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1

Airfoil Leading Edge Flow Separation Control using DBD Plasma Actuators driven by Nanosecond Pulses  

Microsoft Academic Search

This work continues an ongoing exploration of the use of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses (NS-DBD hereafter) for aerodynamic flow control. The NS-DBD transfers very little momentum to the neutral air, but generates compression waves that manipulate flow instabilities similar to localized arc filament plasma actuators. Such devices which are believed to function through thermal

Jesse Little; Chris Rethmel; Keisuke Takashima; Chris Wiet; Igor Adamovich; Mo Samimy

2010-01-01

2

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

3

Optically driven nanotube actuators  

NASA Astrophysics Data System (ADS)

Optically driven actuators have been fabricated from single-wall carbon nanotube-polymer composite sheets. Like natural muscles, the millimetre-scale actuators are assemblies of millions of individual nanotube actuators processed into macroscopic length scales and bonded to an acrylic elastomer sheet to form an actuator that have been shown to generate higher stress than natural muscles and higher strains than high-modulus piezoelectric materials. Strain measurements revealed 0.01%-0.3% elastic strain generated due to electrostatic and thermal effects under visible light intensities of 5-120 mW cm-2. An optically actuated nanotube gripper is demonstrated to show manipulation of small objects. This actuation technology overcomes some of the fundamental limitations such as the use of high voltages or electrochemical solutions for actuation, opening up possibilities for remote light-induced actuation technologies.

Lu, Shaoxin; Panchapakesan, Balaji

2005-11-01

4

Airfoil Leading Edge Flow Separation Control using DBD Plasma Actuators driven by Nanosecond Pulses  

NASA Astrophysics Data System (ADS)

This work continues an ongoing exploration of the use of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses (NS-DBD hereafter) for aerodynamic flow control. The NS-DBD transfers very little momentum to the neutral air, but generates compression waves that manipulate flow instabilities similar to localized arc filament plasma actuators. Such devices which are believed to function through thermal effects and instability manipulation could result in a significant improvement over conventional DBD (AC-DBD) plasmas that rely on momentum addition which limits their performance at high speeds. The efficacy of NS-DBDs has been demonstrated in our laboratory in a preliminary work on an airfoil leading edge up to Mach 0.17 and Re=1x106. The current work extends the investigation to higher Mach (0.27) and Re (1.15x106), the maximum operating conditions of our subsonic wind tunnel, using an 8 inch chord NACA 0015 airfoil. Results show the efficacy of the nanosecond pulse plasma discharge for attaching the nominally separated flow at various post stall angles of attack.

Little, Jesse; Rethmel, Chris; Takashima, Keisuke; Wiet, Chris; Adamovich, Igor; Samimy, Mo

2010-11-01

5

Surface discharge plasma actuator driven by a pulsed 13.56 MHz-5 kHz voltage waveform  

NASA Astrophysics Data System (ADS)

The effect of incorporating pulses of radio-frequency (rf: 13.56 MHz) voltage into the driving waveform of a surface discharge plasma actuator is investigated. Rf voltage is applied to the actuator to increase the production of ions and thereby increase the thrust that is generated by the discharge. This waveform is coupled to the powered electrode in 5 µs pulses and combined with a relatively low-frequency (LF) 5 kHz sinusoid to form a pulsed 13.56 MHz-5 kHz (rf-LF) driving voltage. Measurements of the applied voltage, rf and LF currents, effective power, and velocity field of the surrounding air are undertaken at atmospheric pressure. The thrust that is generated using the rf-LF waveform is estimated from the velocity fields using a momentum balance and is found to increase for increasing rf voltage when the LF voltage remains constant. Maximum thrust is achieved when the rf pulses are positioned at the LF voltage minima and this suggests the importance of negative ions. The efficacy of rf-LF actuation is investigated by comparing the thrust that is generated per unit increase in peak voltage with that obtained using an LF-driven discharge.

Dedrick, J.; Im, S.; Cappelli, M. A.; Boswell, R. W.; Charles, C.

2013-10-01

6

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

SciTech Connect

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

7

Novel applications of plasma actuators  

NASA Astrophysics Data System (ADS)

The current study investigates the effectiveness of two different dielectric barrier discharge plasma actuator configurations, a 3-D annular geometry for use in micro thrusters and internal duct aerodynamics and a jet vectoring actuator that acts as a vortex generator and flow control device. The first configuration consists of a closed circumferential arrangement which yields a body force when a voltage difference is applied across the inner and outer electrodes separated by a dielectric. The primary flow is driven by this zero-net mass flux jet at the wall that then entrains fluid in the core of the duct. PIV experiments in both quiescent flow and freestream are conducted on tubes of different diameters while varying parameters such as the modulation frequency, duty cycle and tunnel speed. The values of the induced velocities increase with the forcing frequency and duty cycle although there is a peak value for the forcing frequency after which the velocity and thrust decrease for each thruster. The velocities and thrust increase as the inner diameter of the tubes are increased while the velocity profiles show a great difference with the (l/di) ratio; recirculation occurs after going below a critical value. Experiments in the wind tunnel illustrate that the jet exit characteristics significantly change upon actuation in freestream flow but the effect tends to diminish with increasing inner diameters and tunnel speeds. Using staged arrays of these thrusters result in higher velocities while operating at both in phase and out of phase. The jet vectoring configuration consists of a single embedded electrode separated from two exposed electrodes on either side by the dielectric. The embedded electrode is grounded while the exposed electrodes are driven with a high frequency high voltage input signal. PIV measurements of the actuator in a freestream show that vectoring the jet yields stronger vortices than a linear configuration and increasing the difference between the duty cycles of the channels increases the vortex strength. It is seen that while the vortex is barely visible at the leading edge with little strength, it grows significantly large in the streamwise direction and reaches its maximum strength around mid-chord locations while the circulation distribution shows that the bulk of the circulation is added here. The motion of the vortex along this direction illustrates a braiding phenomena that can be observed via flow visualizations. Streamwise PIV data for this configuration on a wing with a NACA 0012 airfoil is used to plot the reverse flow probability, which in turn reveals that the use of the jet vectoring actuator as a vortex generator jet does suppress separation, but the actuator tends to lose its efficacy with increasing tunnel speeds.

Ozturk, Arzu Ceren

8

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

9

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

PubMed

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. PMID:24089880

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

2013-09-01

10

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

11

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

12

Bluff Body Flow Control Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.

Thomas, Flint

2005-11-01

13

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.

14

Micro Jet Generation with Annular Plasma Actuators  

NASA Astrophysics Data System (ADS)

The effectiveness of dielectric barrier discharge plasma actuators for use in micro thrusters and internal duct aerodynamics are investigated. The primary flow is driven by tha zero-net mass flux jet at the wall in a closed circumferential arrangemen that then entrains fluid in the core of the duct. This results in a unique configuration for studying impulsively started jet phenomena. Laser flow visualization is utilized to observe detailed flow structure wherein multiple vortex rings are formed immediately after pulsed actuation and evolve into a turbulent jet downstream. Measurements are made using PIV and the effects of modulation frequency and the duty cycle on the induced velocity and resulting thrust are observed. The values of the induced velocities increase with the forcing frequency and duty cycle although there is a peak value for the forcing frequency after which the velocity and thrust decrease. The influence of the length-to-diameter (l/di) ratio is also significant; the velocities and thrust increase as the inner diameter of the tubes are increased. Velocity profiles show a great difference with this ratio. As the inner diameter is increased, a recirculation region at the center of the tube with negative velocities can be observed. The effect of freestream on the induced veloicty profiles is also studied wherein the duct is placed inside a wind tunnel and tests are conducted at different Re.

Ozturk, Ceren; Jacob, Jamey

2008-11-01

15

Pulsed Plasma Actuators for Separation Flow Control  

Microsoft Academic Search

An experimental investigation of separation control using steady and pulsed plasma actuators was carried out on an Eppler E338 airfoil at typical micro air vehicle Reynolds numbers (20,000?Re?140,000). Pulsing was achieved by modulating the high frequency plasma excitation voltage. The actuators were calibrated directly using a laser dop- pler anemometer, with and without free-stream velocity, and this allowed the quantification

B. Göksel; D. Greenblatt; I. Rechenberg; Y. Singh; C. N. Nayeri; C. O. Paschereit

2006-01-01

16

Remotely driven electro-active paper actuator by modulated microwaves  

NASA Astrophysics Data System (ADS)

This paper reports a remotely-driven electro-active paper (EAPap) actuator by modulated microwaves. So far we have demonstrated a remotely driven EAPap actuator by means of rectenna and control circuit. The rectenna consists of dipole antenna and rectifying circuit, which converts microwave to dc power. Once microwaves are incident on the dipole rectenna, it converts microwaves into a dc power and the control circuit feeds the power to the EAPap actuator by alternating it so as to produce a bending motion of the EAPap actuator. However, due to the power consumption of the control circuit, the remotely-driven actuator system requires more dc power to activate the control circuit. Thus, we propose a remotely-driven EAPap actuator that does not require the control circuit. Instead of the control circuit, microwaves are modulated with the control signal, and by rectifying the modulated microwaves with the rectenna, the control signal can be regenerated for activating the EAPap actuator. Detailed modulated microwave, rectenna design, fabrication, characterization and the actuation of rectenna-EAPap by modulated microwave are explained.

Yang, Sang Yeol; K. Mahadeva, Suresha; Kim, Jaehwan; Im, In-Ho

2011-03-01

17

Microscale plasma actuators for improved thrust density  

NASA Astrophysics Data System (ADS)

We present a study of the dielectric barrier discharge (DBD) plasma actuators for microscale applications. Traditional macroscale DBD actuators suffer from relatively small actuation effect as characterized by small induced force density and resulting flow velocity. As a remedy we propose microscale plasma actuators that may induce orders of magnitude higher force density. We study the physics of such actuation using a multiscale ionized gas flow code based on the high-fidelity finite-element procedure. First, a two-dimensional volume discharge with nitrogen as a working gas is investigated using a first-principles approach solving coupled system of hydrodynamic plasma equations and Poisson equation for ion density, electron density, and electric field distribution. The quasi-neutral plasma and the sheath regions are identified. As the gap between electrodes is reduced, the sheath structure dominates the plasma region. Second, we simulate a first generation plasma micropump. We solve multiscale plasma-gas interaction inside a two-dimensional cross section of the microscale pump geometry. The result shows that a reasonable mass flow rate can be pumped using a set of small active electrodes.

Wang, Chin-Cheng; Roy, Subrata

2009-07-01

18

Nano-opto-mechanical actuator driven by gradient optical force  

NASA Astrophysics Data System (ADS)

In this letter, a nanoscale opto-mechanical actuator driven by gradient optical force is designed and demonstrated. The nanoscale actuator can achieve a maximum displacement of 67 nm with a response time of 94.5 ns. The optical force is estimated as 1.01 pN/?m/mW in C-band operating wavelengths. The device is fabricated on silicon-on-insulator wafer using standard dry etching processes. Compared with traditional microelectromechanical systems actuators driven by electrostatic force, the nanoscale opto-mechanical actuator has the advantages of high resolution of actuation, nanoscale displacement, and fast operating speed. It has potential applications in optical signal processing, chemical, and biological sensing.

Cai, H.; Xu, K. J.; Liu, A. Q.; Fang, Q.; Yu, M. B.; Lo, G. Q.; Kwong, D. L.

2012-01-01

19

Cylinder Flow Control Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

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. Two optimized quartz dielectric plasma actuators mounted on the cylinder surface utilizing an improved saw-tooth waveform high-voltage generator allowed flow control at Reynolds number approaching supercritical. Using either steady or unsteady actuation, it is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. PIV based flow fields and wake velocity profiles obtained with hot-wire anemometry show large reductions in vortex shedding, wake width and turbulence intensity.

Kozlov, Alexey; Thomas, Flint

2007-11-01

20

Surface-chemistry-driven actuation in nanoporous gold.  

PubMed

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 of the order of a few tenths of a per cent 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. PMID:19043420

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

2008-11-30

21

Characteristics of chemo-mechanically driven polyacrylonitrile fiber gel actuators  

Microsoft Academic Search

Pure polyacrylonitrile (PAN) fiber gels, exhibiting effective actuation forces and displacements through muscle-like contractile behavior during the volume change when subjected to environmental stimuli, are prepared by electrospinning, twisting (strand creation) and activation process to investigate performance characteristics of chemo-mechanically driven PAN gel actuators. Single PAN strand (yarn) having a dimension of 210 ?m in diameter is used. A typical hysteresis

Deuk Yong Lee; Yena Kim; Se-Jong Lee; Myung-Hyun Lee; Jai-Yeoul Lee; Bae-Yeon Kim; Nam-Ihn Cho

2008-01-01

22

Fabrication of Optical Micro Scanner Driven by PZT Actuators  

NASA Astrophysics Data System (ADS)

We have designed, simulated, fabricated and tested microelectromechanical system (MEMS) based one-dimensional (1D) optical micro scanners driven by piezoelectric actuators. The designed micro scanners have a micro mirror (1 mm × 1 mm) supported by rotation bars connected to hinges and piezoelectric cantilevers. Pt/Ti/PZT/Pt/Ti/SiO2/SOI multi-layered structure was subjected to MEMS fabrication to form the micro scanners. Through the fabrication, we have obtained 3 types of scanners with 5, 10 and 20 ?m-wide hinges. The resonant frequency corresponding to a torsional mode was measured to be 4100, 5563 and 6025 Hz, respectively. We also compared the optical scanning angle of the micro scanners actuated at the resonant frequency. The micro scanner with 10 ?m-wide hinge actuated at 5563 Hz showed the widest scanning angle. The scanning angle reaches 25 deg at the actuation voltage of 20 V.

Kobayashi, Takeshi; Tsaur, Jiunnjye; Maeda, Ryutaro

2005-09-01

23

Biomedical micro robots driven by miniature cybernetic actuator  

Microsoft Academic Search

New type of minimum invasive therapy in the abdominal cavity is proposed. For this purpose, hyper redundant active endoscope (hyper endoscope) should be developed. The first prototype of hyper endoscope driven by miniature cybernetic actuators is constructed and controlled successfully. Next, micro master slave control system with force feedback is verified by introducing “dither” technique. This system is very useful

Koji Ikuta; Makoto Nokata; Satoshi Aritomi

1994-01-01

24

An arm wrestling robot driven by dielectric elastomer actuators  

Microsoft Academic Search

The first arm wrestling match between a human arm and a robotic arm driven by electroactive polymers (EAP) was held at the EAPAD conference in 2005. The primary objective was to demonstrate the potential of the EAP actuator technology for applications in the field of robotics and bioengineering. The Swiss Federal Laboratories for Materials Testing and Research (Empa) was one

Gabor Kovacs; Patrick Lochmatter; Michael Wissler

2007-01-01

25

Carbon nanotube alignment driven rapid actuations.  

PubMed

Suspended micro-beams made from aligned carbon nanotubes and parylene deflect reversibly in an ac field and the deflection rate is three orders of magnitude greater than those for existing devices. The direction of beam deflection is determined by the area moment of inertia and the actuation mechanism involves rapid accumulation of charges at tube surfaces, the creation of Coulomb repulsive forces between tubes, beam dilation and the formation of compressive stresses at beam ends. Tube alignment plays a crucial role in the first step as is verified by experimental data and calculation. PMID:24157470

Lin, Yu-Hsien; Tsai, Hsin-Jung; Chang, Han-Chen; Lin, Wen-Yi; Fang, Wei-Leun; Hsu, Wen-Kuang

2013-10-24

26

Feedback separation control using plasma actuators  

NASA Astrophysics Data System (ADS)

A single-dielectric barrier discharge plasma actuator is used to control the leading edge separation and thereby increase the maximum lift on a general wing section. The actuator is located at the leading edge and designed to direct high momentum air from the free-stream and accelerate it along the wall. A single pressure sensor with sufficient dynamic response, sensed the mean and unsteady pressure fluctuations near the leading edge (x/c=0.1). The wing section was mounted on a lift/drag balance. The time series from the pressure sensor was analyzed and correlated with the lift and drag measurements to determine real-time indicators of the flow separation state. This indicator function was used to control the plasma actuator. The experiments were conducted at chord Reynolds numbers, corrected for blockage, of 0.217× 10^6 and 0.307 × 10^6. The real-time separation control resulted in a substantial increase in both C_L_max and ?_stall, and an L/D improvement of as much as 340%. An optimum frequency corresponding to St=fc/U_?=1 was found to exist for unsteady excitation. Under this condition, the power to the actuator was only 2 Watts.

He, Chuan; Corke, Thomas; Patel, Mehul; Sowle, Zak

2004-11-01

27

A valveless micropump driven by differential SMA actuator  

NASA Astrophysics Data System (ADS)

As fluid power sources, the micropumps are used in various applications such as biomedical engineering, micro electromechanical system and medical field etc. In this paper, a new type of valveless micropump driven by differential shape memory alloy (SMA) actuator is proposed. The valveless pump has inlet and outlet with tapered tube and does not need control of valves. The flow rectification of the valveless pump can be realized based on the nozzle/diffuser action. The differential SMA actuator controlled by alternative current makes the baffle of the valveless pump reciprocating motion. The operation principle, structure and control method of differential SMA actuator, the one-way flow mechanism and structure design of the valveless pump are analyzed. The experimental results indicate that the operation principle and design method of the valveless pump are feasible.

Xia, Liuke; Wang, Fengxiang; Lu, Jun

2007-10-01

28

Dielectric Barrier Discharge Plasma Actuators for Flow Control *  

NASA Astrophysics Data System (ADS)

The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single-dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of the actuator physics. New applications continue to appear through a growing number of programs in the United States, Germany, France, England, the Netherlands, Russia, Australia, Japan, and China. This review provides an overview of the physics and modeling of SDBD plasma actuators. It highlights some of the capabilities of plasma actuators through examples from experiments and simulations.

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

2010-01-01

29

Plasma actuators for separation control on stationary and oscillating airfoils  

Microsoft Academic Search

Given the importance of separation control associated with retreating blade stall on helicopters, the primary objective of this work was to develop a plasma actuator flow control device for its use in controlling leading-edge separation on stationary and oscillating airfoils. The plasma actuator consists of two copper electrodes separated by a dielectric insulator. When the voltage supplied to the electrodes

Martiqua L. Post

2004-01-01

30

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

NASA Astrophysics Data System (ADS)

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 alter the characteristics of the IPMC electrode. In plasma-treated IPMCs, the densely packed platinum nanoparticles have produced a relatively thick electrode layer. This configuration has led to the improvement in the electrical properties of the IPMC: surface resistance is noticeably decreased, whereas electrical capacitance is increased. These changes in the electrical properties have considerably enhanced the actuation parameters: displacement, force and operational life are increased by more than three times relative to the conventional IPMC. Our experimental data suggest a relationship between the IPMC actuator's electrical properties and actuation parameters: actuators with lower surface resistance generate large deflection and actuators with higher capacitance generate large actuation force. The actuation tests including coin lifting suggests the potential of the modified IPMC for artificial muscle applications.

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

2010-10-01

31

Modeling plasma actuators with air chemistry for effective flow control  

NASA Astrophysics Data System (ADS)

An asymmetric dielectric barrier discharge model is presented for real gas air chemistry using a self-consistent multibody system of plasma, dielectric, and neutral gas modeled together to predict the electrodynamic force imparted to the working gas. The equations governing the motion of charged and neutral species are solved with Poisson equation using finite element method using a Galerkin weak formulation. Electric field profile changes with the increase in grounded electrode and the density increases downstream. The electrodynamic force development mechanism is studied over a flat plate due to charge and neutral species production from adjacent air in a radio frequency driven barrier discharge. The time average of the force shows mostly acceleration above the actuator. Numerical simulation confirms that the magnitude of force increases very slightly with the increase in the length of grounded electrode.

Singh, Kunwar Pal; Roy, Subrata

2007-06-01

32

Experimental Study of a Pulsed DC Plasma Flow Control Actuator.  

National Technical Information Service (NTIS)

An experiment on the effects of a pulsed DC plasma actuator on a separated flow in a low speed wind tunnel was conducted. The actuator consisted of two asymmetric copper electrodes oriented normal to the flow separated by a dielectric barrier and mounted ...

J. D. Wall

2006-01-01

33

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

34

Numerical Simulation of Flow Control Over Airfoils Using Plasma Actuators  

Microsoft Academic Search

The goal of this work is to numerically simulate the application of weakly-ionized plasma actuators for improved aerodynamic performance of wings. Computations using the NASA Langley CFL3D unsteady thin layer Navier-Stokes solver have been carried out to calculate flow fields near NACA 0015 airfoil with plasma actuators installed on the suction surface in two different arrangements: one at the leading

Vladimir Voikov; Thomas Corke; Osamah Haddad

2004-01-01

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

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

37

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

38

Experimental Investigation of Hypersonic Flow and Plasma Aerodynamic Actuation Interaction  

NASA Astrophysics Data System (ADS)

For hypersonic flow, it was found that the most effective plasma actuator is derived from an electromagnetic perturbation. An experimental study was performed between hypersonic flow and plasma aerodynamic actuation interaction in a hypersonic shock tunnel, in which a Mach number of 7 was reached. The plasma discharging characteristic was acquired in static flows. In a hypersonic flow, the flow field can affect the plasma discharging characteristics. DC discharging without magnetic force is unstable, and the discharge channel cannot be maintained. When there is a magnetic field, the energy consumption of the plasma source is approximately three to four times larger than that without a magnetic field, and at the same time plasma discharge can also affect the hypersonic flow field. Through schlieren pictures and pressure measurement, it was found that plasma discharging could induce shockwaves and change the total pressure and wall pressure of the flow field.

Sun, Quan; Cheng, Bangqin; Li, Yinghong; Cui, Wei; Yu, Yonggui; Jie, Junhun

2013-09-01

39

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

40

Numerical Simulation of Flow Control Over Airfoils Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

The goal of this work is to numerically simulate the application of weakly-ionized plasma actuators for improved aerodynamic performance of wings. Computations using the NASA Langley CFL3D unsteady thin layer Navier-Stokes solver have been carried out to calculate flow fields near NACA 0015 airfoil with plasma actuators installed on the suction surface in two different arrangements: one at the leading edge and the other at the trailing edge. Location of the plasma actuators was chosen to produce the effect of a wing leading edge slat and a trailing edge flap. The effect of plasma was modeled via body force terms in Navier-Stokes equations. The body force was obtained from the solution of the corresponding electrostatic problem. Based on predicted flow fields, the analysis of the effectiveness of plasma actuators for separation control on wings is presented. Computational tests were conducted at Reynolds number =217000 and Mach number =0.1 in order to compare the obtained numerical results with available experimental data, and assess the accuracy of the solver.

Voikov, Vladimir; Corke, Thomas; Haddad, Osamah

2004-11-01

41

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

42

Separation Control in a Centrifugal Bend Using Plasma Actuators  

NASA Astrophysics Data System (ADS)

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

Arthur, Michael; Corke, Thomas

2011-11-01

43

Electrohydrodynamic force in dielectric barrier discharge plasma actuators  

Microsoft Academic Search

Surface dielectric barrier discharges (DBDs) have been proposed as actuators for flow control. In this paper we discuss the basic mechanisms responsible for the electrohydrodynamic (EHD) force exerted by the discharge on the gas molecules. A two-dimensional fluid model of the DBD is used to describe the plasma dynamics, to understand the basic physics associated with the EHD force and

J. P. Boeuf; Y. Lagmich; Th Unfer; Th Callegari; L. C. Pitchford

2007-01-01

44

Demonstration of Separation Delay with Glow-Discharge Plasma Actuators.  

National Technical Information Service (NTIS)

Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions ...

L. S. Hultgren D. E. Ashpis

2004-01-01

45

Thermally driven multi-layer actuator for 2D cantilever arrays  

NASA Astrophysics Data System (ADS)

The present work reports on novel four-layer thermally driven piezoresistive cantilevers implemented in one- and two-dimensional arrays for parallel proximity scanning. There, the heater (metallic meander), the piezoresistive deflection sensor, and the metal actuation film with significantly higher thermal expansion coefficient make up separate layers. Actuation efficiency and cross-talk of the novel cantilever design are studied and compared with two recent designs: thin metallic film and ion-implanted heater. The novel actuator, integrated on a 240 ?m long and 3 ?m thick silicon cantilever and supplied by V dc=1 V enables deflections up to 5 ?m of the AFM-tip with an actuation efficiency of about 170 nm/mW and suppressed cross-talk between actuator and sensor.

Sarov, Y.; Ivanov, T.; Frank, A.; Rangelow, I. W.

2011-01-01

46

Optical Comparison of Single and Double Dielectric barrier plasma actuators  

NASA Astrophysics Data System (ADS)

Time resolved ICCD pictures are taken for double and single surface barrier discharge plasma actuator for thick and thin powered electrodes. The filament and jet propagation minimum speeds are measured for both single and double barrier actuators. Optical emission spectra are measured using a monochromator. In a typical OES spectrum, O2, O^+, CO, OH, N, N2, N2^+ and also optical emission lines from exposed electrodes (stainless steel, copper and tungsten lines) were observed for single barrier actuators. The optical data are fit by SPECAIR code^1. The translational and rotational temperatures are found to be approximately room temperature while the vibrational temperatures were1700 K and 1200 K, the electron temperatures were 3200 K and 2400 K for thick and thin electrode respectively. The different regimes in a discharge will be discussed.

Hershkowitz, Noah; Oksuz, Lutfi; Hoskinson, Alan

2009-11-01

47

Design and optimization of in-plane actuator driven cantilever with high sensitivity sensors.  

PubMed

We present a new mode of actuation and excitation for cantilevers, which endows cantilevers with large deflection for the specific application. Differing from all of the conventional methods in which the deflection is aroused by the vertical drive of cantilever itself or external vibration, the bending and oscillating actuation here is by means of the in-plane actuators, where the out-of-plane motion of the cantilever is driven by the actuation of integrated in-plane actuators combined with curl-shaped cantilever. Because the driving force of the horizontal actuator can be converted through curl-shaped cantilever into a bending moment that results in cantilever deflection, out-of-plane actuation source for cantilever deflection is independent of the cantilever itself. An in-plane electrostatic actuator with comb-drive structures that has two sets of fixed fingers and one set of moving fingers was introduced for both statically bending and dynamically oscillating the cantilever. The optimal structure was obtained through an analytical model and finite element simulation; it achieves a substantially greater deflection and a concentrated stress distribution located on the hinges, in which the integrated piezoresistive sensors are embedded to suffer from larger stress for high sensitive sensing. PMID:20358930

Chen, Xing; Lee, Dong-Weon

2010-05-01

48

Airflow control by non-thermal plasma actuators  

NASA Astrophysics Data System (ADS)

Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control at high frequency. This paper is a review of the worldwide works on this topic, from its origin to the present. It is divided into two main parts. The first one is dedicated to the recent knowledge concerning the electric wind induced by surface non-thermal plasma actuators, acting in air at atmospheric pressure. Typically, it can reach 8 m s-1 at a distance of 0.5 mm from the wall. In the second part, works concerning active airflow control by these plasma actuators are presented. Very efficient results have been obtained for low-velocity subsonic airflows (typically U? <= 30 m s-1 and Reynolds number of a few 105), and promising results at higher velocities indicate that plasma actuators could be used in aeronautics.

Moreau, Eric

2007-02-01

49

Experimental Characterization of the Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

The plasma synthetic jet is a novel active flow control method because of advantages such as fast response, high frequency and non-moving parts, and it has received more attention recently, especially regarding its application to high-speed flow control. In this paper, the experimental characterization of the plasma synthetic jet actuator is investigated. The actuator consists of a copper anode, a tungsten cathode and a ceramic shell, and with these three parts a cavity can be formed inside the actuator. A pulsed-DC power supply was adopted to generate the arc plasma between the electrodes, through which the gas inside was heated and expanded from the orifice. Discharge parameters such as voltage and current were recorded, respectively, by voltage and current probes. The schlieren system was used for flow visualization, and jet velocities with different discharge parameters were measured. The schlieren images showed that the strength of plasma jets in a series of pulses varies from each other. Through velocity measurement, it is found that at a fixed frequency, the jet velocity hardly increases when the discharge voltage ranges from 16 kV to 20 kV. However, with the discharge voltage fixed, the jet velocity suddenly decreases when the pulse frequency rises above 500 Hz, whereas at other testing frequencies no such decrease was observed. The maximum jet velocity measured in the experiment was up to 110 m/s, which is believed to be effective for high-speed flow control.

Jin, Di; Li, Yinghong; Jia, Min; Song, Huimin; Cui, Wei; Sun, Quan; Li, Fanyu

2013-10-01

50

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

National Technical Information Service (NTIS)

Dielectric Barrier Discharge (DBD) plasma actuators with serpentine shaped electrodes cause a change in the operational behavior of the flow control mechanism relative to the standard linear actuator due to the introduction of fully three dimensional vort...

M. Riherd M. Visbal S. Roy

2011-01-01

51

Wirelessly driven electro-active paper actuator made with cellulose–polypyrrole–ionic liquid and dipole rectenna  

Microsoft Academic Search

This paper reports a wirelessly driven electro-active paper actuator that consists of a dipole rectenna array, a power control circuit and two cellulose–polypyrrole–ionic liquid (CPIL) electro-active paper actuators. The CPIL nanocomposite actuator was fabricated by incorporating nanoscaled PPy onto cellulose by an in situ polymerization technique, which was followed by activation in a room temperature ionic liquid. The CPIL actuator

Sang Yeol Yang; Suresha K Mahadeva; Jaehwan Kim

2010-01-01

52

Optical studies of dielectric barrier plasma aerodynamic actuators  

NASA Astrophysics Data System (ADS)

The optical characteristics of surface dielectric barrier plasma actuators with a wire/planar electrode combination and 1 kHz triangular applied voltages were studied using an intensified charge-coupled device camera and a monochromator in atmospheric pressure air. The spatial and temporal images were recorded both parallel and perpendicular to the aerodynamic actuator surfaces on nanosecond time scales. Arc-shaped discharges jumping from above the powered wire across the dielectric above the grounded planar electrode were observed for the first time. Nitrogen molecular second and first positive band lines were observed and the discharge temperatures were calculated by matching the experimental spectra with SPECAIR lines (Laux et al 2003 Plasma Sources Sci. Technol. 12 125-138). The electron temperatures were found to be 6800 ± 400 K from the SPECAIR code.

Gulec, A.; Oksuz, L.; Hershkowitz, N.

2011-08-01

53

Molecular actuators driven by cooperative spin-state switching.  

PubMed

Molecular switches have great potential to convert different forms of energy into mechanical motion; however, their use is often limited by the narrow range of operating conditions. Here we report on the development of bilayer actuator devices using molecular spin crossover materials. Motion of the bilayer cantilever architecture results from the huge spontaneous strain accompanying the spin-state switching. The advantages of using spin crossover complexes here are substantial. The operating conditions used to switch the device can be manipulated through chemical modification, and there are many existing compounds to choose from. Spin crossover materials may be switched by diverse stimuli including light, temperature, pressure, guest molecules and magnetic field, allowing complex input combinations or highly specific operation. We demonstrate the versatility of this approach by fabricating actuators from four different spin crossover materials and by using both thermal variation and light to induce motion in a controlled direction. PMID:24153221

Shepherd, Helena J; Gural'skiy, Il'ya A; Quintero, Carlos M; Tricard, Simon; Salmon, Lionel; Molnár, Gábor; Bousseksou, Azzedine

2013-10-24

54

Preliminary study of lever-based optical driven micro-actuator  

NASA Astrophysics Data System (ADS)

This study presents a novel type of optically driven lever-based micro-actuator fabricated using two-photon polymerization 3D-microfabrication technique. The lever is composed of a beam, an arch, and a sphere. First, optical tweezers is applied on the spheres to demonstrate the actuation of the lever. A spring is jointed at the lever for verifying the induced forces. Under the dragging by laser focusing, the lever simultaneously turns and results a torque like a mechanical arm. Then, the demonstration of a photo-driven micro-transducer with a mechanical arm and a gear is preformed. The experimental result indicates that our design enables precise manipulation of the mirco-actuator by optical tweezers at micron scale. This study provides a possibility for driving micron-sized structured mechanisms, such as connecting rods, valves. It is expected to contribute on the investigation of "Lab-on-a-chip".

Lin, Chih-Lang; Li, Yi-Hsiung; Lin, Chin-Te; Chiang, Chia-Chin; Liu, Yi-Jui; Chung, Tien-Tung; Baldeck, Patrice L.

2011-11-01

55

Fiber-optical switch using cam-micromotor driven by scratch drive actuators  

Microsoft Academic Search

We fabricated a 1 × 1 fiber-optic switch using a cam-micromotor driven by scratch drive actuators (SDAs). Using the cam-micromotor, mechanical translation and precise positioning of an optical fiber were performed. An optical fiber of diameter 50 µm was bent and pushed out with a cam-mechanism driven by the SDAs fabricated by surface micromachining. The maximum rotation speed of the

Y. Kanamori; Y. Aoki; M. Sasaki; H. Hosoya; A. Wada; K. Hane

2005-01-01

56

Force performance indexes for parallel mechanisms with actuation redundancy, especially for parallel wire-driven manipulators  

Microsoft Academic Search

This paper presents new force performance indexes adapted to parallel mechanisms with actuation redundancy (PMAR) especially parallel wire-driven manipulators (where only tensile forces in cables are possible). Such performance indexes might be used for optimization purpose. At first, the operational force polytope is established. It is the accurate representation of admissible operational forces from the kinetostatic analysis point of view.

Sébastien Krut; François Pierrot

2004-01-01

57

Bistable silicon microvalve with thermoelectrically driven thermopneumatic actuator for liquid flow control  

Microsoft Academic Search

This paper presents a bistable microfluidic valve with a thermopneumatic actuator that is thermoelectrically driven. A functional prototype is fabricated in silicon technology. The majority of the fabrication process, including the integration of the micro-Peltier devices, is performed at wafer level. The tested valves are switched with ±10 V pulses with an energy input of approximately 1 J for closing

Till Huesgen; Gabriel Lenk; Thomas Lemke; Peter Woias

2010-01-01

58

Three-dimensional effects of curved plasma actuators in quiescent air  

NASA Astrophysics Data System (ADS)

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

Wang, Chin-Cheng; Durscher, Ryan; Roy, Subrata

2011-04-01

59

A valveless micro impedance pump driven by electromagnetic actuation  

NASA Astrophysics Data System (ADS)

Over the past two decades, a variety of micropumps have been explored for various applications in microfluidics such as control of pico- and nanoliter flows for drug delivery as well as chemical mixing and analysis. We present the fabrication and preliminary experimental studies of flow performance on the micro impedance pump, a previously unexplored method of pumping fluid on the microscale. The micro impedance pump was constructed of a simple thin-walled tube coupled at either end to glass capillary tubing and actuated electromagnetically. Through the cumulative effects of wave propagation and reflection originating from an excitation located asymmetrically along the length of the elastic tube, a pressure head can be established to drive flow. Flow rates were observed to be reversible and highly dependent on the profile of the excitation. Micro impedance pump flow studies were conducted in open and closed circuit flow configurations. Maximum flow rates of 16 ml min-1 have been achieved under closed loop flow conditions with an elastic tube diameter of 2 mm. Two size scales with channel diameters of 2 mm and 250 µm were also examined in open circuit flow, resulting in flow rates of 191 µl min-1 and 17 µl min-1, respectively.

Rinderknecht, Derek; Iwaniec Hickerson, Anna; Gharib, Morteza

2005-04-01

60

Temporal and spatial characteristics of Dielectric Barrier Plasma Actuators  

NASA Astrophysics Data System (ADS)

The temporal and spatial images of surface dielectric barrier plasma actuators with a wire/planar electrode combination and 1 kHz triangular applied voltages were taken using an intensified charge-coupled device (ICCD) camera and in addition a monochromator was used to measure the optical emission lines of discharges in air. Parallel and perpendicular images recorded with respect to discharge surface. Time resolved (nanosec order) images were used to calculate the discharge speed. Arc shaped discharges jumping from above the powered wire across the dielectric above the grounded planar electrode were observed for the first time. Nitrogen molecular second and first positive band lines were measured and electron and molecular temperatures were calculated using the SPECAIR code (Laux et al. Plasma Sources Sci. Technol. 2003,12,1255-138) and the Boltzmann plot method. The electron temperatures were found to be 6020 ± 1200 and 6800±400 K from the Boltzmann method and SPECAIR code respectively.

Oksuz, Lutfi; Hershkowitz, Noah; Gulec, Ali

2010-11-01

61

Induced flow direction of a single ehd plasma actuator using the one atmosphere uniform glow discharge plasma (OAUDGP)  

Microsoft Academic Search

Summary form only given. EHD plasma actuators have proven effective in delaying separation and re-attaching internal or external low speed flows in wind tunnel experiments that utilize drag balances, Pitot tubes, smoke flow visualization, and fluid dynamic modeling programs. Recent experiments showed that with the additional momentum from a single plasma actuator on its leading edge, the stall angle of

Xin Dai; J. Reece Roth

2006-01-01

62

Optimization of Airfoil Design for Flow Control with Plasma Actuators  

NASA Astrophysics Data System (ADS)

Using computer simulations and design optimization methods, this research examines the implementation of active flow control devices on wind turbine blades. Through modifications to blade geometry in order to maximize the effectiveness of flow control devices, increases in aerodynamic performance and control of aerodynamic performance are expected. Due to this compliant flow, an increase in the power output of wind turbines is able to be realized with minimal modification and investment to existing turbine blades. This is achieved through dynamic lift control via virtual camber control. Methods using strategic flow separation near the trailing edge are analyzed to obtain desired aerodynamic performance. FLUENT is used to determine the aerodynamic performance of potential turbine blade design, and the post-processing uses optimization techniques to determine an optimal blade geometry and plasma actuator operating parameters. This work motivates the research and development of novel blade designs with flow control devices that will be tested at Notre Dame's Laboratory for Enhanced Wind Energy Design.

Williams, Theodore; Corke, Thomas; Cooney, John

2011-11-01

63

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10[sup 3]--10[sup 4] s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. The authors report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Hooper, E.B.; Stallard, B.W.; Makowski, M.A.

1992-10-05

64

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10{sup 3}--10{sup 4} s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. The authors report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Hooper, E.B.; Stallard, B.W.; Makowski, M.A.

1992-10-05

65

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10[sup 3]--10[sup 4] s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. We report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Bickford Hooper, E.; Stallard, B.W.; Makowski, M.A. (Lawrence Livermore National Laboratory L-637, P.O. Box 808 Livermore, CA 94550-9900 (United States))

1993-01-20

66

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

67

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

68

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

PubMed

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

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

2013-01-11

69

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.

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

2013-01-01

70

Surrogate modelling for characterising the performance of a dielectric barrier discharge plasma actuator  

Microsoft Academic Search

The dielectric barrier discharge (DBD) plasma actuator offers promising opportunities for flow control because of its fast response and non-moving parts. In this work, surrogate modelling is adopted to better understand the impact of the materials and operational parameters on the actuator performance, and to provide an efficient approach for performance estimation. The DBD model based on 2-species helium chemistry

Young-Chang Cho; Balaji Jayaraman; Felipe A. C. Viana; Raphael T. Haftka; Wei Shyy

2010-01-01

71

The beam driven plasma neutralizer  

NASA Astrophysics Data System (ADS)

The improvement of the efficiency of neutral beam systems to be compatible with the economic requirements of fusion power plants is a key theme in the European research programme. A novel plasma neutralizer, in which the negative ion beam itself is the source of the plasma, is described. Its success depends on the confinement of the free electrons generated by stripping from the beam and their generation of additional plasma. The device requires no additional power in contrast to the photoneutralizer, presently the main device of research interest. Although the efficiency of the plasma device is not as high as the photoneutralizer it is essentially of a low technological risk, inherently reliable and will not require a significant R&D programme to demonstrate.

Surrey, E.; Holmes, A.

2013-02-01

72

Wirelessly driven electro-active paper actuator made with cellulose-polypyrrole-ionic liquid and dipole rectenna  

NASA Astrophysics Data System (ADS)

This paper reports a wirelessly driven electro-active paper actuator that consists of a dipole rectenna array, a power control circuit and two cellulose-polypyrrole-ionic liquid (CPIL) electro-active paper actuators. The CPIL nanocomposite actuator was fabricated by incorporating nanoscaled PPy onto cellulose by an in situ polymerization technique, which was followed by activation in a room temperature ionic liquid. The CPIL actuator shows its maximum bending displacement of 10 mm at an ambient humidity condition with 30 mW electrical power consumption. The CPIL actuator is very stable in its actuator performance. The dipole rectenna array receives microwaves and converts them to dc power so as to wirelessly supply power to the actuators. Three flexible dipole rectenna arrays are designed, manufactured and characterized. The rectenna array that has nine rectenna elements generates the maximum power of 75 mW. This power was used to successfully activate the two CPIL actuators and the control circuit. Detailed fabrication and characterization of the CPIL actuator and the dipole rectenna array as well as the control circuit are explained.

Yang, Sang Yeol; Mahadeva, Suresha K.; Kim, Jaehwan

2010-10-01

73

Developments in laser-driven plasma accelerators  

NASA Astrophysics Data System (ADS)

Laser-driven plasma accelerators provide acceleration gradients that are three orders of magnitude greater than those generated by conventional accelerators, offering the potential to shrink the length of accelerators by the same factor. To date, laser acceleration of electron beams to produce particle energies comparable to those offered by synchrotron light sources has been demonstrated with plasma acceleration stages that are only a few centimetres long. This Review describes the operation principles of laser-driven plasma accelerators, and gives an overview of their development from their proposal in 1979 to recent demonstrations. Potential applications of plasma accelerators are described, and the challenges that must be overcome before they can become practical tools are discussed.

Hooker, S. M.

2013-10-01

74

A Friction Compensation Method in Positioning Control of Nonresonant Ultrasonic Actuator-Driven Precise Stage  

NASA Astrophysics Data System (ADS)

This research has aimed at the control system development of a non-resonant ultrasonic motor (SPIDER)-driven precision stage. SPIDER is newly developed as an actuator to achieve the positioning performance required for next generation. In this paper, friction compensation is firstly realized considering integral effect of controllers. Next, the compensation is achieved based on the adaptive friction observer. Moreover it is experimentally verified that the stick-slip phenomenon is prevented for an environmental change by the proposal technique, and a quick positioning in the scale resolution becomes possible.

Hashimoto, Seiji; Ohishi, Kiyoshi; Kosaka, Koji; Ishikawa, Takeo; Kubota, Hiroshi; Ohmi, Tadahiro

75

The development of electrically driven mechanochemical actuators that act as artificial muscle  

NASA Astrophysics Data System (ADS)

Ras Labs, LLC, is committed to producing a variety of electroresponsive smart materials that are strong, resilient, and respond quickly and repeatedly to electrical stimuli. By effectively combining the synthetic expertise of Ras Labs with the plasma expertise of the Princeton University Plasma Physics Laboratory (PPPL), Ras Labs is actively developing superior electroresponsive materials and actuators. One of the biggest challenges is the interface between the embedded electric electrodes and the electroresponsive material because of the pronounced movement of the electroresponsive material. If the electroresponsive material moves very quickly, the electric lead is often left behind and thus becomes detached. Preliminary experiments explored the bonding between these electroresponsive materials with plasma treated metals provided by PPPL. The results were encouraging, with much better bond strengths in the plasma treated metals compared to the untreated control. Ras Labs expanded upon improving the attachment of the embedded electric leads to the electroresponsive materials in these actuators using plasma treatment and other treatments to non-corrosive metal leads at PPPL. Water drop contact angle tests were performed on plasma treated stainless steel and titanium. The strength of the metal-polymer interface was determined at TRI/Princeton using modified T-peel tests on samples of electroresponsive material sandwiched between plasma treated stainless steel and titanium foils. Based on the water drop contact angle tests and the T-peel tests, nitrogen plasma treatment of titanium produced the best metal-polymer interface. Metallic plasma treatment allowed for the embedded electric leads and the electroresponsive material to work and move as a unit, with no detachment, by significantly improving the interface between the electric leads and the electroresponsive material.

Rasmussen, Lenore; Meixler, Lewis; Harper, Don; Park, Kimun

2008-05-01

76

Wave-driven plasma centrifuge  

NASA Astrophysics Data System (ADS)

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

Fetterman, Abraham; Fisch, Nathaniel

2009-11-01

77

Current in wave driven plasmas  

SciTech Connect

A theory for the generation of current in a toroidal plasma by radio-frequency waves is presented. The effect of an opposing electric field is included, allowing the case of time varying currents to be studied. The key quantities that characterize this regime are identified and numerically calculated. Circuit equations suitable for use in ray-tracing and transport codes are given.

Karney, C.F.F.; Fisch, N.J.

1985-06-01

78

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

79

Photoemission Driven Charging in Tenuous Plasma  

Microsoft Academic Search

In the cold, tenuous plasma commonly encountered in magnetospheric and interplanetary orbits, and in the case of scientific satellites with nearly all surfaces effectively conducting, surface charging is driven by photoemission current. The differential potential of the few insulating surfaces, such as lenses or insulating grout between solar cells, can be positive or negative depending on the photoemissivity of the

Myron J. Mandell; V. A. Davis; G. T. Davis; R. H. Maurer; C. Herrmann

2012-01-01

80

Microphysics of Cosmic Ray Driven Plasma Instabilities  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

81

Pulsed Plasma Actuators for Active Flow Control at MAV Reynolds Numbers  

Microsoft Academic Search

An experimental investigation of separation control using steady and pulsed plasma actuators was carried out on an Eppler\\u000a E338 airfoil at typical micro air vehicle Reynolds numbers (20,000?Re?140,000). Pulsing was achieved by modulating the high frequency plasma excitation voltage. The actuators were calibrated\\u000a directly using a laser doppler anemometer, with and without free-stream velocity, and this allowed the quantification of

B. Göksel; D. Greenblatt; I. Rechenberg; Y. Kastantin; C. N. NAYERI; C. O. PASCHEREIT

82

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

Microsoft Academic Search

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

Jesse Little; Munetake Nishihara; Igor Adamovich; Mo Samimy

2010-01-01

83

Simulation of a Supersonic Jet Controlled by Plasma Actuators by the CESE Method  

Microsoft Academic Search

This paper reports preliminary CFD of an ideally expanded supersonic jet controlled by localized arc filament plasma actuators. The space-time Conservation Element and Solution Element (CESE) method was employed to solve the three-dimensional Euler equations with and without the application of plasma actuators. A fully expanded Mach 1.3 jet from a 2.54 mm diameter round nozzle is used as the

H. He; I. Adamovich; M. Samimy

2006-01-01

84

Experimental Investigation on the Characteristics of Sliding Discharge Plasma Aerodynamic Actuation  

NASA Astrophysics Data System (ADS)

A new electrical discharge called sliding discharge was developed to generate plasma aerodynamic actuation for flow control. A microsecond-pulse high voltage with a DC component was used to energize a three-electrode actuator to generate sliding discharge. The characteristics of plasma aerodynamic actuation by sliding discharge were experimentally investigated. Discharge morphology shows that sliding discharge is formed when energized by properly adjusting microsecond-pulse and DC voltage. Compared to dielectric barrier discharge (DBD), the plasma extension of sliding discharge is quasi-diffusive and stable but longer and more intensive. Results from particle image velocimetry (PIV) test indicate that plasma aerodynamic actuation by sliding discharge can induce a ‘starting vortex’ and a quasi-steady ‘near-wall jet’. Body force induced by plasma aerodynamic actuation is about the order of mN, which is stronger than that induced by single DBD. It is inferred that microsecond-pulse sliding discharge may be more effective to generate large-scale plasma aerodynamic actuation, which is very promising for improving aircraft aerodynamic characteristics and propulsion efficiency.

Song, Huimin; Li, Yinghong; Zhang, Qiaogen; Jia, Min; Wu, Yun

2011-10-01

85

Data-driven physical parameter estimation for lumped mass structures from a single point actuation test  

NASA Astrophysics Data System (ADS)

Data-driven subspace system identification techniques developed from control theory provide a rich set of analytical tools to estimate state-space models of structural systems. Furthermore, a recent technological advance in physical parameter extraction directly from the identified state-space models paves a way for new developments in experimental structural dynamics. In this study, a practical issue of data-driven physical parameter estimation for lumped mass structures is discussed. To cope with difficulties related to dynamic tests of multiple actuations, this study proposes a signal processing strategy to estimate physical parameters from a dynamic test of single point actuation. To demonstrate the proposed strategy, an experimental study is conducted. A three-story shear frame structure is excited by a modal shaker with an input force measured and the corresponding displacement responses at each floor are scanned using a laser Doppler vibrometer (LDV). Based on the proposed strategy, physically interpretable mass and stiffness matrices, as well as non-proportional damping matrix are estimated solely from the measured experimental data.

Kim, Junhee; Kim, Kiyoung; Sohn, Hoon

2013-09-01

86

Numerical simulation of a plasma actuator based on ion transport  

NASA Astrophysics Data System (ADS)

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

2013-06-01

87

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

88

Progress of Laser-Driven Plasma Accelerators  

SciTech Connect

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

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

2007-07-11

89

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

90

Wave-driven countercurrent plasma centrifuge  

NASA Astrophysics Data System (ADS)

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

Fetterman, Abraham J.; Fisch, Nathaniel J.

2009-11-01

91

Proton-driven plasma-wakefield acceleration  

Microsoft Academic Search

Plasmas excited by laser beams or bunches of relativistic electrons have been used to produce electric fields of 10-100GVm-1. This has opened up the possibility of building compact particle accelerators at the gigaelectronvolt scale. However, it is not obvious how to scale these approaches to the energy frontier of particle physics-the teraelectronvolt regime. Here, we introduce the possibility of proton-bunch-driven

Allen Caldwell; Konstantin Lotov; Alexander Pukhov; Frank Simon

2009-01-01

92

Wave-driven Countercurrent Plasma Centrifuge  

SciTech Connect

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

A.J. Fetterman and N.J. Fisch

2009-03-20

93

Lumped-element Circuit Model for Single-Dielectric Barrier Discharge Plasma Actuator  

NASA Astrophysics Data System (ADS)

This work presents an extension of our previous studies on a single-dielectric barrier discharge (SDBD) plasma actuators. The space-time lumped-element circuit model that had been developed for the actuator is intended to model the details of the ionization process to provide predictions of the body force for a range of parameters without the need of experimental calibration. In this model, the domain over the covered electrode is divided into several parallel equivalent circuit networks, each consisting of resistive and capacitive elements and zenor diodes. The results of this numerical model show very good agreement with the space-time resolved experimental observations of the plasma illumination over the dielectric surface for a range of applied voltage amplitudes and frequencies. These characteristics include plasma sweep-out velocity and spatial extent, and spatial intensity decay. The model provides the boundary conditions on the electric potential over the dielectric that is needed in solving for the actuator space-time body force. The plasma body force is then used in a Navier-Stokes flow solver to study the effects of the plasma actuator. Examples of simulations with the plasma actuator on a flat surface and the leading edge of an airfoil are presented. The simulations show good agreement with comparable experiments. Supported under a USAF SBIR Phase II Contract FA8650-04-C-3405.

Orlov, Dmitri; Corke, Thomas; Patel, Mehul

2006-11-01

94

Dynamic Analysis of Linear Resonant Actuator Driven by DC Motor Taking into Account Contact Resistance Between Brush and Commutator  

Microsoft Academic Search

This paper describes a highly accurate computation technique to obtain the dynamic characteristics of a linear resonant actuator (LRA) driven by the dc brush motor and a magnetic conversion mechanism employing the 3-D finite-element method. In this calculation, the contact resistance between brush and commutator of the dc brush motor is taken into consideration in the electric circuit equation coupled

Tadashi Yamaguchi; Yoshihiro Kawase; Satoshi Suzuki; Katsuhiro Hirata; Tomohiro Ota; Yuya Hasegawa

2008-01-01

95

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

96

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 asymmetric dielectric-barrier-discharge (DBD) actuators is presented. The flow fields are simulated employ- ing an extensively validated high-fidelity Navier-Stokes s olver which is augmented with both phenomenological and first-principles models representing the plasma-induc ed body forces imparted by the actuator on the fluid. Several applications

Miguel R. Visbal; Datta V. Gaitonde; Subrata Roy

97

Spatiotemporal structure of a millimetric annular dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

The spatiotemporal structure of a millimetric annular dielectric barrier discharge plasma actuator is investigated using a photomultiplier tube, a high-sensitivity camera, particle image velocimetry, and electrohydrodynamics simulations. Plasma actuators have typically demonstrated their utility in flow separation control, but on a millimetric scale they have also shown to be promising in the control of crossflow instabilities in crossflow-dominated laminar-turbulent boundary-layer transition. In view of the subtleties associated with creating an initial disturbance to excite subcritical wavelengths, it is desirable to characterize the local plasma discharge structure, body force organization, and induced velocity field in detail. The results show that, similar to their linear centimetric counterpart, the plasma discharge has a highly dynamic and somewhat organized spatiotemporal structure. Under quiescent flow conditions, the actuator induces a velocity field that consists of two counter-rotating vortices, accompanied by a wall-normal synthetic jet region, which in three-dimensions describes a toroidal vortex around the aperture's periphery. The surprising result, however, is that these vortices rotate in the opposite direction to vortices generated by similar centimetric annular designs. Three-dimensional electrohydrodynamics simulations correctly reproduce this behavior. Because the body force organization may be qualitatively perceived as being the axisymmetric counterpart of the more classical linear actuator, this flow reversal is thought to be due to the actuator scale. When an array of millimetric actuators is considered in close proximity, an interaction takes place between the vortices created from each actuator and those of neighboring actuators, resulting in a significant reduction in vortex size compared with the single aperture case, accompanied by an increase in the maximum induced flow velocity magnitude.

Humble, R. A.; Craig, S. A.; Vadyak, J.; McClure, P. D.; Hofferth, J. W.; Saric, W. S.

2013-01-01

98

Power consumption, discharge capacitance and light emission as measures for thrust production of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

A new procedure of determining the time resolved capacitance of a plasma actuator during operation is introduced, representing a simple diagnostic tool that provides insight into the phenomenological behavior of plasma actuators. The procedure is demonstrated by presenting example correlations between consumed electrical energy, size of the plasma region, and the operating voltage. It is shown that the capacitance of a plasma actuator is considerably increased by the presence of the plasma; hence a system that has previously been impedance matched can be considerably de-tuned when varying the operating voltage of the actuator. Such information is fundamental for any attempts to increase the energy efficiency of plasma-actuator systems. A combined analysis of the capacitance, light emission, size of the plasma region, force production, and power consumption is presented.

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

2011-07-01

99

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

100

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

101

Low voltage driven dielectric electro active polymer actuator with integrated piezoelectric transformer based driver  

Microsoft Academic Search

Today's Dielectric Electro Active Polymer (DEAP) actuators utilize high voltage (HV) in the range of kilo volts to fully stress the actuator. The requirement of HV is a drawback for the general use in the industry due to safety concerns and HV regulations. In order to avoid the HV interface to DEAP actuators, a low voltage solution is developed by

T. Andersen; M. S. Rødgaard; O. C. Thomsen; M. A. E. Andersen

2011-01-01

102

Design and characterization of a plasma actuator for controlling dynamic stall  

NASA Astrophysics Data System (ADS)

A repetitive pulsed spark discharge inside of a ˜1 mm cavity generates a high velocity (100-600 m/s) gas jets potentially capable of controlling dynamic stall on an airfoil at Re ˜1e6. High temperature compressible 2D CFD was used to determine the design and geometry of the actuator slot and plasma cavity. Experimental results measuring the time dependent plasma discharge emission and density variations (using gated ICCD and Schlieren) indicate that the plasma can be modeled as constant volume heating over 100 ns. The energy input to the actuator is controlled by the high voltage and capacitance initiating the discharge. During the discharge air in the cavity is rapidly heated. Temperature and pressure increase 5-10x, causing strong gradients and shocks. The flow is directed using an angled slot. In CFD designed geometries shock fronts and high temperature gas velocities are experimentally determined. The force generated by the actuator is also experimentally determined. Experimental results from the actuator show that velocities of 500 m/s can be achieved through 1mm2 orifices with energy inputs of 50 mJ. The CFD model predicts time scales and velocities similar to those observed, and it also indicates cavity cooling as important in optimizing the actuator pulse repetition rate.

Pollard, William; Staack, David

2012-10-01

103

On factors influencing arc filament plasma actuator performance in control of high speed jets  

NASA Astrophysics Data System (ADS)

Localized arc filament plasma actuators (LAFPAs) have been developed and used at The Gas Dynamics and Turbulence Laboratory for the purpose of controlling high-speed and high Reynolds number jets. The ability of LAFPAs for use in both subsonic and supersonic jets has been explored, and experiments to date have shown that these actuators have significant potential for mixing enhancement and noise control applications. While it has been established that the actuators manipulate instabilities of the jet, the exact nature of how the actuation couples to the flow is still unclear. All of the results previously reported have been based on a nozzle extension that has an azimuthal groove of 1 mm width and 0.5 mm depth along the inner surface approximately 1 mm upstream of nozzle extension exit. The ring groove was initially added to shield the plasma arcs from the high-momentum flow. However, the effect of the ring groove on the actuation mechanism is not known. To explore this effect, a new nozzle extension is designed, which relocates the actuators to the nozzle extension face and eliminates the ring groove. Schlieren images, particle image velocimetry and acoustic results of a Mach 0.9 jet of Reynolds number ~6.1 × 105 show similar trends and magnitudes with and without a ring groove. Thus, it is concluded that the ring groove does not play a primary role in the LAFPAs' control mechanism. Furthermore, the effect of the duty cycle of the actuator input pulse on the LAFPAs' control authority is investigated. The results show that the minimum duty cycle that provides complete plasma formation has the largest control over the jet.

Hahn, Casey; Kearney-Fischer, Martin; Samimy, Mo

2011-12-01

104

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

NASA Astrophysics Data System (ADS)

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

Reece Roth, J.

2005-10-01

105

Fabrication and characterization of laterally-driven piezoelectric bimorph MEMS actuator with sol–gel-based high-aspect-ratio PZT structure  

NASA Astrophysics Data System (ADS)

This paper reports on the fabrication and characterization of a novel laterally-driven piezoelectric bimorph micro electro mechanical systems actuator with high aspect-ratio (AR) lead–zirconate–titanate (PZT) structures. The PZT structures (AR=8) sandwiched with Pt sidewall electrodes were fabricated by a nanocomposite sol–gel process with micromachined silicon templates. A single-cantilever-type lateral bimorph actuator was successfully fabricated, and no initial vertical bending was observed, even on a 500 µm long actuator. A lateral displacement of 10 µm was obtained in bimorph actuation at driving voltages of +25 V/?5 V. Then the piezoelectric property of the PZT structure was characterized from the actuator's performance. The lateral piezoelectric actuator has a variety of potential applications as a replacement for electrostatic comb drive actuators occupying a large area.

Yoshida, Shinya; Wang, Nan; Kumano, Masafumi; Kawai, Yusuke; Tanaka, Shuji; Esashi, Masayoshi

2013-06-01

106

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

107

Aerodynamic plasma actuators: A directional micro-jet device  

Microsoft Academic Search

In recent years electroaerodynamic actuators have been rather intensively studied in order to control airflow [H. Velkoff, R. Godfrey, J. of Heat Transfer 101 (1979) 157; S. El-Khabiry, G.M. Colver, Phys. Fluids 9 3 (1997) 587; A. Soldati, S. Banerjee, Phys. Fluids 10 (1998) 1742; R. Vilela Mendes, J.A. Dente, J. Fluids Eng. 120 (1998) 626; A. Schütze, et al.,

Nicolas Bénard; Jérôme Jolibois; Eric Moreau; Roberto Sosa; Guillermo Artana; Gérard Touchard

2008-01-01

108

Preliminary numerical assessment of turbulent skin friction control with plasma actuators  

Microsoft Academic Search

Plasma actuators (PA) introduce a body force in the near-wall region of a fluid flow. This body force has already been successfully used for separation and transition flow control. We investigate the possibility of applying PAs to turbulent skin friction drag reduction by testing the effect of a modelled PA's body force in a numerically simulated turbulent channel flow. The

Bettina Frohnapfel; Antonio Criscione; Cameron Tropea; Yosuke Hasegawa; Nobuhide Kasagi

2009-01-01

109

EDITORIAL: Physics and phenomenology of plasma actuators for control of aeronautical flows  

NASA Astrophysics Data System (ADS)

The subject of atmospheric pressure plasma actuators for aerodynamic flow control originated in the mid-1990s and is now flourishing, particularly in the aeronautical, aerospace, and fluid dynamics literature. The rapid growth of this field can be illustrated by the figure below, which tracks the results of Google searches on 'plasma actuator' from August 2003, at which time there were 19 'hits', to the present, at which time there are more than 600 'hits'. The activity in this field has been growing exponentially, as the figure illustrates. Google plot This special Cluster within Journal of Physics D: Applied Physics begins with a broad survey of past and recent work done world-wide, proceeds with papers that look at the physics and phenomenology of several kinds of plasma actuators, and finally moves on to papers that look at the effects of the momentum addition by plasma actuators to subsonic and supersonic flows. This new technology is likely to have an important effect on military and commercial flight, and it is my hope that this Cluster will contribute to that end.

Reece Roth, J.

2007-02-01

110

Sensitivity of an asymmetric 3D diffuser to plasma-actuator induced inlet condition perturbations  

NASA Astrophysics Data System (ADS)

Experiments were conducted for the flow in a straight-walled 3D diffuser fed by a fully developed turbulent duct flow. Previous work found that this diffuser has a stable 3D separation bubble whose configuration is affected by the secondary flows in the upstream duct. Dielectric barrier discharge plasma actuators were used to produce low-momentum wall jets to determine if the separation behavior could be modified by weak forcing. Actuators producing a streamwise force along the wall where separation occurred in the baseline flow had a relatively small effect. However, spanwise acting plasma actuators that produced a pair of streamwise vortices in the inlet section of the diffuser had a strong effect on the diffuser pressure recovery. The diffuser performance could be either improved or degraded depending on the actuation parameters, including the actuator modulation frequency, duty cycle, and drive voltage. Velocity profile measurements in the diffuser inlet showed that the streamwise vortices affect the uniformity of the streamwise mean velocity accounting for some of the performance changes. However, phase-locked hotwire measurements at the diffuser exit indicate that the periodic nature of the forcing also plays an important role for cases with enhanced pressure recovery.

Grundmann, S.; Sayles, E. L.; Eaton, J. K.

2011-01-01

111

Numerical Investigation and Feasibility Study of a PZT-driven Micro-valve Pulsed-jet Actuator  

Microsoft Academic Search

A micro-valve pulsed-jet vortex-generator driven by piezoelectric actuation was successfully modelled numerically to determine\\u000a the feasibility of such a design. This includes: modelling the dynamic motion of a unimorph cantilever and the fluid-structure\\u000a interaction occurring between the unimorph and the fluid flowing over such a structure; the unsteady developing channel flow\\u000a that would occur through the outlet orifice was also

K. L. Kudar; P. W. Carpenter

2007-01-01

112

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

113

A comb-drive actuator driven by capacitively-coupled-power.  

PubMed

This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator's static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 ?m and 48.9 ?m on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 ?m and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate. PMID:23112635

Chang, Chao-Min; Wang, Shao-Yu; Chen, Rongshun; Yeh, J Andrew; Hou, Max T

2012-08-07

114

A Comb-Drive Actuator Driven by Capacitively-Coupled-Power  

PubMed Central

This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator's static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 ?m and 48.9 ?m on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 ?m and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate.

Chang, Chao-Min; Wang, Shao-Yu; Chen, Rongshun; Yeh, J. Andrew; Hou, Max T.

2012-01-01

115

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

116

Plasma collective modes driven by velocity gradients  

SciTech Connect

Collisional modes driven by shear in the plasma flow velocity V{sub {parallel}}, parallel to the magnetic field, are shown to exist over significant scale distances while subject to the constraints imposed by gradients in the transverse velocity V{sub E} {proportional to} E {times} B. These constraints make the modes localized over finite distances around the surfaces where V{sub E} reaches a maximum or a minimum. Composite modes that can be constructed as a sequence or a superposition of these elementary normal modes can be excited in regions where the transverse velocity acquires a plateau type of profile that is assumed to be formed after macroscopic Kelvin-Helmholtz modes associated with the shear of V{sub E} have reached their saturation stage. Thus a significant rate of longitudinal plasma momentum transport in the transverse direction to the magnetic field can be produced. The relevance of this analysis to the fluctuations observed in the auroral F region is discussed.

Basu, B. (Air Force Geophysics Lab., Bedford, MA (USA)); Coppi, B. (Massachusetts Inst. of Tech., Cambridge (USA))

1990-12-01

117

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

118

Control of oblique shock wave/boundary layer interactions using plasma actuators  

NASA Astrophysics Data System (ADS)

Localized arc filament plasma actuators (LAFPAs) are used for shock wave/boundary layer interaction induced separation control in a Mach 2.3 flow. The boundary layer is fully turbulent with a Reynolds number based on the incompressible momentum thickness of 22,000 and shape factor of 1.37, and the impinging shock wave is generated by a 10° compression ramp. The LAFPAs are observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock and most of the interaction region upstream by approximately one boundary layer thickness (~5 mm). The initial goal of the control was to manipulate the low-frequency ( St~0.03) unsteadiness associated with the interaction region. A detailed investigation of the effect of actuator placement, frequency, and duty cycle on the control authority indicates the actuators' primary control mechanism is not the manipulation of low-frequency unsteadiness. Detailed measurements and analysis indicate that a modification to the boundary layer through heat addition by the actuators is the control mechanism, despite the extremely small power input of the actuators.

Webb, N.; Clifford, C.; Samimy, M.

2013-06-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

120

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

121

High Mach Number Leading-edge Flow Separation Control using AC DBD Plasma Actuators  

NASA Astrophysics Data System (ADS)

Wind tunnel experiments were conducted to quantify the effectiveness of alternating current dielectric barrier discharge flow control actuators to suppress leading-edge stall on a NASA energy efficient transport airfoil at compressible freestream speeds. The objective of this research was to increase lift, reduce drag, and improve the stall characteristics of the supercritical airfoil near stall by flow reattachment at relatively high Mach and Reynolds numbers. In addition, the effect of unsteady (or duty cycle) operation on these aerodynamic quantities was also investigated. The experiments were conducted for a range of Mach numbers between 0.1 and 0.4. corresponding to a Reynolds number range of 560,000 through 2,260,000. Lift, drag, quarter chord moment, and suction side pressures were measured near stall for baseline, steady actuation, and a scan of nondimensional duty cycle frequencies. The results show that the plasma actuators were effective at reattaching the leading-edge separated flow as evidenced by the increase in maximum lift coefficient and stall angle (as much as 2.5 degrees). The experiment also showed that lift was increased the most when the plasma actuator was operated unsteady with a nondimensional frequency of unity.

Kelley, Christopher; Bowles, Patrick; Cooney, John; He, Chuan; Corke, Thomas; Osborne, Bradley; Silkey, Joseph; Zehnle, Joseph

2011-11-01

122

Experimental Studies of Magnetically Driven Plasma Jets  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

123

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

124

Control of the corner separation in a compressor cascade by steady and unsteady plasma aerodynamic actuation  

Microsoft Academic Search

This paper reports experimental results on using steady and unsteady plasma aerodynamic actuation to control the corner separation,\\u000a which forms over the suction surface and end wall corner of a compressor cascade blade passage. Total pressure recovery coefficient\\u000a distribution was adopted to evaluate the corner separation. Corner separation causes significant total pressure loss even\\u000a when the angle of attack is

Ying-hong LiYun; Yun Wu; Min Zhou; Chang-Bing Su; Xiong-Wei Zhang; Jun-Qiang Zhu

2010-01-01

125

Stall control at high angle of attack with plasma sheet actuators  

Microsoft Academic Search

We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic\\u000a forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the\\u000a surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the\\u000a influence

Roberto Sosa; Guillermo Artana; Eric Moreau; Gérard Touchard

2007-01-01

126

On modeling and computer simulation of an electro-thermally driven cascaded nickel micro-actuator  

Microsoft Academic Search

Modeling and finite element (FE) simulation of a multi-cell cascaded laser fabricated electro-thermal micro-actuator (ETMA) made of nickel is presented. The actuator's topology permits adding displacements of each individual cell in the cascade. A proper accounting for temperature-dependent parameters and material properties for the range above 300°C (magnetic phase transition for nickel) is emphasised. The FE simulation is carried over

D. Hill; W. Szyszkowski; E. Bordatchev

2006-01-01

127

Low voltage driven dielectric electro active polymer actuator with integrated piezoelectric transformer based driver  

NASA Astrophysics Data System (ADS)

Today's Dielectric Electro Active Polymer (DEAP) actuators utilize high voltage (HV) in the range of kilo volts to fully stress the actuator. The requirement of HV is a drawback for the general use in the industry due to safety concerns and HV regulations. In order to avoid the HV interface to DEAP actuators, a low voltage solution is developed by integrating the driver electronic into a 110 mm tall cylindrical coreless Push InLastor actuator. To decrease the size of the driver, a piezoelectric transformer (PT) based solution is utilized. The PT is essentially an improved Rosen type PT with interleaved sections. Furthermore, the PT is optimized for an input voltage of 24 V with a gain high enough to achieve a DEAP voltage of 2.5 kV. The PT is simulated and verified through measurements on a working prototype. With the adapted hysteretic based control system; output voltage wave forms of both impulse response and sinusoidal shapes up to 2.5 kV are demonstrated. The control system, together with a carefully designed HV output stage, contributes to low power consumption at a static DEAP force. The HV stage consists of a HV measurement circuit and a triple diode voltage doubler optimized for low leakage current drawn from the DEAP. As a result, a 95 mm x 13 mm x 7 mm driver is integrated in a 110 mm x 32 mm actuator, forming a low voltage interfaced DEAP actuator.

Andersen, T.; Rødgaard, M. S.; Thomsen, O. C.; Andersen, M. A. E.

2011-03-01

128

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

NASA Astrophysics Data System (ADS)

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.

2010-08-01

129

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

130

Effects of plasma aerodynamic actuation on oblique shock wave in a cold supersonic flow  

NASA Astrophysics Data System (ADS)

Wedge oblique shock wave control using an arc discharge plasma aerodynamic actuator was investigated both experimentally and theoretically. Schlieren photography measurements in a small-scale short-duration supersonic wind tunnel indicated that the shock wave angle decreased and its start point shifted upstream with the plasma aerodynamic actuation. Also the shock wave intensity weakened, as shown by the decrease in the gas static pressure ratio of flow downstream and upstream of the shock wave. Moreover, the shock wave control effect was intensified when a static magnetic field was applied. Under test conditions of Mach 2.2, magnetic control and input voltage 3 kV, the start point of the shock wave shifted 4 mm upstream, while its angle and intensity decreased 8.6% and 8.8%, respectively. A thermal choking model was proposed to deduce the change laws of oblique shock wave control by surface arc discharge. The theoretical result was consistent with the experimental result, which demonstrated that the thermal choking model can effectively forecast the effect of plasma actuation on an oblique shock wave in a cold supersonic flow.

Wang, Jian; Li, Yinghong; Cheng, Bangqin; Su, Changbing; Song, Huimin; Wu, Yun

2009-08-01

131

Landau damping of a driven plasma wave from laser pulses  

NASA Astrophysics Data System (ADS)

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

Bu, Zhigang; Ji, Peiyong

2012-01-01

132

Landau damping of a driven plasma wave from laser pulses  

SciTech Connect

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

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

2012-01-15

133

Field-driven gel actuator with versatile long-range locomotion in air  

NASA Astrophysics Data System (ADS)

An approach to fabricate gel actuator using nonionic polymer gels and dielectric liquid pattern was developed. The actuator could be operated in air using a dc electric field and exhibited a rotation-slide complex motion on the horizontal and a snail-like or sliding motion on the slope with controlled path. The average rotational speed and the average climbing speed of the gel could reach 0.35 rad/s and 3.8 mm/s, respectively. The driving force of the gel originated from the electrohydrodynamic flow of the dielectric solvent inside and outside the gel induced by the ion-dragging mechanism under the electric field.

Liang, Songmiao; Weng, Lihui; Tan, Shuaixia; Xu, Jian; Zhang, Xiaoli; Zhang, Lina

2007-04-01

134

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

NASA Astrophysics Data System (ADS)

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

Viswanath, B.; Ramanathan, Shriram

2013-07-01

135

FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air  

NASA Astrophysics Data System (ADS)

Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally using 2.4 kVp-p (peak to peak) 13.56 MHz rf pulses, 20 µs in duration. The results exhibit different characteristics to plasma actuators, which have similar discharge geometry but are typically driven at frequencies of up to about 10 kHz. However, the electrical measurements are similar to some other atmospheric pressure, rf capacitively coupled discharge systems with symmetric electrode configurations and different feed gases.

Dedrick, J.; Boswell, R. W.; Charles, C.

2010-09-01

136

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

137

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

138

Electrostatically driven low-voltage micromechanical RF switches using robust single-crystal silicon actuators  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate an electrostatic RF MEMS switch with a low actuation voltage, which is obtained simply by optimizing the design and fabrication of the robust single-crystal silicon (SCS) actuator, as well as a uniform switch performance. Through the simple approach, the pull-in voltage of the proposed electrostatic switch could be reduced simply and efficiently to approximately 10 V without sacrificing the structural stabilities and degrading the switch performances. For a total of 68 switches on a wafer, the fabrication and measurement yields were obtained to be higher than 94 and 73%, respectively. The switch performances of 50 identical switches except for 4 initially broken and 14 non-actuated switches were successfully characterized. The measured pull-in voltage was 10.7 ± 1.5 V and that of 40 switches (80%) was as low as 12 V. Nevertheless, the 50 identical switches showed considerably good and uniform performances with little deviations in terms of the RF and pull-in voltage characteristics. In addition, self-actuating behavior of the switch was not observed up to the input power of 37 dBm although the actuation voltage was reduced considerably. Low insertion losses of 0.13 ± 0.06, 0.15 ± 0.05, 0.19 ± 0.06 and 0.2 ± 0.07 dB were acquired at 2, 5, 10 and 15 GHz, respectively. The isolation characteristics could be obtained to be 41.25 ± 0.78, 33.25 ± 0.98, 27.17 ± 0.82 and 23.57 ± 0.75 at 2, 5, 10 and 15 GHz, respectively. Numerical calculations and simulations based on the fabricated results of the switches clearly demonstrated that the performance deviations among the tested switches were mainly due to the fabrication errors and not structural deformations.

Kim, Jong-Man; Lee, Sanghyo; Park, Jae-Hyoung; Baek, Chang-Wook; Kwon, Youngwoo; Kim, Yong-Kweon

2010-09-01

139

Application-driven development of plasma source technology  

Microsoft Academic Search

This article reviews major developments in etch- and deposition-driven plasma source technology over the past decades. We first review the radio-frequency parallel plate diode, summarizing its great impact but also its inherent problems. Ensuing sections then treat microwave plasma generation, electron cyclotron resonance power transfer enhancement, inductively coupled plasma sources, and (very briefly) the radio-frequency helicon source. We then introduce

J. Hopwood; T. D. Mantei

2003-01-01

140

Current-driven plasma turbulence in a magnetic flux tube  

Microsoft Academic Search

The behaviour of a multi-component anisotropic plasma in a magnetic flux tube is studied in the presence of current-driven electrostatic ion-cyclot r on turbulence. The plasma transport is considered in both parallel and perpendicular directions with respect to the given tube. As one of the sources of the parallel electric field, the anomalous resistivity of the plasma caused by the

V. E. Zakharov; C.-V. Meister

1999-01-01

141

Laser-driven Acceleration in Clustered Plasmas  

SciTech Connect

We propose a new approach to avoid dephasing limitation of laser wakefield acceleration by manipulating the group velocity of the driving pulse using clustered plasmas. We demonstrated the control of phase velocity in clustered plasmas by third harmonic generation and frequency domain interferometry experiments. The results agree with a numerical model. Based on this model, the group velocity of the driving pulse in clustered plasmas was calculated and the result shows the group velocity can approach the speed of light c in clustered plasmas.

Gao, X.; Wang, X.; Shim, B.; Downer, M. C. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States)

2009-01-22

142

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

143

Stall control at high angle of attack with plasma sheet actuators  

NASA Astrophysics Data System (ADS)

We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the influence of different parameters of the actuation (frequency, input power, electrodes position) on the aerodynamic performance of the airfoil, basing our study on measurements of the surface pressure distribution and of the flow fields with particle image velocimetry technique. The experiments indicated that at moderate Reynolds numbers (150,000 < Re < 333,000) and at high angles of attack, steady or periodic actuations enabled large improvement of the lift and drag/lift aerodynamic coefficients by reattaching the flow along the extrados. However, to attain the same results steady actuations required larger power consumption. When exciting the flow with a moderate value of non-dimensional power coefficient (ratio of electric power flow with the kinetic power flow), a frequency of excitation produced a peak on the coefficients that evaluate the airfoil performance. This peak in terms of a non-dimensional frequency was close to 0.4 and can be associated to an optimal frequency of excitation. However, our work indicates that this peak is not constant for all stalled flow conditions and should be analyzed considering scale factors that take into account the ratio of the length where the forcing acts and the cord length.

Sosa, Roberto; Artana, Guillermo; Moreau, Eric; Touchard, Gérard

2007-01-01

144

Micro robot system with moving micro-car driven by electrostatic comb-drive actuators  

Microsoft Academic Search

This paper describes a silicon micro robot system (MRS) that is capable of driving micro-cars in different directions based\\u000a on a ratchet mechanism and electrostatic comb-drive actuators. Lateral movement of the ratchet racks makes the micro-car move\\u000a in the perpendicular direction with different velocities. Based on MEMS technology, the MRS described in this article was\\u000a fabricated from a silicon on

Phuc Hong Pham; Lam Bao Dang; Hung Ngoc Vu

2010-01-01

145

Large range dual-axis micro-stage driven by electrostatic comb-drive actuators  

NASA Astrophysics Data System (ADS)

This paper presents a micro XY stage that employs electrostatic comb-drive actuators and achieves a bi-directional displacement range greater than 225 µm per motion axis. The proposed XY stage design comprises four rigid stages (ground, motion stage, and two intermediate stages) interconnected via flexure modules. The motion stage, which has two translational degrees of freedom, is connected to two independent single degree of freedom intermediate stages via respective parallelogram (P) transmission flexures. The intermediate stages are connected to the ground via respective clamped paired double parallelogram (C-DP-DP) guidance flexures. The C-DP-DP flexure, unlike conventional flexures such as the paired double parallelogram flexure (DP-DP), provides high bearing direction stiffness (Kb) while maintaining low motion direction stiffness (Km) over a large range of motion direction displacement. This helps delay the onset of sideways instability in the comb-drive actuators that are integrated with the intermediate stages, thereby offering a significantly greater actuation stroke compared to existing designs. The presented work includes closed-form stiffness analysis of the proposed micro-stage, finite elements simulation, and experimental measurements of its static and dynamic behavior.

Olfatnia, Mohammad; Cui, Leqing; Chopra, Pankaj; Awtar, Shorya

2013-10-01

146

Electrically-driven hydrogel actuators in microfluidic channels: fabrication, characterization, and biological application.  

PubMed

The utility of electro-responsive smart materials has been limited by bubble generation (hydrolysis) during application of electrical fields and by biocompatibility issues. Here we describe the design of a device that overcomes these limitations by combining material properties, new design concepts, and microtechnology. 4-hydroxybutyl acrylate (4-HBA) was used as a backbone hydrogel material, and its actuating behavior, bending force, and elasticity were extensively characterized as a function of size and acrylic acid concentration. To prevent bubble generation, the system was designed such that the hydrogel actuator could be operated at low driving voltages (<1.2 V). A microfluidic channel with an integrated electroactive hydrogel actuator was developed for sorting particles. This device could be operated in cell culture media, and the sorting capabilities were initially assessed by sorting droplets in an oil droplet emulsion. Biocompatibility was subsequently tested by sorting mouse embryoid bodies (mEBs) according to size. The sorted and collected mEBs maintained pluripotency, and selected mEBs successfully differentiated into three germ layers: endoderm, mesoderm, and ectoderm. The electroactive hydrogel device, integrated into a microfluidic system, successfully demonstrated the practical application of smart materials for use in cell biology. PMID:20376390

Kwon, Gu Han; Choi, Yoon Young; Park, Joong Yull; Woo, Dong Hun; Lee, Kyu Back; Kim, Jong Hoon; Lee, Sang-Hoon

2010-04-07

147

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

148

Miniature cybernetic actuators using piezoelectric device  

Microsoft Academic Search

A new type of miniature actuator, the so-called cybernetic actuator, for medical application has been proposed and developed. The cybernetic actuator has four driving states: free, increasing, decreasing and locked. A rotary-type cybernetic actuator and a linear-type cybernetic actuator driven by piezoelectric devices have been constructed. The feasibility of both actuators was verified by driving experiments

K. Ikuta; A. Kawahara; S. Yamazumi

1991-01-01

149

Physics of laser-driven plasma-based electron accelerators  

NASA Astrophysics Data System (ADS)

Laser-driven plasma-based accelerators, which are capable of supporting fields in excess of 100GV/m , are reviewed. This includes the laser wakefield accelerator, the plasma beat wave accelerator, the self-modulated laser wakefield accelerator, plasma waves driven by multiple laser pulses, and highly nonlinear regimes. 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 diffraction, electron dephasing, laser pulse energy depletion, and 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 with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Experiments demonstrating key physics, such as the production of high-quality electron bunches at energies of 0.1-1GeV , are summarized.

Esarey, E.; Schroeder, C. B.; Leemans, W. P.

2009-07-01

150

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

151

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

NASA Astrophysics Data System (ADS)

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

Lee, Sangki; Kim, Kwang J.

2006-08-01

152

GASES, PLASMAS, AND ELECTRIC DISCHARGES: Optical Emission Spectroscopy Investigation of a Surface Dielectric Barrier Discharge Plasma Aerodynamic Actuator  

NASA Astrophysics Data System (ADS)

The optical emission spectroscopy of a surface dielectric barrier discharge plasma aerodynamic actuator is investigated with different electrode configurations, applied voltages and driving frequencies. The rotational temperature of N2(C3?u) molecule is calculated according to its rotational emission band near 380.5nm. The average electron energy of the discharge is evaluated by emission intensity ratio of first negative system to second positive system of N2. The rotational temperature is sensitive to the inner space of an electrode pair. The average electron energy shows insensitivity to the applied voltage, the driving frequency and the electrode configuration.

Li, Ying-Hong; Wu, Yun; Jia, Min; Zhou, Zhang-Wen; Guo, Zhi-Gang; Pu, Yi-Kang

2008-11-01

153

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

154

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

155

Attosecond plasma wave dynamics in laser-driven cluster nanoplasmas.  

PubMed

We introduce a microscopic particle-in-cell approach that allows bridging the microscopic and macroscopic realms of laser-driven plasma physics. As a first application, resonantly driven cluster nanoplasmas are investigated. Our analysis reveals an attosecond plasma-wave dynamics in clusters with radii R is approximately equal to 30 nm. The plasma waves are excited by electrons recolliding with the cluster surface and travel toward the center, where they collide and break. In this process, energetic electron hot spots are generated along with highly localized attosecond electric field fluctuations, whose intensity exceeds the driving laser by more than 2 orders of magnitude. The ionization enhancement resulting from both effects generates a strongly nonuniform ion charge distribution. The observed nonlinear plasma-wave phenomena have a profound effect on the ionization dynamics of nanoparticles and offer a route to extreme nanoplasmonic field enhancements. PMID:22680878

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

2012-04-24

156

A voice coil actuator driven active vibration isolation system with the consideration of flexible modes.  

PubMed

We develop a four-mount active vibration isolation system (AVIS) using voice coil actuators. The flexible body modes in the upper plate of the AVIS can cause an instability problem due to control signal whose frequency is close to the resonant frequency of the flexible modes. The loop shaping technique is applied to reduce the amplitude of the control signal. We investigate the performances of the active vibration isolation system proposed in the word in the time domain and frequency domain by comparing to the passive isolation system. PMID:18601436

Park, Kyihwan; Choi, Dongyoub; Ozer, Abdullah; Kim, Sangyoo; Lee, Yongkwan; Joo, Dongik

2008-06-01

157

A voice coil actuator driven active vibration isolation system with the consideration of flexible modes  

NASA Astrophysics Data System (ADS)

We develop a four-mount active vibration isolation system (AVIS) using voice coil actuators. The flexible body modes in the upper plate of the AVIS can cause an instability problem due to control signal whose frequency is close to the resonant frequency of the flexible modes. The loop shaping technique is applied to reduce the amplitude of the control signal. We investigate the performances of the active vibration isolation system proposed in the word in the time domain and frequency domain by comparing to the passive isolation system.

Park, Kyihwan; Choi, Dongyoub; Ozer, Abdullah; Kim, Sangyoo; Lee, Yongkwan; Joo, Dongik

2008-06-01

158

Application-driven development of plasma source technology  

NASA Astrophysics Data System (ADS)

This article reviews major developments in etch- and deposition-driven plasma source technology over the past decades. We first review the radio-frequency parallel plate diode, summarizing its great impact but also its inherent problems. Ensuing sections then treat microwave plasma generation, electron cyclotron resonance power transfer enhancement, inductively coupled plasma sources, and (very briefly) the radio-frequency helicon source. We then introduce the important and relatively new issues of control of the ion energy distribution function and the tailoring of plasma chemistry, including the decoupling of chemistry from pressure and power. The emerging areas of ambient pressure plasma sources and miniature ``plasmas on a chip'' are summarized, and we conclude with a brief view to the future.

Hopwood, J.; Mantei, T. D.

2003-09-01

159

Modeling beam-driven and laser-driven plasma Wakefield accelerators with XOOPIC  

SciTech Connect

We present 2-D particle-in-cell simulations of both beam-driven and laser-driven plasma wakefield accelerators, using the object-oriented code XOOPIC, which is time explicit, fully electromagnetic, and capable of running on massively parallel supercomputers. Simulations of laser-driven wakefields with low ({approximately} 10{sup 16} W/cm{sup 2}) and high ({approximately} 10{sup 18} W/cm{sup 2}) peak intensity laser pulses are conducted in slab geometry, showing agreement with theory. Simulations of the E-157 beam wakefield experiment at the Stanford Linear Accelerator Center, in which a 30 GeV electron beam passes through 1 m of preionized lithium plasma, are conducted in cylindrical geometry, obtaining good agreement with previous work. We briefly describe some of the more significant modifications to XOOPIC required by this work, and summarize the issues relevant to modeling electron-neutral collisions in a particle-in-cell code.

Bruhwiler, David L.; Giacone, Rodolfo; Cary, John R.; Verboncoeur, John P.; Mardahl, Peter; Esarey, Eric; Leemans, Wim

2000-06-01

160

Heating mechanisms in radio-frequency-driven ultracold plasmas  

NASA Astrophysics Data System (ADS)

Several mechanisms by which an external electromagnetic field influences the temperature of a plasma are studied analytically and specialized to the system of an ultracold plasma (UCP) driven by a uniform radio-frequency (rf) field. Heating through collisional absorption is reviewed and applied to UCPs. Furthermore, it is shown that the rf field modifies the three-body recombination process by ionizing electrons from intermediate high-lying Rydberg states and upshifting the continuum threshold, resulting in a suppression of three-body recombination. Heating through collisionless absorption associated with the finite plasma size is calculated in detail, revealing a temperature threshold below which collisionless absorption is ineffective.

Smorenburg, P. W.; Kamp, L. P. J.; Luiten, O. J.

2012-06-01

161

Cyclic Step-voltammetric Analysis of Cation-driven and Anion-driven Actuation in Polypyrrole Films  

NASA Astrophysics Data System (ADS)

Cation-driven and anion-driven electrochemomechanical deformations (ECMD) in electrodeposited polypyrrole (PPy) films have been investigated by means of cyclic voltammetry and cyclic step-voltammetry (CSV). The film deposited from hydrochloric acid (PPyCl) expanded upon anodic reaction (anodic expansion) while that deposited from dodecyl-benzene sulfonic acid (PPyDBS) exhibited cathodic expansion. In the case of the film deposited from p-phenol sulfonic acid (PPyPPS), it was found to show the anodic expansion at 600 mV (vs Ag wire as a reference electrode) along with the cathodic contraction at -800 mV in CSV. The film obtained from the same lot, however, showed cathodic contraction and anodic expansion only by changing the oxidative potential from 600 mV to -100 mV. This phase inversion indicates that not only the polymerization electrolyte but also the redox potential determines the (de)insertion of ions in the PPyPPS film. Contractive electrochemical creeping was only observed in PPyPPS film in chloride salt electrolytes, indicating that the cation insertion induces the deinsertion of initial-dopant anion from the film.

Takashima, Wataru; Pandey, Shyam S.; Fuchiwaki, Masaki; Kaneto, Keiichi

2002-12-01

162

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

163

Drift wave driven zonal flows in plasmas  

NASA Astrophysics Data System (ADS)

The generation of large-scale zonal flows by small-scale electrostatic drift waves in a plasma is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude drift waves. To describe this process a generalized Hasegawa-Mima equation containing both vector and scalar nonlinearities is used. The drift waves are supposed to have arbitrary wavelengths (as compared with the ion Larmor radius). A set of coupled equations describing the nonlinear interaction of drift waves and zonal flows is deduced. The generation of zonal flows turns out to be due to Reynolds stresses produced by finite amplitude drift waves. It is found that the wave vector of the fastest growing mode is perpendicular to that of the drift pump wave. Explicit expressions for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. A comparison with previous results is carried out. The present theory can be used for interpretations of drift wave observations in laboratory plasmas.

Kaladze, T. D.; Wu, D. J.; Pokhotelov, O. A.; Sagdeev, R. Z.; Stenflo, L.; Shukla, P. K.

2005-12-01

164

Drift wave driven zonal flows in plasmas  

SciTech Connect

The generation of large-scale zonal flows by small-scale electrostatic drift waves in a plasma is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude drift waves. To describe this process a generalized Hasegawa-Mima equation containing both vector and scalar nonlinearities is used. The drift waves are supposed to have arbitrary wavelengths (as compared with the ion Larmor radius). A set of coupled equations describing the nonlinear interaction of drift waves and zonal flows is deduced. The generation of zonal flows turns out to be due to Reynolds stresses produced by finite amplitude drift waves. It is found that the wave vector of the fastest growing mode is perpendicular to that of the drift pump wave. Explicit expressions for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. A comparison with previous results is carried out. The present theory can be used for interpretations of drift wave observations in laboratory plasmas.

Kaladze, T.D.; Wu, D.J.; Pokhotelov, O.A.; Sagdeev, R.Z.; Stenflo, L.; Shukla, P.K. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 (China) and Vekua Institute of Applied Mathematics, Tbilisi State University, 2 University Str., 0143 Tbilisi (Georgia); Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 (China); Automatic Control and Systems Engineering, University of Sheffield, Sheffield (United Kingdom) and Institute of Physics of the Earth, 10 B. Gruzinskaya Str., 123995 Moscow (Russian Federation); Department of Physics, University of Maryland, College Park, Maryland 20740 (United States); Department of Physics, Umeaa University, SE-90 187 Umeaa (Sweden); Department of Physics, Umeaa University, SE-90 187 Umeaa (Sweden) and Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2005-12-15

165

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

National Technical Information Service (NTIS)

The short term transient and long term periodic unsteady effects of pulsed plasma actuation are studied using an unsteady, compressible Navier- Stokes solver for the case of a partially separated transitional flow over an SD7003 airfoil at 4 deg angle of ...

D. Rizzetta M. Riherd M. Visbal S. Roy

2011-01-01

166

Plasma Radiation and Acceleration Effectiveness of CME-driven Shocks  

NASA Astrophysics Data System (ADS)

CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME- driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

Gopalswamy, N.; Schmidt, J. M.

2008-05-01

167

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

168

Linear Actuator for Rotary Manipulator Motion.  

National Technical Information Service (NTIS)

An improved, pressure tolerant, underwater actuator for rotary motion between two manipulator arm segments is presented which comprises a hydraulic linear actuator fastened to one manipulator arm segment, a ram shaft driven by the linear actuator, a linea...

R. L. Wernli

1983-01-01

169

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

170

Radiatively driven plasma jets around compact objects  

NASA Astrophysics Data System (ADS)

Matter accreting on to black holes may develop shocks due to the centrifugal barrier. Some of the inflowing matter in the post-shock flow is deflected along the axis in the form of jets. Post-shock flow which behaves like a Compton cloud has `hot' electrons emitting high-energy photons. We study the effect of these `hot' photons on the outflowing matter. Radiation from this region could accelerate the outflowing matter, but radiation pressure should also slow it down. We show that the radiation drag restricts the flow from attaining a very high velocity. We introduce the concept of an `equilibrium velocity' (veq~0.5c), which sets the upper limit of the terminal velocity achieved by a cold plasma due to radiation deposition force in the absence of gravity. If the injection energy is Ein, then we find that the terminal velocity v? satisfies a relation v?2<~veq2+2Ein.

Chattopadhyay, Indranil; Chakrabarti, Sandip K.

2002-06-01

171

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

172

Magnetic Actuation Based SnakeLike Mechanism and Locomotion Driven by Rotating Magnetic Field  

Microsoft Academic Search

Various magnetic micro-robots driven by an external magnetic field have recently been suggested for bio-medical application. The main benefit of control using an external magnetic field that it is wireless and the robot is battery-free. Most locomotion methods of magnetic micro-robots depend on swimming method using an alternatiing magnetic field. In addition, a rotating magnetic field has been used for

S. H. Kim; S. Hashi; K. Ishiyama

2011-01-01

173

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.

Fuentes, Hernan V.; Woolley, Adam T.

2012-01-01

174

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

175

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

176

Self-consistent Langmuir waves in resonantly driven thermal plasmas  

SciTech Connect

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

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

2007-12-15

177

Spin-Gradient-Driven Light Amplification in a Quantum Plasma  

NASA Astrophysics Data System (ADS)

It is shown that the gradient “free-energy” contained in equilibrium spin vorticity can cause electromagnetic modes, in particular the light wave, to go unstable in a spin quantum plasma of mobile electrons embedded in a neutralizing ion background. For densities characteristic of both the solid state and very high density astrophysical systems, the growth rates are sufficiently high to overcome the expected collisional damping. Preliminary results suggest a powerful spin-inhomogeneity driven mechanism for stimulating light amplification.

Braun, Stefanie; Asenjo, Felipe A.; Mahajan, Swadesh M.

2012-10-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

179

Transition to chaos in a driven dusty plasma  

SciTech Connect

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

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

2010-01-15

180

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

2012-03-01

181

Nanocomposite synthesis by absorption of nanoparticles into macroporous hydrogels. Building a chemomechanical actuator driven by electromagnetic radiation  

NASA Astrophysics Data System (ADS)

Macroporous hydrogels irreversibly absorb solid nanoparticles from aqueous dispersions. A nanocomposite is made using a macroporous thermosensitive hydrogel (poly(N-isopropylacrylamide-co-(2-acrylamido-2-methyl propane sulfonic acid)) (poly(NIPAm-co-AMPS)) and conductive polymer (polyaniline, PANI) nanoparticles (PANI NPs). Macroporous gels of poly(NIPAm-co-AMPS) were made by a cryogelation technique. NPs of PANI were produced by precipitation polymerization. It is found that PANI NPs are easily absorbed into the macroporous hydrogels while conventional non-porous hydrogels do not incorporate NPs. It is shown that PANI NPs, dispersed in water, absorb NIR laser light or microwave radiation, increasing their temperature. Upon irradiation of the nanocomposite with microwaves or NIR laser light, the PANI NPs heat up and induce the phase transition of the thermosensitive hydrogel matrix and the internal solution is released. Other nano-objects, such as gold nanorods and PANI nanofibers, are also easily incorporated into the macroporous gel. The resulting nanocomposites also suffer a phase transition upon irradiation with electromagnetic waves. The results suggest that, using a thermosensitive matrix and conducting nanoparticles, mechanical/chemical actuators driven at a distance by electromagnetic radiation can be built. The sensitivity of the nanocomposite to electromagnetic radiation can be modulated by the pH, depending on the nature of the incorporated nanoparticles. Additionally, it is possible to make systems which absorb either NIR or microwaves or both.

Molina, M. A.; Rivarola, C. R.; Miras, M. C.; Lescano, D.; Barbero, C. A.

2011-06-01

182

Plasma Wakes Driven by Neutrinos, Photons and Electron Beams  

NASA Astrophysics Data System (ADS)

There is considerable interest in the propagation dynamics of intense electron and photon neutrino beams in a background dispersive medium such as dense plasmas, particularly in the search for a mechanism to explain the dynamics of type II supernovae. Neutrino interactions with matter are usually considered as single particle interactions. All the single particle mechanisms describing the dynamical properties of neutrino's in matter are analogous with the processes involving single electron interactions with a medium such as Compton scattering, and Cerenkov radiation etc. However, it is well known that beams of electrons moving through a plasma give rise to a new class of processes known as collective interactions such as two stream instabilities which result in either the absorption or generation of plasma waves. Intense photon beams also drive collective interactions such as modulational type instabilities. In both cases relativistic electron beams of electrons and photon beams can drive plasma wakefields in plasmas. Employing the relativistic kinetic equations for neutrinos interacting with dense plasmas via the weak force we explore collective plasma streaming instabilities driven by Neutrino electron and photon beams and demonstrate that all three types of particles can drive wakefields.

Bingham, R.; Silva, L. O.; Mendonca, J. T.; Shukla, P. K.; Mori, W. B.; Serbeto, A.

183

Laser-driven plasma beat-wave propagation in a density-modulated plasma  

SciTech Connect

A laser-driven plasma beat wave, propagating through a plasma with a periodic density modulation, can generate two sideband plasma waves. One sideband moves with a smaller phase velocity than the pump plasma wave and the other propagates with a larger phase velocity. The plasma beat wave with a smaller phase velocity can accelerate modest-energy electrons to gain substantial energy and the electrons are further accelerated by the main plasma wave. The large phase velocity plasma wave can accelerate these electrons to higher energies. As a result, the electrons can attain high energies during the acceleration by the plasma waves in the presence of a periodic density modulation. The analytical results are compared with particle-in-cell simulations and are found to be in reasonable agreement.

Gupta, Devki Nandan [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Nam, In Hyuk; Suk, Hyyong [Advanced Photonics Research Institute and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

2011-11-15

184

Laser-driven plasma beat-wave propagation in a density-modulated plasma.  

PubMed

A laser-driven plasma beat wave, propagating through a plasma with a periodic density modulation, can generate two sideband plasma waves. One sideband moves with a smaller phase velocity than the pump plasma wave and the other propagates with a larger phase velocity. The plasma beat wave with a smaller phase velocity can accelerate modest-energy electrons to gain substantial energy and the electrons are further accelerated by the main plasma wave. The large phase velocity plasma wave can accelerate these electrons to higher energies. As a result, the electrons can attain high energies during the acceleration by the plasma waves in the presence of a periodic density modulation. The analytical results are compared with particle-in-cell simulations and are found to be in reasonable agreement. PMID:22181524

Gupta, Devki Nandan; Nam, In Hyuk; Suk, Hyyong

2011-11-04

185

Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas  

SciTech Connect

Progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported. The turbulence-driven intrinsic torque associated with nonlinear residual stress generation due to zonal flow shear induced asymmetry in the parallel wave number spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current, qualitatively reproducing experimental empirical scalings of intrinsic rotation. The origin of current scaling is found to be enhanced k{sub ||} symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The intrinsic torque is proportional to the pressure gradient because both turbulence intensity and zonal flow shear, which are two key ingredients for driving residual stress, increase with turbulence drive, which is R/L{sub T{sub e}} and R/L{sub n{sub e}} for the trapped electron mode.

Wang, W. X.; Hahm, T. S.; Ethier, S.; Zakharov, L. E.; Diamond, P. H. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)] [University of California, San Diego, La Jolla, California 92093 (United States)

2011-02-25

186

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

SciTech Connect

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

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

2011-01-01

187

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

188

Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams  

SciTech Connect

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

Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-11-04

189

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

190

Plasma rotation driven by static nonresonant magnetic fields  

SciTech Connect

Recent experiments in high temperature DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 64 (2002)] plasmas reported the first observation of plasma acceleration driven by the application of static nonresonant magnetic fields (NRMFs), with resulting improvement in the global energy confinement time. Although the braking effect of static magnetic field asymmetries is well known, recent theory [A. J. Cole et al., Phys. Rev. Lett. 99, 065001 (2007)] predicts that in some circumstances they lead instead to an increase in rotation frequency toward a 'neoclassical offset' rate in a direction opposed to the plasma current. We report the first experimental confirmation of this surprising result. The measured NRMF torque shows a strong dependence on both plasma density and temperature, above expectations from neoclassical theory. The consistency between theory and experiment improves with modifications to the expression of the NRMF torque accounting for a significant role of the plasma response to the external field and for the beta dependence of the plasma response, although some discrepancy remains. The magnitude and direction of the observed offset rotation associated with the NRMF torque are consistent with neoclassical theory predictions. The offset rotation rate is about 1% of the Alfven frequency or more than double the rotation needed for stable operation at high {beta}{sub N} above the n=1 no-wall kink limit in DIII-D.

Garofalo, A. M.; Burrell, K. H.; DeBoo, J. C.; DeGrassie, J. S.; Jackson, G. L.; Schaffer, M. J.; Strait, E. J. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Solomon, W. M.; Park, J.-K. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States); Lanctot, M.; Reimerdes, H. [Columbia University, 2960 Broadway, New York, New York 10027-1754 (United States)

2009-05-15

191

Driven waves in a two-fluid plasma  

NASA Astrophysics Data System (ADS)

We study the physics of wave propagation in a weakly ionized plasma, as it applies to the formation of multifluid, magnetohydrodynamics (MHD) shock waves. We model the plasma as separate charged and neutral fluids which are coupled by ion-neutral friction. At times much less than the ion-neutral drag time, the fluids are decoupled and so evolve independently. At later times, the evolution is determined by the large inertial mismatch between the charged and neutral particles. The neutral flow continues to evolve independently; the charged flow is driven by and slaved to the neutral flow by friction. We calculate this driven flow analytically by considering the special but realistic case where the charged fluid obeys linearized equations of motion. We carry out an extensive analysis of linear, driven, MHD waves. The physics of driven MHD waves is embodied in certain Green functions which describe wave propagation on short time-scales, ambipolar diffusion on long time-scales and transitional behaviour at intermediate times. By way of illustration, we give an approximate solution for the formation of a multifluid shock during the collision of two identical interstellar clouds. The collision produces forward and reverse J shocks in the neutral fluid and a transient in the charged fluid. The latter rapidly evolves into a pair of magnetic precursors on the J shocks, wherein the ions undergo force-free motion and the magnetic field grows monotonically with time. The flow appears to be self-similar at the time when linear analysis ceases to be valid.

Roberge, W. G.; Ciolek, Glenn E.

2007-12-01

192

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

193

Micro-turbulence driven parallel plasma current in tokamaks  

NASA Astrophysics Data System (ADS)

Global gyrokinetic simulations show that ion temperature gradient (ITG) and trapped electron mode (TEM) turbulence can drive a significant parallel current in meso-scale (zonal current). The underlying dynamics is closely related to nonlinear plasma flow generation [1] by turbulent residual stress [2]. However, unlike toroidal momentum which is mostly carried by ions, the turbulent current is mainly carried by electrons in the laboratory frame, and shows finer radial scale in comparison with poloidal and toroidal zonal flows. In both collisonless TEM and ITG turbulence, substantial electron current is first generated in the positive direction of magnetic field and remains quasi-stationary in post-saturation phase. The current generation by turbulence exhibits the similar characteristic dependence on plasma parameters as that of plasma flow generation [3]. Specifically, it increases with pressure gradient, decreases with equilibrium current Ip and increases with the radial variation of safety factor. Also discussed are interesting phase space structures between TEM and ITG turbulence driven current to elucidate the roles of resonant and non-resonant electrons. In collaboration with T. S. Hahm, P. H. Diamond (UCSD), F. L. Hinton (UCSD), A. H. Boozer (Columbia U.), G. Rewoldt, W. M. Tang and W. W. Lee. [1] W. X. Wang et al., Phys. Plasmas 17, 072511 (2010). [2] P. H. Diamond et al., Phys. Plasmas 15, 012303 (2008). [3] W. X. Wang et al., Phys. Rev. Lett. 106, 085001 (2011).

Wang, W. X.; Ethier, S.

2011-11-01

194

Laser-driven instabilities in long scalelength plasmas  

SciTech Connect

In this update lecture we focus on laser-driven instabilities in long scalelength underdense plasmas. Particular attention is given to some recent experiments on Raman scattering of intense laser light. Many important features are in accord with theoretical expectations. These features include a correlation of hot electron generation with Raman scattering, an increase in this scattering as the density scale length increases, and collisional suppression of the instability. Some challenging aspects of the growing data base as well as various deficiencies in the understanding are discussed. The role of the plasmon decay instability 2..omega../sub pe/, Brillouin, and filamentation instabilities is also briefly considered.

Kruer, W.L.

1985-07-31

195

The Nonlinear Landau Damping Rate of a Driven Plasma Wave  

SciTech Connect

In this Letter, we discuss the concept of the nonlinear Landau damping rate, {nu}, of a driven electron plasma wave, and provide a very simple, practical, analytic formula for {nu} which agrees very well with results inferred from Vlasov simulations of stimulated Raman scattering. {nu} actually is more complicated an operator than a plain damping rate, and it may only be seen as such because it assumes almost constant values before abruptly dropping to 0. The decrease of {nu} to 0 is moreover shown to occur later when the wave amplitude varies in the direction transverse to its propagation.

Benisti, D; Strozzi, D J; Gremillet, L; Morice, O

2009-08-04

196

Nonlinear Landau Damping Rate of a Driven Plasma Wave  

SciTech Connect

In this Letter, we discuss the concept of the nonlinear Landau damping rate, nu, of a driven electron plasma wave, and provide a very simple, practical formula for nu, which agrees very well with results inferred from Vlasov simulations of stimulated Raman scattering. nu actually is more complicated an operator than a plain damping rate, and it may only be seen as such because it assumes almost constant values before abruptly dropping to 0. The decrease of nu to 0 is moreover shown to occur later when the wave amplitude varies in the direction transverse to its propagation.

Benisti, Didier; Gremillet, Laurent; Morice, Olivier [CEA, DAM, DIF 91297 Arpajon Cedex (France); Strozzi, David J. [Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (United States)

2009-10-09

197

Nonlinear Landau damping rate of a driven plasma wave.  

PubMed

In this Letter, we discuss the concept of the nonlinear Landau damping rate, nu, of a driven electron plasma wave, and provide a very simple, practical formula for nu, which agrees very well with results inferred from Vlasov simulations of stimulated Raman scattering. nu actually is more complicated an operator than a plain damping rate, and it may only be seen as such because it assumes almost constant values before abruptly dropping to 0. The decrease of nu to 0 is moreover shown to occur later when the wave amplitude varies in the direction transverse to its propagation. PMID:19905646

Bénisti, Didier; Strozzi, David J; Gremillet, Laurent; Morice, Olivier

2009-10-09

198

Active Separation Control over a NACA0024 by DBD Plasma Actuator and FBG Sensor  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge plasma actuators (DBD-PA) and fiber Bragg grating (FBG) sensors have been investigated for active control of flow separation around a NACA0024 airfoil. Tangential jets were produced in the vicinity of the DBD-PA slightly aft of the leading edge of the airfoil. The flow separation control ability was evaluated at low Reynolds number in an open-circuit wind tunnel. Phase- and time-averaged velocity distributions around the airfoil were measured using Particle Image Velocimetry, and the flow separation control ability of the DBD-PA was assessed at 8°, 12° and 16° angle of attack. An FBG sensor was attached to a chord-wise cantilever near the trailing edge of the airfoil on the pressure surface. This was used to measure strain fluctuations in the cantilever root due to flow-induced oscillations. The feasibility of this system to detect flow separation was studied, where the standard deviations of strain fluctuations significantly increased when the flow was separated. This was utilized in an open-loop control system to detect flow separation by FBG then apply active control with the DBD-PA to reattach the flow.

Jukes, Timothy; Segawa, Takehiko; Walker, Seth; Furutani, Hirohide; Iki, Norihiko; Takekawa, Shinya

199

Extremum Seeking Adaptive Separation Control on a Wing with Plasma Synthetic Jet Actuator  

NASA Astrophysics Data System (ADS)

Plasma synthetic jet actuator (PSJA) is a flow control device which has structure that insulator is tucked with electrode pair. It generates electrohydrodynamic (EHD) effect and induces a flow. The experiment was held to investigate the effect of flow control using extremum seeking with PSJA placed on the surface of NACA0012 wing installed in the wind tunnel. Frequency of the input signal to PSJA is modulated to maximize the effect of PSJA in flow control. The wake velocity fluctuation is one of indexes on separation control effect. The wake velocity is minimized over the input frequency by employing extremum seeking. The seeking algorithm calculates the correlation of the modulation frequency and wake velocity fluctuation. The modulation signal frequency where the correlation changes from negative to positive minimizes the wake velocity fluctuation. To detect a local minimum of the wake velocity fluctuation by extremum seeking, it is necessary to change the modulation signal frequency with time. Sine and square waves change the modulation signal frequency to PSJA. The wind tunnel speed was changed as an external factor. The experimental results show that the modulation signal frequency can track the optimum value when the wind tunnel speed is changed. This paper shows that adaptive flow control to optimize the modulation signal frequency with PSJA using extremum seeking enables to suppress turbulence on the flow field of wings.

Ogawara, Kakuji; Kojima, Ryota; Matsumoto, Shoji; Shingin, Hidenori

200

Inter- and intracellular signaling induced by magnetomechanical actuation of plasma membrane channels  

NASA Astrophysics Data System (ADS)

Magnetic particles allow for non-invasive control over their spatial orientation and motion which makes them ideally suitable for studying real-time processes in living cells. Lithographically defined ferromagnetic disks with spin-vortex ground state have the advantage of zero net magnetization in remanence. This eliminates long-range magnetic forces which otherwise lead to the interaction between particles and their agglomeration. Moreover, magnetically soft permalloy particles have high magnetization of saturation thus requiring very low external field for inducing high magnetomotive force, compared to superparamagnetic particles. Our group has previously demonstrated that micron-sized permalloy disks can be used for destruction of cancer cells (D.-H. Kim, E. A. Rozhkova, I. V. Ulasov, S. D. Bader, T. Rajh, M. S. Lesniak, V. Novosad, Nat. Mater. 9, 165-171 (2010). In this work, we investigate the effects of magnetomechanical stimulation of human brain cancer cells with these particles. It will be shown that the actuation of ion channels in cell plasma membrane induces, on the one hand side, intracellular signaling triggering cell apoptosis and, on the other hand, it stimulates the energy transfer between the cells which carries the information about apoptotic signal.

Vitol, Elina A.; Rozhkova, Elena A.; Novosad, Valentyn; Bader, Samuel D.

2012-02-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

202

Development and characterization of plasma actuators for high-speed jet control  

Microsoft Academic Search

Active control of high Reynolds number and high-speed jets has been hampered due to the lack of suitable actuators. Some of the attributes that would make an actuator suitable for such flows are: high amplitude and bandwidth; small size for distribution around the jet; phase-locking ability for jet azimuthal mode forcing; and sufficient ruggedness for hot jets. We have been

M. Samimy; I. Adamovich; B. Webb; J. Kastner; J. Hileman; S. Keshav; P. Palm

2004-01-01

203

String structures in driven 3D complex-plasma clusters  

NASA Astrophysics Data System (ADS)

The structure of driven three-dimensional complex-plasma clusters was studied experimentally. The clusters consisted of around 60 glass microspheres that were suspended in a plasma of rf discharge in argon. The particles were confined in a glass box with conductive yet transparent coating on its four side walls. This allowed manipulating the particle cluster by biasing the confining walls in a certain sequence and direct imaging of the cluster. In this work, a rotating electric field was used to drive the clusters. Depending on the field frequency, the clusters rotated (104-107 times slower than the rotating field) or remained stationary. The cluster structure was neither that of nested spherical shells nor a simple chain structure. Strings of various lengths were found consisting of 2 to 5 particles, their spatial and temporal correlations were studied. The results are compared to recent simulations.

Wörner, L.; Räth, C.; Nosenko, V.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.; Schablinski, J.; Block, D.

2012-11-01

204

Helical dielectric elastomer actuators  

Microsoft Academic Search

This paper presents a new type of contractile polymer-based electromechanical linear actuator. The device belongs to the class of dielectric elastomer actuators, which are typically capable of undergoing large deformations induced by an applied electric field. It is based on a novel helical configuration, suitable for the generation of electrically driven axial contractions and radial expansions. The architecture, the principle

Federico Carpi; Antonio Migliore; Giorgio Serra; Danilo DeRossi

2005-01-01

205

Laser-and Beam-Driven Plasma Accelerators  

NASA Astrophysics Data System (ADS)

Scientists have been trying to use the tremendous electric fields in relativistic plasma waves to accelerate charged particles, and are now making substantial progress. If they succeed, future high energy accelerators will use plasma waves rather than microwave cavities as accelerating structures.Some accelerators, such as those used for radiation therapy will fit on a tabletop. Research on using plasma waves to accelerate particles began in earnest following the suggestion by John Dawson and his colleagues [1-3] that a relativistically propagating plasma wave or a wake field could be excited by using a powerful but short laser -or electron -beam as a driver pulse.Since their original suggestion the research on plasma --based accelerators has spread worldwide A series of experiments by the UCLA/USC/SLAC collaboration ,using the 30 GeV beam of the Stanford Linear Accelerator Center (SLAC), has demonstrated high-gradient acceleration of electrons and positrons using the the wake left by the SLAC beam as it passes through a lithium plasma. Electrons have been accelerated by more than 30 GeV in less than one meter. This acceleration gradient is about a thousand times larger than in conventional microwave-driven accelerators. It is a first step toward a ``plasma afterburner,'' which would be placed at the end of a kilometers-long conventional accelerator and double its beam energy in a few tens of meters. In addition to the acceleration of particle beams, these experiments have demonstrated the rich physics bounty to be reaped from relativistic beam-plasma interactions. This includes the generation of intense and narrowly collimated x-ray beams, refraction of particles at a plasma interface, and the creation of intense beams of positrons. These results are leading the way to similar tabletop accelerators based on plasma wakes excited by lasers rather than electron beams. Applications for tabletop accelerators include gamma radiography, radiation therapy, and ultra-fast materials science. [1] T.Tajima and J.M.Dawson Phys.Rev.Lett. 43,267.(1979) [2] P.Chen et.al. Phys.Rev.Lett.54,693,(1985) [3]C.Joshi et.al. Nature 311,525,(1984) In collaboration with all my past and present students and co-workers and in particular collaborators on E157,162,164 and 167 experiments at SLAC.

Joshi, Chandrashekhar

2006-10-01

206

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

207

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

208

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 Multiplication-Sign 10{sup 10} electrons, 20 Multiplication-Sign 20{mu}m{sup 2} spot, 20 - 100{mu}m length, 20GeV energy) when sent into a plasma source with a nominal density of {approx} 1 Multiplication-Sign 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 Multiplication-Sign 35cm{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 National Accelerator Laboratory, Menlo Park, CA 94025 (United States)

2012-12-21

209

Microrobot actuated by soft actuators based on dielectric elastomer  

Microsoft Academic Search

In this paper a microrobot, mimicking annelid animals like the earthworm, is presented. The robot is composed of several ring-like segments. Each segment is able to generate three degree-of-freedom motions such as pan\\/tilt\\/up-down respectively, and it is actuated by three soft actuators located equidistantly along the circumferential direction. The soft actuator, called antagonistically-driven linear actuator (ANTLA), is based on polymer

H. R. Choi; S. M. Ryew; K. M. Jung; H. M. Kim; J. W. Jeon; J. D. Nam; R. Maeda; K. Tanie

2002-01-01

210

Synergistic effects of hot plasma-driven potentials and wave-driven ion heating on auroral ionospheric plasma transport  

SciTech Connect

Transverse acceleration by waves and parallel acceleration by field-aligned electric fields are important processes in the transport of ionospheric ions along auroral field lines. In order to study the transport of ionospheric plasma in this environment we have developed a generalized semikinetic model which combines the tracking of ionospheric ion gyrocenters with a generalized fluid treatment of ionospheric electrons. Large-scale upward and downward directed electric fields are generated within the model by introducing magnetospheric plasma whose components have differing temperature anisotropies. We study the effects of such potentials when combined with the effect of ion heating by a distribution of waves along the flux tube. We find that the combination of wave heating and an upward electric field results in an order of magnitude increase in O{sup +} outflow (compared to a case with an upward electric field and no wave heating). Under these conditions we observe the formation of bimodal conics. When a downward electric field to a case with wave heating, the energy gained by the ions from the waves increases by a factor of 2 or 3 (over the scenario with wave heating and no hot plasma-driven electric field) owing to their slower transit of the heating region. Typically, the velocity distributions under these conditions are toroids and counterstreaming conics. We also find that the upflowing, dense, heated ionospheric plasma acts to reduce the potential set up by the anisotropies in the magnetospheric components. 33 refs., 16 figs., 1 tab.

Brown, D.G.; Horwitz, J.L.; Wilson, G.R. [Univ. of Alabama, Huntsville, AL (United States)

1995-09-01

211

Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas  

SciTech Connect

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

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

2011-02-07

212

Gas flow driven by thermal creep in dusty plasma  

SciTech Connect

Thermal creep flow (TCF) is a flow of gas driven by a temperature gradient along a solid boundary. Here, TCF is demonstrated experimentally in a dusty plasma. Stripes on a glass box are heated by laser beam absorption, leading to both TCF and a thermophoretic force. The design of the experiment allows isolating the effect of TCF. A stirring motion of the dust particle suspension is observed. By eliminating all other explanations for this motion, we conclude that TCF at the boundary couples by drag to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result provides an experimental verification, for the field of fluid mechanics, that TCF in the slip-flow regime causes steady-state gas flow in a confined volume.

Flanagan, T. M.; Goree, J. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

2009-10-15

213

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

214

Effect of plasma inhomogeneity on plasma wakefield acceleration driven by long bunches  

NASA Astrophysics Data System (ADS)

Effects of plasma inhomogeneity on self-modulating proton bunches and accelerated electrons were studied numerically. The main effect is the change of the wakefield wavelength which results in phase shifts and loss of accelerated particles. This effect imposes severe constraints on density uniformity in plasma wakefield accelerators driven by long particle bunches. The transverse two stream instability that transforms the long bunch into a train of micro-bunches is less sensitive to density inhomogeneity than are the accelerated particles. The bunch freely passes through increased density regions and interacts with reduced density regions.

Lotov, K. V.; Pukhov, A.; Caldwell, A.

2013-01-01

215

Energetic particle driven instability in wall-stabilized high-? plasmas  

NASA Astrophysics Data System (ADS)

We have observed a fishbone-like mode in high-? plasmas above the ideal ? limit without a conducting wall. The mode frequency chirps down, and its initial value is close to the precession frequency of trapped fast ions produced by perpendicularly injected neutral beams. This mode can often induce the resistive wall mode (RWM). The mode is observed mainly in the high-?N plasma where an ideal kink-ballooning mode (IKBM) and the RWM are marginally stable. Since this mode and the RWM were simultaneously observed, the mode is attributed to the interaction between the trapped fast ions and a marginally stable IKBM stabilized by a conducting wall. Actually, the MARG2D analysis shows that the IKBM is wall-stabilized and has a real frequency of the same order as the observed mode frequency. From these results, the observed mode was named 'energetic particle driven wall mode (EWM)'. Moreover, the EWM can change the edge localized mode (ELM) behaviour. For example, it was observed that the ELM was synchronized with the EWM. An energy loss due to the EWM-triggered ELM is smaller, and its frequency becomes higher compared with the usual ELM.

Matsunaga, G.; Shinohara, K.; Aiba, N.; Sakamoto, Y.; Isayama, A.; Asakura, N.; Suzuki, T.; Takechi, M.; Oyama, N.; Urano, H.; JT-60 Team

2010-08-01

216

Beam-plasma interaction experiments using electromagnetically driven shock waves  

NASA Astrophysics Data System (ADS)

Electromagnetically driven shock tubes compatible with in-beam experiments have been developed to examine the stopping power of hot or warm matter over a wide temperature range. The beam-plasma coupling constant ? was calculated under various operating conditions of the shock tube. We found that ?˜0.1 is achievable with 10 keV/u Pb ions and a fully ionized plasma produced by a shock wave with 70-80 km/s in a hydrogen gas of 6-9 kPa. The dissociation effect on the hydrogen stopping power for low-energy protons was also evaluated and a 40-50% increase in the stopping cross-section of dissociated hydrogen was predicted in a projectile energy region of 10-40 keV. For the demonstration of the energy loss measurement using shock-heated gas targets, the developed shock tube was embedded into the beam line and tested on its shock-production abilities. In the preliminary experiment using 375 keV/u carbon projectiles, we successfully detected the signal of a carbon ion penetrating a shock-heat hydrogen target and observed a decrease in the signal height, which probably corresponds to the energy loss.

Hasegawa, J.; Ikagawa, H.; Nishinomiya, S.; Watahiki, T.; Oguri, Y.

2009-07-01

217

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

Microsoft Academic Search

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 over- coming limitations on force computation shown by currently

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

2011-01-01

218

BRIEF COMMUNICATION: On the drift kinetic equation driven by plasma flows  

NASA Astrophysics Data System (ADS)

A drift kinetic equation that is driven by plasma flows has previously been derived by Shaing and Spong 1990 (Phys. Fluids B 2 1190). The terms that are driven by particle speed that is parallel to the magnetic field B have been neglected. Here, such terms are discussed to examine their importance to the equation and to show that these terms do not contribute to the calculations of plasma viscosity in large aspect ratio toroidal plasmas, e.g. tokamaks and stellarators.

Shaing, K. C.

2010-07-01

219

Lift and drag performances of an axisymmetric airfoil controlled by plasma actuator  

Microsoft Academic Search

A Dielectric Barrier Discharge (DBD) is mounted at the leading edge of a NACA 0015 airfoil model. The effects of steady and unsteady actuations on the lift and drag coefficients are investigated by time-averaged force measurements. Results demonstrate that the stall regime can be delayed of one or two degrees while the drag coefficient is reduced. The aerodynamic performances are

N. Benard; J. Jolibois; E. Moreau

2009-01-01

220

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

Microsoft Academic Search

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

R. Mestiri; R. Hadaji; S. Ben Nasrallah

2010-01-01

221

Behavior of Excited Argon Atoms in Inductively Driven Plasmas  

SciTech Connect

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

HEBNER,GREGORY A.; MILLER,PAUL A.

1999-12-07

222

Sheared Buneman Instabilities in Current-Driven Plasmas  

NASA Astrophysics Data System (ADS)

Simulation studies of magnetic reconnection in strongly magnetized plasmas1 have indicated that electron phase-space holes evolve out of current-driven Buneman instabilities and that these holes play an important role in supplying the needed dissipation in the reconnection process by acting as electron scattering centers. Drake and collaborators have shown in simulations that the evolution of electron holes is mediated by lower hybrid waves. We have shown independently, via 2-D simulations of the evolution of Buneman instabilities, that electron phase space holes evolve and interact with lower hybrid waves in a manner similar to that seen in the reconnection simulations2 Perpendicular shear in the parallel velocity and the current will be present near the edges and elsewhere in realistic current sheets associated with magnetic reconnection. We have studied the effects of such shear on the nature and evolution of Buneman instabilities and the resulting electron phase space holes. Both linear theory and 2-D Vlasov simulations are employed. It is shown that even a small amount of velocity shear can have a large effect on the nonlinear evolution of holes and lower hybrid waves. 1Drake, J. F., M. Swisdak, C. Cattell, M. A. Shay, B. N. Rogers, and A.~Zeiler, Formation of Electron Holes and Particle Energization During Magnetic Reconnection, Science, 299, (2003). 2Martin V. Goldman, D. L. Newman, A. Mangeney, F. Califano, Theory and Simulation of Sheared Electron Beam Instabilities in Strongly Magnetized Plasmas, COSPAR04-A-02395; D3.5-0015-04, 35th COSPAR Scientific Assembly Paris, France, 18 - 25 July 2004. This research was supported by DOE, NSF and NASA.

Goldman, M. V.; Newman, D. L.; Sen, N.

2005-05-01

223

Current-less solar wind driven dust acoustic instability in cometary plasma  

SciTech Connect

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar and stellar winds. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion wind plasma in its propagation penetrates through another quasi-neutral plasma which contains dust, electrons, and ions.

Vranjes, J. [Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussels (Belgium)

2011-08-15

224

Magnetic Field Gradient and Curvature-Driven Drift Modes in Toroidal Plasmas  

Microsoft Academic Search

A new kind of instability driven by the magnetic field gradient and curvature (MFGC) in toroidal plasmas is presented. It is found that the MFGC drift modes possess finite growth rates even if the plasma pressure gradient vanishes. In addition, the effects of plasma pressure gradient and safety factor on the MFGC modes have been analysed numerically.

Ai-Ke Wang; H. Sanuki; Jia-Qi Dong; F. Zonca; K. Itoh

2004-01-01

225

Study of driven magnetic reconnection in a laboratory plasma  

SciTech Connect

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

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

1998-12-31

226

Alpha particle-driven toroidal rotation in burning plasmas  

NASA Astrophysics Data System (ADS)

The mechanism of a torque intrinsically produced by alpha particles and the subsequent possibility to create significant toroidal rotation and shear are numerically investigated. In steady-state DEMO plasmas, regardless of the magnetic configuration, the orbit-following Monte Carlo code OFMC predicts that co-directed collisional torque and a counter-directed \\vec{j}\\times\\vec{B} torque always emerge due to the gradient of the source profile of alpha particles and both of them virtually cancel each other out, as analytically predicted earlier. The magnitude of each torque is enhanced in the reversed shear configuration compared with the normal shear configuration, provided that the source gradient is finite and similar in both cases. The resultant rotation velocity estimated by the TASK/TX transport code is far below the threshold to stabilize resistive wall modes (RWMs) through intrinsic alpha-driven torque alone. It is estimated that a neutral beam injection at a moderate power level may be capable of producing toroidal rotation sufficient to stabilize RWMs.

Honda, M.; Takizuka, T.; Tobita, K.; Matsunaga, G.; Fukuyama, A.

2011-07-01

227

Pressure-driven sound turbulence in a high-. beta. plasma  

SciTech Connect

In a large laboratory plasma (1 m diam{times}2 m, {ital n}{sub {ital e}}{le}10{sup 12} cm{sup {minus}3}, {beta}{sub 0}{approx equal}15 G, {beta}{sub {ital e}}={ital nkT}{sub {ital e}}/({beta}{sub 0}{sup 2}/2{mu}{sub 0}){approx equal}0.5), strong density fluctuations ({delta}{ital n}/{ital n}{approx equal}50%) near the lower hybrid frequency ({omega}{sub {ital c}{ital e}}{omega}{sub {ital c}{ital i}}){sup 1/2} are identified as cross-field sound waves ({ital k}{sub {perpendicular}}{much gt}{ital k}{sub {parallel}}, {omega}/{ital k}{sub {perpendicular}}{approx equal}{ital c}{sub {ital s}}) driven unstable by the electron diamagnetic drift {bold v}{sub {ital d}}={del}{ital p}{times}{bold B}/{ital ne}{beta}{sup 2}, {ital v}{sub {ital d}}{gt}{ital c}{sub {ital s}}. Wave steepening and refraction saturate the instability. Wave-enhanced transport but insignificant particle acceleration are observed.

Stenzel, R.L. (Department of Physics, University of California, Los Angeles, CA (USA))

1990-12-10

228

Summary report : working group 5 on 'electron beam-driven plasma and structure based acceleration concepts'.  

SciTech Connect

The talks presented and the work performed on electron beam-driven accelerators in plasmas and structures are summarized. Highlights of the working group include new experimental results from the E-157 Plasma Wakefield Experiment, the E-150 Plasma Lens Experiment and the Argonne Dielectric Structure Wakefield experiments. The presentations inspired discussion and analysis of three working topics: electron hose instability, ion channel lasers and the plasma afterburner.

Conde, M. E.; Katsouleas, T.

2000-10-19

229

Study of the Plasma near the Plasma Electrode by Probes and Photodetachment in ECR-driven Negative Ion Source  

NASA Astrophysics Data System (ADS)

The effect of the plasma electrode bias on the plasma characteristics near the extraction aperture in a large volume hybrid multicusp negative ion source, driven by 2.45 GHz microwaves, is reported. Spatially resolved negative ion and electron density measurements were performed under various pressures (1-4 mTorr) by means of electrostatic probe and photodetachment technique.

Bacal, M.; Svarnas, P.; Béchu, S.; Pelletier, J.

2009-03-01

230

Study of the Plasma near the Plasma Electrode by Probes and Photodetachment in ECR-driven Negative Ion Source  

SciTech Connect

The effect of the plasma electrode bias on the plasma characteristics near the extraction aperture in a large volume hybrid multicusp negative ion source, driven by 2.45 GHz microwaves, is reported. Spatially resolved negative ion and electron density measurements were performed under various pressures (1-4 mTorr) by means of electrostatic probe and photodetachment technique.

Bacal, M.; Svarnas, P. [LPTP, UMR CNRS 7648, Ecole Polytechnique, 91128 Palaiseau (France); Bechu, S.; Pelletier, J. [Laboratoire de Physique Subatomique et de Cosmologie, UMR CNRS 5821, 53 rue des Martyrs, 38026 Grenoble (France)

2009-03-12

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

Effects of finite plasma pressure on centrifugally driven convection in Saturn's magnetosphere  

NASA Astrophysics Data System (ADS)

We have previously shown simulation results for centrifugally driven plasma convection in Saturn's inner magnetosphere, using the Rice Convection Model, including a continuously active distributed plasma source, and effects of the Coriolis force and the pickup current. These simulations result in a quasi-steady state, in which fast, narrow inflow channels alternate with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. Comparison of different plasma source models indicates that the inner plasma source distribution is a key element in determining the plasma convection pattern. Previous simulations, however, did not include the effects of finite plasma pressure and the associated gradient-curvature drift. We will investigate here the effects of finite plasma pressure and gradient-curvature drift by giving the cold plasma a finite temperature. We will also add a source of hot tenuous plasma at the outer simulation boundary in an attempt to simulate the injection/dispersion events observed by Cassini.

Liu, X.; Hill, T. W.

2011-12-01

233

Improved confinement in high li lower hybrid driven steady state plasmas in TORE SUPRA  

Microsoft Academic Search

The global energy confinement of combined ohmic and lower hybrid driven TORE SUPRA plasmas has been analysed at various densities. In contradiction to the L mode ITER scaling law, this analysis indicates that the global energy confinement time depends strongly on the plasma density. Furthermore, the thermal electron energy content of steady state discharges is found to be in good

G. T. Hoang; C. Gil; E. Joffrin; D. Moreau; A. Becoulet; P. Bibet; J. P. Bizarro; R. V. Budny; J. Carrasco; J. P. Coulon; C. DeMichelis; T. Dudok de Wit; P. Monier-Garbet; M. Goniche; R. Guirlet; T. Hutter; S. M. Kaye; J. Lasalle; L. Laurent; P. Lecoustey; X. Litaudon; M. Mattioli; Y. Peysson; A.-L. Pecquet; G. Rey; S. A. Sabbagh; B. Saoutic; G. Tonon; J. C. Vallet

1994-01-01

234

Explosive-Driven Hemispherical Implosions for Generating Fusion Plasmas.  

National Technical Information Service (NTIS)

The UTIAS explosive-driven-implosion facility was used to produce stable, centered and focussed hemispherical implosions to generate neutrons from D-D reactions. A high resolution scintillator-detection system measured the neutrons and gamma-rays resultin...

D. Sagie I. I. Glass

1982-01-01

235

Explosive-Driven Hemispherical Implosions for Generating Fusion Plasmas.  

National Technical Information Service (NTIS)

An explosive-driven-implosion facility was used to produce stable, centered and focussed hemispherical implosions to generate neutrons from D-D reactions. A high resolution scintillator-detection system measured the neutrons and gamma rays resulting from ...

D. Sagie I. I. Glass

1982-01-01

236

Performance of dielectric elastomer actuators and materials  

Microsoft Academic Search

Dielectric elastomer actuators performance depends on their construction and the way they are driven. We describe the governing equations for the dynamic performance of actuators and show examples of their use. Both the properties of the base elastomer material and the compliant electrodes influence the actuators performance. The mechanical and electrical properties of elastomers are discussed with a focus on

Peter Sommer-Larsen; Guggi Kofod; M. H. Shridhar; Mohammed Benslimane; Peter Gravesen

2002-01-01

237

Production of High-Energy Plasmas by Magnetically Driven Shock Waves  

Microsoft Academic Search

High-voltage discharges (5-100 kilovolts) with peak currents in 0.3 to 5 microseconds have been used to produce shock waves in deuterium plasmas. The discharge is struck in a transverse magnetic field and the resultant Lorentz force drives the plasma out of the region of the discharge into a quartz side arm. Velocity measurements of the magnetically driven plasma are discussed

A. C. Kolb

1957-01-01

238

A traveling wave-driven, inductively coupled large area plasma source for flat panel processing  

Microsoft Academic Search

For large area micro-processing, a large area plasma source with low pressure, high density and high uniformity is required. Radio frequency (rf), inductively coupled plasma systems driven at 13.56 MHz are known for their capabilities in generating a high plasma density under low pressure, and for their independent control of ion flux and ion-bombarding energy, which are essential for the

Yaoxi Wu

2000-01-01

239

Visualization by discharge illumination technique and modification by plasma actuator of rarefied Mach 2 airflow around a cylinder  

NASA Astrophysics Data System (ADS)

The use of plasma actuators for flow control has received considerable attention in recent years. This kind of device seems to be an appropriate means of raising abilities in flow control thanks to total electric control, no moving parts and a fast response time. The experimental work presented here shows, firstly, the non-intrusive character of the visualization of the density field of an airflow around a cylinder obtained using a plasma luminescence technique. Experiments are made in a continuous supersonic wind tunnel. The static pressure in the flow is 8 Pa, the mean free path is about 0.3 mm and the airflow velocity is 510 m s?1. Pressure measurements obtained by means of glass Pitot tube without the visualization discharge are proposed. Measured and simulated pressure profiles are in good agreement in the region near the cylinder. There is good correlation between numerical simulations of the supersonic flow field, analytical model predictions and experimental flow visualizations obtained by a plasma luminescence technique. Consequently, we show that the plasma luminescence technique is non-intrusive. Secondly, the effect of a dc discharge on a supersonic rarefied air flow around a cylinder is studied. An electrode is flush mounted on the cylinder. Stagnation pressure profiles are examined for different electrode positions on the cylinder. A shock wave modification depending on the electrode location is observed. The discharge placed at the upstream stagnation point induces an upstream shift of the bow shock, whereas a modification of the shock wave shape is observed when it is placed at 45° or 90°.

Leger, L.; Sellam, M.; Barbosa, E.; Depussay, E.

2013-06-01

240

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

241

Modeling of high-explosive driven plasma compression opening switches  

Microsoft Academic Search

The initial path of the current through a plasma compression switch is through a thin (500-nm thick) metal foil. The current explodes the foil to form the seed for the conducting plasma. The behavior of the foil at this point is the same as an exploding metal fuse for which we have a simple model. We have, therefore, chosen this

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

1986-01-01

242

Inertia driven tearing modes in electron-positron plasmas  

Microsoft Academic Search

It is shown that the particle inertia can cause a tearing instability in an electron-positron collisionless plasma with sheared magnetic fields. An approximate analytical expression for the growth rate is obtained. It characterizes the magnetic reconnection timescale in a magnetized electronpositron plasma.

P. K. Shukla; S. Jammalamadaka; L. Stenflo

1996-01-01

243

Beam Driven Waves in a Positive Ion - Negative Ion Plasma  

Microsoft Academic Search

A plasma containing positive, negative and beam ions, in which all the charge species have comparable mass, is considered. Fluid approximations are employed to give qualitative information about such a system. Comparisons are made to the more familiar electron-ion plasma, with injected beams of electrons or ions. For beam velocity near an ion thermal speed, the \\

Tom Intrator

1982-01-01

244

Light-driven microcantilever actuator based on photoenhanced magnetization in a GaAs-Fe composite film  

NASA Astrophysics Data System (ADS)

Using the recently discovered phenomenon of photoenhanced magnetization in GaAs-Fe semiconductor-ferromagnet composite films [S. Haneda, S. Koshihara, and H. Munekata, Physica E 10, 437 (2001)], we have demonstrated a light-driven microactuator. It consists of a GaAs-Fe/GaAs(100) chip glued onto a 4.3 mm long, 2.1-?m-thick Si cantilever. A deflection of 0.7 ?m was achieved when the cantilever was illuminated with 650 nm, 713 ?W laser light in a magnetic field of 1.7 T at room temperature.

Shinshi, Tadahiko; Kato, Fumihito; Shimokohbe, Akira; Noguchi, Hiroshi; Munekata, Hiroo

2003-10-01

245

Analysis of plasma arcs in arc-driven rail guns  

Microsoft Academic Search

A model for estimating the properties of the arc in arc-driven rail guns is presented. The model assumes that the arc is steady in a reference frame that accelerates with the arc\\/projectile system, and accounts for the effect of finite rail height on the accelerating force and on the arc properties. The model is used to investigate the effect of

J. H. Batteh; J. D. Powell

1984-01-01

246

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

SciTech Connect

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

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

2011-11-15

247

Current Filament Merging Driven by Cross-Field Plasma Flows  

NASA Astrophysics Data System (ADS)

The study of the penetration and mixing of plasmas with differing density, temperature, and species composition has wide-ranging applicability to space plasma systems such as coronal mass ejections, magnetic clouds, galactic jets, and super novae. In these laboratory experiments, two high-beta plasmas are created using a pair of 1.5J, 8ns lasers which strike facing solid carbon targets at right angles to the background magnetic field. The targets are immersed within a low-beta, helium plasma and the lasers are aimed to produce head-on, or glancing collisions. The cylindrical background plasma is 17 m long (10 parallel Alfven wavelengths) by 60 cm wide (300 ?i or 175 c/?pe). The laser-produced plasmas (LPPs) expand as diamagnetic cavities, become polarized, and then E× B drift at speeds of Mach 10 (v/cs) across the field. As they do so, the ambient plasma facilitates charge separation between energetic LPP electrons and relatively unmagnetized 1keV LPP ions. One of the many resulting dynamic features is the release of a continuous stream of electrons from each LPP. Downstream from the LPP merging, the fast electron current filaments come together with reconnection-like X-line field patterns and eventually merge with a broadband spectrum of electromagnetic (whistler wave) fluctuations. Near-miss LPP collisions result in elongated current sheet formations and the shedding of magnetic field eddies. Current sheet thicknesses are a few electron inertial lengths and the width is approximately one ion inertial length. These results will be presented along with 3D measurements of the magnetic fields and the underlying current systems. These experiments are conducted at the Basic Plasma Science Facility, in the upgraded Large Plasma Device (LAPD) located at the University of California, Los Angeles, USA. This work is funded by the United States Department of Energy and the National Science Foundation.

Vincena, S.; Gekelman, W.; Collette, A.; Cooper, C.

2007-05-01

248

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.

Schroeder, C. B.; Benedetti, C.; Esarey, E.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Gruener, F. J. [Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany)

2011-09-30

249

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

250

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

251

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

SciTech Connect

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

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

2010-11-15

252

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

253

The development of laser- and beam-driven plasma accelerators as an experimental field  

NASA Astrophysics Data System (ADS)

Since its inception in the early 1980s, the field of plasma-based particle accelerators has made remarkable advances. Robust plasma accelerating structures can now be excited over centimeter scales using short laser pulses and over meter scales using ultrarelativistic particle beams. Accelerating fields in excess of tens of GV/m can be sustained over these lengths. Laser-driven plasma accelerators now routinely produce monoenergetic, low divergence electron beams in the 100 MeV-1 GeV range, whereas electron-beam driven plasma accelerators have demonstrated the ability to double the energy of 42 GeV electrons using a high-energy collider beam in less than one meter. The development of this field is traced through a series of path breaking experiments.

Joshi, C.

2007-05-01

254

Plasma ignition schemes for the SNS radio-frequency driven H- source  

SciTech Connect

The H{sup -} ion source for the Spallation Neutron Source (SNS) is a cesiated, radio-frequency driven (2 MHz) multicusp volume source which operates at a duty cycle of 6% (1 ms pulses and 60 Hz). In pulsed RF driven plasma sources, ignition of the plasma affects the stability of source operation and the antenna lifetime. We are reporting on investigations of different ignition schemes, based on secondary electron generation in the plasma chamber by UV light, a hot filament, a low power RF plasma (cw, 13.56 MHz), as well as source operation solely with the high power (40 kW) 2 MHz RF. We find that the dual frequency, single antenna scheme is most attractive for the operating conditions of the SNS H{sup -} source.

Schenkel, T.; Staples, J.W.; Thomae, W.; Reijonen, J.; Gough, R.A.; Leung, K.N.; Keller, R.

2001-09-06

255

Laser-driven plasma waves in capillary tubes.  

PubMed

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. PMID:20365282

Wojda, F; Cassou, K; Genoud, G; Burza, M; Glinec, Y; Lundh, O; Persson, A; Vieux, G; Brunetti, E; Shanks, R P; Jaroszynski, D; Andreev, N E; Wahlström, C-G; Cros, B

2009-12-04

256

Plasma-to-flame transition at the AC driven filamentary discharge ignition  

Microsoft Academic Search

Non-equilibrium plasmas make a new effective way for plasma-assisted ignition. The mechanisms of transition toward a flame kernel are investigated for the case of ignition initiated by the ac-driven discharge thanks to fast optical techniques. The study is done under 1-10 bars pressure range for air-propane mixtures. At atmospheric pressure, filaments of the discharge present two regions with the hotter

F. Auzas; M. Makarov; A. Agneray; M. Bellenoue; J. Sotton; S. Labuda; P. Tardiveau; V. Puech

2008-01-01

257

Summary Report of Working Group 5: Electron Beam Driven Plasma Accelerators  

SciTech Connect

Electron beam driven plasma accelerators have seen rapid progress over the last decade. Recent efforts have built on this success by constructing a concept for a plasma wakefield accelerator based linear collider. The needs for any future collider to deliver both energy and luminosity have substantial implications for interpreting current experiments and setting priorities for the future. This working group reviewed current experiments and ideas in the context of the demands of a future collider. The many discussions and presentations are summarized here.

Hogan, Mark J. [SLAC National Accelerator Laboratory Advanced Accelerator Research Department 2575 SandHill Road, Menlo Park, CA 94025 (United States); Conde, Manoel E. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne IL 60439 (United States)

2009-01-22

258

Current-driven solitons and shocks in plasmas having non-Maxwellian electrons  

NASA Astrophysics Data System (ADS)

The current-driven electrostatic solitons and shocks are investigated in flowing plasmas having stationary dust and non-Maxwellian electrons. The propagation of solar wind parallel to the external magnetic field in the boundary regions of dusty magnetospheres of planets can give rise to drift type unstable electrostatic waves and nonlinear structures even if density is homogeneous. These waves can be produced in laboratory plasma experiments as well. Here the theoretical model is applied to Saturn's magnetosphere.

Shan, S. Ali; Saleem, H.

2013-09-01

259

Ultraintense Electromagnetic Radiation in Plasmas: Part II. Relativistic Electromagnetic Solitons and Laser-Driven Ion Acceleration  

Microsoft Academic Search

Two laser-plasma processes among several others, namely the formation of relativistic electromagnetic solitons in warm plasmas\\u000a and the ion acceleration driven by the interaction of ultraintense and ultrafast laser pulses with thin solid targets, have\\u000a attracted great scientific interest in the last few years, both from a fundamental point of view and also in the light of\\u000a the expected future

M. Lontano; M. Passoni

260

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

NASA Astrophysics Data System (ADS)

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 (?) of plasma particles leaking in the forward (spacecraft) direction. By a combination of a few coils, we could decrease ? value without degrading the thrust efficiency. Finally, the shaped propellant is proposed to increase the thrust efficiency.

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

2008-12-01

261

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

262

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

263

Plasma Wakes Driven by Neutrinos, Photons and Electron Beams  

Microsoft Academic Search

There is considerable interest in the propagation dynamics of intense electron and photon neutrino beams in a background dispersive medium such as dense plasmas, particularly in the search for a mechanism to explain the dynamics of type II supernovae. Neutrino interactions with matter are usually considered as single particle interactions. All the single particle mechanisms describing the dynamical properties of

R. Bingham; L. O. Silva; J. T. Mendonca; P. K. Shukla; W. B. Mori; A. Serbeto

2007-01-01

264

Theory of fully developed turbulence in buoyancy-driven fluids and pressure-gradient-driven plasmas  

Microsoft Academic Search

A new theoretical method is presented to analyse turbulence and associated transport in far-non-equilibrium fluids and plasmas. First, direct nonlinear interactions with background turbulence are renormalized into nonlinear dielectric form. The relation between the turbulent intensity spectra of energy and temperature, E( k) and , and the nonlinear transfer rates (dielectric) of momentum and energy, and , are obtained as

S.-I. Itoh; K. Itoh

1998-01-01

265

Particle-in-cell Monte Carlo simulations of an extreme ultraviolet radiation driven plasma  

SciTech Connect

A self-consistent kinetic particle-in-cell model has been developed to describe a radiation driven plasma. Collisions between charged species and the neutral background are represented statistically by Monte Carlo collisions. The weakly ionized plasma is formed when extreme ultraviolet radiation coming from a pulsed discharge photoionizes a low pressure argon gas. The presence of a plasma close to optical components is potentially dangerous in case the ions that are accelerated in the plasma sheath gain enough energy to sputter the optics. The simulations predict the plasma parameters and notably the energy at which ions impact on the plasma boundaries. Finally, sputter rates are estimated on the basis of two sputtering models.

Velden, M.H.L. van der; Brok, W.J.M.; Mullen, J.J.A.M. van der; Goedheer, W.J.; Banine, V. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); FOM-Institute for Plasma Physics Rijnhuizen, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); ASML Netherlands B.V., De Run 6501, 5504 DR Veldhoven (Netherlands)

2006-03-15

266

Plasma driven water shock. Technical report, 24 September 1991-31 March 1994  

Microsoft Academic Search

This report describes the development and testing of the Phase II Plasma Driven Water Shock (PDWS ll) simulator as a continuation of the effort to develop a high energy density alternative to conventional high explosive (HE) water shock systems used for simulation of nuclear generated underwater shocks. The PDWS technique involves the rapid discharge of electrical energy, stored capacitively at

Hess

1996-01-01

267

Stabilization of pressure-driven magnetohydrodynamic modes by separatrix in dipole plasma confinement  

Microsoft Academic Search

The eigenvalue problem is solved for the short-wavelength pressure-driven magnetohydrodynamic modes in configuration with closed magnetic field lines in the poloidal direction. Here we show that the magnetic separatrix (which determines the boundary of the confinement region) provides a substantial stabilizing effect by which the total volume inside the separatrix becomes stable even for very high beta values. The plasma

M. Furukawa; H. Hayashi; Z. Yoshida

2010-01-01

268

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

269

Study of kinetic shear Alfvén modes driven by ion temperature gradient in tokamak plasmas  

Microsoft Academic Search

Discrete kinetic shear Alfvén modes driven by ion temperature gradient (AITG) are investigated in the full gyrokinetic limit. It is shown that AITG instability may occur when the plasma pressure gradient is well below the threshold value for ideal MHD ballooning instabilities and that the critical magnetic shear required to completely stabilize the former is significantly higher than that for

Jiaqi Dong; L. Chen; F. Zonca

1999-01-01

270

Pressure gradient-driven modes in finite beta toroidal plasmas  

Microsoft Academic Search

When the ion temperature gradient is finite, the ideal kinetic theory plasma destabilizes the MHD mode below the critical beta of MHD theory. For a temperature gradient eta i>2\\/3 and inverse aspect ratio epsilon (Ti)<0.35 the electrostatic toroidal eta i-mode is unstable. The coupling between the two modes is investigated by solving the fourth-order system describing the shear Alfven-drift wave

B. G. Hong; W. Horton; Duk-In Choi

1989-01-01

271

Modeling of high-explosive driven plasma compression opening switches  

SciTech Connect

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

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

1986-01-01

272

Current-driven Alfvén waves in dusty magnetospheric plasmas  

NASA Astrophysics Data System (ADS)

It is shown that the sheared flow of electrons and ions in the presence of heavy stationary dust gives rise to unstable Alfvén waves. The coupling of newly studied low frequency electrostatic current-driven mode with the electromagnetic Alfvén and drift waves is investigated. The instability conditions and the growth rates of both inertial and kinetic Alfvén waves are estimated. The theoretical model is applied to the night side boundary regions of Jupiter's magnetosphere which contain positive dust. The growth rates increase with increase in sheared flow speed. In the nonlinear regime, both inertial and kinetic Alfvén waves form dipolar vortices whose speed and amplitude depend upon the magnitude of the zero-order current.

Ali Shan, S.; Haque, Q.; Saleem, H.

2013-10-01

273

Reduced kinetic description of weakly-driven plasma waves  

SciTech Connect

A model of kinetic effects in Langmuir wave dynamics is presented using a nonlinear distribution function that includes particle separatrix crossing and self-consistent electrostatic evolution. This model is based on the adiabatic motion of electrons in the wave to describe Bernstein-Greene-Kruskal-like Langmuir waves over a wide range of temperatures (0.1{<=}k{lambda}{sub D}{<=}0.4). The asymptotic distribution function yields a nonlinear frequency shift of the Langmuir wave that agrees well with Vlasov simulations, and can furthermore be used to determine the electrostatic energy required to develop the phase-mixed, asymptotic state. From this incoherent energy, energy conservation is employed to determine a simplified model of nonlinear Landau damping. The resulting nonlinear, dynamic frequency shift and damping are then used in an extended three-wave-type model of driven Langmuir waves and compared to Vlasov simulations in the context of backward Raman scattering.

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

2008-05-15

274

Kinetic Alfven wave instability driven by electron temperature anisotropy in high-beta plasmas  

SciTech Connect

Based on the kinetic dispersion equation in the low-frequency condition of omegadriven by the electron temperature anisotropy in high-beta plasmas, which is associated with kinetic Alfven waves in the wave vector range of k{sub ||}lambda{sub I}<<1 and k{sub perpendicular}rho{sub i}<<1 (where lambda{sub I} and rho{sub i} are the ion inertial length and gyroradius, respectively), is investigated. The results show that the structures of both the growth rate and the real frequency are different from those driven by the ion temperature anisotropy. The growth rate is larger than that driven by the ion anisotropy. The critical instability condition is modified dramatically, in which the electron driven growth rate does not vanish at the classical critical point and its deviation from zero increases with the kinetic effect due to the short-wavelength modification.

Chen, L. [Purple Mountain Observatory, CAS, Nanjing 210008 (China)] [Graduate School, CAS, Beijing 100012 (China); Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing 210008 (China)

2010-06-15

275

Mirror, firehose and cosmic-ray-driven instabilities in a high-? plasma  

NASA Astrophysics Data System (ADS)

I consider low-frequency instabilities in a plasma with high-? plasma, with ? the ratio of thermal and magnetic pressures. I derive the mirror and firehose instabilities, due to pressure anisotropy, for such a plasma. This derivation uncovers clear modifications with the more familiar, low-? case. I also consider the interplay between these instabilities and the current-driven instability (the Bell-Lucek instability) that occurs near a shock that accelerates cosmic rays. It is shown that the two instability mechanisms in combination can lead to a stronger instability over a wider range of wavelengths.

Achterberg, A.

2013-09-01

276

Dust-acoustic filamentation of a current-driven dusty plasma  

SciTech Connect

The thermal motion effect of charged particles in the filamentation of a current-driven dusty plasma in the dust-acoustic frequency region is investigated by using the Lorentz transformed conductivity of the dusty plasma components and the total dielectric permittivity tensor of the dusty plasma in the laboratory frame. Obtaining the dispersion relation for dust-acoustic waves and considering the filamentation instability, the establishment time of the filamentation structure and the instability development threshold are derived. Moreover, it is shown that the current layer divides into separate current filaments.

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

2011-06-15

277

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

278

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

279

Mirror, firehose and cosmic-ray-driven instabilities in a high-? plasma  

NASA Astrophysics Data System (ADS)

I consider low-frequency instabilities in a plasma with high-? plasma, with ? the ratio of thermal and magnetic pressures. I derive the mirror and firehose instabilities, due to pressure anisotropy, for such a plasma. This derivation uncovers clear modifications with the more familiar, low-? case. I also consider the interplay between these instabilities and the current-driven instability (the Bell-Lucek instability) that occurs near a shock that accelerates cosmic rays. It is shown that the two instability mechanisms in combination can lead to a stronger instability over a wider range of wavelengths.

Achterberg, A.

2013-11-01

280

Spatially resolved simulation of a radio-frequency driven micro-atmospheric pressure plasma jet and its effluent  

Microsoft Academic Search

Radio-frequency driven plasma jets are frequently employed as efficient plasma sources for surface modification and other processes at atmospheric pressure. The radio-frequency driven micro-atmospheric pressure plasma jet (muAPPJ) is a particular variant of that concept whose geometry allows direct optical access. In this work, the characteristics of the muAPPJ operated with a helium-oxygen mixture and its interaction with a helium

Torben Hemke; Alexander Wollny; Markus Gebhardt; Ralf Peter Brinkmann; Thomas Mussenbrock

2011-01-01

281

Study of electromagnetic instabilities driven by ion temperature gradient and parallel sheared flows in high-? plasmas  

NASA Astrophysics Data System (ADS)

The local electromagnetic modes driven by ion temperature gradient (ITG) and parallel sheared flows, including parallel velocity shear (PVS) of ions and plasma current, are studied for any ? (plasma pressure/magnetic pressure) plasma. It is shown that a finite ? not only weakens the driving mechanism directly but also reverses the effect of the current on the modes from weakly destabilizing to stabilizing. However, the local kinetic ITG-PVS modes are unstable in a high-? plasma with a parallel sheared ion flow (positive or negative). The plasma current and current gradient make nearly opposite contributions to the modes. As ?i (the parameter for ion temperature gradient) increases, the effects of the current and current gradient are weakened and then reversed.

Gao, Zhe; Dong, J. Q.; Liu, G. J.; Ying, C. T.

2001-09-01

282

Ion-beam driven dust ion-acoustic solitary waves in dusty plasmas  

NASA Astrophysics Data System (ADS)

The nonlinear propagation of small but finite amplitude dust ion-acoustic waves (DIAWs) in an ion-beam driven plasma consisting of Boltzmannian electrons, positive ions, and stationary negatively charged dust grains is studied by using the standard reductive perturbation technique. It is shown that there exist two critical values (?c1 and ?c2) of ion beam to ion phase velocity ratio (?), above and below which the beam generated solitons are not possible. The effects of the parameters, namely, ?, the ratio of the ion beam to plasma ion density (?i), the dust to ion density ratio (?d), and the ion beam to plasma ion mass ratio (?) on both the amplitude and width of the stationary DIAWs, are analyzed numerically, and applications of the results to laboratory ion beam as well as space plasmas (e.g., auroral plasmas) are explained.

Adhikary, N. C.; Misra, A. P.; Bailung, H.; Chutia, J.

2010-04-01

283

ITG and DTE mode driven transport in a contaminated toroidal plasma  

NASA Astrophysics Data System (ADS)

The electrostatic quasi-linear particle and thermal diffusivities, due to the toroidal ion temperature gradient (ITG) driven modes and the dissipative trapped electron (DTE) mode, are considered in the dissipative limit, ? << vef/epsilon. Impurities are included by assuming a plasma with three particle species (electrons, main ions and impurity ions). The diffusivities are studied by computing interpretative radial transport profiles based on a TEXTOR background variation, using a saturation level approximation. The transport is found to be driven also by impurity modes, in particular when a light impurity species, such as helium, is assumed. The existence of inward fluxes of particles and heat is discussed

Frojdh, M.; Jarmen, A.

1995-05-01

284

Single-pulse driven plasma Pockels cell with 350mm×350mm aperture  

NASA Astrophysics Data System (ADS)

Large-aperture plasma Pockels cell is one of important components for inertial confinement fusion laser facility. We demonstrate a single-pulse driven PPC with 350mm×350mm aperture. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPC meets the optical switching requirement of SGII update laser facility. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, less the maintenance, and higher reliability.

Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Kuixing; Jing, Feng

2010-08-01

285

Characteristics of turbulence-driven plasma flow and origin of experimental empirical scalings of intrinsic rotation  

SciTech Connect

Toroidal plasma flow driven by turbulent torque associated with nonlinear residual stress generation is shown to recover the observed key features of intrinsic rotation in experiments. Specifically, the turbulence-driven intrinsic rotation scales close to linearly with plasma gradients and the inverse of the plasma current, qualitatively reproducing empirical scalings obtained from a large experimental data base. The effect of magnetic shear on the symmetry breaking in the parallel wavenumber spectrum is identified. The origin of the current scaling is found to be the enhanced k{sub ||} symmetry breaking induced by increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic rotation on the pressure gradient comes from the fact that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving the residual stress, are increased with the strength of the turbulence drives, which are R/L{sub T{sub e}} and R/L{sub n{sub e}} for the collisionless trapped electron mode (CTEM). Highlighted results also include robust radial pinches in toroidal flow, heat and particle transport driven by CTEM turbulence, which emerge ''in phase,'' and are shown to play important roles in determining plasma profiles. Also discussed are the experimental tests proposed to validate findings from these gyrokinetic simulations.

Wang, W. X.; Hahm, T. S.; Ethier, S.; Rewoldt, G.; Tang, W. M.; Lee, W. W. [Princeton University, Plasma Physics Laboratory, P. O. Box 451, Princeton, New Jersey 08543 (United States); Diamond, P. H. [University of California, San Diego, La Jolla, California 92093 (United States)

2011-04-15

286

Development of a confined plasma armature design (CPAD) [plasma-driven railguns  

Microsoft Academic Search

Phase I and II SBIR programs were conducted to design, fabricate, and test a confined plasma armature design that would physically contain the high-pressure plasma in an area directly behind the EM projectile. The initial CPAD experiments demonstrated the ability to initiate a confined plasma and achieve some EM acceleration. The inability of the CPAD projectile to conform to the

Moreno White; D. Jacobsen; Christine Barker; Edward Goldman

1993-01-01

287

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

288

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

NASA Astrophysics Data System (ADS)

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.; Gans, T.; O'Connell, D.

2011-07-01

289

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

SciTech Connect

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

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

2007-08-15

290

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

291

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

PubMed

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 (~1.3 x 10(11) cm(-3)) and electron temperature (7-15 eV) at a power density of 5-10 Wcm(2). Ion current densities ranging from a few hundreds to over 1000 mA/cm(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. PMID:18601405

Mathew, Jose V; Chowdhury, Abhishek; Bhattacharjee, Sudeep

2008-06-01

292

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

NASA Astrophysics Data System (ADS)

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 (~1.3×1011 cm-3) and electron temperature (7-15 eV) at a power density of 5-10 W/cm2. Ion current densities ranging from a few hundreds to over 1000 mA/cm2 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

2008-06-01

293

Neutron Signatures of Non-Thermal Ion Distributions in Z-Pinch Driven ICF Plasmas  

NASA Astrophysics Data System (ADS)

In preparation for upcoming ICF experiments on the 26 MA Z machine (e.g., D2 gas puff, MagLIF [1]), we are studying the neutron energy spectra produced by magnetically-driven loads beyond the archetypal single temperature, uniform plasma. Z-pinch sources frequently exhibit evidence of unusual neutron spectra [2], which can be attributed to three-dimensional turbulent motion, high-energy beams, and other phenomena leading to non-Maxwellian ion distributions. Understanding the nature of our plasma neutron sources is critical for understanding how they scale with increasing current. We will show Monte Carlo and analytic calculations for plausible scenarios and discuss the corresponding signatures for the existing set of time-of-flight diagnostics on Z.[4pt] [1] S. A. Slutz et al. Phys. Plasmas 17, 056303 (2010)[0pt] [2] V.V. Vikhrev and V.D. Korolev, Plasma Dynamics, Vol. 33, No. 5 (2007)

Knapp, Patrick; Jennings, Christopher; Sinars, Daniel

2012-10-01

294

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

295

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

296

Channeling of the Energy and Momentum during Energetic-Ion-Driven Instabilities in Fusion Plasmas  

SciTech Connect

New features of instabilities driven by energetic ions are revealed. It is found that these instabilities can affect plasma heating and rotation by channeling the energy and momentum of the energetic ions to the region where the destabilized waves are damped. Because of the energy channeling, the plasma core may not be heated by the energetic ions even when these ions have a very peaked radial distribution. It is likely that this new phenomenon can explain experiments on the spherical torus NSTX where a broadening of the temperature profile and even a drop of the temperature at the plasma center with increasing injected power were observed during Alfven instabilities [D. Stutman et al., Phys. Rev. Lett. 102, 115002 (2009)]. The momentum channeling can lead to plasma rotation and frequency chirping due to the Doppler shift varying in time.

Kolesnichenko, Ya. I.; Yakovenko, Yu. V.; Lutsenko, V. V. [Institute for Nuclear Research, Prospekt Nauky 47, Kyiv 03680 (Ukraine)

2010-02-19

297

Experimental results on current-driven turbulence in plasmas - a survey  

NASA Astrophysics Data System (ADS)

The experimental consequences of plasma turbulence driven by a current parallel to a magnetic field and concurrent anomalous plasma heating are reviewed, with an attempt to deduce universalities in key parameters such as the anomalous electrical conductivities observed in diverse devices. It has been found that the nature of plasma turbulence and turbulent heating depends on several parameters including the electric field, current and magnetic fields. A classification of turbulence regimes based on these parameters has been made. Experimental observations of the anomalous electrical conductivity, plasma heating, skin effect, runaway electron braking and turbulent fluctuations are surveyed, and current theoretical understanding is briefly reviewed. Experimental results recently obtained in stellarators (SIRIUS, URAGAN at Kharkov), and in tokamaks (TORTUR at Nieuwegein, STOR-1M at Saskatoon) are presented in some detail in the light of investigating the feasibility of using turbulent heating as a means of injecting a large power into toroidal devices.

de Kluiver, H.; Perepelkin, N. F.; Hirose, A.

1991-01-01

298

Effects of finite plasma pressure on centrifugally driven convection in Saturn's inner magnetosphere  

NASA Astrophysics Data System (ADS)

We have previously shown simulation results for centrifugally driven plasma convection in Saturn's inner magnetosphere (2 < L < 12) using the Rice Convection Model, including a continuously active distributed plasma source, and the effects of the Coriolis force and the pickup current. These simulations result in a quasi-steady state, in which fast, narrow inflow channels alternate with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. These previous simulations, however, did not include the plasma pressure. We investigate here the effects of finite plasma pressure and the associated gradient-curvature drift current by giving the cold plasma a finite temperature. Our simulations confirm the theoretical expectation that a finite plasma pressure produces a force in the positive radial direction, the same direction as the centrifugal force, and acts as an additional driver of plasma convection. Our simulations also confirm that the radial velocities can be reduced (to keep them within observational constraints) by increasing the assumed ionospheric Pedersen conductance (also within observational constraints).

Liu, X.; Hill, T. W.

2012-07-01

299

Intense Geodesic Acousticlike Modes Driven by Suprathermal Ions in a Tokamak Plasma  

SciTech Connect

Intense axisymmetric oscillations driven by suprathermal ions injected in the direction counter to the toroidal plasma current are observed in the DIII-D tokamak. The modes appear at nearly half the ideal geodesic acoustic mode frequency, in plasmas with comparable electron and ion temperatures and elevated magnetic safety factor (q{sub min}{>=}2). Strong bursting and frequency chirping are observed, concomitant with large (10%-15%) drops in the neutron emission. Large electron density fluctuations (n-tilde{sub e}/n{sub e}{approx_equal}1.5%) are observed with no detectable electron temperature fluctuations, confirming a dominant compressional contribution to the pressure perturbation as predicted by kinetic theory. The observed mode frequency is consistent with a recent theoretical prediction for the energetic-particle-driven geodesic acoustic mode.

Nazikian, R.; Fu, G. Y.; Budny, R. V.; Gorelenkov, N. N.; Kramer, G. J.; Solomon, W. M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Austin, M. E.; Berk, H. L. [University of Texas at Austin, Austin, Texas 78712 (United States); Heidbrink, W. W. [University of California Irvine, Irvine, California 92697 (United States); Holcomb, C. T.; Makowski, M. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); McKee, G. R.; Shafer, M. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Strait, E. J.; Van Zeeland, M. A. [General Atomics, San Diego, California 92186-5608 (United States)

2008-10-31

300

Structure of parallel-velocity-shear-driven mode in toroidal plasmas  

NASA Astrophysics Data System (ADS)

It is shown that the Fourier-ballooning representation is appropriate for the study of short-wavelength drift-like perturbation in toroidal plasmas with a parallel velocity shear (PVS). The radial structure of the mode driven by a PVS is investigated in a torus. The Reynolds stress created by PVS turbulence, and proposed as one of the sources for a sheared poloidal plasma rotation, is analyzed. It is demonstrated that a finite ion temperature may strongly enhance the Reynolds stress creation ability from PVS-driven turbulence. The correlation of this observation with the requirement that ion heating power be higher than a threshold value for the formation of an internal transport barrier is discussed.

Dong, J. Q.; Xu, W. B.; Zhang, Y. Z.; Horton, W.

1998-12-01

301

Structure of parallel-velocity-shear driven mode in toroidal plasmas  

SciTech Connect

It is shown that the Fourier-ballooning representation is appropriate for the study of short wavelength drift-like perturbation in toroidal plasmas with a parallel velocity shear (PVS). The radial structure of the mode driven by a PVS is investigated in a torus. The Reynolds stress created by PVS turbulence and proposed as one of the sources for a sheared poloidal plasma rotation is analyzed. It is demonstrated that a finite ion temperature may strongly enhance the Reynolds stress creation ability from PVS driven turbulence. The correlation of this observation with the requirement that ion heating power be higher than a threshold value for the formation of an internal transport barrier is discussed.

Dong, J.Q.; Xu, W.B.; Zhang, Y.Z. [Southwestern Inst. of Physics, Chengdu (China); Horton, W. [Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies

1998-09-15

302

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

SciTech Connect

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

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

1998-11-01

303

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

304

Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma source.  

PubMed

Performance of a microwave driven upper hybrid resonance multicusp plasma source as a volume negative ion source is reported. Microwaves are directly launched into the plasma chamber predominantly in the TE(11) mode. The source is operated at different discharge conditions to obtain the optimized negative H(-) ion current which is ?33 ?A (0.26 mA?cm(2)). Particle balance equations are solved to estimate the negative ion density, which is compared with the experimental results. Future prospects of the source are discussed. PMID:22380215

Sahu, D; Bhattacharjee, S; Singh, M J; Bandyopadhyay, M; Chakraborty, A

2012-02-01

305

Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma source  

NASA Astrophysics Data System (ADS)

Performance of a microwave driven upper hybrid resonance multicusp plasma source as a volume negative ion source is reported. Microwaves are directly launched into the plasma chamber predominantly in the TE11 mode. The source is operated at different discharge conditions to obtain the optimized negative H- ion current which is ~33 ?A (0.26 mA/cm2). Particle balance equations are solved to estimate the negative ion density, which is compared with the experimental results. Future prospects of the source are discussed.

Sahu, D.; Bhattacharjee, S.; Singh, M. J.; Bandyopadhyay, M.; Chakraborty, A.

2012-02-01

306

Observation of Plasma Rotation Driven by Static Nonaxisymmetric Magnetic Fields in a Tokamak  

SciTech Connect

We present the first evidence for the existence of a neoclassical toroidal rotation driven in a direction counter to the plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, the nonresonant field torque slows down the plasma toward the neoclassical 'offset' rotation rate. With small injected neutral beam momentum, the toroidal rotation is accelerated toward the offset rotation, with resulting improvement in the global energy confinement time. The observed magnitude, direction, and radial profile of the offset rotation are consistent with neoclassical theory predictions [A. J. Cole et al., Phys. Rev. Lett. 99, 065001 (2007)].

Garofalo, A. M.; Burrell, K. H.; DeBoo, J. C.; DeGrassie, J. S.; Jackson, G. L.; Schaffer, M. J.; Strait, E. J. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Lanctot, M.; Reimerdes, H. [Columbia University, 2960 Broadway, New York, New York 10027-1754 (United States); Solomon, W. M. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

2008-11-07

307

Two-dimensional modeling of high explosive driven plasma opening switches  

SciTech Connect

Calculations of high-explosive (HE) driven plasma opening switches have been extended to two dimensions. The goal of our calculations is to determine the role of mixing in the resistance increases that are observed experimentally. We have not included a magnetic field, but have looked at the hydrodynamics of the interface between the cool HE detonation products and the hot plasma. Our calculations indicate that significant mixing can occur if perturbations exist along the interface. We estimate the sensitivity of our results to the wavelength and amplitude of these perturbations.

Greene, A.E.; Bowers, R.L.

1985-01-01

308

Longitudinal space charge amplifier driven by a laser-plasma accelerator  

NASA Astrophysics Data System (ADS)

A longitudinal space charge amplifier (LSCA), operating in VUV anmd soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. The amplification mechanism is broadband and robust, it is practically insensitive to energy chirp and orbit jitter. Therefore, an LSCA can be considered as an alternative to a SASE FEL in the case of using laser-plasma accelerators as drivers of light sources. In this report we study generation of VUV radiation (below 100 nm) in an LSCA driven by a laser-plasma accelerator with the energy of 300 MeV.

Dohlus, Martin; Schneidmiller, Evgeny; Yurkov, Mikhail V.; Henning, Christoph; Grüner, Florian J.

2013-05-01

309

Stabilization of pressure-driven magnetohydrodynamic modes by separatrix in dipole plasma confinement  

SciTech Connect

The eigenvalue problem is solved for the short-wavelength pressure-driven magnetohydrodynamic modes in configuration with closed magnetic field lines in the poloidal direction. Here we show that the magnetic separatrix (which determines the boundary of the confinement region) provides a substantial stabilizing effect by which the total volume inside the separatrix becomes stable even for very high beta values. The plasma inertia and compressibility are properly formulated to give the correct growth rate of the mode.

Furukawa, M.; Hayashi, H.; Yoshida, Z. [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8561 (Japan)

2010-02-15

310

Radiative characteristics of pulsed power driven Z-pinch aluminum plasmas  

Microsoft Academic Search

In this paper, we study the dynamics of a massive aluminum Z-pinch plasma load and evaluate its performance as a soft X-ray radiator. A radiation hydrodynamic model self-consistently driven by a circuit describes the dynamics. Comparisons are made for the K- and L-shell soft X-ray emission as a function of the ionization dynamic model. The ionization dynamic models are represented

Jack Davis; R. W. Clark; J. W. Thornhill; Christopher Deeney

1998-01-01

311

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

312

Two-dimensional plasma model for the arc-driven rail gun  

Microsoft Academic Search

A two-dimensional model is developed for studying the fluid mechanical electrodynamical properties of the plasma in an arc-driven rail gun. A set of general, time-dependent equations is derived whose solution yields the associated properties of the arc. These equations are then solved utilizing the assumptions that the flow variables are steady in a frame of reference which accelerates with the

J. D. Powell; J. H. Batteh

1983-01-01

313

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

314

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

315

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

NASA Astrophysics Data System (ADS)

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&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.

2012-12-01

316

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

317

Laser-driven electron beamlines generated by coupling laser-plasma sources with conventional transport systems  

NASA Astrophysics Data System (ADS)

Laser-driven electron beamlines are receiving increasing interest from the particle accelerator community. In particular, the high initial energy, low emittance, and high beam current of the plasma based electron source potentially allow generating much more compact and bright particle accelerators than what conventional accelerator technology can achieve. Using laser-generated particles as injectors for generating beamlines could significantly reduce the size and cost of accelerator facilities. Unfortunately, several features of laser-based particle beams need still to be improved before considering them for particle beamlines and thus enable the use of plasma-driven accelerators for the multiple applications of traditional accelerators. Besides working on the plasma source itself, a promising approach to shape the laser-generated beams is coupling them with conventional accelerator elements in order to benefit from both a versatile electron source and a controllable beam. In this paper, we perform start-to-end simulations to generate laser-driven beamlines using conventional accelerator codes and methodologies. Starting with laser-generated electrons that can be obtained with established multi-hundred TW laser systems, we compare different options to capture and transport the beams. This is performed with the aim of providing beamlines suitable for potential applications, such as free electron lasers. In our approach, we have analyzed which parameters are critical at the source and from there evaluated different ways to overcome these issues using conventional accelerator elements and methods. We show that electron driven beamlines are potentially feasible, but exploiting their full potential requires extensive improvement of the source parameters or innovative technological devices for their transport and capture.

Antici, P.; Bacci, A.; Benedetti, C.; Chiadroni, E.; Ferrario, M.; Rossi, A. R.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Serafini, L.

2012-08-01

318

Hydrodynamic Scaling Analysis of Nuclear Fusion Driven by Ultra-Intense Laser-Plasma Interactions  

NASA Astrophysics Data System (ADS)

We discuss scaling laws of fusion yields generated by laser-plasma interactions. The yields are found to scale as a function of the laser power. The origin of the scaling law in the laser driven fusion yield is derived in terms of hydrodynamic scaling. We point out that the scaling properties can be attributed to the laser power dependence of three terms: the reaction rate, the density of the plasma and the projected range of the plasma particle in the target medium. The resulting scaling relations have a predictive power that enables estimating the fusion yield for a nuclear reaction which has not been investigated by means of the laser accelerated ion beams.

Kimura, Sachie; Bonasera, Aldo

2012-12-01

319

Miniature hybrid plasma focus extreme ultraviolet source driven by 10 kA fast current pulse  

SciTech Connect

A miniature hybrid plasma focus device, operated in xenon gas medium and driven by a 10 kA fast current pulse, has been used to generate extreme ultraviolet radiation in the range of 6-15 nm. At present the radiation characteristics from xenon plasma were mainly assessed qualitatively using standard tools such as visible light framing camera, extreme ultraviolet (EUV) pinhole camera, and EUV photodiode. Strong pinching of xenon plasma is indicative from both visible and EUV imagings. The maximum size of the EUV emitting zone is estimated to be of the order of 0.21x1.55 mm and the estimated value is within the accepted value as benchmarked by industries. The EUV intensity measurement by photodiode showed fairly isotropic radiation at least in a half solid angle. This device can be developed further as a competent source for EUV metrology or lithography applications.

Mohanty, S.R.; Sakamoto, T.; Kobayashi, Y.; Song, I.; Watanabe, M.; Kawamura, T.; Okino, A.; Horioka, K.; Hotta, E. [Department of Energy Sciences, Tokyo Institute of Technology, Nagatsuta, Yokohama 226-8502 (Japan)

2006-04-15

320

MHD Evolution in Point-Source Helicity Injection Driven Plasmas on Pegasus  

NASA Astrophysics Data System (ADS)

Point-source helicity injection for non-solenoidal startup on Pegasus produces plasmas with Ip<=0.17 MA consistent with Taylor relaxation. The helicity injection supplies an effective loop voltage Veff inversely proportional to the plasma toroidal flux ?T. Accurate measurement of the Veff evolution requires equilibrium reconstructions. Helicity injection-driven plasmas originate on the outboard, low-field side and expand inward to fill the vessel. This evolution increases ?T, reducing Veff from >= 10 V to <= 2 V. Supplemental loop voltage from poloidal field induction is used to obtain higher plasma current. Ip growth is accompanied by bursts of n=1 magnetic activity with frequencies between 10--150 kHz, abrupt inward motion of the plasma, and a drop in internal inductance. This magnetic activity persists during helicity injection. Afterward, MHD quiescence is obtained and persists in discharges subsequently sustained by ohmic induction. The spectral content of these magnetic fluctuations measured with a scanning Mirnov probe does not differ significantly with distance from the plasma edge.

Barr, J. L.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Hinson, E. T.; Redd, A. J.

2011-11-01

321

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

322

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

323

Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves.  

PubMed

A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a nonrelativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for Langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three-velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for nonrelativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances. PMID:20866340

Schroeder, C B; Esarey, E

2010-05-13

324

Toroidal rotation of multiple species of ions in tokamak plasma driven by lower-hybrid-waves  

NASA Astrophysics Data System (ADS)

A numerical simulation is carried out to investigate the toroidal rotation of multiple species of ions and the radial electric field in a tokamak plasma driven by the lower-hybrid-wave (LHW). The theoretical model is based on the neoclassical transport theory associated with the anomalous transport model. Three species of ions (primary ion and two species of impurity ions) are taken into consideration. The predicted toroidal velocity of the trace impurities during the LHW injection agrees reasonably well with the experimental observation. It is shown that the toroidal rotation velocities of the trace impurity ions and the primary ions are close, therefore the trace impurity ions are representative of the primary ions in the toroidal rotation driven by the LHW.

Zuo, Yang; Wang, Shaojie; Pan, Chengkang

2012-10-01

325

Impurity pellet injection into current-driven plasmas of the JIPPT-IIU tokamak  

NASA Astrophysics Data System (ADS)

Impurity pellets of stainless steel and plastic carbon with a size of 0.5 mm diameter and a velocity of 400 + or - 100 m/s have been injected into fast-wave-current-driven plasma with a sustained plasma current of 35-50kA and an electron density of 2-4 x 10 to the 12th/cu cm to study the interaction between them. The current-driven plasmas show no disruption at the pellet injection, whereas all of the ohmic discharges are disruptive. These phenomena are interrupted briefly with results of a sudden decrease of the electron temperature and density rises of 6-8 x 10 to the 12th/cu cm for the iron pellet and 4 x 10 to the 12th/cu cm for the carbon pellet. The electron temperature after the injection is estimated to be about 10 eV from the density rise and the calculation of the impurity charge states. The decaying time of the injected impurity is measured to be 25ms from the time behavior of the soft X-ray emission.

Morita, S.; Kawatoh, E.; Ohkubo, K.; Ida, K.; Ogawa, Y.; Adati, K.; Amano, T.; Fujita, Junji; Hamada, Y.; Hidekuma, S.

1988-12-01

326

Plasma driven permeation of hydrogen through Nb: influence of the surface and bulk defects  

NASA Astrophysics Data System (ADS)

Plasma driven permeation of hydrogen through 25 ?m Nb foils was investigated under low-energy hydrogen ion irradiation in the range of membrane temperature 450-800 K and at different surface conditions. The interaction of hydrogen at molecular, atomic and ionizated states with niobium was under experimental research. The maximum value of low-temperature steady state permeation efficiency (SPE) was observed at Ar plasma cleaned inlet surface and with insignificant influence of outlet surface conditions. Such result is unusual and contradicts the developed classical representations and other published data for high-temperature range plasma-driven permeation. We explain this phenomenon by influence of defect structure of the polycrystalline membrane. The defects lead to the enhanced diffusion of hydrogen atoms along the crystallite sides. Such diffusion can essentially increase SPE of hydrogen through metal at low temperatures. The validity of this explanation was proved by the comparison of molecular hydrogen sorption & desorption measurements in poly- and mono-crystal Nb samples. The weighing method was used in that case. The phase transition ?'-->? in the Nb-H system is important for an explanation of SPE temperature dependencies in low-temperature range. The defects initiate phase transitions. The short-time enhanced hydrogen permeation was observed after irradiation of a membrane surface by Ar ions. The surface dissociation of the molecular ions, excited molecules and partially ordinary unexcited molecules of hydrogen can explain these observations.

Spitsyn, A.; Skovoroda, A.; Petrov, V.; Stolyarov, V.; Pustovoit, Yu; Bykov, D.; Voronkin, E.

2006-05-01

327

Plasma driven permeation of hydrogen through Nb: influence of the surface and bulk defects  

SciTech Connect

Plasma driven permeation of hydrogen through 25 {mu}m Nb foils was investigated under low-energy hydrogen ion irradiation in the range of membrane temperature 450-800 K and at different surface conditions. The interaction of hydrogen at molecular, atomic and ionizated states with niobium was under experimental research. The maximum value of low-temperature steady state permeation efficiency (SPE) was observed at Ar plasma cleaned inlet surface and with insignificant influence of outlet surface conditions. Such result is unusual and contradicts the developed classical representations and other published data for high-temperature range plasma-driven permeation. We explain this phenomenon by influence of defect structure of the polycrystalline membrane. The defects lead to the enhanced diffusion of hydrogen atoms along the crystallite sides. Such diffusion can essentially increase SPE of hydrogen through metal at low temperatures. The validity of this explanation was proved by the comparison of molecular hydrogen sorption and desorption measurements in poly- and mono-crystal Nb samples. The weighing method was used in that case. The phase transition {beta}'{yields}{alpha} in the Nb-H system is important for an explanation of SPE temperature dependencies in low-temperature range. The defects initiate phase transitions. The short-time enhanced hydrogen permeation was observed after irradiation of a membrane surface by Ar ions. The surface dissociation of the molecular ions, excited molecules and partially ordinary unexcited molecules of hydrogen can explain these observations.

Spitsyn, A.; Skovoroda, A.; Stolyarov, V.; Pustovoit, Yu [Nuclear Fusion Institute of RRC 'Kurchatov Institute', Moscow, 123182 (Russian Federation); Petrov, V.; Bykov, D.; Voronkin, E. [Moscow State Institute of Electronics and Mathematics, Moscow, 109028 (Russian Federation)

2006-05-24

328

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

Microsoft Academic Search

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

Nicolas Benard; Eric Moreau

2011-01-01

329

FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air  

Microsoft Academic Search

Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally

J. Dedrick; R. W. Boswell; C. Charles

2010-01-01

330

Fabrication of TiNi shape memory actuator for micropump  

NASA Astrophysics Data System (ADS)

We are attempting to develop a shape memory alloy (SMA) actuated micropump as a component for use in micro analysis or micro dosage systems. In this paper, we will discuss the fabrication process and dynamic actuation properties of an SMA actuator. TiNi thin film of about 6 micrometers in thickness was deposited onto a Si wafer with a square recess on its reverse side, and annealed at 500 degrees C for 1h in a vacuum to memorize an initial flat shape. The TiNi thin film and a Pyrex glass cap of 500 micrometers thickness with a square recess were then anodically bonded together in a vacuum to form a chamber to which a bias pressure was to be applied to deform the TiNi thin film. After removing the remaining 50 $mUm thick Si layer beneath the TiNi thin film by RIE in SF6 plasma, a shape memory diaphragm of 5mm square in size was completed. The fabricated actuator was driven by resistive heating and air-cooling under a bias pressure of 200 kPa, which was applied by a nitrogen gas flow through a small hole pieced in the Pyrex glass cap. Under these conditions, the actuator gave displacements of about 95 micrometers at the center during repeated thermal cycles. A Si check valve structure, to be assembled with the actuator to construct a micropump, was also fabricated through a process of anisotropic etching and fusion bonding. The flow resistance for forward flow proved to be about one-three hundredths of that for backward flow.

Makino, Eiji; Mitsuya, Takashi; Shibata, Takayuki

1999-09-01

331

Kinetic Alfven wave instability driven by a field-aligned current in high-{beta} plasmas  

SciTech Connect

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 Alfven 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{sub D}, is investigated in a high-{beta} plasma, where {beta} 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.

Chen, L.; Wu, D. J.; Hua, Y. P. [Purple Mountain Observatory, CAS, Nanjing 210008, China and Graduate School, CAS, Beijing 100012 (China); Purple Mountain Observatory, CAS, Nanjing 210008 (China); Purple Mountain Observatory, CAS, Nanjing 210008, China and Graduate School, CAS, Beijing 100012 (China)

2011-10-15

332

Kinetic simulation of an extreme ultraviolet radiation driven plasma near a multilayer mirror  

SciTech Connect

Future generation lithography tools will use extreme ultraviolet radiation to enable the printing of sub-50 nanometer features on silicon wafers. The extreme ultraviolet radiation, coming from a pulsed discharge, photoionizes the low pressure background gas in the tool. A weakly ionized plasma is formed, which will be in contact with the optical components of the lithography device. In the plasma sheath region ions will be accelerated towards the surfaces of multilayer mirrors. A self-consistent kinetic particle-in-cell model has been applied to describe a radiation driven plasma. The simulations predict the plasma parameters and notably the energy at which ions impact on the plasma boundaries. We have studied the influence of photoelectron emission from the mirror on the sheath dynamics and on the ion impact energy. Furthermore, the ion impact energy distribution has been convoluted with the formula of Yamamura and Tawara [At. Data Nucl. Data Tables 62, 149 (1996)] for the sputter yield to obtain the rate of physical sputtering. The model predicts that the sputter rate is dominated by the presence of doubly ionized argon ions.

Velden, M. H. L. van der; Brok, W. J. M.; Mullen, J. J. A. M. van der; Banine, V. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); ASML Netherlands B.V., De Run 6501, 5504 DR Veldhoven (Netherlands)

2006-10-01

333

Demonstration of quasi-monoenergetic electron-beam generation in laser-driven plasma acceleration  

SciTech Connect

The generation of a quasi-monoenergetic electron beam in laser-driven plasma acceleration is reported. A monoenergetic electron beam with an energy of 7 MeV was emitted from a high-density plasma (electron density >10{sup 20} cm{sup -3}) produced by a 2 TW 50 fs laser pulse. The divergence of the monoenergetic beam was {+-}1.2 deg. The first Stokes satellite peak of stimulated forward Raman scattering was observed in the spectrum of the light transmitted through the plasma. The plasma wave was excited in the region of which electron density was around 1.3x10{sup 20} cm{sup -3}. The acceleration length was estimated to be 500 {mu}m from the length of the side-scattered light image. It is considered that the monoenergetic beam generation is due to the matching of the acceleration length to the dephasing length determined by the velocity difference between the accelerated electrons and the plasma wave.

Miura, Eisuke; Koyama, Kazuyoshi; Kato, Susumu; Saito, Naoaki; Adachi, Masahiro; Kawada, Yoichi; Nakamura, Tatsufumi; Tanimoto, Mitsumori [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530 (Japan); University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba, Chiba 263-8555 (Japan); Meisei University, 2-1-1 Hodokubo, Hino, Tokyo 191-8506 (Japan)

2005-06-20

334

Anomalous resistivity of current-driven isothermal plasmas due to phase space structuring  

SciTech Connect

The anomalous electric resistivity of collisionless plasmas is an important issue in the physics of hot plasmas, e.g., in the context of auroral particle acceleration and of reconnection in the solar corona. The linear stability theory of isothermal current driven space plasmas predicts an ion-acoustic instability if the relative drift velocity of the current carrying particles exceeds a certain threshold, which, generally, depends on the plasma parameters. The spectrum of waves, excited by a marginal instability, is very narrow. Hence, the wave power at saturation and the corresponding electric resistivity due to wave-particle interaction cannot be obtained by means of a quasilinear, weak turbulence approach and the nonlinear single mode theory provides too small saturation amplitudes. To solve the nonlinear problem a newly developed unsplit conservative Eulerian Vlasov code is applied to simulate a strongly magnetized current driven plasma, which can be considered in 1D1V (one spatial, one velocity space direction). Instead of periodic boundary conditions, usually used as they are simpler to treat, open boundaries are implemented which allow to maintain a constant current flow. Simulated is a typical almost isothermal (T{sub e}=2T{sub i}) hot ({kappa}T{sub i}=1 keV) space plasma for the real mass ratio m{sub i}/m{sub e}=1836. The initial spontaneous instability is followed by a three-stage nonlinear evolution: First electron trapping leads to the formation of electron phase space holes. Due to a steepening of the leading edges of the potential wells the electron phase space holes gradually become asymmetric, they grow in size and deepen. The phase space holes accelerate until they move much faster than the initial ion-acoustic waves. The interaction of the current carriers with the asymmetric potential wells and causes a nonvanishing net momentum transfer between the particles and the self-generated electric field. After a few ion plasma periods ion trapping starts until, finally, an electrostatic double layer arises. It is found that the nonlinear saturated state of the system is dominated by the particle interaction with coherent phase space structures. The corresponding anomalous resistivity is slightly modulated with an oscillation period {tau}{approx_equal}{omega}{sub pi}{sup -1}). For a macroscopic description its major part can be parameterized by means of an effective collision rate {nu}{sub eff} of the order of 10{sup -2}{omega}{sub pe}{approx_equal}0.5{omega}{sub pi}, where {omega}{sub pe} is the electron and {omega}{sub pi} the ion plasma frequency.

Buechner, Joerg; Elkina, Nina [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany)

2006-08-15

335

Investigation of fringe plasma parameters on a high power rf driven ion source.  

PubMed

It has been observed that there are differences between the uncompensated Langmuir probes installed in the upper and lower areas of the rf driven H(-) sources at IPP Garching. The two probes often had substantially different floating potentials or ion saturation currents. In an effort to understand the reasons for these differences a Langmuir probe analysis system was used on the probes to collect the full current voltage characteristic. The results show what is likely the formation of an ion-ion plasma. The paper shows the effect of beam extraction and the presence of caesium on the probe characteristics. PMID:20192418

McNeely, P; Schiesko, L

2010-02-01

336

FIRST MEASUREMENT OF PRESSURE GRADIENT-DRIVEN CURRENTS IN TOKAMAK EDGE PLASMAS  

SciTech Connect

Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured the currents generated in the edge of L- (low) and H- (high confinement) mode discharges on the DIII-D tokamak, utilizing the Zeeman effect in an injected lithium beam to obtain high resolution profiles of the poloidal magnetic field. We find current densities in excess of 1 MA/m{sup 2} in a 1 to 2 cm region near the peak of the edge pressure gradient. These values are sufficient to challenge edge stability theories based on specific current formation models.

THOMAS DM; LEONARD AW; LAO LL; OSBORNE TH; MUELLER HW; FINKENTHAL DK

2003-11-01

337

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

338

Series Elastic Actuators for legged robots  

NASA Astrophysics Data System (ADS)

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

Pratt, Jerry E.; Krupp, Benjamin T.

2004-09-01

339

Experimental Evidence of Predominantly Transverse Electron Plasma Waves Driven by Stimulated Raman Scattering of Picosecond Laser Pulses  

SciTech Connect

We report on highly time- and space-resolved measurements of the evolution of electron plasma waves driven by stimulated Raman scattering of a picosecond, single laser speckle propagating through a preformed underdense plasma. Two-dimensional Thomson scatter spectra indicate that the dominant waves have significant transverse components. These results are supported by particle-in-cell simulations which pinpoint the dominant role of the wave front bowing and of secondary nonlinear electrostatic instabilities in the evolution of the plasma waves.

Rousseaux, C.; Benisti, D.; Gremillet, L. [CEA, DAM, DIF, 91297 Arpajon Cedex (France); Baton, S. D.; Amiranoff, F. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, Route de Saclay, 91128 Palaiseau (France); Adam, J. C.; Heron, A. [Centre de Physique Theorique, UMR 7644, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Strozzi, D. J. [Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (United States)

2009-05-08

340

Soft Actuator for Robotic Applications Based on Dielectric Elastomer: Dynamic Analysis and Applications  

Microsoft Academic Search

In this paper a new soft actuator based on dielectric elastomer is proposed. The actuator, called an antagonistically-driven linear actuator (ANTLA), has the muscle-like characteristics capable of performing the motions such as forward\\/backward\\/controllable compliance. In this paper, its dynamic analysis is performed with experimental verifications, and applications for robotic actuating devices are introduced

Hyoukryeol Choi; Sungmoo Ryew; K. M. Jung; H. M. Kim; Jae Wook Jeon; Jea-do Nam; Ryutaro Maeda; Kazuo Tanie

2002-01-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

342

One-pulse driven plasma Pockels cell with DKDP crystal for repetition-rate application.  

PubMed

Pockels cell (PPC), which can use a thin crystal to perform the uniform electro-optical effect, is ideal component as average-power optical switch with large aperture. In this paper, the key problems in PPC are analyzed for repetition-rate application, and thermo-optical effects are simulated by means of numerical modeling when average power is loaded on the electro-optical crystal. By reformative design and employing a capacity to share the gas discharge voltage, the DKDP PPC driven by one pulse is realized. As gas breakdown delay time is stable, and discharge plasma is uniformly filled the full aperture, it meets the demand of plasma electrode for the repetition-rate PPC with DKDP crystal. The switch efficiency of PPC at the whole aperture is better than 99%. PMID:19770935

Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Yu, Haiwu; Zheng, Jiangang; Cao, Dingxiang; Li, Mingzhong

2009-09-14

343

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

PubMed

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

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

2012-03-26

344

Magnetohydrodynamic plasma instability driven by Alfven waves excited by cosmic rays  

NASA Astrophysics Data System (ADS)

Hydrodynamical equations describing the mutual interaction of cosmic rays, thermal plasma, magnetic field, and Alfven waves scattering the cosmic rays used in cosmic ray shock acceleration theory are analyzed for long-wavelength linear compressible instabilities. It is shown that the backward propagating slow magnetoacoustic mode is driven convectively unstable by the wave pressure of self-excited Alfven waves. The marginal stability curve is derived and the stabilizing effects of a preexisting wave field and propagation oblique to the magnetic field are discussed along with the dependence of the growth rates of the instability on the various parameters. A similar analysis is performed for a plasma which does not behave adiabatically, being dissipatively heated by the self-excited Alfven field. This system is found to be unstale to compressions associated with both backward and forward propagating slow magnetoacoustic waves.

McKenzie, J. F.; Webb, G. M.

1984-04-01

345

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

SciTech Connect

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

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

2007-09-10

346

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

347

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

SciTech Connect

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

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

2012-12-15

348

Plasma evolution from laser-driven gold disks. II. Computational design and analysis  

SciTech Connect

The LASNEX computer code (Comments Plasma Phys. Controlled Fusion {bold 2}, 51 (1975)) was used in the design and analysis of an experimental study of laser-driven plasma blowoff from gold disks. In the study, several temporal profiles of 0.53 mm laser illumination were used, including square pulses, picket pulse trains, and pulses with graduated leading edges. Preliminary modeling suggested diagnostic techniques (time- and space-resolved imaging of {ital M}-band x-ray emission and time- and space-averaged measurements of high-energy (3.5--20 keV) x-ray spectra) that complemented diagnostics already used in such experiments (four-frame holographic imaging to determine the electron-density profile in the underdense corona plasma). In this article, the LASNEX results are analyzed and are compared with the measured plasma electron-density profiles and with time- and space-averaged measurements of the corona temperature. The simulation tracks the observed electron-density profiles fairly well during the early portions of the laser drive, during which the spatial profiles are approximately self-similar, but overestimates the electron density in the later, steady-state segment of the profile. For the corona electron temperature, simulation and experiment agree to within the experimental accuracy of {plus minus}20%.

Ress, D.; Suter, L.J. (Lawrence Livermore National Laboratory, Livermore, CA (USA)); Gabl, E.F.; Failor, B.H. (KMS Fusion, Inc., Ann Arbor, MI (USA))

1990-10-01

349

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

350

Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS)  

NASA Astrophysics Data System (ADS)

CPMI is embarking on the development of a new, innovative liquid divertor PFC that can withstand heat fluxes above 15 MWm-2. It will be based on the lithium-metal infused trenches (LIMIT) concept which has been demonstrated at Illinois and HT-7. TELS will extend the work that has been done at CPMI is four ways: 1. Develop, refine and test new geometries for thermoelectrically driven structures 2. Expansion of the Illinois pulsed and continuous systems so that pulsed plasma heat loads impinge on a surface that already has a continuous heat load on it 3. Increase the magnetic field so that a broader range of ``fusion type environments'' can be studied 4. Include other PFC materials such as tin and tin-lithium eutectics. The importance of testing with a pulsed plasma heat load is clear since magnetic fusion devices surfaces are subject to ELMs, disruptions, start-up and a variety of other plasma incursions and a PFC needs to show that it is robust under these extreme conditions. Plans for building TELS using the flowing lithium experiment (SLiDE), LiMIT and a pulsed-plasma theta pinch (DEVeX) will be presented. Thus heat removal systems can be systematically investigated and prototypes designed for installation on major fusion experiments around the world.

Andruczyk, Daniel; Xu, Wenyu; Jung, Soonwook; Fiflis, Peter; Curreli, Davide; Ruzic, David N.

2012-10-01

351

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

352

High torque miniature rotary actuator  

NASA Astrophysics Data System (ADS)

This paper summarizes the design and the development of a miniature rotary actuator (36 mm diameter by 100 mm length) used in spacecraft mechanisms requiring high torques and/or ultra-fine step resolution. This actuator lends itself to applications requiring high torque but with strict volume limitations which challenge the use of conventional rotary actuators. The design challenge was to develop a lightweight (less than 500 grams), very compact, high bandwidth, low power, thermally stable rotary actuator capable of producing torques in excess of 50 N.m and step resolutions as fine as 0.003 degrees. To achieve a relatively high torsional stiffness in excess of 1000 Nm/radian, the design utilizes a combination of harmonic drive and multistage planetary gearing. The unique design feature of this actuator that contributes to its light weight and extremely precise motion capability is a redundant stepper motor driving the output through a multistage reducing gearbox. The rotary actuator is powered by a high reliability space-rated stepper motor designed and constructed by Moog, Inc. The motor is a three-phase stepper motor of 15 degree step angle, producing twenty-four full steps per revolution. Since micro-stepping is not used in the design, and un-powered holding torque is exhibited at every commanded step, the rotary actuator is capable of reacting to torques as high as 35 Nm by holding position with the power off. The output is driven through a gear transmission having a total train ratio of 5120:1, resulting in a resolution of 0.003 degrees output rotation per motor step. The modular design of the multi-stage output transmission makes possible the addition of designs having different output parameters, such as lower torque and higher output speed capability. Some examples of an actuator family based on this growth capability will be presented in the paper.

Nalbandian, Ruben

2005-07-01

353

Properties of Dielectric-Barrier-Free Atmospheric Pressure Micro Plasma Driven by Sub-Micro Second DC Pulse Voltage  

NASA Astrophysics Data System (ADS)

An atmospheric pressure micro-plasma driven by a DC pulse has been developed. This device consists of He flowing two dielectric-free metal electrodes with a voltage pulse shorter than 500 ns, thus it maintains a glow discharge. Spatio-temporal measurements by the optical emission spectroscopy show that the change of partialpressure ratio between He and N2 is one of the most important factors affecting the discharge properties. The enhancement of the oxygen emissions for higher He flow rate mainly comes during afterglow, which suggests that the dissociative excitation of O2 by He metastable states is critical process for effective generation of oxygen radicals. As an alternative of atmospheric pressure micro plasma jet based on the dielectric barrier discharge or rf- driven micro plasma, dc pulse driven dielectric barrier-free configuration discharge can be used as an efficient and cost effective source for bio-medical and material processing applications.

Lee, Hae June; Ha, Chang Seung; Lee, Ho-Jun; Kim, Dong-Hyun

2009-10-01

354

Measurement of Laser Plasma Instability (LPI) Driven Light Scattering from Plasmas Produced by Nike KrF Laser  

NASA Astrophysics Data System (ADS)

With short wavelength (248 nm), large bandwidth (1˜3 THz), and ISI beam smoothing, Nike KrF laser provides unique research opportunities and potential for direct-drive inertial confinement fusion. Previous Nike experiments observed two plasmon decay (TPD) driven signals from CH plasmas at the laser intensities above ˜2x10^15 W/cm^2 with total laser energies up to 1 kJ of ˜350 ps FWHM pulses. We have performed a further experiment with longer laser pulses (0.5˜4.0 ns FWHM) and will present combined results of the experiments focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. Time- or space-resolved spectral features of TPD were detected at different viewing angles and the absolute intensity calibrated spectra of thermal background were used to obtain blackbody temperatures in the plasma corona. The wave vector distribution in k-space of the participating TPD plasmons will be also discussed. These results show promise for the proposed direct-drive designs.

Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Serlin, V.; Lehmberg, R. H.; McLean, E. A.; Manka, C. K.

2010-11-01

355

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

356

Femtosecond-Laser-Driven Cluster-Based Plasma Source for High-Resolution Ionography  

NASA Astrophysics Data System (ADS)

The intense isotropic source of multicharged ions, with energy above 300 keV, was produced by femtosecond Ti:Sa laser pulses irradiation (intensity of ~4×1017 W/cm2) of the He and CO2 gases mixture expanded in supersonic jet. High contrast ionography images have been obtained for 2000 dpi metal mesh, 1 ?m polypropylene and 100 nm Zr foils, as well as for different biological objects. Images were recorded on 1 mm thick CR-39 ion detector placed in contact with back surface of the imaged samples, at the distances 140-160 mm from the plasma source. The obtained spatial resolution of the image was ~600 nm. A 100 nm object thickness difference was resolved very well for both Zr and polymer foils. The multicharged ion energy for Carbon and Oxygen ions passing through the 1 ?m polypropylene foil is estimated to give the energy of more than 300 keV. An almost equal number of ions were measured with total number of about 108 per shot at a different direction from plasma source. Easy production of different sub-MeV ions in wide space angle, recognizes femtosecond-laser-driven-cluster-based plasma as a well-suited bright source for novel type of submicron ionography to image different media, including nanofoils, membranes, and other low-contrast objects.

Faenov, A. Ya.; Pikuz, T. A.; Fukuda, Y.; Kando, M.; Kotaki, H.; Homma, T.; Kawase, K.; Kameshima, T.; Pirozhkov, A.; Yogo, A.; Tampo, M.; Mori, M.; Sakaki, H.; Hayashi, Y.; Nakamura, T.; Pikuz, S. A.; Kartashev, V.; Skobelev, I. Yu.; Gasilov, S. V.; Giulietti, A.; Cecchetti, C. A.; Boldarev, A. S.; Gasilov, V. A.; Magunov, A.; Kar, S.; Borghesi, M.; Bolton, P.; Daido, H.; Tajima, T.; Kato, Y.; Bulanov, S. V.

2009-07-01

357

Femtosecond-Laser-Driven Cluster-Based Plasma Source for High-Resolution Ionography  

SciTech Connect

The intense isotropic source of multicharged ions, with energy above 300 keV, was produced by femtosecond Ti:Sa laser pulses irradiation (intensity of approx4x10{sup 17} W/cm{sup 2}) of the He and CO{sub 2} gases mixture expanded in supersonic jet. High contrast ionography images have been obtained for 2000 dpi metal mesh, 1 mum polypropylene and 100 nm Zr foils, as well as for different biological objects. Images were recorded on 1 mm thick CR-39 ion detector placed in contact with back surface of the imaged samples, at the distances 140-160 mm from the plasma source. The obtained spatial resolution of the image was approx600 nm. A 100 nm object thickness difference was resolved very well for both Zr and polymer foils. The multicharged ion energy for Carbon and Oxygen ions passing through the 1 mum polypropylene foil is estimated to give the energy of more than 300 keV. An almost equal number of ions were measured with total number of about 10{sup 8} per shot at a different direction from plasma source. Easy production of different sub-MeV ions in wide space angle, recognizes femtosecond-laser-driven-cluster-based plasma as a well-suited bright source for novel type of submicron ionography to image different media, including nanofoils, membranes, and other low-contrast objects.

Faenov, A. Ya.; Pikuz, T. A. [Kansai Photon Science Institute (KPSI), Japan Atomic Energy Agency (JAEA), Kizugawa-shi, Kyoto, 619-0215 (Japan); Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 (Russian Federation); Fukuda, Y.; Kando, M.; Kotaki, H.; Homma, T.; Kawase, K.; Kameshima, T.; Mori, M.; Sakaki, H.; Hayashi, Y.; Nakamura, T. [Kansai Photon Science Institute (KPSI), Japan Atomic Energy Agency (JAEA), Kizugawa-shi, Kyoto, 619-0215 (Japan); Pirozhkov, A.; Yogo, A.; Tampo, M.; Bolton, P.; Daido, H.; Tajima, T. [Kansai Photon Science Institute (KPSI), Japan Atomic Energy Agency (JAEA), Kizugawa-shi, Kyoto, 619-0215 (Japan); Photo-Medical Research Center, JAEA, Kizugawa-city, Kyoto 619-0215 (Japan); Pikuz, S. A. Jr.; Kartashev, V. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 (Russian Federation)

2009-07-25

358

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

SciTech Connect

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

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

2005-09-22

359

Stability threshold of ion temperature gradient driven mode in reversed field pinch plasmas  

SciTech Connect

For the first time in the reversed field pinch (RFP) configuration, the stability threshold of the ion temperature gradient driven (ITG) mode is studied by linear gyrokinetic theory. In comparison with tokamaks, the RFP configuration has a shorter connection length and stronger magnetic curvature drift. These effects result in a stronger instability driving mechanism and a larger growth rate in the fluid limit. However, the kinetic theory shows that the temperature slopes required for the excitation of ITG instability are much steeper than the tokamak ones. This is because the effect of Landau damping also becomes stronger due to the shorter connection length, which is dominant and ultimately determines the stability threshold. The required temperature slope for the instability may only be found in the very edge of the plasma and/or near the border of the dominant magnetic island during the quasi-single helicity state of discharge.

Guo, S. C. [Consorzio RFX, Associazione Euratom-ENEA sulla fusione, Corso Stati Uniti 4, Padova 35127 (Italy)

2008-12-15

360

Numerical Simulation of Rotation-Driven Plasma Transport In the Jovian Magnetosphere  

NASA Astrophysics Data System (ADS)

A Jupiter version of the Rice Convection Model (RCM-J) was developed with support of an earlier NASA SR&T grant. The conversion from Earth to Jupiter included adding currents driven by centrifugal force, reversing the planetary magnetic field, and rescaling various parameters. A series of informative runs was carried out, all of them solving initial value problems. The simulations followed an initial plasma torus configuration as it fell apart by interchange instability. Some conclusions from the simulations were the following: 1. We confirmed that, for conventional values of the torus density and ionospheric conductance, the torus disintegrates by interchange instability on a time scale of approx. one day, which is 1-2 orders of magnitude shorter than the best estimates of the average residence time of plasma in the torus. 2. In the model, the instability could be slowed to an arbitrary degree by the addition of sufficient impounding energetic particles, as suggested earlier by Siscoe et al (1981). However, the observed energetic particles do not seem sufficient to guarantee impoundment (e.g., Mauk et al., 1996). 3. Whether inhibited by impoundment or not, the interchange was found to proceed by the formation of long fingers, which get thinner as they get longer. This picture differed dramatically from the conventional radial-diffusion picture (e.g., Siscoe and Summers (1981)), more superficially with the outward-moving-blob picture (Pontius and Hill, 1989). The obvious limitation of the original RCM-J was that it could not represent a plasma source. We could represent the decay of a pre-existing torus, but we could not represent the way ionization of material from Io continually replenishes the plasma. We consequently were precluded from studying a whole set of fundamental issues of torus theory, including whether the system can come to a steady state.

Wolf, Richard A.

1997-01-01

361

Experimental verification of dynamics modulation in a periodically-driven neon glow discharge plasma  

NASA Astrophysics Data System (ADS)

Two ionization wave modes in a driven neon glow discharge alternate as the dominant mode as their response to the driving force alternates between spatiotemporal and temporal periodic pulling. This phenomenon, termed dynamics modulation, was first noted by Koepke, Weltmann, and Selcher [1], who saw two limited but representative cases and proposed a mechanism [2] by which it occurs. Dynamics modulation is reproduced experimentally in a neon glow discharge plasma. The system is periodically driven near a non-dominant mode using a narrow-band ring dye laser tuned to a wavelength near the metastable neon transition at 588.35 nm. A spatially-fixed photodiode with a narrow band filter that selectively passes the primary neon spectral line at 640 nm is used to acquire the time series of luminosity oscillations. These experimental data are used to verify the proposed mechanism and explore the resulting implications for spontaneous unidirectional mode transitions that occur with a change in discharge current.[4pt] [1] M. E. Koepke, K.-D. Weltmann, and C. A. Selcher, Bull. Am. Phys. Soc. 40, 1716 (1995).[0pt] [2] K. -D. Weltmann, M. E. Koepke, and C. A. Selcher, Phys. Rev. E 62, 2773, (2000).

Miller, P. M.; Koepke, M. E.; Gunell, H.

2010-11-01

362

Microwave power for smart material actuators  

Microsoft Academic Search

The concept of microwave-driven smart material actuators was envisioned and developed as the best option to alleviate the complexity and weight associated with a hard-wire-networked power and control system for smart actuator arrays. The patch rectenna array was initially designed for high current output, but has undergone further development for high voltage output devices used in shape control applications. Test

Sang H Choi; Kyo D Song; Walter Golembiewskii; Sang-Hyon Chu; Glen C King

2004-01-01

363

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

364

Studies of bandwidth dependence of laser plasma instabilities driven by the Nike laser  

NASA Astrophysics Data System (ADS)

Experiments at the Nike laser facility of the Naval Research Laboratory are exploring the influence of laser bandwidth on laser plasma instabilities (LPI) driven by a deep ultraviolet pump (248 nm) that incorporates beam smoothing by induced spatial incoherence (ISI). In early ISI studies with longer wavelength Nd:glass lasers (1054 nm and 527 nm),footnotetextObenschain, PRL 62(1989);Mostovych, PRL 62(1987);Peyser, Phys. Fluids B 3(1991). stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (??/?˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). The current studies will compare the emission signatures of LPI from planar CH targets during Nike operation at large bandwidth (??˜1THz) to observations for narrower bandwidth operation (??˜0.1-0.3THz). These studies will help clarify the relative importance of the short wavelength and wide bandwidth to the increased LPI intensity thresholds observed at Nike. New pulse shapes are being used to generate plasmas with larger electron density scale-lengths that are closer to conditions during pellet implosions for direct drive inertial confinement fusion.

Weaver, J.; Kehne, D.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Oh, J.; Lehmberg, R. H.; Brown, C. M.; Seely, J.; Feldman, U.

2012-10-01

365

A Method of Estimating the Degree of Active Participation During Stepping in a Driven Gait Orthosis Based on Actuator Force Profile Matching  

Microsoft Academic Search

Visual biofeedback with information about the patients' degree of activity is a valuable adjunct to robot-assisted gait training as means of increasing the motivation and participation of the patients during highly repetitive training sessions. In the driven gait orthosis (DGO) Lokomat, an estimation of the patient's activity level was based on man-machine interaction forces as measured at the hip and

Raphael Banz; Marc Bolliger; Stefan Müller; Claudio Santelli; Robert Riener

2009-01-01

366

New insights on Titan's plasma-driven Schumann resonance inferred from Huygens and Cassini data  

NASA Astrophysics Data System (ADS)

After a preliminary analysis of the low-frequency data collected with the electric antenna of the Permittivity, Wave and Altimetry (PWA) experiment onboard the Huygens Probe that landed on Titan on 14 January, 2005, it was anticipated in a previous article [Béghin et al., 2007. A Schumann-like resonance on Titan driven by Saturn's magnetosphere possibly revealed by the Huygens Probe. Icarus, 191, 251-266] that the Extremely Low-Frequency (ELF) signal at around 36 Hz observed throughout the descent, might have been generated in the upper ionosphere of Titan, driven by a plasma instability mechanism associated with the co-rotating Kronian plasma flow. The involved process was proposed as the most likely source of a Schumann resonance in the moon's atmospheric cavity, the second eigenmode of which is actually found by models to occur at around 36 Hz. In this paper, we present a thorough analysis of this signal based upon the Huygens Probe attitude data deduced from the Descent Imager Spectral Radiometer (DISR), and relevant measurements obtained from the Radio Plasma Wave Science (RPWS) experiment and from the magnetometer (MAG) onboard Cassini orbiter during flybys of Titan. We have derived several coherent characteristics of the signal which confirm the validity of the mechanism initially proposed and provide new and significant insights about such a unique type of Schumann resonance in the solar system. Indeed, the 36 Hz signal contains all the characteristics of a polarized wave, with the measured electric field horizontal component modulated by the antenna rotation, and an altitude profile in agreement with a Longitudinal Section Electric (LSE) eigenmode of the atmospheric cavity. In contrast to Earth's conditions where the conventional Transverse Magnetic mode is considered, the LSE mode appears to be the only one complying with the observations and the unexpected peculiar conditions on Titan. These conditions are essentially the lack of any lightning activity that can be ascertained from Cassini observations, the presence of an ionized layer centered around 62 km altitude that was discovered by the PWA instrumentation, and the existence of a subsurface conducting boundary which is mandatory for trapping ELF waves. A simple theoretical model derived from our analysis places tentatively consequential constraints on the conductivity profile in the lower ionosphere. It is also consistent with the presence of a conductive water ocean below an icy crust some tens of kilometers thick.

Béghin, C.; Canu, P.; Karkoschka, E.; Sotin, C.; Bertucci, C.; Kurth, W. S.; Berthelier, J. J.; Grard, R.; Hamelin, M.; Schwingenschuh, K.; Simões, F.

2009-12-01

367

Injection of Plasma into the Nascent Solar Wind via Reconnection Driven by Supergranular Advection  

NASA Astrophysics Data System (ADS)

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; Peter, Hardi; Tu, Chuanyi; Chen, Wenlei; Zhang, Lei; Marsch, Eckart; Wang, Linghua; Feng, Xueshang; Yan, Limei

2013-06-01

368

Piezoelectric multilayer actuator life test.  

PubMed

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one mission life. To test the feasibility of using these commercial actuators for these applications and to determine their reliability and the redundancy requirements, a life test study was undertaken. The nominal actuator requirements for the most critical actuators on the Space Interferometry Mission (SIM) in terms of number of cycles was estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) and these requirements were used to define the study. At a nominal drive frequency of 250 Hz, one mission life is calculated to be 40 billion cycles. In this study, a set of commercial PZT stacks configured in a potential flight actuator configuration (pre-stressed to 18 MPa and bonded in flexures) were tested for up to 100 billion cycles. Each test flexure allowed for two sets of primary and redundant stacks to be mechanically connected in series. The tests were controlled using an automated software control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 V at 2000 Hz to accelerate the life test and mimic the voltage amplitude that is expected to be applied to the stacks during operation. During the life test, 10 primary stacks were driven and 10 redundant stacks, mechanically in series with the driven stacks, were open-circuited. The stroke determined from a strain gauge, the temperature and humidity in the chamber, and the temperature of each individual stack were recorded. Other properties of the stacks, including the displacement from a capacitance gap sensor and impedance spectra were measured at specific intervals. The average degradation in the stroke over the life test was found to be small (<3%) for the primary stacks and <4% for the redundant stacks. It was noted that about half of the stroke reduction occurred within the first 10 billion cycles. At the end of the life test, it was found that the actuator could recover about half of the lost stroke by applying a dc voltage of 100 V at room temperature. The data up to 100 billion cycles for these tests and the analysis of the experimental results are presented in this paper. PMID:21507759

Sherrit, Stewart; Bao, Xiaoqi; Jones, Christopher M; Aldrich, Jack B; Blodget, Chad J; Moore, James D; Carson, John W; Goullioud, Renaud

2011-04-01

369

Chemical kinetics of radio-frequency driven atmospheric-pressure helium-oxygen plasmas in humid air  

NASA Astrophysics Data System (ADS)

We describe the chemical kinetics of radio-frequency (rf) driven atmospheric-pressure helium-based plasmas in ambient air as determined through a zero-dimensional time-dependent global model. The effects of humid-air admixtures on the plasma-induced chemical reactions and the evolution of species concentrations in the helium-oxygen mixture (He-O2, helium with 5000 ppm admixture of oxygen) are studied for wide air impurity levels of 1-5000 ppm with the relative humidity of 0-100%. Comparisons made with experiments using an rf driven micro-scale atmospheric pressure plasma jet and one-dimensional simulations suggest that the plausible air impurity level in the experiments is not more than hundreds ppm. Effects of the air impurity containing water-humidity on electro-negativity and chemical activity are clarified with particular emphasis on reactive oxygen species.

Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William

2011-11-01

370

Application of smart material-hydraulic actuators  

NASA Astrophysics Data System (ADS)

The application of a new class of actuators is considered. The actuators under development combine a high energy density smart material, specifically a piezoelectric material, with internal servohydraulic components. Large displacement outputs are produced, while the high force capacity of the stiff smart material is retained, for a net high-energy output. The actuator is considered "power-by-wire" because only electrical power is provided from the vehicle or system controller. A primary motivating application is in unmanned combat air vehicles (UCAVs). The particular actuation needs of these vehicles, in flight control and other utility functions, are described and distilled to a set of relevant device requirements. Other potential applications, such as flight motion simulation, are also highlighted. The new actuation architecture offers specific advantages over centralized hydraulic systems and has capabilities not present in electromechanical actuators (EMAs). The main advantage over centralized hydraulic systems is the elimination of the need for hydraulic lines. Compared to motor-driven ball screw type EMAs, the new actuators offer higher frequency response, and a larger peak-to-average output. A laboratory test facility designed to represent the loading experienced by a UCAV control surface is described. Key steps necessary to flight qualify the actuator are introduced.

Anderson, Eric H.; Bales, Gregory L.; White, Edward V.

2003-08-01

371

TECHNICAL NOTE: Fabrication of multiferroic composite actuator material by combining superelastic TiNi filler and a magnetostrictive Ni matrix  

NASA Astrophysics Data System (ADS)

This research aims to design and verify a new magnetically driven multiferroic composite actuator material which is characterized by large strain and a rapid response speed. The composite actuator material is designed to consist of a magnetostrictive Ni matrix and superelastic TiNi alloy fiber fillers whose volume fraction was changed. The spark plasma sintering (SPS) method which is characterized by short time and low temperature processing was used to join these two different material elements. Cross-sectional observation by optical micrograph, mechanical compression tests, and magnetostriction measurements were carried out to verify the perfection of the adhesion state of the TiNi filler and nickel matrix as well as the amplification effect of magnetostriction. As the experimental result, the amplification effect of about a maximum of 1.5 times magnetostriction was verified in the fabricated composite actuator.

Hasegawa, Masanobu; Asano, Takahiro; Hashimoto, Kenji; Lee, Gyu Chang; Park, Young Chul; Okazaki, Teiko; Furuya, Yasubumi

2006-10-01

372

On the Transition from Thermally-driven to Ponderomotively-driven Stimulated Brillouin Scattering and Filamentation of Light in Plasma  

SciTech Connect

The dispersion properties of ion acoustic waves and their nonlinear coupling to light waves through ponderomotive and thermal forces are sensitive to the strength of electron-ion collisions. Here, we consider the growth rate of stimulated Brillouin scattering (SBS) when the driven acoustic wave frequency and wavelength span the range of small to large compared to electron-ion collision frequency and mean free path respectively. We find in all cases the thermal contributions to the SBS growth rate are insignificant if the ion acoustic wave frequency is greater than the electron-ion collision frequency and the wavelength is much shorter than the electron-ion mean free path. On the other hand, the purely growing filamentation instability remains thermally driven for shorter wavelengths than SBS even when the growth rate is larger than the acoustic frequency.

R.L. Berger; E.J. Valeo; S. Brunner

2005-04-04

373

Effects of needle response on spray characteristics in high pressure injector driven by piezo actuator for common-rail injection system  

Microsoft Academic Search

The common-rail injection systems, as a new diesel injection system for passenger car, have more degrees of freedom in controlling\\u000a both the injection timing and injection rate with the high pressure. In this study, a piezo-driven injector was applied to\\u000a a high pressure common-rail type fuel injection system for the control capability of the high pressure injector’s needle and\\u000a firstly

Jinwook Lee; Kyoungdoug Min

2005-01-01

374

Basic physics of Alfven instabilities driven by energetic particles in toroidally confined plasmas  

SciTech Connect

Superthermal energetic particles (EP) often drive shear Alfven waves unstable in magnetically confined plasmas. These instabilities constitute a fascinating nonlinear system where fluid and kinetic nonlinearities can appear on an equal footing. In addition to basic science, Alfven instabilities are of practical importance, as the expulsion of energetic particles can damage the walls of a confinement device. Because of rapid dispersion, shear Alfven waves that are part of the continuous spectrum are rarely destabilized. However, because the index of refraction is periodic in toroidally confined plasmas, gaps appear in the continuous spectrum. At spatial locations where the radial group velocity vanishes, weakly damped discrete modes appear in these gaps. These eigenmodes are of two types. One type is associated with frequency crossings of counterpropagating waves; the toroidal Alfven eigenmode is a prominent example. The second type is associated with an extremum of the continuous spectrum; the reversed shear Alfven eigenmode is an example of this type. In addition to these normal modes of the background plasma, when the energetic particle pressure is very large, energetic particle modes that adopt the frequency of the energetic particle population occur. Alfven instabilities of all three types occur in every toroidal magnetic confinement device with an intense energetic particle population. The energetic particles are most conveniently described by their constants of motion. Resonances occur between the orbital frequencies of the energetic particles and the wave phase velocity. If the wave resonance with the energetic particle population occurs where the gradient with respect to a constant of motion is inverted, the particles transfer energy to the wave, promoting instability. In a tokamak, the spatial gradient drive associated with inversion of the toroidal canonical angular momentum P{sub {zeta}} is most important. Once a mode is driven unstable, a wide variety of nonlinear dynamics is observed, ranging from steady modes that gradually saturate, to bursting behavior reminiscent of relaxation oscillations, to rapid frequency chirping. An analogy to the classic one-dimensional problem of electrostatic plasma waves explains much of this phenomenology. EP transport can be convective, as when the wave scatters the particle across a topological boundary into a loss cone, or diffusive, which occurs when islands overlap in the orbital phase space. Despite a solid qualitative understanding of possible transport mechanisms, quantitative calculations using measured mode amplitudes currently underestimate the observed fast-ion transport. Experimentally, detailed identification of nonlinear mechanisms is in its infancy. Beyond validation of theoretical models, the future of the field lies in the development of control tools. These may exploit EP instabilities for beneficial purposes, such as favorably modifying the current profile, or use modest amounts of power to govern the nonlinear dynamics in order to avoid catastrophic bursts.

Heidbrink, W. W. [Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697 (United States)

2008-05-15

375

Remotely powered and controlled EAPap actuator by amplitude modulated microwaves  

NASA Astrophysics Data System (ADS)

This paper reports on a remotely powered and controlled Electro-Active Paper (EAPap) actuator without onboard controller using amplitude modulated microwaves. A rectenna is a key element for microwave power transmission that converts microwaves into dc power through coupling and rectification. In this study, the concept of a remotely controlled and powered EAPap actuator is proposed by means of modulating microwaves with a control signal and demodulating it through the rectenna rectification. This concept is applied to a robust EAPap actuator, namely cellulose-polypyrrole-ionic liquid (CPIL) EAPap. Details of fabrication and characterization of the rectenna and the CPIL-EAPap actuator are explained. Also, the charge accumulation problem of the actuator is explained and resolved by connecting an additional resistor. Since this idea can eliminate the onboard controller by supplying the operating signal through modulation, a compact and lightweight actuator can be achieved, which is useful for biomimetic robots and remotely driven actuators.

Yang, Sang Yeol; Mahadeva, Suresha K.; Kim, Jaehwan

2013-01-01

376

Deformable mirrors: design fundamentals for force actuation of continuous facesheets  

NASA Astrophysics Data System (ADS)

Adaptive Optics is established as essential technology in current and future ground based (extremely) large telescopes to compensate for atmospheric turbulence. Deformable mirrors for astronomic purposes have a high number of actuators (> 10k), a relatively large stroke (> 10?m) on a small spacing (< 10mm) and a high control bandwidth (> 100Hz). The availability of piezoelectric ceramics as an actuator principle has driven the development of many adaptive deformable mirrors towards inappropriately stiff displacement actuation. This, while the use of force actuation supersedes piezos in performance and longevity while being less costly per channel by a factor of 10-20. This paper presents a model which is independent of the actuator type used for actuation of continuous facesheet deformable mirrors, to study the design parameters such as: actuator spacing & coupling, influence function, peak-valley stroke, dynamical behavior: global & local, etc. The model is validated using finite element simulations and its parameters are used to derive design fundamentals for optimization.

Ravensbergen, S. K.; Hamelinck, R. F. H. M.; Rosielle, P. C. J. N.; Steinbuch, M.

2009-08-01

377

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

378

One-Dimensional Vlasov Simulations of Strong Langmuir Turbulence in a Radiation Driven Plasma.  

NASA Astrophysics Data System (ADS)

One-dimensional kinetic Vlasov simulations are developed to investigate Langmuir collapse and strong Langmuir turbulence in an unmagnetized radiation driven plasma. Three types of models are used: (a) a hybrid model of Vlasov electrons and cold fluid ions with periodic boundary conditions; (b) a full Vlasov model of both electrons and ions with periodic boundary conditions; (c) a full Vlasov model of both electrons and ions with open boundary conditions. Six numerical runs of different parameters with self-consistent initial conditions are performed. The exponential growth of the modulational instability and its nonlinear saturation via Langmuir collapse are studied. Dynamic evolutions of both high-frequency Langmuir waves and low-frequency ion-acoustic waves are investigated. The generation of hot particles are simulated, and the collapse-burnout-nucleation cycles of strong Langmuir turbulence are observed. The modified Zakharov equations with linear Landau damping of both Langmuir waves and ion-acoustic waves are simulated with the same parameters and similar initial conditions for all six runs. The results of the Zakharov simulations are compared with those of the Vlasov models to establish the agreement and disagreement regimes between the two models.

Wang, Jin-Gen

379

Impurity transport driven by ion temperature gradient turbulence in tokamak plasmas  

SciTech Connect

Impurity transport driven by electrostatic turbulence is analyzed in weakly collisional tokamak plasmas using a semianalytical model based on a boundary layer solution of the gyrokinetic equation. Analytical expressions for the perturbed density responses are derived and used to determine the stability boundaries and the quasilinear particle fluxes. For moderate impurity charge number Z, the stability boundaries are very weakly affected by the increasing impurity charge for constant effective charge, while for lower impurity charge the influence of impurities is larger, if the amount of impurities is not too small. Scalings of the mode frequencies and quasilinear fluxes with charge number, effective charge, impurity density scale length, and collisionality are determined and compared to quasilinear gyrokinetic simulations with GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] resulting in very good agreement. Collisions do not affect the mode frequencies, growth rates, and impurity fluxes significantly. The eigenfrequencies and growth rates depend only weakly on Z and Z{sub eff} but they are sensitive to the impurity density gradient scale length. An analytical approximate expression of the zero-flux impurity density gradient is derived and used to discuss its parametric dependencies.

Fueloep, T.; Pusztai, I. [Department of Applied Physics, Nuclear Engineering, Chalmers University of Technology and Euratom-VR Association, Goeteborg SE-41296 (Sweden); Braun, S. [Max-Planck-Institut fuer Plasmaphysik, Greifswald 17491 (Germany)

2010-06-15

380

Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser  

NASA Astrophysics Data System (ADS)

The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987);Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (??/?˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (??˜1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets.

Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

2011-11-01

381

Simulation Study of Energetic Particle Driven Geodesic Acoustic Mode in LHD Plasma  

NASA Astrophysics Data System (ADS)

The energetic particle driven geodesic acoustic modes (GAMs) in LHD plasma were simulated using a hybrid simulation code for magnetohydrodynamics (MHD) and energetic particles. The energetic particle distribution employed in the simulation is anisotropic in velocity space. The GAM frequencies in the simulation results are 38kHz for 5.0keV electron temperature and 20kHz for 1.3keV electron temperature. The frequencies agree reasonably with both the experimental observation and the prediction from MHD theory. The poloidal velocity v? with mode number m=0 and perturbed pressure P˜and density n˜with mode number m=1 are observed. The GAM is excited around the normalized minor radius 0.2, and it propagates in radial direction. In addition, the spatial profiles of P˜and n˜rotate in poloidal direction. After the saturation of the instability, redistribution of energetic particles takes place in pitch-angle space both for the lower pitch-angle part and for the higher pitch-angel part.

Wang, Hao; Todo, Yasushi

2011-11-01

382

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

383

Compact hybrid electrohydraulic actuators using smart materials: A review  

Microsoft Academic Search

The development of compact hybrid electrohydraulic actuators driven by various smart materials has been widely reported in the literature in recent years. Such solid-state-induced strain actuators have applications in a variety of aerospace and automotive and mechanical engineering fields. These devices are capable of producing high stroke (or displacement) and high force (or pressures) in a compact form factor by

Anirban Chaudhuri; Norman Wereley

2012-01-01

384

A NOVEL MICROVIBRATION ACTUATOR AND THE PRESENTATION OF TACTILE SENSATIONS  

Microsoft Academic Search

A novel micro-vibration actuator using a shape- memory alloy for the presentation of various tactile sensations to a human skin is introduced in this paper. The authors paid attention to the characteristics of a shape- memory alloy formed into a thread, which changes its length according to its temperature, and developed a vibration- generating actuator electrically driven by periodic signals

Keishi Fukuyama; Yohsuke Mizukami; Hideyuki Sawada

385

FIRST COMPLETE DETERMINATION OF PLASMA PHYSICAL PARAMETERS ACROSS A CORONAL MASS EJECTION-DRIVEN SHOCK  

SciTech Connect

We report on the study of a fast coronal mass ejection (CME)-driven shock associated with the solar eruption of 2002 March 22. This event was observed in the intermediate corona both in white light and the extreme ultraviolet (EUV) by the LASCO and UVCS instruments on board the Solar and Heliospheric Observatory, as well as in metric and decametric wavelengths through space- and ground-based radio observatories. Clear signatures of shock transit are (1) strong type II emission lanes observed after the CME initiation, (2) strong O VI {lambda}{lambda}1032, 1037 line profile broadenings (up to {approx}2 x 10{sup 7} K) associated with the shock transit across the UVCS slit field of view, and (3) a density enhancement located in LASCO images above the CME front. Since the UVCS slit was centered at 4.1 R{sub sun}, in correspondence with the flank of the expanding CME, this observation represents the highest UV detection of a shock obtained so far with the UVCS instrument. White-light and EUV data have been combined in order to estimate not only the shock compression ratio and the plasma temperature, but also the strength of the involved coronal magnetic fields, by applying the Rankine-Hugoniot equations for the general case of oblique shocks. Results show that, for a compression ratio X = 2.06 as derived from LASCO data, the coronal plasma is heated across the shock from an initial temperature of 2.3 x 10{sup 5} K up to 1.9 x 10{sup 6} K, while at the same time the magnetic field undergoes a compression from a pre-shock value of {approx}0.02 G up to a post-shock field of {approx}0.04 G. Magnetic and kinetic energy density increases at the shock are comparable (in agreement with the idea of equipartition of energy), and both are more than two times larger than the thermal energy density increase. This is the first time that a complete characterization of pre- and post-shock plasma physical parameters has been derived in the solar corona.

Bemporad, A.; Mancuso, S., E-mail: bemporad@oato.inaf.i [Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Torino (Italy)

2010-09-01

386

First Complete Determination of Plasma Physical Parameters Across a Coronal Mass Ejection-driven Shock  

NASA Astrophysics Data System (ADS)

We report on the study of a fast coronal mass ejection (CME)-driven shock associated with the solar eruption of 2002 March 22. This event was observed in the intermediate corona both in white light and the extreme ultraviolet (EUV) by the LASCO and UVCS instruments on board the Solar and Heliospheric Observatory, as well as in metric and decametric wavelengths through space- and ground-based radio observatories. Clear signatures of shock transit are (1) strong type II emission lanes observed after the CME initiation, (2) strong O VI ??1032, 1037 line profile broadenings (up to ~2 × 107 K) associated with the shock transit across the UVCS slit field of view, and (3) a density enhancement located in LASCO images above the CME front. Since the UVCS slit was centered at 4.1 R sun, in correspondence with the flank of the expanding CME, this observation represents the highest UV detection of a shock obtained so far with the UVCS instrument. White-light and EUV data have been combined in order to estimate not only the shock compression ratio and the plasma temperature, but also the strength of the involved coronal magnetic fields, by applying the Rankine-Hugoniot equations for the general case of oblique shocks. Results show that, for a compression ratio X = 2.06 as derived from LASCO data, the coronal plasma is heated across the shock from an initial temperature of 2.3 × 105 K up to 1.9 × 106 K, while at the same time the magnetic field undergoes a compression from a pre-shock value of ~0.02 G up to a post-shock field of ~0.04 G. Magnetic and kinetic energy density increases at the shock are comparable (in agreement with the idea of equipartition of energy), and both are more than two times larger than the thermal energy density increase. This is the first time that a complete characterization of pre- and post-shock plasma physical parameters has been derived in the solar corona.

Bemporad, A.; Mancuso, S.

2010-09-01

387

Conducting polymer actuators as engineering materials  

NASA Astrophysics Data System (ADS)

Conducting polymer actuators were first proposed more than ten years ago. Reported performance has improved dramatically, particularly in the past few years, due to changes in synthesis methods, better characterization and an understanding of the underlying mechanisms. These actuators are able to displace large loads (up to 100x greater than mammalian skeletal muscle), with moderate displacements (typically 2 %), and with power to mass ratios similar to that of muscle, while powered using potentials of no more than a few volts. Unlike electric motors and muscle, these actuators exhibit a catch state, enabling them to maintain force without consuming energy. Despite the impressive performance, commercial applications are at an early stage. One reason is the need to carefully consider the details of the actuator construction, including the thickness and surface area of the polymer, the electrolyte conductivity and geometry, the counter electrode spacing, the shape of the input voltage and the means of electrical contact to the polymer, in designing effective actuators. A set of design guidelines is presented that assist the device designer in determining the optimum actuator configuration. These are derived from extensive characterization and modeling of hexafluorophosphate-doped polypyrrole actuators. The set of design tools helps transform conducting polymer actuators into engineering materials that can be selected and designed for particular applications based on rational criteria. Most of the underlying physical principles used in determining these rules also underlie other conducting polymer actuators, polymer devices such as electrochromic displays, supercapacitors and batteries, carbon nanotube actuators, and electrochemically driven devices that involve volumetric charge storage.

Madden, John D.; Madden, Peter G.; Hunter, Ian W.

2002-07-01

388

Efficient generation of noninductive, off-axis, Ohkawa current, driven by electron Bernstein waves in high ?, spherical torus plasmas  

NASA Astrophysics Data System (ADS)

Off-axis rf-driven current can play a critical role in sustaining high ?, spherical torus (ST) plasmas without a central solenoid. Numerical modeling of electron Bernstein wave current drive (EBWCD) for a ?~40% ST plasma predicts efficient, off-axis, Ohkawa EBWCD. Current can be efficiently driven at r/a>0.5 where the large trapped electron fraction precludes conventional Fisch-Boozer current drive and provides favorable conditions for Ohkawa EBWCD. Calculated normalized current drive efficiency increases with r/a and is a factor of 2 higher at r/a=0.7 than has been obtained with electron cyclotron current drive near the axis of large aspect ratio tokamaks.

Taylor, G.; Efthimion, P. C.; Kessel, C. E.; Harvey, R. W.; Smirnov, A. P.; Ershov, N. M.; Carter, M. D.; Forest, C. B.

2004-10-01

389

Statistical analysis of fluctuations and noise-driven transport in particle-in-cell simulations of plasma turbulence  

Microsoft Academic Search

The problem of discrete particle noise has been studied based on direct fluctuation measurements from gyrokinetic particle-in-cell simulations of stable plasmas. From the statistical analysis of electrostatic potential time evolution, the space-time correlation function has been measured. Fluctuation spectra have been constructed and analyzed in detail. Noise-driven transport is calculated using the quasilinear expression for the diffusion coefficient and the

I. Holod; Z. Lin

2007-01-01

390

Pulsatile blood pump with a linear drive actuator  

Microsoft Academic Search

The main purpose of this study was to develop an implantable direct-electromagnetic left ventricular assist system driven\\u000a by a linear actuator (linear LVAS). The linear LVAS is a pulsatile pump with a pusher plate that is driven directly by a linear\\u000a oscillatory actuator (LOA) without any movement converters. This prototype pump unit with a LOA was 100?mm in diameter, 50?mm

Kazuyoshi Fukunaga; Akihiko Homma; Akio Funakubo; Eisuke Tatsumi; Yoshiyuki Taenaka; Soichiro Kitamura; Yasuhiro Fukui

2007-01-01

391

Electromagnetic linear actuators with inductive position sensing  

Microsoft Academic Search

Magnetically driven linear micro-actuators with 1 mN output force and hundreds of microns of total travel have been realized using LIGA-like processing techniques. These devices are driven at resonance frequencies of around 350 Hz and exhibit quality factors of about 300 in air. Exploiting wire-wound electromagnets, 300 ?m resonant displacements have been demonstrated with drive signal currents of about 1

H Guckel; T Earles; J Klein; J. D Zook; T Ohnstein

1996-01-01

392

Smart Material-Actuated Rotor Technology – SMART  

Microsoft Academic Search

Vibration, noise, and aerodynamic design compromises are primary barriers to further improvements in effectiveness of the helicopter. The MD900 light utility helicopter main rotor system is modified to include in-blade smart material actuation for active control. A piezoelectric (PE)-driven trailing edge flap is used for vibration, noise, and aerodynamic performance improvements. A shape memory alloy (SMA)-driven trailing edge trim tab

Friedrich K. Straub; Dennis K. Kennedy; David B. Domzalski; Ahmed A. Hassan; Hieu Ngo; V. Anand; Terry Birchette

2004-01-01

393

Nanoporous carbon actuator and methods of use thereof  

SciTech Connect

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

394

Networked Rectenna Array for Smart Material Actuators.  

National Technical Information Service (NTIS)

The concept of microwave-driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry. Networked rectenna patch array receives and converts microwave power into a DC power for an...

S. H. Choi W. T. Golembiewski K. D. Song

2000-01-01

395

Uniaxial Electric Actuator  

NSDL National Science Digital Library

This site includes a cut-away animation of how a uniaxial electric actuator operates. Objective: Describe how the uniaxial electric actuator works. You can find this animation under the heading "Automation Technology."

2012-12-19

396

Separation Spring Actuator.  

National Technical Information Service (NTIS)

The patent application relates to an actuator adapted for use in separating two interconnected bodies, while maintaining their respective desired directions. In the preferred embodiment, the actuator includes a housing which supports and guides a captive ...

C. F. Seifert

1975-01-01

397

Control of Smart Actuators.  

National Technical Information Service (NTIS)

Hysteresis in smart materials hinders wider applicability of such materials in actuators and sensors. In this dissertation we study modeling, identification and control of hysteresis in smart actuators. While the approaches are applicable to control of a ...

X. Tan

2002-01-01

398

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

399

Folded dielectric elastomer actuators  

Microsoft Academic Search

Polymer-based linear actuators with contractile ability are currently demanded for several types of applications. Within the class of dielectric elastomer actuators, two basic configurations are available today for such a purpose: the multi-layer stack and the helical structure. The first consists of several layers of elementary planar actuators stacked in series mechanically and parallel electrically. The second configuration relies on

Federico Carpi; Claudio Salaris; Danilo DeRossi

2007-01-01

400

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

401

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

402

Paper actuators made with cellulose and hybrid materials.  

PubMed

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

2010-02-26

403

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.

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

2010-01-01

404

A moving-actuator type electromechanical total artificial heart. I. Linear type and mock circulation experiments  

Microsoft Academic Search

A novel type of motor-driven total artificial heart system with a moving-actuator mechanism has been developed. The prototype system consists of a brushless DC motor inside a rolling cylinder, two arcshaped pusher plates, and two polyurethane sacs. The moving-actuator-type electromechanical pump has the structural advantages of small size and light weight, as compared to other motor-driven pumps with fixed actuator

BYOUNG G. MIN; HEE C. KIM; SANG H. LEE; JONG W. KIM; JIN T. KIM; IN Y. KIM; SUNG W. KIM; PAUL D. DIEGEL; DON B. OLSEN

1990-01-01

405

Time-resolved measurement of a shock-driven plasma target for interaction experiments between heavy ions and plasmas  

SciTech Connect

To observe nonlinearity in the stopping power of a nonideal plasma for heavy ions, we are planning a beam-plasma interaction experiment using 10-100 keV/u projectiles. For the interaction experiment, a nonideal hydrogen plasma target was developed by means of a shock technique. Time-resolved spectroscopic measurements determined the temporal evolution of the electron density and temperature of the shock plasma. These data revealed that the structure behind the shock front has an appropriate spatial and temporal distribution to be used as a target. We also evaluated the temporal evolution of the Coulomb coupling constant and the degree of ionization at a fixed position where the projectiles are injected. We discuss the feasibility of the nonlinear stopping experiment by evaluating the beam-plasma coupling constant expected from the measured plasma parameters.

Katagiri, K.; Hasegawa, J.; Nishinomiya, S.; Ikagawa, H.; Oguri, Y. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, O-okayama 2-12-1-N1-14, Meguro-ku, 152-8550 Tokyo (Japan)

2007-12-01

406

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

407

Considerations for contractile electroactive materials and actuators  

NASA Astrophysics Data System (ADS)

Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

Rasmussen, Lenore; Schramm, David; Rasmussen, Paul; Mullally, Kevin; Meixler, Lewis D.; Pearlman, Daniel; Kirk, Alice

2011-03-01

408

Considerations for Contractile Electroactive Materials and Actuators  

SciTech Connect

Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

Lenore Rasmussen, David Schramm, Paul Rasmussen, Kevin Mullaly, Ras Labs, LLC, Intelligent Materials for Prosthetics & Automation, Lewis D. Meixler, Daniel Pearlman and Alice Kirk

2011-05-23

409

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

410

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

Microsoft Academic Search

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

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

2009-01-01

411

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

412

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

413

Proton Radiography of Spontaneous Fields, Plasma Flows and Dynamics in X-Ray Driven Inertial-Confinement Fusion Implosions  

NASA Astrophysics Data System (ADS)

Backlighting of x-ray-driven implosions in empty hohlraums with mono-energetic protons on the OMEGA laser facility has allowed a number of important phenomena to be observed. Several critical parameters were determined, including plasma flow, three types of spontaneous electric fields and megaGauss magnetic fields. These results provide insight into important issues in indirect-drive ICF. Even though the cavity is effectively a Faraday cage, the strong, local fields inside the hohlraum can affect laser-plasma instabilities, electron distributions and implosion symmetry. They are of fundamental scientific importance for a range of new experiments at the frontiers of high-energy-density physics. Future experiments designed to characterize the field formation and evolution in low-Z gas fill hohlraums will be discussed.

Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rosenberg, M.; Zylstra, A. B.; Rinderknecht, H. G.; Petrasso, R. D.; Amendt, P. A.; Landen, O. L.; Town, R. P. J.; Betti, R.; Knauer, J. P.; Meyerhofer, D. D.; Back, C. A.; Kilkenny, J. D.; Nikroo, A.

2010-11-01

414

The PARA: A computer simulation code for plasma driven electromagnetic launchers  

NASA Astrophysics Data System (ADS)

A computer code for simulation of rail type accelerators utilizing a plasma armature was developed and is described in detail. Some time varying properties of the plasma are taken into account in this code thus allowing the development of a dynamical model of the behaviour of plasma in a rail type electromagnetic Launcher. The code is being successfully used to predict and analyze experiments on small calibre rail gun launchers.

Thio, Y. C.

1983-03-01

415

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

416

Breakdown of Electrostatic Predictions for the Nonlinear Dispersion Relation of a Stimulated Raman Scattering-Driven Plasma Wave  

SciTech Connect

The kinetic nonlinear dispersion relation, and frequency shift {delta}{omega}{sub srs}, of a plasma wave driven by stimulated Raman scattering (SRS) are presented. Our theoretical calculations are fully electromagnetic, and use an adiabatic expression for the electron susceptibility which accounts for the change in phase velocity as the wave grows. When k{lambda}{sub D} {approx}> 0.35 (k being the plasma wave number and {lambda}{sub D} the Debye length), {delta}{omega}{sub srs} is significantly larger than could be inferred by assuming that the wave is freely propagating. Our theory is in excellent agreement with 1-D Eulerian Vlasov-Maxwell simulations when 0.3 {le} k{lambda}{sub D} {le} 0.58, and allows discussion of previously proposed mechanisms for Raman saturation. In particular, we find that no 'loss of resonance' of the plasma wave would limit the Raman growth rate, and that saturation through a phase detuning between the plasma wave and the laser drive is mitigated by wave number shifts.

Benisti, D; Strozzi, D J; Gremillet, L

2007-05-08

417

Effect of pressure-driven MHD instabilities on confinement in reactor-relevant high-beta helical plasmas  

SciTech Connect

Through the experiment data analysis in the large helical device (LHD), the influence of the global MHD instability and the relatively short wave length MHD instabilities driven turbulence on the confinement performance in reactor-relevant high-beta helical plasmas is studied. The comparison of the energy confinement time between just before global MHD instability disappears and after that, and the estimation of the saturated mode structure by the multi-channel soft x-ray measurement enable us to quantitatively estimate the influence of the global interchange type MHD instability with different saturated mode structures on the confinement performance. According to the comparison between thermal conductivities in experiments and those predicted by theoretical transport models, the transport properties in the peripheral region of high beta LHD plasmas are quite similar with anomalous transport model based on an interchange type MHD instability driven turbulence, and that result is supported by the dependence of the density fluctuation with relatively short wave length on beta value.

Watanabe, K. Y.; Takemura, Y.; Funaba, H.; Sakakibara, S.; Tanaka, K.; Ohdachi, S.; Toi, K.; Narushima, Y. [National Institute for Fusion Science, Toki 509-5292 (Japan); Masamune, S. [Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan); Watanabe, F. [Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)

2011-05-15

418

Functional reconstitution of an ATP-driven Ca sup 2+ -transport system from the plasma membrane of Commelina communis L  

SciTech Connect

The protein(s) that constitute(s) the ATP-driven Ca{sup 2+}-translocator of plasma membrane enriched vesicles obtained by aqueous two-phase partitioning from leaves of Commelina communis L. has/have been solubilized and reincorporated into tightly sealed liposomes. The reconstituted Ca{sup 2+}-transport system was studied using ATP-driven {sup 45}Ca{sup 2+} import into the proteoliposomes as a measure of activity. The detergent, 3- ((3-cholamidopropyl) dimethylammonio) -1-propane-sulfonate proved to be the most suitable and was used at 10 millimolar concentration, i.e. just above its critical micellar concentration. The presence of additional phospholipid and ATP improved the solubilization and/or reconstitution. The characteristics of the reconstituted system were similar to those of the plasma membrane-bound activity, including the apparent K{sub m} for Ca{sup 2+} inhibition by relatively high levels of vanadate and lacking response to added calmodulin. The reconstituted transport system was very strongly inhibited by erythrosine B and had a low apparent K{sub m} for ATP levels of the Ca{sup 2+}-ionophore A 23187 instantaneously discharged 90% of the Ca{sup 2+} associated with the vesicles, proving that it had been accumulated in the intravesicular volume in soluble, freely exchangeable form. Ca{sup 2+}-transport in the reconstituted system was thus primary active, through a Ca{sup 2+}-translocating ATPase.

Graef, P.; Weiler, E.W. (Ruhr-Universitaet Bochum (West Germany))

1990-10-01

419

An asymmetrically surface-modified graphene film electrochemical actuator.  

PubMed

It is critically important to develop actuator systems for diverse needs ranging from robots and sensors to memory chips. The advancement of mechanical actuators depends on the development of new materials and rational structure design. In this study, we have developed a novel graphene electrochemical actuator based on a rationally designed monolithic graphene film with asymmetrically modified surfaces. Hexane and O(2) plasma treatment were applied to the opposite sides of graphene film to induce the asymmetrical surface properties and hence asymmetrical electrochemical responses, responsible for actuation behaviors. The newly designed graphene actuator demonstrated here opens a new way for actuator fabrication and shows the potential of graphene film for applications in various electromechanical systems. PMID:20828146

Xie, Xuejun; Qu, Liangti; Zhou, Ce; Li, Yan; Zhu, Jia; Bai, Hua; Shi, Gaoquan; Dai, Liming

2010-10-26

420

Sensors and Actuators  

NSDL National Science Digital Library

Sensors and Actuators A (SAAA) disseminates "...information on all aspects of research and development of solid-state devices for transducing physical signals." Sensors and Actuators B (SAAB) "...is an interdisciplinary journal dedicated to covering research and development in the field of chemical sensors, actuators and microsystems." Issues of SAAA available range from September 1999 to the present; issues of SAAB cover January 2000-present.

2001-01-01

421

Fast contracting polypyrrole actuators  

Microsoft Academic Search

Conducting polymer-based actuators are capable of producing at least 10 times more force for a given cross-sectional area (active stress) than skeletal muscle, and potentially 1000 times more, with strains typically between 1% and 10%. Low operating voltages make them particularly attractive for use in micro-electromechanical systems, in place of electrostatic and piezoelectric actuators. A drawback of conducting polymer actuators

John D Madden; Ryan A Cush; Tanya S Kanigan; Ian W Hunter

2000-01-01

422

Microbubble powered actuator  

Microsoft Academic Search

A micromechanical, bubble-powered actuator is presented which can produce mechanical displacements as large as 140 ?m of a polysilicon actuator plate in a direction perpendicular to the substrate with as little as 8.4 mA input current. This device has been designed, fabricated, and successfully tested to have controllable displacement in a nonconducting liquid (Fluorinert FC43). The principle of actuation is

Liwei Lin; Albert P. Pisano; Abraham P. Lee

1991-01-01

423

Remote switch actuator  

DOEpatents

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

424

Electron-Driven Processes: From Single Collision Experiments to High-Pressure Discharge Plasmas  

Microsoft Academic Search

Plasmas are complex systems which consist of various groups of interacting particles (neutral atoms and molecules in their ground states and in excite states, electrons, and positive and negative ions). In principle, one needs to understand and describe all interactions between these particles in order to model the properties of the plasma and to predict its behavior. However, two-body interactions

Kurt Becker

2001-01-01

425

Electroactive polymers (EAP) low-mass muscle actuators  

NASA Astrophysics Data System (ADS)

Actuation devices are used for many space applications with an increasing need to reduce their size, mass, and power consumption as well as cut their cost. Existing transducing actuators, such as piezoceramics, induce limited displacement levels. Potentially, electroactive polymers (EAP) have the potential for low-mass, low-power, inexpensive miniature muscle actuators that are superior to the widely used actuators. Under electrical excitation, EAPs contract and thus form a basis for muscle actuators. Efforts are being made to develop EAP materials that provide large displacements, and two EAP categories were identified to produce actuation strain of more than 10%. These categories include: (1) ion-exchange membrane --platinum composite polymer (so-called ionomers); and (2) electrostatically driven polymers. A comparison between EAP and the widely used transducing actuators shows that, while lagging in force delivering capability, these materials are superior in mass, power consumption and displacement levels. This produces an enabling technology of a new class of devices. Several muscle configurations were constructed to demonstrate the capabilities of these EAP actuators. The emphasis of this manuscript is on ionomer actuators.

Bar-Cohen, Yoseph; Xue, T.; Joffe, Benjamin; Lih, Shyh-Shiuh; Shahinpoor, Mohsen; Simpson, Jaycelyn O.; Smith, J.; Willis, P.

1997-06-01

426

Torsional actuator motor using solid freeform fabricated PZT ceramics  

NASA Astrophysics Data System (ADS)

A torsional actuator has been developed at NRL utilizing the high piezoelectric shear coefficient, d15. This torsional actuator uses an even number of alternately poled segments of electroactive PZT. Under an applied electric field, the torsional actuator produces large angular displacement and a high torque. The solid freeform fabrication technique of the laminated object manufacturing (LOM) is used for rapid prototyping of torsional actuator with potential cost and time saving. First step to demonstrate the feasibility of the LOM technique for the torsional actuator device fabrication is to make near net shape segments. We report a prototype PZT torsional actuator using LOM prepared PZT-5A segments. Fabrication processes and test results are described. The torsional actuator PZT-5A tube has dimensions of 13 cm long, 2.54 cm OD and 1.9 cm ID. Although the piezoelectric strain is small, it may be converted into large displacement via accumulation of the small single cycle displacements over many cycles using AC driving voltage such as with a rotary 'inchworm' actuator or an ultrasonic rotary motor. A working prototype of a full-cycle motor driven by the piezoelectric torsional actuator has been achieved. The rotational speed is 1,200 rpm under 200 V/cm field at the resonant frequency of 4.5 kHz.

Kim, Chulho; Wu, Carl C. M.; Bender, Barry

2004-07-01

427

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

428

A global model for BF3 plasma in a RF-driven multicusp ion source  

Microsoft Academic Search

A volume averaged model for BF3 discharges in a RF-driven, inductively coupled multicusp ion source, such as that used on the ULE2 ion implanter, has been developed. Particle and energy balance equations are solved to determine the electron temperature and the densities of all molecular, atomic, and ionic species of interest, including some multiply charged species, as functions of input

Michael A. Graf; Victor Benveniste; Michael A. Lieberman

1999-01-01

429

A Simple Type of Magnetically Driven Jets: an Astrophysical Plasma Gun  

Microsoft Academic Search

We propose a simple theoretical formulation of the problem of magnetically driven outflows when poloidal magnetic flux surfaces are absent, and the magnetic field has only a toroidal component. The present formulation is the limiting case of the more general Grad-Shafranov one, when Bp\\/Bphi --> 0. We show that the toroidal magnetic field alone is very efficient in accelerating and

J. Contopoulos

1995-01-01

430

Impurity effect on the toroidal ion temperature gradient driven drift mode in a multispecies plasma  

Microsoft Academic Search

The effect of an impurity ion species on the toroidal-ion temperature-gradient driven drift mode is analysed using the fluid model. It is found that the impurity exerts a stabilizing influence when the main species and the impurity ion density profiles are either flat or inwardly peaked and the ion thermal conductivity is neglected; however, when the latter is included, this

G. Murtaza; M. Nadeem; P. K. Shukla

1993-01-01

431

Spectroscopy of Ablated Aluminum Foil Plasmas Driven by MA-LTD  

NASA Astrophysics Data System (ADS)

Spectroscopic analysis has been performed on Al foil plasmas ablated by the Linear Transformer Driver (LTD) at the University of Michigan. The MAIZE LTD can supply 1- MA, 100 kV pulses with 100 ns risetime into a matched load. The plasma load consisted of a 400 nm thick Al foil (cathode) placed between two, planar, current-return anode posts. An optical fiber was placed 1 cm away from the load; plasma light passed through a 0.75-m optical spectrograph and was gated for 10 ns by an intensified CCD detector. The density of the edge plasma was determined through Stark broadening of the H-alpha line. The F