Magnetic multipole redirector of moving plasmas
Crow, James T.; Mowrer, Gary R.
1999-01-01
A method and apparatus for redirecting moving plasma streams using a multiple array of magnetic field generators (e.g., permanent magnets or current bearing wires). Alternate rows of the array have opposite magnetic field directions. A fine wire mesh may be employed to focus as well as redirect the plasma.
Superconducting multipole corrector magnet
Kashikhin, Vladimir; /Fermilab
2004-10-01
A novel concept of superconducting multipole corrector magnet is discussed. This magnet assembled from 12 identical racetrack type coils and can generate any combination of dipole, quadrupole and sextupole magnetic fields. The coil groups are powered from separate power supplies. In the case of normal dipole, quadrupole and sextupole fields the total field is symmetrical relatively the magnet median plane and there are only five powered separately coil groups. This type multipole corrector magnet was proposed for BTeV, Fermilab project and has following advantages: universal configuration, simple manufacturing and high mechanical stability. The results of magnetic design including the field quality and magnetic forces in comparison with known shell type superconducting correctors are presented.
NASA Astrophysics Data System (ADS)
Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro
1998-10-01
Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.
Superconductivity in magnetic multipole states
NASA Astrophysics Data System (ADS)
Sumita, Shuntaro; Yanase, Youichi
2016-06-01
Stimulated by recent studies of superconductivity and magnetism with local and global broken inversion symmetry, we investigate the superconductivity in magnetic multipole states in locally noncentrosymmetric metals. We consider a one-dimensional zigzag chain with sublattice-dependent antisymmetric spin-orbit coupling and suppose three magnetic multipole orders: monopole order, dipole order, and quadrupole order. It is demonstrated that the Bardeen-Cooper-Schrieffer state, the pair-density wave (PDW) state, and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state are stabilized by these multipole orders, respectively. We show that the PDW state is a topological superconducting state specified by the nontrivial Z2 number and winding number. The origin of the FFLO state without macroscopic magnetic moment is attributed to the asymmetric band structure induced by the magnetic quadrupole order and spin-orbit coupling.
Magnetic Multipoles in Theory and Practice.
ERIC Educational Resources Information Center
Smith, D. G.
1980-01-01
A magnetic multipole apparatus suitable for the physics teaching laboratory is described. The apparatus enables the student to measure the magnetic field configuration of a single large coil, and of systems of one or more small coils. (Author/DS)
Permanent multipole magnets with adjustable strength
Halbach, K.
1983-03-01
Preceded by a short discussion of the motives for using permanent magnets in accelerators, a new type of permanent magnet for use in accelerators is presented. The basic design and most important properties of a quadrupole will be described that uses both steel and permanent magnet material. The field gradient produced by this magnet can be adjusted without changing any other aspect of the field produced by this quadrupole. The generalization of this concept to produce other multipole fields, or combination of multipole fields, will also be presented.
Closed expressions for the magnetic field of toroidal multipole configurations
Sheffield, G.V.
1983-04-01
Closed analytic expressions for the vector potential and the magnetic field for the lower order toroidal multipoles are presented. These expressions can be applied in the study of tokamak plasma cross section shaping. An example of such an application is included. These expressions also allow the vacuum fields required for plasma equilibrium to be specified in a general form independent of a particular coil configuration.
Multipole analysis of circular cylindrical magnetic systems
NASA Astrophysics Data System (ADS)
Selvaggi, Jerry P.
This thesis deals with an alternate method for computing the external magnetic field from a circular cylindrical magnetic source. The primary objective is to characterize the magnetic source in terms of its equivalent multipole distribution. This multipole distribution must be valid at points close to the cylindrical source and a spherical multipole expansion is ill-equipped to handle this problem; therefore a new method must be introduced. This method, based upon the free-space Green's function in cylindrical coordinates, is developed as an alternative to the more familiar spherical harmonic expansion. A family of special functions, called the toroidal functions or Q-functions, are found to exhibit the necessary properties for analyzing circular cylindrical geometries. In particular, the toroidal function of zeroth order, which comes from the integral formulation of the free-space Green's function in cylindrical coordinates, is employed to handle magnetic sources which exhibit circular cylindrical symmetry. The toroidal functions, also called Q-functions, are the weighting coefficients in a "Fourier series-like" expansion which represents the free-space Green's function. It is also called a toroidal expansion. This expansion can be directly employed in electrostatic, magnetostatic, and electrodynamic problems which exhibit cylindrical symmetry. Also, it is shown that they can be used as an alternative to the Elliptic integral formulation. In fact, anywhere that an Elliptic integral appears, one can replace it with its corresponding Q-function representation. A number of problems, using the toroidal expansion formulation, are analyzed and compared to existing known methods in order to validate the results. Also, the equivalent multipole distribution is found for most of the solved problems along with its corresponding physical interpretation. The main application is to characterize the external magnetic field due to a six-pole permanent magnet motor in terms of its
Multipole Analysis of Circular Cylindircal Magnetic Systems
Selvaggi, Jerry P.
2005-12-01
This thesis deals with an alternate method for computing the external magnetic field from a circular cylindrical magnetic source. The primary objective is to characterize the magnetic source in terms of its equivalent multipole distribution. This multipole distribution must be valid at points close to the cylindrical source and a spherical multipole expansion is ill-equipped to handle this problem; therefore a new method must be introduced. This method, based upon the free-space Green's function in cylindrical coordinates, is developed as an alternative to the more familiar spherical harmonic expansion. A family of special functions, called the toroidal functions or Q-functions, are found to exhibit the necessary properties for analyzing circular cylindrical geometries. In particular, the toroidal function of zeroth order, which comes from the integral formulation of the free-space Green's function in cylindrical coordinates, is employed to handle magnetic sources which exhibit circular cylindrical symmetry. The toroidal functions, also called Q-functions, are the weighting coefficients in a ''Fourier series-like'' expansion which represents the free-space Green's function. It is also called a toroidal expansion. This expansion can be directly employed in electrostatic, magnetostatic, and electrodynamic problems which exhibit cylindrical symmetry. Also, it is shown that they can be used as an alternative to the Elliptic integral formulation. In fact, anywhere that an Elliptic integral appears, one can replace it with its corresponding Q-function representation. A number of problems, using the toroidal expansion formulation, are analyzed and compared to existing known methods in order to validate the results. Also, the equivalent multipole distribution is found for most of the solved problems along with its corresponding physical interpretation. The main application is to characterize the external magnetic field due to a six-pole permanent magnet motor in terms of
Hierarchical Fast Multipole Simulation of Magnetic Colloids
NASA Astrophysics Data System (ADS)
Günal, Yüksel; Visscher, Pieter
1997-03-01
We have extended the well-known "fast multipole"footnote L. F. Greengard and V. Rokhlin, J. Comp. Phys. 73 p. 325, 1987. methods for molecular-dynamics simulation of large systems of point charges to continuum systems, such as magnetic films or particulate suspensions. (These methods reduce the computational labor from O(N^2) to O(N log N) or O(N), the number of particles). We apply the method to the particular case of a colloidal dispersion of magnetized cylindrical particles. Our method is fully hierarchical, both upward and downward from the particle size scale. The force on each particle is calculated by grouping distant particles into large clusters, nearer particles into smaller clusters, and dividing the nearest particles into segments. The fineness with which the particles are divided is controlled by an error tolerance parameter. The field of each cluster or segment is computed from a multipole expansion. Distant periodic images are also treated as multipoles - this is much faster than standard Fourier-transform or Ewald summation techniques.
NASA Astrophysics Data System (ADS)
Akitsu, Tetsuya
1998-10-01
A plasma-enhanced reactive sputtering was developed for the deposition of oriented thin crustals of metallic-oxide compound. An oxygen plasma was excited with microwave, electron cyclotron resonance discharge at 2.45 GHz and a compact DC magnetron sputtering was combined. The discharge characteristics was compared in two types of magnetic field configurations.using the optical emission spectroscopy and the appearance potential mass-spectrometry. In a divergent magnetic field, the microwave was absorbed in a single electron-cyclotron resonance Layer, 30-45 mm apart from a crystallized ceramic vesse, and the deposition region was exposed to a freely expanding plasma. Next, the end of the magnetic field line was closed with a magnetic circuit and the source plasma was magnetically confined in the local mirror, thus only neutral oxygen was allowed to expand into the deposition region.
Permanent-magnet multipole with adjustable strength
Halbach, K.
1982-09-20
Two or more magnetically soft pole pieces are symmetrically positioned along a longitudinal axis to provide a magnetic field within a space defined by the pole pieces. Two or more permanent magnets are mounted to an external magnetically-soft cylindrical sleeve which rotates to bring the permanent magnets into closer coupling with the pole pieces and thereby adjustably control the field strength of the magnetic field produced in the space defined by the pole pieces. The permanent magnets are preferably formed of rare earth cobalt (REC) material which has a high remanent magnetic field and a strong coercive force. The pole pieces and the permanent magnets have corresponding cylindrical surfaces which are positionable with respect to each other to vary the coupling there between. Auxiliary permanent magnets are provided between the pole pieces to provide additional magnetic flux to the magnetic field without saturating the pole pieces.
Permanent magnet multipole with adjustable strength
Halbach, Klaus
1985-01-01
Two or more magnetically soft pole pieces are symmetrically positioned along a longitudinal axis to provide a magnetic field within a space defined by the pole pieces. Two or more permanent magnets are mounted to an external magnetically-soft cylindrical sleeve which rotates to bring the permanent magnets into closer coupling with the pole pieces and thereby adjustably control the field strength of the magnetic field produced in the space defined by the pole pieces. The permanent magnets are preferably formed of rare earth cobalt (REC) material which has a high remanent magnetic field and a strong coercive force. The pole pieces and the permanent magnets have corresponding cylindrical surfaces which are positionable with respect to each other to vary the coupling therebetween. Auxiliary permanent magnets are provided between the pole pieces to provide additional magnetic flux to the magnetic field without saturating the pole pieces.
Specification of multipole tolerances for the APS quadrupole magnet
Kramer, S.L.
1988-08-01
This note will address a proposed method for specifying the multipole tolerance for the design and production of APS quadrupole magnets. The tolerances for the multipole components for the quadrupole magnets will be set to that level which reduces the dynamic aperture by about 10--15% from the ideal machine dynamic aperture (as specified in CDR-87). This level may appear rather stringent, especially compared to the 50--60% reduction resulting from quad placement errors. However, when all tolerances are taken together, the residual dynamic aperture would be prohibitively small and commissioning would be difficult if these tolerances were at twice this level. The dynamic aperture was determined using the numerical tracking program RACETRACK.
Experience with the SLC permanent magnet multipoles
Gross, G.; Spencer, J.
1994-06-01
Permanent magnets have been used in the SLC Damping Rings and their injection and extraction lines since 1985. Recent upgrades of the DR vacuum chambers provided an opportunity to check DR magnets prior to higher beam current operation. Several PM sextupoles downstream of the injection kickers in the electron ring had exceeded their thermal stabilization values of 80{degrees}C and some showed serious mechanical deformations and radiation >1 R at contact. We discuss our observations, measurements and a few inexpensive modifications that should improve these magnets under such conditions. A new, block matching algorithm allowed us to use magnet blocks that had been considered unusable because of very different remament field strengths and easy axis errors.
Tests of planar permanent magnet multipole focusing elements
Cobb, J.; Tatchyn, R.
1993-08-01
In recent work, planar configurations of permanent magnets were proposed as substitutes for conventional current-driven iron quadrupoles in applications limited by small aperture sizes and featuring small beam occupation diameters. Important examples include the configuring of focusing lattices in small-gap insertion devices, and the implementation of compact mini-beta sections on linear or circular machines. In subsequent analysis, this approach was extended to sextupoles and higher-order multipoles. In this paper we report on initial measurements conducted at the Stanford Linear Accelerator Center on recently fabricated planar permanent magnet quadrupoles and sextupoles configured out of SmCo and NdFe/B.
FURTHER EXPERIENCE WITH SLC PERMANENT MAGNETIC (PM) MULTIPOLES
Spencer, James E.
2003-05-29
PM multipoles have been used in the SLAC damping rings (DR) and their injection and extraction lines since 1985. Due to upgrades of the DR vacuum chambers for higher currents in 1993, there was an opportunity to check some of these magnets[1]. Nothing more was done until a program of real-time radiation measurements was begun in the electron ring to determine causes, levels and effects of integrated gamma and neutron doses on the strengths and harmonic contents for NLC purposes. We discuss results of the latest magnetic measurements, radiation measurement program, semiconductor dosimeters and a few unexpected but interesting conclusions.
Analytical expressions for fringe fields in multipole magnets
NASA Astrophysics Data System (ADS)
Muratori, B. D.; Jones, J. K.; Wolski, A.
2015-06-01
Fringe fields in multipole magnets can have a variety of effects on the linear and nonlinear dynamics of particles moving along an accelerator beam line. An accurate model of an accelerator must include realistic models of the magnet fringe fields. Fringe fields for dipoles are well understood and can be modeled at an early stage of accelerator design in such codes as mad8, madx, gpt or elegant. Existing techniques for quadrupole and higher order multipoles rely either on the use of a numerical field map, or on a description of the field in the form of a series expansion about a chosen axis. Usually, it is not until the later stages of a design project that such descriptions (based on magnet modeling or measurement) become available. Furthermore, series expansions rely on the assumption that the beam travels more or less on axis throughout the beam line; but in some types of machines (for example, Fixed Field Alternating Gradients or FFAGs) this is not a good assumption. Furthermore, some tracking codes, such as gpt, use methods for including space charge effects that require fields to vary smoothly and continuously along a beam line: in such cases, realistic fringe field models are of significant importance. In this paper, a method for constructing analytical expressions for multipole fringe fields is presented. Such expressions allow fringe field effects to be included in beam dynamics simulations from the start of an accelerator design project, even before detailed magnet design work has been undertaken. The magnetostatic Maxwell equations are solved analytically and a solution that fits all orders of multipoles is derived. Quadrupole fringe fields are considered in detail as these are the ones that give the strongest effects. The analytic expressions for quadrupole fringe fields are compared with data obtained from numerical modeling codes in two cases: a magnet in the high luminosity upgrade of the Large Hadron Collider inner triplet, and a magnet in the
Object-Oriented Fast Multipole Simulation: Magnetic Colloids
NASA Astrophysics Data System (ADS)
Visscher, Pieter; Günal, Yüksel
1997-08-01
In simulating a system of N particles, if the interaction is long-ranged all pair interactions must be calculated, requiring CPU time of order N^2. Recently-developed ``fast multipole'' methods (FMM) can reduce this time to order N, at the cost of considerable programming complexity. We have developed an object-oriented approach which uses similar ideas but is conceptually much simpler. The system is represented by a hierarchical tree whose root is the entire system and whose lowest nodes are the particles. The entire calculation of the particle interactions consists of a single call to a recursive function CalculateInteractions(A,B) with A=B=root, which uses a simple opening-angle criterion to choose between multipole expansion and calling itself (subdividing A and B.) The resulting algorithm is essentially equivalent to the FMM, but the choice of when to subdivide (which is laboriously hard-wired in FMM) is made automatically. We will discuss the implementation of periodic BCs and the application of the method to continuum systems (cylindrical magnetic particles).
Multipole-multimode Floquet theory in nuclear magnetic resonance.
Ramachandran, Ramesh; Griffin, Robert G
2005-04-22
In this paper, we present a new analytical approach for describing the spin dynamics of synchronous and asynchronous time-dependent modulations in solid-state nuclear magnetic resonance experiments. The approach, based on multimode Floquet theory, employs the multipole operator basis of Sanctuary for spin description and illustrates the time evolution in the Floquet-Liouville space using the effective Hamiltonians obtained from the contact (or van Vleck) transformation procedure. Since the Hamiltonian and the density operator are expressed in terms of irreducible tensor operators, extensions to higher spin magnitudes (I>12) and multiple spins are quite straightforward and permit analytical treatments for many problems. We outline the general underlying principles involved in this approach with a brief mention of its potential application in other branches of spectroscopy. PMID:15945688
Magnetic assembly of colloidal superstructures with multipole symmetry.
Erb, Randall M; Son, Hui S; Samanta, Bappaditya; Rotello, Vincent M; Yellen, Benjamin B
2009-02-19
The assembly of complex structures out of simple colloidal building blocks is of practical interest for building materials with unique optical properties (for example photonic crystals and DNA biosensors) and is of fundamental importance in improving our understanding of self-assembly processes occurring on molecular to macroscopic length scales. Here we demonstrate a self-assembly principle that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements. The structures are assembled using the magnetostatic interaction between effectively diamagnetic and paramagnetic particles within a magnetized ferrofluid. The resulting multipolar geometries resemble electrostatic charge configurations such as axial quadrupoles ('Saturn rings'), axial octupoles ('flowers'), linear quadrupoles (poles) and mixed multipole arrangements ('two tone'), which represent just a few examples of the type of structure that can be built using this technique.
Magnetic assembly of colloidal superstructures with multipole symmetry.
Erb, Randall M; Son, Hui S; Samanta, Bappaditya; Rotello, Vincent M; Yellen, Benjamin B
2009-02-19
The assembly of complex structures out of simple colloidal building blocks is of practical interest for building materials with unique optical properties (for example photonic crystals and DNA biosensors) and is of fundamental importance in improving our understanding of self-assembly processes occurring on molecular to macroscopic length scales. Here we demonstrate a self-assembly principle that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements. The structures are assembled using the magnetostatic interaction between effectively diamagnetic and paramagnetic particles within a magnetized ferrofluid. The resulting multipolar geometries resemble electrostatic charge configurations such as axial quadrupoles ('Saturn rings'), axial octupoles ('flowers'), linear quadrupoles (poles) and mixed multipole arrangements ('two tone'), which represent just a few examples of the type of structure that can be built using this technique. PMID:19225522
Prager, S C
1982-05-01
Multipoles are being employed as devices to study fusion issues and plasma phenomena at high values of beta (plasma pressure/magnetic pressure) in a controlled manner. Due to their large volume, low magnetic field (low synchrotron radiation) region, they are also under consideration as potential steady state advanced fuel (low neutron yield) reactors. Present experiments are investigating neoclassical (bootstrap and Pfirsch-Schlueter) currents and plasma stability at extremely high beta.
Neptune radio emission in dipole and multipole magnetic fields
NASA Technical Reports Server (NTRS)
Sawyer, C. B.; King, N. V.; Romig, J. H.; Warwick, J. W.
1995-01-01
We study Neptune's smooth radio emission in two ways: we simulate the observations and we then consider the radio effects of Neptune's magnetic multipoles. A procedure to deduce the characteristics of radio sources observed by the Planetary Radio Astronomy experiment minimizes limiting assumptions and maximizes use of the data, including quantitative measurement of circular polarization. Study of specific sources simulates time variation of intensity and apparent polarization of their integrated emission over an extended time period. The method is applied to Neptune smooth recurrent emission (SRE). Time series are modeled with both broad and beamed emission patterns, and at two frequencies which exhibit different time variation of polarization. These dipole-based results are overturned by consideration of more complex models of Neptune's magnetic field. Any smooth emission from the anticipated auroral radio source is weak and briefly observed. Dominant SRE originates complex fields at midlatitude. Possible SRE source locations overlap that of 'high-latitude' emission (HLE) between +(out) and -(in) quadrupoles. This is the first identification of multipolar magnetic structure with a major source of planetary radio emission.
Magnetic design and measurement of nonlinear multipole magnets for the APT beam expander system
Barlow, D.B.; Shafer, R.E.; Martinez, R.P.; Walstrom, P.L.; Kahn, S.; Jain, A.; Wanderer, P.
1997-10-01
Two prototype nonlinear multipole magnets have been designed for use in the 800-MeV beam test of the APT beam-expansion concept at LANSCE. The iron-dominated magnets each consist of three independent coils, two for producing a predominantly octupole field with a tunable duodecapole component, and one for canceling the residual quadrupole field. Two such magnets, one for shaping each transverse plane, are required to produce a rectangular, uniform beam current density distribution with sharp edges on the APT target. This report will describe the magnetic design of these magnets, along with field measurements, and a comparison to the magnetic design.
Selected applications of planar permanent magnet multipoles in FEL insertion device design
Tatchyn, R.
1993-08-01
In recent work, a new class of magnetic multipoles based on planar configurations of permanent magnet (PM) material has been developed. These structures, in particular the quadrupole and sextupole, feature fully open horizontal apertures, and are comparable in effectiveness to conventional iron multipole structures. In this paper results of recent measurements of planar PM quadrupoles and sextupoles are reported and selected applications to FEL insertion device design are considered.
Collective magnetic multipole excitations in open shells: 48Ti
NASA Astrophysics Data System (ADS)
Liu, H.; Zamick, L.
1987-11-01
The magnetic multipole even-parity transitions are calculated in 48Ti with a mind to finding interesting collective behavior and to study the effects of increasing the model space. The single-j shell signature selection rules are compared to those in the neutron-proton interacting boson model with good F spin. There are similarities but also differences. Some behavior of the single-j shell calculation survives as the model space increases, e.g., low lying collective M1 and M7 modes. Configuration mixing is, however, vital to describe the M3 and M5 modes as well as the spin flip M1 modes. The distribution of strength between lower and higher isospins is discussed. Results are compared with calculated transitions in 42Sc. It appears that allowing one-particle excitations from the single-j shell gives the pattern of the strength distribution; the further addition of two-particle excitations leads to a quenching of the strength distribution.
Antimatter Plasmas in a Multipole Trap for Antihydrogen
Andresen, G.; Bowe, P. D.; Hangst, J. S.; Bertsche, W.; Chapman, S.; Deutsch, A.; Fajans, J.; Povilus, A.; Wurtele, J. S.; Boston, A.; Chartier, M.; Nolan, P.; Cesar, C. L.; Silveira, D. M.; Charlton, M.; Jenkins, M. J.; Joergensen, L. V.; Madsen, N.; Telle, H. H.; Werf, D. P. van der
2007-01-12
We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies.
Antimatter plasmas in a multipole trap for antihydrogen.
Andresen, G; Bertsche, W; Boston, A; Bowe, P D; Cesar, C L; Chapman, S; Charlton, M; Chartier, M; Deutsch, A; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Gomberoff, K; Hangst, J S; Hayano, R S; Hydomako, R; Jenkins, M J; Jørgensen, L V; Kurchaninov, L; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Robicheaux, F; Sarid, E; Silveira, D M; Storey, J W; Telle, H H; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y
2007-01-12
We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies.
Magnetic multipole cylinders from mould-injection Nd2Fe14B plastic bonded magnets (abstract)
NASA Astrophysics Data System (ADS)
Nicolaides, G. K.; Niarchos, D.; Tsamakis, D.; Koubouros, I.; Mitsis, A.
1996-04-01
Mould injection Nd2Fe14B magnetic material of density ρ˜4 g/cc and of an energy product (BH)max˜4 MGOe, has been pressed into the form of cylindrical segments in order to investigate the possibility of preparing cylindrical magnetic multipoles which could be used as magnetic gears. The obtained cylindrical bonded magnet segments have a length of 3 cm and an angle width of φ=90° or φ=45°. These segments are easily magnetized along a radial direction at the angle φ/2, using a conventional electromagnet at a magnetic field of 2 T. Subsequently, the opposite magnetized segments are combined and bonded together with ultrasonic technique. The final result of the above procedure is the formation of a magnetic multipole cylinder which could be used as a magnetic gear. Here, except the preparation technique, we report the maximum torque applied versus the magnetization M of the poles and the distance between the gears. The dependence of the applied torque on the rotational frequency is also examined.
Hilgenfeld, Bernd; Haueisen, Jens
2004-09-01
BACKGROUND: Magnetically marked capsules serve for the analysis of peristalsis and throughput times within the intestinal tract. Moreover, they can be used for the targeted disposal of drugs. The capsules get localized in time by field measurements with a superconducting quantum interference device (SQUID) magnetometer array. Here it is important to ensure an online localization with high speed and high suppression of disturbing fields. In this article we use multipole expansions for the simultaneous localization and suppression of disturbing fields. METHODS: We expand the measurement data in terms of inner and outer multipoles. Thereby we obtain directly a separation of marker field and outer disturbing fields. From the inner dipoles and quadrupoles we compute the magnetization and position of the capsule. The outer multipoles get eliminated. RESULTS: The localization goodness has been analyzed depending on the order of the multipoles used and depending on the systems noise level. We found upper limits of the noise level for the usage of certain multipole moments. Given a signal to noise ratio of 40 and utilizing inner dipoles and quadrupoles and outer dipoles, the method enables an accuracy of 5 mm with a speed of 10 localizations per second. CONCLUSION: The multipole localization is an effective method and is capable of online-tracking magnetic markers.
NASA Astrophysics Data System (ADS)
Guo, Zhen; Tang, Jing-Yu; Yang, Zheng; Wang, Xiang-Qi; Sun, Biao
2012-11-01
A novel structure of multipole field magnets is proposed, and it can provide any order either symmetric or anti-symmetric field distribution within a good-field region in a flat rectangular shape with relative field errors of about 1%. Some of these field distributions cannot be obtained by standard multipole magnets but are quite useful in some applications, thanks to the decoupling of the two halves of the magnets by a pair of shielding plates. In addition, the simplified structure compared with the standard one makes the magnet fabrication easier and cost effective. Two-dimensional magnetic field calculations for anti-symmetric sextupole, octupole, decapole and dodecapole fields show that the new types of multipole magnets have good field quality. Three-dimensional magnetic field calculations have confirmed the validity of the two-dimensional calculations. Symmetric field distributions by the simplified multipole field magnets have also been confirmed by two-dimensional field calculations. Two application examples by using numerical simulations are also given to show the effectiveness of simplified multipole field magnets in producing uniform-like beam spots at two different targets with different beam inputs. It is also shown that combinations of the lower order anti-symmetric field magnets - a merit of this magnet structure - are more advantageous than the traditional combination of octupole and dodecapole magnets in beam spot uniformization, besides with cheaper construction and operation costs. The applications of non-standard field distributions such as anti-symmetric sextupole and symmetric octupole field distributions in synchrotrons are to be exploited in the future.
Global Aspects of Charged Particle Motion in Axially Symmetric Multipole Magnetic Fields
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2003-01-01
The motion of a single charged particle in the space outside of a compact region of steady currents is investigated. The charged particle is assumed to produce negligible electromagnetic radiation, so that its energy is conserved. The source of the magnetic field is represented as a point multipole. After a general description, attention is focused on magnetic fields with axial symmetry. Lagrangian dynamical theory is utilized to identify constants of the motion as well as the equations of motion themselves. The qualitative method of Stonner is used to examine charged particle motion in axisymmetric multipole fields of all orders. Although the equations of motion generally have no analytical solutions and must be integrated numerically to produce a specific orbit, a topological examination of dynamics is possible, and can be used, d la Stonner, to completely describe the global aspects of the motion of a single charged particle in a space with an axisymmetric multipole magnetic field.
Theory and application of plane elliptic multipoles for static magnetic fields
NASA Astrophysics Data System (ADS)
Schnizer, P.; Schnizer, B.; Akishin, P.; Fischer, E.
2009-08-01
Standard textbooks on beam dynamics study the impact of the magnetic field quality on the beam using field representations based on circular multipoles. Iron dominated magnets, however, typically provide a good field region with a non-circular aspect ratio (i.e. an ellipse whose axis a is significantly larger than the axis b); a boundary not ideal for circular multipoles. The development of superconductors, originally driven to reach fields above ≈2 T, allows using them today in completely different fields: iron dominated DC magnets, to save the energy for coil powering as well as repeatedly fast ramped magnets. The cold mass of magnets, housed in common cryostats sectors, makes it tedious to implement additional correction magnets at a later stage, as it requires to warm up the sections where the magnets should be installed as well as unwelding the cryostat. Thus the field homogeneity of the magnets and its influence on the beam has to be thoroughly studied during the project planning phase. Elliptic multipoles, a new type of field expansion for static or quasi-static (here magnetic) two-dimensional fields, are proposed and investigated, which are particular solutions of the potential equation in plane elliptic coordinates obtained by the method of separation. The proper subsets of these particular solutions appropriate for representing static real or complex fields regular within an ellipse are identified. Formulas are given for computing expansion coefficients from given fields. The advantage of this new approach is that the expansion is valid, convergent and accurate in a larger domain, namely in an ellipse circumscribed to the reference circle of the common circular multipoles in polar coordinates. Formulas are derived for calculating the circular multipoles from the elliptical ones. The effectiveness of the approach was tested on many different magnet designs and is illustrated here on the dipole design chosen for the core synchrotron (SIS 100) of the FAIR
NASA Astrophysics Data System (ADS)
Hamada, Shoji; Yamamoto, Osamu; Kobayashi, Tetsuo
This paper presents a generalized equivalent multipole-moment method for calculating three-dimensional Laplacian fields in multi-spherical system. The Greengard & Rokhlin's M2M, M2L, and L2L formulae enable the multipole-moment method to calculate the fields in general arrangement of multi-spheres, which involve exclusive and multi-layered spherical arrangement. We applied this method to electric field calculation in biological structures induced by ELF magnetic fields. The induced electric fields in a three eccentric and exclusive spheres system, which models human head with two eyeballs, are calculated under the application of homogeneous and magnetic-dipole fields. The validity of this method is successfully confirmed by comparing the calculated fields with those by the fast-multipole surface-charge-simulation method.
NASA Astrophysics Data System (ADS)
Argin, F.; Ahrens, H.; Klinkenbusch, L.
2012-09-01
The multipole representation of Magnetoencephalography (MEG) signals is known as a useful tool for distinguishing between magnetic fields arising from the brain and external disturbances. In this contribution we extend this concept and show that a closed double-layer surface with magnetometer probes is better suited to determine the corresponding multipole amplitudes αlm than a conventional single-layer surface with gradiometers and magnetometer probes. For two different source configurations we show that the αlm rapidly converge to the exact values. This proof of concept motivates to further optimize the geometry of the double-layer surface and the sensors' positions.
Grooved multi-pole magnetic gratings for high-resolution positioning systems
NASA Astrophysics Data System (ADS)
Xu, Zhi-Hao; Tseng, Bin-Hui; Chang, Ching; Wang, Sheng-Ching; Chin, Tsung-Shune; Sung, Cheng-Kuo
2015-06-01
Magnetic encoders are much advantageous for precision positioning specifically under harsh environments. The finer the magnetic pole-pitches of the magnetic scale in a magnetic encoder the higher the resolution of the encoder. In this paper, a grooved multi-pole magnetic grating (MPMG) is substituted for conventional non-structured magnetic scale. A MPMG with pole-pitch of 200 µm was prepared by photo-lithography and electro-deposition. Simulation was first done to attain the relationship among magnetic flux density, magnetic properties of electrodeposited alloy layers, magnetizing directions and the grating dimensions. The MPMG can be fully magnetized for use by just a single pulse in a solenoid coil. Magnetic properties were investigated in which CoNiP layers were electrodeposited under various current densities. Measured magnetic flux densities versus grating heights, magnetizing directions and detection gaps on magnetized MPMG validate the applicability of ultra-fine pitched MPMG.
Variance and shift of transition arrays for electric and magnetic multipole transitions
NASA Astrophysics Data System (ADS)
Krief, Menahem; Feigel, Alexander
2015-12-01
Generalized analytical expressions for the two-electron relativistic Unresolved-Transition-Array (UTA) energy variance and shift for electric and magnetic transitions of general multipole order are presented. The revised expressions are shown to agree with the exact moments calculated directly from the energy levels of two-electron configurations. We show that for electric transitions of even multipole order and for magnetic transitions, the available expressions in the literature, which are implemented in widely used atomic codes, are incorrect. We suggest an alternative method for the calculation of the UTA energy variance and shift by using the analytical expressions for the two-electron energy levels and line-strengths. The method is much more efficient and simple than the use of the traditional lengthy analytic expressions. Finally, the effect of UTA widths on Super-Transition-Array (STA) spectral opacity is shown for several examples.
Field analysis and enhancement of multi-pole magnetic components fabricated on printed circuit board
NASA Astrophysics Data System (ADS)
Chiu, Kuo-Chi; Chen, Chin-Sen
2007-09-01
A multi-pole magnetic component magnetized with a fine magnetic pole pitch of less than 1 mm is very difficult to achieve by using traditional methods. Moreover, it requires a precise mechanical process and a complicated magnetization system. Different fine magnetic pole pitches of 300, 350 and 400 μm have been accomplished on 9-pole magnetic components through the printed circuit board (PCB) manufacturing technology. Additionally, another fine magnetic pole pitch of 500 μm was also fabricated on a dual-layered (DL) wire circuit structure to investigate the field enhancement. After measurements, a gain factor of 1.37 was obtained in the field strength. The field variations among different magnetic pole pitches were analyzed in this paper.
Nolte, G; Curio, G
1997-01-01
Spatially restricted biological current distributions, like the primary neuronal response in the human somatosensory cortex evoked by electric nerve stimulation, can be described adequately by a current multipole expansion. Here analytic formulas are derived for computing magnetic fields induced by current multipoles in terms of an nth-order derivative of the dipole field. The required differential operators are given in closed form for arbitrary order. The concept is realized in different forms for an expansion of the scalar as well as the dyadic Green's function, the latter allowing for separation of those multipolar source components that are electrically silent but magnetically detectable. The resulting formulas are generally applicable for current sources embedded in arbitrarily shaped volume conductors. By using neurophysiologically relevant source parameters, examples are provided for a spherical volume conductor with an analytically given dipole field. An analysis of the signal-to-noise ratio for multipole coefficients up to the octapolar term indicates that the lateral extent of cortical current sources can be detected by magnetoencephalographic recordings. PMID:9284293
Oxidation of gallium arsenide in a plasma multipole device. Study of the MOS structures obtained
NASA Technical Reports Server (NTRS)
Gourrier, S.; Mircea, A.; Simondet, F.
1980-01-01
The oxygen plasma oxidation of GaAs was studied in order to obtain extremely high frequency responses with MOS devices. In the multipole system a homogeneous oxygen plasma of high density can easily be obtained in a large volume. This system is thus convenient for the study of plasma oxidation of GaAs. The electrical properties of the MOS diodes obtained in this way are controlled by interface states, located mostly in the upper half of the band gap where densities in the 10 to the 13th power/(sq cm) (eV) range can be estimated. Despite these interface states the possibility of fabricating MOSFET transistors working mostly in the depletion mode for a higher frequency cut-off still exists.
Bashful ballerina unveiled: Multipole analysis of the coronal magnetic field
NASA Astrophysics Data System (ADS)
Virtanen, I.; Mursula, K.
2012-12-01
Heliospheric current sheet (HCS) is the continuum of the coronal magnetic equator, dividing the heliospheric magnetic field (HMF) into two sectors (polarities). Because of its wavy structure, the HCS is often called the ballerina skirt. Several studies have proven that the HCS is southward shifted during about three years in the solar declining phase. This persistent phenomenon, called the bashful ballerina, has been verified by geomagnetic indices since 1930s, by OMNI data base since 1960s, by the WSO PFSS model since mid-1970s and by the Ulysses probe measurements during the fast latitude scans in 1994-1995 and 2007. We study here the Wilcox Solar Observatory measurements of the photospheric magnetic field and the PFSS extrapolation of the coronal magnetic field. We show that the quadrupole moment of the photospheric magnetic field, which is important for the HCS asymmetry (bashful ballerina), mainly arises from the difference between northern and southern polar field strengths. According to the WSO data the minimum time quadrupole is mainly due to the difference between the highest northern and southern latitude bins. Related studies imply that the southward shift of the HCS is related to the delayed development of southern coronal holes. We also discuss the suggested connection of the HCS asymmetry to sunspot hemispheric asymmetry.
Orientation measurement based on magnetic inductance by the extended distributed multi-pole model.
Wu, Fang; Moon, Seung Ki; Son, Hungsun
2014-06-27
This paper presents a novel method to calculate magnetic inductance with a fast-computing magnetic field model referred to as the extended distributed multi-pole (eDMP) model. The concept of mutual inductance has been widely applied for position/orientation tracking systems and applications, yet it is still challenging due to the high demands in robust modeling and efficient computation in real-time applications. Recently, numerical methods have been utilized in design and analysis of magnetic fields, but this often requires heavy computation and its accuracy relies on geometric modeling and meshing that limit its usage. On the other hand, an analytical method provides simple and fast-computing solutions but is also flawed due to its difficulties in handling realistic and complex geometries such as complicated designs and boundary conditions, etc. In this paper, the extended distributed multi-pole model (eDMP) is developed to characterize a time-varying magnetic field based on an existing DMP model analyzing static magnetic fields. The method has been further exploited to compute the mutual inductance between coils at arbitrary locations and orientations. Simulation and experimental results of various configurations of the coils are presented. Comparison with the previously published data shows not only good performance in accuracy, but also effectiveness in computation.
NASA Astrophysics Data System (ADS)
Szmytkowski, Radosław; Łukasik, Grzegorz
2016-09-01
We present tabulated data for several families of static electric and magnetic multipole susceptibilities for hydrogenic atoms with nuclear charge numbers from the range 1 ⩽ Z ⩽ 137. Atomic nuclei are assumed to be point-like and spinless. The susceptibilities considered include the multipole electric polarizabilities α E L → E L and magnetizabilities (magnetic susceptibilities) χ M L → M L with 1 ⩽ L ⩽ 4 (i.e., the dipole, quadrupole, octupole and hexadecapole ones), the electric-to-magnetic cross-susceptibilities α E L → M(L - 1) with 2 ⩽ L ⩽ 5 and α E L → M(L + 1) with 1 ⩽ L ⩽ 4, the magnetic-to-electric cross-susceptibilities χ M L → E(L - 1) with 2 ⩽ L ⩽ 5 and χ M L → E(L + 1) with 1 ⩽ L ⩽ 4 (it holds that χ M L → E(L ∓ 1) =α E(L ∓ 1) → M L), and the electric-to-toroidal-magnetic cross-susceptibilities α E L → T L with 1 ⩽ L ⩽ 4. Numerical values are computed from general exact analytical formulas, derived by us elsewhere within the framework of the Dirac relativistic quantum mechanics, and involving generalized hypergeometric functions 3F2 of the unit argument.
Orientation Measurement Based on Magnetic Inductance by the Extended Distributed Multi-Pole Model
Wu, Fang; Moon, Seung Ki; Son, Hungsun
2014-01-01
This paper presents a novel method to calculate magnetic inductance with a fast-computing magnetic field model referred to as the extended distributed multi-pole (eDMP) model. The concept of mutual inductance has been widely applied for position/orientation tracking systems and applications, yet it is still challenging due to the high demands in robust modeling and efficient computation in real-time applications. Recently, numerical methods have been utilized in design and analysis of magnetic fields, but this often requires heavy computation and its accuracy relies on geometric modeling and meshing that limit its usage. On the other hand, an analytical method provides simple and fast-computing solutions but is also flawed due to its difficulties in handling realistic and complex geometries such as complicated designs and boundary conditions, etc. In this paper, the extended distributed multi-pole model (eDMP) is developed to characterize a time-varying magnetic field based on an existing DMP model analyzing static magnetic fields. The method has been further exploited to compute the mutual inductance between coils at arbitrary locations and orientations. Simulation and experimental results of various configurations of the coils are presented. Comparison with the previously published data shows not only good performance in accuracy, but also effectiveness in computation. PMID:24977389
A novel design of iron dominated superconducting multipole magnets with circular coils
Kashikhin, Vladimir; /Fermilab
2009-10-01
Linear accelerators based on superconducting magnet technology use a large number of relatively weak superconducting quadrupoles. In this case an iron dominated quadrupole is the most cost effective solution. The field quality in this magnet is defined by iron poles; the magnet air gap is minimal as are coil ampere-turns. Nevertheless, it has long racetrack type coils, which must be rigid and fixed by a mechanical structure to provide the needed mechanical stability. The novel concept of using circular superconducting coils in such a quadrupole type is described, with a discussion of quadrupole parameters, and results of 3D magnetic designs. Variants of short and long sectional quadrupoles and multipoles are presented.
Pollock, D.; Kim, K.; Gunst, R.; Schucany, W.
1993-05-01
Linear estimation of cold magnetic field quality based on warm multipole measurements is being considered as a quality control method for SSC production magnet acceptance. To investigate prediction uncertainties associated with such an approach, axial-scan (Z-scan) magnetic measurements from SSC Prototype Collider Dipole Magnets (CDM`s) have been studied. This paper presents a preliminary evaluation of the explanatory ability of warm measurement multipole variation on the prediction of cold magnet multipoles. Two linear estimation methods are presented: least-squares regression, which uses the assumption of fixed independent variable (xi) observations, and the measurement error model, which includes measurement error in the xi`s. The influence of warm multipole measurement errors on predicted cold magnet multipole averages is considered. MSD QA is studying warm/cold correlation to answer several magnet quality control questions. How well do warm measurements predict cold (2kA) multipoles? Does sampling error significantly influence estimates of the linear coefficients (slope, intercept and residual standard error)? Is estimation error for the predicted cold magnet average small compared to typical variation along the Z-Axis? What fraction of the multipole RMS tolerance is accounted for by individual magnet prediction uncertainty?
Poloidal OHMIC heating in a multipole
Holly, D.J.
1982-01-01
The feasibility of using poloidal currents to heat plasmas confined by a multipole field has been examined experimentaly in Tokapole II. The machine is operated as a toroidal octupole, with a time-varying toroidal magnetic field driving poloidal plasma currents I/sub plasma/ - 20 kA to give densities n/sub e/ - 10/sup 13/ cm/sup -3/ and temperatures T/sub e/ - 30 eV.
Plasma enclosed in a magnetic field produced by flexible surface magnets.
Schott, L
1978-04-01
A homogeneous steady state plasma with a usable volume of approximately 200 l and with an electron temperature of 1-2 eV and a plasma density of approximately 10(9)-10(10) cm(-3) is produced in a discharge chamber the outside of whose walls is covered with flexible magnetic strips. This magnet arrangement can be built at a fraction of the cost of a conventional system using rigid surface magnets. The magnetic multipole field leads to an increase of the plasma density by one to two orders of magnitude and it is also found to cause trapping of high energy electrons originating from the discharge region.
NASA Astrophysics Data System (ADS)
Lovesey, S. W.
2016-09-01
Zeeman spectra, dichroic signals, and neutron Bragg diffraction patterns generated by copper ions in magnetically ordered copper metaborate (Cu B2O4 ) are investigated within a minimal model of Cu atomic states. A theory platform, common to understanding optical spectra and neutron diffraction patterns, affords the immediate benefit of a unified description of the experimental probes in terms of electronic multipoles. Results for dichroic signals illustrate a nontrivial use of a general, quantum mechanical theory of photon absorption couched in terms of Dirac multipoles that are magnetic and polar. Anapoles (Dirac dipoles) are predicted to generate Bragg spots in magnetic neutron diffraction that are not indexed by the motif of conventional (axial) magnetic-dipole moments. The minimal model of Cu states is informed by magnetic symmetry, derived from an established commensurate antiferromagnetic order, with a sparse number of parameters that comply with available empirical evidence.
Radescu, E E; Vaman, G
2002-04-01
An exact calculation of the radiation intensity, angular momentum loss, and the recoil force for the most general type of source, characterized by electric, magnetic, and toroid multipole moments and radii of any multipolarity and an arbitrary time dependence, is presented. The results are expressed in terms of time derivatives of the multipole moments and mean radii of the corresponding distributions. Although quite cumbersome, the formulas found by us represent exact results in the correct multipole analysis of configurations of charges and currents that contain toroidal sources. So the longstanding problem in classical electrodynamics of relating the radiation properties of a system to quantities completely describing its internal electromagnetic structure is thereby exactly solved. By particularizations to the first multipole contributions, corrections to the familiar formulas from books are found, mostly on account of the toroid moments and their interference with the usual electric and magnetic ones.
Plasma acceleration above martian magnetic anomalies.
Lundin, R; Winningham, D; Barabash, S; Frahm, R; Holmström, M; Sauvaud, J-A; Fedorov, A; Asamura, K; Coates, A J; Soobiah, Y; Hsieh, K C; Grande, M; Koskinen, H; Kallio, E; Kozyra, J; Woch, J; Fraenz, M; Brain, D; Luhmann, J; McKenna-Lawler, S; Orsini, R S; Brandt, P; Wurz, P
2006-02-17
Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration processes on the nightside of Mars. We observed accelerated electrons and ions in the deep nightside high-altitude region of Mars that map geographically to interface/cleft regions associated with martian crustal magnetization regions. By integrating electron and ion acceleration energy down to the upper atmosphere, we saw energy fluxes in the range of 1 to 50 milliwatts per square meter per second. These conditions are similar to those producing bright discrete auroras above Earth. Discrete auroras at Mars are therefore expected to be associated with plasma acceleration in diverging magnetic flux tubes above crustal magnetization regions, the auroras being distributed geographically in a complex pattern by the many multipole magnetic field lines extending into space. PMID:16484488
Plasma acceleration above martian magnetic anomalies.
Lundin, R; Winningham, D; Barabash, S; Frahm, R; Holmström, M; Sauvaud, J-A; Fedorov, A; Asamura, K; Coates, A J; Soobiah, Y; Hsieh, K C; Grande, M; Koskinen, H; Kallio, E; Kozyra, J; Woch, J; Fraenz, M; Brain, D; Luhmann, J; McKenna-Lawler, S; Orsini, R S; Brandt, P; Wurz, P
2006-02-17
Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration processes on the nightside of Mars. We observed accelerated electrons and ions in the deep nightside high-altitude region of Mars that map geographically to interface/cleft regions associated with martian crustal magnetization regions. By integrating electron and ion acceleration energy down to the upper atmosphere, we saw energy fluxes in the range of 1 to 50 milliwatts per square meter per second. These conditions are similar to those producing bright discrete auroras above Earth. Discrete auroras at Mars are therefore expected to be associated with plasma acceleration in diverging magnetic flux tubes above crustal magnetization regions, the auroras being distributed geographically in a complex pattern by the many multipole magnetic field lines extending into space.
High-order magnetic multipoles as a source of gross asymmetry in the distant Jovian magnetosphere
NASA Technical Reports Server (NTRS)
Dessler, A. J.; Hill, T. W.
1975-01-01
The longitudinal asymmetry of the surface magnetic-field strength at Jupiter causes a longitudinal asymmetry in the equatorial plasma mass density within the Jovian magnetosphere. The rotation of these density variations with the planet causes a diurnal variation of the radial distance on the night side at which the centrifugal stress of the magnetospheric plasma exceeds the local magnetic-field tension. This is approximately the distance at which the magnetic field opens to interplanetary space; we estimate that the opening distance can vary by as much as 14% as a result of the observed surface field asymmetry. Such a diurnal variation of the boundary of the particle trapping region can account for the observed ten-hour modulation of relativistic electrons emitted from Jupiter into interplanetary space.
Energy levels and multipole transition properties of C4+ ion in Debye plasmas
NASA Astrophysics Data System (ADS)
Xie, L. Y.; Wang, J. G.; Janev, R. K.; Qu, Y. Z.; Dong, C. Z.
2012-05-01
Plasma screening effects on the energy structure and radiative transition properties of helium-like C4+ ions embedded in Debye plasmas are investigated by using the multi-configuration Dirac-Hartree-Fock method incorporating the Debye-Hückel potential for both the electron-nucleus and electron-electron interactions. Seventeen fine-structure energy levels of the low-lying 1 s 2, 1 s2 l( l = s,p) and 1 s3 l'( l' = s,p,d) configurations, as well as the electric-dipole ( E1), magnetic-dipole ( M1) and magnetic-quadrupole ( M2) transition probabilities and oscillator strengths between these levels have been calculated over a wide range of screening parameters. It is found that the plasma screening leads to a decrease of excitation energies and alters the energy levels remarkably. For Δn ≠ 0 transitions, the spontaneous decay spectra are red-shifted and their oscillator strengths and transition probabilities decrease with increasing the interaction screening, while those for the Δn = 0 transitions exhibit opposite patterns. The influence of electron-nucleus and electron-electron screened interactions on the changes of energy levels and transition properties are analyzed. Comparison is made of present results with other data available in the literature for this ion.
Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim
2016-06-01
We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model. PMID:27370475
NASA Astrophysics Data System (ADS)
Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim
2016-06-01
We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model.
Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim
2016-06-01
We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model.
Nonlinear plasma wave in magnetized plasmas
NASA Astrophysics Data System (ADS)
Bulanov, Sergei V.; Zh. Esirkepov, Timur; Kando, Masaki; Koga, James K.; Hosokai, Tomonao; Zhidkov, Alexei G.; Kodama, Ryosuke
2013-08-01
Nonlinear axisymmetric cylindrical plasma oscillations in magnetized collisionless plasmas are a model for the electron fluid collapse on the axis behind an ultrashort relativisically intense laser pulse exciting a plasma wake wave. We present an analytical description of the strongly nonlinear oscillations showing that the magnetic field prevents closing of the cavity formed behind the laser pulse. This effect is demonstrated with 3D PIC simulations of the laser-plasma interaction. An analysis of the betatron oscillations of fast electrons in the presence of the magnetic field reveals a characteristic "Four-Ray Star" pattern.
NASA Astrophysics Data System (ADS)
de Melo e Souza, R.; Cougo-Pinto, M. V.; Farina, C.; Moriconi, M.
2009-01-01
We show how to obtain the first multipole contributions to the electromagnetic radiation emitted by an arbitrary localized source directly from the Jefimenko equation for the magnetic field and the Panofsky-Phillips equation for the electric field. This procedure avoids the unnecessary calculation of the electromagnetic potentials.
Performance of a magnetic multipole line-cusp argon ion thruster
NASA Technical Reports Server (NTRS)
Sovey, J. S.
1981-01-01
A 17 cm diameter line cusp ion thruster was evaluated with inert gases which are candidate propellants for on orbit and orbit transfer propulsion functions for Large Space Systems. A semiempirical relationship was generated to predict thruster beam current in terms of plasma parameters which would allow initial thruster optimization without ion extraction and the associated large vacuum facilities. The sensitivity of performance to changes in discharge electrode configurations and magnetic circuit was evaluated and is presented. After final optimization a propellant utilization efficiency of 0.9 at a discharge chamber power expenditure of about 260 w per beam ampere was obtained. These performance parameters are the highest yet achieved with argon propellant.
Magnetic insulation for plasma propulsion
NASA Technical Reports Server (NTRS)
Gonzalez, Dora E.
1990-01-01
The design parameters of effective magnetic insulation for plasma engines are discussed. An experimental model used to demonstrate the process of plasma acceleration and magnetic insulation is considered which consists of a copper strap that is wound around a glass tube and connected to a capacitor. In order to adequately model the magnetic insulation mechanisms, a computer algorithm is developed. Plasma engines, with their efficient utilization of the propellant mass, are expected to provide the next-generation advanced propulsion systems.
NASA Astrophysics Data System (ADS)
Zou, Gui-Qing; Lei, Guang-Jiu; Jiang, Shao-Feng; Cao, Jian-Yong; Yu, Li-Ming; Lu, Da-Lun; Yang, Li-Mei; Liu, He; Jiang, Tao; Zhang, Xian-Ming
2009-08-01
A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutral beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV 20 A hydrogen ion beam for less than 100 ms on a test bed, and a 35 keV 13 A ion beam for 300 ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0 ± 0.2 cm at the position of 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al. The maximum of optimum perveance reached 2.2 × 10-6 A/V1.5 for 38 keV beam energy. An ion beam with above 60% H+ species fraction can be achieved, which was measured by Hα light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6 MW was successfully injected into the plasma of the HL-2A Tokomak in 2008.
Multipole expansions and intense fields
NASA Astrophysics Data System (ADS)
Reiss, Howard R.
1984-02-01
In the context of two-body bound-state systems subjected to a plane-wave electromagnetic field, it is shown that high field intensity introduces a distinction between long-wavelength approximation and electric dipole approximation. This distinction is gauge dependent, since it is absent in Coulomb gauge, whereas in "completed" gauges of Göppert-Mayer type the presence of high field intensity makes electric quadrupole and magnetic dipole terms of importance equal to electric dipole at long wavelengths. Another consequence of high field intensity is that multipole expansions lose their utility in view of the equivalent importance of a number of low-order multipole terms and the appearance of large-magnitude terms which defy multipole categorization. This loss of the multipole expansion is gauge independent. Also gauge independent is another related consequence of high field intensity, which is the intimate coupling of center-of-mass and relative coordinate motions in a two-body system.
Measurements of passive correction of magnetization higher multipoles in one meter long dipoles
Green, M.A.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Gilbert, W.S.; Green, M.I.; Scanlan, R.M.; Taylor, C.E.
1990-09-01
The use of passive superconductor to correct the magnetization sextupole and decapole in SSC dipoles appears to be promising. This paper presents the results of a series of experiments of passive superconductor correctors in one meter long dipole magnets. Reduction of the magnetization sextupole by a factor of five to ten has been achieved using the passive superconductor correctors. The magnetization decapole was also reduced. The passive superconductor correctors reduced the sextupole temperature sensitivity by an order of magnitude. Flux creep decay was partially compensated for by the correctors. 13 refs., 7 figs.
Studies of plasma confinement in linear and RACETRACK mirror configurations
Kuthi, A.; Wong, A.Y.
1986-06-30
This report discusses research on the following magnetic mirror configurations: Racetrack; ECRH generated plasmas; RF generated plasmas; potential structures; surface multipole fields, and lamex; hot electron physics; axial loss processes; and RF induced effects.
NASA Astrophysics Data System (ADS)
Styrnoll, T.; Harhausen, J.; Lapke, M.; Storch, R.; Brinkmann, R. P.; Foest, R.; Ohl, A.; Awakowicz, P.
2013-08-01
The application of a multipole resonance probe (MRP) for diagnostic and monitoring purposes in a plasma ion-assisted deposition (PIAD) process is reported. Recently, the MRP was proposed as an economical and industry compatible plasma diagnostic device (Lapke et al 2011 Plasma Sources Sci. Technol. 20 042001). The major advantages of the MRP are its robustness against dielectric coating and its high sensitivity to measure the electron density. The PIAD process investigated is driven by the advanced plasma source (APS), which generates an ion beam in the deposition chamber for the production of high performance optical coatings. With a background neutral pressure of p0 ˜ 20 mPa the plasma expands from the source region into the recipient, leading to an inhomogeneous spatial distribution. Electron density and electron temperature vary over the distance from substrate (ne ˜ 109 cm-3 and Te,eff ˜ 2 eV) to the APS (ne ≳ 1012 cm-3 and Te,eff ˜ 20 eV) (Harhausen et al 2012 Plasma Sources Sci. Technol. 21 035012). This huge variation of the plasma parameters represents a big challenge for plasma diagnostics to operate precisely for all plasma conditions. The results obtained by the MRP are compared to those from a Langmuir probe chosen as reference diagnostics. It is demonstrated that the MRP is suited for the characterization of the PIAD plasma as well as for electron density monitoring. The latter aspect offers the possibility to develop new control schemes for complex industrial plasma environments.
Strongly magnetized classical plasma models
NASA Technical Reports Server (NTRS)
Montgomery, D.; Peyraud, J.; Dewitt, C.
1974-01-01
Discrete particle processes in the presence of a strong external magnetic field were investigated. These processes include equations of state and other equilibrium thermodynamic relations, thermal relaxation phenomena, transport properties, and microscopic statistical fluctuations in such quantities as the electric field and the charge density. Results from the equilibrium statistical mechanics of two-dimensional plasmas are discussed, along with nonequilibrium statistical mechanics of the electrostatic guiding-center plasma (a two-dimensional plasma model).
Condensation modes in magnetized plasmas
NASA Technical Reports Server (NTRS)
An, Chang-Hyuk
1986-01-01
Condensation modes in magnetized cylindrical plasmas, with concentration on how magnetic field affects the stability were studied. It is found that the effects of magnetic field (shear, twist, and strength) on the condensation modes are different depending on the wave vector. For modes whose wave vector is not perpendicular to magnetic field lines the plasma motion is mainly along the field lines; the effects of magnetic field on the modes are negligible except on the heat flow parallel to the field line. For a mode which is localized near a surface where the wave vector is perpendicular to the field line, the plasma moves perpendicular to the line carrying the field line into the condensed region; magnetic field affects the mode by building up magnetic pressure in the condensed region. The stability of condensation modes strongly depends on how density and temperature vary with field twist. The stable nature of global quiescent prominence magnetic configurations implies that prominences form for low field twist for which ideal MHD modes are stable; plasma temperature should increase with field twist for stable prominence formation.
M. Spata, G.A. Krafft
2011-09-01
An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.
Magnetic reconnection in space plasmas
Gosling, J.; Feldman, W.; Walthour, D.
1996-04-01
This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Magnetic reconnection produces fundamental changes in the magnetic field topology of plasmas and leads ultimately to substantial plasma heating and acceleration. The transfer of stored magnetic field energy to the plasma occurs primarily at thin conversion layers that extend outward from the reconnection site. We performed a comparative study of the structure and nature of these conversion layers as observed during reconnection at Earth`s magnetopause and in the geomagnetic tail. Our research utilized plasma and magnetic field data from the Earth-orbiting ISEE satellites during crossings of the conversion layers at the magnetopause and in the geomagnetic tail, as well as data obtained during a long-duration balloon flight in Antarctica and simultaneously from satellites in geosynchronous orbit. We have found that the reconnection layer at the magnetopause usually does not contain a slow mode shock, contrary to earlier theoretical expectations. Through a coordinated analysis of data obtained from balloon altitudes and at geosynchronous orbit, we obtained evidence that reconnection can occur simultaneously in both hemispheres at the magnetopause above the polar caps. The final year of our study was oriented primarily towards the question of determining the magnetic topology of disturbances in the solar wind associated with coronal mass ejections (CMEs) and understanding how that topology is affected by magnetic reconnection occurring near the Sun.
Magnetic Flux Compression in Plasmas
NASA Astrophysics Data System (ADS)
Velikovich, A. L.
2012-10-01
Magnetic flux compression (MFC) as a method for producing ultra-high pulsed magnetic fields had been originated in the 1950s by Sakharov et al. at Arzamas in the USSR (now VNIIEF, Russia) and by Fowler et al. at Los Alamos in the US. The highest magnetic field produced by explosively driven MFC generator, 28 MG, was reported by Boyko et al. of VNIIEF. The idea of using MFC to increase the magnetic field in a magnetically confined plasma to 3-10 MG, relaxing the strict requirements on the plasma density and Lawson time, gave rise to the research area known as MTF in the US and MAGO in Russia. To make a difference in ICF, a magnetic field of ˜100 MG should be generated via MFC by a plasma liner as a part of the capsule compression scenario on a laser or pulsed power facility. This approach was first suggested in mid-1980s by Liberman and Velikovich in the USSR and Felber in the US. It has not been obvious from the start that it could work at all, given that so many mechanisms exist for anomalously fast penetration of magnetic field through plasma. And yet, many experiments stimulated by this proposal since 1986, mostly using pulsed-power drivers, demonstrated reasonably good flux compression up to ˜42 MG, although diagnostics of magnetic fields of such magnitude in HED plasmas is still problematic. The new interest of MFC in plasmas emerged with the advancement of new drivers, diagnostic methods and simulation tools. Experiments on MFC in a deuterium plasma filling a cylindrical plastic liner imploded by OMEGA laser beam led by Knauer, Betti et al. at LLE produced peak fields of 36 MG. The novel MagLIF approach to low-cost, high-efficiency ICF pursued by Herrmann, Slutz, Vesey et al. at Sandia involves pulsed-power-driven MFC to a peak field of ˜130 MG in a DT plasma. A review of the progress, current status and future prospects of MFC in plasmas is presented.
NASA Astrophysics Data System (ADS)
Torres-Díaz, Isaac; Rinaldi, Carlos
The flow of a ferrofluid in a stationary cylindrical container driven by a rotating magnetic field has received considerable attention since the inception of the field of ferrohydrodynamics. Much controversy has resulted regarding the existence, or lack thereof, of bulk flow under conditions of a rotating uniform magnetic field, which can be generated for example, using a two-pole stator winding. The original observations of flow at the interface showed counter-rotation of field and fluid, whereas recent observations of bulk flow using the ultrasound technique have shown co-rotation of field and fluid. Various theories have been advanced over the years to explain the observed phenomena, including the spin diffusion theory of Shliomis and the hypothesis that it is field non-uniformity, generated by non-ideal stator winding distributions, that actually drives the flow, as first proposed by Glazov. We have revisited this problem from an analytical perspective by solving the ferrohydrodynamic and magnetoquasistatic equations self-consistently for the case of ferrofluid in a cylindrical container, with and without an internal co-axial cylinder, and driven by the field generated by a multipole stator winding distribution. In such a winding increasing the number of poles results in increasingly non-uniform fields. It is shown that regardless of the number of poles in the stator winding the ferrohydrodynamic equations do not predict any flow in either geometry as long as the spin viscosity parameter is assumed to be zero. Velocity profiles are obtained for both geometries and arbitrary number of poles for the case of non-zero spin viscosity. It is shown that only for the case of a two-pole stator winding and ferrofluid constrained to the annular space between an inner and outer cylinder do the ferrohydrodynamic equations predict co-rotation of fluid and field close to the outer cylinder and counter-rotation of fluid and field close to the inner cylinder, in qualitative
Smooth Teeth: Why Multipoles Are Perfect Gears
NASA Astrophysics Data System (ADS)
Schönke, Johannes
2015-12-01
A type of gear is proposed based on the interaction of individual multipoles. The underlying principle relies on previously unknown continuous degenerate ground states for pairs of interacting multipoles which are free to rotate around specific axes. These special rotation axes, in turn, form a one-parameter family of possible configurations. This allows for the construction of magnetic bevel gears with any desired inclination angle between the in- and output axes. Further, the design of gear systems with more than two multipoles is possible and facilitates tailored applications. Ultimately, an analogy between multipoles and mechanical gears is revealed. In contrast to the mechanical case, the multipole "teeth" mesh smoothly. As an illustrative application, the example of a quadrupole-dipole interaction is then used to construct a 1 ∶2 gear ratio.
Andresen, G. B.; Bertsche, W.; Butler, E.; Charlton, M.; Humphries, A. J.; Joergensen, L. V.; Kerrigan, S. J.; Madsen, N.; Werf, D. P. van der; Bray, C. C.; Chapman, S.; Fajans, J.; Keller, J.; Povilus, A.; Wurtele, J. S.; Cesar, C. L.; Lambo, R.; Fujiwara, M. C.; Gill, D. R.; Kurchaninov, L.
2009-10-15
In many antihydrogen trapping schemes, antiprotons held in a short-well Penning-Malmberg trap are released into a longer well. This process necessarily causes the bounce-averaged rotation frequency {omega}{sub r} of the antiprotons around the trap axis to pass through zero. In the presence of a transverse magnetic multipole, experiments and simulations show that many antiprotons (over 30% in some cases) can be lost to a hitherto unidentified bounce-resonant process when {omega}{sub r} is close to zero.
Kuthi, A.; Wong, A.Y.
1986-06-30
This report discusses research on the following magnetic mirror configurations: Racetrack; ECRH generated plasmas; RF generated plasmas; potential structures; surface multipole fields, and lamex; hot electron physics; axial loss processes; and RF induced effects.
Rotation of a magnetized plasma
Annaratone, B. M.; Escarguel, A.; Lefevre, T.; Rebont, C.; Claire, N.; Doveil, F.
2011-03-15
The plasma rotation in the axial magnetic field of the linear machine Mistral [A. Escarguel, Eur. Phys. J. D 56, 209 (2010)] is well described by the assumption that the electrons injected from the source exit radially from the central column and are subject to the Lorentz force. Electrons and ions rotate together by ambipolarity. The solution of the momentum equations foresees correctly the observed radial dependence of the ionic radial velocity measured by laser induced fluorescence. The resolution of these equations is also in good agreement with the measured dependence of the rotation frequency on the applied magnetic field and on the background pressure.
15 cm multipole gas ion thruster
NASA Technical Reports Server (NTRS)
Isaacson, G. C.; Kaufman, H. R.
1976-01-01
A 15-cm multipole thruster was operated on argon and xenon. The multipole approach used has been shown capable of low discharge losses and flat ion beam profiles with a minimum of redesign. This approach employs low magnetic field strengths and flat or cylindrical sheet-metal parts, hence is suited to rapid optimization and scaling. Only refractory metal cathodes were used in this investigation.
Fully magnetized plasma flow in a magnetic nozzle
NASA Astrophysics Data System (ADS)
Merino, Mario; Ahedo, Eduardo
2016-02-01
A model of the expansion of a plasma in a magnetic nozzle in the full magnetization limit is presented. The fully magnetized and the unmagnetized-ions limits are compared, recovering the whole range of variability in plasma properties, thrust, and plume efficiency, and revealing the differences in the physics of the two cases. The fully magnetized model is the natural limit of the general, 2D, two-fluid model of Ahedo and Merino [Phys. Plasmas 17, 073501 (2010)], and it is proposed as an analytical, conservative estimator of the propulsive figures of merit of partially magnetized plasma expansions in the near region of the magnetic nozzle.
Two-Dimensional Turbulence in Magnetized Plasmas
ERIC Educational Resources Information Center
Kendl, A.
2008-01-01
In an inhomogeneous magnetized plasma the transport of energy and particles perpendicular to the magnetic field is in general mainly caused by quasi two-dimensional turbulent fluid mixing. The physics of turbulence and structure formation is of ubiquitous importance to every magnetically confined laboratory plasma for experimental or industrial…
Magnetic Detachment and Plume Control in Escaping Magnetized Plasma
P. F. Schmit and N. J. Fisch
2008-11-05
The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment.
Plasma separation from magnetic field lines in a magnetic nozzle
NASA Technical Reports Server (NTRS)
Kaufman, D. A.; Goodwin, D. G.; Sercel, J. C.
1993-01-01
This paper discusses conditions for separation of a plasma from the magnetic field of a magnetic nozzle. The analysis assumes a collisionless, quasineutral plasma, and therefore the results represent a lower bound on the amount of detachment possible for a given set of plasma conditions. We show that collisionless separation can occur because finite electron mass inhibits the flow of azimuthal currents in the nozzle. Separation conditions are governed by a parameter G which depends on plasma and nozzle conditions. Several methods of improving plasma detachment are presented, including moving the plasma generation zone downstream from the region of strongest magnetic field and using dual magnets to focus the plasma beam. Plasma detachment can be enhanced by manipulation of the nozzle configuration.
Parametric instabilities in weakly magnetized plasma
Weatherall, J.C.; Goldman, M.V.; Nicholson, D.R.
1981-05-15
Parametric instabilities in a weakly magnetized plasma are discussed. The results are applied to waves excited by electron streams which travel outward from the Sun along solar-wind magnetic field lines, as in a type III solar radio burst.
Macroscopic magnetic islands and plasma energy transport
Cima, G; Porcelli, F; Rossi, E; Wootton, A J
1998-12-03
A model is presented, based on the combined effects of m=n=l magnetic island dynamics, localized heat sources, large heat diffusivity along magnetic field lines and plasma rotation, which may explain the multipeaked temperature profiles and transport barriers observed in tokamak plasmas heated by electron cyclotron resonant waves.
Magnetic field structure evolution in rotating magnetic field plasmas
Petrov, Yuri; Yang Xiaokang; Huang, T.-S.
2008-07-15
A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.
Magnetized relativistic electron-ion plasma expansion
NASA Astrophysics Data System (ADS)
Benkhelifa, El-Amine; Djebli, Mourad
2016-03-01
The dynamics of relativistic laser-produced plasma expansion across a transverse magnetic field is investigated. Based on a one dimensional two-fluid model that includes pressure, enthalpy, and rest mass energy, the expansion is studied in the limit of λD (Debye length) ≤RL (Larmor radius) for magnetized electrons and ions. Numerical investigation conducted for a quasi-neutral plasma showed that the σ parameter describing the initial plasma magnetization, and the plasma β parameter, which is the ratio of kinetic to magnetic pressure are the key parameters governing the expansion dynamics. For σ ≪ 1, ion's front shows oscillations associated to the break-down of quasi-neutrality. This is due to the strong constraining effect and confinement of the magnetic field, which acts as a retarding medium slowing the plasma expansion.
Magnetized Plasma Experiments Using Thermionic- Thermoelectronic Plasma Emitter
NASA Astrophysics Data System (ADS)
Kawamori, Eiichirou; Cheng, C. Z.; Fujikawa, Nobuko; Lee, Jyun-Yi; Peng, Albert
2008-11-01
We are developing a magnetic mirror device, which is the first magnetized plasma device in Taiwan, to explore basic plasma sciences relevant to fusion, space and astrophysical plasmas. Our research subjects include electromagnetically induced transparency (EIT), Alfven wave physics, and plasma turbulence. A large diameter (> 200 mm) plasma emitter1, which utilizes thermionic- thermoelectronic emission from a mixture of LaB6 (Lanthanum-hexaboride) and beta-eucryptite (lithium type aluminosylicate) powders, is employed as a plasma source because of its production ability of fully ionized plasma and controllability of plasma emission rate. The plasma emitter has been installed recently and investigation of its characteristics will be started. The employment of beta-eucryptite in plasma emitter is the first experimental test because such investigation of beta-eucryptite has previously been used only for Li+-ion source2. Our plan for magnetized plasma experiments and results of the plasma emitter investigation will be presented. 1. K. Saeki, S. Iizuka, N. Sato, and Y. Hatta, Appl. Phys. Lett., 37, 1980, pp. 37-38. 2. M. Ueda, R. R. Silva, R. M. Oliveira, H. Iguchi, J. Fujita and K. Kadota, J. Phys. D: Appl. Phys. 30 1997, pp. 2711--2716.
Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization
Doughty, Frank C.; Spencer, John E.
2000-12-19
In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.
Magnetic field of a combined plasma trap
NASA Astrophysics Data System (ADS)
Kotenko, V. G.; Moiseenko, V. E.; Ågren, O.
2012-06-01
This paper presents numerical simulations performed on the structure of a magnetic field created by the magnetic system of a combined plasma trap. The magnetic system includes the stellarator-type magnetic system and one of the mirror-type. For the stellarator type magnetic system the numeric model contains a magnetic system of an l=2 torsatron with the coils of an additional toroidal magnetic field. The mirror-type magnetic system element is considered as being single current-carrying turn enveloping the region of existence of closed magnetic surfaces of the torsatron. The calculations indicate the existence of a vast area of the values of the additional magnetic field magnitude and magnetic field of the single turn where, in principle, the implementation of the closed magnetic surface configuration is quite feasible.
Magnetic Field Effects on Plasma Plumes
NASA Technical Reports Server (NTRS)
Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.
2012-01-01
Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results
Directed Plasma Flow across Magnetic Field
NASA Astrophysics Data System (ADS)
Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.
2008-04-01
The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.
Magnetic circuit for hall effect plasma accelerator
NASA Technical Reports Server (NTRS)
Manzella, David H. (Inventor); Jacobson, David T. (Inventor); Jankovsky, Robert S. (Inventor); Hofer, Richard (Inventor); Peterson, Peter (Inventor)
2009-01-01
A Hall effect plasma accelerator includes inner and outer electromagnets, circumferentially surrounding the inner electromagnet along a thruster centerline axis and separated therefrom, inner and outer magnetic conductors, in physical connection with their respective inner and outer electromagnets, with the inner magnetic conductor having a mostly circular shape and the outer magnetic conductor having a mostly annular shape, a discharge chamber, located between the inner and outer magnetic conductors, a magnetically conducting back plate, in magnetic contact with the inner and outer magnetic conductors, and a combined anode electrode/gaseous propellant distributor, located at a bottom portion of the discharge chamber. The inner and outer electromagnets, the inner and outer magnetic conductors and the magnetically conducting back plate form a magnetic circuit that produces a magnetic field that is largely axial and radially symmetric with respect to the thruster centerline.
Electrostatic decay in a weakly magnetized plasma.
Layden, A; Cairns, Iver H; Li, B; Robinson, P A
2013-05-01
The kinematics of the electrostatic (ES) decay of a Langmuir wave into a Langmuir wave and an ion sound wave are generalized to a weakly magnetized plasma. Unlike the unmagnetized case, ES decay in a magnetized plasma is always kinematically permitted and can produce daughter Langmuir waves with very small wave numbers, which we demonstrate by quasilinear simulations. The simulations further show that ES decay in magnetized plasmas is consistent with STEREO spacecraft observations of transversely polarized Langmuir waves in the solar wind. PMID:23683206
Magnetic field structure evolution in RMF plasmas
NASA Astrophysics Data System (ADS)
Petrov, Yuri; Yang, Xiaokang; Huang, Tian-Sen
2007-11-01
A study of magnetic field structure evolution during 40-ms plasma discharge had been performed in 80 cm long / 40 cm OD cylindrical chamber. Plasma current Ip˜2--3 kA is produced by applied 500 kHz rotating magnetic field. In experiments, the 2D profile of plasma current is changed by feeding a 10-ms pulse current to additional magnetic coil located at the midplane. Using newly developed magnetic field pick-up coils system, we scanned the magnetic field in cross-section of plasma. Two experimental regimes were studied: without external toroidal field (TF), and with TF produced by applied axial current. When a relatively small current (<0.5 kA) is applied to the midplane coil, in both cases the total plasma current measured with Rogowski coil experiences a jump (up to 100%), but the profile of current remains almost unchanged. When a larger current (1--2 kA) is applied to the midplane coil, the total plasma current drops; the magnetic structure changes differently in two regimes. In regime without TF, the magnetic field of plasma current is reversed at Rplasma current first extends along Z, and then two rings of current are formed at the edge. At smaller radii, the current layer is still approximately uniform along Z. We also show how the magnetic field evolves during initial 1--3 ms transitional period of plasma formation.
Forced Magnetic Reconnection In A Tokamak Plasma
NASA Astrophysics Data System (ADS)
Callen, J. D.; Hegna, C. C.
2015-11-01
The theory of forced magnetic field reconnection induced by an externally imposed resonant magnetic perturbation usually uses a sheared slab or cylindrical magnetic field model and often focuses on the potential time-asymptotic induced magnetic island state. However, tokamak plasmas have significant magnetic geometry and dynamical plasma toroidal rotation screening effects. Also, finite ion Larmor radius (FLR) and banana width (FBW) effects can damp and thus limit the width of a nascent magnetic island. A theory that is more applicable for tokamak plasmas is being developed. This new model of the dynamics of forced magnetic reconnection considers a single helicity magnetic perturbation in the tokamak magnetic field geometry, uses a kinetically-derived collisional parallel electron flow response, and employs a comprehensive dynamical equation for the plasma toroidal rotation frequency. It is being used to explore the dynamics of bifurcation into a magnetically reconnected state in the thin singular layer around the rational surface, evolution into a generalized Rutherford regime where the island width exceeds the singular layer width, and assess the island width limiting effects of FLR and FBW polarization currents. Support by DoE grants DE-FG02-86ER53218, DE-FG02-92ER54139.
NASA Astrophysics Data System (ADS)
Jiang, Xikai; Li, Jiyuan; Zhao, Xujun; Qin, Jian; Karpeev, Dmitry; Hernandez-Ortiz, Juan; de Pablo, Juan J.; Heinonen, Olle
2016-08-01
Large classes of materials systems in physics and engineering are governed by magnetic and electrostatic interactions. Continuum or mesoscale descriptions of such systems can be cast in terms of integral equations, whose direct computational evaluation requires O(N2) operations, where N is the number of unknowns. Such a scaling, which arises from the many-body nature of the relevant Green's function, has precluded wide-spread adoption of integral methods for solution of large-scale scientific and engineering problems. In this work, a parallel computational approach is presented that relies on using scalable open source libraries and utilizes a kernel-independent Fast Multipole Method (FMM) to evaluate the integrals in O(N) operations, with O(N) memory cost, thereby substantially improving the scalability and efficiency of computational integral methods. We demonstrate the accuracy, efficiency, and scalability of our approach in the context of two examples. In the first, we solve a boundary value problem for a ferroelectric/ferromagnetic volume in free space. In the second, we solve an electrostatic problem involving polarizable dielectric bodies in an unbounded dielectric medium. The results from these test cases show that our proposed parallel approach, which is built on a kernel-independent FMM, can enable highly efficient and accurate simulations and allow for considerable flexibility in a broad range of applications.
Microwave Reflectometry for Magnetically Confined Plasmas
Mazzucato, E.
1998-02-01
This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.
Magnetic Lens For Plasma Engine
NASA Technical Reports Server (NTRS)
Sercel, Joel C.
1992-01-01
Low-field electromagnet coils placed downstream of plasma engine, polarized oppositely to higher-field but smaller radius coil in nozzle of engine, reduces divergence of plasma jet, thereby increasing efficiency of engine. Concept tested by computer simulation based on simplified mathematical model of plasma, engine, and coils.
Parametric analysis of a magnetized cylindrical plasma
Ahedo, Eduardo
2009-11-15
The relevant macroscopic model, the spatial structure, and the parametric regimes of a low-pressure plasma confined by a cylinder and an axial magnetic field is discussed for the small-Debye length limit, making use of asymptotic techniques. The plasma response is fully characterized by three-dimensionless parameters, related to the electron gyroradius, and the electron and ion collision mean-free-paths. There are the unmagnetized regime, the main magnetized regime, and, for a low electron-collisionality plasma, an intermediate-magnetization regime. In the magnetized regimes, electron azimuthal inertia is shown to be a dominant phenomenon in part of the quasineutral plasma region and to set up before ion radial inertia. In the main magnetized regime, the plasma structure consists of a bulk diffusive region, a thin layer governed by electron inertia, a thinner sublayer controlled by ion inertia, and the non-neutral Debye sheath. The solution of the main inertial layer yields that the electron azimuthal energy near the wall is larger than the electron thermal energy, making electron resistivity effects non-negligible. The electron Boltzmann relation is satisfied only in the very vicinity of the Debye sheath edge. Ion collisionality effects are irrelevant in the magnetized regime. Simple scaling laws for plasma production and particle and energy fluxes to the wall are derived.
Magnetic Nozzle and Plasma Detachment Experiment
NASA Technical Reports Server (NTRS)
Chavers, Gregory; Dobson, Chris; Jones, Jonathan; Martin, Adam; Bengtson, Roger D.; Briezman, Boris; Arefiev, Alexey; Cassibry, Jason; Shuttpelz, Branwen; Deline, Christopher
2006-01-01
High power plasma propulsion can move large payloads for orbit transfer (such as the ISS), lunar missions, and beyond with large savings in fuel consumption owing to the high specific impulse. At high power, lifetime of the thruster becomes an issue. Electrodeless devices with magnetically guided plasma offer the advantage of long life since magnetic fields confine the plasma radially and keep it from impacting the material surfaces. For decades, concerns have been raised about the plasma remaining attached to the magnetic field and returning to the vehicle along the closed magnetic field lines. Recent analysis suggests that this may not be an issue of the magnetic field is properly shaped in the nozzle region and the plasma has sufficient energy density to stretch the magnetic field downstream. An experiment was performed to test the theory regarding the Magneto-hydrodynamic (MHD) detachment scenario. Data from this experiment will be presented. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) being developed by the Ad Astra Rocket Company uses a magnetic nozzle as described above. The VASIMR is also a leading candidate for exploiting an electric propulsion test platform being considered for the ISS.
Magnetic Flux Compression Experiments Using Plasma Armatures
NASA Technical Reports Server (NTRS)
Turner, M. W.; Hawk, C. W.; Litchford, R. J.
2003-01-01
Magnetic flux compression reaction chambers offer considerable promise for controlling the plasma flow associated with various micronuclear/chemical pulse propulsion and power schemes, primarily because they avoid thermalization with wall structures and permit multicycle operation modes. The major physical effects of concern are the diffusion of magnetic flux into the rapidly expanding plasma cloud and the development of Rayleigh-Taylor instabilities at the plasma surface, both of which can severely degrade reactor efficiency and lead to plasma-wall impact. A physical parameter of critical importance to these underlying magnetohydrodynamic (MHD) processes is the magnetic Reynolds number (R(sub m), the value of which depends upon the product of plasma electrical conductivity and velocity. Efficient flux compression requires R(sub m) less than 1, and a thorough understanding of MHD phenomena at high magnetic Reynolds numbers is essential to the reliable design and operation of practical reactors. As a means of improving this understanding, a simplified laboratory experiment has been constructed in which the plasma jet ejected from an ablative pulse plasma gun is used to investigate plasma armature interaction with magnetic fields. As a prelude to intensive study, exploratory experiments were carried out to quantify the magnetic Reynolds number characteristics of the plasma jet source. Jet velocity was deduced from time-of-flight measurements using optical probes, and electrical conductivity was measured using an inductive probing technique. Using air at 27-inHg vacuum, measured velocities approached 4.5 km/s and measured conductivities were in the range of 30 to 40 kS/m.
Production of a large, quiescent, magnetized plasma
NASA Technical Reports Server (NTRS)
Landt, D. L.; Ajmera, R. C.
1976-01-01
An experimental device is described which produces a large homogeneous quiescent magnetized plasma. In this device, the plasma is created in an evacuated brass cylinder by ionizing collisions between electrons emitted from a large-diameter electron gun and argon atoms in the chamber. Typical experimentally measured values of the electron temperature and density are presented which were obtained with a glass-insulated planar Langmuir probe. It is noted that the present device facilitates the study of phenomena such as waves and diffusion in magnetized plasmas.
Anomalous Diffraction in Cold Magnetized Plasma.
Abelson, Z; Gad, R; Bar-Ad, S; Fisher, A
2015-10-01
Cold magnetized plasma possesses an anisotropic permittivity tensor with a unique dispersion relation that for adequate electron density and magnetic field results in anomalous diffraction of a right-hand circularly polarized beam. In this work, we demonstrate experimentally anomalous diffraction of a microwave beam in plasma. Additionally, decreasing the electron density enables observation of the transition of the material from a hyperbolic to a standard material. Manipulation of the control parameters will enable plasma to serve as a reconfigurable metamaterial-like medium. PMID:26551813
Filamentation instability in a quantum magnetized plasma
Bret, A.
2008-02-15
The filamentation instability occurring when a nonrelativistic electron beam passes through a quantum magnetized plasma is investigated by means of a cold quantum magnetohydrodynamic model. It is proved that the instability can be completely suppressed by quantum effects if and only if a finite magnetic field is present. A dimensionless parameter is identified that measures the strength of quantum effects. Strong quantum effects allow for a much smaller magnetic field to suppress the instability than in the classical regime.
Magnetized Target Fusion Driven by Plasma Liners
NASA Technical Reports Server (NTRS)
Thio, Y. C. Francis; Eskridge, Richard; Smith, James; Lee, Michael; Richeson, Jeff; Schmidt, George; Knapp, Charles E.; Kirkpatrick, Ronald C.; Turchi, Peter J.; Rodgers, Stephen L. (Technical Monitor)
2001-01-01
Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). For the successful implementation of the scheme, plasma jets of the requisite momentum flux density need to be produced. Their transport over sufficiently large distances (a few meters) needs to be assured. When they collide and merge into a liner, relative differences in velocity, density and temperature of the jets could give rise to instabilities in the development of the liner. Variation in the jet properties must be controlled to ensure that the growth rate of the instabilities are not significant over the time scale of the liner formation before engaging with the target plasma. On impact with the target plasma, some plasma interpenetration might occur between the liner and the target. The operating parameter space needs to be identified to ensure that a reasonably robust and conducting contact surface is formed between the liner and the target. A mismatch in the "impedance" between the liner and the target plasma could give rise to undesirable shock heating of the liner leading to increased entropy (thermal losses) in the liner. Any irregularities in the liner will accentuate the Rayleigh-Taylor instabilities during the compression of the target plasma by the liner.
Electromagnetic response of dynamic magnetized plasma
NASA Astrophysics Data System (ADS)
Kalluri, Dikshitulu K.
2000-06-01
An electromagnetic wave is transformed in a remarkable way by a transient magnetoplasma medium. The main effect of the temporal change in the parameters of the medium is the splitting of the source wave into new waves whose frequencies are different from the incident wave frequency. Several transient problems [1] involving slow or fast creation or slow or fast collapse of the plasma medium in the presence of a static magnetic field will be discussed. Approximate perturbation solution for the case of rapid temporal change of the plasma medium, based on time-domain Green's function, will be presented. WKP or Adiabatic analysis for the problem of slow temporal change of the plasma medium will also be presented. Finite Difference Time Domain (FDTD) method of numerical solution will be developed. Several interesting results obtained by the author by using the approximate solutions and verified by the FDTD method will be discussed. The more important results are: (1) frequency upshifting with power intensification of a whistler wave by a collapsing plasma medium, (2) conversion of a whistler wave into a controllable helical wiggler magnetic field, (3) mode coupling due to a magnetized plasma in a cavity, and (4) frequency down-shifting due to switched plasma layers in the presence of a background magnetic field. A switched magentoplasma can act like a frequency transformer. The source wave can be generated in an available frequency band and the switched plasma device converts the source wave into a new wave in a frequency band not easily obtainable by other methods. Frequency shifting mechanism can be applied for plasma cloaking of satellites and aircraft and for producing short-chirped-pulses as ultra wide band signals. Recent proof of the principle experiments confirmed many theoretical results. Many more experiments need to be done to study the scalability of the results. Fast Switching of magnetized plasma is a challenging experimental task.
Oxide Coated Cathode Plasma Source of Linear Magnetized Plasma Device
NASA Astrophysics Data System (ADS)
Hu, Guanghai; Jin, Xiaoli; Yuan, Lin; Zhang, Qiaofeng; Xie, Jinlin; Li, Hong; Liu, Wandong
2016-09-01
Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm2 to 6 A/cm2 in pulsed mode within pulse length 5-20 ms. A 10 cm diameter, 2 m long plasma column with density 1018 m-3 to 1019 m3 and electron temperature Te ≃ 3-7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper. supported by National Natural Science Foundation of China (No. 11275200)
Momentum transfer to rotating magnetized plasma from gun plasma injection
Shamim, Imran; Hassam, A. B.; Ellis, R. F.; Witherspoon, F. D.; Phillips, M. W.
2006-11-15
Numerical simulations are carried out to investigate the penetration and momentum coupling of a gun-injected plasma slug into a rotating magnetized plasma. An experiment along these lines is envisioned for the Maryland Centrifugal Experiment (MCX) [R. F. Ellis et al., Phys. Plasmas 8, 2057 (2001)] using a coaxial plasma accelerator gun developed by HyperV Technologies Corp. [F. D. Witherspoon et al., Bull. Am. Phys. Soc. 50, LP1 87 (2005)]. The plasma gun would be located in the axial midplane and fired off-axis into the rotating MCX plasma annulus. The numerical simulation is set up so that the initial momentum in the injected plasma slug is of the order of the initial momentum of the target plasma. Several numerical firings are done into the cylindrical rotating plasma. Axial symmetry is assumed. The slug is seen to penetrate readily and deform into a mushroom, characteristic of interchange deformations. It is found that up to 25% of the momentum in the slug can be transferred to the background plasma in one pass across a cylindrical chord. For the same initial momentum, a high-speed low density slug gives more momentum transfer than a low-speed high density slug. Details of the numerical simulations and a scaling study are presented.
Oxide Coated Cathode Plasma Source of Linear Magnetized Plasma Device
NASA Astrophysics Data System (ADS)
Hu, Guanghai; Jin, Xiaoli; Yuan, Lin; Zhang, Qiaofeng; Xie, Jinlin; Li, Hong; Liu, Wandong
2016-09-01
Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm2 to 6 A/cm2 in pulsed mode within pulse length 5–20 ms. A 10 cm diameter, 2 m long plasma column with density 1018 m‑3 to 1019 m3 and electron temperature Te ≃ 3–7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper. supported by National Natural Science Foundation of China (No. 11275200)
Dynamics of exploding plasmas in a large magnetized plasma
Niemann, C.; Gekelman, W.; Constantin, C. G.; Everson, E. T.; Schaeffer, D. B.; Clark, S. E.; Zylstra, A. B.; Pribyl, P.; Tripathi, S. K. P.; Bondarenko, A. S.; Winske, D.; Larson, D.; Glenzer, S. H.
2013-01-15
The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfvenic velocity (up to M{sub A}=1.5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B/B{sub 0}=1.5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfven waves ({delta}B/B{sub 0}>25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave.
A model of magneto-electric multipoles
NASA Astrophysics Data System (ADS)
Lovesey, S. W.; Balcar, E.
2015-03-01
A long-known Hamiltonian of electrons with entangled spin and orbital degrees of freedom is re-examined as a model of magneto-electric multipoles (MEs). In the model, a magnetic charge and simple quantum rotator are tightly locked in action, some might say they are enslaved entities. It is shown that MEs almost perfectly accord with those inferred from an analysis of magnetic neutron diffraction data on a ceramic superconductor (YBCO) in the pseudo-gap phase. Nigh on perfection between Stone's model and inferred MEs is achieved by addition to the original model of a crystal-field potential appropriate for the magnetic space group used in the published data analysis. An impression of thermal properties of multipoles is sought from a molecular-field model.
Integrity of the Plasma Magnetic Nozzle
NASA Technical Reports Server (NTRS)
Gerwin, Richard A.
2009-01-01
This report examines the physics governing certain aspects of plasma propellant flow through a magnetic nozzle, specifically the integrity of the interface between the plasma and the nozzle s magnetic field. The injection of 100s of eV plasma into a magnetic flux nozzle that converts thermal energy into directed thrust is fundamental to enabling 10 000s of seconds specific impulse and 10s of kW/kg specific power piloted interplanetary propulsion. An expression for the initial thickness of the interface is derived and found to be approx.10(exp -2) m. An algorithm is reviewed and applied to compare classical resistivity to gradient-driven microturbulent (anomalous) resistivity, in terms of the spatial rate and time integral of resistive interface broadening, which can then be related to the geometry of the nozzle. An algorithm characterizing plasma temperature, density, and velocity dependencies is derived and found to be comparable to classical resistivity at local plasma temperatures of approx. 200 eV. Macroscopic flute-mode instabilities in regions of "adverse magnetic curvature" are discussed; a growth rate formula is derived and found to be one to two e-foldings of the most unstable Rayleigh-Taylor (RT) mode. After establishing the necessity of incorporating the Hall effect into Ohm s law (allowing full Hall current to flow and concomitant plasma rotation), a critical nozzle length expression is derived in which the interface thickness is limited to about 1 ion gyroradius.
Heat flux viscosity in collisional magnetized plasmas
Liu, C.; Fox, W.; Bhattacharjee, A.
2015-05-15
Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a “heat flux viscosity,” is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.
Heat flux viscosity in collisional magnetized plasmas
NASA Astrophysics Data System (ADS)
Liu, C.; Fox, W.; Bhattacharjee, A.
2015-05-01
Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a "heat flux viscosity," is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.
Magnetic curvature effects on plasma interchange turbulence
NASA Astrophysics Data System (ADS)
Li, B.; Liao, X.; Sun, C. K.; Ou, W.; Liu, D.; Gui, G.; Wang, X. G.
2016-06-01
The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.
Magnetic field measurements in tokamak plasmas
Feldman, U.; Seely, J.F.; Sheeley,Jr., N.R.; Suckewer, S.; Title, A.M.
1984-11-01
The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300--9300 A are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.
Plasma transport in mixed magnetic topologies
Hegna, C.C.; Callen, J.D.
1992-12-01
A simple model is introduced to illustrate some features concerning anomalous transport associated with magnetic turbulence. For magnetic topologies that are described as bands of stochasticity separated by regions with good flux surfaces, the transport coefficients deviate significantly from those describing completely stochastic magnetic fields. It is possible to have the electron heat diffusivity exceed a runaway electron diffusion coefficient, despite the existence of widespread magnetic stochasticity. Comparing the ratios of transport coefficients is not an accurate way to determine whether anomalous plasma transport is controlled by electrostatic or electromagnetic fluctuations.
NASA Technical Reports Server (NTRS)
Goldstein, M. L.; Eviatar, A.; Thieman, J. R.
1978-01-01
A geometrical model is presented in which the apparent source locations of the Io-independent decameter radiation are computed. The calculations assume that the radiation is produced by stably trapped electrons radiating near the electron gyrofrequency and that the emission is then beamed onto a conical surface. The maximum occurrence probability of noise storms is associated with regions in the Jovian magnetosphere where the axis of the emission cone is most inclined toward the Jovian equatorial plane. The calculations utilize and compare two of the octupole spherical harmonic expansions of the Jovian magnetic field constructed from data accumulated by the fluxgate and vector helium magnetometers on board Pioneer 11.
Laboratory study of avalanches in magnetized plasmas.
Van Compernolle, B; Morales, G J; Maggs, J E; Sydora, R D
2015-03-01
It is demonstrated that a novel heating configuration applied to a large and cold magnetized plasma allows the study of avalanche phenomena under controlled conditions. Intermittent collapses of the plasma pressure profile, associated with unstable drift-Alfvén waves, exhibit a two-slope power-law spectrum with exponents near -1 at lower frequencies and in the range of -2 to -4 at higher frequencies. A detailed mapping of the spatiotemporal evolution of a single avalanche event is presented.
Exact solutions to magnetized plasma flow
Wang, Zhehui; Barnes, Cris W.
2001-03-01
Exact analytic solutions for steady-state magnetized plasma flow (MPF) using ideal magnetohydrodynamics formalism are presented. Several cases are considered. When plasma flow is included, a finite plasma pressure gradient {nabla}p can be maintained in a force-free state JxB=0 by the velocity gradient. Both incompressible and compressible MPF examples are discussed for a Taylor-state spheromak B field. A new magnetized nozzle solution is given for compressible plasma when U{parallel}B. Transition from a magnetized nozzle to a magnetic nozzle is possible when the B field is strong enough. No physical nozzle would be needed in the magnetic nozzle case. Diverging-, drum- and nozzle-shaped MPF solutions when U{perpendicular}B are also given. The electric field is needed to balance the UxB term in Ohm's law. The electric field can be generated in the laboratory with the proposed conducting electrodes. If such electric fields also exist in stars and galaxies, such as through a dynamo process, then these solutions can be candidates to explain single and double jets.
Scaling laws in magnetized plasma turbulence
Boldyrev, Stanislav
2015-06-28
Interactions of plasma motion with magnetic fields occur in nature and in the laboratory in an impressively broad range of scales, from megaparsecs in astrophysical systems to centimeters in fusion devices. The fact that such an enormous array of phenomena can be effectively studied lies in the existence of fundamental scaling laws in plasma turbulence, which allow one to scale the results of analytic and numerical modeling to the sized of galaxies, velocities of supernovae explosions, or magnetic fields in fusion devices. Magnetohydrodynamics (MHD) provides the simplest framework for describing magnetic plasma turbulence. Recently, a number of new features of MHD turbulence have been discovered and an impressive array of thought-provoking phenomenological theories have been put forward. However, these theories have conflicting predictions, and the currently available numerical simulations are not able to resolve the contradictions. MHD turbulence exhibits a variety of regimes unusual in regular hydrodynamic turbulence. Depending on the strength of the guide magnetic field it can be dominated by weakly interacting Alfv\\'en waves or strongly interacting wave packets. At small scales such turbulence is locally anisotropic and imbalanced (cross-helical). In a stark contrast with hydrodynamic turbulence, which tends to ``forget'' global constrains and become uniform and isotropic at small scales, MHD turbulence becomes progressively more anisotropic and unbalanced at small scales. Magnetic field plays a fundamental role in turbulent dynamics. Even when such a field is not imposed by external sources, it is self-consistently generated by the magnetic dynamo action. This project aims at a comprehensive study of universal regimes of magnetic plasma turbulence, combining the modern analytic approaches with the state of the art numerical simulations. The proposed study focuses on the three topics: weak MHD turbulence, which is relevant for laboratory devices, the solar
On zero frequency magnetic fluctuations in plasmas
Tajima, T.; Cable, S. . Inst. for Fusion Studies); Kulsrud, R.M. . Dept. of Astrophysical Sciences)
1992-01-01
A plasma sustains fluctuations of electromagnetic fields and particle density even in a thermal equilibrium and such fluctuations have a large zero frequency peak. The level of fluctuations in the plasma for a given wavelength and frequency of electromagnetic fields is calculated through the fluctuation-dissipation theorem. The frequency spectrum shows that the energy contained in this peak is complementary to the energy lost'' by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l angle}B{sup 2}{r angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.
On zero frequency magnetic fluctuations in plasmas
Tajima, T.; Cable, S.; Kulsrud, R.M.
1992-01-01
A plasma sustains fluctuations of electromagnetic fields and particle density even in a thermal equilibrium and such fluctuations have a large zero frequency peak. The level of fluctuations in the plasma for a given wavelength and frequency of electromagnetic fields is calculated through the fluctuation-dissipation theorem. The frequency spectrum shows that the energy contained in this peak is complementary to the energy ``lost`` by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l_angle}B{sup 2}{r_angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.
Magnetized Target Fusion Driven by Plasma Liners
NASA Technical Reports Server (NTRS)
Thio, Y. C. Francis; Cassibry, Jason; Eskridge, Richard; Kirkpatrick, Ronald C.; Knapp, Charles E.; Lee, Michael; Martin, Adam; Smith, James; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)
2001-01-01
For practical applications of magnetized target fusion, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Quasi-spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a quasi-spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). Theoretical analysis and computer modeling of the concept are presented. It is shown that, with the appropriate choice of the flow parameters in the liner and the target, the impact between the liner and the target plasma can be made to be shockless in the liner or to generate at most a very weak shock in the liner. Additional information is contained in the original extended abstract.
Spin solitons in magnetized pair plasmas
Brodin, G.; Marklund, M.
2007-11-15
A set of fluid equations, taking into account the spin properties of the electrons and positrons in a magnetoplasma, are derived. The magnetohydrodynamic limit of the pair plasma is investigated. It is shown that the microscopic spin properties of the electrons and positrons can lead to interesting macroscopic and collective effects in strongly magnetized plasmas. In particular, it is found that new Alfvenic solitary structures, governed by a modified Korteweg-de Vries equation, are allowed in such plasmas. These solitary structures vanish if the quantum spin effects are neglected. Our results should be of relevance for astrophysical plasmas, e.g., in pulsar magnetospheres, as well as for low-temperature laboratory plasmas.
Plasma observations at the earth's magnetic equator
NASA Technical Reports Server (NTRS)
Olsen, R. C.; Shawhan, S. D.; Gallagher, D. L.; Chappell, C. R.; Green, J. L.
1987-01-01
New observations of particle and wave data from the magnetic equator from the DE 1 spacecraft are reported. The results demonstrate that the equatorial plasma population is predominantly hydrogen and that the enhanced ion fluxes observed at the equator occur without an increase in the total plasma density. Helium is occasionally found heated along with the protons, and forms about 10 percent of the equatorially trapped population at such times. The heated H(+) ions can be characterized by a bi-Maxwellian with kT(parallel) = 0.5-1.0 eV and kT = 5-50 eV, with a density of 10-100/cu cm. The total plasma density is relatively constant with latitude. First measurements of the equatorially trapped plasma and coincident UHR measurements show that the trapped plasma is found in conjunction with equatorial noise.
Dynamics of Exploding Plasma Within a Magnetized Plasma
Dimonte, G; Dipeso, G; Hewett, D
2002-02-01
This memo describes several possible laboratory experiments on the dynamics of an exploding plasma in a background magnetized plasma. These are interesting scientifically and the results are applicable to energetic explosions in the earth's ionosphere (DOE Campaign 7 at LLNL). These proposed experiments are difficult and can only be performed in the new LAPD device at UCLA. The purpose of these experiments would be to test numerical simulations, theory and reduced models for systems performance codes. The experiments are designed to investigate the affect of the background plasma on (1) the maximum diamagnetic bubble radius given by Eq. 9; and (2) the Alfven wave radiation efficiency produced by the induced current J{sub A} (Eqs. 10-12) These experiments involve measuring the bubble radius using a fast gated optical imager as in Ref [1] and the Alfven wave profile and intensity as in Ref [2] for different values of the exploding plasma energy, background plasma density and temperature, and background magnetic field. These experiments extend the previously successful experiments [2] on Alfven wave coupling. We anticipate that the proposed experiments would require 1-2 weeks of time on the LAPD. We would perform PIC simulations in support of these experiments in order to validate the codes. Once validated, the PIC simulations would then be able to be extended to realistic ionospheric conditions with various size explosions and altitudes. In addition to the Alfven wave coupling, we are interested in the magnetic containment and transport of the exploding ''debris'' plasma to see if the shorting of the radial electric field in the magnetic bubble would allow the ions to propagate further. This has important implications in an ionospheric explosion because it defines the satellite damage region. In these experiments, we would field fast gated optical cameras to obtain images of the plasma expansion, which could then be correlated with magnetic probe measurements. In
Magnetized Target Fusion Driven by Plasma Liners
NASA Technical Reports Server (NTRS)
Thio, Y. C. Francis; Kirkpatrick, Ronald C.; Knapp, Charles E.; Rodgers, Stephen L. (Technical Monitor)
2002-01-01
Magnetized target fusion is an emerging, relatively unexplored approach to fusion for electrical power and propulsion application. The physical principles of the concept are founded upon both inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). It attempts to combine the favorable attributes of both these orthogonal approaches to fusion, but at the same time, avoiding the extreme technical challenges of both by exploiting a fusion regime intermediate between them. It uses a material liner to compress, heat and contain the fusion reacting plasma (the target plasma) mentally. By doing so, the fusion burn could be made to occur at plasma densities as high as six orders of magnitude higher than conventional MCF such as tokamak, thus leading to an approximately three orders of magnitude reduction in the plasma energy required for ignition. It also uses a transient magnetic field, compressed to extremely high intensity (100's T to 1000T) in the target plasma, to slow down the heat transport to the liner and to increase the energy deposition of charged-particle fusion products. This has several compounding beneficial effects. It leads to longer energy confinement time compared with conventional ICF without magnetized target, and thus permits the use of much lower plasma density to produce reasonable burn-up fraction. The compounding effects of lower plasma density and the magneto-insulation of the target lead to greatly reduced compressional heating power on the target. The increased energy deposition rate of charged-particle fusion products also helps to lower the energy threshold required for ignition and increasing the burn-up fraction. The reduction in ignition energy and the compressional power compound to lead to reduced system size, mass and R&D cost. It is a fusion approach that has an affordable R&D pathway, and appears attractive for propulsion application in the nearer term.
Magnetic reconnection in collisionless plasmas - Prescribed fields
NASA Technical Reports Server (NTRS)
Burkhart, G. R.; Drake, J. F.; Chen, J.
1990-01-01
The structure of the dissipation region during magnetic reconnection in collisionless plasma is investigated by examining a prescribed two-dimensional magnetic x line configuration with an imposed inductive electric field E(y). The calculations represent an extension of recent MHD simulations of steady state reconnection (Biskamp, 1986; Lee and Fu, 1986) to the collisionless kinetic regime. It is shown that the structure of the x line reconnection configuration depends on only two parameters: a normalized inductive field and a parameter R which represents the opening angle of the magnetic x lines.
Waves and instabilities in a magnetized plasma
NASA Technical Reports Server (NTRS)
Dawson, J. M.
1982-01-01
Work on computer simulation of waves and instabilities in magnetized plasmas is reviewed. Included are verification of linear theory. Particular emphasis is given to investigation of nonlinear processes involved in the saturation of instabilities and of wave damping; these include a nonlinear cyclotron resonance and particle trapping in intense waves.
Localized whistlers in magnetized spin quantum plasmas
Misra, A. P.; Brodin, G.; Marklund, M.; Shukla, P. K.
2010-11-15
The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schroedinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.
Transparency of Magnetized Plasma at Cyclotron Frequency
G. Shvets; J.S. Wurtele
2002-03-14
Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration.
HPAM: Hirshfeld Partitioned Atomic Multipoles.
Elking, Dennis M; Perera, Lalith; Pedersen, Lee G
2012-02-01
An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank l(max) on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from l(max) = 0 (atomic charges) to l(max) = 4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank l(max) are shown to exactly reproduce ab initio molecular multipole moments of rank L for L ≤ l(max). In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only (l(max) = 0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used.
Relativistic laser pulse compression in magnetized plasmas
Liang, Yun; Sang, Hai-Bo Wan, Feng; Lv, Chong; Xie, Bai-Song
2015-07-15
The self-compression of a weak relativistic Gaussian laser pulse propagating in a magnetized plasma is investigated. The nonlinear Schrödinger equation, which describes the laser pulse amplitude evolution, is deduced and solved numerically. The pulse compression is observed in the cases of both left- and right-hand circular polarized lasers. It is found that the compressed velocity is increased for the left-hand circular polarized laser fields, while decreased for the right-hand ones, which is reinforced as the enhancement of the external magnetic field. We find a 100 fs left-hand circular polarized laser pulse is compressed in a magnetized (1757 T) plasma medium by more than ten times. The results in this paper indicate the possibility of generating particularly intense and short pulses.
Magnetized Plasma Compression for Fusion Energy
NASA Astrophysics Data System (ADS)
Degnan, James; Grabowski, Christopher; Domonkos, Matthew; Amdahl, David
2013-10-01
Magnetized Plasma Compression (MPC) uses magnetic inhibition of thermal conduction and enhancement of charge particle product capture to greatly reduce the temporal and spatial compression required relative to un-magnetized inertial fusion (IFE)--to microseconds, centimeters vs nanoseconds, sub-millimeter. MPC greatly reduces the required confinement time relative to MFE--to microseconds vs minutes. Proof of principle can be demonstrated or refuted using high current pulsed power driven compression of magnetized plasmas using magnetic pressure driven implosions of metal shells, known as imploding liners. This can be done at a cost of a few tens of millions of dollars. If demonstrated, it becomes worthwhile to develop repetitive implosion drivers. One approach is to use arrays of heavy ion beams for energy production, though with much less temporal and spatial compression than that envisioned for un-magnetized IFE, with larger compression targets, and with much less ambitious compression ratios. A less expensive, repetitive pulsed power driver, if feasible, would require engineering development for transient, rapidly replaceable transmission lines such as envisioned by Sandia National Laboratories. Supported by DOE-OFES.
Long-Range Collisions in Magnetized Plasmas
NASA Astrophysics Data System (ADS)
Dubin, D.
2015-12-01
Astrophysical (and earthbound) plasmas in strong magnetic fields exhibit collisional effects that are not described by classical collision theory nor by the standard collision operators, such as the Landau or Balescu-Lenard operators. These theories implicitly neglect "long-range" collisions, i.e. collisions with impact parameters large compared to the cyclotron radius. This presentation will review several important physical effects such collisions have on various phenomena, including cross-magnetic field diffusion, heat conduction, and collisional slowing parallel to the magnetic field. Long-range collisions are analyzed as guiding-centers moving in one-dimension along the magnetic field, with parallel energy and momentum transferred to particles on separate field lines through the screened Coulomb interaction. This causes cross-field heat transport that is independent of magnetic field strength B (as opposed to the classical 1/B2 scaling), and enhances the rate of collisional slowing parallel to B. The Coulomb interaction between guiding centers on different field lines also produces random ExB drifts that enhance cross-magnetic field diffusion compared to the classical theory. The theory of long-range guiding center collisions must also include the novel effect of "collisional caging": plasma noise causes two colliding guiding centers to diffuse in relative parallel velocity, reversing their motion along B and colliding several times before becoming uncorrelated. This further enhances cross-field diffusion from long-range collisions by a factor of three, and enhances parallel slowing by a factor of approximately 1.5.
Critical loss radius in a Penning trap subject to multipole fields
Fajans, J.; Madsen, N.; Robicheaux, F.
2008-03-15
When particles in a Penning trap are subject to a magnetic multipole field, those beyond a critical radius will be lost. The critical radius depends on the history by which the field is applied, and can be much smaller if the particles are injected into a preexisting multipole than if the particles are subject to a ramped multipole. Both cases are relevant to ongoing experiments designed to trap antihydrogen.
Multipole nonlinearity of metamaterials
Petschulat, J.; Chipouline, A.; Tuennermann, A.; Pertsch, T.; Menzel, C.; Rockstuhl, C.; Lederer, F.
2009-12-15
We report on the linear and nonlinear optical response of metamaterials evoked by first- and second-order multipoles. The analytical ground on which our approach is based permits for new insights into the functionality of metamaterials. For the sake of clarity we focus here on a key geometry, namely, the split-ring resonator, although the introduced formalism can be applied to arbitrary structures. We derive the equations that describe linear and nonlinear light propagation where special emphasis is put on second-harmonic generation. This contribution basically aims at stretching versatile and existing concepts to describe light propagation in nonlinear media toward the realm of metamaterials.
Laboratory study of avalanches in magnetized plasmas.
Van Compernolle, B; Morales, G J; Maggs, J E; Sydora, R D
2015-03-01
It is demonstrated that a novel heating configuration applied to a large and cold magnetized plasma allows the study of avalanche phenomena under controlled conditions. Intermittent collapses of the plasma pressure profile, associated with unstable drift-Alfvén waves, exhibit a two-slope power-law spectrum with exponents near -1 at lower frequencies and in the range of -2 to -4 at higher frequencies. A detailed mapping of the spatiotemporal evolution of a single avalanche event is presented. PMID:25871044
Multipole Structure and Coordinate Systems
ERIC Educational Resources Information Center
Burko, Lior M.
2007-01-01
Multipole expansions depend on the coordinate system, so that coefficients of multipole moments can be set equal to zero by an appropriate choice of coordinates. Therefore, it is meaningless to say that a physical system has a nonvanishing quadrupole moment, say, without specifying which coordinate system is used. (Except if this moment is the…
Laser plasma in a magnetic field
Kondo,K.; Kanesue, T.; Tamura, J.; Dabrowski, R.; Okamura, M.
2009-09-20
Laser Ion Source (LIS) is a candidate among various heavy ion sources. A high density plasma produced by Nd:YAG laser with drift velocity realizes high current and high charge state ion beams. In order to obtain higher charged particle ions, we had test experiments of LIS with a magnetic field by which a connement effect can make higher charged beams. We measured total current by Faraday Cup (FC) and analyzed charge distribution by Electrostatic Ion Analyzer (EIA). It is shown that the ion beam charge state is higher by a permanent magnet.
Finding Plasma Equilibria with Magnetic Islands
NASA Astrophysics Data System (ADS)
Miller, G.; Faber, V.; White, A. B., Jr.
1988-12-01
The traditional method of solving the helically symmetric plasma equilibrium equation, of the form L[ G] = F( G, r) where L is an elliptic linear operator, has been the simple iteration L[ Gn + 1 ]= F( Gn, r). A model of a Tokomak equilibrium is constructed and used to illustrate the divergence of the simple iteration for plasma equilibria with magnetic islands. Although the problem of equilibria with magnetic islands is two dimensional, for small islands the numerical stability of the simple iteration may be analyzed using a one-dimensional equation similar to the linearized equilibrium equation used to analyze physical (resistive) instability. This analysis is used to prove that any equilibria of the Tokamak type with small islands cannot be obtained by the simple iteration and to illustrate the superlinear convergence of Newton's method on these problems. The implementation of Newton's method is discussed and examples are given.
Nishimura, Seiya
2014-12-15
Resonant magnetic perturbations (RMPs) produce magnetic islands in toroidal plasmas. Self-healing (annihilation) of RMP-induced magnetic islands has been observed in helical systems, where a possible mechanism of the self-healing is shielding of RMP penetration by plasma flows, which is well known in tokamaks. Thus, fundamental physics of RMP shielding is commonly investigated in both tokamaks and helical systems. In order to check this mechanism, detailed informations of magnetic island phases are necessary. In experiments, measurement of radial magnetic responses is relatively easy. In this study, based on a theoretical model of rotating magnetic islands, behavior of radial magnetic fields during the self-healing is investigated. It is confirmed that flips of radial magnetic fields are typically observed during the self-healing. Such behavior of radial magnetic responses is also observed in LHD experiments.
Toroidal dust motion in magnetized plasmas
Reichstein, Torben; Pilch, Iris; Piel, Alexander
2010-09-15
In a magnetized anodic plasma, dust particles can be confined in a torus-shaped cloud with a distinct dust-free region (void) in its center. The formation of these clouds and their dynamical behavior are experimentally studied with a new observation geometry. The particles rotate about the major axis of the torus. A refined model for the description of the particle dynamics is presented that accounts for inertia and many-body effects.
Landau Fluid Models for Magnetized Plasmas
Sulem, P. L.; Passot, T.; Marradi, L.
2008-10-15
A Landau fluid model for a magnetized plasma, that retains a linear description of low-frequency kinetic effects involving transverse scales significantly smaller than the ion Larmor radius, is discussed and validated in the context of nonlinear wave dynamics. Preliminary simulations of the turbulent regime are presented in one space dimension, as a first step towards more realistic three-dimensional computations, aimed to analyze the combined effect of dispersion and collisionless dissipation on the energy cascade.
Magnetic reconnection in a weakly ionized plasma
Leake, James E.; Lukin, Vyacheslav S.; Linton, Mark G.
2013-06-15
Magnetic reconnection in partially ionized plasmas is a ubiquitous phenomenon spanning the range from laboratory to intergalactic scales, yet it remains poorly understood and relatively little studied. Here, we present results from a self-consistent multi-fluid simulation of magnetic reconnection in a weakly ionized reacting plasma with a particular focus on the parameter regime of the solar chromosphere. The numerical model includes collisional transport, interaction and reactions between the species, and optically thin radiative losses. This model improves upon our previous work in Leake et al.[“Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma,” Astrophys. J. 760, 109 (2012)] by considering realistic chromospheric transport coefficients, and by solving a generalized Ohm's law that accounts for finite ion-inertia and electron-neutral drag. We find that during the two dimensional reconnection of a Harris current sheet with an initial width larger than the neutral-ion collisional coupling scale, the current sheet thins until its width becomes less than this coupling scale, and the neutral and ion fluids decouple upstream from the reconnection site. During this process of decoupling, we observe reconnection faster than the single-fluid Sweet-Parker prediction, with recombination and plasma outflow both playing a role in determining the reconnection rate. As the current sheet thins further and elongates, it becomes unstable to the secondary tearing instability, and plasmoids are seen. The reconnection rate, outflows, and plasmoids observed in this simulation provide evidence that magnetic reconnection in the chromosphere could be responsible for jet-like transient phenomena such as spicules and chromospheric jets.
Harmonic generation in magnetized quantum plasma
NASA Astrophysics Data System (ADS)
Kumar, Punit; Singh, Shiv; Singh, Abhisek Kumar
2016-05-01
A study of second harmonic generation by propagation of a linearly polarized electromagnetic wave through homogeneous high density quantum plasma in the presence of transverse magnetic field. The nonlinear current density and dispersion relations for the fundamental and second harmonic frequencies have been obtained using the recently developed quantum hydrodynamic (QHD) model. The effect of quantum Bohm potential, Fermi pressure and the electron spin have been taken into account. The second harmonic is found to be less dispersed than the first.
Generalized Langmuir Waves in Magnetized Kinetic Plasmas
NASA Technical Reports Server (NTRS)
Willes, A. J.; Cairns, Iver H.
2000-01-01
The properties of unmagnetized Langmuir waves and cold plasma magnetoionic waves (x, o, z and whistler) are well known. However, the connections between these modes in a magnetized kinetic plasma have not been explored in detail. Here, wave properties are investigated by numerically solving the dispersion equation derived from the Vlasov equations both with and without a beam instability present. For omega(sub p)>Omega(sub e), it is shown that the generalized Langmuir mode at oblique propagation angles has magnetic z-mode characteristics at low wave numbers and thermal Langmuir mode characteristics at high wave numbers. For omega(sub p)
Plasma Braking Due to External Magnetic Perturbations
NASA Astrophysics Data System (ADS)
Frassinetti, L.; Olofsson, Kejo; Brunsell, P. R.; Khan, M. W. M.; Drake, J. R.
2010-11-01
The RFP EXTRAP T2R is equipped with a comprehensive active feedback system (128 active saddle coils in the full-coverage array) and active control of both resonant and non-resonant MHD modes has been demonstrated. The feedback algorithms, based on modern control methodology such as reference mode tracking (both amplitude and phase), are a useful tool to improve the ``state of the art'' of the MHD mode control. But this tool can be used also to improve the understanding and the characterization of other phenomena such as the ELM mitigation with a resonant magnetic perturbation or the plasma viscosity. The present work studies plasma and mode braking due to static RMPs. Results show that a static RMP produces a global braking of the flow profile. The study of the effect of RMPs characterized by different helicities will also give information on the plasma viscosity profile. Experimental results are finally compared to theoretical models.
Dust particle dynamics in magnetized plasma sheath
Davoudabadi, M.; Mashayek, F.
2005-07-15
In this paper, the structure of a plasma sheath in the presence of an oblique magnetic field is investigated, and dynamics of a dust particle embedded in the sheath is elaborated. To simulate the sheath, a weakly collisional two-fluid model is implemented. For various magnitudes and directions of the magnetic field and chamber pressures, different plasma parameters including the electron and ion densities, ion flow velocity, and electric potential are calculated. A complete set of forces acting on the dust particle originating from the electric field in the sheath, the static magnetic field, gravity, and ion and neutral drags is taken into account. Through the trapping potential energy, the particle stable and unstable equilibria are studied while the particle is stationary inside the sheath. Other features such as the possibility of the dust levitation and trapping in the sheath, and the effect of the Lorentz force on the charged dust particle motion are also examined. An interesting feature is captured for the variation of the particle charge as a function of the magnetic field magnitude.
Axisymmetric plasma equilibrium in gravitational and magnetic fields
Krasheninnikov, S. I.; Catto, P. J.
2015-12-15
Plasma equilibria in gravitational and open-ended magnetic fields are considered for the case of topologically disconnected regions of the magnetic flux surfaces where plasma occupies just one of these regions. Special dependences of the plasma temperature and density on the magnetic flux are used which allow the solution of the Grad–Shafranov equation in a separable form permitting analytic treatment. It is found that plasma pressure tends to play the dominant role in the setting the shape of magnetic field equilibrium, while a strong gravitational force localizes the plasma density to a thin disc centered at the equatorial plane.
Low-frequency fluctuations in plasma magnetic fields
Cable, S.; Tajima, T.
1992-02-01
It is shown that even a non-magnetized plasma with temperature T sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, non-magnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wavenumber is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac {delta}-function in the collisionless plasma; it is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low frequency cutoff in the typical black-body radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic field were vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes which forms the non-magnetized zero-frequency peak of the isotropic plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves if found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic field fluctuation spectrum as well. For the degenerate plasma, we find that electric field fluctuations and number density fluctuations vanish at zero frequency; however, the magnetic field power spectrum diverges at zero frequency.
NASA Astrophysics Data System (ADS)
Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott; University of New Mexico Collaboration; Los Alamos National Laboratory Collaboration
2013-10-01
A compact coaxial plasma gun is employed for experimental studies of plasma relaxation in a low density background plasma. Experiments are being conducted in the linear HelCat device at UNM. These studies will advance the knowledge of basic plasma physics in the areas of magnetic relaxation and space and astrophysical plasmas, including the evolution of active galactic jets/radio lobes within the intergalactic medium. The gun is powered by a 120pF ignitron-switched capacitor bank which is operated in a range of 5-10 kV and ~100 kA. Multiple diagnostics are employed to investigate plasma relaxation process. Magnetized Argon plasma bubbles with velocities ~1.2Cs and densities ~1020 m-3 have been achieved. Different distinct regimes of operation with qualitatively different dynamics are identified by fast CCD camera images, with the parameter determining the operation regime. Additionally, a B-dot probe array is employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify detached plasma bubble configurations. Experimental data and analysis will be presented.
Plasma sweeper to control the coupling of RF power to a magnetically confined plasma
Motley, Robert W.; Glanz, James
1985-01-01
A device for coupling RF power (a plasma sweeper) from a phased waveguide array for introducing RF power to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the phased waveguide array; and a potential source coupled to the electrode for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.
Magnetic field distribution in the plasma flow generated by a plasma focus discharge
Mitrofanov, K. N.; Krauz, V. I. Myalton, V. V.; Velikhov, E. P.; Vinogradov, V. P.; Vinogradova, Yu. V.
2014-11-15
The magnetic field in the plasma jet propagating from the plasma pinch region along the axis of the chamber in a megajoule PF-3 plasma focus facility is studied. The dynamics of plasma with a trapped magnetic flow is analyzed. The spatial sizes of the plasma jet region in which the magnetic field concentrates are determined in the radial and axial directions. The magnetic field configuration in the plasma jet is investigated: the radial distribution of the azimuthal component of the magnetic field inside the jet is determined. It is shown that the magnetic induction vector at a given point in space can change its direction during the plasma flight. Conclusions regarding the symmetry of the plasma flow propagation relative to the chamber axis are drawn.
Intense Magnetized Plasma-Wall Interaction
Bauer, Bruno S.; Fuelling, Stephan
2013-11-30
This research project studied wall-plasma interactions relevant to fusion science. Such interactions are a critical aspect of Magneto-Inertial Fusion (MIF) because flux compression by a pusher material, in particular the metal for the liner approach to MIF, involves strong eddy current heating on the surface of the pusher, and probably interactions and mixing of the pusher with the interior fuel during the time when fusion fuel is being burned. When the pusher material is a metal liner, high-energy-density conditions result in fascinating behavior. For example, "warm dense matter" is produced, for which material properties such as resistivity and opacity are not well known. In this project, the transformation into plasma of metal walls subjected to pulsed megagauss magnetic fields was studied with an experiment driven by the UNR 1 MA Zebra generator. The experiment was numerically simulated with using the MHRDR code. This simple, fundamental high-energy-density physics experiment, in a regime appropriate to MIF, has stimulated an important and fascinating comparison of numerical modeling codes and tables with experiment. In addition, we participated in developing the FRCHX experiment to compress a field-reversed-configuration (FRC) plasma with a liner, in collaboration with researchers from Air Force Research Laboratory and Los Alamos National Lab, and we helped develop diagnostics for the Plasma Liner Experiment (PLX) at LANL. Last, but not least, this project served to train students in high-energy-density physics.
Magnetized laboratory plasma jets: experiment and simulation.
Schrafel, Peter; Bell, Kate; Greenly, John; Seyler, Charles; Kusse, Bruce
2015-01-01
Experiments involving radial foils on a 1 MA, 100 ns current driver can be used to study the ablation of thin foils and liners, produce extreme conditions relevant to laboratory astrophysics, and aid in computational code validation. This research focuses on the initial ablation phase of a 20 μm Al foil (8111 alloy), in a radial configuration, driven by Cornell University's COBRA pulsed power generator. In these experiments ablated surface plasma (ASP) on the top side of the foil and a strongly collimated axial plasma jet are observed developing midway through the current rise. With experimental and computational results this work gives a detailed description of the role of the ASP in the formation of the plasma jet with and without an applied axial magnetic field. This ∼1 T field is applied by a Helmholtz-coil pair driven by a slow, 150 μs current pulse and penetrates the load hardware before arrival of the COBRA pulse. Several effects of the applied magnetic field are observed: (1) without the field extreme-ultraviolet emission from the ASP shows considerable azimuthal asymmetry while with the field the ASP develops azimuthal motion that reduces this asymmetry, (2) this azimuthal motion slows the development of the jet when the field is applied, and (3) with the magnetic field the jet becomes less collimated and has a density minimum (hollowing) on the axis. PERSEUS, an XMHD code, has qualitatively and quantitatively reproduced all these experimental observations. The differences between this XMHD and an MHD code without a Hall current and inertial effects are discussed. In addition the PERSEUS results describe effects we were not able to resolve experimentally and suggest a line of future experiments with better diagnostics. PMID:25679726
Magnetized laboratory plasma jets: Experiment and simulation
NASA Astrophysics Data System (ADS)
Schrafel, Peter; Bell, Kate; Greenly, John; Seyler, Charles; Kusse, Bruce
2015-01-01
Experiments involving radial foils on a 1 M A , 100 n s current driver can be used to study the ablation of thin foils and liners, produce extreme conditions relevant to laboratory astrophysics, and aid in computational code validation. This research focuses on the initial ablation phase of a 20 μ m Al foil (8111 alloy), in a radial configuration, driven by Cornell University's COBRA pulsed power generator. In these experiments ablated surface plasma (ASP) on the top side of the foil and a strongly collimated axial plasma jet are observed developing midway through the current rise. With experimental and computational results this work gives a detailed description of the role of the ASP in the formation of the plasma jet with and without an applied axial magnetic field. This ˜1 T field is applied by a Helmholtz-coil pair driven by a slow, 150 μ s current pulse and penetrates the load hardware before arrival of the COBRA pulse. Several effects of the applied magnetic field are observed: (1) without the field extreme-ultraviolet emission from the ASP shows considerable azimuthal asymmetry while with the field the ASP develops azimuthal motion that reduces this asymmetry, (2) this azimuthal motion slows the development of the jet when the field is applied, and (3) with the magnetic field the jet becomes less collimated and has a density minimum (hollowing) on the axis. PERSEUS, an XMHD code, has qualitatively and quantitatively reproduced all these experimental observations. The differences between this XMHD and an MHD code without a Hall current and inertial effects are discussed. In addition the PERSEUS results describe effects we were not able to resolve experimentally and suggest a line of future experiments with better diagnostics.
Polynomial interpretation of multipole vectors
NASA Astrophysics Data System (ADS)
Katz, Gabriel; Weeks, Jeff
2004-09-01
Copi, Huterer, Starkman, and Schwarz introduced multipole vectors in a tensor context and used them to demonstrate that the first-year Wilkinson microwave anisotropy probe (WMAP) quadrupole and octopole planes align at roughly the 99.9% confidence level. In the present article, the language of polynomials provides a new and independent derivation of the multipole vector concept. Bézout’s theorem supports an elementary proof that the multipole vectors exist and are unique (up to rescaling). The constructive nature of the proof leads to a fast, practical algorithm for computing multipole vectors. We illustrate the algorithm by finding exact solutions for some simple toy examples and numerical solutions for the first-year WMAP quadrupole and octopole. We then apply our algorithm to Monte Carlo skies to independently reconfirm the estimate that the WMAP quadrupole and octopole planes align at the 99.9% level.
METHOD FOR EXCHANGING ENERGY WITH A PLASMA BY MAGNETIC PUMPING
Hall, L.S.
1963-12-31
A method of heating a plasma confined by a static magnetic field is presented. A time-varying magnetic field having a rise time to a predetermined value substantially less than its fall time is applied to a portion of the plasma. Because of the much shorter rise time, the plasma is reversibly heated. This cycle is repeated until the desired plasma temperature is reached. (AEC)
Magnetized plasma jets in experiment and simulation
NASA Astrophysics Data System (ADS)
Schrafel, Peter; Greenly, John; Gourdain, Pierre; Seyler, Charles; Blesener, Kate; Kusse, Bruce
2013-10-01
This research focuses on the initial ablation phase of a thing (20 micron) Al foil driven on the 1 MA-in-100 ns COBRA through a 5 mm diameter cathode in a radial configuration. In these experiments, ablated surface plasma (ASP) on the top of the foil and a strongly collimated axial plasma jet can be observed developing midway through current-rise. Our goal is to establish the relationship between the ASP and the jet. These jets are of interest for their potential relevance to astrophysical phenomena. An independently pulsed 200 μF capacitor bank with a Helmholtz coil pair allows for the imposition of a slow (150 μs) and strong (~1 T) axial magnetic field on the experiment. Application of this field eliminates significant azimuthal asymmetry in extreme ultraviolet emission of the ASP. This asymmetry is likely a current filamentation instability. Laser-backlit shadowgraphy and interferometry confirm that the jet-hollowing is correlated with the application of the axial magnetic field. Visible spectroscopic measurements show a doppler shift consistent with an azimuthal velocity in the ASP caused by the applied B-field. Computational simulations with the XMHD code PERSEUS qualitatively agree with the experimental results.
Finding plasma equilibria with magnetic islands
Miller, G.; Faber, V.; White A.B. Jr.
1988-12-01
The traditional method of solving the helically symmetric plasma equilibrium equation, of the form L(G) = F(G, r) where L is an elliptic linear operator, has been the simple iteration L(G/sup n//sup +1/) = F(G/sup n/, r). A model of a Tokomak equilibrium is constructed and used to illustrate the divergence of the simple iteration for plasma equilibria with magnetic islands. Although the problem of equilibria with magnetic islands is two dimensional, for small islands the numerical stability of the simple iteration may be analyzed using a one-dimensional equation similar to the linearized equilibrium equation used to analyze physical (resistive) instability. This analysis is used to prove that any equilibria of the Tokamak type with small islands cannot be obtained by the simple iteration and to illustrate the superlinear convergence of Newton's method on these problems. The implementation of Newton's method is discussed and examples are given. copyright 1988 Academic Press, Inc.
Magnetic stochasticity in gyrokinetic simulations of plasma microturbulence
Nevins, W M; Wang, E; Candy, J
2010-02-12
Analysis of the magnetic field structure from electromagnetic simulations of tokamak ion temperature gradient turbulence demonstrates that the magnetic field can be stochastic even at very low plasma pressure. The degree of magnetic stochasticity is quantified by evaluating the magnetic diffusion coefficient. We find that the magnetic stochasticity fails to produce a dramatic increase in the electron heat conductivity because the magnetic diffusion coefficient remains small.
Singular waves in a magnetized pair-ion plasma
Samanta, Sukanta; Misra, Amar P.
2009-07-15
The existence of singular waves along the boundary of a magnetized pair-ion plasma is proved for both plasma-metal and plasma-vacuum interfaces. Such waves are shown to propagate at the points of intersection of the complex-zone boundary and the surface wave dispersion curve in a weakly magnetized plasma. The results could be relevant for negative ion plasmas in the laboratory and space as well as for the modeling of a plasma sustained by a traveling surface wave.
Magnetic confinement of a high-density cylindrical plasma
Ahedo, Eduardo
2011-10-15
The stationary structure of a weakly collisional plasma column, confined by an axial magnetic field and a cylindrical vessel, is studied for the high-density case, when the diamagnetic azimuthal current is large enough to demagnetize partially the plasma. The plasma response is characterized mainly by two dimensionless parameters: the ratios of the electron gyroradius and the electron skin-depth to the plasma radius, and each of them measures the independent influence of the applied magnetic field and the plasma density on the plasma response. The strong magnetic confinement regime, characterized by very small wall losses, is limited to the small gyroradius and large skin-depth ranges. In the high-density case, when the electron skin-depth is smaller than the electron gyroradius, the skin-depth turns out to be the magnetic screening length, so that the bulk of the plasma behaves as unmagnetized.
Status of Magnetic Nozzle and Plasma Detachment Experiment
Chavers, D. Gregory; Dobson, Chris; Jones, Jonathan; Lee, Michael; Martin, Adam; Gregory, Judith; Cecil, Jim; Bengtson, Roger D.; Breizman, Boris; Arefiev, Alexey; Chang-Diaz, Franklin; Squire, Jared; Glover, Tim; McCaskill, Greg; Cassibry, Jason; Li Zhongmin
2006-01-20
High power plasma propulsion can move large payloads for orbit transfer, lunar missions, and beyond with large savings in fuel consumption owing to the high specific impulse. At high power, lifetime of the thruster becomes an issue. Electrodeless devices with magnetically guided plasma offer the advantage of long life since magnetic fields confine the plasma radially and keep it from impacting the material surfaces. For decades, concerns have been raised about the plasma remaining attached to the magnetic field and returning to the vehicle along the closed magnetic field lines. Recent analysis suggests that this may not be an issue if the magnetic field is properly shaped in the nozzle region and the plasma has sufficient energy density to stretch the magnetic field downstream. An experiment is being performed to test the theory regarding the MHD detachment scenario. The status of that experiment will be discussed in this paper.
Analysis of magnetic field plasma interactions using microparticles as probes.
Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin S; Hyde, Truell W
2015-08-01
The interaction between a magnetic field and plasma close to a nonconductive surface is of interest for both science and technology. In space, crustal magnetic fields on celestial bodies without atmosphere can interact with the solar wind. In advanced technologies such as those used in fusion or spaceflight, magnetic fields can be used to either control a plasma or protect surfaces exposed to the high heat loads produced by plasma. In this paper, a method will be discussed for investigating magnetic field plasma interactions close to a nonconductive surface inside a Gaseous Electronics Conference reference cell employing dust particles as probes. To accomplish this, a magnet covered by a glass plate was exposed to a low power argon plasma. The magnetic field was strong enough to magnetize the electrons, while not directly impacting the dynamics of the ions or the dust particles used for diagnostics. In order to investigate the interaction of the plasma with the magnetic field and the nonconductive surface, micron-sized dust particles were introduced into the plasma and their trajectories were recorded with a high-speed camera. Based on the resulting particle trajectories, the accelerations of the dust particles were determined and acceleration maps over the field of view were generated which are representative of the forces acting on the particles. The results show that the magnetic field is responsible for the development of strong electric fields in the plasma, in both horizontal and vertical directions, leading to complex motion of the dust particles. PMID:26382535
Analysis of magnetic field plasma interactions using microparticles as probes.
Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin S; Hyde, Truell W
2015-08-01
The interaction between a magnetic field and plasma close to a nonconductive surface is of interest for both science and technology. In space, crustal magnetic fields on celestial bodies without atmosphere can interact with the solar wind. In advanced technologies such as those used in fusion or spaceflight, magnetic fields can be used to either control a plasma or protect surfaces exposed to the high heat loads produced by plasma. In this paper, a method will be discussed for investigating magnetic field plasma interactions close to a nonconductive surface inside a Gaseous Electronics Conference reference cell employing dust particles as probes. To accomplish this, a magnet covered by a glass plate was exposed to a low power argon plasma. The magnetic field was strong enough to magnetize the electrons, while not directly impacting the dynamics of the ions or the dust particles used for diagnostics. In order to investigate the interaction of the plasma with the magnetic field and the nonconductive surface, micron-sized dust particles were introduced into the plasma and their trajectories were recorded with a high-speed camera. Based on the resulting particle trajectories, the accelerations of the dust particles were determined and acceleration maps over the field of view were generated which are representative of the forces acting on the particles. The results show that the magnetic field is responsible for the development of strong electric fields in the plasma, in both horizontal and vertical directions, leading to complex motion of the dust particles.
Description of Multipole in f-Electron Systems
NASA Astrophysics Data System (ADS)
Kusunose, Hiroaki
2008-06-01
A systematic description of multipole degrees of freedom is discussed on the basis of the Stevens’ operator-equivalent technique. The generalized Stevens’ multiplicative factors are derived for all of the electric and the magnetic multipoles relevant to f-electron systems. With extensive use of the Stevens’ factors, we express the spatial dependences of the electric and the magnetic fields, and the electric and the magnetic charge densities of localized f electrons. The latter is utilized to draw wave functions including their magnetic profile in addition to their shape with the charge density. The definite relation between the operators as quantum-mechanical variables in a multipole exchange model and the multipole moments in expansion of electromagnetic fields is given. The general treatments for the exchange model with the random-phase-approximation (RPA) susceptibility and the Ginzburg-Landau free-energy expansion are discussed, using CexLa1-xB6 as a typical example. The representative formula of the vector spherical harmonics are summarized, which are suitable basis for vector fields in the spherical expansion.
Magnetic Cusp Configuration of the SPL Plasma Generator
Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier
2011-09-26
The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.
Low-frequency turbulence in a linear magnetized plasma.
Rogers, B N; Ricci, Paolo
2010-06-01
Plasma turbulence in a linear device is explored for the first time with three-dimensional global two-fluid simulations, focusing on the plasma parameters of the Large Plasma Device. Three instabilities are present in the simulations: the Kelvin-Helmholtz instability, a sheath-driven instability, and a resistive drift wave instability. The Kelvin-Helmholtz mode is shown to dominate the transport of plasma across the magnetic field. Simple scaling laws are obtained for the plasma profiles. PMID:20867177
Simple loss scaling laws for quadrupoles and higher-order multipoles used in antihydrogen traps
Fajans, J.; Bertsche, W.; Burke, K.; Deutsch, A.; Chapman, S. F.; Gomberoff, K.; Wurtele, J. S.; Werf, D. P. van der
2006-10-18
Simple scaling laws strongly suggest that for antihydrogen relevant parameters, quadrupole magnetic fields will transport particles into, or near to, the trap walls. Consequently quadrupoles are a poor choice for antihydrogen trapping. Higher order multipoles lead to much less transport.
The multipole resonance probe: characterization of a prototype
NASA Astrophysics Data System (ADS)
Lapke, Martin; Oberrath, Jens; Schulz, Christian; Storch, Robert; Styrnoll, Tim; Zietz, Christian; Awakowicz, Peter; Brinkmann, Ralf Peter; Musch, Thomas; Mussenbrock, Thomas; Rolfes, Ilona
2011-08-01
The multipole resonance probe (MRP) was recently proposed as an economical and industry compatible plasma diagnostic device (Lapke et al 2008 Appl. Phys. Lett. 93 051502). This communication reports the experimental characterization of a first MRP prototype in an inductively coupled argon/nitrogen plasma at 10 Pa. The behavior of the device follows the predictions of both an analytical model and a numerical simulation. The obtained electron densities are in excellent agreement with the results of Langmuir probe measurements.
The Physics of Ion Decoupling in Magnetized Plasma Explosions
Hewett, D; Larson, D; Brecht, S
2011-02-08
When a finite pulse of plasma expands into a magnetized background plasma, MHD predicts the pulse expel background plasma and its B-field - i.e. cause a magnetic 'bubble'. The expanding plasma is confined within the bubble, later to escape down the B-field lines. MHD suggests that the debris energy goes to expelling the B-field from the bubble volume and kinetic energy of the displaced background. For HANEs, this is far from the complete story. For many realistic HANE regimes, the long mean-free-path for collisions necessitates a Kinetic Ion Simulation Model (KISM). The most obvious effect is that the debris plasma can decouple and slip through the background plasma. The implications are: (1) the magnetic bubble is not as large as expected and (2) the debris is no longer confined within the magnetic bubble.
A Guide to Electronic Multipoles in Photon Scattering and Absorption
NASA Astrophysics Data System (ADS)
Lovesey, Stephen William; Balcar, Ewald
2013-02-01
The practice of replacing matrix elements in atomic calculations by those of convenient operators with strong physical appeal has a long history, and in condensed matter physics it is perhaps best known through use of operator equivalents in electron resonance by Elliott and Stevens. Likewise, electronic multipoles, created with irreducible spherical-tensors, to represent charge-like and magnetic-like quantities are widespread in modern physics. Examples in recent headlines include a magnetic charge (a monopole), an anapole (a dipole) and a triakontadipole (a magnetic-like atomic multipole of rank 5). In this communication, we aim to guide the reader through use of atomic, spherical multipoles in photon scattering, and resonant Bragg diffraction and dichroic signals in particular. Applications to copper oxide CuO and neptunium dioxide (NpO2) are described. In keeping with it being a simple guide, there is sparse use in the communication of algebra and expressions are gathered from the published literature and not derived, even when central to the exposition. An exception is a thorough grounding, contained in an Appendix, for an appropriate version of the photon scattering length based on quantum electrodynamics. A theme of the guide is application of symmetry in scattering, in particular constraints imposed on results by symmetry in crystals. To this end, a second Appendix catalogues constraints on multipoles imposed by symmetry in crystal point-groups.
Theory of electromagnetic fluctuations for magnetized multi-species plasmas
Navarro, Roberto E. Muñoz, Víctor; Araneda, Jaime; Moya, Pablo S.; Viñas, Adolfo F.; Valdivia, Juan A.
2014-09-15
Analysis of electromagnetic fluctuations in plasma provides relevant information about the plasma state and its macroscopic properties. In particular, the solar wind persistently sustains a small but detectable level of magnetic fluctuation power even near thermal equilibrium. These fluctuations may be related to spontaneous electromagnetic fluctuations arising from the discreteness of charged particles. Here, we derive general expressions for the plasma fluctuations in a multi-species plasma following arbitrary distribution functions. This formalism, which generalizes and includes previous works on the subject, is then applied to the generation of electromagnetic fluctuations propagating along a background magnetic field in a plasma of two proton populations described by drifting bi-Maxwellians.
Laboratory Studies of Supersonic Magnetized Plasma Jets and Radiative Shocks
NASA Astrophysics Data System (ADS)
Lebedev, Sergey
2013-06-01
In this talk I will focus on laboratory plasma experiments producing magnetically driven supersonic plasma jets and on the interaction of these jets with ambient media. The experiments are scalable to astrophysical flows in that the critical dimensionless numbers such as the plasma collisionality, the plasma beta, the Reynolds number and the magnetic Reynolds number are all in the astrophysically appropriate ranges. The experimental results will be compared with computer simulations performed with laboratory plasma codes and with astrophysical codes. In the experiments the jets are driven and collimated by the toroidal magnetic fields and it is found that the level of MHD instabilities in the jets strongly depends on the strength of the field represented by the ratio of the thermal to magnetic field pressures (plasma beta). The experiments show the possibility of formation of episodic outflows, with periodic ejections of magnetic bubbles naturally evolving into a heterogeneous jet propagating inside a channel made of self-collimated magnetic cavities [1,2]. We also found that it is possible to form quasi-laminar jets which are “indirectly” collimated by the toroidal magnetic fields, but this requires the presence of the lower density halo plasma surrounding the central jet [3]. Studies of the radiative shocks formed in the interaction of the supersonic magnetized plasma flows with ambient plasma will be also presented, and the development of cooling instabilities in the post-shock plasma will be discussed. This research was sponsored by EPSRC Grant No. EP/G001324/1 and by the OFES DOE under DOE Cooperative Agreement No. DE-SC-0001063. References 1. A. Ciardi, S.V. Lebedev, A. Frank et al., The Astrophysical Journal, 691: L147-L150 (2009) 2. F.A. Suzuki-Vidal, S.V. Lebedev, S.N. Bland et al., Physics of Plasmas, 17, 112708 (2010). 3. F.A. Suzuki-Vidal, M. Bocchi, S.V. Lebedev et al., Physics of Plasmas, 19, 022708 (2012).
Dual-function magnetic structure for toroidal plasma devices
Brown, Robert L.
1978-01-01
This invention relates to a support system wherein the iron core and yoke of the plasma current system of a tokamak plasma containment device is redesigned to support the forces of the magnet coils. The containment rings, which occupy very valuable space around the magnet coils, are utilized to serve as yokes for the core such that the conventional yoke is eliminated. The overall result is an improved aspect ratio, reduction in structure, smaller overall size, and improved access to the plasma ring.
Photonic Weyl degeneracies in magnetized plasma.
Gao, Wenlong; Yang, Biao; Lawrence, Mark; Fang, Fengzhou; Béri, Benjamin; Zhang, Shuang
2016-01-01
Weyl particles are elusive relativistic fermionic particles with vanishing mass. While not having been found as an elementary particle, they are found to emerge in solid-state materials where three-dimensional bands develop a topologically protected point-like crossing, a so-called Weyl point. Photonic Weyl points have been recently realised in three-dimensional photonic crystals with complex structures. Here we report the presence of a novel type of plasmonic Weyl points in a naturally existing medium-magnetized plasma, in which Weyl points arise as crossings between purely longitudinal plasma modes and transverse helical propagating modes. These photonic Weyl points are right at the critical transition between a Weyl point with the traditional closed finite equifrequency surfaces and the newly proposed 'type II' Weyl points with open equifrequency surfaces. Striking observable features of plasmon Weyl points include a half k-plane chirality manifested in electromagnetic reflection. Our study introduces Weyl physics into homogeneous photonic media, which could pave way for realizing new topological photonic devices. PMID:27506514
Photonic Weyl degeneracies in magnetized plasma
NASA Astrophysics Data System (ADS)
Gao, Wenlong; Yang, Biao; Lawrence, Mark; Fang, Fengzhou; Béri, Benjamin; Zhang, Shuang
2016-08-01
Weyl particles are elusive relativistic fermionic particles with vanishing mass. While not having been found as an elementary particle, they are found to emerge in solid-state materials where three-dimensional bands develop a topologically protected point-like crossing, a so-called Weyl point. Photonic Weyl points have been recently realised in three-dimensional photonic crystals with complex structures. Here we report the presence of a novel type of plasmonic Weyl points in a naturally existing medium--magnetized plasma, in which Weyl points arise as crossings between purely longitudinal plasma modes and transverse helical propagating modes. These photonic Weyl points are right at the critical transition between a Weyl point with the traditional closed finite equifrequency surfaces and the newly proposed `type II' Weyl points with open equifrequency surfaces. Striking observable features of plasmon Weyl points include a half k-plane chirality manifested in electromagnetic reflection. Our study introduces Weyl physics into homogeneous photonic media, which could pave way for realizing new topological photonic devices.
Photonic Weyl degeneracies in magnetized plasma
Gao, Wenlong; Yang, Biao; Lawrence, Mark; Fang, Fengzhou; Béri, Benjamin; Zhang, Shuang
2016-01-01
Weyl particles are elusive relativistic fermionic particles with vanishing mass. While not having been found as an elementary particle, they are found to emerge in solid-state materials where three-dimensional bands develop a topologically protected point-like crossing, a so-called Weyl point. Photonic Weyl points have been recently realised in three-dimensional photonic crystals with complex structures. Here we report the presence of a novel type of plasmonic Weyl points in a naturally existing medium—magnetized plasma, in which Weyl points arise as crossings between purely longitudinal plasma modes and transverse helical propagating modes. These photonic Weyl points are right at the critical transition between a Weyl point with the traditional closed finite equifrequency surfaces and the newly proposed ‘type II' Weyl points with open equifrequency surfaces. Striking observable features of plasmon Weyl points include a half k-plane chirality manifested in electromagnetic reflection. Our study introduces Weyl physics into homogeneous photonic media, which could pave way for realizing new topological photonic devices. PMID:27506514
Radiation reaction of multipole moments
Kazinski, P. O.
2007-08-15
A Poincare-invariant description is proposed for the effective dynamics of a localized system of charged particles in classical electrodynamics in terms of the intrinsic multipole moments of the system. A relativistic-invariant definition for the intrinsic multipole moments of a system of charged particles is given. A new generally covariant action functional for a relativistic perfect fluid is proposed. In the case of relativistic charged dust, it is proven that the description of the problem of radiation reaction of multipole moments by the model of particles is equivalent to the description of this problem by a hydrodynamic model. An effective model is obtained for a pointlike neutral system of charged particles that possesses an intrinsic dipole moment, and the free dynamics of this system is described. The bound momentum of a point dipole is found.
Radiation reaction of multipole moments
NASA Astrophysics Data System (ADS)
Kazinski, P. O.
2007-08-01
A Poincaré-invariant description is proposed for the effective dynamics of a localized system of charged particles in classical electrodynamics in terms of the intrinsic multipole moments of the system. A relativistic-invariant definition for the intrinsic multipole moments of a system of charged particles is given. A new generally covariant action functional for a relativistic perfect fluid is proposed. In the case of relativistic charged dust, it is proven that the description of the problem of radiation reaction of multipole moments by the model of particles is equivalent to the description of this problem by a hydrodynamic model. An effective model is obtained for a pointlike neutral system of charged particles that possesses an intrinsic dipole moment, and the free dynamics of this system is described. The bound momentum of a point dipole is found.
A plasma generator utilizing the high intensity ASTROMAG magnets
NASA Technical Reports Server (NTRS)
Sullivan, James D.; Post, R. S.; Lane, B. G.; Tarrh, J. M.
1986-01-01
The magnet configuration for the proposed particle astrophysics magnet facility (ASTROMAG) on the space station includes a cusp magnetic field with an intensity of a few tesla. With these large magnets (or others) located in the outer ionosphere, many quite interesting and unique plasma physics experiments become possible. First there are studies utilizing the magnet alone to examine the supersonic, sub-Alfvenic interaction with the ambient medium; the scale length for the magnet perturbation is approx. 20 m. The magnetic field geometry when combined with the Earth's and their relative motion will give rise to a host of plasma phenomena: ring nulls, x-points, ion-acoustic and lower-hybrid shocks, electron heating (possible shuttle glow without a surface) launching of Alfvenwaves, etc. Second, active experiments are possible for a controlled study of fundamental plasma phenomena. A controlled variable species plasma can be made by using an RF ion source; use of two soft iron rings placed about the line cusp would give an adequate resonance zone (ECH or ICH) and a confining volume suitable for gas efficiency. The emanating plasma can be used to study free expansion of plasma along and across field lines (polar wind), plasma flows around the space platform, turbulent mixing in the wake region, long wavelength spectrum of convecting modes, plasma-dust interactions, etc.
Initial Results from the Magnetized Dusty Plasma Experiment (MDPX)
NASA Astrophysics Data System (ADS)
Thomas, Edward; Konopka, Uwe; Lynch, Brian; Adams, Stephen; Leblanc, Spencer; Artis, Darrick; Dubois, Ami; Merlino, Robert; Rosenberg, Marlene
2014-10-01
The MDPX device is envisioned as a flexible, multi-user, research instrument that can perform a wide range of studies in fundamental and applied plasma physics. The MDPX device consists of two main components. The first is a four-coil, open bore, superconducting magnet system that is designed to produce uniform magnetic fields of up to 4 Tesla and non-uniform magnetic fields with gradients up to up to 2 T/m configurations. Within the warm bore of the magnet is placed an octagonal vacuum chamber that has a 46 cm outer diameter and is 22 cm tall. The primary missions of the MDPX device are to: (1) investigate the structural, thermal, charging, and collective properties of a plasma as the electrons, ions, and finally charged microparticles become magnetized; (2) study the evolution of a dusty plasma containing magnetic particles (paramagnetic, super-paramagnetic, or ferromagnetic particles) in the presence of uniform and non-uniform magnetic fields; and, (3) explore the fundamental properties of strongly magnetized plasmas (``i.e., dust-free'' plasmas). This presentation will summarize the initial characterization of the magnetic field structure, initial plasma parameter measurements, and the development of in-situ and optical diagnostics. This work is supported by funding from the NSF and the DOE.
Plasma membrane isolation using immobilized concanavalin A magnetic beads.
Lee, Yu-Chen; Srajer Gajdosik, Martina; Josic, Djuro; Lin, Sue-Hwa
2012-01-01
Isolation of highly purified plasma membranes is the key step in constructing the plasma membrane proteome. Traditional plasma membrane isolation method takes advantage of the differential density of organelles. While differential centrifugation methods are sufficient to enrich for plasma membranes, the procedure is lengthy and results in low recovery of the membrane fraction. Importantly, there is significant contamination of the plasma membranes with other organelles. The traditional agarose affinity matrix is suitable for isolating proteins but has limitation in separating organelles due to the density of agarose. Immobilization of affinity ligands to magnetic beads allows separation of affinity matrix from organelles through magnets and could be developed for the isolation of organelles. We have developed a simple method for isolating plasma membranes using lectin concanavalin A (ConA) magnetic beads. ConA is immobilized onto magnetic beads by binding biotinylated ConA to streptavidin magnetic beads. The ConA magnetic beads are used to bind glycosylated proteins present in the membranes. The bound membranes are solubilized from the magnetic beads with a detergent containing the competing sugar alpha methyl mannoside. In this study, we describe the procedure of isolating rat liver plasma membranes using sucrose density gradient centrifugation as described by Neville. We then further purify the membrane fraction by using ConA magnetic beads. After this purification step, main liver plasma membrane proteins, especially the highly glycosylated ones and proteins containing transmembrane domains could be identified by LC-ESI-MS/MS. While not described here, the magnetic bead method can also be used to isolate plasma membranes from cell lysates. This membrane purification method should expedite the cataloging of plasma membrane proteome.
Multipole expansion method for supernova neutrino oscillations
Duan, Huaiyu; Shalgar, Shashank E-mail: shashankshalgar@unm.edu
2014-10-01
We demonstrate a multipole expansion method to calculate collective neutrino oscillations in supernovae using the neutrino bulb model. We show that it is much more efficient to solve multi-angle neutrino oscillations in multipole basis than in angle basis. The multipole expansion method also provides interesting insights into multi-angle calculations that were accomplished previously in angle basis.
Solitary and shock waves in magnetized electron-positron plasma
Lu, Ding; Li, Zi-Liang; Abdukerim, Nuriman; Xie, Bai-Song
2014-02-15
An Ohm's law for electron-positron (EP) plasma is obtained. In the framework of EP magnetohydrodynamics, we investigate nonrelativistic nonlinear waves' solutions in a magnetized EP plasma. In the collisionless limit, quasistationary propagating solitary wave structures for the magnetic field and the plasma density are obtained. It is found that the wave amplitude increases with the Mach number and the Alfvén speed. However, the dependence on the plasma temperature is just the opposite. Moreover, for a cold EP plasma, the existence range of the solitary waves depends only on the Alfvén speed. For a hot EP plasma, the existence range depends on the Alfvén speed as well as the plasma temperature. In the presence of collision, the electromagnetic fields and the plasma density can appear as oscillatory shock structures because of the dissipation caused by the collisions. As the collision frequency increases, the oscillatory shock structure becomes more and more monotonic.
Model of the Dynamics of Plasma-Wave Channels in Magnetized Plasmas
NASA Astrophysics Data System (ADS)
Shirokov, E. A.; Chugunov, Yu. V.
2016-06-01
We analyze the dynamics of the plasma-wave channels excited in magnetized plasmas in the whistler frequency range. A linear theory of excitation of a plasma waveguide by an external source is developed using the quasistatic approximation. Self-consistent spatio-temporal distributions of the electric field of quasipotential waves and plasma density, which are solutions of the nonlinear nonstationary problem of the ionizing self-channeling of waves in plasmas are found on the basis of the linear theory.
HPAM: Hirshfeld partitioned atomic multipoles
NASA Astrophysics Data System (ADS)
Elking, Dennis M.; Perera, Lalith; Pedersen, Lee G.
2012-02-01
An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank l on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from l=0 (atomic charges) to l=4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank l are shown to exactly reproduce ab initio molecular multipole moments of rank L for L⩽l. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only ( l=0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used. Program summaryProgram title: HPAM Catalogue identifier: AEKP_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKP_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License v2 No. of lines in distributed program, including test data, etc.: 500 809 No. of bytes in distributed program, including test data, etc.: 13 424 494 Distribution format: tar.gz Programming language: C Computer: Any Operating system: Linux RAM: Typically, a few hundred megabytes Classification: 16.13 External routines: The program requires 'formatted checkpoint' files obtained from the Gaussian 03 or Gaussian 09 quantum chemistry program. Nature of problem: An ab initio
Internal dynamics of a plasma propelled across a magnetic field
NASA Technical Reports Server (NTRS)
Buneman, Oscar
1992-01-01
When a plasma is pushed across a magnetic field by some nonelectromagnetic force, ions and electrons get turned in opposite directions by the magnetic field. An exact analysis of that process is presented here for the internal region of the plasma. The energy provided by the initial push is used, in part, to create the electric field and in part to create some gyrations inside the plasma. When the rest energy density of the plasma exceeds twice the magnetic energy density (or when the Alfven speed is less than c), there will be enough energy to spare for the plasma to continue across the magnetic field at half its initial momentum. Two cases are considered: an impulsive start and a gentle push such as provided by gravity. The amplitude of the resulting internal gyrations becomes small in the second case. The frequencies of the gyrations are those of extraordinary modes of very long spatial wavelength.
Electromagnetic solitary pulses in a magnetized electron-positron plasma
Shukla, P. K.; Eliasson, B.; Stenflo, L.
2011-03-15
A theory for large amplitude compressional electromagnetic solitary pulses in a magnetized electron-positron (e-p) plasma is presented. The pulses, which propagate perpendicular to the external magnetic field, are associated with the compression of the plasma density and the wave magnetic field. Here the solitary wave magnetic field pressure provides the restoring force, while the inertia comes from the equal mass electrons and positrons. The solitary pulses are formed due to a balance between the compressional wave dispersion arising from the curl of the inertial forces in Faraday's law and the nonlinearities associated with the divergence of the electron and positron fluxes, the nonlinear Lorentz forces, the advection of the e-p fluids, and the nonlinear plasma current densities. The compressional solitary pulses can exist in a well-defined speed range above the Alfven speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas composed of electrons and positrons.
Multi-Scale Investigation of Sheared Flows In Magnetized Plasmas
Edward, Jr., Thomas
2014-09-19
Flows parallel and perpendicular to magnetic fields in a plasma are important phenomena in many areas of plasma science research. The presence of these spatially inhomogeneous flows is often associated with the stability of the plasma. In fusion plasmas, these sheared flows can be stabilizing while in space plasmas, these sheared flows can be destabilizing. Because of this, there is broad interest in understanding the coupling between plasma stability and plasma flows. This research project has engaged in a study of the plasma response to spatially inhomogeneous plasma flows using three different experimental devices: the Auburn Linear Experiment for Instability Studies (ALEXIS) and the Compact Toroidal Hybrid (CTH) stellarator devices at Auburn University, and the Space Plasma Simulation Chamber (SPSC) at the Naval Research Laboratory. This work has shown that there is a commonality of the plasma response to sheared flows across a wide range of plasma parameters and magnetic field geometries. The goal of this multi-device, multi-scale project is to understand how sheared flows established by the same underlying physical mechanisms lead to different plasma responses in fusion, laboratory, and space plasmas.
Neutron plasma propulsion - A precursor to magnetic fusion rocket
NASA Astrophysics Data System (ADS)
Watanabe, Yoichi; Parrish, Ted; Montalvo, Elena; Carrera, Rodolfo
1993-06-01
A novel advanced space propulsion concept, neutron plasma space propulsion (NPP), is proposed. The NPP system is an open cycle nuclear thermal type with a varying specific impulse (800-10 million sec). The NPP system uses a state-of-art magnetic confinement scheme for a hot plasma. The plasma is heated by high energy ions produced by thermal neutron-induced nuclear reactions. The low density plasma is confined in a magnetic bottle for a sufficiently long time period so that the plasma temperature may be high (10 eV to 1 keV). Thermal neutrons are provided by a nuclear fission reactor. A magnetic nozzle is used for the plasma exhaust.
Progress In Magnetized Target Fusion Driven by Plasma Liners
NASA Technical Reports Server (NTRS)
Thio, Francis Y. C.; Kirkpatrick, Ronald C.; Knapp, Charles E.; Cassibry, Jason; Eskridge, Richard; Lee, Michael; Smith, James; Martin, Adam; Wu, S. T.; Schmidt, George; Rodgers, Stephen L. (Technical Monitor)
2001-01-01
Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC).
Studies of Magnetic Reconnection in Colliding Laser-Produced Plasmas
NASA Astrophysics Data System (ADS)
Rosenberg, Michael
2013-10-01
Novel images of magnetic fields and measurements of electron and ion temperatures have been obtained in the magnetic reconnection region of high- β, laser-produced plasmas. Experiments using laser-irradiated foils produce expanding, hemispherical plasma plumes carrying MG Biermann-battery magnetic fields, which can be driven to interact and reconnect. Thomson-scattering measurements of electron and ion temperatures in the interaction region of two colliding, magnetized plasmas show no thermal enhancement due to reconnection, as expected for β ~ 8 plasmas. Two different proton radiography techniques used to image the magnetic field structures show deformation, pileup, and annihilation of magnetic flux. High-resolution images reveal unambiguously reconnection-induced jets emerging from the interaction region and show instabilities in the expanding plasma plumes and supersonic, hydrodynamic jets due to the plasma collision. Quantitative magnetic flux data show that reconnection in experiments with asymmetry in the scale size, density, temperature, and plasma flow across the reconnection region occurs less efficiently than in similar, symmetric experiments. This result is attributed to disruption of the Hall mechanism mediating collisionless reconnection. The collision of plasmas carrying parallel magnetic fields has also been probed, illustrating the deformation of magnetic field structures in high-energy-density plasmas in the absence of reconnection. These experiments are particularly relevant to high- β reconnection environments, such as the magnetopause. This work was performed in collaboration with C. Li, F. Séguin, A. Zylstra, H. Rinderknecht, H. Sio, J. Frenje, and R. Petrasso (MIT), I. Igumenshchev, V. Glebov, C. Stoeckl, and D. Froula (LLE), J. Ross and R. Town (LLNL), W. Fox (UNH), and A. Nikroo (GA), and was supported in part by the NLUF, FSC/UR, U.S. DOE, LLNL, and LLE.
Spectral line intensity irreversibility in circulatory plasma magnetization processes
Qu, Z. Q.; Dun, G. T.
2012-01-23
Spectral line intensity variation is found to be irreversible in circulatory plasma magnetization process by experiments described in this paper, i.e., the curves illustrating spectral line photon fluxes irradiated from a light source immerged in a magnetic field by increasing the magnetic induction cannot be reproduced by decreasing the magnetic induction within the errors. There are two plasma magnetization patterns found. One shows that the intensities are greater at the same magnetic inductions during the magnetic induction decreasing process after the increasing, and the other gives the opposite effect. This reveals that the magneto-induced excitation and de-excitation process is irreversible like ferromagnetic magnetization. But the two irreversible processes are very different in many aspects stated in the text.
Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.
2015-09-03
Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.
Oblique Propagation of Ion Acoustic Solitons in Magnetized Superthermal Plasmas
NASA Astrophysics Data System (ADS)
Devanandhan, S.; Sreeraj, T.; Singh, S.; Lakhina, G. S.
2015-12-01
Small amplitude ion-acoustic solitons are studied in a magnetized plasma consisting of protons, doubly charged helium ions and superthermal electrons. The Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) is derived to examine the properties of ion acoustic solitary structures observed in space plasmas. Our model is applicable for weakly magnetized plasmas. The results will be applied to the satellite observations in the solar wind at 1 AU where magnetized ion acoustic waves with superthermal electrons can exist. The effects of superthermality, temperature and densities on these solitary structures will be discussed.
Relativistic nonlinear plasma waves in a magnetic field
NASA Technical Reports Server (NTRS)
Kennel, C. F.; Pellat, R.
1975-01-01
Five relativistic plane nonlinear waves were investigated: circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativistic Alfven waves, linearly polarized transverse waves propagating in zero magnetic field, and the relativistic analog of the extraordinary mode propagating at an arbitrary angle to the magnetic field. When the ions are driven relativistic, they behave like electrons, and the assumption of an 'electron-positron' plasma leads to equations which have the form of a one-dimensional potential well. The solutions indicate that a large-amplitude superluminous wave determines the average plasma properties.
Zhang Haifeng; Liu Shaobin; Kong Xiangkun
2012-12-15
In this paper, the properties of photonic band gaps and dispersion relations of one-dimensional magnetized plasma photonic crystals composed of dielectric and magnetized plasma layers with arbitrary magnetic declination are theoretically investigated for TM polarized wave based on transfer matrix method. As TM wave propagates in one-dimensional magnetized plasma photonic crystals, the electromagnetic wave can be divided into two modes due to the influence of Lorentz force. The equations for effective dielectric functions of such two modes are theoretically deduced, and the transfer matrix equation and dispersion relations for TM wave are calculated. The influences of relative dielectric constant, plasma collision frequency, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency on transmission, and dispersion relation are investigated, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that plasma collision frequency cannot change the locations of photonic band gaps for both modes, and also does not affect the reflection and transmission magnitudes. The characteristics of photonic band gaps for both modes can be obviously tuned by relative dielectric constant, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency, respectively. These results would provide theoretical instructions for designing filters, microcavities, and fibers, etc.
High Magnetic field generation for laser-plasma experiments
Pollock, B B; Froula, D H; Davis, P F; Ross, J S; Fulkerson, S; Bower, J; Satariano, J; Price, D; Glenzer, S H
2006-05-01
An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system suppling 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented.
Magnetized Target Fusion Propulsion: Plasma Injectors for MTF Guns
NASA Technical Reports Server (NTRS)
Griffin, Steven T.
2003-01-01
To achieve increased payload size and decreased trip time for interplanetary travel, a low mass, high specific impulse, high thrust propulsion system is required. This suggests the need for research into fusion as a source of power and high temperature plasma. The plasma would be deflected by magnetic fields to provide thrust. Magnetized Target Fusion (MTF) research consists of several related investigations into these topics. These include the orientation and timing of the plasma guns and the convergence and interface development of the "pusher" plasma. Computer simulations of the gun as it relates to plasma initiation and repeatability are under investigation. One of the items under development is the plasma injector. This is a surface breakdown driven plasma generator designed to function at very low pressures. The performance, operating conditions and limitations of these injectors need to be determined.
Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A.
2010-08-20
Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.
Understanding of Edge Plasmas in Magnetic Fusion Energy Devices
Rognlien, T
2004-11-01
A limited overview is given of the theoretical understanding of edge plasmas in fusion devices. This plasma occupies the thin region between the hot core plasma and material walls in magnetically confinement configurations. The region is often formed by a change in magnetic topology from close magnetic field lines (i.e., the core region) and open field lines that contact material surfaces (i.e., the scrape-off layer [SOL]), with the most common example being magnetically diverted tokamaks. The physics of this region is determined by the interaction of plasma with neutral gas in the presence of plasma turbulence, with impurity radiation being an important component. Recent advances in modeling strong, intermittent micro-turbulent edge-plasma transport is given, and the closely coupled self-consistent evolution of the edge-plasma profiles in tokamaks. In addition, selected new results are given for the characterization of edge-plasmas behavior in the areas of edge-pedestal relaxation and SOL transport via Edge-Localize Modes (ELMs), impurity formation including dust, and magnetic field-line stochasticity in tokamaks.
Improvement of uniformity in a weakly magnetized inductively coupled plasma
NASA Astrophysics Data System (ADS)
Lee, W. H.; Cheong, H. W.; Kim, J. W.; Whang, K. W.
2015-12-01
Magnetic fields are applied to inductively coupled plasma (ICP) to achieve high plasma densities using electromagnets. If the magnetic fields are set up such that the magnitude of magnetic flux density on the substrate decreases with both radial and axial distances from the substrate’s center (here after referred to as M-ICP-A), the plasma density increases by 237% compared with that for ICP although the non-uniformity of the plasma density for M-ICP-A (11.1%) is higher than that for ICP (10.9%). As the rate of decrease in the magnitude of magnetic flux density on the substrate increases both radially and axially, the non-uniformity in the plasma density increases further. The increase in the non-uniformity for M-ICP-A was confirmed to arise from the flute instability. To suppress the flute instability, we arranged the magnitude of magnetic flux density on the substrate to increase with increasing distance from the substrate center both radially and axially (here after referred to as M-ICP-V). In this configuration, plasma fluctuations were not observed, hence the plasma density non-uniformity was lowered to 8.1%, although the measured plasma density was higher than that for M-ICP-A. The oxide etch-rate non-uniformity in M-ICP-V (2.5%) was also lower than that for ICP (5.2%) or that for M-ICP-A (21.4%).
Counterstreaming magnetized plasmas. II. Perpendicular wave propagation
Tautz, R.C.; Schlickeiser, R.
2006-06-15
The properties of longitudinal and transverse oscillations in magnetized symmetric counterstreaming Maxwellian plasmas with equal thermal velocities for waves propagating perpendicular to the stream direction are investigated on the basis of Maxwell equations and the nonrelativistic Vlasov equation. With the constraint of vanishing particle flux in the stream direction, three distinct dispersion relations are known, which are the ordinary-wave mode, the Bernstein wave mode, and the extraordinary electromagnetic wave mode, where the latter two are only approximations. In this article, all three dispersion relations are evaluated for a counterstreaming Maxwellian distribution function in terms of the hypergeometric function {sub 2}F{sub 2}. The growth rates for the ordinary-wave mode are compared to earlier results by Bornatici and Lee [Phys. Fluids 13, 3007 (1970)], who derived approximate results, whereas in this article the exact dispersion relation is solved numerically. The original results are therefore improved and show differences of up to 21% to the results obtained in this article.
Studies of cryogenic electron plasmas in magnetic mirror fields
NASA Astrophysics Data System (ADS)
Gopalan, Ramesh
This thesis considers the properties of pure electron plasmas in Penning traps which have an axially varying magnetic field. Our theory of the thermal equilibrium of such plasmas in magnetic mirror fields indicates that their behavior may be characterized by the ratio of their temperature to their central density T/n. For cold, dense plasmas the density along the plasma axis scales linearly with the magnetic field, while for hot, tenuous plasmas, at the opposite limit of the parameter range, the density is constant along the axis, similar to the behavior of a neutral plasma in a magnetic mirror. We are able to conclude from this that the electrostatic potential varies along the field lines, in equilibrium. As the plasma charge and potential distribution must be consistent with the grounded potential on the trap walls, the plasma profile does not follow the geometry of the magnetic field lines; the plasma radius in the high-field region is smaller than would be obtained by mapping the field lines from the radial edge of the low-field region. Another interesting feature of these mirror equilibria is that there are trapped populations of particles both in the low-field and high-field regions. Our experiments on the Cryogenic Electron Trap have confirmed many of these theoretical results over a wide parameter range. We have been able to sample the volume charge density at various points on the axis. We have also measured the line-charge distribution of the plasma. Both these experiments are in general agreement with our theory of the global thermal equilibrium in the mirror- field. A surprising observation has been the unexpectedly long- life of the m = 1 diocotron mode in these traps where the magnetic field varies by ~100% across its length. We report these observations, along with plausible explanations for them. The trap we have constructed is intended for the eventual study of very cold electron plasmas in strong magnetic fields, where the plasma electrons are
Electron energy distributions in a magnetized inductively coupled plasma
Song, Sang-Heon E-mail: Sang-Heon.Song@us.tel.com; Yang, Yang; Kushner, Mark J.
2014-09-15
Optimizing and controlling electron energy distributions (EEDs) is a continuing goal in plasma materials processing as EEDs determine the rate coefficients for electron impact processes. There are many strategies to customize EEDs in low pressure inductively coupled plasmas (ICPs), for example, pulsing and choice of frequency, to produce the desired plasma properties. Recent experiments have shown that EEDs in low pressure ICPs can be manipulated through the use of static magnetic fields of sufficient magnitudes to magnetize the electrons and confine them to the electromagnetic skin depth. The EED is then a function of the local magnetic field as opposed to having non-local properties in the absence of the magnetic field. In this paper, EEDs in a magnetized inductively coupled plasma (mICP) sustained in Ar are discussed with results from a two-dimensional plasma hydrodynamics model. Results are compared with experimental measurements. We found that the character of the EED transitions from non-local to local with application of the static magnetic field. The reduction in cross-field mobility increases local electron heating in the skin depth and decreases the transport of these hot electrons to larger radii. The tail of the EED is therefore enhanced in the skin depth and depressed at large radii. Plasmas densities are non-monotonic with increasing pressure with the external magnetic field due to transitions between local and non-local kinetics.
Pattern Formation in a Complex Plasma in High Magnetic Fields
Schwabe, M.; Konopka, U.; Bandyopadhyay, P.; Morfill, G. E.
2011-05-27
Low-pressure room-temperature neon, argon, krypton, and air plasmas were studied in magnetic fields up to flux densities of 2.3 T. Filaments appeared parallel to the magnetic field lines, and patterns such as spirals and concentric circles formed in the perpendicular direction. We link these effects to the magnetization of the ions. We also used a layer of embedded microparticles as probes in the plasma. Their motion changed dramatically from a collective rotation of the whole ensemble in moderate magnetic fields to a rotation in several small vortices centered at the filaments.
Design and Fabrication of a Magnetic System to Investigate Magnetized Dusty Plasmas
NASA Astrophysics Data System (ADS)
Bates, Evan M.; Romero-Talamas, Carlos A.
2013-10-01
The interest in researching the dynamics and equilibrium of magnetized dusty plasma crystallization has led to the design and fabrication of a novel experimental setup at UMBC. The proposed magnets will be an important subsystem of this setup, and will produce a uniform magnetic field of several tesla for a duration of several seconds. The magnets will be arranged in the Helmholtz configuration and will have a cooling system for temperature compensation of the coils, as well as the ability to adjust the orientation of the magnetic field with respect to gravity. Planned experiments include propagation of magnetized waves in dusty plasma crystals under various boundary conditions.
A solvable blob-model for magnetized plasmas
NASA Astrophysics Data System (ADS)
Pécseli, H. L.; Sortland, D. S.; Garcia, O. E.
2016-11-01
A simple analytically solvable model for blobs in magnetized plasmas is proposed. The model gives results for a scaling of the blob velocity and acceleration with varying plasma parameters. Limiting cases are considered: one where the plasma motion is strictly perpendicular to an externally imposed toroidal magnetic field, and one where the electrons can move along magnetic field lines to compensate partly the collective electric fields. For these limiting cases, the model predicts scaling laws for the dependence of the blob velocities and accelerations with varying plasma density, temperature and magnetic field strength. Also the scaling with the dominant ion mass is derived. The analysis is completed by including the effects of collisions between ions and neutrals.
Anomalous skin effects in a weakly magnetized degenerate electron plasma
Abbas, G. Sarfraz, M.; Shah, H. A.
2014-09-15
Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring the ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].
Surface electromagnetic wave equations in a warm magnetized quantum plasma
Li, Chunhua; Yang, Weihong; Wu, Zhengwei; Chu, Paul K.
2014-07-15
Based on the single-fluid plasma model, a theoretical investigation of surface electromagnetic waves in a warm quantum magnetized inhomogeneous plasma is presented. The surface electromagnetic waves are assumed to propagate on the plane between a vacuum and a warm quantum magnetized plasma. The quantum magnetohydrodynamic model includes quantum diffraction effect (Bohm potential), and quantum statistical pressure is used to derive the new dispersion relation of surface electromagnetic waves. And the general dispersion relation is analyzed in some special cases of interest. It is shown that surface plasma oscillations can be propagated due to quantum effects, and the propagation velocity is enhanced. Furthermore, the external magnetic field has a significant effect on surface wave's dispersion equation. Our work should be of a useful tool for investigating the physical characteristic of surface waves and physical properties of the bounded quantum plasmas.
Anomalous skin effects in a weakly magnetized degenerate electron plasma
NASA Astrophysics Data System (ADS)
Abbas, G.; Sarfraz, M.; Shah, H. A.
2014-09-01
Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring the ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].
Edge Plasma Structure with Rotating Resonant Magnetic Perturbations at TEXTOR
NASA Astrophysics Data System (ADS)
Stoschus, H.; Schmitz, O.; Frerichs, H.; Lehnen, M.; Reiser, D.; Unterberg, B.; Samm, U.; Textor Research Team
2011-10-01
Rotating Resonant Magnetic Perturbations impose a characteristic modulation to the electron density and temperature in the TEXTOR plasma edge (r / a > 0 . 9). The modulation matches the position of the magnetic topology modeled in vacuum approximation for low relative rotation of frel = - 0 . 2 kHz between RMP field and toroidal plasma rotation. With increasing relative rotation (frel = 1 . 8 kHz), the plasma structure at the outermost rational flux surface is shifted by π / 2 in counter-Bt direction due to internal plasma response. The shift is correlated to a smaller displacement of the plasma structure in front of the RMP coils of 0 . 1 π . This indicates a competition between the near-field of the RMP coils and the net magnetic field at the rational flux surface. Work supported in part by US DOE under DE-AC05-06OR23100.
NASA Astrophysics Data System (ADS)
Lyatsky, Wladislaw; Pollock, Craig; Goldstein, Melvyn L.; Lyatskaya, Sonya; Avanov, Levon
2016-08-01
In this paper, we examined plasma structures (filaments), observed in the dayside magnetosphere but containing magnetosheath plasma. These filaments show the stable antisunward motion (while the ambient magnetospheric plasma moved in the opposite direction) and the existence of a strip of magnetospheric plasma, separating these filaments from the magnetosheath. These results, however, contradict both theoretical studies and simulations by Schindler (1979), Ma et al. (1991), Dai and Woodward (1994, 1998), and other researchers, who reported that the motion of such filaments through the magnetosphere is possible only when their magnetic field is directed very close to the ambient magnetic field, which is not the situation that is observed. In this study, we show that this seeming contradiction may be related to different events as the theoretical studies and simulations are related to the case when the filament magnetic field is about aligned with filament orientation, whereas the observations show that the magnetic field in these filaments may be rotating. In this case, the rotating magnetic field, changing incessantly its direction, drastically affects the penetration of plasma filaments into the magnetosphere. In this case, the filaments with rotating magnetic field, even if in each moment it is significantly inclined to the ambient magnetic field, may propagate through the magnetosphere, if their average (for the rotation period) magnetic field is aligned with the ambient magnetic field. This shows that neglecting the rotation of magnetic field in these filaments may lead to wrong results.
Magnetic Bubble Expansion Experimental Investigation Using a Compact Coaxial Magnetized Plasma Gun
NASA Astrophysics Data System (ADS)
Zhang, Yue; Lynn, Alan; Hsu, Scott; Li, Hui; Liu, Wei; Gilmore, Mark; Watts, Christopher
2009-11-01
The poster will first discuss the construction and improved design of a compact coaxial magnetized plasma gun. The plasma gun is used for experimental studies of magnetic bubble expansion into a lower pressure background plasma, which as a model for extragalactic radio lobes and solar coronal mass ejections. In this experiment, the plasma bubble's density, electron temperature, and propagation speed are measured by using a multiple-tipped langmuir probe. Also a three axis B-dot probe array is used to measure the magnetic field in three dimensions during the expansion process. In this poster experiment setup and data will be provided. Finally the comparison with the simulation result will be made.
Screened Coulomb potential in a flowing magnetized plasma
NASA Astrophysics Data System (ADS)
Joost, J.-P.; Ludwig, P.; Kählert, H.; Arran, C.; Bonitz, M.
2015-02-01
The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is computed using linear response theory, thereby extending our previous work for unmagnetized plasmas (Ludwig et al 2012 New J. Phys. 14 053016). In addition to the magnetic field, our approach accounts for a finite ion temperature as well as ion-neutral collisions. Our recently introduced code Kielstream is used for an efficient calculation of the dust potential. Increasing the magnetization of the ions, we find that the shape of the potential crucially depends on the Mach number M. In the regime of subsonic ion flow (M < 1), a strong magnetization gives rise to a potential distribution that is qualitatively different from the unmagnetized limit, while for M > 1 the magnetic field effectively suppresses the plasma wakefield.
MAGNETIC END CLOSURES FOR PLASMA CONFINING AND HEATING DEVICES
Post, R.F.
1963-08-20
More effective magnetic closure field regions for various open-ended containment magnetic fields used in fusion reactor devices are provided by several spaced, coaxially-aligned solenoids utilized to produce a series of nodal field regions of uniform or, preferably, of incrementally increasing intensity separated by lower intensity regions outwardly from the ends of said containment zone. Plasma sources may also be provided to inject plasma into said lower intensity areas to increase plasma density therein. Plasma may then be transported, by plasma diffusion mechanisms provided by the nodal fields, into the containment field. With correlated plasma densities and nodal field spacings approximating the mean free partl cle collision path length in the zones between the nodal fields, optimum closure effectiveness is obtained. (AEC)
Simulating Magnetized Laboratory Plasmas with Smoothed Particle Hydrodynamics
Johnson, Jeffrey N.
2009-01-01
The creation of plasmas in the laboratory continues to generate excitement in the physics community. Despite the best efforts of the intrepid plasma diagnostics community, the dynamics of these plasmas remains a difficult challenge to both the theorist and the experimentalist. This dissertation describes the simulation of strongly magnetized laboratory plasmas with Smoothed Particle Hydrodynamics (SPH), a method born of astrophysics but gaining broad support in the engineering community. We describe the mathematical formulation that best characterizes a strongly magnetized plasma under our circumstances of interest, and we review the SPH method and its application to astrophysical plasmas based on research by Phillips [1], Buerve [2], and Price and Monaghan [3]. Some modifications and extensions to this method are necessary to simulate terrestrial plasmas, such as a treatment of magnetic diffusion based on work by Brookshaw [4] and by Atluri [5]; we describe these changes as we turn our attention toward laboratory experiments. Test problems that verify the method are provided throughout the discussion. Finally, we apply our method to the compression of a magnetized plasma performed by the Compact Toroid Injection eXperiment (CTIX) [6] and show that the experimental results support our computed predictions.
Polarization evolution of radiation in hot magnetized plasma with dissipation
NASA Astrophysics Data System (ADS)
Segre, S. E.; Zanza, V.
2005-06-01
A formalism is presented for the analysis of polarization evolution in a magnetized plasma with dissipation due to kinetic effects. Such a plasma in addition to the Faraday and Cotton-Mouton effects also presents dichroism, namely anisotropic absorption. As expected this effect is significant near the cyclotron harmonics.
Polarization evolution of radiation in hot magnetized plasma with dissipation
Segre, S.E.; Zanza, V.
2005-06-15
A formalism is presented for the analysis of polarization evolution in a magnetized plasma with dissipation due to kinetic effects. Such a plasma in addition to the Faraday and Cotton-Mouton effects also presents dichroism, namely anisotropic absorption. As expected this effect is significant near the cyclotron harmonics.
US/Russian Magnetized Target Fusion Plasma Formation Experiments
NASA Astrophysics Data System (ADS)
Benage, John F., Jr.; Mtf Team; Broste, W.; Westley, D.; Mago Team
1998-11-01
Magnetized target fusion (MTF) is a potentially very low cost route to producing a fusion energy source. Many of MTF's plasma properties are intermediate between magnetically confined fusion (MFE) and inertially confined fusion (ICF). MTF consists of first producing a magnetically thermally insulated target plasma with a temperature of 100 eV or more with a lifetime of 5-10 microseconds. The target plasma is then compressed to fusion conditions by a magnetically driven imploding liner. One target plasma candidate is VNIIEF's MAGO, in which a cylindrical chamber with two cavities is filled with DT gas at a pressure of 10 Torr and driven by a current of 2-8 MA. A series of experiments under different plasma conditions have been performed to evaluate MAGO as an MTF target plasma. Diagnostics used to characterize the MAGO plasma include B dot probes to measure the current distribution, filtered silicon diodes to measure the spectrum and duration of the plasma radiation and a UV spectrometer to measure impurity line radiation.
Recent results from CHAMP plasma parameter and magnetic field observations
NASA Astrophysics Data System (ADS)
Stolle, Claudia; Luehr, Hermann; Park, Jaeheung; Xiong, Chao; Fejer, B. G.
The multi-year data base of magnetic field and ionospheric measurements from the CHAMP satellite contains an enormous potential to investigate the behaviour and the origin of currents in the F region. Very prominent phenomena are the post-sunset equatorial plasma irregularities (commonly known as "bubbles", or "Equatorial Spread-F" (ESF)) which cause also signatures in the total magnetic field due to diamagnetic currents. The continuous magnetic observations, available at a 1Hz rate, have allowed for the compilation of a comprehensive climatology of the magnetic signatures due to ESF. It reveals a distinct seasonal/longitudinal (S/L) distribution, and the occurrence rate reduces considerably with decreasing solar flux. The (S/L) distribution of bubbles has been found to correlate very well, up to 90 percent, with the pre-reversal enhancement vertical plasma drift peak. This provides strong evidence for the close relation between these phenomena. Since the amplitude of the diamagnetic effect depends on the ambient magnetic field strength and on the background electron density, the global distribution shows also slight differences to the ESF climatology based on plasma depletions. Although electron density readings are only available every 15s, CHAMP data suggest that the plasma irregularities are less structured at places where the ambient magnetic field is strong (e.g. East Asia, Indonesia). In these regions the bubble statistic based on magnetic signatures is systematically lower than that from plasma measurements.
Plasma expansion in the presence of a dipole magnetic field
Winske, D.; Omidi, N.
2005-07-15
Simulations of the initial expansion of a plasma injected into a stationary magnetized background plasma in the presence of a dipole magnetic field are carried out in two dimensions with a kinetic ion, massless fluid electron (hybrid) electromagnetic code. For small values of the magnetic dipole, the injected ions have large gyroradii compared to the scale length of the dipole field and are essentially unmagnetized. As a result, these ions expand, excluding the ambient magnetic field and plasma to form a diamagnetic cavity. However, for stronger magnetic dipoles, the ratio of the gyroradii of the injected ions to the dipole field scale length is small so that they remain magnetized, and hence trapped in the dipole field, as they expand. The trapping and expansion then lead to additional plasma currents and resulting magnetic fields that not only exclude the background field but also interact with the dipole field in a more complex manner that stretches the closed dipole field lines. A criterion to distinguish between the two regimes is derived and is then briefly discussed in the context of applying the results to the plasma sail scheme for the propulsion of small spacecraft in the solar wind.
Ablation plasma transport using multicusp magnetic field for laser ion source
NASA Astrophysics Data System (ADS)
Takahashi, K.; Umezawa, M.; Uchino, T.; Ikegami, K.; Sasaki, T.; Kikuchi, T.; Harada, N.
2016-05-01
We propose a plasma guiding method using multicusp magnetic field to transport the ablation plasma keeping the density for developing laser ion sources. To investigate the effect of guiding using the magnetic field on the ablation plasma, we demonstrated the transport of the laser ablation plasma in the multicusp magnetic field. The magnetic field was formed with eight permanent magnets and arranged to limit the plasma expansion in the radial direction. We investigated the variation of the plasma ion current density and charge distribution during transport in the magnetic field. The results indicate that the plasma is confined in the radial direction during the transport in the multicusp magnetic field.
Preliminary Experimental Result of Magnetic Reconnection in Laboratory Plasma
NASA Astrophysics Data System (ADS)
Zhang, S. B.; Xie, J. L.; Hu, G. H.; Li, H.; Huang, G. L.; Liu, W. D.
2011-05-01
Magnetic reconnection is one of the most important physical processes in astrophysical plasmas. Lots of theoretical works, numerical simulations and observations have been done. Some experimental programs have been activated to investigate the basic mechanisms of magnetic reconnection. In order to investigate the electron dynamic near the electron diffusion region in magnetic reconnection process, an upgrade is accomplished in the LMP (Linear magnetic plasmas) device at University of Science and Technology of China. The magnetic field of reconnection is produced by passing two identical currents axially through two copper plates. Magnetic field and parallel electric field are measured by magnetic probes and emissive probes, respectively. The existence of a large electric field related to the reconnection process is verified. The plasma is driven by electric field and magnetic field, so the magnetic reconnection appears. The magnitude of axial current is found to scale with the number of passing particles. In the configuration of current bars, passing particles are even more and our measured axial current is about 10 A. Magnetic flux doesn't pile up because of the parameter region in our case, which is consistent with the result of numerical simulation.
Strongly Driven Magnetic Reconnection in a Magnetized High-Energy-Density Plasma
NASA Astrophysics Data System (ADS)
Fiksel, G.; Barnak, D. H.; Chang, P.-Y.; Haberberger, D.; Hu, S. X.; Ivancic, S.; Nilson, P. M.; Fox, W.; Deng, W.; Bhattacharjee, A.; Germaschewski, K.
2014-10-01
Magnetic reconnection in a magnetized high-energy-density plasma is characterized by measuring the dynamics of the plasma density and magnetic field between two counter-propagating and colliding plasma flows. The density and magnetic field were profiled using the 4 ω angular filter refractometry and fast proton deflectometry diagnostics, respectively. The plasma flows are created by irradiating oppositely placed plastic targets with 1.8-kJ, 2-ns laser beams on the OMEGA EP Laser System. The two plumes are magnetized by an externally controlled magnetic field with an x-type null point geometry with B = 0 at the midplane and B = 8 T at the targets. The interaction region is pre-filled with a low-density background plasma. The counterflowing super-Alfvénic plasma plumes sweep up and compress the magnetic field and the background plasma into a pair of magnetized ribbons, which collide, stagnate, and reconnect at the midplane, allowing for the first detailed observation of a stretched current sheet in laser-driven reconnection experiments. The measurements are in good agreement with first-principles particle-in-cell simulations. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and NLUF Grant DE-SC0008655.
Simultaneous Excitation and Analysis of Three Instabilities in Magnetized Plasma
Dimitriu, D. G.; Ionita, C.; Schrittwieser, R. W.
2008-03-19
Experimental results are presented on the simultaneous excitation of three low-frequency instabilities in the magnetized plasma column of a Q-machine, namely the potential relaxation instability, the electrostatic ion-cyclotron instability and the Kelvin-Helmholtz instability. The influence of the magnetic field intensity on the appearance of these instabilities was investigated.
Nonlinear dynamics of large amplitude modes in a magnetized plasma
Brodin, G.; Stenflo, L.
2014-12-15
We derive two equations describing the coupling between electromagnetic and electrostatic oscillations in one-dimensional geometry in a magnetized cold and non-relativistic plasma. The nonlinear interaction between the wave modes is studied numerically. The effects of the external magnetic field strength and the initial electromagnetic polarization are of particular interest here. New results can, thus, be identified.
Dust-Plasma Sheath in an Oblique Magnetic Field
Foroutan, G.; Mehdipour, H.
2008-09-07
Using numerical simulations of the multi fluid equations the structure of the magnetized sheath near a plasma boundary is studied in the presence of charged dust particles. The dependence of the electron, ion, and dust densities as well as the electrostatic potential, dust charge, and ion normal velocity, on the magnetic field strength and the edge dust number density is investigated.
The influence of magnetic field on electron beam generated plasmas
NASA Astrophysics Data System (ADS)
Petrov, G. M.; Boris, D. R.; Lock, E. H.; Petrova, Tz B.; Fernsler, R. F.; Walton, S. G.
2015-06-01
Magnetically confined argon plasma in a long cylindrical tube driven by an electron beam is studied experimentally and theoretically. Langmuir probes are used to measure the electron energy distribution function, electron density and temperature in plasmas generated by 2 keV, 10 mA electron beams in a 25 mTorr argon background for magnetic field strengths of up to 200 Gauss. The experimental results agree with simulations done using a spatially averaged Boltzmann model adapted to treat an electron beam generated plasma immersed in a constant magnetic field. The confining effect of the magnetic field is studied theoretically using fluid and kinetic approaches. The fluid approach leads to two regimes of operation: weakly and strongly magnetized. The former is similar to the magnetic field-free case, while in the latter the ambipolar diffusion coefficient and electron density depend quadratically on the magnetic field strength. Finally, a more rigorous kinetic treatment, which accounts for the impact of the magnetic field over the whole distribution of electrons, is used for accurate description of the plasma.
Generation of magnetic fields by a gravitomagnetic plasma battery
NASA Astrophysics Data System (ADS)
Khanna, Ramon
1998-03-01
The generation of magnetic fields by a battery, operating in an ion-electron plasma around a Kerr black hole, is studied in the 3 + 1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms can less easily be quenched than the classical ones. In axisymmetry the battery can induce only toroidal magnetic fields. Once a toroidal magnetic field is present, however, the coupling of gravitomagnetic and electromagnetic fields generates a poloidal magnetic field even in axisymmetry. A rotating black hole, embedded in plasma, will therefore always generate toroidal and poloidal magnetic fields.
Chirality-induced negative refraction in magnetized plasma
Guo, B.
2013-09-15
Characteristic equations in magnetized plasma with chirality are derived in simple formulations and the dispersion relations for propagation parallel and perpendicular to the external magnetic field are studied in detail. With the help of the dispersion relations of each eigenwave, the author explores chirality-induced negative refraction in magnetized plasma and investigates the effects of parameters (i.e., chirality degree, external magnetic field, etc.) on the negative refraction. The results show that the chirality is the necessary and only one factor which leads to negative refraction without manipulating electrical permittivity and magnetic permeability. Both increasing the degree of chirality and reducing the external magnetic field can result in greater range negative refraction. Parameter dependence of the effects is calculated and discussed.
Propagation of intense laser pulses in strongly magnetized plasmas
Yang, X. H. Ge, Z. Y.; Xu, B. B.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q.; Yu, W.; Xu, H.; Yu, M. Y.; Borghesi, M.
2015-06-01
Propagation of intense circularly polarized laser pulses in strongly magnetized inhomogeneous plasmas is investigated. It is shown that a left-hand circularly polarized laser pulse propagating up the density gradient of the plasma along the magnetic field is reflected at the left-cutoff density. However, a right-hand circularly polarized laser can penetrate up the density gradient deep into the plasma without cutoff or resonance and turbulently heat the electrons trapped in its wake. Results from particle-in-cell simulations are in good agreement with that from the theory.
NASA Astrophysics Data System (ADS)
Yagi, Kent
2014-02-01
Gravitational-wave observations in the near future may allow us to measure tidal deformabilities of neutron stars, which leads us to the understanding of physics at nuclear density. In principle, the gravitational waveform depends on various tidal parameters, which correlate strongly. Therefore, it would be useful if one can express such tidal parameters with a single parameter. Here, we report on universal relations among various ℓth (dimensionless) electric, magnetic, and shape tidal deformabilities in neutron stars and quark stars that do not depend sensitively on the equation of state. Such relations allow us to break the degeneracy among the tidal parameters. In this paper, we focus on gravitational waves from nonspinning neutron-star binary inspirals. We first derive the leading contribution of the ℓth electric and ℓ=2 magnetic tidal deformabilities to the gravitational-wave phase, which enters at 2ℓ+1 and 6 post-Newtonian orders relative to the leading Newtonian one, respectively. We then calculate the useful number of gravitational-wave cycles and show that not only the ℓ=2 but also ℓ=3 electric tidal deformabilities are important for parameter estimation with third-generation gravitational-wave detectors such as LIGO III and Einstein Telescope. Although the correlation between the ℓ=2 and ℓ=3 electric tidal deformabilities deteriorate the measurement accuracy of the former deformability parameter, one can increase its measurement accuracy significantly by using the universal relation. We provide a fitting formula for the LIGO III noise curve in the appendixes.
Observations of Magnetic Reconnection and Plasma Dynamics in Mercury's Magnetosphere
NASA Astrophysics Data System (ADS)
DiBraccio, Gina A.
Mercury's magnetosphere is formed as a result of the supersonic solar wind interacting with the planet's intrinsic magnetic field. The combination of the weak planetary dipole moment and intense solar wind forcing of the inner heliosphere creates a unique space environment, which can teach us about planetary magnetospheres. In this work, we analyze the first in situ orbital observations at Mercury, provided by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Magnetic reconnection and the transport of plasma and magnetic flux are investigated using MESSENGER Magnetometer and Fast Imaging Plasma Spectrometer measurements. Here, we report our results on the effect of magnetic reconnection and plasma dynamics on Mercury's space environment: (1) Mercury's magnetosphere is driven by frequent, intense magnetic reconnection observed in the form of magnetic field components normal to the magnetopause, BN, and as helical bundles of flux, called magnetic flux ropes, in the cross-tail current sheet. The high reconnection rates are determined to be a direct consequence of the low plasma beta, the ratio of plasma to magnetic pressure, in the inner heliosphere. (2) As upstream solar wind conditions vary, we find that reconnection occurs at Mercury's magnetopause for all orientations of the interplanetary magnetic field, independent of shear angle. During the most extreme solar wind forcing events, the influence of induction fields generated within Mercury's highly conducting core are negated by erosion due to persistent magnetopause reconnection. (3) We present the first observations of Mercury's plasma mantle, which forms as a result of magnetopause reconnection and allows solar wind plasma to enter into the high-latitude magnetotail through the dayside cusps. The energy dispersion observed in the plasma mantle protons is used to infer the cross-magnetosphere electric field, providing a direct measurement of solar wind momentum
Transport processes in magnetically confined plasmas
Callen, J.D.
1991-12-01
Intensified studies of plasma transport in toroidal plasmas over the past three to five years have progressed through increased understanding in some areas and changed perceptions about the most important issues in other areas. Recent developments are reviewed for six selected topics: edge fluctuations and transport; L-H mode transition; core fluctuations; modern plasma turbulence theory; transient transport; and global scaling. Some of the developments that are highlighted include: the role of a strongly sheared poloidal flow in edge plasma turbulence, transport and the L-H transition; change of focus from {kappa}{perpendicular}{rho}s {approximately} 1 to {kappa}{perpendicular}{rho}s {much_lt} 1 fluctuations in tokamak plasmas; modern Direct-Interaction-Approximation plasma turbulence and hybrid fluid/kinetic theoretical models; and transient transport experiments that are raising fundamental questions about our conceptions of local transport processes in tokamaks. 104 refs., 6 figs.
Transport processes in magnetically confined plasmas
Callen, J.D.
1991-12-01
Intensified studies of plasma transport in toroidal plasmas over the past three to five years have progressed through increased understanding in some areas and changed perceptions about the most important issues in other areas. Recent developments are reviewed for six selected topics: edge fluctuations and transport; L-H mode transition; core fluctuations; modern plasma turbulence theory; transient transport; and global scaling. Some of the developments that are highlighted include: the role of a strongly sheared poloidal flow in edge plasma turbulence, transport and the L-H transition; change of focus from {kappa}{perpendicular}{rho}s {approximately} 1 to {kappa}{perpendicular}{rho}s {much lt} 1 fluctuations in tokamak plasmas; modern Direct-Interaction-Approximation plasma turbulence and hybrid fluid/kinetic theoretical models; and transient transport experiments that are raising fundamental questions about our conceptions of local transport processes in tokamaks. 104 refs., 6 figs.
A hybrid simulation study of magnetic reconnection in anisotropic plasmas
NASA Astrophysics Data System (ADS)
Guo, Jun; Li, Yi; Lu, Quan-ming; Wang, Shui
2003-10-01
The process of magnetic reconnection in anisotropic plasmas is studied numerically using a 2-dimensional, 3-component hybrid simulation. The results of the calculation show that, when the plasma pressure in the direction perpendicular to magnetic field is larger than that in the parallel direction (e.g. P ⊥/P ‖ = 1.5 ), instability may greatly increase, speeding up the rate of reconnection. When P⊥ is smaller than P‖, (e.g., when P ⊥/P ‖ = 0.6 ), fire hose instability appears, which will restrain the tearing mode instability and the process of magnetic reconnection.
Relativistic nonlinear plasma waves in a magnetic field
NASA Technical Reports Server (NTRS)
Kennel, C. F.; Pellat, R.
1976-01-01
An investigation is conducted of five relativistic plane nonlinear waves, taking into account circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativistic Alfven waves, linearly polarized transverse waves propagating in zero magnetic field, and the relativistic analog of the extraordinary mode propagating at an arbitrary angle to the magnetic field. It is found that a large-amplitude superluminous wave determines the average plasma properties, and not vice versa. Attention is given to the implications of the obtained results for the acceleration of cosmic rays in pulsar magnetospheres.
Magnetic control of particle injection in plasma based accelerators.
Vieira, J; Martins, S F; Pathak, V B; Fonseca, R A; Mori, W B; Silva, L O
2011-06-01
The use of an external transverse magnetic field to trigger and to control electron self-injection in laser- and particle-beam driven wakefield accelerators is examined analytically and through full-scale particle-in-cell simulations. A magnetic field can relax the injection threshold and can be used to control main output beam features such as charge, energy, and transverse dynamics in the ion channel associated with the plasma blowout. It is shown that this mechanism could be studied using state-of-the-art magnetic fields in next generation plasma accelerator experiments.
Characterization of plasma in magnetic multidipole discharges
NASA Astrophysics Data System (ADS)
Guimaraesferreira, Julio
1988-09-01
A characterization of the discharge of the quiescent plasma machine of INPE, and an identification of the most relevant processes in the definition of its plasma properties, were achieved. Measurements of plasma potential, the floating potential, the temperature of the electrons, and the density of the plasma, for pressures ranging from 10(-3) to 10(-1) Pa and for discharge potentials for 45 V to 120 V were accomplished. These measurements were made with a Langmuir spherical probe with 1mm in diameter. In the whole range of operation the presence of two populations of electrons with distinct temperatures in the energy range from 1 to 10 eV was observed, although for pressures approaching 10(-1) Pa the plasma tended to a single population of electrons with temperature of 1eV. The difference between plasma and floating potentials was observed to become smaller as the pressure raised, and the potential difference between plasma and anode reached a value around 2 V when pressure raised above 10(-2) Pa. The plasma density increases approximately linearly with pressure, for values below 10(-2) Pa, but above 10(-1) Pa its increase with pressure is quite reduced. A study on the collision processes in the plasma volume and on loss processes to surfaces allowed to interpret qualitatively the observed plasma behavior and to estimate, by means of simple expressions, some of the plasma parameters. The loss areas for ions and primary electrons were estimated from experimental results. A simple quantitative model which allows the calculation of plasma density in the whole range of operation, reproduced the correct order of magnitude of experimental values. However, an additional work, both theoretical and experimental, is required to obtain better agreement between experimental and theoretical values.
MHD Simulations of the Plasma Flow in the Magnetic Nozzle
NASA Technical Reports Server (NTRS)
Smith, T. E. R.; Keidar, M.; Sankaran, K.; olzin, K. A.
2013-01-01
The magnetohydrodynamic (MHD) flow of plasma through a magnetic nozzle is simulated by solving the governing equations for the plasma flow in the presence of an static magnetic field representing the applied nozzle. This work will numerically investigate the flow and behavior of the plasma as the inlet plasma conditions and magnetic nozzle field strength are varied. The MHD simulations are useful for addressing issues such as plasma detachment and to can be used to gain insight into the physical processes present in plasma flows found in thrusters that use magnetic nozzles. In the model, the MHD equations for a plasma, with separate temperatures calculated for the electrons and ions, are integrated over a finite cell volume with flux through each face computed for each of the conserved variables (mass, momentum, magnetic flux, energy) [1]. Stokes theorem is used to convert the area integrals over the faces of each cell into line integrals around the boundaries of each face. The state of the plasma is described using models of the ionization level, ratio of specific heats, thermal conductivity, and plasma resistivity. Anisotropies in current conduction due to Hall effect are included, and the system is closed using a real-gas equation of state to describe the relationship between the plasma density, temperature, and pressure.A separate magnetostatic solver is used to calculate the applied magnetic field, which is assumed constant for these calculations. The total magnetic field is obtained through superposition of the solution for the applied magnetic field and the self-consistently computed induced magnetic fields that arise as the flowing plasma reacts to the presence of the applied field. A solution for the applied magnetic field is represented in Fig. 1 (from Ref. [2]), exhibiting the classic converging-diverging field pattern. Previous research was able to demonstrate effects such as back-emf at a super-Alfvenic flow, which significantly alters the shape of the
Collimation of laser-produced plasmas using axial magnetic field
Roy, Amitava; Harilal, Sivanandan S.; Hassan, Syed M.; Endo, Akira; Mocek, Tomas; Hassanein, A.
2015-06-01
We investigated the expansion dynamics of laser-produced plasmas expanding into an axial magnetic field. Plasmas were generated by focusing 1.064 µm Nd:YAG laser pulses onto a planar tin target in vacuum and allowed to expand into a 0.5 T magnetic-filed where field lines were aligned along the plume expansion direction. Gated images employing intensified CCD showed focusing of the plasma plume, which were also compared with results obtained using particle-in-cell modelling methods. The estimated density and temperature of the plasma plumes employing emission spectroscopy revealed significant changes in the presence and absence of the 0.5T magnetic field. In the presence of the field, the electron temperature is increased with distance from the target, while the density showed opposite effects.
Plasma flow healing of magnetic islands in stellarators
Hegna, C. C.
2012-05-15
Recent experiments from the large helical device (LHD) demonstrate a correlation between the 'healing' of vacuum magnetic islands in stellarators and changes in the plasma flow. A model explaining this phenomenon is developed based on self-consistent torque balance and island evolution equations. In conventional stellarators, neoclassical flow damping physics plays an important role in establishing the flow profiles. The balance of neoclassical damping and cross-field viscosity produces a radial boundary layer for the plasma rotation profile outside the separatrix of a locked magnetic island. The width of this boundary layer decreases as the plasma becomes less collisional. Associated with these flow effects are plasma currents flowing in the island region that attempt to suppress island formation. These currents are enhanced as the collisionality drops making magnetic island healing occur more readily in high temperature conventional stellarators. The analytic theory produces a critical {beta} for healing that scales monotonically with collisionality and is in qualitative agreement with LHD observations.
Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas
Jardin, S C
2010-09-28
Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.
Plasma Compression in Magnetic Reconnection Regions in the Solar Corona
NASA Astrophysics Data System (ADS)
Provornikova, E.; Laming, J. M.; Lukin, V. S.
2016-07-01
It has been proposed that particles bouncing between magnetized flows converging in a reconnection region can be accelerated by the first-order Fermi mechanism. Analytical considerations of this mechanism have shown that the spectral index of accelerated particles is related to the total plasma compression within the reconnection region, similarly to the case of the diffusive shock acceleration mechanism. As a first step to investigate the efficiency of Fermi acceleration in reconnection regions in producing hard energy spectra of particles in the solar corona, we explore the degree of plasma compression that can be achieved at reconnection sites. In particular, we aim to determine the conditions for the strong compressions to form. Using a two-dimensional resistive MHD numerical model, we consider a set of magnetic field configurations where magnetic reconnection can occur, including a Harris current sheet, a force-free current sheet, and two merging flux ropes. Plasma parameters are taken to be characteristic of the solar corona. Numerical simulations show that strong plasma compressions (≥4) in the reconnection regions can form when the plasma heating due to reconnection is efficiently removed by fast thermal conduction or the radiative cooling process. The radiative cooling process that is negligible in the typical 1 MK corona can play an important role in the low corona/transition region. It is found that plasma compression is expected to be strongest in low-beta plasma β ˜ 0.01–0.07 at reconnection magnetic nulls.
Observation of low magnetic field density peaks in helicon plasma
Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.; Kumar, Sunil; Saxena, Y. C.
2013-04-15
Single density peak has been commonly observed in low magnetic field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low magnetic field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the magnetic field from 0 G to 100 G. The plasma density varies with varying the magnetic field at constant input power and gas pressure and reaches to its peak value at a magnetic field value of {approx}25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using magnetic probes for two magnetic field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode propagation of helicon waves along the resonance cone boundary for these magnetic field values. Further, the observations of larger floating potential fluctuations measured with Langmuir probes at those magnetic field values indicate that near resonance cone boundary; these electrostatic fluctuations take energy from helicon wave and dump power to the plasma causing density peaks.
Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas
Stratton, B. C.; Biter, M.; Hill, K. W.; Hillis, D. L.; Hogan, J. T.
2007-07-18
Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.
Sustenance of inhomogeneous electron temperature in a magnetized plasma column
Karkari, S. K. Mishra, S. K.; Kaw, P. K.
2015-09-15
This paper presents the equilibrium properties of a magnetized plasma column sustained by direct-current (dc) operated hollow cathode discharge in conjunction with a conducting end-plate, acting as the anode. The survey of radial plasma characteristics, performed in argon plasma, shows hotter plasma in the periphery as compared to the central plasma region; whereas the plasma density peaks at the center. The off-centered peak in radial temperature is attributed due to inhomogeneous power deposition in the discharge volume in conjunction with short-circuiting effect by the conducting end plate. A theoretical model based on particle flux and energy balance is given to explain the observed characteristics of the plasma column.
Radio frequency line-plasma source using permanent magnets
Sakawa, Youichi; Yano, Kentaro; Shoji, Tatsuo
2004-09-01
A high-density and uniform line-plasma source is developed by an inductive rf discharge using a rectangular discharge chamber (200x100x20 mm) with a pair of permanent magnets placed on top and bottom of the chamber. Ion-saturation current-density J{sub is} profile is controlled by varying the width of the magnets and the distance between the antenna and the magnets. A 140-mm-wide plasma [plasma density {approx_equal}(1.8-2.5)x10{sup 12} cm{sup -3} for electron temperature =4-8 eV] of a uniformity variation within 90% is produced using a 140-mm-long antenna for an Ar pressure of 20 mTorr and a rf power of 3 kW. The measured J{sub is} profiles are explained by solving the equation of motion for electrons under a magnetic field structure of longitudinal line cusps.
Apparatus for magnetic and electrostatic confinement of plasma
Rostoker, Norman; Binderbauer, Michl
2006-04-11
An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Apparatus for magnetic and electrostatic confinement of plasma
Rostoker, Norman; Binderbauer, Michl
2013-06-11
An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Apparatus for magnetic and electrostatic confinement of plasma
Rostoker, Norman; Binderbauer, Michl
2006-10-31
An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Thermo-galvanometric instabilities in magnetized plasma disks
NASA Astrophysics Data System (ADS)
Franco, Alessio; Montani, Giovanni; Carlevaro, Nakia
2014-11-01
In this work, we present a linear stability analysis of fully-ionized rotating plasma disks with a temperature gradient and a sub-thermal background magnetic field (oriented towards the axial direction). We describe how the plasma reacts when galvanometric and thermo-magnetic phenomena, such as Hall and Nernst-Ettingshausen effects, are taken into account, and meridian perturbations of the plasma are considered. It is shown how, in the ideal case, this leads to a significant overlap of the Magneto-rotational Instability and the Thermo-magnetic one. Considering dissipative effects, an overall damping of the unstable modes, although not sufficient to fully suppress the instability, appears especially in the thermo-magnetic related branch of the curve.
Electrostatic instabilities in circularly polarized microwave produced magnetized plasmas
Ghorbanalilu, M.; Shokri, B.
2009-12-15
The growth rate of electrostatic instabilities of electron oscillation and low-frequency (LF) ion oscillation are investigated for a plasma produced by a circularly polarized microwave field during the breakdown process. The plasma is magnetized by an external homogenous static magnetic field on the direction of microwave field propagation. Numerical calculations show that the electron and ion perturbations are unstable in such an anisotropic plasma. Electron perturbations have the maximum growth rate across the magnetic field. In addition, ion perturbation growth rate is minimum on this direction. The LF ion oscillation is excited by Cherenkov emission mechanism due to the nonequilibrium form of the electron velocity distribution function. Electron oscillation growth rate decreases by increasing the external magnetic field, while the LF ion oscillation increases smoothly and reaches a maximum when the electron oscillation is stopped.
Apparatus for magnetic and electrostatic confinement of plasma
Rostoker, Norman; Binderbauer, Michl
2016-07-05
An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Effect of magnetic and physical nozzles on plasma thruster performance
NASA Astrophysics Data System (ADS)
Takahashi, Kazunori; Charles, Christine; Boswell, Rod; Ando, Akira
2014-08-01
Plasma cross-field diffusion in a magnetic nozzle is inhibited by increasing the magnetic field strength in a helicon plasma thruster attached to a pendulum thrust balance, while maintaining constant plasma density and electron temperature in the source tube, i.e. a constant plasma injection into the magnetic nozzle, where the field strength near the radio frequency (rf) antenna is less than 210 G and the operating argon pressure in the vacuum chamber is 0.8 mTorr. Inhibition of the cross-field diffusion yields a higher electron pressure in the magnetic nozzle and a resultant larger thrust. The thrust component arising from the magnetic nozzle approaches the theoretical limit derived from an ideal magnetic nozzle approximation where no plasma is lost from the nozzle and there is an azimuthal plasma current originating from the electron diamagnetic drift. It is also shown that the momentum of the plasma lost from the magnetic nozzle is captured by a physical nozzle attached at the source exit resulting in a larger thrust. Two physical nozzles of different sizes (nozzle 1 : 10.5 cm in length with a maximum diameter of 20 cm, nozzle 2 : 26 cm in length with a maximum diameter of 36 cm) are tested. The maximum thrust of 20 ± 1 mN is obtained for 25 sccm argon propellant and 2 kW rf power with a reflection power less than 5 W, which gives a specific impulse of 2750 ± 165 s and a thrust efficiency of 13.5 ± 1.5%.
Non-axisymmetric Plasma Response to External Magnetic Perturbations
NASA Astrophysics Data System (ADS)
Chu, M. S.; Lao, L. L.; Evans, T. E.; Schaffer, M. J.; Strait, E. J.; Liu, Y. Q.; Lanctot, M. J.; Reimerdes, H.
2009-11-01
Very low frequency non-axisymmetric magnetic response in tokamaks excited by external magnetic perturbations is studied with the MARS-F code [1] using different assumptions on the plasma dynamics. In the limit of vacuum plasma response, the fields are benchmarked against the SURFMN [2] code and an analytic model. In other plasma models, the response is affected by plasma pressure, resistivity, toroidal flow, and the kinetic effects associated with the particle drifts. Depending on the coil arrangement, the plasma response could be dominated by the resonant or non-resonant components of the external field. The responses can be tested by employing different combinations of currents in appropriately designed external coils as those in DIII-D. The combined magnetic field of the axisymmetric plasma equilibrium and its non-axisymmetic responses corresponds to a perturbed 3D plasma equilibrium. 8pt [1] Y.Q. Liu, et al., Phys. Plasmas 7 (2000) 3681. [2] M.J. Schaffer, et al., Nucl. Fusion 48 (2008) 024004.
A review on ion-ion plasmas created in weakly magnetized electronegative plasmas
NASA Astrophysics Data System (ADS)
Aanesland, A.; Bredin, J.; Chabert, P.
2014-08-01
Ion-Ion plasmas are electronegative plasmas where the electron density is several orders of magnitude lower than the negative ion density. These plasmas have been scarcely observed and investigated since the 1960s and are formed as a transient state of pulsed plasmas or in separate regions in magnetized plasmas. In this review we focus on the latter case of continuous formation of ion-ion plasmas created at the periphery of magnetized plasma columns or downstream localized magnetic barriers. We bring together and review experimental results already published elsewhere and complement them with new results to illustrate the physics important in ion-ion plasma formation and highlight in particular unanswered questions. We show that with a good design the density in the ion-ion region is dropping only by a factor of 2-3 from the initial plasma density. These plasmas can therefore be well suited for various ion source applications when both fluxes or beams of positive and negative ions are desired, and when electrons can cause harmful effects.
Transport equations for partially ionized reactive plasma in magnetic field
NASA Astrophysics Data System (ADS)
Zhdanov, V. M.; Stepanenko, A. A.
2016-06-01
Transport equations for partially ionized reactive plasma in magnetic field taking into account the internal degrees of freedom and electronic excitation of plasma particles are derived. As a starting point of analysis the kinetic equation with a binary collision operator written in the Wang-Chang and Uhlenbeck form and with a reactive collision integral allowing for arbitrary chemical reactions is used. The linearized variant of Grad's moment method is applied to deduce the systems of moment equations for plasma and also full and reduced transport equations for plasma species nonequilibrium parameters.
On the Physics of the Interaction of a Rotating Magnetic Field with a Magnetized Plasma
NASA Astrophysics Data System (ADS)
Karavaev, A. V.; Papadopoulos, K.; Shao, X.; Milikh, G.; Gekelman, W.; Gigliotti, A.; Vincena, S.
2007-12-01
The interaction of Rotating Magnetic Fields (RMF) with plasmas is a fundamental plasma physics problem with implications to fusion related Field-Reversed Configurations (FRC), space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of energetic population in the radiation belts and near zone processes in pulsar magnetospheres. An important but not yet explored application of RMF is as an efficient radiation source of MHD and whistler waves in space plasmas. Despite its importance the basic plasma physics understanding of the interaction of rotating magnetic fields with magneto-plasmas, the scaling laws that control it and the range of potential applications to space plasmas remains unexplored. To zero order a magnetic field rotating at a rate w in a plasma drives plasma currents due to the difference in mass between electrons and ions. The electrons quickly come to a co-rotation with RMF, generating a differential azimuthal current whose maximum is given by Jtheta = nwr . The RMF can be generated either by a pair of polyphase coils, superconducting or else, or a rotating permanent magnet. Key questions include the depth of penetration of the field in the plasma, the spatiotemporal structure of the induced magnetic field as a function of the RMF and plasma parameters and the spatial decay rate magnetic field. Flux conservation arguments indicate that the induced field will decay slower than 1/r**2 and 2D simulation studies indicate that depending on the plasma beta it falls as 1/r**n with n smaller than 1.5. Our preliminary simulations indicate that penetration lengths exceeding 20-30 collisionless skin depths can be reached. The paper will present a combination of analytic/computational results along with preliminary experiments conducted using the Large Plasma Device (LAPD) located at UCLA that emphasize the RMF properties for generating MHD and whistler waves. This work was sponsored by ONR MURI Grant 5-28828
Magnetic reconnection in high-energy-density plasmas in the presence of an external magnetic field
NASA Astrophysics Data System (ADS)
Fox, W.; Bhattacharjee, A.; Fiksel, G.; Nilson, P.; Hu, S.; Chang, P.-Y.; Barnak, D.; Betti, R.
2012-10-01
Magnetic reconnection has recently been observed and studied in high-energy-density, laser-produced plasmas. These experiments are interesting both for obtaining fundamental data on reconnection, and may also be relevant for inertial fusion, as this magnetic reconnection geometry, with multiple, colliding, magnetized plasma bubbles, occurs naturally inside ICF hohlraums. We present initial results of experiments conducted on the OMEGA EP facility on magnetic reconnection between colliding, magnetized blowoff plasmas. While in previous experiments the magnetic fields were self-generated in the plasma by the Biermann battery effect, in these experiments the seed magnetic field is generated by pulsing current through a pair of external foils using the MIFEDS current generator (Magneto-Inertial Fusion Electrical Discharge System) developed at LLE. Time-resolved images of the magnetic fields and plasma dynamics are obtained from proton radiography and x-ray self-emission, respectively. We present initial results of the experiments, including comparison to ``null'' experiments with zero MIFEDS magnetic field, and associated modeling using the radiation-hydro code DRACO and the particle-in-cell code PSC.
Collision-less Coupling between Explosive Debris Plasma and Magnetized Ambient Plasma
NASA Astrophysics Data System (ADS)
Bondarenko, Anton Sergeivich
The explosive expansion of a dense debris plasma cloud into relatively tenuous, magnetized, ambient plasma characterizes a wide variety of astrophysical and space environments, including supernova remnants, interplanetary coronal mass ejections, and ionospheric explosions. In these and other related phenomena, collision-less electro-magnetic processes rather than Coulomb collisions typically mediate the transfer of momentum and energy from the debris plasma to the ambient plasma. In an effort to better understand the detailed physics of collision-less coupling mechanisms, compliment in situ measurements, and provide validation of previous computational and theoretical work, the present research utilizes a unique experimental platform at the University of California, Los Angeles (UCLA) to study the interaction of explosive debris plasma with magnetized ambient plasma in a reproducible laboratory setting. Specifically, by jointly employing the Large Plasma Device (LAPD) and the Phoenix laser facility, the super-Alfvenic, quasi-perpendicular expansion of laser-produced carbon (C) and hydrogen (H) debris plasma through preformed, magnetized helium (He) ambient plasma is investigated via a variety of sophisticated diagnostics, including emission spectroscopy, wavelength-filtered imaging, a magnetic flux probe, and a Langmuir probe. The key result is the direct observation of collision-less coupling via large Doppler shifts in a He II ion spectral line, which indicate that the ambient ions accelerate in response to the explosive debris plasma. Specifically, the He II ions accelerate along a trajectory that qualitatively corresponds to the large-scale laminar electric field generated by the debris expansion. A custom computational approach is utilized to simulate the initial He II ion response to the explosive debris plasma, and a synthetic Doppler-shifted wavelength spectrum constructed from the simulated ion velocities excellently reproduces the experimental
NASA Astrophysics Data System (ADS)
Westlake, J. H.; McNutt, R. L., Jr.; Kasper, J. C.; Case, A. W.; Rymer, A. M.; Khurana, K. K.; Stevens, M. L.; Jia, X.; Slavin, J. A.; Paty, C. S.; Smith, H. T.; Kivelson, M.; Saur, J.; Krupp, N.; Roussos, E.; Korth, H.
2015-12-01
Europa exists in a complicated plasma environment where the tilt of Jupiter's magnetic field and rapid rotation rate leads to a dynamic interaction with Europa's ionospheric plasma. While understanding this plasma interaction is interesting in its own right, it is crucial for successfully magnetically sounding Europa's subsurface ocean. . In magnetic sounding, currents induced in Europa by the changing Jovian plasma produce a detectable secondary magnetic field that reflects properties of Europa's subsurface ocean such as depth and conductivity. This technique was successfully employed with Galileo observations of Europa to demonstrate that Europa indeed has a subsurface ocean containing more liquid water than Earth's oceans. While these Galileo observations contributed to the renewed interest in Europa, the results raised major questions that remain unanswered, in part due to the large uncertainties in the ice shell thickness, ocean depth, and ocean salinity due to limitations in the observations. Here we present the scientific goals of the Plasma Instrument for Magnetic Sounding (PIMS), one of the 9 instruments selected for the Europa Multiple Flyby Mission. We specifically address how PIMS plasma measurements will transform the accuracy of magnetic sounding of Europa's subsurface oceans. We also present synergistic science with other Europa instrumentation such as the ultraviolet spectrometer, mass spectrometer, and the radar.
Plasma transport near the magnetic cavity surrounding comet Halley
NASA Astrophysics Data System (ADS)
Haerendel, G.
1987-07-01
The dominant forces resisting the transport of magnetic field into the inner coma of a comet are ion mass loading from and friction with the expanding neutral atmosphere. A magnetic cavity is thereby created. Close to it the frictional force is most important. Careful interpretation of the magnetic field profile measured during the Giotto flyby of comet P/Halley reveals the existence of an inward directed component of plasma flow of a few km/s, which drops to zero at the boundary of the cavity. The energy transferred from the neutral gas to the plasma by friction and mass loading is responsible for the strongly elevated ion temperatures outside the magnetic cavity. Fitting of the observed magnetic profile and ion temperature distribution yields quantitative determinations of some crucial parameters of the coma.
NASA Astrophysics Data System (ADS)
Vafin, S.; Schlickeiser, R.; Yoon, P. H.
2016-09-01
The general electromagnetic fluctuation theory is a powerful tool to analyze the magnetic fluctuation spectrum of a plasma. Recent works utilizing this theory for a magnetized non-relativistic isotropic Maxwellian electron-proton plasma have demonstrated that the equilibrium ratio of | δ B| /{B}0 can be as high as 10-12. This value results from the balance between spontaneous emission of fluctuations and their damping, and it is considerably smaller than the observed value | δ B| /{B}0 in the solar wind at 1 au, where {10}-3≲ | δ B| /{B}0≲ {10}-1. In the present manuscript, we consider an anisotropic bi-Maxwellian distribution function to investigate the effect of plasma instabilities on the magnetic field fluctuations. We demonstrate that these instabilities strongly amplify the magnetic field fluctuations and provide a sufficient mechanism to explain the observed value of | δ B| /{B}0 in the solar wind at 1 au.
ICTP-IAEA Workshop on Dense Magnetized Plasma and Plasma Diagnostics: an executive summary
NASA Astrophysics Data System (ADS)
Gribkov, V. A.; Mank, G.; Markowicz, A.; Miklaszewski, R.; Tuniz, C.; Crespo, M. L.
2011-12-01
The Workshop on Dense Magnetized Plasma and Plasma Diagnostics was held from 15 to 26 November 2010 at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy. It was attended by 60 participants, including 15 lecturers, 2 tutors and 37 trainees, representing 25 countries.
Equilibrium and magnetic properties of a rotating plasma annulus
Wang Zhehui; Si Jiahe; Liu Wei; Li Hui
2008-10-15
Local linear analysis shows that magneto-rotational instability can be excited in laboratory rotating plasmas with a density of 10{sup 19} m{sup -3}, a temperature on the order of 10 eV, and a magnetic field on the order of 100 G. A laboratory plasma annulus experiment with a dimension of {approx}1 m, and rotation at {approx}0.5 sound speed is described. Correspondingly, magnetic Reynolds number of these plasmas is {approx}1000, and magnetic Prandtl number ranges from about one to a few hundred. A radial equilibrium, {rho}U{sub {theta}}{sup 2}/r=d(p+B{sub z}{sup 2}/2{mu}{sub 0})/dr=K{sub 0}, with K{sub 0} being a nonzero constant, is proposed for the experimental data. Plasma rotation is observed to drive a quasisteady diamagnetic electrical current (rotational current drive) in a high-{beta} plasma annulus. The rotational energy depends on the direction and the magnitude of the externally applied magnetic field. Radial current (J{sub r}) is produced through biasing the center rod at a negative electric potential relative to the outer wall. J{sub r}xB{sub z} torque generates and sustains the plasma rotation. Rotational current drive can reverse the direction of vacuum magnetic field, satisfying a necessary condition for self-generated closed magnetic flux surfaces inside plasmas. The Hall term is found to be substantial and therefore needs to be included in the Ohm's law for the plasmas. Azimuthal magnetic field (B{sub {theta}}) is found to be comparable with the externally applied vacuum magnetic field B{sub z}, and mainly caused by the electric current flowing in the center cylinder; thus, B{sub {theta}}{proportional_to}r{sup -1}. Magnetic fluctuations are anisotropic, radial-dependent, and contain many Fourier modes below the ion cyclotron frequency. Further theoretical analysis reflecting these observations is needed to interpret the magnetic fluctuations.
Magnetic field diffusion and dissipation in reversed-field plasmas
NASA Technical Reports Server (NTRS)
Drake, J. F.; Gladd, N. T.; Huba, J. D.
1981-01-01
A diffusion equation is derived which describes the evolution of a magnetic field in a plasma of arbitrary beta and resistivity. The equation is valid for a one-dimensional slab geometry, assumes the plasma remains in quasi-equilibrium throughout its evolution and does not include thermal transport. Scaling laws governing the rate of change of the magnetic energy, particle drift energy, and magnetic flux are calculated. It is found that the magnetic free energy can be substantially larger than the particle drift energy and can be an important energy reservoir in driving plasma instabilities (e.g., the lower-hybrid-drift instability). In addition, the effect of a spatially varying resistivity on the evolution of a reversed-field plasma is studied. The resistivity model used is based upon the anomalous transport properties associated with the nonlocal mode structure of the lower-hybrid-drift instability. The relevance of this research to laboratory plasmas (e.g., theta pinches, reversed-field theta pinches) and space plasmas (e.g., the earth's magnetotail) is discussed.
Electro-Magnetic Fields and Plasma in the Cosmos
Scott, Donald E.
2006-03-21
It is becoming widely recognized that a majority of baryons in the cosmos are in the plasma state. But, fundamental disagreements about the properties and behavior of electro-magnetic fields in these plasmas exist between the science of modern astronomy and the experimentally verified laws of electrical engineering and physics. Some astronomers claim that magnetic fields can be open-ended - that they begin on or beneath the Sun's surface and extend outward to infinity. Astrophysicists have claimed that galactic magnetic fields begin and end on molecular clouds. Electrical engineers, most physicists, and the pioneers in electromagnetic field theory disagree - magnetic fields have no beginning or end. Since these two viewpoints are mutually exclusive, both cannot be correct; one must be completely false. Many astrophysicists claim that magnetic fields are 'frozen into' electric plasma. We also examine the basis for this claim. It has been shown to be incorrect in the laboratory. The hypothetical 'magnetic merging' mechanism is also reviewed in light of both theoretical and experimental investigations. The cause of large-scale filamentation in the cosmos is also simply revealed by experimental results obtained in plasma laboratories.
The Effects of Magnetic Nozzle Configurations on Plasma Thrusters
NASA Technical Reports Server (NTRS)
Turchi, P. J.
1997-01-01
Over the course of eight years, the Ohio State University has performed research in support of electric propulsion development efforts at the NASA Lewis Research Center, Cleveland, OH. This research has been largely devoted to plasma propulsion systems including MagnetoPlasmaDynamic (MPD) thrusters with externally-applied, solenoidal magnetic fields, hollow cathodes, and Pulsed Plasma Microthrusters (PPT's). Both experimental and theoretical work has been performed, as documented in four master's theses, two doctoral dissertations, and numerous technical papers. The present document is the final report for the grant period 5 December 1987 to 31 December 1995, and summarizes all activities. Detailed discussions of each area of activity are provided in appendices: Appendix 1 - Experimental studies of magnetic nozzle effects on plasma thrusters; Appendix 2 - Numerical modeling of applied-field MPD thrusters; Appendix 3 - Theoretical and experimental studies of hollow cathodes; and Appendix 4 -Theoretical, numerical and experimental studies of pulsed plasma thrusters. Especially notable results include the efficacy of using a solenoidal magnetic field downstream of a plasma thruster to collimate the exhaust flow, the development of a new understanding of applied-field MPD thrusters (based on experimentally-validated results from state-of-the art, numerical simulation) leading to predictions of improved performance, an experimentally-validated, first-principles model for orificed, hollow-cathode behavior, and the first time-dependent, two-dimensional calculations of ablation-fed, pulsed plasma thrusters.
Quark-gluon plasma in an external magnetic field.
Levkova, L; DeTar, C
2014-01-10
Using numerical simulations of lattice QCD we calculate the effect of an external magnetic field on the equation of state of the quark-gluon plasma. The results are obtained using a Taylor expansion of the pressure with respect to the magnetic field for the first time. The coefficients of the expansion are computed to second order in the magnetic field. Our setup for the external magnetic field avoids complications arising from toroidal boundary conditions, making a Taylor series expansion straightforward. This study is exploratory and is meant to serve as a proof of principle.
Lynn, Alan G. Gilmore, Mark
2014-11-15
Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10{sup 4} T (100 Megagauss) over small volumes (∼10{sup −10}m{sup 3}) at high plasma densities (∼10{sup 28}m{sup −3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.
NASA Astrophysics Data System (ADS)
Eliseev, L. G.; Ivanov, N. V.; Kakurin, A. M.; Melnikov, A. V.; Perfilov, S. V.
2015-05-01
Experimental comparison of the m = 2, n = 1 mode and plasma rotation velocities at q = 2 magnetic surface in a wide range of the mode amplitudes is presented. Phase velocity of the mode rotation is measured with a set of poloidal magnetic field sensors located at the inner side of the vacuum vessel wall. Plasma rotation velocity at the q = 2 magnetic surface in the direction of the mode phase velocity is measured with the heavy ion beam probe diagnostics. In the presence of a static Resonant Magnetic Perturbation (RMP), the rotation is irregular that appears as cyclical variations of the mode and plasma instantaneous velocities. The period of these variations is equal to the period of the mode oscillations. In the case of high mode amplitude, the rotation irregularity of the mode is consistent with the rotation irregularity of the resonant plasma layer. On the contrary, the observed rise of the mode rotation irregularity in the case of low mode amplitude occurs without an increase of the rotation irregularity of the resonant plasma layer. The experimental results are simulated and analyzed with the TEAR code based on the two-fluid MHD approximation. Calculated irregularities of the mode and plasma rotation depend on the mode amplitude similar to the experimental data. For large islands, the rotation irregularity is attributed to oscillations of the electromagnetic torque applied to the resonant plasma layer. For small islands, the deviation of the mode rotation velocity from the plasma velocity occurs due to the effect of finite plasma resistivity.
NASA Astrophysics Data System (ADS)
Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott
2014-10-01
We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.
Takakura, Y.; Ono, S.; Teii, S.
1995-12-31
Plasma torch is used in many industrial processes for high temperature sources. In the past, an application of magnetic field is experientially known to stabilize plasma torch operations. However, there is a little discussion regarding to magnetic field effects on plasma torch operating characteristics and plasma parameters. In this work, the influences of magnetic field and plasma gas flow rate on plasma torch current-voltage characteristics and downstream plasma parameters have been experimentally studied, and results are qualitatively analyzed based on the charged particle transport equation.
Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion
Geissel, Matthias; Awe, Thomas James; Bliss, David E.; Campbell, Edward Michael; Gomez, Matthew R.; Harding, Eric; Harvey-Thompson, Adam James; Hansen, Stephanie B.; Jennings, Christopher Ashley; Kimmel, Mark W.; et al
2016-03-04
Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less
Nonlinear laser-plasma interaction in magnetized liner inertial fusion
NASA Astrophysics Data System (ADS)
Geissel, Matthias; Awe, T. J.; Bliss, D. E.; Campbell, M. E.; Gomez, M. R.; Harding, E.; Harvey-Thompson, A. J.; Hansen, S. B.; Jennings, C.; Kimmel, M. W.; Knapp, P.; Lewis, S. M.; McBride, R. D.; Peterson, K.; Schollmeier, M.; Scoglietti, D. J.; Sefkow, A. B.; Shores, J. E.; Sinars, D. B.; Slutz, S. A.; Smith, I. C.; Speas, C. S.; Vesey, R. A.; Porter, J. L.
2016-03-01
Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. While magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Key LPI processes are determined, and mitigation methods are discussed. Results with and without improvement measures are presented.
Plasma transport in a simulated magnetic-divertor configuration
Strawitch, C. M.
1981-03-01
The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult to eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.
Conversion of magnetic energy in the magnetic reconnection layer of a laboratory plasma
Yamada, Masaaki; Yoo, Jongsoo; Jara-Almonte, Jonathan; Ji, Hantao; Kulsrud, Russell M.; Myers, Clayton E.
2014-09-10
Magnetic reconnection, in which magnetic field lines break and reconnect to change their topology, occurs throughout the universe. The essential feature of reconnection is that it energizes plasma particles by converting magnetic energy. Despite the long history of reconnection research, how this energy conversion occurs remains a major unresolved problem in plasma physics. Here we report that the energy conversion in a laboratory reconnection layer occurs in a much larger region than previously considered. The mechanisms for energizing plasma particles in the reconnection layer are identified, and a quantitative inventory of the converted energy is presented for the first timemore » in a well defined reconnection layer; 50% of the magnetic energy is converted to particle energy, 2/3 of which transferred to ions and 1/3 to electrons. Our results are compared with simulations and space measurements, for a key step toward resolving one of the most important problems in plasma physics.« less
Conversion of magnetic energy in the magnetic reconnection layer of a laboratory plasma
Yamada, Masaaki; Yoo, Jongsoo; Jara-Almonte, Jonathan; Ji, Hantao; Kulsrud, Russell M.; Myers, Clayton E.
2014-09-10
Magnetic reconnection, in which magnetic field lines break and reconnect to change their topology, occurs throughout the universe. The essential feature of reconnection is that it energizes plasma particles by converting magnetic energy. Despite the long history of reconnection research, how this energy conversion occurs remains a major unresolved problem in plasma physics. Here we report that the energy conversion in a laboratory reconnection layer occurs in a much larger region than previously considered. The mechanisms for energizing plasma particles in the reconnection layer are identified, and a quantitative inventory of the converted energy is presented for the first time in a well defined reconnection layer; 50% of the magnetic energy is converted to particle energy, 2/3 of which transferred to ions and 1/3 to electrons. Our results are compared with simulations and space measurements, for a key step toward resolving one of the most important problems in plasma physics.
Atomic forces for geometry-dependent point multipole and gaussian multipole models.
Elking, Dennis M; Perera, Lalith; Duke, Robert; Darden, Thomas; Pedersen, Lee G
2010-11-30
In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise because of (1) the transfer of torque between neighboring atoms and (2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In this study, atomic force expressions for geometry-dependent multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first proposing a new general expression for Wigner function derivatives partial derivative D(m'm)(l)/partial derivative Omega. The force equations can be applied to electrostatic models based on atomic point multipoles or gaussian multipole charge density. Hydrogen-bonded dimers are used to test the intermolecular electrostatic energies and atomic forces calculated by geometry-dependent multipoles fit to the ab initio electrostatic potential. The electrostatic energies and forces are compared with their reference ab initio values. It is shown that both static and geometry-dependent multipole models are able to reproduce total molecular forces and torques with respect to ab initio, whereas geometry-dependent multipoles are needed to reproduce ab initio atomic forces. The expressions for atomic force can be used in simulations of flexible molecules with atomic multipoles. In addition, the results presented in this work should lead to further development of next generation force fields composed of geometry-dependent multipole models.
Dusty Plasmas in Planetary Magnetospheres Award
NASA Technical Reports Server (NTRS)
Horanyi, Mihaly
2005-01-01
This is my final report for the grant Dusty Plasmas in Planetary Magnetospheres. The funding from this grant supported our research on dusty plasmas to study: a) dust plasma interactions in general plasma environments, and b) dusty plasma processes in planetary magnetospheres (Earth, Jupiter and Saturn). We have developed a general purpose transport code in order to follow the spatial and temporal evolution of dust density distributions in magnetized plasma environments. The code allows the central body to be represented by a multipole expansion of its gravitational and magnetic fields. The density and the temperature of the possibly many-component plasma environment can be pre-defined as a function of coordinates and, if necessary, the time as well. The code simultaneously integrates the equations of motion with the equations describing the charging processes. The charging currents are dependent not only on the instantaneous plasma parameters but on the velocity, as well as on the previous charging history of the dust grains.
Mass production of magnetic nickel nanoparticle in thermal plasma reactor
Kanhe, Nilesh S.; Nawale, Ashok B.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.
2014-04-24
We report the mass production of Ni metal nanoparticles using dc transferred arc thermal plasma reactor by homogeneous gas phase condensation process. To increase the evaporation rate and purity of Ni nanoparticles small amount of hydrogen added along with argon in the plasma. Crystal structure analysis was done by using X-ray diffraction technique. The morphology of as synthesized nanoparticles was carried out using FESEM images. The magnetic properties were measured by using vibrating sample magnetometer at room temperature.
Mass production of magnetic nickel nanoparticle in thermal plasma reactor
NASA Astrophysics Data System (ADS)
Kanhe, Nilesh S.; Nawale, Ashok B.; Bhoraskar, S. V.; Das, A. K.; Mathe, V. L.
2014-04-01
We report the mass production of Ni metal nanoparticles using dc transferred arc thermal plasma reactor by homogeneous gas phase condensation process. To increase the evaporation rate and purity of Ni nanoparticles small amount of hydrogen added along with argon in the plasma. Crystal structure analysis was done by using X-ray diffraction technique. The morphology of as synthesized nanoparticles was carried out using FESEM images. The magnetic properties were measured by using vibrating sample magnetometer at room temperature.
Electromagnetic treatment of the multipole resonance probe
NASA Astrophysics Data System (ADS)
Lapke, Martin; Mussenbrock, Thomas; Brinkmann, Ralf Peter
2009-10-01
We present an electromagnetic model of the ``multipole resonance probe'' (MRP)-- a diagnostic concept which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The MRP is a radio-frequency driven probe of particular spherical design. In an idealized version the probe consists of two dielectrically shielded, conducting hemispheres. Driven by a radio-frequency source, the hemispheres are powered symmetrically. An analysis of the absorption spectrum shows a multitude of resonances, which allows for an analytical evaluation of the measured signal. The signal provides information on the distribution of the plasma in the probe's vicinity, from which the values of electron density, electron temperature and collision rate can be inferred. In this contribution the MRP will be modeled electromagnetically. Based on a comparision between full electromagnetic and electrostatic treatment, we show that a previously presented electrostatic treatment [1] was well justified.[4pt] [1] M.Lapke et al., Appl. Phys. Lett. 93, 051502 (2008)
Magnetic reconnection in a compressible MHD plasma
Hesse, Michael; Zenitani, Seiji; Birn, Joachim
2011-04-15
Using steady-state resistive MHD, magnetic reconnection is reinvestigated for conditions of high resistivity/low magnetic Reynolds number, when the thickness of the diffusion region is no longer small compared to its length. Implicit expressions for the reconnection rate and other reconnection parameters are derived based on the requirements of mass, momentum, and energy conservation. These expressions are solved via simple iterative procedures. Implications specifically for low Reynolds number/high resistivity are being discussed.
Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas
NASA Astrophysics Data System (ADS)
Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira
2010-11-01
As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.
Slot-Antenna/Permanent-Magnet Device for Generating Plasma
NASA Technical Reports Server (NTRS)
Foster, John E.
2007-01-01
A device that includes a rectangular-waveguide/slot-antenna structure and permanent magnets has been devised as a means of generating a substantially uniform plasma over a relatively large area, using relatively low input power and a low gas flow rate. The device utilizes electron cyclotron resonance (ECR) excited by microwave power to efficiently generate plasma in a manner that is completely electrodeless in the sense that, in principle, there is no electrical contact between the plasma and the antenna. Plasmas generated by devices like this one are suitable for use as sources of ions and/or electrons for diverse material-processing applications (e.g., etching or deposition) and for ion thrusters. The absence of plasma/electrode contact essentially prevents plasma-induced erosion of the antenna, thereby also helping to minimize contamination of the plasma and of objects exposed to the plasma. Consequently, the operational lifetime of the rectangular-waveguide/ slot-antenna structure is long and the lifetime of the plasma source is limited by the lifetime of the associated charged-particle-extraction grid (if used) or the lifetime of the microwave power source. The device includes a series of matched radiating slot pairs that are distributed along the length of a plasma-source discharge chamber (see figure). This arrangement enables the production of plasma in a distributed fashion, thereby giving rise to a uniform plasma profile. A uniform plasma profile is necessary for uniformity in any electron- or ion-extraction electrostatic optics. The slotted configuration of the waveguide/ antenna structure makes the device scalable to larger areas and higher powers. All that is needed for scaling up is the attachment of additional matched radiating slots along the length of the discharge chamber. If it is desired to make the power per slot remain constant in scaling up, then the input microwave power must be increased accordingly. Unlike in prior ECR microwave plasma
The plasma drag and dust motion inside the magnetized sheath
Pandey, B. P.; Vladimirov, S. V.; Samarian, A.
2011-05-15
The motion of micron size dust inside the sheath in the presence of an oblique magnetic field is investigated by self-consistently calculating the charge and various forces acting on the dust. It is shown that the dust trajectory inside the sheath, which is like an Archimedean spiral swinging back and forth between the wall and the plasma-sheath boundary, depends only indirectly on the orientation of the magnetic field. When the Lorentz force is smaller than the collisional momentum exchange, the dust dynamics is insensitive to the obliqueness of the magnetic field. Only when the magnetic field is strong enough, the sheath structure and, thus, the dust dynamics are significantly affected by the field orientation. Balance between the plasma drag, sheath electrostatic field, and gravity plays an important role in determining how far the dust can travel inside the sheath. The dust equilibrium point shifts closer to the wall in the presence of gravity and plasma drag. However, in the absence of plasma drag, dust can sneak back into the plasma if acted only by gravity. The implication of our results to the usability of dust as a sheath probe is discussed.
Plasma Detachment Studies in the VASIMR Magnetic Nozzle
NASA Astrophysics Data System (ADS)
Tarditi, Alfonso G.; Shebalin, John
2004-11-01
Two important issues related to the VASIMR (Variable Specific Impulse Magnetoplasma Rocket, [1]) experiment are the plasma detachment and the collimation of the plume in the magnetic nozzle. These issues are being investigated both through theory/simulation studies and now also experimentally. A 3D, nonlinear MHD/2-fluid model of the magnetic nozzle has been implemented with the NIMROD code. The model has been run both with the actual VASIMR geometry and for an ideal De Laval nozzle configuration. The simulations indicate a distortion of the external field due to the plasma exhaust flow (carrying an azimuthal diamagnetic current) that may to lead to plasma detachment through the formation of magnetic islands. This is also being investigated experimentally. A Hall-effect, one-axis, gaussmeter has shown the local low-frequency magnetic field fluctuations during a plasma pulse. A 2D array of 3-axis "B-dot" probes is being developed for a fast mapping of the field perturbations in the nozzle (on the order of the Alfven time). Finally, a Rogowski coil probe is being designed to measure the azimuthal current profile in the exhaust plasma. [1] F. R. Chang-Diaz et al, Scientific American, p. 90, Nov. 2000
The effects of magnetic nozzle configurations on plasma thrusters
NASA Technical Reports Server (NTRS)
York, Thomas M.
1990-01-01
Plasma thrusters have been operated at power levels from 10 kw to 0.1 MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research effort is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations were studied without applied fields and with applied magnetic nozzle fields. Unique computational studies utilize existing codes which accurately include transport processes. Unique diagnostic studies supported the experimental studies to generate new data. Both computation and diagnostics were combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.
The effects of magnetic nozzle configurations on plasma thrusters
NASA Technical Reports Server (NTRS)
York, Thomas M.
1989-01-01
Plasma thrusters have been operated at power levels from 10kW to 0.1MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations will be studied without applied fields and with applied magnetic nozzle fields. Unique computational studies will utilize existing codes which accurately include transport processes. Unique diagnostic studies will support the experimental studies to generate new data. Both computation and diagnostics will be combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.
Viscosity and Shear Flows in Magnetized Dusty Plasmas
NASA Astrophysics Data System (ADS)
Romero-Talamas, C. A.; Bates, E. M.; Birmingham, W. J.; Rivera, W. F.; Takeno, J.; Knop, S.
2015-11-01
Magnetized dusty plasma experiments are planned at the Dusty Plasma Laboratory of the University of Maryland, Baltimore County (UMBC), to investigate E x B rotation with dust of at least 500 nm in diameter. At this size, individual particles can be tracked and viscosity, shear flow, and temperature can be measured directly using a methodology similar to that used for linear shear flow configurations [Feng et al. PRL 109, 185002 (2012)]. The experiments are planned with a specially designed Bitter-type magnet that can be configured to achieve up to 10 T for at least 10 seconds, to minutes, with much longer operation times at lower fields also possible. At the highest field, the dust will be fully magnetized and thus we aim to achieve direct E x B rotation of the dust (and not just by ion drag). The motivation for these experiments comes from observations of electron and ion temperatures in excess of 100 eV in E x B rotating plasmas [R. Reid et al. Phys. Plasmas 21, 063305 (2014)]. The experimental setup and planned diagnostics for the magnetized dusty plasma are presented.
Alfvénic tornadoes in a magnetized plasma
NASA Astrophysics Data System (ADS)
Shukla, P. K.
2013-01-01
It is shown that three-dimensional (3D) modified-kinetic Alfvén waves (m-KAWs) in a magnetized plasma can propagate in the form of Alfvénic tornadoes characterized by plasma density whirls or magnetic flux ropes carrying orbital angular momentum. By using the two-fluid model, together with Ampère's law, we derive the wave equation for 3D m-KAWs in a magnetoplasma with me/mi ≪ β ≪ 1, where me (mi) is the electron (ion) mass, β=4πn0kB (Te+Ti)/B02, n0 the unperturbed plasma number density, kB the Boltzmann constant, Te(Te) the electron (ion) temperature, and B0 the strength of the ambient magnetic field. The 3D m-KAW equation admits solutions in the form of a Laguerre-Gauss Alfvénic vortex beam or a twisted kinetic Alfvénic wave with plasma density whirls that support the dynamics of shear Alfvénic magnetic flux ropes in plasmas.
Explosive instability and erupting flux tubes in a magnetized plasma
Cowley, S. C.; Cowley, B.; Henneberg, S. A.; Wilson, H. R.
2015-01-01
The eruption of multiple flux tubes in a magnetized plasma is proposed as a mechanism for explosive release of energy in plasmas. A significant fraction of the linearly stable isolated flux tubes are shown to be metastable in a box model magnetized atmosphere in which ends of the field lines are embedded in conducting walls. The energy released by destabilizing such field lines can be a large proportion of the gravitational energy stored in the system. This energy can be released in a fast dynamical time. PMID:26339193
Self-sustained annihilation of magnetic islands in helical plasmas
Itoh, Kimitaka; Itoh, Sanae-I.; Yagi, Masatoshi
2005-07-15
The evolution of the magnetic island which is induced by the resonant deformation by external currents in helical systems (such as the large helical device (LHD) [A. Iiyoshi, Phys. Plasmas 2, 2349 (1995)]) is analyzed. The defect of the bootstrap current, caused by the magnetic island, has a parity which reduces the size of the magnetic island, if the bootstrap current enhances the vacuum rotational transform. The width of magnetic island can be suppressed to the level of ion banana width if the pressure gradient exceeds a threshold value. This island annihilation is self-sustained. That is, the annihilation continues, for fixed beta value, until the external drive for island generation exceeds a threshold. The effects of the reversal of the direction of the bootstrap current and of the sign of radial electric field are also investigated. The possibility of the neoclassical tearing mode in the LHD-like plasma is discussed.
Measurement Of Magnetic Fields In Magnetized Plasmas Using Zeeman Broadening Diagnostics
NASA Astrophysics Data System (ADS)
Haque, Showera; Wallace, Matthew S.; Neill, Paul; Presura, Radu
2015-11-01
The Zeeman effect has been used to measure the magnetic field in high energy density plasmas. The measurements are difficult in this regime because the line broadening due to the high plasma density and temperature surpasses the Zeeman splitting. Using an idea proposed by Tessarin et al. (2011), we have measured the field in magnetized laser plasmas and the magnetized precursor of wire array z-pinches. Time-gated spectra with one-dimensional space-resolution were obtained at the Nevada Terawatt Facility for laser plasmas created by 20 J, 1 ns Leopard laser pulses, and expanding in the azimuthal magnetic field produced by the 0.6 MA Zebra pulsed power generator, and for wire array plasmas driven by the 1 MA configuration of the Zebra generator. We explore the response of the Al III 4s 2S1/2- 4p 2P1 / 2 , 3 / 2 doublet components and the C IV 3s 2S1/2- 3p 2P1 / 2 , 3 / 2 doublet components to the external magnetic field spatially along the plasma. In these measurements the Zeeman splitting was not resolved, but the magnetic field strength was measured from the difference between the widths of the line profiles. This work was supported by the DOE/OFES grant DE-SC0008829 and DOE/NNSA contract DE-FC52-06NA27616.
Asymmetric Magnetic Reconnection in Weakly Ionized Chromospheric Plasmas
NASA Astrophysics Data System (ADS)
Murphy, Nicholas A.; Lukin, Vyacheslav S.
2015-06-01
Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.
Nonlinear stability of magnetic islands in a rotating helical plasma
Nishimura, S.; Toda, S.; Narushima, Y.; Yagi, M.
2012-12-15
Coexistence of the forced magnetic reconnection by a resonant magnetic perturbation (RMP) and the curvature-driven tearing mode is investigated in a helical (stellarator) plasma rotated by helical trapped particle-induced neoclassical flows. A set of Rutherford-type equations of rotating magnetic islands and a poloidal flow evolution equation is revisited. Using the model, analytical expressions of criteria of spontaneous shrinkage (self-healing) of magnetic islands and sudden growth of locked magnetic islands (penetration of RMP) are obtained, where nonlinear saturation states of islands show bifurcation structures and hysteresis characteristics. Considering radial profile of poloidal flows across magnetic islands, it is found that the self-healing is driven by neoclassical viscosity even in the absence of micro-turbulence-induced anomalous viscosity. Effects of unfavorable curvature in stellarators are found to modify the critical values. The scalings of criteria are consistent with low-{beta} experiments in the large helical device.
Neutral Vlasov kinetic theory of magnetized plasmas
Tronci, Cesare; Camporeale, Enrico
2015-02-15
The low-frequency limit of Maxwell equations is considered in the Maxwell-Vlasov system. This limit produces a neutral Vlasov system that captures essential features of plasma dynamics, while neglecting radiation effects. Euler-Poincaré reduction theory is used to show that the neutral Vlasov kinetic theory possesses a variational formulation in both Lagrangian and Eulerian coordinates. By construction, the new model recovers all collisionless neutral models employed in plasma simulations. Then, comparisons between the neutral Vlasov system and hybrid kinetic-fluid models are presented in the linear regime.
Magnetic field measurements for study of fast electron transport in magnetized HED plasma
NASA Astrophysics Data System (ADS)
Sawada, Hiroshi; Griffin, Brandon; Presura, Radu; Haque, Showera; Sentoku, Yasuhiko
2014-10-01
Interaction of megagauss magnetic fields with high energy density (HED) plasma is of great interest in the field of magnetized plasma. The field changes fundamental properties of the HED plasma such as thermal and magnetic diffusion. A coupled capability utilizing the 1.0 MA Zebra pulsed power generator and the 50 TW Leopard laser at Nevada Terawatt Facility enables to create such a condition for studies of magnetized plasma properties. We have conducted an experiment to measure magnetic fields generated by a 1.0 MA, 100 ns Zebra pulsed current in stainless steel coils. Using a 532 nm continuous laser from a single longitudinal mode laser system, the temporal change in the magnetic field was measured with the Faraday rotation in F2 glass. The probe laser passing through the 1.5 mm in radius and 1.75 mm thick glass placed in the vicinity of the inductive coils was split with a Glan-Taylor prism to measure vertical and horizontal polarization components with photodiodes. We will present the analysis of the experimental result and a design of a coupled experiment for study of fast electron transport in the magnetized plasma.
Thermal magnetic fluctuations of whistlers in a Maxwellian plasma
NASA Technical Reports Server (NTRS)
Golubyatnikov, G.; Stenzel, R. L.
1993-01-01
Thermal fluctuations were measured with a magnetic-loop antenna inside a large afterglow plasma in the whistler-wave regime. The magnetic fluctuations exhibit a 1/f-like spectrum for whistlers, no resonant enhancement at the electron cyclotron frequency, and a flat spectrum in the evanescent regime. The observed fluctuations are therefore described neither by blackbody radiation laws nor by cyclotron emission, but resemble the decaying Alfvenic fluctuations spectrum calculated by Cable and Tajima (1992).
Energetics of the magnetic reconnection in laboratory and space plasmas
NASA Astrophysics Data System (ADS)
Yamada, Masaaki
2014-10-01
The essential feature of magnetic reconnection is that it energizes plasma particles by converting magnetic energy to particle energy. This talk addresses this key unresolved question; how is magnetic energy converted to plasma kinetic energy during reconnection? Our recent study on MRX demonstrates that more than half of the incoming magnetic energy is converted to particle energy at a remarkably fast speed (~ 0.2VA) in the reconnection layer. A question arises as to whether the present results should be applied to magnetic reconnection phenomena in the space astrophysical plasmas. In a reconnection region of effectively similar size in the Earth's magnetotail, the energy partition was carefully measured during multiple passages of the Cluster satellites. The half length of the tail reconnection layer (L) was estimated to be 2000-4000 km namely 3-6 di, (ion skin depth); the scale length of this measurement is very similar to the MRX case, L ~ 3di. Reconnection in the magneto-tail is driven by an external force, i.e., the solar wind, and the boundary conditions are very similar to the MRX setup. The observed energy partition is notably similar, namely, more than 50% of the magnetic energy flux is converted to the particle energy flux, which is dominated by the ion enthalpy flux, with smaller contributions from the electron enthalpy and heat flux. A broad implication will be discussed. Supported by DoE, NASA, NSF.
Electron current extraction from a permanent magnet waveguide plasma cathode
Weatherford, B. R.; Foster, J. E.; Kamhawi, H.
2011-09-15
An electron cyclotron resonance plasma produced in a cylindrical waveguide with external permanent magnets was investigated as a possible plasma cathode electron source. The configuration is desirable in that it eliminates the need for a physical antenna inserted into the plasma, the erosion of which limits operating lifetime. Plasma bulk density was found to be overdense in the source. Extraction currents over 4 A were achieved with the device. Measurements of extracted electron currents were similar to calculated currents, which were estimated using Langmuir probe measurements at the plasma cathode orifice and along the length of the external plume. The influence of facility effects and trace ionization in the anode-cathode gap are also discussed.
Practicality of magnetic compression for plasma density control
NASA Astrophysics Data System (ADS)
Gueroult, Renaud; Fisch, Nathaniel J.
2016-03-01
Plasma densification through magnetic compression has been suggested for time-resolved control of the wave properties in plasma-based accelerators [P. F. Schmit and N. J. Fisch, Phys. Rev. Lett. 109, 255003 (2012)]. Using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro-period is investigated. For compression times shorter than the transit time of a compressional Alfven wave across the plasma slab, results show the formation of two counter-propagating shock waves, leading to a highly non-uniform plasma density profile. Furthermore, the plasma slab displays large hydromagnetic like oscillations after the driving field has reached steady state. Peak compression is obtained when the two shocks collide in the mid-plane. At this instant, very large plasma heating is observed, and the plasma β is estimated to be about 1. Although these results point out a densification mechanism quite different and more complex than initially envisioned, these features still might be advantageous in particle accelerators.
Atoms and plasmas in a high-magnetic-field trap
Raithel, G.; Knuffman, B.; Shah, M. H.; Hempel, C.; Paradis, E.; Mhaskar, R.; Zhang, X.; Choi, J.-H.; Povilus, A. P.; Guest, J. R.
2008-08-08
We investigate cold rubidium plasmas in a particle trap that has the unique capability to simultaneously laser-cool and trap neutral atoms as well as to confine plasmas in magnetic fields of about three Tesla. The atom trap is a high-field Ioffe-Pritchard laser trap, while the plasma trap is a Ioffe-Penning trap that traps electrons and ions in separate wells. The observed plasma dynamics is characterized by a breathing-mode oscillation of the positive (ionic) plasma component, which feeds back on the behavior of the negative (electron) component of the plasma. At higher densities, the observed oscillations become nonlinear. The electron component has been found to undergo rapid cooling. We further report on the recombination of magnetized plasmas into Rydberg atoms in transient traps and quasi-steady-state traps. In transient traps, large numbers of recombined Rydberg atoms in high-lying states are observed. In quasi-steady-state traps, the measured numbers of recombined atoms are lower and the binding energies higher.
Practicality of magnetic compression for plasma density control
Gueroult, Renaud; Fisch, Nathaniel J.
2016-03-16
Here, plasma densification through magnetic compression has been suggested for time-resolved control of the wave properties in plasma-based accelerators [P. F. Schmit and N. J. Fisch, Phys. Rev. Lett. 109, 255003 (2012)]. Using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro-period is investigated. For compression times shorter than the transit time of a compressional Alfven wave across the plasma slab, results show the formation of two counter-propagating shock waves, leading to a highly non-uniform plasma density profile. Furthermore, the plasma slab displays large hydromagnetic like oscillations aftermore » the driving field has reached steady state. Peak compression is obtained when the two shocks collide in the mid-plane. At this instant, very large plasma heating is observed, and the plasmaβ is estimated to be about 1. Although these results point out a densification mechanism quite different and more complex than initially envisioned, these features still might be advantageous in particle accelerators.« less
In What Magnetic Environment Are Coronal Loop Plasmas Located?
NASA Astrophysics Data System (ADS)
Lim, Daye; Choe, Gwangson; Yi, Sibaek
2016-04-01
Coronal loop plasmas are often regarded to be confined within magnetic flux ropes as in the case of laboratory plasmas. However, a plasma pressure profile, which decreases from the center of a flux rope to its periphery, can be ideal MHD interchange unstable if individual flux tubes constituting the flux rope are freely movable. In the solar corona, the strong line-tying condition impedes the interchange of flux tube positions, but ubiquitous magnetic reconnection processes can change plasma distribution in such a way that the system moves to a possible lower energy state. In this paper, we present a 2.5D MHD simulation study of the plasma redistribution in the merging process of many small flux ropes possibly representing loop strands. We have found that the redistributed plasma is more concentrated between flux ropes rather than near the center of flux ropes. When flux ropes initially have different amounts of twists, the plasma tends to accumulate in less twisted regions. As larger and larger flux ropes are formed by successive merging processes, the toroidal field of the flux ropes become stronger and stronger, i.e., field lines are less and less twisted. Our study may explain why the observed coronal loops appear very little twisted and quite well ordered in spite of continuous entangling motions in the photosphere and below.
Entrainment and acceleration of ambient plasma in a magnetized, laser-produced plasma
NASA Astrophysics Data System (ADS)
Bonde, Jeffrey; Vincena, Stephen; Gekelman, Walter
2015-11-01
Collisionless momentum coupling of a high energy density plasma expansion to a magnetized, ambient plasma is studied with a laser produced plasma expanding at speeds comparable to the background Alfvén speed, vexp = 1 . 2 ×107 cm/s ~vA . These expansions form diamagnetic cavities in which the background field is fully expelled. A moving Rosenbluth sheath forms at the boundary carrying a charge layer electrostatic sheath and inductive electric field. The total field in the lab frame was derived from emissive probe and magnetic probe measurements in the azimuthally symmetric experiment. Particle orbit tracing of an initially cold, stationary plasma tracked the evolution of the distribution of particles in these fields. A laser-induced fluorescence (LIF) diagnostic captured the resultant flows in the ambient argon plasma. The bulk flow fields from the orbit solvers and LIF are compared and found to agree vorbit ~vLIF ~ 3 ×105 cm/s while the distributions are highly non-Maxwellian. The orientation and magnitude of the flows show that the electrostatic sheath of the rapidly expanding plasma mostly entrains a tenuous background plasma, accelerating ions against the expansion. Orbit solvers show the effect has a significant dependence an ambient ion mass. This experiment was conducted in the Large Plasma Device at the Basic Plasma Science Facility and funded by grants from the US Department of Energy and the National Science Foundation.
Healing of magnetic islands in stellarators by plasma flow
NASA Astrophysics Data System (ADS)
Hegna, C. C.
2011-10-01
Recent experiments from the Large Helical Device (LHD) demonstrate a correlation between the ``healing'' of vacuum magnetic islands in stellarators and changes in the plasma flow. In the LHD experiments, external 3-D coils are intentionally applied to produce magnetic islands in the vacuum configuration. With plasma, both island growth and healing is seen with the two disparate plasma responses distinguished by a sharp boundary in a parameter space defined by the plasma β and collisionality at the rational surface. While island growth is observed at low β and high collisionality, at sufficiently high β and/or low collisionality, the plasma abruptly changes to a configuration with no island. A model explaining this phenomenon is developed reminiscent of ``mode locking/unlocking'' theory of tokamak physics. The theory describes transitions between two asymptotic solutions, a state with a large nonrotating island and a state where rotation shielding suppresses island formation. Transitions between these two states are governed by coupled torque balance and island evolution equations. In conventional stellarators, neoclassical damping physics plays an important role in establishing the flow profiles. The balance of neoclassical damping and cross-field viscosity produces a radial boundary layer for the plasma rotation profile outside the separatrix of a locked magnetic island. The width of this boundary layer decreases as the plasma becomes less collisional. This has the consequence of enhancing the viscous torque at low collisionality making healing magnetic islands occur more readily in high temperature conventional stellarators. The analytic theory produces a critical β for healing [βcrit ~(ν*) 1 / 4 ] that is in qualitative agreement with LHD observations. Research supported by U. S. DoE under grant nos. DE-FG02-99ER54546 and DE-SC0006103.
Magnetic reconnection in a magnetohydrodynamic plasma
Kulsrud, R.M.
1998-05-01
Magnetic reconnection is important because of its connection with the topology of field lines. In general, a change in topology means a change of equilibrium, and a release of energy, such as occurs in solar flares. In the context of the solar flare two models for magnetic reconnection, the Sweet{endash}Parker and the Petschek mechanism are presented. The pros and cons of these two models are presented. The role of anomalous resistivity in the Sweet{endash}Parker model is discussed. The bearing of a laboratory experiment and a boundary layer analysis of the problem are described. {copyright} {ital 1998 American Institute of Physics.}
Magnetic reconnection in a magnetohydrodynamic plasma
NASA Astrophysics Data System (ADS)
Kulsrud, Russell M.
1998-05-01
Magnetic reconnection is important because of its connection with the topology of field lines. In general, a change in topology means a change of equilibrium, and a release of energy, such as occurs in solar flares. In the context of the solar flare two models for magnetic reconnection, the Sweet-Parker and the Petschek mechanism are presented. The pros and cons of these two models are presented. The role of anomalous resistivity in the Sweet-Parker model is discussed. The bearing of a laboratory experiment and a boundary layer analysis of the problem are described.
Electron series resonance plasma discharges: Unmagnetized and magnetized
NASA Astrophysics Data System (ADS)
Qiu, Weiguang
2001-08-01
This thesis explores high frequency electron series resonance in unmagnetized and magnetized bounded plasmas. Special interest is focused on low temperature plasmas in planar systems as such are useful for material processing and fusion devices. Chapter 1, Chapter 2 and Chapter 3 describe simulation studies of unmagnetized electron series resonance (ESR) sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics. The input resistance is small and the drive voltage and current are in phase. The drive voltage is small (˜Te) and the time average plasma potential is low (˜10Te). A strong kinetic phase space bunching process is shown to provide electrons of sufficient energy for ionization, which allows discharge operation at low neutral pressure and low electron temperatures. At low pressure, the ion flux to the wall has a narrow angular spread about the normal and the ion bombarding energy distribution has a sharp peak at the plasma potential. Scaling laws at fixed pressure nr∝w3RF ,s¯∝w -1RF are shown to hold when RF frequency is varied smoothly ("chirping") demonstrating continuous density control. Research on magnetized electron series resonance (MESR) discharges is described in Chapter 4, Chapter 5 and Chapter 6. The resonant frequency is derived from cold plasma theory and shows two resonant modes. Simulations verify these modes to be the natural oscillatory frequencies of weakly magnetized plasmas in a planar plasma diode. A global model is established for magnetized resonant discharges. The interrelations among the plasma parameters and the drive terms are formulated for both resonant modes. The initiation of a MESR discharge and its steady state properties are discussed and compared to the unmagnetized case. Weak lock-on of MESR frequency to the drive frequency is observed in simulation. Similar V - I characteristics as those in ESR are found both in theory and in simulation. Different from the ESR
Construction of a solenoid used on a magnetized plasma experiment
NASA Astrophysics Data System (ADS)
Klein, S. R.; Manuel, M. J.-E.; Pollock, B. B.; Gillespie, R. S.; Deininger, M.; Kuranz, C. C.; Keiter, P. A.; Drake, R. P.
2014-11-01
Creating magnetized jets in the laboratory is relevant to studying young stellar objects, but generating these types of plasmas within the laboratory setting has proven to be challenging. Here, we present the construction of a solenoid designed to produce an axial magnetic field with strengths in the gap of up to 5 T. This novel design was a compact 75 mm × 63 mm × 88 mm, allowing it to be placed in the Titan target chamber. It was robust, surviving over 50 discharges producing fields ≲ 5 T, reaching a peak magnetic field of 12.5 T.
Microseconds-scale magnetic actuators system for plasma feedback stabilization
NASA Astrophysics Data System (ADS)
Kogan, K.; Be'ery, I.; Seemann, O.
2016-10-01
Many magnetic confinement machines use active feedback stabilization with magnetic actuators. We present a novel magnetic actuators system with a response time much faster than previous ones, making it capable of coping with the fast plasma instabilities. The system achieved a response time of 3 μs with maximal current of 500 A in a coil with inductance of 5.2 μH. The system is based on commercial solid-state switches and FPGA state machine, making it easily scalable to higher currents or higher inductivity.
Formation of prominences by condensation modes in magnetized cylindrical plasmas
NASA Technical Reports Server (NTRS)
An, C.-H.
1985-01-01
Condensation modes in a magnetized cylindrical plasma are studied to shed light on the formation and stability of solar prominences. A rigorous mathematical derivation of the perturbation equation is developed, and the effect of field twist on the stability is studied for an equilibrium with uniform field twist, in which temperature increases, but density does not, as pressure increases. The results imply that prominences may form in globally magnetohydrodynamic-stable magnetic loops with very low field twist. Also, prominences are more likely to form in a region of weaker area-averaged magnetic field.
Injection of a coaxial-gun-produced magnetized plasma into a background helicon plasma
NASA Astrophysics Data System (ADS)
Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott
2014-10-01
A compact coaxial plasma gun is employed for experimental investigation of plasma bubble relaxation into a lower density background plasma. Experiments are being conducted in the linear device HelCat at UNM. The gun is powered by a 120-uF ignitron-switched capacitor bank, which is operated in a range of 5 to 10 kV and 100 kA. Multiple diagnostics are employed to investigate the plasma relaxation process. Magnetized argon plasma bubbles with velocities 1.2Cs, densities 1020 m-3 and electron temperature 13eV have been achieved. The background helicon plasma has density 1013 m-3, magnetic field from 200 to 500 Gauss and electron temperature 1eV. Several distinct operational regimes with qualitatively different dynamics are identified by fast CCD camera images. Additionally a B-dot probe array has been employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify plasma bubble configurations. Experimental data and analysis will be presented.
Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.
2015-09-03
Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifiesmore » the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less
Magnetic Field Required for Ignition in a Magnetically Confined Plasma in Reactor-Type Conditions
NASA Astrophysics Data System (ADS)
Panarella, Emilio
1996-11-01
A complete and rigorous analysis will be given of the ignition conditions for a pulsed DT plasma magnetically confined, where the conduction losses are introduced from heat transfer theory, rather than from the empirically defined energy confinement time. It will be shown that the magnetic field required for ignition greatly exceeds any of those presently considered for major machines. It will also be shown that ignition is independent of particle density. On the basis of these results it is argued that ignition is facilitated in an inertially confined plasma, both of the classical type with lasers, or with the Spherical Pinch, or the Magnetized Target Fusion concepts.
Magnetic plasma confinement for laser ion source.
Okamura, M; Adeyemi, A; Kanesue, T; Tamura, J; Kondo, K; Dabrowski, R
2010-02-01
A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.
Effect of the plasma-induced magnetic field on a magnetic nozzle
NASA Astrophysics Data System (ADS)
Merino, Mario; Ahedo, Eduardo
2016-08-01
A two-fluid, two-dimensional model of the plasma expansion in a divergent magnetic nozzle is used to investigate the effect of the plasma-induced magnetic field on the acceleration and divergence of the plasma jet self-consistently. The induced field is diamagnetic and opposes the applied one, increasing the divergence of the magnetic nozzle and weakening its strength. This has a direct impact on the propulsive performance of the device, the demagnetization and detachment of the plasma, and can lead to the appearance of zero-field points and separatrix surfaces downstream. In contrast, the azimuthal induced field, albeit non-zero, is small in all cases of practical interest.
Magnetic Field Measurement in Magnetized Laser Plasmas Using Zeeman Broadening Diagnostics
NASA Astrophysics Data System (ADS)
Haque, S.; Wallace, M. S.; Arias, A.; Morita, T.; Plechaty, C.; Huntington, C.; Martinez, D.; Ross, S. J.; Park, H.-S.; Presura, R.
2013-10-01
The Zeeman effect has been used to measure the magnetic field in high energy density plasmas. The measurements are difficult when the field orientation is fluctuating in the plasma volume or when the line broadening due to the high plasma density and temperature surpasses the Zeeman splitting. Based on an idea proposed by Tessarin et al. (2011), we implemented a solution to this problem to the field measurement in magnetized laser plasmas. High resolution spectra were obtained at the Nevada Terawatt Facility for plasmas created by 20 J, 400 fs Leopard laser pulses in the azimuthal magnetic field produced by the 0.6 MA Zebra pulsed power generator. The components of the Al III 3s 2S1/2 - 3p 2P1 / 2 , 3 / 2 were recorded with space resolution along the direction normal to the target, which coincided with the magnetic field radius. In several shots, the spectra were time gated for 10 ns at different values of the magnetic field. In these measurements the Zeeman splitting was not resolved, but the magnetic field strength can be measured from the difference between the widths of the line profiles. This work was supported by the DOE/OFES grant DE-SC0008829 and DOE/NNSA contract DE-FC52-06NA27616.
Magnetic Diagnostics at the Wisconsin Plasma Astrophysics Laboratory
NASA Astrophysics Data System (ADS)
Peterson, Ethan; Clark, Michael; Egedal, Jan; Wallace, John; Weisberg, David; Forest, Cary
2015-11-01
A flexible suite of magnetic diagnostics is being developed to measure low and high frequency magnetic fields, the 3-D magnetic field structure throughout the plasma volume, and the 2-D structure (polar and azimuthal fields) on the surface of the sphere. The internal 3-D structure is ascertained by scanning insertion probes with high sensitivity, high bandwidth, 3-axis hall effect sensors. Careful engineering of these insertion probes is required to effectively remove the heat load while simultaneously maintaining high performance (hot, dense, steady state) plasmas. A surface array of 3-axis hall-effect sensors and 2-axis flux loops will provide 3-D, low frequency magnetic field measurements as well as high frequency fluctuations in the polar and azimuthal directions due to plasma waves. This surface array can be used to observe the spatial structure of global modes such as spherical ion acoustic waves and can provide insight into the structure and magnitude of internal plasma flows. The engineering and capabilities of these diagnostics is the focus of this poster.
Electron vortex magnetic holes: A nonlinear coherent plasma structure
Haynes, Christopher T. Burgess, David; Sundberg, Torbjorn; Camporeale, Enrico
2015-01-15
We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.
Electron vortex magnetic holes: A nonlinear coherent plasma structure
NASA Astrophysics Data System (ADS)
Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn
2015-01-01
We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.
Plasma flow, turbulence and magnetic islands in TJ-II
NASA Astrophysics Data System (ADS)
Estrada, T.; Ascasíbar, E.; Blanco, E.; Cappa, A.; Hidalgo, C.; Ida, K.; López-Fraguas, A.; van Milligen, B. Ph
2016-02-01
The effect of magnetic islands on plasma flow and turbulence has been experimentally investigated in ohmically induced magnetic configuration scans at the stellarator TJ-II. This operational mode allows sweeping the radial position of a low order rational surface from the plasma core towards the edge in a controlled way, what reveals effects that are difficult to notice in scans performed on a shot to shot basis. The main diagnostic used in the present work is a two-channel Doppler reflectometer that allows the measurement of the perpendicular rotation velocity of the turbulence and density fluctuations with good spatial and temporal resolution. A characteristic signature of the n/m = 3/2 magnetic island as it crosses the measurement position is clearly detected: the perpendicular flow reverses at the center of the magnetic island and a flow shear develops at the island boundaries. Fluctuations of the perpendicular flow and density have been also measured along the 3/2 magnetic island. An increase in the low frequency flow oscillations is measured at the magnetic island boundaries together with a reduction in the density fluctuation level; the later being more pronounced at the inner island boundary. These observations could explain the link between magnetic islands and transport barriers observed in a number of fusion devices.
Performance characterization of a permanent-magnet helicon plasma thruster
NASA Astrophysics Data System (ADS)
Takahashi, Kazunori; Charles, Christine; Boswell, Rod
2012-10-01
Helicon plasma thrusters operated at a few kWs of rf power is an active area of an international research. Recent experiments have clarified part of the thrust-generation mechanisms. Thrust components which have been identified include an electron pressure inside the source region and a Lorentz force due to an electron diamagnetic drift current and a radial component of the applied magnetic field. The use of permanent magnets (PMs) instead of solenoids is one of the solutions for improving the thruster efficiency because it does not require electricity for the magnetic nozzle formation. Here the thrust imparted from a permanent-magnet helicon plasma thruster is directly measured using a pendulum thrust balance. The source consists of permanent magnet (PM) arrays, a double turn rf loop antenna powered by a 13.56 MHz rf generator and a glass source tube. The PM arrays provide a magnetic nozzle near the open exit of the source and two configurations, which have maximum field strengths of about 100 and 270 G, are tested. A thrust of 15 mN, specific impulse of 2000 sec and a thrust efficiency of 8 percent are presently obtained for 2 kW of input power, 24 sccm flow rate of argon and the stronger magnetic field configuration.
Finite Time Lyapunov Exponents for magnetically confined plasmas
NASA Astrophysics Data System (ADS)
Sugiyama, Linda; Krishnan, Harinarayan
2012-10-01
Finite Time Lyapunov Exponents (FTLEs) are applied for the first time to magnetically confined plasmas. The FTLE measures the local divergence or convergence of n-dimensional vector fields. Time-dependent FTLEs are directly related to Lagrangian Coherent Structures, which form the underlying structure of turbulent flows. Modern FTLE methods, developed over the past decade, are evolving rapidly and leading to new practical and theoretical insights into turbulent fluid dynamics. In contrast to fluids, an MHD plasma has two vector fields, the magnetic field and the plasma flow. Accurate methods for computing and visualizing FTLEs for the MHD fields have been developed, based on the VisIt visualization package. They are applied to time slices of a large sawtooth crash in a toroidal plasma, computed by the M3D extended MHD code. The plasma structures for both B and v have unexpected properties that are not brought out by conventional analyses. The sawtooth crash is also found to have well-organized ``flow'' structures in v±B. The FTLE appears to be a sensitive diagnostic for the structure of stochastic magnetic fields. The methods are not restricted to MHD, since they apply to almost any vector field.
Interaction of a neutral cloud moving through a magnetized plasma
NASA Technical Reports Server (NTRS)
Goertz, C. K.; Lu, G.
1990-01-01
Current collection by outgassing probes in motion relative to a magnetized plasma may be significantly affected by plasma processes that cause electron heating and cross field transport. Simulations of a neutral gas cloud moving across a static magnetic field are discussed. The authors treat a low-Beta plasma and use a 2-1/2 D electrostatic code linked with the authors' Plasma and Neutral Interaction Code (PANIC). This study emphasizes the understanding of the interface between the neutral gas cloud and the surrounding plasma where electrons are heated and can diffuse across field lines. When ionization or charge exchange collisions occur a sheath-like structure is formed at the surface of the neutral gas. In that region the crossfield component of the electric field causes the electron to E times B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating. The thermal electron current is significantly enhanced due to this heating.
Negative specific heat of a magnetically self-confined plasma torus
Kiessling, Michael K.-H.; Neukirch, Thomas
2003-01-01
It is shown that the thermodynamic maximum-entropy principle predicts negative specific heat for a stationary, magnetically self-confined current-carrying plasma torus. Implications for the magnetic self-confinement of fusion plasma are considered. PMID:12576553
NASA Astrophysics Data System (ADS)
Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott
2012-10-01
A compact coaxial plasma gun is employed for experimental studies of plasma relaxation process being conducted in the HELCAT device at UNM. These studies will advance the knowledge of basic plasma physics in the areas of magnetic relaxation and space and astrophysical plasmas, including the evolution of active galactic jets/radio lobes. The gun is powered by a 120pF ignitron-switched capacitor bank which is operated in a range of 5 - 10kV. Multiple diagnostics are employed to investigate plasma relaxation process. Magnetized Argon plasma bubbles with velocities 1.2Cs and densities 10e20 m-3 have been achieved. Different distinct regimes of operation with qualitatively different dynamics are identified by fast CCD camera images, with the parameter lambda determining the operation regime. Additionally, a B-dot probe array is employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify detached plasma bubble configurations. Experimental data and analysis will be presented.
Parameter space region in the collisional magnetized electronegative plasma
Yasserian, Kiomars; Aslaninejad, Morteza
2010-02-15
The influence of the elastic collisions on the structure of a magnetized electronegative discharge is investigated. For a constant magnetic field, the profiles of the velocities of positive ions, the density of species, and electric potential are obtained. Furthermore, the positive ion flux is obtained as a function of magnetic field strength for different values of the collision frequency. The results show that in the absence of collision in a constant magnetic field, the discharge structure is uniform while by taking the collision into account, the structure becomes multilayer stratified. By increasing the collision frequency the discharge leaves the multilayer structure, and related oscillations in the plasma potential and space charge vanish. The parameter space region is obtained for collisionless and collisional cases. In this paper it is shown that a combined effect of collision and magnetic field determines the presheath-sheath structure.
Spark plasma sintering of Mn-Al-C hard magnets.
Pasko, A; LoBue, M; Fazakas, E; Varga, L K; Mazaleyrat, F
2014-02-12
Structural and magnetic characterization of isotropic Mn-Al-C bulk samples obtained by spark plasma sintering (SPS) is reported. This technique, to the best of our knowledge, has not been used for preparation of Mn-Al-based permanent magnets previously. Transformation from the parent -phase to the ferromagnetic τ-phase occurred on heating in the process of sintering. The phase constitution of the melt-spun precursors and consolidated samples was determined by x-ray diffraction. Magnetic hysteresis loops were recorded using a vibrating sample magnetometer. The compositional dependence of the coercivity, magnetization and density of the sintered materials is analysed. To combine good magnetic properties with proper densification, further optimization of the production parameters is necessary.
Magnetically Controlled Optical Plasma Waveguide for Electron Acceleration
Pollock, B. B.; Davis, P.; Divol, L.; Glenzer, S. H.; Palastro, J. P.; Price, D.; Froula, D. H.; Tynan, G. R.
2009-01-22
In order to produce multi-Gev electrons from Laser Wakefield Accelerators, we present a technique to guide high power laser beams through underdense plasma. Experimental results from the Jupiter Laser Facility at the Lawrence Livermore National Laboratory that show density channels with minimum plasma densities below 5x10{sup 17} cm{sup -3} are presented. These results are obtained using an external magnetic field (<5 T) to limit the radial heat flux from a pre-forming laser beam. The resulting increased plasma pressure gradient produces a parabolic density gradient which is tunable by changing the external magnetic field strength. These results are compared with 1-D hydrodynamic simulations, while quasi-static kinetic simulations show that for these channel conditions 90% of the energy in a 150 TW short pulse beam is guided over 5 cm and predict electron energy gains of 3 GeV.
Magnetically Controlled Optical Plasma Waveguide for Electron Acceleration
Pollock, B B; Froula, D H; Tynan, G R; Divol, L; Davis, P; Palastro, J P; Price, D; Glenzer, S H
2008-08-28
In order to produce multi-Gev electrons from Laser Wakefield Accelerators, we present a technique to guide high power laser beams through underdense plasma. Experimental results from the Jupiter Laser Facility at the Lawrence Livermore National Laboratory that show density channels with minimum plasma densities below 5 x 10{sup 17} cm{sup -3} are presented. These results are obtained using an external magnetic field (<5 T) to limit the radial heat flux from a pre-forming laser beam. The resulting increased plasma pressure gradient produces a parabolic density gradient which is tunable by changing the external magnetic field strength. These results are compared with 1-D hydrodynamic simulations, while quasi-static kinetic simulations show that for these channel conditions 90% of the energy in a 150 TW short pulse beam is guided over 5 cm and predict electron energy gains of 3 GeV.
Enhanced magnetic ionization in hydrogen reflex discharge plasma source
Toader, E.I.; Covlea, V.N.
2005-03-01
The effect of enhanced magnetic ionization on the external and internal parameters of a high-density, low pressure reflex plasma source operating in hydrogen is studied. The Langmuir probe method and Druyvesteyn procedure coupled with suitable software are used to measure the internal parameters. The bulk plasma region is free of an electric field and presents a high degree of uniformity. The electron energy distribution function is bi-Maxwellian with a dip/shoulder structure around 5.5 eV, independent of external parameters and radial position. Due to the enhanced hollow cathode effect by the magnetic trapping of electrons, the electron density n{sub e} is as high as 10{sup 18} m{sup -3}, and the electron temperature T{sub e} is as low as a few tens of an electron volt, for dissipated energy of tens of Watts. The bulk plasma density scales with the dissipated power.
Toward a Fully Kinetic Theory of Turbulence in Magnetized Plasmas
Yoon, Peter H.
2010-12-30
This paper outlines the present status of the kinetic theory of turbulence in magnetized plasmas as being developed by the present author. The systematic program to formulate the theory of turbulence starting from the Vlasov-Klimontovich formalism began with the works by pioneers of modern plasma physics in the 1960s and 1970s. However, early efforts adopted the heuristic semi-classical method instead of the statistical mechanical formulation, which is necessary for a quantitative analysis. Recently, the present author picked up where the early pioneers left, and began to reformulate the kinetic turbulence theory of turbulence in magnetized plasmas from statistical mechanical formalism. This paper is a brief outline of the progress to date.
Windowed multipole for cross section Doppler broadening
NASA Astrophysics Data System (ADS)
Josey, C.; Ducru, P.; Forget, B.; Smith, K.
2016-02-01
This paper presents an in-depth analysis on the accuracy and performance of the windowed multipole Doppler broadening method. The basic theory behind cross section data is described, along with the basic multipole formalism followed by the approximations leading to windowed multipole method and the algorithm used to efficiently evaluate Doppler broadened cross sections. The method is tested by simulating the BEAVRS benchmark with a windowed multipole library composed of 70 nuclides. Accuracy of the method is demonstrated on a single assembly case where total neutron production rates and 238U capture rates compare within 0.1% to ACE format files at the same temperature. With regards to performance, clock cycle counts and cache misses were measured for single temperature ACE table lookup and for windowed multipole. The windowed multipole method was found to require 39.6% more clock cycles to evaluate, translating to a 7.9% performance loss overall. However, the algorithm has significantly better last-level cache performance, with 3 fewer misses per evaluation, or a 65% reduction in last-level misses. This is due to the small memory footprint of the windowed multipole method and better memory access pattern of the algorithm.
Dynamics of whistler spheromaks in magnetized plasmas.
Eliasson, B; Shukla, P K
2007-11-16
Recent laboratory experiments [Stenzel et al., Phys. Rev. Lett. 96, 095004 (2006)10.1103/PhysRevLett.96.095004] have demonstrated interesting phenomena of propagating nonlinear whistler structures (spheromaks) and stationary field-reversed configurations, whose magnetic fields exceed the ambient magnetic field strength. Our objective here is to present simulation studies for these nonlinear whistler structures based on the three-dimensional nonlinear electron magnetohydrodynamic equations. The robustness and longevity of the propagating whistler spheromaks found in the experiments are confirmed numerically. Varying the toroidal field of the spheromak in the initial conditions, we find that the polarity and the amplitude of the toroidal field determine the propagation direction and speed of the spheromak. Our simulation results are in excellent agreement with those observed in the laboratory experiments.
Dynamics of Whistler Spheromaks in Magnetized Plasmas
Eliasson, B.; Shukla, P. K.
2007-11-16
Recent laboratory experiments [Stenzel et al., Phys. Rev. Lett. 96, 095004 (2006)] have demonstrated interesting phenomena of propagating nonlinear whistler structures (spheromaks) and stationary field-reversed configurations, whose magnetic fields exceed the ambient magnetic field strength. Our objective here is to present simulation studies for these nonlinear whistler structures based on the three-dimensional nonlinear electron magnetohydrodynamic equations. The robustness and longevity of the propagating whistler spheromaks found in the experiments are confirmed numerically. Varying the toroidal field of the spheromak in the initial conditions, we find that the polarity and the amplitude of the toroidal field determine the propagation direction and speed of the spheromak. Our simulation results are in excellent agreement with those observed in the laboratory experiments.
Penetration of resonant magnetic perturbations in turbulent edge plasmas
NASA Astrophysics Data System (ADS)
Monnier, A.; Fuhr, G.; Beyer, P.; Marcus, F. A.; Benkadda, S.; Garbet, X.
2014-06-01
Comprehension of the interactions between tokamak edge plasmas and externally induced resonant magnetic perturbations (RMPs) is an important step in the understanding of the control of edge-localized modes by these RMPs. Such control has been demonstrated experimentally, but previous theoretical investigations have revealed a possible screening of RMPs by a sheared rotation of the plasma. In this work, the penetration of RMPs is investigated via numerical simulations in a reduced magnetohydrodynamic model using the three-dimensional electromagnetic turbulence code EMEDGE3D. In this model, the plasma response to RMPs can be studied in the presence of flux-driven micro-turbulence and a transport barrier induced by sheared plasma rotation. The interplay is, in a first part, studied in a non-turbulent case to deduce a criterion for the penetration in a rotating plasma that is governed by the generation of counter currents. When the plasma is studied in a statistically stationary turbulent state, the self-consistent plasma rotation, governed by Reynolds and Maxwell stresses, leads to a self-organization where RMP penetrates. In a turbulent plasma in the presence of a transport barrier, the RMP harmonic that is resonant at the barrier centre is found to penetrate partially. This partial penetration is sufficient to trigger a local flattening of the pressure gradient that is known to be at the origin of the control of transport barrier relaxations in the present model.
NASA Astrophysics Data System (ADS)
Karlický, M.; Jiricka, K.
2002-10-01
Using the recent model of the radio zebra fine structures (Ledenev et al. 2001) the magnetic fields, plasma densities, and plasma beta parameters are estimated from high-frequency zebra fine structures. It was found that in the flare radio source of high-frequency (1-2 GHz) zebras the densities and magnetic fields vary in the intervals of (1-4)×1010 cm-3 and 40-230 G, respectively. Assuming then the flare temperature as about of 107K, the plasma beta parameters in the zebra radio sources are in the 0.05-0.81 interval. Thus the plasma pressure effects in such radio sources, especially in those with many zebra lines, are not negligible.
Study on spatial distribution of plasma parameters in a magnetized inductively coupled plasma
Cheong, Hee-Woon; Lee, Woohyun; Kim, Ji-Won; Whang, Ki-Woong; Kim, Hyuk; Park, Wanjae
2015-07-15
Spatial distributions of various plasma parameters such as plasma density, electron temperature, and radical density in an inductively coupled plasma (ICP) and a magnetized inductively coupled plasma (M-ICP) were investigated and compared. Electron temperature in between the rf window and the substrate holder of M-ICP was higher than that of ICP, whereas the one just above the substrate holder of M-ICP was similar to that of ICP when a weak (<8 G) magnetic field was employed. As a result, radical densities in M-ICP were higher than those in ICP and the etch rate of oxide in M-ICP was faster than that in ICP without severe electron charging in 90 nm high aspect ratio contact hole etch.
Magnetically controlled deposition of metals using gas plasma. Final report
1998-04-02
This is the first phase of a project that has the objective to develop a method of spraying materials on a substrate in a controlled manner to eliminate the waste and hazardous material generation inherent in present plating processes. The project is considering plasma spraying of metal on a substrate using magneto-hydrodynamics to control the plasma/metal stream. The process being developed is considering the use of commercially available plasma torches to generate the plasma/metal stream. The plasma stream is collimated, and directed using magnetic forces to the extent required for precise control of the deposition material. The project will be completed in phases. Phase one of the project, the subject of this grant, is the development of an analytical model that can be used to determine the feasibility of the process and to design a laboratory scale demonstration unit. The contracted time is complete, and the research is still continuing. This report provides the results obtained to date. As the model and calculations are completed those results will also be provided. This report contains the results of the computer code that have been completed to date. Results from a ASMEE Benchmark problem, flow over a backward step with heat transfer, Couette flow with magnetic forces, free jet flow are presented along with several other check calculations that are representative of the cases that were calculated in the course of the development process. The final cases that define a velocity field in the exit of a plasma spray torch with and without a magnetic field are in process. A separate program (SPRAY) has been developed that can track the plating material to the substrate and describe the distribution of the material on the substrate. When the jet calculations are complete SPRAY will be used to compare the distribution of material on the substrate with and without the effect of the magnetic focus.
Antiproton powered propulsion with magnetically confined plasma engines
NASA Technical Reports Server (NTRS)
Lapointe, Michael R.
1989-01-01
Matter-antimatter annihilation releases more energy per unit mass than any other method of energy production, making it an attractive energy source for spacecraft propulsion. In the magnetically confined plasma engine, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas. The resulting charged annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. The calculated energy transfer efficiencies for a low number density (10(14)/cu cm) hydrogen propellant are insufficient to warrant operating the engine in this mode. Efficiencies are improved using moderate propellant number densities (10(16)/cu cm), but the energy transferred to the plasma in a realistic magnetic mirror system is generally limited to less than 2 percent of the initial proton-antiproton annihilation energy. The energy transfer efficiencies are highest for high number density (10(18)/cu cm) propellants, but plasma temperatures are reduced by excessive radiation losses. Low to moderate thrust over a wide range of specific impulse can be generated with moderate propellant number densities, while higher thrust but lower specific impulse may be generated using high propellant number densities. Significant mass will be required to shield the superconducting magnet coils from the high energy gamma radiation emitted by neutral pion decay. The mass of such a radiation shield may dominate the total engine mass, and could severely diminish the performance of antiproton powered engines which utilize magnetic confinement. The problem is compounded in the antiproton powered plasma engine, where lower energy plasma bremsstrahlung radiation may cause shield surface ablation and degradation.
A Novel Experimental Setup to Investigate Magnetized Dusty Plasmas
NASA Astrophysics Data System (ADS)
Romero-Talamas, C. A.; Larocque, P.; Alvarez, J.; Sardin, J.
2013-10-01
Progress on the design and construction of a novel experimental setup to investigate dusty plasmas at the University of Maryland, Baltimore County (UMBC) is presented. The setup includes separation adjustability of discharge electrodes and their orientation with respect to gravity without breaking vacuum, and a pair of water-cooled coils to produce magnetic fields with strengths of up to several Tesla. The coils' orientation is also designed to be adjustable with respect to gravity. A pulse-forming network to power the coils with flattop times of several seconds is under design. The setup is mounted inside a large glass bell jar to provide wide optical access to the dusty plasmas, and to minimize interference of chamber walls and mounts with imposed electric or magnetic fields. Planned experiments include crystallization and wave propagation under strong magnetic fields.
NASA Astrophysics Data System (ADS)
Bose, Sayak; Chattopadhyay, P. K.; Ghosh, J.; Sengupta, S.; Saxena, Y. C.; Pal, R.
2015-04-01
In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n <= 1%, Luniform ~ 120 cm at argon filling pressure of ~10-4 mbar and axial magnetic field of B = 1090 G.
Corrosion behavior of magnetic ferrite coating prepared by plasma spraying
Liu, Yi; Wei, Shicheng Tong, Hui; Tian, Haoliang; Liu, Ming; Xu, Binshi
2014-12-15
Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surface of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.
A linear radio frequency plasma reactor for potential and current mapping in a magnetized plasma
Faudot, E.; Devaux, S.; Moritz, J.; Heuraux, S.; Molina Cabrera, P.; Brochard, F.
2015-06-15
Langmuir probe measurements in front of high power ion cyclotron resonant frequency antennas are not possible or simply too noisy to be analyzed properly. A linear experiment is a radio frequency (RF) magnetized plasma discharge reactor designed to probe the rectified potential in front of such antennas but at low power level (1 kW) to next improve antenna design and mitigate sheath effects. The maximum magnetic field is 0.1 T, and the RF amplifier can work between 10 kHz and 250 MHz allowing ion cyclotron resonances for argon or helium. The first measurements with no magnetic field are presented here, especially 2D potential maps extracted from the RF compensated probe measurements yield ni ≈ 10{sup 15} m{sup −3} and Te ≈ 2 eV for RF power lower than 100 W. Series resonances in the chamber are highlighted and allow to deduce the plasma parameters from a simple equivalent impedance model of the plasma in helium gas. Next studies will be focused on magnetized plasmas and especially magnetized RF sheaths.
A linear radio frequency plasma reactor for potential and current mapping in a magnetized plasma.
Faudot, E; Devaux, S; Moritz, J; Heuraux, S; Molina Cabrera, P; Brochard, F
2015-06-01
Langmuir probe measurements in front of high power ion cyclotron resonant frequency antennas are not possible or simply too noisy to be analyzed properly. A linear experiment is a radio frequency (RF) magnetized plasma discharge reactor designed to probe the rectified potential in front of such antennas but at low power level (1 kW) to next improve antenna design and mitigate sheath effects. The maximum magnetic field is 0.1 T, and the RF amplifier can work between 10 kHz and 250 MHz allowing ion cyclotron resonances for argon or helium. The first measurements with no magnetic field are presented here, especially 2D potential maps extracted from the RF compensated probe measurements yield ni ≈ 10(15) m(-3) and Te ≈ 2 eV for RF power lower than 100 W. Series resonances in the chamber are highlighted and allow to deduce the plasma parameters from a simple equivalent impedance model of the plasma in helium gas. Next studies will be focused on magnetized plasmas and especially magnetized RF sheaths. PMID:26133834
A 7 T Pulsed Magnetic Field Generator for Magnetized Laser Plasma Experiments
NASA Astrophysics Data System (ADS)
Hu, Guangyue; Liang, Yihan; Song, Falun; Yuan, Peng; Wang, Yulin; Zhao, Bin; Zheng, Jian
2015-02-01
A pulsed magnetic field generator was developed to study the effect of a magnetic field on the evolution of a laser-generated plasma. A 40 kV pulsed power system delivered a fast (~230 ns), 55 kA current pulse into a single-turn coil surrounding the laser target, using a capacitor bank of 200 nF, a laser-triggered switch and a low-impedance strip transmission line. A one-dimensional uniform 7 T pulsed magnetic field was created using a Helmholtz coil pair with a 6 mm diameter. The pulsed magnetic field was controlled to take effect synchronously with a nanosecond heating laser beam, a femtosecond probing laser beam and an optical Intensified Charge Coupled Device (ICCD) detector. The preliminary experiments demonstrate bifurcation and focusing of plasma expansion in a transverse magnetic field.
Simulation of electromagnetically and magnetically induced transparency in a magnetized plasma
NASA Astrophysics Data System (ADS)
Hur, M. S.; Wurtele, J. S.; Shvets, G.
2003-07-01
Electromagnetically induced transparency (EIT), a phenomenon well known in atomic systems, has a natural analogy in a classical magnetized plasma. The magnetized plasma has a resonance for right-hand polarized electromagnetic waves at the electron cyclotron frequency Ω0, so that a probe wave with frequency ω1=Ω0 cannot propagate through the plasma. The plasma can be made transparent to such a probe by the presence of a pump wave. The pump may be an electromagnetic wave or magnetostatic wiggler. Simulations and theory show that the physical reason for the transparency is that the beating of the probe wave with the pump wave sets up a plasma oscillation, and the upper sideband of the pump wave cancels the resonant plasma current due to the probe. The theory of plasma EIT derived here extends that found in the earlier work to include the effects of the lower sideband of the pump and renormalization of the plasma frequency and an analysis of the transient response. A detailed comparison of theory to one-dimensional particle-in-cell simulations is presented and estimates for the performance ion accelerator using the EIT interaction are given. The dispersion relation and estimates for the phase velocity and amplitude of the plasma wave are in good agreement with particle-in-cell simulations.
Ultra-High Intensity Magnetic Field Generation in Dense Plasma
Fisch, Nathaniel J
2014-01-08
I. Grant Objective The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereasthefficient generation of electric current in low-energy-density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-energy-density plasma the ideas for steady-state current drive developed for low-energy-density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-energy-density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.
Radiation from Cerenkov Wakes in a Magnetized Plasma
Yoshii, J.; Lai, C.H.; Katsouleas, T.; Joshi, C.; Mori, W.B.
1997-11-01
The Cerenkov wake excited by a particle beam or a short laser pulse in a perpendicularly magnetized plasma is analyzed. The wake couples to electromagnetic radiation of approximate frequency {omega}{sub p} at the plasma/vacuum boundary. The radiation amplitude is {omega}{sub c}/{omega}{sub p} times the amplitude of the wake excited in the plasma (for a sharp boundary). Particle-in-cell simulations verify the scaling laws. Since plasma wakes as high as a few GeV/m are produced in current experiments, the potential for a high-power (i.e., GW) coherent microwave to THz radiation source exists. {copyright} {ital 1997} {ital The American Physical Society}
The acoustic instabilities in magnetized collisional dusty plasmas
Pandey, B. P.; Vladimirov, S. V.; Dwivedi, C. B.
2014-09-15
The present work investigates the wave propagation in collisional dusty plasmas in the presence of electric and magnetic field. It is shown that the dust ion-acoustic waves may become unstable to the reactive instability whereas dust-acoustic waves may suffer from both reactive and dissipative instabilities. If the wave phase speed is smaller than the plasma drift speed, the instability is of reactive type whereas in the opposite case, the instability becomes dissipative in nature. Plasma in the vicinity of dust may also become unstable to reactive instability with the instability sensitive to the dust material: dielectric dust may considerably quench this instability. This has implications for the dust charging and the use of dust as a probe in the plasma sheath.
Model of magnetic reconnection in space and astrophysical plasmas
NASA Astrophysics Data System (ADS)
Boozer, Allen H.
2013-03-01
Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.
Model of magnetic reconnection in space and astrophysical plasmas
Boozer, Allen H.
2013-03-15
Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.
Plasma-Jet Magnetized-Target Fusion Burn Dynamics
NASA Astrophysics Data System (ADS)
Santarius, John F.
2006-10-01
In magnetized-target fusion (MTF), an imploding, conducting liner compresses a magnetized plasmoid, such as a spheromak or field-reversed configuration (FRC). The increasing magnetic field of the target reduces thermal conduction and the liner's inertia provides transient plasma stability and confinement. This poster explores the burn dynamics of using plasma jets to form the liner [1]. The investigation uses the University of Wisconsin’s 1 D Lagrangian radiation hydrodynamics code, BUCKY, which solves single-fluid equations of motion with pressure contributions from electrons, ions, radiation, and fast charged particles, using either ideal-gas or table-lookup equations of state. BUCKY includes ion-electron interactions, PdV work, and fast-ion energy deposition. For this research, the code has been extended to include the magnetic field evolution as the plasmoid compresses plus the dependence of the thermal conductivity and fusion product energy deposition on the magnetic field.[1] Y.C. F. Thio, et al., ``Magnetized Target Fusion in a Spheroidal Geometry with Standoff Drivers,'' in Current Trends in International Fusion Research, E. Panarella, ed. (National Research Council of Canada, Ottawa, Canada, 1999), p. 113.* Research funded by the DOE Office of Fusion Energy Sciences, grant DE-FG02-04ER54751.
Scaling mechanisms of vapour/plasma shielding from laser-produced plasmas to magnetic fusion regimes
NASA Astrophysics Data System (ADS)
Sizyuk, Tatyana; Hassanein, Ahmed
2014-02-01
The plasma shielding effect is a well-known mechanism in laser-produced plasmas (LPPs) reducing laser photon transmission to the target and, as a result, significantly reducing target heating and erosion. The shielding effect is less pronounced at low laser intensities, when low evaporation rate together with vapour/plasma expansion processes prevent establishment of a dense plasma layer above the surface. Plasma shielding also loses its effectiveness at high laser intensities when the formed hot dense plasma plume causes extensive target erosion due to radiation fluxes back to the surface. The magnitude of emitted radiation fluxes from such a plasma is similar to or slightly higher than the laser photon flux in the low shielding regime. Thus, shielding efficiency in LPPs has a peak that depends on the laser beam parameters and the target material. A similar tendency is also expected in other plasma-operating devices such as tokamaks of magnetic fusion energy (MFE) reactors during transient plasma operation and disruptions on chamber walls when deposition of the high-energy transient plasma can cause severe erosion and damage to the plasma-facing and nearby components. A detailed analysis of these abnormal events and their consequences in future power reactors is limited in current tokamak reactors. Predictions for high-power future tokamaks are possible only through comprehensive, time-consuming and rigorous modelling. We developed scaling mechanisms, based on modelling of LPP devices with their typical temporal and spatial scales, to simulate tokamak abnormal operating regimes to study wall erosion, plasma shielding and radiation under MFE reactor conditions. We found an analogy in regimes and results of carbon and tungsten erosion of the divertor surface in ITER-like reactors with erosion due to laser irradiation. Such an approach will allow utilizing validated modelling combined with well-designed and well-diagnosed LPP experimental studies for predicting
NASA Astrophysics Data System (ADS)
Rafalskyi, Dmytro; Aanesland, Ane
2015-09-01
We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).
Eliseev, L. G.; Ivanov, N. V. Kakurin, A. M.; Perfilov, S. V.; Melnikov, A. V.
2015-05-15
Experimental comparison of the m = 2, n = 1 mode and plasma rotation velocities at q = 2 magnetic surface in a wide range of the mode amplitudes is presented. Phase velocity of the mode rotation is measured with a set of poloidal magnetic field sensors located at the inner side of the vacuum vessel wall. Plasma rotation velocity at the q = 2 magnetic surface in the direction of the mode phase velocity is measured with the heavy ion beam probe diagnostics. In the presence of a static Resonant Magnetic Perturbation (RMP), the rotation is irregular that appears as cyclical variations of the mode and plasma instantaneous velocities. The period of these variations is equal to the period of the mode oscillations. In the case of high mode amplitude, the rotation irregularity of the mode is consistent with the rotation irregularity of the resonant plasma layer. On the contrary, the observed rise of the mode rotation irregularity in the case of low mode amplitude occurs without an increase of the rotation irregularity of the resonant plasma layer. The experimental results are simulated and analyzed with the TEAR code based on the two-fluid MHD approximation. Calculated irregularities of the mode and plasma rotation depend on the mode amplitude similar to the experimental data. For large islands, the rotation irregularity is attributed to oscillations of the electromagnetic torque applied to the resonant plasma layer. For small islands, the deviation of the mode rotation velocity from the plasma velocity occurs due to the effect of finite plasma resistivity.
Electromagnetic wave propagation through an overdense magnetized collisional plasma layer
NASA Astrophysics Data System (ADS)
Thoma, C.; Rose, D. V.; Miller, C. L.; Clark, R. E.; Hughes, T. P.
2009-08-01
The results of investigations into the feasibility of using a magnetic window to propagate electromagnetic waves through a finite-sized overdense plasma slab are described. We theoretically calculate the transmission coefficients for right- and left-handed circularly polarized plane waves through a uniform magnetized plasma slab. Using reasonable estimates for the plasma properties expected to be found in the ionized shock layer surrounding a hypersonic aircraft traveling in the earth's upper atmosphere (radio blackout conditions), and assuming a 1 GHz carrier frequency for the radio communications channel, we find that the required magnetic field for propagation of right-handed circularly polarized, or whistler, waves is on the order of a few hundred gauss. Transmission coefficients are calculated as a function of sheath thickness and are shown to be quite sensitive to the electron collision frequency. One-dimensional particle-in-cell simulations are shown to be in good agreement with the theory. These simulations also demonstrate that Ohmic heating of the electrons can be considerable. Two- and three-dimensional particle-in-cell simulations using a simplified waveguide and antenna model illustrate the same general transmission behavior as the theory and one-dimensional simulations. In addition, a net focusing effect due to the plasma is also observed in two and three dimensions. These simulations can be extended to design and analyze more realistic waveguide and antenna models.
Electromagnetic wave propagation through an overdense magnetized collisional plasma layer
Thoma, C.; Rose, D. V.; Miller, C. L.; Clark, R. E.; Hughes, T. P.
2009-08-15
The results of investigations into the feasibility of using a magnetic window to propagate electromagnetic waves through a finite-sized overdense plasma slab are described. We theoretically calculate the transmission coefficients for right- and left-handed circularly polarized plane waves through a uniform magnetized plasma slab. Using reasonable estimates for the plasma properties expected to be found in the ionized shock layer surrounding a hypersonic aircraft traveling in the earth's upper atmosphere (radio blackout conditions), and assuming a 1 GHz carrier frequency for the radio communications channel, we find that the required magnetic field for propagation of right-handed circularly polarized, or whistler, waves is on the order of a few hundred gauss. Transmission coefficients are calculated as a function of sheath thickness and are shown to be quite sensitive to the electron collision frequency. One-dimensional particle-in-cell simulations are shown to be in good agreement with the theory. These simulations also demonstrate that Ohmic heating of the electrons can be considerable. Two- and three-dimensional particle-in-cell simulations using a simplified waveguide and antenna model illustrate the same general transmission behavior as the theory and one-dimensional simulations. In addition, a net focusing effect due to the plasma is also observed in two and three dimensions. These simulations can be extended to design and analyze more realistic waveguide and antenna models.
A gyrokinetic collision operator for magnetized Lorentz plasmas
NASA Astrophysics Data System (ADS)
Liu, Chang; Qin, Hong; Ma, Chenhao; Yu, Xiongjie
2011-03-01
A gyrocenter collision operator for magnetized Lorentz plasmas is derived using the Fokker-Plank method. The gyrocenter collision operator consists of drift and diffusion terms in the gyrocenter coordinates, including the diffusion of the gyrocenter, which does not exist for the collision operator in the particle phase space coordinates. The gyrocenter collision operator also depends on the transverse electric field explicitly, which is crucial for the correct treatment of collisional effects and transport in the gyrocenter coordinates. The gyrocenter collision operator derived is applied to calculate the particle and heat transport fluxes in a magnetized Lorentz plasma with an electric field. The particle and heat transport fluxes calculated from our gyrocenter collision operator agree exactly with the classical Braginskii's result [S. I. Braginskii, Reviews of Plasma Physics (Consultants Bureau, New York, 1965), Vol. 1, p. 205: P. Helander and D. J. Sigmar, Collisional Transport in Magnetized Plasmas (Cambridge University, Cambridge, 2002), p. 65], which validates the correctness of our collision operator. To calculate the transport fluxes correctly, it is necessary to apply the pullback transformation associated with gyrocenter coordinate transformation in the presence of collisions, which also serves as a practical algorithm for evaluating collisional particle and heat transport fluxes in the gyrocenter coordinates.
Nonlocal electron transport in magnetized plasmas with arbitrary atomic number
Bennaceur-Doumaz, D.; Bendib, A.
2006-09-15
The numerical solution of the steady-state electron Fokker-Planck equation perturbed with respect to a global equilibrium is presented in magnetized plasmas with arbitrary atomic number Z. The magnetic field is assumed to be constant and the electron-electron collisions are described by the Landau collision operator. The solution is derived in the Fourier space and in the framework of the diffusive approximation which captures the spatial nonlocal effects. The transport coefficients are deduced and used to close a complete set of nonlocal electron fluid equations. This work improves the results of A. Bendib et al. [Phys. Plasmas 9, 1555 (2002)] and of A. V. Brantov et al. [Phys. Plasmas 10, 4633 (2003)] restricted to the local and nonlocal high-Z plasma approximations, respectively. The influence of the magnetic field on the nonlocal effects is discussed. We propose also accurate numerical fits of the relevant transport coefficients with respect to the collisionality parameter {lambda}{sub ei}/L and the atomic number Z, where L is the typical scale length and {lambda}{sub ei} is the electron-ion mean-free-path.
Magnetically Controlled Plasma Waveguide For Laser Wakefield Acceleration
Froula, D H; Divol, L; Davis, P; Palastro, J; Michel, P; Leurent, V; Glenzer, S H; Pollock, B; Tynan, G
2008-05-14
An external magnetic field applied to a laser plasma is shown produce a plasma channel at densities relevant to creating GeV monoenergetic electrons through laser wakefield acceleration. Furthermore, the magnetic field also provides a pressure to help shape the channel to match the guiding conditions of an incident laser beam. Measured density channels suitable for guiding relativistic short-pulse laser beams are presented with a minimum density of 5 x 10{sup 17} cm{sup -3} which corresponds to a linear dephasing length of several centimeters suitable for multi-GeV electron acceleration. The experimental setup at the Jupiter Laser Facility, Lawrence Livermore National Laboratory, where a 1-ns, 150 J 1054 nm laser will produce a magnetically controlled channel to guide a < 75 fs, 10 J short-pulse laser beam through 5-cm of 5 x 10{sup 17} cm{sup -3} plasma is presented. Calculations presented show that electrons can be accelerated to 3 GeV with this system. Three-dimensional resistive magneto-hydrodynamic simulations are used to design the laser and plasma parameters and quasi-static kinetic simulations indicate that the channel will guide a 200 TW laser beam over 5-cm.
MHD Simulation of Plasma Flow through the VASIMR Magnetic Nozzle
NASA Astrophysics Data System (ADS)
Tarditi, A. G.; Shebalin, J. V.
2003-10-01
The VASIMR (Variable Specific Impulse Magnetoplasma Rocket, [1]) concept is currently in the experimental development phase at the Advanced Space Propulsion Laboratory, NASA Johnson Space Center. The current experimental effort is mainly focused on the demonstration of the efficient plasma production (light ion helicon source, [2]) and energy boosting (ion cyclotron resonance heating section). Two other critical issues, the plasma detachment process and the collimation of the plasma plume in the magnetic nozzle, are essential for the near term experimental development and are being addressed through an MHD simulation modeling effort with the NIMROD code [3,4]. The model follows the plasma flow up to few meters from the nozzle throat: at that distance the plasma exhaust parameters reach values comparable with the ionospheric plasma background [5]. Results from two-dimensional simulation runs (cylindrical geometry, assuming azimuthal symmetry) aimed in particular at testing the effectiveness of different open-end boundary condition schemes are presented. [1] F. R. Chang-Diaz, Scientific American, p. 90, Nov. 2000 [2] M. D. Carter, et al., Phys. Plasmas 9, 5097-5110, 2002 [3] http://www.nimrodteam.org [4] A. Tarditi et al., 28th Int. Electric Propulsion Conf., IEPC 2003, Toulouse, France, March 2003 [5] A. V. Ilin et al., Proc. 40th AIAA Aerospace Sciences Meeting, Reno, NV, Jan. 2002
Large-Area Permanent-Magnet ECR Plasma Source
NASA Technical Reports Server (NTRS)
Foster, John E.
2007-01-01
A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design - low contamination and long operational life. The device generates a uniform, high-density plasma capable of sustaining uniform ion-current densities at its exit plane while operating at low pressure [<10(exp -4) torr (less than about 1.3 10(exp -2) Pa)] and input power <200 W at a frequency of 2.45 GHz. Though the prototype model operates at 2.45 GHz, operation at higher frequencies can be achieved by straightforward modification to the input microwave waveguide. Higher frequency operation may be desirable in those applications that require even higher background plasma densities. In the design of this ECR plasma source, there are no cumbersome, power-hungry electromagnets. The magnetic field in this device is generated by a permanent-magnet circuit that is optimized to generate resonance surfaces. The microwave power is injected on the centerline of the device. The resulting discharge plasma jumps into a "high mode" when the input power rises above 150 W. This mode is associated with elevated plasma density and high uniformity. The large area and uniformity of the plasma and the low operating pressure are well suited for such material-processing applications as etching and deposition on large silicon wafers. The high exit-plane ion-current density makes it possible to attain a high rate of etching or deposition. The plasma potential is <3 V low enough that there is little likelihood of sputtering, which, in plasma processing, is undesired
Multipole moments of bumpy black holes
Vigeland, Sarah J.
2010-11-15
General relativity predicts the existence of black holes, compact objects whose spacetimes depend only on their mass, spin, and charge in vacuum (the 'no-hair' theorem). As various observations probe deeper into the strong fields of black hole candidates, it is becoming possible to test this prediction. Previous work suggested that such tests can be performed by measuring whether the multipolar structure of black hole candidates has the form that general relativity demands, and introduced a family of 'bumpy black hole' spacetimes to be used for making these measurements. These spacetimes have generalized multipoles, where the deviation from the Kerr metric depends on the spacetime's 'bumpiness'. In this paper, we show how to compute the Geroch-Hansen moments of a bumpy black hole, demonstrating that there is a clean mapping between the deviations used in the bumpy black hole formalism and the Geroch-Hansen moments. We also extend our previous results to define bumpy black holes whose current moments, analogous to magnetic moments of electrodynamics, deviate from the canonical Kerr value.
Jump conditions at fast shocks in an anisotropic magnetized plasma
NASA Astrophysics Data System (ADS)
Vogl, D. F.; Erkaev, N. V.; Biernat, H. K.; Mühlbachler, S.; Farrugia, C. J.
2001-01-01
In this paper we report on the variations of the magnetic field strength and the plasma parameters across a fast shock as functions of upstream Alfvén Mach numbers and pressure anisotropy downstream of the shock. In our study we consider an oblique shock where the angle between the magnetic field vector and the normal vector upstream of the shock is chosen to be 45°. We further use two threshold conditions of plasma instabilities as additional equations to bound the range of the pressure anisotropy, p⊥/ p|, i.e., the criterion of the mirror instability and that of the fire—hose instability. We found that the variations of the parallel pressure, the parallel temperature, as well as the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock, whereas the variations of the plasma density, the normal velocity, the magnetic field strength, and perpendicular pressure and temperature with respect to the magnetic field show much less pronounced dependence on the anisotropy.
Design and Assembly of the Magnetized Dusty Plasma Experiment (MDPX)
NASA Astrophysics Data System (ADS)
Fisher, Ross; Artis, Darrick; Lynch, Brian; Wood, Keith; Shaw, Joseph; Gilmore, Kevin; Robinson, Daniel; Polka, Christian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene
2013-10-01
Over the last two years, the Magnetized Dusty Plasma Experiment (MDPX) has been under construction at Auburn University. This new research device, whose assembly will be completed in late Summer, 2013, uses a four-coil, superconducting, high magnetic field system (|B | >= 4 Tesla) to investigate the confinement, charging, transport, and instabilities in a dusty plasma. A new feature of the MDPX device is the ability to operate the magnetic coils independently to allow a variety of magnetic configurations from highly uniform to quadrapole-like. Envisioned as a multi-user facility, the MDPX device features a cylindrical vacuum vessel whose primary experimental region is an octagonal chamber that has a 35.5 cm inner diameter and is 19 cm tall. There is substantial diagnostics and optical access through eight, 10.2 cm × 12.7 cm side ports. The chamber can also be equipped with two 15.2 cm diameter, 76 cm long extensions to allow long plasma column experiments, particularly long wavelength dust wave studies. This presentation will discuss the final design, assembly, and installation of the MDPX device and will describe its supporting laboratory facility. This work is supported by a National Science Foundation - Major Research Instrumentation (NSF-MRI) award, PHY-1126067.
Analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma
Shukla, Arun; Jat, K. L.
2015-07-31
An analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma has been reported. In the present analytical investigation, the lattice displacement, acousto-optical polarization, susceptibility, acousto-optical gain constant arising due to the induced nonlinear current density and acousto-optical process are deduced in an acoustically perturbed Brillouin active magnetized semiconductor plasma using the hydrodynamical model of plasma and coupled mode scheme. The influence of wave number and magnetic field has been explored. The analysis has been applied to centrosymmetric crystal. Numerical estimates are made for n-type InSb crystal duly irradiated by a frequency doubled 10.6 µm CO{sub 2} laser. It is found that lattice displacement, susceptibility and acousto-optical gain increase linearly with incident wave number and applied dc magnetic field, while decrease with scattering angle. The gain also increases with electric amplitude of incident laser beam. Results are found to be well in agreement with available literature.
Non-Neutral Ion Plasma in a Toroidal Magnetic Field
NASA Astrophysics Data System (ADS)
Boyd, D. A.
1997-11-01
We propose to trap and study the equilibria of a non-neutral ion plasma in a toroidal magnetic field. Such equilibria have been described by O'Neil and Smith(T. M. O'Neil, R. A. Smith, Phys. Plasmas 1, 2430 (1994)). An electron plasma has been studied by Zaveri et al.(Puravi Zaveri, P. I. John, K. Avinash, and P. K. Kaw, Phys. Rev. Lett. 68, 3295 (1992)). Although single ions are not confined in such a trap, for plasmas there exists a large parameter space with radically different regimes for the trapped ions. This is a novel form of ion trap in which to study orbit dynamics, equilibria, and different thermodynamic states by cooling and manipulation of the ion distribution. Barium and Calcium ions produced by photo-ionization would be injected into the trap from a transient magnetic divertor with positively charged target plates. Ions permit a detailed study of their distribution function with non-perturbative techniques. Laser Induced Fluorescence and ion tagging techniques would be used to study the microscopic dynamics of the ions. Image charge probes would be used to study density fluctuations. In the longer term lasers would be used to cool the ions and the distribution altered by externally launched waves coupled to the plasma. A basic description and classification of the stable equilibria will be given as well as the parameters and design of a low cost, experimental trap.
NASA Astrophysics Data System (ADS)
Fox, W.; Deng, W.; Bhattacharjee, A.; Fiksel, G.; Nilson, P.; Haberberger, D.; Chang, P.-Y.; Barnak, D.
2015-11-01
Significant particle energization is observed to occur in many astrophysical environments, and in the standard models this acceleration occurs as a part of the energy conversion processes associated with collisionless shocks or magnetic reconnection. A recent generation of laboratory experiments conducted using magnetized laser-produced plasmas has opened opportunities to study these particle acceleration processes in the laboratory. Ablated plasma plumes are externally magnetized using an externally-applied magnetic field in combination with a low-density background plasma. Colliding unmagnetized plasmas demonstrated ion-driven Weibel instability while colliding magnetized plasmas drive magnetic reconnection. Both magnetized and unmagnetized colliding plasma are modeled with electromagnetic particle-in-cell simulations which provide an end-to-end model of the experiments. Using particle-in-cell simulations, we provide predictions of particle acceleration driven by reconnection, resulting from both direct x-line acceleration and Fermi-like acceleration at contracting magnetic fields lines near magnetic islands.
Magnetic Field Measurements in Plasmas: Beyond the Traditional Zeeman Spectroscopy
Doron, R.; Stambulchik, E.; Tessarin, S.; Kroupp, E.; Citrin, J.; Maron, Y.; Tsigutkin, K.
2009-09-10
We discuss a new approach to measure magnetic fields in situations where the magnetic-field properties and/or the plasma regime make the traditional Zeeman spectroscopy inapplicable. The approach is particularly useful when the field direction and/or magnitude vary significantly in the region viewed or during the diagnostic system's integration time, and hence no Zeeman splitting can be observed. Similar difficulty may also occur for high-energy-density conditions, where the Zeeman pattern is often completely smeared, regardless of the field distribution, due to the dominant contributions of the Stark and Doppler broadenings to the spectral-line shapes. In the new approach, the magnetic field is inferred from the comparison of the line-shapes of different fine-structure components of the same multiplet, which practically have the same Stark and Doppler broadenings, but different magnetic-field-induced contributions. Limitations of the new method are discussed.
Why Magnetically Confined Plasmas Rotate and Why it is Important
NASA Astrophysics Data System (ADS)
Kaye, Stanley
2012-03-01
Rotation in tokamak and spherical tokamak magnetic confinement devices has been found to be critical to enhancing the plasma stability to both the electron and ion gyroradius scale-turbulence as well to magnetohydrodynamic (MHD) modes whose characteristic scales can be of order the device size. Suppression of these modes leads to reduced energy and particle transport losses in these plasmas, thus increasing the potential fusion power production. Rotation can also lead to the avoidance of catastrophic MHD events known as ``disruptions.'' This strong impact of the rotation underscores the importance of developing the knowledge of how rotation is generated in these devices and how the momentum is transported through the plasma. Rotation in these plasmas is generated by a number of different torques, including external momentum input from neutral beam injection, and magnetic torques (toroidal viscosity) resulting from a non-axisymmetric magnetic field structure. One leading theory suggests that rotation can also be self-generated from microturbulence. In this strongly coupled, predator-prey-like system, the plasma can self-organize from a turbulent state to one with directed flow in directions both parallel and perpendicular to the magnetic field. The rotation in the perpendicular direction is often seen to have radial structure and is analogous to the Zonal Flows observed in planetary atmospheres. The self-generated, or intrinsic, rotation that flows mainly along the magnetic field, has been measured on virtually all experimental devices. The theory suggests that the intrinsic torque generating the intrinsic rotation is due to long-wavelength (of order the ion gyroradius) modes, and experimental measurements of intrinsic torque and rotation generally follow the trends predicted by theory. Values of the momentum diffusivity and convective pinch term have been determined from perturbation experiments, and their trends indicate that the same modes that drive intrinsic
Magnetic monopole plasma oscillations and the survival of Galactic magnetic fields
Parker, E.N.
1987-10-01
This paper explores the general nature of magnetic-monopole plasma oscillations as a theoretical possibility for the observed Galactic magnetic field in the presence of a high abundance of magnetic monopoles. The modification of the hydromagnetic induction equation by the monopole oscillations produces the half-velocity effect, in which the magnetic field is transported bodily with a velocity midway between the motion of the conducting fluid and the monopole plasma. Observational studies of the magnetic field in the Galaxy, and in other galaxies, exclude the half-velocity effect, indicating that the magnetic fields is not associated with monopole oscillations. In any case the phase mixing would destroy the oscillations in less than 100 Myr. The conclusion is that magnetic monopole oscillations do not play a significant role in the galactic magnetic fields. Hence the existence of galactic magnetic fields places a low limit on the monopole flux, so that their detection - if they exist at all - requires a collecting area at least as large as a football field. 47 references.
NASA Astrophysics Data System (ADS)
Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G. C.; Ciardi, A.; Chittenden, J. P.; Loureiro, N. F.; Niasse, N.; Suzuki-Vidal, F.; Wu, J.; Yang, Q.; Clayson, T.; Frank, A.; Robinson, T. S.; Smith, R. A.; Stuart, N.
2016-06-01
We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (Ti˜Z ¯ Te , with average ionization Z ¯=7 ). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.
Suttle, L G; Hare, J D; Lebedev, S V; Swadling, G F; Burdiak, G C; Ciardi, A; Chittenden, J P; Loureiro, N F; Niasse, N; Suzuki-Vidal, F; Wu, J; Yang, Q; Clayson, T; Frank, A; Robinson, T S; Smith, R A; Stuart, N
2016-06-01
We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure-two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T_{i}∼Z[over ¯]T_{e}, with average ionization Z[over ¯]=7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities. PMID:27314720
Scaling of the beam plasma discharge for low magnetic fields
NASA Technical Reports Server (NTRS)
Papadopoulos, K.
1986-01-01
A theoretical analysis of the scaling law and the value of the threshold current for beam plasma discharge (BPD) is presented, based on the requirement for an absolute instability near the plasma frequency. It is shown that both the scaling law as well as the numerical values of Ic are consistent with the experimental data, in the low pressure regimes and for weak magnetic field experiments if the dominant particle loss mechanism is due to Bohm diffusion. The implications of the findings to electron injection in space are discussed.
Theory and application of maximum magnetic energy in toroidal plasmas
Chu, T.K.
1992-02-01
The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q{prime}/q (as in reverse field pinches and spheromaks) to have the same {alpha} in all its force-free regions and with a positive q{prime}/q (as in tokamaks) to have centrally peaked {alpha}`s.
Theory and application of maximum magnetic energy in toroidal plasmas
Chu, T.K.
1992-02-01
The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q{prime}/q (as in reverse field pinches and spheromaks) to have the same {alpha} in all its force-free regions and with a positive q{prime}/q (as in tokamaks) to have centrally peaked {alpha}'s.
Coupled Dust-Lattice Modes in Magnetized Complex Plasmas
Farokhi, B.; Shahmansouri, M.
2008-09-07
Dust lattice wave modes in a one dimensional plasma crystal (formed by paramagnetic dust particles) suspended in the plasma sheath are studied. The ion flow in the sheath introduces 'ion wakes' below the crystal particles. The wave dispersion relations are found under the influence of inhomogeneous magnetic field, wake charge effect and equilibrium charge gradient. The expression for the wave dispersion relations clearly show that three branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz forces, charge gradient and wake charge effect. We observe a new coupling between the dust lattice modes, which have not reported so far.
Electrostatic solitary waves in a magnetized dusty plasma
Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.; Pillay, S. R.
2008-11-15
The nonlinear evolution of driven low-frequency electrostatic waves is investigated in a three-component magnetized dusty plasma comprised of a warm dust fluid, electrons, and ions. Electrons as well as ions are considered to have Boltzmann distributions. The fluid equations for the dust along with the quasineutrality condition are used to obtain a single nonlinear differential equation for the electric field. Periodic solutions of the nonlinear differential equation yield sinusoidal, sawtooth and bipolar structures which are similar to nonlinear structures supported in electron-ion plasmas. Results of our findings are applied to Saturn's rings.
On vortex dust structures in magnetized dusty plasmas
Nebbat, E.; Annou, R.
2010-09-15
To explain the generation of vortex patterns of dust grains in a magnetized dusty plasma [Huang et al., Plasma Sci. Technol. 9, 1 (2007)], a time dependent nonlinear model that describes vortices as a result of an instability is proposed. Grain-grain as well as grain-ion interactions, particle attachment, and grains drift and diffusion are key elements in the present model. It is found that the latter reproduces the experimental results quite well, whereas the stability analysis shows that the vortex core is grain size dependent.
A transverse Kelvin-Helmholtz instability in a magnetized plasma
NASA Technical Reports Server (NTRS)
Kintner, P.; Dangelo, N.
1977-01-01
An analysis is conducted of the transverse Kelvin-Helmholtz instability in a magnetized plasma for unstable flute modes. The analysis makes use of a two-fluid model. Details regarding the instability calculation are discussed, taking into account the ion continuity and momentum equations, the solution of a zero-order and a first-order component, and the properties of the solution. It is expected that the linear calculation conducted will apply to situations in which the plasma has experienced no more than a few growth periods.
NASA Astrophysics Data System (ADS)
Saha, Saikat
It has been proposed to extract momentum from the solar wind for spacecraft propulsion in deep space. For this purpose, a magnetic bubble is inflated from the spacecraft. The magnetic bubble inflation is affected by the expansion of a dense warm plasma in the magnetic field created by a solenoid aboard the spacecraft. The interaction between the inflated magnetic field and solar wind is likely to affect the transfer of momentum for the purpose of propulsion. The aim of our research here is to study the feasibility of this propulsion scheme by means of numerical simulations. For this purpose, we developed a 3-D hybrid particle code to model (i) the expansion of plasma in an ambient magnetic field created by a solenoid and (ii) the interaction of a plasma stream with the inflated magnetic field. The code is hybrid in the sense that ions are treated as particles and electrons as an isothermal fluid. We solve the coupled set of Maxwell's equations and the electron momentum equation for the electromagnetic fields using a predictor-corrector method. Using the 3-D simulations, we have demonstrated that when a warm and high-density plasma is injected in solenoidal magnetic fields, the trapping of the plasma in a magnetic mirror creates a dense plasma. When the trapped plasma energy densities (thermal and dynamic) exceed the magnetic energy density, the expanding plasma inflates the magnetic field lines. The extent of field inflation is seen to be greatly dependent on the injection velocity of the thermal plasma. The higher the injection velocity, the larger is the size of the inflated magnetic bubble. It is seen that the original magnetic field, which decreases as R-3, is stretched to the extent where it falls as R-alpha, where R is the distance from the center of the solenoid and alpha is found in the range 1 ≤ alpha ≤ 2. We have also demonstrated that when a plasma stream resembling the solar wind interacts with the expanding magnetic bubble, a magnetopause or bow
NASA Technical Reports Server (NTRS)
Gilland, James H.; Mikekkides, Ioannis; Mikellides, Pavlos; Gregorek, Gerald; Marriott, Darin
2004-01-01
This project has been a multiyear effort to assess the feasibility of a key process inherent to virtually all fusion propulsion concepts: the expansion of a fusion-grade plasma through a diverging magnetic field. Current fusion energy research touches on this process only indirectly through studies of plasma divertors designed to remove the fusion products from a reactor. This project was aimed at directly addressing propulsion system issues, without the expense of constructing a fusion reactor. Instead, the program designed, constructed, and operated a facility suitable for simulating fusion reactor grade edge plasmas, and to examine their expansion in an expanding magnetic nozzle. The approach was to create and accelerate a dense (up to l0(exp 20)/m) plasma, stagnate it in a converging magnetic field to convert kinetic energy to thermal energy, and examine the subsequent expansion of the hot (100's eV) plasma in a subsequent magnetic nozzle. Throughout the project, there has been a parallel effort between theoretical and numerical design and modelling of the experiment and the experiment itself. In particular, the MACH2 code was used to design and predict the performance of the magnetoplasmadynamic (MPD) plasma accelerator, and to design and predict the design and expected behavior for the magnetic field coils that could be added later. Progress to date includes the theoretical accelerator design and construction, development of the power and vacuum systems to accommodate the powers and mass flow rates of interest to out research, operation of the accelerator and comparison to theoretical predictions, and computational analysis of future magnetic field coils and the expected performance of an integrated source-nozzle experiment.
Plasma Density and Magnetic Field Evolution in a 100-ns Plasma Opening Switch
NASA Astrophysics Data System (ADS)
Weingarten, A.; Maron, Y.; Krasik, Ya. E.; Weber, B. V.; Commisso, R. J.
1997-11-01
The electron density and magnetic field evolution in a 100-ns, 170-kA POS are investigated using emission spectroscopy. The plasma is doped by various elements using laser evaporation in order to obtain spatially resolved measurements. The prefilled plasma density, determined from Stark broadening and ionization times, is 1-2× 10^14 cm-3. The opening time was observed to depend on the prefilled plasma azimuthal uniformity. During the pulse, the plasma density drops substantially during 10-20 ns. The drop propagates mainly axially from the plasma generator side to the load side at a velocity of ≈ 2 × 10^8 cm/s. The drop is accompanied by penetration of the magnetic field, determined from the Zeeman effect. A mapping of the density and the magnetic field distributions in the r-z plane will be presented. Proton motion is probably important, but the axial velocities of heavy ions are low (≈ 10^6 cm/s << V_Alfven). These results will be compared with previous results obtained on Gamble I(B. V. Weber et. al.), Appl. Physc. Lett. 45, 1043, (1984).
Toward the Theory of Turbulence in Magnetized Plasmas
Boldyrev, Stanislav
2013-07-26
The goal of the project was to develop a theory of turbulence in magnetized plasmas at large scales, that is, scales larger than the characteristic plasma microscales (ion gyroscale, ion inertial scale, etc.). Collisions of counter-propagating Alfven packets govern the turbulent cascade of energy toward small scales. It has been established that such an energy cascade is intrinsically anisotropic, in that it predominantly supplies energy to the modes with mostly field-perpendicular wave numbers. The resulting energy spectrum of MHD turbulence, and the structure of the fluctuations were studied both analytically and numerically. A new parallel numerical code was developed for simulating reduced MHD equations driven by an external force. The numerical setting was proposed, where the spectral properties of the force could be varied in order to simulate either strong or weak turbulent regimes. It has been found both analytically and numerically that weak MHD turbulence spontaneously generates a “condensate”, that is, concentration of magnetic and kinetic energy at small k{sub {parallel}}. A related topic that was addressed in the project is turbulent dynamo action, that is, generation of magnetic field in a turbulent flow. We were specifically concentrated on the generation of large-scale magnetic field compared to the scales of the turbulent velocity field. We investigate magnetic field amplification in a turbulent velocity field with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan model.
Waves and negative refraction in magnetized plasma with ferrite grains
Mesfin, Belayneh; Mal'nev, V. N.; Martysh, E. V.; Rapoport, Yu. G.
2010-11-15
The propagation of high frequency electromagnetic waves in the low temperature magnetized plasma with ferrite grains (MPFG) is considered. The dispersion properties of MPFG are simultaneously characterized by the permittivity and permeability tensors. The dispersion of the permeability is caused by the high frequency magnetization of the grain subsystem and is important in the vicinity of the frequency of ferromagnetic resonance, which coincides with the electron cyclotron frequency {omega}{sub c}. The MPFG becomes transparent for the waves that cannot propagate in conventional electron-ion magnetized plasma. It is shown that the refractive index of the extraordinary wave propagating along and transversal to the external magnetic field with frequencies close to {omega}{sub c} can be negative as well as positive. For the typical parameters of MPFG, the group velocity of this wave is much smaller than the speed of light. The refractive index of MPFG matched with the free space is obtained for waves propagating at an arbitrary angle with respect to the applied constant magnetic field. The results obtained clearly shows that the dispersion properties of MPFG have all the known properties of left-handed media in the vicinity of {omega}{sub c}.
Modeling of Stark-Zeeman Lines in Magnetized Hydrogen Plasmas
NASA Astrophysics Data System (ADS)
Rosato, J.; Bufferand, H.; Capes, H.; Koubiti, M.; Godbert-Mouret, L.; Marandet, Y.; Stamm, R.
2015-12-01
The action of electric and magnetic fields on atomic species results in a perturbation of the energy level structure, which alters the shape of spectral lines. In this work, we present the Zeeman-Stark line shape simulation method and perform new calculations of hydrogen Lyman and Balmer lines, in the framework of magnetic fusion research. The role of the Zeeman effect, fine structure and the plasma's non-homogeneity along the line-of-sight are investigated. Under specific conditions, our results are applicable to DA white dwarf atmospheres.
Multi-ion Double Layers in a Magnetized Plasma
NASA Astrophysics Data System (ADS)
Shahmansouri, M.; Alinejad, H.; Tribeche, M.
2015-11-01
A theoretical investigation is carried out to study the existence, formation and basic properties of ion acoustic (IA) double layers (DLs) in a magnetized bi-ion plasma consisting of warm/cold ions and Boltzmann distributed electrons. Based on the reductive perturbation technique, an extended Korteweg de-Vries (KdV) equation is derived. The propagation of two possible modes (fast and slow), and their evolution are investigated. The effects of obliqueness, magnitude of the magnetic field, ion concentration, polarity of ions, and ion temperature on the IA DL profile are analyzed, and then the ranges of parameters for which the IA DLs exist are investigated in details.
Evolution of chirped laser pulses in a magnetized plasma channel
Jha, Pallavi; Hemlata,; Mishra, Rohit Kumar
2014-12-15
The propagation of intense, short, sinusoidal laser pulses in a magnetized plasma channel has been studied. The wave equation governing the evolution of the radiation field is set up and a variational technique is used to obtain the equations describing the evolution of the laser spot size, pulse length and chirp parameter. Numerical methods are used to analyze the simultaneous evolution of these parameters. The effect of the external magnetic field on initially chirped as well as unchirped laser pulses on the spot size, pulse length and chirping has been analyzed.
Magnetic insulation of secondary electrons in plasma source ion implantation
Rej, D.J.; Wood, B.P.; Faehl, R.J.; Fleischmann, H.H.
1993-09-01
The uncontrolled loss of accelerated secondary electrons in plasma source ion implantation (PSII) can significantly reduce system efficiency and poses a potential x-ray hazard. This loss might be reduced by a magnetic field applied near the workpiece. The concept of magnetically-insulated PSII is proposed, in which secondary electrons are trapped to form a virtual cathode layer near the workpiece surface where the local electric field is essentially eliminated. Subsequent electrons that are emitted can then be reabsorbed by the workpiece. Estimates of anomalous electron transport from microinstabilities are made. Insight into the process is gained with multi-dimensional particle-in-cell simulations.
Woodruff, S; Hill, D N; Stallard, B W; Bulmer, R; Cohen, B; Holcomb, C T; Hooper, E B; McLean, H S; Moller, J; Wood, R D
2003-03-01
By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.
Collisional relaxation of bi-Maxwellian plasma temperatures in magnetized plasmas
NASA Astrophysics Data System (ADS)
Yoon, Peter H.
2016-07-01
In the literature, collisional processes are customarily discussed within the context of the Boltzmann-Balescu-Lenard-Landau type of collision integral, but such an equation is strictly valid for unmagnetized plasmas. For plasmas immersed in the ambient magnetic field, the foundational equation that describes binary collisions must be generalized to include the effects of magnetic field. The present paper makes use of such an equation in order to describe the collisional relaxation of temperatures under the assumption of bi-Maxwellian velocity distribution function. The formalism derived in the present paper may be useful for studying the effects of binary collisions on the isotropization of temperatures in the solar wind plasma, among possible applications.
Vlasov simulations of plasma-wall interactions in a magnetized and weakly collisional plasma
Devaux, S.; Manfredi, G.
2006-08-15
A Vlasov code is used to model the transition region between an equilibrium plasma and an absorbing wall in the presence of a tilted magnetic field, for the case of a weakly collisional plasma ({lambda}{sub mfp}>>{rho}{sub i}, where {lambda}{sub mfp} is the ion-neutral mean-free path and {rho}{sub i} is the ion Larmor radius). The phase space structure of the plasma-wall transition is analyzed in detail and theoretical estimates of the magnetic presheath width are tested numerically. It is shown that the distribution near the wall is far from Maxwellian, so that temperature measurements should be interpreted with care. Particular attention is devoted to the angular distribution of ions impinging on the wall, which is an important parameter to determine the level of wall erosion and sputtering.
Tail Lobe Revisited: Magnetic Field Modeling Based on Plasma Data
NASA Technical Reports Server (NTRS)
Karlsson, S. B. P.; Tsyganenko, N. A.
1999-01-01
Plasma data from the ISEE-1 and -2 spacecraft during 1977-1980 have been used to determine the distribution of data points in the magnetotail in the range of distances -20 < XGSM < --15, i.e. which of the records that were located in the current sheet, in the tail lobe, in the magnetosheath and in the boundary layers respectively. The ISEE-1 and -2 magnetic field data for the records in the tail lobe were then used to model the tail lobe magnetic field dependence on the solar wind dynamic pressure, on the Interplanetary Magnetic Field (IMF) and on the Dst index. The tail lobe magnetic field was assumed to be dependent on the square root of the dynamic pressure based on the balance between the total magnetic pressure in the tail lobes and the dynamic pressure of the solar wind. The IMF dependent terms, added to the pressure term, were sought in many different forms while the Dst dependence of the tail lobe magnetic field was assumed to be linear. The field shows a strong dependence on the square root of the dynamic pressure and the different IMF dependent terms all constitute a significant contribution to the total field. However, the dependence on the Dst index turned out to be very weak at those down-tail distances. The results of this study are intended to be used for parameterizing future versions of the data-based models of the global magnetospheric magnetic field.
Magnetic stochasticity in gyrokinetic simulations of plasma microturbulence
NASA Astrophysics Data System (ADS)
Wang, Eric
2010-11-01
One of the fundamental components of a steady state tokamak or stellerator fusion reactor is the structural integrity of nested magnetic surfaces. The consequences of losing this integrity can have very serious implications, ranging from sawtooth crashes to disruptions. In the present work, we use GYRO to examine the perturbed magnetic field structure generated by electromagnetic gyrokinetic simulations of the CYCLONE base case as β is varied from .1% to .7%, as first investigated in [J. Candy, Phys. Plasmas 12, 072307 (2005)]. By integrating the self-consistent magnetic field lines to produce Poincare surface of section plots, we demonstrate destruction of magnetic surfaces for all nonzero values of β. Despite widespread stochasticity of the perturbed magnetic fields, no significant increase in electron transport is observed. We can quantify the stochastic electron heat transport by using test particles to estimate the magnetic diffusion coefficient Dst [A.B. Rechester and M.N. Rosenbluth, PRL 40, 38 (1978)] for hundreds of time slices in each simulation and find the time-history of Dst to be highly correlated with the electron heat transport due to ``magnetic-flutter'' computed in the simulations. The mechanism that couples electromagnetic turbulence to the linearly damped high-n tearing modes that are responsible for reconnection will be discussed.
Atomic Forces for Geometry-Dependent Point Multipole and Gaussian Multipole Models
Elking, Dennis M.; Perera, Lalith; Duke, Robert; Darden, Thomas; Pedersen, Lee G.
2010-01-01
In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise due to 1) the transfer of torque between neighboring atoms, and 2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In the current study, atomic force expressions for geometry-dependent multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first proposing a new general expression for Wigner function derivatives ∂Dlm′m/∂Ω. The force equations can be applied to electrostatic models based on atomic point multipoles or Gaussian multipole charge density. Hydrogen bonded dimers are used to test the inter-molecular electrostatic energies and atomic forces calculated by geometry-dependent multipoles fit to the ab initio electrostatic potential (ESP). The electrostatic energies and forces are compared to their reference ab initio values. It is shown that both static and geometry-dependent multipole models are able to reproduce total molecular forces and torques with respect to ab initio, while geometry-dependent multipoles are needed to reproduce ab initio atomic forces. The expressions for atomic force can be used in simulations of flexible molecules with atomic multipoles. In addition, the results presented in this work should lead to further development of next generation force fields composed of geometry-dependent multipole models. PMID:20839297
Magnetostatic solution by hybrid technique and fast multipole method
NASA Astrophysics Data System (ADS)
Gruosso, G.; Repetto, M.
2008-02-01
The use of fast multipole method (FMM) in the solution of a magnetostatic problem is presented. The magnetostatic solution strategy is based on finite formulation of electromagnetic field coupled with an integral formulation for the definition of boundary conditions on the external surface of the unstructured mesh. Due to the hypothesis of micromagnetic problem, the resulting matrix structure is sparse and integral terms are only on the RHS. Magnetic surface charge is used as source of these integral terms and is localized on the faces between tetrahedra. The computation of the integral terms can be performed by analytical formulas for the near field contributes and by FMM for far field ones.
Three-Dimensional EMHD Simulation Studies of Nonlinear Magnetic Structures in Magnetized Plasmas
Eliasson, B.; Shukla, P. K.
2008-10-15
We present a numerical study of strongly nonlinear magnetic vortex-like structures, denoted whistler spheromaks, which have recently been observed in laboratory experiments. The whistler spheromaks are excited with a ring antenna immersed in the magnetized plasma, and are propagating away from the antenna with a constant speed along the ambient magnetic field lines. The wave magnetic field of the spheromaks are of the same order or larger than the ambient magnetic field, and consists of two parts, the poloidal field which is strong enough to reverse the magnetic field in the center of the spheromak, and the toroidal field. We demonstrate numerically that the latter is crucial for the propagation speed and direction of the spheromak, and that the whistler spheromaks are long-lived structures.
Magnetic-Field Generation and Amplification in an Expanding Plasma
NASA Astrophysics Data System (ADS)
Schoeffler, K. M.; Loureiro, N. F.; Fonseca, R. A.; Silva, L. O.
2014-05-01
Particle-in-cell simulations are used to investigate the formation of magnetic fields B in plasmas with perpendicular electron density and temperature gradients. For system sizes L comparable to the ion skin depth di, it is shown that B˜di/L, consistent with the Biermann battery effect. However, for large L/di, it is found that the Weibel instability (due to electron temperature anisotropy) supersedes the Biermann battery as the main producer of B. The Weibel-produced fields saturate at a finite amplitude (plasma β≈100), independent of L. The magnetic energy spectra below the electron Larmor radius scale are well fitted by the power law with slope -16/3, as predicted by Schekochihin et al. [Astrophys. J. Suppl. Ser. 182, 310 (2009)].
Magnetic field-aligned electric potentials in nonideal plasma flows
NASA Technical Reports Server (NTRS)
Schindler, K.; Hesse, M.; Birn, J.
1991-01-01
The electric field component parallel to the magnetic field arising from plasma flows which violate the frozen-in field condition of ideal magnetohydrodynamics is discussed. The quantity of interest is the potential U = integral E parallel ds where the integral is extended along field lines. It is shown that U can be directly related to magnetic field properties, expressed by Euler potentials, even when time-dependence is included. These results are applicable to earth's magnetosphere, to solar flares, to aligned-rotator models of compact objects, and to galactic rotation. On the basis of order-of-magnitude estimates, these results support the view that parallel electric fields associated with nonideal plasma flows might play an important role in cosmic particle acceleration.
Scaling of Magnetic Reconnection in Relativistic Collisionless Pair Plasmas
NASA Technical Reports Server (NTRS)
Liu, Yi-Hsin; Guo, Fan; Daughton, William; Li, Hui; Hesse, Michael
2015-01-01
Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection in electron-positron plasmas from the non-relativistic to ultra-relativistic limit. In the anti-parallel configuration, the inflow speed increases with the upstream magnetization parameter sigma and approaches the speed of light when sigma is greater than O(100), leading to an enhanced reconnection rate. In all regimes, the divergence of the pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x-line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region, modified by the compression factor of proper density, remains approximately 0.1 in both the non-relativistic and relativistic limits.
Double-layer shocks in a magnetized quantum plasma.
Misra, A P; Samanta, S
2010-09-01
The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio δ . The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.
Double-layer shocks in a magnetized quantum plasma
NASA Astrophysics Data System (ADS)
Misra, A. P.; Samanta, S.
2010-09-01
The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio δ . The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.
Exchange interaction effects on waves in magnetized quantum plasmas
Trukhanova, Mariya Iv. Andreev, Pavel A.
2015-02-15
We have applied the many-particle quantum hydrodynamics that includes the Coulomb exchange interaction to magnetized quantum plasmas. We considered a number of wave phenomena that are affected by the Coulomb exchange interaction. Since the Coulomb exchange interaction affects the longitudinal and transverse-longitudinal waves, we focused our attention on the Langmuir waves, the Trivelpiece-Gould waves, the ion-acoustic waves in non-isothermal magnetized plasmas, the dispersion of the longitudinal low-frequency ion-acoustic waves, and low-frequency electromagnetic waves at T{sub e} ≫ T{sub i}. We have studied the dispersion of these waves and present the numeric simulation of their dispersion properties.
Dressed ion-acoustic solitons in magnetized dusty plasmas
El-Labany, S. K.; El-Shamy, E. F.; El-Warraki, S. A.
2009-01-15
In the present research paper, the characteristics of ion acoustic solitary waves are investigated in hot magnetized dusty plasmas consisting of negatively charged dust grains, positively charged ion fluid, and isothermal electrons. Applying a reductive perturbation theory, a nonlinear Korteweg-de Vries (KdV) equation for the first-order perturbed potential and a linear inhomogeneous KdV-type equation for the second-order perturbed potentials are derived. Stationary solutions of these coupled equations are obtained using a renormalization method. The effects of the external oblique magnetic field, hot ion fluid, and higher-order nonlinearity on the nature of the ion acoustic solitary waves are discussed. The results complement and provide new insights into previously published results on this problem [R. S. Tiwari and M. K. Mishra, Phys. Plasmas 13, 062112 (2006)].
Launching and Colliding Magnetized Plasma Jets on the OMEGA Laser
NASA Astrophysics Data System (ADS)
Young, R. P.; Kuranz, C. C.; Drake, R. P.; Froula, D.; Ross, J.; Li, C. K.; Fiksel, G.
2013-10-01
In April 2012, we had a successful shot day on the OMEGA-60 laser, proving that rear irradiation of thin, conical, acrylic foils can produce a fast, hot, dense plasma jet. We will present a selection of data from that day, focusing on the Thomson scattering data and its implications for fundamental fluid parameters such as Reynolds and magnetic Reynolds numbers. We may also present preliminary data from our shot day in August 2013, which is in final planning as this abstract goes to press. The August shot day will build upon our success in April 2012 by adding an imposed magnetic field and proton radiography capabilities to the experiment. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.
Double-layer shocks in a magnetized quantum plasma
Misra, A. P.; Samanta, S.
2010-09-15
The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves obliquely to an external magnetic field is reported in a quantum electron-positron-ion plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter H associated with the Bohm potential and the positron to electron density ratio {delta}. The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.
Magnetic field advection in two interpenetrating plasma streams
Ryutov, D. D.; Kugland, N. L.; Levy, M. C.; Plechaty, C.; Ross, J. S.; Park, H. S.
2013-03-15
Laser-generated colliding plasma streams can serve as a test-bed for the study of various astrophysical phenomena and the general physics of self-organization. For streams of a sufficiently high kinetic energy, collisions between the ions of one stream with the ions of the other stream are negligible, and the streams can penetrate through each other. On the other hand, the intra-stream collisions for high-Mach-number flows can still be very frequent, so that each stream can be described hydrodynamically. This paper presents an analytical study of the effects that these interpenetrating streams have on large-scale magnetic fields either introduced by external coils or generated in the plasma near the laser targets. Specifically, a problem of the frozen-in constraint is assessed and paradoxical features of the field advection in this system are revealed. A possibility of using this system for studies of magnetic reconnection is mentioned.
Penetration of Magnetosheath Plasma into Dayside Magnetosphere: Magnetic Field in Plasma Filaments
NASA Astrophysics Data System (ADS)
Lyatsky, Wladislaw
2016-04-01
In this study, we examined a large number of plasma structures (filaments), observed with the Cluster spacecraft during two years (2007-2008) in the dayside magnetosphere but consisting of magnetosheath plasma. To reduce the effects observed in cusp regions and on magnetosphere flanks, we consider these events inside the narrow cone (≤30°) about the subsolar point. Two important features of these filaments are: (i) their stable anti-sunward motion inside the magnetosphere whereas the ambient magnetospheric plasma moves in the opposite (sunward) direction, and (ii) between these filaments and the magnetopause there is a strip of magnetospheric plasma, separating these filaments from the magnetosheath. The stable earthward motion of these filaments and the existence of a strip of magnetospheric plasma between these filaments and the magnetopause show the disconnection of these filaments from the magnetosheath, as suggested earlier by many researchers. These events cannot also be a consequent of back and forth motions of magnetopause position or surface waves propagating on the magnetopause. However, these observation results contradict the theoretical studies by Schmidt, 1960; Schindler, 1979; Ma et al., 1991; Dai and Woodward, 1994, 1998; et al., who reported that the motion of such filaments through the magnetosphere is possible only when the magnetic field in these filaments is aligned with (or very close to) the ambient magnetic field, that is not consistent with observation results. And the main goal of this study is to resolve this problem. For this purpose, we examined a large number of these events and showed that this contradiction may exist because of the theoretical studies and observations are related to different events: the theoretical studies are related to the case when the magnetic field in these filaments is aligned with the filament orientation, whereas the observation results may be related to the cases of a rotating magnetic field in these
Lerche, I.; Schlickeiser, R.; Tautz, R. C.
2008-02-15
This Comment discusses the representations of infinite sums of Bessel functions that occur in plasma problems involving collisionless plasmas treated from a plasma kinetic viewpoint. In addition, the influence of such summation techniques on dispersion relations for plasma waves involving a background magnetic field is discussed.
Symmetry Constraints on the Dynamics of Magnetically Confined Plasma
Arter, Wayne
2009-05-15
In respect of their symmetry properties, toroidal magnetically confined plasmas have much in common with the Taylor-Couette flow. A symmetry-based analysis (equivalent bifurction theory) has proved very powerful in the analysis of the latter problem. This Letter discusses the applicability of the method to nuclear fusion experiments such as tokamaks and pinches. The likely behavior of the simplest models of rotationally symmetric tokamaks is described, and found to be potentially consistent with observation.
Currents between tethered electrodes in a magnetized laboratory plasma
NASA Technical Reports Server (NTRS)
Stenzel, R. L.; Urrutia, J. M.
1989-01-01
Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.
Weibel magnetic field amplification and saturation in expanding plasmas
NASA Astrophysics Data System (ADS)
Schoeffler, Kevin; Loureiro, Nuno; Silva, Luis; Fonseca, Ricardo
2014-10-01
Recent laser-solid interaction experiments have been used to generate high energy density plasmas with megagauss magnetic fields. These intense magnetic fields are generated by the Biermann battery mechanism via perpendicular temperature and density gradients, and via temperature anisotropy instabilities such as the Weibel instability. Performing particle-in-cell simulations of similar expanding plasmas, we find that in some laser systems as well as in astrophysical shocks the Weibel instability may play the dominant role. Particularly in systems where the Biermann Battery is expected to generate only small fields with plasma β ~ L /di (with system size large compared to ion inertial length), while the Weibel may reach fields close to β ~ 1 . Although the Weibel instability is a popular topic regarding these systems, the mechanism for saturation is not clearly understood. We investigate this saturation, as well as uncover a striking confirmation of gyrokinetic predictions of turbulence (from the Biermann field) with a sub-ρe (electron gyroradius) - 4 / 3 power law for electric field energy and - 16 / 3 for magnetic fields. also affiliated with DCTI/ISCTE Lisbon University Institute, 1649-026 Lisbon, Portugal.
Drift-tearing magnetic islands in tokamak plasmas
Fitzpatrick, R.; Waelbroeck, F. L.
2008-01-15
A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-{beta}, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfven wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the 'sonic' and 'hypersonic' branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.
Electrostatic acceleration of helicon plasma using a cusped magnetic field
Harada, S.; Baba, T.; Uchigashima, A.; Iwakawa, A.; Sasoh, A.; Yokota, S.; Yamazaki, T.; Shimizu, H.
2014-11-10
The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in the field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.
Lithium As Plasma Facing Component for Magnetic Fusion Research
Masayuki Ono
2012-09-10
The use of lithium in magnetic fusion confinement experiments started in the 1990's in order to improve tokamak plasma performance as a low-recycling plasma-facing component (PFC). Lithium is the lightest alkali metal and it is highly chemically reactive with relevant ion species in fusion plasmas including hydrogen, deuterium, tritium, carbon, and oxygen. Because of the reactive properties, lithium can provide strong pumping for those ions. It was indeed a spectacular success in TFTR where a very small amount (~ 0.02 gram) of lithium coating of the PFCs resulted in the fusion power output to improve by nearly a factor of two. The plasma confinement also improved by a factor of two. This success was attributed to the reduced recycling of cold gas surrounding the fusion plasma due to highly reactive lithium on the wall. The plasma confinement and performance improvements have since been confirmed in a large number of fusion devices with various magnetic configurations including CDX-U/LTX (US), CPD (Japan), HT-7 (China), EAST (China), FTU (Italy), NSTX (US), T-10, T-11M (Russia), TJ-II (Spain), and RFX (Italy). Additionally, lithium was shown to broaden the plasma pressure profile in NSTX, which is advantageous in achieving high performance H-mode operation for tokamak reactors. It is also noted that even with significant applications (up to 1,000 grams in NSTX) of lithium on PFCs, very little contamination (< 0.1%) of lithium fraction in main fusion plasma core was observed even during high confinement modes. The lithium therefore appears to be a highly desirable material to be used as a plasma PFC material from the magnetic fusion plasma performance and operational point of view. An exciting development in recent years is the growing realization of lithium as a potential solution to solve the exceptionally challenging need to handle the fusion reactor divertor heat flux, which could reach 60 MW/m2 . By placing the liquid lithium (LL) surface in the path of the main
Fast Magnetic Reconnection: Bridging Laboratory and Space Plasma Physics
Bhattacharjee, Amitava
2012-02-16
Recent developments in experimental and theoretical studies of magnetic reconnection hold promise for providing solutions to outstanding problems in laboratory and space plasma physics. Examples include sawtooth crashes in tokamaks, substorms in the Earth’s Magnetosphere, eruptive solar flares, and more recently, fast reconnection in laser-produced high energy density plasmas. In each of these examples, a common and long-standing challenge has been to explain why fast reconnection proceeds rapidly from a relatively quiescent state. In this talk, we demonstrate the advantages of viewing these problems and their solutions from a common perspective. We focus on some recent, surprising discoveries regarding the role of secondary plasmoid instabilities of thin current sheets. Nonlinearly, these instabilities lead to fast reconnection rates that are very weakly dependent on the Lundquist number of the plasma.
Optimal design of a new multipole bilayer magnetorheological brake
NASA Astrophysics Data System (ADS)
Shiao, Yaojung; Ngoc, Nguyen Anh; Lai, Chien-Hung
2016-11-01
This article presents a new high-torque multipole bilayer magneto-rheological brake (MRB). This MRB has a unique structural design with multiple electromagnetic poles and multiple media layers of magnetorheological fluid (MRF). The MRB has two rotors located on the outer and inner sides of a six-pole stator, and therefore, it can provide higher torque and a larger torque-to-volume ratio (TVR) than conventional single- or multipole single-layer MRBs can. Moreover, the problem of potential MRF leakage is solved by using cylindrical separator rings around the stator. In this study, first, the structure of the proposed MRB is introduced. An analog magnetic circuit was built for the MRB to investigate the effects of the MRB parameters on the magnetic field intensity of the MRF layers. In addition, a 3D electromagnetic model of the MRB was developed to simulate and examine the magnetic flux intensity and corresponding braking torque. An approximate optimization method was then applied to obtain the optimal geometric dimensions for the major dimensional parameters of the MRB. The MRB was manufactured and tested to validate its torque and dynamic characteristics. The results showed that the proposed MRB exhibited great enhancement of the braking torque and TVR.
In situ ``artificial plasma'' calibration of tokamak magnetic sensors
NASA Astrophysics Data System (ADS)
Shiraki, D.; Levesque, J. P.; Bialek, J.; Byrne, P. J.; DeBono, B. A.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.; Rath, N.
2013-06-01
A unique in situ calibration technique has been used to spatially calibrate and characterize the extensive new magnetic diagnostic set and close-fitting conducting wall of the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. A new set of 216 Mirnov coils has recently been installed inside the vacuum chamber of the device for high-resolution measurements of magnetohydrodynamic phenomena including the effects of eddy currents in the nearby conducting wall. The spatial positions of these sensors are calibrated by energizing several large in situ calibration coils in turn, and using measurements of the magnetic fields produced by the various coils to solve for each sensor's position. Since the calibration coils are built near the nominal location of the plasma current centroid, the technique is referred to as an "artificial plasma" calibration. The fitting procedure for the sensor positions is described, and results of the spatial calibration are compared with those based on metrology. The time response of the sensors is compared with the evolution of the artificial plasma current to deduce the eddy current contribution to each signal. This is compared with simulations using the VALEN electromagnetic code, and the modeled copper thickness profiles of the HBT-EP conducting wall are adjusted to better match experimental measurements of the eddy current decay. Finally, the multiple coils of the artificial plasma system are also used to directly calibrate a non-uniformly wound Fourier Rogowski coil on HBT-EP.
Mach Probe Wakes are Important in Weakly Magnetized, Collisional Plasmas
NASA Astrophysics Data System (ADS)
Gosselin, Jordan James; Thakur, Saikat; Sears, Stephanie; McKee, John; Scime, Earl; Tynan, George
2015-11-01
Mach probes are often used as the diagnostic for flow in the scrape off layer (SOL) of tokamaks and in linear devices because of their low cost and ease of construction. However, proper interpretation of the Mach number has been debated, and interpretation methods use different calibration factors for different plasma parameters. The Controlled Shear Decorrelation eXperiment (CSDX) operates in an intermediate magnetization regime. To validate theories in this regime, measurements of the parallel ion velocity were made with Mach probes and laser induced fluorescence (LIF) at magnetic fields from 400 to 1600 gauss. We find that Mach probe measurements indicate higher velocities than LIF at fields above 400 gauss. Reduced downstream plasma density due to probe shadowing is a strong candidate for the cause of the discrepancy. An advective-diffusive model for the geometric shadowing and downstream plasma density is presented. When the model for the density drop is included, the Mach probe results agree with the LIF data. This result should be included by groups using Mach probes to measure parallel velocities in plasmas where the ion-neutral mean free path is shorter than the probe shadow length, Lps = a2Cs /Dperp in linear devices, the SOL, or divertor region of tokamaks. This material is based upon work supported by the U.S. Department of Energy, Office of Science, under Awards Number DE-FG02-07ER54912.
Plasma cleaning of ITER First Mirrors in magnetic field
NASA Astrophysics Data System (ADS)
Moser, Lucas; Steiner, Roland; Leipold, Frank; Reichle, Roger; Marot, Laurent; Meyer, Ernst
2015-08-01
To avoid reflectivity losses in ITER's optical diagnostic systems, plasma sputtering of metallic First Mirrors is foreseen in order to remove deposits coming from the main wall (mainly beryllium and tungsten). Therefore plasma cleaning has to work on large mirrors (up to a size of 200 × 300 mm) and under the influence of strong magnetic fields (several Tesla). This work presents the results of plasma cleaning of aluminium and aluminium oxide (used as beryllium proxy) deposited on molybdenum mirrors. Using radio frequency (13.56 MHz) argon plasma, the removal of a 260 nm mixed aluminium/aluminium oxide film deposited by magnetron sputtering on a mirror (98 mm diameter) was demonstrated. 50 nm of pure aluminium oxide were removed from test mirrors (25 mm diameter) in a magnetic field of 0.35 T for various angles between the field lines and the mirrors surfaces. The cleaning efficiency was evaluated by performing reflectivity measurements, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy.
Thermodynamic Study on Plasma Expansion along a Divergent Magnetic Field
NASA Astrophysics Data System (ADS)
Zhang, Yunchao; Charles, Christine; Boswell, Rod
2016-01-01
Thermodynamic properties are revisited for electrons that are governed by nonlocal electron energy probability functions in a plasma of low collisionality. Measurements in a laboratory helicon double layer experiment have shown that the effective electron temperature and density show a polytropic correlation with an index of γe=1.17 ±0.02 along the divergent magnetic field, implying a nearly isothermal plasma (γe=1 ) with heat being brought into the system. However, the evolution of electrons along the divergent magnetic field is essentially an adiabatic process, which should have a γe=5/3 . The reason for this apparent contradiction is that the nearly collisionless plasma is very far from local thermodynamic equilibrium and the electrons behave nonlocally. The corresponding effective electron enthalpy has a conservation relation with the potential energy, which verifies that there is no heat transferred into the system during the electron evolution. The electrons are shown in nonlocal momentum equilibrium under the electric field and the gradient of the effective electron pressure. The convective momentum of ions, which can be assumed as a cold species, is determined by the effective electron pressure and the effective electron enthalpy is shown to be the source for ion acceleration. For these nearly collisionless plasmas, the use of traditional thermodynamic concepts can lead to very erroneous conclusions regarding the thermal conductivity.
Laboratory study of avalanches in a magnetized plasma
NASA Astrophysics Data System (ADS)
van Compernolle, Bart
2015-11-01
Results of a basic heat transport experiment [] involving an off-axis heat source are presented. Experiments are performed in the Large Plasma Device (LAPD) at UCLA. A ring-shaped electron beam source injects low energy electrons (below ionization energy) along a strong magnetic field into a preexisting, large and cold plasma. The injected electrons are thermalized by Coulomb collisions within a short distance and provide an off-axis heat source that results in a long, hollow, cylindrical region of elevated electron temperature embedded in a colder plasma, and far from the machine walls. It is demonstrated that this heating configuration provides an ideal environment to study avalanche phenomena under controlled conditions. The avalanches are identified as sudden rearrangements of the pressure profile following the growth of fluctuations from ambient noise. The intermittent collapses of the plasma pressure profile are associated with unstable drift-Alfvén waves and exhibit both radial and azimuthal dynamics. After each collapse the plasma enters a quiescent phase in which the pressure profile slowly recovers and steepens until a threshold is exceeded, and the process repeats. The use of reference probes as time markers allows for the visualization of the 2D spatio-temporal evolution of the avalanche events. Avalanches are only observed for a limited combination of heating powers and magnetic fields. At higher heating powers the system transitions from the avalanche regime into a regime dominated by sustained drift-Alfvén wave activity. The pressure profile then transitions to a near steady-state in which anomalous transport balances the external pressure source. Performed at the Basic Plasma Science Facility at UCLA, supported jointly by DOE and NSF.
Measuring Magnetic Fields in Photoionized Interstellar Plasmas (HII Regions)
NASA Astrophysics Data System (ADS)
Spangler, Steven; Costa, Allison
2015-11-01
Hot luminous stars photoionize the interstellar gas around them, creating plasmas with a very high ionization fraction. In astronomical terminology, these are called HII regions. They are dynamic plasmas, expanding due to overpressure with respect to the interstellar medium. We are making diagnostic measurements to determine the strength and structure of magnetic fields in these objects. This paper presents our results on the Rosette Nebula. We diagnose the magnetic field in the Rosette by measurements of Faraday rotation on lines of sight passing through the nebula. These measurements are made with the Very Large Array radio telescope of the National Radio Astronomy Observatory. We have measurements of the rotation measure for 18 lines of sight. Values of the mean, line of sight component of the magnetic field range from about 3 to 5 microGauss. We will discuss comparison of these measurements with models for modification of the interstellar magnetic field by an HII region. This work was supported by grants AST09-07911 and ATM09-56901 from the National Science Foundation.
Electron Energization During m=0 Magnetic Bursts in MST plasmas
NASA Astrophysics Data System (ADS)
Young, W. C.; den Hartog, D. J.; Morton, L. A.; MST Team
2015-11-01
MST reversed-field pinch plasmas develop magnetic modes with both a core-resonant poloidal mode m=1 structure and edge-resonant m=0 structure on the reversal surface. The impact of the m=0 modes on electron energization has been observed with Thomson scattering under plasma conditions with suppressed m=1 modes. Under such conditions, the m=0 modes undergo brief (~100 μs) bursts of localized magnetic activity. These bursts show a localized 4% heating of electrons above a 600-900 eV background temperature, associated with a reduction of magnetic energy. An inward propagating cold pulse follows after the heating as a result of reduced confinement. Ensembles of hundreds of bursts are required to measure small relative heating, however single-shot results from MST's high repetition Thomson scattering diagnostic support the ensemble results. Analysis of Thomson scattering data also provides constraints on non-Maxwellian distributions and upcoming upgrades will improve the ability to resolve electron currents associated with the magnetic bursts. This work is supported by the US DOE and NSF.
Two density peaks in low magnetic field helicon plasma
Wang, Y.; Zhao, G.; Ouyang, J. T. E-mail: lppmchenqiang@hotmail.com; Liu, Z. W.; Chen, Q. E-mail: lppmchenqiang@hotmail.com
2015-09-15
In this paper, we report two density peaks in argon helicon plasma under an axial magnetic field from 0 G to 250 G with Boswell-type antenna driven by radio frequency (RF) power of 13.56 MHz. The first peak locates at 40–55 G and the second one at 110–165 G, as the RF power is sustainably increased from 100 W to 250 W at Ar pressure of 0.35 Pa. The absorbed power of two peaks shows a linear relationship with the magnetic field. End views of the discharge taken by intensified charge coupled device reveal that, when the first peak appeared, the discharge luminance moves to the edge of the tube as the magnetic field increases. For the second peak, the strong discharge area is centered at the two antenna legs after the magnetic field reaches a threshold value. Comparing with the simulation, we suggest that the efficient power absorption of two peaks at which the efficient power absorption mainly appears in the near-antenna region is due to the mode conversion in bounded non-uniform helicon plasma. The two low-field peaks are caused, to some extent, by the excitation of Trivelpiece-Gould wave through non-resonance conversion.
Bifurcation of magnetic island saturation controlled by plasma viscosity
NASA Astrophysics Data System (ADS)
Maget, P.; Février, O.; Lütjens, H.; Luciani, J.-F.; Garbet, X.
2016-05-01
Two nonlinear regimes, depending on the magnetic Prandtl number Prm, are identified for the magnetic islands described by resistive MHD equations. The frontier between these two regimes is sharp, and has the characteristics of a phase transition controlled by plasma viscosity. In the low Prm regime, a new form of the so-called flip instability, consisting of a sudden change in the island phase, is identified. Already known in the context of the forcing by external magnetic perturbations and localized current drive, it occurs spontaneously at low Prm. The main characteristics of this new structural instability are described. The low Prm regime is well described by the slab visco-resistive model in the linear phase, and is characterized by both a large saturation of the island and strong nonlinearly driven zonal flows (that do not significantly impact the island dynamics, however), while curvature physics strongly impacts the viscous regime.
Magnetic apatite for structural insights on the plasma membrane.
Stanca, Sarmiza E; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang
2015-01-21
The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.
Hall MHD Stability and Turbulence in Magnetically Accelerated Plasmas
H. R. Strauss
2012-11-27
The object of the research was to develop theory and carry out simulations of the Z pinch and plasma opening switch (POS), and compare with experimental results. In the case of the Z pinch, there was experimental evidence of ion kinetic energy greatly in excess of the ion thermal energy. It was thought that this was perhaps due to fine scale turbulence. The simulations showed that the ion energy was predominantly laminar, not turbulent. Preliminary studies of a new Z pinch experiment with an axial magnetic field were carried out. The axial magnetic is relevant to magneto - inertial fusion. These studies indicate the axial magnetic field makes the Z pinch more turbulent. Results were also obtained on Hall magnetohydrodynamic instability of the POS.
Pulsating jet-like structures in magnetized plasma
NASA Astrophysics Data System (ADS)
Goncharov, V. P.; Pavlov, V. I.
2016-08-01
The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as "radio pulsars." The estimates of their frequencies are made for conditions typical for the neutron star's ocean.
Magnetic apatite for structural insights on the plasma membrane
NASA Astrophysics Data System (ADS)
Stanca, Sarmiza E.; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang
2015-01-01
The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.
Surface waves in magnetized quantum electron-positron plasmas
NASA Astrophysics Data System (ADS)
Misra, A. P.; Ghosh, N. K.; Shukla, P. K.
2010-02-01
The dispersion properties of electrostatic surface waves propagating along the interface between a quantum magnetoplasma composed of electrons and positrons, and vacuum are studied by using a quantum magnetohydrodynamic plasma model. The general dispersion relation for arbitrary orientation of the magnetic field and the propagation vector is derived and analyzed in some special cases of interest (viz. when the magnetic field is directed parallel and perpendicular to the boundary surface). It is found that the quantum effects facilitate the propagation of electrostatic surface modes in a dense magnetoplasma. The effect of the external magnetic field is found to increase the frequency of the quantum surface wave. The existence of a singular wave on the boundary surface is also proved, and its properties are analyzed numerically. It is shown that the new wave characteristics appear due to the Rayleigh type of the wave.
Electric and magnetic contributions to spatial diffusion in collisionless plasmas
Smets, R.; Belmont, G.; Aunai, N.
2012-10-15
We investigate the role played by the different self-consistent fluctuations for particle diffusion in a magnetized plasma. We focus especially on the contribution of the electric fluctuations and how it combines with the (already investigated) magnetic fluctuations and with the velocity fluctuations. For that issue, we compute with a hybrid code the value of the diffusion coefficient perpendicular to the mean magnetic field and its dependence on the particle velocity. This study is restricted to small to intermediate level of electromagnetic fluctuations and focuses on particle velocities on the order of few times the Alfven speed. We briefly discuss the consequences for cosmic ray modulation and for the penetration of thermal solar wind particles in the Earth magnetosphere.
Critical Issues on Magnetic Reconnection in Space Plasmas
NASA Astrophysics Data System (ADS)
Lui, A. T. Y.; Jacquey, C.; Lakhina, G. S.; Lundin, R.; Nagai, T.; Phan, T.-D.; Pu, Z. Y.; Roth, M.; Song, Y.; Treumann, R. A.; Yamauchi, M.; Zelenyi, L. M.
2005-02-01
The idea of expedient energy transformation by magnetic reconnection (MR) has generated much enthusiasm in the space plasma community. The early concept of MR, which was envisioned for the solar flare phenomenon in a simple two-dimensional (2D) steady-state situation, is in dire need for extension to encompass three-dimensional (3D) non-steady-state phenomena prevalent in space plasmas in nature like in the magnetosphere. A workshop was organized to address this and related critical issues on MR. The essential outcome of this workshop is summarized in this review. After a brief evaluation on the pros and cons of existing definitions of MR, we propose essentially a working definition that can be used to identify MR in transient and spatially localized phenomena. The word “essentially” reflects a slight diversity in the opinion on how transient and localized 3D MR process might be defined. MR is defined here as a process with the following characteristics: (1) there is a plasma bulk flow across a boundary separating regions with topologically different magnetic field lines if projected on the plane of MR, thereby converting magnetic energy into kinetic particle energy, (2) there can be an out-of-the-plane magnetic field component (the so-called guide field) present such that the reconnected magnetic flux tubes are twisted to form flux ropes, and (3) the region exhibiting non-ideal MHD conditions should be localized to a scale comparable to the ion inertial length in the direction of the plasma inflow velocity. This definition captures the most important 3D aspects and preserves many essential characteristics of the 2D case. It may be considered as the first step in the generalization of the traditional 2D concept. As a demonstration on the utility of this definition, we apply it to identify MR associated with plasma phenomena in the dayside magnetopause and nightside magnetotail of the Earth’s magnetosphere. How MR may be distinguished from other competing
Logan, Nikolas C.; Paz-Soldan, Carlos; Park, Jong-Kyu; Nazikian, Raffi
2016-05-03
Using the plasma reluctance, the Ideal Perturbed Equilibrium Code is able to efficiently identify the structure of multi-modal magnetic plasma response measurements and the corresponding impact on plasma performance in the DIII-D tokamak. Recent experiments demonstrated that multiple kink modes of comparable amplitudes can be driven by applied nonaxisymmetric fields with toroidal mode number n = 2. This multi-modal response is in good agreement with ideal magnetohydrodynamic models, but detailed decompositions presented here show that the mode structures are not fully described by either the least stable modes or the resonant plasma response. This paper identifies the measured response fieldsmore » as the first eigenmodes of the plasma reluctance, enabling clear diagnosis of the plasma modes and their impact on performance from external sensors. The reluctance shows, for example, how very stable modes compose a significant portion of the multi-modal plasma response field and that these stable modes drive significant resonant current. Finally, this work is an overview of the first experimental applications using the reluctance to interpret the measured response and relate it to multifaceted physics, aimed towards providing the foundation of understanding needed to optimize nonaxisymmetric fields for independent control of stability and transport.« less
Magnetic properties of Co-Zr-B magnets produced by spark plasma sintering method
Saito, Tetsuji Akiyama, Tomoya
2014-05-07
Magnets of Co-Zr-B, one of the permanent magnetic compounds without rare-earth elements, were successfully produced by the spark plasma sintering method. The resultant Co-Zr-B magnets had high densities of 92%–96% and consisted mainly of the Co{sub x}Zr (x ≈ 5) phase. The coercivity of the Co-Zr-B magnets was highly dependent on the consolidation temperature and the boron content. The highest maximum energy product of 6.0 MGOe, with a remanence of 6.4 kG and the coercivity of 4.0 kOe, was achieved by the Co{sub 80}Zr{sub 18}B{sub 2} magnets consolidated at 873 K.
Multipole analysis of {sup 2}H({gamma},p)n in the {Delta} resonance region
Whisnant, C.S.; Mize, W.K.; Pomarede, D.; Sandorfi, A.M.
1998-07-01
An energy-dependent multipole analysis of the photodisintegration of deuterium has been performed for photon energies between 187 and 314 MeV using recent data taken with linearly polarized photons. A good fit is obtained with 11 free parameters determining eight multipoles. A wide variety of multipole solutions has been examined and in all cases the cross section with photon polarization parallel to the reaction plane is dominated by electric transitions, with E2{bold {center_dot}}E1 interference responsible for the observed forward-backward angular asymmetry. The cross sections observed in perpendicular kinematics are dominated by magnetic multipoles. Several recent N{Delta}/NN coupled-channel calculations have predicted a pronounced 90{degree} dip in the cross section that is absent from the data. This dip can be reproduced by changing the M2 strength distribution in our fit. A comparison is made with multipoles calculated by Wilhelm and Arenh{umlt o}vel at 300 MeV. {copyright} {ital 1998} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Liu, Yang; Wang, Jiachun; Miao, Lei; Li, Zhigang
2015-11-01
Firstly, the dispersion equation of a plane electromagnetic wave in homogeneous and non-magnetized discharge plasma was established. According to the different frequency of electromagnetic wave and plasma parameters, the characteristics were discussed when the plasma interacted with electromagnetic waves. Then the gas discharge approach was put forward according to characteristics of plasma generated by different methods and their advantages and disadvantages. The possibility of using non-magnetized discharge plasma for the military purpose was analyzed. In the end, the principle and characteristics of the application of the non-magnetized discharge plasma were studied in the fields of stealth and protection against strong electromagnetic pulse.
Medicean Moons Sailing Through Plasma Seas: Challenges in Establishing Magnetic Properties
NASA Astrophysics Data System (ADS)
Kivelson, Margaret G.; Jia, Xianzhe; Khurana, Krishan K.
2010-01-01
Jupiter's moons, embedded in the magnetized, flowing plasma of Jupiter's magnetosphere, the plasma seas of the title, are fluids whose highly non-linear interactions imply complex behavior. In a plasma, magnetic fields couple widely separated regions; consequently plasma interactions are exceptionally sensitive to boundary conditions (often ill-specified). Perturbation fields arising from plasma currents greatly limit our ability to establish more than the dominant internal magnetic field of a moon. With a focus on Ganymede and a nod to Io, this paper discusses the complexity of plasma-moon interactions, explains how computer simulations have helped characterize the system and presents improved fits to Ganymede's internal field.
Diagnosing laser-preheated magnetized plasmas relevant to magnetized liner inertial fusion
NASA Astrophysics Data System (ADS)
Harvey-Thompson, A. J.; Sefkow, A. B.; Nagayama, T. N.; Wei, M. S.; Campbell, E. M.; Fiksel, G.; Chang, P.-Y.; Davies, J. R.; Barnak, D. H.; Glebov, V. Y.; Fitzsimmons, P.; Fooks, J.; Blue, B. E.
2015-12-01
We present a platform on the OMEGA EP Laser Facility that creates and diagnoses the conditions present during the preheat stage of the MAGnetized Liner Inertial Fusion (MagLIF) concept. Experiments were conducted using 9 kJ of 3ω (355 nm) light to heat an underdense deuterium gas (electron density: 2.5 ×1020 cm-3=0.025 of critical density) magnetized with a 10 T axial field. Results show that the deuterium plasma reached a peak electron temperature of 670 ± 140 eV, diagnosed using streaked spectroscopy of an argon dopant. The results demonstrate that plasmas relevant to the preheat stage of MagLIF can be produced at multiple laser facilities, thereby enabling more rapid progress in understanding magnetized preheat. Results are compared with magneto-radiation-hydrodynamics simulations, and plans for future experiments are described.
Diagnosing laser-preheated magnetized plasmas relevant to magnetized liner inertial fusion
Harvey-Thompson, Adam James; Sefkow, Adam B.; Nagayama, Taisuke N.; Wei, Mingsheng; Campbell, Edward Michael; Fiksel, Gennady; Chang, Po -Yu; Davies, Jonathan R.; Barnak, Daniel H.; Glebov, Vladimir Y.; Fitzsimmons, Paul; Fooks, Julie; Blue, Brent E.
2015-12-22
In this paper, we present a platform on the OMEGA EP Laser Facility that creates and diagnoses the conditions present during the preheat stage of the MAGnetized Liner Inertial Fusion (MagLIF) concept. Experiments were conducted using 9 kJ of 3ω (355 nm) light to heat an underdense deuterium gas (electron density: 2.5 × 10^{20} cm^{-3} = 0.025 of critical density) magnetized with a 10 T axial field. Results show that the deuterium plasma reached a peak electron temperature of 670 ± 140 eV, diagnosed using streaked spectroscopy of an argon dopant. The results demonstrate that plasmas relevant to the preheat stage of MagLIF can be produced at multiple laser facilities, thereby enabling more rapid progress in understanding magnetized preheat. Results are compared with magneto-radiation-hydrodynamics simulations, and plans for future experiments are described.
Diagnosing laser-preheated magnetized plasmas relevant to magnetized liner inertial fusion
Harvey-Thompson, Adam James; Sefkow, Adam B.; Nagayama, Taisuke N.; Wei, Mingsheng; Campbell, Edward Michael; Fiksel, Gennady; Chang, Po -Yu; Davies, Jonathan R.; Barnak, Daniel H.; Glebov, Vladimir Y.; et al
2015-12-22
In this paper, we present a platform on the OMEGA EP Laser Facility that creates and diagnoses the conditions present during the preheat stage of the MAGnetized Liner Inertial Fusion (MagLIF) concept. Experiments were conducted using 9 kJ of 3ω (355 nm) light to heat an underdense deuterium gas (electron density: 2.5 × 1020 cm-3 = 0.025 of critical density) magnetized with a 10 T axial field. Results show that the deuterium plasma reached a peak electron temperature of 670 ± 140 eV, diagnosed using streaked spectroscopy of an argon dopant. The results demonstrate that plasmas relevant to the preheatmore » stage of MagLIF can be produced at multiple laser facilities, thereby enabling more rapid progress in understanding magnetized preheat. Results are compared with magneto-radiation-hydrodynamics simulations, and plans for future experiments are described.« less
Characteristics of the surface plasma wave in a self-gravitating magnetized dusty plasma slab
Lee, Myoung-Jae; Jung, Young-Dae
2015-11-15
The dispersion properties of surface dust ion-acoustic waves in a self-gravitating magnetized dusty plasma slab are investigated. The dispersion relation is derived by using the low-frequency magnetized dusty dielectric function and the surface wave dispersion integral for the slab geometry. We find that the self-gravitating effect suppresses the frequency of surface dust ion-acoustic wave for the symmetric mode in the long wavelength regime, whereas it hardly changes the frequency for the anti-symmetric mode. As the slab thickness and the wave number increase, the surface wave frequency slowly decreases for the symmetric mode but increases significantly for the anti-symmetric mode. The influence of external magnetic field is also investigated in the case of symmetric mode. We find that the strength of the magnetic field enhances the frequency of the symmetric-mode of the surface plasma wave. The increase of magnetic field reduces the self-gravitational effect and thus the self-gravitating collapse may be suppressed and the stability of dusty objects in space is enhanced.
Magnetic field production in an expanding plasma: Biermann or Weibel?
NASA Astrophysics Data System (ADS)
Schoeffler, Kevin; Loureiro, Nuno; Silva, Luis; Fonseca, Ricardo
2013-10-01
Recent laboratory experiments focusing intense lasers (~ kJ) at solid targets show the production of strong magnetic fields (of order a megaGauss). It is conjectured that these fields arise via the Biermann battery mechanism, due to non-aligned electron density and temperature gradients. We investigate the generation and amplification of such magnetic fields in a kinetic particle-in-cell model, and its dependence on system size, L. For moderate system sizes (L >~di), we find that the strength of the magnetic fields scales as 1 / L , consistent with their origin being due to the Biermann effect. However, for large L /di , we discover that the Weibel instability (due to electron temperature anisotropy) supersedes the Biermann battery effect as the main mechanism behind the production of magnetic fields. The Weibel-produced fields, unlike the ones due to Biermann, saturate at a finite amplitude (plasma β ~ 1) for large L /di . These results have strong implications for the interpretation of laser-solid interaction experiments. They may also be important to the understanding of the origin of the observed magnetic fields in the universe.
Safronova, U I; Safronova, A S; Beiersdorfer, P
2007-10-08
Transition rates and line strengths are calculated for electric-multipole (E2 and E3) and magnetic-multipole (M1, M2, and M3) transitions between 3s{sup 2}3p{sup 6}3d{sup 10}, 3s{sup 2}3p{sup 6}3d{sup 9}4l, 3s{sup 2}3p{sup 5}3d{sup 10}4l, and 3s3p{sup 6}3d{sup 10}4l states (with 4l = 4s, 4p, 4d, and 4f) in Ni-like ions with the nuclear charges ranging from Z = 34 to 100. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate retarded multipole matrix elements. Transition energies used in the calculation of line strengths and transition rates are from second-order RMBPT. Lifetimes of the 3s{sup 2}3p{sup 6}3d{sup 9}4s levels are given for Z = 34-100. Taking into account that calculations were performed in a very broad range of Z, most of the data are presented in graphs as Z-dependencies. The full set of data is given only for Ni-like W ion. In addition, we also give complete results for the 3d4s{sup 3}D{sub 2}-3d4s {sup 3}D{sub 1} magnetic-dipole transition, as the transition may be observed in future experiments, which measure both transition energies and radiative rates. These atomic data are important in the modeling of radiation spectra from Ni-like multiply-charged ions generated in electron beam ion trap experiments as well as for laboratory plasma diagnostics including fusion research.
PDRK: A General Kinetic Dispersion Relation Solver for Magnetized Plasma
NASA Astrophysics Data System (ADS)
Xie, Huasheng; Xiao, Yong
2016-02-01
A general, fast, and effective approach is developed for numerical calculation of kinetic plasma linear dispersion relations. The plasma dispersion function is approximated by J-pole expansion. Subsequently, the dispersion relation is transformed to a standard matrix eigenvalue problem of an equivalent linear system. Numerical solutions for the least damped or fastest growing modes using an 8-pole expansion are generally accurate; more strongly damped modes are less accurate, but are less likely to be of physical interest. In contrast to conventional approaches, such as Newton's iterative method, this approach can give either all the solutions in the system or a few solutions around the initial guess. It is also free from convergence problems. The approach is demonstrated for electrostatic dispersion equations with one-dimensional and two-dimensional wavevectors, and for electromagnetic kinetic magnetized plasma dispersion relation for bi-Maxwellian distribution with relative parallel velocity flows between species. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2015GB110003, 2011GB105001, 2013GB111000), National Natural Science Foundation of China (No. 91130031), the Recruitment Program of Global Youth Experts
Anomalous diffusion across the magnetic field-plasma boundary - The Porcupine artificial plasma jet
NASA Astrophysics Data System (ADS)
Mishin, E. V.; Kapitanov, V. Ia.; Treumann, R. A.
1986-09-01
Very fast magnetic field diffusion into the beam is required for observation of the nearly undisturbed penetration of the Porcupine's dense, fast and heavy ion beam into the magnetized ionospheric plasma after termination of the short adiabatic phase. The diffusion is presently attributed to a transverse electron drift current-driven electrostatic instability that is excited by the diamagnetic current flowing in the boundary layer between the injected beam and the ambient field. The anomalous collision frequencies turn out to be of the order of the local lower hybrid frequency in the dense Xe plasma. Since only a very small fraction of beam energy is dissipated in the diffusion process, no significant deceleration of the ion beam is observable.
Pair production rates in mildly relativistic, magnetized plasmas
NASA Technical Reports Server (NTRS)
Burns, M. L.; Harding, A. K.
1984-01-01
Electron-positron pairs may be produced by either one or two photons in the presence of a strong magnetic field. In magnetized plasmas with temperatures kT approximately sq mc, both of these processes may be important and could be competitive. The rates of one-photon and two-photon pair production by photons with Maxwellian, thermal bremsstrahlung, thermal synchrotron and power law spectra are calculated as a function of temperature or power law index and field strength. This allows a comparison of the two rates and a determination of the conditions under which each process may be a significant source of pairs in astrophysical plasmas. It is found that for photon densities n(gamma) or = 10 to the 25th power/cu cm and magnetic field strengths B or = 10 to the 12th power G, one-photon pair production dominates at kT approximately sq mc for a Maxwellian, at kT approximately 2 sq mc for a thermal bremsstrahlung spectrum, at all temperatures for a thermal synchrotron spectrum, and for power law spectra with indices s approximately 4.
ON THE MAGNETIZATION OF COSMIC OUTFLOWS: PLASMA MODES AND INSTABILITIES OF UNMAGNETIZED PLASMA BEAMS
Michno, M. J.; Schlickeiser, R. E-mail: mjm@tp4.rub.d
2010-05-01
The dissipation of the kinetic energy of cosmic outflows in interactions with ambient collision-free plasmas and the associated generation of electromagnetic plasma turbulence is a fundamental problem of modern astrophysics. Thermalization by elastic two-body Coulomb collisions is orders of magnitudes too slow as compared to interactions with electric and magnetic fields because of the generally low density of cosmic plasmas. Alternative dissipation mechanisms have to be examined such as energy diffusion by second-order Fermi interactions of charged particles with electromagnetic turbulence, which are an intrinsic property of any sufficiently agitated magnetized plasma. We consider the microphysical details of the energy conversion in relativistic and nonrelativistic outflows by investigating the solutions of the linear plasma dispersion relation in an unmagnetized anisotropic beam plasma consisting of two overall-neutral particle beams propagating with arbitrary velocities in the same direction. The general plasma dispersion relation is derived for arbitrary propagation angle {theta} with respect to the beam propagation direction both in the initial laboratory frame and in the counterstream frame of reference. Solutions of the linear dispersion relation are derived for parallel ({theta} = {pi}/2) and perpendicular ({theta} = 0) propagation angle, respectively. For parallel propagation angles, the electrostatic mode is excited and its maximum growth rate depends on the relative bulk Lorentz factor of the flows and their density ratio. For perpendicular propagation angles, the aperiodic filamentation mode is excited and its maximum growth rate depends differently on the relative bulk Lorentz factor of the flow and their density ratio. The respective maximum growth rates indicate that for nonrelativistic flow velocities the electrostatic instability (EI) is excited much faster than the filamentation instability (FI), whereas for relativistic flow velocities the FI
Low pressure characteristics of the multipole resonance probe
NASA Astrophysics Data System (ADS)
Brinkmann, Ralf Peter; Oberrath, Jens
2014-10-01
The term ``Active plasma resonance spectroscopy'' (APRS) denotes a class of related techniques which utilize, for diagnostic purposes, the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe. The basic idea dates back to the early days of discharge physics but has recently found renewed interest as an approach to industry-compatible plasma diagnostics: A radio frequent signal (in the GHz range) is coupled into the plasma via an antenna or probe, the spectral response is recorded (with the same or another antenna or probe), and a mathematical model is used to determine plasma parameters like the electron density or the electron temperature. When the method is applied to low pressure plasmas (of a few Pa and lower), kinetic effects must be accounted for in the mathematical model. This contribution studies a particular realization of the APRS scheme, the geometrically and electrically symmetric Multipole Resonance Probe (MRP). It is shown that the resonances of the MRP exhibit a residual damping in the limit p --> 0 which cannot be explained by Ohmic dissipation but only by kinetic effects. Supported by the German Federal Ministry of Education and Research (BMBF) in the framework of the PluTO project.
Spectral Kinetic Simulation of the Ideal Multipole Resonance Probe
NASA Astrophysics Data System (ADS)
Gong, Junbo; Wilczek, Sebastian; Szeremley, Daniel; Oberrath, Jens; Eremin, Denis; Dobrygin, Wladislaw; Schilling, Christian; Friedrichs, Michael; Brinkmann, Ralf Peter
2015-09-01
The term Active Plasma Resonance Spectroscopy (APRS) denotes a class of diagnostic techniques which utilize the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe: An RF signal in the GHz range is coupled into the plasma via an electric probe; the spectral response of the plasma is recorded, and a mathematical model is used to determine plasma parameters such as the electron density ne or the electron temperature Te. One particular realization of the method is the Multipole Resonance Probe (MRP). The ideal MRP is a geometrically simplified version of that probe; it consists of two dielectrically shielded, hemispherical electrodes to which the RF signal is applied. A particle-based numerical algorithm is described which enables a kinetic simulation of the interaction of the probe with the plasma. Similar to the well-known particle-in-cell (PIC), it contains of two modules, a particle pusher and a field solver. The Poisson solver determines, with the help of a truncated expansion into spherical harmonics, the new electric field at each particle position directly without invoking a numerical grid. The effort of the scheme scales linearly with the ensemble size N.
NASA Astrophysics Data System (ADS)
Rodriguez, L.; Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Zhukov, A. N.; Gulisano, A. M.; Mierla, M.; Kilpua, E.; West, M.; Lacatus, D.; Paraschiv, A.; Janvier, M.
2016-07-01
Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important because of their simple internal magnetic field configuration, which resembles a magnetic flux rope, and because they represent one of the most geoeffective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by the Advance Composition Explorer (ACE), between 1998 and 2006. In this way, we obtain an average profile for each plasma and magnetic field parameter at each point of the cloud. Furthermore, we take a fixed time-window upstream and downstream from the MC to also sample the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal distribution functions. The plasma β and the level of fluctuations in the magnetic field vector are the best parameters to define the boundaries of MCs. We find that one third of the events shows a peak in plasma density close to the trailing edge of the flux ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin (e.g. erupting prominence material) or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the magnetic cloud.
NASA Astrophysics Data System (ADS)
Rodriguez, L.; Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Zhukov, A. N.; Gulisano, A. M.; Mierla, M.; Kilpua, E.; West, M.; Lacatus, D.; Paraschiv, A.; Janvier, M.
2016-08-01
Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important because of their simple internal magnetic field configuration, which resembles a magnetic flux rope, and because they represent one of the most geoeffective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by the Advance Composition Explorer (ACE), between 1998 and 2006. In this way, we obtain an average profile for each plasma and magnetic field parameter at each point of the cloud. Furthermore, we take a fixed time-window upstream and downstream from the MC to also sample the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal distribution functions. The plasma β and the level of fluctuations in the magnetic field vector are the best parameters to define the boundaries of MCs. We find that one third of the events shows a peak in plasma density close to the trailing edge of the flux ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin ( e.g. erupting prominence material) or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the magnetic cloud.
Experiments on beam plasma interactions and EM waves in magnetized plasmas
NASA Astrophysics Data System (ADS)
Phelps, Alan D. R.
2012-04-01
An energetic electron beam can exhibit several types of interesting behaviour when interacting with plasmas and/or magnetic fields. The focus in the present work is on electron cyclotron maser interactions. The instabilities that occur are also often observed in space as well as in the laboratory. Some of the high power sources of electromagnetic radiation, such as gyrodevices, make use of similar instability mechanisms. Laboratory experiments and numerical simulations have led to both a better understanding of natural phenomena and the development of high power electromagnetic radiation sources for several applications in fusion plasma physics. The gyrotron is one such device that is being used to provide auxiliary heating for large tokamaks via electron cyclotron resonance heating (ECRH). It is planned to use a number of gyrotrons supplied by several nations in the ITER experiment. In the ITER experiment these gyrotrons will not only be used for auxiliary heating but also for advanced tailoring of the tokamak plasma properties.
Magnetic field probes for use in radio frequency plasma
Reilly, Michael P.; Miley, George H.; Lewis, William
2009-05-15
An impedance analyzer has been used in the characterization of a magnetic induction probe (B-dot probe) for use in plasma. The role of the impedance analyzer was to determine the frequency response of a B-dot probe up to 100 MHz. The probe was specifically designed to take measurements in rf plasma driven at 13.56 MHz. Probe sensitivity and calibration are considered based on the impedance values obtained when a B-dot probe is swept over a wide frequency range. Effects such as unbalanced loads based on transmission line inductances and termination impedance are shown to be limiting factors on the probes useful frequency range. The use of an impedance analyzer allows these effects to readily be characterized.
Auroral electrostatic solitons and supersolitons in a magnetized nonthermal plasma
Rufai, O. R.
2015-05-15
Exploiting the spacecraft measurements in the auroral region, finite amplitude nonlinear low frequency electrostatic solitons and supersolitons in a magnetized plasma consisting of cold ions fluid, Boltzmann protons, and nonthermal hot electrons are studied by applying a pseudo-potential technique. The localized solution of the nonlinear structures is obtained through the charge neutrality condition. Further numerical investigation shows the existence of supersoliton solutions at supersonic Mach numbers regime. The amplitude of ion-acoustic structures decreased with an increase in nonthermal electrons and ion density ratio. For the plasma parameters relevant to the auroral zone of the Earth's magnetosphere, the electric field amplitude of supersolitons is found to be about 9 mV/m, which is in agreement with satellite observations.
Accumulative coupling between magnetized tenuous plasma and gravitational waves
NASA Astrophysics Data System (ADS)
Zhang, Fan
2016-07-01
We explicitly compute the plasma wave (PW) induced by a plane gravitational wave (GW) traveling through a region of strongly magnetized plasma, governed by force-free electrodynamics. The PW comoves with the GW and absorbs its energy to grow over time, creating an essentially force-free counterpart to the inverse-Gertsenshtein effect. The time-averaged Poynting flux of the induced PW is comparable to the vacuum case, but the associated current may offer a more sensitive alternative to photodetection when designing experiments for detecting/constraining high-frequency gravitational waves. Aside from the exact solutions, we also offer an analysis of the general properties of the GW to PW conversion process, which should find use when evaluating electromagnetic counterparts to astrophysical gravitational waves that are generated directly by the latter as a second-order phenomenon.
A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas
Haskey, S. R.; Blackwell, B. D.; Seiwald, B.; Hole, M. J.; Pretty, D. G.; Howard, J.; Wach, J.
2013-09-15
The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger et al., Fusion Technol. 17, 123 (1990)] plasmas has motivated the installation of a sixteen former, tri-axis helical magnetic probe Mirnov array (HMA). The new array complements two existing poloidal Mirnov arrays by providing polarisation information, higher frequency response, and improved toroidal resolution. The helical placement is ideal for helical axis plasmas because it positions the array as close as possible to the plasma in regions of varying degrees of favourable curvature in the magnetohydrodynamic sense, but almost constant magnetic angle. This makes phase variation with probe position near linear, greatly simplifying the analysis of the data. Several of the issues involved in the design, installation, data analysis, and calibration of this unique array are presented including probe coil design, frequency response measurements, mode number identification, orientation calculations, and mapping probe coil positions to magnetic coordinates. Details of specially designed digitally programmable pre-amplifiers, which allow gains and filters to be changed as part of the data acquisition initialisation sequence and stored with the probe signals, are also presented. The low shear heliac geometry [R. Jiménez-Gómez et al., Nucl. Fusion 51, 033001 (2011)], flexibility of the H-1NF heliac, and wealth of information provided by the HMA create a unique opportunity for detailed study of Alfvén eigenmodes, which could be a serious issue for future fusion reactors.
Hamidi, S. M.
2012-01-15
In this paper, the optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals have been investigated. We use transfer matrix method to solve our magnetized coupled resonator plasma photonic crystals consist of dielectric and magnetized plasma layers. The results of the change in the optical and magneto-optical properties of structure as a result of the alteration in the structural properties such as thickness, plasma frequency and collision frequency, plasma filling factor, number of resonators and dielectric constant of dielectric layers and external magnetic field have been reported. The main feature of this structure is a good magneto-optical rotation that takes place at the defect modes and the edge of photonic band gap of our proposed optical magnetized plasma waveguide. Our outcomes demonstrate the potential applications of the device for tunable and adjustable filters or reflectors and active magneto-optic in microwave devices under structural parameter and external magnetic field.
NASA Astrophysics Data System (ADS)
Hamidi, S. M.
2012-01-01
In this paper, the optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals have been investigated. We use transfer matrix method to solve our magnetized coupled resonator plasma photonic crystals consist of dielectric and magnetized plasma layers. The results of the change in the optical and magneto-optical properties of structure as a result of the alteration in the structural properties such as thickness, plasma frequency and collision frequency, plasma filling factor, number of resonators and dielectric constant of dielectric layers and external magnetic field have been reported. The main feature of this structure is a good magneto-optical rotation that takes place at the defect modes and the edge of photonic band gap of our proposed optical magnetized plasma waveguide. Our outcomes demonstrate the potential applications of the device for tunable and adjustable filters or reflectors and active magneto-optic in microwave devices under structural parameter and external magnetic field.
Magnetic Reconnection: A Fundamental Process in Space Plasmas
NASA Technical Reports Server (NTRS)
Hesse, Michael
2010-01-01
For many years, collisionless magnetic reconnect ion has been recognized as a fundamental process, which facilitates plasma transport and energy release in systems ranging from the astrophysical plasmas to magnetospheres and even laboratory plasma. Beginning with work addressing solar dynamics, it has been understood that reconnection is essential to explain solar eruptions, the interaction of the solar wind with the magnetosphere, and the dynamics of the magnetosphere. Accordingly, the process of magnetic reconnection has been and remains a prime target for space-based and laboratory studies, as well as for theoretical research. Much progress has been made throughout the years, beginning with indirect verifications by studies of processes enabled by reconnection, such as Coronal Mass Ejections, Flux Transfer Events, and Plasmoids. Theoretical advances have accompanied these observations, moving knowledge beyond the Sweet-Parker theory to the recognition that other, collisionless, effects are available and likely to support much faster reconnect ion rates. At the present time we are therefore near a break-through in our understanding of how collisionless reconnect ion works. Theory and modeling have advanced to the point that two competing theories are considered leading candidates for explaining the microphysics of this process. Both theories predict very small spatial and temporal scales. which are. to date, inaccessible to space-based or laboratory measurements. The need to understand magnetic reconnect ion has led NASA to begin the implementation of a tailored mission, Magnetospheric MultiScale (MMS), a four spacecraft cluster equipped to resolve all relevant spatial and temporal scales. In this presentation, we present an overview of current knowledge as well as an outlook towards measurements provided by MMS.
Location of the first plasma response to resonant magnetic perturbations in DIII-D H-mode plasmas
NASA Astrophysics Data System (ADS)
Xiao, W. W.; Evans, T. E.; Tynan, G. R.; Eldon, D.
2016-06-01
The resonant location of the first plasma response to periodic toroidal phase flips of a resonant magnetic perturbation (RMP) field is experimentally identified in the DIII-D tokamak using phase minima of the modulated plasma density and toroidal rotation relative to the RMP field. The plasma response coincides with the q = 3 rational surface and electron fluid velocity null, which is consistent with simulations of the plasma response to the RMP field from resistive magnetohydrodynamics (MHD) modeling. An asymmetric propagation of the particle and the momentum transport from the resonant location of the plasma response to the RMP into the core and into the plasma edge is observed.
NASA Astrophysics Data System (ADS)
Jabbari, S.; Brandenburg, A.
2014-12-01
Recent studies have suggested a new mechanism that can be used to explain the formation of magnetic spots or bipolar regions in highly stratified turbulent plasmas. According to this model, a large-scale magnetic field suppresses the turbulent pressure, which leads to a negative contribution of turbulence to the effective magnetic pressure. Direct numerical simulations (DNS) have confirmed that the negative contribution is large enough so that the effective magnetic pressure becomes negative and leads to a large-scale instability, which we refer to as negative effective magnetic pressure Instability (NEMPI). NEMPI was used to explain the formation of active regions and sunspots on the solar surface. One step toward improving this model was to combine dynamo in- stability with NEMPI. The dynamo is known to be responsible for the solar large-scale magnetic field and to play a role in solar activity. In this context, we studied stratified turbulent plasmas in spherical geometry, where the background field was generated by alpha squared dynamo. For NEMPI to be excited, the initial magnetic field should be in a proper range, so we used quenching function for alpha. Using the Pencil Code and mean field simulations (MFS), we showed that in the presence of dynamo-generated magnetic fields, we deal with a coupled system, where both instabilities, dynamo and NEMPI, work together and lead to the formation of magnetic structures (Jabbari et al. 2013). We also studied a similar system in plane geometry in the presence of rotation and confirmed that for slow rotation NEMPI works, but as the Coriolis number increases, the rotation suppresses NEMPI. By increasing the Coriolis number even further, the combination of fast rotation and high stratification excites a dynamo, which leads again to a coupled system of dynamo and NEMPI (Jabbari et al. 2014). Another important finding concerning NEMPI is the case where the instability is excited by a vertical magnetic field (Brandenburg et
Wave instabilities in an anisotropic magnetized space plasma
NASA Astrophysics Data System (ADS)
Dzhalilov, N. S.; Kuznetsov, V. D.; Staude, J.
2008-10-01
Aims: We study wave instability in an collisionless, rarefied hot plasma (e.g. solar wind or corona). We consider the anisotropy produced by the magnetic field, when the thermal gas pressures across and along the field become unequal. Methods: We apply the 16-moment transport equations (obtained from the Boltzmann-Vlasov kinetic equation) including the anisotropic thermal fluxes. The general dispersion relation for the incompressible wave modes is derived. Results: It is shown that a new, more complex wave spectrum with stable and unstable behavior is possible, in contrast to the classic fire-hose modes obtained in terms of the 13-moment integrated equations.
Magnetic field generation during intense laser channelling in underdense plasma
NASA Astrophysics Data System (ADS)
Smyth, A. G.; Sarri, G.; Vranic, M.; Amano, Y.; Doria, D.; Guillaume, E.; Habara, H.; Heathcote, R.; Hicks, G.; Najmudin, Z.; Nakamura, H.; Norreys, P. A.; Kar, S.; Silva, L. O.; Tanaka, K. A.; Vieira, J.; Borghesi, M.
2016-06-01
Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.
Magnetic Reconnection Rate in Space Plasmas: A Fractal Approach
Materassi, Massimo; Consolini, Giuseppe
2007-10-26
Magnetic reconnection is generally discussed via a fluid description. Here, we evaluate the reconnection rate assuming a fractal topology of the reconnection region. The central idea is that the fluid hypothesis may be violated at the scales where reconnection takes place. The reconnection rate, expressed as the Alfven Mach number of the plasma moving toward the diffusion region, is shown to depend on the fractal dimension and on the sizes of the reconnection or diffusion region. This mechanism is more efficient than prediction of the Sweet-Parker model and even Petschek's model for finite magnetic Reynolds number. A good agreement also with rates given by Hall MHD models is found. A discussion of the fractal assumption on the diffusion region in terms of current microstructures is proposed. The comparison with in-situ satellite observations suggests the reconnection region to be a filamentary domain.
Kinetic theory of weak turbulence in magnetized plasmas: Perpendicular propagation
Yoon, Peter H.
2015-08-15
The present paper formulates a weak turbulence theory in which electromagnetic perturbations are assumed to propagate in directions perpendicular to the ambient magnetic field. By assuming that all wave vectors lie in one direction transverse to the ambient magnetic field, the linear solution and second-order nonlinear solutions to the equation for the perturbed distribution function are obtained. Nonlinear perturbed current from the second-order nonlinearity is derived in general form, but the limiting situation of cold plasma temperature is taken in order to derive an explicit nonlinear wave kinetic equation that describes three-wave decay/coalescence interactions among X and Z modes. A potential application of the present formalism is also discussed.
The Magnetic Field Distribution of Single Exploding Wire Aluminum Plasmas
NASA Astrophysics Data System (ADS)
Blesener, Kate; Pikuz, Sergei; Shelkovenko, Tania; Hammer, David; Maron, Yitzhak; Doron, Ramy; Bernshtam, Vladimir; Weingarten, Leonid; Zarnitsky, Yuri
2013-10-01
The exploding wires were driven by the 13 kA Low Current Pulser LCP3 at Cornell University, employing high-resolution time-gated emission spectroscopy at visible wavelengths to determine the plasma parameters as a function of radial position and time. The distribution of current through single exploding aluminum wires was determined through time resolved studies of the magnitude of the magnetic field as a function of position. To study the magnetic field we used the Zeeman Broadening technique developed at the Weizmann Institute of Science. This research is supported by the DOE/NNSA joint program in HEDLP under contract DE-SC0002263 and by the NNSA SSAA program under DOE Cooperative Agreement DE-NA0001836.
Antiproton powered propulsion with magnetically confined plasma engines
NASA Technical Reports Server (NTRS)
Lapointe, Michael R.
1989-01-01
The reaction of the matter-antimatter annihilation, with its specific energy being over 250 times the specific energy released in nuclear fusion, is considered as an energy source for spacecraft propulsion. A concept of a magnetically confined pulsed plasma engine is described. In this concept, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas; the resulting charge annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. Numerical simulations were developed to calculate the annihilation rate of antiprotons in hydrogen and to follow the resulting ion, muon, and electron/positron number density evolutions.
A pragmatic overview of fast multipole methods
Strickland, J.H.; Baty, R.S.
1995-12-01
A number of physics problems can be modeled by a set of N elements which have pair-wise interactions with one another. A direct solution technique requires computational effort which is O(N{sup 2}). Fast multipole methods (FMM) have been widely used in recent years to obtain solutions to these problems requiring a computational effort of only 0 (N lnN) or O (N). In this paper we present an overview of several variations of the fast multipole method along with examples of its use in solving a variety of physical problems.
The Multipole Structure of Earth's STEP Signal
NASA Technical Reports Server (NTRS)
Nordtvedt, Kenneth
2003-01-01
If there is an interaction in physical law which differentially accelerates the test bodies in a STEP satellite, then the di.erent elements that compose the Earth will most likely have source strengths for this interaction which are not proportional to their mass densities. The rotational flattening of Earth and geographical irregularities of our planet's crust then produces a multipole structure for the Equivalence Principle violating force field which differs from the multipole structure of Earth's ordinary gravity field. Measuring these differences yields key information about the new interaction in physical law which is not attainable by solely measuring differences of test body accelerations.
Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation
You, S.; Yun, G.S.; Bellan, P.M.
2005-07-22
Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated.
Dynamic and stagnating plasma flow leading to magnetic-flux-tube collimation.
You, S; Yun, G S; Bellan, P M
2005-07-22
Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated.
Stoerk, H.B.; Winter, J.; Ihde, J.; Esser, H.G.; Reimer, H.; Freisinger, M
2001-01-15
The TOroidal MAgnetized System (TOMAS) is a simple magnetized torus dedicated to the investigation of wall conditioning methods by microwave-induced plasmas. In the TOMAS facility, an electron cyclotron resonance plasma is produced by microwaves at a frequency of 2.45 GHz and the corresponding resonant magnetic field of 87.6 mT. The facility and the first operational experience of film deposition by means of methane plasmas are described.
NASA Astrophysics Data System (ADS)
Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.
2015-04-01
The magnetized liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot compressed magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter ( ωeτe≫1 ), the effective diffusion coefficients determining the losses of heat and magnetic flux to the liner wall are both shown to decrease with ωeτe as does the Bohm diffusion coefficient c T /(16 e B ) , which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.
Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.
2015-04-15
The magnetized liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot compressed magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter (ω{sub e}τ{sub e}≫1), the effective diffusion coefficients determining the losses of heat and magnetic flux to the liner wall are both shown to decrease with ω{sub e}τ{sub e} as does the Bohm diffusion coefficient cT/(16eB), which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.
Magnetized Plasma-filled Waveguide: A New High-Gradient Accelerating Structure
Avitzour, Yoav; Shvets, Gennady
2009-01-22
Electromagnetic waves confined between the metal plates of a plasma-filled waveguide are investigated. It is demonstrated that when the plasma is magnetized along the metallic plates, there exists a luminous accelerating wave propagating with a very slow group velocity. It is shown that the magnetized plasma 'isolates' the metal wall from the transverse electric field, thereby reducing potential breakdown problems. Applications of the metallic plasma-filled waveguide to particle accelerations and microwave pulse manipulation are described.
Numerical study of laminar plasma dynamo in cylindrical and spherical geometries
NASA Astrophysics Data System (ADS)
Khalzov, Ivan; Bayliss, Adam; Ebrahimi, Fatima; Forest, Cary; Schnack, Dalton
2009-05-01
We have performed the numerical investigation of possibility of laminar dynamo in two new experiments, Plasma Couette and Plasma Dynamo, which have been designed at the University of Wisconsin-Madison. The plasma is confined by a strong multipole magnetic field localized at the boundary of cylindrical (Plasma Couette) or spherical (Plasma Dynamo) chamber. Electrodes positioned between the magnet rings can be biased with arbitrary potentials so that Lorenz force ExB drives any given toroidal velocity profile at the surface. Using the extended MHD code, NIMROD, we have modeled several types of plasma flows appropriate for dynamo excitation. It is found that for high magnetic Reynolds numbers the counter-rotating von Karman flow (in cylinder) and Dudley-James flow (in sphere) can lead to self-generation of non-axisymmetric magnetic field. This field saturates at certain amplitude corresponding to a new stable equilibrium. The structure of this equilibrium is considered.
Magnetic Probe to Study Plasma Jets for Magneto-Inertial Fusion
Martens, Daniel; Hsu, Scott C.
2012-08-16
A probe has been constructed to measure the magnetic field of a plasma jet generated by a pulsed plasma rail-gun. The probe consists of two sets of three orthogonally-oriented commercial chip inductors to measure the three-dimensional magnetic field vector at two separate positions in order to give information about the magnetic field evolution within the jet. The strength and evolution of the magnetic field is one of many factors important in evaluating the use of supersonic plasma jets for forming imploding spherical plasma liners as a standoff driver for magneto-inertial fusion.
Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production
NASA Technical Reports Server (NTRS)
Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.
1983-01-01
A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.
NASA Technical Reports Server (NTRS)
Gonzalez, Dora E.; Karr, Gerald R.
1990-01-01
The purpose of this paper is to review the status of knowledge of the basic concepts needed to establish design parameters for effective magnetic insulation. The objective is to estimate the effectiveness of the magnetic field in insulating the plasma, to calculate the magnitude of the magnetic field necessary to reduce the heat transfer to the walls sufficiently enough to demonstrate the potential of magnetically driven plasma rockets.
Hypersonic drift-tearing magnetic islands in tokamak plasmas
Fitzpatrick, R.; Waelbroeck, F. L.
2007-12-15
A two-fluid theory of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low-{beta} plasmas possessing relatively weak magnetic shear is developed. The model assumes both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in three asymptotically matched regions. The 'inner region' contains the island. However, the island emits electrostatic drift-acoustic waves that propagate into the surrounding 'intermediate region', where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the intermediate region, and vice versa, giving rise to strong velocity shear in the region immediately surrounding the island. The intermediate region is matched to the surrounding 'outer region', in which ideal magnetohydrodynamic holds. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is stabilizing, and increases with increasing island width. Finally, the hypersonic branch of isolated island solutions ceases to exist above a certain critical island width. Hypersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the so-called 'sonic' solution branch.
Diamagnetic boundary layers - A kinetic theory. [for collisionless magnetized plasmas
NASA Technical Reports Server (NTRS)
Lemaire, J.; Burlaga, L. F.
1976-01-01
A kinetic theory is presented for boundary layers associated with MHD tangential 'discontinuities' in a collisionless magnetized plasma, such as those observed in the solar wind. The theory consists of finding self-consistent solutions of Vlasov's equation and Maxwell's equation for stationary one-dimensional boundary layers separating two Maxwellian plasma states. Layers in which the current is carried by electrons are found to have a thickness of the order of a few electron gyroradii, but the drift speed of the current-carrying electrons is found to exceed the Alfven speed, and accordingly such layers are not stable. Several types of layers in which the current is carried by protons are discussed; in particular, cases are considered in which the magnetic-field intensity, direction, or both, changed across the layer. In every case, the thickness was of the order of a few proton gyroradii, and the field changed smoothly, although the characteristics depended somewhat on the boundary conditions. The drift speed was always less than the Alfven speed, consistent with stability of such structures. These results are consistent with observations of boundary layers in the solar wind near 1 AU.
Kim, Kihong; Lee, Dong-Hun
2006-04-15
A new version of the invariant imbedding theory for the propagation of coupled waves in inhomogeneous media is applied to the mode conversion of high frequency electromagnetic waves into electrostatic modes in cold, magnetized, and stratified plasmas. The cases where the external magnetic field is applied perpendicularly to the direction of inhomogeneity and the electron density profile is linear are considered. Extensive and numerically exact results for the mode conversion coefficients, the reflectances, and the wave electric and magnetic field profiles inside the inhomogeneous plasma are obtained. The dependencies of mode conversion phenomena on the magnitude of the external magnetic field, the incident angle, and the wave frequency are explored in detail.
On the magnetic field signal radiated by an atmospheric pressure room temperature plasma jet
Wu, S.; Huang, Q.; Wang, Z.; Lu, X.
2013-01-28
In this paper, the magnetic field signal radiated from an atmospheric pressure room temperature plasma plume is measured. It's found that the magnetic field signal has similar waveform as the current carried by the plasma plume. By calibration of the magnetic field signal, the plasma plume current is obtained by measuring the magnetic field signal radiated by the plasma plume. In addition, it is found that, when gas flow modes changes from laminar regime to turbulence regime, the magnetic field signal waveforms appears different, it changes from a smooth curve to a curve with multiple spikes. Furthermore, it is confirmed that the plasma plume generated by a single electrode (without ground electrode) plasma jet device carries higher current than that with ground electrode.
Experimental and numerical studies on plasma behavior flowing across perpendicular magnetic field
NASA Astrophysics Data System (ADS)
Takezaki, T.; Takahashi, K.; Sasaki, T.; Kikuchi, T.; Harada, N.
2016-05-01
To understand particle acceleration mechanisms in a collisionless shock, we have investigated the behaviors of a one-dimensional fast plasma flow in a perpendicular magnetic field by experimental and numerical simulations in a laboratory scale experiment. The velocity of the plasma flow generated by a taper-cone-shaped plasma focus device has varied by the gradient of the perpendicular magnetic field. The plasma flow has accelerated by applying the magnetic field with the negative gradient. To clarify the behavior of the plasma flow in the perpendicular magnetic field, numerical simulations based on an electromagnetic hybrid particle-in-cell (PIC) method have been carried out. These results indicate that the magnetic field gradient affects the plasma flow velocity.
Ciaccio, G. Spizzo, G.; Schmitz, O. Frerichs, H.; Abdullaev, S. S.; Evans, T. E.; White, R. B.
2015-10-15
The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted by simulations with the Hamiltonian guiding center code ORBIT. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for these effects. An analytical model for the plasma potential is implemented in the code ORBIT, and analyses of ion and electron radial diffusion show that both ion- and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggest that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.
Plasma, magnetic, and electromagnetic measurements at nonmagnetic bodies
NASA Technical Reports Server (NTRS)
Russell, C. T.; Luhmann, J. G.
1993-01-01
The need to explore the magnetospheres of the Earth and the giant planets is widely recognized and is an integral part of our planetary exploration program. The equal need to explore the plasma, magnetic, and electromagnetic environments of the nonmagnetic bodies is not so widely appreciated. The previous, albeit incomplete, magnetic and electric field measurements at Venus, Mars, and comets have proven critical to our understanding of their atmospheres and ionospheres in areas ranging from planetary lightning to solar wind scavenging and accretion. In the cases of Venus and Mars, the ionospheres can provide communication paths over the horizon for low-altitude probes and landers, but we know little about their lower boundaries. The expected varying magnetic fields below these planetary ionospheres penetrates the planetary crusts and can be used to sound the electrical conductivity and the thermal profiles of the interiors. However, we have no knowledge of the levels of such fields, let alone their morphology. Finally, we note that the absence of an atmosphere and an ionosphere does not make an object any less interesting for the purposes of electromagnetic exploration. Even weak remanent magnetism such as that found on the Moon during the Apollo program provides insight into the present and past states of planetary interiors. We have very intriguing data from our space probes during times of both close and distant passages of asteroids that suggest they may have coherent magnetization. If true, this observation will put important constraints on how the asteroids formed and have evolved. Our planetary exploration program must exploit its full range of exploration tools if it is to characterize the bodies of the solar system thoroughly. We should especially take advantage of those techniques that are proven and require low mass, low power, and low telemetry rates to undertake.
Plasma, magnetic, and electromagnetic measurements at nonmagnetic bodies
NASA Astrophysics Data System (ADS)
Russell, C. T.; Luhmann, J. G.
The need to explore the magnetospheres of the Earth and the giant planets is widely recognized and is an integral part of our planetary exploration program. The equal need to explore the plasma, magnetic, and electromagnetic environments of the nonmagnetic bodies is not so widely appreciated. The previous, albeit incomplete, magnetic and electric field measurements at Venus, Mars, and comets have proven critical to our understanding of their atmospheres and ionospheres in areas ranging from planetary lightning to solar wind scavenging and accretion. In the cases of Venus and Mars, the ionospheres can provide communication paths over the horizon for low-altitude probes and landers, but we know little about their lower boundaries. The expected varying magnetic fields below these planetary ionospheres penetrates the planetary crusts and can be used to sound the electrical conductivity and the thermal profiles of the interiors. However, we have no knowledge of the levels of such fields, let alone their morphology. Finally, we note that the absence of an atmosphere and an ionosphere does not make an object any less interesting for the purposes of electromagnetic exploration. Even weak remanent magnetism such as that found on the Moon during the Apollo program provides insight into the present and past states of planetary interiors. We have very intriguing data from our space probes during times of both close and distant passages of asteroids that suggest they may have coherent magnetization. If true, this observation will put important constraints on how the asteroids formed and have evolved. Our planetary exploration program must exploit its full range of exploration tools if it is to characterize the bodies of the solar system thoroughly. We should especially take advantage of those techniques that are proven and require low mass, low power, and low telemetry rates to undertake.
NASA Technical Reports Server (NTRS)
Shuler, Robert L.
1999-01-01
The design and experimental verification of a switched RC multi-pole filter is presented. This highly compact circuit easily obtains sub-Hz, adjustable response utilizing reasonable sized on-chip components, and multiplexing the main resistor and op amp among filter stages. Design considerations for anti-aliasing, noise avoidance, and dynamic op amp compensation are presented.
Soft X-ray measurements in magnetic fusion plasma physics
NASA Astrophysics Data System (ADS)
Botrugno, A.; Gabellieri, L.; Mazon, D.; Pacella, D.; Romano, A.
2010-11-01
Soft X-ray diagnostic systems and their successful application in the field of magnetic fusion plasma physics are discussed. Radiation with wavelength in the region of Soft X-Ray (1-30 keV) is largely produced by high temperature plasmas, carrying important information on many processes during a plasma discharge. Soft X-ray diagnostics are largely used in various fusion devices all over the world. These diagnostic systems are able to obtain information on electron temperature, electron density, impurity transport, Magneto Hydro Dynamic instabilities. We will discuss the SXR diagnostic installed on FTU in Frascati (Italy) and on Tore Supra in Cadarache (France), with special emphasis on diagnostic performances. Moreover, we will discuss the two different inversion methods for tomographic reconstruction used in Frascati and in Cadarache, the first one is relied on a guessed topology of iso-emissivity surfaces, the second one on regularization techniques, like minimum Fisher or maximum entropy. Finally, a new and very fast 2D imaging system with energy discrimination and high time resolution will be summarized as an alternative approach of SXR detection system.