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Sample records for bipolar pulse generator

  1. Bipolar high voltage pulse power generator

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Člupek, Martin; Babický, Václav; Šunka, Pavel

    Monterey, 2005, s. 44. [IEEE International Pulsed Power Conference/15th./. Portola Plaza Hotel, Monterey, CA, USA (US), 13.06.2005-17.06.2005] R&D Projects: GA AV ČR KSK2043105 Keywords : bipolar * pulse power generator * corona discharge Subject RIV: BL - Plasma and Gas Discharge Physics

  2. Bipolar high voltage pulse power generator

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Člupek, Martin; Babický, Václav; Šunka, Pavel

    Monterey : IEEE, 2007 - (Maenchen, J.; Schamiloglu, E.), s. 1061-1064 ISBN 0-7803-9190-X. [IEEE International Pulsed Power Conference/15th./. Portola Plaza Hotel, Monterey (US), 13.06.2005-17.06.2005] R&D Projects: GA AV ČR KSK2043105 Institutional research plan: CEZ:AV0Z20430508 Keywords : bipolar * pulse power generator * corona discharge Subject RIV: BL - Plasma and Gas Discharge Physics

  3. Generation of short electrical pulses based on bipolar transistorsny

    Directory of Open Access Journals (Sweden)

    M. Gerding

    2004-01-01

    Full Text Available A system for the generation of short electrical pulses based on the minority carrier charge storage and the step recovery effect of bipolar transistors is presented. Electrical pulses of about 90 ps up to 800 ps duration are generated with a maximum amplitude of approximately 7V at 50Ω. The bipolar transistor is driven into saturation and the base-collector and base-emitter junctions become forward biased. The resulting fast switch-off edge of the transistor’s output signal is the basis for the pulse generation. The fast switching of the transistor occurs as a result of the minority carriers that have been injected and stored across the base-collector junction under forward bias conditions. If the saturated transistor is suddenly reverse biased the pn-junction will appear as a low impedance until the stored charge is depleted. Then the impedance will suddenly increase to its normal high value and the flow of current through the junction will turn to zero, abruptly. A differentiation of the output signal of the transistor results in two short pulses with opposite polarities. The differentiating circuit is implemented by a transmission line network, which mainly acts as a high pass filter. Both the transistor technology (pnp or npn and the phase of the transfer function of the differentating circuit influence the polarity of the output pulses. The pulse duration depends on the transistor parameters as well as on the transfer function of the pulse shaping network. This way of generating short electrical pulses is a new alternative for conventional comb generators based on steprecovery diodes (SRD. Due to the three-terminal structure of the transistor the isolation problem between the input and the output signal of the transistor network is drastically simplified. Furthermore the transistor is an active element in contrast to a SRD, so that its current gain can be used to minimize the power of the driving signal.

  4. Nine Channel Mid-Power Bipolar Pulse Generator Based on a Field Programmable Gate Array

    OpenAIRE

    Haylock, Ben; Lenzini, Francesco; Kasture, Sachin; Fisher, Paul; Streed, Erik W.; Lobino, Mirko

    2016-01-01

    Many channel arbitrary pulse sequence generation is required for the electro-optic reconfiguration of optical waveguide networks in Lithium Niobate. Here we describe a scalable solution to the requirement for mid-power bipolar parallel outputs, based on pulse patterns generated by an externally clocked field programmable gate array (FPGA). Positive and negative pulses can be generated at repetition rates from up to 80~MHz with pulse width adjustable in increments of 1.6~ns across nine indepen...

  5. Characteristics of pulsed heavy ion beam generated in bipolar pulse accelerator

    International Nuclear Information System (INIS)

    We have developed a new type of a pulsed ion beam accelerator named 'bipolar pulse accelerator' for improvement of the purity of the intense pulsed ion beam. The system utilizes a magnetically insulated accelerate on gap and was operated with the bipolar pulse. A coaxial gas puff plasma gun was used as an ion source, which was placed inside of the grounded anode. Source plasma (nitrogen) of current density of ≈30 A/cm2 and pulse duration of ≈1.0 μs was injected into the acceleration gap. When the bipolar pulse of -114 kV, 70 ns (1st pulse) and 85 kV, 62 ns (2nd pulse) was applied to the drift tube, the ions were successfully accelerated from the grounded anode to the drift tube in the 1st gap by the negative pulse of the bipolar pulse. The pulsed ion beam with current density of 60 A/cm2 and pulse duration of ≈50 ns was obtained at 48 mm downstream from the anode surface. The energy spectrum of the ion beam was evaluated by a magnetic energy spectrometer. The ion energy was in reasonable good agreement with the acceleration voltage, i.e., 1st pulse (negative pulse) voltage of the bipolar pulse. (author)

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

    Science.gov (United States)

    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.

  7. Nine Channel Mid-Power Bipolar Pulse Generator Based on a Field Programmable Gate Array

    CERN Document Server

    Haylock, Ben; Kasture, Sachin; Fisher, Paul; Streed, Erik W; Lobino, Mirko

    2016-01-01

    Many channel arbitrary pulse sequence generation is required for the electro-optic reconfiguration of optical waveguide networks in Lithium Niobate. Here we describe a scalable solution to the requirement for mid-power bipolar parallel outputs, based on pulse patterns generated by an externally clocked field programmable gate array (FPGA). Positive and negative pulses can be generated at repetition rates from up to 80~MHz with pulse width adjustable in increments of 1.6~ns across nine independent outputs. Each channel can provide 1.5W of RF power and it can be synchronised with the operation of other components in an optical network such as light sources and detectors through an external clock with adjustable delay.

  8. Numerical simulation of narrow bipolar electromagnetic pulses generated by thunderstorm discharges

    International Nuclear Information System (INIS)

    Using the concept of avalanche relativistic runaway electrons (REs), we perform numerical simulations of compact intracloud discharge (CID) as a generator of powerful natural electromagnetic pulses (EMPs) in the HF-VHF range, called narrow bipolar pulses (NBPs). For several values of the field overvoltage and altitude at which the discharge develops, the numbers of seed electrons initiating the avalanche are evaluated, with which the calculated EMP characteristics are consistent with the measured NBP parameters. We note shortcomings in the hypothesis assuming participation of cosmic ray air showers in avalanche initiation. The discharge capable of generating NBPs produces REs in numbers close to those in the source of terrestrial γ-ray flashes (TGFs), which can be an argument in favor of a unified NBP and TGF source

  9. Numerical simulation of narrow bipolar electromagnetic pulses generated by thunderstorm discharges

    Science.gov (United States)

    Bochkov, E. I.; Babich, L. P.; Kutsyk, I. M.

    2013-07-01

    Using the concept of avalanche relativistic runaway electrons (REs), we perform numerical simulations of compact intracloud discharge (CID) as a generator of powerful natural electromagnetic pulses (EMPs) in the HF-VHF range, called narrow bipolar pulses (NBPs). For several values of the field overvoltage and altitude at which the discharge develops, the numbers of seed electrons initiating the avalanche are evaluated, with which the calculated EMP characteristics are consistent with the measured NBP parameters. We note shortcomings in the hypothesis assuming participation of cosmic ray air showers in avalanche initiation. The discharge capable of generating NBPs produces REs in numbers close to those in the source of terrestrial γ-ray flashes (TGFs), which can be an argument in favor of a unified NBP and TGF source.

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

    Science.gov (United States)

    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).

  11. Bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A.

    2008-10-21

    A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  12. Development of bipolar pulse accelerator for high-purity intense pulsed ion beam

    International Nuclear Information System (INIS)

    In order to improve the purity of the intense pulsed ion beam, a new type of a pulsed ion beam accelerator named “bipolar pulse accelerator” has been proposed. A double coaxial type bipolar pulse generator was developed as the power supply of the bipolar pulse accelerator. By applying the bipolar pulse with voltage of about ±100 kV and pulse duration of about 70 ns to the drift tube of the bipolar pulse accelerator, the ion beam was successfully accelerated from the grounded anode to the drift tube in the 1st gap by the negative pulse of the bipolar pulse and the pulsed ion beam with current density of 40 A/cm2 and pulse duration of 30 ns was obtained at 50 mm downstream from the anode surface. In addition, part of the ion beam was again accelerated toward the grounded cathode in the 2nd gap by the positive pulse of the bipolar pulse. The pulsed ion beam with the peak ion current density of 2 A/cm2 and the beam pulse duration of 30 ns was obtained at 25 mm downstream from the cathode surface, which suggests the bipolar pulse acceleration. (author)

  13. Unsplit bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A.

    2011-05-24

    A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  14. PSPICE simulation of bipolar pulse converter based on short-circuited coaxial transmission line

    International Nuclear Information System (INIS)

    The operating principle of the bipolar pulse converter based on short-circuited coaxial transmission line type is given. The output bipolar pulses are simulated by using PSPICE program on condition of different electric length and different impedance of the short-circuited coaxial transmission line. The bipolar pulses are generated by using unipolar pulse with pulse width of 2 ns in experiment, the experimental result fit well with the simulation result. (authors)

  15. Electrostatic Changes Observed with Narrow Bipolar Pulses

    Science.gov (United States)

    Karunarathne, S.; Marshall, T. C.; Stolzenburg, M.; Karunarathna, N.

    2015-12-01

    Narrow bipolar pulses (NBPs) or compact intracloud discharges are impulsive discharges that are considered to be the strongest natural emitters in the HF radio band; they usually occur at high altitudes in some thunderstorms. In the summer of 2011, we collected E-change data with wideband flat-plate antennas (0.16 Hz - 2.5 MHz) at ten stations covering an area of nearly 70 km x 100 km in and around Kennedy Space Center, Florida, USA. On one thunderstorm day, 14 August 2011, we detected 226 positive NBPs, and some observations of these pulses were published in Karunarathne et al. [2015, JGR-atmospheres]. Of these 226 NBPs, 50 (22.1 %) occurred within 10 km horizontally of at least one sensor. All of these closer sensors show electrostatic changes associated with corresponding NBPs, with a net electrostatic change in the main bipolar pulse and with a slower electrostatic change after the bipolar pulse that seems similar to short continuing current immediately after some cloud-to-ground return strokes. Although NBPs have been considered as short duration pulses (10 - 20 microseconds), the electrostatic changes after the main bipolar pulse ranged from 0.7 ms to 34 ms and associated charge moments were calculated. The total duration of the electrostatic E-change was strongly dependent on the distance to the sensors. In this presentation, we will present data for these electrostatic changes, some statistics, and physical background and reasoning for the electrostatic changes.

  16. Current Propagation in Narrow Bipolar Pulses

    Science.gov (United States)

    Watson, S. S.; Marshall, T. C.

    2005-12-01

    We model the observed electric fields of a particular narrow bipolar pulse (NBP) published in Eack [2004]. We assume an exponential growth of current carriers due to a runaway breakdown avalanche and show that this leads to a corresponding increase in current. With specific input values for discharge altitude, length, current, and propagation velocity, the model does a good job of reproducing the observed near and far electric field. The ability of the model to reproduce the observed electric fields is an indication that our assumptions concerning the runaway avalanche may be correct, and this indication is further strengthened by the inability of the simple transmission line model to reproduce simultaneously both the near and far electric fields. Eack, K. B. (2004), Electrical characteristics of narrow bipolar events, Geophys. Res. Lett., 31, L20102, doi:10.1029/2004/GL021117.

  17. Flyback Topology TEM Bipolar Pulse Transmitter

    Directory of Open Access Journals (Sweden)

    Guo-fu Wang

    2013-09-01

    Full Text Available In the fields of transient electromagnetic (TEM geophysical exploration, it is necessary to create a bipolar pulse current source with decline edge of high linearity, short turn-off time and high stability. In order to improve detection equipment’s practicality, it’s urgently needed to miniaturize and improve the reliability of the detection equipment. In this paper, a clamp and prompt drop bipolar pulse current circuit based on Flyback topology is represented, which can accelerate the decline of load current by clamping the coil load with fixed high voltage in the period of current declining. Also, because of this circuit’s low power consumption and significantly improvement of the transmitter’s energy utilization, chassis’s cooling equipment can be greatly reduced and it’s easier to miniaturize the transmitter. To start with, the principle of this circuit is represented. Then, the method is given to select the optimal values of circuit’s components. Finally, the results of simulation proves the proposed circuit meeting the requirements much better than those reported, with shorter turn-off time, higher linearity, less energy consumption. In general, this circuit has been successfully applied to a new type of detection equipment.

  18. Inductive Pulse Generation

    OpenAIRE

    Lindblom, Adam

    2006-01-01

    Pulsed power generators are a key component in compact systems for generation of high-power microwaves (HPM). HPM generation by virtual cathode devices such as Vircators put high demands on the source. The rise time and the pulse length of the source voltage are two key issues in the generation of HPM radiation. This thesis describes the construction and tests of several inductive high power pulse generators. The pulse generators were designed with the intent to deliver a pulse with fast rise...

  19. Improvement in the statistical operation of a Blumlein pulse forming line in bipolar pulse mode

    International Nuclear Information System (INIS)

    The paper presents the results of studies on shot-to-shot performance of a water Blumlein pulse forming line of 1–1.2 kJ of stored energy. The experiments were carried using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (150 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. The analysis was carried out for two cases when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. It was found that in bipolar pulse mode the shot-to-shot variation in breakdown voltage of a preliminary spark gap is small, the standard deviation (1σ) does not exceed 2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar-pulse and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we changed the regime of its operation from a self-triggered mode to an externally triggered mode. In the new arrangement the first voltage pulse at the output of Blumlein was used to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a good stability of breakdown voltage and thus allowed to stabilize the duration of the first pulse. The standard deviation of the breakdown voltage and duration of the first pulse did not exceed 2% for a set of 50 pulses. The externally triggered mode of the main gap operation also allowed for a decrease in the charging voltage of the Blumlein to a 0.9–0.95 of self-breakdown voltage of the main spark gap while the energy stored in Marx generator was decreased from 4 kJ to 2.5 kJ. At the same time the energy stored in Blumlein remained the same

  20. A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications

    OpenAIRE

    Xinfan Xia; Lihua Liu; Shengbo Ye; Hongfei Guan; Guangyou Fang

    2014-01-01

    A novel ultra-wideband (UWB) monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs) and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step ...

  1. Characteristics of narrow bipolar pulses observed in Malaysia

    Science.gov (United States)

    Azlinda Ahmad, Noor; Fernando, M.; Baharudin, Z. A.; Cooray, V.; Ahmad, H.; Abdul Malek, Z.

    2010-04-01

    Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6±17.1 [mu]s, while 30.2±12.3 [mu]s was observed for NPBPs. The mean full-width at half-maximum (FWHM) was 2.2±0.7 and 2.4±1.4 [mu]s for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it.

  2. Lower switch rate in depressed patients with bipolar II than bipolar I disorder treated adjunctively with second-generation antidepressants

    NARCIS (Netherlands)

    Altshuler, LL; Suppes, T; Nolen, WA; Leverich, G; Keck, PE; Frye, MA; Kupka, R; McElroy, SL; Grunze, H; Kitchen, CMR; Post, R; Black, D.O.

    2006-01-01

    Objectives: The authors compared the switch rate into hypomania/mania in depressed patients treated with second-generation antidepressants who had either bipolar I or bipolar II disorder. Method: In a 10-week trial, 184 outpatients with bipolar depression (134 with bipolar I disorder, 48 with bipola

  3. Short pulse neutron generator

    Energy Technology Data Exchange (ETDEWEB)

    Elizondo-Decanini, Juan M.

    2016-08-02

    Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and the switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.

  4. Mitigation of impedance changes due to electroporation therapy using bursts of high-frequency bipolar pulses

    Science.gov (United States)

    2015-01-01

    Background For electroporation-based therapies, accurate modeling of the electric field distribution within the target tissue is important for predicting the treatment volume. In response to conventional, unipolar pulses, the electrical impedance of a tissue varies as a function of the local electric field, leading to a redistribution of the field. These dynamic impedance changes, which depend on the tissue type and the applied electric field, need to be quantified a priori, making mathematical modeling complicated. Here, it is shown that the impedance changes during high-frequency, bipolar electroporation therapy are reduced, and the electric field distribution can be approximated using the analytical solution to Laplace's equation that is valid for a homogeneous medium of constant conductivity. Methods Two methods were used to examine the agreement between the analytical solution to Laplace's equation and the electric fields generated by 100 µs unipolar pulses and bursts of 1 µs bipolar pulses. First, pulses were applied to potato tuber tissue while an infrared camera was used to monitor the temperature distribution in real-time as a corollary to the electric field distribution. The analytical solution was overlaid on the thermal images for a qualitative assessment of the electric fields. Second, potato ablations were performed and the lesion size was measured along the x- and y-axes. These values were compared to the analytical solution to quantify its ability to predict treatment outcomes. To analyze the dynamic impedance changes due to electroporation at different frequencies, electrical impedance measurements (1 Hz to 1 MHz) were made before and after the treatment of potato tissue. Results For high-frequency bipolar burst treatment, the thermal images closely mirrored the constant electric field contours. The potato tissue lesions differed from the analytical solution by 39.7 ± 1.3 % (x-axis) and 6.87 ± 6.26 % (y-axis) for conventional unipolar pulses

  5. Bursts of Bipolar Microsecond Pulses Inhibit Tumor Growth

    Science.gov (United States)

    Sano, Michael B.; Arena, Christopher B.; Bittleman, Katelyn R.; Dewitt, Matthew R.; Cho, Hyung J.; Szot, Christopher S.; Saur, Dieter; Cissell, James M.; Robertson, John; Lee, Yong W.; Davalos, Rafael V.

    2015-10-01

    Irreversible electroporation (IRE) is an emerging focal therapy which is demonstrating utility in the treatment of unresectable tumors where thermal ablation techniques are contraindicated. IRE uses ultra-short duration, high-intensity monopolar pulsed electric fields to permanently disrupt cell membranes within a well-defined volume. Though preliminary clinical results for IRE are promising, implementing IRE can be challenging due to the heterogeneous nature of tumor tissue and the unintended induction of muscle contractions. High-frequency IRE (H-FIRE), a new treatment modality which replaces the monopolar IRE pulses with a burst of bipolar pulses, has the potential to resolve these clinical challenges. We explored the pulse-duration space between 250 ns and 100 μs and determined the lethal electric field intensity for specific H-FIRE protocols using a 3D tumor mimic. Murine tumors were exposed to 120 bursts, each energized for 100 μs, containing individual pulses 1, 2, or 5 μs in duration. Tumor growth was significantly inhibited and all protocols were able to achieve complete regressions. The H-FIRE protocol substantially reduces muscle contractions and the therapy can be delivered without the need for a neuromuscular blockade. This work shows the potential for H-FIRE to be used as a focal therapy and merits its investigation in larger pre-clinical models.

  6. Powerful nanosecond pulse train generator

    International Nuclear Information System (INIS)

    A generator permitting to shape on the load pulsed with the repetition frequency of 103-106 Hz and more is described. The amplitude of shaped voltage pulses is up to 150 kV at pulse duration equal to 50 ns. The generator comprises connected in-series with the load two shaping and two transmission lines realized on the base of the KVI-300 low-ohmic cable. The shaping lines are supplied from two independently connected pulse voltage generators for obtaining time interval between pulses > 10-6 s; they may be also supplied from one generator for obtaining time interval -6 s. At the expense of reducing losses in the discharge circuit the amplitude of the second pulse grows with increase of time interval between pulses up to 300 ns, further on the curve flat-topping exists. The described generator is used in high-current accelerators, in which the primary negative pulse results in generation of explosive-emission plasma, and the second positive pulse provides ion beam shaping including ions of heavy metal used for production of a potential electrode. The generator multipulse mode is used for successive ion acceleration in the transport system

  7. Assembly delay line pulse generators

    CERN Multimedia

    1971-01-01

    Assembly of six of the ten delay line pulse generators that will power the ten kicker magnet modules. One modulator part contains two pulse generators. Capacitors, inductances, and voltage dividers are in the oil tank on the left. Triggered high-pressure spark gap switches are on the platforms on the right. High voltage pulse cables to the kicker magnet emerge under the spark gaps. In the centre background are the assembled master gaps.

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

    Science.gov (United States)

    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.

  9. Coiled transmission line pulse generators

    Science.gov (United States)

    McDonald, Kenneth Fox

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  10. Electro-Optical Modulator Bias Control Using Bipolar Pulses

    Science.gov (United States)

    Farr, William; Kovalik, Joseph

    2007-01-01

    An improved method has been devised for controlling the DC bias applied to an electro-optical crystal that is part of a Mach-Zehnder modulator that generates low-duty-cycle optical pulses for a pulse-position modulation (PPM) optical data-communication system. In such a system, it is desirable to minimize the transmission of light during the intervals between pulses, and for this purpose, it is necessary to maximize the extinction ratio of the modulator (the ratio between the power transmitted during an "on" period and the power transmitted during an "off" period). The present method is related to prior dither error feedback methods, but unlike in those methods, there is no need for an auxiliary modulation subsystem to generate a dithering signal. Instead, as described below, dither is effected through alternation of the polarity of the modulation signal. The upper part of Figure 1 schematically depicts a Mach-Zehnder modulator. The signal applied to the electro-optical crystal consists of a radio-frequency modulating pulse signal, VRF, superimposed on a DC bias Vbias. Maximum extinction occurs during the off (VRF = 0) period if Vbias is set at a value that makes the two optical paths differ by an odd integer multiple of a half wavelength so that the beams traveling along the two paths interfere destructively at the output beam splitter. Assuming that the modulating pulse signal VRF has a rectangular waveform, maximum transmission occurs during the "on" period if the amplitude of VRF is set to a value, V , that shifts the length of the affected optical path by a half wavelength so that now the two beams interfere constructively at the output beam splitter. The modulating pulse signal is AC-coupled from an amplifier to the electro-optical crystal. Sometimes, two successive pulses occur so close in time that the operating point of the amplifier drifts, one result being that there is not enough time for the signal level to return to ground between pulses. Also, the

  11. A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications

    Directory of Open Access Journals (Sweden)

    Xinfan Xia

    2014-01-01

    Full Text Available A novel ultra-wideband (UWB monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step recovery diode (SRD effectively to produce a negative narrow pulse. At last, the monocycle pulse forming circuit utilizes a novel inductance L short-circuited stub to generate the monocycle pulse directly. Measurement results show that the waveform of the generated monocycle pulses is over 76 V in peak-to-peak amplitude and 3.2 ns in pulse full-width. These characteristics of the monocycle pulse are advantageous for obtaining long detection range and high resolution, when it is applied to ultra-wideband radar applications.

  12. Computer modeling of electrical and thermal performance during bipolar pulsed radiofrequency for pain relief

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, Juan J. [Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universitat Politècnica de València, Valencia 46022 (Spain); Pérez-Cajaraville, Juan J. [Pain Unit and Department of Anesthesia and Critical Care, Clínica Universidad de Navarra, University of Navarra, Pamplona 31008 (Spain); Muñoz, Víctor [Neurotherm Spain, Barcelona 08303 (Spain); Berjano, Enrique, E-mail: eberjano@eln.upv.es [Biomedical Synergy, Electronic Engineering Department, Universitat Politècnica de València 46022 (Spain)

    2014-07-15

    Purpose: Pulsed RF (PRF) is a nonablative technique for treating neuropathic pain. Bipolar PRF application is currently aimed at creating a “strip lesion” to connect the electrode tips; however, the electrical and thermal performance during bipolar PRF is currently unknown. The objective of this paper was to study the temperature and electric field distributions during bipolar PRF. Methods: The authors developed computer models to study temperature and electric field distributions during bipolar PRF and to assess the possible ablative thermal effect caused by the accumulated temperature spikes, along with any possible electroporation effects caused by the electrical field. The authors also modeled the bipolar ablative mode, known as bipolar Continuous Radiofrequency (CRF), in order to compare both techniques. Results: There were important differences between CRF and PRF in terms of electrical and thermal performance. In bipolar CRF: (1) the initial temperature of the tissue impacts on temperature progress and hence on the thermal lesion dimension; and (2) at 37 °C, 6-min of bipolar CRF creates a strip thermal lesion between the electrodes when these are separated by a distance of up to 20 mm. In bipolar PRF: (1) an interelectrode distance shorter than 5 mm produces thermal damage (i.e., ablative effect) in the intervening tissue after 6 min of bipolar RF; and (2) the possible electroporation effect (electric fields higher than 150 kV m{sup −1}) would be exclusively circumscribed to a very small zone of tissue around the electrode tip. Conclusions: The results suggest that (1) the clinical parameters considered to be suitable for bipolar CRF should not necessarily be considered valid for bipolar PRF, and vice versa; and (2) the ablative effect of the CRF mode is mainly due to its much greater level of delivered energy than is the case in PRF, and therefore at same applied energy levels, CRF, and PRF are expected to result in same outcomes in terms of

  13. Computer modeling of electrical and thermal performance during bipolar pulsed radiofrequency for pain relief

    International Nuclear Information System (INIS)

    Purpose: Pulsed RF (PRF) is a nonablative technique for treating neuropathic pain. Bipolar PRF application is currently aimed at creating a “strip lesion” to connect the electrode tips; however, the electrical and thermal performance during bipolar PRF is currently unknown. The objective of this paper was to study the temperature and electric field distributions during bipolar PRF. Methods: The authors developed computer models to study temperature and electric field distributions during bipolar PRF and to assess the possible ablative thermal effect caused by the accumulated temperature spikes, along with any possible electroporation effects caused by the electrical field. The authors also modeled the bipolar ablative mode, known as bipolar Continuous Radiofrequency (CRF), in order to compare both techniques. Results: There were important differences between CRF and PRF in terms of electrical and thermal performance. In bipolar CRF: (1) the initial temperature of the tissue impacts on temperature progress and hence on the thermal lesion dimension; and (2) at 37 °C, 6-min of bipolar CRF creates a strip thermal lesion between the electrodes when these are separated by a distance of up to 20 mm. In bipolar PRF: (1) an interelectrode distance shorter than 5 mm produces thermal damage (i.e., ablative effect) in the intervening tissue after 6 min of bipolar RF; and (2) the possible electroporation effect (electric fields higher than 150 kV m−1) would be exclusively circumscribed to a very small zone of tissue around the electrode tip. Conclusions: The results suggest that (1) the clinical parameters considered to be suitable for bipolar CRF should not necessarily be considered valid for bipolar PRF, and vice versa; and (2) the ablative effect of the CRF mode is mainly due to its much greater level of delivered energy than is the case in PRF, and therefore at same applied energy levels, CRF, and PRF are expected to result in same outcomes in terms of thermal

  14. Powerful microsecond voltage pulse generator

    International Nuclear Information System (INIS)

    A microsecond voltage pulse generator, designed for investigations of high-power electron and ion beams generation in diode systems connected in parallel into a circuit with an inductive storage and plasma-erosion switch, is described. The generator consists of eight parallel pulsed voltage generators with 12 stages in each, assembled according to the Arkadiev-Marx scheme with two capacitors in each stage. The generator total energy at charged voltage of 80kV is 250 kJ. The main generator parameters are the following: the proper inductance is ≅0.7μH, wave resistance is ≅1.140hm, oscillation period is ≅3.83μs, attenuation is ≅105s-1. The results of the first experiments on generation of a microsecond high-current relativistic electron beam in a coaxial magnetically insulated diode are described

  15. Pulsed neutron generator for logging

    International Nuclear Information System (INIS)

    A pulsed neutron generator for uranium logging is described. This generator is one component of a prototype uranium logging probe which is being developed by SLA to detect, and assay, uranium by borehole logging. The logging method is based on the measurement of epithermal neutrons resulting from the prompt fissioning of uranium from a pulsed source of 17.6 MeV neutrons. An objective of the prototype probe was that its diameter not exceed 2.75 inches, which would allow its use in conventional rotary drill holes of 4.75-inch diameter. This restriction limited the generator to a maximum 2.375-inch diameter. The performance requirements for the neutron generator specified that it operate with a nominal output of 5 x 106 neutrons/pulse at up to 100 pulses/second for a one-hour period. The development of a neutron generator meeting the preliminary design goals was completed and two prototype models were delivered to SLA. These two generators have been used by SLA to log a number of boreholes in field evaluation of the probe. The results of the field evaluations have led to the recommendation of several changes to improve the probe's operation. Some of these changes will require additional development effort on the neutron generator. It is expected that this work will be performed during 1977. The design and operation of the first prototype neutron generators is described

  16. The pulsed microwave damage trend of a bipolar transistor as a function of pulse parameters

    Institute of Scientific and Technical Information of China (English)

    Ma Zhen-Yang; Chai Chang-Chun; Ren Xing-Rong; Yang Yin-Tang; Zhao Ying-Bo; Qiao Li-Ping

    2013-01-01

    In the present paper we conduct a theoretical study of the thermal accumulation effect of a typical bipolar transistor caused by high power pulsed microwaves (HPMs),and investigate the thermal accumulation effect as a function of pulse repetition frequency (PRF) and duty cycle.A study of the damage mechanism of the device is carried out from the variation analysis of the distribution of the electric field and the current density.The result shows that the accumulation temperature increases with PRF increasing and the threshold for the transistor is about 2 kHz.The response of the peak temperature induced by the injected single pulses indicates that the falling time is much longer than the rising time.Adopting the fitting method,the relationship between the peak temperature and the time during the rising edge and that between the peak temperature and the time during the falling edge are obtained.Moreover,the accumulation temperature decreases with duty cycle increasing for a certain mean power.

  17. Plasma induced degradation of Indigo Carmine by bipolar pulsed dielectric barrier discharge(DBD) in the water-air mixture

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ruo-bing; WU Yan; LI Guo-feng; WANG Ning-hui; LI Jie

    2004-01-01

    Degradation of the Indigo Carmine(IC) by the bipolar pulsed DBD in water-air mixture was studied. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetitive rate and ect., on color removal efficiency of dying wastewater were investigated. Concentrations of gas phase O3 and aqueous phase H2O2 under various conditions were measured. Experimental results showed that air bubbling facilitates the breakdown of water and promotes generation of chemically active species. Color removal efficiency of IC solution can be greatly improved by the air aeration under various solution conductivities. Decolorization efficiency increases with the increase of the gas flow rate, and decreases with the increase of the initial solution conductivity. A higher pulse repetitive rate and a larger pulse capacitor Cp are favorable for the decolorization process. Ozone and hydrogen peroxide formed decreases with the increase of initial solution conductivity. In addition, preliminary analysis of the decolorization mechanisms is given.

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

    Science.gov (United States)

    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.

  19. Next Generation Bipolar Plates for Automotive PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Adrianowycz, Orest; Norley, Julian; Stuart, David J; Flaherty, David; Wayne, Ryan; ; Williams, Warren; Tietze, Roger; Nguyen, Yen-Loan H; Zawodzinski, Tom; Pietrasz, Patrick

    2010-04-15

    The results of a successful U.S. Department of Energy (DoE) funded two-year $2.9 MM program lead by GrafTech International Inc. (GrafTech) are reported and summarized. The program goal was to develop the next generation of high temperature proton exchange membrane (PEM) fuel cell bipolar plates for use in transportation fuel cell applications operating at temperatures up to 120 °C. The bipolar plate composite developed during the program is based on GrafTech’s GRAFCELL resin impregnated flexible graphite technology and makes use of a high temperature Huntsman Advanced Materials resin system which extends the upper use temperature of the composite to the DoE target. High temperature performance of the new composite is achieved with the added benefit of improvements in strength, modulus, and dimensional stability over the incumbent resin systems. Other physical properties, including thermal and electrical conductivity of the new composite are identical to or not adversely affected by the new resin system. Using the new bipolar plate composite system, machined plates were fabricated and tested in high temperature single-cell fuel cells operating at 120 °C for over 1100 hours by Case Western Reserve University. Final verification of performance was done on embossed full-size plates which were fabricated and glued into bipolar plates by GrafTech. Stack testing was done on a 10-cell full-sized stack under a simulated drive cycle protocol by Ballard Power Systems. Freeze-thaw performance was conducted by Ballard on a separate 5-cell stack and shown to be within specification. A third stack was assembled and shipped to Argonne National Laboratory for independent performance verification. Manufacturing cost estimate for the production of the new bipolar plate composite at current and high volume production scenarios was performed by Directed Technologies Inc. (DTI). The production cost estimates were consistent with previous DoE cost estimates performed by DTI for the

  20. Pulsed metallic-plasma generators.

    Science.gov (United States)

    Gilmour, A. S., Jr.; Lockwood, D. L.

    1972-01-01

    A pulsed metallic-plasma generator is described which utilizes a vacuum arc as the plasma source. The arc is initiated on the surface of a consumable cathode which can be any electrically conductive material. Ignition is accomplished by using a current pulse to vaporize a portion of a conductive film on the surface of an insulator separating the cathode from the ignition electrode. The film is regenerated during the ensuing arc. Over 100 million ignition cycles have been accomplished by using four 0.125-in. diameter zinc cathodes operating in parallel and high-density aluminum-oxide insulators. Among the applications being investigated for the generator are metal deposition, vacuum pumping, electric propulsion, and high-power dc arc interruption.

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

    Science.gov (United States)

    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.

  2. Discharge Characteristics of Series Surface/Packed-Bed Discharge Reactor Diven by Bipolar Pulsed Power

    Science.gov (United States)

    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)

  3. High-Precision Pulse Generator

    Science.gov (United States)

    Katz, Richard; Kleyner, Igor

    2011-01-01

    A document discusses a pulse generator with subnanosecond resolution implemented with a low-cost field-programmable gate array (FPGA) at low power levels. The method used exploits the fast carry chains of certain FPGAs. Prototypes have been built and tested in both Actel AX and Xilinx Virtex 4 technologies. In-flight calibration or control can be performed by using a similar and related technique as a time interval measurement circuit by measuring a period of the stable oscillator, as the delays through the fast carry chains will vary as a result of manufacturing variances as well as the result of environmental conditions (voltage, aging, temperature, and radiation).

  4. Custom pulse generator for RPC testing

    International Nuclear Information System (INIS)

    We present a pulse generator able to generate pulses statistically similar to the ones produced by RPC cells. The device generates up to four arrays of fast and narrow random-like pulses. Polarity, maximum amplitudes, widths and pulse rate in each channel may be modified independently in order to simulate different RPC setups and environments. This portable and cost-effective pulse generator is a versatile instrument for testing FE-Electronics and different real detector features related with the signal propagation inside the detector. It has been developed in the framework of the ESTRELA project of the HADES experiment at GSI.

  5. Purification of water by bipolar pulsed discharge plasma combined with TiO2 catalysis

    International Nuclear Information System (INIS)

    In the process of water treatment by bipolar pulsed discharge plasma, there are not only the chemical effects such as the cold plasma, but also the physical effects such as the optical radiation. The energy of the optical radiation can be used by photocatalyst. Therefore, the effect of the photocatalyst to the degradation of the organic pollutant was investigated using a packed bed reactor by bipolar pulsed discharge in the air-liquid-solid mixture. The nanoparticle TiO2 photocatalyst was obtained using the sol-gel method and the typical dye solution Indigo Carmine was chosen as the degradation target to test the catalytic effect of the nanoparticle TiO2 photocatalyst. Experiment results proved that the degradation efficiency of the Indigo Carmine solution was increased by a certain extent with the TiO2 photocatalyst. It was totally decolorized within 3 minutes by bipolar pulsed discharge in the condition that the peak voltage was 30 kV and the air flow was 1.0 m3 h−1.

  6. Generating photon pulses with an oscillating cavity

    OpenAIRE

    Lambrecht, A.(Laboratoire Kastler-Brossel, CNRS, ENS, Collège de France, UPMC, Campus Jussieu, 75252 Paris, France); Jaekel, M. T.; Reynaud, S

    1998-01-01

    We study the generation of photon pulses from thermal field fluctuations through opto-mechanical coupling to a cavity with an oscillatory motion. Pulses are regularly spaced and become sharp for a high finesse cavity.

  7. Method for Generating a Compressed Optical Pulse

    DEFF Research Database (Denmark)

    2015-01-01

    There is presented a method of for generating a compressed optical pulse (112) comprising emitting from a wavelength tunable microcavity laser system (102), comprising an optical cavity (104) with a mechanically adjustable cavity length (L), a primary optical pulse (111) having a primary temporal...... width (Tl) while adjusting the optical cavity length (L) so that said primary optical pulse comprises temporally separated photons of different wavelengths, and transmitting said pulse through a dispersive medium (114), so as to generate a compressed optical pulse (112) with a secondary temporal width...

  8. High reliability low jitter pulse generator

    Science.gov (United States)

    Savage, Mark E.; Stoltzfus, Brian S.

    2013-01-01

    A method and concomitant apparatus for generating pulses comprising providing a laser light source, disposing a voltage electrode between ground electrodes, generating laser sparks using the laser light source via laser spark gaps between the voltage electrode and the ground electrodes, and outputting pulses via one or more insulated ground connectors connected to the voltage electrode.

  9. The electromagnetic radiation fields of a relativistic electron avalanche with special attention to the origin of narrow bipolar pulses

    Science.gov (United States)

    Cooray, G. V.; Cooray, G. K.

    2011-12-01

    Gurevich et al. [1] postulated that the source of narrow bipolar pulses, a class of high energy pulses that occur during thunderstorms, could be a runaway electron avalanche driven by the intense electric fields of a thunderstorm. Recently, Watson and Marshall [2] used the modified transmission line model to test the mechanism of the source of narrow bipolar pulses. In a recent paper, Cooray and Cooray [3] demonstrated that the electromagnetic fields of accelerating charges could be used to evaluate the electromagnetic fields from electrical discharges if the temporal and spatial variation of the charges in the discharge is known. In the present study, those equations were utilized to evaluate the electromagnetic fields generated by a relativistic electron avalanche. In the analysis it is assumed that all the electrons in the avalanche are moving with the same speed. In other words, the growth or the decay of the number of electrons takes place only at the head of the avalanche. It is shown that the radiation is emanating only from the head of the avalanche where electrons are being accelerated. It is also shown that an analytical expression for the radiation field of the avalanche at any distance can be written directly in terms of the e-folding length of the avalanche. This makes it possible to extract directly the spatial variation of the e-folding length of the avalanche from the measured radiation fields. In the study this model avalanche was used to investigate whether it can be used to describe the measured electromagnetic fields of narrow bipolar pulses. The results obtained are in reasonable agreement with the two station data of Eack [4] for speeds of propagation around (2 - 2.5) x 10^8 m/s and when the propagation effects on the electric fields measured at the distant station is taken into account. [1] Gurevich et al. (2004), Phys. Lett. A., 329, pp. 348 -361. [2] Watson, S. S. and T. C. Marshall (2007), Geophys. Res. Lett., Vol. 34, L04816, doi: 10

  10. Digital Communication Using Chaotic Pulse Generators

    CERN Document Server

    Rulkov, N F; Tsimring, L S; Volkovskii, A R; Abarbanel, Henry D I; Larson, L; Yao, K

    1999-01-01

    Utilization of chaotic signals for covert communications remains a very promising practical application. Multiple studies indicated that the major shortcoming of recently proposed chaos-based communication schemes is their susceptibility to noise and distortions in communication channels. In this talk we discuss a new approach to communication with chaotic signals, which demonstrates good performance in the presence of channel distortions. This communication scheme is based upon chaotic signals in the form of pulse trains where intervals between the pulses are determined by chaotic dynamics of a pulse generator. The pulse train with chaotic interpulse intervals is used as a carrier. Binary information is modulated onto this carrier by the pulse position modulation method, such that each pulse is either left unchanged or delayed by a certain time, depending on whether ``0'' or ``1'' is transmitted. By synchronizing the receiver to the chaotic pulse train we can anticipate the timing of pulses corresponding to ...

  11. Next generation Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nees, J.; Biswal, S.; Mourou, G. [Univ. Michigan, Center for Ultrafast Optical Science, Ann Arbor, MI (United States); Nishimura, Akihiko; Takuma, Hiroshi

    1998-03-01

    The limiting factors of Chirped Pulse Amplification (CPA) are discussed and experimental results of CPA in Yb:glass regenerative amplifier are given. Scaling of Yb:glass to the petawatt level is briefly discussed. (author)

  12. Elevated levels of urinary markers of oxidatively generated DNA and RNA damage in bipolar disorder

    DEFF Research Database (Denmark)

    Munkholm, Klaus; Poulsen, Henrik Enghusen; Kessing, Lars Vedel;

    2015-01-01

    OBJECTIVES: The pathophysiological mechanisms underlying bipolar disorder and its multi-system nature are unclear. Oxidatively generated damage to nucleosides has been demonstrated in metabolic disorders; however, the extent to which this occurs in bipolar disorder in vivo is unknown. We...... with bipolar disorder during a six- to 12-month period and compared with repeated measurements in healthy control subjects. RESULTS: In linear mixed models, adjusting for demographical, metabolic, and lifestyle factors, the excretion of 8-oxodG and 8-oxoGuo was significantly elevated in euthymic patients...... investigated oxidatively generated damage to DNA and RNA in patients with bipolar disorder and its relationship with the affective phase compared with healthy control subjects. METHODS: Urinary excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo), markers...

  13. Nanosecond pulse generators for induction linear accelerators

    International Nuclear Information System (INIS)

    The paper reviews five different circuits of nanosecond pulse generators for induction linear accelerators. Hydrogen thyratrons which feature a good stability of parameters in time are used as switches. Short voltage pulses (1 - 5 ns) are shaped using nonlinear ferromagnetic lines.The voltage amplitude range on inductor excitation turns is 20-50 kV. 6 refs., 6 figs., 1 tab

  14. Electric pulse generator with a saturable inductance

    International Nuclear Information System (INIS)

    Power supply of induction accelerators is obtained with a pulse generator comprising a coaxial line shaping the pulses and magnetic compression means feeding this line with a capacitor and a saturable inductance, inside the line. A conductor is connected to the end of the inductance and to the median part of the internal electrode and a magnetic commutator discharging the line

  15. Generation of short and intense attosecond pulses

    Science.gov (United States)

    Khan, Sabih Ud Din

    Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ˜100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ˜20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ˜9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ˜100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract

  16. Experimental study on surface modification of PET films under bipolar nanosecond-pulse dielectric barrier discharge in atmospheric air

    International Nuclear Information System (INIS)

    Highlights: • Homogeneous DBD is generated under bipolar nanosecond pulse in atmospheric air. • Effects of surface modification under homogeneous DBD are discussed. • Dielectric properties of the PET films are fully studied from relative dielectric constant εr, dielectric loss tangent tan δ and breakdown voltages Vb. • Oxygen-containing polar groups are considered to be the most essential reason for dielectric property changes. - Abstract: Dielectric barrier discharge (DBD) is widely used for surface modification of polymer films. In this paper, DBD characteristics under bipolar repetitive frequency nanosecond pulse in atmospheric air are studied and surface properties of polyethylene terephthalate films under homogeneous DBD and filamentary DBD modification are compared through scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and dielectric test equipment. It is found that the discharge is homogeneous when gap spacing d is less than 1.2 mm and filamentary when d is within the range of 3.0 mm to 5.8 mm. SEM pictures reveal that films under homogeneous DBD present a smooth surface while intensive “gully-like” etches appear on the surface of the films under filamentary DBD, which can result in local insulation defects and is disadvantageous to surface modification. It is found from the XPS analysis that a number of oxygen-containing polar groups are introduced onto the surface of the film modified by homogeneous DBD compared with the untreated one. Experimental results for dielectric properties indicate that the three parameters: relative dielectric constant εr, dielectric loss tangent tan δ and breakdown voltages Vb are all changed in different degree after surface modification. And possible reason for the phenomenon is discussed

  17. A versatile programmable CAMAC random pulse generator

    International Nuclear Information System (INIS)

    A new technique for generating linear pulses which can be random in both amplitude and time is described. With this technique, desired values for both pulse amplitude and spacing are set for the individual pulses by the software on a pulse-by-pulse basis. The versatility offered by this software programming allows a wide range of distributions to be obtained; with the user having close control on the distribution parameters. A number of such distributions may also be combined into a single output pulse stream. An implementation in a CAMAC module is presented. Both hardware and software aspects are described and typical performance results for amplitude and time distributions of the uniform and Gaussian type are given. Implications of using the pulser in a typical data acquisition environment on both the data acquisition and the pulser performance are considered. Typical applications are discussed together with some of the limitations. (orig.)

  18. Electron density modulation in an asymmetric bipolar pulsed dc magnetron discharge

    International Nuclear Information System (INIS)

    This paper investigates the spatial and temporal variation in plasma electron density over a region between 5 and 10 cm above the race-track region of a pulsed magnetron sputtering target. The pulse operation is performed using an asymmetric bipolar pulsed dc power supply, which provides a sequence of large negative ''on-phase'' voltage (-350 V) and a small positive ''reverse-phase'' voltage (+10 V) for 55% of the pulse duration (10 μs). The electron density is measured using a floating microwave hairpin resonance probe. The results show electron expulsion from the target in the initial on phase, which propagates with a characteristic speed exceeding the ion thermal speed. In the steady state on phase, a consistent higher density is observed. A quantitative model has been developed to explain the resultant density drops in the initial on phase. While in the reverse phase, we observed an anomalous growth in density at a specific location from the target (d>7 cm). The mechanism behind the increase in electron density has been attributed to the modulation in spatial plasma potential, which was measured earlier in the same apparatus using a floating emissive probe [J. W. Bradley et al., Plasma Sources Sci. Technol. 13, 189 (2004)

  19. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  20. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  1. Generation of Femtosecond Electron and Photon Pulses

    CERN Document Server

    Thongbai, Chitrlada; Kangrang, Nopadol; Kusoljariyakul, Keerati; Rhodes, Michael W; Rimjaem, Sakhorn; Saisut, Jatuporn; Vilaithong, Thiraphat; Wichaisirimongkol, Pathom; Wiedemann, Helmut

    2005-01-01

    Femtosecond electron and photon pulses become a tool of interesting important to study dynamics at molecular or atomic levels. Such short pulses can be generated from a system consisting of an RF-gun with a thermionic cathode, an alpha magnet as a magnetic bunch compressor, and a linear accelerator. The femtosecond electron pulses can be used directly or used as sources to produce electromagnetic radiation of equally short pulses by choosing certain kind of radiation pruduction processes. At the Fast Neutron Research Facility (Thailand), we are especially interested in production of radiation in Far-infrared and X-ray regime. In the far-infrared wavelengths which are longer than the femtosecond pulse length, the radiation is emitted coherently producing intense radiation. In the X-ray regime, development of femtosecond X-ray source is crucial for application in ultrafast science.

  2. A high voltage steep-pulse generator

    International Nuclear Information System (INIS)

    The discharge circuit of a Marx generator is analysed and a common calculating program is given. On the basis of theoretical analysis, a high voltage fast-rise pulse generator, whose output voltage is 160 kV, and rise-time is less than 5 ns, has been designed and manufactured

  3. Low-induction pulse current generator

    International Nuclear Information System (INIS)

    A low-inductive generator of pulsed currents with the energy of 15 kJ and operating voltage up to 50 kV is described. The generator makes use of a multichannel discharger with the sliding charge and the inductivity of 8-10 nG

  4. Characteristics of Narrow Bipolar Pulses observed from lightning in Sri Lanka

    Science.gov (United States)

    Gunasekara, T. A. L. N.; Fernando, M.; Sonnadara, U.; Cooray, V.

    2016-02-01

    A detailed study on electric field characteristics of Narrow Bipolar Pulses (NBP) observed in Sri Lanka is presented here. NBPs analyzed in this work were recorded at a coastal location in the Southern part of Sri Lanka (Matara: 5.95 °N, 8.53 °E), from five highly active consecutive thunderstorm days during the month of May in 2013. The waveforms were recorded with a 10 ns resolution within a 100 ms time window. Both positive and negative NBPs were observed in this study with the negative type being the most frequent. Parameters presented in this study were the rise time (Tr), zero crossing time (Tz), the duration of slow front (Ts), the full width of half maximum (FWHM), the pulse duration and the ratio of amplitude of overshoot to the corresponding peak amplitude (Os/Pa). The corresponding average values of negative NBPs for these parameters were found to be 0.58 μs, 3.01 μs, 0.20 μs, 1.38 μs, 19.21 μs and 0.19 respectively. Similarly, for positive events corresponding values were 1.38 μs, 4.66 μs, 0.48 μs, 1.93 μs, 16.42 μs and 0.37 respectively. The above values conforms to a much narrower bipolar events when compared to previously reported values which is considered to be caused by the propagation effects of signals captured by the apparatus.

  5. Nanoplasmonic generation of ultrashort EUV pulses

    Science.gov (United States)

    Choi, Joonhee; Lee, Dong-Hyub; Han, Seunghwoi; Park, In-Yong; Kim, Seungchul; Kim, Seung-Woo

    2012-10-01

    Ultrashort extreme-ultraviolet (EUV) light pulses are an important tool for time-resolved pump-probe spectroscopy to investigate the ultrafast dynamics of electrons in atoms and molecules. Among several methods available to generate ultrashort EUV light pulses, the nonlinear frequency upconversion process of high-harmonic generation (HHG) draws attention as it is capable of producing coherent EUV pulses with precise control of burst timing with respect to the driving near-infrared (NIR) femtosecond laser. In this report, we present and discuss our recent experimental data obtained by the plasmon-driven HHG method that generate EUV radiation by means of plasmonic nano-focusing of NIR femtosecond pulses. For experiment, metallic waveguides having a tapered hole of funnel shape inside were fabricated by adopting the focused-ion-beam process on a micro-cantilever substrate. The plasmonic field formed within the funnelwaveguides being coupled with the incident femtosecond pulse permitted intensity enhancement by a factor of ~350, which creates a hot spot of sub-wavelength size with intensities strong enough for HHG. Experimental results showed that with injection of noble gases into the funnel-waveguides, EUV radiation is generated up to wavelengths of 32 nm and 29.6 nm from Ar and Ne gas atoms, respectively. Further, it was observed that lower-order EUV harmonics are cut off in the HHG spectra by the tiny exit aperture of the funnel-waveguide.

  6. Influence of Bipolar Pulse Poling Technique for Piezoelectric Vibration Energy Harvesters using Pb(Zr,Ti)O3 Films on 200 mm SOI Wafers

    International Nuclear Information System (INIS)

    Piezoelectric vibration energy harvester arrays using Pb(Zr,Ti)O3 thin films on 200 mm SOI wafers were fabricated. In-plane distribution of influence of bipolar pulse poling technique on direct current (DC) power output from the harvesters was investigated. The results indicate that combination poling treatment of DC and bipolar pulse poling increases a piezoelectric property and reduces a dielectric constant. It means that this poling technique improves the figure of merit of sensors and harvesters. Maximum DC power from a harvester treated by DC poling after bipolar pulse poling is about five times larger than a one treated by DC poling only

  7. Plasma effects in attosecond pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, T.J.M. [Centre for Theoretical Physics, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Ondarza-Rovira, R., E-mail: ricardo.ondarza@inin.gob.m [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Mexico 11801, Distrito Federal (Mexico)

    2010-03-29

    Particle-in-cell simulations have been used to explore further the role of plasma effects on the high harmonic spectrum generated in intense ultrarelativistic (UR) laser-plasma interactions. From a study of the electron dynamics during the laser-plasma interaction a strong correlation was established between the reflected laser pulses and plasma effects. The sources of intense attosecond pulses were found to originate within the plasma at sites of high electron density concentrations at which there is a correspondingly strong generation of electrostatic fields.

  8. XUV attosecond pulses: generation and measurement

    International Nuclear Information System (INIS)

    An overview is given of the state-of-the-art in optical attosecond pulse generation and measurements. The emission of ultrashort bursts of XUV radiation from a laser driven plasma is described and analysed in the framework of a semiclassical model that explains essential features of the emitted spectrum. While under most conditions, trains of XUV bursts, separated by the half-cycle time of the driving laser field are emitted, few-cycle laser pulses of a well-defined carrier-envelope phase can yield isolated XUV pulses of sub-femtosecond duration. A time resolving correlation technique that relies on the interaction of electrons with a strong laser light field allows the measurement of attosecond electron dynamics from systems excited by these ultrashort XUV pulses. (topical review)

  9. A self-starting hybrid optoelectronic oscillator generating ultra low jitter 10-GHz optical pulses and low phase noise electrical signals

    DEFF Research Database (Denmark)

    Lasri, J.; Bilenca, A.; Dahan, D.; Sidorov, V.; Eisenstein, G.; Ritter, D.; Yvind, Kresten

    2002-01-01

    In this letter, we describe a self-starting optical pulse source generating ultra low noise 15-ps-wide pulses at 10 GHz. It is based on a hybrid optoelectronic oscillator comprising a fiber extended cavity mode-locked diode laser which injection locks a self-oscillating heterojunction bipolar...

  10. 1 MV low-induction pulse generator

    International Nuclear Information System (INIS)

    A high-voltage pulse generator is described. The generator Uses the Arkadiev-Marx circuit at 1 MV voltage and 12 kJ energy; the inductance of the discharge circuit is 1.3 μN. Low inductance of the generator has been obtained due to the use of low-inductance capacitors and employment of bifilar buses with oil barrier insulation. To provide reliable generator triggering, an ignition circuit has been developed with a resistive coupling between generator steps, based on controlled three-electrode sparkgaps with a distorted field. The generator switching time is slightly dependent on pressure and constitutes 200-300 ns. The generator efficiency is 83%

  11. 21 CFR 870.1750 - External programmable pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false External programmable pacemaker pulse generator... External programmable pacemaker pulse generator. (a) Identification. An external programmable pacemaker pulse generators is a device that can be programmed to produce one or more pulses at...

  12. 21 CFR 870.3600 - External pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false External pacemaker pulse generator. 870.3600... pacemaker pulse generator. (a) Identification. An external pacemaker pulse generator is a device that has a power supply and electronic circuits that produce a periodic electrical pulse to stimulate the...

  13. 21 CFR 870.3610 - Implantable pacemaker pulse generator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Implantable pacemaker pulse generator. 870.3610... pacemaker pulse generator. (a) Identification. An implantable pacemaker pulse generator is a device that has a power supply and electronic circuits that produce a periodic electrical pulse to stimulate...

  14. Device for generation of pulsed corona discharge

    Science.gov (United States)

    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.

  15. A pulse generator for xenon lamps

    CERN Document Server

    Janata, E

    2002-01-01

    A pulse generator is described, which enhances the analyzing light emitted from a xenon lamp as used in kinetic photospectrometry experiments. The lamp current is increased to 600 A for a duration of 3 ms; the current is constant within +-0.2% during a time interval of 2 ms. Because of instabilities of the lamp arc during pulsing, the use of the enhanced light source is limited to measuring times up to 500 mu s. The enhancement in light intensity depends on the wavelength and amounts to more than 400-fold in the UV-region.

  16. Generation and characterization of atto second pulses

    International Nuclear Information System (INIS)

    Atto-second pulse trains in the extreme ultraviolet range can be produced by high-order harmonic generation, by focusing an intense femtosecond pulse in a rare gas jet. In this thesis, we present a temporal characterization of this radiation on the femtosecond and atto-second timescales. By transposing a spectral interferometry technique commonly used in the infrared range (SPIDER), we make a complete single-shot characterization of the temporal profile of individual harmonics, on the femtosecond timescale. In a second part, we study experimentally the atto-second structure of the harmonic radiation, and demonstrate a temporal drift in the emission: the lowest harmonics are emitted before the highest ones. This chirp, which is directly related to the electron dynamics in the generation process, imposes a lower limit to the duration that can be achieved by increasing the spectral range. We show how generating conditions can be optimized in order to enhance the synchronization in the emission, and how atto-second pulses can be re-compressed. Last, we propose a new technique for the complete characterization of arbitrary atto-second pulses: FROGCRAB. This method would allow simultaneous measurements of the femtosecond and atto-second structures of the radiation, and thus a complete knowledge of the atto-second light source in the perspective of applications. (author)

  17. Generating Microwave Radiation Pulses with MCG

    Science.gov (United States)

    Zherlitsyn, A. G.; Kanaev, G. G.; Melnikov, G. V.; Tsvetkov, V. I.; Ushnurtsev, A. E.; Dudin, S. V.; Mintsev, V. B.; Fortov, V. E.

    2004-11-01

    Transformer schemes matching magnetocumulative generators (MCG) with high impedance loads, like vircator, look promising for achieving long pulse duration of 1 μs. An analysis of expected parameters is made here. The necessary MCG and transformer parameters are discussed and the experimental set-up is described. The shots with the MCG simulator were carried out first. At simulator voltage 40 kV and reserved energy 12 kJ, the voltage pulse with amplitude to 600 kV and 320 ns duration is generated on a triode with a virtual cathode. Microwave radiation of 300-400 MW and 200-300 ns duration is generated within a 10 cm wavelength range.

  18. Experimental observation of the behaviour of cogenerated dusty plasma using a bipolar pulsed direct current power supply

    International Nuclear Information System (INIS)

    We have experimentally observed the behaviour of cogenerated dusts in unmagnetized plasma produced using a bipolar pulsed dc power supply. In this experiment, the dust particles have been generated through sputtering of graphite cathode and were stratified between two electrodes. This stratification of dust clouds has obtained at a typical range of plasma parameters, namely, 650 V (peak-to-peak) with 0.2 mbar pressure. In above condition, we detected the Taylor-like instability at the interface of two dusty clouds with different densities. A very less dust density (void like) region inside the lesser dust density portion is also noted. Again, it has been observed that a self excited dust density wave propagates towards the higher density dust fluid inside the system as well as a stationary band structure of thin multiple layers of dust particles when we apply a higher voltage (750 V peak-to-peak). The wavelength, phase velocity, and frequency of the excited wave have also been estimated.

  19. Paired pulse plasticity in the strength and latency of light-evoked lateral inhibition to retinal bipolar cell terminals

    OpenAIRE

    Vickers, Evan; Kim, Mean-Hwan; Vigh, Jozsef; von Gersdorff, Henrique

    2012-01-01

    Synapses in the inner plexiform layer of the retina undergo short-term plasticity that may mediate different forms of adaptation to regularities in light stimuli. Using patch-clamp recordings from axotomized goldfish Mb bipolar cell (BC) terminals with paired-pulse light stimulation, we isolated and quantified the short-term plasticity of GABAergic lateral inhibitory postsynaptic currents (L-IPSCs). Bright light stimulation evoked ON and OFF L-IPSCs in axotomized BCs, which had distinct onset...

  20. Solid-state pulse modulator using Marx generator for a medical linac electron-gun

    Science.gov (United States)

    Lim, Heuijin; Hyeok Jeong, Dong; Lee, Manwoo; Lee, Mujin; Yi, Jungyu; Yang, Kwangmo; Ro, Sung Chae

    2016-04-01

    A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun.

  1. Solid-state pulse modulator using Marx generator for a medical linac electron-gun

    International Nuclear Information System (INIS)

    A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun

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

    Science.gov (United States)

    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.

  3. Pulsed corona generation using a diode-based pulsed power generator

    International Nuclear Information System (INIS)

    Pulsed plasma techniques serve a wide range of unconventional processes, such as gas and water processing, hydrogen production, and nanotechnology. Extending research on promising applications, such as pulsed corona processing, depends to a great extent on the availability of reliable, efficient and repetitive high-voltage pulsed power technology. Heavy-duty opening switches are the most critical components in high-voltage pulsed power systems with inductive energy storage. At the Ioffe Institute, an unconventional switching mechanism has been found, based on the fast recovery process in a diode. This article discusses the application of such a 'drift-step-recovery-diode' for pulsed corona plasma generation. The principle of the diode-based nanosecond high-voltage generator will be discussed. The generator will be coupled to a corona reactor via a transmission-line transformer. The advantages of this concept, such as easy voltage transformation, load matching, switch protection and easy coupling with a dc bias voltage, will be discussed. The developed circuit is tested at both a resistive load and various corona reactors. Methods to optimize the energy transfer to a corona reactor have been evaluated. The impedance matching between the pulse generator and corona reactor can be significantly improved by using a dc bias voltage. At good matching, the corona energy increases and less energy reflects back to the generator. Matching can also be slightly improved by increasing the temperature in the corona reactor. More effective is to reduce the reactor pressure

  4. Generation of picosecond pulsed coherent state superpositions

    DEFF Research Database (Denmark)

    Dong, Ruifang; Tipsmark, Anders; Laghaout, Amine;

    2014-01-01

    We present the generation of approximated coherent state superpositions-referred to as Schrodinger cat states-by the process of subtracting single photons from picosecond pulsed squeezed states of light. The squeezed vacuum states are produced by spontaneous parametric down-conversion (SPDC) in a...... periodically poled KTiOPO4 crystal while the single photons are probabilistically subtracted using a beamsplitter and a single photon detector. The resulting states are fully characterized with time-resolved homodyne quantum state tomography. Varying the pump power of the SPDC, we generated different states...

  5. S100 lathe bed pulse generator applied to pulsed nuclear magnetic resonance

    International Nuclear Information System (INIS)

    The project and construction of four channel pulse generator in the S100 standard plate and its control software for microcomputer are described. The microcomputer has total control on the pulse generator, which has seven programable parameters, defining the position of four pulses and the width for the three first ones. This pulse generator is controlled by a software developed in c language, and is used in pulsed nuclear magnetic resonance experiences. (M.C.K.)

  6. Theoretical model of unipolar and bipolar trains of magnetic field pulses preceding lightning discharges

    Czech Academy of Sciences Publication Activity Database

    Kašpar, Petr; Santolík, Ondřej; Kolmašová, Ivana

    Prague: International Union of Geodesy and Geophysics, 2015. A11p-142. [Earth and Environmental Sciences for Future Generations. General Assembly of International Union of Geodesy and Geophysics /26./. 22.06.2015-02.07.2015, Prague] Institutional support: RVO:68378289 Keywords : magnetic field pulses Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.iugg2015prague.com/abstractcd/data/HtmlApp/main.html#

  7. Photocatalytic activity of bipolar pulsed magnetron sputter deposited TiO2/TiWOx thin films

    Science.gov (United States)

    Weng, Ko-Wei; Hu, Chung-Hsuan; Hua, Li-Yu; Lee, Chin-Tan; Zhao, Yu-Xiang; Chang, Julian; Yang, Shu-Yi; Han, Sheng

    2016-08-01

    Titanium oxide films were formed by sputtering and then TiWOx films were deposited by bipolar pulsed magnetron sputtering with pure titanium and tungsten metal targets. The sputtering of titanium oxide with tungsten enhanced the orientation of the TiO2 (1 0 1) plane of the specimen assemblies. The main varying parameter was the tungsten pulse power. Titanium oxide sputtered with tungsten using a pulsing power of 50 W exhibited a superior hydrophilic property, and a contact angle of 13.1°. This fabrication conditions maximized the photocatalytic decomposition of methylene blue solution. The mechanism by which the titanium oxide was sputtered with tungsten involves the photogeneration of holes and electron traps, inhibiting the hole-electron recombination, enhancing hydrophilicity and reducing the contact angle.

  8. A New Switching Impulse Generator Based on Transformer Boosting and Insulated Gate Bipolar Transistor Trigger Control

    Directory of Open Access Journals (Sweden)

    Ming Ren

    2016-08-01

    Full Text Available To make the switching impulse (SI generator more compact, portable and feasible in field tests, a new approach based on transformer boosting was developed. To address problems such as triggering synchronization and electromagnetic interference involved with the traditional spark gap, an insulated gate bipolar transistor (IGBT module with drive circuit was employed as the impulse trigger. An optimization design for the component parameters of the primary winding side of the transformer was realized by numerical calculation and error correction. Experiment showed that the waveform parameters of SI and oscillating switching impulse (OSI voltages generated by the new generator were consistent with the numerical calculation and the error correction. The generator was finally built on a removable high voltage transformer with small size. Thus the volume of the generator is significantly reduced. Experiments showed that the waveform parameters of SI and OSI voltages generated by the new generator were basically consistent with the numerical calculation and the error correction.

  9. FERRITE-FREE STACKED BLUMLEIN PULSE GENERATOR FOR COMPACT INDUCTION LINACS

    International Nuclear Information System (INIS)

    Stacked Blumlein Pulse Generators comprised of parallel-plate transmission lines are potentially a useful pulse-power architecture for high-gradient, compact, electron-beam induction accelerators. However, like induction accelerators driven by other pulse-power architectures, it is generally a system requirement that the multi-stage accelerator structure be enclosed in a grounded metal enclosure so that the full beam voltage is not developed on the exterior of the machine. In the past, this has been accomplished by using magnetic cores to prevent the external metal case from shorting the accelerating field. However, magnetic cores are heavy, bulky, expensive, lossy, nonlinear, and therefore generally undesirable. Various core-free pulse architectures have been reported in the past. One class uses pairs of lines with widely different dielectric constants while another class uses combinations of open-circuit lines combined with short-circuit lines. These designs are encased in metal and support stackable output pulses without the need for magnetic isolation cores. These configurations are also known as bi-polar or zero-integral configurations because they produce a positive and negative voltage pulse with a net time integral of zero. Some of these designs are inefficient leaving substantial stored energy in the lines while others have never been realized as practical accelerating structures. We present here a particular, realizable, magnetic-core-free induction LINAC geometry that is based on a parallel-plate, stacked Blumlein-like structure, with a symmetric bi-polar, zero integral output pulse, and an outer metal enclosure. Our design is, in theory, 100% efficient into a matched load. We have evaluated the electromagnetic operation of this geometry by computer modeling. We present the results of this modeling

  10. Harmonic Generation with Single-Cycle Light Pulses

    OpenAIRE

    Sukhorukov A.A.; Kozlov S.A.; Drozdov A.A.; Kivshar Yu.S.

    2013-01-01

    We study theoretically spatiotemporal pulse dynamics in cubic nonlinear media with instant response, nonresonant absorption and normal group velocity dispersion and reveal new features of harmonic generation when the pulse duration is reduced, including the suppression of third-harmonic generation for single-cycle light pulses.

  11. Double nanosecond pulses generation in ytterbium fiber laser

    Science.gov (United States)

    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.

  12. An Ultra Low Noise Self-Starting Pulse Generator

    DEFF Research Database (Denmark)

    Lasri, J.; Bilenca, A.; Dahan, D.; Sidorov, V.; Eisenstein, G.; Ritter, D.; Yvind, Kresten

    2002-01-01

    We describe a self-starting optical pulse source generating 10 GHz, 15 ps pulses with an average jitter of 43 fs and a o.15% amplitude noise over a frequency range of 500 Hz - 1 MHz.......We describe a self-starting optical pulse source generating 10 GHz, 15 ps pulses with an average jitter of 43 fs and a o.15% amplitude noise over a frequency range of 500 Hz - 1 MHz....

  13. White-Light Generation with Sub-ps Pulses

    OpenAIRE

    Calendron, Anne-Laure; Çankaya, Hüseyin; Cirmi, Giovanni; Kärtner, Franz X.

    2015-01-01

    We generate white light supercontinuum from slightly sub-picosecond pulses at 1.03 µm and 515 nm. We compare the spectra and stability for various crystals, focusing conditions and pulse durations, and determine the best parameters for sub-picosecond driver pulse duration. Comparing the experimental observations with the theory of white-light generation from Brodeur and Chin, it appears that in this particular range of pump pulse duration, two mechanisms interact and prevent a catastrophic co...

  14. Study of bipolar pulsed plasma electrolytic carbonitriding on nanostructure of compound layer for a gamma Ti-Al alloy

    Institute of Scientific and Technical Information of China (English)

    Mahmood ALIOFKHAZRAEI; Alireza SABOUR ROUHAGHDAM; Mohsen ROOHZENDEH

    2008-01-01

    The surface hardening of a gamma Ti-Al alloy by using bipolar pulsed nanocrystalline plasma electro-lytic carbonitriding has been studied in this investigation. Coating process was performed on a triethanolamine-based electrolyte by a cooling bath. The nanostructure of the obtained compound layer was examined with the figure analysis of the scanning electron microscopy (SEM) nanographs. The effects of the process variables, i.e., fre-quency, temperature of the electrolyte, applied voltage and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of the nanocrystals. Finally, the contribution percentage of the effective factors of the pulsed current was revealed, and the confirmation run showed the validity of the obtained results.

  15. Linear transformer driver for pulse generation

    Science.gov (United States)

    Kim, Alexander A; Mazarakis, Michael G; Sinebryukhov, Vadim A; Volkov, Sergey N; Kondratiev, Sergey S; Alexeenko, Vitaly M; Bayol, Frederic; Demol, Gauthier; Stygar, William A

    2015-04-07

    A linear transformer driver includes at least one ferrite ring positioned to accept a load. The linear transformer driver also includes a first power delivery module that includes a first charge storage devices and a first switch. The first power delivery module sends a first energy in the form of a first pulse to the load. The linear transformer driver also includes a second power delivery module including a second charge storage device and a second switch. The second power delivery module sends a second energy in the form of a second pulse to the load. The second pulse has a frequency that is approximately three times the frequency of the first pulse. The at least one ferrite ring is positioned to force the first pulse and the second pulse to the load by temporarily isolating the first pulse and the second pulse from an electrical ground.

  16. Enhancement and electric charge-assisted tuning of nonlinear light generation in bipolar plasmonics.

    Science.gov (United States)

    Ding, Wei; Zhou, Liangcheng; Chou, Stephen Y

    2014-05-14

    We propose and experimentally demonstrate a new plasmonic nonlinear light generation (NLG) structure, termed plasmonic-enhanced, charge-assisted second-harmonic generator (p-CASH), that not only achieves high second-harmonic generation (SHG) enhancement (76-fold), large SHG tunability by bias (8%/V), wide tuning range (280%), 7.8 × 10(-9) conversion efficiency, and high stability but also exhibits a SHG tuning, that is bipolar rather than unipolar, not due to the third-order nonlinear polarization term, hence fundamentally different from the classic electric field induced SHG-tuning (EFISH). We propose a new SHG tuning mechanism: the second-order nonlinear polarization term enhanced by plasmonic effects, changed by charge injection and negative oxygen vacancies movement, and is nearly 3 orders of magnitude larger than EFISH. p-CASH is a bipolar parallel-plate capacitor with thin layers of plasmonic nanostructures, a TiOx (semiconductor and nonlinear) and a SiO2 (insulator) sandwiched between two electrodes. Fabrication of p-CASH used nanoimprint on 4″ wafer and is scalable to wallpaper-sized areas. The new structure, new properties, and new understanding should open up various new designs and applications of NLG in various fields. PMID:24730390

  17. Development of BMD-1 model standard pulse current generator

    International Nuclear Information System (INIS)

    The BMD-1 Model Standard Pulse Current Generator is a pulse current calibration instrument. It is used to calibrate current probe, amplifier of current probe and other current measurement instruments. The standard pulse current generator uses a perfect current switch to transfer the standard direct current into the standard pulse current. It provides a variable output current ranges from 1 mA to 1 A, current accuracy is +-(0.25% + 2μA). The standard pulse generator provides three work modes of output current: DC, signal pulse and variable frequencies from 10 Hz to 1 MHz, and provides a variable pulse current widths from 0.5 to 50 μs

  18. Generation of nanosecond neutron pulses in vacuum accelerating tubes

    Science.gov (United States)

    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.

  19. Intensity Scalings of Attosecond Pulse Generation by the Relativistic-irradiance Laser Pulses

    Science.gov (United States)

    Pirozhkov, Alexander S.; Bulanov, Sergei V.; Esirkepov, Timur Zh.; Sagisaka, Akito; Tajima, Toshiki; Daido, Hiroyuki

    We present the theoretical comparative analysis of different attosecond pulse generation techniques in which the relativistic-irradiance driver pulses are used. In particular, we concentrate on the intensity scalings of the attosecond pulse duration, wavelength, and conversion efficiency. We also discuss the optimum conditions and the major implementation challenges.

  20. Thermo-acoustic Sound Generation in the Interaction of Pulsed Proton and Laser Beams with a Water Target

    CERN Document Server

    Lahmann, R; Graf, K; Hößl, J; Kappes, A; Katz, U; Mecke, K; Schwemmer, S

    2015-01-01

    The generation of hydrodynamic radiation in interactions of pulsed proton and laser beams with matter is explored. The beams were directed into a water target and the resulting acoustic signals were recorded with pressure sensitive sensors. Measurements were performed with varying pulse energies, sensor positions, beam diameters and temperatures. The obtained data are matched by simulation results based on the thermo-acoustic model with uncertainties at a level of 10%. The results imply that the primary mechanism for sound generation by the energy deposition of particles propagating in water is the local heating of the medium. The heating results in a fast expansion or contraction and a pressure pulse of bipolar shape is emitted into the surrounding medium. An interesting, widely discussed application of this effect could be the detection of ultra-high energetic cosmic neutrinos in future large-scale acoustic neutrino detectors. For this application a validation of the sound generation mechanism to high accur...

  1. Circuit Simulation of Light Ⅱ-A Pulsed Power Generator

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The Light Ⅱ-A pulsed power generator could be divided into the following parts, a Marx generator consisting of 12 spark gap switches and 24 low inductance capacitors (Maxwell Corporation products)

  2. Simple Arduino based pulse generator design for electroporation

    Science.gov (United States)

    Sulaeman, Muhammad Yangki; Widita, Rena

    2015-09-01

    This research will discuss the design of electroporation generator using Arduino as the pulse controller. The pulse parameters are the most important thing in electroporation method, therefore many researches aimed to produce generator to control its parameters easily. Arduino will be used as the microcontroller to create low amplitude signal trigger to get the high voltage pulse for electroporation. 124.4 VDC will be used and tested in cuvette contained NaCl solution with various concentration between 0% - 1%.

  3. Generation of laser pulse trains for tests of multi-pulse laser wakefield acceleration

    Science.gov (United States)

    Shalloo, R. J.; Corner, L.; Arran, C.; Cowley, J.; Cheung, G.; Thornton, C.; Walczak, R.; Hooker, S. M.

    2016-09-01

    In multi-pulse laser wakefield acceleration (MP-LWFA) a plasma wave is driven by a train of low-energy laser pulses separated by the plasma period, an approach which offers a route to driving plasma accelerators with high efficiency and at high pulse repetition rates using emerging technologies such as fibre and thin-disk lasers. Whilst these laser technologies are in development, proof-of-principle tests of MP-LWFA require a pulse train to be generated from a single, high-energy ultrafast pulse. Here we demonstrate the generation of trains of up to 7 pulses with pulse separations in the range 150-170 fs from single 40 fs pulses produced by a Ti:sapphire laser.

  4. USB connection pulse generator using commercial available FPGA circuit board

    International Nuclear Information System (INIS)

    A number of examples have been reported on the NMR pulse generator. However some of them needed custom hardwares and the additional development of drivers. In this article, we report the USB connection NMR pulse generator using commercial available FPGA board. The system consists of only the commercial available FPGA board and free softwares. (author)

  5. Refurbishment Status of Light Ⅱ-A Pulsed Power Generator

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The Light Ⅱ-A pulsed power generator, formerly used to pump KrF laser, was updated around the year 2000 from the original Light Ⅱ, a pulsed power generator built in 1980s at CIAE. This machine was

  6. Generation of high harmonics and attosecond pulses with ultrashort laser pulse filaments and conical waves

    Indian Academy of Sciences (India)

    A Couairon; A Lotti; D Faccio; P Di Trapani; D S Steingrube; E Schulz; T Binhammer; U Morgner; M Kovacev; M B Gaarde

    2014-08-01

    Results illustrating the nonlinear dynamics of ultrashort laser pulse filamentation in gases are presented, with particular emphasis on the filament properties useful for developing attosecond light sources. Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes and subcycle pulses generated within the filament. (ii) Simulation results on the spontaneous formation of conical wavepackets during filamentation in gases, which in turn can be used as efficient driving pulses for the generation of high harmonics and isolated attosecond pulses.

  7. A Marx generator based high voltage high current pulsed power supply with variable pulse width

    International Nuclear Information System (INIS)

    A high voltage pulse power supply using Marx generator with solid-state switches is proposed in this paper. An IGBT based 10 stage Marx bank generator has been designed and developed. A -10 kV /100 A high voltage pulse with a variable pulse width from 100 μS to 1 ms yielding a peak power of 1 mega watt was generated. The 10 cell generator is assembled over a FRP structure where each cell consists of a charging IGBT, a discharging IGBT, a capacitor and a freewheeling diode. The modular design proposed allows cascading of similar structures to generate higher voltages. A unique compact scheme based on pulse transformer is used to drive both the charging and the discharging IGBTs. Two numbers of pulse transformers (one for charging pulse and another for discharging pulse) were designed and developed. Both pulse transformers have a single primary and multiple numbers of secondaries, one for each cell with required high voltage isolation. They are excited with high frequency inverters to generate isolated control supply and firing pulse for IGBT switching. The paper discusses the design and construction of the Marx generator and its operation. (author)

  8. A single-event transient induced by a pulsed laser in a silicon-germanium heterojunction bipolar transistor

    Institute of Scientific and Technical Information of China (English)

    Sun Ya-Bin; Fu Jun; Xu Jun; Wang Yu-Dong; Zhou Wei; Zhang Wei; Cui Jie

    2013-01-01

    A study on the single event transient (SET) induced by a pulsed laser in a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is presented in this work.The impacts of laser energy and collector load resistance on the SET are investigated in detail.The waveform,amplitude,and width of the SET pulse as well as collected charge are used to characterize the SET response.The experimental results are discussed in detail and it is demonstrated that the laser energy and load resistance significantly affect the SET in the SiGe HBT.Furthermore,the underlying physical mechanisms are analyzed and investigated,and a near-ideal exponential model is proposed for the first time to describe the discharge of laser-induced electrons via collector resistance to collector supply when both base-collector and collector-substrate junctions are reverse biased or weakly forward biased.Besides,it is found that an additional multi-path discharge would play an important role in the SET once the base-collector and collector-substrate junctions get strongly forward biased due to a strong transient step charge by the laser pulse.

  9. On-line controlled pulse-train generator for pulsed EPR spectrometer-relaxometer

    International Nuclear Information System (INIS)

    A pulse-train generator including 11 output channels program operated with the ''Elektronika D3-28'' computer is described. High flexibility in shaping different pulse combinations permits to automize the control of EPR relaxometer in all the regimes of investigations. The maximum number of intervals generated by each channel is 16. The range of pulse train variation is 1 μs-4x103 s

  10. Control System for the LLNL Kicker Pulse Generator

    Energy Technology Data Exchange (ETDEWEB)

    Watson, J A; Anaya, R M; Cook, E G; Lee, B S; Hawkins, S A

    2002-06-18

    A solid-state high voltage pulse generator with multi-pulse burst capability, very fast rise and fall times, pulse width agility, and amplitude modulation capability for use with high speed electron beam kickers has been designed and tested at LLNL. A control system calculates a desired waveform to be applied to the kicker based on measured electron beam displacement then adjusts the pulse generators to provide the desired waveform. This paper presents the design of the control system and measure performance data from operation on the ETA-11 accelerator at LLNL.

  11. Current-pulse generator for electromagnet of induction accelerator

    International Nuclear Information System (INIS)

    A thyristor generator is described that produces in the winding of the electromagnet of a betatron unipolar current pulses of sinusoidal and quasisinusoidal shape with deforcing of the field at the beginning of an acceleration cycle and with a plateau on the pulse top at the end of a cycle. The current amplitude is controlled by a pulse-phase method. The generator is used in apparatus with a pulse duration of 1-10 msec, a maximum electromagnet field energy 45-450 J, a winding voltage of 960-1500 V, and a winding current of 100-500 A for a repetition frequency of 50-200 Hz

  12. The waveform analysis for Zarem type high voltage pulse generator

    International Nuclear Information System (INIS)

    The project of the cluster klystron requires a 30 to 40 kV pulse generator to drive the mod-anode. A 30--40 kV pulse generator using Zarem type was developed. A pulse distortion showing a deficiency on the rear top was frequently encountered. This note describes the detail of the pulse forming principle. The encountered distortion was analyzed. Simulations demonstrate the same result. The feature of the spark gap was also addressed. A solution of this problem is given

  13. Electromagnetic pulse reflection at self-generated plasma mirrors: laser pulse shaping and high order harmonic generation

    CERN Document Server

    Bulanov, S S; Maksimchuk, A; Matsuoka, T; Nees, J; Pegoraro, F

    2007-01-01

    A thin layer of overdense plasma is created when an electromagnetic pulse interacts with a rapidly ionizing thin foil. This layer will reflect the incoming pulse, forming a so-called plasma mirror. A simple realistic model based on paired kinetic and wave equations is used to describe analytically the process of mirror formation and the reflection and transmission of the incident pulse. The model incorporates the exact description of the ionization process in the foil and the polarization and conduction currents that follow. The analytical description of the reflected and transmitted pulses as well as their dependence on foil parameters, and initial pulse amplitude and form are presented. Possible application and effectiveness of this process to improve laser pulse contrast are discussed. In the case of the linearly polarized incident pulse, there harmonic generation occurs, that is absent in the case of the circular polarization. The spectra of the reflected pulses for different initial forms and amplitudes ...

  14. Numerical simulation of evolution features of the atmospheric-pressure CF4 plasma generated by the pulsed dielectric barrier discharge

    Science.gov (United States)

    Pan, Jie; Li, Li; Chen, Bo; Song, Yuzhi; Zhao, Yuefeng; Xiu, Xianwu

    2016-06-01

    The atmospheric-pressure CF4 plasma has the high application potential in the field of semiconductor fabrication since it can combine the excellent capability for the CF4 plasma etching with the easy atmospheric-pressure operation. In this work, the fluid model has been carried out to numerically research evolution features of the atmospheric-pressure CF4 plasma generated by the pulsed dielectric barrier discharge. The computational results show that the averaged electron temperature dramatically increases during the rising and the falling phases of the applied voltage pulse, and then swiftly decreases. The discharge current density has the waveform of two bipolar short pulses. The electrons and CF3 + ions form the cathode sheath at the discharge duration. However, the CF3 - and F- negative ions take the place of the electrons to sustain the cathode sheath of the CF4 discharge plasma at the time interval between the two bipolar discharge pulses. During the time interval of the two adjacent applied voltage pulses the discharge region is the quasi-neutral plasma region, and meanwhile CF2 + and CF3 - are the dominated charged species. Moreover, F and CF3 maintain the relatively stable high densities and uniform axial distributions during the whole period of the applied voltage.

  15. Isolated sub-10 attosecond pulse generation by a 6-fs driving pulse and a 5-fs subharmonic controlling pulse

    Directory of Open Access Journals (Sweden)

    Yunhui Wang

    2012-06-01

    Full Text Available We theoretically study high-order harmonic generation by quantum path control in a special two-color laser field, which is synthesized by a 6 fs/800 nm fundamental pulse and a weaker 5 fs/1600 nm subharmonic controlling pulse. Single quantum path is selected without optimizing any carrier phase, which not only broadens the harmonic bandwidth to 400 eV, but also enhances the harmonic conversion efficiency in comparison with the short-plus-long scheme, which is based on 5 fs/800 nm driving pulse and 6 fs/1600 nm control pulse. An isolated 8-attosecond pulse is produced with currently available ultrafast laser sources.

  16. Attosecond-magnetic-field-pulse generation by intense few-cycle circularly polarized UV laser pulses

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-07-01

    Intense attosecond-magnetic-field pulses are predicted to be produced by intense few-cycle attosecond circularly polarized UV pulses. Numerical solutions of the time-dependent Schrödinger equation for H2+ are used to study the electronic dynamical process. Spinning attosecond circular electron wave packets are created on subnanometer molecular dimensions, thus generating attosecond magnetic fields of several tens of Teslas (105 G). Simulations show that the induced magnetic field is critically dependent on the pulse wavelength λ and pulse duration nτ (n is number of cycles) as predicted by a classical model. For ultrashort few-cycle circularly polarized attosecond pulses, molecular orientation influences the generation of the induced magnetic fields as a result of preferential ionization perpendicular to the molecular axis. The nonspherical asymmetry of molecules allows for efficient attosecond-magnetic-field-pulse generation.

  17. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Science.gov (United States)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Krausz, Ferenc; Yu, Wei; Tsakiris, George D.; Veisz, Laszlo

    2015-03-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ˜100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  18. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Guangjin, E-mail: guangjin.ma@mpq.mpg.de [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Krausz, Ferenc [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Department für Physik, Ludwig-Maximilians-Universität, D-85748 Garching (Germany); Yu, Wei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2015-03-15

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  19. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    International Nuclear Information System (INIS)

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

  20. FORMING CAPABILITIES OF A PULSE MAGNETIC FIELD GENERATOR

    Directory of Open Access Journals (Sweden)

    A. A. Petkov

    2015-04-01

    Full Text Available Purpose. Determination of areas ratio of the parameters of the discharge circuit elements of the generator, which ensure the formation of magnetic field pulses of different shapes. Methodology. Numerical simulation using dimensionless variables that determine the nature of the transition process in the discharge circuit of the generator, and use the procedure for determining the pulse points of meeting the conditions of extremum and the transition through zero. Results. Obtained a description of the formation of the three specific areas of waveforms: oscillatory weakly damped oscillatory strongly damped and unipolar pulse with a monotonic rise and fall values. A relation to the choice of parameters of elements of the discharge circuit of the generator, which formed unipolar pulses with a monotonic rise and fall values. Originality. A completed and extended database that implements the mapping of the formal description of the pulse shape with a description of areas ratio parameters for high-voltage pulse discharge circuit test units, with respect to the pulses of current flowing in the formation of the magnetic field. Practical value. The relations obtained allow to select the parameters of the discharge circuit elements of the generator designed to generate test pulses of magnetic field.

  1. Incoherent broadband optical pulse generation using an optical gate

    Institute of Scientific and Technical Information of China (English)

    Biao Chen; Qiong Jiang

    2008-01-01

    In two-dimensional (2D) time-spreading/wavelength-hopping optical code division multiple access (OCDMA) systems, employing less coherent broadband optical pulse sources allows lower electrical operating rate and better system performance. An optical gate based scheme for generating weakly coherent(approximately incoherent) broadband optical pulses was proposed and experimentally demonstrated. Inthis scheme, the terahertz optical asymmetric demultiplexer, together with a coherent narrowband controlpulse source, turns an incoherent broadband continuous-wave (CW) light source into the required pulse source.

  2. Design of Pulsed Strong Magnetic Fields Generator and Preliminary Application

    Institute of Scientific and Technical Information of China (English)

    WEN Jun; QU Xue-min; WANG Xi-gang; LONG Kai-ping

    2015-01-01

    Objective: This paper aims to designing a pulsed strong magnetic fields generator. Methods: A large value capacitor was used to store electric energy, coil was used for producing magnetic fields, main control, circuit control charge, sampling, discharge, etc. Results: The generator provided a pulsed magnetic field with the ampli-tude of intensity from 0.1-2 T and variable time interval of pulse from 4 s-1 min. It was not only to be operated easily but also performed reliably. Conclusion:The generator will be applied in special clinical diagnosis, therapy and other fields.

  3. High-voltage pulse generator for electron gun power supply

    International Nuclear Information System (INIS)

    High-voltage pulse generator with combined capacitive and inductive energy storages for electron gun power supply is described. Hydrogen thyratron set in a short magnetic lense is a current breaker. Times of current interruption in thyratrons are in the range from 100 to 300 ns. With 1 kV charging voltage of capacitive energy storage 25 kV voltage pulse is obtained in the load. The given high-voltage pulse generator was used for supply of an electron gun generating 10-30 keV low-energy electron beam

  4. Current pulse generator of an induction accelerator electromagnet

    International Nuclear Information System (INIS)

    Thyristor generator forming in betatron electromagnet coil sinusoidal and quasisinusoidal current unipolar pulses, the field being deforced at the beginning of acceleration cycle, and with the pulse flat top in the cycle end, is described. The current amplitude is controlled by pulse-phase method. The current pulse time shift permitted to decrease the loss rate in the accumulating capacitor. The generator is used in systems with 1-10 ms pulse duration, electromagnet magnetic field maximal energy - 45-450 J, the voltage amplitude in the coil 960-1500 V and amplitude of the current passing the coil 100-500 A, the repetition frequency being 50-200 Hz. In particular, the generator is used to supply betatrons designed for defectoscopy in nonstationary conditions, the accelerated electron energy being 4, 6, 8 and 15 MeV

  5. High dV/dt spiker pulse generation using magnetic pulse sharpening techniques

    International Nuclear Information System (INIS)

    The use of spiker/sustainer circuitry for exciting excimer lasers is now well established due to its proven high performance. In spiker circuitry reported to date, the rate of rise of spiker voltage incident upon the laser head has been limited by both the turn-on time of the spiker circuit switching element and the spiker circuit inductance. Rise times achieved have generally been limited to between 50ns and 20ns depending upon whether a thyratron or rail-gap is used as the principal switching element. This paper describes an alternative method of generating high voltage pulses whose rise times are no longer limited by the commutation speed of the principal high voltage switch. These pulses are generated in two stages. An initial high voltage pulse with a rise time determined by the principal switching element and circuit geometry is incident upon a ferrite pulse sharpener. This consists of a coaxial transmission line whose inter-conductor region is filled with saturable ferrite material surrounded by high voltage insulation. The pulse drives the ferrite into saturation as it propagates along the cable resulting in the sharpening of the leading edge of the pulse. The rate of rise of the output pulse from the pulse sharpener is determined by the magnitude of the incident voltage pulse, the rate of rise of the incident voltage pulse, the switching constant of the ferrite material and the geometry of the pulse sharpener

  6. Transparent Si-DLC coatings on metals with high repetition bi-polar pulses of a PBII system

    Science.gov (United States)

    Ikeyama, Masami; Sonoda, Tsutomu

    2013-07-01

    Diamond-like carbon (DLC) is widely used because of its good properties. However, the color of DLC is usually dark brown or black. Recently, we have made fairly transparent Si contained DLC (Si-DLC) coatings in visible light region. The fairly transparent Si-DLC was made by using our original bi-polar pulse type plasma based ion implantation (PBII) system, with recently introduced high slew rate pulse power supply. The colors of metal sample surface were uniformly changed as subdued red, yellow, subdued green and subdued blue or violet, with the change of Si-DLC coating's thickness. The colors come from the interference between reflected lights at the surface of the Si-DLC coatings and the surface of the metal samples. The colors were also changed with the angle of glancing. Estimated refractive indexes show well agreements among almost all Si-DLC coatings, instead of the differences of coating conditions. Generally, the longer coating time or slower coating process makes the higher refractive index in near infrared region. Estimated band gap of a Si-DLC coating was about 1.5 eV. The developed Si-DLC coatings must be useful as not only protective but also decorative coatings.

  7. Transparent Si–DLC coatings on metals with high repetition bi-polar pulses of a PBII system

    International Nuclear Information System (INIS)

    Diamond-like carbon (DLC) is widely used because of its good properties. However, the color of DLC is usually dark brown or black. Recently, we have made fairly transparent Si contained DLC (Si–DLC) coatings in visible light region. The fairly transparent Si–DLC was made by using our original bi-polar pulse type plasma based ion implantation (PBII) system, with recently introduced high slew rate pulse power supply. The colors of metal sample surface were uniformly changed as subdued red, yellow, subdued green and subdued blue or violet, with the change of Si–DLC coating’s thickness. The colors come from the interference between reflected lights at the surface of the Si–DLC coatings and the surface of the metal samples. The colors were also changed with the angle of glancing. Estimated refractive indexes show well agreements among almost all Si–DLC coatings, instead of the differences of coating conditions. Generally, the longer coating time or slower coating process makes the higher refractive index in near infrared region. Estimated band gap of a Si–DLC coating was about 1.5 eV. The developed Si–DLC coatings must be useful as not only protective but also decorative coatings

  8. Deposition and characterization of titania-silica optical multilayers by asymmetric bipolar pulsed dc sputtering of oxide targets

    International Nuclear Information System (INIS)

    Titania-silica (TiO2/SiO2) optical multilayer structures have been conventionally deposited by reactive sputtering of metallic targets. In order to overcome the problems of arcing, target poisoning and low deposition rates encountered there, the application of oxide targets was investigated in this work with asymmetric bipolar pulsed dc magnetron sputtering. In order to evaluate the usefulness of this deposition methodology, an electric field optimized Fabry Perot mirror for He-Cd laser (λ = 441.6 nm) spectroscopy was deposited and characterized. For comparison, this mirror was also deposited by the reactive electron beam (EB) evaporation technique. The mirrors developed by the two complementary techniques were investigated for their microstructural and optical reflection properties invoking atomic force microscopy, ellipsometry, grazing incidence reflectometry and spectrophotometry. From these measurements the layer geometry, optical constants, mass density, topography, surface and interface roughness and disorder parameters were evaluated. The microstructural properties and spectral functional characteristics of the pulsed dc sputtered multilayer mirror were found to be distinctively superior to the EB deposited mirror. The knowledge gathered during this study has been utilized to develop a 21-layer high-pass edge filter for radio photoluminescence dosimetry.

  9. Deposition and characterization of titania-silica optical multilayers by asymmetric bipolar pulsed dc sputtering of oxide targets

    Energy Technology Data Exchange (ETDEWEB)

    Sagdeo, P R; Shinde, D D; Misal, J S [Optics and Thin Film Laboratory, Autonagar, BARC-Vizag, Visakhapatnam -530012 (India); Kamble, N M; Tokas, R B; Biswas, A; Poswal, A K; Thakur, S; Bhattacharyya, D; Sahoo, N K; Sabharwal, S C, E-mail: nksahoo@barc.gov.i, E-mail: sahoonk@gmail.co [Spectroscopy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2010-02-03

    Titania-silica (TiO{sub 2}/SiO{sub 2}) optical multilayer structures have been conventionally deposited by reactive sputtering of metallic targets. In order to overcome the problems of arcing, target poisoning and low deposition rates encountered there, the application of oxide targets was investigated in this work with asymmetric bipolar pulsed dc magnetron sputtering. In order to evaluate the usefulness of this deposition methodology, an electric field optimized Fabry Perot mirror for He-Cd laser ({lambda} = 441.6 nm) spectroscopy was deposited and characterized. For comparison, this mirror was also deposited by the reactive electron beam (EB) evaporation technique. The mirrors developed by the two complementary techniques were investigated for their microstructural and optical reflection properties invoking atomic force microscopy, ellipsometry, grazing incidence reflectometry and spectrophotometry. From these measurements the layer geometry, optical constants, mass density, topography, surface and interface roughness and disorder parameters were evaluated. The microstructural properties and spectral functional characteristics of the pulsed dc sputtered multilayer mirror were found to be distinctively superior to the EB deposited mirror. The knowledge gathered during this study has been utilized to develop a 21-layer high-pass edge filter for radio photoluminescence dosimetry.

  10. Generation of Quasi-Gaussian Pulses Based on Correlation Techniques

    Directory of Open Access Journals (Sweden)

    POHOATA, S.

    2012-02-01

    Full Text Available The Gaussian pulses have been mostly used within communications, where some applications can be emphasized: mobile telephony (GSM, where GMSK signals are used, as well as the UWB communications, where short-period pulses based on Gaussian waveform are generated. Since the Gaussian function signifies a theoretical concept, which cannot be accomplished from the physical point of view, this should be expressed by using various functions, able to determine physical implementations. New techniques of generating the Gaussian pulse responses of good precision are approached, proposed and researched in this paper. The second and third order derivatives with regard to the Gaussian pulse response are accurately generated. The third order derivates is composed of four individual rectangular pulses of fixed amplitudes, being easily to be generated by standard techniques. In order to generate pulses able to satisfy the spectral mask requirements, an adequate filter is necessary to be applied. This paper emphasizes a comparative analysis based on the relative error and the energy spectra of the proposed pulses.

  11. The Simplest Method for Generation of an Attosecond Pulse Train

    Directory of Open Access Journals (Sweden)

    Katsuragawa Masayuki

    2013-03-01

    Full Text Available We report an extremely simple approach to generate an attosecond pulse train from more than octave-spanning discrete spectrum by only positioning transparent materials into the optical path without spatially dispersing the frequency components.

  12. Methods of Attosecond X-Ray Pulse Generation

    International Nuclear Information System (INIS)

    We review several proposals for generation of solitary attosecond pulses using two types of free electron lasers which are envisioned as future light sources for studies of ultra-fast dynamics using soft and hard x-rays

  13. Towards efficient generation of attosecond pulses from overdense plasma targets

    International Nuclear Information System (INIS)

    Theoretical studies and computer simulations predict efficient generation of attosecond electromagnetic pulses from overdense plasma targets, driven by relativistically strong laser pulses. These predictions need to be validated in time resolved experiments in order to provide a route for applications. The first available femtosecond sources for these experiments are likely to be 10 fs pulses of a few millijoules, which could provide focal intensities at about the relativistic threshold. With particle-in-cell simulations, we demonstrate that the radiation resulting from interaction of such pulses with solid targets is expected to be attosecond trains with very high conversion efficiency as relativistic effects start to act

  14. Transformer - type pulse high voltage generator

    OpenAIRE

    寺尾, 薫; 高野, 三郎; 入澤, 壽逸

    1995-01-01

    Atriple-resonance pulse transformer cuircuit is compared experimentally to the well-known double-resonance one. The primary circuit of each are fixed and a turn ratio of the transformer is varied from 1:10 to 1:50 by every 10 turns. The triple-resonance mode shows high voltage multiplication and high efficiency of energy transfer compared to the double resonance mode, particularly at high turn ratio of the transformer.

  15. Time and Frequency Domain Analysis of Thunderstorm - Narrow Bipolar Electromagnetic Pulses and Cloud To-Ground Lightning Fields.

    Science.gov (United States)

    Medelius, Pedro Javier

    Single-station electric field (E) and electric field derivative (dE/dt) waveforms were recorded at digitization rates up to 400 MS/s during 1989 and 1990 at the Kennedy Space Center. Narrow bipolar pulses (NBP's) were found to occur separate from typical lightning events, but to be thunderstorm related. Frequency spectra for E obtained from NBP's dropped at a rate of close to 1/f up to 125 MHz. In comparison, the frequency spectra reported by Willett et al. (1989) for similar pulses dropped as 1/f up to about 20 MHz and became flat afterwards up to their 50 MHz Nyquist frequency. NBP's contained higher energy than return strokes above 10-20 MHz. NBP Spectra found from the output of digitally simulated narrowband receivers tended to underestimate the wideband frequency spectra by as much as 10 dB, indicating that the spectra obtained using narrowband receivers are unreliable. Initial E-field peaks of NBP's had a mean rise time of 1.38 mus. Large positive dE/dt pulses had a mean half width of 7 ns, much shorter than the 49 ns reported by Willett et al. (1989). The existence of a single process responsible for VHF radiation from lightning, such as that proposed by Labaune et al. (1990), was tested using deconvolution methods on the NBP waveforms. Our analysis failed to identify a single basic component in these pulses. Electric fields from lightning strikes at distances within 1-2 km consistently exhibited a chaotic behavior during the stepped leader, whereas distant stepped leaders did not. This "chaos" ranged from pulses occurring at rates close to one pulse per mus to a continuous noise-like high frequency signal with frequency components extending beyond 120 MHz. In agreement with other reports in the literature, we found that HF radiation following return strokes peaked 20-30 mus after the onset of the return stroke, and persisted for several tens of microseconds after the peak. However, the short propagation path (less than 7.5 km) over salt water does not

  16. Nonlinear Pulse Shaping in Fibres for Pulse Generation and Optical Processing

    Directory of Open Access Journals (Sweden)

    Sonia Boscolo

    2012-01-01

    Full Text Available The development of new all-optical technologies for data processing and signal manipulation is a field of growing importance with a strong potential for numerous applications in diverse areas of modern science. Nonlinear phenomena occurring in optical fibres have many attractive features and great, but not yet fully explored, potential in signal processing. Here, we review recent progress on the use of fibre nonlinearities for the generation and shaping of optical pulses and on the applications of advanced pulse shapes in all-optical signal processing. Amongst other topics, we will discuss ultrahigh repetition rate pulse sources, the generation of parabolic shaped pulses in active and passive fibres, the generation of pulses with triangular temporal profiles, and coherent supercontinuum sources. The signal processing applications will span optical regeneration, linear distortion compensation, optical decision at the receiver in optical communication systems, spectral and temporal signal doubling, and frequency conversion.

  17. High repetition rate pulse generator for induction synchrotron

    International Nuclear Information System (INIS)

    Recent progress in the development of a power modulator for an Induction Synchrotron which can generate a bipolar rectangular shaped voltage at a very high repetition rate of up to 1 MHz has been presented. Successful operation in the quasi-CW mode of a power modulator with an output voltage of 1.5 kV with a resistor load has been achieved. A wiring technique to minimize the inductance existing throughout the circuit and to avoid the resonant frequency coupled mainly by the output capacitance of MOS-FETs which were the switching elements of an induction power modulator has also been presented. (author)

  18. An 8-GW long-pulse generator based on Tesla transformer and pulse forming network

    International Nuclear Information System (INIS)

    A long-pulse generator TPG700L based on a Tesla transformer and a series pulse forming network (PFN) is constructed to generate intense electron beams for the purpose of high power microwave (HPM) generation. The TPG700L mainly consists of a 12-stage PFN, a built-in Tesla transformer in a pulse forming line, a three-electrode gas switch, a transmission line with a trigger, and a load. The Tesla transformer and the compact PFN are the key technologies for the development of the TPG700L. This generator can output electrical pulses with a width as long as 200 ns at a level of 8 GW and a repetition rate of 50 Hz. When used to drive a relative backward wave oscillator for HPM generation, the electrical pulse width is about 100 ns on a voltage level of 520 kV. Factors affecting the pulse waveform of the TPG700L are also discussed. At present, the TPG700L performs well for long-pulse HPM generation in our laboratory

  19. Powerful nanosecond pulsed generators for linear induction accelerators at JINR

    International Nuclear Information System (INIS)

    The paper presents a review of nanosecond pulse generator schemes for LIA developed at the JINR. The main feature of these schemes consists in the use of relatively low-voltage generators (V∼20-50 kV) with low-resistance output impedance (R∼0.5 Ω). A high power in nanosecond pulses (W∼1 GW) is produced by nonlinear compression schemes with distributed parameters which compress electromagnetic energy in time

  20. New Generation Of Hv Pulse Modulators For Technological Accelertors

    CERN Document Server

    Dolgov, A

    2004-01-01

    New generation of modulators to provide the pulse supply of RF generators of linear accelerators is described. The main features of this pulse modulator is a solid-state switch based on IGBT transistor and the charging power supply, which represents the resonance voltage converter with frequency control based on IGBT transistors. These modulators have the substantially better efficiency and high operation stability and reliability.

  1. System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)

    International Nuclear Information System (INIS)

    A temporally shaped or modified optical output pulse is generated from a bandwidth-encoded optical input pulse in a system in which the input pulse is in the form of a beam which is spectrally spread into components contained within the bandwidth, followed by deflection of the spectrally spread beam (SBD) thereby spatially mapping the components in correspondence with the temporal input pulse profile in the focal plane of a lens, and by spatially selective attenuation of selected components in that focal plane. The shaped or modified optical output pulse is then reconstructed from the attenuated spectral components. The pulse-shaping system is particularly useful for generating optical pulses of selected temporal shape over a wide range of pulse duration, such pulses finding application in the fields of optical communication, optical recording and data storage, atomic and molecular spectroscopy and laser fusion. An optical streak camera is also provided which uses SBD to display the beam intensity in the focal plane as a function of time during the input pulse. 10 figures

  2. Generation of high-energy isolated attosecond pulses

    International Nuclear Information System (INIS)

    Complete text of publication follows. Since the first experimental demonstration of the generation of isolated attosecond pulses, the attosecond technology has become an important branch of ultrafast science. So far, the reported applications of isolated attosecond pulses have been limited by the low photon flux of the available sources. We demonstrate a technique for the generation of isolated attosecond pulses with energy up to 2.1 nJ. The key elements are: the use of few-optical-cycle driving pulses with stable carrier-envelope phase (CEP), linear polarization and peak intensity beyond the saturation intensity of the gas use for HHG; and the optimization of the interaction geometry in terms of gas pressure, position and thickness of the gas cell. We used 5-fs driving pulses with stable CEP to generate XUV radiation by HHG in a 2.5-mm-long cell filled with xenon at static pressure (2.5-3 torr) at a peak intensity I = (2.3±0.3) x 1015 W/cm2. The XUV spectra display an evolution from a continuous behavior to a modulated one by changing the CEP value. The energy of the XUV pulses in the case of continuous spectra was 2.1 nJ, after a 100-nm-thick aluminium filter used to block the fundamental radiation and the low order harmonics. We have also used argon, krypton and neon as generating media: also in such cases clear transition between modulated and continuous XUV spectra were observed upon changing the CEP of the driving pulses. We have measured the temporal characteristics of the attosecond pulses by using the FROGCRAB method. Figure 1 a shows a portion of the FROGCRAB trace; in the reconstructed temporal intensity profile of the XUV pulses, the pulse duration was 155±5 as (the transform limit was ∼ 120 as). The physical mechanism at the basis of this method is related to the ionization dynamics in the generating medium. We used a nonadiabatic three-dimensional numerical model. In agreement with experimental results, the calculated XUV spectra display an

  3. Laser-generated ultrasonic pulse shapes at solid wedges.

    Science.gov (United States)

    Pupyrev, Pavel D; Lomonosov, Alexey M; Mayer, Andreas P

    2016-08-01

    Laser pulses focused near the tip of an elastic wedge generate acoustic waves guided at its apex. The shapes of the acoustic wedge wave pulses depend on the energy and the profile of the exciting laser pulse and on the anisotropy of the elastic medium the wedge is made of. Expressions for the acoustic pulse shapes have been derived in terms of the modal displacement fields of wedge waves for laser excitation in the thermo-elastic regime and for excitation via a pressure pulse exerted on the surface. The physical quantity considered is the local inclination of a surface of the wedge, which is measured optically by laser-probe-beam deflection. Experimental results on pulse shapes in the thermo-elastic regime are presented and confirmed by numerical calculations. They pertain to an isotropic sharp-angle wedge with two wedge-wave branches and to a non-reciprocity phenomenon at rectangular silicon edges. PMID:27135188

  4. An iron free asynchronous pulsed generator for the production of pulsed high magnetic fields

    International Nuclear Information System (INIS)

    The production of long pulsed high fields (> 500 kgaus) with (tau > 1 s) with cryogenic coils requires an initial energy source of several megajoules. Iron free asynchronous pulsed generators are particulary well adapted to this application as they are able to produce this energy at a very competitive price

  5. High Intensity, Pulsed, D-D Neutron Generator

    OpenAIRE

    Williams, D L

    2010-01-01

    Single ion-beam RF-plasma neutron generators are presented as a laboratory source of intense neutrons. The continuous and pulsed operations of such a neutron generator using the deuterium-deuterium fusion reaction are reported. The neutron beam can be pulsed by switching the RF plasma and/or a gate electrode. These generators are actively vacuum pumped so that a continuous supply of deuterium gas is present for the production of ions and neutrons. This contributes to the generator's long l...

  6. Generation of strong pulsed magnetic fields using a compact, short pulse generator

    Science.gov (United States)

    Yanuka, D.; Efimov, S.; Nitishinskiy, M.; Rososhek, A.; Krasik, Ya. E.

    2016-04-01

    The generation of strong magnetic fields (˜50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ˜3.6 kJ, discharge current amplitude of ˜220 kA, and rise time of ˜1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma by either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.

  7. Pulsed power generator by an inductive energy storage system

    International Nuclear Information System (INIS)

    A pulsed power generator using an inductive energy storage system has been constructed. The pulsed power generator, named ASO-I, is extremely compact and light in comparison with a conventional pulsed power generator which consists of a Marx bank and a water pulse forming line. The ASO-I has a two-staged opening switch, consisting of fuses in water and a plasma erosion opening switch, and can be operated hundreds of times a day at the output power of 300kV and 40kA. The plasma erosion opening switch is successfully operated as a second opening switch, and the rise time of the current through the short-circuit load decreases from 250nsec to about 10nsec. (author)

  8. Efficient femtosecond pulse generation using a parabolic amplifier combined with a pulse compressor. I. Stimulated Raman scattering effects

    OpenAIRE

    Soh, D.B.S.; Nilsson, J.; Grudinin, A.B.

    2006-01-01

    The effects of stimulated Raman scattering on femtosecond pulse generation using a parabolic amplifier and a grating pair compressor are presented. We derive an explicit analytical form for the Stokes pulse evolution. We find that the evolution of the Stokes pulse can be divided into four regimes; small Gaussian Stokes pulse, small asymmetric Stokes pulse, signal depletion, and parabolic Raman pulse. In order to achieve efficient pulse compression, the parabolic amplifier should be operated i...

  9. Unipolar and bipolar pulses emitted during the development of lightning flashes

    Czech Academy of Sciences Publication Activity Database

    Kašpar, Petr; Santolík, Ondřej; Kolmašová, Ivana

    2015-01-01

    Roč. 42, č. 17 (2015), 7206–7213. ISSN 0094-8276 R&D Projects: GA ČR(CZ) GA14-31899S Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100421206 Institutional support: RVO:68378289 Keywords : initial breakdown pulses * electric-field pulses * return stroke * magnetic-field * radiation * discharges * cloud * propagation * Earth Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.456, year: 2013

  10. Programmable pseudo-random detector-pulse-pattern generator

    International Nuclear Information System (INIS)

    This report discusses the design and realization of the digital part of the programmable pseudo-random detector pulse-pattern generator. For the design and realization use has been made of F-TTL and high speed special purpose ic's, in particular FAL's (15 ns). The design possibilities offered by the software for pro-gramming of the FAL's have been utilized as much as possible. In this way counters, registers and a state machine with extended control possibilities have been designed and an advanced 8 channel pulse generator has been developed which is controlled via the VME system bus. the generator possesses an internal clock oscillator of 16 MHZ. The moment when a pulse is generated can be adjusted with a step size of 250 ps. 2000 different periods (time windows) can be stored for generating a pattern. (author). 37 refs.; 6 figs

  11. Attosecond Magnetic Field Pulse Generation by Intense Few Cycle Circularly Polarized UV Pulses

    CERN Document Server

    Yuan, Kai-Jun

    2013-01-01

    Intense attosecond magnetic field pulses are predicted to be produced by intense few cycle circularly polarized UV pulses. Numerical solutions of the time dependent Schr\\"{o}dinger equation for H$_2^+$ are used to study the dynamical process. Spiralling attosecond circular electron wave packets are created with nanometer molecular dimensions, thus generating magnetic fields of several tens of Teslas ($10^5$ Gauss). Simulations show that the induced magnetic field is critically dependent on the pulse wavelength $\\lambda$ and pulse duration $n\\tau$ ($n$ number of cycle) as predicted by a classical model. For ultrashort few cycle circularly polarized attosecond pulses, molecular orientation influences the generation of the induced magnetic fields as a result of preferential ionization perpendicular to the molecular axis.

  12. Generation of frequency-chirped optical pulses with felix

    Energy Technology Data Exchange (ETDEWEB)

    Knippels, G.M.H.; Meer, A.F.G. van der; Mols, R.F.X.A.M. [FOM-Institute for Plasma Physics, Nieuwegein (Netherlands)] [and others

    1995-12-31

    Frequency-chirped optical pulses have been produced in the picosecond regime by varying the energy of the electron beam on a microsecond time scale. These pulses were then compressed close to their bandwidth limit by an external pulse compressor. The amount of chirp can be controlled by varying the sweep rate on the electron beam energy and by cavity desynchronisation. To examine the generated chirp we used the following diagnostics: a pulse compressor, a crossed beam autocorrelator, a multichannel electron spectrometer and multichannel optical spectrometer. The compressor is build entirely using reflective optics to permit broad band operation. The autocorrelator is currently operating from 6 {mu}m to 30 {mu}m with one single crystal. It has been used to measure pulses as short as 500 fs. All diagnostics are evacuated to prevent pulse shape distortion or pulse lengthening caused by absorption in ambient water vapour. Pulse length measurements and optical spectra will be presented for different electron beam sweep rates, showing the presence of a frequency chirp. Results on the compression of the optical pulses to their bandwidth limit are given for different electron sweep rates. More experimental results showing the dependence of the amount of chirp on cavity desynchronisation will be presented.

  13. Study on nanosecond pulsed electron beam generation

    Science.gov (United States)

    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.

  14. Study on nanosecond pulsed electron beam generation

    International Nuclear Information System (INIS)

    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

  15. Optical UWB pulse generator using an N tap microwave photonic filter and phase inversion adaptable to different pulse modulation formats.

    Science.gov (United States)

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2009-03-30

    We propose theoretically and demonstrate experimentally an optical architecture for flexible Ultra-Wideband pulse generation. It is based on an N-tap reconfigurable microwave photonic filter fed by a laser array by using phase inversion in a Mach-Zehnder modulator. Since a large number of positive and negative coefficients can be easily implemented, UWB pulses fitted to the FCC mask requirements can be generated. As an example, a four tap pulse generator is experimentally demonstrated which complies with the FCC regulation. The proposed pulse generator allows different pulse modulation formats since the amplitude, polarity and time delay of generated pulse is controlled. PMID:19333263

  16. High Intensity, Pulsed, D-D Neutron Generator

    International Nuclear Information System (INIS)

    Single ion-beam RF-plasma neutron generators are presented as a laboratory source of intense neutrons. The continuous and pulsed operations of such a neutron generator using the deuterium-deuterium fusion reaction are reported. The neutron beam can be pulsed by switching the RF plasma and/or a gate electrode. These generators are actively vacuum pumped so that a continuous supply of deuterium gas is present for the production of ions and neutrons. This contributes to the generator's long life. These single-beam generators are capable of producing up to 1E10 n/s. Previously, Adelphi and LBNL have demonstrated these generators applications in fast neutron radiography, Prompt Gamma Neutron Activation Analysis (PGNAA) and Neutron Activation Analysis (NAA). Together with an inexpensive compact moderator, these high-output neutron generators extend useful applications to home laboratory operations.

  17. Time-Grating for the Generation of STUD Pulse Trains

    Science.gov (United States)

    Zheng, Jun; Wang, Shi-Wei; Xu, Jian-Qiu

    2013-04-01

    Spike train of uneven duration or delay (STUD) pulses hold potential for laser-plasma interaction (LPI) control in laser fusion. The technique based on time grating is applied to generate an STUD pulse train. Time grating, a temporal analogy of the diffraction grating, can control the pulse width, shape, and repetition rate easily through the use of electro-optical devices. The pulse width and repetition rate are given by the modulation frequency and depth of the phase modulation function in theory and numerical calculation. The zero-chirped phase modulation is good for the compression effect of the time grating. A principle experiment of two pulses interfering is shown to verify the time grating function.

  18. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    Directory of Open Access Journals (Sweden)

    Jianqiang Zhu

    2012-01-01

    Full Text Available We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA. The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

  19. Gating attosecond pulse train generation using multicolor laser fields

    International Nuclear Information System (INIS)

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  20. Micro electrical discharge milling of WC-Co using a deionized water spray and a bipolar pulse

    International Nuclear Information System (INIS)

    Micro electrical discharge milling (ED-milling) is an effective machining process for manufacturing micro structures on hard metals. This method of machining generally uses kerosene or deionized water as the working fluid, both of which are associated with some problems. Kerosene results in considerable electrode wear and deionized water causes electrolytic corrosion in workpieces. In particular, when cemented tungsten carbide (WC-Co), which has superior strength, hardness and wear resistance, is machined by electrical discharge machining (EDM), the problem of electrolytic corrosion arises as a matter of course since the material is very susceptible to electrolyzation. In this study, spray ED-milling with a bipolar pulsed power source and deionized water was conducted to solve the above problems. This method uses a water spray, which is a mixture of compressed air and deionized water. The spray is injected into the machining gap between the electrode and the workpiece. WC-Co was used for the workpiece and micro grooves were machined on the workpiece. As a result, using the spray ED-milling method, high-quality micro grooves were manufactured on the WC-Co workpiece with no electrolytic corrosion and almost-zero electrode wear.

  1. Micro electrical discharge milling of WC-Co using a deionized water spray and a bipolar pulse

    Science.gov (United States)

    Song, Ki Young; Chung, Do Kwan; Park, Min Soo; Chu, Chong Nam

    2010-04-01

    Micro electrical discharge milling (ED-milling) is an effective machining process for manufacturing micro structures on hard metals. This method of machining generally uses kerosene or deionized water as the working fluid, both of which are associated with some problems. Kerosene results in considerable electrode wear and deionized water causes electrolytic corrosion in workpieces. In particular, when cemented tungsten carbide (WC-Co), which has superior strength, hardness and wear resistance, is machined by electrical discharge machining (EDM), the problem of electrolytic corrosion arises as a matter of course since the material is very susceptible to electrolyzation. In this study, spray ED-milling with a bipolar pulsed power source and deionized water was conducted to solve the above problems. This method uses a water spray, which is a mixture of compressed air and deionized water. The spray is injected into the machining gap between the electrode and the workpiece. WC-Co was used for the workpiece and micro grooves were machined on the workpiece. As a result, using the spray ED-milling method, high-quality micro grooves were manufactured on the WC-Co workpiece with no electrolytic corrosion and almost-zero electrode wear.

  2. Mitigation of impedance changes due to electroporation therapy using bursts of high-frequency bipolar pulses

    OpenAIRE

    Bhonsle, Suyashree P; Arena, Christopher B.; Sweeney, Daniel C; Davalos, Rafael V.

    2015-01-01

    Abstract Background For electroporation-based therapies, accurate modeling of the electric field distribution within the target tissue is important for predicting the treatment volume. In response to conventional, unipolar pulses, the electrical impedance of a tissue varies as a function of the local electric field, leading to a redistribution of the field. These dynamic impedance changes, which depend on the tissue type and the applied ...

  3. Generation of ultrashort electron bunches by colliding laser pulses

    International Nuclear Information System (INIS)

    A proposed laser-plasma based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses

  4. Pulse generator with intermediate inductive storage as a lightning simulator

    Science.gov (United States)

    Kovalchuk, B. M.; Kharlov, A. V.; Zherlytsyn, A. A.; Kumpyak, E. V.; Tsoy, N. V.

    2016-06-01

    Compact transportable generators are required for simulating a lightning current pulse for electrical apparatus testing. A bi-exponential current pulse has to be formed by such a generator (with a current rise time of about two orders of magnitude faster than the damping time). The objective of this study was to develop and investigate a compact pulse generator with intermediate inductive storage and a fuse opening switch as a simulator of lightning discharge. A Marx generator (six stages) with a capacitance of 1 μF and an output voltage of 240 kV was employed as primary storage. In each of the stages, two IK-50/3 (50 kV, 3 μF) capacitors are connected in parallel. The generator inductance is 2 μH. A test bed for the investigations was assembled with this generator. The generator operates without SF6 and without oil in atmospheric air, which is very important in practice. Straight copper wires with adjustable lengths and diameters were used for the electro-explosive opening switch. Tests were made with active-inductive loads (up to 0.1 Ω and up to 6.3 μH). The current rise time is lower than 1200 ns, and the damping time can be varied from 35 to 125 μs, following the definition of standard lightning current pulse in the IEC standard. Moreover, 1D MHD calculations of the fuse explosion were carried out self-consistently with the electric circuit equations, in order to calculate more accurately the load pulse parameters. The calculations agree fairly well with the tests. On the basis of the obtained results, the design of a transportable generator was developed for a lightning simulator with current of 50 kA and a pulse shape corresponding to the IEEE standard.

  5. N-bit digitally tunable ultra wide-band pulse generator

    OpenAIRE

    Yılmaz, Sertaç; Yilmaz, Sertac

    2006-01-01

    In this thesis, a new digitally tunable UWB pulse generator for an impulse type of pulse generator is developed. The pulse generator is realized with a low cost simple circuitry by using Step Recovery Diode (SRD), PIN diodes and microstrip transmission lines which are employed in the many basic UWB pulse generation circuits. During the pulse generation process, the generator initially generates sharp edges by using a Step Recovery Diode (SRD) from an applied low frequency input sinusoidal sig...

  6. Advances in laser technology for isolated attosecond pulse generation

    International Nuclear Information System (INIS)

    In this review we report on recent advances in laser technology, which have contributed to the fast development of attosecond science. In particular we will concentrate on two experimental methods for the generation of high-peak-power, few-optical-cycle laser pulses with controlled electric field, which are crucial for the generation of isolated attosecond pulses. The first method is the hollow-fiber compression technique, introduced in 1996 and now routinely used in several laboratories. So far, isolated attosecond pulses have been generated by using few-cycle pulses produced by such compression technique, in combination with active stabilization of the carrier-envelope phase. More recently, few-cycle pulses tunable in the infrared region have been generated by optical parametric amplification with passive stabilization of the carrier-envelope phase. Such parametric sources represent excellent drivers for the generation of harmonic radiation with an extended cutoff, and offer the possibility to extend attosecond science towards the soft-X rays region. Finally, we will briefly discuss the basic elements of attosecond metrology

  7. Pulsed power generator using solid-state LTD modules

    International Nuclear Information System (INIS)

    Linear transformer driver (LTD) modules using power MOSFETs as switches have been developed and tested for applications to repetitive, compact pulsed power sources. It is based on the same principle as large-scale LTDs being developed abroad for fusion and high energy-density physics purposes, while having advantages in high repetition rate and turning-off capability. It is expected to become a new approach leading to innovative compact pulsed power generators. (author)

  8. Generation of nanosecond S band microwave pulses based on superradiance

    Energy Technology Data Exchange (ETDEWEB)

    Ginzburg, N.S.; Zotova, I.V.; Rozental, R.M. [Russian Academy of Science, Institute of Applied Physics, Nizhny Novgorod (RU)] [and others

    2002-06-01

    Modeling carried out demonstrates possibility of generation of gigawatt power level S band microwave pulse with duration of several nanoseconds using superradiation of short electron beam moving along slow-wave periodical structure. A 10 ns / 500 keV / 5 kA accelerator of Kanazawa University can be used in such experiments. It is shown that significant increasing peak power can be obtained by optimization of voltage and current pulses waveforms. Required increasing of electron energy and current by the end of electron pulse can be achieved by using self-acceleration of a short beam passing through a system of passive cavities. (author)

  9. Active load equivalent for a superpower microsecond-pulse generator

    International Nuclear Information System (INIS)

    Performance, structure and results of experimental studies of an active dummy lead for super-high-power pulse generator built according to the layout of pulse modulator with capacitor energy storage are described. The active dummy load represents nonlinear artificial shaping line with 2.5 Ohm wave resistance, which gives an opportunity to shape current pulses with amplitude ≅10 kA at storage charging voltage level of 50 kV. The active dummy load application provides for regeneration of more than 50% of storage energy back into power source, and thus it allows one to decrease sufficiently the test cost

  10. Efficient generation of an isolated single-cycle attosecond pulse

    CERN Document Server

    Lan, Pengfei; Cao, Wei; Wang, Xinlin

    2007-01-01

    A new method for efficiently generating an isolated single-cycle attosecond pulse is proposed. It is shown that the ultraviolet (UV) attosecond pulse can be utilized as a robust tool to control the dynamics of electron wave packets (EWPs). By adding a UV attosecond pulse to an infrared (IR) few-cycle pulse at a proper time, only one return of the EWP to the parent ion is selected to effectively contribute to the harmonics, then an isolated two-cycle 130-as pulse with a bandwidth of 45 eV is obtained. After complementing the chirp, an isolated single-cycle attosecond pulse with a duration less than 100 as seems achievable. In addition, the contribution of the quantum trajectories can be selected by adjusting the delay between the IR and UV fields. Using this method, the harmonic and attosecond pulse yields are efficiently enhanced in contrast to the scheme [G. Sansone {\\it et al.}, Science {\\bf314}, 443 (2006)] using a few-cycle IR pulse in combination with the polarization gating technique.

  11. Efficient generation of an isolated single-cycle attosecond pulse

    International Nuclear Information System (INIS)

    A method for efficiently generating an isolated single-cycle attosecond pulse is proposed. It is shown that the ultraviolet (UV) attosecond (as) pulse can be utilized as a robust tool to control the dynamics of electron wave packets (EWPs). By adding a UV attosecond pulse to an infrared (IR) few-cycle pulse at a proper time, only one return of the EWP to the parent ion is selected to effectively contribute to the harmonics; then, an isolated two-cycle 130-as pulse with a bandwidth of 45 eV is obtained. After complementing the chirp, an isolated single-cycle attosecond pulse with a duration less than 100 as seems achievable. In addition, the contribution of the quantum trajectories can be selected by adjusting the delay between the IR and UV fields. Using this method, the harmonic and attosecond pulse yields are efficiently enhanced in contrast to the scheme [G. Sansone et al., Science 314, 443 (2006)] using a few-cycle IR pulse in combination with the polarization gating technique

  12. Single attosecond pulse generation via continuum wave packet interference

    Science.gov (United States)

    Zhou, Shengpeng; Yang, Yujun; Ding, Dajun

    2016-07-01

    A single attosecond pulse generation via continuum-continuum interference is investigated theoretically by exposing a single-electron atom in a femtosecond laser field with the intensity in over-the-barrier ionization regime. We show that the ground state of the atom is depleted in such intense laser field and the high-order harmonics (HHG) via continuum to continuum coherence are generated. In a few-cycle monochromatic laser field (5 fs/800 nm, 1.2×1016 W cm-2), a single attosecond pulse with duration of 49 as is obtained from the HHG. With a two-color laser field combined by 1200 nm (8 fs/7.5×1015 W cm-2) and 800 nm (5 fs/1.0×1016 W cm-2), a shorter single pulse with duration of 29 as can further be produced by changing the relative carrier envelope phase of two laser pulses as a result of controlling the electronic quantum path in the intense electric field. Our results also show that a short single attosecond pulse can be generated in a wide range of the relative carrier envelope phase of the two laser pulses.

  13. High-order harmonic generation spectra and isolated attosecond pulse generation with a two-color time delayed pulse

    Energy Technology Data Exchange (ETDEWEB)

    Feng Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Chu Tianshu, E-mail: tschu@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Investigation of HHG spectra and single isolated attosecond pulse generation. Black-Right-Pointing-Pointer Irradiation from a model Ne atom by two-color time delayed pulse. Black-Right-Pointing-Pointer Observation of time delay effect and relative phase effect. Black-Right-Pointing-Pointer Revelation of the optimal condition for generating isolated attosecond pulse. Black-Right-Pointing-Pointer Generation of a single isolated attosecond pulse of 45as. - Abstract: In this paper, we theoretically investigate the delay time effect on the high-order harmonic generation (HHG) when a model Ne atom is exposed to a two-color time delayed pulse, consisting of a 5fs/800 nm fundamental field and a 20fs/2000 nm controlling field. It shows that the HHG spectra are strongly sensitive to the delay time between the two laser fields, in particular, for the zero carrier-envelope phase (CEP) {phi} case (corresponding to the 800 nm fundamental field), the maximum cutoff energy has been achieved at zero delay time. However, with the introduction of the CEP ({phi} = 180 Degree-Sign ), the delay effect on HHG is changed, exhibiting a 'U' structure harmonic emission from -1 T to 1 T. In addition, the combinations of different controlling pulse frequencies and pulse intensities have also been considered, showing the similar results as the original controlling field case, but with some characteristics. Finally, by properly superposing the optimal harmonic spectrum, an isolated 45as pulse is generated without phase compensation.

  14. Isolated attosecond pulse generation from atom radiated by a three-color laser pulse

    International Nuclear Information System (INIS)

    We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated by superposing supercontinuum from the 160th to the 210th order harmonics. (atomic and molecular physics)

  15. TRIDENT - a megavolt pulse generator using inductive energy storage

    International Nuclear Information System (INIS)

    A megavolt level pulse generator, TRIDENT, has been constructed utilizing an inductive store as the primary pulse forming device. The 2.5 μH coaxial storage inductor can be energized with up to 500 kA obtained from a 500 kJ, 60 kV capacitor bank. Current interruption is accomplished using a three stage opening switch comprised of an explosively actuated switch in parallel with foil and wire fuses. The generator has been operated at the 410 kA charge level (70% energy) to produce 700 kV pulses with risetimes of 150 nsec. Energy has been deposited into a 7.5 Ω resistive load at a rate of 5 x 1010W. Operation with optimized fuse dimensions and at full charge is anticipated to approach megavolt outputs at powers of 1011W. Future experiments include utilizing a homopolar generator as the current source

  16. Pulse-to-pulse interaction analysis and parameter optimization for future-generation ophthalmic laser systems

    Science.gov (United States)

    Tinne, N.; Kaune, B.; Bleeker, S.; Lubatschowski, H.; Krüger, A.; Ripken, T.

    2014-02-01

    The immediate pulse-to-pulse interaction becomes more and more important for future-generation high-repetition rate ophthalmic laser systems. Therefore, we investigated the interaction of two laser pulses with different spatial and temporal separation by time-resolved photography. There are various different characteristic interaction mechanisms which are divided into 11 interaction scenarios. Furthermore, the parameter range has been constricted regarding the medical application; here, the efficiency was optimized to a maximum jet velocity along the scanning axis with minimum applied pulse energy as well as unwanted side effects at the same time. In conclusion, these results are of great interest for the prospective optimization of the ophthalmic surgical process with future-generation fs-lasers.

  17. Single Ultrashort Attosecond Pulse Generation via Combination of Chirped Fundamental Laser and an Ultraviolet Controlling Pulse

    International Nuclear Information System (INIS)

    We theoretically study the high-order harmonic generation (HHG) from a hydrogen atom in an intense few-cycle chirped fundamental laser in combination with an ultraviolet (uv) controlling pulse. The high-order harmonic spectrum is calculated by solving the time-dependent Schroedinger equation using the split-operator method. In our calculation, we present the difference of the high-order harmonic spectrum from one-dimensional (1D) model hydrogen atom and three-dimensional (3D) real hydrogen atom. We found that the plateau of the high-order harmonic generation from the 1D case and 3D case are all extended effectively to Ip + 35Up due to the presence of the chirped laser pulse and the HHG supercontinuum spectrum is generated by adding an ultraviolet controlling pulse at a proper time, but the efficiency of the HHG for 3D case is more higher at the near cut-off region than the 1D case. Therefore, the generation of the attosecond pulse by synthesizing the harmonics near cut-off region have some slight differences between 1D and 3D simulations. As a real 3D case study, we show that an isolated 18 as pulse with a bandwidth of 232.5 eV is generated directly by optmizing the combination laser fields. (atomic and molecular physics)

  18. A repetitive long-pulse power generator based on pulse forming network and linear transformer driver.

    Science.gov (United States)

    Li, Mingjia; Kang, Qiang; Tan, Jie; Zhang, Faqiang; Luo, Min; Xiang, Fei

    2016-06-01

    A compact module for long-pulse power generator, based on Blumlein pulse forming network (PFN), was designed. Two Blumlein PFNs with L-type configuration and 20 Ω characteristic impedance were connected symmetrically to the primary coil of the linear transformer driver (LTD) and driven by an identical high voltage spark switch to ensure two Blumlein PFNs synchronizing operation. The output pulse of the module connected with 10 Ω water load is about 135 kV in amplitude and 200 ns in duration with a rise time of ∼50 ns and a flat top of ∼100 ns. On this basis, a repetitive long-pulse power generator based on PFN-LTD has been developed, which was composed of four modules. The following technical parameters of the generator were achieved on planar diode: output voltage amplitude of ∼560 kV, output current amplitude of ∼10 kA at a repetition rate of 25 Hz. The generator operates stable and outputs more than 10(4) pulses. Meanwhile, the continuous operating time of the generator is up to 60 s. PMID:27370479

  19. A repetitive long-pulse power generator based on pulse forming network and linear transformer driver

    Science.gov (United States)

    Li, Mingjia; Kang, Qiang; Tan, Jie; Zhang, Faqiang; Luo, Min; Xiang, Fei

    2016-06-01

    A compact module for long-pulse power generator, based on Blumlein pulse forming network (PFN), was designed. Two Blumlein PFNs with L-type configuration and 20 Ω characteristic impedance were connected symmetrically to the primary coil of the linear transformer driver (LTD) and driven by an identical high voltage spark switch to ensure two Blumlein PFNs synchronizing operation. The output pulse of the module connected with 10 Ω water load is about 135 kV in amplitude and 200 ns in duration with a rise time of ˜50 ns and a flat top of ˜100 ns. On this basis, a repetitive long-pulse power generator based on PFN-LTD has been developed, which was composed of four modules. The following technical parameters of the generator were achieved on planar diode: output voltage amplitude of ˜560 kV, output current amplitude of ˜10 kA at a repetition rate of 25 Hz. The generator operates stable and outputs more than 104 pulses. Meanwhile, the continuous operating time of the generator is up to 60 s.

  20. Pulsed White Spectrum Neutron Generator for Explosive Detection

    International Nuclear Information System (INIS)

    Successful explosive material detection in luggage and similar sized containers is a critical issue in securing the safety of all airline passengers. Tensor Technology Inc. has recently developed a methodology that will detect explosive compounds with pulsed fast neutron transmission spectroscopy. In this scheme, tritium beams will be used to generate neutrons with a broad energy spectrum as governed by the T(t,2n)4He fission reaction that produces 0-9 MeV neutrons. Lawrence Berkeley National Laboratory (LBNL), in collaboration with Tensor Technology Inc., has designed and fabricated a pulsed white-spectrum neutron source for this application. The specifications of the neutron source are demanding and stringent due to the requirements of high yield and fast pulsing neutron emission, and sealed tube, tritium operation. In a unique co-axial geometry, the ion source uses ten parallel rf induction antennas to externally couple power into a toroidal discharge chamber. There are 20 ion beam extraction slits and 3 concentric electrode rings to shape and accelerate the ion beam into a titanium cone target. Fast neutron pulses are created by using a set of parallel-plate deflectors switching between +-1500 volts and deflecting the ion beams across a narrow slit. The generator is expected to achieve 5 ns neutron pulses at tritium ion beam energies between 80-120 kV. First experiments demonstrated ion source operation and successful beam pulsing

  1. Electrochromic properties of bipolar pulsed magnetron sputter deposited tungsten–molybdenum oxide films

    International Nuclear Information System (INIS)

    There are great interests in electrochromic technology for smart windows and displays over past decades. In this study, the WMoOx thin films were deposited onto indium tin oxide glass and silicon substrates by pulsed magnetron sputter system with W and Mo targets. The films were deposited with fixed W target power while the variant parameter of Mo target power in the range 50, 100, 150 and 200 W was investigated. The working pressure was fixed at 1.33 Pa with a gas mixture of Ar (30 sccm) and O2 (15 sccm). The film thickness increased with the Mo target power. Higher plasma power resulted in a crystalline structure which would reduce the electrochromic property of the film. The influence of plasma powers applied to Mo target on the structural, optical and electrochromic properties of the WMoOx thin films has been investigated. WMoOx films grown at Mo target powers less than 100 W were found to be amorphous. The films deposited at 150 W, which is the optimal fabrication condition, exhibit better electrochromic properties with high optical modulation, high coloration efficiency and less color memory effect at wavelength 400, 550 and 800 nm. The improvement resulted from the effect of doping Mo has been tested. The maximum ΔT (%) values are 36.6% at 400 nm, 65.6% at 550 nm, and 66.6% at 800 nm for pure WO3 film. The addition of Mo content in the WMoOx films provides better resistance to the short wavelength light source and can be used in the concerned application. - Highlights: • WMoOx films are deposited by pulsed magnetron sputter with pure W and Mo targets. • Mo addition in WMoOx provides better resistance to short wavelength light source. • WMoOx films exhibit electrochemical stability in the cycling test

  2. Electrochromic properties of bipolar pulsed magnetron sputter deposited tungsten–molybdenum oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Tai-Nan [Chemical Engineering Division, Institute of Nuclear Energy Research, Taoyuan 325, Taiwan, ROC (China); Lin, Yi Han; Lee, Chin Tan [Department of Electronic Engineering, National Quemoy University, Kinmen 892, Taiwan, ROC (China); Han, Sheng [Center of General Education, National Taichung Institute of Technology, Taichung 404, Taiwan, ROC (China); Weng, Ko-Wei, E-mail: kowei@nqu.edu.tw [Department of Electronic Engineering, National Quemoy University, Kinmen 892, Taiwan, ROC (China)

    2015-06-01

    There are great interests in electrochromic technology for smart windows and displays over past decades. In this study, the WMoO{sub x} thin films were deposited onto indium tin oxide glass and silicon substrates by pulsed magnetron sputter system with W and Mo targets. The films were deposited with fixed W target power while the variant parameter of Mo target power in the range 50, 100, 150 and 200 W was investigated. The working pressure was fixed at 1.33 Pa with a gas mixture of Ar (30 sccm) and O{sub 2} (15 sccm). The film thickness increased with the Mo target power. Higher plasma power resulted in a crystalline structure which would reduce the electrochromic property of the film. The influence of plasma powers applied to Mo target on the structural, optical and electrochromic properties of the WMoO{sub x} thin films has been investigated. WMoO{sub x} films grown at Mo target powers less than 100 W were found to be amorphous. The films deposited at 150 W, which is the optimal fabrication condition, exhibit better electrochromic properties with high optical modulation, high coloration efficiency and less color memory effect at wavelength 400, 550 and 800 nm. The improvement resulted from the effect of doping Mo has been tested. The maximum ΔT (%) values are 36.6% at 400 nm, 65.6% at 550 nm, and 66.6% at 800 nm for pure WO{sub 3} film. The addition of Mo content in the WMoO{sub x} films provides better resistance to the short wavelength light source and can be used in the concerned application. - Highlights: • WMoO{sub x} films are deposited by pulsed magnetron sputter with pure W and Mo targets. • Mo addition in WMoO{sub x} provides better resistance to short wavelength light source. • WMoO{sub x} films exhibit electrochemical stability in the cycling test.

  3. Generation of 1.5 cycle 0.3 TW laser pulses using a hollow-fiber pulse compressor.

    Science.gov (United States)

    Park, Juyun; Lee, Jae-Hwan; Nam, Chang Hee

    2009-08-01

    Pulse compression in a differentially pumped neon-filled hollow fiber was used to generate high-power few-cycle laser pulses. The pulse compression process was optimized by adjusting gas pressure and laser chirp to produce the shortest laser pulses. Precise dispersion control enabled the generation of laser pulses with duration of 3.7 fs and energy of 1.2 mJ. This corresponds to an output of 1.5 cycle, 0.3 TW pulses at a 1 kHz repetition rate using positively chirped 33 fs laser pulses. PMID:19649091

  4. Plasma Approach for Generating Ultra-Intense Single Attosecond Pulse

    International Nuclear Information System (INIS)

    In our previous work, a plasma approach for single attosecond pulse (AP) generation was proposed. A few-cycle relativistic circularly polarized laser pulse will induce a single drastic oscillation of plasma boundary, from which high-order harmonics and furthermore an ultra-intense single AP can be generated naturally after it is reflected. Analytical model and simulations both demonstrate that the process is mostly efficient as the pulse duration is close to the plasma responding time. The effects of plasma density ramp are analyzed here, suggesting that the proposal is still quite efficient with appropriate density gradient in the ramp. At last, a combined approach is employed to obtain single AP with 30 fs incident laser. The relatively large-duration pulse is firstly shortened by a density dropping thin foil, and then reflected from an overdense plasma target. One-dimensional simulation shows that a 600 as single light pulse is generated with peak intensity of 3×1020 W/cm2. (cai awardee's article)

  5. Intense 8-fs pulse generation in the deep ultraviolet

    Energy Technology Data Exchange (ETDEWEB)

    Durfee, C.G. III; Backus, S.; Kapteyn, H.C.; Murnane, M.M. [Center for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel Boulevard, Ann Arbor, Michigan 48109-2099 (United States)

    1999-05-01

    By use of the recently developed technique of guided-wave frequency conversion, the generation of sub-10-fs light pulses in the UV has been demonstrated for what is believed to be the first time. Cross-phase modulation of the light in a hollow waveguide produced a bandwidth of 16thinspthinspnm, with a center frequency of 270thinspthinspnm, at 1thinspthinspkHz. A simple grating pair was used to compress the pulses to a duration of 8thinspthinspfs, as measured by self-diffraction frequency-resolved optical gating. In the experiment the compressed energy was greater than 1 {mu}J , with a peak power of {gt}100 MW ; the technique can be scaled to higher energy. Further improvements should make it possible to generate pulses as short as {approximately}3 fs with this technique. {copyright} {ital 1999} {ital Optical Society of America}

  6. Two-Step Bipolar Electrochemistry: Generation of Composition Gradient and Visual Screening of Electrocatalytic Activity.

    Science.gov (United States)

    Termebaf, Hajar; Shayan, Mohsen; Kiani, Abolfazl

    2015-12-01

    Bipolar electrochemistry (BE) is employed for both creating electrocatalysts composition gradient and visual screening of the prepared composition on a single substrate in just two experiment runs. In a series of proof-of-principle experiments, we demonstrate gradient electrodeposition of Ni-Cu using BE; then the electrocatalytic activity of the prepared composition gradient toward the hydrogen evolution reaction (HER) is visually screened in the BE system using array of BPEs. Moreover, the morphology and the chemical composition of the Ni-Cu gradient are screened along the length of the bipolar electrode (BPE). By measuring the potential gradient over the BPE, it is also demonstrated that by controlling the concentration of the metals precursor and the supporting electrolyte, the length of the bipolar electrodeposited gradient can be controlled. PMID:26595192

  7. Relation of hardness and oxygen flow of Al2O3 coatings deposited by reactive bipolar pulsed magnetron sputtering

    International Nuclear Information System (INIS)

    Aluminum oxide thin films are widely used because of their excellent properties, especially in terms of chemical, thermal, abrasive and corrosive resistance. But many properties of alumina films are significantly deposition parameters dependent. Since different applications and environments demand different kind of properties in thin films, it is important to determine the influence of the deposition parameters on the alumina film properties. In this work, different alumina structures were deposited by means of reactive, bipolar, pulsed, magnetron sputtering. In order to find the appropriate parameter combination to synthesize crystalline alumina (for this investigation γ-Al2O3), substrate temperature, power density at the target and oxygen flow were varied. The γ-Al2O3 films were synthesized at 650 deg. C, 0.2 Pa, 800 W, 1:4 duty cycle, 19.2 kHz, and 11-12% oxygen flow. The structure and morphology of the deposited Al2O3 films were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Since the coating hardness is a decisive factor for many applications, the aim of this paper was to investigate the influence of the oxygen flow on the alumina hardness. It was observed that the hardness and the structure of the PVD-deposited alumina coatings are significantly oxygen flow dependent. The hardness of the alumina films was determined by nanoindentation. It varied between 1 and 25.8 GPa. The hardness increased by increasing oxygen flow until the target reached the poisoned state, where a hardness reduction was clearly observed

  8. Software emulator of nuclear pulse generation with different pulse shapes and pile-up

    Science.gov (United States)

    Pechousek, Jiri; Konecny, Daniel; Novak, Petr; Kouril, Lukas; Kohout, Pavel; Celiktas, Cuneyt; Vujtek, Milan

    2016-08-01

    The optimal detection of output signals from nuclear counting devices represents one of the key physical factors that govern accuracy and experimental reproducibility. In this context, the fine calibration of the detector under diverse experimental scenarios, although time costly, is necessary. However this process can be rendered easier with the use of systems that work in lieu of emulators. In this report we describe an innovative programmable pulse generator device capable to emulate the scintillation detector signals, in a way to mimic the detector performances under a variety of experimental conditions. The emulator generates a defined number of pulses, with a given shape and amplitude in the form of a sampled detector signal. The emulator output is then used off-line by a spectrometric system in order to set up its optimal performance. Three types of pulse shapes are produced by our device, with the possibility to add noise and pulse pile-up effects into the signal. The efficiency of the pulse detection, pile-up rejection and/or correction, together with the dead-time of the system, are therein analyzed through the use of some specific algorithms for pulse processing, and the results obtained validate the beneficial use of emulators for the accurate calibration process of spectrometric systems.

  9. Efficacy and safety of second-generation antipsychotic long-acting injections (SGA LAIs) in maintenance treatment of bipolar disorder: protocol for a systematic review and meta-analysis

    OpenAIRE

    Prajapati, Asta R; Wilson, Jonathan; Maidment, Ian D

    2016-01-01

    Introduction Bipolar disorder requires long-term treatment but non-adherence is a common problem. Antipsychotic long-acting injections (LAIs) have been suggested to improve adherence but none are licensed in the UK for bipolar. However, the use of second-generation antipsychotics (SGA) LAIs in bipolar is not uncommon albeit there is a lack of systematic review in this area. This study aims to systematically review safety and efficacy of SGA LAIs in the maintenance treatment of bipolar disorde...

  10. Generation of a synchronized pulse of extraordinary precision using chirped pulse laser

    International Nuclear Information System (INIS)

    We have developed the generation system of synchronized pulses of high precision using chirped pulse laser. The PW laser is synchronized to Gekko XII beams within 10 picosecond by injecting part of the PW laser into the Gekko XII laser system. A part of the 3 ns/6 nm (pulse width/spectral width) output from the front end is stretched to 5.5 ns/5 nm and is then sliced to 1.1 ns/nm width and injected into Gekko XII system. We have obtained 2.5-kJ output energy at a 532-nm wavelength from 12 semi-Gaussian beams. The pulse width is 1.1 ± 0.1 ns (FWHM) and the conversion efficiency from 1 to 0.5 mm was 43%. (author)

  11. Variable Power, Short Microwave Pulses Generation using a CW Magnetron

    Directory of Open Access Journals (Sweden)

    CIUPA, R.

    2011-05-01

    Full Text Available Fine control of microwave power radiation in medical and scientific applications is a challenging task. Since a commercial Continuous Wave (CW magnetron is the most inexpensive microwave device available today on the market, it becomes the best candidate for a microwave power generator used in medical diathermy and hyperthermia treatments or high efficiency chemical reactions using microwave reactors as well. This article presents a new method for driving a CW magnetron with short pulses, using a modified commercial Zero Voltage Switching (ZVS inverter, software driven by a custom embedded system. The microwave power generator designed with this method can be programmed for output microwave pulses down to 1% of the magnetron's power and allows microwave low frequency pulse modulation in the range of human brain electrical activity, intended for medical applications. Microwave output power continuous control is also possible with the magnetron running in the oscillating area, using a dual frequency Pulse Width Modulation (PWM, where the low frequency PWM pulse is modulating a higher resonant frequency required by the ZVS inverter's transformer. The method presented allows a continuous control of both power and energy (duty-cycle at the inverter's output.

  12. Bipolar membrane electrodialysis for generation of hydrochloric acid and ammonia from simulated ammonium chloride wastewater.

    Science.gov (United States)

    Li, Ya; Shi, Shaoyuan; Cao, Hongbin; Wu, Xinmin; Zhao, Zhijuan; Wang, Liying

    2016-02-01

    Simulated ammonium chloride wastewater was treated by a lab-scale bipolar membrane electrodialysis for the generation of HCl and NH3·H2O and desalination. The influence of initial concentration of NH4Cl, current density, salt solution volume, initial concentration of acid and base and membrane stack structure on the yields of HCl and NH3·H2O was investigated. The current efficiency and energy consumption were also examined under different conditions. The results showed that, at the current density of 48 mA/cm(2), the highest concentration of HCl and NH3·H2O with initial concentration of 110 g/L NH4Cl was 57.67 g/L and 45.85 g/L, respectively. Higher initial concentration of NH4Cl was favor to reduce unit energy consumption and increase current efficiency of the BMED system. The membrane stack voltage of BMED increased quickly under constant current when the concentration of NH4Cl contained in the solution of salt compartment was depleted below the "inflection point concentration" about 8000 mg/L. It means that the concentration of NH4Cl below 8000 mg/L was no longer suitable for BMED because of higher energy consumption. The HCl and NH3·H2O concentration increased more quickly following the increase of current density. When increasing the volume of NH4Cl, the concentration of HCl and NH3·H2O also increased. The high initial concentration of acid and base could improve the final concentration of them, while the growth rate was decreased. Compared with the BMED system with three compartments, the growth rate of HCl concentration with the two compartments was higher and its unit energy consumption was lower. It meant that the performance of the BMED system could be improved by optimizing operation conditions. The application feasibility of the generation of HCl and NH3·H2O and desalination of ammonium chloride wastewater by BMED was proved. PMID:26674548

  13. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2011-08-01

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0×1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schrödinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  14. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    International Nuclear Information System (INIS)

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  15. Attosecond pulse generation by applying a weak static electric field to a few-cycle pulse

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Guangjiu; Guo Xiaolv [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Shao Tianjiao [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Xue Kang, E-mail: gjzhao@dicp.ac.cn [School of Physics, Northeast Normal University, Changchun 130024 (China)

    2011-09-15

    The high-order harmonic generation process under the combination of a few-cycle pulse and a static electric field was investigated in this work. A linear harmonic cutoff extension was observed with its dependence on the relative strength ratio of the static electric field with respect to a single-color, 2.5 optical cycle (oc), 800 nm, 1.4x10{sup 15} W cm{sup -2} few-cycle pulse as the fundamental driving field. Exploiting the relative strength ratio tuning from 0 to 0.1, a linear continuum width extending on the XUV spectrum up to 191 eV, which supports the creation of an 18 attosecond isolated attosecond pulse, was generated. Moreover, classical trajectory calculation and time-frequency analyses for explaining the mechanism are also presented.

  16. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Kai-Jun; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

    2011-08-15

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe{sup 2+} molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x10{sup 14} W/cm{sup 2}, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe{sup 2+}, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  17. Subfemtosecond X-ray Pulses Produced Directly by High Harmonic Generation

    Institute of Scientific and Technical Information of China (English)

    WANG Ying-Song; XU Zhi-Zhan

    2000-01-01

    The generation of subfemtosecond pulses in hydrogen-like atoms through high-harmonic generation by using superintense multicycle driver pulses is numerically investigated. It is shown that a single subfemtosecond pulse can be directly generated when the driver pulse is strong enough to deplete the neutral atoms within several optical cycles. The propagation effect is neglected during the numerical examinations.

  18. Pulsed Yb:KYW laser and UV generation

    OpenAIRE

    Tjörnhammar, Staffan

    2010-01-01

    In this master thesis project, a pulsed UV laser was designed and constructed. Also, the effects of absorption in a volume Bragg grating were investigated. The laser was diode pumped and constructed with Yb:KYW as gain medium. The lasing was at a wavelength of 1029.2 nm with a spectral bandwidth of 0.23 nm, locked by a volume Bragg grating that was used as input coupler for spectral control. Passive Q‑switching was used to generate pulses by placing a Cr:YAG saturable absorber inside the cavi...

  19. Beamlet pulse-generation and wavefront-control system

    Energy Technology Data Exchange (ETDEWEB)

    Van Wonterghem, B.M.; Salmon, J.T.; Wilcox, R.W.

    1996-06-01

    The Beamlet pulse-generation system (or {open_quotes}front end{close_quotes}) refers to the laser hardware that generates the spatially and temporally shaped pulse that is injected into the main laser cavity. All large ICF lasers have pulse-generation systems that typically consist of a narrow-band oscillator, elector-optic modulators for temporal and bandwidth shaping, and one or more preamplifiers. Temporal shaping is used to provide the desired laser output pulse shape and also to compensate for gain saturation effects in the large-aperture amplifiers. Bandwidth is applied to fulfill specific target irradiation requirements and to avoid stimulated Brillouin scattering (SBS) in large-aperture laser components. Usually the sharp edge of the beam`s spatial intensity profile is apodized before injection in the main amplifier beam line. This prevents large-amplitude ripples on the intensity profile. Here the authors briefly review the front-end design and discuss improvements to the oscillator and modulator systems. Their main focus, however, is to describe Beamlet`s novel beam-shaping and wavefront-control systems that have recently been fully activated and tested.

  20. Dynamics of formation of optoacoustic pulses of the first and second sound in He-II, excited by a rectangular pulse of laser radiation by the thermal mechanism

    International Nuclear Information System (INIS)

    A theory of generation of optoacoustic pulses of first and second sound in superfluid helium by the rectangular pulse of laser radiation generated by thermal mechanism was considered. It was found that all of the exciting pulses are formed in competition pulses generated at turning on and off the beam and have opposite phases. Numerical results showed that all generated optoacoustic pulses have bipolar shape.

  1. Nanosecond pulsed power generators with auto-synchronized multiple switches

    International Nuclear Information System (INIS)

    The paper introduces a multiple-switch pulsed power technique based on transmission-line-transformer (TLT). In the circuit, all the switches can synchronize themselves automatically like in a Marx generator. At the output side, a variety of output options are possible, i. e. high voltage, large current or independent pulse generation. A 10-switch, 10-stage TLT system has been successfully developed. At the moment, a repetitive large power generator with 20 switches and a 20-stage TLT is being developed. The peak power is estimated to be 5 GW with a total energy of 140 J per shot. Up to 100 independent simultaneous output can be realized with the same peak power. (authors)

  2. Autonomous portable pulsed-periodical generator of high-power radiofrequency-pulses based on gas discharge with hollow cathode

    Science.gov (United States)

    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%.

  3. Generation and amplification of nanosecond pulses by iodine lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zuev, V.S.; Katulin, V.A.; Nosach, V.Y.; Petrov, A.L.

    1982-12-01

    Results are reported of experimental investigations of high-power photodissociation iodine laser pumped by lamps and by radiation from high-current electric discharges. The basic parameters of the working medium, the parameters of both lamp-pumped and discharge-pumped lasers, and methods of shaping of a short pulse with diffraction directivity of the radiation are investigated. The possibility of effective amplification of a short pulse by an iodine amplifier pumped with an open high-current discharge is demonstrated. An iodine laser generating a pulse of duration 1 nsec, divergence 10/sup -4/ rad, and energy 100 J at a contrast 10/sup 8/ and 300 J at a contrast 10/sup 2/-10/sup 3/ is described.

  4. A three-colour scheme to generate isolated attosecond pulses

    International Nuclear Information System (INIS)

    We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 x 1014 W cm-2 and of wavelength λ = 820 nm, and two properly chosen weak lasers with wavelengths 1.5λ and 0.5λ. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.

  5. A three-colour scheme to generate isolated attosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Orlando, G; Corso, P P; Fiordilino, E; Persico, F, E-mail: orlando@fisica.unipa.i [Dipartimento di Scienze Fisiche ed Astronomiche, Via Archirafi 36, 90123 Palermo (Italy)

    2010-01-28

    We propose a new scheme to produce isolated attosecond pulses, involving the use of three laser pulses: a fundamental laser field of intensity I = 3.5 x 10{sup 14} W cm{sup -2} and of wavelength {lambda} = 820 nm, and two properly chosen weak lasers with wavelengths 1.5{lambda} and 0.5{lambda}. The three lasers have a Gaussian envelope of 36 fs full width at half maximum. The resulting total field is an asymmetric electric field with an isolated peak. We show that a model atom, interacting with the above-defined total field, generates an isolated attosecond pulse as short as 1/10 of a laser period, i.e. approximately 270 as.

  6. CIAE 600 kV ns pulse neutron generator

    International Nuclear Information System (INIS)

    The overall composition of CIAE 600 kV ns Pulse Neutron Generator (CPNG) are introduced, and its characteristic, main technological performance and application were also given. CPNG consists of high voltage power supply with highest output voltage 600 kV, direct current 15 mA, stability and ripple ≤0.1%, 2214 mm x 1604 mm x 1504 mm stainless steel high voltage electrode, built in head equipment uniform field accelerating tube, ns pulsed installation, turbomolecular vacuum pump system and drift pipes at 0 degree and 45 degree. Its characteristics are: (1) high current beam; (2) high current beam ns pulsed installation made use of low energy for chopper and high energy for buncher; (3) compactly laid out and simple in structure

  7. Measuring multimegavolt pulsed voltages using Compton-generated electrons

    Science.gov (United States)

    Swanekamp, S. B.; Weber, B. V.; Pereira, N. R.; Hinshelwood, D. D.; Stephanakis, S. J.; Young, F. C.

    2004-01-01

    The "Compton-Hall" voltmeter is a radiation-based voltage diagnostic that has been developed to measure voltages on high-power (TW) pulsed generators. The instrument collimates photons generated from bremsstrahlung produced in the diode onto an aluminum target to generate Compton-generated electrons. Permanent magnets bend the Compton electron orbits that escape the target toward a silicon pin diode detector. A GaAs photoconductive detector (PCD) detects photons that pass through the Compton target. The diode voltage is determined from the ratio of the electron dose in the pin detector to the x-ray dose in the PCD. The Integrated Tiger Series of electron-photon transport codes is used to determine the relationship between the measured dose ratio and the diode voltage. Variations in the electron beam's angle of incidence on the bremsstrahlung target produce changes in the shape of the photon spectrum that lead to large variations in the voltage inferred from the voltmeter. The voltage uncertainty is minimized when the voltmeter is fielded at an angle of 45° with respect to the bremsstrahlung target. In this position, the photon spectra for different angles of incidence all converge onto a single spectrum reducing the uncertainty in the voltage to less than 10% for voltages below 4 MV. Higher and lower voltages than the range considered in this article can be measured by adjusting the strength of the applied magnetic field or the position of the electron detector relative to the Compton target. The instrument was fielded on the Gamble II pulsed-power generator configured with a plasma opening switch. Measurements produced a time-dependent voltage with a peak (3.7 MV) that agrees with nuclear activation measurements and a pulse shape that is consistent with the measured radiation pulse shape.

  8. Generation of ultrashort electron bunches by colliding laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Esarey, E. [Beam Physics Branch, Plasma Physics Division, Navel Research Laboratory, Washington, District of Columbia 20375 (United States); Leemans, W.P. [Center for Beam Physics, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-07-01

    A proposed laser-plasma based relativistic electron source [E. Esarey {ital et al.}, Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999 American Institute of Physics.}

  9. Single-attosecond pulse generation with an intense multicycle driving pulse

    Science.gov (United States)

    Cao, Wei; Lu, Peixiang; Lan, Pengfei; Wang, Xinlin; Yang, Guang

    2006-12-01

    Higher-order harmonic generation from strong laser-atom interaction in the multicycle regime is investigated using the Lewenstein model. While the peak intensity of the driving laser is oversaturated, the atom will be ionized completely during a few half optical cycles. The harmonic spectrum then reveals a continuous multiplateau structure in the cutoff region because of the ground state depletion. Each subplateau can be superposed to generate single attosecond pulse. Since the intensity of high-order harmonics from ion is comparable to that from atom if the peak intensity is super-intense, appropriate subplateau should be selected for single attosecond pulse generation. It is also shown that the nonadiabatic effect plays a crucial role in tuning the bandwidth of the subplateau.

  10. Single-attosecond pulse generation with an intense multicycle driving pulse

    International Nuclear Information System (INIS)

    Higher-order harmonic generation from strong laser-atom interaction in the multicycle regime is investigated using the Lewenstein model. While the peak intensity of the driving laser is oversaturated, the atom will be ionized completely during a few half optical cycles. The harmonic spectrum then reveals a continuous multiplateau structure in the cutoff region because of the ground state depletion. Each subplateau can be superposed to generate single attosecond pulse. Since the intensity of high-order harmonics from ion is comparable to that from atom if the peak intensity is super-intense, appropriate subplateau should be selected for single attosecond pulse generation. It is also shown that the nonadiabatic effect plays a crucial role in tuning the bandwidth of the subplateau

  11. Portable generator of subnanosecond fast-electron pulses

    International Nuclear Information System (INIS)

    A generator is described which uses a capacitor charge-transfer circuit. The capacitor is built into the high-voltage discharger which reduces the inductance of the charge-transfer circuit and provides a 2.5 kiloamp current pulse with a half-height duration of 0.8 nanoseconds in a stock IA-9 electron tube. The average electron energy in the spectrum is 250 KeV

  12. Propagation of Plasma Generated by Intense Pulsed Ion Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    WU Di; GONG Ye; LIU Jin-Yuan; WANG Xiao-Gang; LIU Yue; MA Teng-Cai

    2006-01-01

    @@ Taking the calculation results based on the established two-dimensional ablation model of the intense-pulsed-ion-beam (IPIB) irradiation process as initial conditions, we build a two-dimensional hydrodynamic ejection model of plasma produced by an IPIB-irradiated metal titanium target into ambient gas. We obtain the conclusions that shock waves generate when the background pressure is around 133 mTorr and also obtain the plume splitting phenomenon that has been observed in the experiments.

  13. GTI-742 stroke pulse generator made in the CAMAC standard

    International Nuclear Information System (INIS)

    A tactstroke generator (GTI-742) made in CAMAC standard is described. The unit ensures output tact pulses with decade frequency intervals from the internal quartz oscillator and can be used as an external signal frequency divider. The number of decades in the unit is 6. Maximum frequency of the quartz oscillator and external signals is 50 mc. Input and output signals have NIM or TTL levels

  14. Vircator experiments on repetitive pulsed power generator 'ETIGO-IV'

    International Nuclear Information System (INIS)

    A new configuration of virtual cathode oscillator is proposed and tested experimentally. A resonant cavity is used to enhance the field feedback to the virtual cathode oscillation. The experiments were carried out on repetitive pulsed power generator 'ETIGO-IV' (400 kV, 13 kA, 120 ns, 1 Hz). The diagnostic results have shown the peak microwave output power of ∼ 450 MW, giving peak-to-peak microwave power efficiency of ∼ 9%

  15. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    International Nuclear Information System (INIS)

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles

  16. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    Science.gov (United States)

    He, Xinkui; Jia, T. Q.; Zhang, Jun; Suzuki, M.; Baba, M.; Ozaki, T.; Li, Ruxin; Xu, Zhizhan; Kuroda, Hiroto

    2007-08-01

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles.

  17. Black phosphorus saturable absorber for ultrashort pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Sotor, J., E-mail: jaroslaw.sotor@pwr.edu.pl; Sobon, G.; Abramski, K. M. [Laser and Fiber Electronics Group, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, Wroclaw 50-370 (Poland); Macherzynski, W.; Paletko, P. [Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego 11/17, Wroclaw 50-372 (Poland)

    2015-08-03

    Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.

  18. Black phosphorus saturable absorber for ultrashort pulse generation

    International Nuclear Information System (INIS)

    Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics

  19. Simple, high-voltage, square pulse generator for ion beam deflection in a neutron generator

    International Nuclear Information System (INIS)

    A fast rise time, low repetition rate, high-voltage, square pulse generator with double-diffused-metal-oxide-semiconductor (DMOS) switching is described. It has been developed for ion beam deflection at an electrostatic deflector in a beam guide system of a neutron generator. The features of the generator are: 1.7 kV amplitude, variable frequency from 2 to 50 Hz, variable width from 0.5 to 5 μs, and 125 ns delay. Output pulses are free of overshoot and backswing with rise and fall times of approximately 45 ns and 5 μs width

  20. Generation of atto-second pulses on relativistic mirror plasma

    International Nuclear Information System (INIS)

    When an ultra intense femtosecond laser (I > 1016 W.cm-2) with high contrast is focused on a solid target, the laser field at focus is high enough to completely ionize the target surface during the rising edge of the laser pulse and form a plasma. This plasma is so dense (the electron density is of the order of hundred times the critical density) that it completely reflects the incident laser beam in the specular direction: this is the so-called 'plasma mirror'. When laser intensity becomes very high, the non-linear response of the plasma mirror to the laser field periodically deforms the incident electric field leading to high harmonic generation in the reflected beam. In the temporal domain this harmonic spectrum is associated to a train of atto-second pulses. The goals of my work were to get a better comprehension of the properties of harmonic beams produced on plasma mirrors and design new methods to control theses properties, notably in order to produce isolated atto-second pulses instead of trains. Initially, we imagined and modeled the first realistic technique to generate isolated atto-second on plasma mirrors. This brand new approach is based on a totally new physical effect: 'the atto-second lighthouse effect'. Its principle consists in sending the atto-second pulses of the train in different directions and selects one of these pulses by putting a slit in the far field. Despite its simplicity, this technique is very general and applies to any high harmonic generation mechanism. Moreover, the atto-second lighthouse effect has many other applications (e.g in metrology). In particular, it paves the way to atto-second pump-probe experiments. Then, we studied the spatial properties of these harmonics, whose control and characterization are crucial if one wants to use this source in future application experiments. For instance, we need to control very precisely the harmonic beam divergence in order to achieve the atto-second lighthouse effect and get isolated

  1. Touch stimulated pulse generation in biomimetic single-layer graphene

    Science.gov (United States)

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-01

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour.Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac

  2. Numerical simulation of compact intracloud discharge and generated electromagnetic pulse

    Science.gov (United States)

    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.

  3. Comparison of performance between bipolar and unipolar double-frequency sinusoidal pulse width modulation in a digitally controlled H-bridge inverter system

    Institute of Scientific and Technical Information of China (English)

    Lei Bo; Xiao Guo-Chun; Wu Xuan-Lü

    2013-01-01

    By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinusoidal pulse width modulation (BSPWM) and unipolar double-frequency sinusoidal pulse width modulation (UDFSPWM)respectively,the performances of the two modulation strategies are analyzed in detail.The circuit parameters,used in this paper,are fixed.When the systems,modulated by BSPWM and UDFSPWM,have the same switching frequency,the stability boundaries of the two systems are the same.However,when the equivalent switching frequencies of the two systems are the same,the BSPWM modulated system is more stable than the UDFSPWM modulated system.In addition,a convenient method of establishing the discrete-time model of piecewise smooth system is presented.Finally,the analytical results are confirmed by circuit simulations and experimental measurements.

  4. Single X-Ray Attosecond Pulse Generation by Using Combined Pulses Irradiating on a United Two-Atom System

    Institute of Scientific and Technical Information of China (English)

    CHEN Ji-Gen; LI Chen; CHI Fang-Ping; YANG Yu-Jun

    2007-01-01

    @@ A scheme of a single x-ray attosecond pulse generation from a two-atom system exposed to the combined laser pulses is proposed. Our numerical results show that a single x-ray attosecond pulse rather than a train one can be produced by modulation of ionization.

  5. A Study of Removing Chlorobenzene by the Synergistic Effect of Catalysts and Dielectric-Barrier Discharge Driven by Bipolar Pulse-Power

    Institute of Scientific and Technical Information of China (English)

    LI Duan; ZHANG Di; WU Yan; LI Jie; LI Guofeng

    2008-01-01

    In this study, the improvement in the removal of chlorobenzene (C6H5Cl) in the air was investigated by combining dielectric barrier discharge (DBD) driven by bipolar pulse-power with catalysts. Molecular sieve 4A (MS-4A) and MnO2/γ-Al2O3 (MnO2/ALP) as two kinds of catalysts were tested at different positions in a DBD reactor. Catalysts were located either in the discharging area between two electrodes, or just behind the discharging area (in the afterglow area) closed to the outlet. The results indicated that DBD reactor with a bipolar pulse power-supply produced strong instant discharge and energetic particles, which can effectively activate catalysts of MS-4A and MnO2/ALP located in the afterglow area to achieve the synergistic effects on effective fission of chemical bonds of chlorobenzene. It was considered that the gas-chlorobenzene and the chlorobenzene adsorbed on the catalysts were decomposed simultaneously.

  6. Generation of high-energy attosecond pulses by the relativistic-irradiance short laser pulse interacting with a thin foil

    International Nuclear Information System (INIS)

    When a thin foil target is irradiated by two laser pulses, or it is irradiated by one pulse under the condition when the charge separation electric field exceeds the laser field, the electron motion in the direction perpendicular to the target surface is suppressed. Electrons can only slide along the foil. Using an analytical model, we describe the new regime of attosecond pulse generation by the relativistic-irradiance short laser pulse interacting with the sliding mirror. Pulses with the duration of few hundred attoseconds can be generated with the conversion efficiency up to few percents

  7. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    OpenAIRE

    Poyé, Alexandre; Hulin, Sébastien; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of ...

  8. Touch stimulated pulse generation in biomimetic single-layer graphene.

    Science.gov (United States)

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-14

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour. PMID:26790981

  9. Photoconductive switch enhancements for use in Blumlein pulse generators

    International Nuclear Information System (INIS)

    Stacked Blumlein pulse generators developed at the University of Texas at Dallas have produced high-power waveforms with risetimes and repetition rates in the range of 0.2-50 ns and 1-300 Hz, respectively, using a conventional thyratron, spark gap or photoconductive switch. Adaptation of the design has enabled the stacked Blumleins to produce 80 MW, nanosecond pulses with risetimes better than 200 ps into nominally matched loads. The device has a compact line geometry and is commutated by a single GaAs photoconductive switch triggered by a low power laser diode array. Our current investigations involve the switch characteristics that affect the broadening of the current channels in the avalanche, pre-avalanche seedings, the switch lifetime and the durability. This report presents the progress toward improving the GaAs switch operation and lifetime in stacked Blumlein pulsers. Advanced switch treatments including diamond film overcoating are implemented and discussed

  10. Generating multiple-pulse bursts for enhanced fluorescence detection

    International Nuclear Information System (INIS)

    The signal-to-background ratio is the limiting factor for fluorescence based detection, sensing, and imaging. A typical background signal will include direct scattering of excitation and Raman scattering of the sample as well as autofluorescence from the sample and additives. To improve the signal-to-background ratio, fluorophores of high brightness and/or high concentration of the fluorophores need to be used. Most of the background is instantaneous and short-lived (picosecond to nanosecond time scale), and using long-lived fluorescence probes combined with time-gated detection allows for significant suppression of unwanted background. Unfortunately, this approach requires substantial sacrifice of the probe signal in order to sufficiently filter the background unless the fluorescence lifetime of the probe is very long. However, long lived probes like ruthenium bipyridyl have relatively low brightness compared to probes that have shorter, 10–30 ns fluorescence lifetimes. We recently presented an approach based on bursts of multiple pulses that allowed for high probe signal amplification using long-lived ruthenium based probe (Ru) and an 80 MHz repetition-rate laser excitation. Unfortunately, Ru represents an extreme case for probe lifetime, and a probe with a shorter lifetime of 20 ns will require excitation from a pulsed source with much higher repetition rate to significantly enhance its signal. Such high repetition rates are not possible to generate with most of today’s available electronics. In this report we present new approaches to optimize and generate bursts of pulses with high repetition rate within the burst and no need for new or improved electronics. The high repetition rates originate from a low-repetition source and are highly tunable. We demonstrate that a burst of 2–10 pulses spaced 3 ns apart (corresponding to a ‘burst repetition rate’ of 330 MHz) allows for high signal enhancement of the 20 ns probe over the sub

  11. Propagation of Partial Discharge and Noise Pulses in Turbine Generators

    DEFF Research Database (Denmark)

    Henriksen, Mogens; Stone, G. C.; Kurtz, M.

    Changes with time in the partial discharge (PD) activity originating in a generator stator's insulation system provide information about the electrical integrity of the stator winding. It is desirable to measure PD during normal service to minimize costs. To do this successfully, the influence of...... electrical interference must be reduced. Tests are reported which characterize the nature of discharge and noise pulses when using capacitive couplers mounted on each of the phase leads and an RF current transformer mounted on the neutral lead for signal detection. Significant differences between PD and...

  12. Entanglement generated between a single atom and a laser pulse

    OpenAIRE

    Silberfarb, Andrew; Deutsch, Ivan H.

    2003-01-01

    We quantify the entanglement generated between an atom and a laser pulse in free space. We find that the entanglement calculated using a simple closed-system Jaynes-Cummings Hamiltonian is in remarkable agreement with a full open-system calculation, even though the free-space geometry is far from the strong coupling regime of cavity QED. We explain this result using a simple model in which the atom couples weakly to the laser while coupling strongly to the vacuum. Additionally we place an upp...

  13. Photonic crystal Fano laser: terahertz modulation and ultrashort pulse generation.

    Science.gov (United States)

    Mork, J; Chen, Y; Heuck, M

    2014-10-17

    We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory. PMID:25361259

  14. Optimising the efficiency of pulsed diode pumped Yb:YAG laser amplifiers for ns pulse generation.

    Science.gov (United States)

    Ertel, K; Banerjee, S; Mason, P D; Phillips, P J; Siebold, M; Hernandez-Gomez, C; Collier, J C

    2011-12-19

    We present a numerical model of a pulsed, diode-pumped Yb:YAG laser amplifier for the generation of high energy ns-pulses. This model is used to explore how optical-to-optical efficiency depends on factors such as pump duration, pump spectrum, pump intensity, doping concentration, and operating temperature. We put special emphasis on finding ways to achieve high efficiency within the practical limitations imposed by real-world laser systems, such as limited pump brightness and limited damage fluence. We show that a particularly advantageous way of improving efficiency within those constraints is operation at cryogenic temperature. Based on the numerical findings we present a concept for a scalable amplifier based on an end-pumped, cryogenic, gas-cooled multi-slab architecture. PMID:22274245

  15. A case study for terahertz-assisted single attosecond pulse generation

    CERN Document Server

    Balogh, Emeric; Tosa, Valer; Varjú, Katalin

    2014-01-01

    We numerically investigate the use of strong THz radiation in assisting single attosecond pulse generation by few-cycle, 800 nm laser pulses. We optimize focusing conditions to generate short and powerful single attosecond pulses of high-energy photons by keeping the parameters of the THz field within the limits achieved experimentally. We show that using optimal focusing geometry isolated attosecond pulses shorter than 100 as can be obtained even in the absence of further gating or XUV compression techniques, using an 8 fs generating pulse. Furthermore, quantum path control of short- and long-trajectory components is demonstrated by varying the delay between the THz and IR pulses.

  16. Bipolar Disorder

    Science.gov (United States)

    Bipolar disorder is a serious mental illness. People who have it go through unusual mood changes. They go ... The down feeling is depression. The causes of bipolar disorder aren't always clear. It runs in families. ...

  17. Bipolar Disorder

    Science.gov (United States)

    Bipolar disorder is a serious mental illness. People who have it go through unusual mood changes. They ... The down feeling is depression. The causes of bipolar disorder aren't always clear. It runs in ...

  18. Bipolar Disorder

    Science.gov (United States)

    ... types of psychotherapies. Other Treatment Options Electroconvulsive Therapy (ECT) : ECT can provide relief for people with severe bipolar ... been able to recover with other treatments. Sometimes ECT is used for bipolar symptoms when other medical ...

  19. High reliability low jitter 80 kV pulse generator

    International Nuclear Information System (INIS)

    Switching can be considered to be the essence of pulsed power. Time accurate switch/trigger systems with low inductance are useful in many applications. This article describes a unique switch geometry coupled with a low-inductance capacitive energy store. The system provides a fast-rising high voltage pulse into a low impedance load. It can be challenging to generate high voltage (more than 50 kilovolts) into impedances less than 10 (Omega), from a low voltage control signal with a fast rise time and high temporal accuracy. The required power amplification is large, and is usually accomplished with multiple stages. The multiple stages can adversely affect the temporal accuracy and the reliability of the system. In the present application, a highly reliable and low jitter trigger generator was required for the Z pulsed-power facility [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats,J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K.W. Struve, W.A. Stygar, L.K. Warne, and J. R. Woodworth, 2007 IEEE Pulsed Power Conference, Albuquerque, NM (IEEE, Piscataway, NJ, 2007), p. 979]. The large investment in each Z experiment demands low prefire probability and low jitter simultaneously. The system described here is based on a 100 kV DC-charged high-pressure spark gap, triggered with an ultraviolet laser. The system uses a single optical path for simultaneously triggering two parallel switches, allowing lower inductance and electrode erosion with a simple optical system. Performance of the system includes 6 ns output rise time into 5.6 (Omega), 550 ps one-sigma jitter measured from the 5 V trigger to the high voltage output, and misfire probability less than 10-4. The design of the system and some key measurements will be shown in the paper. We will discuss the design goals related to high reliability and low jitter. While reliability

  20. High reliability low jitter 80 kV pulse generator.

    Energy Technology Data Exchange (ETDEWEB)

    Savage, Mark Edward; Stoltzfus, Brian Scott

    2009-06-01

    Switching can be considered to be the essence of pulsed power. Time accurate switch/trigger systems with low inductance are useful in many applications. This article describes a unique switch geometry coupled with a low-inductance capacitive energy store. The system provides a fast-rising high voltage pulse into a low impedance load. It can be challenging to generate high voltage (more than 50 kilovolts) into impedances less than 10 {Omega}, from a low voltage control signal with a fast rise time and high temporal accuracy. The required power amplification is large, and is usually accomplished with multiple stages. The multiple stages can adversely affect the temporal accuracy and the reliability of the system. In the present application, a highly reliable and low jitter trigger generator was required for the Z pulsed-power facility [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats,J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K.W. Struve, W.A. Stygar, L.K. Warne, and J. R. Woodworth, 2007 IEEE Pulsed Power Conference, Albuquerque, NM (IEEE, Piscataway, NJ, 2007), p. 979]. The large investment in each Z experiment demands low prefire probability and low jitter simultaneously. The system described here is based on a 100 kV DC-charged high-pressure spark gap, triggered with an ultraviolet laser. The system uses a single optical path for simultaneously triggering two parallel switches, allowing lower inductance and electrode erosion with a simple optical system. Performance of the system includes 6 ns output rise time into 5.6 {Omega}, 550 ps one-sigma jitter measured from the 5 V trigger to the high voltage output, and misfire probability less than 10{sup -4}. The design of the system and some key measurements will be shown in the paper. We will discuss the design goals related to high reliability and low jitter. While

  1. Theoretical exploration of harmonic emission and attosecond pulse generation from H2+ in the presence of terahertz pulse

    Science.gov (United States)

    Liu, Hang; Feng, Liqiang

    2016-06-01

    Harmonic generation spectra from H2+ molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the harmonic cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as v = 3, and by properly adding a THz controlling pulse, the harmonic yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the harmonic extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Finally, by properly superposing the harmonics, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.

  2. Triboelectric-generator-driven pulse electrodeposition for micropatterning.

    Science.gov (United States)

    Zhu, Guang; Pan, Caofeng; Guo, Wenxi; Chen, Chih-Yen; Zhou, Yusheng; Yu, Ruomeng; Wang, Zhong Lin

    2012-09-12

    By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm(3) at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting. PMID:22889363

  3. Generation of pulsed discharge plasma in water with fine bubbles

    Science.gov (United States)

    Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu; Goto laboratory Team

    2015-09-01

    Recently, some researchers have proposed electric discharge methods with bubbles in water because the discharge plasma inside bubble was easy to be generated compared to that in water. Almost all of these methods introduced bubbles in the order of millimeter size from a nozzle placed in water. In these methods, bubbles rose one after another owing to high rising speed of millibubble, leading to inefficient gas consumption. We proposed fine bubbles introduction at the discharge area in water. A fine bubble is determined a bubble with less than 100 μm in a diameter. Fine bubbles exhibit extremely slow rising speed. Fine bubbles decrease in size during bubble rising and subsequently collapse in water with OH radical generation. Therefore, combining the discharge plasma with fine bubbles is expected to generate more active species with small amount of gas consumption. In this work, fine bubbles were introduced in water and pulsed discharge plasma was generated between two cylindrical electrodes which placed in water. We examined effects of fine bubbles on electric discharge in water when argon or oxygen gas was utilized as feed gas. Fine bubbles enhanced optical emission of hydrogen and oxygen atoms from H2O molecules, but that of feed gas was not observed. The formation mechanism of H2O2 by electric discharge was supposed to be different from that with no bubbling. Dissolved oxygen in water played a role in H2O2 formation by the discharge with fine bubbles.

  4. Generation of optical pulse packet using a fiber stacker for time fiducial applications

    Science.gov (United States)

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

    2016-08-01

    We present the concept of multicolor optical pulse packet generation based on modified fiber stackers featured with reflection geometries. Infrared radiation, visible and ultraviolet time fiducials were obtained by the amplification and frequency-conversion of the pulse packet generated in this fiber stacker. Application for the inertial confinement fusion (ICF) experiment diagnosis with time fiducials was demonstrated. With featured reflection geometries, the shaped packet pulses with uniform sub-pulse polarization states in a temporal window of ns range were generated in the fiber stacker. The design greatly simplifies the packet pulse generation for time fiducial and could be used for laser-driven ICF experimental diagnosis.

  5. Stimulated Raman scattering effect on femtosecond pulse generation using a parabolic amplification and a pulse compressor

    OpenAIRE

    Soh, Daniel B.S.; Grudinin, A.B.; Nilsson, J.; Y. Jeong; Yoo, S.; Kim, J.; Codemard, C.; Dupriez, P.

    2005-01-01

    An explicit analytical form for the Stokes pulse evolution in parabolic amplification is derived for the first time. In order to achieve efficient pulse compression, the parabolic amplifiers should be operated in the small Stokes pulse regime where the signal pulse is not seriously deteriorated. An analytical expression to obtain the critical fibre length for small Stokes pulse regime is also derived. The pulse compression of the output signal at various fiber lengths also confirms that ...

  6. Generation of unipolar pulses in a circular Raman-active medium excited by few-cycle optical pulses

    CERN Document Server

    Arkhipov, R M; Babushkin, I; Pakhomov, A V; Tolmachev, Yu A; Rosanov, N N

    2016-01-01

    We study theoretically a new possibility of unipolar pulses generation in Raman-active medium excited by a series of few-cycle optical pulses. We consider the case when the Raman-active particles are uniformly distributed along the circle, and demonstrate a possibility to obtain a unipolar rectangular video pulses with an arbitrarily long duration, ranging from a minimum value equal to the natural period of the low frequency vibrations in the Raman-active medium.

  7. Bipolar semicopulas

    Czech Academy of Sciences Publication Activity Database

    Greco, S.; Mesiar, Radko; Rindone, F.

    Linz: Univesitatsdirektion, JKU Linz, Austria, 2013. s. 63-65. [Linz Seminar on Fuzzy Set Theory /34./. 26.02.2013-02.03.2013, Linz] R&D Projects: GA ČR GAP402/11/0378 Keywords : bipolar integral * bipolar semicopula * bipolar aggregation Subject RIV: BA - General Mathematics http://library.utia.cas.cz/separaty/2013/E/mesiar-0422906.pdf

  8. Choice of parameters for tesla transformer of pulsed power beam generator type

    International Nuclear Information System (INIS)

    The accelerating voltage pulse generators of relativistic electron beams and high-power ion beam accelerators are subdivided into two main types: Marx generators and Tesla transformer type generators.In presented paper the attempt to create the methodology of the engineering substantiation of parameters and designing the Tesla transformer type generator for pulsed power accelerators is undertaken

  9. Songbirds use pulse tone register in two voices to generate low-frequency sound

    DEFF Research Database (Denmark)

    Jensen, Kenneth Kragh; Cooper, Brenton G.; Larsen, Ole Næsbye; Goller, Franz

    2007-01-01

    generation alternates between the left and right sound sources. Spontaneously calling crows can also generate similar pulse characteristics with only one sound generator. Airflow recordings in zebra finches and starlings show that pulse tone sounds can be generated unilaterally, synchronously or by...

  10. Choice of parameters for tesla transformer of pulsed power beam generator type

    CERN Document Server

    Kolchanova, V A; Petrov, A V

    2001-01-01

    The accelerating voltage pulse generators of relativistic electron beams and high-power ion beam accelerators are subdivided into two main types: Marx generators and Tesla transformer type generators.In presented paper the attempt to create the methodology of the engineering substantiation of parameters and designing the Tesla transformer type generator for pulsed power accelerators is undertaken.

  11. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    OpenAIRE

    Haessler, Stefan; Balčiūnas, T.; Fan, G.; Chipperfield, L.; Baltuska, A.

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterb...

  12. Computer controlled MHD power consolidation and pulse generation system

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, R.; Marcotte, K.; Donnelly, M.

    1990-01-01

    The major goal of this research project is to establish the feasibility of a power conversion technology which will permit the direct synthesis of computer programmable pulse power. Feasibility has been established in this project by demonstration of direct synthesis of commercial frequency power by means of computer control. The power input to the conversion system is assumed to be a Faraday connected MHD generator which may be viewed as a multi-terminal dc source and is simulated for the purpose of this demonstration by a set of dc power supplies. This consolidation/inversion (CI), process will be referred to subsequently as Pulse Amplitude Synthesis and Control (PASC). A secondary goal is to deliver a controller subsystem consisting of a computer, software, and computer interface board which can serve as one of the building blocks for a possible phase II prototype system. This report period work summarizes the accomplishments and covers the high points of the two year project. 6 refs., 41 figs.

  13. Neonatal testosterone suppresses a neuroendocrine pulse generator required for reproduction

    Science.gov (United States)

    Israel, Jean-Marc; Cabelguen, Jean-Marie; Le Masson, Gwendal; Oliet, Stéphane H.; Ciofi, Philippe

    2014-02-01

    The pituitary gland releases hormones in a pulsatile fashion guaranteeing signalling efficiency. The determinants of pulsatility are poorly circumscribed. Here we show in magnocellular hypothalamo-neurohypophyseal oxytocin (OT) neurons that the bursting activity underlying the neurohormonal pulses necessary for parturition and the milk-ejection reflex is entirely driven by a female-specific central pattern generator (CPG). Surprisingly, this CPG is active in both male and female neonates, but is inactivated in males after the first week of life. CPG activity can be restored in males by orchidectomy or silenced in females by exogenous testosterone. This steroid effect is aromatase and caspase dependent, and is mediated via oestrogen receptor-α. This indicates the apoptosis of the CPG network during hypothalamic sexual differentiation, explaining why OT neurons do not burst in adult males. This supports the view that stereotypic neuroendocrine pulsatility is governed by CPGs, some of which are subjected to gender-specific perinatal programming.

  14. Generating long sequences of high-intensity femtosecond pulses

    CERN Document Server

    Bitter, Martin

    2015-01-01

    We present an approach to create pulse sequences extending beyond 150~picoseconds in duration, comprised of $100~\\mu$J femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multi-pass Ti:Sapphire amplifier, followed by an external compressor. A periodic sequence of 84~pulses of 120~fs width and an average pulse energy of 107~$\\mu$J, separated by 2~ps, is demonstrated as a proof of principle.

  15. Generating long sequences of high-intensity femtosecond pulses.

    Science.gov (United States)

    Bitter, M; Milner, V

    2016-02-01

    We present an approach to creating pulse sequences extending beyond 150 ps in duration, comprised of 100 μJ femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multipass Ti:sapphire amplifier, followed by an external compressor. A periodic sequence of 84 pulses of 120 fs width and an average pulse energy of 107 μJ, separated by 2 ps, is demonstrated as a proof of principle. PMID:26836087

  16. Analysis of radial and longitudinal force of plasma wakefield generated by a chirped pulse laser

    International Nuclear Information System (INIS)

    In present paper, the chirp effect of an electromagnetic pulse via an analytical model of wakefield generation is studied. Different types of chirps are employed in this study. Our results show that by the use of nonlinear chirped pulse the longitudinal wakefield and focusing force is stronger than that of linear chirped pulse. It is indicated that quadratic nonlinear chirped pulses are globally much efficient than periodic nonlinear chirped pulses. Our calculations also predict that in nonlinear chirped pulse case, the overlap of focusing and accelerating regions is broader than that achieved in linear chirped pulse

  17. Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

    CERN Document Server

    Haessler, Stefan; Fan, Guangyu; Chipperfield, Luke E; Baltuška, Andrius

    2014-01-01

    Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the attosecond time scale. The applicability of these IAP would be widened drastically by increasing their energy. Here we analyze the potential of using multi-colour driving pulses for temporally gating the attosecond pulse generation process. We devise how this approach can enable the generation of IAP with the available high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering 180-fs, 1030-nm pulses). We show theoretically that this requires a three-colour field composed of the fundamental and its second harmonic as well as a lower-frequency auxiliary component. We present pulse characterization measurements of such auxiliary pulses generated directly by white-light seeded OPA with the required significantly shorter pulse duration than the that of the fundamental. This, combined with our recent experimental results on three-colour waveform synthesis [Phys....

  18. Supercontinuum Comb Generation Using Optical Pulse Synthesizer and Highly Nonlinear Dispersion-Shifted Fiber

    Science.gov (United States)

    Choi, Samuel; Tamura, Naoyuki; Kashiwagi, Ken; Shioda, Tatsutoshi; Tanaka, Yosuke; Kurokawa, Takashi

    2009-09-01

    We propose a novel supercontinuum (SC) generation technology using an optical pulse synthesizer and highly nonlinear dispersion-shifted fiber. The optical pulse synthesizer enables us to reshape seed pulses optimized for broadband SC generation. 25.0 and 12.5 GHz SC combs were successfully generated by propagating synthesized seed pulses in the highly nonlinear fiber. We investigated how seed pulse conditions including shape, peak power, repetition rate, and center wavelength affect SC spectral bandwidth. We also evaluated interferometric signal waveforms from a Michelson interferometer using the generated SC comb as the light source. Interferometric peak width improved to 35.5 µm when peak power reached 7.9 W for the Gaussian pulse-based SC comb. Numerical simulation results almost agreed with experimental results. The difference between SC combs generated from Gaussian and sech2 pulses was confirmed by the simulations.

  19. Generation of an intense single isolated attosecond pulse by use of two-colour waveform control

    Science.gov (United States)

    Zeng, Bin; Yu, Yongli; Chu, Wei; Yao, Jinping; Fu, Yuxi; Xiong, Hui; Xu, Han; Cheng, Ya; Xu, Zhizhan

    2009-07-01

    We theoretically demonstrate the generation of an intense single attosecond pulse by superposing a weak sub-harmonic pulse upon a sine-waveform few-cycle driving pulse. By use of a sine-waveform few-cycle pulse instead of its traditionally used cosine waveform counterpart, we show that efficient tunnel ionization for generating electrons which can revisit their parent ion with high kinetic energy can occur only once in the few-cycle laser field, leading to an increase of efficiency by nearly two orders of magnitude in single attosecond pulse generation as compared with the use of a cosine-waveform field.

  20. Generation of an intense single isolated attosecond pulse by use of two-colour waveform control

    International Nuclear Information System (INIS)

    We theoretically demonstrate the generation of an intense single attosecond pulse by superposing a weak sub-harmonic pulse upon a sine-waveform few-cycle driving pulse. By use of a sine-waveform few-cycle pulse instead of its traditionally used cosine waveform counterpart, we show that efficient tunnel ionization for generating electrons which can revisit their parent ion with high kinetic energy can occur only once in the few-cycle laser field, leading to an increase of efficiency by nearly two orders of magnitude in single attosecond pulse generation as compared with the use of a cosine-waveform field.

  1. Single Circularly Polarized Attosecond Pulse Generation by Intense Few Cycle Elliptically Polarized Laser Pulses and Terahertz Fields from Molecular Media

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2013-01-01

    We present a method for producing a single circularly polarized attosecond pulse by an intense few cycle elliptically polarized laser pulse combined with a terahertz field from numerical solutions of the time-dependent Schrödinger equation for the molecular ion H2+. It is found that in the presence of a 62.5 THz (λ=4800nm) field at an intensity of ˜1014W/cm2, a single circularly polarized 114 as pulse can be generated by an elliptical polarized laser pulse at a wavelength of 400 nm with an ellipticity of ɛ=0.59. The efficiency of circular polarization attosecond pulse generation is interpreted based on a classical model of single electron recollision with the parent ion.

  2. GENERATION OF SUBPICOSECOND X-RAY PULSES IN STORAGE RINGS

    International Nuclear Information System (INIS)

    Supicosecond x-ray pulses are routinely produced at ALS, BESSY and SLS with slicing technique and used in pump-probe experiments with controlled delay between laser pump pulses and x-ray probe pulses. New development aiming for a production of a subpicosecond x-ray pulses using rf orbit deflection technique is under way at APS. Both techniques will be reviewed here

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

    Science.gov (United States)

    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.

  4. Physics of giant electromagnetic pulse generation in short-pulse laser experiments

    Science.gov (United States)

    Poyé, A.; Hulin, S.; Bailly-Grandvaux, M.; Dubois, J.-L.; Ribolzi, J.; Raffestin, D.; Bardon, M.; Lubrano-Lavaderci, F.; D'Humières, E.; Santos, J. J.; Nicolaï, Ph.; Tikhonchuk, V.

    2015-04-01

    In this paper we describe the physical processes that lead to the generation of giant electromagnetic pulses (GEMPs) at powerful laser facilities. Our study is based on experimental measurements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralization current in the target holder and the electromagnetic emission shows that the source of the GEMP is the remaining positive charge inside the target after the escape of fast electrons accelerated by the ultra-intense laser. A simple model for calculating this charge in the thick target case is presented. From this model and knowing the geometry of the target holder, it becomes possible to estimate the intensity and the dominant frequencies of the GEMP at any facility.

  5. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    CERN Document Server

    Poyé, Alexandre; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of the GEMP is the remaining positive charge inside the target after the escape of fast electrons accelerated by the ultra-intense laser. A simple model for calculating this charge in the thick target case is presented. From this model and knowing the geometry of the target holder, it becomes possible to estimate the intensity and the dominant frequencies of the GEMP on any facility.

  6. Attosecond pulse generation by a two-color field

    International Nuclear Information System (INIS)

    A method for the generation of attosecond electromagnetic pulses is suggested. The key idea of the method consists in using a two-color laser pump for high-order harmonic generation composed of a low-frequency linearly polarized field and a high-frequency elliptically polarized field. Such a two-color pump can provide for the return of photoelectrons (after atom ionization) to the vicinity of the parent ion with high kinetic energy and their recombination for only specific ionization moments t0. The range of these moments, δt0, is defined by the velocity of electron wave-packet spreading and the time that the photoelectron spent in the continuum (before the recombination). Conditions were found that minimize the range δt0. For the specific parameters of a two-color pump, the duration of recombination emission, τg, can be in the range of 1-10 as. With an increase of pump intensity, the duration τg decreases and can be reduced to the subattosecond scale

  7. Robust generation of isolated attosecond pulse against the variation of carrier envelope phase of driving laser pulses

    International Nuclear Information System (INIS)

    We propose a scheme for generating isolated attosecond pulse (IAP) via high-order harmonic generation in gases using a chirped two-color laser field of multicycle duration. In contrast to previous techniques where the stable carrier-envelope phase (CEP) of the driving laser pulses is a prerequisite for IAP generation, the proposed scheme is robust against the large variation of CEP. We show the generation of IAP with an intensity fluctuation less than 50% and an intensity contrast ratio higher than 5:1 when the CEP shift is as large as 1.35π.

  8. Application of a single-board computer as a low-cost pulse generator

    International Nuclear Information System (INIS)

    A BeagleBone Black (BBB) single-board open-source computer was implemented as a low-cost fully programmable pulse generator. The pulse generator makes use of the BBB Programmable Real-Time Unit (PRU) subsystem to achieve a deterministic temporal resolution of 5 ns, an RMS jitter of 290 ps and a timebase stability on the order of 10 ppm. A Python-based software framework has also been developed to simplify the usage of the pulse generator. (paper)

  9. Application of a single-board computer as a low cost pulse generator

    CERN Document Server

    Fedrizzi, Marcus

    2015-01-01

    A BeagleBone Black (BBB) single-board open-source computer was implemented as a low-cost fully programmable pulse generator. The pulse generator makes use of the BBB Programmable Real-Time Unit (PRU) subsystem to achieve a deterministic temporal resolution of 5 ns, an RMS jitter of 290 ps and a timebase stability on the order of 10 ppm. A python based software framework has also been developed to simplify the usage of the pulse generator.

  10. Towards intense attosecond pulses: using two beams for high order harmonic generation from solid targets

    Science.gov (United States)

    Tarasevitch, A. P.; Kohn, R.; von der Linde, D.

    2009-07-01

    The advantages of using two beam high order harmonic generation (HOHG) from solids are discussed. The two-pulse technique allows additional control of the parameters essential for the attosecond pulse generation. We show that spectral filtering is not necessary for the generation of attosecond pulses. The simple oscillating mirror model is in qualitative agreement with the computer simulations. We present the results of first experiments using two beams for HOHG.

  11. Generation of random nuclear pulse using Fibonacci linear feedback shift registers

    International Nuclear Information System (INIS)

    Generating random nuclear pulses is of great interest in the field of nuclear instrumentation as it can facilitate the testing of front end electronics like pre-amplifiers, amplifiers and associated electronic channels in absence of radiation source and detectors. An algorithm based on Fibonacci Linear feedback shift registers (LFSR) has been developed. It employs LFSRs to generate uniformly distributed random numbers which are then suitably processed to produce random pulses having characteristics of pulses generated by a neutron detector. (author)

  12. LD pumped Yb:YAG regenerative amplifier for high average power short-pulse generation

    International Nuclear Information System (INIS)

    A diode pumped Yb:YAG regenerative amplifier has been developed for short pulse generation. High gain and efficient cooling characteristics were achieved in the laser gain module using a thin square-rod laser structure. Average output power of 10 W was realized at a pulse repetition rate of 100 kHz with 6.2 ps pulse width

  13. Pulse excitation experiment of a superconducting generator; chodendo hatsudenki no parusu reiki shiken

    Energy Technology Data Exchange (ETDEWEB)

    Miyaike, K.; Iimura, T.; Nishimura, M.; Arata, M.; Takabatake, M. [Toshiba Ltd., Tokyo (Japan); Yamada, M.; Kanamori, Y.; Hasegawa, K. [Kansai Electric Power Co., Inc., Osaka (Japan)

    1999-11-10

    Efficiency improvement, improvement in the stability of electric power system it is miniaturization and weight reduction can be expected in comparison with the traditional-model generator superconducting generator. We produce the small superconducting generator for the experiment experimentally, and performance characteristics verification of the generator is carried out experimentally. This time, pulse excitation test of the superconducting generator was carried out, and the ac loss of the conductor by the pulse excitation investigated the effect on the quenching current. (NEDO)

  14. Generation of 25-TW Femtosecond Laser Pulses at 515 nm with Extremely High Temporal Contrast

    Directory of Open Access Journals (Sweden)

    Marco Hornung

    2015-12-01

    Full Text Available We report on the frequency doubling of femtosecond laser pulses at 1030 nm center wavelength generated from the fully diode-pumped laser system POLARIS. The newly generated pulses at a center wavelength of 515 nm have a pulse energy of 3 J with a pulse duration of 120 fs. On the basis of initially ultra-high contrast seed pulses we expect a temporal intensity contrast better 10 17 200 ps before the peak of the main pulse. We analyzed the temporal intensity contrast from milliseconds to femtoseconds with a dynamic range covering more than 20 orders of magnitude. The pulses were focussed with a f/2-focussing parabola resulting in a peak intensity exceeding 10 20 W / cm 2 . The peak power and intensity are to the best of our knowledge the highest values for 515 nm-laser-pulses achieved so far.

  15. Generation of synchronized signal and pump pulses for an optical parametric chirped pulse amplification based multi-terawatt Nd:glass laser system

    Indian Academy of Sciences (India)

    M Raghuramaiah; R K Patidar; R A Joshi; P A Naik; P D Gupta

    2010-11-01

    Synchronized signal (650 ps) and pump (1.3 ns) pulses were generated using 4-pass geometry in a grating pair based pulse stretcher unit. The pump pulse has been further amplified in a high gain regenerative amplifier. This amplified pulse was used as the pump in an optical parametric chirped pulse amplification based Nd:glass laser system. As the chirped signal pulse and the pump pulse originated from the same oscillator, the time jitter between the pump pulse and the signal pulse can be <50 ps.

  16. Generation and Amplification of Cherenkov Superradiance Pulses by Electron Beams with Energy Chirp

    Science.gov (United States)

    Ginzburg, N. S.; Zotova, I. V.; Sergeev, A. S.

    2003-10-01

    We propose a method for increasing the peak power of a superradiance pulse by varying the electron energy along an electron bunch. A one-dimensional time-dependent model describing the evolution of an electromagnetic pulse as well as direct numerical simulations based on the KARAT code show that the power of generated pulses becomes several times greater if the particle energy increases linearly along the bunch. A similar method can be applied to increase the peak power in the case of amplification of a short electromagnetic pulse (and a superradiance pulse generated by an external source) propagated along a quasi-continuous electron beam with a certain particle-energy profile.

  17. LASERS: Efficient source of femtosecond pulses and its use for broadband supercontinuum generation

    Science.gov (United States)

    Tausenev, Anton V.; Kryukov, P. G.; Bubnov, M. M.; Likhachev, M. E.; Romanova, E. Yu; Yashkov, M. V.; Khopin, V. F.; Salganskii, M. Yu

    2005-07-01

    A femtosecond Er3+-doped fibre laser system is developed and studied. The system contains a master oscillator operating in the pulse stretching regime, an amplifier of chirped pulses, and a device for pulse compression. The laser emits 1.55-μm, 100-fs, 90-mW pulses with a pulse repetition rate of 25 MHz. The setup was used for supercontinuum generation in an optical fibre heavily doped with GeO2. The width of the generated supercontinuum was close to an octave.

  18. Modelling of noise-like pulses generated in fibre lasers

    Science.gov (United States)

    Smirnov, Sergey; Kobtsev, Sergey

    2016-03-01

    The present paper for the first time proposes and studies a relatively simple model of noise-like pulses that matches the experimental data well and suggests that there is a correlation between phases of adjacent spectral components of noiselike pulses. Comparison of a relatively basic model of `random' pulses with the results of noise-like pulse modelling in mode-locked fibre lasers based on coupled non-linear Schrödinger equations demonstrates that it adequately reproduces temporal and spectral properties of noise-like pulses as well as correlation between adjacent modes so that it's possible to use the proposed model for highly efficient simulations of promising applications of noise-like pulses, such as material processing, non-linear frequency conversion, microscopy, and others.

  19. Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

    CERN Document Server

    Yao, B C; Wang, Z N; Wu, Y; Zhou, J H; Wu, H; Fan, M Q; Cao, X L; Zhang, W L; Chen, Y F; Li, Y R; Churkin, D; Turitsyn, S; Wong, C W

    2015-01-01

    Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse for...

  20. A CMOS fifth-derivative Gaussian pulse generator for UWB applications

    International Nuclear Information System (INIS)

    A CMOS fifth-derivative Gaussian pulse generator is presented for ultra-wideband (UWB) applications. The design exhibits low power consumption, low circuit complexity, and a precise pulse shape to inherently comply with the FCC spectrum mask for indoor UWB applications without the need for a filter. The pulse generator is implemented with a 1.8-V, 0.18-μm CMOS process. The small core chip size of the pulse generator is only 217 × 121 μm2 because of its all digital circuit design. The measured fifth-derivative Gaussian pulse has a peak-to-peak amplitude of 158 mV and a pulse width of 800 ps. The average power dissipation is 0.6 mW with a pulse repetition frequency of 50 MHz. (semiconductor integrated circuits)

  1. Infrared Two-Color Multicycle Laser Field Synthesis for Generating an Intense Attosecond Pulse

    Science.gov (United States)

    Takahashi, Eiji J.; Lan, Pengfei; Mücke, Oliver D.; Nabekawa, Yasuo; Midorikawa, Katsumi

    2010-06-01

    We propose and demonstrate the generation of a continuum high-order harmonic spectrum by mixing multicycle two-color (TC) laser fields with the aim of obtaining an intense isolated attosecond pulse. By optimizing the wavelength of a supplementary infrared pulse in a TC field, a continuum harmonic spectrum was created around the cutoff region without carrier-envelope phase stabilization. The obtained harmonic spectra clearly show the possibility of generating isolated attosecond pulses from a multicycle TC laser field, which is generated by an 800 nm, 30 fs pulse mixed with a 1300 nm, 40 fs pulse. Our proposed method enables us not only to relax the requirements for the pump pulse duration but also to reduce ionization of the harmonic medium. This concept opens the door to create an intense isolated attosecond pulse using a conventional femtosecond laser system.

  2. Generation of elliptically polarized nitrogen ion laser fields using two-color femtosecond laser pulses

    OpenAIRE

    Ziting Li; Bin Zeng; Wei Chu; Hongqiang Xie; Jinping Yao; Guihua Li; Lingling Qiao; Zhanshan Wang; Ya Cheng

    2016-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized...

  3. Generation of intense coherent attosecond X-ray pulses using relativistic electron mirrors

    Science.gov (United States)

    Kulagin, V. V.; Kornienko, V. N.; Cherepenin, Vladimir A.; Suk, Hyyong

    2013-05-01

    We analyse the steepening of the leading edge of femtosecond petawatt pulses with the use of plasma layers and show that, at an electron density several times higher than the critical one, an asymmetric (in time domain) pulse can be produced with an amplitude of the first half-wave differing little from the maximum pulse amplitude. Using numerical simulation, we have studied the interaction of such pulses with nanometre-thick films, including the generation of relativistic electron mirrors and the reflection of a counterpropagating probe pulse from such mirrors. The resulting coherent X-ray pulses have a duration of ~120 as and a power of ~600 GW at a wavelength of ~13 nm. Our results demonstrate that the reflectivity of a relativistic electron mirror situated in the accelerating pulse field is independent of the probe pulse amplitude when it increases up to the accelerating pulse amplitude.

  4. Generation of intense coherent attosecond X-ray pulses using relativistic electron mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Kulagin, V V; Kornienko, V N; Cherepenin, Vladimir A; Suk, Hyyong

    2013-05-31

    We analyse the steepening of the leading edge of femtosecond petawatt pulses with the use of plasma layers and show that, at an electron density several times higher than the critical one, an asymmetric (in time domain) pulse can be produced with an amplitude of the first half-wave differing little from the maximum pulse amplitude. Using numerical simulation, we have studied the interaction of such pulses with nanometre-thick films, including the generation of relativistic electron mirrors and the reflection of a counterpropagating probe pulse from such mirrors. The resulting coherent X-ray pulses have a duration of {approx}120 as and a power of {approx}600 GW at a wavelength of {approx}13 nm. Our results demonstrate that the reflectivity of a relativistic electron mirror situated in the accelerating pulse field is independent of the probe pulse amplitude when it increases up to the accelerating pulse amplitude. (interaction of laser radiation with matter. laser plasma)

  5. Intense Pulsed Heavy Ion Beam Technology

    Science.gov (United States)

    Masugata, Katsumi; Ito, Hiroaki

    Development of intense pulsed heavy ion beam accelerator technology is described for the application of materials processing. Gas puff plasma gun and vacuum arc discharge plasma gun were developed as an active ion source for magnetically insulated pulsed ion diode. Source plasma of nitrogen and aluminum were successfully produced with the gas puff plasma gun and the vacuum arc plasma gun, respectively. The ion diode was successfully operated with gas puff plasma gun at diode voltage 190 kV, diode current 2.2 kA and nitrogen ion beam of ion current density 27 A/cm2 was obtained. The ion composition was evaluated by a Thomson parabola spectrometer and the purity of the nitrogen ion beam was estimated to be 86%. The diode also operated with aluminum ion source of vacuum arc plasma gun. The ion diode was operated at 200 kV, 12 kA, and aluminum ion beam of current density 230 A/cm2 was obtained. The beam consists of aluminum ions (Al(1-3)+) of energy 60-400 keV, and protons (90-130 keV), and the purity was estimated to be 89 %. The development of the bipolar pulse accelerator (BPA) was reported. A double coaxial type bipolar pulse generator was developed as the power supply of the BPA. The generator was tested with dummy load of 7.5 ohm, bipolar pulses of -138 kV, 72 ns (1st pulse) and +130 kV, 70 ns (2nd pulse) were succesively generated. By applying the bipolar pulse to the drift tube of the BPA, nitrogen ion beam of 2 A/cm2 was observed in the cathode, which suggests the bipolar pulse acceleration.

  6. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    International Nuclear Information System (INIS)

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  7. Optimization of infrared two-color multicycle field synthesis for intense-isolated-attosecond-pulse generation

    Science.gov (United States)

    Lan, Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi

    2010-11-01

    We present the optimization of the two-color synthesis method for generating an intense isolated attosecond pulse (IAP) in the multicycle regime. By mixing an infrared assistant pulse with a Ti:sapphire main pulse, we show that an IAP can be produced using a multicycle two-color pulse with a duration longer than 30 fs. We also discuss the influence of the carrier-envelope phase (CEP) and the relative intensity on the generation of IAPs. By optimizing the wavelength of the assistant field, IAP generation becomes insensitive to the CEP slip. Therefore, the optimized two-color method enables us to relax the requirements of pulse duration and easily produce the IAP with a conventional multicycle laser pulse. In addition, it enables us to markedly suppress the ionization of the harmonic medium. This is a major advantage for efficiently generating intense IAPs from a neutral medium by applying the appropriate phase-matching and energy-scaling techniques.

  8. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  9. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    CERN Document Server

    Balogh, Emeric; Dombi, Peter; Fulop, Jozsef A; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin; 10.1103/PhysRevA.84.023806

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half-cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single atom response yields an attosecond pulse train.

  10. Construction of double discharge pulsed electron beam generator and its applications

    International Nuclear Information System (INIS)

    Generation of fast pulsed electron beam by superposing DC and pulsed hollow cathode discharge is studied. The electrical characteristics and measurements of the electron beam generator are done dc glow discharge and for the pulsed one. The electron beam current, its density and magnetic field effect, pinch effect, have been studied. The dependence of the electron beam parameters with respect to pressure and magnetic field have been studied. The pulsing effect of the beam is reviewed. By using the generator, micron holes drilling and carbon deposition was done at the laboratory. As a target source for carbon deposition methane gas is used and for Hydrogen-free carbon deposition was graphite

  11. Tunable narrowband THz pulse generation in scalable large area photoconductive antennas.

    Science.gov (United States)

    Krause, Johannes; Wagner, Martin; Winnerl, Stephan; Helm, Manfred; Stehr, Dominik

    2011-09-26

    The generation and characterization of narrowband THz pulses by means of chirped pulse difference frequency generation in Auston-switch type photoconductive antennas is reported. Using optical pulses with energies in the range from 1 nJ to 1 µJ, we generate THz pulses with up to 50 pJ in energy and electric field strengths on the order of 1 kV/cm. Two emitter concepts are investigated and circumvention of the fast saturation for small area excitation by scaling of the THz emitter is demonstrated. PMID:21996852

  12. Note: Picosecond impulse generator driven by cascaded step recovery diode pulse shaping circuit.

    Science.gov (United States)

    Choi, Gil Wong; Choi, Jin Joo; Han, Seung Hoon

    2011-01-01

    In this paper, a picosecond impulse generator using step recovery diodes (SRDs) is presented. In order to reduce the pulse width of an impulse generator, we employed a cascaded SRD pulse-shaping circuit. A short impulse generation is confirmed in numerical simulation of a time-transient circuit simulator. Measurements show that the measured pulse width of the cascaded SRD impulse generator is 250 ps at 10% of the peak amplitude, which is improved by 85 ps compared with a conventional SRD impulse generator. PMID:21280869

  13. Application of High Intensity THz Pulses for Gas High Harmonic Generation

    CERN Document Server

    Balogh, Emeric; Hebling, János; Dombi, Péter; Farkas, Győző; Varjú, Katalin

    2013-01-01

    The main effects of an intense THz pulse on gas high harmonic generation are studied via trajectory analysis on the single atom level. Spectral and temporal modifications to the generated radiation are highlighted.

  14. Application of high intensity THz pulses for gas high harmonic generation

    Science.gov (United States)

    Balogh, Emeric; Fülöp, József; Hebling, János; Dombi, Péter; Farkas, Győző; Varjú, Katalin

    2013-09-01

    The main effects of an intense THz pulse on gas high harmonic generation are studied via trajectory analysis on the single atom level. Spectral and temporal modifications to the generated radiation are highlighted.

  15. Generation and structure of extremely large clusters in pulsed jets

    International Nuclear Information System (INIS)

    Extremely large xenon clusters with sizes exceeding the predictions of the Hagena scaling law by several orders of magnitude are shown to be produced in pulsed gas jets. The cluster sizes are determined using single-shot single-particle imaging experiments with short-wavelength light pulses from the free-electron laser in Hamburg (FLASH). Scanning the time delay between the pulsed cluster source and the intense femtosecond x-ray pulses first shows a main plateau with size distributions in line with the scaling laws, which is followed by an after-pulse of giant clusters. For the extremely large clusters with radii of several hundred nanometers the x-ray scattering patterns indicate a grainy substructure of the particles, suggesting that they grow by cluster coagulation

  16. Generation of pulsed light in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Johansson, Sandra; Andersen, Martin; Tidemand-Lichtenberg, Peter;

    We propose a novel generic approach for generation of pulsed light in the visible spectrum based on sum-frequency generation between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser. For demonstration, we used a CW 1342 nm laser mixed with a pass...

  17. A pulsed neutron generator with maximum temperature rating of 150 degree C

    International Nuclear Information System (INIS)

    The author points out the existing problems of the available pulsed neutron generators used in the nuclear logging tools, highlights the technological breakthrough in developing 150 degree C pulsed neutron generator, presents its technical specification and wellsite applications and its contributions to the development of future nuclear well logging tools

  18. Design and characterization of an RF pulse train generator for large-signal analysis

    International Nuclear Information System (INIS)

    In this paper an RF pulse train signal is introduced that can serve as a reference signal for the phase calibration of the large-signal network analyser (LSNA) under modulated excitations. Hence, the pulse train generator is specifically designed to fulfil the requirements of such a calibration signal. The design and characterization of the RF signal generator are discussed in this work

  19. Electromagnetic pulse reflection at self-generated plasma mirrors: laser pulse shaping and high order harmonic generation

    OpenAIRE

    Bulanov, S. S.; Macchi, A.; Maksimchuk, A.; Matsuoka, T.; Nees, J.; Pegoraro, F.

    2007-01-01

    A thin layer of overdense plasma is created when an electromagnetic pulse interacts with a rapidly ionizing thin foil. This layer will reflect the incoming pulse, forming a so-called plasma mirror. A simple realistic model based on paired kinetic and wave equations is used to describe analytically the process of mirror formation and the reflection and transmission of the incident pulse. The model incorporates the exact description of the ionization process in the foil and the polarization and...

  20. Picoseconds pulse generation and pulse width determination processes of a distributed feedback dye laser

    International Nuclear Information System (INIS)

    A mathematical model has been developed to describe the dynamic emission of Nd-glass, distributed feedback dye laser (DFDL), and periodical grating temperature. The suggested model allows the investigation of the time behavior of Nd-glass laser and DFDL pulsed. Moreover, it allows studying the effect of the laser input parameters of Nd-glass laser on the spectral characteristics of the output DFDL pulses such as pulse width, delay time, and time separation

  1. Bipolar Disorder.

    Science.gov (United States)

    Spearing, Melissa

    Bipolar disorder, a brain disorder that causes unusual shifts in a person's mood, affects approximately one percent of the population. It commonly occurs in late adolescence and is often unrecognized. The diagnosis of bipolar disorder is made on the basis of symptoms, course of illness, and when possible, family history. Thoughts of suicide are…

  2. Reconfigurable symmetric pulses generation using on-chip cascaded optical differentiators.

    Science.gov (United States)

    Hou, Jie; Dong, Jianji; Zhang, Xinliang

    2016-09-01

    We report a type of programmable pulse shaping method based on cascaded frequency-detuned optical differentiators. By properly adjusting the central wavelength of each differentiator, a large variety of symmetric pulses can be generated from a transform-limited Gaussian-like pulse. We numerically and experimentally demonstrate the generation of flat-top, parabolic and triangular pulses with tunable pulse widths from a 20-ps Gaussian-like pulse, using no more than three cascaded differentiators. It can be found that as more differentiators are used, higher synthesized accuracy and larger tuning range of pulse widths can be obtained in general. Additionally, in our experiment, we design and fabricate thermally tunable delay interferometers on the silicon-on-insulator (SOI) platform to work as optical differentiators, which can help us realize the shaping system with small footprint (943μm × 395μm) and high stability. PMID:27607657

  3. Dry-type 50 MW, 200 kV Tesla transformer for compact pulse generator

    International Nuclear Information System (INIS)

    Full text: A 15V/200kV, 2μs air-core pulse transformer has been designed and fabricated for a prototype compact pulse generator for generation of intense pulsed electron beams. The transformer can deliver 50 to 100J energy at 50 MW peak power to charge a pulse forming line at 200 kV in 2μs time, which on discharge produces 200kV, 50ns HV pulse. This pulse transformer has also been used for surface flashover studies on insulators in vacuum and transformer oil mediums for sub-micro second region. In this paper, design details of pulse transformer, the test results and a comparative discussion with the conventional systems has been presented in brief

  4. Generation of orthogonal UWB shaping pulses based on compressed chirp signal

    Institute of Scientific and Technical Information of China (English)

    CHE Shu-liang; ZHANG Hong-xin; LU Ying-hua; HE Peng-fei

    2007-01-01

    This study investigates a novel method to numerically generate orthogonal ultrawide band (UWB) shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is used to construct a Hermitian matrix, is produced with a compressed chirp pulse. Sub-nanosecond orthogonal pulses are then generated for UWB by using the Hermitian matrix eigenvectors. The simulation results show that the power spectral density distribution of the UWB shaping pulses met the constraint of Federal communications commissions (FCC) spectral mask. The shaping pulses not only have higher spectrum utilization ratio and very short time duration but also have excellent autocorrelation and cross-correlation properties, which is an advantage to reduce the interference between multiusers. Especially, a method to produce sub-nanosecond orthogonal UWB shaping pulses by using a relatively longer duration chirp signal is presented.

  5. Simulation study on ultrashort pulse electron generation in laser photocathode RF gun linac

    International Nuclear Information System (INIS)

    A new S-band femtosecond electron linear accelerator, which was constructed with a laser driven photocathode RF gun, a linear accelerator (linac) and a magnetic pulse compressor, was developed in Osaka University for the study of radiation-induced ultrafast physical and chemical reactions in femtosecond time regions. In order to generate the ultrashort pulse electrons, we simulated the electron generation in the RF gun with a picosecond Nd: YLF laser light by PARMELA code with space-charge effects. The energy modulation of the electron pulse in the linac was also calculated with the optimum of the RF phase. The pulse compression in the magnetic pulse compressor was simulated by Trace-3D code. A few tens femtosecond electron pulse was obtained by optimizing the magnetic fields in the magnetic pulse compressor. (author)

  6. Bipolar disorder.

    Science.gov (United States)

    Grande, Iria; Berk, Michael; Birmaher, Boris; Vieta, Eduard

    2016-04-01

    Bipolar disorder is a recurrent chronic disorder characterised by fluctuations in mood state and energy. It affects more than 1% of the world's population irrespective of nationality, ethnic origin, or socioeconomic status. Bipolar disorder is one of the main causes of disability among young people, leading to cognitive and functional impairment and raised mortality, particularly death by suicide. A high prevalence of psychiatric and medical comorbidities is typical in affected individuals. Accurate diagnosis of bipolar disorder is difficult in clinical practice because onset is most commonly a depressive episode and looks similar to unipolar depression. Moreover, there are currently no valid biomarkers for the disorder. Therefore, the role of clinical assessment remains key. Detection of hypomanic periods and longitudinal assessment are crucial to differentiate bipolar disorder from other conditions. Current knowledge of the evolving pharmacological and psychological strategies in bipolar disorder is of utmost importance. PMID:26388529

  7. Input energy measurement toward warm dense matter generation using intense pulsed power generator

    Science.gov (United States)

    Hayashi, R.; Ito, T.; Ishitani, T.; Tamura, F.; Kudo, T.; Takakura, N.; Kashine, K.; Takahashi, K.; Sasaki, T.; Kikuchi, T.; Harada, Nob.; Jiang, W.; Tokuchi, A.

    2016-05-01

    In order to investigate properties of warm dense matter (WDM) in inertial confinement fusion (ICF), evaluation method for the WDM with isochoric heating on the implosion time-scale using an intense pulsed power generator ETIGO-II (∼1 TW, ∼50 ns) has been considered. In this study, the history of input energy into the sample is measured from the voltage and the current waveforms. To achieve isochoric heating, a foamed aluminum with pore sizes 600 μm and with 90% porosity was packed into a hollow glass capillary (ø 5 mm × 10 mm). The temperature of the sample is calculated from the numerical calculation using the measured input power. According to the above measurements, the input energy into a sample and the achievable temperature are estimated to be 300 J and 6000 K. It indicates that the WDM state is generated using the proposed method with ICF implosion time-scale.

  8. Generation of a single attosecond pulse from an overdense plasma surface driven by a laser pulse with time-dependent polarization

    International Nuclear Information System (INIS)

    The influence of time-dependent polarization on attosecond pulse generation from an overdense plasma surface driven by laser pulse is discussed analytically and numerically. The results show that the frequency of controlling pulse controls the number and interval of the generated attosecond pulse, that the generation moment of the attosecond pulse is dominated by the phase difference between the controlling and driving pulses, and that the amplitude of the controlling pulse affects the intensity of the attosecond pulse. Using the method of time-dependent polarization, a “single” ultra-strong attosecond pulse with duration τ ≈ 8.6 as and intensity I ≈ 3.08 × 1020 W·cm−2 can be generated. (physics of gases, plasmas, and electric discharges)

  9. Micro-pulses generation in ECR breakdown stimulated by gyrotron radiation at 37,5 GHz

    International Nuclear Information System (INIS)

    The present work is devoted to experimental and theoretical investigation of the creation of short pulsed (< 100 μs) multicharged ion beams. The possibility of quasi-stationary generation of short pulsed beams under conditions of quasi-gasdynamic plasma confinement was shown in recent experiments. Later another way of such beams creation based on the Pre-glow effect was proposed. In present work it was demonstrated that in the case when duration of microwave (MW) pulse is less than formation time of Pre-glow peak, realization of a regime when ion current is negligible during MW pulse and intense multicharged ions flux appears only when MW ends could be possible. Such pulses after the end of MW were called micro-pulses. In the present work the generation of micro-pulses was observed in experiments with ECR discharge stimulated by gyrotron radiation at 37,5 GHz, 100 kW. In this case pulses with duration less than 30 μs were obtained. Probably the same effect was observed in GANIL where 14 GHz radiation was used and pulses with duration about 2 ms were registered. In present work it was shown that the intensity of such micro-pulse could be higher than intensity of Pre-glow peak at the same conditions but with longer MW pulse. The generation of micro-pulses of nitrogen and argon multicharged ions with current of a few mA and length about 30 μs after MW pulse with duration of 30-100 μs was demonstrated. The low level of impurities, high current density and rather high average charge make possible to consider such micro-pulse regime as a possibility for the creation of a short pulsed ion source. The paper is followed by the slides of the presentation. (authors)

  10. MGX: a high-power, pulsed microwave generator development project

    Energy Technology Data Exchange (ETDEWEB)

    Scarpetti, R.; Vogtlin, G.; Lundberg, R.; Burkhart, S.; Hofer, W.

    1983-06-03

    A high-power, short-pulse microwave source, MGX, is being developed at Lawrence Livermore National Laboratory. It will be used for high-power microwave vulnerability and lethality studies, investigation of air breakdown, and high-power microwave diagnostic development. The microwave source, a virtual cathode oscillator (VIRCATOR), is initially designed to operate at 8 GHz, with an output power greater than 1 GW, and 70 ns pulse width. The pulsed power source is a modified one-unit FXR Blumlein system charged to approximately 650 kV. A new insulator and electron-beam diode have been designed. In addition, a water-breakdown gap has been included to suppress diode prepulse and to sharpen the pulse rise time. The VIRCATOR has been extensively modeled with the MASK code at LLNL. Preliminary results are presented.

  11. Generation of ultrashort UV pulses and R2PI measurements of deflected molecules

    OpenAIRE

    Worbs, Lena

    2015-01-01

    This thesis is about the generation and characterization of ultrashort ultraviolet (UV) laser pulses, resonance-enhanced two photon ionization (R2PI) measurements of indole and the electrostatic deflection of indole.UV pulses are generated from a 39 fs Ti:Sapphire Laser with a central wavelength of 800 nm and a bandwidth of 60 nm. To generate UV pulses, the nonlinear process of harmonic generation in a beta-barium-borate (BBO)-crystal is used. A prism compressor ensures group velocity dispers...

  12. Advertising Pulsing Policies for Generating Awareness for New Products

    OpenAIRE

    Vijay Mahajan; Eitan Muller

    1986-01-01

    The question of whether a pulsed advertising policy is superior to an even policy (constant spending over time) is of practical relevance to both advertising practitioners and model builders. This paper presents an analytical model that can be used to analyze the impact of the various pulsing and even policies on awareness. In addition to establishing the relationships between the various advertising policies analytically, an application of the proposed model to the actual Zielske's data is i...

  13. Apparatus and method for generating high density pulses of electrons

    International Nuclear Information System (INIS)

    An apparatus and method are described for the production of high density pulses of electrons using a laser energized emitter. Caesium atoms from a low pressure vapour atmosphere are absorbed on and migrate from a metallic target rapidly heated by a laser to a high temperature. Due to this heating time being short compared with the residence time of the caesium atoms adsorbed on the target surface, copious electrons are emitted which form a high current density pulse. (U.K.)

  14. Generation of a Super Strong Attosecond Pulse from an Atomic Superposition State Irradiated by a Shape-Optimized Short Pulse

    International Nuclear Information System (INIS)

    Using a linearly polarized, phase-stabilized 3-fs driving pulse of 800 nm central wavelength shape-optimized on its ascending edge by its an amplitude-reduced pulse irradiating on a superposition state of the helium atom, we demonstrate theoretically the generation of a super strong isolated 176-attosecond pulse in the spectral region of 93–124 eV. The unusually high intensity of this attosecond pulse is marked by the Rabi-like oscillations emerging in the time-dependent populations of the ground state and the continuum during the occurrence of the electron recombination, which is for the first time observed in this work. (atomic and molecular physics)

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

    Science.gov (United States)

    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

  16. A Novel Approach to Photonic Generation and Modulation of Ultra-Wideband Pulses

    Science.gov (United States)

    Xiang, Peng; Guo, Hao; Chen, Dalei; Zhu, Huatao

    2016-01-01

    A novel approach to photonic generation of ultra-wideband (UWB) signals is proposed in this paper. The proposed signal generator is capable of generating UWB doublet pulses with flexible reconfigurability, and many different pulse modulation formats, including the commonly used pulse-position modulation (PPM) and bi-phase modulation (BPM) can be realized. Moreover, the photonic UWB pulse generator is capable of generating UWB signals with a tunable spectral notch-band, which is desirable to realize the interference avoidance between UWB and other narrow band systems, such as Wi-Fi. A mathematical model describing the proposed system is developed and the generation of UWB signals with different modulation formats is demonstrated via computer simulations.

  17. Diversified pulse generation from frequency shifted feedback Tm-doped fibre lasers

    Science.gov (United States)

    Chen, He; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing

    2016-01-01

    Pulsed fibre lasers operating in the eye-safe 2 μm spectral region have numerous potential applications in areas such as remote sensing, medicine, mid-infrared frequency conversion, and free-space communication. Here, for the first time, we demonstrate versatile 2 μm ps-ns pulses generation from Tm-based fibre lasers based on frequency shifted feedback and provide a comprehensive report of their special behaviors. The lasers are featured with elegant construction and the unparalleled capacity of generating versatile pulses. The self-starting mode-locking is initiated by an intra-cavity acousto-optical frequency shifter. Diversified mode-locked pulse dynamics were observed by altering the pump power, intra-cavity polarization state and cavity structure, including as short as 8 ps single pulse sequence, pulse bundle state and up to 12 nJ, 3 ns nanosecond rectangular pulse. A reflective nonlinear optical loop mirror was introduced to successfully shorten the pulses from 24 ps to 8 ps. Beside the mode-locking operation, flexible Q-switching and Q-switched mode-locking operation can also be readily achieved in the same cavity. Up to 78 μJ high energy nanosecond pulse can be generated in this regime. Several intriguing pulse dynamics are characterized and discussed. PMID:27193213

  18. Diversified pulse generation from frequency shifted feedback Tm-doped fibre lasers

    Science.gov (United States)

    Chen, He; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing

    2016-05-01

    Pulsed fibre lasers operating in the eye-safe 2 μm spectral region have numerous potential applications in areas such as remote sensing, medicine, mid-infrared frequency conversion, and free-space communication. Here, for the first time, we demonstrate versatile 2 μm ps-ns pulses generation from Tm-based fibre lasers based on frequency shifted feedback and provide a comprehensive report of their special behaviors. The lasers are featured with elegant construction and the unparalleled capacity of generating versatile pulses. The self-starting mode-locking is initiated by an intra-cavity acousto-optical frequency shifter. Diversified mode-locked pulse dynamics were observed by altering the pump power, intra-cavity polarization state and cavity structure, including as short as 8 ps single pulse sequence, pulse bundle state and up to 12 nJ, 3 ns nanosecond rectangular pulse. A reflective nonlinear optical loop mirror was introduced to successfully shorten the pulses from 24 ps to 8 ps. Beside the mode-locking operation, flexible Q-switching and Q-switched mode-locking operation can also be readily achieved in the same cavity. Up to 78 μJ high energy nanosecond pulse can be generated in this regime. Several intriguing pulse dynamics are characterized and discussed.

  19. Spatial shaping of intense femtosecond beams for the generation of high-energy attosecond pulses

    Science.gov (United States)

    Constant, E.; Dubrouil, A.; Hort, O.; Petit, S.; Descamps, D.; Mével, E.

    2012-04-01

    We generate high-order harmonics with a spatially shaped TW laser beam. We present and analyse in detail a new approach for shaping an intense laser field to a flat-top intensity profile near focus. We show that this approach is well adapted for high harmonic generation with high-energy fundamental pulses and highlight the possibilities for generating high-energy attosecond pulses.

  20. Spatial shaping of intense femtosecond beams for the generation of high-energy attosecond pulses

    International Nuclear Information System (INIS)

    We generate high-order harmonics with a spatially shaped TW laser beam. We present and analyse in detail a new approach for shaping an intense laser field to a flat-top intensity profile near focus. We show that this approach is well adapted for high harmonic generation with high-energy fundamental pulses and highlight the possibilities for generating high-energy attosecond pulses. (paper)

  1. A fast rise time high voltage pulse generator for bounded-wave EMP simulator

    International Nuclear Information System (INIS)

    A high voltage pulse generator with fast rise time is developed. The output wave of this generator is presented. The electromagnetic environment with 1.2 ns or 2.8 ns rise time and 50 ns pulse width can be produced when this generator is connected to bounded-wave EMP simulator which is used to investigate the EMP coupling effects of electrical equipment. (authors)

  2. On the Generation of Intense Isolated Attosecond Pulses by Many-Cycle Laser Fields

    Science.gov (United States)

    Tzallas, Paris; Skantzakis, Emmanouil; Kruse, Jann E.; Charalambidis, Dimitrios

    Real-time observation of ultrafast dynamics in all states of matter requires temporal resolution on the atomic unit of time (24.189 asec) (1 asec = 1{0}^{-18} s). Tools for tracking such ultrafast dynamics are ultrashort light pulses. During the last decade, continuous efforts in ultrashort pulse engineering led to the development of light pulses width duration close to the atomic unit of time. Attosecond (asec) pulses have been synthesized by broadband coherent extreme ultraviolet (XUV) radiation generated by the interaction of gases or solids with an intense IR fs pulse. Asec pulse trains can be generated when the medium interacts with many-cycle driving IR fs laser fields. In this case, a broadband XUV frequency comb is emitted from the medium. The Fourier synthesis of a part of the comb results in an asec pulse train. Isolated asec pulses are generated when the medium is forced to emit XUV radiation only during few cycles of the driving laser field. This leads to the emission of a broadband quasicontinuum XUV radiation. The Fourier synthesis of the continuum part of the spectrum results in an isolated asec pulse. For the realization of studies of ultrafast dynamics, intense asec pulses are preferable. If the pulses are intense enough to induce a nonlinear process in a target system, they can be used for ultrafast dynamic studies in an XUV pump-probe configuration. Although trains of intense asec pulses are commonly produced nowadays, the generation of intense isolated asec pulses remains a challenge. Here, we review a recently developed approach for the generation of intense asec pulses using high-peak-power many-cycle laser fields. The approach is based on controlling, with asec precession, the response of the atomic dipole to an external many-cycle driving field in such a way as to emit an isolated asec XUV burst. This approach has been implemented by using the inteferometric polarization gating (IPG) technique. The bandwidth of the generated XUV radiation is

  3. Quantum path control and isolated attosecond pulse generation in the combination of near-infrared and terahertz pulses

    Science.gov (United States)

    Zhong, Hui-Ying; Guo, Jing; Zhang, Hong-Dan; Du, Hui; Liu, Xue-Shen

    2015-07-01

    We present an efficient and realizable scheme for the generation of an ultrashort single attosecond (as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz (THz) field. The high-order harmonic generation (HHG) can be obtained by solving the time-dependent Schrödinger equation accurately and efficiently with time-dependent generalized pseudo-spectral (TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time-frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174108, 11104108, and 11271158).

  4. Generation of an isolated sub-40-as pulse using two-color laser pulses: Combined chirp effects

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 (China); Chu, Tianshu [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao, 266071 (China)

    2011-11-15

    In this paper, we theoretically discuss the combined chirp effects on the isolated attosecond generation when a model Ar is exposed to an intense 5-fs, 800-nm fundamental chirped pulse combined with a weak 10-fs, 1200-nm controlling chirped pulse. It shows that for the case of the chirp parameters {beta}{sub 1} = 6.1 (corresponding to the 800-nm field) and {beta}{sub 2} = 4.0 (corresponding to the 1200-nm field), both the harmonic cutoff energy and the supercontinuum can be remarkably extended resulting in a 663-eV bandwidth. Moreover, due to the introduction of the chirps, the short quantum path is selected to contribute to the harmonic spectrum. Finally, by superposing a properly selected harmonic spectrum in the supercontinuum region, an isolated pulse as short as 31 as (5 as) is generated without (with) phase compensation.

  5. Effects of Laser Intensities and Target Shapes on Attosecond Pulse Generation from Irradiated Solid Surfaces

    Science.gov (United States)

    Zheng, Jun; Sheng, Zheng-Ming; Zhang, Jie; Chen, Min; Ma, Yan-Yun

    2006-02-01

    Single attosecond pulses can be generated when an intense laser pulse focused in a volume of a few cubic wavelengths (λ3) is reflected from a solid plasma surface. With relativistic two-dimensional particle-in-cell simulations, we investigate the effects of the incident laser intensity and the target surface profiles on attosecond pulse generation. Usually the width of the reflected attosecond pulse decreases and its electromagnetic energy density increases with increasing laser intensity, while the energy conversion efficiency to the attoseond pulse decreases. By changing the target surface profile, such as using a convex surface or adding proper preplasma, one can further shorten the attosecond pulse duration and meanwhile increase its energy density.

  6. MOSFET-based high voltage double square-wave pulse generator with an inductive adder configuration

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China); Zhang, Qiaogen, E-mail: hvzhang@mail.xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China); Long, Jinghua [College of Physics, Shenzhen University, Shenzhen 518060 (China); Lei, Yunfei; Liu, Jinyuan [Institute of Optoelectronics, Shenzhen University, Shenzhen 518060 (China)

    2015-09-01

    This paper presents a fast MOSFET-based solid-state pulse generator for high voltage double square-wave pulses. The generator consists mainly of an inductive adder system stacked of 20 solid-state modules. Each of the modules has 18 power MOSFETs in parallel, which are triggered by individual drive circuits; these drive circuits themselves are synchronously triggered by a signal from avalanche transistors. Our experiments demonstrate that the output pulses with amplitude of 8.1 kV and peak current of about 405 A are available at a load impedance of 20 Ω. The pulse has a double square-wave form with a rise and fall time of 40 ns and 26 ns, respectively and bottom flatness better than 12%. The interval time of the double square-wave pulses can be adjustable by varying the interval time of the trigger pulses.

  7. Generation of intense, carrier-envelope phase-locked few-cycle laser pulses through filamentation

    Science.gov (United States)

    Hauri, C. P.; Kornelis, W.; Helbing, F. W.; Heinrich, A.; Couairon, A.; Mysyrowicz, A.; Biegert, J.; Keller, U.

    2004-10-01

    Intense, well-controlled light pulses with only a few optical cycles start to play a crucial role in many fields of physics, such as attosecond science. We present an extremely simple and robust technique to generate such carrier-envelope offset (CEO) phase locked few-cycle pulses, relying on self-guiding of intense 43-fs, 0.84 mJ optical pulses during propagation in a transparent noble gas. We have demonstrated 5.7-fs, 0.38 mJ pulses with an excellent spatial beam profile and discuss the potential for much shorter pulses. Numerical simulations confirm that filamentation is the mechanism responsible for pulse shortening. The method is widely applicable and much less sensitive to experimental conditions such as beam alignment, input pulse duration or gas pressure as compared to gas-filled hollow fibers.

  8. An All Solid-State Pulsed Power Generator for Plasma Immersion Ion Implantation (PⅢ)

    Institute of Scientific and Technical Information of China (English)

    LIU Kefu; QIU Jian; WU Yifan

    2009-01-01

    An all solid-state pulsed power generator for plasma immersion ion implantation (PⅢ) is described. The pulsed power system is based on a Marx circuit configuration and semi-conductor switches, which have many advantages in adjustable repetition frequency, pulse width modulation and long serving life compared with the conventional circuit category, tube-based technologies such as gridded vacuum tubes, thyratrons, pulse forming networks and transformers.The operation of PⅢ with pulse repetition frequencies up to 500 Hz has been achieved at a pulse voltage amplitude from 2 kV to 60 kV, with an adjustable pulse duration from 1 μs to 100 μs.The proposed system and its performance, as used to drive a plasma ion implantation chamber,axe described in detail on the basis of the experimental results.

  9. Experimental observation of fundamental and harmonic self pulse generation of single high-order Stokes in Brillouin Erbium fiber laser

    Science.gov (United States)

    Wang, Xiaorui; Yang, Yanfu; Liu, Meng; Yao, Yong

    2016-07-01

    Fundamental and harmonic self-pulse generation was experimentally observed on both first order and higher order Stokes components. The generated pulses with the same order harmonic repetition rate are obtained on multiple Stokes components simultaneously. The pulse generation on first order Stokes component can be attributed to periodic pump depletion in Brillouin gain medium. The pulse generation of high order Stokes component can be considered as pulse oscillation pumped by the former order Stokes. With high Erbium pump power, by setting the proper attenuation between Brillouin medium and Faraday rotation mirror, the harmonic pulse generations up to fifth order have been achieved.

  10. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    OpenAIRE

    Jianqiang Zhu; Xinglong Xie; Meizhi Sun; Qunyu Bi; Jun Kang

    2012-01-01

    We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the K...

  11. Transient Generation of Short Pulses in the APS Storage Ring

    CERN Document Server

    Decker, Glenn

    2005-01-01

    A method for obtaining very short pulses using modulation of the accelerating voltage gradient is described and simulation results given. The idea is to operate the two rf stations with a phase separation adjusted so that the synchronous particle resides on the crest of one of the sources. Phase modulation of the on-crest system at twice the synchrotron frequency induces a longitudinal bunch shape oscillation with significantly reduced bunch length occurring twice each synchrotron period. Pulsed and steady-state operation will be discussed using various accelerator parameters.

  12. A power-efficient ultra-wideband pulse generator based on multiple PM-IM conversions

    OpenAIRE

    Lui, KS; Wong, KKY; Zhou, E.; Xu, X.

    2010-01-01

    A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant w...

  13. Principles and techniques of radiation hardening. Volume 3. Electromagnetic pulse (EMP) and system generated EMP

    International Nuclear Information System (INIS)

    The three-volume book is intended to serve as a review of the effects of thermonuclear explosion induced radiation (x-rays, gamma rays, and beta particles) and the resulting electromagnetic pulse (EMP). Volume 3 deals with the following topics: selected fundamentals of electromagnetic theory; EMP induced currents on antennas and cables; the EMP response of electronics; EMP hardening; EMP testing; injection currents; internal electromagnetic pulse (IEMP); replacement currents; and system generated electromagnetic pulse (SGEMP) hardening

  14. Towards highest spectral efficiency: Optical sinc-shaped Nyquist pulses generation from rectangular frequency comb

    OpenAIRE

    Brès, Camille Sophie; Soto, Marcelo A.; Alem, Mehdi; Shoaie, Mohammad Amin; Vedadi, Armand; Schneider, Thomas; Thévenaz, Luc

    2014-01-01

    In this paper, we review a method to produce optical sinc-shaped Nyquist pulses with unprecedented quality. The method is based on the synthesis of a rectangular shaped and phase-locked frequency comb from a combination of intensity modulators. The result is a highly flexible pulse generator that can easily be integrated in already installed communication systems. All-optical pulse shaping methods for highest spectral efficiencies are attractive since high-bitrate spectrally efficient channel...

  15. Micro-joule sub-10-fs VUV pulse generation by MW pump pulse using highly efficient chirped-four-wave mixing in hollow-core photonic crystal fibers

    OpenAIRE

    Im, Song-Jin

    2013-01-01

    We theoretically study chirped four-wave mixing for VUV pulse generation in hollow-core photonic crystal fibers. We predict the generation of sub-10-fs VUV pulses with energy of up to hundreds of microjoule by broad-band chirped idler pulses at 830 nm and MW pump pulses with narrow-band at 277 nm. MW pump could be desirable to reduce the complexity of the laser system or use a high repetition rate-laser system. The energy conversion efficiency from pump pulse to VUV pulse reaches to 30%. This...

  16. Effects of pressure and gas-jet thickness on the generation of attosecond pulse

    International Nuclear Information System (INIS)

    We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fundamental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure. (atomic and molecular physics)

  17. Bipolar Disorder

    Science.gov (United States)

    ... lows). These aren't the normal periods of happiness and sadness that everyone experiences from time to ... with long-lasting medical conditions (such as asthma , diabetes , or epilepsy ), teens with bipolar disorder need to ...

  18. Modelocking and Femtosecond Pulse Generation in Chip-Based Frequency Combs

    CERN Document Server

    Saha, Kasturi; Shim, Bonggu; Levy, Jacob S; Foster, Mark A; Salem, Reza; Johnson, Adrea R; Lamont, Michael R E; Lipson, Michal; Gaeta, Alexander L

    2012-01-01

    Development of ultrashort pulse sources has had an immense impact on condensed-matter physics, biomedical imaging, high-field physics, frequency metrology, telecommunications, nonlinear optics, and molecular spectroscopy. Although numerous advancements of such sources have been made, it remains a challenge to create a highly compact, robust platform capable of producing femtosecond pulses over a wide range of wavelengths, durations, and repetition rates. Recent observations of frequency comb generation via cascaded parametric oscillation in microresonators11 suggest a path for achieving this goal. Here we investigate the temporal and spectral properties of parametric combs generated in silicon-nitride microresonators and observe a transition to passive modelocking of the comb consistent with soliton-pulse formation, resulting in the generation of 160-fs pulses at a 99-GHz repetition rate. This platform offers the prospect of producing pulses from 10 fs to a few ps at repetition rates from 10 GHz to > 1 THz an...

  19. A Generalized Estimate of the SLR B Polynomial Ripples for RF Pulse Generation.

    Science.gov (United States)

    Raddi; Klose

    1998-06-01

    The nonlinearity of the parameter relations for the Shinnar-Le Roux RF pulse design algorithm has induced to performa classification based on the features of the slice profile dueto the RF pulse. In the present paper a generalization ofthe relation between the ripple amplitudes of the SLR B polynomial and those of the slice profile is given. It allows generation of RF pulses with better slice profiles and slightly reduced energy, avoiding any a priori classification. The effect of our estimation has been shown by generating several pulses by generalized estimation of B polynomial ripples. In addition, their behavior has been compared to that of analogous pulses generated by means of the classification just mentioned. Copyright 1998 Academic Press. PMID:9632551

  20. Ultra-intense single attosecond pulse generated from circularly polarized laser interacting with overdense plasma

    Science.gov (United States)

    Ji, Liangliang; Shen, Baifei; Zhang, Xiaomei; Wen, Meng; Xia, Changquan; Wang, Wenpeng; Xu, Jiancai; Yu, Yahong; Yu, Mingyang; Xu, Zhizhan

    2011-08-01

    Few-cycle relativistic circularly polarized (CP) laser pulse reflected from overdense plasma is investigated by analysis and particle-in-cell simulations. It is found that through the laser-induced one-time drastic oscillation of the plasma boundary, an ultra-intense single attosecond light pulse can be generated naturally. An analytical model is proposed to describe the interaction and it agrees well with simulation results. They both indicate that peak intensity of the generated attosecond pulse is higher when the plasma density is closer to the relativistic transparency threshold and/or the pulse duration is closer to plasma oscillating period. Two dimensional simulation shows that a two-cycle 1021 W/cm2 CP laser can generate a single 230 attosecond 2 × 1021 W/cm2 pulse of light at a conversion efficiency greater than 10-2.

  1. Ultra-intense single attosecond pulse generated from circularly polarized laser interacting with overdense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ji Liangliang; Shen Baifei; Zhang Xiaomei; Wen Meng; Xia Changquan; Wang Wenpeng; Xu Jiancai; Yu Yahong; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P. O. Box 800-211, Shanghai 201800 (China); Yu Mingyang [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

    2011-08-15

    Few-cycle relativistic circularly polarized (CP) laser pulse reflected from overdense plasma is investigated by analysis and particle-in-cell simulations. It is found that through the laser-induced one-time drastic oscillation of the plasma boundary, an ultra-intense single attosecond light pulse can be generated naturally. An analytical model is proposed to describe the interaction and it agrees well with simulation results. They both indicate that peak intensity of the generated attosecond pulse is higher when the plasma density is closer to the relativistic transparency threshold and/or the pulse duration is closer to plasma oscillating period. Two dimensional simulation shows that a two-cycle 10{sup 21} W/cm{sup 2} CP laser can generate a single 230 attosecond 2 x 10{sup 21} W/cm{sup 2} pulse of light at a conversion efficiency greater than 10{sup -2}.

  2. Pulse Sequences for Efficient Multi-Cycle Terahertz Generation in Periodically Poled Lithium Niobate

    CERN Document Server

    Ravi, Koustuban; Kärtner, Franz X

    2016-01-01

    The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled periodically poled lithium niobate is proposed. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of Mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved. The proposed methods are shown to circumvent laser-induced damage at Joule-level pumping by 1$\\mu$m lasers to enable multi-cycle terahertz sources with pulse energies >> 10 milli-joules. Various pulse sequence formats are proposed and analyzed. Numerical calculations for periodically poled structures accounting for cascaded difference frequency generation, self-phase-modulation, cascaded second harmonic generation and laser induced damage are introduced. Unprecedented studies of the ph...

  3. Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

    Science.gov (United States)

    Hébert, H.; Vidal, F.; Martin, F.; Kieffer, J.-C.; Nadeau, A.; Johnston, T. W.; Blouin, A.; Moreau, A.; Monchalin, J.-P.

    2005-08-01

    We have investigated high-frequency ultrasound generated by single laser pulses in thin (50μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80fs and 270ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7J/cm2. For fluences greater than the ablation threshold (0.25 and 0.63J/cm2 for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed.

  4. Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

    International Nuclear Information System (INIS)

    We have investigated high-frequency ultrasound generated by single laser pulses in thin (50 μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80 fs and 270 ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7 J/cm2. For fluences greater than the ablation threshold (0.25 and 0.63 J/cm2 for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed

  5. Bipolar disorder

    OpenAIRE

    Goodwin, Frederick K; Ghaemi, S Nassir

    1999-01-01

    Bipolar disorder's unique combination of three characteristics - clear genetic diathesis, distinctive clinical features, early availability of an effective treatment (lithium) - explains its special place in the history of psychiatry and its contribution to the current explosive growth of neuroscience. This article looks at the state of the art in bipolar disorder from the vantage point of: (i) genetics (possible linkages on chromosomes 18 and 21q, polygenic hypothesis, research into genetic ...

  6. Trains of electron pulses generation using multi-stage cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kamada, Masaki; Mori, Michiya; Sugawara, Kazuyoshi; Yamada, Yoko; Kurihara, Kazuteru; Shirasaka, Haruki; Nishiguchi, Takashi; Ando, Ritoku; Kamada, Keiichi [Kanazawa Univ., Faculty of Science, Dept. of Physics, Kanazawa, Ishikawa (Japan)

    2002-06-01

    Automodulation of an intense relativistic electron beam was reexamined experimentally to obtain trains of subnanosecond electron bunches. Sufficient beam modulation with frequency larger than 1 GHz was expected for the trains of subnanosecond bunches. It was obtained when a short pulse electron beam with energy of 550 keV, current of 4 kA, pulse duration of 12 ns and current rise time of 2ns was injected to a series of four coaxial cavities with the length of 75 mm. However, only a poor modulation was observed when a long pulse electron beam of 700 keV, 4 kA, 175 ns with current rise time of 20 ns was injected to the same cavities. Transmission line theory as well PIC code simulation suggested that the round trip time for the electromagnetic wave in the cavity must be longer than the rise time of the beam current to obtain the high level current modulation. Therefore, we studied experimentally how the ratio between the beam current rise time and the length of the cavity affects on the level of current modulation. Single cavity experiments were carried out with the short pulse beam. Single cavity with the length of 75, 150 or 300 mm was utilized. The round trip times for 75 and 150 mm cavities are shorter than the current rise time of 2 ns. The experiments with a 75 or 150 mm cavity resulted in suppression of the modulation amplitude. In the case of a 300 mm cavity, the high level modulation was obtained. The simulation results showed good agreements with the experimental results. We employed a series of cavities with decreasing lengths to improve the current rise time. For the short pulse beam, the high level current 1 GHz modulation was obtained when two 75 mm cavities were set at the downstream side of cavities with lengths of 300 mm and 150 mm. (author)

  7. Trains of electron pulses generation using multi-stage cavities

    International Nuclear Information System (INIS)

    Automodulation of an intense relativistic electron beam was reexamined experimentally to obtain trains of subnanosecond electron bunches. Sufficient beam modulation with frequency larger than 1 GHz was expected for the trains of subnanosecond bunches. It was obtained when a short pulse electron beam with energy of 550 keV, current of 4 kA, pulse duration of 12 ns and current rise time of 2ns was injected to a series of four coaxial cavities with the length of 75 mm. However, only a poor modulation was observed when a long pulse electron beam of 700 keV, 4 kA, 175 ns with current rise time of 20 ns was injected to the same cavities. Transmission line theory as well PIC code simulation suggested that the round trip time for the electromagnetic wave in the cavity must be longer than the rise time of the beam current to obtain the high level current modulation. Therefore, we studied experimentally how the ratio between the beam current rise time and the length of the cavity affects on the level of current modulation. Single cavity experiments were carried out with the short pulse beam. Single cavity with the length of 75, 150 or 300 mm was utilized. The round trip times for 75 and 150 mm cavities are shorter than the current rise time of 2 ns. The experiments with a 75 or 150 mm cavity resulted in suppression of the modulation amplitude. In the case of a 300 mm cavity, the high level modulation was obtained. The simulation results showed good agreements with the experimental results. We employed a series of cavities with decreasing lengths to improve the current rise time. For the short pulse beam, the high level current 1 GHz modulation was obtained when two 75 mm cavities were set at the downstream side of cavities with lengths of 300 mm and 150 mm. (author)

  8. Sub-10-fs pulse generation directly from a KLM Ti:sapphire laser

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By reducing the effects of frequency dependent mode size and intracavity gain saturation of a KLM Ti: sapphire laser, the pulse bandwidth broadening is enhanced significantly. 8.5 fs pulses with the bandwidth of 92 nm at wavelength of 710 nm have been generated directly from this laser and measured with an extracavity group velocity dispersion compensation system.

  9. Relation of hardness and oxygen flow of Al{sub 2}O{sub 3} coatings deposited by reactive bipolar pulsed magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Bobzin, Kirsten [Chair of Surface Engineering, RWTH Aachen University, Augustinerbach 4-22 52062 Aachen (Germany); Lugscheider, Erich [Chair of Surface Engineering, RWTH Aachen University, Augustinerbach 4-22 52062 Aachen (Germany); Maes, Michel [Chair of Surface Engineering, RWTH Aachen University, Augustinerbach 4-22 52062 Aachen (Germany); Pinero, Carmen [Chair of Surface Engineering, RWTH Aachen University, Augustinerbach 4-22 52062 Aachen (Germany)]. E-mail: pinero@iot.rwth-aachen.de

    2006-01-03

    Aluminum oxide thin films are widely used because of their excellent properties, especially in terms of chemical, thermal, abrasive and corrosive resistance. But many properties of alumina films are significantly deposition parameters dependent. Since different applications and environments demand different kind of properties in thin films, it is important to determine the influence of the deposition parameters on the alumina film properties. In this work, different alumina structures were deposited by means of reactive, bipolar, pulsed, magnetron sputtering. In order to find the appropriate parameter combination to synthesize crystalline alumina (for this investigation {gamma}-Al{sub 2}O{sub 3}), substrate temperature, power density at the target and oxygen flow were varied. The {gamma}-Al{sub 2}O{sub 3} films were synthesized at 650 deg. C, 0.2 Pa, 800 W, 1:4 duty cycle, 19.2 kHz, and 11-12% oxygen flow. The structure and morphology of the deposited Al{sub 2}O{sub 3} films were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Since the coating hardness is a decisive factor for many applications, the aim of this paper was to investigate the influence of the oxygen flow on the alumina hardness. It was observed that the hardness and the structure of the PVD-deposited alumina coatings are significantly oxygen flow dependent. The hardness of the alumina films was determined by nanoindentation. It varied between 1 and 25.8 GPa. The hardness increased by increasing oxygen flow until the target reached the poisoned state, where a hardness reduction was clearly observed.

  10. Isolated attosecond pulse generation with the chirped two-color laser field

    Science.gov (United States)

    Tai, Huiqin; Li, Fang; Wang, Zhe

    2016-07-01

    We propose a scheme to generate isolated attosecond pulse using a linearly chirped two-color laser field, which includes a fundamental laser field and a weak infrared control laser field in the multicycle regime. The fundamental laser field consists of one linearly up-chirped and one linearly down-chirped pulses. The control pulse is chirped free. We compare the attosecond pulse generated in the chirped two-color field and the chirp-free field. It is found that an IAP can be generated even without carrier envelop phase stabilization in the chirped two-color laser field with a duration of 40 fs. We also discuss the influence of the relative intensity, relative phase, time delay, and chirping parameters on the generation of IAPs.

  11. Generation of elliptically polarized nitrogen-ion laser fields using two-color femtosecond laser pulses

    CERN Document Server

    Li, Ziting; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2015-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized molecular nitrogen-ion laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the molecular nitrogen-ion laser.

  12. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    International Nuclear Information System (INIS)

    Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system

  13. Intense ultrashort pulse generation using the JAERI far-infrared free electron laser

    International Nuclear Information System (INIS)

    An intense ultrashort optical pulse has been quasi-continuously generated using a superconducting RF linac-based free-electron laser at a wavelength of 22.5 μm. The pulse shape and width are measured by second-order optical autocorrelation with a birefringent Te crystal. At synchronism of the optical resonator, the pulse shape is a smooth single pulse with an FWHM width of 255 fs and energy of 74 μJ. A train of subpulses is developed by increasing the desynchronism of the optical resonator. The measured results are in good agreement with numerical simulation

  14. Generation of high-power ultrawideband electromagnetic pulses in a system with a coaxial tem horn

    Science.gov (United States)

    Gubanov, V. P.; Korovin, S. D.; Pegel', I. V.; Rostov, V. V.; Stepchenko, A. S.; Tarakanov, V. P.

    1996-12-01

    A coaxial TEM horn was designed on the basis of results from nonstationary computer modeling using code KARAT. With its high dielectric strength, this antenna is capable of radiating high-power ultrawideband nanosecond pulses. The pulse source used was a compact generator built around a coaxial forming line with a built-in Tesla transformer, which shapes pulses up to 1 GW high at repetition frequencies up to 1 kHz. The amplitude of the pulses on a matched load was 20 kV at a duration of 4 nsec. Returns of ultrawideband signals from objects with simple geometric shapes were studied in laboratory experiments using this radiator.

  15. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    Energy Technology Data Exchange (ETDEWEB)

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C. [Departament de Física i Enginyeria Nuclear, Universitat Politècnica Catalunya, Terrassa 08222 (Spain); Sola, I. [Grupo de Investigación en Óptica Extrema (GIOE), Departamento de Física Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Krolikowski, W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Science Program, Texas A and M University at Qatar, Doha (Qatar); Sheng, Y. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2015-06-01

    Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

  16. Generation of proton bunches by ultra-short laser pulses with high contrast

    International Nuclear Information System (INIS)

    Laser accelerated ion or proton bunches offer advantages compared to those generated by conventional accelerators, like better emittance and shorter pulse duration. We present our results on the acceleration of proton/ ion bunches created by ultra-short laser pulses of ultra-thin (d 12. It is shown how the features of the proton/ ion bunches depend on the laser pulse parameters, like intensity and contrast of the laser pulse. The results are discussed on the base of analytical calculation and PIC simulations.

  17. Observation of self-pulsing in singly resonant optical second-harmonic generation with competing nonlinearities

    DEFF Research Database (Denmark)

    Bache, Morten; Lodahl, Peter; Mamaev, Alexander V.;

    2002-01-01

    We predict and experimentally observe temporal self-pulsing in singly resonant intracavity second-harmonic generation under conditions of simultaneous parametric oscillation. The threshold for self-pulsing as a function of cavity tuning and phase mismatch are found from analysis of a three-compon......-component mean-field model. Analytical mean-field calculations of the self-pulsing frequency as well as numerical simulations including the effects of a time-dependent pump pulse agree with the experimentally observed frequencies....

  18. Intense Isolated Ultrashort Attosecond Pulse Generation in a Multi-Cycle Three-Colour Laser Field

    Science.gov (United States)

    Zhang, Gang-Tai

    2014-12-01

    An efficient method for generating an intense isolated ultrashort attosecond pulse is presented theoretically. By adding a 267 nm controlling pulse to a multi-cycle two-colour field, not only the spectral cutoff and the yields of the harmonic spectrum are evidently enhanced, but also the selection of the single quantum path is realised. Then a high-efficiency supercontinuum with a 504 eV bandwidth and smooth structure is obtained, which enables the production of an intense isolated 30 as pulse. In addition, the influences of the laser parameters on the supercontinuum and isolated attosecond pulse are investigated.

  19. Mode-locked picosecond pulse generation from an octave-spanning supercontinuum

    CERN Document Server

    Kielpinski, D; Canning, J; Stevenson, M; Westbrook, P S; Feder, K S

    2011-01-01

    We generate mode-locked picosecond pulses near 1110 nm by spectrally slicing and reamplifying an octave-spanning supercontinuum source pumped at 1550 nm. The 1110 nm pulses are near transform-limited, with 1.7 ps duration over their 1.2 nm bandwidth, and exhibit high interpulse coherence. Both the supercontinuum source and the pulse synthesis system are implemented completely in fiber. The versatile source construction suggests that pulse synthesis from sliced supercontinuum may be a useful technique across the 1000 - 2000 nm wavelength range.

  20. Multiple quantum wells for passive ultra short laser pulse generation

    CERN Document Server

    Quintero-Torres, R; Rodriguez-Rodriguez, E; Stintz, Andreas; Diels, Jean-Claude

    2007-01-01

    Solid state lasers are demanding independent control in the gain media and cavity loss to achieve ultra short laser pulses using passive mode-locking. Recently, laser mode-locking is achieved with a MBE structure with multiple quantum wells, designed to achieve two functions; Bragg mirror and changes in absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser proved to be effective to produce femtosecond pulses. The use of saturable absorbers thus far is a trial and error procedure that is changing due to the correlation with more predictive procedures.

  1. Shaping SHF train of optical picosecond pulses for generating a photoemission in SHF guns

    International Nuclear Information System (INIS)

    The paper analyses a technique of generating optical picosecond pulses (OPP) through laser beam deflection. The OPP generator consists of a laser, deflection system, optical system and amplifier-converter. The technique of OPP generation through laser beam deflection can be successfully used for triggering photoemission in SHF beams. 8 refs., 2 figs

  2. Fuel injection strategy for a next generation pulse detonation engine

    OpenAIRE

    Robbins, Tad J.

    2006-01-01

    The Pulse Detonation Engine offers the Department of Defense a new low cost, light weight, and efficient solution to supersonic flight on many of its small airborne platforms. In the past, both liquid fuel and gaseous fuel designs have been partially developed and tested. Several aspects of these configurations have led to the need for the development of a new design, in particular the reduction of total pressure losses, and the removal of auxiliary oxygen system previously required to ini...

  3. Generation of Ultra-high Intensity Laser Pulses

    International Nuclear Information System (INIS)

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 1025 W/cm2 can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers

  4. Generation of Ultra-high Intensity Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    N.J. Fisch; V.M. Malkin

    2003-06-10

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 10{sup 25} W/cm{sup 2} can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers.

  5. Magnetic field generation by short ultraintense laser pulse in underdense plasmas

    International Nuclear Information System (INIS)

    The theory of magnetic field generation due to the interaction of short relativistic laser pulses with underdense plasmas has been developed. The magnetic field is generated due to the inverse Faraday effect occurring with a circularly polarized laser pulse. The spatial distribution of the magnetic field is investigated. It is shown that the magnetic field magnitude depends on the relationship between the laser beam radius and the plasma skin-depth. (Author)

  6. EEHG-assisted FEL schemes for attosecond X-ray pulses generation

    Energy Technology Data Exchange (ETDEWEB)

    Yan Jun [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Deng Haixiao, E-mail: denghaixiao@sinap.ac.c [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang Dong; Dai Zhimin [Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Shanghai 201800 (China)

    2010-09-21

    In this paper, the schemes of echo-enabled harmonic generation (EEHG) assisted free electron laser (FEL) for generating attosecond soft X-ray pulses are further investigated. We present brief analytical models and three-dimensional simulations for comparison studies of such schemes reported earlier. Moreover, on the basis of these analyses, a more compact and robust EEHG-assisted FEL scheme is proposed for pump-probe experiments using two-color attosecond X-ray pulses.

  7. A Study of a Versatile Low Power CMOS Pulse Generator for Ultra Wideband Radios

    OpenAIRE

    Marsden, Kevin Matthew

    2004-01-01

    Ultra-Wideband (UWB) technologies are at the forefront of wireless communications, offering the possibility to provide extremely high data rate wireless solutions. In addition to high data rate applications, UWB technologies also offer an extremely low cost alternative for many low data rate systems. In this thesis, we describe the design of a CMOS pulse generator for impulse based UWB systems. The structure of our pulse generator is based on the topology of a single tap CMOS power amplifi...

  8. High power pulse generators of the transformer type (the Tomsk High-Current Electronics Institute)

    International Nuclear Information System (INIS)

    Consideration is given to the problems of creation and operation of high-power generators of the transformer type, developed in the Tomsk High-Current Electronics Institute. The power of the largest generators is equal to 2.5 x 1012 W (pulse). Small dimensions, external location of main units, which require routine repair, absence of large volumes of transformer oil make pulse transformers competitive with PVGs. 10 refs., 5 figs

  9. On-Chip Picosecond Pulse Detection and Generation Using Graphene Photoconductive Switches

    OpenAIRE

    Hunter, Nicholas; Mayorov, Alexander S.; Christopher D. Wood; Russell, Christopher; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles; Cunningham, John E.

    2015-01-01

    We report on the use of graphene for room temperature on-chip detection and generation of pulsed terahertz (THz) frequency radiation, exploiting the fast carrier dynamics of light-generated hot carriers, and compare our results with conventional low-temperature-grown gallium arsenide (LT-GaAs) photoconductive (PC) switches. Coupling of picosecond-duration pulses from a biased graphene PC switch into Goubau line waveguides is also demonstrated. A Drude transport model based on the transient ph...

  10. Controlling high-order harmonic generation from the stretched diatom molecules subject to an attosecond pulse

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gao; Lin, Jing-Quan [Changchun University of Science and Technology, Changchun (China); Yang, Yu-Jun [Jilin University, Changchun (China)

    2011-04-15

    We investigate the influence of an attosecond pulse on the high-order harmonic spectra generated from a stretched diatom molecule subjected to a mid-infrared femtosecond pulse by numerically solving the one-dimensional time-dependent Schroedinger equation. We show that, by adding a 750 attosecond pulse with wavelength of 76 nm to a five-cycle mid-infrared femtosecond pulses with wavelength of 1600 nm, the harmonic efficiencies are effectively enhanced compared with the case of only one mid-infrared femtosecond pulse; meanwhile, the enhanced harmonic efficiencies exhibit an obvious feature of a relative phase dependence between the two pulses. The harmonic efficiencies are enhanced overall by 2 - 3 orders of magnitude when the relative phase of the two pulses is set as {phi} = 2T + 0.3T (T is the oscillation period of the mid-infrared pulse), and the harmonic efficiencies near the second cutoff position of I{sub p} + 5.6U{sub p} are enhanced over 4 orders of magnitude when the relative phase is set as {phi} = 2T. This result indicates that frequency-selected enhancement can be realized by adjusting the relative phase of the two pulses. The reason for relative-phase-dependent structure of the spectra is discussed in detail by using the four main mechanisms of harmonic generation in molecules and the property of atomic ionization.

  11. Pulse-periodic generation of supershort avalanche electron beams and X-ray emission

    Science.gov (United States)

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

    2014-05-01

    Pulse-periodic generation of supershort avalanche electron beams (SAEBs) and X-ray emission in nitrogen, as well as the transition from a single-pulse mode to a pulse-periodic mode with a high repetition frequency, was studied experimentally. It is shown that, in the pulse-periodic mode, the full width at halfmaximum of the SAEB is larger and the decrease rate of the gap voltage is lower than those in the single-pulse mode. It is found that, when the front duration of the voltage pulse at a nitrogen pressure of 90 Torr decreases from 2.5 to 0.3 ns, the X-ray exposure dose in the pulse-periodic mode increases by more than one order of magnitude and the number of SAEB electrons also increases. It is shown that, in the pulse-periodic mode of a diffuse discharge, gas heating in the discharge gap results in a severalfold increase in the SAEB amplitude (the number of electrons in the beam). At a generator voltage of 25 kV, nitrogen pressure of 90 Torr, and pulse repetition frequency of 3.5 kHz, a runaway electron beam was detected behind the anode foil.

  12. Single attosecond pulse generation by nonlinear Thomson scattering in a tightly focused intense laser beam

    International Nuclear Information System (INIS)

    The relativistic nonlinear Thomson scattering of a tightly focused intense laser pulse by an electron is investigated, and the temporal and spectral characters of the radiation are discussed. In a tightly focused laser pulse with an intensity of approximately 1020 W/cm2 and a pulse duration of 20 fs, the electron is scattered away from the focus quickly by the ponderomotive force and therefore the radiation emitted at the focus is much higher than that at other regions. As a result, a single ultrashort pulse of 3.8 as is generated and its corresponding spectrum is broadened to 200 orders of the frequency of the driving laser. With increasing the laser intensity, the signal-to-noise of the radiated pulse increases, and the pulse duration decreases. Moreover, the phase behavior of the spectral components and the dependence of the radiated power on the laser intensity are discussed

  13. A megawatt solid-state modulator for high repetition rate pulse generation

    Science.gov (United States)

    Wang, Y.; Pribyl, P.; Gekelman, W.

    2016-02-01

    A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented.

  14. A low-cost programmable pulse generator for physiology and behavior

    Directory of Open Access Journals (Sweden)

    Joshua I Sanders

    2014-12-01

    Full Text Available Precisely timed experimental manipulations of the brain and its sensory environment are often employed to reveal principles of brain function. While complex and reliable pulse trains for temporal stimulus control can be generated with commercial instruments, contemporary options remain expensive and proprietary. We have developed Pulse Pal, an open source device that allows users to create and trigger software-defined trains of voltage pulses with high temporal precision. Here we describe Pulse Pal’s circuitry and firmware, and characterize its precision and reliability. In addition, we supply online documentation with instructions for assembling, testing and installing Pulse Pal. While the device can be operated as a stand-alone instrument, we also provide application programming interfaces in several programming languages. As an inexpensive, flexible and open solution for temporal control, we anticipate that Pulse Pal will be used to address a wide range of instrumentation timing challenges in neuroscience research.

  15. Enhancement of plasma wakefield generation and self-compression of femtosecond laser pulses by ionization gradients

    International Nuclear Information System (INIS)

    As lasers become progressively higher in power, optical damage thresholds will become a limiting factor. Using the non-linear optics of plasma may be a way to circumvent these limits. In this paper, we report on simulations showing an enhancement to plasma wakefield self-compression of femtosecond laser pulses due to an ionization gradient at the leading edge of the pulse. By operating in a regime where wakefield generation is driven by moderately relativistic (∼1018 W cm−2) laser pulses and proper choice of gas species, the ionization front of the pulse can lead to a frequency shift that enhances the ponderomotive force and therefore both the wakefield generation and subsequent pulse compression. (paper)

  16. Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

    International Nuclear Information System (INIS)

    Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR’s intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry

  17. Effect of nonlinear chirped Gaussian laser pulse on plasma wake field generation

    Directory of Open Access Journals (Sweden)

    Saeedeh Afhami

    2014-08-01

    Full Text Available An ultrashort laser pulse propagating in plasma can excite a nonlinear plasma wake field which can accelerate charged particles up to GeV energies within a compact space compared to the conventional accelerator devices. In this paper, the effect of different kinds of nonlinear chirped Gaussian laser pulse on wake field generation is investigated. The numerical analysis of our results depicts that the excitation of plasma wave with large and highly amplitude can be accomplished by nonlinear chirped pulses. The maximum amplitude of excited wake in nonlinear chirped pulse is approximately three times more than that of linear chirped pulse. In order to achieve high wake field generation, chirp parameters and functions should be set to optimal values.

  18. Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

    Directory of Open Access Journals (Sweden)

    Chris Chang

    2016-01-01

    Full Text Available Recently a silicon controlled rectifier (SCR-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR’s intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.

  19. Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

    Science.gov (United States)

    Chang, Chris; Alves, Fabio; Karunasiri, Gamani

    2016-01-01

    Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR's intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.

  20. Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chris, E-mail: chrischang81@gmail.com; Karunasiri, Gamani, E-mail: karunasiri@nps.edu [Department of Physics, Naval Postgraduate School, Monterey, CA 93943 (United States); Alves, Fabio, E-mail: falves@alionscience.com [Alion Science and Technology at NPS, Monterey, CA 93943 (United States)

    2016-01-15

    Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR’s intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.

  1. 50 mm Diameter digital DC/pulse neutron generator for subcritical reactor test

    International Nuclear Information System (INIS)

    A 50 mm diameter digital DC/pulse neutron generator was developed with 25 mm ceramic drive-in target neutron tube. It was applied in the subcritical reactor test of China Institute of Atomic Energy (CIAE). The generator can produce neutron in three modes: DC, pulse and multiple pulse. The maximum neutron yield of the generator is 1 × 108 n/s, while the maximum pulse frequency is 10 kHz, and the minimum pulse width is 10 μs. As a remote controlled generator, it is small in volume, easy to be connected and controlled. The tested results indicate that penning ion source has the feature of delay time in glow discharge, and it is easier for glow discharge to happen when switching the DC voltage of penning ion source into pulse. According to these two characteristics, the generator has been modified. This improved generator can be used in many other areas including Prompt Gamma Neutron Activation Analysis (PGNAA), neutron testing and experiment.

  2. Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

    Science.gov (United States)

    Klaiber, Michael; Hatsagortsyan, Karen Z; Müller, Carsten; Keitel, Christoph H

    2008-02-15

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond pulse train of soft x rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift, which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. This way, short pulses of coherent hard x rays of up to 40 keV energy can be generated. PMID:18278127

  3. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses

    CERN Document Server

    Jukna, Vytautas; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-01-01

    Acoustic signals generated by filamentation of ultrashort TW laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

  4. Controlled supercontinuum generation for optimal pulse compression : a time-warp analysis of nonlinear propagation of ultra-broad-band pulses

    NARCIS (Netherlands)

    Spanner, M; Pshenichnikov, M; Olvo, [No Value; Ivanov, M

    2003-01-01

    We describe the virtues of the pump-probe approach for controlled supercontinuum generation in nonlinear media, using the example of pulse compression by cross-phase modulation in dielectrics. Optimization of a strong (pump) pulse and a weak (probe) pulse at the input into the medium opens the route

  5. Repetitive plasma opening switch for powerful high-voltage pulse generators

    International Nuclear Information System (INIS)

    Results are presented of experimental studies of plasma opening switches that serve to sharpen the pulses of inductive microsecond high-voltage pulse generators. It is demonstrated that repetitive plasma opening switches can be used to create super-powerful generators operating in a quasi-continuous regime. An erosion switching mechanism and the problem of magnetic insulation in repetitive switches are considered. Achieving super-high peak power in plasma switches makes it possible to develop new types of high-power generators of electron beams and X radiation. Possible implementations and the efficiency of these generators are discussed

  6. High-order harmonic generation with short-pulse lasers

    International Nuclear Information System (INIS)

    Recent progress in the understanding of high-order harmonic conversion from atoms and ions exposed to high-intensity, short-pulse optical lasers is reviewed. We find that ions can produce harmonics comparable in strength to those obtained from neutral atoms, and that the emission extends to much higher order. Simple scaling laws for the strength of the harmonic emission and the maximium observable harmonic are suggested. These results imply that the photoemission observed in recent experiments in helium and neon contains contributions from ions as well as neutrals

  7. Pulse Capacitors for Next Generation Linear Colliders. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Hooker, M.W.

    2000-03-03

    During this Phase I SBIR research program, Nanomaterials Research Corporation (NRC) successfully demonstrated high-voltage multilayer capacitors produced from sub-100 nm ceramic powders. The devices produced by NRC exhibited properties that make them particularly useful for pulse power applications. These properties include (1) high capacitance (2) low loss (3) high breakdown voltage (4) high insulation resistance and (5) rapid discharge characteristics. Furthermore, the properties of the nanostructured capacitors were consistently found to exceed those of components that represent the state of the art within the industry. Encouraged by these results, NRC is planning to submit a Phase II proposal with the objective of securing seed capital to continue this development effort.

  8. Generation of Intense THz Pulsed Lasers Pumped Strongly by CO2 Pulsed Lasers

    Institute of Scientific and Technical Information of China (English)

    QI Chun-Chao; CHENG Zu-Hai

    2009-01-01

    A theoretical method dealing with two intense laser fields interacting with a three-level molecular system is proposed.A discussion is presented on the properties of the solutions for time-independent and time-dependent absorption coefficients and gain coemcient on resonance for strong laser fields,based on analytic evaluation of the rate equations for a homogeneously broadened,three-level molecular system.The pump intensity range can be estimated according to the analytic expression of pump saturation intensity.The effects of pulse width,gas pressure and path length on the energy absorbed from pump light are studied theoretically.The results can be applied to the analysis of pulsed,optically pumped terahertz lasers.

  9. A broadband frequency-tripling scheme for an Nd:glass laser-based chirped-pulse amplification system: an approach for efficiently generating ultraviolet petawatt pulses

    International Nuclear Information System (INIS)

    We propose and numerically demonstrate a broadband frequency-tripling scheme for an Nd:glass laser-based chirped-pulse amplification system at 1053 nm. On the basis of the frequency mixing of a broadband chirped pulse with a narrowband laser pulse, the tripling scheme can support a bandwidth as large as 5 nm by alleviating the effects of the group-velocity mismatch involved, and it can be applied to generate ultraviolet petawatt (PW) pulses from a typical Nd:glass petawatt laser system. Both the energy of the ultraviolet pulse and the tripling efficiency (>80%) are boosted by an additional narrowband fundamental laser. The ultraviolet pulse generated can be compressed to a duration shorter than that of the initial Nd:glass PW pulse and its peak power can be increased to 2.5 times that of the Nd:glass PW pulse

  10. Theory of THz generation by Optical Rectification using Tilted-Pulse-Fronts

    CERN Document Server

    Ravi, Koustuban; Carbajo, Sergio; Nanni, Emilio; Schimpf, Damian; Ippen, Erich; Kaertner, Franz

    2014-01-01

    A model for THz generation by optical rectification using tilted-pulse-fronts is developed. It simultaneously accounts for (i) the spatio-temporal distortions of the optical pump pulse, (ii) the nonlinear coupled interaction of THz and optical radiation in two spatial dimensions (2-D), (iii) self-phase modulation and (iv) stimulated Raman scattering. The model is validated by quantitative agreement with experiments and analytic calculations. We show that the optical pump beam is significantly broadened in the transverse-momentum (kx) domain as a consequence of the spectral broadening caused by THz generation. In the presence of this large frequency and transverse-momentum (or angular) spread, group velocity dispersion causes a spatio-temporal break-up of the optical pump pulse which inhibits further THz generation. The implications of these effects on energy scaling and optimization of optical-to-THz conversion efficiency are discussed. This suggests the use of optical pump pulses with elliptical beam profile...

  11. Sulfuric Acid and Ammonia Generation by Bipolar Membranes Electrodialysis: Transport Rate Model for Ion and Water through Anion Exchange Membrane

    OpenAIRE

    Zhang, Xiaoyan; Lu, Wenhua; Ren, HongYan; Cong, Wei

    2008-01-01

    Regeneration of sulfuric acid and ammonia from ammonium sulfate by bipolar membrane electrodialysis (BMED) coupling with stripping ammonia by air-blowing was studied. The result showed that it was feasible to regenerate sulfuric acid and ammonia from ammonium sulfate solution using this method. Empirical models to describe the ion and water transport behaviors through anion exchange membrane for BMED system were successfully developed. The models were valid to evaluate water transport rate an...

  12. Adjustable, High Voltage Pulse Generator with Isolated Output for Plasma Processing

    Science.gov (United States)

    Ziemba, Timothy; Miller, Kenneth E.; Prager, James; Slobodov, Ilia

    2015-09-01

    Eagle Harbor Technologies (EHT), Inc. has developed a high voltage pulse generator with isolated output for etch, sputtering, and ion implantation applications within the materials science and semiconductor processing communities. The output parameters are independently user adjustable: output voltage (0 - 2.5 kV), pulse repetition frequency (0 - 100 kHz), and duty cycle (0 - 100%). The pulser can drive loads down to 200 Ω. Higher voltage pulsers have also been tested. The isolated output allows the pulse generator to be connected to loads that need to be biased. These pulser generators take advantage modern silicon carbide (SiC) MOSFETs. These new solid-state switches decrease the switching and conduction losses while allowing for higher switching frequency capabilities. This pulse generator has applications for RF plasma heating; inductive and arc plasma sources; magnetron driving; and generation of arbitrary pulses at high voltage, high current, and high pulse repetition frequency. This work was supported in part by a DOE SBIR.

  13. Plasma Generated During Pulsed Laser Deposition of Hydroxyapatite

    International Nuclear Information System (INIS)

    Plasma plume induced by laser ablation of a hydroxyapatite (Ca10(PO4)6(OH)2) target was studied in different ambient conditions. ArF excimer laser operated at the wavelength of 193 nm with the pulse energy of 300 mJ and 20 ns pulse duration. The emission spectra of the plasma plume were registered with the use of a fast gate, lens coupled micro-channel plate (MCP) image intensifier placed between a spectrograph and a CCD camera. The electron densities of 1023 divide 1022 m-3 were determined from the Stark broadening of the Ca I lines at distances 0.15- 2.5 cm from the target. Temperatures of 6.5 divide 3.5 kK at distances 1.9- 2.9 cm from the target were determined from the ratio of intensities of Ca lines. The expansion of the plasma plume was studied using the time of flight method. The time-dependent radiation of the Ca I and Ca II lines was registered with the use of a monochromator and photomultiplier in various distances from the target. Velocities of the order of 104 m/s were found. The dynamics of the plasma plume was also imaged by means of fast photography

  14. Generation of intense pulsed electron beams by the pseudospark discharge

    International Nuclear Information System (INIS)

    A low-pressure gas discharge is presented as a source of intense pulsed electron beams. The so-called pseudospark discharge emits a short-duration pinched electron beam during the breakdown phase. At voltages of typically 20 kV, approximately 10 to 20 percent of the total discharge current appears as the electron beam current of typically 20 ns induration. According to the breakdown voltage in the beam, a power density of the order of 109 W/cm2 is reached. Thus, this electron beam turns out to be a good tool for material processing, comparable to pulsed high-power lasers. Besides the drilling of holes into metals and insulators, an interesting application is the production of high-temperature superconducting thin YBa2Cu3O7-x films. The electron beam is used to evaporate material from a stoichiometric 1-2-3 target. Experimental results concerning the propagation behavior in neutral gas, the electron energy distribution, and the interaction with matter are reported

  15. Neutron generator burst timing measured using a pulse shape discrimination plastic scintillator with silicon photomultiplier readout

    Science.gov (United States)

    Preston, R. M.; Eberhardt, J. E.; Tickner, J. R.

    2013-12-01

    An EJ-299-34 plastic scintillator with silicon photomultiplier (SiPM) readout was used to measure the fast neutron output of a pulsed Thermo-Fisher A-325 Deuterium-Tritium sealed tube neutron generator (STNG). The SiPM signals were handled by a prototype digital pulse processing system, based on a free-running analogue to digital converter feeding a digital signal processor (DSP). Pulse shape discrimination was used to distinguish between detected fast-neutrons and gammas. Pulse detection, timing, energy and shape were all processed by the DSP in real-time. The time-dependency of the neutron output of the STNG was measured for various pulsing schemes. The switch-on characteristics of the tube strongly depended on the operating settings, with the delay between pulse turn-on and the production of neutrons ranging between 13 μs to 74 μs for the tested pulse rates and duty cycles. This work will facilitate the optimization and modeling of apparatus that use the neutron generator's pulsing abilities.

  16. Neutron generator burst timing measured using a pulse shape discrimination plastic scintillator with silicon photomultiplier readout

    International Nuclear Information System (INIS)

    An EJ-299-34 plastic scintillator with silicon photomultiplier (SiPM) readout was used to measure the fast neutron output of a pulsed Thermo-Fisher A-325 Deuterium-Tritium sealed tube neutron generator (STNG). The SiPM signals were handled by a prototype digital pulse processing system, based on a free-running analogue to digital converter feeding a digital signal processor (DSP). Pulse shape discrimination was used to distinguish between detected fast-neutrons and gammas. Pulse detection, timing, energy and shape were all processed by the DSP in real-time. The time-dependency of the neutron output of the STNG was measured for various pulsing schemes. The switch-on characteristics of the tube strongly depended on the operating settings, with the delay between pulse turn-on and the production of neutrons ranging between 13 μs to 74 μs for the tested pulse rates and duty cycles. This work will facilitate the optimization and modeling of apparatus that use the neutron generator's pulsing abilities

  17. A Repetitive Nanosecond Pulse Source for Generation of Large Volume Streamer Discharge

    Institute of Scientific and Technical Information of China (English)

    TAO Fengbo; ZHANG Qiaogen; GAO Bo; WANG Hu; LI Zhou

    2008-01-01

    Using a unipolar pulse with the rise time and the pulse duration in the order of microsecond as the primary pulse,a nanosecond pulse with the repetitive frequency of several kilohertz is generated by a spark gap switch.By varying both the inter-pulse duration and the pulse frequency,the voltage recovery rate of the spark gap switch is investigated at different working conditions such as the gas pressure,the gas composition as well as the bias voltage.The results reveal that either increase in gas pressure or addition of SF6 to the air can increase the voltage recovery rate.The effect of gas composition on the voltage recovery rate is discussed based on the transferring and distribution of the residual space charges.The repetitive nanosecond pulse source is also applied to the generation of large volume,and the discharge currents are measured to investigate the effect of pulse repetition rate on the large volume streamer discharge.

  18. Simultaneous VUV and XUV pulse generation and characterization for attosecond pump probe experiments

    CERN Document Server

    Fabris, D; Walke, D; Witting, T; Marangos, J P; Tisch, J W G

    2013-01-01

    We report the generation and characterization of isolated attosecond XUV and VUV pulses generated simultaneously via HHG driven by few-cycle pulses using an in-line dual gas target system. One gas jet target was operated with Kr gas that optimized HHG in the 15-25 eV photon energy range (VUV), whilst the second gas jet target was operated in Ne gas to optimize the high harmonic generation around 90 eV (XUV). Appropriate filters were used to isolate the required spectral components to synthesize isolated pulses. Sn and In filters were used for the VUV region while a Zr filter was used for the XUV. We characterized both the XUV and VUV pulses independently using the attosecond streaking technique and the LSGPA retrieval algorithm obtaining a 1.7$\\pm$0.2 fs pulse using the In filter and a 616$\\pm$50 as pulse using Sn, while preserving a 266$\\pm$10 as isolated XUV pulse.

  19. Generation, shaping, compression, characterization and application of intense ultrashort laser pulses

    CERN Document Server

    Cheng, Z

    2001-01-01

    Recently, the development of intense ultrashort laser pulses has attracted much interest because of their significant applications in many fields of science and technology. This thesis contributes to the generation, shaping, compression, characterization and application of intense ultrashort laser pulses as follows: 1. Laser pulses of 17.5-fs with a peak power of 0.1-TW at 1-kHz repetition rate have been generated by a compact single-stage ten-pass Ti:sapphire amplifier system with a high-order-dispersion-mirror compensator and a spectral shaping for the first time. The experimental results are in reasonable agreement with numerical calculations. 2. The first experimental study on arbitrary shaping of intense ultrashort pulses has been conducted in a kHz amplifier system capable of generating 27 fs pulses by using an acousto-optic programmable dispersive filter (AOPDF). 17-fs transform-limited pulses have been achieved and arbitrary shaping of these 17-fs pulses has been demonstrated both in the temporal and ...

  20. Optical transponder DC probe [for pulsed power generator

    CERN Document Server

    Thompson, M C

    1999-01-01

    The Atlas Pulse Power, Marx Bank will produce significant electromagnetic interference potential (EMI) via its 192 spark-gaps and trigger systems (36 more spark gaps). The authors have a need to measure DC charge components to a fair degree of accuracy during charge to ensure a safe and balanced system. Isolation from elevated- deck and/or high EMI environments during DC voltage or current measurement has classically been approached using frequency modulation (FM) of an imposed carrier on an optical fiber coupled system. There are shortcomings in most systems that can generally be compensated for by various means. In their application of remote sensing, the power to run this remote probe was a central issue. As such the authors took another approach to monitor the DC charge record for the Atlas' Marx banks. (0 refs).

  1. Evaluating the generation efficiency of hydrogen peroxide in water by pulsed discharge over water surface and underwater bubbling pulsed discharge

    Science.gov (United States)

    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.

  2. Generation of an isolated few-attosecond pulse in optimized inhomogeneous two-color fields

    Science.gov (United States)

    Chou, Yi; Li, Peng-Cheng; Ho, Tak-San; Chu, Shih-I.

    2015-08-01

    We present a numerical study for optimization of ultrabroad supercontinuum spectrum by controlling the waveforms of laser fields, with the ultimate goal to generate isolated ultrashort attosecond pulses. Specifically, we extend a derivative-free nonconvex optimization algorithm for maximization of the supercontinnum power spectrum near the high-order harmonic generation (HHG) cutoff. It is found that optimally shaped inhomogeneous two-color mid-infrared laser fields can greatly enhance and extend the high-order harmonic generation plateau. Wavelet time-frequency analysis and classical simulations show that the superposition of resulting hydrogen HHG supercontinuum effectively gives rise to a robust isolated 5-as pulse.

  3. Simulation of the Quasi-Monoenergetic Protons Generation by Parallel Laser Pulses Interaction with Foils

    Science.gov (United States)

    Wang, Wei-Quan; Yin, Yan; Zou, De-Bin; Yu, Tong-Pu; Yang, Xiao-Hu; Xu, Han; Yu, Ming-Yang; Ma, Yan-Yun; Zhuo, Hong-Bin; Shao, Fu-Qiu

    2014-11-01

    A new scheme of radiation pressure acceleration for generating high-quality protons by using two overlapping-parallel laser pulses is proposed. Particle-in-cell simulation shows that the overlapping of two pulses with identical Gaussian profiles in space and trapezoidal profiles in the time domain can result in a composite light pulse with a spatial profile suitable for stable acceleration of protons to high energies. At ~2.46 × 1021 W/cm2 intensity of the combination light pulse, a quasi-monoenergetic proton beam with peak energy ~200 MeV/nucleon, energy spread therapy. The proton beam quality can be controlled by adjusting the incidence points of two laser pulses.

  4. Conditions for the reliable production of attosecond pulses using ultra-short laser generated high harmonics

    International Nuclear Information System (INIS)

    Full text: We outline some of the theoretical tools available for calculating high harmonic structures generated by the interaction of short IR laser pulses with target gases. We demonstrate a simple approach for determining plateau positions in harmonic spectra, and use that to outline the stringent requirements for carrier-envelope phase and intensity stabilization in the laser pulse for reliable attosecond pulse production. Neglecting the phase and intensity characteristics of the laser pulse will lead to large variations in the duration and number of sub-is pulses produced via high harmonics cut-off windowing. We go on to discuss macroscopic influences, such as the effect of positioning and geometry of the laser focus within the gas jet. (author)

  5. Generation of ultrashort radiation pulses by injection locking a regenerative free-electron-laser amplifier

    International Nuclear Information System (INIS)

    We demonstrate how a steady-state train of ultrashort radiation pulses can be produced utilizing a new free-electron laser (FEL) configuration, the injection-locked regenerative klystron amplifier (IRKA). This configuration consists of two elements: (1) a prebuncher, which microbunches the electron beams at the desired output wavelength, and (2) a multipass FEL operated at a very small cavity desynchronism and below the lasing threshold, in the regime of regenerative amplification. The regenerative amplifier is driven by the microbunched electron beam, so that the pulse-to-pulse stability is provided by the pre-buncher. The broad amplification bandwidth of this regenerative amplifier enables generation of ultrashort pulses, much shorter than a slippage length, with high efficiency. The IRKA configuration can produce such ultra-short radiation pulses while avoiding the chaotic dynamics that limits conventional FEL performance. copyright 1997 The American Physical Society

  6. Few-cycle nonlinear mid-IR pulse generated with cascaded quadratic nonlinearities

    DEFF Research Database (Denmark)

    Bache, Morten; Liu, Xing; Zhou, Binbin

    Generating few-cycle energetic and broadband mid-IR pulses is an urgent current challenge in nonlinear optics. Cascaded second-harmonic generation (SHG) gives access to an ultrafast and octave-spanning self-defocusing nonlinearity: when ΔkL >> 2π the pump experiences a Kerr-like nonlinear index...

  7. A Pulse Generator Based on an Arduino Platform for Ultrasonic Applications

    Science.gov (United States)

    Acevedo, Pedro; Vázquez, Mónica; Durán, Joel; Petrearce, Rodolfo

    The objective of this work is to use the Arduino platform as an ultrasonic pulse generator to excite PVDF ultrasonic arrays in transmission. An experimental setup was implemented using a through-transmission configuration to evaluate the performance of the generator.

  8. Quantum random number generator based on the photon number decision of weak laser pulses

    OpenAIRE

    Wei, Wei; Zhang, J W; Liu, Tian; Guo, Hong

    2008-01-01

    We propose an approach to realize a quantum random number generator (QRNG) based on the photon number decision of weak laser pulses. This type of QRNG can generate true random numbers at a high speed and can be adjusted to zero bias conveniently, thus is suitable for the applications in quantum cryptography.

  9. Criteria for fluxon generation in long Josephson junctions by current pulses

    OpenAIRE

    Sakai, S.; Samuelsen, Mogens Rugholm

    1987-01-01

    In recent measurements in the time domain on the fluxon shape in long Josephson junctions the fluxons were generated by a current pulse injected into one end. We present here a perturbation treatment of the fluxon generation which we compare with numerical experiments. The agreement turns out to be excellent. Applied Physics Letters is copyrighted by The American Institute of Physics.

  10. Supercontinuum generation in a photonic crystal fibre using picosecond pulses at 1550 nm

    DEFF Research Database (Denmark)

    Andersen, Peter Andreas; Peucheret, Christophe; Hilligsøe, K.; Berg, Kim Skaalum; Hansen, K. P.; Jeppesen, Palle

    Supercontinuum (SC) generation is demonstrated in a photonic crystal fibre (PCF) at 1550 nm with pulse widths of 0.3 to 2.5 ps. Subsequent band-pass filtering of the generated SC spectrum enables the realisation of an optical clock frequency translator continuously tunable up to the L-band....

  11. Time resolving imaging spectroscopy applied to the analysis of plasmas generated by pulsed lasers

    Energy Technology Data Exchange (ETDEWEB)

    Alvira, F C; Bilmes, G M [Centro de Investigaciones Opticas (CONICET La Plata-CIC) CC 3, 1897, Gonnet, La Plata, Buenos Aires (Argentina); Ponce, L; Arronte, M, E-mail: fcalvira@ciop.unlp.edu.ar [CICATA-IPN, Unidad Altamira, Altamira 89600, Tamps (Mexico)

    2011-01-01

    Time resolved imaging spectroscopy were used to study the spatial and temporal evolution of LIBS (Laser Induced Breakdown Spectroscopy) plasmas generated in Cu substrates by laser pulses of different duration. Long laser pulses (microsecond) and short laser pulses (nanosecond) as well as multipulse emission were used for excitation. Analysis was made by using an imaging spectrometer with time resolved detection. Results show that the use of long laser excitation pulses produce emission spectra with the same signal to noise ratio, but with lower resolution than those produced with shorter ones. The different species generated in LIBS experiments as neutral or single ionized have a different spatial distribution inside the plasma. We demonstrated that using spatial discrimination procedures is possible to obtain spectra with the same signal to noise ratio than those obtained with a gating detector. In this case an appreciable advantage in cost reduction is obtained by replacing the gating detector by a cheap screen.

  12. Time resolving imaging spectroscopy applied to the analysis of plasmas generated by pulsed lasers

    International Nuclear Information System (INIS)

    Time resolved imaging spectroscopy were used to study the spatial and temporal evolution of LIBS (Laser Induced Breakdown Spectroscopy) plasmas generated in Cu substrates by laser pulses of different duration. Long laser pulses (microsecond) and short laser pulses (nanosecond) as well as multipulse emission were used for excitation. Analysis was made by using an imaging spectrometer with time resolved detection. Results show that the use of long laser excitation pulses produce emission spectra with the same signal to noise ratio, but with lower resolution than those produced with shorter ones. The different species generated in LIBS experiments as neutral or single ionized have a different spatial distribution inside the plasma. We demonstrated that using spatial discrimination procedures is possible to obtain spectra with the same signal to noise ratio than those obtained with a gating detector. In this case an appreciable advantage in cost reduction is obtained by replacing the gating detector by a cheap screen.

  13. Generators of fast electron nanosecond pulses with energy of 500 keV

    International Nuclear Information System (INIS)

    Possibility of using IMAS-150Eh commercially produced miniature electron tube in pulse generators of fast electrons with energy of up to 500 keV has been investigated. Structures of two such generators are described. High-voltage nanosecond pulses are shaped by an increasing pulse transformer with subsequent peaking of front. Discharger of high pressure is used for this in one version, in the second-discharger in combination with double shaping line with gas isolation. Electron current pulses of 1.5-2.5 ns duration at a semiheight and amplitude of up to 1200 A. It is concluded that construction simplicity and small quantity of elements in a high- voltage part of the circuit privide high reliability of the devices described

  14. High harmonic generation in underdense plasmas by intense laser pulses with orbital angular momentum

    Science.gov (United States)

    Mendonça, J. T.; Vieira, J.

    2015-12-01

    We study high harmonic generation produced by twisted laser pulses, with orbital angular momentum in the relativistic regime, for pulse propagation in underdense plasma. We consider fast time scale processes associated with an ultra-short pulse, where the ion motion can be neglected. We use both analytical models and numerical simulations using a relativistic particle-in-cell code. The present description is valid for relativistic laser intensities, when the normalized field amplitude is much larger than one, a ≫ 1. We also discuss two distinct processes associated with linear and circular polarization. Using both analytical solutions and particle-in-cell simulations, we are able to show that, for laser pulses in a well defined Laguerre-Gauss mode, angular momentum conservation is observed during the process of harmonic generation. Intensity modulation of the harmonic spectrum is also verified, as imposed by the nonlinear time-scale for energy transfer between different harmonics.

  15. Low-induction pulse current generator with a volume bus arrangement

    International Nuclear Information System (INIS)

    Pulse current generator (PC6) with 38 kj stored energy designed for up to 50 kV charging voltage used to obtain magnetic fields within megagauss range, is described. Space (volume) bus arrangement of its modules is used to reduce eigen inductance of PC6. Current is commutated by solid-body spark gaps. Under 3uH inductive load PC6 provides for formation of up to 2.25 MA current pulse with 3.3x1012 A/s pulse rise time. Technique to determine low inductances as applied to PC6 elements is described. The described PC6 is used for experiments on generation of super-strong pulse magnetic fields in single-loop solenoid with volume occupied by magnetic field, 5-7 mm. Magnetic field with up to 350 T induction amplitude is obtained in these experiments

  16. Properties of periodic multicrystal configurations in walk-off-compensating second harmonic generation of ultrashort pulses

    Institute of Scientific and Technical Information of China (English)

    Huang Jin-Zhe; Zhang Liu-Yang; Shen Tao

    2011-01-01

    This work designs a four-platelet periodic multicrystal configuration in the second harmonic generation of ultrashort pulses as a new walk-off-compensating device. It theoretically investigates a proposed active and a typical passive compensating scheme with the undepleted-pump approximation. The result shows that the angular and spectral bandwidths are proportional to the number of crystal pairs as expected, but the temperature tunability is basically unaltered owing to inter-plate pulse interference. At the same time, an analysis reveals that a misuse of the phase mismatch factor is responsible for a historic controversy about pulse interference. A real design of an ultraviolet second harmonic generation(262.5 nm)is considered in a passive periodic(3-Barium Borate-calcite configuration, where the inter-plate pulse interference is found to form an azimuthal tuning restriction and to lower plate length tolerance. A subsequent numerical simulation with pump depletion is in good accordance with theoretical prediction.

  17. High-energy infrared femtosecond pulses generated by dual-chirped optical parametric amplification.

    Science.gov (United States)

    Fu, Yuxi; Takahashi, Eiji J; Midorikawa, Katsumi

    2015-11-01

    We demonstrate high-energy infrared femtosecond pulse generation by a dual-chirped optical parametric amplification (DC-OPA) scheme [Opt. Express19, 7190 (2011)]. By employing a 100 mJ pump laser, a signal pulse energy exceeding 20 mJ at a wavelength of 1.4 μm was achieved before dispersion compensation. A total output energy of 33 mJ was recorded. Under a further energy scaling condition, the signal pulse was compressed to an almost transform-limited duration of 27 fs using a fused silica prism compressor. Since the DC-OPA scheme is efficient and energy scalable, design parameters for obtaining 100 mJ level infrared pulses are presented, which are suitable as driver lasers for the energy scaling of high-order harmonic generation with sub-keV photon energy. PMID:26512524

  18. High harmonic generation in underdense plasmas by intense laser pulses with orbital angular momentum

    International Nuclear Information System (INIS)

    We study high harmonic generation produced by twisted laser pulses, with orbital angular momentum in the relativistic regime, for pulse propagation in underdense plasma. We consider fast time scale processes associated with an ultra-short pulse, where the ion motion can be neglected. We use both analytical models and numerical simulations using a relativistic particle-in-cell code. The present description is valid for relativistic laser intensities, when the normalized field amplitude is much larger than one, a ≫ 1. We also discuss two distinct processes associated with linear and circular polarization. Using both analytical solutions and particle-in-cell simulations, we are able to show that, for laser pulses in a well defined Laguerre-Gauss mode, angular momentum conservation is observed during the process of harmonic generation. Intensity modulation of the harmonic spectrum is also verified, as imposed by the nonlinear time-scale for energy transfer between different harmonics

  19. High harmonic generation in underdense plasmas by intense laser pulses with orbital angular momentum

    Energy Technology Data Exchange (ETDEWEB)

    Mendonça, J. T., E-mail: josetitomend@gmail.com [IPFN, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal and Instituto de Física, Universidade de São Paulo, 05508-090 São Paulo, SP (Brazil); Vieira, J., E-mail: jorge.vieira@ist.utl.pt [GoLP, IPFN, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa (Portugal)

    2015-12-15

    We study high harmonic generation produced by twisted laser pulses, with orbital angular momentum in the relativistic regime, for pulse propagation in underdense plasma. We consider fast time scale processes associated with an ultra-short pulse, where the ion motion can be neglected. We use both analytical models and numerical simulations using a relativistic particle-in-cell code. The present description is valid for relativistic laser intensities, when the normalized field amplitude is much larger than one, a ≫ 1. We also discuss two distinct processes associated with linear and circular polarization. Using both analytical solutions and particle-in-cell simulations, we are able to show that, for laser pulses in a well defined Laguerre-Gauss mode, angular momentum conservation is observed during the process of harmonic generation. Intensity modulation of the harmonic spectrum is also verified, as imposed by the nonlinear time-scale for energy transfer between different harmonics.

  20. Amplified spontaneous emission pulses for high-power supercontinuum generation

    Directory of Open Access Journals (Sweden)

    Huan Huan Liu

    2016-03-01

    Full Text Available The authors demonstrate an incoherent light source based on a reflective semiconductor optical amplifier as pump for high-power supercontinuum generation for the first time. The obtained power level is about 160 mW and 20 dB spectral bandwidth is around 170 nm.

  1. Ultrabroadband 50-130 THz pulses generated via phase-matcheddifference frequency mixing in LiIO3

    Energy Technology Data Exchange (ETDEWEB)

    Zentgraf, Thomas; Huber, Rupert; Nielsen, Nils C.; Chemla, DanielS.; Kaindl, Robert A.

    2006-10-10

    We report the generation of ultrabroadband pulses spanningthe 50-130 THz frequency range via phase-matched difference frequencymixing within the broad spectrum of sub-10 fs pulses in LiIO_3. Modelcalculations reproduce the octave-spanning spectra and predict few-cycleTHz pulse durations less than 20~;fs. The applicability of this scheme isdemonstrated with 9-fs pulses from a Ti:sapphire oscillator and with 7-fsamplified pulses from a hollow fiber compressor as pumpsources.

  2. Development of a compact generator for gigawatt, nanosecond high-voltage pulses

    Science.gov (United States)

    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.

  3. Prediction of electromagnetic pulse generation by picosecond avalanches in high-pressure air

    International Nuclear Information System (INIS)

    The gas avalanche switch is a laser-activated, high-voltage switch, consisting of a set of pulse-charged electrodes in a high-pressure gas. Induced electrons from a picosecond-scale laser pulse initiate an avalanche discharge between high-voltage and grounded electrodes. If the voltage, pressure, and dimensions are correct, the rapid avalanche, fueled by the immense number of electrons available in the gas, collapses the applied voltage in picoseconds and generates electromagnetic pulses with widths as short as 1-10 ps and 3 dB bandwidths of 20-120 GHz. With proper voltage or pressure detuning, wider pulses and lower bandwidths occur. In addition to picosecond electromagnetic pulse generation, application of this switch should result in ultra-fast Marx bank pulsers. A number of versions of the switch are possible. The simplest is a parallel plate capacitor, consisting of a gas between two parallel plate conductors. High voltage is applied across the two plates. A parallel plate, Blumlein geometry features a center electrode between two grounded parallel plates. This geometry emits a single pulse in each direction along the parallel plates. A frozen wave geometry with multiple, oppositely charged center electrodes will emit AC pulses. Series switches consisting of gas gaps between two electrodes are also possible

  4. Burst train generator of high energy femtosecond laser pulses for driving heat accumulation effect during micromachining.

    Science.gov (United States)

    Rezaei, Saeid; Li, Jianzhao; Herman, Peter R

    2015-05-01

    A new method for generating high-repetition-rate (12.7-38.2 MHz) burst trains of femtosecond laser pulses has been demonstrated for the purpose of tailoring ultrashort laser interactions in material processing that can harness the heat accumulation effect among pulses separated by a short interval (i.e., 26 ns). Computer-controlled time delays were applied to synchronously trigger the high frequency switching of a high voltage Pockels cell to specify distinctive values of polarization rotation for each round-trip of a laser pulse cycling within a passive resonator. Polarization dependent output coupling facilitated the flexible shaping of the burst envelope profile to provide burst trains of up to ∼1  mJ of burst energy divided over a selectable number (1 to 25) of pulses. Individual pulses of variable energy up to 150 μJ and with pulse duration tunable over 70 fs to 2 ps, were applied in burst trains to generate deep and high aspect ratio holes that could not form with low-repetition-rate laser pulses. PMID:25927785

  5. Mechanical effects induced by shock waves generated by high energy laser pulses

    OpenAIRE

    Fournier, J.; Ballard, P.; P. Merrien; Barralis, J.; Castex, L.; Fabbro, R.

    1991-01-01

    Specimens made of low alloy and non alloyed medium carbon steels were subjected to high energy laser pulses. Direct ablation and confined plasma procedures were both investigated. An optimum impulse momentum transfer to the material is attained with a pulse duration of 30 ns and a power density of 10 GW .cm2. Fatigue testing shows that the fatigue strengths of the selected materials are significantly increased. This can be related to the fact that laser shock processing generates an appropria...

  6. Characteristics of an actuator-driven pulsed water jet generator to dissecting soft tissue.

    Science.gov (United States)

    Seto, Takeshi; Yamamoto, Hiroaki; Takayama, Kazuyoshi; Nakagawa, Atsuhiro; Tominaga, Teiji

    2011-05-01

    This paper reports characteristics of an actuator-driven pulsed water jet generator applied, in particular, to dissect soft tissues. Results of experiments, by making use of high speed recording of optical visualization and varying nozzle diameter, actuator time interval, and their effects on dissection performance are presented. Jet penetration characteristics are compared with continuous water jet and hence potential assessment of pulsed water jets to clinical applications is performed. PMID:21639536

  7. Dissipative Rogue Waves Generated by Chaotic Pulse Bunching in a Mode-Locked Laser

    Science.gov (United States)

    Lecaplain, C.; Grelu, Ph.; Soto-Crespo, J. M.; Akhmediev, N.

    2012-06-01

    Rare events of extremely high optical intensity are experimentally recorded at the output of a mode-locked fiber laser that operates in a strongly dissipative regime of chaotic multiple-pulse generation. The probability distribution of these intensity fluctuations, which highly depend on the cavity parameters, features a long-tailed distribution. Recorded intensity fluctuations result from the ceaseless relative motion and nonlinear interaction of pulses within a temporally localized multisoliton phase.

  8. Pulse shaping via forward second harmonic generation in nonlinear photonic crystals

    International Nuclear Information System (INIS)

    We have theoretically designed a method for obtaining short laser pulses by second harmonic generation in periodically and aperiodically poled quadratic nonlinear photonic crystals. An efficient algorithm is developed to construct quasi-phase matching gratings which allow one to shape the required amplitude and phase of second-harmonic pulses considering energy exchange. Developed method could be applied for designing of nonlinear photonic crystals. (authors)

  9. Soliton pulse compression through cascaded quadratic nonlinearity in difference-frequency generation

    Institute of Scientific and Technical Information of China (English)

    WANG Ke; QIAN LieJia; ZHU HeYuan

    2008-01-01

    Cascaded nonlinearity based soliton pulse compression in the process of femtosecond difference frequency generation is studied theoretically. A set of simplified coupled wave equations under the conditions of large phase mismatch and matched group velocities is obtained, which reveals the physical mechanism of soliton compression in this process. Numerical simulations demonstrate that in the presence of group velocity dispersion and equivalent cross phase modulation, both the pump and the signal pulses can be compressed with a high compression ratio.

  10. Fast waveform metrology : generation, measurement and application of sub-picosecond electrical pulses

    OpenAIRE

    A. J. A. Smith

    1996-01-01

    This thesis describes work performed at the National Physical Laboratory to improve the electrical risetime calibration of instruments such as fast sampling oscilloscopes. The majority of the work can be divided into four sections: development of an ultrafast optoelectronic pulse generator; measurement of fast electrical pulses with an electrooptic sampling system; de-embedding of transmission line and transition effects as measured at different calibration reference planes; an...

  11. Electrical short pulses generation using a resonant tunneling diode nonlinear transmission line

    International Nuclear Information System (INIS)

    In this paper, the generation of short electrical pulses based on nonlinear active wave propagation effects along the resonant tunneling diode transmission line is studied. The principle of operation is discussed and it is shown by computer experiments that an input rectangular pulse as well as a sinusoidal input signal can be converted into a set of output spikes, suitable for A/D conversion at millimeter wave frequencies.

  12. Electrical short pulses generation using a resonant tunneling diode nonlinear transmission line

    Science.gov (United States)

    Essimbi, B. Z.; Jäger, D.

    2012-03-01

    In this paper, the generation of short electrical pulses based on nonlinear active wave propagation effects along the resonant tunneling diode transmission line is studied. The principle of operation is discussed and it is shown by computer experiments that an input rectangular pulse as well as a sinusoidal input signal can be converted into a set of output spikes, suitable for A/D conversion at millimeter wave frequencies.

  13. Noise characterization of a pulse train generated by actively mode-locked lasers

    OpenAIRE

    Eliyahu, Danny; Salvatore, Randal A.; Yariv, Amnon

    1996-01-01

    We analyze the entire power spectrum of pulse trains generated by a continuously operating actively mode-locked laser in the presence of noise. We consider the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes. Effects of correlations between different parameters of these fluctuations are studied also. The nonstationary timing-jitter fluctuations of passively mode-locked lasers and their influence on the power spectrum is discussed...

  14. Nanosecond neutron pulse generation in diode acceleration tubes with vacuum arc discharge and laser deuteron sources

    International Nuclear Information System (INIS)

    Nonsteady process of deuteron pulse formation and acceleration to neutron produced target at vacuum acceleration tubes is investigated. Deuterons are emitted from vacuum arc discharge or laser deuteron sources. This generation mechanism has been studied by numerical simulations using a relativistic electromagnetic PIC code. The results obtained shows essential dependence of deuteron plasma emission, forming and accelerating processes in diode from the final deuteron current. Neutron flow calculation can be done based on short pulse dynamic investigation.

  15. Controllable nonlocal behaviour by cascaded second-harmonic generation of fs pulses

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw; Moses, Jeffrey; Wise, Frank W.

    Second-harmonic generation (SHG) of ultra-short pulses can act as a prototypical nonlocal nonlinear model, since the strength and nature of the temporal nonlocality can be controlled through the phase-mismatch parameter. The presence of a group-velocity mismatch namely implies that when the phase...... compression to few-cycle pulses in the cascaded quadratic soliton compressor, the spectral content of the full coupled SHG model is predicted by the nonlocal model even when few-cycle pulses are interacting....

  16. Quasi-phase-matching of high harmonic generation using counter-propagating pulses

    OpenAIRE

    O’Keeffe K.; Hooker S. M.

    2013-01-01

    We investigate quasi-phase-matching over a range of harmonic orders using trains of up to 8 uniformly-spaced counter-propagating pulses. For trains of up to 4 pulses the measured enhancement of the harmonic signal scales with the number of pulses N as (N+1)2, as expected. However, for trains with N > 4, no further enhancement of the harmonic signal is observed. The effect is ascribed to changes in the coherence length with the generating medium. The pressure dependence of quasi-phase-matching...

  17. New schemes for high-voltage pulsed generators based on stepped transmission lines

    International Nuclear Information System (INIS)

    Wave processes were analyzed from the point of effective energy delivery in pulsed power systems based on transmission lines. A series of new schemes for the pulsed generators based on multistage stepped transmission lines both with the capacitive and inductive energy storage was found. These devices can provide voltage or current transformation up to 5-10 times due to wave processes if stage's characteristic impedances are in a certain correlation. The schemes suggested can be widely applied in the new powerful pulsed power accelerators. The theoretical conclusions are justified experimentally

  18. Genetic optimization of attosecond pulse generation in light-field synthesizers

    CERN Document Server

    Balogh, E; Tosa, V; Goulielmakis, E; Varjú, K; Dombi, P

    2014-01-01

    We demonstrate control over attosecond pulse generation and shaping by numerically optimizing the synthesis of few-cycle to sub-cycle driver waveforms. The optical waveform synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single and double attosecond pulse production (with tunable separation) revealing the potentials of the light wave synthesizer device demonstrated by Wirth et al. [Science 334, 195 (2011)]. The results are also analyzed with respect to attosecond pulse propagation phenomena.

  19. Genetic optimization of attosecond-pulse generation in light-field synthesizers

    Science.gov (United States)

    Balogh, E.; Bódi, B.; Tosa, V.; Goulielmakis, E.; Varjú, K.; Dombi, P.

    2014-08-01

    We demonstrate control over attosecond-pulse generation and shaping by numerically optimizing the synthesis of few-cycle to subcycle driver wave forms. The optical wave-form synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single- and double-attosecond-pulse production (with tunable separation), revealing the potentials of the light wave synthesizer device demonstrated by A. Wirth et al. [Science 334, 195 (2011), 10.1126/science.1210268]. The robustness of the results are also analyzed with respect to attosecond-pulse propagation phenomena.

  20. Generation of an isolated sub-100 attosecond pulse in the water-window spectral region

    International Nuclear Information System (INIS)

    We propose a scheme to generate isolated attosecond pulses in the water-window spectral region. Based on the numerical solutions of the single active electron model, we investigate high-order harmonic generation in helium atoms driven by a multi-cycle two-colour optical field synthesized by an intense 2000 nm, 20 fs pulse and its frequency-doubled pulse. When the latter is slightly detuned and properly phase shifted with respect to the fundamental laser pulse, an ultra-broad extreme ultraviolet supercontinuum with a spectral width of 130 eV can be generated in the 270–400 eV spectral regions. A supercontinuum from 280–340 eV in the water window can be selected to yield an isolated 67 attosecond pulse without employing any phase compensation. This water window coherent x-ray pulse with less than 100 attosecond duration is a potential tool for studying the ultrafast electronic dynamics of biological samples in water. (geophysics, astronomy and astrophysics)

  1. Fabrication of Multi-Harmonic Buncher for Pulsed Proton Beam Generation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H. S.; Kwon, H. J.; Cho, Y. S. [Korea Multipurpose Accelerator Complex, Gyeongju (Korea, Republic of)

    2015-05-15

    Fast neutrons with a broad spectrum can be generated by irradiating the proton beams on target materials. To measure the neutron energy by time of flight (TOF) method, the short pulse width of the proton beam is preferred because the neutron energy uncertainty is proportional to the pulse width. In addition, the pulse repetition rate should be low enough to extend the lower limit of the available neutron energy. Pulsed proton beam generation system is designed based on an electrostatic deflector and slit system as shown in Fig. 1. In a simple deflector with slit system, most of the proton beam is blocked by slit, especially when the beam pulse width is short. The ideal field pattern inside the buncher cavity is saw-tooth wave. To make the field pattern similar to the saw-tooth waveform, we adopted a multi-harmonic buncher (MHB). The design for the multi-harmonic buncher including 3D electromagnetic calculation has been performed. Based on the design, a multi-harmonic buncher cavity was fabricated. It consists of two resonators, two drift tubes and a vacuum chamber. The resonator is a quarter-wave coaxial resonator type. The drift tube is connected to the resonator by using a coaxial vacuum feedthrough. Design summary and detailed fabrication method of the multi-harmonic buncher is presented in this paper. A multi-harmonic buncher for a proton beam chopper system to generate a short pulse neutron beam was designed, fabricated and assembled.

  2. Micro-joule sub-10-fs VUV pulse generation by MW pump pulse using highly efficient chirped-four-wave mixing in hollow-core photonic crystal fibers

    CERN Document Server

    Im, Song-Jin

    2013-01-01

    We theoretically study chirped four-wave mixing for VUV pulse generation in hollow-core photonic crystal fibers. We predict the generation of sub-10-fs VUV pulses with energy of up to hundreds of microjoule by broad-band chirped idler pulses at 830 nm and MW pump pulses with narrow-band at 277 nm. MW pump could be desirable to reduce the complexity of the laser system or use a high repetition rate-laser system. The energy conversion efficiency from pump pulse to VUV pulse reaches to 30%. This generation can be realized in kagome-lattice hollow-core PCF filled with noble gas of high pressure with core-diameter less than 40 micrometers which would enable technically simple or highly efficient coupling to fundamental mode of the fiber.

  3. High-energy Few-cycle Pulses Directly Generated from Strongly Phase-mismatched Lithium Niobate Crystal

    DEFF Research Database (Denmark)

    Zhou, Binbin; Chong, A.; Wise, F.W.;

    2012-01-01

    We show that effective soliton compression can be realized in strongly phase-mismatched quadratic media. Sub-15 fs pulses are experimentally generated directly from 10-mm-long bulk lithium niobate crystal by 120-fs input pulses at 1300 nm.......We show that effective soliton compression can be realized in strongly phase-mismatched quadratic media. Sub-15 fs pulses are experimentally generated directly from 10-mm-long bulk lithium niobate crystal by 120-fs input pulses at 1300 nm....

  4. On Bipolar Soft Sets

    OpenAIRE

    Shabir, Muhammad; Naz, Munazza

    2013-01-01

    We have studied the concept of bipolarity of information in the soft sets. We have defined bipolar soft sets and basic operations of union, intersection and complementation for bipolar soft sets. Examples of bipolar soft sets and an application of bipolar soft sets in a decision making problem with general algorithms have also been presented at the end.

  5. Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)

  6. Effect of pulse duration on plasmonic enhanced ultrafast laser-induced bubble generation in water

    Science.gov (United States)

    Lachaine, R.; Boulais, E.; Bourbeau, E.; Meunier, M.

    2013-07-01

    Bubbles generated in water by focusing femtosecond and picosecond laser pulses in the presence of 100 nm gold nanoparticles have been investigated in the fluence range usually used for efficient cell transfection (100-200 mJ/cm2). Since resulting bubbles are at the nanoscale, direct observation using optical microscopy is not possible. An optical in-situ method has been developed to monitor the time-resolved variation in the extinction cross-section of an irradiated nanoparticle solution sample. This method is used to measure the bubbles lifetime and deduce their average diameter. We show that bubbles generated with femtosecond pulses (40-500 fs) last two times longer and are larger in average than those generated with picosecond pulses (0.5-5 ps). Controlling those bubble properties is necessary for optimizing off-resonance plasmonic enhanced ultrafast laser cell transfection.

  7. Generation of scalable terahertz radiation from cylindrically focused laser pulses in air

    Science.gov (United States)

    Kuk, Donghoon; Yoo, Yungjun; Rosenthal, Eric; Jhajj, Nihal; Milchberg, Howard; Kim, Ki-Yong

    We have demonstrated scalable terahertz (THz) generation via cylindrical focusing of two-color laser pulses in air. In this experiment, we have used a terawatt (TW) laser system which can deliver >50 mJ, 800 nm, 50 fs pulses at a 10 Hz repetition rate. A 800 nm pulse passing through a nonlinear crystal (BBO) generates its second harmonic pulse (400 nm). Both pulses pass through a cylindrical lens and are focused together to generate a 2-dimensional plasma sheet in air. This yields two diverging THz lobes, characterized by an uncooled microbolometer. This observed radiation angle and pattern is explained by the optical-Cherenkov radiation theory. The diverging THz radiation is re-focused to yield strong THz field strengths (>20 MV/cm) at the focus. At laser energy of 40 mJ, cylindrical focusing provides THz energy of >30 microjoules, far exceeding the output produced by spherical focusing. This shows that cylindrical focusing can effectively minimize ionization-induced defocusing, previously observed in spherical focusing, and can allow scalable THz generation with relatively high laser energies (>20 mJ). Work supported by DOE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. 014216-001.

  8. High-speed dental radiography achieved with a kilohertz-range pulsed x-ray generator

    International Nuclear Information System (INIS)

    The development of a high-intensity kilohertz-range pulsed x-ray generator and its application to dental radiography are described. The pulsed x-ray generator consisted of the following major components: a constant high-voltage power supply, a high-voltage main condenser, a hot-cathode triode, a DC power supply for the filament (hot cathode), and a grid controller. The main condenser of 0.5 microF-100 kV in the pulser was charged from 50 to 70 kV by the power supply, and the electric charges in the condenser were discharged to the triode by the grid controller. To be exact, the tube voltage decreased during the discharging for generating pulsed x-rays, yet the maximum value was equivalent to the initial charging voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 30 kHz, respectively. The pulse width of the x-rays ranged from approximately 20 to 400 micros, and the x-ray intensity with a charging voltage of 70 kV and a total resistance of 5.1 MΩ was about 0.83 microC/kg at 1.0 m per pulse. Using this generator, high-speed dental radiography, e.g., delayed radiography and multiple-shot radiography, was performed

  9. Generation of High-Repetition-Rate Pulse Trains through the Continuous-Wave Perturbed by a Weak Gaussian Pulse in an Optical Fiber

    International Nuclear Information System (INIS)

    A new means of generating all-optically high-repetition-rate pulse trains is proposed and numerically demonstrated in an optical fiber. Our numerical simulations show that, due to the modulation instability effect, the initial continuous-wave with a weak optical pulse instead of conventional weak sinusoidal modulation imposed on it can gradually evolve into high-repetition-rate pulse trains. However, the generated pulse trains take on different features from the conventional case in terms of their widths, intensities, intervals, numbers, and pedestals. (fundamental areas of phenomenology(including applications))

  10. Generation of intense pulsed ion beam by a Br type magnetically insulated ion diode with carbon plasma gun

    International Nuclear Information System (INIS)

    To apply the pulsed heavy ion beam (PHIB) to an implantation process of semiconductor, purity of the ion beam is very important. To obtain a pure PHIB we have proposed a new type of accelerator using bipolar pulse. To develop the accelerator we are developing a new type of Br ion diode using a carbon plasma gun. By using the plasma gun, ion source plasma of ion current density approx. = 30 A/cm2 was obtained. The Br ion diode was successfully operated with plasma gun at diode voltage approx. = 100 kV, diode current approx. = 1 kA, pulse duration approx. = 200 ns and 3 A/cm2 of ion current density was obtained. (author)

  11. Numerical simulation study on spiral pulse generator with high Jantage and μs-class pulse width

    International Nuclear Information System (INIS)

    A method to analyze electric field distribution of the accelerator based on CST and PSpice software is introduced,and the dynamic three-dimensional electric field distribution and Jantage of the device are obtained. The models for numerical simulation of the spiral pulse generator are set up, and detailed results are presented. The changing rules of Jantage obtained by CST are similar to that by PSpice software. The numerical simulation results indicate that higher electric fields appear at the seams and the joint surface of the spiral bands, and the interior of the dielectric strut. (authors)

  12. Single bubble generated by a pulsed discharge in liquids as a plasma microreactor

    Energy Technology Data Exchange (ETDEWEB)

    Kanemaru, M; Sorimachi, S; Ibuka, S; Ishii, S, E-mail: kanemaru@pwr.ee.titech.ac.jp [Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2011-06-15

    We discuss a single bubble, generated by a pulsed discharge in liquids, in which reactive plasmas interact with gases and liquids. Double-pulsed microdischarges with variable time intervals were used. The first microdischarge was used to generate the bubble and the second one was used to create plasmas in it, which worked as a microcavity for plasma processing. The bubble remained for a period of 400-600 {mu}s, which was affected by discharge energy. The electrode erosion caused by the discharge in or without the bubble was characterized.

  13. Single bubble generated by a pulsed discharge in liquids as a plasma microreactor

    Science.gov (United States)

    Kanemaru, M.; Sorimachi, S.; Ibuka, S.; Ishii, S.

    2011-06-01

    We discuss a single bubble, generated by a pulsed discharge in liquids, in which reactive plasmas interact with gases and liquids. Double-pulsed microdischarges with variable time intervals were used. The first microdischarge was used to generate the bubble and the second one was used to create plasmas in it, which worked as a microcavity for plasma processing. The bubble remained for a period of 400-600 µs, which was affected by discharge energy. The electrode erosion caused by the discharge in or without the bubble was characterized.

  14. High-Harmonic Generation by Initial Coherent States in a Short Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    王兵兵; 程太旺; 李晓峰; 傅盘铭

    2004-01-01

    We study high-order harmonic generation (HHG) in an intense laser pulse vhen the initial state is prepared as a coherent superposition of the ground and first excited states. By examining the populations of these states for different laser intensity regions, the role of the excited state in the harmonic generation process can be identified.We also find that high conversion effciency and high cutoff frequency of HHG can be achieved if the intensity of the laser pulse is high enough to cause considerable ionization of the first excited state but not sufficient to ionize the ground state.

  15. Generation of the numerator=2 rational harmonic mode-locked pulses in fiber ring lasers

    Institute of Scientific and Technical Information of China (English)

    Pinghe Wang(汪平河); Li Zhan(詹黎); Qinghao Ye(叶庆好); Yuxing Xia(夏宇兴)

    2004-01-01

    In conventional rational harmonic mode-locking, optical pulse trains with the repetition rate of(pn + 1)fc are generated when the modulation frequency of the in-cavity modulator is set at fm=(n + 1/p)fc, where n and p are both integers, fc is the fundamental cavity frequency. In this paper, we report that rational harmonic mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at fm =(n + 2/p)fc. The pulse generations are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational harmonic mode-locking.

  16. High frequency optical pulse generation by frequency doubling using polarization rotation

    Science.gov (United States)

    Liu, Yang

    2016-05-01

    In this work, we propose and experimentally characterize a stable 40 GHz optical pulse generation by frequency doubling using polarization rotation in a phase modulator (PM). Only half the electrical driving frequency is required (i.e. 20 GHz); hence the deployment cost can be reduced. Besides, precise control of the bias of the PM is not required. The generated optical pulses have a high center-mode-suppression-ratio (CMSR) of  >  28 dB. The single sideband (SSB) noise spectrum is also measured, and the time-domain waveforms under different CMSRs are also analyzed and discussed.

  17. Magnetic generator of high-voltage pulses with a small decay time

    International Nuclear Information System (INIS)

    The circuit of a generator allowing to obtain the voltage pulse amplitude up to 100 kV, pulse decay time less than 1 ns and relative amplitude of afterpulses not more than 15% on the load 75 Ohm is described. A filled ferrite short circuited line forming shock waves is used in the generator. Magnetic unite is used to rise the power. Thyratron TGI1-2500/50 is a commutator. The main causes of the existence of the afterpulses and the ways of their amplitude reduction are considered

  18. Status of the upgraded version of the NRL GAMBLE II pulse power generator

    International Nuclear Information System (INIS)

    The GAMBLE II water dielectric pulse power generator, in 1970, was the forerunner of the high energy (> 50 kJ) class of water dielectric generators. It has been redesigned internally to make maximum use of its original outer conductor shell and to optimize it for the positive polarity mode of operation for positive ion beam experimentation. The new design also initiates the use of an oil dielectric multi-channel switch at the output of the pulse forming line. This switch, because of its low capacitance, eliminates the need for an extra prepulse switch. The upgraded version has been tested up to power and energy levels which are nearly twice the original

  19. Generation of sub-30 fs tunable infrared pulses by parametric visible-to-infrared frequency conversion

    Science.gov (United States)

    Darginavičius, J.; Tamošauskas, G.; Valiulis, G.; Piskarskas, A.; Dubietis, A.

    2012-07-01

    We propose visible-to-infrared frequency conversion method that is based on difference frequency generation and two-stage collinear optical parametric amplification in BBO crystal. The proof-of-principle experiments demonstrate efficient frequency down conversion of sub-30 fs pulses from a commercial blue-pumped noncollinear optical parametric amplifier that yields generation of sub-30-fs broadly tunable pulses in the range of 1.2 to 2.4 μm with up to 100 μJ energy.

  20. Generation of short and intense isolated Attosecond pulses by field-controlled excited states

    Science.gov (United States)

    Jooya, Hossein Z.; Li, Peng-Cheng; Liao, Sheng-Lun; Chu, Shih-I.

    2014-05-01

    A new mechanism for the coherent control of the generation of an isolated and ultrashort attosecond laser pulse with enhanced intensity is reported. Frequency and time delay of a weak high harmonics, added to a two color laser, are optimized to produce a 45 attosecond pulse with intensity of more than 70 times bigger than the original one. Resonance excitation and subsequent ionization are analyzed, along with electron trajectory investigation from wavelet time-frequency profile to explain the mechanism of the observed augmentation in this high-harmonic generation. This work is partially supported by DOE.

  1. Generation of Phase-Stable Sub-Cycle Mid-Infrared Pulses from Filamentation in Nitrogen

    Directory of Open Access Journals (Sweden)

    Takao Fuji

    2013-02-01

    Full Text Available Sub-single-cycle pulses in the mid-infrared (MIR region were generated through a laser-induced filament. The fundamental (ω1 and second harmonic (ω2 output of a 30-fs Ti:sapphire amplifier were focused into nitrogen gas and produce phase-stable broadband MIR pulses (ω0 by using a four-wave mixing process (ω1 + ω1 - ω2 → ω0 through filamentation. The spectrum spread from 400 cm-1 to 5500 cm-1, which completely covered the MIR region. The low frequency components were detected by using an electro-optic sampling technique with a gaseous medium. The efficiency of the MIR pulse generation was very sensitive to the delay between the fundamental and second harmonic pulses. It was revealed that the delay dependence of the efficiency came from the interference between two opposite parametric processes, ω1 + ω1 - ω2 → ω0 and ω2 - ω1 - ω1 → ω0. The pulse duration was measured as 6.9 fs with cross-correlation frequency-resolved optical gating by using four-wave mixing in nitrogen. The carrier-envelope phase of the MIR pulse was passively stabilized. The instability was estimated as 154 mrad rms in 2.5 h.

  2. Power microwave pulse generation of resonant relativistic backward wave tube with power supply based on explosive magnetocumulative generators

    International Nuclear Information System (INIS)

    High-power microwave radiation has been generated using a resonant relativistic backward wave oscillator (BWO) powered by a high voltage source comprising an inductive energy storage and an electric-explosion current switch, the results of the experiment are provided. The high voltage source and the BWO magnetic system are energy pumped by explosive magnetocumulative generators. In the experiments the setup generated 30-ns single-mode radiation pulses with a carrier frequency of 3.6 GHz at a peak power of 0.75 GW

  3. Isolated atto-second pulse generated by spatial shaping of femtosecond laser beam

    International Nuclear Information System (INIS)

    We study numerically the time-dependent HHG phase-matching in the laser beam having a flat-top radial intensity profile. A flat-top profile is the key to produce similar ionization degree at the axis and at the periphery and thus to achieve simultaneous phase-matched generation. Such a profile can be obtained experimentally by using two concentric phase plates that introduce a specific phase shift between the central and the outer part of a focused Gaussian beam. We find realistic laser field parameters and medium density that allow obtaining (after spectral filtering) single atto-second pulse using 10 fs driving laser pulse. Our technique provides isolated atto-second pulse emission almost insensitive on the CEP of the laser pulse. Moreover, the technique is effective both for the mid-plateau and the cut-off spectral range. In particular, the XUV from Ar target in the cut-off spectral range (compatible with the Zr filter) provides isolated atto-second pulse with 185 as duration at a central energy of 92 eV. Using achievable multi mJ 10 fs laser pulses this technique could provide atto-second pulses approaching the μJ energy range. (authors)

  4. Study of a figure-eight laser generating noise-like pulses with adjustable characteristics

    Science.gov (United States)

    Pottiez, O.; Ibarra-Escamilla, B.; Kuzin, E. A.; Hernandez-Garcia, J. C.

    2011-09-01

    In this work we study experimentally and numerically a passively mode-locked figure-eight fiber laser that includes a polarization-imbalanced Nonlinear Optical Loop Mirror (NOLM), whose switching power can be adjusted through a wave retarder plate. The laser emits broadband noise-like pulses with a bandwidth that can exceed 50 nm. The pulses are actually sub-nanosecond wave packets with an inner fine structure of sub-ps pulses with random amplitude and duration. The duration of the pulses as well as their spectral width can be adjusted through the variation of the NOLM switching power. Numerical simulations are in good agreement with experimental results, confirming in particular the strong dependence of the pulse properties on the value of the NOLM switching power, although NOLM switching alone does not explain the appearance of the noise-like pulsing mode. The properties of this kind of pulses, like their wide bandwidth and energy, make them attractive for applications like supercontinuum generation and metrology.

  5. Ultra-short photon pulse generation in relativistic laser-plasmas

    International Nuclear Information System (INIS)

    Optical pulse compression by the linear reflection of a laser pulse from a relativistically moving plasma is studied. Using Lorentz transformations, covariance of Maxwell's equations and the principle of phase invariance to transform between the rest frame and the moving frame, analytics can be exactly performed in the moving frame. Closed-form formulae for reflected waveforms as a function of incident angle show temporal compression and intensity amplification by a factor of 2γ and 4γ2, respectively, where γ is the Lorentz factor of the relativistic electron plasma. As an independent test, fully relativistic electromagnetic particle simulations agree well with analytical results, predicting pulse compression and large amplification to be of relevance to the generation of attosecond optical pulses. (paper)

  6. Analytical solution for the diffusion of a capacitor discharge generated magnetic field pulse in a conductor

    Science.gov (United States)

    Grants, Ilmārs; Bojarevičs, Andris; Gerbeth, Gunter

    2016-06-01

    Powerful forces arise when a pulse of a magnetic field in the order of a few tesla diffuses into a conductor. Such pulses are used in electromagnetic forming, impact welding of dissimilar materials and grain refinement of solidifying alloys. Strong magnetic field pulses are generated by the discharge current of a capacitor bank. We consider analytically the penetration of such pulse into a conducting half-space. Besides the exact solution we obtain two simple self-similar approximate solutions for two sequential stages of the initial transient. Furthermore, a general solution is provided for the external field given as a power series of time. Each term of this solution represents a self-similar function for which we obtain an explicit expression. The validity range of various approximate analytical solutions is evaluated by comparison to the exact solution.

  7. Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

    Science.gov (United States)

    Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti

    2003-12-01

    Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

  8. Simple Method to Generate Terawatt-Attosecond X-Ray Free-Electron-Laser Pulses.

    Science.gov (United States)

    Prat, Eduard; Reiche, Sven

    2015-06-19

    X-ray free-electron lasers (XFELs) are cutting-edge research tools that produce almost fully coherent radiation with high power and short-pulse length with applications in multiple science fields. There is a strong demand to achieve even shorter pulses and higher radiation powers than the ones obtained at state-of-the-art XFEL facilities. In this context we propose a novel method to generate terawatt-attosecond XFEL pulses, where an XFEL pulse is pushed through several short good-beam regions of the electron bunch. In addition to the elements of conventional XFEL facilities, the method uses only a multiple-slotted foil and small electron delays between undulator sections. Our scheme is thus simple, compact, and easy to implement both in already operating as well as future XFEL projects. We present numerical simulations that confirm the feasibility and validity of our proposal. PMID:26196979

  9. Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion

    International Nuclear Information System (INIS)

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization and hence experience a large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with a duration less than 50 as

  10. Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion

    International Nuclear Information System (INIS)

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization, experiencing large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with the duration less than 50 as.

  11. Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors.

    Science.gov (United States)

    Romeira, Bruno; Javaloyes, Julien; Ironside, Charles N; Figueiredo, José M L; Balle, Salvador; Piro, Oreste

    2013-09-01

    We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics. PMID:24103966

  12. Cayley Bipolar Fuzzy Graphs

    OpenAIRE

    Alshehri, Noura O.; Muhammad Akram

    2013-01-01

    We introduce the concept of Cayley bipolar fuzzy graphs and investigate some of their properties. We present some interesting properties of bipolar fuzzy graphs in terms of algebraic structures. We also discuss connectedness in Cayley bipolar fuzzy graphs.

  13. Transtorno bipolar

    Directory of Open Access Journals (Sweden)

    Alda Martin

    1999-01-01

    Full Text Available Os resultados de estudos de famílias sugerem que o transtorno bipolar tenha uma base genética. Essa hipótese foi reforçada em estudos de adoção e de gêmeos. A herança do transtorno bipolar é complexa, envolve vários genes, além de apresentar heterogeneidade e interação entre fatores genéticos e não-genéticos. Achados, que já foram replicados, já implicaram os cromossomos 4, 12, 18 e 21, entre outros, na busca por genes de suscetibilidade. Os resultados mais promissores foram obtidos através de estudos de ligação. Por outro lado, os estudos de associação geraram dados interessantes, mas ainda vagos. Os estudos de populações de pacientes homogêneos e a melhor definição do fenótipo deverão contribuir para avanços futuros. A identificação dos genes relacionados ao transtorno bipolar irá permitir o melhor entendimento e tratamento dessa doença.

  14. Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry.

    Science.gov (United States)

    Hong, Zuofei; Zhang, Qingbin; Lu, Peixiang

    2013-04-22

    A novel compact dual-crystal optical parametric amplification (DOPA) scheme, collinearly pumped by a Ti:sapphire laser (0.8 μm), is theoretically investigated for efficiently generating broadband IR pulses at non-degenerate wavelengths (1.2 μm~1.4 μm and 1.8 μm~2.1 μm). By inserting a pair of barium fluoride (BaF(2)) wedges between two thin β-barium borate (BBO) crystals, the group velocity mismatch (GVM) between the three interacting pulses can be compensated simultaneously. In this case, the obtained signal spectrum centered at 1.3 μm is nearly 20% broader and the conversion efficiency is increased, but also the pulse contrast and beam quality are improved due to the better temporal overlap. Furthermore, sub-two-cycle idler pulses with carrier-envelope phase (CEP) fluctuation of sub-100-mrad root mean square (RMS) can be generated. Because a tunable few-cycle IR pulse with millijoule energy is attainable in this scheme, it will contribute to ultrafast community and be particularly useful as a driving or controlling field for the generation of ultrafast coherent x-ray supercontinuum. PMID:23609660

  15. Generation of tunable few optical-cycle pulses by visible-to-infrared frequency conversion

    Science.gov (United States)

    Darginavičius, J.; Tamošauskas, G.; Piskarskas, A.; Valiulis, G.; Dubietis, A.

    2012-07-01

    We demonstrate a simple method for infrared few optical-cycle pulse generation, which is based on collinear visible-to-infrared frequency conversion and involves difference-frequency generation and subsequent two-step optical parametric amplification. The numerical simulations and experiments using BBO crystals show an efficient frequency down conversion of visible ˜20 fs pulses from a commercial blue-pumped noncollinear optical parametric amplifier yielding 1.2-2.4 μm tunable sub-100 μJ pulses with duration of 3 to 5 optical-cycles. The proposed method could be readily extended to generate few optical-cycle pulses in the mid-infrared spectral range (up to 5.5 μm) using, e.g., LiIO3 and LiNbO3 crystals, as demonstrated by the numerical simulations. In these crystals, even shorter, two-optical-cycle mid-infrared pulses could be obtained at particular wavelengths where group velocity matching between the signal and idler waves is achieved.

  16. Generation of Attosecond X-Ray Pulse through Coherent Relativistic Nonlinear Thomson Scattering

    CERN Document Server

    Lee, K; Jeong, Y U; Lee, B C; Park, S H

    2005-01-01

    In contrast to some recent experimental results, which state that the Nonlinear Thomson Scattered (NTS) radiation is incoherent, a coherent condition under which the scattered radiation of an incident laser pulse by a bunch of electrons can be coherently superposed has been investigated. The Coherent Relativistic Nonlinear Thomson Scattered (C-RNTS) radiation makes it possible utilizing the ultra-short pulse nature of NTS radiation with a bunch of electrons, such as plasma or electron beams. A numerical simulation shows that a 25 attosecond X-ray pulse can be generated by irradiating an ultra-intense laser pulse of 4x10(19) W/cm2 on an ultra-thin solid target of 50 nm thickness, which is commercially available. The coherent condition can be easily extended to an electron beam from accelerators. Different from the solid target, much narrower electron beam is required for the generation of an attosecond pulse. Instead, this condition could be applied for the generation of intense Compton scattered X-rays with a...

  17. Role of phase matching in pulsed second-harmonic generation: Walk-off and phase-locked twin pulses in negative-index media

    International Nuclear Information System (INIS)

    The present investigation is concerned with the study of pulsed second-harmonic generation under conditions of phase and group velocity mismatch, and generally low conversion efficiencies and pump intensities. In positive-index, nonmetallic materials, we generally find qualitative agreement with previous reports regarding the presence of a double-peaked second harmonic signal, which comprises a pulse that walks off and propagates at the nominal group velocity one expects at the second-harmonic frequency, and a second pulse that is 'captured' and propagates under the pump pulse. We find that the origin of the double-peaked structure resides in a phase-locking mechanism that characterizes not only second-harmonic generation, but also χ(3) processes and third-harmonic generation. The phase-locking mechanism that we describe occurs for arbitrarily small pump intensities, and so it is not a soliton effect, which usually relies on a threshold mechanism, although multicolor solitons display similar phase locking characteristics. Thus, in second harmonic generation a phase-matched component is always generated, even under conditions of material phase mismatch: This component is anomalous, because the material does not allow energy exchange between the pump and the second-harmonic beam. On the other hand, if the material is phase matched, phase locking and phase matching are indistinguishable, and the conversion process becomes efficient. We also report a similar phase-locking phenomenon in negative index materials. A spectral analysis of the pump and the generated signals reveals that the phase-locking phenomenon causes the forward moving, phase-locked second-harmonic pulse to experience the same negative index as the pump pulse, even though the index of refraction at the second-harmonic frequency is positive. Our analysis further shows that the reflected second-harmonic pulse generated at the interface and the forward-moving, phase-locked pulse appear to be part of the

  18. Molecular orbital imaging using attosecond pulses generated in N2

    International Nuclear Information System (INIS)

    Complete text of publication follows. The strong interaction of a molecule with a laser field frees by tunnel ionization an attosecond electron wave packet that probes its bound state half a laser cycle later as it re-collides with the core. Rich information on ths (possibly transient) electronic and nuclear configuration is encoded in the attosecond XUV burst emitted during recombination, a process called high-order harmonic generation (HHG). Complete characterization (intensity, phase and polarization) of this observable gives access to the transition dipole moment over a large momentum span. This transition dipole may allow direct imaging of the radiating molecular orbital using a tomographic procedure. For the first time we succeeded to characterize the intensity, phase and polarization of the XUV emission in aligned N2 molecules. Our measurements evidence multi-orbital contributions to the attosecond emission and also reveal the ellipticity of the harmonics. Recent experimental and theoretical studies have revealed that molecules could be tunnel ionized from several orbitals simultaneously. These different orbitals lead to interfering contributions in the attosecond emission. We were able to separate these contributions and by using the tomographic molecular orbital reconstruction technique, HOMO and HOMO-1 orbitals were reconstructed in N2. These reconstructions show remarkable agreement with theoretical simulations and also provide us with the sign changes in the orbital wave functions. An investigation was addressed to the validity of the plane wave approximation in our calculation. The coherent superposition of the HOMO and HOMO-1 orbitals provides time-resolved experimental images of the wave packet ('hole') left empty after coherent tunnel ionization from both orbitals. The recombining electron wave packet probes the 'hole' at the instant of recombination providing information about the electronic structure of the molecule at that moment. This imaging of

  19. Sub-20 fs energetic near-IR pulses generated with cascaded soliton compression in short lithium niobate crystals

    DEFF Research Database (Denmark)

    Zhou, Binbin; Chong, Andy; Wise, Frank W.; Bache, Morten

    2011-01-01

    We show experimentally that sub-20 fs near-infrared pulses can be generated through soliton compression of energetic femtosecond pulses.e compression relies on cascaded type-0 second-harmonic generation in a just 1 mm long lithium niobate crystal.......We show experimentally that sub-20 fs near-infrared pulses can be generated through soliton compression of energetic femtosecond pulses.e compression relies on cascaded type-0 second-harmonic generation in a just 1 mm long lithium niobate crystal....

  20. Laser plasma as a source of intense attosecond pulses via high-order harmonic generation

    International Nuclear Information System (INIS)

    The incredible progress in ultrafast laser technology and Ti:sapphire lasers have lead to many important applications, one of them being high-order harmonic generation (HHG). HHG is a source of coherent extreme ultraviolet (XUV) radiation, which has opened new frontiers in science by extending nonlinear optics and time-resolved spectroscopy to the XUV region, and pushing ultrafast science to the attosecond domain. Progress in attosecond science has revealed many new phenomena that have not been seen with femtosecond pulses. Clearly, the next frontier is to study nonlinear effects at the attosecond timescale and in the XUV. However, a problem with present-day attosecond pulses is that they are just too weak to induce measurable nonlinearities, which severely limits the application of this source. While HHG from solid targets has shown promise for higher conversion efficiency, there is no experiment so far that demonstrates isolated attosecond pulse generation. The generation of isolated, several 100-as pulses with few-µJ energy will enable us to enter a completely new phase in attoscience. In past works, we have demonstrated that high-order harmonics from lowly ionized plasma is a highly efficient method to generate coherent XUV pulses. For example, indium plasma has been shown to generate intense 13th harmonic of the Ti:sapphire laser, with conversion efficiency of 10-4. However, the quasi-monochromatic nature of indium harmonics would make it difficult to generate attosecond pulses. We have also demonstrated that one could increase the harmonic yield by using nanoparticle targets. Specifically, we showed that by using indium oxide nanoparticles or C60 film, we could obtain intense harmonics between wavelengths of 50 to 90 nm. The energy in each of these harmonic orders was measured to be a few µJ, which is sufficient for many applications. However, the problem of using nanoparticle or film targets is the rapid decrease in the harmonic intensity, due to the rapid

  1. Generation of Al nanoparticles via ablation of bulk Al in liquids with short laser pulses.

    Science.gov (United States)

    Stratakis, Emmanuel; Barberoglou, Marios; Fotakis, Costas; Viau, Guillaume; Garcia, Cecile; Shafeev, Georgy A

    2009-07-20

    Highly stable aluminum nanoparticles (NPs) are generated via ablation of bulk Al in ethanol using either femtosecond (fs) or picosecond (ps) laser sources. The colloidal NPs solutions obtained with fs pulses exhibit a yellow coloration and show an increased optical absorption between 300 and 400 nm, tentatively assigned to the plasmon resonance of nanosized Al. The corresponding solutions after ps ablation are gray colored and opalescent. The average size of the NPs formed ranges from 20 nm for the fs case to 60 nm for the ps case, while a narrower distribution is obtained using the shorter pulses. High Resolution Transmission Electron Microscopy (HRTEM) studies indicate that the NPs are mostly amorphous with single crystalline inclusions. Al NPs generated with short laser pulses slowly react with air oxygen due to the presence of a native oxide cladding, which efficiently passivates their surface against further oxidation. PMID:19654669

  2. AREA OPTIMIZED FPGA IMPLEMENTATION FOR GENERATION OF RADAR PULSE COM-PRESSION SEQUENCES

    Directory of Open Access Journals (Sweden)

    P. Tirumala rao

    2011-10-01

    Full Text Available Pulse compression technique is most widely used in radar and communication areas. Its implementationrequires an opti-mized and dedicated hardware. The real time implementation places several constraintssuch as area occupied, power con-sumption, etc. The good design needs optimization of these constraints.This paper concentrates on the design of optimized model which can reduce these. In the proposedarchitecture a single chip is used for generating the pulse compression se-quence like BPSk, QPSk, 6-PSKand other Polyphase codes. The VLSI architecture is implemented on the Field Programm-able Gate Array(FPGA as it provides the flexibility of reconfigurability and reprogrammability .It was found that the proposedarchitecture has generated the pulse compression sequences efficiently while improving some of theparameters like area, power consumption and delay when compared to previous methods.

  3. AREA OPTIMIZED FPGA IMPLEMENTATION FOR GENERATION OF RADAR PULSE COM-PRESSION SEQUENCES

    Directory of Open Access Journals (Sweden)

    P. Tirumala rao

    2015-11-01

    Full Text Available Pulse compression technique is most widely used in radar and communication areas. Its implementation requires an opti-mized and dedicated hardware. The real time implementation places several constraints such as area occupied, power con-sumption, etc. The good design needs optimization of these constraints.This paper concentrates on the design of optimized model which can reduce these. In the proposed architecture a single chip is used for generating the pulse compression sequence like BPSk, QPSk, 6-PSKand other Poly phase codes. The VLSI architecture is implemented on the Field Programmable Gate Array(FPGA as it provides the flexibility of reconfigurability and reprogrammability .It was found that the proposed architecture has generated the pulse compression sequences efficiently while improving some of the parameters like area, power consumption and delay when compared to previous methods.

  4. Laer Pulse Driven THz Generation via Resonant Transition Radiation in Inhomogeneous Plasmas

    CERN Document Server

    Miao, Chenlong; Antonsen, Thomas M

    2016-01-01

    An intense, short laser pulse propagating across a plasma boundary ponderomotively drives THz radiation. Full format PIC simulations and theoretical analysis are conducted to investigate the properties of this radiation. Simulation results show the THz emission originates in regions of varying density and covers a broad spectrum with maximum frequency close to the maximum plasma frequency. In the case of a sharp vacuum-plasma boundary, the radiation is generated symmetrically at the plasma entrance and exit, and its properties are independent of plasma density when the density exceeds a characteristic value determined by the product of the plasma frequency and the laser pulse duration. For a diffuse vacuum-plasma boundary, the emission from the plasma entrance and exit is asymmetric: increasing and decreasing density ramps enhance and diminish the radiated energy respectively. Enhancements by factors of 50 are found and simulations show that a 1.66 J, 50 fs driver pulse can generate ~400 \\mu J of THz radiatio...

  5. Multipass relativistic high-order-harmonic generation for intense attosecond pulses

    Science.gov (United States)

    Edwards, Matthew R.; Mikhailova, Julia M.

    2016-02-01

    We demonstrate that the total reflected field produced by the interaction of a moderately relativistic laser with dense plasma is itself an efficient driver of high-order-harmonic generation. A system of two or more successive interactions of an incident laser beam on solid targets may therefore be an experimentally realizable method of optimizing conversion of laser energy to high-order harmonics. Particle-in-cell simulations suggest that attosecond pulse intensity may be increased by up to four orders of magnitude in a multipass system, with decreased duration of the attosecond pulse train. We discuss high-order-harmonic wave-form engineering for enhanced attosecond pulse generation with an electron trajectory model, present the behavior of multipass systems over a range of parameters, and offer possible routes towards experimental implementation of a two-pass system.

  6. A high voltage pulse generator for exciting a discharge pumped KrF laser amplifier

    International Nuclear Information System (INIS)

    A high voltage pulse generator capable of repetitive operation for exciting a KrF laser amplifier is described. It consists of a constant current source, an energy storage capacitor, a transfer switch, a low impedance Blumlein line, and a multichannel rail-gap switch. The configurations of the Blumlein line and the rail-gap switch are presented. The performance characteristics of the circuits in the charge and discharge loops are analysed. The adjustment of the generator is performed and the experimental results are given. With DC charge voltage 30 kV of the storage capacitor, the Blumlein line output pulse up to 60 kV with a pulse width of 80 ns and a rise time of 30 ns is obtained

  7. Optical short pulse generation at high repetition rate over 80 GHz from a monolithic passively modelocked DBR laser diode

    Science.gov (United States)

    Arahira, S.; Matsui, Y.; Kunii, T.; Oshiba, S.; Ogawa, Y.

    1993-05-01

    Optical short pulses at high repetition rate over 80 GHz were successfully generated using a monolithically fabricated passively modelocked distributed Bragg reflector laser diode for the first time. By using linear fibre compression, a transform-limited optical pulse train with a duration of 2.7 ps was obtained. The pulse envelope closely matched a sech(sup 2) waveform.

  8. Supercontinuum Generation in Normal-dispersion Photonic Crystal Fiber Using Picosecond Pulse

    Institute of Scientific and Technical Information of China (English)

    YAO Li; HE Li; YANG Bo-jun

    2007-01-01

    Studied is the Super-continuum(SC) generation of a normal-dispersion photonic crystal fiber(PCF) using picosecond pulse excitation. In experimental analyses, a 237 nm broadband infrared continuum was generated pumped at 1 550 nm(normal dispersion regime) by 1.6 ps pulses from an erbium-doped fiber laser. In addition, we conduct the numerical analyses of SC based on generalized nonlinear Schr dionger equation. The results have been applied to investigate the dominant physical processes underlie the generation of SC. We conclude that dispersion, self-phase modulation(SPM),four-wave-mixing(FWM) and Raman scattering are determinants of SC generation rather than fission of soliton in normal-dispersion PCF.

  9. UWB doublet signal generation and modulation based on DFB laser under optical pulses injection

    Science.gov (United States)

    Chen, Dalei; Wang, Rong; Xiang, Peng; Pu, Tao; Fang, Tao; Zhou, Hua; Zhao, Jiyong; Huang, Long; Zhu, Huatao; Wang, Peng

    2016-05-01

    In this paper, a novel scheme to generate ultra-wideband (UWB) doublet signals based on the cross-gain modulation (XGM) effect in the DFB lasers is proposed and experimentally demonstrated, the modulation and transmission of the generated UWB doublet signals are also researched. In the proposed system, a gain-switched laser (GSL) is used as a master laser (ML) and the optical pulses from the ML are optically injected into two paralleled DFB lasers, which are used as slave lasers (SL). Then the outputs from the SLs are detected by a balanced photodiode (BPD) to generate the Bi-phased UWB signals. By properly setting the system parameters, UWB signals with various modulation formats such as on-off keying (OOK), pulse amplitude modulation (PAM) as well as the phase-shift keying (PSK) can be generated. In addition, fiber transmission of the modulated UWB signals is also experimentally investigated.

  10. High-order harmonic and attosecond pulse generation on plasma mirrors: basic mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Thaury, C; Quere, F, E-mail: fabien.quere@cea.f [Service des Photons, Atomes et Molecules, Commissariat l' Energie Atomique, DSM/IRAMIS, CEA Saclay, 91191 Gif sur Yvette (France)

    2010-11-14

    When an intense femtosecond laser pulse hits an optically polished surface, it generates a dense plasma that itself acts as a mirror, known as the plasma mirror. As this mirror reflects the high-intensity laser field, its nonlinear temporal response can lead to a periodic temporal distortion of the reflected wave, associated with a train of attosecond light pulses, and, in the frequency domain, to the generation of high-order harmonics of the laser. This tutorial presents detailed theoretical and numerical analysis of the two dominant harmonic generation mechanisms identified so far, coherent wake emission and the relativistic oscillating mirror. Parametric studies of the emission efficiency are presented for these two regimes, and the phase properties of the corresponding harmonics are discussed. This theoretical study is complemented by a synthesis of recent experimental results, which establishes that these two mechanisms indeed dominate harmonic generation on plasma mirrors. (phd tutorial)

  11. High-order harmonic and attosecond pulse generation on plasma mirrors: basic mechanisms

    International Nuclear Information System (INIS)

    When an intense femtosecond laser pulse hits an optically polished surface, it generates a dense plasma that itself acts as a mirror, known as the plasma mirror. As this mirror reflects the high-intensity laser field, its nonlinear temporal response can lead to a periodic temporal distortion of the reflected wave, associated with a train of attosecond light pulses, and, in the frequency domain, to the generation of high-order harmonics of the laser. This tutorial presents detailed theoretical and numerical analysis of the two dominant harmonic generation mechanisms identified so far, coherent wake emission and the relativistic oscillating mirror. Parametric studies of the emission efficiency are presented for these two regimes, and the phase properties of the corresponding harmonics are discussed. This theoretical study is complemented by a synthesis of recent experimental results, which establishes that these two mechanisms indeed dominate harmonic generation on plasma mirrors. (phd tutorial)

  12. Generation of isolated attosecond pulses with a specific waveform two-color laser field

    Institute of Scientific and Technical Information of China (English)

    Jinping Yao; Yao Li; Ya Cheng

    2011-01-01

    We theorotically propose a new methed for generating intense isolated attosceond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an, 8O0-nm, 4-fs elliptically pollarized laser field and a 1400-nm, ~43-fs linearly polarized laser field. With this method, the supercontinua with a spectral width above 200 eV are obtained, which call support a ~15-as isolated pulse after phase compensation Classical and quantum analyses explain the controlling effects well. In particular, when the pules duration of the 800-nm laser field increases to 20- fs,sub-1O0-as isolated pules can be obtained even without any phase compensation%@@ We theoretically propo8e a new method for generating intense isolated attosecond pulses during high-order harmonic generation (HHG) process by accurately controlling electron motion with a two-color laser field,which consists of an 800-nm, 4-fs elliptically polarized laser field and a 1400-nm, ~43-fs linearly polarized laser field.With this method, the supercontinua with a spectral width above 200 eV are obtained, which can support a ~15-as isolated pulse after phase compensation.Classical and quantum analyses explain the controlling effects well.In particular, when the puLse duration of the 800-nm laser field increases to 20-fs, sub-lOO-as isolated pulses can be obtained even without any phase compensation.

  13. Generation of time-dependent ultra-short optical pulse trains in the presence of self-steepening effect

    Institute of Scientific and Technical Information of China (English)

    Zhong Xian-Qiong; Xiang An-Ping

    2009-01-01

    Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as timc gocs on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intcnsity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.

  14. Generation of time-dependent ultra-short optical pulse trains in the presence of self-steepening effect

    International Nuclear Information System (INIS)

    Starting from the extended nonlinear Schrödinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider. (classical areas of phenomenology)

  15. Analysis and simulation for startup process of pulsed motor generators in HL-2A

    International Nuclear Information System (INIS)

    In this paper the startup process of the high-power motor-flywheel pulsed generators in HL-2A is briefly introduced. The simulation models for the startup process of the motor generators are discussed and set up in detail by using the Matlab/Simulink. Some waveforms from a primary simulation result are given out. They almost correspond with that from the real startup process of the motor generators at the similar conditions. So the models can be used as an important tool to study the dynamic characteristic and the control rules of the startup process of the motor generators in HL-2A. (authors)

  16. Second harmonic generation and pulse shaping in positively and negatively spatially dispersive nanowaveguides: comparative analysis

    CERN Document Server

    Popov, Alexander K

    2015-01-01

    Comparative analysis of second harmonic generation in ordinary and backward-wave settings is presented. Extraordinary properties of frequency doubling nonlinear optical reflectivity and pulse shaping through phase matching of ordinary and backward electromagnetic waves in the nanowaveguides with mixed negative/positive spatial dispersion is demonstrated with numerical simulations.

  17. Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction

    Institute of Scientific and Technical Information of China (English)

    李玉同; 张杰; 陈黎明; 赵理曾; 夏江帆; 魏志义; 江文勉

    2000-01-01

    The quasistatic axial magnetic fields in plasmas produced by ultrashort laser pulses were measured by measuring the Faraday rotation angle of the backscattered emission. The spatial distribution of the axial magnetic field was obtained with a peak value as high as 170 Tesla. Theory suggests that the axial magnetic field is generated by dynamo effect in laser-plasma interaction.

  18. 76 FR 64223 - Cardiovascular Devices; Reclassification of External Pacemaker Pulse Generator Devices

    Science.gov (United States)

    2011-10-17

    ... premarket approval for external pacemaker pulse generator devices (52 FR 17732, May 11, 1987). In 2009, FDA... rule (44 FR 13284, March 9, 1979 and 44 FR 13372, March 9, 1979), the Cardiovascular Devices Panel..., 2009 (74 FR 16214, April 9, 2009). In response to that order, FDA received reclassification...

  19. Broadband supercontinuum generation in an extremely nonlinear extruded lead silicate holey fiber using weak fs pulses

    OpenAIRE

    Leong, J.Y.Y.; Petropoulos, P.; Price, J.H.V.; Ebendorff-Heidepriem, H.; Asimakis, S.; Moore, R. C.; Frampton, K.E.; Finazzi, V.; X. Feng; Monro, T.M.; Richardson, D. J.

    2005-01-01

    Broadband supercontinuum generation at 1.06 ?m spanning > 1000 nm and extending to the visible is observed in a dispersion optimized holey fiber with a record-high nonlinearity (1860 W at 1.55 ?m), for launched pulse energies < 100 pJ.

  20. Picosecond strain pulses generated by a supersonically expanding electron-hole plasma in GaAs

    Science.gov (United States)

    Young, E. S. K.; Akimov, A. V.; Campion, R. P.; Kent, A. J.; Gusev, V.

    2012-10-01

    Strain pulses with picosecond duration are generated directly in GaAs by optical excitation from a femtosecond laser. The photons are absorbed in a 15-nm layer near the surface, creating the electron-hole plasma, which diffusively expands into the bulk of the GaAs. At an early time, the drift velocity of the expanding plasma exceeds the speed of longitudinal sound, and the generated strain pulses cannot escape the plasma cloud. Such supersonic generation of strain pulses results in specific temporal and spatial shapes of the generated strain pulses, where the compression part has a much lower amplitude than the tensile part. This phenomenon is studied experimentally at low temperatures and analyzed theoretically based on the wave and diffusion equations for strain and plasma density, respectively. Two mechanisms, deformation potential and thermoelasticity, are responsible for the experimental observations. The relative contributions from these mechanisms are governed by the nonradiative recombination rate in the plasma and depend on the optical excitation density, inducing such nonlinear optoacoustic effects as shortening of the leading strain front and a superlinear/quadratic increase in its amplitude with the rise of pump laser fluence.