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Sample records for bipolar pulse generator

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bochkov, E. I.; Babich, L. P., E-mail: babich@elph.vniief.ru; Kutsyk, I. M. [All-Russia Research Institute of Experimental Physics, Russian Federal Nuclear Center (Russian Federation)

    2013-07-15

    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 {gamma}-ray flashes (TGFs), which can be an argument in favor of a unified NBP and TGF source.

  7. 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.

  8. 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).

  9. 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.

  10. 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...

  11. 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 ...

  12. 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.

  13. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  14. 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

  15. 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.

  16. Pulsed Artificial Electrojet Generation

    Science.gov (United States)

    Papadopoulos, K.

    2008-12-01

    Traditional techniques for generating low frequency signals in the ULF/ELF range (.1-100 Hz) and rely on ground based Horizontal Electric Dipole (HED) antennas. It is, furthermore, well known that a Vertical Electric Dipole (VED) is by more than 50 dB more efficient than a HED with the same dipole current moment. However, the prohibitively long length of VED antennas in the ELF/ULF range coupled with voltage limitations due to corona discharge in the atmosphere make them totally impracticable. In this paper we discuss a novel concept, inspired by the physics of the equatorial electrojet, that allows for the conversion of a ground based HED to a VED in the E-region of the equatorial ionosphere with current moment comparable to the driving HED. The paper focuses in locations near the dip-equator, where the earth's magnetic is in predominantly in the horizontal direction. The horizontal electric field associated with a pulsed HED drives a large Hall current in the ionospheric E-region, resulting in a vertical current. It is shown that the pulsed vertical current in the altitude range 80-130 km, driven by a horizontal electric field of, approximately, .1 mV/m at 100 km altitude, is of the order of kA. This results in a pulsed VED larger than 106 A-m. Such a pulsed VED will drive ELF/ULF pulses with amplitude in excess of .1 nT at a lateral range larger than few hundred kilometers. This is by three orders of magnitude larger than the one expected by a HED with comparable current moment. The paper will conclude with the description of a sneak-through technique that allows for creating pulsed electric fields in the ionosphere much larger than expected from steady state oscillatory HED antennas.

  17. 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.

  18. 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.

  19. Coiled transmission line pulse generators

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, Kenneth Fox (Columbia, MO)

    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.

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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.

  5. QUALITY TESTING OF HEAT TREATMENT OF MEDIUM-CARBON STEEL CONSTRUCTION ITEMS BASED ON THE BIPOLAR PULSED REMAGNETIZATION

    Directory of Open Access Journals (Sweden)

    V. F. Matyuk

    2014-01-01

    Full Text Available The features of bipolar pulsed remagnetization of construction medium-carbon steel items for testing the heat treatment temperature and structure of these items are discussed, the methods of bipolar pulse remagnetization providing testing of items of considered steels are suggested.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. A Vector Network Analyzer Based on Pulse Generators

    Directory of Open Access Journals (Sweden)

    B. Schulte

    2005-01-01

    Full Text Available A fast four channel network analyzer is introduced to measure S-parameters in a frequency range from 10MHz to 3GHz. The signal generation for this kind of analyzer is based on pulse generators, which are realized with bipolar transistors. The output signal of the transistor is differentiated and two short pulses, a slow and a fast one, with opposite polarities are generated. The slow pulse is suppressed with a clipping network. Thus the generation of very short electrical pulses with a duration of about 100ps is possible. The structure of the following network analyzer is similar to the structure of a conventional four channel network analyzer. All four pulses, which contain the high frequency information of the device under test, are evaluated after the digitalization of intermediate frequencies. These intermediate frequencies are generated with sampling mixers. The recorded data is evaluated with a special analysis technique, which is based on a Fourier transformation. The calibration techniques used are the same as for conventional four channel network analyzers, no new calibration techniques need to be developed.

  11. 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)

  12. High-speed pulse-shape generator, pulse multiplexer

    Science.gov (United States)

    Burkhart, Scott C.

    2002-01-01

    The invention combines arbitrary amplitude high-speed pulses for precision pulse shaping for the National Ignition Facility (NIF). The circuitry combines arbitrary height pulses which are generated by replicating scaled versions of a trigger pulse and summing them delayed in time on a pulse line. The combined electrical pulses are connected to an electro-optic modulator which modulates a laser beam. The circuit can also be adapted to combine multiple channels of high speed data into a single train of electrical pulses which generates the optical pulses for very high speed optical communication. The invention has application in laser pulse shaping for inertial confinement fusion, in optical data links for computers, telecommunications, and in laser pulse shaping for atomic excitation studies. The invention can be used to effect at least a 10.times. increase in all fiber communication lines. It allows a greatly increased data transfer rate between high-performance computers. The invention is inexpensive enough to bring high-speed video and data services to homes through a super modem.

  13. 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 ...

  14. 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

  15. 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)

  16. 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

  17. 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

  18. 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.)

  19. 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 ...

  20. 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.

  1. 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

  2. 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

  3. Brain structure-function associations in multi-generational families genetically enriched for bipolar disorder.

    Science.gov (United States)

    Fears, Scott C; Schür, Remmelt; Sjouwerman, Rachel; Service, Susan K; Araya, Carmen; Araya, Xinia; Bejarano, Julio; Knowles, Emma; Gomez-Makhinson, Juliana; Lopez, Maria C; Aldana, Ileana; Teshiba, Terri M; Abaryan, Zvart; Al-Sharif, Noor B; Navarro, Linda; Tishler, Todd A; Altshuler, Lori; Bartzokis, George; Escobar, Javier I; Glahn, David C; Thompson, Paul M; Lopez-Jaramillo, Carlos; Macaya, Gabriel; Molina, Julio; Reus, Victor I; Sabatti, Chiara; Cantor, Rita M; Freimer, Nelson B; Bearden, Carrie E

    2015-07-01

    Recent theories regarding the pathophysiology of bipolar disorder suggest contributions of both neurodevelopmental and neurodegenerative processes. While structural neuroimaging studies indicate disease-associated neuroanatomical alterations, the behavioural correlates of these alterations have not been well characterized. Here, we investigated multi-generational families genetically enriched for bipolar disorder to: (i) characterize neurobehavioural correlates of neuroanatomical measures implicated in the pathophysiology of bipolar disorder; (ii) identify brain-behaviour associations that differ between diagnostic groups; (iii) identify neurocognitive traits that show evidence of accelerated ageing specifically in subjects with bipolar disorder; and (iv) identify brain-behaviour correlations that differ across the age span. Structural neuroimages and multi-dimensional assessments of temperament and neurocognition were acquired from 527 (153 bipolar disorder and 374 non-bipolar disorder) adults aged 18-87 years in 26 families with heavy genetic loading for bipolar disorder. We used linear regression models to identify significant brain-behaviour associations and test whether brain-behaviour relationships differed: (i) between diagnostic groups; and (ii) as a function of age. We found that total cortical and ventricular volume had the greatest number of significant behavioural associations, and included correlations with measures from multiple cognitive domains, particularly declarative and working memory and executive function. Cortical thickness measures, in contrast, showed more specific associations with declarative memory, letter fluency and processing speed tasks. While the majority of brain-behaviour relationships were similar across diagnostic groups, increased cortical thickness in ventrolateral prefrontal and parietal cortical regions was associated with better declarative memory only in bipolar disorder subjects, and not in non-bipolar disorder family

  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. Thyristor stack for pulsed inductive plasma generation.

    Science.gov (United States)

    Teske, C; Jacoby, J; Schweizer, W; Wiechula, J

    2009-03-01

    A thyristor stack for pulsed inductive plasma generation has been developed and tested. The stack design includes a free wheeling diode assembly for current reversal. Triggering of the device is achieved by a high side biased, self supplied gate driver unit using gating energy derived from a local snubber network. The structure guarantees a hard firing gate pulse for the required high dI/dt application. A single fiber optic command is needed to achieve a simultaneous turn on of the thyristors. The stack assembly is used for switching a series resonant circuit with a ringing frequency of 30 kHz. In the prototype pulsed power system described here an inductive discharge has been generated with a pulse duration of 120 micros and a pulse energy of 50 J. A maximum power transfer efficiency of 84% and a peak power of 480 kW inside the discharge were achieved. System tests were performed with a purely inductive load and an inductively generated plasma acting as a load through transformer action at a voltage level of 4.1 kV, a peak current of 5 kA, and a current switching rate of 1 kA/micros. PMID:19334940

  7. Thyristor stack for pulsed inductive plasma generation.

    Science.gov (United States)

    Teske, C; Jacoby, J; Schweizer, W; Wiechula, J

    2009-03-01

    A thyristor stack for pulsed inductive plasma generation has been developed and tested. The stack design includes a free wheeling diode assembly for current reversal. Triggering of the device is achieved by a high side biased, self supplied gate driver unit using gating energy derived from a local snubber network. The structure guarantees a hard firing gate pulse for the required high dI/dt application. A single fiber optic command is needed to achieve a simultaneous turn on of the thyristors. The stack assembly is used for switching a series resonant circuit with a ringing frequency of 30 kHz. In the prototype pulsed power system described here an inductive discharge has been generated with a pulse duration of 120 micros and a pulse energy of 50 J. A maximum power transfer efficiency of 84% and a peak power of 480 kW inside the discharge were achieved. System tests were performed with a purely inductive load and an inductively generated plasma acting as a load through transformer action at a voltage level of 4.1 kV, a peak current of 5 kA, and a current switching rate of 1 kA/micros.

  8. 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

    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...... of oxidatively generated DNA and RNA damage, respectively, was measured in 37 rapid cycling patients with bipolar disorder and in 40 age- and gender-matched healthy control subjects. Employing a longitudinal design, repeated measurements of both markers were evaluated in various affective phases in patients...... 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...

  9. 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%

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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...

  16. 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.

  17. 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...

  18. Coal analysis using the pulsed neutron generator

    Institute of Scientific and Technical Information of China (English)

    JING Shi-Wei; CHI Yan-Tao; ZHAO Xin-Hui; LIU Lin-Mao; GU De-Shan; QIAO Shuang; SANG Hai-Feng; ZHANG Yong-Xiang; ZHANG Zhong-Hua; CAO Xi-Zheng; TIAN Yu-Bing

    2003-01-01

    A prototype of elemental analyzer for coal has been developed by using a PFTNA (pulse fast thermalneutron analysis) system. The PFTNA technology is based on the reactions such as (n, γ), (n, n'γ), (n, Pγ), etc. byexamining the characteristic gamma rays emitted. In our prototype a pulsed neutron generator provides 14 MeV pulseneutrons, which contribute to the separation of spectrum Ⅱ (the sum of capture and activation spectrum) fiom spec-trum Ⅰ (the sum of inelastic, capture and activation spectrum), and thus to the measurement of C and O contents incoal. Data management is completed by computer program using the least-square regression method. The experimentin Changshan Power Plant for 3 months showed that the precision of calorific value, whole water, volatile content andash content is 0.5 k J/kg, 1.0 wt%, 2.0 wt% and 1.5 wt%, respectively.

  19. High voltage pulse generator. [Patent application

    Science.gov (United States)

    Fasching, G.E.

    1975-06-12

    An improved high-voltage pulse generator is described which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of the first rectifier connected between the first and second capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. The output voltage can be readily increased by adding additional charging networks. The circuit allows the peak level of the output to be easily varied over a wide range by using a variable autotransformer in the charging circuit.

  20. Dynamic parabolic pulse generation using temporal shaping of wavelength to time mapped pulses.

    Science.gov (United States)

    Nguyen, Dat; Piracha, Mohammad Umar; Mandridis, Dimitrios; Delfyett, Peter J

    2011-06-20

    Self-phase modulation in fiber amplifiers can significantly degrade the quality of compressed pulses in chirped pulse amplification systems. Parabolic pulses with linear frequency chirp are suitable for suppressing nonlinearities, and to achieve high peak power pulses after compression. In this paper, we present an active time domain technique to generate parabolic pulses for chirped pulse amplification applications. Pulses from a mode-locked laser are temporally stretched and launched into an amplitude modulator, where the drive voltage is designed using the spectral shape of the input pulse and the transfer function of the modulator, resulting in the generation of parabolic pulses. Experimental results of pulse shaping with a pulse train from a mode-locked laser are presented, with a residual error of less than 5%. Moreover, an extinction ratio of 27 dB is achieved, which is ideal for chirped pulse amplification applications.

  1. Generation And Measurement Of High Contrast Ultrashort Intense Laser Pulses

    CERN Document Server

    Konoplev, O A

    2000-01-01

    In this thesis, the generation and measurement of high contrast, intense, ultrashort pulses have been studied. Various factors affecting the contrast and pulse shape of ultrashort light pulses from a chirped pulse amplification (CPA) laser system are identified. The level of contrast resulting from influence of these factors is estimated. Methods for improving and controlling the pulse shape and increasing the contrast are discussed. Ultrahigh contrast, 1-ps pulses were generated from a CPA system with no temporal structure up to eleven orders of magnitude. This is eight orders of magnitude higher contrast than the original pulse. This contrast boost was achieved using two techniques. One is the optical pulse cleaning based on the nonlinear birefringence of the chirping fiber and applied to the pulses before amplification. The other is the fast saturable absorber. The fast saturable absorber was placed after amplification and compression of the pulse. The measurements of high-contrast, ultrashort pulse with h...

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. An Ultra Low Noise Self-Starting Pulse Generator

    DEFF Research Database (Denmark)

    Lasri, J.; Bilenca, A.; Dahan, D.;

    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....

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Generation of life events in bipolar spectrum disorders: a re-examination and extension of the stress generation theory.

    Science.gov (United States)

    Bender, Rachel E; Alloy, Lauren B; Sylvia, Louisa G; Urosevic, Snezana; Abramson, Lyn Y

    2010-09-01

    The extent to which stress generation occurs in bipolar spectrum disorders (BSD) is not well understood. The present study examined whether 75 BSD participants experienced elevated rates of behavior-dependent life events, as compared with 38 normal control participants. Within the BSD group, we also examined whether depressive or hypomanic symptoms prospectively predicted increases in various types of negative and positive life events. Results indicated that BSD participants experienced overall increases in behavior-dependent events over the follow-up, as compared with normal controls. At the symptom level, the event generation process occurred in more specific event domains. Results suggest that the stress generation theory of unipolar depression can be extended to BSD and that the type of generated events may be polarity-specific.

  13. 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.

  14. 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%.

  15. 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)

  16. Exawatt-Zettawatt Pulse Generation and Applications

    CERN Document Server

    Mourou, G A; Malkin, V M; Toroker, Z; Khazanov, E A; Sergeev, A M; Tajima, T

    2011-01-01

    A new amplification method, weaving the three basic compression techniques, Chirped Pulse Amplification (CPA), Optical Parametric Chirped Pulse Amplification (OPCPA) and Plasma Compression by Backward Raman Amplification (BRA) in plasma, is proposed. It is called C3 for Cascaded Conversion Compression. It has the capability to compress with good efficiency kilojoule to megajoule, nanosecond laser pulses into femtosecond pulses, to produce exawatt and beyond peak power. In the future, C3 could be used at large-scale facilities such as the National Ignition Facility (NIF) or the Laser Megajoule (LMJ) and open the way to zettawatt level pulses. The beam will be focused to a wavelength spot size with a f#1. The very small beam size, i.e. few centimeters, along with the low laser repetition rate laser system will make possible the use of inexpensive, precision, disposable optics. The resulting intensity will approach the Schwinger value, thus opening up new possibilities in fundamental physics.

  17. 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.

  18. 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...

  19. 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

  20. 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)

  1. Influence of the external component on the damage of the bipolar transistor induced by the electromagnetic pulse

    Science.gov (United States)

    Xiaowen, Xi; Changchun, Chai; Xingrong, Ren; Yintang, Yang; Zhenyang, Ma; Jing, Wang

    2010-07-01

    A study on the influence of the external resistor and the external voltage source during the injection of the electromagnetic pulse (EMP) into the bipolar transistor (BJT) is carried out. Research shows that the increase of the external resistor Rb at base makes the burnout time of the device decrease slightly, the increase of the external voltage source Vbe at base can aid the damage of the device when the magnitude of the injecting voltage is relatively low and has little influence when the magnitude is sufficiently high causing the device appearing the PIN structure damage, and the increase of the external resistor Re can remarkably reduce the voltage drops added to the device and improve the durability of the device. In the final analysis, the effect of the external circuit component on the BJT damage is the influence on the condition which makes the device appear current-mode second breakdown.

  2. Optical pulse generation system for the National Ignition Facility (NIF)

    Energy Technology Data Exchange (ETDEWEB)

    Penko, F; Braucht,; Browning, D; Crane, J K; Dane, B; Deadrick, F; Dreifuerst, G; Henesian, M; Jones, B A; Kot, L; Laumann, C; Martinez, M; Moran, B; Rothenberg, J E; Skulina, K; Wilcox, R B

    1998-06-18

    We describe the Optical Pulse Generation (OPG) system for the National Ignition Facility ( NIF ). The OPG system begins with the Master Oscillator Room ( MOR ) where the initial, seed pulse for the entire laser system is produced and properly formatted to enhance ignition in the target. The formatting consists of temporally shaping the pulse and adding additional bandwidth to increase the coupling of the laser generated x-rays to the high density target plasma. The pulse produced in the MOR fans out to 48 identical preamplifier modules where it is amplified by a factor of ten billion and spatially shaped for injection into the 192 main amplifier chai

  3. 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

  4. 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.

  5. 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.

  6. 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 ...

  7. 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.

  8. 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.

  9. Effects of chirp of pump pulses on broadband terahertz pulse spectra generated by optical rectification

    Science.gov (United States)

    Hamazaki, Junichi; Furusawa, Kentaro; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-11-01

    The effects of the chirp of the pump pulse in broadband terahertz (THz) pulse generation by optical rectification (OR) in GaP were systematically investigated. It was found that the pre-compensation for the dispersion of GaP is important for obtaining smooth and single-peaked THz spectra as well as high power-conversion efficiency. It was also found that an excessive amount of chirp leads to distortions in THz spectra, which can be quantitatively analyzed by using a simple model. Our results highlight the importance of accurate control over the chirp of the pump pulse for generating broadband THz pulses by OR.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. Resonant dispersive waves generated with multi-input femtosecond pulses

    Science.gov (United States)

    Wang, Kai; Peng, Jiahui; Sokolov, Alex

    2010-10-01

    We investigated the resonant dispersive waves generated by high-order dispersion theoretically. We considered different femtosecond pulses propagating in the kagome-lattice hollow-core photonics crystal fibers. The two third order and fourth order resonant dispersive waves would be produced in the visible range to produce the ultrashort pulse.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

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

    Science.gov (United States)

    Su, Jiancang; Zhang, Xibo; Li, Rui; Zhao, Liang; Sun, Xu; Wang, Limin; Zeng, Bo; Cheng, Jie; Wang, Ying; Peng, Jianchang; Song, Xiaoxin

    2014-06-01

    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.

  2. 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

  3. 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.

  4. A PC-controlled voltage pulse generator for electroanalytical applications

    Science.gov (United States)

    Heredia-López, Francisco J.; Góngora-Alfaro, José L.; Alvarez-Cervera, Fernando J.; Bata-García, José Luis

    1997-04-01

    We present the design of a voltage pulse generator controlled by an IBM or compatible AT Personal Computer (PC) capable of synthesizing some of the voltage pulse wave forms commonly used in electrochemical studies. The included signals are: differential pulse voltametry, differential normal pulse voltametry, and differential pulse amperometry. Additionally, a triangular wave form and a constant-voltage signal, used in the pretreatment of carbon fiber microelectrodes for neurochemical analysis, are also available. Operating the generator imposes a minimum of restrictions on the specification of the duration, amplitude, and type of wave shapes. Low-cost PC-based design allows for compatibility, portability, and versatility. The operating ranges of the wave form parameters for the three voltametric signals are: initial voltage, -0.9-+0.9 V; step amplitude, 0.1-900 mV; period, 6 ms-60 s; measuring pulse amplitude, 0.1-900 mV; measuring pulse duration, 2 ms-20 s; prepulse duration, 2 ms-20 s. In the electrode pretreatment mode, the operating ranges are: amplitude, 0-±5 V; duration, unlimited; frequency, 15-240 Hz. The generator uses its own time base for the generation of all signals, thereby rendering it independent of processor clock speed or power-line frequency. The results of the experimental evaluation indicate that the system is accurate within ±10% of the expected values, taking into account the errors associated with the signal synthesis and the digitizing process. The maximum achievable scan rate is 500 V/s, and the highest frequency for the triangular wave form is 240 Hz. Therefore, the pulse generator could be used for fast cyclic voltametry (FCV). FCV and other wave forms could be added through software modules, without any hardware changes. We conclude that the PC-based electrochemistry pulse generator represents an economical and flexible alternative for electroanalytical applications.

  5. 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

  6. 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)

  7. 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...

  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. Generation of Low Jitter Laser Diode Pulse With External Pulse Injection

    Institute of Scientific and Technical Information of China (English)

    Olaf; Reimann; Dieter; Huhse; Dieter; Bimberg

    2003-01-01

    One gain-switched laser diode(LD) was used as external injection seeding source, to reduce the timing jitter of another gain-switched LD, This technique can generate low jitter, frequency-free and wavelength tunable laser pulse.

  10. 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)

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  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. 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

  19. 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.

  20. 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. PMID:27370452

  1. A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

    Science.gov (United States)

    Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

    2010-03-01

    A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

  2. 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...

  3. 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)

  4. 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 ...

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Generation of attosecond pulse pair in polar media by chirped few-cycle pulses

    Science.gov (United States)

    Hu, Pidong; Niu, Yueping; Wang, Xiangxin; Gong, Shangqing; Liu, Chengpu

    2016-09-01

    The high-order harmonic generation in a polar medium driven by an initially chirped few-cycle laser pulse is investigated via numerically solving the nonlinear Bloch or Maxwell-Bloch equations based on whether propagation effects are taken into account or not. As a result of the reduction of quantum trajectories number due to the introduction of chirps, an attosecond pulse pair (APP) is generated instead of a general attosecond pulse train. Moreover, the time delay between the two attosecond pulses is tunable. When propagation effects take roles, the peak intensities of the APP can be enhanced at suitable propagation distances without observable duration broadening, and such an enhancement can be modulated by changing medium density.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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}

  15. High-voltage pulsed generators for electro-discharge technologies

    Science.gov (United States)

    Kovalchuk, B. M.; Kharlov, A. V.; Kumpyak, E. V.; Sinebrykhov, V. A.

    2013-09-01

    A high-voltage pulse technology is one of effective techniques for the disintegration and milling of rocks, separation of ores and synthesized materials, recycling of building and elastoplastic materials. We present here the design and test results of two portable HV pulsed generators, designed for materials fragmentation, though some other technological applications are possible as well. Generator #1 consists of low voltage block, high voltage transformer, high voltage capacitive storage block, two electrode gas switch, fragmentation chamber and control system block. Technical characteristics of the #1 generator: stored energy in HV capacitors can be varied from 50 to 1000 J, output voltage up to 300 kV, voltage rise time ~ 50 ns, typical operation regime 1000 pulses bursts with a repetitive rate up to 10 Hz. Generator #2 is made on an eight stages Marx scheme with two capacitors (100 kV-400 nF) per stage, connected in parallel. Two electrode spark gap switches, operated in atmospheric air, are used in the Marx generator. Parameters of the generator: stored energy in capacitors 2÷8 kJ, amplitude of the output voltage 200÷400 kV, voltage rise time on a load 50÷100 ns, repetitive rate up to 0.5 Hz. The fragmentation process can be controlled within a wide range of parameters for both generators.

  16. 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.

  17. Characterization of oxide films formed on magnesium alloys using bipolar pulse microarc oxidation in phosphate solutions

    Institute of Scientific and Technical Information of China (English)

    WANG Li-shi; CAI Qi-zhou; WEI Bo-kang; LIU Quan-xin

    2005-01-01

    The surface morphology and chemical composition of the oxide films formed on pure magnesium and AZ91D alloy in aqueous electrolytes which contained sodium hexafluorinealuminate(Na3 AlF6), potassium hydroxide (KOH), sodium hexametahposphate ((NaPO3)6), and triethanolamine were investigated by X-ray diffraction (XRD), scanning electron microscope(SEM) and energy dispersive spectroscopy(EDX). The results show that the input of the negative pulse has great influences on the quantity and the appearance of the microdischarges. Three types of pores can be distinguished on the surface of the oxide film and their size ranges are 0.5 - 1 μm, 1 -2μm and 4- 7 μm, respectively. A few microcracks are seen around the large pores. There exists a remarkable fluorideenriched zone of about 4 -6 μm for pure magnesium and 3 -5 μm for AZ91D alloy at the coating/substrate interface.

  18. 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

  19. Photoacoustic-pulse generation and propagation in a metal vapor.

    Science.gov (United States)

    Tam, A C; Zapka, W; Chiang, K; Imaino, W

    1982-01-01

    Photoacoustic-pulse generation by breakdown is achieved in dense cesium metal vapors of vapor pressures ranging from 2 to 130 Torr by using a dye laser pulse of energy variable from 10(-6) to 10(-3) J, tuned to the Cs transition at 6010 A. The acoustic-pulse propagation is detected by the transient photorefractive deflection of a cw probe laser beam that is displaced from but parallel to the pulsed laser beam. The temperature-dependent velocity of infinitesimal ultrasonic waves in a corrosive metal vapor is measured for the first time. The supersonic propagation of finite amplitude acoustic pulses (blast waves) obtained with a higher pulse energy is also studied. Our data, with Mach numbers ranging from 2.1 down to below 1.01, agree surprisingly well with the prediction of Vlases and Jones for cylindrical blast waves. This provides a new experimental support for their theoretical trajectory formula for blast waves in the extremely weak amplitude limit. PMID:20372402

  20. 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.

  1. 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...

  2. 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.

  3. Repetition rate tunable ultra-short optical pulse generation based on electrical pattern generator

    Institute of Scientific and Technical Information of China (English)

    Xin Fu; Hongming Zhang; Meng Yan; Minyu Yao

    2009-01-01

    @@ An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator.By changing the repetition rate of the electrical patterns applied on the in-cavity modulator, the repetition rate of the output optical pulse sequences changes accordingly while the pulse width of the optical pulse train remains almost constant.In other words, the output ultra-short pulse train has a tunable duty cycle.In a proof-of-principle experiment, optical pulses with repetition rates of 10, 5, 2.5 and 1.25 GHz are obtained by adjusting the electrical pattern applied on the in-cavity modulator while their pulse widths remain almost unchanged.

  4. 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%.

  5. 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%.

  6. A 70 kV solid-state high voltage pulse generator based on saturable pulse transformer.

    Science.gov (United States)

    Fan, Xuliang; Liu, Jinliang

    2014-02-01

    High voltage pulse generators are widely applied in many fields. In recent years, solid-state and operating at repetitive mode are the most important developing trends of high voltage pulse generators. A solid-state high voltage pulse generator based on saturable pulse transformer is proposed in this paper. The proposed generator is consisted of three parts. They are charging system, triggering system, and the major loop. Saturable pulse transformer is the key component of the whole generator, which acts as a step-up transformer and main switch during working process of this generator. The circuit and working principles of the proposed pulse generator are introduced first in this paper, and the saturable pulse transformer used in this generator is introduced in detail. Circuit of the major loop is simulated to verify the design of the system. Demonstration experiments are carried out, and the results show that when the primary energy storage capacitor is charged to a high voltage, such as 2.5 kV, a voltage with amplitude of 86 kV can be achieved on the secondary winding. The magnetic core of saturable pulse transformer is saturated deeply and the saturable inductance of the secondary windings is very small. The switch function of the saturable pulse transformer can be realized ideally. Therefore, a 71 kV output voltage pulse is formed on the load. Moreover, the magnetic core of the saturable pulse transformer can be reset automatically.

  7. 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.

  8. 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.

  9. 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.}

  10. Nanosecond pulsed laser generation of holographic structures on metals

    Science.gov (United States)

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

    2016-03-01

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

  11. 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.

  12. 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%

  13. 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

  14. 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.

  15. 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

  16. A Simple Picosecond Pulse Generator Based on a Pair of Step Recovery Diodes

    CERN Document Server

    Zou, Lianfeng; Caloz, Christophe

    2016-01-01

    A picosecond pulse generator based on a pair of step recovery diodes (SRD), leveraging the transient response of the SRD PN junction and controlling the pulse width by a resistor, is proposed. We first explain the operation principle of the device, decomposing the pulse generation into different phases, and then demonstrate an experimental prototype with two different resistance, and hence pulse width, values.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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 ...

  2. 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.

  3. Photoconductive switch enhancements for use in Blumlein pulse generators

    Science.gov (United States)

    Davanloo, F.; Park, H.; Collins, C. B.; Agee, F. J.

    1999-06-01

    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.

  4. 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

  5. Bipolar Disorder.

    Science.gov (United States)

    Miller, Thomas H

    2016-06-01

    Bipolar disorder is a chronic mental health disorder that is frequently encountered in primary care. Many patients with depression may actually have bipolar disorder. The management of bipolar disorder requires proper diagnosis and awareness or referral for appropriate pharmacologic therapy. Patients with bipolar disorder require primary care management for comorbidities such as cardiovascular and metabolic disorders. PMID:27262007

  6. Generation of sub-50 fs pulses from a high-power Yb-doped fiber amplifier.

    Science.gov (United States)

    Deng, Yujun; Chien, Ching-Yuan; Fidric, Bernard G; Kafka, James D

    2009-11-15

    We demonstrate the generation of 48 fs pulses with 18 W average power and 226 nJ of pulse energy from a Yb-doped fiber amplifier. The system uses a simple stretcher-free single-stage amplifier configuration operating in the parabolic pulse regime. The gain fiber length and pump wavelength are chosen in order to reduce the gain per unit length and generate both shorter pulses and higher pulse energy.

  7. 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...

  8. 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

  9. Metabolic syndrome and serum homocysteine in patients with bipolar disorder and schizophrenia treated with second generation antipsychotics.

    Science.gov (United States)

    Vuksan-Ćusa, Bjanka; Jakovljević, Miro; Sagud, Marina; Mihaljević Peleš, Alma; Marčinko, Darko; Topić, Radmila; Mihaljević, Sanea; Sertić, Jadranka

    2011-08-30

    There is accumulating evidence for an increased prevalence of metabolic syndrome (MetS) in bipolar patients, which is comparable to the prevalence of MetS in patients with schizophrenia. Hyperhomocysteinaemia has emerged as an independent and graded risk factor for the development of cardiovascular disease (CVD), which is, at the same time, the primary clinical outcome of MetS. The aim of this study was to ascertain if the presence of MetS was associated with hyperhomocysteinaemia in patients with bipolar disorder (N=36) and schizophrenia (N=46) treated with second-generation antipsychotics (SGA). MetS was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP-III) criteria and the cut-off point for hyperhomocysteinaemia was set up at 15 μmoll(-1). Results of the study indicated that the presence of the MetS is statistically significantly associated with the elevated serum homocysteine in all participants. As hyperhomocysteinaemia has emerged as an independent risk factor for psychiatric disorder and CVD, it could be useful to include fasting homocysteine serum determination in the diagnostic panels of psychiatric patients to obtain a better assessment of their metabolic risk profile. PMID:21216014

  10. Near-Nyquist optical pulse generation with fiber optical parametric amplification.

    Science.gov (United States)

    Vedadi, Armand; Shoaie, Mohammad Amin; Brès, Camille-Sophie

    2012-12-10

    A novel method using optical fiber parametric amplification and phase modulation is proposed in order to generate Nyquist pulses. Using parabolic pulses as a pump, we show theoretically that it is possible to generate Nyquist pulses. Furthermore, we show that by using a sinusoidal pump (pump intensity modulated by an RF tone), it is possible to obtain pulses with characteristics that are close to Nyquist limited pulses. We demonstrate experimentally the generation of bandwidth limited pulses with full width half maximum of 14 ps at 10 GHz repetition rate. We also discuss limitations of this method and means to overcome these limitations.

  11. 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.

  12. 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

  13. 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

  14. 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 ...

  15. High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander Roy [Univ. of Michigan, Ann Arbor, MI (United States); Krushelnick, Karl [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-09-08

    We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactions at 1021 Wcm-2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.

  16. 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.

  17. Electro-generation of TGA by Ni-mSA-mCS bipolar membrane

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ni-mSA-mCS bipolar membrane (BM) was prepared by sodium alginate (SA) and chitosan (CS), which were modified by Ca2+and glutaraldehyde as linking reagents, respectively. mSA-mCS membrane was characterized by FTIR, SEM, TG and used as a separator in the electrolysis cell to produce thioglycolic acid (TGA). The experiment results show that TGA was prepared effectively by electro-reduction of dithiodiglycolic acid (DTDGA) with the mixture of TGA and DTDGA in the cathodic chamber. The current efficiency was up to 66.7% at the room temperature (25 ℃) during the current density of 10 mA/cm2. Compared with the traditional metal reduction method, the electro-reduction technology saves the zinc powder and eliminates the pollution to environment.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Preparation of CS-CMC Bipolar Membrane and its Application in Electro-generated FeO42-

    Institute of Scientific and Technical Information of China (English)

    Yu Xi REN; Zhen CHEN; Ri Yao CHEN; Xi ZHEN; Ya Ming GENG

    2006-01-01

    CS-CMC bipolar membrane was prepared and the cross-section photograph of CS-CMC BM was observed by SEM. FT-IR spectrum indicated that CS-CMC BM contained -N=CRH2+and -COO- functional groups. The charge density of -N=CRH2+ in CS membrane was about 14.13 mmol/g and the charge density of -COO- in CMC membrane was about 9.01 mmol/g. The electrochemistry properties of CS-CMC BM were also studied. CS-CMC BM not only can effectively stop FeO42- from diffusing into the cathode chamber, but also plays an important role in the supply of OH- consumed during the electro-generated FeO42- process.

  3. Generation of High Energy Pulses from a Fiber-based Femtosecond Oscillator

    Science.gov (United States)

    An, Jungkwuen; Kim, Dongeon; Dawson, Jay W.; Messerly, Michael J.; Barty, Christopher P. J.

    The high energy pulse can be achieved by exploiting self-similar prapagation regime. In this regime, mode-lock pulse can be generated without dispersive optics such as gratings or prisms in the cavity.

  4. Management of bipolar depression

    Directory of Open Access Journals (Sweden)

    Jae Seung Chang

    2011-01-01

    Full Text Available Patients with bipolar disorder spend more time in a depressed than manic state, even with individualized treatment. To date, bipolar depression is often misdiagnosed and ineffectively managed both for acute episodes and residual symptoms. This review attempts to summarize the current status of available treatment strategies in the treatment of bipolar depression. For acute and prophylactic treatment, a substantial body of evidence supports the antidepressive efficacy of lithium for bipolar disorders and its antisuicidal effects. Among numerous anticonvulsants with mood-stabilizing properties, valproate and lamotrigine could be first-line options for bipolar depression. Due to receptor profile, mood-stabilizing properties of second-generation antipsychotics have been explored, and up to date, quetiapine and olanzapine appear to be a reasonable option for bipolar depression. The usefulness of antidepressants in bipolar depression is still controversial. Current guidelines generally recommend the cautious antidepressant use in combination with mood stabilizers to reduce the risk of mood elevation or cycle acceleration. Results from clinical trials on psychosocial intervention are promising, especially when integrated with pharmacotherapy. Most patients with bipolar depression need individualized and combined treatment, although the published evidence on this type of treatment strategy is limited. Future studies on the utility of currently available agents and modalities including psychosocial intervention are required.

  5. 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...

  6. 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.

  7. Bipolar Disorder

    Science.gov (United States)

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

  8. 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 ...

  9. Generating ultra-short energetic pulses with cascaded soliton compression in lithium niobate crystals

    DEFF Research Database (Denmark)

    Zhou, Binbin; Bache, Morten; Chong, A.;

    2010-01-01

    By launching energetic femtosecond pulses in a lithium niobate crystal, the phase mismatched second-harmonic generation process compresses the 50 fs input pulse at 1250 nm to 30 fs through a soliton effect.......By launching energetic femtosecond pulses in a lithium niobate crystal, the phase mismatched second-harmonic generation process compresses the 50 fs input pulse at 1250 nm to 30 fs through a soliton effect....

  10. 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.

  11. 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....

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

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Bin; Yu Yongli; Chu Wei; Yao Jinping; Fu Yuxi; Xiong Hui; Xu Han; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai 201800 (China)], E-mail: ycheng-45277@hotmail.com, E-mail: zzxu@mail.shcnc.ac.cn

    2009-07-28

    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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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)

  18. 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.

  19. High energy protons generation by two sequential laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaofeng; Shen, Baifei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn; Zhang, Xiaomei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn; Wang, Wenpeng; Xu, Jiancai; Yi, Longqing; Shi, Yin [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2015-04-15

    The sequential proton acceleration by two laser pulses of relativistic intensity is proposed to produce high energy protons. In the scheme, a relativistic super-Gaussian (SG) laser pulse followed by a Laguerre-Gaussian (LG) pulse irradiates dense plasma attached by underdense plasma. A proton beam is produced from the target and accelerated in the radiation pressure regime by the short SG pulse and then trapped and re-accelerated in a special bubble driven by the LG pulse in the underdense plasma. The advantages of radiation pressure acceleration and LG transverse structure are combined to achieve the effective trapping and acceleration of protons. In a two-dimensional particle-in-cell simulation, protons of 6.7 GeV are obtained from a 2 × 10{sup 22 }W/cm{sup 2} SG laser pulse and a LG pulse at a lower peak intensity.

  20. Subpicosecond-pulse generation through cross-phase-modulation-induced modulational instability in optical fibers.

    Science.gov (United States)

    Gouveia-Neto, A S; Faldon, M E; Sombra, A S; Wigley, P G; Taylor, J R

    1988-10-01

    We report subpicosecond-pulse generation at 1.319 microm in a single-mode optical fiber by modulational instability induced through cross-phase modulation by 1.06-microm pulses propagating in the normal dispersion regime. Pulse-repetition rates approaching 300 GHz were achieved.

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. 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...

  7. 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)

  8. Generation of individually modulated femtosecond pulse string by multilayer volume holographic gratings.

    Science.gov (United States)

    Yan, Xiaona; Gao, Lirun; Yang, Xihua; Dai, Ye; Chen, Yuanyuan; Ma, Guohong

    2014-10-20

    A scheme to generate individually modulated femtosecond pulse string by multilayer volume holographic grating (MVHG) is proposed. Based on Kogelnik's coupled-wave theory and matrix optics, temporal and spectral expressions of diffracted field are given when a femtosecond pulse is diffracted by a MVHG. It is shown that the number of diffracted sub-pulses in the pulse string equals to the number of grating layers of the MVHG, peak intensity and duration of each diffracted sub-pulse depend on thickness of the corresponding grating layer, whereas pulse interval between adjacent sub-pulses is related to thickness of the corresponding buffer layer. Thus by modulating parameters of the MVHG, individually modulated femtosecond pulse string can be acquired. Based on Bragg selectivity of the volume grating and phase shift provided by the buffer layers, we give an explanation on these phenomena. The result is useful to design MVHG-based devices employed in optical communications, pulse shaping and processing.

  9. 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...

  10. Temperature measurement on neurological pulse generators during MR scans

    Directory of Open Access Journals (Sweden)

    Alesch François

    2002-09-01

    Full Text Available Abstract According to manufacturers of both magnetic resonance imaging (MRI machines, and implantable neurological pulse generators (IPGs, MRI is contraindicated for patients with IPGs. A major argument for this restriction is the risk to induce heat in the leads due to the electromagnetic field, which could be dangerous for the surrounding brain parenchyma. The temperature change on the surface of the case of an ITREL-III (Medtronic Inc., Minneapolis, MN and the lead tip during MRI was determined. An anatomical realistic and a cubic phantom, filled with phantom material mimicking human tissue, and a typical lead configuration were used to imitate a patient who carries an IPG for deep brain stimulation. The measurements were performed in a 1.5 T and a 3.0 T MRI. 2.1°C temperature increases at the lead tip uncovered the lead tip as the most critical part concerning heating problems in IPGs. Temperature increases in other locations were low compared to the one at the lead tip. The measured temperature increase of 2.1°C can not be considered as harmful to the patient. Comparison with the results of other studies revealed the avoidance of loops as a practical method to reduce heating during MRI procedures.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Optimized Second Harmonic Generation of Femtosecond Pulse by Phase-Blanking Effect in Aperiodically Optical Superlattice

    Institute of Scientific and Technical Information of China (English)

    KONG Yan; CHEN Xian-Feng; XIA Yu-Xing

    2008-01-01

    @@ In order to minimize the effect of the unconsidered frequency components on the generated compression pulse,the phasing-blanking effect is taken into account of designing the one-dimensional aperiodic domain reversal structure. Hierarchic genetic algorithm for the design of a domain reversal grating to modulate the spectrum and phase of the generated SH pulse simultaneously are presented. Our simulation shows that the quality of an output pulse is fairly improved.

  16. 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

  17. Generation of high-energy self-phase-stabilized pulses by difference-frequency generation followed by optical parametric amplification.

    Science.gov (United States)

    Manzoni, C; Vozzi, C; Benedetti, E; Sansone, G; Stagira, S; Svelto, O; De Silvestri, S; Nisoli, M; Cerullo, G

    2006-04-01

    We produce ultrabroadband self-phase-stabilized near-IR pulses by a novel approach where a seed pulse, obtained by difference-frequency generation of a hollow-fiber broadened supercontinuum, is amplified by a two-stage optical parametric amplifier. Energies up to 20 microJ with a pulse spectrum extending from 1.2 to 1.6 microm are demonstrated, and a route for substantial energy scaling is indicated.

  18. 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...

  19. Powerful 170-attosecond XUV pulses generated with few-cycle laser pulses and broadband multilayer optics

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Goulielmakis, E [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Uiberacker, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Hofstetter, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Kim, J [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, D [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Krausz, F [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Kleineberg, U [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2007-07-15

    Single 170-as extreme ultraviolet (XUV) pulses delivering more than 10{sup 6} photons/pulse at {approx}100 eV at a repetition rate of 3 kHz are produced by ionizing neon with waveform-controlled sub-5 fs near-infrared (NIR) laser pulses and spectrally filtering the emerging near-cutoff high-harmonic continuum with a broadband, chirped multilayer molybdenum-silicon (Mo/Si) mirror.

  20. 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...

  1. Analysis of generation and annihilation of deep level defects in a silicon-irradiated bipolar junction transistor

    Science.gov (United States)

    Madhu, K. V.; Kulkarni, S. R.; Ravindra, M.; Damle, R.

    2007-08-01

    A commercial bipolar junction transistor (2 N 2219 A, npn), irradiated with 120 MeV Si9+ ions with a fluence of the order of 1012 ions cm-2, is studied for radiation-induced gain degradation and deep level defects. I-V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep level transient spectroscopy (DLTS). Minority carrier trap energy levels with energies ranging from EC - 0.160 eV to EC - 0.581 eV are observed in the base-collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from EV + 0.182 eV to EV + 0.401 eV. The identification of the defect type is made on the basis of its finger prints such as activation energy, annealing temperature and capture cross section by comparing with those reported in the literature. New energy levels for the defects A-center, di-vacancy and Si-interstitial are also observed. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation.

  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. 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.

  6. 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.

  7. Generation and storage of double slow light pulses in a solid

    Institute of Scientific and Technical Information of China (English)

    Fan Yun-Fei; Wang Hai-Hua; Wang Rong; Zhang Xiao-Jun; Kang Zhi-Hui; Wu Jin-Hui; Zhang Han-Zhuang; Gao Jin-Yue

    2012-01-01

    We experimentally study the generation and storage of double slow light pulses in a Pr3+:Y2SiO5 crystal.Under electromagnetically induced transparency,a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information,the spin coherence is converted into two slow light pulses with distinct frequencies.Furthermore,the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields.This study of double slow light pulses may have practical applications in information processing and all-optical networks.

  8. 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.)

  9. 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...

  10. Research and development of RHIC injection kicker upgrade with nano second FID pulse generator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang W.; Sandberg, J.; Hahn, H.; Fischer, W.; Liaw, C.J.; Pai, C.; Tuozzolo, J.

    2012-05-20

    Our recent effort to test a 50 kV, 1 kA, 50 ns pulse width, 10 ns pulse rise time FID pulse generator with a 250 ft transmission cable, resistive load, and existing RHIC injection kicker magnet has produced unparalleled results. This is the very first attempt to drive a high strength fast kicker magnet with a nano second high pulsed power (50 MVA) generator for large accelerator and colliders. The technology is impressive. We report here the result and future plan of RHIC Injection kicker upgrade.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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).

  18. 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)

  19. Design and Simulation of Sub Nanosecond Pulse Generator for Uitra-Wideband Communication

    Institute of Scientific and Technical Information of China (English)

    XU Ping-ping; OUYANG Yong-yan; FAN Xiang-ning

    2003-01-01

    A new sub-nanosecond pulse generator scheme is proposed in the opinion of frequency field in this paper.The filtering techniques used in the UWB (ultra-wideband) generator make the circuit simple and suitable for integration. The theoretical analysis and simulation results show that monocycle form generated in the scheme have a good balance between positive and negative shape and small traipse by circuit parameter control and has improved the quality of UWB pulse form.

  20. Flat-top pulse generation by the optical Fourier transform technique for ultrahigh speed signal processing

    DEFF Research Database (Denmark)

    Palushani, Evarist; Oxenløwe, Leif Katsuo; Galili, Michael;

    2009-01-01

    This paper reports on the generation of 1.6-ps fullwidth at half-maximum flat-top pulses by the optical Fourier transform technique, and the utilization of these pulses in a 320-Gb/s demultiplexing experiment. It is demonstrated how a narrow pulse having a 15-nm wide third-order super-Gaussian sp......This paper reports on the generation of 1.6-ps fullwidth at half-maximum flat-top pulses by the optical Fourier transform technique, and the utilization of these pulses in a 320-Gb/s demultiplexing experiment. It is demonstrated how a narrow pulse having a 15-nm wide third-order super...

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. 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.

  7. 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...

  8. 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

  9. 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...

  10. 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)

  11. 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...

  12. Single 100-terawatt attosecond X-ray light pulse generation

    CERN Document Server

    Xu, X R; Zhang, Y X; Lu, H Y; Zhang, H; Dromey, B; Zhu, S P; Zhou, C T; Zepf, M; He, X T

    2016-01-01

    The birth of attosecond light sources is expected to inspire a breakthrough in ultrafast optics, which may extend human real-time measurement and control techniques into atomic-scale electronic dynamics. For applications, it is essential to obtain a single attosecond pulse of high intensity, large photon energy and short duration. Here we show that single 100-terawatt attosecond X-ray light pulse with intensity ${1\\times10^{21}}\\textrm{W}/\\textrm{cm}^{{ 2}}$ and duration ${7.9} \\textrm{as}$ can be produced by intense laser irradiation on a capacitor-nanofoil target composed of two separate nanofoils. In the interaction, a strong electrostatic potential develops between two nanofoils, which drags electrons out of the second foil and piles them up in vacuum, forming an ultradense relativistic electron nanobunch. This nanobunch exists in only half a laser cycle and smears out in others, resulting in coherent synchrotron emission of a single pulse. Such an unprecedentedly giant attosecond X-ray pulse may bring us...

  13. Kinetics of decolorization of azo dye by bipolar pulsed barrier discharge in a three-phase discharge plasma reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ruobing [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)]. E-mail: zrbingdut@163.com; Zhang Chi [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Cheng Xingxin [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Wang Liming [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Wu Yan [Institute of Electrostatics and Special Power, Dalian University of Technology, Dalian 116024 (China); Guan Zhicheng [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2007-04-02

    Removal of amaranth, a commercial synthetic azo dye widely used in the dye and food industry, was examined as a possible remediation technology for treating dye-contaminated water. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetition frequency, etc., on decolorization kinetics were investigated. Experimental results show that an aqueous solution of 24 mg/l dye is 81.24% decolorized following 30 min plasma treatment for a 50 kV voltage and 0.75 m{sup 3}/h gas flow rate. Decolorization reaction of amaranth in the plasma reactor is a pseudo first order reaction. Rate constant (k) of decolorization increases quickly with increasing the applied voltage, pulse repetition frequency and the gas flow rate. However, when the applied voltage is beyond 50 kV and increases further, increase rate of k decreases. In addition, k decreases quickly when the solution conductivity increases from 200 to 1481 {mu}S/cm. The decolorization reaction has a high rate constant (k = 0.0269 min{sup -1}) when the solution pH is beyond 10. Rate constant k decreases with the decrease of pH and reaches minimum at a pH of about 5 (k {sub min} = 0.01603 min{sup -1}), then increases to 0.02105 min{sup -1} when pH decreases to 3.07. About 15% of the initial TOC can be degraded only in about 120 min non-thermal plasma treatment.

  14. 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.

  15. 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;

    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 alternating between the two sides. Vocal fry-like dynamics therefore represent a common production mechanism for low-frequency sounds in songbirds. These results also illustrate that complex vibration patterns can emerge from the mechanical properties of the coupled sound generators in the syrinx. The use...... of vocal fry-like dynamics in the songbird syrinx extends the similarity to this unusual vocal register with mammalian sound production mechanisms....

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

    Science.gov (United States)

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

    2016-01-01

    We experimentally investigate generation of nitrogen molecular 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 laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the laser. PMID:26888182

  17. 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.

  18. 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....

  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. 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.

  1. 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 ...

  2. 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.

  3. 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.

  4. 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 ...

  5. 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.

  6. 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

  7. 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.

  8. 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.

  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. 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...

  11. 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)

  12. 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.

  13. 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.

  14. 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

  15. Generating of short pulses with high amplitudes by using of standard Current-Feedback-Amplifier

    CERN Document Server

    Zantis, Franz Peter

    2013-01-01

    The traditional method to generate pulses in the range of some nanoseconds with high amplitudes, is the using of the avalanche-effect of transistors. However the problem with this method is the poor possibility for parameterizing. That was the trigger to look for a different way: under using of modern electronic components, a pulse generator, which is parameterizable, was developed. The parameters can be set by using a Windows- or Linux-PC. The pulse width can be adjusted in the range of 3....80 ns; the pulse amplitude in the range of 18...84 V and the pulse repetition rate in the range of 1 Hz to 50 kHz.

  16. 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)

  17. 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.

  18. 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.

  19. Influence of Initial Pulse Chirp on Rainbow-Like Supercontinuum Generation from Filamentation in Air

    Institute of Scientific and Technical Information of China (English)

    HAO Zuo-Qiang; ZHANG Jie; ZHANG Zhe; LU Xin; JIN Zhan; ZHONG Jia-Yong; LIU Yun-Quan; WANG Zhao-Hua

    2008-01-01

    @@ Supercontinuum (SC) generation from laser filamentation in air is found to depend strongly on the pulse duration.Rainbow-like SC generation is observed only for a pulse of appropriate negative chirp that agrees with the predictions put forward by Golubtsov et al. [Quantum Electron. 33 (2003) 525]. The conversion efficiency of an 800-nm laser light to rainbow-like SC is found to be the highest for 257fs pulses with an initial negative chirp.A larger chirp will lead to ffiamentation surviving at longer distance.

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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...

  6. Optical Nyquist pulse generation using a time lens with spectral slicing.

    Science.gov (United States)

    Wang, Dong; Huo, Li; Xing, Yanfei; Jiang, Xiangyu; Lou, Caiyun

    2015-02-23

    Optical Nyquist pulse generation based on a time lens with subsequent optical filtering is proposed. A nearly chirp-free 10-GHz 8.1-ps Nyquist pulse generator is experimentally demonstrated. By inserting group velocity dispersion (GVD) between cascaded phase and amplitude modulators, 11 tones ultraflat optical frequency comb (OFC) of 10-GHz frequency spacing within 0.9 dB power variation is obtained. The quasi-rectangular shape spectrum is then filtered out with a tunable rectangular-shaped optical band-pass filter (OBPF) and the quasi-linear chirp is compensated by a segment of standard single mode fiber (SSMF). By changing the wavelength of the continuous wave (CW) light, nearly chirp-free Nyquist pulses over C band are obtained. Furthermore, simultaneous dual-wavelength pulse generation is also demonstrated.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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 ...

  13. 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).

  14. Investigation on Nyquist pulse generation using a single dual-parallel Mach-Zehnder modulator.

    Science.gov (United States)

    Wu, Jian; Zang, Jizhao; Li, Yan; Kong, Deming; Qiu, Jifang; Zhou, Siyuan; Shi, Jindan; Lin, Jintong

    2014-08-25

    The generation of Nyquist pulses with a dual parallel Mach-Zehnder modulator (DPMZM) driven by a single RF signal is demonstrated theoretically and experimentally. A complete theoretical analysis is developed and the limitation of the proposed scheme is also discussed. It is theoretically proved that Nyquist pulses with a spectrum of 5 flat comb lines can be generated using a single DPMZM, which is also verified with simulation. 7 flat comb lines in frequency domain can also be obtained if a large RF driving voltage is applied to DPMZM but the generated waveforms won't present a sinc-shape. This scheme is further investigated experimentally. 40 GHz Nyquist pulses with full-width-at-half-maximum (FWHM) less than 4.65 ps, signal-to-noise ratio (SNR) better than 29.5 dB, and normalized root-mean-square error (NRMSE) less than 2.4% are generated. It is found that a tradeoff exists between the insertion loss of the DPMZM and the deviation of generated pulses. The tunability of repetition rate is experimentally verified by generation of 1 GHz to 40 GHz Nyquist pulses with SNR better than 28.4 dB and NRMSE less than 6.15%.

  15. 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.

  16. 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

  17. 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.

  18. Terahertz Generation in Lithium Niobate Driven by Ti:Sapphire Laser Pulses and its Limitations

    CERN Document Server

    Wu, Xiaojun; Ravi, Koustuban; Ahr, Frederike; Cirmi, Giovanni; Zhou, Yue; Mücke, Oliver D; Kärtner, Franz X

    2014-01-01

    We experimentally investigate the limits to 800 nm-to-terahertz (THz) energy conversion in lithium niobate at room temperature driven by amplified Ti:Sapphire laser pulses with tilted-pulse-front. The influence of the pump central wavelength, pulse duration, and fluence on THz generation is studied. We achieved a high peak efficiency of 0.12% using transform limited 150 fs pulses and observed saturation of the optical to THz conversion efficiency at a fluence of 15 mJ/cm2. We experimentally identify two main limitations for the scaling of optical-to-THz conversion efficiencies: (i) the large spectral broadening of the optical pump spectrum in combination with large angular dispersion of the tilted-pulse-front and (ii) free-carrier absorption of THz radiation due to multi-photon absorption of the 800 nm radiation.

  19. 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.

  20. 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...

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Generating Picosecond X-Ray Pulses with Beam Manipulation in Synchrotron Light Sources

    CERN Document Server

    Guo, Weiming; Harkay, Katherine C; Sajaev, Vadim; Yang Bing Xin

    2005-01-01

    The length of x-ray pulses generated by storage ring light sources is usually tens of picoseconds. For example, the value is 40 ps rms at the Advanced Photon Source (APS). Methods of x-ray pulse compression are of great interest at the APS. One possible method, per Zholents et al., is to tilt the electron bunch with deflecting rf cavities.* Alternately, we found that the electron bunch can develop a tilt after application of a vertical kick in the presence of nonzero chromaticity. After slicing, the x-ray pulse length is determined by the tilt angle and the vertical beam size. In principal, sub-picosecond pulses can be obtained at APS. To date we have observed 6 ps rms visible light pulses with a streak camera. Efforts are underway to attempt further compression of the x-ray pulse and to increase the brilliance. This method can be easily applied to any storage ring light sources to generate x-ray pulses up to two orders of magnitude shorter than the electron bunch length. In this paper, we will present the th...

  13. 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.

  14. 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

  15. 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.

  16. 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...

  17. 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)

  18. 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.

  19. 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.

  20. Protection from electromagnetic interference for operation of powerful pulse-radiation generators

    Energy Technology Data Exchange (ETDEWEB)

    Zavada, N.I.; Gevorkyan, G.G.; Lyamin, V.I.; Pilipenko, A.V.

    1976-01-01

    Measures for normalizing the electromagnetic environment during the operation of powerful pulsed accelerators are considered. The mounting of an electromagnetic grid-type shield around the pulse-voltage generator, the use of the optimal configuration for the cable-laying system, and the introduction of effective decouplings in the circuit ensured a reduction of the level of the fields and interferences by a factor of 30 to 50.

  1. 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.

  2. 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.

  3. Equal-Amplitude Optical Pulse Generation from a Rational Harmonic Mode-Locked Fibre Laser

    Institute of Scientific and Technical Information of China (English)

    FENG Xin-Huan; YUAN Shu-Zhong; LI Yao; LIU Yan-Ge; KAI Gui-Yun; DONG Xiao-Yi

    2004-01-01

    A simple technique for the generation of equal-amplitude high repetition rate pulses from a rational harmonic mode-locked fibre ring laser is demonstrated. The principle is based on the combination of the nonlinear characteristics of the modulator and the effect of rational harmonic mode-locking. The two sources act on each other and the integrated effect eventually leads to the pulse amplitude-equalization. We obtain amplitude-equalized short pulses up to the fifth-order rational harmonic mode-locking with an optimum bias level and modulation depth of the modulator, which demonstrates the efficiency of this method.

  4. Color center generation in sodium-calcium silicate glass by nanosecond and femtosecond laser pulses

    Science.gov (United States)

    Siiman, Leo A.; Glebov, Leonid B.

    2005-12-01

    It was found that high purity soda lime glass shows a markedly different induced absorption spectra when exposed to different types of ionizing radiation such as UV lamp or femtosecond and nanosecond laser pulses. The following irradiation was used in the experiments: nanosecond pulses at the fundamental and harmonics of a Nd:YAG laser (λ = 1064, 532, 355, and 266 nm), femtosecond pulses of a Ti:sapphire laser operating at λ = 780 nm, ultraviolet rays from a high pressure Xe lamp, X-rays, and Gamma rays. Features of radiation defect generations are discussed.

  5. 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...

  6. 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

  7. 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.

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

    Science.gov (United States)

    Im, Song-Jin

    2015-03-01

    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 µJ by broad-band chirped idler pulses at 830 nm and MW pump pulses with narrow-band at 277 nm. The 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 a kagome-lattice hollow-core PCF filled with noble gas of high pressure with core diameter less than 40 µm, which would enable technically simple or highly efficient coupling to the fundamental mode of the fiber.

  9. 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.

  10. 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.

  11. 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....

  12. Kisspeptin is a component of the pulse generator for GnRH secretion in female sheep but not the pulse generator.

    Science.gov (United States)

    Ezzat, Ahmed; Pereira, Alda; Clarke, Iain J

    2015-05-01

    We tested the hypothesis that kisspeptin cells constitute the "pulse generator" for GnRH secretion. In ewes, we determined whether iv administered kisspeptin elicits a secretory pulse of LH in anaesthetized, sex-steroid suppressed ovariectomized ewes. A response was seen in both anaesthetized and conscious animals, which was not associated with induction of c-Fos labeling in GnRH cells, supporting the notion that kisspeptin acts on the neurosecretory GnRH terminals. Response was lower in the anaesthetized animals, suggesting that some nonkisspeptin elements may be involved in GnRH responses. Microinjection of kisspeptin (100 nmol) into the median eminence of conscious ewes elicited a pulse of LH, indicating that kisspeptin acts at this level to cause GnRH secretion. To determine which cells are activated at the time of GnRH secretion, we blood sampled 18 ewes during the luteal phase of the estrous cycle and harvested brains after 3 hours. Three of these ewes displayed a pulse of LH within 30 minutes of euthanasia. An increase in c-Fos labeling was seen in kisspeptin and glutamate cells of the arcuate nucleus but not in GnRH neurons, preoptic kisspeptin neurons, or preoptic glutamate neurons. Immunohistochemistry in 4 hypothalami showed that 72% of arcuate kisspeptin cells receive glutamatergic input. These data support the concept that the kisspeptin cells of the arcuate nucleus drive pulsatile secretion of GnRH at the level of the median eminence, but this may involve "upstream" input from glutamate cells. We conclude that the pulse generator for GnRH secretion involves more than 1 element.

  13. High energy electron generation by the 15 mJ ultrashort pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Takano, K; Hotta, E; Nemoto, K [Department of Energy Sciences Tokyo Institute of Technology 4259 Nagatsuta-cho Midori-ku Yokohama 226-8502 (Japan); Nayuki, T; Oishi, Y; Fujii, T; Zhidkov, A [Central Research Institute of Electric Power Industry 2-6-1 Nagasaka, Yokosuka, Kanagawa, 240-0196 (Japan); Todoriki, M; Hasegawa, S [University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8654 (Japan)], E-mail: k-tn@plasma.es.titech.ac.jp

    2008-05-01

    We propose a small size high energy X-ray source utilizing ultrashort pulse lasers, and a new scheme for generating quasi-monoenergetic electrons. In this paper, we developed a compact laser electron generator and performed experiment that generated energetic electrons over 1 MeV electrons with only 15 mJ laser energy. The temperatures of emitted electrons were measured to be 0.2 MeV and 0.25 MeV without and with prepulse, respectively.

  14. 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.)

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  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. Spectral Phase Modulation and chirped pulse amplification in High Gain Harmonic Generation

    CERN Document Server

    Wu, Zilu; Krinsky, Sam; Loos, Henrik; Murphy, James; Shaftan, Timur; Sheehy, Brian; Shen, Yuzhen; Wang, Xijie; Yu Li Hua

    2004-01-01

    High Gain Harmonic Generation (HGHG), because it produces longitudinally coherent pulses derived from a coherent seed, presents remarkable possibilities for manipulating FEL pulses. If spectral phase modulation imposed on the seed modulates the spectral phase of the HGHG in a deterministic fashion, then chirped pulse amplification, pulse shaping, and coherent control experiments at short wavelengths become possible. In addition, the details of the transfer function will likely depend on electron beam and radiator dynamics and so prove to be a useful tool for studying these. Using the DUVFEL at the National Synchrotron Light Source at Brookhaven National Laboratory, we present spectral phase analyses of both coherent HGHG and incoherent SASE ultraviolet FEL radiation, applying Spectral Interferometry for Direct Electric Field Reconstruction (SPIDER), and assess the potential for employing compression and shaping techniques.

  6. 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)

  7. Generation of ultra-short THz pulses in new optical nonlinear materials based on organic polymers

    Science.gov (United States)

    Mikerin, S. L.; Plekhanov, A. I.; Simanchuk, A. E.; Yakimanskii, A. V.

    2016-07-01

    Using the method of optical rectification of femtosecond laser pulses, we report the generation of short (a few field cycles) terahertz pulses in the samples of films based on polyimides with covalently bound chromophore molecules of DR type. The spectral width of the produced pulses is limited by the pump pulse duration. The quadratic nonlinear optical properties are imparted to the films in the process of their fabrication by orienting the chromophore molecules in the external electric field of the applied electrodes having an original configuration. The samples are compared with the ZnTe crystal. Using the methods of coherent spectroscopy, their transmission and refractive index dispersion spectra are investigated in the frequency range 0.5 – 2.6 THz. The studied polymer composition is promising for the application in coherent spectrometers both for increasing the working spectral range without dips and for improving the spatial resolution in the near-field terahertz spectroscopy.

  8. 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.

  9. 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.

  10. 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

  11. Ultrafast pulse generation in a mode-locked Erbium chip waveguide laser

    CERN Document Server

    Khurmi, Champak; Zhang, Wen Qi; V., Shahraam Afshar; Chen, George; Genest, Jérôme; Monro, Tanya M; Lancaster, David G

    2016-01-01

    We report mode-locked ~1550 nm output of transform-limited ~180 fs pulses from a large mode-area (diameter ~ 50 {\\mu}m) guided-wave erbium fluorozirconate glass laser. The passively mode-locked oscillator generates pulses with 25 nm bandwidth at 156 MHz repetition rate and peak-power of 260 W. Scalability to higher repetition rate is demonstrated by transform-limited 410 fs pulse output at 1.3 GHz. To understand the origins of the broad spectral output, the laser cavity is simulated by using a numerical solution to the Ginzburg-Landau equation. This paper reports the widest bandwidth and shortest pulses achieved from an ultra-fast laser inscribed waveguide laser.

  12. 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

  13. Note: High resolution ultra fast high-power pulse generator for inductive load using digital signal processor.

    Science.gov (United States)

    Flaxer, Eli

    2014-08-01

    We present a new design of a compact, ultra fast, high resolution and high-powered, pulse generator for inductive load, using power MOSFET, dedicated gate driver and a digital signal controller. This design is an improved circuit of our old version controller. We demonstrate the performance of this pulse generator as a driver for a new generation of high-pressure supersonic pulsed valves.

  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.

  15. Tapering photonic crystal fibers for generating self-similar ultrashort pulses at 1550 nm

    Science.gov (United States)

    Manimegalai, Annamalai; Senthilnathan, Krishnamoorthy; Nakkeeran, Kaliyaperumal; Babu, Padmanabhan Ramesh

    2016-06-01

    The generation of high-quality self-similar ultrashort pulses at 1550 nm by tapering the photonic crystal fibers (PCFs) is numerically demonstrated. We taper the PCF to achieve the exponentially decreasing dispersion and exponentially increasing nonlinearity profiles, which turn out to be the fundamental requirements for generating the chirped self-similar pulses. Further, we find that the chirped solitons could also be generated with the other three possible exponential variations. Thus, for the first time, we attempt tapering the PCFs for bringing in these exponentially varying dispersion and nonlinear profiles. We carry out the detailed pulse compression studies for various decay rates of the dispersion profiles as the decay rates of dispersion depend on the initial chirp and hence on compression factor, too. The unique feature of this pulse compressor lies in the fact that the required length of the tapered PCF is about 20 times less than that of the previously reported pulse compressor operating at 850 nm.

  16. 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

  17. 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.

  18. 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...

  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.;

    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. Optical amplification and pulse interleaving for low noise photonic microwave generation

    CERN Document Server

    Quinlan, Franklyn; Fortier, Tara M; Zhou, Qiugui; Cross, Allen; Campbell, Joe C; Diddams, Scott A

    2013-01-01

    We investigate the impact of pulse interleaving and optical amplification on the spectral purity of microwave signals generated by photodetecting the pulsed output of an Er:fiber-based optical frequency comb. It is shown that the microwave phase noise floor can be extremely sensitive to delay length errors in the interleaver, and the contribution of the quantum noise from optical amplification to the phase noise can be reduced ~10 dB for short pulse detection. We exploit optical amplification, in conjunction with high power handling modified uni-traveling carrier photodetectors, to generate a phase noise floor on a 10 GHz carrier of -175 dBc/Hz, the lowest ever demonstrated in the photodetection of a mode-locked fiber laser. At all offset frequencies, the photodetected 10 GHz phase noise performance is comparable to or better than the lowest phase noise results yet demonstrated with stabilized Ti:sapphire frequency combs.

  2. Limitations to THz generation by optical rectification using tilted pulse fronts

    CERN Document Server

    Ravi, Koustuban; Carbajo, Sergio; Wu, Xiaojun; Kartner, Franz

    2014-01-01

    Terahertz (THz) generation by optical rectification (OR) using tilted pulse fronts is studied. We show that the back-action of THz on the optical pulse causes the large experimentally observed cascaded frequency down shift and spectral broadening of the optical pump pulse. In the presence of this large spectral broadening, group velocity dispersion due to angular dispersion enhances phase mismatch and is shown to be the strongest limitation to terahertz generation in lithium niobate. It is seen that the exclusion of THz back-action in modeling OR, leads to a significant overestimation of optical to THz conversion efficiencies. 1-D and 2-D spatial models which for the first time simultaneously include terahertz back-action, angular and material dispersion, absorption, self-phase modulation and stimulated Raman scattering are developed to study the process. The simulation results are supported by experiments.

  3. 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

  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. 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.

  6. 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.

  7. Transtorno bipolar

    OpenAIRE

    Alda Martin

    1999-01-01

    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 d...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 40 Gb/s Pulse Generation Using Gain Switching of a Commercially Available Laser Module

    DEFF Research Database (Denmark)

    Nørregaard, Jesper; Hanberg, Jesper; Franck, Thorkild;

    1999-01-01

    , and a photodiode for optical power monitoring.The RF input port was connected to the driver circuit using a coplanar microwave probe. A DC bias and a large signal modulation at 10 GHz was applied to the module to generate chirped pulses. A linear as well as a non-linear soliton compression was used with optical...

  16. A photonic ultra-wideband pulse generator based on relaxation oscillations of a semiconductor laser

    DEFF Research Database (Denmark)

    Yu, Xianbin; Gibbon, Timothy Braidwood; Pawlik, Michal;

    2009-01-01

    A photonic ultra-wideband (UWB) pulse generator based on relaxation oscillations of a semiconductor laser is proposed and experimentally demonstrated. We numerically simulate the modulation response of a direct modulation laser (DML) and show that due to the relaxation oscillations of the laser...

  17. Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction

    Institute of Scientific and Technical Information of China (English)

    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. Ultra-Short Optical Pulse Generation with Single-Layer Graphene

    CERN Document Server

    Lee, C -C; Bunch, J S; Schibli, T R

    2010-01-01

    Pulses as short as 260 fs have been generated in a diode-pumped low-gain Er:Yb:glass laser by exploiting the nonlinear optical response of single-layer graphene. The application of this novel material to solid-state bulk lasers opens up a way to compact and robust lasers with ultrahigh repetition rates.

  19. Controllable nonlocal behaviour by cascaded second-harmonic generation of fs pulses

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;

    2008-01-01

    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...

  20. Erosion resistant anti-ice surfaces generated by ultra short laser pulses

    NARCIS (Netherlands)

    Del Cerro, D.A.; Römer, G.R.B.E.; Huis in't Veld, A.J.

    2010-01-01

    Wetting properties of a wide range of materials can be modified by accurate laser micromachining with ultra short laser pulses. Controlling the surface topography in a micro and sub-micrometer scale allows the generation of water-repellent surfaces, which remain dry and prevent ice accumulation unde

  1. 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)

  2. Generation and Stability Analysis of Self Similar Pulses Through Dispersion Tailored Passive Microstructured Optical Fibers in Mid Infrared Regime

    CERN Document Server

    Biswas, Piyali; Biswas, Abhijit; Ghosh, Somnath

    2015-01-01

    We report a numerical study on generation and stability of a parabolic pulse during its propagation through a highly nonlinear specialty optical fiber. Here, we have generated a parabolic pulse at 2.1 $\\mu$m wavelength from a Gaussian input pulse with 1.9 ps FWHM and 75 W peak power after travelling through only 20 cm length of a chalcogenide glass based microstructured optical fiber (MOF). The stability of such a parabolic pulse has been analyzed by introducing a variable loss profile within the loss window of the MOF. Moreover, three different dispersion regimes of propagation have been considered to achieve most stable propagation of the pulse.

  3. A systematic investigation of high harmonic generation using mid-infrared driving laser pulses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We report on a systematic investigation of the influences of gas pressure,focal position and focusing geometry on high harmonic generation by use of mid-infrared femtosecond laser pulses. We also discuss the spatial characteristics of harmonics under different focusing conditions. By optimizing the parameters,we experimentally observed the generation of 1 kHz,low divergence coherent X-ray beams in the water-window region.

  4. A comparison of electrical and photonic pulse generation for IR-UWB on fiber links

    OpenAIRE

    Rodes Lopez, Roberto; Caballero Jambrina, Antonio; Yu, Xianbin; Gibbon, Timothy Braidwood; Jensen, Jesper Bevensee; Tafur Monroy, Idelfonso

    2010-01-01

    We present and compare experimental results for electrical and photonic generation of 2-Gb/s pulses for impulse radio ultra-wideband on fiber transmission systems based on direct current modulation of a semiconductor laser diode and external optical injection of a semiconductor laser diode, respectively. We assess the performance of the two generation approaches in terms of bit-error rate after propagation over 20 km of optical fiber followed by wireless transmission.

  5. Third-Order Harmonic Generation in Atmospheric Air with Focused Intense Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    朱长军; 秦元东; 杨宏; 王树峰; 龚旗煌

    2001-01-01

    Generation of third-order harmonics at 800 nm of femtosecond laser pulses is studied in neutral atmospheric air and in plasma of optical breakdown in air. Its efficiency is measured at different fundamental laser intensities. A maximum efficiency is observed at the intensity when optical breakdown in atmospheric air starts. The factors that exhibit the main effects on the harmonic generation, including self-focusing in a neutral air and self-focusing in plasma, are discussed.

  6. Fifth-Order Harmonic Generation using a Coherent Controlled Two-Pulsed Optical Field

    Institute of Scientific and Technical Information of China (English)

    刘婷婷; 王大威; 陆伟新; 孙泉; 杨宏; 蒋红兵; 龚旗煌

    2002-01-01

    We have experimentally studied the characteristics of fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase. The intensities of harmonic generation are found to increase vith the coherent degree. In one optical period, the temporal variation of harmonics exhibits an asymmetric characteristic, vhich is interpreted in terms of ionization theory and the deformation of the wave packets of fundamental field contribution to harmonic generation.

  7. A comparison of electrical and photonic pulse generation for IR-UWB on fiber links

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto; Caballero Jambrina, Antonio; Yu, Xianbin;

    2010-01-01

    We present and compare experimental results for electrical and photonic generation of 2-Gb/s pulses for impulse radio ultra-wideband on fiber transmission systems based on direct current modulation of a semiconductor laser diode and external optical injection of a semiconductor laser diode......, respectively. We assess the performance of the two generation approaches in terms of bit-error rate after propagation over 20 km of optical fiber followed by wireless transmission....

  8. Generating photon pairs from a silicon microring resonator using an electronic step recovery diode for pump pulse generation

    CERN Document Server

    Savanier, Marc

    2016-01-01

    Generation of photon pairs from compact, manufacturable and inexpensive silicon (Si) photonic devices at room temperature may help develop practical applications of quantum photonics. An important characteristic of photon-pair generation is the two-photon joint spectral intensity (JSI), which describes the frequency correlations of the photon pair. In particular, heralded single-photon generation requires uncorrelated photons, rather than the highly anti-correlated photons conventionally obtained under continuous-wave (CW) pumping. Recent attempts to achieve such a factorizable JSI have used short optical pulses from mode-locked lasers, which are much more expensive and bigger table-top or rack-sized instruments compared to the Si microchip pair generator, dominate the cost and inhibit the miniaturization of the source. Here, we generate photon pairs from a Si microring resonator by using an electronic step-recovery diode to drive an electro-optic modulator which carves the pump light from a CW optical diode ...

  9. All-optical control of unipolar pulse generation in spatially extended arrays of optical oscillators with nonlinear field coupling

    CERN Document Server

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

    2016-01-01

    We study the optical response of a resonant medium possessing the nonlinear coupling to external field under excitation by few-cycle pump pulses. A theoretical approach is developed, allowing to analyze unipolar half-cycle pulse generation in such a geometry. Our approach is applicable for the arbitrary coupling functions as well as arbitrarily curved pump pulse wavefronts and defines a general framework to produce unipolar pulses of desired form.

  10. Generation of intense 10-ps, 193-nm pulses using simple distributed feedback dye lasers and an ArF(*) amplifier.

    Science.gov (United States)

    Hatten, D L; Cui, Y; Iii, W T; Mikes, T; Goldhar, J

    1992-11-20

    A pair of holographic distributed feedback dye lasers is used to generate 10-ps pulses at two selected wavelengths that are mixed in a BBO crystal to produce a pulse ~ 10 ps in duration at 193 nm. This seed pulse is subsequently amplified in an ArF(*) excimer laser to an energy of 10-15 mJ with <40 microJ in amplified spontaneous emission. The pulses are nearly transform limited and diffraction limited.

  11. Generation of intense 10-ps, 193-nm pulses using simple distributed feedback dye lasers and an ArF(*) amplifier.

    Science.gov (United States)

    Hatten, D L; Cui, Y; Iii, W T; Mikes, T; Goldhar, J

    1992-11-20

    A pair of holographic distributed feedback dye lasers is used to generate 10-ps pulses at two selected wavelengths that are mixed in a BBO crystal to produce a pulse ~ 10 ps in duration at 193 nm. This seed pulse is subsequently amplified in an ArF(*) excimer laser to an energy of 10-15 mJ with <40 microJ in amplified spontaneous emission. The pulses are nearly transform limited and diffraction limited. PMID:20802565

  12. Polarization and Thickness Dependent Absorption Properties of Black Phosphorus: New Saturable Absorber for Ultrafast Pulse Generation

    Science.gov (United States)

    Li, Diao; Jussila, Henri; Karvonen, Lasse; Ye, Guojun; Lipsanen, Harri; Chen, Xianhui; Sun, Zhipei

    2015-10-01

    Black phosphorus (BP) has recently been rediscovered as a new and interesting two-dimensional material due to its unique electronic and optical properties. Here, we study the linear and nonlinear optical properties of BP flakes. We observe that both the linear and nonlinear optical properties are anisotropic and can be tuned by the film thickness in BP, completely different from other typical two-dimensional layered materials (e.g., graphene and the most studied transition metal dichalcogenides). We then use the nonlinear optical properties of BP for ultrafast (pulse duration down to ~786 fs in mode-locking) and large-energy (pulse energy up to >18 nJ in Q-switching) pulse generation in fiber lasers at the near-infrared telecommunication band ~1.5 μm. We observe that the output of our BP based pulsed lasers is linearly polarized (with a degree-of-polarization ~98% in mode-locking, >99% in Q-switching, respectively) due to the anisotropic optical property of BP. Our results underscore the relatively large optical nonlinearity of BP with unique polarization and thickness dependence, and its potential for polarized optical pulse generation, paving the way to BP based nonlinear and ultrafast photonic applications (e.g., ultrafast all-optical polarization switches/modulators, frequency converters etc.).

  13. Carrier-wave steepened pulses and gradient-gated high-order harmonic generation

    CERN Document Server

    Radnor, S B P; Kinsler, P; New, G H C

    2008-01-01

    We show how to optimize the process of high-harmonic generation (HHG) by gating the interaction using the field gradient of the driving pulse. Since maximized field gradients are efficiently generated by self-steepening processes, we first present a generalized theory of optical carrier-wave self-steepened (CSS) pulses. This goes beyond existing treatments, which only consider third-order nonlinearity, and has the advantage of describing pulses whose wave forms have a range of symmetry properties. Although a fertile field for theoretical work, CSS pulses are difficult to realize experimentally because of the deleterious effect of dispersion. We therefore consider synthesizing CSS-like profiles using a suitably phased sub-set of the harmonics present in a true CSS wave form. Using standard theoretical models of HHG, we show that the presence of gradient-maximized regions on the wave forms can raise the spectral cut-off and so yield shorter attosecond pulses. We study how the quality of the attosecond bursts cr...

  14. Control Loop for a Pulse Generator of a Fast Septum Magnet using DSP and Fuzzy Logic

    CERN Document Server

    Aldaz-Carroll, E; Dieperink, J H; Schröder, G; Vossenberg, Eugène B

    1997-01-01

    A prototype of a fast pulsed eddy current septum magnet for one of thebeam extraction's from the SPS towards LHC is under development. The precision of the magnetic field must be better than ±1.0 10-4 during a flat top of 30 µs. The current pulse is generated by discharging the capacitors of a LC circuit that resonates on the 1st and on the 3rd harmonic of a sine wave with a repetition rate of 15 s. The parameters of the circuit and the voltage on the capacitors must be carefully adjusted to meet the specifications. Drifts during operation must be corrected between two pulses by mechanically adjusting the inductance of the coil in the generator as well as the primary capacitor voltage. This adjustment process is automated by acquiring the current pulse waveform with sufficient time and amplitude resolution, calculating the corrections needed and applying these corrections to the hardware for the next pulse. A very cost-effective and practical solution for this adjustment process is the integration of off-th...

  15. On the generation of grooves on crystalline silicon irradiated by femtosecond laser pulses.

    Science.gov (United States)

    He, Shutong; Nivas, Jijil J J; Vecchione, Antonio; Hu, Minglie; Amoruso, Salvatore

    2016-02-22

    Irradiation of crystalline silicon with femtosecond laser pulses produces a variety of quasi-periodic surface structures, among which sub-wavelength ripples creation is largely studied. Here we report an experimental investigation and a theoretical interpretation focusing on the seldom considered issue of quasi-periodic, micron spaced grooves formation. We characterize the morphological evolution of the grooves generation and experimentally single out the variation of the threshold fluence for their formation with the number of pulses N, while typical ripples simultaneously produced in the irradiated area are always considered for comparison. Our experimental findings evidence a power law dependence of the threshold fluence on the number of pulses both for ripples and grooves formation, typical of an incubation behavior. The incubation factor and single pulse threshold are (0.76 ± 0.04) and (0.20 ± 0.04) J/cm2 for ripples and (0.84 ± 0.03) and (0.54 ± 0.08) J/cm2 for grooves, respectively. Surface-scattered wave theory, which allows modeling irradiation with a single pulse on a rough surface, is exploited to interpret the observed structural modification of the surface textures. A simple, empirical scaling approach is proposed associating the surface structures generated in multiple-pulse experiments with the predictions of the surface-scattered wave theory, at laser fluencies around the grooves formation threshold. This, in turn, allows proposing a physical mechanism interpreting the grooves generation as well as the coexistence and relative prominence of grooves and ripples in the irradiated area. PMID:26906987

  16. A Tapered Chalcogenide Microstructured Optical Fiber for Mid-IR Parabolic Pulse Generation: Design and Performance Study

    CERN Document Server

    Barh, Ajanta; Varshney, Ravi K; Pal, Bishnu P

    2013-01-01

    This paper presents a theoretical design of chalcogenide glass based tapered microstructured optical fiber (MOF) to generate high power parabolic pulses (PPs) at the mid-IR wavelength (~ 2 {\\mu}m). We optimize fiber cross-section by the multipole method and studied pulse evolution by well known Symmetrized Split-Step Fourier Method. Our numerical investigation reveals the possibility of highly efficient PP generation within a very short length (~ 18 cm) of this MOF for a Gaussian input pulse of 60 W peak power and FWHM of 3.5 ps. We examined quality of the generated PP by calculating the misfit parameter including the third order dispersion and fiber loss. Further, the effects of variations in input pulse power, pulse width and pulse energy on generated PP were also studied.

  17. Stable supercontinuum pulse generated by modulation instability in a dispersion-managed fiber

    Science.gov (United States)

    Duan, Liang; Yang, Zhan-Ying; Zhao, Li-Chen; Yang, Wen-Li

    2016-08-01

    We study on non-linear localized waves on continuous wave background in a dispersion and non-linearity management fibre. We find a stable supercontinuum pulse can be generated from a small modulation on continuous wave in a proper management way, for which the pulse spectrum width and its growth rate can be controlled well by the management parameters. Additionally, we demonstrate a Kuznetsov-Ma breather like non-linear localized wave can exist in a periodic dispersion management fibre, and its spectrum evolution is distinctive from the Kuznetsov-Ma breather's.

  18. 120 nm Bandwidth noise-like pulse generation in an erbium-doped fiber laser

    Science.gov (United States)

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

    2008-01-01

    We report on the generation of noise-like pulses with up to 120 nm bandwidth in a passively mode-locked erbium-doped fiber ring laser. By inserting a segment of slightly normal dispersion fiber in a mode-locked fiber laser cavity, we found that the spectrum of the noise-like pulse emission of the laser can be significantly broadened as a result of the four-wave-mixing and the soliton self-frequency shift effects in the inserted fiber.

  19. Generation and coherent control of pure spin currents via terahertz pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schüler, Michael, E-mail: michael.schueler@physik.uni-halle.de; Berakdar, Jamal [Institute for Physics, Martin-Luther University Halle-Wittenberg, 06099 Halle (Germany)

    2014-04-21

    We inspect the time and spin-dependent, inelastic tunneling in engineered semiconductor-based double quantum well driven by time-structured terahertz pulses. An essential ingredient is an embedded spin-active structure with vibrational modes that scatter the pulse driven carriers. Due to the different time scales of the charge and spin dynamics, the spin-dependent electron-vibron coupling may result in pure net spin current (with negligible charge current). Heating the vibrational site may affect the resulting spin current. Furthermore, by controlling the charge dynamics, the spin dynamics and the generated spin current can be manipulated and switched on and off coherently.

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

    OpenAIRE

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

    2007-01-01

    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. I...

  1. Attosecond x-Ray Pulse Generation by Linear Thomson Scattering of Intense Laser Beam with Relativistic Electron

    Institute of Scientific and Technical Information of China (English)

    TIAN You-Wei; YU Wei; LU Pei-Xiang; Vinod Senecha; HE Feng; DENG De-Gang; XU Han

    2006-01-01

    Linear Thomson scattering of a short pulse laser by relativistic electron has been investigated using computer simulations. It is shown that scattering of an intense laser pulse of~33 fs full width at haff maximum, with an electron of γ0 = 10 initial energy, generates an ultrashort, pulsed radiation of 76 attoseconds with a photon wavelength of 2.5 nm in the backward direction. The scattered radiation generated by a highly relativistic electron has superior quality in terms of its pulse width and angular distribution in comparison to the one generated by lower relativistic energy electron.

  2. Photonic multi-shape UWB pulse generation using a semiconductor optical amplifier-based nonlinear optical loop mirror

    Institute of Scientific and Technical Information of China (English)

    Luo Bo-Wen; Dong Jian-Ji; Yu Yuan; Yang Ting; Zhang Xin-Liang

    2013-01-01

    We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband (UWB) signal generation using a semiconductor optical amplifier (SOA) based nonlinear optical loop mirror (NOLM).By employing the cross phase modulation (XPM) effect,cross gain modulation (XGM),or both,multi-shape UWB waveforms are generated including monocycle,doublet,triplet,and quadruplet pulses.Both the shapes and polarities of the generated pulses are flexible to adjust,which may be very useful in UWB pulse shape modulation and pulse polarity modulation.

  3. [Study on the Supercontinuum Generation with Femtosecond Pulse in Photonic Crystal Fiber].

    Science.gov (United States)

    Wei, Yuan-fei; Zhao, Fu-li; Shen, Peng-gao; Wu, Shi-qiang

    2015-12-01

    Physical mechanism of supercontinuum generation in photonic crystal fiber by femtosecond laser pulse has been investigated experimentally. In this study, we used the tunable output wavelength Ti: sapphire optical parametric amplifier as the pump source and the fiber spectrometer acquired the spectrogram of supercontinuum generation in photonic crystal fiber under different power and wavelength conditions, then we normalized the spectrograms and make a comparison of them. PCF supercontinuum differences affected by physical mechanisms were analyzed. We found that when increasing the incident pump pulse power, the spectral width will be gradually widened, there are more peaks, part of the energy will transfer in to the short-wave- length region; as long as it reaches a certain intensity, width of supercontinuum finally saturated, the shape of supercontinuum was also stabilized. As the incident power was settled at 300 milliwatt and the length of PCF was settled at 105 millimeter, experimental results show that width and shape of supercontinuum are affected by the wavelength of pump pulse, in the range of 760 to 840 nm, there appears more and more peaks with the increase of incident wavelength; at anomalous dispersion the spectrogram of supercontinuum generation will be more flat and more wider as the wavelength of pump pulse closer to zero point. PMID:26964194

  4. Application of Pulsed Eddy Current for Depth Measurement of Steam Generator's Wear scar tube standard

    International Nuclear Information System (INIS)

    The integrity of stem generator tube in nuclear power plant is the critical problem but the particular area on the stem generator tube could be worn away by inside impurities, fluid flow and vibration from the outside environment. At the present, the inspection of stem generator tube has been performed by using a conventional eddy current testing. Although the conventional eddy current testing is a powerful method to detect flaws of tube in online processing, it is difficult to measure the deep depth differences of the tube. Because eddy current density has changed its magnitude with distance from the surface. Whereas, the pulsed eddy current technique has been widely employed for deep depth inspection of structures such as plate, tubes. For more effective inspection, the pulsed eddy current system is enveloped to control a depth difference and submitted the multi-pointing method to select a criteria which could be obtained depth differences by the period of resistivity on the pulsed eddy current transient signals. In this paper, we used the pulsed eddy current technique to improve the capability of depth difference measurement and studied multi-pointing method to evaluate the thickness with variation of resistivity.

  5. Generation of ultrashort VUV and THz pulses at the DELTA storage ring

    International Nuclear Information System (INIS)

    The optical klystron (two undulators, separated by a dispersive section) at DELTA, formerly operated as storage ring FEL, will be seeded with ultrashort pulses from a Ti:Sapphire laser. This will induce an energy modulation of the electron bunch in the first undulator, which is, after passing the dispersive chicane, converted to a density modulation. In the second undulator, the electrons will coherently emit ultrashort pulses at harmonics of the fundamental seeding wavelength. This process, called ''coherent harmonic generation'' (CHG), shall also be exploited in pump-probe measurements due to its natural synchronization with the seeding laser. Nonlinear frequency conversion techniques for the seeding laser allow for the generation of CHG pulses at different wavelengths. Additionally, coherent ultrashort THz pulses will be generated several meters downstream of the optical klystron by the laser-induced gap in the electron bunch. These will be extracted using a dedicated beamline. Unlike the first CHG experiments at other facilities, the project at DELTA aims at the application of CHG during standard user operation and hence will deliver stable and reliable radiation for user experiments.

  6. Low-inductive section of Fitch-scheme power high-voltage pulse generator

    International Nuclear Information System (INIS)

    In the Fitch scheme generator unit actuated by the Arkadiev-Marx generator and consisting of two four-cascade modules one obtained experimentally 5- kA current amplitude, the rate of current rise constituted 3x1012 A/s at up to 440 kV breakdown voltage of the basic modules, at 142 nH internal induction of the unit and at short-circuit load. The cascade in the Fitch generator module is characterized by 40 nH induction. The unit is located in the air medium under the atmospheric pressure.The unit and its components may be repaired. Upon 104 pulse operation life the unit is in good working order. The designed service life of the unit is equal to 105 pulses

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

    Science.gov (United States)

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

    2013-10-01

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

  8. Controlling micro-sized droplet generation using electrical pulses for studying liquid-liquid systems

    Science.gov (United States)

    Fernandino, M.; La Forgia, N.; Vera, A. J.; Bjerknes, J.; Dorao, C. A.

    2014-04-01

    Water droplets removal from oil is a critical process in several industries, in particular in the oil and gas industry. Water/oil separation is commonly done in large gravitational sedimentation tanks, which are over dimensioned due to the lack of accurate models to allow for optimization. This can become challenging for off-shore and subsea processing installations. One of the bottlenecks to study droplet dynamics in the micron range, is the generation of droplets with less than 100μm in diameter. In this regard, one of the most promising techniques for controlling the generated droplet size is based on the use of a high voltage electrical signal or electro-hydrodynamic technique (EHD). Although much work on EHD and droplet generation can been found in the literature, many challenges still remain. One of this is the generation of droplets smaller than 100μm in diameter in a controllable, on-demand manner. In this work, the effect of the meniscus shape and the electric pulse characteristics on the size of the generated droplet is investigated. Both the meniscus height and width help to determine the droplet size, with the latter having a stronger effect. No significant influence of the pulse amplitude and pulse width was observed for the tested conditions.

  9. Third Harmonic Generation of a Short Pulse Laser in a Tunnel Ionizing Plasma: Effect of Self-Defocusing

    OpenAIRE

    Niti Kant

    2013-01-01

    Third harmonic generation of a Gaussian short pulse laser in a tunnel ionizing plasma is investigated. A Gaussian short pulse laser propagating through a tunnel ionizing plasma generates third harmonic wave. Inhomogeneity of the electric field along the wavefront of the fundamental laser pulse causes more ionization along the axis of propagation while less ionization off axis, leading to strong density gradient with its maximum on the axis of propagation. The medium acts like a diverging lens...

  10. A Tapered Chalcogenide Microstructured Optical Fiber for Mid-IR Parabolic Pulse Generation: Design and Performance Study

    OpenAIRE

    Barh, Ajanta; Ghosh, S.; Varshney, Ravi K.; Pal, Bishnu P.

    2013-01-01

    This paper presents a theoretical design of chalcogenide glass based tapered microstructured optical fiber (MOF) to generate high power parabolic pulses (PPs) at the mid-IR wavelength (~ 2 {\\mu}m). We optimize fiber cross-section by the multipole method and studied pulse evolution by well known Symmetrized Split-Step Fourier Method. Our numerical investigation reveals the possibility of highly efficient PP generation within a very short length (~ 18 cm) of this MOF for a Gaussian input pulse ...

  11. Controls for the generation of high-order harmonics and attosecond pulses by an infrared laser field combined with a low-frequency pulse

    Institute of Scientific and Technical Information of China (English)

    He Hai-Xiang; Guo Ya-Hui; He Guo-Zhong

    2012-01-01

    We investigate high-order harmonic generations by controlling various quantum paths of harmonics in an infrared laser field which combines a low-frequency pulse.Both classical theory and the quantum wavelet transform method are used to understand the physics of harmonics.By adjusting the carrier envelope phase of the fundamental field,the intensities of harmonic spectra increase and the harmonics in the plateau become regular.Attosecond pulses each with a duration of 58 as are obtained directly by compressing the harmonics,and with phase compensation an isolated attosecond pulse less than 30 as can be generated.

  12. Compact repetitive high voltage nanosecond pulse generator%紧凑型重复频率高压纳秒脉冲电源及其仿真模型

    Institute of Scientific and Technical Information of China (English)

    庞磊; 陈纲亮; 何堃; 任保忠; 张乔根

    2012-01-01

    纳秒脉冲等离子体在诸多实际的工程应用中依赖于小型化且可靠的纳秒脉冲电源实现.设计了一种紧凑型全固态高压纳秒脉冲电源,该电源主要由直流电源部分、绝缘栅双极晶体管及其驱动控制电路、可饱和脉冲变压器、磁脉冲压缩网络等组成.通过理论计算分析、PSpice电路仿真以及实验研究表明,其最终可以在800 Ω的输出负载阻抗上获得幅值40 kV、脉冲宽度100 ns左右、脉冲上升沿约50 ns的高电压脉冲,重复频率最高可达5 kHz.%The application of nanosecond discharge plasma in many fields depends greatly on a compact repetitive high voltage nanosecond pulse generator. In this paper. a compact high voltage nanosecond pulse generator is presented > which is constructed with all-solid-state components. The pulse generator consists of DC module, insulated-gate bipolar transistors and its drivers, saturable pulse transformer and magnetic switch and so on. Simulation analysis and experimental investigation show that, the pulse generator can output pulsed voltage of 40 kV with duration about 100 ns and rise-time of 50 ns. Its highest repetitive frequency can be up to 5 kHz.

  13. Generation of subterawatt-attosecond pulses in a soft x-ray free-electron laser

    Science.gov (United States)

    Huang, Senlin; Ding, Yuantao; Huang, Zhirong; Marcus, Gabriel

    2016-08-01

    We propose a novel scheme to generate attosecond soft x rays in a self-seeded free-electron laser (FEL) suitable for enabling attosecond spectroscopic investigations. A time-energy chirped electron bunch with additional sinusoidal energy modulation is adopted to produce a short seed pulse through a self-seeding monochromator. This short seed pulse, together with high electron current spikes and a cascaded delay setup, enables a high-efficiency FEL with a fresh bunch scheme. Simulations show that using the Linac Coherent Light Source (LCLS) parameters, soft x-ray pulses with a FWHM of 260 attoseconds and a peak power of 0.5 TW can be obtained. This scheme also has the feature of providing a stable central wavelength determined by the self-seeding monochromator.

  14. Dual-wavelength stable nanosecond pulses generation from cladding-pumped fiber laser

    Institute of Scientific and Technical Information of China (English)

    Shuling Hu; Jing Yu; Chunqing Gao; Guanghui Wei; Fuyun Lü

    2006-01-01

    In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Ybdoped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulatedBrillouin scattering (SBS). When the pump power achieves the SBS threshold, the fiber laser changes from the start resonator to the SBS resonator. With different reflectivities of the second mirror, stable dual-wavelength pulses with the pulse width range from 10 ns to less than 2 ns are obtained. The resultwas explained theoretically by birefringency (including stochastic birefringency and bend birefringency).

  15. Method to generate a pulse train of few-cycle coherent radiation

    Science.gov (United States)

    Garcia, Bryant; Hemsing, Erik; Raubenheimer, Tor; Campbell, Lawrence T.; McNeil, Brian W. J.

    2016-09-01

    We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. We discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. We examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.

  16. Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

    Science.gov (United States)

    Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

    2016-04-01

    In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser. PMID:27106311

  17. New method for attosecond-terawatt pulse generation in X-ray free electron laser

    International Nuclear Information System (INIS)

    We propose a novel scheme for generating a terawatt-attosecond pulse from X-ray free-electron laser (XFEL), which is perfectly synchronized to the few cycle IR pulse. Our approach utilizes baseline configuration similar to PAL-XFEL, but adds a current enhanced self-amplified emission (ESASE) module inserted between the linac and the undulater that introduces only a few cycle energy and current modulation in the electron beam. Our scheme is compact and easy to implement and does not require a slotted foil, thereby leading to improved longitudinal coherence of the beam. We demonstrate the viability of our scheme with simulations using PAL-XFEL beam parameters. Attosecond science has emerged as an important research area of ultrafast phenomena during the past decade as it provides a direct access to capturing, measuring and controlling the electronic dynamics in atoms, molecules and condensed matters. However, high-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments spectroscopy are still lacking. Therefore, techniques are to be further developed to make a powerful isolated attosecond pulse in the x-ray range (1 keV and higher). Several techniques have been proposed to achieve attosecond pulses in a free electron laser (FEL). In this vein, we demonstrate in simulation a TW-attosecond pulse in FEL. In our scheme, it utilizes a laser-induced energy modulation to generate a few-cycle current modulation and small optical-delays between undulator modules for radiation alignment. In this work, we are able to show that an isolated 280 attosecond FWHM, 1 TW pulse at 1 keV (1.25 nm) photon energy and an 100 attosecond FWHM, 1 TW pulse at 12.4 keV (0.1 mn) can be generated. This scheme is simple and easy to implement and can be adapted to the existing FEL facilities. It is worthwhile to mention that in this scheme there is still a room for higher power even for shorter undulator lengths via tapering of the undulator or high

  18. Production of quasi ellipsoidal laser pulses for next generation high brightness photoinjectors

    Science.gov (United States)

    Rublack, T.; Good, J.; Khojoyan, M.; Krasilnikov, M.; Stephan, F.; Hartl, I.; Schreiber, S.; Andrianov, A.; Gacheva, E.; Khazanov, E.; Mironov, S.; Potemkin, A.; Zelenogorskii, V. V.; Syresin, E.

    2016-09-01

    The use of high brightness electron beams in Free Electron Laser (FEL) applications is of increasing importance. One of the most promising methods to generate such beams is the usage of shaped photocathode laser pulses. It has already demonstrated that temporal and transverse flat-top laser pulses can produce very low emittance beams [1]. Nevertheless, based on beam simulations further improvements can be achieved using quasi-ellipsoidal laser pulses, e.g. 30% reduction in transverse projected emittance at 1 nC bunch charge. In a collaboration between DESY, the Institute of Applied Physics of the Russian Academy of Science (IAP RAS) in Nizhny Novgorod and the Joint Institute of Nuclear Research (JINR) in Dubna such a laser system capable of producing trains of laser pulses with a quasi-ellipsoidal distribution, has been developed. The prototype of the system was installed at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and is currently in the commissioning phase. In the following, the laser system will be introduced, the procedure of pulse shaping will be described and the last experimental results will be shown.

  19. Characterization of pulsed atmospheric-pressure plasma streams (PAPS) generated by a plasma gun

    International Nuclear Information System (INIS)

    An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107–108 cm s−1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications. (paper)

  20. High-harmonic generation in benzene with linearly- and circularly-polarised laser pulses

    CERN Document Server

    Wardlow, Abigail

    2015-01-01

    High harmonic generation in benzene is studied using a mixed quantum-classical approach in which the electrons are described using time-dependent density functional theory while the ions move classically. The interaction with both circularly- and linearly-polarised infra-red ($\\lambda = 800$ nm) laser pulses of duration 10 cycles (26.7 fs) is considered. The effect of allowing the ions to move is investigated as is the effect of including self-interaction corrections to the exchange-correlation functional. Our results for circularly-polarised pulses are compared with previous calculations in which the ions were kept fixed and self-interaction corrections were not included while our results for linearly-polarised pulses are compared with both previous calculations and experiment. We find that even for the short duration pulses considered here, the ionic motion greatly influences the harmonic spectra. While ionization and ionic displacements are greatest when linearly-polarised pulses are used, the response to ...

  1. Carrier Envelope Phase Controlled High-Order Harmonic Generation in Ultrashort Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    WANG Bing-Bing; CHEN Jing; LIU Jie; LI Xiao-Feng; FU Pan-Ming

    2005-01-01

    @@ We investigate the carrier envelope phase (CEP) effects on high-order harmonic generation (HHG) in ultrashort pulses with the pulse duration 2.5fs when the laser intensity is high enough so that the initial state is ionized effectively during the laser pulse but remains about 20% population at the end of the laser pulse. We find that the ionization process of the initial state is very sensitive to the CEP during the laser pulse. The ionization process of the initial state determines the continuum state population and hence influences dramatically the weights of the classical trajectories that contribute to HHG. In such a case we can not predict the cutoff and the structure of the harmonic spectrum only by the number and the kinetic energy of the classical trajectories. The harmonic spectrum exhibits abundant characters for different CEP cases. As a result, we can control the cutoff frequency and the plateau structure of the harmonic spectrum with CEP by controlling the time behaviour of the ionization of the initial state.

  2. Systems of Electronic Overcurrent Protection in Pulse Power Generator Operating on Plasma Load

    Directory of Open Access Journals (Sweden)

    Dmitriy V. Godun

    2013-01-01

    Full Text Available Schematic peculiarities of pulsed power source and modulator-shaper for working on high instability plasma load are discussed. In its construction should be provided for several levels of overcurrent protection. First of all modules of electronic protection should be integrated into the control driver system of IGBT modules and must provide a quick disconnect power switches in excess of the allowable values of pulse current. The next level of overcurrent protection in pulse power generator is a protection against overcurrent in the load circuit. Operating threshold of current protection in this case must be set to the maximum value of current in the secondary circuit. In order to limit the emission of stray voltage on the power pulses in a moment of switching of power switches a restrictive RC snubbers parallel to the collectors and the emitters of transistors must be installed. It is also appropriate application of software-controlled configurating of electrical power at the outputof a pulsed power supply.

  3. Plasma-based generation and control of a single few-cycle high-energy ultrahigh-intensity laser pulse.

    Science.gov (United States)

    Tamburini, M; Di Piazza, A; Liseykina, T V; Keitel, C H

    2014-07-11

    A laser-boosted relativistic solid-density paraboloidal foil is known to efficiently reflect and focus a counterpropagating laser pulse. Here we show that in the case of an ultrarelativistic counterpropagating pulse, a high-energy and ultrahigh-intensity reflected pulse can be more effectively generated by a relatively slow and heavy foil than by a fast and light one. This counterintuitive result is explained with the larger reflectivity of a heavy foil, which compensates for its lower relativistic Doppler factor. Moreover, since the counterpropagating pulse is ultrarelativistic, the foil is abruptly dispersed and only the first few cycles of the counterpropagating pulse are reflected. Our multidimensional particle-in-cell simulations show that even few-cycle counterpropagating laser pulses can be further shortened (both temporally and in the number of laser cycles) with pulse amplification. A single few-cycle, multipetawatt laser pulse with several joules of energy and with a peak intensity exceeding 10(23)  W/cm(2) can be generated already employing next-generation high-power laser systems. In addition, the carrier-envelope phase of the generated few-cycle pulse can be tuned provided that the carrier-envelope phase of the initial counterpropagating pulse is controlled. PMID:25062199

  4. A Kicker Pulse Generator for Measurement of the Tune and Dynamic Aperture in the LHC

    CERN Document Server

    Carlier, E; Vossenberg, E

    2007-01-01

    The large hadron collider (LHC) at CERN will be equipped with fast pulsed two-function magnets, which will be part of the measurement system for the tune and the dynamic aperture. For the tune measurement, the magnets will excite coherent oscillations of part of the beam. This is achieved by means of a generator producing a 5.1 mus base half-sine pulse of 1.2 kA amplitude, superimposed with a 3rd harmonic to produce a -2 mus flat top. A kick repetition rate of 2 Hz is possible. The maximum generator voltage is 3.3 kV, with a dynamic range of about 20. A 5.2 kV press-pack capsule IGBT is used as switching element. A fast 30 A gate driver is used for triggering. The generator pulse current interruption is obtained with an extra-fast small recovery series diode. Several advantages of the press-pack IGBT construction with respect to conventional IGBT modules will be discussed. To measure the dynamic aperture of the LHC at different beam energies, the same magnets will also be driven by a more powerful generator w...

  5. Generation of Pedestal-free 10 GHz Pulses from a Comb-Like Dispersion Profiled Fiber Compressor and Its Application in Supercontinuum Generation

    Institute of Scientific and Technical Information of China (English)

    HAN Ming; LOU Cai-Yun; WU Yue; CHANG Guo-Qing; GAO Yi-Zhi; LI Yu-Hua

    2000-01-01

    We built a pulse compressor using a comb-like dispersion-profiled fiber (CDPF). The CDPF consists of 12-segment fibers with the dispersion alternatively high and low. Using this compressor and a 17 dBm Erbium-doped fiber amplifier, the 10 GHz, 12ps pulses generated from an actively mode-lo.cked Er3+ doped fiber ring laser was compressed to ~2ps without pedestal. We also show that compared with the high order soliton pulse compressor, the power efficiency can be doubled in supercontinuum generation by using the pump pulses compressed by this CDPF compressor.

  6. High-average-power femtosecond pulse generation in the blue using BiB3O6

    Science.gov (United States)

    Ghotbi, M.; Ebrahim-Zadeh, M.; Majchrowski, A.; Michalski, E.; Kityk, I. V.

    2004-11-01

    Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375-435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100-µm-thick ß-BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with ß-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.

  7. High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander Roy [University of Michigan; Regents of the University of Michigan; Krushelnick, Karl [Regents of the University of Michigan; University of Michigan

    2016-09-08

    Summary of findings • First high harmonic generation in laser-solid interactions at 1021 Wcm-2 • Demonstration of harmonic focusing • Study of ion motion effects in high harmonic generation in laser-solid interactions • Demonstration of harmonic amplification

  8. Use of a pulsed neutron generator for in vivo measurement of body carbon

    International Nuclear Information System (INIS)

    The measurement of total body fat is of importance in studies of nutritional assessment, dietary regimens, and for the management of obesity. In the past, fat has been determined either by anthropometric methods, which introduce high uncertainties, or by model-dependent estimation of fat-free tissue. The validity, however, of the different models in disease is questionable. Total body carbon measurements provide a more direct evaluation of body fat both in normal subjects and in patients. The authors present here a facility for carbon measurements without the use of a major accelerator. The same facility can be used for the measurement of other major body elements and for the evaluation of the body's compartments. Carbon is measured in vivo through neutron inelastic scattering, by detecting the 4.44 MeV gamma rays. A miniature (10 cm long) 14 MeV D-T neutron generator is used. The short half-life of the 4.44 MeV state of carbon requires detection of the gamma rays simultaneously with the 10 μs neutron pulse. Generators with low pulsing rate were found inappropriate for carbon measurement because of their low duty-cycle (high neutron output during pulse). The detection system consists of NaI(T1) detectors and fast electronics for handling the high even rate during the neutron pulse. A description of the facility and an evaluation of the technique will be presented

  9. Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

    Energy Technology Data Exchange (ETDEWEB)

    Tamura, Jun, E-mail: jtamura@post.j-parc.jp [J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195 (Japan); Kumaki, Masafumi [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kondo, Kotaro [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Kanesue, Takeshi; Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2016-02-15

    We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe{sup 21+}) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe{sup 19+}). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

  10. PHz-wide Supercontinua of Nondispersing Subcycle Pulses Generated by Extreme Modulational Instability

    Science.gov (United States)

    Tani, F.; Travers, J. C.; Russell, P. St. J.

    2013-07-01

    Modulational instability (MI) of 500 fs, 5μJ pulses, propagating in gas-filled hollow-core kagome photonic crystal fiber, is studied numerically and experimentally. By tuning the pressure and launched energy, we control the duration of the pulses emerging as a consequence of MI and hence are able to study two regimes: the classical MI case leading to few-cycle solitons of the nonlinear Schrödinger equation; and an extreme case leading to the formation of nondispersing subcycle pulses (0.5 to 2 fs) with peak intensities of order 1014Wcm-2. Insight into the two regimes is obtained using a novel statistical analysis of the soliton parameters. Numerical simulations and experimental measurements show that, when a train of these pulses is generated, strong ionization of the gas occurs. This extreme MI is used to experimentally generate a high energy (>1μJ) and spectrally broad supercontinuum extending from the deep ultraviolet (320 nm) to the infrared (1300 nm).

  11. UV PRE-IONIZED RAIL-GAP SWITCH FOR STACKED BLUMLEIN PULSE GENERATORS*

    Energy Technology Data Exchange (ETDEWEB)

    Rhodes, M A

    2005-05-09

    Stacked Blumlein Pulse Generators comprised of parallel-plate transmission lines are potentially a useful pulse-power architecture for high-gradient, compact, electron-beam accelerators and other applications. Such pulse generators require a low-inductance, fast (<5ns) switch per stage to erect the stack and produce the desired output pulse. We are developing a rail-gap switch tightly integrated with the stack for this application. We employ ultraviolet light (UV) to pre-ionize the switch, which facilitates prompt, low-jitter, and potentially multichannel operation. A novel aspect of our switch is that the source of the UV is a conventional Xenon flashlamp. This allows variation of the switch pressure and gas without affecting the flashlamp operation. We can operate our switch in either triggered or self-breaking mode. Here we present initial results of a two-stage, stacked Blumlein operating in self-break mode. We compare the switch performance to gas-switch scaling laws with respect to resistive-phase risetime and trigger delay as a function of gas density, gap-length, and gap-voltage.

  12. Intense giga watt pulsed electron accelerators for HPM and FXR generation

    International Nuclear Information System (INIS)

    New development in the field of high power pulsed accelerator is the KALI-30GW system capable of delivering 1 MV, 30 kA, 80 ns electron beam pulses. This system has all indigenous components including energy storage capacitors and transformer oil as the dielectric and insulating medium. The energy balance in each stage of sub-system has been maintained to have better efficiency of energy transfer and improving the life of associated insulators. It has been used for high power microwaves generation using reflex triode and relativistic magnetron successfully. A suitable flash-X-rays gun is also designed and developed for this system. The results of these experiments will be presented in this paper. In order to make pulsed electron accelerators compact and repetitive, two more systems are developed in Accelerator and Pulse Power Division, BTDG, BARC which are Linear Induction Accelerator (LIA-400) tested up to 400 kV, 4 kA,100 ns,1-300 Hz and repetitive Marx generator rated for 300 kV, 12 kA, 300 ns, 10 Hz are also developed which are being used for Intentional ElectroMagnetic Interference (IEMI) studies of various electronics circuitry/devices. A few experimental investigations are also done using these systems to understand the effect of cathode material, relativistic electron beam and flash-X-rays emission. Latest results are being illustrated. (author)

  13. Self-stabilizing optical clock pulse-train generator using SOA and saturable absorber for asynchronous optical packet processing.

    Science.gov (United States)

    Nakahara, Tatsushi; Takahashi, Ryo

    2013-05-01

    We propose a novel, self-stabilizing optical clock pulse-train generator for processing preamble-free, asynchronous optical packets with variable lengths. The generator is based on an optical loop that includes a semiconductor optical amplifier (SOA) and a high-extinction spin-polarized saturable absorber (SA), with the loop being self-stabilized by balancing out the gain and absorption provided by the SOA and SA, respectively. The optical pulse train is generated by tapping out a small portion of a circulating seed pulse. The convergence of the generated pulse energy is enabled by the loop round-trip gain function that has a negative slope due to gain saturation in the SOA. The amplified spontaneous emission (ASE) of the SOA is effectively suppressed by the SA, and a backward optical pulse launched into the SOA enables overcoming the carrier-recovery speed mismatch between the SOA and SA. Without external control for the loop gain, a stable optical pulse train consisting of more than 50 pulses with low jitter is generated from a single 10-ps seed optical pulse even with a variation of 10 dB in the seed pulse intensity. PMID:23669927

  14. Neutrality in bipolar structures

    DEFF Research Database (Denmark)

    Montero, Javier; Rodríguez, J. Tinguaro; Franco, Camilo;

    2014-01-01

    In this paper, we want to stress that bipolar knowledge representation naturally allows a family of middle states which define as a consequence different kinds of bipolar structures. These bipolar structures are deeply related to the three types of bipolarity introduced by Dubois and Prade, but our...

  15. Generation of scalable terahertz radiation from cylindrically focused two-color laser pulses in air

    Science.gov (United States)

    Kuk, D.; Yoo, Y. J.; Rosenthal, E. W.; Jhajj, N.; Milchberg, H. M.; Kim, K. Y.

    2016-03-01

    We demonstrate scalable terahertz (THz) generation by focusing terawatt, two-color laser pulses in air with a cylindrical lens. This focusing geometry creates a two-dimensional air plasma sheet, which yields two diverging THz lobe profiles in the far field. This setup can avoid plasma-induced laser defocusing and subsequent THz saturation, previously observed with spherical lens focusing of high-power laser pulses. By expanding the plasma source into a two-dimensional sheet, cylindrical focusing can lead to scalable THz generation. This scheme provides an energy conversion efficiency of 7 × 10-4, ˜7 times better than spherical lens focusing. The diverging THz lobes are refocused with a combination of cylindrical and parabolic mirrors to produce strong THz fields (>21 MV/cm) at the focal point.

  16. Supercontinuum and ultra-short pulse generation from nonlinear Thomson and Compton scattering

    CERN Document Server

    Krajewska, K; Kamiński, J Z

    2013-01-01

    Nonlinear Thomson and Compton processes, in which energetic electrons collide with an intense optical pulse, are investigated in the framework of classical and quantum electrodynamics. Spectral modulations of the emitted radiation, appearing as either oscillatory or pulsating structures, are observed and explained. It is shown that both processes generate a bandwidth radiation spanning the range of few MeV, which occurs in a small cone along the propagation direction of the colliding electrons. Most importantly, these broad bandwidth structures are temporarily coherent which proves that Thomson and Compton processes lead to generation of a supercontinuum. It is demonstrated that the radiation from the supercontinuum can be synthesized into zeptosecond (possibly even yoctosecond) pulses. Thus, confirming that Thomson and Compton scattering can be used as novel sources of an ultra-short radiation, opening routes to new physical domains for strong laser physics.

  17. Femtosecond pulse generation from a Topological Insulator mode-locked fiber laser

    CERN Document Server

    Liu, Hao; Liu, Meng; Zhao, Nian; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng; Zhang, Han; Zhao, Chu-Jun; Wen, Shuang-Chun

    2014-01-01

    We reported on the generation of femtosecond pulse in an anomalous-dispersion fiber ring laser by using a polyvinyl alcohol (PVA)-based Topological Insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device.

  18. Femtosecond pulse generation from a topological insulator mode-locked fiber laser.

    Science.gov (United States)

    Liu, Hao; Zheng, Xu-Wu; Liu, Meng; Zhao, Nian; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng; Zhang, Han; Zhao, Chu-Jun; Wen, Shuang-Chun

    2014-03-24

    We reported on the generation of femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based topological insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device. PMID:24664035

  19. Theoretical analysis of ozone generation by pulsed dielectric barrier discharge in oxygen

    Science.gov (United States)

    Wei, L. S.; Zhou, J. H.; Wang, Z. H.; Cen, K. F.

    2007-08-01

    The use of very short high-voltage pulses combined with a dielectric layer results in high-energy electrons that dissociate oxygen molecules into atoms, which are a prerequisite for the subsequent production of ozone by collisions with oxygen molecules and third particles. The production of ozone depends on both the electrical and the physical parameters. For ozone generation by pulsed dielectric barrier discharge in oxygen, a mathematical model, which describes the relation between ozone concentration and these parameters that are of importance in its design, is developed according to dimensional analysis theory. A formula considering the ozone destruction factor is derived for predicting the characteristics of the ozone generation, within the range of the corona inception voltage to the gap breakdown voltage. The trend showing the dependence of the concentration of ozone in oxygen on these parameters generally agrees with the experimental results, thus confirming the validity of the mathematical model.

  20. Composite pulses in Hyper-Ramsey spectroscopy for the next generation of atomic clocks

    CERN Document Server

    Zanon-Willette, T; Yudin, V I; Taichenachev, A V

    2016-01-01

    The next generation of atomic frequency standards based on an ensemble of neutral atoms or a single-ion will provide very stringent tests in metrology, applied and fundamental physics requiring a new step in very precise control of external systematic corrections. In the proceedings of the 8th Symposium on Frequency Standards and Metrology, we present a generalization of the recent Hyper-Ramsey spectroscopy with separated oscillating fields using composites pulses in order to suppress field frequency shifts induced by the interrogation laser itself. Sequences of laser pulses including specific selection of phases, frequency detunings and durations are elaborated to generate spectroscopic signals with a strong reduction of the light-shift perturbation by off resonant states. New optical clocks based on weakly allowed or completely forbidden transitions in atoms, ions, molecules and nuclei will benefit from these generalized Ramsey schemes to reach relative accuracies well below the 10$^{-18}$ level.

  1. Composite pulses in Hyper-Ramsey spectroscopy for the next generation of atomic clocks

    Science.gov (United States)

    Zanon-Willette, T.; Minissale, M.; Yudin, V. I.; Taichenachev, A. V.

    2016-06-01

    The next generation of atomic frequency standards based on an ensemble of neutral atoms or a single-ion will provide very stringent tests in metrology, applied and fundamental physics requiring a new step in very precise control of external systematic corrections. In the proceedings of the 8th Symposium on Frequency Standards and Metrology, we present a generalization of the recent Hyper-Ramsey spectroscopy with separated oscillating fields using composites pulses in order to suppress field frequency shifts induced by the interrogation laser itself. Sequences of laser pulses including specific selection of phases, frequency detunings and durations are elaborated to generate spectroscopic signals with a strong reduction of the light-shift perturbation by off resonant states. New optical clocks based on weakly allowed or completely forbidden transitions in atoms, ions, molecules and nuclei will benefit from these generalized Ramsey schemes to reach relative accuracies well below the 10-18 level.

  2. High-order harmonic generation with Rydberg atoms by using an intense few-cycle pulse

    Science.gov (United States)

    Zhai, Zhen; Zhu, Qiren; Chen, Jing; Yan, Zong-Chao; Fu, Panming; Wang, Bingbing

    2011-04-01

    We demonstrate that high-order harmonic generation (HHG) with both high cutoff frequency and high conversion efficiency can be realized by using a Rydberg atom in a few-cycle laser pulse. This is because a Rydberg state has a large electron orbital radius and small binding energy; therefore an electron in the Rydberg state can be ionized easily and accelerated directly toward the core under the interaction of a few-cycle laser pulse, leading to emission of harmonic photons. In this case, the tunneling process of the electron is not involved and, hence, the conversion efficiency and the cutoff frequency of harmonic generation can be higher than that predicted by the conventional three-step model.

  3. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    Science.gov (United States)

    Li, Heting; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-07-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

  4. Fault-tolerant Algorithms for Tick-Generation in Asynchronous Logic: Robust Pulse Generation

    CERN Document Server

    Dolev, Danny; Lenzen, Christoph; Schmid, Ulrich

    2011-01-01

    Today's hardware technology presents a new challenge in designing robust systems. Deep submicron VLSI technology introduced transient and permanent faults that were never considered in low-level system designs in the past. Still, robustness of that part of the system is crucial and needs to be guaranteed for any successful product. Distributed systems, on the other hand, have been dealing with similar issues for decades. However, neither the basic abstractions nor the complexity of contemporary fault-tolerant distributed algorithms match the peculiarities of hardware implementations. This paper is intended to be part of an attempt striving to overcome this gap between theory and practice for the clock synchronization problem. Solving this task sufficiently well will allow to build a very robust high-precision clocking system for hardware designs like systems-on-chips in critical applications. As our first building block, we describe and prove correct a novel Byzantine fault-tolerant self-stabilizing pulse syn...

  5. All-fiber generation of 29-fs pulses at 1.3-{\\mu}m via Cherenkov radiation

    CERN Document Server

    Luo, Hao; Wang, Zhiqiang; Zhang, Liang; Feng, Cheng

    2016-01-01

    We have experimentally demonstrated the all-fiber generation of 1.3-{\\mu}m femtosecond pulses via Cherenkov radiation (CR) from an ultrafast Er-doped fiber laser. The experiment shows that the pulses maintain below 40 fs in the range from 1270 to 1315 nm with multi-milliwatt average output power. The shortest generated pulses can be as short as 29 fs. This ultrashort pulse source in 1.3-{\\mu}m window can bring the benefits to many fields such as the bio-imaging and the ultrafast spectroscopy, and so on.

  6. Generation of 10 GHz 2ps Short Laser Pulses Using an Electroabsorption Modulator and Two-Stage Compression

    Institute of Scientific and Technical Information of China (English)

    HUO Li; LOU Cai-Yun; GAO Yi-Zhi

    2005-01-01

    @@ A short pulse generator based on a commercially available bulk material electroabsorption modulator was experimentally demonstrated. By optimizing the length of the dispersion compensation fibre, nearly transform limited pulse was generated. There are a 2-ps-pulsed train with a timing jitter of 650 fs and a repetition rate of 10 GHz obtained with two-stage nonlinear compression. The quality of the pulse was further verified by 4 × 10 Gbit/s optical time-division-multiplexed communication system experiment in which a low demultiplexing power penalty of 0.3 dB was achieved.

  7. A report on older-age bipolar disorder from the International Society for Bipolar Disorders Task Force

    DEFF Research Database (Denmark)

    Sajatovic, Martha; Strejilevich, Sergio A; Gildengers, Ariel G;

    2015-01-01

    OBJECTIVES: In the coming generation, older adults with bipolar disorder (BD) will increase in absolute numbers as well as proportion of the general population. This is the first report of the International Society for Bipolar Disorder (ISBD) Task Force on Older-Age Bipolar Disorder (OABD). METHO...

  8. Gate-controlled generation of optical pulse trains using individual carbon nanotubes

    OpenAIRE

    Jiang, M; Kumamoto, Y.; Ishii, A; Yoshida, M.; Shimada, T; Kato, Y. K.

    2014-01-01

    In single-walled carbon nanotubes, electron–hole pairs form tightly bound excitons because of limited screening. These excitons display a variety of interactions and processes that could be exploited for applications in nanoscale photonics and optoelectronics. Here we report on optical pulse-train generation from individual air-suspended carbon nanotubes under an application of square-wave gate voltages. Electrostatically induced carrier accumulation quenches photoluminescence, while a voltag...

  9. Efficient generation of ultra-intense few-cycle radially polarized laser pulses

    OpenAIRE

    Carbajo, Sergio; Granados, Eduardo; Schimpf, Damian; Sell, Alexander; Hong, Kyung-Han; Moses, Jeffrey; Kaertner, Franz

    2014-01-01

    We report on efficient generation of millijoule-level, kilohertz-repetition-rate few-cycle laser pulses with radial polarization by combining a gas-filled hollow-waveguide compression technique with a suitable polarization mode converter. Peak power levels >85  GW are routinely achieved, capable of reaching relativistic intensities >1019  W/cm2 with carrier-envelope-phase control, by employing readily accessible ultrafast high-energy laser technology.

  10. Efficient generation of ultra-intense few-cycle radially polarized laser pulses.

    Science.gov (United States)

    Carbajo, Sergio; Granados, Eduardo; Schimpf, Damian; Sell, Alexander; Hong, Kyung-Han; Moses, Jeffrey; Kärtner, Franz X

    2014-04-15

    We report on efficient generation of millijoule-level, kilohertz-repetition-rate few-cycle laser pulses with radial polarization by combining a gas-filled hollow-waveguide compression technique with a suitable polarization mode converter. Peak power levels >85  GW are routinely achieved, capable of reaching relativistic intensities >10(19)  W/cm2 with carrier-envelope-phase control, by employing readily accessible ultrafast high-energy laser technology. PMID:24979025

  11. Second harmonic generation in a centrosymmetric gas medium with spatiotemporally focused intense femtosecond laser pulses

    CERN Document Server

    Li, Guihua; Xie, Hongqiang; Zeng, Bin; Yao, Jinping; Chu, Wei; Zhang, Haisu; Jing, Chenrui; He, Fei; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2013-01-01

    We demonstrate unexpectedly strong second harmonic generation (SHG) in Argon gas by use of spatiotemporally focused (SF) femtosecond laser pulses. The resulting SHG by the SF scheme at a 75 cm distance shows a significantly enhanced efficiency than that achieved with conventional focusing scheme, which offers a new promising possibility for standoff applications. Our theoretical calculations reasonably reproduce the experimental observations, which indicate that the observed SHG mainly originates from the gradient of nonuniform plasma dynamically controlled by the SF laser field.

  12. The foundations of a 95 MVA motor-generator set for pulsed duty

    CERN Document Server

    Probst, P H

    1972-01-01

    The vibration forces produced by the 95 MVA motor-generator set for the main ring magnets of the 28 GeV proton synchrotron at CERN in Geneva recur cyclically every few seconds and necessitate a special foundation for the set. Its function is to prevent any disturbing vibration energy reaching the accelerator and to eliminate any build- up in oscillation from successive vibration pulses. The final design incorporates a platform mounted on helical springs and fitted with additional dampers. (4 refs).

  13. Contrast generation in the nuclear-spin tomography by pulsed ultrasound

    International Nuclear Information System (INIS)

    In the framework of this thesis a combined method of ultrasound and nuclear-spin tomography is presented. Via ultrasound pulses by the sound-radiation force in liquids and tissue phantoms motions are generated, which depend on ther viscoelastic properties. This motions are made visible by a motion-sensitive tomograph sequence in the phase image of the tomograph in form of a phase change. The first measurements on simple phantoms and liquids are presented.

  14. Quasistatic Magnetic Field Generation by an Intense Ultrashort Laser Pulse in Underdense Plasma

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chun-Yang; ZHU Shao-Ping; HE Xian-Tu

    2000-01-01

    The quasistatic magnetic field created in the interaction of intense ultrashort laser pulses with underdense plasmas has been investigated by two-dimensional particle simulation. The relativistic ponderomotive force and plasma wave excited in self-modulation processes can drive intense electron current mainly in the propagation direction.As a result, an azimuthal, multi-mega Gauss order quasi-static magnetic field can be generated around the laserbeam.

  15. Temporal order of bipolar cell genesis in the neural retina

    Directory of Open Access Journals (Sweden)

    Chen C-M Amy

    2008-01-01

    Full Text Available Abstract Background Retinal bipolar cells comprise a diverse group of neurons. Cone bipolar cells and rod bipolar cells are so named for their connections with cone and rod photoreceptors, respectively. Morphological criteria have been established that distinguish nine types of cone bipolar cells and one type of rod bipolar cell in mouse and rat. While anatomical and physiological aspects of bipolar types have been actively studied, little is known about the sequence of events that leads to bipolar cell type specification and the potential relationship this process may have with synapse formation in the outer plexiform layer. In this study, we have examined the birth order of rod and cone bipolar cells in the developing mouse and rat in vivo. Results Using retroviral lineage analysis with the histochemical marker alkaline phosphatase, the percentage of cone and rod bipolar cells born on postnatal day 0 (P0, P4, and P6 were determined, based upon the well characterized morphology of these cells in the adult rat retina. In this in vivo experiment, we have demonstrated that cone bipolar genesis clearly precedes rod bipolar genesis. In addition, in the postnatal mouse retina, using a combination of tritiated-thymidine birthdating and immunohistochemistry to distinguish bipolar types, we have similarly found that cone bipolar genesis precedes rod bipolar genesis. The tritiated-thymidine birthdating studies also included quantification of the birth of all postnatally generated retinal cell types in the mouse. Conclusion Using two independent in vivo methodologies in rat and mouse retina, we have demonstrated that there are distinct waves of genesis of the two major bipolar cell types, with cone bipolar genesis preceding rod bipolar genesis. These waves of bipolar genesis correspond to the order of genesis of the presynaptic photoreceptor cell types.

  16. Generation of a few femtoseconds pulses in seeded FELs using a seed laser with small transverse size

    Science.gov (United States)

    Li, Heting; Jia, Qika

    2016-09-01

    We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the center portion of the electron beam and then short pulses at high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse based on the HGHG scheme and 9 nm soft x-ray pulse based on the EEHG scheme with duration of about 8 fs (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 μm. This new scheme can provide an optional operation mode for the existing seeded FEL facilities to meet the requirement of short-pulse FEL.

  17. Optimization of the vacuum insulator stack of the MIG pulsed power generator

    Science.gov (United States)

    Khamzakhan, G.; Chaikovsky, S. A.

    2014-11-01

    The MIG multi-purpose pulsed power machine is intended to generate voltage pulses of amplitude up to 6 MV with electron-beam loads and current pulses of amplitude up to 2.5 MA and rise time '00 ns with inductive loads like Z pinches. The MIG generator is capable of producing a peak power of 2.5 TW. Its water transmission line is separated from the vacuum line by an insulator stack. In the existing design of the insulator, some malfunctions have been detected. The most serious problems revealed are the vacuum surface flashover occurring before the current peaks and the deep discharge traces on the water-polyethylene interface of the two rings placed closer to the ground. A comprehensive numerical simulation of the electric field distribution in the insulator of the MIG generator has been performed. It has been found that the chief drawbacks are nonuniform voltage grading across the insulator rings and significant enhancement of the electric field at anode triple junctions. An improved design of the insulator stack has been developed. It is expected that the proposed modification that requires no rearrangement of either the water line or the load-containing vacuum chamber will provide higher electric strength of the insulator.

  18. Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

    Institute of Scientific and Technical Information of China (English)

    T.NAMIHIRA; S.SAKAI; M.MATSUDA; D.WANG; T.KIYAN; H.AKIYAMA; K.OKAMOTO; K.TODA

    2007-01-01

    Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure,acute respiratory distress syndrome and other illnesses related to the lungs.Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO.This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder.The presence of NO in the air leads to the formation of nitric dioxide (NO2),which is toxic to the lungs.Therefore,an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease.To develop the NO inhalation system without a gas cylinder,which would include a high concentration of NO,NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge.In the present work,the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition.The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds.In addition,it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.

  19. Numerical studies of powerful terahertz pulse generation from a super-radiant surface wave oscillator

    International Nuclear Information System (INIS)

    The results of theoretical and numerical studies of coherent stimulated terahertz radiation from intense, subnanosecond electron beam are presented. The mechanism of terahertz pulse generation is associated with self-bunching of the beam and slippage of the wave over the whole electron flow. This so called Cherenkov super-radiance (SR) is used to propose a compact terahertz generator with high peak power. A large cross-section (overmoded), slow wave structure is designed to support the high power handling capability, and the mode competition is avoided by operating the device in the surface wave status. With 2.5 D particle-in-cell simulation, the 'hot' characteristics of the proposed super-radiant terahertz generator are investigated, and the numerical results show that the SR peak power could be further increased by optimizing the amplitude profile of electron pulse. Under the condition of 0.5 ns pulsewidth, 500 kV voltage, and 1.5 kA current, the 110 ps, 680 MW, and 0.14 THz SR pulse is achieved with a power efficiency of 90.67% in TM01 mode.

  20. Optimization of the vacuum insulator stack of the MIG pulsed power generator

    International Nuclear Information System (INIS)

    The MIG multi-purpose pulsed power machine is intended to generate voltage pulses of amplitude up to 6 MV with electron-beam loads and current pulses of amplitude up to 2.5 MA and rise time '00 ns with inductive loads like Z pinches. The MIG generator is capable of producing a peak power of 2.5 TW. Its water transmission line is separated from the vacuum line by an insulator stack. In the existing design of the insulator, some malfunctions have been detected. The most serious problems revealed are the vacuum surface flashover occurring before the current peaks and the deep discharge traces on the water-polyethylene interface of the two rings placed closer to the ground. A comprehensive numerical simulation of the electric field distribution in the insulator of the MIG generator has been performed. It has been found that the chief drawbacks are nonuniform voltage grading across the insulator rings and significant enhancement of the electric field at anode triple junctions. An improved design of the insulator stack has been developed. It is expected that the proposed modification that requires no rearrangement of either the water line or the load-containing vacuum chamber will provide higher electric strength of the insulator

  1. Mid-infrared ultrafast laser pulses induced third harmonic generation in nitrogen molecules on an excited state

    OpenAIRE

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

    2015-01-01

    We report on generation of third harmonic from nitrogen molecules on the excited state with a weak driver laser pulse at a mid-infrared wavelength. The excited nitrogen molecules are generated using a circularly polarized intense femtosecond pulse which produces energetic electrons by photoionization to realize collisional excitation of nitrogen molecules. Furthermore, since the third harmonic is generated using a pump-probe scheme, it enables investigation of the excited-state dynamics of ni...

  2. High-Order Harmonic Generation by Two Non-collinear Coherent Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    陆伟新; 刘婷婷; 杨宏; 孙騊亨; 龚旗煌

    2003-01-01

    We have studied the high-order harmonic generated by two coherent pulses in argon gas produced by a gas jet. A loop in the relationship of the harmonic intensity versus the absolute values of relative phase difference was observed for non-collinear arrangement. Compared with the collinear arrangement, increase of 10 times of the conversion efficiency for 17th-order harmonic generation at an appropriate relative phase difference was obtained. The calculation of the intensity and phase for the laser field near the focus gives a simple reason for these phenomena.

  3. Synchronized and timing-stabilized pulse generation from a gain-switched laser diode for stimulated Raman scattering microscopy

    Science.gov (United States)

    Tokunaga, Kyoya; Fang, Yi-Cheng; Yokoyama, Hiroyuki; Ozeki, Yasuyuki

    2016-03-01

    We present a picosecond laser source based on a gain-switched laser diode (GS-LD) that can be applied to stimulated Raman scattering (SRS) microscopy. A 1.06-μm GS-LD was used to generate 14-ps pulses at a repetition rate of 38 MHz. The GS-LD was driven by 200-ps electrical pulses, which were triggered through a toggle flip-flop (T-FF). As a result, the GS-LD pulses were subharmonically synchronized to Ti:sapphire laser (TSL) pulses at a repetition rate of 76 MHz. We investigated the timing jitter of GS-LD pulses and found it to be less than 2.5 ps. We also show that the trigger delay can be less sensitive to the optical power of TSL pulses by controlling the threshold voltage of the T-FF. As a result, GS-LD pulses sufficiently overlapped with TSL pulses even when we scanned the wavelength of the TSL pulses. We demonstrate the SRS imaging of HeLa cells with GS-LD pulses and TSL pulses, proving that GS-LD is readily applicable to SRS microscopy as a compact and stable pulse source.

  4. SESAM-modelocked Yb:CaF2 thin-disk-laser generating 285 fs pulses with 1.78 μJ of pulse energy

    Science.gov (United States)

    Dannecker, Benjamin; Abdou Ahmed, Marwan; Graf, Thomas

    2016-05-01

    We report on a SESAM-modelocked Yb:CaF2 thin-disk oscillator designed to generate more than 1 μJ of pulse energy at a moderate pulse repetition rate. The goal of our experiment was to explore the potential of Yb:CaF2 in a thin-disk laser (TDL) architecture for high power at pulse durations shorter than 300 fs as compared to other Yb-doped crystals exhibiting broad gain bandwidth. At a repetition rate of 10 MHz the laser produced an average output power of up to 17.8 W (1.78 μJ of pulse energy) with a beam quality factor M 2 below 1.2. The pulse duration was measured to be 285 fs, which results in a peak power of 5.5 MW. To the best of our knowledge, this is the highest pulse energy and peak power demonstrated to date with sub-300 fs pulses generated by SESAM-modelocked oscillators, leading to the conclusion that Yb:CaF2 is a very promising crystal for TDL technology.

  5. Post-compression of high energy terawatt-level femtosecond pulses and application to high order harmonic generation

    CERN Document Server

    Hort, Ondřej; Cabasse, Amélie; Petit, Stéphane; Mével, Eric; Descamps, Dominique; Constant, Eric

    2015-01-01

    We perform a post-compression of high energy pulses by using optical-field ionization of low pressure helium gas in a guided geometry. We apply this approach to a TW chirped-pulse-amplification based Ti:Sapphire laser chain and show that spectral broadening can be controlled both with the input pulse energy and gas pressure. Under optimized conditions, we generate 10 fs pulses at TW level directly under vacuum and demonstrate a high stability of the post compressed pulse duration. These high energy post-compressed pulses are thereafter used to perform high harmonic generation in a loose focusing geometry. The XUV beam is characterized both spatially and spectrally on a single shot basis and structured continuous XUV spectra are observed.

  6. Photonic ultra-wideband pulse generation, hybrid modulation and dispersion-compensation-free transmission in multi-access communication systems.

    Science.gov (United States)

    Tan, Kang; Shao, Jing; Sun, Junqiang; Wang, Jian

    2012-01-16

    We propose and demonstrate a scheme for optical ultrawideband (UWB) pulse generation by exploiting a half-carrier-suppressed Mach-Zehnder modulator (MZM) and a delay-interferometer- and wavelength-division-multiplexer-based, reconfigurable and multi-channel differentiator (DWRMD). Multi-wavelength, polarity- and shape-switchable UWB pulses of monocycle, doublet, triplet, and quadruplet are experimentally generated simply by tuning two bias voltages to modify the carrier-suppression ratio of MZM and the differential order of DWRMD respectively. The pulse position modulation, pulse shape modulation, pulse amplitude modulation and binary phase-shift keying modulation of UWB pulses can also be conveniently realized with the same scheme structure, which indicates that the hybrid modulation of those four formats can be achieved. Consequently, the proposed approach has potential applications in multi-shape, multi-modulation and multi-access UWB-over-fiber communication systems.

  7. Third Harmonic Generation of a Short Pulse Laser in a Tunnel Ionizing Plasma: Effect of Self-Defocusing

    Directory of Open Access Journals (Sweden)

    Niti Kant

    2013-08-01

    Full Text Available Third harmonic generation of a Gaussian short pulse laser in a tunnel ionizing plasma is investigated. A Gaussian short pulse laser propagating through a tunnel ionizing plasma generates third harmonic wave. Inhomogeneity of the electric field along the wavefront of the fundamental laser pulse causes more ionization along the axis of propagation while less ionization off axis, leading to strong density gradient with its maximum on the axis of propagation. The medium acts like a diverging lens and pulse defocuses strongly. The normalized third harmonic amplitude varies periodically with the distance with successive maxima acquiring lower value. The self-defocusing of the fundamental laser pulse decays the intensity of the third harmonic pulse.

  8. Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses

    CERN Document Server

    Mondal, S; Ding, W J; Hafez, H A; Fareed, M A; Laramée, A; Ropagnol, X; Zhang, G; Sun, S; Sheng, Z M; Zhang, J; Ozaki, T

    2016-01-01

    We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with length 5 \\mu m, a maximum 13.8 times enhancement in the THz pulse energy (in $\\leq$ 20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies ($\\leq$ 20THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20 - 200 THz). For the latter, we measure a maximum energy enhancement of 28 times for the nanorod targets of length 60 \\mu m . Particle-in-cell simulations reveal that THz pulses are mostly generated by coherent transition radiation of laser produced hot electrons, which are efficiently enhanced with the use of nanorod targets. Good agreement is found between the simulation and experimental results.

  9. Electronic measurement system for pulse generators supplying industrial pollution abatement electro-filters

    International Nuclear Information System (INIS)

    We had to measure and display the following parameters of pulse generators: 1. the height and the time characteristics of the current and voltage pulses (within the ranges: 0-10 kA; 0-100 kV; 10-500 μsec.); 2. the pulse frequency (0-300 Hz); 3. the supply voltage and current (0-5 kV; 0-10 A). The voltage and current transducers convert these parameters to 0-10 V voltage signals. To measure the time evolution and the pulse height we are using 'samplehold' circuits and peak detectors. The difficulties were determined by the high speed of the signals (about 5 V/μsec.). To display the measurement results we used special digital-analog devices instruments. As a more economical solution we developed an original analog-digital converter, from 0-10 V to 3 digits numbers. These numbers are displayed with LED circuits. The display changing rate is 1 Hz. To reduce the electromagnetic noise influence, we are using C-MOS integrated circuit. All the components are made in Romania. (Author)

  10. Blue-Extended Supercontinuum Generation in Photonic Crystal Fibers with Picosecond Pulse Pumping

    International Nuclear Information System (INIS)

    We report supercontinuum generation extending to the blue spectral region using pulses of 1.8 ps duration at 1040 nm in GeO2-doped core photonic crystal fibers. A spectrum in fundamental mode spanning from 415 nm to beyond 1750 nm is generated in a uniform photonic crystal fiber (PCF). A zero dispersion wavelength decreasing PCF is fabricated to optimize the parameters for deeper blue components generated by cross-phase modulation and group-velocity matching. Although the PCF is pumped at a low input power of 1.3 W in anomalous dispersion and relatively far from the zero dispersion wavelength, a flat continuum covering 406.1–671.8 nm is generated, which is of primary importance in a number of bio-photonic applications such as fluorescence imaging microscopy

  11. Axial magnetic field generation by intense circularly polarized laser pulses in underdense plasmas

    International Nuclear Information System (INIS)

    Axial magnetic field generation by intense circularly polarized laser beams in underdense plasmas has been studied with three-dimensional particle-in-cell simulations and by means of theoretical analysis. Comparisons between analytical models and simulation results have identified an inverse Faraday effect as the main mechanism of the magnetic field generation in inhomogeneous plasmas. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach a maximum strength of several tens of megagauss for laser pulses undergoing relativistic self-focusing and channeling in moderately relativistic regime. Ultrarelativistic laser conditions inhibit magnetic field generation by directly reducing a source term and by generating fully evacuated plasma channels.

  12. Different pulse pattern generation by frequency detuning in pulse modulated actively mode-locked ytterbium doped fiber laser

    Science.gov (United States)

    Chen, He; Chen, Sheng-Ping; Si, Lei; Zhang, Bin; Jiang, Zong-Fu

    2015-10-01

    We report the results of our recent experimental investigation of the modulation frequency detuning effect on the output pulse dynamics in a pulse modulated actively mode-locked ytterbium doped fiber laser. The experimental study shows the existence of five different mode-locking states that mainly depend on the modulation frequency detuning, which are: (a) amplitude-even harmonic/fundamental mode-locking, (b) Q-switched harmonic/fundamental mode-locking, (c) sinusoidal wave modulation mode, (d) pulses bundle state, and (e) noise-like state. A detailed experimental characterization of the output pulses dynamics in each operating mode is presented.

  13. Ultrashort-pulse generation in a YAG:Nd(3+) laser in a scheme with colliding pulses

    Energy Technology Data Exchange (ETDEWEB)

    Prokhorenko, V.I.; Tikhonov, E.A.; Iatskiv, D.IA.; Bushmakin, E.N.

    1987-04-01

    The time, energy, and statistical characteristics of a picosecond mode-locked YAG:Nd(3+) laser with colliding pulses are studied. Under these conditions, no additional pulse shortening occurs as compared to a laser utilizing an absorber which is in contact with the nontransmitting mirror. However, this mode of operation is characterized by a greater reproducibility of the emitted pulse duration. A direct recording of the duration and the spectrum is used. It is shown that spectrally limited pulses are emitted only when the cell with a saturable absorber (dye No. 3274) is located in the center of the antiresonant reflector. 11 references.

  14. Direct generation of intense extreme ultraviolet supercontinuum with chirped 11-mJ pulses from a femtosecond laser amplifier

    CERN Document Server

    Zeng, Bin; Li, Guihua; Yao, Jinping; Ni, Jielei; Zhang, Haisu; Cheng, Ya; Xu, Zhizhan

    2011-01-01

    We report on the generation of intense extreme ultraviolet (EUV) supercontinuum with photon energies spanning from 35 eV to 50 eV (i. e., supporting an isolated attosecond pulse with a duration of ~271 as) by loosely focusing 11-mJ chirped pulses from a femtosecond laser amplifier into a 10-mm long gas cell filled with krypton gas. We observe that when high-order harmonics are generated with transformed-limited ~35 fs pulses, only discrete harmonics can be produced; whereas for negatively chirped 188 fs pulses, EUV supercontinuum can be observed in single-shot harmonic spectrum. The dramatic change of spectral and temporal properties of the driver pulses after passing through the gas cell indicates that propagation effects play a significant role in promoting the generation of the EUV supercontinuum.

  15. 不同中心频率下双极电脉冲的生物医学效应分析%An Analysis on Biomedical Effects of Bipolar Electric Pulses at Different Central Frequency

    Institute of Scientific and Technical Information of China (English)

    谈亚芳; 杨宏春; 徐军; 张怡; 吴明和; 邹姮

    2012-01-01

    采用多层球对称细胞模型,针对恶性Tonsillar B细胞和Jurkat T淋巴细胞,利用电路分析方法,计算了不同中心频率的一阶高斯脉冲在细胞各部分的电压分布;给出了中心频率与细胞膜跨膜电压间的定量关系和细胞核膜电穿孔的最佳频率;研究了细胞膜电穿孔和纳秒脉冲致DNA降解的原因.本文工作为双极瞬态脉冲应用于恶性肿瘤治疗提供了参考.%Adopting the cell model of multilayer spherical symmetry and the circuit analysis? the present paper gives the calculated results of the voltages on each of several parts of malignant Tonsillar B-ceIls and Jurkat T lymphocytes when the first-order Gaussian pulses at different central frequency apposed on them. The relationship between the central frequency and the transmembrane voltages of plasma membrane is also given. The optimum frequency causing electroporation in nuclear envelope is given as well. The paper discusses the reasons of electroporation in membrane and DNA degradation in nuclear. The work provides a reference for usage of transient bipolar electric pulses in cancer treatment.

  16. 双极性窄脉冲介质阻挡放电合成臭氧的研究%Experimental Study on Ozone Synthesis in Dielectric Barrier Discharge Triggered by Bipolar Narrow Pulse

    Institute of Scientific and Technical Information of China (English)

    刘钟阳; 吴彦; 王宁会

    2001-01-01

    The new dielectric barrier discharge (DBD) is introduced in this paper, which is triggered by bipolar narrow pulse using high voltage power with spark gap switch. The experimental phenomena demonstrate that the new DBD have advantages of both ordinary DBD and pulse corona discharge. The efficient is higher comparing with ordinary DBD. And the energy efficiency is increased over 30% by this method. When the concentration of ozone is 4~8 g/m3 and the fed gas is air, the efficiency is 90~120 g/(kWh). When the concentration of ozone is 3~20 g/m3 and the fed gas is oxygen, the efficiency is 300~390 g/(kWh).%利用火花隙开关的双极性陡前沿窄脉冲高压电源,产生双极性陡前沿窄脉冲,在放电反应器中引发介质阻挡放电。试验结果表明:该种形式的放电兼有短脉冲电晕放电和介质阻挡放电的优点,合成臭氧产率高:进气为露点30%。

  17. Dual branch high voltage pulse generator for the beam extraction of the Large Hadron Collider

    CERN Document Server

    Bonthond, J; Ducimetière, L; Jansson, U; Vossenberg, Eugène B

    2002-01-01

    The LHC beam extraction kicker system, MKD, is composed of 15 fast kicker magnets per beam to extract the particles in one turn from the collider and to dispose them, after dilution, on an external absorber. Each magnet is powered by a separate pulse generator. The original single branch generator consisted of a discharge capacitor in series with a solid state closing switch left bracket 1 right bracket operating at 30 kV. In combination with a parallel freewheel diode stack this generator produced a current pulse of 2.7 mus rise time, 18.5 kA amplitude and about 1.8 ms fall time, of which only about 90 mus are needed to dump the beam. The freewheel diode circuit is equipped with a flat top current droop compensation network, consisting of a low voltage, low stray inductance, high current discharge capacitor. Extensive reliability studies have meanwhile suggested to further increase the operational safety of this crucial system by equipping each generator with two parallel branches. This paper presents the re...

  18. Nearly penalty-free, less than 4 ps supercontinuum Gbit/s pulse generation over 1535-1560 nm

    Science.gov (United States)

    Morioka, T.; Kawanishi, S.; Mori, K.; Saruwatari, M.

    1994-05-01

    Nearly penalty-free less than 4ps supercontinuum WDM pulses are generated at 6.3 Gbit/s over 1535-1560 nm for the first time using a 200 nm superbroadened supercontinuum in an optical fibre pumped by 1.7 W, 3.3 ps, 1542 nm short pulses from an Er(3+)-doped fibre ring laser.

  19. High-energy Few-cycle Pulses Directly Generated from Strongly Phase-mismatched Lithium Niobate Crystal

    OpenAIRE

    Zhou, Binbin; Chong, A.; Wise, F.W.; Bache, Morten

    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.

  20. High power, single mode, all-fiber source of femtosecond pulses at 1550 nm and its use in supercontinuum generation

    Science.gov (United States)

    Nicholson, Jeffrey W.; Yablon, A. D.; Westbrook, P. S.; Feder, K. S.; Yan, M. F.

    2004-06-01

    We present a source of high power femtosecond pulses at 1550 nm with compressed pulses at the end of a single mode fiber (SMF) pigtail. The system generates 34 femtosecond pulses at a repetition rate of 46 MHz, with average powers greater than 400 mW. The pulses are generated in a passively modelocked, erbium-doped fiber laser, and amplified in a short, erbium-doped fiber amplifier. The output of the fiber amplifier consists of highly chirped picosecond pulses. These picosecond pulses are then compressed in standard single mode fiber. While the compressed pulses in the SMF pigtail do show a low pedestal that could be avoided with the use of bulk-optic compression, the desire to compress the pulses in SMF is motivated by the ability to splice the single mode fiber to a nonlinear fiber, for continuum generation applications. We demonstrate that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, we generate a supercontinuum spectrum that spans more than an octave, with an average power 400 mW. Such a high power, all-fiber supercontinuum source has many important applications including frequency metrology and bio-medical imaging.

  1. Studies on an improved indigenous pressure wave generator and its testing with a pulse tube cooler

    Science.gov (United States)

    Jacob, S.; Karunanithi, R.; Narsimham, G. S. V. L.; Kranthi, J. Kumar; Damu, C.; Praveen, T.; Samir, M.; Mallappa, A.

    2014-01-01

    Earlier version of an indigenously developed Pressure Wave Generator (PWG) could not develop the necessary pressure ratio to satisfactorily operate a pulse tube cooler, largely due to high blow by losses in the piston cylinder seal gap and due to a few design deficiencies. Effect of different parameters like seal gap, piston diameter, piston stroke, moving mass and the piston back volume on the performance is studied analytically. Modifications were done to the PWG based on analysis and the performance is experimentally measured. A significant improvement in PWG performance is seen as a result of the modifications. The improved PWG is tested with the same pulse tube cooler but with different inertance tube configurations. A no load temperature of 130 K is achieved with an inertance tube configuration designed using Sage software. The delivered PV power is estimated to be 28.4 W which can produce a refrigeration of about 1 W at 80 K.

  2. Exploring pulse-voltage-triggered optically induced electrohydrodynamic instability for femtolitre droplet generation

    Science.gov (United States)

    Wang, Feifei; Fei, Fei; Liu, Lianqing; Yu, Haibo; Yu, Peng; Wang, Yuechao; Lee, Gwo-Bin; Jung Li, Wen

    2014-06-01

    We present a multipoint "virtual dispenser" to draw femtolitre droplets from a dielectric fluidic thin film using pulse-voltage-triggered optically induced electrohydrodynamic instability (PVT-OEHI). The "virtual dispenser" generates instability nucleation sites by controlling the optically induced lateral electrical stress and thermocapillary flow inside an optoelectronics chip. A time scale analysis shows that the electrohydrodynamic (EHD) instability phenomenon is present; however, its external manifestation is suppressed by OEHI. We observed two droplet dispensing mechanisms which correspond to different EHD states: Taylor cone formation and optically induced EHD jet. The EHD states transition could be realized by adjusting the pulse voltage parameters to alter the morphology of dispensed micron-scale polymer droplets, which could then be formed into organized arrays of microlenses with controllable diameter and curvature based on surface tension effect.

  3. Nanosecond pulsed laser induced generation of open macro porosity on sintered ZnO pellet surface

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.K., E-mail: anilks@barc.gov.in [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai (India); Samanta, Soumen [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Sinha, Sucharita [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai (India)

    2015-01-15

    Highlights: • Zinc oxide (ZnO) targets have been surface treated using a frequency doubled nanosecond pulsed Nd:YAG laser at laser fluence levels ranging between 2 and 9 J/cm{sup 2}. • Our observations establish that laser irradiation provides an effective technique for generation of surface macro porosity in case of ZnO pellets. • Extent of surface porosity and the mean pore size could be controlled by appropriately varying the incident laser fluence. • Such laser treated ZnO surfaces with enhanced surface porosity and large size pores (mean pore area ∼2–5 μm{sup 2}) can serve as potential candidate for humidity sensors with high sensitivity and fast response time, particularly in high humidity range. - Abstract: Surface porosity and pore size distribution of sensing material greatly influence performance parameters such as sensitivity, reproducibility and response time of sensors. Various approaches have been employed to generate surface porosity having varying pore size distribution. This paper presents our results on pulsed laser irradiation based surface microstructuring of sintered zinc oxide (ZnO) pellets leading to generation of enhanced surface porosity. ZnO targets have been surface treated using a frequency doubled nanosecond pulsed Nd:YAG laser at laser fluence levels ranging between 2 and 9 J/cm{sup 2}. Our observations establish that laser irradiation provides an effective technique for generation of surface macro porosity in case of ZnO pellets. Also, extent of surface porosity and the mean pore size could be controlled by appropriately varying the incident laser fluence. Such laser treated ZnO surfaces with enhanced surface porosity and large size pores can serve as potential candidate for humidity sensors with high sensitivity and fast response time, particularly in high humidity range.

  4. Program-controlled generator of delayed pulses for nanosecond time-to-digital converter control

    International Nuclear Information System (INIS)

    The structure of a delayed pulse generator designed for testing microchannel markers, amplification assemblies, time-to-digital converters, being a part of charged particle time-of-flight spectrometers, is described. The generator is included into a complex of automated test means of spectrometers and it is aimed at interfacing with the ELEKTRONIKA-60 microcomputer channel. The generator circuit is made on the basis of transistor matrices of series 198. The compensation circuit of the accumulation condensator charge permits to stabilize the initial zero potential, that besides high stability of thresholds of discriminating elements 521SA4, permits to obtain accuracy of time interval representation with near 2 ns ± 0.3%

  5. On-chip two-octave supercontinuum generation by enhancing self-steepening of optical pulses

    CERN Document Server

    Zhang, Lin; Yue, Yang; Lin, Qiang; Painter, Oskar; Beausoleil, Raymond G; Willner, Alan E

    2011-01-01

    Dramatic advances in supercontinuum generation have been made recently using photonic crystal fibers, but it is quite challenging to obtain an octave-spanning supercontinuum on a chip, partially because of strong dispersion in high-index-contrast nonlinear integrated waveguides. We show by simulation that extremely flat and low dispersion can be achieved in silicon nitride slot waveguides over a wavelength band of 500 nm. Different from previously reported supercontinua that were generated either by higher-order soliton fission in anomalous dispersion regime or by self phase modulation in normal dispersion regime, a two-octave supercontinuum from 630 to 2650 nm (360 THz in total) can be generated by greatly enhancing self-steepening in nonlinear pulse propagation in almost zero dispersion regime, when an optical shock as short as 3 fs is formed, which enables on-chip ultra-wide-band applications.

  6. Classical Dynamics of Harmonic Generation of the Hydrogen Molecular Ion Interacting with Ultrashort Intense Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    LI Chao-Hong; DUAN Yi-Wu; Wing-Ki Liu; Jian-Min Yuan

    2001-01-01

    Within Born-Oppenheimer approximation, by using the classical trajectory theory, a description for the high order harmonic generation of the hydrogen molecular ion interacting with ultrashort laser pulses has been pre sented. The Coulomb singularities have been remedied by the regularization. The action-angle variables have been used to generate the initial inversion symmetry microcanonical distribution. Within a proper intensity range, a harmonic plateau with only odd harmonics appears. For a larger intensity, because of the existence of chaos, the harmonic spectra become noisier. For a large enough intensity, the ionization takes place and the harmonics disappear. So the chaos causes the noises, the ionization suppresses the harmonic generation, and the onset of the ionization follows the onset of chaos.

  7. Photonic generation of ultrawideband monocycle and doublet pulses by using a semiconductor-optical-amplifier-based wavelength converter

    DEFF Research Database (Denmark)

    Zhou, Enbo; Yu, Xianbin; Zhang, Xinliang;

    2009-01-01

    Photonic generation of ultrawideband (UWB) monocycle and doublet pulses is experimentally demonstrated using a cascaded electroabsorption modulator (EAM) and semiconductor optical amplifier by exploiting a combination of cross-absorption modulation and cross-gain modulation. The polarities and...

  8. I-V and DLTS study of generation and annihilation of deep-level defects in an oxygen-ion irradiated bipolar junction transistor

    Science.gov (United States)

    Madhu, K. V.; Kulkarni, S. R.; Ravindra, M.; Damle, R.

    A commercial bipolar junction transistor (2N 2219A, npn) irradiated with 84 MeV O6+-ions with fluence of the order of 1013 ions cm-2 is studied for radiation-induced gain degradation and deep-level defects or recombination centers. I-V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep-level transient spectroscopy. Minority carrier trap energy levels with energies ranging from EC -0.17 eV to EC -0.55 eV are observed in the base-collector junction of the transistor. Majority carrier defect levels are also observed with energies ranging from EV +0.26 eV to EV +0.44 eV. The irradiated device is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for an increase in base current through Shockley-Read-Hall or multi-phonon recombination and consequent transistor gain degradation.

  9. Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers

    International Nuclear Information System (INIS)

    We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs

  10. Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zajnulina, M.; Giannone, D.; Haynes, R.; Roth, M. M. [innoFSPEC-VKS, Leibniz Institute for Astrophysics, An der Sternwarte 16, 14482 Potsdam (Germany); Böhm, M. [innoFSPEC-InFaSe, University of Potsdam, Am Mühlenberg 3, 14476 Golm (Germany); Blow, K. [Aston Institute of Photonic Technologies, Aston Triangle, Birmingham B4 7ET (United Kingdom); Rieznik, A. A. [Instituto Tecnologico de Buenos Aires and CONICET, Buenos Aires (Argentina)

    2015-10-15

    We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.

  11. Generation of ultra-short x-ray pulses in a cluster system during ionization by femto-second optical pulse

    International Nuclear Information System (INIS)

    Full text: We present the results of modelling generation of the atto-second VUV and x-ray pulses during ionization of atomic and cluster systems by femto-second optical laser pulse. The concrete data are received for the Ar cluster response, the molecular 2D H2+ response for different inter-nuclear distances (R=2.5, 3.5, 7.4, 16 a.u.) with smoothed Coulomb potential and atomic (H) response (spectral dependence) under ionization of the system by femto-second optical pulse. Our calculation show that the generation of the atto-second x-ray pulses in the cluster system is more effective and profitable (as minimum the 2-3 orders) than in similar molecular atomic one. The generation of the atto-second pulses in the molecular system is more profitable too (as minimum the 1-2 orders) than in similar atomic one. The last achievements in this field demonstrate a possibility of construction of the compact x-ray radiation sources. (author)

  12. Energy Efficiency of Inductive Energy Storage System Pulsed Power Generator Using Fast Recovery Diode

    Science.gov (United States)

    Go, Tomio; Kanesawa, Kyousuke; Yamazaki, Nobuyuki; Mukaigawa, Seiji; Takaki, Koichi; Fujiwara, Tamiya

    Characteristics of inductive energy storage system pulsed power generator with semiconductor opening switch (SOS) diodes are investigated with focusing on an energy transfer efficiency from the generator to the resistive load. Fast recovery diodes VMI K100UF were used as SOS and were connected in series and/or in parallel to realize a large current and a high output voltage. The output voltage increases with increasing circuit inductance L and/or primary capacitor capacitance C. The reverse pumping time also increases with LC value and is saturated to 100 ns at LC=50×10-15 HF. The pulse width of the output voltage increases gradually with increasing value of the LC multiplication. The energy transfer efficiency of the generator to the resistive load has a maximum value of 71% at C=4nF and L=12.6μH when the load resistance is 122 Ω. This value is almost two times larger than 56 Ω of the surge impedance Zs=√L/C and much smaller than impedance of the SOS diodes after interrupting the circuit current. The maximum energy transfer efficiency decreases from 71 to 32% with decreasing LC value from 50×10-15 to 1.2×10-15 HF.

  13. High harmonic generation in H$_2^+$ and HD$^+$ by two-colour femtosecond laser pulses

    Indian Academy of Sciences (India)

    Farzana Sharmin; Samir Saha; S S Bhattacharyya

    2013-12-01

    We have theoretically investigated the high harmonic generation (HHG) spectra of H$_2^+$ and HD$^+$ using a time-dependent wave packet approach for the nuclear motion with combined twocolour (1$_L$–3$_L$) pulsed lasers for ωL corresponding to wavelengths 1064 nm and 800 nm. The 1$_L$ and 3$_L$ lasers have peak intensities of $I_1^0 = 5.0 × 10^{13}$ W/cm$^2$ and $I_2^0 = 2.0 × 10^{14}$ W/cm$^2$, respectively. We have taken the pulse duration of $T = 50$ fs for both the fields, and the molecular initial vibrational level 0 = 0. We have argued that for these combinations, the harmonic generation due to transitions in the electronic continuum by tunnelling or multiphoton ionization may be neglected and only the electronic transitions within the two lowest electronic states would be important. Thus, the characteristic features of HHG spectra in the two-colour field are determined, in our model, by the nuclear motions on the two lowest field-coupled electronic states between which interelectronic and intraelectronic (due to the intrinsic dipole moments in case of HD+) radiative transitions can take place. We have studied the role of relative phase ($\\varphi$) of the two fields on the HHG spectra of the molecular ions. In case of HD+, the effect of nonadiabatic (NA) nonradiative interaction between the two lowest Born–Oppenheimer (BO) electronic states (1$s_g$, 2$p_u$) has been taken into account. Our calculations give realistic HHG spectra which are reasonably efficient and extended for both H$_2^+$ and HD$^+$ in the mixed two-colour field without involving the electronic continuum. The use of two-colour (1$_L$–3$_L$) field enables us to generate high harmonics beyond that achievable with a single 1$_L$ or 3$_L$ field of the corresponding intensity, frequency and pulse time.

  14. Energy-scalable temporal cleaning device for femtosecond laser pulses based on cross-polarized wave generation

    International Nuclear Information System (INIS)

    We report on a compact energy-scalable device for generating high-fidelity femtosecond laser pulses based on spatial filtering through a hollow-core fiber followed by a nonlinear crystal for cross polarized wave (XPW) generation. This versatile device is suited for temporal pulse cleaning over a wide range of input energies (from 0.1 to ≥10 mJ) and is successfully qualified on different ultrafast laser systems. Full characterization of the XPW output is presented. In particular, we demonstrate the generation of 1.6 mJ energy pulses starting from 11 mJ input pulse energy. The temporal contrast of the pulses is enhanced by more than 4 orders of magnitude. In addition, pulse shortening from 40 fs down to 15 fs Fourier-transform limit yields an overall peak-power transmission of up to 50%. This device not only serves as an integrated pulse contrast filter inside an ultrafast laser amplifier but also as a simple back-end solution for temporal post-compression of amplified pulses. (authors)

  15. Generation of parabolic similaritons in tapered silicon photonic wires: comparison of pulse dynamics at telecom and mid-infrared wavelengths.

    Science.gov (United States)

    Lavdas, Spyros; Driscoll, Jeffrey B; Jiang, Hongyi; Grote, Richard R; Osgood, Richard M; Panoiu, Nicolae C

    2013-10-01

    We study the generation of parabolic self-similar optical pulses in tapered Si photonic nanowires (Si-PhNWs) at both telecom (λ=1.55 μm) and mid-infrared (λ=2.2 μm) wavelengths. Our computational study is based on a rigorous theoretical model, which fully describes the influence of linear and nonlinear optical effects on pulse propagation in Si-PhNWs with arbitrarily varying width. Numerical simulations demonstrate that, in the normal dispersion regime, optical pulses evolve naturally into parabolic pulses upon propagation in millimeter-long tapered Si-PhNWs, with the efficiency of this pulse-reshaping process being strongly dependent on the spectral and pulse parameter regime in which the device operates, as well as the particular shape of the Si-PhNWs.

  16. Generating femtosecond X-ray pulses using an emittance-spoiling foil in free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Y., E-mail: ding@slac.stanford.edu; Coffee, R.; Decker, F.-J.; Emma, P.; Field, C.; Huang, Z.; Krejcik, P.; Krzywinski, J.; Loos, H.; Lutman, A.; Marinelli, A.; Maxwell, T. J.; Turner, J. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Behrens, C. [Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg (Germany); Helml, W. [Technische Universität München, James-Franck-Straße 1, 85748 Garching (Germany)

    2015-11-09

    Generation of femtosecond to sub-femtosecond pulses is attracting much attention in X-ray free-electron laser user community. One method is to use a slotted, emittance-spoiling foil which was proposed before (P. Emma et al., Phys. Rev. Lett. 92, 074801 (2004)) and has been widely used at the Linac Coherent Light Source. Direct experimental characterization of the slotted-foil performance was previously unfeasible due to a lack of appropriate diagnostics. With a recently installed X-band radio-frequency transverse deflector, we are able to characterize the electron bunch spoiling effect and X-ray pulse when using the slotted foil. We show that few-femtosecond X-ray pulses are generated with flexible control of the single-pulse duration or double-pulse separation with comparison to the theoretical model.

  17. Efficient third harmonic generation of microjoule picosecond pulses at 355 nm in BiB3O6

    Science.gov (United States)

    Ghotbi, M.; Sun, Z.; Majchrowski, A.; Michalski, E.; Kityk, I. V.; Ebrahim-Zadeh, M.

    2006-10-01

    The authors report efficient third harmonic generation of microjoule picosecond pulses at 355nm in the nonlinear optical material BiB3O6. Using two crystals of BiB3O6 cut for type I (e +e→o) phase matching in optical yz plane for second and third harmonic generation and fundamental pulses from a mode-locked, amplified picosecond Nd:YAG laser at 1.064μm, they have achieved conversion efficiencies of as much as 50% at 355nm. Third harmonic pulse energies of up to 216μJ in 29ps pulses at 25Hz repetition rate have been obtained for 35ps fundamental pulses. They have also determined the magnitude of two-photon absorption coefficient in BiB3O6 at 355nm to be 0.71 and 1.37cm /GW for ordinary and extraordinary polarizations, respectively.

  18. Generating femtosecond X-ray pulses using an emittance-spoiling foil in free-electron lasers

    International Nuclear Information System (INIS)

    Generation of femtosecond to sub-femtosecond pulses is attracting much attention in X-ray free-electron laser user community. One method is to use a slotted, emittance-spoiling foil which was proposed before (P. Emma et al., Phys. Rev. Lett. 92, 074801 (2004)) and has been widely used at the Linac Coherent Light Source. Direct experimental characterization of the slotted-foil performance was previously unfeasible due to a lack of appropriate diagnostics. With a recently installed X-band radio-frequency transverse deflector, we are able to characterize the electron bunch spoiling effect and X-ray pulse when using the slotted foil. We show that few-femtosecond X-ray pulses are generated with flexible control of the single-pulse duration or double-pulse separation with comparison to the theoretical model

  19. A proposal for the generation of ultra-short x-ray pulses

    International Nuclear Information System (INIS)

    In this paper it is shown that optical stochastic cooling in a 150 MeV electron storage ring will allow production of a beam with longitudinal emittance 4.5 x 10-6 MeV·m. Such a small emittance accompanied with a bunch compression technique based upon the transformation in the longitudinal phase space will allow achieving a bunch length 30 μm. This bunch could then be used for the generation of ultra-short x-ray pulses by the Compton scattering of laser photons

  20. X-Y coupling generation with AC/pulsed skew quadrupole and its application

    International Nuclear Information System (INIS)

    The new method of x-y coupling generation with AC or pulsed skew quadrupole is proposed. With this method, no difference resonance is requested; therefore the horizontal and vertical tunes should not be the same value. The AC skew quadrupole is driven by the difference frequency of horizontal and vertical betatron frequency to convert the horizontal position frequency to the vertical kick frequency and vice versa, therefore the coupling with this method is on resonance and can be driven to full coupling strength. In this report, the principle, simulation result, and possible applications are descried. (author)