the enstrophy fields are used to calculate both the vorticity-containing mass entering from the shear layer and the mass entrained from the quiescent surroundings.
Tomographic PIV Study of Hairpin Vortices
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; Rossmann, Tobias
2014-11-01
Tomographic PIV is used in a free surface water channel to quantify the flow behavior of hairpin vortices that are artificially generated in a laminar boundary layer. Direct injection from a 32:1 aspect ratio slot at low blowing ratios (0 . 1 < BR < 0 . 2) is used to generate an isolated hairpin vortex in a thick laminar boundary layer (485 < Reδ* < 600). Due to the large dynamic range of length and velocity scales (the resulting vortices have advection velocities 5X greater than their tangential velocities), a tailored optical arrangement and specialized post processing techniques are required to fully capture the small-scale behavior and long-time development of the flow field. Hairpin generation and evolution are presented using the λ2 criterion derived from the instantaneous, three-dimensional velocity field. The insight provided by the tomographic data is also compared to the conclusions drawn from 2D PIV and passive scalar visualizations. Finally, the three-dimensional behavior of the measured velocity field is correlated with that of a simultaneously imaged, passive scalar dye that marks the boundary of the injected fluid, allowing the examination of the entrainment behavior of the hairpin. Supported by the National Science Foundation under Grant CBET-1040236.
Close relative equilibria of identical point vortices
NASA Astrophysics Data System (ADS)
Dirksen, Tobias; Aref, Hassan
2011-11-01
Via numerical solution of the classical problem of relative equilibria for identical point vortices on the unbounded plane we have found configurations that are very close to the analytically known, centered, symmetrically arranged, nested equilateral triangles. Numerical solutions of this kind were found for 3 n + 1 vortices, where n = 2 , 3 , ... , 30 . A sufficient, although apparently not necessary, condition for this phenomenon of close solutions is that the ``core'' of the configuration is marginally stable, as occurs for a central vortex surrounded by an equilateral triangle. The open, regular heptagon also has this property, and new relative equilibria close to the nested, symmetrically arranged, regular heptagons have been found. The centered regular nonagon is also marginally stable. Again, a new family of close relative equilibria has been found. The closest relative equilibrium pairs occur, however, for symmetrically nested equilateral triangles. The numerical evidence is surveyed and related recent work mentioned. A Letter in Physics of Fluids 23 (2011) 051706 is available. Supported in part by the Danish National Research Foundation through a Niels Bohr visiting professorship.
Dynamics of Quantized Vortices Before Reconnection
NASA Astrophysics Data System (ADS)
Andryushchenko, V. A.; Kondaurova, L. P.; Nemirovskii, S. K.
2016-04-01
The main goal of this paper is to investigate numerically the dynamics of quantized vortex loops, just before the reconnection at finite temperature, when mutual friction essentially changes the evolution of lines. Modeling is performed on the base of vortex filament method using the full Biot-Savart equation. It was discovered that the initial position of vortices and the temperature strongly affect the dependence on time of the minimum distance δ (t) between tips of two vortex loops. In particular, in some cases, the shrinking and collapse of vortex loops due to mutual friction occur earlier than the reconnection, thereby canceling the latter. However, this relationship takes a universal square-root form δ ( t) =√{( κ/2π ) ( t_{*}-t) } at distances smaller than the distances, satisfying the Schwarz reconnection criterion, when the nonlocal contribution to the Biot-Savart equation becomes about equal to the local contribution. In the "universal" stage, the nearest parts of vortices form a pyramid-like structure with angles which neither depend on the initial configuration nor on temperature.
Monopoles and fractional vortices in chiral superconductors
Volovik, G. E.
2000-01-01
I discuss two exotic objects that must be experimentally identified in chiral superfluids and superconductors. These are (i) the vortex with a fractional quantum number (N = 1/2 in chiral superfluids, and N = 1/2 and N = 1/4 in chiral superconductors), which plays the part of the Alice string in relativistic theories and (ii) the hedgehog in the ^l field, which is the counterpart of the Dirac magnetic monopole. These objects of different dimensions are topologically connected. They form the combined object that is called a nexus in relativistic theories. In chiral superconductors, the nexus has magnetic charge emanating radially from the hedgehog, whereas the half-quantum vortices play the part of the Dirac string. Each half-quantum vortex supplies the fractional magnetic flux to the hedgehog, representing 1/4 of the “conventional” Dirac string. I discuss the topological interaction of the superconductor's nexus with the ‘t Hooft–Polyakov magnetic monopole, which can exist in Grand Unified Theories. The monopole and the hedgehog with the same magnetic charge are topologically confined by a piece of the Abrikosov vortex. Such confinement makes the nexus a natural trap for the magnetic monopole. Other properties of half-quantum vortices and monopoles are discussed as well, including fermion zero modes. PMID:10716980
State of hadron collider physics
Grannis, P.D. |
1993-12-01
The 9th Topical Workshop on Proton-Antiproton Collider Physics in Tsukuba Japan demonstrated clearly the enormous breadth of physics accessible in hadron cowders. Although no significant chinks were reported in the armor of the Standard Model, new results presented in this meeting have expanded our knowledge of the electroweak and strong interactions and have extended the searches for non-standard phenomena significantly. Much of the new data reported came from the CDF and D0 experiments at the Fermilab cowder. Superb operation of the Tevatron during the 1992-1993 Run and significant advances on the detector fronts -- in particular, the emergence of the new D0 detector as a productive physics instrument in its first outing and the addition of the CDF silicon vertex detector -- enabled much of this advance. It is noteworthy however that physics from the CERN collider experiments UA1 and UA4 continued to make a large impact at this meeting. In addition, very interesting summary talks were given on new results from HERA, cosmic ray experiments, on super-hadron collider physics, and on e{sup +}e{sup {minus}} experiments at LEP and TRISTAN. These summaries are reported in elsewhere in this volume.
Fermilab Collider: Performance and plans
Finley, D.A.
1993-12-01
The Fermilab collider program has completed its first physics run with two major detectors, CDF and DO. Recent performance of the Fermilab accelerator complex during Run Ia is presented, along with plans to improve the luminosity of the collider. The beam-beam tune shift limitations of previous runs have been avoided by the successful implementation of electrostatic separators in the Tevatron. The simultaneous operation of two high luminosity sections is provided by two matched low beta inserts. The Antiproton Source has increased its performance over the previous run as measured by stack size and stacking rate. The Linac will be upgraded from 200 MeV to 400 MeV in order to lessen the space charge tune shift upon injection into the Booster and provide proton beams with increased intensity with the same emittance. Higher luminosity requires more bunches in the Tevatron to again avoid the limitation due to the beam-beam interaction. Until it is replaced with the Main Injector, the Main Ring will remain as the most significant bottleneck on the performance of the collider.
NASA Astrophysics Data System (ADS)
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to
Separating Internal Waves and Vortical Structure in the Open Ocean
NASA Astrophysics Data System (ADS)
Lauffenburger, N. E.; Sanford, T. B.; Lien, R.
2012-12-01
Deviating from past oceanographic surveys, a new, powerful array of profiling floats has been deployed for three weeks in the Sargasso Sea to monitor the evolving sub-mesoscale field. Using 18-20 EM-APEX floats, profiling to 100 m depth simultaneously, velocity (U and V), temperature, salinity and microstructure measurements (χ) were made on horizontal scales between 100 m and 10 km. This strategy provided a 3-D snapshot of the physical properties every half hour, which significantly reduces temporal aliasing. Area-averaged relative vorticity, vortex stretching, non-linear twisting, horizontal divergence and Ertel's potential vorticity have been computed and projected onto isopycnal surfaces. Since vortical modes carry Ertel's potential vorticity (and internal waves do not), this is a useful step in understanding the energetic contribution of vortical motions to the background internal wave field on small scales. In addition, the temporal material conservation law of Ertel's potential vorticity will be tested for the first time by determining the advection of the floats' measurements relative to the motion of the water parcels and by computing the horizontal gradients of the potential vorticity signal. The three deployments provide data to analyze the interaction of inertial waves, vortical processes and barotropic tides in and out of active frontogenesis.
Numerical Capture of Wing-tip Vortex Using Vorticity Confinement
NASA Astrophysics Data System (ADS)
Zhang, Baili; Lou, Jing; Kang, Chang Wei; Wilson, Alexander; Lundberg, Johan; Bensow, Rickard
2012-11-01
Tracking vortices accurately over large distances is very important in many areas of engineering, for instance flow over rotating helicopter blades, ship propeller blades and aircraft wings. However, due to the inherent numerical dissipation in the advection step of flow simulation, current Euler and RANS field solvers tend to damp these vortices too fast. One possible solution to reduce the unphysical decay of these vortices is the application of vorticity confinement methods. In this study, a vorticity confinement term is added to the momentum conservation equations which is a function of the local element size, the vorticity and the gradient of the absolute value of vorticity. The approach has been evaluated by a systematic numerical study on the tip vortex trailing from a rectangular NACA0012 half-wing. The simulated structure and development of the wing-tip vortex agree well with experiments both qualitatively and quantitatively without any adverse effects on the global flow field. It is shown that vorticity confinement can negate the effect of numerical dissipation, leading to a more or less constant vortex strength. This is an approximate method in that genuine viscous diffusion of the vortex is not modeled, but it can be appropriate for vortex dominant flows over short to medium length scales where viscous diffusion can be neglected.
Towards a theory of stochastic vorticity-augmentation. [tornado model
NASA Technical Reports Server (NTRS)
Liu, V. C.
1977-01-01
A new hypothesis to account for the formation of tornadoes is presented. An elementary one-dimensional theory is formulated for vorticity transfer between an ambient sheared wind and a transverse penetrating jet. The theory points out the relevant quantities to be determined in describing the present stochastic mode of vorticity augmentation.
Vorticity amplification near the stagnation point of landing gear wheels
NASA Astrophysics Data System (ADS)
Feltham, G.; Ekmekci, A.
2014-04-01
The vicinity near the forward stagnation point of landing-gear wheels has been found to support a mechanism for oncoming streams of weak vorticity to collect, grow, and amplify into discrete large-scale vortical structures that then shed with a distinct periodicity. To the authors' knowledge, such a flow phenomenon has never been reported before for landing gear wheels, which are in essence finite (three-dimensional) cylinders. To gain further insight into this phenomenon, a detailed experimental study has been undertaken employing the hydrogen bubble visualization and Particle Image Velocimetry techniques. A very thin platinum wire, similar to those used in hydrogen bubble visualization applications, was placed upstream of the wheel model to produce two streams of weak vorticity (with opposite sign) that convected toward the model. As the vorticity streams enter the stagnation region of the wheels, significant flow deceleration and vorticity stretching act to collect, grow, and amplify the incoming vorticity streams into large-scale vortical structures. Experiments were performed at a fixed Reynolds number, with a value of 32 500 when defined based on the diameter of the wheel and a value of 21 based on the diameter of the vorticity-generating upstream wire. First, to establish a baseline, the natural flow field (without the presence of an upstream wire) was characterized, where experimentally determined values for the stagnation boundary-layer thickness and the velocity profile along the stagnation streamline were both found to agree with the values provided in the literature for two-dimensional cylinders. Subsequently, the dynamics of vorticity collection, growth, amplification, and shedding were studied. The size, stand-off distance and the shedding frequency of the vortical structures forming near the stagnation region were all found to strongly depend on the impingement location of the inbound vorticity on the wheel. A simple relationship between the non
Numerical study of vorticity-enhanced heat transfer
NASA Astrophysics Data System (ADS)
Wang, Xiaolin; Alben, Silas
2013-11-01
Vortices produced by vibrated reeds and flapping foils can improve heat transfer efficiency in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we modeled and simulated the fluid flow and temperature in a 2-D channel flow with vortices injected at the upstream boundary. We classified four types of vortex streets depending on the Reynolds number and vortices' strengths and spacings, and studied the different vortex dynamics in each situation. We then used Lagrangian coherent structures (LCS) to study the effect of the vortices on mixing and determined how the Nusselt number and Coefficients of performance vary with flow parameters and Peclet numbers.
Formation and early development of wingtip vortices
NASA Astrophysics Data System (ADS)
Giuni, Michea
Wingtip vortices are extremely important phenomena in fluid dynamics for their negative effects in many applications. Despite the many studies on this particular flow, the current understanding is still poor in providing a form base for the design of effective tip geometry modifications and vortex control devices. A rectangular wing with squared and rounded wingtips was tested in order to identify the main mechanisms involved in the formation of the vortex on the wing and in its early development in the wake. The complementarity of a number of experimental techniques adopted, such as surface flow visualizations, wall pressure measurements, smoke visualizations and stereoscopic particle image velocimetry (SPIV), gave a richer insight of the physics and the basic mechanisms of the vortex development. Furthermore, a large number of configurations were tested exploring the effects of several parameters such as wing chord, aspect ratio, wingtip geometry, angle of attack and Reynolds number. The development of the vortex along the wing showed the formation of several secondary vortices which interacted with the primary vortex generating low frequency fluctuations. The structure of the flow at this stage was analysed introducing a compact description through characteristic lines of the vortex system defined from the velocity vector field in the vicinity of the wing surface. The high spatial resolution achieved by the SPIV arrangement allowed a deeper understanding of the vortex structure in the early wake and the turbulence production and dissipation within the vortex core. The relaminarization process of the vortex core promoted by centrifugal motion was observed. The relation between vortex meandering, turbulence, secondary vortices and wake sheet was discussed. A comparison of different methods for the averaging of instantaneous planar vector fields was performed showing the effects and importance of the meandering. An axial acceleration of the flow within the vortex
Vorticity is a marker of right ventricular diastolic dysfunction.
Fenster, Brett E; Browning, James; Schroeder, Joyce D; Schafer, Michal; Podgorski, Chris A; Smyser, Jamie; Silveira, Lori J; Buckner, J Kern; Hertzberg, Jean R
2015-09-15
Right ventricular diastolic dysfunction (RVDD) is an important prognostic indicator in pulmonary arterial hypertension (PAH). RV vortex rings have been observed in healthy subjects, but their significance in RVDD is unknown. Vorticity, the local spinning motion of an element of fluid, may be a sensitive measure of RV vortex dynamics. Using four-dimensional (4D) flow cardiac magnetic resonance imaging (CMR), we investigated the relationship between right heart vorticity with echocardiographic indexes of RVDD. Thirteen (13) PAH subjects and 10 controls underwent same-day 4D flow CMR and echocardiography. RV diastolic function was assessed using trans-tricuspid valve (TV) early (E) and late (A) velocities, E/A ratio, and e' and a' tissue Doppler velocities. RV and right atrial (RA) integrated mean vorticity was calculated for E and A-wave filling periods using 4D datasets. Compared with controls, A-wave vorticity was significantly increased in RVDD subjects in both the RV [2343 (1,559-3,295) vs. 492 (267-2,649) 1/s, P = 0.028] and RA [30 (27-44) vs. 9 (5-27) 1/s, P = 0.005]. RA E vorticity was significantly decreased [13 (7-22) vs. 28 (15-31) 1/s, P = 0.038] in RVDD. E-wave vorticity correlated TV e', E-,and TV E/A (P < 0.05), and A-wave vorticity associated with both TV A and E/A (P < 0.02). RVDD is associated with alterations in E- and A-wave vorticity, and vorticity correlates with multiple echocardiographic markers of RVDD. Vorticity may be a robust noninvasive research tool for the investigation of RV fluid and tissue mechanical interactions in PAH. PMID:26254331
Large-deviation statistics of vorticity stretching in isotropic turbulence.
Johnson, Perry L; Meneveau, Charles
2016-03-01
A key feature of three-dimensional fluid turbulence is the stretching and realignment of vorticity by the action of the strain rate. It is shown in this paper, using the cumulant-generating function, that the cumulative vorticity stretching along a Lagrangian path in isotropic turbulence obeys a large deviation principle. As a result, the relevant statistics can be described by the vorticity stretching Cramér function. This function is computed from a direct numerical simulation data set at a Taylor-scale Reynolds number of Re(λ)=433 and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected, the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramér functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of the largest FTLE. In an attempt to relate the vorticity stretching statistics to the vorticity magnitude probability density function in statistically stationary conditions, a model Kramers-Moyal equation is constructed using the statistics encoded in the Cramér function. The model predicts a stretched-exponential tail for the vorticity magnitude probability density function, with good agreement for the exponent but significant difference (35%) in the prefactor.
Large-deviation statistics of vorticity stretching in isotropic turbulence
NASA Astrophysics Data System (ADS)
Johnson, Perry L.; Meneveau, Charles
2016-03-01
A key feature of three-dimensional fluid turbulence is the stretching and realignment of vorticity by the action of the strain rate. It is shown in this paper, using the cumulant-generating function, that the cumulative vorticity stretching along a Lagrangian path in isotropic turbulence obeys a large deviation principle. As a result, the relevant statistics can be described by the vorticity stretching Cramér function. This function is computed from a direct numerical simulation data set at a Taylor-scale Reynolds number of Reλ=433 and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected, the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramér functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of the largest FTLE. In an attempt to relate the vorticity stretching statistics to the vorticity magnitude probability density function in statistically stationary conditions, a model Kramers-Moyal equation is constructed using the statistics encoded in the Cramér function. The model predicts a stretched-exponential tail for the vorticity magnitude probability density function, with good agreement for the exponent but significant difference (35%) in the prefactor.
Large-deviation statistics of vorticity stretching in isotropic turbulence.
Johnson, Perry L; Meneveau, Charles
2016-03-01
A key feature of three-dimensional fluid turbulence is the stretching and realignment of vorticity by the action of the strain rate. It is shown in this paper, using the cumulant-generating function, that the cumulative vorticity stretching along a Lagrangian path in isotropic turbulence obeys a large deviation principle. As a result, the relevant statistics can be described by the vorticity stretching Cramér function. This function is computed from a direct numerical simulation data set at a Taylor-scale Reynolds number of Re(λ)=433 and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected, the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramér functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of the largest FTLE. In an attempt to relate the vorticity stretching statistics to the vorticity magnitude probability density function in statistically stationary conditions, a model Kramers-Moyal equation is constructed using the statistics encoded in the Cramér function. The model predicts a stretched-exponential tail for the vorticity magnitude probability density function, with good agreement for the exponent but significant difference (35%) in the prefactor. PMID:27078458
Sound Generation by Aircraft Wake Vortices
NASA Technical Reports Server (NTRS)
Hardin, Jay C.; Wang, Frank Y.
2003-01-01
This report provides an extensive analysis of potential wake vortex noise sources that might be utilized to aid in their tracking. Several possible mechanisms of aircraft vortex sound generation are examined on the basis of discrete vortex dynamic models and characteristic acoustic signatures calculated by application of vortex sound theory. It is shown that the most robust mechanisms result in very low frequency infrasound. An instability of the vortex core structure is discussed and shown to be a possible mechanism for generating higher frequency sound bordering the audible frequency range. However, the frequencies produced are still low and cannot explain the reasonably high-pitched sound that has occasionally been observed experimentally. Since the robust mechanisms appear to generate only very low frequency sound, infrasonic tracking of the vortices may be warranted.
Dynamics of coupled vortices in perpendicular field
Jain, Shikha; Novosad, Valentyn Fradin, Frank Y.; Pearson, John E.; Bader, Samuel D.
2014-02-24
We explore the coupling mechanism of two magnetic vortices in the presence of a perpendicular bias field by pre-selecting the polarity combinations using the resonant-spin-ordering approach. First, out of the four vortex polarity combinations (two of which are degenerate), three stable core polarity states are achieved by lifting the degeneracy of one of the states. Second, the response of the stiffness constant for the vortex pair (similar polarity) in perpendicular bias is found to be asymmetric around the zero field, in contrast to the response obtained from a single vortex core. Finally, the collective response of the system for antiparallel core polarities is symmetric around zero bias. The vortex core whose polarization is opposite to the bias field dominates the response.
Monitoring Wake Vortices for More Efficient Airports
NASA Technical Reports Server (NTRS)
2005-01-01
Wake vortices are generated by all aircraft during flight. The larger the aircraft, the stronger the wake, so the Federal Aviation Administration (FAA) separates aircraft to ensure wake turbulence has no effect on approaching aircraft. Currently, though, the time between planes is often larger than it needs to be for the wake to dissipate. This unnecessary gap translates into arrival and departure delays, but since the wakes are invisible, the delays are nearly inevitable. If, however, the separation between aircraft can be reduced safely, then airport capacity can be increased without the high cost of additional runways. Scientists are currently studying these patterns to identify and introduce new procedures and technologies that safely increase airport capacity. NASA, always on the cutting edge of aerospace research, has been contributing knowledge and testing to these endeavors.
Geometric investigations of a vorticity model equation
NASA Astrophysics Data System (ADS)
Bauer, Martin; Kolev, Boris; Preston, Stephen C.
2016-01-01
This article consists of a detailed geometric study of the one-dimensional vorticity model equation which is a particular case of the generalized Constantin-Lax-Majda equation. Wunsch showed that this equation is the Euler-Arnold equation on Diff (S1) when the latter is endowed with the right-invariant homogeneous H ˙ 1 / 2-metric. In this article we prove that the exponential map of this Riemannian metric is not Fredholm and that the sectional curvature is locally unbounded. Furthermore, we prove a Beale-Kato-Majda-type blow-up criterion, which we then use to demonstrate a link to our non-Fredholmness result. Finally, we extend a blow-up result of Castro-Córdoba to the periodic case and to a much wider class of initial conditions, using a new generalization of an inequality for Hilbert transforms due to Córdoba-Córdoba.
Dynamic Assembly of Magnetic Colloidal Vortices.
Mohorič, Tomaž; Kokot, Gašper; Osterman, Natan; Snezhko, Alexey; Vilfan, Andrej; Babič, Dušan; Dobnikar, Jure
2016-05-24
Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications. PMID:27128501
Computational simulations of vorticity enhanced diffusion
NASA Astrophysics Data System (ADS)
Vold, Erik L.
1999-11-01
Computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity. The central issue under study here is the increase in scalar flux down the gradient and across the vortex field. The numerical scheme uses cylindrical coordinates centered with the vortex flow which allows an exact advective solution and 1D or 2D diffusion using simple numerical methods. In the results, the ratio of transport across a localized vortex region in the presence of the vortex flow over that expected for diffusion alone is evaluated as a measure of VED. This ratio is seen to increase dramatically while the absolute flux across the vortex decreases slowly as the diffusion coefficient is decreased. Similar results are found and compared for varying diffusion coefficient, D, or vortex rotation time, τv, for a constant background gradient in the transported scalar vs an interface in the transported quantity, and for vortex flow fields constant in time vs flow which evolves in time from an initial state and with a Schmidt number of order unity. A simple analysis shows that for a small diffusion coefficient, the flux ratio measure of VED scales as the vortex radius over the thickness for mass diffusion in a viscous shear layer within the vortex characterized by (Dτv)1/2. The phenomenon is linear as investigated here and suggests that a significant enhancement of mixing in fluids may be a relatively simple linear process. Discussion touches on how this vorticity enhanced diffusion may be related to mixing in nonlinear turbulent flows.
Dynamics of Giant Planet Polar Vortices
NASA Astrophysics Data System (ADS)
Brueshaber, Shawn R.; Sayanagi, Kunio M.
2016-10-01
The polar atmospheres of the giant planets have come under increasing interest since a compact, warm-core, stable, cyclonic polar vortex was discovered at each of Saturn's poles. In addition, the south pole of Neptune appears to have a similar feature, and Uranus' north pole is exhibiting activity that could indicate the formation of a polar vortex. We investigate the formation and maintenance of these giant planet polar vortices by varying several key atmospheric dynamics parameters in a forced-dissipative, 1.5-layer shallow water model. Our simulations are run using the EPIC (Explicit Planetary Isentropic Coordinate) global circulation model, to which we have added a gamma-plane rectangular grid option appropriate for simulating polar atmospheric dynamics.In our numerical simulations, we vary the atmospheric deformation radius, planetary rotation rate, storm forcing intensity, and storm vorticity (cyclone-to-anticyclone) ratio to determine what combination of values favors the formation of a polar vortex. We find that forcing the atmosphere by injecting small-scale mass perturbations ("storms") to form either all cyclones, all anticyclones, or equal numbers of both, may all result in a cyclonic polar vortex. Additionally, we examine the role of eddy momentum convergence in the intensification and maintenance of a polar cyclone.Our simulation results are applicable to understanding all four of the solar system giant planets. In the future, we plan to expand our modeling effort with a more realistic 3D primitive equations model, also with a gamma-plane rectangular grid using EPIC. With our 3D primitive equations model, we will study how various vertical atmospheric stratification structures influence the formation and maintenance of a polar cyclone. While our shallow-water model only involves storms of a single layer, a 3D primitive equations model allows us to study how storms of finite vertical extent and at differing levels in the atmosphere may further favor
Visualization of vorticity and vortices in wall-bounded turbulent flows.
Helgeland, Anders; Pettersson Reif, B Anders; Andreassen, Øyvind; Wasberg, Carl Erik
2007-01-01
This study was initiated by the scientifically interesting prospect of applying advanced visualization techniques to gain further insight into various spatio-temporal characteristics of turbulent flows. The ability to study complex kinematical and dynamical features of turbulence provides means of extracting the underlying physics of turbulent fluid motion. The objective is to analyze the use of a vorticity field line approach to study numerically generated incompressible turbulent flows. In order to study the vorticity field, we present a field line animation technique which uses a specialized particle advection and seeding strategy. Efficient analysis is achieved by decoupling the rendering stage from the preceding stages of the visualization method. This allows interactive exploration of multiple fields simultaneously, which sets the stage for a more complete analysis of the flow field. Multifield visualizations are obtained using a flexible volume rendering framework which is presented in this paper. Vorticity field lines have been employed as indicators to provide a means to identify "ejection" and "sweep" regions; two particularly important spatio-temporal events in wall-bounded turbulent flows. Their relation to the rate of turbulent kinetic energy production and viscous dissipation, respectively, have been identified. PMID:17622687
LHC: The Large Hadron Collider
Lincoln, Don
2015-03-04
The Large Hadron Collider (or LHC) is the world’s most powerful particle accelerator. In 2012, scientists used data taken by it to discover the Higgs boson, before pausing operations for upgrades and improvements. In the spring of 2015, the LHC will return to operations with 163% the energy it had before and with three times as many collisions per second. It’s essentially a new and improved version of itself. In this video, Fermilab’s Dr. Don Lincoln explains both some of the absolutely amazing scientific and engineering properties of this modern scientific wonder.
Colliding-beam-accelerator lattice
Claus, J.; Cornacchia, M.; Courant, E.D.; Parzen, G.
1983-01-01
We describe the lattice of the Colliding Beam Accelerator, a 400 x 400 GeV pp facility proposed for construction at Brookhaven National Laboratory. The structure adopted is very versatile, in part in consequence of its desirable behavior as function of momentum deviation and as function of the betatron tunes. Each of the six insertions can be arranged to meet specific requirements at the crossing points as illustrated by a discussion of the tuneable low-beta insertions. The luminosity in these low-beta insertions (2 x 10/sup 33/ cm/sup -2/ sec/sup -1/) would be an order of magnitude larger than the standard insertions.
Tevatron instrumentation: boosting collider performance
Shiltsev, Vladimir; Jansson, Andreas; Moore, Ronald; /Fermilab
2006-05-01
The Tevatron in Collider Run II (2001-present) is operating with six times more bunches, many times higher beam intensities and luminosities than in Run I (1992-1995). Beam diagnostics were crucial for the machine start-up and the never-ending luminosity upgrade campaign. We present the overall picture of the Tevatron diagnostics development for Run II, outline machine needs for new instrumentation, present several notable examples that led to Tevatron performance improvements, and discuss the lessons for the next big machines--LHC and ILC.
LHC: The Large Hadron Collider
Lincoln, Don
2016-07-12
The Large Hadron Collider (or LHC) is the worldâs most powerful particle accelerator. In 2012, scientists used data taken by it to discover the Higgs boson, before pausing operations for upgrades and improvements. In the spring of 2015, the LHC will return to operations with 163% the energy it had before and with three times as many collisions per second. Itâs essentially a new and improved version of itself. In this video, Fermilabâs Dr. Don Lincoln explains both some of the absolutely amazing scientific and engineering properties of this modern scientific wonder.
Muon Colliders and Neutrino Factories
Kaplan, Daniel M.
2015-05-29
Muon colliders and neutrino factories are attractive options for future facilities aimed at achieving the highest lepton-antilepton collision energies and precision measurements of Higgs boson and neutrino mixing matrix parameters. The facility performance and cost depend on how well a beam of muons can be cooled. Recent progress in muon cooling design studies and prototype tests nourishes the hope that such facilities could be built starting in the coming decade. The status of the key technologies and their various demonstration experiments is summarized. Prospects "post-P5" are also discussed.
Fast feedback for linear colliders
Hendrickson, L.; Adolphsen, C.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Minty, M.; Sass, R.
1995-05-01
A fast feedback system provides beam stabilization for the SLC. As the SLC is in some sense a prototype for future linear colliders, this system may be a prototype for future feedbacks. The SLC provides a good base of experience for feedback requirements and capabilities as well as a testing ground for performance characteristics. The feedback system controls a wide variety of machine parameters throughout the SLC and associated experiments, including regulation of beam position, angle, energy, intensity and timing parameters. The design and applications of the system are described, in addition to results of recent performance studies.
Colliders and brane vector phenomenology
Clark, T. E.; Love, S. T.; Xiong, C.; Nitta, Muneto; Veldhuis, T. ter
2008-12-01
Brane world oscillations manifest themselves as massive vector gauge fields. Their coupling to the standard model is deduced using the method of nonlinear realizations of the spontaneously broken higher dimensional space-time symmetries. Brane vectors are stable and weakly interacting and therefore escape particle detectors unnoticed. LEP and Tevatron data on the production of a single photon in conjunction with missing energy are used to delineate experimentally excluded regions of brane vector parameter space. The additional region of parameter space accessible to the LHC as well as a future lepton linear collider is also determined by means of this process.
Colliding with a crunching bubble
Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen
2007-03-26
In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.
Tevatron collider operations and plans
Peter H. Garbincius
2004-06-17
Fermilab's Tevatron is a proton-antiproton collider with center of mass energy of 1.96 TeV. The antiprotons are produced by 125 GeV protons from the Main Injector striking a stainless steel target. The 8 GeV antiprotons are collected and cooled in the Debuncher and Accumulator rings of the Antiproton Source and, just recently, in the Recycler ring before acceleration by the Main Injector and the Tevatron. In addition to energy, a vital parameter for generating physics data is the Luminosity delivered to the experiments given by a formula that is listed in detail in the paper.
Estimates of Fermilab Tevatron collider performance
Dugan, G.
1991-09-01
This paper describes a model which has been used to estimate the average luminosity performance of the Tevatron collider. In the model, the average luminosity is related quantitatively to various performance parameters of the Fermilab Tevatron collider complex. The model is useful in allowing estimates to be developed for the improvements in average collider luminosity to be expected from changes in the fundamental performance parameters as a result of upgrades to various parts of the accelerator complex.
FUTURE LEPTON COLLIDERS AND LASER ACCELERATION
PARSA,Z.
2000-05-30
Future high energy colliders along with their physics potential, and relationship to new laser technology are discussed. Experimental approaches and requirements for New Physics exploration are also described.
SLAC-Linac-Collider (SLC) Project
Wiedemann, H.
1981-02-01
The proposed SLAC Linear Collider Project (SLC) and its features are described in this paper. In times of ever increasing costs for energy the electron storage ring principle is about to reach its practical limit. A new class of colliding beam beam facilities, the Linear Colliders, are getting more and more attractive and affordable at very high center-of-mass energies. The SLC is designed to be a poineer of this new class of colliding beam facilities and at the same time will serve as a valuable tool to explore the high energy physics at the level of 100 GeV in the center-of-mass system.
NASA Astrophysics Data System (ADS)
Mamunuru, Meenakshi
The focus of this work is modeling and simulation of low temperature plasma discharges (LTPs). The first part of the thesis consists of the study of dielectric barrier (DBD) plasma actuators. Use of DBD plasma actuators on airfoil surfaces is a promising method for increasing airfoil efficiency. Actuators produce a surface discharge that causes time averaged thrust in the neutral gas. The thrust modifies the boundary layer properties of the flow and prevents the occurrence of separation bubbles. In simulating the working of an actuator, the focus is on the spatial characteristics of the thrust produced by the discharge over very short time and space scales. The results provide an understanding of the causes of thrust, and the basic principles behind the actuator operation. The second part of this work focusses on low pressure plasma discharges used for silicon nanoparticle synthesis. When reactive semiconductor precursor gases are passed through capacitively coupled plasma (CCP) radio frequency (RF) reactors, nano sized particles are formed. When the reactors are operated at high enough powers, a very high fraction of the nanoparticles are crystallized in the chamber. Nanoparticle crystallization in plasma is a very complex process and not yet fully understood. It can be inferred from experiments that bulk and surface processes initiated due to energetic ion impaction of the nanoparticles are responsible for reordering of silicon atoms, causing crystallization. Therefore, study of plasma-particle interactions is the first step towards understanding how particles are crystallized. The specific focus of this work is to investigate the experimental evidence that hydrogen gas presence in argon discharges used for silicon nanocrystal synthesis, leads to a superior quality of nanocrystals. Influence of hydrogen gas on plasma composition and discharge characteristics is studied. Via Monte Carlo simulation, distribution of ion energy impacting particles surface is studied
Evolution of Imposed Vortices Over Concave Surfaces in Hypervelocity Flow
NASA Astrophysics Data System (ADS)
Flaherty, William; Austin, Joanna
2012-11-01
Steamwise oriented vortices in the boundary layer of a hypersonic flow have the potential to affect heat transfer and skin friction significantly. These effects can be exacerbated by the addition of extra strain rates associated with concave surface curvature. Vortices can either occur naturally (in the form of Goertler vortices), or be introduced by some form of mechanical distortion (such as a protuberance). In this work we experimentally investigate the effect of concave surface curvature on the propagation of imposed vortices. These experiments are carried out in the Hypervelocity Expansion Tube at the University of Illinois. This facility is capable of generating flows with high enthalpies (4-9MJ/kg) and Mach numbers (3-7). Using a novel, fast-response pressure sensitive paint we are able to observe the development of vortices which are induced using diamond-shaped vortex generators. Models with varying amount of surface curvature (encompassing Goertler numbers between 10-22) are used to investigate the dynamics of vortex propagation and interaction. Our results show that the vortices remain attached and of constant strength for 10-12cm (80 boundary layer thicknesses) along the curved surfaces, while on flat plates the vortices are no longer apparent within 6 cm downstream.
Vorticity Generation on a Flat Surface in 3D Flows
NASA Astrophysics Data System (ADS)
Casciola, C. M.; Piva, R.; Bassanini, P.
1996-12-01
Vortex methods, based on the splitting into Euler and Stokes operators, have been successfully adopted in numerical solutions of three-dimensional Navier-Stokes equations in free-space. Here we deal with their application to flows bounded by solid walls, discussing in particular the boundary conditions for vorticity and their approximation. In two dimensions this has been accomplished by introducing a vortex sheet at the wall, determined by the local slip-velocity, as an approximation of the vorticity source. For three-dimensional flows, we analyze in the context of the Stokes substep the integral equation for the vorticity source and its connection with the creation algorithm adopted in vortex methods. The present analysis leads to a formulation which shows the connection between the exact vorticity source at the wall and the discrete vorticity creation operator adopted in the Chorin-Marsden formula. In particular, the slip velocity at the wall is identified as an approximate solution of the integral equation for the vorticity source and the corresponding error estimate is also discussed. Besides showing the consistency of this approximation, we indicate a numerical procedure which provides a wall-generation of solenoidal vorticity. This is a crucial issue for an accurate application of vortex methods to three-dimensional flows.
The motion of point vortices on closed surfaces
Dritschel, D. G.; Boatto, S.
2015-01-01
We develop a mathematical framework for the dynamics of a set of point vortices on a class of differentiable surfaces conformal to the unit sphere. When the sum of the vortex circulations is non-zero, a compensating uniform vorticity field is required to satisfy the Gauss condition (that the integral of the Laplace–Beltrami operator must vanish). On variable Gaussian curvature surfaces, this results in self-induced vortex motion, a feature entirely absent on the plane, the sphere or the hyperboloid. We derive explicit equations of motion for vortices on surfaces of revolution and compute their solutions for a variety of surfaces. We also apply these equations to study the linear stability of a ring of vortices on any surface of revolution. On an ellipsoid of revolution, as few as two vortices can be unstable on oblate surfaces or sufficiently prolate ones. This extends known results for the plane, where seven vortices are marginally unstable (Thomson 1883 A treatise on the motion of vortex rings, pp. 94–108; Dritschel 1985 J. Fluid Mech. 157, 95–134 (doi:10.1017/S0022112088003088)), and the sphere, where four vortices may be unstable if sufficiently close to the equator (Polvani & Dritschel 1993 J. Fluid Mech. 255, 35–64 (doi:10.1017/S0022112093002381)).
Determining Grain-scale Vorticity Axes from Crystallographic Orientation Data
NASA Astrophysics Data System (ADS)
Michels, Z. D.; Kruckenberg, S. C.; Davis, J. R.; Tikoff, B.
2015-12-01
Aggregates deformed by crystal plastic mechanisms often contain grains that exhibit crystallographic distortion (e.g., kinking, undulose extinction, subgrain development). In such grains, crystallographic orientations are typically dispersed along small circles on lower hemisphere equal-area plots. Thus, we consider that an intragranular dispersion axis represents a grain-scale axis of material rotation, and its position coincides with that of a highly localized vorticity axis. We present a new method for determining the position of a grain-scale vorticity axis from intragranular crystallographic orientation data. This method leverages a method of rotational statistics known as principal geodesic analysis to identify a single best-fit rotational axis that matches the rotational dispersion of crystallographic orientations in a deformed grain. We further demonstrate that populations of such grain-scale vorticity axes can be used to infer a preferred vorticity axis for volumes of deformed aggregates. As an example of this type of application, we calculate intragranular vorticity axes from a sample-scale selection of grains (i.e., all the grains mapped in an EBSD orientation map) and use kernel density estimation to identify a preferred, sample-scale vorticity axis. The results of our bulk analysis match the vorticity axis inferred in previous studies of rocks deformed in the same shear zones.
Chao, A.W.; Palmer, R.B. |; Evans, L.; Gareyte, J.; Siemann, R.H.
1992-12-31
The nominal SSC and LHC designs should operate conservatively at luminosities up to 10{sup 33} cm{sup {minus}2} s{sup {minus}1}. This luminosity is dictated by the event rates that can be handled by the detectors. However, this limit is event dependent (e.g. it does not take much of a detector to detect the event pp {yields} elephant; all one needs is extremely high luminosity). As such, it is useful to explore the possibility of going beyond the 10{sup 33} cm{sup {minus}2} s{sup {minus}1} level. Such exploration will also improve the accelerator physics understanding of pp collider designs. If the detector limitations are removed, the first accelerator limits occur when the luminosity is at the level of 10{sup 34} cm{sup {minus}2}s{sup {minus}1}. These accelerator limits will first be reviewed. The authors will then continue on to explore even higher luminosity as the ultimate limit of pp colliders. Accelerator technologies needed to achieve this ultimate luminosity as well as the R and D needed to reach it are discussed.
Very large hadron collider (VLHC)
1998-09-01
A VLHC informal study group started to come together at Fermilab in the fall of 1995 and at the 1996 Snowmass Study the parameters of this machine took form. The VLHC as now conceived would be a 100 TeV hadron collider. It would use the Fermilab Main Injector (now nearing completion) to inject protons at 150 GeV into a new 3 TeV Booster and then into a superconducting pp collider ring producing 100 TeV c.m. interactions. A luminosity of {approximately}10{sup 34} cm{sup -2}s{sup -1} is planned. Our plans were presented to the Subpanel on the Planning for the Future of US High- Energy Physics (the successor to the Drell committee) and in February 1998 their report stated ``The Subpanel recommends an expanded program of R&D on cost reduction strategies, enabling technologies, and accelerator physics issues for a VLHC. These efforts should be coordinated across laboratory and university groups with the aim of identifying design concepts for an economically and technically viable facility`` The coordination has been started with the inclusion of physicists from Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL), and Cornell University. Clearly, this collaboration must expanded internationally as well as nationally. The phrase ``economically and technically viable facility`` presents the real challenge.
RF sources for future colliders
NASA Astrophysics Data System (ADS)
Phillips, Robert M.
1997-02-01
As we push particle colliders to 1-TeV center-of-mass collision energy and beyond, we require much more from our RF energy sources, both in terms of the RF performance and the number required for a given machine. In order to conserve real estate, the operating frequency of future colliders is apt to be higher than the S-band used for the SLAC SLC. It is this inevitable trend toward higher frequencies which presents the source designer with the greatest challenge. This paper is about that challenge. For reasons which will become clear, as we go to frequencies substantially above X-band, we will require sources other than klystrons, probably of the type referred to as "fast-wave devices," such as FEL or gyro-based amplifiers, or two-beam accelerators. Because these are discussed elsewhere in this conference, I will stick to the klystron as my model in describing the challenges to be overcome, as well as the criteria which must be met by alternative sources for new accelerators.
Heat transfer enhancement using tip and junction vortices
NASA Astrophysics Data System (ADS)
Gentry, Mark Cecil
1998-10-01
Single-phase convective heat transfer can be enhanced by modifying the heat transfer surface to passively generate streamwise vortices. The swirling flow of the vortices modifies the temperature field, thinning the thermal boundary layer and increasing surface convection. Tip vortices generated by delta wings and junction vortices generated by hemispherical protuberances were studied in laminar flat-plate and developing channel flows. Local and average convective measurements were obtained, and the structure of the vortices was studied using quantitative flow visualization and vortex strength measurements. The pressure drop penalty associated with the heat transfer enhancement was also investigated. Tip vortices generated by delta wings enhanced local convection by as much as 300% over a flat-plate boundary layer flow. Vortex strength increased with Reynolds number based on chord length, wing aspect ratio, and wing angle of attack. As the vortices were advected downstream, they decayed because of viscous interactions. In the developing channel flow, tip vortices produced a significant local heat transfer enhancement on both sides of the channel. The largest spatially averaged heat transfer enhancement was 55%; it was accompanied by a 100% increase in the pressure drop relative to the same channel flow with no delta-wing vortex generator. Junction vortices created by hemispherical surface protuberances provided local heat transfer enhancements as large as 250%. Vortex strength increased with an increasing ratio of hemisphere radius to local boundary layer thickness on a flat plate. In the developing channel flows, heat transfer enhancements were observed on both sides of the channel. The largest spatially averaged heat transfer enhancement was 50%; it was accompanied by a 90% pressure drop penalty relative to the same channel flow with no hemispherical vortex generator. This research is important in compact heat exchanger design. Enhancing heat transfer can lead to
Lankford, A.J.
1990-05-01
A number of issues for computing and data handling in the online in environment at future high-luminosity, high-energy colliders, such as the Superconducting Super Collider (SSC) and Large Hadron Collider (LHC), are outlined. Requirements for trigger processing, data acquisition, and online processing are discussed. Some aspects of possible solutions are sketched. 6 refs., 3 figs.
Kinetic study of ion-acoustic plasma vortices
Khan, S. A.; Aman-ur-Rehman; Mendonca, J. T.
2014-09-15
The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.
Stability and nesting of dissipative vortex solitons with high vorticity
NASA Astrophysics Data System (ADS)
Aleksić, B. N.; Aleksić, N. B.; Skarka, V.; Belić, M.
2015-04-01
Using the variational method extended to dissipative systems and numerical simulations, an analytical stability criterion is established allowing the determination of stability domains of parameters for vortices with high topological charge S. Parameters from these domains are used as inputs for numerical self-generation of previously unexplored coexisting stable vortex solitons with topological charge ranging from S =3 to S =20 . The nesting of low-vorticity solitons within those of higher vorticity is discovered. Such a self-organized structuring of light allows for selective dynamic nanophotonic tweezing.
Origin, Evolution, and Imaging of Vortices in Atomic Processes
Macek, Joseph H; Sternberg, James; Ovchinnikov, Serguei Yurevich; Lee, Teck G; Schultz, David Robert
2009-01-01
Vortices are usually associated with systems containing large numbers of particles. Of particular topical interest though are those formed within atomic-scale wave functions and observed in macroscopic systems such as superfluids and quantum condensates. We uncover them here in one of the most fundamental quantum systems consisting of just one electron and two protons. Moreover, the results of novel simulations of the dynamics of this system reveal previously unknown mechanisms of angular momentum transfer and new ways to image atomic-scale quantized vortices at macroscopic distances. Probing of vortices and vortex-driven dynamics in quantum systems is thereby illustrated.
Dynamics of circular arrangements of vorticity in two dimensions.
Swaminathan, Rohith V; Ravichandran, S; Perlekar, Prasad; Govindarajan, Rama
2016-07-01
The merger of two like-signed vortices is a well-studied problem, but in a turbulent flow, we may often have more than two like-signed vortices interacting. We study the merger of three or more identical corotating vortices initially arranged on the vertices of a regular polygon. At low to moderate Reynolds numbers, we find an additional stage in the merger process, absent in the merger of two vortices, where an annular vortical structure is formed and is long lived. Vortex merger is slowed down significantly due to this. Such annular vortices are known at far higher Reynolds numbers in studies of tropical cyclones, which have been noticed to a break down into individual vortices. In the preannular stage, vortical structures in a viscous flow are found here to tilt and realign in a manner similar to the inviscid case, but the pronounced filaments visible in the latter are practically absent in the former. Five or fewer vortices initially elongate radially, and then reorient their long axis closer to the azimuthal direction so as to form an annulus. With six or more vortices, the initial alignment is already azimuthal. Interestingly at higher Reynolds numbers, the merger of an odd number of vortices is found to proceed very differently from that of an even number. The former process is rapid and chaotic whereas the latter proceeds more slowly via pairing events. The annular vortex takes the form of a generalized Lamb-Oseen vortex (GLO), and diffuses inward until it forms a standard Lamb-Oseen vortex. For lower Reynolds number, the numerical (fully nonlinear) evolution of the GLO vortex follows exactly the analytical evolution until merger. At higher Reynolds numbers, the annulus goes through instabilities whose nonlinear stages show a pronounced difference between even and odd mode disturbances. Here again, the odd mode causes an early collapse of the annulus via decaying turbulence into a single central vortex, whereas the even mode disturbance causes a more
Dynamics of circular arrangements of vorticity in two dimensions
NASA Astrophysics Data System (ADS)
Swaminathan, Rohith V.; Ravichandran, S.; Perlekar, Prasad; Govindarajan, Rama
2016-07-01
The merger of two like-signed vortices is a well-studied problem, but in a turbulent flow, we may often have more than two like-signed vortices interacting. We study the merger of three or more identical corotating vortices initially arranged on the vertices of a regular polygon. At low to moderate Reynolds numbers, we find an additional stage in the merger process, absent in the merger of two vortices, where an annular vortical structure is formed and is long lived. Vortex merger is slowed down significantly due to this. Such annular vortices are known at far higher Reynolds numbers in studies of tropical cyclones, which have been noticed to a break down into individual vortices. In the preannular stage, vortical structures in a viscous flow are found here to tilt and realign in a manner similar to the inviscid case, but the pronounced filaments visible in the latter are practically absent in the former. Five or fewer vortices initially elongate radially, and then reorient their long axis closer to the azimuthal direction so as to form an annulus. With six or more vortices, the initial alignment is already azimuthal. Interestingly at higher Reynolds numbers, the merger of an odd number of vortices is found to proceed very differently from that of an even number. The former process is rapid and chaotic whereas the latter proceeds more slowly via pairing events. The annular vortex takes the form of a generalized Lamb-Oseen vortex (GLO), and diffuses inward until it forms a standard Lamb-Oseen vortex. For lower Reynolds number, the numerical (fully nonlinear) evolution of the GLO vortex follows exactly the analytical evolution until merger. At higher Reynolds numbers, the annulus goes through instabilities whose nonlinear stages show a pronounced difference between even and odd mode disturbances. Here again, the odd mode causes an early collapse of the annulus via decaying turbulence into a single central vortex, whereas the even mode disturbance causes a more
Thermal convection and emergence of isolated vortices in soap bubbles.
Seychelles, F; Amarouchene, Y; Bessafi, M; Kellay, H
2008-04-11
A novel thermal convection cell consisting of half a soap bubble heated at the equator is introduced to study thermal convection and the movement of isolated vortices. The soap bubble, subject to stratification, develops thermal convection at its equator. A particular feature of this cell is the emergence of isolated vortices. These vortices resemble hurricanes or cyclones and similarities between our observed structures and these natural objects are found. This is brought forth through a study of the mean square displacement of these objects showing signs of superdiffusion. PMID:18518038
On the propagation of vorticity in multi-species plasmas
Núñez, Manuel
2013-12-15
The evolution of plasmas formed by several species is governed by one fluid equation for each species, all of them linked by an electromagnetic forcing and collisional terms, and the Maxwell equations. It is found that in the collisionless case, the field lines of a combination of fluid vorticity and magnetic field are transported by the flow as material points. In consequence, the vorticity propagates at the same velocity as the magnetic field. This is studied in depth for a number of simple configurations, showing that the vorticity travels at a certain fraction of the speed of light, depending on the size of the spatial mode.
Thermal convection and emergence of isolated vortices in soap bubbles.
Seychelles, F; Amarouchene, Y; Bessafi, M; Kellay, H
2008-04-11
A novel thermal convection cell consisting of half a soap bubble heated at the equator is introduced to study thermal convection and the movement of isolated vortices. The soap bubble, subject to stratification, develops thermal convection at its equator. A particular feature of this cell is the emergence of isolated vortices. These vortices resemble hurricanes or cyclones and similarities between our observed structures and these natural objects are found. This is brought forth through a study of the mean square displacement of these objects showing signs of superdiffusion.
CH4-CO2 reforming in surface DBD reactor with ZnO-Cu and NiO catalysts
NASA Astrophysics Data System (ADS)
Lazzaroni, Claudia; Rahmani, Abdelkader; Nikravech, Mehrdad; MP4 Team
2015-09-01
Dry reforming of methane (CH4) is carried out in an atmospheric pressure Dielectric Barrier Discharge (DBD) reactor. The two 3 mm thickness aluminum electrodes are separated by a 3 mm thickness dielectric sheet made of quartz. The electrodes present 3 branches and the space between two adjacent branches is filled with beads of catalyst which are 2 mm diameter alumina beads coated with ZnO-Cu or NiO. The coating is performed in two different ways: (i) by impregnation and (ii) by fluidized spray plasma. A 30 kHz and several kV AC voltage is applied to the electrodes. The feedstock gas is a mixture of argon, carbon dioxide (CO2) and methane with individual fluxes varying from 20 to 80 mL/min. At the reactor outlet, the gas goes through a condenser at 4°C to condense liquid products. The reforming reaction products are identified by liquid and gas phase chromatography. The effect of the applied power and the catalyst nature on the product distribution is studied. Whatever the catalyst, the conversion rate of CH4 and CO2 increases with the applied power while the selectivity of gas products is almost independent of the power. The condensed liquids collected under our experimental conditions, such as ethanol or acetic acid, represent more than 10% of the products. This work is partially supported by the Programme Interdisciplinaire SPC: Énergie, Société, Territoire.
NASA Astrophysics Data System (ADS)
Berardinelli, Annachiara; Vannini, Lucia; Ragni, Luigi; Guerzoni, M. Elisabetta
The effects of gas plasma generated by a Dielectric Barrier Discharge (DBD) device on "Abate Fetel" fresh pears were assessed following exposure times from 10 to 90 min. In particular the decontamination efficacy towards the indigenous microflora naturally occurring on the surface of the fruit was evaluated. The main results showed that total mesophilic bacteria, yeasts and moulds had different inactivation dynamics. However, maximum cell decreases of 2.5 Log CFU/fruit were achieved for all the microbial groups after 90 min of treatment at a relative humidity level of 60% (22°C). Immediately after the treatments, no significant effects were observed on the measured quality traits. After storage for 5 days at 20°C significant changes were detected only in the peel (colour and antioxidant capacity) of fruit samples treated for 90 min. The Magness-Taylor flesh firmness (MTf), the soluble solid content (SSC) and the antioxidant capacity of fruits were unaffected by the tested treatments.
Research and Development of Future Muon Collider
Yonehara, K.; /Fermilab
2012-05-01
Muon collider is a considerable candidate of the next generation high-energy lepton collider machine. A novel accelerator technology must be developed to overcome several intrinsic issues of muon acceleration. Recent research and development of critical beam elements for a muon accelerator, especially muon beam phase space ionization cooling channel, are reviewed in this paper.
Search for top quark at Fermilab Collider
Sliwa, K.; The CDF Collaboration
1991-10-01
The status of a search for the top quark with Collider Detector at Fermilab (CDF), based on a data sample recorded during the 1988--1989 run is presented. The plans for the next Fermilab Collider run in 1992--1993 and the prospects of discovering the top quark are discussed. 19 refs., 4 figs., 2 tabs.
Polarization Effects at a Muon Collider
Parsa, Z.
1998-11-01
For Muon Colliders, Polarization will be a useful tool if high polarization is achievable with little luminosity loss. Formulation and effects of beam polarization and luminosity including polarization effects in Higgs resonance studies are discussed for improving precision measurements and Higgs resonance ''discovery'' capability e.g. at the First Muon Collider (FMC).
Bilepton production at hadron colliders
NASA Astrophysics Data System (ADS)
Dion, B.; Grégoire, T.; London, D.; Marleau, L.; Nadeau, H.
1999-04-01
We examine, as model-independently as possible, the production of bileptons at hadron colliders. When a particular model is necessary or useful, we choose the 3-3-1 model. We consider a variety of processes: qq¯-->Y++Y--, ud¯-->Y++Y-, ūd-->Y+Y--, qq¯-->Y++e-e-, qq¯-->φ++φ--, ud¯-->φ++φ-, and ūd-->φ+φ--, where Y and φ are vector and scalar bileptons, respectively. Given the present low-energy constraints, we find that, at the Fermilab Tevatron, vector bileptons are unobservable, while light scalar bileptons (Mφ<~300 GeV) are just barely observable. At the CERN LHC, the reach is extended considerably: vector bileptons of mass MY<~1 TeV are observable, as are scalar bileptons of mass Mφ<~850 GeV.
Disformal dark energy at colliders
NASA Astrophysics Data System (ADS)
Brax, Philippe; Burrage, Clare; Englert, Christoph
2015-08-01
Disformally coupled, light scalar fields arise in many of the theories of dark energy and modified gravity that attempt to explain the accelerated expansion of the Universe. They have proved difficult to constrain with precision tests of gravity because they do not give rise to fifth forces around static nonrelativistic sources. However, because the scalar field couples derivatively to standard model matter, measurements at high-energy particle colliders offer an effective way to constrain and potentially detect a disformally coupled scalar field. Here we derive new constraints on the strength of the disformal coupling from LHC run 1 data and provide a forecast for the improvement of these constraints from run 2. We additionally comment on the running of disformal and standard model couplings in this scenario under the renormalization group flow.
XXth Hadron Collider Physics Symposium
NASA Astrophysics Data System (ADS)
In 2009, the Hadron Collider Physics Symposium took place in Evian (France), on the shore of the Geneva Lake, from 16-20 November. It was jointly organised by CERN and the French HEP community (CNRS-IN2P3 and CEA-IRFU). This year's symposium come at an important time for both the Tevatron and LHC communities. It stimulated the completion of analyses for a significant Tevatron data sample, and it allowed an in-depth review of the readiness of the LHC and its detectors just before first collisions. The programme includes sessions on top-quark and electro-weak physics, QCD, B physics, new phenomena, electro-weak symmetry breaking, heavy ions, and the status and commissioning of the LHC machine and its experiments. Conference website : http://hcp2009.in2p3.fr/
Collider searches for extra dimensions
Landsberg, Greg; /Brown U.
2004-12-01
Searches for extra spatial dimensions remain among the most popular new directions in our quest for physics beyond the Standard Model. High-energy collider experiments of the current decade should be able to find an ultimate answer to the question of their existence in a variety of models. Until the start of the LHC in a few years, the Tevatron will remain the key player in this quest. In this paper, we review the most recent results from the Tevatron on searches for large, TeV{sup -1}-size, and Randall-Sundrum extra spatial dimensions, which have reached a new level of sensitivity and currently probe the parameter space beyond the existing constraints. While no evidence for the existence of extra dimensions has been found so far, an exciting discovery might be just steps away.
Collider Detector at Fermilab (CDF)
Jensen, H.B.
1985-10-01
A description of the Collider Detector at Fermilab (CDF) is given. It is a calorimetric detector, which covers almost the complete solid angle around the interaction region with segmented calorimeter ''towers''. A 1.5 Tesla superconducting solenoid, 3m in diameter and 5m long, provides a uniform magnetic field in the central region for magnetic analysis of charged particles. The magnetic field volume is filled with a large cylindrical drift chamber and a set of Time Projection Chambers. Muon detection is accomplished with drift chambers outside the calorimeters in the central region and with large magnetized steel toroids and associated drift chambers in the forward-backward regions. The electronics has a large dynamic range to allow measurement of both high energy clusters and small energy depositions made by penetrating muons. Interesting events are identified by a trigger system which, together with the rest of the data acquisition system, is FASTBUS based.
A numerical study of vorticity-enhanced heat transfer
NASA Astrophysics Data System (ADS)
Wang, Xiaolin; Alben, Silas
2012-11-01
The Glezer lab at Georgia Tech has found that vorticity produced by vibrated reeds can improve heat transfer in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we simulate the heat transfer process in a 3-dimensional plate-fin heat sink. We propose a simplified model by considering flow and temperature in a 2-D channel, and extend the model to the third dimension using a 1-D heat fin model. We simulate periodically steady-state solutions. We determine how the global Nusselt number is increased, depending on the vortices' strengths and spacings, in the parameter space of Reynolds and Peclet numbers. We find a surprising spatial oscillation of the local Nusselt number due to the vortices. Support from NSF-DMS grant 1022619 is acknowledged.
The decay of longitudinal vortices shed from airfoil vortex generators
NASA Technical Reports Server (NTRS)
Wendt, Bruce J.; Reichert, Bruce A.; Foster, Jeffry D.
1995-01-01
An experimental study is conducted to examine the crossplane structure and streamwise decay of vortices shed from airfoil-type vortex generators. The vortex generators are set in a counter-rotating array spanning the full circumference of a straight pipe. The span of the vortex generators above the duct surface, h, is approximately equal to the local turbulent boundary layer thickness, delta. Measurement of three-component mean flow velocity in downstream crossplanes are used to characterize the structure of the shed vortices. Measurements in adjacent crossplanes (closely spaced along the streamwise coordinate) characterize the interaction and decay of the embedded vortices. A model constructed by the superposition of Oseen vortices is compared to the data for one test case.
Comparing the dynamics of skyrmions and superconducting vortices
NASA Astrophysics Data System (ADS)
Olson Reichhardt, C. J.; Lin, S. Z.; Ray, D.; Reichhardt, C.
2014-08-01
Vortices in type-II superconductors have attracted enormous attention as ideal systems in which to study nonequilibrium collective phenomena, since the self-ordering of the vortices competes with quenched disorder and thermal effects. Dynamic effects found in vortex systems include depinning, nonequilibrium phase transitions, creep, structural order-disorder transitions, and melting. Understanding vortex dynamics is also important for applications of superconductors which require the vortices either to remain pinned or to move in a controlled fashion. Recently, topological defects called skyrmions have been realized experimentally in chiral magnets. Here we highlight similarities and differences between skyrmion dynamics and vortex dynamics. Many of the previous ideas and experimental setups that have been applied to superconducting vortices can also be used to study skyrmions. We also discuss some of the differences between the two systems, such as the potentially large contribution of the Magnus force in the skyrmion system that can dramatically alter the dynamics and transport properties.
EFFECTS OF DUST FEEDBACK ON VORTICES IN PROTOPLANETARY DISKS
Fu, Wen; Liang, Edison; Li, Hui; Li, Shengtai; Lubow, Stephen
2014-11-10
We carried out two-dimensional, high-resolution simulations to study the effect of dust feedback on the evolution of vortices induced by massive planets in protoplanetary disks. Various initial dust to gas disk surface density ratios (0.001-0.01) and dust particle sizes (Stokes number 4 × 10{sup –4}-0.16) are considered. We found that while dust particles migrate inward, vortices are very effective at collecting them. When dust density becomes comparable to gas density within the vortex, a dynamical instability is excited and it alters the coherent vorticity pattern and destroys the vortex. This dust feedback effect is stronger with a higher initial dust/gas density ratio and larger dust grain. Consequently, we found that the disk vortex lifetime can be reduced up to a factor of 10. We discuss the implications of our findings on the survivability of vortices in protoplanetary disks and planet formation.
Potential Vorticity and Ozone in Martian Polar Regions
NASA Astrophysics Data System (ADS)
Holmes, J. A.; Lewis, S. R.; Patel, M. R.
2016-09-01
The link between potential vorticity, a dynamical tracer, and ozone is explored for the first time in the polar regions of Mars using a global climate model. Preliminary results and potential applications are discussed.
Chirp-driven giant phase space vortices
NASA Astrophysics Data System (ADS)
Trivedi, Pallavi; Ganesh, Rajaraman
2016-06-01
In a collisionless, unbounded, one-dimensional plasma, modelled using periodic boundary conditions, formation of steady state phase space coherent structures or phase space vortices (PSV) is investigated. Using a high resolution one-dimensional Vlasov-Poisson solver based on piecewise-parabolic advection scheme, the formation of giant PSV is addressed numerically. For an infinitesimal external drive amplitude and wavenumber k, we demonstrate the existence of a window of chirped external drive frequency that leads to the formation of giant PSV. The linear, small amplitude, external drive, when chirped, is shown to couple effectively to the plasma and increase both streaming of "untrapped" and "trapped" particle fraction. The steady state attained after the external drive is turned off and is shown to lead to a giant PSV with multiple extrema and phase velocities, with excess density fraction, defined as the deviation from the Maxwellian background, Δ n / n 0 ≃ 20 % - 25 % . It is shown that the process depends on the chirp time duration Δt. The excess density fraction Δn/n0, which contains both trapped and untrapped particle contribution, is also seen to scale with Δt, only inhibited by the gradient of the distribution in velocity space. Both single step drive and multistep chirp processes are shown to lead to steady state giant PSV, with multiple extrema due to embedded holes and clumps, long after the external drive is turned off.
Non-Abelian vortices with a twist
NASA Astrophysics Data System (ADS)
Forgács, Péter; Lukács, Árpád; Schaposnik, Fidel A.
2015-06-01
Non-Abelian flux-tube (string) solutions carrying global currents are found in the bosonic sector of four-dimensional N =2 supersymmetric gauge theories. The specific model considered here possesses U(2 ) local×SU(2 ) global symmetry, with two scalar doublets in the fundamental representation of SU(2). We construct string solutions that are stationary and translationally symmetric along the x3 direction, and they are characterized by a matrix phase between the two doublets, referred to as "twist." Consequently, twisted strings have nonzero (global) charge, momentum, and in some cases even angular momentum per unit length. The planar cross section of a twisted string corresponds to a rotationally symmetric, charged non-Abelian vortex, satisfying first-order Bogomolny-type equations and second-order Gauss constraints. Interestingly, depending on the nature of the matrix phase, some of these solutions even break cylindrical symmetry in R3. Although twisted vortices have higher energy than the untwisted ones, they are expected to be linearly stable since one can keep their charge (or twist) fixed with respect to small perturbations.
Potential vorticity patterns in Mediterranean hurricanes
NASA Astrophysics Data System (ADS)
Laviola, Sante; Marcello Miglietta, M.; Cerrai, Diego; Cattani, Elsa; Levizzani, Vincenzo
2016-04-01
Two new variables have been introduced to better identify the potential vorticity (PV) anomalies due to the intrusion of dry stratospheric air from those induced by the diabatic latent heating. This new approach has been applied to the analysis of three Mediterranean tropical-like cyclones characterized by heavy precipitation patterns. Model simulations show that the interaction between an upper level PV streamer, located on the left exit of a jet stream and a middle-low level PV anomaly, induced by the convection development around the low level vortex, plays a key role in the intensification of cyclones in all cases. These anomalies, despite their strong mutual interaction, do not form a fully developed PV tower. In the mature stage, the shape of the upper level PV anomaly around the cyclone is different for each case and appears somehow dependent on the lifetime of the vortex. A first comparison with satellite-derived products seems to confirm the initial results from model simulations.
The fate of stratospheric potential vorticity cutoffs
NASA Astrophysics Data System (ADS)
Portmann, Raphael; Crezee, Bas; Quinting, Julian; Wernli, Heini
2016-04-01
Stratospheric cutoffs of potential vorticity (PV) frequently form through non-linear breaking of Rossby waves in mid-latitudes. Through destabilisation of the tropospheric layers beneath, they can trigger convection. Alternatively, through their induced horizontal advection they can produce intense precipitation events near topography and in regions with a background baroclinicity. PV cutoff lifecycles show high variability: their lifetime ranges between 1 and more than 10 days and the end of the lifecycle can occur through diabatic decay - leading to stratosphere-troposphere exchange - or re-absorption by the polar stratospheric reservoir. The relative frequency of these two processes is however unclear, as is the quantitative link between cutoffs and convective and large-scale precipitation. Two case studies are performed by using ECMWF analysis data, backward trajectories and radio soundings to look in detail at the processes involved in the diabatic decay. It is found that latent heating in convective updrafts - and the associated cross-isentropic transport of low PV air - largely explains the diabatic decay of the cutoffs. Using a tracking algorithm we produce an ERA-Interim cutoff climatology that provides information about the statistics of the cutoff lifetime and the relative frequency of stratospheric re-absorption versus diabatic decay. In addition, we track atmospheric stability and total column water beneath the cutoffs in order to investigate why certain cutoffs decay faster than others. The results contribute to a better understanding of the lifecycle of PV cutoffs and a particular process of stratosphere-troposphere exchange.
Control of vortical separation on conical bodies
NASA Technical Reports Server (NTRS)
Mourtos, Nikos J.; Roberts, Leonard
1987-01-01
In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.
Spiral inertial waves emitted from geophysical vortices
NASA Astrophysics Data System (ADS)
Wang, Peng; Özgökmen, Tamay M.
2016-03-01
By numerically simulating an initially unstable geophysical vortex, we discover for the first time a special kind of inertial waves, which are emitted in a spiral manner from the vortices; we refer to these waves as spiral inertial waves (SIWs). SIWs appear at small Rossby numbers (0.01 ≤ Ro ≤ 1) according to our parameter sweep experiments; the amplitude, wavelength and frequency of SIWs are sensitive to Rossby numbers. We extend the Lighthill-Ford radiation into inertial waves, and propose an indicator for the emission of inertial waves; this indicator may be adopted into general circulation models to parameterize inertial waves. Additionally, in our tracer releasing experiments, SIWs organize tracers into spirals, and modify the tracer's local rate of change by advecting tracers vertically. Further, the spirals of SIWs resembles some spiral features observed in the ocean and atmosphere, such as spiral ocean eddies and spiral hurricane rainbands; thus, SIWs may offer another mechanism to form spiral eddies and rainbands. Since no density anomaly is required to generate the spirals of SIWs, we infer that the density anomaly, hence the baroclinic or frontal instability, is unlikely to be the key factor in the formation of these spiral features.
Nonparaxial optical vortices and Kummer laser beams
NASA Astrophysics Data System (ADS)
Kovalev, Alexey A.; Kotlyar, Victor V.; Nalimov, Anton G.
2013-09-01
Two approaches to describe nonparaxial optical vortices were considered. One approach is to use a revised Kirchhoff integral, which does not neglect the relief of an optical element. Using this integral and the finite-difference time-domain method it is shown that an optical vortex generated by a refractive spiral plate with a relief step has an asymmetric profile. The annular diffraction pattern in the vortex beam cross-section is found to be disturbed not only for the near-field diffraction but also for the middle-field diffraction, at a distance of several Fresnel lengths. Another approach is to solve the Helmholtz equation without any approximations. An analytical solution to describe propagation of a light beam in the positive direction of the optical axis was found. The complex amplitude of such a beam is found to be in direct proportion to the product of two linearly independent solutions of Kummer's differential equation. Relationships for a particular case of such beams-namely, the Hankel-Bessel (HB) beams-are deduced. The autofocusing of the HB beams is studied.
Mutual colliding impact fast ignition
Winterberg, Friedwardt
2014-09-15
It is proposed to apply the well established colliding beam technology of high energy physics to the fast hot spot ignition of a highly compressed DT (deuterium-tritium) target igniting a larger D (deuterium) burn, by accelerating a small amount of solid deuterium, and likewise a small amount of tritium, making a head-on collision in the center of the target, projecting them through conical ducts situated at the opposite side of the target and converging in its center. In their head-on collision, the relative collision velocity is 5/3 times larger compared to the collision velocity of a stationary target. The two pieces have for this reason to be accelerated to a smaller velocity than would otherwise be needed to reach upon impact the same temperature. Since the velocity distribution of the two head-on colliding projectiles is with its two velocity peaks non-Maxwellian, the maximum cross section velocity product turns out to be substantially larger than the maximum if averaged over a Maxwellian. The D and T projectiles would have to be accelerated with two sabots driven by powerful particle or laser beams, permitting a rather large acceleration length. With the substantially larger cross section-velocity product by virtue of the non-Maxwellian velocity distribution, a further advantage is that the head-on collision produces a large magnetic field by the thermomagnetic Nernst effect, enhancing propagating burn. With this concept, the ignition of the neutron-less hydrogen-boron (HB{sup 11}) reaction might even be possible in a heterogeneous assembly of the hydrogen and the boron to reduce the bremsstrahlung-losses, resembling the heterogeneous assembly in a graphite-natural uranium reactor, there to reduce the neutron losses.
2011-01-01
Background Various members of the family of BTB/POZ zinc-finger transcription factors influence patterns of dendritic branching. One such member, Broad, is notable because its BrZ3 isoform is widely expressed in Drosophila in immature neurons around the time of arbor outgrowth. We used the metamorphic remodeling of an identified sensory neuron, the dorsal bipolar dendrite sensory neuron (dbd), to examine the effects of BrZ3 expression on the extent and pattern of dendrite growth during metamorphosis. Results Using live imaging of dbd in Drosophila pupae, we followed its normal development during metamorphosis and the effect of ectopic expression of BrZ3 on this development. After migration of its cell body, dbd extends a growth-cone that grows between two muscle bands followed by branching and turning back on itself to form a compact dendritic bundle. The ectopic expression of the BrZ3 isoform, using the GAL4/UAS system, caused dbd's dendritic tree to transform from its normal, compact, fasciculated form into a comb-like arbor that spread over on the body wall. Time-lapse analysis revealed that the expression of BrZ3 caused the premature extension of the primary dendrite onto immature myoblasts, ectopic growth past the muscle target region, and subsequent elaboration onto the epidermis. To control the timing of expression of BrZ3, we used a temperature-sensitive GAL80 mutant. When BrZ3 expression was delayed until after the extension of the primary dendrite, then a normal arbor was formed. By contrast, when BrZ3 expression was confined to only the early outgrowth phase, then ectopic arbors were subsequently formed and maintained on the epidermis despite the subsequent absence of BrZ3. Conclusions The adult arbor of dbd is a highly branched arbor whose branches self-fasciculate to form a compact dendritic bundle. The ectopic expression of BrZ3 in this cell causes a premature extension of its growth-cone, resulting in dendrites that extend beyond their normal muscle
Simulating living organisms with populations of point vortices
Schmieder, R.W.
1995-07-01
The author has found that time-averaged images of small populations of point vortices can exhibit motions suggestive of the behavior of individual organisms. As an example, the author shows that collections of point vortices confined in a box and subjected to heating can generate patterns that are broadly similar to interspecies defense in certain sea anemones. It is speculated that other simple dynamical systems can be found to produce similar complex organism-like behavior.
Large-Eddy Simulations of Dust Devils and Convective Vortices
NASA Astrophysics Data System (ADS)
Spiga, Aymeric; Barth, Erika; Gu, Zhaolin; Hoffmann, Fabian; Ito, Junshi; Jemmett-Smith, Bradley; Klose, Martina; Nishizawa, Seiya; Raasch, Siegfried; Rafkin, Scot; Takemi, Tetsuya; Tyler, Daniel; Wei, Wei
2016-09-01
In this review, we address the use of numerical computations called Large-Eddy Simulations (LES) to study dust devils, and the more general class of atmospheric phenomena they belong to (convective vortices). We describe the main elements of the LES methodology. We review the properties, statistics, and variability of dust devils and convective vortices resolved by LES in both terrestrial and Martian environments. The current challenges faced by modelers using LES for dust devils are also discussed in detail.
Visualization and Quantification of Rotor Tip Vortices in Helicopter Flows
NASA Technical Reports Server (NTRS)
Kao, David L.; Ahmad, Jasim U.; Holst, Terry L.
2015-01-01
This paper presents an automated approach for effective extraction, visualization, and quantification of vortex core radii from the Navier-Stokes simulations of a UH-60A rotor in forward flight. We adopt a scaled Q-criterion to determine vortex regions and then perform vortex core profiling in these regions to calculate vortex core radii. This method provides an efficient way of visualizing and quantifying the blade tip vortices. Moreover, the vortices radii are displayed graphically in a plane.
Onishchenko, O. G.; Horton, W.; Scullion, E.; Fedun, V.
2015-12-15
The new type of large-scale vortex structures of dispersionless Alfvén waves in collisionless plasma is investigated. It is shown that Alfvén waves can propagate in the form of Alfvén vortices of finite characteristic radius and characterised by magnetic flux ropes carrying orbital angular momentum. The structure of the toroidal and radial velocity, fluid and magnetic field vorticity, the longitudinal electric current in the plane orthogonal to the external magnetic field are discussed.
NASA Astrophysics Data System (ADS)
Onishchenko, O. G.; Pokhotelov, O. A.; Horton, W.; Scullion, E.; Fedun, V.
2015-12-01
The new type of large-scale vortex structures of dispersionless Alfvén waves in collisionless plasma is investigated. It is shown that Alfvén waves can propagate in the form of Alfvén vortices of finite characteristic radius and characterised by magnetic flux ropes carrying orbital angular momentum. The structure of the toroidal and radial velocity, fluid and magnetic field vorticity, the longitudinal electric current in the plane orthogonal to the external magnetic field are discussed.
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
Wen Linghua; Xiong Hongwei; Wu Biao
2010-11-15
We study vortex formation in a Bose-Einstein condensate in a rotating double-well potential. In addition to the ordinary quantized vortices and elusive ghost vortices, 'hidden' vortices are found distributed along the central barrier. These hidden vortices are invisible like ghost vortices but carry angular momentum. Moreover, their core size is not given by the healing length, but is strongly influenced by the external potential. We find that the Feynman rule can be well satisfied only after including the hidden vortices. There is no critical rotation frequency for the formation of hidden vortices while there is one for the formation of ordinary visible vortices. Hidden vortices can be revealed in the free expansion of Bose-Einstein condensates. In addition, the hidden vortices in a Bose-Einstein condensate can appear in other external potentials, such as a rotating anisotropic toroidal trap.
Hybrid Manipulation of Streamwise Vorticity in a Diffuser Boundary Layer
NASA Astrophysics Data System (ADS)
Gissen, Abraham; Vukasinovic, Bojan; Culp, John; Glezer, Ari
2010-11-01
The formation of streamwise vorticity concentrations by exploiting the interaction of surface-mounted passive (micro-vanes) and active (synthetic jets) flow control elements with the cross flow is investigated experimentally in a small-scale serpentine duct at high subsonic speeds (up to M = 0.6). Streamwise vortices can be a key element in the mitigation of the adverse effects on pressure recovery and distortion caused by the naturally occurring secondary flows in embedded propulsion systems with complex inlet geometries. Counter rotating and single-sense vortices are formed using conventional passive micro-vanes and active high-power synthetic jet actuators. Interaction of the flow control elements is examined through a hybrid actuation scheme whereby synthetic jet actuation augments the primary vanes' vortices resulting in dynamic enhancement of their strength. It is shown that such sub-boundary layer individual vortices can merge and evolve into duct-scale vortical structures that counteract the inherent secondary flow and mitigates global flow distortion.
The structure of intense vorticity in homogeneous isotropic turbulence
NASA Technical Reports Server (NTRS)
Jimenez, J.; Wray, A. A.; Saffman, P. G.; Rogallo, R. S.
1992-01-01
The structure of the intense vorticity regions is studied in numerically simulated homogeneous, isotropic, equilibrium turbulent flow fields at four different Reynolds numbers in the range Re(sub lambda) = 36-171. In accordance with previous investigators, this vorticity is found to be organized in coherent, cylindrical or ribbon-like, vortices ('worms'). A statistical study suggests that they are just especially intense features of the background, O(omega'), vorticity. Their radii scale with the Kolmogorov microscale and their lengths with the integral scale of the flow. An interesting observation is that the Reynolds number based on the circulation of the intense vortices, gamma/nu, increases monotonically with Re(sub lambda), raising the question of the stability of the structures in the limit of Re(sub lambda) approaching infinity. One and two-dimensional statistics of vorticity and strain are presented; they are non-gaussian, and the behavior of their tails depends strongly on the Reynolds number. There is no evidence of convergence to a limiting distribution in our range of Re(sub lambda), even though the energy spectra and the energy dissipation rate show good asymptotic properties in the higher Reynolds number cases. Evidence is presented to show that worms are natural features of the flow and that they do not depend on the particular forcing scheme.
Observations of ionospheric convection vortices - Signatures of momentum transfer
NASA Technical Reports Server (NTRS)
Mchenry, M. A.; Clauer, C. R.; Friis-Christensen, E.; Kelly, J. D.
1988-01-01
Several classes of traveling vortices in the dayside ionospheric flow have been detected and tracked using the Greenland magnetometer chain. One class observed during quiet times consists of a continuous series of vortices moving generally antisunward for several hours at a time. Assuming each vortex to be the convection pattern produced by a small field aligned current moving across the ionosphere, the amount of field aligned current was found by fitting a modeled ground magnetic signature to measurements from the chain of magnetometers. The calculated field aligned current is seen to be steady for each vortex and neighboring vortices have currents of opposite sign. Low altitude DMSP observations indicate the vortices are on field lines which map to the inner edge of the low latitude boundary layer. Because the vortices are conjugate to the boundary layer, repeat in a regular fashion and travel antisunward, it is argued that this class of vortices is caused by surface waves at the magnetopause. No strong correlations between field aligned current strength and solar wind density, velocity, or Bz is found.
Comparison between ionospheric convection vortices and the associated equivalent currents
NASA Astrophysics Data System (ADS)
Liang, J.; Benkevitch, L.; Sofko, G. J.; Koustov, A. V.
2004-12-01
The equivalent current pattern derived from CANOPUS, NRCAN/GSC and MACCS magnetometers has been compared with the ionospheric convection pattern observed by SuperDARN HF radars. The discrepancies between the equivalent convection (EQC) and the SuperDARN-observed convection (SDC) patterns are explained in terms of the effect of day-night photoionization conductance gradient and the coupling between field-aligned currents (FACs) and ionospheric conductances. In particular, the agreement between the EQC and SDC patterns is usually worse for a counterclockwise convection vortex than for a clockwise cell, but a consistent pattern of discrepancy for counterclockwise convection vortices has been found. We suggest that the discrepancies are due to a downward FAC-conductance coupling process. Since the counterclockwise vortices and clockwise vortices occur predominantly in the dawn and dusk sectors, respectively, in accordance with the usual 2-cell global convection pattern, the asymmetry between the EQC and SDC patterns for counterclockwise vortices and clockwise vortices would naturally lead to a dawn-dusk asymmetry as well. This is revealed by a global statistical study of the deviation of direction between the magnetic equivalent convection and the SuperDARN convection in different time sectors and latitudes. In the dawn sector, the statistical results reveal that, at lower latitudes, the EQC direction deviation is slightly counterclockwise with respect to the SDC direction, whereas the deviation is significantly clockwise at high latitudes. These deviations are consistent with the discrepancy pattern for counterclockwise convection vortices, as found in the individual vortex event studies.
The treatment of convected vortices in compressible potential flow
NASA Technical Reports Server (NTRS)
Steinhoff, J.; Ramachandran, K.; Suryanarayanan, K.
1983-01-01
A method is described for incorporating line vortices into the three dimensional compressible potential flow equation. A modified Biot-Savart law is used to compute a vortical velocity field, which is added to the gradient of the potential to form a total velocity. A rapidly converging approximate factorization (AFZ) scheme is then used to compute a potential such that the modified potential flow equation as well as the appropriate boundary conditions, based on total velocity, are satisfied. As part of a coupled iteration procedure, the positions of the line vortices are computed so that they convect with the total flow. The method is used to compute the field due to a single line vortex convecting past a wing. This represents an approximation of the effect of a canard or other lifting surface ahead of the wing, which sheds a tip vortex. It is seen that the flow field is substantially modified by the passage of the vortex. Unlike Euler equation schemes, which are also used to compute these flows, the solutions exhibit no numerical diffusion: The convected vortices retain their initial upstream width. Euler solutions, on the other hand, involve a vorticity which is numerically convected in an Eulerian frame and, unless extensive adaptive grid refinement is used they result in vortices with spread as they convect. Also, the potential flow method requires approximately two orders of magnitude less computing time and much less computer storage than the Euler methods.
Quasi-steady linked vortices with chaotic streamlines
NASA Astrophysics Data System (ADS)
Velasco Fuentes, Oscar; Romero Arteaga, Angelica
2010-11-01
We study the dynamics of two or more toroidal filamentary vortices ---i.e. thin tubular vortices coiled on an immaterial torus--- in an otherwise quiescent, ideal fluid. Assuming that the vortices are identical and equally spaced on a meridional section of the torus, the flow evolution depends on the torus aspect ratio (R), the number of vortices (N), and the vortex topology (Vp,q, where p and q are coprime integers such that the Vp,q vortex winds p times round the torus symmetry axis and q times round the torus centerline). The evolution of sets of V1,1 and V1,2 vortices was computed using the Rosenhead--Moore approximation to evaluate the velocity field and a fourth-order Runge-Kutta scheme to advance in time. It was found that vortex sets with N<6 and R<0.15 progressed along and rotated around the torus symmetry axis in an almost steady manner while each vortex in the set approximately preserved its shape. The velocity field, observed in the comoving frame, has two stagnation points. The stream tube starting at the forward stagnation point and the stream tube ending at the backward stagnation point transversely intersect along a finite number of streamlines. The three-dimensional chaotic tangle that arises has a geometry which depends primarily on the number of vortices N.
Two-dimensional nonlinear dynamics of four driven vortices
Guzdar, P.N.; Finn, J.M.; Rogalsky, A.V.; Drake, J.F. )
1994-03-01
The interaction of four alternately driven counterrotating vortices in a two-dimensional box, with inpenetrable free-slip boundary conditions in the [ital x] direction and periodic boundary conditions in the [ital y] direction, has been studied numerically. For viscosity above a critical value the nonlinear state consists of four alternately counterrotating vortices. For a lower value of the viscosity the system evolves to a nonlinear steady state consisting of four vortices and shear flow generated by the peeling instability'' [Drake [ital et] [ital al]., Phys. Fluids B 4, 447 (1992)]. For a still lower viscosity the steady-state nonlinear state undergoes a Hopf bifurcation. The periodic state is caused by a secondary instability associated with vortex pairing. However, the vorticity of the shear flow, though periodic, has a definite sign. With a further decrease in the viscosity, a global bifurcation gives rise to a periodic state during which the vorticity of the shear flow changes sign. At even lower viscosity, there is a transition to a steady state, involving dominantly shear flow and a two-vortex state. Finally, this state undergoes a bifurcation to a temporally chaotic state, with the further decrease of viscosity. The results are compared to some recent experiments in fluids with driven vortices [P. Tabeling [ital et] [ital al]., J. Fluid Mech. 215, 511 (1990)].
A study of the temporal stability of multiple cell vortices
NASA Technical Reports Server (NTRS)
Khorrami, Mehdi R.
1989-01-01
The effect of initial mean velocity field on the stability characteristics of longitudinal vortices is documented in detail. The temporal stability of isolated multiple cell vortices is considered. The types of vortices studied include single cell as well as two and three cell vortices. It is shown that cell multiplicity in the vortex core has drastic effects on the stability characteristics. On the basis of numerical calculations, it is concluded that the growth rates of instabilities in multiple cell vortices are substantially larger (two to threefold increases are observed) than those of a single cell vortex. It is also determined that there is a substantial increase in the effective range of axial and azimuthal wavenumbers where instabilities are present. But most importantly, there is the appearance of a variety of viscous modes of instability. In the case of vortices, these latter instabilities which highlight the importance of viscous forces have never been reported before. These effects are discussed in detail for the case of a two cell vortex.
3D Zombie Vortices in Rotating Stratified Shear
NASA Astrophysics Data System (ADS)
Marcus, Philip; Pei, Suyang; Jiang, Chung-Hsiang; Hassanzadeh, Pedram; Barranco, Joseph; Lecoanet, Daniel
2013-11-01
We have shown that there is a finite-amplitude instability in linearly-stable, rotating, vertically-stratified, horizontally-shearing flows. The instability is due to excitations of baroclinic critical layers in which the vertical velocity of a neutrally-stable eigenmode is singular in the inviscid limit. This singularity coupled with the Coriolis and stretching terms in the vertical vorticity equation create intense vortex layers. Those layers roll-up into 3D vortices, which then de-stabilize other critical layers. These vortices, which we call zombie vortices, can fill the dead zone of a protoplanetary disk around a forming star. The vortices, either by themselves or by exciting inertio-gravity waves or acoustic waves, can transport angular momentum in a protoplanetary disk and thereby allow a protostar to form into a star. We find that the zombie vortices are similar in flows with Boussinesq, anelastic, and fully compressible equations of state. However, the rates of angular momentum transport and the mechanisms by which it is transported vary significantly in flows with different equations of state.
Objective detection of vortices in massively-separated flow
NASA Astrophysics Data System (ADS)
Huang, Yangzi; Hadjighasem, Alireza; Green, Melissa; Haller, George
2015-11-01
We study the formation and shedding of vortices in two vortex-dominated flows around a pitching panel in order to detect coherent structures objectively (i.e., in a frame invariant fashion) in massively-separated flow. We employ a recently developed objective definition and extraction technique for rotationally coherent Lagrangian vortices. This methods renders material vortex boundaries as outermost convex level surfaces of the Lagrangian-Averaged Vorticity Deviation (LAVD), i.e., the trajectory integral of the normed deviation of the vorticity from its spatial mean. We also employ the derivative of the LAVD, the Instantaneous Vorticity Deviation (IVD), to uncover instantaneous Eulerian vortex boundaries in an objective fashion. These Eulerian vortex boundaries, therefore, remain the same in all possible rotating and translating unsteady frames. The multiple methods we use identify and track both leading edge and trailing edge vortices as they form and shed. This helps in describing the relationship between the vortex dynamics and the loss of lift during dynamic stall on a 2D flat plate undergoing a 45 degree pitch-up maneuver. Dr. Jeff Eldredge and his research group at UCLA are gratefully acknowledged for sharing the database of simulation results for the current research. This work was supported by the Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1.
Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus).
Maia, Anabela; Sheltzer, Alex P; Tytell, Eric D
2015-03-01
In their natural environment, fish must swim stably through unsteady flows and vortices, including vertical vortices, typically shed by posts in a flow, horizontal cross-flow vortices, often produced by a step or a waterfall in a stream, and streamwise vortices, where the axis of rotation is aligned with the direction of the flow. Streamwise vortices are commonly shed by bluff bodies in streams and by ships' propellers and axial turbines, but we know little about their effects on fish. Here, we describe how bluegill sunfish use more energy and are destabilized more often in flow with strong streamwise vorticity. The vortices were created inside a sealed flow tank by an array of four turbines with similar diameter to the experimental fish. We measured oxygen consumption for seven sunfish swimming at 1.5 body lengths (BL) s(-1) with the turbines rotating at 2 Hz and with the turbines off (control). Simultaneously, we filmed the fish ventrally and recorded the fraction of time spent maneuvering side-to-side and accelerating forward. Separately, we also recorded lateral and ventral video for a combination of swimming speeds (0.5, 1.5 and 2.5 BL s(-1)) and turbine speeds (0, 1, 2 and 3 Hz), immediately after turning the turbines on and 10 min later to test for accommodation. Bluegill sunfish are negatively affected by streamwise vorticity. Spills (loss of heading), maneuvers and accelerations were more frequent when the turbines were on than in the control treatment. These unsteady behaviors, particularly acceleration, correlated with an increase in oxygen consumption in the vortex flow. Bluegill sunfish are generally fast to recover from roll perturbations and do so by moving their pectoral fins. The frequency of spills decreased after the turbines had run for 10 min, but was still markedly higher than in the control, showing that fish partially adapt to streamwise vorticity, but not completely. Coping with streamwise vorticity may be an important energetic
On calculating the potential vorticity flux
Hsu, Pei-Chun; Diamond, P. H.
2015-03-15
We discuss and compare different approaches to calculating the dynamics of anisotropic flow structure formation in quasi two-dimensional turbulence based on potential vorticity (PV) transport in real space. The general structure of the PV flux in the relaxation processes is deduced non-perturbatively. The transport coefficients of the PV flux are then systematically calculated using perturbation theory. We develop two non-perturbative relaxation models: the first is a mean field theory for the dynamics of minimum enstrophy relaxation based on the requirement that the mean flux of PV dissipates total potential enstrophy but conserves total fluid kinetic energy. The results show that the structure of PV flux has the form of a sum of a positive definite hyper-viscous and a negative or positive viscous flux of PV. Turbulence spreading is shown to be related to PV mixing via the link of turbulence energy flux to PV flux. In the relaxed state, the ratio of the PV gradient to zonal flow velocity is homogenized. This homogenized quantity sets a constraint on the amplitudes of PV and zonal flow in the relaxed state. The second relaxation model is derived from symmetry principles alone. The form of PV flux contains a nonlinear convective term in addition to viscous and hyper-viscous terms. For both cases, the transport coefficients are calculated using perturbation theory. For a broad turbulence spectrum, a modulational calculation of the PV flux gives both a negative viscosity and a positive hyper-viscosity. For a narrow turbulence spectrum, the result of a parametric instability analysis shows that PV transport is also convective. In both relaxation and perturbative analyses, it is shown that turbulent PV transport is sensitive to flow structure, and the transport coefficients are nonlinear functions of flow shear.
Complex Convective Thermal Fluxes and Vorticity Structure
NASA Astrophysics Data System (ADS)
Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita
2015-04-01
Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied
Mixing and Vorticity Structure in Stratified Oceans
NASA Astrophysics Data System (ADS)
Magdalena Matulka, Anna; Redondo, Jose M.
2010-05-01
Several series of experiments in stratified and in rotating/stratified decaying flows after a grid is used to stir the two layer stable fluid brine and fresh water set up. (Matulka 2009). We measure by comparing the gained potential energy with the available kinetic energy AKE, the relative efficiency of mixing. The experiments in stratified rotating flows with grid driven turbulence were both periodic (quasi stationary) and non-monotonic (decaying) forcing(Matulka et al. 2008). A complex Parameter Space Using Ri, Ro, Re is used to compare field, experimental and numerical observations on the mixing structure and Topology(Redondo 2004, Redondo et al 1996) of the Stratified Rotating Flows. The horizontal spectra changes appreciable with slopes from 1.1 to 5, but relevant to dispersion, vorticity and local circulation, not only the spectral slope is important, but also the initial topology and forcing of the AKE (in Elliptical, vortex core regions ) or in hyperbolic regions dominated by shear). Using multi-fractal geometry as well, we can establish now a theoretical pattern for the turbulence behavior that is reflected in the different descriptors (volume fraction, velocity and vorticity and thus obtain a certain classification relating D3 and the sum (integral) of the different fractal dimensions D2 for different levels of scalar (volume fraction intensity or temperature). Vorticity evolution is smoother and different than that of scalar or tracer density. The correlation between the local Ri and the fractal dimension detected from energy or entropy is good. Using multi-fractal geometry we can also establish certain regions of higher local activity used to establish the geometry of the turbulence mixing, that needs to be studied in detail when interpreting the complex balance between the direct 3D Kolmogorov type cascade and the Inverse 2D Kraichnan type cascade. A large collection of SAR images obtained from three European coastal areas (Gade and Redondo 1999
Complex Convective Thermal Fluxes and Vorticity Structure
NASA Astrophysics Data System (ADS)
Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita
2015-04-01
Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied
NASA Astrophysics Data System (ADS)
Ambrico, Paolo F.; Ambrico, Marianna; Schiavulli, Luigi; De Benedictis, Santolo
2014-07-01
The charge trapping effect due to the exposure of alumina surfaces to plasma has been studied in a volume dielectric barrier discharge (DBD) in Ar and He noble gases. The long lasting charge trapping of alumina dielectric plates, used as barriers in DBDs, is evidenced by an ex situ thermoluminescence (TL) experiment performed with a standard and a custom two-dimensional (2D)-TL apparatus. The spatial density of trapped surface charges is found to be strongly correlated to the plasma morphology, and the surface spatial memory lasted for several minutes to hours after plasma exposure. In the case of Ar, the plasma channel impact signature on the surface shows a higher equivalent radiation dose with respect to the surface plasma wave and the post-discharge species signature. As a consequence, for the development of discharges, inside the dielectric surface the availability of lower energy trapped electrons is larger in the first region of plasma impact. The reported spatial memory increases the likelihood of the occurrence of plasma filaments in the same position in different runs. In He plasmas, the dielectric barrier shows an almost uniform distribution of trapped charges, meaning that there is no preferred region for the development of the discharge. In all cases a slight asymmetry was shown in the direction of the gas flow. This can be interpreted as being due to the long-living species moving in the direction of the gas flow, corresponding with the TL side experiment on the sample exposed to the plasma afterglow. The maximum values and the integral of the 2D-TL images showed a linear relation with the total charge per ac cycle, corresponding with findings for the TL glow curve. In conclusion, 2D-TL images allow the retrieval of information regarding the plasma surface interaction such as the plasma morphology, trap sites and their activation temperature.
NASA Astrophysics Data System (ADS)
Ozkan, A.; Dufour, T.; Bogaerts, A.; Reniers, F.
2016-08-01
Dielectric barrier discharges (DBDs) are commonly used to generate cold plasmas at atmospheric pressure. Whatever their configuration (tubular or planar), the presence of a dielectric barrier is mandatory to prevent too much charge build up in the plasma and the formation of a thermal arc. In this article, the role of the barrier thickness (2.0, 2.4 and 2.8 mm) and of the kind of dielectric material (alumina, mullite, pyrex, quartz) is investigated on the filamentary behavior in the plasma and on the CO2 conversion in a tubular flowing DBD, by means of mass spectrometry measurements correlated with electrical characterization and IR imaging. Increasing the barrier thickness decreases the capacitance, while preserving the electrical charge. As a result, the voltage over the dielectric increases and a larger number of microdischarges is generated, which enhances the CO2 conversion. Furthermore, changing the dielectric material of the barrier, while keeping the same geometry and dimensions, also affects the CO2 conversion. The highest CO2 conversion and energy efficiency are obtained for quartz and alumina, thus not following the trend of the relative permittivity. From the electrical characterization, we clearly demonstrate that the most important parameters are the somewhat higher effective plasma voltage (yielding a somewhat higher electric field and electron energy in the plasma) for quartz, as well as the higher plasma current (and thus larger electron density) and the larger number of microdischarge filaments (mainly for alumina, but also for quartz). The latter could be correlated to the higher surface roughness for alumina and to the higher voltage over the dielectric for quartz.
SLAC linear collider conceptual design report
Not Available
1980-06-01
The linear collider system is described in detail, including the transport system, the collider lattice, final focusing system, positron production, beam damping and compression, high current electron source, instrumentation and control, and the beam luminosity. The experimental facilities and the experimental uses are discussed along with the construction schedule and estimated costs. Appendices include a discussion of space charge effects in the linear accelerator, emittance growth in the collider, the final focus system, beam-beam instabilities and pinch effects, and detector backgrounds. (GHT)
The principles and construction of linear colliders
Rees, J.
1986-09-01
The problems posed to the designers and builders of high-energy linear colliders are discussed. Scaling laws of linear colliders are considered. The problem of attainment of small interaction areas is addressed. The physics of damping rings, which are designed to condense beam bunches in phase space, is discussed. The effect of wake fields on a particle bunch in a linac, particularly the conventional disk-loaded microwave linac structures, are discussed, as well as ways of dealing with those effects. Finally, the SLAC Linear Collider is described. 18 refs., 17 figs. (LEW)
On the Future High Energy Colliders
Shiltsev, Vladimir
2015-09-28
High energy particle colliders have been in the forefront of particle physics for more than three decades. At present the near term US, European and international strategies of the particle physics community are centered on full exploitation of the physics potential of the Large Hadron Collider (LHC) through its high-luminosity upgrade (HL-LHC). A number of the next generation collider facilities have been proposed and are currently under consideration for the medium and far-future of accelerator-based high energy physics. In this paper we offer a uniform approach to evaluation of various accelerators based on the feasibility of their energy reach, performance potential and cost range.
International Workshop on Linear Colliders 2010
None
2016-07-12
IWLC2010 International Workshop on Linear Colliders 2010ECFA-CLIC-ILC joint meeting: Monday 18 October - Friday 22 October 2010Venue: CERN and CICG (International Conference Centre Geneva, Switzerland)Â This year, the International Workshop on Linear Colliders organized by the European Committee for Future Accelerators (ECFA) will study the physics, detectors and accelerator complex of a linear collider covering both CLIC and ILC options.Contact Workshop SecretariatÂ Â IWLC2010 is hostedÂ by CERN
Compensatable muon collider calorimeter with manageable backgrounds
Raja, Rajendran
2015-02-17
A method and system for reducing background noise in a particle collider, comprises identifying an interaction point among a plurality of particles within a particle collider associated with a detector element, defining a trigger start time for each of the pixels as the time taken for light to travel from the interaction point to the pixel and a trigger stop time as a selected time after the trigger start time, and collecting only detections that occur between the start trigger time and the stop trigger time in order to thereafter compensate the result from the particle collider to reduce unwanted background detection.
Beamstrahlung spectra in next generation linear colliders
Barklow, T.; Chen, P. ); Kozanecki, W. )
1992-04-01
For the next generation of linear colliders, the energy loss due to beamstrahlung during the collision of the e{sup +}e{sup {minus}} beams is expected to substantially influence the effective center-of-mass energy distribution of the colliding particles. In this paper, we first derive analytical formulae for the electron and photon energy spectra under multiple beamstrahlung processes, and for the e{sup +}e{sup {minus}} and {gamma}{gamma} differential luminosities. We then apply our formulation to various classes of 500 GeV e{sup +}e{sup {minus}} linear collider designs currently under study.
Imaging of quantum vortices in superfluid helium droplets
NASA Astrophysics Data System (ADS)
Vilesov, Andrey
Helium nanodroplets are especially promising for exploring quantum hydrodynamics in self-contained, isolated superfluids. However, until very recently, the dynamic properties of individual droplets, such as vorticity, could not be assessed experimentally. Here we investigate the rotation of single superfluid 4-He droplets ranging from 200 to 2000 nm in diameter at T = 0.4 K via single-shot femtosecond X-ray coherent diffractive imaging. The droplets were produced by free jet expansion of liquid helium into vacuum. The angular velocities of the droplets were estimated from the centrifugal distortion and span a range from vanishing to those close to the disintegration limit. For visualization of vortices, Xe atoms were added to the droplets where they gather in cores forming nm-thin filaments. A newly developed phase retrieval technique enables the reconstruction of the instantaneous positions and shapes of the vortices from the diffraction images with about 20 nm resolution. The vorticity attainable in the nano-droplets was found to be about six orders of magnitude larger than achieved in previous experiments in the bulk. Stationary configurations of vortices are represented by triangular lattice in large (2 μm) droplets and symmetric arrangements of few vortices in smaller (200 nm) droplets. Evidence for non-stationary vortex dynamics comes from observation of asymmetric formations of vortices in some droplets. This collaborative work was performed at Linac Coherent Light Source, the free electron laser within SLAC National Accelerator Laboratory. The experiments and the full list of collaborators are reported in: L. F. Gomez et. al. Science, 345 (2014) 906.
MHD Flow Visualization of Magnetopause and Polar Cusps Vortices
NASA Technical Reports Server (NTRS)
Collado-Vega, Y. M.; Kessel, R. L.; Shao, X.; Boller, R. A.
2007-01-01
Detailed analysis of Wind, Geotail, and Cluster data shows how magnetopause boundary and polar cusps vortices associated with high speed streams can be a carrier of energy flux to the Earth's magnetosphere. For our analysis time interval, March 29 . - April 5 2002, the Interplanetary Magnetic Field (IMF) is primarily northward and MHD simulations of vortices along the flanks within nine hours of the time interval suggest that a Kelvin Helmholtz (KH) instability is likely present. Vortices were classified by solar wind input provided by the Wind satellite located 70-80 RE upstream from Earth. We present statistics for a total of 304 vortices found near the ecliptic plane on the magnetopause flanks, 273 with northward IMF and 31 with southward IMF. The vortices generated under northward IMF were more driven into the dawnside than into the duskside, being substantially more ordered on the duskside. Most of the vortices were large in scale, up to 10 RE, and with a rotation axis closely aligned with the Z(sub GSE) direction. They rotated preferentially clockwise on the dawnside, and. counter-clockwise on the duskside. Those generated under southward IMF were less ordered, fewer in number, and also smaller in diameter. Significant vortex activity occurred on the nightside region of the magnetosphere for these southward cases in contrast to the northward IMF cases on which most of the activity was driven onto the magnetopause flanks. Magnetopause crossings seen by the Geotail spacecraft for the time interval were analyzed and compared with the MHD simulation to validate our results. Vortices over the polar cusps are also being analyzed and the simulation results will be compared to the multi-point measurements of the four Cluster satellites.
MHD Flow Visualization of Magnetopause and Polar Cusps Vortices
NASA Technical Reports Server (NTRS)
Collado-Vega, Y. M.; Kessel, R. L.; Shao, X.; Boller, R. A.
2006-01-01
Detailed analysis of Wind, Geotail, and Cluster data shows how magnetopause boundary and polar cusps vortices associated with high speed streams can be a carrier of energy flux to the Earth s magnetosphere. For our analysis time interval, March 29 . - April 5 2002, the Interplanetary Magnetic Field (IMF) is primarily northward and MHD simulations of vortices along the flanks within nine hours of the time interval suggest that a Kelvin Helmholtz (KH) instability is likely present. Vortices were classified by solar wind input provided by the Wind satellite located 70-80 RE upstream from Earth. We present statistics for a total of 304 vortices found near the ecliptic plane on the magnetopause flanks, 273 with northward IMF and 31 with southward IMF. The vortices generated under northward IMF were more driven into the dawnside than into the duskside, being substantially more ordered on the duskside. Most of the vortices were large in scale, up to 10 RE, and with a rotation axis closely aligned with the ZGSE direction. They rotated preferentially clockwise on the dawnside, and. counter-clockwise on the duskside. Those generated under southward IMF were less ordered, fewer in number, and also smaller in diameter. Significant vortex activity occurred on the nightside region of the magnetosphere for these southward cases in contrast to the northward IMF cases on which most of the activity was driven onto the magnetopause flanks. Magnetopause crossings seen by the Geotail spacecraft for the time interval were analyzed and compared with the MHD simulation to validate our results. Vortices over the polar cusps are also being analyzed and the simulation results will be compared to the multi-point measurements of the four Cluster satellites.
Proton-antiproton collider physics
Shochet, M.J.
1995-07-01
The 9th {anti p}p Workshop was held in Tsukuba, Japan in October, 1993. A number of important issues remained after that meeting: Does QCD adequately describe the large cross section observed by CDF for {gamma} production below 30 GeV? Do the CDF and D0 b-production cross sections agree? Will the Tevatron live up to its billing as a world-class b-physics facility? How small will the uncertainty in the W mass be? Is there anything beyond the Minimal Standard Model? And finally, where is the top quark? Presentations at this workshop addressed all of these issues. Most of them are now resolved, but new questions have arisen. This summary focuses on the experimental results presented at the meeting by CDF and D0 physicists. Reviews of LEP and HERA results, future plans for hadron colliders and their experiments, as well as important theoretical presentations are summarized elsewhere in this volume. Section 1 reviews physics beyond the Minimal Standard Model. Issues in b and c physics are addressed in section 3. Section 4 focuses on the top quark. Electroweak physics is reviewed in section 5, followed by QCD studies in section 6. Conclusions are drawn in section 7.
Flavourful production at hadron colliders
NASA Astrophysics Data System (ADS)
Giudice, Gian Francesco; Gripaios, Ben; Sundrum, Raman
2011-08-01
We ask what new states may lie at or below the TeV scale, with sizable flavour-dependent couplings to light quarks, putting them within reach of hadron colliders via resonant production, or in association with Standard Model states. In particular, we focus on the compatibility of such states with stringent flavour-changing neutral current and electric-dipole moment constraints. We argue that the broadest and most theoretically plausible flavour structure of the new couplings is that they are hierarchical, as are Standard Model Yukawa couplings, although the hierarchical pattern may well be different. We point out that, without the need for any more elaborate or restrictive structure, new scalars with "diquark" couplings to standard quarks are particularly immune to existing constraints, and that such scalars may arise within a variety of theoretical paradigms. In particular, there can be substantial couplings to a pair of light quarks or to one light and one heavy quark. For example, the latter possibility may provide a flavour-safe interpretation of the asymmetry in top quark production observed at the Tevatron. We thereby motivate searches for diquark scalars at the Tevatron and LHC, and argue that their discovery represents one of our best chances for new insight into the Flavour Puzzle of the Standard Model.
The Relativistic Heavy Ion Collider
NASA Astrophysics Data System (ADS)
Fischer, Wolfram
The Relativistic Heavy Ion Collider (RHIC), shown in Fig. 1, was build to study the interactions of quarks and gluons at high energies [Harrison, Ludlam and Ozaki (2003)]. The theory of Quantum Chromodynamics (QCD) describes these interactions. One of the main goals for the RHIC experiments was the creation and study of the Quark-Gluon Plasma (QGP), which was expected to be formed after the collision of heavy ions at a temperature of approximately 2 trillion kelvin (or equivalently an energy of 150 MeV). The QGP is the substance which existed only a few microseconds after the Big Bang. The QGP was anticipated to be weakly interacting like a gas but turned out to be strongly interacting and more like a liquid. Among its unusual properties is its extremely low viscosity [Auerbach and Schlomo (2009)], which makes the QGP the substance closest to a perfect liquid known to date. The QGP is opaque to moderate energy quarks and gluons leading to a phenomenon called jet quenching, where of a jet and its recoil jet only one is observable and the other suppressed after traversing and interacting with the QGP [Jacak and Müller (2012)]...
Nonglobal correlations in collider physics
Moult, Ian; Larkoski, Andrew J.
2016-01-13
Despite their importance for precision QCD calculations, correlations between in- and out-of-jet regions of phase space have never directly been observed. These so-called non-global effects are present generically whenever a collider physics measurement is not explicitly dependent on radiation throughout the entire phase space. In this paper, we introduce a novel procedure based on mutual information, which allows us to isolate these non-global correlations between measurements made in different regions of phase space. We study this procedure both analytically and in Monte Carlo simulations in the context of observables measured on hadronic final states produced in e+e- collisions, though itmore » is more widely applicable.The procedure exploits the sensitivity of soft radiation at large angles to non-global correlations, and we calculate these correlations through next-to-leading logarithmic accuracy. The bulk of these non-global correlations are found to be described in Monte Carlo simulation. They increase by the inclusion of non-perturbative effects, which we show can be incorporated in our calculation through the use of a model shape function. As a result, this procedure illuminates the source of non-global correlations and has connections more broadly to fundamental quantities in quantum field theory.« less
Photon Collider Physics with Real Photon Beams
Gronberg, J; Asztalos, S
2005-11-03
Photon-photon interactions have been an important probe into fundamental particle physics. Until recently, the only way to produce photon-photon collisions was parasitically in the collision of charged particles. Recent advances in short-pulse laser technology have made it possible to consider producing high intensity, tightly focused beams of real photons through Compton scattering. A linear e{sup +}e{sup -} collider could thus be transformed into a photon-photon collider with the addition of high power lasers. In this paper they show that it is possible to make a competitive photon-photon collider experiment using the currently mothballed Stanford Linear Collider. This would produce photon-photon collisions in the GeV energy range which would allow the discovery and study of exotic heavy mesons with spin states of zero and two.
The Status of the International Linear Collider
NASA Astrophysics Data System (ADS)
Harrison, Michael
2016-03-01
The International Linear Collider is under consideration in Japan as the next major global high energy physics facility. In this talk we shall describe the site and accelerator footprint together with the latest technical information on the superconducting RF technology.
Test facilities for future linear colliders
Ruth, R.D.
1995-12-01
During the past several years there has been a tremendous amount of progress on Linear Collider technology world wide. This research has led to the construction of the test facilities described in this report. Some of the facilities will be complete as early as the end of 1996, while others will be finishing up around the end 1997. Even now there are extensive tests ongoing for the enabling technologies for all of the test facilities. At the same time the Linear Collider designs are quite mature now and the SLC is providing the key experience base that can only come from a working collider. All this taken together indicates that the technology and accelerator physics will be ready for a future Linear Collider project to begin in the last half of the 1990s.
Magnet R&D for future colliders
Sabbi, Gian Luca
2001-06-14
High-energy colliders complementing and expanding the physics reach of LHC are presently under study in the United States, Europe and Japan. The magnet system is a major cost driver for hadron colliders at the energy frontier, and critical to the successful operation of muon colliders. Under most scenarios, magnet design as well as vacuum and cryogenic systems are complicated by high radiation loads. Magnet R&D programs are underway worldwide to take advantage of new developments in superconducting materials, achieve higher efficiency and simplify fabrication while preserving accelerator-class field quality. A review of recent progress in magnet technology for future colliders is presented, with emphasis on the most innovative design concepts and fabrication techniques.
A Family of Vortices to Study Axisymmetric Vortex Breakdown and Reconnection
NASA Technical Reports Server (NTRS)
Young, Larry A.
2007-01-01
A new analytic model describing a family of vortices has been developed to study some of the axisymmetric vortex breakdown and reconnection fluid dynamic processes underlying body-vortex interactions that are frequently manifested in rotorcraft and propeller-driven fixed-wing aircraft wakes. The family of vortices incorporates a wide range of prescribed initial vorticity distributions -- including single or dual-core vorticity distributions. The result is analytical solutions for the vorticity and velocities for each member of the family of vortices. This model is of sufficient generality to further illustrate the dependence of vortex reconnection and breakdown on initial vorticity distribution as was suggested by earlier analytical work. This family of vortices, though laminar in nature, is anticipated to provide valuable insight into the vortical evolution of large-scale rotor and propeller wakes.
Pressure distribution based optimization of phase-coded acoustical vortices
Zheng, Haixiang; Gao, Lu; Dai, Yafei; Ma, Qingyu; Zhang, Dong
2014-02-28
Based on the acoustic radiation of point source, the physical mechanism of phase-coded acoustical vortices is investigated with formulae derivations of acoustic pressure and vibration velocity. Various factors that affect the optimization of acoustical vortices are analyzed. Numerical simulations of the axial, radial, and circular pressure distributions are performed with different source numbers, frequencies, and axial distances. The results prove that the acoustic pressure of acoustical vortices is linearly proportional to the source number, and lower fluctuations of circular pressure distributions can be produced for more sources. With the increase of source frequency, the acoustic pressure of acoustical vortices increases accordingly with decreased vortex radius. Meanwhile, increased vortex radius with reduced acoustic pressure is also achieved for longer axial distance. With the 6-source experimental system, circular and radial pressure distributions at various frequencies and axial distances have been measured, which have good agreements with the results of numerical simulations. The favorable results of acoustic pressure distributions provide theoretical basis for further studies of acoustical vortices.
Vorticity Transport on a Flexible Wing in Stall Flutter
NASA Astrophysics Data System (ADS)
Akkala, James; Buchholz, James; Farnsworth, John; McLaughlin, Thomas
2014-11-01
The circulation budget within dynamic stall vortices was investigated on a flexible NACA 0018 wing model of aspect ratio 6 undergoing stall flutter. The wing had an initial angle of attack of 6 degrees, Reynolds number of 1 . 5 ×105 and large-amplitude, primarily torsional, limit cycle oscillations were observed at a reduced frequency of k = πfc / U = 0 . 1 . Phase-locked stereo PIV measurements were obtained at multiple chordwise planes around the 62.5% and 75% spanwise locations to characterize the flow field within thin volumetric regions over the suction surface. Transient surface pressure measurements were used to estimate boundary vorticity flux. Recent analyses on plunging and rotating wings indicates that the magnitude of the pressure-gradient-driven boundary flux of secondary vorticity is a significant fraction of the magnitude of the convective flux from the separated leading-edge shear layer, suggesting that the secondary vorticity plays a significant role in regulating the strength of the primary vortex. This phenomenon is examined in the present case, and the physical mechanisms governing the growth and evolution of the dynamic stall vortices are explored. This work was supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program monitored by Dr. Douglas Smith, and through the 2014 AFOSR/ASEE Summer Faculty Fellowship Program (JA and JB).
Effect of finite strain on clast-based vorticity gauges
NASA Astrophysics Data System (ADS)
Stahr, Donald W., III; Law, Richard D.
2011-07-01
Clast-based vorticity gauges utilize orientations of grains assumed to have behaved as isolated rigid particles suspended in a flowing viscous matrix. A fundamental assumption behind use of the method is that sufficient strain has accumulated for high aspect ratio grains to rotate into positions approaching their stable sink orientation, and that clasts below a critical aspect ratio may be observed in any orientation relative to the flow plane. We constructed a numerical model to explore the effect of variable finite strain on development of the orientation distribution of a large population of rigid clasts embedded in a viscous medium for end-member pure and simple shear and for several distinct general shear flows. Our model predicts the technique will tend to produce vorticity overestimates for lower vorticity flows for a wide range of finite strain. The model also indicates that clast populations in moderate to high vortical flows tend to develop shape preferred orientations that closely resemble those expected for flows of lower vorticity. We conclude that clast-based methods are not effective for extracting detailed kinematic information from a mylonite deformed in a flow with arbitrary boundary conditions. In fact, it appears that most general shear flows continued long enough to develop moderate-high finite strains will tend to produce a clast orientation distribution that will yield a visual estimate of the critical aspect ratio that suggests approximately equal contributions of pure and simple shear components.
Inviscid Interactions Between Wake Vortices and Shear Layers
NASA Technical Reports Server (NTRS)
Zheng, Z. C.; Baek, K.
1998-01-01
Aircraft trailing vortices can be influenced significantly by atmospheric conditions such as crosswind, turbulence, and stratification. According to the NASA 1994 and 1995 field measurement program in Memphis, Tennessee, the descending aircraft wake vortices could stall or be deflected at the top of low-level temperature inversions that usually produce pronounced shear zones. Numerical simulations of vortex/shear interactions with ground effects have been performed by several groups. Burnham used a series of evenly spaced line vortices at a particular altitude to model the ground shear layer of the cross- wind. He found that the wind shear was swept up around the downwind vortex and caused the downwind vortex to move upward, and claimed that the effect was actually produced by the vertical gradient in the wind shear rather than by the wind shear directly, because uniformly distributed wind-shear vortices would have no effect on the trailing vortex vertical motion. Recently, Proctor et al. numerically tested the effects of narrow shear zones on the behavior of the vortex pair, motivated by the observation of the Memphis field data. The shear-layer sensitivity tests indicated that the downwind vortex was more sensitive and deflected to a higher altitude than its upwind counterpart. The downstream vortex contained vorticity of opposite sign to that of the shear. There was no detectable preference for the downwind vortex (or upwind vortex) to weaken (or strengthen) at a greater rate.
Vortical Flow Prediction Using an Adaptive Unstructured Grid Method
NASA Technical Reports Server (NTRS)
Pirzadeh, Shahyar Z.
2003-01-01
A computational fluid dynamics (CFD) method has been employed to compute vortical flows around slender wing/body configurations. The emphasis of the paper is on the effectiveness of an adaptive grid procedure in "capturing" concentrated vortices generated at sharp edges or flow separation lines of lifting surfaces flying at high angles of attack. The method is based on a tetrahedral unstructured grid technology developed at the NASA Langley Research Center. Two steady-state, subsonic, inviscid and Navier-Stokes flow test cases are presented to demonstrate the applicability of the method for solving practical vortical flow problems. The first test case concerns vortex flow over a simple 65 delta wing with different values of leading-edge radius. Although the geometry is quite simple, it poses a challenging problem for computing vortices originating from blunt leading edges. The second case is that of a more complex fighter configuration. The superiority of the adapted solutions in capturing the vortex flow structure over the conventional unadapted results is demonstrated by comparisons with the wind-tunnel experimental data. The study shows that numerical prediction of vortical flows is highly sensitive to the local grid resolution and that the implementation of grid adaptation is essential when applying CFD methods to such complicated flow problems.
On the local stability of vortices in differentially rotating discs
NASA Astrophysics Data System (ADS)
Railton, A. D.; Papaloizou, J. C. B.
2014-12-01
In order to circumvent the loss of solid material through radial drift towards the central star, the trapping of dust inside persistent vortices in protoplanetary discs has often been suggested as a process that can eventually lead to planetesimal formation. Although a few special cases have been discussed, exhaustive studies of possible quasi-steady configurations available for dust-laden vortices and their stability are yet to be undertaken, thus their viability or otherwise as locations for the gravitational instability to take hold and seed planet formation is unclear. In this paper we generalize and extend the well-known Kida solution to obtain a series of steady-state solutions with varying vorticity and dust density distributions in their cores, in the limit of perfectly coupled dust and gas. We then present a local stability analysis of these configurations, considering perturbations localized on streamlines. Typical parametric instabilities found have growth rates of 0.05ΩP, where ΩP is the angular velocity at the centre of the vortex. Models with density excess can exhibit many narrow parametric instability bands while those with a concentrated vorticity source display internal shear which significantly affects their stability. However, the existence of these parametric instabilities may not necessarily prevent the possibility of dust accumulation in vortices.
Bacterial aggregation and biofilm formation in a vortical flow
Yazdi, Shahrzad; Ardekani, Arezoo M.
2012-01-01
Bacterial aggregation and patchiness play an important role in a variety of ecological processes such as competition, adaptation, epidemics, and succession. Here, we demonstrate that hydrodynamics of their environment can lead to their aggregation. This is specially important since microbial habitats are rarely at rest (e.g., ocean, blood stream, flow in porous media, and flow through membrane filtration processes). In order to study the dynamics of bacterial collection in a vortical flow, we utilize a microfluidic system to mimic some of the important microbial conditions at ecologically relevant spatiotemporal scales. We experimentally demonstrate the formation of “ring”-shaped bacterial collection patterns and subsequently the formation of biofilm streamers in a microfluidic system. Acoustic streaming of a microbubble is used to generate a vortical flow in a microchannel. Due to bacteria's finite-size, the microorganisms are directed to closed streamlines and trapped in the vortical flow. The collection of bacteria in the vortices occurs in a matter of seconds, and unexpectedly, triggers the formation of biofilm streamers within minutes. Swimming bacteria have a competitive advantage to respond to their environmental conditions. In order to investigate the role of bacterial motility on the rate of collection, two strains of Escherichia coli bacteria with different motilities are used. We show that the bacterial collection in a vortical flow is strongly pronounced for high motile bacteria. PMID:24339847
Vorticity isotropy in high Karlovitz number premixed flames
NASA Astrophysics Data System (ADS)
Bobbitt, Brock; Blanquart, Guillaume
2016-10-01
The isotropy of the smallest turbulent scales is investigated in premixed turbulent combustion by analyzing the vorticity vector in a series of high Karlovitz number premixed flame direct numerical simulations. It is found that increasing the Karlovitz number and the ratio of the integral length scale to the flame thickness both reduce the level of anisotropy. By analyzing the vorticity transport equation, it is determined that the vortex stretching term is primarily responsible for the development of any anisotropy. The local dynamics of the vortex stretching term and vorticity resemble that of homogeneous isotropic turbulence to a greater extent at higher Karlovitz numbers. This results in small scale isotropy at sufficiently high Karlovitz numbers and supports a fundamental similarity of the behavior of the smallest turbulent scales throughout the flame and in homogeneous isotropic turbulence. At lower Karlovitz numbers, the vortex stretching term and the vorticity alignment in the strain-rate tensor eigenframe are altered by the flame. The integral length scale has minimal impact on these local dynamics but promotes the effects of the flame to be equal in all directions. The resulting isotropy in vorticity does not reflect a fundamental similarity between the smallest turbulent scales in the flame and in homogeneous isotropic turbulence.
Accelerator considerations of large circular colliders
NASA Astrophysics Data System (ADS)
Chao, Alex
2016-07-01
As we consider the tremendous physics reaches of the big future circular electron-positron and proton-proton colliders, it might be advisable to keep a close track of what accelerator challenges they face. Good progresses are being made, and yet it is reported here that substantial investments in funding, manpower, as well as a long sustained time to the R&D efforts will be required in preparation to realize these dream colliders.
RF pulse compression for future linear colliders
Wilson, P.B.
1995-05-01
Future (nonsuperconducting) linear colliders will require very high values of peak rf power per meter of accelerating structure. The role of rf pulse compression in producing this power is examined within the context of overall rf system design for three future colliders at energies of 1.0--1.5 TeV, 5 TeV and 25 TeV. In order keep the average AC input power and the length of the accelerator within reasonable limits, a collider in the 1.0--1.5 TeV energy range will probably be built at an x-band rf frequency, and will require a peak power on the order of 150--200 MW per meter of accelerating structure. A 5 TeV collider at 34 GHz with a reasonable length (35 km) and AC input power (225 MW) would require about 550 MW per meter of structure. Two-beam accelerators can achieve peak powers of this order by applying dc pulse compression techniques (induction linac modules) to produce the drive beam. Klystron-driven colliders achieve high peak power by a combination of dc pulse compression (modulators) and rf pulse compression, with about the same overall rf system efficiency (30--40%) as a two-beam collider. A high gain (6.8) three-stage binary pulse compression system with high efficiency (80%) is described, which (compared to a SLED-11 system) can be used to reduce the klystron peak power by about a factor of two, or alternately, to cut the number of klystrons in half for a 1.0--1.5 TeV x-band collider. For a 5 TeV klystron-driven collider, a high gain, high efficiency rf pulse compression system is essential.
World lays groundwork for future linear collider
Feder, Toni
2010-07-15
With the Large Hadron Collider at CERN finally working, the particle-physics community can now afford to divide its attention between achieving LHC results and preparing for the next machine on its wish list, an electron-positron linear collider. The preparations involve developing and deciding on the technology for such a machine, the mode of its governance, and how to balance regional and global particle- and accelerator-physics programs.
RF pulse compression for future linear colliders
NASA Astrophysics Data System (ADS)
Wilson, Perry B.
1995-07-01
Future (nonsuperconducting) linear colliders will require very high values of peak rf power per meter of accelerating structure. The role of rf pulse compression in producing this power is examined within the context of overall rf system design for three future colliders at energies of 1.0-1.5 TeV, 5 TeV, and 25 TeV. In order to keep the average AC input power and the length of the accelerator within reasonable limits, a collider in the 1.0-1.5 TeV energy range will probably be built at an x-band rf frequency, and will require a peak power on the order of 150-200 MW per meter of accelerating structure. A 5 TeV collider at 34 GHz with a reasonable length (35 km) and AC input power (225 MW) would require about 550 MW per meter of structure. Two-beam accelerators can achieve peak powers of this order by applying dc pulse compression techniques (induction linac modules) to produce the drive beam. Klystron-driven colliders achieve high peak power by a combination of dc pulse compression (modulators) and rf pulse compression, with about the same overall rf system efficiency (30-40%) as a two-beam collider. A high gain (6.8) three-stage binary pulse compression system with high efficiency (80%) is described, which (compared to a SLED-II system) can be used to reduce the klystron peak power by about a factor of two, or alternatively, to cut the number of klystrons in half for a 1.0-1.5 TeV x-band collider. For a 5 TeV klystron-driven collider, a high gain, high efficiency rf pulse compression system is essential.
NASA Astrophysics Data System (ADS)
Di, Lanbo; Zhan, Zhibin; Zhang, Xiuling; Qi, Bin; Xu, Weijie
2016-05-01
Cold plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure was adopted for preparation of commercial TiO2 Degussa P25 supported Au catalysts (Au/P25-P) with the assistance of the deposition-precipitation procedure. The influences of the plasma reduction time and calcination on the performance of the Au/P25-P catalysts were investigated. CO oxidation was performed to investigate the catalytic activity of the Au/P25 catalysts. The results show that DBD cold plasma for the fabrication of Au/P25-P catalysts is a fast process, and Au/P25-P (4 min) exhibited the highest CO oxidation activity due to the complete reduction of Au compounds and less consumption of oxygen vacancies. In order to form more oxygen vacancies active species, Au/P25-P was calcined to obtain Au/P25-PC catalysts. Interestingly, Au/P25-PC exhibited the highest activity for CO oxidation among the Au/P25 samples. The results of transmission electron microscopy (TEM) indicated that the smaller size and high distribution of Au nanoparticles are the mean reasons for a high performance of Au/P25-PC. Atmospheric-pressure DBD cold plasma was proved to be of great efficiency in preparing high performance supported Au catalysts. supported by National Natural Science Foundation of China (Nos. 11505019, 21173028), the Science and Technology Research Project of Liaoning Provincial Education Department (No. L2013464), the Scientific Research Foundation for the Doctor of Liaoning Province (No. 20131004), and the Dalian Jinzhou New District Science and Technology Plan Project (No. KJCX-ZTPY-2014-0001)
NASA Technical Reports Server (NTRS)
Ashpis, David E.; Thurman, Douglas R.
2011-01-01
Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it
NASA Astrophysics Data System (ADS)
Oldham, Christopher J.; King, Matthew R.; Guarnieri, C. Richard; Cuomo, Jerome J.
2008-10-01
This work studied a P-PECVD process for the deposition of silicon based materials. In the process, the RF power is applied in specific ``on'' and ``off'' cycles. The process is operated in a DBD configuration at atmospheric pressure. In this pressure range, vapor phase growth typically dominates conventional processes, rather than the desired film growth. Our work has found by using the P-PECVD process, gas phase growth was eliminated and adhesion to the substrate was achieved. A growth process similar to atomic layer deposition (ALD) and conventional PECVD processing will be discussed.
Stability of model flocks in a vortical flow
NASA Astrophysics Data System (ADS)
Baggaley, A. W.
2016-06-01
We investigate the stability of self-propelled particle flocks in the Taylor-Green vortex, a steady vortical flow. We consider a model in which particles align themselves to a combination of the orientation and the acceleration of particles within a critical radius. We identify two distinct regimes: If alignment with orientation is dominant, the particles tend to be expelled from regions of high vorticity. In contrast, if anticipation is dominant, the particles accumulate in areas of large vorticity. In both regimes, the relative order of the flock is reduced. However, we show that there can be a critical balance of the two effects that stabilizes the flock in the presence of external fluid forcing. This strategy could provide a mechanism for animal flocks to remain globally ordered in the presence of fluid forcing, and it may also have applications in the design of flocking autonomous drones and artificial microswimmers.
Transverse commensurability effect for vortices on periodic pinning arrays
Reichhardt, Charles; Reichhardt, Cynthia J
2008-01-01
Using computer simulations, we demonstrate a type of commensurability that occurs for vortices moving longitudinally through periodic pinning arrays in the presence of an additional transverse driving force. As a function of vortex density, there is a series of broad maxima in the transverse critical depinning force that do not fall at the matching fields where the number of vortices equals an integer multiple of the number of pinning sites. The commensurability effects are associated with dynamical states in which evenly spaced structures consisting of one or more moving rows of vortices form between rows of pinning sites. Remarkably, the critical transverse depinning force can be more than an order of magnitude larger than the longitudinal depinning force.
Coherent vorticity extraction in turbulent channel flow using anisotropic wavelets
NASA Astrophysics Data System (ADS)
Yoshimatsu, Katsunori; Sakurai, Teluo; Schneider, Kai; Farge, Marie; Morishita, Koji; Ishihara, Takashi
2014-11-01
We examine the role of coherent vorticity in a turbulent channel flow. DNS data computed at friction-velocity based Reynolds number 320 is analyzed. The vorticity is decomposed using three-dimensional anisotropic orthogonal wavelets. Thresholding of the wavelet coefficients allows to extract the coherent vorticity, corresponding to few strong wavelet coefficients. It retains the vortex tubes of the turbulent flow. Turbulent statistics, e.g., energy, enstrophy and energy spectra, are close to those of the total flow. The nonlinear energy budgets are also found to be well preserved. The remaining incoherent part, represented by the large majority of the weak coefficients, corresponds to a structureless, i.e., a noise-like background flow.
Rapid expulsion of microswimmers by a vortical flow
Sokolov, Andrey; Aranson, Igor S.
2016-01-01
Interactions of microswimmers with their fluid environment are exceptionally complex. Macroscopic shear flow alters swimming trajectories in a highly nontrivial way and results in dramatic reduction of viscosity and heterogeneous bacterial distributions. Here we report on experimental and theoretical studies of rapid expulsion of microswimmers, such as motile bacteria, by a vortical flow created by a rotating microparticle. We observe a formation of a macroscopic depletion area in a high-shear region, in the vicinity of a microparticle. The rapid migration of bacteria from the shear-rich area is caused by a vortical structure of the flow rather than intrinsic random fluctuations of bacteria orientations, in stark contrast to planar shear flow. Our mathematical model reveals that expulsion is a combined effect of motility and alignment by a vortical flow. Our findings offer a novel approach for manipulation of motile microorganisms and shed light on bacteria–flow interactions. PMID:27005581
Large Eddy Simulation of Aircraft Wake Vortices: Atmospheric Turbulence Effects
NASA Technical Reports Server (NTRS)
Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Kao, C.-T.
1997-01-01
Crow instability can develop in most atmospheric turbulence levels, however, the ring vortices may not form in extremely strong turbulence cases due to strong dissipation of the vortices. It appears that strong turbulence tends to accelerate the occurrences of Crow instability. The wavelength of the most unstable mode is estimated to be about 5b(sub 0), which is less than the theoretical value of 8.6b(sub 0) (Crow, 1970) and may be due to limited domain size and highly nonlinear turbulent flow characteristics. Three-dimensional turbulence can decay wake vortices more rapidly. Axial velocity may be developed by vertical distortion of a vortex pair due to Crow instability or large turbulent eddy motion. More experiments with various non-dimensional turbulence levels are necessary to get useful statistics of wake vortex behavior due to turbulence. Need to investigate larger turbulence length scale effects by enlarging domain size or using grid nesting.
Feedback control of flow vorticity at low Reynolds numbers.
Zeitz, Maria; Gurevich, Pavel; Stark, Holger
2015-03-01
Our aim is to explore strategies of feedback control to design and stabilize novel dynamic flow patterns in model systems of complex fluids. To introduce the control strategies, we investigate the simple Newtonian fluid at low Reynolds number in a circular geometry. Then, the fluid vorticity satisfies a diffusion equation. We determine the mean vorticity in the sensing area and use two control strategies to feed it back into the system by controlling the angular velocity of the circular boundary. Hysteretic feedback control generates self-regulated stable oscillations in time, the frequency of which can be adjusted over several orders of magnitude by tuning the relevant feedback parameters. Time-delayed feedback control initiates unstable vorticity modes for sufficiently large feedback strength. For increasing delay time, we first observe oscillations with beats and then regular trains of narrow pulses. Close to the transition line between the resting fluid and the unstable modes, these patterns are relatively stable over long times.
Rapid expulsion of microswimmers by a vortical flow
NASA Astrophysics Data System (ADS)
Sokolov, Andrey; Aranson, Igor S.
2016-03-01
Interactions of microswimmers with their fluid environment are exceptionally complex. Macroscopic shear flow alters swimming trajectories in a highly nontrivial way and results in dramatic reduction of viscosity and heterogeneous bacterial distributions. Here we report on experimental and theoretical studies of rapid expulsion of microswimmers, such as motile bacteria, by a vortical flow created by a rotating microparticle. We observe a formation of a macroscopic depletion area in a high-shear region, in the vicinity of a microparticle. The rapid migration of bacteria from the shear-rich area is caused by a vortical structure of the flow rather than intrinsic random fluctuations of bacteria orientations, in stark contrast to planar shear flow. Our mathematical model reveals that expulsion is a combined effect of motility and alignment by a vortical flow. Our findings offer a novel approach for manipulation of motile microorganisms and shed light on bacteria-flow interactions.
Pipelike current-carrying vortices in two-component condensates
Chernodub, M. N.; Nedelin, A. S.
2010-06-15
We study straight vortices with global longitudinal currents in the Bogomolny limit of the Abelian Higgs model with two charged scalar fields. The model possesses global SU(2) and local electromagnetic U(1) symmetries spontaneously broken to a global U(1) group, and corresponds to a semilocal limit of the standard electroweak model. We show that the contribution of the global SU(2) current to the vortex energy is proportional to the total current squared. Locally, these vortices carry also longitudinal electromagnetic currents, while the total electromagnetic current flowing through a transverse section of the vortex is always zero. The vortices with high winding numbers have, in general, a nested pipelike structure. The magnetic field of the vortex is concentrated at a certain distance from the geometric center of the vortex, thus resembling a 'pipe'. This magnetic pipe is layered between two electrically charged pipes that carry longitudinal electric currents in opposite directions.
Decay of Far-Flowfield in Trailing Vortices
NASA Technical Reports Server (NTRS)
Baldwin, B. S.; Chigier, N. A.; Sheaffer, Y. S.
1973-01-01
Methods for reduction of velocities in trailing vortices of large aircraft are of current interest for the purpose of shortening the waiting time between landings at central airports. We have made finite-difference calculations of the flow in turbulent wake vortices as an aid to interpretation of wind-tunnel and flight experiments directed toward that end. Finite-difference solutions are capable of adding flexibility to such investigations if they are based on an adequate model of turbulence. Interesting developments have been taking place in the knowledge of turbulence that may lead to a complete theory in the future. In the meantime, approximate methods that yield reasonable agreement with experiment are appropriate. The simplified turbulence model we have selected contains features that account for the major effects disclosed by more sophisticated models in which the parameters are not yet established. Several puzzles are thereby resolved that arose in previous theoretical investigations of wake vortices.
Numerical Investigation of Buoyancy-Induced Columnar Vortices
NASA Astrophysics Data System (ADS)
Malaya, Nicholas; Stogner, Roy; Moser, Robert
2014-11-01
Buoyancy driven columnar vortices arise naturally in the atmosphere. A new energy harvesting approach makes use of this phenomenon by creating and anchoring the vortices artificially and extracting energy from them. In this talk, we explore the characteristics of these ``solar vortices'' through numerical simulation. Computational models of the turning vane system used to generate the solar vortex and the turbine used to extract energy have been developed. The formulation of these models and their validation against available experimental measurements will be discussed, as will the details of the columnar vortex structure and its interaction with the turbine. In addition, the computational models are being used to optimize the turning vane configuration and the turbine characteristics to maximize the power extraction, and to characterize the effects of environmental conditions such as cross winds and topography. Preliminary results from these studies will also be presented. This work supported by the Department of Energy [ARPA-E] under Award Number [DE-FOA-0000670].
Internal Avalanches in a Growing Pile of Superconducting Vortices
NASA Astrophysics Data System (ADS)
Lee, Choong-Seop; Bassler, Kevin E.; Paczuski, Maya
2002-03-01
Avalanches of magnetic vortices produced by systematically increasing an external magnetic field applied to a type-II superconductor are studied using a simple ``sandpile'' type cellular model (K. E. Bassler and M. Paczuski, Phys. Rev. Lett. 81), 3761 (1998).. The cellular model describes the over-damped stick-slip dynamics of the vortices, which results in avalanches of vortex motion as the magnetic field increased. Driving the system by very slowly increasing the magnetic field, the system reaches a self-organized critical state in which the average density of vortices is increasing. In that state, the scaling properties and critical exponents describing the avalanche statistics are measured, and compared with recent experiments.
Vorticity scaling and intermittency in drift-interchange plasma turbulence
Dura, P. D.; Hnat, B.; Robinson, J.; Dendy, R. O.
2012-09-15
The effects of spatially varying magnetic field strength on the scaling properties of plasma turbulence, modelled by an extended form of Hasegawa-Wakatani model, are investigated. We study changes in the intermittency of the velocity, density, and vorticity fields, as functions of the magnetic field inhomogeneity C=-{partial_derivative} ln B/{partial_derivative}x. While the velocity fluctuations are always self-similar and their scaling is unaffected by the value of C, the intermittency levels in density and vorticity change with parameter C, reflecting morphological changes in the coherent structures due to the interchange mechanism. Given the centrality of vorticity in conditioning plasma transport, this result is of interest in scaling the results of transport measurements and simulations in tokamak edge plasmas, where drift-interchange turbulence in the presence of a magnetic field gradient is likely to occur.
Numerical Modeling Studies of Wake Vortices: Real Case Simulations
NASA Technical Reports Server (NTRS)
Shen, Shao-Hua; Ding, Feng; Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Proctor, Fred H.
1999-01-01
A three-dimensional large-eddy simulation model, TASS, is used to simulate the behavior of aircraft wake vortices in a real atmosphere. The purpose for this study is to validate the use of TASS for simulating the decay and transport of wake vortices. Three simulations are performed and the results are compared with the observed data from the 1994-1995 Memphis field experiments. The selected cases have an atmospheric environment of weak turbulence and stable stratification. The model simulations are initialized with appropriate meteorological conditions and a post roll-up vortex system. The behavior of wake vortices as they descend within the atmospheric boundary layer and interact with the ground is discussed.
Stability of model flocks in a vortical flow.
Baggaley, A W
2016-06-01
We investigate the stability of self-propelled particle flocks in the Taylor-Green vortex, a steady vortical flow. We consider a model in which particles align themselves to a combination of the orientation and the acceleration of particles within a critical radius. We identify two distinct regimes: If alignment with orientation is dominant, the particles tend to be expelled from regions of high vorticity. In contrast, if anticipation is dominant, the particles accumulate in areas of large vorticity. In both regimes, the relative order of the flock is reduced. However, we show that there can be a critical balance of the two effects that stabilizes the flock in the presence of external fluid forcing. This strategy could provide a mechanism for animal flocks to remain globally ordered in the presence of fluid forcing, and it may also have applications in the design of flocking autonomous drones and artificial microswimmers. PMID:27415360
Warping and interactions of vortices in exciton-polariton condensates
NASA Astrophysics Data System (ADS)
Toledo-Solano, M.; Mora-Ramos, M. E.; Figueroa, A.; Rubo, Y. G.
2014-01-01
We investigate the properties of the vortex singularities in two-component exciton-polariton condensates in semiconductor microcavities in the presence of transverse-electric-transverse-magnetic (TE-TM) splitting of the lower polariton branch. This splitting does not change qualitatively the basic (lemon and star) geometry of half-quantum vortices (HQVs), but results in warping of both the polarization field and the supercurrent streamlines around these entities. The TE-TM splitting has a pronounced effect on the HQV energies and interactions, as well as on the properties of integer vortices, especially on the energy of the hedgehog polarization vortex. The energy of this vortex can become smaller than the energies of HQVs. This leads to modification of the Berezinskii-Kosterlitz-Thouless transition from the proliferation of half-vortices to the proliferation of hedgehog-based vortex molecules.
Vorticity Preserving Flux Corrected Transport Scheme for the Acoustic Equations
Lung, Tyler B.; Roe, Phil; Morgan, Nathaniel R.
2012-08-15
Long term research goals are to develop an improved cell-centered Lagrangian Hydro algorithm with the following qualities: 1. Utilizes Flux Corrected Transport (FCT) to achieve second order accuracy with multidimensional physics; 2. Does not rely on the one-dimensional Riemann problem; and 3. Implements a form of vorticity control. Short term research goals are to devise and implement a 2D vorticity preserving FCT solver for the acoustic equations on an Eulerian mesh: 1. Develop a flux limiting mechanism for systems of governing equations with symmetric wave speeds; 2. Verify the vorticity preserving properties of the scheme; and 3. Compare the performance of the scheme to traditional MUSCL-Hancock and other algorithms.
Generation of self-healing and transverse accelerating optical vortices
NASA Astrophysics Data System (ADS)
Wei, Bing-Yan; Chen, Peng; Ge, Shi-Jun; Duan, Wei; Hu, Wei; Lu, Yan-Qing
2016-09-01
Self-healing and transverse accelerating optical vortices are generated via modulating Gaussian beams through subsequent liquid crystal q-plate and polarization Airy mask. We analyze the propagation dynamics of these vortex Airy beams, and find that they possess the features of both optical vortices and Airy beams. Topological charges and characteristics of nondiffraction, self-healing, and transverse acceleration are experimentally verified. In addition, vortex Airy beams with both topological charge and radial index are demonstrated and mode switch among Gaussian, vortex, vector, Airy beams and their combinations can be acquired easily. Our design provides a flexible and highly efficient way to generate unique optical vortices with self-healing and transverse acceleration properties, and facilitates prospective applications in optics and photonics.
Vortical susceptibility of finite-density QCD matter
NASA Astrophysics Data System (ADS)
Aristova, A.; Frenklakh, D.; Gorsky, A.; Kharzeev, D.
2016-10-01
The susceptibility of finite-density QCD matter to vorticity is introduced, as an analog of magnetic susceptibility. It describes the spin polarization of quarks and antiquarks in finite-density QCD matter induced by rotation. We estimate this quantity in the chirally broken phase using the mixed gauge-gravity anomaly at finite baryon density. It is proposed that the vortical susceptibility of QCD matter is responsible for the polarization of Λ and overline{Λ} hyperons observed recently in heavy ion collisions at RHIC by the STAR collaboration.
Vortical flow aerodynamics - Physical aspects and numerical simulation
NASA Technical Reports Server (NTRS)
Newsome, Richard W.; Kandil, Osama A.
1987-01-01
Progress in the numerical simulation of vortical flow due to three-dimensional flow separation about flight vehicles at high angles of attack and quasi-steady flight conditions is surveyed. Primary emphasis is placed on Euler and Reynolds-averaged Navier-Stokes methods where the vortices are 'captured' as a solution to the governing equations. A discussion of the relevant flow physics provides a perspective from which to assess numerical solutions. Current numerical prediction capabilities and their evolutionary development are surveyed. Future trends and challenges are identified and discussed.
Phase singularity of surface plasmon polaritons generated by optical vortices.
Tan, P S; Yuan, G H; Wang, Q; Zhang, N; Zhang, D H; Yuan, X-C
2011-08-15
We demonstrate an experimental result that shows the phase singularity of surface plasmon waves generated by the direct transform of optical vortices at normal incidence focused on a structureless metal surface. The near-field two-dimensional intensity distribution near the focal plane is experimentally examined by using near-field scanning optical microscopy and shows a good agreement with the finite-difference time-domain simulation result. The experimental realization demonstrates a potential of the proposed excitation scheme to be reconfigured locally with advantages over structures milled into optically thick metallic films for plasmonics applications involving plasmonic vortices. PMID:21847236
Interaction of ultrasound with vortices in type-II superconductors
Sonin, E.B.
1996-04-01
The theory of ultrasound in the mixed state of type-II superconductors is suggested which takes into account the Magnus force on vortices, the anti-Magnus force on ions, and diamagnetism of the mixed state. The acoustic Faraday effect (rotation of polarization of the transverse ultrasonic wave propagating along vortices) is linear in the Magnus force in any regime of the flux flow for wavelengths now used in the ultrasound experiments. Therefore, in contrast to previous predictions, the Faraday effect should be looked for only in clean superconductors with a strong Magnus force. {copyright} {ital 1996 The American Physical Society.}
Unfolding of Vortices into Topological Stripes in a Multiferroic Material
NASA Astrophysics Data System (ADS)
Wang, X.; Mostovoy, M.; Han, M. G.; Horibe, Y.; Aoki, T.; Zhu, Y.; Cheong, S.-W.
2014-06-01
Multiferroic hexagonal RMnO3 (R =rare earths) crystals exhibit dense networks of vortex lines at which six domain walls merge. While the domain walls can be readily moved with an applied electric field, the vortex cores so far have been impossible to control. Our experiments demonstrate that shear strain induces a Magnus-type force pulling vortices and antivortices in opposite directions and unfolding them into a topological stripe domain state. We discuss the analogy between this effect and the current-driven dynamics of vortices in superconductors and superfluids.
Explosion of relativistic electron vortices in laser plasmas
NASA Astrophysics Data System (ADS)
Lezhnin, K. V.; Kamenets, F. F.; Esirkepov, T. Zh.; Bulanov, S. V.; Gu, Y. J.; Weber, S.; Korn, G.
2016-09-01
The interaction of high intensity laser radiation with an underdense plasma may lead to the formation of electron vortices. Though being quasistationary on the electron timescales, these structures tend to expand on a proton timescale due to Coulomb repulsion of ions. Using a simple analytical model of a stationary vortex as an initial condition, 2D PIC simulations are performed. A number of effects are observed such as vortex boundary field intensification, multistream instabilities at the vortex boundary, and bending of the vortex boundary with the subsequent transformation into smaller electron vortices.
Rectilinear lattices of polarization vortices with various spatial polarization distributions.
Fu, Shiyao; Zhang, Shikun; Wang, Tonglu; Gao, Chunqing
2016-08-01
In this paper, we propose a type of rectilinear lattices of polarization vortices, each spot in which has mutually independent, and controllable spatial polarization distributions. The lattices are generated by two holograms under special design. In the experiment, the holograms are encoded on two spatial light modulators, and the results fit very well with theory. Our scheme makes it possible to generate multiple polarization vortices with various polarization distributions simultaneously, for instance, radially and azimuthally polarized beams, and can be used in the domains as polarization-based data transmission system, optical manufacture, polarization detection and so on. PMID:27505812
Z2 x Z3 Symmetry of Multferroic Vortices
NASA Astrophysics Data System (ADS)
Cheong, Sang-Wook
2014-03-01
Hexagonal REMnO3 (RE = rare earths) with RE =Ho-Lu, Y, and Sc, is an improper ferroelectric where the size mismatch between RE and Mn induces a trimerization-type structural phase transition, and this structural transition leads to three structural domains, each of which can support two directions of ferroelectric polarization. We reported that domains in h-REMnO3 meet in cloverleaf arrangements that cycle through all six domain configurations, Occurring in pairs, the cloverleafs can be viewed as vortices and antivortices, in which the cycle of domain configurations is reversed. Vortices and antivortices are topological defects: even in a strong electric field they won't annihilate. These ferroelectric vortices/antivortices are found to be associated with intriguing collective magnetism at domain walls, reflecting the multiferroic nature of vortices. We have found that an intriguing, but seemingly irregular network of a zoo of multiferroic vortices and antivortices in h-REMnO3 can be neatly analyzed in terms of graph theory, and this graph theoretical analysis reveals the emergence of Z2 × Z3 symmetry in the vortices/antivortices network. In addition, poling or self-poling due to a surface charge boundary condition induces global topological condensation of the network through breaking of the Z2 part of the Z2 × Z3 symmetry. The opposite process of restoring the Z2 symmetry can be considered as topological evaporation. It turns out that these Z2xZ3 vortices are, in fact, three-dimensional vortex loops, which result from the emergent continuous U(1) symmetry near the critical temperature. This spontaneous trapping of topological defects in the process of undergoing a continuous phase transition is important to understand numerous novel phenomena such as the early stage of universe after big bang. The so-called Kibble-Zurek mechanism was proposed for the trapping process of topological defects right after big bang. It appears that the Kibble-Zurek mechanism is also
Turbulence in Flowing Soap Films: Velocity, Vorticity, and Thickness Fields
Rivera, M.; Vorobieff, P.; Ecke, R.E.
1998-08-01
We report experimental measurements of the velocity, vorticity, and thickness fields of turbulent flowing soap films using a modified particle-image velocimetry technique. These data yield the turbulent energy and enstrophy of the two-dimensional flows with microscale Reynolds numbers of about 100 and demonstrate the effects of compressibility arising from variations in film thickness. Despite the compressibility of the flow, real-space correlations of velocity, vorticity, and enstrophy flux are consistent with theoretical predictions for two-dimensional turbulence. {copyright} {ital 1998} {ital The American Physical Society }
Status of the Future Circular Collider Study
NASA Astrophysics Data System (ADS)
Benedikt, Michael
2016-03-01
Following the 2013 update of the European Strategy for Particle Physics, the international Future Circular Collider (FCC) Study has been launched by CERN as host institute, to design an energy frontier hadron collider (FCC-hh) in a new 80-100 km tunnel with a centre-of-mass energy of about 100 TeV, an order of magnitude beyond the LHC's, as a long-term goal. The FCC study also includes the design of a 90-350 GeV high-luminosity lepton collider (FCC-ee) installed in the same tunnel, serving as Higgs, top and Z factory, as a potential intermediate step, as well as an electron-proton collider option (FCC-he). The physics cases for such machines will be assessed and concepts for experiments will be developed in time for the next update of the European Strategy for Particle Physics by the end of 2018. The presentation will summarize the status of machine designs and parameters and discuss the essential technical components to be developed in the frame of the FCC study. Key elements are superconducting accelerator-dipole magnets with a field of 16 T for the hadron collider and high-power, high-efficiency RF systems for the lepton collider. In addition the unprecedented beam power presents special challenges for the hadron collider for all aspects of beam handling and machine protection. First conclusions of geological investigations and implementation studies will be presented. The status of the FCC collaboration and the further planning for the study will be outlined.
PROSPECTS FOR COLLIDERS AND COLLIDER PHYSICS TO THE 1 PEV ENERGY SCALE
KING,B.J.
2000-05-05
A review is given of the prospects for future colliders and collider physics at the energy frontier. A proof-of-plausibility scenario is presented for maximizing the authors progress in elementary particle physics by extending the energy reach of hadron and lepton colliders as quickly and economically as might be technically and financially feasible. The scenario comprises 5 colliders beyond the LHC--one each of e{sup +}e{sup {minus}} and hadron colliders and three {mu}{sup +}{mu}{sup {minus}} colliders--and is able to hold to the historical rate of progress in the log-energy reach of hadron and lepton colliders, reaching the 1 PeV constituent mass scale by the early 2040's. The technical and fiscal requirements for the feasibility of the scenario are assessed and relevant long-term R and D projects are identified. Considerations of both cost and logistics seem to strongly favor housing most or all of the colliders in the scenario in a new world high energy physics laboratory.
String resonances at hadron colliders
NASA Astrophysics Data System (ADS)
Anchordoqui, Luis A.; Antoniadis, Ignatios; Dai, De-Chang; Feng, Wan-Zhe; Goldberg, Haim; Huang, Xing; Lüst, Dieter; Stojkovic, Dejan; Taylor, Tomasz R.
2014-09-01
We consider extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. Assuming that the fundamental string mass scale Ms is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (integrated luminosity =3000 fb-1) with a center-of-mass energy of √s =14 TeV and at potential future pp colliders, HE-LHC and VLHC, operating at √s =33 and 100 TeV, respectively (with the same integrated luminosity). In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and γ +jet are completely independent of the details of compactification and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first (n=1) and second (n=2) resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV) lowest massive Regge excitations are open to discovery at the ≥5σ in dijet (γ +jet) HL-LHC data. We also show that for n=1 the dijet discovery potential at HE-LHC and VLHC exceedingly improves: up to 15 TeV and 41 TeV, respectively. To compute the signal-to-noise ratio for n=2 resonances, we first carry out a complete calculation of all relevant decay widths of the second massive level string states (including decays into massless particles and a massive n=1 and a massless particle), where we rely on factorization and conformal field theory techniques. Helicity wave functions of arbitrary higher spin massive bosons are also constructed. We demonstrate that for string scales Ms≲10.5 TeV (Ms≲28 TeV) detection of n =2 Regge recurrences at HE-LHC (VLHC) would become the smoking gun for D
NASA Astrophysics Data System (ADS)
Rezaei, Fatemeh; Shokri, Babak; Sharifian, M.
2016-01-01
This paper reports polymethyl methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid-base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.
Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates.
Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming
2014-02-27
Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction.
Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates
Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming
2014-01-01
Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction. PMID:24573303
On issues concerning flow separation and vortical flows in three dimensions
NASA Technical Reports Server (NTRS)
Peake, D. J.; Tobak, M.
1983-01-01
Vortical flows in three dimensional configurations that are of typical interest to aerodynamicists and researchers in fluid mechanics are reviewed. A list of 10 issues was compiled to understanding complex vortical flows.
3D visualization of unsteady 2D airplane wake vortices
NASA Technical Reports Server (NTRS)
Ma, Kwan-Liu; Zheng, Z. C.
1994-01-01
Air flowing around the wing tips of an airplane forms horizontal tornado-like vortices that can be dangerous to following aircraft. The dynamics of such vortices, including ground and atmospheric effects, can be predicted by numerical simulation, allowing the safety and capacity of airports to be improved. In this paper, we introduce three-dimensional techniques for visualizing time-dependent, two-dimensional wake vortex computations, and the hazard strength of such vortices near the ground. We describe a vortex core tracing algorithm and a local tiling method to visualize the vortex evolution. The tiling method converts time-dependent, two-dimensional vortex cores into three-dimensional vortex tubes. Finally, a novel approach calculates the induced rolling moment on the following airplane at each grid point within a region near the vortex tubes and thus allows three-dimensional visualization of the hazard strength of the vortices. We also suggest ways of combining multiple visualization methods to present more information simultaneously.
Vortices in dust clouds under microgravity: A simple explanation.
Goedheer, W J; Akdim, M R
2003-10-01
Clouds of dust particles in radio frequency discharges often show a periodic vortexlike motion, especially near the edges of the electrodes or near the tip of an electrostatic probe. These vortices often last as long as the discharge is powered. In a previous paper we have followed a small number of individual dust particles in a discharge under microgravity conditions, moving under the influence of forces computed by means of a self-consistent two-dimensional hydrodynamic model, and interacting via a screened Coulomb potential. The resulting motion showed the vortexlike rotation. In this paper we discuss this phenomenon in more detail, using a simplified model with harmonic forces, but extending the simulations to three dimensions. Stable vortices are observed, which show a more chaotic behavior than in the two-dimensional situation. Particles frequently jump up and down between two counterrotating vortices. The generation of the vortices can be ascribed to a nonzero rotation of the net global force vector field, which is the sum of the ion drag force, the electric force, and the thermophoretic force in case of the experiments. Comparison of experimental data with simulations using a model potential may open a way to unravel the forces inside a cloud of dust particles.
Vortical Flow Prediction Using an Adaptive Unstructured Grid Method
NASA Technical Reports Server (NTRS)
Pirzadeh, Shahyar Z.
2001-01-01
A computational fluid dynamics (CFD) method has been employed to compute vortical flows around slender wing/body configurations. The emphasis of the paper is on the effectiveness of an adaptive grid procedure in "capturing" concentrated vortices generated at sharp edges or flow separation lines of lifting surfaces flying at high angles of attack. The method is based on a tetrahedral unstructured grid technology developed at the NASA Langley Research Center. Two steady-state, subsonic, inviscid and Navier-Stokes flow test cases are presented to demonstrate the applicability of the method for solving practical vortical flow problems. The first test case concerns vortex flow over a simple 65deg delta wing with different values of leading-edge bluntness, and the second case is that of a more complex fighter configuration. The superiority of the adapted solutions in capturing the vortex flow structure over the conventional unadapted results is demonstrated by comparisons with the windtunnel experimental data. The study shows that numerical prediction of vortical flows is highly sensitive to the local grid resolution and that the implementation of grid adaptation is essential when applying CFD methods to such complicated flow problems.
Propagation of magnetic vortices using nanocontacts as tunable attractors.
Manfrini, M; Kim, Joo-Von; Petit-Watelot, S; Van Roy, W; Lagae, L; Chappert, C; Devolder, T
2014-02-01
Magnetic vortices in thin films are in-plane spiral spin configurations with a core in which the magnetization twists out of the film plane. Vortices result from the competition between atomic-scale exchange forces and long-range dipolar interactions. They are often the ground state of magnetic dots, and have applications in medicine, microwave generation and information storage. The compact nature of the vortex core, which is 10-20 nm wide, makes it a suitable probe of magnetism at the nanoscale. However, thus far the positioning of a vortex has been possible only in confined structures, which prevents its transport over large distances. Here we show that vortices can be propagated in an unconstrained system that comprises electrical nanocontacts (NCs). The NCs are used as tunable vortex attractors in a manner that resembles the propelling of space craft with gravitational slingshots. By passing current from the NCs to a ferromagnetic film, circulating magnetic fields are generated, which nucleate the vortex and create a potential well for it. The current becomes spin polarized in the film, and thereby drives the vortex into gyration through spin-transfer torques. The vortex can be guided from one NC to another by tuning attractive strengths of the NCs. We anticipate that NC networks may be used as multiterminal sources of vortices and spin waves (as well as heat, spin and charge flows) to sense the fundamental interactions between physical objects and fluxes of the next-generation spintronic devices. PMID:24336405
A vorticity stretching diagnostic for turbulent and transitional flows
NASA Astrophysics Data System (ADS)
Malm, Johan; Schlatter, Philipp; Sandham, Neil D.
2012-12-01
Vorticity stretching in wall-bounded turbulent and transitional flows has been investigated by means of a new diagnostic measure, denoted by Γ, designed to pick up regions with large amounts of vorticity stretching. It is based on the maximum vorticity stretching component in every spatial point, thus yielding a three-dimensional scalar field. The measure was applied in four different flows with increasing complexity: (a) the near-wall cycle in an asymptotic suction boundary layer (ASBL), (b) K-type transition in a plane channel flow, (c) fully turbulent channel flow at Re τ = 180 and (d) a complex turbulent three-dimensional separated flow. Instantaneous data show that the coherent structures associated with intense vorticity stretching in all four cases have the shape of flat `pancake' structures in the vicinity of high-speed streaks, here denoted `h-type' events. The other event found is of `l-type', present on top of an unstable low-speed streak. These events (l-type) are further thought to be associated with the exponential growth of streamwise vorticity in the turbulent near-wall cycle. It was found that the largest occurrence of vorticity stretching in the fully turbulent wall-bounded flows is present at a wall-normal distance of y + = 6.5, i.e. in the transition between the viscous sublayer and buffer layer. The associated structures have a streamwise length of ~200-300 wall units. In K-type transition, the Γ-measure accurately locates the regions of interest, in particular the formation of high-speed streaks near the wall (h-type) and the appearance of the hairpin vortex (l-type). In the turbulent separated flow, the structures containing large amounts of vorticity stretching increase in size and magnitude in the shear layer upstream of the separation bubble but vanish in the backflow region itself. Overall, the measure proved to be useful in showing growing instabilities before they develop into structures, highlighting the mechanisms creating high
Lattice of the NICA Collider Rings
Sidorin, Anatoly; Kozlov, Oleg; Meshkov, Igor; Mikhaylov, Vladimir; Trubnikov, Grigoriy; Lebedev, Valeri Nagaitsev, Sergei; Senichev, Yurij; /Julich, Forschungszentrum
2010-05-01
The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex being constructed at JINR. It is designed for collider experiments with ions and protons and has to provide ion-ion (Au{sup 79+}) and ion-proton collisions in the energy range 1 {divided_by} 4.5 GeV/n and collisions of polarized proton-proton and deuteron-deuteron beams. Collider conceptions with constant {gamma}{sub tr} and with possibility of its variation are considered. The ring has the racetrack shape with two arcs and two long straight sections. Its circumference is about 450m. The straight sections are optimized to have {beta}* {approx} 35cm in two IPs and a possibility of final betatron tune adjustment.
Seismic studies for Fermilab future collider projects
Lauh, J.; Shiltsev, V.
1997-11-01
Ground motion can cause significant beam emittance growth and orbit oscillations in large hadron colliders due to a vibration of numerous focusing magnets. Larger accelerator ring circumference leads to smaller revolution frequency and, e.g. for the Fermilab Very Large Hadron Collider(VLHC) 50-150 Hz vibrations are of particular interest as they are resonant with the beam betatron frequency. Seismic measurements at an existing large accelerator under operation can help to estimate the vibrations generated by the technical systems in future machines. Comparison of noisy and quiet microseismic conditions might be useful for proper choice of technical solutions for future colliders. This article presents results of wide-band seismic measurements at the Fermilab site, namely, in the tunnel of the Tevatron and on the surface nearby, and in two deep tunnels in the Illinois dolomite which is though to be a possible geological environment of the future accelerators.
The Tevatron Hadron Collider: A short history
Tollestrup, A.V.
1994-11-01
The subject of this presentation was intended to cover the history of hadron colliders. However this broad topic is probably better left to historians. I will cover a much smaller portion of this subject and specialize my subject to the history of the Tevatron. As we will see, the Tevatron project is tightly entwined with the progress in collider technology. It occupies a unique place among accelerators in that it was the first to make use of superconducting magnets and indeed the basic design now forms a template for all machines using this technology. It was spawned in an incredibly productive era when new ideas were being generated almost monthly and it has matured into our highest energy collider complete with two large detectors that provide the major facility in the US for probing high Pt physics for the coming decade.
The Superconducting Super Collider: A status report
Schwitters, R.F.
1993-04-01
The design of the Superconducting Super Collider (SSC) is briefly reviewed, including its key machine parameters. The scientific objectives are twofold: (1) investigation of high-mass, low-rate, rare phenomena beyond the standard model; and (2) investigation of processes within the domain of the standard model. Machine luminosity, a key parameter, is a function of beam brightness and current, and it must be preserved through the injector chain. Features of the various injectors are discussed. The superconducting magnet system is reviewed in terms of model magnet performance, including the highly successful Accelerator System String Test Various magnet design modifications are noted, reflecting minor changes in the collider arcs and improved installation procedures. The paper concludes with construction scenarios and priority issues for ensuring the earliest collider commissioning.
The Large Hadron Collider: Redefining High Energy
Demers, Sarah
2007-06-19
Particle physicists have a description of the forces of nature known as the Standard Model that has successfully withstood decades of testing at laboratories around the world. Though the Standard Model is powerful, it is not complete. Important details like the masses of particles are not explained well, and realities as fundamental as gravity, dark matter, and dark energy are left out altogether. I will discuss gaps in the model and why there is hope that some puzzles will be solved by probing high energies with the Large Hadron Collider. Beginning next year, this machine will accelerate protons to record energies, hurling them around a 27 kilometer ring before colliding them 40 million times per second. Detectors the size of five-story buildings will record the debris of these collisions. The new energy frontier made accessible by the Large Hadron Collider will allow thousands of physicists to explore nature's fundamental forces and particles from a fantastic vantage point.
Collider and detector protection at beam accidents
I. L. Rakhno; N. V. Mokhov; A. I. Drozhdin
2003-12-10
Dealing with beam loss due to abort kicker prefire is considered for hadron colliders. The prefires occurred at Tevatron (Fermilab) during Run I and Run II are analyzed and a protection system implemented is described. The effect of accidental beam loss in the Large Hadron Collider (LHC) at CERN on machine and detector components is studied via realistic Monte Carlo calculations. The simulations show that beam loss at an unsynchronized beam abort would result in severe heating of conventional and superconducting magnets and possible damage to the collider detector elements. A proposed set of collimators would reduce energy deposition effects to acceptable levels. Special attention is paid to reducing peak temperature rise within the septum magnet and minimizing quench region length downstream of the LHC beam abort straight section.
Visible-Frequency Metasurface for Structuring and Spatially Multiplexing Optical Vortices.
Mehmood, M Q; Mei, Shengtao; Hussain, Sajid; Huang, Kun; Siew, S Y; Zhang, Lei; Zhang, Tianhang; Ling, Xiaohui; Liu, Hong; Teng, Jinghua; Danner, Aaron; Zhang, Shuang; Qiu, Cheng-Wei
2016-04-01
A multifocus optical vortex metalens, with enhanced signal-to-noise ratio, is presented, which focuses three longitudinal vortices with distinct topological charges at different focal planes. The design largely extends the flexibility of tuning the number of vortices and their focal positions for circularly polarized light in a compact device, which provides the convenience for the nanomanipulation of optical vortices. PMID:26833667
Progress report on the SLAC Linear Collider
Kozanecki, W.
1987-11-01
In this paper we report on the status of the SLAC Linear Collider (SLC), the prototype of a new generation of colliding beam accelerators. This novel type of machine holds the potential of extending electron-positron colliding beam studies to center-of-mass (c.m.) energies far in excess of what is economically achievable with colliding beam storage rings. If the technical challenges posed by linear colliders are solvable at a reasonable cost, this new approach would provide an attractive alternative to electron-positron rings, where, because of rapidly rising synchrotron radiation losses, the cost and size of the ring increases with the square of the c.m. energy. In addition to its role as a test vehicle for the linear collider principle, the SLC aims at providing an abundant source of Z/sup 0/ decays to high energy physics experiments. Accordingly, two major detectors, the upgraded Mark II, now installed on the SLC beam line, and the state-of-the-art SLD, currently under construction, are preparing to probe the Standard Model at the Z/sup 0/ pole. The SLC project was originally funded in 1983. Since the completion of construction, we have been commissioning the machine to bring it up to a performance level adequate for starting the high energy physics program. In the remainder of this paper, we will discuss the status, problems and performance of the major subsystems of the SLC. We will conclude with a brief outline of the physics program, and of the planned enhancements to the capabilities of the machine. 26 refs., 7 figs.
International linear collider reference design report
Aarons, G.
2007-06-22
The International Linear Collider will give physicists a new cosmic doorway to explore energy regimes beyond the reach of today's accelerators. A proposed electron-positron collider, the ILC will complement the Large Hadron Collider, a proton-proton collider at the European Center for Nuclear Research (CERN) in Geneva, Switzerland, together unlocking some of the deepest mysteries in the universe. With LHC discoveries pointing the way, the ILC -- a true precision machine -- will provide the missing pieces of the puzzle. Consisting of two linear accelerators that face each other, the ILC will hurl some 10 billion electrons and their anti-particles, positrons, toward each other at nearly the speed of light. Superconducting accelerator cavities operating at temperatures near absolute zero give the particles more and more energy until they smash in a blazing crossfire at the centre of the machine. Stretching approximately 35 kilometres in length, the beams collide 14,000 times every second at extremely high energies -- 500 billion-electron-volts (GeV). Each spectacular collision creates an array of new particles that could answer some of the most fundamental questions of all time. The current baseline design allows for an upgrade to a 50-kilometre, 1 trillion-electron-volt (TeV) machine during the second stage of the project. This reference design provides the first detailed technical snapshot of the proposed future electron-positron collider, defining in detail the technical parameters and components that make up each section of the 31-kilometer long accelerator. The report will guide the development of the worldwide R&D program, motivate international industrial studies and serve as the basis for the final engineering design needed to make an official project proposal later this decade.
The Next Linear Collider: NLC2001
D. Burke et al.
2002-01-14
Recent studies in elementary particle physics have made the need for an e{sup +}e{sup -} linear collider able to reach energies of 500 GeV and above with high luminosity more compelling than ever [1]. Observations and measurements completed in the last five years at the SLC (SLAC), LEP (CERN), and the Tevatron (FNAL) can be explained only by the existence of at least one particle or interaction that has not yet been directly observed in experiment. The Higgs boson of the Standard Model could be that particle. The data point strongly to a mass for the Higgs boson that is just beyond the reach of existing colliders. This brings great urgency and excitement to the potential for discovery at the upgraded Tevatron early in this decade, and almost assures that later experiments at the LHC will find new physics. But the next generation of experiments to be mounted by the world-wide particle physics community must not only find this new physics, they must find out what it is. These experiments must also define the next important threshold in energy. The need is to understand physics at the TeV energy scale as well as the physics at the 100-GeV energy scale is now understood. This will require both the LHC and a companion linear electron-positron collider. A first Zeroth-Order Design Report (ZDR) [2] for a second-generation electron-positron linear collider, the Next Linear Collider (NLC), was published five years ago. The NLC design is based on a high-frequency room-temperature rf accelerator. Its goal is exploration of elementary particle physics at the TeV center-of-mass energy, while learning how to design and build colliders at still higher energies. Many advances in accelerator technologies and improvements in the design of the NLC have been made since 1996. This Report is a brief update of the ZDR.
Internal and vorticity waves in decaying stratified flows
NASA Astrophysics Data System (ADS)
Matulka, A.; Cano, D.
2009-04-01
Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.
Potential vorticity of the south polar vortex of Venus
NASA Astrophysics Data System (ADS)
Garate-Lopez, I.; Hueso, R.; Sánchez-Lavega, A.; García Muñoz, A.
2016-04-01
Venus' atmosphere shows highly variable warm vortices over both of the planet's poles. The nature of the mechanism behind their formation and properties is still unknown. Potential vorticity is a conserved quantity when advective processes dominate over friction and diabatic heating and is a quantity frequently used to model balanced flows. As a step toward understanding the vortices' dynamics, we present maps of Ertel's potential vorticity (EPV) at Venus' south polar region. We analyze three configurations of the south polar vortex at the upper cloud level (P ~ 240 mbar; z ~ 58 km), based on our previous analyses of cloud motions and thermal structure from data acquired by the Visual and InfraRed Thermal Imaging Spectrometer instrument on board Venus Express. Additionally, we tentatively estimate EPV at the lower cloud level (P ~ 2200 mbar; z ~ 43 km), based on our previous wind measurements and on static stability data from Pioneer Venus and the Venus International Reference Atmosphere (VIRA) model. Values of EPV are on the order of 10-6 and 10-8 K m2 kg-1 s-1 at the upper and lower cloud levels, respectively, being 3 times larger than the estimated errors. The morphology observed in EPV maps is mainly determined by the structures of the vertical component of the relative vorticity. This is in contrast to the vortex's morphology observed in 3.8 or 5 µm images which are related to the thermal structure of the atmosphere at the cloud top. Some of the EPV maps point to a weak ringed structure in the upper cloud, while a more homogenous EPV field is found in the lower cloud.
Wind turbine response to parameter variation of analytic inflow vortices
NASA Astrophysics Data System (ADS)
Hand, M. Maureen; Robinson, Michael C.; Balas, Mark J.
2006-05-01
As larger wind turbines are placed on taller towers, rotors frequently operate in atmospheric conditions that support organized, coherent turbulent structures. It is hypothesized that these structures have a detrimental impact on the blade fatigue life experienced by the wind turbine. These structures are extremely difficult to identify with sophisticated anemometry such as ultrasonic anemometers. This study was performed to identify the vortex characteristics that contribute to high-amplitude cyclic blade loads, assuming that these vortices exist under certain atmospheric conditions. This study does not attempt to demonstrate the existence of these coherent turbulent structures. In order to ascertain the idealized worst-case scenario for vortical inflow structures impinging on a wind turbine rotor, we created a simple, analytic vortex model. The Rankine vortex model assumes that the vortex core undergoes solid body rotation to avoid a singularity at the vortex centre and is surrounded by a two-dimensional potential flow field. Using the wind turbine as a sensor and the FAST wind turbine dynamics code with limited degrees of freedom, we determined the aerodynamic loads imparted to the wind turbine by the vortex structure. We varied the size, strength, rotational direction, plane of rotation, and location of the vortex over a wide range of operating parameters. We identified the vortex conformation with the most significant effect on the blade root bending moment cyclic amplitude. Vortices with radii on the scale of the rotor diameter or smaller caused blade root bending moment cyclic amplitudes that contribute to high damage density. The rotational orientation, clockwise or counter-clockwise, produces little difference in the bending moment response. Vortices in the XZ plane produce bending moment amplitudes significantly greater than vortices in the YZ plane. Published in 2005 by John Wiley & Sons, Ltd.Received: 9 April 2004; Revised: 14 March 2005; Accepted: 19
Vorticity dynamics for transient high-pressure liquid injectiona)
NASA Astrophysics Data System (ADS)
Jarrahbashi, D.; Sirignano, W. A.
2014-10-01
The liquid jet from a round orifice during the transient start-up and steady mass flux periods of a high pressure injector is studied via Navier-Stokes and level-set computations. Via post-processing, the role of vorticity dynamics is examined and shown to reveal crucial new insights. A brief review of relevant literature is made. An unsteady, axisymmetric full-jet case is solved. Then, a less computationally intensive case is studied with a segment of the jet core undergoing temporal instability; agreement with the full-jet calculation is satisfactory justifying the segment analysis for three-dimensional computation. The results for surface-shape development are in agreement with experimental observations and other three-dimensional computations; the initial, axisymmetric waves at the jet surface created by Kelvin-Helmholtz (KH) instability distort to cone shapes; next, three-dimensional character develops through an azimuthal instability that leads to the creation of streamwise vorticity, lobe shapes on the cones, and formation of liquid ligaments which extend from lobes on the cones. The cause of this azimuthal instability has been widely described as a Rayleigh-Taylor instability. However, additional and sometimes more important causes are identified here. Counter-rotating, streamwise vortices within and around the ligaments show a relationship in the instability behavior for jets flowing into like-density fluid; thus, density difference cannot explain fully the three-dimensional instability as previously suggested. Furthermore, the formation of ligaments that eventually break into droplets and the formation of streamwise vorticity are caused by the same vortical dynamics. Waviness is identified on the ligaments which should result in droplet formation. The nonlinear development of the shorter azimuthal waves and ligament waves explains the experimental results that droplet sizes are usually smaller than KH wavelengths. The higher the relative velocity and
Top quark studies at hadron colliders
Sinervo, P.K.; CDF Collaboration
1996-08-01
The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag {ital b} quark jets in candidate events. The most recent measurements of top quark properties by the CDF and D{null} collaborations are reviewed, including the top quark cross section, mass, branching fractions and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Beam instrumentation for the Tevatron Collider
Moore, Ronald S.; Jansson, Andreas; Shiltsev, Vladimir; /Fermilab
2009-10-01
The Tevatron in Collider Run II (2001-present) is operating with six times more bunches and many times higher beam intensities and luminosities than in Run I (1992-1995). Beam diagnostics were crucial for the machine start-up and the never-ending luminosity upgrade campaign. We present the overall picture of the Tevatron diagnostics development for Run II, outline machine needs for new instrumentation, present several notable examples that led to Tevatron performance improvements, and discuss the lessons for future colliders.
Suppressing Electron Cloud in Future Linear Colliders
Pivi, M; Kirby, R.E.; Raubenheimer, T.O.; Le Pimpec, F.; /PSI, Villigen
2005-05-27
Any accelerator circulating positively charged beams can suffer from a build-up of an electron cloud (EC) in the beam pipe. The cloud develops through ionization of residual gases, synchrotron radiation and secondary electron emission and, when severe, can cause instability, emittance blow-up or loss of the circulating beam. The electron cloud is potentially a luminosity limiting effect for both the Large Hadron Collider (LHC) and the International Linear Collider (ILC). For the ILC positron damping ring, the development of the electron cloud must be suppressed. This paper discusses the state-of-the-art of the ongoing SLAC and international R&D program to study potential remedies.
FFAG Designs for Muon Collider Acceleration
Berg, J. Scott
2014-01-13
I estimate FFAG parameters for a muon collider with a 70mm longitudinal emittance. I do not discuss the lower emittance beam for a Higgs factory. I produce some example designs, giving only parameters relevant to estimating cost and performance. The designs would not track well, but the parameters of a good design will be close to those described. I compare these cost estimates to those for a fast-ramping synchrotron and a recirculating linear accelerator. I conclude that FFAGs do not appear to be cost-effective for the large longitudinal emittance in a high-energy muon collider.
Top quark studies at hadron colliders
Sinervo, P.K.
1997-01-01
The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Hoffmann, Ch; Lücke, M; Pinter, A
2004-05-01
We present numerical simulations of vortices that appear via primary bifurcations out of the unstructured circular Couette flow in the Taylor-Couette system with counter rotating as well as with corotating cylinders. The full, time dependent Navier Stokes equations are solved with a combination of a finite difference and a Galerkin method for a fixed axial periodicity length of the vortex patterns and for a finite system of aspect ratio 12 with rigid nonrotating ends in a setup with radius ratio eta=0.5. Differences in structure, dynamics, symmetry properties, bifurcation, and stability behavior between spiral vortices with azimuthal wave numbers M=+/-1 and M=0 Taylor vortices are elucidated and compared in quantitative detail. Simulations in axially periodic systems and in finite systems with stationary rigid ends are compared with experimental spiral data. In a second part of the paper we determine how the above listed properties of the M=-1, 0, and 1 vortex structures are changed by an externally imposed axial through flow with Reynolds numbers in the range -40< or =Re< or =40. Among other things we investigate when left handed or right handed spirals or toroidally closed vortices are preferred.
Vorticity and upscaled dispersion in 3D heterogeneous porous media
NASA Astrophysics Data System (ADS)
Di Dato, Mariaines; Chiogna, Gabriele; de Barros, Felipe; Bellin, Alberto; Fiori, Aldo
2015-04-01
Modeling flow in porous media is relevant for many environmental, energy and industrial applications. From an environmental perspective, the relevance of porous media flow becomes evident in subsurface hydrology. In general, flow in natural porous media is creeping, yet the large variability in the hydraulic conductivity values encountered in natural aquifers leads to highly heterogeneous flow fields. This natural variability in the conductivity field will affect both dilution rates of chemical species and reactive mixing. A physical consequence of this heterogeneity is also the presence of a various localized kinematical features such as straining, shearing and vorticity in aquifers, which will influence the shape of solute clouds and its fate and transport. This work aims in fundamentally characterizing the vorticity field in spatially heterogeneous flow fields as a function of their statistical properties in order to analyze the impact on transport processes. In our study, three-dimensional porous formations are constructed with an ensemble of N independent, non-overlapping spheroidal inclusions submerged into an homogeneous matrix, of conductivity K0. The inclusions are randomly located in a domain of volume W and are fully characterized by the geometry of spheroid (oblate or prolate), their conductivity K (random and drawn from a given probability density function fκ), the centroid location ¯x, the axes ratio e, the orientation of the rotational axis (α1,α2) and the volume w. Under the assumption of diluted medium, the flow problem is solved analitically by means of only two parameters: the conductivity contrast κ = K/K0 and the volume fraction n = Nw/W . Through the variation of these parameters of the problem, it is possible to approximate the structure of natural heterogeneous porous media. Using a random distribution of the orientation of the inclusions, we create media defined by the same global anisotropy f = Iz/Ix but different micro
Dynamics of restricted three and four vortices problem on the plane
NASA Astrophysics Data System (ADS)
Andrade, J.; Boatto, S.; Vidal, C.
2016-04-01
The dynamics of a test particle (a particle with zero vorticity) advected by the velocity field of N point-vortices with vorticities Γj, j = 1, …N, is considered. Making an analogy with similar studies in celestial mechanics, we call such a study a "restricted N-vortex problem" or (N + 1)-vortex problem. In particular, we study and characterize the global planar dynamics of some restricted 3 and 4-vortex problems, as a function of the vorticities Γj of the vortices.
A numerical method of tracing a vortical axis along local topological axis line
NASA Astrophysics Data System (ADS)
Nakayama, Katsuyuki; Hasegawa, Hideki
2016-06-01
A new numerical method is presented to trace or identify a vortical axis in flow, which is based on Galilean invariant flow topology. We focus on the local flow topology specified by the eigenvalues and eigenvectors of the velocity gradient tensor, and extract the axis component from its flow trajectory. Eigen-vortical-axis line is defined from the eigenvector of the real eigenvalue of the velocity gradient tensor where the tensor has the conjugate complex eigenvalues. This numerical method integrates the eigen-vortical-axis line and traces a vortical axis in terms of the invariant flow topology, which enables to investigate the feature of the topology-based vortical axis.
Proton-proton colliding beam facility ISABELLE
Hahn, H
1980-01-01
This paper attempts to present the status of the ISABELLE construction project, which has the objective of building a 400 + 400 GeV proton colliding beam facility. The major technical features of the superconducting accelerators with their projected performance are described. Progress made so far, difficulties encountered, and the program until completion in 1986 is briefly reviewed.
Black Holes and the Large Hadron Collider
ERIC Educational Resources Information Center
Roy, Arunava
2011-01-01
The European Center for Nuclear Research or CERN's Large Hadron Collider (LHC) has caught our attention partly due to the film "Angels and Demons." In the movie, an antimatter bomb attack on the Vatican is foiled by the protagonist. Perhaps just as controversial is the formation of mini black holes (BHs). Recently, the American Physical Society…
From the LHC to future colliders
De Roeck, A.; Assamagan, K.; Ellis, J.; Grojean, C.; Heinemeyer, S.; Jakobs, K.; Weiglien, G.; Well, J.; Azuelos, G.; Dawson, S.; Gripaios, B.; Han, T.; Hewett, J.; Lancaster, M.; Mariotti, C.; Moortgat, F.; Moortgat-Pick, G.; Polesello, G.; Riemann, S.; Schumacher, M.; Bechtle, P.; Carena, M.; Chachamis, G.; Chen, K.F.; De Curtis, S.; Desch, K.; Dittmar, M.; Dreiner, H.; Duhrssen, M.; Foster, B.; Frandsen, M.T.; Giammanco, A.; Godbole, R.; Gopalakrishna, S.; Govoni, P.; Gunion, J.; Hollik, W.; Hou, W.S.; Isidori, G.; Juste, A.; Kalinowski, J.; Korytov, A.; Kou, E.; Kraml, S.; Krawczyk, M.; Martin, A.; Milstead, D.; Morton-Thurtle, V.; Moenig, K.; Mele, B.; Ozcan, E.; Pieri, M.; Plehn, T.; Reina, L.; Richter-Was, E.; Rizzo, T.; Rolbiecki, K.; Sannino, F.; Schram, M.; Smillie, J.; Sultansoy, S.; Tattersall, J.; Uwer, P., Webber, B.; and Wienemann, P.
2010-03-02
Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300 fb{sup -1} of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10 fb{sup -1} of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. In the contexts of these scenarios, the Working Groups reviewed the capabilities of the future colliders to study in more detail whatever new physics may be discovered by the LHC. Their reports provide the particle physics community with some tools for reviewing the scientific priorities for future colliders after the LHC produces its first harvest of new physics from multi-TeV collisions.
Recent results from proton-antiproton colliders
Geer, S. . High Energy Physics Lab.)
1990-03-01
New results from the CERN and Fermilab proton-antiproton colliders are summarised. The areas covered are jet physics, direct photon production, W and Z production and decay, heavy flavor production, the search for the top quark, and the search for more exotic phenomena. 46 refs., 20 figs., 4 tabs.
Experiment and Radiation Safety at Colliders
NASA Astrophysics Data System (ADS)
Pugatch, V.
The emphasis is made on the novel radiation monitoring systems at colliders based on the Metal Foil Detector technology. The radiation monitoring systems for the HERA-B experiment (DESY, Hamburg) as well as for the Silicon Tracker of the LHCb experiment (CERN, Geneva) are described. The micro-strip Metal Foil Detector used for the beam profile monitoring is briefly presented.
QCD parton model at collider energies
Ellis, R.K.
1984-09-01
Using the example of vector boson production, the application of the QCD improved parton model at collider energies is reviewed. The reliability of the extrapolation to SSC energies is assessed. Predictions at ..sqrt..S = 0.54 TeV are compared with data. 21 references.
Beam dynamics issues for linear colliders
Ruth, R.D.
1987-09-01
In this paper we discuss various beam dynamics issues for linear colliders. The emphasis is to explore beam dynamics effects which lead to an effective dilution of the emittance of the beam and thus to a loss of luminosity. These considerations lead to various tolerances which are evaluated for a particular parameter set.
Future Accelerators, Muon Colliders, and Neutrino Factories
Richard A Carrigan, Jr.
2001-12-19
Particle physics is driven by five great topics. Neutrino oscillations and masses are now at the fore. The standard model with extensions to supersymmetry and a Higgs to generate mass explains much of the field. The origins of CP violation are not understood. The possibility of extra dimensions has raised tantalizing new questions. A fifth topic lurking in the background is the possibility of something totally different. Many of the questions raised by these topics require powerful new accelerators. It is not an overstatement to say that for some of the issues, the accelerator is almost the experiment. Indeed some of the questions require machines beyond our present capability. As this volume attests, there are parts of the particle physics program that have been significantly advanced without the use of accelerators such as the subject of neutrino oscillations and many aspects of the particle-cosmology interface. At this stage in the development of physics, both approaches are needed and important. This chapter first reviews the status of the great accelerator facilities now in operation or coming on within the decade. Next, midrange possibilities are discussed including linear colliders with the adjunct possibility of gamma-gamma colliders, muon colliders, with precursor neutrino factories, and very large hadron colliders. Finally visionary possibilities are considered including plasma and laser accelerators.
Linear Collider Accelerator Physics Issues Regarding Alignment
Seeman, J.T.; /SLAC
2005-08-12
The next generation of linear colliders will require more stringent alignment tolerances than those for the SLC with regard to the accelerating structures, quadrupoles, and beam position monitors. New techniques must be developed to achieve these tolerances. A combination of mechanical-electrical and beam-based methods will likely be needed.
Physics Case for the International Linear Collider
Fujii, Keisuke; Grojean, Christophe; Peskin, Michael E.; Barklow, Tim; Gao, Yuanning; Kanemura, Shinya; Kim, Hyungdo; List, Jenny; Nojiri, Mihoko; Perelstein, Maxim; Poeschl, Roman; Reuter, Juergen; Simon, Frank; Tanabe, Tomohiko; Yu, Jaehoon; Wells, James D.; Murayama, Hitoshi; Yamamoto, Hitoshi; /Tohoku U.
2015-06-23
We summarize the physics case for the International Linear Collider (ILC). We review the key motivations for the ILC presented in the literature, updating the projected measurement uncertainties for the ILC experiments in accord with the expected schedule of operation of the accelerator and the results of the most recent simulation studies.
From the LHC to Future Colliders
De Roeck, A.; Ellis, J.; Grojean, C.; Heinemeyer, S.; Jakobs, K.; Weiglein, G.; Azuelos, G.; Dawson, S.; Gripaios, B.; Han, T.; Hewett, J.; Lancaster, M.; Mariotti, C.; Moortgat, F.; Moortgat-Pick, G.; Polesello, G.; Riemann, S.; Assamagan, K.; Bechtle, P.; Carena, M.; Chachamis, G.; /more authors..
2010-06-11
Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300 fb{sup -1} of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10 fb{sup -1} of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. In the contexts of these scenarios, theWorking Groups reviewed the capabilities of the future colliders to study in more detail whatever new physics may be discovered by the LHC. Their reports provide the particle physics community with some tools for reviewing the scientific priorities for future colliders after the LHC produces its first harvest of new physics from multi-TeV collisions.
Progress in the Next Linear Collider Design
NASA Astrophysics Data System (ADS)
Raubenheimer, T. O.
2001-07-01
An electron/positron linear collider with a center-of-mass energy between 0.5 and 1 TeV would be an important complement to the physics program of the LHC. The Next Linear Collider (NLC) is being designed by a US collaboration (FNAL, LBNL, LLNL, and SLAC) which is working closely with the Japanese collaboration that is designing the Japanese Linear Collider (JLC). The NLC main linacs are based on normal conducting 11 GHz rf. This paper will discuss the technical difficulties encountered as well as the many changes that have been made to the NLC design over the last year. These changes include improvements to the X-band rf system as well as modifications to the injector and the beam delivery system. They are based on new conceptual solutions as well as results from the R&D programs which have exceeded initial specifications. The net effect has been to reduce the length of the collider from about 32 km to 25 km and to reduce the number of klystrons and modulators by a factor of two. Together these lead to significant cost savings.
Difficult Decisions: The Superconducting Super Collider.
ERIC Educational Resources Information Center
Newton, David E.; Slesnick, Irwin L.
1990-01-01
The fundamental principles of the superconducting super collider are presented. Arguments for the construction of this apparatus and policy issues surrounding its construction are discussed. Charts of the fundamental atomic particles and forces and the history of particle accelerators are provided. An activity for discussing this controversial…
Tau physics at p{bar p} colliders
Konigsberg, J.
1993-01-01
Tau detection techniques in hadron colliders are discussed together with the measurements and searches performed so far. We also underline the importance tau physics has in present and future collider experiments.
Linear Collider Physics Resource Book Snowmass 2001
Ronan , M.T.
2001-06-01
The American particle physics community can look forward to a well-conceived and vital program of experimentation for the next ten years, using both colliders and fixed target beams to study a wide variety of pressing questions. Beyond 2010, these programs will be reaching the end of their expected lives. The CERN LHC will provide an experimental program of the first importance. But beyond the LHC, the American community needs a coherent plan. The Snowmass 2001 Workshop and the deliberations of the HEPAP subpanel offer a rare opportunity to engage the full community in planning our future for the next decade or more. A major accelerator project requires a decade from the beginning of an engineering design to the receipt of the first data. So it is now time to decide whether to begin a new accelerator project that will operate in the years soon after 2010. We believe that the world high-energy physics community needs such a project. With the great promise of discovery in physics at the next energy scale, and with the opportunity for the uncovering of profound insights, we cannot allow our field to contract to a single experimental program at a single laboratory in the world. We believe that an e{sup +}e{sup -} linear collider is an excellent choice for the next major project in high-energy physics. Applying experimental techniques very different from those used at hadron colliders, an e{sup +}e{sup -} linear collider will allow us to build on the discoveries made at the Tevatron and the LHC, and to add a level of precision and clarity that will be necessary to understand the physics of the next energy scale. It is not necessary to anticipate specific results from the hadron collider programs to argue for constructing an e{sup +}e{sup -} linear collider; in any scenario that is now discussed, physics will benefit from the new information that e{sup +}e{sup -} experiments can provide. This last point merits further emphasis. If a new accelerator could be designed and
Vorticity budget investigation of a simulated long-lived mesoscale vortex in South China
NASA Astrophysics Data System (ADS)
Chen, Min; Zheng, Yongguang
2004-12-01
A vorticity budget investigation is performed using the output data from a numerical simulation of a typical MCV (mesoscale convectively generated votex) case in South China. Results suggest that the divergence caused by convection in the low troposphere is the main producer of positive vorticity, while vertical vorticity transferred by the tilting term from the horizontal vorticity compensates the upward output of cyclonic vorticity. Scale analyses of the vorticity equation suggest that the advection of planetary vorticity can be neglected owing to the low latitude, which is different from the larger scale systems in high latitude areas. In addition, the distribution of relative vorticity tendency on pressure level is not uniform. A vortex will move along the vector from the negative to the positive vorticity tendency region. The mechanism of the phenomenon—that nearly all of the convectively ascending region is located southward/southeastward of the vortex center—is also discussed. Convergence with regard to latent heat release would be in favor of the spin-up of meso-vortex, however, the horizontal vorticity caused by wind shear is tilted by vertical motion due to convection. Consequently, the negative and positive vorticity tendencies are located symmetrically about the convective center, which suggests that the vortex southward movement is dynamically driven by convection.
Towards a Future Linear Collider and The Linear Collider Studies at CERN
None
2016-07-12
During the week 18-22 October, more than 400 physicists will meet at CERN and in the CICG (International Conference Centre Geneva) to review the global progress towards a future linear collider. The 2010 International Workshop on Linear Colliders will study the physics, detectors and accelerator complex of a linear collider covering both the CLIC and ILC options. Among the topics presented and discussed will be the progress towards the CLIC Conceptual Design Report in 2011, the ILC Technical Design Report in 2012, physics and detector studies linked to these reports, and an increasing numbers of common working group activities. The seminar will give an overview of these topics and also CERNâs linear collider studies, focusing on current activities and initial plans for the period 2011-16. n.b: The Council Chamber is also reserved for this colloquium with a live transmission from the Main Auditorium.
Spanwise Spacing Effects on the Initial Structure and Decay of Axial Vortices
NASA Technical Reports Server (NTRS)
Wendt, B. J.; Reichert, B. A.
1996-01-01
The initial structure and axial decay of an array of streamwise vortices embedded in a turbulent pipe boundary layer is experimentally investigated. The vortices are shed in counter-rotating fashion from an array of equally-spaced symmetric airfoil vortex generators. Vortex structure is quantified in terms of crossplane circulation and peak streamwise vorticity. Flow conditions are subsonic and incompressible. The focus of this study is on the effect of the initial spacing between the parent vortex generators. Arrays with vortex generators spaced at 15 and 30 degrees apart are considered. When the spacing between vortex generators is decreased the circulation and peak vorticity of the shed vortices increases. Analysis indicates this strengthening results from regions of fluid acceleration in the vicinity of the vortex generator array. Decreased spacing between the constituent vortices also produces increased rates of circulation and peak vorticity decay.
High-brightness injectors for hadron colliders
Wangler, T.P.
1990-01-01
The counterrotating beams in collider rings consist of trains of beam bunches with N{sub B} particles per bunch, spaced a distance S{sub B} apart. When the bunches collide, the interaction rate is determined by the luminosity, which is defined as the interaction rate per unit cross section. For head-on collisions between cylindrical Gaussian beams moving at speed {beta}c, the luminosity is given by L = N{sub B}{sup 2}{beta}c/4{pi}{sigma}{sup 2}S{sub B}, where {sigma} is the rms beam size projected onto a transverse plane (the two transverse planes are assumed identical) at the interaction point. This beam size depends on the rms emittance of the beam and the focusing strength, which is a measure of the 2-D phase-space area in each transverse plane, and is defined in terms of the second moments of the beam distribution. Our convention is to use the rms normalized emittance, without factors of 4 or 6 that are sometimes used. The quantity {tilde {beta}} is the Courant-Synder betatron amplitude function at the interaction point, a characteristic of the focusing lattice and {gamma} is the relativistic Lorentz factor. Achieving high luminosity at a given energy, and at practical values of {tilde {beta}} and S{sub B}, requires a large value for the ratio N{sub B}{sup 2}/{var epsilon}{sub n}, which implies high intensity and small emittance. Thus, specification of the luminosity sets the requirements for beam intensity and emittance, and establishes the requirements on the performance of the injector to the collider ring. In general, for fixed N{sub B}, the luminosity can be increased if {var epsilon}{sub n} can be reduced. The minimum emittance of the collider is limited by the performance of the injector; consequently the design of the injector is of great importance for the ultimate performance of the collider.
An Afterburner at the ILC: The Collider Viewpoint
Raubenheimer, Tor O.
2004-12-07
The concept of a high-gradient plasma wakefield accelerator is considered as an upgrade path for the International Linear Collider, a future linear collider. Basic parameters are presented based on those developed for the SLC 'Afterburner'. Basic layout considerations are described and the primary concerns related to the collider operation are discussed.
An Afterburner at the ILC: The Collider Viewpoint
Raubenheimer, T
2004-09-01
The concept of a high-gradient plasma wakefield accelerator is considered as an upgrade path for the International Linear Collider, a future linear collider. Basic parameters are presented based on those developed for the SLC ''Afterburner.'' Basic layout considerations are described and the primary concerns related to the collider operation are discussed.
Electron viscosity, current vortices and negative nonlocal resistance in graphene
NASA Astrophysics Data System (ADS)
Levitov, Leonid; Falkovich, Gregory
2016-07-01
Quantum-critical strongly correlated electron systems are predicted to feature universal collision-dominated transport resembling that of viscous fluids. However, investigation of these phenomena has been hampered by the lack of known macroscopic signatures of electron viscosity. Here we identify vorticity as such a signature and link it with a readily verifiable striking macroscopic d.c. transport behaviour. Produced by the viscous flow, vorticity can drive electric current against an applied field, resulting in a negative nonlocal voltage. We argue that the latter may play the same role for the viscous regime as zero electrical resistance does for superconductivity. Besides offering a diagnostic that distinguishes viscous transport from ohmic currents, the sign-changing electrical response affords a robust tool for directly measuring the viscosity-to-resistivity ratio. A strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.
Vortices of self-gravitating grains in dusty plasmas
Nebbat, E.; Annou, R.
2012-09-15
Vortices are an attractive expression of the non-linear dynamics of fluids along with plasmas. In complex plasmas, Nebbat and Annou [Phys. Plasmas 17, 093702 (2010)] proposed a time dependent non-linear model that considers vortices as a consequence of an instability. The model is augmented hereafter by incorporating the gravitational grain-grain attraction, particle drift due to self-gravity field, self-consistent inter-particle distance, the permeability of grains along with the grain charge excess due to the non-linear dependence of the grain capacitance on its size. Effects of the latter parameters as well as the effect of grain mass to charge ratio on the characteristics of the vortex such as density are investigated.