Sample records for plasma actuators driven

  1. Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control

    NASA Astrophysics Data System (ADS)

    Dawson, Robert; Little, Jesse

    2013-03-01

    Positive polarity nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are studied experimentally in quiescent atmosphere. Pulse energy and instantaneous pulse power (hereafter referred to as energy and power) are calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length, and dielectric thickness. Schlieren imaging is used to provide a relative estimate of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on the individual voltage and current traces which are reflected in the energy and power values. Power is mainly dependent on actuator length which is inconsistent with schlieren data as expected. Higher per unit length energy indicates a stronger compression wave for a given actuator geometry, but this is not universally true across different actuators suggesting some constructions more efficiently couple energy to the gas. Energy and compression wave strength are linearly related. Higher pulse frequency produces higher energy but is primarily attributed to heating of the actuator and power supply components and not to an optimal discharge frequency. Both energy and wave strength increase as peak voltage to the power of approximately 3.5 over a substantial range similar to ac-DBD plasma actuators.

  2. Effects of pulse polarity on nanosecond pulse driven dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Dawson, Robyn A.; Little, Jesse

    2014-01-01

    Nanosecond pulse driven dielectric barrier discharge plasma actuators are studied in quiescent air using a power supply capable of producing negative and positive polarity waveforms. High voltage pulses are applied to the exposed electrode of typical asymmetric actuator geometry. In addition to polarity, the effects of pulse amplitude, actuator length, and dielectric thickness are also investigated. Schlieren images are used to estimate the relative near surface gas heating, while electrical measurements are acquired simultaneously. Negative polarity pulses develop slightly more energy per unit length for thin dielectrics, while positive polarity is slightly higher for thick dielectrics. In most cases, the difference in per unit length energy produced by positive and negative pulses on equivalent actuators is not outside the measurement uncertainty. Negative polarity pulses are found to produce a stronger pressure wave for a given peak voltage and pulse energy across the test matrix. Results indicate that the negative polarity pulse more efficiently couples electrical energy to the near surface gas as heat. This suggests negative polarity pulses may be preferred for aerodynamic flow control applications employing this actuator arrangement.

  3. Characteristics of sheath-driven tangential flow produced by a low-current DC surface glow discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Shin, Jichul; Shajid Rahman, Mohammad

    2014-08-01

    An experimental investigation of low-speed flow actuation at near-atmospheric pressure is presented. The flow actuation is achieved via low-current ( \\lesssim 1.0 mA) continuous or pulsed DC surface glow discharge plasma. The plasma actuator, consisting of two sharp-edged nickel electrodes, produces a tangential flow in a direction from anode to cathode, and is visualized using high-speed schlieren photography. The induced flow velocity estimated via the schlieren images reaches up to 5 m/s in test cases. The actuation capability increases with pressure and electrode gap distances, and the induced flow velocity increases logarithmically with the discharge power. Pulsed DC exhibits slightly improved actuation capability with better directionality. An analytic estimation of induced flow velocity obtained based on ion momentum in the cathode sheath and gas dynamics in one-dimensional flow yields values similar to those measured.

  4. Stable electroosmotically driven actuators

    NASA Astrophysics Data System (ADS)

    Sritharan, Deepa; Motsebo, Mylene; Tumbic, Julia; Smela, Elisabeth

    2013-04-01

    We have previously presented "nastic" actuators based on electroosmotic (EO) pumping of fluid in microchannels using high electric fields for potential application in soft robotics. In this work we address two challenges facing this technology: applying EO to meso-scale devices and the stability of the pumping fluid. The hydraulic pressure achieved by EO increases with as 1/d2, where d is the depth of the microchannel, but the flow rate (which determines the stroke and the speed) is proportional to nd, where n is the number of channels. Therefore to get high force and high stroke the device requires a large number of narrow channels, which is not readily achievable using standard microfabrication techniques. Furthermore, for soft robotics the structure must be soft. In this work we present a method of fabricating a three-dimensional porous elastomer to serve as the array of channels based on a sacrificial sugar scaffold. We demonstrate the concept by fabricating small pumps. The flexible devices were made from polydimethylsiloxane (PDMS) and comprise the 3D porous elastomer flanked on either side by reservoirs containing electrodes. The second issue addressed here involves the pumping fluid. Typically, water is used for EO, but water undergoes electrolysis even at low voltages. Since EO takes place at kV, these systems must be open to release the gases. We have recently reported that propylene carbonate (PC) is pumped at a comparable rate as water and is also stable for over 30 min at 8 kV. Here we show that PC is, however, degraded by moisture, so future EO systems must prevent water from reaching the PC.

  5. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B.; Macheret, Sergey O.

    2008-08-01

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

  6. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    SciTech Connect

    Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Macheret, Sergey O. [Lockheed Martin Aeronautics Company, Palmdale, California 93599 (United States)

    2008-08-15

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

  7. Light-Driven Polymeric Bimorph Actuators

    NASA Technical Reports Server (NTRS)

    Adamovsky, Gregory; Sarkisov, Sergey S.; Curley, Michael J.

    2009-01-01

    Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of light energy causes heating, which, in turn, causes thermal expansion.

  8. Gear-Driven Turnbuckle Actuator

    NASA Technical Reports Server (NTRS)

    Rivera, Ricky N.

    2010-01-01

    This actuator design allows the extension and contraction of turnbuckle assemblies. It can be operated manually or remotely, and is extremely compact. It is ideal for turnbuckles that are hard to reach by conventional tools. The tool assembly design solves the problem of making accurate adjustments to the variable geometry guide vanes without having to remove and reinstall the actuator system back on the engine. The actuator does this easily by adjusting the length of the turnbuckles while they are still attached to the engine.

  9. Stochastic static analysis of link driven by actuator bundles

    Microsoft Academic Search

    Takahiro Yoshimura; Mizuho Shibata; Shinichi Hirai

    2009-01-01

    This paper describes a stochastic static analysis of link angle driven by actuator bundles. We first demonstrate a movement of a link driven by actuator bundles in terms of high driving force. The variation of actuator parameters influences the movement of this mechanism. We confirm the link may shift and twist because of the variation of actuator parameters. We then

  10. A vacuum-driven peristaltic micropump with valved actuation chambers

    NASA Astrophysics Data System (ADS)

    Cui, Jianguo; Pan, Tingrui

    2011-06-01

    This paper presents a simple peristaltic micropump design incorporated with valved actuation chambers and propelled by a pulsed vacuum source. The vacuum-driven peristaltic micropump offers high pumping rates, low backflow, appreciable tolerance to air bubbles, and minimal destruction to fluid contents. The pumping device, fabricated by laser micromachining and plasma bonding of three polydimethylsiloxane (PDMS) layers, includes a pneumatic network, actuation membranes, and microfluidic channels. As the key to peristaltic motion, the sequential deflection of the elastic membranes is achieved by periodic pressure waveforms (negative) traveling through the pneumatic network, provided by a vacuum source regulated by an electromagnetic valve. This configuration eliminates the complicated control logic typically required in peristaltic motion. Importantly, the valved actuation chambers substantially reduce backflow and improve the pumping rates. In addition, the pneumatic network with negative pressure provides a means to effectively remove air bubbles present in the microflow through the gas-permeable PDMS membrane, which can be highly desired in handling complex fluidic samples. Experimental characterization of the micropump performance has been conducted by controlling the resistance of the pneumatic network, the number of normally closed valves, the vacuum pressure, and the frequency of pressure pulses. A maximal flow rate of 600 µL min-1 has been optimized at the pulsed vacuum frequency of 30 Hz with a vacuum pressure of 50 kPa, which is comparable to that of compressed air-actuated peristaltic micropumps.

  11. Plasma actuators for bluff body flow control

    NASA Astrophysics Data System (ADS)

    Kozlov, Alexey V.

    The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding noise. A tandem cylinder configuration with the plasma actuation on the upstream cylinder is investigated using surface dynamic pressure sensors. As a result of the plasma actuation, the surface pressure fluctuations on the downstream cylinder are reduced by about two times at the free-stream velocity of 40 m/s (ReD = 164,000). In addition, this study presents the results of a parametric experimental investigation aimed at optimizing the body force produced by single dielectric barrier discharge (SDBD) plasma actuators used for aerodynamic flow control. A primary goal of the study is the improvement of actuator authority for flow control applications at higher Reynolds number than previously possible. The study examines the effects of dielectric material and thickness, applied voltage amplitude and frequency, voltage waveform, exposed electrode geometry, covered electrode width and multiple actuator arrays. The metric used to evaluate the performance of the actuator in each case is the measured actuator-induced thrust which is proportional to the total body force. It is demonstrated that actuators constructed with thick dielectric material of low dielectric constant and operated at low frequency AC voltage produce a body force that is an order of magnitude larger than that obtained by the Kapton-based actuators used in many previous plasma flow control studies. These actuators allow operation at much higher applied voltages without the formation of discrete streamers which lead to body force saturation.

  12. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    Microsoft Academic Search

    Dmitry F. Opaits; Alexandre V. Likhanskii; Gabriele Neretti; Sohail Zaidi; Mikhail N. Shneider; Richard B. Miles; Sergey O. Macheret

    2008-01-01

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations

  13. Optimization of a dual acting, magnetically driven, linear actuator

    E-print Network

    Willerton, Justin Ryan

    2002-01-01

    In this study the geometry of a dual acting, magnetically driven, linear motion actuator will be optimized. This will be accomplished by modeling the system through a set of differential equations to be solved in Matlab. An ANSYS finite element...

  14. Electrically actuated, pressure-driven microfluidic pumps.

    PubMed

    Munyan, Jason W; Fuentes, Hernan V; Draper, Melissa; Kelly, Ryan T; Woolley, Adam T

    2003-11-01

    In order to make the lab-on-a-chip concept a reality, it is desirable to have an integrated component capable of pumping fluids through microchannels. We have developed novel, electrically actuated micropumps and have integrated them with microfluidic systems. These devices utilize the build-up of electrolysis gases to achieve pressure-driven pumping, only require small voltages (approximately 10 V), and have approximate dimensions of 5 cm x 3 cm x 2 cm. Furthermore, these micropumps are composed of relatively inexpensive materials, and the reversible sealability of their poly(dimethylsiloxane) body to different microfluidic arrays enables repeated uses of the same pump. Under an applied potential of 10 V, three different micropumps had average flow rates of 8-13 microL min(-1) for water being pumped through five different 2 cm-long, 5500 microm(2) cross-sectional-area channels in poly(methyl methacrylate), in approximate agreement with predicted pump rates. We have also evaluated pump operation at the lower applied potential of 8 V and observed an average flow rate of 6.1 microL min(-1) for a pump-channel system. The current micropump design is capable of sustaining pumping pressures in the range of 300 kPa. The various advantages of these micropumps make them well suited for use in lab-on-a-chip analysis techniques. PMID:15007448

  15. Dielectric Barrier Discharge Plasma Actuator for Flow Control

    NASA Technical Reports Server (NTRS)

    Opaits, Dmitry, F.

    2012-01-01

    This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

  16. Simulations of Serpentine Plasma Actuators in a Laminar Boundary Layer

    E-print Network

    Roy, Subrata

    Simulations of Serpentine Plasma Actuators in a Laminar Boundary Layer Mark Riherd and Subrata Roy to the addition of the serpentine actuation are also measured. Nomenclature u, v, w Flow velocities p Pressure U geometry actuator,17,18 and the serpentine geometry actuator.18 The geometry relevant to the present work

  17. Dielectric Barrier Discharge Plasma Actuators for Flow Control

    Microsoft Academic Search

    Thomas C. Corke; C. Lon Enloe; Stephen P. Wilkinson

    2010-01-01

    The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single-dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is

  18. Scalability of Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2008-01-01

    Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

  19. Design analysis of a piezoelectrically driven synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Yang, An-Shik

    2009-12-01

    Technological advancement is being realized by using piezoelectric synthetic jet actuators to generate managing forces and moments with zero-net-mass-flux oscillatory jets for various air flow control applications. This paper firstly explores the synthetic jet flow behavior for a dual-diaphragm piezoelectrically driven synthetic jet actuator. In the experimental study, a flow visualization system was utilized to acquire the particle streak images scattered from red fluorescent spheres for examining the synthetic jet flow. The centerline velocity of the jet was measured with a hot-wire anemometer. For exploring the formation progression of synthetic jets, the numerical analysis implemented unsteady three-dimensional conservation equations of mass and momentum with a standard k-? two-equation turbulent model adopted for turbulence closure. The moving boundary was also treated to represent the motion of the piezo diaphragm under actuation. For a complete sinusoidal actuation cycle at an operating frequency of 648 Hz, the synthetic jet flow pattern was simulated and compared with the visualized image and measured centerline velocity distribution to validate the computer software. In general, the far-field flow structure was fairly similar to a common continuous turbulent air jet; whereas, the predicted time-recurring formation of a vortex pair was observed in the near field. The surrounding air close to the slot was also drawn into the cavity of the actuator when vortex pairs advected sufficiently downstream. Numerical experiments were then extended to assess the performance of synthetic jet actuators by systematically varying the driving voltage, relative phase delay of frequency, width of the slot and depth of the actuator cavity.

  20. Plasma actuators for separation control on stationary and oscillating airfoils

    NASA Astrophysics Data System (ADS)

    Post, Martiqua L.

    Given the importance of separation control associated with retreating blade stall on helicopters, the primary objective of this work was to develop a plasma actuator flow control device for its use in controlling leading-edge separation on stationary and oscillating airfoils. The plasma actuator consists of two copper electrodes separated by a dielectric insulator. When the voltage supplied to the electrodes is sufficiently high, the surrounding air ionizes forms plasma in the regions of high electrical field potential. The ionized air, in the presence of an electric field gradient, results in a body force on the flow. The effect of plasma actuator was experimentally investigated and characterized through a systematic set of experiments. It was then applied to NACA 66 3018 and NACA 0015 airfoils for the purpose of leading-edge separation control. The effectiveness of the actuator was documented through surface pressure measurements on the airfoil, mean wake velocity profiles, and flow visualization records. For the stationary airfoil, the actuator prevented flow separation for angles of attack up to 22°, which was 8° past the static stall angle. This resulted in as much as a 300% improvement in the lift-to-drag ratio. For the oscillating airfoil, the measurements were phase-conditioned to the oscillation motion. Three cases with the plasma actuator were investigated: steady actuation, unsteady plasma actuation, and so-called "smart" actuation in which the actuator is activated during portions of the oscillatory cycle. All of the cases exhibited a higher cycle-integrated lift and an improvement in the lift cycle hysteresis. The steady plasma actuation increased the lift over most of the cycle, except at the peak angle of attack where it was found to suppress the dynamic stall vortex. Because of this, the sharp drop in the lift coefficient past the maximum angle of attack was eliminated. The unsteady plasma actuation produced significant improvements in the lift coefficient during the pitch-down portion of the cycle, especially near the minimum angle of attack. A "smart" actuator approach produced the best improvement in the lift cycle with the highest integrated lift, and elimination of the sharp stall past the maximum angle of attack. It is possible that the "smart" actuation could be optimized further. However, these results are extremely promising for improving helicopter rotor performance.

  1. Characterization of linear plasma synthetic jet actuators in an initially quiescent medium

    SciTech Connect

    Santhanakrishnan, Arvind [Department of Mathematics, Phillips Hall, CB 3250, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3250 (United States); Reasor, Daniel A. Jr. [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); LeBeau, Raymond P. Jr. [Department of Mechanical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)

    2009-04-15

    The plasma synthetic jet actuator (PSJA) is a geometrical variant of the aerodynamic plasma actuator that can be used to produce zero-mass flux jets similar to those created by mechanical devices. This jet can be either three-dimensional using annular electrode arrays (annular PSJA) or nearly two dimensional using two rectangular-strip exposed electrodes and one embedded electrode (linear PSJA). Unsteady pulsing of the PSJA at time scales decoupled to the ac input frequency results in a flow field dominated by counter-rotating vortical structures similar to conventional synthetic jets, and the peak velocity and momentum of the jet is found to be affected by a combination of the pulsing frequency and input power. This paper investigates the fluid dynamic characteristics of linear plasma synthetic jet actuators in an initially quiescent medium. Two-dimensional particle image velocimetry measurements on the actuator are used to validate a previously developed numerical model wherein the plasma behavior is introduced into the Navier-Stokes equations as an electrohydrodynamic force term calculated from Maxwell's equations and solved for the fluid momentum. The numerical model was implemented in an incompressible, unstructured grid code. The results of the simulations are observed to reproduce some aspects of the qualitative and quantitative experimental behavior of the jet for steady and pulsed modes of actuator operation. The self-similarity behavior of plasma synthetic jets are examined and compared to mechanically driven continuous and synthetic jets.

  2. Surface plasma actuators modeling for flow control

    NASA Astrophysics Data System (ADS)

    Shang, J. S.; Huang, P. G.

    2014-05-01

    The surface plasma actuators over the entire speed region have been intensely investigated for flow control. Most of the fundamental phenomena have been firmly identified by experimental observations but ambiguities still remained. The direct computational simulation for multiple microdischarges is presently beyond our reach, thus the essential physics may be better understood on the framework of physics-based modeling. To achieve this objective, the drift-diffusion approximation is adopted as a transport property approximation to the nonequilibrium air plasma. The most challenging issue of electron impact ionization process at the low-temperature environment is addressed by the Townsend mechanism together with electron attachment, detachment, bulk, and ion-ion recombination. The effects and quantifications of Joule heating, periodic electrostatic force, as well as, the Lorentz acceleration for flow control are examined. The clarification to the hot spot of heat transfer in direct current discharge and the orientations of the periodic force associated with AC cycle of dielectric barrier discharge are also included.

  3. Dielectric material degradation monitoring of dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald E.; Houser, Nicole M.; Lavoie, Philippe

    2014-01-01

    It is a known phenomenon that some dielectric materials used to construct plasma actuators degrade during operation. However, the rate at which this process occurs, to what extent, as well as a method to monitor is yet to be established. In this experimental study, it is shown that electrical measurements can be used to monitor changes in the material of the plasma actuators. The procedure we introduce for monitoring the actuators follows from the work of Kriegseis, Grundmann, and Tropea [Kriegseis et al., J. Appl. Phys. 110, 013305 (2011)], who used Lissajous figures to measure actuator power consumption and capacitance. In the present study, we quantify changes in both the power consumption and capacitance of the actuators over long operating durations. It is shown that the increase in the effective capacitance of the actuator is related to degradation (thinning) of the dielectric layer, which is accompanied by an increase in actuator power consumption. For actuators constructed from layers of Kapton® polyimide tape, these changes are self-limiting. Although the polyimide film degrades relatively quickly, the underlying adhesive layer appears to remain intact. Over time, the effective capacitance was found to increase by up to 36%, 25%, and 11% for actuators constructed with 2, 3, and 4 layers of Kapton tape, respectively. A method is presented to prevent erosion of the Kapton dielectric layer using a coating of Polydimethylsiloxane oil. It is shown the application of this treatment can delay the onset of degradation of the Kapton dielectric material.

  4. Instability wave control in turbulent jet by plasma actuators

    NASA Astrophysics Data System (ADS)

    Kopiev, V. F.; Akishev, Y. S.; Belyaev, I. V.; Berezhetskaya, N. K.; Bityurin, V. A.; Faranosov, G. A.; Grushin, M. E.; Klimov, A. I.; Kopiev, V. A.; Kossyi, I. A.; Moralev, I. A.; Ostrikov, N. N.; Taktakishvili, M. I.; Trushkin, N. I.; Zaytsev, M. Yu

    2014-12-01

    Instability waves in the shear layer of turbulent jets are known to be a significant source of jet noise, which makes their suppression important for the aviation industry. In this study we apply plasma actuators in order to control instability waves in the shear layer of a turbulent air jet at atmospheric pressure. Three types of plasma actuators are studied: high-frequency dielectric barrier discharge, slipping surface discharge, and surface barrier corona discharge. Particle image velocimetry measurements of the shear layer demonstrate that the plasma actuators have control authority over instability waves and effectively suppress the instability waves artificially generated in the shear layer. It makes these actuators promising for application in active control systems for jet noise mitigation.

  5. Fast, strong and compliant pneumatic actuation for dexterous tendon-driven hands

    E-print Network

    Todorov, Emanuel

    Fast, strong and compliant pneumatic actuation for dexterous tendon-driven hands Vikash Kumar, Zhe Xu and Emanuel Todorov Abstract--We describe a pneumatic actuation system for dexterous robotic hands for dexterous manipulation, yet it has never before been achieved with a tendon-driven system, let alone

  6. Driven one-component plasmas

    SciTech Connect

    Rizzato, Felipe B.; Pakter, Renato; Levin, Yan [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, Porto Alegre 91501-970, RS (Brazil)

    2009-08-15

    A statistical theory is presented that allows the calculation of the stationary state achieved by a driven one-component plasma after a process of collisionless relaxation. The stationary Vlasov equation with appropriate boundary conditions is reduced to an ordinary differential equation, which is then solved numerically. The solution is then compared with the molecular-dynamics simulation. A perfect agreement is found between the theory and the simulations. The full current-voltage phase diagram is constructed.

  7. Plasma actuated heat transfer Subrata Roya

    E-print Network

    Roy, Subrata

    with cold fluid film is common- place in many engineering problems including vertical/short takeoff in the vicinity of an actuator using an electrodynamic mechanism that induces attachment of cold jet to the work blade lifetime. In this process, cold gas is injected from a row of holes located spanwise into the hot

  8. Bluff Body Flow Control Using Dielectric Barrier Discharge Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Thomas, Flint; Kozlov, Alexey

    2008-11-01

    The results of an experimental investigation involving the use of dielectric barrier discharge plasma actuators to control bluff body flow is presented. The motivation for the work is plasma landing gear noise control for commercial transport aircraft. For these flow control experiments, the cylinder in cross-flow is chosen for study since it represents a generic flow geometry that is similar in all essential aspects to a landing gear strut. The current work is aimed both at extending the plasma flow control concept to Reynolds numbers typical of landing approach and take-off and on the development of optimum plasma actuation strategies. The cylinder wake flow with and without actuation are documented in detail using particle image velocimetry (PIV) and constant temperature hot-wire anemometry. The experiments are performed over a Reynolds number range extending to ReD=10^5. Using either steady or unsteady plasma actuation, it is demonstrated that even at the highest Reynolds number Karman shedding is totally eliminated and turbulence levels in the wake decrease by more than 50%. By minimizing the unsteady flow separation from the cylinder and associated large-scale wake vorticity, the radiated aerodynamic noise is also reduced.

  9. Stabilization of boundary layer streaks by plasma actuators

    NASA Astrophysics Data System (ADS)

    Riherd, Mark; Roy, Subrata

    2014-03-01

    A flow's transition from laminar to turbulent leads to increased levels of skin friction. In recent years, dielectric barrier discharge actuators have been shown to be able to delay the onset of turbulence in boundary layers. While the laminar to turbulent transition process can be initiated by several different instability mechanisms, so far, only stabilization of the Tollmien-Schlichting path to transition has received significant attention, leaving the stabilization of other transition paths using these actuators less explored. To fill that void, a bi-global stability analysis is used here to examine the stabilization of boundary layer streaks in a laminar boundary layer. These streaks, which are important to both transient and by-pass instability mechanisms, are damped by the addition of a flow-wise oriented plasma body force to the boundary layer. Depending on the magnitude of the plasma actuation, this damping can be up to 25% of the perturbation's kinetic energy. The damping mechanism appears to be due to highly localized effects in the immediate vicinity of the body force, and when examined using a linearized Reynolds-averaged Navier-Stokes energy balance, indicate negative production of the perturbation's kinetic energy. Parametric studies of the stabilization have also been performed, varying the magnitude of the plasma actuator's body force and the spanwise wavenumber of the actuation. Based on these parametric studies, the damping of the boundary layer streaks appears to be linear with respect to the total amount of body force applied to the flow.

  10. Advanced control for nano-positioner driven by piezo actuator

    Microsoft Academic Search

    Xinkai Chen; Chun-Yi Su

    2010-01-01

    The piezo-actuated stage is composed of a piezo electric actuator (PEA) and a positioning mechanism (PM). Due to the existence of hysteretic nonlinearity in the PEA and the friction in the PM, the high precision control of the piezo-actuated stage is a challenging task. This paper discusses the high precision adaptive control for the piezo-actuated stage, where the hysteresis is

  11. Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roy

    E-print Network

    Roy, Subrata

    Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roy Citation: J. Appl://jap.aip.org/authors #12;Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roya) Applied. Plasma actuators with novel geometries, including the serpentine geometry, have been effective

  12. A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Nguyen, Canh Toan; Phung, Hoa; Dat Nguyen, Tien; Lee, Choonghan; Kim, Uikyum; Lee, Donghyouk; Moon, Hyungpil; Koo, Jachoon; Nam, Jae-do; Ryeol Choi, Hyouk

    2014-06-01

    A kind of dielectric elastomer (DE) material, called ‘synthetic elastomer’, has been developed based on acrylonitrile butadiene rubber (NBR) to be used as a dielectric elastomer actuator (DEA). By stacking single layers of synthetic elastomer, a linear actuator, called a multistacked actuator, is produced, and used by mechatronic and robotic systems to generate linear motion. In this paper, we demonstrate the application of the multistacked dielectric elastomer actuator in a biomimetic legged robot. A miniature robot driven by a biomimetic actuation system with four 2-DOF (two-degree-of-freedom) legged mechanisms is realized. Based on the experimental results, we evaluate the performance of the proposed robot and validate the feasibility of the multistacked actuator in a locomotion system as a replacement for conventional actuators.

  13. Broadband flow-induced sound control using plasma actuators

    NASA Astrophysics Data System (ADS)

    Huang, Xun; Zhang, Xin; Li, Yong

    2010-06-01

    Plasma actuators were used in this work to control flow-induced broadband noise radiated from a bluff body. The model consists of a cylinder and a component (torque link) that is installed on the lee side of the cylinder. The objective is to reduce the broadband noise mainly generated through the impingement of the cylinder wake on the torque link. The flow-structure interactions between the cylinder wake and the torque link are reduced by manipulating the cylinder wake with the externally imposed body force from the plasma actuators, which lead to the attenuation of the broadband noise. The control performance with the plasma actuators is studied in an anechoic chamber facility by examining far-field sound level and near-field acoustic source changes. At a free stream speed of 30 m/s, corresponding to the Reynolds number of 2.1×105, far-field measurements suggested that a reduction of up to 3.2 dB in overall sound pressure level. The near-field beamforming results also show approximately 3 dB reduction in the interested frequency ranges. The physical mechanisms related to broadband noise control were also discussed. This work suggests that plasma actuators offer the potential for solving flow-induced noise control problem at broadband frequencies.

  14. Separation Control in a Centrifugal Bend Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Arthur, Michael; Corke, Thomas

    2011-11-01

    An experiment and CFD simulation are presented to examine the use of plasma actuators to control flow separation in a 2-D channel with a 135^o inside-bend that is intended to represent a centrifugal bend in a gas turbine engine. The design inlet conditions are P=330,sia., T=1100^oF, and M=0.24. For these conditions, the flow separates on the inside radius of the bend. A CFD simulation was used to determine the location of the flow separation, and the conditions (location and voltage) of a plasma actuator that was needed to keep the flow attached. The plasma actuator body force model used in the simulation was updated to include the effect of high-pressure operation. An experiment was used to validate the simulation and to further investigate the effect of inlet pressure and Mach number on the flow separation control. This involved a transient high-pressure blow-down facility. The flow field is documented using an array of static pressure taps in the channel outside-radius side wall, and a rake of total pressure probes at the exit of the bend. The results as well as the pressure effect on the plasma actuators are presented.

  15. Dielectric barrier discharge plasma actuator for flow control

    Microsoft Academic Search

    Dmitry Florievich Opaits

    2010-01-01

    Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness

  16. SDBD plasma actuator with nanosecond pulse-periodic discharge

    Microsoft Academic Search

    A. Yu Starikovskii; A. A. Nikipelov; M. M. Nudnova; D. V. Roupassov

    2009-01-01

    This paper presents a detailed explanation of the physical mechanism of the nanosecond pulsed surface dielectric barrier discharge (SDBD) effect on the flow. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed show overheating in the discharge region on fast (tau sime 1 µs) thermalization of the plasma input energy. The mean values of such heating of

  17. Use of Plasma Actuators as a Moving-Wake Generator

    NASA Technical Reports Server (NTRS)

    Corke, Thomas C.; Thomas, Flint O.; Klapetzky Michael J.

    2007-01-01

    The work documented in this report tests the concept of using plasma actuators as a simple and easy way to generate a simulated moving-wake and the disturbances associated with it in turbines. This wake is caused by the blades of the upstream stages of the turbine. Two types of devices, one constructed of arrays of NACA 0018 airfoils, and the one constructed of flat plates were studied. The airfoils or plates were equipped with surface mounted dielectric barrier discharge (DBD) plasma actuators, which were used to generate flow disturbances resembling moving-wakes. CTA hot-wire anemometry and flow visualization using a smoke-wire were used to investigate the wake independence at various spacings and downstream locations. The flat plates were found to produce better results than the airfoils in creating large velocity fluctuations in the free-stream flow. Different dielectric materials, plasma actuator locations, leading edge contours, angles of attack and plate spacings were investigated, some with positive results. The magnitudes of the velocity fluctuations were found to be comparable to existing mechanical moving-wake generators, thus proving the feasibility of using plasma actuators as a moving-wake generator.

  18. Design of a high-speed, meso-scale nanopositioners driven by electromagnetic actuators

    E-print Network

    Golda, Dariusz, 1979-

    2008-01-01

    The purpose of this thesis is to generate the design and fabrication knowledge that is required to engineer high-speed, six-axis, meso-scale nanopositioners that are driven by electromagnetic actuators. When compared to ...

  19. American Institute of Aeronautics and Astronautics Induced Flow from Serpentine Plasma Actuators Acting in

    E-print Network

    Roy, Subrata

    American Institute of Aeronautics and Astronautics 1 Induced Flow from Serpentine Plasma Actuators on a dielectric barrier discharge (DBD) plasma actuator with the electrodes in a serpentine design of the actuator. In this work the serpentine configuration is constructed from patterned circular arcs

  20. Indirect Adaptive Robust Control of Electro-Hydraulic Systems Driven by Single-Rod Hydraulic Actuator

    E-print Network

    Yao, Bin

    Indirect Adaptive Robust Control of Electro-Hydraulic Systems Driven by Single-Rod Hydraulic) of electro-hydraulic systems driven by single- rod hydraulic actuators. Unlike the tracking that the proposed IARC achieves good tracking performance and accurate parameter estimation. INTRODUCTION Electro-hydraulic

  1. Centrifugally driven diffusion of Iogenic plasma

    Microsoft Academic Search

    G. L. Siscoe; Danny Summers

    1981-01-01

    The plasma distribution around Io as measured by Voyager 1 displays an asymmetric discontinuity at Io's orbit that has been suggested to be the signature of centrifugally driven interchange diffusion fed by plasma derived from Io. This hypothesis is explored further and found to be valid. The particular form for the diffusion coefficient appropriate to centrifugally driven turbulence is derived.

  2. Finite element modeling analysis of photostrictively driven optical actuators for excitation of microdevices

    NASA Astrophysics Data System (ADS)

    Rahman, Mosfequr; Nawaz, Masud

    2011-11-01

    Photostriction is a phenomenon in which strain is induced in the sample by incident light. In principle, this effect arises from a superposition of the photovoltaic effect, i.e. the generation of large voltage from the irradiation of light, and the converse piezoelectric effect, i.e. expansion or contraction under the voltage applied. Photostrictive materials are ferrodielectric ceramics that have a photostrictive effect. Some photostrictive materials are (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, called PLZT, which exhibit large photostriction under uniform illumination with high-energy light. They have potential use in numerous micro-electro-mechanical system (MEMS) devices where actuation of microbeams is a common phenomenon. The objective of this research is to develop and analyze a finite element model to study the feasibility of photostrictively driven actuators for excitation of microdevices. Much work has been carried out toward developing microdevices which are capacitively driven or piezoelectrically driven. The effect of different parameters such as actuator thickness, incident light intensity and convective heat transfer coefficient on the actuation of a beam using thin film photostrictive actuators has been investigated. Also the derived finite element for static analysis of photostrictive thin films has been used to investigate the application of photostrictive actuators for different structures and various boundary conditions of microbeams with various actuator locations and lengths. A successful conclusion of these tasks will affirm the potential of the technology for use in actual microdevices.

  3. Shock Generation and Control Using DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.

    2012-01-01

    This report is the final report of a NASA Phase I SBIR contract, with some revisions to remove company proprietary data. The Shock Boundary Layer Interaction (SBLI) phenomena in a supersonic inlet involve mutual interaction of oblique shocks with boundary layers, forcing the boundary layer to separate from the inlet wall. To improve the inlet efficiency, it is desired to prevent or delay shock-induced boundary layer separation. In this effort, Innovative Technology Applications Company (ITAC), LLC and the University of Notre Dame (UND) jointly investigated the use of dielectric-barrier-discharge (DBD) plasma actuators for control of SBLI in a supersonic inlet. The research investigated the potential for DBD plasma actuators to suppress flow separation caused by a shock in a turbulent boundary layer. The research involved both numerical and experimental investigations of plasma flow control for a few different SBLI configurations: (a) a 12 wedge flow test case at Mach 1.5 (numerical and experimental), (b) an impinging shock test case at Mach 1.5 using an airfoil as a shock generator (numerical and experimental), and (c) a Mach 2.0 nozzle flow case in a simulated 15 X 15 cm wind tunnel with a shock generator (numerical). Numerical studies were performed for all three test cases to examine the feasibility of plasma flow control concepts. These results were used to guide the wind tunnel experiments conducted on the Mach 1.5 12 degree wedge flow (case a) and the Mach 1.5 impinging shock test case (case b) which were at similar flow conditions as the corresponding numerical studies to obtain experimental evidence of plasma control effects for SBLI control. The experiments also generated data that were used in validating the numerical studies for the baseline cases (without plasma actuators). The experiments were conducted in a Mach 1.5 test section in the University of Notre Dame Hessert Laboratory. The simulation results from cases a and b indicated that multiple spanwise actuators in series and at a voltage of 75 kVp-p could fully suppress the flow separation downstream of the shock. The simulation results from case c showed that the streamwise plasma actuators are highly effective in creating pairs of counter-rotating vortices, much like the mechanical vortex generators, and could also potentially have beneficial effects for SBLI control. However, to achieve these effects, the positioning and the quantity of the DBD actuators used must be optimized. The wind tunnel experiments mapped the baseline flow with good agreement to the numerical simulations. The experimental results were conducted with spanwise actuators for cases a and b, but were limited by the inability to generate a sufficiently high voltage due to arcing in the wind-tunnel test-section. The static pressure in the tunnel was lower than the static pressure in an inlet at flight conditions, promoting arching and degrading the actuator performance.

  4. A novel MEMS actuator with large lateral stroke driven by Lorentz force

    NASA Astrophysics Data System (ADS)

    Lv, Xingdong; Wei, Weiwei; Mao, Xu; Yang, Jinling; Yang, Fuhua

    2015-02-01

    This paper presents a novel MEMS actuator driven by Lorentz force. The actuator has a structure of folded beams, which is favorable for a large lateral stroke. A displacement of more than 47??m was achieved with a magnetic field of 0.3?T and a driving current of 8?mA. The actuator can generate a large displacement under a low driving voltage and can easily be integrated with CMOS circuits. Lorentz force is proportional to the magnetic field and the driving current, which results in a linear dependence of the lateral displacement on the driving current.

  5. Competition between pressure effects and airflow influence for the performance of plasma actuators

    NASA Astrophysics Data System (ADS)

    Kriegseis, J.; Barckmann, K.; Frey, J.; Tropea, C.; Grundmann, S.

    2014-05-01

    The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1-1 bar) and airflow velocities (U?=0-100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

  6. Competition between pressure effects and airflow influence for the performance of plasma actuators

    SciTech Connect

    Kriegseis, J., E-mail: kriegseis@kit.edu [Institute of Fluid Mechanics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Barckmann, K.; Grundmann, S., E-mail: grundmann@csi.tu-darmstadt.de [Center of Smart Interfaces, Technische Universität Darmstadt, Darmstadt (Germany); Frey, J. [Institute for Aerospace Engineering, Technische Universität Dresden, Dresden (Germany); Tropea, C. [Center of Smart Interfaces, Technische Universität Darmstadt, Darmstadt (Germany); Institute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, Darmstadt (Germany)

    2014-05-15

    The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p?=?0.1–1 bar) and airflow velocities (U{sub ?}=0?100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

  7. Combustion stabilization using serpentine plasma actuators Chin-Cheng Wang and Subrata Roya)

    E-print Network

    Roy, Subrata

    Combustion stabilization using serpentine plasma actuators Chin-Cheng Wang and Subrata Roya 2011) This letter presents a numerical model for combustion stabilization with plasma actuators of Physics. [doi:10.1063/1.3615292] The topic of plasma assisted combustion (PAC) has been investigated

  8. Plasma Actuators for Turbomachinery Flow Control

    NASA Technical Reports Server (NTRS)

    Miles, Richard, B; Shneider, Mikhail, N.

    2012-01-01

    This report is Part I of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. The period of performance was January 1, 2007 to December 31, 2010. This report includes the project summary, a list of publications and reprints of the publications that appeared in archival journals. Part II of the final report includes a Ph.D. dissertation and is published separately as NASA/CR-2012-2172655. The research performed under this project was focused on the operation of surface dielectric barrier discharge (DBD) devices driven by high voltage, nanosecond scale pulses plus constant or time varying bias voltages. The main interest was in momentum production and the range of voltages applied eliminated significant heating effects. The approach was experimental supplemented by computational modeling. All the experiments were conducted at Princeton University. The project provided comprehensive understanding of the associated physical phenomena. Limitations on the performance of the devices for the generation of high velocity surface jets were established and various means for overcoming those limitations were proposed and tested. The major limitations included the maximum velocity limit of the jet due to electrical breakdown in air and across the dielectric, the occurrence of backward breakdown during the short pulse causing reverse thrust, the buildup of surface charge in the dielectric offsetting the forward driving potential of the bias voltage, and the interaction of the surface jet with the surface through viscous losses. It was also noted that the best performance occurred when the nanosecond pulse and the bias voltage were of opposite sign. Solutions include the development of partially conducting surface coatings, the development of a semiconductor diode inlaid surface material to suppress the backward breakdown. Extension to long discharge channels was studied and a new ozone imaging method developed for more quantitative determination of surface jet properties.

  9. 3rd AIAA Flow Control Conference, Jun. 58, 2006, San Francisco,CA Flow Control Using Plasma Actuators and

    E-print Network

    Jacob, Jamey

    Actuators and Linear/Annular Plasma Synthetic Jet Actuators Arvind Santhanakrishnan and Jamey D. Jacob Dept different actuator geometries have been tested: a conven- tional design using two rectangular strip electrodes (the linear actuator) that produces a nearly two-dimensional horizontal wall jet upon actuation

  10. Transient ejection phase modeling of a Plasma Synthetic Jet actuator

    NASA Astrophysics Data System (ADS)

    Laurendeau, F.; Chedevergne, F.; Casalis, G.

    2014-12-01

    For several years, a promising Plasma Synthetic Jet actuator for high-speed flow control has been under development at ONERA. So far, its confined geometry and small space-time scales at play have prevented its full experimental characterization. Complementary accurate numerical simulations are then considered in this study in order to provide a complete aerothermodynamic description of the actuator. Two major obstacles have to be overcome with this approach: the modeling of the energy deposited by the electric arc and the accurate computation of the transient response of the cavity generating the pulsed jet. To solve the first problem, an Euler solver coupled with an electric circuit model was used to evaluate the energy deposition in the cavity. Such a coupling is performed by considering the electric field between the two electrodes. The second issue was then addressed by injecting these source terms in large Eddy simulations of the entire actuator. Aerodynamic results were finally compared with Schlieren visualizations. Using the proposed methodology, the temporal evolution of the jet front is remarkably well predicted.

  11. Three-dimensional effects of curved plasma actuators in quiescent air

    SciTech Connect

    Wang Chincheng; Durscher, Ryan; Roy, Subrata

    2011-04-15

    This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength ({lambda}) and amplitude ({Lambda}) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.

  12. Mechanical wave propagation in carbon nanotubes driven by an oscillating tip actuator

    E-print Network

    Liu, Feng

    . The wavelength and velocities of longitudinal, transverse, and torsional waves were obtained, and a relationshipMechanical wave propagation in carbon nanotubes driven by an oscillating tip actuator Min Chen,1; published online 23 January 2009 We investigate the mechanical wave propagation in single-walled carbon

  13. Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Number

    E-print Network

    Roy, Subrata

    1 Numerical Investigation of Serpentine Plasma Actuators for Separation Control at Low Reynolds Discharge (DBD) plasma actuators with serpentine shaped electrodes cause a change in the operational parameters, in particular the geometric amplitude of the serpentine geometry as it is flattened out

  14. Analytic model and frequency characteristics of plasma synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Zong, Hao-hua; Wu, Yun; Li, Ying-hong; Song, Hui-min; Zhang, Zhi-bo; Jia, Min

    2015-02-01

    This paper reports a novel analytic model of a plasma synthetic jet actuator (PSJA), considering both the heat transfer effect and the inertia of the throat gas. Both the whole cycle characteristics and the repetitive working process of PSJA can be predicted with this model. The frequency characteristics of a PSJA with 87 mm3 volume and different orifice diameters are investigated based on the analytic model combined with experiments. In the repetitive working mode, the actuator works initially in the transitional stage with 20 cycles and then in the dynamic balanced stage. During the transitional stage, major performance parameters of PSJA experience stepped growth, while during the dynamic balanced stage, these parameters are characterized by periodic variation. With a constant discharge energy of 6.9 mJ, there exists a saturated frequency of 4 kHz/6 kHz for an orifice diameter of 1 mm/1.5 mm, at which the time-averaged total pressure of the pulsed jet reaches a maximum. Between 0.5 mm and 1.5 mm, a larger orifice diameter leads to a higher saturated frequency due to the reduced jet duration time. As the actuation frequency increases, both the time-averaged cavity temperature and the peak jet velocity initially increase and then remain almost unchanged at 1600 K and 280 m/s, respectively. Besides, with increasing frequency, the mechanical energy incorporated in single pulsed jet, the expelled mass per pulse, and the time-averaged density in the cavity, decline in a stair stepping way, which is caused by the intermittent decrease of refresh stage duration in one period.

  15. Study of flow induced by sine wave and saw tooth plasma actuators

    NASA Astrophysics Data System (ADS)

    Liu, Zhifeng; Wang, Lianze; Fu, Song

    2011-11-01

    The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated. The measurement results are compared with a corresponding standard configuration (conventional design using two rectangular strip electrodes)—the actuator that produces a nearly two-dimensional horizontal wall jet upon actuation. PIV measurements are used to characterize the actuators in a quiescent chamber. Operating in a steady manner, the new actuators result in the formation of streamwise and spanwise vortices. That is to say, the new actuators render the plasma actuators inducing three-dimensional variations in the shear layer, offering significant flexibility in flow control. The affected flowfield with the new actuators is significantly larger than that with the conventional linear actuators. While the conventional linear actuators affect primarily the boundary layer flow on a scale of about 1 cm above the wall, the new actuators affect the near wall region at a significantly larger scale. This new design broadens the applicability and enhances the flow control effects and it is potentially a more efficient flow control device.

  16. Control of supersonic axisymmetric base flows using passive splitter plates and pulsed plasma actuators

    NASA Astrophysics Data System (ADS)

    Reedy, Todd Mitchell

    An experimental investigation evaluating the effects of flow control on the near-wake downstream of a blunt-based axisymmetric body in supersonic flow has been conducted. To better understand and control the physical phenomena that govern these massively separated high-speed flows, this research examined both passive and active flow-control methodologies designed to alter the stability characteristics and structure of the near-wake. The passive control investigation consisted of inserting splitter plates into the recirculation region. The active control technique utilized energy deposition from multiple electric-arc plasma discharges placed around the base. The flow-control authority of both methodologies was evaluated with experimental diagnostics including particle image velocimetry, schlieren photography, surface flow visualization, pressure-sensitive paint, and discrete surface pressure measurements. Using a blowdown-type wind tunnel reconstructed specifically for these studies, baseline axisymmetric experiments without control were conducted for a nominal approach Mach number of 2.5. In addition to traditional base pressure measurements, mean velocity and turbulence quantities were acquired using two-component, planar particle image velocimetry. As a result, substantial insight was gained regarding the time-averaged and instantaneous near-wake flow fields. This dataset will supplement the previous benchmark point-wise laser Doppler velocimetry data of Herrin and Dutton (1994) for comparison with new computational predictive techniques. Next, experiments were conducted to study the effects of passive triangular splitter plates placed in the recirculation region behind a blunt-based axisymmetric body. By dividing the near-wake into 1/2, 1/3, and 1/4 cylindrical regions, the time-averaged base pressure distribution, time-series pressure fluctuations, and presumably the stability characteristics were altered. While the spatial base pressure distribution was influenced considerably, the area-integrated pressure was only slightly affected. Normalized RMS levels indicate that base pressure fluctuations were significantly reduced with the addition of the splitter plates. Power-spectral-density estimates revealed a spectral broadening of fluctuating energy for the 1/2 cylinder configuration and a bimodal distribution for the 1/3 and 1/4 cylinder configurations. It was concluded that the recirculation region is not the most sensitive location to apply flow control; rather, the shear layer may be a more influential site for implementing flow control methodologies. For active flow control, pulsed plasma-driven fluidic actuators were investigated. Initially, the performance of two plasma actuator designs was characterized to determine their potential as supersonic flow control devices. For the first actuator considered, the pulsed plasma jet, electro-thermal heating from an electric discharge heats and pressurizes gas in a small cavity which is exhausted through a circular orifice forming a synthetic jet. Depending on the electrical energy addition, peak jet velocities ranged between 130 to nearly 500 m/s when exhausted to quiescent, ambient conditions. The second plasma actuator investigated is the localized arc filament plasma actuator (LAFPA), which created fluidic perturbations through the rapid, local thermal heating, generated from an electric arc discharge between two electrodes within a shallow open cavity. Electrical and emission properties of the LAFPA were first documented as a function of pressure in a quiescent, no-flow environment. Rotational and vibrational temperatures from N2 spectra were obtained for select plasma conditions and ambient pressures. Results further validate that the assumption of optically thin conditions for these electric arc plasmas is not necessary valid, even at low ambient pressure. Breakdown voltage, sustained plasma voltage, power, and energy per pulse were demonstrated to decrease with decreasing pressure. Implementing an array of eight electric arcs circumferentially around the base nea

  17. Turbine Tip Clearance Active Flow Control using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Vanness, Daniel

    2005-11-01

    A low-speed linear cascade was used to examine the tip gap leakage flow and leakage vortex that exists within the low pressure turbine stage of a gas-turbine engine. The cascade array is composed of nine Pratt & Whitney ``PakB" blades, with the center blade having a variable tip gap up to five percent chord. Reynolds numbers based on axial chord varied from 10^4 to 10^5. Static pressure taps located at the midspan and near the tip of the blade were used to characterize the blade pressure distribution. A five-hole probe was also traversed in the downstream blade wake to ascertain velocity vectors and total pressure loss. Flow control in the form of a single-dielectric-barrier plasma actuator mounted on the blade tip was used to alter the leakage vortex by acting on the blade tip separation bubble, the blade tip shear layer instability, or the gap flow jet instability through the production of high frequency unsteady disturbances. The flow was documented through measurements with and without flow control for varying tip gaps and Reynolds numbers. The effect of the actuation on the tip leakage vortex and efficiency are investigated.

  18. Real time control of the plasma current and elongation in tokamaks using ECRH actuators

    Microsoft Academic Search

    J. I. Paley; S. Coda

    2007-01-01

    Real time control of the plasma elongation and plasma current using electron cyclotron resonance heating (ECRH) actuators has been demonstrated on TCV. Tokamak plasmas may be elongated by off-axis ECRH. The associated flattening of the current density profile increases the plasma's vertical stability, enabling higher elongations to be obtained, at lower currents than would be possible in Ohmic conditions. Successful

  19. Design and analysis of a novel flexure-based XY micro-positioning stage driven by electromagnetic actuators

    Microsoft Academic Search

    Shunli Xiao; Yangmin Li; Xinhua Zhao

    2011-01-01

    The paper presents the design and analysis of a novel compliant flexure-based totally decoupled XY micro- positioning stage which is driven by electromagnetic actuators. The stage is constructed with a very simple structure by employing double parallelogram flexures and four contactless electromagnetic force actuators. The kinematics and dynamic modeling of the mechanical system of the stage are conducted by resorting

  20. Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator

    SciTech Connect

    Nishida, Hiroyuki [Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Abe, Takashi [Institute of Space and Astronautical Science, JAXA, Sagamihara, Kanagawa 229-8510 (Japan)

    2011-07-01

    Time evolution of the discharge plasma in the dielectric barrier discharge (DBD) plasma actuator was simulated by the simple fluid model in which the electron and single positive ion species were considered. The characteristics of the discharge plasma evolution were investigated in detail, and the following results were obtained. When the positive-going voltage is applied, the streamer discharge is formed periodically. The periodically formed streamer expands from the exposed electrode, and its length becomes longer than the previous one. Periodic breakdown of the gas and step-by-step plasma expansion are also observed during the negative-going voltage; however, the streamer is not formed and the breakdown frequency is much higher. The simulation results with a triangular applied voltage waveform show the same characteristics as observed in the experiment; large discharge current spikes are observed during both the positive- and negative-going voltage phase, and the plasma in the negative-going voltage phase expands more smoothly than that in the positive phase because of its higher breakdown frequency. It was shown that even the simple numerical model could provide valuable insights into the physics of DBD plasma actuator; this indicates that the positive ions and electrons play a prominent role in determining the general characteristics of the plasma evolution.

  1. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    2013-10-01

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  2. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  3. Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Akansu, Y. E.; Karakaya, F.; ?anl?soy, A.

    2013-04-01

    In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. Theinduced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectricthickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied atReynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0°, 5°, 10°, 15° and 20°. The results indicate that up to the 15° attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kVpp voltage was insufficient to reattach the flow at 20° angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.

  4. Progress of Laser-Driven Plasma Accelerators

    SciTech Connect

    Nakajima, Kazuhisa [High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2007-07-11

    There is a great interest worldwide in plasma accelerators driven by ultra-intense lasers which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world.Harnessing the recent advance of ultra-intense ultra-short pulse lasers, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale, so called ''dream beams on a table top'', which represents monoenergetic electron beams from laser wakefield accelerators and GeV acceleration by capillary plasma-channel laser wakefield accelerators. This lecture reviews recent progress of results on laser-driven plasma based accelerator experiments to quest for particle acceleration physics in intense laser-plasma interactions and to present new outlook for the GeV-range high-energy laser plasma accelerators.

  5. ACTIVE CONTROL OF NEAR-WALL TURBULENCE WITH PERIODIC FORCING BY PLASMA ACTUATOR

    E-print Network

    Kasagi, Nobuhide

    undertaken to reduce skin friction drag by applying spatially periodic forcing in the near wall region of a turbulent channel flow with micro plasma actuators. Measurements are made by a laser Doppler velocimeter

  6. Variable Structure Model for Flow-Induced Tonal Noise Control with Plasma Actuators

    E-print Network

    Huang, Xun

    ,14] demonstrated the use of plasma actuators for attenuating cavity tonal noise that is similar to landing gear bay motion to the surrounding neutral gas that can serve flow control applications [1­11]. Several types

  7. High-lift airfoil trailing edge separation control using a single dielectric barrier discharge plasma actuator

    Microsoft Academic Search

    Jesse Little; Munetake Nishihara; Igor Adamovich; Mo Samimy

    2010-01-01

    Control of flow separation from the deflected flap of a high-lift airfoil up to Reynolds numbers of 240,000 (15 m\\/s) is explored\\u000a using a single dielectric barrier discharge (DBD) plasma actuator near the flap shoulder. Results show that the plasma discharge\\u000a can increase or reduce the size of the time-averaged separated region over the flap depending on the frequency of actuation.

  8. Inductive currents in an rf driven plasma

    SciTech Connect

    Kinsey, J.; Ehst, D.A.

    1991-08-01

    Inductive effects are included in a self-consistent current drive model for axisymmetric tokamak plasmas used in the two-dimensional current drive/MHD equilibrium code, RIP. Previous simulations of current driven equilibria allowed for the steady-state calculation of bootstrap and RF currents. The addition of an inductive current is applied to enhance accurate design and interpretation of tokamak experiments. A convenient expression for the ohmic resistance in a tokamak plasma is derived to aid in the design of reactor grade MHD equilibria. 7 refs., 3 figs., 1 tab.

  9. Active Joint Mechanism Driven by Multiple Actuators Made of Flexible Bags: A Proposal of Dual Structural Actuator

    PubMed Central

    Inou, Norio

    2013-01-01

    An actuator is required to change its speed and force depending on the situation. Using multiple actuators for one driving axis is one of the possible solutions; however, there is an associated problem of output power matching. This study proposes a new active joint mechanism using multiple actuators. Because the actuator is made of a flexible bag, it does not interfere with other actuators when it is depressurized. The proposed joint achieved coordinated motion of multiple actuators. This report also discusses a new actuator which has dual cylindrical structure. The cylinders are composed of flexible bags with different diameters. The joint torque is estimated based on the following factors: empirical formula for the flexible actuator torque, geometric relationship between the joint and the actuator, and the principle of virtual work. The prototype joint mechanism achieves coordinated motion of multiple actuators for one axis. With this motion, small inner actuator contributes high speed motion, whereas large outer actuator generates high torque. The performance of the prototype joint is examined by speed and torque measurements. The joint showed about 30% efficiency at 2.0?Nm load torque under 0.15?MPa air input. PMID:24385868

  10. Wave-driven Countercurrent Plasma Centrifuge

    SciTech Connect

    A.J. Fetterman and N.J. Fisch

    2009-03-20

    A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the ? channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

  11. Numerical simulation of a plasma actuator based on ion transport

    SciTech Connect

    Yamamoto, Seiya; Fukagata, Koji [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)] [Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522 (Japan)

    2013-06-28

    Two-dimensional numerical simulation of ion transport and flow around a single dielectric barrier discharge plasma actuator (PA) is performed. Spatial distributions of ions and electrons as well as their time evolution are obtained by solving the transport equations of monovalent positive ions, monovalent negative ions, and electrons. Voltage and frequency of the driving alternating-current signal are assumed to be 8 kV and 5 kHz, respectively. Special focus is laid upon the effect of voltage gradient dV/dt on the magnitude of the body force. The validity of steady force models often used in flow simulation is also examined. The simulation results show that the magnitude of the body force induced by the PA increases as the voltage gradient dV/dt increases and its increase rate becomes milder at higher voltage. The mechanism of body force generation is explained from the time evolution of number density fields of ions and electrons. A comparison between flow simulations using a time-resolved body force and its time-averaged counterpart demonstrates that the time-averaged model gives sufficiently accurate results when the time scale of the flow is more than 30 times greater than that of the PA.

  12. Abstract--A cable-driven, rotary Series Elastic Actuator named MARIONET (Moment arm Adjustment for Remote

    E-print Network

    MacIver, Malcolm A.

    Abstract-- A cable-driven, rotary Series Elastic Actuator named MARIONET (Moment arm Adjustment, and in future versions, the ability to span multiple joints. This cable-driven, compliant mechanism should prove important limitations. We conclude with potential applications of this type of mechanism. I. INTRODUCTION

  13. Modeling and control of a novel X-Y parallel piezoelectric-actuator driven nanopositioner.

    PubMed

    Liu, Pengbo; Yan, Peng; Zhang, Zhen; Leng, Tongtong

    2014-11-24

    In this paper, a novel X-Y parallel piezoelectric-actuator driven nanopositioner is studied from the perspectives of design optimization, dynamical modeling, as well as controller synthesis for high precision positioning. FEM (Finite Element Method) and dynamical modeling are provided to analyze the mechatronic structure of the proposed two-dimensional nano-stage, where the system model, including the hysteresis loop, is derived analytically and further verified experimentally. A robust control architecture incorporating an H? controller and an anti-windup compensator is then developed to deal with the hysteresis and saturation nonlinearities of the piezoelectric actuators. Real time experiments on the nano-stage platform demonstrate good robustness, high precision positioning and tracking performance, as well as recovery speed in the presence of saturation. PMID:25467308

  14. Bio-inspired Polymer Composite Actuator and Generator Driven by Water Gradients

    PubMed Central

    Ma, Mingming; Guo, Liang; Anderson, Daniel G.; Langer, Robert

    2013-01-01

    Here we describe the development of a water-responsive polymer film; combining both a rigid matrix (polypyrrole) and a dynamic network (polyol-borate), strong and flexible polymer films were developed that can exchange water with the environment to induce film expansion and contraction, resulting in rapid and continuous locomotion. The film actuator can generate contractile stress up to 27 MPa, lift objects 380 times heavier than itself, and transport cargo 10 times heavier than itself. We have assembled a generator by associating this actuator with a piezoelectric element. Driven by water gradients, this generator outputs alternating electricity at ?0.3 Hz, with a peak voltage of ?1.0 V. The electrical energy is stored in capacitors that could power micro- and nano-electronic devices. PMID:23307738

  15. A multi-responsive water-driven actuator with instant and powerful performance for versatile applications

    PubMed Central

    Mu, Jiuke; Hou, Chengyi; Zhu, Bingjie; Wang, Hongzhi; Li, Yaogang; Zhang, Qinghong

    2015-01-01

    Mechanical actuators driven by water that respond to multiple stimuli, exhibit fast responses and large deformations, and generate high stress have potential in artificial muscles, motors, and generators. Meeting all these requirements in a single device remains a challenge. We report a graphene monolayer paper that undergoes reversible deformation. Its graphene oxide cells wrinkle and extend in response to water desorption and absorption, respectively. Its fast (~0.3?s), powerful (>100?MPa output stress, 7.5 × 105?N kg?1 unit mass force), and controllable actuation can be triggered by moisture, heat, and light. The graphene monolayer paper has potential in artificial muscles, robotic hands, and electromagnetic-free generators. PMID:25826443

  16. Bio-Inspired Polymer Composite Actuator and Generator Driven by Water Gradients

    NASA Astrophysics Data System (ADS)

    Ma, Mingming; Guo, Liang; Anderson, Daniel G.; Langer, Robert

    2013-01-01

    Here we describe the development of a water-responsive polymer film. Combining both a rigid matrix (polypyrrole) and a dynamic network (polyol-borate), strong and flexible polymer films were developed that can exchange water with the environment to induce film expansion and contraction, resulting in rapid and continuous locomotion. The film actuator can generate contractile stress up to 27 megapascals, lift objects 380 times heavier than itself, and transport cargo 10 times heavier than itself. We have assembled a generator by associating this actuator with a piezoelectric element. Driven by water gradients, this generator outputs alternating electricity at ~0.3 hertz, with a peak voltage of ~1.0 volt. The electrical energy is stored in capacitors that could power micro- and nanoelectronic devices.

  17. Bio-inspired polymer composite actuator and generator driven by water gradients.

    PubMed

    Ma, Mingming; Guo, Liang; Anderson, Daniel G; Langer, Robert

    2013-01-11

    Here we describe the development of a water-responsive polymer film. Combining both a rigid matrix (polypyrrole) and a dynamic network (polyol-borate), strong and flexible polymer films were developed that can exchange water with the environment to induce film expansion and contraction, resulting in rapid and continuous locomotion. The film actuator can generate contractile stress up to 27 megapascals, lift objects 380 times heavier than itself, and transport cargo 10 times heavier than itself. We have assembled a generator by associating this actuator with a piezoelectric element. Driven by water gradients, this generator outputs alternating electricity at ~0.3 hertz, with a peak voltage of ~1.0 volt. The electrical energy is stored in capacitors that could power micro- and nanoelectronic devices. PMID:23307738

  18. Turbulent Boundary Layer Separation Control on a Convex Ramp using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Schatzman, David M.

    2005-11-01

    This work is focused toward the development of active feedback control of turbulent boundary layer separation from a convex ramp surface. The work reported here is performed in a subsonic wind tunnel facility and utilizes single dielectric barrier discharge plasma actuators for separation control. Smoke and oil surface flow visualization are used to characterize the separation in the absence of actuation. The surface mounted plasma actuators are positioned upstream of the flow separation locations. Plasma-induced blowing transfers additional momentum to the boundary layer along the ramp surface and has a beneficial effect on flow reattachment. Experimental results are presented which demonstrate the effects of both steady and unsteady actuation. The effectiveness of the active flow control is documented through surface pressure measurements, LDV measurements, and downstream wake surveys.

  19. Effect of dielectric barrier discharge plasma actuators on non-equilibrium hypersonic flows

    NASA Astrophysics Data System (ADS)

    Bhatia, Ankush; Roy, Subrata; Gosse, Ryan

    2014-10-01

    A numerical study employing discontinuous Galerkin method demonstrating net surface heat reduction for a cylindrical body in Mach 17 hypersonic flow is presented. This application focuses on using sinusoidal dielectric barrier discharge plasma actuators to inject momentum near the stagnation point. A 5 species finite rate air chemistry model completes the picture by analyzing the effect of the actuator on the flow chemistry. With low velocity near the stagnation point, the plasma actuator sufficiently modifies the fluid momentum. This results in redistribution of the integrated surface heating load on the body. Specifically, a particular configuration of normally pinching plasma actuation is predicted to reduce the surface heat flux at the stagnation point. An average reduction of 0.246% for the integrated and a maximum reduction of 7.68% are reported for the surface heat flux. The temperature contours in the fluid flow (with maximum temperature over 12 000 K) are pinched away from the stagnation point, thus resulting in reduced thermal load. Plasma actuation in this configuration also affects the species concentration distribution near the wall, in addition to the temperature gradient. The combined effect of both, thus results in an average reduction of 0.0986% and a maximum reduction of 4.04% for non-equilibrium calculations. Thus, this study successfully demonstrates the impact of sinusoidal dielectric barrier discharge plasma actuation on the reduction of thermal load on a hypersonic body.

  20. Comparison of plasma treatment and sandblast preprocessing for IPMC actuator

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Chen, Hualing; Wang, Yanjie; Wang, Yongquan; Jia, Shuhai

    2014-03-01

    As a new kind of ionic-driven smart materials, ionic polymer metal composite (IPMC ) is normally fabricated by depositing noble metal (gold, platinum, palladium etc.) on both sides of base membrane (Nafion, Flemion etc.) and shows large bending deflection under low voltage. In the process of fabricating IPMC, surface roughening of base membrane has a significant effect on the performance of IPMC. At present, there are many ways to roughen the base membrane, including physical and chemical ways. In this paper, we analyze the effects of different surface treatment time by plasma etching on surface resistance and mechanical properties of IPMCs fabricated by the treated base membranes. Experimental results show that the base membrane treated by plasma etching displays uniform surface roughness, consequently reducing IPMC's surface resistance effectively and forming more uniform and homogeneous external and penetrative electrodes. However, due to the use of reactive gas, the plasma treatment leads to complex chemical reaction on Nafion surface, changing element composition and material properties and resulting in the performance degradation of IPMC. And sandblast way should be adopted and improved without any changes on element and material structure.

  1. An innovative ultra-capacitor driven shape memory alloy actuator with an embedded control system

    NASA Astrophysics Data System (ADS)

    Li, Peng; Song, Gangbing

    2014-08-01

    In this paper, an innovative ultra-capacitor driven shape memory alloy (SMA) actuator with an embedded control system is proposed targeting high power high-duty cycle SMA applications. The ultra-capacitor, which is capable of delivering massive amounts of instantaneous current in a compact dimension for high power applications, is chosen as the main component of the power supply. A specialized embedded system is designed from the ground up to control the ultra-capacitor driven SMA system. The control of the ultra-capacitor driven SMA is different from that of a regular constant voltage powered SMA system in that the energy and the voltage of the ultra-capacitor decrease as the system load increases. The embedded control system is also different from a computer-based control system in that it has limited computational power, and the control algorithm has to be designed to be simple while effective so that it can fit into the embedded system environment. The problem of a variable voltage power source induced by the use of the ultra-capacitor is solved by using a fuzzy PID (proportional integral and derivative) control. The method of using an ultra-capacitor to drive SMA actuators enabled SMA as a good candidate for high power high-duty cycle applications. The proposed embedded control system provides a good and ready-to-use solution for SMA high power applications.

  2. Force generation due to three-dimensional plasma discharge on a conical forebody using pulsed direct current actuators

    E-print Network

    Roy, Subrata

    Force generation due to three-dimensional plasma discharge on a conical forebody using pulsed Understanding the behavior of three-dimensional plasmas around a pulsed dc actuator can be useful for its direct current actuators Kunwar Pal Singh and Subrata Roya Computational Plasma Dynamics Laboratory

  3. Linearization of a two-axis MEMS scanner driven by vertical comb-drive actuators

    NASA Astrophysics Data System (ADS)

    Tsai, Jui-che; Lu, Li-Cheng; Hsu, Wei-Chi; Sun, Chia-Wei; Wu, Ming C.

    2008-01-01

    A driving scheme using a pair of differential voltages (Vx, Vy) over a bias voltage is proposed to linearize the dc characteristic (angle versus voltage) of a two-axis MEMS scanner. The micromirror has a gimbal-less structure and is driven by vertical comb-drive actuators in conjunction with a leverage mechanism. At an optimal bias voltage of 53 V, a linear optical scan range of ±3.2° is achieved experimentally in both the x and y directions with the differential voltages ranging from -10 V to + 10 V.

  4. Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.

    2012-01-01

    This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.

  5. Optical and electrical characterization of a surface dielectric barrier discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Biganzoli, I.; Barni, R.; Riccardi, C.; Gurioli, A.; Pertile, R.

    2013-04-01

    An experimental characterization of the properties of asymmetric surface dielectric barrier discharges used as plasma actuators was performed. Optical emission spectroscopy was used to measure the radiated power and some plasma parameters such as the electron and vibrational temperature. Electrical characterization of the discharge was executed by recording individual current pulses with high temporal resolution, and collecting a large dataset of these events. Statistical analysis performed on them allowed one to correlate microdischarge (MD) properties with the voltage phase and to spot differences arising from the actual breakdown mechanism in such asymmetric configurations. In particular, the asymmetry between the two different half-cycles of the discharges was characterized, and it was found that it directly influences plasma actuator efficiency. Differences arising in the multiplicity, amplitude and temporal duration of the MDs were investigated. Some effects connected with the dielectric material and high voltage supply properties were evaluated and correlated with the induced velocity provided by the plasma actuators.

  6. Biomimetic cilia arrays - fabrication, magnetic actuation, and driven fluid transport phenomena

    NASA Astrophysics Data System (ADS)

    Shields, Adam

    The cilium is one of biology's most basic functional nanostructures, present on nearly every cell and increasingly realized as vital to many aspects of human health. A fundamental reason for the ubiquity of cilia is their ability to effectively interact with fluids at the microscale, where the Reynolds number is low and thus inertia is irrelevant. This ability makes cilia an attractive and popular candidate for an engineered biomimic with potential applications in microfluidics and sensing. In addition, biological ciliated systems are difficult to study for many reasons, and so I demonstrate how a functional biomimetic system can also serve as a model platform for highly controlled studies of biologically relevant, cilia-driven hydrodynamics. Using the template-based microfabrication of a magnetic nanoparticle/polymer composite, I fabricate arrays of magnetically actuated biomimetic cilia at the scale of their biological analogues. I will discuss this fabrication technique and the magnetic actuation of these arrays to mimic the beat of biological cilia. I also report on the nature of the fluid flows driven by the cilia beat, and demonstrate how these cilia arrays can simultaneously generate long-range fluid transport and mixing in distinct fluid flow regimes. Finally, I present these results within the context of canonical hydrodynamics problems and discuss the implications for biological systems, such as the motile cilia recently discovered in the embryonic node.

  7. Noise control of subsonic cavity flows using plasma actuated receptive channels

    NASA Astrophysics Data System (ADS)

    Das Gupta, Arnob; Roy, Subrata

    2014-12-01

    We introduce a passive receptive rectangular channel at the trailing edge of an open rectangular cavity to reduce the acoustic tones generated due to coherent shear layer impingement. The channel is numerically tested at Mach 0.3 using an unsteady three-dimensional large eddy simulation. Results show reduction in pressure fluctuations in the cavity due to which sound pressure levels are suppressed. Two linear dielectric barrier discharge plasma actuators are placed inside the channel to enhance the flow through it. Specifically, acoustic suppression of 7?dB was obtained for Mach 0.3 flow with the plasma actuated channel. Also, the drag coefficient for the cavity reduced by over three folds for the channel and over eight folds for the plasma actuated channel. Such a channel can be useful in noise and drag reduction for various applications, including weapons bay, landing gear and branched piping systems.

  8. Phase effect on flow control for dielectric barrier plasma actuators

    SciTech Connect

    Singh, K. P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

    2006-07-03

    Active control of flow has a wide range of applications. Specifically, mitigation of detachment due to the weakly ionized gas flow past a flat plate at an angle of attack is studied using two asymmetric sets of electrode pairs kept at a phase lag. The equations governing the dynamics of electrons, helium ions, and neutrals are solved self-consistently with charge-Poisson equation. The electrodynamic forces produced by two actuators largely depend on the relative phase between the potentials applied to rf electrodes and distance between them. A suitable phase and an optimum distance exist between two actuators for effective separation control.

  9. Comparisons of Force Measurement Methods for DBD Plasma Actuators in Quiescent Air

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

    2009-01-01

    We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators with cylindrical exposed electrodes, as the electrode diameter decrease the force efficiencies increase much faster than a previously reported linear trend. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. Actuators with rectangular cross-section exposed electrodes do not show the same rapid increase at small thicknesses. We have also shown that the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

  10. Performance Envelope of Flow Velocity Induced by a Single OAUGDP^ Electrohydrodynamic (EHD) Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Reece Roth, J.

    2005-10-01

    Electrohydrodynamic (EHD) plasma actuators using the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP^) are emerging as a promising aerodynamic flow control technology.^1 It has been found that a single plasma actuator on the leading edge of a NACA-0015 airfoil increased its stall angle from 15^o to 21^o at free-steam flow velocities up to 75 m/s,^2 promising flow control applications at aircraft take-off and landing speeds. We are conducting a research program to maximize the induced flow velocity and minimize the power consumption of plasma actuators by adjusting the electrode width, width ratio, gap distance, dielectric thickness, and dielectric material.^3 In this paper, we report the induced flow velocity and input power to the actuator as functions of the dielectric material, and RF voltage and frequency. We find that quartz and Teflon are superior dielectric materials. ^1J. R. Roth: Physics of Plasmas, Vol. 10, No. 5 (2003). ^2D.F.Opaits et al., 43rd AIAA Aerospace Sciences Meeting Reno, NV, January 10-14, 2005. ^3J. R. Roth, Xin Dai, Jozef Rahel, and D. M. Sherman, 43rd AIAA Aerospace Sciences Meeting Reno, NV, January 10-14, 2005

  11. TEST RESULTS FOR A STIRLING-ENGINE-DRIVEN HEAT-ACTUATED HEAT PUMP BREADBOARD SYSTEM T.M. Moynihan

    E-print Network

    Oak Ridge National Laboratory

    849044 TEST RESULTS FOR A STIRLING-ENGINE-DRIVEN HEAT-ACTUATED HEAT PUMP BREADBOARD SYSTEM T and hydraulic transmission (Figure 2). Engine power is transferred to the i A Free-Piston Stirling Engine prime's performance/ Stirling Engine - Spring operation over the specified operating range, Driver -'i. i, C

  12. Transpiration actuation: the design, fabrication and characterization of biomimetic microactuators driven by the surface tension of water

    Microsoft Academic Search

    Ruba T Borno; Joseph D Steinmeyer; Michel M Maharbiz

    2006-01-01

    We have designed, fabricated and characterized large displacement distributed-force polymer actuators driven only by the surface tension of water. The devices were inspired by the hygroscopic spore dispersal mechanism in fern sporangia. Microdevices were fabricated through a single mask process using a commercial photo-patternable silicone polymer to mimic the mechanical characteristics of plant cellulose. An analytical model for predicting the

  13. A tunable millimeter-wave phase shifter driven by dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Araromi, O. A.; Romano, P.; Rosset, S.; Perruisseau-Carrier, J.; Shea, H. R.

    2014-03-01

    We present the successful operation of the first dielectric elastomer actuator (DEA) driven tunable millimeter-wave phase shifter. The development of dynamically reconfigurable microwave/millimeter-wave (MW/MMW) antenna devices is becoming a prime need in the field of telecommunications and sensing. The real time updating of antenna characteristics such as coverage or operation frequency is particularly desired. However, in many circumstances currently available technologies suffer from high EM losses, increased complexity and cost. Conversely, reconfigurable devices based on DEAs offer low complexity, low electromagnetic (EM) losses and analogue operation. Our tunable phase shifter consists of metallic strips suspended a fixed distance above a coplanar waveguide (CPW) by planar DEAs. The planar actuators displace the metallic strips (10 mm in length) in-plane by 500 ?m, modifying the EM field distribution, resulting in the desired phase shift. The demanding spacing (50 +/-5 ?m between CPW and metallic strips) and parallel alignment criteria required for optimal device operation are successfully met in our device design and validated using bespoke methods. Our current device, approximately 60 mm x 60 mm in planar dimensions, meets the displacement requirements and we observe a considerable phase shift (~95° at 25 GHz) closely matching numerical simulations. Moreover, our device achieves state of the art performance in terms of phase shift per EM loss ~235°/dB (35 GHz), significantly out performing other phase shifter technologies, such as MMIC phase shifters.

  14. Physics of Laser-driven plasma-based acceleration

    SciTech Connect

    Esarey, Eric; Schroeder, Carl B.

    2003-06-30

    The physics of plasma-based accelerators driven by short-pulse lasers is reviewed. This includes the laser wake-field accelerator, the plasma beat wave accelerator, the self-modulated laser wake-field accelerator, and plasma waves driven by multiple laser pulses. The properties of linear and nonlinear plasma waves are discussed, as well as electron acceleration in plasma waves. Methods for injecting and trapping plasma electrons in plasma waves are also discussed. Limits to the electron energy gain are summarized, including laser pulse direction, electron dephasing, laser pulse energy depletion, as well as beam loading limitations. The basic physics of laser pulse evolution in underdense plasmas is also reviewed. This includes the propagation, self-focusing, and guiding of laser pulses in uniform plasmas and plasmas with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Recent experimental results are summarized.

  15. Refinement, validation, and implementation of lumped circuit element model for single dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Mertz, Benjamin E.

    Single dielectric barrier discharge (SDBD) plasma actuators have been applied to a wide variety of aerodynamic flow control applications ranging from stall suppression of airfoils at high angles of attack to reducing tip leakage in jet engine turbine blades. With increased interest in applying plasma actuators to various engineering problems comes the need for an efficient model of the actuators that can be used in a CFD simulation. Prior to the current work, a model was developed that captured many of the spatial and temporal dynamics of the actuator by using circuits consisting of resistors and capacitors to model the plasma and dielectric material. In the current work, this model was refined by casting the governing equations in terms of a generalized coordinate system so that it can be applied to curved surfaces, the grid dependence of the model was eliminated, and the method of applying this model as a boundary condition to the electrostatic equations to calculate the body forces generated by the actuator was studied. This new formulation of the lumped circuit element model was then validated against various experimental observations including force vector orientation needed to produce observed induced flow, the scaling of the force with input voltage, and the directivity patterns and pressure time-series from acoustic measurements. The model was also implemented in a flow solver for the case of an impulsively started actuator on a flat plate and compared to experimental data found in literature. Finally, the utility of the model was demonstrated by simulating the use of actuators for flow control of the flow over a circular cylinder and a modified blunt trailing edge wind turbine blade.

  16. Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

    SciTech Connect

    Chuang Ren

    2013-02-13

    This grant has supported a study of some fundamental problems in current- and flow-driven instabilities in plasmas and their applications in inertial confinement fusion (ICF) and astrophysics. It addressed current-driven instabilities and their roles in fast ignition, and flow-driven instabilities and their applications in astrophysics.

  17. Single mask, simple structure micro rotational motor driven by electrostatic comb-drive actuators

    NASA Astrophysics Data System (ADS)

    Pham, Phuc Hong; Viet Dao, Dzung; Dang, Lam Bao; Sugiyama, Susumu

    2012-01-01

    We report a design and fabrication of a new micro rotational motor (MRM) using silicon micromachining technology with the overall diameter of 2.4 mm. This motor utilizes four silicon electrostatic comb-drive actuators to drive the outer ring (or rotor) through ratchet teeth. The novel design of the anti-reverse structure helps us to overcome the gap problem after deep reactive ion etching of silicon. The MRM was fabricated by using silicon on insulator wafer with the thickness of the device layer being 30 µm and one mask only. The motor was successfully tested for performance. It was driven by periodic voltage with different frequencies ranging from 1 to 50 Hz. The angular velocity of the outer ratchet ring was proportional to the frequency. Moreover, when the driving frequency is lower than 30 Hz, the experiment results perfectly match the theoretical calculation.

  18. Performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator.

    PubMed

    Zhang, Tao; Wang, Qing-Ming

    2006-02-01

    Presented in this paper is the study of the performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator. The application of this micropump is to circulate fuel inside a miniaturized direct methanol fuel cell (DMFC) power system. A theoretical model based on the theory of plates and shells is established to estimate the deflection and the volume change of this micropump without liquid loading. Both finite-element method (FEM) and experimental method are applied to verify this model. Using this model, the optimal design parameters such as the dimensions and the mechanical properties of the micropump can be obtained. Furthermore, various system parameters that will affect the performance of the micropump system with liquid loading are identified and analyzed experimentally. It is expected that this study will provide some vital information for many micropump applications such as fuel delivery in fuel cells, ink jet printers, and biofluidics. PMID:16529122

  19. Adaptive control of rigid-link electrically-driven robots actuated with brushless DC motors

    SciTech Connect

    Bridges, M.M. [Univ. of Michigan, Ann Arbor, MI (United States); Dawson, D.M. [Clemson Univ., SC (United States)

    1994-12-31

    In this paper, we extend the work of [1] and [2] to design an adaptive controller for rigid-link electrically-driven (RLED) robot manipulators specifically actuated with Brushless Direct Current (BLDC) motors. In particular the adaptive controller presented is tailored to handle the multi-link dynamics of a rigid-link robot as opposed to a simple inertial load. Furthermore, the linear electrical dynamics of brushed DC motors used in the development of [1], are replaced with the multiple input nonlinear dynamics of BLDC motors. The result is an adaptive controller that guarantees globally asymptotic convergence of the link position tracking error in spite of parametric uncertainty throughout the entire electro-mechanical model.

  20. Propagating-arc magnetohydrodynamic plasma actuator for directional high-authority flow control in atmospheric air

    NASA Astrophysics Data System (ADS)

    Pafford, Brent; Sirohi, Jayant; Raja, Laxminarayan L.

    2013-12-01

    A propagating-arc magnetohydrodynamic plasma actuator for aerodynamic flow control is reported. The actuator comprises two rail electrodes flush mounted on an aerodynamic surface. A pulsed arc is propelled down the length of the rails by Lorentz forces supported by a self-induced magnetic field. The arc induces a high velocity pulsed air wall jet due to the pushing and entrainment actions. Experiments in quiescent air demonstrate that the plasma arc achieves a peak velocity of around 100 m s-1 and requires a discharge energy on the order of 300 J per pulse. Wind tunnel tests on a 14.5 inch chord airfoil section, at a Reynolds number of 0.45 million show induced flow velocities on the order of 10's m s-1 with significant penetration of the flow actuation effect perpendicular to the wall surface.

  1. Velocity-information-based force-term estimation of dielectric-barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Kriegseis, J.; Schwarz, C.; Tropea, C.; Grundmann, S.

    2013-02-01

    Particle image velocimetry measurements in close proximity to dielectric-barrier discharge plasma actuators are conducted to quantify the momentum transfer of the plasma to the surrounding air flow. Based on these data a comparative analysis of six existing approaches to estimate the induced body force is presented. Integral methods calculate an integral value for the actuator force based on the momentum-balance equation. Insight into the spatial distribution of the body force is provided by differential methods, which are based either on the Navier-Stokes equations or on the vorticity equation. It is demonstrated that the intensity as well as the domain of the force increase with increasing operating power levels. Emphasis is also placed on the issue of self-induced drag. It is shown that 30% of the induced momentum is consumed by wall friction. All results are validated with previously obtained balance force data and luminosity analysis of identical actuators.

  2. Numerical and Experimental Investigation of Plasma Actuator Control of Modified Flat-back Airfoil

    NASA Astrophysics Data System (ADS)

    Mertz, Benjamin; Corke, Thomas

    2010-11-01

    Flat-back airfoil designs have been proposed for use on the inboard portion of large wind turbine blades because of their good structural characteristics. These structural characteristics are achieved by adding material to the aft portion of the airfoil while maintaining the camber of the origional airfoil shape. The result is a flat vertical trailing edge which increases the drag and noise produced by these airfoils. In order to improve the aerodynamic efficiency of these airfoils, the use of single dielectric barrier discharge (SDBD) plasma actuators was investigated experimentally and numerically. To accomplish this, a rounded trailing edge was added to traditional flat-back airfoil and plasma actuators were used symmetrically to control the flow separation casued by the blunt trailing edge. The actuators were used asymmetrically in order to vector the wake and increase the lift produced by the airfoil similar to adding camber.

  3. Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

    2006-01-01

    The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are similar in both small GDTL and larger NASA jets. However, the actuation authority seems to fall short in the larger jet at higher Mach numbers, resulting in decreased amplitude response compared to the small jet, which is attributed at this point to the lack of sufficient number of actuators. The preliminary results seem also to suggest that amplitude of actuation tones is similar in both the small and larger jets.

  4. Capacitances and energy deposition curve of nanosecond pulse surface dielectric barrier discharge plasma actuator.

    PubMed

    Pang, Lei; He, Kun; Di, Dongxu; Zhang, Qiaogen; Liu, Chunliang

    2014-05-01

    Nanosecond pulse surface dielectric barrier discharge (NPSDBD) plasma actuator is preferred to generate aerodynamic actuation which relies on the deposited energy during nanosecond time scale, named as the mechanism of fast thermalization. It is very important to understand the energy deposition process of NPSDBD plasma actuator. In this paper, an equivalent circuit model is presented to describe a typical asymmetric NPSDBD plasma actuator first. Of the three key capacitances in the equivalent circuit, the values of Capacitance C(m) and C(g) can be gotten by the calculation of the electric field, with the method of undetermined coefficients, while the value of Capacitance C(d) is determined from the charge-voltage (Q-V) plot, also called Lissajous figure. It is found that the value of Capacitance C(d) varies with the amplitude of applied pulse voltage, due to the change of the dimension of plasma sheet. Based on the circuit parameters and the measured waveforms of discharge voltage and current, the time varying characteristics of deposited energy can be obtained finally. It is indicated that the calculated results of deposited energy show a good agreement with conventional method. PMID:24880363

  5. American Institute of Aeronautics and Astronautics Novel Multi-Barrier Plasma Actuators for Increased Thrust

    E-print Network

    Roy, Subrata

    American Institute of Aeronautics and Astronautics 1 Novel Multi-Barrier Plasma Actuators by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;American Institute of Aeronautics and Astronautics 2 and 1-20 kHz, respectively. Such a high potential difference weakly ionizes

  6. LES of a Jet Excited by the Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2011-01-01

    The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.

  7. Separation Control from the Flap of a High-Lift Airfoil Using DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Little, Jesse; Nishihara, Munetake; Adamovich, Igor; Samimy, Mo

    2008-11-01

    Control of separation from the flap of a high-lift airfoil using a single dielectric barrier discharge (DBD) plasma actuator has been investigated experimentally. This project is motivated by the desire to replace existing multi-element flap configurations with a single simple flap to allow more efficient high-lift generation. The results show that a single DBD plasma actuator located at the flap shoulder can increase or reduce the size of the time-averaged separation bubble over the flap depending on the frequency of actuation. In the latter case, the lift on the airfoil is increased due to improved circulation around the model, but it does not result in full reattachment on the deflected flap. These findings are consistent with previous research on high-lift airfoil configurations. The work will be expanded by exploring the effect of multiple actuators as well as their geometry and location on the size and structure of the separated region over the flap. This portion of the work will be done with an emphasis on optimizing the relative phase of each actuator and its effect on the separated flow region.

  8. One-equation modeling and validation of dielectric barrier discharge plasma actuator thrust

    NASA Astrophysics Data System (ADS)

    Yoon, Jae-San; Han, Jae-Hung

    2014-10-01

    Dielectric barrier discharge (DBD) plasma actuators with an asymmetric electrode configuration can generate a wall-bounded jet without mechanical moving parts, which require considerable modifications of existing aeronautical objects and which incur high maintenance costs. Despite this potential, one factor preventing the wider application of such actuators is the lack of a reliable actuator model. It is difficult to develop such a model because calculating the ion-electric field and fluid interaction consume a high amount calculation effort during the numerical analysis. Thus, the authors proposed a semi-empirical model which predicted the thrust of plasma actuators with a simple equation. It gave a numeric thrust value, and we implemented the value on a computational fluid dynamics (CFD) solver to describe the two-dimensional flow field induced by the actuator. However, the model had a narrow validation range, depending on the empirical formula, and it did not fully consider environment variables. This study presents an improved model by replacing the empirical formulae in the previous model with physical equations that take into account physical phenomena and environmental variables. During this process, additional operation parameters, such as pressure, temperature and ac waveforms, are newly taken to predict the thrust performance of the actuators with a wider range of existing parameters, the thickness of the dielectric barrier, the exposed electrode, the dielectric constant, the ac frequency and the voltage amplitude. Thrust prediction curves from the model are compared to those of earlier experimental results, showing that the average error is less than 5% for more than one hundred instances of data. As in the earlier work, the predicted thrust value is implemented on a CFD solver, and two-dimensional wall-jet velocity profiles induced by the actuator are compared to the previous experimental results.

  9. The use of plasma actuators for bluff body broadband noise control

    NASA Astrophysics Data System (ADS)

    Li, Yong; Zhang, Xin; Huang, Xun

    2010-08-01

    Experiments were conducted using plasma actuators to control broadband noise generated by a bluff body flow. The motivation behind the study was to explore the potential of plasma actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness of both dielectric barrier discharge and sliding discharge plasma actuators were tested in laboratory environment, using a representative bluff body consisting of a circular cylinder and an oblique strut. Noise measurements were taken in an anechoic chamber using a phased microphone array and far-field microphones. Results showed that the upstream directed plasma forcing, located at ±90 deg on the upstream cylinder with respect to the approaching flow, could effectively attenuate the broadband noise radiated from the wake flow interaction with the downstream strut. With the same AC electrical power consumption, the sliding discharge with additional DC voltage was found to be more effective due to its elongated plasma distribution and higher induced flow momentum. Measurements using particle image velocimetry suggested that the flow speed impinging on the downstream strut was reduced by the upstream plasma forcing, contributing to the reduced noise.

  10. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce [Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  11. Experimental Studies of Magnetically Driven Plasma Jets

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Bland, S. N.; Hall, G. N.; Swadling, G.; Harvey-Thompson, A. J.; Burdiak, G.; de Grouchy, P.; Chittenden, J. P.; Marocchino, A.; Bocchi, M.; Ciardi, A.; Frank, A.; Bott, S. C.

    2011-11-01

    We present experimental results on the formation of supersonic, radiatively cooled jets driven by pressure due to the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which a jet on the axis of a magnetic cavity is collimated by a toroidal magnetic field as it expands into the ambient medium. The jets in the experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets. Additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration allows for the generation of episodic magnetic cavities, suggesting that periodic fluctuations near the source may be responsible for some of the variability observed in astrophysical jets. Preliminary measurements of kinetic, magnetic and Poynting energy of the jets in our experiments are presented and discussed, together with estimates of their temperature and trapped toroidal magnetic field.

  12. Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

    2008-01-01

    We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

  13. Landau damping of a driven plasma wave from laser pulses

    SciTech Connect

    Bu Zhigang [Department of Physics, Shanghai University, Shanghai 200444 (China); Ji Peiyong [Department of Physics, Shanghai University, Shanghai 200444 (China); The Shanghai Key Lab of Astrophysics, Shanghai 200234 (China)

    2012-01-15

    The interaction between a laser pulse and a driven plasma wave with a phase velocity approaching the speed of light is studied, and our investigation is focused on the Gaussian laser pulse. It is demonstrated that when the resonance condition between the plasma wave and the laser pulse is satisfied, the Landau damping phenomenon of the plasma wave originated from the laser pulse will emerge. The dispersion relations for the plasma waves in resonance and non-resonance regions are obtained. It is proved that the Landau damping rate for a driven plasma wave is {gamma}>0 in the resonance region, so the laser pulse can produce an inverse damping effect, namely Landau growth effect, which leads an instability for the plasma wave. The Landau growth means that the energy is transmitted from the laser pulse to the plasma wave, which could be an effective process for enhancing the plasma wave.

  14. Nanosecond-pulsed plasma actuation in quiescent air and laminar boundary layer

    NASA Astrophysics Data System (ADS)

    Correale, G.; Michelis, T.; Ragni, D.; Kotsonis, M.; Scarano, F.

    2014-03-01

    An experimental investigation of the working principles of a nanosecond-pulsed dielectric barrier discharge (ns-DBD) plasma actuator has been conducted. Special emphasis is given on the thermal effects accompanying the rapid deposition of energy associated with this kind of actuation. A ns-DBD plasma actuator has been operated in quiescent air conditions as well as in a flat plate laminar boundary layer, with external flow velocity of 5 and 10 m s-1. Schlieren imaging and particle image velocimetry have been used to characterize the actuation. Additionally, the back-current shunt technique has been used for current measurements, from which energy input (per pulse) is calculated. Cases of 10-, 20- and 50-pulse bursts are tested. Schlieren imaging in still air conditions shows the formation of a high-temperature region in the vicinity of the discharge volume. The spatial extent of the visible ‘hot spot’ depends upon the number of pulses within the burst, following a power law. Schlieren imaging of the span-wise effect of the plasma actuator reveals weak compression waves originating from the loci of discharge filaments. The thermal ‘hot spots’ exhibit significant three-dimensionality. Particle image velocimetry is used to measure the velocity field resulting from the ns-DBDs acting on a laminar boundary layer. The disturbance leads to formation of a Tollmien-Schlichting wave train, with spectral content in good agreement with linear stability theory. It is observed that the group length of the wave train is proportional to the number of pulses within the burst.

  15. Non-linear adaptive robust control of electro-hydraulic systems driven by double-rod actuators

    Microsoft Academic Search

    Bin Yao; Fanping Bu; George T. C. Chiu

    2001-01-01

    This paper studies the high performance robust motion control of electro-hydraulic servo-systems driven by double-rod hydraulic actuators. The dynamics of hydraulic systems are highly non-linear and the system may be subjected to non-smooth and discontinuous non-linearities due to directional change of valve opening, friction and valve overlap. Aside from the non-linear nature of hydraulic dynamics, hydraulic servosystems also have large

  16. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, M. C.; Muggli, Patric; Yakimenko, Vitaly; Babzien, Marcus; Kusche, Karl; Fedurin, Mikhail

    2010-11-01

    Beam-driven plasma wakefield accelerators (PWFA), such as the ``plasma afterburner,'' are a promising approach for significantly increasing the particle energies of conventional accelerators. The study and optimization of PWFA would benefit from an experimental correlation between the parameters of the drive bunch, the accelerated bunch and the corresponding, accelerating plasma wave structure. However, the plasma wave structure has not yet been observed directly in PWFA. We will report our current work on noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) visualization of beam-driven plasma waves. Both techniques employ two laser pulses (probe and reference) co-propagating with the particle drive-beam and its plasma wake. The reference pulse precedes the drive bunch, while the probe overlaps the plasma wave and maps its longitudinal and transverse structure. The experiment is being developed at the BNL/ATF Linac to visualize wakes generated by two and multi-bunch drive beams.

  17. Continuous flow actuation between external reservoirs in small-scale devices driven by surface acoustic waves.

    PubMed

    Dentry, Michael B; Friend, James R; Yeo, Leslie Y

    2014-02-21

    We have designed and characterized a surface acoustic wave (SAW) fluid actuation platform that significantly improves the transmission of sound energy from the SAW device into the fluid in order to obtain enhanced performance. This is in distinct contrast to previous SAW microfluidic devices where the SAW substrate is simply interfaced with a microchannel without due consideration given to the direction in which the sound energy is transmitted into the fluid, thus resulting in considerable reflective and dissipative losses due to reflection and absorption at the channel walls. For the first time, we therefore demonstrate the ability for continuous fluid transfer between independent reservoirs driven by the SAW in a miniature device and report the associated pressure-flow rate relationship, in which a maximum flow rate of 100 ?l min(-1) and pressure of 15 Pa were obtained. The pumping efficiency is observed to increase with input power and, at peak performance, offers an order-of-magnitude improvement over that of existing SAW micropumps that have been reported to date. PMID:24336764

  18. Combining Model-Based and Feature-Driven Diagnosis Approaches - A Case Study on Electromechanical Actuators

    NASA Technical Reports Server (NTRS)

    Narasimhan, Sriram; Roychoudhury, Indranil; Balaban, Edward; Saxena, Abhinav

    2010-01-01

    Model-based diagnosis typically uses analytical redundancy to compare predictions from a model against observations from the system being diagnosed. However this approach does not work very well when it is not feasible to create analytic relations describing all the observed data, e.g., for vibration data which is usually sampled at very high rates and requires very detailed finite element models to describe its behavior. In such cases, features (in time and frequency domains) that contain diagnostic information are extracted from the data. Since this is a computationally intensive process, it is not efficient to extract all the features all the time. In this paper we present an approach that combines the analytic model-based and feature-driven diagnosis approaches. The analytic approach is used to reduce the set of possible faults and then features are chosen to best distinguish among the remaining faults. We describe an implementation of this approach on the Flyable Electro-mechanical Actuator (FLEA) test bed.

  19. Numerical study of boundary layer separation control using magnetogasdynamic plasma actuators

    SciTech Connect

    Kalra, Chiranjeev S.; Shneider, Mikhail N.; Miles, Richard B. [Department of Mechanical and Aerospace Engineering, Applied Physics Group, Princeton University, Princeton, New Jersey 08544 (United States)

    2009-10-15

    In this study, an efficient, time dependent, two-dimensional Navier-Stokes numerical code for shockwave boundary layer interaction in air is developed. Nonthermal surface plasma actuation is evaluated for effective shockwave induced boundary layer separation control within supersonic inlets. Specifically, high speed magnetogasdynamic plasma actuators are of interest. In these, localized ionization is produced close to the wall surface and then the flow is accelerated using strong magnetic fields. To replicate the experiments done at large boundary layer thickness, the code is divided into time independent and time dependent regimes to significantly reduce computation time. Computational results are in good agreement with experiments in terms of the flow structure as shown by Schlieren imaging, acetone planar laser scattering, and the static pressure profile on the test section wall.

  20. Driven plasma rotation in the Compact Auburn Torsatron

    Microsoft Academic Search

    E. Thomas; S. Knowlton; R. Gandy; J. Cooney; D. Pritchard; T. Pruitt

    1998-01-01

    Poloidal plasma rotation has been driven in the Compact Auburn Torsatron (CAT) [R. F. Gandy et al., Fusion Technol. 18, 281 (1990)]. In these studies, a biased electrode is used to establish the rotation. Currents of up to 1 A are injected into hydrogen, helium, and argon plasmas from a biased electrode placed inside of the last closed magnetic flux

  1. Simple and inexpensive current-driven magnetic multipole plasma homogenizer

    Microsoft Academic Search

    P. Machima; M. M. M. Bilek; O. R. Monteiro; I. G. Brown

    2000-01-01

    Magnetic multipole plasma confinement geometries employing permanent magnets are commonly used to confine laboratory plasmas and improve uniformity. Here we describe the design and operation of a particularly simple and low-cost kind of current-driven multipole system that makes use of a similar magnetic field structure but does not require permanent magnets. The magnetic field is generated by current carrying wires

  2. Numerical Simulations of Flow Separation Control in Low-Pressure Turbines using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.

    2007-01-01

    A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been further developed and improved in order to expand its use to complicated actuator geometries. The new modeling approach eliminates the requirement of an empirical charge density distribution shape by using the embedded electrode as a source for the charge density. The resulting model is validated against a flat plate experiment with quiescent environment. The modeling approach incorporates the effect of the plasma actuators on the external flow into Navier Stokes computations as a body force vector which is obtained as a product of the net charge density and the electric field. The model solves the Maxwell equation to obtain the electric field due to the applied AC voltage at the electrodes and an additional equation for the charge density distribution representing the plasma density. The new modeling approach solves the charge density equation in the computational domain assuming the embedded electrode as a source therefore automatically generating a charge density distribution on the surface exposed to the flow similar to that observed in the experiments without explicitly specifying an empirical distribution. The model is validated against a flat plate experiment with quiescent environment.

  3. Shockwave—boundary layer interaction control by plasma aerodynamic actuation: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Sun, Quan; Cui, Wei; Li, Ying-Hong; Cheng, Bang-Qin; Jin, Di; Li, Jun

    2014-07-01

    The potential of controlling shockwave—boundary layer interactions (SWBLIs) in air by plasma aerodynamic actuation is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism.

  4. Airflow control by non-thermal plasma actuators

    Microsoft Academic Search

    Eric Moreau

    2007-01-01

    Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control

  5. Force-free magnetic relaxation in driven plasmas

    Microsoft Academic Search

    Xianzhu Tang; Allen H. Boozer

    2004-01-01

    J. B. Taylor (1974) postulated that the helicity-conserving minimum magnetic energy state is the consequence of plasma self-organization via turbulent relaxation bounded by a magnetic surface. The Taylor state j=lambda B is a force-free plasma with lambda a global constant. For a driven plasma with open flux intercepting the boundary B\\\\cdothat nneq 0, Taylor relaxation is constrained by the Jensen-Chu

  6. Simulation of an asymmetric single dielectric barrier plasma actuator

    SciTech Connect

    Singh, K.P.; Roy, Subrata [Computational Plasma Dynamics Laboratory, Mechanical Engineering, Kettering University, Flint, Michigan 48504 (United States)

    2005-10-15

    Continuity equations governing electron and ion density are solved with Poisson's equation to obtain spatial and temporal profiles of electron density, ion density, and voltage. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field. Electron deposition downstream of the overlap region of the electrode results in formation of a virtual negative electrode that always attracts the charge separation. The value of charge separation e(n{sub i}-n{sub e}) and the force per volume F=e(n{sub i}-n{sub e})E have been obtained near the dielectric surface for the 50th cycle. Domain integration of the force F=e(n{sub i}-n{sub e})E has been obtained for different plasma densities, frequencies, and rf voltage wave forms. The time average of the x force is positive and the y force is negative over the domain; therefore there is an average net force on the plasma in the positive x and negative y directions. This will result in a moving wave of plasma over the dielectric surface in the positive x direction, which can find application in flow control.

  7. Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.

    2012-01-01

    The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.

  8. An instant multi-responsive porous polymer actuator driven by solvent molecule sorption

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Dunlop, John W. C.; Qiu, Xunlin; Huang, Feihe; Zhang, Zibin; Heyda, Jan; Dzubiella, Joachim; Antonietti, Markus; Yuan, Jiayin

    2014-07-01

    Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24?kPa, 20?°C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200?°C, 24?h) and pressing-pressure (100?MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn ‘inert’ objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials.

  9. CNT/conductive polymer composites for low-voltage driven EAP actuators

    NASA Astrophysics Data System (ADS)

    Sugino, Takushi; Shibata, Yoshiyuki; Kiyohara, Kenji; Asaka, Kinji

    2012-04-01

    We investigated the effects of additives incorporated into the electrode layer in order to improve the actuation performance of dry-type carbon nanotube (CNT) actuators. Especially, the addition of conductive nano-particles such as polyaniline (PANI) and polypyrrole (PPy) improves actuation performance very much rather than the addition of nonconductive nano-particles such as mesoprous silica (MCM-41 type). In this paper, we studied on the influences of applied voltage, species of ionic liquid (IL), amounts of IL, thickness of actuator to optimize actuation performance. Imidazolium type ionic liquids with three different anions, that is, 1-ethyl-3-methylimidazolium (EMI) as a cation and tetrafluoroborate (BF4), trifluoromethanesulfonate (OTf), and bis(trifluoromethanesulfonyl)imide (TFSI) as anions were chosen in this study. EMIBF4 is the most suitable IL for our CNT actuator including PANI in the electrode layer. We tuned the amount of IL and the thickness of actuator. As a result, the strain was improved to be 2.2% at 0.1 Hz by applying the voltage of 2.5 V. This improved value is almost 2 times larger than our previous results. We also show the potential of improved CNT actuators for a thin and light Braille display.

  10. Experimental Application of Piezoelectric Actuator-Driven Pulsed Water Jets in Retinal Vascular Surgery

    PubMed Central

    Kunikata, Hiroshi; Tanaka, Yuji; Aizawa, Naoko; Nakagawa, Atsuhiro; Tominaga, Teiji; Nakazawa, Toru

    2014-01-01

    Purpose To report on the effectiveness and safety of an ophthalmic piezoelectric actuator-driven pulsed water jet (ADPJ) system adapted for intraocular use. Methods First, we determined the highest ADPJ flow rate that did not cause an unsafe rise in intraoperative intraocular pressure (IOP) in rabbits (n = 4). Next, we determined the most effective ADPJ frequency (in hertz) at that flow rate. Finally, we visualized the ADPJ stream, measured its pressure, and determined the minimum voltage and distance between the ADPJ needle and retinal veins to induce intravenous displacement of the blood column (DBC) through massage of the outer retinal vessels (n = 3) while not causing retinal tearing or hemorrhage. Results We found that a 0.05 mL/min ADPJ flow rate caused IOP to rise above 40 mm Hg after 1 minute, but that at 0.025 mL/min, IOP stayed below 40 mm Hg even after 3 minutes. Moreover, we found that a 0.025 mL/min ADPJ stream was stable at a pulse frequency of 10 Hz and that at this flow rate/frequency the ADPJ pressure was closely correlated with the applied voltage (P < 0.001, r2 = 0.9991). The minimum voltage and distance to achieve intravenous DBC without causing retinal tearing or hemorrhage were 40 V and 0.5 mm, respectively. Conclusions With an appropriate flow rate and surgical time, ADPJ successfully induced massage of the retinal vessels and intravenous DBC while maintaining safe IOP and not causing retinal complications. Translational Relevance The ADPJ system has promise as a safe and minimally invasive instrument for the intraocular surgical treatment of human retinal vascular diseases. PMID:25674359

  11. Magnetized Target Fusion Driven by Plasma Liners

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Eskridge, Richard; Smith, James; Lee, Michael; Richeson, Jeff; Schmidt, George; Knapp, Charles E.; Kirkpatrick, Ronald C.; Turchi, Peter J.; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). For the successful implementation of the scheme, plasma jets of the requisite momentum flux density need to be produced. Their transport over sufficiently large distances (a few meters) needs to be assured. When they collide and merge into a liner, relative differences in velocity, density and temperature of the jets could give rise to instabilities in the development of the liner. Variation in the jet properties must be controlled to ensure that the growth rate of the instabilities are not significant over the time scale of the liner formation before engaging with the target plasma. On impact with the target plasma, some plasma interpenetration might occur between the liner and the target. The operating parameter space needs to be identified to ensure that a reasonably robust and conducting contact surface is formed between the liner and the target. A mismatch in the "impedance" between the liner and the target plasma could give rise to undesirable shock heating of the liner leading to increased entropy (thermal losses) in the liner. Any irregularities in the liner will accentuate the Rayleigh-Taylor instabilities during the compression of the target plasma by the liner.

  12. Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array

    NASA Astrophysics Data System (ADS)

    Neretti, Gabriele; Cristofolini, Andrea; Borghi, Carlo A.

    2014-04-01

    The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0-6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

  13. Beam-driven acceleration in ultra-dense plasma media

    NASA Astrophysics Data System (ADS)

    Shin, Young-Min

    2014-09-01

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 1025 m-3 and 1.6 × 1028 m-3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers ˜20% higher acceleration gradient by enlarging the channel radius (r) from 0.2 ?p to 0.6 ?p in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g., nanotubes) of high electron plasma density.

  14. Analytical Model for the Microwave Driven Double ICP Plasma Jet

    NASA Astrophysics Data System (ADS)

    Arshadi, Ali; Eremin, Denis; Mussenbrock, Thomas; Brinkmann, Ralf Peter; Awakowicz, Peter; Porteanu, Horia-Eugen; Gesche, Roland; Wandel, Klaus

    2012-10-01

    For many technical applications, microwave driven plasma jets are possible alternatives to conventional RF plasma sources. Their construction is uncomplicated and they have the advantages of small size and large electrical efficiency. The microwave driven double ICP plasma jet is a recently developed variant. The core of the device is a cavity resonator with a resonance frequency close to 2 GHz. In good approximation, the resonator can be described as a circuit of two cylindrical one-turn coils parallel to a planar capacitor. Inside the coils are ceramic tubes which contain the plasma. Electromagnetic fields in the bulk and sheath reagion can be computed based on Maxwell's equations and the cold plasma model considering boundary conditions and the electric field due to the source on metalic cavity. A comparison of the simulation results with experimental data is performed.

  15. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    SciTech Connect

    Zgadzaj, Rafal; Downer, Michael C. [University of Texas, Austin, TX 78712 (United States); Muggli, Patric [Univesity of Southern California, Los Angeles, CA 90089 (United States); Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus [Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2010-11-04

    Bunch driven plasma wakefield accelerators (PWFA), such as the 'plasma afterburner', are a promising emerging method for significantly increasing the energy output of conventional particle accelerators. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two and multi-bunch drive beams.

  16. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-01

    Bunch driven plasma wakefield accelerators (PWFA), such as the "plasma afterburner," are a promising emerging method for significantly increasing the energy output of conventional particle accelerators [1]. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) [2] and Holographic (FDH) [3] diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two [4] and multi-bunch [5] drive beams.

  17. Magnetized Target Fusion Driven by Plasma Liners

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Cassibry, Jason; Eskridge, Richard; Kirkpatrick, Ronald C.; Knapp, Charles E.; Lee, Michael; Martin, Adam; Smith, James; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    For practical applications of magnetized target fusion, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Quasi-spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a quasi-spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). Theoretical analysis and computer modeling of the concept are presented. It is shown that, with the appropriate choice of the flow parameters in the liner and the target, the impact between the liner and the target plasma can be made to be shockless in the liner or to generate at most a very weak shock in the liner. Additional information is contained in the original extended abstract.

  18. Design and analysis of hydraulically driven actuation system For a parabolic solar trough

    E-print Network

    Popovi?, Katarina, S.B. Massachusetts Institute of Technology

    2013-01-01

    This thesis documents Katarina Popovic's contribution to the design of hydraulic cylinder actuation system for day to day solar trough sun tracking, a semester long project within 2.752 Development of Mechanical Products ...

  19. Experimental investigation of filamentary and non-filamentary regimes in a surface dielectric barrier plasma actuator

    NASA Astrophysics Data System (ADS)

    Biganzoli, I.; Barni, R.; Gurioli, A.; Pertile, R.; Riccardi, C.

    2014-11-01

    Asymmetric surface dielectric barrier discharges fed by a high-voltage sinusoidal low-frequency drive are currently proposed as plasma actuators, because they can induce a directed airflow in the gas surrounding the surface. However, it is known that the induced airflow speed can not be increased as much as desired because a saturation is generally observed for sufficient high voltages. In this paper we show that when the voltage amplitude is increased enough the discharge does not appear uniform any more, but a pattern of plasma filaments becomes evident. We have thus studied plasma properties in both filamentary and nonfilamentary regimes, by means of a Rogowski coil for the measurement of the current associated to the discharge. This is interesting in order to understand what happens at high voltages, when the saturation of the induced airflow speed occurs.

  20. Test results for a Stirling-engine-driven heat-actuated heat pump breadboard system

    Microsoft Academic Search

    T. M. Moynihan; R. A. Ackermann

    1984-01-01

    A Free-Piston Stirling Engine prime mover has been coupled to a Rankine-cycle, linearresonant refrigerant compressor through a diaphragm-actuated hydraulic coupling. The system, developed at Mechanical Technology Incorporated, is a heat-actuated heat pump (HAHP) that was developed for residential applications. This paper describes the breadboard system, and presents the data obtained during testing the past year. The system was successfully tested

  1. A New Inductively Driven Plasma Generator (IPG) Source

    NASA Astrophysics Data System (ADS)

    Hyde, Truell; Laufer, Rene; Herdrich, Georg; Dropmann, Michael; Peters, Susanne; Matthews, Lorin; Cook, Michael; Schmoke, Jimmy

    2011-11-01

    As part of the partnership between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University and the Institut fur Raumfahrtsysteme (IRS) at the University of Stuttgart, a new design for a modular, inductively driven plasma generator (IPG) source is being developed and tested within CASPER and the IRS. The current IPG design is built on a well-established heritage of modular inductively driven plasma generators designed and operated at IRS. This latest IPG source enables the electrodeless generation of high-enthalpy plasmas and will provide CASPER researchers the ability to operate with various gases at plasma powers of approximately 20 KW. It will also provide minimized field losses and operation over a wide scope of parameters not possible using existing designs requiring flow-controlled stabilization. Both research and technical applications will be discussed.

  2. Magnetized Target Fusion Driven by Plasma Liners

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Kirkpatrick, Ronald C.; Knapp, Charles E.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Magnetized target fusion is an emerging, relatively unexplored approach to fusion for electrical power and propulsion application. The physical principles of the concept are founded upon both inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). It attempts to combine the favorable attributes of both these orthogonal approaches to fusion, but at the same time, avoiding the extreme technical challenges of both by exploiting a fusion regime intermediate between them. It uses a material liner to compress, heat and contain the fusion reacting plasma (the target plasma) mentally. By doing so, the fusion burn could be made to occur at plasma densities as high as six orders of magnitude higher than conventional MCF such as tokamak, thus leading to an approximately three orders of magnitude reduction in the plasma energy required for ignition. It also uses a transient magnetic field, compressed to extremely high intensity (100's T to 1000T) in the target plasma, to slow down the heat transport to the liner and to increase the energy deposition of charged-particle fusion products. This has several compounding beneficial effects. It leads to longer energy confinement time compared with conventional ICF without magnetized target, and thus permits the use of much lower plasma density to produce reasonable burn-up fraction. The compounding effects of lower plasma density and the magneto-insulation of the target lead to greatly reduced compressional heating power on the target. The increased energy deposition rate of charged-particle fusion products also helps to lower the energy threshold required for ignition and increasing the burn-up fraction. The reduction in ignition energy and the compressional power compound to lead to reduced system size, mass and R&D cost. It is a fusion approach that has an affordable R&D pathway, and appears attractive for propulsion application in the nearer term.

  3. Current Transport in Tokamak Plasmas with Neutral Beam Driven Currents

    NASA Astrophysics Data System (ADS)

    Forest, C. B.

    1997-11-01

    Recent neutral beam current drive (NBCD) experiments on DIII--D have focused on independently measuring the conductivity and neutral beam driven currents to investigate the physical processes limiting noninductive ramp-up via NBCD. Detailed comparisons with theory indicate that frequently the current transport models are inadequate to describe the experimental results. As with studies of particle and heat transport, there is an ambiguity which arises when attempting to separately determine the sources and transport coefficients; in this problem, the source is the noninductively driven current and the transport coefficient is the plasma resistivity. These quantities can only be independently resolved through transient techniques. Using determination of the local current density and parallel electric field from internal measurements of the time evolving poloidal magnetic field,(C.B. Forest, et.al.), Phys. Rev. Lett. (1995). a measurement of the electrical skin depth (and thus the conductivity) has been made by modulating the plasma current and measuring the amplitude and phase of the perturbed electric field. Comparisons of the measured conductivity with neoclassical theory offer a new technique for characterizing the MHD activity. Under the assumption of neoclassical resistivity, measurements of the neutral beam driven current profile have been made for a large range of plasma parameters and compared with theory. Under conditions in which tearing modes are present, the neutral beam driven current is anomalously low (by up to 80%) when compared to TRANSP and ONETWO calculations of neutral beam driven currents.(C.B. Forest, et.al.), to be published in Phys. Rev. Lett. July 7, 1997. This reduction in neutral beam driven currents due to the soft ? limit imposed by neoclassical MHD illustrates the need for including islands in the modeling, and it places a strong constraint on plasma current ramp-up by neutral beam injection. Low density (2×10^13 cm-3) high-?p H--mode plasmas have been obtained using the newly installed cryopump, for the purpose of optimizing the fraction of beam driven current. Plasma currents have been sustained for up to 3 s with no applied flux from the external coils, yet local analysis shows that the 30% of the current is being inductively driven by the back EMF produced by the slowly decaying plasma current.

  4. Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators.

    PubMed

    Biganzoli, I; Capone, C; Barni, R; Riccardi, C

    2015-02-01

    Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow. PMID:25725896

  5. Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators

    NASA Astrophysics Data System (ADS)

    Biganzoli, I.; Capone, C.; Barni, R.; Riccardi, C.

    2015-02-01

    Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow.

  6. On the benefits of hysteresis effects for closed-loop separation control using plasma actuation

    NASA Astrophysics Data System (ADS)

    Benard, N.; Cattafesta, L. N.; Moreau, E.; Griffin, J.; Bonnet, J. P.

    2011-08-01

    Flow separation control by a non-thermal plasma actuator is considered for a NACA 0015 airfoil at a chord Reynolds number of 1.9 × 105. Static hysteresis in the lift coefficient is demonstrated for increasing and then decreasing sinusoidal voltage amplitude supplying a typical single dielectric barrier discharge actuator at the leading edge of the model. In addition to these open-loop experiments, unsteady surface pressure signals are examined for transient processes involving forced reattachment and natural separation. The results show that strong pressure oscillations in the relatively slow separation process, compared to reattachment, precede the ultimate massive flow separation. To enhance the contrast between the parts of the signal related to the attached flow and those related to the incipient separation, RMS estimate of filtered values of Cp is used to define a flow separation predictor that is implemented in feedback control. Two simple controllers are proposed, one based on a predefined threshold of the unsteady Cp and another that utilizes the flow separation predictor to identify incipient separation. The latter effectively leverages the hysteresis in the post-stall regime to reduce the electrical power consumed by the actuator while maintaining continuously attached flow.

  7. Theoretical modeling of radiation-driven plasma turbulence in an unmagnetized plasma

    Microsoft Academic Search

    L.-H. Li; M. Matsuoka

    1996-01-01

    The radiation-driven plasma-turbulence problem is in essence an application problem of electrodynamics. In electrodynamics, electromagnetic fields at any point are determined by all charges and currents in the underlying physical system, the fields' history and physical constraints. Starting from this standpoint, we have proved that radiation-driven electromagnetic turbulence in a plasma can be studied in the same way we study

  8. Electromagnetically driven solitons in inhomogeneous overdense plasma

    Microsoft Academic Search

    A. V. Kochetov; V. A. Mironov; V. N. Bubukina; G. I. Terina

    2001-01-01

    In the framework of nonlinear Schrödinger equation (NSE), the dynamics of soliton excitation by an incident electromagnetic wave in an inhomogeneous overdense plasma is investigated. The periodic and chaotic regimes of the excitation are obtained, the thresholds for periodic and chaotic regimes are found. It is shown that the regimes depend on the unique parameter, which is determined by the

  9. Test results for a Stirling-engine-driven heat-actuated heat pump breadboard system

    SciTech Connect

    Moynihan, T.M.; Ackermann, R.A.

    1984-08-01

    A Free-Piston Stirling Engine prime mover has been coupled to a Rankine-cycle, linearresonant refrigerant compressor through a diaphragm-actuated hydraulic coupling. The system, developed at Mechanical Technology Incorporated, is a heat-actuated heat pump (HAHP) that was developed for residential applications. This paper describes the breadboard system, and presents the data obtained during testing the past year. The system was successfully tested at four designated operating points in over 250 hours of operating time, during which time extensive data was recorded that characterizes the system's performance/ operation over the specified operating range, and defines the future product potential.

  10. Aerospace induction motor actuators driven from a 20-kHz power link

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1990-01-01

    Aerospace electromechanical actuators utilizing induction motors are under development in sizes up to 40 kW. While these actuators have immediate application to the Advanced Launch System (ALS) program, several potential applications are currently under study including the Advanced Aircraft Program. Several recent advances developed for the Space Station Freedom have allowed induction motors to be selected as a first choice for such applications. Among these technologies are bi-directional electronics and high frequency power distribution techniques. Each of these technologies are discussed with emphasis on their impact upon induction motor operation.

  11. Direct in situ observation of structural transition driven actuation in VO2 utilizing electron transparent cantilevers.

    PubMed

    Viswanath, B; Ramanathan, Shriram

    2013-08-21

    Direct imaging and quantification of actuation in nanostructures that undergo structural phase transitions could advance our understanding of collective phenomena in the solid state. Here, we demonstrate visualization of structural phase transition induced actuation in a model correlated insulator vanadium dioxide by in situ Fresnel contrast imaging of electron transparent cantilevers. We quantify abrupt, reversible cantilever motion occurring due to the stress relaxation across the structural transition from a monoclinic to tetragonal phase with increasing temperature. Deflections measured in such nanoscale cantilevers can be directly correlated with macroscopic stress measurements by wafer curvature studies as well as temperature dependent electrical conduction allowing one to interrogate lattice dynamics across length scales. PMID:23832192

  12. Large range dual-axis micro-stage driven by electrostatic comb-drive actuators This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-print Network

    Awtar, Shorya

    Large range dual-axis micro-stage driven by electrostatic comb-drive actuators This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2013 J. Micromech-stage driven by electrostatic comb-drive actuators Mohammad Olfatnia, Leqing Cui, Pankaj Chopra and Shorya

  13. Data-driven neural network methodology to remaining life predictions for aircraft actuator components

    Microsoft Academic Search

    Carl S. Byington; M. Watson; D. Edwards

    2004-01-01

    Actuators are complex electro-hydraulic or mechanical mechanisms utilized in aircraft to drive flight control surfaces, landing gear, cargo doors, and weapon systems. Impact has developed a prognostic and health management (PHM) methodology for these critical systems that includes signal processing and neural network tracking techniques, along with automated reasoning, classification, knowledge fusion, and probabilistic failure mode progression algorithms. The processing

  14. Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

    1990-01-01

    The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

  15. Simultaneous gas and plasma driven hydrogen transport in solids

    SciTech Connect

    Brice, D.K.; Doyle, B.L.

    1986-01-01

    The transport parameter formalism for evaluating the steady state hydrogen (tritium) inventory, permeation rate and recycle time for surfaces exposed to the plasma of an operating magnetic confinement fusion reactor has been extended to include synergistic effects of gas and plasma driven permeation. This steady state formalism includes hydrogen trapping, recombination barriers to release at inner and outer surfaces, diffusion, and effects of thermal gradients (e.g., Ludwig-Soret effect), and is applicable to simultaneous plasma-driven and gas-driven hydrogen injection. In addition to providing a simple way of calculating the magnitude of these important tritium-related concerns, the transport parameter together with the ratio of the recombination coefficients at the two surfaces can also be used to classify the nature of these processes as to whether they are rate limited by bulk diffusion or surface recombination. New simple equations are derived which define these various regimes, and a new regime is identified which could influence permeation-probe measurements of plasma-edge fluxes.

  16. Simultaneous gas- and plasma-driven hydrogen transport in solids

    SciTech Connect

    Brice, D.K.; Doyle, B.L.

    1987-07-01

    The transport parameter formalism for evaluating the steady-state hydrogen (tritium) inventory, permeation rate, and recycle time for surfaces exposed to the plasma of an operating magnetic confinement fusion reactor has been extended to include synergistic effects of gas- and plasma-driven permeation. This steady-state formalism includes hydrogen trapping, recombination barriers to release at inner and outer surfaces, diffusion, and effects of thermal gradients (e.g., Ludwig--Soret effect) and is applicable to simultaneous plasma-driven and gas-driven hydrogen injection. In addition to providing a simple way of calculating the magnitude of these important tritium-related concerns, the transport parameter together with the ratio of the recombination coefficients at the two surfaces can also be used to classify the nature of these processes as to whether they are rate limited by bulk diffusion or surface recombination. New simple equations are derived which define these various regimes, and a new regime is identified which could influence permeation-probe measurements of plasma-edge fluxes.

  17. Simple and inexpensive current-driven magnetic multipole plasma homogenizer

    SciTech Connect

    Machima, P. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Bilek, M. M. M. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Monteiro, O. R. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Brown, I. G. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

    2000-09-01

    Magnetic multipole plasma confinement geometries employing permanent magnets are commonly used to confine laboratory plasmas and improve uniformity. Here we describe the design and operation of a particularly simple and low-cost kind of current-driven multipole system that makes use of a similar magnetic field structure but does not require permanent magnets. The magnetic field is generated by current carrying wires attached to the inside wall of a cylindrical supporting structure to provide a magnetic field resembling that of permanent multipole magnetic homogenizers. We demonstrate the use of the current-driven homogenizer to improve the uniformity of the radial density profile of a vacuum arc generated metal plasma. Our configuration of metal plasma gun, macroparticle filter, and current-driven homogenizer was used for thin film deposition, and was able to produce a relatively homogeneous film thickness profile while maintaining a deposition rate comparable to that at the peak point of the freely expanded beam at the same location. (c) 2000 American Institute of Physics.

  18. Observations of velocity shear driven plasma turbulence

    NASA Technical Reports Server (NTRS)

    Kintner, P. M., Jr.

    1976-01-01

    Electrostatic and magnetic turbulence observations from HAWKEYE-1 during the low altitude portion of its elliptical orbit over the Southern Hemisphere are presented. The magnetic turbulence is confined near the auroral zone and is similar to that seen at higher altitudes by HEOS-2 in the polar cusp. The electrostatic turbulence is composed of a background component with a power spectral index of 1.89 + or - .26 and an intense component with a power spectral index of 2.80 + or - .34. The intense electrostatic turbulence and the magnetic turbulence correlate with velocity shears in the convective plasma flow. Since velocity shear instabilities are most unstable to wave vectors perpendicular to the magnetic field, the shear correlated turbulence is anticipated to be two dimensional in character and to have a power spectral index of 3 which agrees with that observed in the intense electrostatic turbulence.

  19. Force-free magnetic relaxation in driven plasmas

    NASA Astrophysics Data System (ADS)

    Tang, Xianzhu; Boozer, Allen H.

    2004-11-01

    J. B. Taylor (1974) postulated that the helicity-conserving minimum magnetic energy state is the consequence of plasma self-organization via turbulent relaxation bounded by a magnetic surface. The Taylor state j=? B is a force-free plasma with ? a global constant. For a driven plasma with open flux intercepting the boundary B\\cdothat nneq 0, Taylor relaxation is constrained by the Jensen-Chu theory (1984), which predicted rigorous barriers in ? for the accessible relaxed state. Both the magnetic helicity and energy formally diverge at the eigenvalues (?_i) of linear equation nabla×B=?i B with homogeneous boundary condition B\\cdothat n=0. The Jensen-Chu-Taylor paradigm suggests that force-free magnetic relaxation in a driven plasma results in a constant ? state with ? bounded by the smallest eigenvalue ?_1. More complicated force-free solutions such as toroidal field reversal (e.g. flipped spheromak) and multiple internal magnetic islands, are not energetically accessible. In an actual driven plasma, the plasma can be force-free but only partially relaxed, i.e. ?(?)=?0 + ? sumi c_i?^i weakly depends on the magnetic flux (? ? 1). We find that the Jensen-Chu singularities are regularized and a broad range of force-free solutions become accessible, sometimes suggesting a tortured path toward relaxation. This new result contradicts an earlier work by Kitson and Browning (1990). Its implications on laboratory helicity injection experiments and the structure of astrophysical magnetic field will be explained. Work supported by DOE OFES.

  20. Coherent structures in plasma-actuator controlled supersonic jets: Axisymmetric and mixed azimuthal modes

    NASA Astrophysics Data System (ADS)

    Gaitonde, D. V.; Samimy, M.

    2011-09-01

    High-fidelity simulations are employed to study the effect of eight localized arc filament plasma actuators placed around the periphery of a Mach 1.3 converging-diverging nozzle exit. Emphasis is placed on understanding the coherent structures generated by axisymmetric (m = 0), flapping or first mixed (m = ±1) and second mixed (m = ±2) modes, which are excited at the jet column-mode frequency corresponding to a Strouhal number based on jet diameter of 0.3. Baseline (no control) and constant excitation (actuators on continuously) cases are also simulated. Comparisons with experimental results indicate that the computational model reproduces the main features induced by the actuators. Furthermore, the mean flow exhibits many similarities with the theoretical predictions of Cohen and Wygnanski [J. Fluid Mech. 176, 221 (1987)]. Overall, the results indicate a complex coherent structure generation, evolution, and disintegration process. For m = ±1, the phase-averaged flow reveals successive distorted elliptic vortex rings with axes in the flapping plane but alternating on either side of the jet axis. This generates a chain of structures each of which interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual induction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up. The m = ±2 mode yields elliptic structures with major axes of successive rings being aligned with the two symmetry planes, which are orthogonal to each other. The minor axis side is pulled downstream faster than the rest of the structure because of the higher velocity near the jet centerline and self-induced effects, yielding a horse-shoe shape when viewed in profile. The m = 0 mode exhibits axisymmetric roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures. The constant excitation (with largest energy input) and baseline cases are similar to each other, indicating that the direct effect of heating is negligible.

  1. Beam-driven acceleration in ultra-dense plasma media

    SciTech Connect

    Shin, Young-Min [Department of Physics, Northern Illinois University, Dekalb, Illinois 60115 (United States); Accelerator Physics Center (APC), Fermi National Accelerator Laboratory (FNAL), Batavia, Illinois 60510 (United States)

    2014-09-15

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10{sup 25?}m{sup ?3} and 1.6?×?10{sup 28?}m{sup ?3} plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers ?20% higher acceleration gradient by enlarging the channel radius (r) from 0.2 ?{sub p} to 0.6 ?{sub p} in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g., nanotubes) of high electron plasma density.

  2. Helicity-Flux-Driven ? Effect in Laboratory and Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Ebrahimi, F.; Bhattacharjee, A.

    2014-03-01

    The constraint imposed by magnetic helicity conservation on the ? effect is considered for both magnetically and flow dominated self-organizing plasmas. Direct numerical simulations are presented for a dominant contribution to the ? effect, which can be cast in the functional form of a total divergence of an averaged helicity flux, called the helicity-flux-driven ? (H?) effect. Direct numerical simulations of the H? effect are presented for two examples—the magnetically dominated toroidal plasma unstable to tearing modes, and the flow-dominated accretion disk.

  3. Thermal Efficiency of Laser Driven Inductively Coupled Plasma Generator Flows

    NASA Astrophysics Data System (ADS)

    Matsui, Makoto; Yamagishi, Suisei; Komurasaki, Kimiya; Yamagiwa, Yoshiki; Arakawa, Yoshihiro

    A laser driven inductively coupled plasma generator was developed. Firstly, the radio frequency (RF) of 13.56 MHz was applied to the atmospheric argon laser sustained plasma (LSP) in a quartz tube. As a result, the RF was successfully coupled to the LSP and following expansion of an emission region was observed. Next, the LSP was produced ahead of a ceramic convergent-divergent nozzle throat and the RF was applied from outside of the nozzle. The thermal efficiency estimated by a sonic flow method was ranged from 26 % to 13 %.

  4. Self-consistent Langmuir waves in resonantly driven thermal plasmas

    SciTech Connect

    Lindberg, R. R.; Charman, A. E.; Wurtele, J. S. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States) and Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2007-12-15

    The longitudinal dynamics of a resonantly driven Langmuir wave are analyzed in the limit that the growth of the electrostatic wave is slow compared to the bounce frequency. Using simple physical arguments, the nonlinear distribution function is shown to be nearly invariant in the canonical particle action, provided both a spatially uniform term and higher-order spatial harmonics are included along with the fundamental in the longitudinal electric field. Requirements of self-consistency with the electrostatic potential yield the basic properties of the nonlinear distribution function, including a frequency shift that agrees closely with driven, electrostatic particle simulations over a range of temperatures. This extends earlier work on nonlinear Langmuir waves by Morales and O'Neil [G. J. Morales and T. M. O'Neil, Phys. Rev. Lett. 28, 417 (1972)] and Dewar [R. L. Dewar, Phys. Plasmas 15, 712 (1972)], and could form the basis of a reduced kinetic treatment of plasma dynamics for accelerator applications or Raman backscatter.

  5. 44th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 912, 2006, Reno, NV On Plasma Synthetic Jet Actuators

    E-print Network

    Jacob, Jamey

    44th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 9­12, 2006, Reno, NV On Plasma Synthetic Jet (typ- ically rectangular strips) separated by dielectric material that can be used as active flow jet actuator (PSJA), is experimentally investigated in this paper. This particular geometry creates

  6. Biological contractile regulation of micropillar actuator driven by insect dorsal vessel tissue

    Microsoft Academic Search

    Yoshitake Akiyama; Kikuo Iwabuchi; Yuji Furukawa; Keisuke Morishima

    2008-01-01

    This paper examines biological regulation of micropillar actuation by insect dorsal vessel tissue. Micromechanical devices using mammalian cardiomyocytes have been reported, but they work only at only at 37degC and at pH of around 7.4. On the other hand, insect cells can survive and proliferate at 20 to 30degC and at pH 6 to 8. We have already proposed utilization

  7. Energetic-ion-driven global instabilities in stellarator/helical plasmas and comparison with tokamak plasmas

    SciTech Connect

    Toi, K. [National Institute for Fusion Science, Toki, Japan; Ogawa, K. [Nagoya University, Japan; Isobe, M. [National Institute for Fusion Science, Toki, Japan; Osakabe, M. [National Institute for Fusion Science, Toki, Japan; Spong, Donald A [ORNL; Todo, Yasushi [National Institute for Fusion Science, Toki, Japan

    2011-01-01

    Comprehensive understanding of energetic-ion-driven global instabilities such as Alfven eigenmodes (AEs) and their impact on energetic ions and bulk plasma is crucially important for tokamak and stellarator/helical plasmas and in the future for deuterium-tritium (DT) burning plasma experiments. Various types of global modes and their associated enhanced energetic ion transport are commonly observed in toroidal plasmas. Toroidicity-induced AEs and ellipticity-induced AEs, whose gaps are generated through poloidal mode coupling, are observed in both tokamak and stellarator/helical plasmas. Global AEs and reversed shear AEs, where toroidal couplings are not as dominant were also observed in those plasmas. Helicity induced AEs that exist only in 3D plasmas are observed in the large helical device (LHD) and Wendelstein 7 Advanced Stellarator plasmas. In addition, the geodesic acoustic mode that comes from plasma compressibility is destabilized by energetic ions in both tokamak and LHD plasmas. Nonlinear interaction of these modes and their influence on the confinement of the bulk plasma as well as energetic ions are observed in both plasmas. In this paper, the similarities and differences in these instabilities and their consequences for tokamak and stellarator/helical plasmas are summarized through comparison with the data sets obtained in LHD. In particular, this paper focuses on the differences caused by the rotational transform profile and the 2D or 3D geometrical structure of the plasma equilibrium. Important issues left for future study are listed.

  8. Non-linear adaptive robust control of electro-hydraulic systems driven by double-rod actuators BIN YAO{*. FANPING BU{ and GEORGE T. C. CHIU{

    E-print Network

    Yao, Bin

    Non-linear adaptive robust control of electro-hydraulic systems driven by double-rod actuators BIN of hydraulic systems are highly non-linear and the system may be subjected to non- smooth and discontinuous non-linearities due to directional change of valve opening, friction and valve overlap. Aside from the non-linear

  9. Control of a high Reynolds number Mach 0.9 heated jet using plasma actuators

    SciTech Connect

    Kearney-Fischer, M.; Kim, J.-H.; Samimy, M. [Department of Mechanical Engineering, Gas Dynamics and Turbulence Laboratory, Ohio State University (GDTL/OSU), 2300 West Case Road, Columbus, Ohio 43235-7531 (United States)

    2009-09-15

    The results of particle image velocimetry (PIV) measurements in a high subsonic, heated, jet forced using localized arc filament plasma actuators (LAFPAs) show that LAFPAs can consistently produce significant mixing enhancement over a wide range of temperatures. These actuators have been used successfully in high Reynolds number, high-speed unheated jets. The facility consists of an axisymmetric jet with different nozzle blocks of exit diameter of 2.54 cm and variable jet temperature in an anechoic chamber. The focus of this paper is on a high subsonic (M{sub j}=0.9) jet. Twelve experiments with various forcing azimuthal modes (m=0, 1, and {+-}1) and temperatures (T{sub o}/T{sub a}=1.0, 1.4, and 2.0) at a fixed forcing Strouhal number (St{sub DF}=0.3) have been conducted and PIV results compared with the baseline results to characterize the effectiveness of LAFPAs for mixing enhancement. Centerline velocity and turbulent kinetic energy as well as jet width are used for determining the LAFPAs' effectiveness. The characteristics of large-scale structures are analyzed through the use of Galilean streamlines and swirling strength. Across the range of temperatures collected, the effectiveness of LAFPAs improves as temperature increases. Possible reasons for the increase in effectiveness are discussed.

  10. Transition to chaos in a driven dusty plasma

    SciTech Connect

    Sheridan, T. E.; Theisen, W. L. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

    2010-01-15

    Dynamical chaos has previously been observed experimentally in a driven dusty plasma with three particles [T. E. Sheridan, Phys. Plasmas 12, 080701 (2005)]. In the present work, the transition to chaos in this system is studied as a function of the amplitude of a periodic driving force for two different driving frequencies f{sub d}. It is found that the system follows a quasiperiodic route to chaos. The dusty plasma's center-of-mass modes are driven by the first harmonic of f{sub d} and lock to the driving force for small driving amplitudes. The breathing mode is driven by the second harmonic of f{sub d} and shows asymmetric spectral features indicating quasiperiodic dynamics for intermediate driving amplitudes. For large driving forces both the center-of-mass and breathing modes are entrained and a region of low-dimensional chaotic dynamics due to a resonance overlap is observed. In the chaotic regime the correlation dimension and Lyapunov exponent are found to increase with the driving force.

  11. Design of IPMC actuator-driven valve-less micropump and its flow rate estimation at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Lee, Sangki; Kim, Kwang J.

    2006-08-01

    This paper presents the design and flow rate predictions of an IPMC (ionic polymer-metal composite) actuator-driven valve-less micropump. It should be noted that IPMC is a promising material candidate for micropump applications since it can be operated with low input voltages and can produce large stroke volumes, while having controllable flow rates. The micropump manufacturing process with IPMC is also convenient; it is anticipated that the manufacturing cost of the IPMC micropump is competitive with other technologies. In order to design an effective IPMC diaphragm that functions as an actuating motor for a micropump, a finite element analysis (FEA) was utilized to optimize the electrode shape of the IPMC diaphragm and estimate its stroke volumes. In addition, the effect of the pump chamber pressure on the stroke volume was numerically investigated. Appropriate inlet and outlet nozzle/diffuser elements were also studied for the valve-less micropump. Based on the selected geometry of nozzle/diffuser elements and the estimated stroke volume of the IPMC diaphragm, the flow rate of the micropump was estimated at a low Reynolds number of about 50.

  12. Rubber gas actuator driven by hydrogen storage alloy for in-pipe inspection mobile robot with flexible structure

    Microsoft Academic Search

    Toshio FUKUDA; Hidemi HOSOKAI; Masahiro UEMURA

    1989-01-01

    The authors describe rubber actuators using a hydrogen storage alloy for an in-pipe inspection robot, which is capable of moving inside pipelines with inner diameter as small as 2 in. Rubber actuators with both stretching and shrinking capability are shown for realization of such a robot. The proposed robot uses twelve actuators, including six kinds of independently controlled actuators, so

  13. Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R.; Leemans, W.P.

    2010-06-01

    Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator design and the different physical mechanisms of laser-driven and beam-driven plasma acceleration are discussed. Driver propagation is examined, as well as the effects of the excited plasma wave phase velocity. The driver coupling to subsequent plasma accelerator stages for high-energy physics applications is addressed.

  14. A New Type of Plasma Wakefield Accelerator Driven By Magnetowaves

    SciTech Connect

    Chen, Pisin; /KIPAC, Menlo Park /Taiwan, Natl. Taiwan U.; Chang, Feng-Yin; Lin, Guey-Lin; /Taiwan, Natl. Chiao Tung U. /Taiwan, Natl. Taiwan U.; Noble, Robert J.; /SLAC; Sydora, Richard; /Alberta U.

    2011-09-12

    We present a new concept for a plasma wakefield accelerator driven by magnetowaves (MPWA). This concept was originally proposed as a viable mechanism for the 'cosmic accelerator' that would accelerate cosmic particles to ultra-high energies in the astrophysical setting. Unlike the more familiar plasma wakefield accelerator (PWFA) and the laser wakefield accelerator (LWFA) where the drivers, the charged-particle beam and the laser, are independently existing entities, MPWA invokes the high-frequency and high-speed whistler mode as the driver, which is a medium wave that cannot exist outside of the plasma. Aside from the difference in drivers, the underlying mechanism that excites the plasma wakefield via the ponderomotive potential is common. Our computer simulations show that under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over many plasma wavelengths. We suggest that in addition to its celestial application, the MPWA concept can also be of terrestrial utility. A proof-of-principle experiment on MPWA would benefit both terrestrial and celestial accelerator concepts.

  15. Short Wavelength Temperature Gradient Driven Modes in Tokamak Plasmas A. I. Smolyakov,1,2

    E-print Network

    Smolyakov, Andrei

    Short Wavelength Temperature Gradient Driven Modes in Tokamak Plasmas A. I. Smolyakov,1,2 M. Yagi,3 August 2002) New unstable temperature gradient driven modes in an inhomogeneous tokamak plasma are identified. These modes represent temperature gradient (ion and electron) driven modes destabilized

  16. Observation of Centrifugally Driven Interchange Instabilities in a Plasma Confined by a Magnetic Dipole

    E-print Network

    Mauel, Michael E.

    Observation of Centrifugally Driven Interchange Instabilities in a Plasma Confined by a Magnetic) Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic electrostatic dipole vortex [3] that transports mass, energy, and charge [4]. The centrifugally driven

  17. Flow control over a NACA 0012 airfoil using dielectric-barrier-discharge plasma actuator with a Gurney flap

    NASA Astrophysics Data System (ADS)

    Feng, Li-Hao; Jukes, Timothy N.; Choi, Kwing-So; Wang, Jin-Jun

    2012-06-01

    Flow control study of a NACA 0012 airfoil with a Gurney flap was carried out in a wind tunnel, where it was demonstrated that a dielectric-barrier-discharge (DBD) plasma actuator attached to the flap could increase the lift further, but with a small drag penalty. Time-resolved PIV measurements of the near-wake region indicated that the plasma forcing shifted the wake downwards, reducing its recirculation length. Analysis of wake vortex dynamics suggested that the plasma actuator initially amplified the lower wake shear layer by adding momentum along the downstream surface of the Gurney flap. This enhanced mutual entrainment between the upper and lower wake vortices, leading to an increase in lift on the airfoil.

  18. Self-injected petawatt laser-driven plasma electron acceleration in 1017 cm-3 plasma

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zgadzaj, R.; Yi, S. A.; Khudik, V.; Henderson, W.; Fazel, N.; Chang, Y.-Y.; Korzekwa, R.; Tsai, H.-E.; Pai, C.-H.; Li, Z.; Gaul, E.; Martinez, M.; Dyer, G.; Quevedo, H.; Bernstein, A.; Donovan, M.; Shvets, G.; Ditmire, T.; Downer, M. C.; Downer

    2012-08-01

    We report production of a self-injected, collimated (8 mrad divergence), 600 pC bunch of electrons with energies up to 350 MeV from a petawatt laser-driven plasma accelerator in a plasma of electron density ne = 1017 cm-3, an order of magnitude lower than previous self-injected laser-plasma accelerators. The energy of the focused drive laser pulse (150 J, 150 fs) was distributed over several hot spots. Simulations show that these hot spots remained independent over a 5 cm interaction length, and produced weakly nonlinear plasma wakes without bubble formation capable of accelerating pre-heated (~1 MeV) plasma electrons up to the observed energies. The required pre-heating is attributed tentatively to pre-pulse interactions with the plasma.

  19. Solar Wind Driven Plasma Fluxes from the Venus Ionosphere

    NASA Astrophysics Data System (ADS)

    Perez De Tejada, H. A.; Lundin, R. N.; Zhang, T.; Sauvaud, J. A.; Reyes-Ruiz, M.

    2012-12-01

    SOLAR WIND DRIVEN PLASMA FLUXES FROM THE VENUS IONOSPHERE H. Pérez-de-Tejada (1), R. Lundin (2), H. Durand-Manterola (1), S. Barabash (2), T. L. Zhang (3), J. A., Sauvaud (4), and M. Reyes-Ruiz (5) 1 - Institute of Geophysics, UNAM, México, D. F. 2 - Swedish Institute of Space Physics, Kiruna, Sweden 3 - Space Research Institute, Graz, Austria 4 - CESR, Toulouse, France 5 - Institute of Astronomy, UNAM, Ensenada, México Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the kinetic pressure of planetary O+ ion fluxes measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. The momentum flux of the O+ ions leads to superalfvenic flow conditions. It is suggested that such O+ ion beams are produced in the vicinity of the magnetic polar regions of the Venus ionosphere where the solar wind erodes the local plasma leading to plasma channels that extend downstream from those regions.

  20. Magnetic Fluctuation-Driven Intrinsic Flow in a Toroidal Plasma

    NASA Astrophysics Data System (ADS)

    Brower, D. L.; Ding, W. X.; Lin, L.; Almagri, A. F.; den Hartog, D. J.; Sarff, J. S.

    2012-10-01

    Magnetic fluctuations have been long observed in various magnetic confinement configurations. These perturbations may arise naturally from plasma instabilities such as tearing modes and energetic particle driven modes, but they can also be externally imposed by error fields or external magnetic coils. It is commonly observed that large MHD modes lead to plasma locking (no rotation) due to torque produced by eddy currents on the wall, and it is predicted that stochastic field induces flow damping where the radial electric field is reduced. Flow generation is of great importance to fusion plasma research, especially low-torque devices like ITER, as it can act to improve performance. Here we describe new measurements in the MST reversed field pinch (RFP) showing that the coherent interaction of magnetic and particle density fluctuations can produce a turbulent fluctuation-induced kinetic force, which acts to drive intrinsic plasma rotation. Key observations include; (1) the average kinetic force resulting from density fluctuations, ˜ 0.5 N/m^3, is comparable to the intrinsic flow acceleration, and (2) between sawtooth crashes, the spatial distribution of the kinetic force is directed to create a sheared parallel flow profile that is consistent with the measured flow profile in direction and amplitude, suggesting the kinetic force is responsible for intrinsic plasma rotation.

  1. Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate

    NASA Astrophysics Data System (ADS)

    Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

    2014-12-01

    This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

  2. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexandre

    2012-01-01

    This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

  3. IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 35, NO. 3, JUNE 2007 693 Atmospheric Plasma Actuators for

    E-print Network

    Huang, Xun

    . The corresponding results were discussed in this paper. Index Terms--Aeroacoustics, atmospheric pressure glow dis- charges, flow control. I. INTRODUCTION PLASMA, operating in atmospheric pressure air conditions, holds] demonstrated the use of atmospheric pressure air glow discharges [2] for attenuating the tonal noise

  4. IEEE TRANSACTIONS ON ROBOTICS, VOL. 29, NO. 5, OCTOBER 2013 1085 Robots Driven by Compliant Actuators: Optimal

    E-print Network

    Vijayakumar, Sethu

    a control strategy that makes use of the intrinsic dynamics and capacity of compliant actuators experiments 1) demonstrate the effects of actuation constraints during impedance control, 2) show under experimental conditions. Index Terms--Dynamics, optimal impedance control, redundant robots

  5. MARIONET: An Exotendon-Driven Rotary Series Elastic Actuator for Exerting Joint Torque

    E-print Network

    named MARIONET (Moment arm Adjustment for Remote Induction Of Net Effective Torque) is introduced-driven, compliant mechanism should prove very useful in a variety of human-robot interactions. Here we present of mechanism. I. INTRODUCTION HERE are many different modalities for producing torque at a joint, and many

  6. Instability-driven electromagnetic fields in coronal plasmas

    DOE PAGESBeta

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-01-01

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S#2;eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of #2;210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  7. A compact and continuously driven supersonic plasma and neutral source

    SciTech Connect

    Asai, T.; Itagaki, H.; Numasawa, H.; Terashima, Y.; Hirano, Y. [Department of Physics, College of Science and Technology, Nihon University, Tokyo 101-8308 (Japan); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

    2010-10-15

    A compact and repetitively driven plasma source has been developed by utilizing a magnetized coaxial plasma gun (MCPG) for diagnostics requiring deep penetration of a large amount of neutral flux. The system consists of a MCPG 95mm in length with a DN16 ConFlat connection port and an insulated gate bipolar transistor (IGBT) inverter power unit. The power supply consists of an array of eight IGBT units and is able to switch the discharge on and off at up to 10 kV and 600 A with a maximum repetitive frequency of 10 kHz. Multiple short duration discharge pulses maximize acceleration efficiency of the plasmoid. In the case of a 10 kHz operating frequency, helium-plasmoids in the velocity range of 20 km/s can be achieved.

  8. Spherically symmetric simulation of plasma liner driven magnetoinertial fusion

    SciTech Connect

    Samulyak, Roman [Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, New York 11794 (United States); Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973 (United States); Parks, Paul [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Wu Lingling [Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, New York 11794 (United States)

    2010-09-15

    Spherically symmetric simulations of the implosion of plasma liners and compression of plasma targets in the concept of the plasma jet driven magnetoinertial fusion have been performed using the method of front tracking. The cases of single deuterium and xenon liners and double layer deuterium-xenon liners compressing various deuterium-tritium targets have been investigated, optimized for maximum fusion energy gains, and compared with theoretical predictions and scaling laws of [P. Parks, Phys. Plasmas 15, 062506 (2008)]. In agreement with the theory, the fusion gain was significantly below unity for deuterium-tritium targets compressed by Mach 60 deuterium liners. The most optimal setup for a given chamber size contained a target with the initial radius of 20 cm compressed by a 10 cm thick, Mach 60 xenon liner, achieving a fusion energy gain of 10 with 10 GJ fusion yield. Simulations also showed that composite deuterium-xenon liners reduce the energy gain due to lower target compression rates. The effect of heating of targets by alpha particles on the fusion energy gain has also been investigated.

  9. Betatron radiation from a beam driven plasma source

    NASA Astrophysics Data System (ADS)

    Litos, M.; Corde, S.

    2012-12-01

    Photons produced by the betatron oscillation of electrons in a beam-driven plasma wake provide a uniquely intense and high-energy source of hard X-rays and gamma rays. This betatron radiation is interesting not only for its high intensity and spectral characteristics, but also because it can be used as a diagnostic for beam matching into the plasma, which is critical for maximizing the energy extraction efficiency of a plasma accelerator stage. At SLAC, gamma ray detection devices have been installed at the dump area of the FACET beamline where the betatron radiation from the plasma source used in the E200 plasma wakefield acceleration experiment may be observed. The ultra-dense, high-energy beam at FACET (2 × 1010 electrons, 20 × 20?m2 spot, 20 - 100?m length, 20GeV energy) when sent into a plasma source with a nominal density of ˜ 1 × 1017 cm-3 will generate synchrotron-like spectra with critical energies well into the tens of MeV. The intensity of the radiation can be increased by introducing a radial offset to the centroid of the witness bunch, which may be achieved at FACET through the use of a transverse deflecting RF cavity. The E200 gamma ray detector has two main components: a 30 × 35cm2 phosphorescent screen for observing the transverse extent of the radiation, and a sampling electromagnetic calorimeter outfitted with photodiodes for measuring the on-axis spectrum. To estimate the spectrum, the observed intensity patterns across the calorimeter are fit with a Gaussian-integrated synchrotron spectrum and compared to simulations. Results and observations from the first FACET user run (April-June 2012) are presented.

  10. Betatron Radiation from a Beam Driven Plasma Source

    SciTech Connect

    Litos, M.; Corde, S.; /SLAC

    2012-08-13

    Photons produced by the betatron oscillation of electrons in a beam-driven plasma wake provide a uniquely intense and high-energy source of hard X-rays and gamma rays. This betatron radiation is interesting not only for its high intensity and spectral characteristics, but also because it can be used as a diagnostic for beam matching into the plasma, which is critical for maximizing the energy extraction efficiency of a plasma accelerator stage. At SLAC, gamma ray detection devices have been installed at the dump area of the FACET beamline where the betatron radiation from the plasma source used in the E200 plasma wakefield acceleration experiment may be observed. The ultra-dense, high-energy beam at FACET (2 x 10{sup 10} electrons, 20 x 20 {micro}m{sup 2} spot, 20-100 {micro}m length, 20 GeV energy) when sent into a plasma source with a nominal density of {approx} 1 x 10{sup 17} cm{sup -3} will generate synchrotron-like spectra with critical energies well into the tens of MeV. The intensity of the radiation can be increased by introducing a radial offset to the centroid of the witness bunch, which may be achieved at FACET through the use of a transverse deflecting RF cavity. The E200 gamma ray detector has two main components: a 30 x 35 cm{sup 2} phosphorescent screen for observing the transverse extent of the radiation, and a sampling electromagnetic calorimeter outfitted with photodiodes for measuring the on-axis spectrum. To estimate the spectrum, the observed intensity patterns across the calorimeter are fit with a Gaussian-integrated synchrotron spectrum and compared to simulations. Results and observations from the first FACET user run (April-June 2012) are presented.

  11. Integrated magnetic and kinetic control of advanced tokamak plasmas on DIII-D based on data-driven models

    NASA Astrophysics Data System (ADS)

    Moreau, D.; Walker, M. L.; Ferron, J. R.; Liu, F.; Schuster, E.; Barton, J. E.; Boyer, M. D.; Burrell, K. H.; Flanagan, S. M.; Gohil, P.; Groebner, R. J.; Holcomb, C. T.; Humphreys, D. A.; Hyatt, A. W.; Johnson, R. D.; La Haye, R. J.; Lohr, J.; Luce, T. C.; Park, J. M.; Penaflor, B. G.; Shi, W.; Turco, F.; Wehner, W.; the ITPA-IOS Group members; experts

    2013-06-01

    The first real-time profile control experiments integrating magnetic and kinetic variables were performed on DIII-D in view of regulating and extrapolating advanced tokamak scenarios to steady-state devices and burning plasma experiments. Device-specific, control-oriented models were obtained from experimental data using a generic two-time-scale method that was validated on JET, JT-60U and DIII-D under the framework of the International Tokamak Physics Activity for Integrated Operation Scenarios (Moreau et al 2011 Nucl. Fusion 51 063009). On DIII-D, these data-driven models were used to synthesize integrated magnetic and kinetic profile controllers. The neutral beam injection (NBI), electron cyclotron current drive (ECCD) systems and ohmic coil provided the heating and current drive (H&CD) sources. The first control actuator was the plasma surface loop voltage (i.e. the ohmic coil), and the available beamlines and gyrotrons were grouped to form five additional H&CD actuators: co-current on-axis NBI, co-current off-axis NBI, counter-current NBI, balanced NBI and total ECCD power from all gyrotrons (with off-axis current deposition). Successful closed-loop experiments showing the control of (a) the poloidal flux profile, ?(x), (b) the poloidal flux profile together with the normalized pressure parameter, ?N, and (c) the inverse of the safety factor profile, \\bar{\\iota}(x)=1/q(x) , are described.

  12. Integrated Plasma Simulation of Ion Cyclotron and Lower Hybrid Range of Frequencies Actuators in Tokamaks

    NASA Astrophysics Data System (ADS)

    Bonoli, P. T.; Shiraiwa, S.; Wright, J. C.; Harvey, R. W.; Batchelor, D. B.; Berry, L. A.; Chen, Jin; Poli, F.; Kessel, C. E.; Jardin, S. C.

    2012-10-01

    Recent upgrades to the ion cyclotron RF (ICRF) and lower hybrid RF (LHRF) components of the Integrated Plasma Simulator [1] have made it possible to simulate LH current drive in the presence of ICRF minority heating and mode conversion electron heating. The background plasma is evolved in these simulations using the TSC transport code [2]. The driven LH current density profiles are computed using advanced ray tracing (GENRAY) and Fokker Planck (CQL3D) [3] components and predictions from GENRAY/CQL3D are compared with a ``reduced'' model for LHCD (the LSC [4] code). The ICRF TORIC solver is used for minority heating with a simplified (bi-Maxwellian) model for the non-thermal ion tail. Simulation results will be presented for LHCD in the presence of ICRF heating in Alcator C-Mod. [4pt] [1] D. Batchelor et al, Journal of Physics: Conf. Series 125, 012039 (2008).[0pt] [2] S. C. Jardin et al, J. Comp. Phys. 66, 481 (1986).[0pt] [3] R. W. Harvey and M. G. McCoy, Proc. of the IAEA Tech. Comm. Meeting on Simulation and Modeling of Therm. Plasmas, Montreal, Canada (1992).[0pt] [4] D. Ignat et al, Nucl. Fus. 34, 837 (1994).[0pt] [5] M. Brambilla, Plasma Phys. and Cont. Fusion 41,1 (1999).

  13. Experimental Study of Episodic Magnetically Driven Radiatively Cooled Plasma Jets

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Bland, S. N.; Chittenden, J. P.; Hall, G. N.; Harvey-Thompson, A.; Marocchino, A.; Ciardi, A.; Stehle, C.; Bott, S. C.; Frank, A.; Blackman, E. G.; Ray, T.

    2007-11-01

    Previous experiments on the 1MA MAGPIE generator have successfully showed the formation of magnetically driven radiatively cooled plasma jets which are relevant to the launching of astrophysical jets. The jets in these experiments are driven by the pressure of the toroidal magnetic field produced by the current, which leads to the formation of a ``magnetic tower'' structure. This scenario is characterized by the formation of a magnetic ``bubble'' surrounding a collimated plasma jet on axis. A modification of this experimental configuration, in which radial wire array is replaced by radial metallic foil, results in the formation of episodic magnetic tower outflows which emerge periodically on timescales of ˜30ns. The subsequent magnetic bubbles propagate with higher velocities (increasing from ˜100km/s to ˜300km/s) and interacting with previous eruptions leading to the formation of shocks. This experimental setup also allows the study of the interaction of episodic outflows with an ambient medium. This research was supported by the EU JETSET network and the NNSA under DOE Cooperative Agreement DE-FC03-02NA00057.

  14. A piezoelectric actuator-driven loading device for mechanical condition during bone tissue engineering

    NASA Astrophysics Data System (ADS)

    Zhang, C. Q.; Wu, H.; Dong, X.

    2008-10-01

    Bone cells live in an environment heavily influenced by mechanical forces. The researches of bone cell responses in hard scaffolds under differently mechanical conditions will be greatly beneficial to elucidating the mechanisms of bone mechanotransduction as well as applications of mechanical condition in bone tissue engineering. However, the appropriate device for the experiments is prerequisite. A loading device suitable to hard scaffold for study on mechanical responses of bone cells was made by usage of a kind of long-travel, high-load piezoelectric actuator. The device, which is so small enough to work in a standard incubator, can cause hard scaffolds with directly uniaxial compressive strains with more magnitudes, frequency components, and waveforms, including bone physiologically mechanical state, precisely controlled by a computer. The device achieves precise mechanical conditions by testing verification. The device may produce a model that will be suitable for investigating the influences of mechanical responses on bone cells in 3D hard scaffolds in vitro matching that in cancellous bone in vivo and may be applied during bone tissue engineering culture.

  15. Large-scale solvent driven actuation of polyelectrolyte multilayers based on modulation of dynamic secondary interactions.

    PubMed

    Gu, Yuanqing; Huang, Xiayun; Wiener, Clinton G; Vogt, Bryan D; Zacharia, Nicole S

    2015-01-28

    Polyelectrolyte multilayers (PEMs), assembled from weak polyelectrolytes, have often been proposed for use as smart or responsive materials. However, such response to chemical stimuli has been limited to aqueous environments with variations in ionic strength or pH. In this work, a large in magnitude and reversible transition in both the swelling/shrinking and the viscoelastic behavior of branched polyethylenimine/poly(acrylic acid) multilayers was realized in response to exposure with various polar organic solvents (e.g., ethanol, dimethyl sulfoxide, and tetrahydrofuran). The swelling of the PEM decreases with an addition of organic content in the organic solvent/water mixture, and the film contracts without dissolution in pure organic solvent. This large response is due to both the change in dielectric constant of the medium surrounding the film as well as an increase in hydrophobic interactions within the film. The deswelling and shrinking behavior in organic solvent significantly enhances its elasticity, resulting in a stepwise transition from an initially liquid-like film swollen in pure water to a rigid solid in pure organic solvents. This unique and recoverable transition in the swelling/shrinking behaviors and the rheological performances of weak polyelectrolyte multilayer film in organic solvents is much larger than changes due to ionic strength or pH, and it enables large scale actuation of a freestanding PEM. The current study opens a critical pathway toward the development of smart artificial materials. PMID:25539141

  16. Laboratory Studies of Magnetically Driven, Radiatively Cooled Supersonic Plasma Jets

    NASA Astrophysics Data System (ADS)

    Lebedev, Sergey V.

    2010-05-01

    Results of the recent experiments with radiatively cooled jets performed on the pulsed power MAGPIE facility (1.5MA, 250ns) at Imperial College will be presented. The experiments are scalable to astrophysical flows in that critical dimensionless numbers such as the plasma collisionality, the plasma beta, Reynolds number and the magnetic Reynolds number are all in the astrophysically appropriate ranges. The experimental results will be compared with computer simulations performed with laboratory plasma codes and with astrophysical codes. The main part of the presentation will concentrate on the dynamics of magnetically driven jets, in particular on formation of episodic outflows [1]. The experimental results show the periodic ejections of magnetic bubbles naturally evolving into a heterogeneous jet propagating inside a channel made of self-collimated magnetic cavities. Experimental data on the energy balance in the magnetically driven jets, the conversion of the Poynting flux energy into kinetic energy of the outflow, will be also presented. *) In collaboration with A. CIARDI, F.A. SUZUKI-VIDAL, S.N. BLAND, M. BOCCHI, G. BURDIAK, J.P. CHITTENDEN, P. de GROUCHY, G. HALL, A. HARVEY-THOMSON, A. MAROCCHINO, G. SWADLING, A. FRANK, E. G. BLACKMAN, C. STEHLE, M. CAMENZIND. This research was sponsored by EPSRC, by the OFES DOE, by the NNSA under DOE Cooperative Agreement No. DE-FC03-02NA00057 and by the European Community's Marie Curie Actions within the JETSET network under Contract No. MRTNCT- 2004 005592. References [1] A. Ciardi, S.V. Lebedev, A. Frank et al., The Astrophysical Journal, 691: L147-L150 (2009).

  17. Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control

    NASA Astrophysics Data System (ADS)

    Benard, Nicolas; Moreau, Eric

    2014-11-01

    The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

  18. Deep Drilling and Sampling via the Wireline Auto-Gopher Driven by Piezoelectric Percussive Actuator and EM Rotary Motor

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Badescu, Mircea; Sherrit, Stewart; Zacny, Kris; Paulsen, Gale L; Beegle, Luther; Bao, Xiaoqi

    2012-01-01

    The ability to penetrate subsurfaces and perform sample acquisition at depths of meters is critical for future NASA in-situ exploration missions to bodies in the solar system, including Mars and Europa. A corer/sampler was developed with the goal of acquiring pristine samples by reaching depths on Mars beyond the oxidized and sterilized zone. To developed rotary-hammering coring drill, called Auto-Gopher, employs a piezoelectric actuated percussive mechanism for breaking formations and an electric motor rotates the bit to remove the powdered cuttings. This sampler is a wireline mechanism that is incorporated with an inchworm mechanism allowing thru cyclic coring and core removal to reach great depths. The penetration rate is being optimized by simultaneously activating the percussive and rotary motions of the Auto-Gopher. The percussive mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) mechanism that is driven by piezoelectric stack and that was demonstrated to require low axial preload. The Auto-Gopher has been produced taking into account the a lessons learned from the development of the Ultrasonic/Sonic Gopher that was designed as a percussive ice drill and was demonstrated in Antarctica in 2005 to reach about 2 meters deep. A field demonstration of the Auto-Gopher is currently being planned with objective of reaching as deep as 3 to 5 meters in tufa subsurface.

  19. Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Joshi, Chan; Malka, Victor

    2010-04-01

    The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Sc?rer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin, S Mangles, L O Silva, R Fonseca and P A Norreys Electro-optic shocks from blowout laser wakefields D F Gordon, A Ting, M H Helle, D Kaganovich and B Hafizi Onset of self-steepening of intense laser pulses in plasmas J Vieira, F Fiúza, L O Silva, M Tzoufras and W B Mori Analysis of laser wakefield dynamics in capillary tubes N E Andreev, K Cassou, F Wojda, G Genoud, M Burza, O Lundh, A Persson, B Cros, V E Fortov and C-G Wahlstrom Characterization of the beam loading effects in a laser plasma accelerator C Rechatin, J Faure, X Davoine, O Lundh, J Lim, A Ben-Ismaïl, F Burgy, A Tafzi, A Lifschitz, E Lefebvre and V Malka Energy gain scaling with plasma length and density in the plasma wakefield accelerator P Muggli, I Blumenfeld, C E Clayton, F J Decker, M J Hogan, C Huang, R Ischebeck, R H Iverson, C Joshi, T Katsouleas, N Kirby, W Lu, K A Marsh, W B Mori, E Oz, R H Siemann, D R Walz and M Zhou Generation of tens of GeV quasi-monoenergetic proton beams from a moving double layer formed by ultraintense lasers at intensity 1021-1023Wcm-2 Lu-Le Yu, Han Xu, Wei-Min Wang, Zheng-Ming Sheng, Bai-Fei Shen, Wei Yu and Jie Zhang Carbon ion acceleration from thin foil targets irradiated by ultrahigh-contrast, ultraintense laser pulses D C Carroll, O Tresca, R Prasad, L Romagnani, P S Foster, P Gallegos, S Ter-Avetisyan, J S Green, M J V Streeter, N Dover, C A J Palmer, C M Brenner, F H Cameron, K E Quinn, J Schreiber, A P L Robinson, T Baeva, M N Quinn, X H Yuan, Z Najmudin, M Zepf, D Neely, M Borghesi and P McKenna Numerical modelling of a 10-cm-long multi-GeV laser wakefield accelerator driven by a self-guided petawatt pulse S Y Kalmykov, S A Yi, A Beck, A F Lifschitz, X Davoine, E Lefebvre, A Pukhov, V Khudik, G Shvets, S A Reed, P Dong, X Wang, D Du, S Bedacht, R Zgadzaj, W Henderson, A Bernstein, G Dyer, M Martinez, E Gaul, T Ditmire and M C Downer Effects of laser prepulses on laser-induced proton generation D Batani, R Jafer, M Veltcheva, R Dezulian, O Lundh, F Lindau, A Persson, K Osvay, C-G Wahlström, D C Carroll, P McKenna, A Flacco and V Malka Proton accelerati

  20. Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas

    SciTech Connect

    Wang, W. X.; Hahm, T. S.; Ethier, S.; Zakharov, L. E.

    2011-02-07

    Recent progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported with emphasis on electron thermal transport dominated regimes. The turbulence driven intrinsic torque associated with nonlinear residual stress generation by the fluctuation intensity and the intensity gradient in the presence of zonal flow shear induced asymmetry in the parallel wavenumber spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current. These results qualitatively reproduce empirical scalings of intrinsic rotation observed in various experiments. The origin of current scaling is found to be due to enhanced kll symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic torque on pressure gradient is that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving residual stress, increase with the strength of turbulence drive, which is R0/LTe and R0/Lne for the trapped electron mode. __________________________________________________

  1. Documentation and Control of Flow Separation on a Low Pressure Turbine Linear Cascade of Pak-B Blades Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Corke, Thomas c.; Thomas, FLint, O.; Huang, Junhui

    2007-01-01

    This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "Pak-B" shaped blades. Flow visualization, surface pressure measurements, LDV measurements, and hot-wire anemometry were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers (based on axial chord and inlet velocity) from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/U(infinity) = 0.08 to 2.85 percent. The blade pressure distributions were measured and used to identify the region of separation that depends on Reynolds number and the turbulence intensity. Separation control was performed using dielectric barrier discharge (DBD) plasma actuators. Both steady and unsteady actuation were implemented and found to work well. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. For the steady actuators, it was found that the separated region is significantly reduced. For the unsteady actuators, where the signal was pulsed, the separation was eliminated. The total pressure losses (a low Reynolds number) was reduced by approximately a factor of two. It was also found that lowest plasma duty cycle (10 percent in this work) was as effective as the highest plasma duty cycle (50 percent in this work). The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

  2. Pressure-driven, resistive magnetohydrodynamic interchange instabilities in laser-produced high-energy-density plasmas

    E-print Network

    Pressure-driven, resistive magnetohydrodynamic interchange instabilities in laser-produced high magnetized plasma instabilities in laser-produced high-energy-density plasmas. Time-gated proton radiograph- quence of pressure-driven, resistive magnetohydrodynamic MHD interchange instabilities. In contrast

  3. CENTER FOR PULSED POWER DRIVEN HIGH ENERGY DENSITY PLASMA STUDIES

    SciTech Connect

    Professor Bruce R. Kusse; Professor David A. Hammer

    2007-04-18

    This annual report summarizes the activities of the Cornell Center for Pulsed-Power-Driven High-Energy-Density Plasma Studies, for the 12-month period October 1, 2005-September 30, 2006. This period corresponds to the first year of the two-year extension (awarded in October, 2005) to the original 3-year NNSA/DOE Cooperative Agreement with Cornell, DE-FC03-02NA00057. As such, the period covered in this report also corresponds to the fourth year of the (now) 5-year term of the Cooperative Agreement. The participants, in addition to Cornell University, include Imperial College, London (IC), the University of Nevada, Reno (UNR), the University of Rochester (UR), the Weizmann Institute of Science (WSI), and the P.N. Lebedev Physical Institute (LPI), Moscow. A listing of all faculty, technical staff and students, both graduate and undergraduate, who participated in Center research activities during the year in question is given in Appendix A.

  4. DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Thurman, Douglas R.

    2011-01-01

    Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.

  5. MTF Driven by Plasma Liner Dynamically Formed by the Merging of Plasma Jets: An Overview

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    One approach for standoff delivery of the momentum flux for compressing the target in MTF consists of using a spherical array of plasma jets to form a spherical plasma shell imploding towards the center of a magnetized plasma, a compact toroid (Figure 1). A 3-year experiment (PLX-1) to explore the physics of forming a 2-D plasma liner (shell) by merging plasma jets is described. An overview showing how this 3-year project (PLX-1) fits into the program plan at the national and international level for realizing MTF for energy and propulsion is discussed. Assuming that there will be a parallel program in demonstrating and establishing the underlying physics principles of MTF using whatever liner is appropriate (e.g. a solid liner) with a goal of demonstrating breakeven by 2010, the current research effort at NASA MSFC attempts to complement such a program by addressing the issues of practical embodiment of MTF for propulsion. Successful conclusion of PLX-1 will be followed by a Physics Feasibility Experiment (PLX-2) for the Plasma Liner Driven MTF.

  6. A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Séguin, F. H.; Town, R. P. J.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-02-01

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely directed field lines collide. In most natural circumstances, the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. In addition, the regime of strongly driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed the experiments to probe reconnection in asymmetric, strongly driven, laser-generated plasmas. Here we show that, in this strongly driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. In addition, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.

  7. Laser-driven plasma-based accelerators: Wakefield excitation, channel guiding, and laser triggered particle injection*

    E-print Network

    Wurtele, Jonathan

    Laser-driven plasma-based accelerators: Wakefield excitation, channel guiding, and laser triggered; accepted 18 February 1998 Plasma-based accelerators are discussed in which high-power short pulse lasers are the power source, suitably tailored plasma structures provide guiding of the laser beam and support large

  8. Behavior of Excited Argon Atoms in Inductively Driven Plasmas

    SciTech Connect

    HEBNER,GREGORY A.; MILLER,PAUL A.

    1999-12-07

    Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s{sub 5} and 1s{sub 4}, in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s{sub 5} level is metastable and the 1s{sub 4} level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the discharge while the density at the edge of the discharge was unaffected. The spatially resolved excited state density measurements were combined with previous line integrated measurements in the same discharge geometry to derive spatially resolved, absolute densities of the 1s{sub 5} and 1s{sub 4} argon excited states and gas temperature spatial distributions. Fluorescence lifetime was a strong fi.mction of the rf power, pressure, argon fraction and spatial location. Increasing the power or pressure resulted in a factor of two decrease in the fluorescence lifetime while adding Cl{sub 2} or BCl{sub 3} increased the fluorescence lifetime. Excited state quenching rates are derived from the data. When Cl{sub 2} or BCl{sub 3} was added to the plasma, the maximum argon metastable density depended on the gas and ratio. When chlorine was added to the argon plasma, the spatial density profiles were independent of chlorine fraction. While it is energetically possible for argon excited states to dissociate some of the molecular species present in this discharge, it does not appear to be a significant source of dissociation. The major source of interaction between the argon and the molecular species BCl{sub 3} and Cl{sub 2} appears to be through modification of the electron density.

  9. Research on a New Type of Sea Water Hydraulic Servovalve Driven by Diphase Oppositing Giant Magnetostrictive Self-Sensing Actuator

    Microsoft Academic Search

    Wang Xinhua; Wang Simin; Liu Juyin; Li Wei

    2009-01-01

    A new concept of diphase oppositing giant magnetostrictive self-sensing actuator is put forward, combining with sea water servo control technology, a flapper-nozzle force feedback sea water servo control valve is designed. Bridge analysis model based on variable inductance is established, dynamic balance separation technology for giant magnetostrictive self-sensing actuators is come true by least means square self-adapting(LSM) algorithm. With the

  10. Analysis, Design and Control of a Planar Micro-robot Driven by two Centripetal-force Actuators

    Microsoft Academic Search

    Panagiotis Vartholomeos; Evangelos Papadopoulos

    2006-01-01

    This paper presents the motion analysis, design and position control of a novel, low cost, sliding micro-robot, which is actuated by centripetal forces generated by robot mounted vibration micro-motors. A new, two-micromotor design of the platform is presented, that improves system energy efficiency, and further does not necessitate for synchronous actuator operation and robot symmetry. The motion behavior of the

  11. Enhanced Design of Turbo-jet LPT by Separation Control Using Phased Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Ashpis, David (Technical Monitor); Corke, Thomas C.; Thomas, Flint O.

    2003-01-01

    This work deals with the documentation and control of flow separation that occurs over turbine blades in the low-pressure turbine stage at low Reynolds numbers that exist at high altitude cruise. We utilize a specially constructed linear cascade that is designed to study the flow field over a generic LPT cascade consisting of Pratt & Whitney 'Pak B' shaped blades. This facility was constructed under a previous one-year NASA Glenn RC initiative. The center blade in the cascade is instrumented to measure the surface pressure coefficient distribution. Optical access allows two-component LDV measurement for boundary layer profiles. Experimental conditions have been chosen to give a range of chord Reynolds numbers from 10 to 100K, and a range of free-stream turbulence levels from u'/U(sub infinity)= 0.08 to 3 percent. The surface pressure measurements were used to define a region of separation and reattachment that depend on the free-stream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, reattachment location was very sensitive to the turbulence level and Reynolds number. Excellent agreement was found between the measured pressure distributions and predictions from Euler and RANS simulations. Two-component LDV measurements are presently underway to document the mean and fluctuating velocity components in the boundary layer over the center blade for the range of experimental conditions. The fabrication of the plasma actuator is underway. These are designed to produce either streamwise vortices, or a downstream-directed wall jet. A precursor experiment for the former approach was performed with an array of vortex generators placed just upstream of the separation line. These led to reattachment except for the lowest Reynolds number. Progress has also been made on the proposed concept for a laterally moving wake. This involved constructing a smaller wind tunnel and molding an array of symmetric airfoils to form an array. Following its development, it will be scaled up and used to introduce lateral moving wakes upstream up the Pak-B cascade.

  12. Laboratory Astrophysics Experiments with Magnetically Driven Plasma Jets

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Bland, S. N.; Hall, G. N.; Swadling, G.; Harvey-Thompson, A. J.; Burdiak, G.; de Grouchy, P.; Chittenden, J. P.; Bocchi, M.; Bott, S. C.; Frank, A.

    2014-05-01

    We present experimental results on the formation of supersonic, radiatively cooled jets driven by the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which the jet on the axis of a magnetic cavity expanding into an ambient medium is collimated by a toroidal magnetic field. The jets in our experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets and additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration generates episodic magnetic cavities, suggesting that periodic formation of jets in astrophysical situations could be responsible for some of the variability observed in astrophysical jets. The dynamics of the formation of laboratory jets are presented, together with new results including preliminary measurements of magnetic, kinetic and Poynting energy of the outflows. In addition first estimates of jet temperature and trapped toroidal magnetic field are presented and discussed.

  13. Study of driven magnetic reconnection in a laboratory plasma

    SciTech Connect

    Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Bretz, N.; Jobes, F.; Ono, Yasushi; Perkins, F.

    1998-12-31

    The Magnetic Reconnection Experiment (MRX) has been constructed to investigate the fundamental physics of magnetic reconnection in a well controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic (MHD) plasma (S {much_gt} 1, {rho}{sub i} {much_lt} L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied. Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (anti-parallel or null-helicity reconnection), a thin double-Y shaped diffusion region is identified. A neutral sheet current profile is measured accurately to be as narrow as order ion gyro-radius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration.

  14. Design of a DBD Plasma Actuator Array to Control Stationary Cross Flow Modes in a Supersonic Boundary Layer

    NASA Astrophysics Data System (ADS)

    Schuele, Chan-Yong; Matlis, Eric; Corke, Thomas; Wilkinson, Stephen

    2010-11-01

    The control of cross flow dominated laminar turbulent transition is crucial for the improvement of efficiency of supersonic aircraft. Passive methods such as distributed micron sized roughness elements have proven to work efficiently as laminar flow control devices in subsonic and as we could recently show in supersonic flows. This study describes the replacement of micron sized roughness elements with an array of dielectric barrier discharge (DBD) plasma actuators in order to excite less amplified stationary cross flow modes. These are intended to suppress the growth of the naturally occurring most amplified stationary modes. The use of DBD plasma actuators allows for a dynamic control that can respond to changing flight conditions, which is difficult to achieve with traditional roughness elements. Experiments have been performed in the 0.5,Mach 3.5 NASA LaRC Supersonic Low Disturbance Tunnel on a 7^o half angle sharp cone at a 4.3^o angle of attack, and a unit Reynolds number of 250000/in.

  15. Parameter sensitivity of plasma wakefields driven by self-modulating proton beams

    SciTech Connect

    Lotov, K. V.; Minakov, V. A.; Sosedkin, A. P. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk, Russia and Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

    2014-08-15

    The dependence of wakefield amplitude and phase on beam and plasma parameters is studied in the parameter area of interest for self-modulating proton beam-driven plasma wakefield acceleration. The wakefield phase is shown to be extremely sensitive to small variations of the plasma density, while sensitivity to small variations of other parameters is reasonably low. The study of large parameter variations clarifies the effects that limit the achievable accelerating field in different parts of the parameter space: nonlinear elongation of the wakefield period, insufficient charge of the drive beam, emittance-driven beam divergence, and motion of plasma ions.

  16. Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

    SciTech Connect

    Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

    2010-05-03

    Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

  17. RESEARCH ARTICLE The use of plasma actuators for bluff body broadband

    E-print Network

    Huang, Xun

    actuators to reduce landing gear noise during approach phase of an aircraft. The control effectiveness Exp Fluids DOI 10.1007/s00348-009-0806-3 #12;source of airframe noise is the landing gears where the approach to landing phase, especially when the aircraft is equipped with modern high bypass ratio engines

  18. Self-consistent Langmuir waves in resonantly driven thermal plasmas R. R. Lindberg,a

    E-print Network

    Wurtele, Jonathan

    Self-consistent Langmuir waves in resonantly driven thermal plasmas R. R. Lindberg,a A. E. Charman The longitudinal dynamics of a resonantly driven Langmuir wave are analyzed in the limit that the growth on nonlinear Langmuir waves by Morales and O'Neil G. J. Morales and T. M. O'Neil, Phys. Rev. Lett. 28, 417 1972

  19. Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters

    NASA Astrophysics Data System (ADS)

    Friz, Paul Daniel

    This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

  20. A Comparison between Plasma Synthetic Jets and Conventional Jets

    Microsoft Academic Search

    Arvind Santhanakrishnan; Jamey Jacob

    2007-01-01

    The flow field of a jet created by an actuator employing a surface dielectric barrier discharge (DBD) is investigated experimentally via PIV measurements, and a comparison of its fluid dynamic characteristics with mechanically driven continuous and synthetic jets is presented. The plasma synthetic jet actuator consists of two electrodes arranged asymmetrically separated by a dielectric material and under an input

  1. Analysis, Design and Control of a Planar Micro-robot Driven by Two Centripetal-Force Actuators*

    E-print Network

    Papadopoulos, Evangelos

    vibration micro-motors. A new, two-micromotor design of the platform is presented, that improves system. The motion behavior of the micro-robot, for asynchronous actuation operation, is expressed analytically motor speed controllers, and a platform position controller is designed. The control system performance

  2. Current Driven Acoustic Perturbations in Partially Ionized Collisional Plasmas

    NASA Astrophysics Data System (ADS)

    Vranjes, J.; Poedts, S.; Tanaka, M. Y.; Pandey, B. P.

    2008-03-01

    A fluid and kinetic analysis is presented of the ion sound mode in a weakly ionized collisional plasma in the regime when the ion collision frequency exceeds the ion gyro-frequency while the electrons remain magnetized. Under these conditions, an ion sound wave can propagate at arbitrary angles with respect to the direction of the magnetic field. In the presence of an electron flow along the magnetic lines the sound mode can grow. Due to the electron collisions the mode is unstable while ion collisions cause an angle dependent instability threshold which is such that the mode is most easily excited at very large angles. Hot ion effects in one part of the work are included by means of an effective viscosity which effectively describes the ion Landau damping effect. In the presence of an additional light ion specie, the mode frequency and increment in a certain parameter range are increased. Several additional effects are discussed, including the electron-ion collisions, the perturbations of the neutral gas, and the electromagnetic perturbations. The electron-ion collisions are shown to modify the previously obtained angle dependent instability threshold for the driving electron flow. The inclusion of the neutral dynamics implies an additional neutral sound mode which couples to the current driven ion acoustic mode, and these two modes can interchange their identities in certain parameter regimes. The electromagnetic effects, which in the present model imply a bending of the magnetic field lines, result in a further destabilization of an already unstable ion acoustic wave. In the case when the ion collision frequency is arbitrary the ion species is to be described by a collisional Boltzman kinetic equation. In the same time the electron collision frequency is high enough so that the fluid description is used for the electrons in the presence of an electron drift in the perpendicular direction. This results in the instability of accidentally excited ion sound oscillations, which turn out to be highly unstable for practically all physically acceptable values of the electron drift. In addition, the presence of a population of hotter electrons is shown to reduce the perpendicular electron drift and to increase the instability threshold.

  3. Progress In Magnetized Target Fusion Driven by Plasma Liners

    NASA Technical Reports Server (NTRS)

    Thio, Francis Y. C.; Kirkpatrick, Ronald C.; Knapp, Charles E.; Cassibry, Jason; Eskridge, Richard; Lee, Michael; Smith, James; Martin, Adam; Wu, S. T.; Schmidt, George; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC).

  4. A 30 mm Wide DC-Driven Brush-Shaped Cold Air Plasma Without Airflow Supplement

    NASA Astrophysics Data System (ADS)

    Chen, Zhaoquan; Zheng, Xiaoliang; Xia, Guangqing; Li, Ping; Hu, Yelin; Du, Zhiwen; Zhu, Longji; Liu, Minghai; Chen, Minggong; Hu, Xiwei

    2014-04-01

    This paper reports a cold atmospheric pressure DC-driven air plasma brush. Three stainless steel needles are symmetrically mounted on a slot shaped PVC slab to act as the electrodes. The brush driven by a direct current (DC) power supply can generate an air plasma glow up to 30 mm wide with no inert gas addition and no air flow supplement. The plasma glow appears uniform no matter what kinds of material are processed. The measured current and the simulated current all show that each pulsed discharge including two peaks always occurs for different gaps between electrodes. Emission spectra measurement result shows that the obtained rotational temperatures are 300 K and the vibrational temperatures are 2250 K. Some reactive species are presented in the plasma glow, which suggest that the proposed plasma brush is beneficial to practical applications.

  5. Prospects for studying temperature-anisotropy-driven instabilities in a high-beta laboratory plasma

    NASA Astrophysics Data System (ADS)

    Carter, T. A.; Dorfman, S. E.; Bardoczi, L.; Geraldini, A.; Robertson, J.; Tang, S.; Tripathi, S.; Vincena, S. T.; Gekelman, W. N.

    2013-12-01

    The mirror and firehose instabilities are driven unstable in magnetized, high-beta plasmas with anisotropic ion distribution functions. Evidence for the action of these instabilities has been found in space plasmas, in particular solar wind observations [1], and they are thought to be important in a number of astrophysical plasmas (e.g. accretion disks). Studying these important instabilities in the lab requires a high-beta, magnetized plasma and the creation of sufficient temperature anisotropy. We will discuss prospects for laboratory experiments making use of the Enormous Toroidal Plasma Device (ETPD) at UCLA. Firehose-unstable (T? > T?) ion distributions might be driven in plasmas flowing into an expanding magnetic field (similar to the solar wind). Enhanced anisotropy could be provided by the formation of a double layer in the expanding plasma, which leads to the production of ion beams in expanding laboratory plasmas [2]. We will report on: initial experiments in LAPD studying expanding plasmas, measurements of plasma parameters in ETPD and on theoretical projections for acheivable anisotropy and instability thresholds in ETPD. [1] S.D. Bale, et al., PRL 103, 211101 (2009). [2] C. Charles, et al., PoP 11, 1706 (2004).

  6. Comparison of plasma and gas driven permeation of deuterium through titanium diboride

    NASA Astrophysics Data System (ADS)

    Kerst, R. A.; Swansiger, W. A.

    1985-09-01

    Plasma driven and gas driven permeation of deuterium through Kovar and TiB 2 coated Kovar membranes have been measured. The transport of deuterium through the coated surface was found to be fundamentally different for the two drivers. For gas driven permeation, essentially no deuterium diffuses through the coating, but a significant quantity reaches the Kovar substrate through microcracks in the coating. The permeation rate is thus determined by the extent to which the coating masks the substrate. For plasma driven permeation, on the other hand, the ions are implanted into the coating and diffuse through to the substrate. The data were used to determine the diffusivity of deuterium in TiB 2 at 500°C. The implications for tritium permeation through coated components in fusion reactors are discussed.

  7. Characteristics of a Direct Current-driven plasma jet operated in open air

    SciTech Connect

    Li, Xuechen; Bao, Wenting [College of Physics Science and Technology, Hebei University, Baoding 071002 (China) [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Key Laboratory of Photo-Electronics Information Materials of Hebei Province, Baoding 071002 (China); Di, Cong; Jia, Pengying [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)] [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)

    2013-09-30

    A DC-driven plasma jet has been developed to generate a diffuse plasma plume by blowing argon into the ambient air. The plasma plume, showing a cup shape with a diameter of several centimeters at a higher voltage, is a pulsed discharge despite a DC voltage is applied. The pulse frequency is investigated as a function of the voltage under different gap widths and gas flow rates. Results show that plasma bullets propagate from the hollow needle to the plate electrode by spatially resolved measurement. A supposition about non-electroneutral trail of the streamer is proposed to interpret these experimental phenomena.

  8. Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Kang, Sung Kil; Choi, Myeong Yeol; Koo, Il Gyo; Kim, Paul Y.; Kim, Yoonsun; Kim, Gon Jun; Mohamed, Abdel-Aleam H.; Collins, George J.; Lee, Jae Koo

    2011-04-01

    We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H2O2 entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state •OH generation inside the plasma and relative •OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing •OH generation and reached a maximum 5-log10 reduction with 0.6% H2O2 vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H2O2 vapor to the plasma.

  9. On the velocity variation in atmospheric pressure plasma plumes driven by positive and negative pulses

    SciTech Connect

    Xiong, Z.; Lu, X.; Xian, Y.; Jiang, Z.; Pan, Y [College of Electrical and Electronic Engineering, HuaZhong University of Science and Technology, WuHan, Hubei 430074 (China)

    2010-11-15

    To better understand the variation in the ''plasma bullet'' velocity, the dynamics of an atmospheric pressure plasma plume driven by positive and negative pulses are investigated in detail. It is found that, before the plasma exits the nozzle, the plasma propagates at a speed of about 30 km/s for both positive and negative pulses. As soon as the plasma exits the nozzle, the plasma propagation speed increases dramatically for both cases. The peak velocity for the case of the positive pulse is much higher than that of the negative pulse, it is approximately 150 km/s and 70 km/s, respectively. According to the optical emission spectra, the acceleration behavior of the plasma bullet when it exits the nozzle is due to the increase in the N{sub 2}{sup +} concentration.

  10. Generation and diagnostics of atmospheric pressure CO{sub 2} plasma by laser driven plasma wind tunnel

    SciTech Connect

    Matsui, Makoto; Yamagiwa, Yoshiki [Department of Mechanical Engineering, Shizuoka University, 3-5-4 Johoku, Naka, Hamamatsu, 432-8561 Shizuoka (Japan); Tanaka, Kensaku; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1 Hongo, Bunkyo, 113-0033 Tokyo (Japan); Nomura, Satoshi; Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8583 Chiba (Japan)

    2012-08-01

    Atmospheric pressure CO{sub 2} plasma was generated by a laser driven plasma wind tunnel. At an ambient pressure of 0.38 MPa, a stable plasma was maintained by a laser power of 1000 W for more than 20 min. The translational temperature was measured using laser absorption spectroscopy with the atomic oxygen line at 777.19 nm. The measured absorption profiles were analyzed by a Voigt function considering Doppler, Stark, and pressure-broadening effects. Under the assumption of thermochemical equilibrium, all broadening effects were consistent with each other. The measured temperature ranged from 8500 K to 8900 K.

  11. Filamentation instability of current-driven dust ion-acoustic waves in a collisional dusty plasma

    SciTech Connect

    Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 19839-63113 (Iran, Islamic Republic of); Haghtalab, T.; Khorashadizadeh, S. M. [Physics Department, Birjand University, Birjand 97179-63384 (Iran, Islamic Republic of)

    2011-11-15

    A theoretical investigation has been made of the dust ion-acoustic filamentation instability in an unmagnetized current-driven dusty plasma by using the Lorentz transformation formulas. The effect of collision between the charged particles with neutrals and their thermal motion on this instability is considered. Developing the filamentation instability of the current-driven dust ion-acoustic wave allows us to determine the period and the establishment time of the filamentation structure and threshold for instability development.

  12. A Laboratory Study of Asymmetric Magnetic Reconnection in Strongly-Driven Plasmas

    DOE PAGESBeta

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R. P.J.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-02-04

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely-directed field lines collide. In most natural circumstances the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. Additionally, the regime of strongly-driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed experiments to probe reconnection in asymmetric, strongly-driven, laser-generated plasmas. Here we show that, in this strongly-driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. Additionally, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.

  13. A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas.

    PubMed

    Rosenberg, M J; Li, C K; Fox, W; Igumenshchev, I; Séguin, F H; Town, R P J; Frenje, J A; Stoeckl, C; Glebov, V; Petrasso, R D

    2015-01-01

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely directed field lines collide. In most natural circumstances, the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. In addition, the regime of strongly driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed the experiments to probe reconnection in asymmetric, strongly driven, laser-generated plasmas. Here we show that, in this strongly driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. In addition, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows. PMID:25648079

  14. Current Transport in Tokamak Plasmas with Neutral Beam Driven Currents

    Microsoft Academic Search

    C. B. Forest

    1997-01-01

    Recent neutral beam current drive (NBCD) experiments on DIII--D have focused on independently measuring the conductivity and neutral beam driven currents to investigate the physical processes limiting noninductive ramp-up via NBCD. Detailed comparisons with theory indicate that frequently the current transport models are inadequate to describe the experimental results. As with studies of particle and heat transport, there is an

  15. Numerical simulation of plasma transport driven by the Io torus

    NASA Technical Reports Server (NTRS)

    Yang, Y. S.; Wolf, R. A.; Spiro, R. W.; Dessler, A. J.

    1992-01-01

    The Rice convection model (RCM) has been modified to a form suitable for Jupiter (RCM-J) to study plasma interchange motion in and near the Io plasma torus. The net result of the interchange is that flux tubes, heavily loaded with torus plasma, are transported outward, to be replaced by tubes containing little low-energy (less than 1 keV) plasma. The process is numerically simulated in terms of time evolution from an initial torus that is longitudinally asymmetric and with gradually decreasing density outward from Io's orbit. In the simulations, the nonlinear stage of the instability characteristically exhibits outreaching fingers of heavily-loaded flux tubes that lengthen at an accelerating rate. The principal finding is that the primary geometrical form of outward transport of torus plasma in Jupiter's magnetosphere is through long, outward-moving fingers of plasma. In the simulations, the fingers mainly form in the active sector of the Io torus (the heavier side of the asymmetric torus), and they are spaced longitudinally roughly 20 deg apart.

  16. Experimental study and optimization of Plasma Actuators for Flow control in subsonic regime

    NASA Astrophysics Data System (ADS)

    Moise, Pradeep; Mathew, Joseph; Venkatraman, Kartik; Thomas, Joy

    2010-11-01

    The induced jet produced by a dielectric barrier discharge (DBD) setup is capable of preventing flow separation on airfoils at high angles of attack. The effect of various parameters on the velocity of this induced jet was studied experimentally. The glow discharge was created at atmospheric conditions by using a high voltage RF power supply. Flow visualization, photographic studies of the plasma, and hot-wire measurements on the induced jet were performed. The parametric investigation of the characteristics of the plasma show that the width of the plasma in the uniform glow discharge regime was an indication of the velocity induced. It was observed that the spanwise and streamwise overlap of the two electrodes, dielectric thickness, voltage and frequency of the applied voltage are the major parameters that govern the velocity and the extent of plasma. The effect of the optimized configuration on the performance characteristics of an airfoil was studied experimentally.

  17. Two-dimensional scanning realized by an asymmetry fiber cantilever driven by single piezo bender actuator for optical coherence tomography.

    PubMed

    Wu, Tong; Ding, Zhihua; Wang, Kai; Chen, Minghui; Wang, Chuan

    2009-08-01

    We develop a fiber based probe that is capable of two-dimensional scanning applicable in optical coherence tomography (OCT). Based on the resonance of the fiber cantilever with asymmetry structure which has two distinguished resonant frequencies in orthogonal directions, Lissajous pattern is produced suitable for two-dimensional scanning upon a sample. Orthogonal resonances of the fiber cantilever are simultaneously excited by single piezo bender actuator with one driving signal consisting of two components corresponding to above-mentioned two resonant frequencies. By integrating a backward-placed two-dimensional position sensitive detector (PSD) into the probe, real-time lateral position of the scanning pattern is registered simultaneously for image reconstruction. Dynamical characteristics of the fiber cantilever are experimentally studied with special consideration on factors determining the resolution of the scanning pattern, including frequency and amplitude ratios between two components of the driving signal and fetching duration used for an en face image. With the developed probe implemented in our established OCT system, en face OCT images of typical samples are obtained with satisfying resolution and contrast, demonstrating the feasibility of such fiber cantilever with asymmetry structure for realizing two dimensional scanning by single actuator, potentially applicable to endoscopic OCT imaging. PMID:19654788

  18. Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    Modem low-pressure turbines, in general, utilize highly loaded airfoils in an effort to improve efficiency and to lower the number of airfoils needed. Typically, the airfoil boundary layers are turbulent and fully attached at takeoff conditions, whereas a substantial fraction of the boundary layers on the airfoils may be transitional at cruise conditions due to the change of density with altitude. The strong adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation at the latter low Reynolds number conditions. Large separation bubbles, particularly those which fail to reattach, cause a significant degradation of engine efficiency. A component efficiency drop of the order 2% may occur between takeoff and cruise conditions for large commercial transport engines and could be as large as 7% for smaller engines at higher altitude. An efficient means of of separation elimination/reduction is, therefore, crucial to improved turbine design. Because the large change in the Reynolds number from takeoff to cruise leads to a distinct change in the airfoil flow physics, a separation control strategy intended for cruise conditions will need to be carefully constructed so as to incur minimum impact/penalty at takeoff. A complicating factor, but also a potential advantage in the quest for an efficient strategy, is the intricate interplay between separation and transition for the situation at hand. Volino gives a comprehensive discussion of several recent studies on transition and separation under low-pressure-turbine conditions, among them one in the present facility. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions. If the transition occurs early in the boundary layer then separation may be reduced or completely eliminated. Transition in the shear layer of a separation bubble can lead to rapid reattachment. This suggests using control mechanisms to trigger and enhance early transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

  19. Current-Driven Plasma Acceleration Versus Current-Driven Energy Dissipation

    E-print Network

    Choueiri, Edgar

    modes of the MPD accelerator plasma as well as to derive the corresponding anomalous transport accelerators for high thrust efficiency as well as experiments to test the validity of the optimizing solutions

  20. Alfvénic instabilities driven by runaways in fusion plasmas

    SciTech Connect

    Fülöp, T. [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden); Newton, S. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

    2014-08-15

    Runaway particles can be produced in plasmas with large electric fields. Here, we address the possibility that such runaway ions and electrons excite Alfvénic instabilities. The magnetic perturbation induced by these modes can enhance the loss of runaways. This may have important implications for the runaway electron beam formation in tokamak disruptions.

  1. Plasma size and power scaling of ion temperature gradient driven turbulence

    SciTech Connect

    Idomura, Yasuhiro [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan)] [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan); Nakata, Motoki [Japan Atomic Energy Agency, Obuchi-Omotedate 2-166, Rokkasho, Kamikita, Aomori 039-3212 (Japan)] [Japan Atomic Energy Agency, Obuchi-Omotedate 2-166, Rokkasho, Kamikita, Aomori 039-3212 (Japan)

    2014-02-15

    The transport scaling with respect to plasma size and heating power is studied for ion temperature gradient driven turbulence using a fixed-flux full-f gyrokinetic Eulerian code. It is found that when heating power is scaled with plasma size, the ion heat diffusivity increases with plasma size in a local limit regime, where fixed-gradient ?f simulations predict a gyro-Bohm scaling. In the local limit regime, the transport scaling is strongly affected by the stiffness of ion temperature profiles, which is related to the power degradation of confinement.

  2. American Institute of Aeronautics and Astronautics Microscale Dielectric Barrier Discharge Plasma Actuators

    E-print Network

    Roy, Subrata

    American Institute of Aeronautics and Astronautics 1 Microscale Dielectric Barrier Discharge Plasma by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission of Aeronautics and Astronautics 2 d = damped frequency n = natural frequency = damping ratio I. Introduction

  3. Design and analysis of a novel flexure-based XY micro-positioning stage driven by electromagnetic actuators

    E-print Network

    Li, Yangmin

    . Many precise micro/nano-positioning stages are composed of compliant materials and flexure hinges [1Design and analysis of a novel flexure-based XY micro-positioning stage driven by electromagnetic's accuracy in our laboratory. I. INTRODUCTION Compliant positioning stages with ultrahigh precision play more

  4. Modeling of high-explosive driven plasma compression opening switches

    SciTech Connect

    Greene, A.E.; Lindemuth, I.R.; Goforth, J.H.

    1986-01-01

    The initial path of the current through a plasma compression switch is through a thin (500-nm thick) metal foil. The current explodes the foil to form the seed for the conducting plasma. The behavior of the foil at this point is the same as an exploding metal fuse for which we have a simple model. We have, therefore, chosen this model as our starting point. The fuse model assumes that the foil material is homogeneous and is characterized by a single temperature and density. The thickness of the foil is assumed to be much less than the magnetic diffusion skin depth so that the magnetic field varies linearly across the foil. For the present application we assume that the side of the foil away from the channel is fixed in space while the side by the channel is untamped. The foil/plasma will, therefore, cross the channel at the expansion velocity as the foil explodes. Equations for the electrical resistance of the foil, the magnetic fields, the motion of the foil, and the kinetic and internal energies are all solved selfconsistantly. The electrical resistivity, the pressure, and the specific energy of aluminium are taken from the Los Alamos SESAME EOS library. In the case of aluminum we have created a SESAME-style table based on the theory of More and Lee which we have modified to agree with experiment where possible.

  5. Sensor Driven Intelligent Control System For Plasma Processing

    SciTech Connect

    Bell, G.; Campbell, V.B.

    1998-02-23

    This Cooperative Research and Development Agreement (CRADA) between Innovative Computing Technologies, Inc. (IC Tech) and Martin Marietta Energy Systems (MMES) was undertaken to contribute to improved process control for microelectronic device fabrication. Process data from an amorphous silicon thin film deposition experiment was acquired to validate the performance of an intelligent, adaptive, neurally-inspired control software module designed to provide closed loop control of plasma processing machines used in the microelectronics industry. Data acquisition software was written using LabView The data was collected from an inductively coupled plasma (ICP) source, which was available for this project through LMES's RF/Microwave Technology Center. Experimental parameters measured were RF power, RF current and voltage on the antenna delivering power to the plasma, hydrogen and silane flow rate, chamber pressure, substrate temperature and H-alpha optical emission. Experimental results obtained were poly-crystallin silicon deposition rate, crystallinity, crystallographic orientation and electrical conductivity. Owing to experimental delays resulting from hardware failures, it was not possible to assemble a complete data for IC Tech use within the time and resource constraints of the CRADA. IC Tech was therefore not able to verify the performance of their existing models and control structures and validate model performance under this CRADA.

  6. Investigation of Turbulence, Intermittent Structures and Driven Flow in Magnetized Plasma Using Visible light Imaging

    NASA Astrophysics Data System (ADS)

    Guice, Daniel; Schaffner, David; Carter, Troy; Rossi, Giovanni; Vincena, Steve

    2012-10-01

    A fast framing camera is used to image plasma in the Large Plasma Device (LAPD) at UCLA. The use of a camera enables high spatial resolution in a single plasma discharge, without perturbing the plasma. Correlation between light fluctuations and plasma density is high, giving a physical link to what the camera records. From the light fluctuations instantaneous velocity fields are calculated using a wavelet based method that gives us the ability to estimate particle flux and Reynolds stress. These quantities are compared with results obtained with probes. Flow and flow shear is driven in the LAPD through applied bias on newly installed limiters; allowing for a detailed study of how shear flow modifies particle flux. Intermittent coherent structures (``blobs'' and ``holes'') have also been observed in the edge turbulence adjacent to the shear flow layer, and there effects on transport are investigated.

  7. A New Scheme for High-Intensity Laser-Driven Electron Acceleration in a Plasma 2

    E-print Network

    Sadykova, S P; Samkharadze, T G

    2015-01-01

    We propose a new approach to high-intensity relativistic laser-driven electron acceleration in a plasma. Here, we demonstrate that a plasma wave generated by a stimulated forward-scattering of an incident laser pulse can be in the longest acceleration phase with injected relativistic beam electrons. This is why the plasma wave has the maximum amplification coefficient which is determined by the acceleration time and the breakdown (overturn) electric field in which the acceleration of the injected beam electrons occurs. We must note that for the longest acceleration phase the relativity of the injected beam electrons plays a crucial role in our scheme. We estimate qualitatively the acceleration parameters of relativistic electrons in the field of a plasma wave generated at the stimulated forward-scattering of a high-intensity laser pulse in a plasma.

  8. Generation of powerful terahertz emission in a beam-driven strong plasma turbulence

    E-print Network

    Arzhannikov, A V

    2012-01-01

    Generation of terahertz electromagnetic radiation due to coalescence of upper-hybrid waves in the long-wavelength region of strong plasma turbulence driven by a high-current relativistic electron beam in a magnetized plasma is investigated. The width of frequency spectrum as well as angular characteristics of this radiation for various values of plasma density and turbulence energy are calculated using the simple theoretical model adequately describing beam-plasma experiments at mirror traps. It is shown that the power density of electromagnetic emission at the second harmonic of plasma frequency in the terahertz range for these laboratory experiments can reach the level of 1 ${MW/cm}^3$ with 1% conversion efficiency of beam energy losses to electromagnetic emission.

  9. The superdense plasma sheet in the magnetosphere during high-speed-stream-driven storms: Plasma transport timescales

    Microsoft Academic Search

    Michael H. Denton; Joseph E. Borovsky

    2009-01-01

    The superdense plasma sheet in the Earth's magnetosphere is studied via a superposition of multispacecraft data collected during 124 high-speed-stream-driven storms. The storm onsets tend to occur after the passage of the IMF sector reversal and before the passage of the stream interface, and the storms continue on for days during the passage of the high-speed stream. The superdense phase

  10. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2008-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  11. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2010-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  12. Characterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow

    Microsoft Academic Search

    Jichul Shin; V. Narayanaswamy; Laxminarayan L. Raja; Noel T. Clemens

    2007-01-01

    DOI: 10.2514\\/1.27197 An experimental study of a direct-current, nonequilibrium glow plasma discharge in the presence of a Mach 2.85 supersonic flow is presented. The discharge is generated with pinlike electrodes flush-mounted on a plane surface with sustaining currents between 25 to 300 mA. In the presence of a supersonic flow, two distinct discharge modes (diffuse and constricted) are observed depending

  13. Plasma wakefields driven by an incoherent combination of laser pulses: A path towards high-average power laser-plasma acceleratorsa)

    E-print Network

    Geddes, Cameron Guy Robinson

    Plasma wakefields driven by an incoherent combination of laser pulses: A path towards high on a time scale short compared to the plasma period. Incoherent combination of multiple laser pulses may accelerating structures.1,2 In a laser plasma accelerator (LPA), a short and intense laser pulse propagat- ing

  14. Electron beam driven lower hybrid waves in a dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi-110 068 (India)] [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi-110 068 (India); Sharma, Suresh C. [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi-110 042 (India)] [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi-110 042 (India); Gupta, Ruby [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi-110 036 (India)] [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi-110 036 (India)

    2013-05-15

    An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed.

  15. Influence of electromagnetic oscillating two-stream instability on the evolution of laser-driven plasma beat-wave

    SciTech Connect

    Gupta, D. N.; Singh, K. P.; Suk, H. [Center for Advanced Accelerators, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Computational Plasma Dynamics Laboratory, Kettering University, Flint, Michigan 48504 (United States); Center for Advanced Accelerators, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of)

    2007-01-15

    The electrostatic oscillating two-stream instability of laser-driven plasma beat-wave was studied recently by Gupta et al. [Phys. Plasmas 11, 5250 (2004)], who applied their theory to limit the amplitude level of a plasma wave in the beat-wave accelerator. As a self-generated magnetic field is observed in laser-produced plasma, hence, the electromagnetic oscillating two-stream instability may be another possible mechanism for the saturation of laser-driven plasma beat-wave. The efficiency of this scheme is higher than the former.

  16. Mechanism of high density plasma processes for ion-driven etching of materials

    NASA Astrophysics Data System (ADS)

    Lee, J. W.; Donohue, J. F.; Mackenzie, K. D.; Westerman, R.; Johnson, D.; Pearton, S. J.

    1999-09-01

    We propose a mechanism for ion-driven etching of materials in a high density plasma (>10 11 cm -3) system. An inductively coupled plasma (ICP) reactor was used to model the etch mechanism. Ion density and plasma potential were measured with a Langmuir probe and the self-induced dc bias simultaneously recorded. Power density (i.e. ion flux times ion energy) was found to be the most influential factor for predicting the etch rate of ion-driven materials, like dielectrics and III-nitrides, especially when running in a high density plasma (HDP) mode. Power density is also shown to be a function of ion mass, ion density, ion charge, dc bias and plasma potential. The relation between these plasma parameters and power density can be correlated with process parameters such as ICP source power, rf chuck power, chamber pressure and gas flow rate. This correlation was modeled with the aid of a design of experiment (DOE) simulation. We have demonstrated the use of a power density model to explain the mechanism responsible for HDP etching of SiO 2, which is one example of a high-bond strength material.

  17. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); Gans, T.; O'Connell, D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); York Plasma Institute, Department of Physics, University of York, Innovation Way, Heslington York YO10 5DQ (United Kingdom)

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  18. Characteristics of Turbulence-driven Plasma Flow and Origin of Experimental Empirical Scalings of Intrinsic Rotation

    SciTech Connect

    Wang, W. X.; Hahm, T. S.; Ethier, S.; Rewoldt, G.; Tang, W. M.; Lee, W. W.; Diamond, P. H.

    2011-03-20

    Toroidal plasma flow driven by turbulent torque associated with nonlinear residual stress generation is shown to recover the observed key features of intrinsic rotation in experiments. Specifically, the turbulence-driven intrinsic rotation scales close to linearly with plasma gradients and the inverse of the plasma current, qualitatively reproducing empirical scalings obtained from a large experimental data base. The effect of magnetic shear on the symmetry breaking in the parallel wavenumber spectrum is identified. The origin of the current scaling is found to be the enhanced kll#3; symmetry breaking induced by increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic rotation on the pressure gradient comes from the fact that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving the residual stress, are increased with the strength of the turbulence drives, which are R/LTe and R/Lne for the collisionless trapped electron mode (CTEM). Highlighted results also include robust radial pinches in toroidal flow, heat and particle transport driven by CTEM turbulence, which emerge "in phase", and are shown to play important roles in determining plasma profiles. Also discussed are experimental tests proposed to validate findings from these gyrokinetic simulations.

  19. Robust control of a shape memory alloy wire actuated flap

    Microsoft Academic Search

    Gangbing Song; Ning Ma

    2007-01-01

    In this paper, shape memory alloy (SMA) wire actuators are used to control the flap movement of a model airplane wing. Conventionally, the flap of an aircraft wing is driven by electric motors or hydraulic actuators. The use of SMA actuators has the advantage of significant weight reduction. Two SMA actuators are used: one to move the flap up and

  20. Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators: New Anti-Thrust Hypothesis, Frequency Sweeps Methodology, Humidity and Enclosure Effects

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.

    2014-01-01

    We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust, or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a grounded large-diameter metal sleeve. Strong dependence on humidity is also shown; the thrust significantly increased with decreasing humidity, e.g., 44 percent increase as relative humidity changed from 18 percent and dew point 33 degF to 50 percent and dew point of 57 degF.

  1. Current-driven plasma acceleration versus current-driven energy dissipation. III - Anomalous transport

    SciTech Connect

    Choueiri, E.Y.; Kelly, A.J.; Jahn, R.G. (Princeton University, NJ (United States))

    1992-07-01

    In the present paper the linear stability description and weak turbulence theory are used to develop a second order description of wave-particle transport and anomalous dissipation. The goal is to arrive at anomalous transport coefficients that can be readily included in fluid flow codes. In particular, expressions are derived for the heating rates of ions and electrons by the unstable waves and for the electron-wave momentum exchange rate that controls the anomalous resistivity effect. Comparative calculations were undertaken assuming four different saturation models: ion trapping, electron trapping, ion resonance broadening, and thermodynamic bound. A foremost finding is the importance of the role of electron Hall parameter in scaling the level of anomalous dissipation for the parameter range of the MPD thruster plasma. Polynomial expressions of the relevant transport coefficients cast solely in terms of macroscopic parameters are also obtained for inclusion in plasma fluid codes for the self-consistent numerical simulation of real thruster flows including microturbulent effects. 29 refs.

  2. High-Harmonic Fast Wave Driven H-mode Plasmas on NSTX

    SciTech Connect

    B.P. LeBlanc; R.E. Bell; S.I. Bernabei; K. Indireshkumar; S.M. Kaye; R. Maingi; T.K. Mau; D.W. Swain; G. Taylor; P.M. Ryan; J.B Wilgen; J.R. Wilson

    2003-05-01

    The launch of High-Harmonic Fast Waves (HHFW) routinely provides auxiliary power to NSTX plasmas, where it is used to heat electrons and pursue drive current. H-mode transitions have been observed in deuterium discharges, where only HHFW and ohmic heating, and no neutral beam injection (NBI), were applied to the plasma. The usual H-mode signatures are observed. A drop of the Da light marks the start of a stored energy increase, which can double the energy content. These H-mode plasmas also have the expected kinetic profile signatures with steep edge density and electron temperature pedestal. Similar to its NBI driven counterpart--also observed on NSTX-- the HHFW H mode have density profiles that features ''ears'' in the peripheral region. These plasmas are likely candidates for long pulse operation because of the combination of bootstrap current, associated with H-mode kinetic profiles, and active current drive, which can be generated with HHFW power.

  3. Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma

    SciTech Connect

    Kang, Sung Kil; Lee, Jae Koo [Department of Electronic and Electrical Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Choi, Myeong Yeol; Koo, Il Gyo; Kim, Paul Y.; Kim, Yoonsun; Kim, Gon Jun; Collins, George J. [Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States); Mohamed, Abdel-Aleam H. [Department of Electronic and Electrical Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Department of Physics, Faculty of Science, Taibah University, Almadinah Almunawwarah (Saudi Arabia)

    2011-04-04

    We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H{sub 2}O{sub 2} entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state OH generation inside the plasma and relative OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing OH generation and reached a maximum 5-log{sub 10} reduction with 0.6%H{sub 2}O{sub 2} vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H{sub 2}O{sub 2} vapor to the plasma.

  4. Status of microwave driven atmospheric plasma for oxidation of hydrocarbons

    SciTech Connect

    Ruden, T.E. [Ruden (Thomas E.), Newton Highlands, MA (United States); Lee, D.J. [Aneptek Corp., Natick, MA (United States)

    1998-12-31

    Initial results on oxidation of volatile organic compounds using a microwave created plasma in a TM{sub 010} cavity were presented at ICOPS. Work has continued with the use of improved diagnostic tools to determine the decomposition efficiency. Investigation of methods to achieve breakdown of air at atmospheric pressure using nominal levels of microwave power are in progress. Certified GC/MS analysis has confirmed a high level of decomposition of 100 ppm of isobutylene (C{sub 4}H{sub 8}) in air. Tests on the more complex hydrocarbon toluene are planned. Results on decomposition efficiency as a function of power level, flow rate, and gas temperature will be presented. Experimental test of the TM{sub 010} cavity with modified geometry has resulted in air breakdown at atmospheric pressure without resorting to an initial reduction in air pressure. A comparison of methods for achieving breakdown of air at atmospheric pressure under conditions of high volume flow rate will be presented.

  5. Experimental investigation of explosive-driven plasma-compression opening switches

    SciTech Connect

    Goforth, J.H.; Caird, R.S.

    1983-01-01

    Plasma-compression opening-switch techniques are being developed for use in explosive-driven magnetic-flux-compresssion-generator applications. A new test bed for performing low-cost experimentation is described. Experiments with approx.0.15 MA/cm linear current density in the switch have achieved resistance increases of a factor of 10 in a few hundred nanoseconds. Peak field strengths of 30 kV/cm are generated in these tests. Data are presented from preliminary tests that indicate reduced pressure in the plasma cavity enhanced switch performance.

  6. Distributed forcing flow control in the wake of a blunt trailing edge profiled body using plasma actuators

    NASA Astrophysics Data System (ADS)

    Naghib-Lahouti, A.; Hangan, H.; Lavoie, P.

    2015-03-01

    A modern flow control technique for reducing the drag associated with the periodic shedding of von Kármán vortices in the wake of a blunt trailing edge profiled body is presented. The technique involves distributed forcing of the wake flow using an array of dielectric barrier discharge plasma actuators, with a spanwise spacing matched to the spanwise wavelength of the dominant secondary wake instability. The experiments include measurement of the velocity field in multiple vertical and horizontal planes in the wake using particle image velocimetry, as well as base pressure, at Reynolds numbers of 2000, 3000, and 5000 based on trailing edge thickness. The flow control technique causes elongation of the vortex formation region across the span, and significant reduction of the fluctuating and total drag forces, up to a maximum of 94% and 18%, respectively. The effectiveness of the flow control technique is shown to be dependent on the induced momentum coefficient. Proper orthogonal decomposition analysis is used to investigate the mechanism of interaction of the flow control technique with the wake flow. Two distinct flow regimes are observed depending on the induced momentum coefficient. The effect of the control on the wake flow structure in the first regime is similar to those observed in previous studies involving mild spanwise-periodic geometric perturbations at the trailing edge, where control leads to streamwise displacement of the vortices and a shift in shedding frequency. However, an incremental increase in the momentum coefficient leads to a second flow regime similar to those previously observed in the case of large-amplitude geometric perturbations, with an almost complete attenuation of vortex shedding in the near-wake region.

  7. Formation of episodic magnetically driven radiatively cooled plasma jets in the laboratory

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Bland, S. N.; Chittenden, J. P.; Hall, G. N.; Harvey-Thompson, A.; Marocchino, A.; Ning, C.; Stehle, C.; Frank, A.; Blackman, E. G.; Bott, S. C.; Ray, T.

    2009-08-01

    We report on experiments in which magnetically driven radiatively cooled plasma jets were produced by a 1 MA, 250 ns current pulse on the MAGPIE pulsed power facility. The jets were driven by the pressure of a toroidal magnetic field in a “magnetic tower” jet configuration. This scenario is characterized by the formation of a magnetically collimated plasma jet on the axis of a magnetic “bubble”, confined by the ambient medium. The use of a radial metallic foil instead of the radial wire arrays employed in our previous work allows for the generation of episodic magnetic tower outflows which emerge periodically on timescales of ˜30 ns. The subsequent magnetic bubbles propagate with velocities reaching ˜300 km/s and interact with previous eruptions leading to the formation of shocks.

  8. Survey of electric field shear driven by radio frequency waves in tokamak plasmas

    SciTech Connect

    Jaeger, E.F.; Berry, L.A.; Batchelor, D.B.

    1998-11-01

    The stabilization of plasma turbulence by sheared poloidal rotation is thought to explain enhanced confinement in tokamak plasmas. One method proposed for controlling sheared flow is the use of externally driven radio-frequency (RF) waves. A number of calculations and some experiments have suggested that a modest amount of power in the ion cyclotron range of frequencies (ICRF) can drive the needed flows. Previous calculations have relied on incompressible fluid models which balance RF forces in the poloidal direction against neoclassical viscosity. But the incompressible assumption is not always valid, particularly for ion Bernstein waves (IBW). Also, since the IBW is a kinetic wave by nature, a fully consistent model should include kinetic effects. In this paper, RF driven flows are calculated from both compressible fluid and kinetic points of view.

  9. Shear-flow-driven ion cyclotron and ion sound-drift instabilities of cylindrical inhomogeneous plasma

    SciTech Connect

    Mikhailenko, V. S.; Chibisov, D. V. [Kharkov National University, 61108, Kharkov (Ukraine)

    2007-08-15

    The effects of the shear flow along the magnetic field on the development of the ion cyclotron, ion sound, and drift instabilities in the radially inhomogeneous cylindrical plasma are studied on the ground of a kinetic approach. It is shown that flow shear not only modifies the frequencies and growth rates of known current driven electrostatic ion cyclotron, ion sound, and drift instabilities, but is the source of the development of specific shear-flow-driven ion cyclotron, ion sound, and drift instabilities. These instabilities are excited at the levels of current along the ambient magnetic field which is below the critical value for the development of the modified by flow shear current driven ion cyclotron, ion sound, and drift instabilities.

  10. Plasma-Driven Catalysis Process for Toluene Abatement: Effect of Water Vapor

    Microsoft Academic Search

    Haibao Huang; Daiqi Ye; Dennis Y. C. Leung

    2011-01-01

    Plasma-driven catalysis (PDC) was used to remove toluene in air. Water vapor is a critical operating parameter in this process. Its effect on toluene removal efficiency, carbon balance, CO2 selectivity, and outlet O3 concentration was systematically investigated. Results showed that water vapor imposed negative effect on toluene decomposition since it depressed the formation and catalytic decomposition of O3. Water vapor

  11. The Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence: A Dynamical Systems Approach

    SciTech Connect

    R.A. Kolesnikov; J.A. Krommes

    2004-10-21

    The transition to collisionless ion-temperature-gradient-driven plasma turbulence is considered by applying dynamical systems theory to a model with ten degrees of freedom. Study of a four-dimensional center manifold predicts a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows and establishes the exact value of that shift in terms of physical parameters. For insight into fundamental physical mechanisms, the method provides a viable alternative to large simulations.

  12. A High-Density Hydrogen-Based Capillary Plasma Source for Particle-Beam-Driven Wakefield Accelerator Applications

    Microsoft Academic Search

    Hao Chen; Efthymios Kallos; Patric Muggli; Thomas C. Katsouleas; Martin A. Gundersen

    2009-01-01

    We report the generation of variable plasma densities up to 1019 cm-3 in hydrogen-filled hollow cathode capillary discharges and consider their applications as a practical plasma source for particle-beam-driven plasma wakefield accelerators. The capillary consists of a transparent cylindrical borosilicate glass tube. The plasma density is determined as a function of time, using Stark broadening of the Halpha line, with

  13. Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, Francisco; Lebedev, Sergey V.; Bland, Simon N.; Hall, Gareth N.; Swadling, George; Harvey-Thompson, Adam J.; Chittenden, Jeremy P.; Marocchino, Alberto; Ciardi, Andrea; Frank, Adam; Blackman, Eric G.; Bott, Simon C.

    2010-11-01

    We present experimental results of the formation of magnetically driven plasma jets, showing for the first time a way of producing episodic jet/ouflows in the laboratory. The jets are produced using a 6.5 ?m thick aluminum disk (a radial foil), which is subjected to the 1 MA, 250 ns current pulse from the MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]. The early time motion of the foil is characterized by the bulk motion of the mass due to the magnetic pressure, together with the formation of a surface plasma following the direction of the J×B force. A low density plasma fills the region above the foil preceding the formation of subsequent magnetically driven jets on the axis of expanding magnetic bubbles. The outflows emerge in timescales of ~30-40 ns and their episodic nature is the result of current reconnection in the foil, aided by the formation of current-driven instabilities in the jet and the distribution of mass available from the foil. The additional inductance due to the new current path inside the cavities was measured using an inductive probe, allowing to estimate the energy balance associated with the episodes. The measured temperature of the compressed jet resulted in Te~300 eV and a magnetic Reynolds number of ReM~200-1000, allowing the experiments to be in the regime relevant for scaled representations of astrophysical outflows.

  14. Fusion for Space Propulsion and Plasma Liner Driven MTF

    NASA Technical Reports Server (NTRS)

    Thio, Y.C. Francis; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    The need for fusion propulsion for interplanetary flights is discussed. For a propulsion system, there are three important system attributes: (1) The absolute amount of energy available, (2) the propellant exhaust velocity, and (3) the jet power per unit mass of the propulsion system (specific power). For human exploration and development of the solar system, propellant exhaust velocity in excess of 100 km/s and specific power in excess of 10 kW/kg are required. Chemical combustion cannot meet the requirement in propellant exhaust velocity. Nuclear fission processes typically result in producing energy in the form of heat that needs to be manipulated at temperatures limited by materials to about 2,800 K. Using the energy to heat a low atomic weight propellant cannot overcome the problem. Alternatively the energy can be converted into electricity which is then used to accelerate particles to high exhaust velocity. The necessary power conversion and conditioning equipment, however, increases the mass of the propulsion system for the same jet power by more than two orders of magnitude over chemical system, thus greatly limits the thrust-to-weight ratio attainable. If fusion can be developed, fusion appears to have the best of all worlds in terms of propulsion - it can provide the absolute amount, the propellant exhaust velocity, and the high specific jet power. An intermediate step towards pure fusion propulsion is a bimodal system in which a fission reactor is used to provide some of the energy to drive a fusion propulsion unit. The technical issues related to fusion for space propulsion are discussed. There are similarities as well as differences at the system level between applying fusion to propulsion and to terrestrial electrical power generation. The differences potentially provide a wider window of opportunities for applying fusion to propulsion. For example, pulsed approaches to fusion may be attractive for the propulsion application. This is particularly so in the light of significant development of the enabling pulsed power component technologies that have occurred in the last two decades because of defense and other energy requirements. The extreme states of matter required to produce fusion reactions may be more readily realizable in the pulsed states with less system mass than in steady states. Significant saving in system mass may result in pulsed fusion systems using plasmas in the appropriate density regimes. Magnetized target fusion, which attempts to combine the favorable attributes of magnetic confinement and inertial compression-containment into one single integrated fusion scheme, appears to have benefits that are worth exploring for propulsion application.

  15. Statistics of beam-driven waves in plasmas with ambient fluctuations: Reduced-parameter approach

    NASA Astrophysics Data System (ADS)

    Tyshetskiy, Yu.; Cairns, I. H.; Robinson, P. A.

    2008-09-01

    A reduced-parameter (RP) model of quasilinear wave-plasma interactions is used to analyze statistical properties of beam-driven waves in plasmas with ambient density fluctuations. The probability distribution of wave energies in such a system is shown to have a relatively narrow peak just above the thermal wave level, and a power-law tail at high energies, the latter becoming progressively more evident for increasing characteristic amplitude of the ambient fluctuations. To better understand the physics behind these statistical features of the waves, a simplified model of stochastically driven thermal waves is developed on the basis of the RP model. An approximate analytic solution for stationary statistical distribution of wave energies W is constructed, showing a good agreement with that of the original RP model. The "peak" and "tail" features of the wave energy distribution are shown to be a result of contributions of two groups of wave clumps: those subject to either very slow or very fast random variations of total wave growth rate (due to fluctuations of ambient plasma density), respectively. In the case of significant ambient plasma fluctuations, the overall wave energy distribution is shown to have a clear power-law tail at high energies, P(W )?W-?, with nontrivial exponent 1plasma waves observed by the Ulysses spacecraft in some interplanetary type III burst sources. This resemblance is discussed qualitatively, and it is suggested that the stochastically driven thermal waves might be a candidate for explaining the power-law tails in the observed wave statistics without invoking mechanisms such as self-organized criticality or nonlinear wave collapse.

  16. Computational model of collisional-radiative nonequilibrium plasma in an air-driven type laser propulsion

    SciTech Connect

    Ogino, Yousuke; Ohnishi, Naofumi [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2010-05-06

    A thrust power of a gas-driven laser-propulsion system is obtained through interaction with a propellant gas heated by a laser energy. Therefore, understanding the nonequilibrium nature of laser-produced plasma is essential for increasing available thrust force and for improving energy conversion efficiency from a laser to a propellant gas. In this work, a time-dependent collisional-radiative model for air plasma has been developed to study the effects of nonequilibrium atomic and molecular processes on population densities for an air-driven type laser propulsion. Many elementary processes are considered in the number density range of 10{sup 12}/cm{sup 3}<=N<=10{sup 19}/cm{sup 3} and the temperature range of 300 K<=T<=40,000 K. We then compute the unsteady nature of pulsively heated air plasma. When the ionization relaxation time is the same order as the time scale of a heating pulse, the effects of unsteady ionization are important for estimating air plasma states. From parametric computations, we determine the appropriate conditions for the collisional-radiative steady state, local thermodynamic equilibrium, and corona equilibrium models in that density and temperature range.

  17. PROTOPLASMA - Proton-driven plasma-wakefield experiment at Fermilab: Stages and approach

    SciTech Connect

    Thangaraj, J. C. T.; Park, C. S.; Lewis, J. D.; Spentzouris, P.; An, W.; Mori, W.; Joshi, C. [Fermi National Accelerator Laboratory, IL (United States); Univ. of California, Los Angeles, CA (United States)

    2012-12-21

    Generation of TeV-scale electron beams using conventional RF technology appears expensive for building the next generation of colliders. Proton-driven plasma-wakefield acceleration of electrons promises an alternative route to generate TeV-scale electron beams using existing proton machines. PROTOPLASMA is the proposed R and D project at Fermilab that plans to use a proton beam driven plasma-wakefield to accelerate electrons. The project is planned in stages with the project's path guided by simulations. First, a 60-120 GeV proton beam will be injected into 1-2 meters of plasma to observe selfmodulation instability in the proton beam. Next, an injected 5 MeV electron beam will be accelerated by the plasma. In this paper, we report on the basic project plan and outline our staged approach. We report on first simulation results that show self-modulation of a proton bunch and discuss beam optics requirements and other limits.

  18. LETTER: Effect of plasma rotation on the beam-driven current

    NASA Astrophysics Data System (ADS)

    Cottrell, G. A.; Kemp, R.

    2009-04-01

    In a rotating plasma, with co-neutral beam injection (NBI), the Doppler shift of the NBI particles, as viewed in the frame of the plasma, can result in a significant reduction in the beam-driven (Ohkawa) current when the rotation is strong (i.e. with rotational Mach numbers, M >= 0.5). The correction applies to the toroidal fast ion current calculated for a non-rotating plasma and is independent of the normal Zeff and electron trapping terms. A simple analytical model is presented to estimate the magnitude of the effect for plasmas with arbitrary toroidal rotation and the conditions where this is important have been identified. This model has been compared with the results from existing Monte Carlo neutral beam codes and found to reproduce their results. The important parameters in this problem are the ratio, \\rho^{Lab} = v_{f0}^Lab/v_crit , of the NBI injection particle velocity (in the laboratory frame) to the critical velocity of the plasma, and the ratio ?phi = vphi/vcrit which is related to the rotational Mach number. A phase plot in dimensionless (?Lab, ?phi) space is presented which enables the fast ion current drive efficiencies to be compared for different tokamaks. For strongly rotating plasmas, the degradation in fast ion current efficiency is significant for ?Lab <= 1. However, when ?Lab is larger than this, the degradation in fast ion current drive is less severe. Approaches to improve the fast ion current drive efficiency are briefly discussed.

  19. Two-dimensional Vlasov Simulation of Driven, Nonlinear Electron Plasma Waves

    NASA Astrophysics Data System (ADS)

    Hittinger, J. A.; Banks, J. W.; Berger, R. L.; Cohen, B. I.; Brunner, S.

    2010-11-01

    In the VALHALLA project at LLNL, we are developing advanced, scalable algorithms for the continuum solution of Vlasov-Maxwell that differ from traditional approaches to continuum Vlasov methods.ootnotetextJ. Banks and J.Hittinger, sub. to IEEE Trans. Plas. Sci. (Dec 2009), LLNL-JRNL-420843. Here, continuum solution of the Vlasov-Maxwell system using these techniques is extended to two spatial dimensions and two velocity dimensions. We report Vlasov simulation studies of ponderomotively driven electron plasma waves (EPW) with fixed ions. Motivated plasma waves driven by SRS in light speckles, we consider a driving potential with a finite transverse width. This localization introduces losses as the waves propagate transversely out of the driven region and the particles are only transiently trapped. Linearly, the transverse localization leads to constant phase surfaces that defocus the EPW while nonlinearly, the constant phase surfaces from trapping-induced frequency shifts focus the EPW. We show how these processes are affected by the system length and the boundary conditions.

  20. Numerical Modeling and Testing of an Inductively-Driven and High-Energy Pulsed Plasma Thrusters

    NASA Technical Reports Server (NTRS)

    Parma, Brian

    2004-01-01

    Pulsed Plasma Thrusters (PPTs) are advanced electric space propulsion devices that are characterized by simplicity and robustness. They suffer, however, from low thrust efficiencies. This summer, two approaches to improve the thrust efficiency of PPTs will be investigated through both numerical modeling and experimental testing. The first approach, an inductively-driven PPT, uses a double-ignition circuit to fire two PPTs in succession. This effectively changes the PPTs configuration from an LRC circuit to an LR circuit. The LR circuit is expected to provide better impedance matching and improving the efficiency of the energy transfer to the plasma. An added benefit of the LR circuit is an exponential decay of the current, whereas a traditional PPT s under damped LRC circuit experiences the characteristic "ringing" of its current. The exponential decay may provide improved lifetime and sustained electromagnetic acceleration. The second approach, a high-energy PPT, is a traditional PPT with a variable size capacitor bank. This PPT will be simulated and tested at energy levels between 100 and 450 joules in order to investigate the relationship between efficiency and energy level. Arbitrary Coordinate Hydromagnetic (MACH2) code is used. The MACH2 code, designed by the Center for Plasma Theory and Computation at the Air Force Research Laboratory, has been used to gain insight into a variety of plasma problems, including electric plasma thrusters. The goals for this summer include numerical predictions of performance for both the inductively-driven PPT and high-energy PFT, experimental validation of the numerical models, and numerical optimization of the designs. These goals will be met through numerical and experimental investigation of the PPTs current waveforms, mass loss (or ablation), and impulse bit characteristics.

  1. Formation of Episodic Magnetically Driven Radiatively Cooled Plasma Jets in Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, Francisco; Lebedev, Sergey V.; Ciardi, Andrea; Bland, Simon N.; Chittenden, Jeremy P.; Hall, Gareth N.; Harvey-Thompson, Adam; Marocchino, Alberto; Ning, Cheng; Stehle, Chantal; Frank, Adam; Blackman, Eric G.; Bott, Simon C.; Ray, Tom

    We report on experiments in which magnetically driven radiatively cooled plasma jets were produced by a 1 MA, 250 ns current pulse on the MAGPIE pulsed power facility. The jets were driven by the pressure of a toroidal magnetic field in a "magnetic tower" jet configuration. This scenario is characterized by the formation of a magnetically collimated plasma jet on the axis of a magnetic cavity, confined by the ambient medium. The use of a radial metallic foil instead of the radial wire arrays employed in our previous work allows for the generation of episodic magnetic tower outflows which emerge periodically on timescales of ˜ 30 ns. The subsequent magnetic bubbles propagate with velocities reaching ˜ 300 km/s and interact with previous eruptions. This setup also allowed for the addition of a neutral gas above the foil in order to study the effect of the ambient density on the dynamics of both the early time hydrodynamic jet formed from plasma ablated from the foil and of the subsequent magnetic tower outflows.

  2. Compact disposal of high-energy electron beams using passive or laser-driven plasma decelerating stage

    SciTech Connect

    Bonatto, A.; Schroeder, C.B.; Vay, J.-L.; Geddes, C.R.; Benedetti, C.; Esarey and, E.; Leemans, W.P.

    2014-07-13

    A plasma decelerating stage is investigated as a compact alternative for the disposal of high-energy beams (beam dumps). This could benefit the design of laser-driven plasma accelerator (LPA) applications that require transportability and or high-repetition-rate operation regimes. Passive and laser-driven (active) plasma-based beam dumps are studied analytically and with particle-in-cell (PIC) simulations in a 1D geometry. Analytical estimates for the beam energy loss are compared to and extended by the PIC simulations, showing that with the proposed schemes a beam can be efficiently decelerated in a centimeter-scale distance.

  3. Laser experiments to simulate coronal mass ejection driven magnetospheres and astrophysical plasma winds on compact magnetized stars

    NASA Astrophysics Data System (ADS)

    Horton, W.; Ditmire, T.; Zakharov, Yu. P.

    2010-06-01

    Laboratory experiments using a plasma wind generated by laser-target interaction are proposed to investigate the creation of a shock in front of the magnetosphere and the dynamo mechanism for creating plasma currents and voltages. Preliminary experiments are shown where measurements of the electron density gradients surrounding the obstacles are recorded to infer the plasma winds. The proposed experiments are relevant to understanding the electron acceleration mechanisms taking place in shock-driven magnetic dipole confined plasmas surrounding compact magnetized stars and planets. Exploratory experiments have been published [P. Brady, T. Ditmire, W. Horton, et al., Phys. Plasmas 16, 043112 (2009)] with the one Joule Yoga laser and centimeter sized permanent magnets.

  4. Scissor thrust valve actuator

    DOEpatents

    DeWall, Kevin G.; Watkins, John C; Nitzel, Michael E.

    2006-08-29

    Apparatus for actuating a valve includes a support frame and at least one valve driving linkage arm, one end of which is rotatably connected to a valve stem of the valve and the other end of which is rotatably connected to a screw block. A motor connected to the frame is operatively connected to a motor driven shaft which is in threaded screw driving relationship with the screw block. The motor rotates the motor driven shaft which drives translational movement of the screw block which drives rotatable movement of the valve driving linkage arm which drives translational movement of the valve stem. The valve actuator may further include a sensory control element disposed in operative relationship with the valve stem, the sensory control element being adapted to provide control over the position of the valve stem by at least sensing the travel and/or position of the valve stem.

  5. Rotary actuators

    Microsoft Academic Search

    A. M. Pawlak; S. Schultz; V. Gangla

    1994-01-01

    Rotary actuators are electromagnetic devices developing mechanical torque with limited rotary motion. Because of their simplicity and low cost they are finding more and more applications, especially in the automotive field. This paper describes a novel homopolar rotary actuator with a ring-type radially-magnetized multipolar permanent magnet featuring a high force density “transverse flux” configuration which performs a spring action by

  6. Global Hybrid Simulations of Energetic Particle-driven Modes in Toroidal Plasmas

    SciTech Connect

    G.Y. Fu; J. Breslau; E. Fredrickson; W. Park; H.R. Strauss

    2004-12-14

    Global hybrid simulations of energetic particle-driven MHD modes have been carried out for tokamaks and spherical tokamaks using the hybrid code M3D. The numerical results for the National Spherical Tokamak Experiments (NSTX) show that Toroidal Alfven Eigenmodes are excited by beam ions with their frequencies consistent with the experimental observations. Nonlinear simulations indicate that the n=2 mode frequency chirps down as the mode moves out radially. For ITER, it is shown that the alpha-particle effects are strongly stabilizing for internal kink mode when central safety factor q(0) is sufficiently close to unity. However, the elongation of ITER plasma shape reduces the stabilization significantly.

  7. Numerical Simulation of Waves Driven by Plasma Currents Generated by Low-Frequency Alfven Waves in a Multi-Ion Plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2003-01-01

    When multi-ion plasma consisting of heavy and light ions is permeated by a lowfrequency Alfien (LFA) wave, the EXB and the polarization drifts of the different ion species and the electrons could be quite different. The relative drifts between the charged-particle species drive waves, which energize the plasma. Using 2.5-D particle-in-cell simulations, we study this process of wave generation and its nonlinear consequences in terms of acceleration and heating plasma. Specifically we study the situation for LFA wave frequency being lower than the heavyion cyclotron frequency in a multi-ion plasma. We impose such a wave to the plasma assuming that its wavelength is much larger than that of the waves generated by the relative drifts. For better understanding, the LFA-wave driven simulations are augmented by those driven by initialized ion beams.

  8. Electron-ion hybrid instabilities driven by velocity shear in a magnetized plasma

    NASA Technical Reports Server (NTRS)

    Romero, H.; Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

    1992-01-01

    The stability of a magnetized plasma is investigated in which a sheared electron flow channel is present. The flow's peak velocity and shear scale length are denoted by V and L, respectively. If the velocity channel is perpendicular to the confining magnetic field and L is less than the ion Larmor radius, an electrostatic instability develops whose frequency is on the order of the lower hybrid frequency. It is concluded that velocity shear is the only source of free energy. Further, it is shown that density gradients do not stabilize this mode. It follows that the mode presented in this work can not be identified with the well-known modified two-stream instability. If the velocity channel is parallel to the confining magnetic field and the plasma is weakly magnetized, an instability driven by velocity shear is shown to exist.

  9. A novel global model for radio-frequency driven plasmas at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Hemke, Torben; Mussenbrock, Thomas; Brinkmann, Ralf Peter

    2012-10-01

    Over the last years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are the so called plasma jets. Besides the more elaborated fluid or hybrid approaches the so called global models offer the ability to explore averaged species densities and energies while remaining computationally efficient. This contribution investigates a coplanar radio-frequency driven plasma jet by means of a novel global model. The model takes into account the strong modulation of the electric field in time and space both in the sheath and bulk region. By means of a consistent scale analysis we find an analytical expression for the electric field. We compare our obtained electric field to results from PIC simulations and present the general concept for this novel global model of the microplasma jet.

  10. Free-electron laser driven by the LBNL laser-plasma accelerator

    SciTech Connect

    Schroeder, C. B.; Fawley, W. M.; Gruner, F.; Bakeman, M.; Nakamura, K.; Robinson, K. E.; Toth, Cs.; Esarey, E.; Leemans, W. P.

    2008-08-04

    A design of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, XUV pulses is presented. The FEL is driven by ahigh-current, 0.5 GeV electron beam from the Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few centimeters. The proposed ultra-fast source (~;;10 fs) would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science. Owing to the high current (>10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 10^13 photons/pulse. Devices based both on self-amplified spontaneous emission and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered.

  11. Design of a free-electron laser driven by the LBNLlaser-plasma-accelerator

    SciTech Connect

    Schroeder, C.B.; Fawley, W.M.; Montgomery, A.L.; Robinson, K.E.; Gruner, F.; Bakeman, M.; Leemans, W.P.

    2007-09-10

    We discuss the design and current status of a compactfree-electron laser (FEL), generating ultra-fast, high-peak flux, VUVpulses driven by a high-current, GeV electron beam from the existingLawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator,whose active acceleration length is only a few cm. The proposedultra-fast source would be intrinsically temporally synchronized to thedrive laser pulse, enabling pump-probe studies in ultra-fast science withpulse lengths of tens of fs. Owing to the high current (&10 kA) ofthe laser-plasma-accelerated electron beams, saturated output fluxes arepotentially greater than 1013 photons/pulse. Devices based both on SASEand high-harmonic generated input seeds, to reduce undulator length andfluctuations, are considered.

  12. Kinetic simulation of capacitively coupled plasmas driven by trapezoidal asymmetric voltage pulses

    SciTech Connect

    Diomede, Paola, E-mail: padiomede@gmail.com; Economou, Demetre J., E-mail: economou@uh.edu [Plasma Processing Laboratory, Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004 (United States)

    2014-06-21

    A kinetic Particle-In-Cell simulation with Monte Carlo Collisions was performed of a geometrically symmetric capacitively coupled, parallel-plate discharge in argon, driven by trapezoidal asymmetric voltage pulses with a period of 200?ns. The discharge was electrically asymmetric, making the ion energy distributions at the two electrodes different from one another. The fraction of the period (?), during which the voltage was kept at a constant (top-flat) positive value, was a critical control parameter. For the parameter range investigated, as ? increased, the mean ion energy on the grounded electrode increased and the ions became more directional, whereas the opposite was found for the ions striking the powered electrode. The absolute value of the DC self-bias voltage decreased as ? increased. Plasma instabilities, promoted by local double layers and electric field reversals during the time of the positive voltage excursion, were characterized by electron plasma waves launched from the sheath edge.

  13. Self-organized T(sub)e Redistribution during Driven Reconnection Processes in High Temperature Plasmas

    SciTech Connect

    Park, H.K.; Mazzucato, E.; Luhmann, N.C., Jr.; Domier, C.W.; Xia, Z.; Munsat, T.; Donné, A.J.H.; Classen, I.G.J.; van de Pol, M.J.; TEXTOR team

    2005-12-01

    Two-dimensional (2-D) images of electron temperature fluctuations with a high temporal and spatial resolution were employed to study the sawtooth oscillation in TEXTOR tokamak plasmas. The new findings are: 1) 2-D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. 2) The combination of a pressure driven mode and a kink instability leads to an "X-point" reconnection process. 3) Reconnection can take place anywhere along the q~1 rational magnetic surface (both high and low field sides). 4) Heat flow from the core to the outside of the inversion radius during the reconnection time is highly asymmetric and the behavior is collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas.

  14. Kinetic simulation of capacitively coupled plasmas driven by trapezoidal asymmetric voltage pulses

    NASA Astrophysics Data System (ADS)

    Diomede, Paola; Economou, Demetre J.

    2014-06-01

    A kinetic Particle-In-Cell simulation with Monte Carlo Collisions was performed of a geometrically symmetric capacitively coupled, parallel-plate discharge in argon, driven by trapezoidal asymmetric voltage pulses with a period of 200 ns. The discharge was electrically asymmetric, making the ion energy distributions at the two electrodes different from one another. The fraction of the period (?), during which the voltage was kept at a constant (top-flat) positive value, was a critical control parameter. For the parameter range investigated, as ? increased, the mean ion energy on the grounded electrode increased and the ions became more directional, whereas the opposite was found for the ions striking the powered electrode. The absolute value of the DC self-bias voltage decreased as ? increased. Plasma instabilities, promoted by local double layers and electric field reversals during the time of the positive voltage excursion, were characterized by electron plasma waves launched from the sheath edge.

  15. Weibel-Induced Filamentation during an Ultrafast Laser-Driven Plasma Expansion

    NASA Astrophysics Data System (ADS)

    Quinn, K.; Romagnani, L.; Ramakrishna, B.; Sarri, G.; Dieckmann, M. E.; Wilson, P. A.; Fuchs, J.; Lancia, L.; Pipahl, A.; Toncian, T.; Willi, O.; Clarke, R. J.; Notley, M.; Macchi, A.; Borghesi, M.

    2012-03-01

    The development of current instabilities behind the front of a cylindrically expanding plasma has been investigated experimentally via proton probing techniques. A multitude of tubelike filamentary structures is observed to form behind the front of a plasma created by irradiating solid-density wire targets with a high-intensity (I˜1019W/cm2), picosecond-duration laser pulse. These filaments exhibit a remarkable degree of stability, persisting for several tens of picoseconds, and appear to be magnetized over a filament length corresponding to several filament radii. Particle-in-cell simulations indicate that their formation can be attributed to a Weibel instability driven by a thermal anisotropy of the electron population. We suggest that these results may have implications in astrophysical scenarios, particularly concerning the problem of the generation of strong, spatially extended and sustained magnetic fields in astrophysical jets.

  16. Weibel-induced filamentation during an ultrafast laser-driven plasma expansion.

    PubMed

    Quinn, K; Romagnani, L; Ramakrishna, B; Sarri, G; Dieckmann, M E; Wilson, P A; Fuchs, J; Lancia, L; Pipahl, A; Toncian, T; Willi, O; Clarke, R J; Notley, M; Macchi, A; Borghesi, M

    2012-03-30

    The development of current instabilities behind the front of a cylindrically expanding plasma has been investigated experimentally via proton probing techniques. A multitude of tubelike filamentary structures is observed to form behind the front of a plasma created by irradiating solid-density wire targets with a high-intensity (I ~ 10(19) W/cm(2)), picosecond-duration laser pulse. These filaments exhibit a remarkable degree of stability, persisting for several tens of picoseconds, and appear to be magnetized over a filament length corresponding to several filament radii. Particle-in-cell simulations indicate that their formation can be attributed to a Weibel instability driven by a thermal anisotropy of the electron population. We suggest that these results may have implications in astrophysical scenarios, particularly concerning the problem of the generation of strong, spatially extended and sustained magnetic fields in astrophysical jets. PMID:22540706

  17. Plasma turbulence driven by transversely large-scale standing shear Alfven waves

    SciTech Connect

    Singh, Nagendra; Rao, Sathyanarayan [Electrical and Computer Engineering, University of Alabama, Huntsville, Alabama 35899 (United States)

    2012-12-15

    Using two-dimensional particle-in-cell simulations, we study generation of turbulence consisting of transversely small-scale dispersive Alfven and electrostatic waves when plasma is driven by a large-scale standing shear Alfven wave (LS-SAW). The standing wave is set up by reflecting a propagating LS-SAW. The ponderomotive force of the standing wave generates transversely large-scale density modifications consisting of density cavities and enhancements. The drifts of the charged particles driven by the ponderomotive force and those directly caused by the fields of the standing LS-SAW generate non-thermal features in the plasma. Parametric instabilities driven by the inherent plasma nonlinearities associated with the LS-SAW in combination with the non-thermal features generate small-scale electromagnetic and electrostatic waves, yielding a broad frequency spectrum ranging from below the source frequency of the LS-SAW to ion cyclotron and lower hybrid frequencies and beyond. The power spectrum of the turbulence has peaks at distinct perpendicular wave numbers (k{sub Up-Tack }) lying in the range d{sub e}{sup -1}-6d{sub e}{sup -1}, d{sub e} being the electron inertial length, suggesting non-local parametric decay from small to large k{sub Up-Tack }. The turbulence spectrum encompassing both electromagnetic and electrostatic fluctuations is also broadband in parallel wave number (k{sub ||}). In a standing-wave supported density cavity, the ratio of the perpendicular electric to magnetic field amplitude is R(k{sub Up-Tack }) = |E{sub Up-Tack }(k{sub Up-Tack })/|B{sub Up-Tack }(k{sub Up-Tack })| Much-Less-Than V{sub A} for k{sub Up-Tack }d{sub e} < 0.5, where V{sub A} is the Alfven velocity. The characteristic features of the broadband plasma turbulence are compared with those available from satellite observations in space plasmas.

  18. Preparation of magnetized nanodusty plasmas in a radio frequency-driven parallel-plate reactor

    SciTech Connect

    Tadsen, Benjamin, E-mail: tadsen@physik.uni-kiel.de; Greiner, Franko; Piel, Alexander [IEAP, Christian-Albrechts-Universität, D-24098 Kiel (Germany)

    2014-10-15

    Nanodust is produced in an rf-driven push-pull parallel-plate reactor using argon with an acetylene admixture at 5–30?Pa. A scheme for the preparation of nanodust clouds with particle radii up to 400?nm for investigations in magnetized plasmas is proposed. The confinement that keeps the nanodust of different radii inside a moderately magnetized discharge (B???500?mT) is investigated by a comparison of 2d-Langmuir probe measurements in the dust-free plasma without and with a magnetic field and by the analysis of scattered light of nanodust clouds. It is shown that the dust cloud changes its shape when the dust density changes. This results in a reversed ?-?{sup ?} transition from a dense dust cloud with a central disk-like void to a dilute dust cloud with a toroidal void. When the dust density is further reduced, filaments are observed in the central part of the cloud, which were absent in the high-density phase. It is concluded that the dense nanodust cloud is able to suppress plasma filamentation in magnetized plasmas.

  19. High and low frequency instabilities driven by counter-streaming electron beams in space plasmas

    SciTech Connect

    Mbuli, L. N. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200, Republic of South Africa (South Africa); University of the Western Cape, Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa); Maharaj, S. K. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200, Republic of South Africa (South Africa); Bharuthram, R. [University of the Western Cape, Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa)

    2014-05-15

    A four-component plasma composed of a drifting (parallel to ambient magnetic field) population of warm electrons, drifting (anti-parallel to ambient magnetic field) cool electrons, stationary hot electrons, and thermal ions is studied in an attempt to further our understanding of the excitation mechanisms of broadband electrostatic noise (BEN) in the Earth's magnetospheric regions such as the magnetosheath, plasmasphere, and plasma sheet boundary layer (PSBL). Using kinetic theory, beam-driven electrostatic instabilities such as the ion-acoustic, electron-acoustic instabilities are found to be supported in our multi-component model. The dependence of the instability growth rates and real frequencies on various plasma parameters such as beam speed, number density, temperature, and temperature anisotropy of the counter-streaming (relative to ambient magnetic field) cool electron beam are investigated. It is found that the number density of the anti-field aligned cool electron beam and drift speed play a central role in determining which instability is excited. Using plasma parameters which are closely correlated with the measurements made by the Cluster satellites in the PSBL region, we find that the electron-acoustic and ion-acoustic instabilities could account for the generation of BEN in this region.

  20. A gas-puff-driven theta pinch for plasma-surface interaction studies

    NASA Astrophysics Data System (ADS)

    Jung, Soonwook; Kesler, Leigh; Yun, Hyun-Ho; Curreli, Davide; Andruczyk, Daniel; Ruzic, David

    2012-10-01

    DEVeX is a theta pinch device used to investigate fusion-related material interaction such as vapor shielding and ICRF antenna interactions with plasma-pulses in a laboratory setting. The simulator is required to produce high heat-flux plasma enough to induce temperature gradient high enough to study extreme conditions happened in a plasma fusion reactor. In order to achieve it, DEVeX is reconfigured to be combined with gas puff system as gas puffing may reduce heat flux loss resulting from collisions with neutral. A gas puff system as well as a conical gas nozzle is manufactured and several diagnostics including hot wire anemometer and fast ionization gauge are carried out to quantitatively estimate the supersonic flow of gas. Energy deposited on the target for gas puffing and static-filled conditions is measured with thermocouples and its application to TELS, an innovative concept utilizing a thermoelectric-driven liquid metal flow for plasma facing component, is discussed.

  1. Convection in galaxy-cluster plasmas driven by active galactic nuclei and cosmic-ray buoyancy

    E-print Network

    Benjamin D. G. Chandran

    2004-12-20

    Turbulent heating may play an important role in galaxy-cluster plasmas, but if turbulent heating is to balance radiative cooling in a quasi-steady state, some mechanism must set the turbulent velocity to the required value. This paper explores one possible regulating mechanism associated with an active galactic nucleus at cluster center. A steady-state model for the intracluster medium is presented in which radiative cooling is balanced by a combination of turbulent heating and thermal conduction. The turbulence is generated by convection driven by the buoyancy of cosmic rays produced by a central radio source. The cosmic-ray luminosity is powered by the accretion of intracluster plasma onto a central black hole. The model makes the rather extreme assumption that the cosmic rays and thermal plasma are completely mixed. Although the intracluster medium is convectively unstable near cluster center in the model solutions, the specific entropy of the thermal plasma still increases outwards because of the cosmic-ray modification to the stability criterion. The model provides a self-consistent calculation of the turbulent velocity as a function of position, but fails to reproduce the steep central density profiles observed in clusters. The principal difficulty is that in order for the fully mixed intracluster medium to become convectively unstable, the cosmic-ray pressure must become comparable to or greater than the thermal pressure within the convective region. The large cosmic-ray pressure gradient then provides much of the support against gravity, reducing the thermal pressure gradient near cluster center and decreasing the central plasma density gradient. A more realistic AGN-feedback model of intracluster turbulence in which relativistic and thermal plasmas are only partially mixed may have greater success.

  2. Formation of Magnetically Driven Radiatively Cooled Plasma Jets in the Laboratory

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Bland, S. N.; Chittenden, J. P.; Hall, G.; Harvey-Thompson, A.; Marocchino, A.; Ning, C.; Ciardi, A.; Stehle, C.; Frank, A.; Blackman, E. G.; Bott, S. C.; Ray, T.

    2008-04-01

    Previous experiments have successfully showed the formation of magnetically driven radiatively cooled plasma jets which are relevant to the launching of astrophysical jets. The jets in these experiments are driven by the pressure of the toroidal magnetic field produced by the MAGPIE generator which leads to the formation of a ``magnetic tower'' structure. This scenario is characterized by the formation of a magnetic ``bubble'' surrounding a collimated plasma jet on axis. A modification of this experimental configuration, in which radial wire array is replaced by radial metallic foil, results in the formation of episodic magnetic tower outflows which emerge periodically on timescales of ˜30ns. The subsequent magnetic bubbles propagate with velocities reaching ˜300km/s and interacting with previous eruptions leading to the formation of shocks. This research was supported by the European Community's Marie Curie JETSET network (contract MRTN-CT-2004 005592) and the SSAA program of the NNSA (DOE Cooperative Agreement DE-FC03-02NA00057).

  3. Numerical simulation of an atmospheric pressure RF-driven plasma needle and heat transfer to adjacent human skin using COMSOL.

    PubMed

    Schröder, Maximilian; Ochoa, Angel; Breitkopf, Cornelia

    2015-01-01

    Plasma medicine is an emerging field where plasma physics is used for therapeutical applications. Temperature is an important factor to take into account with respect to the applications of plasma to biological systems. During the treatment, the tissue temperature could increase to critical values. In this work, a model is presented, which is capable of predicting the skin temperature during a treatment with a radio frequency driven plasma needle. The main gas was helium. To achieve this, a discharge model was coupled to a heat transfer and fluid flow model. The results provide maximum application times for different power depositions in order to avoid reaching critical skin temperatures. PMID:25850416

  4. On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

    Microsoft Academic Search

    Nicolas Benard; Eric Moreau

    2011-01-01

    Commercial and military aircrafts or miniature aerial vehicles can suffer from massive flow separation when high angles of\\u000a attack are required. Single dielectric barrier discharge (DBD) actuators have demonstrated their capability of controlling\\u000a such a separated flow at low external velocity. However, the processes resulting in the improvement of the flight performances\\u000a remain unclear. In the present study, the reattachment

  5. Valves Based on Amplified Piezoelectric Actuators

    Microsoft Academic Search

    R. Le Letty; N. Lhermet; G. Patient; F. Claeyssen; M. Lang

    2004-01-01

    Amplified Piezo Actuators have been developed at CEDRAT TECHNOLOGIES for several years and found several applications in space. Their well-known advantages (rapid response and precise positioning) have been used in valve designs to obtain either rapid or fine proportional valves. A first gas valve is using a small amplified piezo actuator and is further driven with a switched amplifier to

  6. Improvements In Ball-Screw Linear Actuators

    NASA Technical Reports Server (NTRS)

    Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

    1996-01-01

    Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

  7. First Observation of the High Field Side Sawtooth Crash and Heat Transfer during Driven Reconnection Processes in Magnetically Confined Plasmas

    SciTech Connect

    Park, HK; Luhmann, NC; Donne, AJH; Classen, IGJ; Domier, CW; Mazzucato, E; Munsat, T; van de Pol, MJ; Xia, Z

    2005-12-01

    High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an "X-point" reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic.

  8. Effect of dust charge fluctuations on current-driven electrostatic ion-cyclotron instability in a collisional magnetized plasma

    SciTech Connect

    Sharma, Suresh C.; Sharma, Kavita; Gahlot, Ajay [Department of Applied Physics, Delhi Technological University (DTU), Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India)] [Department of Applied Physics, Delhi Technological University (DTU), Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India)

    2013-05-15

    Current-driven electrostatic ion-cyclotron (EIC) instability is studied in a collisional magnetized dusty plasma. The growth rate and unstable mode frequencies were evaluated based on existing physical parameters relevant to ion cyclotron waves in dusty plasmas. It is found that the unstable mode frequency and growth rate of current-driven EIC instability increase with ? (ion-to-electron density ratio). Moreover, the increase in electron neutral collisional frequency (?{sub e}) has no effect on the unstable mode frequency while the normalized growth rate has linear dependence on ?{sub e}.

  9. Fourier-domain study of drift turbulence driven sheared flow in a laboratory plasma

    SciTech Connect

    Xu, M.; Tynan, G. R.; Holland, C.; Muller, S. H. [Center for Momentum Transport and Flow Organization, University of California-San Diego, La Jolla, California 92093 (United States); Center for Energy Research, University of California-San Diego, La Jolla, California 92093 (United States); Yan, Z. [Center for Energy Research, University of California-San Diego, La Jolla, California 92093 (United States); Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yu, J. H. [Center for Energy Research, University of California-San Diego, La Jolla, California 92093 (United States)

    2010-03-15

    Frequency-resolved nonlinear internal and kinetic energy transfer rates have been measured in the Controlled Shear Decorrelation Experiment (CSDX) linear plasma device using a recently developed technique [Xu et al., Phys. Plasmas 16, 042312 (2009)]. The results clearly show a net kinetic energy transfer into the zonal flow frequency region, consistent with previous time-domain observations of turbulence-driven shear flows [Tynan et al., Plasma Phys. Controlled Fusion 48, S51 (2006)]. The experimentally measured dispersion relation has been used to map the frequency-resolved energy transfer rates into the wave number domain, which shows that the shear flow drive comes from midrange (k{sub t}hetarho{sub S}>0.3) drift fluctuations, and the strongest flow drive comes from k{sub t}hetarho{sub S}approx =1 fluctuations. Linear growth rates have been inferred from a linearized Hasegawa-Wakatani model [Hasegawa et al., Phys. Fluids 22, 2122 (1979)], which indicates that the m=0 mode is linearly stable and the m=1-10 modes (corresponding to k{sub t}hetarho{sub S}>0.3) are linearly unstable for the n=1 and n=2 radial eigenmodes. This is consistent with our energy transfer measurements.

  10. Effects of neutral interactions on velocity-shear-driven plasma waves

    SciTech Connect

    Enloe, C. L. [Physics Department, US Air Force Academy, Colorado Springs, Colorado 80840 (United States); Tejero, E. M.; Amatucci, W. E.; Crabtree, C.; Ganguli, G. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Sotnikov, V. [Sensors Directorate, Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

    2014-06-15

    In a laboratory experiment, we demonstrate the substantial effects that collisions between charged and neutral particles have on low-frequency (?{sub i}????????{sub e}) shear-driven electrostatic lower hybrid waves in a plasma. We establish a strong (up to 2.5?kV/m) highly localized electric field with a length scale shorter than the ion gyroradius, so that the ions in the plasma, unlike the electrons, do not develop the full E?×?B drift velocity. The resulting shear in the particle velocities initiates the electron-ion hybrid (EIH) instability, and we observe the formation of strong waves in the vicinity of the shear with variations in plasma densities of 10% or greater. Our experimental configuration allows us to vary the neutral background density by more than a factor of two while holding the charged particle density effectively constant. Not surprisingly, increasing the neutral density decreases the growth rate/saturation amplitude of the waves and increases the threshold electric field necessary for wave formation, but the presence of neutrals affects the dominant wave frequency as well. We show that a 50% increase in the neutral density decreases the wave frequency by 20% while also suppressing the electric field dependence of the frequency that is observed when fewer neutrals are present. The majority of these effects, as well as the values of the frequencies we observe, closely match the predictions of previously developed linear EIH instability theory, for which we present the results of a numerical solution.

  11. Boltzmann-equation simulations of radio-frequency-driven, low-temperature plasmas

    SciTech Connect

    Drallos, P.J.; Riley, M.E.

    1995-01-01

    We present a method for the numerical solution of the Boltzmann equation (BE) describing plasma electrons. We apply the method to a capacitively-coupled, radio-frequency-driven He discharge in parallel-plate (quasi-1D) geometry which contains time scales for physical processes spanning six orders of magnitude. Our BE solution procedure uses the method of characteristics for the Vlasov operator with interpolation in phase space at early time, allowing storage of the distribution function on a fixed phase-space grid. By alternating this BE method with a fluid description of the electrons, or with a novel time-cycle-average equation method, we compute the periodic steady state of a He plasma by time evolution from startup conditions. We find that the results compare favorably with measured current-voltage, plasma density, and ``cited state densities in the ``GEC`` Reference Cell. Our atomic He model includes five levels (some are summed composites), 15 electronic transitions, radiation trapping, and metastable-metastable collisions.

  12. Mechanisms of Streamer Propagation Affected by Driven Voltage Polarity in a Cold Atmospheric Pressure Plasma Jet

    NASA Astrophysics Data System (ADS)

    Yang, Lanlan

    2015-01-01

    A two-dimensional self-consistent fluid model is used to investigate the effects of DC-voltage polarity in plasma initiation and propagation of helium plasma jet. The simulation results indicate that the difference in initial breakdown for the positive jet and negative jet leads to a difference in the electron density of about 4 orders of magnitude, even with the same initial electric field, which also influences the subsequent propagation. In the propagation process of negative jets, the ionization process exists in a longer gas channel behind the streamer head. In addition, the drift process to the infinite grounded electrode driven by the electric field results in higher energy consumption in the ionization process. However, in the positive jet, the ionization process mainly exists in the streamer head. Therefore, the differences in the initial breakdown and propagation process make the electric field intensity and the ionization weaker in the streamer head of the negative jet, which explains the weaker and shorter appearance of the negative jet compared to the positive jet. Our model can adequately reproduce the experimental results, viz. a bullet-like propagation in the positive jet and a continuous plasma plume in the negative jet. Furthermore, it also indicates that the streamer velocity shows the same variations as the electron drift velocity for both positive and negative jets.

  13. Combined actuator and latch for cartridge powered actuator

    NASA Technical Reports Server (NTRS)

    Murphy, D. W.

    1967-01-01

    Combined attenuator and latch stops and latches in place a given mass which is to be moved a discrete distance to effect a desired condition. This device is used in a retraction actuator driven by a pyrotechnic thruster, and can be tailored to meet specific design requirements.

  14. Parallel-coupled micro-macro actuators

    SciTech Connect

    Morrell, J.B.; Salisbury, J.K. [MIT Artificial Intelligence Lab., Cambridge, MA (United States)

    1998-07-01

    This paper presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the parallel-coupled micro-macro actuator, or PaCMMA. In this system, the micro-actuator is capable of high-bandwidth force control owing to its low mass and direct-drive connection to the output shaft. The compliant transmission of the macro-actuator reduces the impedance (stiffness) at the output shaft, and increases the dynamic range of force. Performance improvement over single-actuator systems was expected in force control, impedance control, force distortion, and transient impact force reduction. Several theoretical performance limits are derived from the saturation limits of the system. A control law is presented. A prototype test bed was built and an experimental comparison was performed between this actuator concept and two single-actuator systems. A set of quantitative measures is proposed and the actuator system is evaluated against them with the following results: force bandwidth of 56 Hz, torque dynamic range of 800:1, peak torque of 1,040 mNm, and minimum torque of 1.3 mNm. Peak impact force, force distortion, and back-driven impedance of the PaCMMA system are shown to be better than either of the single-actuator configurations considered.

  15. Identification of the background plasma damping mechanisms of antenna-driven toroidal Alfven eigenmodes of medium n on JET

    NASA Astrophysics Data System (ADS)

    Panis, Theodoros; Fasoli, Ambrogio; Testa, Duccio; Mellet, Nicolas; Sharapov, Sergei

    2010-11-01

    In tokamak burning plasma experiments such as ITER, it is expected that Alfvén eigenmode (AE) instabilities of, typically, medium and high toroidal mode number n will be triggered by populations of energetic ions, such as ?-particles. The stability of this specific class of AEs is studied experimentally in the Joint European Torus by observing the plasma response to antenna-driven frequency-sweeping perturbations at the plasma edge. During the 2008/9 experimental campaigns, the complete set of the new antennas was operated and medium-n AEs were excited under various plasma conditions. A big collection of damping rate measurements of, mainly, toroidal AEs (TAEs) has been obtained following the technical optimization of the diagnostic. A subset of these measurements are compared to different plasma models, as implemented in the codes LEMan and CASTOR, allowing the identification of the background plasma damping mechanisms that come into play.

  16. Filamentation instability of nonextensive current-driven plasma in the ion acoustic frequency range

    NASA Astrophysics Data System (ADS)

    Khorashadizadeh, S. M.; Rastbood, E.; Niknam, A. R.

    2014-12-01

    The filamentation and ion acoustic instabilities of nonextensive current-driven plasma in the ion acoustic frequency range have been studied using the Lorentz transformation formulas. Based on the kinetic theory, the possibility of filamentation instability and its growth rate as well as the ion acoustic instability have been investigated. The results of the research show that the possibility and growth rate of these instabilities are significantly dependent on the electron nonextensive parameter and drift velocity. Besides, the increase of electrons nonextensive parameter and drift velocity lead to the increase of the growth rates of both instabilities. In addition, the wavelength region in which the filamentation instability occurs is more stretched in the presence of higher values of drift velocity and nonextensive parameter. Finally, the results of filamentation and ion acoustic instabilities have been compared and the conditions for filamentation instability to be dominant mode of instability have been presented.

  17. Bifurcation Theory of the Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence

    SciTech Connect

    Kolesnikov, R.A.; Krommes, J.A.

    2005-09-22

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  18. Magnetic compressibility and ion-temperature-gradient-driven microinstabilities in magnetically confined plasmas

    E-print Network

    Zocco, A; Connor, J W

    2015-01-01

    The electromagnetic theory of the strongly driven ion-temperature-gradient (ITG) instability in magnetically confined toroidal plasmas is developed. Stabilizing and destabilizing effects are identified, and a critical $\\beta_{e}$ (the ratio of the electron to magnetic pressure) for stabilization of the toroidal branch of the mode is calculated for magnetic equilibria independent of the coordinate along the magnetic field. Its scaling is $\\beta_{e}\\sim L_{Te}/R,$ where $L_{Te}$ is the characteristic electron temperature gradient length, and $R$ the major radius of the torus. We conjecture that a fast particle population can cause a similar stabilization due to its contribution to the equilibrium pressure gradient. For sheared equilibria, the boundary of marginal stability of the electromagnetic correction to the electrostatic mode is also given. For a general magnetic equilibrium, we find a critical length (for electromagnetic stabilization) of the extent of the unfavourable curvature along the magnetic field....

  19. Laser-Driven Plasma Deceleration of Electron Beams for Compact Photon Sources

    NASA Astrophysics Data System (ADS)

    Vay, J.-L.; Geddes, C. G. R.; Rykovanov, S. G.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2015-10-01

    Particle accelerators are in widespread use as intense, precisely controllable photon sources, but many applications, including nuclear nonproliferation, are limited by size. Laser-driven plasma accelerators (LPAs) reduce accelerator size, but a compact system also requires addressing radiation hazards resulting from disposal of particle beam energy after photon production, typically requiring large and heavy "beam dumps". In this paper, we investigate, through 3-D Particle-In-Cell simulations, an LPA stage demonstrating equal effectiveness at accelerating and decelerating an electron beam over a very short distance. This indicates that in addition to providing compact accelerators, such structures can effectively reduce beam energy after photon production and hence beam dump weight and volume. This is important to the development of compact photon source systems which can satisfy needs including transportable operation or operation in populated areas.

  20. Bifurcation theory of the transition to collisionless ion-temperature-gradient-driven plasma turbulence

    SciTech Connect

    Kolesnikov, R.A.; Krommes, J.A. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

    2005-12-15

    The collisionless limit of the transition to ion-temperature-gradient-driven plasma turbulence is considered with a dynamical-systems approach. The importance of systematic analysis for understanding the differences in the bifurcations and dynamics of linearly damped and undamped systems is emphasized. A model with ten degrees of freedom is studied as a concrete example. A four-dimensional center manifold (CM) is analyzed, and fixed points of its dynamics are identified and used to predict a 'Dimits shift' of the threshold for turbulence due to the excitation of zonal flows. The exact value of that shift in terms of physical parameters is established for the model; the effects of higher-order truncations on the dynamics are noted. Multiple-scale analysis of the CM equations is used to discuss possible effects of modulational instability on scenarios for the transition to turbulence in both collisional and collisionless cases.

  1. Normalization schemes for ultrafast x-ray diffraction using a table-top laser-driven plasma source

    SciTech Connect

    Schick, D.; Bojahr, A.; Herzog, M. [Institut fuer Physik and Astronomie, Universitaet Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany); Korff Schmising, C. von [Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Strasse des 17. Juni 135, 10623 Berlin (Germany); Shayduk, R.; Leitenberger, W.; Gaal, P.; Bargheer, M. [Helmholtz Zentrum Berlin, Albert-Einstein-Strasse 15, 12489 Berlin (Germany)

    2012-02-15

    We present an experimental setup of a laser-driven x-ray plasma source for femtosecond x-ray diffraction. Different normalization schemes accounting for x-ray source intensity fluctuations are discussed in detail. We apply these schemes to measure the temporal evolution of Bragg peak intensities of perovskite superlattices after ultrafast laser excitation.

  2. T-Slide Linear Actuators

    NASA Technical Reports Server (NTRS)

    Vranish, John

    2009-01-01

    T-slide linear actuators use gear bearing differential epicyclical transmissions (GBDETs) to directly drive a linear rack, which, in turn, performs the actuation. Conventional systems use a rotary power source in conjunction with a nut and screw to provide linear motion. Non-back-drive properties of GBDETs make the new actuator more direct and simpler. Versions of this approach will serve as a long-stroke, ultra-precision, position actuator for NASA science instruments, and as a rugged, linear actuator for NASA deployment duties. The T slide can operate effectively in the presence of side forces and torques. Versions of the actuator can perform ultra-precision positioning. A basic T-slide actuator is a long-stroke, rack-and-pinion linear actuator that, typically, consists of a T-slide, several idlers, a transmission to drive the slide (powered by an electric motor) and a housing that holds the entire assembly. The actuator is driven by gear action on its top surface, and is guided and constrained by gear-bearing idlers on its other two parallel surfaces. The geometry, implemented with gear-bearing technology, is particularly effective. An electronic motor operating through a GBDET can directly drive the T slide against large loads, as a rack and pinion linear actuator, with no break and no danger of back driving. The actuator drives the slide into position and stops. The slide holes position with power off and no brake, regardless of load. With the T slide configuration, this GBDET has an entire T-gear surface on which to operate. The GB idlers coupling the other two T slide parallel surfaces to their housing counterpart surfaces provide constraints in five degrees-of-freedom and rolling friction in the direction of actuation. Multiple GB idlers provide roller bearing strength sufficient to support efficient, rolling friction movement, even in the presence of large, resisting forces. T-slide actuators can be controlled using the combination of an off-the-shelf, electric servomotor, a motor angle resolution sensor (typically an encoder or resolver), and microprocessor-based intelligent software. In applications requiring precision positioning, it may be necessary to add strain gauges to the T-slide housing. Existing sensory- interactive motion control art will work for T slides. For open-loop positioning, a stepping motor emulation technique can be used.

  3. Trapped energetic electron driven modes with second stable regime in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    He, Hongda; Dong, J. Q.; Zhao, K.; He, Zhixiong; Zheng, G. Y.; Lu, Gaimin; Hao, G. Z.; Tao, Xie; Wang, L. F.

    2014-06-01

    Features of fishbone-like trapped energetic electrons driven modes (TEEMs), which are a particular manifestation of the fishbone gap modes, are investigated taking into account model radial profile and the pitch angle distribution of the energetic electrons (EEs). The TEEMs are found unstable only when the beta values of EEs ?h (=pressure of the energetic electrons/pressure of magnetic field) are higher than certain critical values which are proportional to perturbed energy ?W ?c of background plasma and much lower than that for traditional fishbone modes. In addition, TEEMs become stable again and enter a second stable regime when ?h values are higher than second critical values. Furthermore, the modes can only be excited in plasmas which are stable for MHD instabilities. The real frequency and growth rate of the modes are approximately linear and parabolic functions of ?h, respectively. The real frequency is very low but not zero in the vicinity of lower beta region, whereas it is comparable to the toroidal precession frequency of the EEs in higher critical beta region. The numerical results show that the second stable regime is easy to form when q = 1 flux surface is close to the magnetic axis. Suitable density gradient of EEs and magnetic shear are other two necessary conditions for excitation of the TEEMs.

  4. Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

    SciTech Connect

    Schaeffer, D. B., E-mail: dschaeffer@physics.ucla.edu; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Gekelman, W.; Niemann, C. [Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, California 90095 (United States); Winske, D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-05-15

    The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.

  5. Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Hellinger, Petr; Trávní?ek, Pavel M.; Trávní?ek

    2015-01-01

    Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the corresponding (anomalous) transport coefficients dominate over the collisional ones and their properties are similar to those in collisionless plasmas.

  6. Trapped energetic electron driven modes with second stable regime in tokamak plasmas

    SciTech Connect

    He, Hongda; He, Zhixiong; Zheng, G. Y.; Lu, Gaimin; Hao, G. Z.; Tao, Xie; Wang, L. F. [Southwestern Institute of Physics, Chengdu (China); Dong, J. Q. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou (China); Southwestern Institute of Physics, Chengdu (China); Zhao, K. [Southwest University for Nationalities, Chengdu (China)

    2014-06-15

    Features of fishbone-like trapped energetic electrons driven modes (TEEMs), which are a particular manifestation of the fishbone gap modes, are investigated taking into account model radial profile and the pitch angle distribution of the energetic electrons (EEs). The TEEMs are found unstable only when the beta values of EEs ?{sub h} (=pressure of the energetic electrons/pressure of magnetic field) are higher than certain critical values which are proportional to perturbed energy ?W{sup ^}{sub c} of background plasma and much lower than that for traditional fishbone modes. In addition, TEEMs become stable again and enter a second stable regime when ?{sub h} values are higher than second critical values. Furthermore, the modes can only be excited in plasmas which are stable for MHD instabilities. The real frequency and growth rate of the modes are approximately linear and parabolic functions of ?{sub h}, respectively. The real frequency is very low but not zero in the vicinity of lower beta region, whereas it is comparable to the toroidal precession frequency of the EEs in higher critical beta region. The numerical results show that the second stable regime is easy to form when q?=?1 flux surface is close to the magnetic axis. Suitable density gradient of EEs and magnetic shear are other two necessary conditions for excitation of the TEEMs.

  7. Microwave Power for Smart Membrane Actuators

    NASA Technical Reports Server (NTRS)

    Choi, Sang H.; Song, Kyo D.; Golembiewski, Walter T.; Chu, Sang-Hyon; King, Glen C.

    2002-01-01

    The concept of microwave-driven smart membrane actuators is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry. A large, ultra-light space structure, such as solar sails and Gossamer spacecrafts, requires a distribution of power into individual membrane actuators to control them in an effective way. A patch rectenna array with a high voltage output was developed to drive smart membrane actuators. Networked patch rectenna array receives and converts microwave power into a DC power for an array of smart actuators. To use microwave power effectively, the concept of a power allocation and distribution (PAD) circuit is developed and tested for networking a rectenna/actuator patch array. For the future development, the PAD circuit could be imbedded into a single embodiment of rectenna and actuator array with the thin-film microcircuit embodiment. Preliminary design and fabrication of PAD circuitry that consists of a sixteen nodal elements were made for laboratory testing.

  8. Series Elastic Actuators for legged robots

    NASA Astrophysics Data System (ADS)

    Pratt, Jerry E.; Krupp, Benjamin T.

    2004-09-01

    Series Elastic Actuators provide many benefits in force control of robots in unconstrained environments. These benefits include high force fidelity, extremely low impedance, low friction, and good force control bandwidth. Series Elastic Actuators employ a novel mechanical design architecture which goes against the common machine design principal of "stiffer is better." A compliant element is placed between the gear train and driven load to intentionally reduce the stiffness of the actuator. A position sensor measures the deflection, and the force output is accurately calculated using Hooke"s Law (F=Kx). A control loop then servos the actuator to the desired output force. The resulting actuator has inherent shock tolerance, high force fidelity and extremely low impedance. These characteristics are desirable in many applications including legged robots, exoskeletons for human performance amplification, robotic arms, haptic interfaces, and adaptive suspensions. We describe several variations of Series Elastic Actuators that have been developed using both electric and hydraulic components.

  9. Thermally Actuated Hydraulic Pumps

    NASA Technical Reports Server (NTRS)

    Jones, Jack; Ross, Ronald; Chao, Yi

    2008-01-01

    Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research vessels. Heretofore, electrically actuated hydraulic pumps have been used for this purpose. By eliminating the demand for electrical energy for pumping, the use of the thermally actuated hydraulic pumps could prolong the intervals between battery charges, thus making it possible to greatly increase the durations of undersea exploratory missions.

  10. INJECTION OF PLASMA INTO THE NASCENT SOLAR WIND VIA RECONNECTION DRIVEN BY SUPERGRANULAR ADVECTION

    SciTech Connect

    Yang Liping; He Jiansen; Tu Chuanyi; Chen Wenlei; Zhang Lei; Wang Linghua; Yan Limei [School of Earth and Space Sciences, Peking University, 100871 Beijing (China); Peter, Hardi [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Strasse, D-37191 Katlenburg-Lindau (Germany); Marsch, Eckart [Institute for Experimental and Applied Physics, Christian Albrechts University at Kiel, D-24118 Kiel (Germany); Feng, Xueshang, E-mail: jshept@gmail.com [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, 100871 Beijing (China)

    2013-06-10

    To understand the origin of the solar wind is one of the key research topics in modern solar and heliospheric physics. Previous solar wind models assumed that plasma flows outward along a steady magnetic flux tube that reaches continuously from the photosphere through the chromosphere into the corona. Inspired by more recent comprehensive observations, Tu et al. suggested a new scenario for the origin of the solar wind, in which it flows out in a magnetically open coronal funnel and mass is provided to the funnel by small-scale side loops. Thus mass is supplied by means of magnetic reconnection that is driven by supergranular convection. To validate this scenario and simulate the processes involved, a 2.5 dimensional (2.5D) numerical MHD model is established in the present paper. In our simulation a closed loop moves toward an open funnel, which has opposite polarity and is located at the edge of a supergranulation cell, and magnetic reconnection is triggered and continues while gradually opening up one half of the closed loop. Its other half connects with the root of the open funnel and forms a new closed loop which is submerged by a reconnection plasma stream flowing downward. Thus we find that the outflowing plasma in the newly reconnected funnel originates not only from the upward reconnection flow but also from the high-pressure leg of the originally closed loop. This implies an efficient supply of mass from the dense loop to the dilute funnel. The mass flux of the outflow released from the funnel considered in our study is calculated to be appropriate for providing the mass flux at the coronal base of the solar wind, though additional heating and acceleration mechanisms are necessary to keep the velocity at the higher location. Our numerical model demonstrates that in the funnel the mass for the solar wind may be supplied from adjacent closed loops via magnetic reconnection as well as directly from the footpoints of open funnels.

  11. Laboratory astrophysics experiments studying hydrodynamic and magnetically-driven plasma jets

    NASA Astrophysics Data System (ADS)

    Suzuki-Vidal, F.; Lebedev, S. V.; Krishnan, M.; Bocchi, M.; Skidmore, J.; Swadling, G.; Harvey-Thompson, A. J.; Burdiak, G.; de Grouchy, P.; Pickworth, L.; Suttle, L.; Bland, S. N.; Chittenden, J. P.; Hall, G. N.; Khoory, E.; Wilson-Elliot, K.; Madden, R. E.; Ciardi, A.; Frank, A.

    2012-06-01

    Laboratory astrophysics is a novel approach to study different types of astrophysical phenomena by the means of carefully scaled laboratory experiments. Particularly, the formation of highly supersonic, radiatively cooled plasma jets for the study of protostellar jets is an active area of research at present. At Imperial College London, different experimental configurations allow producing plasma flows which are scalable to protostellar jets. The plasma is produced by introducing a ~1.4 MA, 250 ns current pulse from the MAGPIE generator into a load. By varying the geometry of the load it is possible to study different regions of interest in the jet. For instance, the effect of magnetic fields in the launching and collimation of the jet, and the propagation of the jet far away from the launching region as it interacts with the ambient medium. Two main experiments can address such regions of interest: radial wire arrays and radial foils. By using a radial wire array it is possible to produce a jet driven by a predominant toroidal magnetic field on the axis of a magnetic "bubble", which expands with velocities up to ~300 km/s. In a radial foil the wires are replaced by a continuous disk allowing to produce a hydrodynamic jet, i.e. a jet in which magnetic fields are not dynamically significant. With this particular configuration it is possible to introduce a neutral gas above the foil in order to study jet-ambient interactions. Experimental results from different diagnostics will be presented together with 3-D MHD simulations using the GORGON code.

  12. Numerical Simulations of Plasma Based Flow Control Applications

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Jacob, J. D.; Ashpis, D. E.

    2005-01-01

    A mathematical model was developed to simulate flow control applications using plasma actuators. The effects of the plasma actuators on the external flow are incorporated into Navier Stokes computations as a body force vector. In order to compute this body force vector, the model solves two additional equations: one for the electric field due to the applied AC voltage at the electrodes and the other for the charge density representing the ionized air. The model is calibrated against an experiment having plasma-driven flow in a quiescent environment and is then applied to simulate a low pressure turbine flow with large flow separation. The effects of the plasma actuator on control of flow separation are demonstrated numerically.

  13. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  14. Numerical Simulation of Waves Driven by Plasma Currents Generated by Low-Frequency Alfven Waves in a Multi-Ion Plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2004-01-01

    When multi-ion plasma consisting of heavy and light ions is permeated by a low-frequency Alfven (LFA) wave, the crossed-electric-and-magnetic field (E x B), and the polarization drifts of the different ion species and the electrons could be quite different. The relative drifts between the charged-particle species drive waves, which energize the plasma. Using 2.5-dimensional (2.5-D) particle-in-cell simulations, we study this process of wave generation and its nonlinear consequences in terms of acceleration and heating plasma. Specifically, we study the situation for LFA wave frequency being lower than the heavy-ion cyclotron frequency in a multi-ion plasma. We impose such a wave to the plasma assuming that its wavelength is much larger than that of the waves generated by the relative drifts. For better understanding, the LFA-wave driven simulations are augmented by those driven by initialized ion beams. The driven high-frequency (HF) wave modes critically depend on the heavy ion density nh; for small values of nh, the lower hybrid (LH) waves dominate. On the other hand, for large nh a significantly enhanced level of waves occurs over a much broader frequency spectrum below the LH frequency and such waves are interpreted here as the ion Bernstein (IB) mode near the light ion cyclotron harmonics. Irrespective of the driven wave modes, both the light and heavy ions undergo significant transverse acceleration, but for the large heavy-ion densities, even the electrons are significantly accelerated in the parallel direction by the waves below the LH frequency. Even when the LFA wave drive is maintained, the ion heating leads to the cessation of HF wave excitation just after a few cycles of the former wave. On the basis of marginal stability seen in the simulations, an empirical relation for LFA wave amplitude, frequency and ion temperature is given.

  15. Nonlinear Pulse Propagation and Phase Velocity of Laser-Driven Plasma Waves C. B. Schroeder, C. Benedetti, E. Esarey, and W. P. Leemans

    E-print Network

    Geddes, Cameron Guy Robinson

    Nonlinear Pulse Propagation and Phase Velocity of Laser-Driven Plasma Waves C. B. Schroeder, C by a relativistically intense short-pulse laser in underdense plasma are investigated in the broad pulse limit, including the effects of pulse steepening, frequency redshifting, and energy depletion. The nonlinear plasma

  16. Fast-acting valve actuator

    DOEpatents

    Cho, Nakwon (Knoxville, TN)

    1980-01-01

    A fast-acting valve actuator utilizes a spring driven pneumatically loaded piston to drive a valve gate. Rapid exhaust of pressurized gas from the pneumatically loaded side of the piston facilitates an extremely rapid piston stroke. A flexible selector diaphragm opens and closes an exhaust port in response to pressure differentials created by energizing and de-energizing a solenoid which controls the pneumatic input to the actuator as well as selectively providing a venting action to one side of the selector diaphragm.

  17. Design of an energy efficient and economical actuator for automobile windows

    E-print Network

    Durand, Keith (Keith V.)

    2007-01-01

    This thesis describes the design and analysis of an efficient, yet low cost, drum driven window actuation system for an automotive power window. The design uses a novel approach that involves using cables to both actuate ...

  18. Theoretical Modeling of Radiation-driven Atomic Kinetics of a Neon Photoionized Plasma

    NASA Astrophysics Data System (ADS)

    Durmaz, Tunay

    We report on a theoretical study on atomic kinetics modeling of a photoionized neon plasma at conditions relevant to laboratory experiments performed at the Z-machine in Sandia National Laboratories. We describe an atomic kinetics model and code, ATOKIN, that was developed and used to compute the atomic level population distribution. The study includes atomic level sensitivity with respect to energy level structure, radiation and transient effects, electron temperature and x-ray drive sensitivity and an idea for electron temperature extraction from a level population ratio. The neon atomic model considers several ionization stages of highly-charged neon ions as well as a detailed structure of non-autoionizing and autoionizing energy levels in each ion. In the energy level sensitivity study, the atomic model was changed by adding certain types of energy levels such as singly-excited, auto-ionizing doubly-excited states. Furthermore, these levels were added ion by ion for the most populated ions. Atomic processes populating and de-populating the energy levels consider photoexcitation and photoionization due to the external radiation flux, and spontaneous and collisional atomic processes including plasma radiation trapping. Relevant atomic cross sections and rates were computed with the atomic structure and scattering FAC code. The calculations were performed at constant particle number density and driven by the time-histories of temperature and external radiation flux. These conditions were selected in order to resemble those achieved in photoionized plasma experiments at the Z facility of Sandia National Laboratories. For the same set of time histories, calculations were done in a full time-dependent mode and also as a sequence of instantaneous, steady states. Differences between both calculations are useful to identify transient effects in the ionization and atomic kinetics of the photoionized plasma, and its dependence on the atomic model and plasma environmental conditions. We also calculated transmission spectra in an effort to identify time-dependent effects in observed spectral features. Furthermore, all the steady state and time-dependent calculations were performed for different electron temperature histories to investigate electron temperature effects in the same way transient effects were examined. The idea for electron temperature extraction based on the population ratio of two energy levels close in energy was investigated after preliminary estimations revealed evidence of dominant electron collisional excitation and de-excitation over photo-excitation and spontaneous radiative decay between the ground state, 1s22 s, and the first excited state, 1s22 p, levels of Li-like Ne. Since the populations of these levels were determined from the analysis of transmission spectra, it was then possible to estimate the temperature via a Boltzmann factor. Further studies were performed for various plasma conditions such as temperature and density in order to confirm the reliability of the method. Calculations were performed for a sequence of steady states and in a full time-dependent mode. Finally, the instantaneous spectra was integrated over several time intervals in order to test the method on conditions similar to those of laboratory experiments.

  19. On the Transition from Thermally-driven to Ponderomotively-driven Stimulated Brillouin Scattering and Filamentation of Light in Plasma

    SciTech Connect

    R.L. Berger; E.J. Valeo; S. Brunner

    2005-04-04

    The dispersion properties of ion acoustic waves and their nonlinear coupling to light waves through ponderomotive and thermal forces are sensitive to the strength of electron-ion collisions. Here, we consider the growth rate of stimulated Brillouin scattering (SBS) when the driven acoustic wave frequency and wavelength span the range of small to large compared to electron-ion collision frequency and mean free path respectively. We find in all cases the thermal contributions to the SBS growth rate are insignificant if the ion acoustic wave frequency is greater than the electron-ion collision frequency and the wavelength is much shorter than the electron-ion mean free path. On the other hand, the purely growing filamentation instability remains thermally driven for shorter wavelengths than SBS even when the growth rate is larger than the acoustic frequency.

  20. Electrorepulsive actuator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr. (inventor); Curry, Kenneth C. (inventor)

    1992-01-01

    The invention is a linear actuator that operates under the principle that like charges repel and opposite charges attract. The linear actuator consists of first and second pairs of spaced opposed conductors where one member of each pair of conductors is attached to a fixed member, and where the other member of each pair of conductors is attached to a movable member such as an elongated rod. The two pairs of spaced conductors may be provided in the form of two spacedly interwound helical vanes where the conductors are located on the opposite sides of the two helical vanes. One helical vane extends inwardly from a housing and the other helical vane extends outwardly from an elongated rod. The elongated rod may be caused to move linearly with respect to the housing by applying appropriate charges of like or opposite polarity to the electrical conductors on the helical vanes.

  1. Resonantly LaserDriven Plasma Waves for Electron Acceleration D. Umstadter, 1;2 J. Kim, 1 E. Esarey, 1;3 E. Dodd, 1 and T. Neubert 1;4

    E-print Network

    Umstadter, Donald

    ­rise­time sine shapes. A resonant region of the plasma wave phase space is found where the plasma wave is driven, nonlinear effects cause the wavelength of the plasma wave to increase and, hence, the resonant frequencyResonantly Laser­Driven Plasma Waves for Electron Acceleration D. Umstadter, 1;2 J. Kim, 1 E

  2. Modular droplet actuator drive

    NASA Technical Reports Server (NTRS)

    Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

    2011-01-01

    A droplet actuator drive including a detection apparatus for sensing a property of a droplet on a droplet actuator; circuitry for controlling the detection apparatus electronically coupled to the detection apparatus; a droplet actuator cartridge connector arranged so that when a droplet actuator cartridge electronically is coupled thereto: the droplet actuator cartridge is aligned with the detection apparatus; and the detection apparatus can sense the property of the droplet on a droplet actuator; circuitry for controlling a droplet actuator coupled to the droplet actuator connector; and the droplet actuator circuitry may be coupled to a processor.

  3. 1316 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Schlieren Imaging of Flow Actuation Produced

    E-print Network

    Raja, Laxminarayan L.

    1316 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Schlieren Imaging of Flow, and Laxminarayan L. Raja Abstract--Schlieren imaging of flow field structure produced by direct-current surface of a 30 wedge. Schlieren imaging reveals that for cathodes located upstream of the anodes, the discharge

  4. Dielectric Actuation of Polymers

    NASA Astrophysics Data System (ADS)

    Niu, Xiaofan

    Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP in tactile display is investigated by the prototyping of a large scale refreshable Braille display device. Braille is a critical way for the vision impaired community to learn literacy and improve life quality. Current piezoelectrics-based refreshable Braille display technologies are limited to up to 1 line of Braille text, due to the bulky size of bimorph actuators. Based on the unique actuation feature of BSEP, refreshable Braille display devices up to smartphone-size have been demonstrated by polymer sheet laminates. Dots in the devices can be individually controlled via incorporated field-driven BSEP actuators and Joule heater units. A composite material consisting of silver nanowires (AgNW) embedded in a polymer substrate is brought up as a compliant electrode candidate for BSEP application. The AgNW composite is highly conductive (Rs: 10 ?/sq) and remains conductive at strains as high as 140% (Rs: <10 3 ?/sq). The baseline conductivity has only small changes up to 90% strain, which makes it low enough for both field driving and stretchable Joule heating. An out-of-plane bistable area strain up to 68% under Joule heating is achieved.

  5. Impurity transport driven by ion temperature gradient turbulence in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Fülöp, T.; Braun, S.; Pusztai, I.

    2010-06-01

    Impurity transport driven by electrostatic turbulence is analyzed in weakly collisional tokamak plasmas using a semianalytical model based on a boundary layer solution of the gyrokinetic equation. Analytical expressions for the perturbed density responses are derived and used to determine the stability boundaries and the quasilinear particle fluxes. For moderate impurity charge number Z, the stability boundaries are very weakly affected by the increasing impurity charge for constant effective charge, while for lower impurity charge the influence of impurities is larger, if the amount of impurities is not too small. Scalings of the mode frequencies and quasilinear fluxes with charge number, effective charge, impurity density scale length, and collisionality are determined and compared to quasilinear gyrokinetic simulations with GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] resulting in very good agreement. Collisions do not affect the mode frequencies, growth rates, and impurity fluxes significantly. The eigenfrequencies and growth rates depend only weakly on Z and Zeff but they are sensitive to the impurity density gradient scale length. An analytical approximate expression of the zero-flux impurity density gradient is derived and used to discuss its parametric dependencies.

  6. Impurity transport driven by ion temperature gradient turbulence in tokamak plasmas

    SciTech Connect

    Fueloep, T.; Pusztai, I. [Department of Applied Physics, Nuclear Engineering, Chalmers University of Technology and Euratom-VR Association, Goeteborg SE-41296 (Sweden); Braun, S. [Max-Planck-Institut fuer Plasmaphysik, Greifswald 17491 (Germany)

    2010-06-15

    Impurity transport driven by electrostatic turbulence is analyzed in weakly collisional tokamak plasmas using a semianalytical model based on a boundary layer solution of the gyrokinetic equation. Analytical expressions for the perturbed density responses are derived and used to determine the stability boundaries and the quasilinear particle fluxes. For moderate impurity charge number Z, the stability boundaries are very weakly affected by the increasing impurity charge for constant effective charge, while for lower impurity charge the influence of impurities is larger, if the amount of impurities is not too small. Scalings of the mode frequencies and quasilinear fluxes with charge number, effective charge, impurity density scale length, and collisionality are determined and compared to quasilinear gyrokinetic simulations with GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] resulting in very good agreement. Collisions do not affect the mode frequencies, growth rates, and impurity fluxes significantly. The eigenfrequencies and growth rates depend only weakly on Z and Z{sub eff} but they are sensitive to the impurity density gradient scale length. An analytical approximate expression of the zero-flux impurity density gradient is derived and used to discuss its parametric dependencies.

  7. A self-organized criticality model for ion temperature gradient mode driven turbulence in confined plasma

    SciTech Connect

    Isliker, H.; Pisokas, Th.; Vlahos, L. [Department of Physics, Section of Astrophysics, Astronomy, and Mechanics, Aristotle University of Thessaloniki, Association Euratom--Hellenic Republic, GR-54124 Thessaloniki (Greece); Strintzi, D. [National Technical University of Athens, Association Euratom--Hellenic Republic, GR-15773 Athens (Greece)

    2010-08-15

    A new self-organized criticality (SOC) model is introduced in the form of a cellular automaton (CA) for ion temperature gradient (ITG) mode driven turbulence in fusion plasmas. Main characteristics of the model are that it is constructed in terms of the actual physical variable, the ion temperature, and that the temporal evolution of the CA, which necessarily is in the form of rules, mimics actual physical processes as they are considered to be active in the system, i.e., a heating process and a local diffusive process that sets on if a threshold in the normalized ITG R/L{sub T} is exceeded. The model reaches the SOC state and yields ion temperature profiles of exponential shape, which exhibit very high stiffness, in that they basically are independent of the loading pattern applied. This implies that there is anomalous heat transport present in the system, despite the fact that diffusion at the local level is imposed to be of a normal kind. The distributions of the heat fluxes in the system and of the heat out-fluxes are of power-law shape. The basic properties of the model are in good qualitative agreement with experimental results.

  8. Ion motion in the wake driven by long particle bunches in plasmas

    SciTech Connect

    Vieira, J.; Silva, L. O. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisbon (Portugal); Fonseca, R. A. [GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisbon (Portugal); DCTI, ISCTE – Instituto Universitário de Lisboa, 1649-026 Lisboa (Portugal); Mori, W. B. [Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095 (United States)

    2014-05-15

    We explore the role of the background plasma ion motion in self-modulated plasma wakefield accelerators. We employ Dawson's plasma sheet model to derive expressions for the transverse plasma electric field and ponderomotive force in the narrow bunch limit. We use these results to determine the on-set of the ion dynamics and demonstrate that the ion motion could occur in self-modulated plasma wakefield accelerators. Simulations show the motion of the plasma ions can lead to the early suppression of the self-modulation instability and of the accelerating fields. The background plasma ion motion can nevertheless be fully mitigated by using plasmas with heavier plasmas.

  9. Current-driven Langmuir oscillations and amplitude modulations—Another view on electron beam-plasma interaction

    NASA Astrophysics Data System (ADS)

    Sauer, K.; Sydora, R. D.

    2015-01-01

    origin of Langmuir amplitude modulations and harmonic waves observed in the solar wind and in planetary foreshock regions is investigated in beam plasmas where the saturation process of the beam instability is accompanied with the formation of a plateau distribution. This saturated state represents a current which is shown to drive homogeneous electric field oscillations at the plasma frequency. This simple mechanism has been ignored in most numerical studies based on Vlasov or particle-in-cell simulations because of the use of the Poisson equation which is not suitable to describe the mechanism of current drive in plasmas with immobile ions; instead, Ampere's law must be used. A simple fluid description of stable plateau plasmas, coupled with Ampere's law, is applied to illustrate the basic elements of current-driven Langmuir oscillations. If beam-generated Langmuir/electron-acoustic waves with frequencies above or below the plasma frequency are simultaneously present, beating of both wave modes leads to Langmuir amplitude modulations, thus providing an alternative to parametric decay. Furthermore, very important implications of our studies (presented separately) concern the electrostatic and electromagnetic second harmonic generation by nonlinear interaction of Langmuir oscillations with finite wave number modes which are driven by the plateau current as well.

  10. Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas

    SciTech Connect

    O'Neill, C.; Waskoenig, J. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Gans, T. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)

    2012-10-08

    A multi-scale numerical model based on hydrodynamic equations with semi-kinetic treatment of electrons is used to investigate the influence of dual frequency excitation on the effective electron energy distribution function (EEDF) in a radio-frequency driven atmospheric pressure plasma. It is found that variations of power density, voltage ratio, and phase relationship provide separate control over the electron density and the mean electron energy. This is exploited to directly influence both the phase dependent and time averaged effective EEDF. This enables tailoring the EEDF for enhanced control of non-equilibrium plasma chemical kinetics at ambient pressure and temperature.

  11. Plasma structuring by the gradient drift instability at high latitudes and comparison with velocity shear driven processes

    NASA Technical Reports Server (NTRS)

    Basu, Sunanda; Mackenzie, E.; Basu, S.; Coley, W. R.; Sharber, J. R.; Hoegy, W. R.

    1990-01-01

    Using results of the in situ measurements made by the DE 2 satellite, the nature of plasma structuring at high latitudes, caused by the gradient drift instability process, is described. Using noon-midnight and dawn-dusk orbits of the DE 2 satellite, it was possible to examine the simultaneous density and electric field spectra of convecting large-scale plasma density enhancements in the polar cap known as 'patches', in directions parallel and perpendicular to their antisunward convection. The results provide evidence for the existence of at least two generic classes of instabilities operating in the high-latitude ionosphere: one driven by large-scale density gradients in a homogeneous convection field with respect to the neutrals, and the other driven by the structured convection field itself in an ambient ionosphere where density fluctuations are ubiquitous.

  12. Efficient generation of noninductive, off-axis, Ohkawa current, driven by electron Bernstein waves in high ?, spherical torus plasmas

    NASA Astrophysics Data System (ADS)

    Taylor, G.; Efthimion, P. C.; Kessel, C. E.; Harvey, R. W.; Smirnov, A. P.; Ershov, N. M.; Carter, M. D.; Forest, C. B.

    2004-10-01

    Off-axis rf-driven current can play a critical role in sustaining high ?, spherical torus (ST) plasmas without a central solenoid. Numerical modeling of electron Bernstein wave current drive (EBWCD) for a ?˜40% ST plasma predicts efficient, off-axis, Ohkawa EBWCD. Current can be efficiently driven at r/a>0.5 where the large trapped electron fraction precludes conventional Fisch-Boozer current drive and provides favorable conditions for Ohkawa EBWCD. Calculated normalized current drive efficiency increases with r/a and is a factor of 2 higher at r/a=0.7 than has been obtained with electron cyclotron current drive near the axis of large aspect ratio tokamaks.

  13. Parallel rf Force Driven by the Inhomogeneity of Power Absorption in Magnetized Plasma Zhe Gao,1,2,* Jiale Chen,2

    E-print Network

    Parallel rf Force Driven by the Inhomogeneity of Power Absorption in Magnetized Plasma Zhe Gao,1,2,* Jiale Chen,2 and Nathaniel J. Fisch3 1 Department of Engineering Physics, Tsinghua University, Beijing

  14. Studies of ion kinetic effects in shock-driven inertial confinement fusion implosions at OMEGA and the NIF and magnetic reconnection using laser-produced plasmas at OMEGA

    E-print Network

    Rosenberg, Michael Jonathan

    2014-01-01

    Studies of ion kinetic effects during the shock-convergence phase of inertial confinement fusion (ICF) implosions and magnetic reconnection in strongly-driven, laser-produced plasmas have been facilitated by the use of ...

  15. TECHNICAL NOTE: Fabrication of multiferroic composite actuator material by combining superelastic TiNi filler and a magnetostrictive Ni matrix

    NASA Astrophysics Data System (ADS)

    Hasegawa, Masanobu; Asano, Takahiro; Hashimoto, Kenji; Lee, Gyu Chang; Park, Young Chul; Okazaki, Teiko; Furuya, Yasubumi

    2006-10-01

    This research aims to design and verify a new magnetically driven multiferroic composite actuator material which is characterized by large strain and a rapid response speed. The composite actuator material is designed to consist of a magnetostrictive Ni matrix and superelastic TiNi alloy fiber fillers whose volume fraction was changed. The spark plasma sintering (SPS) method which is characterized by short time and low temperature processing was used to join these two different material elements. Cross-sectional observation by optical micrograph, mechanical compression tests, and magnetostriction measurements were carried out to verify the perfection of the adhesion state of the TiNi filler and nickel matrix as well as the amplification effect of magnetostriction. As the experimental result, the amplification effect of about a maximum of 1.5 times magnetostriction was verified in the fabricated composite actuator.

  16. Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

    NASA Astrophysics Data System (ADS)

    Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

    2012-03-01

    An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108?m-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

  17. Stirling engine heat-actuated heat pump

    Microsoft Academic Search

    R. A. Ackerman; J. English; T. Moynihan

    1983-01-01

    A Stirling-engine-driven heat-actuated heat pump (HAHP) system developed at Mechanical Technology Incorporated (MTI) consists of a free-piston Stirling engine (FPSE) driver, a diaphragm-actuated hydraulic coupling, and a Rankine-cycle, resonant-linear refrigerant compressor. This system has been under development at MTI for the past two years; within the last six months, the unit has been placed on test. This paper describes the

  18. Stirling engine heat-actuated heat pump

    SciTech Connect

    Ackerman, R.A.; English, J.; Moynihan, T.

    1983-08-01

    A Stirling-engine-driven heat-actuated heat pump (HAHP) system developed at Mechanical Technology Incorporated (MTI) consists of a free-piston Stirling engine (FPSE) driver, a diaphragm-actuated hydraulic coupling, and a Rankine-cycle, resonant-linear refrigerant compressor. This system has been under development at MTI for the past two years; within the last six months, the unit has been placed on test. This paper describes the system and test results achieved to date.

  19. Actuator Exerts Tensile Or Compressive Axial Load

    NASA Technical Reports Server (NTRS)

    Nozzi, John; Richards, Cuyler H.

    1994-01-01

    Compact, manually operated mechanical actuator applies controlled, limited tensile or compressive axial force. Designed to apply loads to bearings during wear tests in clean room. Intended to replace hydraulic actuator. Actuator rests on stand and imparts axial force to part attached to clevis inside or below stand. Technician turns control screw at one end of lever. Depending on direction of rotation of control screw, its end of lever driven downward (for compression) or upward (for tension). Lever pivots about clevis pin at end opposite of control screw; motion drives downward or upward link attached via shearpin at middle of lever. Link drives coupling and, through it, clevis attached to part loaded.

  20. X-ray source characterization of aluminum X-pinch plasmas driven by the 0. 5 TW LION accelerator

    SciTech Connect

    Qi, N.; Hammer, D.A.; Kalantar, D.H.; Rondeau, G.D.; Workman, J.B. (Laboratory of Plasma Studies, Cornell University, Ithaca, NY (USA)); Richardson, M.C.; Hong Chen (Laboratory for Laser Energetics, University of Rochester, Rochester, NY (USA))

    1989-12-01

    Recent experiments at Cornell have been performed to investigate X-pinch plasmas as intense x-ray sources which might be used to pump resonant photoexcitation lasers. Crossed Al wires have been driven by up to 600 kA current for 40 ns. High density bright spots are observed at the crossing point(s). Various diagnostics were used to characterize the X-pinch plasmas as a function of initial mass loading for several specific wire configurations. The optimum mass loading for different ionization stages of Al, and the total x-ray energy yields, which are on the order of hundreds of Joules, were examined. Estimates of plasma density, {similar to}10{sup 20} cm{sup {minus}3}, and temperature, about 400 eV, were obtained.

  1. All-Optical Control of Nonlinear Self-Focusing in Plasmas Using Non-Resonantly Driven Plasma Wave

    Microsoft Academic Search

    S. Y. Kalmykov; B. A. Shadwick; M. C. Downer

    2010-01-01

    Excitation of plasma density perturbations by an initially bi-color laser pulse helps to control nonlinear refraction in the plasma and enables various types of laser self-guiding. In this report we consider a setup that not only makes possible the transport of laser energy over cm-long relatively dense plasmas (n0 = 1018 cm-3) but also transforms the pulse into the unique

  2. All-Optical Control of Nonlinear Self-Focusing in Plasmas Using Non-Resonantly Driven Plasma Wave

    Microsoft Academic Search

    S. Y. Kalmykov; B. A. Shadwick; M. C. Downer

    2010-01-01

    Excitation of plasma density perturbations by an initially bi-color laser pulse helps to control nonlinear refraction in the plasma and enables various types of laser self-guiding. In this report we consider a setup that not only makes possible the transport of laser energy over cm-long relatively dense plasmas (n0 = 1018 cm?3) but also transforms the pulse into the unique

  3. Application of smart material-hydraulic actuators

    NASA Astrophysics Data System (ADS)

    Anderson, Eric H.; Bales, Gregory L.; White, Edward V.

    2003-08-01

    The application of a new class of actuators is considered. The actuators under development combine a high energy density smart material, specifically a piezoelectric material, with internal servohydraulic components. Large displacement outputs are produced, while the high force capacity of the stiff smart material is retained, for a net high-energy output. The actuator is considered "power-by-wire" because only electrical power is provided from the vehicle or system controller. A primary motivating application is in unmanned combat air vehicles (UCAVs). The particular actuation needs of these vehicles, in flight control and other utility functions, are described and distilled to a set of relevant device requirements. Other potential applications, such as flight motion simulation, are also highlighted. The new actuation architecture offers specific advantages over centralized hydraulic systems and has capabilities not present in electromechanical actuators (EMAs). The main advantage over centralized hydraulic systems is the elimination of the need for hydraulic lines. Compared to motor-driven ball screw type EMAs, the new actuators offer higher frequency response, and a larger peak-to-average output. A laboratory test facility designed to represent the loading experienced by a UCAV control surface is described. Key steps necessary to flight qualify the actuator are introduced.

  4. Strategies for mitigating the ionization-induced beam head erosion problem in an electron-beam-driven plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    An, W.; Zhou, M.; Vafaei-Najafabadi, N.; Marsh, K. A.; Clayton, C. E.; Joshi, C.; Mori, W. B.; Lu, W.; Adli, E.; Corde, S.; Litos, M.; Li, S.; Gessner, S.; Frederico, J.; Hogan, M. J.; Walz, D.; England, J.; Delahaye, J. P.; Muggli, P.

    2013-10-01

    Strategies for mitigating ionization-induced beam head erosion in an electron-beam-driven plasma wakefield accelerator (PWFA) are explored when the plasma and the wake are both formed by the transverse electric field of the beam itself. Beam head erosion can occur in a preformed plasma because of a lack of focusing force from the wake at the rising edge (head) of the beam due to the finite inertia of the electrons. When the plasma is produced by field ionization from the space charge field of the beam, the head erosion is significantly exacerbated due to the gradual recession (in the beam frame) of the 100% ionization contour. Beam particles in front of the ionization front cannot be focused (guided) causing them to expand as in vacuum. When they expand, the location of the ionization front recedes such that even more beam particles are completely unguided. Eventually this process terminates the wake formation prematurely, i.e., well before the beam is depleted of its energy. Ionization-induced head erosion can be mitigated by controlling the beam parameters (emittance, charge, and energy) and/or the plasma conditions. In this paper we explore how the latter can be optimized so as to extend the beam propagation distance and thereby increase the energy gain. In particular we show that, by using a combination of the alkali atoms of the lowest practical ionization potential (Cs) for plasma formation and a precursor laser pulse to generate a narrow plasma filament in front of the beam, the head erosion rate can be dramatically reduced. Simulation results show that in the upcoming “two-bunch PWFA experiments” on the FACET facility at SLAC national accelerator laboratory the energy gain of the trailing beam can be up to 10 times larger for the given parameters when employing these techniques. Comparison of the effect of beam head erosion in preformed and ionization produced plasmas is also presented.

  5. Thermo-magnetic materials for use in designing intelligent actuators

    SciTech Connect

    Ohtani, Yoshimutsu; Yoshimura, Fumikatsu; Hatakeyama, Iwao [NTT Interdisciplinary Research Labs., Tokai, Ibaraki (Japan); Ishii, Yoshikazu [NTT Interdisciplinary Research Labs., Musashino, Tokyo (Japan)

    1994-12-31

    The authors present the concept of an intelligent thermal actuator designed by using thermally sensitive magnetic materials. The use of the magnetic transition of FeRh alloy is very effective in increasing the actuator functions. These functions are freedom of direction, tuning temperature, and increasing both sensitivity and power. Two new types of actuator, a remote controlled optical driven thermo-magnetic motor and a temperature sensitive spring-less valve, are proposed and experimental results are shown.

  6. Experimental investigation of a surface DBD plasma actuator at atmospheric pressure in different N2/O2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Audier, P.; Rabat, H.; Leroy, A.; Hong, D.

    2014-12-01

    This paper presents an investigation of the influence of nitrogen and oxygen on the behavior of a surface dielectric barrier discharge (SDBD) used for active flow control. The SDBD operated in a controlled atmosphere under several N2/O2 gas mixture ratios. For each gas mixture, the consumed power was measured as a function of voltage amplitude. Then, for a given applied high voltage, the plasma morphology was recorded and commented and lastly, ionic wind velocity measurements were performed. Results show that the induced ionic wind velocity is mainly due to oxygen negative ions during the negative half-cycle. Nevertheless, the contribution of nitrogen to velocity is not negligible during the positive half-cycle. Moreover, the propagation of negative spark filaments during the negative half-cycle is linked to the proportion of O2 in the gas mixture. Increasing this proportion beyond 20% leads to a shift in the saturation effect to lower voltages and to a decrease in the maximum ionic wind velocity value.

  7. Evaluation of piezoceramic actuators for control of aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Lefebvre, Sylvie; Metcalf, Vern L.; Beyer, Todd B.; Fuller, Chris R.

    1992-01-01

    Results of an experiment to evaluate piezoceramic actuators as the control actuator for active control of interior noise in a large-scale fuselage model are presented. Control was demonstrated for tonal excitation using a time domain least mean squares algorithm. A maximum of four actuator channels and six error signals were used. The actuators were employed for control of noise at frequencies where interior cavity modes were the dominant response and for driven acoustic responses where a structure resonance was dominant. Global reductions of 9 to 12 dB were obtained for the cases examined. The most effective configuration of skin-mounted actuators was found to be a pure in-plane forcing function as opposed to a bending excitation. The frame-mounted actuators were found to be equally effective as the skin-mounted actuators. However, both configurations resulted in local regions of unacceptably high vibration response in the structure.

  8. Efficient active actuation to imitate locomotion of gecko's toes using an ionic polymer-metal composite actuator enhanced by carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yu, Min; He, Qingsong; Yu, Dingshan; Zhang, Xiaoqing; Ji, Aihong; Zhang, Hao; Guo, Ce; Dai, Zhendong

    2012-10-01

    Active actuation of the adhesive pads is important for a gecko-robot climbing on walls. We demonstrate the fabrication of an ionic polymer-metal composite (IPMC) actuator enhanced with carbon nanotubes (CNTs) and its use for actively actuating an adhesive array to imitate the locomotion of gecko's toes. The as-fabricated IPMC actuator doped with CNTs exhibits a maximum blocking force of 3.59 gf driven at a low voltage of 3 V. It can be easily controlled by voltage signals to actuate an artificial gecko's toe to attach and detach from a surface. This will allow active, distributed actuation in a gecko robot.

  9. Linear electrochemical gel actuators

    NASA Astrophysics Data System (ADS)

    Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

    2012-04-01

    By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

  10. Linear electrochemical gel actuators

    NASA Astrophysics Data System (ADS)

    Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

    2011-11-01

    By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

  11. The influence of surface properties on the plasma dynamics in radio-frequency driven oxygen plasmas: Measurements and simulations

    SciTech Connect

    Greb, Arthur; Niemi, Kari; O'Connell, Deborah; Gans, Timo [York Plasma Institute, Department of Physics, University of York, York, YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, York, YO10 5DD (United Kingdom)

    2013-12-09

    Plasma parameters and dynamics in capacitively coupled oxygen plasmas are investigated for different surface conditions. Metastable species concentration, electronegativity, spatial distribution of particle densities as well as the ionization dynamics are significantly influenced by the surface loss probability of metastable singlet delta oxygen (SDO). Simulated surface conditions are compared to experiments in the plasma-surface interface region using phase resolved optical emission spectroscopy. It is demonstrated how in-situ measurements of excitation features can be used to determine SDO surface loss probabilities for different surface materials.

  12. Flight control actuation system

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Gaines, Louie T. (Inventor); Evans, Paul S. (Inventor); Kern, James I. (Inventor)

    2004-01-01

    A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.

  13. Nonlinear pulse propagation and phase velocity of laser-driven plasma waves

    SciTech Connect

    Schroeder, Carl B.; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

    2011-03-25

    Laser evolution and plasma wave excitation by a relativistically-intense short-pulse laser in underdense plasma are investigated in the broad pulse limit, including the effects of pulse steepening, frequency red-shifting, and energy depletion. The nonlinear plasma wave phase velocity is shown to be significantly lower than the laser group velocity and further decreases as the pulse propagates owing to laser evolution. This lowers the thresholds for trapping and wavebreaking, and reduces the energy gain and efficiency of laser-plasma accelerators that use a uniform plasma profile.

  14. Microprocessor controlled force actuator

    NASA Technical Reports Server (NTRS)

    Zimmerman, D. C.; Inman, D. J.; Horner, G. C.

    1986-01-01

    The mechanical and electrical design of a prototype force actuator for vibration control of large space structures (LSS) is described. The force actuator is an electromagnetic system that produces a force by reacting against a proof-mass. The actuator has two colocated sensors, a digital microcontroller, and a power amplifier. The total weight of actuator is .998 kg. The actuator has a steady state force output of approximately 2.75 N from approximately 2 Hz to well beyond 1000 Hz.

  15. Nonparaxial theory of laser-driven plasma waves phase velocity in partially stripped magneto-plasma channels and wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Sharma, B. S.; Jain, Arachna

    2013-02-01

    A nonlinear theory of nonparaxial propagation of ultraintense and ultrashort circularly polarized Gaussian laser pulses through an inhomogeneous partially stripped underdense magneto-plasma channel with a parabolic radial density profile is examined analytically and by one-dimensional particle-in-cell simulations. The direction of magnetic field is considered along the direction of propagation of the pulse. An analytical expression for the wakefield is derived. It is observed that wakefield structures depend on the applied external magnetic field and inhomogeneity of a plasma. Further, equations for the plasma waves phase velocity and the laser pulse group velocity are derived and examined numerically. It is observed that the group velocity of a laser pulse is significantly greater than the plasma waves phase velocity. These velocities depend on the applied magnetic field and the polarization state of the electric field of the laser pulse.

  16. Photoelectron Emission from Metal Surfaces Induced by VUV-emission of Filament Driven Hydrogen Arc Discharge Plasma

    E-print Network

    Laulainen, J; Koivisto, H; Komppula, J; Tarvainen, O

    2015-01-01

    Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H^- ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

  17. Near-GeV acceleration of electrons by a nonlinear plasma wave driven by a self-guided laser pulse.

    PubMed

    Kneip, S; Nagel, S R; Martins, S F; Mangles, S P D; Bellei, C; Chekhlov, O; Clarke, R J; Delerue, N; Divall, E J; Doucas, G; Ertel, K; Fiuza, F; Fonseca, R; Foster, P; Hawkes, S J; Hooker, C J; Krushelnick, K; Mori, W B; Palmer, C A J; Phuoc, K Ta; Rajeev, P P; Schreiber, J; Streeter, M J V; Urner, D; Vieira, J; Silva, L O; Najmudin, Z

    2009-07-17

    The acceleration of electrons to approximately 0.8 GeV has been observed in a self-injecting laser wakefield accelerator driven at a plasma density of 5.5x10(18) cm(-3) by a 10 J, 55 fs, 800 nm laser pulse in the blowout regime. The laser pulse is found to be self-guided for 1 cm (>10zR), by measurement of a single filament containing >30% of the initial laser energy at this distance. Three-dimensional particle in cell simulations show that the intensity within the guided filament is amplified beyond its initial focused value to a normalized vector potential of a0>6, thus driving a highly nonlinear plasma wave. PMID:19659287

  18. Particle in cell simulations of Buneman instability of a current-driven plasma with q-nonextensive electron velocity distribution

    SciTech Connect

    Niknam, A. R., E-mail: a-niknam@sbu.ac.ir; Roozbahani, H.; Komaizi, D. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Hashemzadeh, M. [Faculty of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of)

    2014-09-15

    The nonlinear evolution of low frequency Buneman instability in an unmagnetized current-driven plasma with q-nonextensive electron velocity distribution is investigated using particle in cell simulation. Simulation results show that the generation of electron phase space holes and the counter-streaming current induced in the plasma strongly depend on the q-parameter. It is found that by increasing the nonextensive parameter, the distribution of electron density becomes highly peaked. This density steepening or grating-like pattern occurs at the saturation time. In addition, a generalized dispersion relation is obtained using the kinetic theory. Analysis of the dispersion relation and the temporal evolution of the electric field energy density reveal that the growth rate of instability increases by increasing the q-parameter. Finally, the results of Maxwellian and q-nonextensive velocity distributions have been compared and discussed.

  19. Observations of electron phase-space holes driven during magnetic reconnection in a laboratory plasma

    E-print Network

    Katz, N.

    This work presents detailed experimental observations of electron phase-space holes driven during magnetic reconnection events on the Versatile Toroidal Facility. The holes are observed to travel on the order of or faster ...

  20. Conducting polymer actuators as engineering materials

    NASA Astrophysics Data System (ADS)

    Madden, John D.; Madden, Peter G.; Hunter, Ian W.

    2002-07-01

    Conducting polymer actuators were first proposed more than ten years ago. Reported performance has improved dramatically, particularly in the past few years, due to changes in synthesis methods, better characterization and an understanding of the underlying mechanisms. These actuators are able to displace large loads (up to 100x greater than mammalian skeletal muscle), with moderate displacements (typically 2 %), and with power to mass ratios similar to that of muscle, while powered using potentials of no more than a few volts. Unlike electric motors and muscle, these actuators exhibit a catch state, enabling them to maintain force without consuming energy. Despite the impressive performance, commercial applications are at an early stage. One reason is the need to carefully consider the details of the actuator construction, including the thickness and surface area of the polymer, the electrolyte conductivity and geometry, the counter electrode spacing, the shape of the input voltage and the means of electrical contact to the polymer, in designing effective actuators. A set of design guidelines is presented that assist the device designer in determining the optimum actuator configuration. These are derived from extensive characterization and modeling of hexafluorophosphate-doped polypyrrole actuators. The set of design tools helps transform conducting polymer actuators into engineering materials that can be selected and designed for particular applications based on rational criteria. Most of the underlying physical principles used in determining these rules also underlie other conducting polymer actuators, polymer devices such as electrochromic displays, supercapacitors and batteries, carbon nanotube actuators, and electrochemically driven devices that involve volumetric charge storage.

  1. Advanced neural network model of plasma-driven integrated circuit process data

    Microsoft Academic Search

    Byungwhan Kim; Changki Min; Donghwan Kim

    2007-01-01

    Plasma processes are key means to deposit or etch thin films during the manufacture of integrated circuits. An advanced model of plasma process data was constructed by applying genetic algorithm to the set of typical training factors combined with multi-parameterized gradients of neuron activation functions. The presented technique was evaluated with plasma etch data, collected during silica etching in CHF3-CF4

  2. Electron properties and air mixing in radio frequency driven argon plasma jets at atmospheric pressure

    SciTech Connect

    Gessel, Bram van; Bruggeman, Peter [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)] [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Brandenburg, Ronny [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands) [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Leibniz Institute for Plasma Science and Technology (INP Greifswald), Felix-Hausdorff-Str. 2, D-17489 Greifswald (Germany)

    2013-08-05

    A time modulated radio frequency (RF) plasma jet operated with an Ar mixture is investigated by measuring the electron density and electron temperature using Thomson scattering. The measurements have been performed spatially resolved for two different electrode configurations and as a function of the plasma dissipated power and air concentration admixed to the Ar. Time resolved measurements of electron densities and temperatures during the RF cycle and after plasma power switch-off are presented. Furthermore, the influence of the plasma on the air entrainment into the effluent is studied using Raman scattering.

  3. High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.

    PubMed

    Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

    2013-12-13

    We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness bunches. This injection principle is explained by example of three-dimensional particle-in-cell calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blowout regime inside a fully ionized hydrogen plasma of density 5×10(17)cm-3. Within an embedded 100???m long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a 1.5 kA peak current, 1.5???m transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length. PMID:24483670

  4. Superconducting linear actuator

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce; Hockney, Richard

    1993-01-01

    Special actuators are needed to control the orientation of large structures in space-based precision pointing systems. Electromagnetic actuators that presently exist are too large in size and their bandwidth is too low. Hydraulic fluid actuation also presents problems for many space-based applications. Hydraulic oil can escape in space and contaminate the environment around the spacecraft. A research study was performed that selected an electrically-powered linear actuator that can be used to control the orientation of a large pointed structure. This research surveyed available products, analyzed the capabilities of conventional linear actuators, and designed a first-cut candidate superconducting linear actuator. The study first examined theoretical capabilities of electrical actuators and determined their problems with respect to the application and then determined if any presently available actuators or any modifications to available actuator designs would meet the required performance. The best actuator was then selected based on available design, modified design, or new design for this application. The last task was to proceed with a conceptual design. No commercially-available linear actuator or modification capable of meeting the specifications was found. A conventional moving-coil dc linear actuator would meet the specification, but the back-iron for this actuator would weigh approximately 12,000 lbs. A superconducting field coil, however, eliminates the need for back iron, resulting in an actuator weight of approximately 1000 lbs.

  5. Intense Geodesic Acousticlike Modes Driven by Suprathermal Ions in a Tokamak Plasma R. Nazikian,1

    E-print Network

    such as ITER [1] is to explore the accessibility of steady state reactor regimes in plasmas that are pre, in part, to develop predictive tools for assessing collective fast ion phenomena in steady state reactor factor (qmin ! 2) and with comparable ion and electron temperatures, relevant to steady state plasma

  6. Observation of current-driven ion sound wave in a turbulently heated plasma: The Mach 2

    Microsoft Academic Search

    Y. Amagishi; H. Iguchi; A. Mase; T. Tsukishima

    1977-01-01

    The microwave scattering method was used to measure the dynamic characteristics of turbulence in a turbulently heated plasma. Scattered signals were observed at the time before the plasma becomes resistive. The phase velocity of the wave increases with time. The value of the phase velocity is found to be consistent with that of the ion sound wave propagating across the

  7. Ion temperature gradient driven mode in presence of transverse velocity-shear in magnetized plasmas

    E-print Network

    confined plasmas is the anomaly of particle and heat transport by plasma convection across the magnetic described by various drift wave models3,4 . Several experiments2,5,6 have revealed the existence calculations8,9 predict that unstable modes in tokamaks may be stabilized by a critical shear flow. Also, fully

  8. Recent developments in DBD plasma flow control

    NASA Astrophysics Data System (ADS)

    Wang, Jin-Jun; Choi, Kwing-So; Feng, Li-Hao; Jukes, Timothy N.; Whalley, Richard D.

    2013-10-01

    Flow control using DBD (dielectric-barrier-discharge) plasma actuators is a relatively new, but rapidly expanding area of research. There are a number of review papers available on this subject, but few discuss on their latest developments. The purpose of the present article is to “fill the gap” by reviewing the recent trend of plasma actuator design and to summarise aerodynamic control techniques. Here, we review new plasma actuators, such as plasma synthetic jet actuators, plasma spark jet actuators, three-dimensional plasma actuators and plasma vortex generators, which can induce three-dimensional flows away from the wall. We also review the starting vortex that leads to formation of a plasma wall jet. This is an important subject not only for a better understanding of the flow induced by DBD plasma actuators, but also as a database that can be used to calibrate the numerical models for plasma flow control. Design of DBD plasma actuators to obtain turbulent skin-friction reduction is shown and the modifications to near-wall turbulence structures are summarised. Novel applications of DBD plasma actuators for aerodynamic control are then discussed, including pitch and roll control, plasma jet vectoring, circulation control and plasma flap, showing a potential of DBD plasma actuators for replacing movable, aircraft control surfaces. Finally, vortex shedding control techniques by a number of different plasma actuators are surveyed.

  9. Persistence of magnetic field driven by relativistic electrons in a plasma

    E-print Network

    Flacco, A; Lifschitz, A; Sylla, F; Kahaly, S; Veltcheva, M; Silva, L O; Malka, V

    2015-01-01

    The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma le...

  10. Direct calculation of inverse-bremsstrahlung absorption in strongly coupled, nonlinearly driven laser plasmas

    NASA Astrophysics Data System (ADS)

    Pfalzner, Susanne; Gibbon, Paul

    1998-04-01

    Inverse-bremsstrahlung absorption in strongly coupled plasmas produced by high-intensity lasers is studied numerically. The simultaneous presence of high density and intensity makes it difficult to treat this problem with standard methods. A technique for modeling collisional plasmas is demonstrated which uses a hierarchical tree code-an accelerated molecular dynamics algorithm with an N log N computation time-adapted to model periodic, non-equilibrium two-component plasmas. Good agreement is found with standard theoretical results for classical, weakly coupled plasmas. In a series of further simulations, the dependence of the inverse-bremsstrahlung absorption coefficient on plasma coupling parameter, laser frequency, and the ratio of quiver to thermal velocity v0/vte is computed. An important outcome of this study is that the Langdon effect-a change of the velocity distribution function due to an imbalance of heating and equilibration rates-is verified in a direct microscopic particle simulation.

  11. Piston actuated nastic materials

    E-print Network

    Shah, Viral

    2009-05-15

    piston actuators distributed through the beam?s outer core provide the internal work needed. By actuating the piston elements in their axial direction, which is transverse to the beam?s central axis, the beam twists as desired. This study?s objective...?s shape. An actuator?s design depends on the application?s requirements and available methods for pressurizing the system internally. The actuator?s shape provides maximum work energy density in the axial direction. Nastic material?s concept...

  12. Nanoporous carbon actuator and methods of use thereof

    DOEpatents

    Biener, Juergen (San Leandro, CA); Baumann, Theodore F. (Discovery Bay, CA); Shao, Lihua (Karlsruhe, DE); Weissmueller, Joerg (Stutensee, DE)

    2012-07-31

    An electrochemically driveable actuator according to one embodiment includes a nanoporous carbon aerogel composition capable of exhibiting charge-induced reversible strain when wetted by an electrolyte and a voltage is applied thereto. An electrochemically driven actuator according to another embodiment includes a nanoporous carbon aerogel composition wetted by an electrolyte; and a mechanism for causing charge-induced reversible strain of the composition. A method for electrochemically actuating an object according to one embodiment includes causing charge-induced reversible strain of a nanoporous carbon aerogel composition wetted with an electrolyte to actuate the object by the strain.

  13. Power generating machine actuated by ocean swells

    Microsoft Academic Search

    Parr

    1976-01-01

    A power generating machine which is actuated by the continuous swells occurring in the ocean is described. The machine is supported on a pair of spaced main floats, between which is a power float connected to a linkage which allows the power float to reciprocate vertically with the passing swells. A flywheel is driven through a one way clutch connected

  14. Iogenic Plasma and its Rotation-Driven Transport in Jupiter's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Smyth, William H.

    2001-01-01

    Model calculations are reported for the Iogenic plasma source created by atomic oxygen and sulfur above Io's exobase in the corona and extended clouds (Outer Region). On a circumplanetary scale, two-dimensional distributions produced by integrating the proper three dimensional rate information for electron impact and charge exchange processes along the magnetic field lines are presented for the pickup ion rates, the net-mass and total-mass loading rates, the mass per unit magnetic flux rate, the pickup conductivity, the radial pickup current, and the net-energy loading rate for the plasma torus. All of the two-dimensional distributions are highly peaked at Io's location and hence highly asymmetric about Jupiter. The Iogenic plasma source is also calculated on a much smaller near-Io scale to investigate the structure of the highly peak rates centered about lo's instantaneous location. The Iogenic plasma source for the Inner Region (pickup rates produced below Io's exobase) is, however, expected to be the dominant source near lo for the formation of the plasma torus ribbon and to be a comparable source, if not a larger contributor, to the energy budget of the plasma torus, so as to provide the necessary power to sustain the plasma torus radiative loss rate.

  15. Electrostatic instability in magnetically confined inhomogeneous plasma driven by nonlinear force

    NASA Astrophysics Data System (ADS)

    Borgohain, A.; Deka, P. N.

    2014-02-01

    A theoretical investigation on amplification of electrostatic ion acoustic wave in magnetically confined plasma has been presented in this paper. This investigation considers nonlinear wave-particle interaction process, called plasma maser effect, in presence of drift wave turbulence supported by magnetically confined inhomogeneous plasma. The role of associated nonlinear dissipative force in this effect in a confined plasma has been analyzed. The nonlinear force, which arises as a result of resonant interaction between electrons and modulated fields, is shown to drive the instability. Using the ion fluid equation and the ion equation of continuity, the nonlinear dispersion relation of a test ion acoustic wave has been derived, and the growth rate of ion acoustic wave in presence of low frequency drift wave turbulence has been estimated using Helimak data.

  16. Uniaxial Electric Actuator

    NSDL National Science Digital Library

    This site includes a cut-away animation of how a uniaxial electric actuator operates. Objective: Describe how the uniaxial electric actuator works. You can find this animation under the heading "Automation Technology."

  17. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  18. Low backlash direct drive actuator

    DOEpatents

    Kuklo, T.C.

    1994-10-25

    A low backlash direct drive actuator is described which comprises a motor such as a stepper motor having at least 200 steps per revolution; a two part hub assembly comprising a drive hub coaxially attached to the shaft of the motor and having a plurality of drive pins; a driven hub having a plurality of bores in one end thereof in alignment with the drive pins in the drive hub and a threaded shaft coaxially mounted in an opposite end of the driven hub; and a housing having a central bore therein into which are fitted the drive hub and driven hub, the housing having a motor mount on one end thereof to which is mounted the stepper motor, and a closed end portion with a threaded opening therein coaxial with the central bore in the housing and receiving therein the threaded shaft attached to the driven hub. Limit switches mounted to the housing cooperate with an enlarged lip on the driven hub to limit the lateral travel of the driven hub in the housing, which also acts to limit the lateral travel of the threaded shaft which functions as a lead screw. 10 figs.

  19. Low backlash direct drive actuator

    DOEpatents

    Kuklo, Thomas C. (Oakland, CA)

    1994-01-01

    A low backlash direct drive actuator is described which comprises a motor such as a stepper motor having at least 200 steps per revolution; a two part hub assembly comprising a drive hub coaxially attached to the shaft of the motor and having a plurality of drive pins; a driven hub having a plurality of bores in one end thereof in alignment with the drive pins in the drive hub and a threaded shaft coaxially mounted in an opposite end of the driven hub; and a housing having a central bore therein into which are fitted the drive hub and driven hub, the housing having a motor mount on one end thereof to which is mounted the stepper motor, and a closed end portion with a threaded opening therein coaxial with the central bore in the housing and receiving therein the threaded shaft attached to the driven hub. Limit switches mounted to the housing cooperate with an enlarged lip on the driven hub to limit the lateral travel of the driven hub in the housing, which also acts to limit the lateral travel of the threaded shaft which functions as a lead screw.

  20. Powered glove with electro-pneumatic actuation unit for the disabled

    Microsoft Academic Search

    Kosuke Kawakami; Shinichi Kumano; Shunji Moromugi; Takakazu Ishimatsu

    2007-01-01

    Authors have been developing a powered glove for people suffering from paralysis on their fingers to support their daily activity. Small air cylinders are used as actuators for this glove. Pneumatically-driven system has high advantages in case soft actuation is preferable. However, there are some problems to be solved in the pneumatically-driven system if the system is supposed to be

  1. Gas-puff z-pinch plasmas driven by inductive energy storage pulsed power generator

    Microsoft Academic Search

    K. Murayama; T. Shinkai; S. Katsuki; H. Akiyama

    1997-01-01

    ASO-II, an inductive energy storage pulsed power generator developed at Kumamoto University, is used as a power source for gas-puff z-pinch plasmas. The plasma characteristics are compared with those generated by a fast capacitive bank that supplies the same energy. Also, solid and mesh cathode electrodes are compared with respect to the pinch behavior. Using ASO-II in the case of

  2. Direct calculation of inverse-bremsstrahlung absorption in strongly coupled, nonlinearly driven laser plasmas

    Microsoft Academic Search

    Susanne Pfalzner; Paul Gibbon

    1998-01-01

    Inverse-bremsstrahlung absorption in strongly coupled plasmas produced by high-intensity lasers is studied numerically. The simultaneous presence of high density and intensity makes it difficult to treat this problem with standard methods. A technique for modeling collisional plasmas is demonstrated which uses a hierarchical tree code-an accelerated molecular dynamics algorithm with an N log N computation time-adapted to model periodic, non-equilibrium

  3. Design of an XUV FEL Driven by the Laser-Plasma Accelerator at theLBNL LOASIS Facility

    SciTech Connect

    Schroeder, Carl B.; Fawley, W.M.; Esarey, Eric; Leemans, W.P.

    2006-09-01

    We present a design for a compact FEL source of ultrafast, high-peak flux, soft x-ray pulses employing a high-current, GeV-energy electron beam from the existing laser-plasma accelerator at the LBNL LOASIS laser facility. The proposed ultra-fast source would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science with pulse lengths of tens of fs. Owing both to the high current ({approx} 10 kA) and reasonable charge/pulse ({approx} 0.1-0.5 nC) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially 10{sup 13}--10{sup 14} photons/pulse. We examine devices based both on SASE and high-harmonic generated input seeds to give improved coherence and reduced undulator length, presenting both analytic scalings and numerical simulation results for expected FEL performance. A successful source would result in a new class of compact laser-driven FELs in which a conventional RF accelerator is replaced by a GeV-class laser-plasma accelerator whose active acceleration region is only a few cm in length.

  4. Paper Actuators Made with Cellulose and Hybrid Materials

    PubMed Central

    Kim, Jaehwan; Yun, Sungryul; Mahadeva, Suresha K.; Yun, Kiju; Yang, Sang Yeol; Maniruzzaman, Mohammad

    2010-01-01

    Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated. PMID:22294882

  5. Simulation of sloshing dynamics induced forces and torques actuated on dewar container driven by gravity gradient and jitter accelerations in microgravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Pan, H. L.

    1993-01-01

    Some experimental spacecraft use superconducting sensors for gyro read-out and so must be maintained at a very low temperature. The boil-off from the cryogenic liquid used to cool the sensors can also be used, as the Gravity Probe B (GP-B) spacecraft does, as propellant to maintain attitude control and drag-free operation of the spacecraft. The cryogenic liquid for such spacecraft is, however, susceptible to both slosh-like motion and non-axisymmetric configurations under the influence of various kinds of gravity jitter and gravity gradient accelerations. Hence, it is important to quantify the magnitude of the liquid-induced perturbations on the spacecraft. We use the example of the GP-B to investigate such perturbations by numerical simulations. For this spacecraft disturbances can be imposed on the liquid by atmospheric drag, spacecraft attitude control maneuvers, and the earth's gravity gradient. More generally, onboard machinery vibrations and crew motion can also create disturbances. Recent studies suggest that high frequency disturbances are relatively unimportant in causing liquid motions in comparison to low frequency ones. The results presented here confirm this conclusion. After an initial calibration period, the GP-B spacecraft rotates in orbit at 0.1 rpm about the tank symmetry axis. For this rotation rate, the equilibrium liquid free surface shape is a 'doughnut' configuration for all residual gravity levels of 10(exp -6) g(sub 0) or less, as shown by experiments and by numerical simulations; furthermore, the superfluid behavior of the 1.8 K liquid helium used in GP-B eliminates temperature gradients and therefore such effects as Marangoni convection do not have to be considered. Classical fluid dynamics theory is used as the basis of the numerical simulations here, since Mason's experiments show that the theory is applicable for cryogenic liquid helium in large containers. To study liquid responses to various disturbances, we investigate and simulate three levels of gravity jitter (10(exp -6), 10(exp -7), and 10(exp -8) g(sub 0)) each at three predominant frequencies (0.1, 1.0, and 10 Hz), combined with a gravity gradient appropriate for the GP-B orbit. Dynamical evolution of sloshing dynamics excited fluid forces and torque fluctuations exerted on the dewar container driven by the combined gravity gradient and jitter accelerations are also investigated and simulated.

  6. The algorithm and program complex for splitting on a parts the records of acoustic waves recorded during the work of plasma actuator flush-mounted in the model plane nozzle with the purpose of analyzing their robust spectral and correlation characteristics

    NASA Astrophysics Data System (ADS)

    Chernousov, A. D.; Malakhov, D. V.; Skvortsova, N. N.

    2014-03-01

    Currently acute problem of developing new technologies by reducing the noise of aircraft engines, including the directional impact on the noise on the basis of the interaction of plasma disturbances and sound generation pulsations. One of the devices built on this principle being developed in GPI RAS. They are plasma actuators (group of related to each other gaps, built on the perimeter of the nozzle) of various shapes and forms. In this paper an algorithm was developed which allows to separate impulses from the received experimental data, acquired during the work of plasma actuator flush-mounted in the model plane nozzle. The algorithm can be adjusted manually under a variety of situations (work of actuator in a nozzle with or without airflow, adjustment to different frequencies and pulse duration of the actuator). And program complex is developed on the basis of MatLab software, designed for building sustainable robust spectral and autocovariation functions of acoustic signals recorded during the experiments with the model of a nozzle with working actuator.

  7. Considerations for Contractile Electroactive Materials and Actuators

    SciTech Connect

    Lenore Rasmussen, David Schramm, Paul Rasmussen, Kevin Mullaly, Ras Labs, LLC, Intelligent Materials for Prosthetics & Automation, Lewis D. Meixler, Daniel Pearlman and Alice Kirk

    2011-05-23

    Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

  8. Sensitivity of RF-Driven Plasma Filaments to Trace Gases in Neon

    NASA Astrophysics Data System (ADS)

    Burin, M. J.; Saucedo, L.; Wilson, D. R.; Zweben, S. J.; Zwicker, A.; Brunkhorst, C.

    2012-10-01

    Filamentary structures have been observed in many types of plasma discharges in both natural and industrial systems (e.g. upper-atmospheric discharge phenomena and dielectric barrier discharges). Various aspects of their physics remain unclear. A common example can be found within a toy plasma globe (or plasma ball), wherein a primarily Neon gas mixture in a spherical glass vessel near atmospheric pressure (˜ 740 Torr) clearly and aesthetically displays filamentation. Recent work has provided the first characterization of these plasma globe filaments [Campanell et al, Physics of Plasmas 2010], where it was noticed that discharges of pure gases tend not to produce filaments. We have extended this initial work to quantify the dependence on trace gases and absolute pressure on filament properties (e.g. average number, thickness). These initial results using a custom globe apparatus are here presented along with some preliminary discussion of the effects possible with a programmable high voltage supply. Ultimately, high-speed photography and in-situ probes will be used to characterize filament dynamics, allowing for a more detailed comparison with theory and simulations.

  9. A wireless actuating drug delivery system

    NASA Astrophysics Data System (ADS)

    Jo, Won-Jun; Baek, Seung-Ki; Park, Jung-Hwan

    2015-04-01

    A wireless actuating drug delivery system was devised. The system is based on induction heating for drug delivery. In this study, thermally generated nitrogen gas produced by induction heating of azobisisobutyronitrile (AIBN) was utilized for pressure-driven release of the drug. The delivery device consists of an actuator chamber, a drug reservoir, and a microchannel. A semicircular copper disc (5 and 6?mm in diameter and 100?µm thick), and thermal conductive tape were integrated as the heating element in the actuator chamber. The final device was 2.7?mm thick. 28?µl of drug solution were placed in the reservoir and the device released the drug quickly at the rate of 6?µl?s?1 by induction heating at 160?µT of magnetic intensity. The entire drug solution was released and dispersed after subcutaneous implantation under identical experimental condition. This study demonstrates that the device was simply prepared and drug delivery could be achieved by wireless actuation of a thin, pressure-driven actuator.

  10. Laser-driven hole boring and gamma-ray emission in high-density plasmas

    NASA Astrophysics Data System (ADS)

    Nerush, E. N.; Kostyukov, I. Y.

    2015-03-01

    Ion acceleration in laser-produced dense plasmas is a key topic of many recent investigations thanks to its potential applications. Indeed, at forthcoming laser intensities (I ? 1023 W cm?2) interaction of laser pulses with plasmas can be accompanied by copious gamma-ray emission. Here we demonstrate the mutual influence of gamma-ray emission and ion acceleration during relativistic hole boring in high-density plasmas with ultra-intense laser pulses. If the gamma-ray emission is abundant, laser pulse reflection and hole-boring velocity are lower and gamma-ray radiation pattern is narrower than in the case of low emission. Conservation of energy and momentum allows one to elucidate the effects of the gamma-ray emission which are more pronounced at higher hole-boring velocities.

  11. Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source

    NASA Astrophysics Data System (ADS)

    Todorov, D.; Tarnev, Kh.; Paunska, Ts.; Lishev, St.; Shivarova, A.

    2014-02-01

    Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure.

  12. Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.

    PubMed

    Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

    2014-02-01

    Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure. PMID:24593544

  13. Linear and nonlinear dynamics of current-driven waves in dusty plasmas

    SciTech Connect

    Ahmad, Ali [National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Department of Physics, COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan); Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); Ali Shan, S.; Haque, Q. [National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); Saleem, H. [National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Department of Physics, COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan)

    2012-09-15

    The linear and nonlinear dynamics of a recently proposed plasma mode of dusty plasma is studied using kappa distribution for electrons. This electrostatic wave can propagate in the plasma due to the sheared flow of electrons and ions parallel to the external magnetic field in the presence of stationary dust. The coupling of this wave with the usual drift wave and ion acoustic wave is investigated. D'Angelo's mode is also modified in the presence of superthermal electrons. In the nonlinear regime, the wave can give rise to dipolar vortex structures if the shear in flow is weaker and tripolar vortices if the flow has steeper gradient. The results have been applied to Saturn's magnetosphere corresponding to negatively charged dust grains. But the theoretical model is applicable for positively charged dust as well. This work will be useful for future observations and studies of dusty environments of planets and comets.

  14. The effect of plasma heating on sublimation-driven flow in Io's atmosphere

    NASA Technical Reports Server (NTRS)

    Wong, Mau C.; Johnson, Robert E.

    1995-01-01

    The atmospheric flow on Io is numerically computed in a flat 2-D axisymmetric geometry for a sublimation atmosphere on the trailing hemisphere subjected to plasma bombardment, UV heating, and IR cooling. Calculations are performed for subsolar vapor pressures of approximately 6.5 x 10(exp -3) Pa (approximately 3 x 10(exp 18) SO2/sq cm) and 6.8 x 10(exp -4) Pa (approximately 4 x 10(exp 17) SO2/sq cm); the latter approximates the vapor pressure of F. P. Fanale et al. (1982). The amount of plasma energy deposited in the atmosphere is 20% of the plasma flow energy due to corotation (J. A. Linker et al., 1988). It is found that plasma heating significantly inflates the upper atmosphere, increasing both the exobase altitude and the amount of surface covered by more than an exospheric column of gas. This in turn controls the supply of the Io plasma torus (M. A. McGrath and R. E. Johnson, 1987). The horizontal flow of mass and energy is also important in determining the exobase altitude; and it is shown that IR cooling can be important, although our use of the equilibrium, cool-to-space approximation for a pure SO2 gas (E. Lellouch et al., 1992) may overestimate this effect. The calculated exobase altitudes are somewhat lower than those suggested by McGrath and Johnson (1987) for supplying the torus, indicating the details of the plasma energy deposition and sputter ejection rate near the exobase, as well as the IR emission from this region need to be examined. In addition, the molecules sublimed (or sputtered) from the surface are transported to the exobase in times short compared to the molecular photodissociation time. Therefore, the exobase is dominated by molecular species and the exobase is supplied by a small region of the surface.

  15. Stimulated Raman Scattering (SRS) Driven by 30 fs Laser Pulse in Underdense Plasmas

    NASA Astrophysics Data System (ADS)

    Matsuoka, T.; Horovitz, Y.; McGuffey, C.; Cummings, P. G.; Chvykov, V.; Kalintchenko, G.; Rousseau, P.; Dollar, F.; Bulanov, S. S.; Yanovsky, V.; Thomas, A. G. R.; Maksimchuk, A.; Krushelnick, K.

    2009-11-01

    Propagation of an ultra-short laser pulse in underdense plasma was studied in the parameter range relevant for laser wakefield accelerators (LWFA) at 100 TW laser power. Filamentation of the transmitted laser pulse observed with the transverse interferpmetry was well correlated with stimulated side Raman scattering (SSRS). Experimentally measured scattered light angle relative to the laser axis is well reproduced by an analytic formula for SSRS in the range of the experimental plasma densities. Spectra orthogonal to the laser pulse showed spatially modulated intensity profile and laser intensity dependent shift for Stokes light. 2D-PIC simulation showed the evolution of the laser pulse due to SSRS.

  16. Possible energy gain for a plasma-liner-driven magneto-inertial fusion concept

    NASA Astrophysics Data System (ADS)

    Knapp, C. E.; Kirkpatrick, R. C.

    2014-07-01

    A one-dimensional parameter study of a Magneto-Inertial Fusion (MIF) concept indicates that significant gain may be achievable. This concept uses a dynamically formed plasma shell with inwardly directed momentum to drive a magnetized fuel to ignition, which in turn partially burns an intermediate layer of unmagnetized fuel. The concept is referred to as Plasma Jet MIF or PJMIF. The results of an adaptive mesh refinement Eulerian code (Crestone) are compared to those of a Lagrangian code (LASNEX). These are the first published results using the Crestone and LASNEX codes on the PJMIF concept.

  17. Fusion and Plasma Physics are at the Core of Nature's Most Powerful Self-Driven Systems

    E-print Network

    nD nT watts m-3 , note: ~ T2 @ 10 keV #12;Energy/Fuel Recovery Qp Fuel Fuel (Li, D) RPE Waste: nD = nT = ne/2 = n/2, n 2 UVp/4 = P is the alpha heating power, CBT 1/2 ne 2 Vp is the radiationE = 3kT U (Q+5)/4Q - CBT 1/2 where Q = Pfusion/ Paux-heat Q = 1 is Plasma Breakeven, Q = is Plasma

  18. Effects of eletron heating on the current driven electrostatic ion cyclotron instability and plasma transport processes along auroral field lines

    NASA Technical Reports Server (NTRS)

    Ganguli, Supriya B.; Mitchell, Horace G.; Palmadesso, Peter J.

    1988-01-01

    Fluid simulations of the plasma along auroral field lines in the return current region have been performed. It is shown that the onset of electrostatic ion cyclotron (EIC) related anomalous resistivity and the consequent heating of electrons leads to a transverse ion temperature that is much higher than that produced by the current driven EIC instability (CDICI) alone. Two processes are presented for the enhancement of ion heating by anomalous resistivity. The anomalous resistivity associated with the turbulence is limited by electron heating, so that CDICI saturates at transverse temperature that is substantially higher than in the absence of resistivity. It is suggested that this process demonstrates a positive feedback loop in the interaction between CDICI, anomalous resistivity, and parallel large-scale dynamics in the topside ionosphere.

  19. Bimorphic polymeric photomechanical actuator

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

    2006-01-01

    A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

  20. Omnidirectional Actuator Handle

    NASA Technical Reports Server (NTRS)

    Moetteli, John B.

    1995-01-01

    Proposed actuator handle comprises two normally concentric rings, cables, and pulleys arranged such that relative displacement of rings from concentricity results in pulling of cable and consequent actuation of associated mechanism. Unlike conventional actuator handles like levers on farm implements, actuated from one or two directions only, proposed handle reached from almost any direction and actuated by pulling or pushing inner ring in any direction with respect to outer ring. Flanges installed on inner ring to cover gap between inner ring and housing to prevent clothing from being caught.

  1. Networked Rectenna Array for Smart Material Actuators

    NASA Technical Reports Server (NTRS)

    Choi, Sang H.; Golembiewski, Walter T.; Song, Kyo D.

    2000-01-01

    The concept of microwave-driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry. Networked rectenna patch array receives and converts microwave power into a DC power for an array of smart actuators. To use microwave power effectively, the concept of a power allocation and distribution (PAD) circuit is adopted for networking a rectenna/actuator patch array. The PAD circuit is imbedded into a single embodiment of rectenna and actuator array. The thin-film microcircuit embodiment of PAD circuit adds insignificant amount of rigidity to membrane flexibility. Preliminary design and fabrication of PAD circuitry that consists of a few nodal elements were made for laboratory testing. The networked actuators were tested to correlate the network coupling effect, power allocation and distribution, and response time. The features of preliminary design are 16-channel computer control of actuators by a PCI board and the compensator for a power failure or leakage of one or more rectennas.

  2. Lower hybrid instability driven by mono-energy {alpha}-particles with finite pitch angle spread in a plasma

    SciTech Connect

    Kumar, Pawan; Singh, Vishwesh; Tripathi, V. K. [Department of Physics, IIT Delhi, New Delhi-110016 (India)

    2013-02-15

    A kinetic formalism of lower hybrid wave instability, driven by mono-energy {alpha}-particles with finite pitch angle spread, is developed. The instability arises through cyclotron resonance interaction with high cyclotron harmonics of {alpha}-particles. The {alpha}-particles produced in D-T fusion reactions have huge Larmor radii ({approx}10 cm) as compared to the wavelength of the lower hybrid wave, whereas their speed is an order of magnitude smaller than the speed of light in vacuum. As a result, large parallel phase velocity lower hybrid waves, suitable for current drive in tokamak, are driven unstable via coupling to high cyclotron harmonics. The growth rate decreases with increase in pitch angle spread of the beam. At typical electron density of {approx}10{sup 19} m{sup -3}, magnetic field {approx}4 Tesla and {alpha}-particle concentration {approx}0.1%, the large parallel phase velocity lower hybrid wave grows on the time scale of 20 ion cyclotron periods. The growth rate decreases with plasma density.

  3. plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, H. Y.; Jin, C. G.; Yang, Y.; Ye, C.; Zhuge, L. J.; Wu, X. M.

    2014-12-01

    As-deposited HfO2 films were modified by CHF3, C4F8, and mixed C4F8/O2 plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF3, C4F8, and C4F8/O2 were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO2 films by either CHF3 or C4F8 plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO2 films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O2 gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO2 phase was investigated in both samples treated with CHF3 and C4F8 plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO2 films. The mechanism of the t-HfO2 formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C4F8/O2 plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO2 was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF3 plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO2 films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.

  4. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

    E-print Network

    Rice, John E.

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60??km/s in the central region of the plasma (r/a~<0.4). This modification of the toroidal ...

  5. Ion anisotropy driven waves in the earth`s magnetosheath and plasma depletion layer

    SciTech Connect

    Denton, R.E.; Hudson, M.K. [Dartmouth Coll., Hanover, NH (United States). Dept. of Physics and Astronomy; Anderson, B.J. [Johns Hopkins Univ., Laurel, MD (United States). Applied Physics Lab.; Fuselier, S.A. [Lockheed Palo Alto Research Labs., CA (United States); Gary, S.P. [Los Alamos National Lab., NM (United States)

    1993-05-01

    Recent studies of low frequency waves ({omega}{sub r} {le} {Omega}{sub p}, where {Omega}{sub p} is the proton gyrofrequency) observed by AMPTE/CCE in the plasma depletion layer and magnetosheath proper arereviewed. These waves are shown to be well identified with ion cyclotron and mirror mode waves. By statistically analyzing the transitions between the magnetopause and time intervals with ion cyclotron and mirror mode waves, it is established that the regions in which ion cyclotron waves occur are between the magnetopause and the regions where the mirror mode is observed. This result is shown to follow from the fact that the wave spectral properties are ordered with respect to the proton parallel beta, {beta}{sub {parallel}p}. The later result is predicted by linear Vlasov theory using a simple model for the magnetosheath and plasma depletion layer. Thus, the observed spectral type can be associated with relative distance from the magnetopause. The anisotropy-beta relation, A{sub p} {triple_bond} (T{perpendicular}/T{sub {parallel}}){sub p} {minus} 1 = 0.50{beta}{sub {parallel}p}{sup {minus}0.48} results from the fact that the waves pitch angle scatter the particles so that the plasma is near marginal stability, and is a fundamental constraint on the plasma.

  6. Cyclotron-resonance maser driven by magnetic compression of rarefied plasma.

    PubMed

    Golubev, S V; Shalashov, A G

    2007-11-16

    Conditions are found at which adiabatic magnetic compression of plasma confined in a mirror magnetic trap is accompanied by the accumulation of significant energy in a hot anisotropic electron tail with the subsequent release of this energy as a pulse of coherent electromagnetic radiation. The possibilities of creating THz radiation sources up to the GW power level are discussed. PMID:18233148

  7. Cyclotron-Resonance Maser Driven by Magnetic Compression of Rarefied Plasma

    Microsoft Academic Search

    S. V. Golubev; A. G. Shalashov

    2007-01-01

    Conditions are found at which adiabatic magnetic compression of plasma confined in a mirror magnetic trap is accompanied by the accumulation of significant energy in a hot anisotropic electron tail with the subsequent release of this energy as a pulse of coherent electromagnetic radiation. The possibilities of creating THz radiation sources up to the GW power level are discussed.

  8. Cyclotron-Resonance Maser Driven by Magnetic Compression of Rarefied Plasma

    SciTech Connect

    Golubev, S. V.; Shalashov, A. G. [Institute of Applied Physics, Russian Academy of Sciences, Ulyanova Street 46, 603950 Nizhny Novgorod (Russian Federation)

    2007-11-16

    Conditions are found at which adiabatic magnetic compression of plasma confined in a mirror magnetic trap is accompanied by the accumulation of significant energy in a hot anisotropic electron tail with the subsequent release of this energy as a pulse of coherent electromagnetic radiation. The possibilities of creating THz radiation sources up to the GW power level are discussed.

  9. Study of driven magnetic reconnection in a laboratory plasma* Masaaki Yamada,

    E-print Network

    Ji, Hantao

    in the evolution of solar flares5­9 and in the dynamics of the earth's magneto- sphere.10­14 It also occurs as one the confinement characteristics of high- temperature fusion plasmas. The study of solar flares has been Solar flares provide a paradigm for physical systems where magnetic energy is stored in a force- free

  10. Tuneable Auxiliary Control Mechanisms For RUM Actuators

    NASA Technical Reports Server (NTRS)

    Polites, Michael E.; Alhorn, Dean C.

    1995-01-01

    Tuneable auxiliary control mechanisms for rotating unbalanced-mass (RUM) actuators used to maximize scan amplitudes and/or minimize power consumption during changing conditions. This type of mechanism more sophisticated version of type of mechanism described in "Auxiliary Control Mechanisms for RUM Actuators" (MFS-28817). Torsional stiffness of torsionally flexible coupling made adjustable on command. Torsionally flexible coupling in tuneable version of auxiliary control mechanism adjustable by use of stepping-motor-driven worm-gear mechanism that varies bending length of flexible blade.

  11. The Next Generation of Space Plasma Analyzer - Deployable Radial Imaging for Velocity, Energy, and Density (DRIVEN)

    NASA Astrophysics Data System (ADS)

    Collinson, G. A.; Moore, T. E.; Durachka, D.; Olson, D. K.; Knudsen, D. J.; Rozmarynowski, P.; Beamer, A. A.; Klenzing, J. H.

    2010-12-01

    We present initial developments towards a space plasma analyzer capable of making simultaneous observations of cold (<1eV) and high-energy (5keV) space plasmas at revolutionary temporal and spatial resolution. "Top Hat" plasma analyzers [1] (the current "state of the art") typically have modest azimuthal resolution (c.f. 10 degrees, for reasons of electronic practicality), and can only read out a single energy at a time, thereby requiring a swept voltage to sample a range of energies. True energy imaging of particle populations was achieved with the Freja Cold Plasma Analyzer [2], and at higher time and energy resolution on subsequent sounding rocket flights using a CCD-based detection scheme, but only at energies below 200 eV [3]. We propose to overcome these shortcomings using novel particle optics and directly imaging space plasma distributions using a revolutionary 2D position-sensitive readout technique, thereby covering particle energies from cold to energetic while eliminating the need for an energy sweep. Measurements of <1eV electrons and ions are currently very challenging owing to effects of spacecraft charging. Existing s/c systems such as ASPOC on Cluster are complex, expensive and have a limited lifetime. Our boom-mounted sensor will automatically compensate for changes in spacecraft potential through the reverse biasing of its outer skin according to measurements from an integrated Langmuir probe. [1] Carlson et al., Adv. Space Res., 2(7), 67, (1982) [2] Whalen et al., Space Sci. Rev., (70), 541. (1994) [3] Knudsen et al., Rev. Sci. Instrum., (74), 202. (2003)

  12. Electroactive polymer (EAP) actuators for planetary applications

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, Yoseph; Leary, Sean P.; Shahinpoor, Mohsen; Harrison, Joycelyn S.; Smith, J.

    1999-05-01

    NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers (EAP) are offering an effective alternative to current actuators. In this study, two families of EAP materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, include the operation of the bending-EAP at conditions that exceed the harsh environment on Mars, and identify the obstacles that its properties and characteristics are posing to using them as actuators. Analysis of the electrical characteristics of the ionomer EAP showed that it is a current driven material rather than voltage driven and the conductivity distribution on the surface of the material greatly influences the bending performance. An accurate equivalent circuit modeling of the ionomer EAP performance is essential for the design of effective drive electronics. The ionomer main limitations are the fact that it needs to be moist continuously and the process of electrolysis that takes place during activation. An effective coating technique using a sprayed polymer was developed extending its operation in air from a few minutes to about four months. The coating technique effectively forms the equivalent of a skin to protect the moisture content of the ionomer. In parallel to the development of the bending EAP, the development of computer control of actuated longitudinal EAP has been pursued. An EAP driven miniature robotic arm was constructed and it is controlled by a MATLAB code to drop and lift the arm and close and open EAP fingers of a 4-finger gripper.

  13. Plasma-Density Determination from X-Ray Radiography of Laser-Driven Spherical Implosions

    SciTech Connect

    Marshall, F. J.; McKenty, P. W.; Delettrez, J. A.; Epstein, R.; Knauer, J. P.; Smalyuk, V. A.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.; Seguin, F. H.; Mancini, R. C. [Laboratory for Laser Energetics, University of Rochester 250 E. River Road, Rochester, New York 14623 (United States); Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)

    2009-05-08

    The fuel layer density of an imploding laser-driven spherical shell is inferred from framed x-ray radiographs. The density distribution is determined by using Abel inversion to compute the radial distribution of the opacity {kappa} from the observed optical depth {tau}. With the additional assumption of the mass of the remaining fuel, the absolute density distribution is determined. This is demonstrated on the OMEGA laser system with two x-ray backlighters of different mean energies that lead to the same inferred density distribution independent of backlighter energy.

  14. Kinetic simulation of radio-frequency driven plasmas in He/O2 mixtures at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Eremin, Denis; Hemke, Torben; Brinkmann, Ralf Peter; Mussenbrock, Thomas

    2011-11-01

    Over the past years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are radio-frequency plasma jets. This contribution investigates radio-frequency driven plasmas with an electrode gap of below 1 mm. The discharge is operated in a mixture of He and O2 (0.5 percent) at atmospheric pressure. A typical simulation of this kind of discharges is based on the hydrodynamic approximation of the relevant species. Sometimes this approach is extended by a quasi-kinetic treatment of the fast electron component (hybrid codes). Still certain kinetic effects are neglected in both of these methods. In this work a 1d self-consistent Particle-in-Cell model of the discharge is developed, to investigate kinetic effects and to verify the validity of the corresponding fluid model. All the relevant species and reactions regarding the underlying chemistry are taken into account by means of a Monte Carlo Collision model.

  15. Project Icarus: Analysis of Plasma jet driven Magneto-Inertial Fusion as potential primary propulsion driver for the Icarus probe

    NASA Astrophysics Data System (ADS)

    Stanic, M.; Cassibry, J. T.; Adams, R. B.

    2013-05-01

    Hopes of sending probes to another star other than the Sun are currently limited by the maturity of advanced propulsion technologies. One of the few candidate propulsion systems for providing interstellar flight capabilities is nuclear fusion. In the past many fusion propulsion concepts have been proposed and some of them have even been explored in detail, Project Daedalus for example. However, as scientific progress in this field has advanced, new fusion concepts have emerged that merit evaluation as potential drivers for interstellar missions. Plasma jet driven Magneto-Inertial Fusion (PJMIF) is one of those concepts. PJMIF involves a salvo of converging plasma jets that form a uniform liner, which compresses a magnetized target to fusion conditions. It is an Inertial Confinement Fusion (ICF)-Magnetic Confinement Fusion (MCF) hybrid approach that has the potential for a multitude of benefits over both ICF and MCF, such as lower system mass and significantly lower cost. This paper concentrates on a thermodynamic assessment of basic performance parameters necessary for utilization of PJMIF as a candidate propulsion system for the Project Icarus mission. These parameters include: specific impulse, thrust, exhaust velocity, mass of the engine system, mass of the fuel required etc. This is a submission of the Project Icarus Study Group.

  16. Wakefield driven by Gaussian (1,0) mode laser pulse and laser-plasma electron acceleration

    SciTech Connect

    Che, H. O.; Kong, Q.; Mao, Q. Q.; Wang, P. X.; Ho, Y. K. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Kawata, S. [Department of Electrical and Electronic Engineering, Utsunomiya University, Yohtoh 7-1-2, Utsunomiya 321-8585 (Japan)

    2009-08-31

    An ultraintense Gaussian (1,0) mode pulsed laser applied to laser-plasma electron acceleration is investigated based on 2.5-dimensional particle-in-cell simulation (PIC). It has been found that Gaussian (1,0) mode laser pulse may blow out plasma electrons and form two symmetrical electron cavities with an electron wall between them. This electron wall separates two twisting bunches of transverse injected electrons and lets each of them be accelerated in one cavity, respectively. At the front of the wall, a bunch of reflux electrons with a magnetic field contributes to the electron self-bunching effect. This mechanism may generate two symmetrical, high-density, and monoenergetic electron beams with small transverse emittances.

  17. Observation of the saturation of Langmuir waves driven by ponderomotive force in a large scale plasma

    SciTech Connect

    Kirkwood, R. K.; Moody, J. D.; MacGowan, B. J.; Glenzer, S. H.; Kruer, W. L.; Estabrook, K. G.; Wharton, K. B.; Williams, E. A.; Berger, R. L. [University of California, Lawrence Livermore National Lab., CA (United States)

    1997-06-22

    We report the observation of amplification of a probe laser beam (I {le} 1 {times} 10{sup 14} W/cm{sup 2}) in a large scale ({approximately} 1 mm) plasma by interaction with a pumping laser beam (I = 2 {times} 10{sup 15} W/cm{sup 2}) and a stimulated Langmuir wave. When the plasma density is adjusted to allow the Langmuir wave dispersion to match the difference frequency and wave number of the two beams, amplification factors as high as {times} 2.5 result. Interpretation of this amplification as scattering of pump beam energy by the Langmuir wave that is produced by the ponderomotive force of the two beams, allows the dependence of Langmuir wave amplitude on ponderomotive force to be measured. It is found that the Langmuir wave amplitude saturates at a level that depends on ion wave damping, and is generally consistent with secondary ion wave instabilities limiting its growth. 20 refs., 4 figs.

  18. 'PK-4' - Laser-driven shear flow in a DC discharge complex plasma

    SciTech Connect

    Kretschmer, M.; Hoefner, H.; Thoma, M.; Fink, M.; Ratynskaia, S.; Morfill, G.; Tarantik, K. [Max-Planck-Institut fuer extraterrestrische Physik (MPE), 85740 Garching (Germany); Fortov, V.; Petrov, O.; Usachev, A.; Zobnin, A.; Gerasimov, Yu. [Institute for High Energy Densities (IHED), RAS, Izhorskaya, 13/19, 125412, Moscow (Russian Federation)

    2005-10-31

    Flows, shear flows, laminar and turbulent flows on the microscopic scales are one of the fundamental issues in fluid dynamics. Due to their special properties, complex plasmas provide an excellent opportunity to study these flows, even on the scale of individual particles. To this end, experiments were conducted in the 'Plasmakristall 4' (PK-4) experimental device that uses the positive column of a high voltage DC discharge to produce complex (dusty) plasmas. The linear geometry of PK-4 provides the opportunity to study all these kinds of flow phenomena as well as waves and collisions. Since gravity distorts most of the effects to be studied with PK-4, the facility is planned to be operated onboard the International Space Station ISS from 2008. In order to generate a high-velocity shear flow PK-4 is now upgraded with a 20W manipulation laser system.

  19. Gas-Puff Z-Pinch Plasmas Driven by Inductive Energy Storage Pulsed Power Generator

    Microsoft Academic Search

    Koichi Murayama; Toshinori Shinkai; Sunao Katsuki; Hidenori Akiyama

    1998-01-01

    An inductive energy storage pulsed power generator is used as a power source of gas-puff z-pinch plasmas to investigate the effect of the steepened current rise on the intensity of soft X-rays and the spatial reproducibility of the hot spots. Furthermore, two kinds of electrodes, which are solid and mesh type, are used to investigate the influence of the incident

  20. Laser fusion with nonlinear force driven plasma blocks: Thresholds and dielectric effects

    Microsoft Academic Search

    H. Hora

    2009-01-01

    Anomalous interaction of picosecond laser pulses of terawatt to petawatt power is due to suppression of relativistic self- focusing if prepulses are cut-off by a contrast ratio higher than 108, resulting in quasi-neutral directed plasma blocks with deuterium tritium ion current densities above 1011 A\\/cm2. This is still not high enough for ignition of solid-state density deuterium tritium because the

  1. Fusion and Plasma Physics are at the Core of Nature's Most Powerful Self-Driven Systems

    E-print Network

    @ 10 keV #12;Energy/Fuel Recovery Qp Fuel Fuel (Li, D) RPE Waste PE Balance of Plant Plasma Confinement/4 = P is the alpha heating power, CBT 1/2 ne 2 Vp is the radiation loss, Wp = 3nkTVp and E = Wp/(Paux-heat - dWp/dt) is the energy confinement time. In Steady-state: nE = 3kT U (Q+5)/4Q - CBT 1/2 where Q

  2. Beam driven upper-hybrid-wave instability in quantized semiconductor plasmas

    NASA Astrophysics Data System (ADS)

    Jamil, M.; Rasheed, A.; Rozina, Ch.; Moslem, W. M.; Salimullah, M.

    2014-02-01

    The excitation of Upper-Hybrid waves (UHWs) induced by electron beam in semiconductor plasma is examined using quantum hydrodynamic model. Various quantum effects are taken into account including recoil effect, Fermi degenerate pressure, and exchange-correlation potential. The bandwidth of the UHWs spectrum shows that the system supports purely growing unstable mode. The latter has been studied for diversified parameters of nano-sized GaAs semiconductor.

  3. Beam driven upper-hybrid-wave instability in quantized semiconductor plasmas

    SciTech Connect

    Jamil, M. [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan)] [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Rasheed, A. [Department of Physics, Government College University, Faisalabad 38000 (Pakistan)] [Department of Physics, Government College University, Faisalabad 38000 (Pakistan); Rozina, Ch. [Department of Physics, Government M.A.O. College, Lahore 54000 (Pakistan)] [Department of Physics, Government M.A.O. College, Lahore 54000 (Pakistan); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said 42521 (Egypt) [Department of Physics, Faculty of Science, Port Said University, Port Said 42521 (Egypt); Centre for Theoretical Physics, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt); Salimullah, M. [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh)] [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh)

    2014-02-15

    The excitation of Upper-Hybrid waves (UHWs) induced by electron beam in semiconductor plasma is examined using quantum hydrodynamic model. Various quantum effects are taken into account including recoil effect, Fermi degenerate pressure, and exchange-correlation potential. The bandwidth of the UHWs spectrum shows that the system supports purely growing unstable mode. The latter has been studied for diversified parameters of nano-sized GaAs semiconductor.

  4. The effects of nonthermal electron distributions on ion-temperature-gradient driven drift-wave instabilities in electron-ion plasma

    SciTech Connect

    Batool, Nazia [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); National Center of Physics (NCP), Quaid-i-Azam University campus, Islamabad (Pakistan); Masood, W. [National Center of Physics (NCP), Quaid-i-Azam University campus, Islamabad (Pakistan); Theoretical Plasma Physics Division, PINSTECH P. O. Nilore, Islamabad (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2012-08-15

    The effects of nonthermal electron distributions on electrostatic ion-temperature-gradient (ITG) driven drift-wave instabilities in the presence of equilibrium density, temperature, and magnetic field gradients are investigated here. By using Braginskii's transport equations for ions and Cairns as well as Kappa distribution for electrons, the coupled mode equations are derived. The modified ITG driven modes are derived, and it is found both analytically as well as numerically that the nonthermal distribution of electrons significantly modify the real frequencies as well as the growth rate of the ITG driven drift wave instability. The growth rate of ion-temperature-gradient driven instability is found to be maximum for Cairns, intermediate for Kappa, and minimum for the Maxwellian distributed electron case. The results of present investigation might be helpful to understand several wave phenomena in space and laboratory plasmas in the presence of nonthermal electrons.

  5. Ion beam driven ion-acoustic waves in a plasma cylinder with negatively charged dust grains

    SciTech Connect

    Sharma, Suresh C.; Walia, Ritu [Department of Physics, Maharaja Agrasen Institute of Technology, PSP Area Plot No.-1, Sector-22, Rohini, Delhi 110 086 (India); Sharma, Kavita [Department of Physics, Bhagwan Parshuram Institute of Technology, Sector-17, Rohini, New Delhi 110 089 (India)

    2012-07-15

    An ion beam propagating through a magnetized potassium plasma cylinder having negatively charged dust grains drives electrostatic ion-acoustic waves to instability via Cerenkov interaction. The phase velocity of sound wave increases with the relative density of negatively charged dust grains. The unstable wave frequencies and the growth rate increase, with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales as one-third power of the beam density. The real part of frequency of the unstable mode increases with the beam energy and scales as almost the one-half power of the beam energy.

  6. Comparison of Velocity Shear with Turbulence Reduction Driven by Biasing in a Simple Cylindrical Slab Plasma

    NASA Astrophysics Data System (ADS)

    W. Gentle, K.; Liao, K.; K., Lee; L. Rowan, W.

    2010-08-01

    In an experimental realization of the sheared cylindrical slab, the level of plasma turbulence is strongly reduced by application of a sufficient bias potential difference in the radial direction. Density fluctuation levels ?nrms/n decrease by more than a factor of five. The ion flow velocity profile is measured spectroscopically from the Doppler shift of an argon ion line. Comparison of the shearing rates with the turbulent amplitudes as a function of bias show no relation between the shearing rate and turbulence reduction, contrary to expectations.

  7. Ion-beam driven lower hybrid waves in a magnetized dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi 110 068 (India)] [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi 110 068 (India); Sharma, Suresh C. [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India)] [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India); Gupta, Ruby [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi 110 036 (India)] [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi 110 036 (India)

    2013-06-15

    An ion beam drives lower hybrid waves to instability in a magnetized dusty plasma via Cerenkov interaction. A dispersion relation and the growth rate of the lower hybrid waves have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave instability increase with relative density of negatively charged dust grains. The lower hybrid modes with phase velocity comparable to the beam velocity possess a large growth rate. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density.

  8. Laser-driven plasma jets propagating in an ambient gas studied with optical and proton diagnostics

    SciTech Connect

    Gregory, C. D.; Loupias, B.; Koenig, M. [Laboratoire pour l'Utilisation des Lasers Intenses, UMR7605, CNRS-CEA-Universite, Paris VI-Ecole Polytechnique, 91128 Palaiseau Cedex (France); Waugh, J.; Woolsey, N. C. [Department of Physics, University of York, Heslington YO10 5DD (United Kingdom); Dono, S.; Kuramitsu, Y.; Sakawa, Y. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Bouquet, S.; Falize, E. [CEA-DAM-DIF, F-91297 Arpajon (France); Michaut, C. [LUTH, Observatoire de Paris, CNRS, Universite Paris Diderot, Place Jules Janssen, 92190 Meudon (France); Nazarov, W. [School of Chemistry, University of St Andrews, Purdie Blg, St Andrews KY16 9ST (United Kingdom); Pikuz, S. A. Jr. [Joint Institute for High Temperatures of RAS, Izhorskaya 13/19, Moscow 125412 (Russian Federation)

    2010-05-15

    The results of an experiment to propagate laser-generated plasma jets into an ambient medium are presented. The jets are generated via laser irradiation of a foam-filled cone target, the results and characterization of which have been reported previously [Loupias et al., Phys. Rev. Lett. 99, 265001 (2007)] for propagation in vacuum. The introduction of an ambient medium of argon at varying density is seen to result in the formation of a shock wave, and the shock front displays perturbations that appear to grow with time. The system is diagnosed with the aid of proton radiography, imaging the perturbed structure in the dense parts of the shock with high resolution.

  9. Fusion and Plasma Physics are at the Core of Nature's Most Powerful Self-Driven Systems

    E-print Network

    : ~ T2 @ 10 keV #12;Energy/Fuel Recovery Qp Fuel Fuel (Li, D) RPE Waste PE Balance of Plant Plasma/4 = P is the alpha heating power, CBT 1/2 ne 2 Vp is the radiation loss, Wp = 3nkTVp and E = Wp/(Paux-heat - dWp/dt) is the energy confinement time. In Steady-state: nE = 3kT U (Q+5)/4Q - CBT 1/2 where Q

  10. Electronic excitation as a mode of heat dissipation in laser-driven cluster plasmas

    SciTech Connect

    Rajeev, R.; Rishad, K. P. M.; Madhu Trivikram, T.; Krishnamurthy, M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-5 (India)] [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-5 (India)

    2013-12-15

    Electrons streaming out of laser plasma are known for non-local heat transport and energy deposition by the ionization wave. At 100 eV electron temperature, since the electronic excitation cross section is comparable to that of ionization for Ar and CO{sub 2}, a non-local excitation wave akin to the ionization wave is envisaged where energy deposition in excitations forms a excited cluster sheath beyond the laser focus. Here, we show that nano-cluster systems have the right parameters to form such an exciton sheath and experimentally demonstrate this via charge transfer reactions.

  11. Spectroscopic observation of ablation plasma generated with a laser-driven extreme ultraviolet light source

    NASA Astrophysics Data System (ADS)

    Masuda, Masaya; Tanaka, Nozomi; Hane, Kazuyoshi; Sunahara, Atsushi; Fujioka, Shinsuke; Nishimura, Hiroaki

    2015-02-01

    An extreme ultraviolet (EUV) light source (? = 9-25 nm, 10 Hz) was developed to study EUV ablation physics and applications. The EUV source device including an elliptical total reflection mirror was optimized to provide EUV irradiance as high as 4.2 × 109 W/cm2 on ablation samples. Time-resolved spectroscopic observation of ablation plasma from a Si plate was conducted to derive electron temperature and density, and compared with those for laser-produced ablation at the same irradiance. Difference in ablation mechanism between two sources is discussed.

  12. MEMS fluidic actuator

    DOEpatents

    Kholwadwala, Deepesh K. (Albuquerque, NM); Johnston, Gabriel A. (Trophy Club, TX); Rohrer, Brandon R. (Albuquerque, NM); Galambos, Paul C. (Albuquerque, NM); Okandan, Murat (Albuquerque, NM)

    2007-07-24

    The present invention comprises a novel, lightweight, massively parallel device comprising microelectromechanical (MEMS) fluidic actuators, to reconfigure the profile, of a surface. Each microfluidic actuator comprises an independent bladder that can act as both a sensor and an actuator. A MEMS sensor, and a MEMS valve within each microfluidic actuator, operate cooperatively to monitor the fluid within each bladder, and regulate the flow of the fluid entering and exiting each bladder. When adjacently spaced in a array, microfluidic actuators can create arbitrary surface profiles in response to a change in the operating environment of the surface. In an embodiment of the invention, the profile of an airfoil is controlled by independent extension and contraction of a plurality of actuators, that operate to displace a compliant cover.

  13. Modeling piezoelectric actuators

    Microsoft Academic Search

    H. J. M. T. S. Adriaens; W. L. De Koning; R. Banning

    2000-01-01

    The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 ?m. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential

  14. Remote switch actuator

    DOEpatents

    Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

    2013-01-29

    The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

  15. Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma

    NASA Astrophysics Data System (ADS)

    Sengupta, M.; Ganesh, R.

    2014-02-01

    The dynamics of cylindrically trapped electron plasma has been investigated using a newly developed 2D Electrostatic PIC code that uses unapproximated, mass-included equations of motion for simulation. Exhaustive simulations, covering the entire range of Brillouin ratio, were performed for uniformly filled circular profiles in rigid rotor equilibrium. The same profiles were then loaded away from equilibrium with an initial value of rigid rotation frequency different from that required for radial force balance. Both these sets of simulations were performed for an initial zero-temperature or cold load of the plasma with no spread in either angular velocity or radial velocity. The evolution of the off-equilibrium initial conditions to a steady state involve radial breathing of the profile that scales in amplitude and algebraic growth with Brillouin fraction. For higher Brillouin fractions, the growth of the breathing mode is followed by complex dynamics of spontaneous hollow density structures, excitation of poloidal modes, leading to a monotonically falling density profile.

  16. Ion anisotropy driven waves in the earth's magnetosheath and plasma depletion layer

    SciTech Connect

    Denton, R.E.; Hudson, M.K. (Dartmouth Coll., Hanover, NH (United States). Dept. of Physics and Astronomy); Anderson, B.J. (Johns Hopkins Univ., Laurel, MD (United States). Applied Physics Lab.); Fuselier, S.A. (Lockheed Palo Alto Research Labs., CA (United States)); Gary, S.P. (Los Alamos National Lab., NM (United States))

    1993-01-01

    Recent studies of low frequency waves ([omega][sub r] [le] [Omega][sub p], where [Omega][sub p] is the proton gyrofrequency) observed by AMPTE/CCE in the plasma depletion layer and magnetosheath proper arereviewed. These waves are shown to be well identified with ion cyclotron and mirror mode waves. By statistically analyzing the transitions between the magnetopause and time intervals with ion cyclotron and mirror mode waves, it is established that the regions in which ion cyclotron waves occur are between the magnetopause and the regions where the mirror mode is observed. This result is shown to follow from the fact that the wave spectral properties are ordered with respect to the proton parallel beta, [beta][sub [parallel]p]. The later result is predicted by linear Vlasov theory using a simple model for the magnetosheath and plasma depletion layer. Thus, the observed spectral type can be associated with relative distance from the magnetopause. The anisotropy-beta relation, A[sub p] [triple bond] (T[perpendicular]/T[sub [parallel

  17. Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma

    SciTech Connect

    Sengupta, M.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)] [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

    2014-02-15

    The dynamics of cylindrically trapped electron plasma has been investigated using a newly developed 2D Electrostatic PIC code that uses unapproximated, mass-included equations of motion for simulation. Exhaustive simulations, covering the entire range of Brillouin ratio, were performed for uniformly filled circular profiles in rigid rotor equilibrium. The same profiles were then loaded away from equilibrium with an initial value of rigid rotation frequency different from that required for radial force balance. Both these sets of simulations were performed for an initial zero-temperature or cold load of the plasma with no spread in either angular velocity or radial velocity. The evolution of the off-equilibrium initial conditions to a steady state involve radial breathing of the profile that scales in amplitude and algebraic growth with Brillouin fraction. For higher Brillouin fractions, the growth of the breathing mode is followed by complex dynamics of spontaneous hollow density structures, excitation of poloidal modes, leading to a monotonically falling density profile.

  18. Ion beam driven resonant ion-cyclotron instability in a magnetized dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi 110 068 (India)] [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi 110 068 (India); Sharma, Suresh C. [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India)] [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi 110 042 (India); Gupta, Ruby [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi 110 036 (India)] [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi 110 036 (India)

    2014-03-15

    Electrostatic ion cyclotron waves are excited by axial ion beam in a dusty plasma via Cerenkov and slow cyclotron interaction. The dispersion relation of the instability is derived in the presence of positively/negatively charged dust grains. The minimum beam velocity needed for the excitation is estimated for different values of relative density of negatively charged dust grains. It is shown that the minimum beam velocity needed for excitation increases as the charge density carried by dust increases. Temperature of electrons and ions, charge and mass of dust grains, external static magnetic field and finite boundary of dusty plasma significantly modify the dispersion properties of these waves and play a crucial role in the growth of resonant ion cyclotron instability. The ion cyclotron modes with phase velocity comparable to the beam velocity possess a large growth rate. The maximum value of growth rate increases with the beam density and scales as the one-third power of the beam density in Cerenkov interaction and is proportional to the square root of beam density in slow cyclotron interaction.

  19. Implementation and analysis of an innovative digital charge amplifier for hysteresis reduction in piezoelectric stack actuators

    SciTech Connect

    Bazghaleh, Mohsen, E-mail: mohsen.bazghaleh@adelaide.edu.au; Grainger, Steven; Cazzolato, Ben; Lu, Tien-Fu [School of Mechanical Engineering, The University of Adelaide, North Terrace, South Australia 5005 (Australia)] [School of Mechanical Engineering, The University of Adelaide, North Terrace, South Australia 5005 (Australia); Oskouei, Reza [School of Computer Science, Engineering and Mathematics, Flinders University, Bedford Park, South Australia 5042 (Australia)] [School of Computer Science, Engineering and Mathematics, Flinders University, Bedford Park, South Australia 5042 (Australia)

    2014-04-15

    Smart actuators are the key components in a variety of nanopositioning applications, such as scanning probe microscopes and atomic force microscopes. Piezoelectric actuators are the most common smart actuators due to their high resolution, low power consumption, and wide operating frequency but they suffer hysteresis which affects linearity. In this paper, an innovative digital charge amplifier is presented to reduce hysteresis in piezoelectric stack actuators. Compared to traditional analog charge drives, experimental results show that the piezoelectric stack actuator driven by the digital charge amplifier has less hysteresis. It is also shown that the voltage drop of the digital charge amplifier is significantly less than the voltage drop of conventional analog charge amplifiers.

  20. A Method for Evaluating the Electro-Mechanical Characteristics of Piezoelectric Actuators during Motion

    PubMed Central

    Jin, Tao; Takita, Akihiro; Djamal, Mitra; Hou, Wenmei; Jia, Hongzhi; Fujii, Yusaku

    2012-01-01

    The electro-mechanical characteristics of piezoelectric actuators which have being driven are evaluated in this paper. The force generated by actuators is measured as an inertial force of a corner cub prism which is attached to the actuators. The Doppler frequency shift of a laser beam, due to the motion of actuator, is accurately measured by a heterodyne interferometer. Subsequently, the mechanical quantities, such as velocity, acceleration, force, power and displacement, are calculated from the Doppler frequency shift. With the measurement results of current and voltage of the actuator, the relationships between electrical and mechanical characteristics are evaluated.

  1. Hydrostatic actuation in MEMS

    NASA Astrophysics Data System (ADS)

    Mutzenich, Simon; Vinay, Thurai; Rosengarten, Gary

    2002-11-01

    Hydrostatic actuation is a novel method of actuation in Micro Electro Mechanical Systems (MEMS) and provides advantages over other actuation techniques in current use. Hydrostatic actuation utilises a contained pressurised medium to straighten a bent hollow beam, similar to the Bourdon tube used to measure pressure in the macro world. Research has commenced at RMIT University to design and fabricate a microgripper prototype to validate this work. To simplify the design of this microgripper a virtual prototype has been initiated. This paper looks at the work carried out and verification of this virtual prototype using mathematical and finite element modelling. Further work to be undertaken will also be discussed.

  2. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2004-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

  3. Cost-effective actuator tester

    NASA Technical Reports Server (NTRS)

    Kopp, G. F.; Wyllie, C. E.

    1977-01-01

    Group of preprogrammed plug-in cards and control module converts breadboard control electronics of actuator assembly to actuator tester. System utilizes electronic control, and hydraulic systems of breadboard actuator into which it is installed.

  4. Spectro-polarimetric properties of small-scale plasma eruptions driven by magnetic vortex tubes

    NASA Astrophysics Data System (ADS)

    Kitiashvili, Irina N.

    2014-12-01

    The highly turbulent nature of convection on the Sun causes strong multi-scale interaction of subsurface layers with the photosphere and chromosphere. According to realistic 3D radiative magnetohydrodynamic numerical simulations, ubiquitous small-scale vortex tubes are generated by turbulent flows below the visible surface and concentrated in the intergranular lanes. The vortex tubes can capture and amplify magnetic field, penetrate into chromospheric layers and initiate quasi-periodic flow eruptions that generate Alfvénic waves, and transport mass and energy into the solar atmosphere. The simulations revealed high-speed flow patterns, and complicated thermodynamic and magnetic structures in the erupting vortex tubes. The spontaneous eruptions are initiated and driven by strong pressure gradients in the near-surface layers, and accelerated by the Lorentz force in the low chromosphere. In this paper, the simulation data are used to further investigate the dynamics of the eruptions, their spectro-polarimetric characteristics for the Fe I 6301.5 and 6302.5 Å spectral lines, and demonstrate expected signatures of the eruptions in the Hinode Spectro-Polarimeter (SP) data. We found that the complex dynamical structure of vortex tubes (downflows in the vortex core and upflows on periphery) can be captured by the Stokes I profiles. During an eruption, the ratio of down and upflows can suddenly change, and this effect can be observed in the Stokes V profile. Also, during the eruption the linear polarization signal increases, and this also can be detected with Hinode SP.

  5. Stable long range proton acceleration driven by intense laser pulse with underdense plasmas

    SciTech Connect

    Gu, Y. J. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Institute of Physics of the ASCR, ELI-Beamlines project, Na Slovance 2, Prague 18221 (Czech Republic); Zhu, Z.; Li, X. F.; Yu, Q.; Huang, S.; Zhang, F.; Kong, Q., E-mail: qkong@fudan.edu.cn [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Kawata, S. [Department of Advanced Interdisciplinary Sciences, Utsunomiya University, Yohtoh 7-1-2, Utsunomiya 321-8585 (Japan)

    2014-06-15

    Proton acceleration is investigated by 2.5-dimensional particle-in-cell simulations in an interaction of an ultra intense laser with a near-critical-density plasma. It was found that multi acceleration mechanisms contribute together to a 1.67?GeV collimated proton beam generation. The W-BOA (breakout afterburner based on electrons accelerated by a wakefield) acceleration mechanism plays an important role for the proton energy enhancement in the area far from the target. The stable and continuous acceleration maintains for a long distance and period at least several pico-seconds. Furthermore, the energy scalings are also discussed about the target density and the laser intensity.

  6. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

    NASA Astrophysics Data System (ADS)

    Ince-Cushman, A.; Rice, J. E.; Reinke, M.; Greenwald, M.; Wallace, G.; Parker, R.; Fiore, C.; Hughes, J. W.; Bonoli, P.; Shiraiwa, S.; Hubbard, A.; Wolfe, S.; Hutchinson, I. H.; Marmar, E.; Bitter, M.; Wilson, J.; Hill, K.

    2009-01-01

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60km/s in the central region of the plasma (r/ã<0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (˜100ms) but longer than the energy and momentum confinement times (˜20ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch.

  7. An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator

    SciTech Connect

    Anania, M. P. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); INFN, Laboratori Nazionali di Frascati, I-00044 Frascati (Italy); Brunetti, E.; Wiggins, S. M.; Grant, D. W.; Welsh, G. H.; Issac, R. C.; Cipiccia, S.; Shanks, R. P.; Manahan, G. G.; Aniculaesei, C.; Jaroszynski, D. A., E-mail: d.a.jaroszynski@strath.ac.uk [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Geer, S. B. van der; Loos, M. J. de [Pulsar Physics, Burghstraat 47, 5614 BC Eindhoven (Netherlands); Poole, M. W.; Shepherd, B. J. A.; Clarke, J. A. [ASTeC, STFC, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Gillespie, W. A. [SUPA, School of Engineering, Physics and Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom); MacLeod, A. M. [School of Computing and Creative Technologies, University of Abertay Dundee, Dundee DD1 1HG (United Kingdom)

    2014-06-30

    Narrow band undulator radiation tuneable over the wavelength range of 150–260?nm has been produced by short electron bunches from a 2?mm long laser plasma wakefield accelerator based on a 20?TW femtosecond laser system. The number of photons measured is up to 9?×?10{sup 6} per shot for a 100 period undulator, with a mean peak brilliance of 1?×?10{sup 18} photons/s/mrad{sup 2}/mm{sup 2}/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120–130?MeV with the radiation pulse duration in the range of 50–100 fs.

  8. Stable long range proton acceleration driven by intense laser pulse with underdense plasmas

    NASA Astrophysics Data System (ADS)

    Gu, Y. J.; Zhu, Z.; Li, X. F.; Yu, Q.; Huang, S.; Zhang, F.; Kong, Q.; Kawata, S.

    2014-06-01

    Proton acceleration is investigated by 2.5-dimensional particle-in-cell simulations in an interaction of an ultra intense laser with a near-critical-density plasma. It was found that multi acceleration mechanisms contribute together to a 1.67 GeV collimated proton beam generation. The W-BOA (breakout afterburner based on electrons accelerated by a wakefield) acceleration mechanism plays an important role for the proton energy enhancement in the area far from the target. The stable and continuous acceleration maintains for a long distance and period at least several pico-seconds. Furthermore, the energy scalings are also discussed about the target density and the laser intensity.

  9. Intrinsic rotation driven by the electrostatic turbulence in up-down asymmetric toroidal plasmas

    SciTech Connect

    Camenen, Y.; Peeters, A. G.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P. [Department of Physics, Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Angioni, C. [EURATOM-IPP Association, Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Strintzi, D. [EURATOM Association, National Technical University of Athens, GR-15773 Athens (Greece)

    2009-06-15

    The transport of parallel momentum by small scale fluctuations is intrinsically linked to symmetry breaking in the direction of the magnetic field. In tokamaks, an up-down asymmetry in the equilibrium proves to be an efficient parallel symmetry breaking mechanism leading to the generation of a net radial flux of parallel momentum by the electrostatic turbulence [Y. Camenen et al., Phys. Rev. Lett. 102, 125001 (2009)]. This flux is neither proportional to the toroidal rotation nor to its gradient and arises from an incomplete cancellation of the local contributions to the parallel momentum flux under the flux surface average. The flux of parallel momentum then depends on the asymmetry of the curvature drift and on the extension of the fluctuations around the low field side midplane. In this paper, the mechanisms underlying the generation of the flux of parallel momentum are highlighted and the main dependences on plasma parameters investigated using linear gyrokinetic simulations.

  10. Strongly-Driven Laser Plasmas with Self-Consistent Electron Distributions

    NASA Astrophysics Data System (ADS)

    Kruer, William L.; Afeyan, Bedros B.; Wilks, Scott C.; Chou, Albert E.

    1996-11-01

    In high temperature hohlraums and many other applications,footnote For example, see talks by T. Orzechowski and R. Kirkwood (Anomalous Absorption Conference 1996). the laser heated electrons have a zeroth-order distribution function which is quite different footnote A.B. Langdon, Phys. Rev. Lett 44, 575 (1980); R. Jones and K. Lee, Phys. Fluids 25, 2307 (1992). footnote For general distribution, see J.P. Matte et al., Plasma Phys. Conference Fusion 30, 1665 (1988). from Maxwellian. The numerous consequences include changes in the Landau damping and instability thresholds, reductions in the inverse bremsstrahlung coefficient, as well as changes in the heat transport, density profiles and atomic physics. In addition, unexpected absorption processes can be introduced. These absorption mechanisms are discussed and illustrated in fluid and PIC simulations.

  11. Carbon nanotube array actuators

    NASA Astrophysics Data System (ADS)

    Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

    2013-09-01

    Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 ?m with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 ?m and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

  12. Piezoelectric ceramic assembly tubes for torsional actuators

    NASA Astrophysics Data System (ADS)

    Kim, Chulho; Glazounov, Alexandre E.; Flippen, Luther D.; Pattnaik, Amitav; Zhang, Qi Ming; Lewis, David, III

    1999-07-01

    The efforts described here are intended to provide a basis for the utilization of novel piezoelectric actuators in smart materials and structures. The actuator design developed in this study is a segmented, piezoelectric tube, with the individual segments driven in a d15 shear mode. The PZT-5A tubes were cut longitudinally in to an even number of equal slender segments. These slender segments were poled individually along their length using a continuous poling technique developed at NRL. The polarization of the poled segments alternates in direction between adjacent segments. The segments were reassembled with a conductive epoxy so that it serves as both joint and electrode. The assembled actuator tubes were evaluated by applying electric field normal to the polarization direction of the segments, demonstrating proof of concept. These solid state prototype devices were driven to precise angular displacement and torque output. Reliability test, including both fatigue and mechanical loading of the device, were conducted. In conjunction with this effort, numerical computation analyses were performed with respect to structural integrity versus segment joint thickness, and the relative effect of cylindrical versus polygonal configurations. These studies facilitated the successful production of prototypes. Projected actuator outputs based on electromechanical test results are also discussed in terms of requirements for noise and vibration control of helicopter rotor blades.

  13. Stirling-engine heat-actuated heat pump

    SciTech Connect

    Ackermann, R.A.; English, J.D.; Moynihan, T.M.

    1983-01-01

    A Stirling-engine-driven heat-actuated heat pump (HAHP) system developed at Mechanical Technology Incorporated (MTI) consists of a free-piston Stirling engine (FPSE) driver, a diaphragm-actuated hydraulic coupling, and a Rankine-cycle, resonant-linear refrigerant compressor. This system has been under development at MTI for the past two years; within the last six months, the unit has been placed on test. The system and test results achieved to date are described.

  14. Stirling-engine heat-actuated heat pump

    Microsoft Academic Search

    R. A. Ackermann; J. D. English; T. M. Moynihan

    1983-01-01

    A Stirling-engine-driven heat-actuated heat pump (HAHP) system developed at Mechanical Technology Incorporated (MTI) consists of a free-piston Stirling engine (FPSE) driver, a diaphragm-actuated hydraulic coupling, and a Rankine-cycle, resonant-linear refrigerant compressor. This system has been under development at MTI for the past two years; within the last six months, the unit has been placed on test. The system and test

  15. Control of a hydraulically-actuated quadruped robot leg

    Microsoft Academic Search

    Michele Focchi; Emanuele Guglielmino; Claudio Semini; Thiago Boaventura Cunha; Yousheng Yang; Darwin G. Caldwell

    2010-01-01

    This paper is focussed on the modelling and control of a hydraulically-driven biologically-inspired robotic leg. The study is part of a larger project aiming at the development of an autonomous quadruped robot (hyQ) for outdoor operations. The leg has two hydraulically-actuated degrees of freedom (DOF), the hip and knee joints. The actuation system is composed of proportional valves and asymmetric

  16. Vehicle Exhaust Gas Clearance by Low Temperature Plasma-Driven Nano-Titanium Dioxide Film Prepared by Radiofrequency Magnetron Sputtering

    PubMed Central

    Yu, Shuang; Liang, Yongdong; Sun, Shujun; Zhang, Kai; Zhang, Jue; Fang, Jing

    2013-01-01

    A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO2) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O3 destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas. PMID:23560062

  17. Vehicle exhaust gas clearance by low temperature plasma-driven nano-titanium dioxide film prepared by radiofrequency magnetron sputtering.

    PubMed

    Yu, Shuang; Liang, Yongdong; Sun, Shujun; Zhang, Kai; Zhang, Jue; Fang, Jing

    2013-01-01

    A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO2) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O3 destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas. PMID:23560062

  18. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    SciTech Connect

    Niemi, K.; O'Connell, D.; Gans, T. [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Oliveira, N. de; Joyeux, D.; Nahon, L. [Synchrotron Soleil, l'Orme des Merisiers, St. Aubin BP 48, 91192 Gif sur Yvette Cedex (France); Booth, J. P. [Laboratoire de Physique des Plasmas-CNRS, Ecole Polytechnique, 91128 Palaiseau (France)

    2013-07-15

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N{sub 2}/O{sub 2} (4:1) admixtures. A maximum in the O-atom concentration of (9.1 {+-} 0.7) Multiplication-Sign 10{sup 20} m{sup -3} was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 {+-} 0.4) Multiplication-Sign 10{sup 19} m{sup -3} at 0.1 vol. %.

  19. Applications of compact laser-driven EUV/XUV plasma sources

    NASA Astrophysics Data System (ADS)

    Barkusky, Frank; Bayer, Armin; Döring, Stefan; Flöter, Bernhard; Großmann, Peter; Peth, Christian; Reese, Michael; Mann, Klaus

    2009-05-01

    In recent years, technological developments in the area of extreme ultraviolet lithography (EUVL) have experienced great improvements. So far, intense light sources based on discharge or laser plasmas, beam steering and imaging optics as well as sensitive detectors are available. Currently, applications of EUV radiation apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis come more and more into focus. In this contribution we present an overview on the EUV/XUV activities of the Laser-Laboratorium Göttingen based on table-top laser-produced plasma (LPP) sources. As target materials gaseous or liquid jets of noble gases or solid Gold are employed. Depending on the applications, the very clean but low intense gaseous targets are mainly used for metrology, whereas the targets for high brilliances (liquid, solid) are used for microscopy and direct structuring. For the determination of interaction mechanisms between EUV radiation and matter, currently the solid Gold target is used. In order to obtain a small focal spot resulting in high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to this source. By demagnified (10x) imaging of the Au plasma an EUV spot of 3 ?m diameter with a maximum energy density of ~1.3 J/cm2 is generated (pulse duration 8.8 ns). First applications of this integrated source and optics system reveal its potential for high-resolution modification and direct structuring of solid surfaces. For chemical analysis of various samples a NEXAFS setup was developed. It consists of a LPP, using gaseous Krypton as a broadband emitter in the water-window range, as well as a flat field spectrograph. The laboratory system is set to the XUV spectral range around the carbon K-edge (4.4 nm). The table-top setup allows measurements with spectral accuracy comparable to synchrotron experiments. NEXAFS-experiments in transmission and reflection are demonstrated. Beside chemical investigations, also microscopy applications are performed within the XUV spectral range. For this reason a water-window microscope was developed, based on a liquid argon LPP target. The XUV radiation is focused by a Cr/Sc multilayer mirror, leading to spectral narrow band radiation on the sample. For magnifying the sample, a Fresnel zone plate will be used with an outer zone width of 50 nm. Additionally to these applications, an EUV/XUV setup for structural analysis was developed. Using a spectral broad band emitting Xenon gaseous target combined with a grazing incidence optics (Kirkpatrick-Baez arrangement), it offers the possibility to perform angular resolved reflectivity-, diffraction- and scattering experiments as well as NEXAFS analysis in one setup. In completion to these experiments with LPP sources, an EUV/XUV Hartmann-type wavefront sensor has been developed in collaboration with DESY HASYLAB. It consists of a pinhole array, positioned in front of a XUV sensitive CCD camera with quantum converter. With custom-developed software the incident wavefront can be determined. This sensor is currently used at the free electron laser FLASH in Hamburg for beam characterization.

  20. Observation of Self Generated Flows in Tokamak Plasmas With Lower Hybrid Driven Current

    NASA Astrophysics Data System (ADS)

    Ince-Cushman, Alexander; Rice, John; Reinke, Matthew; Bitter, Manfred; Hill, Kenneth; Greenwald, Martin; Wallace, Gregory; Parker, Ronald; Hughes, Jerry; Bonoli, Paul; Fiore, Catherine; Shiraiwa, Shunichi; Hubbard, Amanda; Wolfe, Stephen; Hutchinson, Ian; Wilson, Randy; Marmar, Earl

    2008-11-01

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a counter-current change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a ˜< 0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (˜100ms) but longer than the energy and momentum confinement times (˜20ms). Comparison of co-and counter-current injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate strongly sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch. Supported by USDoE award DE-FC02-99ER54512.

  1. STUDIES OF A FREE ELECTRON LASER DRIVEN BY A LASER-PLASMA ACCELERATOR

    SciTech Connect

    Montgomery, A.; Schroeder, C.; Fawley, W.

    2008-01-01

    A free electron laser (FEL) uses an undulator, a set of alternating magnets producing a periodic magnetic fi eld, to stimulate emission of coherent radiation from a relativistic electron beam. The Lasers, Optical Accelerator Systems Integrated Studies (LOASIS) group at Lawrence Berkeley National Laboratory (LBNL) will use an innovative laserplasma wakefi eld accelerator to produce an electron beam to drive a proposed FEL. In order to optimize the FEL performance, the dependence on electron beam and undulator parameters must be understood. Numerical modeling of the FEL using the simulation code GINGER predicts the experimental results for given input parameters. Among the parameters studied were electron beam energy spread, emittance, and mismatch with the undulator focusing. Vacuum-chamber wakefi elds were also simulated to study their effect on FEL performance. Energy spread was found to be the most infl uential factor, with output FEL radiation power sharply decreasing for relative energy spreads greater than 0.33%. Vacuum chamber wakefi elds and beam mismatch had little effect on the simulated LOASIS FEL at the currents considered. This study concludes that continued improvement of the laser-plasma wakefi eld accelerator electron beam will allow the LOASIS FEL to operate in an optimal regime, producing high-quality XUV and x-ray pulses.

  2. The role of Nonlinear Ion Temperature Gradient Driven Drift Modes in a Reversed Field Pinch Plasma

    NASA Astrophysics Data System (ADS)

    Tangri, Varun; Terry, Paul; Waltz, R. E.

    2009-11-01

    The Ion Temperature gradient (ITG) mode has been rarely investigated in Reversed Field pinch (RFP) plasmas, although its role tokamak turbulence has been studied extensively. In this work, we investigate if it is plausible that ITG may play a role in particle and heat confinement in such devices. The linear stability and nonlinear saturation of ITG is investigated in the RFP geometry by modifying the gyrokinetic code GYROfootnotetextJ. Candy and R.E. Waltz, J. Comp. Phys. 186, 545 (2003). in a low beta, collisionless limit with and without non-adiabatic electrons. A simple toroidal equilibrium has been devised that is specified by just two parameters: the pinch parameter and the radial position. The level of transport is shown to be sensitive to temperature and density gradients and the threshold is found. To determine the nature of the instability, we study parametric scaling and also compare results with the well-known CYCLONE base case for tokamak simulations. We also estimate mixing level transport for MST parameters using linear simulations to determine if the instability is relevant to the small-scale turbulence observed in MST.

  3. Einstein's Tea Leaf Analogy to Electrohydrodynamically-Driven Microfluidic Blood Plasma Separation.

    NASA Astrophysics Data System (ADS)

    Friend, James; Yeo, Leslie; Arifin, Dian

    2006-11-01

    The application of a voltage upon a sharp electrode tip, mounted at an inclination angle above the liquid surface of a microfluidic chamber, generates an electrohydrodynamic air thrust that shears the liquid surface and hence induces liquid recirculation consisting of a primary azimuthal rotation and a secondary bulk meridional flow. Colloidal particles suspended within the liquid are then observed to be swept by the recirculation in a helical swirl-like motion and deposited at a stagnation point located centrally at the bottom of the microfluidic chamber. This is due to a delayed centrifugal force and an enhanced inward radial force at the base. We propose that the flow, which is similar to Batchelor flows arising between rotating and stationary disks, is analogous to Einstein's paradoxical observation of tea leaves centrally accumulating at the base of a stirred teacup and show that the phenomenon can be exploited for bioparticle trapping and concentration. In particular, we demonstrate the rapid separation of red blood cells from blood plasma for miniaturized blood diagnostic kits.

  4. Upper-hybrid wave-driven Alfvenic turbulence in magnetized dusty plasmas

    SciTech Connect

    Misra, A. P. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Banerjee, S. [Department of Mathematics, Politecnico di Torino, 10129 Torino (Italy)

    2011-03-15

    The nonlinear dynamics of coupled electrostatic upper-hybrid (UH) and Alfven waves (AWs) is revisited in a magnetized electron-ion plasma with charged dust impurities. A pair of nonlinear equations that describe the interaction of UH wave envelopes (including the relativistic electron mass increase) and the density as well as the compressional magnetic field perturbations associated with the AWs are solved numerically to show that many coherent solitary patterns can be excited and saturated due to modulational instability of unstable UH waves. The evolution of these solitary patterns is also shown to appear in the states of spatiotemporal coherence, temporal as well as spatiotemporal chaos, due to collision and fusion among the patterns in stochastic motion. Furthermore, these spatiotemporal features are demonstrated by the analysis of wavelet power spectra. It is found that a redistribution of wave energy takes place to higher harmonic modes with small wavelengths, which, in turn, results in the onset of Alfvenic turbulence in dusty magnetoplasmas. Such a scenario can occur in the vicinity of Saturn's magnetosphere as many electrostatic solitary structures have been observed there by the Cassini spacecraft.

  5. Upper-hybrid wave-driven Alfvénic turbulence in magnetized dusty plasmas.

    PubMed

    Misra, A P; Banerjee, S

    2011-03-01

    The nonlinear dynamics of coupled electrostatic upper-hybrid (UH) and Alfvén waves (AWs) is revisited in a magnetized electron-ion plasma with charged dust impurities. A pair of nonlinear equations that describe the interaction of UH wave envelopes (including the relativistic electron mass increase) and the density as well as the compressional magnetic field perturbations associated with the AWs are solved numerically to show that many coherent solitary patterns can be excited and saturated due to modulational instability of unstable UH waves. The evolution of these solitary patterns is also shown to appear in the states of spatiotemporal coherence, temporal as well as spatiotemporal chaos, due to collision and fusion among the patterns in stochastic motion. Furthermore, these spatiotemporal features are demonstrated by the analysis of wavelet power spectra. It is found that a redistribution of wave energy takes place to higher harmonic modes with small wavelengths, which, in turn, results in the onset of Alfvénic turbulence in dusty magnetoplasmas. Such a scenario can occur in the vicinity of Saturn's magnetosphere as many electrostatic solitary structures have been observed there by the Cassini spacecraft. PMID:21517632

  6. Electron and ion kinetic effects on non-linearly driven electron plasma and ion acoustic waves

    SciTech Connect

    Berger, R. L.; Chapman, T.; Divol, L.; Still, C. H. [Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States); Brunner, S. [Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CRPP-PPB, CH-1015 Lausanne (Switzerland); Valeo, E. J. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

    2013-03-15

    Fully non-linear kinetic simulations of electron plasma and ion acoustic waves (IAWs) have been carried out with a new multi-species, parallelized Vlasov code. The numerical implementation of the Vlasov model and the methods used to compute the wave frequency are described in detail. For the first time, the nonlinear frequency of IAWs, combining the contributions from electron and ion kinetic effects and from harmonic generation, has been calculated and compared to Vlasov results. Excellent agreement of theory with simulation results is shown at all amplitudes, harmonic generation being an essential component at large amplitudes. For IAWs, the positive frequency shift from trapped electrons is confirmed and is dominant for the effective electron-to-ion temperature ratio, Z T{sub e}/T{sub i} Greater-Than-Or-Equivalent-To 10 with Z as the charge state. Furthermore, numerical results demonstrate unambiguously the dependence [R. L. Dewar, Phys. Fluids 15, 712 (1972)] of the kinetic shifts on details of the distribution of the trapped particles, which depends in turn on the conditions under which the waves were generated. The trapped particle fractions and energy distributions are derived and, upon inclusion of harmonic effects, shown to agree with the simulation results, completing a consistent picture. Fluid models of the wave evolution are considered but prove unable to capture essential details of the kinetic simulations. Detrapping by collisions and sideloss is also discussed.

  7. High Displacement Actuator (HDA)

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Positioned beneath a fiber optic displacement sensor is the new High Displacement Actuator (HDA) developed by scientists at NASA Langley Research Center. The high displacement actuator significantly improves the state-of-the-art piezoelectric technology and provides inordinately large mechanical displacements. The HDA is also applicable to high performance sensor applications such as microphones, non-destructive testing, and vibration sensing. Test results on the high displacement actuators show displacements 50 times greater than device thickness and several orders of magnitude increase over state-of-the-art devices. The actuators can be used from DC to frequencies in excess of a megahertz and with displacement loads exceeding 10 Kg (25 lbs). The actuator can also produce displacements comparable to state-of-the-art devices with an order reduction in operating voltage. The high displacement actuators are reliable. They have been laboratory tested to beyond 400 million cycles without failure. The highly efficient electrically- insulated actuator can be operated in a vacuum, in liquids, and in the upper atmosphere. The HDA is versatile and rugged allowing for use in harsh environments for hundreds of commercial applications. In many device applications the high displacement actuator wafer itself can serve the function of several components, e.g. in simple pumps it take the place of piston, piston-rod and crank. The HDA is a packaged flexible laminate of pre-stressed polymeric materials and a piezoelectric ceramic that form a robust, low cost, user friendly device.

  8. Self-actuated device

    DOEpatents

    Hecht, Samuel L. (Richland, WA)

    1984-01-01

    A self-actuated device, of particular use as a valve or an orifice for nuclear reactor fuel and blanket assemblies, in which a gas produced by a neutron induced nuclear reaction gradually accumulates as a function of neutron fluence. The gas pressure increase occasioned by such accumulation of gas is used to actuate the device.

  9. Plasma synthesis of polymer-capped dye-sensitised anatase nanopowders for visible-light-driven hydrogen evolution.

    PubMed

    Kruth, Angela; Hansen, Sven; Beweries, Torsten; Brüser, Volker; Weltmann, Klaus-Dieter

    2013-01-01

    Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days. PMID:23184471

  10. High-quality electron beams from field-induced ionization injection in the strong blow-out regime of beam-driven plasma accelerators

    NASA Astrophysics Data System (ADS)

    Martinez de la Ossa, A.; Behrens, C.; Grebenyuk, J.; Mehrling, T.; Schaper, L.; Osterhoff, J.

    2014-03-01

    We use three-dimensional (3D) simulations with the particle-in-cell (PIC) code OSIRIS to demonstrate the theoretical production of high-quality electron bunches in beam-driven plasma wakefield accelerators (PWFA) by means of field-induced ionization injection. In these simulations, two realistic scenarios for PWFA have been considered: the FLASHForward project at DESY and the FACET experiment at SLAC. These two examples illustrate two different strategies for injection. The first one uses the transverse electric fields of the beam to induce injection, and the second constitutes a new method which utilizes only the wakefields to enable ionization and trapping of high quality electron bunches into beam driven plasma wakes. The produced bunches feature multi-kA peak currents, ~1 ?m transverse normalized emittances, uncorrelated energy spreads of ?1% on a GeV-energy scale, and few femtosecond bunch lengths.

  11. Plasma rotation and NTM onset driven by central EC deposition in TCV tokamak

    SciTech Connect

    Nowak, S.; Lazzaro, E. [Istituto di Fisica del Plasma CNR, Euratom Association, 20125 Milano (Italy); Sauter, O.; Canal, G.; Duval, B.; Federspiel, L.; Karpushov, A. N.; Kim, D.; Reimerders, H.; Rossel, J.; Testa, D.; Wagner, D. [Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas (CRPP), Association EURATOM-Confederation Suisse, 1015 Lausanne (Switzerland); Raju, D. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India); Collaboration: TCV Team

    2014-02-12

    The effects of the central electron cyclotron heating (ECH) and current drive (ECCD) on the spontaneous plasma rotation and on the presence of Tearing Modes (TM), observed in the TCV tokamak[1], were recently investigated as an interplay between the toroidal velocity and NTM onset in absence of sawteeth, ELMs and error fields [2–3]. In a set of reproducible TCV discharges (I{sub p}? ?150 kA, B{sub t}? ?1.4 T, ne,{sub av?} 1.5 10{sup 19} m{sup ?3}, T{sub e}? 3 keV and T{sub i}?0.25 keV, q{sub 95}?5.8) with both pure EC heating and current drive the cnt-Ip toroidal velocity was observed to be reduced with subsequent co-Ip appearance of 3/2 and 2/1 modes during the ramp up EC phases. The understanding of the capability of the on-axis EC power to modify the rotation profiles before and after the TM onset and of the sudden disappearance of 3/2 mode when 2/1 starts is the main purpose of this work. The velocity profile modifications are due to a direct effect of the EC absorbed power and also related to some variation of the perpendicular diffusion of the toroidal momentum and to magnetic braking effects of the kind of neoclassical toroidal viscosity (NTV) due to the NTM resonant field perturbations associated to the presence of TM. Numerical investigations are performed using a 1D toroidal momentum balance equation including contributions by external sources, as EC power, and NTV torques. Furthermore, the combined evolution of the 3/2 and 2/1 modes requires considering also coupling effects included in a generalized Rutherford equation for the modelling of the TM time growth.

  12. Flame stabilization by a plasma driven radical jet in a high speed flow

    NASA Astrophysics Data System (ADS)

    Choi, Woong-Sik

    In current afterburners combustion is stabilized by the high temperature, recirculating region behind bluff body flame holders, such as V-gutters. Blocking the high speed flow with bluff bodies causes a significant pressure drop, and heating the flame holder by the hot combustion product causes a thermal signature, which is a critical problem in a military jet. To reduce these problems, ignition methods using a high frequency (HF) spark discharge, or a radical jet generator (RJG) were developed. The HF discharge ignited and stabilized a flame successfully in a premixed methane-air flow. The electrical power consumption was very small compared to the combustion heat release, as long as the operating velocity was relatively low. However, a theoretical study showed that the ratio of the electrical power consumption to the heat generation by the stabilized flame increases rapidly with increasing flow velocity. For flame stabilization in a high velocity flow, the developed RJG showed much better performance than direct exposure to a plasma. The present study investigated the characteristics of a radical jet produced in a RJG and injected into a main combustor. The limits of flame stabilization by this jet was measured experimentally, and compared to those of bluff body flame holders. The flame holding performance of the radical jet was also experimentally compared to that of a thermal jet. The effect of radicals on flame stabilization was examined using CHEMKIN, and the limit of flame stabilization by the radical jet was estimated for a simple flow configuration using an approximate solution. The results suggest that the reduction of local spontaneous ignition delay time by active species in the radical jet and the longer length of a typical radical jet compared to the dimension of the recirculation zone behind a bluff body increases the maximum velocity at which a flame can be stabilized.

  13. Decomposition of gas-phase benzene using plasma-driven catalyst (PDC) reactor packed with Ag\\/TiO 2 catalyst

    Microsoft Academic Search

    Hyun-Ha Kim; Seung-Min Oh; Atsushi Ogata; Shigeru Futamura

    2005-01-01

    This paper describes the decomposition of gas-phase benzene using a plasma-driven catalyst (PDC) reactor packed with 1.0wt.% Ag\\/TiO2 catalysts. The decomposition of benzene preferentially produced CO2 and CO, and formic acid as minor one. Carbon balance based on these products was satisfactory at around 100%. For the concentration lower than 110ppm, the PDC reactor successfully decomposed benzene with specific input

  14. Electrostatic actuators for portable microfluidic systems

    NASA Astrophysics Data System (ADS)

    Tice, Joshua

    Both developed and developing nations have an urgent need to diagnose disease cheaply, reliably, and independently of centralized facilities. Microfulidic platforms are well-positioned to address the need for portable diagnostics, mainly due to their obvious advantage in size. However, most microfluidic methods rely on equipment outside of the chip either for driving fluid flow (e.g., syringe pumps) or for taking measurements (e.g., lasers or microscopes). The energy and space requirements of the whole system inhibit portability and contribute to costs. To capitalize on the strengths of microfluidic platforms and address the serious needs of society, system components need to be miniaturized. Also, miniaturization should be accomplished as simply as possible, considering that simplicity is usually requisite for achieving truly transformative technology. Herein, I attempt to address the issue of controlling fluid flow in portable microfluidic systems. I focus on systems that are driven by elastomer-based membrane valves, since these valves are inherently simple, yet they are capable of sophisticated fluid manipulation. Others have attempted to modify pneumatic microvalves for portable applications, e.g., by transitioning to electromagnetic, thermopneumatic, or piezoelectric actuation principles. However, none of these strategies maintain the proper balance of simplicity, functionality, and ease of integration. My research centers on electrostatic actuators, due to their conceptual simplicity and the efficacy of electrostatic forces on the microscale. To ensure easy integration with polymer-based systems, and to maintain simplicity in the fabrication procedure, the actuators were constructed solely from poly(dimethylsiloxane) and multi-walled carbon nanotubes. In addition, the actuators were fabricated exclusively with soft-lithographic techniques. A mathematical model was developed to identify actuator parameters compatible with soft-lithography, and also to minimize actuation potentials while eliminating stiction. Two strategies were developed to overcome challenges with electrode screening in the presence of aqueous fluids. First, instead of using the electrostatic actuators to interact directly with aqueous solutions, the actuators were used to regulate pressurized control lines for pneumatic microvalves. Secondly, by adopting a normally-closed architecture, the actuators were converted into microvalves capable of directly interacting with aqueous solutions. The two strategies are complementary, and together should enable sophisticated microfluidic systems for applications ranging from point-of-care diagnostics to portable chemical detection. To conclude the dissertation, I demonstrate a proof-of-principle microfluidic system that contained sixteen independently-operated electrostatic valves, operated with battery-operated electrical ancillaries in a hand-held format.

  15. Cryogenic Piezoelectric Actuator

    NASA Technical Reports Server (NTRS)

    Jiang, Xiaoning; Cook, William B.; Hackenberger, Wesley S.

    2009-01-01

    In this paper, PMN-PT single crystal piezoelectric stack actuators and flextensional actuators were designed, prototyped and characterized for space optics applications. Single crystal stack actuators with footprint of 10 mm x10 mm and the height of 50 mm were assembled using 10 mm x10mm x0.15mm PMN-PT plates. These actuators showed stroke > 65 - 85 microns at 150 V at room temperature, and > 30 microns stroke at 77 K. Flextensional actuators with dimension of 10mm x 5 mm x 7.6 mm showed stroke of >50 microns at room temperature at driving voltage of 150 V. A flextensional stack actuator with dimension of 10 mm x 5 mm x 47 mm showed stroke of approx. 285 microns at 150 V at room temperature and > 100 microns at 77K under driving of 150 V should be expected. The large cryogenic stroke and high precision of these actuators are promising for cryogenic optics applications.

  16. Electro-Mechanical Actuators

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The electro-mechanical actuator, a new electronics technology, is an electronic system that provides the force needed to move valves that control the flow of propellant to the engine. It is proving to be advantageous for the main propulsion system plarned for a second generation reusable launch vehicle. Hydraulic actuators have been used successfully in rocket propulsion systems. However, they can leak when high pressure is exerted on such a fluid-filled hydraulic system. Also, hydraulic systems require significant maintenance and support equipment. The electro-mechanical actuator is proving to be low maintenance and the system weighs less than a hydraulic system. The electronic controller is a separate unit powering the actuator. Each actuator has its own control box. If a problem is detected, it can be replaced by simply removing one defective unit. The hydraulic systems must sustain significant hydraulic pressures in a rocket engine regardless of demand. The electro-mechanical actuator utilizes power only when needed. A goal of the Second Generation Reusable Launch Vehicle Program is to substantially improve safety and reliability while reducing the high cost of space travel. The electro-mechanical actuator was developed by the Propulsion Projects Office of the Second Generation Reusable Launch Vehicle Program at the Marshall Space Flight Center.

  17. Considerations for Contractile Electroactive Materials and Actuators

    SciTech Connect

    Rasmussen, Lenore; Erickson, Carl J.; Meixler, Lewis D.; Ascione, George; Gentile, Charles A.; Tilson, Carl; Bernasek, Stephen L.; Abelev, Esta

    2010-02-19

    Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

  18. Fast Positioning of Cutting Tool by a Voice Coil Actuator for Micro-Lens Fabrication

    Microsoft Academic Search

    Young Jin Noh; Masayuki Nagashima; Yoshikazu Arai; Wei Gao

    2009-01-01

    This paper describes the design, characteristics evalu- ation and experiment of a fast tool positioning (FTP) unit driven by a voice coil actuator. Three types of springs for coupling the actuator and the cutting tool, are compared for displacement constant, stiffness, and dynamic response based results of theoretical analysis and experiments. Micro-lens fabrication experiments on an aluminum alloy workpiece are

  19. Model-based Trajectory Control of Robots with Pneumatic Actuator Dynamics

    E-print Network

    Tedrake, Russ

    and applications; for example, hydraulic actuators are used in the rough-terrain quadruped robot[1] and forceModel-based Trajectory Control of Robots with Pneumatic Actuator Dynamics Ryuma Niiyama Abstract on underactuated robots. We present two case studies: an underactuated cart-pole system with the cart driven

  20. New experimental results on vibration damping of a hydraulically actuated flexible robot

    Microsoft Academic Search

    Werner Bernzen

    1998-01-01

    The paper presents an effective approach to vibration damping of hydraulically driven flexible robots using virtual passive elements. As it is impossible to obtain an accurate analytic model for multilink flexible robots with hydraulic actuators due to the closed kinematic loops this approach was developed. Here the hydraulic actuator is designed to have passive mechanical properties by suitable (velocity) control.