Linear pinch driven by a moving compact torus

International Nuclear Information System (INIS)

Hartman, C.W.; Hammer, J.H.; Eddleman, J.L.

1984-01-01

In principle, a Z-pinch of sufficiently large aspect ratio can provide arbitrarily high magnetic field intensity for the confinement of plasma. In practice, however, achievable field intensities and timescales are limited by parasitic inductances, pulse driver power, current, voltage, and voltage standoff of nearby insulating surfaces or surrounding gas. Further, instabilities may dominate to prevent high fields (kink mode) or enhance them (sausage mode) but in a nonuniform and uncontrollable way. In this paper we discuss an approach to producing a high-field-intensity pinch using a moving compact torus. The moving torus can serve as a very high power driver and may be used to compress a pre-established pinch field, switch on an accelerating pinch field, or may itself be reconfigured to form an intense pinch. In any case, the high energy, high energy density, and high velocity possible with an accelerated compact torus can provide extremely high power to overcome, by a number of orders of magnitude, the limitations to pinch formation described earlier. In this paper we will consider in detail pinches formed by reconfiguration of the compact torus

Rotational instability in a linear theta pinch

International Nuclear Information System (INIS)

Ekdahl, C.; Bartsch, R.R.; Commisso, R.J.; Gribble, R.F.; McKenna, K.F.; Miller, G.; Siemon, R.E.

1980-01-01

The m=1 ''wobble'' instability of the plasma column in a 5-m linear theta pinch has been studied using an axial array of orthogonally viewing position detectors to resolve the wavelength and frequency of the column motion. The experimental results are compared with recent theoretical predictions that include finite Larmor orbit effects. The frequency and wavelength characteristics at saturation agree with the predicted dispersion relation for a plasma rotating faster than the diamagnetic drift speed. Measurements of the magnetic fields at the ends of the pinch establish the existence of currents flowing in such a way that they short out the radial electric fields in the plasma column. The magnitude of rotation, the observed delay in the onset of m=1 motion, and the magnitude of end-shorting currents can all be understood in terms of the torsional Alfven waves that communicate to the central plasma column the information that the ends have been shorted. The same waves are responsible for the torque which rotates the plasma and leads to the observed m=1 instability. Observations of the plasma in the presence of solid end plugs indicate a stabilization of high-m number modes and a reduction of the m=1 amplitude

Progress in Z-pinch research driven by the mega-ampere device SPEED2

International Nuclear Information System (INIS)

Pavez, Cristian; Soto, Leopoldo; Moreno, Jose; Sylvester, Gustavo; Tarifeno, Ariel

2008-01-01

Several pinch configurations have being studied at the Chilean Nuclear Energy Commission using the SPEED2 generator: plasma focus, gas embedded z-pinch and wire arrays. SPEED2 is a generator based on Marx technology (4.1 μF equivalent Marx generator capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns rise time, dI/dt∼10 13 A/s). Currently the device is being operated at 70kJ stored energy producing a peak current of 2.4 MA in short circuit. In this work results related to studies in gas embedded z-pinch in deuterium and studies in wire arrays are presented.

Progress in Z-pinch research driven by the mega-ampere device SPEED2

International Nuclear Information System (INIS)

Pavez, Cristian; Soto, Leopoldo; Moreno, Jose; Tarifeno, Ariel; Sylvester, Gustavo

2008-01-01

Several pinch configurations have being studied at the Chilean Nuclear Energy Commission using the SPEED2 generator: plasma focus, gas embedded z-pinch and wire arrays. SPEED2 is a generator based on Marx technology (4.1 μF equivalent Marx generator capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns rise time, dI/dt∼10 13 A/s). Currently the device is being operated at 70kJ stored energy producing a peak current of 2.4 MA in short circuit. In this work results related to studies in gas embedded z-pinch in deuterium and studies in wire arrays are presented

Recent studies of Reversed-Field Pinch reactors

International Nuclear Information System (INIS)

Hagenson, R.L.; Krakowski, R.A.

1981-01-01

The reactor prognoses of a class of confinement scheme that relies primarily on self-fields induced by axial currents flowing within a plasma column are presented. The primary focus has been placed on the toroidal Reversed-Field Pinch (RFP). At the limit of very large current densities is the gas-embedded Dense Z-Pinch (DZP), a small-radius, linear device. Past conventional RFP reactor designs are reviewed. The extention of these conventional RFP reactors to DD advanced-fuel operation is described. The implications are summarized of operating higher-density, compact RFPs as reactors, wherein the current density rather than physical dimensions are scaled. Lastly, the application of very high current densities supported in a sub-millimeter linear current channel, as embodied in the DZP reactor, is reviewed

Resistive wall modes in the EXTRAP T2R reversed-field pinch

Science.gov (United States)

Brunsell, P. R.; Malmberg, J.-A.; Yadikin, D.; Cecconello, M.

2003-10-01

Resistive wall modes (RWM) in the reversed field pinch are studied and a detailed comparison of experimental growth rates and linear magnetohydrodynamic (MHD) theory is made. RWM growth rates are experimentally measured in the thin shell device EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43, 1 (2001)]. Linear MHD calculations of RWM growth rates are based on experimental equilibria. Experimental and linear MHD RWM growth rate dependency on the equilibrium profiles is investigated experimentally by varying the pinch parameter Θ=Bθ(a)/ in the range Θ=1.5-1.8. Quantitative agreement between experimental and linear MHD growth rates is seen. The dominating RWMs are the internal on-axis modes (having the same helicity as the central equilibrium field). At high Θ, external nonresonant modes are also observed. For internal modes experimental growth rates decrease with Θ while for external modes, growth rates increase with Θ. The effect of RWMs on the reversed-field pinch plasma performance is discussed.

Kinetic description of linear theta-pinch equilibria

International Nuclear Information System (INIS)

Batchelor, D.B.; Davidson, R.C.

1975-01-01

Equilibrium properties of linear theta-pinch plasmas are studied within the framework of the steady-state (o/x=0) Vlasov-Maxwell equations. The analysis is carried out for an infinitely long plasma column aligned parallel to an externally applied axial magnetic field Bsub(z)sup(ext)esub(z). Equilibrium properties are calculated for the class of rigid-rotor Vlasov equilibria, in which the th component distribution function (Hsub(perpendicular), Psub(theta), upsilonsub(z) depends on perpendicular energy H and canonical angular momentum Psub(theta), exclusively through the linear combination Hsub(perpendicular)-ωsub(j)Psub(theta), where ω;=const.=angular velocity of mean rotation. General equilibrium relations that pertain to the entire class of rigid-rotor Vlasov equilibria are discussed; and specific examples of sharp- and diffuse-boundary equilibrium configurations are considered. Rigid-rotor density and magnetic field profiles are compared with experimentally observed profiles. A general prescription is given for determining the functional dependence of the equilibrium distribution function on Hsub(perpendicular)-ωsub(j)Psub(theta) in circumstances, where the density profile or magnetic field profile is specified. (author)

Engineering and physics considerations for a linear theta-pinch hybrid reactor (LTPHR)

International Nuclear Information System (INIS)

Krakowski, R.A.; Miller, R.L.; Hagenson, R.L.

1976-01-01

A fusion-fission hybrid reactor based on pulsed, high-β, linear theta-pinch magnetic confinement is considered. A preliminary design which incorporates key physics, engineering and economic considerations is presented. An extensive presentation of the system energy balance is made, and this energy balance is evaluated parametrically. The feasibility of end-loss reduction is addressed

Data-acquisition system of the reversed field pinch device REPUTE-1

International Nuclear Information System (INIS)

Tsuzuki, N.; Aoki, H.; Shinohara, H.; Toyama, H.; Morikawa, J.

1988-01-01

The new, compact data-acquisition system of the reversed field pinch device, REPUTE-1, is reported. Its distinctive feature is high flexibility and easy handling. The interface between the computer and measurement devices is CAMAC. The computer and the CAMAC devices are connected to a CAMAC byte serial highway that transmits setup parameters and acquisition data. The computer carries out setup of CAMAC devices and data acquisition automatically by use of CAMAC parameters and the acquisition data base. The maintenance tools for the data base are also provided. The computer system, which consists of a ''TOSBAC DS-600,'' has been in operation for REPUTE-1 since 1985

Dense transient pinches and pulsed power technology: research and applications using medium and small devices

International Nuclear Information System (INIS)

Soto, Leopoldo; Pavez, Cristian; Moreno, Jose; Cardenas, Miguel; Zambra, Marcelo; Tarifeno, Ariel; Huerta, Luis; Tenreiro, Claudio; Giordano, Jose Luis; Lagos, Miguel; Escobar, Rodrigo; Ramos, Jorge; Altamirano, Luis; Retamal, Cesar; Silva, Patricio

2008-01-01

The Plasma Physics and Plasma Technology Group of the Chilean Nuclear Energy Commission (CCHEN) has, since about ten years ago, used plasma production devices to study dense hot plasmas, particularly Z-pinches and plasma foci (PFs). In the case of Z-pinches, the studies include studies on the dynamics and stability of gas-embedded Z-pinches at currents of thermonuclear interest, and preliminary studies on wire arrays. For PF research, the aim of the work has been to characterize the physics of these plasmas and also to carry out the design and construction of smaller devices-in terms of both input energy and size-capable of providing dense hot plasmas. In addition, taking advantage of the experience in pulsed power technology obtained from experimental researches in dense transient plasmas, an exploratory line of pulsed power applications is being developed. In this paper, a brief review listing the most important results achieved by the Plasma Physics and Plasma Technology Group of the CCHEN is presented, including the scaling studies, PF miniaturization and diagnostics and research on Z-pinches at currents of thermonuclear interest. Then, exploratory applications of pulsed power are presented, including nanoflashes of radiation for radiography and substances detection, high pulsed magnetic fields generation and rock fragmentation.

A Pressure Controlled Pinched Flow Fractionation Device for Continuous Particle Separation

DEFF Research Database (Denmark)

Christiansen, Thomas Lehrmann; Trosborg, Jacqueline; Tanzi, Simone

2012-01-01

In this work the problem of separating small particles of di↵erent sizes is solved by developing a simple microfluidic device using pinched flow fractionation (PFF), a technique originally presented by Yamada et al. in 2004 [1]. The present work takes the concept of PFF to the next level by makin...... Polymers GmbH) using a micro machined silicon master. The functionality of the device was confirmed using polymer beads, and by adjusting the pressure accordingly a complete separation of 2 μm and 4.5 μm beads was demonstrated....

A comparison between linear and toroidal Extrap systems

International Nuclear Information System (INIS)

Lehnert, B.

1988-09-01

The Extrap scheme consists of a Z-pinch immersed in an octupole field generated by currents in a set of external conductors. A comparison between linear and toroidal Extrap geometry is made in this paper. As compared to toroidal systems, linear geometry has the advantages of relative simplicity and of a current drive by means of electrodes. Linear devices are convenient for basic studies of Extrap, at moderately high pinch currents and plasma temperatures. Within the parameter ranges of experiments at high pinch currents and plasma temperatures, linear systems have on the other hand some substantial disadvantages, on account of the plasma interaction with the end regions. This results in a limitation of the energy confinement time, and leads in the case of an ohmically heated plasma to excessively high plasma densities and small pinch radii which also complicate the introduction of the external conductors. (author)

A reversed-field theta-pinch plasma machine

International Nuclear Information System (INIS)

Yasojima, Yoshiyuki; Ueda, Yoshihiro; Sasao, Hiroyuki; Ueno, Noboru; Tanaka, Toshihide

1984-01-01

Mitsubishi Electric has constructed a reversed-field theta-pinch machine at its Central Research Laboratory and initiated a series of plasma diagnostics and control studies for development of nuclear-fusion technology. Although the device has a linear configuration, a stable high-temperature, high-density toroidal plasma can be generated. The article describes the overall structure, vacuum system, power-supply system, and diagnostics and control system of the plasma machine. (author)

Microlocal analysis of a seismic linearized inverse problem

NARCIS (Netherlands)

Stolk, C.C.

1999-01-01

The seismic inverse problem is to determine the wavespeed c x in the interior of a medium from measurements at the boundary In this paper we analyze the linearized inverse problem in general acoustic media The problem is to nd a left inverse of the linearized forward map F or equivalently to nd the

Effect of liner non-uniformity on plasma instabilities in an inverse Z-pinch magnetized target fusion system: liner-on-plasma simulations and comparison with linear stability analysis

International Nuclear Information System (INIS)

Subhash, P V; Madhavan, S; Chaturvedi, S

2008-01-01

Two-dimensional (2D) magneto-hydrodynamic (MHD) liner-on-plasma computations have been performed to study the growth of instabilities in a magnetized target fusion system involving the cylindrical compression of an inverse Z-pinch target plasma by a metallic liner. The growth of modes in the plasma can be divided into two phases. During the first phase, the plasma continues to be Kadomtsev stable. The dominant mode in the liner instability is imposed upon the plasma in the form of a growing perturbation. This mode further transfers part of its energy to its harmonics. During the second phase, however, non-uniform implosion of the liner leads to axial variations in plasma quantities near the liner-plasma interface, such that certain regions of the plasma locally violate the Kadomtsev criteria. Further growth ofthe plasma modes is then due to plasma instability. The above numerical study has been complemented with a linear stability analysis for the plasma, the boundary conditions for this analysis being obtained from the liner-on-plasma simulation. The stability of axisymmetric modes in the first phase is found to satisfy the Kadomtsev condition Q 0 1 modes, using equilibrium profiles from the 2D MHD study, shows that their growth rates can exceed those for m=0 by as much as an order of magnitude

Study of flow and loss processes at the ends of a linear theta pinch. Progress report, June 1, 1978--May 31, 1979

International Nuclear Information System (INIS)

York, T.M.; Klevans, E.H.

1979-02-01

Experimental and analytical studies of end loss from a linear theta pinch have been carried out. Analysis of reduced data on loss from a 25 cm long theta pinch has indicated: rotation at the end of pinch collapse, which appears to persist; ejection of the plasma in two modes, the first of which includes reversed, trapped fields; unique patterns of radial and axial variation of electron density in the end loss flow; substantial inaccuracies in plasma properties indicated by spectroscopy as compared to Thomson scattering. Studies of loss in a 50 cm long pinch with 50 eV, 2 x 10 16 cm -3 plasma are underway

Plasma dynamics in a staged pinch device

International Nuclear Information System (INIS)

Khattak, N.A.D.; Ahmed, Z.; Mirza, A.M.; Murtaza, G.

1998-01-01

Plasma parameters in fiber initiated fast and dense theta-pinch plasma driven by an annular finite-thickness gas-puff Z-pinch are studied. The imploding gas-puff Z-pinch plasma traps an axial magnetic field B/sub z/, compressing it to large values (of the order of several megagauss) in an extremely short time. The rapidly changing magnetic flux of this field induces an azimuthal current on the surface of the coaxially placed fiber, with a rise time an order of magnitude shorter than the applied Z-pinch current. The shorter rise time of the current stabilizes the pinch against sausage mode of MHD instabilities. Our numerical results demonstrate that for a relatively thick gas-puff layer, the compression occurs before the current saturates. At the peak compression the fuel densities of the order of 10/sup 25/ cm/sup -3/ and temperature above 10 keV can be achieved on a time scale of 0.1 nanoseconds, yielding the Lawson Criterion parameters n tau is approximately equal to 10/sup 14/ sec cm/sup -3/ for D-T fuel. The snow-plow effect incorporated in our model exercise a strong influence on the onset and growth rate of sausage and Rayleigh-Taylor (R-T) modes of instabilities. Imposing a rotational velocity on the outer thin gas-puff plasma can control the Rayleigh-Taylor instability. Numerical results indicate that the choice of the spin velocity is critical. Large values of the spin velocity, though provide stabilization against the R-T instability at the final stage of compression, however, it adversely reduce the plasma parameters so essential to achieve controlled fusion. Our analysis, therefore, suggests that a judicious choice of the spin velocity is necessary to obtain the desired temperature and density, especially when we seed D-T fiber plasma with a small fraction of high-Z Kr impurity to initiate the radiative collapse. (author)

Accurate approximation of the dispersion differential equation of ideal magnetohydrodynamics: The diffuse linear pinch

International Nuclear Information System (INIS)

Barnes, D.C.; Cayton, T.E.

1980-01-01

The ideal magnetohydrodynamic stability of the diffuse linear pinch is studied in the special case when the poloidal magnetic field component is small compared with the axial field component. A two-term approximation for growth rates is derived by straightforward asymptotic expansion in terms of a small parameter that is proportional to (B/sub theta//rB/sub z/). Evaluation of the second term in the expansion requires only a trivial amount of additional computation after the leading-order eigenvalue and eigenfunction are determined. For small, but finite, values of the expansion parameter the second term is found to be non-negligible compared with the leading term. The approximate solution is compared with exact solutions and the range of validity of the approximation is investigated. Implications of these results to a wide class of problems involving weakly unstable near theta-pinch configurations are discussed

Improved zero dimensional model of a reversed field pinch fusion device

International Nuclear Information System (INIS)

Haynes, K.E.

1987-01-01

A zero-dimensional model has been developed which accurately predicts conditions observed during several runs of the ZT-40M reversed field pinch fusion device at Los Alamos National Laboratory. The model is based on a physical model developed by E.H. Klevans at Penn State University. Improvements made to this model included the use of coronal non-equilibrium equations for predicting impurity effects, the inclusion of an exponentially decaying ion heating term, and the relaxation of the assumption that ion and electron densities are equal in the device. The model has been used to simulate ZT-40M in both flat-top and slowly ramped current modes. Using experimentally measured density and current evolutions, the model accurately predicts observed tau/sub E/, β/sub Θ/, T/sub e/, T/sub i/, Z/sub eff/, and radiated power. The continuing goal of this work is to predict conditions in the ZT-H device, which is under construction. 28 refs., 18 figs

Plasma and current structures in dynamical pinches

International Nuclear Information System (INIS)

Butov, I.Ya.; Matveev, Yu.V.

1981-01-01

Dynamics of plasma layers and current structure in aZ-pinch device has been experimentally investigated. It is found that shaping of a main current envelope is ended with its explosion-like expansion, the pinch decaying after compression to separated current filaments. It is also shown that filling of a region outside the pinch with plasma and currents alternating in directions occurs owing to interaction of current loops (inductions) formed in a magnetic piston during its compression with reflected shock wave. Current circulating in the loops sometimes exceeds 1.5-2 times the current of discharge circuit. The phenomena noted appear during development of superheat instability and can be realized, for example, in theta-pinches, plasma focuses, tokamaks. The experiments were carried out at the Dynamic Zeta-pinch device at an energy reserse of up to 15 kJ (V 0 =24 kV) in a capacitor bank. Half-period of the discharge current is 9 μs; Isub(max)=3.5x10sup(5) A. Back current guide surrounding a china chamber of 28 cm diameter and 50 cm length is made in the form of a hollow cylinder. Initial chamber vacuum is 10 -6 torr [ru

Preliminary results from the flow-through z-pinch experiments: ZaP

International Nuclear Information System (INIS)

Shumlak, U.; Nelson, B.A.; Goilingo, R.P.; Tang, D.; Crawford, E.; Hartog, D.J.D.; Holly, D.J.

1999-01-01

The stabilizing effect of an axial flow on the m = 1 kink instability in z-pinches has been studied numerically by reducing the linearized ideal MHD equations to a one-dimensional eigenvalue equation for the radial displacement. A diffuse z-pinch equilibrium is chosen that is made marginally stable to the m = 0 sausage mode by tailoring the pressure profile. The principal result reveals that a sheared axial flow does stabilize the kink mode when the shear exceeds a threshold value which is inversely proportional to the wavelength of the mode. This threshold value can be satisfied with a peak flow which is less than the Alfven speed for certain wavelengths. Additionally, the m = 0 sausage mode is driven from marginal stability into the stable regime which suggests that the equilibrium pressure profile control can be relaxed. The flow stabilization agrees with experimental observations. The details of the theoretical development will be presented

Study of flow and loss processes at the ends of a linear theta pinch. Progress report, June 1, 1979-September 30, 1980

International Nuclear Information System (INIS)

York, T.M.; Klevans, E.H.

1980-05-01

Experimental and analytical studies of particle and energy loss at the ends of a linear theta pinch have been carried out. A study of transients occurring in the formation of reversed trapped fields within the coil, and of transients in the end region of a 25 cm long device was completed. A 1-D code has proven to be highly accurate in describing loss events and defining transport mechanisms in different experiments and is described here. A study of loss along field lines in a 50 cm long device has generated new information on loss velocity, axial and radial temperature gradients, and has established an initial effort in understanding thermal loss to the walls. Rotation and parallel trapped fields have been added to the existing 0-D code. A new technique crowbar switch and magnetic field prediction code have been developed. Direct measurment of electron velocity with Thomson scattering was accomplished experimentally. A Nd-glass laser system, frequency doubled, is being developed for low density diagnostics. Theoretical results that accurately predict confinement in FRX devices are described

Parametric dependences of momentum pinch and Prandtl number in JET

DEFF Research Database (Denmark)

Tala, T.; Salmi, A.; Angioni, C.

2011-01-01

Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density...... gradient length, with an experimental scaling for the pinch number being -Rvpinch/χφ = 1.2R/Ln +1.4. There is no dependence of the pinch number on collisionality, whereas the pinch seems to depend weakly on q-profile, the pinch number decreasing with increasing q. The Prandtl number was not found to depend...... either on R/Ln, collisionality or on q. The gyro-kinetic simulations show qualitatively similar dependence of the pinch number on R/Ln, but the dependence is weaker in the simulations. Gyro-kinetic simulations do not find any clear parametric dependence in the Prandtl number, in agreement...

Experiments on screw-pinch plasmas with elongated cross section

International Nuclear Information System (INIS)

Lassing, H.W.

1989-01-01

In this thesis experiments are described carried out with SPICA II, a toroidal screw-pinch plasma device. this device is the last one in a series of plasma machines of the toroidal screw-pinch differing from its predecessor in its race-track shaped section. In devices of the type toroidal screw-pinch stable confinement is possible of plasmas with larger β values than in a tokamak discharge. In a pinch the plasma is screwed up, during the formation, in such a way that in a relatively small volume a plasma is formated with a high pressure. During the screwing up the plasma is heated by shock heating as well as adiabatic compression. With the modified snowplow model the density and temperature after the formation can be calculated, starting from the initial conditions. When all ions arrive into the plasma column, the density in the column is determined by the volume compression. First purpose of the experiments was to find a stable discharge. Subsequently discharges have been made with a high as possible β in order to investigate at which maximum β it is possible to confine screw-pinch plasmas stably. When these had been found, the nature and importance could be investigated of the processes following which the screw-pinch plasma looses its energy. (author), 75 res.; 95 figs.; 8 tabs

Plasma sheath dynamics in pinch discharge

International Nuclear Information System (INIS)

Mansour, A.A.Abd-Fattah

1995-01-01

The main interest of the study was to understand the dynamic and to determine the plasma parameters in the 3.5 meter θ-pinch discharge. The 3.5 meter thetatron plasma device has been reconstructed and developed which consist of four capacitor banks: a) Main pinch capacitor bank, (θ-pinch bank) consists of 40 capacitors connected in parallel each of 1.5 μ F., with maximum energy equal to 48 k Joule. b) Preionization capacitor bank (z-pinch) consists of capacitors connected in series each of 1.5μ F., with maximum energy to 0.94 k Joule. c) Bias field bank consists of 4 capacitors connected in parallel each of 38μ F., with maximum energy equal to 4.46 k Joule. d) Screw pinch capacitor bank consists of 5 capacitors connected in parallel each of 1.5μ F., with maximum energy equal to 6 k Joule

Deuterium Liner and Multiparameter Investigation of the Inverse Z-Pinch Formation Process

CERN Document Server

Bystritskii, Vyach M; Grebenyuk, V M; Parzhitsky, S S; Penkov, F M; Stolupin, V A; Boznyak, J; Gula, E; Dudkin, G N; Nechaev, B A; Padalko, V M; Mesyats, G A; Ratakhin, N A; Sorokin, S A

2001-01-01

A description of the methods and results of the measurements of the ion energy distribution of the deuterium liner accelerated in the inverse Z-pinch configuration are presented - the liner plasma is radially accelerated from the outward small radius. The knowledge of the experiment deuteron energy distribution is crucially important for correct interpretation of the results on the study of the dd-reaction at infralow collision energies using the liner plasma. Experiments were fulfilled in the HCEI (Tomsk, Russia) at a nanosecond pulsed high current generator (I=950 kA, pulse duration \\tau=80 ns). The hollow deuterium liner of 20 mm length was accelerated from the initial radius of \\sim 15 mm to 45 mm. Measurement of the liner characteristics was produced by means of the light detectors (detection of H_\\alpha and H_\\beta deuterium lines) and magnetic B-dot probes, placed on the various radii of the expanding liner. Besides, the measurement of the neutron radiation intensity due to reaction d+d\\to^{3}He+n was ...

Experimental studies of an Extrap Z-Pinch

International Nuclear Information System (INIS)

Drake, J.R.

1983-01-01

Experimental studies of the formation, equilibrium and stability of a linear Extrap Z-pinch are reported on. The Z-pinch discharge is generated between electrodes along the Z-axis of a linear octupole field produced by currents in four Z-directed rods. The combined discharge current and rod currents produce a magnetic field having a separatrix with four null X-points which define the corners of a square shaped region where the high beta plasma discharge is contained. Bounding the pinch discharge with a separatrix produces equilibria which are stable against global kink modes for the 50-μsec duration of the discharge which corresponds to about 100 Alfven transit times. The equilibria, with line densities of about 3 x 10 18 m - 1 , are consistent in magnitude and scaling with the Bennet relation. (Author)

Metal Wire-array Load for Z-pinch Used as X-ray Source

Institute of Scientific and Technical Information of China (English)

1999-01-01

<正> The inertial confinement fusion （ICF） has evident minatory applications becasuse ICF ignites the fusion fuel with high energy media. As a method of ICF, Z-pinch has obtained evidently increased X-ray power PX-ray and energy EX-ray. The scientists have noticed this promising achievement. The Z-accelerator which is an operating Z-pinch device in Sandia national laboratory （SNL） in USA achieved 290 TW Px-ray in 1997 and the energy and defense departments of USA will finance SNL for a larger Z-pinch device. The early Z-pinch aimed to obtain high tempera

Cylindrical Field Effect Transistor: A Full Volume Inversion Device

KAUST Repository

Fahad, Hossain M.

2010-12-01

The increasing demand for high performance as well as low standby power devices has been the main reason for the aggressive scaling of conventional CMOS transistors. Current devices are at the 32nm technology node. However, due to physical limitations as well as increase in short-channel effects, leakage, power dissipation, this scaling trend cannot continue and will eventually hit a barrier. In order to overcome this, alternate device topologies have to be considered altogether. Extensive research on ultra thin body double gate FETs and gate all around nanowire FETs has shown a lot of promise. Under strong inversion, these devices have demonstrated increased performance over their bulk counterparts. This is mainly attributed to full carrier inversion in the body. However, these devices are still limited by lithographic and processing challenges making them unsuitable for commercial production. This thesis explores a unique device structure called the CFET (Cylindrical Field Effect Transistors) which also like the above, relies on complete inversion of carriers in the body/bulk. Using dual gates; an outer and an inner gate, full-volume inversion is possible with benefits such as enhanced drive currents, high Ion/Ioff ratios and reduced short channel effects.

On the problem of linear calibration for a reading system of measuring devices

International Nuclear Information System (INIS)

Shigaev, V.N.

1978-01-01

The problem of gauging the frame of reference of a measuring device has been giVen a general approach which consists in finding an approximated inverse transformation on the basis of a partial diagram of a direct transformation which is defined on a given set, D, within the limits of the device measuring range. The following linear models of frame of reference are discussed: a general oblique system; a rectangular system with axes having different scales; a rectangular system with similar scale axes. Linear distortion for two rectangular models has been assessed. It is pointed out that the best approximation to the reduction operation should be found over the D set

Inverse Modelling Problems in Linear Algebra Undergraduate Courses

Science.gov (United States)

Martinez-Luaces, Victor E.

2013-01-01

This paper will offer an analysis from a theoretical point of view of mathematical modelling, applications and inverse problems of both causation and specification types. Inverse modelling problems give the opportunity to establish connections between theory and practice and to show this fact, a simple linear algebra example in two different…

Pinching evidences in a miniature plasma focus with fast pseudospark switch

International Nuclear Information System (INIS)

Hassan, S M; Zhang, T; Patran, A; Rawat, R S; Springham, S V; Tan, T L; Wong, D; Wang, W; Lee, S; Gribkov, V A; Mohanty, S R; Lee, P

2006-01-01

We report the observations of pinching in a miniature plasma focus (PF) (58-160 J) operated in repetitive mode using fast pseudospark switch (PSS). The size of the device, which includes the capacitor bank, PSS and the focus chamber, is of the order of 22 cm x 22 cm x 38 cm. Several diagnostic tools, the gated imager, streak camera, current and voltage probe, are employed simultaneously to confirm the occurrence of pinching in this fast miniature PF device. The device is optimized for operation in neon and hydrogen as the working gas. The best focus formation was obtained at pressures between 0.5 to 8.0 mbar for neon and between 7.0 to 15.0 mbar for hydrogen. When the system was operated at 100 J with hydrogen as the filling gas, the typical dip in the current derivative signal and the typical peak in the voltage signal associated with pinch compression, are observed to be most intense indicating efficient pinching in the miniature PF device

2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches

International Nuclear Information System (INIS)

Hammer, J.H.; Eddleman, J.L.; Springer, P.T.

1995-01-01

Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile

Theory of neutron spectra from d-d-reactions in the linear z-pinch and the plasma focus

International Nuclear Information System (INIS)

Deutsch, R.; Kaeppeler, H.J.

1982-05-01

Because of a finite gyroradius effect, the equilibrium probability density function of the ions in the azimuthal magnetic field of a linear z-pinch becomes anisotropic. This density function was derived by solving the Vlasov equation and used to determine the neutron spectra produced in the deuterium plasma of a z-pinch. The neutron spectra were calculated for two models, differing in the energy distribution of the fast ions. A background plasma with 'slow' ions was also considered. The interactions of the fast ions with the slow ions and 'beam-beam' interactions between fast ions were considered. Typical spectra for arbitrary directions to the cylindrical axis are given. The anisotropy factors were calculated. Considering the influence of the azimuthal magnetic field on the equilibrium density function of the deuterons, the well known particularities of the neutron spectra are obtained without any of the contradictions typical of the traditional models. (orig.)

Linear System of Equations, Matrix Inversion, and Linear Programming Using MS Excel

Science.gov (United States)

El-Gebeily, M.; Yushau, B.

2008-01-01

In this note, we demonstrate with illustrations two different ways that MS Excel can be used to solve Linear Systems of Equation, Linear Programming Problems, and Matrix Inversion Problems. The advantage of using MS Excel is its availability and transparency (the user is responsible for most of the details of how a problem is solved). Further, we…

Inverse problems in linear transport theory

International Nuclear Information System (INIS)

Dressler, K.

1988-01-01

Inverse problems for a class of linear kinetic equations are investigated. The aim is to identify the scattering kernel of a transport equation (corresponding to the structure of a background medium) by observing the 'albedo' part of the solution operator for the corresponding direct initial boundary value problem. This means to get information on some integral operator in an integrodifferential equation through on overdetermined boundary value problem. We first derive a constructive method for solving direct halfspace problems and prove a new factorization theorem for the solutions. Using this result we investigate stationary inverse problems with respect to well posedness (e.g. reduce them to classical ill-posed problems, such as integral equations of first kind). In the time-dependent case we show that a quite general inverse problem is well posed and solve it constructively. (orig.)

Study of energy transfer in table-top X-pinch driven by a water line

International Nuclear Information System (INIS)

Beg, F N; Zhang, T; Fedin, D; Beagen, B; Chua, E; Lee, J Y; Rawat, R S; Lee, P

2007-01-01

The current passing through X-pinches and the energy transferring from the pulse forming line to the load are modelled using a simple LCR circuit. A comparison of the electrical properties of two table-top X-pinch devices is made. It was found that up to 25% of the stored energy is transferred from the water transmission line to the load in the University of California,San Diego (UCSD) table-top X-pinch before x-ray emission starts. The highest energy transmitted (75%) is found after the current peak. In comparison, only 3% of the energy is transferred to the load in the National Institute of Education (NIE) X-pinch device just after the maximum current peak. The highest energy (25%) transmitted to the plasma occurs long after the current peak. The plasma in both devices is visually and qualitatively similar. However, the UCSD device emits intense x-rays with no x-rays observed in the NIE device. This observation is consistent with the electrical circuit analysis

Linearized inversion frameworks toward high-resolution seismic imaging

KAUST Repository

Aldawood, Ali

2016-09-01

Seismic exploration utilizes controlled sources, which emit seismic waves that propagate through the earth subsurface and get reflected off subsurface interfaces and scatterers. The reflected and scattered waves are recorded by recording stations installed along the earth surface or down boreholes. Seismic imaging is a powerful tool to map these reflected and scattered energy back to their subsurface scattering or reflection points. Seismic imaging is conventionally based on the single-scattering assumption, where only energy that bounces once off a subsurface scatterer and recorded by a receiver is projected back to its subsurface position. The internally multiply scattered seismic energy is considered as unwanted noise and is usually suppressed or removed from the recorded data. Conventional seismic imaging techniques yield subsurface images that suffer from low spatial resolution, migration artifacts, and acquisition fingerprint due to the limited acquisition aperture, number of sources and receivers, and bandwidth of the source wavelet. Hydrocarbon traps are becoming more challenging and considerable reserves are trapped in stratigraphic and pinch-out traps, which require highly resolved seismic images to delineate them. This thesis focuses on developing and implementing new advanced cost-effective seismic imaging techniques aiming at enhancing the resolution of the migrated images by exploiting the sparseness of the subsurface reflectivity distribution and utilizing the multiples that are usually neglected when imaging seismic data. I first formulate the seismic imaging problem as a Basis pursuit denoise problem, which I solve using an L1-minimization algorithm to obtain the sparsest migrated image corresponding to the recorded data. Imaging multiples may illuminate subsurface zones, which are not easily illuminated by conventional seismic imaging using primary reflections only. I then develop an L2-norm (i.e. least-squares) inversion technique to image

A Reactor Development Scenario for the FUZE Shear-flow Stabilized Z-pinch

Science.gov (United States)

McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Golingo, R. P.; Weber, T. R.

2016-10-01

We present a conceptual design, scaling calculations, and a development path for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device have demonstrated stable operation for 40 us at 150 kA total discharge current (with 100 kA in the pinch) for pinches that are 1cm in diameter and 100 cm long. Scaling calculations show that achieving stabilization for a pulse of 100 usec, for discharge current 1.5 MA, in a shortened pinch 50 cm, results in a pinch diameter of 200 um and a reactor plant Q 5 for reasonable assumptions of the various system efficiencies. We propose several key intermediate performance levels in order to justify further development. These include achieving operation at pinch currents of 300 kA, where Te and Ti are calculated to exceed 1 keV, 700 kA where fusion power exceeds pinch input power, and 1 MA where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPAe ALPHA Program and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-697801.

A Reactor Development Scenario for the FuZE Sheared-Flow Stabilized Z-pinch

Science.gov (United States)

McLean, Harry S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.

2017-10-01

We present a conceptual design, scaling calculations, and development path for a pulsed fusion reactor based on a flow-stabilized Z-pinch. Experiments performed on the ZaP and ZaP-HD devices have largely demonstrated the basic physics of sheared-flow stabilization at pinch currents up to 100 kA. Initial experiments on the FuZE device, a high-power upgrade of ZaP, have achieved 20 usec of stability at pinch current 100-200 kA and pinch diameter few mm for a pinch length of 50 cm. Scaling calculations based on a quasi-steady-state power balance show that extending stable duration to 100 usec at a pinch current of 1.5 MA and pinch length of 50 cm, results in a reactor plant Q 5. Future performance milestones are proposed for pinch currents of: 300 kA, where Te and Ti are calculated to exceed 1-2 keV; 700 kA, where DT fusion power would be expected to exceed pinch input power; and 1 MA, where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPA-E and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-734770.

Evidence of flow stabilization in the ZaP Z pinch experiment

International Nuclear Information System (INIS)

Shumlak, U.; Crawford, E.; Golingo, R.P.; Nelson, B.A.; Zyrmpas, A.; Den Hartog, D.J.; Holly, D.J.

2001-01-01

The stabilizing effect of an axial flow on the m = 1 kink instability in Z pinches has been studied numerically with a linearized ideal MHD model to reveal that a sheared axial flow stabilizes the kink mode when the shear exceeds a threshold. The sheared flow stabilizing effect is investigated with the flow-through Z pinch experiment, ZaP. An azimuthal array of surface mounted magnetic probes located at the midplane of the 50 cm long pinch plasma measures the fluctuation levels of the azimuthal modes m=1, 2, and 3. After pinch formation a quiescent period is found where the mode activity is reduced to a few percent of the average field. Optical images from a fast framing camera and a HeNe interferometer also indicate a stable pinch plasma during this time. Doppler shift measurements of a C-III line correspond to an axial flow velocity of 9.6x10 4 m/s internal to the pinch. During the time when the axial plasma flow is high, the plasma experiences a quiescent period which lasts approximately 800 exponential growth times predicted by linear theory for a static plasma. (author)

Proposal for the ZT-40 reversed-field Z-pinch experiment

International Nuclear Information System (INIS)

Baker, D.A.; Machalek, M.D.

1977-08-01

A next-generation, toroidal, reversed-field Z-pinch experiment to be constructed at LASL is proposed. On the basis of encouraging ZT-I and ZT-S experimental results, a larger device with a 40-cm bore and a 114-cm major radius is proposed, to extend the confinement time by about an order of magnitude. The new experiment will explore the physics of programming reversed-field pinches in a size range unexplored by previous reversed-field pinch experiments. Model reversed-field pinch reactor calculations show that, if stability is assumed, small fusion reactors are possible if the pinch current density is high. A basic aim will be to delineate the plasma and current density ranges in which stable reversed-field pinches can be produced. Improved vacuum techniques will be used to overcome the radiation losses that probably kept electron temperatures low in the earlier, smaller experiments

Overview of the Fusion Z-Pinch Experiment FuZE

Science.gov (United States)

Weber, T. R.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; UW/LLNL Team

2016-10-01

Previously, the ZaP device, at the University of Washington, demonstrated sheared flow stabilized (SFS) Z-pinch plasmas. Instabilities that have historically plagued Z-pinch plasma confinement were mitigated using sheared flows generated from a coaxial plasma gun of the Marshall type. Based on these results, a new SFS Z-pinch experiment, the Fusion Z-pinch Experiment (FuZE), has been constructed. FuZE is designed to investigate the scaling of SFS Z-pinch plasmas towards fusion conditions. The experiment will be supported by high fidelity physics modeling using kinetic and fluid simulations. Initial plans are in place for a pulsed fusion reactor following the results of FuZE. Notably, the design relies on proven commercial technologies, including a modest discharge current (1.5 MA) and voltage (40 kV), and liquid metal electrodes. Supported by DoE FES, NNSA, and ARPA-E ALPHA.

Resistive Wall Mode Stability and Control in the Reversed Field Pinch

International Nuclear Information System (INIS)

Yadikin, Dmitriy

2006-03-01

Control of MHD instabilities using a conducting wall together with external magnetic fields is an important route to improved performance and reliability in fusion devices. Active control of MHD modes is of interest for both the Advanced Tokamak and the Reversed Field Pinch (RFP) configurations. A wide range of unstable, current driven MHD modes is present in the RFP. An ideally conducting wall facing the plasma can in principle provide stabilization to these modes. However, a real, resistive wall characterized by a wall field diffusion time, cannot stabilize the ideal MHD modes unless they rotate with Alfvenic velocity, which is usually not the case. With a resistive wall, the ideal modes are converted into resistive wall modes (RWM) with growth rates comparable to the inverse wall time. Resistive wall modes have been studied in the EXTRAP T2R thin shell RFP device. Growth rates have been measured and found in agreement with linear MHD stability calculations. An advanced system for active control has been developed and installed on the EXTRAP T2R device. The system includes an array of 128 active saddle coils, fully covering the torus surface. Experiments on EXTRAP T2R have for the first time demonstrated simultaneous active suppression of multiple independent RWMs. In experiments with a partial array, coupling of different modes due to the limited number of feedback coils has been observed, in agreement with theory. Different feedback strategies, such as the intelligent shell, the rotating shell, and mode control have been studied. Further, feedback operation with different types of magnetic field sensors, measuring either the radial or the toroidal field components have been compared

Linearized versus non-linear inverse methods for seismic localization of underground sources

DEFF Research Database (Denmark)

Oh, Geok Lian; Jacobsen, Finn

2013-01-01

The problem of localization of underground sources from seismic measurements detected by several geophones located on the ground surface is addressed. Two main approaches to the solution of the problem are considered: a beamforming approach that is derived from the linearized inversion problem, a...

Vacuum ultraviolet emission from argon, krypton, and xenon in a radial-viewed theta pinch

International Nuclear Information System (INIS)

Engleman, R. Jr.; Thomson, D.B.; Monaghan, D.A.

1976-03-01

Vacuum ultraviolet line emission from argon, krypton, and xenon (5 percent in deuterium) has been observed from a plasma (approximately 50 eV and N/sub e/ approximately 10 17 /cm 3 ) produced by the Scyllar linear theta-pinch device. More than 50 emission lines in the 30- to 500-A region have been measured for each gas mixture. Some lines have been identified as due to Ar VII through XI, Kr IX and X, and Xe IX, but many lines remain unassigned

X-Pinch And Its Applications In X-ray Radiograph

International Nuclear Information System (INIS)

Zou Xiaobing; Wang Xinxin; Liu Rui; Zhao Tong; Zeng Naigong; Zhao Yongchao; Du Yanqiang

2009-01-01

An X-pinch device and the related diagnostics of x-ray emission from X-pinch were briefly described. The time-resolved x-ray measurements with photoconducting diodes show that the x-ray pulse usually consists of two subnanosecond peaks with a time interval of about 0.5 ns. Being consistent with these two peaks of the x-ray pulse, two point x-ray sources of size ranging from 100 μm to 5 μm and depending on cut-off x-ray photon energy were usually observed on the pinhole pictures. The x-pinch was used as x-ray source for backlighting of the electrical explosion of single wire and the evolution of X-pinch, and for phase-contrast imaging of soft biological objects such as a small shrimp and a mosquito.

Experimental study of the initial plasma formation stage in a linear theta pinch of inverted field

International Nuclear Information System (INIS)

Casin, G.C.; Alvarez, Ricardo; Rojkind, R.H.; Rodrigo, A.B.

1986-01-01

The initial stage of the plasma formation was studied in a linear theta pinch. Experiments were made to determine the machine operating conditions for good shot-to-shot reproducibility. Spectroscopic measurements of electron density and of electron and ion temperature were made afterwards to characterize the plasma at different stages of its heating process. The results obtained indicate that shot-to-shot reproducibility is strongly influenced by the presence of impurities and by the plasma preionization technique used. Under proper operating conditions, excellent reproducibility was observed. The measured values of the plasma parameters are compatible with those determined for similar machines. (Author) [es

Cylindrical Field Effect Transistor: A Full Volume Inversion Device

KAUST Repository

Fahad, Hossain M.

2010-01-01

inversion in the body. However, these devices are still limited by lithographic and processing challenges making them unsuitable for commercial production. This thesis explores a unique device structure called the CFET (Cylindrical Field Effect Transistors

Pinched Nerve

Science.gov (United States)

... You are here Home » Disorders » All Disorders Pinched Nerve Information Page Pinched Nerve Information Page What research is being done? Within the NINDS research programs, pinched nerves are addressed primarily through studies associated with pain ...

Linear and nonlinear development of m=0 instability in a diffuse Bennett Z-pinch equilibrium with sheared axial flow

International Nuclear Information System (INIS)

Paraschiv, I.; Bauer, B. S.; Lindemuth, I. R.; Makhin, V.

2010-01-01

The effect of sheared axial flow on the Z-pinch sausage instability has been examined with two-dimensional magnetohydrodynamic simulations. Diffuse Bennett equilibria in the presence of axial flows with parabolic and linear radial profiles have been considered, and a detailed study of the linear and nonlinear development of small perturbations from these equilibria has been performed. The consequences of both single-wavelength and random-seed perturbations were calculated. It was found that sheared flows changed the internal m=0 mode development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. High spatial frequency modes were stabilized to small amplitudes and only long wavelengths continued to grow. Full stability was obtained for supersonic plasma flows.

Parametric dependences of momentum pinch and Prandtl number in JET

NARCIS (Netherlands)

Tala, T.; Salmi, A.; Angioni, C.; Casson, F. J.; Corrigan, G.; Ferreira, J.; Giroud, C.; Mantica, P.; Naulin, V.; Peeters, A.G.; Solomon, W. M.; Strintzi, D.; Tsalas, M.; Versloot, T. W.; de Vries, P. C.; Zastrow, K. D.

2011-01-01

Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density

Explosive instabilities of reaction-diffusion equations including pinch effects

International Nuclear Information System (INIS)

Wilhelmsson, H.

1992-01-01

Particular solutions of reaction-diffusion equations for temperature are obtained for explosively unstable situations. As a result of the interplay between inertial, diffusion, pinch and source processes certain 'bell-shaped' distributions may grow explosively in time with preserved shape of the spatial distribution. The effect of the pinch, which requires a density inhomogeneity, is found to diminish the effect of diffusion, or inversely to support the inertial and source processes in creating the explosion. The results may be described in terms of elliptic integrals or. more simply, by means of expansions in the spatial coordinate. An application is the temperature evolution of a burning fusion plasma. (au) (18 refs.)

A study of Z-pinch in capillary filled by boron vapours

Czech Academy of Sciences Publication Activity Database

Vrba, Pavel; Vrbová, M.; Bobrova, N. A.; Sasorov, P. V.

2009-01-01

Roč. 51, č. 2 (2009), s. 481-486 ISSN 1434-6079. [Symposium on Plasma Physics and Technology/23rd./. Praha, 16.06.2008-19.06.2008] R&D Projects: GA ČR GA102/07/0275; GA MŠk LA08024 Institutional research plan: CEZ:AV0Z20430508 Keywords : Z-pinches * plasma focus and other pinch devices * Plasma devices for generation of coherent radiation * Magnetohydrodynamics and fluid equation Subject RIV: BH - Optics, Masers, Lasers www.edpsciences.org/epjd nebo www.epj.org

Taming waveform inversion non-linearity through phase unwrapping of the model and objective functions

KAUST Repository

Alkhalifah, Tariq Ali

2012-09-25

Traveltime inversion focuses on the geometrical features of the waveform (traveltimes), which is generally smooth, and thus, tends to provide averaged (smoothed) information of the model. On other hand, general waveform inversion uses additional elements of the wavefield including amplitudes to extract higher resolution information, but this comes at the cost of introducing non-linearity to the inversion operator, complicating the convergence process. We use unwrapped phase-based objective functions in waveform inversion as a link between the two general types of inversions in a domain in which such contributions to the inversion process can be easily identified and controlled. The instantaneous traveltime is a measure of the average traveltime of the energy in a trace as a function of frequency. It unwraps the phase of wavefields yielding far less non-linearity in the objective function than that experienced with conventional wavefields, yet it still holds most of the critical wavefield information in its frequency dependency. However, it suffers from non-linearity introduced by the model (or reflectivity), as reflections from independent events in our model interact with each other. Unwrapping the phase of such a model can mitigate this non-linearity as well. Specifically, a simple modification to the inverted domain (or model), can reduce the effect of the model-induced non-linearity and, thus, make the inversion more convergent. Simple numerical examples demonstrate these assertions.

Taming waveform inversion non-linearity through phase unwrapping of the model and objective functions

KAUST Repository

Alkhalifah, Tariq Ali; Choi, Yun Seok

2012-01-01

Traveltime inversion focuses on the geometrical features of the waveform (traveltimes), which is generally smooth, and thus, tends to provide averaged (smoothed) information of the model. On other hand, general waveform inversion uses additional elements of the wavefield including amplitudes to extract higher resolution information, but this comes at the cost of introducing non-linearity to the inversion operator, complicating the convergence process. We use unwrapped phase-based objective functions in waveform inversion as a link between the two general types of inversions in a domain in which such contributions to the inversion process can be easily identified and controlled. The instantaneous traveltime is a measure of the average traveltime of the energy in a trace as a function of frequency. It unwraps the phase of wavefields yielding far less non-linearity in the objective function than that experienced with conventional wavefields, yet it still holds most of the critical wavefield information in its frequency dependency. However, it suffers from non-linearity introduced by the model (or reflectivity), as reflections from independent events in our model interact with each other. Unwrapping the phase of such a model can mitigate this non-linearity as well. Specifically, a simple modification to the inverted domain (or model), can reduce the effect of the model-induced non-linearity and, thus, make the inversion more convergent. Simple numerical examples demonstrate these assertions.

Dense sheet Z-pinches

International Nuclear Information System (INIS)

Tetsu, Miyamoto

1999-01-01

The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed. (author)

Producing High-Performance, Stable, Sheared-Flow Z-Pinches in the FuZE project

Science.gov (United States)

Golingo, R. P.; Shumlak, U.,; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; University of Washington (UW) Collaboration; Lawrence Livermore National Laboratory (LLNL) Collaboration

2017-10-01

The Fusion Z-Pinch Experiment (FuZE) has made significant strides towards generating high-performance, stable Z-pinch plasmas with goals of ne = 1018 cm-3 and T =1 keV. The Z-pinch plasmas are stabilized with a sheared axial flow that is driven by a coaxial accelerator. The new FuZE device has been constructed and reproduces the major scientific achievements the ZaP project at the University of Washington; ne = 1016 cm-3,T = 100 eV, r20 μs. These parameters are measured with an array of magnetic field probes, spectroscopy, and fast framing cameras. The plasma parameters are achieved using a small fraction of the maximum energy storage and gas injection capability of the FuZE device. Higher density, ne = 5×1017 cm-3, and temperature, T = 500 eV, Z-pinch plasmas are formed by increasing the pinch current. At the higher voltages and currents, the ionization rates in the accelerator increase. By modifying the neutral gas profile in the accelerator, the plasma flow from the accelerator is maintained, driving the flow shear. Formation and sustainment of the sheared-flow Z-pinch plasma will be discussed. Experimental data demonstrating high performance plasmas in a stable Z-pinches will be shown. This work is supported by an award from US ARPA-E.

Frequency-domain full-waveform inversion with non-linear descent directions

Science.gov (United States)

Geng, Yu; Pan, Wenyong; Innanen, Kristopher A.

2018-05-01

Full-waveform inversion (FWI) is a highly non-linear inverse problem, normally solved iteratively, with each iteration involving an update constructed through linear operations on the residuals. Incorporating a flexible degree of non-linearity within each update may have important consequences for convergence rates, determination of low model wavenumbers and discrimination of parameters. We examine one approach for doing so, wherein higher order scattering terms are included within the sensitivity kernel during the construction of the descent direction, adjusting it away from that of the standard Gauss-Newton approach. These scattering terms are naturally admitted when we construct the sensitivity kernel by varying not the current but the to-be-updated model at each iteration. Linear and/or non-linear inverse scattering methodologies allow these additional sensitivity contributions to be computed from the current data residuals within any given update. We show that in the presence of pre-critical reflection data, the error in a second-order non-linear update to a background of s0 is, in our scheme, proportional to at most (Δs/s0)3 in the actual parameter jump Δs causing the reflection. In contrast, the error in a standard Gauss-Newton FWI update is proportional to (Δs/s0)2. For numerical implementation of more complex cases, we introduce a non-linear frequency-domain scheme, with an inner and an outer loop. A perturbation is determined from the data residuals within the inner loop, and a descent direction based on the resulting non-linear sensitivity kernel is computed in the outer loop. We examine the response of this non-linear FWI using acoustic single-parameter synthetics derived from the Marmousi model. The inverted results vary depending on data frequency ranges and initial models, but we conclude that the non-linear FWI has the capability to generate high-resolution model estimates in both shallow and deep regions, and to converge rapidly, relative to a

Acoustic bubble enhanced pinched flow fractionation for microparticle separation

International Nuclear Information System (INIS)

Zhou, Ran; Wang, Cheng

2015-01-01

Pinched flow fractionation is a simple method for separating micron-sized particles by size, but has certain intrinsic limitations, e.g. requirement of a pinched segment similar to particle size and limited separation distance. In this paper, we developed an acoustic bubble enhanced pinched flow fractionation (PFF) method for microparticle separation. The proposed technique utilized microbubble streaming flows to overcome the limitations of conventional PFF. Our device has demonstrated separation of different sized microparticles (diameters 10 and 2 μm) with a larger pinched segment (60 μm) and at different buffer/particle solution flow rate ratios (5–25). The separation distances between particles are larger (as much as twice as large) than those achieved with conventional PFF. In addition, the separation position and distance can be adjusted by changing the driving voltage. The robust performance is due to the unique features of the flow field inside the pinched segment. We investigated several factors, including flow rate ratio, total flow rate and driving voltage, that affect the separation performance. (paper)

Energy storage and transfer with homopolar machine for a linear theta-pinch hybrid reactor

International Nuclear Information System (INIS)

Vogel, H.F.; Brennan, M.; Dase, W.G.; Tolk, K.M.; Weldon, W.F.

1975-12-01

This report describes the energy storage and transfer system for the compression coil system of a linear theta-pinch hybrid reactor (LTPHR). High efficiency and low cost are the principal requirements for the energy storage and transfer of 25 MJ/m or 25 GJ for a 1-km LTPHR. The circuit efficiency must be approximately 90 percent, and the cost for the circuit 5 to 6 cents/J. Scaling laws and simple relationships between circuit efficiency and cost per unit energy as a function of the half cycle time are presented. Capacitors and homopolor machines are considered as energy storage elements with both functioning basically as capacitors. The advantage of the homopolar machine in this application is its relatively low cost, whereas that of capacitors is better efficiency

ZAPP: Z-pinch atomic physics program

International Nuclear Information System (INIS)

Reed, K.

1983-01-01

High-density and high-temperature plasmas have been produced in a z-pinch with a hollow gas puff. A number of interesting atomic-physics phenomena occur in these plasmas and some of these phenomena provide important diagnostic information for characterizing the plasmas. We have been interested in collisions of high-energy electrons with highly stripped ions in these plasmas. Such collisions may produce a population inversion which could result in stimulated emission in the x-ray regime

Experimental study of the 'NOVA' Z-pinch equipment working as vacuum-gap

International Nuclear Information System (INIS)

Acuna, H.; Bernal, L.; Cortazar, D.; Iglesias, G.; Pouzo, J.

1990-01-01

The Z-pinch device 'NOVA' (2 kjoule, 10 kV, 250 kA) is operated as a vacuum gap. The plasma is generated in high vacuum (10 -5 mb) by the material let loose from the copper electrodes. Many strong compressions (micro pinches) are produced in the pinch column over the first quarter of the current period. This is detected by the observable pulses in the dI/dt signal. Hard X-rays generated in coincidence with the micro pinches are detected using a scintillator-photomultiplier system. This work studies the plasma evolution, by taking pictures of the pinch with obturation times of about 15 ns, temporally correlated with the dI/dt signal. Instabilities of types m=0 and m=1 are observed. (Author). 3 refs., 6 figs

Magnetostatic Analysis of a Pinch Mode Magnetorheological Valve

Directory of Open Access Journals (Sweden)

Gołdasz Janusz

2017-09-01

Full Text Available The study deals with the pinch mode of magnetorheological (MR fluids’ operation and its application in MR valves. By applying the principle in MR valves a highly non-uniform magnetic field can be generated in flow channels in such a way to solidify the portion of the material that is the nearest to the flow channel’s walls. This is in contrary to well-known MR flow mode valves. The authors investigate a basic pinch mode valve in several fundamental configurations, and then examine their magnetic circuits through magnetostatic finite-element (FE analysis. Flux density contour maps are revealed and basic performance figures calculated and analysed. The FE analysis results yield confidence in that the performance of MR pinch mode devices can be effectively controlled through electromagnetic means.

Estimation of biological parameters of marine organisms using linear and nonlinear acoustic scattering model-based inversion methods.

Science.gov (United States)

Chu, Dezhang; Lawson, Gareth L; Wiebe, Peter H

2016-05-01

The linear inversion commonly used in fisheries and zooplankton acoustics assumes a constant inversion kernel and ignores the uncertainties associated with the shape and behavior of the scattering targets, as well as other relevant animal parameters. Here, errors of the linear inversion due to uncertainty associated with the inversion kernel are quantified. A scattering model-based nonlinear inversion method is presented that takes into account the nonlinearity of the inverse problem and is able to estimate simultaneously animal abundance and the parameters associated with the scattering model inherent to the kernel. It uses sophisticated scattering models to estimate first, the abundance, and second, the relevant shape and behavioral parameters of the target organisms. Numerical simulations demonstrate that the abundance, size, and behavior (tilt angle) parameters of marine animals (fish or zooplankton) can be accurately inferred from the inversion by using multi-frequency acoustic data. The influence of the singularity and uncertainty in the inversion kernel on the inversion results can be mitigated by examining the singular values for linear inverse problems and employing a non-linear inversion involving a scattering model-based kernel.

Kinetic theory of the sausage instability of a z-pinch

International Nuclear Information System (INIS)

Isichenko, M.B.; Kulyabin, K.L.; Yan'kov, V.V.

1989-01-01

A linear problem of z-pinch sausage development is considered taking into account the influence of kinetic effects for ideal scanning current. Plasma electrons are considered to be cold and ions - collisionless. It is also supposed that the magnetic field inside a pinch doesn't affect the motion of ions, which are reflected like in a mirror from a jump of an electric potential arising on the plasma boundary. In case of long-wave perturbations ka >1 the acount of kinetics leads to considerable decrease of the increment [(ka) 1/2 times] in comparison with the hydrodynamic description, that permits to explain the increased instability of z-pinches observed in experiments

LinvPy : a Python package for linear inverse problems

OpenAIRE

Beaud, Guillaume François Paul

2016-01-01

The goal of this project is to make a Python package including the tau-estimator algorithm to solve linear inverse problems. The package must be distributed, well documented, easy to use and easy to extend for future developers.

Treating experimental data of inverse kinetic method by unitary linear regression analysis

International Nuclear Information System (INIS)

Zhao Yusen; Chen Xiaoliang

2009-01-01

The theory of treating experimental data of inverse kinetic method by unitary linear regression analysis was described. Not only the reactivity, but also the effective neutron source intensity could be calculated by this method. Computer code was compiled base on the inverse kinetic method and unitary linear regression analysis. The data of zero power facility BFS-1 in Russia were processed and the results were compared. The results show that the reactivity and the effective neutron source intensity can be obtained correctly by treating experimental data of inverse kinetic method using unitary linear regression analysis and the precision of reactivity measurement is improved. The central element efficiency can be calculated by using the reactivity. The result also shows that the effect to reactivity measurement caused by external neutron source should be considered when the reactor power is low and the intensity of external neutron source is strong. (authors)

Effect of inversion layer at iron pyrite surface on photovoltaic device

Science.gov (United States)

Uchiyama, Shunsuke; Ishikawa, Yasuaki; Uraoka, Yukiharu

2018-03-01

Iron pyrite has great potential as a thin-film solar cell material because it has high optical absorption, low cost, and is earth-abundant. However, previously reported iron pyrite solar cells showed poor photovoltaic characteristics. Here, we have numerically simulated its photovoltaic characteristics and band structures by utilizing a two-dimensional (2D) device simulator, ATLAS, to evaluate the effects of an inversion layer at the surface and a high density of deep donor defect states in the bulk. We found that previous device structures did not consider the inversion layer at the surface region of iron pyrite, which made it difficult to obtain the conversion efficiency. Therefore, we remodeled the device structure and suggested that removing the inversion layer and reducing the density of deep donor defect states would lead to a high conversion efficiency of iron pyrite solar cells.

Z-Pinch at extreme energies: Nanofocus of less than 1J. Plasma Focus of 400 J. Gas embedded Z-pinch operating at MA

International Nuclear Information System (INIS)

Pavez Morales, Cristian A

2007-01-01

The work presented in this thesis is in relation with an experimental study developed in three different pulsed plasma generators. Two of them were already operating in the plasma laboratory of the Chilean Nuclear Energy Commission (CCHEN ) at the beginning of this thesis and they are: a) plasma focus PF-40OJ ((880nF, 30kV, 120kA, 400J, 300ns maximum current, dl/dt4x10 11 A/s) which is one of the first plasma focus devices at low energy that produces neutron pulses of fusion and b) the pulsed power generator SPEED-2 (4.1μF equivalent capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns at maximum current, dl/dt∼10 13 A/s) designed to operate in a plasma focus configuration. The third experiment corresponds to a plasma focus device at energy lower than 1J (Nanofocus), which was designed, constructed and characterized during the development of this thesis. The performed work can be summarized in two general aspects: the experimental study of the scaling in plasma focus devices at low energy and the development of a linear Z-pinch configuration using the SPEED-2 generator. In this last situation, a mechanism of preionization was developed in order to create a gas embedded Z-pinch discharge (Deuterium in the case of our experiment) that was conveniently coupled to the electrical characteristics of the generator. In every experiment, the plasma properties were studied (density, dynamics, size, radiation emission) and they reported the state of it. In the plasma focus device PF-40OJ, the electronic density was characterized for discharges in H 2 by using optical refractive techniques, measuring density values in the pinch ∼10 25 m -3 , similar to those reported in plasma focus devices at higher energies. The anisotropy was measured in the distribution of the intensity in the neutron emission for discharges in D 2 using track detector techniques CR-39. A distribution for the neutron flux characterized by an isotropic contribution of 57.5% and also by other

Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

Science.gov (United States)

Zhou, Lin; Li, Zhenghong; Wang, Zhen; Liang, Chuan; Li, Mingjia; Qi, Jianmin; Chu, Yanyun

2016-03-01

The linear-transformer-driver (LTD) is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a Z -pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array Z -pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is 32 cm /μ s when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on the fast Z pinch and technologies for repetition-rate-operated accelerators.

Inverse Boundary Value Problem for Non-linear Hyperbolic Partial Differential Equations

OpenAIRE

Nakamura, Gen; Vashisth, Manmohan

2017-01-01

In this article we are concerned with an inverse boundary value problem for a non-linear wave equation of divergence form with space dimension $n\\geq 3$. This non-linear wave equation has a trivial solution, i.e. zero solution. By linearizing this equation at the trivial solution, we have the usual linear isotropic wave equation with the speed $\\sqrt{\\gamma(x)}$ at each point $x$ in a given spacial domain. For any small solution $u=u(t,x)$ of this non-linear equation, we have the linear isotr...

Putting the pinch on reactors

International Nuclear Information System (INIS)

Glavic, P.; Kravanja, Z.; Homsak, M.

1990-01-01

Pinch technology has proven to be a powerful tool for designing new processes and retrofitting old ones. But, until recently, it was thought to pertain only to heat exchanger networks, separators and power devices (such as heat engines and heat pumps). Regarded as process background, reactors have been left out of heat integrations. Their structure, however, can be changed and, within limits, their parameters modified to better exploit energy. In a pinch-designed plant, heat is transferred between the hot and cold process streams so efficiently that the plant's utility requirements (heat sources and sinks) are minimal. The design procedure is discussed. It involves two steps: finding a nearly optimal process structure by means of an analysis of process-temperature-vs.- enthalpy diagrams, and then optimizing the structure by means of grid diagrams or a computerized procedure

A Projected Non-linear Conjugate Gradient Method for Interactive Inverse Kinematics

DEFF Research Database (Denmark)

Engell-Nørregård, Morten; Erleben, Kenny

2009-01-01

Inverse kinematics is the problem of posing an articulated figure to obtain a wanted goal, without regarding inertia and forces. Joint limits are modeled as bounds on individual degrees of freedom, leading to a box-constrained optimization problem. We present A projected Non-linear Conjugate...... Gradient optimization method suitable for box-constrained optimization problems for inverse kinematics. We show application on inverse kinematics positioning of a human figure. Performance is measured and compared to a traditional Jacobian Transpose method. Visual quality of the developed method...

Self-Organization Observed in Numerical Simulations of a Hard-Core Diffuse Z Pinch

International Nuclear Information System (INIS)

Makhin, V; Siemon, R E; Bauer, B S; Esaulov, A; Lindemuth, I R; Ryutov, D D; Sheehey, P T; Sotnikov, V I

2005-04-01

The evolution of an unstable plasma profile into a stable profile, which we term self-organization, appears to be a robust process. Although it was not termed self organization, the same effect has been noted in past simulations with the same code. The result has been made easier to discern by the introduction of z-averaged profiles. A recent report of PIC simulations in the hard-core z-pinch configuration also shows self-organization. Figures 3 and 4 in Reference 21 show how pressure profiles in a low-β PIC simulation relax from unstable to stable. The non-linear evolution of the interchange motion has been studied under controlled initial conditions that result in exponential growth of a mode with a prescribed axial wavelength. An interesting feature of such growth is an abrupt transition from coherent to incoherent motion, after which the z-averaged pressure, current, and temperature profiles become quasi stationary. According to our understanding of MAGO experiments, the observed plasma behavior is consistent with the expectation of self-organization, but the diagnostics are not sufficiently detailed thus far to make a definite conclusion. The results of this simulations reported in this paper add motivation to planned experiments on an inverse pinch at UNR

Finite-Larmor-radius effects on z-pinch stability

Science.gov (United States)

Scheffel, Jan; Faghihi, Mostafa

1989-06-01

The effect of finite Larmor radius (FLR) on the stability of m = 1 small-axial-wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. We use the incompressible FLR MHD model; a collisionless fluid model that consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD, 2r dp/dr + m2B2/μ0 ≥ 0 predicts instability for internal modes unless the current density is singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the FLR terms are included, a normal-mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall term has a damping (but not absolutely stabilizing) effect - in agreement with earlier work. On specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m = 1 modes are then fully stabilized over the crosssection for wavelengths λ/a ≤ 1, where a denotes the pinch radius. As a general z-pinch result a critical line-density limit Nmax = 5 × 1018 m-1 is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. This limit corresponds to about five Larmor radii along the pinch radius. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 1020 m-1.

Finite-Larmor-radius effects on z-pinch stability

Energy Technology Data Exchange (ETDEWEB)

Scheffel, J.; Faghihi, M. (Royal Inst. of Tech., Stockholm (Sweden))

1989-06-01

The effect of finite Larmor radius (FLR) on the stability of m = 1 small-axial-wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. The incompressible FLR MHD model is used; a collisionless fluid model that consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD, 2rdp/dr+m{sup 2}B{sup 2}/{mu}{sub 0}{ge}0 predicts instability for internal modes unless the current density is singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the LFR terms are included, a normal-mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall term has a damping (but no absolutely stabilizing) effect - in agreement with earlier work. On specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m = 1 modes are then fully stabilized over the cross-section for wavelengths {lambda}/{alpha}{le}1, where {alpha} denotes the pinch radius. As a general z-pinch result a critical line-density limit ''N''{sub max}=5x10{sup 18}m{sup -1} is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. This limit corresponds to about five Larmor radii along the pinch radius. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 10{sup 20} m{sup -1}. (author).

Finite-Larmor-radius effects on z-pinch stability

International Nuclear Information System (INIS)

Scheffel, J.; Faghihi, M.

1989-01-01

The effect of finite Larmor radius (FLR) on the stability of m = 1 small-axial-wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. The incompressible FLR MHD model is used; a collisionless fluid model that consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD, 2rdp/dr+m 2 B 2 /μ 0 ≥0 predicts instability for internal modes unless the current density is singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the LFR terms are included, a normal-mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall term has a damping (but no absolutely stabilizing) effect - in agreement with earlier work. On specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m = 1 modes are then fully stabilized over the cross-section for wavelengths λ/α≤1, where α denotes the pinch radius. As a general z-pinch result a critical line-density limit ''N'' max =5x10 18 m -1 is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. This limit corresponds to about five Larmor radii along the pinch radius. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 10 20 m -1 . (author)

Linearized inversion of two components seismic data; Inversion linearisee de donnees sismiques a deux composantes

Energy Technology Data Exchange (ETDEWEB)

Lebrun, D.

1997-05-22

The aim of the dissertation is the linearized inversion of multicomponent seismic data for 3D elastic horizontally stratified media, using Born approximation. A Jacobian matrix is constructed; it will be used to model seismic data from elastic parameters. The inversion technique, relying on single value decomposition (SVD) of the Jacobian matrix, is described. Next, the resolution of inverted elastic parameters is quantitatively studies. A first use of the technique is shown in the frame of an evaluation of a sea bottom acquisition (synthetic data). Finally, a real data set acquired with conventional marine technique is inverted. (author) 70 refs.

Flow effects on the stability of z-pinches

International Nuclear Information System (INIS)

Shumlak, U.; Hartman, C.W.

1996-01-01

The effect of an axial flow on the m = 1 kink instability in z-pinches is studied numerically by reducing the linearized ideal MHD equations to a one-dimensional eigenvalue equation for the radial displacement. The derivation of the displacement equation for equilibria with axial flows will be presented. A diffuse z-pinch equilibrium is chosen that is made marginally stable to the m = 0 sausage mode by tailoring the pressure profile. The principle result reveals that a sheared axial flow does stabilize the kink mode when the shear exceeds a threshold value. Additionally, the m = 0 sausage mode is driven from marginal stability into the stable regime which suggests that the equilibrium pressure profile control can be relaxed. Fast z-pinches such as liner implosions are plagued by the Rayleigh-Taylor instability which destroys the liner and disrupts the current path before the liner arrives on axis. A sheared axial flow in a liner may quench the Rayleigh-Taylor instability in the same way that it quenches MHD instabilities in a diffuse z-pinch. Simulation results will be presented showing the effect of a sheared axial flow on the Rayleigh-Taylor instability in a fast liner implosion

Z-pinches

International Nuclear Information System (INIS)

Yan'kov, V.V.

1991-01-01

Although pinches, unlike tokamaks, have not occupied a central position in fusion research, their structural simplicity and the wealth of physical processes associated with plasma foci have maintained a steady interest. The development of Z-pinches, including plasma foci, micropinches, and dense Z-pinches, is reviewed. Attention is focused on theoretical as opposed to experimental questions, and on recent work rather than the basic results now found in textbooks. Finally, Soviet work is discussed more fully than work done abroad, and applications to controlled fusion are emphasized

The quest for a z-pinch based fusion energy source—a historical perspective

Science.gov (United States)

Sethian, John

1997-05-01

Ever since 1958, when Oscar Anderson observed copious neutrons emanating from a "magnetically self-constricted column of deuterium plasma," scientists have attempted to develop the simple linear pinch into a fusion power source. After all, simple calculations show that if one can pass a current of slightly less than 2 million amperes through a stable D-T plasma, then one could achieve not just thermonuclear break-even, but thermonuclear gain. Moreover, several reactor studies have shown that a simple linear pinch could be the basis for a very attractive fusion system. The problem is, of course, that the seemingly simple act of passing 2 MA through a stable pinch has proven to be quite difficult to accomplish. The pinch tends to disrupt due to instabilities, either by the m=0 (sausage) or m=1 (kink) modes. Curtailing the growth of these instabilities has been the primary thrust of z-pinch fusion research, and over the years a wide variety of formation techniques have been tried. The early pinches were driven by relatively slow capacitive discharges and were formed by imploding a plasma column. The advent of fast pulsed power technology brought on a whole new repertoire of formation techniques, including: fast implosions, laser or field-enhanced breakdown in a uniform volume of gas, a discharge inside a small capillary, a frozen deuterium fiber isolated by vacuum, and staged concepts in which one pinch implodes upon another. And although none of these have yet to be successful, some have come tantalizingly close. This paper will review the history of this four-decade long quest for fusion power.

Reversed field pinch diagnostics

International Nuclear Information System (INIS)

Weber, P.G.

1986-01-01

The Reversed Field Pinch (RFP) is a toroidal, axisymmetric magnetic confinement configuration characterized by a magnetic field configuration in which the toroidal magnetic field is of similar strength to the poloidal field, and is reversed at the edge compared to the center. The RFP routinely operates at high beta, and is a strong candidate for a compact fusion device. Relevant attributes of the configuration will be presented, together with an overview of present and planned experiments and their diagnostics. RFP diagnostics are in many ways similar to those of other magnetic confinement devices (such as tokamaks); these lectures will point out pertinent differences, and will present some diagnostics which provide special insights into unique attributes of the RFP

Architecture of petawatt-class z-pinch accelerators

Directory of Open Access Journals (Sweden)

W. A. Stygar

2007-03-01

Full Text Available We have developed an accelerator architecture that can serve as the basis of the design of petawatt-class z-pinch drivers. The architecture has been applied to the design of two z-pinch accelerators, each of which can be contained within a 104-m-diameter cylindrical tank. One accelerator is driven by slow (∼1   μs Marx generators, which are a mature technology but which necessitate significant pulse compression to achieve the short pulses (≪1   μs required to drive z pinches. The other is powered by linear transformer drivers (LTDs, which are less mature but produce much shorter pulses than conventional Marxes. Consequently, an LTD-driven accelerator promises to be (at a given pinch current and implosion time more efficient and reliable. The Marx-driven accelerator produces a peak electrical power of 500 TW and includes the following components: (i 300 Marx generators that comprise a total of 1.8×10^{4} capacitors, store 98 MJ, and erect to 5 MV; (ii 600 water-dielectric triplate intermediate-store transmission lines, which also serve as pulse-forming lines; (iii 600 5-MV laser-triggered gas switches; (iv three monolithic radial-transmission-line impedance transformers, with triplate geometries and exponential impedance profiles; (v a 6-level 5.5-m-diameter 15-MV vacuum insulator stack; (vi six magnetically insulated vacuum transmission lines (MITLs; and (vii a triple-post-hole vacuum convolute that adds the output currents of the six MITLs, and delivers the combined current to a z-pinch load. The accelerator delivers an effective peak current of 52 MA to a 10-mm-length z pinch that implodes in 95 ns, and 57 MA to a pinch that implodes in 120 ns. The LTD-driven accelerator includes monolithic radial transformers and a MITL system similar to those described above, but does not include intermediate-store transmission lines, multimegavolt gas switches, or a laser trigger system. Instead, this accelerator is driven by 210

Pinched hysteresis behavior in a PID-controlled resistor

Directory of Open Access Journals (Sweden)

M.A. Carrasco-Aguilar

2018-06-01

Full Text Available A current-controlled grounded resistor that exhibits a frequency-dependent pinched hysteresis loop is described. A mathematical model describing this behavior is derived and validated numerically, which has the form of a Proportional Integral-Derivative (PID controller. The proposed topology is build by using AD844 commercially available active device configured as second-generation current conveyor and experimental tests are compared with numerical simulations, showing a good agreement among them. Moreover, the proposed PID-controlled resistor can be reconfigured in order to be used in future applications such as programmable analog circuits. Keyword: Pinched hysteresis, Current conveyors, Nonlinear resistor, Proportional-Integral-Derivative Controller

Current-driven instabilities of the kinetic shear Alfven wave: Application to reversed field pinches and spheromaks

International Nuclear Information System (INIS)

Meyerhofer, D.D.; Perkins, F.W.

1984-01-01

The kinetic Alfven wave is studied in a cylindrical force-free plasma with self-consistent magnetic fields. This equilibrium represents a reversed field pinch or a spheromak. The stability of the wave is found to depend on the ratio of the electron drift velocity to the Alfven velocity. This ratio varies inversely with the square root of the plasma line density. The critical line density using the Spitzer--Harm electron distribution function is found for reversed field pinches with deuterium plasmas to be approximately 2 x 10 18 and is 5 x 10 17 m -1 in spheromaks with hydrogen plasmas. The critical line density is in reasonable agreement with experimental data for reversed field pinches

Current driven instabilities of the kinetic shear Alfven wave: application to reversed field pinches and spheromaks

International Nuclear Information System (INIS)

Meyerhofer, D.D.; Perkins, F.W.

1984-04-01

The kinetic Alfven wave is studied in a cylindrical force-free plasma with self-consistent magnetic fields. This equilibrium represents a reversed field pinch or a spheromak. The stability of the wave is found to depend on the ratio of the electron drift velocity to the Alfven velocity. This ratio varies inversely with the square root of the plasma line density. The critical line density using the Spitzer-Harm electron distribution function is found for reversed field pinches with deuterium plasmas to be approximately 2 x 10 18 m -1 and is 5 x 10 17 m -1 in spheromaks with hydrogen plasmas. The critical line density is in reasonable agreement with experimental data for reversed field pinches

Energy storage and transfer with homopolar machine for a linear theta-pinch hybrid reactor

International Nuclear Information System (INIS)

Vogel, H.F.; Brennan, M.; Dase, W.G.; Tolk, K.M.; Weldon, W.F.

1976-01-01

The energy storage and transfer system for the compression coils of a linear theta-pinch hybrid reactor (LTPHR) are described. High efficiency and low cost are the principal requirements for the energy storage and transfer of 25MJ/m or 25GJ for a 1-km LTPHR. The circuit efficiency must be approximately 90%, and the cost for the circuit 5-6c/J. Scaling laws and simple relationships between circuit efficiency and cost-per-unit energy as a function of the half cycle time are presented. An important consideration concerns the pulse repetition rate of 2.25 pulses per second, 70x10 6 shots/yr, or 1.7x10 9 shots over the 25-yr plant life. Current interruption to initiate energy transfer is not feasible at this rate. Therefore, a simple ringing circuit with contactors to make and break at the periodically occurring zero-current instances, is considered

Structural design aspects of magnetic coils for a linear theta-pinch hybrid reactor

International Nuclear Information System (INIS)

Bartholomew, R.J.

1976-02-01

The structural design aspects of a linear theta-pinch hybrid reactor (LTPHR) are centered in the solenoidal adiabatic compression coil (ACC) which must support the high magnetic pulse forces that tend to expand the coil and separate the leads. The structural model is represented by the theory of elasticity solution to a thick-walled cylinder. Dynamic amplification (or attenuation) is considered by a shock spectrum technique. A composite material is postulated, where the conductor material for each strand is clad with a high-strength stainless steel with insulation considered. Yield strength (for isolated-pulse operation) and endurance limit (for repetitive-pulse operation) for the high-strength steel impose magnetic field strength constraints on the coil design. These constraints are combined in an overall energy balance calculation that includes neutronic considerations to determine an optimum ACC design. The computer code ENBAL was used to incorporate neutronic, electrical, and structural constraints into the overall energy balance of the LTPHR. The lead separation problem is solved by designing spaced clamps to hold the leads together over great distances

Design of the PST: A Diagnostic for 1-D Imaging of Fast Z-Pinch Power Emissions

International Nuclear Information System (INIS)

Rochau, Gregory A.; Derzon, Mark S.; Chandler, Gordon A.; Lazier, Steven Earl

2000-01-01

Fast Z-pinch technology developed on the Z machine at Sandia National Laboratories can produce up to 230 TW of thermal x-ray power for applications in inertial confinement fusion (ICF) and weapons physics experiments. During implosion, these Z-pinches develop Rayleigh-Taylor (R-T) instabilities which are very difficult to diagnose and which functionally diminish the overall pinch quality. The Power-Space-Time (PST) instrument is a newly configured diagnostic for measuring the pinch power as a function of both space and time in a Z-pinch. Placing the diagnostic at 90 degrees from the Z-pinch axis, the PST provides a new capability in collecting experimental data on R-T characteristics for making meaningful comparisons to magneto-hydrodynamic computer models. This paper is a summary of the PST diagnostic design. By slit-imaging the Z-pinch x-ray emissions onto a linear scintillator/fiber-optic array coupled to a streak camera system, the PST can achieve ∼100 microm spatial resolution and ∼1.3 ns time resolution. Calculations indicate that a 20 microm thick scintillating detection element filtered by 1,000 angstrom of Al is theoretically linear in response to Plankian x-ray distributions corresponding to plasma temperatures from 40 eV to 150 eV, By calibrating this detection element to x-ray energies up to 5,000 eV, the PST can provide pinch power as a function of height and time in a Z-pinch for temperatures ranging from ∼40 eV to ∼400 eV. With these system pm-meters, the PST can provide data for an experimental determination of the R-T mode number, amplitude, and growth rate during the late-time pinch implosion

Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

Directory of Open Access Journals (Sweden)

Zhou Lin

2016-03-01

Full Text Available The linear-transformer-driver (LTD is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a Z-pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array Z-pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%–90% can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is 32  cm/μs when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%–30%, providing a high efficient facility for research on the fast Z pinch and technologies for repetition-rate-operated accelerators.

Inverse kinematics of a dual linear actuator pitch/roll heliostat

Science.gov (United States)

Freeman, Joshua; Shankar, Balakrishnan; Sundaram, Ganesh

2017-06-01

This work presents a simple, computationally efficient inverse kinematics solution for a pitch/roll heliostat using two linear actuators. The heliostat design and kinematics have been developed, modeled and tested using computer simulation software. A physical heliostat prototype was fabricated to validate the theoretical computations and data. Pitch/roll heliostats have numerous advantages including reduced cost potential and reduced space requirements, with a primary disadvantage being the significantly more complicated kinematics, which are solved here. Novel methods are applied to simplify the inverse kinematics problem which could be applied to other similar problems.

The possibilities of linearized inversion of internally scattered seismic data

KAUST Repository

Aldawood, Ali

2014-08-05

Least-square migration is an iterative linearized inversion scheme that tends to suppress the migration artifacts and enhance the spatial resolution of the migrated image. However, standard least-square migration, based on imaging single scattering energy, may not be able to enhance events that are mainly illuminated by internal multiples such as vertical and nearly vertical faults. To alleviate this problem, we propose a linearized inversion framework to migrate internally multiply scattered energy. We applied this least-square migration of internal multiples to image a vertical fault. Tests on synthetic data demonstrate the ability of the proposed method to resolve a vertical fault plane that is poorly resolved by least-square imaging using primaries only. We, also, demonstrate the robustness of the proposed scheme in the presence of white Gaussian random observational noise and in the case of imaging the fault plane using inaccurate migration velocities.

The possibilities of linearized inversion of internally scattered seismic data

KAUST Repository

Aldawood, Ali; Alkhalifah, Tariq Ali; Hoteit, Ibrahim; Zuberi, Mohammad; Turkiyyah, George

2014-01-01

Least-square migration is an iterative linearized inversion scheme that tends to suppress the migration artifacts and enhance the spatial resolution of the migrated image. However, standard least-square migration, based on imaging single scattering energy, may not be able to enhance events that are mainly illuminated by internal multiples such as vertical and nearly vertical faults. To alleviate this problem, we propose a linearized inversion framework to migrate internally multiply scattered energy. We applied this least-square migration of internal multiples to image a vertical fault. Tests on synthetic data demonstrate the ability of the proposed method to resolve a vertical fault plane that is poorly resolved by least-square imaging using primaries only. We, also, demonstrate the robustness of the proposed scheme in the presence of white Gaussian random observational noise and in the case of imaging the fault plane using inaccurate migration velocities.

A Sparse Approximate Inverse Preconditioner for Nonsymmetric Linear Systems

Czech Academy of Sciences Publication Activity Database

Benzi, M.; Tůma, Miroslav

1998-01-01

Roč. 19, č. 3 (1998), s. 968-994 ISSN 1064-8275 R&D Projects: GA ČR GA201/93/0067; GA AV ČR IAA230401 Keywords : large sparse systems * interative methods * preconditioning * approximate inverse * sparse linear systems * sparse matrices * incomplete factorizations * conjugate gradient -type methods Subject RIV: BA - General Mathematics Impact factor: 1.378, year: 1998

Plasma resistivity in a slow rising current theta-pinch device

International Nuclear Information System (INIS)

Kayama, Milton Eiji; Dobrowolsky, Marcelo Shubert; Honda, Roberto Yzumi; Aramaki, Emilia Akemi; Algatti, Mauricio Antonio

1998-01-01

Anomalous behavior of plasma resistivity was observed in a Theta-pinch plasma. A comparative analysis was performed with a hybrid numerical code where the Chodura s resistivity algorithm is included. Good agreement was found in the radial plasma dynamic description. The experimental value of resistivity at null field point was found to be one order of magnitude greater than the theoretical prediction. (author)

Collisional tearing in a field-reversed sheet pinch assuming nonparallel propagation

International Nuclear Information System (INIS)

Quest, K.B.; Coroniti, F.V.

1985-01-01

We examine the linear stability properties of the collisional tearing mode in a reversed-field sheet pinch assuming that the wave vector is not parallel to B, where B is the equilibrium magnetic field. We show that pressure balance in the direction of the equilibrium current requires a nonzero perturbed current component deltaJ/sub z/ that is driven toward tyhe center of the pinch. At the center of the pinch, deltaJ/sub z/ goes to zero, and momentum is balanced by coupling to the ion-acoustic mode. In order to achieve current closure, a large perturbed field-aligned current is generated that is strongly localized about the dissipative tearing layer. The relation of this work to the collisionless case is discussed

Parameter scaling toward high-energy density in a quasi-steady flow Z-pinch

Science.gov (United States)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.

2016-10-01

Sheared axial flows are utilized by the ZaP Flow Z-Pinch Experiment to stabilize MHD instabilities. The pinches formed are 50 cm long with radii ranging from 0.3 to 1.0 cm. The plasma is generated in a coaxial acceleration region, similar to a Marshall gun, which provides a steady supply of plasma for approximately 100 us. The power to the plasma is partially decoupled between the acceleration and pinch assembly regions through the use of separate power supplies. Adiabatic scaling of the Bennett relation gives targets for future devices to reach high-energy density conditions or fusion reactors. The applicability of an adiabatic assumption is explored and work is done experimentally to clarify the plasma compression process, which may be more generally polytropic. The device is capable of a much larger parameter space than previous machine iterations, allowing flexibility in the initial conditions of the compression process to preserve stability. This work is supported by DoE FES and NNSA.

Properties of the edge plasma in the rebuilt Extrap-T2R reversed field pinch experiment

International Nuclear Information System (INIS)

Vianello, N; Spolaore, M; Serianni, G; Bergsaker, H; Antoni, V; Drake, J R

2002-01-01

The edge region of the rebuilt Extrap-T2R reversed field pinch experiment has been investigated using Langmuir probes. Radial profiles of main plasma parameters are obtained and compared with those of the previous device Extrap-T2. The spontaneous setting up of a double shear layer of ExB toroidal velocity is confirmed. The particle flux induced by electrostatic fluctuations is calculated and the resulting effective diffusion coefficient is consistent with the Bohm estimate. A close relationship between electrostatic fluctuations at the edge and non-linear coupling of MHD modes in the core is found

Properties of the edge plasma in the rebuilt Extrap-T2R reversed field pinch experiment

Science.gov (United States)

Vianello, N.; Spolaore, M.; Serianni, G.; Bergsåker, H.; Antoni, V.; Drake, J. R.

2002-12-01

The edge region of the rebuilt Extrap-T2R reversed field pinch experiment has been investigated using Langmuir probes. Radial profiles of main plasma parameters are obtained and compared with those of the previous device Extrap-T2. The spontaneous setting up of a double shear layer of E×B toroidal velocity is confirmed. The particle flux induced by electrostatic fluctuations is calculated and the resulting effective diffusion coefficient is consistent with the Bohm estimate. A close relationship between electrostatic fluctuations at the edge and non-linear coupling of MHD modes in the core is found.

Continuity and general perturbation of the Drazin inverse for closed linear operators

Directory of Open Access Journals (Sweden)

N. Castro González

2002-01-01

Full Text Available We study perturbations and continuity of the Drazin inverse of a closed linear operator A and obtain explicit error estimates in terms of the gap between closed operators and the gap between ranges and nullspaces of operators. The results are used to derive a theorem on the continuity of the Drazin inverse for closed operators and to describe the asymptotic behavior of operator semigroups.

The effect of sheared axial flow on nonlinear Z-pinch dynamics

International Nuclear Information System (INIS)

Kassapakis, N.

2000-01-01

A two dimensional Eulerian fluid code has been used to study three problems related to Z-pinch and laser produced plasmas. a) The nonlinear evolution of a localised m=0 MHD mode neck is studied in order to extract some scaling laws for the size and form of the artificial neck. We examine whether the ubiquitous m=0 instability could be beneficially used to assist in the formation of a transient localised dense plasma. The results obtained were in satisfactory agreement with experiments and other theoretical work where available. b) The development of the m=0 instability on a Z-pinch although beneficial in the previous case, is detrimental from a stability point of view and thus to the utilisation of the device as a fusion reactor by itself. This is because the timescales of the instability development are faster than the confinement time needed for fusion to occur. Sheared axial flow is a proposed mechanism for the non-linear saturation of this particular instability. Indeed the linear growth rate also can be substantially reduced. It is hoped that it can inhibit the growth of the instabilities or at least delay their development sufficiently for fusion to take place. The numerical study of the effect of sheared axial flow on the nonlinear dynamics of the Z-pinch carried out, demonstrates that sheared flow with velocity u z z >4 Alfven speed other modes, of the Kelvin-Helmholtz type, are excited which take over from the fastest growing mode in the static case. c) The expansion of the ablated plasma in laser-solid interactions is an important phenomenon for a plethora of reasons one of which is ICF. The simulations were in direct agreement with previous experimental work regarding the bulk properties of the ablation surface. They also provided justification for some assumptions made during the analysis of the observations and helped to confirm the calibration of the diagnostics timewise. The most striking feature of the experiments, namely the density dip on the

An Entropic Estimator for Linear Inverse Problems

Directory of Open Access Journals (Sweden)

Amos Golan

2012-05-01

Full Text Available In this paper we examine an Information-Theoretic method for solving noisy linear inverse estimation problems which encompasses under a single framework a whole class of estimation methods. Under this framework, the prior information about the unknown parameters (when such information exists, and constraints on the parameters can be incorporated in the statement of the problem. The method builds on the basics of the maximum entropy principle and consists of transforming the original problem into an estimation of a probability density on an appropriate space naturally associated with the statement of the problem. This estimation method is generic in the sense that it provides a framework for analyzing non-normal models, it is easy to implement and is suitable for all types of inverse problems such as small and or ill-conditioned, noisy data. First order approximation, large sample properties and convergence in distribution are developed as well. Analytical examples, statistics for model comparisons and evaluations, that are inherent to this method, are discussed and complemented with explicit examples.

Comparison of confinement in resistive-shell reversed-field pinch devices with two different magnetic shell penetration times

International Nuclear Information System (INIS)

Gravestijn, R M; Drake, J R; Hedqvist, A; Rachlew, E

2004-01-01

A loop voltage is required to sustain the reversed-field pinch (RFP) equilibrium. The configuration is characterized by redistribution of magnetic helicity but with the condition that the total helicity is maintained constant. The magnetic field shell penetration time, τ s , has a critical role in the stability and performance of the RFP. Confinement in the EXTRAP device has been studied with two values of τ s , first (EXTRAP-T2) with tau s of the order of the typical relaxation cycle timescale and then (EXTRAP-T2R) with τ s much longer than the relaxation cycle timescale, but still much shorter than the pulse length. Plasma parameters show significant improvements in confinement in EXTRAP-T2R. The typical loop voltage required to sustain comparable electron poloidal beta values is a factor of 3 lower in the EXTRAP-T2R device. The improvement is attributed to reduced magnetic turbulence

Sparse contrast-source inversion using linear-shrinkage-enhanced inexact Newton method

KAUST Repository

Desmal, Abdulla

2014-07-01

A contrast-source inversion scheme is proposed for microwave imaging of domains with sparse content. The scheme uses inexact Newton and linear shrinkage methods to account for the nonlinearity and ill-posedness of the electromagnetic inverse scattering problem, respectively. Thresholded shrinkage iterations are accelerated using a preconditioning technique. Additionally, during Newton iterations, the weight of the penalty term is reduced consistently with the quadratic convergence of the Newton method to increase accuracy and efficiency. Numerical results demonstrate the applicability of the proposed method.

Sparse contrast-source inversion using linear-shrinkage-enhanced inexact Newton method

KAUST Repository

Desmal, Abdulla; Bagci, Hakan

2014-01-01

A contrast-source inversion scheme is proposed for microwave imaging of domains with sparse content. The scheme uses inexact Newton and linear shrinkage methods to account for the nonlinearity and ill-posedness of the electromagnetic inverse scattering problem, respectively. Thresholded shrinkage iterations are accelerated using a preconditioning technique. Additionally, during Newton iterations, the weight of the penalty term is reduced consistently with the quadratic convergence of the Newton method to increase accuracy and efficiency. Numerical results demonstrate the applicability of the proposed method.

Stable Alfven-wave dynamo action in the reversed-field pinch

International Nuclear Information System (INIS)

Werley, K.A.

1984-01-01

Previous theoretical work has suggested that Alfven waves may be related to the anomalous toroidal magnetic flux generation and extended (over classical expectations) discharge times observed in the reversed-field pinch. This thesis examines the dynamo action of stable Alfven waves as a means of generating toroidal flux. Recent advances in linear resistive MHD stability analysis are used to calculate the quasi-linear dynamo mean electromotive force of Alfven waves. This emf is incorporated into a one-dimensional transport and mean-field evolution code. The changing equilibrium is then fed back to the stability code to complete a computational framework that self-consistently evaluates a dynamic plasma dynamo. This technique is readily extendable to other plasmas in which dynamic stable model action is of interest. Such plasmas include Alfven wave current-drive and plasma heating for fusion devices, as well as astrophysical and geophysical dynamo systems. This study also contains extensive studies of resistive Alfven wave properties. This includes behavior versus spectral location, magnetic Reynolds number and wave number

Fusion with Z-pinches

International Nuclear Information System (INIS)

Cook, D.

1998-06-01

In the past thirty-six months, great progress has been made in x-ray production using high-current z-pinches. Today, the x-ray energy and power output of the Z accelerator (formerly PBFA-II) is the largest available in the laboratory. These z-pinch x-ray sources have the potential to drive high-yield ICF reactions at affordable cost if several challenging technical problems can be overcome. In this paper, the recent technical progress with Z-pinches will be described, and a technical strategy for achieving high-yield ICF with z-pinches will be presented

Theory of wire number scaling in wire-array Z pinches

International Nuclear Information System (INIS)

Desjarlais, M.P.; Marder, B.M.

1999-01-01

Pulsed-power-driven Z pinches, produced by imploding cylindrical arrays of many wires, have generated very high x-ray radiation powers (>200 TW) and energies (2 MJ). Experiments have revealed a steady improvement in Z-pinch performance with increasing wire number at fixed total mass and array radius. The dominant mechanism acting to limit the performance of these devices is believed to be the Rayleigh-Taylor instability which broadens the radially imploding plasma sheath and consequently reduces the peak radiation power. A model is presented which describes an amplification over the two-dimensional Rayleigh-Taylor growth rate brought about by kink-like forces on the individual wires. This amplification factor goes to zero as the number of wires approaches infinity. This model gives results which are in good agreement with the experimental data and provides a scaling for wire-array Z pinches. copyright 1999 American Institute of Physics

Development of an effective pinch bar

CSIR Research Space (South Africa)

Ottermann, RW

2003-02-01

Full Text Available . ....................................10 Figure 3-3: Layout of lightweight pinch bar extruded fibreglass tube. ..................................11 Figure 3-4: XDM lightweight pinch bar with manufactured glass fibre bar. ..........................12 Figure 3-5: XDM lightweight pinch... bar with extruded glass fibre tube. ................................12 Figure 3-6: Stiffness of a 2.8m lightweight pinch bar with an extruded glass fibre tube and a 25mm steel pinch bar...

Energy- and particle-confinement properties of an end-plugged, linear, theta pinch

International Nuclear Information System (INIS)

Commisso, R.J.; Bartsch, R.R.; Ekdahl, C.A.; McKenna, K.F.; Siemon, R.E.

1979-01-01

Experiments show that axial confinement of plasma in a straight theta-pinch solenoid is improved by placing solid lithium deuteride plugs at the ends. The energy confinement is increased nearly threefold in agreement with theoretical estimates which assume classical electron thermal conduction and no convective losses. The confinement of deuterium ions is explained by classical Coulomb collisions in the ablated lithium deuteride plasma

The reversed-field pinch as a poloidal-field-dominated, compact, high-power-density fusion system

International Nuclear Information System (INIS)

Krakowski, R.A.

1988-01-01

This paper discusses the feasibility of reversed-field pinch devices as future thermonuclear reactors. Safety, cost, ion temperatures, Lawson numbers, and power densities are reviewed for these types of devices. 12 refs., 2 figs., 1 tab

Isotropic-resolution linear-array-based photoacoustic computed tomography through inverse Radon transform

Science.gov (United States)

Li, Guo; Xia, Jun; Li, Lei; Wang, Lidai; Wang, Lihong V.

2015-03-01

Linear transducer arrays are readily available for ultrasonic detection in photoacoustic computed tomography. They offer low cost, hand-held convenience, and conventional ultrasonic imaging. However, the elevational resolution of linear transducer arrays, which is usually determined by the weak focus of the cylindrical acoustic lens, is about one order of magnitude worse than the in-plane axial and lateral spatial resolutions. Therefore, conventional linear scanning along the elevational direction cannot provide high-quality three-dimensional photoacoustic images due to the anisotropic spatial resolutions. Here we propose an innovative method to achieve isotropic resolutions for three-dimensional photoacoustic images through combined linear and rotational scanning. In each scan step, we first elevationally scan the linear transducer array, and then rotate the linear transducer array along its center in small steps, and scan again until 180 degrees have been covered. To reconstruct isotropic three-dimensional images from the multiple-directional scanning dataset, we use the standard inverse Radon transform originating from X-ray CT. We acquired a three-dimensional microsphere phantom image through the inverse Radon transform method and compared it with a single-elevational-scan three-dimensional image. The comparison shows that our method improves the elevational resolution by up to one order of magnitude, approaching the in-plane lateral-direction resolution. In vivo rat images were also acquired.

Computational investigation of single mode vs multimode Rayleigh endash Taylor seeding in Z-pinch implosions

International Nuclear Information System (INIS)

Douglas, M.R.; Deeney, C.; Roderick, N.F.

1998-01-01

A series of two-dimensional magnetohydrodynamic calculations have been carried out to investigate single and multimode growth and mode coupling for magnetically-driven Rayleigh endash Taylor instabilities in Z pinches. Wavelengths ranging from 5.0 mm down to 1.25 mm were considered. Such wavelengths are comparable to those observed at stagnation using a random density open-quotes seedingclose quotes method. The calculations show that wavelengths resolved by less than 10 cells exhibit an artificial decrease in initial Fourier spectrum amplitudes and a reduction in the corresponding amplitude growth. Single mode evolution exhibits linear exponential growth and the development of higher harmonics as the mode transitions into the nonlinear phase. The mode growth continues to exponentiate but at a slower rate than determined by linear hydrodynamic theory. In the two and three mode case, there is clear evidence of mode coupling and inverse cascade. In addition, distinct modal patterns are observed late in the implosion, resulting from finite shell thickness and magnetic field effects. copyright 1998 American Institute of Physics. thinsp

On The Structure of The Inverse of a Linear Constant Multivariable ...

African Journals Online (AJOL)

On The Structure of The Inverse of a Linear Constant Multivariable System. ... It is shown that the use of this representation has certain advantages in the design of multivariable feedback systems. typical examples were considered to indicate the corresponding application. Keywords: Stability Functions, multivariable ...

Overview of quasi single helicity experiments in reversed field pinches

International Nuclear Information System (INIS)

Martin, P.; Marrelli, L.; Spizzo, G.

2003-01-01

We report the results of an experimental and theoretical project dedicated to the study of Quasi Single Helicity Reversed Field Pinch plasmas. The project has involved several RFP devices and numerical codes. It appears that QSH spectra are a feature common to all the experiments. (author)

IB-LBM study on cell sorting by pinched flow fractionation.

Science.gov (United States)

Ma, Jingtao; Xu, Yuanqing; Tian, Fangbao; Tang, Xiaoying

2014-01-01

Separation of two categories of cells in pinched flow fractionation(PFF) device is simulated by employing IB-LBM. The separation performances at low Reynolds number (about 1) under different pinched segment widths, flow ratios, cell features, and distances between neighboring cells are studied and the results are compared with those predicted by the empirical formula. The simulation indicates that the diluent flow rate should approximate to or more than the flow rate of particle solution in order to get a relatively ideal separation performance. The discrepancy of outflow position between numerical simulation and the empirical prediction enlarges, when the cells become more flexible. Too short distance between two neighboring cells could lead to cell banding which would result in incomplete separation, and the relative position of two neighboring cells influences the banding of cells. The present study will probably provide some new applications of PFF, and make some suggestions on the design of PFF devices.

Reconsideration of the m=0 Z-pinch stability

International Nuclear Information System (INIS)

Scheffel, J.; Coppins, M.

1993-01-01

Possible paths for obtaining linear stability against the m=0 mode in the Z-pinch are studied. Using a generalized energy principle, the necessary and sufficient Chew-Goldberger-Low (CGL) m=0 stability criterion is derived. This criterion is less restrictive than that of ideal MHD, although it also requires the boundary plasma pressure to be finite. It is shown that the edge pressure cannot be stably upheld by a surface current. By instead assuming a finite pressure external gas, it is found that an edge pressure to on-axis pressure ratio of 0.5 is required for stability of a constant current density profile. A parabolic current density profile lowers the limit to the value 0.17. The growth rates are shown to be monotonically decreasing as a function of the external gas pressure. Detailed derivations of the boundary conditions are also given. The results aid in clarifying the experimental stability of four major Z-pinch experiments. Finite Larmor radius stabilization is hence required to maintain stability in future fibre pinch experiments in vacuum, implying line densities less than 10 19 m -1 . (author). 28 refs, 10 figs

Helical-D pinch

International Nuclear Information System (INIS)

Schaffer, M.J.

1997-08-01

A stabilized pinch configuration is described, consisting of a D-shaped plasma cross section wrapped tightly around a guiding axis. The open-quotes helical-Dclose quotes geometry produces a very large axial (toroidal) transform of magnetic line direction that reverses the pitch of the magnetic lines without the need of azimuthal (poloidal) plasma current. Thus, there is no need of a open-quotes dynamoclose quotes process and its associated fluctuations. The resulting configuration has the high magnetic shear and pitch reversal of the reversed field pinch (RFP). (Pitch = P = qR, where R = major radius). A helical-D pinch might demonstrate good confinement at q << 1

Necessary stability condition for field-reversed theta pinches

International Nuclear Information System (INIS)

Cary, J.R.

1981-03-01

Toroidal systems of arbitrary cross section without toroidal magnetic field are analyzed via the double adiabatic fluid equations. Such systems are shown to be unstable if there exists one closed field line on which the average of kapparB 2 is positive, where kappa is the curvature. A similar criterion is derived for linear systems and is applied to a noncircular z-pinch

Pinch modes in the SPEED2 plasma focus

International Nuclear Information System (INIS)

Kies, W.; Decker, G.; Berntien, U.; Glushkov, D.A.; Sidelnikov, Yu.V.; Koshelev, K.N.; Simanovskij, D.M.; Bobashev, S.V.

2001-01-01

Deuterium discharges in the SPEED2 plasma focus (80 kJ, 200 kV, 2 MA, 400 ns) have been found unexpectedly stable within the operational regime as a neutron source. Only at higher filling pressures (above 6 mbar) sometimes m=0 instabilities appeared in the pinch column, especially in discharges of lower efficiency (moderate dynamics and neutron yield). Enhancing the electromagnetic radiation by doping these discharges with heavy gases (e.g. neon, argon) distinctly two pinch modes are produced, the micropinch mode (MPM) or the stable column mode (SCM), with a transition regime where the initial SCM is followed by the MPM. Micropinches are local radiative collapses initiated by m=0 instabilities of low-energy-density pinch plasmas. These instabilities and the successive micropinches can be suppressed by kinetic deuterons produced during dynamical compression of high-energy-density deuterium plasma sheaths. Depending on the relaxation of this fast deuteron component the pinch column can be stabilized for several tens of nanoseconds. While the short-lived (appr.1 ns) micropinches erratically appear as point-like successive flashes along the pinch axis with temperatures about 1 keV and about solid density the reproducible SCM, optimized with respect to the compression ratio, forms a powerful linear radiation source of temperatures and densities similar to the MPM. The SCM needs powerful (fast) drivers in order to use the kinetic ion stabilization, but not necessarily MA currents as available from the SPEED2 driver. This opens the possibility to establish the SCM also in compact experiments like SPEED3 (8 kJ, 80 kV, 0.8 MA, 300 ns) or even SPEED4 (2 kJ, 40 kV 250 kA, 300 ns). (author)

Development of fast pulsed power driver for radiography and Z-pinch

International Nuclear Information System (INIS)

Qiu Aici; Sun Fengju

2008-01-01

Z-pinch and flash X-ray radiography have an important application in inertial confine fusion (ICF) and nuclear radiation effects simulation and high performance hydrodynamic test, etc. Z-pinch ICF and multi-pulse multi-axis high energy X-ray radiography put forward a huge challenge for pulsed power driver, so the direct-driven-load fast pulsed power driver are developed actively in home and abroard. The paper summarized the recent advances and developing trends of the fast pulsed power driver based on fast Marx(FMG) and fast linear transformer driver (LTD), and analysized the advantages and disadvantages and restricting factors about FMG and FLTD and their key technologies, then introduced the state-of-arts on the investigation in Northwest Institute of Nuclear Technology. In the end, the paper presented some advices and views about studying fast pulsed power driver applied to Z-pinch and flash X-ray radiography in home. (authors)

The optimisation of an intense Z-pinch discharge as a plasma source for absorption spectroscopy investigations

International Nuclear Information System (INIS)

Sandolache, Gabriela; Zoita, Vasile; Iova, Iancu; Fleurier, Claude; Hong, Dunpin; Bauchire, Jean Marc

2002-01-01

The characterisation of the low voltage circuit breaker arc from the optical and plasma physics points of view represents an element of importance for understanding the operating mechanism and the current interruption process. The development of the broad band optical absorption spectroscopy method seems to be well adapted in order to perform the circuit breaker arc analysis. A pulsed power device based on a Z-pinch type discharge has been developed as a plasma source for absorption spectroscopy investigations. The spatial extension of this radiation source, its brightness, reproducibility are well adapted to characterize the circuit-breaker arc. In addition, a very short emission period compared to the lifetime of the arc discharge provides an excellent time resolution for the absorption spectroscopy method. The first compression phase of the linear pinch produced in argon has been studied from the point of view of its use as a light source. The initial pressure of argon was varied from 0.5 to 2 mbar and the condenser bank energy from 5.1 to 8.7 kJ. The characterization of the emitted radiation, especially the influence of the condenser bank voltage and the argon pressure on the discharge has been studied. Collapse dynamics of the argon compressional pinch and the spectrally resolved continuum emission at the time of maximum compression have been observed. A very satisfactory plasma source optimisation has been achieved that fulfils the conditions required for the absorption spectroscopy method. (authors)

Stability analysis of sharp-boundary Vlasov-fluid screw-pinch equilibria

International Nuclear Information System (INIS)

Lewis, H.R.; Turner, L.

1975-01-01

The Vlasov-fluid model is being used to study the linear stability of sharp-boundary screw pinches numerically. The numerical method appears to work well, and some preliminary results are reported. The sharp-boundary calculation is useful for gaining insight and for comparing with known MHD results. (auth)

Multidisciplinary Inverse Reliability Analysis Based on Collaborative Optimization with Combination of Linear Approximations

Directory of Open Access Journals (Sweden)

Xin-Jia Meng

2015-01-01

Full Text Available Multidisciplinary reliability is an important part of the reliability-based multidisciplinary design optimization (RBMDO. However, it usually has a considerable amount of calculation. The purpose of this paper is to improve the computational efficiency of multidisciplinary inverse reliability analysis. A multidisciplinary inverse reliability analysis method based on collaborative optimization with combination of linear approximations (CLA-CO is proposed in this paper. In the proposed method, the multidisciplinary reliability assessment problem is first transformed into a problem of most probable failure point (MPP search of inverse reliability, and then the process of searching for MPP of multidisciplinary inverse reliability is performed based on the framework of CLA-CO. This method improves the MPP searching process through two elements. One is treating the discipline analyses as the equality constraints in the subsystem optimization, and the other is using linear approximations corresponding to subsystem responses as the replacement of the consistency equality constraint in system optimization. With these two elements, the proposed method realizes the parallel analysis of each discipline, and it also has a higher computational efficiency. Additionally, there are no difficulties in applying the proposed method to problems with nonnormal distribution variables. One mathematical test problem and an electronic packaging problem are used to demonstrate the effectiveness of the proposed method.

Global numerical modeling of magnetized plasma in a linear device

DEFF Research Database (Denmark)

Magnussen, Michael Løiten

Understanding the turbulent transport in the plasma-edge in fusion devices is of utmost importance in order to make precise predictions for future fusion devices. The plasma turbulence observed in linear devices shares many important features with the turbulence observed in the edge of fusion dev...... with simulations performed at different ionization levels, using a simple model for plasma interaction with neutrals. It is found that the steady state and the saturated state of the system bifurcates when the neutral interaction dominates the electron-ion collisions.......Understanding the turbulent transport in the plasma-edge in fusion devices is of utmost importance in order to make precise predictions for future fusion devices. The plasma turbulence observed in linear devices shares many important features with the turbulence observed in the edge of fusion...... devices, and are easier to diagnose due to lower temperatures and a better access to the plasma. In order to gain greater insight into this complex turbulent behavior, numerical simulations of plasma in a linear device are performed in this thesis. Here, a three-dimensional drift-fluid model is derived...

Z-pinches

International Nuclear Information System (INIS)

Yan'kov, V.V.

1991-01-01

The development of Z-pinches, including plasma foci, micropinches and dense Z-pinches are reviewed. A special attention is paid to the physics of sausage instability development. Theoretical questions are discussed in more detail that the experimental ones, recent works - to a fuller extent than the fundamental pioneer ones which are included in the textbooks. The Soviet works are given a greater coverage as compared to the foreign ones. An emphasis is made on the problem of controlled thermonuclear fusion

Velocity-space particle loss in field-reversed theta pinches

International Nuclear Information System (INIS)

Hsiao, M.Y.

1983-01-01

A field-reversed theta pinch (FRTP) is a compact device for magnetic fusion. It has attracted much attention in recent years since encouraging experimental results have been obtained. However, the definite causes for the observed particle loss rate and plasma rotation are not well known. In this work, we study the velocity-space particle loss (VSPL), i.e., particle loss due to the existence of a loss region in velocity space, in FRTP's in order to have a better understanding about the characteristics of this device

Finite Larmor radius effects on Z-pinch stability

International Nuclear Information System (INIS)

Scheffel, J.; Faghihi, M.

1987-10-01

The effect of finite Larmor radius (FLR) on the stability of m=1 small axial wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. We use the Incompressible FLR MHD model; a collisionless fluid model which consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD 2rdp/dr+m 2 B 2 /μ 0 >=0 predicts instability for internal modes unless the current density becomes singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the FLR terms are included, a normal mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall terms have a damping, however not stabilizing, effect, in agreement with earlier work. Specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m=1 modes are then fully stabilized over the cross-section for wavelengths λ/a max =3-5x10 18 m -1 is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 10 20 m -1 . (authors)

A spectroscopic study of radiation produced in a theta-pinch

International Nuclear Information System (INIS)

Trigueiros, A.; Machida, M.; Pagan, C.J.B.

1988-01-01

Preliminary results of the analysis of the spectra of four times ionized Krypton, Kr-V, are presented. 28 transitions were classified and for five of then the classification is new. We also present the UNICAMP theta-pinch for the study of highly ionized atoms. This device is now in testing. (author) [pt

Experimental study of ultra-low q discharges in the linear Extrap L1 device

International Nuclear Information System (INIS)

Brunsell, P.; Karlsson, Per.

1991-01-01

Linear pinch discharges with combined octupole and longitudinal magnetic fields are experimentally studied in the Extrap L1 device. Plasma currents are around I p =10 kA, plasma temperautres are up to T e =50 eV and plasma densities are of the order of n=5x10 21 m -3 . The plasma equilibria are in the ultra-low q (ULQ) regime corresponding to operation with plasma currents in excess of the Kruskal-Shafranov stability limit (q less than 1). The plasma current exhibits the typical time behaviour seen in toroidal ULQ experiments; the unstable setting up phase and the step-wise decay with current levels corresponding to q-values in windows between rational values. Longitudinal plasma current generated by radial plasma diffusion is seen, with amplitudes up to 30% of the externally driven current during the initial phase of the discharge. The effect of the octupole magnetic field on the ULQ confinement is investigated. The plasma temperature increases by more than a factor of two, for the optimum octupole rod current (I v =I p ), compared to the case without octupole field. A plasma current limitation for stable operation corresponding to q bigger than 1/2 is observed, excepts for low axial magnetic field strength. In the low axial field regime, the octupole field alone provides sufficient stabilization for operation with q less than 1/2. Plasma density and temperature both increase linearly with applied axial magnetic field. The density shows a strong, approximately exponential, dependence on discharge voltage. (au)

A short-pulse mode for the SPHINX LTD Z-pinch driver

Science.gov (United States)

D'Almeida, Thierry; Lassalle, Francis; Zucchini, Frederic; Loyen, Arnaud; Morell, Alain; Chuvatin, Alexander

2015-11-01

The SPHINX machine is a 6MA, 1 μs, LTD Z-pinch driver at CEA Gramat (France) and primarily used for studying radiation effects. Different power amplification concepts were examined in order to reduce the current rise time without modifying the generator discharge scheme, including the Dynamic Load Current Multiplier (DLCM) proposed by Chuvatin. A DLCM device, capable of shaping the current pulse without reducing the rise time, was developed at CEA. This device proved valuable for isentropic compression experiments in cylindrical geometry. Recently, we achieved a short pulse operation mode by inserting a vacuum closing switch between the DLCM and the load. The current rise time was reduced to ~300 ns. We explored the use of a reduced-height wire array for the Dynamic Flux Extruder in order to improve the wire array compression rate and increase the efficiency of the current transfer to the load. These developments are presented. Potential benefits of these developments for future Z pinch experiments are discussed.

Pinch Related Research At Institute For Plasma Research, India

International Nuclear Information System (INIS)

Shyam, Anurag

2006-01-01

Several pinch related experiment, their drivers and related diagnostics are being developed in our laboratory. The first set of experiments is to investigate various aspects of magnetized target fusion (MTF/MAGO). To drive the liner, in Z or theta pinch configuration, a 1.2 MJ, 3.6 MA capacitor bank is developed. For liner diagnostics flash radiography, VISAR and pyrometery are being developed. To produce magnetized (target) plasma a 120 kJ, 3 MA and several other banks are developed. Hot magnetized Plasma will be diagnosed by optical schlieren, interferometery and X-Ray spectrometry. A terra-watt system consisting of a Marx bank and water line delivering 800 kA at 1.6 MV will be commissioned, soon. The device will be used to study different pinch (wire array) configurations for production of electro-magnetic radiations. Smaller pulsed power systems, consisting of 1MV/500 kV Marx bank/tesla transformer and than water or solid state (cables) pulse forming network (coax) are also being developed for capillary discharge and other experiments. Two plasma foci experiments are also being conducted. The effort is produce a repetitively operating compact plasma focus

New bifocal pinch experiment SPEED 3

International Nuclear Information System (INIS)

Raacke, J.; Berntien, U.; Decker, G.; Kies, W.; Roewekamp, P.

1996-01-01

The SPEED 3 compact plasma focus device will be used as a soft x-ray source for various practical applications. It exploits a bifocal configuration with a plane insulator, very short accelerator and a hollow inner electrode. The discharge is driven by eight parallel two-stage Marx modules, capable of delivering up to 1.25 MA of current with the rise time of 0.3 s. The key parts of the device, the plasma diagnostic systems used, and the processes in the discharge are described in the paper. Framing camera pictures of a typical discharge are shown for illustration. The results of preliminary experiments are discussed, dealing almost exclusively with the discharge inaction, sheath and pinch formation. (J.U.). 1 tab., 3 figs., 2 refs

New bifocal pinch experiment SPEED 3

Energy Technology Data Exchange (ETDEWEB)

Raacke, J; Berntien, U; Decker, G; Kies, W; Roewekamp, P [Heinrich-Heine-Univ., Duesseldorf (Germany). Inst. fuer Experimentalphysik

1997-12-31

The SPEED 3 compact plasma focus device will be used as a soft x-ray source for various practical applications. It exploits a bifocal configuration with a plane insulator, very short accelerator and a hollow inner electrode. The discharge is driven by eight parallel two-stage Marx modules, capable of delivering up to 1.25 MA of current with the rise time of 0.3 s. The key parts of the device, the plasma diagnostic systems used, and the processes in the discharge are described in the paper. Framing camera pictures of a typical discharge are shown for illustration. The results of preliminary experiments are discussed, dealing almost exclusively with the discharge inaction, sheath and pinch formation. (J.U.). 1 tab., 3 figs., 2 refs.

Upper pinch radius limit in EXTRAP

International Nuclear Information System (INIS)

Lehnert, B.

1989-12-01

A simple static equilibrium model of the Z-pinch is considered where a hot plasma core is surrounded by a cold-mantle (gas blanket). The pinch radius, defined as the radial extension of the fully ionized plasma core, is uniquely determined by the plasma particle. momentum and heat balance equations. In Extrap configurations an octupole field is introduced which imposes a magnetic separatrix on Z-pinch geometry. This makes the conditions for Extrap equilibrium 'overdetermined' when the characteristic pinch radium given by the plasma parameters tends to exceed the characteristic radius of the magnetic separatrix. In this case no conventional pinch equilibrium can exist, and part of the current which is forced into the plasma discharge by external sources must be channelled outside of the separatrix, i.e. into the surrounding support structure of the Extrap conductors and the vessel walls. A possibly existing bootstrap current in the plasma boundary layer is further expected to be 'scraped off' in this case. The present paper gives some illustrations of the marginal case of this upper pinch radius limit, in a state where the pinch current is antiparallel to the external rod currents which generate the octupole field. (authors)

Introduction to Pinch Technology

DEFF Research Database (Denmark)

Rokni, Masoud

? How to put energy efficiency and other targets like reducing emissions, increasing plant capacities, improve product qualities etc, into a one coherent strategic plan for the overall site? All these questions and more can be answered with a full understanding of Pinch Technology and an awareness...... of the available tools for applying it in a practical way. The aim here is to provide the basic knowledge of pinch technology concept and how it can be applied across a wide range of process industries. The pinch technology was proposed firstly for optimization of heat exchangers and therefore it is introduced...

D-D fusion experiments using fast z pinches

International Nuclear Information System (INIS)

Spielman, R.B.; Baldwin, G.T.; Cooper, G.

1994-01-01

The development of high current (I > 10 MA) drivers provides us with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I 2 and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast ( 2 fiber arrays were imploded in a fast z-pinch configuration on Sandia's Saturn facility generating up to 3 x 10 12 D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, we intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices

D-D fusion experiments using fast Z pinches

International Nuclear Information System (INIS)

Spielman, R.B.; Baldwin, G.T.; Cooper, G.

1998-03-01

The development of high current (I > 10 MA) drivers provides the authors with a new tool for the study of neutron-producing plasmas in the thermal regime. The imploded deuterium mass (or collisionality) increases as I 2 and the ability of the driver to heat the plasma to relevant fusion temperatures improves as the power of the driver increases. Additionally, fast ( 2 fiber arrays were imploded in a fast z-pinch configuration on Sandia's Saturn facility generating up to 3 x 10 12 D-D neutrons. These experiments were designed to explore the physics of neutron-generating plasmas in a z-pinch geometry. Specifically, the authors intended to produce neutrons from a nearly thermal plasma where the electrons and ions have a nearly Maxwellian distribution. This is to be clearly differentiated from the more usual D-D beam-target neutrons generated in many dense plasma focus (DPF) devices

High density linear systems for fusion power

International Nuclear Information System (INIS)

Ellis, W.R.; Krakowski, R.A.

1975-01-01

The physics and technological limitations and uncertainties associated with the linear theta pinch are discussed in terms of a generalized energy balance, which has as its basis the ratio (Q/sub E/) of total electrical energy generated to net electrical energy consumed. Included in this total is the virtual energy of bred fissile fuel, if a hybrid blanket is used, as well as the actual of real energy deposited in the blanket by the fusion neutron. The advantages and disadvantages of the pulsed operation demanded by the linear theta pinch are also discussed

Simulation of high-energy particle production through sausage and kink instabilities in pinched plasma discharges

International Nuclear Information System (INIS)

Haruki, Takayuki; Yousefi, Hamid Reza; Masugata, Katsumi; Sakai, Jun-Ichi; Mizuguchi, Yusuke; Makino, Nao; Ito, Hiroaki

2006-01-01

In an experimental plasma, high-energy particles were observed by using a plasma focus device, to obtain energies of a few hundred keV for electrons, up to MeV for ions. In order to study the mechanism of high-energy particle production in pinched plasma discharges, a numerical simulation was introduced. By use of a three-dimensional relativistic and fully electromagnetic particle-in-cell code, the dynamics of a Z-pinch plasma, thought to be unstable against sausage and kink instabilities, are investigated. In this work, the development of sausage and kink instabilities and subsequent high-energy particle production are shown. In the model used here, cylindrically distributed electrons and ions are driven by an external electric field. The driven particles spontaneously produce a current, which begins to pinch by the Lorentz force. Initially the pinched current is unstable against a sausage instability, and then becomes unstable against a kink instability. As a result high-energy particles are observed

Intrinsic suppression of turbulence in linear plasma devices

Science.gov (United States)

Leddy, J.; Dudson, B.

2017-12-01

Plasma turbulence is the dominant transport mechanism for heat and particles in magnetised plasmas in linear devices and tokamaks, so the study of turbulence is important in limiting and controlling this transport. Linear devices provide an axial magnetic field that serves to confine a plasma in cylindrical geometry as it travels along the magnetic field from the source to the strike point. Due to perpendicular transport, the plasma density and temperature have a roughly Gaussian radial profile with gradients that drive instabilities, such as resistive drift-waves and Kelvin-Helmholtz. If unstable, these instabilities cause perturbations to grow resulting in saturated turbulence, increasing the cross-field transport of heat and particles. When the plasma emerges from the source, there is a time, {τ }\\parallel , that describes the lifetime of the plasma based on parallel velocity and length of the device. As the plasma moves down the device, it also moves azimuthally according to E × B and diamagnetic velocities. There is a balance point in these parallel and perpendicular times that sets the stabilisation threshold. We simulate plasmas with a variety of parallel lengths and magnetic fields to vary the parallel and perpendicular lifetimes, respectively, and find that there is a clear correlation between the saturated RMS density perturbation level and the balance between these lifetimes. The threshold of marginal stability is seen to exist where {τ }\\parallel ≈ 11{τ }\\perp . This is also associated with the product {τ }\\parallel {γ }* , where {γ }* is the drift-wave linear growth rate, indicating that the instability must exist for roughly 100 times the growth time for the instability to enter the nonlinear growth phase. We explore the root of this correlation and the implications for linear device design.

Characterization of laser-cut copper foil X-pinches

Science.gov (United States)

Collins, G. W.; Valenzuela, J. C.; Hansen, S. B.; Wei, M. S.; Reed, C. T.; Forsman, A. C.; Beg, F. N.

2016-10-01

Quantitative data analyses of laser-cut Cu foil X-pinch experiments on the 150 ns quarter-period, ˜250 kA GenASIS driver are presented. Three different foil designs are tested to determine the effects of initial structure on pinch outcome. Foil X-pinch data are also presented alongside the results from wire X-pinches with comparable mass. The X-ray flux and temporal profile of the emission from foil X-pinches differed significantly from that of wire X-pinches, with all emission from the foil X-pinches confined to a ˜3 ns period as opposed to the delayed, long-lasting electron beam emission common in wire X-pinches. Spectroscopic data show K-shell as well as significant L-shell emission from both foil and wire X-pinches. Fits to synthetic spectra using the SCRAM code suggest that pinching foil X's produced a ˜1 keV, ne ≥ 1023 cm-3 plasma. The spectral data combined with the improved reliability of the source timing, flux, and location indicate that foil X-pinches generate a reproducible, K-shell point-projection radiography source that can be easily modified and tailored to suit backlighting needs across a variety of applications.

Studies of end loss from a theta pinch using a Twyman--Green interferometer. Scientific report 77-4

International Nuclear Information System (INIS)

Freeman, R.S.

1977-11-01

The transient rate of flow of plasma from the ends of a short, high density, low temperature linear theta pinch was studied experimentally and analytically. Diagnostic devices were used to study the discharge and plasma properties; these included a Rogowski coil, a magnetic field probe and a Twyman-Green double pass interferometer which was illuminated by a 7 mW He--He laser. The interferometer was used to monitor the passage of fringes with respect to time at two radial positions simultaneously by the use of a photodetector consisting of two fast silicon photodiodes with supporting circuitry. One complete fringe represented a change in number density of 2.942 x 10 16 cm -3

Inverse scattering solution of non-linear evolution equations in one space dimension: an introduction

International Nuclear Information System (INIS)

Alvarez-Estrada, R.F.

1979-01-01

A comprehensive review of the inverse scattering solution of certain non-linear evolution equations of physical interest in one space dimension is presented. We explain in some detail the interrelated techniques which allow to linearize exactly the following equations: (1) the Korteweg and de Vries equation; (2) the non-linear Schrodinger equation; (3) the modified Korteweg and de Vries equation; (4) the Sine-Gordon equation. We concentrate in discussing the pairs of linear operators which accomplish such an exact linearization and the solution of the associated initial value problem. The application of the method to other non-linear evolution equations is reviewed very briefly

Linear studies of resistive interchange modes in a cylindrical reversed field pinch

International Nuclear Information System (INIS)

Mirin, A.A.; O'Neill, N.J.; Killeen, J.; Bonugli, R.J.; Ellis, M.J.

1986-01-01

Resistive interchange modes in a cylindrical reversed field pinch are studied using a one-dimensional, linear, compressible initial value code. Separate equations for the electron and ion temperature perturbations are solved. Hall terms and the thermal force vector are included in Ohm's law. Anisotropic thermal conductivity and viscosity are included in the code model. Calculations are carried out for various values of poloidal and toroidal mode number, Lundquist number, Suydam parameter, Hall parameter, thermal conductivity, viscosity, etc., with respect to uniform density equilibria known to be stable to tearing modes. It is shown that in the cold ion limit sufficiently large Hall terms cause all modes that are tested to become stable. However for T/sub i/ = T/sub e/ and ignoring the effects of viscosity and thermal conductivity, there is a critical value of the ratio of Alfven to ion cyclotron frequency above which the ''even'' mode not only dominates the ''odd'' mode but is likely to have a growth rate significantly larger than that of the odd mode in the absence of Hall terms. Inclusion of a classical tensor thermal conductivity, while having little effect on the odd mode in the absence of Hall terms, does stabilize the even mode for sufficiently large Hall parameter. Inclusion of a classical tensor viscosity reduces the growth rate of (but does not necessarily stabilize) the odd mode. Inclusion of Hall and thermal force terms, tensor thermal conductivity and tensor viscosity causes all modes that are tested to stabilize. Results are compared to other contemporary studies

Chamber and Wall Response to Target Implosion in Inertial and Z-Pinch Fusion and Lithography Devices

International Nuclear Information System (INIS)

Hassanein, A.; Konkashbaev, I.; Morozov, V.; Sizyuk, V.

2006-01-01

The chamber walls, both solid and liquid, in inertial fusion energy (IFE) and Z-pinch reactors and Lithography devices are exposed to harsh conditions following each target implosion or pinching of plasma. Key issues of the cyclic IFE operation include intense photon and ion deposition, wall thermal and hydrodynamic evolution, wall erosion and fatigue lifetime, and chamber clearing and evacuation to ensure desirable conditions prior to target implosion. Detailed models have been developed for reflected laser light, emitted photons, neutrons, and target debris deposition and interaction with chamber components and have been implemented in the comprehensive HEIGHTS software package. The hydrodynamic response of chamber walls in bare or in gas-filled cavities and the photon transport of the deposited energy has been calculated by means of new and advanced numerical techniques for accurate shock treatment and propagation. These models include detail media hydrodynamics, non-LTE multi-group for both continuum and line radiation transport, and dynamics of eroded debris resulting from the intense energy deposition. The focus of this study is to critically assess the reliability and the dynamic response of chamber walls in various proposed protection methods for IFE systems. Key requirements are that: (i) the chamber wall accommodates the cyclic energy deposition while providing the required lifetime due to various erosion mechanisms, such as vaporization, chemical and physical sputtering, melt/liquid splashing and explosive erosion, and fragmentation of liquid walls, and (ii) after each shot the chamber is cleared and returned to a quiescent state in preparation for the target injection and the firing of the driver for the subsequent shot. This paper investigates in details these two important issues and found that the required operating frequency of the IFE reactors for power production may be severely limited due to these two requirements. (author)

Measurements of high-current electron beams from X pinches and wire array Z pinches

International Nuclear Information System (INIS)

Shelkovenko, T. A.; Pikuz, S. A.; Blesener, I. C.; McBride, R. D.; Bell, K. S.; Hammer, D. A.; Agafonov, A. V.; Romanova, V. M.; Mingaleev, A. R.

2008-01-01

Some issues concerning high-current electron beam transport from the X pinch cross point to the diagnostic system and measurements of the beam current by Faraday cups are discussed. Results of computer simulation of electron beam propagation from the pinch to the Faraday cup give limits for the measured current for beams having different energy spreads. The beam is partially neutralized as it propagates from the X pinch to a diagnostic system, but within a Faraday cup diagnostic, space charge effects can be very important. Experimental results show evidence of such effects.

Fiber Z-pinch experiments and calculations in the finite Larmor radius regime

International Nuclear Information System (INIS)

Haines, M.G.; Dangor, A.E.; Coppins, M.

1996-01-01

The dense Z-pinch project at Imperial College is aimed at achieving radiative collapse to high density in a hydrogen plasma, and also to study plasmas close to controlled fusion conditions. To this end, the MAGPIE generator (2.4 MV, 1.25 Ω, and 200 ns) has been built and tested, and is now giving preliminary experimental data at 60% of full voltage for carbon and CD 2 fibers. These discharges are characterized by an initial radial expansion followed by the occurrence of m = 0 structures with transient X-ray emission from bright spots. Late in the discharge a disruption can occur, accompanied by hard X-ray emission from the anode due to an energetic electron beam and, in the case of CD 2 fibers, a neutron burst. Concomitant theoretical studies have solved the linear stability problem for a Z-pinch with large ion Larmor radii, showing that a reduction in growth rate of m = 0 and m = 1 modes to about 20% of the magnetohydrodynamic (MHD) value can occur for a parabolic density profile when the Larmor radius is optimally 20% of the pinch radius. Two-dimensional MHD simulations of Z-pinches in two extremes of focussed short-pulse laser-plasma interactions and of galactic jets reveal a nonlinear stabilizing effect in the presence of sheared flow. One-dimensional simulations show that at low line density the lower hybrid drift instability can lead to coronal radial expansion of a Z-pinch plasma. (Author)

Lower pinch radius limit in EXTRAP

International Nuclear Information System (INIS)

Lehnert, B.

1989-01-01

In an Extrap pinch there is a superimposed magnetic octupole field which forms a magnetic separatrix with the field generated by the pinch current. Earlier experiments have shown that the octupole field has a stabilizing influence on the plasma. Regardless of the details of this stabilizing mechanism, it is expected that the influence of the octupole field should become negligible for a sufficiently small ratio between the characteristic pinch and separatrix radii. In other words, there should exist a lower limit of this ratio below which the system approaches the state of an ordinary unstabilized Z-pinch. The present paper presents an extended version of an earlier theoretical model of this lower limit, and its relation to the corresponding critical ratio between the external conductor and pinch currents. This ratio is found to vary substantially with the plasma parameters. (authors)

Research on pinch devices of tens of kA to MA

Energy Technology Data Exchange (ETDEWEB)

Soto, L.; Silva, P.; Moreno, J.; Silvester, G.; Zambra, M. [Comision Chilena de Energia Nuclear, Santiago (Chile); Pavez, C.; Saavedra, R. [Univ. de Concepcion (Chile); Bruzzone, H. [Pladema (Antiqua and Barbuda)]|[Univ. de Mar del Plata and CONICET (Argentina); Barbaglia, M. [Pladema (Antiqua and Barbuda); Mayer, R. [Pladema (Antiqua and Barbuda)]|[Inst. Balseiro, Bariloche, CNEA and CONICET (Argentina); Sidelnikov, Y.; Kies, W. [Heinrich-Heine-Univ., Duesseldorf (Germany)

2004-07-01

At present the Plasma Physics and Plasma Technology Group of the Comision Chilena de Energia Nuclear (CCHEN) has the experimental facilities in order to study dense transient discharges in a wide range of energy and current, namely: (I) energy from tens of joules to hundred of kilojoules, (II) current from tens of kiloamperes to some mega-amperes. Also several diagnostics have been implemented. An overview of the work being carried out on dense pinch discharges at the Comision Chilena de Energia Nuclear is presented. (orig.)

Research on pinch devices of tens of kA to MA

International Nuclear Information System (INIS)

Soto, L.; Silva, P.; Moreno, J.; Silvester, G.; Zambra, M.; Pavez, C.; Saavedra, R.; Bruzzone, H.; Barbaglia, M.; Mayer, R.; Sidelnikov, Y.; Kies, W.

2004-01-01

At present the Plasma Physics and Plasma Technology Group of the Comision Chilena de Energia Nuclear (CCHEN) has the experimental facilities in order to study dense transient discharges in a wide range of energy and current, namely: (I) energy from tens of joules to hundred of kilojoules, (II) current from tens of kiloamperes to some mega-amperes. Also several diagnostics have been implemented. An overview of the work being carried out on dense pinch discharges at the Comision Chilena de Energia Nuclear is presented. (orig.)

An ultra miniature pinch-focus discharge

International Nuclear Information System (INIS)

Soto, L.; Pavez, C.; Moreno, J.; Pavez, C.; Barbaglia, M.; Clausse, A.

2004-01-01

As a way to investigate the minimum energy to produce a pinch plasma focus discharge, an ultra miniature device has been designed and constructed (nano focus NF: 5 nF, 5-10 kV, 5-10 kA, 60-250 mJ, 16 ns time to peak current). Sub-millimetric anode radius covered by a coaxial insulator were used for experiments in hydrogen. Evidence of pinch was observed in electrical signals in discharges operating at 60 mJ. A single-frame image converter camera (4 ns exposure) was used to obtain plasma images in the visible range. The dynamics observed from the photographs is consistent with: a) formation of a plasma sheath close to the insulator surface, b) fast axial motion of the plasma sheath, c) radial compression over the anode, and d) finally the plasma is detached from the anode in the axial direction. The total time since stage a) to d) was observed to be about 30 ns. X ray and neutron emission is being studied. Neutron yield of the order of 10 3 neutrons per shot is expected for discharges operating in deuterium at 10 kA. (authors)

Reversed-Field Pinch plasma model

International Nuclear Information System (INIS)

Miley, G.H.; Nebel, R.A.; Moses, R.W.

1979-01-01

The stability of a Reversed-Field Pinch (RFP) is strongly dependent on the plasma profile and the confining sheared magnetic field. Magnetic diffusion and thermal transport produce changing conditions of stability. Despite the limited understanding of RFP transport, modelling is important to predict general trends and to study possible field programming options. To study the ZT-40 experiment and to predict the performance of future RFP reactors, a one-dimensional transport code has been developed. This code includes a linear, ideal MHD stability check based on an energy principle. The transport section integrates plasma profiles forward in time while the stability section periodically checks the stability of the evolving plasma profile

Contributed Review: Experimental characterization of inverse piezoelectric strain in GaN HEMTs via micro-Raman spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Bagnall, Kevin R.; Wang, Evelyn N. [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2016-06-15

Micro-Raman thermography is one of the most popular techniques for measuring local temperature rise in gallium nitride (GaN) high electron mobility transistors with high spatial and temporal resolution. However, accurate temperature measurements based on changes in the Stokes peak positions of the GaN epitaxial layers require properly accounting for the stress and/or strain induced by the inverse piezoelectric effect. It is common practice to use the pinched OFF state as the unpowered reference for temperature measurements because the vertical electric field in the GaN buffer that induces inverse piezoelectric stress/strain is relatively independent of the gate bias. Although this approach has yielded temperature measurements that agree with those derived from the Stokes/anti-Stokes ratio and thermal models, there has been significant difficulty in quantifying the mechanical state of the GaN buffer in the pinched OFF state from changes in the Raman spectra. In this paper, we review the experimental technique of micro-Raman thermography and derive expressions for the detailed dependence of the Raman peak positions on strain, stress, and electric field components in wurtzite GaN. We also use a combination of semiconductor device modeling and electro-mechanical modeling to predict the stress and strain induced by the inverse piezoelectric effect. Based on the insights gained from our electro-mechanical model and the best values of material properties in the literature, we analyze changes in the E{sub 2} high and A{sub 1} (LO) Raman peaks and demonstrate that there are major quantitative discrepancies between measured and modeled values of inverse piezoelectric stress and strain. We examine many of the hypotheses offered in the literature for these discrepancies but conclude that none of them satisfactorily resolves these discrepancies. Further research is needed to determine whether the electric field components could be affecting the phonon frequencies apart from the

Contributed Review: Experimental characterization of inverse piezoelectric strain in GaN HEMTs via micro-Raman spectroscopy

International Nuclear Information System (INIS)

Bagnall, Kevin R.; Wang, Evelyn N.

2016-01-01

Micro-Raman thermography is one of the most popular techniques for measuring local temperature rise in gallium nitride (GaN) high electron mobility transistors with high spatial and temporal resolution. However, accurate temperature measurements based on changes in the Stokes peak positions of the GaN epitaxial layers require properly accounting for the stress and/or strain induced by the inverse piezoelectric effect. It is common practice to use the pinched OFF state as the unpowered reference for temperature measurements because the vertical electric field in the GaN buffer that induces inverse piezoelectric stress/strain is relatively independent of the gate bias. Although this approach has yielded temperature measurements that agree with those derived from the Stokes/anti-Stokes ratio and thermal models, there has been significant difficulty in quantifying the mechanical state of the GaN buffer in the pinched OFF state from changes in the Raman spectra. In this paper, we review the experimental technique of micro-Raman thermography and derive expressions for the detailed dependence of the Raman peak positions on strain, stress, and electric field components in wurtzite GaN. We also use a combination of semiconductor device modeling and electro-mechanical modeling to predict the stress and strain induced by the inverse piezoelectric effect. Based on the insights gained from our electro-mechanical model and the best values of material properties in the literature, we analyze changes in the E_2 high and A_1 (LO) Raman peaks and demonstrate that there are major quantitative discrepancies between measured and modeled values of inverse piezoelectric stress and strain. We examine many of the hypotheses offered in the literature for these discrepancies but conclude that none of them satisfactorily resolves these discrepancies. Further research is needed to determine whether the electric field components could be affecting the phonon frequencies apart from the inverse

Point source reconstruction principle of linear inverse problems

International Nuclear Information System (INIS)

Terazono, Yasushi; Matani, Ayumu; Fujimaki, Norio; Murata, Tsutomu

2010-01-01

Exact point source reconstruction for underdetermined linear inverse problems with a block-wise structure was studied. In a block-wise problem, elements of a source vector are partitioned into blocks. Accordingly, a leadfield matrix, which represents the forward observation process, is also partitioned into blocks. A point source is a source having only one nonzero block. An example of such a problem is current distribution estimation in electroencephalography and magnetoencephalography, where a source vector represents a vector field and a point source represents a single current dipole. In this study, the block-wise norm, a block-wise extension of the l p -norm, was defined as the family of cost functions of the inverse method. The main result is that a set of three conditions was found to be necessary and sufficient for block-wise norm minimization to ensure exact point source reconstruction for any leadfield matrix that admit such reconstruction. The block-wise norm that satisfies the conditions is the sum of the cost of all the observations of source blocks, or in other words, the block-wisely extended leadfield-weighted l 1 -norm. Additional results are that minimization of such a norm always provides block-wisely sparse solutions and that its solutions form cones in source space

Warm dense matter study and pulsed-power developments for X-pinch equipment in Nagaoka University of Technology

International Nuclear Information System (INIS)

Sasaki, Toru; Miki, Yasutoshi; Tachinami, Fumitaka; Saito, Hirotaka; Takahashi, Takuya; Anzai, Nobuyuki; Kikuchi, Takashi; Aso, Tsukasa; Harada, Nob.

2014-01-01

In order to explore high energy density physics, we have performed WDM experiment by using several pulsed-power devices. To generate well-defined warm dense state for evaluating electrical conductivity and its properties, we have proposed an isochoric heating of foamed metal by using pulsed-power discharge. The proposed technique yields the electrical conductivity of warm dense matter with a well-defined temperature. To observe the warm dense matter, a pulsed-power generator based on a pulse-forming-network (PFN) was studied toward generating an intense point-spot-like X-ray source from X-pinch technique. From comparison of the designing and the actual inductances of the X-pinch system, the actual inductance of X-pinch system is 3.5 times higher than the designing inductance. To reduce the total inductance of X-pinch system, we will modify the gap switch system such as multi spake gap

Analysis of pinching in deterministic particle separation

Science.gov (United States)

Risbud, Sumedh; Luo, Mingxiang; Frechette, Joelle; Drazer, German

2011-11-01

We investigate the problem of spherical particles vertically settling parallel to Y-axis (under gravity), through a pinching gap created by an obstacle (spherical or cylindrical, center at the origin) and a wall (normal to X axis), to uncover the physics governing microfluidic separation techniques such as deterministic lateral displacement and pinched flow fractionation: (1) theoretically, by linearly superimposing the resistances offered by the wall and the obstacle separately, (2) computationally, using the lattice Boltzmann method for particulate systems and (3) experimentally, by conducting macroscopic experiments. Both, theory and simulations, show that for a given initial separation between the particle centre and the Y-axis, presence of a wall pushes the particles closer to the obstacle, than its absence. Experimentally, this is expected to result in an early onset of the short-range repulsive forces caused by solid-solid contact. We indeed observe such an early onset, which we quantify by measuring the asymmetry in the trajectories of the spherical particles around the obstacle. This work is partially supported by the National Science Foundation Grant Nos. CBET- 0731032, CMMI-0748094, and CBET-0954840.

Model of emittance growth in a self-pinched beam

International Nuclear Information System (INIS)

Lee, E.P.; Yu, S.S.

1979-01-01

A semi-phenomenological formula is proposed for the change of emittance of a self-pinched beam which is not matched to its equilibrium radius. Near equilibrium this formula, coupled with an envelope equation, yields the damped sausage oscillations observed in simulation and experiments. For a beam which is injected cold (no transverse velocity spread), the formula coincides with the analytically calculated initial growth of emittance. The basic theory is developed here and used to compute the linear damping rate for several current profiles. The resultant non-linear increase in equilibrium quantities is also calculated in lowest order of the degree of mismatch

Injection molded pinched flow fractionation device for enrichment of somatic cells in cow milk

DEFF Research Database (Denmark)

Jensen, Marie Pødenphant; Marie, Rodolphe; Olesen, Tom

2014-01-01

In this paper the continuous microfluidic separation technique pinched flow fractionation is applied to the enrichment of somatic cells from cow milk. Somatic cells were separated from the smallest fat particles and proteins thus better imaging and analysis of the cells can be achieved...

H-Shaped Multiple Linear Motor Drive Platform Control System Design Based on an Inverse System Method

Directory of Open Access Journals (Sweden)

Caiyan Qin

2017-12-01

Full Text Available Due to its simple mechanical structure and high motion stability, the H-shaped platform has been increasingly widely used in precision measuring, numerical control machining and semiconductor packaging equipment, etc. The H-shaped platform is normally driven by multiple (three permanent magnet synchronous linear motors. The main challenges for H-shaped platform-control include synchronous control between the two linear motors in the Y direction as well as total positioning error of the platform mover, a combination of position deviation in X and Y directions. To deal with the above challenges, this paper proposes a control strategy based on the inverse system method through state feedback and dynamic decoupling of the thrust force. First, mechanical dynamics equations have been deduced through the analysis of system coupling based on the platform structure. Second, the mathematical model of the linear motors and the relevant coordinate transformation between dq-axis currents and ABC-phase currents are analyzed. Third, after the main concept of inverse system method being explained, the inverse system model of the platform control system has been designed after defining relevant system variables. Inverse system model compensates the original nonlinear coupled system into pseudo-linear decoupled linear system, for which typical linear control methods, like PID, can be adopted to control the system. The simulation model of the control system is built in MATLAB/Simulink and the simulation result shows that the designed control system has both small synchronous deviation and small total trajectory tracking error. Furthermore, the control program has been run on NI controller for both fixed-loop-time and free-loop-time modes, and the test result shows that the average loop computation time needed is rather small, which makes it suitable for real industrial applications. Overall, it proves that the proposed new control strategy can be used in

Characteristics of the TPE reversed-field pinch plasmas in conventional and improved confinement regimes

International Nuclear Information System (INIS)

Sakakita, H.; Asai, T.; Fiksel, G.; Yagi, Y.; Frassinetti, L.; Hayase, K.; Hirano, Y.; Kiyama, S.; Koguchi, H.; Shimada, T.; Innocente, P.; Spizzo, G.; Terranova, D.; Sato, Y.; Yoshikawa, M.

2005-01-01

We present the characteristics and experimental scaling laws of reversed-field pinch (RFP) plasmas, which are obtained from the recently established toroidal pinch experiment (TPE) database. The database contains information for approximately 1500 discharges consistently selected from four TPE RFP devices, and covers two decades of RFP experiments under conventional operating conditions at the National Institute of Advanced Industrial Science and Technology. We present the physics of the pulsed poloidal current drive (PPCD) discharges in the TPE-RX RFP device, and a comparison of the improved energy confinement time in PPCD, τ E P PCD , with τ E s caling as the reference scaling law (τ E s caling ∼ a 1.63 (I P 0.78 (I P /N) 0.33 Θ 2.97 ) in the TPE database, is attempted. The result shows that τ E P PCD agrees well with τ E s caling because of the strong pinch parameter dependence on the TPE scaling law. A potential improved confinement mode in the quasi-single-helicity (QSH) state is also investigated in TPE-RX, with respect to the operation conditions under which the QSH spontaneously appears in the core region, where a typical island structure is observed by means of soft Xray tomography. (author)

Pinch-off Scaling Law of Soap Bubbles

Science.gov (United States)

Davidson, John; Ryu, Sangjin

2014-11-01

Three common interfacial phenomena that occur daily are liquid drops in gas, gas bubbles in liquid and thin-film bubbles. One aspect that has been studied for these phenomena is the formation or pinch-off of the drop/bubble from the liquid/gas threads. In contrast to the formation of liquid drops in gas and gas bubbles in liquid, thin-film bubble pinch-off has not been well documented. Having thin-film interfaces may alter the pinch-off process due to the limiting factor of the film thickness. We observed the pinch-off of one common thin-film bubble, soap bubbles, in order to characterize its pinch-off behavior. We achieved this by constructing an experimental model replicating the process of a human producing soap bubbles. Using high-speed videography and image processing, we determined that the minimal neck radius scaled with the time left till pinch-off, and that the scaling law exponent was 2/3, similar to that of liquid drops in gas.

Linear theory of drift-tearing and interchange modes in a screw pinch

International Nuclear Information System (INIS)

Copenhaver, C.

1978-04-01

A drift dispersion relation, as applied to a resistive incompressible plasma in a screw pinch, is derived. This dispersion relation incorporates both drift-tearing and drift-interchange modes and is valid throughout the collisional regime by including kinetic theory factors. The dispersion relation reduces to the drift-tearing dispersion relation in the zero pressure gradient limit, and to the classical resistive dispersion relation in the zero drift limit. The electron temperature gradient instability is still present. Now, however, the introduction of the interchange-drift instability increases the growth rate further above the tearing-drift case. (orig.) [de

Two-Dimensional Linear Inversion of GPR Data with a Shifting Zoom along the Observation Line

Directory of Open Access Journals (Sweden)

Raffaele Persico

2017-09-01

Full Text Available Linear inverse scattering problems can be solved by regularized inversion of a matrix, whose calculation and inversion may require significant computing resources, in particular, a significant amount of RAM memory. This effort is dependent on the extent of the investigation domain, which drives a large amount of data to be gathered and a large number of unknowns to be looked for, when this domain becomes electrically large. This leads, in turn, to the problem of inversion of excessively large matrices. Here, we consider the problem of a ground-penetrating radar (GPR survey in two-dimensional (2D geometry, with antennas at an electrically short distance from the soil. In particular, we present a strategy to afford inversion of large investigation domains, based on a shifting zoom procedure. The proposed strategy was successfully validated using experimental radar data.

Conjugate heat transfer analysis of an energy conversion device with an updated numerical model obtained through inverse identification

International Nuclear Information System (INIS)

Hey, Jonathan; Malloy, Adam C.; Martinez-Botas, Ricardo; Lamperth, Michael

2015-01-01

Highlights: • Conjugate heat transfer analysis of an electric machine. • Inverse identification method for estimating the model parameters. • Experimentally determined thermal properties and electromagnetic losses. • Coupling of inverse identification method with a numerical model. • Improved modeling accuracy through introduction of interface material. - Abstract: Energy conversion devices undergo thermal loading during their operation as a result of inefficiencies in the energy conversion process. This will eventually lead to degradation and possible failure of the device if the heat generated is not properly managed. The ability to accurately predict the thermal behavior of such a device during the initial developmental stage is an important requirement. However, accurate predictions of critical temperature is challenging due to the variation of heat transfer parameters from one device to another. The ability to determine the model parameters is key to accurately representing the heat transfer in such a device. This paper presents the use of an inverse identification technique to estimate the model parameters of an energy conversion device designed for vehicular applications. To simulate the imperfect contact and the presence of insulating materials in the permanent magnet electric machine, thin material are introduced at the component interface of the numerical model. The proposed inverse identification method is used to estimate the equivalent thermal conductance of the thin material. In addition, the electromagnetic losses generated in the permanent magnet is also derived indirectly from the temperature measurement using the same method. With the thermal properties and input parameters of the numerical model obtained from the inverse identification method, the critical temperature of the device can be predicted more accurately. The deviation between the maximum measured and predicted winding temperature is less than 2.4%

Mixed linear-nonlinear fault slip inversion: Bayesian inference of model, weighting, and smoothing parameters

Science.gov (United States)

Fukuda, J.; Johnson, K. M.

2009-12-01

Studies utilizing inversions of geodetic data for the spatial distribution of coseismic slip on faults typically present the result as a single fault plane and slip distribution. Commonly the geometry of the fault plane is assumed to be known a priori and the data are inverted for slip. However, sometimes there is not strong a priori information on the geometry of the fault that produced the earthquake and the data is not always strong enough to completely resolve the fault geometry. We develop a method to solve for the full posterior probability distribution of fault slip and fault geometry parameters in a Bayesian framework using Monte Carlo methods. The slip inversion problem is particularly challenging because it often involves multiple data sets with unknown relative weights (e.g. InSAR, GPS), model parameters that are related linearly (slip) and nonlinearly (fault geometry) through the theoretical model to surface observations, prior information on model parameters, and a regularization prior to stabilize the inversion. We present the theoretical framework and solution method for a Bayesian inversion that can handle all of these aspects of the problem. The method handles the mixed linear/nonlinear nature of the problem through combination of both analytical least-squares solutions and Monte Carlo methods. We first illustrate and validate the inversion scheme using synthetic data sets. We then apply the method to inversion of geodetic data from the 2003 M6.6 San Simeon, California earthquake. We show that the uncertainty in strike and dip of the fault plane is over 20 degrees. We characterize the uncertainty in the slip estimate with a volume around the mean fault solution in which the slip most likely occurred. Slip likely occurred somewhere in a volume that extends 5-10 km in either direction normal to the fault plane. We implement slip inversions with both traditional, kinematic smoothing constraints on slip and a simple physical condition of uniform stress

High energy density Z-pinch plasmas using flow stabilization

Energy Technology Data Exchange (ETDEWEB)

Shumlak, U., E-mail: shumlak@uw.edu; Golingo, R. P., E-mail: shumlak@uw.edu; Nelson, B. A., E-mail: shumlak@uw.edu; Bowers, C. A., E-mail: shumlak@uw.edu; Doty, S. A., E-mail: shumlak@uw.edu; Forbes, E. G., E-mail: shumlak@uw.edu; Hughes, M. C., E-mail: shumlak@uw.edu; Kim, B., E-mail: shumlak@uw.edu; Knecht, S. D., E-mail: shumlak@uw.edu; Lambert, K. K., E-mail: shumlak@uw.edu; Lowrie, W., E-mail: shumlak@uw.edu; Ross, M. P., E-mail: shumlak@uw.edu; Weed, J. R., E-mail: shumlak@uw.edu [Aerospace and Energetics Research Program, University of Washington, Seattle, Washington, 98195-2250 (United States)

2014-12-15

The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes – Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. A sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results and

The physics of fast Z pinches

International Nuclear Information System (INIS)

Ryutov, D.D.; Derzon, M.S.; Matzen, M.K.

1998-07-01

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizes the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z-pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 52 figures and nearly 300 references

The Physics of Fast Z Pinches

Energy Technology Data Exchange (ETDEWEB)

RYUTOV,D.D.; DERZON,MARK S.; MATZEN,M. KEITH

1999-10-25

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 36 figures and more than 300 references.

Determining the resistance of X-pinch plasma

International Nuclear Information System (INIS)

Zhao Shen; Zhu Xin-Lei; Zhang Ran; Luo Hai-Yun; Zou Xiao-Bing; Wang Xin-Xin; Xue Chuang; Ning Cheng; Ding Ning; Shu Xiao-Jian

2013-01-01

The current and the voltage of an X-pinch were measured. The inductance of the X-pinch was assumed to be a constant and estimated by the calculation of the magnetic field based on the well-known Biot—Savart's Law. The voltage of the inductance was calculated with L · di/dt and subtracted from the measured voltage of the X-pinch. Then, the resistance of the X-pinch was determined and the following results were obtained. At the start of the current flow the resistance of the exploding wires is several tens of Ohms, one order of magnitude, higher than the metallic resistance of the wires at room temperature, and then it falls quickly to about 1 Ω, which reflects the physical processes occurring in the electrically exploding wires, i.e., a current transition from the highly resistive wire core to the highly conductive plasma. It was shown that the inductive contribution to the voltage of the X-pinch is less than the resistive contribution. For the wires we used, the wires' material and diameter have no strong influence on the resistance of the X-pinch, which may be explained by the fact that the current flows through the plasma rather than through the metallic wire itself. As a result, the current is almost equally divided between two parallel X-pinches even though the diameter and material of the wires used for these two X-pinches are significantly different. (physics of gases, plasmas, and electric discharges)

X-Pinch Plasma Generation Testing for Neutron Source Development and Nuclear Fusion

Directory of Open Access Journals (Sweden)

Hossam A.Gabbar

2018-04-01

Full Text Available Nuclear fusion is a sought-out technology in which two light elements are fused together to create a heavier element and releases energy. Two primary nuclear fusion technologies are being researched today: magnetic and inertial confinement. However, a new type of nuclear fusion technology is currently being research: multi-pinch plasma beams. At the University of Ontario Institute of Technology, there is research on multi-pinch plasma beam technology as an alternative to nuclear fusion. The objective is to intersect two plasma arcs at the center of the chamber. This is a precursor of nuclear fusion using multi-pinch. The innovation portion of the students’ work is the miniaturization of this concept using high energy electrical DC pulses. The experiment achieved the temperature of 2300 K at the intersection. In comparison to the simulation data, the temperature from the simulation is 7000 K at the intersection. Additionally, energy harvesting devices, both photovoltaics and a thermoelectric generator, were placed in the chamber to observe the viable energy extraction.

Progress on z-pinch inertial fusion energy

International Nuclear Information System (INIS)

Olson, C.; Rochau, G.; Matzen, M.K.

2005-01-01

The goal of z-pinch inertial fusion energy (IFE) is to extend the single-shot z-pinch inertial confinement fusion (ICF) results on Z to a repetitive-shot z-pinch power plant concept for the economical production of electricity. Z produces up to 1.8 MJ of x-rays at powers as high as 230 TW. Recent target experiments on Z have demonstrated capsule implosion convergence ratios of 14-21 with a double-pinch driven target, and DD neutron yields up to 8x10exp10 with a dynamic hohlraum target. For z-pinch IFE, a power plant concept is discussed that uses high-yield IFE targets (3 GJ) with a low rep-rate per chamber (0.1 Hz). The concept includes a repetitive driver at 0.1 Hz, a Recyclable Transmission Line (RTL) to connect the driver to the target, high-yield targets, and a thick-liquid wall chamber. Recent funding by a U.S. Congressional initiative for $4M for FY04 is supporting research on RTLs, repetitive pulsed power drivers, shock mitigation, full RTL cycle planned experiments, high-yield IFE targets, and z-pinch power plant technologies. Recent results of research in all of these areas are discussed, and a Road Map for Z-Pinch IFE is presented. (author)

History of the Z-pinch

International Nuclear Information System (INIS)

Lovberg, R.H.

1988-01-01

The plasma Z-Pinch occupies a unique position in the history of controlled fusion research as the first confinement and heating scheme to be tried experimentally. In contrast to the sophistication of programs being conducted today, in which extensive theoretical and experimental forces are in close collaboration, early pinch experiments were designed on quite elementary theoretical grounds. Indeed, these systems and the results from them provided the focus for much of the rapid development of theoretical plasma physics and magnetohydrodynamics during the 1950's. In comparison to present programs, these early experiments had the considerable advantage of small size and minimal managerial encumbrance. After nearly three decades of abandonment because of difficulties with MHD instabilities, the Z-pinch is arising once again in a new incarnation characterized by microscopic size and time scales, and very high density. Uniquely in the history of the pinch, the new experimental surprises seem encouraging, rather than discouraging, to the goal of thermonuclear fusion

Study of low insertion loss and miniaturization wavelet transform and inverse transform processor using SAW devices.

Science.gov (United States)

Jiang, Hua; Lu, Wenke; Zhang, Guoan

2013-07-01

In this paper, we propose a low insertion loss and miniaturization wavelet transform and inverse transform processor using surface acoustic wave (SAW) devices. The new SAW wavelet transform devices (WTDs) use the structure with two electrode-widths-controlled (EWC) single phase unidirectional transducers (SPUDT-SPUDT). This structure consists of the input withdrawal weighting interdigital transducer (IDT) and the output overlap weighting IDT. Three experimental devices for different scales 2(-1), 2(-2), and 2(-3) are designed and measured. The minimum insertion loss of the three devices reaches 5.49dB, 4.81dB, and 5.38dB respectively which are lower than the early results. Both the electrode width and the number of electrode pairs are reduced, thus making the three devices much smaller than the early devices. Therefore, the method described in this paper is suitable for implementing an arbitrary multi-scale low insertion loss and miniaturization wavelet transform and inverse transform processor using SAW devices. Copyright © 2013 Elsevier B.V. All rights reserved.

Compression Models for Plasma Focus Devices

International Nuclear Information System (INIS)

Gonzalez, Jose; Calusse, Alejandro; Ramos, Ruben; Rodriguez Palomino, Luis

2003-01-01

Using a numerical model that calculates the dynamics of Plasma Focus devices, we compared the results of three different compression models of the plasma pinch.One of the main objectives in this area is to develop a simplified model to calculate the neutron production of Plasma Focus devices, to study the influence of the main parameters in this neutron yield.The dynamics is thoroughly studied, and the model predicts fairly well values such as maximum currents and times for pinch collapse.Therefore, we evaluate here different models of pinch compression, to try to predict the neutron production with good agreement with the rest of the variables involved.To fulfill this requirement, we have experimental results of neutron production as a function of deuterium filling pressure in the chamber, and typical values of other main variables in the dynamics of the current sheet

Z-Pinch Fusion for Energy Applications

Energy Technology Data Exchange (ETDEWEB)

SPIELMAN,RICK B.

2000-01-01

Z pinches, the oldest fusion concept, have recently been revisited in light of significant advances in the fields of plasma physics and pulsed power engineering. The possibility exists for z-pinch fusion to play a role in commercial energy applications. We report on work to develop z-pinch fusion concepts, the result of an extensive literature search, and the output for a congressionally-mandated workshop on fusion energy held in Snowmass, Co July 11-23,1999.

Z-Pinch Fusion for Energy Applications

International Nuclear Information System (INIS)

SPIELMAN, RICK B.

2000-01-01

Z pinches, the oldest fusion concept, have recently been revisited in light of significant advances in the fields of plasma physics and pulsed power engineering. The possibility exists for z-pinch fusion to play a role in commercial energy applications. We report on work to develop z-pinch fusion concepts, the result of an extensive literature search, and the output for a congressionally-mandated workshop on fusion energy held in Snowmass, Co July 11-23,1999

Computing with volatile memristors: an application of non-pinched hysteresis

Science.gov (United States)

Pershin, Y. V.; Shevchenko, S. N.

2017-02-01

The possibility of in-memory computing with volatile memristive devices, namely, memristors requiring a power source to sustain their memory, is demonstrated theoretically. We have adopted a hysteretic graphene-based field emission structure as a prototype of a volatile memristor, which is characterized by a non-pinched hysteresis loop. A memristive model of the structure is developed and used to simulate a polymorphic circuit implementing stateful logic gates, such as the material implication. Specific regions of parameter space realizing useful logic functions are identified. Our results are applicable to other realizations of volatile memory devices, such as certain NEMS switches.

X-ray backlighting of two-wire Z-pinch plasma using X-pinch

International Nuclear Information System (INIS)

Tong, Zhao; Xiao-Bing, Zou; Ran, Zhang; Xin-Xin, Wang

2010-01-01

Two 50-μm Mo wires in parallel used as a Z-pinch load are electrically exploded with a pulsed current rising to 275 kA in 125 ns and their explosion processes are backlighted using an X-pinch as an x-ray source. The backlighting images show clearly the processes similar to those occurring in the initial stages of a cylindrical wire-array Z-pinch, including the electric explosion of single wires characterised by the dense wire cores surrounded by a low-density coronal plasma, the expansion of the exploding wire, the sausage instability (m = 0) in the coronal plasma around each wire, the motion of the coronal plasma as well as the wire core toward the current centroid, the formation of the precursor plasma column with a twist structure something like that of higher mode instability, especially the kink instability (m = 1). (fluids, plasmas and electric discharges)

High-density fusion and the Z-pinch

International Nuclear Information System (INIS)

Hartman, C.W.; Eddleman, J.L.; Munger, R.H.

1975-01-01

The formation of a Z-pinch in dense gas is investigated using numerical modeling in one and two dimensions. Hot, dense Z-pinches are calculated with n approximately 2 x 10 21 cm 3 and T = 10 keV. Relaxation by sausage instability of an unstable pinch profile to a marginally stable one is calculated along with end losses in 2 dimensions to show that, if plasma is confined for N = 50 to 200 sound transits across the radius a, pinches with length L = Na are of interest for fusion power. A conceptual, ''no-wall'' fusion reactor is discussed. (author)

Pinch Strengths in Healthy Iranian Children and Young Adult Population

Directory of Open Access Journals (Sweden)

Iman Dianat

2015-03-01

Full Text Available Background: Data on the physical strength capabilities are essential for design-ing safe and usable products and are useful in a wide range of clinical settings especially during treatment of disease affecting the function of the hand. The purpose of this study was to determine peak lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions in a healthy Iranian children and young adult population.Methods: The study was conducted among 511 participants (242 males and 269 females aged 7-30 years. Measurements were carried out with both dominant and non-dominant hands in standard sitting posture using a B&L pinch gauge. Two repetitions of each strength measurement were recorded for each condition and the average value of the two trials was used in the subsequent analysis.Results: The results showed significant differences in the pinch strength data in terms of the age, gender and hand dominance. The lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions by females were 68.4%, 68.8%, 78.8% and 81.8% of those exerted by males, respectively. Strength exertions with the non-dominant hand were 6.4%, 5.2%, 6.6% and 5.1% lower than strength exertions of the dominant hand for the lat-eral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions, respectively.Conclusion: These findings can be used to fill the gaps in strength data for Iranian population.

Hybrid simulations of current-carrying instabilities in Z-pinch plasmas with sheared axial flow

International Nuclear Information System (INIS)

Sotnikov, Vladimir I.; Makhin, Volodymyr; Bauer, Bruno S.; Hellinger, Petr; Travnicek, Pavel; Fiala, Vladimir; Leboeuf, Jean-Noel

2002-01-01

The development of instabilities in z-pinch plasmas has been studied with three-dimensional (3D) hybrid simulations. Plasma equilibria without and with sheared axial flow have been considered. Results from the linear phase of the hybrid simulations compare well with linear Hall magnetohydrodynamics (MHD) calculations for sausage modes. The hybrid simulations show that sheared axial flow has a stabilizing effect on the development of both sausage and kink modes

Characterisation of Plasma Filled Rod Pinch electron beam diode operation

Science.gov (United States)

MacDonald, James; Bland, Simon; Chittenden, Jeremy

2016-10-01

The plasma filled rod pinch diode (aka PFRP) offers a small radiographic spot size and a high brightness source. It operates in a very similar to plasma opening switches and dense plasma focus devices - with a plasma prefill, supplied via a number of simple coaxial plasma guns, being snowploughed along a thin rod cathode, before detaching at the end. The aim of this study is to model the PFRP and understand the factors that affect its performance, potentially improving future output. Given the dependence on the PFRP on the prefill, we are making detailed measurements of the density (1015-1018 cm-3), velocity, ionisation and temperature of the plasma emitted from a plasma gun/set of plasma guns. This will then be used to provide initial conditions to the Gorgon 3D MHD code, and the dynamics of the entire rod pinch process studied.

An ICF system based on Z-pinch radiation produced by an explosive magnetic generator

International Nuclear Information System (INIS)

Garanin, S.G.; Ivanovsky, A.V.; Mkhitariyan, L.S.

2011-01-01

It is known that a thermonuclear target can be ignited by an implosion accomplished with X-radiation generated by means of laser radiation conversion or by a Z pinch formed by a high-power current pulse. For these purposes laser facility NIF has been constructed in the USA, 'Megajoule' is being constructed in France and there is a project of laser facility UFL in Russia. The project of stationary facility X has been developed in SNL USA to produce a Z pinch capable of generating an x-ray pulse with parameters close to the ignition threshold. There is a great chance, however, that the already tested technologies, including disc explosive magnetic generators (DEMG), systems of current peaking based on electrically exploded foil opening switches and high-voltage switching devices, allow the intriguing problem of the ignition feasibility to be solved and the quickest and cheapest way to accomplish this to be provided. To explore this possibility, the paper will sequentially analyse the ignition conditions. The required parameters of Z pinch X-radiation and the size of the DEMG-based facility to obtain these parameters will be evaluated. Capabilities of the new current sources based on the DEMG and of the devices shaping a current pulse will be presented and compared with those required for the ignition.

The ZaP Flow Z-Pinch Project

International Nuclear Information System (INIS)

Shumlak, U.; Nelson, B. A.

2005-01-01

The results from the ZaP experiment are consistent with the theoretical predictions of sheared flow stabilization. Z pinches with a sheared flow are generated in the ZaP experiment using a coaxial accelerator coupled to an assembly region. The current sheet in the accelerator initially acts as a snowplow. As the Z pinch forms, plasma formation in the accelerator transits to a deflagration process. The plasma exits the accelerator and maintains the flow in the Z pinch. During the quiescent period in the magnetic mode activity at z=0 cm, a stable Z pinch is seen on the axis of the assembly region. The evolution of the axial velocity profile shows a large velocity shear is measured at the edge of the Z pinch during the quiescent period. The velocity shear is above the theoretical threshold. As the velocity shear decreases towards 0.1kV A , the predicted stability threshold, the quiescent period ends. The present understanding of the ZaP experiment shows that it may be possible for the Z pinch to operate in a steady state if the deflagration process can be maintained by constantly supplying neutral gas or plasma to the accelerator

Investigation on the pinch point position in heat exchangers

Science.gov (United States)

Pan, Lisheng; Shi, Weixiu

2016-06-01

The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the iterative method in all conditions rather than taking for granted.

Self-pinched lithium beam transport experiments on SABRE

International Nuclear Information System (INIS)

Hanson, D.L.; Olson, C.L.; Poukey, J.W.; Shokir, I.; Cuneo, M.E.; Menge, P.R.; Johnston, R.R.; Welch, D.R.

1996-01-01

Self-pinched transport of ion beams has many advantages for ion-driven ICF applications involving high yield and energy production. The authors are currently preparing for a self-pinched lithium beam transport experiment on the SABRE accelerator. There are three transport elements that must eventually be demonstrated: (1) efficient lithium beam generation and ballistic transport to a focus at the self-pinched transport channel entrance; (2) self-pinched transport in the channel, requiring optimized injection conditions and gas breakdown; and (3) self-pinched transport of the equilibrated beam from the channel into free space, with associated aiming and stability considerations. In the present experiment, a hollow annular lithium beam from an applied-B extraction ion diode will be focused to small radius (r ≤ 2 cm) in a 60 cm long ballistic focus section containing argon gas at a pressure of a few Torr. The self-pinched transport channel will contain a low pressure background gas of 10--40 mTorr argon to allow sufficient net current to confine the beam for long distance transport. IPROP simulations are in progress to optimize the design of the ballistic and self-pinched transport sections. Progress on preparation of this lithium self-pinched transport experiment, including a discussion of transport system design, important gas breakdown issues, and diagnostics, will be presented

Field reversed theta pinch TC-I UNICAMP

International Nuclear Information System (INIS)

Honda, R.Y.; Machida, M.; Aramaki, E.A.; Porto, P.; Berni, L.A.

1990-01-01

Field reversed configuration TC-I device is 16 cm diameter, 1 meter long with two mirror coils and 30 kJ field reversed theta pinch working for over two years at University of Campinas. Its implosion dynamics and field reversal parameters have been studied using flux excluded loops, internal magnetic probe, visible spectroscopy, photodiode array and image converter camera. The vacuum vessel is a pyrex tube of 14,5 cm diameter pumped with a liquid nitrogen cooled diffusion pump to a base pressure of 6 x 10 -7 Torr. The schematic view of the machine and experimental set up are shown. (Author)

Efficient Implementation of Solvers for Linear Model Predictive Control on Embedded Devices

DEFF Research Database (Denmark)

Frison, Gianluca; Kwame Minde Kufoalor, D.; Imsland, Lars

2014-01-01

This paper proposes a novel approach for the efficient implementation of solvers for linear MPC on embedded devices. The main focus is to explain in detail the approach used to optimize the linear algebra for selected low-power embedded devices, and to show how the high-performance implementation...

Inverse chaos synchronization in linearly and nonlinearly coupled systems with multiple time-delays

International Nuclear Information System (INIS)

Shahverdiev, E.M.; Hashimov, R.H.; Nuriev, R.A.; Hashimova, L.H.; Huseynova, E.M.; Shore, K.A.

2005-04-01

We report on inverse chaos synchronization between two unidirectionally linearly and nonlinearly coupled chaotic systems with multiple time-delays and find the existence and stability conditions for different synchronization regimes. We also study the effect of parameter mismatches on synchonization regimes. The method is tested on the famous Ikeda model. Numerical simulations fully support the analytical approach. (author)

Spill-Detector-and-Shutoff Device

Science.gov (United States)

Jarvis, M. R.; Fulton, D. S.

1985-01-01

Overflow in liquid chromatography systems rapidly detected and stopped. Spill-detector-and-shutoff device incorporated into liquid-chromatography system. When liquid from output nozzle spills on liquid sensor, device automatically shuts off pump and releases solenoid to pinch off flow in tube. Device uses common type of alarm circuit reset manually before normal operation resumes.

Measurements for the radiation spectra of fast Z-pinches produced at compression of multi-wire arrays on the 'Angara-5-1' facility

International Nuclear Information System (INIS)

Bolkhovitinov, E.A.; Rupasov, A.A.; Shikanov, A.S.; Fedulov, M.V.; Grabovsky, E.V.; Gritsuk, A.N.; Oleinik, G.M.; Volkov, G.S.

2010-01-01

Complete text of publication follows. The measurements results on the radiation spectra of fast z-pinches produced at compression of cylindrical multi-wire tungsten and aluminum arrays in the experiments on a high-current 'Angara-5-1' facility are presented. Cylindrical multi-wire arrays has linear mass 200-400 μg/cm and the initial diameter 12-20 mm. The pinch current was about 3 MA with pulse duration of 140 ns and peak power 3 TW. The radiation spectra are measured within the range of 50-900 eV quanta by a spectrometer with transmission diffraction grating, where the radiation is recorded on the UF-4 X-ray film. An electromagnetic curtain shutter was used to protect the transmission grating from fast microparticles produced by the erosion of high-voltage electrodes. The radiation spectrum of 1-3 keV quanta was recorded by a convex crystal wide-range spectrometer. Total yield of the radiation was measured by a thermocouple calorimeter. The main part of the tungsten plasma radiative energy proves to correspond to the quasi-continuous spectrum within the range of 80-300 eV quanta. Measurements of the tungsten plasma radiation spectrum with spatial resolution by a pinch radius have shown that the effective transversal size (diameter) of the pinch as not higher than 1 mm. In the case of aluminum plasma an intensive linear radiation of the [H]- and [He]-like ions have been recorded along with a continuous and linear radiation of the [Li]- and [Be]-like ions with the range of 100-300 eV quanta. Spectral measurements of the aluminum plasma radiation with spatial resolution by the pinch radius have shown that the effective transversal size (diameter) of the pinch is around the value of 1.5 mm. Within the framework of the stationary collisional-radiative model, in respect of the [H]- and [He]-like ion spectral lines relative intensities, the parameters of the aluminum plasma pinch, namely, the electron temperature T e ∼ 550 eV and electron density n e ∼ 3 x 10 20 cm

Pinch density measurements in compact plasma foci of 400J and 50J

International Nuclear Information System (INIS)

Tarifeño-Saldivia, Ariel; Pavez, Cristian; Soto, Leopoldo

2014-01-01

A Mach-Zehnder interferometer using a pulsed Nd-YAG laser (600 mJ, 532 nm, 8 ns) was implemented to measure the electron density and the dimensions of the pinch column in two sub-kJ compact plasma focus devices operating at hundred joules (PF-400J) and tens of joules (PF-50J).

The static pinch

Energy Technology Data Exchange (ETDEWEB)

Longmire, Conrad L [University of California, Los Alamos Scientific Laboratory, Los Alamos, NM (United States)

1958-07-01

In a pinch, the outward diffusion of plasma due to collisions can be balanced by the inward drift resulting from ExB, where E is the applied electric field and B the magnetic field. From the equation expressing the balance of these two effects, together with the pressure balance equation, one obtains the perpendicular conductivity, which is about one-half of the classical parallel conductivity. This result has been applied to the problem of a static pinch under the assumptions: 1) there is an applied longitudinal (B{sub z}) magnetic field; 2) the plasma is isothermal; 3) the solution depends only on the radial coordinate.

Theoretical study on the laser-driven ion-beam trace probe in toroidal devices with large poloidal magnetic field

Science.gov (United States)

Yang, X.; Xiao, C.; Chen, Y.; Xu, T.; Yu, Y.; Xu, M.; Wang, L.; Wang, X.; Lin, C.

2018-03-01

Recently, a new diagnostic method, Laser-driven Ion-beam Trace Probe (LITP), has been proposed to reconstruct 2D profiles of the poloidal magnetic field (Bp) and radial electric field (Er) in the tokamak devices. A linear assumption and test particle model were used in those reconstructions. In some toroidal devices such as the spherical tokamak and the Reversal Field Pinch (RFP), Bp is not small enough to meet the linear assumption. In those cases, the error of reconstruction increases quickly when Bp is larger than 10% of the toroidal magnetic field (Bt), and the previous test particle model may cause large error in the tomography process. Here a nonlinear reconstruction method is proposed for those cases. Preliminary numerical results show that LITP could be applied not only in tokamak devices, but also in other toroidal devices, such as the spherical tokamak, RFP, etc.

Inverse eigenvalue problems for Sturm-Liouville equations with spectral parameter linearly contained in one of the boundary conditions

OpenAIRE

Guliyev, Namig J.

2008-01-01

International audience; Inverse problems of recovering the coefficients of Sturm–Liouville problems with the eigenvalue parameter linearly contained in one of the boundary conditions are studied: 1) from the sequences of eigenvalues and norming constants; 2) from two spectra. Necessary and sufficient conditions for the solvability of these inverse problems are obtained.

Progress in symmetric ICF capsule implosions and wire-array z-pinch source physics for double z-pinch driven hohlraums

International Nuclear Information System (INIS)

Bliss, David Emery; Vesey, Roger Alan; Rambo, Patrick K.; Lebedev, Sergey V.; Hanson, David L.; Nash, Thomas J.; Yu, Edmund P.; Matzen, Maurice Keith; Afeyan, Bedros B.; Smith, Ian Craig; Stygar, William A.; Porter, John Larry Jr.; Cuneo, Michael Edward; Bennett, Guy R.; Campbell, Robert B.; Sinars, Daniel Brian; Chittenden, Jeremy Paul; Waisman, Eduardo Mario; Mehlhorn, Thomas Alan

2005-01-01

Over the last several years, rapid progress has been made evaluating the double-z-pinch indirect-drive, inertial confinement fusion (ICF) high-yield target concept (Hammer et al 1999 Phys. Plasmas 6 2129). We have demonstrated efficient coupling of radiation from two wire-array-driven primary hohlraums to a secondary hohlraum that is large enough to drive a high yield ICF capsule. The secondary hohlraum is irradiated from two sides by z-pinches to produce low odd-mode radiation asymmetry. This double-pinch source is driven from a single electrical power feed (Cuneo et al 2002 Phys. Rev. Lett. 88 215004) on the 20 MA Z accelerator. The double z-pinch has imploded ICF capsules with even-mode radiation symmetry of 3.1 ± 1.4% and to high capsule radial convergence ratios of 14-21 (Bennett et al 2002 Phys. Rev. Lett. 89 245002; Bennett et al 2003 Phys. Plasmas 10 3717; Vesey et al 2003 Phys. Plasmas 10 1854). Advances in wire-array physics at 20 MA are improving our understanding of z-pinch power scaling with increasing drive current. Techniques for shaping the z-pinch radiation pulse necessary for low adiabat capsule compression have also been demonstrated.

Study of flow and loss processes at the ends of a linear theta pinch. Progress report, June 1, 1977--May 31, 1978

International Nuclear Information System (INIS)

York, T.M.; Klevans, E.H.

1978-02-01

Experimental and analytical studies of end loss from a theta pinch have been carried out. Detailed diagnostic studies of a 25 cm long theta pinch operating with reversed trapped fields have been completed; spectroscopic studies, magnetic probe, pressure probe, double diamagnetic loop, luminosity studies and Thomson scattering studies of the plasma have been carried out over the 8 μsec duration of the transient loss. Two new diagnostic techniques have been developed based on the available Thomson scattering laser source. A study of plasma loss from a 10.5 long theta pinch with an axial Twyman-Green interferometer has been completed and reported. The basic studies needed for subsequent experimental work on heat conduction loss being diagnosed by Thomson scattering data in the end region, with and without mirror coil, has been completed as a part of the mirror field studies

Compact reversed-field pinch reactors (CRFPR)

International Nuclear Information System (INIS)

Krakowski, R.A.; Miller, R.L.; Bathke, C.G.; Hagenson, R.L.; Copenhaver, C.; Werley, K.A.

1986-01-01

The unique confinement properties of the Reversed-Field Pinch (RFP) are exploited to examine physics and technical issues related to a compact, high-power-density fusion reactor. This resistive-coil, steady-state, toroidal device would use a dual-media power cycle driven by a fusion power core (FPC, i.e., plasma chamber, first wall, blanket, shield, and coils) with a power density and mass approaching values characteristic of pressurized-water fission rectors. A 1000-MWe(net) base case is selected from a comprehensive trade-off study to examine technological issues related to operating a high-power-density FPC. After describing the main physics and technology issues for this base-case reactor, directions for future study are suggested

Sausage mode of a high density Z-pinch

International Nuclear Information System (INIS)

Pereira, N.; Rostoker, N.

1983-01-01

In Z-pinch experiments at Maxwell Laboratories, Inc., growth rates have been measured by observing optical emission along the pinch axis. Growth rates estimated by means of the usual model of a pinch involving an incompressible fluid and a surface current are too large by a factor of 2-4. X-ray pinhole photographs generally have the appearance of a series of beads that would be expected from instability of the sausage mode. In some cases, particularly the implosion of large diameter wire arrays with BLACKJACK 5, the beads disappear and only the kink instability is apparent. Generalizing the pinch model to include compressibility does not significantly alter the predictions. A further generalization to include distributed current has therefore been considered. It seems likely that the current can penetrate significantly during the lifetime of the pinch. We consider a model of the pinch that is initially an infinite cylinder. For the sausage mode, stability is determined by a simple second order differential equation together with the boundary condition that follows from the wave number and the frequency of the instability

Nonlinear stage of a Z-pinch instability

International Nuclear Information System (INIS)

Garanin, S.F.; Chernyshev, Y.D.

1987-01-01

The nonlinear evolution of the sausage instability is analyzed for a Z-pinch with a fully developed skin effect in the current. Two-dimensional numerical calculations carried out on the sausage instability show that its occurrence leads to a stage describable by a self-similar solution when the length of the neck is fixed and the plasma compression is isentropic. At a perturbation wavelength small in comparison with the pinch radius, this stage is preceded by a stage which reduces to a nonlinear Rayleigh--Taylor instability. The dynamics of the motion of magnetic field ''bubbles'' and of plasma ''jets'' is analyzed in this case. The plasma jets emerging from the pinch do not block the pinch from the current source

Development of pulsed high current drivers for fast Z-pinch

International Nuclear Information System (INIS)

Sun Fengju; Qiu Aici; Zeng Zhengzhong; Zeng Jiangtao; Kuai Bin; Yang Hailiang

2006-01-01

It is required that the peak current of high power pulsed drive for fast Z-pinch reaches 60 MA to realize inertial confine fusion (ICF) and high yield (HY). With the conventional technological methods similar to the Z or Saturn apparatus, increasing driver current further is impractical and difficult according to the cost, structure complexity and reliability of the driver, so it is necessary to develop novel fast pulsed high current driver. The present art-of-state and trends of fast Z-pinch driver are summarized, and the typical conceptual designs and technological methods on ICF/HY PRS (plasma radiation source) and destroying-level super X-ray simulators in USA and Russia are outlined, such as HCEI's UGXX1 driver and new Saturn driver based on fast linear transformer driver (FLTD) and novel driver based on fast Marx generator (FMG) with current of 15 MA. The crucial technological problems and requirements to investigate in the future are presented. (authors)

Reconstruction of the eddy current distribution on the vacuum vessel in a reversed field pinch device based on the external magnetic sensor signals

International Nuclear Information System (INIS)

Itagaki, Masafumi; Sanpei, Akio; Masamune, Sadao; Watanabe, Kiyomasa

2014-01-01

For the MHD equilibrium reconstruction of a reverse field pinch device, it is a big issue to identify accurately the strong eddy current flow on the shell. In the present work, boundary integrals of the eddy current along the shell are added to the conventional Cauchy-condition surface method formulation. The eddy current profile is unknown in advance but straightforwardly identified using only the signals from magnetic sensors located outside the plasma. Two ideas are introduced to overcome the numerical difficulties encountered in the problem. One is an accurate boundary integral scheme to damp out the near singularity occurring at the sensor position very close to the shell. The other is the modified truncated singular value decomposition technique to solve an ill-conditioned matrix equation when a large number of nodal points exist on the shell. The capability of the new method is demonstrated for a test problem modeling the RELAX device. (author)

An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

Science.gov (United States)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

Plasma focus - dense Z pinch and their applications

International Nuclear Information System (INIS)

Ishii, Shozo

1986-02-01

''Workshop on the possibility of Z-pinch as a intense pulse light source'' in 1983 and ''Research meeting on plasma focus and Z-pinch'' in 1984 were held at Institute of Plasma Physics, Nagoya University under a collaborating research program. Research activities reported at the meetings on plasma focus, dense Z-pinch, and related phenomena are summerized. (author)

TeV e+e- linear colliders

International Nuclear Information System (INIS)

Le Duff, J.

1987-12-01

The basic philosophy and performance and technical constraints of linear e + e - colliders at TeV energies are summarized. Collider luminosity, pinch effects due to beam interaction, beam-beam bremsstrahlung, and typical parameters for an e + e - linear collider are discussed. Accelerating structures, HF power sources, electron guns, positron production, and storage rings are considered [fr

Optical and EUV studies of laser triggered Z-pinch discharges

OpenAIRE

Tobin, Isaac

2014-01-01

This thesis describes the results of experiments with two geometries of laser assisted discharge plasma. Both devices are designed for fast Z-pinch discharge, triggered by laser produced plasma generated by ablation of one or both electrodes. The laser plasma parameters are adjusted to control the plasma load while the discharge parameters are adjusted to yield a rate of rise of current greater than 1010 A/s. The expansion dynamics and emission characteristics of the plasma were analysed, wit...

1/4-pinched contact sphere theorem

DEFF Research Database (Denmark)

Ge, Jian; Huang, Yang

2016-01-01

Given a closed contact 3-manifold with a compatible Riemannian metric, we show that if the sectional curvature is 1/4-pinched, then the contact structure is universally tight. This result improves the Contact Sphere Theorem in [EKM12], where a 4/9-pinching constant was imposed. Some tightness...

Modeling and inverse feedforward control for conducting polymer actuators with hysteresis

International Nuclear Information System (INIS)

Wang, Xiangjiang; Alici, Gursel; Tan, Xiaobo

2014-01-01

Conducting polymer actuators are biocompatible with a small footprint, and operate in air or liquid media under low actuation voltages. This makes them excellent actuators for macro- and micro-manipulation devices, however, their positioning ability or accuracy is adversely affected by their hysteresis non-linearity under open-loop control strategies. In this paper, we establish a hysteresis model for conducting polymer actuators, based on a rate-independent hysteresis model known as the Duhem model. The hysteresis model is experimentally identified and integrated with the linear dynamics of the actuator. This combined model is inverted to control the displacement of the tri-layer actuators considered in this study, without using any external feedback. The inversion requires an inverse hysteresis model which was experimentally identified using an inverse neural network model. Experimental results show that the position tracking errors are reduced by more than 50% when the hysteresis inverse model is incorporated into an inversion-based feedforward controller, indicating the potential of the proposed method in enabling wider use of such smart actuators. (paper)

Architecture of petawatt-class z-pinch accelerators

International Nuclear Information System (INIS)

Stygar, William A.; Mazarakis, Michael Gerrassimos; Cuneo, Michael Edward; Leeper, Ramon Joe; Ives, H.C.; Headley, D.I.; Wagoner, Tim C.; Porter, John Larry Jr.

2006-01-01

We have developed an accelerator architecture that can serve as the basis of the design of petawatt-class z-pinch drivers. The architecture has been applied to the design of two z-pinch accelerators, each of which can be contained within a 104-m-diameter cylindrical tank. One accelerator is driven by slow (∼1 (micro)s) Marx generators, which are a mature technology but which necessitate significant pulse compression to achieve the short pulses ( 4 capacitors, store 98 MJ, and erect to 5 MV; (ii) 600 water-dielectric triplate intermediate-store transmission lines, which also serve as pulse-forming lines; (iii) 600 5-MV laser-triggered gas switches; (iv) three monolithic radial-transmission-line impedance transformers, with triplate geometries and exponential impedance profiles; (v) a 6-level 5.5-m-diameter 15-MV vacuum insulator stack; (vi) six magnetically insulated vacuum transmission lines (MITLs); and (vii) a triple-post-hole vacuum convolute that adds the output currents of the six MITLs, and delivers the combined current to a z-pinch load. The accelerator delivers an effective peak current of 52 MA to a 10-mm-length z pinch that implodes in 95 ns, and 57 MA to a pinch that implodes in 120 ns. The LTD-driven accelerator includes monolithic radial transformers and a MITL system similar to those described above, but does not include intermediate-store transmission lines, multimegavolt gas switches, or a laser trigger system. Instead, this accelerator is driven by 210 LTD modules that include a total of 1 x 10 6 capacitors and 5 x 10 5 200-kV electrically triggered gas switches. The LTD accelerator stores 182 MJ and produces a peak electrical power of 1000 TW. The accelerator delivers an effective peak current of 68 MA to a pinch that implodes in 95 ns, and 75 MA to a pinch that implodes in 120 ns. Conceptually straightforward upgrades to these designs would deliver even higher pinch currents and faster implosions

On the internal stability of non-linear dynamic inversion: application to flight control

Czech Academy of Sciences Publication Activity Database

Alam, M.; Čelikovský, Sergej

2017-01-01

Roč. 11, č. 12 (2017), s. 1849-1861 ISSN 1751-8644 R&D Projects: GA ČR(CZ) GA17-04682S Institutional support: RVO:67985556 Keywords : flight control * non-linear dynamic inversion * stability Subject RIV: BC - Control Systems Theory OBOR OECD: Automation and control systems Impact factor: 2.536, year: 2016 http://library.utia.cas.cz/separaty/2017/TR/celikovsky-0476150.pdf

If it’s pinched it’s a memristor

International Nuclear Information System (INIS)

Chua, Leon

2014-01-01

This paper presents an in-depth review of the memristor from a rigorous circuit-theoretic perspective, independent of the material the device is made of. From an experimental perspective, a memristor is best defined as any two-terminal device that exhibits a pinched hysteresis loop in the voltage–current plane when driven by any periodic voltage or current signal that elicits a periodic response of the same frequency. This definition greatly broadens the scope of memristive devices to encompass even non-semiconductor devices, both organic and inorganic, from many unrelated disciplines, including biology, botany, brain science, etc. For pedagogical reasons, the broad terrain of memristors is partitioned into three classes of increasing generality, dubbed Ideal Memristors, Generic Memristors, and Extended Memristors. Each class is distinguished from the others via unique fingerprints and signatures. This paper clarifies many confusing issues, such as non-volatility, dc V–I curves, high-frequency v–i curves, local activity, as well as nonlinear dynamical and bifurcation phenomena that are the hallmarks of memristive devices. Above all, this paper addresses several fundamental issues and questions that many memristor researchers do not comprehend but are afraid to ask. (tutorial)

Resolution limits of migration and linearized waveform inversion images in a lossy medium

KAUST Repository

Schuster, Gerard T.; Dutta, Gaurav; Li, Jing

2017-01-01

The vertical-and horizontal-resolution limits Delta x(lossy) and Delta z(lossy) of post-stack migration and linearized waveform inversion images are derived for lossy data in the far-field approximation. Unlike the horizontal resolution limit Delta x proportional to lambda z/L in a lossless medium which linearly worsens in depth z, Delta x(lossy) proportional to z(2)/QL worsens quadratically with depth for a medium with small Q values. Here, Q is the quality factor, lambda is the effective wavelength, L is the recording aperture, and loss in the resolution formulae is accounted for by replacing lambda with z/Q. In contrast, the lossy vertical-resolution limit Delta z(lossy) only worsens linearly in depth compared to Delta z proportional to lambda for a lossless medium. For both the causal and acausal Q models, the resolution limits are linearly proportional to 1/Q for small Q. These theoretical predictions are validated with migration images computed from lossy data.

Resolution limits of migration and linearized waveform inversion images in a lossy medium

KAUST Repository

Schuster, Gerard T.

2017-03-10

The vertical-and horizontal-resolution limits Delta x(lossy) and Delta z(lossy) of post-stack migration and linearized waveform inversion images are derived for lossy data in the far-field approximation. Unlike the horizontal resolution limit Delta x proportional to lambda z/L in a lossless medium which linearly worsens in depth z, Delta x(lossy) proportional to z(2)/QL worsens quadratically with depth for a medium with small Q values. Here, Q is the quality factor, lambda is the effective wavelength, L is the recording aperture, and loss in the resolution formulae is accounted for by replacing lambda with z/Q. In contrast, the lossy vertical-resolution limit Delta z(lossy) only worsens linearly in depth compared to Delta z proportional to lambda for a lossless medium. For both the causal and acausal Q models, the resolution limits are linearly proportional to 1/Q for small Q. These theoretical predictions are validated with migration images computed from lossy data.

Engineering feasibility evaluation of a peristaltic pinch

International Nuclear Information System (INIS)

Boicourt, G.P.

1977-04-01

A recent proposal for reducing the end loss of a linear theta pinch is to produce moving magnetic mirrors at the coil ends. The concept entails the sequential pulsing of an axially arranged series of two-turn coaxial coils. The electrical design of such a system presents some unique problems. Ideally, the individual pulse circuits should be completely independent. This would facilitate the design by eliminating interactive effects. In practice, the circuits must be interconnected through isolating inductors to enable the production of a uniform biasing magnetic field. Moreover, the coils must be located physically close together. This produces strong magnetic coupling between the pulse circuits, which can seriously affect the shape and speed of the inward-moving magnetic-mirror field. Possible systems were modeled for the NET-2 circuit analysis code. The models took account of the inductive coupling between the individual circuits in the model. The results show that an increasing magnetic mirror can be produced provided the radius of the theta pinch is not too great compared to the intercoil spacing. The peristaltic field can be maintained for several cycles in the inner coils. The voltage hold-off requirements on the pulse circuit switches are found to be severe, but not impossible to meet

Magnetohydrodynamic effects of current profile control in reversed field pinches

International Nuclear Information System (INIS)

Sovinec, C.R.; Prager, S.C.

1999-01-01

Linear and non-linear MHD computations are used to investigate reversed field pinch configurations with magnetic fluctuations reduced through current profile control. Simulations with reduced ohmic drive and moderate auxiliary current drive, represented generically with an electron force term, applied locally in radius near the plasma edge show magnetic fluctuation energies that are orders of magnitude smaller than those in simulations without profile control. The core of the improved configurations has reduced magnetic shear and closed flux surfaces in some cases, and reversal is sustained through the auxiliary current drive. Modes resonant near the edge may become unstable with auxiliary drive, but their saturation levels can be controlled. The space of auxiliary drive parameters is explored, and the ill effects of deviating far from optimal conditions is demonstrated in non-linear simulations. (author)

On the stability limits of the Pinch-conductor current ratio in Extrap

International Nuclear Information System (INIS)

Lehnert, B.

1987-12-01

A first attempt is made to take the special stability features of the Extrap confinement scheme into account, thereby including kinetic large Larmor radius (LLR) effects. This approach predicts Extrap to be unstable outside a domain defined by a lower and an upper ratio a - /a x is related to the ratio J p /J v between the pinch current J p and the conductor current J v . Stability within the predicted domain seems to agree with so far performed linear and toroidal experiments, and can explain the observed increase in J p /J v and in the plasma temperature, in terms of an increased ratio a - /a x . According to present analysis, an optimum value of the conductor current J v should further exist with respect to pinch equilibrium and stability, as given by the condition a - approx = a x . (author)

Experimental study on gas-puff Z-pinch load characteristics on yang accelerator

International Nuclear Information System (INIS)

Ren Xiaodong; Huang Xianbin; Yang Libing; Dan Jiakun; Duan Shuchao; Zhang Zhaohui; Zhou Shaotong

2010-01-01

A supersonic single-shell gas-puff load has been developed for Z-pinch experiments on 'Yang' accelerator. Using a fast responding pressure probe to measure the supersonic gas flow, impact pressure at different position and plenum pressure were acquired, which were combined with gas dynamics formulas to determine gas pressures and densities. The radial density profile displays that positions of gas shell varies with axial position, and the gas densities on axis increases as the distance from nozzle increases. Integral radial densities indicates that the linear mass density peaks at nozzle exit and decreases as increasing the distance from nozzle. Using single-shell supersonic gas-puff load, Z-pinch implosion experiments were performed on 'Yang' accelerator. Primary analysis of implosion process was presented, and computational trajectories of imploding plasma shell using snowplow model are in agreement with the experimental results. (authors)

An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

Science.gov (United States)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

Radiation hydrodynamics of z-pinch plasmas

International Nuclear Information System (INIS)

Davis, J.

1993-01-01

Over the years there has been a sustained interest in and fascination with Z-pinch plasmas. Whether the interest is in radiation source development, fusion plasmas, or basic research there exits an extensive bibliography of literature promulgating and perpetuating a variety of claims regarding the performance of Z-pinch plasmas. In this paper an attempt will be made to present a coherent picture of the documented and commonly held views for a class of Z-pinch plasmas concerned primarily with soft x-ray radiation source development. Many of the issues and findings are common to Z-pinch plasmas in general but the attention here will be focused on gas puffs and multiple wire arrays. The role and importance of radiation on the dynamics and the interplay between the radiation and the dynamics will also be presented and discussed. A number of comparisons with experimental results will be made with 0-, 1-, and 2-D numerical simulations for several pulsed power drivers ranging in current from several mega-amps to 10's of mega-amps for a variety of risetimes and load materials

Hybrid Z-Θ Pinches with fused capacitor banks

International Nuclear Information System (INIS)

Grandey, R.; Gersten, M.; Loter, N.; Rauch, J.; Rostoker, N.; Thompson, W.; Ware, K.

1987-01-01

The Hybrid Z-Θ Pinch circuit equations in the thin shell model were reexamined to see what advantages can be obtained by using a fused, high-energy (>--1MJ) bank driver. The DNA ACE facility at MLI utilizes a 36 μF capacitor band which can be charged to 120 kV to provide 250 kJ of stored energy. This configuration appears to be very appropriate to test the performance of a hybrid-stabilized fused-bank driven pinch. The circuit analyses suggest that the energy transfer efficiency from the bank to a pinched plasma can be increased from less than 1%, for a nonfused bank, to about 10% for a fused configuration. In the applicable region of parameter space, the Hybrid Pinch does not increase the efficiency of energy transfer into the plasma over that obtainable from a Z-pinch. The additional stability may allow larger initial radii to be used with concomitant improved coupling into radiation above 1 keV

Transverse equilibria in linear collider beam-beam collisions

International Nuclear Information System (INIS)

Rosenzweig, J.B.; Chen, Pisin

1991-01-01

It has been observed in simulations of the beam-beam interaction in linear colliders that a near equilibrium pinched state of the colliding beams develops when the disruption parameter is large (D much-gt 1). In this state the beam transverse density distributions are peaked at center, with long tails. The authors present here an analytical model of the equilibrium approached by the beams, that of a generalized Bennett pinch which develops through collisionless damping due to the strong nonlinearity of the beam-beam interaction. In order to calculate the equilibrium pinched beam size, an estimation of the rms emittance growth is made which takes into account the partial adiabaticity of the collision. This pinched beam size is used to derive the luminosity enhancement factors whose scaling is in agreement with the simulation results for both D and thermal factor A = σ z /β * large, and explains the previously noted cubic relationship between round and flat beam enhancement factors

Energy balance in a Z pinch with suppressed Rayleigh-Taylor instability

Science.gov (United States)

Baksht, R. B.; Oreshkin, V. I.; Rousskikh, A. G.; Zhigalin, A. S.

2018-03-01

At present Z-pinch has evolved into a powerful plasma source of soft x-ray. This paper considers the energy balance in a radiating metallic gas-puff Z pinch. In this type of Z pinch, a power-law density distribution is realized, promoting suppression of Rayleigh-Taylor (RT) instabilities that occur in the pinch plasma during compression. The energy coupled into the pinch plasma, is determined as the difference between the total energy delivered to the load from the generator and the magnetic energy of the load inductance. A calibrated voltage divider and a Rogowski coil were used to determine the coupled energy and the load inductance. Time-gated optical imaging of the pinch plasma showed its stable compression up to the stagnation phase. The pinch implosion was simulated using a 1D two-temperature radiative magnetohydrodynamic code. Comparison of the experimental and simulation results has shown that the simulation adequately describes the pinch dynamics for conditions in which RT instability is suppressed. It has been found that the proportion of the Ohmic heating in the energy balance of a Z pinch with suppressed RT instability is determined by Spitzer resistance and makes no more than ten percent.

On the instability increments of a stationary pinch

International Nuclear Information System (INIS)

Bud'ko, A.B.

1989-01-01

The stability of stationary pinch to helical modes is numerically studied. It is shown that in the case of a rather fast plasma pressure decrease to the pinch boundary, for example, for an isothermal diffusion pinch with Gauss density distribution instabilities with m=0 modes are the most quickly growing. Instability increments are calculated. A simple analytical expression of a maximum increment of growth of sausage instability for automodel Gauss profiles is obtained

On the Heating of Ions in Noncylindrical Z-Pinches

Science.gov (United States)

Svirsky, E. B.

2018-01-01

The method proposed here for analyzing processes in a hot plasma of noncylindrical Z-pinches is based on separation of the group of high-energy ions into a special fraction. Such ions constitute an insignificant fraction ( 10%) of the total volume of the Z-pinch plasma, but these ions contribute the most to the formation of conditions in which the pinch becomes a source of nuclear fusion products and X-ray radiation. The method allows a quite correct approach to obtaining quantitative estimates of the plasma parameters, the nuclear fusion energy yield, and the features of neutron fluxes in experiments with Z-pinches.

Staged theta pinch experiments

International Nuclear Information System (INIS)

Linford, R.K.; Downing, J.N.; Gribble, R.F.; Jacobson, A.R.; Platts, D.A.; Thomas, K.S.

1976-01-01

Two implosion heating circuits are being experimentally tested. The principal experiment in the program is the 4.5-m-long Staged Theta Pinch (STP). It uses two relatively low energy (50kJ and 100 kJ), high voltage (125 kV) capacitor banks to produce the theta pinch plasma inside the 20 cm i.d. quartz discharge tube. A lower voltage (50 kV), higher energy (750 kJ) capacitor bank is used to contain the plasma and provide a variable amount of adiabatic compression. Because the experiment produces a higher ratio of implosion heating to compressional heating than conventional theta pinches, it should be capable of producing high temperature plasmas with a much larger ratio of plasma radius to discharge tube radius than has been possible in the past. The Resonant Heating Experiment (RHX) in its initial configuration is the same as a 0.9-m-long section of the high voltage part of the STP experiment and all the plasma results here were obtained with the experiment in that configuration. Part of the implosion bank will be removed and a low inductance crowbar added to convert it to the resonant heating configuration. (U.K.)

Angle-domain inverse scattering migration/inversion in isotropic media

Science.gov (United States)

Li, Wuqun; Mao, Weijian; Li, Xuelei; Ouyang, Wei; Liang, Quan

2018-07-01

The classical seismic asymptotic inversion can be transformed into a problem of inversion of generalized Radon transform (GRT). In such methods, the combined parameters are linearly attached to the scattered wave-field by Born approximation and recovered by applying an inverse GRT operator to the scattered wave-field data. Typical GRT-style true-amplitude inversion procedure contains an amplitude compensation process after the weighted migration via dividing an illumination associated matrix whose elements are integrals of scattering angles. It is intuitional to some extent that performs the generalized linear inversion and the inversion of GRT together by this process for direct inversion. However, it is imprecise to carry out such operation when the illumination at the image point is limited, which easily leads to the inaccuracy and instability of the matrix. This paper formulates the GRT true-amplitude inversion framework in an angle-domain version, which naturally degrades the external integral term related to the illumination in the conventional case. We solve the linearized integral equation for combined parameters of different fixed scattering angle values. With this step, we obtain high-quality angle-domain common-image gathers (CIGs) in the migration loop which provide correct amplitude-versus-angle (AVA) behavior and reasonable illumination range for subsurface image points. Then we deal with the over-determined problem to solve each parameter in the combination by a standard optimization operation. The angle-domain GRT inversion method keeps away from calculating the inaccurate and unstable illumination matrix. Compared with the conventional method, the angle-domain method can obtain more accurate amplitude information and wider amplitude-preserved range. Several model tests demonstrate the effectiveness and practicability.

Resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell reversed-field pinch

Science.gov (United States)

Malmberg, J.-A.; Brunsell, P. R.

2002-01-01

Observations of resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell (τw=6 ms) reversed field pinch are described. A nonresonant mode (m=1,n=-10) with the same handedness as the internal field grows nearly exponentially with an average growth time of about 2.6 ms (less than 1/2 of the shell time) consistent with linear stability theory. The externally nonresonant unstable modes (m=1,n>0), predicted by linear stability theory, are observed to have only low amplitudes (in the normal low-Θ operation mode of the device). The radial field of the dominant internally resonant tearing modes (m=1,n=-15 to n=-12) remain low due to spontaneous fast mode rotation, corresponding to angular phase velocities up to 280 krad/s. Phase aligned mode structures are observed to rotate toroidally with an average angular velocity of 40 krad/s, in the opposite direction of the plasma current. Toward the end of the discharge, the radial field of the internally resonant modes grows as the modes slow down and become wall-locked, in agreement with nonlinear computations. Fast rotation of the internally resonant modes has been observed only recently and is attributed to a change of the front-end system (vacuum vessel, shell, and TF coil) of the device.

An investigation on the solutions for the linear inverse problem in gamma ray tomography

International Nuclear Information System (INIS)

Araujo, Bruna G.M.; Dantas, Carlos C.; Santos, Valdemir A. dos; Finkler, Christine L.L.; Oliveira, Eric F. de; Melo, Silvio B.; Santos, M. Graca dos

2009-01-01

This paper the results obtained in single beam gamma ray tomography are investigated according to direct problem formulation and the applied solution for the linear system of equations. By image reconstruction based algebraic computational algorithms are used. The sparse under and over-determined linear system of equations was analyzed. Build in functions of Matlab software were applied and optimal solutions were investigate. Experimentally a section of the tube is scanned from various positions and at different angles. The solution, to find the vector of coefficients μ, from the vector of measured p values through the W matrix inversion, constitutes an inverse problem. A industrial tomography process requires a numerical solution of the system of equations. The definition of inverse problem according to Hadmard's is considered and as well the requirement of a well posed problem to find stable solutions. The formulation of the basis function and the computational algorithm to structure the weight matrix W were analyzed. For W full rank matrix the obtained solution is unique as expected. Total Least Squares was implemented which theory and computation algorithm gives adequate treatment for the problems due to non-unique solutions of the system of equations. Stability of the solution was investigating by means of a regularization technique and the comparison shows that it improves the results. An optimal solution as a function of the image quality, computation time and minimum residuals were quantified. The corresponding reconstructed images are shown in 3D graphics in order to compare with the solution. (author)

Novel AC Servo Rotating and Linear Composite Driving Device for Plastic Forming Equipment

Science.gov (United States)

Liang, Jin-Tao; Zhao, Sheng-Dun; Li, Yong-Yi; Zhu, Mu-Zhi

2017-07-01

The existing plastic forming equipment are mostly driven by traditional AC motors with long transmission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for complicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion without transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on the dynamic test benches are conducted. The results indicate that the output torque can attain to 420 N·m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive. the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accuracy direct driving device in plastic forming equipment.

Linear MHD equilibria

International Nuclear Information System (INIS)

Scheffel, J.

1984-03-01

The linear Grad-Shafranov equation for a toroidal, axisymmetric plasma is solved analytically. Exact solutions are given in terms of confluent hyper-geometric functions. As an alternative, simple and accurate WKBJ solutions are presented. With parabolic pressure profiles, both hollow and peaked toroidal current density profiles are obtained. As an example the equilibrium of a z-pinch with a square-shaped cross section is derived.(author)

Kinetic simulation of neutron production in a deuterium z-pinch

International Nuclear Information System (INIS)

Mostrom, C.; Stygar, William A.; Thoma, Carsten; Welch, Dale Robert; Clark, R.E.; Leeper, Ramon Joe; Rose, David V.

2010-01-01

We have found computationally that, at sufficiently high currents, half of the neutrons produced by a deuterium z pinch are thermonuclear in origin. Early experiments below 1-MA current found that essentially all of the neutrons produced by a deuterium pinch are not thermonuclear, but are initiated by an instability that creates beam-target neutrons. Many subsequent authors have supported this result while others have claimed that pinch neutrons are thermonuclear. To resolve this issue, we have conducted fully kinetic, collisional, and electromagnetic simulations of the complete time evolution of a deuterium pinch. We find that at 1-MA pinch currents, most of the neutrons are, indeed, beam-target in origin. At much higher current, half of the neutrons are thermonuclear and half are beam-target driven by instabilities that produce a power law fall off in the ion energy distribution function at large energy. The implications for fusion energy production with such pinches are discussed.

Current redistribution and generation of kinetic energy in the stagnated Z pinch.

Science.gov (United States)

Ivanov, V V; Anderson, A A; Papp, D; Astanovitskiy, A L; Talbot, B R; Chittenden, J P; Niasse, N

2013-07-01

The structure of magnetic fields was investigated in stagnated wire-array Z pinches using a Faraday rotation diagnostic at the wavelength of 266 nm. The distribution of current in the pinch and trailing material was reconstructed. A significant part of current can switch from the main pinch to the trailing plasma preheated by x-ray radiation of the pinch. Secondary implosions of trailing plasma generate kinetic energy and provide enhanced heating and radiation of plasma at stagnation. Hot spots in wire-array Z pinches also provide enhanced radiation of the Z pinch. A collapse of a single hot spot radiates 1%-3% of x-ray energy of the Z pinch with a total contribution of hot spots of 10%-30%.

Generalized inverses theory and computations

CERN Document Server

Wang, Guorong; Qiao, Sanzheng

2018-01-01

This book begins with the fundamentals of the generalized inverses, then moves to more advanced topics. It presents a theoretical study of the generalization of Cramer's rule, determinant representations of the generalized inverses, reverse order law of the generalized inverses of a matrix product, structures of the generalized inverses of structured matrices, parallel computation of the generalized inverses, perturbation analysis of the generalized inverses, an algorithmic study of the computational methods for the full-rank factorization of a generalized inverse, generalized singular value decomposition, imbedding method, finite method, generalized inverses of polynomial matrices, and generalized inverses of linear operators. This book is intended for researchers, postdocs, and graduate students in the area of the generalized inverses with an undergraduate-level understanding of linear algebra.

Application of charge coupled devices as spatially-resolved detectors for X-ray spectrograph

Energy Technology Data Exchange (ETDEWEB)

Attelan-Langlet, S; Etlicher, B [Ecole Polytechnique, Palaiseau (France); Mishenskij, V O; Papazyan, Yu V; Smirnov, V P; Volkov, G S; Zajtsev, V I [Inst. for Thermonuclear and Innovation Investigations, Troitsk (Russian Federation)

1997-12-31

An X-ray crystal spectrograph which contains a CCD linear array as the position-sensitive detector is described. Radiation detection is performed directly onto CCD. The spectrograph has a limit of sensitivity at about 2 J/(A.ster), spectral resolution about 1000 and dynamic range 100-120. The device operates on-line with IBM-PC based control system. Software provides all data acquisition and treatment. Output spectra are presented in absolute units. The device was used during composite Z-pinch experiments at pulse-power installations ``Angara-5-1`` (TRINITI, Troitsk, Russia) and ``GAEL`` (Ecole Polytechnique, Palaiseau, France). Currently the spectrograph is included in the set of diagnostics of the ``Angara-5-1`` facility. Some of the spectra obtained are presented and discussed. (author). 4 figs., 9 refs.

Development of Rayleigh-Taylor and bulk convection instabilities in the dynamics of plasma liners and pinches

International Nuclear Information System (INIS)

Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.

1989-01-01

A solution is derived for the problem of the initial, linear stage of the growth of small perturbations in the course of the cylindrically symmetric compression and expansion of a plasma liner and a Z-pinch with a sharp boundary. In these systems, Rayleigh-Taylor instabilities localized near the plasma boundaries are the most dangerous. Bulk convective instabilities develop in addition to these Rayleigh-Taylor instabilities. The various instability modes, including local and global Rayleigh-Taylor modes, which grown in an accelerated plasma with distributed profiles of hydrodynamic variables, are classified. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The shape of these spectra reveals an explanation of the stratification and filamentation of the plasma observed experimentally in pinches and liners. The imposition of a longitudinal magnetic field gives rise to a stability window in the space of the flow parameters. In this window, the Rayleigh-Taylor modes are suppressed completely by magnetic shear, while the bulk convective modes are suppressed to a significant extent

Few-photon Non-linearities in Nanophotonic Devices for Quantum Information Technology

DEFF Research Database (Denmark)

Nysteen, Anders

In this thesis we investigate few-photon non-linearities in all-optical, on-chip circuits, and we discuss their possible applications in devices of interest for quantum information technology, such as conditional two-photon gates and single-photon sources. In order to propose efficient devices...... the scattered photons. Even though the non-linearity also alters the pulse spectrum due to a four-wave mixing process, we demonstrate that input pulses with a Gaussian spectrum can be mapped to the output with up to 80 % fidelity. Using two identical two-level emitters, we propose a setup for a deterministic...... by the capturing process. Semiconductor quantum dots (QDs) are promising for realizing few-photon non-linearities in solid-state implementations, although coupling to phonon modes in the surrounding lattice have significant influence on the dynamics. By accounting for the commonly neglected asymmetry between...

Does shaping bring an advantage for reversed field pinch plasmas?

International Nuclear Information System (INIS)

Guo, S.C.; Xu, X.Y.; Wang, Z.R.; Liu, Y.Q.

2013-01-01

The MHD–kinetic hybrid toroidal stability code MARS-K (Liu et al 2008 Phys. Plasmas 15 112503) is applied to study the shaping effects on magnetohydrodynamic (MHD) stabilities in reversed field pinch (RFP) plasmas, where both elongation and triangularity are taken into account. The ideal wall β (the ratio of the gaso-kinetic to magnetic pressures) limit set by the ideal kink mode/resistive wall mode in shaped RFP is investigated first, followed by a study of the kinetic damping on the resistive wall mode. Physics understanding of the results is provided by a systematic numerical analysis. Furthermore, the stability boundary of the linear resistive tearing mode in shaped RFP plasmas is computed and compared with that of the circular case. Finally, bootstrap currents are calculated for both circular and shaped RFP plasmas. Overall, the results of these studies indicate that the current circular cross-section is an appropriate choice for RFP devices, in the sense that the plasma shaping does not bring an appreciable advantage to the RFP performance in terms of macroscopic stabilities. In order to reach a steady-state operation, future RFP fusion reactors will probably need a substantial fraction of external current drives, due to the unfavourable scaling for the plasma-generated bootstrap current in the RFP configuration. (paper)

Self-similar oscillations of the Extrap pinch

International Nuclear Information System (INIS)

Tendler, M.

1987-11-01

The method of the dynamic stabilization is invoked to explain the enhanced stability of a Z-pinch in EXTRAP configuration. The oscillatory motion is assumed to be forced on EXTRAP due to self-similar oscillations of a Z-pinch. Using a scaling for the net energy loss with plasma density and temperature typical for divertor configurations, a new analytic, self-similar solution of the fluid equations is presented. Strongly unharmonic oscillations of the plasma parameters in the pinch arise. These results are used in a discussion on the stability of EXTRAP, considered as a system with a time dependent internal magnetic field. The effect of the dynamic stabilization is considered by taking estimates. (author)

The linearized inversion of the generalized interferometric multiple imaging

KAUST Repository

Aldawood, Ali

2016-09-06

The generalized interferometric multiple imaging (GIMI) procedure can be used to image duplex waves and other higher order internal multiples. Imaging duplex waves could help illuminate subsurface zones that are not easily illuminated by primaries such as vertical and nearly vertical fault planes, and salt flanks. To image first-order internal multiple, the GIMI framework consists of three datuming steps, followed by applying the zero-lag cross-correlation imaging condition. However, the standard GIMI procedure yields migrated images that suffer from low spatial resolution, migration artifacts, and cross-talk noise. To alleviate these problems, we propose a least-squares GIMI framework in which we formulate the first two steps as a linearized inversion problem when imaging first-order internal multiples. Tests on synthetic datasets demonstrate the ability to localize subsurface scatterers in their true positions, and delineate a vertical fault plane using the proposed method. We, also, demonstrate the robustness of the proposed framework when imaging the scatterers or the vertical fault plane with erroneous migration velocities.

Growth of Rayleigh-Taylor and bulk convective instabilities in dynamics of plasma liners and pinches

International Nuclear Information System (INIS)

Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.

1989-01-01

Perturbation growth is studied for the initial, linear stage of an instability development in the course of a cylindrically-symmetric compression and expansion of plasma liners and Z-pinches with a sharp boundary. The hydrodynamic instabilities are Rayleigh-Taylor and bulk convective ones, the former being the most dengerous. Classification of the instability modes developing in accelerated plasmas, inclusing the local and global Rayleigh-Taylor modes, is given. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The properties of the spectra appear to explain the filamentation and stratification of plasmas observed in the experiments with liners and Z-pinches. An axial magnetic field is shown to create a window of stability in the space of the flow parameters, where th Rayleigh-Taylor modes are fully suppressed by the magnetic shear, and the bulk convective ones - to a considerable extent. The axial magnetic field required to stabilize the implosion of a liner is estimated as B z0 =(10-30 kG)I(MA)/R 0 (cm), where I is the average current, R 0 - the initial radius of the liner

Performance improvement of centrifugal compressor stage with pinched geometry or vaned diffuser

Energy Technology Data Exchange (ETDEWEB)

Jaatinen, A.

2009-07-01

Centrifugal compressors are widely used for example in refrigeration processes, the oil and gas industry, superchargers, and waste water treatment. In this work, five different vaneless diffusers and six different vaned diffusers are investigated numerically. The vaneless diffusers vary only by their diffuser width, so that four of the geometries have pinch implemented to them. Pinch means a decrease in the diffuser width. Four of the vaned diffusers have the same vane turning angle and a different number of vanes, and two have different vane turning angles. The flow solver used to solve the flow fields is Finfo, which is a Navier-Stokes solver. All the cases are modeled Chien's k-epsilon turbulence model. All five vaneless diffusers and three vaned diffusers are investigated also experimentally. For each construction, the compressor operating map is measured according to relevant standards. In addition to this, the flow fields before and after the diffuser are measured with static and total pressure, flow angle and total temperature measurements k-omega SST turbulence model. The simulation results indicate that it is possible to improve the efficiency with the pinch, and according to the numerical results, the two best geometries are the ones with most pinch at the shroud. These geometries have approximately 4 percentage points higher effciency than the unpinched vaneless diffusers. The hub pinch does not seem to have any major benefits. In general, the pinches make the flow fields before and after the diffuser more uniform. The pinch also seems to improve the impeller effciency. This is down to two reasons. The major reason is that the pinch decreases the size of slow flow and possible backflow region located near the shroud after the impeller. Secondly, the pinches decrease the flow velocity in the tip clearance, leading to a smaller tip leakage flow and therefore slightly better impeller efficiency. Also some of the vaned diffusers improve the efficiency

Analysis of X-ray iron and nickel radiation and jets from planar wire arrays and X-pinches

International Nuclear Information System (INIS)

Safronova, A S; Kantsyrev, V L; Esaulov, A A; Ouart, N D; Shlyaptseva, V; Williamson, K M; Shrestha, I; Osborne, G C; Weller, M E

2010-01-01

University-scale Z-pinch devices are able to produce plasmas with a broad range of sizes, temperatures, densities, their gradients, and opacity properties. Radiative properties of such plasmas depend on material, mass, and configuration of the wire array loads. Experiments with two different types of loads, double planar wire arrays (DPWA) and X-pinches, performed on the 1 MA Zebra generator at UNR are analyzed. X-pinches are made from Stainless Steel (69% Fe, 20% Cr, and 9% Ni) wires. Combined DPWAs consist of one plane from SS wires and another plane from Alumel (95% Ni, 2% Al, 2% Si) wires. The main focus of this work is on the analysis of plasma jets at the early phase of plasma formation and the K-and L-shell radiation generation at the implosion and stagnation phases in experiments with the two aforementioned wire loads. The relevant theoretical tools that guide the data analysis include non-LTE collisional-radiative and wire ablation dynamics models. The astrophysical relevance of the plasma jets as well as of spectroscopic and imaging studies are demonstrated.

Effects of boundary conditions on temperature and density in an EXTRAP Z-pinch

International Nuclear Information System (INIS)

Drake, J.R.; Karlsson, P.

1985-08-01

Using the fluid equations, we examine transport in an Extrap configuration by carrying out calculations incorporating model profiles for the density and temperature. The goal of this analysis is to examine the scaling of the pinch equilibrium plasma density, temperature and radius with parameters that are characteristic for Extrap Z-pinches. These parameters include the discharge current, the neutral hydrogen filling density, an oxygen impurity fractional concentration and the condition at the pinch boundary. An Extrap Z-pinch is a pinch discharge where the current channel has a characteristic non-circular cross-section achieved by bounding the discharge by a magnetic separatrix produced when a vacuum octupole magnetic field, generated by currents in external conductors, combines with the self-magnetic field produced by the discharge current. The pinch boundary is changed from a plasma-vacuum boundary to an interface between a high-beta pinch plasma and a low-beta plasma contained in the vacuum magnetic field. The energy that is lost from the pinch region sustains this boundary layer. The introduction of a separatrix boundary around the pinch with four X-point nulls deteriorates the containment of the pinch somewhat. However the presence of the warm, low-beta plasma scrape-off layer, which provides a boundary condition on the pinch, tends to counteract the negative effects of the poorer confinement. Thus the equilibrium parameters that characterize the pinch may not be severely deteriorated by the introduction of the separatrix when the entire configuration, including the scrape-off layer, is considered. (author)

Development of a Z-pinch-driven ICF hohlraum concept on Z

International Nuclear Information System (INIS)

Cuneo, M.E.; Porter, J.L. Jr.; Vesey, R.A.

1999-01-01

Recent development of high power z-pinches (> 150 MW) on the Z driver has permitted the study of high-temperature, radiation-driven hohlraums. Three complementary, Z-pinch source-hohlraum-ICF capsule configurations are being developed to harness the x-ray output of these Z-pinch's. These are the dynamic-hohlraum, static-wall hohlraum, and Z-pinch-driven hohlraum concepts. Each has different potential strengths and concerns. In this paper, the authors report on the first experiments with the Z-pinch-driven hohlraum (ZPDH) concept. A high-yield ICF capsule design for this concept appears feasible, when driven by z-pinches from a 60 MA-class driver. Initial experiments characterize the behavior of the spoke array on Z-pinch performance and x-ray transmission, and the uniformity of radiation flux incident on a foam capsule in the secondary, for a single-sided drive. Measurements of x-ray wall re-emission power and spectrum, radiation temperatures, spoke-plasma location, and drive uniformity will be presented and compared with 0-D energetics, 2-D Lasnex rad-hydro, and 3-D radiosity calculations of energy transport and drive uniformity

Development of a Z-pinch-driven ICF hohlraum concept on Z

Energy Technology Data Exchange (ETDEWEB)

Cuneo, M E; Porter, Jr, J L; Vesey, R A [and others

1999-07-01

Recent development of high power z-pinches (> 150 MW) on the Z driver has permitted the study of high-temperature, radiation-driven hohlraums. Three complementary, Z-pinch source-hohlraum-ICF capsule configurations are being developed to harness the x-ray output of these Z-pinch's. These are the dynamic-hohlraum, static-wall hohlraum, and Z-pinch-driven hohlraum concepts. Each has different potential strengths and concerns. In this paper, the authors report on the first experiments with the Z-pinch-driven hohlraum (ZPDH) concept. A high-yield ICF capsule design for this concept appears feasible, when driven by z-pinches from a 60 MA-class driver. Initial experiments characterize the behavior of the spoke array on Z-pinch performance and x-ray transmission, and the uniformity of radiation flux incident on a foam capsule in the secondary, for a single-sided drive. Measurements of x-ray wall re-emission power and spectrum, radiation temperatures, spoke-plasma location, and drive uniformity will be presented and compared with 0-D energetics, 2-D Lasnex rad-hydro, and 3-D radiosity calculations of energy transport and drive uniformity.

Study of 1D complex resistivity inversion using digital linear filter technique; Linear filter ho wo mochiita fukusohi teiko no gyakukaisekiho no kento

Energy Technology Data Exchange (ETDEWEB)

Sakurai, K; Shima, H [OYO Corp., Tokyo (Japan)

1996-10-01

This paper proposes a modeling method of one-dimensional complex resistivity using linear filter technique which has been extended to the complex resistivity. In addition, a numerical test of inversion was conducted using the monitoring results, to discuss the measured frequency band. Linear filter technique is a method by which theoretical potential can be calculated for stratified structures, and it is widely used for the one-dimensional analysis of dc electrical exploration. The modeling can be carried out only using values of complex resistivity without using values of potential. In this study, a bipolar method was employed as a configuration of electrodes. The numerical test of one-dimensional complex resistivity inversion was conducted using the formulated modeling. A three-layered structure model was used as a numerical model. A multi-layer structure with a thickness of 5 m was analyzed on the basis of apparent complex resistivity calculated from the model. From the results of numerical test, it was found that both the chargeability and the time constant agreed well with those of the original model. A trade-off was observed between the chargeability and the time constant at the stage of convergence. 3 refs., 9 figs., 1 tab.

A solvable self-similar model of the sausage instability in a resistive Z pinch

International Nuclear Information System (INIS)

Lampe, M.

1991-01-01

A solvable model is developed for the linearized sausage mode within the context of resistive magnetohydrodynamics. The model is based on the assumption that the fluid motion of the plasma is self-similar, as well as several assumptions pertinent to the limit of wavelength long compared to the pinch radius. The perturbations to the magnetic field are not assumed to be self-similar, but rather are calculated. Effects arising from time dependences of the z-independent perturbed state, e.g., current rising as t α , Ohmic heating, and time variation of the pinch radius, are included in the analysis. The formalism appears to provide a good representation of ''global'' modes that involve coherent sausage distortion of the entire cross section of the pinch, but excludes modes that are localized radially, and higher radial eigenmodes. For this and other reasons, it is expected that the model underestimates the maximum instability growth rates, but is reasonable for global sausage modes. The net effect of resistivity and time variation of the unperturbed state is to decrease the growth rate if α approx-lt 1, but never by more than a factor of about 2. The effect is to increase the growth rate if α approx-gt 1

Impact of PINCH expression on survival in colorectal cancer patients

International Nuclear Information System (INIS)

Lööf, Jasmine; Rosell, Johan; Bratthäll, Charlotte; Doré, Siv; Starkhammar, Hans; Zhang, Hong; Sun, Xiao-Feng

2011-01-01

The adaptor protein PINCH is overexpressed in the stroma of several types of cancer, and is an independent prognostic marker in colorectal cancer. In this study we further investigate the relationship of PINCH and survival regarding the response to chemotherapy in colorectal cancer. Paraffin-embedded tissue sections from 251 primary adenocarcinomas, 149 samples of adjacent normal mucosa, 57 samples of distant normal mucosa and 75 lymph node metastases were used for immunohistochemical staining. Stromal staining for PINCH increased from normal mucosa to primary tumour to metastasis. Strong staining in adjacent normal mucosa was related to worse survival independently of sex, age, tumour location, differentiation and stage (p = 0.044, HR, 1.60, 95% CI, 1.01-2.52). PINCH staining at the invasive margin tended to be related to survival (p = 0.051). In poorly differentiated tumours PINCH staining at the invasive margin was related to survival independently of sex, age and stage (p = 0.013, HR, 1.90, 95% CI, 1.14-3.16), while in better differentiated tumours it was not. In patients with weak staining, adjuvant chemotherapy was related to survival (p = 0.010, 0.013 and 0.013 in entire tumour area, invasive margin and inner tumour area, respectively), but not in patients with strong staining. However, in the multivariate analysis no such relationship was seen. PINCH staining in normal adjacent mucosa was related to survival. Further, PINCH staining at the tumour invasive margin was related to survival in poorly differentiated tumours but not in better differentiated tumours, indicating that the impact of PINCH on prognosis was dependent on differentiation status

Influence of pinches on magnetic reconnection in turbulent space plasmas

Science.gov (United States)

Olshevsky, Vyacheslav; Lapenta, Giovanni; Markidis, Stefano; Divin, Andrey

A generally accepted scenario of magnetic reconnection in space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is widely studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present nitially, and Z-pinches are formed during the simulation. The X-points are relatively stable, and no substantial energy dissipation is associated with them. On contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of approximately 1.5 percent per ion gyro period. Current channels and twisted magnetic fields are ubiquitous in turbulent space plasmas, so pinches can be responsible for the observed high magnetic reconnection rates.

Experimental studies of the argon-puff Z-pinch implosion process

International Nuclear Information System (INIS)

Huang Xianbin; Yang Libing; Gu Yuanchao; Deng Jianjun; Zhou Rongguo; Zou Jie; Zhou Shaotong; Zhang Siqun; Chen Guanghua; Chang Lihua; Li Fengping; Ouyang Kai; Li Jun; Yang Liang; Wang Xiong; Zhang Zhaohui

2006-01-01

A preliminary experiment for studying the argon-puff Z-pinch implosion process has been performed on the Yang accelerator. The ten-frame nanosecond temporal and spatial gated camera, visible high-speed scanning camera, differential laser interferometer, X-ray time integration pinhole camera and X-ray power system have been used to investigated the evolution of the argon-puff Z-pinch. Some typical results of argon-puff Z-pinch during implosion and pinch phase, including the 'zipper' effect, necking phenomenon, sausage instability, temperature changes and the effect of load current rise time, are given and analyzed as examples, and some relevant conclusions are drawn. (authors)

Determination of plasma Z-pinch effect by intrinsic stimulated emission

International Nuclear Information System (INIS)

Lue, J.T.; Liang, J.M.

1977-01-01

The plasma Z-pinch behavior has been observed in a relatively small-bore diameter tube and low bank voltage discharge system. The instant of the occurrence of the laser line at 4880 A coincides with the plasma pinch time calculated by using a one-fluid snow-plow model. A determination of plasma pinch parameters by measuring the intrinsic stimulated emission of the ions is described

Asymmetric flux generation and its relaxation in reversed field pinch

International Nuclear Information System (INIS)

Arimoto, H.; Masamune, S.; Nagata, A.

1985-02-01

The toroidally asymmetric flux enhancement [''dynamo effect''] and the axisymmetrization of the enhanced fluxes that follows in the setting up phase of Reversed Field Pinch are investigated on the STP-3[M] device. A rapid increase in the toroidal flux generated by the dynamo effect is first observed near the poloidal and toroidal current feeders. Then, this inhomogeneity of the flux propagates toroidally towards the plasma current. The axisymmetrization of the flux is attained just after the maximum of plasma current. The MHD activities decrease significantly after this axisymmetrization and the quiescent period is obtained. (author)

Development of a sub-nanometer positioning device: combining a new linear motor with linear motion ball guide ways

International Nuclear Information System (INIS)

Otsuka, J; Tanaka, T; Masuda, I

2010-01-01

A new type of linear motor described in this note has some advantages compared with conventional motors. The attractive magnetic force between the stator (permanent magnets) and mover (armature) is diminished almost to zero. The efficiency is better because the magnetic flux leakage is very small, the size of motor is smaller and detent (force ripple) is smaller than for conventional motors. Therefore, we think that this motor is greatly suitable for ultra-precision positioning as an actuator. An ultra-precision positioning device using this motor and linear motion ball guide ways is newly developed by making the device very rigid and using a suitable control method. Moreover, the positioning performance is evaluated by a positioning resolution, and deviation and dispersion errors. As a result of repeated step response tests, the positioning resolution is 0.3 nm, with the deviation error and dispersion error (3σ) being sub-nanometer. Consequently, the positioning device achieves sub-nanometer positioning. (technical design note)

Development of sausage-type instability in a Z-pinch plasma column

International Nuclear Information System (INIS)

Vikhrev, V.V.; Ivanov, V.V.; Rozanova, G.A.

1993-01-01

The development of sausage-type instabilities in an initially homogeneous Z-pinch plasma column has been investigated by means of numerical modelling. It is shown that in the presence of short-wave perturbations of a Z-pinch boundary and a rarefied plasma surrounding the pinch, cavities filled with a rarefied plasma and with a magnetic field are formed in the plasma column. As a result of this cavity growth, small columns of dense plasma form on the axis in the Z-pinch which have a temperature substantially higher than the average plasma temperature in the plasma column. When deuterium is present in the pinch, these dense high temperature bunches can become a source of intensive neutron radiation. (author). 24 refs, 7 figs

ANALYSIS OF POWER GRIP AND PINCH GRIP AMONG HEALTH CARE PROFESSIONALS

Directory of Open Access Journals (Sweden)

Zakariya M P

2016-02-01

Full Text Available Background: Grip and pinch strength are commonly employed indices of strength used in hand evaluations. Pinch grip and power grip strengths are used as indices of strength in hand therapy assessments. For all professions grip strength is an important criterion to be successful in their profession. Such phenomena may be explained by differences in nature of work, working environment, and objects workers handle. Method: 200 healthy subjects, satisfying the selection criteria were included and assessed with standardized procedure for power grip and pinch grip (lateral pinch, pad-pad, and tip-tip strength. They were divided in four groups, 50 group each according to profession i.e. medical surgeons, dentist, physiotherapists and nurses. Results: The mean power grip strength shows highly significant difference between medical vs. dental (p>0.01 and medical vs. physiotherapy group (p> 0.05 .The mean lateral pinch strength shows there is highly significant difference (p< 0.001 between dental vs. nursing profession and dental vs. physiotherapy group. No significant difference among other groups. The mean pad-pad pinch strength shows there is significant difference between dental vs. nursing (p< 0.05 and dental vs physiotherapy group (p< 0.05. The mean Tip-Tip pinch strength shows there is significant difference between dental vs nursing profession(p< 0.05 and dental vs. physiotherapy(p< 0.05. No significant different among other groups. Conclusion: Surgeons have highest power grip strength followed by Nursing, Physiotherapy and Dental professionals. Dentists have the maximum pinch strength in all three positions, followed by Surgeons, Nurses and Physiotherapists. Surgeons have maximum pinch strength next to Dentists.

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas.

Science.gov (United States)

Wallace, M S; Haque, S; Neill, P; Pereira, N R; Presura, R

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Pulsed x-ray generation from a plasma focus device

International Nuclear Information System (INIS)

Zambra, M; Bruzzone, H; Sidelnikov, Y; Kies, W; Moreno, C; Sylvester, G; Silva, P; Moreno, J; Soto, L

2003-01-01

Dynamical pinches coupled to electrodes like the dense Z-pinch or the dense plasma focus have been intensively studied in the last four decades for their high fusion efficiency and their application potential. Though the expectations of the eighties of the last century, scaling these pinches up to fusion reactors, did not come true, the development of fast and powerful experiments resulted in new insights in pinch physics and paved the way for developing compact dynamical pinches as pulsed neutron and X-radiation sources for many applications. There is a permanent and growing interest in the research community for understanding and determining the generation properties of X-rays, neutrons and charged particles emitted from a high-temperature high-density plasmas, especially in the plasma focus configuration. The Plasma Physics and Plasma Technology Group of the CCHEN has developed the SPEED4 fast-plasma focus device, in collaboration with the Plasma Physics Group of the Dusseldorf University, in order to perform experimental studies such as X-ray and neutron emission, and electron and ion beam characterization (author)

3-dimensional simulation of dynamo effect of reversed field pinch

International Nuclear Information System (INIS)

Koide, Shinji.

1990-09-01

A non-linear numerical simulation of the dynamo effect of a reversed field pinch (RFP) with finite beta is presented. It is shown that the m=-1, n=(9,10,11,....,19) modes cause the dynamo effect and sustain the field reversed configuration. The role of the m=0 modes on the dynamo effect is carefully examined. Our simulation shows that the magnetic field fluctuation level scales as S -0.2 or S -0.3 in the range of 10 3 5 , while Nebel, Caramana and Schnack obtained the fluctuation level is independent of S for a pressureless RFP plasma. (author)

Effect of transcranial magnetic stimulation on force of finger pinch

Science.gov (United States)

Odagaki, Masato; Fukuda, Hiroshi; Hiwaki, Osamu

2009-04-01

Transcranial magnetic stimulation (TMS) is used to explore many aspects of brain function, and to treat neurological disorders. Cortical motor neuronal activation by TMS over the primary motor cortex (M1) produces efferent signals that pass through the corticospinal tracts. Motor-evoked potentials (MEPs) are observed in muscles innervated by the stimulated motor cortex. TMS can cause a silent period (SP) following MEP in voluntary electromyography (EMG). The present study examined the effects of TMS eliciting MEP and SP on the force of pinching using two fingers. Subjects pinched a wooden block with the thumb and index finger. TMS was applied to M1 during the pinch task. EMG of first dorsal interosseous muscles and pinch forces were measured. Force output increased after the TMS, and then oscillated. The results indicated that the motor control system to keep isotonic forces of the muscles participated in the finger pinch was disrupted by the TMS.

Scaling of X pinches from 1 MA to 6 MA

International Nuclear Information System (INIS)

Bland, Simon Nicholas; McBride, Ryan D.; Wenger, David Franklin; Sinars, Daniel Brian; Chittenden, Jeremy Paul; Pikuz, Sergei A.; Harding, Eric; Jennings, Christopher A.; Ampleford, David J.; Yu, Edmund P.; Cuneo, Michael Edward; Shelkovenko, Tatiana A.; Hansen, Stephanie B.

2010-01-01

This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

Experimental study of the neck formation in an X pinch

International Nuclear Information System (INIS)

Artyomov, A P; Chaikovsky, S A; Fedunin, A V; Labetskaya, N A; Rousskikh, A G; Zhigalin, A S; Oreshkin, V I

2014-01-01

X-pinch experiments have been performed on a compact 250 kA, 180 ns pulsed power generator specially designed for this purpose at the Institute of High Current Electronics (Tomsk, Russia). The X pinches were composed of two molybdenum wires of diameter 25 μm making an angle of 36° with the z-axis. The X-pinch dynamics was recorded with a 3 ns exposure time using an HSFC Pro four-frame camera. Axial plasma jets propagating toward both the anode and the cathode were observed. The jets became noticeable within 10 ns after the onset of current flow, which approximately corresponded to the time at which the electrical explosion of the X-pinch wires occurred. The velocity of the anode-directed jet reached 10 7 cm/s, which was about 1.5 times the velocity of the cathode-directed jet. These high jet velocities are inconsistent with the plasma temperature resulting from the wire explosion. Hence, these jets seem to develop due to implosion of the light plasma layer stripped by magnetic forces from the wire surface, and the increase in their velocities is perhaps due to cumulative effects taking place at the X-pinch axis. The X-pinch neck formed as a rule above the initial wire cross point (closer to the anode). In this region, the plasma diameter gradually increased with time and then drastically decreased 10-15 ns prior to the x-ray pulse. Immediately before the x-ray pulse, in the (250-300 μm long) plasma neck, a lower scale constriction developed, forming a h ot spot . It has been confirmed that the anode-directed plasma jet could take some part of the X-pinch wire current because of the evident jet pinching in the anode region. This process seems to determine the neck length

A vented pump limiter for the reversed field pinch RFX

International Nuclear Information System (INIS)

Sonato, P.

1998-01-01

The reversed field pinch (RFP) plasma performance, as in the Tokamak, is strongly correlated with the edge neutral particle control. The drawbacks of the conventional magnetic divertors and throat limiters on the RFP plasma have slackened the application of an active particle control system in existing devices. An advanced solution, based on the idea of the 'vented pump limiter' experimented on Tore Supra, has been conceived for RFX. This type of pump limiter is very attractive for a RFP. In this paper, the design of a 'vented limiter' prototype for RFX is presented. Up to six modules of this limiter can be installed at the equatorial plane of RFX, allowing a particle exhaust efficiency comparable with a divertor or a throat limiter working in a Tokamak. Finally, the optimization of this concept for the next step RFP device is presented. (orig.)

Investigation of layered Z-pinches on ANGARA-5-1

Energy Technology Data Exchange (ETDEWEB)

Branitskij, A V; Grabovskij, E V; Zakharov, S V; Zurin, M V; Nedoseev, S L; Olejnik, G M; Smirnov, V P; Frolov, I N [Troitsk Inst. of Innovative and Fusion Research (Russian Federation)

1997-12-31

Experimental results of layered Z-pinch investigations on Angara-5-1 are presented. The level of current was 3-4 MA through a load with a 70-90 ns rise time. The initial-to-final radius ratio increased from 10-15 for a conventional single pinch, up to 30-50 for the double layered design. A power flux of about 8-12 TW/cm{sup 2} was achieved with front rise time about 3 ns. The final pinch diameter was down to 0.5-1 mm. (author). 4 figs., 1 ref.

X-ray sources by Z-pinch for inertial confinement fusion

International Nuclear Information System (INIS)

Akiyama, Hidenori; Katsuki, Sunao; Lisitsyn, Igor

1999-01-01

Inertial confinement nuclear fusion driven by X-ray from Z-pinch plasmas has been developed. Recently, extremely high X-ray power (290 TW) and energy (1.8 MJ) were produced in fast Z-pinch implosions on the Z accelerator (Sandia National Laboratories). Wire arrays are used to produce the initial plasma. The X-ray from Z-pinch plasmas produced by pulsed power has great potential as a driver of inertial confinement nuclear fusion. (author)

SLAC linear collider conceptual design report

Energy Technology Data Exchange (ETDEWEB)

1980-06-01

The linear collider system is described in detail, including the transport system, the collider lattice, final focusing system, positron production, beam damping and compression, high current electron source, instrumentation and control, and the beam luminosity. The experimental facilities and the experimental uses are discussed along with the construction schedule and estimated costs. Appendices include a discussion of space charge effects in the linear accelerator, emittance growth in the collider, the final focus system, beam-beam instabilities and pinch effects, and detector backgrounds. (GHT)

SLAC linear collider conceptual design report

International Nuclear Information System (INIS)

1980-06-01

The linear collider system is described in detail, including the transport system, the collider lattice, final focusing system, positron production, beam damping and compression, high current electron source, instrumentation and control, and the beam luminosity. The experimental facilities and the experimental uses are discussed along with the construction schedule and estimated costs. Appendices include a discussion of space charge effects in the linear accelerator, emittance growth in the collider, the final focus system, beam-beam instabilities and pinch effects, and detector backgrounds

The stability of the High-Density Z-Pinch

International Nuclear Information System (INIS)

Glasser, A.H.; Nebel, R.A.

1989-01-01

Fiber-initiated High Density Z-Pinches at Los Alamos, NRL, and Karlsruhe have shown anomalously good stability. Kink modes are never seen, and sausage modes are at least delayed until late in the discharge. The success of these devices in reaching fusion conditions may depend on maintaining and understanding this anomalous stability. We have developed two numerical methods to study the stability in the regime where fluid theory is valid. While our methods are applicable to all modes, we will describe them only for the m = 0 sausage mode. The appearance of sausage modes late in the discharge and the total absence of kink modes suggest that an understanding of sausage modes is more urgent, and it is also simpler. 14 refs., 8 figs

The stability of the high-density z-pinch

International Nuclear Information System (INIS)

Glasser, A.H.; Nebel, R.A.

1989-01-01

Fiber-initiated High Density Z-Pinches at Los Alamos, NRL, and Karlsruhe have shown anomalously good stability. Kink modes are never seen, and sausage modes are at least delayed until late in the discharge. The success of these devices in reaching fusion conditions may depend on maintaining and understanding this anomalous stability. We have developed two numerical methods to study the stability in the regime where fluid theory is valid. While our methods are applicable to all modes, we will describe them only for the m=0 sausage mode. The appearance of sausage modes late in the discharge and the total absence of kink modes suggest that an understanding of sausage modes is more urgent, and it is also simpler

Inverse problems of geophysics

International Nuclear Information System (INIS)

Yanovskaya, T.B.

2003-07-01

This report gives an overview and the mathematical formulation of geophysical inverse problems. General principles of statistical estimation are explained. The maximum likelihood and least square fit methods, the Backus-Gilbert method and general approaches for solving inverse problems are discussed. General formulations of linearized inverse problems, singular value decomposition and properties of pseudo-inverse solutions are given

Basis set expansion for inverse problems in plasma diagnostic analysis

Energy Technology Data Exchange (ETDEWEB)

Jones, B.; Ruiz, C. L. [Sandia National Laboratories, PO Box 5800, Albuquerque, New Mexico 87185 (United States)

2013-07-15

A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)] is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20–25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.

The ZaP Flow Z-Pinch Project - Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Shumlak, Uri [Univ. of Washington, Seattle, WA (United States); Nelson, Brian A. [Univ. of Washington, Seattle, WA (United States)

2013-12-31

The ZaP Flow Z-Pinch Project is a project to extend the performance of the flow Z-pinch experiment at the University of Washington to investigate and isolate the relevant physics of the stabilizing effect of plasma flow. Experimental plasmas have exhibited an enhanced stability under certain operating parameters which generate a flow state (axial flows in Z-pinches and VH mode in tokamaks). Flow has also been suggested as the stabilizing mechanism in astrophysical jets.

Computational modeling of z-pinch-driven hohlraum experiments on Z

International Nuclear Information System (INIS)

Vesey, R.A.; Porter, J.L. Jr.; Cuneo, M.E.

1999-01-01

The high-yield inertial confinement fusion concept based on a double-ended z-pinch driven hohlraum tolerates the degree of spatial inhomogeneity present in z-pinch plasma radiation sources by utilizing a relatively large hohlraum wall surface to provide spatial smoothing of the radiation delivered to the fusion capsule. The z-pinch radiation sources are separated from the capsule by radial spoke arrays. Key physics issues for this concept are the behavior of the spoke array (effect on the z-pinch performance, x-ray transmission) and the uniformity of the radiation flux incident on the surface of the capsule. Experiments are underway on the Z accelerator at Sandia National laboratories to gain understanding of these issues in a single-sided drive geometry. These experiments seek to measure the radiation coupling among the z-pinch, source hohlraum, and secondary hohlraum, as well as the uniformity of the radiation flux striking a foam witness ball diagnostic positioned in the secondary hohlraum. This paper will present the results of computational modeling of various aspects of these experiments

A note on the relationship between the emittance, the beta function and the energy in a linear collider

International Nuclear Information System (INIS)

Rees, J.

1986-11-01

Scaling laws for linear colliders are considered for the case of laterally round Gaussian beams and for the case that mutual pinching of the beams can be ignored. Based on these assumptions, the relationship is found between the interaction area, beta function, beam emittance, and energy for a linear collider in order to show the need for substantial improvements in the feasible values of accelerator parameters to reach a center of mass energy of 0.7 TeV. Pinch is then taken into account

The pinch of cold ions from recycling in the tokamak edge pedestal

International Nuclear Information System (INIS)

Wan Weigang; Parker, Scott E.; Chen Yang; Park, Gun-Young; Chang, Choong-Seock; Stotler, Daren

2011-01-01

We apply the ''natural fueling mechanism'' [W. Wan, S. E. Parker, Y. Chen, and F. W. Perkins, Phys. Plasmas 17, 040701 (2010)] to the edge pedestal. The natural fueling mechanism is where cold ions naturally pinch radially inward for a heat-flux dominated plasma. It is shown from neoclassical-neutral transport coupled simulations that the recycling neutrals and the associated source ions are colder than the main ions in the edge pedestal. These recycling source ions will pinch radially inward due to microturbulence. Gyrokinetic turbulence simulations indicate that near the top of the pedestal, the pinch velocity of the recycling source ions is much higher than the main ion outgoing flow velocity. The turbulent pinch of the recycling source ions may play a role in the edge pedestal transport and dynamics. The cold ion temperature significantly enhances the pinch velocity of the recycling source ions near to the pedestal top. Neoclassical calculations show a cold ion pinch in the pedestal as well.

High current density toroidal pinch discharges with weak toroidal fields

International Nuclear Information System (INIS)

Brunsell, P.; Brzozowski, J.; Drake, J.R.; Hellblom, G.; Kaellne, E.; Mazur, S.; Nordlund, P.

1990-01-01

Toroidal discharges in the ultralow q regime (ULQ) have been studied in the rebuilt Extrap TI device. ULQ discharges are sustained for pulse lengths exceeding 1 ms, which corresponds to more than 10 resistiv shell times. Values for the safety factor at the vacuum vessel wall are between rational values: 1/(n+1) -2 . The magnetic fluctuation level increases during the transition between rational values of q(a). For very low values of q(a), the loop voltage increases and the toroidal field development in the discharge exhibits the characteristic behaviour of the setting-up phase of a field reversed pinch. (author) 1 ref., 2 figs., 1 tab

Thermoelectric efficiency of nanoscale devices in the linear regime

Science.gov (United States)

Bevilacqua, G.; Grosso, G.; Menichetti, G.; Pastori Parravicini, G.

2016-12-01

We study quantum transport through two-terminal nanoscale devices in contact with two particle reservoirs at different temperatures and chemical potentials. We discuss the general expressions controlling the electric charge current, heat currents, and the efficiency of energy transmutation in steady conditions in the linear regime. With focus in the parameter domain where the electron system acts as a power generator, we elaborate workable expressions for optimal efficiency and thermoelectric parameters of nanoscale devices. The general concepts are set at work in the paradigmatic cases of Lorentzian resonances and antiresonances, and the encompassing Fano transmission function: the treatments are fully analytic, in terms of the trigamma functions and Bernoulli numbers. From the general curves here reported describing transport through the above model transmission functions, useful guidelines for optimal efficiency and thermopower can be inferred for engineering nanoscale devices in energy regions where they show similar transmission functions.

Particle orbits and non-ideal MHD stability of Z-pinches

International Nuclear Information System (INIS)

Faghihi, M.

1987-01-01

Particle orbits in a linear EXTRAP vacuum magnetic field configuration are computed. The results indicate that, with an applied electric field along the axis, the particles starting near the magnetic stagnation line would gain substantial energy in the 'free fall', and are the most efficient ones to participate in the ionization process. The acquired energy depends on the electric field strength; the required value of the field is determined. The influence of the pressure anisotropy on the small wavelength internal kink (m=1) mode instability in a Z-pinch, using a generalization of Freidbergs perpendicular MHD model, is investigated. It is found that the stability criterion can not be fulfilled without violation of the fire hose stability condition. This investigation is also performed using the double-adiabatic theory. A finite Larmor radius treatment of the small wavelength kink instabilities for a Z-pinch geometry is presented. It is shown that, when the gyroviscosity is included in the perpendicular MHD model, exponentially growing Alfven waves are predicted even in a homogeneous static equilibrium with isotropic plasma pressure. The Hall effect in the incompressible Hall fluid model is considered. It is found that the Hall parameter reduces the growth rates of the kink modes, but it does not yield complete stabilization (author)

Particle orbits and non-ideal MHD stability of Z-pinches

Energy Technology Data Exchange (ETDEWEB)

Faghihi, M.

1987-01-01

Particle orbits in a linear EXTRAP vacuum magnetic field configuration are computed. The results indicate that, with an applied electric field along the axis, the particles starting near the magnetic stagnation line would gain substantial energy in the 'free fall', and are the most efficient ones to participate in the ionization process. The acquired energy depends on the electric field strength; the required value of the field is determined. The influence of the pressure anisotropy on the small wavelength internal kink (m=1) mode instability in a Z-pinch, using a generalization of Freidbergs perpendicular MHD model, is investigated. It is found that the stability criterion can not be fulfilled without violation of the fire hose stability condition. This investigation is also performed using the double-adiabatic theory. A finite Larmor radius treatment of the small wavelength kink instabilities for a Z-pinch geometry is presented. It is shown that, when the gyroviscosity is included in the perpendicular MHD model, exponentially growing Alfven waves are predicted even in a homogeneous static equilibrium with isotropic plasma pressure. The Hall effect in the incompressible Hall fluid model is considered. It is found that the Hall parameter reduces the growth rates of the kink modes, but it does not yield complete stabilization

High-flux first-wall design for a small reversed-field pinch reactor

International Nuclear Information System (INIS)

Cort, G.E.; Graham, A.L.; Christensen, K.E.

1982-01-01

To achieve the goal of a commercially economical fusion power reactor, small physical size and high power density should be combined with simplicity (minimized use of high-technology systems). The Reversed-Field Pinch (RFP) is a magnetic confinement device that promises to meet these requirements with power densities comparable to those in existing fission power plants. To establish feasibility of such an RFP reactor, a practical design for a first wall capable of withstanding high levels of cyclic neutron wall loadings is needed. Associated with the neutron flux in the proposed RFP reactor is a time-averaged heat flux of 4.5 MW/m 2 with a conservatively estimated transient peak approximately twice the average value. We present the design for a modular first wall made from a high-strength copper alloy that will meet these requirements of cyclic thermal loading. The heat removal from the wall is by subcooled water flowing in straight tubes at high linear velocities. We combined a thermal analysis with a structural fatigue analysis to design the heat transfer module to last 10 6 cycles or one year at 80% duty for a 26-s power cycle. This fatigue life is compatible with a radiation damage life of 14 MW/yr/m 2

Diffusion-driven steady states of the Z-pinch

International Nuclear Information System (INIS)

Lehnert, B.

1988-01-01

Steady states of a Z-pinch where no electric field is imposed along the pinch axis by external means are investigated. In this case, diffusion-driven states become possible when imposed volume sources of particles and heat drive a radial diffusion velocity that, in its turn, generates the electric plasma current. The particle sources can be from pellet injection or a neutral gas blanket, and the heat sources provided by thermonuclear reactions or auxiliary heating. The present analysis and associated kinetic considerations indicate that steady diffusion-driven operation should become possible for certain classes of plasma profiles, without running into singularity problems at the pinch axis. Such operation leads to higher axial currents in a Z-pinch without an axial magnetic field than in a tokamaklike case under similar plasma conditions. The technical difficulty in realizing a volume distribution of particle sinks introduces certain constraints on the plasma and current profiles. This fact has to be taken into account in a stability analysis. Neoclassical or anomalous diffusion will increase the diffusion velocity of the plasma but is not expected to affect the main physical features of the present results

Dynamic stability of self-similar solutions for a plasma pinch

International Nuclear Information System (INIS)

Ma, Sifeng.

1988-01-01

Linear Magnetohydrodynamic (MHD) stability theory is applied to a class of self-similar solutions which describe implosion, expansion and oscillation of an infinitely conducting plasma column. The equations of perturbation are derived in the Lagrangian coordinate system. Numerical procedures via the finite-element method are formulated, and general aspects of dynamic stability are discussed, The dynamic stability of the column when it is oscillatory is studied in detail using the Floquet theory, and the characteristic exponent is calculated numerically. A-pinch configuration is examined. It is found that self-similar oscillations in general destabilize the continua in the MHD spectrum, and parametric instability results

Filamentation and networking of electric currents in dense Z-pinch plasmas

International Nuclear Information System (INIS)

Kukushkin, A.B.; Rantsev-Kartinov, V.A.

2001-01-01

The results of high-resolution processing using the multilevel dynamical contrasting method of earlier experiments on linear Z-pinches are presented which illustrate formation of a dynamical percolating network woven by long-living filaments of electric current. A qualitative approach is outlined which treats long-living filaments as a classical plasma formation governed by the long-range quantum bonds provided, at the microscopical level, by nanotubes of elements of optimal valence. The self-similarity of structuring in laboratory and cosmic plasmas is shown, and examples are found of nanotube-like and/or fullerene-like structures of cosmic length scales. (author)

Filamentation and networking of electric currents in dense Z-pinch plasmas

International Nuclear Information System (INIS)

Kukushkin, A.B.; Rantsev-Kartinov, V.A.

1999-01-01

The results of high-resolution processing using the multilevel dynamical contrasting method of earlier experiments on linear Z-pinches are presented which illustrate formation of a dynamical percolating network woven by long-living filaments of electric current. A qualitative approach is outlined which treats long-living filaments as a classical plasma formation governed by the long-range quantum bonds provided, at the micro-scopical level, by nanotubes of elements of optimal valence. The self-similarity of structuring in laboratory and cosmic plasmas is shown, and examples are found of nanotube-like and/or fullerene-like structures of cosmic length scales. (author)

The belt-screw-pinch reactor and other high-beta systems

International Nuclear Information System (INIS)

Bustraan, M.; Klippel, H.Th.; Veringa, H.J.; Verschuur, K.A.

1981-01-01

In a screw-pinch reactor the expenditure for plasma implosion and compression can be reduced and the reacting volume and burn time can be enlarged. This is possible by pinch ignition of only a few percent of the fuel. Fusion energy then ignites injected fuel pellets and expands the plasma. The magnitude of the pulsed magnetic fields is such as to make the application of superconducting coils feasible. An economical reactor model is described. A comparison is made with tokamak and reversed field pinch reactor designs. (author)

Developments of sausages in a z-pinch with short-wave perturbation of a boundary

International Nuclear Information System (INIS)

Vikhrev, V.V.; Ivanov, V.V.; Rozanova, G.A.

1989-01-01

A numeric simulation of sausage evolution in z-pinch during short-wave excitation of the boundary of plasma column pinch is carried out. The simulation has shown that due to nonlinear development of sausages in a pinch plasma colomn the cavities filled with a magnetic field in a rarefied pinch plasma are formed. Simultaneously compact column of tense plasma whose temperature is much higher than the average temperature of pinch plasma column are formed on the pinch axis. In the region of inlet in the cavity plasma is radially directed due to ponderomotoric force 1/2 x jB up to velocities greatly increasing the thermal velocity of ions in a plasma column

Mechanism of neutron generation in Z-pinches

International Nuclear Information System (INIS)

Vikhrev, V.V.

1986-01-01

The review of experimental and theoretical investigations in a mechanism of neutron generation in Z-pinches is presented. Special attention is paid to the thermonuclear mechanism of neutron generation occuring due to the formation of high-temperature plasma regions in Z-pinch sausage-type instabilities. This mechanism is shown to be predominant in charges with the neutron yield more than 10 9 per a charge. Experimental data, which are considered to be contradicting to thermonuclear nature of neutron radiation, are explained

Seeded perturbations in wire array Z-Pinches

International Nuclear Information System (INIS)

Robinson, Allen Conrad; Fedin, Dmitry; Kantsyrev, Victor Leonidovich; Wunsch, Scott Edward; Oliver, Bryan Velten; Lebedev, Sergey V.; Coverdale, Christine Anne; Ouart, Nicholas D.; LePell, Paul David; Safronova, Alla S.; Shrestha, I.; McKenney, John Lee; Ampleford, David J.; Rapley, J.; Bott, S.C.; Palmer, J.B.A.; Sotnikov, Vladimir Isaakovich; Bland, Simon Nicholas; Ivanov, Vladimir V.; Chittenden, Jeremy Paul; Jones, B.; Garasi, Christopher Joseph; Hall, Gareth Neville; Yilmaz, M. Faith; Mehlhorn, Thomas Alan; Deeney, Christopher; Pokala, S.; Nalajala, V.

2005-01-01

Controlled seeding of perturbations is employed to study the evolution of wire array z-pinch implosion instabilities which strongly impact x-ray production when the 3D plasma stagnates on axis. Wires modulated in radius exhibit locally enhanced magnetic field and imploding bubble formation at discontinuities in wire radius due to the perturbed current path. Wires coated with localized spectroscopic dopants are used to track turbulent material flow. Experiments and MHD modeling offer insight into the behavior of z-pinch instabilities.

Z-pinch driven hohlraums design for the 100 nanoseconds current time scale

International Nuclear Information System (INIS)

Hamann, F.

2003-12-01

This work estimates Z-pinch driven hohlraums capabilities to obtain high temperatures (>200 eV). Simple models are proposed to calculate the performances offered by currents of 5 to 100 MA in 100 ns. The one dimensional physics of the Z-pinch at the length scale of its thickness and the hydrodynamics instabilities are studied. Then the enhancement of hohlraums performances with double nested Z-pinches or the use of an axial magnetic field is analysed. Z-pinch direct drive approach for inertial confinement fusion is finally considered. All the presented results are based on theoretical and 2D numerical approach and on the analysis of experimental results which were obtained on the american 'Z' generator. Annexes recall radiation MHD equations and check their validity for Z-pinch implosion. (author)

The effects of shoulder load and pinch force on electromyographic activity and blood flow in the forearm during a pinch task

DEFF Research Database (Denmark)

Visser, Bart; Kofoed Nielsen, Pernille; de Kraker, Heleen

2006-01-01

loaded with 4.95 kg each) were combined with intermittent pinch forces at 0, 10 and 25% of the maximum voluntary contraction (MVC). Blood flow to the forearm was measured with Doppler ultrasound. Myoelectric activity of the forearm and neck-shoulder muscles was recorded to check for the workload levels....... Across all levels of shoulder load, blood flow increased significantly with increasing pinch force (21% at 10% MVC and by 44% at 25% MVC). Blood flow was significantly affected by shoulder load, with the lowest blood flow at the highest shoulder load. Interactions of pinch force and shoulder load were....... The results of this study indicate that shoulder load might influence blood flow to the forearm....

Spatially and temporally resolved EUV emissions from SATURN z-pinches

International Nuclear Information System (INIS)

Nash, T.J.; Breeze, S.; Mock, R.; Jobe, D.

1995-01-01

EUV emissions can be used to measure several z-pinch parameters. The authors have measured implosion velocity from Doppler splitting of lines and estimated electron temperature during run-in from the mean ionization state of line emissions. In an argon pinch they measure an electron temperature of 100 eV before stagnation. To date Doppler split lines have measured implosion velocities less than 40 cm/microsecond. They are presently attempting to measure magnetic field or load current from Zeeman splitting and it may be possible to measure electron density from a Stark-broadened line. Opacity and ion thermal broadening may also contribute to line width information. The spectrometer utilizes a variable line space grating to give a flat focal field. Spectral resolution with a 60 micron detector resolution is up to 3,000 and generally increases with wavelength. This is sufficient to detect several plasma line broadening mechanisms. The spectrometer may detect lines above 100 angstrom and below 1,400 angstrom. Spectral range across a microchannel plate stripline detector decreases with increasing wavelength setting. The authors may gate two striplines with 1 to 12 nsec gates at any time during the pinch discharge. Each stripline spatially images the pinch diameter perpendicular to the direction of dispersion. Spatial resolution in the pinch diameter is 1 mm. Spatial acquisition along the z axis is also 1 mm. Data are presented from argon, krypton, and aluminum z-pinch discharges on the SATURN accelerator

PBFA Z: A 20-MA z-pinch driver for plasma radiation sources

International Nuclear Information System (INIS)

Spielman, R.B.; Breeze, S.F.; Deeney, C.

1996-01-01

Sandia National Laboratories is completing a major modification to the PBFA-II facility. PBFA Z will be a z-pinch driver capable of delivering up to 20 MA to a z-pinch load. It optimizes the electrical coupling to the implosion energy of z pinches at implosion velocities of ∼ 40 cm/μs. Design constraints resulted in an accelerator with a 0.12-Ω impedance, a 10.25-nH inductance, and a 120-ns pulse width. The design required new water transmission lines, insulator stack, and vacuum power feeds. Current is delivered to the z-pinch load through four, self-magnetically-insulated vacuum transmission lines and a double post-hole convolute. A variety of design codes are used to model the power flow. These predict a peak current of 20 MA to a z-pinch load having a 2-cm length, a 2-cm radius, and a 15--mg mass, coupling 1.5 MJ into kinetic energy. We present 2-D Rad-Hydro calculations showing MJ x-ray outputs from tungsten wire-array z pinches

Dynamical analysis of surface-insulated planar wire array Z-pinches

Science.gov (United States)

Li, Yang; Sheng, Liang; Hei, Dongwei; Li, Xingwen; Zhang, Jinhai; Li, Mo; Qiu, Aici

2018-05-01

The ablation and implosion dynamics of planar wire array Z-pinches with and without surface insulation are compared and discussed in this paper. This paper first presents a phenomenological model named the ablation and cascade snowplow implosion (ACSI) model, which accounts for the ablation and implosion phases of a planar wire array Z-pinch in a single simulation. The comparison between experimental data and simulation results shows that the ACSI model could give a fairly good description about the dynamical characteristics of planar wire array Z-pinches. Surface insulation introduces notable differences in the ablation phase of planar wire array Z-pinches. The ablation phase is divided into two stages: insulation layer ablation and tungsten wire ablation. The two-stage ablation process of insulated wires is simulated in the ACSI model by updating the formulas describing the ablation process.

Reversed field pinch operation with intelligent shell feedback control in EXTRAP T2R

Science.gov (United States)

Brunsell, P. R.; Kuldkepp, M.; Menmuir, S.; Cecconello, M.; Hedqvist, A.; Yadikin, D.; Drake, J. R.; Rachlew, E.

2006-11-01

Discharges in the thin shell reversed field pinch (RFP) device EXTRAP T2R without active feedback control are characterized by growth of non-resonant m = 1 unstable resistive wall modes (RWMs) in agreement with linear MHD theory. Resonant m = 1 tearing modes (TMs) exhibit initially fast rotation and the associated perturbed radial fields at the shell are small, but eventually TMs wall-lock and give rise to a growing radial field. The increase in the radial field at the wall due to growing RWMs and wall-locked TMs is correlated with an increase in the toroidal loop voltage, which leads to discharge termination after 3-4 wall times. An active magnetic feedback control system has been installed in EXTRAP T2R. A two-dimensional array of 128 active saddle coils (pair-connected into 64 independent m = 1 coils) is used with intelligent shell feedback control to suppress the m = 1 radial field at the shell. With feedback control, active stabilization of the full toroidal spectrum of 16 unstable m = 1 non-resonant RWMs is achieved, and TM wall locking is avoided. A three-fold extension of the pulse length, up to the power supply limit, is observed. Intelligent shell feedback control is able to maintain the plasma equilibrium for 10 wall times, with plasma confinement parameters sustained at values comparable to those obtained in thick shell devices of similar size.

Reversed field pinch operation with intelligent shell feedback control in EXTRAP T2R

International Nuclear Information System (INIS)

Brunsell, P.R.; Kuldkepp, M.; Menmuir, S.; Cecconello, M.; Hedqvist, A.; Yadikin, D.; Drake, J.R.; Rachlew, E.

2006-01-01

Discharges in the thin shell reversed field pinch (RFP) device EXTRAP T2R without active feedback control are characterized by growth of non-resonant m = 1 unstable resistive wall modes (RWMs) in agreement with linear MHD theory. Resonant m = 1 tearing modes (TMs) exhibit initially fast rotation and the associated perturbed radial fields at the shell are small, but eventually TMs wall-lock and give rise to a growing radial field. The increase in the radial field at the wall due to growing RWMs and wall-locked TMs is correlated with an increase in the toroidal loop voltage, which leads to discharge termination after 3-4 wall times. An active magnetic feedback control system has been installed in EXTRAP T2R. A two-dimensional array of 128 active saddle coils (pair-connected into 64 independent m = 1 coils) is used with intelligent shell feedback control to suppress the m = 1 radial field at the shell. With feedback control, active stabilization of the full toroidal spectrum of 16 unstable m = 1 non-resonant RWMs is achieved, and TM wall locking is avoided. A three-fold extension of the pulse length, up to the power supply limit, is observed. Intelligent shell feedback control is able to maintain the plasma equilibrium for 10 wall times, with plasma confinement parameters sustained at values comparable to those obtained in thick shell devices of similar size

Direction of Impurity Pinch and Auxiliary Heating in Tokamak Plasmas

International Nuclear Information System (INIS)

Angioni, C.; Peeters, A.G.

2006-01-01

A mechanism of particle pinch for trace impurities in tokamak plasmas, arising from the effect of parallel velocity fluctuations in the presence of a turbulent electrostatic potential, is identified analytically by means of a reduced fluid model and verified numerically with a gyrokinetic code for the first time. The direction of such a pinch reverses as a function of the direction of rotation of the turbulence in agreement with the impurity pinch reversal observed in some experiments when moving from dominant auxiliary ion heating to dominant auxiliary electron heating

Torus C-I field reversed theta-pinch at UNICAMP

International Nuclear Information System (INIS)

Machida, M.; Collares, M.P.; Honda, R.Y.; Sakanaka, P.H.; Scheid, V.H.B.

1984-01-01

The influence of multipole fields (octopole and quadrupole) on supressing the n=2 rotational instability, field reconnection, particle loss effects is studied, and the viability of transforming the theta-pinch from Campinas, Brazil (100Kv, 55Kj) to the field reversed theta-pinch with plasma translation program is analyzed. (E.G.) [pt

Preliminary study of Rayleigh-Taylor instability in wire-array Z-pinch

International Nuclear Information System (INIS)

He Kaihui; Feng Kaiming; Li Qiang; Gao Chunming

2000-01-01

It is important to research into the MHD Rayleigh-Taylor instability developed in Z-pinch implosion. A snowplough model of the single wire Z-pinch is presented. The perturbation amplitude of Rayleigh-Taylor instability in the wire-array Z-pinch is analyzed quantitatively. Sheared axial flow is put forward to mitigate and reduce the Rayleigh-Taylor instability. And other approaches used to mitigate MHD instability in such a super-fast process are explored

Linking natural microstructures with numerical modeling of pinch-and-swell structures

Science.gov (United States)

Peters, Max; Berger, Alfons; Herwegh, Marco; Regenauer-Lieb, Klaus

2016-04-01

dominated deformation at relatively high extensional strains in the pinches. The numerical simulations indicate that viscosity weakening due to dissipated heat from grain size reduction marks the onset of localization, resulting in continuous necking of the layer. Interestingly, there exist multiple steady states, i.e. a first homogeneous state out of which localization arises, steady states of the stable end-member structure, expressed by homogeneous conditions in both pinches and swells, and in the surrounding matrix, the latter obeying a linear rheology. Based on our microstructural and numerical results, we suggest that the onset of localization represents a fundamental material bifurcation. This implies that the studied structures can be described as ductile instabilities. Finally, we discuss the profound role of the energy theory of localization described here, which allows deriving the paleo-deformation conditions, as well as fundamental material properties in a self-consistent manner. REFERENCES Herwegh, M., Poulet, T., Karrech, A. and Regenauer-Lieb, K. (2014): Journal of Geophysical Research 119, doi:10.1002/2013JB010701 Peters, M., Veveakis, M., Poulet, T., Karrech, A., Herwegh, M. and Regenauer-Lieb, K. (2015): Journal of Structural Geology 78, doi:10.1016/j.jsg.2015.06.005

Basis set expansion for inverse problems in plasma diagnostic analysis

Science.gov (United States)

Jones, B.; Ruiz, C. L.

2013-07-01

A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)], 10.1063/1.1482156 is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20-25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.

Radiative collapse of a Bennett-relaxed z-pinch

International Nuclear Information System (INIS)

Turner, L.

1989-01-01

The global evolution of a z-pinch has been studied with the assumption of a relaxed state consisting of ions and electrons, each in a rigidly drifting isothermal Maxwellian distribution. This speculative approach has the pragmatic feature of possessing phenomenologically useful global parameters such as drift velocity and temperature that vary in accordance with global physical quantities such as energy and entropy. The plasma gains energy from a time-dependent electric field by means of Poynting's vector. Coulomb collisions between electrons and ions is calculated with a Fokker-Planck treatment analogous to that used by Dreicer to calculate runaways. For a variety of initial conditions and time-independent applied electric fields, the pinch evolution always culminates in a time-independent (attractor) state whose current is the Pease-Braginskii current and whose final radius is proportional to (line density)/sup 3/4//(electric field)/sup 1/2/. Before the final state is attained, the pinch may bounce toward and away from a highly collapsed state. For the case of a Bennett pinch, the classical limit of the resistivity is attained when the line density is much greater than 4πm/sub e//e 2 μ/sub o/; i.e., 3.55 /times/ 10 14 m/sup /minus/1/. 6 refs., 2 figs

Deuterated fibre Z-pinch on the S-300 generator

NARCIS (Netherlands)

Klir, D.; Kravarik, J.; Kubes, P.; Bakshaev, Yu L.; Blinov, P. I.; Chernenko, A. S.; Danko, S. A.; Korolev, V. D.; Ustroev, G. I.; Ivanov, M. I.; Cai, Hongchun

2006-01-01

Dense Z-pinch experiments were carried out on the S-300 generator (3.5 MA, 100 ns, 0.15 Omega) at the Kurchatov Institute in Moscow. The experiments were performed at a peak current of 2 MA with a rise time of about 100 ns. The Z-pinch was formed from a deuterated polyethylene fibre of 100 mu m

Evolution of sausage and helical modes in magnetized thin-foil cylindrical liners driven by a Z-pinch

Science.gov (United States)

Yager-Elorriaga, D. A.; Lau, Y. Y.; Zhang, P.; Campbell, P. C.; Steiner, A. M.; Jordan, N. M.; McBride, R. D.; Gilgenbach, R. M.

2018-05-01

In this paper, we present experimental results on axially magnetized (Bz = 0.5 - 2.0 T), thin-foil (400 nm-thick) cylindrical liner-plasmas driven with ˜600 kA by the Michigan Accelerator for Inductive Z-Pinch Experiments, which is a linear transformer driver at the University of Michigan. We show that: (1) the applied axial magnetic field, irrespective of its direction (e.g., parallel or anti-parallel to the flow of current), reduces the instability amplitude for pure magnetohydrodynamic (MHD) modes [defined as modes devoid of the acceleration-driven magneto-Rayleigh-Taylor (MRT) instability]; (2) axially magnetized, imploding liners (where MHD modes couple to MRT) generate m = 1 or m = 2 helical modes that persist from the implosion to the subsequent explosion stage; (3) the merging of instability structures is a mechanism that enables the appearance of an exponential instability growth rate for a longer than expected time-period; and (4) an inverse cascade in both the axial and azimuthal wavenumbers, k and m, may be responsible for the final m = 2 helical structure observed in our experiments. These experiments are particularly relevant to the magnetized liner inertial fusion program pursued at Sandia National Laboratories, where helical instabilities have been observed.

Advanced-fuel reversed-field pinch reactor (RFPR)

International Nuclear Information System (INIS)

Hagenson, R.L.; Krakowski, R.A.

1981-10-01

The utilization of deuterium-based fuels offers the potential advantages of greater flexibility in blanket design, significantly reduced tritium inventory, potential reduction in radioactivity level, and utilization of an inexhaustible fuel supply. The conventional DT-fueled Reversed-Field Pinch Reactor (RFPR) designs are reviewed, and the recent extension of these devices to advanced-fuel (catalyzed-DD) operation is presented. Attractive and economically competitive DD/RFPR systems are identified having power densities and plasma parameters comparable to the DT systems. Converting an RFP reactor from DT to DD primarily requires increasing the magnetic field levels a factor of two, still requiring only modest magnet coil fields (less than or equal to 4 T). When compared to the mainline tokamak, the unique advantages of the RFP (e.g., high beta, low fields at the coils, high ohmic-heating power densities, unrestricted aspect ratio) are particularly apparent for the utilization of advanced fuels

Ohmic heating of the reversed-field pinch

International Nuclear Information System (INIS)

Gerwin, R.

1980-04-01

Simple analytic expressions are found for the global heating rate and the time needed to achieve global power balance with radiation and other losses, in useful agreement with large RFP transport codes. A simple condition is noted, which insures that the heating can be accomplished before appreciable resistive evolution occurs in the pinch profile. The product of poloidal beta, β/sub theta/, and toroidal current, I, that characterizes a condition of global power balance is derived subject to the above-mentioned condition without making key assumptions used by earlier investigators. First, a perfectly steady state (with local power balance) is not assumed, nor is it appropriate to do so. Secondly, the cross-field resistivity is not required to be classical. Since the value of (β/sub theta/ I) plays a fundamental role in determining the kind of device one requires, the foundations of this value are important

Plasma-erosion-enhanced neutron emission in fiber-generated dense Z-pinches

International Nuclear Information System (INIS)

Mosher, D.; Colombant, D.

1990-01-01

Experiments in which dense z-pinches are created from high-current discharges through frozen deuterium fibers have reported neutron yields far in excess of those expected from thermal processes. A simple analysis based on pinch collapse due to the sausage instability has successfully predicted the relative variation of neutron yield with discharge current, but model assumptions precluded prediction of absolute values of the yield. A pinch-collapse model derived from a 2-dimensional, nonlinear treatment of the sausage instability, combined with space-charged-limited (SCL) ion orbital dynamic for the vacuum region above the pinches and between the expanding flares, leads to neutron yields four or more orders-of-magnitude below experimental values. Here, the same pinch-collapse model is used in conjunction with a low-density plasma background above the collapsing pinches. Ions are accelerated across the space-charge sheath separating the background plasma from the flares, which electron emission from the flares is strongly insulated by the z-discharge magnetic field. The sheath gap increases in time, i.e., the background plasma erodes, at a rate determined by its density and the SCL ion current density which, in turn, depends on the z-discharge dynamics and the associated induced electromagnetic fields. A model incorporating the above processes is used to determine the accelerated ion energy spectrum and associated neutron yield as functions of the discharge, instability, and background parameters

PBFA Z: A 60-TW/5-MJ Z-pinch driver

International Nuclear Information System (INIS)

Spielman, R.B.; Deeney, C.; Chandler, G.A.; Douglas, M.R.; Fehl, D.L.; Matzen, M.K.; McDaniel, D.H.; Nash, T.J.; Porter, J.L.; Sanford, T.W.; Seamen, J.F.; Stygar, W.A.; Struve, K.W.; Breeze, S.P.; McGurn, J.S.; Torres, J.A.; Zagar, D.M.; Gilliland, T.L.; Jobe, D.O.; McKenney, J.L.; Mock, R.C.; Vargas, M.; Wagoner, T.; Peterson, D.L.

1997-01-01

PBFA Z, a new 60-TW/5-MJ electrical accelerator located at Sandia National Laboratories, is now the world's most powerful z-pinch driver. PBFA Z stores 11.4 MJ in its 36 Marx generators, couples 5 MJ into a 60-TW/105-ns FWHM pulse to the 120-mΩ water transmission lines, and delivers 3.0 MJ and 50 TW of electrical energy to the z-pinch load. Depending on load parameters, we attain peak load currents of 16-20 MA with a current rise time of ∼105ns with wire-array z-pinch loads. We have extended the x-ray performance of tungsten wire-array z pinches from earlier Saturn experiments. Using a 2-cm-radius, 2-cm-long tungsten wire array with 240, 7.5-μm diameter wires (4.1-mg mass), we achieved an x-ray power of 210 TW and an x-ray energy of 1.9 MJ. Preliminary spectral measurements suggest a mostly optically-thick, Planckian-like radiator below 1000 eV. Data indicate ∼100kJ of x rays radiated above 1000 eV. An intense z-pinch x-ray source with an overall coupling efficiency greater than 15% has been demonstrated. copyright 1997 American Institute of Physics

Self-pinched transport of intense ion beams

International Nuclear Information System (INIS)

Ottinger, P.F.; Neri, J.M.; Stephanakis, S.J.

1999-01-01

Electron beams with substantial net currents have been routinely propagated in the self-pinched mode for the past two decades. However, as the physics of gas breakdown and beam neutralization is different for ion beams, previous predictions indicated insufficient net current for pinching so that ion beam self-pinched transport (SPT) was assumed impossible. Nevertheless, recent numerical simulations using the IPROP code have suggested that ion SPT is possible. These results have prompted initial experiments to investigate SPT of ion beams. A 100-kA, 1.2-MeV, 3-cm-radius proton beam, generated on the Gamble II pulsed-power accelerator at NRL, has been injected into helium in the 30- to 250-mTorr regime to study this phenomenon. Evidence of self-pinched ion beam transport was observed in the 35- to 80-mTorr SPT pressure window predicted by IPROP. Measured signals from a time- and space-resolved scattered proton diagnostic and a time-integrated Li(Cu) nuclear activation diagnostic, both of which measure protons striking a 10-cm diameter target 50 cm into the transport region, are significantly larger in this pressure window than expected for ballistic transport. These results are consistent with significant self-magnetic fields and self-pinching of the ion beam. On the other hand, time-integrated signals from these same two diagnostics are consistent with ballistic transport at pressures above and below the SPT window. Interferometric electron line-density measurements, acquired during beam injection into the helium gas, show insignificant ionization below 35 mTorr, a rapidly rising ionization fraction with pressure in the SPT window, and a plateau in ionization fraction at about 2% for pressures above 80 mTorr. These and other results are consistent with the physical picture for SPT. IPROP simulations, which closely model the Gamble II experimental conditions, produce results that are in qualitative agreement with the experimental results. The advantages of SPT for

Inverse and Ill-posed Problems Theory and Applications

CERN Document Server

Kabanikhin, S I

2011-01-01

The text demonstrates the methods for proving the existence (if et all) and finding of inverse and ill-posed problems solutions in linear algebra, integral and operator equations, integral geometry, spectral inverse problems, and inverse scattering problems. It is given comprehensive background material for linear ill-posed problems and for coefficient inverse problems for hyperbolic, parabolic, and elliptic equations. A lot of examples for inverse problems from physics, geophysics, biology, medicine, and other areas of application of mathematics are included.

UV Laser Diagnostics of the 1-MA Z-pinch Plasmas

International Nuclear Information System (INIS)

Altemara, S. D.; Ivanov, V. V.; Astanovitskiy, A. L.; Haboub, A.

2009-01-01

The 532 nm laser diagnostic set at the Zebra generator shows the details of the ablation and stagnation phases in cylindrical, planar, and star-like wire arrays but it cannot show the structure of the stagnated z-pinch and the implosion in small diameter loads, 1-3 mm in diameter. The absorption increment and the refraction angle of the 532 nm laser, when passing through the plasma, are too great to obtain quality images. An ultraviolet probing beam at the wavelength of 266 nm was developed to study small-diameter loads and to investigate the structure of the 1-MA z-pinch. The UV radiation has a much smaller absorption increment and refraction angles in plasmas than the 532 nm light and allows for better imaging of the z-pinch plasmas. Estimates showed that UV probing would be able to probe the high-density z-pinch plasma in experiments on the Zebra generator, and the early results of UV probing on the Zebra generator have shown promise.

Evaluating the Usability of Pinchigator, a system for Navigating Virtual Worlds using Pinch Gloves

Science.gov (United States)

Hamilton, George S.; Brookman, Stephen; Dumas, Joseph D. II; Tilghman, Neal

2003-01-01

Appropriate design of two dimensional user interfaces (2D U/I) utilizing the well known WIMP (Window, Icon, Menu, Pointing device) environment for computer software is well studied and guidance can be found in several standards. Three-dimensional U/I design is not nearly so mature as 2D U/I, and standards bodies have not reached consensus on what makes a usable interface. This is especially true when the tools for interacting with the virtual environment may include stereo viewing, real time trackers and pinch gloves instead of just a mouse & keyboard. Over the last several years the authors have created a 3D U/I system dubbed Pinchigator for navigating virtual worlds based on the dVise dV/Mockup visualization software, Fakespace Pinch Gloves and Pohlemus trackers. The current work is to test the usability of the system on several virtual worlds, suggest improvements to increase Pinchigator s usability, and then to generalize about what was learned and how those lessons might be applied to improve other 3D U/I systems.

Mechanism of hot spots formation in magnetic Z-pinch

Energy Technology Data Exchange (ETDEWEB)

Kubes, P; Kravarik, J [Ceske Vysoke Uceni Technicke, Prague (Czech Republic). Fakulta Elektrotechnicka; Kolacek, K; Krejci, A [Akademie Ved Ceske Republiky, Prague (Czech Republic). Ustav Fyziky Plazmatu; Paduch, M; Tomaszewski, K [Inst. of Plasma Physics and Laser Microfusion, Warsaw (Poland)

1997-12-31

The evolution of neon implosion of low energy discharge (4 kJ, 40 kV, 150 kA, 1.1 {mu}s) was studied using X-ray, schlieren and high speed electrooptical visible gated Quadro camera diagnostics. The geometry, the helical structure of pinched column, two steps of pinching and X-ray emission were studied. The diameters, electron density and temperature of the hot spots were determined. The hypothesis of axial component of magnetic field generation, of helical shape of magnetic and electric field lines, of the possibility of the release of magnetic energy and of the acceleration of the keV electrons and ions due to voltage induction during the second pinching of the column are discussed. (author). 3 figs., 5 refs.

An analytic model of radiative collapse of a Z-pinch

International Nuclear Information System (INIS)

Haines, M.G.

1989-01-01

There is a critical current I PB of about 1 MA (the Pease-Braginskii current) at which Ohmic heating and bremsstrahlung losses balance in a Z-pinch under pressure equilibrium. An analytic zero-dimensional model shows the process of radiative collapse when the prescribed current exceeds the critical current. In particular for a linearly rising current radiative collapse is complete when the current is 3 I PB . However, in practice the voltage limitation imposed by an external circuit prevents such a total collapse, and by including this in the model a maximum density (10 30 -10 32 m -3 )can occur followed by an expansion and damped oscillation about an equilibrium at which the current equals the Pease-Braginskii current. In the absence of alpha-particle pressure the maximum density is limited by the resistance of the narrow column, the large voltage across which (∼10 8 V) is balanced essentially bu a large negative LI; it occurs when the current is I PB [(δ-1)/(δ-2)] 1/2 where δ=7/3+4/3 In(R/a), where a is the pinch radius and R is the radius of the current return. The minimum current following maximum density is shown to be greater than I PB /√2. Degeneracy effects can be included in the model. (author) 5 refs., 1 fig

An analytic model of radiative collapse of a Z-pinch

International Nuclear Information System (INIS)

Haines, M.G.

1989-01-01

There is a critical current I PB of about 1 MA (the Pease-Braginskii current) at which Ohmic heating and Bremsstrahlung losses balance in a Z-pinch under pressure equilibrium. An analytic zero-dimensional model shows the process of radiative collapse when the prescribed current exceeds the critical current. In particular for a linearly rising current radiative collapse is complete when the current is √3 I PB . However in practice the voltage limitation imposed by an external circuit prevents such a total collapse, and by including this in the model a maximum density (∼ 10 30 -10 32 m -3 ) can occur followed by an expansion and damped oscillation about an equilibrium at which the current equals the Pease-Braginskii current. In the absence of alpha-particle pressure the maximum density is limited by the resistance of the narrow column, the large voltage across which (∼ 10 8 V) is balanced essentially by a large negative LI radical; it occurs when the current is I PB [(δ-1)/(δ-2)] 1/2 where δ = 7/3+4/3 1n (R w /a), where a is the pinch radius and R w is the radius of the current return. The minimum current following maximum density is shown to be greater than I PB /√2. Degeneracy effects can be included in the model. (author)

Controllable rotational inversion in nanostructures with dual chirality.

Science.gov (United States)

Dai, Lu; Zhu, Ka-Di; Shen, Wenzhong; Huang, Xiaojiang; Zhang, Li; Goriely, Alain

2018-04-05

Chiral structures play an important role in natural sciences due to their great variety and potential applications. A perversion connecting two helices with opposite chirality creates a dual-chirality helical structure. In this paper, we develop a novel model to explore quantitatively the mechanical behavior of normal, binormal and transversely isotropic helical structures with dual chirality and apply these ideas to known nanostructures. It is found that both direction and amplitude of rotation can be finely controlled by designing the cross-sectional shape. A peculiar rotational inversion of overwinding followed by unwinding, observed in some gourd and cucumber tendril perversions, not only exists in transversely isotropic dual-chirality helical nanobelts, but also in the binormal/normal ones when the cross-sectional aspect ratio is close to 1. Beyond this rotational inversion region, the binormal and normal dual-chirality helical nanobelts exhibit a fixed directional rotation of unwinding and overwinding, respectively. Moreover, in the binormal case, the rotation of these helical nanobelts is nearly linear, which is promising as a possible design for linear-to-rotary motion converters. The present work suggests new designs for nanoscale devices.

X-Pinch soft x-ray source for microlithography

International Nuclear Information System (INIS)

Glidden, S.C.; Hammer, D.A.; Kalantar, D.H.; Qi, N.

1993-01-01

The x-pinch soft x-ray source is described for application in submicron resolution lithography. Experiments have been performed to characterize the radiation emitted from magnesium wire x-pinch plasmas using an 80 ns, ≤500 kA pulse. Yields of 14.2 J averaged over three independent calibrated diagnostics at 445 kA have been measured in magnesium K-shell radiation (predominantly 8.4 angstrom to 9.4 angstrom or 1.5 keV to 1.3 keV) from a submillimeter source, with as little as 5-10% of the yield below the 6.74 angstrom silicon absorption edge. A new ≤700 kA, 100 ns pulser being used for x-pinch physics experiments is described. The design of a 40 pulse per second pulsed power system and wire loading mechanism for exposing a resist in 1 second at a distance 40 cm is presented

Stage theta pinch experiments

International Nuclear Information System (INIS)

Linford, R.K.; Downing, J.N.; Gribble, R.F.; Jacobson, A.R.; Platts, D.A.; Thomas, K.S.

1975-01-01

The Staged Theta Pinch program is designed to study the technological and physics problems associated with producing fat plasmas and separating the implosion heating from the adiabatic compression. Several methods of implosion heating are discussed. Circuit diagrams and theoretical magnetic field behavior are described for the STP and resonant heating experiments. (MOW)

Filamentation instability of a self-pinched hollow electron beam

International Nuclear Information System (INIS)

Uhm, H.S.; Hughes, T.P.

1986-01-01

Filamentation stability properties of a self-pinched hollow electron beam propagating through a collisional plasma channel are investigated within the framework of linearized Vlasov--Maxwell equations, assuming that the beam is thin and that the equilibrium and perturbed space-charge fields are neutralized by background plasma. It is further assumed that the perturbations are well tuned with kβ/sub b/c+lω/sub b/ and satisfy la 0 , where l and k are the azimuthal and axial wavenumbers, β/sub b/c and ω/sub b/ are the axial velocity and the rotational frequency of the beam, and 2a and R 0 are the thickness and mean radius of the beam. From the stability analysis, two distinctive unstable mechanisms are identified: the return-current driven instability and the resistively driven instability. It is also found that high-l-mode perturbations are easily stabilized by a spread in the canonical angular momentum. Making use of a linearized particle-in-cell code, numerical simulations are performed. The agreement between the analytical results and those of simulations is excellent

Plasma performance and scaling laws in the RFX-mod reversed-field pinch experiment

International Nuclear Information System (INIS)

Innocente, P.; Alfier, A.; Canton, A.; Pasqualotto, R.

2009-01-01

The large range of plasma currents (I p = 0.2-1.6 MA) and feedback-controlled magnetic boundary conditions of the RFX-mod experiment make it well suited to performing scaling studies. The assessment of such scaling, in particular those on temperature and energy confinement, is crucial both for improving the operating reversed-field pinch (RFP) devices and for validating the RFP configuration as a candidate for the future fusion reactors. For such a purpose scaling laws for magnetic fluctuations, temperature and energy confinement have been evaluated in stationary operation. RFX-mod scaling laws have been compared with those obtained from other RFP devices and numerical simulations. The role of the magnetic boundary has been analysed, comparing discharges performed with different active control schemes of the edge radial magnetic field.

Electron-Cloud Pinch Dynamics in Presence of Lattice Magnet Fields

CERN Document Server

Franchetti, G

2011-01-01

The pinch of the electron cloud due to a passing proton bunch was extensively studied in a field free region and in a dipolar magnetic field. For the latter study, a strong field approximation helped to formulate the equations of motion and to understand the complex electron pinch dynamics, which exhibited some similarities with the field-free situation. Here we extend the analysis to the case of electron pinch in quadrupoles and in sextupoles. We discuss the limits of validity for the strong field approximation and we evaluate the relative magnitude of the peak tune shift along the bunch expected for the different fields.

Plasma channel and Z-pinch dynamics for heavy ion transport

Energy Technology Data Exchange (ETDEWEB)

Ponce-Marquez, David [Univ. of California, Berkeley, CA (United States)

2002-01-01

A self stabilized, free standing, z-pinch plasma channel has been proposed to deliver the high intensity heavy ion beam from the end of a driver to the fuel target in a heavy ion inertial fusion power plant. The z-pinch relaxes emittance and energy spread requirements requiring a lower cost driver. A z-pinch transport would reduce the number of beam entry port holes to the target chamber from over a hundred to four as compared to neutralized ballistic focusing thus reducing the driver hardware exposure to neutron flux. Experiments where a double pulse discharge technique is used, z-pinch plasma channels with enhanced stability are achieved. Typical parameters are 7 kV pre-pulse discharge and 30 kV main bank discharge with 50 kA of channel current in a 7 torr background gas atmosphere. This work is an experimental study of these plasma channels examining the relevant physics necessary to understand and model such plasmas. Laser diagnostics measured the dynamical properties of neutrals and plasma. Schlieren and phase contrast techniques probe the pre-pulse gas dynamics and infrared interferometry and faraday effect polarimetry are used on the z-pinch to study its electron density and current distribution. Stability and repeatability of the z-pinch depend on the initial conditions set by the pre-pulse. Results show that the z-pinch channel is wall stabilized by an on-axis gas density depression created by the pre-pulse through hydrodynamic expansion where the ratio of the initial gas density to the final gas density is > 10/1. The low on-axis density favors avalanching along the desired path for the main bank discharge. Pinch time is around 2 s from the main bank discharge initiation with a FWHM of ~ 2 cm. Results also show that typical main bank discharge plasma densities reach 10¹⁷ cm^-3 peak on axis for a 30 kV, 7 torr gas nitrogen discharge. Current rise time is limited by the circuit-channel inductance with the highest contribution to the

Experiments on the ZT-S reversed-field pinch, August--December 1978

International Nuclear Information System (INIS)

Jacobson, A.R.

1979-06-01

During the latter half of 1978 the ZT-S reversed-field pinch was used to explore the utility of pitch-programming techniques in setting up stable diffuse pinch profiles. Several experimental observations relating to this goal are presented

Spontaneous quasi single helicity regimes in EXTRAP T2R reversed-field pinch

Science.gov (United States)

Frassinetti, L.; Brunsell, P. R.; Drake, J. R.; Menmuir, S.; Cecconello, M.

2007-11-01

In recent years, good progress toward a better understanding and control of the plasma performance in reversed-field pinch devices has been made. These improvements consist both of the discovery of spontaneous plasma regimes, termed the quasi single helicity (QSH) regime, in which part of the plasma core is no longer stochastic, and of the development of techniques for active control of plasma instabilities. In this paper, a systematic study of spontaneous QSH in the EXTRAP T2R device [P. R. Brunsell, H. Bergsaker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] is presented. In this device, QSH states can occur spontaneously and it is associated with magnetic and thermal structures. A statistical analysis to determine the most favorable experimental conditions to have a transition to the QSH regime will be presented. The results described here are useful to understand the underlying properties of QSH regimes in view of future applications of the QSH active control in EXTRAP T2R; they are also important to have a comparison with the QSH studied in other devices.

Energy transfer efficiency measurements in a theta-pinch

International Nuclear Information System (INIS)

Cavalcanti, G.H.; Luna, F.R.T.; Trigueiros, A.G.

1993-01-01

An increase in energy transfer efficiency of the capacitor bank to the plasma was obtained when the electrical system of a theta-pinch was changed so that the ratio of total inductance to coil inductance was switched of 1/6 to 1/2. A further increase about 20% was obtained for 16/1 ratio. The measurements were made through the current discharge decay, and the spectral analysis of the emitted light from theta-pinch shows a correspondent efficiency increase. (author)

Developing models for simulation of pinched-beam dynamics in heavy ion fusion. Revision 1

International Nuclear Information System (INIS)

Boyd, J.K.; Mark, J.W.K.; Sharp, W.M.; Yu, S.S.

1984-01-01

For heavy-ion fusion energy applications, Mark and Yu have derived hydrodynamic models for numerical simulation of energetic pinched-beams including self-pinches and external-current pinches. These pinched-beams are applicable to beam propagation in fusion chambers and to the US High Temperature Experiment. The closure of the Mark-Yu model is obtained with adiabatic assumptions mathematically analogous to those of Chew, Goldberger, and Low for MHD. Features of this hydrodynamic beam model are compared with a kinetic treatment

Ionization effects and linear stability in a coaxial plasma device

Science.gov (United States)

Kurt, Erol; Kurt, Hilal; Bayhan, Ulku

2009-03-01

A 2-D computer simulation of a coaxial plasma device depending on the conservation equations of electrons, ions and excited atoms together with the Poisson equation for a plasma gun is carried out. Some characteristics of the plasma focus device (PF) such as critical wave numbers a c and voltages U c in the cases of various pressures Pare estimated in order to satisfy the necessary conditions of traveling particle densities ( i.e. plasma patterns) via a linear analysis. Oscillatory solutions are characterized by a nonzero imaginary part of the growth rate Im ( σ) for all cases. The model also predicts the minimal voltage ranges of the system for certain pressure intervals.

High Cable Forces Deteriorate Pinch Force Control in Voluntary-Closing Body-Powered Prostheses.

Directory of Open Access Journals (Sweden)

Mona Hichert

Full Text Available It is generally asserted that reliable and intuitive control of upper-limb prostheses requires adequate feedback of prosthetic finger positions and pinch forces applied to objects. Body-powered prostheses (BPPs provide the user with direct proprioceptive feedback. Currently available BPPs often require high cable operation forces, which complicates control of the forces at the terminal device. The aim of this study is to quantify the influence of high cable forces on object manipulation with voluntary-closing prostheses.Able-bodied male subjects were fitted with a bypass-prosthesis with low and high cable force settings for the prehensor. Subjects were requested to grasp and transfer a collapsible object as fast as they could without dropping or breaking it. The object had a low and a high breaking force setting.Subjects conducted significantly more successful manipulations with the low cable force setting, both for the low (33% more and high (50% object's breaking force. The time to complete the task was not different between settings during successful manipulation trials.High cable forces lead to reduced pinch force control during object manipulation. This implies that low cable operation forces should be a key design requirement for voluntary-closing BPPs.

Self-stabilized pinch (SSP) concept

International Nuclear Information System (INIS)

Sugisaki, Kiwamu; Hirano, Keiichi.

1985-01-01

Self-Stabilized pinch (SSP) consept is revealed. SSP providcs many attractive features for application to a fusion reactor. Design studies for high temperature plasma production are carried out. Use of adiabatic compression leads to a remarkable reduction of required power source. (author)

Compact reversed-field pinch reactors (CRFPR)

International Nuclear Information System (INIS)

Krakowski, R.A.; Hagenson, R.L.; Schnurr, N.M.; Copenhaver, C.; Bathke, C.G.; Miller, R.L.; Embrechts, M.J.

1986-01-01

The unique confinement properties of the poloidal-field-dominated Reversed-Field Pinch (RFP) are exploited to examine physics and technical issues related to a compact high-power-density fusion reactor. This resistive-coil, steady-state, toroidal device would use a dual-media (i.e., two separate coolants) power cycle that would be driven by a fusion power core (FPC, i.e., plasma chamber, first wall, blanket, shield, and coils) having a power density and mass approaching pressurized-water-fission reactor values. A 1000-MWe(net) base case is selected from a comprehensive trade-off study to examine technological issues related to operating a high-power-density FPC. A general rationale outlining the need for improved fusion concepts is given, followed by a description of the RFP principle, a detailed systems and trade-off analysis, and a conceptual FPC design for the ∝ 20-MW/m 2 (neutrons) compact RFP reactor, CRFPR(20). Key FPC components are quantified, and full power-balance, thermal, and mechanical FPC integrations are given. (orig.)

Ultra-low q and reversed field pinch experiments in Extrap T1 with a resistive shell

International Nuclear Information System (INIS)

Brunsell, P.; Drake, J.R.; Mazur, S.; Nordlund, P.

1991-02-01

The Extrap T1 device is a high aspect ratio toroidal pinch with the dimensions R/a = 0.5 m/0.057 m. In the experiments described here, the stainless steel bellows vacuum vessels was surrounded by a resistive shell with a perpendicular field penetration time of 75 μs. The ULQ discharges, with toroidal currents in the range 20-50 kA and pulse lengths up to 2 ms, showed the typical step-wise decay of the plasma current. The current steps corresponded to transitions of the edge q-value across rational values 1/4, 1/3, 1/2, and 1. During a step through a rational q value, there was an increase in the fluctuation activity and a corresponding increase in the plasma resistance. As part of the ULQ studies, discharges with four poloidal field nulls were produced by applying an octupole magnetic field, thus demonstrating that it is possible to sustain ULQ equilibria with poloidal field x-points and a magnetic separatix. In another study, the transition from ULQ discharges to relaxed state discharges was investigated. When the initial bias toroidal field was reduced so that q was less than about 1/6, which corresponded to a pinch parameter of about 0.6, a change in the discharge character was observed. The loop voltage required to sustain a given current increased and stochastic fluctuations were seen. Toroidal flux was generated and relaxed state equilibira developed. For higher pinch parameter, in the range of 1.5 to 2.0, a reversed field pinch could be set up if the toroidal field power supply provided a reversed current in the coils. The plasma resistivity was again lower and the pulse lengths in the RFP mode were up to 1 ms, corresponding to over 10 shell penetration times. (au)

Approximate inverse preconditioning of iterative methods for nonsymmetric linear systems

Energy Technology Data Exchange (ETDEWEB)

Benzi, M. [Universita di Bologna (Italy); Tuma, M. [Inst. of Computer Sciences, Prague (Czech Republic)

1996-12-31

A method for computing an incomplete factorization of the inverse of a nonsymmetric matrix A is presented. The resulting factorized sparse approximate inverse is used as a preconditioner in the iterative solution of Ax = b by Krylov subspace methods.

Gas-puff Z-pinch experiment on the LIMAY-I

International Nuclear Information System (INIS)

Takasugi, K.; Miyamoto, T.; Akiyama, H.; Shimomura, N.; Sato, M.; Tazima, T.

1989-01-01

A gas-puff z-pinch plasma has been produced on the pulsed power generator LIMAY-I at IPP Nagoya University. The stored energy of the generator is 13 kJ, and it generates 600 kV-70 ns-3 Ω power pulse. Ar or He gas is puffed from a hollow nozzle with 18 mm diameter, and a z-pinch plasma is produced by a discharge between 3 mm gap electrodes

Quasi-steady accelerator operation on the ZAP flow Z-pinch

Energy Technology Data Exchange (ETDEWEB)

Hughes, M. C., E-mail: mchugs@uw.edu; Shumlak, U., E-mail: mchugs@uw.edu; Golingo, R. P., E-mail: mchugs@uw.edu; Nelson, B. A., E-mail: mchugs@uw.edu; Ross, M. P., E-mail: mchugs@uw.edu [Aerospace and Energetics Research Program, University of Washington, Seattle, WA 98195 (United States)

2014-12-15

The ZaP Flow Z-Pinch Experiment utilizes sheared flows to stabilize an otherwise unstable equilibrium. The sheared flows are maintained by streaming high velocity plasma parallel to the pinch. Previous operations of the machine show depletion of the accelerator’s neutral gas supply late in the pulse leading to pinch instability. The current distribution in the accelerator exhibits characteristic modes during this operation, which is corroborated by interferometric signals. The decrease in density precipitates a loss of plasma quiescence in the pinch, which occurs on a timescale related to the flow velocity from the plasma source. To abate the depletion, the geometry of the accelerator is altered to increase the neutral gas supply. The design creates a standing deflagration front in the accelerator that persists for the pulse duration. The new operating mode is characterized by the same diagnostics as the previous mode. The lessons learned in the accelerator operations have been applied to the design of a new experiment, ZaP-HD. This work was supported by grants from the Department of Energy and the National Nuclear Security Administration.

Model of enhanced energy deposition in a Z-pinch plasma

International Nuclear Information System (INIS)

Velikovich, A. L.; Davis, J.; Thornhill, J. W.; Giuliani, J. L. Jr.; Rudakov, L. I.; Deeney, C.

2000-01-01

In numerous experiments, magnetic energy coupled to strongly radiating Z-pinch plasmas exceeds the thermalized kinetic energy, sometimes by a factor of 2-3. An analytical model describing this additional energy deposition based on the concept of macroscopic magnetohydrodynamic (MHD) turbulent pinch heating proposed by Rudakov and Sudan [Phys. Reports 283, 253 (1997)] is presented. The pinch plasma is modeled as a foam-like medium saturated with toroidal ''magnetic bubbles'' produced by the development of surface m=0 Rayleigh-Taylor and MHD instabilities. As the bubbles converge to the pinch axis, their magnetic energy is converted to thermal energy of the plasma through pdV work. Explicit formulas for the average dissipation rate of this process and the corresponding contribution to the resistance of the load, which compare favorably to the experimental data and simulation results, are presented. The possibility of using this enhanced (relative to Ohmic heating) dissipation mechanism to power novel plasma radiation sources and produce high K-shell yields using long current rise time machines is discussed. (c) 2000 American Institute of Physics

Steady state theta pinch concept for slow formation of FRC

International Nuclear Information System (INIS)

Hirano, K.

1987-05-01

A steady state high beta plasma flow through a channel along the magnetic field increasing downstream can be regarded as a ''steady state theta pinch'', because if we see the plasma riding on the flow we should observe very similar process taking place in a theta pinch. Anticipating to produce an FRC without using very high voltage technics such as the ones required in a conventional theta pinch, we have studied after the analogy a ''steady state reversed field theta pinch'' which is brought about by steady head-on collision of counter plasma streams along the channel as ejected from two identical co-axial plasma sources mounted at the both ends of the apparatus. The ideal Poisson and shock adiabatic flow models are employed for the analysis of the steady colliding process. It is demonstrated that an FRC involving large numbers of particles is produced only by the weak shock mode which is achieved in case energetic plasma flow is decelerated almost to be stagnated through Poisson adiabatic process before the streams are collided. (author)

0-d energetics scaling models for Z-pinch-driven hohlraums

International Nuclear Information System (INIS)

CUNEO, MICHAEL E.; VESEY, ROGER A.; HAMMER, J.H.; PORTER, JOHN L.

2000-01-01

Wire array Z-pinches on the Z accelerator provide the most intense laboratory source of soft x-rays in the world. The unique combination of a highly-Planckian radiation source with high x-ray production efficiency (15% wall plug), large x-ray powers and energies ( >150 TW, ge1 MJ in 7 ns), large characteristic hohlraum volumes (0.5 to >10 cm 3 ), and long pulse-lengths (5 to 20 ns) may make Z-pinches a good match to the requirements for driving high-yield scale ICF capsules with adequate radiation symmetry and margin. The Z-pinch driven hohlraum approach of Hammer and Porter [Phys.Plasmas, 6, 2129(1999)] may provide a conservative and robust solution to the requirements for high yield, and is currently being studied on the Z accelerator. This paper describes a multiple region, 0-d hohlraum energetic model for Z-pinch driven hohlraums in four configurations. The authors observe consistency between the models and the measured x-ray powers and hohlraum wall temperatures to within ±20% in flux, for the four configurations

PBFA Z: A 20-MA Z-pinch driver for plasma radiation sources

International Nuclear Information System (INIS)

Spielman, R.B.; Breeze, S.F.; Deeney, C.

1996-01-01

Sandia National Laboratories is completing a major modification to the PBFA-II facility. PBFA Z will be capable of delivering up to 20 MA to a z-pinch load. It optimizes the electrical coupling to the implosion energy of z pinches at implosion velocities of ∼ 40 cm/μs. Design constraints resulted in an accelerator with a 0.12-Ω impedance, a 10.25-nH inductance, and a 120-ns pulse width. The design required new water transmission lines, insulator stack, and vacuum power feeds. Current is delivered to the z-pinch load through four self-magnetically-insulated vacuum transmission lines and a double post-hole convolute. A variety of design codes are used to model the power flow. These predict a peak current of 20 MA to a z-pinch load having a 2-cm length, a 2-cm radius, and a 15-mg mass, coupling 1.5 MJ into kinetic energy. Calculations are presented showing MJ x-ray outputs from tungsten wire-array z pinches. (author). 4 figs., 14 refs

PBFA Z: A 20-MA Z-pinch driver for plasma radiation sources

Energy Technology Data Exchange (ETDEWEB)

Spielman, R B; Breeze, S F; Deeney, C [Sandia Labs., Albuquerque, NM (United States); and others

1997-12-31

Sandia National Laboratories is completing a major modification to the PBFA-II facility. PBFA Z will be capable of delivering up to 20 MA to a z-pinch load. It optimizes the electrical coupling to the implosion energy of z pinches at implosion velocities of {approx} 40 cm/{mu}s. Design constraints resulted in an accelerator with a 0.12-{Omega} impedance, a 10.25-nH inductance, and a 120-ns pulse width. The design required new water transmission lines, insulator stack, and vacuum power feeds. Current is delivered to the z-pinch load through four self-magnetically-insulated vacuum transmission lines and a double post-hole convolute. A variety of design codes are used to model the power flow. These predict a peak current of 20 MA to a z-pinch load having a 2-cm length, a 2-cm radius, and a 15-mg mass, coupling 1.5 MJ into kinetic energy. Calculations are presented showing MJ x-ray outputs from tungsten wire-array z pinches. (author). 4 figs., 14 refs.

Gravity inversion code

International Nuclear Information System (INIS)

Burkhard, N.R.

1979-01-01

The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables

''Turbulent Equipartition'' Theory of Toroidal Momentum Pinch

International Nuclear Information System (INIS)

Hahm, T.S.; Diamond, P.H.; Gurcan, O.D.; Rewaldt, G.

2008-01-01

The mode-independent part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density (Hahm et al., Phys. Plasmas 14,072302 (2007)) which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of 'magnetically weighted angular momentum density', nm i U # parallel# R/B 2 , and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.

Liquid conductor model of instabilities in a pinched discharge

Energy Technology Data Exchange (ETDEWEB)

Dattnery, A; Lehnert, B [Dept. of Electronics, Royal Institute of Technology, Stockholm (Sweden); Lundquist, S [Swedish State Power Board (Sweden)

1958-07-01

The pinched gas discharge experiments seem to have been handicapped by the great speed with which the instability develops as well as by the light coming from impurities instead of the main body of pinched gas. In the present work a liquid conductor is used in order to study the structure of the instabilities. The study of a pinch was made with and without the axial magnetic field. In cases with a magnetic field, the currents and fields were chosen so as to give a longitudinal magnetic field equal to or three times the azimuthal field at the boundary of the mercury stream. The study of the results shows that in the case without an external magnetic field there is a similarity between the behavior of the pinch in a stream of mercury and in an ionized gas column. The stabilizing action of the surface tension is small and the instabilities develop easily. The case with an external magnetic field is more complicated. The magnetic lines of force are not frozen into the medium; they can 'escape' from the medium. In this case the magnetic field has no stabilizing effect. The influence of conducting walls around the mercury column will be studied in forthcoming experiments.

Progress of research and development of nuclear fusion and development of large nuclear fusion device technology

International Nuclear Information System (INIS)

1994-01-01

In the last several years, the results of tokamak experiments were conspicuous, and the progress of plasma confinement performance, transport mechanism, divertors and impurities, helium transport and exhaust, electric current drive, magnetic field ripple effect and high speed particle transport and DT experiment are reported. The other confinement methods than tokamak, the related theories and reactor technology are described. The conceptual design of ITER was carried out by the cooperation of Japan, USA, EC and the former USSR. The projects of developing nuclear fusion in various countries, the design and the required research and development of ITER, the reconstruction and the required research and development of JT-60, JET and TFTR, the design and the required research and development of large helical device, the state of research and development of laser nuclear fusion and inversion magnetic field pinch nuclear fusion, the activities and roles of industrial circles in large nuclear fusion device technology, and the long term perspective of the technical development of nuclear fusion are described. (K.I.)

The belt pinch - a high-β tokamak with non-circular cross-section

International Nuclear Information System (INIS)

Gruber, O.; Peiry, J.M.; Wilhelm, R.

1975-10-01

The stability behaviour of non-circular plasma cross-sections is discussed on the basis of present known theory. Then the technical arrangement and the preionization of the Belt Pinch is described. The following section deals with the establishment of the non-circular equilibrium and summarizes the essential plasma paramters and the used diagnostic methods. The stability properties of the Belt Pinch, lead to a critical q-value. Finnaly, supporting experiments for the future Belt Pinch programm are presented. (orig./GG) [de

Simplified scaling model for the THETA-pinch

Science.gov (United States)

Ewing, K. J.; Thomson, D. B.

1982-02-01

A simple ID scaing model for the fast Theta pinch was developed and written as a code that would be flexible, inexpensive in computer time, and readily available for use with the Los Alamos explosive-driven high magnetic field program. The simplified model uses three successive separate stages: (1) a snowplow-like radial implosion, (2) an idealized resistive annihilation of reverse bias field, and (3) an adiabatic compression stage of a Beta = 1 plasma for which ideal pressure balance is assumed to hold. The code uses one adjustable fitting constant whose value was first determined by comparison with results from the Los Alamos Scylla III, Scyllacita, and Scylla IA Theta pinches.

Numerical investigations of Z-pinch plasma instabilities

International Nuclear Information System (INIS)

Duan Yaoyong; Guo Yonghui; Wang Wensheng; Qiu Aici

2004-01-01

A two-dimensional, radiation magneto-hydrodynamics model is applied to the simulation of Z-pinch plasma sausage instability. Different implosion mechanisms in the cases of the existence and the non-existence of instability are analyzed, and the effects of various initial density perturbation levels on the x-ray power and energy are investigated. Numerical results show that x-ray energy output is not susceptive to sausage instabilities in a certain extent but x-ray power versus time is evidently dependent on the instabilities. In addition, this paper also studies the effects of numerical treatment of extreme low density in Z-pinch simulations on numerical results

A tentative opinion of modeling plasma formation in metallic wire Z pinch

International Nuclear Information System (INIS)

Ding Ning

2002-01-01

Numerous experiments in both single wire and in wire arrays have attracted much attention. For the wire array Z-pinch implosions the plasma formation in the metallic wire Z pinches is a key question. By means of analyzing a number of single-wire and multi-wire experiments, two models to describe the behavior of a wire array Z-pinch in initial phase are suggested. In this phase each wire carries a rising current and behaves independently in a way similar to that found in single wire Z-pinch experiments in which a comparable current in one wire is employed. Based on one- or/and two-dimensional magnetohydrodynamics (MHD) theory, one model is used to simulate the electrical explosion stage of the metallic wire, another is used to simulate the wire-plasma formation stage

Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

International Nuclear Information System (INIS)

Ivanov, Vladimir V.

2016-01-01

Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution 20 MG, suggested in micropinches, Cotton-Mouton and cutoff diagnostics will be applied. A picosecond optical Kerr shutter will be tested to increase a sensitivity of UV methods for application at multi-MA Z pinches. The proposal is based on the experimental capability of NTF. The Zebra generator produces 1-1.7 MA Z-pinches with electron plasma density of 10"2"0-10"2"1cm"-"3, electron temperature of 0.5-1 keV, and magnetic fields >10 MG. The Leopard laser was upgraded to energy of 90-J at 0.8 ns. This regime will be used for laser initiation

The Z-pinch as plasma lens for the focusing of heavy ion beams

International Nuclear Information System (INIS)

Elfers, M.

1992-04-01

In the present thesis the influence of a Z-pinch plasma on the shape of heavy-ion beams and the for the understanding of this interaction most important plasma parameters were studied. For this the Z-pinch at the heavy-ion accelerator UNILAC was operated. The magnet field gradients of up to (25 ± 3) T/m occuring in the Z-pinch lead to the plasma-lens effect - the focusing of a charged-particle beam traversing axially the Z-pinch. In this thesis for the first time the focusing of a heavy-ion beam by the azimutal magnetic field of a Z-pinch is described. Different beams with an original diameter of 10 mm were focused. The smallest measured beam diameter amounts to 1 mm half-width. The beam energy amounts to 11.4 MeV/u, which leads at gold as projectile matter to a beam energy of 2.25 GeV. (orig./HSI) [de

Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

Energy Technology Data Exchange (ETDEWEB)

Ivanov, Vladimir V. [Univ. of Nevada, Reno, NV (United States)

2016-08-17

Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated

Evolution of the MHD sheet pinch

International Nuclear Information System (INIS)

Matthaeus, W.H.; Montgomery, D.

1979-01-01

A magnetohydrodynamic (MHD) problem of recurrent interest for both astrophysical and laboratory plasmas is the evolution of the unstable sheet pinch, a current sheet across which a dc magnetic field reverses sign. The evolution of such a sheet pinch is followed with a spectral-method, incompressible, two-dimensional, MHD turbulence code. Spectral diagnostics are employed, as are contour plots of vector potential (magnetic field lines), electric current density, and velocity stream function (velocity streamlines). The nonlinear effect which seems most important is seen to be current filamentation: the concentration of the current density onto sets of small measure near a mgnetic X point. A great deal of turbulence is apparent in the current distribution, which, for high Reynolds numbers, requires large spatial grids (greater than or equal to (64) 2 ). 11 figures, 1 table

Nonlinear development of the sausage instability in dense Z-pinches

International Nuclear Information System (INIS)

Colombant, D.; Mosher, D.

1989-01-01

In this paper, a 2d envelope model is described for the nonlinear development of the sausage instability in dense Z-pinches. Numerical solutions for various cases of interest are provided which lay the foundation for a quantitative model of nonthermal neutron emission in dense Z-pinches by determining the induced electric fields associated with the development of the instability

Numerical studies of neon gas-puff Z-pinch dynamic processes

International Nuclear Information System (INIS)

Ning Cheng; Yang Zhenhua; Ding Ning

2003-01-01

Dynamic processes of neon gas-puff Z-pinch are studied numerically in this paper. A high temperature plasma with a high density can be generated in the process. Based on some physical analysis and assumption, a set of equations of one-dimensional Lagrangian radiation magneto-hydrodynamic (MHD) and its code are developed to solve the problem. Spatio-temporal distributions of plasma parameters in the processes are obtained, and their dynamic variations show that the major results are self-consistent. The duration for the plasma pinched to centre, as well as the width and the total energy of the x-ray pulse caused by the Z-pinch are in reasonable agreement with experimental results of GAMBLE-II. A zipping effect is also clearly shown in the simulation

Multi-scale characterization of an upcurrent turbiditic pinch-out

Science.gov (United States)

Daghdevirenian, L. J. P.; Migeon, S.; Rubino, J. L., Sr.; Raisson, F.

2017-12-01

Continental margins with a steep topographic profile between their continental shelf and the basin exhibit a sudden slope break at the base of their continental slope. This slope break favors strong erosion or a by-pass and a fast accumulation of sediments on the base of the continental slope due to the hydraulic jump phenomena. Such a process is responsible for the construction of thick accumulations of limited extension and generally disconnected from the feeding tributaries. These accumulations usually onlap against the continental slope but their modality of pinch out is still questioned and it is the subject of this work. The Tabernas basin is located in South East of Spain, in the continuity of the Sorbas basin. Recent field works allowed identifying a "sedimentary" onlap associated with a small-scale sandy turbidite system that we discovered near the so-called El Buho area. The superb quality of the outcrops revealed, the presence of three successive onlap structures consisting in each case of a direct contact between fluvial conglomerates / marines conglomerates / marine marls / turbidite sands. Reconstruction of paleo-current direction gives a flow direction around N00, from north to south, suggesting the outcrops are cutting the pinch out of the sandy system in a longitudinal direction. A longitudinal and vertical transition of facies can be thus observed from marines' conglomerates to turbidite sands, respectively over distances of 500 m and 70 m. The complete evolution of facies along the pinch out consists of thick conglomerates in the proximal part to sandy turbidite channels then lobes in the distal part. The three successive onlap structures are located inside the channelize part of the system, just above a slope break structure. The basal units of the pinch out consist of an alternation of conglomerates and sandy bed, while the overlying units exhibits more sandy dominated beds. In order to reconstruct the architecture of the pinch out and to

Final Technical Report, DOE Grant DE-FG02-98ER54496, Physics of High-Energy-Density X Pinch Plasmas

International Nuclear Information System (INIS)

Hammer, David

2008-01-01

as short as 30 trillionths of a second. Additional experiments have demonstrated that a spherical shell of plasma expands away from the cross point region after the x-ray burst. It reaches millimeter scale in a few billionths of a second, leaving a small (less than 0.1 millimeter) gap in the middle that enables energetic electrons to be accelerated to 10 or a few 10's of kilovolts of energy. In addition to gaining an understanding of the physics of the X pinch plasmas, we have had to develop several new X-ray diagnostic devices in order to obtain and verify the above results. On the non-technical side, 4 students have completed Ph.D.s working under the auspices of this project, including one woman, and another woman has begun her Ph.D. research under this project. In addition, several undergraduate students have worked with us on the X-pinch experiments, including one who is now a graduate student in plasma physics at Princeton University.

Seismic inverse scattering in the downward continuation approach

NARCIS (Netherlands)

Stolk, C.C.; de Hoop, M.V.

Seismic data are commonly modeled by a linearization around a smooth background medium in combination with a high frequency approximation. The perturbation of the medium coefficient is assumed to contain the discontinuities. This leads to two inverse problems, first the linearized inverse problem

Nonlinear tearing modes in the reversed field pinch

International Nuclear Information System (INIS)

Miller, G.

1989-01-01

Finite-amplitude islands, which are the saturated states of tearing modes in the reversed field pinch, are calculated. These states are bifurcated noncylindrical equilibrium states. With σ(r) (σequivalentj x B/B 2 ) nonuniform across the plasma, as is consistent with experiment, a variety of m = 1 and m = 0 bifurcated equilibria are possible, instead of just the m = 1 helix calculated for uniform σ(r) by Taylor [in Pulsed High Beta Plasmas, edited by D. Evans (Pergamon, Oxford, 1976), p. 59]. Assuming the magnetic field lines in the reversed field pinch are weakly stochastic, the growth time of an unstable tearing mode is on the inertial time scale, as in the Taylor model, in constrast to growth on the resistive time scale predicted from nonlinear tearing mode theory when magnetic surfaces exist. The dependence of the saturated island width on radius of a conducting shell is investigated. Islands in the reversed field pinch often have magnetic wells in the island interior, which may result in improved confinement in the island regions

Space and time resolved observations of plasma dynamics in a compressional gas embedded Z-pinch

International Nuclear Information System (INIS)

Soto, L.; Chuaqui, H.; Favre, M.; Saavedra, R.; Wyndham, E.; Aliaga-Rossel, R.; Mitchell, I.

1996-01-01

Recent experiments in a gas embedded compressional Z-pinch are presented. The experiments have been carried out in H 2 at 1/3 atm, using a pulse power generator capable of delivering a dl/dt > 10 12 A/s. The pinch is initiated by a focused laser pulse, which is coaxial with a cylindrical DC microdischarge. This configuration results in double column pinch at early times, which at current rise evolves into a gas embedded compressional Z-pinch. Diagnostics used are Rogowski coil, single frame holographic interferometry, and holographic shadowgraphy, visible streak camera images from which current, density, line density, pinch radius and plasma motion are obtained. The pinch is characterized by a maximum on axis density which is much higher than the expected value from the filling pressure, with a Bennett temperature of 40 eV at 130 kA. The results shown confirm the high degree of compression achievable with the composite preionization scheme. (author). 4 figs., 5 refs

Numerical simulation of a Z-pinch compressed by imploding liner

International Nuclear Information System (INIS)

Bilbao, L.; Linhart, J.G.; Verri, G.; Bernal, L.

2001-01-01

The spark created in a neck of a dense Z-pinch can ignite a fusion detonation in the adjacent D-T plasma channel. Using an appropriate transition between the ignited D-T plasma and an inertially confined cylinder of highly compressed advanced fuel plasma it is possible to amplify the spark energy to a level adequate for the ignition of a detonation wave in the advanced fuel. An m=0 instability of a Z-pinch carrying a current of the order of 10 MA, with a rise time inferior to 10 ns can generate a spark capable of igniting a fusion detonation in the adjacent D-T plasma channel. Such μZ-pinch may be produced by a fast implosion of a cylindrical liner, while a conical channel properly chosen can amplify the spark energy. In order to derive some general rules for the parameters of the spark, the transition, the cylinder of advanced fuel and the liner different numerical models were used. We present here a review of these results and an outline of a possible experimental arrangement for obtaining such a Z-pinch compression

A linear atomic quantum coupler

Energy Technology Data Exchange (ETDEWEB)

El-Orany, Faisal A A [Department of Mathematics and computer Science, Faculty of Science, Suez Canal University 41522, Ismailia (Egypt); Wahiddin, M R B, E-mail: el_orany@hotmail.co, E-mail: faisal.orany@mimos.m, E-mail: mridza@mimos.m [Cyberspace Security Laboratory, MIMOS Berhad, Technology Park Malaysia, 57000 Kuala Lumpur (Malaysia)

2010-04-28

In this paper we develop the notion of the linear atomic quantum coupler. This device consists of two modes propagating into two waveguides, each of which includes a localized atom. These waveguides are placed close enough to allow exchange of energy between them via evanescent waves. Each mode interacts with the atom in the same waveguide in the standard way as the Jaynes-Cummings model (JCM) and with the atom-mode system in the second waveguide via the evanescent wave. We present the Hamiltonian for this system and deduce its wavefunction. We investigate the atomic inversions and the second-order correlation function. In contrast to the conventional coupler the atomic quantum coupler is able to generate nonclassical effects. The atomic inversions can exhibit a long revival-collapse phenomenon as well as subsidiary revivals based on the competition among the switching mechanisms in the system. Finally, under certain conditions the system can yield the results of the two-mode JCM.

2D Effective Electron Mass at the Fermi Level in Accumulation and Inversion Layers of MOSFET Nano Devices.

Science.gov (United States)

Singh, S L; Singh, S B; Ghatak, K P

2018-04-01

In this paper an attempt is made to study the 2D Fermi Level Mass (FLM) in accumulation and inversion layers of nano MOSFET devices made of nonlinear optical, III-V, ternary, Quaternary, II-VI, IV-VI, Ge and stressed materials by formulating 2D carrier dispersion laws on the basis of k → ⋅ p → ⋅ formalism and considering the energy band constants of a particular material. It is observed taking accumulation and inversion layers of Cd3As2, CdGeAs2, InSb, Hg1-xCdxTe and In1-xGaxAsyP1-y lattice matched to InP, CdS, GaSb and Ge as examples that the FLM depends on sub band index for nano MOSFET devices made of Cd3As2 and CdGeAs2 materials which is the characteristic features such 2D systems. Besides, the FLM depends on the scattering potential in all the cases and the same mass changes with increasing surface electric field. The FLM exists in the band gap which is impossible without heavy doping.

Oscillatory device for use with linear tribometer, for tribological evaluation of biomaterials

Science.gov (United States)

Athayde, J. N.; Siqueira, C. J. M.; Kuromoto, N. K.; Cambraia, H. N.

2017-07-01

Orthopedic implants still have limitations regarding their durability, despite being in use for over fifty years. Particles arising from wear due to the relative motion of their surfaces remain responsible for aseptic failure. This paper presents a device to be coupled with a reciprocal linear tribometer to reproduce the ex vivo wear of biomaterials, allowing the measurement of force and coefficient of friction. The device consists of a structure connected to the tribometer that transforms its reciprocal linear motion into one that is oscillatory for the mechanical assembly that contains the samples to test the desired biomaterials. The tribological pair used for testing consisted of Ultra High Molecular Weight Polyethylene (UHMWPE) in conjunction with the austenitic stainless steel AISI 316L in dry lubrication. The results showed that the values of the coefficient of friction in the linear mode and oscillatory mode and the UHMWPE life curve in the oscillatory mode were consistent with those cited in the literature for tests in a dry lubrication environment. Moreover, the UHMWPE sample life curve showed a reduction in the wear rate that can be explained by the preponderance of a wear mechanism over the others. The volumetric wear showed an increase with the number of cycles.

Pinch grafting for chronic venous leg ulcers in general practice

OpenAIRE

Steele, Keith

1985-01-01

Twenty-five patients with chronic venous leg ulcers were treated in general practice by pinch grafting. Fifteen of the ulcers (60%) were completely healed one year after grafting. Prior to grafting 19 patients (76%) complained of daily pain in the ulcer. These patients experienced complete relief from pain after grafting. Pinch grafting is a simple, safe and effective therapy when applied in a domiciliary environment.

Numerical simulation on the screw pinch by 2-D MHD pinch code 'topics' including impurities and neutrals effects

International Nuclear Information System (INIS)

Nagata, A.; Ashida, H.; Okamoto, M.; Hirano, K.

1981-03-01

Two dimentional fluid simulation code ''TOPICS'' is developed for the STP-2, the shock heated screw pinch at Nagoya. It involves the effects of impurity ions and neutral atoms. In order to estimate the radiation losses, the impurity continuity equations with ionizations and recombinations are solved simultaneously with the plasma fluid equations. The results are compared with the coronal equilibrium model. It is found that the coronal equilibrium model underestimates the radiation losses from shock heated pinch plasmas in its initial dynamic phase. The present calculations including impurities and neutrals show the importance of the radiation losses from the plasma of the STP-2. Introducing the anomalous resistivity caused by the ion acoustic instability, the observed magnetic field penetration is explained fairly well. (author)

FOREWORD: 5th International Workshop on New Computational Methods for Inverse Problems

Science.gov (United States)

Vourc'h, Eric; Rodet, Thomas

2015-11-01

This volume of Journal of Physics: Conference Series is dedicated to the scientific research presented during the 5th International Workshop on New Computational Methods for Inverse Problems, NCMIP 2015 (http://complement.farman.ens-cachan.fr/NCMIP_2015.html). This workshop took place at Ecole Normale Supérieure de Cachan, on May 29, 2015. The prior editions of NCMIP also took place in Cachan, France, firstly within the scope of ValueTools Conference, in May 2011, and secondly at the initiative of Institut Farman, in May 2012, May 2013 and May 2014. The New Computational Methods for Inverse Problems (NCMIP) workshop focused on recent advances in the resolution of inverse problems. Indeed, inverse problems appear in numerous scientific areas such as geophysics, biological and medical imaging, material and structure characterization, electrical, mechanical and civil engineering, and finances. The resolution of inverse problems consists of estimating the parameters of the observed system or structure from data collected by an instrumental sensing or imaging device. Its success firstly requires the collection of relevant observation data. It also requires accurate models describing the physical interactions between the instrumental device and the observed system, as well as the intrinsic properties of the solution itself. Finally, it requires the design of robust, accurate and efficient inversion algorithms. Advanced sensor arrays and imaging devices provide high rate and high volume data; in this context, the efficient resolution of the inverse problem requires the joint development of new models and inversion methods, taking computational and implementation aspects into account. During this one-day workshop, researchers had the opportunity to bring to light and share new techniques and results in the field of inverse problems. The topics of the workshop were: algorithms and computational aspects of inversion, Bayesian estimation, Kernel methods, learning methods

Operational characteristics of a high voltage plasma focus device working with deuterium and heavy gas mixture

International Nuclear Information System (INIS)

Zoita, V.; Presura, R.; Gherendi, F.; Dumitrescu-Zoita, C.; Aliaga, R.

1992-01-01

The addition of a few neon percents to the deuterium gas filling of a medium energy plasma focus device (PFD) changes dramatically the radiation characteristics of the discharge as well as the pinch configuration. One exceptional result is the generation of high aspect ratio pinches shown clearly and reproducibly on X-ray pinhole camera images and on schlieren pictures. Another remarkable result is that these pinches which show no macroscopic instabilities copiously produce neutrons and hard X-rays. This confirms an experimental fact previously identified on a lower voltage PFD: the macroscopic instabilities do not play the decisive role in the neutronic performance of medium energy PFD's. (Author)

Characterization of Radiation Hardened Bipolar Linear Devices for High Total Dose Missions

Science.gov (United States)

McClure, Steven S.; Harris, Richard D.; Rax, Bernard G.; Thorbourn, Dennis O.

2012-01-01

Radiation hardened linear devices are characterized for performance in combined total dose and displacement damage environments for a mission scenario with a high radiation level. Performance at low and high dose rate for both biased and unbiased conditions is compared and the impact to hardness assurance methodology is discussed.

Surface waves tomography and non-linear inversion in the southeast Carpathians

International Nuclear Information System (INIS)

Raykova, R.B.; Panza, G.F.

2005-11-01

A set of shear-wave velocity models of the lithosphere-asthenosphere system in the southeast Carpathians is determined by the non-linear inversion of surface wave group velocity data, obtained from a tomographic analysis. The local dispersion curves are assembled for the period range 7 s - 150 s, combining regional group velocity measurements and published global Rayleigh wave dispersion data. The lithosphere-asthenosphere velocity structure is reliably reconstructed to depths of about 250 km. The thickness of the lithosphere in the region varies from about 120 km to 250 km and the depth of the asthenosphere between 150 km and 250 km. Mantle seismicity concentrates where the high velocity lid is detected just below the Moho. The obtained results are in agreement with recent seismic refraction, receiver function, and travel time P-wave tomography investigations in the region. The similarity among the results obtained from different kinds of structural investigations (including the present work) highlights some new features of the lithosphere-asthenosphere system in southeast Carpathians, as the relatively thin crust under Transylvania basin and Vrancea zone. (author)

Inverse m-matrices and ultrametric matrices

CERN Document Server

Dellacherie, Claude; San Martin, Jaime

2014-01-01

The study of M-matrices, their inverses and discrete potential theory is now a well-established part of linear algebra and the theory of Markov chains. The main focus of this monograph is the so-called inverse M-matrix problem, which asks for a characterization of nonnegative matrices whose inverses are M-matrices. We present an answer in terms of discrete potential theory based on the Choquet-Deny Theorem. A distinguished subclass of inverse M-matrices is ultrametric matrices, which are important in applications such as taxonomy. Ultrametricity is revealed to be a relevant concept in linear algebra and discrete potential theory because of its relation with trees in graph theory and mean expected value matrices in probability theory. Remarkable properties of Hadamard functions and products for the class of inverse M-matrices are developed and probabilistic insights are provided throughout the monograph.

Limits to Nonlinear Inversion

DEFF Research Database (Denmark)

Mosegaard, Klaus

2012-01-01

For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our......-heuristics are inefficient for large-scale, non-linear inverse problems, and that the 'no-free-lunch' theorem holds. We discuss typical objections to the relevance of this theorem. A consequence of the no-free-lunch theorem is that algorithms adapted to the mathematical structure of the problem perform more efficiently than...... pure meta-heuristics. We study problem-adapted inversion algorithms that exploit the knowledge of the smoothness of the misfit function of the problem. Optimal sampling strategies exist for such problems, but many of these problems remain hard. © 2012 Springer-Verlag....

Linearity correction device for a scintillation camera

Energy Technology Data Exchange (ETDEWEB)

Lange, Kai

1978-06-16

This invention concerns the scintillation cameras still called gamma ray camera. The invention particularly covers the improvement in the resolution and the uniformity of these cameras. Briefly, in the linearity correction device of the invention, the sum is made of the voltage signals of different amplitudes produced by the preamplifiers of all the photomultiplier tubes and the signal obtained is employed to generate bias voltages which represent predetermined percentages of the sum signal. In one design mode, pairs of transistors are blocked when the output signal of the corresponding preamplifier is under a certain point on its gain curve. When the summation of the energies of a given scintillation exceeds this level which corresponds to a first percentage of the total signal, the first transistor of each pair of each line is unblocked, thereby modifying the gain and curve slop. When the total energy of an event exceeds the next preset level, the second transistor is unblocked to alter the shape again, so much so that the curve shows two break points. If needs be, the device can be designed so as to obtain more break points for the increasingly higher levels of energy. Once the signals have been processed as described above, they may be used for calculating the co-ordinates of the scintillation by one of the conventional methods.

Studies of implosion processes of nested tungsten wire-array Z-pinch

International Nuclear Information System (INIS)

Ning Cheng; Ding Ning; Liu Quan; Yang Zhenhua

2006-01-01

Nested wire-array is a kind of promising structured-load because it can improve the quality of Z-pinch plasma and enhance the radiation power of X-ray source. Based on the zero-dimensional model, the assumption of wire-array collision, and the criterion of optimized load (maximal load kinetic energy), optimization of the typical nested wire-array as a load of Z machine at Sandia Laboratory was carried out. It was shown that the load has been basically optimized. The Z-pinch process of the typical load was numerically studied by means of one-dimensional three-temperature radiation magneto-hydrodynamics (RMHD) code. The obtained results reproduce the dynamic process of the Z-pinch and show the implosion trajectory of nested wire-array and the transfer process of drive current between the inner and outer array. The experimental and computational X-ray pulse was compared, and it was suggested that the assumption of wire-array collision was reasonable in nested wire-array Z-pinch at least for the current level of Z machine. (authors)

Experimental studies of Z-pinches of mixed wire array with aluminum and tungsten

International Nuclear Information System (INIS)

Ning Cheng; Li Zhenghong; Hua Xinsheng; Xu Rongkun; Peng Xianjue; Xu Zeping; Yang Jianlun; Guo Cun; Jiang Shilun; Feng Shuping; Yang Libing; Yan Chengli; Song Fengjun; Smirnov, V.P.; Kalinin, Yu.G.; Kingsep, A.S.; Chernenko, A.S.; Grabovsky, E.V.

2004-01-01

In the form of joint experiment between China and Russia, the experimental studies of Z-pinches of mixed wire array of aluminum (A1) and tungsten (W) were carried out on S-300 generator, which was located on Kurchatov Institute of Russia. The experimental results were compared with those of single A1 array and single W array, respectively. There are obvious difference between mixed one and single one in their photon spectral distributions. The intensity of K-series emission lines from the mixed wire array Z-pinch is lower than that from single A1 array. The radiated lines with wavelengths less than 1.6 nm were not found in single W array Z-pinches. In the Z-pinch processes, the area radiating x-rays in mixed wire array is smaller than that of single A1 array, but is slightly lower than that from single W array. The FWHM of x-ray pulse with a maximal power 0.3-0.5 TW and total energy 10-20 kJ is about 25 ns, which radiated from Z-pinches with a radial convergence of 4-5 on S-300 generator. The shadow photograph of the mixed wire-array Z-pinch plasma by laser probe shows that the core-corona configuration was formed and the corona was moving toward the center axis during the wire-array plasma formation, that the interface of the plasma is not clear, and that there are a number structures inside. They also suggests that there was an obvious development of Magneto Rayleigh-Taylor instability in the Z-pinch process as well

The design and implementation of a windowing interface pinch force measurement system

Science.gov (United States)

Ho, Tze-Yee; Chen, Yuanu-Joan; Chung, Chin-Teng; Hsiao, Ming-Heng

2010-02-01

This paper presents a novel windowing interface pinch force measurement system that is basically based on an USB (Universal Series Bus) microcontroller which mainly processes the sensing data from the force sensing resistance sensors mounted on five digits. It possesses several friendly functions, such as the value and curve trace of the applied force by a hand injured patient displayed in real time on a monitoring screen, consequently, not only the physician can easily evaluate the effect of hand injury rehabilitation, but also the patients get more progressive during the hand physical therapy by interacting with the screen of pinch force measurement. In order to facilitate the pinch force measurement system and make it friendly, the detail hardware design and software programming flowchart are described in this paper. Through a series of carefully and detailed experimental tests, first of all, the relationship between the applying force and the FSR sensors are measured and verified. Later, the different type of pinch force measurements are verified by the oscilloscope and compared with the corresponding values and waveform traces in the window interface display panel to obtain the consistency. Finally, a windowing interface pinch force measurement system based on the USB microcontroller is implemented and demonstrated. The experimental results show the verification and feasibility of the designed system.

Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield

International Nuclear Information System (INIS)

Sharpe, Robin Arthur; Kingsep, Alexander S.; Smith, David Lewis; Olson, Craig Lee; Ottinger, Paul F.; Schumer, Joseph Wade; Welch, Dale Robert; Kim, Alexander; Kulcinski, Gerald L.; Kammer, Daniel C.; Rose, David Vincent; Nedoseev, Sergei L.; Pointon, Timothy David; Smirnov, Valentin P.; Turgeon, Matthew C.; Kalinin, Yuri G.; Bruner, Nichelle

2007-01-01

Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot z-pinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO 2 production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber. Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-of-Principle) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is

Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.

Energy Technology Data Exchange (ETDEWEB)

Sharpe, Robin Arthur; Kingsep, Alexander S. (Kurchatov Institute, Moscow, Russia); Smith, David Lewis; Olson, Craig Lee; Ottinger, Paul F. (Naval Research Laboratory, Washington, DC); Schumer, Joseph Wade (Naval Research Laboratory, Washington, DC); Welch, Dale Robert (Voss Scientific, Albuquerque, NM); Kim, Alexander (High Currents Institute, Tomsk, Russia); Kulcinski, Gerald L. (University of Wisconsin, Madison, WI); Kammer, Daniel C. (University of Wisconsin, Madison, WI); Rose, David Vincent (Voss Scientific, Albuquerque, NM); Nedoseev, Sergei L. (Kurchatov Institute, Moscow, Russia); Pointon, Timothy David; Smirnov, Valentin P. (Kurchatov Institute, Moscow, Russia); Turgeon, Matthew C.; Kalinin, Yuri G. (Kurchatov Institute, Moscow, Russia); Bruner, Nichelle " Nicki" (Voss Scientific, Albuquerque, NM); Barkey, Mark E. (University of Alabama, Tuscaloosa, AL); Guthrie, Michael (University of Wisconsin, Madison, WI); Thoma, Carsten (Voss Scientific, Albuquerque, NM); Genoni, Tom C. (Voss Scientific, Albuquerque, NM); Langston, William L.; Fowler, William E.; Mazarakis, Michael Gerrassimos

2007-01-01

Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot z-pinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO{sub 2} production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber. Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-of-Principle) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is

Linear motion device and method for inserting and withdrawing control rods

International Nuclear Information System (INIS)

Smith, J. E.

1984-01-01

A linear motion device, more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core, is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism

Studies of a poloidal divertor reversed field pinch

International Nuclear Information System (INIS)

Sarff, J.S.; Almagri, A.F.; Assadi, S.; Den Hartog, D.J.; Dexter, R.N.; Prager, S.C.; Sprott, J.C.

1988-07-01

An attempt has been made to form a reversed field pinch (RFP) in a poloidal divertor configuration which position the plasma far from a conducting wall. In this configuration, the plasma is localized within a magnetic separatrix formed by the combination of toroidal currents in the plasma and four internal aluminum rings. Plasmas were formed with plasma current /approximately/135 kA, toroidal field reversal lasting /approximately/1 msec, line-averaged density /approximately/1--2 /times/ 10 13 cm/sup /minus/3/ and central electron temperature /approximately/55 eV, but a large asymmetry in the magnetic field (δB/B /approximately/40%) onset at about the time the toroidal field reversed at the wall. Symmetric, poloidal divertor RFP equilibria were not formed. This behavior might be expected based on linear MHD stability analysis of a cylindrical plasma bounded by a large vacuum region and distant conducting wall. The symmetric equilibrium before the asymmetry develops and the asymmetry itself are described. 15 refs., 3 figs

Seeded perturbations in wire array z-pinches

International Nuclear Information System (INIS)

Robinson, Allen Conrad; Kantsyrev, Victor Leonidovich; Wunsch, Scott Edward; Oliver, Bryan Velten; Lebedev, Sergey V.; Safronova, Alla S.; Maxwell, J.; McKenney, John Lee; Ampleford, David J.; Rapley, J.; Bott, S.C.; Palmer, J.B.A.; Bland, Simon Nicholas; Jones, Brent Manley; Chittenden, Jeremy Paul; Garasi, Christopher Joseph; Hall, Gareth Neville; Mehlhorn, Thomas Alan; Deeney, Christopher

2004-01-01

The impact of 3D structure on wire array z-pinch dynamics is a topic of current interest, and has been studied by the controlled seeding of wire perturbations. First, Al wires were etched at Sandia, creating 20% radial perturbations with variable axial wavelength. Observations of magnetic bubble formation in the etched regions during experiments on the MAGPIE accelerator are discussed and compared to 3D MHD modeling. Second, thin NaF coatings of 1 mm axial extent were deposited on Al wires and fielded on the Zebra accelerator. Little or no axial transport of the NaF spectroscopic dopant was observed in spatially resolved K-shell spectra, which places constraints on particle diffusivity in dense z-pinch plasmas. Finally, technology development for seeding perturbations is discussed

Magnetic islands at the field reversal surface in reversed field pinches

International Nuclear Information System (INIS)

Pinsker, R.I.; Reiman, A.H.

1985-09-01

In the reversed field pinch (RFP), magnetic field perturbations having zero poloidal mode number and any toroidal mode number are resonant at the field reversal surface. Such perturbations are a particular threat to the RFP because of their weak radial dependence at low toroidal mode number, and because the toroidal field ripple is essentially of this type. The widths of the resulting islands are calculated in this paper. The self-consistent plasma response is included through the assumption that the plasma relaxes to a Taylor force-free state. The connection with linear tearing mode theory is established for those limits where arbitrarily large islands result from infinitesimal perturbations. Toroidal effects are considered, and application of the theory to RFP experiments is discussed

Anomalous diffusion, clustering, and pinch of impurities in plasma edge turbulence

DEFF Research Database (Denmark)

Priego, M.; Garcia, O.E.; Naulin, V.

2005-01-01

The turbulent transport of impurity particles in plasma edge turbulence is investigated. The impurities are modeled as a passive fluid advected by the electric and polarization drifts, while the ambient plasma turbulence is modeled using the two-dimensional Hasegawa-Wakatani paradigm for resistive...... drift-wave turbulence. The features of the turbulent transport of impurities are investigated by numerical simulations using a novel code that applies semi-Lagrangian pseudospectral schemes. The diffusive character of the turbulent transport of ideal impurities is demonstrated by relative...... orientation determined by the charge of the impurity particles. Second, a radial pinch scaling linearly with the mass-charge ratio of the impurities is discovered. Theoretical explanation for these observations is obtained by analysis of the model equations. (C) 2005 American Institute of Physics....

High-β, improved confinement reversed-field pinch plasmas at high density

International Nuclear Information System (INIS)

Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Bonomo, F.; Franz, P.; Brower, D. L.

2008-01-01

In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching n e =4x10 19 m -3 . Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch

Soft X-Ray Measurements of Z-Pinch-Driven Vacuum Hohlraums

International Nuclear Information System (INIS)

Baker, K.L.; Porter, J.L.; Ruggles, L.E.; Chandler, G.A.; Deeney, Chris; Varas, M.; Moats, Ann; Struve, Ken; Torres, J.; McGurn, J.; Simpson, W.W.; Fehl, D.L.; Chrien, R.E.; Matuska, W.; Idzorek, G.C.

1999-01-01

This article reports the experimental characterization of a z-pinch driven-vacuum hohlraum. The authors have measured soft x-ray fluxes of 5 x 10 12 W/cm 2 radiating from the walls of hohlraums which are 2.4--2.5 cm in diameter by 1 cm tall. The x-ray source used to drive these hohlraums was a z-pinch consisting of a 300 wire tungsten array driven by a 2 MA, 100 ns current pulse. In this hohlraum geometry, the z-pinch x-ray source can produce energies in excess of 800 kJ and powers in excess of 100 TW to drive these hohlraums. The x-rays released in these hohlraums represent greater than a factor of 25 in energy and more than a factor of three in x-ray power over previous laboratory-driven hohlraums

The Inverse System Method Applied to the Derivation of Power System Non—linear Control Laws

Institute of Scientific and Technical Information of China (English)

DonghaiLI; XuezhiJIANG; 等

1997-01-01

The differential geometric method has been applied to a series of power system non-linear control problems effectively.However a set of differential equations must be solved for obtaining the required diffeomorphic transformation.Therefore the derivation of control laws is very complicated.In fact because of the specificity of power system models the required diffeomorphic transformation may be obtained directly,so it is unnecessary to solve a set of differential equations.In addition inverse system method is equivalent to differential geometric method in reality and not limited to affine nonlinear systems,Its physical meaning is able to be viewed directly and its deduction needs only algebraic operation and derivation,so control laws can be obtained easily and the application to engineering is very convenient.Authors of this paper take steam valving control of power system as a typical case to be studied.It is demonstrated that the control law deduced by inverse system method is just the same as one by differential geometric method.The conclusion will simplify the control law derivations of steam valving,excitation,converter and static var compensator by differential geometric method and may be suited to similar control problems in other areas.

Advances in memristors, memristive devices and systems

CERN Document Server

Volos, Christos

2017-01-01

This book reports on the latest advances in and applications of memristors, memristive devices and systems. It gathers 20 contributed chapters by subject experts, including pioneers in the field such as Leon Chua (UC Berkeley, USA) and R.S. Williams (HP Labs, USA), who are specialized in the various topics addressed in this book, and covers broad areas of memristors and memristive devices such as: memristor emulators, oscillators, chaotic and hyperchaotic memristive systems, control of memristive systems, memristor-based min-max circuits, canonic memristors, memristive-based neuromorphic applications, implementation of memristor-based chaotic oscillators, inverse memristors, linear memristor devices, delayed memristive systems, flux-controlled memristive emulators, etc. Throughout the book, special emphasis is given to papers offering practical solutions and design, modeling, and implementation insights to address current research problems in memristors, memristive devices and systems. As such, it offers a va...

Support minimized inversion of acoustic and elastic wave scattering

International Nuclear Information System (INIS)

Safaeinili, A.

1994-01-01

This report discusses the following topics on support minimized inversion of acoustic and elastic wave scattering: Minimum support inversion; forward modelling of elastodynamic wave scattering; minimum support linearized acoustic inversion; support minimized nonlinear acoustic inversion without absolute phase; and support minimized nonlinear elastic inversion

Plasma confinement of Nagoya high-beta toroidal-pinch experiments

International Nuclear Information System (INIS)

Hirano, K.; Kitagawa, S.; Wakatani, M.; Kita, Y.; Yamada, S.; Yamaguchi, S.; Sato, K.; Aizawa, T.; Osanai, Y.; Noda, N.

1977-01-01

Two different types of high-β toroidal pinch experiments, STP [1] and CCT [2,3], have been done to study the confinement of the plasma produced by a theta-pinch. The STP is an axisymmetric toroidal pinch of high-β tokamak type, while the CCT consists of multiply connected periodic toroidal traps. Internal current-carrying copper rings are essential to the CCT. Since both apparatuses use the same fast capacitor bank system, they produce rather similar plasma temperatures and densities. The observed laser scattering temperature and density is about 50 eV and 4x10 15 cm -3 , respectively, when the filling pressure is 5 mtorr. In the STP experiment, strong correlations are found between the βsub(p) value and the amplitude of m=2 mode. It has a minimum around the value of βsub(p) of 0.8. The disruptive instability is observed to expand the pinched plasma column without lowering the plasma temperature. Just before the disruption begins, the q value around the magnetic axis becomes far less than 1 and an increase of the amplitude of m=2 mode is seen. The CCT also shows rapid plasma expansion just before the magnetic field reaches its maximum. Then the trap is filled up with the plasma by this irreversible expansion and stable plasma confinement is achieved. The energy confinement time of the CCT is found to be about 35 μs. (author)

Pinch analysis for bioethanol production process from lignocellulosic biomass

International Nuclear Information System (INIS)

Fujimoto, S.; Yanagida, T.; Nakaiwa, M.; Tatsumi, H.; Minowa, T.

2011-01-01

Bioethanol produced from carbon neutral and renewable biomass resources is an attractive process for the mitigation of greenhouse gases from vehicle exhaust. This study investigated energy utilization during bioethanol production from lignocellulose while avoiding competition with food production from corn and considering the potential mitigation of greenhouse gases. Process design and simulations were performed for bioethanol production using concentrated sulfuric acid. Mass and heat balances were obtained by process simulations, and the heat recovery ratio was determined by pinch analysis. An energy saving of 38% was achieved. However, energy supply and demand were not effectively utilized in the temperature range from 95 to 100 o C. Therefore, a heat pump was used to improve the temperature range of efficient energy supply and demand. Results showed that the energy required for the process could be supplied by heat released during the process. Additionally, the power required was supplied by surplus power generated during the process. Thus, pinch analysis was used to improve the energy efficiency of the process. - Highlights: → Effective energy utilization of bioethanol production was studied by using pinch analysis. → It was found that energy was not effectively utilized in the temperature range from 95 to 100 o C. → Use of a heat pump was considered to improve the ineffective utilization. → Then, remarkable energy savings could be achieved by it. → Pinch analysis effectively improved the energy efficiency of the bioethanol production.

Two-dimensional integrated Z-pinch ICF design simulations

International Nuclear Information System (INIS)

Lash, J.S.

1999-01-01

The dynamic hohlraum ICF concept for a Z-pinch driver utilizes the imploding wire array collision with a target to produce a radiation history suitable for driving an embedded inertial confinement fusion (ICF) capsule. This target may consist of various shaped layers of low-density foams or solid-density materials. The use of detailed radiation magneto-hydrodynamic (RMHD) modeling is required for understanding and designing these complex systems. Critical to producing credible simulations and designs is inclusion of the Rayleigh-Taylor unstable wire-array dynamics; the bubble and spike structure of the collapsing sheath may yield regions of low-opacity enhancing radiation loss as well as introduce non-uniformities in the capsule's radiation drive. Recent improvements in LASNEX have allowed significant progress to be made in the modeling of unstable z-pinch implosions. Combining this with the proven ICF capsule design capabilities of LASNEX, the authors now have the modeling tools to produce credible, fully-integrated ICF dynamic hohlraum simulations. They present detailed two-dimensional RMHD simulations of recent ICF dynamic hohlraum experiments on the Sandia Z-machine as well as design simulations for the next-generation Z-pinch facility and future high-yield facility

Two-dimensional integrated Z-pinch ICF design simulations

Energy Technology Data Exchange (ETDEWEB)

Lash, J.S.

1999-07-01

The dynamic hohlraum ICF concept for a Z-pinch driver utilizes the imploding wire array collision with a target to produce a radiation history suitable for driving an embedded inertial confinement fusion (ICF) capsule. This target may consist of various shaped layers of low-density foams or solid-density materials. The use of detailed radiation magneto-hydrodynamic (RMHD) modeling is required for understanding and designing these complex systems. Critical to producing credible simulations and designs is inclusion of the Rayleigh-Taylor unstable wire-array dynamics; the bubble and spike structure of the collapsing sheath may yield regions of low-opacity enhancing radiation loss as well as introduce non-uniformities in the capsule's radiation drive. Recent improvements in LASNEX have allowed significant progress to be made in the modeling of unstable z-pinch implosions. Combining this with the proven ICF capsule design capabilities of LASNEX, the authors now have the modeling tools to produce credible, fully-integrated ICF dynamic hohlraum simulations. They present detailed two-dimensional RMHD simulations of recent ICF dynamic hohlraum experiments on the Sandia Z-machine as well as design simulations for the next-generation Z-pinch facility and future high-yield facility.

Development and characterization of a Z-pinch-driven hohlraum high-yield inertial confinement fusion target concept

International Nuclear Information System (INIS)

Cuneo, Michael E.; Vesey, Roger A.; Porter, John L. Jr.; Chandler, Gordon A.; Fehl, David L.; Gilliland, Terrance L.; Hanson, David L.; McGurn, John S.; Reynolds, Paul G.; Ruggles, Laurence E.; Seamen, Hans; Spielman, Rick B.; Struve, Ken W.; Stygar, William A.; Simpson, Walter W.; Torres, Jose A.; Wenger, David F.; Hammer, James H.; Rambo, Peter W.; Peterson, Darrell L.

2001-01-01

Initial experiments to study the Z-pinch-driven hohlraum high-yield inertial confinement fusion (ICF) concept of Hammer, Tabak, and Porter [Hammer et al., Phys. Plasmas 6, 2129 (1999)] are described. The relationship between measured pinch power, hohlraum temperature, and secondary hohlraum coupling ('hohlraum energetics') is well understood from zero-dimensional semianalytic, and two-dimensional view factor and radiation magnetohydrodynamics models. These experiments have shown the highest x-ray powers coupled to any Z-pinch-driven secondary hohlraum (26±5 TW), indicating the concept could scale to fusion yields of >200 MJ. A novel, single-sided power feed, double-pinch driven secondary that meets the pinch simultaneity requirements for polar radiation symmetry has also been developed. This source will permit investigation of the pinch power balance and hohlraum geometry requirements for ICF relevant secondary radiation symmetry, leading to a capsule implosion capability on the Z accelerator [Spielman et al., Phys. Plasmas 5, 2105 (1998)

The belt-shaped screw-pinch reactor

International Nuclear Information System (INIS)

Bustraan, M.; Klippel, H.Th.; Veringa, H.J.; Verschuur, K.A.; Lievense, K.

1981-12-01

The belt-shaped screw pinch is a pulsed toroidal plasma with an elongated cross-section. Force-free currents in an outer plasma envelope of low density allow beta to rise to high values in the order of 50%. This is a potential possibility to develop an economically attractive reactor. The physical requirements of its realization are described: formation, heating and ignition of a very small amount of the fuel to be burnt in one pulse by the fields generated by normal or superconducting coils. Then follows injection of the greater part of the fuel by D-T pellets and consequent plasma heating and expansion by nuclear reactions without undue disturbing of the plasma current configuration. Technical requirements include an insulating first wall and fast rising magnetic fields produced by superconducting coils. This reactor system is compared with the tokamak and the reversed-field pinch system

LASL toroidal reversed-field pinch program

International Nuclear Information System (INIS)

Baker, D.A.; Buchenauer, C.J.; Burkhardt, L.C.

1978-01-01

The determination of the absolute energy loss due to radiation from impurities in the LASL toroidal reversed-field pinch experiment ZT-S is reported. The measurements show over half of the energy loss is accounted for by this mechanism. Thomson scattering electron density measurements indicate only a gradual increase in temperature as the filling pressure is reduced indicating an increased energy loss at lower pressures. Cylindrical and toroidal simulations of the experiment indicate either that a highly radiative pinch boundary or anomalous transport are needed to match the experimental results. New effects on the equilibrium due to plasma flows induced by the toroidal geometry are predicted by the toroidal simulations. The preliminary results on the low temperature discharge cleaning of the ZT-S torus are reported. A description of the upgrade of the ZT-S experiment and the objectives, construction and theoretical predictions for the new ZT-40 experiment are given

Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

International Nuclear Information System (INIS)

Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Maisonny, Rémi; Toury, Martial; Hourdin, Laurent; Cartier, Frédéric; Cartier, Stéphanie; D'Almeida, Thierry; Delbos, Christophe; Garrigues, Alain; Plouhinec, Damien; Ritter, Sandra; Sol, David; Zucchini, Frédéric; Caron, Michel

2013-01-01

The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV,” Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the electrode

Simultaneous retrieval of aerosols and ocean properties: A classic inverse modeling approach. I. Analytic Jacobians from the linearized CAO-DISORT model

International Nuclear Information System (INIS)

Spurr, Robert; Stamnes, Knut; Eide, Hans; Li Wei; Zhang Kexin; Stamnes, Jakob

2007-01-01

In this paper and the sequel, we investigate the application of classic inverse methods based on iterative least-squares cost-function minimization to the simultaneous retrieval of aerosol and ocean properties from visible and near infrared spectral radiance measurements such as those from the SeaWiFS and MODIS instruments. Radiance measurements at the satellite are simulated directly using an accurate coupled atmosphere-ocean-discrete-ordinate radiative transfer (CAO-DISORT) code as the main component of the forward model. For this kind of cost-function inverse problem, we require the forward model to generate weighting functions (radiance partial derivatives) with respect to the aerosol and marine properties to be retrieved, and to other model parameters which are sources of error in the retrievals. In this paper, we report on the linearization of the CAO-DISORT model. This linearization provides a complete analytic differentiation of the coupled-media radiative transfer theory, and it allows the model to generate analytic weighting functions for any atmospheric or marine parameter. For high solar zenith angles, we give an implementation of the pseudo-spherical (P-S) approach to solar beam attenuation in the atmosphere in the linearized model. We summarize a number of performance enhancements such as the use of an exact single-scattering calculation to improve accuracy. We derive inherent optical property inputs for the linearized CAO-DISORT code for a simple 2-parameter bio-optical model for the marine environment coupled to a 2-parameter bimodal atmospheric aerosol medium

MHD turbulence models for the reversed field pinch

International Nuclear Information System (INIS)

Gimblett, C.G.; Watkins, M.L.

1976-01-01

A kinematic model which describes the effect of isotropic, non-mirror symmetric turbulence on a mean magnetic field is used to examine the temporal behaviour of magnetic field in high beta pinch experiments. Solutions to the model can indicate the formation of a steady-state, force-free configuration that corresponds to the state of lowest magnetic energy and the reversal of the toroidal magnetic field at the plasma boundary in accordance with experimental observations on toroidal pinches such as ZETA and HBTX. This model neglects both the dynamic interaction between fluid and field and the associated anisotropy. These effects are examined in a further model. (author)

Review of effects of dielectric coatings on electrical exploding wires and Z pinches

Science.gov (United States)

Wu, Jian; Li, Xingwen; Li, Mo; Li, Yang; Qiu, Aici

2017-10-01

As the most powerful x-ray source in the laboratories, the wire array Z pinches have been of great relevance to inertial confinement fusions, laboratory astrophysics, and other high-energy density applications. In order to produce x-ray with greater power and higher efficiency, the dynamics of wire array has been investigated extensively, and various methods have been proposed to improve the implosion quality of the wire array. This review focuses on the experimental and theoretical investigations regarding the effects of the dielectric coatings on electrical exploding wires and Z pinches. Since the early 2000, the electrical wire explosion related to the first stage of the wire array Z pinches has been studied extensively, and the results indicated that the dielectric coatings can significantly increase the joule energy deposition into a wire in the initial stage, and even the corona free explosion of tungsten wires can be achieved. Recently, there is an increasing interest in the dynamics of insulated wire array Z pinches. By applying dielectric coatings, the ablation process is suppressed, the x-ray start time is delayed, and the possibility of multi-peak radiation is decreased. This review is organized by the evolution dynamics of wire array Z pinches, and a broad introduction to relevant scientific concepts and various other applications are presented. According to the current research status, the challenges, opportunities and further developments of Z pinch loads using dielectric coatings are proposed to further promote the researches and their applications.

Review of effects of dielectric coatings on electrical exploding wires and Z pinches

International Nuclear Information System (INIS)

Wu, Jian; Li, Mo; Li, Yang; Li, Xingwen; Qiu, Aici

2017-01-01

As the most powerful x-ray source in the laboratories, the wire array Z pinches have been of great relevance to inertial confinement fusions, laboratory astrophysics, and other high-energy density applications. In order to produce x-ray with greater power and higher efficiency, the dynamics of wire array has been investigated extensively, and various methods have been proposed to improve the implosion quality of the wire array. This review focuses on the experimental and theoretical investigations regarding the effects of the dielectric coatings on electrical exploding wires and Z pinches. Since the early 2000, the electrical wire explosion related to the first stage of the wire array Z pinches has been studied extensively, and the results indicated that the dielectric coatings can significantly increase the joule energy deposition into a wire in the initial stage, and even the corona free explosion of tungsten wires can be achieved. Recently, there is an increasing interest in the dynamics of insulated wire array Z pinches. By applying dielectric coatings, the ablation process is suppressed, the x-ray start time is delayed, and the possibility of multi-peak radiation is decreased. This review is organized by the evolution dynamics of wire array Z pinches, and a broad introduction to relevant scientific concepts and various other applications are presented. According to the current research status, the challenges, opportunities and further developments of Z pinch loads using dielectric coatings are proposed to further promote the researches and their applications. (topical review)

High-energy electron acceleration in the gas-puff Z-pinch plasma

Energy Technology Data Exchange (ETDEWEB)

Takasugi, Keiichi, E-mail: takasugi@phys.cst.nihon-u.ac.jp [Institute of Quantum Science, Nihon University, 1-8 Kanda-Surugadai, Chiyoda, Tokyo 101-8308 (Japan); Miyazaki, Takanori [Institute of Quantum Science, Nihon University, 1-8 Kanda-Surugadai, Chiyoda, Tokyo 101-8308, Japan and Dept. Innovation Systems Eng., Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan); Nishio, Mineyuki [Anan National College of Technology, 265 Aoki, Minobayashi, Anan, Tokushima 774-0017 (Japan)

2014-12-15

The characteristics of hard x-ray generation were examined in the gas-puff z-pinch experiment. The experiment on reversing the voltage was conducted. In both of the positive and negative discharges, the x-ray was generated only from the anode surface, so it was considered that the electrons were accelerated by the induced electromagnetic force at the pinch time.

Novel type of linear mitochondrial genomes with dual flip-flop inversion system in apicomplexan parasites, Babesia microti and Babesia rodhaini

Directory of Open Access Journals (Sweden)

Hikosaka Kenji

2012-11-01

Full Text Available Abstract Background Mitochondrial (mt genomes vary considerably in size, structure and gene content. The mt genomes of the phylum Apicomplexa, which includes important human pathogens such as the malaria parasite Plasmodium, also show marked diversity of structure. Plasmodium has a concatenated linear mt genome of the smallest size (6-kb; Babesia and Theileria have a linear monomeric mt genome (6.5-kb to 8.2-kb with terminal inverted repeats; Eimeria, which is distantly related to Plasmodium and Babesia/Theileria, possesses a mt genome (6.2-kb with a concatemeric form similar to that of Plasmodium; Cryptosporidium, the earliest branching lineage within the phylum Apicomplexa, has no mt genome. We are interested in the evolutionary origin of linear mt genomes of Babesia/Theileria, and have investigated mt genome structures in members of archaeopiroplasmid, a lineage branched off earlier from Babesia/Theileria. Results The complete mt genomes of archaeopiroplasmid parasites, Babesia microti and Babesia rodhaini, were sequenced. The mt genomes of B. microti (11.1-kb and B. rodhaini (6.9-kb possess two pairs of unique inverted repeats, IR-A and IR-B. Flip-flop inversions between two IR-As and between two IR-Bs appear to generate four distinct genome structures that are present at an equi-molar ratio. An individual parasite contained multiple mt genome structures, with 20 copies and 2 – 3 copies per haploid nuclear genome in B. microti and B. rodhaini, respectively. Conclusion We found a novel linear monomeric mt genome structure of B. microti and B. rhodhaini equipped with dual flip-flop inversion system, by which four distinct genome structures are readily generated. To our knowledge, this study is the first to report the presence of two pairs of distinct IR sequences within a monomeric linear mt genome. The present finding provides insight into further understanding of evolution of mt genome structure.

Computer modeling of a small neon gas-puff pinch

International Nuclear Information System (INIS)

Ullschmied, J.

1996-01-01

The macroscopic dynamics of a cylindrical gas-puff pinch and conditions of radiation plasma collapse are studied by using a one-dimensional ('mechanical') computer model. Besides the Joule plasma heating, compressional heating, magnetic field freezing in a plasma and recombination losses, also the real temperature- and density-dependences of radiation plasma loss are taken into account. The results of calculations are compared with experimental data taken from a small neon-puff z-pinch experiment operated at the Institute of Plasma Physics in Prague. (author). 7 figs., 11 refs

Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

Energy Technology Data Exchange (ETDEWEB)

Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hebert, David [CEA, DAM, CESTA, F-33114 Le Barp (France); Bernigaud, Virgile; Magnin, Laurent; Nicolas, Remi; Poulet, Frederic; Tailleur, Yaeel [CEA, DAM, VALDUC, F-21120 Is sur Tille (France); Caron, Michel; Cartier, Frederic; Cartier, Stephanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle [CEA, DAM, GRAMAT, F-46500 Gramat (France); and others

2012-09-15

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization of a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to

Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

International Nuclear Information System (INIS)

Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hébert, David; Bernigaud, Virgile; Magnin, Laurent; Nicolas, Rémi; Poulet, Frédéric; Tailleur, Yaël; Caron, Michel; Cartier, Frédéric; Cartier, Stéphanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle

2012-01-01

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567–570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., “Negative polarity rod pinch diode experiments on the ASTERIX generator,” in Conference Records–Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most

Experimental study of CF4 conical theta pinch plasma expanding into vacuum

International Nuclear Information System (INIS)

Pedrow, P.D.; Nasiruddin, A.M.

1989-01-01

Langmuir probe, photodiode, and optical multichannel analyzer (OMA) measurements have been made on a pulsed CF 4 conical theta pinch plasma. A cloud of CF 4 gas was puffed into a conical theta pinch coil, converted to plasma, and propelled into the vacuum region ahead of the expanding gas cloud. At a position 67 cm away from the conical theta pinch coil, the plasma arrived in separate packets that were about 20 μs in duration. The average drift velocity of these packets corresponded to an energy of about 3 eV. The OMA measurements showed that the second packet contained neutral atomic fluorine as well as charged particles

Confinement characteristics of the TPE reversed field pinch plasmas and effects of the boundary configuration

International Nuclear Information System (INIS)

Yagi, Y.; Maejima, Y.; Zollino, G.

2001-01-01

Confinement characteristics of the TPE series reversed field pinch (RFP) machines, TPE-1RM15, TPE-1RM20 and TPE-1RM20mod, at Electrotechnical Laboratory (ETL) are summarized. Especially data are synthesized in respect to the effects of the different boundary structures of the machines, where shell proximity and overlapped poloidal shell gaps by the multi-layered shell structure are featured. Comparison of the experimental results is shown in terms of the characteristics of magnetic fluctuations, global confinement properties in general, operation capability of the improved confinement in high pinch parameter (Q) discharges and locked mode events. Linear growth rate of the unstable modes as a function of the shell distance is numerically simulated. Understandings of RFP plasma physics have also made progress by the most recent intensive experiments on correlation studies between fast electrons and dynamo activities and measurement of the plasma and mode rotation. TPE-1RM20mod was shutdown in December 1996 and new RFP experiment has started in TPE-RX from March 1998. The new machine also succeeds the concept of the shell configuration of the TPE-1RM20. (author)

Planktonic food webs revisited: Reanalysis of results from the linear inverse approach

Science.gov (United States)

Hlaili, Asma Sakka; Niquil, Nathalie; Legendre, Louis

2014-01-01

Identification of the trophic pathway that dominates a given planktonic assemblage is generally based on the distribution of biomasses among food-web compartments, or better, the flows of materials or energy among compartments. These flows are obtained by field observations and a posteriori analyses, including the linear inverse approach. In the present study, we re-analysed carbon flows obtained by inverse analysis at 32 stations in the global ocean and one large lake. Our results do not support two "classical" views of plankton ecology, i.e. that the herbivorous food web is dominated by mesozooplankton grazing on large phytoplankton, and the microbial food web is based on microzooplankton significantly consuming bacteria; our results suggest instead that phytoplankton are generally grazed by microzooplankton, of which they are the main food source. Furthermore, we identified the "phyto-microbial food web", where microzooplankton largely feed on phytoplankton, in addition to the already known "poly-microbial food web", where microzooplankton consume more or less equally various types of food. These unexpected results led to a (re)definition of the conceptual models corresponding to the four trophic pathways we found to exist in plankton, i.e. the herbivorous, multivorous, and two types of microbial food web. We illustrated the conceptual trophic pathways using carbon flows that were actually observed at representative stations. The latter can be calibrated to correspond to any field situation. Our study also provides researchers and managers with operational criteria for identifying the dominant trophic pathway in a planktonic assemblage, these criteria being based on the values of two carbon ratios that could be calculated from flow values that are relatively easy to estimate in the field.

Comparative study of millennials' (age 20-34 years) grip and lateral pinch with the norms.

Science.gov (United States)

Fain, Elizabeth; Weatherford, Cara

Cross-sectional research design. Clinical practice continues to use normative data for grip and pinch measurements that were established in 1985. There is no updated norms despite different hand usage patterns in today's society. Measuring and comparing grip and pinch strengths with normative data is a valid method to determine hand function. This research was implemented to compare the grip and pinch measurements obtained from healthy millennials to the established norms and to describe hand usage patterns for millennials. Grip and lateral pinch measurements were obtained from a sample of 237 healthy millennials (ages 20-34 years). Strength scores were statistically lower that older normative data in all millennial grip strengths, with the exception of the women in the age group of 30-34 years. Specifically, this statistically significant trend was observed in all male grip strengths, as well as in women in the age group of 20-24 years (bilateral grip) and 25-29 years (right grip). However, the lateral pinch data reflected was similar to the older norms with variances of 0.5-1 kg. Current data reflect statistically significant differences from the norms for all male grip measurements, as well as for women in the age group of 20-24 years (bilateral grip) and 25-29 years (right grip). No statistical significance was observed in the independent-sample t tests for the lateral pinch in men of all age groups. Statistical significance was noted for lateral pinch for female age groups for the left hand (20-24 years) and for bilateral lateral pinches (30-34 years). IV. Copyright © 2016 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Development of a visible framing camera diagnostic for the study of current initiation in z-pinch plasmas

International Nuclear Information System (INIS)

Muron, D.J.; Hurst, M.J.; Derzon, M.S.

1996-01-01

The authors assembled and tested a visible framing camera system to take 5 ns FWHM images of the early time emission from a z-pinch plasma. This diagnostic was used in conjunction with a visible streak camera allowing early time emissions measurements to diagnose current initiation. Individual frames from gated image intensifiers were proximity coupled to charge injection device (CID) cameras and read out at video rate and 8-bit resolution. A mirror was used to view the pinch from a 90-degree angle. The authors observed the destruction of the mirror surface, due to the high surface heating, and the subsequent reduction in signal reflected from the mirror. Images were obtained that showed early time ejecta and a nonuniform emission from the target. This initial test of the equipment highlighted problems with this measurement. They observed non-uniformities in early time emission. This is believed to be due to either spatially varying current density or heating of the foam. Images were obtained that showed early time ejecta from the target. The results and suggestions for improvement are discussed in the text

A simplified MHD model of capillary Z-Pinch compared with experiments

Energy Technology Data Exchange (ETDEWEB)

Shapolov, A.A.; Kiss, M.; Kukhlevsky, S.V. [Institute of Physics, University of Pecs (Hungary)

2016-11-15

The most accurate models of the capillary Z-pinches used for excitation of soft X-ray lasers and photolithography XUV sources currently are based on the magnetohydrodynamics theory (MHD). The output of MHD-based models greatly depends on details in the mathematical description, such as initial and boundary conditions, approximations of plasma parameters, etc. Small experimental groups who develop soft X-ray/XUV sources often use the simplest Z-pinch models for analysis of their experimental results, despite of these models are inconsistent with the MHD equations. In the present study, keeping only the essential terms in the MHD equations, we obtained a simplified MHD model of cylindrically symmetric capillary Z-pinch. The model gives accurate results compared to experiments with argon plasmas, and provides simple analysis of temporal evolution of main plasma parameters. The results clarify the influence of viscosity, heat flux and approximations of plasma conductivity on the dynamics of capillary Z-pinch plasmas. The model can be useful for researchers, especially experimentalists, who develop the soft X-ray/XUV sources. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

3D modeling of instabilities in multi-wire Z pinches

International Nuclear Information System (INIS)

Haill, T.A.; Desjarlais, M.P.; Marder, B.M.; Robinson, A.C.

1998-01-01

Recent success in generating large x-ray energies and powers from large wire-number Z pinch arrays has revived a strong interest in MHD and magneto-Rayleigh-Taylor (RT) instabilities. Two-dimensional r-z simulations of Z pinches typically start calculations with a preformed plasma sheath and seed RT instabilities with a random density perturbation. The magnitude of the random density perturbation is tuned so that the calculated x-ray radiation pulse matches the amplitude and pulse-width of experimentally measured data. While these calculations have been extremely useful in understanding the effect of RT instabilities on experiments, they do not capture all of the three-dimension structure seen in experimental images and are not truly predictive in nature. To remedy this shortcoming Sandia is developing a 3D nature of Z pinch dynamics, namely the merger of arrays of wires into a plasma sheath

Dose-current discharge correlation analysis in a Mather type Plasma Focus device for medical applications

Science.gov (United States)

Sumini, M.; Mostacci, D.; Tartari, A.; Mazza, A.; Cucchi, G.; Isolan, L.; Buontempo, F.; Zironi, I.; Castellani, G.

2017-11-01

In a Plasma Focus device the plasma collapses into the pinch where it reaches thermonuclear conditions for a few tens of nanoseconds, becoming a multi-radiation source. The nature of the radiation generated depends on the gas filling the chamber and the device working parameters. The self-collimated electron beam generated in the backward direction with respect to the plasma motion is one of the main radiation sources of interest also for medical applications. The electron beam may be guided against a high Z material target to produce an X-ray beam. This technique offers an ultra-high dose rate source of X-rays, able to deliver during the pinch a massive dose (up to 1 Gy per discharge for the PFMA-3 test device), as measured with EBT3 GafchromicⒸfilm tissue equivalent dosimeters. Given the stochastic behavior of the discharge process, a reliable on-line estimate of the dose-delivered is a very challenging task, in some way preventing a systematic application as a potentially interesting therapy device. This work presents an approach to linking the dose registered by the EBT3 GafchromicⒸfilms with the information contained in the signal recorded during the current discharge process. Processing the signal with the Wigner-Ville distribution, a spectrogram was obtained, displaying the information on intensity at various frequency scales, identifying the band of frequencies representative of the pinch events and define some patterns correlated with the dose.

Dynamics of low density coronal plasma in low current x-pinches

International Nuclear Information System (INIS)

Haas, D; Bott, S C; Vikhrev, V; Eshaq, Y; Ueda, U; Zhang, T; Baranova, E; Krasheninnikov, S I; Beg, F N

2007-01-01

Experiments were performed on an x-pinch using a pulsed power current generator capable of producing an 80 kA current with a rise time of 50 ns. Molybdenum wires with and without gold coating were employed to study the effect of high z coating on the low-density ( 18 cm -3 ) coronal plasma dynamics. A comparison of images from XUV frames and optical probing shows that the low density coronal plasma from the wires initially converges at the mid-plane immediately above and below the cross-point. A central jet is formed which moves with a velocity of 6 x 10 4 ms -1 towards both electrodes forming a z-pinch column before the current maximum. A marked change in the low density coronal plasma dynamics was observed when molybdenum wires coated with ∼ 0.09 μm of gold were used. The processes forming the jet structure were delayed relative to bare Mo x-pinches, and the time-resolved x-ray emission also showed differences. An m = 0 instability was observed in the coronal plasma along the x-pinch legs, which were consistent with x-ray PIN diode signals in which x-ray pulses were observed before x-ray spot formation. These early time x-ray pulses were not observed with pure molybdenum x-pinches. These observations indicate that a thin layer of gold coating significantly changes the coronal plasma behaviour. Two dimensional MHD simulations were performed and qualitatively agree with experimental observations of low density coronal plasma

On the dynamics of cylindrical z-pinch

International Nuclear Information System (INIS)

Solov'ev, L.S.

1984-01-01

The stationary configurations of cylindrical plasma flow in the framework of two-liquid relativistic electromagnetic gas dynamics (REMG)) and nonlinear radial oscillations of the plasma cylinder with longitudinal current in the framework of classical monoliquid MGD are considered. It is shown that at sufficiently high conductivity Z-pinch is stable relative to one-dimensional radial perturbations and its motion represents respectively nonlinear radial oscillations. In case of a rather low conductivity or low particle concentration there is in cross section a stability also in relation to the development of sausage type instability. The performed investigations of cylindrical equilibrium and radial oscillations give a qualitative representation on plasma behaviour in Z-pinch at the initial stage of it compression and expansion as well as on motion in an average plane of the developing sausage type instability

A large inversion in the linear chromosome of Streptomyces griseus caused by replicative transposition of a new Tn3 family transposon.

Science.gov (United States)

Murata, M; Uchida, T; Yang, Y; Lezhava, A; Kinashi, H

2011-04-01

We have comprehensively analyzed the linear chromosomes of Streptomyces griseus mutants constructed and kept in our laboratory. During this study, macrorestriction analysis of AseI and DraI fragments of mutant 402-2 suggested a large chromosomal inversion. The junctions of chromosomal inversion were cloned and sequenced and compared with the corresponding target sequences in the parent strain 2247. Consequently, a transposon-involved mechanism was revealed. Namely, a transposon originally located at the left target site was replicatively transposed to the right target site in an inverted direction, which generated a second copy and at the same time caused a 2.5-Mb chromosomal inversion. The involved transposon named TnSGR was grouped into a new subfamily of the resolvase-encoding Tn3 family transposons based on its gene organization. At the end, terminal diversity of S. griseus chromosomes is discussed by comparing the sequences of strains 2247 and IFO13350.

Damping constant measurement and inverse giant magnetoresistance in spintronic devices with Fe4N

Directory of Open Access Journals (Sweden)

Xuan Li

2017-12-01

Full Text Available Fe4N is one of the attractive materials for spintronic devices due to its large spin asymmetric conductance and negative spin polarization at the Fermi level. We have successfully deposited Fe4N thin film with (001 out-of-plane orientation using a DC facing-target-sputtering system. A Fe(001/Ag(001 composite buffer layer is selected to improve the (001 orientation of the Fe4N thin film. The N2 partial pressure during sputtering is optimized to promote the formation of Fe4N phase. Moreover, we have measured the ferromagnetic resonance (FMR of the (001 oriented Fe4N thin film using coplanar waveguides and microwave excitation. The resonant fields are tested under different microwave excitation frequencies, and the experimental results match well with the Kittel formula. The Gilbert damping constant of Fe4N is determined to be α = 0.021±0.02. We have also fabricated and characterized the current-perpendicular-to-plane (CPP giant magnetoresistance (GMR device with Fe4N/Ag/Fe sandwich. Inverse giant magnetoresistance is observed in the CPP GMR device, which suggests that the spin polarization of Fe4N and Fe4N/Ag interface is negative.

Review of the current status of linear hybrid reactor concepts

International Nuclear Information System (INIS)

Schultz, K.R.

1977-07-01

A review was made of the current status of linear fusion-fission hybrid reactor design studies in the USA. The linear hybrid reactor concepts reviewed include the linear theta-pinch hybrid reactor being studied at Los Alamos Scientific Laboratory, the electron beam-heated solenoid hybrid reactor under development at Physics International Co., the laser-heated solenoid hybrid reactor being investigated at Mathematical Sciences Northwest, Inc., and the linear fusion waste burning reactor being studied at General Atomic Company. The discussion addresses confinement and heating mechanisms for each concept, as well as the hybrid blanket designs. The current state of the four reactor designs is summarized and the performance of the various concepts compared

A Comparison of Closed-Loop Performance of Multirotor Configurations Using Non-Linear Dynamic Inversion Control

Directory of Open Access Journals (Sweden)

Murray L. Ireland

2015-06-01

Full Text Available Multirotor is the umbrella term for the family of unmanned aircraft, which include the quadrotor, hexarotor and other vertical take-off and landing (VTOL aircraft that employ multiple main rotors for lift and control. Development and testing of novel multirotor designs has been aided by the proliferation of 3D printing and inexpensive flight controllers and components. Different multirotor configurations exhibit specific strengths, while presenting unique challenges with regards to design and control. This article highlights the primary differences between three multirotor platforms: a quadrotor; a fully-actuated hexarotor; and an octorotor. Each platform is modelled and then controlled using non-linear dynamic inversion. The differences in dynamics, control and performance are then discussed.

LASL toroidal reversed-field pinch programme

International Nuclear Information System (INIS)

Baker, D.A.; Buchenauer, C.J.; Burkhardt, L.C.

1979-01-01

The determination of the absolute energy loss due to radiation from impurities in the LASL toroidal reversed-field pinch experiment ZT-S is reported. The measurements show that over half the energy loss is accounted for by this mechanism. Thomson-scattering electron density measurements indicate only a gradual increase in temperature as the filling pressure is reduced, indicating an increased energy loss at lower pressures. Cylindrical and toroidal simulations of the experiment indicate either that a highly radiative pinch boundary or anomalous transport is needed to match the experimental results. New effects on the equilibrium due to plasma flows induced by the toroidal geometry are predicted by the toroidal simulations. The preliminary results on the low-temperature discharge cleaning of the ZT-S torus are reported. A description of the upgrade of the ZT-S experiment and the objectives, construction and theoretical predictions for the new ZT-40 experiment are given. (author)

Estimation of Amount of Scattered Neutrons at Devices PFZ and GIT-12 by MCNP Simulations

Directory of Open Access Journals (Sweden)

Ondrej Šíla

2013-01-01

Full Text Available Our work is dedicated to pinch effect occurring during current discharge in deuterium plasma, and our results are connected with two devices – plasma focus PFZ, situated in the Faculty of Electrical Engineering, CTU, Prague, and Z-pinch GIT-12, which is situated in the Institute of High Current Electronics, Tomsk. During fusion reactions that proceed in plasma during discharge, neutrons are produced. We use neutrons as instrument for plasma diagnostics. Despite of the advantage that neutrons do not interact with electric and magnetic fields inside device, they are inevitably scattered by materials that are placed between their source and probe, and information about plasma from which they come from is distorted. For estimation of rate of neutron scattering we use MCNP code.

Design changes of device to investigation of alloys linear contraction and shrinkage stresses

Directory of Open Access Journals (Sweden)

J. Mutwil

2009-07-01

Full Text Available Some design changes in device elaborated by author to examination of linear contraction and shrinkage stresses progress of metals and alloys during– and after solidification have been described. The introduced changes have been focused on design of closing of shrinkage test rod mould. The introduced changes have been allowed to simplify a mounting procedure of thermocouples measuring a temperature of the shrinkage rod casting (in 6 points. Exemplary investigation results of linear contraction and shrinkage stresses development in Al-Si13.5% alloy have been presented.

Comparative Studies of Traditional (Non-Energy Integration and Energy Integration of Catalytic Reforming Unit using Pinch Analysis

Directory of Open Access Journals (Sweden)

M. Alta

2012-12-01

Full Text Available Energy Integration of Catalytic Reforming Unit (CRU of Kaduna Refinery and petrochemicals Company Kaduna Nigeria was carried out using Pinch Technology. The pinch analysis was carried out using Maple. Optimum minimum approach temperature of 20 °C was used to determine the energy target. The pinch point temperature was found to be 278 °C. The utilities targets for the minimum approach temperature were found to be 72711839.47 kJ/hr and 87105834.43 kJ/hr for hot and cold utilities respectively. Pinch analysis as an energy integration technique was found to save more energy and utilities cost than the traditional energy technique. Key words: Pinch point, CRU, Energy Target, Maple

Linear motion device and method for inserting and withdrawing control rods

Science.gov (United States)

Smith, J.E.

Disclosed is a linear motion device and more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core. The CRDM and method disclosed is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism.

Design and experimental research on a self-magnetic pinch diode under MV

Science.gov (United States)

Pengfei, ZHANG; Yang, HU; Jiang, SUN; Yan, SONG; Jianfeng, SUN; Zhiming, YAO; Peitian, CONG; Mengtong, QIU; Aici, QIU

2018-01-01

A self-magnetic pinch diode (SMPD) integrating an anode foil-reinforced electron beam pinch focus and a small high-dose x-ray spot output was designed and optimized. An x-ray focal spot measuring system was developed in accordance with the principle of pinhole imaging. The designed SMPD and the corresponding measuring system were tested under ∼MV, with 1.75 × 2 mm2 oval x-ray spots (AWE defined) and forward directed dose 1.6 rad at 1 m. Results confirmed that the anode foil can significantly strengthen the electron beam pinch focus, and the focal spot measuring system can collect clear focal spot images. This finding indicated that the principle and method are feasible.

Design and experimental research on a self-magnetic pinch diode under MV

Institute of Scientific and Technical Information of China (English)

Pengfei ZHANG; Yang HU; Jiang SUN; Yan SONG; Jianfeng SUN; Zhiming YAO; Peitian CONG; Mengtong QIU; Aici QIU

2018-01-01

A self-magnetic pinch diode (SMPD) integrating an anode foil-reinforced electron beam pinch focus and a small high-dose x-ray spot output was designed and optimized.An x-ray focal spot measuring system was developed in accordance with the principle of pinhole imaging.The designed SMPD and the corresponding measuring system were tested under ～MV,with 1.75 × 2 mm2 oval x-ray spots (AWE defined) and forward directed dose 1.6 rad at 1 m.Results confirmed that the anode foil can significantly strengthen the electron beam pinch focus,and the focal spot measuring system can collect clear focal spot images.This finding indicated that the principle and method are feasible.

Diagnostics for Z-pinch implosion experiments on PTS

Energy Technology Data Exchange (ETDEWEB)

Ren, X. D., E-mail: amosrxd@163.com; Huang, X. B., E-mail: amosrxd@163.com; Zhou, S. T., E-mail: amosrxd@163.com; Zhang, S. Q., E-mail: amosrxd@163.com; Dan, J. K., E-mail: amosrxd@163.com; Li, J., E-mail: amosrxd@163.com; Cai, H. C., E-mail: amosrxd@163.com; Wang, K. L., E-mail: amosrxd@163.com; Ouyang, K., E-mail: amosrxd@163.com; Xu, Q., E-mail: amosrxd@163.com; Duan, S. C., E-mail: amosrxd@163.com; Chen, G. H., E-mail: amosrxd@163.com; Wang, M., E-mail: amosrxd@163.com; Feng, S. P., E-mail: amosrxd@163.com; Yang, L. B., E-mail: amosrxd@163.com; Xie, W. P., E-mail: amosrxd@163.com; Deng, J. J., E-mail: amosrxd@163.com [Key Lab of Pulsed Power, Institute of Fluid Physics, CAEP, P.O. Box 919-108, Mianyang, Sichuan 621999 (China)

2014-12-15

The preliminary experiments of wire array implosion were performed on PTS, a 10 MA z-pinch driver with a 70 ns rise time. A set of diagnostics have been developed and fielded on PTS to study pinch physics and implosion dynamics of wire array. Radiated power measurement for soft x-rays was performed by multichannel filtered x-ray diode array, and flat spectral responses x-ray diode detector. Total x-ray yield was measured by a calibrated, unfiltered nickel bolometer which was also used to obtain pinch power. Multiple time-gated pinhole cameras were used to produce spatial-resolved images of x-ray self-emission from plasmas. Two time-integrated pinhole cameras were used respectively with 20-μm Be filter and with multilayer mirrors to record images produced by >1-keV and 277±5 eV self-emission. An optical streak camera was used to produce radial implosion trajectories, and an x-ray streak camera paired with a horizontal slit was used to record a continuous time-history of emission with one-dimensional spatial resolution. A frequency-doubled Nd:YAG laser (532 nm) was used to produce four frame laser shadowgraph images with 6 ns time interval. We will briefly describe each of these diagnostics and present some typical results from them.

Exact self-similar solutions for the magnetized Noh Z pinch problem

International Nuclear Information System (INIS)

Velikovich, A. L.; Giuliani, J. L.; Thornhill, J. W.; Zalesak, S. T.; Gardiner, T. A.

2012-01-01

A self-similar solution is derived for a radially imploding cylindrical plasma with an embedded, azimuthal magnetic field. The plasma stagnates through a strong, outward propagating shock wave of constant velocity. This analysis is an extension of the classic Noh gasdynamics problem to its ideal magnetohydrodynamics (MHD) counterpart. The present exact solution is especially suitable as a test for MHD codes designed to simulate linear Z pinches. To demonstrate the application of the new solution to code verification, simulation results from the cylindrical R-Z version of Mach2 and the 3D Cartesian code Athena are compared against the analytic solution. Alternative routines from the default ones in Athena lead to significant improvement of the results, thereby demonstrating the utility of the self-similar solution for verification.

Stabilization of long wavelength sausage and kink modes of a Z-pinch by nonlinear radial oscillations

International Nuclear Information System (INIS)

Bud'ko, A.B.; Karlson, E.T.; Liberman, M.A.

1992-01-01

A number of experiments with fiber-initiated dense Z-pinches, with compressional and gas-embedded Z-pinches, with imploding gas-puff Z-pinches and the straight Extrap configuration performed in the last decade demonstrated sufficiently improved stability of Z-pinch configurations. The striking stability with respect to the sausage modes can be explained, in principle, by ideal MHD theory as well as by finite plasma conductivity effects. The global kink mode can not be stabilized by the appropriate choice of the unperturbed profiles neither within the scope of the ideal MHD nor taking into account finite ion Larmor radius and viscous damping effects. In this report we shall demonstrate that stabilization of the global kink modes can be explained by the assumption that pinch is not in a stationary but in a dynamic equilibrium. (author) 12 refs., 2 figs

FOREWORD: 4th International Workshop on New Computational Methods for Inverse Problems (NCMIP2014)

Science.gov (United States)

2014-10-01

This volume of Journal of Physics: Conference Series is dedicated to the scientific contributions presented during the 4th International Workshop on New Computational Methods for Inverse Problems, NCMIP 2014 (http://www.farman.ens-cachan.fr/NCMIP_2014.html). This workshop took place at Ecole Normale Supérieure de Cachan, on May 23, 2014. The prior editions of NCMIP also took place in Cachan, France, firstly within the scope of ValueTools Conference, in May 2011 (http://www.ncmip.org/2011/), and secondly at the initiative of Institut Farman, in May 2012 and May 2013, (http://www.farman.ens-cachan.fr/NCMIP_2012.html), (http://www.farman.ens-cachan.fr/NCMIP_2013.html). The New Computational Methods for Inverse Problems (NCMIP) Workshop focused on recent advances in the resolution of inverse problems. Indeed, inverse problems appear in numerous scientific areas such as geophysics, biological and medical imaging, material and structure characterization, electrical, mechanical and civil engineering, and finances. The resolution of inverse problems consists of estimating the parameters of the observed system or structure from data collected by an instrumental sensing or imaging device. Its success firstly requires the collection of relevant observation data. It also requires accurate models describing the physical interactions between the instrumental device and the observed system, as well as the intrinsic properties of the solution itself. Finally, it requires the design of robust, accurate and efficient inversion algorithms. Advanced sensor arrays and imaging devices provide high rate and high volume data; in this context, the efficient resolution of the inverse problem requires the joint development of new models and inversion methods, taking computational and implementation aspects into account. During this one-day workshop, researchers had the opportunity to bring to light and share new techniques and results in the field of inverse problems. The topics of the

Advanced linear algebra for engineers with Matlab

CERN Document Server

Dianat, Sohail A

2009-01-01

Matrices, Matrix Algebra, and Elementary Matrix OperationsBasic Concepts and NotationMatrix AlgebraElementary Row OperationsSolution of System of Linear EquationsMatrix PartitionsBlock MultiplicationInner, Outer, and Kronecker ProductsDeterminants, Matrix Inversion and Solutions to Systems of Linear EquationsDeterminant of a MatrixMatrix InversionSolution of Simultaneous Linear EquationsApplications: Circuit AnalysisHomogeneous Coordinates SystemRank, Nu

Introduction to the mathematics of inversion in remote sensing and indirect measurements

CERN Document Server

Twomey, S

2013-01-01

Developments in Geomathematics, 3: Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements focuses on the application of the mathematics of inversion in remote sensing and indirect measurements, including vectors and matrices, eigenvalues and eigenvectors, and integral equations. The publication first examines simple problems involving inversion, theory of large linear systems, and physical and geometric aspects of vectors and matrices. Discussions focus on geometrical view of matrix operations, eigenvalues and eigenvectors, matrix products, inverse of a matrix, transposition and rules for product inversion, and algebraic elimination. The manuscript then tackles the algebraic and geometric aspects of functions and function space and linear inversion methods, as well as the algebraic and geometric nature of constrained linear inversion, least squares solution, approximation by sums of functions, and integral equations. The text examines information content of indirect sensing m...

On the calibration process of film dosimetry: OLS inverse regression versus WLS inverse prediction

International Nuclear Information System (INIS)

Crop, F; Thierens, H; Rompaye, B Van; Paelinck, L; Vakaet, L; Wagter, C De

2008-01-01

The purpose of this study was both putting forward a statistically correct model for film calibration and the optimization of this process. A reliable calibration is needed in order to perform accurate reference dosimetry with radiographic (Gafchromic) film. Sometimes, an ordinary least squares simple linear (in the parameters) regression is applied to the dose-optical-density (OD) curve with the dose as a function of OD (inverse regression) or sometimes OD as a function of dose (inverse prediction). The application of a simple linear regression fit is an invalid method because heteroscedasticity of the data is not taken into account. This could lead to erroneous results originating from the calibration process itself and thus to a lower accuracy. In this work, we compare the ordinary least squares (OLS) inverse regression method with the correct weighted least squares (WLS) inverse prediction method to create calibration curves. We found that the OLS inverse regression method could lead to a prediction bias of up to 7.3 cGy at 300 cGy and total prediction errors of 3% or more for Gafchromic EBT film. Application of the WLS inverse prediction method resulted in a maximum prediction bias of 1.4 cGy and total prediction errors below 2% in a 0-400 cGy range. We developed a Monte-Carlo-based process to optimize calibrations, depending on the needs of the experiment. This type of thorough analysis can lead to a higher accuracy for film dosimetry

Magnetoacoustic heating and FCT-equilibria in the belt pinch

International Nuclear Information System (INIS)

Erckmann, V.

1983-02-01

In the HECTOR belt pinch of high β plasma is produced by magnetic compression in a Tokamak geometry. After compresseion the initial β value can be varied between 0.2 and 0.8. During 5 μs the plasma is further heated by a fast magnetoacoustic wave with a frequency near the first harmonic of the ion cyclotronfrequency. For the first time the β-value of a pinch plasma could be increased further from 0.34 after compression to 0.46 at the end of the rf-heating cycle. By proper selection of the final β-value the region for resonance absorption of the heating wave can be shifted. Strong heating (200 MW) has been observed in the cases, where the resonance region has been located in the center of the plasma. In deuterium discharges an increase in ion temperature is observed during the heating process, whereas the electrons are energetically decoupled, showing no temperature increase. Strong plasma losses are found in the 200 MW range after the rf-heating process. The dominant mechanisms are charge exchange collisions with neutral gas atoms. During rf-heating and the subsequent cooling phase the magnetic flux is frozen due to the high conductivity of the plasma. The observed equilibria could be identified as flux conserving Tokamak (FCT) equilibria. Based on a two-dimensional code the time-evolution of the equilibria has been calculated. The q-profiles are time-independent, with increasing β the magnetic axis of the plasma is shifted towards the outer boundary of the torus, and finally the linear relation between β and βsub(pol), which is characteristic for low-β-equilibria, is no longer valid. Thus for the first time the existence of FCT-equilibria at high β has been demonstrated experimentally together with a qualitative agreement with FCT-theory. (orig./AH) [de

An approximate inversion method of geoelectrical sounding data using linear and bayesian statistical approaches. Examples of Tritrivakely volcanic lake and Mahitsy area (central part of Madagascar)

International Nuclear Information System (INIS)

Ranaivo Nomenjanahary, F.; Rakoto, H.; Ratsimbazafy, J.B.

1994-08-01

This paper is concerned with resistivity sounding measurements performed from single site (vertical sounding) or from several sites (profiles) within a bounded area. The objective is to present an accurate information about the study area and to estimate the likelihood of the produced quantitative models. The achievement of this objective obviously requires quite relevant data and processing methods. It also requires interpretation methods which should take into account the probable effect of an heterogeneous structure. In front of such difficulties, the interpretation of resistivity sounding data inevitably involves the use of inversion methods. We suggest starting the interpretation in simple situation (1-D approximation), and using the rough but correct model obtained as an a-priori model for any more refined interpretation. Related to this point of view, special attention should be paid for the inverse problem applied to the resistivity sounding data. This inverse problem is nonlinear, while linearity inherent in the functional response used to describe the physical experiment. Two different approaches are used to build an approximate but higher dimensional inversion of geoelectrical data: the linear approach and the bayesian statistical approach. Some illustrations of their application in resistivity sounding data acquired at Tritrivakely volcanic lake (single site) and at Mahitsy area (several sites) will be given. (author). 28 refs, 7 figs

Far-infrared laser interferometry measurements on the STP-3(M) reversed-field pinch

International Nuclear Information System (INIS)

Kubota, Shigeyuki; Nagatsu, Masaaki; Tsukishima, Takashige; Arimoto, Hideki; Sato, Koichi; Matsuoka, Akio.

1993-09-01

Far-infrared laser interferometry at 432 μm was carried out on the STP-3(M) reversed-field pinch. Measurements along two vertical chords showed a change from a parabolic-like to a flat-like electron density profile after field reversal. A density profile inversion and a correlated toroidal magnetic flux perturbation were also observed during the transition from the current rising to the current decay phase. Measurements of electron density fluctuations indicated relative fluctuation levels of ∼10% for both chords during the current rising phase and ∼5% and ∼15% during the current decay phase for the central and outer chords, respectively. Spectral analysis showed a ∼30 kHz mode consistent with poloidal mode number m=0 magnetic fluctuations, and a ∼90 kHz mode localized to the outer region of the plasma, which was strongly excited during the current decay phase and may be connected to particle and energy transport in STP-3(M). (author)

Study of X-ray emission in aluminium z-pinches

International Nuclear Information System (INIS)

Rosch, R.

1999-01-01

Previous experiments, at 0.1. TX level, have shown that stability and x-ray emission of fast Z-pinches, could be strongly increased by imploding an aluminium vapor jet onto a very thin coaxial wire. We present here first results of an aluminium Z-pinch, using a similar liner, but at mega-ampere level. The pinch is driven by AMBIORIX high-power facility, a 2 TW, 0.5 Ω, 2 MA, 50 ns pulse-line generator. We study the effect of an aluminium wire and its diameter (20-50 μm) on the implosion dynamics, on x-ray yield on MHD stability of the column at stagnation. Analysis of A1 jet on A1 wire shots demonstrates that x-ray yield due to emission processes in the H- and He- like ionization stages (i.e. the K-shell) is significantly enhanced, relative to that of A1 jet only ones. The wire also leads to better symmetry of the implosion, and to better reproducibility of shots. X-ray signals exhibit two similar pulses, 10 ns in width, 15 ns spaced. To discern spectral origin of both pulses, experiments are realized with stainless steel wire (25 μm in diameter). Results show that liner and wire radial simultaneously and contribute to both pulses. Analysis of a typical A1 jet on A1 wire shot, using detailed collisional-radiative equilibrium (CRE) model is also given in this thesis. View o the pinch at stagnation as a cola-dense core surrounded by a hot-low density corona reproduces all features of the X-ray data. (author)

LS-APC v1.0: a tuning-free method for the linear inverse problem and its application to source-term determination

Czech Academy of Sciences Publication Activity Database

Tichý, Ondřej; Šmídl, Václav; Hofman, Radek; Stohl, A.

2016-01-01

Roč. 9, č. 11 (2016), s. 4297-4311 ISSN 1991-959X R&D Projects: GA MŠk(CZ) 7F14287 Institutional support: RVO:67985556 Keywords : Linear inverse problem * Bayesian regularization * Source-term determination * Variational Bayes method Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 3.458, year: 2016 http://library.utia.cas.cz/separaty/2016/AS/tichy-0466029.pdf

Experimental studies of the MHD stability of non-circular Extrap Z-pinches

International Nuclear Information System (INIS)

Drake, J.R.

1985-01-01

Extrap Z-pinches, which can be sustained for many Alfven times, can be characterized as non-circular Z-pinch discharges bounded by a magnetic separatrix acting somewhat like a limiter. The magnetic separatrix is produced when a vacuum magnetic field, generated by currents in external conductors, combines with the self-magnetic field produced by the discharge current. The separatrix deforms the pinch cross-section and affects the equilibrium at the pinch boundary; both effects improve stability. Experiments have been performed which indicate that both effects are necessary for the successful generation of sustained Extrap discharges. In one experiment, the importance of the non-circularity of the cross-section was investigated. The deformation provided by the vacuum field can provide regions in the discharge where field lines have good curvature, which improves the stability of the configuration against internal modes. In configurations apparently lacking good curvature, discharges could not be sustained. In a second experiment, the dependence of the amplitude of global kink instabilities on the discharge current density profile were studied. The behaviour of the modes was consistent with that which would be expected for surface current-driven modes. (orig.)

Experimental studies of the MHD stability of non-circular extrap Z-pinches

International Nuclear Information System (INIS)

Drake, J.R.

1984-12-01

Extrap Z-pinches, which can be sustained for many Alfven times, can be characterized as non-circular Z-pinch discharges bounded by a magnetic separatrix acting somewhat like a limiter. The magnetic separatrix is produced when a vacuum magnetic field, generated by currents in external conductors, combines with the self-magnetic field produced by the discharge current. The separatrix deforms the pinch cross-section and affects the equilibrium at the pinch boundary; both effects improve stability. Experiments have been performed which indicate that both effects are necessary for the successful generation of sustained Extrap discharges. In one experiment, the importance of the non-circularity of the cross-section was investigated. The deformation provided by the vacuum field can provide regions in the discharge where field lines have good curvature, which improves the stability of the configuration against internal modes. In configurations apparently lacking good curvature, discharges could not be sustained. In a second experiment, the dependence of the amplitude of global kink instabilities on the discharge current density profile were studied. The behaviour of the modes was consistent with that which would be expected for surface current-driven modes. (Author)

A heuristic model of the wire array z-pinch

International Nuclear Information System (INIS)

Haines, M.G.

1998-01-01

Recent experimental results at the Sandia National Laboratory have shown that the X-ray power increases as the number of wires n employed is increased, with a sharper increase in power when the wire gap is below a critical value. This paper proposes a model that can not only explain these phenomena, but also shows how the initial perturbations that lead to the Rayleigh-Taylor instability scale as n -1/2 . The model predicts the shell thickness at merger of the expanding separate wires which will mainly determine the final pinch radius. The largest amplitude Rayleigh-Taylor mode at the pinch time is also found, in reasonable agreement with experiment

Computer programs for the solution of systems of linear algebraic equations

Science.gov (United States)

Sequi, W. T.

1973-01-01

FORTRAN subprograms for the solution of systems of linear algebraic equations are described, listed, and evaluated in this report. Procedures considered are direct solution, iteration, and matrix inversion. Both incore methods and those which utilize auxiliary data storage devices are considered. Some of the subroutines evaluated require the entire coefficient matrix to be in core, whereas others account for banding or sparceness of the system. General recommendations relative to equation solving are made, and on the basis of tests, specific subprograms are recommended.

Study of X-ray emission in aluminium z-pinches; Etude de l'emission X dans les plasmas d'aluminium de type Z-pinch

Energy Technology Data Exchange (ETDEWEB)

Rosch, R [CEA/DAM-Ile de France, Dept. de Conception et Realisation des Experimentations (DCRE), 91 - Bruyeres-le-Chatel (France); [Paris-11 Univ., 91 - Orsay (France)

1999-07-01

Previous experiments, at 0.1. TX level, have shown that stability and x-ray emission of fast Z-pinches, could be strongly increased by imploding an aluminium vapor jet onto a very thin coaxial wire. We present here first results of an aluminium Z-pinch, using a similar liner, but at mega-ampere level. The pinch is driven by AMBIORIX high-power facility, a 2 TW,0.5 {omega}, 2 MA, 50 ns pulse-line generator. We study the effect of an aluminium wire and its diameter (20-50 {mu}m) on the implosion dynamics, on x-ray yield on MHD stability of the column at stagnation. Analysis of A1 jet on A1 wire shots demonstrates that x-ray yield due to emission processes in the H- and He- like ionization stages (i.e. the K-shell) is significantly enhanced, relative to that of A1 jet only ones. The wire also leads to better symmetry of the implosion, and to better reproducibility of shots. X-ray signals exhibit two similar pulses, 10 ns in width, 15 ns spaced. To discern spectral origin of both pulses, experiments are realized with stainless steel wire (25 {mu}m in diameter). Results show that liner and wire radial simultaneously and contribute to both pulses. Analysis of a typical A1 jet on A1 wire shot, using detailed collisional-radiative equilibrium (CRE) model is also given in this thesis. View o the pinch at stagnation as a cola-dense core surrounded by a hot-low density corona reproduces all features of the X-ray data. (author)

DT ignition in a Z pinch compressed by an imploding liner

International Nuclear Information System (INIS)

Bilbao, L.; Bernal, L.; Linhart, J.G.; Verri, G.

2001-01-01

It has been shown that an m=0 instability of a Z pinch carrying a current of the order of 10 MA with a rise time of less than 10 ns can generate a spark capable of igniting a fusion detonation in the adjacent DT plasma channel. A possible method for generating such currents, necessary for the implosion of an initial large radius, low temperature Z pinch, can be a radial implosion of a cylindrical fast liner. The problem has been addressed in previous publications without considering the role played by an initially impressed m=0 perturbation, a mechanism indispensable for the generation of a spark. The liner-Z pinch dynamics can be solved at several levels of physical model completeness. The first corresponds to a zero dimensional model in which the liner has a given mass per unit length and a zero thickness, the plasma is compressed adiabatically and is isotropic, and there are no energy losses or Joule heating. The second level is one dimensional. The Z pinch plasma is described by the full set of MHD, two-fluid equations. The liner is treated first as thin and incompressible, and subsequently it is assumed that it has a finite thickness and is composed of a heavy ion plasma, having an artificial but realistic equation of state. Both plasma and liner are considered uniform in the Z direction and only DT reactions are considered. It is shown that, given sufficient energy and speed of the liner, the Z pinch can reach a volume ignition. The third level is two dimensional. Plasma and liner are treated as in the second level but either the Z pinch or the liner is perturbed by an m=0 non-uniformity. Provided the liner energy is high enough and the initial m=0 perturbation is correctly chosen, the final neck plasma can act as a spark for DT ignition. It is also shown that the liner energy required for generating a spark and the subsequent detonation propagation are considerably less than in the case of volume ignition. (author)

Linear analysis of sheared flow stabilization of global magnetohydrodynamic instabilities based on the Hall fluid model

International Nuclear Information System (INIS)

Sotnikov, V.I.; Paraschiv, I.; Makhin, V.; Bauer, B.S.; Leboeuf, J.N.; Dawson, J.M.

2002-01-01

A systematic study of the linear stage of sheared flow stabilization of Z-pinch plasmas based on the Hall fluid model with equilibrium that contains sheared flow and an axial magnetic field is presented. In the study we begin with the derivation of a general set of equations that permits the evaluation of the combined effect of sheared flow and axial magnetic field on the development of the azimuthal mode number m=0 sausage and m=1 kink magnetohydrodynamic (MHD) instabilities, with the Hall term included in the model. The incorporation of sheared flow, axial magnetic field, and the Hall term allows the Z-pinch system to be taken away from the region in parameter space where ideal MHD is applicable to a regime where nonideal effects tend to govern stability. The problem is then treated numerically by following the linear development in time of an initial perturbation. The numerical results for linear growth rates as a function of axial sheared flow, an axial magnetic field, and the Hall term are reported

Trimming and procrastination as inversion techniques

Science.gov (United States)

Backus, George E.

1996-12-01

By examining the processes of truncating and approximating the model space (trimming it), and by committing to neither the objectivist nor the subjectivist interpretation of probability (procrastinating), we construct a formal scheme for solving linear and non-linear geophysical inverse problems. The necessary prior information about the correct model xE can be either a collection of inequalities or a probability measure describing where xE was likely to be in the model space X before the data vector y0 was measured. The results of the inversion are (1) a vector z0 that estimates some numerical properties zE of xE; (2) an estimate of the error δz = z0 - zE. As y0 is finite dimensional, so is z0, and hence in principle inversion cannot describe all of xE. The error δz is studied under successively more specialized assumptions about the inverse problem, culminating in a complete analysis of the linear inverse problem with a prior quadratic bound on xE. Our formalism appears to encompass and provide error estimates for many of the inversion schemes current in geomagnetism, and would be equally applicable in geodesy and seismology if adequate prior information were available there. As an idealized example we study the magnetic field at the core-mantle boundary, using satellite measurements of field elements at sites assumed to be almost uniformly distributed on a single spherical surface. Magnetospheric currents are neglected and the crustal field is idealized as a random process with rotationally invariant statistics. We find that an appropriate data compression diagonalizes the variance matrix of the crustal signal and permits an analytic trimming of the idealized problem.

Observation of helical structure in a low energy plasma focus pinch

International Nuclear Information System (INIS)

Rout, R.K.; Shyam, A.

1989-01-01

Helical structure and hot spots were observed in a Mather-type plasma focus operated at 3 KJ of bank energy. The experiments were carried out with the help of a fast optical framing camera and two X-ray pin-hole cameras with different filters. It was observed that initially a conical pinch (with base diameter of 6 mm and length of 14 mm) with temperature of ≅ 10 2 eV was formed. This pinch disintegrated after ≅ 50 ns by a single lobe sausage instability into a central high temperature (≅ 10 3 eV) filament of 1 mm diameter and 8 mm length containing a high emissivity helical structure. This helix is probably responsible for generation of axial magnetic field and relaxation of the focus pinch. Hot spots of high X-ray intensity and temperature (≅ 10 3 eV) were also observed much beyond the filament region. (author)

X pinch a point x-ray source

International Nuclear Information System (INIS)

Garg, A.B.; Rout, R.K.; Shyam, A.; Srinivasan, M.

1993-01-01

X ray emission from an X pinch, a point x-ray source has been studied using a pin-hole camera by a 30 kV, 7.2 μ F capacitor bank. The wires of different material like W, Mo, Cu, S.S.(stainless steel) and Ti were used. Molybdenum pinch gives the most intense x-rays and stainless steel gives the minimum intensity x-rays for same bank energy (∼ 3.2 kJ). Point x-ray source of size (≤ 0.5 mm) was observed using pin hole camera. The size of the source is limited by the size of the pin hole camera. The peak current in the load is approximately 150 kA. The point x-ray source could be useful in many fields like micro lithography, medicine and to study the basic physics of high Z plasmas. (author). 4 refs., 3 figs

Energy transformation in Z-pinch and plasma focus discharges with wire and wire-in-liner loads

International Nuclear Information System (INIS)

Kubes, Pavel; Kravarik, Jozef; Klir, Daniel; Scholz, Marek; Paduch, Marian; Tomaszewski, Krzysztof; Karpinski, Leslaw; Bakshaev, Yury L.; Blinov, Peter I.; Chernenko, Andrey S.; Dan'ko, Sergey A.; Korolev, Valery D.; Shashkov, Andrey Y.; Tumanov, Victor I.

2002-01-01

The results of the study of the Z-pinch and plasma-focus plasmas at presence of the axial C, Al, or Cu wires of sufficient high diameter are discussed in this paper. The wire was positioned on the top of the inner electrode of the PF 1000 plasma focus (1.8 MA, IPPLM Warsaw), or at the axis with or without the tungsten or alumine wire array load at the S-300 facility (3 MA, RRC Kurchatov Institute, Moscow), and at the axis of the small Z-pinch Z-150 (50 kA, CTU Prague). The plasma corona around the wire was generated both by the current going through the wires and by the implosion of the wire array or of the current sheath. The experiments showed interesting results often observed in some shots of Z-pinch type discharges - existence of helical structures, two relatively long and stable pinch phases, oscillation of pinch diameter, and back return of the plasma exploding from the pinch. All these observed phenomena can be evolved by spontaneous self-generation and transformation of the axial magnetic field in the pinch during the plasma implosion and explosion. A configuration of axial and azimuthal magnetic field confines the plasma and later transforms or dissipates during a few tens or hundreds ns. A fast transformation of internal magnetic fields can induce a sufficiently high electric field for generation of keV particles and radiation. Study and usage of Z-pinch discharges is connected with solving of two principal problems, limitation of instability development and a way of generation of high energy particles and radiation. The first problem is partially solved by the faster increase of the current, by better cylindrical symmetry of the load and plasma, by higher density of the plasma or by the presence of a stronger magnetized plasma

Finite-dimensional linear algebra

CERN Document Server

Gockenbach, Mark S

2010-01-01

Some Problems Posed on Vector SpacesLinear equationsBest approximationDiagonalizationSummaryFields and Vector SpacesFields Vector spaces Subspaces Linear combinations and spanning sets Linear independence Basis and dimension Properties of bases Polynomial interpolation and the Lagrange basis Continuous piecewise polynomial functionsLinear OperatorsLinear operatorsMore properties of linear operatorsIsomorphic vector spaces Linear operator equations Existence and uniqueness of solutions The fundamental theorem; inverse operatorsGaussian elimination Newton's method Linear ordinary differential eq

An investigation of the plasma behaviour in a Filippov type plasma focus device

Energy Technology Data Exchange (ETDEWEB)

Mahabadi, T D [Plasma Physics Research Center, I.A.U, PO Box 14665-678, Tehran (Iran, Islamic Republic of); Tafreshi, M A [School of Plasma Physics and Nuclear Fusion, Institute of Nuclear Science and Technology, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)

2007-09-15

Plasma behaviour in the 90 kJ Filippov type plasma focus (PF) device Dena, is studied both experimentally and theoretically. The latest experimental data obtained by the use of the Dena facility are presented. Then the experimental data are compared with the simulated data obtained through the ML model. This study shows that the ML model, to a good extent, is capable of predicting the plasma behaviour in the Filippov type PF. The experimental and the theoretical results show that the increment of the discharge voltage leads to an almost linear decrement of the pinch time. It is also shown that the increment of the pressure leads to a decrement of the current sheath expansion velocity. Finally, a semiempirical method for determination of the permitted values of the current efficiency factor and the mass shedding factor is presented.

Three-dimensional inversion of multisource array electromagnetic data

Science.gov (United States)

Tartaras, Efthimios

Three-dimensional (3-D) inversion is increasingly important for the correct interpretation of geophysical data sets in complex environments. To this effect, several approximate solutions have been developed that allow the construction of relatively fast inversion schemes. One such method that is fast and provides satisfactory accuracy is the quasi-linear (QL) approximation. It has, however, the drawback that it is source-dependent and, therefore, impractical in situations where multiple transmitters in different positions are employed. I have, therefore, developed a localized form of the QL approximation that is source-independent. This so-called localized quasi-linear (LQL) approximation can have a scalar, a diagonal, or a full tensor form. Numerical examples of its comparison with the full integral equation solution, the Born approximation, and the original QL approximation are given. The objective behind developing this approximation is to use it in a fast 3-D inversion scheme appropriate for multisource array data such as those collected in airborne surveys, cross-well logging, and other similar geophysical applications. I have developed such an inversion scheme using the scalar and diagonal LQL approximation. It reduces the original nonlinear inverse electromagnetic (EM) problem to three linear inverse problems. The first of these problems is solved using a weighted regularized linear conjugate gradient method, whereas the last two are solved in the least squares sense. The algorithm I developed provides the option of obtaining either smooth or focused inversion images. I have applied the 3-D LQL inversion to synthetic 3-D EM data that simulate a helicopter-borne survey over different earth models. The results demonstrate the stability and efficiency of the method and show that the LQL approximation can be a practical solution to the problem of 3-D inversion of multisource array frequency-domain EM data. I have also applied the method to helicopter-borne EM

Target design for high fusion yield with the double Z-pinch-driven hohlraum

International Nuclear Information System (INIS)

Vesey, R. A.; Herrmann, M. C.; Lemke, R. W.; Desjarlais, M. P.; Cuneo, M. E.; Stygar, W. A.; Bennett, G. R.; Campbell, R. B.; Christenson, P. J.; Mehlhorn, T. A.; Porter, J. L.; Slutz, S. A.

2007-01-01

A key demonstration on the path to inertial fusion energy is the achievement of high fusion yield (hundreds of MJ) and high target gain. Toward this goal, an indirect-drive high-yield inertial confinement fusion (ICF) target involving two Z-pinch x-ray sources heating a central secondary hohlraum is described by Hammer et al. [Phys. Plasmas 6, 2129 (1999)]. In subsequent research at Sandia National Laboratories, theoretical/computational models have been developed and an extensive series of validation experiments have been performed to study hohlraum energetics, capsule coupling, and capsule implosion symmetry for this system. These models have been used to design a high-yield Z-pinch-driven ICF target that incorporates the latest experience in capsule design, hohlraum symmetry control, and x-ray production by Z pinches. An x-ray energy output of 9 MJ per pinch, suitably pulse-shaped, is sufficient for this concept to drive 0.3-0.5 GJ capsules. For the first time, integrated two-dimensional (2D) hohlraum/capsule radiation-hydrodynamics simulations have demonstrated adequate hohlraum coupling, time-dependent radiation symmetry control, and the successful implosion, ignition, and burn of a high-yield capsule in the double Z-pinch hohlraum. An important new feature of this target design is mode-selective symmetry control: the use of burn-through shields offset from the capsule that selectively tune certain low-order asymmetry modes (P 2 ,P 4 ) without significantly perturbing higher-order modes and without a significant energy penalty. This paper will describe the capsule and hohlraum design that have produced 0.4-0.5 GJ yields in 2D simulations, provide a preliminary estimate of the Z-pinch load and accelerator requirements necessary to drive the system, and suggest future directions for target design work

Linear integrated circuits

CERN Document Server

Carr, Joseph

1996-01-01

The linear IC market is large and growing, as is the demand for well trained technicians and engineers who understand how these devices work and how to apply them. Linear Integrated Circuits provides in-depth coverage of the devices and their operation, but not at the expense of practical applications in which linear devices figure prominently. This book is written for a wide readership from FE and first degree students, to hobbyists and professionals.Chapter 1 offers a general introduction that will provide students with the foundations of linear IC technology. From chapter 2 onwa

A one-dimensional plasma and impurity transport model for reversed field pinches

International Nuclear Information System (INIS)

Veerasingam, R.

1991-11-01

In this thesis a one-dimensional (1-D) plasma and impurity transport model is developed to address issues related to impurity behavior in Reversed Field Pinch (RFP) fusion plasmas. A coronal non-equilibrium model is used for impurities. The impurity model is incorporated into an existing one dimensional plasma transport model creating a multi-species plasma transport model which treats the plasma and impurity evolution self-consistently. Neutral deuterium particles are treated using a one-dimensional (slab) model of neutral transport. The resulting mode, RFPBI, is then applied to existing RFP devices such as ZT-40M and MST, and also to examine steady state behavior of ZTH based on the design parameters. A parallel algorithm for the impurity transport equations is implemented and tested to determine speedup and efficiency

The stability of Z-pinches with equilibrium flows

International Nuclear Information System (INIS)

Howell, D.F.

1999-01-01

According to Ideal Magnetohydrodynamic (MHD) theory the Z-pinch is an inherently unstable magnetic configuration. However it is possible that there exist regimes of operation whereby the predicted instabilities may be reduced or even eliminated. We must look to effects normally ignored in the Ideal MHD model in order to predict such regimes. In this thesis various non-ideal effects will be studied, namely the inclusion of equilibrium flow and finite Larmor radius effects. Astrophysical jets, for example those seen to be emitted from active galactic nuclei, are seen to persist for a greater time than suggested by Ideal MHD before the onset of instabilities. It is postulated that one of the contributing factors to this enhanced stability is the presence of a sheared axial flow. In this thesis we study the stability properties of the Z-pinch where flow is present in the equilibrium. It is found that a sheared axial flow generally has a stabilising effect, the degree of which is determined by the equilibrium and flow profiles, but that absolute stability cannot be achieved due to the onset of the Kelvin-Helmholtz instability. The effect of adding rotation has also been studied. It is found that adding rotation changes the equilibrium density profiles from the static case, and that it always has a destabilising effect. Another postulated method of stabilising the Z-pinch is by increasing the ratio of the ion Larmor radius to the pinch radius, and it is seen to have a stabilising effect for some equilibria in the collisionless regime. In this thesis we study the effects of increasing the Larmor radius in the collisional regime using the Hall fluid model. It is found that for free boundary modes the stability properties are unchanged for experimentally realistic values of the Larmor radius, but for fixed boundary modes a small stabilising effect is noted for some equilibria. (author)

Zero-dimensional model of a reversed field pinch fusion reactor

International Nuclear Information System (INIS)

Veerasingam, R.

1987-12-01

A zero-dimensional model for the energy balance for electrons and ions of a Reversed Field Pinch (RFP) device has been developed. The model can be used as a tool for parametric studies and has been applied to simulate some ZT-40M experiments. In the model multiplicative coefficients C 1 , C 2 , C 3 and C 4 are introduced to treat anomalous resistivity, electron and ion energy confinement times and to account for the instability driven ion heating that is observed in RFP experiments. Parametric studies were performed to determine the sensitivity of the model to changes in multiplicative coefficients. A set of coefficients which can simulate a number of ZT-40M experiments have been obtained and the sensitivity of T/sub e/ and T/sub i/ to these coefficients was examined. Both flat top and ramp current waveforms were studied. The effects of different levels of impurities were also examined. The results showed that while all the three impurities used, viz., carbon, oxygen and nickel contributed to Z/sub eff/, nickel dominated the impurity radiation power. The results were then applied to study the behavior of the ZT-H device which is being built in the Confinement Physics Research Facility at the Los Alamos National Laboratory. 30 refs., 39 figs., 12 tabs

Stabilization of sausage and kink instability modes of a plasma pinch by radial oscillations

International Nuclear Information System (INIS)

Bud'ko, A.B.; Kravchenko, Y.P.; Liberman, M.A.

1995-01-01

The growth of the global sausage (m=0) and kink (m=1) perturbations of a Z-pinch subject to radial oscillations is considered. It is demonstrated that the oscillations result in significant reduction of the growth rate of both kink and sausage instability modes with wavelengths long compared to the pinch radius. The analysis of stability is carried out in two ways. The first method is based on the averaging magnetohydrodynamic equations over the period of radial oscillations. The second one consists in the analysis of the growth of Fourier-components of perturbations. Numerical simulation demonstrates that even moderate radial oscillations cause reduction of the growth rate of long-wavelength sausage instabilities and complete stabilization of long kinks. This can be understood as a result of the effective gravitational field produced in the pinch by the oscillations. The effect in question can explain the anomalous stability of pinches with respect to the kink perturbations observed in experiments. copyright 1995 American Institute of Physics