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1

Modelling of plasma aerodynamic actuation driven by nanosecond SDBD discharge  

NASA Astrophysics Data System (ADS)

A two-dimensional air plasma kinetics model (16 species and 44 processes) for nanosecond discharge under atmospheric pressure was developed to reveal the spatial and temporal distribution of discharge characteristics of a surface dielectric barrier discharge (SDBD) actuator. An energy transfer model, including two channels for energy release from external power source to gas, was developed to couple plasma with hydrodynamics directly in the same dimension. The governing equations included the Poisson equation for the electric potential, continuity equations for each species, electron energy equations for electrons taking part in reactions, and Navier-Stokes equations for non-isothermal fluid. The model was validated through current-voltage profile and electron temperature obtained from experiments. Calculations for discharge characteristics as well as the responses of fluid field from tens of nanoseconds to tens of seconds were performed. Results have shown that local air is heated to 1170 K within tens of nanoseconds and then decreases to 310 K at the end of a discharge period. 30% of the total power is transferred from electric field to electrons while only 20% of this energy is then released to gas through quenching processes. 9% of the total energy is released through ion collision. A micro-shock wave is formed and propagates at the speed of sound. High local density gradient and dynamic viscosity induces vortexes which whirl the heated air downstream. The combined effects of heating convection and vortexes in repetitive pulse discharges lead to the formation of a steady jet, in agreement with experimental results.

Zhu, Yifei; Wu, Yun; Cui, Wei; Li, Yinghong; Jia, Min

2013-09-01

2

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

NASA Astrophysics Data System (ADS)

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.

Dawson, Robyn A.; Little, Jesse

2014-01-01

3

Modeling of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses  

SciTech Connect

A detailed physical model for an asymmetric dielectric barrier discharge (DBD) in air driven by repetitive nanosecond voltage pulses is developed. In particular, modeling of DBD with high voltage repetitive negative and positive nanosecond pulses combined with positive dc bias is carried out. Operation at high voltage is compared with operation at low voltage, highlighting the advantage of high voltages, however the effect of backward-directed breakdown in the case of negative pulses results in a decrease of the integral momentum transferred to the gas. The use of positive repetitive pulses with dc bias is demonstrated to be promising for DBD performance improvement. The effects of the voltage waveform not only on force magnitude, but also on the spatial profile of the force, are shown. The crucial role of background photoionization in numerical modeling of ionization waves (streamers) in DBD plasmas is demonstrated.

Likhanskii, Alexandre V.; Shneider, Mikhail N.; Macheret, Sergey O.; Miles, Richard B. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Lockheed Martin Skunk Works, 1011 Lockheed Way, Palmdale, California 93599 (United States); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2007-07-15

4

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

SciTech Connect

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.

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

5

Light-Driven Polymeric Bimorph Actuators  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

6

Tendon Driven Finger Actuation System  

NASA Technical Reports Server (NTRS)

A humanoid robot includes a robotic hand having at least one finger. An actuation system for the robotic finger includes an actuator assembly which is supported by the robot and is spaced apart from the finger. A tendon extends from the actuator assembly to the at least one finger and ends in a tendon terminator. The actuator assembly is operable to actuate the tendon to move the tendon terminator and, thus, the finger.

Ihrke, Chris A. (Inventor); Reich, David M. (Inventor); Bridgwater, Lyndon (Inventor); Linn, Douglas Martin (Inventor); Askew, Scott R. (Inventor); Diftler, Myron A. (Inventor); Platt, Robert (Inventor); Hargrave, Brian (Inventor); Valvo, Michael C. (Inventor); Abdallah, Muhammad E. (Inventor); Permenter, Frank Noble (Inventor); Mehling, Joshua S. (Inventor)

2013-01-01

7

Surface chemistry driven actuation in nanoporous gold  

SciTech Connect

Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry driven actuation can be realized in high surface area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes in the order of a few tenths of a percent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response thus opening the door to surface-chemistry driven actuator and sensor technologies.

Biener, J; Wittstock, A; Zepeda-Ruiz, L; Biener, M M; Zielasek, V; Kramer, D; Viswanath, R N; Weissmuller, J; Baumer, M; Hamza, A V

2008-04-14

8

Note: A novel rotary actuator driven by only one piezoelectric actuator  

NASA Astrophysics Data System (ADS)

This paper presents a novel piezo-driven rotary actuator based on the parasitic motion principle. Output performances of the rotary actuator were tested and discussed. Experiment results indicate that using only one piezoelectric actuator and simple sawtooth wave control, the rotary actuator reaches the rotation velocity of about 20 097 ?rad/s when the driving voltage is 100 V and the driving frequency is 90 Hz. The actuator can rotate stably with the minimum resolution of 0.7 ?rad. This paper verifies feasibility of the parasitic motion principle for applications of rotary actuators, providing new design ideas for precision piezoelectric rotary actuators.

Huang, Hu; Fu, Lu; Zhao, Hongwei; Shi, Chengli; Ren, Luquan; Li, Jianping; Qu, Han

2013-09-01

9

A vacuum-driven peristaltic micropump with valved actuation chambers  

NASA Astrophysics Data System (ADS)

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.

Cui, Jianguo; Pan, Tingrui

2011-06-01

10

Plasma actuators for bluff body flow control  

NASA Astrophysics Data System (ADS)

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.

Kozlov, Alexey V.

11

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator  

E-print Network

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator Kunwar Pal Singh July 2007; published online 23 August 2007 A typical dielectric barrier discharge plasma actuator reflected power from the plasma actuator back to the power supply. This does not contribute to plasma

Roy, Subrata

12

Optimization of a dual acting, magnetically driven, linear actuator  

E-print Network

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...

Willerton, Justin Ryan

2002-01-01

13

A Study on a Microwave-Driven Smart Material Actuator  

NASA Technical Reports Server (NTRS)

NASA s Next Generation Space Telescope (NGST) has a large deployable, fragmented optical surface (greater than or = 2 8 m in diameter) that requires autonomous correction of deployment misalignments and thermal effects. Its high and stringent resolution requirement imposes a great deal of challenge for optical correction. The threshold value for optical correction is dictated by lambda/20 (30 nm for NGST optics). Control of an adaptive optics array consisting of a large number of optical elements and smart material actuators is so complex that power distribution for activation and control of actuators must be done by other than hard-wired circuitry. The concept of microwave-driven smart actuators is envisioned as the best option to alleviate the complexity associated with hard-wiring. A microwave-driven actuator was studied to realize such a concept for future applications. Piezoelectric material was used as an actuator that shows dimensional change with high electric field. The actuators were coupled with microwave rectenna and tested to correlate the coupling effect of electromagnetic wave. In experiments, a 3x3 rectenna patch array generated more than 50 volts which is a threshold voltage for 30-nm displacement of a single piezoelectric material. Overall, the test results indicate that the microwave-driven actuator concept can be adopted for NGST applications.

Choi, Sang H.; Chu, Sang-Hyon; Kwak, M.; Cutler, A. D.

2001-01-01

14

Dielectric Barrier Discharge Plasma Actuator for Flow Control  

NASA Technical Reports Server (NTRS)

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.

Opaits, Dmitry, F.

2012-01-01

15

DNS Modeling of Plasma Array Flow Actuators  

NASA Astrophysics Data System (ADS)

As a part of a continuing effort toward the development of weakly ionized plasma actuators as a means for flow control, this study presents a numerical simulation of the response of the bulk flow to the actuators. For this simulation, solutions for the two-dimensional, unsteady, incompressible Navier-Stokes equations are obtained. The effect of the plasma is modeled as a body force in the momentum equations. Due to the Debye shielding effect, which leads to a localized body force near the electrodes, these equations are solved on a non-uniform grid using a 4th order compact finite-difference scheme. The code is initially validated on benchmark problems. In addition, digital PIV measurements are used to validate the simulations. The obtained results were found to favorably compare to the experiments. Our objective is to simulate the response of plasma actuators that are operated in different time-dependent conditions produced by transient or periodic inputs at different frequencies and phase shifts. The obtained results will be utilized to lead to optimum designs that enhance the actuators effectiveness at producing unsteady disturbances as a means to prevent or delay boundary layer separation.

Orlov, Dmitriy; Corke, Thomas; Haddad, Osamah

2003-11-01

16

Scalability of Localized Arc Filament Plasma Actuators  

NASA Technical Reports Server (NTRS)

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.

Brown, Clifford A.

2008-01-01

17

Optically driven actuators using poly(vinylidene difluoride)  

NASA Astrophysics Data System (ADS)

Optically driven actuators have a feature of a non-contact method supplied by light energy. A new method is proposed with three poly(vinylidene difluoride) (PVDF) cantilevers as the legs and a polymer film as the body. The PVDF cantilevers are coated with silver on one surface. When one side of the cantilever is irradiated by a laser beam, an electric field is produced along a cross-section of the cantilever by the pyroelectric effect and a mechanical displacement occurs by the piezoelectric effect. Its response time and its generated force are measured experimentally. Two types of optically driven actuators using PVDF film are proposed to move using different characteristics.

Mizutani, Yasuhiro; Otani, Yukitoshi; Umeda, Norihiro

2008-05-01

18

Improving Wind Turbine Efficiency with Plasma Actuators  

NASA Astrophysics Data System (ADS)

As increasing the efficiency of modern wind turbines becomes more difficult, the use of active flow control now represents a more attractive means of possible improvement. This ongoing study examines utilizing single dielectric barrier discharge (SDBD) plasma actuators on wind turbine rotors to increase power generation. Blade element momentum (BEM) theory is used to identify regimes with the greatest potential for improvement and to estimate possible gains. Wind tunnel tests are conducted with plasma actuators to determine the amount of aerodynamic control achievable. In addition, the scope of a new "Laboratory for Enhanced Wind Energy Design" is outlined. Most critically, this resource includes two full-scale wind turbines to balance the known limitations of existing theory and wind tunnel testing by providing the capability to test novel blade designs and control strategies in the field.

Cooney, John; Corke, Thomas; Nelson, Robert

2010-11-01

19

Light-driven actuators based on polymer films  

NASA Astrophysics Data System (ADS)

We describe new light-driven actuators based on films of polymer polyvinylidene fluoride, known as PVDF. The actuators employ the photomechanic bending of the polymer film caused by low-power (10 mW and less) laser radiation. The photomechanic effect combines various physical mechanisms, such as thermal expansion, the converse piezoelectric mechanism, and the photovoltaic and pyroelectric mechanisms, while the mechanism of thermal expansion is dominant. The force applied by the actuators to external objects is measured with a torsion balance. It is proportional to the power of laser beam and could be as high as 10-4 N for a 50-µm film illuminated with a 10-mW laser beam. We demonstrate mechanical vibrations of a 1×7-mm strip actuator at a frequency of 0.3 kHz. As examples of possible applications, a photonic switch and an actuator with a closed-loop motion that could drive the inner workings of a conventional mechanical clock were demonstrated. The proposed actuators have a potential of being used as propulsion components of future light-driven micro/nano systems.

Sarkisov, Sergey S.; Curley, Michael J.; Huey, LaQuieta; Fields, Aisha B.; Sarkisov, Sergey S., II; Adamovsky, Grigory

2006-03-01

20

Design analysis of a piezoelectrically driven synthetic jet actuator  

NASA Astrophysics Data System (ADS)

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.

Yang, An-Shik

2009-12-01

21

A nanoelectromechanical systems actuator driven and controlled by Q-factor attenuation of ring resonator  

E-print Network

A nanoelectromechanical systems actuator driven and controlled by Q- factor attenuation of ring://apl.aip.org/authors #12;A nanoelectromechanical systems actuator driven and controlled by Q-factor attenuation of ring) actuator, which is controlled by the Q-factor attenuation of micro-ring resonator, is demonstrated

Suo, Zhigang

22

Optically driven actuators using poly(vinylidene difluoride)  

Microsoft Academic Search

Optically driven actuators have a feature of a non-contact method supplied by light energy. A new method is proposed with\\u000a three poly(vinylidene difluoride) (PVDF) cantilevers as the legs and a polymer film as the body. The PVDF cantilevers are\\u000a coated with silver on one surface. When one side of the cantilever is irradiated by a laser beam, an electric field

Yasuhiro Mizutani; Yukitoshi Otani; Norihiro Umeda

2008-01-01

23

Variable area nozzle for gas turbine engines driven by shape memory alloy actuators  

NASA Technical Reports Server (NTRS)

A gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

Rey, Nancy M. (Inventor); Miller, Robin M. (Inventor); Tillman, Thomas G. (Inventor); Rukus, Robert M. (Inventor); Kettle, John L. (Inventor); Dunphy, James R. (Inventor); Chaudhry, Zaffir A. (Inventor); Pearson, David D. (Inventor); Dreitlein, Kenneth C. (Inventor); Loffredo, Constantino V. (Inventor)

2001-01-01

24

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

SciTech Connect

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.

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

25

Note: A novel curvature-driven shape memory alloy torsional actuator  

NASA Astrophysics Data System (ADS)

This paper presents a novel, extremely simple torsional actuator which employs a special shape setting treated shape memory alloy coil. The actuator works with a so-called curvature-driven principle and can directly generate a rotary motion without any motion converting mechanism. Experiments were performed to study the output performances of several actuators with different geometry parameters. The test results show the actuator can output a rotary motion fluently, and the output torque is about several mN mm.

Yan, Xiaojun; Huang, Dawei; Zhang, Xiaoyong

2014-12-01

26

Charge driven piezoelectric actuators for structural vibration control: issues and implementation  

Microsoft Academic Search

Piezoelectric actuators have been traditionally driven by voltage amplifiers. When driven at large voltages these actuators exhibit a significant amount of distortion, known as hysteresis, which may reduce the stability robustness of the system in feedback control applications. Electric charge is known to reduce the effects of this nonlinearity. To date little research has been done on the coupling between

B J G Vautier; S O R Moheimani

2005-01-01

27

Positron driven plasma wakefields  

NASA Astrophysics Data System (ADS)

The LHC is producing high-energy, high-charge proton bunches (1e11 protons at 1-7 TeV each) that could be used to accelerate ``witness'' electron bunches to TeV range eneregies via a plasma wakefield accelerator (PWFA). Simulations [1] suggest that a proton ``drive'' bunch is able to excite large wakefields if the bunch size is on the order of 100 ?m; however, the LHC paramters are currently on the 1 cm scale. SLAC'S FACET is able to supply positorn bunchs with the ideal parameters for driving a PWFA. Although at lower energy (2e10 positrons at 23 GeV each), initial simiulations in QuickPIC show that the physics of a positron drive bunch is very similar to that of a proton drive bunch. Differences in the physics arise from the mass difference: slower dephasing but faster transverse bunch evolution. Other considerations include driver head erosion and purity of the wakefield ion column. The physics of positive drivers for PWFA and the viability of this scheme for future high-energy colliders will be investigated at SLAC's FACET.[4pt] [1] Caldwell, et al. Nature Physics 5, 363 (2009).[0pt] [2] C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006).

Pinkerton, S.; Shi, Y.; Huang, C.; An, W.; Mori, W. B.; Muggli, P.

2010-11-01

28

Electro-actuation characteristics of Cl2 and SF6 plasma-treated IPMC actuators  

Microsoft Academic Search

This paper describes plasma treatments that improve the actuation properties by modifying the surface morphology of ionic polymer metal composites (IPMC). The proposed Cl2 and SF6 plasmas change the surface appearance of the electroactive polymer, and scanning electron microscopy (SEM) of the plasma-treated surfaces reveals the development of round and cone-shaped microstructures. After electroless chemical metal plating, these microstructures significantly

Saim Saher; Woojin Kim; Sungwon Moon; H. Jin Kim; Yong Hyup Kim

2010-01-01

29

Boundary Layer Control by Means of Plasma Actuators  

SciTech Connect

The development of controlled transition in a flat-plate boundary layer is investigated using Large Eddy Simulations (LES) with the dynamic Smagorinsky model. The analysis of flow control with the objective to optimize the effects of Tollmien-Schlichting waves on a flat plate by means of plasma actuators was studied. The plasma effect is modeled as a body force in the momentum equations. These equations are solved in a uniform grid using a 2nd-order finite difference scheme in time and space. The response of plasma actuators operating in different time-dependent conditions, produced by transient or periodic inputs at different frequencies, is also analyzed.

Quadros, R. [UFRGS/PPGMAp-TUD-Stroemungslehre und Aerodynamik, Technische Universitaet Darmstadt, Petersenstr. 30, 64287 Darmstadt (Germany); Bortoli, A. L. de [UFRGS/DMPA-Departamento de Matematica Pura e Aplicada, Bento Goncalves 9500, Agronomia-P.O. Box 15080, Porto Alegre-RS (Brazil); Tropea, C. [TUD/SLA-Stroemungslehre und Aerodynamik, Technische Universitaet Darmstadt, Petersenstr. 30, 64287 Darmstadt (Germany)

2007-09-06

30

Active Flow Control in Turbomachinery Using Phased Plasma Actuators  

Microsoft Academic Search

This paper shall present the possibilities of new emerging active flow control techniques in turbomachinery using phased plasma actuators. The major gas turbine applications are low Reynolds number separation flow control in LPT turbine blades, active inlet flow control, active flow control on fan blades and compressor vanes, active control of tip clearance flows in the blade tip-casing region, plasma-assisted

B. Göksel; I. Rechenberg

31

Design of an Active Noise Control System using Plasma Actuators  

E-print Network

and analysed from sensors located in the test case (Figure 2 #12;U Trailing edge microphone Leading edgeDesign of an Active Noise Control System using Plasma Actuators Xun Huang, Sammie Chan, Xin Zhang variation in the flow field that can lead to the attenuation of flow-induced tonal noise [3, 4]. The plasma

Huang, Xun

32

On the mechanical efficiency of dielectric barrier discharge plasma actuators  

SciTech Connect

The mechanical power production and electrical power consumption of the dielectric barrier discharge plasma actuator is investigated for different operating conditions. The ratio of these two values delivers the mechanical efficiency of the actuator as a flow acceleration device. The general trend is that higher carrier frequencies and voltages lead to higher values of the efficiency. The values that were found for the mechanical efficiency are very small, the highest recorded value is only 0.18%.

Giepman, R. H. M.; Kotsonis, M. [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, Delft 2629HS (Netherlands)

2011-05-30

33

Switching Behavior of a Plasma-Fluidic Actuator James W. Gregory*  

E-print Network

presents the plasma-fluidic actuator as a new type of flow control actuator. The device combines the best flow rates that current actuators cannot deliver. Jet thrust vectoring on a flight vehicle is oneSwitching Behavior of a Plasma-Fluidic Actuator James W. Gregory* , Joseph C. Ruotolo , Aaron R

Gregory, James W.

34

Simulation of an asymmetric single dielectric barrier plasma actuator K. P. Singha  

E-print Network

Simulation of an asymmetric single dielectric barrier plasma actuator K. P. Singha and Subrata Roy because of its applications in flow actuation in aerospace and many other areas.1,2 These actuators use plasma actuator is shown in Fig. 1. The grounded electrode for this configuration is em- bedded

Singh, Kunwar Pal

35

Electrochemically driven actuators from conducting polymers, hydrogels, and carbon nanotubes  

NASA Astrophysics Data System (ADS)

The mechanisms of actuation operating in polymeric actuators are reviewed along with a comparison of actuator performance. Polymer hydrogel actuators show very large dimensional changes, but relatively low response times. The mechanism of actuation involves several processes including electro-osmosis and electrochemical effects. Conducting polymer actuators operate by Faradaic reactions causing oxidation and reduction of the polymer backbone. Associated ion movements produce dimensional changes of typically up to 3%. The maximum stress achieved to date from conducting polymers is not more than 10 MPA. Carbon nanotubes have recently been demonstrated as new actuator materials. The nanotubes undergo useful dimensional changes (approximately 1%) but have the capacity to respond very rapidly (kHz) and generate giant stresses (600 MPa). The advantages of nanotube actuators stem from their exceptional mechanical properties and the non-Faradaic actuation mechanism.

Spinks, Geoffrey M.; Wallace, Gordon G.; Lewis, Trevor W.; Fifield, Leonard S.; Dai, Liming; Baughman, Ray H.

2001-04-01

36

Force approximation for a plasma actuator operating in atmospheric air  

SciTech Connect

A plasma actuator has been studied using a self-consistent multibody system of quiescent air, plasma, and dielectric. Equations governing the motion of charged and neutral species have been solved with Poisson's equation. Based on first principles analysis, a functional relationship between electrodynamic force and electrical and physical control parameters has been approximated and numerically tested for air. The magnitude of approximated force increases with the fourth power of the amplitude of rf potential. Thus, the induced fluid velocity also increases. The induced velocity shows momentum injection very close to the actuator surface. There is, however, a very small increase in the induced velocity with the forcing frequency. For the specific range of operational parameters considered, the proposed force relation may help speed up the plasma actuator design process.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2008-01-01

37

Suppression of Trailing-Edge Noise Using a Plasma Actuator  

NASA Astrophysics Data System (ADS)

Suppression control of noise generation from an airfoil trailing edge is examined experimentally by using a plasma actuator for a NACA0012 airfoil at an angle of attack of -2°, at a chord Reynolds number Re = 1.54 × 105. The boundary layer on the suction surface undergoes transition to turbulence at a location upstream of the trailing edge at the present flow condition and the generation of tonal trailing-edge noise is governed by vortex roll-up of boundary layer on the pressure surface in the vicinity of the trailing-edge which produces a strong acoustic (dipole) source by diffraction of vortex-induced fluctuations at the trailing-edge. When the plasma actuator is operated at an appropriate location on the pressure-side boundary layer, the trailing-edge noise is completely suppressed through delaying the development of the boundary-layer instability wave by the blowing effect of plasma actuator.

Inasawa, A.; Asai, M.; Itoh, K.; Kamijo, T.

2011-09-01

38

Numerical simulation of the effect of plasma aerodynamic actuation on improving film hole cooling performance  

NASA Astrophysics Data System (ADS)

The primary goal of this paper is to study film cooling performance for a cylindrical hole with plasma aerodynamic actuation. The simulation model of plasma aerodynamic actuation on improving film hole cooling effectiveness was established. The heat effect of plasma aerodynamic actuation model was taken into consideration. It was firstly found that the velocity and blowing ratio greatly affect the film cooling effectiveness. Then, position, power input, and the number of plasma actuators were particularly investigated.

Yu, Jin-Lu; He, Li-ming; Zhu, Yi-fei; Ding, Wei; Wang, Yu-qian

2013-06-01

39

Plasma actuated heat transfer Subrata Roya  

E-print Network

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

Roy, Subrata

40

Bluff Body Flow Control Using Dielectric Barrier Discharge Plasma Actuators  

NASA Astrophysics Data System (ADS)

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.

Thomas, Flint; Kozlov, Alexey

2008-11-01

41

A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators  

NASA Astrophysics Data System (ADS)

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.

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

42

Stabilization of boundary layer streaks by plasma actuators  

NASA Astrophysics Data System (ADS)

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.

Riherd, Mark; Roy, Subrata

2014-03-01

43

Resonant control of structural vibration using charge-driven piezoelectric actuators  

Microsoft Academic Search

Driving piezoelectric actuators by charge, or current rather than voltage is known to significantly reduce the hysteretic nature of these actuators. This paper further investigates properties of piezoelectric transducers driven by charge amplifiers, and proposes multivariable resonant controllers for vibration control of piezoelectric laminates. The paper reports experimental implementation of a multivariable resonant controller on a piezoelectric laminate cantilevered beam.

S. O. R. Moheimani; B. J. G. Vautier

2004-01-01

44

Streamwise and spanwise plasma actuators for flow-induced cavity noise control  

E-print Network

March 2008 Plasma actuators operating in atmospheric air can induce a body force through collisions plasma actuators operating in at- mospheric pressure air2 holds the potential to reduce flow- induced/suction jets pose installation and maintenance is- sues. In contrast, plasma actuators are simple and cheap

Huang, Xun

45

Force Production Mechanisms of a Dielectric-Barrier Discharge Plasma Actuator  

E-print Network

Force Production Mechanisms of a Dielectric-Barrier Discharge Plasma Actuator James W. Gregory* , C-barrier discharge plasma actuator. A theoretical derivation shows that the force produced is due to the acceleration affecting the amount of force produced by the plasma actuator. Nomenclature a = Acceleration b = Coefficient

Gregory, James W.

46

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

E-print Network

of a turbulent channel flow with micro plasma actuators. Measurements are made by a laser Doppler velocimeter (LDV) at Re! = 297 and 602. We fabricate arrayed micro plasma actuators and reproduce spatially the exposed electrode. Okochi et al. (2009) fabricated micro plasma actuators for wall turbulence control

Kasagi, Nobuhide

47

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

E-print Network

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 ...

Golda, Dariusz, 1979-

2008-01-01

48

Centrifugally driven diffusion of Iogenic plasma  

Microsoft Academic Search

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.

G. L. Siscoe; Danny Summers

1981-01-01

49

Suppression of Trailing-Edge Noise Using a Plasma Actuator  

Microsoft Academic Search

Suppression control of noise generation from an airfoil trailing edge is examined experimentally by using a plasma actuator for a NACA0012 airfoil at an angle of attack of -2°, at a chord Reynolds number Re = 1.54 × 105. The boundary layer on the suction surface undergoes transition to turbulence at a location upstream of the trailing edge at the

A. Inasawa; M. Asai; K. Itoh; T. Kamijo

2011-01-01

50

Broadband flow-induced sound control using plasma actuators  

NASA Astrophysics Data System (ADS)

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.

Huang, Xun; Zhang, Xin; Li, Yong

2010-06-01

51

Note: A novel curvature-driven shape memory alloy torsional actuator.  

PubMed

This paper presents a novel, extremely simple torsional actuator which employs a special shape setting treated shape memory alloy coil. The actuator works with a so-called curvature-driven principle and can directly generate a rotary motion without any motion converting mechanism. Experiments were performed to study the output performances of several actuators with different geometry parameters. The test results show the actuator can output a rotary motion fluently, and the output torque is about several mN mm. PMID:25554345

Yan, Xiaojun; Huang, Dawei; Zhang, Xiaoyong

2014-12-01

52

Electro-driven polypyrrole actuators working in air  

NASA Astrophysics Data System (ADS)

The combination of electrical and hygroscopic nature of conducting polymers provided an insight into the development of a new class of electro-driven actuators or artificial muscle systems that worked in ambient air. The electrochemically synthesized polypyrrole films underwent quick and intensive bending in air as a result of a dimensional change due to the sorption of water vapor from one side of the film. Furthermore, an application of electric field caused contraction of the film in air. The dimensional change of the polypyrrole film under the electric field was expressed by two processes: one was the contraction due to the desorption of water vapor and the other was the thermal expansion of polymer chains both caused by Joule heating. The degree of contraction attained 1.2% under 2 V, where the initial speeds of contraction and elongation of the film were 4.4 and 1.8%/min, respectively. Under loading conditions, the power density increased with increasing load and the value attained 0.78 W/kg (6 ?W) under the load of 60 g (4 MPa). Under isometric conditions, when dc 2 V is applied to the film under the thermostatic conditions (25°C, 50% RH), the film generated contractile stress repeatedly in response to the applied voltage. The stress reached 6.1 MPa, which was 4 orders of magnitude larger than its own weight and nearly 20 times that of skeletal muscle in animals. The generated stress under 2 V increased to 8.9 MPa upon stretching the film by 1%, which could be associated with the Young's modulus of the film rose due to the desorption of water vapor that plasticized polymer chains. The work capacity of the film increased as the applied voltage became higher and reached 48.2 kJ/m3 at 3 V, while the energy efficiency, defined as the ratio of work capacity to the electric energy, was the order of 10-3%.

Okuzaki, Hidenori; Saido, Tomooki

2005-05-01

53

Force approximation for a plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya  

E-print Network

Force approximation for a plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata November 2006; published online 10 January 2008 A plasma actuator has been studied using a self momentum injection very close to the actuator surface. There is, however, a very small increase

Roy, Subrata

54

Physics of plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya  

E-print Network

Physics of plasma actuator operating in atmospheric air Kunwar Pal Singh and Subrata Roya; published online 19 March 2008 The physics of plasma actuator operating in the atmospheric air has been, and turbulent separation over a wall-mounted hump. Unsteady flow actuation with a duty factor seemed to perform

Roy, Subrata

55

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

E-print Network

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

Yao, Bin

56

The manipulation of an unstarting supersonic flow by plasma actuator  

NASA Astrophysics Data System (ADS)

The manipulation of an unstarting supersonic flow is demonstrated using a dielectric barrier discharge (DBD). Experiments are carried out in a Mach 4.7 model inlet flow. Flow features, such as boundary layers and shockwaves at low freestream static pressure (1 kPa) and temperature (60 K) are visualized with Rayleigh scattering from condensed CO2 particles. Flow unstart, initiated by mass injection, is studied for three model inlet flow configurations, distinguished by the initial conditions (untripped or tripped, plasma actuated or not) of the boundary layers. Unstart in the presence of thick, tripped boundary layers is characterized by the formation of an oblique unstart shock just upstream of a separating and propagating boundary layer. The presence of plasma actuation of this tripped boundary layer seems to arrest the boundary layer separation and leads to the formation of a quasi-stationary pseudo-shock, delaying unstart. The flow generated with DBD actuation is more characteristic of what is seen when unstart is generated in a model flow in which thin boundary layers grow naturally. Planar laser Rayleigh scattering visualizations suggest that the DBD actuation thins the tripped boundary layer over the exposed electrode region.

Im, S.; Do, H.; Cappelli, M. A.

2012-12-01

57

Shock Generation and Control Using DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

58

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

59

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

E-print Network

Analysis, Design and Control of a Planar Micro-robot Driven by Two Centripetal-Force Actuators of a novel, low cost, sliding micro-robot, which is actuated by centripetal forces generated by robot mounted. The motion behavior of the micro-robot, for asynchronous actuation operation, is expressed analytically

Papadopoulos, Evangelos

60

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

SciTech Connect

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.

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

61

Micro-Ball-Lens Optical Switch Driven by SMA Actuator  

NASA Technical Reports Server (NTRS)

The figure is a simplified cross section of a microscopic optical switch that was partially developed at the time of reporting the information for this article. In a fully developed version, light would be coupled from an input optical fiber to one of two side-by-side output optical fibers. The optical connection between the input and the selected output fiber would be made via a microscopic ball lens. Switching of the optical connection from one output fiber to another would be effected by using a pair of thin-film shape-memory-alloy (SMA) actuators to toggle the lens between two resting switch positions. There are many optical switches some made of macroscopic parts by conventional fabrication techniques and some that are microfabricated and, hence, belong to the class of microelectromechanical systems (MEMS). Conventionally fabricated optical switches tend to be expensive. MEMS switches can be mass-produced at relatively low cost, but their attractiveness has been diminished by the fact that, heretofore, MEMS switches have usually been found to exhibit high insertion losses. The present switch is intended to serve as a prototype of low-loss MEMS switches. In addition, this is the first reported SMA-based optical switch. The optical fibers would be held in V grooves in a silicon frame. The lens would have a diameter of 1 m; it would be held by, and positioned between, the SMA actuators, which would be made of thin films of TiNi alloy. Although the SMA actuators are depicted here as having simple shapes for the sake of clarity of illustration, the real actuators would have complex, partly net-like shapes. With the exception of the lens and the optical fibers, the SMA actuators and other components of the switch would be made by microfabrication techniques. The components would be assembled into a sandwich structure to complete the fabrication of the switch. To effect switching, an electric current would be passed through one of the SMA actuators to heat it above its transition temperature, thereby causing it to deform to a different "remembered" shape. The two SMA actuators would be stiff enough that once switching had taken place and the electrical current was turned off, the lens would remain latched in the most recently selected position. In a test, the partially developed switch exhibited an insertion loss of only -1.9 dB and a switching contrast of 70 dB. One the basis of prior research on SMA actuators and assuming a lens displacement of 125 m between extreme positions, it has been estimated that the fully developed switch would be capable of operating at a frequency as high as 10 Hz.

Yang, Eui-Hyeok

2003-01-01

62

Plasma Actuators for Turbomachinery Flow Control  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

63

Streamwise and spanwise plasma actuators for flow-induced cavity noise control  

SciTech Connect

Plasma actuators operating in atmospheric air can induce a body force through collisions between electrically charged particles and neutral air molecules by an externally applied electric field. The fast response and the simple structure make the plasma actuator a promising option in aerospace applications. In this work, experiments were performed with several alternative current excited plasma (streamwise and spanwise) actuators to control flow-induced noise from a cavity. It was found that the streamwise actuator induced three-dimensional variations in the shear layer. The spanwise actuator, however, has little influence on the global flow field. As a result, the streamwise actuator is more effective than the spanwise actuator in cavity noise attenuation.

Huang Xun; Zhang Xin [Aeronautics and Astronautics, School of Engineering Sciences, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2008-03-15

64

TECHNICAL NOTE: A 3-DOFs mobile robot driven by a piezoelectric actuator  

Microsoft Academic Search

In this paper, a novel miniature-step mobile robot with three degrees of freedom (DOFs) is developed based on the inchworm principle. This device, driven by a piezo stack actuator, utilizes a rhombic flexure hinge mechanism and four electromagnetic legs to achieve large stroke translation and rotation with high resolution on a platform. The design process of the rhombic flexible frame

Shaoze Yan; Fuxing Zhang; Zhen Qin; Shizhu Wen

2006-01-01

65

Modeling and control of a piezoelectric actuator driven system with asymmetric hysteresis  

Microsoft Academic Search

This study describes the high-precision positioning control of a system with asymmetric hysteresis. A switching system concept is adopted to describe the Preisach-type hysteresis, and a systematic modeling procedure is established to obtain the parameters of the system. A piezoelectric actuator system driven by a voltage amplifier is used to verify the modeling accuracy. A control structure, comprising a feedforward

Ming-Jyi Jang; Chieh-Li Chen; Jie-Ren Lee

2009-01-01

66

Combustion-Driven Jet Actuators for Flow Control  

NASA Astrophysics Data System (ADS)

The development and characterization of a novel, high-power small-scale combustion-based fluidic actuator for flow control applications is described. The actuator produces a momentary jet by the ignition of premixed fuel and oxidizer in a small (cm3 scale) combustion chamber. The combustion cycle begins with the injection of mixture into the combustion chamber, displacing remaining combustion products from the previous cycle. The mixture is ignited by a miniature spark, and a combustion process ensues which typically lasts 1-3 milliseconds (depending on the type of fuel, mixture ratio, and physical sizes of the combustor and chamber orifices), resulting in a rapid pressure rise in the chamber and the ejection of single or multiple momentary high-speed jets. The actuator frequency can be continuously varied by independently controlling the flow rate of the fuel/oxidizer and the ignition frequency. Operating frequencies of greater than 150 Hz have been achieved with chamber pressures of up to 5 atm, producing sonic velocities at the jet orifice. Jet penetration into a cross-flow at Mach numbers up to 0.7 has been demonstrated. *Supported by DARPA

Crittenden, Thomas; Glezer, Ari

2001-11-01

67

Transient ejection phase modeling of a Plasma Synthetic Jet actuator  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

68

Research on the Peristaltic Flow Acceleration Performance of Asynchronous and Duty Cycle Pulsed DBD Plasma Actuation  

NASA Astrophysics Data System (ADS)

Using a plexiglas plate model, the performance of peristaltic flow acceleration induced by multiple DBD (dielectric barrier discharge) plasma actuators was studied based on PIV (particle image velocimetry). The asynchronous and the duty cycle pulsed actuation modes were proposed and tested. The velocity fields induced by multiple DBD plasma actuators with different phase angles and duty cycle ratios were acquired and the momentum transfer characteristics of the flow field were discussed. Consequently, the mechanism of the peristalsis-acceleration multiple DBD plasma actuation was analyzed. The results show that the peristaltic flow acceleration effect of multiple plasma actuators occurs mainly in paraelectric direction, and the mechanism of peristaltic flow acceleration is ejection pushing effect rather than injection pumping effect. The asynchronous and the duty cycle pulsed actuation modes can, with energy consumption increase of merely 10%, achieve 65% and 42% increase of downstream velocity, and thus are promising in velocity improvement and energy saving.

Li, Feng; Gao, Chao; Zheng, Borui; Wang, Yushuai

2014-09-01

69

American Institute of Aeronautics and Astronautics On Multi-Barrier Plasma Actuators  

E-print Network

barrier plasma actuator at or near atmospheric pressures have been widely documented in the last one charged air which manifests itself as a primarily tangential wall jet. Varying aspectsAmerican Institute of Aeronautics and Astronautics 1 On Multi-Barrier Plasma Actuators Ryan

Roy, Subrata

70

Update of Proton Driven Plasma Wakefield Acceleration  

SciTech Connect

In this paper, the update of proton driven plasma wakefield acceleration (PDPWA) is given. After a brief introduction to the scheme of PDPWA, a future demonstration experiment is discussed. The particle-in-cell simulation results based on the realistic proton beams from the CERN Super Proton Synchrotron (SPS) are presented, followed by a simulation study of proton bunch compression.

Xia, G.; Caldwell, A. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Lotov, K. [Budker Institute for Nuclear Physics, Novisibirsk (Russian Federation); Pukhov, A.; Kumar, N. [Duesseldorf University, Duesseldorf (Germany); An, W.; Lu, W.; Mori, W. B.; Joshi, C. [University of California, Los Angeles, CA (United States); Huang, C. [Los Alamos National Laboratory, NM (United States); Muggli, P. [University of Southern California, CA (United States); Assmann, R.; Zimmermann, F. [CERN, Geneva (Switzerland)

2010-11-04

71

Receptivity of Laminar Boundary Layers to Spanwise-Periodic Forcing by an Array of Plasma Actuators  

NASA Astrophysics Data System (ADS)

This work is concerned with the response of a Blasius boundary layer to dielectric-barrier- discharge (DBD) plasma actuators for the purpose of using these devices in bypass transition control. The plasma actuators consist of a spanwise-periodic array of high voltage electrodes, which are oriented to produce streamwise vortex pairs. The structure of actuator-induced streaks is measured using hot-wire anemometry over a streamwise distance of approximately 100 boundary layer thicknesses, and is decomposed into 4 span-wise Fourier modes. The modal content and corresponding streamwise growth characteristics are discussed for ten plasma actuator geometries over multiple excitation voltages and freestream velocities. Actuator power consumption was found to control the streak amplitude, whereas freestream velocity affected both amplitude and streamwise extent of the streaks. A common relationship between disturbance energy and power consumption was found among actuators of different dielectric thickness and similar electrode geometry.

Osmokrovic, Luke

72

Tunable microlens actuated via a thermoelectrically driven liquid heat engine  

NASA Astrophysics Data System (ADS)

We have developed a thermally actuated liquid microlens. An embedded thermoelectric element is used to actuate the liquid based heat engine. A closed-loop system is harnessed to drive and stabilize the temperature of the heat engine. Direct contact between the thermoelectric device and the water results in greatly improved, sub-second thermal rise time (0.8 s). The water based heat engine reacts to the variation in the temperature via expansion and contraction. In turn, the shape of a pinned water-oil meniscus at a lens aperture is deformed in response to the net volume change in the water, creating a tunable microlens. A method to fabricate microfluidic devices with relatively high thickness (250-750 ?m) and large length-to-depth aspect ratio (280:1) was developed and used in the process. After fabrication and thermal calibration, optical characteristic of the microlens was assessed. Back focal length of the microlens was shown to vary continuously from -19.6 mm to -6.5 mm as the temperature increased from 5 °C to 35 °C. A thin film air was further introduced to insulate the heat engine from the substrate to protect the microlens area from the temperature fluctuation of the heat engine, thus preventing the change of the refractive indices and thermally induced aberrations. Wavefront aberration measurement was conducted. Surface profile of the microlens was mapped and found to have a conical shape. Both 3-dimensional and 1-dimensional thermal models for the device structure were developed and thermal simulation of the device was performed.

Ashtiani, Alireza Ousati; Jiang, Hongrui

2014-06-01

73

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

NASA Astrophysics Data System (ADS)

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

Reedy, Todd Mitchell

74

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

NASA Astrophysics Data System (ADS)

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.

Liu, Zhifeng; Wang, Lianze; Fu, Song

2011-11-01

75

Physics of plasma actuator operating in atmospheric air  

SciTech Connect

The physics of plasma actuator operating in the atmospheric air has been numerically investigated. The O{sup -}, O{sub 2}{sup -}, O{sub 2}{sup +}, and N{sub 2}{sup +} ions have been included in the air chemistry to identify their role. For the specific case study, we find the density of positive ions is an order of magnitude higher at the positive peak of the cycle than that at the negative peak of the cycle. This difference in density levels of the species causes the development of the directional bias of the electrodynamic force. Numerical simulations indicate that positive ions play major role in the development of the positive force.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611-6300 (United States)

2008-03-17

76

System identification of a Scott–Russell amplifying mechanism with offset driven by a piezoelectric actuator  

Microsoft Academic Search

The micro-positioning Scott–Russell (SR) mechanism driven by a piezoelectric actuator (PA) is designed to magnify the displacement of the PA. The main feature of the SR mechanism is its straight-line output for a given input displacement. In this paper, the main objective is to propose a complete mathematical model, including the driving circuit, Bouc–Wen hysteresis and mechanical equation, to describe

Ching-Ming Chen; Yen-Chun Hsu; Rong-Fong Fung

77

Strategies for control of transitional and turbulent flows using plasma-based actuators  

Microsoft Academic Search

An exploratory numerical study of the control of transitional and turbulent separated flows by means of dielectric-barrier-discharge (DBD) actuators is presented. The flow fields are simulated employing a high-fidelity Navier–Stokes solver augmented with a phenomenological model representing the plasma-induced body forces imparted by the actuator on the fluid. Several applications are considered, including interaction of an actuator with a laminar

Miguel R. Visbal

2010-01-01

78

Influence of the energy dissipation rate in the discharge of a plasma synthetic jet actuator  

Microsoft Academic Search

A promising actuator for high-speed flow control, referred to as a plasma synthetic jet (PSJ), is being studied by the DMAE department of the ONERA, and the Laplace laboratory of the CNRS, in France. This actuator was inspired by the 'sparkjet' device developed by the Johns Hopkins University Applied Physics Laboratory. The PSJ, which produces a synthetic jet with high

A. Belinger; P. Hardy; P. Barricau; J. P. Cambronne; D. Caruana

2011-01-01

79

Local and Bi-Global Stability Analysis of a Plasma Actuated Boundary Layer  

E-print Network

Local and Bi-Global Stability Analysis of a Plasma Actuated Boundary Layer Mark Riherd and Subrata discharge actuators on a laminar, zero pressure gradi- ent boundary layer. Both methods indicate layer. The general behavior of boundary layer stabilization is consistent with experimental results

Roy, Subrata

80

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

PubMed

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

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

2014-11-24

81

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

PubMed Central

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

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

2013-01-01

82

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

PubMed Central

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

Inou, Norio

2013-01-01

83

Numerical simulation of a plasma actuator based on ion transport  

SciTech Connect

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.

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

84

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

NASA Astrophysics Data System (ADS)

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.

Li, Peng; Song, Gangbing

2014-08-01

85

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

NASA Astrophysics Data System (ADS)

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.

Schatzman, David M.

2005-11-01

86

Comparison of plasma treatment and sandblast preprocessing for IPMC actuator  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

87

Influence of circulation on a rounded-trailing-edge airfoil using plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental study on influence of circulation around a symmetric airfoil with a rounded trailing edge is presented. Flow control is achieved by the use of dielectric barrier discharge plasma actuators placed at the trailing edge of the airfoil. Direct lift and drag measurements are taken using an external load balance at freestream velocities of 10, 15 and 20 m/s corresponding to chord Reynolds number of 140,000, 210,000, 280,000. Additionally, time-resolved particle image velocimetry is used in order to elucidate the topology and dynamical response of the wake flow under the influence of actuation. Results indicate an increase in lift coefficient of approximately 0.1 for the lowest tested Reynolds number using the plasma actuator. Flowfield measurements indicate the successful manipulation of the Kutta condition enabled by the plasma actuator. The actuator is enhancing the mixing of the wake near the trailing edge while reducing the dominant shedding frequency. Proper orthogonal decomposition analysis reveals further details regarding the dynamics of the wake flow in presence of actuation, suggesting the sensitivity of the control concept to the positioning of the actuator as well as the angle of attack.

Kotsonis, Marios; Pul, Robin; Veldhuis, Leo

2014-07-01

88

Plasma Jet Driven Magneto-Inertial Fusion (PJMIF)  

E-print Network

Plasma Jet Driven Magneto-Inertial Fusion (PJMIF) Scott Hsu Physics Division, LANL Fusion Power National Security, LLC for NNSA LA-UR-11-07030 #12;Plasma jet experiments can provide cm National Security, LLC for NNSA Imploding plasma liner formed by 30 merging plasma jets with 1.5 MJ

89

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

90

Physics of Laser-driven plasma-based acceleration  

SciTech Connect

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.

Esarey, Eric; Schroeder, Carl B.

2003-06-30

91

Noise control of subsonic cavity flows using plasma actuated receptive channels  

NASA Astrophysics Data System (ADS)

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.

Das Gupta, Arnob; Roy, Subrata

2014-12-01

92

Actuator-valve interface optimization. [Explosive actuators  

SciTech Connect

The interface of explosive actuator driven valves can be optimized to maximize the velocity of the valve plunger by using the computer code Actuator-Valve Response. Details of the AVR model of the actuator driven valve plunger and the results of optimizing an actuator-valve interface with AVR are presented. 5 refs., 5 figs., 3 tabs.

Burchett, O.L.; Jones, R.L.

1987-02-01

93

Design and experimental research of a novel inchworm type piezo-driven rotary actuator with the changeable clamping radius.  

PubMed

In this paper, a novel piezo-driven rotary actuator with the changeable clamping radius is developed based on the inchworm principle. This actuator mainly utilizes three piezoelectric actuators, a flexible gripper, a clamping block, and a rotor to achieve large stroke rotation with high resolution. The design process of the flexible gripper consisting of the driving unit and the clamping unit is described. Lever-type mechanisms were used to amplify the micro clamping displacements. The amplifying factor and parasitic displacement of the lever-type mechanism in the clamping unit was analyzed theoretically and experimentally. In order to investigate the rotation characteristics of the actuator, a series of experiments was carried out. Experimental results indicate that the actuator can rotate at a speed of 77,488 ?rad/s with a driving frequency of 167 Hz. The rotation resolution and maximum load torque of the actuator are 0.25 ?rad and 37 N mm, respectively. The gripper is movable along the z direction based on an elevating platform, and the clamping radius can change from 10.6 mm to 25 mm. Experimental results confirm that the actuator can achieve different rotation speeds by changing the clamping radius. PMID:23387686

Zhao, Hongwei; Fu, Lu; Ren, Luquan; Huang, Hu; Fan, Zunqiang; Li, Jianping; Qu, Han

2013-01-01

94

Design and experimental research of a novel inchworm type piezo-driven rotary actuator with the changeable clamping radius  

NASA Astrophysics Data System (ADS)

In this paper, a novel piezo-driven rotary actuator with the changeable clamping radius is developed based on the inchworm principle. This actuator mainly utilizes three piezoelectric actuators, a flexible gripper, a clamping block, and a rotor to achieve large stroke rotation with high resolution. The design process of the flexible gripper consisting of the driving unit and the clamping unit is described. Lever-type mechanisms were used to amplify the micro clamping displacements. The amplifying factor and parasitic displacement of the lever-type mechanism in the clamping unit was analyzed theoretically and experimentally. In order to investigate the rotation characteristics of the actuator, a series of experiments was carried out. Experimental results indicate that the actuator can rotate at a speed of 77 488 ?rad/s with a driving frequency of 167 Hz. The rotation resolution and maximum load torque of the actuator are 0.25 ?rad and 37 N mm, respectively. The gripper is movable along the z direction based on an elevating platform, and the clamping radius can change from 10.6 mm to 25 mm. Experimental results confirm that the actuator can achieve different rotation speeds by changing the clamping radius.

Zhao, Hongwei; Fu, Lu; Ren, Luquan; Huang, Hu; Fan, Zunqiang; Li, Jianping; Qu, Han

2013-01-01

95

Phase effect on flow control for dielectric barrier plasma actuators  

SciTech Connect

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.

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

2006-07-03

96

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

97

Aerogel and ferroelectric dielectric materials for plasma actuators  

Microsoft Academic Search

This paper presents performance evaluation of two thick materials with extreme permittivity as dielectric barrier discharge actuators. Specifically, the use of silica aerogels and ferroelectrics is investigated. Due to high polarizability of the ferroelectric material the supplied power manifests itself primarily as heat generation with no measurable thrust. The silica aerogel, however, has a significant impact on thrust saturation as

Ryan Durscher; Subrata Roy

2012-01-01

98

Damping Tollmien-Schlichting waves in a boundary layer using plasma actuators  

NASA Astrophysics Data System (ADS)

The response of a zero pressure gradient boundary layer modified by flow-wise oriented momentum injection similar to that of a plasma actuator is calculated using a two-dimensional (bi-global) stability analysis. It is found that the addition of momentum into the boundary layer has a significant impact on Tollmien-Schlichting waves, which may be damped by up to two orders of magnitude. Changes to the exponential growth rate of the perturbations are also measured. These stabilizing effects are largely due to the momentum addition modifying the downstream boundary layer profiles, but localized stabilization effects are also noted. The relative stabilization of the TS wave appears to be a linear function with respect to the ratio of the plasma-induced wall jet velocity under quiescent conditions and the free-stream velocity for lower levels of plasma actuation (i.e. velocity ratios less than 0.1). For higher levels of plasma actuation, the relative stabilization of the TS wave appears to be exponential with respect to the total momentum addition to the boundary layer by the plasma actuator.

Riherd, Mark; Roy, Subrata

2013-12-01

99

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

100

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

NASA Astrophysics Data System (ADS)

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.

Mertz, Benjamin; Corke, Thomas

2010-11-01

101

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

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

102

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

E-print Network

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

Roy, Subrata

103

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

NASA Astrophysics Data System (ADS)

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 Cm and Cg can be gotten by the calculation of the electric field, with the method of undetermined coefficients, while the value of Capacitance Cd is determined from the charge-voltage (Q-V) plot, also called Lissajous figure. It is found that the value of Capacitance Cd 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.

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

2014-05-01

104

Noise reduction in a heated Mach 1.3 jet using plasma actuators  

Microsoft Academic Search

Heating capabilities have recently been added to the free jet facility at the Gas Dynamics and Turbulence Laboratory (GDTL) of the Ohio State University using a storage-based off-line electric heater. This addition makes it possible to test the effectiveness of the localized arc filament plasma actuators (LAFPAs) for the purpose of either noise mitigation or mixing enhancement over a wide

Martin Kearney-Fischer; Mo Samimy

2009-01-01

105

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

NASA Technical Reports Server (NTRS)

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.

Brown, Clifford A.

2011-01-01

106

Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields  

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

107

Effect of external flow velocity on momentum transfer of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

An experimental study is performed towards identifying cross-talk effects between DBD plasma actuators and external flow. An actuator is positioned in a boundary layer operated in a range of free stream velocities from 0 to 60 m/s, and tested both in counter-flow and co-flow forcing configurations. Electrical measurements are used for estimating the power consumption and the discharge formation is visualized using a CCD camera. The actuator's force is measured using a sensitive load cell. Results show the power consumption is constant for different flow velocities and actuator configurations. The plasma light emission is constant for co-flow forcing but shows a trend of increasing intensity with counter-flow forcing for increasing free stream velocities. The measured force is constant for free stream velocities larger than 20 m/s, with same magnitude and opposite direction for the counter-flow and co-flow configurations. In quiescent conditions, the measured force is smaller due to the change in wall shear force by the induced wall-jet. An analytical model is presented to estimate the influence of external flow on the actuator force. It is based on conservation of momentum through the ion-neutral collisional process while including the contribution of the wall shear force. Satisfactory agreement is found between the prediction of the model and experimental data at different external flow velocities.

Pereira, Ricardo; Ragni, Daniele; Kotsonis, Marios

2014-09-01

108

The use of plasma actuators for bluff body broadband noise control  

NASA Astrophysics Data System (ADS)

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.

Li, Yong; Zhang, Xin; Huang, Xun

2010-08-01

109

Separation control in low pressure turbines using plasma actuators with passing wakes  

NASA Astrophysics Data System (ADS)

A Dielectric Barrier Discharge (DBD) plasma actuator is operated in flow over the suction surface of a Pack-B Low Pressure Turbine (LPT) airfoil at a Reynolds number of 50,000 (based on exit velocity and suction surface length) and inlet free-stream turbulence intensity of 2.5%. Preliminary characterization studies were made of the effect of varying actuator pulsing frequency and duty cycle, actuator edge effects, and orientation of the actuator with the flow. Flow control was demonstrated with the actuator imparting momentum opposite to the stream-wise flow direction, showing that it is possible to use disturbances alone to destabilize the flow and effect transition. No frequencies of strong influence were found over the range tested, indicating that a broad band of effective frequencies exists. Edge effects were found to considerably enhance separation control. Total pressure measurements of the flow without passing wakes were taken using a glass total-pressure tube. Corrections for streamline displacement due to shear and wall effects were made, and comparisons with previous hot-wire measurements were used to validate data. Performance features of conventional two-electrode and a novel three-electrode actuator configuration were compared. Hot-wire anemometry was used to take time-varying ensemble-averaged near-wall velocity measurements of the flow with periodic passing wakes. Corrections were made for near-wall effects, temperature effects, and interference of the electric field. The wakes were generated by a wake generator mechanism located upstream of the airfoil passage. The near-suction-surface total pressure field (flow without wakes) and velocity field (flow with wakes) in the trailing part of the airfoil passage, and the wall-normal gradient of these quantities, were used to demonstrate effective prevention of flow separation using the plasma actuator. Both flows (with and without passing wakes) showed fully attached flow (or very thin separation zones) when the actuator was activated. The flow with passing wakes and the actuator on showed relatively little time variation in the boundary layer, and qualitative similarities to the corresponding flow without passing wakes and with the actuator on were noted.

Burman, Debashish

110

Plasma bolometry using a multislit shutter with piezoelectric actuator  

NASA Astrophysics Data System (ADS)

We offer to apply a shutter with a piezoelectric bimorph actuator as a modulator of radiation and particle fluxes. Such shutters may be useful to provide measurements in steady state regimes of tokamaks and stellarators because they allow one to avoid amplifier drifts and to simplify diagnostics calibration. Signal modulation makes it possible to apply the lock-in amplification technique, increasing the sensitivity and reducing the neutron doze collected by sensors. Experiments with pyroelectric sensors (LiTaO3) at 350 Hz modulation frequency have demonstrated the detection limit at 30 Hz equal to 15 ?W/cm2, which is comparable to metallic bolometers.

Kuteev, Boris V.; Outkine, Andrew A.; Gabdullin, Pavel G.; Kostrioukov, Artem Yu.; Kapralov, Vladimir G.

2004-10-01

111

Low voltage driven piggy-back actuator of hard disk drives  

Microsoft Academic Search

Fine positioning by a piggy-back actuator is essential in order to increase the recording density of hard disk drives (HDDs). We therefore developed a piggy-back actuator that generates a 1.4-?m displacement at 5 V. This displacement is twice as large as that of the usual piggy-back actuators. This actuator satisfies all requirements for HDDs including track density of 30 kilotracks

I. Naniwa; S. Nakamura; S. Saegusa; K. Sato

1999-01-01

112

Plasma actuator electron density measurement using microwave perturbation method  

NASA Astrophysics Data System (ADS)

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.

Mirhosseini, Farid; Colpitts, Bruce

2014-07-01

113

Sensors and Actuators A 121 (2005) 162171 A slim type microvalve driven by PZT films  

E-print Network

. Passiveandactivemicrovalveshavebeenactivelyresearched. Passive microvalves are checked valves or flap valves that regulate fluid flow in one direction- mally actuated inline microvalve, for which actuators use the high volumetric expansion of a sealed on a Si membrane for ac- tuating a normally closed thermal bimorph. But the thermal bimorph can actuate

Kim, Jongwon

114

Performance enhancement of IPMC actuator by plasma surface treatment  

Microsoft Academic Search

IPMC (ionic polymer metal composite) is composed of ionic polymer and metal electrodes on both surfaces of the polymer. In this study, we changed the surface morphology of the ionic polymer by using plasma treatment. Plasma treatment made needle-shaped microstructures on the surface of the polymer and the microstructures helped to form a thicker uniform metal electrode which is deposited

Seong Jun Kim; In Taek Lee; Yong Hyup Kim

2007-01-01

115

Generation of prescribed strain waves in an elastic bar by use of piezoelectric actuators driven by a linear power amplifier  

Microsoft Academic Search

The problem of generating prescribed strain waves in an elastic bar by means of a pair of piezoelectric actuators driven in phase by a linear power amplifier was considered theoretically and experimentally. The power amplifier was characterized by its DC voltage gain and 3dB cut-off frequency unloaded, and by its output resistance and inductance. With the assumption of one-dimensional (1D)

A. Jansson; U. Valdek; B. Lundberg

2007-01-01

116

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

Microsoft Academic Search

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

Sangki Lee; Kwang J. Kim

2006-01-01

117

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

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

118

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

PubMed

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

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

2014-02-21

119

Beam-driven acceleration in ultra-dense plasma media  

NASA Astrophysics Data System (ADS)

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.

Shin, Young-Min

2014-09-01

120

Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields  

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

121

Design of piezostack-driven trailing-edge flap actuator for helicopter rotors  

NASA Astrophysics Data System (ADS)

A piezoelectric actuator is investigated to activate a trailing-edge flap mechanism for helicopter vibration suppression. This paper presents the development of a piezostack-based actuator with a new stroke amplification mechanism. A double-lever amplification concept is introduced, which is a dual-stage lever-fulcrum stroke amplifier that extends the capability of the conventional lever-fulcrum mechanism. Both the design and fabrication of the on-blade trailing-edge flap actuator are addressed. The first prototype actuator was designed and fabricated using two piezostack segments. An amplification factor of 19.4 and constant response covering up to 8/rev (52.3 Hz) were measured under non-rotating conditions, and a consistent actuator displacement of up to 600g of centrifugal loading was experimentally obtained for the vacuum spin testing. A major design refinement resulted in the second prototype actuator that uses five piezostack segments. The bench-top testing of the second prototype actuator showed 1.87 mm (73.7 mil) of free stroke, and uniform performance of up to 150 Hz. In vacuum spin testing, the second prototype actuator showed approximately 13% loss in actuation stroke at 700g of centrifugal loading, and no further degradation at 115% overloading condition. The double-lever amplification mechanism with piezostack actuation showed the potential for operation in a rotating environment.

Lee, Taeoh; Chopra, Inderjit

2001-02-01

122

Magnetized Target Fusion Driven by Plasma Liners  

NASA Technical Reports Server (NTRS)

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.

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

123

Numerical study of boundary layer separation control using magnetogasdynamic plasma actuators  

NASA Astrophysics Data System (ADS)

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.

Kalra, Chiranjeev S.; Shneider, Mikhail N.; Miles, Richard B.

2009-10-01

124

Numerical study of boundary layer separation control using magnetogasdynamic plasma actuators  

SciTech Connect

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.

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

125

Dynamics of Lane Formation in Driven Binary Complex Plasmas  

SciTech Connect

The dynamical onset of lane formation is studied in experiments with binary complex plasmas under microgravity conditions. Small microparticles are driven and penetrate into a cloud of big particles, revealing a strong tendency towards lane formation. The observed time-resolved lane-formation process is in good agreement with computer simulations of a binary Yukawa model with Langevin dynamics. The laning is quantified in terms of the anisotropic scaling index, leading to a universal order parameter for driven systems.

Suetterlin, K. R.; Ivlev, A. V.; Raeth, C.; Thomas, H. M.; Rubin-Zuzic, M.; Morfill, G. E. [Max Planck Institute for Extraterrestrial Physics, 85741 Garching (Germany); Wysocki, A.; Loewen, H. [Heinrich-Heine-Universitaet Duesseldorf, 40225 Duesseldorf (Germany); Goedheer, W. J. [FOM-Institute for Plasma Physics Rijnhuizen, 3430 BE Nieuwegein (Netherlands); Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Petrov, O. F. [Joint Institute for High Temperatures, 125412 Moscow (Russian Federation)

2009-02-27

126

RLS-ESN based PID control for rehabilitation robotic arms driven by PMTS actuators  

Microsoft Academic Search

To drive a single joint of rehabilitation robotic arm, we propose a new PM-TS actuator comprising a Pneumatic Muscle (PM) and a Torsion Spring (TS). Unlike the traditional agonist\\/antagonist PM actuator, the PM is arranged in appropriate place as agonist and the torsion spring provides opposing torque as antagonist in the proposed actuator. The 1-DOF and 2-DOF rehabilitation robotic arm

Jun Wu; Jian Huang; Yongji Wang; Kexin Xing

2010-01-01

127

Nonlinear dynamics of curved IPMC actuators undergoing electrically driven large deformations  

Microsoft Academic Search

The nonlinear dynamics of curved ionic polymer–metal composite (IPMC) actuators having large tip displacement and periodical jumping locomotion was investigated experimentally. Through snap-through phenomena, the actuator generates much larger tip displacement and shows abrupt jumps in the transitions of upswings and downswings with low input energy. Two curved IPMC cantilever actuators having two different constant curvatures of 0.01 mm and

Jin-Han Jeon; Choonghee Jo; Il-Kwon Oh

2012-01-01

128

Active control of massively separated high-speed/base flows with electric arc plasma actuators  

NASA Astrophysics Data System (ADS)

The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations of actuator geometry in the supersonic base flow determined that inclined cavity and normal cavity actuators positioned on the base near the base edge could produce significant disturbances in the shear layer. The disturbances were able to be tracked in time with phase-locked schlieren imaging and particle image velocimetry (PIV). The final set of flow control experiments were therefore performed with an eight-actuator base using the inclined cavity actuator geometry. The actuators were able to cause moderate influences on the axisymmetric shear layer velocity profile and base pressure. The most substantial changes to the shear layer and base pressure were noted for the highest current and duty cycle tests. At 1 A and 20% duty cycle, the base pressure was reduced by 3.5%. Similar changes were noted for all modes and a range of frequencies from about 10-30 kHz. Increases in duty cycle between 4% and 20% caused a nearly linear decrease in base pressure. Analysis of the shear layer velocity profiles acquired through PIV show a local thickening of the shear layer in the region of the disturbances caused by the actuator. A slight increase in thickness was also observed away from the disturbance. Disturbances were able to be tracked at all frequencies and translated along the shear layer at a convective velocity of 430 +/- 20 m/s. A fairly clear trend of increasing velocity disturbance amplitude correlating to increasing base pressure changes was noted. Moreover, the ability of the disturbances to stay well organized further down the shear layer also appears to be a significant factor in the actuators' effect on base pressure. Consistent with these observations, it appears that increased duty cycle causes increased shear layer disturbance amplitudes. The use of PIV has enabled substantial insight to be gained into the effects of the actuators on the ensemble-averaged flow field and on the variability of the instantaneous flow field with and without control. A sensitive bimodal recirculation region behavior was found in the no-control flow field tha

DeBlauw, Bradley G.

129

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

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

130

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

131

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

SciTech Connect

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S. [Ecole Nationale d'Ingenieurs de Monastir, Monastir 5019 (Tunisia)

2010-08-15

132

One-dimensional analytical model development of a plasma-based actuator  

NASA Astrophysics Data System (ADS)

This dissertation provides a method for modeling the complex, multi-physics, multi-dimensional processes associated with a plasma-based flow control actuator, also known as the SparkJet, by using a one-dimensional analytical model derived from the Euler and thermodynamic equations, under varying assumptions. This model is compared to CFD simulations and experimental data to verify and/or modify the model where simplifying assumptions poorly represent the real actuator. The model was exercised to explore high-frequency actuation and methods of improving actuator performance. Using peak jet momentum as a performance metric, the model shows that a typical SparkJet design (1 mm orifice diameter, 84.8 mm3 cavity volume, and 0.5 J energy input) operated over a range of frequencies from 1 Hz to 10 kHz shows a decrease in peak momentum corresponding to an actuation cutoff frequency of 800 Hz. The model results show that the cutoff frequency is primarily a function of orifice diameter and cavity volume. To further verify model accuracy, experimental testing was performed involving time-dependent, cavity pressure and arc power measurements as a function of orifice diameter, cavity volume, input energy, and electrode gap. The cavity pressure measurements showed that pressure-based efficiency ranges from 20% to 40%. The arc power measurements exposed the deficiency in assuming instantaneous energy deposition and a calorically perfect gas and also showed that arc efficiency was approximately 80%. Additional comparisons between the pressure-based modeling and experimental results show that the model captures the actuator dependence on orifice diameter, cavity volume, and input energy but over-estimates the duration of the jet flow during Stage 2. The likely cause of the disagreement is an inaccurate representation of thermal heat transfer related to convective heat transfer or heat loss to the electrodes.

Popkin, Sarah Haack

133

A New Inductively Driven Plasma Generator (IPG) Source  

NASA Astrophysics Data System (ADS)

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.

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

2011-11-01

134

Magnetized Target Fusion Driven by Plasma Liners  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

135

Simulation of an asymmetric single dielectric barrier plasma actuator  

SciTech Connect

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.

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

2005-10-15

136

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

137

Energy Analysis of Piezoelectric-Actuated Structures Driven by Linear Amplifiers  

Microsoft Academic Search

Energy expressions for a piezoelectric actuator coupled to a resonant mechanical load are analyzed for the purpose of determining the energy requirements of controlled structures. The analysis illustrates that the energy dissipated within the linear amplifier is a function of four parameters: the driving frequency, the piezoelectric coupling coefficient, the relative stiffness of the actuator and load, and the amplifier

Donald J. Leo

1999-01-01

138

Resonant control of structural vibration using charge-driven piezoelectric actuators  

Microsoft Academic Search

Driving piezoelectric actuators by charge, or current rather than voltage is known to significantly reduce the hysteretic nature of these actuators. Although this feature of piezoelectric transducers has been known to the researchers for some time, still voltage amplifiers are being used as the main driving mechanism for piezoelectric devices. This is due to the perceived difficulty in building charge\\/current

S. O. Reza Moheimani; Benjamin J. G. Vautier

2005-01-01

139

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

PubMed Central

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.

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

2014-01-01

140

Direct Measurement of Wall-Shear Stress of Plane Shear Layer with Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

One of the useful ways to measure the effect of the flow control devise is to use the wall-shear stress sensor to measure the wall-shear stress directly. The sensor used in this paper measures the wall-shear stress, which is reduced by the flow control devise. In this paper, the wall-shear stress of the plane shear layer with the plasma synthetic jet actuator (PSJA) is investigated. PSJA is a flow control device composed of electrodes with A.C. signal. The actuator uses electrohydrodynamic (EHD) effect and induces flow around the electrodes. PSJA has great advantage such as miniaturization, maintenance free, and easy to control compared to other actuators. In this paper, the wall-shear stress of plane shear layer in a low-speed turbulent wind tunnel is observed to measure the effect of the PSJA. The results show that the PSJA changes the flow condition of shear layer by accelerating the flow in shear layer. The wall-shear stress reduces and increases according to the displacement of the wall-shear stress sensor and the actuator.

Higuchi, Takehiro; Ogawara, Kakuji; Mochizuki, Shinsuke

141

Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

142

Plasma synthetic jet actuator: electrical and optical analysis of the discharge  

NASA Astrophysics Data System (ADS)

Active flow control is based on the development of robust actuators which are reliable, small and easy to integrate. A promising actuator referred to as plasma synthetic jet actuator produces a synthetic jet with high exhaust velocities and holds the promise of enabling high-speed flows. With this high velocity jet, it is possible to reduce fluid phenomena such as transition and turbulence, thus making it possible to increase an aircraft's performance whilst at the same time reducing its environmental impact. This high velocity jet is produced by a pulsed discharge in a microcavity. In this paper, we focus on the properties of the discharge in order to understand the functioning of the actuator. In the first part an electrical description of the discharge in presented. Afterwards, optical measurements (optical emission spectroscopy and ICCD photograph) enable the determination of temperature, volume and duration of the discharge. At the end of the paper we present an electrical model of the discharge, which can be obtained both from electrical measurements and from macroscopic properties of the discharge (temperature, volume). This electrical model can easily be included in electrical simulation software.

Belinger, A.; Naudé, N.; Cambronne, J. P.; Caruana, D.

2014-08-01

143

A neuromusculoskeletal model of the human lower limb: towards EMG-driven actuation of multiple joints in powered orthoses.  

PubMed

This paper presents a novel neuromusculoskeletal (NMS) model of the human lower limb that uses the electromyo-graphic (EMG) signals from 16 muscles to estimate forces generated by 34 musculotendon actuators and the resulting joint moments at the hip, knee and ankle joints during varied contractile conditions. Our proposed methodology allows overcoming limitations on force computation shown by currently available NMS models, which constrain the operation of muscles to satisfy joint moments about one single degree of freedom (DOF) only (i.e. knee flexion-extension). The design of advanced human machine interfaces can benefit from the application of our proposed multi-DOF NMS model. The better estimates of the human internal state it provides with respect to single-DOF NMS models, will allow designing more intuitive human-machine interfaces for the simultaneous EMG-driven actuation of multiple joints in lower limb powered orthoses. PMID:22275641

Sartori, Massimo; Reggiani, Monica; Lloyd, David G; Pagello, Enrico

2011-01-01

144

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

145

Feedback control of slowly-varying transient growth by an array of plasma actuators  

NASA Astrophysics Data System (ADS)

Closed-loop feedback control of boundary layer streaks embedded in a laminar boundary layer and experiencing transient growth, which is inherent to bypass boundary layer transition, is experimentally investigated. Streaky disturbances are introduced by a spanwise array of cylindrical roughness elements, and a counter disturbance is provided by a spanwise array of plasma actuators, which are capable of generating spanwise-periodic counter rotating vortices in the boundary layer. Feedback is provided by a spanwise array of shear stress sensors. An input/output model of the system is obtained from measurements of the boundary layer response to steady forcing, and used to design and analyze a proportional-integral controller, which targets a specific spanwise wavenumber of the disturbance. Attention is directed towards a quasi-steady case in which the controller update is slower than the convective time scale. This choice enables addressing issues pertinent to sensing, actuation, and control strategy that are also relevant to the control of unsteady disturbances but without the full complexity of transient effects. The feedback controller and plasma actuators perform well, attenuating the streamwise streaks both in the vicinity of the sensors and farther downstream. The controller remains effective for a range of off-design flow conditions, such as when the free-stream velocity is varied.

Hanson, Ronald E.; Bade, Kyle M.; Belson, Brandt A.; Lavoie, Philippe; Naguib, Ahmed M.; Rowley, Clarence W.

2014-02-01

146

Current driven instability in collisional dusty plasmas  

SciTech Connect

The current driven electromagnetic instability in a collisional, magnetized, dusty medium is considered in the present work. It is shown that in the presence of the magnetic field aligned current, the low-frequency waves in the medium can become unstable if the ratio of the current to the ambient field is larger than the light speed times the wave number. The growth rate of the instability depends upon the ratio of the Alfven to the dust cyclotron frequency as well as on the ratio of the current density J to the dust charge density Zen{sub d}, where Z is the number of electronic charge on the grain, e is the electron charge, and n{sub d} is the dust number density. The typical growth rate of this instability is on the order of Alfven frequency which compares favorably with the electrostatic, cross-field current driven, Farley-Buneman instability and thus could play an important role in the Earth's ionosphere.

Pandey, B. P. [Department of Physics, Macquarie University, Sydney, New South Wales 2109 (Australia); Vladimirov, S. V.; Samarian, A. [Complex Systems, School of Physics, University of Sydney, New South Wales 2006 (Australia)

2009-11-15

147

Micro Actuators Electrostatic actuator  

E-print Network

film #12;W for PVDF film #12;Electrical to Mechanical l W t #12;#12;Bimorph Piezoelectric Actuators #12Micro Actuators ·Electrostatic actuator - comb drive actuator ·Magnetic actuator ·Thermal actuator ·Piezoelectric actuator ·Shape memory alloy actuator ·Pneumatic actuator Ref: AIP Handbook of Modern Sensors http

Leu, Tzong-Shyng "Jeremy"

148

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

E-print Network

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 ...

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

2013-01-01

149

Study of Transient and Unsteady Effects of Plasma Actuation in Transitional Flow over an SD7003 Airfoil  

E-print Network

at the trailing edge. Nomenclature c = Chord length Cd = Coefficient of drag Cf = Coefficient of skin friction Cl = Coefficient of lift Cm = Coefficient of moment Cp = Coefficient of pressure Dc = Nondimensional plasma force and plunging. The effects of Dielectric Barrier Discharge (DBD) plasma actuation as a flow control device have

Roy, Subrata

150

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

E-print Network

as dielectric barrier discharge actuators (or OAUGDPTM , one atmosphere uniform glow discharge plasma1 of a high voltage, high frequency AC, a region of dielectric barrier discharge plasma is created­9 They are commonly produced by using an oscillating diaphragm mounted in a cavity that is embedded flush

Jacob, Jamey

151

Design of piezostack-driven trailing-edge flap actuator for helicopter rotors  

Microsoft Academic Search

A piezoelectric actuator is investigated to activate a trailing-edge flap mechanism for helicopter vibration suppression. This paper presents the development of a piezostack-based actuator with a new stroke amplification mechanism. A double-lever amplification concept is introduced, which is a dual-stage lever-fulcrum stroke amplifier that extends the capability of the conventional lever-fulcrum mechanism. Both the design and fabrication of the on-blade

Taeoh Lee; Inderjit Chopra

2001-01-01

152

Experimental Study of Driven Magnetic Relaxation in a Laboratory Plasma  

NASA Astrophysics Data System (ADS)

The physics goal of the Driven Relaxation Experiment (DRX) is to form and sustain simply-connected driven-relaxed plasmas above the first Jensen-Chu linear resonance of the force-free equation (where the first resonance is the ``flipped'' Rosenbluth- Bussac spheromak). As shown recently by Tang & Boozer (PRL, 2005), the linear resonances are regularized in partially relaxed systems, thus removing the energy barriers which have been thought to constrain relaxed states to exist only below the first resonance. DRX will apply an ``over-driven'' boundary condition at the coaxial gun source, with ?gun 30 m-1 3?1. The DRX power system (10 kV, 125 kJ) will form and sustain the ˜10 eV plasma for about 0.5 ms, which is about 10 Sweet-Parker reconnection times and sufficient for the plasma to reach a driven-relaxed steady-state. We will measure the 2D structure of the equilibrium magnetic field and compare it with the first several linear eigenmodes of the force-free equation, and subsequently study the k-spectrum of the magnetic energy as well as the dynamics of relaxation. Other topics we will study include magnetic flux amplification and the role of boundary elongation on equilibrium/stability. Better understanding of these issues could lead to new ideas for confinement configurations. This poster will provide an overview of DRX and first experimental data. Supported by the LANL LDRD Program.

Hsu, S.; Madziwa-Nussinov, T.; Sirajuddin, D.; Light, M.

2007-11-01

153

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

154

Scaling Laws for Plasma Jets-Driven Liner Implosions  

NASA Astrophysics Data System (ADS)

Plasma jets driven magnetoinertial fusion (PJMIF) is a fusion energy concept which consists of an imploding plasma liner that shock heats and compresses a magnetized target plasma. The liner can be formed by the merging of a cylindrical or spherical distribution of plasma jets, which are launched by a salvo of plasma accelerators. Confinement of the target is inertial, with the thermal conduction suppressed by the magnetic field. Imploding plasma liners can also be an inexpensive path to creating high energy density (HED) plasmas in the laboratory with cm and ?s spatial and temporal scales, respectively. In this poster, we use analytical and smoothed particle hydrodynamic (SPH) modeling to develop scaling relations for peak pressure and confinement time for liner collapse onto a cavity, and for select cases with an adiabatic target. The primary goal is to estimate the initial conditions required for plasma liners in reaching 0.1 to 1 Mbar pressure using imploding shocks. We will use SPH to study selected 1D to 3D cases, with the latter to include the formation of a liner from discrete jets. Scaling relations are developed for peak conditions as a function of the initial jet conditions, specifically the number of jets, thermodynamic properties, and dimensions. We also discuss possible PJMIF scenarios that may be capable of reaching interesting fusion gains (G ˜ 5--20).

Cassibry, J.; Thompson, S.; Hsu, S.; Witherspoon, D.

2008-11-01

155

Plasma morphology and induced airflow characterization of a DBD actuator with serrated electrode  

NASA Astrophysics Data System (ADS)

Plasma morphology and airflow induced by a dielectric barrier discharge (DBD) actuator, whose exposed electrode geometry is designed with a serrated configuration, are investigated in quiescent air and compared with a DBD actuator consisting of electrodes designed with a standard linear strip configuration. ICCD imaging, electrical measurements and three-component laser Doppler velocimetry were carried out to compare various features of these two actuators. With the serrated configuration, ICCD images of the discharge show that streamers are bent, whereas with the linear configuration they are straight. These curved streamers induce a three-dimensional flow topology, which is confirmed by friction line visualization and velocity measurements. Whereas a two-dimensional wall-jet is induced with the linear configuration, a transverse velocity component is measured with the serrated configuration, implying the creation of spanwise-periodic vorticity. Phase-averaged velocity measurements allow the temporal variation of this transverse velocity to be highlighted. On both sides of a tooth, it has qualitatively the same variation as the longitudinal velocity with respect to the negative or positive half-cycles of the high voltage signal. Moreover, with the same electrical operating parameters, the measured longitudinal velocity was higher, particularly at the tips.

Joussot, R.; Leroy, A.; Weber, R.; Rabat, H.; Loyer, S.; Hong, D.

2013-03-01

156

Spectroscopic investigation of wave driven microwave plasmas  

SciTech Connect

Large H atom line broadening was found throughout the volume of surface wave generated He-H{sub 2} and H{sub 2} microwave plasmas at low pressures. The measured Doppler temperatures corresponding to the H{sub b}eta, H{sub g}amma, H{sub d}elta, H{sub e}psilon, and H{sub z}eta line profiles were found to be higher than the rotational temperature of the hydrogen molecular Fulcher-alpha band and the Doppler temperature of the 667.1 nm singlet He line. No excessive broadening has been found. The Lorentzian and Gaussian widths as determined by fitting the spectral lines with a Voigt profile increase with the principal quantum number of the upper level. In contrast, no such dependence for the Gaussian width has been observed in an Ar-H{sub 2} discharge. No population inversion has been observed from measurements of the relative intensities of transitions within the Balmer series.

Wijtvliet, R. [Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Eindhoven University of Technology, Eindhoven (Netherlands); Felizardo, E.; Tatarova, E.; Dias, F. M.; Ferreira, C. M. [Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Nijdam, S.; Veldhuizen, E. V.; Kroesen, G. [Eindhoven University of Technology, Eindhoven (Netherlands)

2009-11-15

157

Beam-driven acceleration in ultra-dense plasma media  

SciTech Connect

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.

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

158

Development of a plasma driven permeation experiment for TPE  

SciTech Connect

Experiments on retention of hydrogen isotopes (including tritium) at temperatures less than 800 ?C have been carried out in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory [1,2]. To provide a direct measurement of plasma driven permeation in plasma facing materials at temperatures reaching 1000 ?C, a new TPE membrane holder has been built to hold test specimens (=1 mm in thickness) at high temperature while measuring tritium permeating through the membrane from the plasma facing side. This measurement is accomplished by employing a carrier gas that transports the permeating tritium from the backside of the membrane to ion chambers giving a direct measurement of the plasma driven tritium permeation rate. Isolation of the membrane cooling and sweep gases from TPE’s vacuum chamber has been demonstrated by sealing tests performed up to 1000 ?C of a membrane holder design that provides easy change out of membrane specimens between tests. Simulations of the helium carrier gas which transports tritium to the ion chamber indicate a very small pressure drop (~700 Pa) with good flow uniformity (at 1000 sccm). Thermal transport simulations indicate that temperatures up to 1000 ?C are expected at the highest TPE fluxes.

Dean Buchenauer; Robert Kolasinski; Masa Shimada; David Donovan; Dennis Youchison; Brad Merrill

2014-04-01

159

Modeling and optimization of a novel two-axis mirror-scanning mechanism driven by piezoelectric actuators  

NASA Astrophysics Data System (ADS)

Mirror-scanning mechanisms are a key component in optical systems for diverse applications. However, the applications of existing piezoelectric scanners are limited due to their small angular travels. To overcome this problem, a novel two-axis mirror-scanning mechanism, which consists of a two-axis tip-tilt flexure mechanism and a set of piezoelectric actuators, is proposed in this paper. The focus of this research is on the design, theoretical modeling, and optimization of the piezoelectric-driven mechanism, with the goal of achieving large angular travels in a compact size. The design of the two-axis tip-tilt flexure mechanism is based on two nonuniform beams, which translate the limited linear output displacements of the piezoelectric actuators into large output angles. To exactly predict the angular travels, we built a voltage-angle model that characterizes the relationship between the input voltages to the piezoelectric actuators and the output angles of the piezoelectric-driven mechanism. Using this analytical model, the optimization is performed to improve the angular travels. A prototype of the mirror-scanning mechanism is fabricated based on the optimization results, and experiments are implemented to test the two-axis output angles. The experimental result shows that the angular travels of the scanner achieve more than 50 mrad, and the error between the analytical model and the experiment is about 11%. This error is much smaller than the error for the model built using the previous method because the influence of the stiffness of the mechanical structure on the deformation of the piezoelectric stack is considered in the voltage-angle model.

Jing, Zijian; Xu, Minglong; Feng, Bo

2015-02-01

160

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

SciTech Connect

Understanding the behavior of three-dimensional plasmas around a pulsed dc actuator can be useful for its efficient operation in many applications. The effect of such actuators is studied using a self-consistent multibody system of neutral oxygen species and its plasma. The equations governing the motion of charged species are solved with the drift diffusion approximation. The electrostatic potential is computed from Poisson's equation. The electric field and ionization level are the highest close to the junction of electrodes and dielectric. The plasma body force thus generated also follows a similar characteristic. Results also show some dc corona instabilities. The temporal average of such force shows mostly acceleration from anode to cathode above the actuator.

Singh, Kunwar Pal; Roy, Subrata [Computational Plasma Dynamics Laboratory and Test Facility, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2008-05-15

161

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

NASA Astrophysics Data System (ADS)

Comprehensive understanding of energetic-ion-driven global instabilities such as Alfvén 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.

Toi, K.; Ogawa, K.; Isobe, M.; Osakabe, M.; Spong, D. A.; Todo, Y.

2011-02-01

162

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

NASA Technical Reports Server (NTRS)

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.

Hansen, Irving G.

1990-01-01

163

Experimental study of driven magnetic relaxation in a laboratory plasma  

NASA Astrophysics Data System (ADS)

The Driven Relaxation Experiment (DRX) has been built at LANL to investigate the possibility of exploiting resonances in the nonlinear force-free equation [1] to optimize magnetic flux amplification and current multiplication for driven-relaxed spheromak-like plasmas, and to explore the application of these ideas to plasma astrophysics problems [2]. It is also our goal to see whether relaxed states with ?> ?1 can be formed and sustained. The experiment uses a planar magnetized coaxial gun (100--180 kA, 1--7 mWb) to generate driven- relaxed plasmas within a cylindrical flux-conserving boundary (0.9 m diameter). Unique features of DRX include high ?gun up to 3?1, and a continuously adjustable boundary elongation. The gun is powered by a 3- stage capacitor bank to form (10 kV, 500 ?F) and sustain (5 kV, 8 mF) the plasma for up to 500 ?s, corresponding to >10 Sweet-Parker times which allows the plasma to reach a quasi-steady-state. The primary diagnostic is a 48- channel 2D magnetic probe array that will map out a poloidal cross-section of the magnetic field configuration at one toroidal position. The full equilibrium magnetic field will be constructed using a combination of the experimental data and a nonlinear force-free equilibrium solver. We will present details of the experimental setup and the first experimental data. Supported by LANL LDRD. [1] Tang & Boozer, PRL 94, 225004 (2005); PRL 98, 175001 (2007) [2] Tang, ApJ 679, 1000 (2008).

Hsu, S. C.; Tang, X. Z.

2008-11-01

164

Response of a circular cylinder wake to a symmetric actuation by non-thermal plasma discharges  

NASA Astrophysics Data System (ADS)

In this study, the flow past a circular cylinder is manipulated by two plasma discharges placed on both sides of the model (at ±50°). A parametric investigation by force balance is conducted to define the sensitivity of the flow field to unsteady perturbations imparted by plasma actuators (dielectric barrier discharge) at 15.6 m/s ( Re D = 40,000). Effects of simple sinusoidal waveform, burst modulation and amplitude modulation are compared for low-frequency excitations. Regardless of the excitation mode, the cylinder experiences a large increase in the drag coefficient. The larger drag increase is observed for excitation related to the lock-on regime. Fast PIV measurements and triple decomposition by proper orthogonal decomposition are performed to extract the dynamical changes in the cylinder wake and to discriminate the control effects on the coherent and fluctuating turbulence. As expected, the control principally acts on the coherent flow structures. When forced, the vortices form closer to the base of the cylinder regardless of the actuation mode. This results in the drag increase observed by force measurements. The effectiveness of burst modulation is also due to the suppression of irregular shedding that is observed in the natural flow sequence and to a high level of correlation between the upper and lower vortex shedding. Finally, flow visualizations indicate that similar results can be obtained at higher Reynolds number ( Re D = 128,000, 50 m/s).

Benard, N.; Moreau, E.

2013-02-01

165

Safety active catheter with multi-segments driven by innovative hydro-pressure micro actuators  

Microsoft Academic Search

We proposed and developed an innovative active catheter with multi-segments that can bend in the narrow blood vessel. Micro hydraulic actuator system based on new principle has been developed by the authors. Moreover, new three dimensional micro fabrication method named \\

Koji IKUTA; Hironobu ICHIKAWA; Katsuya SUZUKI; Takahiro YAMAMOTO

2003-01-01

166

Development of a search type rescue robot driven by pneumatic actuator  

Microsoft Academic Search

Recently, the large earthquake including Hanshin-Awaji (Kobe) Earthquake has occurred. A lot of lives have been lost due to these earthquakes. In order to find and save victims even one, many researches and developments of the rescue robot have been done. In such studies, most of the rescue robot used the electric actuator for travelling. In those cases, there is

Kengo Harihara; S. Dohta; T. Akagi; Feng Zhang

2010-01-01

167

A New Type of Plasma Wakefield Accelerator Driven By Magnetowaves  

SciTech Connect

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.

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

168

Energetic-particle-driven global instabilities in helical plasmas and comparison with tokamak plasmas  

NASA Astrophysics Data System (ADS)

Similarities and differences in energetic-particle-driven global instabilities such as Alfvén eigenmodes and their consequences for helical/ stellarator and tokamak plasmas are discussed through comparison with the data obtained in the Large Helical Device (LHD). In particular, this lecture stresses on the differences caused by the variations on the rotational transform profile and the two-dimensional or three-dimensional geometrical structure of the plasma equilibrium. Important and interesting issues left for future study are listed up.

Toi, Kazuo

2012-09-01

169

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

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. To address these challenging issues, the recently proposed adaptive robust control (ARC) is applied

Yao, Bin

170

Safety-Active Catheter with Multiple-Segments Driven by Micro-hydraulic Actuators  

Microsoft Academic Search

We proposed and developed an innovative active catheter with multi-segments that can bend in the narrow blood vessel. Micro\\u000a hydraulic actuator system based on new principle has been developed by the authors. Moreover, new micro fabrication method\\u000a named hybrid stereolithograpy (IH process) requiring any assemble process is introduced for leakage-free packaging catheter.\\u000a Total system with pressure control system was made.

Koji Ikuta; Hironobu Ichikawa; Katsuya Suzuki

2002-01-01

171

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

Microsoft Academic Search

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

Yoshitake Akiyama; Kikuo Iwabuchi; Yuji Furukawa; Keisuke Morishima

2008-01-01

172

Solar Wind Driven Plasma Fluxes from the Venus Ionosphere  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

173

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

NASA Astrophysics Data System (ADS)

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.

Gaitonde, D. V.; Samimy, M.

2011-09-01

174

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

SciTech Connect

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.

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

175

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

NASA Astrophysics Data System (ADS)

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 (Mj=0.9) jet. Twelve experiments with various forcing azimuthal modes (m =0, 1, and ±1) and temperatures (To/Ta=1.0, 1.4, and 2.0) at a fixed forcing Strouhal number (StDF=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.

Kearney-Fischer, M.; Kim, J.-H.; Samimy, M.

2009-09-01

176

Noise reduction in a heated Mach 1.3 jet using plasma actuators  

NASA Astrophysics Data System (ADS)

Heating capabilities have recently been added to the free jet facility at the Gas Dynamics and Turbulence Laboratory (GDTL) of the Ohio State University using a storage-based off-line electric heater. This addition makes it possible to test the effectiveness of the localized arc filament plasma actuators (LAFPAs) for the purpose of either noise mitigation or mixing enhancement over a wide range of temperatures. These actuators have been used successfully at GDTL in high Reynolds number, high-speed unheated jets. The facility consists of an axisymmetric jet of exit diameter 2.54 cm with different nozzle blocks and variable jet temperature in an anechoic chamber. Previous work with a Mach 0.9 jet has shown significant increases in noise reduction effectiveness with increasing temperature. The next step is to determine if and how this trend continues in supersonic heated jets. A number of combinations of forcing azimuthal mode and temperature ratio at a wide range of forcing frequencies are experimented in a perfectly-expanded Mach 1.3 axisymmetric jet to examine LAFPAs effectiveness for far-field noise mitigation. The preliminary results to be presented indicate that the trends observed in the previous work continue in this supersonic jet.

Kearney-Fischer, Martin; Samimy, Mo

2009-11-01

177

A compact and continuously driven supersonic plasma and neutral sourcea)  

NASA Astrophysics Data System (ADS)

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.

Asai, T.; Itagaki, H.; Numasawa, H.; Terashima, Y.; Hirano, Y.; Hirose, A.

2010-10-01

178

A compact and continuously driven supersonic plasma and neutral source.  

PubMed

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. PMID:21033984

Asai, T; Itagaki, H; Numasawa, H; Terashima, Y; Hirano, Y; Hirose, A

2010-10-01

179

A compact and continuously driven supersonic plasma and neutral source  

SciTech Connect

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.

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

180

Spherically symmetric simulation of plasma liner driven magnetoinertial fusion  

SciTech Connect

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.

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

181

Betatron radiation from a beam driven plasma source  

NASA Astrophysics Data System (ADS)

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.

Litos, M.; Corde, S.

2012-12-01

182

Betatron Radiation from a Beam Driven Plasma Source  

SciTech Connect

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.

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

2012-08-13

183

Distributed electrostatic micro actuator  

Microsoft Academic Search

A micro actuator that is called a distributed electrostatic actuator, because it consists of many driving units, and that is driven by electrostatic force is described. Each driving unit has wavelike electrodes, which are insulated and pull each other by the electrostatic force. The deformation of this actuator depends on the electrostatic force, the elasticity of the structure, and the

Motoharu Yamaguchi; Shuji Kawamura; Kazuyuki Minami; Masayoshi Esashi

1993-01-01

184

Experimental Study of Episodic Magnetically Driven Radiatively Cooled Plasma Jets  

NASA Astrophysics Data System (ADS)

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.

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

185

Photo-actuation of liquids for light-driven microfluidics: state of the art and perspectives.  

PubMed

Using light to control liquid motion is a new paradigm for the actuation of microfluidic systems. We review here the different principles and strategies to induce or control liquid motion using light, which includes the use of radiation pressure, optical tweezers, light-induced wettability gradients, the thermocapillary effect, photosensitive surfactants, the chromocapillary effect, optoelectrowetting, photocontrolled electroosmotic flows and optical dielectrophoresis. We analyze the performance of these approaches to control using light many kinds of microfluidic operations involving discrete pL- to ?L-sized droplets (generation, driving, mixing, reaction, sorting) or fluid flows in microchannels (valve operation, injection, pumping, flow rate control). We show that a complete toolbox is now available to control microfluidic systems by light. We finally discuss the perspectives of digital optofluidics as well as microfluidics based on all optical fluidic chips and optically reconfigurable devices. PMID:22864577

Baigl, Damien

2012-10-01

186

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

NASA Astrophysics Data System (ADS)

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

Joshi, Chan; Malka, Victor

2010-04-01

187

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

E-print Network

the power efficiency. Rather than using linear power amplifier [2], [8], our power supply uses power- marized. To improve the power efficiency, several plasma driving signals were tested on a real-time system the potential to reduce flow-induced noise generated during the takeoff and approach-to-landing of aircraft

Huang, Xun

188

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

NASA Technical Reports Server (NTRS)

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.

Likhanskii, Alexandre

2012-01-01

189

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

E-print Network

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams C. B. Schroeder, E of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator-charge force of a charged particle beam. Laser-driven plasma accelerators (LPAs) were first proposed in 1979

Geddes, Cameron Guy Robinson

190

Ion temperature gradient driven mode in presence of transverse velocity-shear in magnetized plasmas  

E-print Network

Ion temperature gradient driven mode in presence of transverse velocity-shear in magnetized plasmas flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma has significant effects on the linear Ion Tem- perature Gradient (ITG) mode also. In this paper, we

191

Numerical Simulation of Plasma Behavior in a Magnetic Nozzle of a Laser-plasma Driven Nuclear Electric Propulsion System  

Microsoft Academic Search

Numerical simulations of plasma behavior in a magnetic nozzle of a Laser-Plasma Driven Nuclear Electric Propulsion System are conducted. The propellant is heated and accelerated by the laser and expanded isotropically. The magnetic nozzle is a combination of solenoidal coils and used to collimate and guide the plasma to produce thrust. Simulation calculations by a three-dimensional hybrid code are conducted

Y. Kajimura; N. Matsuda; K. Hayashida; A. Maeno; H. Nakashima

2008-01-01

192

Modeling of an IPMC Actuator-driven Zero-Net-Mass-Flux Pump for Flow Control  

Microsoft Academic Search

In this article, a systematic design method on an ionic polymer-metal composite (IPMC)-driven zero-net-mass-flux (ZNMF) pump is introduced for the flow control on a micro air vehicle ’s (MAV) wing. Since IPMC can generate a large deformation under a low input voltage along with its ability to operate in air, and its easier manufacture in a small size, it is

Sangki Lee; Kwang J. Kim; Hoon Cheol Park

2006-01-01

193

Pulsed radiobiology with laser-driven plasma accelerators  

NASA Astrophysics Data System (ADS)

Recently, a high efficiency regime of acceleration in laser plasmas has been discovered, allowing table top equipment to deliver doses of interest for radiotherapy with electron bunches of suitable kinetic energy. In view of an R&D program aimed to the realization of an innovative class of accelerators for medical uses, a radiobiological validation is needed. At the present time, the biological effects of electron bunches from the laser-driven electron accelerator are largely unknown. In radiobiology and radiotherapy, it is known that the early spatial distribution of energy deposition following ionizing radiation interactions with DNA molecule is crucial for the prediction of damages at cellular or tissue levels and during the clinical responses to this irradiation. The purpose of the present study is to evaluate the radio-biological effects obtained with electron bunches from a laser-driven electron accelerator compared with bunches coming from a IORT-dedicated medical Radio-frequency based linac's on human cells by the cytokinesis block micronucleus assay (CBMN). To this purpose a multidisciplinary team including radiotherapists, biologists, medical physicists, laser and plasma physicists is working at CNR Campus and University of Pisa. Dose on samples is delivered alternatively by the "laser-linac" operating at ILIL lab of Istituto Nazionale di Ottica and an RF-linac operating for IORT at Pisa S. Chiara Hospital. Experimental data are analyzed on the basis of suitable radiobiological models as well as with numerical simulation based on Monte Carlo codes. Possible collective effects are also considered in the case of ultrashort, ultradense bunches of ionizing radiation.

Giulietti, Antonio; Grazia Andreassi, Maria; Greco, Carlo

2011-05-01

194

Transient chaos and crisis phenomena in butterfly valves driven by solenoid actuators  

NASA Astrophysics Data System (ADS)

Chilled water systems used in the industry and on board ships are critical for safe and reliable operation. It is hence important to understand the fundamental physics of these systems. This paper focuses in particular on a critical part of the automation system, namely, actuators and valves that are used in so-called "smart valve" systems. The system is strongly nonlinear, and necessitates a nonlinear dynamic analysis to be able to predict all critical phenomena that affect effective operation and efficient design. The derived mathematical model includes electromagnetics, fluid mechanics, and mechanical dynamics. Nondimensionalization has been carried out in order to reduce the large number of parameters to a few critical independent sets to help carry out a broad parametric analysis. The system stability analysis is then carried out with the aid of the tools from nonlinear dynamic analysis. This reveals that the system is unstable in a certain region of the parameter space. The system is also shown to exhibit crisis and transient chaotic responses; this is characterized using Lyapunov exponents and power spectra. Knowledge and avoidance of these dangerous regimes is necessary for successful and safe operation.

Naseradinmousavi, Peiman; Nataraj, C.

2012-11-01

195

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

PubMed

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

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

2015-01-28

196

ELECTRICALLY ACTUATED, PRESSURE-DRIVEN LIQUID CHROMATOGRAPHY SEPARATIONS IN MICROFABRICATED DEVICES  

PubMed Central

Electrolysis-based micropumps integrated with microfluidic channels in micromachined glass substrates are presented. Photolithography combined with wet chemical etching and thermal bonding enabled the fabrication of multi-layer devices containing electrically actuated micropumps interfaced with sample and mobile phase reservoirs. A stationary phase was deposited on the microchannel walls by coating with 10% (w/w) chlorodimethyloctadecylsilane in toluene. Pressure-balanced injection was implemented by controlling the electrolysis time and voltage applied in the two independent micropumps. Current fluctuations in the micropumps due to the stochastic formation of bubbles on the electrode surfaces were determined to be the main cause of variation between separations. On-chip electrochemical pumping enabled the loading of pL samples with no dead volume between injection and separation. A mobile phase composed of 70% acetonitrile and 30% 50 mM acetate buffer (pH 5.45) was used for the chromatographic separation of three fluorescently labeled amino acids in <40 s with an efficiency of >3000 theoretical plates in a 2.5-cm-long channel. Our results demonstrate the potential of electrochemical micropumps integrated with microchannels to perform rapid chromatographic separations in a microfabricated platform. Importantly, these devices represent a significant step toward the development of miniaturized and fully integrated liquid chromatography systems. PMID:17960281

Fuentes, Hernan V.; Woolley, Adam T.

2012-01-01

197

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

198

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

199

Deep drilling and sampling via the wireline auto-gopher driven by piezoelectric percussive actuator and EM rotary motor  

NASA Astrophysics Data System (ADS)

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, Europa, and Enceladus. A corer/sampler was developed with the goal of acquiring pristine samples by reaching depths on Mars beyond the oxidized and sterilized zone. The 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 drill that is incorporated with an inchworm mechanism allowing thru cyclic coring and core removal to reach great depths. The penetration rate is 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, which is driven by a piezoelectric stack, demonstrated to require low axial preload. The Auto-Gopher has been produced taking into account the 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 the objective of reaching as deep as 3 to 5 meters in tufa formation.

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

2012-04-01

200

Investigation of the cylinder wake under spanwise periodic forcing with a segmented plasma actuator  

NASA Astrophysics Data System (ADS)

The wake response to three-dimensional forcing of flow over a circular cylinder was studied. Spanwise-segmented dielectric-barrier discharge plasma actuators were mounted on the cylinder in a square wave pattern for active forcing of the cylinder wake. The buried electrodes were placed periodically to create a spanwise-modulated blowing profile, with the aim of targeting three-dimensional instabilities in the wake. Considerable spanwise variation in the wake was achieved, which was a direct consequence of the difference in the location of shed spanwise vortices from the cylinder, along with the generation of streamwise vorticity. Two distinct power levels were used for forcing the flow, with different flow response observed between the two conditions. With low power, the segmented forcing caused the large-scale spanwise structures in the forcing region to lead those in the no-forcing region, with an accompanying shift away from the centerline and generation of streamwise vorticity. While vortex shedding was not substantially attenuated with low-power forcing, the shedding in the near wake was significantly attenuated with high-power forcing. This attenuation in the shedding strength was accompanied by a decrease in the peak shedding frequency, indicating an increase in the formation length. High-power forcing caused elongation of the Kármán vortices due to the induced strain field and strong differential development of the wake shedding frequency. In both forcing regimes, the wake three-dimensionality increased as shown by the increased width of the spectral peaks.

Bhattacharya, S.; Gregory, James W.

2015-01-01

201

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

NASA Astrophysics Data System (ADS)

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.

Benard, Nicolas; Moreau, Eric

2014-11-01

202

Analysis of flexural hinge orientation for amplified piezo-driven actuators  

NASA Astrophysics Data System (ADS)

In this paper, we show that aligning the hinges in a flexure-based rhombus-shaped piezo-driven amplifying mechanism increases its performance. A simplified analytical model is first proposed based on the definition of the input and the output stiffnesses of an amplifying mechanism. Approximate analytical expressions for both stiffnesses are then derived for two hinge configurations: parallel and aligned. The model predicts increases in the free stroke, the blocking force and the efficiency which are confirmed by numerical simulations. Most importantly, a reduction of the bending in the hinges is confirmed both numerically and analytically. As a matter of fact, simulations show a significant decrease (40%) of the maximal stress when the hinges are aligned.

Mottard, Patrick; St-Amant, Yves

2009-03-01

203

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)

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.

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

2007-01-01

204

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)

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.

Ashpis, David E.; Thurman, Douglas R.

2011-01-01

205

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

SciTech Connect

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.

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

206

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

SciTech Connect

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.

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

2010-05-03

207

Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma  

SciTech Connect

Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies.

Ogino, Yousuke; Sawada, Keisuke [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan); Ohnishi, Naofumi [Department of Aerospace Engineering, Tohoku University, Sendai 980-8579 (Japan); Center for Research Strategy and Support, Tohoku University, Sendai 980-8579 (Japan)

2008-04-28

208

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

E-print Network

Laser-driven plasma-based accelerators: Wakefield excitation, channel guiding, and laser triggered particle injection* W. P. Leemans,,a) P. Volfbeyn, K. Z. Guo, and S. Chattopadhyay Ernest Orlando Lawrence; accepted 18 February 1998 Plasma-based accelerators are discussed in which high-power short pulse lasers

Wurtele, Jonathan

209

Query-driven Analysis of Plasma-based Particle Acceleration Data Oliver Rubel  

E-print Network

Query-driven Analysis of Plasma-based Particle Acceleration Data Oliver R¨ubel LBNL Cameron G. R=high, blue=low). ABSTRACT Plasma-based particle accelerators can produce and sustain thou- sands of times to the problem of the growing size and cost of conventional particle accelerators. There is a pressing need

210

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

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

211

Design and test of a novel cost-effective piezo driven actuator with a two-stage flexure amplifier for chopping mirrors  

NASA Astrophysics Data System (ADS)

A fast chopping secondary mirror is the critical functioning assembly in an astronomical telescope for infrared observation. Normally, a chopping mirror is driven by precision high-load and high-stiffness linear actuators which are expected to be lightweight, compact and further cost-effective. The stroke of the actuator is typically required to up to several hundred microns with typical load capacity up to several hundred Newtons. We developed a novel piezo-based prototype linear actuator with a two-stage rhombic flexure amplifier. In this paper, first we present the detail design scheme of the actuator by analytical calculations with comprehensive Finite Element Analysis (FEA) verification. Afterwards, we also present the procedures and results of tests of linearity, load capacity, eigenfrequency, stability and repeatability. The selected piezoelectric drive unit is a block of 35x10x10 mm3 with output force up to 4000 N. The two-stage displacement amplifier is simply integrated by two identical singular rhombic flexures orthogonally mounted together. Each stage, one rhombic flexure with a longer axis of 76 mm long, is designed with an ideal amplification ratio of 3, which leads to a final theoretical compound amplification ration of 9. In order to realize the basic triangular-amplification principle in a rhombic flexure, we introduced flexure joints at all the eight ends of its four edge bars. The singular rhombic flexures can be efficiently manufactured by electrical discharge wire-cutting process at a time in batch by being overlapped in layers. Afterwards we carried out related measurements to test its performance.

Wu, Qingguo; Yang, Dehua; Li, Aihua; Zhou, Guohua; Yang, Bintang

2012-09-01

212

RESEARCH ARTICLE The use of plasma actuators for bluff body broadband  

E-print Network

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 fairings can be applied, potentially leading to a reduction of radi- ated noise by shielding the downstream

Huang, Xun

213

Progress In Magnetized Target Fusion Driven by Plasma Liners  

NASA Technical Reports Server (NTRS)

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).

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

214

Ferroelectric actuators in the electromechanical interface  

Microsoft Academic Search

The requirements of a control actuator are examined, and the unique capabilities of the type of an actuator driven by ferroelectric materials that exhibit piezoelectric characteristics when electrically poled to meet these requirements are demonstrated. It is shown that, when substantial energy is required from an actuator, actuators configured as stacks of ferroelectric disks are most suitable. They develop high

C. G. O'Neill; C. H. O'Neill

1990-01-01

215

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

NASA Astrophysics Data System (ADS)

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).

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

216

Time-resolved measurements of plasma-induced momentum in air and nitrogen under dielectric barrier discharge actuation  

SciTech Connect

There has been much recent interest in boundary layer (BL) actuation by offset surface dielectric barrier discharges (SDBD). These discharges either act directly on the gas momentum through the mechanism of charge separation or they increase the flow stability through the creation of disturbances to the BL at a particular frequency. The objective of the work reported here is to clarify the physical mechanism of plasma-flow interaction. Two problems are considered in detail: the exact spatial/temporal distribution of the plasma-related force, and the specific role of negative ions in the net force budget. The experiments were made with an offset electrode configuration of SDBD at voltage amplitude U{<=}12 kV and frequency f=0.02-2 kHz. The main data were obtained by time-resolved Pitot tube pressure measurements in air and nitrogen at atmospheric pressure. Three main features of SDBD behavior were considered. First, the strong inhomogeneity in the spatial distribution of the plasma-induced flow were detected. Second, the principal role of negative ions in plasma-induced flow generation was established. Third, the two types of gas disturbances were observed: the thermal effect and momentum transfer effect (ion wind). To explain the aforementioned features of SDBD behavior in air and nitrogen the results of numerical simulation have been used.

Leonov, Sergey [Joint Institute for High Temperature, RAS, Moscow 125412 (Russian Federation); Opaits, Dmitry; Miles, Richard [Princeton University, Princeton, New Jersey 08544 (United States); Soloviev, Victor [Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow Region 141700 (Russian Federation)

2010-11-15

217

Comparison of the characteristics of potential drop and current-driven double layers. [of auroral plasma  

NASA Technical Reports Server (NTRS)

The characteristics of double layers driven by an applied potential drop and by an injected current into a plasma are compared. In the latter case the potential drop across the double layer appears because of the formation of a virtual cathode. The double layers formed by the two mechanisms show striking similarities with regard to their structure, temporal evolution, and dynamics. However, in the case of current-driven double layers a large energization of ions trapped in the virtual cathode region is observed. Such a large energization of trapped ions is not seen in the case of the potential-drop driven double layers. The interrelation between the field-aligned currents and potential drops for the auroral plasma is discussed. For current-driven double layers, it is found that the current density is proportional to the 1/2 power of the potential drop.

Singh, N.; Schunk, R. W.

1983-01-01

218

High power Tesla driven miniature plasma opening switch  

NASA Astrophysics Data System (ADS)

The plasma opening switch (POS) is used in pulsed power systems where a very fast opening and high current switch is required. Plasma is injected into the switch, which carries a large conduction current, before it opens in a process that lasts for a few nanosecond and transfers the current to a parallel-connected load at a much increased voltage and with a much shorter rise time. The conduction and opening times of the switch are dependent on plasma parameters such as the distribution, speed and species, all of which are determined by the plasma source. Most of the earlier reported work involves large dimension POSs and a correspondingly high input current (more than 100 kA) and uses carbon plasma. One main objective of the present research was to achieve a low input current (20 kA) and miniaturised POS by using hydrogen plasma rather than carbon plasma on account of its lower mass. A cable gun was selected for producing the plasma, since although this produces both hydrogen and carbon plasma these arise different times during its operation.. For the present application a Tesla transformer was used in preference to a Marx generator to produce an initial high voltage pulse for the system, on the basis of its simpler design and cost effectiveness. This transformer together with an associated water PFL (pulse forming line) and pressurised switch was capable of producing a load current in excess of 20 kA with a rise time of 53 ns, which was fed through the POS to the final load. Special diagnostics arrangements were necessary to measure the fast high current and voltage pulse a in nonintrusive way. Faraday cups and a high speed camera were used to measure the plasma parameters. The overall system built (i.e. including the POS) is capable of producing a 22 kA current with a rise time of 5 ns, and of generating a power of more than 10 GW..

Kumar, Rajesh

219

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

NASA Astrophysics Data System (ADS)

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.

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

220

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

NASA Astrophysics Data System (ADS)

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.

Li, Xuechen; Di, Cong; Jia, Pengying; Bao, Wenting

2013-09-01

221

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

SciTech Connect

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.

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

222

Growth and phase velocity of self-modulated beam-driven plasma waves  

SciTech Connect

A long, relativistic particle beam propagating in an overdense plasma is subject to the self-modulation instability. This instability is analyzed and the growth rate is calculated, including the phase relation. The phase velocity of the wake is shown to be significantly less than the beam velocity. These results indicate that the energy gain of a plasma accelerator driven by a self-modulated beam will be severely limited by dephasing. In the long-beam, strongly-coupled regime, dephasing is reached in a homogeneous plasma in less than four e-foldings, independent of beam-plasma parameters.

Benedetti, Carlo; Esarey, Eric; Gruener, Florian; Leemans, Wim

2011-09-20

223

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

SciTech Connect

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.

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

224

The European turbulence code benchmarking effort: turbulence driven by thermal gradients in magnetically confined plasmas  

Microsoft Academic Search

A cross-comparison and verification of state-of-the-art European codes describing gradient-driven plasma turbulence in the core and edge regions of tokamaks, carried out within the EFDA Task Force on Integrated Tokamak Modelling, is presented. In the case of core ion temperature gradient (ITG) driven turbulence with adiabatic electrons (neglecting trapped particles), good\\/reasonable agreement is found between various gyrokinetic\\/gyrofluid codes. The main

G. L. Falchetto; B. D. Scott; P. Angelino; A. Bottino; T. Dannert; V. Grandgirard; S. Janhunen; F. Jenko; S. Jolliet; A. Kendl; B. F. McMillan; V. Naulin; A. H. Nielsen; M. Ottaviani; A. G. Peeters; M. J. Pueschel; D. Reiser; T. T. Ribeiro; M. Romanelli

2008-01-01

225

Current-driven plasma waves in the Versatile Toroidal Facility (VTF)  

SciTech Connect

The authors have been conducting laboratory experiments to investigate plasma turbulence that can affect the propagation of electromagnetic waves. This work is aimed at simulating the ionospheric plasma turbulence and cross-checking the radar experiments at Arecibo, Puerto Rico. The large toroidal plasma device, called the Versatile Toroidal Facility (VTF), can produce a radially inhomogeneous plasma imposed in a helically shaped magnetic field. VTF plasma has a sharp density gradient and an intense magnetic field-aligned current, simulating well the plasma environment in the auroral ionosphere. A broad spectrum of plasma waves can be exited in VTF by the injected microwaves and electron beams. In this paper, the authors discuss the excitation of low-frequency plasma waves driven by electric currents, including ion acoustic waves and current-convective modes. A good agreement has been found between the experimental results and the theories developed for the VTF plasmas. However, their experimental results are quite different from those obtained in the rocket/space shuttle experiments. The difference in the laboratory experiments and space experiments arise form two facts. One is that the plasma inhomogeneity does not play a significant role in the space experiments. The other is that the electron beam injected in the space experiments does not produce a drifting Maxwellian plasma as seen in the VTF plasmas. The contrast between the VTF experiments and the active space experiments show that VTF can adequately simulate the ionospheric plasma turbulence and complement the rocket/space shuttle experiments.

Moriarty, D.T.; Lee, M.C.; Riddolls, R.J.; Murphy, S.M.; Rowlands, M.J. [Massachusetts Inst. of Technology, Cambridge, MA (United States). Plasma Fusion Center

1995-12-31

226

AGN-driven convection in galaxy-cluster plasmas  

E-print Network

This paper describes how active galactic nuclei can heat galaxy-cluster plasmas by driving convection in the intracluster medium. A model is proposed in which a central supermassive black hole accretes intracluster plasma at the Bondi rate and powers a radio source. The central radio source produces cosmic rays, which mix into the thermal plasma. The cosmic-ray luminosity is proportional to the mass accretion rate. The cosmic-ray pressure gradient drives convection, which causes plasma heating. It is assumed that plasma heating balances radiative cooling. The plasma heating rate is self-regulating because the Bondi accretion rate is a decreasing function of the specific entropy near the cluster center; if heating exceeds cooling, then the central entropy increases, the Bondi rate and cosmic-ray luminosity decrease, and the convective heating rate is reduced. This paper focuses on the role of intracluster magnetic fields, which affect convection by causing heat and cosmic rays to diffuse primarily along magnetic field lines. A new stability criterion is derived for convection in a thermal-plasma/cosmic-ray fluid, and equations for the average fluid properties in a convective cluster are obtained with the use of a nonlocal two-fluid mixing length theory. Numerical solutions of the model equations compare reasonably well with observations without requiring fine tuning of the model parameters.

Benjamin D. G. Chandran

2005-06-04

227

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

PubMed

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

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

228

Microscale plasma actuators for improved thrust density Chin-Cheng Wang and Subrata Roya  

E-print Network

is investigated using a first-principles approach solving coupled system of hydrodynamic plasma equations. © 2009 American Institute of Physics. DOI: 10.1063/1.3160304 I. INTRODUCTION The plasma that has been in which elect

Roy, Subrata

229

Curvature-driven instabilities in a hot-electron plasma: radial analysis  

SciTech Connect

The theory of unfavorable curvature-driven instabilities is developed for a plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic theory. A z-pinch model is used to emphasize the radial structure of the problem. Stability criteria are obtained for the five possible modes of instability: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies larger than the ion cyclotron frequency), a compressional instability, a background pressure-driven interchange, and an interacting pressure-driven interchange.

Berk, H.L.; Van Dam, J.W.; Rosenbluth, M.N.; Spong, D.A.

1981-12-01

230

Numerical Simulation of Plasma Behavior in a Magnetic Nozzle of a Laser-plasma Driven Nuclear Electric Propulsion System  

SciTech Connect

Numerical simulations of plasma behavior in a magnetic nozzle of a Laser-Plasma Driven Nuclear Electric Propulsion System are conducted. The propellant is heated and accelerated by the laser and expanded isotropically. The magnetic nozzle is a combination of solenoidal coils and used to collimate and guide the plasma to produce thrust. Simulation calculations by a three-dimensional hybrid code are conducted to examine the plasma behaviors in the nozzle and to estimate the thrust efficiency. We also estimate a fraction ({alpha}) of plasma particles leaking in the forward (spacecraft) direction. By a combination of a few coils, we could decrease {alpha} value without degrading the thrust efficiency. Finally, the shaped propellant is proposed to increase the thrust efficiency.

Kajimura, Y. [Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Japan Science and Technology Agency (JST), CREST 4-1-8 Hon-chou, Kawaguchi, Saitama 332-0012 (Japan); Matsuda, N.; Hayashida, K.; Maeno, A.; Nakashima, H. [Department of Advanced Energy Engineering Science, Interdisciplinary Graduate school of Engineering Sciences, Kyushu University, Kasugakouen 6-1, Kasuga, Fukuoka 816-580 (Japan)

2008-12-31

231

Contribution of positive and negative ions to the electrohydrodynamic force in a dielectric barrier discharge plasma actuator operating in air  

SciTech Connect

We present a parametric study of the electrohydrodynamic force generated by surface dielectric barrier discharge plasma actuators in air for sinusoidal voltage waveforms. The simulation results confirm that momentum is transferred from the charged particles to the neutral species in the same direction during both positive and negative parts of the cycle. The momentum transfer is due to positive ions during the positive part of the cycle (electrode above the dielectric layer is the anode), and to negative ions during the negative part of the cycle. The relative contribution of the positive and negative parts of the cycle depends on the voltage amplitude and frequency. The model predicts that the contribution of negative ions tends to be dominant at low voltage frequencies and high voltage amplitudes.

Boeuf, J. P.; Lagmich, Y.; Pitchford, L. C. [UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); LAPLACE, CNRS, F-31062 Toulouse (France)

2009-07-15

232

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

SciTech Connect

Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic field. The instabilities appear when an equatorial mesh is biased to drive a radial current that causes rapid axisymmetric plasma rotation. The observed instabilities are quasicoherent in the laboratory frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. Results from a self-consistent nonlinear simulation reproduce the measured mode structures.

Levitt, B.; Maslovsky, D.; Mauel, M.E. [Department of Applied Physics and Applied Mathematics Columbia University, New York, New York 10027 (United States)

2005-05-06

233

Nonlinear Hybrid Simulations of Multiple Energetic Particle driven Alfven Modes in Toroidal Plasmas  

NASA Astrophysics Data System (ADS)

Understanding of nonlinear behavior of energetic particle-driven instabilities in tokamaks is of fundamental importance for burning plasmas. Here we report recent advances in self-consistent nonlinear simulations of fast beam ion-driven Alfven modes in NSTX and DIII-D using the extended MHD code M3D [1]. In the hybrid model, the thermal electrons and ions are treated as an ideal fluid while the energetic species is described by either drift-kinetic equation or gyrokinetic equation. The effects of energetic particles are coupled to the MHD equations via the stress tensor term in the momentum equation. The hybrid code has been recently applied to study nonlinear dynamics of fishbone instability [2]. The code was also used to simulate nonlinear evolution of a single beam-driven TAE mode in NSTX. The result showed a weak frequency chirping about 20% consistent with experimental measurement [3]. In this work, we use the M3D code to simulate beam ion driven Alfven modes in NSTX plasmas with multiple unstable Alfven modes. It is found that mode saturation level of each mode can be enhanced significantly by presence of other unstable modes indicating strong nonlinear interaction between different modes. It is also found that a linearly stable n=2 mode can be nonlinearly driven by an n=1 mode at significant mode amplitude. These results together with simulation results of beam ion-driven Alfven modes in DIII-D reversed shear plasmas [4] will be presented. [1] W. Park, E.V. Belova, G.Y. Fu et al., Phy. Plasmas 6, 1796 (1999) [2] Fu, GY, Park, W, Strauss HR et al. PHYSICS OF PLASMAS 13, 052517 (2006) [3] Fu GY, Breslau J, Fredrickson E et al. ,Proceedings of 2004 IAEA Fusion Energy Conference, Vilamoura, Portugal, Paper TH/P4-38. [4] M.A., Van Zeeland, G.J. Kramer, M.E. Austin et al., Phys. Rev. Lett. 97, 135001 (2006).

Fu, Guoyong

2007-11-01

234

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

Large range dual-axis micro-stage driven by electrostatic comb-drive actuators This article has. Microeng. 23 (2013) 105008 (11pp) doi:10.1088/0960-1317/23/10/105008 Large range dual-axis micro-stage September 2013 Online at stacks.iop.org/JMM/23/105008 Abstract This paper presents a micro XY stage

Awtar, Shorya

235

Laser-driven plasma waves in capillary tubes  

SciTech Connect

The excitation of plasma waves over a length of up to 8 cm is demonstrated using laser guiding of intense laser pulses through hydrogen-filled glass capillary tubes. The plasma waves are diagnosed by spectral analysis of the transmitted laser radiation. The dependence of the spectral redshift--measured as a function of filling pressure, capillary tube length, and incident laser energy - is in excellent agreement with simulation results. The longitudinal accelerating field inferred from the simulations is in the range of 1-10 GV/m.

Wojda, F.; Cassou, K.; Cros, B. [Laboratoire Physique Gaz et Plasmas, CNRS-Universite Paris-Sud 11, F-91405 Orsay Cedex (France); Genoud, G.; Burza, M.; Glinec, Y.; Lundh, O.; Persson, A.; Wahlstroem, C.-G. [Department of Physics, Lund University, P.O. Box 118, S-22100 Lund (Sweden); Vieux, G.; Brunetti, E.; Shanks, R. P.; Jaroszynski, D. [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Andreev, N. E. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation)

2009-12-15

236

Alfvénic instabilities driven by runaways in fusion plasmas  

SciTech Connect

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.

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

237

Plasma diagnostics for x-ray driven foils at Z  

SciTech Connect

We report the development of techniques to diagnose plasmas produced by x-ray photoionization of thin foils placed near the Z-pinch on the Sandia Z Machine. The development of 100+ TW x-ray sources enables access to novel plasma regimes, such as the photoionization equilibrium. To diagnose these plasmas one must simultaneously characterize both the foil and the driving pinch. The desired photoionized plasma equilibrium is only reached transiently for a 2-ns window, placing stringent requirements on diagnostic synchronization. We have adapted existing Sandia diagnostics and fielded an additional gated three-crystal Johann spectrometer with dual lines of sight to meet these requirements. We present sample data from experiments using 1-cm, 180-eV tungsten pinches to photoionize foils made of 200 Aa Fe and 300 Aa NaF co-mixed and sandwiched between 1000 Aa layers of Lexan (C16H14O3), and discuss the application of this work to benchmarking astrophysical models.

Heeter, R. F.; Bailey, J. E.; Cuneo, M. E.; Emig, J.; Foord, M. E.; Springer, P. T.; Thoe, R. S.

2001-01-01

238

Study of driven magnetic reconnection in a laboratory plasma  

Microsoft Academic Search

MRX (Magnetic Reconnection Experiment) was constructed in the fall of 1995 to investigate the fundamental physics of magnetic reconnection(M. Yamada et al. Bull. APS, vol.40 1877 (1995)), and has yielded many exciting and original results. The MRX experiment satisfies the criteria for MHD plasmas ( S >> 1, rhoi << L), and the boundary condition can be controlled externally. In

Masaaki Yamada; Hantao Ji; Scott Hsu; Troy Carter; Russell Kulsrud; Norton Bretz; Forrest Jobes; Yasushi Ono; Francis Perkins

1997-01-01

239

Plasma Wakefield Accelerator Driven by a Train of Electron Bunches  

Microsoft Academic Search

We study experimentally the physics of the interaction between a train of electron bunches and a plasma whose density can be varied. The train of electron bunches consists of equidistant (˜300 microns) drive bunches followed by a witness bunch (˜450 microns from the last drive bunch). Each bunch length is about half the drive bunch spacing (˜150 microns). The bunch

Patric Muggli; Brian Allen; Vitaly Yakimenko; Karl Kusche; Marcus Babzien

2009-01-01

240

Supersonic Ionization Wave Driven by Radiation Transport in a Short-Pulse Laser-Produced Plasma  

Microsoft Academic Search

Through the use of an ultrashort (2ps) optical probe, we have time resolved the propagation of an ionization wave into solid fused silica. This ionization wave results when a plasma is created by the intense irradiation of a solid target with a 2ps laser pulse. We find that the velocity of the ionization wave is consistent with radiation driven thermal

T. Ditmire; E. T. Gumbrell; R. A. Smith; L. Mountford; M. H. Hutchinson

1996-01-01

241

Comment on "Spin-Gradient-Driven Light Amplification in a Quantum Plasma''  

E-print Network

A comment on the Letter by S. Braun, F. A. Asenjo and S. M. Mahajan, Phys. Rev. Lett., 109, 175003 (2012). We show that recent arguments for light amplification driven by inhomogeneous quantum spin fields in low temperature electron plasmas in metals are invalid. In essence, a neglect of Pauli `blocking' led the authors to over-estimate the effects of intrinsic spin.

Krishnaswami, Govind S; Sen, Abhijit; Thyagaraja, Anantanarayanan

2014-01-01

242

Computational simulations of explosive-driven plasma-quench opening switches  

SciTech Connect

High-explosive-driven plasma opening switches have been modeled in one dimension using the Lagrangian MHD code RAVEN. These calculations have been made in both cylindrical and planar geometry. Simple compression can account for observed resistance increases at early times (time-of-flight of the high-explosive detonation products across the plasma conducting channel). Our results suggest that some improvements in switch performance might be achieved through a judicious choice of gases in the plasma channel and by lowering the pressure in the channel.

Greene, A.E.; Oliphant, T.A.; Brownell, J.H.; Nickel, G.H.; Weiss, D.L.

1983-01-01

243

Visualization of Shock Wave Driven by Millimeter Wave Plasma in a Parabolic Thruster  

SciTech Connect

By focusing a high-power millimeter wave beam generated by a 170 GHz gyrotron, a breakdown occurred and a shock wave was driven by plasma heated by following microwave energy. The shock wave and the plasma around a focal point of a parabolic thruster were visualized by a shadowgraph method, and a transition of structures between the shock wave and the plasma was observed. There was a threshold local power density to make the transition, and the propagation velocity at the transition was around 800 m/s.

Yamaguchi, Toshikazu; Shimada, Yutaka; Shiraishi, Yuya; Shibata, Teppei; Komurasaki, Kimiya [Department of Advanced Energy, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba, 277-8561 (Japan); Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi [Plasma Heating Technology Group, Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki, 311-0193 (Japan); Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan)

2010-05-06

244

Phase effect on flow control for dielectric barrier plasma actuators K. P. Singh and Subrata Roya  

E-print Network

power supply to the electrodes.1 The plasma when energized emits an acoustic signal which can provide low power a few watts levels, in a wide range of applications to suppress separation. Wings and fuselage of aircraft may be covered with a thin layer of glow discharge plasma which can pro- vide, through

Roy, Subrata

245

TECHNICAL NOTE: Performance enhancement of IPMC actuator by plasma surface treatment  

Microsoft Academic Search

IPMC (ionic polymer metal composite) is composed of ionic polymer and metal electrodes on both surfaces of the polymer. In this study, we changed the surface morphology of the ionic polymer by using plasma treatment. Plasma treatment made needle-shaped microstructures on the surface of the polymer and the microstructures helped to form a thicker uniform metal electrode which is deposited

Seong Jun Kim; In Taek Lee; Yong Hyup Kim

2007-01-01

246

Plasma-driven tunable liquid adhesion of superoleophobic aluminum surfaces  

NASA Astrophysics Data System (ADS)

With the aim of tuning adhesion with various liquids, we develop a convenient route to achieve sliding superoleophobicity and sticky superoleophobicity on the aluminum surfaces by surface fluorination and masked plasma treatment. Droplets of various liquids, such as oils, organic liquids, and water, can be tuned between rolling state and pinned state on the superoleophobic surfaces. The tunable adhesion of the superoleophobic surface is demonstrated by visible experimental results and measurements. The key to this effect is the combination of the oleophobic domains produced by masked plasma treatment as well as a permanently superoleophobic substrate and the hierarchical texture. Our results gave a useful attempt in understanding the fabrication principle of preparing superoleophobic surfaces with tunable liquid adhesion.

Yang, Jin; Song, Haojie; Tang, Hua; Ji, Haiyan; Li, Changsheng

2013-09-01

247

Sensor Driven Intelligent Control System For Plasma Processing  

SciTech Connect

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.

Bell, G.; Campbell, V.B.

1998-02-23

248

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

E-print Network

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.

Sadykova, S P; Samkharadze, T G

2015-01-01

249

Laser Plasma Jet Driven Microparticles for DNA/Drug Delivery  

PubMed Central

This paper describes a microparticle delivery device that generates a plasma jet through laser ablation of a thin metal foil and uses the jet to accomplish particle delivery into soft living targets for transferring biological agents. Pure gold microparticles of 1 µm size were coated with a plasmid DNA, pIG121Hm, and were deposited as a thin layer on one surface of an aluminum foil. The laser (Nd:YAG, 1064 nm wavelength) ablation of the foil generated a plasma jet that carried the DNA coated particles into the living onion cells. The particles could effectively penetrate the target cells and disseminate the DNA, effecting the transfection of the cells. Generation of the plasma jet on laser ablation of the foil and its role as a carrier of microparticles was visualized using a high-speed video camera, Shimadzu HPV-1, at a frame rate of 500 kfps (2 µs interframe interval) in a shadowgraph optical set-up. The particle speed could be measured from the visualized images, which was about 770 m/s initially, increased to a magnitude of 1320 m/s, and after a quasi-steady state over a distance of 10 mm with an average magnitude of 1100 m/s, started declining, which typically is the trend of a high-speed, pulsed, compressible jet. Aluminum launch pad (for the particles) was used in the present study to make the procedure cost-effective, whereas the guided, biocompatible launch pads made of gold, silver or titanium can be used in the device during the actual clinical operations. The particle delivery device has a potential to have a miniature form and can be an effective, hand-held drug/DNA delivery device for biological applications. PMID:23226394

Menezes, Viren; Mathew, Yohan; Takayama, Kazuyoshi; Kanno, Akira; Hosseini, Hamid

2012-01-01

250

Pressure-driven reconnection and quasi periodical oscillations in plasmas  

SciTech Connect

This paper presents a model for an ohmically heated plasma in which a feedback exists between thermal conduction and transport, on one side, and the magneto-hydro-dynamical stability of the system, on the other side. In presence of a reconnection threshold for the magnetic field, a variety of periodical or quasi periodical oscillations for the physical quantities describing the system are evidenced. The model is employed to interpret the observed quasi periodical oscillations of electron temperature and perturbed magnetic field around the so called “Single Helical” state in the reversed field pinch, but its relevance for other periodical phenomena observed in magnetic confinement systems, especially in tokamaks, is suggested.

Paccagnella, R., E-mail: roberto.paccagnella@igi.cnr.it [Consorzio RFX and Istituto Gas Ionizzati del Consiglio Nazionale delle Ricerche (CNR), Padova (Italy)

2014-03-15

251

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

SciTech Connect

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.

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

252

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

SciTech Connect

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.

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

253

Subcutoff microwave driven plasma ion sources for multielemental focused ion beam systems  

SciTech Connect

A compact microwave driven plasma ion source for focused ion beam applications has been developed. Several gas species have been experimented including argon, krypton, and hydrogen. The plasma, confined by a minimum B multicusp magnetic field, has good radial and axial uniformity. The octupole multicusp configuration shows a superior performance in terms of plasma density ({approx}1.3x10{sup 11} cm{sup -3}) and electron temperature (7-15 eV) at a power density of 5-10 W/cm{sup 2}. Ion current densities ranging from a few hundreds to over 1000 mA/cm{sup 2} have been obtained with different plasma electrode apertures. The ion source will be combined with electrostatic Einzel lenses and should be capable of producing multielemental focused ion beams for nanostructuring and implantations. The initial simulation results for the focused beams have been presented.

Mathew, Jose V.; Chowdhury, Abhishek; Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India)

2008-06-15

254

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

SciTech Connect

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.

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

255

Shock creation and particle acceleration driven by plasma expansion into a rarefied medium  

SciTech Connect

The expansion of a dense plasma through a more rarefied ionized medium is a phenomenon of interest in various physics environments ranging from astrophysics to high energy density laser-matter laboratory experiments. Here this situation is modeled via a one-dimensional particle-in-cell simulation; a jump in the plasma density of a factor of 100 is introduced in the middle of an otherwise equally dense electron-proton plasma with an uniform proton and electron temperature of 10 eV and 1 keV, respectively. The diffusion of the dense plasma, through the rarefied one, triggers the onset of different nonlinear phenomena such as a strong ion-acoustic shock wave and a rarefaction wave. Secondary structures are detected, some of which are driven by a drift instability of the rarefaction wave. Efficient proton acceleration occurs ahead of the shock, bringing the maximum proton velocity up to 60 times the initial ion thermal speed.

Sarri, G.; Kourakis, I.; Borghesi, M. [Centre for Plasma Physics, The Queen's University of Belfast, Belfast BT7 1NN (United Kingdom); Dieckmann, M. E. [VITA ITN, Linkoping University, 60174 Norrkoping (Sweden)

2010-08-15

256

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

SciTech Connect

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.

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

257

Kinetic Alfvén wave instability driven by a field-aligned current in high-? plasmas.  

PubMed

Including the ion-gyroradius effect, a general low-frequency kinetic dispersion equation is presented, which simultaneously takes account of a field-aligned current and temperature anisotropy in plasmas. Based on this dispersion equation, kinetic Alfvén wave (KAW) instability driven by the field-aligned current, which is carried by the field-aligned drift of electrons relative to ions at a drift velocity V(D), is investigated in a high-? plasma, where ? is the kinetic-to-magnetic pressure ratio in the plasma. The numerical results show that the KAW instability driven by the field-aligned current has a nonzero growth rate in the parallel wave-number range 0plasma particles, the result shows that the instability conditions for these two driven mechanisms are both modified considerably, in which the growing parametric ranges of KAWs widen. The results have potential importance in understanding the physics of space and astrophysical plasma active phenomena since the field-aligned current, also called the Birkeland current, is one of the most active factors in plasma phenomena. PMID:22181282

Chen, L; Wu, D J; Hua, Y P

2011-10-01

258

Piezoelectric actuators for dynamic applications  

Microsoft Academic Search

The main advantages of piezoelectrical actuators are their high resolution in motion and their excellent dynamic behavior. Especially the very short response times of solid state actuators presents new opportunities in developing high dynamical systems with unsurpassable characteristics. New concepts of piezoelectrically driven microoptical devices, e.g. optical fiber switches, intensity modulators and choppers, can be developed. Very compact systems with

Peter Buecker; Bernt Goetz; Thomas Martin

1998-01-01

259

American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma Actuator for Improving  

E-print Network

1 American Institute of Aeronautics and Astronautics Physics Based Analysis of Horseshoe Plasma. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. #12;2 American Institute of Aeronautics and Astronautics I. Introduction rossflow jets have been widely used in many

Roy, Subrata

260

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

E-print Network

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

Roy, Subrata

261

Experimental investigation of explosive-driven plasma-compression opening switches  

SciTech Connect

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.

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

1983-01-01

262

Plasma-driven self-organization of Ni nanodot arrays on Si(100)  

NASA Astrophysics Data System (ADS)

The results of the combined experimental and numerical study suggest that nonequilibrium plasma-driven self-organization leads to better size and positional uniformity of nickel nanodot arrays on a Si(100) surface compared with neutral gas-based processes under similar conditions. This phenomenon is explained by introducing the absorption zone patterns, whose areas relative to the small nanodot sizes become larger when the surface is charged. Our results suggest that strongly nonequilibrium and higher-complexity plasma systems can be used to improve ordering and size uniformity in nanodot arrays of various materials, a common and seemingly irresolvable problem in self-organized systems of small nanoparticles.

Levchenko, I.; Ostrikov, K.; Diwan, K.; Winkler, K.; Mariotti, D.

2008-11-01

263

Turbulence in Toroidally Confined Plasma: Ion - - Gradient-Driven Turbulence; Dynamics of Magnetic Relaxation in Current-Carrying Plasma  

NASA Astrophysics Data System (ADS)

This thesis is devoted to two studies of low-frequency turbulence in toroidally confined plasma. Low-frequency turbulence is believed to play an important role in anomalous transport in toroidal confinement devices. The first study pertains the the development of an analytic theory of ion-temperature-gradient-driven turbulence in tokamaks. Energy-conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion-temperature-gradient-driven turbulence. Corrections to mixing-length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity is derived and is found to be consistent with experimentally-deduced ion thermal diffusivities. The associated electron thermal diffusivity, particle and heat-pinch velocities are also calculated. The effects of impurity gradients on saturated ion-temperature-gradient-driven turbulence are discussed and a related explanation of density profile steepening during Z-mode operation is proposed. The second study is devoted to the role of multiple helicity nonlinear interactions of tearing modes and dynamics of magnetic relaxation in a high-temperature current-carrying plasma. To extend the resistive MHD theory of magnetic fluctuations and dynamo activity observed in the reversed field pinch, the fluid equations for high-temperature regime are derived and basic nonlinear interaction mechanism and the effects of diamagnetic corrections to the MHD turbulence theory are studied for the case of fully developed, densely packed turbulence. Modifications to the MHD dynamo theory and anomalous thermal transport and confinement scaling predictions are examined.

Lee, Gyung Su.

264

Subharmonic Resonances in Plasmas: Exponential and Superexponential Growth of Driven Relativistic Plasma Waves  

NASA Astrophysics Data System (ADS)

Subharmonic resonant beat-wave excitation of nonlinear relativistic plasma waves is studied analytically and in particle-in-cell simulations. We find that if the frequency separation of the lasers, ??, is 2?p or 3?p ( ?p is the plasma frequency), then plasma waves are still excited at ?p but they grow exponentially or superexponentially rather than secularly. Both of these subharmonic resonant instabilities saturate due to relativistic detuning. The analytical growth rates and saturation levels agree with the simulation results.

Ren, C.; Dodd, E. S.; Gordon, D.; Mori, W. B.

2000-10-01

265

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

SciTech Connect

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.

R.A. Kolesnikov; J.A. Krommes

2004-10-21

266

Microwave Reflection Measurements of Electron Densities in Electromagnetically Driven Shock-Produced Plasmas  

Microsoft Academic Search

The electron densities from 1013 to 1017 cm?3 in plasmas produced by electromagnetically driven, propagating, or reflected shock waves are measured by a microwave reflection method. The Mach number of the shock waves is varied from 9 to 25 in argon, air, and helium at initial pressures from 0.4 to 2.0 Torr. A 35-GHz microwave reflection probe is inserted into

Akimasa Funahashi; Susumu Takeda

1968-01-01

267

Bidirectional jet formation during driven magnetic reconnection in two-beam laser-plasma interactions  

NASA Astrophysics Data System (ADS)

Measurements of the bidirectional plasma jets that form at the surface of a solid target during a laser-generated driven magnetic reconnection are presented. Resistivity enhancement of at least 25× the classical Spitzer value is required when applying the Sweet-Parker model of reconnection to reconcile the experimentally observed reconnection time scale. Analytic calculations show that a fast reconnection model, which includes a priori the effects of microturbulent resistivity enhancement, better reproduces the experimental observations.

Nilson, P. M.; Willingale, L.; Kaluza, M. C.; Kamperidis, C.; Minardi, S.; Wei, M. S.; Fernandes, P.; Notley, M.; Bandyopadhyay, S.; Sherlock, M.; Kingham, R. J.; Tatarakis, M.; Najmudin, Z.; Rozmus, W.; Evans, R. G.; Haines, M. G.; Dangor, A. E.; Krushelnick, K.

2008-09-01

268

Localized arc filament plasma actuators for noise mitigation and mixing enhancement  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

269

Localized arc filament plasma actuators for noise mitigation and mixing enhancement  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

270

Fusion for Space Propulsion and Plasma Liner Driven MTF  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

271

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

SciTech Connect

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){proportional_to}W{sup -{alpha}}, with nontrivial exponent 1<{alpha}<2, while for weak fluctuations it is close to the lognormal distribution predicted by pure stochastic growth theory. The model's wave statistics resemble the statistics of plasma 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.

Tyshetskiy, Yu.; Cairns, I. H.; Robinson, P. A. [School of Physics, University of Sydney, Sydney, 2006 New South Wales (Australia)

2008-09-15

272

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

SciTech Connect

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.

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

273

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

SciTech Connect

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.

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

2010-05-06

274

Instability of magnetic fields in electroweak plasma driven by neutrino asymmetries  

NASA Astrophysics Data System (ADS)

The magnetohydrodynamics (MHD) is modified to incorporate the parity violation in the Standard Model leading to a new instability of magnetic fields in the electroweak plasma in the presence of nonzero neutrino asymmetries. The main ingredient for such a modified MHD is the antisymmetric part of the photon polarization tensor in plasma, where the parity violating neutrino interaction with charged leptons is present. We calculate this contribution to the polarization tensor connected with the Chern-Simons term in effective Lagrangian of the electromagnetic field. The general expression for such a contribution which depends on the temperature and the chemical potential of plasma as well as on the photon's momentum is derived. The instability of a magnetic field driven by the electron neutrino asymmetry for the ?-burst during the first second of a supernova explosion can amplify a seed magnetic field of a protostar, and, perhaps, can explain the generation of strongest magnetic fields in magnetars. The growth of a cosmological magnetic field driven by the neutrino asymmetry density ?n? = n?-nbar nu?0 is provided by a lower bound on |??e| = |??e|/T which is consistent with the well-known Big Bang nucleosynthesis (upper) bound on neutrino asymmetries in a hot universe plasma.

Dvornikov, Maxim; Semikoz, Victor B.

2014-05-01

275

Subharmonic resonances in plasmas: exponential and superexponential growth of driven relativistic plasma waves  

PubMed

Subharmonic resonant beat-wave excitation of nonlinear relativistic plasma waves is studied analytically and in particle-in-cell simulations. We find that if the frequency separation of the lasers, Deltaomega, is 2omega(p) or 3omega(p) ( omega(p) is the plasma frequency), then plasma waves are still excited at omega(p) but they grow exponentially or superexponentially rather than secularly. Both of these subharmonic resonant instabilities saturate due to relativistic detuning. The analytical growth rates and saturation levels agree with the simulation results. PMID:11030909

Ren; Dodd; Gordon; Mori

2000-10-16

276

Natural noise and external wakefield seeding in a proton-driven plasma accelerator  

NASA Astrophysics Data System (ADS)

An accurate description of noise levels is of crucial importance for the correct simulation of instability-driven processes, such as the density modulation of a long proton bunch traversing a plasma. To insure that the correct instability develops, a seed field must be larger than the cumulative shot noise. We develop an analytical theory of the noise field and compare it with multidimensional simulations. We find that the natural noise wakefield generated in a plasma by the CERN Super Proton Synchrotron bunches is very low, at the level of 10kV/m. This fortunate fact eases the requirements on the seed. Our three-dimensional simulations show that even a few tens MeV electron bunch precursor of a very moderate intensity is sufficient to seed the proton bunch self-modulation in plasma.

Lotov, K. V.; Lotova, G. Z.; Lotov, V. I.; Upadhyay, A.; Tückmantel, T.; Pukhov, A.; Caldwell, A.

2013-04-01

277

Beam-Driven Plasma Wakefield Acceleration of Electrons in Lithium and Rubidium Plasmas  

NASA Astrophysics Data System (ADS)

We report on the plasma wakefield experiments performed at the newly commissioned FACET facility at the SLAC National Laboratory. A beam of 2x10^10 20.5 GeV electrons was focused through a 20-40 cm long vapor column of lithium or rubidium produced in a heat-pipe oven. The electron beam tunnel-ionized the metal vapor and then drove a large amplitude plasma wake. The resulting interaction was investigated for different plasma densities and beam parameters. The primary diagnostic was the energy gain and loss features observed using an imaging magnetic spectrometer. Preliminary data and a comparison between acceleration in rubidium and lithium plasmas will be presented.

Vafaei-Najafabadi, Navid; Marsh, Kenneth; Clayton, Christopher; Joshi, Chandrasekhar; Adli, Erik; Corde, Sebastien; Litos, Michael; Li, Selina; Gessner, Spencer; Frederico, Joel; Hogan, Mark; Walz, Dieter; England, Joel; An, Weiming; Lu, Wei; Mori, Warren; Muggli, Patric; Delahaye, Jean-Pierre

2012-10-01

278

A new on-chip whole blood/plasma separator driven by asymmetric capillary forces.  

PubMed

A new on-chip whole blood/plasma separator driven by asymmetric capillary forces, which are produced through a microchannel with sprayed nanobead multilayers, has been designed, fabricated and fully characterized. The silica nanobead multilayers revealing as superhydrophilic surfaces have been fabricated using a spray layer-by-layer (LbL) nano-assembly method. This new on-chip blood plasma separator has been targeted for a sample-to-answer (S-to-A) microfluidic lab-on-a-chip (LOC) toward point-of-care clinical testing (POCT). Effective plasma separation from undiluted whole blood was achieved through the microchannel which was composed of asymmetric superhydrophilic surfaces with a 10 mm hydrophobic patch. Blood cells were continuously accumulated over the hydrophobic patch while the blood plasma was able to flow over the patch. Therefore, the blood plasma was successfully separated from the whole blood throughout the accumulated blood cells which worked as a so-called 'self-built-in blood cell microfilter'. The separated plasma was approximately 102 nL from a single drop of 3 ?L whole blood within 10 min, which is very suitable for single-use disposable POCT devices. PMID:23793507

Lee, Kang Kug; Ahn, Chong H

2013-08-21

279

Novel micro-pneumatic actuator for MEMS  

Microsoft Academic Search

This paper presents a micro-pneumatic actuator utilizing a new actuation principle for micro-mechanical systems. As a first application, a micro-gripper driven by two bellow-type micro-pneumatic actuators, is described. The basic structures of the micro-pneumatic actuator and the micro-gripper are fabricated by silicon dry etching in a single etching step. The device consists of a Pyrex–silicon–Pyrex sandwich structure which was assembled

Sebastian Bütefisch; Volker Seidemann; Stephanus Büttgenbach

2002-01-01

280

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)

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.

Ashpis, David E.; Laun, Matthew C.

2014-01-01

281

Fully microscopic analysis of laser-driven finite plasmas using the example of clusters  

NASA Astrophysics Data System (ADS)

We discuss a microscopic particle-in-cell (MicPIC) approach that allows bridging of the microscopic and macroscopic realms of laser-driven plasma physics. The simultaneous resolution of collisions and electromagnetic field propagation in MicPIC enables the investigation of processes that have been inaccessible to rigorous numerical scrutiny so far. This is illustrated by the two main findings of our analysis of pre-ionized, resonantly laser-driven clusters, which can be realized experimentally in pump-probe experiments. In the linear response regime, MicPIC data are used to extract the individual microscopic contributions to the dielectric cluster response function, such as surface and bulk collision frequencies. We demonstrate that the competition between surface collisions and radiation damping is responsible for the maximum in the size-dependent lifetime of the Mie surface plasmon. The capacity to determine the microscopic underpinning of optical material parameters opens new avenues for modeling nano-plasmonics and nano-photonics systems. In the non-perturbative regime, we analyze the formation and evolution of recollision-induced plasma waves in laser-driven clusters. The resulting dynamics of the electron density and local field hot spots opens a new research direction for the field of attosecond science.

Peltz, Christian; Varin, Charles; Brabec, Thomas; Fennel, Thomas

2012-06-01

282

Attempting a classification for electrical polymeric actuators  

NASA Astrophysics Data System (ADS)

Polymeric actuators, electroactive polymer actuators, electromechanical polymeric actuators, artificial muscles, and other, are usual expressions to name actuators developed during the last 15-20 years based on interactions between the electric energy and polymer films. The polymeric actuators can be divided into two main fields: electromechanical actuators working by electrostatic interactions between the polymer and the applied electric fields, and electrochemomechanical actuators, or reactive actuators, working by an electrochemical reaction driven by the flowing electric current. The electromechanical actuators can be classified into electrostrictive, piezoelectric, ferroelectric, electrostatic and electrokinetic. They can include a solvent (wet) or not (dry), or they can include a salt or not. Similitude and differences related to the rate and position control or to the possibility or not to include sensing abilities are discussed.

Otero, T. F.; López Cascales, J.; Fernández-Romero, A. J.

2007-04-01

283

A water bag model of driven phase space holes in non-neutral plasmas L. Friedland,1,a  

E-print Network

A water bag model of driven phase space holes in non-neutral plasmas I. Barth,1 L. Friedland,1,a, quasi-one-dimensional water bag model of this excitation for an initially flat-top distribution plasmas. A multiwater bag approach allows us to generalize the theory to other initial distributions

Friedland, Lazar

284

Excitation of the centrifugally driven interchange instability in a plasma confined by a magnetic dipole  

SciTech Connect

The centrifugally driven electrostatic interchange instability is excited for the first time in a laboratory magnetoplasma. The plasma is confined by a dipole magnetic field, and the instability is excited when an equatorial mesh is biased to induce a radial current that creates rapid axisymmetric plasma rotation. The observed instabilities appear quasicoherent in the lab frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. The mode structure is measured using a multiprobe correlation technique as well as a novel 96-point polar imaging diagnostic which measures particle flux along field lines that map to the pole. Interchange instabilities caused by hot electron pressure are simultaneously observed at the hot electron drift frequency. Adjusting the hot electron fraction {alpha} modifies the stability as well as the structures of the centrifugally driven modes. In the presence of larger fractions of energetic electrons, m=1 is observed to be the dominant mode. For faster rotating plasmas containing fewer energetic electrons, m=2 dominates. Results from a self-consistent nonlinear simulation reproduce the measured mode structures in both regimes. The low azimuthal mode numbers seen in the experiment and simulation can also be interpreted with a local, linear dispersion relation of the electrostatic interchange instability. Drift resonant hot electrons give the instability a real frequency, inducing stabilizing ion polarization currents that preferentially suppress high-m modes.

Levitt, B.; Maslovsky, D.; Mauel, M.E.; Waksman, J. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2005-05-15

285

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

NASA Technical Reports Server (NTRS)

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.

Parma, Brian

2004-01-01

286

Transport driven plasma flows in the scrape-off layer of ADITYA Tokamak in different orientations of magnetic field  

SciTech Connect

Parallel plasma flows in the scrape-off layer of ADITYA tokamak are measured in two orientations of total magnetic field. In each orientation, experiments are carried out by reversing the direction of the toroidal magnetic field and the plasma current. The transport-driven component is determined by averaging flow Mach numbers, measured in two directions of the toroidal magnetic field and the plasma current for the same orientation. It is observed that there is a significant transport-driven component in the measured flow and the component depends on the field orientation.

Sangwan, Deepak; Jha, Ratneshwar; Brotankova, Jana; Gopalkrishna, M. V. [Institute for Plasma Research, Gandhinagar 382428 (India)

2014-06-15

287

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

SciTech Connect

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.

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

2014-07-13

288

Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma  

Microsoft Academic Search

To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To

E. Edqvist; N. Snis; S. Johansson

2008-01-01

289

Superdiffusion and non-Gaussian statistics in a driven-dissipative 2D dusty plasma.  

PubMed

Anomalous diffusion and non-Gaussian statistics are detected experimentally in a two-dimensional driven-dissipative system. A single-layer dusty plasma suspension with a Yukawa interaction and frictional dissipation is heated with laser radiation pressure to yield a structure with liquid ordering. Analyzing the time series for mean-square displacement, superdiffusion is detected at a low but statistically significant level over a wide range of temperatures. The probability distribution function fits a Tsallis distribution, yielding q, a measure of nonextensivity for non-Gaussian statistics. PMID:18352381

Liu, Bin; Goree, J

2008-02-01

290

Characterization of Heat-Wave Propagation through Laser-Driven Ti-Doped Underdense Plasma  

SciTech Connect

The propagation of a laser-driven heat-wave into a Ti-doped aerogel target was investigated. The temporal evolution of the electron temperature was derived by means of Ti K-shell x-ray spectroscopy, and compared with two-dimensional radiation hydrodynamic simulations. Reasonable agreement was obtained in the early stage of the heat-wave propagation. In the later phase, laser absorption, the propagation of the heat wave, and hydrodynamic motion interact in a complex manner, and the plasma is mostly re-heated by collision and stagnation at the target central axis.

Tanabe, M; Nishimura, H; Ohnishi, N; Fournier, K B; Fujioka, S; Iwamae, A; Hansen, S B; Nagai, K; Girard, F; Primout, M; Villette, B; Brebion, D; Mima, K

2009-02-23

291

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

SciTech Connect

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.

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

292

Coherent and incoherent XUV emission in helium and neon, laser-driven plasmas  

SciTech Connect

The authors present results of measurements of high-order harmonic generation and XUV spontaneous emission in helium and neon plasmas excited by a short-pulse laser at intensities between 10[sup 14] and 5 [times] 10[sup 17]W/cm[sup 2]. The authors compare the observed behavior of the harmonics with recent single atom calculations in helium. The authors observe a wavelength dependence to the efficiency of harmonic generation that has not been previously reported. The authors observe line emission from excited state transitions in Ne[sup 7+] for the first time in a short pulse laser-driven plasma. In particular, the authors see strong emission and a rapid recombination rate for the 9.8 nm (3d-2p) transition that is a possible candidate for a recombination-pumped X-ray laser.

Crane, J.K.; Perry, M.D.; Strickland, D.; Herman, S. (Lawrence National Lab., CA (United States)); Falcone, R.W. (Univ. of California, Berkeley (United States))

1993-02-01

293

Multidimensional Plasma Sheath Modeling Using The Three Fluid Plasma Model in General Geometries  

NASA Astrophysics Data System (ADS)

There has been renewed interest in the use of plasma actuators for high speed flow control applications. In the plasma actuator, current is driven through the surrounding weakly ionized plasma to impart control moments on the hypersonic vehicle. This expanded general geometry study employs the three-fluid (electrons, ions,neutrals) plasma model as it allows the capture of electron inertial effects, as well as energy and momentum transfer between the charged and neutral species. Previous investigations have typically assumed an electrostatic electric field. This work includes the full electrodynamics in general geometries. Past work utilizing the research code WARPX (Washington Approximate Riemann Problem) employed cartesian grids. In this work, the problem is expanded to general geometries with the euler fluid equations employing Braginskii closure. In addition, WARPX general geometry grids are generated from Cubit or CAD files. Comparisons are made against AFRL magnetized plasma actuator experiments.

Lilly, Robert; Shumlak, Uri

2012-10-01

294

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

SciTech Connect

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.

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

2014-10-15

295

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

SciTech Connect

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.

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

296

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

NASA Astrophysics Data System (ADS)

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 ?-?' 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.

Tadsen, Benjamin; Greiner, Franko; Piel, Alexander

2014-10-01

297

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

NASA Astrophysics Data System (ADS)

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.

Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.

2014-05-01

298

Formation of Magnetically Driven Radiatively Cooled Plasma Jets in the Laboratory  

NASA Astrophysics Data System (ADS)

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).

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

299

CO2 impact ionization-driven plasma instability observed by Pioneer Venus Orbiter at Periapsis  

NASA Technical Reports Server (NTRS)

Observations of enhanced ac electric field noise about Pioneer Venus periapsis are shown to be related to spacecraft-generated impact ionization of the ambient CO2. The frequency of the electric field noise is found to peak in the vicinity of the CO2(+) ion plasma frequency and to closely follow the form of the neutral CO2 density profile. When the electric field noise in all channels is normalized by the square root of the CO2 number density, the ratio is constant. Since the impact electron density measured by the Pioneer Venus Langmuir probe, is observed to scale directly with the neutral CO2, the growth of the electric field amplitude is found to be linear in time with a growth rate proportional to the CO2(+) ion plasma frequency. On the basis of these results the impact ionization-driven instability is shown to be the ion acoustic instability. Implications for the lack of observations by Pioneer Venus of reflected-O(+)-driven instabilities, as have been proposed for the space shuttle, are discussed.

Curtis, S. A.; Brace, L. H.; Niemann, H. B.; Scarf, F. L.

1985-01-01

300

Gas- and plasma-driven hydrogen permeation through a reduced activation ferritic steel alloy F82H  

NASA Astrophysics Data System (ADS)

The first wall of a magnetic fusion power reactor will be subjected to hydrogen isotope permeation by the two mechanisms: one is gas-driven and the other is plasma-driven. Hydrogen transport through a reduced activation ferritic steel alloy F82H has been investigated using a steady-state laboratory-scale plasma device. Permeation parameters including permeability, solubility and diffusivity have been measured in the temperature range from 150 to 520 °C. The surface recombination coefficient for hydrogen has also been estimated by a one-dimensional steady-state permeation model with the input data taken from experiments. Using these parameters, the hydrogen plasma-driven permeation flux and inventory for a 0.5 cm thick first wall around 500 °C are estimated to be ?1.0 × 1013 atom cm-2 s-1 and ?2 × 1016 atom cm-3, respectively. Also, the implications of all these data on reactor operation are discussed.

Zhou, Haishan; Hirooka, Yoshi; Ashikawa, Naoko; Muroga, Takeo; Sagara, Akio

2014-12-01

301

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

SciTech Connect

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}.

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

302

Electron Injection and Acceleration with Petawatt Laser Driven Wakefield Accelerator in 10^17cm-3 Plasma  

NASA Astrophysics Data System (ADS)

Here we report observation of self-injected laser-plasma acceleration of electrons up to ˜ 350 MeV in a tenuous plasma (˜10^17 cm-3) driven by the Texas Petawatt laser (TPL). The generated electron beam contains a charge of over 30 pC, and is well collimated (< 10 mrad divergence). Electrons generated by TPL are not quasi monoenergetic and do not reach GeV level. This is likely due to imperfect PW laser quality. Simulations have shown that, driven by a high-Strehl-ratio TPL pulse, the laser plasma accelerator (LPA) can self-inject electrons and accelerate them to 3 GeV in such a tenuous plasma. The continuous electron energy spectrum also indicates that electron injection into plasma structure is continuous. Nevertheless, the observation of efficient self-injection at such low plasma density is a promising first step toward achieving multi-GeV LPAs in tenuous plasma. Simulations show that mild nonlinear plasma waves (a0˜1) are generated and a trapped electron can be accelerated up to ˜350MeV in this 5cm long tenuous plasma. Possible electron injection mechanisms are also discussed.

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

2011-11-01

303

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

NASA Astrophysics Data System (ADS)

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.

Yang, Lanlan

2015-01-01

304

The AWAKE Proton-driven Plasma Wakefield Acceleration Experiment at CERN  

NASA Astrophysics Data System (ADS)

We are planning an experiment at CERN to accelerate externally injected electrons e^- on the wake driven by a long, self-modulated proton p^+ bunch. In the plan the 12cm-long bunch from the SPS with 10^11 p^+ experiences a two-stream transverse instability that modulates the bunch radius at the plasma wake period. The bunch is focused to 200?m into a plasma with density in the 10^14-10^15cm-3 range. The modulation instability is seeded by co-propagating with the p^+ bunch a short laser pulse that ionizes a gas or vapor. The modulation resonantly drives wakefields to large amplitude. The low energy e^- ( 5-20MeV) produced by a rf-photoinjector gun are injected after the instability has saturated, 3-5m into the plasma and is accelerated to the GeV energy range. The e^- energy spectrum is measured by a large energy acceptance magnetic spectrometer. Bunch modulation diagnostics such as time resolved OTR and electro-optic measurements are also included. The general plans for the experiment as well as the latest developments will be presented.

Muggli, Patric

2012-10-01

305

A water bag model of driven phase space holes in non-neutral plasmas  

SciTech Connect

The formation and control of stable multiphase space hole structures and the associated Bernstein-Greene-Kruskal modes in trapped pure ion plasmas driven by an oscillating, chirped frequency perturbation are considered. The holes are formed by passing kinetic bounce resonances {omega}{sub d}=n{pi}u/L in the system, u and L are the longitudinal velocity of the plasma species and the length of the trap, and n is the multiplicity of the resonance (the number of the phase space holes). An adiabatic, quasi-one-dimensional water bag model of this excitation for an initially flat-top distribution of the ions in the trap is suggested, based on the isomorphism with a related problem in infinite quasineutral plasmas. A multiwater bag approach allows us to generalize the theory to other initial distributions. Numerical simulations yield a very good agreement with the theory until the coherent phase space structure is destroyed due to the resonance overlap when the decreasing driving frequency passes a critical value estimated within the water bag theory.

Barth, I.; Friedland, L. [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Shagalov, A. G. [Institute of Metal Physics, Ekaterinburg 620219 (Russian Federation)

2008-08-15

306

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

NASA Astrophysics Data System (ADS)

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.

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

2015-10-01

307

Microwave production from a plasma driven by a high power relativistic electron beam  

SciTech Connect

Microwave emission from an unmagnetized, electron beam driven plasma has been measured. Argon, contained in a Lucite tube, is pre-ionized by a 90 ..mu..s, 90 A electron source. The electron current is then injected into the tube. A diode is placed over the tube's aperture as the electron source for the microwave radiation. A spectrometer measures the output from 2 to 47 GHz in 3 bands. The emission takes place in two distinct phases. The 2 to 6 GHz output rises promptly with current pulse and then decays. For 6 GHz and above, there appears a low level microwave prepulse simultaneous with the 2 to 6 GHz output. This output rises sharply 25 ns after the current pulse begins, and includes frequencies beyond 40 GHz. The radio frequency output falls off before the current pulse ends. The microwave intensity decays monotonically with frequency. (JDH)

Di Capua, M.S.; Fulkerson, E.S.; Meeker, D.; DeGroot, J.

1986-12-01

308

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

309

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

SciTech Connect

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.

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

310

Piezoelectric ultrasonic micro\\/milli-scale actuators  

Microsoft Academic Search

A growing demand for actuators with a volume of less than 1mm3 has driven researchers to produce a varied range of micro\\/milli-scale designs. By examining the underlying physics of the actuator operation we are able to demonstrate why piezoelectric ultrasonic actuators have the greatest potential to meet this need. Moreover, it allows us to create a new classification system for

B. Watson; J. Friend; L. Yeo

2009-01-01

311

Development and characterization of plasma targets for controlled injection of electrons into laser-driven wakefields  

NASA Astrophysics Data System (ADS)

Laser-driven wakefield acceleration within capillary discharge waveguides has been used to generate high-quality electron bunches with GeV-scale energies. However, owing to fluctuations in laser and plasma conditions in combination with a difficult to control self-injection mechanism in the non-linear wakefield regime these bunches are often not reproducible and can feature large energy spreads. Specialized plasma targets with tailored density profiles offer the possibility to overcome these issues by controlling the injection and acceleration processes. This requires precise manipulation of the longitudinal density profile. Therefore our target concept is based on a capillary structure with multiple gas in- and outlets. Potential target designs are simulated using the fluid code OpenFOAM and those meeting the specified criteria are fabricated using femtosecond-laser machining of structures into sapphire plates. Density profiles are measured over a range of inlet pressures utilizing gas-density profilometry via Raman scattering and pressure calibration with longitudinal interferometry. In combination these allow absolute density mapping. Here we report the preliminary results.

Kleinwaechter, Tobias; Goldberg, Lars; Palmer, Charlotte; Schaper, Lucas; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2012-10-01

312

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

NASA Astrophysics Data System (ADS)

abstract-type="normal"> 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.

Hellinger, Petr; Trávní?ek, Pavel M.

2015-01-01

313

Characteristics of Muti-pulsing CHI driven ST plasmas on HIST  

NASA Astrophysics Data System (ADS)

The flux amplification and sustainment of the ST configurations by operating in Multi-pulsing Coaxial Helicity Injection (M-CHI) method have been demonstrated on HIST. The multi-pulsing experiment was demonstrated in the SSPX spheromak device at LLNL. In the double pulsing discharges, we have observed that the plasma current has been sustained much longer against the resistive decay as compared to the single CHI. We have measured the radial profiles of the flow velocities by using Ion Doppler Spectrometer and Mach probes. The result shows that poloidal shear flow exists between the open flux column and the most outer closed flux surface. The poloidal velocity shear at the interface may be caused by the ion diamagnetic drift, because of a steep density gradient there. The radial electric field is determined by the flow velocities and the ion pressure gradient through the radial momentum balance equation. We have investigated the contribution of ExB or the ion pressure gradient on the poloidal velocity shear by comparing the impurity ion flow obtained from the IDS with the bulk ion flow from the Mach probe. It should be noted that the diamagnetic drift velocity of the impurity is much smaller than ExB drift velocity. We will discuss characteristics of M-CHI-driven ST plasmas by varying TF coil current and the line averaged electron density.

Ishihara, M.; Hanao, T.; Ito, K.; Matsumoto, K.; Higashi, T.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2011-11-01

314

Valves Based on Amplified Piezoelectric Actuators  

Microsoft Academic Search

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

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

2004-01-01

315

Zeeman splitting of laser-driven soft x-ray laser line by the enhancement of magnetic field in plasma  

NASA Astrophysics Data System (ADS)

We observed a laser-driven plasma soft x-ray laser (SXRL) line at the wavelength of 18.895 nm from the nickel-like molybdenum ions under the existence of external magnetic field. In this experiment, 4 mm-diameter magnetic coil driven by an electrical pulsed power supply provided the external magnetic field of 15 T along the direction of the plasma column, and we could obtain the left-handed circular and right-handed circular polarization components separately. The experimental Zeeman splitting indicated that the strength of the magnetic field was enhanced by a factor of more than 10 than that of the applied field, which implied that the compression of magnetic field occurred in the dynamics of intense laser-plasma interaction.

Kawachi, T.; Hasegawa, N.; Iwamae, A.; Yoneda, H.

2014-11-01

316

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

SciTech Connect

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.

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

317

Spatio-temporal dynamics of the resonantly excited relativistic plasma wave driven by a CO2 laser  

NASA Astrophysics Data System (ADS)

The dynamics of a relativistic plasma wave (RPW) resonantly excited by a two frequency CO2 laser pulse and the effects of this wave on a co-propagating relativistic electron beam were studied through experiments and supporting simulations. The amplitude of the RPW and its harmonics were resolved in time and space with a Thomson scattering diagnostic. In addition, the plasma wave amplitude-length product and temporal duration were independently measured through time and frequency resolved forward scattering. The transverse electric and magnetic fields associated with the RPW were studied by the scattering of a 2 MeV electron beam, and the eventual heating of the plasma after the breakup of the RPW was measured from the x-ray radiation spectrum. The experiments and simulations show that the RPW reaches a peak amplitude of approximately 30%, with the amplitude limited by plasma blowout driven by the radial ponderomotive forces of the plasma wave.

Lal, A. K.; Gordon, D.; Wharton, K.; Clayton, C. E.; Marsh, K. A.; Mori, W. B.; Joshi, C.; Everett, M. J.; Johnston, T. W.

1997-05-01

318

Polymeric Actuators.  

PubMed

Actuators are materials and devices that are able to change their shape in response to changes in environmental conditions and perform mechanical work on nano-, micro-, and macroscales. Among the huge variety of different actuators, polymer-based ones are highly attractive because of a number of properties such as sensitivity to a broad range of stimuli and good mechanical properties. The goal of this review is to provide a general picture of different mechanisms and working principles of polymeric actuators as well as to show a palette of their applications. PMID:25386998

Ionov, Leonid

2014-11-11

319

Fabrication and test of a micro electromagnetic actuator  

Microsoft Academic Search

This paper presents the fabrication, test results and the finite element analysis of an electromagnetic micro actuator with three diaphragms that can be driven individually. The actuator consists of parylene diaphragms, spiral copper coils and permanent magnets. Parylene is waterproof and its Young’s modulus is small compared with metals, silicon and silicon compounds. So, it is adequate for the actuator

Ki Hoon Kim; Hyeun Joong Yoon; Ok Chan Jeong; Sang Sik Yang

2005-01-01

320

Chandrasekaran and Lindner 1 Power Flow Through Controlled Piezoelectric Actuators  

E-print Network

augmentation loop. When the piezoelectric actuator is driven by a current amplifier, we show that accelerationRevised Chandrasekaran and Lindner 1 Power Flow Through Controlled Piezoelectric Actuators Sriram of Intelligent Material Systems and Structures JIMSS-00-033 October, 2000 Keywords : piezoelectric actuators

Lindner, Douglas K.

321

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

NASA Technical Reports Server (NTRS)

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.

Singh, Nagendra; Khazanov, George

2004-01-01

322

Electromechanical actuators  

NASA Technical Reports Server (NTRS)

Materials illustrating a presentation on the development of electromechanical actuators (EMA) for electric flight systems are presented. Technology issues are identified, and major steps relative to EMA development, NASA's role, and a technology procurement plan are outlined.

Bigham, J.

1982-01-01

323

Numerical Simulations of Plasma Based Flow Control Applications  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

324

Parallel-coupled micro-macro actuators  

SciTech Connect

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.

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

1998-07-01

325

Micro actuators on the basis of thin SMA foils  

Microsoft Academic Search

Three innovative micro actuator concepts on the basis of the differential SMA principle are presented in this paper: a high\\u000a adaptive multi-actuator system, which is driven by numerous identical single actuators connected in parallel and in series,\\u000a a micro gripper for handling and assembling of complex hybrid micro systems and a micro actuator system in medical tools for\\u000a the percutaneous

M. Leester-Schädel; B. Hoxhold; C. Lesche; S. Demming; S. Büttgenbach

2008-01-01

326

A self-organized criticality model for ion temperature gradient mode driven turbulence in confined plasma  

SciTech Connect

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.

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

327

Bunch decompression for laser-plasma driven free-electron laser demonstration schemes  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers (FELs) require a very high electron beam quality in terms of emittance and energy spread. Since 2004 high quality electrons produced by laser-wakefield accelerators have been demonstrated, but the electron quality up to now did not allow the operation of a compact x-ray FEL using these electrons. Maier et al. [Phys. Rev. X 2, 031019 (2012)PRXHAE2160-330810.1103/PhysRevX.2.031019] suggested a concept for a proof-of-principle experiment allowing FEL operation in the vacuum ultraviolet range based on an optimized undulator and bunch decompression using electron bunches from a laser-plasma accelerator as currently available. In this paper we discuss in more detail how a chicane can be used as a bunch stretcher instead of a bunch compressor to allow the operation of a laser-wakefield accelerator driven FEL using currently available electrons. A scaling characterizing the impact of bunch decompression on the gain length is derived and the feasibility of the concept is tested numerically in a demanding scenario.

Seggebrock, T.; Maier, A. R.; Dornmair, I.; Grüner, F.

2013-07-01

328

Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

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.

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

329

Numerical study of secondary electron emission in a coaxial radio-frequency driven plasma jet at atmospheric pressure  

E-print Network

In this work we investigate a numerical model of a coaxial RF-driven plasma jet operated at atmospheric pressure. Due to the cylindrical symmetry an adequate 2-D representation of the otherwise 3-dimensional structure is used. A helium-oxygen chemistry reaction scheme is applied. We study the effect of secondary electrons emitted at the inner electrode as well as the inserted dielectric tube and discuss their impact on the discharge behavior. We conclude that a proper choice of materials can improve the desired mode of operation of such plasma jets in terms of materials and surface processing.

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

2011-01-01

330

Plasma structuring by the gradient drift instability at high latitudes and comparison with velocity shear driven processes  

NASA Technical Reports Server (NTRS)

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.

Basu, Sunanda; Mackenzie, E.; Basu, S.; Coley, W. R.; Sharber, J. R.; Hoegy, W. R.

1990-01-01

331

Q-factor enhancement for self-actuated self-sensing piezoelectric MEMS resonators applying a lock-in driven feedback loop  

NASA Astrophysics Data System (ADS)

This paper presents a robust Q-control approach based on an all-electrical feedback loop enhancing the quality factor of a resonant microstructure by using the self-sensing capability of a piezoelectric thin film actuator made of aluminium nitride. A lock-in amplifier is used to extract the feedback signal which is proportional to the piezoelectric current. The measured real part is used to replace the originally low-quality and noisy feedback signal to modulate the driving voltage of the piezoelectric thin-film actuator. Since the lock-in amplifier reduces the noise in the feedback signal substantially, the proposed enhancement loop avoids the disadvantage of a constant signal-to-noise ratio, which an analogue feedback circuit usually suffers from. The quality factor was increased from the intrinsic value of 1766 to a maximum of 34 840 in air. These promising results facilitate precise measurements for self-actuated and self-sensing MEMS cantilevers even when operated in static viscous media.

Kucera, M.; Manzaneque, T.; Sánchez-Rojas, J. L.; Bittner, A.; Schmid, U.

2013-08-01

332

Microwave Power for Smart Membrane Actuators  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

333

Thermally Actuated Hydraulic Pumps  

NASA Technical Reports Server (NTRS)

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.

Jones, Jack; Ross, Ronald; Chao, Yi

2008-01-01

334

Current-driven plasma waves in the Versatile Toroidal Facility (VTF)  

Microsoft Academic Search

Summary form only given, as follows. We have been conducting laboratory experiments to investigate plasma turbulence that can affect the propagation of electromagnetic waves. This work is aimed at simulating the ionospheric plasma turbulence and cross-checking our radar experiments at Arecibo, Puerto Rico. The large toroidal plasma device, called the Versatile Toroidal Facility (VTF), can produce a radially inhomogeneous plasma

D. T. Moriarty; M. C. Lee; R. J. Riddolls; S. M. Murphy; M. J. Rowlands

1995-01-01

335

An Improved Wideband Amplifier for Piezoelectric Actuator  

Microsoft Academic Search

Piezoelectric actuators are becoming increasingly important in such fields as vibration control, precision positioning, acoustics and sonar, and it is mainly driven by voltage in practical application. The amplifier driven by voltage has good stability and static characteristic, but in high speed motion conditions, we have to sacrifice frequency response bandwidth to ensure stability, so its closed loop frequency response

Changhai Ru; Chun Huang; Xiufen Ye; Shuxiang Guo

2007-01-01

336

Fast-acting valve actuator  

DOEpatents

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.

Cho, Nakwon (Knoxville, TN)

1980-01-01

337

Actuated atomizer  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

338

Design of an energy efficient and economical actuator for automobile windows  

E-print Network

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 ...

Durand, Keith (Keith V.)

2007-01-01

339

Strategies for mitigating the ionization-induced beam head erosion problem in an electron-beam-driven plasma wakefield accelerator  

NASA Astrophysics Data System (ADS)

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.

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

340

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

E-print Network

Recent experiments using proton backlighting of laser-foil interactions provide unique opportunities for studying magnetized plasma instabilities in laser-produced high-energy-density plasmas. Time-gated proton radiograph ...

Li, Chikang

341

Dielectric Actuation of Polymers  

NASA Astrophysics Data System (ADS)

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.

Niu, Xiaofan

342

Alternating current-driven non-thermal arc plasma torch working with air medium at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This work is devoted to the investigation of the discharge characteristics of high-frequency alternating current (ac) plasma torch working with air medium using electrical and spectroscopic techniques. A simple structure and compact ac plasma torch associated with a resonance power supply allows the generation of low power discharges (lower than 1 kW) with high voltage and low current. The discharge shows a negative resistance characteristic, and its curve shifts up with gas flow increased. The effects of power on the emission intensity of NO (A 2?+ ? X 2?), OH (A 2? ? X 2?, 0-0), N2(C 3?u ? B 3?g), H? and O (3p^{5}P \\to 3S^{5}S_{2}^{0}) and their spatial distributions in plasma jet axial direction were investigated. It has been found that the emission intensities of NO, OH, N2, H? and O rise with an increase in power dissipation. With increasing axial distances of plasma jet from nozzle exit, the emission intensity of OH increases and then decreases, while the emission intensities of other species decrease sharply. The vibrational temperature is much higher than the gas temperature, which demonstrates the ac-driven arc discharge deviation from thermal equilibrium plasma.

Ni, Guohua; Lin, Qifu; Li, Lei; Cheng, Cheng; Chen, Longwei; Shen, Jie; Lan, Yan; Meng, Yuedong

2013-11-01

343

Electron shear-flow-driven instability in magnetized plasmas with magnetic field gradient  

SciTech Connect

It is found that the zero-order current associated with electron shear flow produces a drift wave in magnetized plasmas, which can become unstable under certain conditions. This wave will be particularly important in low density and low temperature plasmas of heavy ions. As an example, numerical estimates are presented for a barium plasma with parameters compatible with experiments.

Saleem, Hamid [National Centre for Physics (NCP), Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Eliasson, Bengt [Faculty of Physics and Astronomy, Ruhr-University Bochum, Bochum 44780 (Germany)

2011-05-15

344

Modular droplet actuator drive  

NASA Technical Reports Server (NTRS)

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.

Pollack, Michael G. (Inventor); Paik, Philip (Inventor)

2011-01-01

345

Electrorepulsive actuator  

NASA Technical Reports Server (NTRS)

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.

Collins, Earl R., Jr. (inventor); Curry, Kenneth C. (inventor)

1992-01-01

346

Microwave production from a plasma driven by a high power relativistic electron beam  

SciTech Connect

Microwave emission from an unmagnetized plasma (T = 1 eV, n/sub e/ = 1.5 x 10/sup 11/ cm/sup -3/) driven by an electron beam (2.7 < I/sub b/ < 60 kA, 1.2 < V/sub b/ < 1.4 MV, t/sub rise/ = 15 ns, t/sub pulse/ = 60 ns) emitted from a 93 cm/sup 2/ velvet cathode with anode cathode gaps of 3.5 and 6.0 cm has been measured. A 90 ..mu..s, 80 A current pulse, emitted from a thermionic lanthanum hexaboride electron source, preionizes a 1.4 mT argon fill in a 1-m-long, 15-cm-diameter Lucite tube. A 6 ..cap omega.. water dielectric accelerator injects the electron current, 50 ..mu..s into the afterglow, into the tube through an aluminized Mylar anode. A Microwave spectrometer measures the radio frequency output in 2 to 18, 18 to 26, and 26 to 47 GHz bands that filters separate into narrower subbands. Digitizers record beam voltage, current, and microwave power obtained from diode detectors. The intrinsic electrical noise of the system is 15 mV p-p. A 3.36 cm-gap diode, delivering a 1.2 MeV, 90 kA beam into the tube, produces an intense pinch beyond the aluminized Mylar anode with little microwave output. A diode with a 6 cm gap, fills the aperture of the tube with 200 A/cm/sup 2/ (35 kA) of 1.4 MeV electrons that result in intense microwave radiation. The emission takes place in two distinct phases. The 2 to 6 GHz output, that includes ..omega../sub p/, rises promptly with the current pulse and then decays. For 6 GHz and above, there appears a low level microwave prepulse simultaneous with the 2 to 6 GHz output. This output raises sharply 25 ns after the current pulse begins, and includes frequencies out to and beyond 40 GHz. The radio frequency output falls off before the current pulse ends. The microwave intensity decays monotonically with frequency.

Di Capua, M.S.; Fulkerson, E.S.; Meeker, D.; DeGroot, J.

1986-06-09

347

A new amplifier for improving piezoelectric actuator linearity based on current switching in precision positioning  

Microsoft Academic Search

Piezoelectric actuators have traditionally been driven by voltage amplifiers. When driven at large voltages these actuators exhibit a significant amount of distortion, known as hysteresis, which may reduce the stability robustness of the system in feedback control applications. Piezoelectric transducers are known to exhibit less hysteresis when driven with current or charge rather than voltage. Despite this advantage, such methods

Changhai Ru; Liguo Chen; Bing Shao; Weibin Rong; Lining Sun

2008-01-01

348

Nonlinear pulse propagation and phase velocity of laser-driven plasma waves  

SciTech Connect

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.

Schroeder, Carl B.; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

2011-03-25

349

Stirling engine heat-actuated heat pump  

SciTech Connect

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.

Ackerman, R.A.; English, J.; Moynihan, T.

1983-08-01

350

Observations of electron phase-space holes driven during magnetic reconnection in a laboratory plasma  

E-print Network

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 ...

Katz, N.

351

Plasma-Density Determination from X-Ray Radiography of Laser-Driven Spherical Implosions  

E-print Network

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 ...

Frenje, Johan A.

352

Particle in cell simulations of Buneman instability of a current-driven plasma with q-nonextensive electron velocity distribution  

SciTech Connect

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.

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

353

One-dimensional hybrid simulation of the dc/RF combined driven capacitively coupled CF{sub 4} plasmas  

SciTech Connect

We developed a one-dimensional hybrid model to simulate the dc/RF combined driven capacitively coupled plasma for CF{sub 4} discharges. The numerical results show the influence of the dc source on the plasma density distribution, ion energy distributions (IEDs), and ion angle distributions (IADs) on both RF and dc electrodes. The increase of dc voltage impels more ions with high energy to the electrode applied to the dc source, which makes the IEDs at the dc electrode shift toward higher energy and the peaks in IADs shift toward the small angle region. At the same time, it also decreases ion-energy at the RF electrode and enlarges the ion-angles which strike the RF electrode.

Wang Shuai [School of Science, Northeastern University, Shenyang 110891 (China); Xu Xiang; Wang Younian [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2012-11-15

354

Particle in cell simulations of Buneman instability of a current-driven plasma with q-nonextensive electron velocity distribution  

NASA Astrophysics Data System (ADS)

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.

Niknam, A. R.; Roozbahani, H.; Hashemzadeh, M.; Komaizi, D.

2014-09-01

355

Micro actuators and their applications  

Microsoft Academic Search

Driving principles, configurations and applications of micromachined actuators are reviewed. Examples, taken from our research activities, include an optical matrix switch composed of arrayed torsional micromirrors which are driven by electrostatic force; a microactuator using thin film shape memory alloy (TiNi); a microactuator for scanning a microwave antenna and a self-assembly of three-dimensional microstructures by scratch drive microactuators. A system

Hiroyuki Fujita; Hiroshi Toshiyoshi

1998-01-01

356

Memory metal actuator  

NASA Technical Reports Server (NTRS)

A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator.

Ruoff, C. F. (inventor)

1985-01-01

357

Nonlinear Relativistic Dynamics of a Plasma Foil Driven by Radiation Pressure  

SciTech Connect

Laboratory experiments with relativistic plasma mirrors make it possible to explore with relatively small size experiments physical phenomena that occur in nature over much larger spatial scales. Under appropriate conditions, the reflection of ultraintense electromagnetic radiation from a plasma mirror can be exploited in order to push the mirror to relativistic energies. On the other hand plasmas are susceptible to instabilities that need be controlled as they may provide powerful energy amplification mechanisms but, at the same time, can disrupt the coherent response of the particle in the plasma.

Pegoraro, F. [Physics Department and CNISM, University of Pisa, Largo Pontecorvo, 3, 56127 Pisa (Italy); Bulanov, S. V. [Advanced Photon Research Center, JAEA, 8-1 Umemidai, Kizugawa, 619-0215 Kyoto, Japan and A. M. Prokhorov Institute of General Physics, RAS, Vavilov street, 38, 119991 Moscow (Russian Federation)

2009-07-25

358

Electron properties and air mixing in radio frequency driven argon plasma jets at atmospheric pressure  

NASA Astrophysics Data System (ADS)

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.

van Gessel, Bram; Brandenburg, Ronny; Bruggeman, Peter

2013-08-01

359

High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.  

PubMed

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

Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

2013-12-13

360

Reduction of time-averaged irradiation speckle nonuniformity in laser-driven plasmas due to target ablation  

NASA Astrophysics Data System (ADS)

In inertial confinement fusion (ICF) experiments, irradiation uniformity is improved by passing laser beams through distributed phase plates (DPPs), which produce focused intensity profiles with well-controlled, reproducible envelopes modulated by fine random speckle. [C. B. Burckhardt, Appl. Opt. 9, 695 (1970); Y. Kato and K. Mima, Appl. Phys. B 29, 186 (1982); Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984); Laboratory for Laser Energetics LLE Review 33, NTIS Document No. DOE/DP/40200-65, 1987 (unpublished), p. 1; Laboratory for Laser Energetics LLE Review 63, NTIS Document No. DOE/SF/19460-91, 1995 (unpublished), p. 1.] A uniformly ablating plasma atmosphere acts to reduce the contribution of the speckle to the time-averaged irradiation nonuniformity by causing the intensity distribution to move relative to the absorption layer of the plasma. This occurs most directly as the absorption layer in the plasma moves with the ablation-driven flow, but it is shown that the effect of the accumulating ablated plasma on the phase of the laser light also makes a quantitatively significant contribution. Analytical results are obtained using the paraxial approximation applied to the beam propagation, and a simple statistical model is assumed for the properties of DPPs. The reduction in the time-averaged spatial spectrum of the speckle due to these effects is shown to be quantitatively significant within time intervals characteristic of atmospheric hydrodynamics under typical ICF irradiation intensities.

Epstein, R.

1997-09-01

361

All-Optical Control of Nonlinear Self-Focusing in Plasmas Using Non-Resonantly Driven Plasma Wave  

SciTech Connect

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 (n{sub 0} = 10{sup 18} cm{sup -3}) but also transforms the pulse into the unique format inaccessible to the conventional amplification techniques (relativistically intense periodic trains of few-cycle spikes). This well focusable pulse train is a novel light source interesting for ultra-fast high-field science applications. The opposite case of suppression of nonlinear self-focusing and dynamical self-guiding of an over-critical multi-frequency pulse is proposed for the proof-of-principle experimental study.

Kalmykov, S. Y.; Shadwick, B. A. [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States); Downer, M. C. [The Department of Physics, C1500, University of Texas at Austin, Austin, TX 78712 (United States)

2010-11-04

362

A Comparison between Plasma Synthetic Jets and Conventional Jets  

NASA Astrophysics Data System (ADS)

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 of high voltage, high frequency AC at ambient conditions of pressure and temperature, a region of DBD plasma is formed starting from the edges of the exposed electrode. In an initially quiescent medium, this plasma region is observed to induce and sustain entrainment of near wall fluid, the volume of which is ejected out from the base of the actuator in the form of a jet. The electrodes are shaped either in the form of annular arrays for rendering a circular jet, or linear arrays for rendering a rectangular jet. 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. The jet outputs are found to be affected by a variety of system inputs, including the input electrical power, pulsing frequency, and actuator dimension. The effects of varying the above parameters on the self similarity behavior of plasma synthetic jets are examined and compared to mechanically driven jets.

Santhanakrishnan, Arvind; Jacob, Jamey

2007-11-01

363

An optimal real-time controller for vertical plasma stabilization  

E-print Network

Modern Tokamaks have evolved from the initial axisymmetric circular plasma shape to an elongated axisymmetric plasma shape that improves the energy confinement time and the triple product, which is a generally used figure of merit for the conditions needed for fusion reactor performance. However, the elongated plasma cross section introduces a vertical instability that demands a real-time feedback control loop to stabilize the plasma vertical position and velocity. At the Tokamak \\`a Configuration Variable (TCV) in-vessel poloidal field coils driven by fast switching power supplies are used to stabilize highly elongated plasmas. TCV plasma experiments have used a PID algorithm based controller to correct the plasma vertical position. In late 2013 experiments a new optimal real-time controller was tested improving the stability of the plasma. This contribution describes the new optimal real-time controller developed. The choice of the model that describes the plasma response to the actuators is discussed. The ...

Cruz, N; Coda, S; Duval, B P; Le, H B; Rodrigues, A P; Varandas, C A F; Correia, C M B A; Goncalves, B S

2014-01-01

364

Revisiting shock-driven exploding pushers: Insights into plasma flows and fields, stopping power, nucleosynthesis, and  

E-print Network

, nucleosynthesis, and kinetic effects Richard D Petrasso Plasma Science and Fusion Center Massachusetts Institute in plasmas, to study reactions important for nucleosynthesis, and to identify and study kinetic phenomena topics such as nucleosynthesis and kinetic and/or multi-ion fluid phenomena. For nucleosynthesis

365

Trapped electron acceleration by a laser-driven relativistic plasma wave  

NASA Astrophysics Data System (ADS)

THE aim of new approaches for high-energy particle acceleration1 is to push the acceleration rate beyond the limit (~100 MeV m-1) imposed by radio-frequency breakdown in conventional accelerators. Relativistic plasma waves, having phase velocities very close to the speed of light, have been proposed2-6 as a means of accelerating charged particles, and this has recently been demonstrated7,8. Here we show that the charged particles can be trapped by relativistic plasma waves-a necessary condition for obtaining the maximum amount of energy theoretically possible for such schemes. In our experiments, plasma waves are excited in a hydrogen plasma by beats induced by two collinear laser beams, the difference in whose frequencies matches the plasma frequency. Electrons with an energy of 2 MeV are injected into the excited plasma, and the energy spectrum of the exiting electrons is analysed. We detect electrons with velocities exceeding that of the plasma wave, demonstrating that some electrons are 'trapped' by the wave potential and therefore move synchronously with the plasma wave. We observe a maximum energy gain of 28 MeV, corresponding to an acceleration rate of about 2.8 GeV m-1.

Everett, M.; Lal, A.; Gordon, D.; Clayton, C. E.; Marsh, K. A.; Joshi, C.

1994-04-01

366

Application of a pulsed, RF-driven, multicusp source for low energy plasma immersion ion implantation  

SciTech Connect

The multicusp ion source can produce large volumes of uniform, quiescent, high density plasmas. A plasma chamber suited for plasma immersion ion implantation (PIII) was readily made. Conventional PIII pulses the bias voltage applied to the substrate which is immersed in a CW mode plasma. Here, a method by which the plasma itself is pulsed was developed. Typically pulse lengths of 500 {mu}s are used and are much shorter than that of the substrate voltage pulse (5-15 ms). This approach, together with low gas pressures and low bias voltages, permits the constant energy implantation of an entire wafer simultaneously without glow discharge. Results show that this process can yield implant currents of up to 2.5 mA/cm{sup 2}; thus very short implant times can be achieved. Uniformity of the ion flux is also discussed. As this method can be scaled to any dimension, it can be made to handle any size wafer.

Wengrow, A.B.; Leung, K.N.; Perkins, L.T.; Pickard, D.S.; Rickard, M.; Williams, M.D. [Lawrence Berkeley Lab., CA (United States); Tucker, M. [Spectrum Sciences, Inc., Santa Clara, CA (United States)

1996-06-01

367

Toward standardization of EAP actuators test procedures  

NASA Astrophysics Data System (ADS)

Since the field of Electroactive Polymers (EAP) actuators is fairly new there are no standard testing processes for such intelligent materials. This drawback can seriously limit the scope of application of EAP actuators, since the targeted industrial sectors (aerospace, biomedical...) demand high reliability and product assurance. As a first iteration two elements are required to define a test standard for an EAP actuator: a Unit Tester, and a Component Specification. In this paper a EAP Unit Tester architecture is presented along with the required classification of measurements to be included in the EAP actuator Component Specification. The proposed EAP Unit Tester allows on-line monitoring and recording of the following properties of the specimen under test: large deformation, small tip displacement, temperature at the electrodes, weight of the specimen, voltage and current driven into the EAP, load being applied to the actuator, output voltage of the EAP in sensing operation and mode of operation (structure/sensor/actuator/smart). The measurements are taken simultaneously, in real-time. The EAP Unit Tester includes a friendly Graphical User Interface. It uses embedded Excel tools to visualize data. In addition, real-time connectivity with MATLAB allows an easy testing of control algorithms. A novel methodology to measure the properties of EAP specimens versus a variable load is also presented. To this purpose a force signals generator in the range of mN was developed. The device is based on a DC mini-motor. It generates an opposing force to the movement of the EAP actuator. Since the device constantly opposes the EAP actuator movement it has been named Digital Force Generator (DFG). The DFG design allows simultaneous length and velocity measuring versus different load signals. By including such a device in the EAP Unit Tester the most suitable application for the specimen under test can be easily identified (vibration damper, large deformation actuator, large force actuator, fast actuator...).

Fernandez, Diego; Moreno, Luis; Baselga, Juan

2005-05-01

368

Iogenic Plasma and its Rotation-Driven Transport in Jupiter's Magnetosphere  

NASA Technical Reports Server (NTRS)

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.

Smyth, William H.

2001-01-01

369

Plasma Physical Parameters along Coronal-mass-ejection-driven Shocks. I. Ultraviolet and White-light Observations  

NASA Astrophysics Data System (ADS)

In this work, UV and white-light (WL) coronagraphic data are combined to derive the full set of plasma physical parameters along the front of a shock driven by a coronal mass ejection. Pre-shock plasma density, shock compression ratio, speed, and inclination angle are estimated from WL data, while pre-shock plasma temperature and outflow velocity are derived from UV data. The Rankine-Hugoniot (RH) equations for the general case of an oblique shock are then applied at three points along the front located between 2.2 and 2.6 R ? at the shock nose and at the two flanks. Stronger field deflection (by ~46°), plasma compression (factor ~2.7), and heating (factor ~12) occur at the nose, while heating at the flanks is more moderate (factor 1.5-3.0). Starting from a pre-shock corona where protons and electrons have about the same temperature (Tp ~ Te ~ 1.5 × 106 K), temperature increases derived with RH equations could better represent the proton heating (by dissipation across the shock), while the temperature increase implied by adiabatic compression (factor ~2 at the nose, ~1.2-1.5 at the flanks) could be more representative of electron heating: the transit of the shock causes a decoupling between electron and proton temperatures. Derived magnetic field vector rotations imply a draping of field lines around the expanding flux rope. The shock turns out to be super-critical (sub-critical) at the nose (at the flanks), where derived post-shock plasma parameters can be very well approximated with those derived by assuming a parallel (perpendicular) shock.

Bemporad, A.; Susino, R.; Lapenta, G.

2014-04-01

370

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)

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.

Yu, Min; He, Qingsong; Yu, Dingshan; Zhang, Xiaoqing; Ji, Aihong; Zhang, Hao; Guo, Ce; Dai, Zhendong

2012-10-01

371

Porcelain-coated antenna for radio-frequency driven plasma source  

DOEpatents

A new porcelain-enamel coated antenna creates a clean plasma for volume or surface-conversion ion sources. The porcelain-enamel coating is hard, electrically insulating, long lasting, non fragile, and resistant to puncture by high energy ions in the plasma. Plasma and ion production using the porcelain enamel coated antenna is uncontaminated with filament or extraneous metal ions because the porcelain does not evaporate and is not sputtered into the plasma during operation. Ion beams produced using the new porcelain-enamel coated antenna are useful in ion implantation, high energy accelerators, negative, positive, or neutral beam applications, fusion, and treatment of chemical or radioactive waste for disposal. For ion implantation, the appropriate species ion beam generated with the inventive antenna will penetrate large or small, irregularly shaped conducting objects with a narrow implantation profile. 8 figs.

Leung, K.N.; Wells, R.P.; Craven, G.E.

1996-12-24

372

Porcelain-coated antenna for radio-frequency driven plasma source  

DOEpatents

A new porcelain-enamel coated antenna creates a clean plasma for volume or surface-conversion ion sources. The porcelain-enamel coating is hard, electrically insulating, long lasting, non fragile, and resistant to puncture by high energy ions in the plasma. Plasma and ion production using the porcelain enamel coated antenna is uncontaminated with filament or extraneous metal ion because the porcelain does not evaporate and is not sputtered into the plasma during operation. Ion beams produced using the new porcelain-enamel coated antenna are useful in ion implantation, high energy accelerators, negative, positive, or neutral beam applications, fusion, and treatment of chemical or radioactive waste for disposal. For ion implantation, the appropriate species ion beam generated with the inventive antenna will penetrate large or small, irregularly shaped conducting objects with a narrow implantation profile.

Leung, Ka-Ngo (Hercules, CA); Wells, Russell P. (Kensington, CA); Craven, Glen E. (Fremont, CA)

1996-01-01

373

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

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.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2011-11-01

374

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

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.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2012-04-01

375

Piezoelectric polymer actuators in a vibration isolation application  

Microsoft Academic Search

We present results from development and testing of lightweight actuators made of the piezoelectric polymer PVDF. The prototype being developed is intended for microgravity applications in space and has been tested aboard NASA's Reduced Gravity Platform. The design has been driven by the requirements for a full 3D environment. Incorporation of additional electrical leads into the actuators themselves may remove

Gary W. Bohannan; V. Hugo Schmidt; R. J. Conant; Jil Hallenberg; Connie Nelson; Ashley Childs; Chip Lukes; Jason Ballensky; Joe Wehri; Bryan Tikalsky; Erica McKenzie

2000-01-01

376

Optical driving of actuator using poly-vinylidine difluoride cantilever  

Microsoft Academic Search

Optically driven actuators are a non-contact method for the remote application of light energy. We propose a new method for optically driving actuators which uses three polyvinylidine difluoride (PVDF) cantilevers as the legs and a polymer film as the body. The PVDF cantilevers are coated with silver on one surface. PVDF is a ferroelectric polymer that has both pyroelectric and

Y. Mizutani; S. Nishimura; Y. Otani; N. Umeda

2006-01-01

377

Surface resistance experiments with IPMC sensors and actuators  

Microsoft Academic Search

This paper describes experiments with the surface resistance of IPMC actuators and sensors. We measure the surface resistance of samples working as sensors or as a voltage driven actuators, as well as when insulated. The results show that in all cases the surface resistance of a sample is highly correlated to material curvature. Based on these observations we present an

A. Punning; M. Kruusmaa; A. Aabloo

2007-01-01

378

NDE and Advanced Actuators for Space Applications at JPL  

NASA Technical Reports Server (NTRS)

Nondestructive Evaluation and Advanced Actuators (NDEAA) are presented. The focus areas are on mechanisms and devices that are driven by acoustic or elastic waves. The topics include: 1) Nondestructive Evaluation; 2) Advanced Actuators; 3) Ultrasonic Medical Diagnostics and Treatment; and 4) Telerobotics.

Bar-Cohen, Yoseph

1999-01-01

379

National Ignition Facility targets driven at high radiation temperature: Ignition, hydrodynamic stability, and laser-plasma interactions  

NASA Astrophysics Data System (ADS)

A target design driven indirectly to ignition at a radiation temperature of 350 eV for the National Ignition Facility (NIF) is reported in integrated radiation-hydrodynamic simulations which detail the necessary specifications to achieve ignition and burn. The target is further analyzed to determine its hydrodynamic stability as well as its vulnerability to laser-plasma interactions. This target shows enhanced hydrodynamic stability over targets previously designed at lower radiation temperatures [S. W. Haan, S. M. Pollaine, J. D. Lindl et al., Phys. Plasmas 2, 2480 (1995); W. J. Krauser, N. M. Hoffman, D. C. Wilson et al., ibid.3, 2084 (1996); D. C. Wilson, P. A. Bradley, N. M. Hoffman et al., ibid.5, 1953 (1998); P. A. Bradley and D. C. Wilson, ibid.6, 4293 (1999)]. To control laser-plasma instabilities, both polarization and temporal smoothing of the spatially smoothed NIF laser beams is necessary. Analyses of laser scatter in target blow-off at peak power demonstrate saturation in both the 300 and 350 eV designs by nonlinear processes such as rescatter of the scattered laser light and the Langmuir decay instability.

Hinkel, D. E.; Haan, S. W.; Langdon, A. B.; Dittrich, T. R.; Still, C. H.; Marinak, M. M.

2004-03-01

380

Control of ultra-intense single attosecond pulse generation in laser-driven overdense plasmas.  

PubMed

Ultra-intense single attosecond pulse (AP) can be obtained from circularly polarized (CP) laser interacting with overdense plasma. High harmonics are naturally generated in the reflected laser pulses due to the laser-induced one-time drastic oscillation of the plasma boundary. Using two-dimensional (2D) planar particle-in-cell (PIC) simulations and analytical model, we show that multi-dimensional effects have great influence on the generation of AP. Self-focusing and defocusing phenomena occur in front of the compressed plasma boundary, which lead to the dispersion of the generated AP in the far field. We propose to control the reflected high harmonics by employing a density-modulated foil target (DMFT). When the target density distribution fits the laser intensity profile, the intensity of the attosecond pulse generated from the center part of the plasma has a flatten profile within the center range in the transverse direction. It is shown that a single 300 attosecond (1 as = 10(-18)s) pulse with the intensity of 1.4 × 10(21) W cm(-2) can be naturally generated. Further simulations reveal that the reflected high harmonics properties are highly related to the modulated density distribution and the phase offset between laser field and the carrier envelope. The emission direction of the AP generated from the plasma boundary can be controlled in a very wide range in front of the plasma surface by combining the DMFT and a suitable driving laser. PMID:24514788

Liu, Qingcao; Xu, Yanxia; Qi, Xin; Zhao, Xiaoying; Ji, Liangliang; Yu, Tongpu; Wei, Luo; Yang, Lei; Hu, Bitao

2013-12-30

381

Flight control actuation system  

NASA Technical Reports Server (NTRS)

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.

Wingett, Paul T. (Inventor); Gaines, Louie T. (Inventor); Evans, Paul S. (Inventor); Kern, James I. (Inventor)

2006-01-01

382

Recent developments in DBD plasma flow control  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

383

MICRO ELECTROSTRICTIVE ACTUATOR WITH METAL COMPLIANT ELECTRODES FOR FLOW CONTROL APPLICATIONS  

E-print Network

MICRO ELECTROSTRICTIVE ACTUATOR WITH METAL COMPLIANT ELECTRODES FOR FLOW CONTROL APPLICATIONS of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan ABSTRACT A micro synthetic jet actuator driven using micro actuators have received significant attention in the last few decades [1]. However

Kasagi, Nobuhide

384

Microwave-driven plasmas in hollow-core photonic crystal fibres  

NASA Astrophysics Data System (ADS)

Argon micro-plasmas a few centimetres long are generated at low gas pressure (6 mbar) in hollow-core photonic crystal fibres with 100 µm core diameter, using microwave excitation (2.45 GHz) based on a surfatron, with no damage to the host structure. Electromagnetic simulations assist the design of the surfatron cavity, finding optimal conditions for discharge ignition and maintenance. The plasma characterization reveals an electron density in the range 8 × 1014-1015 cm-3 (estimated from a semi-empirical analysis of the power coupled to the plasma, along the axial-direction) and a gas temperature of 1100-1300 K at the centre of the fibre (measured by optical emission spectroscopy diagnostics), thus showing an impressive ionization degree of ˜10-2 for power densities of ˜0.1 MW cm-3. The micro-plasma dynamics is investigated using a self-consistent one-dimensional (radial) fluid model, describing the charged particle and the electron energy transport, the electromagnetic excitation and the gas heating. Model results are used to confirm the diagnostics, revealing an extreme plasma confinement and a steep temperature gradient that give rise to the main operation features of this novel compact UV source.

Debord, B.; Alves, L. L.; Gérôme, F.; Jamier, R.; Leroy, O.; Boisse-Laporte, C.; Leprince, P.; Benabid, F.

2014-02-01

385

Microprocessor controlled force actuator  

NASA Technical Reports Server (NTRS)

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.

Zimmerman, D. C.; Inman, D. J.; Horner, G. C.

1986-01-01

386

Simulations in One Dimension of Unstable Mix in the Ablation Region in Laser-Driven Plasmas  

Microsoft Academic Search

The effects of Rayleigh-Taylor flow in laser-driven ablation are simulated within the one-dimensional hydrocode LILAC as a diffusive transport process where material constituents are redistributed continuously along with their thermal and mix-motion energy within a growing mix region whose boundaries are obtained from a saturable linear multimode model of the Rayleigh-Taylor instability. The mix-transport coefficients and the mix-motion energy are

R. Epstein; J. A. Delettrez; D. K. Bradley; C. P. Verdon; U. Alon; D. Shvarts

1996-01-01

387

Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.  

PubMed

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

Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

2014-02-01

388

The effect of plasma heating on sublimation-driven flow in Io's atmosphere  

NASA Technical Reports Server (NTRS)

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.

Wong, Mau C.; Johnson, Robert E.

1995-01-01

389

Multilayer Piezoelectric Stack Actuator Characterization  

NASA Technical Reports Server (NTRS)

Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

2008-01-01

390

Possible energy gain for a plasma-liner-driven magneto-inertial fusion concept  

SciTech Connect

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.

Knapp, C. E.; Kirkpatrick, R. C. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-07-15

391

Electrode-plasma-driven radiation cutoff in long-pulse, high-power microwave devices  

SciTech Connect

The impact of electrode plasma dynamics on the radiation production in a high power microwave device is examined using particle-in-cell simulations. Using the design of a compact 2.4 GHz magnetically insulated line oscillator (MILO) as the basis for numerical simulations, we characterize the time-dependent device power and radiation output over a range of cathode plasma formation rates. These numerical simulations can self-consistently produce radiation characteristics that are similar to measured signals in long pulse duration MILOs. This modeling capability should result in improved assessment of existing high-power microwave devices and lead to new designs for increased radiation pulse durations.

Rose, D. V.; Miller, C. L.; Welch, D. R. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Portillo, S. [Naval Surface Warfare Center, Dahlgren, Virginia 22448 (United States)

2013-03-15

392

Superfluid helium sloshing dynamics induced oscillations and fluctuations of angular momentum, force and moment actuated on spacecraft driven by gravity gradient or jitter acceleration associated with slew motion  

NASA Technical Reports Server (NTRS)

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by the gravity gradient and jitter accelerations associated with slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) for slew motion which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid-vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers have also been derived. Examples are also given for cases applicable to the AXAF-S spacecraft sloshing dynamics associated with slew motion.

Hung, R. J.

1994-01-01

393

Nanotube micro-optomechanical actuators  

Microsoft Academic Search

In this letter we demonstrate a simple carbon nanotube patterning technique that combines nanotube film bonding, photolithography, and O2 plasma etching. Well defined carbon nanotube film structures with line widths less than ~1.5 mum and thickness ranging from 40 to 780 nm were readily fabricated. A micro-optomechanical actuator based on this process has been demonstrated. This patterning process can be

Shaoxin Lu; Balaji Panchapakesan

2006-01-01

394

Lower hybrid instability driven by mono-energy {alpha}-particles with finite pitch angle spread in a plasma  

SciTech Connect

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.

Kumar, Pawan; Singh, Vishwesh; Tripathi, V. K. [Department of Physics, IIT Delhi, New Delhi-110016 (India)

2013-02-15

395

Ion temperature gradient driven instability in high beta plasmas of a sheared slab  

Microsoft Academic Search

A set of simplified integral eigenmode equations with neglecting of the magnetic gradient drift effects are derived and employed to investigate the ion temperature gradient modes in plasmas of sheared slab geometry. Perturbations of both perpendicular and parallel components of magnetic vector potential are considered, as well as the perturbation of the electrostatic potential. The characteristics of the ion temperature

Songfen Liu; Wei Kong; Beilai Hu; Feng Liu; Jiaqi Dong; Zhe Gao

2009-01-01

396

GeV ELECTRON BEAMS FROM A CENTIMETER-SCALE LASER-DRIVEN PLASMA ACCELERATOR  

E-print Network

discharge waveguide [1, 2]. Electron beams were not observed without a plasma channel, indicating that self frequency (RF) accelerators is limited by electrical breakdown within the accelerating cavity to a few tens] are discussed. A hydrogen-filled capillary discharge waveguide [6, 7, 8] guided high-intensity laser pulses over

Geddes, Cameron Guy Robinson

397

Nanoporous carbon actuator and methods of use thereof  

DOEpatents

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.

Biener, Juergen (San Leandro, CA); Baumann, Theodore F. (Discovery Bay, CA); Shao, Lihua (Karlsruhe, DE); Weissmueller, Joerg (Stutensee, DE)

2012-07-31

398

Comparison of drive amplifier for piezoelectric actuators  

Microsoft Academic Search

The power requirements imposed on the amplifier by piezoelectric actuators in both open and closed loop vibration suppression control systems is discussed. We consider a two-degree-of-freedom mechanical system driven by a piezoelectric stack for the purpose of analyzing power flow and power dissipation. A state space model for this system that includes the electrical input and output variables of the

Douglas K. Lindner; Nikola Vujic; Donald J. Leo

2001-01-01

399

First results with a surface conversion H ion source based on helicon wave mode-driven plasma discharge  

SciTech Connect

The currently employed converter-type negative ion source at Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H{sup -} ion beams in a filament-driven discharge. The extracted H{sup -} beam current is limited by the achievable plasma density, which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which degrades the performance of the H{sup -} conversion surface. In order to overcome these limitations we have designed and tested a prototype of a surface conversion H{sup -} ion source, based on excitation of helicon plasma wave mode with an external antenna. The source has been operated with and without cesium injection. An H{sup -} beam current of over 12 mA has been transported through the low energy beam transport of the LANSCE ion source test stand. The results of these experiments and the effects of different source parameters on the extracted beam current are presented. The limitations of the source prototype are discussed and future improvements are proposed based on the experimental observations.

Tarvainen, Ollie A [Los Alamos National Laboratory; Geros, Ernest [Los Alamos National Laboratory; Rouleau, Gary [Los Alamos National Laboratory; Zaugg, Thomas J [Los Alamos National Laboratory

2008-01-01

400

Numerical solution to an electromagnetic model with Neumann boundary conditions, for a microwave-driven plasma reactor  

NASA Astrophysics Data System (ADS)

This work deals with the two-dimensional electromagnetic modelling of a microwave-driven plasma reactor, operated by an axial injection torch (AIT). The model solves Maxwell's equations, which are discretized using a finite difference scheme within staggered grids, adopting a time-harmonic description at fixed 2.45 GHz excitation frequency. The study focuses upon azimuthal axis-symmetric situations, which can be described by a single second-order Helmholtz-type differential equation for the transverse magnetic field. Perfect-conductor boundary conditions are imposed at metal walls, corresponding to zero derivatives for the magnetic field. In situations where convergence requires a more restrictive framework, these Neumann boundary conditions are better replaced by equivalent Dirichlet conditions, whose boundary values depend on the problem solution. Here, we propose a simple numerical algorithm to manage these situations, by tailoring the Dirichlet boundary values to satisfy the physical Neumann conditions. The algorithm is applied to an air-filled circular wave-guide (as a test system) and to the AIT-reactor device (in the presence of plasma). Solution benchmarking checks its accuracy with respect to the corresponding analytical solution (for the circular wave-guide), and analyses its numerical precision by using different integral expressions to calculate the power transmission coefficient (for the AIT-reactor). Results show a 99% accuracy and precision errors lower than 0.1%, for a mesh with 104 grid points.

Álvarez, R.; Alves, L. L.

2008-11-01

401

Seeding magnetic fields for laser-driven flux compression in high-energy-density plasmas  

SciTech Connect

A compact, self-contained magnetic-seed-field generator (5 to 16 T) is the enabling technology for a novel laser-driven flux-compression scheme in laser-driven targets. A magnetized target is directly irradiated by a kilojoule or megajoule laser to compress the preseeded magnetic field to thousands of teslas. A fast (300 ns), 80 kA current pulse delivered by a portable pulsed-power system is discharged into a low-mass coil that surrounds the laser target. A >15 T target field has been demonstrated using a <100 J capacitor bank, a laser-triggered switch, and a low-impedance (<1 {Omega}) strip line. The device has been integrated into a series of magnetic-flux-compression experiments on the 60 beam, 30 kJ OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The initial application is a novel magneto-inertial fusion approach [O. V. Gotchev et al., J. Fusion Energy 27, 25 (2008)] to inertial confinement fusion (ICF), where the amplified magnetic field can inhibit thermal conduction losses from the hot spot of a compressed target. This can lead to the ignition of massive shells imploded with low velocity--a way of reaching higher gains than is possible with conventional ICF.

Gotchev, O. V. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Fusion Science Center for Extreme States of Matter and Fast Ignition Physics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Knauer, J. P.; Shoup, M. J. III [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Chang, P. Y. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Jang, N. W. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Meyerhofer, D. D.; Betti, R. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Fusion Science Center for Extreme States of Matter and Fast Ignition Physics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

2009-04-15

402

Seeding magnetic fields for laser-driven flux compression in high-energy-density plasmas.  

PubMed

A compact, self-contained magnetic-seed-field generator (5 to 16 T) is the enabling technology for a novel laser-driven flux-compression scheme in laser-driven targets. A magnetized target is directly irradiated by a kilojoule or megajoule laser to compress the preseeded magnetic field to thousands of teslas. A fast (300 ns), 80 kA current pulse delivered by a portable pulsed-power system is discharged into a low-mass coil that surrounds the laser target. A >15 T target field has been demonstrated using a <100 J capacitor bank, a laser-triggered switch, and a low-impedance (<1 Omega) strip line. The device has been integrated into a series of magnetic-flux-compression experiments on the 60 beam, 30 kJ OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The initial application is a novel magneto-inertial fusion approach [O. V. Gotchev et al., J. Fusion Energy 27, 25 (2008)] to inertial confinement fusion (ICF), where the amplified magnetic field can inhibit thermal conduction losses from the hot spot of a compressed target. This can lead to the ignition of massive shells imploded with low velocity-a way of reaching higher gains than is possible with conventional ICF. PMID:19405657

Gotchev, O V; Knauer, J P; Chang, P Y; Jang, N W; Shoup, M J; Meyerhofer, D D; Betti, R

2009-04-01

403

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)

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.

Hung, R. J.; Pan, H. L.

1993-01-01

404

Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses.  

PubMed

A new scheme to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. By use of unipolarlike or subcycle laser pulses irradiating a thin foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with duration of several hundred attoseconds. The pulse also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to 8 × 10(12) Vm(-1) can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications. PMID:24977575

Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

2014-06-16

405

Intense isolated few-cycle attosecond XUV pulses from overdense plasmas driven by tailored laser pulses  

NASA Astrophysics Data System (ADS)

A method to generate an intense isolated few-cycle attosecond XUV pulse is demonstrated using particle-in-cell simulations. When a tailored laser pulse with a sharp edge irradiates a foil target, a strong transverse net current can be excited, which emits a few-cycle XUV pulse from the target rear side. The isolated pulse is ultrashort in the time domain with a duration of several hundred attoseconds. It also has a narrow bandwidth in the spectral domain compared to other XUV sources of high-order harmonics. It has most energy confined around the plasma frequency and no low-harmonic orders below the plasma frequency. It is also shown that XUV pulse of peak field strength up to $ 8\\times 10^{12} $ V$\\mathrm{m}^{-1}$ can be produced. Without the need for pulse selecting and spectral filtering, such an intense few-cycle XUV pulse is better suited to a number of applications.

Chen, Zi-Yu; Li, Xiao-Ya; Chen, Li-Ming; Li, Yu-Tong; Zhu, Wen-Jun

2014-06-01

406

The MHD interaction and plasma properties in a shock tube driven disk generator with swirl  

Microsoft Academic Search

A 15-cm-diameter shock tube with cesium injection is used to study the use of inlet swirl in a disk generator for high-efficiency MHD power generation. In particular, the study is concerned with flow-interaction effects and plasma properties in a small disk with a 45-deg inlet swirl and a Mach number of 2.2. Electron density and temperature, voltage, and pressure measurements

W. J. Loubsky; J. K. Lytle; J. D. Teare; J. F. Louis

1978-01-01

407

Large-scale magnetic field generation by alpha effect driven by collective neutrino-plasma interaction.  

PubMed

We suggest a new mechanism for the generation of a large-scale magnetic field in the hot plasma of the early Universe which is based on parity violation in weak interactions and depends neither on the helicity of matter turbulence resulting in the standard alpha effect nor on general rotation. The mechanism can result in a self-excitation of an (almost) uniform cosmological magnetic field. PMID:15089594

Semikoz, V B; Sokoloff, D D

2004-04-01

408

Low backlash direct drive actuator  

DOEpatents

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.

Kuklo, Thomas C. (Oakland, CA)

1994-01-01

409

Low backlash direct drive actuator  

DOEpatents

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.

Kuklo, T.C.

1994-10-25

410

Spectro-Polarimetric Properties of Small-Scale Plasma Eruptions Driven by Magnetic Vortex Tubes  

E-print Network

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 MHD 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 generates Alfv\\'enic waves, 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...

Kitiashvili, Irina N

2014-01-01

411

Modeling and Simulation of the sheath in radio-frequency driven plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Microplasmas at atmospheric pressure recently gained increasing attention. Due to their extraordinary characteristics new fields of applications are explored. Various aspects of the discharge mechanisms have to be considered to model and simulate microplasmas. Since microplasmas are dominated by their spatial boundaries, this particularly holds for the sheaths. In this paper we focus on the sheath of radio-frequency driven microplasmas at atmospheric pressure. To account for the chemistry of characteristic applications we set up a multi-species model of the sheath. Based on a scale analysis in time and space we discuss resulting assumptions for the fluid equations for electrons and ions. We solve for these equations self-consistently coupled to Poisson's equation for the electrostatic potential. Finally, we present the density profiles of the electrons and ions depending on various discharge parameters.

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

2011-11-01

412

Full wave effects on the lower hybrid wave spectrum and driven current profile in tokamak plasmas  

SciTech Connect

A numerical modeling of current profile modification by lower hybrid current drive (LHCD) using a fullwave/Fokker-Planck simulation code is presented. A MHD stable LHCD discharge on Alcator C-Mod was analyzed, and the current profile from full wave simulations was found to show better agreement with the experiment than a ray-tracing code. Comparison of full wave and ray-tracing simulation shows that, although ray-tracing can reproduce the stochastic wave spectrum broadening, the full wave calculation predicts even wider spectrum broadening, and the wave spectrum fills all of the kinematically allowed domain. This is the first demonstration of LHCD current profile modeling using a full wave simulation code in a multi-pass absorption regime, showing the clear impact of full wave effects on the LHCD driven current profile.

Shiraiwa, S.; Ko, J.; Meneghini, O.; Parker, R.; Schmidt, A. E.; Greenwald, M.; Hubbard, A. E.; Hughes, J.; Ma, Y.; Podpaly, Y.; Rice, J. E.; Wallace, G.; Wolfe, S. M.; C-Mod Group, Alcator [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Scott, S.; Wilson, J. R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton New Jersey 08543 (United States)

2011-08-15

413

Paper Actuators Made with Cellulose and Hybrid Materials  

PubMed Central

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

Kim, Jaehwan; Yun, Sungryul; Mahadeva, Suresha K.; Yun, Kiju; Yang, Sang Yeol; Maniruzzaman, Mohammad

2010-01-01

414

Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm  

NASA Astrophysics Data System (ADS)

A series of steep plasma depletions was observed in the dayside polar cap during an interval of highly enhanced electron density on 14 October 2000 through EISCAT Svalbard Radar (ESR) field-aligned measurements and northward-directed low-elevation measurements. Each depletion started with a steep dropoff to as low as 1011 m- 3 from the enhanced level of ˜3 × 1012 m-3 at F2 region altitudes, and it continued for 10-15 min before returning to the enhanced level. These depletions moved poleward at a speed consistent with the observed ion drift velocity. DMSP spacecraft observations over an extended period of time which includes the interval of these events indicate that a region of high ion densities extended into the polar cap from the equatorward side of the cusp, i.e., a tongue of ionization existed, and that the ion densities were very low on its prenoon side. Solar wind observations show that a sharp change from IMF By > 0 to By < 0 is associated with each appearance of the ESR electron density dropoff. From this unprecedented clear correlation we present a specific scenario: the series of plasma density depletions observed using the ESR is a result of the poleward drift of the undulating boundary of the tongue of ionization; this undulation is created in the cusp roughly 20 min before the ESR observation by the azimuthal intrusion, in response to the rapid prenoon shift of the footprint of the reconnection line, of the low-density plasmas originating in the morning sector.

Sakai, J.; Taguchi, S.; Hosokawa, K.; Ogawa, Y.

2013-01-01

415

Ion beam driven ion-acoustic waves in a plasma cylinder with negatively charged dust grains  

SciTech Connect

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.

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

416

Plasma Jets Driven by Ultraintense-Laser Interaction with Thin Foils  

SciTech Connect

Experimental evidence of plasma jets ejected from the rear side of thin solid targets irradiated by ultraintense (>10{sup 19} W cm{sup -2}) laser pulses is presented. The jets, detected by transverse interferometric measurements with high spatial and temporal resolutions, show collimated expansion lasting for several hundreds of picoseconds and have substantially steep density gradients at their periphery. The role played by radiation pressure of the laser in the jet formation process is highlighted analytically and by extensive two-dimensional particle-in-cell simulations.

Kar, S.; Borghesi, M.; Romagnani, L. [School of Mathematics and Physics, Queen's University, Belfast, BT7 1NN (United Kingdom); Bulanov, S. V. [APRC, JAEA, Kizugawa, Kyoto 6129-0215 (Japan); Key, M. H.; Mackinnon, A. J.; Patel, P. K. [Lawrence Livermore National Laboratory, Livermore California 94550 (United States); Liseykina, T. V. [ICT, SB-RAS, Novosibirsk (Russian Federation) and MPI-K, Heidelberg (Germany); Macchi, A. [polyLAB, CNR-INFM and Physics Department, University of Pisa, Pisa (Italy); Schiavi, A. [Dipartimento di Energetica, Universita di Roma 1 'La Sapienza', Roma (Italy); Willi, O. [Institut fuer Laser-und Plasmaphysik, Heinrich-Heine-Universitaet, Duesseldorf (Germany)

2008-06-06

417

Low Speed Nano/Micro/Meso-Scale Rarefied Flows Driven by Temperature and Pressure Gradients  

E-print Network

-scale actuators, and perhaps nano/micro/macro-scale actuators. The nano/micro/macro-scale actuators are envisioned as a macro-scale assemblage of large numbers of component nano/micro-scale actuators. The predominantLow Speed Nano/Micro/Meso-Scale Rarefied Flows Driven by Temperature and Pressure Gradients E

Alexeenko, Alina

418

International Workshop on Principles of Diagnosis, 2010 Combining Model-Based and Feature-Driven Diagnosis  

E-print Network

in this domain are that only a small number of each vehicle type is usually built, and the onboard actuators-Driven Diagnosis Approaches ­ A Case Study on Electromechanical Actuators Sriram Narasimhan1 , Indranil-mechanical Actuator (FLEA) test bed. 1 INTRODUCTION Electro-mechanical Actuators (EMAs) are used in a variety

Roychoudhury, Indranil

419

Micromachined electrostatic vertical actuator  

DOEpatents

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.

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

420

Carbon nanotube actuators  

PubMed

Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology. PMID:10334985

Baughman; Cui; Zakhidov; Iqbal; Barisci; Spinks; Wallace; Mazzoldi; De Rossi D; Rinzler; Jaschinski; Roth; Kertesz

1999-05-21

421

Target designs for plasma-implosion-driven, photoionization-pumped soft X-ray lasers  

NASA Astrophysics Data System (ADS)

Designs are proposed for layered, hollow cylindrical targets to be placed on the axis of an imploding, hollow Z-pinch plasma that can create the approximate plasma conditions, as well as radiation spectrum, for a photoionization pumped, Ne-like recombination laser. The lasant must research the Ne-like state and be at the appropriate density concurrent with the photoionizing pump radiation. This places severe constraints on designs for such targets with the vertical vacuum feed diode on Proto 2. Target designs are further constrained by the fact that the 3s--2p resonance line, which depopulates the lower lasing state, must not be highly trapped and by the fact that the upper lasing state must not be collisionally depopulated. We find that hollow, cylindrical targets consisting of a few micron CH strongback, coated on the inside with a thin layer of Ni lasant and on the outside with an Al converter layer, can be optimized to achieve appropriate conditions for lasing. We note that a trade-off exists between larger targets, which better isolate the target from the shock of stagnation, and smaller targets, which deliver a higher intensity pump flux. We also find that trapping, together with uncertainties in the inward expansion of the lasant layer, are significant, and may limit optium available gain.

Hussey, T. W.; Matzen, M. K.; McGuire, E. J.; Dalhed, H. E.

1988-05-01

422

Plasma-implosion-driven, photoionization-pumped, soft X-ray laser targets  

NASA Astrophysics Data System (ADS)

Designs are proposed, based on a series of one-dimensional calculations, for layered, hollow cylindrical targets to be placed on the axis of an imploding, hollow Z-pinch plasma that can create the approximate plasma conditions, as well as radiation spectrum, for a photoionization pumped, Ne-like recombination laser. The lasant must reach the Ne-like state and be at the appropriate density at the same time that the photoionizing pump radiation is present, placing severe constraints on designs for such targets. Target-designs are further constrained by the fact that the 3s-2p resonance line, which depopulates the lower lasing state, must not be highly trapped, and by the fact that the upper lasing state must not be collisionally depopulated. It is found that hollow, cylindrical targets consisting of a few-micron-thick CH strongback, coated on the inside with a thin layer of Ni lasant and on the outside with an Al converter layer, can be optimized to achieve appropriate conditions for lasing and modest levels of gain.

Hussey, T. W.; Matzen, M. K.; McGuire, E. J.; Dalhed, H. E.

1989-11-01

423

Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma  

NASA Astrophysics Data System (ADS)

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.

Sengupta, M.; Ganesh, R.

2014-02-01

424

Ion beam driven resonant ion-cyclotron instability in a magnetized dusty plasma  

SciTech Connect

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.

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

425

Inertia driven radial breathing and nonlinear relaxation in cylindrically confined pure electron plasma  

SciTech Connect

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.

Sengupta, M.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)] [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

2014-02-15

426

Numerical simulation of torus-driven plasma transport in the Jovian magnetosphere  

NASA Technical Reports Server (NTRS)

The Rice convection model has been modified for application to the transport of Io-generated plasma through the Jovian magnetosphere. The new code, called the RCM-J, has been used for several ideal-magnetohydrodynamic (MHD) numerical simulations to study how interchange instability causes an initially assumed torus configuration to break up. In simulations that start from a realistic torus configuration but include no energetic particles, the torus disintegrates too quickly (approximately 50 hours). By adding an impounding distribution of energetic particles to suppress the interchange instability, resonable lifetimes were obtained. For cases in which impoundment is insufficient to produce ideal-MHD stability, the torus breaks up predominantly into long fingers, unless the initial condition strongly favors some other geometrical form. If the initial torus has more mass on one side of the planet than the other, fingers form predominatly on the heavy side (which we associate with the active sector). Coriolis force bends the fingers to lag corotation. The simulation results are consistent with the idea that the fingers are formed with a longitudinal thickness that is roughly equal to the latitudinal distance over which the invariant density declines at the outer edges of the initial torus. Our calculations give an average longitudinal distance between plasma fingers of about 15 deg which corresponds to 20 to 30 minutes of rotation of the torus. We point to some Voyager and Ulysses data that are consistent with this scale of torus longitudinal irregularity.

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

1994-01-01

427

Electromagnetic rotational actuation.  

SciTech Connect

There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.

Hogan, Alexander Lee

2010-08-01

428

Advances in shape-memory polymer actuation  

NASA Astrophysics Data System (ADS)

Shape memory polymer (SMP) is a promising smart material, which is able to perform a large deformation upon applying an external stimulus, such as heat, light and moisture, etc. In recent years, many investigations have been advanced in thermo-responsive SMP actuation, and several novel actuations have been applied in SMP. In this paper, the mechanism and demonstration of three types of SMP actuations (infrared laser, physical swelling effect and electricity) are presented. These novel actuation approaches may help SMP to fully reach its potential application. Firstly, for the infrared laser-activated SMP, it is concerned about the drive of SMP by infrared light. The infrared laser, transmitted through the optical fiber embedded in the SMP matrix, was chosen to drive the SMP. The working frequency of infrared laser was installed in 3-4?m. Moreover, this paper presents a study on the effects of solution on the glass transition temperature (Tg). It shows that the hydrogen bonding of SMP was aroused by the absorbed solution that significantly reduces transition temperature of polymer. In this way, the shape memory effect (SME) can undergo solution-driven shape recovery. Finally, the actuation of two types of electro-active SMP composites filled with electrically conductive powders (carbon black, nickel powers) have been carried out, and the SMP composite can be driven by applying a relatively low voltage.

Leng, Jinsong; Liu, Yanju; Lan, Xin

2009-03-01

429

Introduction to Actuators LM  

NSDL National Science Digital Library

This page from the Southwest Center for Microsystems Education covers an overview of actuators. The documents in this learning module are designed to introduce students to actuators in the micro and macro scales. Included are a student guide, instructor guide, and narrated presentation to the Introduction to Actuators lesson.

2014-07-09

430

An electrochemical micro actuator  

Microsoft Academic Search

In this paper an investigation of the feasibility of a new electrochemical micro actuator is presented. The actuator is fabricated using silicon micro-machining techniques. A gas pressure is generated by electrolysis of an aqueous electrolyte solution. The build up pressure is used to change the deflection of a membrane. The actuator has three states: the electrolysis state, in which the

M. W. Hamber