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Sample records for nanosecond pulse discharges

  1. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    SciTech Connect

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-15

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  2. Energy coupling to the plasma in repetitive nanosecond pulse discharges

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor V.; Nishihara, Munetake; Choi, Inchul; Uddi, Mruthunjaya; Lempert, Walter R.

    2009-11-01

    A new analytic quasi-one-dimensional model of energy coupling to nanosecond pulse discharge plasmas in plane-to-plane geometry has been developed. The use of a one-dimensional approach is based on images of repetitively pulsed nanosecond discharge plasmas in dry air demonstrating that the plasma remains diffuse and uniform on a nanosecond time scale over a wide range of pressures. The model provides analytic expressions for the time-dependent electric field and electron density in the plasma, electric field in the sheath, sheath boundary location, and coupled pulse energy. The analytic model predictions are in very good agreement with numerical calculations. The model demonstrates that (i) the energy coupled to the plasma during an individual nanosecond discharge pulse is controlled primarily by the capacitance of the dielectric layers and by the breakdown voltage and (ii) the pulse energy coupled to the plasma during a burst of nanosecond pulses decreases as a function of the pulse number in the burst. This occurs primarily because of plasma temperature rise and resultant reduction in breakdown voltage, such that the coupled pulse energy varies approximately proportionally to the number density. Analytic expression for coupled pulse energy scaling has been incorporated into the air plasma chemistry model, validated previously by comparing with atomic oxygen number density measurements in nanosecond pulse discharges. The results of kinetic modeling using the modified air plasma chemistry model are compared with time-resolved temperature measurements in a repetitively pulsed nanosecond discharge in air, by emission spectroscopy, and purely rotational coherent anti-Stokes Raman spectroscopy showing good agreement.

  3. Characteristics of 2-heptanone decomposition using nanosecond pulsed discharge plasma

    NASA Astrophysics Data System (ADS)

    Nakase, Yuki; Fukuchi, Yuichi; Wang, Douyan; Namihira, Takao; Akiyama, Hidenori; Kumamoto University Collaboration

    2015-09-01

    Volatile organic compounds (VOC) evaporate at room temperature. VOCs typically consist of toluene, benzene and ethyl acetate, which are used in cosmetics, dry cleaning products and paints. Exposure to elevated levels of VOCs may cause headaches, dizziness and irritation to the eyes, nose, and throat; they may also cause environmental problems such as air pollution, acid rain and photochemical smog. As such, they require prompt removal. Nanosecond pulsed discharge is a kind of non-thermal plasma consisting of a streamer discharge. Several advantages of nanosecond pulsed discharge plasma have been demonstrated by studies of our research group, including low heat loss, highly energetic electron generation, and the production of highly active radicals. These advantages have shown ns pulsed discharge plasma capable of higher energy efficiency for processes, such as air purification, wastewater treatment and ozone generation. In this research, nanosecond pulsed discharge plasma was employed to treat 2-heptanone, which is a volatile organic compound type and presents several harmful effects. Characteristics of treatment dependent on applied voltage, gas flow rate and input energy density were investigated. Furthermore, byproducts generated by treatment were also investigated.

  4. Computational Simulation of Nanosecond Pulsed Discharge for Plasma Assisted Ignition

    NASA Astrophysics Data System (ADS)

    Takana, H.; Adamovich, I. V.; Nishiyama, H.

    2014-11-01

    Detailed two dimensional numerical simulations of a nanosecond pulsed pin-to-pin discharge in a lean methane/air mixture were conducted under 10 atm and 600 K for plasma assisted combustion in internal combustion engines. It was clarified from this study that the produced radicals were locally higher in the vicinity of electrodes, and high density radicals are more widely distributed on the anode side rather than the cathode side which the streamer is propagating toward. The electron energy partition has been clarified during a single pulse. Total electron energy increases with fuel equivalent ratio under the same applied voltage. Pronounced enhancement of ignition delay has been shown by nanosecond pulsed discharge.

  5. Rotational CARS Temperature Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Zuzeek, Yvette; Takashima, Keisuke; Adamovich, Igor; Lempert, Walter

    2009-10-01

    Time-resolved and spatially resolved temperatures in repetitively pulsed nanosecond discharges in air and ethylene-air mixtures have been measured by purely rotational Coherent Anti-Stokes Raman Specroscopy (CARS). The experiments have been done in a capacitively coupled plane-to-plane discharge and in an atmospheric pressure near-surface Dielectric Barrier Discharge (DBD), both powered by repetitive nanosecond duration voltage pulses. Gated ICCD camera images demonstrated that the capacitively coupled discharge plasma remains diffuse and stable, with no sign of arc filaments. Comparison of the experimental results with plasma chemical kinetic modeling calculations shows good agreement. The results demonstrate that the rate of heating in the fuel-air plasma is significantly more rapid compared to the one in the air plasma. Kinetic model analysis shows that this occurs due to exothermic reactions of fuel with radical species generated in the plasma, such as O atoms. The present results provide additional insight into kinetics of hydrocarbon fuel oxidation in low-temperature plasmas and into the mechanism of localized heating of air flows by nanosecond DBD discharges.

  6. Numerical simulation of nanosecond-pulse electrical discharges

    NASA Astrophysics Data System (ADS)

    Poggie, J.; Adamovich, I.; Bisek, N.; Nishihara, M.

    2013-02-01

    Recent experiments with a nanosecond-pulse, dielectric barrier discharge at the stagnation point of a Mach 5 cylinder flow have demonstrated the formation of weak shock waves near the electrode edge, which propagate upstream and perturb the bow shock. This is a promising means of flow control, and understanding the detailed physics of the conversion of electrical energy into gas motion will aid in the design of efficient actuators based on the concept. In this work, a simplified configuration with planar symmetry was chosen as a vehicle to develop a physics-based model of nanosecond-pulse discharges, including realistic air kinetics, electron energy transport, and compressible bulk gas flow. A reduced plasma kinetic model (23 species and 50 processes) was developed to capture the dominant species and reactions for energy storage and thermalization in the discharge. The kinetic model included electronically and vibrationally excited species, and several species of ions and ground state neutrals. The governing equations included the Poisson equation for the electric potential, diffusion equations for each neutral species, conservation equations for each charged species, and mass-averaged conservation equations for the bulk gas flow. The results of calculations with this model highlighted the path of energy transfer in the discharge. At breakdown, the input electrical energy was transformed over a time scale on the order of 1 ns into chemical energy of ions, dissociation products, and vibrationally and electronically excited particles. About 30% of this energy was subsequently thermalized over a time scale of 10 µs. Since the thermalization time scale was faster than the acoustic time scale, the heat release led to the formation of weak shock waves originating near the sheath edge, consistent with experimental observations. The computed translational temperature rise (40 K) and nitrogen vibrational temperature rise (370 K) were of the same order of magnitude as

  7. Energy balance in nanosecond pulse discharges in nitrogen and air

    NASA Astrophysics Data System (ADS)

    Shkurenkov, Ivan; Adamovich, Igor V.

    2016-02-01

    Kinetic modeling is used to analyze energy partition and energy transfer in nanosecond pulse discharges sustained between two spherical electrodes in nitrogen and air. The modeling predictions are compared with previous time-resolved temperature and {{\\text{N}}2}≤ft(X {}1Σ\\text{g}+,v=0-9\\right) vibrational population measurements by picosecond broadband coherent anti-Stokes Raman spectroscopy (CARS) and phase-locked Schlieren imaging. The model shows good agreement with experimental data, reproducing experimental discharge current pulse waveforms, as well as dominant processes of energy transfer in the discharge and the afterglow. Specifically, the results demonstrate that the temperature rise in the plasma occurs in two stages, (i) ‘rapid’ heating on sub-acoustic time scale, dominated by {{\\text{N}}2}≤ft(A {}3Σ\\text{u}+\\right) energy pooling processes, N2(B 3Πg) and N(2P,2D) quenching (in nitrogen), and by quenching of excited electronic states of N2 molecules by O2 (in air), and (ii) ‘slow’ heating due to N2 vibrational relaxation by O atoms (in air), nearly completely missing in nitrogen. Comparison of the model predictions with N2 vibrational level populations confirms that the N2 vibrational temperature rises after the discharge pulse is caused by the ‘downward’ vibrational-vibrational exchange depopulating higher vibrational levels and populating vibrational level v  =  1. The model reproduces temporal dynamics of vibrational level populations and temperature in the discharge and the afterglow, indicating that energy partition among different modes (vibrational, electronic, dissociation, and ionization) is predicted accurately. At the present conditions, energy fraction coupled to the positive column of the discharge filament in air is approximately 50%, with the rest coupled to the cathode layer. Nearly 10% of the total pulse energy is spent on O atom generation, and about 10% is thermalized on a sub-acoustic time scale

  8. Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge

    NASA Astrophysics Data System (ADS)

    Goldberg, Benjamin M.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-08-01

    The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly ‘flat top’ distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present

  9. Discharge Characteristics of SF6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses

    NASA Astrophysics Data System (ADS)

    Ran, Huijuan; Wang, Lei; Wang, Jue; Wang, Tao; Yan, Ping

    2014-05-01

    The characteristics of high pressure sulphur hexafluoride (SF6) discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper. The influencing factors on discharge process, such as gas pressure, pulse repetition frequency (PRF), and number of applied pulses, are analyzed. Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses. Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current. The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure. The reduced electric field (E/p) decreases with the increase of PRF in all circumstances. The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.

  10. Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge

    SciTech Connect

    Nishihara, M.; Takashima, K.; Rich, J. W.; Adamovich, I. V.

    2011-06-15

    Bow shock perturbations in a Mach 5 air flow, produced by low-temperature, nanosecond pulse, and surface dielectric barrier discharge (DBD), are detected by phase-locked schlieren imaging. A diffuse nanosecond pulse discharge is generated in a DBD plasma actuator on a surface of a cylinder model placed in air flow in a small scale blow-down supersonic wind tunnel. Discharge energy coupled to the actuator is 7.3-7.8 mJ/pulse. Plasma temperature inferred from nitrogen emission spectra is a few tens of degrees higher than flow stagnation temperature, T = 340 {+-} 30 K. Phase-locked Schlieren images are used to detect compression waves generated by individual nanosecond discharge pulses near the actuator surface. The compression wave propagates upstream toward the baseline bow shock standing in front of the cylinder model. Interaction of the compression wave and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The compression wave speed behind the bow shock and the perturbed bow shock velocity are inferred from the Schlieren images. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated in a single-pulse regime (at pulse repetition rates of a few hundred Hz) and in a quasi-continuous mode (using a two-pulse sequence at a pulse repetition rate of 100 kHz). The results demonstrate feasibility of hypersonic flow control by low-temperature, repetitive nanosecond pulse discharges.

  11. Plasma-Enhanced Combustion of Hydrocarbon Fuels and Fuel Blends Using Nanosecond Pulsed Discharges

    SciTech Connect

    Cappelli, Mark; Mungal, M Godfrey

    2014-10-28

    This project had as its goals the study of fundamental physical and chemical processes relevant to the sustained premixed and non-premixed jet ignition/combustion of low grade fuels or fuels under adverse flow conditions using non-equilibrium pulsed nanosecond discharges.

  12. Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in Airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Gao, Wei; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Volume diffuse dielectric barrier discharge (DBD) plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra (OES), the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap. supported by National Natural Science Foundation of China (No. 51437002)

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

    SciTech Connect

    Likhanskii, Alexandre V.; Shneider, Mikhail N.; Macheret, Sergey O.; Miles, Richard B.

    2007-07-15

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

  14. Verification of antitumor effect in vivo using nanosecond pulsed streamer discharge

    NASA Astrophysics Data System (ADS)

    Yonetamari, Kenta; Shirakawa, Yuki; Akiyama, Taketoshi; Mizuno, Kazue; Ono, Ryo

    2015-09-01

    Cancer treatment using plasma has intensively studied these days. In this work, antitumor effect by nanosecond pulsed streamer discharge was investigated. Nanosecond pulsed streamer plasma was used as a plasma source, which can generate stable streamer discharge by using a nanosecond pulsed power supply. The rod electrode of 3 mm diameter is made of copper. Its end is formed into a semispherical shape of 1.5 mm curvature. The electrode is inserted into a quartz tube (inner diameter: 4 mm, thickness: 1 mm) concentrically, so any gas can be introduced. B16F10 cells were selected to perform in vivo antitumor study. These cells were injected under the skin of leg of mice to make cancer tumor. One week later from injections, plasma was applied to the cancer tumor. Mice were randomly assigned into three groups which were one control group and two plasma treatment groups. In the control group, mice were not treated. In the plasma treatment groups, plasma with dry N2 and wet O2 as a working gas were irradiated for 5 consecutive days. Processing time was 10 min and the gap distance between the electrode and tumor was 4 mm. After 5 days plasma treatment, antitumor effect was observed. The result indicates that the streamer discharge has a potential for cancer treatment.

  15. Numerical Simulation of a Nanosecond-Pulse Discharge for High-Speed Flow Control

    NASA Astrophysics Data System (ADS)

    Poggie, Jonathan; Adamovich, Igor

    2012-10-01

    Numerical calculations were carried out to examine the physics of the operation of a nanosecond-pulse, single dielectric barrier discharge in a configuration with planar symmetry. This simplified configuration was chosen as a vehicle to develop a physics based nanosecond discharge model, including realistic air plasma chemistry and compressible bulk gas flow. First, a reduced plasma kinetic model was developed by carrying out a sensitivity analysis of zero-dimensional plasma computations with an extended chemical kinetic model. Transient, one- dimensional discharge computations were then carried out using the reduced kinetic model, incorporating a drift-diffusion formulation for each species, a self-consistent computation of the electric potential using the Poisson equation, and a mass-averaged gas dynamic formulation for the bulk gas motion. Discharge parameters (temperature, pressure, and input waveform) were selected to be representative of recent experiments on bow shock control with a nanosecond discharge in a Mach 5 cylinder flow. The computational results qualitatively reproduce many of the features observed in the experiments, including the rapid thermalization of the input electrical energy and the consequent formation of a weak shock wave. At breakdown, input electrical energy is rapidly transformed (over roughly 1 ns) into ionization products, dissociation products, and electronically excited particles, with subsequent thermalization over a relatively longer time-scale (roughly 10 μs).

  16. A compact repetitive high-voltage nanosecond pulse generator for the application of gas discharge.

    PubMed

    Pang, Lei; Zhang, Qiaogen; Ren, Baozhong; He, Kun

    2011-04-01

    Uniform and stable discharge plasma requires very short duration pulses with fast rise times. A repetitive high-voltage nanosecond pulse generator for the application of gas discharge is presented in this paper. It is constructed with all solid-state components. Two-stage magnetic compression is used to generate a short duration pulse. Unlike in some reported studies, common commercial fast recovery diodes instead of a semiconductor opening switch (SOS) are used in our experiment that plays the role of SOS. The SOS-like effects of four different kinds of diodes are studied experimentally to optimize the output performance. It is found that the output pulse voltage is higher with a shorter reverse recovery time, and the rise time of pulse becomes faster when the falling time of reverse recovery current is shorter. The SOS-like effect of the diodes can be adjusted by changing the external circuit parameters. Through optimization the pulse generator can provide a pulsed voltage of 40 kV with a 40 ns duration, 10 ns rise time, and pulse repetition frequency of up to 5 kHz. Diffuse plasma can be formed in air at standard atmospheric pressure using the developed pulse generator. With a light weight and small packaging the pulse generator is suitable for gas discharge application. PMID:21529005

  17. A compact repetitive high-voltage nanosecond pulse generator for the application of gas discharge

    NASA Astrophysics Data System (ADS)

    Pang, Lei; Zhang, Qiaogen; Ren, Baozhong; He, Kun

    2011-04-01

    Uniform and stable discharge plasma requires very short duration pulses with fast rise times. A repetitive high-voltage nanosecond pulse generator for the application of gas discharge is presented in this paper. It is constructed with all solid-state components. Two-stage magnetic compression is used to generate a short duration pulse. Unlike in some reported studies, common commercial fast recovery diodes instead of a semiconductor opening switch (SOS) are used in our experiment that plays the role of SOS. The SOS-like effects of four different kinds of diodes are studied experimentally to optimize the output performance. It is found that the output pulse voltage is higher with a shorter reverse recovery time, and the rise time of pulse becomes faster when the falling time of reverse recovery current is shorter. The SOS-like effect of the diodes can be adjusted by changing the external circuit parameters. Through optimization the pulse generator can provide a pulsed voltage of 40 kV with a 40 ns duration, 10 ns rise time, and pulse repetition frequency of up to 5 kHz. Diffuse plasma can be formed in air at standard atmospheric pressure using the developed pulse generator. With a light weight and small packaging the pulse generator is suitable for gas discharge application.

  18. Studies of nanosecond pulse surface ionization wave discharges over solid and liquid dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Petrishchev, Vitaly; Leonov, Sergey; Adamovich, Igor V.

    2014-12-01

    Surface ionization wave discharges generated by high-voltage nanosecond pulses, propagating over a planar quartz surface and over liquid surfaces (distilled water and 1-butanol) have been studied in a rectangular cross section test cell. The discharge was initiated using a custom-made, alternating polarity, high-voltage nanosecond pulse plasma generator, operated at a pulse repetition rate of 100-500 Hz, with a pulse peak voltage and current of 10-15 kV and 7-20 A, respectively, a pulse FWHM of ˜100 ns, and a coupled pulse energy of 2-9 mJ/pulse. Wave speed was measured using a capacitive probe. ICCD camera images demonstrated that the ionization wave propagated predominantly over the quartz wall or over the liquid surface adjacent to the grounded waveguide placed along the bottom wall of the test cell. Under all experimental conditions tested, the surface plasma ‘sheet’ was diffuse and fairly uniform, both for positive and negative polarities. The parameters of ionization wave discharge propagating over distilled water and 1-butanol surfaces were close to those of the discharge over a quartz wall. No perturbation of the liquid surface by the discharge was detected. In most cases, the positive polarity surface ionization wave propagated at a higher speed and over a longer distance compared to the negative polarity wave. For all three sets of experiments (surface ionization wave discharge over quartz, water and 1-butanol), wave speed and travel distance decreased with pressure. Diffuse, highly reproducible surface ionization wave discharge was also observed over the liquid butanol-saturated butanol vapor interface, as well as over the distilled water-saturated water vapor interface, without buffer gas flow. No significant difference was detected between surface ionization discharges sustained using single-polarity (positive or negative), or alternating polarity high-voltage pulses. Plasma emission images yielded preliminary evidence of charge removal from the

  19. The influencing factors of nanosecond pulse homogeneous dielectric barrier discharge in air.

    PubMed

    Zhang, Shuai; Jia, Li; Wang, Wen-chun; Yang, De-zheng; Tang, Kai; Liu, Zhi-jie

    2014-01-01

    In this paper, a bipolar nanosecond high pulse voltage with 20 ns rising time was employed to generate homogeneous dielectric barrier discharges using the plate-plate electrode configuration in air at atmospheric pressure. The effects of pulse peak voltage, gas discharge gap, and dielectric plates made by different materials or thicknesses on the discharge homogeneity, voltage-current waveform, and optical emission spectra were investigated. Results show that aforementioned parameters have a strongly impact on the discharge homogeneity and the optical emission spectra, but it is hard to identify definitely their influences on the discharge voltage-current waveform. Homogeneous discharges were easily observed when using low permittivity dielectric plate and the emission intensity of N2 (C(3)Πu→B(3)Πg, 0-0, 337.1 nm) increases with the rising of pulse peak voltage and the permittivity of dielectric material but decreases with the increasing of gas discharge gap and the dielectric plate thickness. The rotational and vibrational temperatures (Trot and Tvib) were determined at Trot=350±5 K and Tvib=3045 K via fitting the simulative spectra of N2 (C(3)Πu→B(3)Πg, 0-2) with the measured one. PMID:24036046

  20. The influencing factors of nanosecond pulse homogeneous dielectric barrier discharge in air

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Jia, Li; Wang, Wen-chun; Yang, De-zheng; Tang, Kai; Liu, Zhi-jie

    2014-01-01

    In this paper, a bipolar nanosecond high pulse voltage with 20 ns rising time was employed to generate homogeneous dielectric barrier discharges using the plate-plate electrode configuration in air at atmospheric pressure. The effects of pulse peak voltage, gas discharge gap, and dielectric plates made by different materials or thicknesses on the discharge homogeneity, voltage-current waveform, and optical emission spectra were investigated. Results show that aforementioned parameters have a strongly impact on the discharge homogeneity and the optical emission spectra, but it is hard to identify definitely their influences on the discharge voltage-current waveform. Homogeneous discharges were easily observed when using low permittivity dielectric plate and the emission intensity of N2 (C3Πu → B3Πg, 0-0, 337.1 nm) increases with the rising of pulse peak voltage and the permittivity of dielectric material but decreases with the increasing of gas discharge gap and the dielectric plate thickness. The rotational and vibrational temperatures (Trot and Tvib) were determined at Trot = 350 ± 5 K and Tvib = 3045 K via fitting the simulative spectra of N2 (C3Πu → B3Πg, 0-2) with the measured one.

  1. Spatial and temporal evolutions of ozone in a nanosecond pulse corona discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Duten, X.; Redolfi, M.; Aggadi, N.; Vega, A.; Hassouni, K.

    2011-10-01

    This paper deals with the experimental determination of the spatial and temporal evolutions of the ozone concentration in an atmospheric pressure pulsed plasma, working in the nanosecond regime. We observed that ozone was produced in the localized region of the streamer. The ozone transport requires a characteristic time well above the millisecond. The numerical modelling of the streamer expansion confirms that the hydrodynamic expansion of the filamentary discharge region during the streamer propagation does not lead to a significant transport of atomic oxygen and ozone. It appears therefore that only diffusional transport can take place, which requires a characteristic time of the order of 50 ms.

  2. Oh Laser-Induced Fluorescence Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Choi, Inchul; Adamovich, Igor V.; Lempert, Walter R.

    2010-06-01

    We present recent results of laser-induced fluorescence measurements of hydroxyl radical density in repetitively pulsed nanosecond plasmas, created using 10-20 nsec duration, high (up to 20 kV) voltage pulsers, capable of operation at repetition rates as high as 40-50 kHz. OH mole fraction as a function of time with respect to discharge creation is determined, with absolute calibration performed using a Hencken flat flame burner. This paper will focus on a series of low temperature, non-equilibrium kinetics measurements in hydrogen and hydrocarbon-air mixtures, with results compared to predictions of a recently developed plasma chemical oxidation model.

  3. Nanosecond repetitively pulsed discharges in air at atmospheric pressure—the spark regime

    NASA Astrophysics Data System (ADS)

    Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.

    2010-12-01

    Nanosecond repetitively pulsed (NRP) spark discharges have been studied in atmospheric pressure air preheated to 1000 K. Measurements of spark initiation and stability, plasma dynamics, gas temperature and current-voltage characteristics of the spark regime are presented. Using 10 ns pulses applied repetitively at 30 kHz, we find that 2-400 pulses are required to initiate the spark, depending on the applied voltage. Furthermore, about 30-50 pulses are required for the spark discharge to reach steady state, following initiation. Based on space- and time-resolved optical emission spectroscopy, the spark discharge in steady state is found to ignite homogeneously in the discharge gap, without evidence of an initial streamer. Using measured emission from the N2 (C-B) 0-0 band, it is found that the gas temperature rises by several thousand Kelvin in the span of about 30 ns following the application of the high-voltage pulse. Current-voltage measurements show that up to 20-40 A of conduction current is generated, which corresponds to an electron number density of up to 1015 cm-3 towards the end of the high-voltage pulse. The discharge dynamics, gas temperature and electron number density are consistent with a streamer-less spark that develops homogeneously through avalanche ionization in volume. This occurs because the pre-ionization electron number density of about 1011 cm-3 produced by the high frequency train of pulses is above the critical density for streamer-less discharge development, which is shown to be about 108 cm-3.

  4. Electron emission mechanism during the nanosecond high-voltage pulsed discharge in pressurized air

    NASA Astrophysics Data System (ADS)

    Levko, D.; Yatom, S.; Vekselman, V.; Krasik, Ya. E.

    2012-02-01

    A comparison between the results of x-ray absorption spectroscopy of runaway electrons (RAEs) generated during nanosecond timescale high-voltage (HV) gas discharge and the simulated attenuation of the x-ray flux produced by the runaway electron spectrum calculated using particle-in-cell numerical modeling of such a type of discharge is presented. The particle-in-cell simulation considered the field and explosive emissions (EEs) of the electrons from the cathode. It is shown that the field emission is the dominant emission mechanism for the short-duration (<2.5 ns) high-voltage pulses, while for the long-duration (>5 ns) high-voltage pulses, the explosive emission is likely to play a significant role.

  5. Temporally resolved optical emission spectroscopic investigations on a nanosecond self-pulsing micro-thin-cathode discharge

    NASA Astrophysics Data System (ADS)

    Du, Beilei; Sadeghi, Nader; Tsankov, Tsanko V.; Luggenhölscher, Dirk; Czarnetzki, Uwe

    2012-08-01

    At atmospheric pressure in Ar, a micro-thin-cathode discharge operates in a self-pulsing mode due to periodic ignition of a nanosecond spark discharge with a long living afterglow (several hundred nanoseconds). In this mode, optical emission spectra of the nanosecond spark and the afterglow are investigated. The electron density and temperature in the pure Ar discharge are measured by the Stark broadening and shift of the Ar 3p6 → 1s5 transition (415.859 nm). The nanosecond spark has an electron density of the order of 1017 cm-3 and an electron temperature of 5 eV. The gas temperature is obtained by analyzing the emission spectra of the N2 second positive system with an admixture of 0.5% N2. The measured gas temperature agrees very well with the result of a zero-dimensional kinetic simulation. The temporal development of the spatial distribution of separate emission lines shows that not only the nanosecond spark but the afterglow is also strongly localized. The temporal development of the emission spectrum provides powerful proof that the nanosecond spark discharge, due to thermionic emission, occurs in the self-pulsing mode with nanosecond current peaks.

  6. The formation of diffuse discharge by short-front nanosecond voltage pulses and the modification of dielectrics in this discharge

    NASA Astrophysics Data System (ADS)

    Orlovskii, V. M.; Panarin, V. A.; Shulepov, M. A.

    2014-07-01

    The dynamics of diffuse discharge formation under the action of nanosecond voltage pulses with short fronts (below 1 ns) in the absence of a source of additional preionization and the influence of a dielectric film on this process have been studied. It is established that the diffuse discharge is induced by the avalanche multiplication of charge initiated by high-energy electrons and then maintained due to secondary breakdowns propagating via ionized gas channels. If a dielectric film (polyethylene, Lavsan, etc.) is placed on the anode, then multiply repeated discharge will lead to surface and bulk modification of the film material. Discharge-treated polyethylene film exhibits a change in the optical absorption spectrum in the near-IR range.

  7. Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air.

    PubMed

    Li, Lee; Liu, Yun-Long; Ge, Ya-Feng; Bin, Yu; Huang, Jia-Jia; Lin, Fo-Chan

    2013-10-01

    Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ~30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented. PMID:24182161

  8. Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air

    NASA Astrophysics Data System (ADS)

    Li, Lee; Liu, Yun-Long; Ge, Ya-Feng; Bin, Yu; Huang, Jia-Jia; Lin, Fo-Chan

    2013-10-01

    Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ˜30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented.

  9. Study of microdischarge arrays excited by DC or nanosecond pulsed discharges

    NASA Astrophysics Data System (ADS)

    Martin, Virginie; Bauville, Gerard; Puech, Vincent

    2011-10-01

    The spatio-temporal behavior of the optical emission of microdischarge arrays was studied through fast imaging technique. The device basically consisted of a metal/dielectric/metal sandwich drilled with many microholes, and was powered either by direct current or by nanosecond high voltage pulses. Microdischarges operating in DC mode were widely used for producing VUV emission from rare-gas excimers. However for biological applications, pulsed UV sources emitting in the range 200-280 nm, corresponding to the DNA absorption band, are required. Thus the electrical and optical characteristics of discharges operating either in pure rare-gas (argon) or in rare gas/halide mixtures (Kr/Cl2) , in which intense UV-C emissions could been achieved, were studied. It will be shown that the DC excitation induces a progressive ignition of the different micro-cavities, but the maximum number of ignited microplasmas is limited. On the other hand, nanosecond high-voltage pulses, applied at high repetition frequency, allow the simultaneous ignition of all the microcavities even in absence of ballasting resistors.

  10. Impacts of air pressure on the evolution of nanosecond pulse discharge products

    NASA Astrophysics Data System (ADS)

    Yu, Jin-Lu; He, Li-Ming; Ding, Wei; Wang, Yu-Qian; Du, Chun

    2013-05-01

    Based on the nonequilibrium plasma dynamics of air discharge, a dynamic model of zero-dimensional plasma is established by combining the component density equation, the Boltzmann equation, and the energy transfer equation. The evolution properties of nanosecond pulse discharge (NPD) plasma under different air pressures are calculated. The results show that the air pressure has significant impacts on the NPD products and the peak values of particle number density for particles such as O atoms, O3 molecules, N2(A3) molecules in excited states, and NO molecules. It increases at first and then decreases with the increase of air pressure. On the other hand, the peak values of particle number density for N2(B3) and N2(C3) molecules in excited states are only slightly affected by the air pressure.

  11. Investigation of flow separation control by nanosecond pulsed dielectric barrier discharge actuators

    NASA Astrophysics Data System (ADS)

    Grech, N.; Leyland, P.; Peschke, Ph.; Ott, P.

    2015-06-01

    The ability of nanosecond pulsed dielectric barrier discharge (DBD) actuators to control flow separation was investigated on a NACA (National Advisory Committee for Aeronautics) 0015 profile for velocities up to 24 m/s (Re = 230,000). The optimal location for the actuator was determined from oil flow experiments. Moderate voltage levels were applied (3 and 6 kV) and the actuator was operated at frequencies ranging from 0.058 to 10 kHz in pulse and burst modes. The peak effectiveness of the actuator occurred at reduced frequency values of around 1. Plasma influence was observed at all tested angles of attack (up to 26°) and the stall angle was delayed by 8°.

  12. Conversion of CH4 /CO2 by a nanosecond repetitively pulsed discharge

    NASA Astrophysics Data System (ADS)

    Scapinello, M.; Martini, L. M.; Dilecce, G.; Tosi, P.

    2016-02-01

    A possible way to store both renewable energy and CO2 in chemical energy is to produce value-added chemicals and fuels starting from CO2 and green electricity. This can be done by exploiting the non-equilibrium properties of gaseous electrical discharges. Discharges, in addition, can be switched on and off quickly, thus being suitable to be coupled with an intermittent energy source. In this study, we have used a nanosecond pulsed discharge to dissociate CO2 and CH4 in a 1:1 mixture at atmospheric pressure, and compared our results with literature data obtained by other discharges. The main products are CO, H2, C2H2, water and solid carbon. We estimate an energy efficiency of 40% for syngas (CO and H2) production, higher if other products are also considered. Such values are among the highest compared to other discharges, and, although not very high on an absolute scale, are likely improvable via possible routes discussed in the paper and by coupling to the discharge a heterogeneous catalysis stage.

  13. Nanosecond Repetitively Pulsed Discharges in Air at Atmospheric Pressure -- Experiment and Theory of Regime Transitions

    NASA Astrophysics Data System (ADS)

    Pai, David; Lacoste, Deanna; Laux, Christophe

    2009-10-01

    In atmospheric pressure air preheated from 300 to 1000 K, the Nanosecond Repetitively Pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and inter-electrode gap distance) of each discharge regime. Notably, there is a minimum gap distance for the existence of the glow regime that increases with decreasing gas temperature. A theory is developed to describe the Corona-to-Glow (C-G) and Glow-to-Spark (G-S) transitions for NRP discharges. The C-G transition is shown to depend on the Avalanche-to-Streamer Transition (AST) as well as the electric field strength in the positive column. The G-S transition is due to the thermal ionization instability. The minimum gap distance for the existence of the glow regime can be understood by considering that the applied voltage of the AST must be lower than that of the thermal ionization instability. This is a previously unknown criterion for generating glow discharges, as it does not correspond to the Paschen minimum or to the Meek-Raether criterion.

  14. Improvement of Spatial Uniformity of Nanosecond-Pulse Diffuse Discharges in a Multi-Needle-to-Plane Gap

    NASA Astrophysics Data System (ADS)

    Gu, Jianwei; Zhang, Cheng; Wang, Ruixue; Yan, Ping; Shao, Tao

    2016-03-01

    Large-scale non-thermal plasmas generated by nanosecond-pulse discharges have been used in various applications, including surface treatment, biomedical treatment, flow control etc. In this paper, atmospheric-pressure diffuse discharge was produced by a homemade nanosecond-pulse generator with a full width at half maximum of 100 ns and a rise time of 70 ns. In order to increase the discharge area, multi-needle electrodes with a 3×3 array were designed. The electrical characteristics of the diffuse discharge array and optical images were investigated by the voltage-current waveforms and discharge images. The experimental results showed that the intensity of diffuse discharges in the center was significantly weaker than those at the margins, resulting in an inhomogeneous spatial uniformity in the diffuse discharge array. Simulation of the electric field showed that the inhomogeneous spatial uniformity was caused by the non-uniform distribution of the electric field in the diffuse discharge array. Moreover, the spatial uniformity of the diffuse discharge array could be improved by increasing the length of the needle in the centre of the array. Finally, the experimental results confirmed the simulation results, and the spatial uniformity of the nanosecond-pulse diffuse discharge array was significantly improved. supported by National Natural Science Foundation of China (Nos. 51222701, 51477164) and the National Basic Research Program of China (No. 2014CB239505-3)

  15. A volume pulsed corona formed during nanosecond pulsed periodic discharge of negative polarity in narrow gaps with airflow at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Lepekhin, N. M.; Priseko, Yu. S.; Puresev, N. I.; Filippov, V. G.

    2014-06-01

    A volume mode of spatially homogeneous nanosecond pulsed-periodic corona discharge of negative polarity has been obtained using an edge-to-edge electrode geometry in narrow gaps with airflow at atmospheric pressure and natural humidity. The parameters of discharge are estimated, and a factor limiting the power deposited in discharge is determined.

  16. Species and temperature measurements of methane oxidation in a nanosecond repetitively pulsed discharge

    PubMed Central

    Lefkowitz, Joseph K; Guo, Peng; Rousso, Aric; Ju, Yiguang

    2015-01-01

    Speciation and temperature measurements of methane oxidation during a nanosecond repetitively pulsed discharge in a low-temperature flow reactor have been performed. Measurements of temperature and formaldehyde during a burst of pulses were made on a time-dependent basis using tunable diode laser absorption spectroscopy, and measurements of all other major stable species were made downstream of a continuously pulsed discharge using gas chromatography. The major species for a stoichiometric methane/oxygen/helium mixture with 75% dilution are H2O, CO, CO2, H2, CH2O, CH3OH, C2H6, C2H4 and C2H2. A modelling tool to simulate homogeneous plasma combustion kinetics is assembled by combining the ZDPlasKin and CHEMKIN codes. In addition, a kinetic model for plasma-assisted combustion (HP-Mech/plasma) of methane, oxygen and helium mixtures has been assembled to simulate the measurements. Predictions can accurately capture reactant consumption as well as production of the major product species. However, significant disagreement is found for minor species, particularly CH2O and CH3OH. Further analysis revealed that the plasma-activated low-temperature oxidation pathways, particularly those involving CH3O2 radical reactions and methane reactions with O(1D), are responsible for this disagreement. PMID:26170433

  17. Nanosecond-pulsed dielectric barrier discharges in Kr/Cl2 for production of ultraviolet radiation

    NASA Astrophysics Data System (ADS)

    Gregório, J.; Aubert, X.; Hagelaar, G. J. M.; Puech, V.; Pitchford, L. C.

    2014-02-01

    In this paper, we present a study of nanosecond-pulsed, coaxial dielectric barrier discharges for generation of UV radiation in Kr/Cl2 mixtures with total pressures of 25 and 50 mbar. This study is based on an ensemble of experimental and modeling results and aims to identify the dominant physical mechanisms leading to the production of KrCl* (B state). The emission band of KrCl* is peaked at 222 nm, which is in the wavelength range of interest for applications in microbial decontamination. We find that for the same energy per pulse deposited in the discharge, more UV radiation is emitted at higher pressures where relatively more of the energy deposited in the gas goes into heating the electrons, with less going to heating the ions in the sheath. The Cl2 partial pressure significantly affects the KrCl* time-averaged, spatial profiles, leading to different optimal conditions for average and for peak UV power densities. Model results show that the highest KrCl* number density occurs near the walls and is associated with the development of cathode sheaths during the voltage pulse.

  18. Time-resolved temperature and O atom measurements in nanosecond pulse discharges in combustible mixtures

    NASA Astrophysics Data System (ADS)

    Lanier, Suzanne; Bowman, Sherrie; Burnette, David; Adamovich, Igor V.; Lempert, Walter R.

    2014-11-01

    The paper presents results of time-resolved rotational temperature measurements, by pure rotational coherent anti-Stokes Raman spectroscopy and absolute O atom number density measurements, by two-photon absorption laser induced fluorescence. The experiments were conducted in nanosecond pulse discharges in H2-O2-Ar and C2H4-O2-Ar mixtures, initially at room temperature, operated at a high pulse repetition rate of 40 kHz, in a plane-to-plane double dielectric barrier geometry at a pressure of 40 Torr. Intensified charge-coupled device images show that O2-Ar and H2-O2-Ar plasmas remain diffuse and volume-filling during the entire burst. Images taken in C2H4-O2-Ar plasma demonstrate significant discharge filamentation and constriction along the center plane and in the corners of the test section. The experimental results demonstrate high accuracy of pure rotational psec CARS for thermometry measurements at low partial pressures of oxygen in nonequilibrium plasmas. The results are compared with kinetic modeling calculations, using two different H2-O2 chemistry and C2H4-O2 chemistry mechanisms. In H2-O2-Ar mixtures, the kinetic modeling predictions are in fairly good agreement with the data, predicting temperature rise and O atom accumulation in long discharge bursts, up to 450 pulses. The results show that adding hydrogen to the mixture results in an additional temperature rise, due to its partial oxidation by radicals generated in the plasma, essentially without chain branching. In C2H4-O2-Ar mixtures, the model consistently underpredicts both temperature and O atom number density. The most likely reason for the difference between the experimental data and model predictions is discharge filamentation developing when ethylene is added to the O2-Ar mixture, at fairly low temperatures.

  19. Optical and application study of gas-liquid discharge excited by bipolar nanosecond pulse in atmospheric air

    NASA Astrophysics Data System (ADS)

    Wang, Sen; Wang, Wen-chun; Yang, De-zheng; Liu, Zhi-jie; Zhang, Shuai

    2014-10-01

    In this study, a bipolar nanosecond pulse with 20 ns rising time is employed to generate air gas-liquid diffuse discharge plasma with room gas temperature in quartz tube at atmospheric pressure. The image of the discharge and optical emission spectra of active species in the plasma are recorded. The plasma gas temperature is determined to be approximately 390 K by compared the experimental spectra with the simulated spectra, which is slightly higher than the room temperature. The result indicated that the gas temperature rises gradually with pulse peak voltage increasing, while decreases slightly with the electrode gap distance increasing. As an important application, bipolar nanosecond pulse discharge is used to sterilize the common microorganisms (Actinomycetes, Candida albicans and Escherichia coli) existing in drinking water, which performs high sterilization efficiency.

  20. Nanosecond Pulsed Discharges in Liquid Phase: Optical diagnostics of positive versus negative modes of initiation in water

    NASA Astrophysics Data System (ADS)

    Seepersad, Yohan; Fridman, Alexander; Dobrynin, Danil; Applied Physics Group Team

    2013-09-01

    Recent work on nanosecond pulsed discharges in liquids has shown the possibility of producing plasma directly in the liquid phase without bubble formation or heating of the liquid. Paramount to understanding the physical processes leading to this phenomenon is a thorough understanding of the way these discharges behave under various conditions. This work explores the development of nanosecond pulsed discharges in water, for both positively and negatively applied pulses in a pin-to-plane configuration. Time resolved nanosecond ICCD imaging is used to trace the development of the discharge for applied voltages up to 24 kV. From the results we are able to identify breakdown thresholds at which discharge is initiated for both modes. At voltages below the critical breakdown value, Schlieren and shadowgraphy techniques are used to investigate perturbations in the liquid layers near the electrode tip as a consequence of these fat rising pulses. This work was supported by Defense Advanced Research Projects Agency (grant #DARPA-BAA-11-31).

  1. Simulation study on nitrogen vibrational kinetics in a single nanosecond pulse high voltage air discharge

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Zhou, Qianhong; Dong, Zhiwei

    2016-05-01

    We report a simulation study on nitrogen vibrational kinetics N 2 ( X 1 Σg + , v = 0 - 12 ) in a single nanosecond pulse high voltage discharge in dry-air at a pressure of 100 Torr. Apart from the usual processes such as vibrational-vibrational exchange and vibrational-translational relaxation, the state-specific vibrational kinetics take into account the electronic-vibrational (E-V) process and chemical-vibrational process. The vibrational kinetics, coupled with electron Boltzmann equation solver, plasma chemical kinetics, and gas thermal balance are used to model the 100 ns discharge and its subsequent 10 ms afterglow. The self-consistent model shows good agreement with recent experimental results, with regard to time-resolved vibrational and translational temperature. According to the modeling results, The E-V mechanism has a small but non-negligible effect (about 2%) in rising of vibrational quanta in the early afterglow from 100 ns to 1μs. Another possible reason is the convective transport associated with the gas dynamic expansion in time delays around 1μs to 10 μs.

  2. Optical emission characteristics of surface nanosecond pulsed dielectric barrier discharge plasma

    SciTech Connect

    Wu Yun; Li Yinghong; Jia Min; Song Huimin; Liang Hua

    2013-01-21

    This paper reports an experimental study of the optical emission characteristics of the surface dielectric barrier discharge plasma excited by nanosecond pulsed voltage. N{sub 2}(C{sup 3}{Pi}{sub u}) rotational and vibrational temperatures are almost the same with upper electrode powered with positive polarity and lower electrode grounded or upper electrode grounded and lower electrode powered with positive polarity. While the electron temperature is 12% higher with upper electrode powered with positive polarity and lower electrode grounded. When the frequency is below 2000 Hz, there is almost no influence of applied voltage amplitude and frequency on N{sub 2}(C{sup 3}{Pi}{sub u}) rotational, vibrational temperature and electron temperature. As the pressure decreases from 760 Torr to 5 Torr, N{sub 2}(C{sup 3}{Pi}{sub u}) rotational temperature remains almost unchanged, while its vibrational temperature decreases initially and then increases. The discharge mode changes from a filamentary type to a glow type around 80 Torr. In the filamentary mode, the electron temperature remains almost unchanged. In the glow mode, the electron temperature increases while the pressure decreases.

  3. Nitric Oxide Studies in Low Temperature Plasmas Generated with a Nanosecond Pulse Sphere Gap Electrical Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David Dean

    This dissertation presents studies of NO kinetics in a plasma afterglow using various nanosecond pulse discharges across a sphere gap. The discharge platform is developed to produce a diffuse plasma volume large enough to allow for laser diagnostics in a plasma that is rich in vibrationally-excited molecules. This plasma is characterized by current and voltage traces as well as ICCD and NO PLIF images that are used to monitor the plasma dimensions and uniformity. Temperature and vibrational loading measurements are performed via coherent anti-Stokes Raman spectroscopy (CARS). Absolute NO concentrations are obtained by laser-induce fluorescence (LIF) measurements, and N and O densities are found using two photon absorption laser-induced fluorescence (TALIF). For all dry air conditions studied, the NO behavior is characterized by a rapid rate of formation consistent with an enhanced Zeldovich process involving electronically-excited nitrogen species that are generated within the plasma. After several microseconds, the NO evolution is entirely controlled by the reverse Zeldovich process. These results show that under the chosen range of conditions and even in extreme instances of vibrational loading, there is no formation channel beyond ~2 musec. Both the NO formation and consumption mechanisms are strongly affected by the addition of fuel species, producing much greater NO concentrations in the afterglow.

  4. Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes

    SciTech Connect

    Li, Lee Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan

    2014-07-15

    In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

  5. An atmospheric air gas-liquid diffuse discharge excited by bipolar nanosecond pulse in quartz container used for water sterilization

    NASA Astrophysics Data System (ADS)

    Wang, Sen; Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Liu, Zhi-Jie; Tang, Kai; Song, Ying

    2013-12-01

    In this Letter, we report that the air gas-liquid diffuse discharge plasma excited by bipolar nanosecond pulse in quartz container with different bottom structures at atmospheric pressure. Optical diagnostic measurements show that bountiful chemically and biologically active species, which are beneficial for effective sterilization in some areas, are produced. Such diffuse plasmas are then used to treat drinking water containing the common microorganisms (Candida albicans and Escherichia coli). It is found that these plasmas can sterilize the microorganisms efficiently.

  6. Nanosecond Pulsed Discharge in Water without Bubbles: A Fundamental Study of Initiation, Propagation and Plasma Characteristics

    NASA Astrophysics Data System (ADS)

    Seepersad, Yohan

    The state of plasma is widely known as a gas-phase phenomenon, but plasma in liquids have also received significant attention over the last century. Generating plasma in liquids however is theoretically challenging, and this problem is often overcome via liquid-gas phase transition preceding the actual plasma formation. In this sense, plasma forms in gas bubbles in the liquid. Recent work at the Drexel Plasma Institute has shown that nanosecond pulsed electric fields can initiate plasma in liquids without any initial cavitation phase, at voltages below theoretical direct-ionization thresholds. This unique regime is poorly understood and does not fit into any current descriptive mechanisms. As with all new phenomena, a complete fundamental description is paramount to understanding its usefulness to practical applications. The primary goals of this research were to qualitatively and quantitatively understand the phenomenon of nanosecond pulsed discharge in liquids as a means to characterizing properties that may open up niche application possibilities. Analysis of the plasma was based on experimental results from non-invasive, sub-nanosecond time-resolved optical diagnostics, including direct imaging, transmission imaging (Schlieren and shadow), and optical emission spectroscopy. The physical characteristics of the plasma were studied as a function of variations in the electric field amplitude and polarity, liquid permittivity, and pulse duration. It was found that the plasma size and emission intensity was dependent on the permittivity of the liquid, as well as the voltage polarity, and the structure and dynamics were explained by a 'cold-lightning' mechanism. The under-breakdown dynamics at the liquid-electrode interface were investigated by transmission imaging to provide evidence for a novel mechanism for initiation based on the electrostriction. This mechanism was proposed by collaborators on the project and developed alongside the experimental work in this

  7. Temporal evolution of temperature and OH density produced by nanosecond repetitively pulsed discharges in water vapour at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Sainct, F. P.; Lacoste, D. A.; Kirkpatrick, M. J.; Odic, E.; Laux, C. O.

    2014-02-01

    We report on an experimental study of the temporal evolution of OH density and gas temperature in spark discharges created by nanosecond repetitively pulsed discharges in pure water vapour at 475 K and atmospheric pressure. The plasma was generated by 20 kV, 20 ns pulses, at a repetition frequency of 10 kHz. The temperature was measured during the discharge by optical emission spectroscopy of the second positive system of N2, and between two discharges by two-colour OH-planar laser induced fluorescence (OH-PLIF) using two pairs of rotational transitions. Between two successive discharges, the relative density of OH was measured by OH-PLIF and was found to decay very slowly, with a 1/e decay time of about 50 µs. With the use of a chemical kinetics model, the OH density was placed on an absolute scale.

  8. Two-stage energy thermalization mechanism in nanosecond pulse discharges in air and hydrogen-air mixtures

    NASA Astrophysics Data System (ADS)

    Lanier, Suzanne; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2015-04-01

    Time-resolved and spatially resolved temperature measurements, by pure rotational picosecond broadband coherent anti-Stokes Raman spectroscopy (CARS), and kinetic modeling calculations are used to study kinetics of energy thermalization in nanosecond pulse discharges in air and hydrogen-air mixtures. The diffuse filament, nanosecond pulse discharge (pulse duration ˜100 ns) is sustained between two spherical electrodes and is operated at a low pulse repetition rate to enable temperature measurements over a wide range of time scales after the discharge pulse. The experimental results demonstrate high accuracy of pure rotational ps CARS for thermometry measurements in highly transient non-equilibrium plasmas. Rotational-translational temperatures are measured for time delays after the pulse ranging from tens of ns to tens of ms, spanning several orders of magnitude of time scales for energy thermalization in non-equilibrium plasmas. In addition, radial temperature distributions across the plasma filament are measured for several time delays after the discharge pulse. Kinetic modeling calculations using a state-specific master equation kinetic model of reacting hydrogen-air plasmas show good agreement with experimental data. The results demonstrate that energy thermalization and temperature rise in these plasmas occur in two clearly defined stages, (i) ‘rapid’ heating, caused by collisional quenching of excited electronic states of N2 molecules by O2, and (ii) ‘slow’ heating, caused primarily by N2 vibrational relaxation by O atoms (in air) and by chemical energy release during partial oxidation of hydrogen (in H2-air). The results have major implications for plasma assisted combustion and plasma flow control.

  9. Investigation of nanosecond pulsed dielectric barrier discharge using plate-to-plate electrode with asymmetric dielectric arrangement in airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Atmospheric pressure dielectric barrier discharge plasma is produced in airflow by applying nanosecond high voltage pulses with peak voltage about 35 kV and rising time about 40 ns on a plate-to-plate electrode arrangement. The effects of airflow rate (0-50 m/s) on the discharge characteristics are investigated under different barrier conditions (the bare anode case and the bare cathode case). For both cases, the breakdown voltage and the time lag increase distinctly and the discharge intensity decreases sharply when the airflow rate increases from 0 to 30 m/s, and then keep almost constant until the airflow rate is further increased to 50 m/s. For the bare anode case (the cathode is covered by dielectric plate), the discharge mode transforms gradually from filamentary to diffuse discharge with the increasing airflow rate. While for the bare cathode case, some micro-discharge channels are still excited, though the discharge becomes more diffuse when the airflow rate is higher than 30 m/s. By acquiring the time-resolved images of the discharge, it is proved that it is the primary discharge which becomes diffuse when airflow is introduced and the following two discharges of the same voltage pulse occur principally at the positions where the primary discharge is more intense. And in both cases, the plasma temperatures are reduced, but the degree is different. All the phenomena can be explained mainly by the variation of the space charge distribution when the airflow is introduced into the discharge gap. And it is indicated that the bare anode case has an advantage in obtaining diffuse discharge.

  10. Transitions between corona, glow, and spark regimes of nanosecond repetitively pulsed discharges in air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.

    2010-05-01

    In atmospheric pressure air preheated from 300 to 1000 K, the nanosecond repetitively pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and interelectrode gap distance) of each discharge regime. In particular, the experimental conditions necessary for the glow regime of NRP discharges have been determined, with the notable result that there exists a minimum and maximum gap distance for its existence at a given ambient gas temperature. The minimum gap distance increases with decreasing gas temperature, whereas the maximum does not vary appreciably. To explain the experimental results, an analytical model is developed to explain the corona-to-glow (C-G) and glow-to-spark (G-S) transitions. The C-G transition is analyzed in terms of the avalanche-to-streamer transition and the breakdown field during the conduction phase following the establishment of a conducting channel across the discharge gap. The G-S transition is determined by the thermal ionization instability, and we show analytically that this transition occurs at a certain reduced electric field for the NRP discharges studied here. This model shows that the electrode geometry plays an important role in the existence of the NRP glow regime at a given gas temperature. We derive a criterion for the existence of the NRP glow regime as a function of the ambient gas temperature, pulse repetition frequency, electrode radius of curvature, and interelectrode gap distance.

  11. Plasma density enhancement in atmospheric-pressure dielectric-barrier discharges by high-voltage nanosecond pulse in the pulse-on period: a PIC simulation

    NASA Astrophysics Data System (ADS)

    Sang, Chaofeng; Sun, Jizhong; Wang, Dezhen

    2010-02-01

    A particle-in-cell (PIC) plus Monte Carlo collision simulation is employed to investigate how a sustainable atmospheric pressure single dielectric-barrier discharge responds to a high-voltage nanosecond pulse (HVNP) further applied to the metal electrode. The results show that the HVNP can significantly increase the plasma density in the pulse-on period. The ion-induced secondary electrons can give rise to avalanche ionization in the positive sheath, which widens the discharge region and enhances the plasma density drastically. However, the plasma density stops increasing as the applied pulse lasts over certain time; therefore, lengthening the pulse duration alone cannot improve the discharge efficiency further. Physical reasons for these phenomena are then discussed.

  12. Numerical studies of nitric oxide formation in nanosecond-pulsed discharge-stabilized flames of premixed methane/air.

    PubMed

    Bak, Moon Soo; Cappelli, Mark A

    2015-08-13

    A simulation is developed to investigate the kinetics of nitric oxide (NO) formation in premixed methane/air combustion stabilized by nanosecond-pulsed discharges. The simulation consists of two connected parts. The first part calculates the kinetics within the discharge while considering both plasma/combustion reactions and species diffusion, advection and thermal conduction to the surrounding flow. The second part calculates the kinetics of the overall flow after mixing the discharge flow with the surrounding flow to account for the effect that the discharge has on the overall kinetics. The simulation reveals that the discharge produces a significant amount of atomic oxygen (O) as a result of the high discharge temperature and dissociative quenching of excited state nitrogen by molecular oxygen. This atomic oxygen subsequently produces hydroxyl (OH) radicals. The fractions of these O and OH then undergo Zel'dovich reactions and are found to contribute to as much as 73% of the total NO that is produced. The post-discharge simulation shows that the NO survives within the flow once produced. PMID:26170428

  13. Investigation of nanosecond pulse dielectric barrier discharges in still air and in transonic flow by optical methods

    NASA Astrophysics Data System (ADS)

    Peschke, P.; Goekce, S.; Leyland, P.; Ott, P.

    2016-01-01

    In the present study the interaction of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators with aerodynamic flow up to transonic velocities was investigated. The primary focus was on the influence of the flow on the discharge and the effects of the discharge itself. In addition, the influence of the ns-DBD on a shock-wave was studied. The aim was to improve the understanding of the plasma-flow interaction, a topic that is not yet fully understood, in particular for ns-DBD. The actuator was integrated in two different models, a NACA 3506 compressor blade profile and a bump geometry at the bottom of the wind tunnel. The effect of the rapid energy deposition close to the discharge was examined with the phase-locked schlieren visualisation technique. Images of the plasma acquired with short exposure times revealed information on the discharge evolution. The results show a significant effect of the flow on the discharge characteristics, in particular due to the drop of static pressure. On the other hand, no significant effect of the ns-DBD on the flow was observed due to unfavourable flow conditions, which underlines the importance of the actuator’s placement.

  14. Pulsed nanosecond discharge in air at high specific deposited energy: fast gas heating and active particle production

    NASA Astrophysics Data System (ADS)

    Popov, N. A.

    2016-08-01

    The results of a numerical study on kinetic processes initiated by a pulsed nanosecond discharge in air at high specific deposited energy, when the dissociation degree of oxygen molecules is high, are presented. The calculations of the temporal dynamics of the electron concentration, density of atomic oxygen, vibrational distribution function of nitrogen molecules, and gas temperature agree with the experimental data. It is shown that quenching of electronically excited states of nitrogen N2(B3Πg), N2(С3Πu), N2(a‧1 Σ \\text{u}- ) by oxygen molecules leads to the dissociation of O2. This conclusion is based on the comparison of calculated dynamics of atomic oxygen in air, excited by a pulsed nanosecond discharge, with experimental data. In air plasma at a high dissociation degree of oxygen molecules ([O]/[O2]  >  10%), relaxation of the electronic energy of atoms and molecules in reactions with O atoms becomes extremely important. Active production of NO molecules and fast gas heating in the discharge plasma due to the quenching of electronically excited N2(B3Πg, C3Πu, a‧1 Σ \\text{u}- ) molecules by oxygen atoms is notable. Owing to the high O atom density, electrons are effectively detached from negative ions in the discharge afterglow. As a result, the decay of plasma in the afterglow is determined by electron–ion recombination, and the electron density remains relatively high between the pulses. An increase in the vibrational temperature of nitrogen molecules at the periphery of the plasma channel at time delay t  =  1–30 μs after the discharge is obtained. This is due to intense gas heating and, as a result, gas-dynamic expansion of a hot gas channel. Vibrationally excited N2(v) molecules produced near the discharge axis move from the axial region to the periphery. Consequently, at the periphery the vibrational temperature of nitrogen molecules is increased.

  15. Kinetics of excited states and radicals in a nanosecond pulse discharge and afterglow in nitrogen and air

    NASA Astrophysics Data System (ADS)

    Shkurenkov, Ivan; Burnette, David; Lempert, Walter R.; Adamovich, Igor V.

    2014-12-01

    The present kinetic modelling calculation results provide key new insights into the kinetics of vibrational excitation of nitrogen and plasma chemical reactions in nanosecond pulse, ‘diffuse filament’ discharges in nitrogen and dry air at a moderate energy loading per molecule, ˜0.1 eV per molecule. It is shown that it is very important to take into account Coulomb collisions between electrons because they change the electron energy distribution function and, as a result, strongly affect populations of excited states and radical concentrations in the discharge. The results demonstrate that the apparent transient rise of N2 ‘first level’ vibrational temperature after the discharge pulse, as detected in the experiments, is due to the net downward V-V energy transfer in N2-N2 collisions, which increases the N2(X 1Σ, v = 1) population. Finally, a comparison of the model's predictions with the experimental data shows that NO formation in the afterglow occurs via reactive quenching of multiple excited electronic levels of nitrogen molecule, N2\\ast , by O atoms. ) published in this volume, which focuses on the kinetic modelling of the experiments. This paper presents the results of the experiments.

  16. Temporal evolution of the electron density produced by nanosecond repetitively pulsed discharges in water vapor at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Sainct, Florent; Lacoste, Deanna; Kirkpatrick, Michael; Odic, Emmanuel; Laux, Christophe

    2014-10-01

    A study of plasma discharges produced by nanosecond repetitive pulses (NRP) in water vapor at 450 K and 1 atm is presented. The plasma was generated between two point electrodes with 20-ns duration, high-voltage (0--20 kV) pulses, at a repetition frequency of 10 kHz, in the spark regime (2 mJ/pulse). Atomic lines measured by optical emission spectroscopy were used to determine the electron number density in this non-equilibrium water-vapor plasma. The broadenings and shifts of the Hα and Hβ lines of the hydrogen Balmer series and of the atomic oxygen triplet at 777 nm were analyzed. For a maximum reduced electric field of about 200 Td, a maximum electron density of 2 × 1018 cm-3 was measured, corresponding to an ionization level of about 10 %. This ionization level is two orders of magnitude higher than the one obtained for similar NRP discharges in air at atmospheric pressure.

  17. Uniform and non-uniform modes of nanosecond-pulsed dielectric barrier discharge in atmospheric air: fast imaging and spectroscopic measurements of electric field

    PubMed Central

    Liu, Chong; Dobrynin, Danil; Fridman, Alexander

    2014-01-01

    In this study, we report experimental results on fast ICCD imaging of development of nanosecond-pulsed dielectric barrier discharge (DBD) in atmospheric air and spectroscopic measurements of electric field in the discharge. Uniformity of the discharge images obtained with nanosecond exposure times were analyzed using chi-square test. The results indicate that DBD uniformity strongly depends on applied (global) electric field in the discharge gap, and is a threshold phenomenon. We show that in the case of strong overvoltage on the discharge gap (provided by fast rise times), there is transition from filamentary to uniform DBD mode which correlates to the corresponding decrease of maximum local electric field in the discharge. PMID:25071294

  18. Influence of air flow parameters on nanosecond repetitively pulsed discharges in a pin-annular electrode configuration

    NASA Astrophysics Data System (ADS)

    Heitz, Sylvain A.; Moeck, Jonas P.; Schuller, Thierry; Veynante, Denis; Lacoste, Deanna A.

    2016-04-01

    The effect of various air flow parameters on the plasma regimes of nanosecond repetitively pulsed (NRP) discharges is investigated at atmospheric pressure. The two electrodes are in a pin-annular configuration, transverse to the mean flow. The voltage pulses have amplitudes up to 15 kV, a duration of 10 ns and a repetition frequency ranging from 15 to 30 kHz. The NRP corona to NRP spark (C-S) regime transition and the NRP spark to NRP corona (S-C) regime transition are investigated for different steady and harmonically oscillating flows. First, the strong effect of a transverse flow on the C-S and S-C transitions, as reported in previous studies, is verified. Second, it is shown that the azimuthal flow imparted by a swirler does not affect the regime transition voltages. Finally, the influence of low frequency harmonic oscillations of the air flow, generated by a loudspeaker, is studied. A strong effect of frequency and amplitude of the incoming flow modulation on the NRP plasma regime is observed. Results are interpreted based on the cumulative effect of the NRP discharges and an analysis of the residence times of fluid particles in the inter-electrode region.

  19. Dependence of MnOx Catalyst Position on Toluene Decomposition using Nanosecond Pulsed Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Han, Junkai; Ogasawara, Akihiko; Wang, Jinlong; Wang, Douyan; Namihira, Takao; Sasaki, Mitsuru; Akiyama, Hidenori; Zhang, Pengyi; Kumamoto University Collaboration; Tsinghua University Collaboration

    2015-09-01

    Plasma catalysis, which combines advantages of high selectivity due to the catalysis and with fast ignition and response due to plasma technique, appears to be a promising technology to simultaneously resolve both efficiency and workability issues. In practice, a catalyst can be combined with NTP in two ways: by introducing the catalyst in the discharge zone (in-plasma catalytic reactor) or by placing the catalyst after the discharge zone (post-plasma catalytic reactor). This work aims to clarify combined effects by coupling MnOx catalyst with ns pulsed discharge system for decomposition of 100 ppm toluene utilizing three methods: plasma alone, in-plasma catalytic and post-plasma catalytic methods, in atmospheric pressure at room temperature. As the results, toluene removal ratio reached 100% at approximately 50 J/L under the in-plasma catalytic and post-plasma catalytic methods, while it was 70% under the plasma alone method. The concentrations of O3, HCOOH, and CO under the plasma alone method were higher compared with the in-plasma catalytic or post-plasma catalytic methods. CO2 selectivity under the post-plasma catalytic method was the highest of these three methods when toluene removal ratio exceeded 80%.

  20. Surface charge dynamics and OH and H number density distributions in near-surface nanosecond pulse discharges at a liquid / vapor interface

    NASA Astrophysics Data System (ADS)

    Winters, Caroline; Petrishchev, Vitaly; Yin, Zhiyao; Lempert, Walter R.; Adamovich, Igor V.

    2015-10-01

    The present work provides insight into surface charge dynamics and kinetics of radical species reactions in nanosecond pulse discharges sustained at a liquid-vapor interface, above a distilled water surface. The near-surface plasma is sustained using two different discharge configurations, a surface ionization wave discharge between two exposed metal electrodes and a double dielectric barrier discharge. At low discharge pulse repetition rates (~100 Hz), residual surface charge deposition after the discharge pulse is a minor effect. At high pulse repetition rates (~10 kHz), significant negative surface charge accumulation over multiple discharge pulses is detected, both during alternating polarity and negative polarity pulse trains. Laser induced fluorescence (LIF) and two-photon absorption LIF (TALIF) line imaging are used for in situ measurements of spatial distributions of absolute OH and H atom number densities in near-surface, repetitive nanosecond pulse discharge plasmas. Both in a surface ionization wave discharge and in a double dielectric barrier discharge, peak measured H atom number density, [H] is much higher compared to peak OH number density, due to more rapid OH decay in the afterglow between the discharge pulses. Higher OH number density was measured near the regions with higher plasma emission intensity. Both OH and especially H atoms diffuse out of the surface ionization wave plasma volume, up to several mm from the liquid surface. Kinetic modeling calculations using a quasi-zero-dimensional H2O vapor / Ar plasma model are in qualitative agreement with the experimental data. The results demonstrate the experimental capability of in situ radical species number density distribution measurements in liquid-vapor interface plasmas, in a simple canonical geometry that lends itself to the validation of kinetic models.

  1. Study on the mode-transition of nanosecond-pulsed dielectric barrier discharge between uniform and filamentary by controlling pressures and pulse repetition frequencies

    NASA Astrophysics Data System (ADS)

    Yu, S.; Pei, X.; Hasnain, Q.; Nie, L.; Lu, X.

    2016-02-01

    In this paper, we investigate the temporally resolved evolution of the nanosecond pulsed dielectric barrier discharge (DBD) in a moderate 6 mm discharge gap under various pressures and pulse repetition frequencies (PRFs) by intensified charge-coupled device (ICCD) images, using dry air and its components oxygen and nitrogen. It is found that the pressures are very different when the mode transits between uniform and filamentary in air, oxygen, and nitrogen. The PRFs can also obviously affect the mode-transition. The transition mechanism in the pulsed DBD is not Townsend-to-Streamer, which is dominant in the traditional alternating-voltage DBD. The pulsed DBD in a uniform mode develops in the form of plane ionization wave due to overlap of primary avalanches, while the increase in pressure disturbs the overlap and discharge develops in streamer, corresponding to the filamentary mode. Increasing the initial electron density by pre-ionization may contribute to discharge uniformity at higher pressures. We also found that the dependence of homogeneity upon PRF is a non-monotonic one.

  2. A diffuse plasma generated by bipolar nanosecond pulsed dielectric barrier discharge in nitrogen

    NASA Astrophysics Data System (ADS)

    Jia, Li; Yang, De-Zheng; Shi, Heng-Chao; Wang, Wen-Chun; Wang, Sen

    2014-05-01

    In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3Πu → B3 Πg, 0-2) and the first negative bands of N2+ (B2 Σu+ → X2 Σg+, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH (A 2Σ → X2Π, 0-0) and N2+ (B2 Σu+ → X2 Σg+, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH(A2Σ → X2Π, 0-0) and N2+ (B2 Σu+ → X2 Σg+, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3Πu → B3Πg, 0-0, 337.1 nm) and OH (A2Σ → X2Π, 0-0) are more greater than that on the emission intensity of N2+ (B2 Σu+ → X2 Σg+, 0-0, 391.4 nm).

  3. A comparative study for the inactivation of multidrug resistance bacteria using dielectric barrier discharge and nano-second pulsed plasma

    PubMed Central

    Hoon Park, Ji; Kumar, Naresh; Hoon Park, Dae; Yusupov, Maksudbek; Neyts, Erik C.; Verlackt, Christof C. W.; Bogaerts, Annemie; Ho Kang, Min; Sup Uhm, Han; Ha Choi, Eun; Attri, Pankaj

    2015-01-01

    Bacteria can be inactivated through various physical and chemical means, and these have always been the focus of extensive research. To further improve the methodology for these ends, two types of plasma systems were investigated: nano-second pulsed plasma (NPP) as liquid discharge plasma and an Argon gas-feeding dielectric barrier discharge (Ar-DBD) as a form of surface plasma. To understand the sterilizing action of these two different plasma sources, we performed experiments with Staphylococcus aureus (S. aureus) bacteria (wild type) and multidrug resistant bacteria (Penicillum-resistant, Methicillin-resistant and Gentamicin-resistant). We observed that both plasma sources can inactivate both the wild type and multidrug-resistant bacteria to a good extent. Moreover, we observed a change in the surface morphology, gene expression and β-lactamase activity. Furthermore, we used X-ray photoelectron spectroscopy to investigate the variation in functional groups (C-H/C-C, C-OH and C=O) of the peptidoglycan (PG) resulting from exposure to plasma species. To obtain atomic scale insight in the plasma-cell interactions and support our experimental observations, we have performed molecular dynamics simulations to study the effects of plasma species, such as OH, H2O2, O, O3, as well as O2 and H2O, on the dissociation/formation of above mentioned functional groups in PG. PMID:26351132

  4. Influence of pulsed nanosecond volume discharge in atmospheric-pressure air on the electrical characteristics of MCT epitaxial films

    NASA Astrophysics Data System (ADS)

    Grigoryev, Denis V.; Voitsekhovskii, Alexandr V.; Lozovoy, Kirill A.; Nesmelov, Sergey N.; Dzyadukh, Stanislav M.; Tarasenko, Viktor F.; Shulepov, Michail A.; Dvoretskii, Sergei A.

    2015-12-01

    The purpose of this paper was investigating the effect of volume nanosecond discharge in air at atmospheric pressure on the electro-physical properties of the HgCdTe (MCT) epitaxial films grown by molecular beam epitaxy. Hall measurements of electro-physical parameters of MCT samples after irradiation have shown that there is a layer of epitaxial films exhibiting n-type conductivity that is formed in the near-surface area. After more than 600 pulses of influence parameters and thickness of the resulting n-layer is such that the measured field dependence of Hall coefficient corresponds to the material of n-type conductivity. Also it is shown that the impact of the discharge leads to significant changes in electro-physical characteristics of MIS structures. This fact is demonstrated by increase in density of positive fixed charge, change in the hysteresis type of the capacitance-voltage characteristic, an increase in density of surface states. The preliminary results show that it is possible to use such actions in the development of technologies of the controlled change in the properties of MCT.

  5. Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, De-zheng; Wang, Wen-chun; Liu, Zhi-jie; Wang, Sen; Jiang, Peng-chao; Zhang, Shuai

    2014-09-01

    In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20 K lower than the unipolar discharge plasma.

  6. A simple method for experimental determination of electron temperature and electron density in a nanosecond pulsed longitudinal discharge used for excitation of high-power atomic and ionic metal and metal halide vapour lasers

    NASA Astrophysics Data System (ADS)

    Temelkov, K. A.; Vuchkov, N. K.

    2016-05-01

    A simple method based on the time-resolved measurement of electrical discharge parameters, such as tube voltage and discharge current, is developed and applied for determination of electron temperature and electron density in the discharge period of a nanosecond pulsed longitudinal discharge, exciting high-power DUV Cu+ Ne-CuBr, He-Hg+ and He-Sr+ lasers.

  7. Decomposition of three volatile organic compounds by nanosecond pulsed corona discharge: Study of by-product formation and influence of high voltage pulse parameters

    SciTech Connect

    Jarrige, Julien; Vervisch, Pierre

    2006-06-01

    Increasing concerns over atmospheric pollution has motivated research into technologies able to remove volatile organic compounds (VOC's) from gas streams. The aim of this paper is to understand the chemical and physical mechanisms implied in the decomposition of VOC's in a filamentary nonthermal plasma discharge. Experiments have been carried out on three pollutants (propane, propene, and isopropyl alcohol) in dry air at atmospheric pressure using a wire to cylinder corona discharge generated by a homemade nanosecond rise time high voltage pulse generator. The resulting plasma efficiently destructs propane, propene, or isopropyl alcohol at a concentration of 500 ppm with low specific input energies (less than 500 J/L), but the poor oxidation rate leads to the formation of numerous by-products (acetone, formaldehyde, formic acid, and methyl nitrate) whose concentration can reach some hundreds of ppm. We also investigated the effect of pulse parameters on VOC removal efficiency. Neither pulse peak value nor rise time (in the range of 4-12 ns) appears to have a significant influence on the VOC decomposition rates. Therefore, we believe that the way the energy is deposited in the plasma does not modify the density of active species (radicals, ions) in the streamers. The production of energetic electrons is not enhanced by the external applied field, and the only effective parameter may be the local field in the streamer head, which is almost the same (around 500 Td) whatever the voltage (above the inception value)

  8. A Simulation of the Effects of Varying Repetition Rate and Pulse Width of Nanosecond Discharges on Premixed Lean Methane-Air Combustion

    DOE PAGESBeta

    Bak, Moon Soo; Cappelli, Mark A.

    2012-01-01

    Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond repetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied from 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger amounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested repetition rates. The shorter pulse width is found to favor the production of species in higher electronicmore » states, but the varying effects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that determines the extent of stabilization over this range of discharge properties studied.« less

  9. Evolution of metastable state molecules N2(A3 Σu+) in a nanosecond pulsed discharge: A particle-in-cell/Monte Carlo collisions simulation

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Sun, Jizhong; Feng, Chunlei; Bai, Jing; Ding, Hongbin

    2012-01-01

    A particle-in-cell plus Monte Carlo collisions method has been employed to investigate the nitrogen discharge driven by a nanosecond pulse power source. To assess whether the production of the metastable state N2(A3 Σu+) can be efficiently enhanced in a nanosecond pulsed discharge, the evolutions of metastable state N2(A3 Σu+) density and electron energy distribution function have been examined in detail. The simulation results indicate that the ultra short pulse can modulate the electron energy effectively: during the early pulse-on time, high energy electrons give rise to quick electron avalanche and rapid growth of the metastable state N2(A3 Σu+) density. It is estimated that for a single pulse with amplitude of -9 kV and pulse width 30 ns, the metastable state N2(A3 Σu+) density can achieve a value in the order of 109 cm-3. The N2(A3 Σu+) density at such a value could be easily detected by laser-based experimental methods.

  10. 2D numerical modelling of gas temperature in a nanosecond pulsed longitudinal He-SrBr2 discharge excited in a high temperature gas-discharge tube for the high-power strontium laser

    NASA Astrophysics Data System (ADS)

    Chernogorova, T. P.; Temelkov, K. A.; Koleva, N. K.; Vuchkov, N. K.

    2016-05-01

    An active volume scaling in bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He-SrBr2 discharge is carried out. Considering axial symmetry and uniform power input, a 2D model (r, z) is developed by numerical methods for determination of gas temperature in a new large-volume high-temperature discharge tube with additional incompact ZrO2 insulation in the discharge free zone, in order to find out the optimal thermal mode for achievement of maximal output laser parameters. A 2D model (r, z) of gas temperature is developed by numerical methods for axial symmetry and uniform power input. The model determines gas temperature of nanosecond pulsed longitudinal discharge in helium with small additives of strontium and bromine.

  11. 2D numerical modelling of the gas temperature in a high-temperature high-power strontium atom laser excited by nanosecond pulsed longitudinal discharge in a He-SrBr2 mixture

    NASA Astrophysics Data System (ADS)

    Chernogorova, T. P.; Temelkov, K. A.; Koleva, N. K.; Vuchkov, N. K.

    2014-05-01

    Assuming axial symmetry and a uniform power input, a 2D model (r, z) is developed numerically for determination of the gas temperature in the case of a nanosecond pulsed longitudinal discharge in He-SrBr2 formed in a newly-designed large-volume high-temperature discharge tube with additional incompact ZrO2 insulation in the discharge-free zone, in order to find the optimal thermal mode for achievement of maximal output laser parameters. The model determines the gas temperature of a nanosecond pulsed longitudinal discharge in helium with small additives of strontium and bromine.

  12. Simulations of atmospheric pressure discharge in a high-voltage nanosecond pulse using the particle-in-cell Monte Carlo collision model in noble gases

    NASA Astrophysics Data System (ADS)

    Shi, Feng; Wang, Dezhen; Ren, Chunsheng

    2008-06-01

    Atmospheric pressure discharge nonequilibrium plasmas have been applied to plasma processing with modern technology. Simulations of discharge in pure Ar and pure He gases at one atmospheric pressure by a high voltage trapezoidal nanosecond pulse have been performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model coupled with a renormalization and weighting procedure (mapping algorithm). Numerical results show that the characteristics of discharge in both inert gases are very similar. There exist the effects of local reverse field and double-peak distributions of charged particles' density. The electron and ion energy distribution functions are also observed, and the discharge is concluded in the view of ionization avalanche in number. Furthermore, the independence of total current density is a function of time, but not of position.

  13. Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Du, Hai; Shi, Zhiwei; Cheng, Keming; Wei, Dechen; Li, Zheng; Zhou, Danjie; He, Haibo; Yao, Junkai; He, Chengjun

    2016-06-01

    Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

  15. A ‘frozen electric-field’ approach to simulate repetitively pulsed nanosecond plasma discharges and ignition of hydrogen-air mixtures

    NASA Astrophysics Data System (ADS)

    Nagaraja, Sharath; Yang, Vigor

    2014-09-01

    High-fidelity modelling of nanosecond repetitively pulsed discharges (NRPDs) is burdened by the multiple time and length scales and large chemistry mechanisms involved, which prohibit detailed analyses and parametric studies. In the present work, we propose a ‘frozen electric-field’ modelling approach to expedite the NRPD simulations without adverse effects on the solution accuracy. First, a burst of nanosecond voltage pulses is simulated self-consistently until the discharge reaches a stationary state. The calculated spatial distributions and temporal evolution of the electric field, electron density and electron energy during the last pulse are then stored in a library and the electrical characteristics of subsequent pulses are frozen at these values. This strategy allows the timestep for numerical integration to be increased by four orders of magnitude (from 10-13 to 10-9 s), thereby significantly improving the computational efficiency of the process. Reduced calculations of a burst of 50 discharge pulses show good agreement with the predictions from a complete plasma model (electrical characteristics calculated during each pulse). The error in species densities is less than 20% at the centre of the discharge volume and about 30% near the boundaries. The deviations in temperature, however, are much lower, at 5% in the entire domain. The model predictions are in excellent agreement with measured ignition delay times and temperatures in H2-air mixtures subject to dielectric barrier NRPD over a pressure range of 54-144 Torr with equivalence ratios of 0.7-1.2. The OH density increases with pressure and triggers low-temperature fuel oxidation, which leads to rapid temperature rise and ignition. The ignition delay decreases by a factor of 2, with an increase in pressure from 54 to 144 Torr. In contrast, an increase in the H2-air equivalence ratio from 0.7 to 1.2 marginally decreases the ignition delay by about 20%. This behaviour is attributed to the insensitivity

  16. Effect of Airflows on Repetitive Nanosecond Volume Discharges

    NASA Astrophysics Data System (ADS)

    Tang, Jingfeng; Wei, Liqiu; Huo, Yuxin; Song, Jian; Yu, Daren; Zhang, Chaohai

    2016-03-01

    Atmospheric pressure discharges excited by repetitive nanosecond pulses have attracted significant attention for various applications. In this paper, a plate-plate discharge with airflows is excited by a repetitive nanosecond pulse generator. Under different experiment conditions, the applied voltages, discharge currents, and discharge images are recorded. The plasma images presented here indicate that the volume discharge modes vary with airflow speeds, and a diffuse and homogeneous volume discharge occurs at the speed of more than 35 m/s. The role of airflows provides different effects on the 2-stage pulse discharges. The 1st pulse currents nearly maintain consistency for different airflow speeds. However, the 2nd pulse current has a change trend of first decreasing and then rapidly increasing, and the value difference for 2nd pulse currents is about 20 A under different airflows. In addition, the experimental results are discussed according to the electrical parameters and discharge images. supported by National Natural Science Foundation of China (Nos. 51006027, 51437002, and 51477035)

  17. Time-resolved investigation of nanosecond discharge in dense gas sustained by short and long high-voltage pulse

    NASA Astrophysics Data System (ADS)

    Yatom, S.; Gleizer, J. Z.; Levko, D.; Vekselman, V.; Gurovich, V.; Hupf, E.; Hadas, Y.; Krasik, Ya. E.

    2011-12-01

    The results of experimental and numerical studies of the generation of runaway electrons (RAE) in a pressurized air-filled diode under the application of 20 ns, 5 ns and 1 ns duration high-voltage pulses with an amplitude up to 160 kV are presented. It is shown that with a 1 ns pulse, RAE with energy >=20 keV reach the anode prior to the formation of the plasma channel between the cathode and anode. Conversely, with 20 ns or 5 ns pulses, RAE with energy >=20 keV were obtained at the anode only after the formation of the plasma channel. In addition, the high- and low-impedance stages of the development of the discharge were found. Finally, a comparison between experimental and numerical simulation results is presented.

  18. Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric-pressure N2 and N2/H2O mixtures

    NASA Astrophysics Data System (ADS)

    van der Horst, R. M.; Verreycken, T.; van Veldhuizen, E. M.; Bruggeman, P. J.

    2012-08-01

    In this contribution, nanosecond pulsed discharges in N2 and N2/0.9% H2O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high-voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N2(C-B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emission when H2O is added is very similar, except the small contribution of Hα and the intensity of the molecular N2(C-B) emission is less. The gas temperature during the ignition phase is about 350 K, during the discharge the gas temperature increases and is 1 µs after ignition equal to 750 K. The electron density is obtained by the broadening of the N emission line at 746 nm and, if water is added, the Hα line. The electron density reaches densities up to 4 × 1024 m-3. Addition of water has no significant influence on the gas temperature and electron density. The diagnostics used in this study are described in detail and the validity of different techniques is compared with previously reported results of other groups.

  19. Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Tang, Kai; Wang, Wenchun; Yang, Dezheng; Zhang, Shuai; Yang, Yang; Liu, Zhijie

    2013-08-01

    In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3Πu → B3Πg 1-3) and N2 (C3Πu → B3Πg 0-2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3Πu → B3Πg, 0-0, 337.1 nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3Πu → B3Πg, 0-0, 337.1 nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

  20. Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure.

    PubMed

    Tang, Kai; Wang, Wenchun; Yang, Dezheng; Zhang, Shuai; Yang, Yang; Liu, Zhijie

    2013-08-01

    In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C(3)Πu→B(3)Πg 1-3) and N2 (C(3)Πu→B(3)Πg 0-2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C(3)Πu→B(3)Πg, 0-0, 337.1 nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C(3)Πu→B(3)Πg, 0-0, 337.1 nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material. PMID:23673240

  1. Nitric oxide density measurements in air and air/fuel nanosecond pulse discharges by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Uddi, M.; Jiang, N.; Adamovich, I. V.; Lempert, W. R.

    2009-04-01

    Laser induced fluorescence is used to measure absolute nitric oxide concentrations in air, methane-air and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single pulse, 20 kV peak voltage, 25 ns pulse duration discharge. A mixture of NO and nitrogen with known composition (4.18 ppm NO) is used for calibration. Peak NO density in air at 60 Torr, after a single pulse, is ~8 × 1012 cm-3 (~4.14 ppm) occurring at ~250 µs after the pulse, with decay time of ~16.5 ms. Peak NO atom mole fraction in a methane-air mixture with equivalence ratio of phiv = 0.5 is found to be approximately equal to that in air, with approximately the same rise and decay rate. In an ethylene-air mixture (also with equivalence ratio of phiv = 0.5), the rise and decay times are comparable to air and methane-air, but the peak NO concentration is reduced by a factor of approximately 2.5. Spontaneous emission measurements show that excited electronic states N2(C 3Π) and NO(A 2Σ) in air at P = 60 Torr decay within ~20 ns and ~1 µs, respectively. Kinetic modelling calculations incorporating air plasma kinetics complemented with the GRI Mech 3.0 hydrocarbon oxidation mechanism are compared with the experimental data using three different NO production mechanisms. It is found that NO concentration rise after the discharge pulse is much faster than predicted by Zel'dovich mechanism reactions, by two orders of magnitude, but much slower compared with reactions of electronically excited nitrogen atoms and molecules, also by two orders of magnitude. It is concluded that processes involving long lifetime (~100 µs) metastable states, such as N2(X 1Σ,v) and O2(b 1Σ), formed by quenching of the metastable N2(A 3Σ) state by ground electronic state O2, may play a dominant role in NO formation. NO decay, in all cases, is found to be dominated by the reverse Zel'dovich reaction, NO + O → N + O2, as well as by conversion into NO2 in a reaction of NO with ozone.

  2. Measurement of OH, O, and NO densities and their correlations with mouse melanoma cell death rate treated by a nanosecond pulsed streamer discharge

    NASA Astrophysics Data System (ADS)

    Yagi, Ippei; Shirakawa, Yuki; Hirakata, Kenta; Akiyama, Taketoshi; Yonemori, Seiya; Mizuno, Kazue; Ono, Ryo; Oda, Tetsuji

    2015-10-01

    Mouse melanoma cells in a culture medium are treated using a nanosecond pulsed streamer discharge plasma and the correlations between the rate of cell death and the densities of reactive species (OH, O, and NO) in the plasma are measured. The plasma is irradiated onto the culture medium surface with a vertical gas flow of an O2/N2 mixture from a glass tube at various gas flow rates and O2 concentrations. The densities of the reactive species are measured very close to the culture medium surface, where the reactive species interact with the culture medium, using laser-induced fluorescence. In the case of the N2 discharge (O2 = 0%), an increase in gas flow rate decreases OH density because it lowers the water vapor concentration by diluting the vapor, which is required for OH production. The increase in gas flow rate also leads to a decreased cell death rate. In the case of the O2/N2 discharge, on the other hand, an increase in O2 concentration at a fixed flow rate does not affect the rate of cell death, although it considerably changes the O and NO densities. These findings indicate that some reactive species derived from water vapor such as OH are responsible for the melanoma cell death, whereas those from O2, such as O and NO, are less likely responsible. They also indicate the importance of water evaporation from the culture medium surface in cell treatment.

  3. Thyratron-choke switch for high-current nanosecond pulses

    SciTech Connect

    Vizir, V.A.; Chervyakov, V.V.; Laier, A.V.; Shubkin, N.G.

    1986-06-01

    Electric-discharge excimer lasers and high-current nanosecond accelerators, i.e., linear induction accelerators, require highcurrent nanosecond pulse (HCNP) generators with high repetition frequencies. This paper describes a design and some formulas for a thyratron-choke assembly for switching high-current nanosecond pulses, which consists of a thyratron and a single turn nonlinear choke connected in series with it; these are enclosed in a coaxial shield. The operation of a thyratronchoke assembly with a TGI1-1000/25 thyratron in switching pulses of up to 10kA with a duration of 250 nsec is studied. The current rise rate is 200 kA/usec, the pulse repetition frequency is 200 Hz, and the average switched power is 5kW.

  4. Kinetics of NO formation and decay in nanosecond pulse discharges in Air, H2-Air, and C2H4-Air mixtures

    NASA Astrophysics Data System (ADS)

    Burnette, David; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-04-01

    Time-resolved, absolute NO and N atom number densities are measured by NO Laser Induced Fluorescence (LIF) and N Two-Photon Absorption LIF in a diffuse plasma filament, nanosecond pulse discharge in dry air, hydrogen-air, and ethylene-air mixtures at 40 Torr, over a wide range of equivalence ratios. The results are compared with kinetic modeling calculations incorporating pulsed discharge dynamics, kinetics of vibrationally and electronically excited states of nitrogen, plasma chemical reactions, and radial transport. The results show that in air afterglow, NO decay occurs primarily by the reaction with N atoms, NO  +  N  →  N2  +  O. In the presence of hydrogen, this reaction is mitigated by reaction of N atoms with OH, N  +  OH  →  NO  +  H, resulting in significant reduction of N atom number density in the afterglow, additional NO production, and considerably higher NO number densities. In fuel-lean ethylene-air mixtures, a similar trend (i.e. N atom concentration reduction and NO number density increase) is observed, although [NO] increase on ms time scale is not as pronounced as in H2-air mixtures. In near-stoichiometric and fuel-lean ethylene-air mixtures, when N atom number density was below detection limit, NO concentration was measured to be lower than in air plasma. These results suggest that NO kinetics in hydrocarbon-air plasmas is more complex compared to air and hydrogen-air plasmas, additional NO reaction pathways may well be possible, and their analysis requires further kinetic modeling calculations.

  5. A nanosecond surface dielectric barrier discharge in air at high pressures and different polarities of applied pulses: transition to filamentary mode

    NASA Astrophysics Data System (ADS)

    Stepanyan, S. A.; Starikovskiy, A. Yu; Popov, N. A.; Starikovskaia, S. M.

    2014-08-01

    The development of a nanosecond surface dielectric barrier discharge in air at pressures 1-6 bar is studied. At atmospheric pressure, the discharge develops as a set of streamers starting synchronously from the high-voltage electrode and propagating along the dielectric layer. Streamers cover the dielectric surface creating a ‘quasi-uniform’ plasma layer. At high pressures and high voltage amplitudes on the cathode, filamentation of the discharge is observed a few nanoseconds after the discharge starts. Parameters of the observed ‘streamers-to-filaments’ transition are measured; physics of transition is discussed on the basis of theoretical estimates and numerical modeling. Ionization-heating instability on the boundary of the cathode layer is suggested as a mechanism of filamentation.

  6. Nanosecond component in a femtosecond laser pulse

    SciTech Connect

    Shneider, M. N.; Semak, V. V.; Zhang Zhili

    2012-11-15

    Experimental and computational results show that the coherent microwave scattering from a laser-induced plasma can be used for measuring the quality of a fs laser pulse. The temporal dynamics of the microwave scattered signal from the fs-laser induced plasma can be related to the effect of nanosecond tail of the fs laser pulse.

  7. NO density and gas temperature measurements in atmospheric pressure nanosecond repetitively pulsed (NRP) discharges by Mid-IR QCLAS

    NASA Astrophysics Data System (ADS)

    Simeni Simeni, Marien; Stancu, Gabi-Daniel; Laux, Christophe

    2014-10-01

    Nitric oxide is a key species for many processes: in combustion, in human skin physiology... Recently, NO-ground state absolute density measurements produced by atmospheric pressure NRP discharges were carried out in air as a function of the discharge parameters, using Quantum Cascade Laser Absorption Spectroscopy. These measurements were space averaged and performed in the post-discharge region in a large gas volume. Here we present radial profiles of NO density and temperature measured directly in the discharge for different configurations. Small plasma volume and species densities, high temperature and EM noise environment make the absorption diagnostic challenging. For this purpose the QCLAS sensitivity was improved using a two-detector system. We conducted lateral absorbance measurements with a spatial resolution of 300 μm for two absorption features at 1900.076 and 1900.517 cm-1. The radial temperature and NO density distributions were obtained from the Abel inverted lateral measurements. Time averaged NO densities of about 1.E16 cm-3 and gas temperature of about 1000K were obtained in the center of the discharge. PLASMAFLAME Project (Grant No ANR-11-BS09-0025).

  8. Enhanced window breakdown dynamics in a nanosecond microwave tail pulse

    SciTech Connect

    Chang, Chao; Zhu, Meng; Li, Shuang; Xie, Jialing; Yan, Kai; Luo, Tongding; Zhu, Xiaoxin; Verboncoeur, John

    2014-06-23

    The mechanisms of nanosecond microwave-driven discharges near a dielectric/vacuum interface were studied by measuring the time- and space-dependent optical emissions and pulse waveforms. The experimental observations indicate multipactor and plasma developing in a thin layer of several millimeters above interface. The emission brightness increases significantly after main pulse, but emission region widens little. The mechanisms are studied by analysis and simulation, revealing intense ionization concentrated in a desorbed high-pressure layer, leading to a bright light layer above surface; the lower-voltage tail after main pulse contributes to heat electron energy tails closer to excitation cross section peaks, resulting in brighter emission.

  9. Effect of Pulse Nanosecond Volume Discharge in Air at Atmospheric Pressure on Electrical Properties of Mis Structures Based on p-HgCdTe Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.; Grigor'ev, D. V.; Tarasenko, V. F.; Shulepov, M. A.

    2015-11-01

    The effect of the pulse nanosecond volume discharge in air at atmospheric pressure on the admittance of MIS structures based on MBE graded-gap p-Hg0.78Cd0.22Te is studied in a wide range of frequencies and temperatures. It is shown that the impact of the discharge leads to significant changes in electrical characteristics of MIS structures (the density of positive fixed charge increases), to the changes in the nature of the hysteresis of capacitance-voltage characteristics, and to an increase in the density of surface states. A possible reason for the changes in the characteristics of MIS structures after exposure to the discharge is substantial restructuring of the defect-impurity system of the semiconductor near the interface.

  10. Nanosecond discharge in sulfur hexafluoride and the generation of an ultrashort avalanche electron beam

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Burachenko, A. G.; Erofeev, M. V.; Lomaev, M. I.; Rybka, D. V.; Sorokin, D. A.; Tarasenko, V. F.

    2008-06-01

    A discharge in the presence of a nonuniform electric field and the generation of an ultrashort avalanche electron beam (UAEB) are studied in the insulating gas SF6 at the pressures 0.01 2.50 atm. High-voltage nanosecond pulses (about 150 and 250 kV) and the voltage pulses with an amplitude of 25 kV and a duration of tens of nanoseconds are applied across the gap. An electron beam is obtained behind the AlBe foil with a thickness of 45 μm at a sulfur hexafluoride pressure in a gas-filled diode of up to 2 atm. It is demonstrated that, at relatively high pressures (greater than 1 atm) and in the presence of high-voltage nanosecond pulses across the gap, the UAEB pulse FWHM increases. The spectra of the diffuse and contracted discharges in sulfur hexafluoride are measured.

  11. Dynamics of plasma evolution in a nanosecond underwater discharge

    NASA Astrophysics Data System (ADS)

    Marinov, Ilya; Starikovskaia, Svetlana; Rousseau, Antoine

    2014-06-01

    A positive discharge in water is generated by applying a 30 ns high-voltage (HV) pulse on a micrometre scale electrode. The applied voltage ranges from 6 to 15 kV and a fast plasma propagating mode is launched with a velocity of up to 60 km s-1. Time-resolved shadowgraphy and spectroscopy are performed to monitor the time evolution of the discharge structure and of the plasma emission spectra. By analysing the dynamics of the shock front velocity and the lateral expansion of the plasma channel, it is possible to estimate the pressure at the ignition of the plasma by two independent methods: very good agreement is found at 6 kV giving initial pressures of 0.4 GPa and 0.3 GPa, respectively. At 15 kV, only the shock front velocity method is applicable under our experimental conditions, giving an estimate of the initial pressure of 5.8 GPa. Such high initial pressures show that, under a nanosecond HV pulse, the plasma is ignited directly in the dense phase. Emission spectra show a strong continuum emission as well as a broad Balmer α line with a strong red shift, with an estimate of the initial plasma density of 1.3 × 1026 m-3. The relaxation of discharge pressure and plasma density is studied under a series of six successive pulses.

  12. Nanosecond pulsed laser blackening of copper

    NASA Astrophysics Data System (ADS)

    Tang, Guang; Hourd, Andrew C.; Abdolvand, Amin

    2012-12-01

    Nanosecond (12 ns) pulsed laser processing of copper at 532 nm resulted in the formation of homogenously distributed, highly organized microstructures. This led to the fabrication of large area black copper substrates with absorbance of over 97% in the spectral range from 250 nm to 750 nm, and a broadband absorbance of over 80% between 750 nm and 2500 nm. Optical and chemical analyses of the fabricated black metal are presented and discussed. The employed laser is an industrially adaptable source and the presented technique for fabrication of black copper could find applications in broadband thermal radiation sources, solar energy absorbers, irradiative heat transfer devices, and thermophotovoltaics.

  13. The streamer-to-spark transition in a transient spark: a dc-driven nanosecond-pulsed discharge in atmospheric air

    NASA Astrophysics Data System (ADS)

    Janda, Mário; Machala, Zdenko; Niklová, Adriana; Martišovitš, Viktor

    2012-08-01

    We present a study of the streamer-to-spark transition in a self-pulsing dc-driven discharge called a transient spark (TS). The TS is a streamer-to-spark transition discharge with short spark duration (˜10-100 ns), based on charging and discharging of the internal capacity of the electric circuit with repetition frequency 1-10 kHz. The TS can be maintained under relatively low energy conditions (0.1-1 mJ pulse-1). It generates a very reactive non-equilibrium air plasma applicable for flue gas cleaning or bio-decontamination. Thanks to the short spark current pulse duration, the steady-state gas temperature, measured at the beginning of the streamers initiating the TS, increases from an initial value of ˜300 K only up to ˜550 K at 10 kHz. The streamer-to-spark transition is governed by the subsequent increase in the gas temperature in the plasma channel up to ˜1000 K. This breakdown temperature does not change with increasing repetition frequency f. The heating after the streamer accelerates with increasing f, leading to a decrease in the average streamer-to-spark transition time from a few µs to less than 100 ns.

  14. Ignition modes of nanosecond discharge with bubbles in distilled water

    NASA Astrophysics Data System (ADS)

    Hamdan, Ahmad; Cha, Min Suk

    2015-10-01

    Here, we present the microscopic physical characteristics of nanosecond discharges with an array of bubbles in distilled water. In particular, applying a single high-voltage pulse, four delayed intensified charge-coupled device cameras successfully visualized four successive images during a single discharge event. We identified three distinctive modes of ignition inside a bubble, depending on the relative location of the bubble with respect to pin-to-hollow needle electrodes when a single bubble was located in an inter-electrode gap of 1 mm: anode-driven ignition, cathode-driven ignition, and co-ignition near both electrodes. Anode- and cathode-driven ignitions evolved into either a complete propagation of the streamer or an incomplete propagation, which were limited in location by proximity to an ignition location, while co-ignitions consistently showed complete propagation. When we increased the gap to 2 mm to accommodate multiple bubbles in the gap, an ignited bubble near the cathode was able to cause the ignition of an upper adjacent bubble. Bubble-bubble interface zones can also be spots of ignition, such that we observed simultaneous co-ignitions in the zones of bubble-bubble interfaces and near electrodes with triple bubbles. We compared the experimental results of discharge propagation with different ignition modes between Ar, He, and N2 bubbles. In addition, numerical simulations for static electric fields reasonably supported observed ignition behavior such that field intensity was locally enhanced.

  15. Modulated corona nanosecond discharge in air under ambient pressure

    NASA Astrophysics Data System (ADS)

    Lepekhin, N. M.; Priseko, Yu. S.; Filippov, V. G.; Bulatov, M. U.; Sukharevskii, D. I.; Syssoev, V. S.

    2015-04-01

    A unique type of corona discharge-modulated corona nanosecond discharge-has been obtained, the parameters of which have been determined in a geometric system of electrodes with a sharply heterogeneous electric field in air under ambient pressure and natural humidity.

  16. Rapid breakdown mechanisms of open air nanosecond dielectric barrier discharges.

    PubMed

    Ito, Tsuyohito; Kanazawa, Tatsuya; Hamaguchi, Satoshi

    2011-08-01

    The discharge initiation mechanism of nanosecond dielectric barrier discharges in open air has been clarified with time-dependent measurement of the discharge electric field by electric-field-induced coherent Raman scattering and optical emission. Our experimental observations have revealed that, in the prebreakdown phase of a nanosecond dielectric barrier discharge, the externally applied fast-rising electric field is strongly enhanced near the cathode due to large accumulation of space charge, which then strongly enhances ionization near the cathode. Once a sufficiently large number of ionizations take place, the location of peak ionization forms a front and propagates toward the cathode with strong optical emission, which establishes the discharge. This process is essentially different from the well-known Townsend mechanism for slower discharges. PMID:21902331

  17. Rapid Breakdown Mechanisms of Open Air Nanosecond Dielectric Barrier Discharges

    NASA Astrophysics Data System (ADS)

    Ito, Tsuyohito; Kanazawa, Tatsuya; Hamaguchi, Satoshi

    2011-08-01

    The discharge initiation mechanism of nanosecond dielectric barrier discharges in open air has been clarified with time-dependent measurement of the discharge electric field by electric-field-induced coherent Raman scattering and optical emission. Our experimental observations have revealed that, in the prebreakdown phase of a nanosecond dielectric barrier discharge, the externally applied fast-rising electric field is strongly enhanced near the cathode due to large accumulation of space charge, which then strongly enhances ionization near the cathode. Once a sufficiently large number of ionizations take place, the location of peak ionization forms a front and propagates toward the cathode with strong optical emission, which establishes the discharge. This process is essentially different from the well-known Townsend mechanism for slower discharges.

  18. Hybrid micromachining using a nanosecond pulsed laser and micro EDM

    NASA Astrophysics Data System (ADS)

    Kim, Sanha; Kim, Bo Hyun; Chung, Do Kwan; Shin, Hong Shik; Chu, Chong Nam

    2010-01-01

    Micro electrical discharge machining (micro EDM) is a well-known precise machining process that achieves micro structures of excellent quality for any conductive material. However, the slow machining speed and high tool wear are main drawbacks of this process. Though the use of deionized water instead of kerosene as a dielectric fluid can reduce the tool wear and increase the machine speed, the material removal rate (MRR) is still low. In contrast, laser ablation using a nanosecond pulsed laser is a fast and non-wear machining process but achieves micro figures of rather low quality. Therefore, the integration of these two processes can overcome the respective disadvantages. This paper reports a hybrid process of a nanosecond pulsed laser and micro EDM for micromachining. A novel hybrid micromachining system that combines the two discrete machining processes is introduced. Then, the feasibility and characteristics of the hybrid machining process are investigated compared to conventional EDM and laser ablation. It is verified experimentally that the machining time can be effectively reduced in both EDM drilling and milling by rapid laser pre-machining prior to micro EDM. Finally, some examples of complicated 3D micro structures fabricated by the hybrid process are shown.

  19. Time-resolved measurement of pressure evolution in underwater nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Marinov, Ilya; Guaitella, Olivier; Starikovskaia, Svetlana; Rousseau, Antoine

    2012-10-01

    Electrical discharges in water and other dielectric liquids have been extensively studied since almost fifty years, however reliable data on plasma parameters within the propagation phase is still missing. We report on shadowgraphic imaging and optical emission spectroscopy (OES) both with nanosecond time resolution of pulsed nanosecond discharge generated with point to wire electrode configuration. High voltage pulses of 10 kV and 30 ns duration (FWHM) are delivered by commercial pulse generator FPG 10 (FIG GmbH). Sub-millimeter discharge with filamentary structure develops at 50 km/s in axial direction of pin electrode. Using Hugoniot equations maximal discharge pressure at ignition can be obtained from shock wave front velocity. Analytical model of supersonic cavity expansion based on Kirkwood-Bethe approximation gives discharge pressure evolution from experimentally measured discharge channel expansion velocity profile. Thus, the pressure of 5 GPa is measured at the discharge ignition and drops drastically by the end of voltage pulse. Time-resolved OES spectrum shows a strong broadening of atomic Hydrogen (Balmer series) and oxygen (OI 777 nm) lines with almost continuum emission in the region 300-700 nm. Complex Hα and OI 777 profiles are due to combined contribution of Van Der Waals and Stark broadening. Electronic density can be deduced from lorentzian fit of Stark broadening and gives for electronic density 10^24 - 10^25 m-3.

  20. Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality

    PubMed Central

    Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

    2016-01-01

    In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed. PMID:27125663

  1. Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

    2016-04-01

    In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed.

  2. Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality.

    PubMed

    Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

    2016-01-01

    In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed. PMID:27125663

  3. Nanosecond square pulse generation in fiber lasers with normal dispersion

    NASA Astrophysics Data System (ADS)

    Zhao, L. M.; Tang, D. Y.; Cheng, T. H.; Lu, C.

    2007-04-01

    We report on the generation of nanosecond square pulses in a passively mode-locked fiber ring laser made of purely normal dispersive fibers. Different to the noise-like pulse operation of the laser, the generated square pulses are stable and have no internal structures. We show that the formation of the square pulse is due to the combined action of the pulse peak clamping effect caused by the cavity and the almost linear pulse propagation in the normal dispersive fibers.

  4. Conductivity of nanosecond discharges in nitrogen and sulfur hexafluoride studied by particle-in-cell simulations

    SciTech Connect

    Levko, D.; Gurovich, V. Tz.; Krasik, Ya. E.

    2012-06-15

    The conductivity of the discharge gap during the nanosecond high-voltage pulsed discharge in nitrogen and sulfur hexafluoride is studied using particle-in-cell numerical simulations. It is shown that the conductivity in different locations of the cathode-anode gap is not uniform and that the conductivity is determined by both the runaway and the plasma electrons. In addition, it is shown that runaway electrons generated prior to the virtual cathode formation pre-ionize the discharge gap, which makes it conductive.

  5. Fast Rise Time and High Voltage Nanosecond Pulses at High Pulse Repetition Frequency

    NASA Astrophysics Data System (ADS)

    Miller, Kenneth E.; Ziemba, Timothy; Prager, James; Picard, Julian; Hashim, Akel

    2015-09-01

    Eagle Harbor Technologies (EHT), Inc. is conducting research to decrease the rise time and increase the output voltage of the EHT Nanosecond Pulser product line, which allows for independently, user-adjustable output voltage (0 - 20 kV), pulse width (20 - 500 ns), and pulse repetition frequency (0 - 100 kHz). The goals are to develop higher voltage pulses (50 - 60 kV), decrease the rise time from 20 to below 10 ns, and maintain the high pulse repetition capabilities. These new capabilities have applications to pseudospark generation, corona production, liquid discharges, and nonlinear transmission line driving for microwave production. This work is supported in part by the US Navy SBIR program.

  6. Discharge pulse phenomenology

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.

    1985-01-01

    A model was developed which places radiation induced discharge pulse results into a unified conceptual framework. Only two phenomena are required to interpret all space and laboratory results: (1) radiation produces large electrostatic fields inside insulators via the trapping of a net space charge density; and (2) the electrostatic fields initiate discharge streamer plasmas similar to those investigated in high voltage electrical insulation materials; these streamer plasmas generate the pulsing phenomena. The apparent variability and diversity of results seen is an inherent feature of the plasma streamer mechanism acting in the electric fields which is created by irradiation of the dielectrics. The implications of the model are extensive and lead to constraints over what can be done about spacecraft pulsing.

  7. Ignition in Ethanol-Containing Mixtures after Nanosecond Discharge

    NASA Astrophysics Data System (ADS)

    Kosarev, Ilya; Pakhomov, Aleksandr; Kindysheva, Svetlana; Aleksandrov, Nikolay; Starikovskiy, Andrey; MIPT Team; PU Team

    2013-09-01

    We study experimentally and numerically kinetics of ethanol ignition after a high-voltage nanosecond discharge. Active particles are produced in a high-voltage nanosecond discharge to favor the ignition of C2H5OH-containing mixtures at elevated gas temperatures. We consider stoichiometric (φ = 1) and lean (φ = 0.5) C2H5OH:O2 mixtures (10%) diluted with Ar (90%). The gas temperature behind a reflected shock wave ranges from 1100 to 2000 K and the corresponding pressure ranges from 0.2 to 1 atm; these parameters are obtained from measured shock wave velocity. The ignition delay time is measured behind a reflected shock wave with and without the discharge using detection of CH radiation. Generation of the discharge plasma is shown to lead to an order of magnitude decrease in ignition delay time. It is shown that the observed effect of nonequilibrium discharge plasma on ethanol ignition is induced by chain reaction acceleration due to active species generation in the discharge rather than due to fast gas heating. The calculated ignition delay times are compared with the experimental data.

  8. Capacitor discharge pulse analysis.

    SciTech Connect

    Baker, Michael Sean; Griffiths, Stewart K.; Tanner, Danelle Mary

    2013-08-01

    Capacitors used in firing sets and other high discharge current applications are discharge tested to verify performance of the capacitor against the application requirements. Parameters such as capacitance, inductance, rise time, pulse width, peak current and current reversal must be verified to ensure that the capacitor will meet the application needs. This report summarizes an analysis performed on the discharge current data to extract these parameters by fitting a second-order system model to the discharge data and using this fit to determine the resulting performance metrics. Details of the theory and implementation are presented. Using the best-fit second-order system model to extract these metrics results in less sensitivity to noise in the measured data and allows for direct extraction of the total series resistance, inductance, and capacitance.

  9. Energy distribution of runaway electrons generated by a nanosecond discharge in atmospheric-pressure air

    NASA Astrophysics Data System (ADS)

    Tarasenko, V. F.; Baksht, E. Kh.; Burachenko, A. G.; Kostyrya, I. D.; Lomaev, M. I.; Petin, V. K.; Rybka, D. V.; Shlyakhtun, S. V.

    2008-12-01

    The spectra of an ultrashort avalanche electron beam generated by a nanosecond discharge in atmospheric-pressure air were investigated. The temporal characteristics of the beam current pulses, gap voltage, and discharge current in a gas diode were measured with a time resolution of ˜0.1 ns. A simple technique was developed for recovering electron spectra from the curves of beam attenuation by aluminum foils. The effect of the cathode design, electrode gap length, and generator parameters on the electron spectra were studied using seven setups. It is shown that generation of electrons with anomalously high energies requires the use of cathodes with increased curvature radius.

  10. Generation of Atmospheric Pressure Plasma by Repetitive Nanosecond Pulses in Air Using Water Electrodes

    NASA Astrophysics Data System (ADS)

    Shao, Tao; Yu, Yang; Zhang, Cheng; Jiang, Hui; Yan, Ping; Zhou, Yuanxiang

    2011-12-01

    Dielectric barrier discharge (DBD) excitated by pulsed power is a promising method for producing nonthermal plasma at atmospheric pressure. Discharge characteristic in a DBD with salt water as electrodes by a home-made unipolar nanosecond-pulse power source is presented in this paper. The generator is capable of providing repetitive pulses with the voltage up to 30 kV and duration of 70 ns at a 300 Ω resistive load. Applied voltage and discharge current are measured under various experimental conditions. The DBD created between two liquid electrodes shows that the discharge is homogeneous and diffuse in the whole discharge regime. Spectra diagnosis is conducted by an optical emission spectroscopy. The air plasma has strong emission from nitrogen species below 400 nm, notably the nitrogen second positive system.

  11. A comparison between characteristics of atmospheric-pressure plasma jets sustained by nanosecond- and microsecond-pulse generators in helium

    SciTech Connect

    Zhang, Cheng; Shao, Tao Wang, Ruixue; Yan, Ping; Zhou, Zhongsheng; Zhou, Yixiao

    2014-10-15

    Power source is an important parameter that can affect the characteristics of atmospheric-pressure plasma jets (APPJs), because it can play a key role on the discharge characteristics and ionization process of APPJs. In this paper, the characteristics of helium APPJs sustained by both nanosecond-pulse and microsecond-pulse generators are compared from the aspects of plume length, discharge current, consumption power, energy, and optical emission spectrum. Experimental results showed that the pulsed APPJ was initiated near the high-voltage electrode with a small curvature radius, and then the stable helium APPJ could be observed when the applied voltage increased. Moreover, the discharge current of the nanosecond-pulse APPJ was larger than that of the microsecond-pulse APPJ. Furthermore, although the nanosecond-pulse generator consumed less energy than the microsecond-pulse generator, longer plume length, larger instantaneous power per pulse and stronger spectral line intensity could be obtained in the nanosecond-pulse excitation case. In addition, some discussion indicated that the rise time of the applied voltage could play a prominent role on the generation of APPJs.

  12. Enabling pulsed power technologies for the generation of intense, nanosecond electric fields

    NASA Astrophysics Data System (ADS)

    Sanders, Jason M.

    This dissertation focuses on the design and implementation of pulsed power systems with an emphasis on systems that generate high peak powers on nanosecond and subnanosecond timescales. These systems are an enabling technology for many areas of scientific research focused on the effects of intense, nanosecond pulsed electric fields or pulsed discharges on physical processes. Researchers at USC use these systems in a variety of diverse application areas, including research into ignition and combustion using nanosecond discharges, research into the effects of pulsed electric fields on biological systems, and research into the efficacy of cold plasma discharges for disinfection. Each of these applications has its own set of pulsed power parameters, and in most cases these parameters necessitate that the systems be custom developed. The bulk of what follows will address the design methodologies, materials, and implementation techniques required for systems capable of generating high current (20 -- 500 Amperes), high voltage (1 kV -- 100 kV), nanosecond pulses. These principles culminate in the presentation of a new, compact, solid state architecture, which has been implemented into a system called the Rapid Pulser. This architecture uses diode opening switches at the output to switch inductively stored energy into a resistive load. To switch properly, these diodes must be pumped in the forward and reverse directions by a current, and this new architecture introduces a pumping circuit that significantly improves pulse shape as well as reduces amplitude jitter, time jitter, complexity, cost, and size. At 1.6 kg, this is the lightest pulsed power system developed at USC's Pulsed Power Lab, which is significant because minimizing size and weight is necessary for applications focused on the ignition and combustion of fuels. A summary of research focused on magnetic and dielectric materials for nonlinear energy compression will also be presented. Nonlinearities inherent to

  13. Characterization of a DBD-Based Plasma Jet Using a Variable Pulse Width Nanosecond Pulser

    NASA Astrophysics Data System (ADS)

    Ziemba, Timothy; Picard, Julian; Prager, James; Miller, Kenneth; Carscadden, John

    2015-11-01

    Most high voltage pulsers used to drive dielectric barrier discharges (DBDs), produce a single pulse shape (width and voltage), thus making it challenging to assess the effect of pulse shape on the production of different chemical species during a discharge. Eagle Harbor Technologies, Inc. (EHT) has developed a high voltage nanosecond pulser that enables independent control of the output voltage, pulse width, and pulse repetition frequency. This pulser has been specifically designed to drive dielectric barrier discharges (DBD). EHT has used this pulser to conduct a parametric investigation of a DBD-based jet utilizing spectroscopic diagnostics. A better understanding of this parameter dependency can allow for more targeted and effective application of plasma in medical, environmental, industrial, and other applications. Results comparing DBD voltage and current waveforms with plasma spectrographic measurements will be presented.

  14. Atmospheric air homogenous DBD plasma excited by bipolar nanosecond pulse used for improving the hydrophilic property of polypropylene

    NASA Astrophysics Data System (ADS)

    Yang, Dezheng; Wang, Wenchun; Zhang, Shuai; Liu, Zhijie; Jia, Li; Dai, Leyang

    2013-06-01

    In this paper, an air homogenous dielectric barrier discharge excited by bipolar nanosecond pulse voltage is obtained and used for the surface modification of polypropylene non-woven fabric at atmospheric pressure. Compared with the DBD plasma excited by sine alternating current (AC) voltage, nanosecond pulsed dielectric barrier discharge exhibits obvious advantages, e.g., better discharge homogeneity, lower energy cost, and lower plasma gas temperature etc. Hence it presents the potential application in improving the hydrophilic property of polypropylene non-woven fabric with high energy efficiency and without surface damage. To reduce the water contact angle of the polypropylene surface from 145° to 110°, the average energy cost of the nanosecond pulsed dielectric barrier discharge is only about 0.1 J/cm2, which is about 1/20 of AC dielectric barrier discharge. On the other hand, the surface damage of non-woven fabric induced by nanosecond pulsed dielectric barrier discharge plasma cannot be distinguished by SEM photographs.

  15. Fast magneto-optic switch based on nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Weng, Zi-Hua; Ruan, Jian-Jian; Lin, Shao-Han; Chen, Zhi-Min

    2011-09-01

    The paper studies an all fiber high-speed magneto-optic switch which includes an optical route, a nanosecond pulse generator, and a magnetic field module in order to reduce the switching time of the optical switch in the all optical network. A compact nanosecond pulse generator can be designed based on the special character of the avalanche transistor. The output current pulse of the nanosecond pulse generator is less than 5 ns, while the pulse amplitude is more than 100 V and the pulse width is about 10 to 20 ns, which is able to drive a high-speed magnetic field. A solenoid is used as the magnetic field module, and a bismuth-substituted rare-earth iron garnet single crystal is chosen as the Faraday rotator. By changing the direction of current in the solenoid quickly, the magnetization of the magneto-optic material is reversed, and the optical beam can be rapidly switched. The experimental results indicate that the switching time of the device is about 100 to 400 ns, which can partially meet the demand of the rapid development of the all optical network.

  16. Supershort avalanche electron beams and x-ray in high-pressure nanosecond discharges

    NASA Astrophysics Data System (ADS)

    Tarasenko, V. F.; Baksht, E. H.; Kostyrya, I. D.; Lomaev, M. I.; Rybka, D. V.

    2008-10-01

    The properties of a supershort avalanche electron beam (S AEB) and X-ray radiation produced using a nanosecond volume discharge are examined. An electron beam of the runaway electrons with amplitude of ~ 50 A has been obtained in air atmospheric pressure. It is reported that S AEB is formed in the angle above 2π sr. Three groups of the runaway electrons are formed in a gas diode under atmospheric air pressure, when nanosecond voltage pulses with amplitude of hundreds of kilovolts are applied. The electron beam has been generated behind a 45 μm thick AlBe foil in SF6 and Xe under the pressure of 2 arm, and in He under the pressure of about 12 atm. The paper gives the analysis of a generation mechanism of SAEB.

  17. Double nanosecond pulses generation in ytterbium fiber laser.

    PubMed

    Veiko, V P; Lednev, V N; Pershin, S M; Samokhvalov, A A; Yakovlev, E B; Zhitenev, I Yu; Kliushin, A N

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode. PMID:27370433

  18. Double nanosecond pulses generation in ytterbium fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Lednev, V. N.; Pershin, S. M.; Samokhvalov, A. A.; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N.

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  19. Self-similar spatial structure of a streamer-free nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Karelin, V. I.; Tren'kin, A. A.

    2008-03-01

    The microstructure of a current channel is experimentally found under the conditions when homogeneous air gaps are subjected to nanosecond voltage pulses in an electric field insufficient for streamer generation. As a possible mechanism of microstructure formation, instability of the ionization process at the avalanche stage leading to the formation of a self-similar spatial structure is considered. The fractal dimension of this structure is determined. In inhomogeneous gaps, the avalanche is shown to be unstable as well. The energy benefit of structuring is considered. It is demonstrated that the microstructure of streamer discharges in homogeneous gaps can also be treated in terms of the model suggested.

  20. Sub-nanosecond dynamics of atmospheric air discharge under highly inhomogeneous and transient electric field

    NASA Astrophysics Data System (ADS)

    Tardiveau, Pierre; Magne, Lionel; Pasquiers, Stephane; Jeanney, Pascal; Bournonville, Blandine

    2015-09-01

    The effects of the application of extreme overvoltages (>500%) in air gaps over less than a few nanoseconds bring us to reconsider the classical physics of streamer used to describe air discharges at atmospheric pressure. Non equilibrium discharges created by extremely transient and intense electric fields in standard conditions of pressure and temperature exhibit unusual diffuse and large structure. In point-to-plane electrode configurations, a plasma cloud is observed which properties depend on voltage pulses features (amplitude, rise time, length, and frequency) and electrodes properties (material, shape, and gap length). Our parametric experimental study is based on fast electrical characterization and sub-nanosecond imaging and shows the different stages of propagation of the cloud. This work details the conditions to maximize the cloud size without moving towards a multi-channel streamer regime. Based on the analysis and the Abel transform processing of the emission of excited states of nitrogen from the discharge, a focus is made on the structuration of the plasma cloud while it is propagating. It shows how much, according to the experimental conditions, the external electric field can be screened by the plasma and, inversely, how deep and how long a high electric field can be sustained in the gap, that is challenging for pulsed atmospheric plasmas applications. This work benefits from the financial support of the National Agency of Research within the framework of the project ANR-13-BS09-0014.

  1. Skyrmion Creation and Manipulation by Nano-Second Current Pulses.

    PubMed

    Yuan, H Y; Wang, X R

    2016-01-01

    Easy creation and manipulation of skyrmions is important in skyrmion based devices for data storage and information processing. We show that a nano-second current pulse alone is capable of creating/deleting and manipulating skyrmions in a spin valve with a perpendicularly magnetized free layer and broken chiral symmetry. Interestingly, for an in-plane magnetized fixed layer, the free layer changes from a single domain at zero current to a Neel wall at an intermediate current density. Reverse the current polarity, the Neel wall changes to its image inversion. A properly designed nano-second current pulse, that tends to convert one type of Neel walls to its image inversion, ends up to create a stable skyrmion without assistance of external fields. For a perpendicularly magnetized fixed layer, the skyrmion size can be effectively tuned by a current density. PMID:26934954

  2. Skyrmion Creation and Manipulation by Nano-Second Current Pulses

    PubMed Central

    Yuan, H. Y.; Wang, X. R.

    2016-01-01

    Easy creation and manipulation of skyrmions is important in skyrmion based devices for data storage and information processing. We show that a nano-second current pulse alone is capable of creating/deleting and manipulating skyrmions in a spin valve with a perpendicularly magnetized free layer and broken chiral symmetry. Interestingly, for an in-plane magnetized fixed layer, the free layer changes from a single domain at zero current to a Neel wall at an intermediate current density. Reverse the current polarity, the Neel wall changes to its image inversion. A properly designed nano-second current pulse, that tends to convert one type of Neel walls to its image inversion, ends up to create a stable skyrmion without assistance of external fields. For a perpendicularly magnetized fixed layer, the skyrmion size can be effectively tuned by a current density. PMID:26934954

  3. Nanosecond electric pulses trigger actin responses in plant cells

    SciTech Connect

    Berghoefer, Thomas; Eing, Christian; Flickinger, Bianca; Hohenberger, Petra; Wegner, Lars H.; Frey, Wolfgang; Nick, Peter

    2009-09-25

    We have analyzed the cellular effects of nanosecond pulsed electrical fields on plant cells using fluorescently tagged marker lines in the tobacco cell line BY-2 and confocal laser scanning microscopy. We observe a disintegration of the cytoskeleton in the cell cortex, followed by contraction of actin filaments towards the nucleus, and disintegration of the nuclear envelope. These responses are accompanied by irreversible permeabilization of the plasma membrane manifest as uptake of Trypan Blue. By pretreatment with the actin-stabilizing drug phalloidin, the detachment of transvacuolar actin from the cell periphery can be suppressed, and this treatment can also suppress the irreversible perforation of the plasma membrane. We discuss these findings in terms of a model, where nanosecond pulsed electric fields trigger actin responses that are key events in the plant-specific form of programmed cell death.

  4. Skyrmion Creation and Manipulation by Nano-Second Current Pulses

    NASA Astrophysics Data System (ADS)

    Yuan, H. Y.; Wang, X. R.

    2016-03-01

    Easy creation and manipulation of skyrmions is important in skyrmion based devices for data storage and information processing. We show that a nano-second current pulse alone is capable of creating/deleting and manipulating skyrmions in a spin valve with a perpendicularly magnetized free layer and broken chiral symmetry. Interestingly, for an in-plane magnetized fixed layer, the free layer changes from a single domain at zero current to a Neel wall at an intermediate current density. Reverse the current polarity, the Neel wall changes to its image inversion. A properly designed nano-second current pulse, that tends to convert one type of Neel walls to its image inversion, ends up to create a stable skyrmion without assistance of external fields. For a perpendicularly magnetized fixed layer, the skyrmion size can be effectively tuned by a current density.

  5. Portable nanosecond pulsed air plasma jet

    SciTech Connect

    Walsh, J. L.; Kong, M. G.

    2011-08-22

    Low-temperature atmospheric pressure plasmas are of great importance in many emerging biomedical and materials processing applications. The redundancy of a vacuum system opens the gateway for highly portable plasma systems, for which air ideally becomes the plasma-forming gas and remote plasma processing is preferred to ensure electrical safety. Typically, the gas temperature observed in air plasma greatly exceeds that suitable for the processing of thermally liable materials; a large plasma-sample distance offers a potential solution but suffers from a diluted downstream plasma chemistry. This Letter reports a highly portable air plasma jet system which delivers enhanced downstream chemistry without compromising the low temperature nature of the discharge, thus forming the basis of a powerful tool for emerging mobile plasma applications.

  6. Study on nanosecond pulsed electron beam generation

    NASA Astrophysics Data System (ADS)

    Ponomarev, D.; Kholodnaya, G.; Remnev, G.; Kaikanov, M.; Sazonov, R.

    2014-11-01

    The paper presents the findings of an investigation on volt-ampere characteristics of the diode with explosive emission cathodes of different constructions (blade metal-dielectric (MD-cathode) and solid graphite cathodes) under the change of the anode-cathode gap in wide ranges. The investigations were carried out using the TEA-500 pulsed electron accelerator. The total current of the electron beam was measured using the Faraday cup (FC). A 0.5-mm foiled glass fiber laminate was used as an emitting edge of the cathode in the experimental study with the explosive emission blade MD-cathode. Based on the obtained results, the conclusion was made that the graphite cathode has the most effective efficiency factor.

  7. Discharge current and current of supershort avalanche E-beam at volume nanosecond discharge in non-uniform electric field

    NASA Astrophysics Data System (ADS)

    Tarasenko, Victor F.; Rybka, Dmitrii V.; Baksht, Evgenii H.; Kostyrya, Igor'D.; Lomaev, Mikhail I.

    2008-01-01

    The gas diode current-voltage characteristics at the voltage pulses applied from the RADAN and SM-3NS pulsers, and generation of an supershort avalanche electron beam (SAEB) have been studied experimentally in an inhomogeneous electric field upon a nanosecond breakdown in an air gap at atmospheric pressure. Displacement currents with amplitude over 1 kA have been observed and monitored. It is shown that the displacement current amplitude gets increased due to movement of the dense plasma front and charging of a "capacitor" formed between plasma and anode. The SAEB generation time relatively to the discharge current pulses and the gap voltage were determined in the experiments. It is shown that the SAEB current maximum at the pulser voltages of hundreds kV is registered on the discharge current pulse front, before the discharge current peak of the gas diode capacitance, and the delay time of these peaks is determined by the value of an interelectrode spacing. The delay time in case of a gap of 16 mm and air breakdown at atmospheric pressure was ~100 ps, and in case of 10 mm it was less than 50 ps.

  8. Controlled electron emission and vacuum breakdown with nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Seznec, B.; Dessante, Ph; Caillault, L.; Babigeon, J.-L.; Teste, Ph; Minea, T.

    2016-06-01

    Vacuum electron sources exploiting field emission are generally operated in direct current (DC) mode. The development of nanosecond and sub-nanosecond pulsed power supplies facilitates the emission of compact bunches of electrons of high density. The breakdown level is taken as the highest value of the voltage avoiding the thermo-emission instability. The effect of such ultra-fast pulses on the breakdown voltage and the emitted electron current is discussed as a result of the thermo-emission modelling applied to a significant protrusion. It is found that pulsing very rapidly the vacuum breakdown occurs at higher voltage values than for the DC case, because it rises faster than the heat diffusion. In addition, the electron emission current increases significantly regardless of the theoretical approach is used. A comparative study of this theoretical work is discussed for several different forms of the protrusion (elliptic and hyperbolic) and different metals (hence varying the melting point), particularly refractory (tungsten) versus conductor (titanium). Pulsed mode operation can provide an increase on breakdown voltage (up to 18%) and a significant increase (up to 330%) of the electron extracted current due to its high non-linear dependency with the voltage, for the case for the case with a hyperbolic protrusion.

  9. TALIF measurements of oxygen atom density in the afterglow of a capillary nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Klochko, A. V.; Lemainque, J.; Booth, J. P.; Starikovskaia, S. M.

    2015-04-01

    The atomic oxygen density has been measured in the afterglow of a capillary nanosecond discharge in 24-30 mbar synthetic air (N2 : O2 = 4 : 1) by the two-photon absorption laser-induced fluorescence (TALIF) technique, combined with absolute calibration by comparison with xenon TALIF. The discharge was initiated by a train of 30 ns FWHM pulses of alternating positive-negative-positive polarity, separated by 250 ns, with a train repetition frequency of 10 Hz. The amplitude of the first pulse was 10 kV in the cable. A flow of synthetic air through the tube provided complete gas renewal between pulse trains. The O-atom density measurements were made over the time interval 200 ns-2 µs after the initial pulse. The gas temperature was determined by analysis of the molecular nitrogen second positive system optical emission spectrum. The influence of the gas temperature on the atom density measurements, and the reactions producing O atoms, are discussed.

  10. Nanosecond pulsed fast neutron analysis - a progress report

    SciTech Connect

    Gozani, T.

    1994-12-31

    The status of the nanosecond Pulsed Fast Neutron Analysis (PFNA) at the time of the conference will be given. PFNA is a new technique researched and developed over the last several years to detect non-intrusively, a large variety of materials in containers as small as luggage or as large as trucks. The first full sized truck/container inspection system is being assembled at the Science Applications International Corporation (SAIC) Santa Clara facility for test and evaluation. Following this, the system will be operationally field tested at a designated government test bed in the Port of Tacoma, Washington.

  11. Efficient Formation of Ultracold Molecules with Chirped Nanosecond Pulses.

    PubMed

    Carini, J L; Kallush, S; Kosloff, R; Gould, P L

    2016-05-19

    We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted. PMID:26652642

  12. Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure.

    PubMed

    Zhang, Cheng; Shao, Tao; Yu, Yang; Niu, Zheng; Yan, Ping; Zhou, Yuanxiang

    2010-12-01

    Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution. PMID:21198017

  13. Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Gibert, T.; Mikikian, M.; Rabat, H.; Kovačević, E.; Berndt, J.

    2016-05-01

    Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10-6%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon-acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

  14. Pulsed discharge production Ar* metastables

    NASA Astrophysics Data System (ADS)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  15. Impact of nanosecond pulsed electric fields on primary hippocampal neurons

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Payne, Jason A.; Kuipers, Marjorie A.; Thompson, Gary L.; Wilmink, Gerald J.; Ibey, Bennett L.

    2012-02-01

    Cellular exposure to nanosecond pulsed electric fields (nsPEF) are believed to cause immediate creation of nanopores in the plasma membrane. These nanopores enable passage of small ions, but remain impermeable to larger molecules like propidium iodide. Previous work has shown that nanopores are stable for minutes after exposure, suggesting that formation of nanopores in excitable cells could lead to prolonged action potential inhibition. Previously, we measured the formation of nanopores in neuroblastoma cells by measuring the influx of extracellular calcium by preloading cells with Calcium Green-AM. In this work, we explored the impact of changing the width of a single nsPEF, at constant amplitude, on uptake of extracellular calcium ions by primary hippocampal neurons (PHN). Calcium Green was again used to measure the influx of extracellular calcium and FM1-43 was used to monitor changes in membrane conformation. The observed thresholds for nanopore formation in PHN by nsPEF were comparable to those measured in neuroblastoma. This work is the first study of nsPEF effects on PHN and strongly suggests that neurological inhibition by nanosecond electrical pulses is highly likely at doses well below irreversible damage.

  16. Anode initiated impulse breakdown in water: the dependence on pulse rise time for nanosecond and sub-nanosecond pulses and initiation mechanism based on electrostriction

    NASA Astrophysics Data System (ADS)

    Seepersad, Yohan; Fridman, Alexander; Dobrynin, Danil

    2015-10-01

    The effect of the voltage rise time on nanosecond and sub-nanosecond impulse breakdown of distilled water is studied. The dependence of anode initiated streamer inception on this parameter is shown to be more intricate than previously reported, particularly as it relates to mechanisms directly in the liquid phase. Dynamics of the emission phase for sub-nanosecond pulses with 600 ps rise time are presented to enable comparison with previous work on nanosecond initiation features. Schlieren imaging is also used to show the development of optical density perturbations and rarefactions as a result of electrostriction in the liquid which were previously found for nanosecond pulses as well. The mechanism of nanopore generation in the liquid due to fast impulses proposed by Shneider, Pekker and Fridman is used to explain the results.

  17. Production of picosecond, kilojoule, and petawatt laser pulses via Raman amplification of nanosecond pulses.

    PubMed

    Trines, R M G M; Fiúza, F; Bingham, R; Fonseca, R A; Silva, L O; Cairns, R A; Norreys, P A

    2011-09-01

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion. PMID:21981507

  18. Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields

    PubMed Central

    Xie, Fei; Varghese, Frency; Pakhomov, Andrei G.; Semenov, Iurii; Xiao, Shu; Philpott, Jonathan; Zemlin, Christian

    2015-01-01

    Background Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations. Methods We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2–4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5–20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12–18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume. Results In all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters. Conclusions Ablation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation. PMID:26658139

  19. Nanosecond electric pulses deprive zinc ions of carboxypeptidase G2.

    PubMed

    Yu, Tinghe; Fu, Xiao

    2015-02-01

    Nanosecond electric pulses (nsEP, 10kV/cm with a pulse duration of 8, 16 or 24ns) inhibited the activity of carboxypeptidase G2 (CPG2), a zinc-dependent homodimer; the relative activity was <20% when the total exposure time was >120s. No alterations were detected in electrophoresis, chromatography, mass spectroscopy and circular dichroism, thus demonstrating intactness of the apoenzyme. Inductively coupled plasma-mass spectrometry indicated that zinc levels were 3.30μg/mg protein in control CPG2, and decreased to 0.40, 0.12 or 0.38μg/mg protein after 240s of 8-, 16- or 24-ns pulses, respectively. In CPG2 exposed to 240s of 8-, 16- and 24-ns pulses, the reloading of zinc with redialysis recovered the activity to 94.7±3.4%, 84.0±5.2% and 81.7±7.0%, respectively (p=0.0853, 0.0741, 0.0668). These data demonstrated that nsEP inhibited CPG2 via removal of zinc, and that nsEP can be used to modulate CPG2. PMID:25049063

  20. Generation of nanosecond neutron pulses in vacuum accelerating tubes

    NASA Astrophysics Data System (ADS)

    Didenko, A. N.; Shikanov, A. E.; Rashchikov, V. I.; Ryzhkov, V. I.; Shatokhin, V. L.

    2014-06-01

    The generation of neutron pulses with a duration of 1-100 ns using small vacuum accelerating tubes is considered. Two physical models of acceleration of short deuteron bunches in pulse neutron generators are described. The dependences of an instantaneous neutron flux in accelerating tubes on the parameters of pulse neutron generators are obtained using computer simulation. The results of experimental investigation of short-pulse neutron generators based on the accelerating tube with a vacuum-arc deuteron source, connected in the circuit with a discharge peaker, and an accelerating tube with a laser deuteron source, connected according to the Arkad'ev-Marx circuit, are given. In the experiments, the neutron yield per pulse reached 107 for a pulse duration of 10-100 ns. The resultant experimental data are in satisfactory agreement with the results of computer simulation.

  1. Fluid modeling of a high-voltage nanosecond pulsed xenon microdischarge

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Raja, Laxminarayan L.

    2016-07-01

    A computational modeling study of high-voltage nanosecond pulsed microdischarge in xenon gas at 10 atm is presented. The discharge is observed to develop as two streamers originating from the cathode and the anode, and propagating toward each other until they merge to form a single continuous discharge channel. The peak plasma density obtained in the simulations is ˜1024 m-3, i.e., the ionization degree of plasma does not exceed 1%. The influence of the initial gas pre-ionization is established. It is seen that an increase in the seeded plasma density results in an increase in the streamer propagation velocity and an increase in the plasma density obtained after the merging of two streamers.

  2. Spectroscopic and electrical characters of SBD plasma excited by bipolar nanosecond pulse in atmospheric air.

    PubMed

    Zhao, Zi-Lu; Yang, De-Zheng; Wang, Wen-Chun; Yuan, Hao; Zhang, Li; Wang, Sen; Liu, Zhi-Jie; Zhang, Shuai

    2016-05-15

    In this paper, an atmospheric surface barrier discharge (SBD) generated by annular electrodes in quartz tube is presented through employing bipolar nanosecond pulse voltage in air. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra emitted from the discharges are recorded and calculated. A spectra simulation method is developed to separate the overlap of the secondary diffraction spectra which are produced by grating in monochromator, and N2 (B(3)Πg→A(3)Σu(+)) and O (3p(5)P→3s(5)S2(o)) are extracted. The effects of pulse voltage and discharge power on the emission intensities of OH (A(2)Σ(+)→X(2)Пi), N2(+) (B(2)Σu(+)→X(2)Σg(+)), N2 (C(3)Πu→B(3)Πg), N2 (B(3)Πg→A(3)Σu(+)), and O (3p(5)P→3s(5)S2(o)) are investigated. It is found that increasing the pulse peak voltage can lead to an easier formation of N2(+) (B(2)Σu(+)) than that of N2 (C(3)Πu). Additionally, vibrational and rotational temperatures of the plasma are determined by comparing the experimental and simulated spectra of N2(+) (B(2)Σu(+)→X(2)Σg(+)), and the results show that the vibrational and rotational temperatures are 3250±20K and 350±5K under the pulse peak voltage of 28kV, respectively. PMID:26924210

  3. Spectroscopic and electrical characters of SBD plasma excited by bipolar nanosecond pulse in atmospheric air

    NASA Astrophysics Data System (ADS)

    Zhao, Zi-Lu; Yang, De-Zheng; Wang, Wen-Chun; Yuan, Hao; Zhang, Li; Wang, Sen; Liu, Zhi-Jie; Zhang, Shuai

    2016-05-01

    In this paper, an atmospheric surface barrier discharge (SBD) generated by annular electrodes in quartz tube is presented through employing bipolar nanosecond pulse voltage in air. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra emitted from the discharges are recorded and calculated. A spectra simulation method is developed to separate the overlap of the secondary diffraction spectra which are produced by grating in monochromator, and N2 (B3Πg → A3Σu+) and O (3p5P → 3s5S2o) are extracted. The effects of pulse voltage and discharge power on the emission intensities of OH (A2Σ+ → X2Пi), N2+ (B2Σu+ → X2Σg+), N2 (C3Πu → B3Πg), N2 (B3Πg → A3Σu+), and O (3p5P → 3s5S2o) are investigated. It is found that increasing the pulse peak voltage can lead to an easier formation of N2+ (B2Σu+) than that of N2 (C3Πu). Additionally, vibrational and rotational temperatures of the plasma are determined by comparing the experimental and simulated spectra of N2+ (B2Σu+ → X2Σg+), and the results show that the vibrational and rotational temperatures are 3250 ± 20 K and 350 ± 5 K under the pulse peak voltage of 28 kV, respectively.

  4. Accessing defect dynamics using intense, nanosecond pulsed ion beams

    SciTech Connect

    Persaud, A.; Barnard, J. J.; Guo, H.; Hosemann, P.; Lidia, S.; Minor, A. M.; Seidl, P. A.; Schenkel, T.

    2015-06-18

    Gaining in-situ access to relaxation dynamics of radiation induced defects will lead to a better understanding of materials and is important for the verification of theoretical models and simulations. We show preliminary results from experiments at the new Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory that will enable in-situ access to defect dynamics through pump-probe experiments. Here, the unique capabilities of the NDCX-II accelerator to generate intense, nanosecond pulsed ion beams are utilized. Preliminary data of channeling experiments using lithium and potassium ions and silicon membranes are shown. We compare these data to simulation results using Crystal Trim. Furthermore, we discuss the improvements to the accelerator to higher performance levels and the new diagnostics tools that are being incorporated.

  5. Accessing defect dynamics using intense, nanosecond pulsed ion beams

    DOE PAGESBeta

    Persaud, A.; Barnard, J. J.; Guo, H.; Hosemann, P.; Lidia, S.; Minor, A. M.; Seidl, P. A.; Schenkel, T.

    2015-06-18

    Gaining in-situ access to relaxation dynamics of radiation induced defects will lead to a better understanding of materials and is important for the verification of theoretical models and simulations. We show preliminary results from experiments at the new Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory that will enable in-situ access to defect dynamics through pump-probe experiments. Here, the unique capabilities of the NDCX-II accelerator to generate intense, nanosecond pulsed ion beams are utilized. Preliminary data of channeling experiments using lithium and potassium ions and silicon membranes are shown. We compare these data to simulation results using Crystalmore » Trim. Furthermore, we discuss the improvements to the accelerator to higher performance levels and the new diagnostics tools that are being incorporated.« less

  6. Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

    SciTech Connect

    Liu, Chunyang Sui, Xin; Yang, Fang; Ma, Wei; Li, Jishun; Xue, Yujun; Fu, Xing

    2014-03-15

    A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of the microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.

  7. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  8. Nanosecond laser ablation for pulsed laser deposition of yttria

    NASA Astrophysics Data System (ADS)

    Sinha, Sucharita

    2013-09-01

    A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

  9. Considering effects of nanosecond pulsed electric fields on proteins.

    PubMed

    Beebe, Stephen J

    2015-06-01

    Most, if not all, effects of intense, pulsed electric fields are analyzed in terms of electrical charging of plasma membranes and/or subcellular membranes. However, not all cell responses from nanosecond pulsed electric fields (nsPEFs) are fully explained by poration of cell membranes. Observations that nsPEFs induce a Ca2-dependent dissipation of the mitochondria membrane potential (ΔΨm), which is enhanced when high frequency components are present in fast rise-fall waveforms, are not compatible with a poration event. Ca(2+) is shown to have little or no effect on propidium iodide uptake as a measure of plasma membrane poration and consequently intracellular membranes. Since most if not all Ca(2+)-regulated events are mediated by proteins, actions of nsPEFs on a protein(s) that regulate and/or affect the mitochondria membrane potential are possible. To show that nsPEFs can directly affect proteins, nsPEFs non-thermally inactivated the catalytic (phosphotransferase) activity of the catalytic subunit of the cAMP-dependent protein kinase, which is the prototype of the protein kinase superfamily that share a common catalytic mechanism and whose functions are highly dependent on their structure. These studies present indirect and direct evidences that nsPEFs can affect proteins and their functions, at least in part, by affecting their structure. PMID:25218277

  10. Effects of nanosecond pulse electric fields on cellular elasticity.

    PubMed

    Dutta, Diganta; Asmar, Anthony; Stacey, Michael

    2015-05-01

    We investigated the effects of a single 60 nanosecond pulsed electric field (nsPEF) of low (15 kV/cm) and high (60 kV/cm) field strengths on cellular morphology and membrane elasticity in Jurkat cells using fluorescent microscopy and atomic force microscopy (AFM). We performed force displacement measurements on cells using AFM and calculated the Young's modulus for membrane elasticity. Differential effects were observed depending upon pulsing conditions. We found that a single nsPEF of low field strength did not induce any apparent cytoskeletal breakdown and had minor morphological changes. Interestingly, force measurements and calculation of Young's modulus showed a significant decrease in membrane elasticity. A single nsPEF of high field strength induced stark morphological changes due to disruption of the actin cytoskeleton and a marked decrease in elasticity likely caused by irreversible membrane damage. We suggest that the cellular morphology is mainly dependent on stabilization by the actin cytoskeleton, while the elasticity changes are partially dependent on the cytoskeletal integrity. PMID:25732004

  11. An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses

    SciTech Connect

    Zhao, Liang; Cang Su, Jian; Bo Zhang, Xi; Feng Pan, Ya; Min Wang, Li; Peng Fang, Jin; Sun, Xu; Lui, Rui

    2013-08-15

    A group of complete images on the discharge channel developed in PMMA in quasi-uniform electric field under nanosecond pulses are observed with an on-line transmission microscope. The characteristics of the cumulative breakdown process are also generalized, which include initiating from the vicinity of the cathode, developing to the anode with a branch-like shape, and taking on a wormhole appearance when final breakdown occurs. The concluded characteristics are explained by referring to the conceptions of “low density domain” and “free radical” and considering the initial discharge channel as a virtual needle. The characteristics are helpful for designers to enhance the lifetime of insulators employed on a nanosecond time scale.

  12. Thermal and hydrodynamic effects of nanosecond discharges in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Xu, D. A.; Shneider, M. N.; Lacoste, D. A.; Laux, C. O.

    2014-06-01

    We present quantitative schlieren measurements and numerical analyses of the thermal and hydrodynamic effects of a nanosecond repetitively pulsed (NRP) discharge in atmospheric pressure air at 300 and 1000 K. The plasma is created by voltage pulses at an amplitude of 10 kV and a duration of 10 ns, applied at a frequency of 1-10 kHz between two pin electrodes separated by 2 or 4 mm. The electrical energy of each pulse is of the order of 1 mJ. We recorded single-shot schlieren images starting from 50 ns to 3 µs after the discharge. The time-resolved images show the shock-wave propagation and the expansion of the heated gas channel. Gas density profiles simulated in 1D cylindrical coordinates have been used to reconstruct numerical schlieren images for comparison with experimental ones. We propose an original method to determine the initial gas temperature and the fraction of energy transferred into ultrafast gas heating, using a comparison of the contrast profiles obtained from experimental and numerical schlieren images. This method is found to be much more sensitive to these parameters than the direct comparison of measured and predicted shock-wave and heated channel radii. The results show that a significant fraction of the electric energy is converted into gas heating within a few tens of ns. The values range from about 25% at a reduced electric field of 164 Td to about 75% at 270 Td, with a strong dependance on the initial gas temperature. These experiments support the fast heating processes via dissociative quenching of N2(B3 Πg, C3 Πu) by molecular oxygen.

  13. Retinal threshold studies for nanosecond and picosecond visible laser pulses

    NASA Astrophysics Data System (ADS)

    Roach, William P.; DiCarlo, Cheryl D.; Noojin, Gary D.; Stolarski, David J.; Amnotte, Rodney E.; Smith, Audrey B.; Rogers, Mark E.; Cain, Clarence P.

    1995-05-01

    Threshold measurements for Minimum Visible Lesions (MVL) at the retina are reported for 60 picoseconds (ps) and 4 nanoseconds (ns), single laser pulses in rhesus monkey eyes using a visible wavelength of 532 nanometers (nm) from a doubled Nd:YAG laser. The 50% probability for damage (ED50) dosages are calculated for 1 hour and 24 hour post exposures using 95% fiducial limits. For both pulsewidths, the threshold values calculated by probit analysis decrease between the 1 hour and 24 hour ophthalmoscopic evaluations. The ED50 value determined for the 60 ps pulsewidth was less than half the value at 4 ns (0.43 (mu) J/60 ps vs. 0.90 (mu) J/4 ns at 24 hours) for both readings. Of the 136 exposures for pulse energies ranging from 0.03 to 5.0 (mu) J no hemorrhagic lesions were produced for either pulsewidth studied. However, at 6.6 (mu) J one intraretinal hemorrhagic lesion was observed for 60 ps. The slope of the probit curve was higher for 60 ps when compared with the 4 ns value (3.03 at 60 ps vs. 2.68 at 4 ns). MVL threshold doses calculated are comparable with those reported in the literature. However, the 4 ns MVL values is less than one order of magnitude (a factor 4.7) above the Maximum Permissible Exposure (MPE) level as defined by the 'American National Standard For The Safe Use Of Lasers', ANSI Z136.1-19932. We present the current MVL data as it compares with previous data obtained for picosecond and femtosecond laser pulse thresholds and provide a preliminary assessment of how the ANSI MPE standard might be amended.

  14. High-power megavolt pulse generator with nanosecond rise time

    SciTech Connect

    Basov, G.F.; Bastrikov, A.N.; Koval`chuk, B.M.

    1995-10-01

    A pulse generator with a power of 0.1 TW, an amplitude of up to 2 MV and {approximately}1.5-nsec rise time is described. A Marx voltage pulse generator charges a low-inductance capacitor (1.8 nF) and a radial line (0.9 nF) to a voltage of {approximately}2 MV in 200 nsec. At the peak voltage, a water switch is actuated at the center of the radial line resulting in {approximately} 2.5-MV voltage pulse at the end of the line. This pulse propagates along the oil-insulated line. The line is connected to an oil-filled peaking switch with a metal diaphragm, which reduces the transfer capacitance of the discharge gap to 5 pF to match the radial-line wave impedance to the load connected to the switch output. A crossover switch may be used when operating in the short-pulse mode. A pulse with a width of up to 20 nsec has been generated across a load equivalent matched to the line.

  15. Bipolar nanosecond electric pulses are less efficient at electropermeabilization and killing cells than monopolar pulses

    PubMed Central

    Ibey, Bennett L.; Ullery, Jody; Pakhomova, Olga N.; Roth, Caleb C.; Semenov, Iurri; Beier, Hope T.; Tarango, Melissa; Xiao, Shu; Schoenbach, Karl; Pakhomov, Andrei G.

    2014-01-01

    Multiple studies have shown that bipolar (BP) electric pulses in the microsecond range are more effective at permeabilizing cells while maintaining similar cell survival rates as compared to monopolar (MP) pulse equivalents. In this paper, we investigated whether the same advantage existed for BP nanosecond-pulsed electric fields (nsPEF) as compared to MP nsPEF. To study permeabilization effectiveness, MP or BP pulses were delivered to single Chinese hamster ovary (CHO) cells and the response of three dyes, Calcium Green-1, Propidium Iodide (PI), and FM1-43, was measured by confocal microscopy. Results show that BP pulses were less effective at increasing intracellular calcium concentration or PI uptake and cause less membrane reorganization (FM1-43) than MP pulses. Twenty-four hour survival was measured in three cell lines (Jurkat, U937, CHO) and over ten times more BP pulses were required to induce death as compared to MP pulses of similar magnitude and duration. Flow cytometry analysis of CHO cells after exposure (15 minutes) revealed that to achieve positive FITC-Annexin V and PI expression, ten times more BP pulses were required than MP pulses. Overall, unlike longer pulse exposures, BP nsPEF exposures proved far less effective at both membrane permeabilization and cell killing than MP nsPEF. PMID:24332942

  16. The influence of the repetition rate on the nanosecond pulsed pin-to-pin microdischarges

    NASA Astrophysics Data System (ADS)

    Huang, Bang-Dou; Takashima, Keisuke; Zhu, Xi-Ming; Pu, Yi-Kang

    2014-10-01

    The effect of repetition rate on a nanosecond atmospheric pressure discharge is investigated. The discharge is generated between two pins in a mixture of Ne and Ar. The voltage, current, power waveforms and the temporally and spatially resolved electron density and an ‘effective’ electron temperature are measured, with a pulse interval between 1.5 and 200 µs. It is found that not only does the repetition rate have a strong influence on the breakdown voltage and the peak discharge power, but it can also affect the rise rate of the volume averaged electron density and its peak value. Temporally and spatially resolved measurement of the electron density and the effective electron temperature show that the spatial distributions of both quantities are also influenced by the repetition rate. In the initial discharge period of all cases, the sharp rise of the electron density correlates with the drastic drop of the effective electron temperature. It is suggested that the residual charges have a strong impact on the axial distribution of the electric field and energetic electrons between the electrodes during the breakdown period, as illustrated by a simple sheath model.

  17. A high voltage nanosecond pulser with independently adjustable output voltage, pulse width, and pulse repetition frequency

    NASA Astrophysics Data System (ADS)

    Prager, James; Ziemba, Timothy; Miller, Kenneth; Carscadden, John; Slobodov, Ilia

    2014-10-01

    Eagle Harbor Technologies (EHT) is developing a high voltage nanosecond pulser capable of generating microwaves and non-equilibrium plasmas for plasma medicine, material science, enhanced combustion, drag reduction, and other research applications. The EHT nanosecond pulser technology is capable of producing high voltage (up to 60 kV) pulses (width 20-500 ns) with fast rise times (<10 ns) at high pulse repetition frequency (adjustable up to 100 kHz) for CW operation. The pulser does not require the use of saturable core magnetics, which allows for the output voltage, pulse width, and pulse repetition frequency to be fully adjustable, enabling researchers to explore non-equilibrium plasmas over a wide range of parameters. A magnetic compression stage can be added to improve the rise time and drive lower impedance loads without sacrificing high pulse repetition frequency operation. Work supported in part by the US Navy under Contract Number N00014-14-P-1055 and the US Air Force under Contract Number FA9550-14-C-0006.

  18. A nanosecond surface dielectric barrier discharge at elevated pressures: time-resolved electric field and efficiency of initiation of combustion

    NASA Astrophysics Data System (ADS)

    Kosarev, I. N.; Khorunzhenko, V. I.; Mintoussov, E. I.; Sagulenko, P. N.; Popov, N. A.; Starikovskaia, S. M.

    2012-08-01

    We study a nanosecond surface dielectric barrier discharge (SDBD) initiated by negative or positive polarity pulses 10-15 kV in amplitude in a cable, 25-30 ns FWHM, 5 ns rise time, in the regime of a single shot or 3 Hz repetitive frequency. Discharge parameters, namely spatial structure of the discharge and time- and space-resolved electric field are studied in a N2 : O2 = 4 : 1 mixture for P = 1-5 atm. The possibility of igniting a combustible mixture with the help of an SDBD is demonstrated using the example of a stoichiometric C2H6 : O2 mixture at ambient initial temperature and at 1 atm pressure. Flame propagation and ignited volume as a function of time are compared experimentally for two discharge geometries: SDBD and pin-to-pin configurations at the same shape and amplitude of the incident pulse. It is shown that the SDBD can be considered as a multi-point ignition system with maximum energy release near the high-voltage electrode. Numerical modeling of the discharge and subsequent combustion kinetics for the SDBD conditions is performed. The discharge action leads to the production of atoms and radicals as well as to fast gas heating, due to the relaxation of electronic and vibrational degrees of freedom. The calculated ignition delay time is in reasonable agreement with the experimental results.

  19. Diamondoid synthesis by nanosecond pulsed microplasmas generated in He at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Stauss, Sven; Shizuno, Tomoki; Oshima, Fumito; Pai, David Z.; Terashima, Kazuo

    2012-10-01

    Diamondoids are sp^3 hybridized carbon nanomaterials that possess interesting properties making them attractive for biotechnology, medicine, and opto- and nanoelectronics. So far, larger diamondoids have been synthesized using the smallest diamondoid (adamantane) as a precursor. For this electric discharges and pulsed laser plasmas generated in supercritical fluids, and hot filament chemical vapor deposition have been used, but these methods are difficult to realize or very time-consuming. We have developed a more convenient approach where diamondoids are synthesized by high-voltage nanosecond pulsed microplasmas (voltage 15 kVp-p, frequency 1 Hz, pulse width 10 ns) generated in He at atmospheric pressure using point-to-plane tungsten electrodes. Adamantane was used as a precursor, and synthesis was conducted for 10^5 pulses at gas temperatures of 297, 373 and 473 K. Energy dispersive X-ray and micro-Raman spectroscopy were conducted to determine the composition of the products, and gas chromatography - mass spectra indicated the formation of diamantane. It was found that synthesis is more efficient at room temperature than at higher temperatures, and time-resolved optical emission spectroscopy suggest that the chemical reactions take place in the afterglow.

  20. Damage to dry plasmid DNA induced by nanosecond XUV-laser pulses

    NASA Astrophysics Data System (ADS)

    Nováková, Eva; Davídková, Marie; Vyšín, Ludék; Burian, Tomáš; Grisham, Michael E.; Heinbuch, Scott; Rocca, Jorge J.; Juha, Libor

    2011-06-01

    Ionizing radiation induces a variety of DNA damages including single-strand breaks (SSBs), double-strand breaks (DSBs), abasic sites, modified sugar and bases. Most theoretical and experimental studies have been focused on DNA strand scissions, in particular production of DNA double-strand breaks. DSBs have been proven to be a key damage at a molecular level responsible for the formation of chromosomal aberrations, leading often to cell death. The complexity of lesions produced in DNA by ionizing radiations is thought to depend on the amount of energy deposited at the site of each lesion. We have studied the nature of DNA damage induced directly by the pulsed 46.9 nm radiation provided by a capillary-discharge Ne-like Ar laser (CDL). Different surface doses were delivered with a repetition rate of a few Hz and an average pulse energy ~ 1 μJ. A simple model DNA molecule, i.e., dried closed-circular plasmid DNA (pBR322), was irradiated. The agarose gel electrophoresis method was used for determination of both SSB and DSB yields. Results are compared with a previous study of plasmid DNA irradiated with a single sub-nanosecond 1-keV X-ray pulse produced by a large-scale, double-stream gas puff target, illuminated by sub-kJ, near-infrared (NIR) focused laser pulses at the PALS facility (Prague Asterix Laser System).

  1. Fluid and hybrid modeling of nanosecond surface discharges: effect of polarity and secondary electrons emission

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu; Tereshonok, Dmitry V.; Naidis, George V.

    2016-08-01

    In this paper, we report on results from a computational investigation of nanosecond pulsed surface discharges of positive and negative polarity using a 2D fluid and fluid-Monte Carlo simulation. The streamers propagate along the dielectric surface in an asymmetric actuator geometry. The essential difference between the streamers of positive and negative polarities is observed. For positive polarity the intense sheath region is formed near the surface having high values of the electric field. The negative streamer has a lower field at the streamer front and in the sheath region. The disparity between the positive and negative surface streamers increases when electron Monte Carlo simulation is used that treats the energetic secondary electrons in a fully kinetic way. We also found that for a negative polarity applied to the exposed electrode, a thin layer of precursor electrons ahead of a streamer is formed having a shape of a narrow protruding needle. The effect is attributed to the production and trapping of fast secondary electrons in the narrow anodic sheath region.

  2. Conditions for uniform impact of the plasma of a runaway-electron-induced pulsed diffuse discharge on an anode

    NASA Astrophysics Data System (ADS)

    Erofeev, M. V.; Baksht, E. Kh.; Burachenko, A. G.; Tarasenko, V. F.

    2015-09-01

    The subject matters in this work are (i) the spatial structure of a volume (diffuse) discharge initiated in atmospheric-pressure air in a heavily nonuniform electric field by nanosecond voltage pulses and (ii) the influence of its plasma on the surface of a plane aluminum anode. It is shown that a diffuse discharge initiated by nanosecond voltage pulses makes it possible to uniformly process the anode's surface in atmospheric-pressure air in contrast to a spark discharge, which results in microcracking, locally changes the surface properties, and thereby degrades the surface.

  3. Material micromachining using a pulsed fiber laser platform with fine temporal nanosecond pulse shaping capability

    NASA Astrophysics Data System (ADS)

    Deladurantaye, Pascal; Gay, David; Cournoyer, Alain; Roy, Vincent; Labranche, Bruno; Levesque, Marc; Taillon, Yves

    2009-02-01

    We report on recent advances in laser material processing using a novel pulsed fiber laser platform providing pulse shape agility at the nanosecond time scale and at high repetition rates. The pulse shapes can be programmed with a time resolution of 2.5 ns and with an amplitude resolution of 10 bits. Depending on the desired laser performances, the pulses are generated either by directly modulating the drive current of a seed laser diode or by modulating the output of a seed laser diode operated in CW with electro-optic modulators. The pulses are amplified in an amplifier chain in a MOPA configuration. Advanced polarization maintaining LMA fiber designs enable output energy per pulse up to 60 μJ at 1064 nm at a repetition rate of 200 kHz with excellent beam quality (M2< 1.1) and narrow line widths suitable for efficient frequency conversion. Micro-milling experiments were carried out with stainless steel, in which processing microstructures of a few tens of microns in size usually represents a challenge, and aluminum, whose thermal conductivity is about 20 times higher than stainless steel. The results obtained with two metals having very different thermal properties using different pulse shapes with durations varying between 3 ns and 80 ns demonstrate the benefits of using lasers offering flexible pulse durations and controllable pulse intensity profiles for rapidly optimizing a process in different applications while using the same laser with respect to conventional methods based on pulsed laser with fixed pulse shapes. Numerous applications are envisioned in a near future, like the micromachining of multi-layered structures, in particular when working with the harmonics of the laser.

  4. Nanosecond pulsed electric fields and the cell cycle

    NASA Astrophysics Data System (ADS)

    Mahlke, Megan A.

    Exposure to nanosecond pulsed electrical fields (nsPEFs) can cause poration of external and internal cell membranes, DNA damage, and disassociation of cytoskeletal components, all of which are capable of disrupting a cell's ability to replicate. The phase of the cell cycle at the time of exposure is linked to differential sensitivities to nsPEFs across cell lines, as DNA structure, membrane elasticity, and cytoskeletal structure change dramatically during the cell cycle. Additionally, nsPEFs are capable of activating cell cycle checkpoints, which could lead to apoptosis or slow population growth. NsPEFs are emerging as a method for treating tumors via apoptotic induction; therefore, investigating the relevance of nsPEFs and the cell cycle could translate into improved efficacy in tumor treatment. Populations of Jurkat and Chinese Hamster Ovary (CHO) cells were examined post-exposure (10 ns pulse trains at 150kV/cm) by analysis of DNA content via propidium iodide staining and flow cytometric analysis at various time points (1, 6, and 12h post-exposure) to determine population distribution in cell cycle phases. Additionally, CHO and Jurkat cells were synchronized in G1/S and G2/M phases, pulsed, and analyzed to evaluate the role of cell cycle phase in survival of nsPEFs. CHO populations appeared similar to sham populations post-nsPEFs but exhibited arrest in the G1 phase at 6h after exposure. Jurkat cells exhibited increased cell death after nsPEFs compared to CHO cells but did not exhibit checkpoint arrest at any observed time point. The G1/S phase checkpoint is partially controlled by the action of p53; the lack of an active p53 response in Jurkat cells could contribute to their ability to pass this checkpoint and resist cell cycle arrest. Both cell lines exhibited increased sensitivity to nsPEFs in G2/M phase. Live imaging of CHO cells after nsPEF exposure supports the theory of G1/S phase arrest, as a reduced number of cells undergo mitosis within 24 h when

  5. Evolution of Striation in Pulsed Glow Discharges

    NASA Astrophysics Data System (ADS)

    Liu, Yuanye; He, Feng; Zhao, Xiaofei; Ouyang, Jiting

    2016-01-01

    In this work, striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision (PIC/MCC) simulation. The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed. The processes of striation formation in pulsed glow discharges and dielectric barrier discharges (DBD) are compared. The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other. The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge. During a pulsed breakdown, the striations are formed one by one towards the anode in a weak field channel. This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons. supported by National Natural Science Foundation of China (Nos. 10875010 and 11175017)

  6. A Nanosecond Pulsed Plasma Brush for Surface Decontamination

    NASA Astrophysics Data System (ADS)

    Neuber, Johanna; Malik, Muhammad; Song, Shutong; Jiang, Chunqi

    2015-11-01

    This work optimizes a non-thermal, atmospheric pressure plasma brush for surface decontamination. The generated plasma plumes with a maximum length of 2 cm are arranged in a 5 cm long, brush-like array. The plasma was generated in ambient air with <= 10 kV, 200 ns pulses at a repetition rate of 1.5 kHz. The energy per pulse and average power are in the range of 1-3 mJ and 0.5-1.5 W, respectively. Helium containing varying concentrations of water vapor was evaluated as the carrier gas and was fed into the plasma chamber at a rate varying between 1 to 7 SLPM. Optimization of the cold plasma brush for surface decontamination was tested in a study of the plasma inactivation of two common pathogens, Staphylococcus aureus and Acinetobacter baumannii. Laminate surfaces inoculated with over-night cultured bacteria were subject to the plasma treatment for varying water concentrations in He, flow rates and discharge voltages. It was found that increasing the water content of the feed gas greatly enhanced the bactericidal effect. Emission spectroscopy was performed to identify the reactive plasma species that contribute to this variation. Additional affiliation: Frank Reidy Research Center for Bioelectrics

  7. Characterization of acoustic shockwaves generated by exposure to nanosecond electrical pulses

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Maswadi, Saher; Ibey, Bennett L.; Beier, Hope T.; Glickman, Randolph D.

    2014-03-01

    Despite 30 years of research, the mechanism behind the induced breakdown of plasma membranes by electrical pulses, termed electroporation, remains unknown. Current theories treat the interaction between the electrical field and the membrane as an entirely electrical event pointing to multiple plausible mechanisms. By investigating the biophysical interaction between plasma membranes and nanosecond electrical pulses (nsEP), we may have identified a non-electric field driven mechanism, previously unstudied in nsEP, which could be responsible for nanoporation of plasma membranes. In this investigation, we use a non-contact optical technique, termed probe beam deflection technique (PBDT), to characterize acoustic shockwaves generated by nsEP traveling through tungsten wire electrodes. We conclude these acoustic shockwaves are the result of the nsEP exposure imparting electrohydraulic forces on the buffer solution. When these acoustic shockwaves occur in close proximity to lipid bilayer membranes, it is possible that they impart a sufficient amount of mechanical stress to cause poration of that membrane. This research establishes for the first time that nsEP discharged in an aqueous medium generate measureable pressure waves of a magnitude capable of mechanical deformation and possibly damage to plasma membranes. These findings provide a new insight into the longunanswered question of how electric fields cause the breakdown of plasma membranes.

  8. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    NASA Astrophysics Data System (ADS)

    Ilgner, Justus F. R.; Wehner, Martin M.; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2006-01-01

    We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10µm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20µm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 µJ, beam diameter 36 µm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mm/s. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

  9. Intense Nanosecond-Pulsed Cavity-Dumped Laser Radiation at 1.04 THz

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas

    2013-03-01

    We report first results of intense far-infrared (FIR) nanosecond-pulsed laser radiation at 1.04 THz from a previously described[2] cavity-dumped, optically-pumped molecular gas laser. The gain medium, methyl fluoride, is pumped by the 9R20 line of a TEA CO2 laser[3] with a pulse energy of 200 mJ. The THz laser pulses contain of 30 kW peak power in 5 nanosecond pulse widths at a pulse repetition rate of 10 Hz. The line width, measured by a scanning metal-mesh FIR Fabry-Perot interferometer, is 100 MHz. The novel THz laser is being used in experiments to resonantly excite coherent ns-pulsed 1.04 THz longitudinal acoustic phonons in silicon doping-superlattices. The research is supported by NASA EPSCoR NNX11AM04A and AFOSR FA9550-12-1-0100 awards.

  10. Supershort avalanche electron beams and x-ray in high-pressure nanosecond discharges

    NASA Astrophysics Data System (ADS)

    Tarasenko, V.

    2008-07-01

    Since 2003, an interest to investigation of e-beams generation in gas-filled diodes with high pressures has been rekindled. In 2005, the advanced recording methods of electron beams and the use of digital oscilloscopes with wide bandwidth provided the measurements of the beam current duration with time resolution of sim 100 ps. In this paper, the recent measurement results on duration and amplitude of a beam, generated at a nanosecond discharge in different gases have been summarized (Tarasenko et al. 2005, Baksht et al. 2007, Tarasenko et al. 2008). Voltage pulses sim 25, sim 150 and sim 250 kV in amplitude were applied to the gas gap with inhomogeneous electric field. It is presented that the current of supershort avalanche electrons beam (SAEB) recording through a area with a small diameter the pulse duration behind a foil from the gas diode with air at atmospheric pressure is no more than 90 ps. For recording, the pulse shape it is necessary to use a small-sized coaxial collector, loaded to a high-frequency cable, and the same collector is used for taking the charge density distribution over the foil surface in order to determine the SAEB amplitude. The electron distribution over the foil section should be compared with a per pulse distribution. In these experiments, we have compared the distributions obtained per pulse on a RF-3 and luminophore films, placed behind a foil. Besides that, intensity distribution of X-ray radiation at the gas diode output was recorded by using a multi-channel detection device based on microstrip arsenide-gallium detectors of ionizing radiation. An analysis of those data shows that at the beam current duration (FWHM) of sim 90 ps the beam current amplitude behind the 10- mu m thickness Al-foil at atmospheric pressure of air is sim 50 A. Discharge formation and SAEB generation in sulfur hexafluoride and xenon at pressure of 0.01-2.5 atm and helium of 10^-4 - 12 atm have been investigated. The beam of runaway electrons behind 45 mu m

  11. Investigation of capillary nanosecond discharges in air at moderate pressure: comparison of experiments and 2D numerical modelling

    NASA Astrophysics Data System (ADS)

    Klochko, Andrei V.; Starikovskaia, Svetlana M.; Xiong, Zhongmin; Kushner, Mark J.

    2014-09-01

    Nanosecond electrical discharges in the form of ionization waves are of interest for rapidly ionizing and exciting complex gas mixtures to initiate chemical reactions. Operating with a small discharge tube diameter can significantly increase the specific energy deposition and so enable optimization of the initiation process. Analysis of the uniformity of energy release in small diameter capillary tubes will aid in this optimization. In this paper, results for the experimentally derived characteristics of nanosecond capillary discharges in air at moderate pressure are presented and compared with results from a two-dimensional model. The quartz capillary tube, having inner and outer diameters of 1.5 and 3.4 mm, is about 80 mm long and filled with synthetic dry air at 27 mbar. The capillary tube with two electrodes at the ends is inserted into a break of the central wire of a long coaxial cable. A metal screen around the tube is connected to the cable ground shield. The discharge is driven by a 19 kV 35 ns voltage pulse applied to the powered electrode. The experimental measurements are conducted primarily by using a calibrated capacitive probe and back current shunts. The numerical modelling focuses on the fast ionization wave (FIW) and the plasma properties in the immediate afterglow after the conductive plasma channel has been established between the two electrodes. The FIW produces a highly focused region of electric field on the tube axis that sustains the ionization wave that eventually bridges the electrode gap. Results from the model predict FIW propagation speed and current rise time that agree with the experiment.

  12. Pulsed Corona Discharge Generated By Marx Generator

    NASA Astrophysics Data System (ADS)

    Sretenovic, G. B.; Obradovic, B. M.; Kovacevic, V. V.; Kuraica, M. M.; Puric J.

    2010-07-01

    The pulsed plasma has a significant role in new environmental protection technologies. As a part of a pulsed corona system for pollution control applications, Marx type repetitive pulse generator was constructed and tested in arrangement with wire-plate corona reactor. We performed electrical measurements, and obtained voltage and current signals, and also power and energy delivered per pulse. Ozone formation by streamer plasma in air was chosen to monitor chemical activity of the pulsed corona discharge.

  13. Plasma Discharge Process in a Pulsed Diaphragm Discharge System

    NASA Astrophysics Data System (ADS)

    Duan, Jianjin; Hu, Jue; Zhang, Chao; Wen, Yuanbin; Meng, Yuedong; Zhang, Chengxu

    2014-12-01

    As one of the most important steps in wastewater treatment, limited study on plasma discharge process is a key challenge in the development of plasma applications. In this study, we focus on the plasma discharge process of a pulsed diaphragm discharge system. According to the analysis, the pulsed diaphragm discharge proceeds in seven stages: (1) Joule heating and heat exchange stage; (2) nucleated site formation; (3) plasma generation (initiation of the breakdown stage); (4) avalanche growth and plasma expansion; (5) plasma contraction; (6) termination of the plasma discharge; and (7) heat exchange stage. From this analysis, a critical voltage criterion for breakdown is obtained. We anticipate this finding will provide guidance for a better application of plasma discharges, especially diaphragm plasma discharges.

  14. Dynamics of a wire-to-cylinder atmospheric pressure high-voltage nanosecond discharge

    SciTech Connect

    Levko, Dmitry; Raja, Laxminarayan L.

    2015-08-15

    The dynamics of a wire-to-cylinder atmospheric pressure high-voltage nanosecond discharge is studied by the one-dimensional Particle-in-Cell Monte Carlo collisions model in cylindrical coordinates. The x-ray photons emitted from the anode are found to be inconsequential to the generation of dense plasma in the gap. Rather, the electron impact ionization resulting from acceleration of naturally occurring background electrons in the discharge gap are enough to explain the generation of high-density (∼10{sup 15 }cm{sup −3}) non-equilibrium plasma. The influence of the high-voltage rise time on the plasma parameters is discussed.

  15. Characterization of combined power plasma jet using AC high voltage and nanosecond pulse for reactive species composition control

    NASA Astrophysics Data System (ADS)

    Takashima, Keisuke; Konishi, Hideaki; Kato, Toshiaki; Kaneko, Toshiro

    2014-10-01

    In the application studies for both bio-medical and agricultural applications, the roles of the reactive oxide and/or nitride species generated in the plasma has been reported as a key to control the effects and ill-effects on the living organism. The correlation between total OH radical exposure from an air atmospheric pressure plasma jet and the sterilization threshold on Botrytis cinerea is presented. With the increase of the OH radical exposure to the Botrytis cinerea, the probability of sterilization is increased. In this study, to resolve the roles of reactive species including OH radicals, a combined power plasma jet using nanosecond pulses and low-frequency sinusoidal AC high voltage (a few kHz) is studied for controlling the composition of the reactive species. The nanosecond pulses are superimposed on the AC voltage which is in synchronization with the AC phase. The undergoing work to characterize the combined power discharge with electric charge and voltage cycle on the plasma jet will also be presented to discuss the discharge characteristics to control the composition of the reactive species.

  16. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

    PubMed

    Binh, P H; Trong, V D; Renucci, P; Marie, X

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power. PMID:24007048

  17. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power

    NASA Astrophysics Data System (ADS)

    Binh, P. H.; Trong, V. D.; Renucci, P.; Marie, X.

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

  18. Numerical simulation of impurity desorption induced by nanosecond and femtosecond laser pulses

    SciTech Connect

    Chi Yinsheng; Lin Xiaohui; Chen Minhua; Chen Yunfei

    2006-08-01

    A model based on a stochastic process was developed to study the impurity molecule desorption from a substrate induced by nanosecond and femtosecond lasers. The dynamics of adsorbed molecules irradiated by the laser pulses can be considered to be a Brownian motion in the bath of excited energy carriers. A two-step model was used to describe the nonequilibrium heating process induced by the femtosecond laser pulses. The difference between the desorption processes induced by nanosecond and femtosecond lasers was discussed based on the numerical results for the desorption of CO molecules from a Ru surface. Results indicate that the femtosecond laser is a much better tool for desorption than the nanosecond laser.

  19. The design of nanosecond high-voltage ultra wide band bipolar pulse generator

    NASA Astrophysics Data System (ADS)

    Shi, Jincheng; Liu, Baiyu; Gou, Yongsheng

    2015-10-01

    The design of nanosecond high-voltage ultra wide band bipolar pulse generator is shown in this paper. By analyzing the principle of the avalanche diode and doing the research of the related circuit acting on the pulse, this generator can generate a nanosecond high-voltage ultra wide band bipolar pulse, which its peak-to-peak voltage is about 400V and the pulse time width is 2ns. The experimental results showed a good agreement with the simulation results. A negative unipolar high-voltage pulse, having a fast falling-edge and a slowly exponential rising-edge, was firstly generated by the MARX circuit consist of the avalanche diodes. Then the use of the high speed avalanche diode could generate a negative unipolar high-voltage narrow Gaussian pulse, having a fast falling-edge and a fast rising-edge. In an attempt to cancel the reflection of the pulse made by the impedance mismatch, the circuit introduced the capacitor(C) and inductor(L) by calculating. Eventually a nanosecond high-voltage ultra wide band bipolar pulse could be got after going through the differentiator consist of introducing the right resistance, capacitance and inductance by calculation and experiment, and a filter with 2GHz bandwidth makes the bipolar smooth and perfect.

  20. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Joly, Alan G.; Tonkyn, Russell G.; Kay, Bruce D.; Kimmel, Greg A.

    2016-04-01

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ˜1010 K/s for temperature increases of ˜100-200 K are obtained. Subsequent rapid cooling (˜5 × 109 K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ˜±2.7% leading to a temperature uncertainty of ˜±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  1. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum.

    PubMed

    Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A

    2016-04-28

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces. PMID:27131543

  2. Explosive boiling of metals upon irradiation by a nanosecond laser pulse

    SciTech Connect

    Mazhukin, V I; Demin, M M; Shapranov, A V; Samokhin, A A

    2014-04-28

    A repeated effect of explosive boiling has been found in metals exposed to a nanosecond laser pulse in the framework of molecular dynamic simulations combined with a continuum description of a conduction band electrons system. This effect can be used, in particular, as a marker of approaching critical parameters of the region in the irradiated matter. (letters)

  3. Gene transfer into mammalian cells by use of a nanosecond pulsed laser-induced stress wave

    NASA Astrophysics Data System (ADS)

    Terakawa, Mitsuhiro; Ogura, Makoto; Sato, Shunichi; Wakisaka, Hitoshi; Ashida, Hiroshi; Uenoyama, Maki; Masaki, Yoshinori; Obara, Minoru

    2004-06-01

    Plasmid DNA has been successfully delivered to mammalian cells by applying a nanosecond pulsed laser-induced stress wave (LISW). Cells exposed to a LISW were selectively transfected with plasmids coding for green fluorescent protein. It was also shown that transient, mild cellular heating (~43 °C) was effective in improving the transfection efficiency.

  4. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    NASA Astrophysics Data System (ADS)

    Krastelev, E. G.; Sedin, A. A.; Tugushev, V. I.

    2015-12-01

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80-90 ns, and a pulse repetition rate of up to 16 Hz.

  5. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    SciTech Connect

    Krastelev, E. G. Sedin, A. A.; Tugushev, V. I.

    2015-12-15

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.

  6. Development of a nanosecond-laser-pumped Raman amplifier for short laser pulses in plasma

    NASA Astrophysics Data System (ADS)

    Ping, Y.; Kirkwood, R. K.; Wang, T.-L.; Clark, D. S.; Wilks, S. C.; Meezan, N.; Berger, R. L.; Wurtele, J.; Fisch, N. J.; Malkin, V. M.; Valeo, E. J.; Martins, S. F.; Joshi, C.

    2009-12-01

    Progress on developing a plasma amplifier/compressor based on stimulated Raman scattering of nanosecond laser pulses is reported. Generation of a millijoule seed pulse at a wavelength that is redshifted relative to the pump beam has been achieved using an external Raman gas cell. By interacting the shifted picosecond seed pulse and the nanosecond pump pulse in a gas jet plasma at a density of ˜1019 cm-3, the upper limit of the pump intensity to avoid angular spray of the amplified seed has been determined. The Raman amplification has been studied as a function of the pump and seed intensities. Although the heating of plasma by the nanosecond pump pulse results in strong Landau damping of the plasma wave, an amplified pulse with an energy of up to 14 mJ has been demonstrated, which is, to the best of our knowledge, the highest output energy so far by Raman amplification in a plasma. One-dimensional particle-in-cell simulations indicate that the saturation of amplification is consistent with onset of particle trapping, which might be overcome by employing a shorter seed pulse.

  7. Development of a nanosecond-laser-pumped Raman amplifier for short laser pulses in plasma

    SciTech Connect

    Ping, Y.; Kirkwood, R. K.; Clark, D. S.; Wilks, S. C.; Meezan, N.; Berger, R. L.; Wang, T.-L.; Martins, S. F.; Joshi, C.; Wurtele, J.; Fisch, N. J.; Malkin, V. M.; Valeo, E. J.

    2009-12-15

    Progress on developing a plasma amplifier/compressor based on stimulated Raman scattering of nanosecond laser pulses is reported. Generation of a millijoule seed pulse at a wavelength that is redshifted relative to the pump beam has been achieved using an external Raman gas cell. By interacting the shifted picosecond seed pulse and the nanosecond pump pulse in a gas jet plasma at a density of approx10{sup 19} cm{sup -3}, the upper limit of the pump intensity to avoid angular spray of the amplified seed has been determined. The Raman amplification has been studied as a function of the pump and seed intensities. Although the heating of plasma by the nanosecond pump pulse results in strong Landau damping of the plasma wave, an amplified pulse with an energy of up to 14 mJ has been demonstrated, which is, to the best of our knowledge, the highest output energy so far by Raman amplification in a plasma. One-dimensional particle-in-cell simulations indicate that the saturation of amplification is consistent with onset of particle trapping, which might be overcome by employing a shorter seed pulse.

  8. Device for generation of pulsed corona discharge

    DOEpatents

    Gutsol, Alexander F.; Fridman, Alexander; Blank, Kenneth; Korobtsev, Sergey; Shiryaevsky, Valery; Medvedev, Dmitry

    2012-05-08

    The invention is a method and system for the generation of high voltage, pulsed, periodic corona discharges capable of being used in the presence of conductive liquid droplets. The method and system can be used, for example, in different devices for cleaning of gaseous or liquid media using pulsed corona discharge. Specially designed electrodes and an inductor increase the efficiency of the system, permit the plasma chemical oxidation of detrimental impurities, and increase the range of stable discharge operations in the presence of droplets of water or other conductive liquids in the discharge chamber.

  9. Permeabilization of yeast Saccharomyces cerevisiae cell walls using nanosecond high power electrical pulses

    NASA Astrophysics Data System (ADS)

    Stirke, A.; Zimkus, A.; Balevicius, S.; Stankevic, V.; Ramanaviciene, A.; Ramanavicius, A.; Zurauskiene, N.

    2014-12-01

    The electrical field-induced changes of the yeast Saccharomyces cerevisiae cells permeabilization to tetraphenylphosphonium (TPP+) ions were studied using square-shaped, nanosecond duration high power electrical pulses. It was obtained that pulses having durations ranging from 10 ns to 60 ns, and generating electric field strengths up to 190 kV/cm significantly (up to 65 times) increase the absorption rate of TPP+ ions without any detectible influence on the yeast cell viability. The modelling of the TPP+ absorption process using a second order rate equation demonstrates that depending on the duration of the pulses, yeast cell clusters of different sizes are homogeniously permeabilized. It was concluded, that nanosecond pulse-induced permeabilization can be applied to increase the operational speed of whole cell biosensors.

  10. Over 0.5 MW green laser from sub-nanosecond giant pulsed microchip laser

    NASA Astrophysics Data System (ADS)

    Zheng, Lihe; Taira, Takunori

    2016-03-01

    A sub-nanosecond green laser with laser head sized 35 × 35 × 35 mm3 was developed from a giant pulsed microchip laser for laser processing on organic superconducting transistor with a flexible substrate. A composite monolithic Y3Al5O12 (YAG) /Nd:YAG/Cr4+:YAG/YAG crystal was designed for generating giant pulsed 1064 nm laser. A fibercoupled 30 W laser diode centered at 808 nm was used with pump pulse duration of 245 μs. The 532 nm green laser was obtained from a LiB3O5 (LBO) crystal with output energy of 150 μJ and pulse duration of 268 ps. The sub-nanosecond green laser is interesting for 2-D ablation patterns.

  11. High on/off ratio nanosecond laser pulses for a triggered single-photon source

    NASA Astrophysics Data System (ADS)

    Jin, Gang; Liu, Bei; He, Jun; Wang, Junmin

    2016-07-01

    An 852 nm nanosecond laser pulse chain with a high on/off ratio is generated by chopping a continuous-wave laser beam using a Mach–Zehnder-type electro-optic intensity modulator (MZ-EOIM). The detailed dependence of the MZ-EOIM’s on/off ratio on various parameters is characterized. By optimizing the incident beam polarization and stabilizing the MZ-EOIM temperature, a static on/off ratio of 12600:1 is achieved. The dynamic on/off ratios versus the pulse repetition rate and the pulse duty cycle are measured and discussed. The high-on/off-ratio nanosecond pulsed laser system was used in a triggered single-photon source based on a trapped single cesium atom, which reveals clear antibunching.

  12. Cluster ion control by simultaneous irradiations of femtosecond laser and nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kamada, H.; Hiratani, Y.; Toyoda, K.

    2002-09-01

    Generation of multiply charged ions and molecular ions have been investigated using simultaneous irradiation of high intensity and ultrashort pulse of Ti:sapphire laser and fourth harmonics of Q-switched nanosecond pulse of Nd:YAG laser on carbon targets [Morimoto et al., in: Proceedings of the 13th International Conference on High-Power Particles Beams (BEAMS2000),Vol. PB-89, Nagaoka, 2000, p. 359; Toyoda et al., in: Proceedings of the 8th International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference (GCL-HPL2000), Vol. P1.60, 2000, p. 101]. The ion current waveforms have been analyzed by means of time-of-flight (tof) mass measurement. Simultaneous irradiation of high intensity and ultrashort pulse of Ti:sapphire laser and fourth harmonics of Q-switched nanosecond pulse of Nd:YAG laser on carbon targets was found to generate molecular ions of carbon.

  13. OES characterization of streamers in a nanosecond pulsed SDBD using N2 and Ar transitions

    NASA Astrophysics Data System (ADS)

    Goekce, S.; Peschke, P.; Hollenstein, Ch; Leyland, P.; Ott, P.

    2016-08-01

    The characterization of non-thermal homogeneous plasmas is possible using optical emission spectroscopy (OES), notably by estimating the reduced electric field. This method was applied to characterize streamers generated by a nanosecond pulsed surface dielectric barrier discharge (SDBD) operated in quiescent air at atmospheric pressure and also at 0.5 atm. The average reduced electric field associated with the surface streamers was determined using four different sets of transitions occurring in air plasmas, the first negative system (FNS) of \\text{N}2+ , the first positive system (FPS) and second positive system (SPS) of {{\\text{N}}2} and argon transitions 2{{p}x}-1{{s}y} . The analysis of the results allowed to critically assess the validity of the estimated reduced electric field for the present conditions. It is shown experimentally that the inhomogeneous nature of the streamer head influences significantly the estimation of the reduced electric field. Moreover, the estimated reduced electric field is not sufficient to characterize the processes taking place in the streamer head, due to the steep variation of both the reduced electric field E/N and the electron density n e in space and time. To overcome this limitation, a new method is proposed to take into account the spatial structure of a streamer head. The applicability of the new method is demonstrated for these experimental conditions and shows a very good agreement for the transitions tested.

  14. Improved laser triggering and guiding of meqavolt discharges with dual fs-ns pulses

    SciTech Connect

    Mejean, Guillaume; Ackermann, Roland; Kasparian, Jerome; Salmon, Estelle; Yu Jin; Wolf, Jean-Pierre; Rethmeier, Kay; Kalkner, Wilfried; Rohwetter, Philipp; Stelmaszczyk, Kamil; Woeste, Ludger

    2006-01-09

    We demonstrate that the capacity of ultrashort high-power laser pulses to trigger and guide high-voltage discharges can be significantly enhanced by a subsequent visible nanosecond laser pulse. The femtosecond pulse induces a bundle of filaments, which creates a conducting channel of low density and cold plasma connecting the electrodes. The subsequent laser pulse photodetaches electrons from O{sub 2}{sup -} ions in the electrode leader. The resulting electrons allow efficient heating by Joule effect in a retroaction loop, resulting in a 5% reduction of the breakdown voltage.

  15. 188 W nanosecond pulsed fiber amplifier at 1064 nm

    NASA Astrophysics Data System (ADS)

    Li, Zebiao; Guo, Chao; Li, Qi; Zhao, Pengfei; Li, Chengyu; Huang, Zhihua; Tang, Xuan; Lin, Honghuan; Xu, Shanhui; Yang, Zhongmin; Wang, Jianjun; Jing, Feng

    2016-07-01

    We report an all-fiber high power nanosecond pulsed laser at a center wavelength of 1064 nm. Optimizing the coiling diameter of the active fiber, 188 W average power is achieved at a repetition rate of 40 kHz. The pulse width is measured as 101 ns, while the peak power can be estimated to 46.5 kW.

  16. Interaction Of CO2 Laser Nanosecond Pulse Train With The Metallic Targets In Optical Breakdown Regime

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Firsov, K. N.; Konov, V. I.; Nikitin, P. I.; Prokhorov, A. M.; Silenok, A. S.; Sorochenko, V. R.

    1986-11-01

    In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

  17. An IGBT-based High Voltage, Variable Pulse Width Nanosecond Pulser for Plasma Creation Applications

    NASA Astrophysics Data System (ADS)

    Ziemba, Timothy; Miller, Kenneth; Prager, James; Carscadden, John

    2013-10-01

    Eagle Harbor Technologies (EHT) has developed a modular solid state power supply based on IGBT technology, which can support a wide array of applications. The EHT Integrated Power Module (IPM) incorporates fast gate drive technology, high voltage isolation (~30 kV), fiber optic control, and optional crowbar diodes into a single unit. The EHT IPM can be configured to produce variable pulsed width (20 to 1000 ns), high voltage (>20 kV) high repetition frequency (2 MHz) nanosecond pulser. Nanosecond pulser applications include plasma creation for drag reduction, medical applications, water decontamination, fuel mixing and control of flue gas emissions.

  18. Percussion drilling of metals using bursts of nanosecond pulses.

    PubMed

    Hendow, Sami T; Romero, Rosa; Shakir, Sami A; Guerreiro, Paulo T

    2011-05-23

    The effect of ns bursting on percussion drilling of metal is investigated experimentally and analytically, and compared with the efficiency and quality of drilling using single ns pulses. Key advantages are demonstrated, correlating well with the results from a thermal theoretical model. The 1064 nm bursts contain up to 14 pulses of various pulse widths and spacing, and at frequencies of tens of MHz within the burst. The individual pulses have pulse widths of 10 to 200 ns, and up to 12 kW peak power. Burst repetition frequency is single shot to 500 kHz. PMID:21643280

  19. Plasma density evolution during nanosecond discharge in hydrogen gas at (1-3) × 105 Pa pressure

    NASA Astrophysics Data System (ADS)

    Yatom, S.; Krasik, Ya E.

    2014-05-01

    The results of a study of the nanosecond discharge in H2 gas at pressures of (1-3) × 105 Pa using fast-framing photography and space- and time-resolved spectroscopy are presented. The discharge is initiated by the application of a high-voltage pulse with an amplitude of ˜100 kV and duration of ˜5 ns to a blade cathode placed at a distance of 20 mm from the anode. The results show the dynamics of the discharge formation and the build-up of the plasma electron density in the discharge channels close to and at a distance from the edge of the cathode. The results obtained are compared to those obtained in recent studies of similar discharges in air and He gas. It was shown that the time and space evolution of the plasma light emission in the H2 gas discharge is very similar to that in air. Namely, the generation of the plasma is mainly confined to the plasma channels initiated at the top and bottom edges of the cathode electrode and that there are no new plasma channels formed from the explosive emission centres along the blade as it was obtained in earlier experiments with He gas. Spectroscopic measurements showed that the plasma density reaches 2 × 1017 cm-3 and 1.6 × 1016 cm-3 in the vicinity of the cathode and the middle of the anode-cathode gap, respectively, for a plasma electron temperature of <1.5 eV. The values of plasma electron density and the previously presented results of electric field measurements allow calculation of the resistance of the plasma channels.

  20. Plasma in a Pulsed Discharge Environment

    NASA Technical Reports Server (NTRS)

    Remy, J.; Bienier, L.; Salama, F.

    2005-01-01

    The plasma generated in a pulsed slit discharge nozzle is used to form molecular ions in an astrophysically relevant environment. The plasma has been characterized as a glow discharge in the abnormal regime. Laboratory studies help understand the formation processes of polycyclic aromatic hydrocarbon (PAH) ions that are thought to be the source of the ubiquitous unidentified infrared bands.

  1. Spatial and temporal dependence of interspark interactions in femtosecond-nanosecond dual-pulse laser-induced breakdown spectroscopy.

    PubMed

    Scaffidi, Jon; Pearman, William; Lawrence, Marion; Carter, J Chance; Colston, Bill W; Angel, S Michael

    2004-09-20

    A femtosecond air spark has recently been combined with a nanosecond ablative pulse in order to map the spatial and temporal interactions of the two plasmas in femtosecond-nanosecond orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Good spatial and temporal correlation was found for reduced atomic emission from atmospheric species (nitrogen and oxygen) and increased atomic emission from ablated species (copper and aluminum) in the femtosecond-nanosecond plasma, suggesting a potential role for atmospheric pressure or nitrogen/oxygen concentration reduction following air spark formation in generating atomic emission enhancements in dual-pulse LIBS. PMID:15473246

  2. Spatial and Temporal Dependence of Interspark Interactions in Femtosecond-Nanosecond Dual-Pulse Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Scaffidi, Jon; Pearman, William; Lawrence, Marion; Chance Carter, J.; Colston, Bill W., Jr.; Angel, S. Michael

    2004-09-01

    A femtosecond air spark has recently been combined with a nanosecond ablative pulse in order to map the spatial and temporal interactions of the two plasmas in femtosecond-nanosecond orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Good spatial and temporal correlation was found for reduced atomic emission from atmospheric species (nitrogen and oxygen) and increased atomic emission from ablated species (copper and aluminum) in the femtosecond-nanosecond plasma, suggesting a potential role for atmospheric pressure or nitrogen/oxygen concentration reduction following air spark formation in generating atomic emission enhancements in dual-pulse LIBS.

  3. Mechanisms of deflagration-to-detonation transition under initiation by high-voltage nanosecond discharges

    SciTech Connect

    Rakitin, Aleksandr E.; Starikovskii, Andrei Yu.

    2008-10-15

    An experimental study of detonation initiation in a stoichiometric propane-oxygen mixture by a high-voltage nanosecond gas discharge was performed in a detonation tube with a single-cell discharge chamber. The discharge study performed in this geometry showed that three modes of discharge development were realized under the experimental conditions: a spark mode with high-temperature channel formation, a streamer mode with nonuniform gas excitation, and a transient mode. Under spark and transient initiation, simultaneous ignition inside the discharge channel occurred, forming a shock wave and leading to a conventional deflagration-to-detonation transition (DDT) via an adiabatic explosion. The DDT length and time at 1 bar of initial pressure in the square smooth tube with a 20-mm transverse size amounted to 50 mm and 50{mu}s, respectively. The streamer mode of discharge development at an initial pressure of 1 bar resulted in nonuniform mixture excitation and a successful DDT via a gradient mechanism, which was confirmed by high-speed time resolved ICCD imaging. The gradient mechanism implied a longer DDT time of 150{mu}s, a DDT run-up distance of 50 mm, and an initiation energy of 1 J, which is two orders of magnitude less than the direct initiation energy for a planar detonation under these conditions. (author)

  4. Ion transport into cells exposed to monopolar and bipolar nanosecond pulses.

    PubMed

    Schoenbach, Karl H; Pakhomov, Andrei G; Semenov, Iurii; Xiao, Shu; Pakhomova, Olga N; Ibey, Bennett L

    2015-06-01

    Experiments with CHO cells exposed to 60 and 300 ns pulsed electric fields with amplitudes in the range from several kV/cm to tens of kV/cm showed a decrease of the uptake of calcium ions by more than an order of magnitude when, immediately after a first pulse, a second one of opposite polarity was applied. This effect is assumed to be due to the reversal of the electrophoretic transport of ions through the electroporated membrane during the second phase of the bipolar pulse. This assumption, however, is only valid if electrophoresis is the dominant transport mechanism, rather than diffusion. Comparison of calculated calcium ion currents with experimental results showed that for nanosecond pulses, electrophoresis is at least as important as diffusion. By delaying the second pulse with respect to the first one, the effect of reverse electrophoresis is reduced. Consequently, separating nanosecond pulses of opposite polarity by up to approximately hundred microseconds allows us to vary the uptake of ions from very small values to those obtained with two pulses of the same polarity. The measured calcium ion uptake obtained with bipolar pulses also allowed us to determine the membrane pore recovery time. The calculated recovery time constants are on the order of 10 μs. PMID:25212701

  5. Observations in collinear femtosecond-nanosecond dual-pulse laser-induced breakdown spectroscopy.

    PubMed

    Scaffidi, J; Pearman, W; Carter, J C; Angel, S M

    2006-01-01

    In the work reported herein, we have combined a short-lived femtosecond laser-induced plasma (LIP) and a longer-lived nanosecond LIP in a collinear pulse configuration to examine the source(s) of atomic emission and signal-to-noise enhancement in dual-pulse laser-induced breakdown spectroscopy (LIBS). Initial studies indicate that the primary source of dual-pulse LIBS enhancement in the collinear configuration may in large part be a matter of pulse focus; focusing on the sample surface, for example, yields atomic emission enhancements whose lifetime correlates reasonably well with the femtosecond LIP emissive lifetime, suggesting that plasma-plasma coupling may play an important role at that pulse focus. At a second "optimal" focal position above the sample surface, alternatively, atomic emission and signal-to-noise enhancements correlate quite well with the nitrogen and oxygen atomic emission reductions previously seen following use of a femtosecond air spark and a nanosecond ablative pulse in the orthogonal dual-pulse configuration, suggesting that pressure or number density reductions due to femtosecond LIP formation in air may be significant at that pulse focus. PMID:16454914

  6. Ion transport into cells exposed to monopolar and bipolar nanosecond pulses

    PubMed Central

    Schoenbach, Karl H.; Pakhomov, Andrei G.; Semenov, Iurii; Xiao, Shu; Pakhomova, Olga N.; Ibey, Bennet L.

    2014-01-01

    Experiments with CHO cells exposed to 60 and 300 ns pulsed electric fields with amplitudes in the range from several kV/cm to tens of kV/cm, showed a decrease of the uptake of calcium ions by more than an order of magnitude when, immediately after a first pulse, a second one of opposite polarity was applied. This effect is assumed to be due to the reversal of the electrophoretic transport of ions through the electroporated membrane during the second phase of the bipolar pulse. This assumption, however, is only valid if electrophoresis is the dominant transport mechanism, rather than diffusion. Comparison of calculated calcium ion currents with experimental results showed that for nanosecond pulses, electrophoresis is at least as important as diffusion. By delaying the second pulse with respect to the first one, the effect of reverse electrophoresis is reduced. Consequently, separating nanosecond pulses of opposite polarity by up to approximately hundred microseconds allows us to vary the uptake of ions from very small values to that obtained with two pulses of the same polarity. The measured calcium ion uptake obtained with bipolar pulses also allowed us to determine the membrane pore recovery time. The calculated recovery time constants are on the order of ten microseconds. PMID:25212701

  7. Studies on laser material processing with nanosecond and sub-nanosecond and picosecond and sub-picosecond pulses

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

    2016-03-01

    In this paper, laser ablation of widely used metal (Al, Cu. stainless-steel), semiconductor (Si), transparent material (glass, sapphire), ceramic (Al2O3, AlN) and polymer (PI, PMMA) in industry were systematically studied with pulse width from nanosecond (5-100ns), picosecond (6-10ps) to sub-picosecond (0.8-0.95ps). A critical damage zone (CDZ) of up to 100um with ns laser, <=50um with ps laser, and <=20um with sub-ps laser, respectively was observed as a criteria of selecting the laser pulse width. The effects of laser processing parameters on speed and efficiency were also investigated. This is to explore how to provide industry users the best laser solution for device micro-fabrication with best price. Our studies of cutting and drilling with ns, ps, and sub-ps lasers indicate that it is feasible to achieve user accepted quality and speed with cost-effective and reliable laser by optimizing processing conditions.

  8. Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation

    NASA Astrophysics Data System (ADS)

    Kang, Chen; Hua, Liang

    2016-02-01

    Plasma flow control (PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle (UAV) by nanosecond discharge plasma aerodynamic actuation (NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge (30 A) is much bigger than that for millisecond discharge (0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation (MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control. Project supported by the National Natural Science Foundation of China (Grant Nos. 61503302, 51207169, and 51276197), the China Postdoctoral Science Foundation (Grant No. 2014M562446), and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2015JM1001).

  9. A Single Pulse Sub-Nanosecond Proton RFQ

    SciTech Connect

    Hamm, R W; Pearce-Percy, H; Pearson, D; Rougieri, M; Weir, J; Zografos, A; Guethlein, G; Hawkins, S; Falabella, S; Poole, B; Blackfield, D

    2011-03-29

    A Radio Frequency Quadrupole (RFQ) linac system has been developed to provide a single pulse of 2 MeV protons with a beam pulse width of {approx}300 ps and a charge of 30 pC, either for injection into a pulsed Dielectric Wall Accelerator or for bombardment of a target to produce a fast neutron pulse. The 1.2 m long RFQ structure operates at 425 MHz and bunches and accelerates a single 2.35 ns beam pulse injected into it at 35 keV using a parallel plate deflector placed directly in front of the RFQ entrance. The input acceptance properties of the RFQ allow a simple dc bias voltage on the plates to block acceleration of the unwanted beam, with a short rf voltage pulse applied to null the deflection field for the ions within the 8 mm 'kicker' plate length. The use of the RFQ as the accelerating structure allows one to efficiently produce a large charge in a single sub-ns bunch. In addition, the kicker can also be used without the dc bias voltage to produce a 'notch' in the normal RFQ output beam for synchrotron injection.

  10. Nanosecond pulse pumped, narrow linewidth all-fiber Raman amplifier with stimulated Brillouin scattering suppression

    NASA Astrophysics Data System (ADS)

    Su, Rongtao; Zhou, Pu; Wang, Xiaolin; Lü, Haibin; Xu, Xiaojun

    2014-01-01

    We report on a narrow linewidth nanosecond all-fiber Raman amplifier core pumped by a pulsed laser at approximately 1030 nm. The Raman amplifier was based on a standard single-mode fiber with a length of ∼1 km, and stimulated Brillouin scattering (SBS) was suppressed by employing pulses with a short pulse width. 1083 nm pulses with an average power of 32.6 mW, a repetition rate of 2 MHz, and pulse widths of ∼7.2 ns were achieved. A maximum slope efficiency of 46.1% and a gain of 31 dB were obtained. The output Raman power can be scaled further by using fiber with shorter lengths and pump pulses with a higher power.

  11. Conductive versus capacitive coupling for cell electroporation with nanosecond pulses

    NASA Astrophysics Data System (ADS)

    French, David M.; Uhler, Michael D.; Gilgenbach, Ronald M.; Lau, Y. Y.

    2009-10-01

    Experiments and simulations were performed to determine the difference between capacitive coupling and conductive connection for the electroporation of cells. The pulses used in the experiments have a peak voltage of 24 kV, 0.6 ns rise time, and 1.6 ns full width at half maximum. Experiments performed compare the conductive connection of the cell suspension versus a capacitively coupled cell suspension. The magnitude of the electric field was 16 kV/cm in both cases; however, the pulse shape is different. For the conductively connected case the cells located between the electrodes experienced an electric field in one direction only, whereas cells located between the electrodes in the capacitive coupling case were subject to an electric field that reverses direction. For the capacitively coupled case the bipolar pulse leads to no net cell charging. The conductive connection case is different, in that cells are left with a net polarization after the pulse is applied. Experimentally, only cells subject to the pulse with conductive connection demonstrated electroporation with the drug Bleomycin.

  12. Effects of high voltage nanosecond electric pulses on eukaryotic cells (in vitro): A systematic review.

    PubMed

    Batista Napotnik, Tina; Reberšek, Matej; Vernier, P Thomas; Mali, Barbara; Miklavčič, Damijan

    2016-08-01

    For this systematic review, 203 published reports on effects of electroporation using nanosecond high-voltage electric pulses (nsEP) on eukaryotic cells (human, animal, plant) in vitro were analyzed. A field synopsis summarizes current published data in the field with respect to publication year, cell types, exposure configuration, and pulse duration. Published data were analyzed for effects observed in eight main target areas (plasma membrane, intracellular, apoptosis, calcium level and distribution, survival, nucleus, mitochondria, stress) and an additional 107 detailed outcomes. We statistically analyzed effects of nsEP with respect to three pulse duration groups: A: 1-10ns, B: 11-100ns and C: 101-999ns. The analysis confirmed that the plasma membrane is more affected with longer pulses than with short pulses, seen best in uptake of dye molecules after applying single pulses. Additionally, we have reviewed measurements of nsEP and evaluations of the electric fields to which cells were exposed in these reports, and we provide recommendations for assessing nanosecond pulsed electric field effects in electroporation studies. PMID:26946156

  13. Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion

    SciTech Connect

    Wu, Jian; Wei, Wenfu; Li, Xingwen; Jia, Shenli; Qiu, Aici

    2013-04-22

    We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm{sup 2} in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag model was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.

  14. Laser breakdown in alcohols and water induced by λ = 1064 nm nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Kovalchuk, Tatiana; Toker, Gregory; Bulatov, Valery; Schechter, Israel

    2010-11-01

    Laser breakdown, induced by nanosecond pulses of 1064 nm wavelength, was studied in four alcohols and in water. The time dependent structure and physical properties of the breakdown were measured at high temporal and spatial resolutions, using Mach-Zehnder interferometry, shadow and Schlieren diagnostic techniques. The results indicate that just after the laser pulse the spark column has essentially discrete character and in all liquids it consists of a train of plasma micro-balls, triggered by microscopic inclusion particles. At longer times, namely in a few nanoseconds, micro-bubbles and associated micro-spherical shockwaves appear. These structures and their time-evolution were measured. Warmed channels were observed in the focal volume in all studied liquids.

  15. Investigation of Vacuum Insulator Surface Dielectric Strength with Nanosecond Pulses

    SciTech Connect

    Nunnally, W C; Krogh, M; Williams, C; Trimble, D; Sampayan, S; Caporaso, G

    2003-06-03

    The maximum vacuum insulator surface dielectric strength determines the acceleration electric field gradient possible in a short pulse accelerator. Previous work has indicated that higher electric field strengths along the insulator-vacuum interface might be obtained as the pulse duration is decreased. In this work, a 250 kV, single ns wide impulse source was applied to small diameter, segmented insulators samples in a vacuum to evaluate the multi-layer surface dielectric strength of the sample construction. Resonances in the low inductance test geometry were used to obtain unipolar, pulsed electric fields in excess of 100 MV/m on the insulator surface. The sample construction, experimental arrangement and experimental results are presented for the initial data in this work. Modeling of the multi-layer structure is discussed and methods of improving insulator surface dielectric strength in a vacuum are proposed.

  16. Nonlinear-optical transformation of nanosecond laser pulses and controlled supercontinuum generation in photonic-crystal fibers

    SciTech Connect

    Fedotov, I. V. Fedotov, A. B.; Zheltikov, A. M.

    2007-11-15

    Photonic-crystal fibers are shown to allow efficient spectral transformation of nanosecond laser pulses through parametric four-wave mixing and stimulated Raman scattering. Regimes providing highly efficient transformation of nanosecond laser pulses into white-light broadband radiation (supercontinuum) are identified. A strong parametric coupling between Stokes and anti-Stokes Raman sidebands around the wavelength of zero group-velocity dispersion is shown to increase the bandwidth and to improve the spectral quality of supercontinuum radiation.

  17. Conversion of high explosive chemical energy into energy of powerful nanosecond high-current pulses

    NASA Astrophysics Data System (ADS)

    Gorbachev, K. V.; Mikhaylov, V. M.; Nesterov, E. V.; Stroganov, V. A.; Chernykh, E. V.

    2015-01-01

    This study is a contribution into the development of physicotechnical foundations for generation of powerful nanosecond high-current pulses on the basis of explosively driven magnetic flux compression generators. This problem is solved by using inductive storage of energy for matching comparatively low-voltage explosively driven magnetic flux compression generators and high-impedance loads; short forming lines and vacuum diodes. Experimental data of charging of forming lines are given.

  18. Electric Field in a Plasma Channel in a High-Pressure Nanosecond Discharge in Hydrogen: A Coherent Anti-Stokes Raman Scattering Study

    NASA Astrophysics Data System (ADS)

    Yatom, S.; Tskhai, S.; Krasik, Ya. E.

    2013-12-01

    Experimental results of a study of the electric field in a plasma channel produced during nanosecond discharge at a H2 gas pressure of (2-3)×105 Pa by the coherent anti-Stokes scattering method are reported. The discharge was ignited by applying a voltage pulse with an amplitude of ˜100 kV and a duration of ˜5 ns to a blade cathode placed at a distance of 10 and 20 mm from the anode. It was shown that this type of gas discharge is characterized by the presence of an electric field in the plasma channel with root-mean-square intensities of up to 30 kV/cm. Using polarization measurements, it was found that the direction of the electric field is along the cathode-anode axis.

  19. Nanosecond pulsed laser generation of holographic structures on metals

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, Krystian L.; Ardron, Marcus; Weston, Nick J.; Hand, Duncan P.

    2016-03-01

    A laser-based process for the generation of phase holographic structures directly onto the surface of metals is presented. This process uses 35ns long laser pulses of wavelength 355nm to generate optically-smooth surface deformations on a metal. The laser-induced surface deformations (LISDs) are produced by either localized laser melting or the combination of melting and evaporation. The geometry (shape and dimension) of the LISDs depends on the laser processing parameters, in particular the pulse energy, as well as on the chemical composition of a metal. In this paper, we explain the mechanism of the LISDs formation on various metals, such as stainless steel, pure nickel and nickel-chromium Inconel® alloys. In addition, we provide information about the design and fabrication process of the phase holographic structures and demonstrate their use as robust markings for the identification and traceability of high value metal goods.

  20. UV laser removal of varnish on tempera paints with nanosecond and femtosecond pulses.

    PubMed

    Oujja, Mohamed; García, Ana; Romero, Carolina; Vázquez de Aldana, Javier R; Moreno, Pablo; Castillejo, Marta

    2011-03-14

    Two laser cleaning approaches based on ablation by ultraviolet laser pulses of femtosecond (fs) and nanosecond (ns) durations for the removal of shellac varnish from egg-yolk based tempera paints are investigated. Laser irradiation effects, induced on the varnish layer and on the underlying temperas by multiple pulses in the fs domain at 398 and 265 nm and single pulses in the ns domain at 213 nm, were examined following a spectroanalytical approach. By using optical microscopy, colorimetry and laser induced fluorescence it was found that irradiation of the varnished temperas with fs pulses changes the texture of the varnish surface and results in degradation of the underlying coloured paint. In contrast, operating with pulses of 15 ns at the highly absorbed wavelength of 213 nm, controlled micrometric layer removal of the varnish is possible without noticeable modification of the coloured temperas. These results widen the choice of laser conditions for painting restoration. PMID:21264373

  1. Energy deposition characteristics of nanosecond dielectric barrier discharge plasma actuators: Influence of dielectric material

    NASA Astrophysics Data System (ADS)

    Correale, G.; Winkel, R.; Kotsonis, M.

    2015-08-01

    An experimental study aimed at the characterization of energy deposition of nanosecond Dielectric Barrier Discharge (ns-DBD) plasma actuators was carried out. Special attention was given on the effect of the thickness and material used for dielectric barrier. The selected materials for this study were polyimide film (Kapton), polyamide based nylon (PA2200), and silicone rubber. Schlieren measurements were carried out in quiescent air conditions in order to observe density gradients induced by energy deposited. Size of heated area was used to qualify the energy deposition coupled with electrical power measurements performed using the back-current shunt technique. Additionally, light intensity measurements showed a different nature of discharge based upon the material used for barrier, for a fixed thickness and frequency of discharge. Finally, a characterisation study was performed for the three tested materials. Dielectric constant, volume resistivity, and thermal conductivity were measured. Strong trends between the control parameters and the energy deposited into the fluid during the discharge were observed. Results indicate that efficiency of energy deposition mechanism relative to the thickness of the barrier strongly depends upon the material used for the dielectric barrier itself. In general, a high dielectric strength and a low volumetric resistivity are preferred for a barrier, together with a high heat capacitance and a low thermal conductivity coefficient in order to maximize the efficiency of the thermal energy deposition induced by an ns-DBD plasma actuator.

  2. Generation and dynamics of single-electrode nanosecond pulsed microplasma jets

    NASA Astrophysics Data System (ADS)

    Jiang, Chunqi; Lane, Jamie; Song, Shutong; Plasma; Pulsed Power Lab at ODU-CBE Team

    2015-11-01

    Several millimeter long, 160 - 260 micrometer-in-width, helium plasma jets were generated in ambient atmosphere when a needle electrode was excited with nanosecond high voltage pulses at single shot or up to 500 Hz. This single-electrode system does not require the use of ground electrode for plasma generation, and thus has advantages in simplicity and small-dimension for a variety of biomedical applications. Dynamics of the microplasma jet powered by high voltage pulses with two different nanosecond pulses - 5 ns and 164 ns, was studied with high speed imaging, and spatiotemporally resolved optical emission spectroscopy. Whereas the plasma jet exhibits three different modes including a positive-streamer mode, a stochastic transition, and a negative streamer-like mode when it was excited with 164 ns kilovolt pulses, such modes and transitions in the plasma development were not observed for the 5 ns pulsed excitation. Shorter pulses with shorter rise times allowed higher energy deposition into the plasma and promote rapid acceleration of the plasma wavefronts; 5 ns pulsed excitation resulted in 4 times increase in the wavefront velocity compared with the 164 ns pulsed excitation. Importantly, the production of excited atomic oxygen increased by a factor of 2 for the 5 ns pulsed plasma jet when compared with that for a 164 ns pulsed plasma jet, whereas the other excited species including He, O, H, OH, N2(C-B) and N2+(B-X) were produced at comparable rates for the two plasma jets. Work supported by the Air Force Office of Scientific Research (AFOSR Award No. FA9550-11-1-0190).

  3. A Tesla-type repetitive nanosecond pulse generator for solid dielectric breakdown research.

    PubMed

    Zhao, Liang; Pan, Ya Feng; Su, Jian Cang; Zhang, Xi Bo; Wang, Li Min; Fang, Jin Peng; Sun, Xu; Lui, Rui

    2013-10-01

    A Tesla-type repetitive nanosecond pulse generator including a pair of electrode and a matched absorption resistor is established for the application of solid dielectric breakdown research. As major components, a built-in Tesla transformer and a gas-gap switch are designed to boost and shape the output pulse, respectively; the electrode is to form the anticipated electric field; the resistor is parallel to the electrode to absorb the reflected energy from the test sample. The parameters of the generator are a pulse width of 10 ns, a rise and fall time of 3 ns, and a maximum amplitude of 300 kV. By modifying the primary circuit of the Tesla transformer, the generator can produce both positive and negative pulses at a repetition rate of 1-50 Hz. In addition, a real-time measurement and control system is established based on the solid dielectric breakdown requirements for this generator. With this system, experiments on test samples made of common insulation materials in pulsed power systems are conducted. The preliminary experimental results show that the constructed generator is capable to research the solid dielectric breakdown phenomenon on a nanosecond time scale. PMID:24182170

  4. A Tesla-type repetitive nanosecond pulse generator for solid dielectric breakdown research

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Pan, Ya Feng; Su, Jian Cang; Zhang, Xi Bo; Wang, Li Min; Fang, Jin Peng; Sun, Xu; Lui, Rui

    2013-10-01

    A Tesla-type repetitive nanosecond pulse generator including a pair of electrode and a matched absorption resistor is established for the application of solid dielectric breakdown research. As major components, a built-in Tesla transformer and a gas-gap switch are designed to boost and shape the output pulse, respectively; the electrode is to form the anticipated electric field; the resistor is parallel to the electrode to absorb the reflected energy from the test sample. The parameters of the generator are a pulse width of 10 ns, a rise and fall time of 3 ns, and a maximum amplitude of 300 kV. By modifying the primary circuit of the Tesla transformer, the generator can produce both positive and negative pulses at a repetition rate of 1-50 Hz. In addition, a real-time measurement and control system is established based on the solid dielectric breakdown requirements for this generator. With this system, experiments on test samples made of common insulation materials in pulsed power systems are conducted. The preliminary experimental results show that the constructed generator is capable to research the solid dielectric breakdown phenomenon on a nanosecond time scale.

  5. The effects of gaseous bubble composition and gap distance on the characteristics of nanosecond discharges in distilled water

    NASA Astrophysics Data System (ADS)

    Hamdan, Ahmad; Cha, Min Suk

    2016-06-01

    Electric discharge in liquids with bubbles can reduce the energy consumption, which increases treatment efficiency. We present an experimental study of nanosecond discharges in distilled water bubbled with the monoatomic gas argon and with the polyatomic gases methane, carbon dioxide, and propane. We monitor the time evolution of the voltage and current waveforms, and calculate the injected charges to characterize the discharge. We establish a relationship between the injected charges and the shape of the plasma by time-resolved imaging to find that increasing the size of the gap reduces the injected charges. Moreover, we determine the plasma characteristics, including electron density, excitation temperatures (for atoms and ions), and rotational temperature of the OH and C2 radicals found in the plasma. Our space- and time-averaged measurements allow us to propose a spatial distribution of the plasma that is helpful for understanding the plasma dynamics necessary to develop and optimize applications based on nanosecond discharges in bubbled liquids.

  6. Studies of nanosecond pulsed power for modifications of biomaterials and nanomaterials (SWCNT)

    NASA Astrophysics Data System (ADS)

    Chen, Meng-Tse

    This work investigates the modification of biological materials through the applications of modern nanosecond pulsed power, along with other forms of nanotechnologies. The work was initially envisaged as a study of the effect of intense nanosecond pulsed electric fields on cancer cells. As the work progressed, the studies suggested incorporation of additional technologies, in particular, cold plasmas, and carbon nanotubes. The reasons for these are discussed below, however, they were largely suggested by the systems that we were studying, and resulted in new and potentially important medical therapies. Using nanosecond cold plasmas powered with nanosecond pulses, collaboration with endodontists and biofilm experts demonstrated a killing effect on biofilms deep within root canals, suggesting a fundamentally new approach to an ongoing problem of root canal sterilization. This work derived from the application of nanosecond pulsed power, resulting in effective biofilm disinfection, without excessive heating, and is being investigated for additional dental and other medical applications. In the second area, collaboration with medical and nanotube experts, studies of gliomamultiforme (GBM) led to the incorporation of functionalized carbon nanotubes. Single-walled carbon nanotube-fluorescein carbazide (SWCNT-FC) conjugates demonstrated that the entry mechanism of the single-walled carbon nanotubes (SWCNTs) was through an energy-dependent endocytotic pathway. Finally, a monotonic pH sensitivity of the intracellular fluorescence emission of SWCNT-FC conjugates in human ovarian cancer cells suggests these conjugates may serve as intracellular pH sensors. Light-stimulated intracellular hydrolysis of the amide linkage and localized intracellular pH changes are proposed as mechanisms. The use of SWCNTs for cancer therapy of gliomas, resulting in hyperthermia effect after 808 nm infrared radiations, absorbed specifically by SWCNTs but not by biological tissue. Heat was only

  7. Conductivity affects nanosecond electrical pulse induced pressure transient formation

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.; Beier, Hope T.; Glickman, Randolph D.

    2016-03-01

    Nanoporation occurs in cells exposed to high amplitude short duration (< 1μs) electrical pulses. The biophysical mechanism(s) responsible for nanoporation is unknown although several theories exist. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. Our group has shown that mechanical forces of substantial magnitude are also generated during nsEP exposures. We hypothesize that these mechanical forces may contribute to pore formation. In this paper, we report that alteration of the conductivity of the exposure solution also altered the level of mechanical forces generated during a nsEP exposure. By reducing the conductivity of the exposure solutions, we found that we could completely eliminate any pressure transients normally created by nsEP exposure. The data collected for this proceeding does not definitively show that the pressure transients previously identified contribute to nanoporation; however; it indicates that conductivity influences both survival and pressure transient formation.

  8. In vivo imaging rhodopsin distribution in the photoreceptors with nano-second pulsed scanning laser ophthalmoscopy

    PubMed Central

    Liu, Tan; Liu, Xiaojing; Wen, Rong; Lam, Byron L.

    2015-01-01

    Background Rhodopsin is a biomarker for the function of rod photoreceptors, the dysfunction of which is related to many blinding diseases like retinitis pigmentosa and age-related macular degeneration. Imaging rhodopsin quantitatively may provide a powerful clinical tool for diagnosis of these diseases. To map rhodopsin distribution accurately in the retina, absorption by rhodopsin intermediates need to be minimized. Methods and materials We developed nano-second pulsed scanning laser ophthalmoscopy (SLO) to image rhodopsin distribution in the retina. The system takes advantage of the light-induced shift of rhodopsin absorption spectra, which in turn affects the fundus spectral reflection before and after photo-bleaching. By imaging the retina twice, one in the dark-adapted state and the other one in the light-adapted state, the rhodopsin absorption change can be calculated from the differential image, which is a function of the rhodopsin concentration in the rod photoreceptors. Results The system was successfully applied to in vivo imaging of rat retina in different bleaching conditions to verify its feasibility. Our studies showed that the differential image between the dark- and light-adapted states represents rhodopsin distribution in the retina. We also conducted a dynamic bleaching experiment to prove the importance of reducing light absorption of rhodopsin intermediates. Conclusions The preliminary results showed that our nano-second pulsed-light SLO is promising in imaging the functional biomarker of the rod photoreceptors. By using nanosecond pulsed laser, in which one laser pulse generates one pixel of the image, the absorption of rhodopsin intermediates can be reduced. PMID:25694955

  9. Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

    SciTech Connect

    Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.

    2015-08-15

    The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.

  10. Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.

    2015-08-01

    The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.

  11. Long-lived plasma and fast quenching of N2(C3Π u ) by electrons in the afterglow of a nanosecond capillary discharge in nitrogen

    NASA Astrophysics Data System (ADS)

    Lepikhin, N. D.; Klochko, A. V.; Popov, N. A.; Starikovskaia, S. M.

    2016-08-01

    Quenching of electronically excited nitrogen state, {{\\text{N}}2}≤ft({{\\text{C}}3}{{\\Pi}u},{{v}\\prime}=0\\right) , in the afterglow of nanosecond capillary discharge in pure nitrogen is studied. It is found experimentally that an additional collisional mechanism appears and dominates at high specific deposited energies leading to the anomalously fast quenching of the {{\\text{N}}2}≤ft({{\\text{C}}3}{{\\Pi}u}\\right) in the afterglow. On the basis of obtained experimental data and of the analysis of possible quenching agents, it is concluded that the anomalously fast deactivation of the {{\\text{N}}2}≤ft({{\\text{C}}3}{{\\Pi}u}\\right) can be explained by quenching by electrons. Long-lived plasma at time scale of hundreds nanoseconds after the end of the pulse is observed. High electron densities, about 1014 cm‑3 at 27 mbar, are sustained by reactions of associative ionization. Kinetic 1D numerical modeling and comparison of calculated results with experimentally measured electric fields in the second high-voltage pulse 250 ns after the initial pulse, and electron density measurements in the afterglow confirm the validity of the suggested mechanism.

  12. Picosecond and nanosecond pulse delivery through a hollow-core Negative Curvature Fiber for micro-machining applications.

    PubMed

    Jaworski, Piotr; Yu, Fei; Maier, Robert R J; Wadsworth, William J; Knight, Jonathan C; Shephard, Jonathan D; Hand, Duncan P

    2013-09-23

    We present high average power picosecond and nanosecond pulse delivery at 1030 nm and 1064 nm wavelengths respectively through a novel hollow-core Negative Curvature Fiber (NCF) for high-precision micro-machining applications. Picosecond pulses with an average power above 36 W and energies of 92 µJ, corresponding to a peak power density of 1.5 TWcm⁻² have been transmitted through the fiber without introducing any damage to the input and output fiber end-faces. High-energy nanosecond pulses (>1 mJ), which are ideal for micro-machining have been successfully delivered through the NCF with a coupling efficiency of 92%. Picosecond and nanosecond pulse delivery have been demonstrated in fiber-based laser micro-machining of fused silica, aluminum and titanium. PMID:24104161

  13. Dynamics of the microstructure of current channels and the generation of high-energy electrons in nanosecond discharges in air

    SciTech Connect

    Karelin, V. I.; Trenkin, A. A. Fedoseev, I. G.

    2015-12-15

    The results of the three-dimensional numerical simulation of the dynamics of the microstructure of high-voltage nanosecond discharges in air at atmospheric pressure are presented. It is established that the fast (at a time of ≈10 ns) broadening and significant decrease in the gas concentration in the microchannels occur as a result of the ohmic heating of microchannels with the diameter of 1–30 μm. It was shown that the broadening of microchannels in a nanosecond diffusive discharge provides an increase in the ratio of the electric field strength to the gas concentration in microchannels to values sufficient for the generation highenergy electron beams and X-ray bremsstrahlung in them. Features of the dynamics of the system of microchannels and its effect on the efficiency of the generation of high-energy electrons in discharges developing in the microstructuring regime of the current channels are considered.

  14. Time resolved optical methods for investigation of phase transformations in materials exposed to nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Martan, J.; Semmar, N.; Cibulka, O.

    2011-06-01

    Infrared (IR) radiometry and time resolved reflectivity (TRR) methods can be used for investigation of laser pulse effects on materials in nanosecond time scale. The methods in combination are capable to quantify object temperature and detect phase transformations in the solid state, melting and plasma formation from vapour. Measurements with different laser pulse energy densities provide threshold of the transformation. The melt duration can be also determined. The experimental system is described. It contains KrF excimer laser with homogenizer and variable attenuator, fast IR detector for radiometry, continuous probing laser with Si photodiode for reflectivity measurement and UV detector for pump laser pulse reflection measurement. The system was applied to investigation of responses to laser light of silicon and different pure metals and alloys. The range of energy densities used was 1-5500 mJ.cm-2 and measurements were done with temporal resolution of 6 ns for radiometry and 1 ns for reflectivity.

  15. 100  J-level nanosecond pulsed diode pumped solid state laser.

    PubMed

    Banerjee, Saumyabrata; Mason, Paul D; Ertel, Klaus; Jonathan Phillips, P; De Vido, Mariastefania; Chekhlov, Oleg; Divoky, Martin; Pilar, Jan; Smith, Jodie; Butcher, Thomas; Lintern, Andrew; Tomlinson, Steph; Shaikh, Waseem; Hooker, Chris; Lucianetti, Antonio; Hernandez-Gomez, Cristina; Mocek, Tomas; Edwards, Chris; Collier, John L

    2016-05-01

    We report on the successful demonstration of a 100 J-level, diode pumped solid state laser based on cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier technology. When operated at 175 K, the system delivered a pulse energy of 107 J at a 1 Hz repetition rate and 10 ns pulse duration, pumped by 506 J of diode energy at 940 nm, corresponding to an optical-to-optical efficiency of 21%. To the best of our knowledge, this represents the highest energy obtained from a nanosecond pulsed diode pumped solid state laser. This demonstration confirms the energy scalability of the diode pumped optical laser for experiments laser architecture. PMID:27128081

  16. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    SciTech Connect

    Mahdieh, Mohammad Hossein Akbari Jafarabadi, Marzieh

    2015-12-15

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  17. Amplitude decay of photoacoustic signals in biological tissue when irradiated by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Dewhurst, Richard J.; Li, Teng; Gondek, Grzegorz

    2007-02-01

    In this paper, we report on sequential decreases in the amplitude of photoacoustic (PA) signals from nanosecond laser pulse irradiation of various samples. These samples include biological tissues, such as dental-enamel and chicken/turkey breast as well as some non-biological samples. Laser energy densities in the range of 80mJ/cm2 to 300mJ/cm2 were used in our experiments, typical of those used in PA imaging regimes. Induced temperature rises are modelled to show that the average temperature rise for each pulse in those biological tissues is less than one degree centigrade. Measurements reveal a rapid decay of photoacoustic signals within the first few laser pulses absorbed by the sample and this decay is irreversible in the short term. The phenomenon indicates that laser irradiation interacts with biological samples, causing long-term physical changes that can be attributed to a reduction of optical absorption within the samples.

  18. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Mahdieh, Mohammad Hossein; Akbari Jafarabadi, Marzieh

    2015-12-01

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  19. Kinetic mechanism of plasma recombination in methane, ethane and propane after high-voltage nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Anokhin, E. M.; Popov, M. A.; Kochetov, I. V.; Starikovskiy, A. Yu; Aleksandrov, N. L.

    2016-08-01

    The results of the experimental and numerical study of high-voltage nanosecond discharge afterglow in pure methane, ethane and propane are presented for room temperature and pressures from 2 to 20 Torr. Time-resolved electron density during the plasma decay was measured with a microwave interferometer for initial electron densities in the range between 5  ×  1010 and 3  ×  1012 cm‑3 and the effective recombination coefficients were obtained. Measured effective recombination coefficients increased with gas pressure and were much higher than the recombination coefficients for simple molecular hydrocarbon ions. The properties of plasma in the discharge afterglow were numerically simulated by solving the balance equations for charged particles and electron temperature. Calculations showed that electrons had time to thermalize prior to the recombination. The measured data were interpreted under the assumption that cluster hydrocarbon ions are formed during the plasma decay that is controlled by the dissociative electron recombination with these ions at electron room temperature. Based on the analysis of the experimental data, the rates of three-body formation of cluster ions and recombination coefficients for these ions were estimated.

  20. Targeted gene transfer into rat facial muscles by nanosecond pulsed laser-induced stress waves.

    PubMed

    Kurita, Akihiro; Matsunobu, Takeshi; Satoh, Yasushi; Ando, Takahiro; Sato, Shunichi; Obara, Minoru; Shiotani, Akihiro

    2011-09-01

    We investigate the feasibility of using nanosecond pulsed laser-induced stress waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis. PMID:21950944

  1. Targeted gene transfer into rat facial muscles by nanosecond pulsed laser-induced stress waves

    NASA Astrophysics Data System (ADS)

    Kurita, Akihiro; Matsunobu, Takeshi; Satoh, Yasushi; Ando, Takahiro; Sato, Shunichi; Obara, Minoru; Shiotani, Akihiro

    2011-09-01

    We investigate the feasibility of using nanosecond pulsed laser-induced stress waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis.

  2. Controlled oxide films formation by nanosecond laser pulses for color marking.

    PubMed

    Veiko, Vadim; Odintsova, Galina; Ageev, Eduard; Karlagina, Yulia; Loginov, Anatoliy; Skuratova, Alexandra; Gorbunova, Elena

    2014-10-01

    A technology of laser-induced coloration of metals by surface oxidation is demonstrated. Each color of the oxide film corresponds to a technologic chromacity coefficient, which takes into account the temperature of the sample after exposure by sequence of laser pulses with nanosecond duration and effective time of action. The coefficient can be used for the calculation of laser exposure regimes for the development of a specific color on the metal. A correlation between the composition of the films obtained on the surface of stainless steel AISI 304 and commercial titanium Grade 2 and its color and chromacity coordinates is shown. PMID:25322009

  3. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Genc, Suzanne L.; Ma, Huan; Venugopalan, Vasan

    2014-08-01

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of Ep ≈ 4-5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (Rmax = 2-20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy EB. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (Ep = 11-20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1-2 orders of magnitude larger in size ( R max ≳ 100 μ m ) due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA.

  4. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses

    PubMed Central

    Genc, Suzanne L.; Ma, Huan; Venugopalan, Vasan

    2014-01-01

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of Ep ≈ 4–5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (Rmax = 2–20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy EB. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (Ep = 11–20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1–2 orders of magnitude larger in size (Rmax≳100 μm) due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA. PMID:25278618

  5. Low-density plasma formation in aqueous biological media using sub-nanosecond laser pulses.

    PubMed

    Genc, Suzanne L; Ma, Huan; Venugopalan, Vasan

    2014-08-11

    We demonstrate the formation of low- and high-density plasmas in aqueous media using sub-nanosecond laser pulses delivered at low numerical aperture (NA = 0.25). We observe two distinct regimes of plasma formation in deionized water, phosphate buffered saline, Minimum Essential Medium (MEM), and MEM supplemented with phenol red. Optical breakdown is first initiated in a low-energy regime and characterized by bubble formation without plasma luminescence with threshold pulse energies in the range of E p ≈ 4-5 μJ, depending on media formulation. The onset of this regime occurs over a very narrow interval of pulse energies and produces small bubbles (R max = 2-20 μm) due to a tiny conversion (η < 0.01%) of laser energy to bubble energy E B. The lack of visible plasma luminescence, sharp energy onset, and low bubble energy conversion are all hallmarks of low-density plasma (LDP) formation. At higher pulse energies (E p = 11-20 μJ), the process transitions to a second regime characterized by plasma luminescence and large bubble formation. Bubbles formed in this regime are 1-2 orders of magnitude larger in size [Formula: see text] due to a roughly two-order-of-magnitude increase in bubble energy conversion (η ≳ 3%). These characteristics are consistent with high-density plasma formation produced by avalanche ionization and thermal runaway. Additionally, we show that supplementation of MEM with fetal bovine serum (FBS) limits optical breakdown to this high-energy regime. The ability to produce LDPs using sub-nanosecond pulses focused at low NA in a variety of cell culture media formulations without FBS can provide for cellular manipulation at high throughput with precision approaching that of femtosecond pulses delivered at high NA. PMID:25278618

  6. Radiative Characteristics of the Pulse-Periodic Discharge Plasma Initiated by Runaway Electrons

    NASA Astrophysics Data System (ADS)

    Lomaev, M. I.; Beloplotov, D. V.; Tarasenko, V. F.; Sorokin, D. A.

    2016-07-01

    Results of experimental investigations of amplitude-temporal and spectral characteristics of radiation of a pulse-periodic discharge plasma initiated in nitrogen by runaway electrons are presented. The discharge was initiated by high-voltage nanosecond voltage pulses with repetition frequency of 60 Hz in a sharply inhomogeneous electric field in a gap between the conic potential cathode and the planar grounded aluminum anode. It is established that intensive lines of Al I atoms and Al II atomic ions, lines of N I atoms and N II ions, bands of the first (1+) and second positive (2+) nitrogen systems, as well as bands of cyanogen CN are observed in the emission spectrum of the discharge plasma under the given excitation conditions.

  7. Transient features in nanosecond pulsed electric fields differentially modulate mitochondria and viability.

    PubMed

    Beebe, Stephen J; Chen, Yeong-Jer; Sain, Nova M; Schoenbach, Karl H; Xiao, Shu

    2012-01-01

    It is hypothesized that high frequency components of nanosecond pulsed electric fields (nsPEFs), determined by transient pulse features, are important for maximizing electric field interactions with intracellular structures. For monopolar square wave pulses, these transient features are determined by the rapid rise and fall of the pulsed electric fields. To determine effects on mitochondria membranes and plasma membranes, N1-S1 hepatocellular carcinoma cells were exposed to single 600 ns pulses with varying electric fields (0-80 kV/cm) and short (15 ns) or long (150 ns) rise and fall times. Plasma membrane effects were evaluated using Fluo-4 to determine calcium influx, the only measurable source of increases in intracellular calcium. Mitochondria membrane effects were evaluated using tetramethylrhodamine ethyl ester (TMRE) to determine mitochondria membrane potentials (ΔΨm). Single pulses with short rise and fall times caused electric field-dependent increases in calcium influx, dissipation of ΔΨm and cell death. Pulses with long rise and fall times exhibited electric field-dependent increases in calcium influx, but diminished effects on dissipation of ΔΨm and viability. Results indicate that high frequency components have significant differential impact on mitochondria membranes, which determines cell death, but lesser variances on plasma membranes, which allows calcium influxes, a primary determinant for dissipation of ΔΨm and cell death. PMID:23284682

  8. Nanosecond laser-induced phase transitions in pulsed laser deposition-deposited GeTe films

    SciTech Connect

    Sun, Xinxing Thelander, Erik; Lorenz, Pierre; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

    2014-10-07

    Phase transformations between amorphous and crystalline states induced by irradiation of pulsed laser deposition grown GeTe thin films with nanosecond laser pulses at 248 nm and pulse duration of 20 ns are studied. Structural and optical properties of the Ge-Te phase-change films were studied by X-ray diffraction and optical reflectivity measurements as a function of the number of laser pulses between 0 and 30 pulses and of the laser fluence up to 195 mJ/cm². A reversible phase transition by using pulse numbers ≥ 5 at a fluence above the threshold fluence between 11 and 14 mJ/cm² for crystallization and single pulses at a fluence between 162 and 182 mJ/cm² for amorphization could be proved. For laser fluences from 36 up to 130 mJ/cm², a high optical contrast of 14.7% between the amorphous and crystalline state is measured. A simple model is used that allows the discussion on the distribution of temperature in dependency on the laser fluence.

  9. Reliability performance of pulse discharge capacitors

    SciTech Connect

    Edwards, L.R.

    1997-02-01

    There is a void of public specifications for pulse discharge capacitor applications. Sandia National Laboratories has developed, over the past 25 years, specifications and test procedures for evaluating capacitor designs for this specialized use. There are three primary destructive tests that are used to assess the reliability potential of a given design at a required rated voltage. These are ultimate short time breakdown strength, life at voltage, and pulse discharge life. The strategy of the method is to accelerate the test conditions so that failures are observable and then extrapolate to the desired use conditions where the failure rates are low. This paper will present the statistical methodologies employed to analyze experimental data and to provide a point estimate of reliability with a lower confidence bound as a function of rated voltage. In addition, methods for establishing lot-acceptance-criteria specifications will be discussed. The techniques will be illustrated with actual data on a commercially available, low-inductance, pulse-discharge capacitor. The capacitor is an impregnated dual dielectric (mica-paper/polymer film), extended-foil type.

  10. Generation of neutrons in a nanosecond low-pressure discharge in deuterium

    NASA Astrophysics Data System (ADS)

    Lomaev, M. I.; Nechaev, B. A.; Padalko, V. N.; Dudkin, G. N.; Sorokin, D. A.; Tarasenko, V. F.; Shuvalov, E. N.

    2015-04-01

    The neutron yield is measured in a high-voltage Townsend discharge in deuterium with a hollow cylinder made of tungsten or steel used as a polarizing anode of electrons. A flat metallic plate covered by a layer of deuterated zirconium is applied as a grounded cathode. The highest yield of neutrons in the reaction 2H(d,n)3He, ˜1.2 × 104 neutrons per pulse, is observed in the case of the tungsten anode at a deuterium pressure on the order of 100 Pa. The pulsed neutron flux duration estimated with data obtained from a scintillation detector is roughly equal to 1.5 ns.

  11. Characterization of Wet Air Plasma Jet Powered by Sinusoidal High Voltage and Nanosecond Pulses for Plasma Agricultural Application

    NASA Astrophysics Data System (ADS)

    Takashima, Keisuke; Shimada, Keisuke; Konishi, Hideaki; Kaneko, Toshiro

    2015-09-01

    Not only for the plasma sterilization but also for many of plasma life-science applications, atmospheric pressure plasma devices that allowed us to control its state and reactive species production are deserved to resolve the roles of the chemical species. Influence of the hydroxyl radical and ozone on germination of conidia of a strawberry pathogen is presented. Water addition to air plasma jet significantly improves germination suppression performance, while measured reactive oxygen species (ROS) are reduced. Although the results show a negative correlation between ROS and the germination suppression, this infers the importance of chemical composition generated by plasma. For further control of the plasma product, a plasma jet powered by sinusoidal high voltage and nanosecond pulses is developed and characterized with the voltage-charge Lissajous. Control of breakdown phase and discharge power by pulse-imposed phase is presented. This work is supported by JSPS KAKENHI Grant-in-Aid for Young Scientists (B) Grant Number 15K17480 and Exploratory Research Grant Number 23644199.

  12. Micrometric rods grown by nanosecond pulsed laser deposition of boron carbide

    NASA Astrophysics Data System (ADS)

    Lopez-Quintas, Ignacio; Oujja, Mohamed; Sanz, Mikel; Benitez-Cañete, Antonio; Chater, Richard J.; Cañamares, Maria Vega; Marco, José F.; Castillejo, Marta

    2015-02-01

    Micrometric size rods have been fabricated via pulsed laser deposition in vacuum from boron carbide targets using nanosecond pulses of 1064 and 266 nm and room temperature Si (1 0 0) substrates. Morphological, structural and chemical characterization of the microrods was made by applying scanning electron microscopy, focussed ion beam microscopy coupled to secondary ion mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Ablation at 1064 nm favours the formation of microrods with high aspect ratio, sharp edges and pyramidal tips, typically 10 μm long with a cross section of around 2 μm × 2 μm. Differently, at 266 nm the microrods are of smaller size and present a more globular aspect. The analyses of the microrods provide information about their crystalline nature and composition, based on a mixture which includes boron, boron oxide and boron carbide, and allows discussion of the wavelength dependent growth mechanisms involved.

  13. Nanosecond near-spinodal homogeneous boiling of water superheated by a pulsed CO2 laser

    NASA Astrophysics Data System (ADS)

    Kudryashov, Sergey I.; Lyon, Kevin; Allen, Susan D.

    2007-03-01

    The fast boiling dynamics of superheated surface layers of bulk water cavitating under near-spinodal conditions during nanosecond CO2 laser heating pulses was studied using contact broad-band photoacoustic spectroscopy. Characteristic pressure-tension cycles recorded by an acoustic transducer at different incident laser fluences represent (a) weak random oscillations of transient nanometer-sized near-critical bubbles-precursors and (b) well-defined stimulated oscillations of micron-sized supercritical bubbles and their submicrosecond coalescence products. These findings provide an important insight into basic thermodynamic parameters, spatial and temporal scales of bubble nucleation during explosive liquid/vapor transformations in absorbing liquids ablated by short laser pulses in the thermal confinement regime.

  14. Amplification of picosecond pulses in F{sub 2}{sup -}:LiF crystals synchronously pumped by picosecond and nanosecond laser pulses

    SciTech Connect

    Basiev, Tasoltan T; Karasik, Aleksandr Ya; Konyushkin, V A; Osiko, Vyacheslav V; Papashvili, A G; Chunaev, D S

    2005-04-30

    A method for amplification of picosecond pulses in F{sub 2}{sup -}:LiF crystals synchronously pumped by picosecond and nanosecond pulses is proposed and demonstrated. Due to two-stage amplification of a train of 22-ps, 1150-nm SRS pulses generated by a PbMoO{sub 4} crystal, a power gain of (2-4)x 10{sup 3} is achieved and single 6-ps, 0.88-mJ pulses are obtained. (lasers)

  15. Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

    NASA Astrophysics Data System (ADS)

    Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

    2004-07-01

    Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.

  16. Nanoparticle mediated thermal ablation of breast cancer cells using a nanosecond pulsed electric field.

    PubMed

    Burford, Christopher D; Bhattacharyya, Kiran D; Boriraksantikul, Nattaphong; Whiteside, Paul J D; Robertson, Benjamin P; Peth, Sarah M; Islam, Naz E; Viator, John A

    2013-06-01

    In the past, ablation of cancer cells using radiofrequency heating techniques has been demonstrated, but the current methodology has many flaws, including inconsistent tumor ablation and significant ablation of normal cells. Other researchers have begun to develop a treatment that is more selective for cancer cells using metallic nanoparticles and constant electric field exposure. In these studies, cell necrosis is induced by heating antibody functionalized metallic nanoparticles attached to cancer cells. Our approach to studying this phenomenon is to use similarly functionalized metallic nanoparticles that are specific for the T47D breast cancer cell line, exposing these nanoparticle cell conjugates to a nanosecond pulsed electric field. Using fluorescent, polystyrene-coated, iron-oxide nanoparticles, the results of our pilot study indicated that we were able to ablate up to approximately 80% of the cells using 60 ns pulses in increasing numbers of pulses and up to approximately 90% of the cells using 300 ns pulses in increasing numbers of pulses. These quantities of ablated cells were achieved using a cumulative exposure time 6 orders of magnitude less than most in vitro constant electric field studies. PMID:23694696

  17. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  18. High frequency application of nanosecond pulsed electric fields alters cellular membrane disruption and fluorescent dye uptake

    NASA Astrophysics Data System (ADS)

    Steelman, Zachary A.; Tolstykh, Gleb P.; Beier, Hope T.; Ibey, Bennett L.

    2016-03-01

    Cells exposed to nanosecond-pulsed electric fields (nsPEF) exhibit a wide variety of nonspecific effects, including blebbing, swelling, intracellular calcium bursts, apoptotic and necrotic cell death, formation of nanopores, and depletion of phosphatidylinositol 4,5-biphosphate (PIP2) to induce activation of the inositol trisphosphate/diacylglycerol pathway. While several studies have taken place in which multiple pulses were delivered to cells, the effect of pulse repetition rate (PRR) is not well understood. To better understand the effects of PRR, a laser scanning confocal microscope was used to observe CHO-K1 cells exposed to ten 600ns, 200V pulses at varying repetition rates (5Hz up to 500KHz) in the presence of either FM 1-43, YO-PRO-1, or Propidium Iodide (PI) fluorescent dyes, probes frequently used to indicate nanoporation or permeabilization of the plasma membrane. Dye uptake was monitored for 30 seconds after pulse application at a rate of 1 image/second. In addition, a single long pulse of equivalent energy (200V, 6 μs duration) was applied to test the hypothesis that very fast PRR will approximate the biological effects of a single long pulse of equal energy. Upon examination of the data, we found strong variation in the relationship between PRR and uptake in each of the three dyes. In particular, PI uptake showed little frequency dependence, FM 1-43 showed a strong inverse relationship between frequency and internal cell fluorescence, and YO-PRO-1 exhibited a "threshold" point of around 50 KHz, after which the inverse trend observed in FM 1-43 was seen to reverse itself. Further, a very high PRR of 500 KHz only approximated the biological effects of a single 6 μs pulse in cells stained with YO-PRO-1, suggesting that uptake of different dyes may proceed by different physical mechanisms.

  19. Nanosecond-range multi-pulses synchronization based on magnetic switch and saturable pulse transformer.

    PubMed

    Liu, Jinliang; Fan, Xuliang; Zhang, Yu

    2012-12-01

    Magnetic switch has been widely used in the field of pulsed power system for its advantages of solid state, high repetition rate, and long lifetime. In this paper, the synchronization of ns-range multi-pulses based on magnetic switch is studied and two kinds of technical methods are proposed. One of which is based on magnetic switches on a communal magnetic core. It was proved that the synchronization accuracy of 3 pulses is about 2 ns. Another proposed method is ns-range multi-pulse synchronization based on saturable pulse transformer and the experimental result showed that the synchronization accuracy of 2 pulses could achieve 2.5 ns. In contrast to other multi-pulse synchronization methods controlled by high-voltage pulse trigger or laser trigger, the synchronization based on magnetic switch and saturable pulse transformer has the advantages of high synchronization accuracy, long lifetime, and exemption from external trigger signals. PMID:23278010

  20. Non-equilibrium nanosecond-pulsed plasma generation in the liquid phase (water, PDMS) without bubbles: fast imaging, spectroscopy and leader-type model

    NASA Astrophysics Data System (ADS)

    Dobrynin, Danil; Seepersad, Yohan; Pekker, Mikhail; Shneider, Mikhail; Friedman, Gary; Fridman, Alexander

    2013-03-01

    In this paper we report the results on study of the non-equilibrium nanosecond discharge generation in liquid media. Here we studied the discharge in both water and silicon transformer oil, and present our findings on discharge behaviour depending on global (applied) electric, discharge emission spectrum and shadow imaging of the discharge. We also discuss possible scenarios of non-equilibrium nanosecond discharge development and suggest that the discharge operates in a leader-type regime supported by the electrostriction effect—creation of nano-sized pores in liquid due to high local electric field.

  1. Investigation of a direct effect of nanosecond pulse electric fields on mitochondria

    NASA Astrophysics Data System (ADS)

    Estlack, Larry E.; Roth, Caleb C.; Cerna, Cesario Z.; Wilmink, Gerald J.; Ibey, Bennett L.

    2014-03-01

    The unique cellular response to nanosecond pulsed electric field (nsPEF) exposure, as compared to longer pulse exposure, has been theorized to be due to permeabilization of intracellular organelles including the mitochondria. In this investigation, we utilized a high-throughput oxygen and pH sensing system (Seahorse® XF24 extracellular flux analyzer) to assess the mitochondrial activity of Jurkat and U937 cells after nsPEF. The XF Analyzer uses a transient micro-chamber of only a few μL in specialized cell culture micro-plates to enable oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) to be monitored in real-time. We found that for nsPEF exposures of 10 pulses at 10-ns pulse width and at 50 kV/cm e-field, we were able to cause an increase in OCR in both U937 and Jurkat cells. We also found that high pulse numbers (>100) caused a significant decrease in OCR. Higher amplitude 150 kV/cm exposures had no effect on U937 cells and yet they had a deleterious effect on Jurkat cells, matching previously published 24 hour survival data. These results suggest that the exposures were modulating metabolic activity in cells possibly due to direct effects on the mitochondria themselves. To validate this hypothesis, we isolated mitochondria from U937 cells and exposed them similarly and found no significant change in metabolic activity for any pulse number. In a final experiment, we removed calcium from the buffer solution that the cells were exposed in and found that no significant enhancement in metabolic activity was observed. These results suggest that direct permeabilization of the mitochondria is unlikely a primary effect of nsPEF exposure and calcium-mediated intracellular pathway activation is likely responsible for observed pulse-induced mitochondrial effects.

  2. Raising the avermectins production in Streptomyces avermitilis by utilizing nanosecond pulsed electric fields (nsPEFs)

    NASA Astrophysics Data System (ADS)

    Guo, Jinsong; Ma, Ruonan; Su, Bo; Li, Yinglong; Zhang, Jue; Fang, Jing

    2016-05-01

    Avermectins, a group of anthelmintic and insecticidal agents produced from Streptomyces avermitilis, are widely used in agricultural, veterinary, and medical fields. This study presents the first report on the potential of using nanosecond pulsed electric fields (nsPEFs) to improve avermectin production in S. avermitilis. The results of colony forming units showed that 20 pulses of nsPEFs at 10 kV/cm and 20 kV/cm had a significant effect on proliferation, while 100 pulses of nsPEFs at 30 kV/cm exhibited an obvious effect on inhibition of agents. Ultraviolet spectrophotometry assay revealed that 20 pulses of nsPEFs at 15 kV/cm increased avermectin production by 42% and reduced the time for reaching a plateau in fermentation process from 7 days to 5 days. In addition, the decreased oxidation reduction potential (ORP) and increased temperature of nsPEFs-treated liquid were evidenced to be closely associated with the improved cell growth and fermentation efficiency of avermectins in S. avermitilis. More importantly, the real-time RT-PCR analysis showed that nsPEFs could remarkably enhance the expression of aveR and malE in S. avermitilis during fermentation, which are positive regulator for avermectin biosynthesis. Therefore, the nsPEFs technology presents an alternative strategy to be developed to increase avermectin output in fermentation industry.

  3. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    DOE PAGESBeta

    Grills, David C.; Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Bernstein, Herbert J.; Wishart, James F.

    2015-04-27

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of amore » unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330-1051 cm⁻¹. The response time of the TRIR detection setup is ~40 ns, with a typical sensitivity of ~100 µOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. As a result, this new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.« less

  4. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    SciTech Connect

    Grills, David C.; Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Bernstein, Herbert J.; Wishart, James F.

    2015-04-27

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330-1051 cm⁻¹. The response time of the TRIR detection setup is ~40 ns, with a typical sensitivity of ~100 µOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. As a result, this new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  5. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    SciTech Connect

    Grills, David C. Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Wishart, James F.; Bernstein, Herbert J.

    2015-04-15

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm{sup −1}. The response time of the TRIR detection setup is ∼40 ns, with a typical sensitivity of ∼100 μOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  6. Temperature dependence of nanosecond laser pulse thresholds of melanosome and microsphere microcavitation

    NASA Astrophysics Data System (ADS)

    Schmidt, Morgan S.; Kennedy, Paul K.; Noojin, Gary D.; Thomas, Robert J.; Rockwell, Benjamin A.

    2016-01-01

    Melanosome microcavitation is the threshold-level retinal pigment epithelium (RPE) damage mechanism for nanosecond (ns) pulse exposures in the visible and near-infrared (NIR). Thresholds for microcavitation of isolated bovine RPE melanosomes were determined as a function of temperature (20 to 85°C) using single ns laser pulses at 532 and 1064 nm. Melanosomes were irradiated using a 1064-nm Q-switched Nd:YAG (doubled for 532-nm irradiation). For comparison to melanosome data, a similar temperature (20 to 65°C) dependence study was also performed for 532 nm, ns pulse exposures of black polystyrene microbeads. Results indicated a decrease in the microcavitation average radiant exposure threshold with increasing sample temperature for both 532- and 1064-nm single pulse exposures of melanosomes and microbeads. Threshold data and extrapolated nucleation temperatures were used to estimate melanosome absorption coefficients in the visible and NIR, and microbead absorption coefficients in the visible, indicating that melanin is a better absorber of visible light than black polystyrene. The NIR melanosome absorption coefficients ranged from 3713 cm-1 at 800 nm to 222 cm-1 at 1319 nm. These data represent the first temperature-dependent melanosome microcavitation study in the NIR and provide additional information for understanding melanosome microcavitation threshold dependence on wavelength and ambient temperature.

  7. Raising the avermectins production in Streptomyces avermitilis by utilizing nanosecond pulsed electric fields (nsPEFs).

    PubMed

    Guo, Jinsong; Ma, Ruonan; Su, Bo; Li, Yinglong; Zhang, Jue; Fang, Jing

    2016-01-01

    Avermectins, a group of anthelmintic and insecticidal agents produced from Streptomyces avermitilis, are widely used in agricultural, veterinary, and medical fields. This study presents the first report on the potential of using nanosecond pulsed electric fields (nsPEFs) to improve avermectin production in S. avermitilis. The results of colony forming units showed that 20 pulses of nsPEFs at 10 kV/cm and 20 kV/cm had a significant effect on proliferation, while 100 pulses of nsPEFs at 30 kV/cm exhibited an obvious effect on inhibition of agents. Ultraviolet spectrophotometry assay revealed that 20 pulses of nsPEFs at 15 kV/cm increased avermectin production by 42% and reduced the time for reaching a plateau in fermentation process from 7 days to 5 days. In addition, the decreased oxidation reduction potential (ORP) and increased temperature of nsPEFs-treated liquid were evidenced to be closely associated with the improved cell growth and fermentation efficiency of avermectins in S. avermitilis. More importantly, the real-time RT-PCR analysis showed that nsPEFs could remarkably enhance the expression of aveR and malE in S. avermitilis during fermentation, which are positive regulator for avermectin biosynthesis. Therefore, the nsPEFs technology presents an alternative strategy to be developed to increase avermectin output in fermentation industry. PMID:27181521

  8. Nanosecond laser pulse stimulation of the inner ear—a wavelength study

    PubMed Central

    Schultz, Michael; Baumhoff, Peter; Maier, Hannes; Teudt, Ingo U.; Krüger, Alexander; Lenarz, Thomas; Kral, Andrej

    2012-01-01

    Optical stimulation of the inner ear, the cochlea, is discussed as a possible alternative to conventional cochlear implants with the hypothetical improvement of dynamic range and frequency resolution. In this study nanosecond-pulsed optical stimulation of the hearing and non-hearing inner ear is investigated in vivo over a wide range of optical wavelengths and at different beam delivery locations. Seven anaesthetized guinea pigs were optically stimulated before and after neomycin induced destruction of hair cells. An optical parametric oscillator was tuned to different wavelengths (420 nm–2150 nm, ultraviolet to near-infrared) and delivered 3–5 ns long pulses with 6 µJ pulse energy via a multimode optical fiber located either extracochlearly in front of the intact round window membrane or intracochlearly within the scala tympani. Cochlear responses were measured using registration of compound action potentials (CAPs). With intact hair cells CAP similar to acoustic stimulation were measured at both locations, while the neomycin treated cochleae did not show any response in any case. The CAP amplitudes of the functional cochleae showed a positive correlation to the absorption coefficient of hemoglobin and also to moderate water absorption. A negative correlation of CAP amplitude with a water absorption coefficient greater than 5.5 cm−1 indicates additional phenomena. We conclude that in our stimulation paradigm with ns-pulses the most dominant stimulation effect is of optoacoustic nature and relates to functional hair cells. PMID:23243582

  9. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    NASA Astrophysics Data System (ADS)

    Grills, David C.; Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Bernstein, Herbert J.; Wishart, James F.

    2015-04-01

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm-1. The response time of the TRIR detection setup is ˜40 ns, with a typical sensitivity of ˜100 μOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  10. Raising the avermectins production in Streptomyces avermitilis by utilizing nanosecond pulsed electric fields (nsPEFs)

    PubMed Central

    Guo, Jinsong; Ma, Ruonan; Su, Bo; Li, Yinglong; Zhang, Jue; Fang, Jing

    2016-01-01

    Avermectins, a group of anthelmintic and insecticidal agents produced from Streptomyces avermitilis, are widely used in agricultural, veterinary, and medical fields. This study presents the first report on the potential of using nanosecond pulsed electric fields (nsPEFs) to improve avermectin production in S. avermitilis. The results of colony forming units showed that 20 pulses of nsPEFs at 10 kV/cm and 20 kV/cm had a significant effect on proliferation, while 100 pulses of nsPEFs at 30 kV/cm exhibited an obvious effect on inhibition of agents. Ultraviolet spectrophotometry assay revealed that 20 pulses of nsPEFs at 15 kV/cm increased avermectin production by 42% and reduced the time for reaching a plateau in fermentation process from 7 days to 5 days. In addition, the decreased oxidation reduction potential (ORP) and increased temperature of nsPEFs-treated liquid were evidenced to be closely associated with the improved cell growth and fermentation efficiency of avermectins in S. avermitilis. More importantly, the real-time RT-PCR analysis showed that nsPEFs could remarkably enhance the expression of aveR and malE in S. avermitilis during fermentation, which are positive regulator for avermectin biosynthesis. Therefore, the nsPEFs technology presents an alternative strategy to be developed to increase avermectin output in fermentation industry. PMID:27181521

  11. Nanosecond pulsed electric field thresholds for nanopore formation in neural cells

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Tolstykh, Gleb P.; Payne, Jason A.; Kuipers, Marjorie A.; Thompson, Gary L.; DeSilva, Mauris N.; Ibey, Bennett L.

    2013-03-01

    The persistent influx of ions through nanopores created upon cellular exposure to nanosecond pulse electric fields (nsPEF) could be used to modulate neuronal function. One ion, calcium (Ca), is important to action potential firing and regulates many ion channels. However, uncontrolled hyper-excitability of neurons leads to Ca overload and neurodegeneration. Thus, to prevent unintended consequences of nsPEF-induced neural stimulation, knowledge of optimum exposure parameters is required. We determined the relationship between nsPEF exposure parameters (pulse width and amplitude) and nanopore formation in two cell types: rodent neuroblastoma (NG108) and mouse primary hippocampal neurons (PHN). We identified thresholds for nanoporation using Annexin V and FM1-43, to detect changes in membrane asymmetry, and through Ca influx using Calcium Green. The ED50 for a single 600 ns pulse, necessary to cause uptake of extracellular Ca, was 1.76 kV/cm for NG108 and 0.84 kV/cm for PHN. At 16.2 kV/cm, the ED50 for pulse width was 95 ns for both cell lines. Cadmium, a nonspecific Ca channel blocker, failed to prevent Ca uptake suggesting that observed influx is likely due to nanoporation. These data demonstrate that moderate amplitude single nsPEF exposures result in rapid Ca influx that may be capable of controllably modulating neurological function.

  12. Rhodamine B as an optical thermometer in cells focally exposed to infrared laser light or nanosecond pulsed electric fields

    PubMed Central

    Moreau, David; Lefort, Claire; Burke, Ryan; Leveque, Philippe; O’Connor, Rodney P.

    2015-01-01

    The temperature-dependent fluorescence property of Rhodamine B was used to measure changes in temperature at the cellular level induced by either infrared laser light exposure or high intensity, ultrashort pulsed electric fields. The thermal impact of these stimuli were demonstrated at the cellular level in time and contrasted with the change in temperature observed in the extracellular bath. The method takes advantage of the temperature sensitivity of the fluorescent dye Rhodamine B which has a quantum yield linearly dependent on temperature. The thermal effects of different temporal pulse applications of infrared laser light exposure and of nanosecond pulsed electric fields were investigated. The temperature increase due to the application of nanosecond pulsed electric fields was demonstrated at the cellular level. PMID:26504658

  13. Rhodamine B as an optical thermometer in cells focally exposed to infrared laser light or nanosecond pulsed electric fields.

    PubMed

    Moreau, David; Lefort, Claire; Burke, Ryan; Leveque, Philippe; O'Connor, Rodney P

    2015-10-01

    The temperature-dependent fluorescence property of Rhodamine B was used to measure changes in temperature at the cellular level induced by either infrared laser light exposure or high intensity, ultrashort pulsed electric fields. The thermal impact of these stimuli were demonstrated at the cellular level in time and contrasted with the change in temperature observed in the extracellular bath. The method takes advantage of the temperature sensitivity of the fluorescent dye Rhodamine B which has a quantum yield linearly dependent on temperature. The thermal effects of different temporal pulse applications of infrared laser light exposure and of nanosecond pulsed electric fields were investigated. The temperature increase due to the application of nanosecond pulsed electric fields was demonstrated at the cellular level. PMID:26504658

  14. Nanosecond laser pulse induced stress waves enhanced magnetofection of human carcinoma cells in vitro

    NASA Astrophysics Data System (ADS)

    Durdík, Š.; Babincová, M.; Bergemann, C.; Babinec, P.

    2012-09-01

    We have developed a novel platform for efficient gene delivery into cells using magnetic force for pre-concentration of gene-magnetic nanoparticle complex on the surface of cells with subsequent nanosecond laser pulse for generation of stress waves in transfection chamber which is able to permeabilize cell membrane for the facilitated delivery of gene into the cell interior. Combination of these two physical factors increased the efficiency of three different human carcinoma cells transfection with plasmid coding green fluorescence protein from 43% to 67%, from 35% to 54%, and from 23% to 39%, for HeLa (cervical carcinoma), MCF-7 (breast carcinoma), and UCI-107 (ovarian carcinoma) cells, respectively, as compared with using only magnetofection. Proposed fast, simple, and efficient method may have far reaching applications for cancer gene therapy.

  15. Understanding the physics limitations of PFNA — the nanosecond pulsed fast neutron analysis

    NASA Astrophysics Data System (ADS)

    Gozani, Tsahi

    1995-05-01

    The PFNA was conceived by Sawa, Gozani and Ryge, in late 1987 as a means to achieve the highest possible sensitivity for detecting small amounts of explosives concealed in luggage. This could be attained because 1) all the elements present in explosives, i.e., O,N,C (and H, indirectly) can be measured via the (n,n'γ) process with fast neutrons, 2) using nanosecond pulses of neutrons and the time-of-flight (TOF) technique, a full direct imaging of the elements and hence all present materials can be obtained, and 3) the TOF assures the best signal to background ratio, as the signal-stimulated γ-rays are measured before the background — neutron interacting in the detector environment — arrives. The PFNA technology has made great strides since the autumn of 1987. It enables the detection of narcotics, explosives, many hazardous materials and most dutiable goods carried in trucks and containers.

  16. Explosive boiling of a metallic glass superheated by nanosecond pulse laser ablation

    NASA Astrophysics Data System (ADS)

    Jiang, M. Q.; Wei, Y. P.; Wilde, G.; Dai, L. H.

    2015-01-01

    We report an explosive boiling in a Zr-based (Vitreloy 1) bulk metallic glass irradiated by a nanosecond pulse laser with a single shot. This critical phenomenon is accompanied by the ejection of high-temperature matter from the target and the formation of a liquid-gas spinodal pattern on the irradiated area. An analytical model reveals that the glassy target experiences the normal heating (melting) and significant superheating, eventually culminating in explosive boiling near the spinodal limit. Furthermore, the time lag of nucleation and the critical radius of vapor bubbles are theoretically predicted, which are in agreement with the experimental observations. This study provides the investigation on the instability of a metallic glass liquid near the thermodynamic critical temperature.

  17. Explosive boiling of a metallic glass superheated by nanosecond pulse laser ablation

    SciTech Connect

    Jiang, M. Q. E-mail: lhdai@lnm.imech.ac.cn; Wei, Y. P.; Wilde, G.; Dai, L. H. E-mail: lhdai@lnm.imech.ac.cn

    2015-01-12

    We report an explosive boiling in a Zr-based (Vitreloy 1) bulk metallic glass irradiated by a nanosecond pulse laser with a single shot. This critical phenomenon is accompanied by the ejection of high-temperature matter from the target and the formation of a liquid-gas spinodal pattern on the irradiated area. An analytical model reveals that the glassy target experiences the normal heating (melting) and significant superheating, eventually culminating in explosive boiling near the spinodal limit. Furthermore, the time lag of nucleation and the critical radius of vapor bubbles are theoretically predicted, which are in agreement with the experimental observations. This study provides the investigation on the instability of a metallic glass liquid near the thermodynamic critical temperature.

  18. The breakdown process in an atmospheric pressure nanosecond parallel-plate helium/argon mixture discharge

    NASA Astrophysics Data System (ADS)

    Huang, Bang-Dou; Takashima, Keisuke; Zhu, Xi-Ming; Pu, Yi-Kang

    2016-02-01

    The breakdown process in an atmospheric pressure nanosecond helium/argon mixture discharge with parallel-plate electrodes is investigated by temporally and spatially resolved optical emission spectroscopy (OES). The spatially resolved electric field is obtained from the Stark splitting of the He i 492.1 nm line. Using the emissions from the He ii 468.6 nm, He i 667.8 nm, and Ar i 750.4 nm lines and a collisional-radiative model, the spatially resolved T e, high and T e, low (representing the effective T e in the high energy and low energy part of the EEDF, respectively) are obtained. It is found that, compared with the average electric field provided by the external pulser, the electric field is greatly enhanced at certain location and is significantly weakened at other places. This observation shows the effect of the ionization wave propagation, as predicted in [1, 2]. The value of T e, high is much larger than that of T e, low, which indicates that an elevated high energy tail in the EEDF is built up under the influence of strong electric field during the breakdown process. Initially, the spatial distribution of the T e, low and the T e, high generally follows that of the electric field. However, at the end of the breakdown period, the location of the highest T e, low and T e, high is shifted away from the cathode sheath, where the electric field is strongest. This indicates the existence of a non-local effect and is supported by the result from a simple Monte-Carlo simulation.

  19. Lysosomal exocytosis in response to subtle membrane damage following nanosecond pulse exposure

    NASA Astrophysics Data System (ADS)

    Dalzell, Danielle R.; Roth, Caleb C.; Bernhard, Joshua A.; Payne, Jason A.; Wilmink, Gerald J.; Ibey, Bennett L.

    2011-03-01

    The cellular response to subtle membrane damage following exposure to nanosecond electric pulses (nsEP) is not well understood. Recent work has shown that when cells are exposed to nsEP, ion permeable nanopores (< 2nm) are created in the plasma membrane in contrast to larger diameter pores (> 2nm) created by longer micro and millisecond duration pulses. Macroscopic damage to a plasma membrane by a micropipette has been shown to cause internal vesicles (lysosomes) to undergo exocytosis to repair membrane damage, a calcium mediated process called lysosomal exocytosis. Formation of large pores in the plasma membrane by electrical pulses has been shown to elicit lysosomal exocytosis in a variety of cell types. Our research objective is to determine whether lysosomal exocytosis will occur in response to nanopores formed by exposure to nsEP. In this paper we used propidium iodide (PI) and Calcium Green-1 AM ester (CaGr) to differentiate between large and small pores formed in CHO-K1 cells following exposure to either 1 or 20, 600-ns duration electrical pulses at 16.2 kV/cm. This information was compared to changes in membrane organization observed by increases in FM1-43 fluorescence, both in the presence and absence of calcium ions in the outside buffer. In addition, we monitored the real time migration of lysosomes within the cell using Cellular Lights assay to tag LAMP-1, a lysosomal membrane protein. Both 1 and 20 pulses elicited a large influx of extracellular calcium, while little PI uptake was observed following a single pulse exposure. Statistically significant increases in FM1-43 fluorescence were seen in samples containing calcium suggesting that calcium-triggered membrane repair may be occurring. Lastly, density of lysosomes within cells, specifically around the nucleus, appeared to change rapidly upon nsEP stimulation suggesting lysosomal migration.

  20. Cutting and drilling of carbon fiber reinforced plastics (CFRP) by 70W short pulse nanosecond laser

    NASA Astrophysics Data System (ADS)

    Jaeschke, Peter; Stolberg, Klaus; Bastick, Stefan; Ziolkowski, Ewa; Roehner, Markus; Suttmann, Oliver; Overmeyer, Ludger

    2014-02-01

    Continuous carbon fibre reinforced plastics (CFRP) are recognized as having a significant lightweight construction potential for a wide variety of industrial applications. However, a today`s barrier for a comprehensive dissemination of CFRP structures is the lack of economic, quick and reliable manufacture processes, e.g. the cutting and drilling steps. In this paper, the capability of using pulsed disk lasers in CFRP machining is discussed. In CFRP processing with NIR lasers, carbon fibers show excellent optical absorption and heat dissipation, contrary to the plastics matrix. Therefore heat dissipation away from the laser focus into the material is driven by heat conduction of the fibres. The matrix is heated indirectly by heat transfer from the fibres. To cut CFRP, it is required to reach the melting temperature for thermoplastic matrix materials or the disintegration temperature for thermoset systems as well as the sublimation temperature of the reinforcing fibers simultaneously. One solution for this problem is to use short pulse nanosecond lasers. We have investigated CFRP cutting and drilling with such a laser (max. 7 mJ @ 10 kHz, 30 ns). This laser offers the opportunity of wide range parameter tuning for systematic process optimization. By applying drilling and cutting operations based on galvanometer scanning techniques in multi-cycle mode, excellent surface and edge characteristics in terms of delamination-free and intact fiber-matrix interface were achieved. The results indicate that nanosecond disk laser machining could consequently be a suitable tool for the automotive and aircraft industry for cutting and drilling steps.

  1. Properties of water surface discharge at different pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Ruma, Hosseini, S. H. R.; Yoshihara, K.; Akiyama, M.; Sakugawa, T.; Lukeš, P.; Akiyama, H.

    2014-09-01

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H2O2) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H2O2 and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  2. Properties of water surface discharge at different pulse repetition rates

    SciTech Connect

    Ruma,; Yoshihara, K.; Hosseini, S. H. R. Sakugawa, T.; Akiyama, H.; Akiyama, M.; Lukeš, P.

    2014-09-28

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H₂O₂) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H₂O₂ and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  3. Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Primo, Gastón A.; Alvarez Igarzabal, Cecilia I.; Pino, Gustavo A.; Ferrero, Juan C.; Rossa, Maximiliano

    2016-04-01

    This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

  4. Role of cytoskeleton and elastic moduli in cellular response to nanosecond pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Thompson, Gary L.; Roth, Caleb; Tolstykh, Gleb; Kuipers, Marjorie; Ibey, Bennett L.

    2013-02-01

    Nanosecond pulsed electric fields (nsPEFs) are known to increase cell membrane permeability to small molecules in accordance with dosages. As previous work has focused on nsPEF exposures in whole cells, electrodeformation may contribute to this induced-permeabilization in addition to other biological mechanisms. Here, we hypothesize that cellular elasticity, based upon the cytoskeleton, affects nsPEF-induced decrease in cellular viability. Young's moduli of various types of cells have been calculated from atomic force microscopy (AFM) force curve data, showing that CHO cells are stiffer than non-adherent U937 and Jurkat cells, which are more susceptible to nsPEF exposure. To distinguish any cytoskeletal foundation for these observations, various cytoskeletal reagents were applied. Inhibiting actin polymerization significantly decreased membrane integrity, as determined by relative propidium uptake and phosphatidylserine externalization, upon exposure at 150 kV/cm with 100 pulses of 10 ns pulse width. Exposure in the presence of other drugs resulted in insignificant changes in membrane integrity and 24-hour viability. However, Jurkat cells showed greater lethality than latrunculin-treated CHO cells of comparable elasticity. From these results, it is postulated that cellular elasticity rooted in actin-membrane interaction is only a minor contributor to the differing responses of adherent and non-adherent cells to nsPEF insults.

  5. Calcium influx affects intracellular transport and membrane repair following nanosecond pulsed electric field exposure

    NASA Astrophysics Data System (ADS)

    Thompson, Gary Lee; Roth, Caleb C.; Dalzell, Danielle R.; Kuipers, Marjorie; Ibey, Bennett L.

    2014-05-01

    The cellular response to subtle membrane damage following exposure to nanosecond pulsed electric fields (nsPEF) is not well understood. Recent work has shown that when cells are exposed to nsPEF, ion permeable nanopores (<2 nm) are created in the plasma membrane in contrast to larger diameter pores (>2 nm) created by longer micro- and millisecond duration pulses. Nanoporation of the plasma membrane by nsPEF has been shown to cause a transient increase in intracellular calcium concentration within milliseconds after exposure. Our research objective is to determine the impact of nsPEF on calcium-dependent structural and repair systems in mammalian cells. Chinese hamster ovary (CHO-K1) cells were exposed in the presence and absence of calcium ions in the outside buffer to either 1 or 20, 600-ns duration electrical pulses at 16.2 kV/cm, and pore size was determined using propidium iodide and calcium green. Membrane organization was observed with morphological changes and increases in FM1-43 fluorescence. Migration of lysosomes, implicated in membrane repair, was followed using confocal microscopy of red fluorescent protein-tagged LAMP1. Microtubule structure was imaged using mEmerald-tubulin. We found that at high 600-ns PEF dosage, calcium-induced membrane restructuring and microtubule depolymerization coincide with interruption of membrane repair via lysosomal exocytosis.

  6. Permeabilization of the nuclear envelope following nanosecond pulsed electric field exposure.

    PubMed

    Thompson, Gary L; Roth, Caleb C; Kuipers, Marjorie A; Tolstykh, Gleb P; Beier, Hope T; Ibey, Bennett L

    2016-01-29

    Permeabilization of cell membranes occurs upon exposure to a threshold absorbed dose (AD) of nanosecond pulsed electric fields (nsPEF). The ultimate, physiological bioeffect of this exposure depends on the type of cultured cell and environment, indicating that cell-specific pathways and structures are stimulated. Here we investigate 10 and 600 ns duration PEF effects on Chinese hamster ovary (CHO) cell nuclei, where our hypothesis is that pulse disruption of the nuclear envelope membrane leads to observed cell death and decreased viability 24 h post-exposure. To observe short-term responses to nsPEF exposure, CHO cells have been stably transfected with two fluorescently-labeled proteins known to be sequestered for cellular chromosomal function within the nucleus - histone-2b (H2B) and proliferating cell nuclear antigen (PCNA). H2B remains associated with chromatin after nsPEF exposure, whereas PCNA leaks out of nuclei permeabilized by a threshold AD of 10 and 600 ns PEF. A downturn in 24 h viability, measured by MTT assay, is observed at the number of pulses required to induce permeabilization of the nucleus. PMID:26721436

  7. Biophysical Studies of Nanosecond Pulsed Electric Field Induced Cell Membrane Permeabilization

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Hsuan

    Nanosecond megavolts-per-meter pulsed electric field (nsPEF) offers a non-invasive manipulation of intracellular organelles and functions of biological cells. Accordingly, nsPEF is a potential technique for biophysical research and cancer therapy, and is of growing interest. Although, the application of nsPEF has shown electroperturbation on cell plasma membranes and intracellular membranes as well, the mechanisms underlying the electropermeabilization are still not clear. In this thesis, we systematically study nsPEFs (5 and 30 ns) induced membrane permeability change in biological cell in-vitro with different pulse parameters. In Chapter 3, we investigate the nsPEF-induced intracellular membrane permeabilization of mitochondria which play key roles in activating apoptosis in mammalian cells. The results show the evidences of nsPEF-induced membrane permeability increase in mitochondria, and suggest that nsPEF is a potential technology for cancer cell ablation without delivery of drug or gene into cells. In Chapter 2, 4 and 6, we study the properties of nsPEF-induced plasma membrane permeabilization. In the beginning, the change of plasma membrane permeability is studied by uptake of YO-PRO-1 and propidium iodide, fluorescent dyes specifically used as indicators of plasma membrane permeabilization. However, the detection is limited by the fluorescent emission efficiency and detector capability. To increase the detection sensitivity, we later develop a method based on cell volume change due to regulation of osmotic balance that causes water and small ions transport through plasma membrane. We find that even a single 10 MV/m pulse of 5 ns duration produces measureable cell swelling. The results demonstrate that cell swelling is susceptible to nsPEF and can detect membrane permeabilization more easily and precisely than fluorescent dyes. We compare the effects of different pulse parameters (pulse duration, pulse number, electric field amplitude and pulse repetition

  8. Long term survival of mice with hepatocellular carcinoma after pulse power ablation with nanosecond pulsed electric fields.

    PubMed

    Chen, X; Zhuang, J; Kolb, J F; Schoenbach, K H; Beebe, S J

    2012-02-01

    Novel therapies are needed for treating hepatocellular carcinoma (HCC) without recurrence in a single procedure. In this work we evaluated anti-neoplastic effects of a pulse power ablation (PPA) with nanosecond pulsed electric fields (nsPEFs), a non-thermal, non-drug, local, regional method and investigated its molecular mechanisms for hepatocellular carcinoma tumor ablation in vivo. An ectopic tumor model was established using C57BL/6 mice with Hepa1-6 hepatocellular carcinoma cells. Pulses with durations of 30 or 100 ns and fast rise times were delivered by a needle or ring electrode with different electric field strengths (33, 50 and 68 kV/cm), and 900 pulses in three treatment sessions (300 pulses each session) or a single 900 pulse treatment. Treated and control tumor volumes were monitored by ultrasound and apoptosis and angiogenesis markers were evaluated by immunohistochemistry. Seventy five percent of primary hepatocellular carcinoma tumors were eradicated with 900 hundred pulses at 100 ns pulses at 68 kV/cm in a single treatment or in three treatment sessions without recurrence within 9 months. Using quantitative analysis, tumors in treated animals showed nsPEF-mediated nuclear condensation (3 h post-pulse), cell shrinkage (1 h), increases in active executioner caspases (caspase-3 > -7 > -6) and terminal deoxynucleotidyl transferase dUTP nick-end-labeling (1 h) with decreases in vascular endothelial growth factor expression (7d) and micro-vessel density (14d). NsPEF ablation eliminated hepatocellular carcinoma tumors by targeting two therapeutic sites, apoptosis induction and inhibition of angiogenesis, both important cancer hallmarks. These data indicate that PPA with nsPEFs is not limited to treating skin cancers and provide a rationale for continuing to investigate pulse power ablation for hepatocellular carcinoma using other models in pre-clinical applications and ultimately in clinical trials. Based on present treatments for specific HCC stages, it

  9. Pulsed-discharge carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Willetts, David V.

    1990-01-01

    The purpose is to attempt a general introduction to pulsed carbon dioxide lasers of the kind used or proposed for laser radar applications. Laser physics is an excellent example of a cross-disciplinary topic, and the molecular spectroscopy, energy transfer, and plasma kinetics of the devices are explored. The concept of stimulated emission and population inversions is introduced, leading on to the molecular spectroscopy of the CO2 molecule. This is followed by a consideration of electron-impact pumping, and the pertinent energy transfer and relaxation processes which go on. Since the devices are plasma pumped, it is necessary to introduce a complex subject, but this is restricted to appropriate physics of glow discharges. Examples of representative devices are shown. The implications of the foregoing to plasma chemistry and gas life are discussed.

  10. Damage threshold and focusability of mid-infrared free-electron laser pulses gated by a plasma mirror with nanosecond switching pulses

    SciTech Connect

    Wang, Xiaolong; Nakajima, Takashi; Zen, Heishun; Kii, Toshiteru; Ohgaki, Hideaki

    2013-11-04

    The presence of a pulse train structure of an oscillator-type free-electron laser (FEL) results in the immediate damage of a solid target upon focusing. We demonstrate that the laser-induced damage threshold can be significantly improved by gating the mid-infrared FEL pulses with a plasma mirror. Although the switching pulses we employ have a nanosecond duration which does not guarantee the clean wavefront of the gated FEL pulses, the high focusability is experimentally confirmed through the observation of spectral broadening by a factor of 2.1 when we tightly focus the gated FEL pulses onto the Ge plate.

  11. Self-consistent evolution of plasma discharge and electromagnetic fields in a microwave pulse compressor

    SciTech Connect

    Shlapakovski, A. S.; Beilin, L.; Krasik, Ya. E.; Hadas, Y.; Schamiloglu, E.

    2015-07-15

    Nanosecond-scale evolution of plasma and RF electromagnetic fields during the release of energy from a microwave pulse compressor with a plasma interference switch was investigated numerically using the code MAGIC. The plasma was simulated in the scope of the gas conductivity model in MAGIC. The compressor embodied an S-band cavity and H-plane waveguide tee with a shorted side arm filled with pressurized gas. In a simplified approach, the gas discharge was initiated by setting an external ionization rate in a layer crossing the side arm waveguide in the location of the electric field antinode. It was found that with increasing ionization rate, the microwave energy absorbed by the plasma in the first few nanoseconds increases, but the absorption for the whole duration of energy release, on the contrary, decreases. In a hybrid approach modeling laser ignition of the discharge, seed electrons were set around the electric field antinode. In this case, the plasma extends along the field forming a filament and the plasma density increases up to the level at which the electric field within the plasma decreases due to the skin effect. Then, the avalanche rate decreases but the density still rises until the microwave energy release begins and the electric field becomes insufficient to support the avalanche process. The extraction of the microwave pulse limits its own power by terminating the rise of the plasma density and filament length. For efficient extraction, a sufficiently long filament of dense plasma must have sufficient time to be formed.

  12. Self-consistent evolution of plasma discharge and electromagnetic fields in a microwave pulse compressor

    NASA Astrophysics Data System (ADS)

    Shlapakovski, A. S.; Beilin, L.; Hadas, Y.; Schamiloglu, E.; Krasik, Ya. E.

    2015-07-01

    Nanosecond-scale evolution of plasma and RF electromagnetic fields during the release of energy from a microwave pulse compressor with a plasma interference switch was investigated numerically using the code MAGIC. The plasma was simulated in the scope of the gas conductivity model in MAGIC. The compressor embodied an S-band cavity and H-plane waveguide tee with a shorted side arm filled with pressurized gas. In a simplified approach, the gas discharge was initiated by setting an external ionization rate in a layer crossing the side arm waveguide in the location of the electric field antinode. It was found that with increasing ionization rate, the microwave energy absorbed by the plasma in the first few nanoseconds increases, but the absorption for the whole duration of energy release, on the contrary, decreases. In a hybrid approach modeling laser ignition of the discharge, seed electrons were set around the electric field antinode. In this case, the plasma extends along the field forming a filament and the plasma density increases up to the level at which the electric field within the plasma decreases due to the skin effect. Then, the avalanche rate decreases but the density still rises until the microwave energy release begins and the electric field becomes insufficient to support the avalanche process. The extraction of the microwave pulse limits its own power by terminating the rise of the plasma density and filament length. For efficient extraction, a sufficiently long filament of dense plasma must have sufficient time to be formed.

  13. Thickness dependent self limiting 1-D tin oxide nanowire arrays by nanosecond pulsed laser irradiation

    SciTech Connect

    Shirato, N.; Strader, J.; Kumar, Amit; Vincent, A.; Zhang, P.; Karakoti, Ajay S.; Nachimuthu, Ponnusamy; Cho, H-J.; Seal, Sudipta; Kalyanaraman, R.

    2011-01-23

    Fast, sensitive and discriminating detection of hydrogen at room temperature is crucial for storage, transportation, and distribution of hydrogen as an energy source. One dimensional nanowires of SnO2 are potential candidates for improved H2 sensor performance. The single directional conducting continuous nanowires can decrease electrical noise, and their large active surface area could improve the response and recovery time of the sensor. In this work we discuss synthesis and characterization of nanowire arrays made using nanosecond ultraviolet wavelength (266 nm) laser interference processing of ultrathin SnO2 films on SiO2 substrates. The laser energy was chosen to be above the melting point of the films. The results show that the final nanowire formation is dominated by preferential evaporation as compared to thermocapillary flow. The nanowire height (and hence wire aspect ratio) increased with increasing initial film thickness ho and with increasing laser energy density Eo. Furthermore, a self-limiting effect was observed where-in the wire formation ceased at a specific final remaining thickness of SnO2 that was almost independent of ho for a given Eo. To understand these effects, finite element modeling of the nanoscale laser heating was performed. This showed that the temperature rise under laser heating was a strong non-monotonic function of film thickness. As a result, the preferential evaporation rate varies as wire formation occurs, eventually leading to a shut-off of evaporation at a characteristic thickness. This results in the stoppage of wire formation. This combination of nanosecond pulsed laser experiments and thermal modeling shows that several unique synthesis approaches can be utilized to control the nanowire characteristics.

  14. Compact and efficient nanosecond pulsed tuneable OPO in the mid-IR spectral range

    NASA Astrophysics Data System (ADS)

    Hellström, J.; Jänes, P.; Elgcrona, G.; Karlsson, H.

    2013-05-01

    A compact, robust and efficient nanosecond pulsed optical parametric oscillator (OPO) generating radiation in the mid- IR spectral range is reported. The OPO is based on periodically poled material for the efficient non-linear processes of up-converting 1064 nm radiation to 1538 and 3450 nm respectively. Pulsed emission exceeding 130 mW average power at the idler (3450 nm) with a total conversion efficiency of 30%, including both signal and idler, has been reached. The maximum pulse energy of the idler is 11 μJ, pulse duration around 4 ns and peak power close to 3 kW. The results are achieved for an optical pump power of 1.4 W at the entrance of the OPO and an electrical pump power of 14 W. The total size of the OPO device is only 125x70x45 mm3 (LxWxH) including the pump laser at 1064 nm. The idler output radiation is narrowed by spectral filtering to < 1.5nm and temperature tuneable over > 50 nm. The OPO has a robust design and withstands shocks up to 60g at 8 ms and the storage temperature is -20 °C to + 60 °C. The compact size and low power consumption make this OPO device suitable for many kinds of molecular spectroscopy applications in the areas of environmental monitoring and pollution control as well as in combustion physics and process control. Integration of the OPO source into compact equipment for Photo Acoustic Spectroscopy (PAS) allowing fast and highly sensitive detection of methane and ethanol at ppb-levels is also described.

  15. Inactivation of Ricin Toxin by Nanosecond Pulsed Electric Fields Including Evidences from Cell and Animal Toxicity

    NASA Astrophysics Data System (ADS)

    Wei, Kai; Li, Wei; Gao, Shan; Ji, Bin; Zang, Yating; Su, Bo; Wang, Kaile; Yao, Maosheng; Zhang, Jue; Wang, Jinglin

    2016-01-01

    Ricin is one of the most toxic and easily produced plant protein toxin extracted from the castor oil plant, and it has been classified as a chemical warfare agent. Here, nanosecond pulsed electric fields (nsPEFs) at 30 kV/cm (pulse durations: 10 ns, 100 ns, and 300 ns) were applied to inactivating ricin up to 4.2 μg/mL. To investigate the efficacy, cells and mice were tested against the ricin treated by the nsPEFs via direct intraperitoneal injection and inhalation exposure. Results showed that nsPEFs treatments can effectively reduce the toxicity of the ricin. Without the nsPEFs treatment, 100% of mice were killed upon the 4 μg ricin injection on the first day, however 40% of the mice survived the ricin treated by the nsPEFs. Compared to injection, inhalation exposure even with higher ricin dose required longer time to observe mice fatality. Pathological observations revealed damages to heart, lung, kidney, and stomach after the ricin exposure, more pronounced for lung and kidney including severe bleeding. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) and circular dichroism (CD) analyses revealed that although the primary structure of ricin was not altered, its secondary structures (beta-sheet and beta-turn) underwent transition upon the nsPEFs treatment.

  16. Infrared nanosecond pulsed laser irradiation of stainless steel: micro iron-oxide zones generation.

    PubMed

    Ortiz-Morales, M; Frausto-Reyes, C; Soto-Bernal, J J; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2014-07-15

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas. PMID:24699286

  17. Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation

    NASA Astrophysics Data System (ADS)

    Ortiz-Morales, M.; Frausto-Reyes, C.; Soto-Bernal, J. J.; Acosta-Ortiz, S. E.; Gonzalez-Mota, R.; Rosales-Candelas, I.

    2014-07-01

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

  18. Cells exposed to nanosecond electrical pulses exhibit biomarkers of mechanical stress

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.; Beier, Hope T.; Moen, Erick K.; Glickman, Randolph D.

    2015-03-01

    Exposure of cells to very short (<1 μs) electric pulses in the megavolt/meter range have been shown to cause disruption of the plasma membrane. This disruption is often characterized by the formation of numerous small pores (<2 nm in diameter) in the plasma membrane that last for several minutes, allowing the flow of ions into the cell. These small pores are called nanopores and the resulting damage to the plasma membrane is referred to as nanoporation. Nanosecond electrical pulse (nsEP) exposure can impart many different stressors on a cell, including electrical, electro-chemical, and mechanical stress. Thus, nsEP exposure is not a "clean" insult, making determination of the mechanism of nanoporation quite difficult. We hypothesize that nsEP exposure creates acoustic shock waves capable of causing nanoporation. Microarray analysis of primary adult human dermal fibroblasts (HDFa) exposed to nsEP, indicated several genes associated with mechanical stress were selectively upregulated 4 h post exposure. The idea that nanoporation is caused by external mechanical force from acoustic shock waves has, to our knowledge, not been investigated. This work will critically challenge the existing paradigm that nanoporation is caused solely by an electric-field driven event and could provide the basis for a plausible explanation for electroporation.

  19. Inactivation of Ricin Toxin by Nanosecond Pulsed Electric Fields Including Evidences from Cell and Animal Toxicity

    PubMed Central

    Wei, Kai; Li, Wei; Gao, Shan; Ji, Bin; Zang, Yating; Su, Bo; Wang, Kaile; Yao, Maosheng; Zhang, Jue; Wang, Jinglin

    2016-01-01

    Ricin is one of the most toxic and easily produced plant protein toxin extracted from the castor oil plant, and it has been classified as a chemical warfare agent. Here, nanosecond pulsed electric fields (nsPEFs) at 30 kV/cm (pulse durations: 10 ns, 100 ns, and 300 ns) were applied to inactivating ricin up to 4.2 μg/mL. To investigate the efficacy, cells and mice were tested against the ricin treated by the nsPEFs via direct intraperitoneal injection and inhalation exposure. Results showed that nsPEFs treatments can effectively reduce the toxicity of the ricin. Without the nsPEFs treatment, 100% of mice were killed upon the 4 μg ricin injection on the first day, however 40% of the mice survived the ricin treated by the nsPEFs. Compared to injection, inhalation exposure even with higher ricin dose required longer time to observe mice fatality. Pathological observations revealed damages to heart, lung, kidney, and stomach after the ricin exposure, more pronounced for lung and kidney including severe bleeding. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) and circular dichroism (CD) analyses revealed that although the primary structure of ricin was not altered, its secondary structures (beta-sheet and beta-turn) underwent transition upon the nsPEFs treatment. PMID:26728251

  20. External stimulation by nanosecond pulsed electric fields to enhance cellular uptake of nanoparticles

    NASA Astrophysics Data System (ADS)

    Franklin, Samantha; Beier, Hope T.; Ibey, Bennett L.; Nash, Kelly

    2015-03-01

    As an increasing number of studies use gold nanoparticles (AuNPs) for potential medicinal, biosensing and therapeutic applications, the synthesis and use of readily functional, bio-compatible nanoparticles is receiving much interest. For these efforts, the particles are often taken up by the cells to allow for optimum sensing or therapeutic measures. This process typically requires incubation of the particles with the cells for an extended period. In an attempt to shorten and control this incubation, we investigated whether nanosecond pulsed electric field (nsPEF) exposure of cells will cause a controlled uptake of the particles. NsPEF are known to induce the formation of nanopores in the plasma membrane, so we hypothesized that by controlling the number, amplitude or duration of the nsPEF exposure, we could control the size of the nanopores, and thus control the particle uptake. Chinese hamster ovary (CHO-K1) cells were incubated sub-10 nm AuNPs with and without exposure to 600-ns electrical pulses. Contrary to our hypothesis, the nsPEF exposure was found to actually decrease the particle uptake in the exposed cells. This result suggests that the nsPEF exposure may be affecting the endocytotic pathway and processes due to membrane disruption.

  1. Thermal and microstructural effects of nanosecond pulsed Nd:YAG laser irradiation on tooth root surface

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.; Grill, G.; Liaw, Lih-Huei L.; Berns, Michael W.

    1995-05-01

    Plaque, calculus and altered cementum removal by scaling and root planing is a fundamental procedure in periodontal treatment. However, the residual smear layer contains cytotoxic and inflammatory mediators which adversely affect healing. Chemical smear layer removal is also problematic. In previous investigations effective smear layer removal was achieved using long pulsed irradiation at 1.06 (mu) . However, laser irradiation was not adequate as an alternative to scaling and root planing procedures and concurrent temperature rises exceeded thermal thresholds for pulpal and periodontal safety. It was the aim of this study to determine whether nanosecond pulsed irradiation at 1.06 (mu) could be used as an alternative or an adjunct to scaling and root planing. Sixty freshly extracted teeth were divided as follows: 5 control, 5 root planed only, 25 irradiated only, 25 root planed and irradiated. Irradiation was performed at fluences of 0.5 - 2.7 J/cm2, total energy densities of 12 - 300 J/cm2, frequencies of 2 - 10 Hz using the Medlite (Continuum) laser. Irradiation-induced thermal events were recorded using a thermocouple within the root canal and a thermal camera to monitor surface temperatures. SEM demonstrated effective smear layer removal with minimal microstructural effects. Surface temperatures increased minimally (< 3 C) at all parameters, intrapulpal temperature rises remained below 4 C at 2 and 5 Hz, F < 0.5 J/cm2. Without prior scaling and root planing, laser effects did not provide an adequately clean root surface.

  2. Inactivation of Ricin Toxin by Nanosecond Pulsed Electric Fields Including Evidences from Cell and Animal Toxicity.

    PubMed

    Wei, Kai; Li, Wei; Gao, Shan; Ji, Bin; Zang, Yating; Su, Bo; Wang, Kaile; Yao, Maosheng; Zhang, Jue; Wang, Jinglin

    2016-01-01

    Ricin is one of the most toxic and easily produced plant protein toxin extracted from the castor oil plant, and it has been classified as a chemical warfare agent. Here, nanosecond pulsed electric fields (nsPEFs) at 30 kV/cm (pulse durations: 10 ns, 100 ns, and 300 ns) were applied to inactivating ricin up to 4.2 μg/mL. To investigate the efficacy, cells and mice were tested against the ricin treated by the nsPEFs via direct intraperitoneal injection and inhalation exposure. Results showed that nsPEFs treatments can effectively reduce the toxicity of the ricin. Without the nsPEFs treatment, 100% of mice were killed upon the 4 μg ricin injection on the first day, however 40% of the mice survived the ricin treated by the nsPEFs. Compared to injection, inhalation exposure even with higher ricin dose required longer time to observe mice fatality. Pathological observations revealed damages to heart, lung, kidney, and stomach after the ricin exposure, more pronounced for lung and kidney including severe bleeding. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) and circular dichroism (CD) analyses revealed that although the primary structure of ricin was not altered, its secondary structures (beta-sheet and beta-turn) underwent transition upon the nsPEFs treatment. PMID:26728251

  3. Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

    DOE PAGESBeta

    Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; Moody, Neville R.

    2015-11-14

    Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protectivemore » thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.« less

  4. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    SciTech Connect

    Teng, Yun; Li, Lee Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-15

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  5. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    NASA Astrophysics Data System (ADS)

    Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-01

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  6. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    NASA Astrophysics Data System (ADS)

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; El-Sayed, Hany A.; Birss, Viola I.; Shi, Yujun J.

    2015-05-01

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H2SO4 and HF solution. Pt thin films (3-5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6-9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm2. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm2, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  7. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    SciTech Connect

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.; Shi, Yujun J.; El-Sayed, Hany A.

    2015-05-18

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  8. The Nonlinear Behaviors in Atmospheric Dielectric Barrier Multi Pulse Discharges

    NASA Astrophysics Data System (ADS)

    Zhang, Dingzong; Wang, Yanhui; Wang, Dezhen

    2016-08-01

    An in-depth and comprehensive understanding of the complex nonlinear behaviors in atmospheric dielectric barrier discharge is significant for the stable operation and effective control of the plasma. In this paper, we study the nonlinear behaviors in argon atmospheric dielectric barrier multi pulse discharges by a one-dimensional fluid model. Under certain conditions, the multi pulse discharge becomes very sensitive with the increase of frequency, and the multi pulse period-doubling bifurcation, inverse period-doubling bifurcation and chaos appear frequently. The discharge can reach a relatively steady state only when the discharges are symmetrical between positive and negative half cycle. In addition, the effects of the voltage on these nonlinear discharges are also studied. It is found that the amplitude of voltage has no effects on the number of discharge pulses in multi-pulse period-doubling bifurcation sequences; however, to a relatively stable periodic discharge, the discharge pulses are proportional to the amplitude of the applied voltage within a certain range. supported by National Natural Science Foundation of China (No. 11447244), the Science Foundation of Hengyang Normal University of China (No. 14B41), the Construct Program of the Key Discipline in Hunan Province, and the Hunan Provincial Applied Basic Research Base of Optoelectronic Information Technology of China (No. GDXX010)

  9. Theranostic system for drug delivery and pharmacokinetic imaging based on nanosecond pulsed light-induced photomechanical and photoacoustic effects

    NASA Astrophysics Data System (ADS)

    Tsunoi, Yasuyuki; Sato, Shunichi; Kawauchi, Satoko; Akutsu, Yusuke; Miyagawa, Yoshihiro; Araki, Koji; Shiotani, Akihiro; Terakawa, Mitsuhiro

    2015-11-01

    For efficient and side effects-free pharmacological treatment, we here propose a theranostic system that enables transvascular drug delivery by photomechanical waves (PMWs) and photoacoustic (PA) imaging of the drug distribution; both functions are based on nanosecond laser pulses and can therefore be integrated in one system. Through optical fibers arranged around an ultrasound sensor, low-energy and high-energy nanosecond light pulses were transmitted respectively for PA imaging and PMW-based drug delivery by temporal switching. With the system, we delivered a test drug (Evans blue) to tumors in mice and visualized distributions of both the blood vessels and drug in the tissue in vivo, showing the validity of the system.

  10. Nanosecond pulses in a THz gyrotron oscillator operating in a mode-locked self-consistent Q-switch regime.

    PubMed

    Alberti, S; Braunmueller, F; Tran, T M; Genoud, J; Hogge, J-Ph; Tran, M Q; Ansermet, J-Ph

    2013-11-15

    An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE(7,2) transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations. PMID:24289692

  11. Development of a nanosecond pulsed HV atmospheric pressure plasma source: preliminary assessment of its electrical characteristics and degree of thermal nonequilibrium

    NASA Astrophysics Data System (ADS)

    Evans, M. D. G.; Sainct, F. P.; Aristizabal, F.; Bergthorson, J. M.; Coulombe, S.

    2015-06-01

    This paper discusses the development and characteristics of a distributed nanosecond-pulsed glow-like discharge plasma in air at atmospheric pressure. The produced pulse is of 6.4 kV with duration at half maximum of less than 80 ns, and an average pulse repetition frequency of 150 Hz. The discharge operates in air in a concentric electrode configuration. Spectroscopic studies are presented in order to assess the thermal characteristics of the plasma as well as its spatial characteristics. Electrical diagnostics are presented along with time averaged ICCD imaging of the radially distributed plasma. Although variations occur, it is found that the plasma has uniform vibrational and rotational temperatures across the inter electrode gap illustrating a high degree of disequilibrium in the plasma. Band head intensity analysis proves the existence of a negative glow in the near cathode region. Finally, the sensitivity of individual vibrational bands to vibrational and rotational temperatures is presented as a means to most accurately evaluate the uncertainty of spectrally determined temperatures.

  12. System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range

    SciTech Connect

    Laity, G.; Neuber, A.; Rogers, G.; Frank, K.

    2010-08-15

    Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.

  13. Fast pulse nonthermal plasma reactor

    DOEpatents

    Rosocha, Louis A.

    2005-06-14

    A fast pulsed nonthermal plasma reactor includes a discharge cell and a charging assembly electrically connected thereto. The charging assembly provides plural high voltage pulses to the discharge cell. Each pulse has a rise time between one and ten nanoseconds and a duration of three to twenty nanoseconds. The pulses create nonthermal plasma discharge within the discharge cell. Accordingly, the nonthermal plasma discharge can be used to remove pollutants from gases or break the gases into smaller molecules so that they can be more efficiently combusted.

  14. Absolute calibration of OH density in a nanosecond pulsed plasma filament in atmospheric pressure He-H2O: comparison of independent calibration methods

    NASA Astrophysics Data System (ADS)

    Verreycken, T.; van der Horst, R. M.; Sadeghi, N.; Bruggeman, P. J.

    2013-11-01

    The absolute density of OH radicals generated in a nanosecond pulsed filamentary discharge in atmospheric pressure He +0.84% H2O is measured independently by UV absorption and laser induced fluorescence (LIF) calibrated with Rayleigh scattering. For the calibration of LIF with Rayleigh scattering, two LIF models, with six levels and four levels, are studied to investigate the influence of the rotational and vibrational energy transfers. In addition, a chemical model is used to deduce the OH density in the afterglow from the relative LIF intensity as function of time. The different models show good correspondence and by comparing these different methods, the accuracy and the effect of assumptions on the obtained OH density are discussed in detail. This analysis includes an analysis of the sensitivity to parameters used in the LIF models.

  15. Transistorized Marx bank pulse circuit provides voltage multiplication with nanosecond rise-time

    NASA Technical Reports Server (NTRS)

    Jung, E. A.; Lewis, R. N.

    1968-01-01

    Base-triggered avalanche transistor circuit used in a Marx bank pulser configuration provides voltage multiplication with nanosecond rise-time. The avalanche-mode transistors replace conventional spark gaps in the Marx bank. The delay time from an input signal to the output signal to the output is typically 6 nanoseconds.

  16. Continuum emission-based electron diagnostics for atmospheric pressure plasmas and characteristics of nanosecond-pulsed argon plasma jets

    NASA Astrophysics Data System (ADS)

    Park, Sanghoo; Choe, Wonho; Kim, Holak; Park, Joo Young

    2015-06-01

    Electron diagnostics based on electron-neutral atom (e-a) bremsstrahlung in the UV and visible range emitted from atmospheric pressure plasmas is presented. Since the spectral emissivity of the e-a bremsstrahlung is determined by electron density (ne) and mean electron temperature (Te) representing the Maxwellian electron energy distribution, their diagnostics is possible. As an example, emission spectra measured from capacitive discharges are presented, which show good agreement with the theoretically calculated emissivity of the e-a bremsstrahlung. For a single pin electrode nanosecond-pulsed plasma jet (n-PPJ) in argon, we investigate the electron properties and the temporal behavior of the positive streamers. Streamers with many branches are clearly observed inside the dielectric tube, while a few main streamers propagate outside the tube along the jet axis. A two-dimensional (2D) measurement of the time-averaged Te distribution was developed using a commercial digital camera and optical band pass filters based on the emissivity ratio of two wavelengths of the e-a bremsstrahlung. The viable measurement range of Te is 0.5-7 eV for the choice of two wavelengths of 300s and 900s nm and 0.5-4 eV for two wavelengths of 400s and 900s nm, which are uncontaminated by the atomic and/or molecular spectra. The 2D Te distribution obtained using 514.5 and 632.8 nm emissions helps to reveal the role of electrons in streamer characteristics in the argon n-PPJ. Time-averaged Te of 2.0 eV and 1.0 eV inside and outside the tube, respectively, were measured. The streamer dynamics of the n-PPJ is shown to be dependent on Te.

  17. Design, construction, and testing of solution resistive divider applied in hundreds of kilovolts nanosecond pulse measurement

    NASA Astrophysics Data System (ADS)

    Ge, Ya-Feng; Li, Lee; Liu, Yun-Long; Li, Mingjia; Kang, Qiang

    2014-10-01

    The solution resistive divider is often used considering its excellent high-frequency and withstanding voltage characteristics. This paper develops a nanosecond pulse measurement system based on the CuSO4 solution resistive divider, which can be used to measure high voltage impulses with rise time of 50 ns and amplitude of 300 kV. The low-voltage arm of the newly designed solution resistive divider is composed of noninductive metal film resistors. The newly designed resistive divider combines the advantages of the conventional solution resistive divider and metal film resistive divider. The stray parameters of the resistive divider are theoretically calculated and the circuit simulation is studied. Besides, the square wave response characteristics of the resistive divider are studied in the experiments. Considering the effect of frequency on the surge impedance of the cable, a matching cable of the same type with the transmission cable instead of a common matching resistor is used to improve the matching effects. In order to reduce the effects of electromagnetic interference on the measurement results, some shielding measures are taken. The experimental results show that the measurement system has good response characteristics in the practical application.

  18. Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Barnes, Ronald A., Jr.; Ibey, Bennett L.; Beier, Hope T.; Christopher Mimun, L.; Maswadi, Saher M.; Shadaram, Mehdi; Glickman, Randolph D.

    2015-10-01

    The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane.

  19. Mechanisms governing the interaction of metallic particles with nanosecond laser pulses.

    PubMed

    Demos, Stavros G; Negres, Raluca A; Raman, Rajesh N; Shen, Nan; Rubenchik, Alexander M; Matthews, Manyalibo J

    2016-04-01

    The interaction of nanosecond laser pulses at 1064- and 355-nm with micro-scale, nominally spherical metallic particles is investigated in order to elucidate the governing interaction mechanisms as a function of material and laser parameters. The experimental model used involves the irradiation of metal particles located on the surface of transparent plates combined with time-resolved imaging capable of capturing the dynamics of particle ejection, plume formation and expansion along with the kinetics of the dispersed material from the liquefied layer of the particle. The mechanisms investigated in this work are informative and relevant across a multitude of materials and irradiation geometries suitable for the description of a wide range of specific applications. The experimental results were interpreted using physical models incorporating specific processes to assess their contribution to the overall observed behaviors. Analysis of the experimental results suggests that the induced kinetic properties of the particle can be adequately described using the concept of momentum coupling introduced to explain the interaction of plane metal targets to large-aperture laser beams. The results also suggest that laser energy deposition on the formed plasma affects the energy partitioning and the material modifications to the substrate. PMID:27137063

  20. Activation of autophagy in response to nanosecond pulsed electric field exposure.

    PubMed

    Ullery, Jody C; Tarango, Melissa; Roth, Caleb C; Ibey, Bennett L

    2015-03-01

    Previous work demonstrated significant changes in cellular membranes following exposure of cells to nanosecond pulsed electric fields (nsPEF), including nanoporation and increases in intracellular calcium concentration. While it is known that nsPEF exposure can cause cell death, how cells repair and survive nsPEF-induced cellular damage is not well understood. In this paper, we investigated whether autophagy is stimulated following nsPEF exposure to repair damaged membranes, proteins, and/or organelles in a pro-survival response. We hypothesized that autophagy is activated to repair nsPEF-induced plasma membrane damage and overwhelming this compensatory mechanism results in cell death. Activation of autophagy and subsequent cell death pathways were assessed measuring toxicity, gene and protein expression of autophagy markers, and by monitoring autophagosome formation and maturation using fluorescent microscopy. Results show that autophagy is activated at subtoxic nsPEF doses, as a compensatory mechanism to repair membrane damage. However, prolonged exposure results in increased cell death and a concomitant decrease in autophagic markers. These results suggest that cells take an active role in membrane repair, through autophagy, following exposure to nsPEF. PMID:25660455

  1. Breakdown in a bulk of transparent solids under irradiation of a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Rehman, Z. U.; Grigorov, Y. V.; Tran, K. A.; Janulewicz, K. A.

    2014-10-01

    A single pulse of a nanosecond laser was tightly focused in the bulk of transparent materials (soda lime glass, borosilicate glass, fused silica , sapphire and Gorilla Glass) to a beam spot diameter of ~ 2.1μm. A value of the total energy absorbed in the materials was measured with corrections for the transmitted, scattered and reflected components of the incident energy. It was found that 3-11% of the incident radiation was scattered but the total absorption still achieved a very high level of up to 88%. Absorptance dependence on the incident fluence was reasonably approximated by the sigmoidal Hill function. Here we suggest using this analytical description to identify empirical intrinsic laser-induced breakdown threshold (LIBT). Optical damage threshold (ODT) was identified by optical inspection. The results for some materials suggest significantly lower breakdown threshold than that reported earlier for more loosely focused beams. A study of the damage area morphology with a scanning electron microscope (SEM) and a high resolution transmission microscope (HRTEM) revealed existence of the shock waves-affected area with a localized nano-crystallization. Spectroscopic study of the light emission accompanying breakdown showed typical quasi-continuum emission with temperature as high as 8917K (0.8 eV).

  2. Evidence of water reorientation on model electrocatalytic surfaces from nanosecond-laser-pulsed experiments.

    PubMed

    García-Aráez, Nuria; Climent, Víctor; Feliu, Juan M

    2008-03-26

    The behavior of water at the interface formed between a quasi-perfect Pt(111) single-crystal electrode and an aqueous electrolyte solution is studied by means of the laser-induced temperature jump method. This method is based on the use of nanosecond laser pulses to suddenly increase the temperature at the interface. The measurement of the response of the interface toward the laser heating under coulostatic conditions provides evidence on the net orientation of water at the interface. Especially interesting is the study of the effect on the interfacial water caused by the selective deposition of foreign metal adatoms, because these bimetallic systems usually exhibit appealing electrocatalytic properties. The T-jump methodology shows that the surface composition strongly affects the interaction of water with the surface. The most representative parameter to characterize this interaction is the potential where water reorientation occurs; this potential shifts in different directions, depending on the relative values of the electronegativity of the adatom and the substrate. These results are discussed in the light of available information about the effect of adatom deposition on the work function and the surface potential of the modified surface. Finally, some implications on the enhancement of the electrocatalytic activity are briefly discussed. PMID:18321095

  3. Nanosecond multi-pulse laser milling for certain area removal of metal coating on plastics surface

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Jia, Zhenyuan; Ma, Jianwei; Liu, Wei; Wang, Ling

    2014-12-01

    Metal coating with functional pattern on engineering plastics surface plays an important role in industry applications; it can be obtained by adding or removing certain area of metal coating on engineering plastics surface. However, the manufacturing requirements are improved continuously and the plastic substrate presents three-dimensional (3D) structure-many of these parts cannot be fabricated by conventional processing methods, and a new manufacturing method is urgently needed. As the laser-processing technology has many advantages like high machining accuracy and constraints free substrate structure, the machining of the parts is studied through removing certain area of metal coating based on the nanosecond multi-pulse laser milling. To improve the edge quality of the functional pattern, generation mechanism and corresponding avoidance strategy of the processing defects are studied. Additionally, a prediction model for the laser ablation depth is proposed, which can effectively avoid the existence of residual metal coating and reduces the damage of substrate. With the optimal machining parameters, an equiangular spiral pattern on copper-clad polyimide (CCPI) is machined based on the laser milling at last. The experimental results indicate that the edge of the pattern is smooth and consistent, the substrate is flat and without damage. The achievements in this study could be applied in industrial production.

  4. Characterization of nanosecond pulse electrical field shock waves using imaging techniques

    NASA Astrophysics Data System (ADS)

    Mimun, L. Chris; Ibey, Bennett L.; Roth, Caleb C.; Barnes, Ronald A.; Sardar, Dhiraj K.; Beier, Hope T.

    2015-03-01

    Nanosecond pulsed electric fields (nsPEF) cause the formation of small pores, termed nanopores, in the membrane of cells. Current nanoporation models treat nsPEF exposure as a purely electromagnetic phenomenon, but recent publications showing pressure transients, ROS production, temperature gradients, and pH waves suggest the stimulus may be physically and chemically multifactorial causing elicitation of diverse biological conditions and stressors. Our research group's goal is to quantify the breadth and participation of these stressors generated during nsPEF exposure and determine their relative importance to the observed cellular response. In this paper, we used advanced imaging techniques to identify a possible source of nsPEF-induced acoustic shock waves. nsPEFs were delivered in an aqueous media via a pair of 125 μm tungsten electrodes separated by 100 μm, mirroring our previously published cellular exposure experiments. To visualize any pressure transients emanating from the electrodes or surrounding medium, we used the Schlieren imaging technique. Resulting images and measurements confirmed that mechanical pressure waves and electrode-based stresses are formed during nsPEF, resulting in a clearer understanding of the whole exposure dosimetry. This information will be used to better quantify the impact of nsPEF-induced acoustic shock waves on cells, and has provided further evidence of non-electrical-field induced exposures for elicitation of bioieffects.

  5. Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure

    PubMed Central

    Roth, Caleb C.; Barnes Jr., Ronald A.; Ibey, Bennett L.; Beier, Hope T.; Christopher Mimun, L.; Maswadi, Saher M.; Shadaram, Mehdi; Glickman, Randolph D.

    2015-01-01

    The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane. PMID:26450165

  6. Characterization of Pressure Transients Generated by Nanosecond Electrical Pulse (nsEP) Exposure.

    PubMed

    Roth, Caleb C; Barnes, Ronald A; Ibey, Bennett L; Beier, Hope T; Christopher Mimun, L; Maswadi, Saher M; Shadaram, Mehdi; Glickman, Randolph D

    2015-01-01

    The mechanism(s) responsible for the breakdown (nanoporation) of cell plasma membranes after nanosecond pulse (nsEP) exposure remains poorly understood. Current theories focus exclusively on the electrical field, citing electrostriction, water dipole alignment and/or electrodeformation as the primary mechanisms for pore formation. However, the delivery of a high-voltage nsEP to cells by tungsten electrodes creates a multitude of biophysical phenomena, including electrohydraulic cavitation, electrochemical interactions, thermoelastic expansion, and others. To date, very limited research has investigated non-electric phenomena occurring during nsEP exposures and their potential effect on cell nanoporation. Of primary interest is the production of acoustic shock waves during nsEP exposure, as it is known that acoustic shock waves can cause membrane poration (sonoporation). Based on these observations, our group characterized the acoustic pressure transients generated by nsEP and determined if such transients played any role in nanoporation. In this paper, we show that nsEP exposures, equivalent to those used in cellular studies, are capable of generating high-frequency (2.5 MHz), high-intensity (>13 kPa) pressure transients. Using confocal microscopy to measure cell uptake of YO-PRO®-1 (indicator of nanoporation of the plasma membrane) and changing the electrode geometry, we determined that acoustic waves alone are not responsible for poration of the membrane. PMID:26450165

  7. Interdiffusion studies in Bi-based layered systems with nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Missana, T.; Afonso, C. N.; da Silva, M. F.

    1994-12-01

    Interdiffusion processes are induced by nanosecond laser pulses from an excimer laser. The Bi-based systems studied are formed by a Bi layer and a Sb or Ge layer. Configurations with Bi at the surface layer or at the innermost layer are both studied. Real-time reflectivity measurements are performed during the irradiation to determine the process kinetics and times and Rutherford backscattering spectrometry is used to obtain the concentration depth profiles. It will be shown that there is an interfacially initiated diffusion process in the Bi-Sb system and that the diffusion coefficients of this system within the liquid phase are in the 10-5 10-6 cm2/s range. The Bi-Ge system shows instead little mixing, the diffusion coefficients of the system within the liquid phase being at least two orders of magnitude lower. The differences observed when Bi is the surface layer or the innermost one are related to the different thermal responses of the system.

  8. Discharge processes of UV pre-ionized electric-discharge pulsed DF laser

    NASA Astrophysics Data System (ADS)

    Pan, Qikun; Xie, Jijiang; Shao, Chunlei; Wang, Chunrui; Shao, Mingzhen; Guo, Jin

    2016-03-01

    The discharge processes of ultraviolet (UV) pre-ionized electric-discharge pulsed DF laser operating with a SF6-D2 gas mixture are studied. A mathematical model based on continuity equation of electrons and Kirchhoff equations for discharge circuit is established to describe the discharge processes. Voltage and current waveforms of main discharge and voltage waveforms of pre-ionization are solved numerically utilizing the model. The calculations correctly display some physical processes, such as the delay time between pre-ionization and main discharge, breakdown of the main electrode and self-sustained volume discharge (SSVD). The results of theory are consistent with the experiments, which are performed in our non-chain pulsed DF laser. Then the delay inductance and peak capacitance are researched to analyze their influences on discharge processes, and the circuit parameters of DF laser are given which is useful to improve the discharge stability.

  9. Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses

    PubMed Central

    Pérez-Gutiérrez, Francisco G.; Camacho-López, Santiago; Evans, Rodger; Guillén, Gabriel; Goldschmidt, Benjamin S.; Viator, John A.

    2010-01-01

    Circulating tumor cells (CTCs) photoacoustic detection systems can aid clinical decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond laser pulses generates photoacoustic waves that make its detection possible. This study aims at: (1) determining melanoma cell survival after laser pulses of 6 ns at λ = 355 and 532 nm; (2) comparing the potential enhancement in the photoacoustic signal using λ = 355 nm in contrast with λ = 532 nm; (3) determining the critical laser fluence at which melanin begins to leak out from melanoma cells; and (4) developing a time-resolved imaging (TRI) system to study the intracellular interactions and their effect on the plasma membrane integrity. Monolayers of melanoma cells were grown on tissue culture-treated clusters and irradiated with up to 1.0 J/cm2. Surviving cells were stained with trypan blue and counted using a hemacytometer. The phosphate buffered saline absorbance was measured with a nanodrop spectrophotometer to detect melanin leakage from the melanoma cells post-laser irradiation. Photoacoustic signal magnitude was studied at both wavelengths using piezoelectric sensors. TRI with 6 ns resolution was used to image plasma membrane damage. Cell survival decreased proportionally with increasing laser fluence for both wavelengths, although the decrease is more pronounced for 355 nm radiation than for 532 nm. It was found that melanin leaks from cells equally for both wavelengths. No significant difference in photoacoustic signal was found between wavelengths. TRI showed clear damage to plasma membrane due to laser-induced bubble formation. PMID:20589533

  10. A protective effect after clearance of orthotopic rat hepatocellular carcinoma by nanosecond pulsed electric fields.

    PubMed

    Chen, Ru; Sain, Nova M; Harlow, K Tyler; Chen, Yeong-Jer; Shires, Peter K; Heller, Richard; Beebe, Stephen J

    2014-10-01

    Strategies for treating liver cancer using radiation, chemotherapy combinations and tyrosine kinase inhibitors targeting specific mutations have provided longer survival times, yet multiple treatments are often needed and recurrences with new malignant phenotypes are not uncommon. New and innovative treatments are undoubtedly needed to successfully treat liver cancer. Over the last decade, nanosecond pulsed electric fields (nsPEFs) have shown promise in pre-clinical studies; however, these have been limited to treatment of skin cancers or xenographs in mice. In the present report, an orthotopic hepatocellular carcinoma (HCC) model is established in rats using N1-S1 HCC cells. Data demonstrate a response rate of 80-90% when 1000 pulses are delivered with 100ns durations, electric field strengths of 50kV/cm and repetition rates of 1Hz. N1-S1 tumours treated with nsPEFs expressed significant number of cells with active caspase-3 and caspase-9, but not caspase-8, indicating an intrinsic apoptosis mechanism(s) as well as caspase-independent mechanisms. Most remarkably, rats with successfully ablated tumours failed to re-grow tumours when challenged with a second injection of N1-S1 cells when implanted in the same or different liver lobe that harboured the original tumour. Given this protective effect, infiltration of immune cells and the presence of granzyme B expressing cells within days of treatment suggest the possibility of an anti-tumour adaptive immune response. In conclusion, NsPEFs not only eliminate N1-S1 HCC tumours, but also may induce an immuno-protective effect that defends animals against recurrences of the same cancer. PMID:25081978

  11. Dynamic effects and applications for nanosecond pulsed electric fields in cells and tissues

    NASA Astrophysics Data System (ADS)

    Beebe, Stephen J.; Blackmore, Peter F.; Hall, Emily; White, Jody A.; Willis, Lauren K.; Fauntleroy, Laura; Kolb, Juergen F.; Schoenbach, Karl H.

    2005-04-01

    Nanosecond, high intensity pulsed electric fields [nsPEFs] that are below the plasma membrane [PM] charging time constant have decreasing effects on the PM and increasing effects on intracellular structures and functions as the pulse duration decreases. When human cell suspensions were exposed to nsPEFs where the electric fields were sufficiently intense [10-300ns, <=300 kV/cm.], apoptosis signaling pathways could be activated in several cell models. Multiple apoptosis markers were observed in Jurkat, HL-60, 3T3L1-preadipocytes, and isolated rat adipocytes including decreased cell size and number, caspase activation, DNA fragmentation, and/or cytochrome c release into the cytoplasm. Phosphatidylserine externalization was observed as a biological response to nsPEFs in 3T3-L1 preadipocytes and p53-wildtype and -null human colon carcinoma cells. B10.2 mouse fibrosarcoma tumors that were exposed to nsPEFs ex vivo and in vivo exhibited DNA fragmentation, elevated caspase activity, and reduced size and weight compared to contralateral sham-treated control tumors. When nsPEF conditions were below thresholds for apoptosis and classical PM electroporation, non-apoptotic responses were observed similar to those initiated through PM purinergic receptors in HL-60 cells and thrombin in human platelets. These included Ca2+ mobilization from intracellular stores [endoplasmic reticulum] and subsequently through store-operated Ca2+ channels in the PM. In addition, platelet activation measured as aggregation responses were observed in human platelets. Finally, when nsPEF conditions followed classical electroporation-mediated transfection, the expression intensity and number of GFP-expressing cells were enhanced above cells exposed to electroporation conditions alone. These studies demonstrate that application of nsPEFs to cells or tissues can modulate cell-signaling mechanisms with possible applications as a new basic science tool, cancer treatment, wound healing, and gene therapy.

  12. Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

    NASA Astrophysics Data System (ADS)

    Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

    2016-06-01

    Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1-10 Hz) at various laser fluences ranging from 0.2 to 11 J cm-2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He-Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm-2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm-2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

  13. Changes in protein expression of U937 and Jurkat cells exposed to nanosecond pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Moen, Erick K.; Roth, Caleb C.; Cerna, Caesar; Estalck, Larry; Wilmink, Gerald; Ibey, Bennett L.

    2013-02-01

    Application of nanosecond pulsed electric fields (nsPEF) to various biological cell lines has been to shown to cause many diverse effects, including poration of the plasma membrane, depolarization of the mitochondrial membrane, blebbing, apoptosis, and intracellular calcium bursts. The underlying mechanism(s) responsible for these diverse responses are poorly understood. Of specific interest in this paper are the long-term effects of nsPEF on cellular processes, including the regulation of genes and production of proteins. Previous studies have reported transient activation of select signaling pathways involving mitogen-activated protein kinases (MAPKs), protein phosphorylation and downstream gene expression following nsPEF application. We hypothesize that nsPEF represents a unique stimulus that could be used to externally modulate cellular processes. To validate our hypothesis, we performed a series of cuvette-based exposures at 10 and 600ns pulse widths using a custom Blumlien line pulser system. We measured acute changes in the plasma membrane structure using flow cytometry by tracking phosphatidylserine externalization via FITC-Annexin V labeling and poration via propidium iodide uptake. We then compared these results to viability of the cells at 24 hours post exposure using MTT assay and changes in the MAPK family of proteins at 8 hours post-exposure using Luminex assay. By comparing exposures at 10 and 600ns duration, we found that most MAPK family-protein expression increased in Jurkat and U937 cell lines following exposure and compared well with drops in viability and changes in plasma membrane asymmetry. What proved interesting is that some MAPK family proteins (e.g. p53, STAT1), were expressed in one cell line, but not the other. This difference may point to an underlying mechanism for observed difference in cellular sensitivity to nsPEFinduced stresses.

  14. All-optical programmable shaping of narrow-band nanosecond pulses with picosecond accuracy by use of adapted chirps and quadratic nonlinearities.

    PubMed

    Ribeyre, X; Rouyer, C; Raoult, F; Husson, D; Sauteret, C; Migus, A

    2001-08-01

    We experimentally demonstrate pure optical pulse picosecond shaping of narrow-bandwidth nanosecond pulses. The method used is based on the manipulation in the spectral domain of strongly chirped femtosecond pulses and on the use of either frequency addition or frequency difference. PMID:18049553

  15. Dynamical studies of model membrane and cellular response to nanosecond, high-intensity pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Hu, Qin

    The dynamics of electroporation of biological cells subjected to nanosecond, high intensity pulses are studied based on a coupled scheme involving the current continuity and Smoluchowski equations. The improved pore formation energy model includes a dependence on pore population and density. It also allows for variable surface tension and incorporates the effects of finite conductivity on the electrostatic correction term, which was not considered by the simple energy models in the literature. It is shown that E(r) becomes self-adjusting with variations in its magnitude and profile. The whole scheme is self-consistent and dynamic. An electromechanical analysis based on thin-shell theory is presented to analyze cell shape changes in response to external electric fields. The calculations demonstrate that at large fields, the spherical cell geometry can be modified, and even ellipsoidal forms may not be appropriate to account for the resulting shape. It is shown that, in keeping with reports in the literature, the final shape depends on membrane thickness. This has direct implications for tissues in which significant molecular restructuring can occur. This study is also focused on obtaining qualitative predictions of pulse width dependence to apoptotic cell irreversibility that has been observed experimentally. The analysis couples a distributed electrical model for current flow with the Smoluchowski equation to provide self-consistent, time-dependent transmembrane voltages. The model captures the essence of the experimentally observed pulse-width dependence, and provides a possible physical picture that depends only on the electrical trigger. Different cell responses of normal and malignant (Farage) tonsillar B-cell are also compared and discussed. It is shown that subjecting a cell to an ultrashort, high-intensity electric pulse is the optimum way for reversible intracellular manipulation. Finally, a simple but physical atomistic model is presented for molecular

  16. Fiber grating compression of giant-chirped nanosecond pulses from an ultra-long nanotube mode-locked fiber laser.

    PubMed

    Woodward, R I; Kelleher, E J R; Runcorn, T H; Loranger, S; Popa, D; Wittwer, V J; Ferrari, A C; Popov, S V; Kashyap, R; Taylor, J R

    2015-02-01

    We demonstrate that the giant chirp of coherent, nanosecond pulses generated in an 846 m long, all-normal dispersion, nanotube mode-locked fiber laser can be compensated using a chirped fiber Bragg grating compressor. Linear compression to 11 ps is reported, corresponding to an extreme compression factor of ∼100. Experimental results are supported by numerical modeling, which is also used to probe the limits of this technique. Our results unequivocally conclude that ultra-long cavity fiber lasers can support stable dissipative soliton attractors and highlight the design simplicity for pulse-energy scaling through cavity elongation. PMID:25680054

  17. High-repetition-rate short-pulse gas discharge.

    PubMed

    Tulip, J; Seguin, H; Mace, P N

    1979-09-01

    A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW. PMID:18699678

  18. Pulsed positive streamer discharges in air at high temperatures

    NASA Astrophysics Data System (ADS)

    Ono, Ryo; Kamakura, Taku

    2016-08-01

    Atmospheric-pressure air pulsed positive streamer discharges are generated in a 13 mm point-plane gap in the temperature range of 293 K–1136 K, and the effect of temperature on the streamer discharges is studied. When the temperature is increased, the product of applied voltage and temperature VT proportional to the reduced electric field can be used as a primary parameter that determines some discharge parameters regardless of temperature. For a given VT, the transferred charge per pulse, streamer diameter, product of discharge energy and temperature, and length of secondary streamer are almost constant regardless of T, whereas the streamer velocity decreases with increasing T and the decay rate of the discharge current is proportional to 1/T. The N2(C) emission intensity is approximately determined by the discharge energy independent of T. These results are useful to predict the streamer discharge and its reactive species production when the ambient temperature is increased.

  19. On the applicability of arbitrarily shaped nanosecond laser pulses for high-quality, high-efficiency micromachining

    NASA Astrophysics Data System (ADS)

    Eiselen, Sasia; Riedel, Sebastian; Schmidt, Michael

    2014-05-01

    Progressive developments in temporal shaping of short laser pulses offer entirely new approaches at influence and investigate laser-matter-interactions. Commonly used parameters for describing the behavior of short or ultrashort pulses or pulse trains are fluence and intensity. However, fluence does not imply any information about the temporal behavior of energy input during specific pulse duration τ while using the pulse intensity as describing parameter is more meaningful. Nevertheless it still is an averaging over pulse duration and no change in intensity can be determined if the temporal pulse shape changes within a certain combination of pulse duration and pulse energy. Using a flexible programmable MOPA fiber laser experimental studies on the impact of temporal energy distribution within one single laser pulse in micro machining applications were therefore carried out. With this laser source a direct modulation of the temporal pulse shape in the nanosecond regime can easily be controlled. Experiments were carried out with moved as well as with un-moved beam resulting in areas and dimples respectively drilling holes. The presented results clearly show that any averaging over pulse duration results in missing information about time-dependent interactions but can at the same time lead to significant differences in ablation results. Thus, resulting surface roughness Sa can be decreased up to 25 % when changing the pulse shape at constant parameters of fluence and pulse peak power at a pulse duration of 30 ns. It can be observed that the combination of an intensity peak and a lower edge within one pulse can lead to increasing ablation efficiency as well as higher ablation quality compared to the commonly used Gaussian-like temporal pulse shape.

  20. Development of a stereo-symmetrical nanosecond pulsed power generator composed of modularized avalanche transistor Marx circuits

    NASA Astrophysics Data System (ADS)

    Li, Jiang-Tao; Zhong, Xu; Cao, Hui; Zhao, Zheng; Xue, Jing; Li, Tao; Li, Zheng; Wang, Ya-Nan

    2015-09-01

    Avalanche transistors have been widely studied and used in nanosecond high voltage pulse generations. However, output power improvement is always limited by the low thermal capacities of avalanche transistors, especially under high repetitive working frequency. Parallel stacked transistors can effectively improve the output current but the controlling of trigger and output synchronism has always been a hard and complex work. In this paper, a novel stereo-symmetrical nanosecond pulsed power generator with high reliability was developed. By analyzing and testing the special performances of the combined Marx circuits, numbers of meaningful conclusions on the pulse amplitude, pulse back edge, and output impedance were drawn. The combining synchronism of the generator was confirmed excellent and lower conducting current through the transistors was realized. Experimental results showed that, on a 50 Ω resistive load, pulses with 1.5-5.2 kV amplitude and 5.3-14.0 ns width could be flexibly generated by adjusting the number of combined modules, the supply voltage, and the module type.

  1. DNA Electrophoretic Migration Patterns Change after Exposure of Jurkat Cells to a Single Intense Nanosecond Electric Pulse

    PubMed Central

    Romeo, Stefania; Zeni, Luigi; Sarti, Maurizio; Sannino, Anna; Scarfì, Maria Rosaria; Vernier, P. Thomas; Zeni, Olga

    2011-01-01

    Intense nanosecond pulsed electric fields (nsPEFs) interact with cellular membranes and intracellular structures. Investigating how cells respond to nanosecond pulses is essential for a) development of biomedical applications of nsPEFs, including cancer therapy, and b) better understanding of the mechanisms underlying such bioelectrical effects. In this work, we explored relatively mild exposure conditions to provide insight into weak, reversible effects, laying a foundation for a better understanding of the interaction mechanisms and kinetics underlying nsPEF bio-effects. In particular, we report changes in the nucleus of Jurkat cells (human lymphoblastoid T cells) exposed to single pulses of 60 ns duration and 1.0, 1.5 and 2.5 MV/m amplitudes, which do not affect cell growth and viability. A dose-dependent reduction in alkaline comet-assayed DNA migration is observed immediately after nsPEF exposure, accompanied by permeabilization of the plasma membrane (YO-PRO-1 uptake). Comet assay profiles return to normal within 60 minutes after pulse delivery at the highest pulse amplitude tested, indicating that our exposure protocol affects the nucleus, modifying DNA electrophoretic migration patterns. PMID:22164287

  2. Development of a stereo-symmetrical nanosecond pulsed power generator composed of modularized avalanche transistor Marx circuits.

    PubMed

    Li, Jiang-Tao; Zhong, Xu; Cao, Hui; Zhao, Zheng; Xue, Jing; Li, Tao; Li, Zheng; Wang, Ya-Nan

    2015-09-01

    Avalanche transistors have been widely studied and used in nanosecond high voltage pulse generations. However, output power improvement is always limited by the low thermal capacities of avalanche transistors, especially under high repetitive working frequency. Parallel stacked transistors can effectively improve the output current but the controlling of trigger and output synchronism has always been a hard and complex work. In this paper, a novel stereo-symmetrical nanosecond pulsed power generator with high reliability was developed. By analyzing and testing the special performances of the combined Marx circuits, numbers of meaningful conclusions on the pulse amplitude, pulse back edge, and output impedance were drawn. The combining synchronism of the generator was confirmed excellent and lower conducting current through the transistors was realized. Experimental results showed that, on a 50 Ω resistive load, pulses with 1.5-5.2 kV amplitude and 5.3-14.0 ns width could be flexibly generated by adjusting the number of combined modules, the supply voltage, and the module type. PMID:26429438

  3. Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier.

    PubMed

    Rogers, C E; Gould, P L

    2016-02-01

    We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized. PMID:26906832

  4. Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier

    NASA Astrophysics Data System (ADS)

    Rogers, C. E.; Gould, P. L.

    2016-02-01

    We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized.

  5. Self-pulsing of hollow cathode discharge in various gases

    SciTech Connect

    Qin, Y.; He, F. Jiang, X. X.; Ouyang, J. T.; Xie, K.

    2014-07-15

    In this paper, we investigate the self-pulsing phenomenon of cavity discharge in a cylindrical hollow cathode in various gases including argon, helium, nitrogen, oxygen, and air. The current-voltage characteristics of the cavity discharge, the waveforms of the self-pulsing current and voltage as well as the repetition frequency were measured. The results show that the pulsing frequency ranges from a few to tens kilohertz and depends on the averaged current and the pressure in all gases. The pulsing frequency will increase with the averaged current and decrease with the pressure. The rising time of the current pulse is nearly constant in a given gas or mixture. The self-pulsing does not depend on the external ballast but is affected significantly by the external capacitor in parallel with the discharge cell. The low-current self-pulsing in hollow cathode discharge is the mode transition between Townsend and glow discharges. It can be described by the charging-discharging process of an equivalent circuit consisting of capacitors and resistors.

  6. Lead extraction by selective operation of a nanosecond-pulsed 355nm laser

    NASA Astrophysics Data System (ADS)

    Herzog, Amir; Bogdan, Stefan; Glikson, Michael; Ishaaya, Amiel A.; Love, Charles

    2016-03-01

    Lead extraction (LE) is necessary for patients who are suffering from a related infection, or in opening venous occlusions that prevent the insertion of additional lead. In severe cases of fibrous encapsulation of the lead within a vein, laser-based cardiac LE has become one of the foremost methods of removal. In cases where the laser radiation (typically at 308 nm wavelength) interacts with the vein wall rather than with the fibrotic lesion, severe injury and subsequent bleeding may occur. Selective tissue ablation was previously demonstrated by a laser operating in the UV regime; however, it requires the use of sensitizers (e.g.: tetracycline). In this study, we present a preliminary examination of efficacy and safety aspects in the use of a nanosecond-pulsed solid-state laser radiation, at 355 nm wavelength, guided in a catheter consisting of optical fibers, in LE. Specifically, we demonstrate a correlation between the tissue elasticity and the catheter advancement rate, in ex-vivo experiments. Our results indicate a selectivity property for specific parameters of the laser radiation and catheter design. The selectivity is attributed to differences in the mechanical properties of the fibrotic tissue and a normal vein wall, leading to a different photomechanical response of the tissue's extracellular matrix. Furthermore, we performed successful in-vivo animal trials, providing a basic proof of concept for using the suggested scheme in LE. Selective operation using a 355 nm laser may reduce the risk of blood vessel perforation as well as the incidence of major adverse events.

  7. Nanosecond electric pulses affect a plant-specific kinesin at the plasma membrane.

    PubMed

    Kühn, Sebastian; Liu, Qiong; Eing, Christian; Frey, Wolfgang; Nick, Peter

    2013-12-01

    Electric pulses with high field strength and durations in the nanosecond range (nsPEFs) are of considerable interest for biotechnological and medical applications. However, their actual cellular site of action is still under debate--due to their extremely short rise times, nsPEFs are thought to act mainly in the cell interior rather than at the plasma membrane. On the other hand, nsPEFs can induce membrane permeability. We have revisited this issue using plant cells as a model. By mapping the cellular responses to nsPEFs of different field strength and duration in the tobacco BY-2 cell line, we could define a treatment that does not impinge on short-term viability, such that the physiological responses to the treatment can be followed. We observe, for these conditions, a mild disintegration of the cytoskeleton, impaired membrane localization of the PIN1 auxin-efflux transporter and a delayed premitotic nuclear positioning followed by a transient mitotic arrest. To address the target site of nsPEFs, we made use of the plant-specific KCH kinesin, which can assume two different states with different localization (either near the nucleus or at the cell membrane) driving different cellular functions. We show that nsPEFs reduce cell expansion in nontransformed cells but promote expansion in a line overexpressing KCH. Since cell elongation and cell widening are linked to the KCH localized at the cell membrane, the inverted response in the KCH overexpressor provides evidence for a direct action of nsPEFs, also at the cell membrane. PMID:24062185

  8. Real time kinetic flow cytometry measurements of cellular parameter changes evoked by nanosecond pulsed electric field.

    PubMed

    Orbán, Csaba; Pérez-García, Esther; Bajnok, Anna; McBean, Gethin; Toldi, Gergely; Blanco-Fernandez, Alfonso

    2016-05-01

    Nanosecond pulsed electric field (nsPEF) is a novel method to increase cell proliferation rate. The phenomenon is based on the microporation of cellular organelles and membranes. However, we have limited information on the effects of nsPEF on cell physiology. Several studies have attempted to describe the effects of this process, however no real time measurements have been conducted to date. In this study we designed a model system which allows the measurement of cellular processes before, during and after nsPEF treatment in real time. The system employs a Vabrema Mitoplicator(TM) nsPEF field generating instrument connected to a BD Accuri C6 cytometer with a silicon tube led through a peristaltic pump. This model system was applied to observe the effects of nsPEF in mammalian C6 glioblastoma (C6 glioma) and HEK-293 cell lines. Viability (using DRAQ7 dye), intracellular calcium levels (using Fluo-4 dye) and scatter characteristics were measured in a kinetic manner. Data were analyzed using the FACSKin software. The viability and morphology of the investigated cells was not altered upon nsPEF treatment. The response of HEK-293 cells to ionomycin as positive control was significantly lower in the nsPEF treated samples compared to non-treated cells. This difference was not observed in C6 cells. FSC and SSC values were not altered significantly by the nsPEF treatment. Our results indicate that this model system is capable of reliably investigating the effects of nsPEF on cellular processes in real time. © 2016 International Society for Advancement of Cytometry. PMID:26990601

  9. Simulation of nanosecond pulsed laser ablation of copper samples: A focus on laser induced plasma radiation

    NASA Astrophysics Data System (ADS)

    Aghaei, M.; Mehrabian, S.; Tavassoli, S. H.

    2008-09-01

    A thermal model for nanosecond pulsed laser ablation of Cu in one dimension and in ambient gas, He at 1 atm, is proposed in which equations concerning heat conduction in the target and gas dynamics in the plume are solved. These equations are coupled to each other through the energy and mass balances at interface between the target and the vapor and also Knudsen layer conditions. By assumption of local thermal equilibrium, Saha-Eggert equations are used to investigate plasma formation. The shielding effect of the plasma, due to photoionization and inverse bremsstrahlung processes, is considered. Bremsstrahlung and blackbody radiation and spectral emissions of the plasma are also investigated. Spatial and temporal distribution of the target temperature, number densities of Cu and He, pressure and temperature of the plume, bremsstrahlung and blackbody radiation, and also spectral emissions of Cu at three wavelengths (510, 516, and 521 nm) are obtained. Results show that the spectral power of Cu lines has the same pattern as CuI relative intensities from National Institute of Standard and Technology. Investigation of spatially integrated bremsstrahlung and blackbody radiation, and also Cu spectral emissions indicates that although in early times the bremsstrahlung radiation dominates the two other radiations, the Copper spectral emission is the dominant radiation in later times. It should be mentioned that the blackbody radiation has the least values in both time intervals. The results can be used for prediction of the optimum time and position of the spectral line emission, which is applicable in some time resolved spectroscopic techniques such as laser induced breakdown spectroscopy. Furthermore, the results suggest that for distinguishing between the spectral emission and the bremsstrahlung radiation, a spatially resolved spectroscopy can be used instead of the time resolved one.

  10. Pulse volume discharges in high pressure gases

    NASA Astrophysics Data System (ADS)

    Yamshchikov, V. A.

    2015-11-01

    New approach for suppression of plasma inhomogeneities and instabilities in the volume self-sustained discharge is offered. The physical model is offered and conditions of obtaining extremely homogeneous self-sustained discharge are defined (with full suppression of plasma inhomogeneity and instability). Results of calculations agree with experiments.

  11. Efficient neutron production from sub-nanosecond laser pulse accelerating deuterons on target front side

    SciTech Connect

    Klir, D.; Krasa, J.; Velyhan, A.; Cikhardt, J.; Rezac, K.; Dudzak, R.; Krousky, E.; Pfeifer, M.; Skala, J.; Ullschmied, J.; Sila, O.

    2015-09-15

    Neutron-producing experiments have been carried out on the Prague Asterix Laser System. At the fundamental wavelength of 1.315 μm, the laser pulse of a 600 J energy and 300 ps duration was focused on a thick deuterated-polyethylene target. Neutron yields reached (4.1 ± 0.8) × 10{sup 8} at the peak intensity of ≈3 × 10{sup 16 }W/cm{sup 2}. A more detailed analysis of neutron time-of-flight signals showed that a significant fraction of neutron yields was produced both by the {sup 2}H(d,n){sup 3}He reaction and by other neutron-producing reactions. Neutron energies together with delayed neutron and gamma emission showed that MeV deuterons escaped from a laser-produced plasma and interacted ≈50 ns later with a borosilicate blast-shield glass. In order to increase DD neutron yields and to characterize deuteron beams via nuclear reactions, a secondary deuterated polyethylene target was used in a pitcher-catcher scheme at the target front side. In this experimental arrangement, the neutron yield reached (2.0 ± 0.5) × 10{sup 9} with the peak neutron fluence of (2.5 ± 0.5) × 10{sup 8 }n/sr. From the neutron yield, it was calculated that the secondary target was bombarded by 2 × 10{sup 14} deuterons in the 0.5–2.0 MeV energy range. The neutron yield of 2 × 10{sup 9} at the laser energy of 600 J implied the production efficiency of 3 × 10{sup 6 }n/J. A very important result is that the efficient neutron production was achieved with the low contrast, sub-nanosecond laser pulse of the intensity of 10{sup 16 }W/cm{sup 2}. The latter parameters can be achieved in a rep-rate mode more easily than ultra-high intensities and contrasts.

  12. Electron beam switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, Lyn D.; Murray, John R.; Goldhar, Julius; Bradley, Laird P.

    1981-01-01

    Method and apparatus for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  13. Inductively stabilized, long pulse duration transverse discharge apparatus

    DOEpatents

    Sze, Robert C.

    1986-01-01

    An inductively stabilized, long pulse duration transverse discharge apparatus. The use of a segmented electrode where each segment is attached to an inductive element permits high energy, high efficiency, long-pulsed laser outputs to be obtained. The present apparatus has been demonstrated with rare-gas halide lasing media. Orders of magnitude increase in pulse repetition frequency are obtained in lasing devices that do not utilize gas flow.

  14. Spatio-temporal characterization of pulses obtained from a high-energy sub-nanosecond laser system.

    PubMed

    Feng, Chengyong; Xu, Xiaozhen; Diels, Jean-Claude

    2016-03-01

    Spatio-temporal profiles of laser pulses, obtained from each stage of a high-energy sub-nanosecond laser system, are investigated. The laser system is composed of a Q-switched Nd:YAG unstable oscillator, a chain of Nd:YAG amplifiers, a second-harmonic generator, and a high-energy pulse compressor based on stimulated Brillouin scattering (SBS). A curved energy front, i.e., the pulses emerging away from the beam center being gradually delayed from the center pulse, is shown to originate from the unstable oscillator. Our comparative study shows that injection seeding will enlarge the energy front curvature, via reduction of the effective gain. After the laser amplifiers, the energy front curvature is more than doubled due to the gain saturation effect. The latter also modifies the spatial pulse width distribution. While there is a negligible pulse duration spread across the oscillator beam, the amplified pulses are found to have gradually reduced pulse duration away from the beam center. More interestingly, after the SBS pulse compression, not only the pulse width but also the delay is compressed down. This is, to the best of our knowledge, the first study of the spatio-temporal profile of the SBS compressed pulse. To compare with the experiments, two numerical models are developed to simulate the evolution of spatio-temporal profiles within the Nd:YAG laser system and during the SBS pulse compression, respectively. The first model is demonstrated to reproduce the experimental results very well, while the second model predicts part of the features of the SBS compressed pulse. The limitation on the latter is discussed. PMID:26974618

  15. A simple highly stable and temporally synchronizable Nd:glass laser oscillator delivering laser pulses of variable pulse duration from sub-nanosecond to few nanoseconds

    NASA Astrophysics Data System (ADS)

    Sharma, A. K.; Joshi, R. A.; Patidar, R. K.; Naik, P. A.; Gupta, P. D.

    2007-04-01

    A simple flash lamp pumped Nd:phosphate glass laser oscillator has been designed and set up delivering laser pulses of variable duration from ˜800 ps to 6 ns. It is based on Q-switching and full-wavelength cavity dumping and provides single laser pulse energy of 5 mJ and 11 mJ corresponding to pulse duration of ˜800 ps and 6 ns respectively at an electrical pump energy of 50 J. While the maximum pulse duration is governed by the cavity round trip time, the lower limit is decided by the switching speed of the high voltage pulse to the Pockels cell of the cavity dumper. Output laser pulses have shown enhanced pulse energy stability by dumping the cavity four round trips after the peak buildup. The laser pulses were synchronized with 250 ps positively chirped laser pulse train derived from an independent commercial cw mode locked Nd:fluorophosphate glass laser oscillator. The temporal jitter between these two pulses was measured to be ˜200 ps, limited by the speed of the electronics used.

  16. Optimized Nanosecond Pulsed Electric Field Therapy Can Cause Murine Malignant Melanomas to Self-Destruct with a Single Treatment

    PubMed Central

    Nuccitelli, Richard; Tran, Kevin; Sheikh, Saleh; Athos, Brian; Kreis, Mark; Nuccitelli, Pamela

    2010-01-01

    We have identified a new, nanosecond pulsed electric field (nsPEF) therapy capable of eliminating murine melanomas located in the skin with a single treatment. When these optimized parameters are used, nsPEFs initiate apoptosis without hyperthermia. We have developed new suction electrodes that are compatible with human skin and have applied them to a xenograft nude mouse melanoma model system to identify the optimal field strength, pulse frequency and pulse number for the treatment of murine melanomas. A single treatment using the optimal pulse parameters (2000 pulses, 100 ns in duration, 30 kV/cm in amplitude at a pulse frequency of 5–7 pulses/s) eliminated all 17 melanomas treated with those parameters in 4 mice. This was the highest pulse frequency that we could use without raising the treated skin tumor temperature above 40 °C. We also demonstrate that the effects of nsPEF therapy are highly localized to only cells located between electrodes and results in very little scarring of the nsPEF-treated skin. PMID:20473857

  17. High energy green nanosecond and picosecond pulse delivery through a negative curvature fiber for precision micro-machining.

    PubMed

    Jaworski, Piotr; Yu, Fei; Carter, Richard M; Knight, Jonathan C; Shephard, Jonathan D; Hand, Duncan P

    2015-04-01

    In this paper we present an anti-resonant guiding, low-loss Negative Curvature Fiber (NCF) for the efficient delivery of high energy short (ns) and ultrashort (ps) pulsed laser light in the green spectral region. The fabricated NCF has an attenuation of 0.15 dB/m and 0.18 dB/m at 532 nm and 515 nm respectively, and provided robust transmission of nanosecond and picosecond pulses with energies of 0.57 mJ (10.4 kW peak power) and 30 µJ (5 MW peak power) respectively. It provides single-mode, stable (low bend-sensitivity) output and maintains spectral and temporal properties of the source laser beam. The practical application of fiber-delivered pulses has been demonstrated in precision micro-machining and marking of metals and glass. PMID:25968688

  18. In situ observation of self-organizing nanodot formation under nanosecond-pulsed laser irradiation on Si surface

    NASA Astrophysics Data System (ADS)

    Watanabe, S.; Yoshida, Y.; Kayashima, S.; Yatsu, S.; Kawai, M.; Kato, T.

    2010-11-01

    An in situ observation of the formation of a laser-irradiation-induced nanodot array on a Si surface was performed using a pulsed-laser-equipped high-voltage electron microscope (laser-HVEM). Under multiple nanosecond (ns) pulsed laser irradiation shots, atomic clusters were first formed and distributed on the surface in order to grow them epitaxially into protruded dots with diameters of ten nanometers or less. This is followed by their diffusion induced by successive laser shots to cannibalize and merge them into a ripple line with aligned, larger dots. We conclude that the present subwavelength two-dimensionally-ordered nanodot array is formed by self-organization under pulsed laser irradiation.

  19. Feedback-free single-beam pattern formation by nanosecond pulses in dye-doped liquid crystals

    NASA Astrophysics Data System (ADS)

    Lepeshkin, Nick N.; Lukishova, Svetlana G.; Boyd, Robert W.; Marshall, Kenneth L.

    2006-08-01

    Generally, optical feedback and/or two counter-propagating beams are necessary to form high-definition patterns in the cross section of a laser beam after passing through a nonlinear medium. In this paper we present an observation of pattern formation in liquid crystal media in a single laser beam without any external feedback. We found that after irradiation of a dye-doped liquid crystal cell with repetitive nanosecond pulses, the beam coming out of the liquid crystal cell exhibits a spectacular kaleidoscopic change of beam patterns in the far field. The patterns vary from pulse to pulse in an ordered manner cycling through a variety of complicated forms. We speculate that localized phase separation of the dye from the liquid crystal host occurs in the focal region of the beam in our experiments, and that the observed far-field patterns result from the laser-beam diffraction on these absorptive and refractive inhomogeneities.

  20. Laser-induced damage of hafnia coatings as a function of pulse duration in the femtosecond to nanosecond range

    SciTech Connect

    Gallais, Laurent; Mangote, Benoit; Zerrad, Myriam; Commandre, Mireille; Melninkaitis, Andrius; Mirauskas, Julius; Jeskevic, Maksim; Sirutkaitis, Valdas

    2011-03-20

    Laser-damage thresholds and morphologies of hafnia single layers exposed under femtosecond, picosecond, and nanosecond single pulses (1030/1064nm) are reported. The samples were made with different deposition parameters in order to study how the damage behavior of the samples evolves with the pulse duration and how it is linked to the deposition process. In the femtosecond to picosecond regime, the scaling law of the laser-induced damage threshold as a function of pulse duration is in good agreement with the models of photo and avalanche ionization based on the rate equation for free electron generation. However, differences in the damage morphologies between samples are shown. No correlation between the nanosecond and femtosecond/picosecond laser-damage resistance of hafnia coatings could be established. We also report evidence of the transition in damage mechanisms for hafnia, from an ablation process linked to intrinsic properties of the material to a defect-induced process, that exists between a few picoseconds and a few tens of picoseconds.

  1. White-light emission from solid carbon in aqueous solution during hydrogen generation induced by nanosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Akimoto, Ikuko; Yamamoto, Shota; Maeda, Kosuke

    2016-07-01

    We previously discovered a novel method of hydrogen generation from high-grade charcoal in an aqueous solution using nanosecond laser pulse irradiation. In this paper, white-light emission during this reaction is reported: A broad spectrum over the visible range is observed above a threshold excitation energy density. The white-light emission is a simultaneous product of the hydrogen generation reaction and is attributed to blackbody radiation in accordance with Planck's Law at a temperature above 3800 K. Consequently, we propose that hydrogen generation induced by laser irradiation proceeds similarly to classical coal gasification, which features reactions at high pressure and high temperature.

  2. 105 W ultra-narrowband nanosecond pulsed laser at 2 μm based on monolithic Tm-doped fiber MOPA.

    PubMed

    Wang, Xiong; Jin, Xiaoxi; Zhou, Pu; Wang, Xiaolin; Xiao, Hu; Liu, Zejin

    2015-02-23

    We present a high power ultra-narrowband pulsed fiber amplifier at 2 μm. A single frequency fiber laser was modulated by a phase modulator and an intensity modulator to serve as the ultra-narrowband pulsed seed laser with a bandwidth of 307 MHz. The pulsed seed laser was amplified by a monolithic Tm-doped fiber master oscillator power amplifier (MOPA). The average output power reaches 105 W with a slope efficiency of 0.41. The output pulse train has a repetition rate of 1 MHz and a pulse width of 66 ns. The output power is limited by the onset of stimulated Brillouin scattering. Higher output power can be achieved by further broadening the linewidth or narrowing the pulse width to several nanoseconds. To the best of our knowledge, this is the first demonstration on a monolithic ultra-narrowband nanosecond pulsed MOPA at 2 μm with an average power exceeding 100 W. PMID:25836461

  3. Lead acid battery pulse discharge investigation. Final report

    SciTech Connect

    Dowgiallo, E

    1980-04-01

    The effects of high current pulses caused by electric vehicle silicon-controlled rectifier and transistor chopper controllers on battery energy, lifetime, and microstructure were studied. Test equipment and results are described. It was found that the energy of improved golf cart-type batteries deteriorated under pulsed conditions by about 10% with respect to dc conditions for pulses between 16 and 333 Hz - no difference was noted above 333 Hz. Frequencies and duty cycles characteristic of electric vehicle controllers produce ampere-hour capacities similar in magnitude to dc discharges of the same average currents. The amount of positive plate corrosion under pulsed conditions was about twice that ot the unpulsed. Unusually large lead sulfate crystals were found in isolated colonies in pulsed plates, whereas a battery that had been discharged each cycle at an equivalent steady state did not show these large crystals. 5 figures, 3 tables. (RWR)

  4. Sub-ten nanosecond laser pulse shaping using lithium niobate modulators and a double-passed tapered amplifier

    NASA Astrophysics Data System (ADS)

    Rogers, C. E., III; Gould, P. L.

    2015-05-01

    We present progress on developing a laser pulse shaping system capable of generating pulses shorter than ten nanoseconds and frequency chirps of up to about 5 GHz in 2.5 ns. Shaped control of phase and amplitude on this timescale may prove useful for producing ultracold molecules and controlling atomic hyperfine state populations. The pulses are generated by passing 780 nm light from an external cavity diode laser through a fiber-coupled lithium niobate (LN) phase modulator (PM) in series with an LN intensity modulator (IM). The modulators are driven with a single-channel 8 GS/s arbitrary waveform generator configured with an RF delay line for quasi-two channel pulsed operation. The optical pulses are then amplified in a double-pass tapered amplifier (TA). The TA's intrinsic mode structure leads to an etalon effect that modulates the pulse amplitude during a frequency chirp. To reduce this unwanted effect, a compensating intensity modulation can be programmed onto the seed pulse. This work is supported by DOE.

  5. Influence of cerium on the pulsed UV nanosecond laser processing of photostructurable glass ceramic materials

    NASA Astrophysics Data System (ADS)

    Livingston, F. E.; Adams, P. M.; Helvajian, H.

    2005-07-01

    Photostructurable glass ceramic (PSGC) materials contain a sensitizer that is used to facilitate the optical exposure process. The primary role of the sensitizer is to absorb incident radiation and generate photoelectrons. With thermal treatment, these photoelectrons can then interact with nascent metal ions to induce the formation of metallic clusters and the precipitation of a soluble crystalline phase in the glass matrix. The photo-ionization efficiency of the sensitizer species is strongly dependent on its spectral absorption and oxidation state in the base glass. Stabilizing compounds are typically added to the glass matrix to maintain the photo-active oxidation state and promote efficient exposure. To investigate the effectiveness of the photo-initiator, we have conducted experiments in which sample coupons of a commercial PSGC material (Foturan™, Schott Corp., Germany) were carefully exposed to various photon doses by pulsed UV nanosecond lasers at λ = 266 nm and 355 nm. Foturan is a lithium aluminosilicate glass that contains trace amounts of cerium as the photosensitive agent (0.01-0.04 wt.% admixture Ce 2O 3). The photo-initiator efficiency was investigated by using samples with cerium and without cerium. The irradiation wavelengths were selected because they lie above and below the primary absorption band of the cerium photo-initiator. Optical transmission spectroscopy (OTS) was employed to identify and monitor the population density of the photo-induced trapped electron state as a function of incident laser irradiance. The irradiated samples were thermally processed and then analyzed again with OTS to measure the quenching of the trapped electron state and the concurrent growth of a spectral band associated with the formation of nanometer-scale metallic clusters. The growth of metallic clusters signifies the "fixing" of the exposure and permanent image formation in the glass. The OTS results reveal that for λ = 266 nm laser irradiation, at least two

  6. Multiple nanosecond electric pulses increase the number but not the size of long-lived nanopores in the cell membrane.

    PubMed

    Pakhomov, Andrei G; Gianulis, Elena; Vernier, P Thomas; Semenov, Iurii; Xiao, Shu; Pakhomova, Olga N

    2015-04-01

    Exposure to intense, nanosecond-duration electric pulses (nsEP) opens small but long-lived pores in the plasma membrane. We quantified the cell uptake of two membrane integrity marker dyes, YO-PRO-1 (YP) and propidium (Pr) in order to test whether the pore size is affected by the number of nsEP. The fluorescence of the dyes was calibrated against their concentrations by confocal imaging of stained homogenates of the cells. The calibrations revealed a two-phase dependence of Pr emission on the concentration (with a slower rise at<4μM) and a linear dependence for YP. CHO cells were exposed to nsEP trains (1 to 100 pulses, 60ns, 13.2kV/cm, 10Hz) with Pr and YP in the medium, and the uptake of the dyes was monitored by time-lapse imaging for 3min. Even a single nsEP triggered a modest but detectable entry of both dyes, which increased linearly when more pulses were applied. The influx of Pr per pulse was constant and independent of the pulse number. The influx of YP per pulse was highest with 1- and 2-pulse exposures, decreasing to about twice the Pr level for trains from 5 to 100 pulses. The constant YP/Pr influx ratio for trains of 5 to 100 pulses suggests that increasing the number of pulses permeabilizes cells to a greater extent by increasing the pore number and not the pore diameter. PMID:25585279

  7. Nanosecond pulse passively Q-switched Yb-doped fiber laser with Cr4+: YAG as saturable absorber

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Liu, Jiang; Wang, Pu

    2011-06-01

    We report a passively Q-switched Yb-doped fiber laser with Cr4+:YAG saturable absorber and get stable nanosecond pulse trains. Three kinds of laser cavity configurations, including a cladding-pumped ring cavity, a cladding-pumped linear cavity and a core-pumped linear cavity were studied, and they all can effectively restrain the generation of Stimulated Brillouin scattering and the generation of self-pulse. Cladding-pumped ring-avity fiber laser with Cr4+:YAG as saturable absorber inside is established for the first time to obtain stable 1 μs pulse trains. The amplitude fluctuation and timing jitter are below 5% (rms). Further more, we can also get stable pulse trains by using a high reflective fiber Bragging grating as a resonator mirror in a cladding-pumped linear cavity and a core-pumped linear cavity fiber laser respectively. In the cladding-pumped linear cavity fiber laser, the tunable pulse repetition rate is from 9.1 kHz to 30.3 kHz and the minimum pulse duration is 156 ns. And in the core-pumped linear cavity fiber laser, the tunable pulse repetition rate is from 15 kHz to 33 kHz and the minimum pulse duration is 24 ns which much less than those reported before. Although the average output power is only hundreds milli-Watts now, the laser uses a fiber coupler as the output of pulse trains, it is convinient to boost the power with a stage of fiber amplifier. This kind of pulse laser can be used as a seed source, and amplified to tens of Watts for practical applications in the future.

  8. Long-pulse plasma discharge on the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Mutoh, T.; Saito, K.; Seki, T.; Nakamura, Y.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Ohkubo, K.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Kobayashi, M.; Ogawa, H.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Watari, T.; Watanabe, T.; Sakamoto, M.; Ichimura, M.; Takase, Y.; Notake, T.; Takeuchi, N.; Torii, Y.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Y.; Kwak, J. G.; Yoon, J. S.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD experiment Group

    2006-03-01

    A long-pulse plasma discharge of more than 30 min duration was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8 × 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. The total injected heating energy was 1.3 GJ. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by sweeping the magnetic axis inward and outward. Causes limiting the long pulse plasma discharge are discussed. An ion impurity penetration limited further long-pulse discharge in the 8th experimental campaign (2004).

  9. Pulsed electrical discharge in gas bubbles in water

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia

    A phenomenological picture of pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging methods. The discharge is generated by applying one microsecond long 5 to 20 kilovolt pulses between the needle and disk electrodes submerged in water. A gas bubble is generated at the tip of the needle electrode. The study includes detailed experimental investigation of the discharge in argon bubbles and a brief look at the discharge in oxygen bubbles. Imaging, electrical characteristics, and time-resolved optical emission data point to a fast streamer propagation mechanism and formation of a plasma channel in the bubble. Spectroscopic methods based on line intensity ratios and Boltzmann plots of line intensities of argon, atomic hydrogen, and argon ions and the examination of molecular emission bands from molecular nitrogen and hydroxyl radicals provide evidence of both fast beam-like electrons and slow thermalized ones with temperatures of 0.6 -- 0.8 electron-volts. The collisional nature of plasma at atmospheric pressure affects the decay rates of optical emission. Spectroscopic study of rotational-vibrational bands of hydroxyl radical and molecular nitrogen gives vibrational and rotational excitation temperatures of the discharge of about 0.9 and 0.1 electron-volt, respectively. Imaging and electrical evidence show that discharge charge is deposited on the bubble wall and water serves as a dielectric barrier for the field strength and time scales of this experiment. Comparing the electrical and imaging information for consecutive pulses applied at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from long-lived chemical species, such as ozone and oxygen. Intermediate values for the discharge gap and pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique

  10. Few-nanosecond pulse switching with low write error for in-plane nanomagnets using the spin-Hall effect

    NASA Astrophysics Data System (ADS)

    Aradhya, Sriharsha; Rowlands, Graham; Shi, Shengjie; Oh, Junseok; Ralph, D. C.; Buhrman, Robert

    Magnetic random access memory (MRAM) using spin transfer torques (STT) holds great promise for replacing existing best-in-class memory technologies in several application domains. Research on conventional two-terminal STT-MRAM thus far has revealed the existence of limitations that constrain switching reliability and speed for both in-plane and perpendicularly magnetized devices. Recently, spin torque arising from the giant spin-Hall effect in Ta, W and Pt has been shown to be an efficient mechanism to switch magnetic bits in a three-terminal geometry. Here we report highly reliable, nanosecond timescale pulse switching of three-terminal devices with in-plane magnetized magnetic tunnel junctions. We obtain write error rates (WER) down to ~10-5 using pulses as short as 2 ns, in contrast to conventional in-plane STT-MRAM devices where write speeds were limited to a few tens of nanoseconds for comparable WER. Utilizing micro-magnetic simulations, we discuss the differences from conventional MRAM that allow for this unanticipated and significant performance improvement. Finally, we highlight the path towards practical application enabled by the ability to separately optimize the read and write pathways in three-terminal devices.

  11. Evaluating the generation efficiency of hydrogen peroxide in water by pulsed discharge over water surface and underwater bubbling pulsed discharge

    NASA Astrophysics Data System (ADS)

    Shang, Kefeng; Li, Jie; Wang, Xiaojing; Yao, Dan; Lu, Na; Jiang, Nan; Wu, Yan

    2016-01-01

    Pulsed electric discharge over water surface/in water has been used to generate reactive species for decomposing the organic compounds in water, and hydrogen peroxide (H2O2) is one of the strong reactive species which can be decomposed into another stronger oxidative species, hydroxyl radical. The production efficacy of H2O2 by a gas phase pulsed discharge over water surface and an underwater bubbling pulsed discharge was evaluated through diagnosis of H2O2 by a chemical probe method. The experimental results show that the yield and the production rate of H2O2 increased with the input energy regardless of the electric discharge patterns, and the underwater bubbling pulsed discharge was more advantageous for H2O2 production considering both the yield and the production rate of H2O2. Results also indicate that the electric discharge patterns also influenced the water solution properties including the conductivity, the pH value and the water temperature.

  12. Pulsed-ultraviolet laser Raman diagnostics of plasma processing discharges

    SciTech Connect

    Hargis P.J. Jr.; Greenberg, K.E.

    1988-11-07

    Spontaneous Raman spectroscopy with pulsed-ultraviolet laser excitation of the Stokes vibrational Raman lines was used to measure the percent dissociation of nitrogen and sulfur hexafluoride in low-pressure radio refrequency discharges of the type used for processing semiconductor materials. Measurements of the percent dissociation of sulfur hexafluoride, at pressures between 200 and 600 mTorr, show a strong pressure dependence which is consistent with recombination playing an important role in sulfur hexafluoride discharge kinetics.

  13. Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Farrokhi, H.; Gruzdev, V.; Zheng, H. Y.; Rawat, R. S.; Zhou, W.

    2016-06-01

    A constant magnetic field can significantly improve the quality and speed of ablation by nanosecond laser pulses. These improvements are usually attributed to the confinement of laser-produced plasma by the magnetic field and specific propagation effects in the magnetized plasma. Here we report a strong influence of constant axial magnetic field on the ablation of silicon by 20-ns laser pulses at wavelength 355 nm, which results in an increase of ablation depth by a factor of 1.3 to 69 depending on laser parameters and magnitude of the magnetic field. The traditional plasma effects do not explain this result, and magneto-absorption of silicon is proposed as one of the major mechanisms of the significant enhancement of ablation.

  14. High voltage pulse ignition of mercury discharge hollow cathodes

    NASA Technical Reports Server (NTRS)

    Wintucky, E. G.

    1973-01-01

    A high voltage pulse generated by a capacitor discharge into a step-up transformer has been demonstrated capable of consistently igniting hollow cathode mercury discharges at propellant flows and heater power levels much below those required by conventional cathode starting. Results are presented for 3.2-mm diameter enclosed and open keeper cathodes. Starting characteristics are shown to depend on keeper voltage, mercury flow rate, heater power, keeper orifice size, emissive materials, and electrode to which the pulse is applied. This starting technique has been used to start a cathode over 10,000 times without any degradation of starting capability.

  15. Simulating the inception of pulsed discharges near positive electrodes

    NASA Astrophysics Data System (ADS)

    Teunissen, Jannis; Ebert, Ute

    2013-09-01

    With 3D particle simulations we study the inception of pulsed discharges near positive electrodes. In different geometries, we first determine the breakdown voltage. Then we study the probability of inception for a fast voltage pulse. This probability mostly depends on the availability of seed electrons to generate the initial electron avalanches. These results are compared with experimental observations. Then we investigate how the shape of a starting discharge affects its further development. In particular, we discuss the formation of so-called ``inception clouds.'' JT was supported by STW-project 10755.

  16. Microsecond-scale electric field pulses in cloud lightning discharges

    NASA Technical Reports Server (NTRS)

    Villanueva, Y.; Rakov, V. A.; Uman, M. A.; Brook, M.

    1994-01-01

    From wideband electric field records acquired using a 12-bit digitizing system with a 500-ns sampling interval, microsecond-scale pulses in different stages of cloud flashes in Florida and New Mexico are analyzed. Pulse occurrence statistics and waveshape characteristics are presented. The larger pulses tend to occur early in the flash, confirming the results of Bils et al. (1988) and in contrast with the three-stage representation of cloud-discharge electric fields suggested by Kitagawa and Brook (1960). Possible explanations for the discrepancy are discussed. The tendency for the larger pulses to occur early in the cloud flash suggests that they are related to the initial in-cloud channel formation processes and contradicts the common view found in the atmospheric radio-noise literature that the main sources of VLF/LF electromagnetic radiation in cloud flashes are the K processes which occur in the final, or J type, part of the cloud discharge.

  17. Efficient Intracellular Delivery of Molecules with High Cell Viability Using Nanosecond-Pulsed Laser-Activated Carbon Nanoparticles

    PubMed Central

    2015-01-01

    Conventional physical and chemical methods that efficiently deliver molecules into cells are often associated with low cell viability. In this study, we evaluated the cellular effects of carbon nanoparticles believed to emit photoacoustic waves due to nanosecond-pulse laser activation to test the hypothesis that this method could achieve efficient intracellular delivery while maintaining high cell viability. Suspensions of DU145 human prostate carcinoma cells, carbon black (CB) nanoparticles, and calcein were exposed to 5–9 ns long laser pulses of near-infrared (1064 nm wavelength) light and then analyzed by flow cytometry for intracellular uptake of calcein and cell viability by propidium iodide staining. We found that intracellular uptake increased and in some cases saturated at high levels with only small losses in cell viability as a result of increasing laser fluence, laser exposure time, and as a unifying parameter, the total laser energy. Changing interpulse spacing between 0.1 and 10 s intervals showed no significant change in bioeffects, suggesting that the effects of each pulse were independent when spaced by at least 0.1 s intervals. Pretreatment of CB nanoparticles to intense laser exposure followed by mixing with cells also had no significant effect on uptake or viability. Similar uptake and viability were seen when CB nanoparticles were substituted with India ink, when DU145 cells were substituted with H9c2 rat cardiomyoblast cells, and when calcein was substituted with FITC-dextran. The best laser exposure conditions tested led to 88% of cells with intracellular uptake and close to 100% viability, indicating that nanosecond-pulse laser-activated carbon nanoparticles can achieve efficient intracellular delivery while maintaining high cell viability. PMID:24547946

  18. Electron beam-switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, L.D.; Murray, J.R.; Goldhar, J.; Bradley, L.P.

    1979-12-11

    A method and apparatus are designed for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  19. Degradation of pentachlorophenol in soil by pulsed corona discharge plasma.

    PubMed

    Wang, Tie Cheng; Lu, Na; Li, Jie; Wu, Yan

    2010-08-15

    The remediation of pentachlorophenol (PCP) contaminated soil using pulsed corona discharge plasma was reported in this study. The effect of practical run parameters such as peak pulse voltage, pulse frequency, gas atmospheres (air, O(2), Ar and N(2)), air flow rate and pollution time on PCP degradation was investigated, and the intermediate products were also studied. The results indicated that PCP degradation efficiency increased with an increase in peak pulse voltage or pulse frequency, due to the enhancement of energy input. There existed a maximal PCP degradation efficiency with the change of air flow rate. PCP degradation efficiencies under oxygen and air atmospheres were achieved 92% and 77% after 45 min of discharge treatment at 14.0 kV, respectively, which were only 19% and 8% under argon and nitrogen atmospheres, respectively. O(3) played an important role in PCP degradation. However, other processes also contributed to PCP degradation, such as N, N(2)(+), N(+) and OH. The pollution time evidenced slight influence on PCP degradation. The main intermediate products produced during the treatment process were identified as tetrachlorocatechol, tetrachlorohydroquinone, acetic acid, formic acid and oxalic acid by HPLC/MS and ion chromatography. This study is expected to provide reference for the application of pulsed corona discharge in soil remediation. PMID:20452725

  20. Identification of the formation phases of filamentary damage induced by nanosecond laser pulses in bulk fused silica

    SciTech Connect

    Shen, Chao; Xu, Zhongjie; Chambonneau, Maxime E-mail: jiangtian198611@163.com; Cheng, Xiang'ai; Jiang, Tian E-mail: jiangtian198611@163.com

    2015-09-14

    Employing a pump-probe polarization-based two-frame shadowgraphy setup, the formation of filamentary damage induced in bulk fused silica by a nanosecond pulse at 1064 nm is investigated with a picosecond probe. Three different phases are exhibited in the damage experiments. The first phase is the formation of a micrometric plasma channel along the laser direction during the beginning of the pulse likely caused by multi-photon ionization. This channel exhibits growth during ∼400 ps, and the newly grown plasma is discrete. Then, during the end of the pulse, this channel evolves into a tadpole-like morphology showing an elliptical head upstream the laser flux followed by a thin tail. This observed asymmetry is attributed to shielding effects caused by both the plasma and hot modified silica. Once the damage shows its almost final morphology, a last phase consists in the launch of a pressure wave enlarging it after the laser pulse. The physical mechanisms that might be involved in the formation of plasma channels are discussed. The experimental data are first confronted to the moving breakdown model which overestimates the filamentary damage length. Finally, taking into account the temporal shape of the laser pulses, the coupling between Kerr-induced self-focusing and stimulated Brillouin scattering is discussed to interpret the observations.

  1. Probing with randomly interleaved pulse train bridges the gap between ultrafast pump-probe and nanosecond flash photolysis.

    PubMed

    Nakagawa, Tatsuo; Okamoto, Kido; Hanada, Hiroaki; Katoh, Ryuzi

    2016-04-01

    Despite the long-standing importance of transient absorption (TA) spectroscopy, many researchers remain frustrated by the difficulty of measuring the nanosecond range in a wide spectral range. To address this shortcoming, we propose a TA spectrophotometer in which there is no synchronization between a pump pulse and a train of multiple probe pulses from a picosecond supercontinuum light source, termed the randomly-interleaved-pulse-train (RIPT) method. For each pump pulse, many monochromatized probe pulses impinge upon the sample, and the associated pump-probe time delays are determined passively shot by shot with subnanosecond accuracy. By repeatedly pumping with automatically varying time delays, a TA temporal profile that covers a wide dynamic range from subnanosecond to milliseconds is simultaneously obtained. By scanning wavelength, this single, simple apparatus acquires not only wide time range TA profiles, but also broadband TA spectra from the visible through the near-infrared regions. Furthermore, we present a typical result to demonstrate how the RIPT method may be used to correct for fluorescence, which often pollutes TA curves. PMID:27192271

  2. Identification of the formation phases of filamentary damage induced by nanosecond laser pulses in bulk fused silica

    NASA Astrophysics Data System (ADS)

    Shen, Chao; Chambonneau, Maxime; Cheng, Xiang'ai; Xu, Zhongjie; Jiang, Tian

    2015-09-01

    Employing a pump-probe polarization-based two-frame shadowgraphy setup, the formation of filamentary damage induced in bulk fused silica by a nanosecond pulse at 1064 nm is investigated with a picosecond probe. Three different phases are exhibited in the damage experiments. The first phase is the formation of a micrometric plasma channel along the laser direction during the beginning of the pulse likely caused by multi-photon ionization. This channel exhibits growth during ˜400 ps, and the newly grown plasma is discrete. Then, during the end of the pulse, this channel evolves into a tadpole-like morphology showing an elliptical head upstream the laser flux followed by a thin tail. This observed asymmetry is attributed to shielding effects caused by both the plasma and hot modified silica. Once the damage shows its almost final morphology, a last phase consists in the launch of a pressure wave enlarging it after the laser pulse. The physical mechanisms that might be involved in the formation of plasma channels are discussed. The experimental data are first confronted to the moving breakdown model which overestimates the filamentary damage length. Finally, taking into account the temporal shape of the laser pulses, the coupling between Kerr-induced self-focusing and stimulated Brillouin scattering is discussed to interpret the observations.

  3. Accumulated destructive effect of nanosecond repetitive voltage pulses on the insulated coatings of Fe-based nanocrystalline ribbon

    SciTech Connect

    Zhang, Yu; Liu, Jinliang

    2013-03-11

    Fe-based nanocrystalline ribbon is widely employed in pulsed power devices and accelerators. A temperature accumulation model is put forward to explain the accumulated destructive effect of discharge plasma bombardment on the TiO{sub 2} coatings of nanocrystalline ribbon under 50 Hz/100 ns voltage pulses. Experimental results revealed that the plasma channel expansion caused by air breakdown in the coating crack heated the coating repetitively, and the coating temperature was increased and accumulated around the crack. The fact that repetitive voltage pulses were more destructive than a single pulse with the same amplitude was caused by the intensified coating ablation under the temperature accumulation effect.

  4. Radiation-induced insulator discharge pulses in the CRRES internal discharge monitor satellite experiment

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.; Mullen, E. G.; Brautigam, D. H.; Kerns, K. J.

    1992-01-01

    The Internal Discharge Monitor (IDM) was designed to observe electrical pulses from common electrical insulators in space service. The sixteen insulator samples included twelve planar printed circuit boards and four cables. The samples were fully enclosed, mutually isolated, and space radiation penetrated 0.02 cm of aluminum before striking the samples. Pulsing began on the seventh orbit, the maximum pulse rate occurred on the seventeenth orbit when 13 pulses occurred, and the pulses slowly diminished to about one per 3 orbits six months later. After 8 months, the radiation belts abruptly increased and the pulse rates attained a new high. These pulse rates were in agreement with laboratory experience on shorter time scales. Several of the samples never pulsed. If the pulses were not confined within IDM, the physical processes could spread to become a full spacecraft anomaly. The IDM results indicate the rate at which small insulator pulses occur. Small pulses are the seeds of larger satellite electrical anomalies. The pulse rates are compared with space radiation intensities, L shell location, and spectral distributions from the radiation spectrometers on the Combined Release and Radiation Effects Satellite.

  5. Plasma discharge self-cleaning filtration system

    DOEpatents

    Cho, Young I.; Fridman, Alexander; Gutsol, Alexander F.; Yang, Yong

    2014-07-22

    The present invention is directed to a novel method for cleaning a filter surface using a plasma discharge self-cleaning filtration system. The method involves utilizing plasma discharges to induce short electric pulses of nanoseconds duration at high voltages. These electrical pulses generate strong Shockwaves that disintegrate and dislodge particulate matter located on the surface of the filter.

  6. Theoretical modeling of pulse discharge cycle in dielectric barrier discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Sato, Shintaro; Ohnishi, Naofumi

    2016-07-01

    Simple models based on two-dimensional simulations are proposed to estimate intervals of periodically observed current pulses with a positive-going voltage in a dielectric barrier discharge plasma actuator. There are two distinct peaks in one streamer discharge; one is related to the formation of an ion cloud and the other is related to a filamentary discharge that is identified as a streamer. Simulation results show that the intervals of the current pulses depend on the slope of the applied voltage. For the ion-cloud formation phase, we model the time evolution of electron number density at the exposed electrode with ionization frequency. For the ion-cloud expansion phase, a positive ion cylinder model is proposed to estimate the electric field generated by surface charge on the dielectric. These models well reproduce the discharge intervals obtained in the numerical simulations.

  7. Pulsed discharge ionization source for miniature ion mobility spectrometers

    DOEpatents

    Xu, Jun; Ramsey, J. Michael; Whitten, William B.

    2004-11-23

    A method and apparatus is disclosed for flowing a sample gas and a reactant gas (38, 43) past a corona discharge electrode (26) situated at a first location in an ion drift chamber (24), applying a pulsed voltage waveform comprising a varying pulse component and a dc bias component to the corona discharge electrode (26) to cause a corona which in turn produces ions from the sample gas and the reactant gas, applying a dc bias to the ion drift chamber (24) to cause the ions to drift to a second location (25) in the ion drift chamber (24), detecting the ions at the second location (25) in the drift chamber (24), and timing the period for the ions to drift from the corona discharge electrode to the selected location in the drift chamber.

  8. Pulse discharge cleaning for open-ended systems

    SciTech Connect

    Garner, H.R.; Aoki, T.

    1986-05-01

    A significant improvement in plasma parameters (ion temperature and electron temperature) has been achieved through the use of pulse discharge cleaning in the mirror machine, RFC-XX-M, in Nagoya, Japan. The essence of this technique is to use pulsed-off-resonance ion cyclotron heating (10-ms duration every 10 s), gas puffing, and electron cyclotron heating preionization in conjunction with baking (to 100 to 150/sup 0/C) in order to prepare the machine surfaces for full-power normal experimental shots. It was also found that RFC-XX-M could operate at nearly full parameters without titanium gettering after discharge cleaning, whereas without discharge cleaning and titanium gettering it is difficult to sustain a plasma.

  9. Electrical properties of pulsed glow discharge Two new aspects

    NASA Astrophysics Data System (ADS)

    Efimova, V. V.; Voronov, M. V.; Hoffmann, V.; Eckert, J.

    2008-07-01

    At the application of pulsed glow discharge (PGD) a transient power of several kW can be reached. This leads to a significant increase of the excitation and ionization efficiency of the sputtered sample atoms. Moreover, with pulsed mode temporally resolved optical emission spectrometry (OES) and mass spectrometry (MS) deliver additional information about the chemical bonds (Harrison 1998, Bengtson et al. 2000, Hang et al. 1996, Klingler et al. 1990, Lewis et al. 2001, Jackson and King 2003). However, the practical application of pulsed glow discharge (PGD) requires an understanding of the processes taking place in the pulsed system. There are some publications, where attention was paid on the voltage current characteristics and the current signal shape of PGD (King and Pan 1993, Lewis et al. 2003). Nevertheless more attention should be paid on the electrical properties of the PGD. In this work the shapes of current, voltage and emission intensity signals, obtained with two different pulse generators are compared. For better understanding of processes, taking place in the discharge the knowledge of the gas temperature is very important. Several authors have mentioned that heating of the cathode leads to changes of the voltage current curve, mainly a decrease of the current at the same voltage. This can be explained by a lower gas density at the same pressure but at higher temperatures (Chenlong et al. 1999, Tian and Chu 2001, Kasik et al. 2002). This phenomenon gives an approach to estimate the gas temperature of the plasma.

  10. Optical emission spectroscopy observations of fast pulsed capillary discharge plasmas

    NASA Astrophysics Data System (ADS)

    Avaria, G.; Ruiz, M.; Guzmán, F.; Favre, M.; Wyndham, E. S.; Chuaqui, H.; Bhuyan, H.

    2014-05-01

    We present time resolved optical emission spectroscopic (OES) observations of a low energy, pulsed capillary discharage (PCD). The optical emission from the capillary plasma and plasma jets emitted from the capillary volume was recorded with with a SpectraPro 275 spectrograph, fitted with a MCP gated OMA system, with 15 ns time resolution. The discharge was operated with different gases, including argon, nitrogen, hydrogen and methane, in a repetitive pulsed discharge mode at 10-50 Hz, with, 10-12 kV pulses applied at the cathode side. The time evolution of the electron density was measured using Stark broadening of the Hβ line. Several features of the capillary plasma dynamics, such as ionization growth, wall effects and plasma jet evolution, are inferred from the time evolution of the optical emission.

  11. Generation of high-power nanosecond pulses from laser diode-pumped Nd:YAG lasers

    NASA Technical Reports Server (NTRS)

    Chan, Kinpui

    1988-01-01

    Simulation results are used to compare the pulse energy levels and pulse energy widths that can be achieved with LD-pumped Nd:YAG lasers for both the pulse-transmission mode (PTM) and pulse-reflection mode (PRM) Q-switching methods for pulse energy levels up to hundreds of microjoules and pulse widths as short as 1 ns. It is shown that high-power pulses with pulse widths as short as 1 ns can be generated with PTM Q-switched in LD-pumped Nd:YAG lasers. With the PRM Q-switching method, pulse widths as short as 2 ns and pulse energy at the level of a few hundred microjoules can also be achieved but require pumping with 8-10-mJ AlGaAs laser diode arrays.

  12. Heat and Momentum Transfer on the Rapid Phase Change of Liquid Induced by Nanosecond-Pulsed Laser Irradiation.

    NASA Astrophysics Data System (ADS)

    Park, Hee Kuwon

    1994-01-01

    This study examines the physics of the liquid -vapor phase transition phenomenon induced by nanosecond -pulsed ultraviolet laser irradiation. This work is concerned with the science and technological applications of the phenomenon of rapid nucleation and explosive vaporization of a liquid in contact with a pulsed-laser heated solid surface. The thermodynamics of the phase transition, the kinetics of collective bubble growth and collapse, and the transient development of pressure field have been investigated experimentally by various fast optical sensing techniques. The purpose of this study is to provide new insight into the physics of the liquid-vapor transition and the interaction between laser and liquid-solid interface. A detailed study on the practical aspects of a novel technological application, the laser cleaning technology, is also included. A model system investigated throughout this work is pure water, methanol, or isopropanol in contact with a solid chromium surface that is heated by ultraviolet KrF excimer laser pulses of nanosecond duration. The dynamics of bubble nucleation, growth, and collapse is studied by optical specular reflectance and scattering probe, which isolates the onset of phase transformation with great accuracy. The thermodynamics of phase transition and metastability of liquid matter have been studied by transient photothermal reflectance probe, which monitors the transient temperature field non-intrusively with nanosecond time resolution. The transient response from the photothermal reflectance probe which utilizes temperature-dependent optical properties of an embedded thin film sensor are coupled with heat transfer modeling results in order to predict the thermodynamic condition for the vaporization in nanosecond time scale. The generation of transient pressure pulses by bubble growth and the effect of static pressure on the phase transition are studied by the piezoelectric transducer probe, photoacoustic probe beam deflection

  13. Experimental investigation of the spectro-temporal dynamics of the light pulses of Q-switched Nd:YAG lasers and nanosecond optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Anstett, G.; Wallenstein, R.

    2004-11-01

    We report an experimental investigation of the spectro-temporal dynamics of the pulse formation in Q-switched Nd:YAG lasers and in nanosecond optical parametric oscillators (OPOs). The temporal evolution of the spectral intensity distribution of the light pulses was measured with a 1-m Czerny Turner spectrometer in combination with a fast streak camera. This detection system allows the analysis of temporal changes in the spectrum of single nanosecond pulses. The measurements were performed for a flashlamp-pumped, Q-switched Nd:YAG laser and for an unseeded as well as for a seeded singly-resonant nanosecond OPO. The laser output spectrum varies strongly from pulse to pulse and even within a single pulse due to mode beating. In an unseeded OPO, individual spectral modes start to oscillate statistically from the parametric noise for pump powers close to the OPO threshold. With increasing pump power a strong modulation in the spectral formation of the pulse is observed, resulting from a strong interaction of parametric conversion and back conversion of signal and idler radiation into pump radiation. By means of injection seeding, the starting condition was controlled for a single mode. Due to the seed radiation, the seeded mode starts sooner than the unseeded modes. These are suppressed completely in the case of sufficient seed power and moderate pump power. The observations are in good agreement with results of corresponding numerical simulations.

  14. Experimental observation of the luminescence flash at the collapse phase of a bubble produced by pulsed discharge in water

    SciTech Connect

    Huang, Yifan; Zhang, Liancheng; Zhu, Xinlei; Liu, Zhen Yan, Keping; Chen, Jim

    2015-11-02

    This letter presents an experimental observation of luminescence flash at the collapse phase of an oscillating bubble produced by a pulsed discharge in water. According to the high speed records, the flash lasts around tens of microseconds, which is much longer than the lifetime of laser and ultrasound induced luminescence flashes in nanoseconds and picoseconds, respectively. The pulse width of temperature waveform and minimum radius calculated at the collapse phase also show that the thermodynamic and dynamic signatures of the bubbles in this work are much larger than those of ultrasound and laser induced bubbles both in time and space scales. However, the peak temperature at the point of collapse is close to the results of ultrasound and laser induced bubbles. This result provides another possibility for accurate emission spectrum measurement other than amplification of the emitted light, such as increasing laser energy or sound energy or substituting water with sulphuric acid.

  15. Experimental observation of the luminescence flash at the collapse phase of a bubble produced by pulsed discharge in water

    NASA Astrophysics Data System (ADS)

    Huang, Yifan; Zhang, Liancheng; Chen, Jim; Zhu, Xinlei; Liu, Zhen; Yan, Keping

    2015-11-01

    This letter presents an experimental observation of luminescence flash at the collapse phase of an oscillating bubble produced by a pulsed discharge in water. According to the high speed records, the flash lasts around tens of microseconds, which is much longer than the lifetime of laser and ultrasound induced luminescence flashes in nanoseconds and picoseconds, respectively. The pulse width of temperature waveform and minimum radius calculated at the collapse phase also show that the thermodynamic and dynamic signatures of the bubbles in this work are much larger than those of ultrasound and laser induced bubbles both in time and space scales. However, the peak temperature at the point of collapse is close to the results of ultrasound and laser induced bubbles. This result provides another possibility for accurate emission spectrum measurement other than amplification of the emitted light, such as increasing laser energy or sound energy or substituting water with sulphuric acid.

  16. Formation of crownlike and related nanostructures on thin supported gold films irradiated by single diffraction-limited nanosecond laser pulses.

    PubMed

    Kulchin, Yu N; Vitrik, O B; Kuchmizhak, A A; Emel'yanov, V I; Ionin, A A; Kudryashov, S I; Makarov, S V

    2014-08-01

    A type of laser-induced surface relief nanostructure-the nanocrown-on thin metallic films was studied both experimentally and theoretically. The nanocrowns, representing a thin corrugated rim of resolidified melt and resembling well-known impact-induced water-crown splashes, were produced by single diffraction-limited nanosecond laser pulses on thin gold films of variable thickness on low-melting copper and high-melting tungsten substrates, providing different transient melting and adhesion conditions for these films. The proposed model of the nanocrown formation, based on a hydrodynamical (thermocapillary Marangoni) surface instability and described by a Kuramoto-Sivashinsky equation, envisions key steps of the nanocrown appearance and gives qualitative predictions of the acquired nanocrown parameters. PMID:25215830

  17. Possibility of applying a hydrodynamic model to describe the laser erosion of metals irradiated by high-intensity nanosecond pulses

    SciTech Connect

    Kozadaev, K V

    2014-04-28

    We report the results of experimental investigations of the production and development of plasma-vapour plumes upon irradiation of metal targets by nanosecond (10–100 ns) pulses with a high (10{sup 8}–10{sup 10} W cm{sup -2}) power density under atmospheric conditions. The transition from a quasi-stationary thermal mechanism of metal erosion to an explosion hydrodynamic one takes place when the radiation power density increases from 10{sup 8} to 10{sup 9} W cm{sup -2}. The resultant experimental information is extremely important for the laser deposition of metal nanostructures under atmospheric conditions, which is possible only for power densities of 10{sup 8}–10{sup 9} W cm{sup -2}. (interaction of laser radiation with matter)

  18. Communication: influence of nanosecond-pulsed electric fields on water and its subsequent relaxation: dipolar effects and debunking memory.

    PubMed

    Avena, Massimiliano; Marracino, Paolo; Liberti, Micaela; Apollonio, Francesca; English, Niall J

    2015-04-14

    Water has many intriguing and anomalous physical properties that have puzzled and titillated the scientific community for centuries, perhaps none more so than the proposition that water may retain some (permanent) "memory" of conditions (e.g., dilution) or electric fields to which it has been subject. Here, we have performed non-equilibrium molecular dynamics simulations of liquid water in external electric-field nanosecond pulses, at 260-310 K, and gauged significant non-thermal field effects in terms of dipolar response. Response of both system- and individual-dipoles has been investigated, and autocorrelation functions of both show more significant effects in stronger fields, with more sluggish relaxation. Crucially, we show that once the field is removed, the dipoles relax, exhibiting no memory or permanent dipolar alignment. We also quantify the time scales for system dynamical-dipolar properties to revert to zero-field equilibrium behaviour. PMID:25877554

  19. Communication: Influence of nanosecond-pulsed electric fields on water and its subsequent relaxation: Dipolar effects and debunking memory

    NASA Astrophysics Data System (ADS)

    Avena, Massimiliano; Marracino, Paolo; Liberti, Micaela; Apollonio, Francesca; English, Niall J.

    2015-04-01

    Water has many intriguing and anomalous physical properties that have puzzled and titillated the scientific community for centuries, perhaps none more so than the proposition that water may retain some (permanent) "memory" of conditions (e.g., dilution) or electric fields to which it has been subject. Here, we have performed non-equilibrium molecular dynamics simulations of liquid water in external electric-field nanosecond pulses, at 260-310 K, and gauged significant non-thermal field effects in terms of dipolar response. Response of both system- and individual-dipoles has been investigated, and autocorrelation functions of both show more significant effects in stronger fields, with more sluggish relaxation. Crucially, we show that once the field is removed, the dipoles relax, exhibiting no memory or permanent dipolar alignment. We also quantify the time scales for system dynamical-dipolar properties to revert to zero-field equilibrium behaviour.

  20. Off-axis quartz-enhanced photoacoustic spectroscopy using a pulsed nanosecond mid-infrared optical parametric oscillator.

    PubMed

    Lassen, Mikael; Lamard, Laurent; Feng, Yuyang; Peremans, Andre; Petersen, Jan C

    2016-09-01

    A trace-gas sensor, based on quartz-enhanced photoacoustic spectroscopy (QEPAS), consisting of two acoustically coupled micro-resonators (mR) with an off-axis 20 kHz quartz tuning fork (QTF) is demonstrated. The complete acoustically coupled mR system is optimized based on finite-element simulations and is experimentally verified. The QEPAS sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared optical parametric oscillator. The sensor is used for spectroscopic measurements on methane in the 3.1-3.5 μm wavelength region with a resolution bandwidth of 1  cm-1 and a detection limit of 0.8 ppm. An Allan deviation analysis shows that the detection limit at the optimum integration time for the QEPAS sensor is 32 ppbv at 190 s, and that the background noise is due solely to the thermal noise of the QTF. PMID:27607987

  1. Single all-fiber-based nanosecond-pulsed supercontinuum source for multispectral photoacoustic microscopy and optical coherence tomography.

    PubMed

    Shu, Xiao; Bondu, Magalie; Dong, Biqin; Podoleanu, Adrian; Leick, Lasse; Zhang, Hao F

    2016-06-15

    We report the usefulness of a single all-fiber-based supercontinuum (SC) source for combined photoacoustic microscopy (PAM) and optical coherence tomography (OCT). The SC light is generated by a tapered photonic crystal fiber pumped by a nanosecond pulsed master oscillator power amplifier at 1064 nm. The spectrum is split into a shorter wavelength band (500-800 nm) for single/multi-spectral PAM and a longer wavelength band (800-900 nm) band for OCT. In vivo mouse ear imaging was achieved with an integrated dual-modality system. We further demonstrated its potential for spectroscopic photoacoustic imaging by doing multispectral measurements on retinal pigment epithelium and blood samples with 15-nm linewidth. PMID:27304278

  2. Energy efficiency in nanoscale synthesis using nanosecond plasmas

    PubMed Central

    Pai, David Z.; (Ken) Ostrikov, Kostya; Kumar, Shailesh; Lacoste, Deanna A.; Levchenko, Igor; Laux, Christophe O.

    2013-01-01

    We report a nanoscale synthesis technique using nanosecond-duration plasma discharges. Voltage pulses 12.5 kV in amplitude and 40 ns in duration were applied repetitively at 30 kHz across molybdenum electrodes in open ambient air, generating a nanosecond spark discharge that synthesized well-defined MoO3 nanoscale architectures (i.e. flakes, dots, walls, porous networks) upon polyamide and copper substrates. No nitrides were formed. The energy cost was as low as 75 eV per atom incorporated into a nanostructure, suggesting a dramatic reduction compared to other techniques using atmospheric pressure plasmas. These findings show that highly efficient synthesis at atmospheric pressure without catalysts or external substrate heating can be achieved in a simple fashion using nanosecond discharges. PMID:23386976

  3. Discharge Characteristics of Series Surface/Packed-Bed Discharge Reactor Diven by Bipolar Pulsed Power

    NASA Astrophysics Data System (ADS)

    Hu, Jian; Jiang, Nan; Li, Jie; Shang, Kefeng; Lu, Na; Wu, Yan; Mizuno, Akira

    2016-03-01

    The discharge characteristics of the series surface/packed-bed discharge (SSPBD) reactor driven by bipolar pulse power were systemically investigated in this study. In order to evaluate the advantages of the SSPBD reactor, it was compared with traditional surface discharge (SD) reactor and packed-bed discharge (PBD) reactor in terms of the discharge voltage, discharge current, and ozone formation. The SSPBD reactor exhibited a faster rising time and lower tail voltage than the SD and PBD reactors. The distribution of the active species generated in different discharge regions of the SSPBD reactor was analyzed by optical emission spectra and ozone analysis. It was found that the packed-bed discharge region (3.5 mg/L), rather than the surface discharge region (1.3 mg/L) in the SSPBD reactor played a more important role in ozone generation. The optical emission spectroscopy analysis indicated that more intense peaks of the active species (e.g. N2 and OI) in the optical emission spectra were observed in the packed-bed region. supported by National Natural Science Foundation of China (No. 51177007), the Joint Funds of National Natural Science Foundation of China (No. U1462105), and Dalian University of Technology Fundamental Research Fund of China (No. DUT15RC(3)030)

  4. Influence of voltage pulse width on the discharge characteristics in an atmospheric dielectric-barrier-discharge plasma jet

    NASA Astrophysics Data System (ADS)

    Uchida, Giichiro; Takenaka, Kosuke; Setsuhara, Yuichi

    2016-01-01

    We present here the analysis of the discharge characteristics of a He dielectric-barrier-discharge (DBD) plasma jet operated in the voltage duty ratio of 20 to 80% under the condition of driving voltage frequency 5 kHz. Discharge strength is sensitive to the voltage pulse width, and the pulse width of 70 µs, which corresponds to the duty ratio of 35%, leads to high O optical emission intensity. We also performed time-resolved optical emission measurements in a transient pulse discharge driven by various voltage duty ratios. Two distinct pulse discharges are observed in the rising and falling periods of the positive rectangular voltage, and the first and second discharges have a peak intensity of optical emission at different duty ratio. The observations indicate that an adequate voltage pulse width could ignite a strong discharge both in the rising and falling period of applied voltage, which could produce a large amount of reactive excited O atoms.

  5. Numerical simulation of compact intracloud discharge and generated electromagnetic pulse

    NASA Astrophysics Data System (ADS)

    Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.

    2015-06-01

    Using the concept of the relativistic runaway electron avalanche, numerical simulation of compact intracloud discharge as a generator of powerful natural electromagnetic pulses (EMPs) in the HF-UHF range was conducted. We evaluated the numbers of electrons initiating the avalanche, with which the calculated EMP characteristics are consistent with measured ones. The discharge capable of generating EMPs produces runaway electrons in numbers close to those in the source of terrestrial γ-flashes (TGF) registered in the nearest space, which may be an argument for a joint EMP and TGF source.

  6. Nanosecond pulsed electric field (nsPEF) enhance cytotoxicity of cisplatin to hepatocellular cells by microdomain disruption on plasma membrane.

    PubMed

    Yin, Shengyong; Chen, Xinhua; Xie, Haiyang; Zhou, Lin; Guo, Danjing; Xu, Yuning; Wu, Liming; Zheng, Shusen

    2016-08-15

    Previous studies showed nanosecond pulsed electric field (nsPEF) can ablate solid tumors including hepatocellular carcinoma (HCC) but its effect on cell membrane is not fully understood. We hypothesized nsPEF disrupt the microdomains on outer-cellular membrane with direct mechanical force and as a result the plasma membrane permeability increases to facilitate the small molecule intake. Three HCC cells were pulsed one pulse per minute, an interval longer than nanopore resealing time. The cationized ferritin was used to mark up the electronegative microdomains, propidium iodide (PI) for membrane permeabilization, energy dispersive X-ray spectroscopy (EDS) for the negative cell surface charge and cisplatin for inner-cellular cytotoxicity. We demonstrated that the ferritin marked-microdomain and negative cell surface charge were disrupted by nsPEF caused-mechanical force. The cell uptake of propidium and cytotoxicity of DNA-targeted cisplatin increased with a dose effect. Cisplatin gains its maximum inner-cellular cytotoxicity when combining with nsPEF stimulation. We conclude that nsPEF disrupt the microdomains on the outer cellular membrane directly and increase the membrane permeabilization for PI and cisplatin. The microdomain disruption and membrane infiltration changes are caused by the mechanical force from the changes of negative cell surface charge. PMID:27375200

  7. Nanosecond time-resolved microscopic spectroscopy for diagnostics of an atmospheric-pressure discharge plasma formed in aqueous solution

    NASA Astrophysics Data System (ADS)

    Banno, Motohiro; Kanno, Kenta; Someya, Yuu; Yui, Hiroharu

    2015-06-01

    Glow discharge plasma formed in solution under atmospheric pressure has been expected to provide reaction fields with characteristic physical and chemical properties owing to the frequent collisions and reactions of reactive particles inside and the rapid quenching of the products by the surrounding cold solutions. In particular, when an aqueous solution is utilized as the surrounding solution, the atmospheric-pressure in-solution glow (ASG) plasma contains hydrogen and hydroxyl radicals showing large activities for reduction and oxidation, respectively. In addition, because the ASG plasma is formed under atmospheric pressure, the collision frequencies between the particles contained in the plasma are higher than those in other plasmas ordinarily formed under low pressure. This feature should result in rapid energy redistribution among particles contained in the plasma. In the present study, time-resolved optical emission spectroscopy with nanosecond time resolution was applied for the diagnostics of the ASG plasma with chemical species selectivity. The time-resolved measurements revealed that the temporal evolutions of the temperatures of blackbody, hydrogen radical, and hydroxyl radical contained in the ASG plasma consist of two stages: initial rise within 0.15 µs (rising stage) and fluctuation around certain values for about 1 µs (fluctuating stage). In the time region corresponding to the rising stage, the electron number density is about ten times larger than the value temporally averaged during the plasma emission. The initial rise should result from frequent collisions between charged particles accelerated by the applied voltage and unexcited particles. In the fluctuating stage, the electron number density strongly correlates with the increase in the radical temperatures. It is concluded that the electron number density, rather than the electron temperature, is a key parameter determining the temperatures of reactive species in the ASG plasma.

  8. Oxidation of aqueous pharmaceuticals by pulsed corona discharge.

    PubMed

    Panorel, Iris; Preis, Sergei; Kornev, Iakov; Hatakka, Henry; Louhi-Kultanen, Marjatta

    2013-01-01

    Oxidation of aromatic compounds of phenolic (paracetamol, beta-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction. PMID:23837343

  9. Effects of ion and nanosecond-pulsed laser co-irradiation on the surface nanostructure of Au thin films on SiO{sub 2} glass substrates

    SciTech Connect

    Yu, Ruixuan; Meng, Xuan; Takayanagi, Shinya; Shibayama, Tamaki Yatsu, Shigeo; Ishioka, Junya; Watanabe, Seiichi

    2014-04-14

    Ion irradiation and short-pulsed laser irradiation can be used to form nanostructures on the surfaces of substrates. This work investigates the synergistic effects of ion and nanosecond-pulsed laser co-irradiation on surface nanostructuring of Au thin films deposited under vacuum on SiO{sub 2} glass substrates. Gold nanoparticles are randomly formed on the surface of the substrate after nanosecond-pulsed laser irradiation under vacuum at a wavelength of 532 nm with a repetition rate of 10 Hz and laser energy density of 0.124 kJ/m{sup 2}. Gold nanoparticles are also randomly formed on the substrate after 100-keV Ar{sup +} ion irradiation at doses of up to 3.8 × 10{sup 15} ions/cm{sup 2}, and nearly all of these nanoparticles are fully embedded in the substrate. With increasing ion irradiation dose (number of incident laser pulses), the mean diameter of the Au nanoparticles decreases (increases). However, Au nanoparticles are only formed in a periodic surface arrangement after co-irradiation with 6000 laser pulses and 3.8 × 10{sup 15} ions/cm{sup 2}. The periodic distance is ∼540 nm, which is close to the wavelength of the nanosecond-pulsed laser, and the mean diameter of the Au nanoparticles remains at ∼20 nm with a relatively narrow distribution. The photoabsorption peaks of the ion- or nanosecond-pulsed laser-irradiated samples clearly correspond to the mean diameter of Au nanoparticles. Conversely, the photoabsorption peaks for the co-irradiated samples do not depend on the mean nanoparticle diameter. This lack of dependence is likely caused by the periodic nanostructure formed on the surface by the synergistic effects of co-irradiation.

  10. Thresholds for Phosphatidylserine Externalization in Chinese Hamster Ovarian Cells following Exposure to Nanosecond Pulsed Electrical Fields (nsPEF)

    PubMed Central

    Vincelette, Rebecca L.; Roth, Caleb C.; McConnell, Maureen P.; Payne, Jason A.; Beier, Hope T.; Ibey, Bennett L.

    2013-01-01

    High-amplitude, MV/m, nanosecond pulsed electric fields (nsPEF) have been hypothesized to cause nanoporation of the plasma membrane. Phosphatidylserine (PS) externalization has been observed on the outer leaflet of the membrane shortly after nsPEF exposure, suggesting local structural changes in the membrane. In this study, we utilized fluorescently-tagged Annexin V to observe the externalization of PS on the plasma membrane of isolated Chinese Hamster Ovary (CHO) cells following exposure to nsPEF. A series of experiments were performed to determine the dosimetric trends of PS expression caused by nsPEF as a function of pulse duration, τ, delivered field strength, ED, and pulse number, n. To accurately estimate dose thresholds for cellular response, data were reduced to a set of binary responses and ED50s were estimated using Probit analysis. Probit analysis results revealed that PS externalization followed the non-linear trend of (τ*ED2)−1 for high amplitudes, but failed to predict low amplitude responses. A second set of experiments was performed to determine the nsPEF parameters necessary to cause observable calcium uptake, using cells preloaded with calcium green (CaGr), and membrane permeability, using FM1-43 dye. Calcium influx and FM1-43 uptake were found to always be observed at lower nsPEF exposure parameters compared to PS externalization. These findings suggest that multiple, higher amplitude and longer pulse exposures may generate pores of larger diameter enabling lateral diffusion of PS; whereas, smaller pores induced by fewer, lower amplitude and short pulse width exposures may only allow extracellular calcium and FM1-43 uptake. PMID:23658665

  11. Thresholds for phosphatidylserine externalization in Chinese hamster ovarian cells following exposure to nanosecond pulsed electrical fields (nsPEF).

    PubMed

    Vincelette, Rebecca L; Roth, Caleb C; McConnell, Maureen P; Payne, Jason A; Beier, Hope T; Ibey, Bennett L

    2013-01-01

    High-amplitude, MV/m, nanosecond pulsed electric fields (nsPEF) have been hypothesized to cause nanoporation of the plasma membrane. Phosphatidylserine (PS) externalization has been observed on the outer leaflet of the membrane shortly after nsPEF exposure, suggesting local structural changes in the membrane. In this study, we utilized fluorescently-tagged Annexin V to observe the externalization of PS on the plasma membrane of isolated Chinese Hamster Ovary (CHO) cells following exposure to nsPEF. A series of experiments were performed to determine the dosimetric trends of PS expression caused by nsPEF as a function of pulse duration, τ, delivered field strength, ED, and pulse number, n. To accurately estimate dose thresholds for cellular response, data were reduced to a set of binary responses and ED50s were estimated using Probit analysis. Probit analysis results revealed that PS externalization followed the non-linear trend of (τ*ED (2))(-1) for high amplitudes, but failed to predict low amplitude responses. A second set of experiments was performed to determine the nsPEF parameters necessary to cause observable calcium uptake, using cells preloaded with calcium green (CaGr), and membrane permeability, using FM1-43 dye. Calcium influx and FM1-43 uptake were found to always be observed at lower nsPEF exposure parameters compared to PS externalization. These findings suggest that multiple, higher amplitude and longer pulse exposures may generate pores of larger diameter enabling lateral diffusion of PS; whereas, smaller pores induced by fewer, lower amplitude and short pulse width exposures may only allow extracellular calcium and FM1-43 uptake. PMID:23658665

  12. Selective removal of carious human dentin using a nanosecond pulsed laser operating at a wavelength of 5.85 μ m

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-05-01

    Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm. The present study investigated the irradiation effect of the light on carious human dentin classified into "remove," "not remove," and "unclear" categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm2 and irradiation time of 2 s, the ablation depth of "remove" and "not remove," and also the ablation depth of "unclear" and "not remove," were significantly different (p<0.01). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85 μm proved an effective less-invasive caries treatment.

  13. Sub-nanosecond ranging possibilities of optical radar at various signal levels and transmitted pulse widths

    NASA Technical Reports Server (NTRS)

    Poultney, S. K.

    1971-01-01

    The behavior of the photomultiplier is considered, as well as the method of derivation of the photomultiplier output pulse and its relation to the reflected light pulse width and amplitude, and the calibration of range precision and accuracy. Pulsed laser radars with light pulse widths of 30, 3, and 0.1 nanosec a considered, with the 0.1 nanosec system capable of highest precision in several modes of operation, including a high repetition rate, single photoelectron reception mode. An alternate calibration scheme using a fast, triggerable light pulser is described in detail.

  14. Pulsed corona discharge at atmospheric and supercritical conditions

    NASA Astrophysics Data System (ADS)

    Lock, Evgeniya Hristova

    Pulsed corona discharge is one of the non-equilibrium plasma techniques, by which electrical power is mainly utilized to generate high-energy electrons. These react further with the background gas to produce radicals, which can be further employed in chemically selective reactions. Study of the initiation of pulsed corona discharge in carbon dioxide and air was conducted. Furthermore due to its high removal efficiency, energy yields and good economy, the pulsed corona discharge was employed for removal of methanol and dimethyl sulfide. These compounds are part of the volatile organic compounds (VOC) air pollutants, which are subject of severe environmental regulations due to their toxicity, environmental persistence and intensity of smell. The study provides experimental data for the destruction of methanol and dimethyl sulfide from dry and humid air streams. The effects of the process parameters, including applied voltage, pulse repetition rate, initial concentration of pollutants, temperature and humidity on the destruction and removal efficiency and energy cost are analyzed. Specific consideration is given to the formation of unwanted byproducts. The study on plasma application for pollution control showed that small amounts of dispersed liquid droplets increase the efficiency of the chemical utilization of the high-energy electrons and reduce the required power. So media that could facilitate homogeneous and heterogeneous chemistry at the same time would enhance the efficiency of the removal process. Such medium that has properties intermediate between the gas and liquid phase is the supercritical fluid. Generation of plasma in supercritical fluids is an unexplored area in plasma science. The generation of plasma at elevated pressures usually requires high voltages or small interelectrode distances. The supercritical phase is characterized by extensive cluster formation in the vicinity of the critical point. Typically the clusters have lower ionization

  15. Numerical Study of Control of Flow Separation Over a Ramp with Nanosecond Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Khoo, B. C.; Cui, Y. D.; Zhao, Z. J.; Li, J.

    2016-06-01

    The nanosecond plasma discharge actuator driven by high voltage pulse with typical rise and decay time of several to tens of nanoseconds is emerging as a promising active flow control means in recent years and is being studied intensively. The characterization study reveals that the discharge induced shock wave propagates through ambient air and introduces highly transient perturbation to the flow. On the other hand, the residual heat remaining in the discharge volume may trigger the instability of external flow. In this study, this type of actuator is used to suppress flow separation over a ramp model. Numerical simulation is carried out to investigate the interaction of the discharge induced disturbance with the external flow. It is found that the flow separation region over the ramp can be reduced significantly. Our work may provide some insights into the understanding of the control mechanism of nanosecond pulse actuator.

  16. Excimer emission from pulsed microhollow cathode discharges in xenon

    SciTech Connect

    Lee, B.-J.; Nam, S. H.; Rahaman, H.; Iberler, M.; Jacoby, J.; Frank, K.

    2013-12-15

    Direct current (dc) microhollow cathode discharge (MHCD) is an intense source for excimer radiation in vacuum ultraviolet at a wavelength of 172 nm in a high pressure xenon (Xe) gas. The concentration of precursors for the excimer formation, i.e., excited and ionized gas atoms, increases significantly by applying high voltage pulse onto the dc MHCD over the pulse duration range from 20 to 100 ns. The intensity of the excimer emission for the voltage pulse of 20 ns duration exceeds that of the emission intensity obtained from the same MHCD operated only in the dc mode, by one order of magnitude. In addition, the emission intensity increases by one order of magnitude over the pulse duration range from 20 to 100 ns. It can be assumed that the emission intensity of the MHCD source increases as long as the duration of the high voltage pulse is shorter than the electron relaxation time. For the high voltage pulse of 100 ns duration, the emission intensity has been found to be further enhanced by a factor of three when the gas pressure is increased from 200 to 800 mbar.

  17. The physics of pulsed streamer discharge in high pressure air and applications to engine techonologies

    NASA Astrophysics Data System (ADS)

    Lin, Yung-Hsu

    The goal of this dissertation is to study high pressure streamers in air and apply it to diesel engine technologies. Nanosecond scale pulsed high voltage discharges in air/fuel mixtures can generate radicals which in turn have been shown to improve combustion efficiency in gasoline fueled internal combustion engines. We are exploring the possibility to extend such transient plasma generation and expected radical species generation to the range of pressures encountered in compression-ignition (diesel) engines having compression ratios of ˜20:1, thereby improving lean burning efficiency and extending the range of lean combustion. At the beginning of this dissertation, research into streamer discharges is reviewed. Then, we conducted experiments of streamer propagation at high pressures, calculated the streamer velocity based on both optical and electrical measurements, and the similarity law was checked by analyzing the streamer velocity as a function of the reduced electric field, E/P. Our results showed that the similarity law is invalid, and an empirical scaling factor, E/√P, is obtained and verified by dimensional analysis. The equation derived from the dimensional analysis will be beneficial to proper electrode and pulse generator design for transient plasma assisted internal engine experiments. Along with the high pressure study, we applied such technique on diesel engine to improve the fuel efficiency and exhaust treatment. We observed a small effect of transient plasma on peak pressure, which implied that transient plasma has the capability to improve the fuel consumption. In addition, the NO can be reduced effectively by the same technique and the energy cost is 30 eV per NO molecule.

  18. Averaging of Replicated Pulses for Enhanced-Dynamic-Range Single-Shot Measurement of Nanosecond Optical Pulses

    SciTech Connect

    Marciante, J.R.; Donaldson, W.R.; Roides, R.G.

    2007-10-04

    Measuring optical pulse shapes beyond the dynamic range of oscilloscopes is achieved by temporal pulse stacking in a low-loss, passive, fiber-optic network. Optical pulses are averaged with their time-delayed replicas without introducing additional noise or jitter, allowing for high-contrast pulse-shape measurements of single-shot events. A dynamic-range enhancement of three bits is experimentally demonstrated and compared with conventional multi-shot averaging. This technique can be extended to yield an increase of up to seven bits of additional dynamic range over nominal oscilloscope performance.

  19. Numerical investigation of heating of a gold nanoparticle and the surrounding microenvironment by nanosecond laser pulses for nanomedicine applications.

    PubMed

    Sassaroli, E; Li, K C P; O'Neill, B E

    2009-09-21

    We have modeled, by finite element analysis, the process of heating of a spherical gold nanoparticle by nanosecond laser pulses and of heat transfer between the particle and the surrounding medium, with no mass transfer. In our analysis, we have included thermal conductivity changes, vapor formation, and changes of the dielectric properties as a function of temperature. We have shown that such changes significantly affect the temperature reached by the particle and surrounding microenvironment and therefore the thermal and dielectric properties of the medium need to be known for a correct determination of the temperature elevation. We have shown that for sufficiently low intensity and long pulses, it is possible to establish a quasi-steady temperature profile in the medium with no vapor formation. As the intensity is increased, a phase-change with vapor formation takes place around the gold nanoparticle. As phase-transition starts, an additional increase in the intensity does not significantly increase the temperature of the gold nanoparticle and surrounding environment. The temperature starts to rise again above a given intensity threshold which is particle and environment dependent. The aim of this study is to provide useful insights for the development of molecular targeting of gold nanoparticles for applications such as remote drug release of therapeutics and photothermal cancer therapy. PMID:19717888

  20. Comparison of the ablation behavior of polymer films in the IR and UV with nanosecond and picosecond pulses

    SciTech Connect

    Hahn, C.; Lippert, T.; Wokaun, A.

    1999-02-25

    Experiments are performed to compare the ablation behavior in the IR and UV spectral regions of a doped standard polymer, PMMA, and a specially tailored photopolymer, i.e., a triazene copolyester, to elucidate the underlying mechanisms. The results are discussed in light of current theories about photochemical and photothermal pathways of ablation. Further experiments are performed with nanosecond and picosecond pulses to study the impact of pulse length on the material. From the failure to induce ablation in the IR by doping the specialty polymer with an optical molecular heater the authors conclude that etching in the UV of this compound is mainly governed by a photochemical process. This result is contrasted by successful ablation of doped PMMA in the IR via a thermal unzipping mechanism. With respect to practical applications, the results show convincingly that the presence of an absorbing chromophore in the polymer is a prerequisite for achieving high-resolution structuring, since molecular absorption is required for an efficient distribution of incorporated photonic energy.

  1. Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

    SciTech Connect

    Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; Moody, Neville R.

    2015-11-14

    Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protective thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.

  2. Non-contact acoustic tests based on nanosecond laser ablation: Generation of a pulse sound source with a small amplitude

    NASA Astrophysics Data System (ADS)

    Hosoya, Naoki; Kajiwara, Itsuro; Inoue, Tatsuo; Umenai, Koh

    2014-09-01

    A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 1012-1014 W/m2, which is less than that for laser-induced breakdown (1015 W/m2), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam-irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube.

  3. The CRRES IDM spacecraft experiment for insulator discharge pulses. [Internal Discharge Monitor

    NASA Technical Reports Server (NTRS)

    Frederickson, A. R.; Mullen, E. G.; Kerns, K. J.; Robinson, P. A.; Holeman, E. G.

    1993-01-01

    The Internal Discharge Monitor (IDM) is designed to observe electrical pulses from common electrical insulators in space service. The characteristics of the instrument are described. The IDM was flown on the Combined Release and Radiation Effects Satellite (CRRES). The sixteen insulator samples included G10 circuit boards, FR4 and PTFE fiberglass circuit boards, FEP Teflon, alumina, and wires with common insulations. The samples are fully enclosed, mutually isolated, and space radiation penetrates 0.02 cm of aluminum before striking the samples. Published data in the literature provides a simple method for determining the flux of penetrating electrons. The pulse rate is compared to the penetrating flux of electrons.

  4. Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    SciTech Connect

    Kononenko, Taras V; Konov, Vitalii I; Garnov, Sergei V; Danielius, R; Piskarskas, A; Tamosauskas, G; Dausinger, F

    1999-08-31

    A series of studies was carried out on the ablation of steel, Si{sub 3}N{sub 4} ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 - 10{sup 3} J cm{sup -2}). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed. (interaction of laser radiation with matter. laser plasma)

  5. Application of a nanosecond laser pulse to evaluate dynamic hardness under ultra-high strain rate

    NASA Astrophysics Data System (ADS)

    Radziejewska, Joanna

    2016-04-01

    The paper presents results of experimental tests of plastic metals deformation generated by a shock wave induced by laser pulse. Tests were carried out on the Nd:YAG laser with a wavelength of 1064 nm and the laser pulse of 10 ns duration. The shock wave generate by the laser pulse was used to induced local plastic deformation of the material surface. The study examined the possibility of application the process to develop a new method of measuring the dynamic hardness of materials under ultra-high strain rate. It has been shown that the shock wave induced by the laser pulse with an energy of 0.35-1.22 J causes a repeatable plastic deformation of surface of commercially available metals and alloys without thermal effects on the surfaces. Based on the knowledge of an imprint geometry, it is possible to evaluate the dynamic hardness of materials at strain rate in the range of 107 s-1.

  6. Measurement and simulation of Joule heating during treatment of B-16 melanoma tumors in mice with nanosecond pulsed electric fields.

    PubMed

    Pliquett, Uwe; Nuccitelli, Richard

    2014-12-01

    Experimental evidence shows that nanosecond pulsed electric fields (nsPEF) trigger apoptosis in skin tumors. We have postulated that the energy delivered by nsPEF is insufficient to impart significant heating to the treated tissue. Here we use both direct measurements and theoretical modeling of the Joule heating in order to validate this assumption. For the temperature measurement, thermo-sensitive liquid crystals (TLC) were used to determine the surface temperature while a micro-thermocouple (made from 30 μm wires) was used for measuring the temperature inside the tissue. The calculation of the temperature distribution used an asymptotic approach with the repeated calculation of the electric field, Joule heating and heat transfer, and the subsequent readjustment of the electrical tissue conductivity. This yields a temperature distribution both in space and time. It can be shown that for the measured increase in temperature an unexpectedly high electrical conductivity of the tissue would be required, which was indeed found by using voltage and current monitoring during the experiment. Using impedance measurements within t(after)=50 μs after the pulse revealed a fast decline of the high conductivity state when the electric field ceases. The experimentally measured high conductance of a skin fold (mouse) between plate electrodes was about 5 times higher than those of the maximally expected conductance due to fully electroporated membrane structures (G(max)/G(electroporated))≈5. Fully electroporated membrane structure assumes that 100% of the membranes are conductive which is estimated from an impedance measurement at 10 MHz where membranes are capacitively shorted. Since the temperature rise in B-16 mouse melanoma tumors due to equally spaced (Δt=2 s) 300 ns-pulses with E=40 kV/cm usually does not exceed ΔΤ=3 K at all parts of the skin fold between the electrodes, a hyperthermic effect on the tissue can be excluded. PMID:24680133

  7. Formation of plasma channels in the interaction of a nanosecond laser pulse at moderate intensities with helium gas jets.

    PubMed

    De Wispelaere, E; Malka, V; Hüller, S; Amiranoff, F; Baton, S; Bonadio, R; Casanova, M; Dorchies, F; Haroutunian, R; Modena, A

    1999-06-01

    We report on a detailed study of channel formation in the interaction of a nanosecond laser pulse with a He gas jet. A complete set of diagnostics is used in order to characterize the plasma precisely. The evolution of the plasma radius and of the electron density and temperature are measured by Thomson scattering, Schlieren imaging, and Mach-Zehnder interferometry. In gas jets, one observes the formation of a channel with a deep density depletion on axis. Because of ionization-induced defocusing which increases the size of the focal spot and decreases the maximum laser intensity, no channel is observed in the case of a gas-filled chamber. The results obtained in various gas-jet and laser conditions show that the channel radius, as well as the density along the propagation axis, can be adjusted by changing the laser energy and gas-jet pressure. This is a crucial issue when one wants to adapt the channel parameters in order to guide a subsequent high-intensity laser pulse. The experimental results and their comparison with one-dimensional (1D) and two-dimensional hydrodynamic simulations show that the main mechanism for channel formation is the hydrodynamic evolution behind a supersonic electron heat wave propagating radially in the plasma. It is also shown from 2D simulations that a fraction of the long pulse can be self-guided in the channel it creates. The preliminary results and analyses on this subject have been published before [V. Malka et al., Phys. Rev. Lett. 79, 2979 (1997)]. PMID:11969699

  8. Impact of external medium conductivity on cell membrane electropermeabilization by microsecond and nanosecond electric pulses

    PubMed Central

    Silve, Aude; Leray, Isabelle; Poignard, Clair; Mir, Lluis M.

    2016-01-01

    The impact of external medium conductivity on the efficiency of the reversible permeabilisation caused by pulsed electric fields was investigated. Pulses of 12 ns, 102 ns or 100 μs were investigated. Whenever permeabilisation could be detected after the delivery of one single pulse, media of lower conductivity induced more efficient reversible permeabilisation and thus independently of the medium composition. Effect of medium conductivity can however be hidden by some saturation effects, for example when pulses are cumulated (use of trains of 8 pulses) or when the detection method is not sensitive enough. This explains the contradicting results that can be found in the literature. The new data are complementary to those of one of our previous study in which an opposite effect of the conductivity was highlighted. It stresses that the conductivity of the medium influences the reversible permeabilization by several ways. Moreover, these results clearly indicate that electropermeabilisation does not linearly depend on the energy delivered to the cells. PMID:26829153

  9. Development of a compact generator for gigawatt, nanosecond high-voltage pulses.

    PubMed

    Zhou, Lin; Jiang, Zhanxing; Liang, Chuan; Li, Mingjia; Wang, Wenchuan; Li, Zhenghong

    2016-03-01

    A compact generator producing 2.2-ns 1.5 GW high-voltage pulses was developed. The generator employed a 27.6 Ω, 0.9 ns pulse-forming-line (PFL), which was charged by an iron core transformer with a turn ratio of 2:33.5 and a coefficient of 0.94. A 1.2 μF, 20 kV capacitor and a hydrogen thyratron were used in the primary circuit. When the thyratron closed at 14.5 kV, 3.4% of the energy stored in the capacitor was delivered to the PFL in 850 ns, producing a peak voltage of up to ∼500 kV. In addition, the principle of triple resonance transformation was employed by adding a 50 pF tuning capacitor and a 1.15 mH inductor between the transformer and the PFL, which led to a significant reduction of the duration and peak value of the transformer voltage without reducing that in the PFL. Meanwhile, an adjustable self-break oil switch was applied. By using transmission lines with impedance overmatched to that of the PFL, the generator delivered a 512 kV pulse across an electron beam diode, generating radiation with a dose of 20 mR/pulse at 20 cm ahead of the diode. The generator provides an excellent ultra-short radiation pulse source for the studies on radiation physics. PMID:27036805

  10. Propagation of the pulsed electron beam of nanosecond duration in gas composition of high pressure

    NASA Astrophysics Data System (ADS)

    Kholodnaya, G.; Sazonov, R.; Ponomarev, D.; Remnev, G.

    2015-11-01

    This paper presents the results of the investigation of the propagation of an electron beam in the high-pressure gas compositions (50, 300, and 760 Torr): sulfur hexafluoride and hydrogen, sulfur hexafluoride and nitrogen, sulfur hexafluoride and argon. The experiments have been performed using the TEA-500 laboratory accelerator. The main parameters of the accelerator are as follows: an accelerating voltage of 500 kV; an electron beam current of 10 kA; a pulse width at half maximum of 60 ns; a pulse energy of 200 J; a pulse repetition rate of up to 5 pulses per second, a beam diameter of 5 cm. The pulsed electron beam was injected into a 55 cm metal drift tube. The drift tube is equipped with three reverse-current shunts with simultaneous detecting of signals. The obtained results of the investigation make it possible to conclude that the picture of the processes occurring in the interaction of an electron beam in the high-pressure gas compositions is different from that observed in the propagation of the electron beam in the low-pressure gas compositions (1 Torr).

  11. Heating and ablation of tokamak graphite by pulsed nanosecond Nd-YAG lasers

    SciTech Connect

    Semerok, A.; Fomichev, S. V.; Weulersse, J.-M.; Brygo, F.; Thro, P.-Y.; Grisolia, C.

    2007-04-15

    The results on laser heating and ablation of graphite tiles of thermonuclear tokamaks are presented. Two pulsed Nd-YAG lasers (20 Hz repetition rate, 5 ns pulse duration and 10 kHz repetition rate, 100 ns pulse duration) were applied for ablation measurements. The ablation thresholds (1.0{+-}0.5 J/cm{sup 2} for 5 ns and 2.5{+-}0.5 J/cm{sup 2} for 100 ns laser pulses) were determined for the Tore Supra tokamak graphite tiles (backside) nonexposed to plasma. The high repetition rate Nd-YAG laser (10 kHz, 100 ns pulse duration) and the developed pyrometer system were applied for graphite heating measurements. Some unexpected features of laser heating of the graphite surface were observed. They were explained by the presence of a thin surface layer with the properties different from those of the bulk graphite. The theoretical models of laser heating and near-threshold ablation of graphite with imperfectly adhered layer were developed to interpret the experimental results.

  12. Development of a compact generator for gigawatt, nanosecond high-voltage pulses

    NASA Astrophysics Data System (ADS)

    Zhou, Lin; Jiang, Zhanxing; Liang, Chuan; Li, Mingjia; Wang, Wenchuan; Li, Zhenghong

    2016-03-01

    A compact generator producing 2.2-ns 1.5 GW high-voltage pulses was developed. The generator employed a 27.6 Ω, 0.9 ns pulse-forming-line (PFL), which was charged by an iron core transformer with a turn ratio of 2:33.5 and a coefficient of 0.94. A 1.2 μF, 20 kV capacitor and a hydrogen thyratron were used in the primary circuit. When the thyratron closed at 14.5 kV, 3.4% of the energy stored in the capacitor was delivered to the PFL in 850 ns, producing a peak voltage of up to ˜500 kV. In addition, the principle of triple resonance transformation was employed by adding a 50 pF tuning capacitor and a 1.15 mH inductor between the transformer and the PFL, which led to a significant reduction of the duration and peak value of the transformer voltage without reducing that in the PFL. Meanwhile, an adjustable self-break oil switch was applied. By using transmission lines with impedance overmatched to that of the PFL, the generator delivered a 512 kV pulse across an electron beam diode, generating radiation with a dose of 20 mR/pulse at 20 cm ahead of the diode. The generator provides an excellent ultra-short radiation pulse source for the studies on radiation physics.

  13. Convoluted effect of laser fluence and pulse duration on the property of a nanosecond laser-induced plasma into an argon ambient gas at the atmospheric pressure

    SciTech Connect

    Bai Xueshi; Ma Qianli; Motto-Ros, Vincent; Yu Jin; Sabourdy, David; Nguyen, Luc; Jalocha, Alain

    2013-01-07

    We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between laser fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high fluence of about 160 J/cm{sup 2} where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower fluence of about 65 J/cm{sup 2}, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-ablation interaction between the generated plume and the tailing part of the laser pulse. We demonstrate that the ionization of the layer of ambient gas surrounding the ablation vapor plays an important role in plasma shielding. Such ionization is the consequence of laser-supported absorption wave and directly dependent on the laser fluence and the pulse duration. Further observations of the structure of the generated plume in its early stage of expansion support our explanations.

  14. Inertial electrostatic confinement and nuclear fusion in the interelectrode plasma of a nanosecond vacuum discharge. I: Experiment

    NASA Astrophysics Data System (ADS)

    Kurilenkov, Yu. K.; Skowronek, M.

    2010-12-01

    Properties of an aerosol substance with a high power density in the interelectrode space of a nano- second vacuum discharge are studied. The possibilities of emission and/or trapping of fast ions and hard X-rays by ensembles of clusters and microparticles are analyzed. The possibility of simultaneous partial trapping (diffusion) of X-rays and complete trapping of fast ions by a cluster ensemble is demonstrated experimentally. Due to such trapping, the aerosol ensemble transforms into a "dusty" microreactor that can be used to investigate a certain class of nuclear processes, including collisional DD microfusion. Operating regimes of such a microreactor and their reproducibility were studied. On the whole, the generation efficiency of hard X-rays and neutrons in the proposed vacuum discharge with a hollow cathode can be higher by two orders of magnitude than that in a system "high-power laser pulse-cluster cloud." Multiply repeated nuclear fusion accompanied by pulsating DD neutron emission was reproducibly detected in experiment. Ion acceleration mechanisms in the interelectrode space and the fundamental role of the virtual cathode in observed nuclear fusion processes are discussed.

  15. Inertial electrostatic confinement and nuclear fusion in the interelectrode plasma of a nanosecond vacuum discharge. I: Experiment

    SciTech Connect

    Kurilenkov, Yu. K.; Skowronek, M.

    2010-12-15

    Properties of an aerosol substance with a high power density in the interelectrode space of a nano- second vacuum discharge are studied. The possibilities of emission and/or trapping of fast ions and hard X-rays by ensembles of clusters and microparticles are analyzed. The possibility of simultaneous partial trapping (diffusion) of X-rays and complete trapping of fast ions by a cluster ensemble is demonstrated experimentally. Due to such trapping, the aerosol ensemble transforms into a 'dusty' microreactor that can be used to investigate a certain class of nuclear processes, including collisional DD microfusion. Operating regimes of such a microreactor and their reproducibility were studied. On the whole, the generation efficiency of hard X-rays and neutrons in the proposed vacuum discharge with a hollow cathode can be higher by two orders of magnitude than that in a system 'high-power laser pulse-cluster cloud.' Multiply repeated nuclear fusion accompanied by pulsating DD neutron emission was reproducibly detected in experiment. Ion acceleration mechanisms in the interelectrode space and the fundamental role of the virtual cathode in observed nuclear fusion processes are discussed.

  16. Autonomous portable pulsed-periodical generator of high-power radiofrequency-pulses based on gas discharge with hollow cathode

    NASA Astrophysics Data System (ADS)

    Bulychev, Sergey V.; Dubinov, Alexander E.; L'vov, Igor L.; Popolev, Vyacheslav L.; Sadovoy, Sergey A.; Sadchikov, Eugeny A.; Selemir, Victor D.; Valiulina, Valeria K.; Vyalykh, Dmitry V.; Zhdanov, Victor S.

    2016-05-01

    Portable autonomous generator of high-power RF-pulses based on the gas discharge with hollow cathode has been designed, fabricated, and tested. Input and output characteristics are the following: discharge current amplitude is 800 A, duration of generated RF-pulses is 350 ns, carrier frequency is ˜90 MHz, power in RF-pulse is 0.5 MW, pulse repetition rate is 0.5 kHz, and device efficiency is ˜25%.

  17. Autonomous portable pulsed-periodical generator of high-power radiofrequency-pulses based on gas discharge with hollow cathode.

    PubMed

    Bulychev, Sergey V; Dubinov, Alexander E; L'vov, Igor L; Popolev, Vyacheslav L; Sadovoy, Sergey A; Sadchikov, Eugeny A; Selemir, Victor D; Valiulina, Valeria K; Vyalykh, Dmitry V; Zhdanov, Victor S

    2016-05-01

    Portable autonomous generator of high-power RF-pulses based on the gas discharge with hollow cathode has been designed, fabricated, and tested. Input and output characteristics are the following: discharge current amplitude is 800 A, duration of generated RF-pulses is 350 ns, carrier frequency is ∼90 MHz, power in RF-pulse is 0.5 MW, pulse repetition rate is 0.5 kHz, and device efficiency is ∼25%. PMID:27250451

  18. Pulse-discharge plasmas for plasma-accelerator applications

    SciTech Connect

    Clayton, C. E.; Joshi, C.; Lopes, N. C.

    2012-12-21

    For particle-beam-driven plasma wakefield accelerators, a long and fully-ionized plasma is desirable. We describe an experiment at UCLA to develop a prototype of such plasma using a pulsed-current discharge. Scaling of the plasma density with glass-tube diameter and with discharge-circuit parameters is currently underway. We have found that 4 Torr of Argon can be fully ionized to a density of about 1.3 Multiplication-Sign 10{sup 17} cm{sup -3} when the current density in the 1 inch diameter, 1.2 meter-long tube is around 2 kA/cm{sup 2}, at least at one point along the discharge. The homogeneity of the plasma density in the longitudinal direction is crucial to prevent slippage of the driven plasma structures with the particles. Equally important are the transverse gradients since any dipole asymmetry in the transverse direction can lead to 'steering' of the particle beam. The longitudinal and transverse gradients may be a function of time into the discharge, the shape of the electrodes, the tube size, and the fractional ionization for a given fill pressure. These issues are currently under investigation.

  19. Progress of long pulse discharges by ECH in LHD

    NASA Astrophysics Data System (ADS)

    Yoshimura, Y.; Kasahara, H.; Tokitani, M.; Sakamoto, R.; Ueda, Y.; Ito, S.; Okada, K.; Kubo, S.; Shimozuma, T.; Igami, H.; Takahashi, H.; Tsujimura, T. I.; Makino, R.; Kobayashi, S.; Mizuno, Y.; Akiyama, T.; Ashikawa, N.; Masuzaki, S.; Motojima, G.; Shoji, M.; Suzuki, C.; Tanaka, H.; Tanaka, K.; Tokuzawa, T.; Tsuchiya, H.; Yamada, I.; Goto, Y.; Yamada, H.; Mutoh, T.; Komori, A.; Takeiri, Y.; the LHD Experiment Group

    2016-04-01

    Using ion cyclotron heating and electron cyclotron heating (ECH), or solo ECH, trials of steady state plasma sustainment have been conducted in the superconducting helical/stellarator, large helical device (LHD) (Ida K et al 2015 Nucl. Fusion 55 104018). In recent years, the ECH system has been upgraded by applying newly developed 77 and 154 GHz gyrotrons. A new gas fueling system applied to the steady state operations in the LHD realized precise feedback control of the line average electron density even when the wall condition varied during long pulse discharges. Owing to these improvements in the ECH and the gas fueling systems, a stable 39 min discharge with a line average electron density n e_ave of 1.1  ×  1019 m-3, a central electron temperature T e0 of over 2.5 keV, and a central ion temperature T i0 of 1.0 keV was successfully performed with ~350 kW EC-waves. The parameters are much improved from the previous 65 min discharge with n e_ave of 0.15  ×  1019 m-3 and T e0 of 1.7 keV, and the 30 min discharge with n e_ave of 0.7  ×  1019 m-3 and T e0 of 1.7 keV.

  20. Pulsed wire discharge apparatus for mass production of copper nanopowders.

    PubMed

    Suematsu, H; Nishimura, S; Murai, K; Hayashi, Y; Suzuki, T; Nakayama, T; Jiang, W; Yamazaki, A; Seki, K; Niihara, K

    2007-05-01

    A pulsed wire discharge (PWD) apparatus for the mass production of nanopowders has been developed. The apparatus has a continuous wire feeder, which is operated in synchronization with a discharging circuit. The apparatus is designed for operation at a maximum repetition rate of 1.4 Hz at a stored energy of 160 J. In the present study, Cu nanopowder was synthesized using the PWD apparatus and the performance of the apparatus was examined. Cu nanopowder of 2.0 g quantity was prepared in N(2) gas at 100 kPa for 90 s. The particle size distribution of the Cu nanopowder was analyzed by transmission electron microscopy and the mean surface diameter was determined to be 65 nm. The ratio of the production mass of the powder to input energy was 362 g/kW h. PMID:17552867

  1. Injection-seeded optical parametric amplifier for generating chirped nanosecond pulses.

    PubMed

    Miyake, Shinichirou; Ohshima, Yasuhiro

    2013-03-11

    We constructed an optical parametric amplifier with BiBO crystals, which was injection seeded by a phase-modulated cw beam in the 1,040-1,070 nm region. Two-stage pre-amplification by Yb-doped fibers were implemented for stable injection to the OPA. The frequency chirp in the OPA pulse was actively controlled by adjusting the RF wave for the phase modulation and its synchronization to the OPA firing. Down/up chirps with up to 500 MHz shift were demonstrated. The output pulse energy was ~40 mJ, which is sufficient for future application of frequency conversion and coherent population transfer. PMID:23482098

  2. Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2013-11-01

    In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.

  3. Increase of bone volume by a nanosecond pulsed laser irradiation is caused by a decreased osteoclast number and an activated osteoblasts.

    PubMed

    Ninomiya, Tadashi; Hosoya, Akihiro; Nakamura, Hiroaki; Sano, Kazuo; Nishisaka, Tsuyoshi; Ozawa, Hidehiro

    2007-01-01

    The biostimulatory effects of laser irradiation focus not only in the field of soft tissue but also bone formation. Studies have shown that the light of a nanosecond pulsed laser which has a high peak power can produce stress waves in tissue. We have hypothesized that nanosecond pulsed laser irradiation stimulates bone formation. Our aim was to clarify the mechanism of increased bone volume by nanosecond pulsed laser irradiation. Rat femur was irradiated with a Q-switched Nd:YAG laser, which has a wavelength of 1064 nm. The quantification of trabecular architecture using three-dimensional morphometric analysis and measurement of bone mineral density (BMD) using pQCT was performed on day 1, day 3, day 5, and day 7 after laser irradiation. The laser effects on bone cells were also investigated using histological and immunohistochemical analysis. On day 1 after laser irradiation, bone volume (BV/TV), trabecular thickness (Tb.Th), and other parameters of the irradiated group did not significantly differ from the non-irradiation group (control). However, the mean BV/TV, Tb.Th, mineral apposition rate, and BMD of the laser group on day 7 after laser irradiation were significantly greater than those of the control. On histological analysis, the number of TRAP-positive osteoclasts was lower on day 3 after laser irradiation. Osteoblasts with activated clearance were seen in the laser irradiated group on day 1 and day 3. These data reveal that the increased bone volume by nanosecond pulsed laser irradiation causes an increase in osteoblast activity and a decrease in osteoclast number. PMID:16978938

  4. ICRF Heated Long-Pulse Plasma Discharges in LHD

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Seki, T.; Mutoh, T.; Saito, K.; Watari, T.; Nakamura, Y.; Sakamoto, M.; Watanabe, T.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Notake, T.; Torii, Y.; Okada, H.; Ichimura, M.; Higaki, H.; Takase, Y.; Kasahara, H.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Yanping; Yoon, J. S.; Kwak, J. G.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD Experimental Group

    2006-01-01

    A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8× 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 GJ, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.

  5. An experimental investigation of pulsed multichannel discharge across solid insulators

    NASA Technical Reports Server (NTRS)

    Lakdawala, V. K.; Ko, S. T.; Lee, J. H.

    1985-01-01

    An experimental study of pulsed surface flashover across a solid insulator in a vacuum is reported, with application of fast impulse voltages of a few tens of ns rise time and a few microsec tail time. Following the flashover voltage experiments, no visible degradation of the surface was found for the BaTiO3 sample, whereas for the TiO2 sample a distinct track mark could be seen where the flashover occurred. Three schemes for obtaining multichannel discharges were studied for plexiglass specimens, and results showed the number of shots to decrease as the number of channels increased.

  6. Analysis of material modifications caused by nanosecond pulsed UV laser processing of SiC and GaN

    NASA Astrophysics Data System (ADS)

    Krüger, Olaf; Wernicke, Tim; Würfl, Joachim; Hergenröder, Roland; Tränkle, Günther

    2008-10-01

    The effects of direct UV laser processing on single crystal SiC in ambient air were investigated by cross-sectional transmission electron microscopy, Auger electron spectroscopy, and measurements of the electrical resistance using the transfer length method (TLM). Scanning electron microscopy was applied to study the morphology and dimensions of the laser-treated regions. After laser processing using a nanosecond pulsed solid-state laser the debris consisting of silicon oxide was removed by etching in buffered hydrofluoric acid. A layer of resolidified material remains at the surface indicating the thermal impact of the laser process. The Si/C ratio is significantly disturbed at the surface of the resolidified layer and approaches unity in a depth of several tens of nanometers. A privileged oxidation of carbon leaves elementary resolidified silicon at the surface, where nanocrystalline silicon was detected. Oxygen and nitrogen were detected near the surface down to a depth of some tens of nanometers. A conductive surface film is formed, which is attributed to the thermal impact causing the formation of the silicon-rich surface layer and the incorporation of nitrogen as dopant. No indications for microcrack or defect formation were found beneath the layer of resolidified material.

  7. Active photo-physical processes in the pulsed UV nanosecond laser exposure of photostructurable glass ceramic materials

    NASA Astrophysics Data System (ADS)

    Livingston, Frank E.; Adams, Paul M.; Helvajian, Henry

    2004-10-01

    We have performed experiments in which sample coupons of a commercial photostructurable glass ceramic (PSGC) material have been carefully exposed to various photon doses by pulsed UV nanosecond lasers at λ = 266 nm and λ = 355 nm. Following UV laser irradiation, the samples were analyzed by optical transmission spectroscopy to investigate the latent image and identify the photo-induced trapped (defect) state. The irradiated samples were thermally processed and the quenching of this trapped state and the concurrent growth of a spectral band associated with the formation of nanometer-scale metallic clusters was then observed using optical transmission spectroscopy. The results show that exposure at λ = 266 nm generates a defect state distribution that is markedly broader compared with the defect state distribution that is generated via λ = 355 nm excitation. The defect concentration formed with λ = 266 nm radiation is also much larger compared with the defect concentration associated with λ = 355 nm exposure. The results reveal that the metallic cluster concentration saturates with increasing laser irradiance, while the defect state concentration does not saturate. These studies have identified two precursor states of the exposed PSGC material that are tractable via spectroscopic techniques and could be used to refine the laser exposure and thermal processing of PSGC materials.

  8. Fabrication of a micro-hole array on metal foil by nanosecond pulsed laser beam machining using a cover plate

    NASA Astrophysics Data System (ADS)

    Ha, Kyoung Ho; Lee, Se Won; Kim, Janggil; Jee, Won Young; Chu, Chong Nam

    2015-02-01

    A novel laser beam machining (LBM) method is proposed to achieve higher precision and better quality beyond the limits of a commercialized nanosecond pulsed laser system. The use of a cover plate is found to be effective for the precision machining of a thin metal foil at micro scale. For verifying the capability of cover plate laser beam machining (c-LBM) technology, a 30 by 30 array of micro-holes was fabricated on 8 µm-thick stainless steel 304 (STS) foil. As a result, thermal deformation and cracks were significantly reduced in comparison with the results using LBM without a cover plate. The standard deviation of the inscribed and circumscribed circle of the holes with a diameter of 12 µm was reduced to 33% and 81%, respectively and the average roundness improved by 77%. Moreover, the smallest diameter obtainable by c-LBM in the given equipment was found to be 6.9 µm, which was 60% less than the minimum size hole by LBM without a cover plate.

  9. Evaluation of the Genetic Response of U937 and Jurkat Cells to 10-Nanosecond Electrical Pulses (nsEP).

    PubMed

    Roth, Caleb C; Glickman, Randolph D; Tolstykh, Gleb P; Estlack, Larry E; Moen, Erick K; Echchgadda, Ibtissam; Beier, Hope T; Barnes, Ronald A; Ibey, Bennett L

    2016-01-01

    Nanosecond electrical pulse (nsEP) exposure activates signaling pathways, produces oxidative stress, stimulates hormone secretion, causes cell swelling and induces apoptotic and necrotic death. The underlying biophysical connection(s) between these diverse cellular reactions and nsEP has yet to be elucidated. Using global genetic analysis, we evaluated how two commonly studied cell types, U937 and Jurkat, respond to nsEP exposure. We hypothesized that by studying the genetic response of the cells following exposure, we would gain direct insight into the stresses experienced by the cell and in turn better understand the biophysical interaction taking place during the exposure. Using Ingenuity Systems software, we found genes associated with cell growth, movement and development to be significantly up-regulated in both cell types 4 h post exposure to nsEP. In agreement with our hypothesis, we also found that both cell lines exhibit significant biological changes consistent with mechanical stress induction. These results advance nsEP research by providing strong evidence that the interaction of nsEPs with cells involves mechanical stress. PMID:27135944

  10. Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Guan, Y. C.; Zhou, W.; Zheng, H. Y.; Li, Z. L.

    2013-09-01

    Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200 nm to 1100 nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

  11. Cell Death Induced on Cell Cultures and Nude Mouse Skin by Non-Thermal, Nanosecond-Pulsed Generated Plasma

    PubMed Central

    Bousquet, Guilhem; Gapihan, Guillaume; Starikovskaia, Svetlana M.; Rousseau, Antoine; Janin, Anne

    2013-01-01

    Non-thermal plasmas are gaseous mixtures of molecules, radicals, and excited species with a small proportion of ions and energetic electrons. Non-thermal plasmas can be generated with any high electro-magnetic field. We studied here the pathological effects, and in particular cell death, induced by nanosecond-pulsed high voltage generated plasmas homogeneously applied on cell cultures and nude mouse skin. In vitro, Jurkat cells and HMEC exhibited apoptosis and necrosis, in dose-dependent manner. In vivo, on nude mouse skin, cell death occurred for doses above 113 J/cm2 for the epidermis, 281 J/cm2 for the dermis, and 394 J/cm2 for the hypodermis. Using electron microscopy, we characterized apoptosis for low doses and necrosis for high doses. We demonstrated that these effects were not related to thermal, photonic or pH variations, and were due to the production of free radicals. The ability of cold plasmas to generate apoptosis on cells in suspension and, without any sensitizer, on precise skin areas, opens new fields of application in dermatology for extracorporeal blood cell treatment and the eradication of superficial skin lesions. PMID:24358244

  12. Growth and characterization of Cu(In,Ga)Se2 thin films by nanosecond and femtosecond pulsed laser deposition

    PubMed Central

    2014-01-01

    In this work, CuIn1 - x Ga x Se2 (CIGS) thin films were prepared by nanosecond (ns)- and femtosecond (fs)-pulsed laser deposition (PLD) processes. Different film growth mechanisms were discussed in perspective of the laser-produced plasmas and crystal structures. The fs-PLD has successfully improved the inherent flaws, Cu2 - x Se, and air voids ubiquitously observed in ns-PLD-derived CIGS thin films. Moreover, the prominent antireflection and excellent crystalline structures were obtained in the fs-PLD-derived CIGS thin films. The absorption spectra suggest the divergence in energy levels of radiative defects brought by the inhomogeneous distribution of elements in the fs-PLD CIGS, which has also been supported by comparing photoluminescence (PL) spectra of ns- and fs-PLD CIGS thin films at 15 K. Finally, the superior carrier transport properties in fs-PLD CIGS were confirmed by fs pump-probe spectroscopy and four-probe measurements. The present results indicate a promising way for preparing high-quality CIGS thin films via fs-PLD. PMID:24959108

  13. Selective excavation of human carious dentin using the nanosecond pulsed laser in 5.8-μm wavelength range

    NASA Astrophysics Data System (ADS)

    Kita, Tetsuya; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, 5.8 μm wavelength range was found to be effective for selective excavation of human carious dentin.

  14. Nanosecond pulsed platelet-rich plasma (nsPRP) improves mechanical and electrical cardiac function following myocardial reperfusion injury.

    PubMed

    Hargrave, Barbara; Varghese, Frency; Barabutis, Nektarios; Catravas, John; Zemlin, Christian

    2016-02-01

    Ischemia and reperfusion (I/R) of the heart is associated with biochemical and ionic changes that result in cardiac contractile and electrical dysfunction. In rabbits, platelet-rich plasma activated using nanosecond pulsed electric fields (nsPRP) has been shown to improve left ventricular pumping. Here, we demonstrate that nsPRP causes a similar improvement in mouse left ventricular function. We also show that nsPRP injection recovers electrical activity even before reperfusion begins. To uncover the mechanism of nsPRP action, we studied whether the enhanced left ventricular function in nsPRP rabbit and mouse hearts was associated with increased expression of heat-shock proteins and altered mitochondrial function under conditions of oxidative stress. Mouse hearts underwent 30 min of global ischemia and 1 h of reperfusion in situ. Rabbit hearts underwent 30 min of ischemia in vivo and were reperfused for 14 days. Hearts treated with nsPRP expressed significantly higher levels of Hsp27 and Hsp70 compared to hearts treated with vehicle. Also, pretreatment of cultured H9c2 cells with nsPRP significantly enhanced the "spare respiratory capacity (SRC)" also referred to as "respiratory reserve capacity" and ATP production in response to the uncoupler FCCP. These results suggest a cardioprotective effect of nsPRP on the ischemic heart during reperfusion. PMID:26908713

  15. Evaluation of the Genetic Response of U937 and Jurkat Cells to 10-Nanosecond Electrical Pulses (nsEP)

    PubMed Central

    Glickman, Randolph D.; Tolstykh, Gleb P.; Estlack, Larry E.; Moen, Erick K.; Echchgadda, Ibtissam; Beier, Hope T.; Barnes, Ronald A.; Ibey, Bennett L.

    2016-01-01

    Nanosecond electrical pulse (nsEP) exposure activates signaling pathways, produces oxidative stress, stimulates hormone secretion, causes cell swelling and induces apoptotic and necrotic death. The underlying biophysical connection(s) between these diverse cellular reactions and nsEP has yet to be elucidated. Using global genetic analysis, we evaluated how two commonly studied cell types, U937 and Jurkat, respond to nsEP exposure. We hypothesized that by studying the genetic response of the cells following exposure, we would gain direct insight into the stresses experienced by the cell and in turn better understand the biophysical interaction taking place during the exposure. Using Ingenuity Systems software, we found genes associated with cell growth, movement and development to be significantly up-regulated in both cell types 4 h post exposure to nsEP. In agreement with our hypothesis, we also found that both cell lines exhibit significant biological changes consistent with mechanical stress induction. These results advance nsEP research by providing strong evidence that the interaction of nsEPs with cells involves mechanical stress. PMID:27135944

  16. Industrial applications of high-average power high-peak power nanosecond pulse duration Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Harrison, Paul M.; Ellwi, Samir

    2009-02-01

    Within the vast range of laser materials processing applications, every type of successful commercial laser has been driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive industries. Applications such as these tend to require working spots that have uniform intensity distribution using specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link between the application, the key laser characteristics and the beam delivery system that link these together.

  17. Synergistic effect of nanosecond pulsed electric field combined with low-dose of pingyangmycin on salivary adenoid cystic carcinoma.

    PubMed

    Qi, Wei; Guo, Jinsong; Wu, Shan; Su, Bo; Zhang, Lei; Pan, Jie; Zhang, Jue

    2014-05-01

    Adenoid cystic carcinoma (ACC) is one of the most common malignant neoplasms in salivary glands. To evaluate the therapeutic effects of nanosecond pulsed electric field (nsPEF) combined with pingyangmycin (PYM) on salivary gland adenoid cystic carcinoma (SACC), ACC high metastatic cell line (SACC-LM) and low metastatic cell line (SACC‑83) were tested by CCK-8 assay, cell clonogenic assay, flow cytometry and Transwell assay. Extracellular matrix metalloproteinase inducer (EMMPRIN) expression was tested by western blotting to verify the synergistic mechanism of nsPEF and PYM. The results showed that nsPEF inhibited the cell proliferation of both cell lines, and the inhibitory effect was strongly associated with time and electrical field strength. Moreover, PYM combined with nsPEF may enhance the suppression effect significantly, even at a very low dose (0.01 µg/ml). The synergistic effects may contribute to the downregulation of EMMPRIN expression resulting from the application of nsPEF. For SACC, nsPEF combined with chemotherapy agents may be a valuable strategy not only to improve the treatment effect and prognosis, but also to reduce the side-effects of chemotherapy. PMID:24604118

  18. Opportunities afforded by the intense nanosecond neutron pulses from a plasma focus source for neutron capture therapy and the preliminary simulation results

    NASA Astrophysics Data System (ADS)

    Giannini, G.; Gribkov, V.; Longo, F.; Ramos Aruca, M.; Tuniz, C.

    2012-11-01

    The use of short and powerful neutron pulses for boron neutron capture therapy (BNCT) can potentially increase selectivity and reduce the total dose absorbed by the patient. The biological effects of radiation depend on the dose, the dose power and the spatial distribution of the microscopic energy deposition. A dense plasma focus (DPF) device emits very short (in the nanosecond range) and extremely intense pulses of fast neutrons (2.5 or 14 MeV neutrons—from D-D or D-T nuclear reactions) and x-rays. Optimal spectra of neutrons formed for use in BNCT must contain an epithermal part to ensure a reasonable penetration depth into tissues at high enough cross-section on boron. So the powerful nanosecond pulses of fast neutrons generated by DPF must be moderated. After this moderation, the pulse duration must be shorter compared with the duration of the reaction with free radicals, that is, ⩾1 μs. In this work we focus on the development of a detailed simulation of interaction of short-pulse radiation from a DPF with the device's materials and with different types of moderators to estimate the dose power at the cells for this dynamic case. The simulation was carried out by means of the Geant4 toolkit in two main steps: the modeling of the pulsed neutron source device itself; the study of the interaction of fast mono-energetic neutrons with a moderator specific for BNCT.

  19. Impact of the nanosecond volume discharge in atmospheric pressure air on the distribution of the surface potential of epitaxial HgCdTe

    NASA Astrophysics Data System (ADS)

    Novikov, V. A.; Grigoryev, D. V.; Bezrodnyy, D. A.; Tarasenko, V. F.; Shulepov, M. A.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-03-01

    In this paper we present the results of our research of the impact of nanosecond volume discharge on the electronic properties of the near-surface region of epitaxial Hg1-x Cd x Te films. We show that the distribution of the surface potential and, as a consequence, the material composition of the individual crystal grains that form V-defects possess a complex structure and contain regions with elevated content of both mercury and cadmium. The volume discharge treatment of the film surface leads to a decrease of the mercury content in individual crystal grains compared to the bulk of Hg1-x Cd x Te epitaxial film. This indicates a higher mercury desorption rate from the V-defect region.

  20. Pulsed microwave discharges in powder mixtures: Status, problems, and prospects

    NASA Astrophysics Data System (ADS)

    Batanov, G. M.; Kossyi, I. A.

    2015-10-01

    Results of experiments on the excitation of pulsed microwave discharges by gyrotron radiation (λ = 4 mm, P 0 = 100-500 kW, τ = 1-10 ms) in the volumes and on the surfaces of metal-dielectric powder mixtures are presented. It is shown that there are two phases of discharge development: the spark phase, accompanied by a partial evaporation of the powder material, and the phase of a developed discharge, characterized by a plasma density of ˜1017 cm-3, high absorption, and high temperatures (˜5-10 kK) in a thin layer (˜0.1-0.2 mm) of plasma and vapor. It is demonstrated that the conductivity induced in the targets by UV radiation play an important role in the microwave absorption by powder grains. It is found that, in the course of the discharge, a conductive metal mesh forms in the powder volume as a result of metal evaporation. Reactions of high-temperature synthesis were initiated in various powder mixtures (Ti + B, Al + Fe2O3, Mo + B, etc.). It is shown that the reactions of high-temperature synthesis last for up to 0.1 s and are accompanied by the evaporation of powder grains and the formation of an aerosol cloud due to free expansion of reactants from the sample surface. The possibility of experimentally studying the kinetics of reactions of high-temperature synthesis is demonstrated. It is noticed that microwave discharges can be used to initiate plasmachemical reactions on the surfaces of radioparent materials in active gaseous media.

  1. Pulsed microwave discharges in powder mixtures: Status, problems, and prospects

    SciTech Connect

    Batanov, G. M. Kossyi, I. A.

    2015-10-15

    Results of experiments on the excitation of pulsed microwave discharges by gyrotron radiation (λ = 4 mm, P{sub 0} = 100–500 kW, τ = 1–10 ms) in the volumes and on the surfaces of metal-dielectric powder mixtures are presented. It is shown that there are two phases of discharge development: the spark phase, accompanied by a partial evaporation of the powder material, and the phase of a developed discharge, characterized by a plasma density of ∼10{sup 17} cm{sup –3}, high absorption, and high temperatures (∼5–10 kK) in a thin layer (∼0.1–0.2 mm) of plasma and vapor. It is demonstrated that the conductivity induced in the targets by UV radiation play an important role in the microwave absorption by powder grains. It is found that, in the course of the discharge, a conductive metal mesh forms in the powder volume as a result of metal evaporation. Reactions of high-temperature synthesis were initiated in various powder mixtures (Ti + B, Al + Fe{sub 2}O{sub 3}, Mo + B, etc.). It is shown that the reactions of high-temperature synthesis last for up to 0.1 s and are accompanied by the evaporation of powder grains and the formation of an aerosol cloud due to free expansion of reactants from the sample surface. The possibility of experimentally studying the kinetics of reactions of high-temperature synthesis is demonstrated. It is noticed that microwave discharges can be used to initiate plasmachemical reactions on the surfaces of radioparent materials in active gaseous media.

  2. NOx diesel exhaust treatment using a pulsed corona discharge: the pulse repetition rate effect

    NASA Astrophysics Data System (ADS)

    Yankelevich, Y.; Wolf, M.; Baksht, R.; Pokryvailo, A.; Vinogradov, J.; Rivin, B.; Sher, E.

    2007-05-01

    The pulsed corona offers real promise for degradation of pollutants in gas and water streams. This paper presents a study of NOx removal from diesel exhaust. Special emphasis is laid on the investigation of the dependence of the NO removal rate and efficiency on the pulse repetition rate (PRR). A nanosecond solid state power supply (45 kV, 60 ns, up to 1 kHz) was used for driving the corona reactor. A Mitsubishi 10 kW 3-cylinder diesel-generator engine with a total volume of 1300 cm3 was used as a source of exhaust gas. At an NO removal rate of 35% the NO removal efficiency was 53 g kW-1h-1 for PRR = 500 Hz and the initial NO concentration was 375 ppm. A semi-empirical expression for the corona reactor removal efficiency related both to PRR and to the residence time is presented. The removal efficiency decreases with increasing PRR at constant flow rate or constant residence time. This expression demonstrates reasonable agreement between the calculation results and the experimental data.

  3. Nanosecond square high voltage pulse generator for electro-optic switch

    NASA Astrophysics Data System (ADS)

    Feng, Xian-wang; Long, Xing-wu; Tan, Zhong-qi

    2011-07-01

    A scalable square high voltage pulse generator, which has the properties of fast rise time, fast fall time, powerful driving capability, and long lifetime, is presented in this paper by utilizing solid state circuitry. A totem-pole topology is designed to supply a powerful driving capability for the electro-optic (EO) crystal which is of capacitive load. Power MOSFETs are configured in series to sustain high voltage, and proper driving circuits are introduced for the specific MOSFETs configurations. A 3000 V pulse generator with ˜49.04 ns rise time and ˜10.40 ns fall time of the output waveform is presented. This kind of generator is desirable for electro-optic switch. However, it is not specific to EO switch and may have broad applications where high voltage fast switching is required.

  4. Nanosecond square high voltage pulse generator for electro-optic switch.

    PubMed

    Feng, Xian-wang; Long, Xing-wu; Tan, Zhong-qi

    2011-07-01

    A scalable square high voltage pulse generator, which has the properties of fast rise time, fast fall time, powerful driving capability, and long lifetime, is presented in this paper by utilizing solid state circuitry. A totem-pole topology is designed to supply a powerful driving capability for the electro-optic (EO) crystal which is of capacitive load. Power MOSFETs are configured in series to sustain high voltage, and proper driving circuits are introduced for the specific MOSFETs configurations. A 3000 V pulse generator with ~49.04 ns rise time and ~10.40 ns fall time of the output waveform is presented. This kind of generator is desirable for electro-optic switch. However, it is not specific to EO switch and may have broad applications where high voltage fast switching is required. PMID:21806222

  5. Nanosecond pulsed laser ablation of brass in a dry and liquid-confined environment

    NASA Astrophysics Data System (ADS)

    Bashir, Shazia; Vaheed, Hamza; Mahmood, Khaliq

    2013-02-01

    The effect of ambient environment (dry or wet) and overlapping laser pulses on the laser ablation performance of brass has been investigated. For this purpose, a Q-switched, frequency doubled Nd:YAG laser with a wavelength of 532 nm, pulse energy of 150 mJ, pulse width of 6 ns and repetition rate of 10 Hz is employed. In order to explore the effect of ambient environments, brass targets have been exposed in deionized water, methanol and air. The targets are exposed for 1000, 2000, 3000 and 4000 succeeding pulses in each atmosphere. The surface morphology and chemical composition of ablated targets have been characterized by using Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Attenuated Total Reflection (ATR) techniques. In case of liquid environment, various features like nano- and micro-scale laser-induced periodic surface structures with periodicity 500 nm-1 μm, cavities of size few micrometers with multiple ablative layers and phenomenon of thermal stress cracking are observed. These features are originated by various chemical and thermal phenomena induced by laser heating at the liquid-solid interfaces. The convective bubble motion, explosive boiling, pressure gradients, cluster and colloid formation due to confinement effects of liquids are possible cause for such kind of features. The metal oxides and alcohol formed on irradiated surface are also playing the significant role for the formation of these kinds of structure. In case of air one huge crater is formed along with the redeposition of sputtered material and is ascribed to laser-induced evaporation and oxide formation.

  6. Selective Field Effects on Intracellular Vacuoles and Vesicle Membranes with Nanosecond Electric Pulses

    PubMed Central

    Tekle, Ephrem; Oubrahim, Hammou; Dzekunov, Sergey M.; Kolb, Juergen F.; Schoenbach, Karl H.; Chock, P. B.

    2005-01-01

    Electric pulses across intact vesicles and cells can lead to transient increase in permeability of their membranes. We studied the integrity of these membranes in response to external electric pulses of high amplitude and submicrosecond duration with a primary aim of achieving selective permeabilization. These effects were examined in two separate model systems comprising of 1), a mixed population of 1,2-di-oleoyl-sn-glycero-3-phosphocholine phospholipid vesicles and in 2), single COS-7 cells, in which large endosomal membrane vacuoles were induced by stimulated endocytosis. It has been shown that large and rapidly varying external electric fields, with pulses shorter than the charging time of the outer-cell membrane, could substantially increase intracellular fields to achieve selective manipulations of intracellular organelles. The underlying principle of this earlier work is further developed and applied to the systems studied here. Under appropriate conditions, we show preferential permeabilization of one vesicle population in a mixed preparation of vesicles of similar size distribution. It is further shown that large endocytosed vacuoles in COS-7 cells can be selectively permeabilized with little effect on the integrity of outer cell membrane. PMID:15821165

  7. Electrosensitization assists cell ablation by nanosecond pulsed electric field in 3D cultures

    PubMed Central

    Muratori, Claudia; Pakhomov, Andrei G.; Xiao, Shu; Pakhomova, Olga N.

    2016-01-01

    Previous studies reported a delayed increase of sensitivity to electroporation (termed “electrosensitization”) in mammalian cells that had been subjected to electroporation. Electrosensitization facilitated membrane permeabilization and reduced survival in cell suspensions when the electric pulse treatments were split in fractions. The present study was aimed to visualize the effect of sensitization and establish its utility for cell ablation. We used KLN 205 squamous carcinoma cells embedded in an agarose gel and cell spheroids in Matrigel. A local ablation was created by a train of 200 to 600 of 300-ns pulses (50 Hz, 300–600 V) delivered by a two-needle probe with 1-mm inter-electrode distance. In order to facilitate ablation by engaging electrosensitization, the train was split in two identical fractions applied with a 2- to 480-s interval. At 400–600 V (2.9–4.3 kV/cm), the split-dose treatments increased the ablation volume and cell death up to 2–3-fold compared to single-train treatments. Under the conditions tested, the maximum enhancement of ablation was achieved when two fractions were separated by 100 s. The results suggest that engaging electrosensitization may assist in vivo cancer ablation by reducing the voltage or number of pulses required, or by enabling larger inter-electrode distances without losing the ablation efficiency. PMID:26987779

  8. Nanosecond pulse generation in a passively Q-switched Nd:GGG laser at 1331 nm by CVD graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Wang, Yi; Cheng, Yongjie; Yang, Han; Xu, Huiying; Cai, Zhiping

    2015-10-01

    We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:GGG laser at the low-gain transition line of 1331 nm. A three-layer CVD graphene thin film was transferred from Cu foil to a BK7 glass substrate for the use of saturable absorber. A stable Q-switching laser operation was obtained with maximum average output power of 0.69 W and slope efficiency of about 11.0% with respect to the absorbed pump power. The shortest pulse duration and the maximum repetition rate of the pulse trains were registered to be 556 ns and 166.7 kHz with corresponding maximum pulse energy 4.14 μJ and pulse peak power 7.45 W. This is the first demonstration of CVD-graphene-based Q-switched laser operation at 1.3 μm, to the best of our knowledge.

  9. Mechanisms of iodine atoms production by pulse discharge

    NASA Astrophysics Data System (ADS)

    Napartovich, Anatoly; Kochetov, Igor; Vagin, Nikolay; Yuryshev, Nikolay

    2007-10-01

    Pulsed electric discharge is most effective to turn COIL operation into pulse mode by instant production of iodine atoms. Numerical model is developed for simulations of an electric discharge in a mixture of gas flow outgoing from the singlet oxygen generator (SOG) with CF3I. Electron scattering cross sections from CF3I molecules are analyzed to reproduce recently published swarm data for CF3I and N2 mixtures. The model comprises a system of kinetic equations for neutral and charged species, electric circuit equation, gas thermal balance equation, and the photon balance equation. Reaction rate coefficients for processes involving electrons are found by solving the electron Boltzmann equation, which is re-calculated in a course of computations when plasma parameters changed. The processes accounted for in the Boltzmann equation include excitation, dissociation and ionization of atoms and molecules, electron-ion recombination, electron-electron collisions, second-kind collisions, and stepwise excitation of molecules. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the SOG. Results of numerical simulations for conditions of the experiments are compared with results of measurements.

  10. Laser Thomson Scattering Diagnostics of Pulsed Filamentary Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Bolouki, Nima

    2012-10-01

    Laser Thomson scattering (LTS) has been applied to measure spatiotemporal evolution of electron density and electron temperature in a pulsed filamentary discharge. The light source of LTS is the second harmonics Nd:YAG laser with a energy of 8 mJ. Also a triple grating spectrometer (TGS) having high rejection rate for stray light is used to measure LTS spectra. In our experimental conditions, non-thermal and non-equilibrium micro-plasmas are generated at round atmospheric pressure. Moreover, the electrode set in this experiment is consisted of a needle electrode and a hemispherical electrode with an inter-electrode gap of 0.5 mm. The total electric charge that flows through the discharge channel vary from 20 nC to 850 nC by changing capacitance in electrical circuit. We could show that the total charge variation leads to increase in electron density from 10^22 m-3 to 10^23 m-3. However, the electron temperature remains almost constant at the main discharge. In order to investigate the streamer phase, we changed the gap up to 16mm, and then performed the LTS method to measure the electron density and electron temperature.

  11. Effects of ionic liquid electrode on pulse discharge plasmas in the wide range of gas pressures

    SciTech Connect

    Chen Qiang; Hatakeyama, Rikizo; Kaneko, Toshiro

    2010-11-15

    Gas-liquid interfacial pulse discharge plasmas are generated in the wide range of gas pressures, where an ionic liquid is used as the liquid electrode. By analyzing the characteristics of discharge voltage and current, the discharge mechanisms at low and high pressures are found to be dominated by secondary electron emission and first Townsend ionization, respectively. Therefore, the discharge properties at low and high pressures are mainly determined by the cathode material and the discharge gas type, respectively. Furthermore, the plasma properties are investigated by a double Langmuir probe. The density of the positive pulse plasma is found to be much smaller than that of the negative pulse plasma, although the discharge voltage and current of the negative and positive pulse plasmas are of the same order of magnitude. The positive pulse discharge plasma is considered to quickly diffuse onto the chamber wall from the radially central region due to its high plasma potential compared with that in the peripheral region.

  12. Spatio-temporal characteristics of self-pulse in hollow cathode discharge

    NASA Astrophysics Data System (ADS)

    Jing, Ha; He, Shoujie

    2015-02-01

    The characteristics of self-pulse in hollow cathode discharge at low pressure have been investigated. The voltage-current (V-I) curves, the influence of ballast resistor on the self-pulses, and the evolution of current and voltage are measured. Both the axial and radial spatio-temporal discharge images of self-pulse are recorded. The results show that there exists the hysteresis effect in the present hollow cathode discharge. The high value of ballast resistors is favourable for the observation of self-pulses. The process of the self-pulse can be divided into three stages from the temporal discharge images, i.e., the pre-discharge, the transition from mainly axial electric field to mainly radial electric field, and the decaying process. The self-pulse is suggested to originate from the mode transition of the discharge in essence.

  13. Spatio-temporal characteristics of self-pulse in hollow cathode discharge

    SciTech Connect

    Jing, Ha; He, Shoujie

    2015-02-15

    The characteristics of self-pulse in hollow cathode discharge at low pressure have been investigated. The voltage-current (V-I) curves, the influence of ballast resistor on the self-pulses, and the evolution of current and voltage are measured. Both the axial and radial spatio-temporal discharge images of self-pulse are recorded. The results show that there exists the hysteresis effect in the present hollow cathode discharge. The high value of ballast resistors is favourable for the observation of self-pulses. The process of the self-pulse can be divided into three stages from the temporal discharge images, i.e., the pre-discharge, the transition from mainly axial electric field to mainly radial electric field, and the decaying process. The self-pulse is suggested to originate from the mode transition of the discharge in essence.

  14. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  15. Real-time measurement of temperature variation during nanosecond pulsed-laser-induced contamination deposition.

    PubMed

    Kokkinos, Dimitrios; Gailly, Patrick; Georges, Marc P; Tzeremes, Georgios; Rochus, Pierre; Fleury-Frenette, Karl

    2015-12-20

    In this paper, a study of heat generation during UV laser-induced contamination (LIC) and potentially resulting subsequent thermal damage are presented. This becomes increasingly interesting when optics with delicate coatings are involved. During LIC, radiation can interact with outgassing molecules, both in the gas phase and at the surface, thus triggering chemical and photo-fixation reactions. This is a major hazard, in particular for laser units operating under vacuum conditions such as in space applications. The intense photon flux not only affects the contaminant deposition rate but also alters their chemical structure, which can increase their absorption coefficient. Over cumulative irradiation shots, these molecules formed deposits that increasingly absorb photons and produce heat as a by-product of de-excitation, eventually leading to thermal damage. One could better assess the risk of the latter with the knowledge of temperature during the contamination process. For this purpose, a thermoreflectance technique is used here to estimate the temperature variation from pulse to pulse during contamination deposition through the analysis of a temperature-dependent surface reflectance signal. PMID:26837020

  16. Multi-diagnostic comparison of femtosecond and nanosecond pulsed laser plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; VanRompay, P. A.; Nees, J. A.; Pronko, P. P.

    2002-09-01

    Understanding and fully characterizing highly dynamic and rapidly streaming laser ablation plasmas requires multiple techniques for monitoring effects at different stages. By combining multiple diagnostic methods, it is possible to analyze the broad time window over which these ablation plasmas develop and to learn more about the related physical processes that occur. Two laser sources, an 80 fs Ti:Sapphire laser (780 nm) and a 6 ns Nd:YAG laser (1.06 mum), are used in this work in order to compare pulse duration effects at similar wavelengths. Characteristics of the plasma produced by these two lasers are compared under conditions of comparable ablation flux. Results are presented involving correlation of time-resolved Langmuir probe data and electrostatic energy analysis for aluminum plasmas as a representative investigation for metallic systems. In addition, continuous-wave refractive index laser beam deflection is used to characterize the plasma and hot gas generated from boron nitride targets in terms of their ion and neutral atom densities. A self-similarity plasma expansion model is used to analyze the plumes under various conditions. Fundamental data obtained in this way can be relevant to laser micro-machining, laser induced breakdown spectroscopy, and pulsed laser deposition.

  17. Influence of the voltage polarity on the properties of a nanosecond surface barrier discharge in atmospheric-pressure air

    SciTech Connect

    Nudnova, M. M.; Aleksandrov, N. L.; Starikovskii, A. Yu.

    2010-01-15

    The properties of a surface barrier discharge in atmospheric-pressure air at different polarities of applied voltage were studied experimentally. The influence of the voltage polarity on the spatial structure of the discharge and the electric field in the discharge plasma was determined by means of spectroscopic measurements. It is found that the energy deposited in the discharge does not depend on the voltage polarity and that discharges of positive polarity are more homogenous and the electric fields in them are higher.

  18. Complete characterization of damage threshold in titanium doped sapphire crystals with nanosecond, picosecond, and femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Canova, F.; Chambaret, J.-P.; Mourou, G.; Sentis, M.; Uteza, O.; Delaporte, P.; Itina, T.; Natoli, J.-Y.; Commandre, M.; Amra, C.

    2005-12-01

    The major bottleneck for the development of robust and cost-effective femtosecond amplification systems is the uncertainty concerning the damage threshold of Ti: Sapphire crystals. Up to now, Ti: Sapphire is the only material that supports the generation of temporally short pulses (few femtosecond) at high repetition rates, and overcoming this bottleneck will represent a major advance in laser performance for all the femtosecond community. Currently, when pumped at 532nm, the uncertainty on Ti:Sapphire damage threshold, is about a factor of ten. The empirically estimated threshold is 10J/cm2 but for safety reasons the femtosecond laser community (especially the companies producing the lasers) uses the conservative value of 1J/cm2. Such a low pumping fluency means low extraction efficiency during the amplification process and a great waste of pumping energy, the most expensive part of a Ti:Sapphire amplifier. In order to remove this bottleneck, we launch a complete analysis of all the factors that influence the damage threshold in Ti:Sapphire Crystals. Our program is to first measure the bulk threshold to define the upper threshold limit, and the influence of Ti ion concentration in the crystal garnet. Then, we will analyze all the surface effects that influence the value of the threshold. These effects depend on the polishing, on the cleaning process, as well as the type of anti-reflective coating. Only a complete understanding of all the mechanisms involved in threshold limitation will allow us to produce Ti:Sa crystals with the best performances. The study of the characteristics of the Ti:Sapphire damage threshold will not be complete and reliable without a complete characterization of the pump beams (temporal and spatial modulations), and this analysis will be done with nanosecond and picosecond pulses at 532nm. Finally, to complete the exploration of the the behavior of the titanium doped sapphire crystal, we will characterize the damage threshold with

  19. Effects of nanosecond pulsed electrical fields (nsPEFs) on the cell cycle of CHO and Jurkat cells

    NASA Astrophysics Data System (ADS)

    Mahlke, Megan A.; Navara, Christopher; Ibey, Bennett L.

    2014-03-01

    Exposure to nano-second pulsed electrical fields (nsPEFs) can cause poration of external and internal cell membranes, DNA damage, and disassociation of cytoskeletal components, all of which are capable of disrupting a cell's ability to replicate. Variations between cell lines in membrane and cytoskeletal structure as well as in survival of nsPEF exposure should correspond to unique line-dependent cell cycle effects. Additionally, phase of cell cycle during exposure may be linked to differential sensitivities to nsPEFs across cell lines, as DNA structure, membrane elasticity, and cytoskeletal structure change dramatically during the cell cycle. Populations of Jurkat and Chinese Hamster Ovary (CHO) cells were examined post-exposure (10 ns pulse trains at 150kV/cm) by analysis of DNA content via propidium iodide staining and flow cytometric analysis at various time points (1, 6, and 12h post-exposure) to determine population distribution in cell cycle phases. Additionally, CHO and Jurkat cells were synchronized in G1/S and G2/M phases, pulsed, and analyzed to evaluate role of cell cycle phase in survival of nsPEFs. CHO populations recovered similarly to sham populations postnsPEF exposure and did not exhibit a phase-specific change in response. Jurkat cells exhibited considerable apoptosis/necrosis in response to nsPEF exposure and were unable to recover and proliferate in a manner similar to sham exposed cells. Additionally, Jurkat cells appear to be more sensitive to nsPEFs in G2/M phases than in G1/S phases. Recovery of CHO populations suggests that nsPEFs do not inhibit proliferation in CHO cells; however, inhibition of Jurkat cells post-nsPEF exposure coupled with preferential cell death in G2/M phases suggest that cell cycle phase during exposure may be an important factor in determining nsPEF toxicity in certain cell lines. Interestingly, CHO cells have a more robust and rigid cytoskeleton than Jurkat cells which is thought to contribute to their ability to

  20. Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

    2007-10-01

    Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

  1. Thermal denaturation of egg protein under nanosecond pulsed laser heating of gold nanoparticles

    SciTech Connect

    Meshalkin, Yu P; Lapin, I N; Svetlichnyi, Valery A

    2011-08-31

    Thermal denaturation of egg protein in the presence of gold nanoparticles via their heating at the plasmon resonance wavelength by the pulsed radiation of the second harmonic of an Nd:YAG laser (532 nm) is investigated. The experimental dependence of the protein denaturation time on the mean laser power is obtained. The heating temperature of the medium with gold nanoparticles is calculated. The numerical estimates of the temperature of the heated medium containing protein and gold nanoparticles (45.3 deg. C at the moment of protein denaturation) are in good agreement with the literature data on its thermal denaturation and with the data of pyrometric measurements (42.0 {+-} 1.5 deg. C). The egg protein may be successfully used to investigate the specific features of laser heating of proteins in the presence of metal nanoparticles under their excitation at the plasmon resonance wavelength. (laser methods in biology)

  2. Laser ablation in a liquid-confined environment using a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Lee, Ho; Welch, Ashley J.

    2008-04-01

    Laser ablation of aluminum metal with 1ns, 800nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.

  3. Diffuse, non-polar electropermeabilization and reduced propidium uptake distinguish the effect of nanosecond electric pulses.

    PubMed

    Semenov, Iurii; Zemlin, Christian; Pakhomova, Olga N; Xiao, Shu; Pakhomov, Andrei G

    2015-10-01

    Ca2+ activation and membrane electroporation by 10-ns and 4-ms electric pulses (nsEP and msEP) were compared in rat embryonic cardiomyocytes. The lowest electric field which triggered Ca2+ transients was expectedly higher for nsEP (36 kV/cm) than for msEP (0.09 kV/cm) but the respective doses were similar (190 and 460 mJ/g). At higher intensities, both stimuli triggered prolonged firing in quiescent cells. An increase of basal Ca2+ level by >10 nM in cells with blocked voltage-gated Ca2+ channels and depleted Ca2+ depot occurred at 63 kV/cm (nsEP) or 0.14 kV/cm (msEP) and was regarded as electroporation threshold. These electric field values were at 150-230% of stimulation thresholds for both msEP and nsEP, notwithstanding a 400,000-fold difference in pulse duration. For comparable levels of electroporative Ca2+ uptake, msEP caused at least 10-fold greater uptake of propidium than nsEP, suggesting increased yield of larger pores. Electroporation by msEP started Ca2+ entry abruptly and locally at the electrode-facing poles of cell, followed by a slow diffusion to the center. In a stark contrast, nsEP evoked a "supra-electroporation" pattern of slower but spatially uniform Ca2+ entry. Thus nsEP and msEP had comparable dose efficiency, but differed profoundly in the size and localization of electropores. PMID:26112464

  4. Efficient multiline nanosecond pulse amplification in planar waveguide CO₂ amplifier for extreme UV laser-produced plasma source.

    PubMed

    Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru; Sumitani, Akira; Endo, Akira

    2014-04-01

    In this Letter, we report on recent experimental results of a short pulse amplification at 10.6 μm wavelength required to drive a tin laser-produced plasma (LPP) extreme ultraviolet (UV) source. We report for the first time, to our best knowledge, a highly efficient pulsed amplification in a multipass amplifier built on RF-discharge-excited, diffusion-cooled CO2, planar waveguide industrial CO2 laser. About 2 kW of output average power was obtained from about 100 W input average power in ∼15  ns pulses at 100 kHz pulse repetition frequency. As much as 60% relative extraction efficiency, as compared to continuous-wave amplification in similar conditions, and 5.8% wall-plug efficiency was recorded and believed to be the highest reported so far. An improvement of extraction efficiency by ∼10% is reported when driving the amplifier with two lines of CO2 regular band in good agreement with expectations. PMID:24686647

  5. Pulse modulated high-pressure caesium discharge lamp

    NASA Astrophysics Data System (ADS)

    Gu, H.; Muzeroll, M. E.; Chamberlain, J. C.; Maya, J.

    2001-02-01

    The high-pressure caesium discharge has a favourable spectral distribution consisting of a smooth recombination continuum in the visible range. When operated on a continuous power source, the spectrum in the visible region is close to blackbody radiation; however, the lamp efficacy is restrained by the self-reversed resonance lines occurring at 825 nm and 894 nm. Pulse modulation significantly increases the core plasma temperature, suppresses the near-infrared segment of the spectrum, strongly enhances the continuous radiation in the visible region, and successfully avoids overloading (<40 W cm-2) the arc tubes. The spectrum in the visible appears to have the same shape as blackbody radiation when the lamp is operated on a multiple pulse modulated power source. The arc tube geometry, caesium/mercury compositions, and power supply waveforms were optimized for photometric performance through a series of comparison tests. The lamp efficacy increased with narrower diameter arc tubes, higher lamp currents, as well as higher current crest factors (ratio of current pulse peak to RMS current). The highest efficacy achieved for the lamp operated on the pulse modulated power supply was 46 lpw. The lamp exhibits excellent dimming characteristics and has a colour rendering index (CRI) very close to a thermal source such as a tungsten halogen lamp. This study provides a framework for the design of a new lamp/ballast system which features excellent dimming characteristics, a near-perfect CRI, an efficacy above 40 lpw, and long life. The application for this light source could be a replacement for a high-end tungsten halogen or a white high-pressure sodium lamp.

  6. Physical Mechanism of Initial Breakdown Pulses in Lightning Discharges

    NASA Astrophysics Data System (ADS)

    Da Silva, C.; Pasko, V. P.

    2014-12-01

    The initial breakdown stage of a lightning flash encompasses its first several to tens of milliseconds and it is characterized by a sequence of pulses typically detected with electric field change sensors on the ground [e.g., Villanueva et al., JGR, 99, D7, 1994]. A typical (referred to as "classical") initial breakdown pulse (IBP) has duration of tens of microseconds and it is one of the largest pulses at the beginning of a lightning flash, but a wide range of pulse durations and amplitudes also occur [e.g., Nag et al., Atmos. Res., 91, 316, 2009]. Recent results by Marshall et al. [JGR, 119, 445, 2014] suggest that IBPs should be observable in all lightning discharges. Complementarily, Stolzenburg et al. [JGR, 118, 2918, 2013] correlated individual IBPs to bursts of light that appear to be illumination of a lightning leader channel and Karunarathne et al. [JGR, 118, 7129, 2013] have determined that as a flash evolves the location of IBP sources inside the cloud coincide with the position of negative leaders as determined by a VHF lightning mapping system. In view of the above listed properties of IBPs, we have developed a new numerical model to investigate the electromagnetic signatures associated with these events and to relate them to the initial lightning leader development. The model is built on a bidirectional (zero-net-charge) lightning leader concept [e.g., Mazur and Ruhnke, JGR, 103, D18, 1998]. We simulate a finite-length finite-conductivity leader elongating in the thunderstorm electric field and we solve a set of integro-differential equations to retrieve the full dynamics of charges and currents induced in it. Our proposed approach is a generalization of the transmission-line [e.g., Nag and Rakov, JGR, 115, D20102, 2010] and electrostatic [e.g., Pasko, GRL, 41, 179, 2014] approximations used for analysis of in-cloud discharge processes. We also allow for different propagation mechanisms at the different polarity leader extremities, i.e., continuous

  7. Cellular regulation of extension and retraction of pseudopod-like blebs produced by nanosecond pulsed electric field (nsPEF)

    PubMed Central

    Rassokhin, Mikhail A.; Pakhomov, Andrei G.

    2014-01-01

    Recently we described a new phenomenon of anodotropic pseudopod-like blebbing in U937 cells exposed to nanosecond pulsed electric field (nsPEF). In Ca2+-free buffer such exposure initiates formation of pseudopod-like blebs (PLBs), protrusive cylindrical cell extensions that are distinct from apoptotic and necrotic blebs. PLBs nucleate predominantly on anode-facing cell pole and extend towards anode during nsPEF exposure. Bleb extension depends on actin polymerization and availability of actin monomers. Inhibition of intracellular Ca2+, cell contractility and RhoA produced no effect on PLB initiation. Meanwhile, inhibition of WASP by wiskostatin causes dose-dependent suppression of PLB growth. Soon after the end of nsPEF exposure PLBs lose directionality of growth and then retract. Microtubule toxins nocodazole and paclitaxel did not show immediate effect on PLBs; however, nocodazole increased mobility of intracellular components during PLB extension and retraction. Retraction of PLBs is produced by myosin activation and corresponding increase in PLB cortex contractility. Inhibition of myosin by blebbistatin reduces retraction while inhibition of RhoA-ROCK pathway by Y-27632 completely prevents retraction. Contraction of PLBs can produce cell translocation resembling active cell movement. Overall, the formation, properties, and lifecycle of PLBs share common features with protrusions associated with amoeboid cell migration. PLB lifecycle may be controlled through activation of WASP by its upstream effectors such as Cdc42 and PIP2, and main ROCK activator - RhoA. Parallels between pseudopod-like blebbing and motility blebbing may provide new insights into their underlying mechanisms. PMID:24488232

  8. Cellular regulation of extension and retraction of pseudopod-like blebs produced by nanosecond pulsed electric field (nsPEF).

    PubMed

    Rassokhin, Mikhail A; Pakhomov, Andrei G

    2014-07-01

    Recently we described a new phenomenon of anodotropic pseudopod-like blebbing in U937 cells exposed to nanosecond pulsed electric field (nsPEF). In Ca(2+)-free buffer such exposure initiates formation of pseudopod-like blebs (PLBs), protrusive cylindrical cell extensions that are distinct from apoptotic and necrotic blebs. PLBs nucleate predominantly on anode-facing cell pole and extend toward anode during nsPEF exposure. Bleb extension depends on actin polymerization and availability of actin monomers. Inhibition of intracellular Ca(2+), cell contractility, and RhoA produced no effect on PLB initiation. Meanwhile, inhibition of WASP by wiskostatin causes dose-dependent suppression of PLB growth. Soon after the end of nsPEF exposure PLBs lose directionality of growth and then retract. Microtubule toxins nocodazole and paclitaxel did not show immediate effect on PLBs; however, nocodazole increased mobility of intracellular components during PLB extension and retraction. Retraction of PLBs is produced by myosin activation and the corresponding increase in PLB cortex contractility. Inhibition of myosin by blebbistatin reduces retraction while inhibition of RhoA-ROCK pathway by Y-27632 completely prevents retraction. Contraction of PLBs can produce cell translocation resembling active cell movement. Overall, the formation, properties, and life cycle of PLBs share common features with protrusions associated with ameboid cell migration. PLB life cycle may be controlled through activation of WASP by its upstream effectors such as Cdc42 and PIP2, and main ROCK activator-RhoA. Parallels between pseudopod-like blebbing and motility blebbing may provide new insights into their underlying mechanisms. PMID:24488232

  9. Angular Distribution of Tungsten Material and Ion Flux during Nanosecond Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Hussain, M. S.; Dogar, A. H.; Qayyum, A.; Abbasi, S. A.

    2016-01-01

    Tungsten thin films were prepared by pulsed laser deposition (PLD) technique on glass substrates placed at the angles of 0∘ to 70∘ with respect to the target surface normal. Rutherford backscattering Spectrometry (RBS) analysis of the films indicated that about 90% of tungsten material flux is distributed in a cone of 40∘ solid angle while about 54% of it lies even in a narrower cone of 10∘ solid angle. Significant diffusion of tungsten in glass substrate has been observed in the films deposited at smaller angles with respect to target surface normal. Time-of-flight (TOF) measurements performed using Langmuir probe indicated that the most probable ion energy decreases from about 600 to 91eV for variation of θ from 0∘ to 70∘. In general ion energy spread is quite large at all angles investigated here. The enhanced tungsten diffusion in glass substrate observed at smaller angles is most probably due to the higher ion energy and ion assisted recoil implantation of already deposited tungsten.

  10. Computational study of nanosecond pulsed laser ablation and the application to momentum coupling

    SciTech Connect

    Yuan Hong; Tong Huifeng; Li Mu; Sun Chengwei

    2012-07-15

    During the evaporation and ablation of a matter induced by intensive laser radiation, the vapor plasma is ejected from the surface of the target which induces the recoil pressure and impulse in the target. Impulse coupling of laser beams with matter has been extensively studied as the basis of laser propulsion and laser clearing space debris. A one-dimensional (1D) bulk absorption model to simulate the solid target ablated directly by the laser beam is presented; numerical calculation of impulse acting on the target in vacuum with different laser parameters is performed with fluid dynamics theory and 1D Lagrange difference scheme. The calculated results of the impulse coupling coefficients are in good agreement with the experimental results and Phipps' empirical value. The simulated results show that the mechanical coupling coefficients decrease with the increment of laser intensity when the laser pulses generate plasma. The present model can be applied when the laser intensity is 10{sup 8} - 10{sup 10} W/cm{sup 2}, which will provide a guide to the study of momentum coupling of laser beams with matter.

  11. Mouse embryonic fibroblasts accumulate differentially on titanium surfaces treated with nanosecond laser pulses.

    PubMed

    Radmanesh, Mitra; Ektesabi, Amin M; Wyatt, Rachael A; Crawford, Bryan D; Kiani, Amirkianoosh

    2016-01-01

    Biomaterial engineering, specifically in bone implant and osseointegration, is currently facing a critical challenge regarding the response of cells to foreign objects and general biocompatibility of the materials used in the production of these implants. Using the developing technology of the laser surface treatment, this study investigates the effects of the laser repetition rate (frequency) on cell distribution across the surface of the titanium substrates. The main objective of this research is building a fundamental understanding of how cells interact with treated titanium and how different treatments affect cell accumulation. Cells respond differently to surfaces treated with different frequency lasers. The results of this research identify the influence of frequency on surface topography properties and oxidation of titanium, and their subsequent effects on the pattern of cell accumulation on its surface. Despite increased oxidation in laser-treated regions, the authors observe that fibroblast cells prefer untreated titanium to laser-treated regions, except the regions treated with 25 kHz pulses, which become preferentially colonized after 72 h. PMID:27581527

  12. Supercontinuum generation with the use of nanosecond pulses at the wavelength of 1550nm

    NASA Astrophysics Data System (ADS)

    Swiderski, Jacek; Maciejewska, Maria

    2013-01-01

    Broadband and spectrally flat supercontinuum (SC) generation in standard single-mode passive and Tm-doped fibers pumped by 1.55 μm pulses in the anomalous dispersion region is presented. Initial results on SC generation in a singlemode fluoride fiber are also presented. Using only a piece of commercially available SMF-28 as a nonlinear medium, the SC covering the spectral range from ~1.3 μm to 2.5 μm with the mean power of 1.71 W and a 5 dB spectral flatness of 640 nm is reported. When pumping a piece of Tm-doped fiber, the spectrum spreading from ~1.4 μm to 2.65 μm with its significant part located over 1.8 μm wavelength was recorded. SC generated in a fluoride fiber spread from ~0.9 μm to 3.2 μm with the average power of 0.85 W (out of which, over 0.1 W was located beyond 2.4 μm) was achieved.

  13. Pulsed corona discharge for oxidation of gaseous elemental mercury

    NASA Astrophysics Data System (ADS)

    Ko, Kyung Bo; Byun, Youngchul; Cho, Moohyun; Namkung, Won; Hamilton, Ian P.; Shin, Dong Nam; Koh, Dong Jun; Kim, Kyoung Tae

    2008-06-01

    Positive pulsed corona discharge has been applied for the oxidation of gaseous elemental mercury (Hg0) from a simulated flue gas. The oxidation of Hg0 to HgO and HgCl2 can significantly enhance the mercury removal from flue gas. At a gas condition of O2 (10%), H2O (3%), and N2 (balance), Hg0 oxidation efficiency of 84% was achieved at an input energy density of 45J /l. The presence of NO, however, hinders Hg0 oxidation due to the preferential reaction of NO with O and O3. On the contrary, SO2 shows little effect on Hg0 oxidation due to its preferential reaction with OH. It has been also observed that the HCl in gas stream can be dissociated to Cl and Cl2 and can induce additional Hg0 oxidation to HgCl2.

  14. Note: All solid-state high repetitive sub-nanosecond risetime pulse generator based on bulk gallium arsenide avalanche semiconductor switches

    NASA Astrophysics Data System (ADS)

    Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Fan, Yajun; Liu, Chunliang

    2016-08-01

    An all solid-state high repetitive sub-nanosecond risetime pulse generator featuring low-energy-triggered bulk gallium arsenide (GaAs) avalanche semiconductor switches and a step-type transmission line is presented. The step-type transmission line with two stages is charged to a potential of 5.0 kV also biasing at the switches. The bulk GaAs avalanche semiconductor switch closes within sub-nanosecond range when illuminated with approximately 87 nJ of laser energy at 905 nm in a single pulse. An asymmetric dipolar pulse with peak-to-peak amplitude of 9.6 kV and risetime of 0.65 ns is produced on a resistive load of 50 Ω. A technique that allows for repetition-rate multiplication of pulse trains experimentally demonstrated that the parallel-connected bulk GaAs avalanche semiconductor switches are triggered in sequence. The highest repetition rate is decided by recovery time of the bulk GaAs avalanche semiconductor switch, and the operating result of 100 kHz of the generator is discussed.

  15. Note: All solid-state high repetitive sub-nanosecond risetime pulse generator based on bulk gallium arsenide avalanche semiconductor switches.

    PubMed

    Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Fan, Yajun; Liu, Chunliang

    2016-08-01

    An all solid-state high repetitive sub-nanosecond risetime pulse generator featuring low-energy-triggered bulk gallium arsenide (GaAs) avalanche semiconductor switches and a step-type transmission line is presented. The step-type transmission line with two stages is charged to a potential of 5.0 kV also biasing at the switches. The bulk GaAs avalanche semiconductor switch closes within sub-nanosecond range when illuminated with approximately 87 nJ of laser energy at 905 nm in a single pulse. An asymmetric dipolar pulse with peak-to-peak amplitude of 9.6 kV and risetime of 0.65 ns is produced on a resistive load of 50 Ω. A technique that allows for repetition-rate multiplication of pulse trains experimentally demonstrated that the parallel-connected bulk GaAs avalanche semiconductor switches are triggered in sequence. The highest repetition rate is decided by recovery time of the bulk GaAs avalanche semiconductor switch, and the operating result of 100 kHz of the generator is discussed. PMID:27587178

  16. Nanosecond pulsed electric fields (nsPEFs) low cost generator design using power MOSFET and Cockcroft-Walton multiplier circuit as high voltage DC source

    NASA Astrophysics Data System (ADS)

    Sulaeman, M. Y.; Widita, R.

    2014-09-01

    Purpose: Non-ionizing radiation therapy for cancer using pulsed electric field with high intensity field has become an interesting field new research topic. A new method using nanosecond pulsed electric fields (nsPEFs) offers a novel means to treat cancer. Not like the conventional electroporation, nsPEFs able to create nanopores in all membranes of the cell, including membrane in cell organelles, like mitochondria and nucleus. NsPEFs will promote cell death in several cell types, including cancer cell by apoptosis mechanism. NsPEFs will use pulse with intensity of electric field higher than conventional electroporation, between 20-100 kV/cm and with shorter duration of pulse than conventional electroporation. NsPEFs requires a generator to produce high voltage pulse and to achieve high intensity electric field with proper pulse width. However, manufacturing cost for creating generator that generates a high voltage with short duration for nsPEFs purposes is highly expensive. Hence, the aim of this research is to obtain the low cost generator design that is able to produce a high voltage pulse with nanosecond width and will be used for nsPEFs purposes. Method: Cockcroft-Walton multiplier circuit will boost the input of 220 volt AC into high voltage DC around 1500 volt and it will be combined by a series of power MOSFET as a fast switch to obtain a high voltage with nanosecond pulse width. The motivation using Cockcroft-Walton multiplier is to acquire a low-cost high voltage DC generator; it will use capacitors and diodes arranged like a step. Power MOSFET connected in series is used as voltage divider to share the high voltage in order not to damage them. Results: This design is expected to acquire a low-cost generator that can achieve the high voltage pulse in amount of -1.5 kV with falltime 3 ns and risetime 15 ns into a 50Ω load that will be used for nsPEFs purposes. Further detailed on the circuit design will be explained at presentation.

  17. Nanosecond pulsed electric fields (nsPEFs) low cost generator design using power MOSFET and Cockcroft-Walton multiplier circuit as high voltage DC source

    SciTech Connect

    Sulaeman, M. Y.; Widita, R.

    2014-09-30

    Purpose: Non-ionizing radiation therapy for cancer using pulsed electric field with high intensity field has become an interesting field new research topic. A new method using nanosecond pulsed electric fields (nsPEFs) offers a novel means to treat cancer. Not like the conventional electroporation, nsPEFs able to create nanopores in all membranes of the cell, including membrane in cell organelles, like mitochondria and nucleus. NsPEFs will promote cell death in several cell types, including cancer cell by apoptosis mechanism. NsPEFs will use pulse with intensity of electric field higher than conventional electroporation, between 20–100 kV/cm and with shorter duration of pulse than conventional electroporation. NsPEFs requires a generator to produce high voltage pulse and to achieve high intensity electric field with proper pulse width. However, manufacturing cost for creating generator that generates a high voltage with short duration for nsPEFs purposes is highly expensive. Hence, the aim of this research is to obtain the low cost generator design that is able to produce a high voltage pulse with nanosecond width and will be used for nsPEFs purposes. Method: Cockcroft-Walton multiplier circuit will boost the input of 220 volt AC into high voltage DC around 1500 volt and it will be combined by a series of power MOSFET as a fast switch to obtain a high voltage with nanosecond pulse width. The motivation using Cockcroft-Walton multiplier is to acquire a low-cost high voltage DC generator; it will use capacitors and diodes arranged like a step. Power MOSFET connected in series is used as voltage divider to share the high voltage in order not to damage them. Results: This design is expected to acquire a low-cost generator that can achieve the high voltage pulse in amount of −1.5 kV with falltime 3 ns and risetime 15 ns into a 50Ω load that will be used for nsPEFs purposes. Further detailed on the circuit design will be explained at presentation.

  18. Numerical investigation of the discharge characteristics of the pulsed discharge nozzle

    NASA Astrophysics Data System (ADS)

    Broks, B. H. P.; Brok, W. J. M.; Remy, J.; van der Mullen, J. J. A. M.; Benidar, A.; Biennier, L.; Salama, F.

    2005-03-01

    The characteristics of the plasma generated by a pulsed discharge slit nozzle (PDN) are investigated. The PDN source is designed to produce and cool molecular ions creating an astrophysically relevant environment in the laboratory. A discharge model is applied to this system to provide a qualitative as well as a quantitative picture of the plasma. We find that the plasma’s properties and behavior are characteristic of those of a glow discharge. We model the electron density and energy, as well as the argon ion and metastable atom number density. The results reveal a high abundance of metastable argon atoms in the expansion region, which is more than one order of magnitude higher than the abundance of electrons and ions. These findings confirm experimental observations, which concluded that large molecular ions are dominantly formed through Penning ionization of the neutral molecular precursors seeded in the supersonic expansion of argon gas. The simulations presented here will help optimize the yield of formation of molecular ions and radicals in the PDN source; they will also provide key physical insight into the characteristics of interstellar molecules and ions analogs in laboratory experiments.

  19. Repetitively pulsed atmospheric pressure discharge treatment of rough polymer surfaces: I. Humid air discharges

    NASA Astrophysics Data System (ADS)

    Bhoj, Ananth N.; Kushner, Mark J.

    2008-08-01

    Plasmas generated at atmospheric pressure are used to functionalize the surfaces of polymers by creating new surface-resident chemical groups. The polymers used in textiles and biomedical applications often have non-planar surfaces whose functionalization requires penetration of plasma generated species into sometimes complex surface features. In this regard, the atmospheric pressure plasma treatment of a rough polypropylene surface was computationally investigated using a two-dimensional plasma hydrodynamics model integrated with a surface kinetics model. Repetitively pulsed discharges produced in a dielectric barrier-corona configuration in humid air were considered to affix O. Macroscopic non-uniformities in treatment result from the spatial variations in radical densities which depend on the polarity of the discharge. Microscopic non-uniformities arise due to the higher reactivity of plasma produced species, such as OH radicals, which are consumed before they can diffuse deeper into surface features. The consequences of applied voltage magnitude and polarity, and the relative humidity on discharge dynamics and radical generation leading to surface functionalization, are discussed.

  20. Pulsed corona discharge oxidation of aqueous carbamazepine micropollutant.

    PubMed

    Ajo, Petri; Krzymyk, Ewelina; Preis, Sergei; Kornev, Iakov; Kronberg, Leif; Louhi-Kultanen, Marjatta

    2016-08-01

    The anti-epileptic drug carbamazepine (CBZ) receives growing attention due to slow biodegradation and inherent accumulation in the aquatic environment. The application of a gas-phase pulsed corona discharge (PCD) was investigated to remove CBZ from synthetic solutions and spiked wastewater effluent from a municipal wastewater treatment facility. The treated water was showered between high voltage (HV) wires and grounded plate electrodes, to which ultra-short HV pulses were applied. CBZ was readily oxidized and 1-(2-benzaldehyde)-4-hydroquinazoline-2-one (BQM) and 1-(2-benzaldehyde)-4-hydro-quinazoline-2,4-dione (BQD) were identified as the most abundant primary transformation products, which, contrary to CBZ ozonation data available in the literature, were further easily oxidized with PCD: BQM and BQD attributed to only a minor portion of the target compound oxidized. In concentrations commonly found in wastewater treatment plant effluents (around 5 µg L(-1)), up to 97% reduction in CBZ concentration was achieved at mere 0.3 kW h m(-3) energy consumption, and over 99.9% was removed at 1 kW h m(-3). The PCD application proved to be efficient in the removal of both the parent substance and its known transformation products, even with the competing reactions in the complex composition of wastewater. PMID:26758812