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Sample records for short pulse sources

  1. RF synchronized short pulse laser ion source

    SciTech Connect

    Fuwa, Yasuhiro Iwashita, Yoshihisa; Tongu, Hiromu; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji; Okamura, Masahiro; Yamazaki, Atsushi

    2016-02-15

    A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

  2. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  3. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung

    1992-12-31

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  4. Short Pulse High Brightness X-ray Production with the PLEIADES Thomson Scattering Source

    SciTech Connect

    Anderson, S G; Barty, C P J; Betts, S M; Brown, W J; Crane, J K; Cross, R R; Fittinghoff, D N; Gibson, D J; Hartemann, F V; Kuba, J; LaSage, G P; Rosenzweig, J B; Slaughter, D R; Springer, P T; Tremaine, A M

    2003-07-01

    We describe PLEIADES, a compact, tunable, high-brightness, ultra-short pulse, Thomson x-ray source. The peak brightness of the source is expected to exceed 10{sup 20} photons/s/0.1% bandwidth/mm{sup 2}/mrad{sup 2}. Initial results are reported and compared to theoretical calculations.

  5. Characterization of short-pulse laser driven neutron source

    NASA Astrophysics Data System (ADS)

    Falk, Katerina; Jung, Daniel; Guler, Nevzat; Deppert, Oliver; Devlin, Matthew; Fernandez, J. C.; Gautier, D. C.; Geissel, M.; Haight, R. C.; Hegelich, B. M.; Henzlova, Daniela; Ianakiev, K. D.; Iliev, Metodi; Johnson, R. P.; Merrill, F. E.; Schaumann, G.; Schoenberg, K.; Shimada, T.; Taddeucci, T. N.; Tybo, J. L.; Wagner, F.; Wender, S. A.; Wurden, G. A.; Favalli, Andrea; Roth, Markus

    2014-10-01

    We present a full spectral characterization of a novel laser driven neutron source, which employed the Break Out Afterburner ion acceleration mechanism. Neutrons were produced by nuclear reactions of the ions deposited on Be or Cu converters. We observed neutrons at energies up to 150 MeV. The neutron spectra were measured by five neutron time-of-flight detectors at various positions and distances from the source. The nTOF detectors observed that emission of neutrons is a superposition of an isotropic component peaking at 3.5--5 MeV resulting from nuclear reactions in the converter and a directional component at 25--70 MeV, which was a product of break-up reaction of the forward moving deuterons. Energy shifts due to geometrical effects in BOA were also observed.

  6. Short x-ray pulse generation using deflecting cavities at the Advanced Photon Source.

    SciTech Connect

    Sajaev, V.; Borland, M.; Chae, Y.-C.; Decker, G.; Dejus, R.; Emery, L.; Harkay, K.; Nassiri, A.; Shastri, S.; Waldschmidt, G.; Yang, B.; Anfinrud, P.; Dolgashev, V.; NIH; SLAC

    2007-11-11

    Storage-ring-based third-generation light sources can provide intense radiation pulses with durations as short as 100 ps. However, there is growing interest within the synchrotron radiation user community in performing experiments with much shorter X-ray pulses. Zholents et al. [Nucl. Instr. and Meth. A 425 (1999) 385] recently proposed using RF orbit deflection to generate sub-ps X-ray pulses. In this scheme, two deflecting cavities are used to deliver a longitudinally dependent vertical kick to the beam. An optical slit can then be used to slice out a short part of the radiation pulse. Implementation of this scheme is planned for one APS beamline in the near future. In this paper, we summarize our feasibility study of this method and the expected X-ray beam parameters. We find that a pulse length of less than two picoseconds can be achieved.

  7. Short X-ray pulse generation using deflecting cavities at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Sajaev, V.; Borland, M.; Chae, Y.-C.; Decker, G.; Dejus, R.; Emery, L.; Harkay, K.; Nassiri, A.; Shastri, S.; Waldschmidt, G.; Yang, B.; Anfinrud, P.; Dolgashev, V.

    2007-11-01

    Storage-ring-based third-generation light sources can provide intense radiation pulses with durations as short as 100 ps. However, there is growing interest within the synchrotron radiation user community in performing experiments with much shorter X-ray pulses. Zholents et al. [Nucl. Instr. and Meth. A 425 (1999) 385] recently proposed using RF orbit deflection to generate sub-ps X-ray pulses. In this scheme, two deflecting cavities are used to deliver a longitudinally dependent vertical kick to the beam. An optical slit can then be used to slice out a short part of the radiation pulse. Implementation of this scheme is planned for one APS beamline in the near future. In this paper, we summarize our feasibility study of this method and the expected X-ray beam parameters. We find that a pulse length of less than two picoseconds can be achieved.

  8. Laser fusion neutron source employing compression with short pulse lasers

    DOEpatents

    Sefcik, Joseph A; Wilks, Scott C

    2013-11-05

    A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

  9. Superconducting Cavity Design for Short-Pulse X-Rays at the Advanced Photon Source

    SciTech Connect

    G.J. Waldschmidt, R. Nassiri, G. Cheng, R.A. Rimmer, H. Wang

    2011-03-01

    Superconducting cavities have been analyzed for the short-pulse x-ray (SPX) project at the Advanced Photon Source (APS). Due to the strong damping requirements in the APS storage ring, single-cell superconducting cavities have been designed. The geometry has been optimized for lower-order and higher-order mode damping, reduced peak surface magnetic fields, and compact size. The integration of the cavity assembly, with dampers and waveguide input coupler, into a cryomodule will be discussed.

  10. The Wakefield Effects of Pulsed Crab Cavities at the Advanced Photon Source for Short-X-ray Pulse Generation

    SciTech Connect

    Chae, Y.-C.; Waldschmidt, G.; Dolgashev, V.; /SLAC

    2007-11-07

    In recent years we have explored the application to the Advanced Photon Source (APS) of Zholents' crab-cavity based scheme for production of short x-ray pulses. As a near-term project, the APS has elected to pursue a pulsed system using room-temperature cavities. The cavity design has been optimized to heavily damp parasitic modes while maintaining large shunt impedance for the deflecting dipole mode. We evaluated a system consisting of three crab cavities as an impedance source and determined their effect on the single- and multi-bunch instabilities. In the single-bunch instability we used the APS impedance model as the reference system in order to predict the overall performance of the ring when the crab cavities are installed in the future. For multi-bunch instabilities we used a realistic fill pattern, including hybrid-fill, and tracked multiple bunches where each bunch was treated as soft in distribution.

  11. High Energy X-Ray Source Generation by Short Pulse High Intensity Lasers

    SciTech Connect

    Park, H-S; Koch, J A; Landen, O L; Phillips, T W; Goldsack, T; Clark, E; Eagleton, R; Edwards, R

    2003-09-02

    We are studying the feasibility of utilizing K{alpha} x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray K{alpha} sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand K{alpha} source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the K{alpha} source. We find that the K{alpha} conversion efficiency from the laser energy at 22 keV is {approx} 3 x 10{sup -4}.

  12. Short pulse neutron generator

    SciTech Connect

    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.

  13. Development of short pulse laser driven micro-hohlraums as a source of EUV radiation

    NASA Astrophysics Data System (ADS)

    Krushelnick, Karl; Batson, Thomas; McKelvey, Andrew; Raymond, Anthony; Thomas, Alec; Yanovsky, Victor; Nees, John; Maksimchuk, Anatoly

    2015-11-01

    Experiments at large scale laser facilities such as NIF allow the radiativ properties of dens, high-temperature matter to be studied at previously unreachable regime, but are limited by cost and system availability. A scaled system using a short laser pulses and delivering energy to much smaller hohlraum could be capable of reaching comparable energy densities by depositing the energy in a much smaller volume before ablation of the wall material closes the cavit. The laser is tightl focused through the cavity and then expands to illuminate the wall. Experiments were performe using the Hercules Ti:Sapphire laser system at Michiga. Targets include cavities machined in bulk material using low laser power, and then shot in situ with a single full power pulse as well as micron scale pre-fabricate target. Spectral characteristics were measured using a soft X-ray spectromete, K-alpha x-ray imaging system and a filtered photo cathode array. Scalings of the radiation temperature were made for variations in the hohlraum cavit, the pulse duration as well as the focusing conditions. Proof of principle time resolved absorption spectroscopy experiments were also performe. These sources may allow opacity and atomic physics measurements with plasma an radiation temperatures comparable to much larger hohlraums, but with much higher repetition rate and in a university scale laboratory. We acknowledge funding from DTRA grant HDTRA1-11-1-0066.

  14. Neutron imaging with the short-pulse laser driven neutron source at the Trident laser facility

    NASA Astrophysics Data System (ADS)

    Guler, N.; Volegov, P.; Favalli, A.; Merrill, F. E.; Falk, K.; Jung, D.; Tybo, J. L.; Wilde, C. H.; Croft, S.; Danly, C.; Deppert, O.; Devlin, M.; Fernandez, J.; Gautier, D. C.; Geissel, M.; Haight, R.; Hamilton, C. E.; Hegelich, B. M.; Henzlova, D.; Johnson, R. P.; Schaumann, G.; Schoenberg, K.; Schollmeier, M.; Shimada, T.; Swinhoe, M. T.; Taddeucci, T.; Wender, S. A.; Wurden, G. A.; Roth, M.

    2016-10-01

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at the laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ˜5 × 109 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5-35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ˜1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. These experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical work into the

  15. Epithermal Neutron Source for Neutron Resonance Spectroscopy (NRS) using High Intensity, Short Pulse Lasers

    SciTech Connect

    Higginson, D P; McNaney, J M; Swift, D C; Bartal, T; Hey, D S; Pape, S L; Mackinnon, A; Mariscal, D; Nakamura, H; Nakanii, N; Beg, F N

    2010-04-22

    A neutron source for neutron resonance spectroscopy (NRS) has been developed using high intensity, short pulse lasers. This measurement technique will allow for robust measurements of interior ion temperature of laser-shocked materials and provide insight into equation of state (EOS) measurements. The neutron generation technique uses protons accelerated by lasers off of Cu foils to create neutrons in LiF, through (p,n) reactions with {sup 7}Li and {sup 19}F. The distribution of the incident proton beam has been diagnosed using radiochromic film (RCF). This distribution is used as the input for a (p,n) neturon prediction code which is compared to experimentally measured neutron yields. From this calculation, a total fluence of 1.8 x 10{sup 9} neutrons is infered, which is shown to be a reasonable amount for NRS temperature measurement.

  16. Compact Short-Pulsed Electron Linac Based Neutron Sources for Precise Nuclear Material Analysis

    NASA Astrophysics Data System (ADS)

    Uesaka, M.; Tagi, K.; Matsuyama, D.; Fujiwara, T.; Dobashi, K.; Yamamoto, M.; Harada, H.

    2015-10-01

    An X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the melted fuel debris analysis and nuclear security in Fukushima is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, etc., especially in epithermal (0.1-10 eV) neutrons. Therefore, we have decided to modify and install the linac in the core space of the experimental nuclear reactor "Yayoi" which is now under the decommission procedure. Due to the compactness of the X-band linac, an electron gun, accelerating tube and other components can be installed in a small space in the core. First we plan to perform the time-of-flight (TOF) transmission measurement for study of total cross sections of the nuclei for 0.1-10 eV energy neutrons. Therefore, if we adopt a TOF line of less than 10m, the o-pulse length of generated neutrons should be shorter than 100 ns. Electronenergy, o-pulse length, power, and neutron yield are ~30 MeV, 100 ns - 1 micros, ~0.4 kW, and ~1011 n/s (~103 n/cm2/s at samples), respectively. Optimization of the design of a neutron target (Ta, W, 238U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. We are upgrading the electron gun and a buncher to realize higher current and beam power with a reasonable beam size in order to avoid damage of the neutron target. Although the neutron flux is limited in case of the X-band electron linac based source, we take advantage of its short pulse aspect and availability for nuclear data measurement with a short TOF system. First, we form a tentative configuration in the current experimental room for Compton scattering in 2014. Then, after the decommissioning has been finished, we move it to the "Yayoi" room and perform

  17. Point source of UV-radiation with a frequency of 1 khz and short pulse duration

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Tarasenko, V. F.; Shut'ko, Yu. V.; Erofeev, M. V.

    2012-04-01

    Radiation of the discharge plasma from a nanosecond breakdown in a nonuniform electric field of short interelectrode gaps is investigated. Voltage pulses with incident wave amplitude of ~10 kV, pulse duration of ~1 ns (FWHM), and pulse front duration of ~0.2 ns are used. It is demonstrated that for pulsed-periodic breakdown of the gap 0.5 mm long in air at atmospheric pressure, the main contribution to plasma radiation give lines of the electrode material and the continuum, and the maximum radiation intensity is registered in the region of 200-300 nm, where ~40% of total radiation energy is concentrated.

  18. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    SciTech Connect

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

    2016-06-14

    We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  19. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    DOE PAGES

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; ...

    2016-06-14

    We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

  20. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    NASA Astrophysics Data System (ADS)

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  1. Short pulse test set

    NASA Astrophysics Data System (ADS)

    1990-11-01

    This report discusses the construction and operation of the Short Pulse Test Set that has been built for the U.S. Army Missile Command for the purpose of applying short (25 to 100 nanosecond), high voltage pulses to electronic explosive devices (EEDs) in both the pin-to-pin and pins-to-case mode. The test set employs the short pulse generating techniques first described in the Franklin Institute Research Laboratories (now Franklin Research Center) Report I-C3410, 'Pins-to-Case Short Pulse Sensitivity Studies for the Atlas DC Switch', December 1974. This report, authored by Ramie H. Thompson, was prepared for Picatinny Arsenal under contract DAAA21-72C-0766. The test set described herein utilizes a computer controlled high speed digitizer to monitor the pulse voltage and current and provides software to process and display these data.

  2. Short X-ray pulses from third-generation light sources.

    PubMed

    Stepanov, A G; Hauri, C P

    2016-01-01

    High-brightness X-ray radiation produced by third-generation synchrotron light sources (TGLS) has been used for numerous time-resolved investigations in many different scientific fields. The typical time duration of X-ray pulses delivered by these large-scale machines is about 50-100 ps. A growing number of time-resolved studies would benefit from X-ray pulses with two or three orders of magnitude shorter duration. Here, techniques explored in the past for shorter X-ray pulse emission at TGLS are reviewed and the perspective towards the realisation of picosecond and sub-picosecond X-ray pulses are discussed.

  3. DEVELOPMENT OF A COMPACT PHOTO-INJECTOR WITH RFFOCUSING LENS FOR SHORT PULSE ELECTRON SOURCE APPLICATION

    SciTech Connect

    Grabenhofer, Alexander; Eaton, Douglas W.

    2013-09-01

    For development of compact ultrafast electron source system, we are currently designing a short-pulse RF-gun with RF focusing structure by means of a series of comprehensive modeling analysis processes. EM design of a 2.5 cell resonant cavity with input coupler, acceleration dynamics of photo-emitted electron bunch, EM design of RF-lens with input coupler, and phasespace analysis of focused electron bunch are systematically examined with multi-physics simulators. All the features of the 2.856 GHz cavity geometry were precisely engineered for acceleration energies ranging from 100 keV to 500 keV (safety limited) to be powered by our 5 MW S-band klystron. The klystron (Thales TH2163) and modulator system (ScandiNova K1 turnkey system) were successfully installed and tested. Performance tests of the klystron system show peak output power > 5 MW, as per operation specifications. At the quasi-relativistic energies, the electron source is capable of generating 100fC – 1 pC electron bunch with pulse duration close to 30 fs – 1 ps and transverse size of a few hundred microns. PIC simulations have shown that the electron bunch undergoes fast RF acceleration, rapidly reaching the desired energies, which can be controlled by tuning RF injection phase and input driving power. It has been shown that it is possible to also focus/compress the bunch longitudinally using a RF-lens, which would allow us to control the temporal resolution of the system as well. While our primary analysis has been performed on a 2.5 cell design, we are also looking into half-cell (single cavity) design that is expected to provide the same range of beam energy with a simple configuration.

  4. SHORT PULSE STRETCHER

    DOEpatents

    Branum, D.R.; Cummins, W.F.

    1962-12-01

    >A short pulse stretching circuit capable of stretching a short puise to enable it to be displayed on a relatively slow sweeping oscilloscope is described. Moreover, the duration of the pulse is increased by charging a capacitor through a diode and thereafter discharging the capacitor at such time as is desired. In the circuit the trigger pulse alone passes through a delay line, whereas the main signal passes through the diode only, and results in over-all circuit losses which are proportional to the low losses of the diode only. (AEC)

  5. Optical design of the Short Pulse Soft X-ray Spectroscopy beamline at the Advanced Photon Source

    PubMed Central

    Reininger, R.; Keavney, D. J.; Borland, M.; Young, L.

    2013-01-01

    The Short Pulse X-ray facility planned for the Advanced Photon Source (APS) upgrade will provide two sectors with photon beams having picosecond pulse duration. The Short Pulse Soft X-ray Spectroscopy (SPSXS) beamline will cover the 150–2000 eV energy range using an APS bending magnet. SPSXS is designed to take full advantage of this new timing capability in addition to providing circular polarized radiation. Since the correlation between time and electron momentum is in the vertical plane, the monochromator disperses in the horizontal plane. The beamline is designed to maximize flux and preserve the time resolution by minimizing the number of optical components. The optical design allows the pulse duration to be varied from 1.5 to 100 ps full width at half-maximum (FWHM) without affecting the energy resolution, and the resolution to be changed with minimal effect on the pulse duration. More than 109 photons s−1 will reach the sample with a resolving power of 2000 and a pulse duration of ∼2 ps for photon energies between 150 and 1750 eV. The spot size expected at the sample position will vary with pulse duration and exit slit opening. At 900 eV and at a resolving power of 2000 the spot will be ∼10 µm × 10 µm with a pulse duration of 2.3 ps FWHM. PMID:23765311

  6. Preliminary characterization of ultra-short pulse laser-produced miniature hohlraum XUV sources

    NASA Astrophysics Data System (ADS)

    McKelvey, A.; Vargas, M.; Montier, L.; Nees, J.; Hou, B.; Maksimchuk, A.; Thomas, A. G. R.; Krushelnick, K.

    2012-10-01

    Experiments at the National Ignition Facility (NIF) allow the radiative properties of dense, high-temperature matter to be studied at previously unreachable regimes, but are limited by cost and system availability. A scaled down system using ultra-short laser pulses and delivering energy to a much smaller hohlraum could be capable of reaching comparable energy densities and depositing the energy before the wall material ablation closes the cavity. The Lambda Cubed laser system at University of Michigan--a high-power (0.3 TW), short pulse (30fs), 500 Hz repetition rate tabletop laser system-is used to machine 20-100 micron diameter cavities in copper targets. These cavities are machined with low laser powers, and then shot in situ with a single full power pulse. The emitted radiation is analyzed with an XUV spectrometer. This method may allow studies such as opacity measurements using plasma and radiation with the temperatures comparable to NIF type hohlraums, but with a significantly higher repetition rate and in a university scale system.

  7. Development of a short pulsed corona discharge ionization source for ion mobility spectrometry

    SciTech Connect

    An Yuan; Aliaga-Rossel, R.; Choi, Peter; Gilles, Jean-Paul

    2005-08-15

    The development of a pulsed corona discharge ionization source and its use in ion mobility spectrometry (IMS) is presented. In a point-plane electrode geometry, an electrical pulse up to 12 kV, 150 ns rise time and 500 ns pulse width was used to generate a corona discharge in air. A single positive high voltage pulse was able to generate about 1.6x10{sup 10} ions at energy consumption of 22 {mu}J. Since the temporal distribution of ions is in a pulsed form, the possibility of removal the ion gate has been investigated. By purposely arranging the interface between discharge field and drift field, nearly 10{sup 7} positive ions were drawn into the drift region with absence of the ion gate after every single discharge. The positive spectrum of acetone dimer (working at room temperature) was obtained with a resolving power of 20 by using this configuration. The advantages of this new scheme are the low power consumption compared with the dc method as well as the simplicity of the IMS cell structure.

  8. High power and short pulse RF-excited CO II laser MOPA system for LLP EUV light source

    NASA Astrophysics Data System (ADS)

    Ariga, Tatsuya; Hoshino, Hideo; Miura, Taisuke; Endo, Akira

    2006-02-01

    Laser produced plasma EUV source is the candidate for high quality, 115 W EUV light source for the next generation lithography. Cost effective laser driver is the key requirement for the realization of the concept as a viable scheme. A CO II laser driven LPP system with a Xenon droplet target is therefore a promising light source alternative for EUV. We are developing a high power and high repetition rate CO II laser system to achieve 10 W intermediate focus EUV power. High conversion efficiency (CE) from the laser energy to EUV in-band energy is the primarily important issue for the concept to be realized. Numerical simulation analysis of a Xenon plasma target shows that a short laser pulse less than 15 ns is necessary to obtain a high CE by a CO II laser. This paper describes on the development of a CO II laser system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz, based on RF-excited, axial flow CO II laser amplifiers. Output power of 1 kW has been achieved with a pulse length 15 ns at 100 kHz repletion rate in a small signal amplification condition with P(20) single line. The CO II laser system is reported on the conceptual design for a LPP EUV light source, and amplification performance in CW and short pulse using RF-excited axial flow lasers as amplifiers. Additional approach to increase the amplification efficiency is discussed.

  9. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    SciTech Connect

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1996-08-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several {mu}s) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution.

  10. 20-100 keV K(alpha) X-Ray Source Generation by Short Pulse High Intensity Lasers

    SciTech Connect

    Park, H-S; Koch, J A; Landen, O L; Phillips, T W; Goldsack, T

    2003-08-22

    We are studying the feasibility of utilizing K{alpha} x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray K{alpha} sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand K{alpha} source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the K{alpha} source. We find that the K{alpha} conversion efficiency from the laser energy is {approx} 3 x 10{sup -4}.

  11. Status of the Short-Pulse X-ray Project (SPX) at the Advanced Photon Source (APS)

    SciTech Connect

    Nassiri, R; Berenc, G; Borland, M; Bromberek, D J; Chae, Y -C; Decker, G; Emery, L; Fuerst, J D; Grelick, A E; Horan, D; Lenkszus, F; Lill, R M; Sajaev, V; Smith, T L; Waldschmidt, G J; Wu, G; Yang, B X; Zholents, A; Byrd, J M; Doolittle, L R; Huang, G; Cheng, G; Ciovati, G; Henry, J; Kneisel, P; Mammosser, J D; Rimmer, R A; Turlington, L; Wang, H

    2011-03-01

    The Advanced Photon Source Upgrade project (APS-U) at Argonne includes implementation of Zholents’* deflecting cavity scheme for production of short x-ray pulses. This is a joint project between Argonne National Laboratory, Thomas Jefferson National Laboratory, and Lawrence Berkeley National Laboratory. This paper describes performance characteristics of the proposed source and technical issues related to its realization. Ensuring stable APS storage ring operation requires reducing quality factors of these modes by many orders of magnitude. These challenges reduce to those of the design of a single-cell SC cavity that can achieve the desired operating deflecting fields while providing needed damping of all these modes. The project team is currently prototyping and testing several promising designs for single-cell cavities with the goal of deciding on a winning design in the near future. Here

  12. K{sub α} and bremsstrahlung x-ray radiation backlighter sources from short pulse laser driven silver targets as a function of laser pre-pulse energy

    SciTech Connect

    Jarrott, L. C.; Mariscal, D.; McGuffey, C.; Beg, F. N.; Kemp, A. J.; Divol, L.; Chen, C.; Hey, D.; Maddox, B.; Hawreliak, J.; Park, H.-S.; Remington, B.; MacPhee, A.; Westover, B.; Suggit, M.; Wei, M. S.

    2014-03-15

    Measurements of silver K-shell and bremsstrahlung emission from thin-foil laser targets as a function of laser prepulse energy are presented. The silver targets were chosen as a potential 22 keV backlighter source for the National Ignition Facility Experiments. The targets were irradiated by the Titan laser with an intensity of 8 × 10{sup 17} W/cm{sup 2} with 40 ps pulse length. A secondary nanosecond timescale laser pulse with controlled, variable energy was used to emulate the laser prepulse. Results show a decrease in both K{sub α} and bremsstrahlung yield with increasing artificial prepulse. Radiation hydrodynamic modeling of the prepulse interaction determined that the preplasma and intact target fraction were different in the three prepulse energies investigated. Interaction of the short pulse laser with the resulting preplasma and target was then modeled using a particle-in-cell code PSC which explained the experimental results. The relevance of this work to future Advanced Radiographic Capability laser x-ray backlighter sources is discussed.

  13. Long pulse production from short pulses

    DOEpatents

    Toeppen, J.S.

    1994-08-02

    A method of producing a long output pulse from a short pump pulse is disclosed, using an elongated amplified fiber having a doped core that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding. A seed beam of the longer wavelength is injected into the core at one end of the fiber and a pump pulse of the shorter wavelength is injected into the cladding at the other end of the fiber. The counter-propagating seed beam and pump pulse will produce an amplified output pulse having a time duration equal to twice the transit time of the pump pulse through the fiber plus the length of the pump pulse. 3 figs.

  14. Long pulse production from short pulses

    DOEpatents

    Toeppen, John S.

    1994-01-01

    A method of producing a long output pulse (SA) from a short pump pulse (P), using an elongated amplified fiber (11) having a doped core (12) that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding 13. A seed beam (S) of the longer wavelength is injected into the core (12) at one end of the fiber (11) and a pump pulse (P) of the shorter wavelength is injected into the cladding (13) at the other end of the fiber (11). The counter-propagating seed beam (S) and pump pulse (P) will produce an amplified output pulse (SA) having a time duration equal to twice the transit time of the pump pulse (P) through the fiber (11) plus the length of the pump pulse (P).

  15. Numerical Investigation on Atmospheric-Pressure Dielectric Barrier Discharges Driven by Combined rf and Short-Pulse Sources in Co-Axial Electrodes

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Sun, Ji-zhong; Nozaki, Tomohiro; Wang, De-zhen

    Atmospheric-pressure discharges driven by combined rf and short-pulse sources in co-axial electrodes were investigated in this work using a one-dimensional self-consistent fluid model. It demonstrated that the plasma intensity in the rf discharge could be enhanced drastically when an additional low-duty-ratio pulse source was applied to the discharge. The study investigated how the plasma density varied with the voltage amplitude of the pulse source. Results showed that the discharge mode turned into glow mode as the pulse amplitude exceeded a critical value. Two cases were investigated on the premise that the outer electrode was electrically grounded: in the first case the positive pulse was applied to the inner electrode while in the second case the negative pulse was used instead, and the spatial discharge characteristics were compared.

  16. Superconducting Multi-Cell Deflecting Cavity for Short-Pulse X-Ray Generation at the Advanced Photon Source

    SciTech Connect

    G.J. Waldschmidt, L.H. Morrison, R. Nassiri, R.A. Rimmer, K. Tian, H. Wang

    2009-05-01

    A superconducting multi-cell cavity for the production of short x-ray pulses at the Advanced Photon Source (APS) has been explored as an alternative to a single-cell cavity design in order to improve the packing factor and potentially reduce the number of high-power RF systems and low-level RF controls required. The cavity will operate at 2815 MHz in the APS storage ring and will require heavy damping of parasitic modes to maintain stable beam operation. Novel on-cell dampers, attached directly to the cavity body, have been utilized by taking advantage of the magnetic field null on the equatorial plane in order to enhance damping. Design issues and simulation results will be discussed.

  17. High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source

    SciTech Connect

    Waldschmidt, G J; Liu, J; Middendorf, M E; Nassiri, A; Smith, T L; Wu, G; Henry, J; Mammosser, J D; Rimmer, R A; Wiseman, M

    2012-07-01

    High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.

  18. Absolute measurements of short-pulse, long-pulse, and capsule-implosion backlighter sources at x-ray energies greater than 10 keV

    NASA Astrophysics Data System (ADS)

    Maddox, Brian

    2010-11-01

    Laser-generated x-ray backlighters with x-ray energies > 10 keV are becoming essential diagnostic tools for many high energy density experiments. Examples include studies of high areal density cores for ignition designs, mid- to high-Z capsule implosion experiments, absolute equation of state experiments, dynamic diffraction under extreme pressures, and the study of material strength. Significant progress has been made recently using short pulse lasers, coupled to metal foil targets [1], and imploding capsules for producing high energy backlighters. Measuring the absolute x-ray flux and spectra from these sources is required for quantitative analysis of experimental data and for the design and planning of future experiments. We have performed an extensive series of experiments to measure the absolute x-ray flux and spectra on the Titan, Omega, Omega-EP, and NIF laser systems, employing single-photon-counting detectors, crystal spectrometers, and multichannel differential filtering (Ross-pair) and filter stack bremsstrahlung spectrometers. Calibrations were performed on these instruments [2] enabling absolute measurements of backlighter spectra to be made from 10 keV to 1 MeV. Various backlighter techniques that generate either quasi-monochromatic sources or broadband continuum sources will be presented and compared. For Molybdenum Kα backlighters at x-ray energy of ˜17 keV we measure conversion efficiencies of 1.3x10-4 using 1 μm wavelength short-pulse lasers at an intensity of ˜1x10^17 W/cm^2. This is a factor of ˜2 high than using 0.3 μm wavelength long-pulse lasers at an intensity of ˜1x10^16 W/cm^2. Other types of backlighter targets include capsule implosion backlighters that can generate a very bright ``white-light'' continuum x-ray source and high-Z gas filled capsules that generate a quasi-line-source of x rays. We will present and compare the absolute laser energy to x-ray conversion efficiencies for these different backlighter techniques and give

  19. Nuclear Material Detection by One-Short-Pulse-Laser-Driven Neutron Source

    SciTech Connect

    Favalli, Andrea; Aymond, F.; Bridgewater, Jon S.; Croft, Stephen; Deppert, O.; Devlin, Matthew James; Falk, Katerina; Fernandez, Juan Carlos; Gautier, Donald Cort; Gonzales, Manuel A.; Goodsell, Alison Victoria; Guler, Nevzat; Hamilton, Christopher Eric; Hegelich, Bjorn Manuel; Henzlova, Daniela; Ianakiev, Kiril Dimitrov; Iliev, Metodi; Johnson, Randall Philip; Jung, Daniel; Kleinschmidt, Annika; Koehler, Katrina Elizabeth; Pomerantz, Ishay; Roth, Markus; Santi, Peter Angelo; Shimada, Tsutomu; Swinhoe, Martyn Thomas; Taddeucci, Terry Nicholas; Wurden, Glen Anthony; Palaniyappan, Sasikumar; McCary, E.

    2015-01-28

    Covered in the PowerPoint presentation are the following areas: Motivation and requirements for active interrogation of nuclear material; laser-driven neutron source; neutron diagnostics; active interrogation of nuclear material; and, conclusions, remarks, and future works.

  20. Pulse shaper assisted short laser pulse characterization

    NASA Astrophysics Data System (ADS)

    Galler, A.; Feurer, T.

    2008-03-01

    We demonstrate that a pulse shaper is able to simultaneously act as an optical waveform generator and a short pulse characterization device when combined with an appropriate nonlinear element. We present autocorrelation measurements and their frequency resolved counterparts. We show that control over the carrier envelope phase allows continuous tuning between an intensity-like and an interferometric autocorrelation. By changing the transfer function other measurement techniques, for example STRUT, are easily realized without any modification of the optical setup.

  1. PULSED ION SOURCE

    DOEpatents

    Anderson, C.E.; Ehlers, K.W.

    1958-06-17

    An ion source is described for producing very short high density pulses of ions without bcam scattering. The ions are created by an oscillating electron discharge within a magnetic field. After the ions are drawn from the ionization chamber by an accelerating electrode the ion beam is under the influence of the magnetic field for separation of the ions according to mass and, at the same time, passes between two neutralizing plntes maintained nt equal negative potentials. As the plates are formed of a material having a high ratio of secondary electrons to impinging ions, the ion bombardment of the plntes emits electrons which neutralize the frirge space-charge of the beam and tend to prevent widening of the beam cross section due to the mutual repulsion of the ions.

  2. Ultra-short pulse generator

    DOEpatents

    McEwan, T.E.

    1993-12-28

    An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shock wave diode, which increases and sharpens the pulse even more. 5 figures.

  3. Ultra-short pulse generator

    DOEpatents

    McEwan, Thomas E.

    1993-01-01

    An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shockwave diode, which increases and sharpens the pulse even more.

  4. Pulsed spallation Neutron Sources

    SciTech Connect

    Carpenter, J.M.

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  5. Pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-05-01

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology.

  6. Ultra-short ion and neutron pulse production

    DOEpatents

    Leung, Ka-Ngo; Barletta, William A.; Kwan, Joe W.

    2006-01-10

    An ion source has an extraction system configured to produce ultra-short ion pulses, i.e. pulses with pulse width of about 1 .mu.s or less, and a neutron source based on the ion source produces correspondingly ultra-short neutron pulses. To form a neutron source, a neutron generating target is positioned to receive an accelerated extracted ion beam from the ion source. To produce the ultra-short ion or neutron pulses, the apertures in the extraction system of the ion source are suitably sized to prevent ion leakage, the electrodes are suitably spaced, and the extraction voltage is controlled. The ion beam current leaving the source is regulated by applying ultra-short voltage pulses of a suitable voltage on the extraction electrode.

  7. Pulsed ion beam source

    DOEpatents

    Greenly, John B.

    1996-01-01

    An improved magnetically-confined anode plasma pulsed ion beam source. Beam rotation effects and power efficiency are improved by a magnetic design which places the separatrix between the fast field flux structure and the slow field structure near the anode of the ion beam source, by a gas port design which localizes the gas delivery into the gap between the fast coil and the anode, by a pre-ionizer ringing circuit connected to the fast coil, and by a bias field means which optimally adjusts the plasma formation position in the ion beam source.

  8. Pulsed ion beam source

    DOEpatents

    Greenly, John B.

    1997-01-01

    An improved pulsed ion beam source having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center.

  9. From reactors to long pulse sources

    SciTech Connect

    Mezei, F. |

    1995-12-31

    We will show, that by using an adapted instrumentation concept, the performance of a continuous source can be emulated by one switch on in long pulses for only about 10% of the total time. This 10 fold gain in neutron economy opens up the way for building reactor like sources with an order of magnitude higher flux than the present technological limits. Linac accelerator driven spallation lends itself favorably for the realization of this kind of long pulse sources, which will be complementary to short pulse spallation sources, the same way continuous reactor sources are.

  10. Pulsed ion beam source

    DOEpatents

    Greenly, J.B.

    1997-08-12

    An improved pulsed ion beam source is disclosed having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center. 12 figs.

  11. X-ray reverberations and the giant X-ray bursts. [short duration pulse in plasma cloud surrounding X-ray source

    NASA Technical Reports Server (NTRS)

    Canizares, C. R.

    1976-01-01

    It is shown that the shape and spectral evolution of the giant X-ray bursts from the source 3U 1820-30 can be explained by Compton scattering of a short, intense X-ray pulse in a cloud surrounding the source. Pulse shapes due to Thomson scattering of an X-ray burst in an electron cloud were calculated for the (1) optically thin case on the assumption of one scattering per photon, (2) intermediate case with optical depth of about unity, and (3) optically thick case where the process is regarded as diffusion of photons through a uniform sphere. For the intermediate case, the effects of the reverberation were determined explicitly by Monte Carlo calculation. For an optical depth of 3, square pulse duration of 2 sec, characteristic cloud radius of 70,000 km, characteristic cloud density of 4 times 10 to the 14th per cu cm, and temperature of 5-30 keV, the calculations give a reasonably accurate description of X-ray bursts from 3U 1820-30. The scattering model does not imply the existence of a supermassive, central black hole.

  12. Optical design of the short pulse x-ray imaging and microscopy time-angle correlated diffraction beamline at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Reininger, R.; Dufresne, E. M.; Borland, M.; Beno, M. A.; Young, L.; Kim, K.-J.; Evans, P. G.

    2013-05-01

    The short pulse x-ray imaging and microscopy beamline is one of the two x-ray beamlines that will take full advantage of the short pulse x-ray source in the Advanced Photon Source (APS) upgrade. A horizontally diffracting double crystal monochromator which includes a sagittally focusing second crystal will collect most of the photons generated when the chirped electron beam traverses the undulator. A Kirkpatrick-Baez mirror system after the monochromator will deliver to the sample a beam which has an approximately linear correlation between time and vertical beam angle. The correlation at the sample position has a slope of 0.052 ps/μrad extending over an angular range of 800 μrad for a cavity deflection voltage of 2 MV. The expected time resolution of the whole system is 2.6 ps. The total flux expected at the sample position at 10 keV with a 0.9 eV energy resolution is 5.7 × 1012 photons/s at a spot having horizontal and vertical full width at half maximum of 33 μm horizontal by 14 μm vertical. This new beamline will enable novel time-dispersed diffraction experiments on small samples using the full repetition rate of the APS.

  13. Short pulse free electron laser amplifier

    DOEpatents

    Schlitt, Leland G.; Szoke, Abraham

    1985-01-01

    Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

  14. Short Pulse Laser Applications Design

    SciTech Connect

    Town, R J; Clark, D S; Kemp, A J; Lasinski, B F; Tabak, M

    2008-02-11

    facility, called HiPER, designed to demonstrate FI. Our design work has focused on the NIF, which is the only facility capable of forming a full-scale hydro assembly, and could be adapted for full-scale FI by the conversion of additional beams to short-pulse operation.

  15. Plasma Physics Applications to Intense Radiation Sources, Pulsed Power and Space Physics. Short Pulse Ultra Intense Laser-Plasma Interaction Experiment

    DTIC Science & Technology

    1993-05-31

    applications, including gas insulated spark gaps, thyratrons, saturable magnetic inductors, surface flashover switches , etc. Each has different capabilities...result of potentially severe erosion problems on the main output switches of the NIKE laser at the Naval Research Laboratory (NRL), NRL has funded...having to store the full pulse energy at each stage and by making the triggered stage (prior to the magnetic switches ) output pulse as narrow as possible

  16. High K-alpha X-ray Conversion Efficiency From Extended Source Gas Jet Targets Irradiated by Ultra Short Laser Pulses

    SciTech Connect

    Kugland, N L; Constantin, C; Collette, A; Dewald, E; Froula, D; Glenzer, S H; Kritcher, A; Neumayer, P; Ross, J S; Niemann, C

    2007-11-01

    The absolute laser conversion efficiency to K{sub {alpha}}-like inner shell x-rays (integrated from K{sub {alpha}} to K{sub {beta}}) is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K{sub {alpha}} is the same in gas jets as in solid targets. These results demonstrate that gas jet targets are bright, high conversion efficiency, high repetition rate, debris-free multi-keV x-ray sources for spectrally resolved scattering and backlighting of rapidly evolving dense matter.

  17. POPULATION KINETICS MODELING FOR NON-LTE AND NON-MAXWELLIAN PLASMAS GENERATED IN FINITE TEMPERATURE DENSE MATTER EXPERIMENTS ARISING FROM SHORT PULSE X-RAY SOURCE

    SciTech Connect

    Chung, H; Lee, R W; Morgan, W L

    2003-12-23

    The short pulse x-ray sources will provide a major advance in dense matter studies important to understand implosion physics for ICF as a generator of warm dense matter or a probe of finite temperature dense matter. The interaction of such a high-energy photon pulse with the initially solid matter creates highly transient states of plasmas initially whose relaxation processes are of interest to the equation of states or spectral properties of these matter. For these plasmas, assumptions such as LTE population distributions or Maxwellian electron energy distributions should be tested by employing a method that does not make these assumption a priori. Our goal is to present a model that can be used to simulate the electron distributions, the ionization balance and the spectral output of transient systems generated in the future ICF experiments. We report on the progress in developing a non-LTE atomic population kinetics code integrated with Boltzmann equation solver to provide a self-consistent time-dependent solution of the level populations and the particle energy distributions.

  18. Short-pulsed diode lasers as an excitation source for time-resolved fluorescence applications and confocal laser scanning microscopy in PDT

    NASA Astrophysics Data System (ADS)

    Kress, Matthias; Meier, Thomas H.; El-Tayeb, Tarek A. A.; Kemkemer, Ralf; Steiner, Rudolf W.; Rueck, Angelika C.

    2001-11-01

    This article describes a setup for subcellular time-resolved fluorescence spectroscopy and fluorescence lifetime measurements using a confocal laser scanning microscope in combination with a short pulsed diode laser for fluorescence excitation and specimen illumination. The diode laser emits pulses at 398 nm wavelength with 70 ps full width at half maximum (FWHM) duration. The diode laser can be run at a pulse repetition rate of 40 MHz down to single shot mode. For time resolved spectroscopy a spectrometer setup consisting of an Czerny Turner spectrometer and a MCP-gated and -intensified CCD camera was used. Subcellular fluorescence lifetime measurements were achieved using a time-correlated single photon counting (TCSPC) module instead of the spectrometer setup. The capability of the short pulsed diode laser for fluorescence imaging, fluorescence lifetime measurements and time-resolved spectroscopy in combination with laser scanning microscopy is demonstrated by fluorescence analysis of several photosensitizers on a single cell level.

  19. Generation of short and intense attosecond pulses

    NASA Astrophysics Data System (ADS)

    Khan, Sabih Ud Din

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

  20. Short-pulse laser materials processing

    SciTech Connect

    Stuart, B.C.; Perry, M.D.; Myers, B.R.; Banks, P.S.; Honea, E.C.

    1997-06-18

    While there is much that we have learned about materials processing in the ultrashort-pulse regime, there is an enormous amount that we don`t know. How short does the pulse have to be to achieve a particular cut (depth, material, quality)? How deep can you cut? What is the surface roughness? These questions are clearly dependent upon the properties of the material of interest along with the short-pulse interaction physics. From a technology standpoint, we are asked: Can you build a 100 W average power system ? A 1000 W average power system? This proposal seeks to address these questions with a combined experimental and theoretical program of study. Specifically, To develop an empirical database for both metals and dielectrics which can be used to determine the pulse duration and wavelength necessary to achieve a specific machining requirement. To investigate Yb:YAG as a potential laser material for high average power short-pulse systems both directly and in combination with titanium doped sapphire. To develop a conceptual design for a lOOW and eventually 5OOW average power short-pulse system.

  1. Ultra short pulse reconstruction software: GROG

    NASA Astrophysics Data System (ADS)

    Galletti, M.; Galimberti, M.; Giulietti, D.; Curcio, A.

    2016-07-01

    A new algorithmic method based on the 1D Conjugate Gradient Minimization Method, is presented. The purpose is, analyzing experimental FROG/GRENOUILLE traces, to accurately retrieve intensity and phase both in temporal and spectral domain so as to completely characterize an Ultra Short High Power laser pulse. This algorithm shows important features in the reconstruction of many different pulse classes. The employment of this algorithm also permits the inclusion of material response function present in the FROG/GRENOUILLE set-up.

  2. Correlation dynamics after short-pulse photoassociation

    SciTech Connect

    Koch, Christiane P.; Kosloff, Ronnie

    2010-06-15

    Two atoms in an ultracold gas are correlated at short interatomic distances due to threshold effects in which the potential energy of their interaction dominates the kinetic energy. The correlations manifest themselves in a distinct nodal structure of the density matrix at short interatomic distances. Pump-probe spectroscopy has recently been suggested [Phys. Rev. Lett. 103, 260401 (2009)] to probe these pair correlations: A suitably chosen, short photoassociation laser pulse depletes the ground-state pair density within the photoassociation window, creating a nonstationary wave packet in the electronic ground state. The dynamics of this nonstationary wave packet is monitored by time-delayed probe and ionization pulses. Here we discuss how the choice of the pulse parameters affects the experimental feasibility of this pump-probe spectroscopy of two-body correlations.

  3. An integrable coupled short pulse equation

    NASA Astrophysics Data System (ADS)

    Feng, Bao-Feng

    2012-03-01

    An integrable coupled short pulse (CSP) equation is proposed for the propagation of ultra-short pulses in optical fibers. Based on two sets of bilinear equations to a two-dimensional Toda lattice linked by a Bäcklund transformation, and an appropriate hodograph transformation, the proposed CSP equation is derived. Meanwhile, its N-soliton solutions are given by the Casorati determinant in a parametric form. The properties of one- and two-soliton solutions are investigated in detail. Same as the short pulse equation, the two-soliton solution turns out to be a breather type if the wave numbers are complex conjugate. We also illustrate an example of soliton-breather interaction.

  4. Pulsed reflex ion source studies

    SciTech Connect

    Bickes, Jr., R. W.; O'Hagan, J. B.

    1980-11-01

    Parametric studies of demountable versions of the pulsed ion source used in Controlatron and Zetatron neutron tubes were carried out. The goal of these experiments, a continuation of earlier work by Bacon and O'Hagan, was to investigate the deuteron beam intensity as a function of source geometry, electrode materials, operating conditions and pulse length. Geometric variations produced only modest changes in the ion beam intensity; the most sensitive parameter was the length of the secondary cathode. There is some evidence that the addition of oxygen either in the gas feed or using alumina on the cathode surfaces can increase the atomic ion fraction. The lowest reliable operating source pressure was approximately 1.33 Pa. The longest pulse length was about 1.2 ms. Difficulties in measuring the ion currents are discussed and suggestions for future experiments are briefly outlined.

  5. Ventricular fibrillation threshold of rapid short pulses.

    PubMed

    Walcott, Gregory P; Kroll, Mark W; Ideker, Raymond E

    2011-01-01

    The risk of VF (ventricular fibrillation) from continuous AC utility (50/60 Hz) power has been well quantified and is reflected in accepted standards. Similarly, the required charge for a single pulse delivered during the T-wave of the ECG is also quantified. However, there are no studies that deal with the VF risk of a train of multiple short pulses such as those used in electric fences and conducted electrical weapons (CEWs). We studied 5 swine with an electrode placed through the anterior chest such that the tip was 10 mm from the epicardium. A return electrode was attached remotely to the lower abdomen. Five-second trains of 100 μs pulses at rates of 10-70 PPS (pulses per second) were delivered with gradually increasing charges until VF was induced. The VF threshold was also determined for 60 Hz AC current. As expected, the VF charge threshold decreased with increasing rates. For pulse rates between 10-30 PPS, the aggregate current (= charge • pulse rate) was constant at the VF threshold. The VF threshold in terms of AC RMS current was 7.4 ± 1.9 times the aggregate current VF threshold for the rapid short pulses. These results may have utility for setting safety standards for electric fences and for CEWs such as TASER® CEWs. This also allows for the risk assessment of CEWs by comparison to international electrical safety standards. The output of these weapons appears to be well below the VF risk limits as set by these standards.

  6. Electromagnetic Pulses at Short-Pulse Laser Facilities

    SciTech Connect

    Brown, Jr., C G; Throop, A; Eder, D; Kimbrough, J

    2007-08-28

    Electromagnetic Pulse (EMP) is a known issue for short-pulse laser facilities, and will also be an issue for experiments using the advanced radiographic capability (ARC) at the National Ignition Facility (NIF). The ARC diagnostic uses four NIF beams that are compressed to picosecond durations for backlighting ignition capsules and other applications. Consequently, we are working to understand the EMP due to high-energy (MeV) electrons escaping from targets heated by short-pulse lasers. Our approach is to measure EMP in the Titan short-pulse laser at Lawrence Livermore National Laboratory (LLNL) and to employ that data to establish analysis and simulation capabilities. We have installed a wide variety of probes inside and outside the Titan laser chamber. We have high-frequency B-dots and D-dots, a photodiode, and fast current-viewing and integrating current transformers. The probe outputs are digitized by 10 and 20 Gsample/s oscilloscopes. The cables and oscilloscopes are well shielded to reduce noise. Our initial measurement campaign has yielded data useful mainly from hundreds of MHz to several GHz. We currently are supplementing our high-frequency probes with lower-frequency ones to obtain better low-frequency data. In order to establish analysis and simulation capabilities we are modeling the Titan facility using various commercial and LLNL numerical electromagnetic codes. We have simulated EMP generation by having a specified number of electrons leave the target and strike the chamber wall and other components in the chamber. This short impulse of electrons has a corresponding broad spectrum, exciting high-frequency structure in the resulting EMP. In this paper, we present results of our initial measurement campaign and comparisons between the measurements and simulations.

  7. Electromagnetic Pulses at Short-Pulse Laser Facilities

    SciTech Connect

    Brown, C G; Throop, A; Eder, D; Kimbrough, J

    2008-02-04

    Electromagnetic Pulse (EMP) is a known issue for short-pulse laser facilities, and will also be an issue for experiments using the advanced radiographic capability (ARC) at the National Ignition Facility (NIF). The ARC diagnostic uses four NIF beams that are compressed to picosecond durations for backlighting ignition capsules and other applications. Consequently, we are working to understand the EMP due to high-energy (MeV) electrons escaping from targets heated by short-pulse lasers. Our approach is to measure EMP in the Titan short-pulse laser at Lawrence Livermore National Laboratory (LLNL) and to employ that data to establish analysis and simulation capabilities. We have installed a wide variety of probes inside and outside the Titan laser chamber. We have high-frequency B-dot and D-dot probes, a photodiode, and fast current-viewing and integrating current transformers. The probe outputs are digitized by 10 and 20 Gsample/s oscilloscopes. The cables and oscilloscopes are well shielded to reduce noise. Our initial measurement campaign has yielded data useful mainly from several hundreds of MHz to several GHz. We currently are supplementing our high-frequency probes with lower-frequency ones to obtain better low-frequency data. In order to establish analysis and simulation capabilities we are modeling the Titan facility using various commercial and LLNL numerical electromagnetics codes. We have simulated EMP generation by having a specified number of electrons leave the target and strike the chamber wall and other components in the chamber. This short impulse of electrons has a correspondingly broad spectrum, exciting high-frequency structure in the resulting EMP. In this paper, we present results of our initial measurement campaign and comparisons between the measurements and simulations.

  8. Short pulse generation by laser slicing at NSLSII

    SciTech Connect

    Yu, L.; Blednykh, A.; Guo, W.; Krinsky, S.; Li, Y.; Shaftan, T.; Tchoubar, O.; Wang, G.; Willeke, F.; Yang, L.

    2011-03-28

    We discuss an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. We discuss its basic parameters and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring. There is a rapid growth of ultrafast user community interested in science using sub-pico-second x-ray pulses. In BNL's Short Pulse Workshop, the discussion from users shows clearly the need for a sub-pico-second pulse source using laser slicing method. In the proposal submitted following this workshop, NSLS team proposed both hard x-ray and soft x-ray beamlines using laser slicing pulses. Hence there is clearly a need to consider the R&D efforts of laser slicing short pulse generation at NSLSII to meet these goals.

  9. A new method to produce short pulses

    NASA Astrophysics Data System (ADS)

    Germer, Rudolf

    2005-03-01

    If a coaxial cable or a strip line has an open end, then the incoming signal is reflected there. Due to the propagation velocity, an incoming rectangular pulse has a length in space which depends on its length in time. If the pulse length is twice the cable length, then after the reflection at the end, the pulse energy is distributed in an electrical field along the cable. Input and output current are compensating. At this time, it is possible to take out the energy simultanously through several switched connections at the same time. The result is a shorter pulse of much higher power which can drive a load of low impedance or with the pulse transformer presented at the 25th ICHSPP give a short pulse of very high voltage. This concentration in time of the electrical energy is planed to be used for x-ray flash systems. If the input pulse is not rectangular, then it is possible to take off the energy at the time of best peak power. Bei einem Bandleiter oder Koaxialkabel mit offenem Ende wird das auf der Leitung laufende Signal reflektiert. Die Ausdehnung eines Rechteckimpulses auf einer solchen Leitung entspricht seiner Dauer und der Ausbreitungsgeschwindigkeit auf der Leitung. Wenn die Impulsausdehnung doppelt so gross ist wie die Leitungslange, dann kann die gesamte Energie des Impulses nach der Reflexion im elektrischen Feld gespeichert sein, Eingangs und Reflexionsstrom kompensieren sich. Zu dieser Zeit ist es moglich, fast die ganze Energie gleichzeitig seitlich durch einen ausgedehnten oder mit mehreren einzelnen Schaltern an einen niederohmigen Verbraucher weiterzuleiten oder mit einem Impulstransformator ( gezeigt auf dem 25. ICHSPP ) an dessen Impedanz anzupassen. Der Ausgangsimpuls ist sehr kurz und von vervielfachter Leistung. Diese zeitliche Energiekonzentration soll spater fur Rontgenbltzsysteme verwendet werden. Im Falle eines nicht rechteckformigen Eingangsimpulses kann die Energie wahrend der hochsten Spitzenleistung entnommen werden.

  10. Laser short pulse heating of metal nano-wires

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Al-Dweik, A. Y.

    2012-11-01

    Non-equilibrium energy transfer takes place in a solid substrate during a short-pulse laser irradiation and temperature field can be obtained analytically in the irradiated region. In the present study, laser short-pulse heating of metal nano-wire is considered and the analytical solution for two-dimensional axisymmetric nano-wire is presented. Since the absorption of the incident beam takes place in the skin of the irradiated surface, a volumetric heat source resembling the absorption process is incorporated in the analysis. Three different nano-wire materials are introduced in the analysis for the comparison reason. These include silver, chromium, and copper. It is found that temperature decay is gradual on the surface vicinity and temporal variation of the surface temperature follows almost the laser pulse intensity profile at the irradiated center.

  11. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P

    2009-08-24

    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  12. Making relativistic positrons using ultraintense short pulse lasers

    SciTech Connect

    Chen Hui; Wilks, S. C.; Bonlie, J. D.; Chen, S. N.; Cone, K. V.; Elberson, L. N.; Price, D. F.; Schneider, M. B.; Shepherd, R.; Stafford, D. C.; Tommasini, R.; Van Maren, R.; Beiersdorfer, P.; Gregori, G.; Meyerhofer, D. D.; Myatt, J.

    2009-12-15

    This paper describes a new positron source using ultraintense short pulse lasers. Although it has been theoretically studied since the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at the Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2x10{sup 10} positrons/s ejected at the back of approximately millimeter thick gold targets were detected. The targets were illuminated with short (approx1 ps) ultraintense (approx1x10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser-based positron source with its unique characteristics may complement the existing sources based on radioactive isotopes and accelerators.

  13. A tuneable ultra-compact high-power, ultra-short pulsed, bright gamma-ray source based on bremsstrahlung radiation from laser-plasma accelerated electrons

    SciTech Connect

    Cipiccia, S.; Wiggins, S. M.; Shanks, R. P.; Islam, M. R.; Vieux, G.; Issac, R. C.; Brunetti, E.; Ersfeld, B.; Welsh, G. H.; Anania, M. P.; Jaroszynski, D. A.; Maneuski, D.; Shea, V. O.; Lemos, N. R. C.; Bendoyro, R. A.; Dias, J. M.; Bourgeois, N.; Ibbotson, T. P. A.; and others

    2012-03-15

    The laser driven plasma wakefield accelerator is a very compact source of high energy electrons. When the quasi-monoenergetic beam from these accelerators passes through dense material, high energy bremsstrahlung photons are emitted in a collimated beam with high flux. We show how a source based on this emission process can produce more than 10{sup 9} photons per pulse with a mean energy of 10 MeV. We present experimental results that show the feasibility of this method of producing high energy photons and compare the experimental results with GEANT4 Montecarlo simulations, which also give the scaling required to evaluate its suitability as method to produce radioisotopes via photo-nuclear reactions or for imaging applications.

  14. A tuneable ultra-compact high-power, ultra-short pulsed, bright gamma-ray source based on bremsstrahlung radiation from laser-plasma accelerated electrons

    NASA Astrophysics Data System (ADS)

    Cipiccia, S.; Wiggins, S. M.; Shanks, R. P.; Islam, M. R.; Vieux, G.; Issac, R. C.; Brunetti, E.; Ersfeld, B.; Welsh, G. H.; Anania, M. P.; Maneuski, D.; Lemos, N. R. C.; Bendoyro, R. A.; Rajeev, P. P.; Foster, P.; Bourgeois, N.; Ibbotson, T. P. A.; Walker, P. A.; Shea, V. O.; Dias, J. M.; Jaroszynski, D. A.

    2012-03-01

    The laser driven plasma wakefield accelerator is a very compact source of high energy electrons. When the quasi-monoenergetic beam from these accelerators passes through dense material, high energy bremsstrahlung photons are emitted in a collimated beam with high flux. We show how a source based on this emission process can produce more than 109 photons per pulse with a mean energy of 10 MeV. We present experimental results that show the feasibility of this method of producing high energy photons and compare the experimental results with GEANT4 Montecarlo simulations, which also give the scaling required to evaluate its suitability as method to produce radioisotopes via photo-nuclear reactions or for imaging applications.

  15. Photoconductive Semiconductor Switch Technology for Short Pulse Electromagnetics and Lasers

    SciTech Connect

    Denison, Gary J.; Helgeson, Wesley D.; Hjalmarson, Harold P.; Loubriel, Guillermo M.; Mar, Alan; O'Malley, Martin W.; Zutavern, Fred J.

    1999-08-05

    High gain photoconductive semiconductor switches (PCSS) are being used to produce high power electromagnetic pulses foc (1) compact, repetitive accelerators, (2) ultra-wide band impulse sources, (3) precision gas switch triggers, (4) optically-activated firesets, and (5) high power optical pulse generation and control. High power, sub-nanosecond optical pulses are used for active optical sensors such as compact optical radars and range-gated hallistic imaging systems. Following a brief introduction to high gain PCSS and its general applications, this paper will focus on PCSS for optical pulse generation and control. PCSS technology can be employed in three distinct approaches to optical pulse generation and control: (1) short pulse carrier injection to induce gain-switching in semiconductor lasers, (2) electro-optical Q-switching, and (3) optically activated Q-switching. The most significant PCSS issues for these applications are switch rise time, jitter, and longevity. This paper will describe both the requirements of these applications and the most recent results from PCSS technology. Experiments to understand and expand the limitations of high gain PCSS will also be described.

  16. High Average Power, High Energy Short Pulse Fiber Laser System

    SciTech Connect

    Messerly, M J

    2007-11-13

    Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources of high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.

  17. SANSPOL at a pulsed source.

    SciTech Connect

    Bleuel, M.; Lang, E.; Krist, T.; Wagner, W.; Lal, J.; Intense Pulsed Neutron Source; Hahn Meitner Inst.; PSI

    2007-07-15

    Neutron polarization has not been implemented successfully on a time-of-flight small angle neutron scattering (TOF-SANS) machine to this date anywhere in the world. Designing a suitable one for the small angle scattering instrument (SASI) at IPNS, and implementing it, is an important first on a pulsed source. To achieve this, the installation of a solid-state supermirror-based polarizer, a gradient field adiabatic spin flipper, and a new collimator package were required. A polarizing solid-state bender without adsorbing layers, designed to transmit one polarized spin state and reflect the other has been purchased from Neutron Optics Berlin (NOB). By placing this package upstream of the collimation only the transmitted spin-state passes through to the sample. The polarization achieved with this technique up to now is 80% for neutrons in a wavelength range of 3-8 Angstroms and 67% for larger wavelengths. The polarizer is placed on a linear translator so it can be easily removed from the beam, when regular SANS measurements are desired. The first experimental results from a two-phase CuNiFe alloy sample are reported here.

  18. Plasma physics applications to intense radiation sources, pulsed power and space physics. Short pulse ultra intense laser-plasma interaction experiment. Final report, 1 January 1990-31 May 1993

    SciTech Connect

    Sudan, R.N.

    1993-05-31

    Intense bright x-ray sources from dense z-pinch and x-pinch plasmas are being investigated for photo-pumping x-ray laser media. Crossed Aluminum wire X-pinches with mass line density up to hundreds of micrograms per centimeter have been imploded by up to 600 kA current for 40 ns using a 0.5 TW pulsed power generator. High density bright spots are observed. Soft x-ray spectroscopy was used to infer plasma density of up to approx. 10 to the 20th power per cubic cm and temperature of 100 -300 eV. The optimum mass loading for different ionization stages of Aluminum ions was examined. Parallel wire z-pinches yielded both lower density up to approx. 10(19)cm-3, and lower temperatures (70 - 200 eV), than the X-pinch plasmas.

  19. Short-pulse laser interactions with disordered materials and liquids

    SciTech Connect

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L.

    1995-12-31

    High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regime in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.

  20. Stimulated brillouin backscatter of a short-pulse laser

    SciTech Connect

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-11-03

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x{prime} = x {minus} V{sub g}t, t{prime} = t, where V{sub g} is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency).

  1. Pulsed source ion implantation apparatus and method

    DOEpatents

    Leung, K.N.

    1996-09-24

    A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted. 16 figs.

  2. Pulsed source ion implantation apparatus and method

    DOEpatents

    Leung, Ka-Ngo

    1996-01-01

    A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted.

  3. Fiber Optic Solutions for Short Pulse Lasers

    SciTech Connect

    Beach, R; Dawson, J; Liao, Z; Jovanovic, I; Wattellier, B; Payne, S; Barty, C P

    2003-01-29

    For applications requiring high beam quality radiation from efficient, compact and rugged sources, diffraction limited fiber lasers are ideal, and to date have been demonstrated at average CW power levels exceeding 100 W with near diffraction limited: output. For conventional single-core step-index single-mode fibers, this power level represents the sealing limit because of nonlinear and laser damage considerations. Higher average powers would exceed nonlinear process thresholds such as the Raman and stimulated Brillouin scattering limit, or else damage the fiber due to the high intensity level in the fiber's core. The obvious way to increase the average power capability of fibers is to increase the area of their core. Simply expanding the core dimensions of the fiber allows a straightforward power sealing due to enhanced nonlinear and power handling characteristics that scale directly with the core area. Femtosecond, chirped-pulse, fiber lasers with pulse energies greater than 1mJ have been demonstrated in the literature [2] using this technique. This output energy was still limited by the onset of stimulated Raman scattering. We have pursued an alternative and complimentary approach which is to reduce the intensity of light propagating in the core by distributing it more evenly across the core area via careful design of the refractive index profile [3]. We have also sought to address the primary issue that results from scaling the core. The enhanced power handling capability comes at the expense of beam quality, as increasing the core diameter in standard step index fibers permits multiple transverse modes to lase simultaneously. Although this problem of multimode operation can be mitigated to some extent by appropriately designing the fiber's waveguide structure, limitations such as bend radius loss, sensitivity to thermally induced perturbations of the waveguide structure, and refractive index control, all become more stringent as the core diameter grows

  4. Giant-chirp oscillators for short-pulse fiber amplifiers.

    PubMed

    Renninger, William H; Chong, Andy; Wise, Frank W

    2008-12-15

    A new regime of pulse parameters in a normal-dispersion fiber laser is identified. Dissipative solitons exist with remarkably large pulse duration and chirp, along with large pulse energy. A low-repetition-rate oscillator that generates pulses with large and linear chirp can replace the standard oscillator, stretcher, pulse-picker, and preamplifier in a chirped-pulse fiber amplifier. The theoretical properties of such a giant-chirp oscillator are presented. A fiber laser designed to operate in the new regime generates approximately 150 ps pulses at a 3 MHz repetition rate. Amplification of these pulses to 1 microJ energy with pulse duration as short as 670 fs demonstrates the promise of this new approach.

  5. Molecular π pulses: Population inversion with positively chirped short pulses

    NASA Astrophysics Data System (ADS)

    Cao, Jianshu; Bardeen, Christopher J.; Wilson, Kent R.

    2000-08-01

    Detailed theoretical analysis and numerical simulation indicate that nearly complete electronic population inversion of molecular systems can be achieved with intense positively chirped broadband laser pulses. To provide a simple physical picture, a two-level model is used to examine the condition for the so-called π pulses and a four-level model is designed to demonstrate for molecular systems the correlation between the sign of the chirp and the excited state population. The proposed molecular π pulse is the combined result of vibrational coherence in the femtosecond regime and adiabatic inversion in the picosecond regime. Numerical results for a displaced oscillator, for LiH and for I2, show that the proposed molecular π pulse scheme is robust with respect to changes in field parameters such as the linear positive chirp rate, field intensity, bandwidth, and carrier frequency, and is stable with respect to thermal and condensed phase conditions including molecular rotation, rovibronic coupling, and electronic dephasing.

  6. High intensity, pulsed thermal neutron source

    DOEpatents

    Carpenter, J.M.

    1973-12-11

    This invention relates to a high intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons, a moderator block adjacent to the last neutron source, a reflector block which encases the fast neutron source and the moderator block and has a thermal neutron exit port extending therethrough from the moderator block, and a neutron energy- dependent decoupling reflector liner covering the interior surfaces of the thermal neutron exit port and surrounding all surfaces of the moderator block except the surface viewed by the thermal neutron exit port. (Official Gazette)

  7. Monitoring the sea surface with a short pulse radar

    NASA Technical Reports Server (NTRS)

    Le Vine, D. M.

    1974-01-01

    A solution is presented for the scattering of short pulses from a stochastic, corrugated surface relative to the sea for the case of a narrow-beam transmitting antenna pointing near nadir. The spectrum of the received power and its time history are calculated and this solution is used to show that a measure of the variance of the surface ordinant can be obtained from the backscattered power. Included explicitly in the analysis is the finite nature of the source and the role of the small-scale wave structure (capillary wave range). It is shown that when sufficiently short pulses are transmitted, one can obtain a measure of the variance of the large scale surface ordinant from either the temporal spacing of the peaks in the returned power or from the envelope of the spectrum of the received power. Assuming an appropriate model for the statistics and spectrum of the surface ordinate, the variance can be used to compute the wind speed and the significant wave height of the surface.

  8. High pulse power rf sources for linear colliders

    SciTech Connect

    Wilson, P.B.

    1983-09-01

    RF sources with high peak power output and relatively short pulse lengths will be required for future high gradient e/sup +/e/sup -/ linear colliders. The required peak power and pulse length depend on the operating frequency, energy gradient and geometry of the collider linac structure. The frequency and gradient are in turn constrained by various parameters which depend on the beam-beam collision dynamics, and on the total ac wall-plug power that has been committed to the linac rf system. Various rf sources which might meet these requirements are reviewed. Existing source types (e.g., klystrons, gyrotrons) and sources which show future promise based on experimental prototypes are first considered. Finally, several proposals for high peak power rf sources based on unconventional concepts are discussed. These are an FEL source (two beam accelerator), rf energy storage cavities with switching, and a photocathode device which produces an rf current by direct emission modulation of the cathode.

  9. Design of self-refocused pulses under short relaxation times.

    PubMed

    Issa, Bashar

    2009-06-01

    The effect of using self-refocused RF pulses of comparable duration to relaxation times is studied in detail using numerical simulation. Transverse magnetization decay caused by short T2 and longitudinal component distortion due to short T1 are consistent with other studies. In order to design new pulses to combat short T1 and T2 the relaxation terms are directly inserted into the Bloch equations. These equations are inverted by searching the RF solution space using simulated annealing global optimization technique. A new T2-decay efficient excitation pulse is created (SDETR: single delayed excursion T2 resistive) which is also energy efficient. Inversion pulses which improve the inverted magnetization profile and achieve better suppression of the remaining transverse magnetization are also created even when both T1 and T2 are short. This is achieved, however, on the expense of a more complex B1 shape of larger energy content.

  10. Phase Noise Comparision of Short Pulse Laser Systems

    SciTech Connect

    S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

    2006-12-01

    This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

  11. On Acceptable Exposures to Short Pulses of Electromagnetic Fields

    DTIC Science & Technology

    2015-09-01

    standards and other research on the safety to humans of short pulses of electromagnetic radiation . Special attention is paid to a ten nanosecond...pulses of electromagnetic radiation have been considered. Considerations for implanted medical devices and implanted metal objects and the like are...of Electromagnetic Precursors,” Proceedings of the International Conference on Electromagnetics in Advanced Applications, Torino, Italy, September

  12. Temporal narrowing of neutrons produced by high-intensity short-pulse lasers

    SciTech Connect

    Higginson, D. P.; Vassura, L.; Gugiu, M. M.; Antici, P.; Borghesi, M.; Brauckmann, S.; Diouf, C.; Green, A.; Palumbo, L.; Petrascu, H.; Sofia, S.; Stardubtsev, M.; Willi, O.; Kar, S.; Negoita, F.; Fuchs, J.

    2015-07-28

    The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ~3 ns duration neutron pulse with 104 n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. Finally, this neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

  13. Temporal narrowing of neutrons produced by high-intensity short-pulse lasers

    DOE PAGES

    Higginson, D. P.; Vassura, L.; Gugiu, M. M.; ...

    2015-07-28

    The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ~3 ns duration neutron pulse with 104 n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. Finally, this neutron pulse compares favorably to the duration of conventional accelerator sources and shouldmore » scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.« less

  14. Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers.

    PubMed

    Higginson, D P; Vassura, L; Gugiu, M M; Antici, P; Borghesi, M; Brauckmann, S; Diouf, C; Green, A; Palumbo, L; Petrascu, H; Sofia, S; Stardubtsev, M; Willi, O; Kar, S; Negoita, F; Fuchs, J

    2015-07-31

    The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ∼3  ns duration neutron pulse with 10(4)  n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

  15. Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers

    NASA Astrophysics Data System (ADS)

    Higginson, D. P.; Vassura, L.; Gugiu, M. M.; Antici, P.; Borghesi, M.; Brauckmann, S.; Diouf, C.; Green, A.; Palumbo, L.; Petrascu, H.; Sofia, S.; Stardubtsev, M.; Willi, O.; Kar, S.; Negoita, F.; Fuchs, J.

    2015-07-01

    The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ˜3 ns duration neutron pulse with 104 n /MeV /sr /shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

  16. Tunable pulsed narrow bandwidth light source

    DOEpatents

    Powers, Peter E.; Kulp, Thomas J.

    2002-01-01

    A tunable pulsed narrow bandwidth light source and a method of operating a light source are provided. The light source includes a pump laser, first and second non-linear optical crystals, a tunable filter, and light pulse directing optics. The method includes the steps of operating the pump laser to generate a pulsed pump beam characterized by a nanosecond pulse duration and arranging the light pulse directing optics so as to (i) split the pulsed pump beam into primary and secondary pump beams; (ii) direct the primary pump beam through an input face of the first non-linear optical crystal such that a primary output beam exits from an output face of the first non-linear optical crystal; (iii) direct the primary output beam through the tunable filter to generate a sculpted seed beam; and direct the sculpted seed beam and the secondary pump beam through an input face of the second non-linear optical crystal such that a secondary output beam characterized by at least one spectral bandwidth on the order of about 0.1 cm.sup.-1 and below exits from an output face of the second non-linear optical crystal.

  17. Pulsed pyroelectric crystal-powered gamma source

    SciTech Connect

    Chen, A. X.; Antolak, A. J.; Leung, K.-N.; Raber, T. N.; Morse, D. H.

    2013-04-19

    A compact pulsed gamma generator is being developed to replace radiological sources used in commercial, industrial and medical applications. Mono-energetic gammas are produced in the 0.4 - 1.0 MeV energy range using nuclear reactions such as {sup 9}Be(d,n{gamma}){sup 10}B. The gamma generator employs an RF-driven inductively coupled plasma ion source to produce deuterium ion current densities up to 2 mA/mm{sup 2} and ampere-level current pulses can be attained by utilizing an array extraction grid. The extracted deuterium ions are accelerated to approximately 300 keV via a compact stacked pyroelectric crystal system and then bombard the beryllium target to generate gammas. The resulting microsecond pulse of gammas is equivalent to a radiological source with curie-level activity.

  18. Diffraction imaging characteristics of slit for ultra-short laser pulse

    NASA Astrophysics Data System (ADS)

    Yu, Xiang-yang; Wu, Kun-xi; Lu, Long-zhao

    2015-08-01

    We propose a simple and concise mathematical method based on the Fraunhofer approximation to analyze the imaging characteristics of slit for broadband light sources. Taking Gaussian-shaped ultra-short laser pulse for example, we investigated the diffraction imaging characteristics of ultra-short light sources through a single-slit and a double-slit. We deduced the mathematical expressions of the intensity distribution of far-field diffraction, and conducted numerical calculation and analysis. It turns out the pulse width of the ultra-short light source plays an important role in the diffraction imaging characteristics of slit. We also provide a quantitative criterion to measure the deviation in terms of far-field diffraction intensity distribution between broadband light source and the ideal monochromatic light source.

  19. Physical source realization of complex source pulsed beams

    PubMed

    Heyman; Lomakin; Kaiser

    2000-04-01

    Complex source pulsed beams (CSPB) are exact wave-packet solutions of the time-dependent wave equation that are modeled mathematically in terms of radiation from a pulsed point source located at a complex space-time coordinate. In the present paper, the physical source realization of the CSPB is explored. This is done in the framework of the acoustic field, as a concrete physical example, but a similar analysis can be applied for electromagnetic CSPB. The physical realization of the CSPB is addressed by deriving exact expressions for the acoustic source distribution in the real coordinate space that generates the CSPB, and by exploring the power and energy flux near these sources. The exact source distribution is of finite support. Special emphasis is placed on deriving simplified source functions and parametrization for the special case where the CSPB are well collimated.

  20. Shock profile induced by short laser pulses

    NASA Astrophysics Data System (ADS)

    Couturier, S.; de Rességuier, T.; Hallouin, M.; Romain, J. P.; Bauer, F.

    1996-06-01

    Standard 25-μm-thick polyvinilydene fluoride (PVDF) piezoelectric gauges and new 450-μm-thick P(VDF 70%, TrFE 30%) piezoelectric copolymer have been used to record shock profiles at the back face of metallic targets irradiated by laser pulses of 2.5 and 0.6 ns duration at a 1.06 μm wavelength. The records are fully explained with simplified space-time diagram analysis. The pressure profile applied at the front face of the target has been determined from these records combined with numerical simulations of wave propagation through the target. A numerical code describing the interaction of laser with matter (FILM) has also been used for computing the applied pressure. Both methods lead to very close results. The peak pressure dependence on incident laser intensity is determined up to 30 GPa at 1012 W/cm2.

  1. Supporting technologies for a long-pulse spallation source

    SciTech Connect

    Russell, G.J.; Weinacht, D.J.; Ferguson, P.D.; Pitcher, E.J.; Court, J.D.; Greene, G.L.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project is directed toward the development of the technologies required for a long-pulse, spallation neutron source (LPSS). Traditionally, spallation neutron sources have used proton accelerators that provide intense, short ({le} 1{micro}s) pulses of high-energy protons to a spallation target. A LPSS uses a proton pulse with longer time duration ({approx} 1 ms) and offers the possibility of achieving very high spallation neutron fluxes at substantially lower cost. The performance of a LPSS is very dependent on the neutronic performance of the target-moderator system. A detailed study of this performance has been carried out using Monte Carlo simulations. It should be noted that a LPSS is optimally suited to a fully coupled moderator. Neutron production per proton from such a moderator is a factor of five to seven greater than that produce d by moderators used at short pulse sources. The results of these efforts have been published in a series of articles.

  2. Precision short-pulse damage test station utilizing optical parametric chirped-pulse amplification

    SciTech Connect

    Jovanovic, I; Brown, C; Wattellier, B; Nielsen, N; Molander, W; Stuart, B; Pennington, D; Barty, C J

    2004-03-22

    The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression, due to their high efficiency and high damage threshold for picosecond pulses. The peak power of HEPW lasers will be determined by the aperture and damage threshold of the final dielectric grating in the pulse compressor and final focusing optics. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. Our damage test station is based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier (OPCPA) operating at 1053 nm at a repetition rate of 10 Hz. We present the design of our OPCPA system pumped by a commercial Q-switched pump laser and the results of the full system characterization. Initial short-pulse damage experiments in the far field using our system have been performed.

  3. Assessment and Mitigation of Electromagnetic Pulse (EMP) Impacts at Short-pulse Laser Facilities

    SciTech Connect

    Brown, Jr., C G; Bond, E; Clancy, T; Dangi, S; Eder, D C; Ferguson, W; Kimbrough, J; Throop, A

    2009-10-02

    The National Ignition Facility (NIF) will be impacted by electromagnetic pulse (EMP) during normal long-pulse operation, but the largest impacts are expected during short-pulse operation utilizing the Advanced Radiographic Capability (ARC). Without mitigation these impacts could range from data corruption to hardware damage. We describe our EMP measurement systems on Titan and NIF and present some preliminary results and thoughts on mitigation.

  4. Assessment and Mitigation of Electromagnetic Pulse (EMP) Impacts at Short-pulse Laser Facilities

    SciTech Connect

    Brown, Jr., C G; Bond, E; Clancy, T; Dangi, S; Eder, D C; Ferguson, W; Kimbrough, J; Throop, A

    2010-02-04

    The National Ignition Facility (NIF) will be impacted by electromagnetic pulse (EMP) during normal long-pulse operation, but the largest impacts are expected during short-pulse operation utilizing the Advanced Radiographic Capability (ARC). Without mitigation these impacts could range from data corruption to hardware damage. We describe our EMP measurement systems on Titan and NIF and present some preliminary results and thoughts on mitigation.

  5. Correlated states of a quantum oscillator acted by short pulses

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1993-01-01

    Correlated squeezed states for a quantum oscillator are constructed based on the method of quantum integrals of motion. The quantum oscillator is acted upon by short duration pulses. Three delta-kickings of frequency are used to model the pulses' dependence upon the time aspects of the frequency of the oscillator. Additionally, the correlation coefficient and quantum variances of operations of coordinates and momenta are written in explicit form.

  6. Medical applications of ultra-short pulse lasers

    SciTech Connect

    Kim, B M; Marion, J E

    1999-06-08

    The medical applications for ultra short pulse lasers (USPLs) and their associated commercial potential are reviewed. Short pulse lasers offer the surgeon the possibility of precision cutting or disruption of tissue with virtually no thermal or mechanical damage to the surrounding areas. Therefore the USPL offers potential improvement to numerous existing medical procedures. Secondly, when USPLs are combined with advanced tissue diagnostics, there are possibilities for tissue-selective precision ablation that may allow for new surgeries that cannot at present be performed. Here we briefly review the advantages of short pulse lasers, examine the potential markets both from an investment community perspective, and from the view. of the technology provider. Finally nominal performance and cost requirements for the lasers, delivery systems and diagnostics and the present state of development will be addressed.

  7. Source of coherent short wavelength radiation

    DOEpatents

    Villa, Francesco

    1990-01-01

    An apparatus for producing coherent radiation ranging from X-rays to the far ultraviolet (i.e., 1 Kev to 10 eV) utilizing the Compton scattering effect. A photon beam from a laser is scattered on a high energy electron bunch from a pulse power linac. The short wavelength radiation produced by such scattering has sufficient intensity and spatial coherence for use in high resolution applications such as microscopy.

  8. Short Pulse Nd: YAG Laser for Optical Fuze Applications.

    DTIC Science & Technology

    1981-02-01

    guidance systems or optical communications links. The primary concern of this work was optical proximity fuze systems, so the Nd:YAG laser system has been...AD-A099 042 HARRY DIAMOND LASS AOELPMI MO F/6 19/1 SHORT PULSE NO: YAG LASER FOR OPTICAL FUZE APPLICATIONS.(U) FEB 81 R WELLMAN, 4 NEMARICH...Subtitle) S TYPE OF I IPoRT & PERIOD COVERED Short Pulse Nd:YAG Laser for Optical Fuze Applications& _Technical t .,-Itp -PERFORMING OR;5. REPO*T NIUBER

  9. Shutterless ion mobility spectrometer with fast pulsed electron source

    NASA Astrophysics Data System (ADS)

    Bunert, E.; Heptner, A.; Reinecke, T.; Kirk, A. T.; Zimmermann, S.

    2017-02-01

    Ion mobility spectrometers (IMS) are devices for fast and very sensitive trace gas analysis. The measuring principle is based on an initial ionization process of the target analyte. Most IMS employ radioactive electron sources, such as 63Ni or 3H. These radioactive materials have the disadvantage of legal restrictions and the electron emission has a predetermined intensity and cannot be controlled or disabled. In this work, we replaced the 3H source of our IMS with 100 mm drift tube length with our nonradioactive electron source, which generates comparable spectra to the 3H source. An advantage of our emission current controlled nonradioactive electron source is that it can operate in a fast pulsed mode with high electron intensities. By optimizing the geometric parameters and developing fast control electronics, we can achieve very short electron emission pulses for ionization with high intensities and an adjustable pulse width of down to a few nanoseconds. This results in small ion packets at simultaneously high ion densities, which are subsequently separated in the drift tube. Normally, the required small ion packet is generated by a complex ion shutter mechanism. By omitting the additional reaction chamber, the ion packet can be generated directly at the beginning of the drift tube by our pulsed nonradioactive electron source with only slight reduction in resolving power. Thus, the complex and costly shutter mechanism and its electronics can also be omitted, which leads to a simple low-cost IMS-system with a pulsed nonradioactive electron source and a resolving power of 90.

  10. Cavity Optical Pulse Extraction: ultra-short pulse generation as seeded Hawking radiation.

    PubMed

    Eilenberger, Falk; Kabakova, Irina V; de Sterke, C Martijn; Eggleton, Benjamin J; Pertsch, Thomas

    2013-01-01

    We show that light trapped in an optical cavity can be extracted from that cavity in an ultrashort burst by means of a trigger pulse. We find a simple analytic description of this process and show that while the extracted pulse inherits its pulse length from that of the trigger pulse, its wavelength can be completely different. Cavity Optical Pulse Extraction is thus well suited for the development of ultrashort laser sources in new wavelength ranges. We discuss similarities between this process and the generation of Hawking radiation at the optical analogue of an event horizon with extremely high Hawking temperature. Our analytic predictions are confirmed by thorough numerical simulations.

  11. Pulsed source of energetic atomic oxygen

    NASA Technical Reports Server (NTRS)

    Caledonia, George E.; Krech, Robert H.

    1987-01-01

    A pulsed high flux source of nearly monoenergetic atomic oxygen was designed, built, and successfully demonstrated. Molecular oxygen at several atmospheres pressure is introduced into an evacuated supersonic expansion nozzle through a pulsed molecular beam valve. An 18 J pulsed CO2 TEA laser is focused to intensities greater than 10(9) W/sq cm in the nozzle throat to generate a laser-induced breakdown. The resulting plasma is heated in excess of 20,000 K by a laser supported detonation wave, and then rapidly expands and cools. Nozzle geometry confines the expansion to provide rapid electron-ion recombination into atomic oxygen. Average O atom beam velocities from 5 to 13 km/s were measured at estimated fluxes to 10(18) atoms per pulse. Preliminary materials testing has produced the same surface oxygen enrichment in polyethylene samples as obtained on the STS-8 mission. Scanning electron microscope examinations of irradiated polymer surfaces reveal an erosion morphology similar to that obtained in low Earth orbit, with an estimated mass removal rate of approx. 10(-24) cu cm/atom. The characteristics of the O atom source and the results of some preliminary materials testing studies are reviewed.

  12. CIDME: Short distances measured with long chirp pulses.

    PubMed

    Doll, Andrin; Qi, Mian; Godt, Adelheid; Jeschke, Gunnar

    2016-12-01

    Frequency-swept pulses have recently been introduced as pump pulses into double electron-electron resonance (DEER) experiments. A limitation of this approach is that the pump pulses need to be short in comparison to dipolar evolution periods. The "chirp-induced dipolar modulation enhancement" (CIDME) pulse sequence introduced in this work circumvents this limitation by means of longitudinal storage during the application of one single or two consecutive pump pulses. The resulting six-pulse sequence is closely related to the five-pulse "relaxation-induced dipolar modulation enhancement" (RIDME) pulse sequence: While dipolar modulation in RIDME is due to stochastic spin flips during longitudinal storage, modulation in CIDME is due to the pump pulse during longitudinal storage. Experimentally, CIDME is examined for Gd-Gd and nitroxide-nitroxide distance determination using a high-power Q-band spectrometer. Since longitudinal storage results in a 50% signal loss, comparisons between DEER using short chirp pump pulses of 64ns duration and CIDME using longer pump pulses are in favor of DEER. While the lower sensitivity restrains the applicability of CIDME for routine distance determination on high-power spectrometers, this result is not to be generalized to spectrometers having lower power and to specialized "non-routine" applications or different types of spin labels. In particular, the advantage of prolonged CIDME pump pulses is demonstrated for experiments at large frequency offset between the pumped and observed spins. At a frequency separation of 1GHz, where broadening due to dipolar pseudo-secular contributions becomes largely suppressed, a Gd-Gd modulation depth larger than 10% is achieved. Moreover, a CIDME experiment at deliberately reduced power underlines the potential of the new technique for spectrometers with lower power, as often encountered at higher microwave frequencies. With longitudinal storage times T below 10μs, however, CIDME appears rather

  13. CIDME: Short distances measured with long chirp pulses

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Qi, Mian; Godt, Adelheid; Jeschke, Gunnar

    2016-12-01

    Frequency-swept pulses have recently been introduced as pump pulses into double electron-electron resonance (DEER) experiments. A limitation of this approach is that the pump pulses need to be short in comparison to dipolar evolution periods. The "chirp-induced dipolar modulation enhancement" (CIDME) pulse sequence introduced in this work circumvents this limitation by means of longitudinal storage during the application of one single or two consecutive pump pulses. The resulting six-pulse sequence is closely related to the five-pulse "relaxation-induced dipolar modulation enhancement" (RIDME) pulse sequence: While dipolar modulation in RIDME is due to stochastic spin flips during longitudinal storage, modulation in CIDME is due to the pump pulse during longitudinal storage. Experimentally, CIDME is examined for Gd-Gd and nitroxide-nitroxide distance determination using a high-power Q-band spectrometer. Since longitudinal storage results in a 50% signal loss, comparisons between DEER using short chirp pump pulses of 64 ns duration and CIDME using longer pump pulses are in favor of DEER. While the lower sensitivity restrains the applicability of CIDME for routine distance determination on high-power spectrometers, this result is not to be generalized to spectrometers having lower power and to specialized "non-routine" applications or different types of spin labels. In particular, the advantage of prolonged CIDME pump pulses is demonstrated for experiments at large frequency offset between the pumped and observed spins. At a frequency separation of 1 GHz, where broadening due to dipolar pseudo-secular contributions becomes largely suppressed, a Gd-Gd modulation depth larger than 10% is achieved. Moreover, a CIDME experiment at deliberately reduced power underlines the potential of the new technique for spectrometers with lower power, as often encountered at higher microwave frequencies. With longitudinal storage times T below 10 μs, however, CIDME appears rather

  14. Fiber Laser Front Ends for High Energy, Short Pulse Lasers

    SciTech Connect

    Dawson, J; Messerly, M; Phan, H; Siders, C; Beach, R; Barty, C

    2007-06-21

    We are developing a fiber laser system for short pulse (1-10ps), high energy ({approx}1kJ) glass laser systems. Fiber lasers are ideal for these systems as they are highly reliable and enable long term stable operation.

  15. Compact chopper spectrometers for pulsed sources

    NASA Astrophysics Data System (ADS)

    Voigt, J.; Violini, N.; Schweika, W.

    2016-09-01

    We report on the opportunities for direct geometry chopper spectrometers (DGCS) by polychromatic illumination of the sample. At pulsed sources the use of multiple initial neutron energies appears naturally, if the repetition rate of chopper in front of the sample is larger than the repetition rate of the source. As a consequence, a large part of the spectrum is measured redundantly with variable energy and momentum transfer resolution. This can be used to optimize a chopper instrument for deep inelastic scattering, relaxing the requirements on the pulse length, by which the sample is illuminated, and on the secondary flight path, while the width of the spectral distribution must be narrowed down. This can open the path to new types of compact direct geometry chopper spectrometers, which need comparably small areas of detector coverage and allow very high repetition rates to provide a high intensity even if sample size and divergence distributions are limited.

  16. Short-pulse, compressed ion beams at the Neutralized Drift Compression Experiment

    NASA Astrophysics Data System (ADS)

    Seidl, P. A.; Barnard, J. J.; Davidson, R. C.; Friedman, A.; Gilson, E. P.; Grote, D.; Ji, Q.; Kaganovich, I. D.; Persaud, A.; Waldron, W. L.; Schenkel, T.

    2016-05-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.

  17. Short-pulse, compressed ion beams at the Neutralized Drift Compression Experiment

    DOE PAGES

    Seidl, P. A.; Barnard, J. J.; Davidson, R. C.; ...

    2016-05-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted onmore » the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.« less

  18. Improving luminous efficacy using dual sustain pulse waveform associated with short sustain pulse width in AC-plasma display panels

    NASA Astrophysics Data System (ADS)

    Park, Hyung Dal; Kim, Jae Hyun; Shin, Bhum Jae; Seo, Jeong Hyun; Tae, Heung-Sik

    2015-05-01

    In the previous work, we reported that the luminous efficacy was significantly improved using the short sustain pulse width with sufficiently long off-time between sustain pulses. In this paper, we have proposed the dual sustain pulse as an alternative of short sustain pulse width when the off-time is short. We demonstrate that the luminous efficacy can be significantly improved by using the new dual sustain waveform, which is attribute to the effects of the dual sustain pulse as well as short sustain pulse width when the off-time is 1μs. The proper adjustment of the 1st sustain discharge can induce the 2nd sustain discharge out of the sustain pulse, resulting in the high luminous efficacy. Comparing to the luminous efficacy of the conventional case, it is improved by approximately 130 % due to the effects of dual sustain pulse as well as short sustain pulse width.

  19. Shaped cathodes for the production of ultra-short multi-electron pulses

    PubMed Central

    Petruk, Ariel Alcides; Pichugin, Kostyantyn; Sciaini, Germán

    2017-01-01

    An electrostatic electron source design capable of producing sub-20 femtoseconds (rms) multi-electron pulses is presented. The photoelectron gun concept builds upon geometrical electric field enhancement at the cathode surface. Particle tracer simulations indicate the generation of extremely short bunches even beyond 40 cm of propagation. Comparisons with compact electron sources commonly used for femtosecond electron diffraction are made. PMID:28191483

  20. Coherent combs in ionization by intense and short laser pulses

    NASA Astrophysics Data System (ADS)

    Krajewska, K.; Kamiński, J. Z.

    2016-03-01

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented.

  1. Quantum Quenching of Radiation Losses in Short Laser Pulses.

    PubMed

    Harvey, C N; Gonoskov, A; Ilderton, A; Marklund, M

    2017-03-10

    Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.

  2. Quantum Quenching of Radiation Losses in Short Laser Pulses

    NASA Astrophysics Data System (ADS)

    Harvey, C. N.; Gonoskov, A.; Ilderton, A.; Marklund, M.

    2017-03-01

    Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.

  3. Mitigation of Electromagnetic Pulse (EMP) Effects from Short-Pulse Lasers and Fusion Neutrons

    SciTech Connect

    Eder, D C; Throop, A; Brown, Jr., C G; Kimbrough, J; Stowell, M L; White, D A; Song, P; Back, N; MacPhee, A; Chen, H; DeHope, W; Ping, Y; Maddox, B; Lister, J; Pratt, G; Ma, T; Tsui, Y; Perkins, M; O'Brien, D; Patel, P

    2009-03-06

    Our research focused on obtaining a fundamental understanding of the source and properties of EMP at the Titan PW(petawatt)-class laser facility. The project was motivated by data loss and damage to components due to EMP, which can limit diagnostic techniques that can be used reliably at short-pulse PW-class laser facilities. Our measurements of the electromagnetic fields, using a variety of probes, provide information on the strength, time duration, and frequency dependence of the EMP. We measure electric field strengths in the 100's of kV/m range, durations up to 100 ns, and very broad frequency response extending out to 5 GHz and possibly beyond. This information is being used to design shielding to mitigate the effects of EMP on components at various laser facilities. We showed the need for well-shielded cables and oscilloscopes to obtain high quality data. Significant work was invested in data analysis techniques to process this data. This work is now being transferred to data analysis procedures for the EMP diagnostics being fielded on the National Ignition Facility (NIF). In addition to electromagnetic field measurements, we measured the spatial and energy distribution of electrons escaping from targets. This information is used as input into the 3D electromagnetic code, EMSolve, which calculates time dependent electromagnetic fields. The simulation results compare reasonably well with data for both the strength and broad frequency bandwidth of the EMP. This modeling work required significant improvements in EMSolve to model the fields in the Titan chamber generated by electrons escaping the target. During dedicated Titan shots, we studied the effects of varying laser energy, target size, and pulse duration on EMP properties. We also studied the effect of surrounding the target with a thick conducting sphere and cube as a potential mitigation approach. System generated EMP (SGEMP) in coaxial cables does not appear to be a significant at Titan. Our results

  4. Development and Characterization of Pulsed Neutron Sources at NTF

    NASA Astrophysics Data System (ADS)

    McKee, Erik; Hammel, Ben; Lowe, Danny; Presura, Radu; Ivanov, Vladimir; Haque, Showera; Covington, Aaron; Iratcabal, Jeremy; McCormick, Zephyr; Darling, Tim; NTF Team; Nevada Security Technologies, LLC Collaboration

    2015-11-01

    Short duration, high-intensity pulsed neutron sources are being developed on the Zebra 1-MA/100ns pulsed-power generator. Ion beam collisions above threshold energies in a Z-pinch containing deuterium are the primary production mechanism of the 2.45 MeV neutrons. Deuterium treated palladium wire-arrays have been successfully used to produce neutrons on Zebra, but the deuterium content of the Pd wire storage diminishes rapidly. More traditional single-shell gas puffs have also been designed and implemented and allow for much higher repetition rates and ability to control the load composition; both pure deuterium and binary mixtures of krypton and deuterium gases were used. Both sources are capable of producing 1e10 neutrons per pulse. The yield and spectrum of the neutron pulse was measured by a combination of Ag and Y activation detectors and time-of-flight scintillator-PMT detectors. A model of the experimental area was used in the MCNP code to determine the scattering contribution and assist in calibration of the neutron detectors. Support for this work is provided by DOE/NNSA grant DE-NA0002075.

  5. GINGER simulations of short-pulse effects in the LEUTL FEL

    SciTech Connect

    Huang, Z.; Fawley, W.M.

    2001-07-01

    While the long-pulse, coasting beam model is often used in analysis and simulation of self-amplified spontaneous emission (SASE) free-electron lasers (FELs), many current SASE demonstration experiments employ relatively short electron bunches whose pulse length is on the order of the radiation slippage length. In particular, the low-energy undulator test line (LEUTL) FEL at the Advanced Photon Source has recently lased and nominally saturated in both visible and near-ultraviolet wavelength regions with a sub-ps pulse length that is somewhat shorter than the total slippage length in the 22-m undulator system. In this paper we explore several characteristics of the short pulse regime for SASE FELs with the multidimensional, time-dependent simulation code GINGER, concentrating on making a direct comparison with the experimental results from LEUTL. Items of interest include the radiation gain length, pulse energy, saturation position, and spectral bandwidth. We address the importance of short-pulse effects when scaling the LEUTL results to proposed x-ray FELs and also briefly discuss the possible importance of coherent spontaneous emission at startup.

  6. Directly driven source of multi-gigahertz, sub-picosecond optical pulses

    DOEpatents

    Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.; Gibson, David J.; Prantil, Matthew A.; Cormier, Eric

    2015-10-20

    A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulses or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.

  7. The diagnostics of ultra-short pulse laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Roth, Markus

    2011-09-01

    Since the invention of the laser, coherent light has been used to break down solid or gaseous material and transform it into a plasma. Over the last three decades two things have changed. Due to multiple advancements and design of high power lasers it is now possible to increase the electric and magnetic field strength that pushed the electron motion towards the regime of relativistic plasma physics. Moreover, due to the short pulse duration of the driving laser the underlying physics has become so transient that concepts like thermal equilibrium (even a local one) or spatial isotropy start to fail. Consequently short pulse laser-driven plasmas have become a rich source of new phenomena that we are just about beginning to explore. Such phenomena, like particle acceleration, nuclear laser-induced reactions, the generation of coherent secondary radiation ranging from THz to high harmonics and the production of attosecond pulses have excited an enormous interest in the study of short pulse laser plasmas. The diagnostics of such ultra-short pulse laser plasmas is a challenging task that involves many and different techniques compared to conventional laser-produced plasmas. While this review cannot cover the entire field of diagnostics that has been developed over the last years, we will try to give a summarizing description of the most important techniques that are currently being used.

  8. Modulated Pulsed Laser Sources for Imaging Lidars

    DTIC Science & Technology

    2007-10-01

    17 GHz in frequency-space implying SBS will not be a major concern while amplifying with 10 pm large mode area ( LMA ) fiber. Figure 1. Spectral plot... 10 /125 Pm Yb-doped gain fiber showing the effect of amplifier saturation. As the graph in Figure 11I shows, with a fixed pump power, the higher the...COVERED (From - To) 24- 10 -2007 Final Report April 2007 to October 2007 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Modulated Pulsed Laser Sources for

  9. Filamentation of a relativistic short pulse laser in a plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Tripathi, V. K.; Sawhney, B. K.

    2006-06-01

    An intense short pulse laser propagating through a plasma undergoes filamentation instability under the combined effects of relativistic mass variation and ponderomotive force-induced electron density depression. These two nonlinearities superimpose each other. In a tenuous plasma, the filament size scales as {\\sim}( c / \\omega _p\\; a_0 ) \\sqrt 2 \\gamma _0^{1/2} , where ω p is the plasma frequency, a0 is the normalized laser amplitude and γ 0 is the relativistic gamma factor.

  10. Short spatial filters with spherical lenses for high-power pulsed lasers

    SciTech Connect

    Burdonov, K F; Soloviev, A A; Shaikin, A A; Potemkin, A K; Egorov, A S

    2013-11-30

    We report possible employment of short spatial filters based on spherical lenses in a pulsed laser source (neodymium glass, 300 J, 1 ns). The influence of the spherical aberration on the quality of output radiation and coefficient of conversion to the second harmonics is studied. The ultra-short aberration spatial filter of length 1.9 m with an aperture of 122 mm is experimentally tested. A considerable shortening of multi-cascade pump lasers for modern petawatt laser systems is demonstrated by the employment of short spatial filters without expensive aspherical optics. (elements of laser systems)

  11. Delaying Trains of Short Light Pulses in WGM Resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey; Iltchenko, Vladimir; Strekalov, Dmitry; Savchenkov, Anatoliy; Maleki, Lute

    2008-01-01

    Suitably configured whispering-gallery-mode (WGM) optical resonators have been proposed as delay lines for trains of short light pulses. Until now, it has been common practice to implement an optical delay line as a coiled long optical fiber, which is bulky and tends to be noisy. An alternative has been to implement an optical delay line as a coupled-resonator optical waveguide (a chain of coupled optical resonators), which is compact but limits the width of the pulse spectrum to the width of an optical resonance and thereby places a lower limit on the duration of a pulse. In contrast, a delay line according to the proposal could be implemented as a single WGM resonator, and the pulses delayed by the resonator could be so short that their spectral widths could greatly exceed the spectral width of any single resonance. The proposal emerged from theoretical and experimental studies of the propagation of a pulse train in a WGM resonator. An important element of the theoretical study was recognition that the traditional definition of group velocity in effect, the velocity of a single pulse comprising a packet of waves propagating in a medium, the responsivity of which is a monotonous function of frequency does not necessarily apply in the case of a WGM resonator or other medium having a spectrum consisting of discrete resonance peaks at different frequencies. A new definition of group velocity, applicable to a train of pulses propagating in such a medium, was introduced and found to lead to the discovery of previously unknown features of propagation. Notably, it was found that in a micro - sphere optical resonator that supports a suitable combination of WGM modes, the group velocity for a train of light pulses could be positive, zero, or negative. A positive group velocity could be so small that the delay could be much longer than the ring-down time of the resonator; a delay of such great length is impossible for a single pulse interacting with either a linearly

  12. Why Are Short Pulses More Efficient in Tissue Erosion Using Pulsed Cavitational Ultrasound Therapy (Histotripsy)?

    NASA Astrophysics Data System (ADS)

    Wang, Tzu-Yin; Maxwell, Adam D.; Park, Simone; Xu, Zhen; Fowlkes, J. Brian; Cain, Charles A.

    2010-03-01

    Histotripsy produces mechanical tissue fractionation through controlled cavitation. The histotripsy induced tissue erosion is more efficient with shorter (i.e., 3-6 cycles) rather than longer (i.e. 24 cycles) pulses. In this study, we investigated the reasons behind this observation by studying dynamics of the cavitating bubble clouds and individual bubbles during and after a therapy pulse. Bubble clouds were generated at a gel-water interface using 5 to 30-cycle 1 MHz pulses at P-/P+>19/125-MPa pressure and 1-kHz pulse repetition frequency. The evolution of the overall bubble cloud and individual bubbles were studied using high speed photography. Results show that: 1) within the first 10-15 cycles, the overall cloud grew to its maximum size; the individual bubbles underwent violent expansion and collapse, and grew in size with each cycle of ultrasound; 2) between the 15th cycle and the end of the pulse, the overall cloud size did not change even if further cycles of ultrasound were delivered; the individual bubbles no longer underwent violent collapse; 3) after the pulse, the overall cloud gradually dissolved; the individual bubbles may coalesce into larger bubbles for 0-40 μs, and then gradually dissolved. These observations suggest that violent growth and collapse of individual bubbles occur within the first few cycles of ultrasound pulse most often. This may explain why extremely short pulses are more energy efficient in histotripsy-induced tissue erosion.

  13. Monte-Carlo simulations for instrumentation at pulsed and continuous sources

    NASA Astrophysics Data System (ADS)

    Wechsler, D.; Zsigmond, G.; Streffer, F.; Stride, J. A.; Mezei, F.

    2000-03-01

    The simulation of instrumentation serves as an important guideline for optimised resolution/intensity ratios, moderator-instrument correspondence and for the development of new types of instruments. The first version of the program package VITESS is capable of simulating neutrons stemming from pulsed and continuous sources to obtain comparisons which refer to competing types of instruments housed on a short pulsed spallation source (SPSS), long pulsed spallation source (LPSS), or continuous wave source (CWS). Detailed simulations are reported for high-resolution TOF powder diffraction and the crystal analyser instrument IRIS.

  14. Missing pulse detector for a variable frequency source

    DOEpatents

    Ingram, Charles B.; Lawhorn, John H.

    1979-01-01

    A missing pulse detector is provided which has the capability of monitoring a varying frequency pulse source to detect the loss of a single pulse or total loss of signal from the source. A frequency-to-current converter is used to program the output pulse width of a variable period retriggerable one-shot to maintain a pulse width slightly longer than one-half the present monitored pulse period. The retriggerable one-shot is triggered at twice the input pulse rate by employing a frequency doubler circuit connected between the one-shot input and the variable frequency source being monitored. The one-shot remains in the triggered or unstable state under normal conditions even though the source period is varying. A loss of an input pulse or single period of a fluctuating signal input will cause the one-shot to revert to its stable state, changing the output signal level to indicate a missing pulse or signal.

  15. Metal Processing with Ultra-Short Laser Pulses

    SciTech Connect

    Banks, P S; Feit, M D; Komashko, A M; Perry, M D; Rubenchik, A M; Stuart, B C

    2000-05-01

    Femtosecond laser ablation has been shown to produce well-defined cuts and holes in metals with minimal heat effect to the remaining material. Ultrashort laser pulse processing shows promise as an important technique for materials processing. We will discuss the physical effects associated with processing based experimental and modeling results. Intense ultra-short laser pulse (USLP) generates high pressures and temperatures in a subsurface layer during the pulse, which can strongly modify the absorption. We carried out simulations of USLP absorption versus material and pulse parameters. The ablation rate as function of the laser parameters has been estimated. Since every laser pulse removes only a small amount of material, a practical laser processing system must have high repetition rate. We will demonstrate that planar ablation is unstable and the initially smooth crater bottom develops a corrugated pattern after many tens of shots. The corrugation growth rate, angle of incidence and the polarization of laser electric field dependence will be discussed. In the nonlinear stage, the formation of coherent structures with scales much larger than the laser wavelength was observed. Also, there appears to be a threshold fluence above which a narrow, nearly perfectly circular channel forms after a few hundred shots. Subsequent shots deepen this channel without significantly increasing its diameter. The role of light absorption in the hole walls will be discussed.

  16. Electron detachment from negative ions in a short laser pulse

    SciTech Connect

    Shearer, S. F. C.; Smyth, M. C.; Gribakin, G. F.

    2011-09-15

    We present an efficient and accurate method to study electron detachment from negative ions by a few-cycle linearly polarized laser pulse. The adiabatic saddle-point method of Gribakin and Kuchiev [Phys. Rev. A 55, 3760 (1997)] is adapted to calculate the transition amplitude for a short laser pulse. Its application to a pulse with N optical cycles produces 2(N+1) saddle points in complex time, which form a characteristic 'smile.' Numerical calculations are performed for H{sup -} in a 5-cycle pulse with frequency 0.0043 a.u. and intensities of 10{sup 10}, 5x10{sup 10}, and 10{sup 11} W/cm{sup 2}, and for various carrier-envelope phases. We determine the spectrum of the photoelectrons as a function of both energy and emission angle, as well as the angle-integrated energy spectra and total detachment probabilities. Our calculations show that the dominant contribution to the transition amplitude is given by 5-6 central saddle points, which correspond to the strongest part of the pulse. We examine the dependence of the photoelectron angular distributions on the carrier-envelope phase and show that measuring such distributions can provide a way of determining this phase.

  17. Short-pulse CO₂ laser with longitudinal tandem discharge tube.

    PubMed

    Uno, K; Akitsu, T; Jitsuno, T

    2014-10-01

    We developed a longitudinally excited CO2 laser with a tandem discharge tube. The tandem scheme was constituted of two 30-cm long discharge tubes connected with an intermediate electrode. Two parts, each consisting of a charged capacitance and a 30-cm long discharge tube, were electrically connected in parallel and switched by a spark gap. The tandem scheme produced a short laser pulse like that of a TEA-CO2 laser with a charging voltage of -24.8 kV, which was smaller than the -40.0 kV charging voltage of our previous CO2 laser. At a gas pressure of 3.8 kPa, the spike pulse width was 145 ns, the pulse tail length was 58.8 μs, the output energy was 52.0 mJ, and the spike pulse energy was 2.4 mJ. We also investigated the dependence of the laser pulse and the discharge voltage on gas pressure.

  18. SLIM, Short-pulse Technology for High Gradient Induction Accelerators

    SciTech Connect

    Arntz, Floyd; Kardo-Sysoev, A.; Krasnykh, A.; /SLAC

    2008-12-16

    A novel short-pulse concept (SLIM) suited to a new generation of a high gradient induction particle accelerators is described herein. It applies advanced solid state semiconductor technology and modern microfabrication techniques to a coreless induction method of charged particle acceleration first proven on a macro scale in the 1960's. Because this approach avoids use of magnetic materials there is the prospect of such an accelerator working efficiently with accelerating pulses in the nanosecond range and, potentially, at megahertz pulse rates. The principal accelerator section is envisioned as a stack of coreless induction cells, the only active element within each being a single, extremely fast (subnanosecond) solid state opening switch: a Drift Step Recovery Diode (DSRD). Each coreless induction cell incorporates an electromagnetic pulse compressor in which inductive energy developed within a transmission-line feed structure over a period of tens of nanoseconds is diverted to the acceleration of the passing charge packet for a few nanoseconds by the abrupt opening of the DSRD switch. The duration of this accelerating output pulse--typically two-to-four nanoseconds--is precisely determined by a microfabricated pulse forming line connected to the cell. Because the accelerating pulse is only nanoseconds in duration, longitudinal accelerating gradients approaching 100 MeV per meter are believed to be achievable without inciting breakdown. Further benefits of this approach are that, (1) only a low voltage power supply is required to produce the high accelerating gradient, and, (2) since the DSRD switch is normally closed, voltage stress is limited to a few nanoseconds per period, hence the susceptibility to hostile environment conditions such as ionizing radiation, mismatch (e.g. in medical applications the peak beam current may be low), strong electromagnetic noise levels, etc is expected to be minimal. Finally, we observe the SLIM concept is not limited to linac

  19. Status of the intense pulsed neutron source

    SciTech Connect

    Carpenter, J.M.; Brown, B.S.; Kustom, R.L.; Lander, G.H.; Potts, C.W.; Schulke, A.W.; Wuestefeld, G.

    1985-01-01

    Fortunately in spite of some premature reports of its impending demise, IPNS has passed the fourth anniversary of the first delivery of protons to the targets (May 5, 1981) and is approaching the fourth anniversary of its operation as a scattering facility (August 4, 1981). On June 10, 1984, the RCS delivered its one billionth pulse to the IPNS target - the total number of protons delivered to the targets amounted then to 75 stp cm/sup 3/ of H/sub 2/ gas. Since startup IPNS has improved steadily in terms of the performance of the Rapid Cycling Synchrotron, the source and its moderators and the scattering instruments, and a substantial and productive user program has evolved. This report summarizes the current status of the Intense Pulsed Neutron Source at Argonne National Laboratory. We include reference to recent accelerator operating experience, neutron facility operating experience, improvements to these systems, design work on the ASPUN high-current facility, booster target design, the new solid methane moderator, characterization of the room temperature moderators, and provide some examples of recent results from several of the spectrometers.

  20. Amplification of ultra-short laser pulses via resonant backward Raman amplification in plasma

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Andreev, A.

    2016-08-01

    In this paper, we have examined the possibility of using resonant backward Raman amplification (BRA) as an efficient mechanism in amplifying the low intensity ultra-short ( ≤ fs ) pulses using plasma as intermediate amplifying medium; such pulses are anticipated to get produced in the form of the secondary sources at ALPS (Attosecond Light Pulse Source) center of ELI (Extreme Light Infrastructure). In preliminary assessment of the scheme, the analytical expressions for the pump/seed laser pulses and plasma characteristic features are obtained which concisely describe the parameter regime of resonant BRA applicability in achieving significant amplification. The consistency of the scheme in the context of ELI-ALPS sources has been validated through particle in cell (PIC) simulations. The peak intensity of the amplified seed pulse predicted via simulation results is found in reasonable agreement with the analytical estimates. Utilizing these analytical expressions as a basis in perspective of ELI-ALPS parameter access, a specific example displaying the key plasma and laser parameters for amplifying weak seed pulse has been configured; the limitations and conceivable remedies in resonant BRA implementation have also been highlighted.

  1. Characterization of a Pulse Neutron Source Yield under Field Conditions

    SciTech Connect

    Barzilov, Alexander; Novikov, Ivan; Womble, Phillip C.; Hopper, Lindsay

    2009-03-10

    Technique of rapid evaluation of a pulse neutron sources such as neutron generators under field conditions has been developed. The phoswich sensor and pulse-shape discrimination techniques have been used for the simultaneous measurements of fast neutrons, thermal neutrons, and photons. The sensor has been calibrated using activation neutron detectors and a pulse deuterium-tritium fusion neutron source.

  2. Broadband spectroscopy of dynamic impedances with short chirp pulses.

    PubMed

    Min, M; Land, R; Paavle, T; Parve, T; Annus, P; Trebbels, D

    2011-07-01

    An impedance spectrum of dynamic systems is time dependent. Fast impedance changes take place, for example, in high throughput microfluidic devices and in operating cardiovascular systems. Measurements must be as short as possible to avoid significant impedance changes during the spectrum analysis, and as long as possible for enlarging the excitation energy and obtaining a better signal-to-noise ratio (SNR). The authors propose to use specific short chirp pulses for excitation. Thanks to the specific properties of the chirp function, it is possible to meet the needs for a spectrum bandwidth, measurement time and SNR so that the most accurate impedance spectrogram can be obtained. The chirp wave excitation can include thousands of cycles when the impedance changes slowly, but in the case of very high speed changes it can be shorter than a single cycle, preserving the same excitation bandwidth. For example, a 100 kHz bandwidth can be covered by the chirp pulse with durations from 10 µs to 1 s; only its excitation energy differs also 10(5) times. After discussing theoretical short chirp properties in detail, the authors show how to generate short chirps in the microsecond range with a bandwidth up to a few MHz by using digital synthesis architectures developed inside a low-cost standard field programmable gate array.

  3. Superradiance of short electron pulses in regular and corrugated waveguides

    SciTech Connect

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

    1995-12-31

    The report is devoted to theoretical and experimental study of superradiance of short electron pulses moving through waveguide systems. It is suggested that electrons oscillate or in undulator field (undulator SR) or in homogeneous magnetic field (cyclotron SR). We studied specific regimes of SR which may occur due to peculiarities of waveguide dispersion. Among them there are regimes of radiation near cut-off frequency as well as regimes of group synchronism. At the last operating regimes an electron bunch longitudinal velocity coincide with group velocity of e.m. wave. It is found the increasing of the SR instability grows rate and energy extraction efficiency in such regimes. It is also possible to observe the same enhancement using external feedback in periodically corrugated waveguide when Bragg resonance condition with forward propagated e.m. wave is fulfill. For experimental observation of cyclotron SR we intend to use compact subnanosecond accelerator RADAN 303B on the base of the high voltage generator with special subnansecond transformer. Accelerator generates short 0.3ns electron pulses with current about 1kA and particles energy 200keV. Design of magnetic confound system provide possibility to install an active locker to impose to electrons cyclotron rotation with pitch-factor about 1-1.5. According to numerical simulation at the mm and submm wavebands it is possible to achieve radiation pick power about 5-10MW with pulse duration less than 1ns.

  4. Upconversion imaging using short-wave infrared picosecond pulses.

    PubMed

    Mathez, Morgan; Rodrigo, Peter John; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    2017-02-01

    To the best of our knowledge, we present the first demonstration of short-wavelength infrared image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm-both with a pulse width of 1 ps and a pulse repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs a bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm-enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination.

  5. Microwave subsecond pulses in solar flares - source localization, emission mechanism

    NASA Astrophysics Data System (ADS)

    Altyntsev, A. T.; Kardapolova, N. N.; Kuznetsov, A. A.; Lesovoi, S. V.; Meshalkina, N. S.; Yan, Y.

    The observations of bursts with fine temporal structures is one of few ways to study the primary energy release sites in solar flares. The localization of their sources in a flare region using the Siberian Solar Radio Telescope data (5.7 GHz) provide us with the unique possibility to determine plasma parameters, and to verify emission mechanisms. The simultaneous spectral observations (5.2 - 7.7 GHz) were provided by National Astronomical Observatories/Beijing spectropolarimeters. An analysis is made of the subsecond pulses of different types: short duration wide band pulses, U-type cm-bursts, the bursts with the "zebra" pattern. The suggestion is justified that in many cases the frequency drifts are response to the plasma density dynamics in the local sites in flare loops. It is argued that the conditions of emission escaping from the source strongly influent the apparent source sizes and the polarization degree of the subsecond sources. This research was supported by Grants 02-02-39030 and 03-02-16229 of RFBR, and E02-3.2-489 of Education department of Russia.

  6. Computational modeling of ultra-short-pulse ablation of enamel

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  7. Pulsed-Source Interferometry in Acoustic Imaging

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill; Gutierrez, Roman; Tang, Tony K.

    2003-01-01

    A combination of pulsed-source interferometry and acoustic diffraction has been proposed for use in imaging subsurface microscopic defects and other features in such diverse objects as integrated-circuit chips, specimens of materials, and mechanical parts. A specimen to be inspected by this technique would be mounted with its bottom side in contact with an acoustic transducer driven by a continuous-wave acoustic signal at a suitable frequency, which could be as low as a megahertz or as high as a few hundred gigahertz. The top side of the specimen would be coupled to an object that would have a flat (when not vibrating) top surface and that would serve as the acoustical analog of an optical medium (in effect, an acoustical "optic").

  8. Pulse shaping effects on weld porosity in laser beam spot welds : contrast of long- & short- pulse welds.

    SciTech Connect

    Ellison, Chad M.; Perricone, Matthew J.; Faraone, Kevin M.; Norris, Jerome T.

    2007-10-01

    Weld porosity is being investigated for long-pulse spot welds produced by high power continuous output lasers. Short-pulse spot welds (made with a pulsed laser system) are also being studied but to a much small extent. Given that weld area of a spot weld is commensurate with weld strength, the loss of weld area due to an undefined or unexpected pore results in undefined or unexpected loss in strength. For this reason, a better understanding of spot weld porosity is sought. Long-pulse spot welds are defined and limited by the slow shutter speed of most high output power continuous lasers. Continuous lasers typically ramp up to a simmer power before reaching the high power needed to produce the desired weld. A post-pulse ramp down time is usually present as well. The result is a pulse length tenths of a second long as oppose to the typical millisecond regime of the short-pulse pulsed laser. This study will employ a Lumonics JK802 Nd:YAG laser with Super Modulation pulse shaping capability and a Lasag SLS C16 40 W pulsed Nd:YAG laser. Pulse shaping will include square wave modulation of various peak powers for long-pulse welds and square (or top hat) and constant ramp down pulses for short-pulse welds. Characterization of weld porosity will be performed for both pulse welding methods.

  9. Pulsed magnetic field-electron cyclotron resonance ion source operation

    SciTech Connect

    Muehle, C.; Ratzinger, U.; Joest, G.; Leible, K.; Schennach, S.; Wolf, B.H.

    1996-03-01

    The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states. {copyright} {ital 1996 American Institute of Physics.}

  10. Applications of Ultra-Intense, Short Laser Pulses

    NASA Astrophysics Data System (ADS)

    Ledingham, Ken W. D.

    The high intensity laser production of electron, proton, ion and photon beams is reviewed particularly with respect to the laser-plasma interaction which drives the acceleration process. A number of applications for these intense short pulse beams is discussed e.g. ion therapy, PET isotope production and laser driven transmutation studies. The future for laser driven nuclear physics at the huge new, multi-petawatt proposed laser installation ELI in Bucharest is described. Many people believe this will take European nuclear research to the next level.

  11. Nuclear Excitation by a Strong Short Laser Pulse

    SciTech Connect

    Weidenmueller, Hans A.

    2011-05-06

    We derive the conditions on laser energy and photon number under which a short strong laser pulse excites a collective nuclear mode. We use the Giant Dipole Resonance as a representative example, and a random-matrix description of the fine-structure states and perturbation theory as tools. We identify the relevant observable as the nuclear time-decay function. That function is the Fourier transform of the autocorrelation function of the associated scattering matrix and contains information not otherwise available. We evaluate that function in specific cases and show that it may deviate significantly from an exponential.

  12. Relativistic Positron Creation Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Liang, E; Myatt, J; Price, D; Meyerhofer, D; Beiersdorfer, P

    2008-08-25

    We measure up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets when illuminated with short ({approx} 1 ps) ultra-intense ({approx} 1 x 10{sup 20} W/cm{sup 2}) laser pulses. Positrons produced predominately by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. The measurements indicate the laser produced, relativistic positron densities ({approx} 10{sup 16} positrons/cm{sup 3}) are the highest ever created in the laboratory.

  13. Short-Pulse Laser-Matter Computational Workshop Proceedings

    SciTech Connect

    Town, R; Tabak, M

    2004-11-02

    For three days at the end of August 2004, 55 plasma scientists met at the Four Points by Sheraton in Pleasanton to discuss some of the critical issues associated with the computational aspects of the interaction of short-pulse high-intensity lasers with matter. The workshop was organized around the following six key areas: (1) Laser propagation/interaction through various density plasmas: micro scale; (2) Anomalous electron transport effects: From micro to meso scale; (3) Electron transport through plasmas: From meso to macro scale; (4) Ion beam generation, transport, and focusing; (5) ''Atomic-scale'' electron and proton stopping powers; and (6) K{alpha} diagnostics.

  14. Relativistic Positron Creation Using Ultraintense Short Pulse Lasers

    SciTech Connect

    Chen Hui; Wilks, Scott C.; Bonlie, James D.; Price, Dwight F.; Beiersdorfer, Peter; Liang, Edison P.; Myatt, Jason; Meyerhofer, David D.

    2009-03-13

    We measure up to 2x10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets when illuminated with short ({approx}1 ps) ultraintense ({approx}1x10{sup 20} W/cm{sup 2}) laser pulses. Positrons are produced predominately by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. Modeling based on the measurements indicate the positron density to be {approx}10{sup 16} positrons/cm{sup 3}, the highest ever created in the laboratory.

  15. Pulsed thermal neutron source at the fast neutron generator.

    PubMed

    Tracz, Grzegorz; Drozdowicz, Krzysztof; Gabańska, Barbara; Krynicka, Ewa

    2009-06-01

    A small pulsed thermal neutron source has been designed based on results of the MCNP simulations of the thermalization of 14 MeV neutrons in a cluster-moderator which consists of small moderating cells decoupled by an absorber. Optimum dimensions of the single cell and of the whole cluster have been selected, considering the thermal neutron intensity and the short decay time of the thermal neutron flux. The source has been built and the test experiments have been performed. To ensure the response is not due to the choice of target for the experiments, calculations have been done to demonstrate the response is valid regardless of the thermalization properties of the target.

  16. Short-pulse laser heating of metals: a new approach

    NASA Astrophysics Data System (ADS)

    Huettner, Bernd

    1997-04-01

    Recently, several groups have demonstrated that the spatial and temporal temperature distribution inside metals resulting from femtosecond laser pulses cannot be fully explained by the two-temperature model for the electrons and phonons. Since these short pulse lengths may be comparable to the electron temperature relaxation time, we introduce a heat flow which is nonlocal in time. By this way we are taking into account in first order a non-equilibrium distribution of the electrons. As a consequence, three additional terms appear in the differential equation for the electron temperature. Furthermore, we offer an explanation for the different response of metals to the laser radiation on the basis of the electron-phonon coupling constant and the average phonon frequencies squared, well-known quantities in McMillan's theory on superconductivity. Using a double temperature model with nonlocal heat flow and a laser pulse length of 1 ps, the calculated surface temperatures of the electron and phonon subsystems are presented for Cu, Nb, and Pb. This is compared with the results of a local heat flow approach and with the conventional theory as well. Additionally we present calculations of the electron surface temperature of a thin Au film. We find that our model is capable of describing the new measurements on Au films more consistently than the standard double temperature model.

  17. Computational Design of Short Pulse Laser Driven Iron Opacity Experiments

    NASA Astrophysics Data System (ADS)

    Martin, Madison E.; London, Richard A.; Goluoglu, Sedat; Whitley, Heather D.

    2015-11-01

    Opacity is a critical parameter in the transport of radiation in systems such as inertial confinement fusion capsules and stars. The resolution of current disagreements between solar models and helioseismological observations would benefit from experimental validation of theoretical opacity models. Short pulse lasers can be used to heat targets to higher temperatures and densities than long pulse lasers and pulsed power machines, thus potentially enabling access to emission spectra at conditions relevant to solar models. In order to ensure that the relevant plasma conditions are accessible and that an emission measurement is practical, we use computational design of experiments to optimize the target characteristics and laser conditions. Radiation-hydrodynamic modeling, using HYDRA, is used to investigate the effects of modifying laser irradiance, target dimensions, and dopant dilution on the plasma conditions and emission of an iron opacity target. Several optimized designs reaching temperatures and densities relevant to the radiative zone of the sun will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.

  18. Optical polarizing neutron devices designed for pulsed neutron sources

    SciTech Connect

    Takeda, M.; Kurahashi, K.; Endoh, Y.; Itoh, S.

    1997-09-01

    We have designed two polarizing neutron devices for pulsed cold neutrons. The devices have been tested at the pulsed neutron source at the Booster Synchrotron Utilization Facility of the National Laboratory for High Energy Physics. These two devices proved to have a practical use for experiments to investigate condensed matter physics using pulsed cold polarized neutrons.

  19. Fast pulsed operation of a small non-radioactive electron source with continuous emission current control

    SciTech Connect

    Cochems, P.; Kirk, A. T.; Bunert, E.; Runge, M.; Goncalves, P.; Zimmermann, S.

    2015-06-15

    Non-radioactive electron sources are of great interest in any application requiring the emission of electrons at atmospheric pressure, as they offer better control over emission parameters than radioactive electron sources and are not subject to legal restrictions. Recently, we published a simple electron source consisting only of a vacuum housing, a filament, and a single control grid. In this paper, we present improved control electronics that utilize this control grid in order to focus and defocus the electron beam, thus pulsing the electron emission at atmospheric pressure. This allows short emission pulses and excellent stability of the emitted electron current due to continuous control, both during pulsed and continuous operations. As an application example, this electron source is coupled to an ion mobility spectrometer. Here, the pulsed electron source allows experiments on gas phase ion chemistry (e.g., ion generation and recombination kinetics) and can even remove the need for a traditional ion shutter.

  20. Detection limits of organic compounds achievable with intense, short-pulse lasers.

    PubMed

    Miles, Jordan; De Camillis, Simone; Alexander, Grace; Hamilton, Kathryn; Kelly, Thomas J; Costello, John T; Zepf, Matthew; Williams, Ian D; Greenwood, Jason B

    2015-06-21

    Many organic molecules have strong absorption bands which can be accessed by ultraviolet short pulse lasers to produce efficient ionization. This resonant multiphoton ionization scheme has already been exploited as an ionization source in time-of-flight mass spectrometers used for environmental trace analysis. In the present work we quantify the ultimate potential of this technique by measuring absolute ion yields produced from the interaction of 267 nm femtosecond laser pulses with the organic molecules indole and toluene, and gases Xe, N2 and O2. Using multiphoton ionization cross sections extracted from these results, we show that the laser pulse parameters required for real-time detection of aromatic molecules at concentrations of one part per trillion in air and a limit of detection of a few attomoles are achievable with presently available commercial laser systems. The potential applications for the analysis of human breath, blood and tissue samples are discussed.

  1. Short-pulsed gain-switched Cr2+:ZnSe laser

    NASA Astrophysics Data System (ADS)

    Gorajek, L.; Jabczynski, J. K.; Kaskow, M.

    2014-04-01

    We report the first demonstration of gain-switched, ultra-low-threshold Cr2+:ZnSe laser generating pulses as short as 1.75 ns. A diode pumped Tm3+:YLF laser delivering up to 5 mJ energy in 11 ns pulses was utilized as a pump source. The laser operated at 20 Hz repetition rate with 0.1 duty factor allowing us to reduce thermal effects in an active crystal. In a short resonator (length, 70 mm) we obtained more than 0.5 mJ of output energy and 300 kW of corresponding peak power. The Cr2+:ZnSe laser was characterized by very low losses manifesting themselves by an extremely low generation threshold of less than 7 μJ and very high slope efficiency (reaching the quantum efficiency) determined with respect to absorbed pump power.

  2. Laser system using ultra-short laser pulses

    DOEpatents

    Dantus, Marcos; Lozovoy, Vadim V.; Comstock, Matthew

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  3. Studying the mechanism of micromachining by short pulsed laser

    NASA Astrophysics Data System (ADS)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  4. Pulsed Source Of Energetic Oxygen Atoms

    NASA Technical Reports Server (NTRS)

    Caledonia, George; Krech, Robert; Green, David; Pirri, Anthony

    1988-01-01

    Apparatus developed that generates high-flux pulses of oxygen atoms to bombard specimens in experiments on aging and degradation of materials in low Earth-orbit environment. Preliminary studies of specimens irradiated with atomic oxygen provided spectral evidence of erosion, in addition to measurable mass loss. Intense atomic oxygen pulses also useful in studies of microfabrication techniques.

  5. Extending ultra-short pulse laser texturing over large area

    NASA Astrophysics Data System (ADS)

    Mincuzzi, G.; Gemini, L.; Faucon, M.; Kling, R.

    2016-11-01

    Surface texturing by Ultra-Short Pulses Laser (UPL) for industrial applications passes through the use of both fast beam scanning systems and high repetition rate, high average power P, UPL. Nevertheless unwanted thermal effects are expected when P exceeds some tens of W. An interesting strategy for a reliable heat management would consists in texturing with a low fluence values (slightly higher than the ablation threshold) and utilising a Polygon Scanner Heads delivering laser pulses with unrepeated speed. Here we show for the first time that with relatively low fluence it is possible over stainless steel, to obtain surface texturing by utilising a 2 MHz femtosecond laser jointly with a polygonal scanner head in a relatively low fluence regime (0.11 J cm-2). Different surface textures (Ripples, micro grooves and spikes) can be obtained varying the scan speed from 90 m s-1 to 25 m s-1. In particular, spikes formation process has been shown and optimised at 25 m s-1 and a full morphology characterization by SEM has been carried out. Reflectance measurements with integrating sphere are presented to compare reference surface with high scan rate textures. In the best case we show a black surface with reflectance value < 5%.

  6. Adaptive optics for ultra short pulsed lasers in UHV environment

    NASA Astrophysics Data System (ADS)

    Deneuville, Francois; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-02-01

    ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.

  7. Short infrared (IR) laser pulses can induce nanoporation

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Short infrared (IR) laser pulses on the order of hundreds of microseconds to single milliseconds with typical wavelengths of 1800-2100 nm, have shown the capability to reversibly stimulate action potentials (AP) in neuronal cells. While the IR stimulation technique has proven successful for several applications, the exact mechanism(s) underlying the AP generation has remained elusive. To better understand how IR pulses cause AP stimulation, we determined the threshold for the formation of nanopores in the plasma membrane. Using a surrogate calcium ion, thallium, which is roughly the same shape and charge, but lacks the biological functionality of calcium, we recorded the flow of thallium ions into an exposed cell in the presence of a battery of channel antagonists. The entry of thallium into the cell indicated that the ions entered via nanopores. The data presented here demonstrate a basic understanding of the fundamental effects of IR stimulation and speculates that nanopores, formed in response to the IR exposure, play an upstream role in the generation of AP.

  8. Control of Brillouin short-pulse seed amplification by chirping the pump pulse

    SciTech Connect

    Lehmann, G.; Spatschek, K. H.

    2015-04-15

    Seed amplification via Brillouin backscattering of a long pump pulse is considered. Similar to Raman amplification, several obstructive effects may occur during short-pulse Brillouin amplification. One is the spontaneous Raman backscattering of the pump before interacting with the seed. Preforming the plasma and/or chirping the pump will reduce unwanted pump backscattering. Optimized regions for low-loss pump propagation were proposed already in conjunction with Raman seed amplification. Hence, the influence of the chirp of the pump during Brillouin interaction with the seed becomes important and will be considered here. Both, the linear as well as the nonlinear evolution phases of the seed caused by Brillouin amplification under the action of a chirped pump are investigated. The amplification rate as well as the seed profiles are presented as function of the chirping rate. Also the dependence of superradiant scaling rates on the chirp parameter is discussed.

  9. High-energy ultra-short pulse thin-disk lasers: new developments and applications

    NASA Astrophysics Data System (ADS)

    Michel, Knut; Klingebiel, Sandro; Schultze, Marcel; Tesseit, Catherine Y.; Bessing, Robert; Häfner, Matthias; Prinz, Stefan; Sutter, Dirk; Metzger, Thomas

    2016-03-01

    We report on the latest developments at TRUMPF Scientific Lasers in the field of ultra-short pulse lasers with highest output energies and powers. All systems are based on the mature and industrialized thin-disk technology of TRUMPF. Thin Yb:YAG disks provide a reliable and efficient solution for power and energy scaling to Joule- and kW-class picosecond laser systems. Due to its efficient one dimensional heat removal, the thin-disk exhibits low distortions and thermal lensing even when pumped under extremely high pump power densities of 10kW/cm². Currently TRUMPF Scientific Lasers develops regenerative amplifiers with highest average powers, optical parametric amplifiers and synchronization schemes. The first few-ps kHz multi-mJ thin-disk regenerative amplifier based on the TRUMPF thindisk technology was developed at the LMU Munich in 20081. Since the average power and energy have continuously been increased, reaching more than 300W (10kHz repetition rate) and 200mJ (1kHz repetition rate) at pulse durations below 2ps. First experiments have shown that the current thin-disk technology supports ultra-short pulse laser solutions >1kW of average power. Based on few-picosecond thin-disk regenerative amplifiers few-cycle optical parametric chirped pulse amplifiers (OPCPA) can be realized. These systems have proven to be the only method for scaling few-cycle pulses to the multi-mJ energy level. OPA based few-cycle systems will allow for many applications such as attosecond spectroscopy, THz spectroscopy and imaging, laser wake field acceleration, table-top few-fs accelerators and laser-driven coherent X-ray undulator sources. Furthermore, high-energy picosecond sources can directly be used for a variety of applications such as X-ray generation or in atmospheric research.

  10. Transient Self-Amplified Cerenkov Radiation with a Short Pulse Electron Beam

    SciTech Connect

    Poole, B R; Blackfield, D T; Camacho, J F

    2009-01-22

    An analytic and numerical examination of the slow wave Cerenkov free electron maser is presented. We consider the steady state amplifier configuration as well as operation in the selfamplified spontaneous emission (SASE) regime. The linear theory is extended to include electron beams that have a parabolic radial density inhomogeneity. Closed form solutions for the dispersion relation and modal structure of the electromagnetic field are determined in this inhomogeneous case. To determine the steady state response, a macro-particle approach is used to develop a set of coupled nonlinear ordinary differential equations for the amplitude and phase of the electromagnetic wave, which are solved in conjunction with the particle dynamical equations to determine the response when the system is driven as an amplifier with a time harmonic source. We then consider the case in which a fast rise time electron beam is injected into a dielectric loaded waveguide. In this case, radiation is generated by SASE, with the instability seeded by the leading edge of the electron beam. A pulse of radiation is produced, slipping behind the leading edge of the beam due to the disparity between the group velocity of the radiation and the beam velocity. Short pulses of microwave radiation are generated in the SASE regime and are investigated using particle-in-cell (PIC) simulations. The nonlinear dynamics are significantly more complicated in the transient SASE regime when compared with the steady state amplifier model due to the slippage of the radiation with respect to the beam. As strong self-bunching of the electron beam develops due to SASE, short pulses of superradiant emission develop with peak powers significantly larger than the predicted saturated power based on the steady state amplifier model. As these superradiant pulses grow, their pulse length decreases and forms a series of soliton-like pulses. Comparisons between the linear theory, macro-particle model, and PIC simulations are

  11. Liouville Correspondence Between the Short-Pulse Hierarchy and the Sine-Gordon Hierarchy

    NASA Astrophysics Data System (ADS)

    Kang, Jing; Liu, Xiaochuan; Qu, Changzheng

    2016-12-01

    The Liouville correspondence between the short-pulse integrable hierarchy and the sine-Gordon integrable hierarchy is studied. It is shown that the transformation relating the short-pulse equation with the sine-Gordon equation also establishes the correspondence between their flows and Hamiltonian conservation laws in respective hierarchy. This proposes an alternative approach to derive the Hamiltonian conservation laws of the short-pulse equation from the known ones of the classical sine-Gordon equation.

  12. Miniaturized X-ray Generation by Pyroelectric Effect using Short Pulse Laser

    DTIC Science & Technology

    2011-11-30

    1 Report of AOARD Program CONTRACT NO: FA23861014160 Miniaturized X-ray Generation by Pyroelectric Effect using Short Pulse Laser...induced currents by short- pulse high-power laser irradiation II-1: Experiments and results II-2: Theoretical calculations ~Analysis of currents...effect using short pulse laser aiming at miniaturized X-ray generator 5a. CONTRACT NUMBER FA23861014160 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

  13. Simple Short-Pulse CO2 Laser Excited by Longitudinal Discharge without High-Voltage Switch

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Jitsuno, Takahisa; Akitsu, Tetsuya

    2012-05-01

    We have developed a longitudinally excited CO2 laser without a high-voltage switch. The laser produces a short laser pulse similar to those from TEA and Q-switched CO2 lasers. This system, which is the simplest short-pulse CO2 laser yet constructed, includes a pulsed power supply, a high-speed step-up transformer, a storage capacitor, and a laser tube. At high pressure (4.2 kPa and above), a rapid discharge produces a short laser pulse with a sharp spike pulse. In mixed gas (CO2: N2: He = 1: 1: 2) at a pressure of 9.0 kPa, the laser pulse contains a spike pulse of 218 ns and has a pulse tail length of 16.7 μs.

  14. Diagnostics of high-brightness short-pulse lasers and the plasmas they generate

    SciTech Connect

    Kyrala, G.A.; Fulton, R.D.; Cobble, J.A.; Schappert, G.T.; Taylor, A.J.

    1994-02-01

    The properties of a laser influence the interaction of the intense laser light with materials. The authors will describe some of the diagnostics that they have implemented at the Los Alamos Bright Source to correlate the changes in the x-ray spectrum and temporal history of a laser generated silicon plasmas with the changes of the incident XeCl laser light. One property is of special interest, the existence of a short prepulse. They find that the prepulse enhances the generation of the x-rays from a later pulse.

  15. Rapidly pulsed, high intensity, incoherent light source

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.; Brandhorst, H. W., Jr. (Inventor)

    1974-01-01

    A rapid pulsing, high intensity, incoherent light is produced by selectively energizing a plurality of discharge lamps with a triggering circuit. Each lamp is connected to a capacitor, and a power supply is electrically connected to all but one of the capacitors. This last named capacitor is electrically connected to a discharge lamp which is connected to the triggering circuit.

  16. SiO2-glass drilling by short-pulse CO2 laser with controllable pulse-tail energy

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Yamamoto, Takuya; Watanabe, Miyu; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-03-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with the almost same spike-pulse energy of about 0.8 mJ and the controllable pulse-tail energy of 6.33-23.08 mJ. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance and a spark-gap switch. The dependence of SiO2 glass drilling on the fluence and the number was investigated by four types of short-pulse CO2 lasers. In this work, the effective short laser pulse with the spike pulse energy of 0.8 mJ for SiO2 glass drilling was the laser pulse with the pulse tail energy of 19.88 mJ, and produces the drilling depth per the fluence of 124 μm/J/cm2.

  17. Computational design of short pulse laser driven iron opacity experiments

    DOE PAGES

    Martin, M. E.; London, R. A.; Goluoglu, S.; ...

    2017-02-23

    Here, the resolution of current disagreements between solar parameters calculated from models and observations would benefit from the experimental validation of theoretical opacity models. Iron's complex ionic structure and large contribution to the opacity in the radiative zone of the sun make iron a good candidate for validation. Short pulse lasers can be used to heat buried layer targets to plasma conditions comparable to the radiative zone of the sun, and the frequency dependent opacity can be inferred from the target's measured x-ray emission. Target and laser parameters must be optimized to reach specific plasma conditions and meet x-ray emissionmore » requirements. The HYDRA radiation hydrodynamics code is used to investigate the effects of modifying laser irradiance and target dimensions on the plasma conditions, x-ray emission, and inferred opacity of iron and iron-magnesium buried layer targets. It was determined that plasma conditions are dominantly controlled by the laser energy and the tamper thickness. The accuracy of the inferred opacity is sensitive to tamper emission and optical depth effects. Experiments at conditions relevant to the radiative zone of the sun would investigate the validity of opacity theories important to resolving disagreements between solar parameters calculated from models and observations.« less

  18. Overview of LANL short-pulse ion acceleration activities

    SciTech Connect

    Flippo, Kirk A.; Schmitt, Mark J.; Offermann, Dustin; Cobble, James A.; Gautier, Donald; Kline, John; Workman, Jonathan; Archuleta, Fred; Gonzales, Raymond; Hurry, Thomas; Johnson, Randall; Letzring, Samuel; Montgomery, David; Reid, Sha-Marie; Shimada, Tsutomu; Gaillard, Sandrine A.; Sentoku, Yasuhiko; Bussman, Michael; Kluge, Thomas; Cowan, Thomas E.; Rassuchine, Jenny M.; Lowenstern, Mario E.; Mucino, J. Eduardo; Gall, Brady; Korgan, Grant; Malekos, Steven; Adams, Jesse; Bartal, Teresa; Chawla, Surgreev; Higginson, Drew; Beg, Farhat; Nilson, Phil; Mac Phee, Andrew; Le Pape, Sebastien; Hey, Daniel; Mac Kinnon, Andy; Geissel, Mattias; Schollmeier, Marius; Stephens, Rich

    2009-12-02

    An overview of Los Alamos National Laboratory's activities related to short-pulse ion acceleration is presented. LANL is involved is several projects related to Inertial Confinement Fusion (Fast Ignition) and Laser-Ion Acceleration. LANL has an active high energy X-ray backlighter program for radiographing ICF implosions and other High Energy Density Laboratory Physics experiments. Using the Trident 200TW laser we are currently developing high energy photon (>10 keV) phase contrast imaging techniques to be applied on Omega and the NIF. In addition we are engaged in multiple programs in laser ion acceleration to boost the ion energies and efficiencies for various potential applications including Fast Ignition, active material interrogation, and medical applications. Two basic avenues to increase ion performance are currently under study: one involves ultra-thin targets and the other involves changing the target geometry. We have recently had success in boosting proton energies above 65 MeV into the medical application range. Highlights covered in the presentation include: The Trident Laser System; X-ray Phase Contrast Imaging for ICF and HEDLP; Improving TNSA Ion Acceleration; Scaling Laws; Flat Targets; Thin Targets; Cone Targets; Ion Focusing;Trident; Omega EP; Scaling Comparisons; and, Conclusions.

  19. Optical Constants of Ultra-Short-Pulse Laser Heated Metal

    NASA Astrophysics Data System (ADS)

    Yoneda, Hitoki; Morikami, Hidetoshi; Ueda, Ken-Ichi; More, Richard M.

    The complex refractive index (n + ik) of ultra-short-pulse laser heated gold metal was measured with a new ellipsometric pump-probe technique. Two ratios of four different probe-beam polarizations were used to determine s- and p-reflectivity and their phase difference. In the early stage of heating, only the imaginary part of the dielectric constant ɛ(Im[ɛ] = 2nk) increased while real part of e (Re[ɛ] = n²-k²) was almost constant. This agrees with the Drude model. We observe a pause in the rise of Im[ɛ] at the boiling temperature. Beyond this point, Re[ɛ] started to change and the observed parameters disagree with the Drude theory. It was found that the parameters of the expanding plasma follow a unique trajectory in n, k space, even though time variation of Re[ɛ] and Im[ɛ] are different for various pump intensities. This means the gold remains in a unique state such as the neutral groundstate in this intensity range.

  20. Covert situational awareness with handheld ultrawideband short-pulse radar

    NASA Astrophysics Data System (ADS)

    Barnes, Mark A.; Nag, Soumya; Payment, Tim

    2001-08-01

    Law enforcement and emergency services all face the difficult task of determining the locations of people within a building. A handheld radar able to detect motion through walls and other obstructions has been developed to fill this need. This paper describes the attributes and difficulties of the radar design and includes test results of the radar's performance. This discussion begins by summarizing key user requirements and the electromagnetic losses of typical building materials. Ultra-wideband (UWB) short pulse radars are well suited for a handheld sensor primarily because of their inherit time isolation in high clutter environments and their capability to achieve high resolution at low spectral center frequencies. There are also constraints that complicate the system design. Using a technique referred to as time-modulation allows the radars to reject range ambiguities and enhances electromagnetic compatibility with similar radars and ambient systems. An outline of the specifications of the radar developed and a process diagram on how it generates a motion map showing range and direction of the people moving within structures is included. Images are then presented to illustrate its performance. The images include adults, child, and a dog. The test results also include data showing the radar's performance through a variety of building materials.

  1. Computational design of short pulse laser driven iron opacity experiments

    NASA Astrophysics Data System (ADS)

    Martin, M. E.; London, R. A.; Goluoglu, S.; Whitley, H. D.

    2017-02-01

    The resolution of current disagreements between solar parameters calculated from models and observations would benefit from the experimental validation of theoretical opacity models. Iron's complex ionic structure and large contribution to the opacity in the radiative zone of the sun make iron a good candidate for validation. Short pulse lasers can be used to heat buried layer targets to plasma conditions comparable to the radiative zone of the sun, and the frequency dependent opacity can be inferred from the target's measured x-ray emission. Target and laser parameters must be optimized to reach specific plasma conditions and meet x-ray emission requirements. The HYDRA radiation hydrodynamics code is used to investigate the effects of modifying laser irradiance and target dimensions on the plasma conditions, x-ray emission, and inferred opacity of iron and iron-magnesium buried layer targets. It was determined that plasma conditions are dominantly controlled by the laser energy and the tamper thickness. The accuracy of the inferred opacity is sensitive to tamper emission and optical depth effects. Experiments at conditions relevant to the radiative zone of the sun would investigate the validity of opacity theories important to resolving disagreements between solar parameters calculated from models and observations.

  2. Pulsed Beamless High Power Microwave (HPM) Source with Integrated Antenna

    DTIC Science & Technology

    2013-06-01

    gral part of t utilized for source ope d. The peak asured to be 2 ns. SS HIGH IN kach Institu .Mironenk iv 04073, U SA; Ya. T 1 er Microwave W...Pulsed Beamless High Power Microwave (HPM) Source With Integrated Antenna 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...NOTES See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International

  3. Seismic Pulses Derivation from the Study of Source Signature Characteristics

    SciTech Connect

    Rahman, Syed Mustafizur; Nawawi, M. N. Mohd.; Saad, Rosli

    2010-07-07

    This paper deals with a deterministic technique for the derivation of seismic pulses by the study of source characteristics. The spectral characteristics of the directly or the nearest detected seismic signal is analyzed and considered as the principle source signature. Using this signature seismic pulses are derived with accurate time position in the seismic traces. The technique is applied on both synthetic and field refraction seismic traces. In both cases it has estimated that the accurate time shifts along with amplitude coefficients.

  4. Hard-tissue drilling by short-pulse CO2 laser with controllable pulse-tail energy

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Sasaki, Tatsufumi; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with the almost same spike-pulse energy of about 0.8 mJ and the controllable pulse-tail energy of 0-21.26 mJ. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance and a spark-gap switch. In single-shot irradiation using these laser pulses, the dependence of the drilling depth of dry ivory samples on the fluence was investigated. The drilling depth increased with the fluence in the same laser pulse waveform. In this work, the effective short laser pulse for the hard tissue drilling was the laser pulse with the spike pulse energy of 0.87 mJ and the pulse tail energy of 6.33 mJ that produced the drilling depth of 28.1 μm at the fluence of 3.48 J/cm2 and the drilling depth per the fluence of 7.27 μm/J/cm2.

  5. Ultra-wideband short-pulse radar with range accuracy for short range detection

    SciTech Connect

    Rodenbeck, Christopher T; Pankonin, Jeffrey; Heintzleman, Richard E; Kinzie, Nicola Jean; Popovic, Zorana P

    2014-10-07

    An ultra-wideband (UWB) radar transmitter apparatus comprises a pulse generator configured to produce from a sinusoidal input signal a pulsed output signal having a series of baseband pulses with a first pulse repetition frequency (PRF). The pulse generator includes a plurality of components that each have a nonlinear electrical reactance. A signal converter is coupled to the pulse generator and configured to convert the pulsed output signal into a pulsed radar transmit signal having a series of radar transmit pulses with a second PRF that is less than the first PRF.

  6. Glass drilling by longitudinally excited CO2 laser with short laser pulse

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2015-03-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse and a pulse tail. The energy of the pulse tail was controlled by adjusting medium gas. Using three types of CO2 laser pulse with the same spike-pulse energy and the different pulse-tail energy, the characteristics of the hole drilling of synthetic silica glass was investigated. Higher pulse-tail energy gave deeper ablation depth. In the short laser pulse with the spike-pulse energy of 1.2 mJ, the spike pulse width of 162 ns, the pulse-tail energy of 24.6 mJ, and the pulse-tail length of 29.6 μs, 1000 shots irradiation produced the ablation depth of 988 μm. In the hole drilling of synthetic silica glass by the CO2 laser, a crack-free process was realized.

  7. An Overview of High Energy Short Pulse Technology for Advanced Radiography of Laser Fusion Experiments

    SciTech Connect

    Barty, C J; Key, M; Britten, J; Beach, R; Beer, G; Brown, C; Bryan, S; Caird, J; Carlson, T; Crane, J; Dawson, J; Erlandson, A C; Fittinghoff, D; Hermann, M; Hoaglan, C; Iyer, A; Jones, L; Jovanovic, I; Komashko, A; Landen, O; Liao, Z; Molander, W; Mitchell, A; Moses, E; Nielsen, N; Nguyen, H; Nissen, J; Payne, S; Pennington, D; Risinger, L; Rushford, M; Skulina, K; Spaeth, M; Stuart, B; Tietbohl, G; Wattellier, B

    2004-06-18

    The technical challenges and motivations for high-energy, short-pulse generation with NIF-class, Nd:glass laser systems are reviewed. High energy short pulse generation (multi-kilojoule, picosecond pulses) will be possible via the adaptation of chirped pulse amplification laser techniques on the NIF. Development of meter-scale, high efficiency, high-damage-threshold final optics is a key technical challenge. In addition, deployment of HEPW pulses on NIF is constrained by existing laser infrastructure and requires new, compact compressor designs and short-pulse, fiber-based, seed-laser systems. The key motivations for high energy petawatt pulses on NIF is briefly outlined and includes high-energy, x-ray radiography, proton beam radiography, proton isochoric heating and tests of the fast ignitor concept for inertial confinement fusion.

  8. Improving the resolution of chopper spectrometers at pulsed neutron sources

    SciTech Connect

    Carpenter, J.M. ); Mildner, D.F.R. . Center for Analytical Chemistry)

    1990-01-01

    We examine the relationships between intensity and resolution in pulsed-source chopper spectrometers, including the effects of Soller collimation, narrower rotor slits and higher rotor speeds. The basis is a simplified description of a spectrometer, approximately optimizing the rotor pulse and lighthouse effects. the analysis includes a new treatment of the angular distribution transmitted through a system consisting of a coarse collimator and a Soller collimator. The results encourage the prospect for a reasonably easily accomplished, higher resolution, optional configuration of the pulsed source chopper spectrometers at IPNS. 6 refs., 5 figs.

  9. Study of channel formation and relativistic ultra-short laser pulse propagation in helium plasma

    NASA Astrophysics Data System (ADS)

    Yu, Changhai; Tian, Ye; Li, Wentao; Zhang, Zhijun; Qi, Rong; Wang, Wentao; Wang, Cheng; Liu, Jiansheng

    2016-05-01

    In this study, plasma channel formation in pure He plasma (ionization electron density 0.01-0.1n c ) interacting with ultra-short relativistic laser pulses (50 fs, >1019 W cm-2) was observed and analyzed. By appropriately selecting the laser pulse and gas backing pressure of the gas jet, a clear density channel longer than 300 μm and wider than 25 μm was achieved in less than 1.5 ps following the passage of the laser pulse, with a radial electron density gradient of ~1023 cm-4 at the channel walls. Numerical simulations for studying the affects of the plasma density, kinetic motion of electrons and ions, and nonlinear laser propagation on the plasma channel formation were carried out, which reproduced the experimental features. These density channels were mainly driven by the radial expulsion of plasma ions, with strong continuous laser self-focusing acting to improve the channeling efficiency. These channels can guide the propagation of ultra-intense laser pulses and supply several advanced applications in high-energy physics, including fast-ignition inertial confinement fusion, plasma-based particle accelerations, and sources of radiation.

  10. Development of the dense plasma focus for short-pulse applications

    DOE PAGES

    Bennett, N.; Blasco, M.; Breeding, K.; ...

    2017-01-05

    The dense plasma focus (DPF) has long been considered a compact source for pulsed neutrons and has traditionally been optimized for the total neutron yield. Here, we describe the efforts to optimize the DPF for short-pulse applications by introducing a reentrant cathode at the end of the coaxial plasma gun. We reduced the resulting neutron pulse widths by an average of 21±921±9% from the traditional long-drift DPF design. Pulse widths and yields achieved from deuterium-tritium fusion at 2 MA are 61.8±30.761.8±30.7 ns FWHM and 1.84±0.49×10121.84±0.49×1012 neutrons per shot. Simulations were conducted concurrently to elucidate the DPF operation and confirm themore » role of the reentrant cathode. Furthermore, a hybrid fluid-kinetic particle-in-cell modeling capability demonstrates correct sheath velocities, plasma instabilities, and fusion yield rates. Consistent with previous findings that the DPF is dominated by beam-target fusion from superthermal ions, we estimate that the thermonuclear contribution is at the 1% level.« less

  11. Ion heating and short wavelength fluctuations in a helicon plasma source

    SciTech Connect

    Scime, E. E.; Carr, J. Jr.; Galante, M.; Magee, R. M.; Hardin, R.

    2013-03-15

    For typical helicon source parameters, the driving antenna can couple to two plasma modes; the weakly damped 'helicon' wave, and the strongly damped, short wavelength, slow wave. Here, we present direct measurements, obtained with two different techniques, of few hundred kHz, short wavelength fluctuations that are parametrically driven by the primary antenna and localized to the edge of the plasma. The short wavelength fluctuations appear for plasma source parameters such that the driving frequency is approximately equal to the lower hybrid frequency. Measurements of the steady-state ion temperature and fluctuation amplitude radial profiles suggest that the anomalously high ion temperatures observed at the edge of helicon sources result from damping of the short wavelength fluctuations. Additional measurements of the time evolution of the ion temperature and fluctuation profiles in pulsed helicon source plasmas support the same conclusion.

  12. Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

    SciTech Connect

    Labat, M.; Couprie, M. E.; Joly, N.; Bruni, C.

    2009-12-31

    We investigate a fundamental limitation occurring in vacuum ultraviolet and extreme ultraviolet seeded free electron lasers (FELs). For a given electron beam and undulator configuration, an increase of the FEL output energy at saturation can be obtained via an increase of the seed pulse duration. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect. Numerical studies of the Colson-Bonifacio FEL equations reveal that slippage length and seed laser pulse wings are core ingredients of the dynamics.

  13. LIBS using dual- and ultra-short laser pulses.

    PubMed

    Angel, S M; Stratis, D N; Eland, K L; Lai, T; Berg, M A; Gold, D M

    2001-02-01

    Pre-ablation dual-pulse LIBS enhancement data for copper, brass and steel using ns laser excitation are reported. Although large enhancements are observed for all samples, the magnitude of the enhancement is matrix dependent. Whereas all of the dual-pulse studies used ns laser excitation we see interesting effects when using ps and fs laser excitation for single-pulse LIBS. LIBS spectra of copper using 1.3 ps and 140 fs laser pulses show much lower background signals compared to ns pulse excitation. Also, the atomic emission decays much more rapidly with time. Because of relatively low backgrounds when using ps and fs pulses, non-gated detection of LIBS is shown to be very effective. The plasma dissipates quickly enough using ps and fs laser pulses, that high pulse rates, up to 1,000 Hz, are effective for increasing the LIBS signal, for a given measurement time. Finally, a simple near-collinear dual-pulse fiber-optic LIBS probe is shown to be useful for enhanced LIBS measurements.

  14. Propagation of intense and short circularly polarized pulses in a molecular gas: From multiphoton ionization to nonlinear macroscopic effects

    NASA Astrophysics Data System (ADS)

    Lytova, M.; Lorin, E.; Bandrauk, A. D.

    2016-07-01

    We present a detailed analysis of the propagation dynamics of short and intense circularly polarized pulses in an aligned diatomic gas. Compared to linearly polarized intense pulses, high harmonic generation (HHG) and the coherent generation of attosecond pulses in the intense-circular-polarization case are a new research area. More specifically, we numerically study the propagation of intense and short circularly polarized pulses in the one-electron H2+ molecular gas, using a micro-macro Maxwell-Schrödinger model. In this model, the macroscopic polarization is computed from the solution of a large number of time-dependent Schrödinger equations, the source of dipole moments, and using a trace operator. We focus on the intensity and the phase of harmonics generated in the H2+ gas as a function of the pulse-propagation distance. We show that short coherent circularly polarized pulses of same helicity can be generated in the molecular gas as a result of cooperative phase-matching effects.

  15. Small plasma focus as neutron pulsed source for nuclides identification

    SciTech Connect

    Milanese, M.; Moroso, R.; Barbaglia, M.; Niedbalski, J.; Mayer, R.; Castillo, F.

    2013-10-15

    In this paper, we present preliminary results on the feasibility of employing a low energy (2 kJ, 31 kV) plasma focus device as a portable source of pulsed neutron beams (2.45 MeV) generated by nuclear fusion reactions D-D, for the “in situ” analysis of substances by nuclear activation. This source has the relevant advantage of being pulsed at requirement, transportable, not permanently radioactive, without radioactive waste, cheap, among others. We prove the feasibility of using this source showing several spectra of the characteristic emission line for manganese, gold, lead, and silver.

  16. Traveling wave pumping of ultra-short pulse x-ray lasers

    SciTech Connect

    Snavely, R.A.; Da Silva, L.B.; Eder, D.C.; Matthews, D.L.; Moon, S.J.

    1997-11-10

    Pumping of proposed inner-shell photo-ionized (ISPI) x-ray lasers places stringent requirements on the optical pump source. We investigate these requirements for an example x-ray laser (XRL) in Carbon lasing on the 2p-1s transition at 45 A. Competing with this lasing transition is the very fast Auger decay rate out of the upper lasing state, such that the x-ray laser would self-terminate on a femto- second time scale. XRL gain may be demonstrated if pump energy is delivered in a time short when compared to the Auger rate. The fast self-termination also demands that we sequentially pump the length of the x-ray laser at the group velocity of the x-ray laser. This is the classical traveling wave requirement. It imposes a condition on the pumping source that the phase angle of the pump laser be precisely de- coupled from the pulse front angle. At high light intensities, this must be performed with a vacuum grating delay line. We will also include a discussion of issues related to pump energy delivery, i.e. pulse-front curvature, temporal blurring and puke fidelity. An all- reflective optical system with low aberration is investigated to see if it fulfills the requirements. It is expected that these designs together with new high energy (>1J) ultra-short pulse (< 40 fs) pump lasers now under construction may fulfill our pump energy conditions and produce a tabletop x-ray laser.

  17. Interaction of ultrashort laser pulses and silicon solar cells under short circuit conditions

    NASA Astrophysics Data System (ADS)

    Mundus, M.; Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W.

    2015-02-01

    Ultrashort pulse lasers are promising tools for numerous measurement purposes. Among other benefits their high peak powers allow for efficient generation of wavelengths in broad spectral ranges and at spectral powers that are orders of magnitude higher than in conventional light sources. Very recently this has been exploited for the establishment of sophisticated measurement facilities for electrical characterization of photovoltaic (PV) devices. As the high peak powers of ultrashort pulses promote nonlinear optical effects they might also give rise to nonlinear interactions with the devices under test that possibly manipulate the measurement outcome. In this paper, we present a comprehensive theoretical and experimental study of the nonlinearities affecting short circuit current (ISC) measurements of silicon (Si) solar cells. We derive a set of coupled differential equations describing the radiation-device interaction and discuss the nonlinearities incorporated in those. By a semi-analytical approach introducing a quasi-steady-state approximation and integrating a Green's function we solve the system of equations and obtain simulated ISC values. We validate the theoretical model by ISC ratios obtained from a double ring resonator setup capable for reproducible generation of various ultrashort pulse trains. Finally, we apply the model to conduct the most prominent comparison of ISC generated by ultrashort pulses versus continuous illumination. We conclude by the important finding that the nonlinearities induced by ultrashort pulses are negligible for the most common ISC measurements. However, we also find that more specialized measurements (e.g., of concentrating PV or Si-multijunction devices as well as highly localized electrical characterizations) will be biased by two-photon-absorption distorting the ISC measurement.

  18. Pulsed Orotron - A new microwave source for submillimeter pulse high-field electron paramagnetic resonance spectroscopy

    SciTech Connect

    Grishin, Yu.A.; Fuchs, M.R.; Schnegg, A.; Dubinskii, A.A.; Dumesh, B.S.; Rusin, F.S.; Bratman, V.L.; Moebius, K.

    2004-09-01

    A vacuum-tube device for the generation of pulsed microwave radiation in the submillimeter range (up to 380 GHz) is presented, designed for use as a source in a 360 GHz high-field/high-frequency electron paramagnetic resonance (EPR) spectrometer - the pulsed Orotron. Analogous to the known continuous wave (cw) version, in the pulsed Orotron microwave radiation is generated by the interaction of a nonrelativistic electron beam with a diffraction grating (stimulated Smith-Purcell radiation) in feedback with an open Fabry-Perot resonator construction. The presented design extends the cw Orotron by a gate electrode and a high-voltage pulsing unit to control the electron beam current. The generated pulses at 360 GHz have pulse lengths from 100 ns-10 {mu}s and a pulse power of (22{+-}5) mW. The output in a broader frequency band between 320 and 380 GHz ranges from 20 up to 60 mW. Within a 10 {mu}s time slot, incoherent pulse trains of arbitrary duration can be generated. The pulsed Orotron has been incorporated in the quasioptical microwave bridge of a heterodyne induction mode EPR spectrometer. The first free induction decay measurements at a microwave frequency of 360 GHz and a magnetic field of 12.8 T on a polycrystalline perylenyl-ion sample are presented and future applications and extensions of Orotron-EPR spectroscopy are discussed.

  19. A pulsed xenon megawatt arc plasma source

    NASA Technical Reports Server (NTRS)

    Michels, C. J.

    1973-01-01

    The exhaust of the source flowing into vacuum was measured by Thomson scattering diagnosis. Mean electron temperatures and densities were found to be 4-8 eV and of order ten to the 13th power cm/3 respectively over the 8 cm exhaust diameter at 30 cm from the source. Large shot to shot variations were noted. After a transient spike passes, these conditions persist during the power time of 125 microsecond. These exhaust conditions are marginal for evaluation of a proposed near resonant charge exchange pumped laser theory.

  20. Spectral characteristics of ultra-short laser pulses in plasma amplifiers

    SciTech Connect

    Riconda, C.; Weber, S.; Lancia, L.; Marquès, J.-R.; Fuchs, J.; Mourou, G. A.

    2013-08-15

    Amplification of laser pulses based on the backscattering process in plasmas can be performed using either the response of an electron plasma wave or an ion-acoustic wave. However, if the pulse durations become very short and the natural spread in frequency a substantial amount of the frequency itself, the Raman and Brillouin processes start to mix. Kinetic simulations show the transition from a pure amplification regime, in this case strong-coupling Brillouin, to a regime where a considerable downshift of the frequency of the amplified pulse takes place. It is conjectured that in the case of very short pulses, multi-modes are excited which contribute to the amplification process.

  1. Method and apparatus for producing durationally short ultraviolet or X-ray laser pulses

    DOEpatents

    MacGowan, Brian J.; Matthews, Dennis L.; Trebes, James E.

    1988-01-01

    A method and apparatus is disclosed for producing ultraviolet or X-ray laser pulses of short duration (32). An ultraviolet or X-ray laser pulse of long duration (12) is progressively refracted, across the surface of an opaque barrier (28), by a streaming plasma (22) that is produced by illuminating a solid target (16, 18) with a pulse of conventional line focused high power laser radiation (20). The short pulse of ultraviolet or X-ray laser radiation (32), which may be amplified to high power (40, 42), is separated out by passage through a slit aperture (30) in the opaque barrier (28).

  2. Method and apparatus for producing durationally short ultraviolet or x-ray laser pulses

    DOEpatents

    MacGowan, B.J.; Matthews, D.L.; Trebes, J.E.

    1987-05-05

    A method and apparatus is disclosed for producing ultraviolet or x- ray laser pulses of short duration. An ultraviolet or x-ray laser pulse of long duration is progressively refracted, across the surface of an opaque barrier, by a streaming plasma that is produced by illuminating a solid target with a pulse of conventional line focused high power laser radiation. The short pulse of ultraviolet or x-ray laser radiation, which may be amplified to high power, is separated out by passage through a slit aperture in the opaque barrier.

  3. Defocusing complex short-pulse equation and its multi-dark-soliton solution.

    PubMed

    Feng, Bao-Feng; Ling, Liming; Zhu, Zuonong

    2016-05-01

    In this paper, we propose a complex short-pulse equation of both focusing and defocusing types, which governs the propagation of ultrashort pulses in nonlinear optical fibers. It can be viewed as an analog of the nonlinear Schrödinger (NLS) equation in the ultrashort-pulse regime. Furthermore, we construct the multi-dark-soliton solution for the defocusing complex short-pulse equation through the Darboux transformation and reciprocal (hodograph) transformation. One- and two-dark-soliton solutions are given explicitly, whose properties and dynamics are analyzed and illustrated.

  4. Defocusing complex short-pulse equation and its multi-dark-soliton solution

    NASA Astrophysics Data System (ADS)

    Feng, Bao-Feng; Ling, Liming; Zhu, Zuonong

    2016-05-01

    In this paper, we propose a complex short-pulse equation of both focusing and defocusing types, which governs the propagation of ultrashort pulses in nonlinear optical fibers. It can be viewed as an analog of the nonlinear Schrödinger (NLS) equation in the ultrashort-pulse regime. Furthermore, we construct the multi-dark-soliton solution for the defocusing complex short-pulse equation through the Darboux transformation and reciprocal (hodograph) transformation. One- and two-dark-soliton solutions are given explicitly, whose properties and dynamics are analyzed and illustrated.

  5. Short-pulse laser formation of monatomic metallic glass in tantalum nanowire

    NASA Astrophysics Data System (ADS)

    Gan, Yong; Sun, Zheng; Shen, Yaogen

    2017-01-01

    The short-pulse laser heating of a tantalum nanowire is simulated by a hybrid method coupling the two-temperature model into the molecular dynamics. It is shown that the monatomic metallic glasses can be formed by short-pulse lasers. The critical cooling rate for vitrifying the pure metallic liquids in tantalum nanowire is estimated to be on the order of 1013 K s-1. Further simulations with different laser parameters and heated spot size are performed, demonstrating that the short-pulse laser quenching is a robust and promising alternative to the vitrification of monatomic metallic liquids into glassy state.

  6. Integrable semi-discretization of a multi-component short pulse equation

    NASA Astrophysics Data System (ADS)

    Feng, Bao-Feng; Maruno, Ken-ichi; Ohta, Yasuhiro

    2015-04-01

    In the present paper, we mainly study the integrable semi-discretization of a multi-component short pulse equation. First, we briefly review the bilinear equations for a multi-component short pulse equation proposed by Matsuno [J. Math. Phys. 52, 123702 (2011)] and reaffirm its N-soliton solution in terms of pfaffians. Then by using a Bäcklund transformation of the bilinear equations and defining a discrete hodograph (reciprocal) transformation, an integrable semi-discrete multi-component short pulse equation is constructed. Meanwhile, its N-soliton solution in terms of pfaffians is also proved.

  7. Tip-based source of femtosecond electron pulses at 30 keV

    SciTech Connect

    Hoffrogge, Johannes; Paul Stein, Jan; Krüger, Michael; Förster, Michael; Hammer, Jakob; Ehberger, Dominik; Hommelhoff, Peter; Baum, Peter

    2014-03-07

    We present a nano-scale photoelectron source, optimized for ultrashort pulse durations and well-suited for time-resolved diffraction and advanced laser acceleration experiments. A tungsten tip of several-ten-nanometers diameter mounted in a suppressor-extractor electrode configuration allows the generation of 30 keV electron pulses with an estimated pulse duration of 9 fs (standard deviation; 21 fs full width at half maximum) at the gun exit. We infer the pulse duration from particle tracking simulations, which are in excellent agreement with experimental measurements of the electron-optical properties of the source in the spatial domain. We also demonstrate femtosecond-laser triggered operation of the apparatus. The temporal broadening of the pulse upon propagation to a diffraction sample can be greatly reduced by collimating the beam. Besides the short electron pulse duration, a tip-based source is expected to feature a large transverse coherence and a nanometric emittance.

  8. Testing a scale pulsed modulator for an IEC neutron source into a resistive load

    SciTech Connect

    Dale, Gregory E; Wheat, Robert M; Aragonez, Robert

    2009-01-01

    A 1/10th scaled prototype pulse modulator for an Inertial Electrostatic Confinement (IEC) neutron source has been designed and tested at Los Alamos National Laboratory (LANL). The scaled prototype modulator is based on a solid-state Marx architecture and has an output voltage of 13 kV and an output current of 10 A. The modulator has a variable pulse width between 50 {micro}s and 1 ms with < 5% droop at all pulse widths. The modulator operates with a duty factor up to 5% and has a maximum pulse repetition frequency of 1 kHz. The use of a solid-state Marx modulator in this application has several potential benefits. These benefits include variable pulse width and amplitude, inherent switch overcurrent and transient overvoltage protection, and increased efficiency over DC supplies used in this application. Several new features were incorporated into this design including inductorless charging, fully snubberless operation, and stage fusing. The scaled prototype modulator has been tested using a 1 k{Omega} resistive load. Test results are given. Short (50 {micro}s) and long (1 ms) pulses are demonstrated as well as high duty factor operation (1 kHz rep rate at a 50 {micro}s pulse width for a 5% duty factor). Pulse agility of the modulator is demonstrated through turning the individual Marx stages on and off in sequence producing ramp, pyramid, and reverse pyramid waveforms.

  9. Extreme intensity pulses in a semiconductor laser with a short external cavity.

    PubMed

    Reinoso, Jose A; Zamora-Munt, Jordi; Masoller, Cristina

    2013-06-01

    We present a numerical study of the pulses displayed by a semiconductor laser with optical feedback in the short-cavity regime, such that the external cavity round-trip time is shorter than the laser relaxation oscillation period. For certain parameters there are occasional pulses, which are high enough to be considered extreme events. We characterize the bifurcation scenario that gives rise to such extreme pulses and study the influence of noise. We demonstrate intermittency when the extreme pulses appear and hysteresis when the attractor that sustains these pulses is destroyed. We also show that this scenario is robust under the inclusion of noise.

  10. Adiabatic propagation of short pulses under conditions of electromagnetically induced transparency

    SciTech Connect

    Arkhipkin, V G; Timofeev, I V

    2000-02-28

    The spatial and temporal dynamics of two short pulses propagating in an optically dense medium of resonant three-level {Lambda}-atoms is investigated numerically and analytically. The maximum coherence for the Raman transition due to coherent population trapping. It is shown that, at the initial stage of propagation, the waveforms of such pulses only slightly change along the length of the medium, which may considerably exceed the length of linear absorption for a single weak pulse. As the length of the absorbing medium increases, the energy of the probe (first) pulse is completely transferred into the second (control) pulse. (laser applications and other topics in quantum electronics)

  11. Picosecond pulse generation in a hybrid Q-switched laser source by using a microelectromechanical mirror.

    PubMed

    Couderc, Vincent; Crunteanu, Aurelian; Fabert, Marc; Doutre, Florent; El Bassri, Farid; Pagnoux, Dominique; Jalocha, Alain

    2012-02-27

    We present a novel Q-switched laser source using a micro-optical-electromechanical mirror (MOEM) designed for short pulse emission. It is based on a hybrid configuration including a passively Q-switched microchip laser coupled to a fiber cavity closed by a cantilever type MOEM acting as an active modulator. This specially designed mirror with a single reflecting gold membrane is switched by low bias voltage ~50 V (peak to peak). This device emits pulses at tunable repetition rates up to 1.6 kHz, with ~564 ps duration and 3.4 kW peak power, which constitutes the shortest pulse duration ever reported with MOEMs based pulsed lasers.

  12. Fiber laser as the pulse source for a laser rangefinder system

    NASA Astrophysics Data System (ADS)

    Nissilae, Seppo M.; Kostamovaara, Juha T.

    1993-05-01

    Active fibers, i.e. optically pumped doped fibers, have been developed and studied intensively during the last few years, and an optical amplifier based mainly on erbium-doped fibers has just been launched on the expanding telecommunications market. Fiber lasers have a market of their own in the sensor applications. The use of fiber lasers as pulse sources in laser rangefinder applications is studied here. The main advantages with respect to high energy pulses and a small emitting area are listed, the problems and disadvantages are discussed and some practical solutions to these problems are given. Possible Q-switching techniques for obtaining short, powerful pulses (> 10 W) of about 10 ns are studied as are liquid-crystal, PLZT crystal, acousto-optic and Pockels Cell modulators. Finally, the practicability of these modulators for laser pulsing in industrial environments is discussed.

  13. Phase-locked MHz pulse selector for x-ray sources.

    PubMed

    Förster, Daniel F; Lindenau, Bernd; Leyendecker, Marko; Janssen, Franz; Winkler, Carsten; Schumann, Frank O; Kirschner, Jürgen; Holldack, Karsten; Föhlisch, Alexander

    2015-05-15

    Picosecond x-ray pulses are extracted with a phase-locked x-ray pulse selector at 1.25 MHz repetition rate from the pulse trains of the accelerator-driven multiuser x-ray source BESSY II preserving the peak brilliance at high pulse purity. The system consists of a specially designed in-vacuum chopper wheel rotating with ≈1  kHz angular frequency. The wheel is driven in an ultrahigh vacuum and is levitated on magnetic bearings being capable of withstanding high centrifugal forces. Pulses are picked by 1252 high-precision slits of 70 μm width on the outer rim of the wheel corresponding to a temporal opening window of the chopper of 70 ns. We demonstrate how the electronic phase stabilization of ±2  ns together with an arrival time jitter of the individual slits of the same order of magnitude allows us to pick short single bunch x-ray pulses out of a 200 ns ion clearing gap in a multibunch pulse train as emitted from a synchrotron facility at 1.25 MHz repetition rate with a pulse purity below the shot noise detection limit. The approach is applicable to any high-repetition pulsed radiation source, in particular in the x-ray spectral range up to 10 keV. The opening window in a real x-ray beamline, its stability, as well as the limits of mechanical pulse picking techniques in the MHz range are discussed.

  14. Peculiarities of the propagation of multidimensional extremely short optical pulses in germanene

    NASA Astrophysics Data System (ADS)

    Zhukov, Alexander V.; Bouffanais, Roland; Konobeeva, Natalia N.; Belonenko, Mikhail B.

    2016-09-01

    In this Letter, we study the propagation characteristics of both two-dimensional and three-dimensional extremely short optical pulses in germanene. A distinguishing feature of germanene-in comparison with other graphene-like structures-is the presence of a significant spin-orbit interaction. The account of this interaction has a significant impact on the evolution of extremely short pulses in such systems. Specifically, extremely short optical pulses, consisting of two electric field oscillations, cause the appearance of a tail associated with the excitation of nonlinear waves. Due to the large spin-orbit interaction in germanene, this tail behind the main pulse is much smaller in germanene-based samples as compared to graphene-based ones, thereby making germanene a preferred material for the stable propagation of pulses along the sample.

  15. Nonlinear wave interactions between short pulses of different spatio-temporal extents

    PubMed Central

    Sivan, Y.; Rozenberg, S.; Halstuch, A.; Ishaaya, A. A.

    2016-01-01

    We study the nonlinear wave interactions between short pulses of different spatio-temporal extents. Unlike the well-understood mixing of quasi-monochromatic waves, this configuration is highly non-intuitive due to the complex coupling between the spatial and temporal degrees of freedom of the interacting pulses. We illustrate the process intuitively with transitions between different branches of the dispersion curves and interpret it in terms of spectral exchange between the interacting pulses. We verify our interpretation with an example whereby a spectrally-narrow pulse “inherits” the wide spectrum of a pump pulse centered at a different wavelength, using exact numerical simulations, as well as a simplified coupled mode analysis and an asymptotic analytical solution. The latter also provides a simple and intuitive quantitative interpretation. The complex wave mixing process studied here may enable flexible spatio-temporal shaping of short pulses and is the starting point of the study of more complicated systems. PMID:27381552

  16. Nonlinear wave interactions between short pulses of different spatio-temporal extents

    NASA Astrophysics Data System (ADS)

    Sivan, Y.; Rozenberg, S.; Halstuch, A.; Ishaaya, A. A.

    2016-07-01

    We study the nonlinear wave interactions between short pulses of different spatio-temporal extents. Unlike the well-understood mixing of quasi-monochromatic waves, this configuration is highly non-intuitive due to the complex coupling between the spatial and temporal degrees of freedom of the interacting pulses. We illustrate the process intuitively with transitions between different branches of the dispersion curves and interpret it in terms of spectral exchange between the interacting pulses. We verify our interpretation with an example whereby a spectrally-narrow pulse “inherits” the wide spectrum of a pump pulse centered at a different wavelength, using exact numerical simulations, as well as a simplified coupled mode analysis and an asymptotic analytical solution. The latter also provides a simple and intuitive quantitative interpretation. The complex wave mixing process studied here may enable flexible spatio-temporal shaping of short pulses and is the starting point of the study of more complicated systems.

  17. Some general reflections on {open_quotes}long pulse{close_quotes} neutron sources

    SciTech Connect

    Bauer, G.S.

    1995-12-31

    A long pulse spallation neutron source (LPSS) having about 20 times more time average thermal flux than its short pulse counterpart (SPSS) at the same proton beam power and featuring a pronounced time structure not available on CW sources (CWNS) of equal time average flux can in principle host instruments typical for both classes of facilities. While the need for additional choppers introduces some restrictions on inverted time of flight techniques typical for SPSS and high incident neutron energies are not easier to use on LPSS than on CWNS, taking advantage of the pulsed nature of the neutron flux can enhance significantly the performance of direct time of flight instruments and of crystal spectrometers or diffractometers. In the paper some of the options are reviewed in a general manner and criteria are discussed which can be used to optimize the performance enhancement.

  18. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Collision frequency shift of a short electromagnetic pulse

    NASA Astrophysics Data System (ADS)

    Chegotov, M. V.

    2004-03-01

    The frequency shift of a short electromagnetic pulse interaction with a plasma-like medium is discovered and studied. The shift is caused by elastic collisions of free electrons with ions or neutral particles.

  19. Deterministic processing of alumina with ultra-short laser pulses

    SciTech Connect

    Furmanski, J; Rubenchik, A M; Shirk, M D; Stuart, B C

    2007-06-27

    Ultrashort pulsed lasers can accurately ablate materials which are refractory, transparent, or are otherwise difficult to machine by other methods. The typical method of machining surfaces with ultrashort laser pulses is by raster scanning, or the machining of sequentially overlapping linear trenches. Experiments in which linear trenches were machined in alumina at various pulse overlaps and incident fluences are presented, and the dependence of groove depth on these parameters established. A model for the machining of trenches based on experimental data in alumina is presented, which predicts and matches observed trench geometry. This model is then used to predict optimal process parameters for the machining of trenches for maximal material removal rate for a given laser.

  20. Short-pulse, high-intensity lasers at Los Alamos

    SciTech Connect

    Taylor, A.J.; Roberts, J.P.; Rodriguez, G.; Fulton, R.D.; Kyrala, G.A.; Schappert, G.T.

    1994-03-01

    Advances in ultrafast lasers and optical amplifiers have spurred the development of terawatt-class laser systems capable of delivering focal spot intensities approaching 10{sup 20} W/cm{sup 2}. At these extremely high intensities, the optical field strength is more than twenty times larger than the Bohr electric field, permitting investigations of the optical properties of matter in a previously unexplored regime. The authors describe two laser systems for high intensity laser interaction experiments: The first is a terawatt system based on amplification of femtosecond pulses in XeCl which yields 250 mJ in 275 fs and routinely produces intensifies on target in excess of 10{sup 18} W/cm{sup 2}. The second system is based on chirped pulse amplification of 100-fs pulses in Ti:sapphire.

  1. Short pulse width widens the therapeutic window of subthalamic neurostimulation

    PubMed Central

    Reich, Martin M; Steigerwald, Frank; Sawalhe, Anna D; Reese, Rene; Gunalan, Kabilar; Johannes, Silvia; Nickl, Robert; Matthies, Cordula; McIntyre, Cameron C; Volkmann, Jens

    2015-01-01

    We explored the impact of pulse durations <60 μsec on the therapeutic window of subthalamic neurostimulation in Parkinson's disease. Current thresholds for full rigidity control and first muscle contractions were evaluated at pulse durations between 20 and 120 μsec during a monopolar review session in four patients. The average therapeutic window was 2.16 mA at 60 μsec, which proportionally increased by 182% at 30 μsec, while decreasing by 46% at 120 μsec. Measured chronaxies and model data suggest, that pulse durations <60 μsec lead to a focusing of the neurostimulation effect on smaller diameter axons close to the electrode while avoiding stimulation of distant pyramidal tract fibers. PMID:25909087

  2. Developing a High-Flux Isolated Attosecond Pulse Source

    NASA Astrophysics Data System (ADS)

    Kamalov, Andrei; Ware, Matthew; Bucksbaum, Philip; Cryan, James

    2016-05-01

    High harmonic based light sources have proven to be valuable experimental tools that facilitate studies of electron dynamics at their natural timescale, the attosecond regime. The nature of driving laser sources used in high harmonic generation make it difficult to attain attosecond pulses that are both isolated in time and of a high intensity. We present our progress in commissioning a beamline designed to produce high-flux isolated attosecond pulses. A multistep amplification process provides us with 30 mJ, 25 fs pulses centered around 800 nm with 100 Hz repetition rate. These pulses are spatially split and focused into a gas cell. A non-collinear optical gating scheme is used to produce a lighthouse source of high harmonic radiation wherein each beamlet is an isolated attosecond pulse. A variable-depth grazing-incidence stepped mirror is fabricated to extend the optical path length of the older beamlets and thus overlap the beamlets in time. The combined beam is tightly focused and ensuing mechanics will be studied with an electron spectrometer as well as a xuv photon spectrometer. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

  3. Short pulse fiber lasers mode-locked by carbon nanotubes and graphene

    NASA Astrophysics Data System (ADS)

    Yamashita, Shinji; Martinez, Amos; Xu, Bo

    2014-12-01

    One and two dimensional forms of carbon, carbon nanotubes and graphene, have interesting and useful, not only electronic but also photonic, properties. For fiber lasers, they are very attractive passive mode lockers for ultra-short pulse generation, since they have saturable absorption with inherently fast recovery time (<1 ps). In this paper, we review the photonic properties of graphene and CNT and our recent works on fabrication of fiber devices and applications to ultra-short pulse mode-locked fiber lasers.

  4. Space Debris-de-Orbiting by Vaporization Impulse using Short Pulse Laser

    SciTech Connect

    Early, J; Bibeau, C; Claude, P

    2003-09-16

    Space debris constitutes a significant hazard to low earth orbit satellites and particularly to manned spacecraft. A quite small velocity decrease from vaporization impulses is enough to lower the perigee of the debris sufficiently for atmospheric drag to de-orbit the debris. A short pulse (picosecond) laser version of the Orion concept can accomplish this task in several years of operation. The ''Mercury'' short pulse Yb:S-FAP laser being developed at LLNL for laser fusion is appropriate for this task.

  5. Development and Use of a Modified Pulse Electrospinning Setup for Producing Short Fibers

    NASA Astrophysics Data System (ADS)

    Aliyev, Y. T.; Dabynov, B. M.; Bodykov, D. U.; Musabekov, U. S.; Mansurov, Z. A.

    2016-01-01

    A brief literature review is given of studies concerning the method of standard electrospinning, which is used for producing long nanofibers. Experimental setups — the first version and the new, modified pulse electrospinning setup — are described. The results of works on producing short fibers using pulse electrospinning are reported in the present article. Data on short fibers produced experimentally from such polymers as polymethyl methacrylate and cellulose acetate are presented.

  6. Assessment of the limits to peak power of 1100nm broad area single emitter diode lasers under short pulse conditions

    NASA Astrophysics Data System (ADS)

    Wang, X.; Crump, P.; Pietrzak, A.; Schultz, C.; Klehr, A.; Hoffmann, T.; Liero, A.; Ginolas, A.; Einfeldt, S.; Bugge, F.; Erbert, G.; Tränkle, G.

    2009-02-01

    High power diode lasers are the root source of optical energy in all high performance laser systems. As their performance advances, diode lasers are increasingly taking the place of other sources. Short pulse, sub-microsecond-class, high power lasers are important for many applications but historically, diode lasers have not been able to reach high enough peak pulse powers with adequate reliability, limited by physical effects such as facet failure. By combining robust facet passivation with thick super large optical cavity waveguides, greatly increased optical output power can be achieved. We present here the results of a study using commercial high current short pulse sources (>200A, <500ns) to assess the performance and endurance limits of high power broad area devices. We find that our lasers can be driven with a peak power density of over 110MWcm-2 without failure for more than 3×107 pulses. For example, on testing to 240A, single emitter 200μm stripe 1100nm broad area devices reach 124W (46μJ) without failure, and 60μm stripes reach 88W. In practice, high injection effects such as carrier accumulation in waveguide typically limit peak power. We review these remaining limitations, and discuss how they can be overcome.

  7. High Energy, Short Pulse Fiber Injection Lasers at Lawrence Livermore National Laboratory

    SciTech Connect

    Dawson, J W; Messerly, M J; Phan, H H; Crane, J K; Beach, R J; Siders, C W; Barty, C J

    2008-09-10

    A short pulse fiber injection laser for the Advanced Radiographic Capability (ARC) on the National Ignition Facility (NIF) has been developed at Lawrence Livermore National Laboratory (LLNL). This system produces 100 {micro}J pulses with 5 nm of bandwidth centered at 1053 nm. The pulses are stretched to 2.5 ns and have been recompressed to sub-ps pulse widths. A key feature of the system is that the pre-pulse power contrast ratio exceeds 80 dB. The system can also precisely adjust the final recompressed pulse width and timing and has been designed for reliable, hands free operation. The key challenges in constructing this system were control of the signal to noise ratio, dispersion management and managing the impact of self phase modulation on the chirped pulse.

  8. Isolated short attosecond pulse generation in an orthogonally polarized multicycle chirped laser field

    SciTech Connect

    Xu Junjie

    2011-03-15

    We theoretically demonstrate the generation of a high-order harmonic and isolated attosecond pulse in an orthogonally polarized laser field, which is synthesized by an 800-nm chirped laser pulse and an 800-nm chirp-free laser pulse. Owing to the instantaneous frequency increasingly reducing close to the center of the driving pulse, the extreme ultraviolet supercontinuum for the chirped synthesized field is even broader than that for an orthogonal chirp-free two-color laser field. It is found that the broadband supercontinuum spectrum can be achieved for the driving pulse with ten and above optical cycles. After phase compensation an isolated attosecond pulse with a duration of {approx}16 as is produced. Furthermore, the optimization of the chirping rate parameters is investigated to achieve cutoff extension and an isolated short attosecond pulse.

  9. Proposal for a High-Brightness Pulsed Electron Source

    SciTech Connect

    Zolotorev, M.; Commins, E.D.; Heifets, S.; Sannibale, F.; /LBL, Berkeley /UC, Berkeley /SLAC

    2006-10-16

    We propose a novel scheme for a high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography. A description of the proposed scheme is presented.

  10. Neutron science opportunities at pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-12-31

    Using the IPNS Upgrade plan developed at Argonne National Laboratory as a worked example of the design of a pulsed spallation neutron source, this paper explores some of the scientific applications of an advanced facility for materials science studies and the instrumentation for those purposes.

  11. Development of Lightweight Prime Power Source Components for Pulsed Applications

    DTIC Science & Technology

    1991-06-01

    lbs, 22 11 long, 18" diameter, 7 lbsjsec mass flow rate, 1, 700 degree F turbine inlet temperature. (1] ALTERNATOR CONSIDERATIONS The choice of...provides an overview of system integration for the 1 MW power source components and power source integration with the pulsed load . This will...indicated that peak power flow into the capacitor occurs about midway through the charge cycle. The varying power flow gives rise to cyclic

  12. Short haul air passenger data sources in the United States

    NASA Technical Reports Server (NTRS)

    Al-Kazily, J.; Gosling, G.; Horonjeff, R.

    1977-01-01

    The sources and characteristics of existing data on short haul air passenger traffic in the United States domestic air market are described along with data availability, processing, and costs. Reference is made to data derived from aircraft operations since these data can be used to insure that no short haul operators are omitted during the process of assembling passenger data.

  13. Measurement and compensation schemes for the pulse front distortion of ultra-intensity ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wu, Fenxiang; Xu, Yi; Yu, Linpeng; Yang, Xiaojun; Li, Wenkai; Lu, Jun; Leng, Yuxin

    2016-11-01

    Pulse front distortion (PFD) is mainly induced by the chromatic aberration in femtosecond high-peak power laser systems, and it can temporally distort the pulse in the focus and therefore decrease the peak intensity. A novel measurement scheme is proposed to directly measure the PFD of ultra-intensity ultra-short laser pulses, which can work not only without any extra struggle for the desired reference pulse, but also largely reduce the size of the required optical elements in measurement. The measured PFD in an experimental 200TW/27fs laser system is in good agreement with the calculated result, which demonstrates the validity and feasibility of this method effectively. In addition, a simple compensation scheme based on the combination of concave lens and parabolic lens is also designed and proposed to correct the PFD. Based on the theoretical calculation, the PFD of above experimental laser system can almost be completely corrected by using this compensator with proper parameters.

  14. Laser-induced resonance states as dynamic suppressors of ionization in high-frequency short pulses

    SciTech Connect

    Barash, Danny; Orel, Ann E.; Baer, Roi

    2000-01-01

    An adiabatic-Floquet formalism is used to study the suppression of ionization in short laser pulses. In the high-frequency limit the adiabatic equations involve only the pulse envelope where transitions are purely ramp effects. For a short-ranged potential having a single-bound state we show that ionization suppression is caused by the appearance of a laser-induced resonance state, which is coupled by the pulse ramp to the ground state and acts to trap ionizing flux. (c) 1999 The American Physical Society.

  15. Short intense laser pulse collapse in near-critical plasma.

    PubMed

    Sylla, F; Flacco, A; Kahaly, S; Veltcheva, M; Lifschitz, A; Malka, V; d'Humières, E; Andriyash, I; Tikhonchuk, V

    2013-02-22

    It is observed that the interaction of an intense ultrashort laser pulse with a near-critical gas jet results in the pulse collapse and the deposition of a significant fraction of the energy. This deposition happens in a small and well-localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over ~ 150 μm at a subrelativistic velocity (~ c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated with the hot electron current. Numerical simulations in good agreement with the observations suggest the acceleration in the collapse region of relativistic electrons, along with the excitation of a sizable magnetic dipole that sustains the electron current over several picoseconds.

  16. Cross sections for short pulse single and double ionization ofhelium

    SciTech Connect

    Palacios, Alicia; Rescigno, Thomas N.; McCurdy, C. William

    2007-11-27

    In a previous publication, procedures were proposed for unambiguously extracting amplitudes for single and double ionization from a time-dependent wavepacket by effectively propagating for an infinite time following a radiation pulse. Here we demonstrate the accuracy and utility of those methods for describing two-photon single and one-photon double ionization of helium. In particular it is shown how narrow features corresponding to autoionizing states are easily resolved with these methods.

  17. Generation of ultra-short hydrogen atom pulses by bunch-compression photolysis

    NASA Astrophysics Data System (ADS)

    Kaufmann, Sven; Schwarzer, Dirk; Reichardt, Christian; Wodtke, Alec M.; Bünermann, Oliver

    2014-11-01

    Ultra-short light pulses enable many time-resolved studies in chemistry, especially when used in pump-probe experiments. However, most chemical events are not initiated by light, but rather by collisions. Time-resolved collisional experiments require ultra-short pulses of atoms and molecules—sadly, methods for producing such pulses are so far unknown. Here we introduce bunch-compression photolysis, an approach to forming ultra-short and highly intense pulses of neutral atoms. We demonstrate H-atom pulses of 1.2±0.3 ns duration, far shorter than any previously reported. Owing to its extraordinarily simple physical principles, we can accurately model the method—the model shows H-atom pulses as short as 110-ps are achievable. Importantly, due to the bunch-compression, large (mm3) photolysis volumes are possible, a key advantage for pulse intensity. This technique overcomes the most challenging barrier to a new class of experiments on time-resolved collisions involving atoms and molecules.

  18. Laser zona dissection using short-pulse ultraviolet lasers

    NASA Astrophysics Data System (ADS)

    Neev, Joseph; Tadir, Yona; Ho, Peter D.; Whalen, William E.; Asch, Richardo H.; Ord, Teri; Berns, Michael W.

    1992-06-01

    The interaction of pulsed ultraviolet radiation with the zona pellucida of human oocytes which had failed to fertilize in standard IVF cycles, was investigated. Two lasers were studied: a 100 ps pulsed Nd:YAG with a nonlinear crystal emitting light at 266 nm, and a 15 ns XeCl excimer laser with 308 nm radiation. Incisions in the zona were made by aiming the beam tangentially to the oocyte. The results indicate superior, high precision performance by the excimer laser creating trenches as narrow as 1 micrometers and as shallow as 1 micrometers . The incision size was found to be sensitive to the laser's energy and to the position of the microscope's objective focal plane, but relatively insensitive to the laser pulse repetition rate. Once the minimum spot size was defined by the system parameters, the laser beam was used to curve out any desired zona shape. This laser microsurgery technique as applied to partial zone dissection or zona drilling could prove very useful as a high-precision, non-contact method for treatments of low fertilization rate and for enhancing embryo implantation rates in patients undergoing IVF treatments.

  19. Strong Field Molecular Ionization in the Impulsive Limit: Freezing Vibrations with Short Pulses.

    PubMed

    Sándor, Péter; Tagliamonti, Vincent; Zhao, Arthur; Rozgonyi, Tamás; Ruckenbauer, Matthias; Marquetand, Philipp; Weinacht, Thomas

    2016-02-12

    We study strong-field molecular ionization as a function of pulse duration. Experimental measurements of the photoelectron yield for a number of molecules reveal competition between different ionization continua (cationic states) which depends strongly on pulse duration. Surprisingly, in the limit of short pulse duration, we find that a single ionic continuum dominates the yield, whereas multiple continua are produced for longer pulses. Using calculations which take vibrational dynamics into account, we interpret our results in terms of nuclear motion and nonadiabatic dynamics during the ionization process.

  20. Curvature aided long range propagation of short laser pulses in the atmosphere

    SciTech Connect

    Yedierler, Burak

    2013-03-15

    The pre-filamentation regime of propagation of a short and intense laser pulse in the atmosphere is considered. Spatiotemporal self-focusing dynamics of the laser beam are investigated by calculating the coupled differential equations for spot size, pulse length, phase, curvature, and chirp functions of a Gaussian laser pulse via a variational technique. The effect of initial curvature parameter on the propagation of the laser pulse is taken into consideration. A method relying on the adjustment of the initial curvature parameter can expand the filamentation distance of a laser beam of given power and chirp is proposed.

  1. Dual wavelength laser damage mechanisms in the ultra-short pulse regime

    NASA Astrophysics Data System (ADS)

    Gyamfi, Mark; Costella, Marion; Willemsen, Thomas; Jürgens, Peter; Mende, Mathias; Jensen, Lars; Ristau, Detlev

    2016-12-01

    New ultrashort pulse laser systems exhibit an ever increasing performance which includes shorter pulses and higher pulse energies. Optical components used in these systems are facing increasing requirements regarding their durability, and therefore understanding of the damage mechanism is crucial. In the ultra-short pulse regime electron ionization processes control the damage mechanisms. For the single wavelength, single pulse regime the Keldysh [1] and the Drude model [2] allow a quantitative description of these ionization processes. However, in this model, the electrical field is restricted to a single wavelength, and therefore it cannot be applied in the case of irradiation with two pulses at different wavelengths. As frequency conversion is becoming more common in ultra-short pulse applications, further research is needed in this field to predict the damage resistance of optical components. We investigate the damage behavior of high reflective mirrors made of different metal oxide materials under simultaneous exposure to ultra-short pulses at the wavelengths 387.5 nm and 775 nm, respectively.

  2. SHORT-PULSE ELECTROMAGNETIC TRANSPONDER FOR HOLE-TO-HOLE USE.

    USGS Publications Warehouse

    Wright, David L.; Watts, Raymond D.; Bramsoe, Erik

    1983-01-01

    Hole-to-hole observations were made through nearly 20 m of granite using an electromagnetic transponder (an active reflector) in one borehole and a single-hole short-pulse radar in another. The transponder is inexpensive, operationally simple, and effective in extending the capability of a short-pulse borehole radar system to allow hole-to-hole operation without requiring timing cables. A detector in the transponder senses the arrival of each pulse from the radar. Each pulse detection triggers a kilovolt-amplitude pulse for retransmission. The transponder 'echo' may be stronger than that of a passive reflector by a factor of as much as 120 db. The result is an increase in range capability by a factor which depends on attenuation in the medium and hole-to-hole wavepath geometry.

  3. Pulse-modulated light source for psychometric and vision experiments.

    PubMed

    Scholfield, C N; Murdock, M

    1987-03-01

    Light-emitting diodes (LED) of various colours were used to produce accurately controllable light sources. Variable light intensity was obtained by applying 800-ns current pulses to the LEDs at frequencies 1-1000 kHz using a single potentiometer. These current pulses were generated from an oscillator which was voltage-controlled from a potentiometer and an antilogarithmic amplifier. Its output was gated to produce an optional flicker of 1-100 Hz. The light intensity was indicated by a frequency meter connected to the oscillator. The reading of this was found to linearly indicate light intensity.

  4. Single and repetitive short-pulse high-power microwave window breakdown

    SciTech Connect

    Chang, C.; Tang, C. X.; Shao, H.; Chen, C. H.; Huang, W. H.

    2010-05-15

    The mechanisms of high-power microwave breakdown for single and repetitive short pulses are analyzed. By calculation, multipactor saturation with electron density much higher than the critical plasma density is found not to result in microwave cutoff. It is local high pressure about Torr class that rapid plasma avalanche and final breakdown are realized in a 10-20 ns short pulse. It is found by calculation that the power deposited by saturated multipactor and the rf loss of protrusions are sufficient to induce vaporizing surface material and enhancing the ambient pressure in a single short pulse. For repetitive pulses, the accumulation of heat and plasma may respectively carbonize the surface material and lower the repetitive breakdown threshold.

  5. Plasma shape control by pulsed solenoid on laser ion source

    DOE PAGES

    Sekine, M.; Ikeda, S.; Romanelli, M.; ...

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled bymore » the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.« less

  6. Plasma shape control by pulsed solenoid on laser ion source

    SciTech Connect

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.

  7. Plasma shape control by pulsed solenoid on laser ion source

    NASA Astrophysics Data System (ADS)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  8. Effect of nonlinear absorption on self focusing of short laser pulse in a plasma

    SciTech Connect

    Kumar, Ashok

    2012-06-15

    Paraxial theory of self focusing of short pulse laser in a plasma under transient and saturating effects of nonlinearity and nonlinear absorption is developed. The absorption is averaged over the cross-section of the beam and is different for different time segments of the pulse. The electron temperature includes cumulative effect of previous history of temporal profile of pulse intensity, however, the ambipolar diffusion is taken to be faster than the heating time. The relaxation effect causes self-distortion of the pulse temporal profile where as the nonlinear absorption weakens self focusing. For the pulses of duration comparable to the electron ion collision time, the front part of the pulse gets defocused where as the latter part undergoes periodic self focusing.

  9. Comparison of Single Event Transients Generated by Short Pulsed X-Rays, Lasers and Heavy Ions

    SciTech Connect

    Cardoza, David; LaLumondiere, Stephen D.; Tockstein, Michael A.; Brewe, Dale L.; Wells, Nathan P.; Koga, Rokutaro; Gaab, K. M.; Lotshaw, William T.; Moss, Steven C.

    2014-12-01

    We report an experimental study of the transients generated by pulsed x-rays, heavy ions, and different laser wavelengths in a Si p-i-n photodiode. We compare the charge collected by all of the excitation methods to determine the equivalent LET for pulsed x-rays relative to heavy ions. Our comparisons show that pulsed x-rays from synchrotron sources can generate a large range of equivalent LET and generate transients similar to those excited by laser pulses and heavy ion strikes. We also look at how the pulse width of the transients changes for the different excitation methods. We show that the charge collected with pulsed x-rays is greater than expected as the x-ray photon energy increases. Combined with their capability of focusing to small spot sizes and of penetrating metallization, pulsed x-rays are a promising new tool for high resolution screening of SEE susceptibility

  10. Development of a short pulsed solid propellant plasma thruster

    NASA Technical Reports Server (NTRS)

    Guman, W. J.

    1974-01-01

    The experimental results are summarized that were obtained in the development of a Teflon solid propellant pulsed plasma thruster. The feasibility was established of storing and feeding solid propellant in the form of an open circular loop into an operational thruster. This technique was verified to be practical by feeding over 20 inches of Teflon into a micro-thruster over an accumulated life test of 1858 hours. High energy density capacitors were evaluated under vacuum conditions when the capacitor is coupled directly to a plasma thruster. Numerous early capacitor failures were encountered. It was concluded that essentially all of the failures encountered in a vacuum environment are due to an internal electrical breakdown that will occur inside a capacitor that is not truly hermetically sealed. A steady input power significantly in excess of 130 watts can safely be tolerated if heat conduction can be provided to a sink whose temperature is about 16 C. A vacuum life test of the capacitor bank was carried out while discharging into a milli-lb. (milli-Newton) type pulsed plasma thruster. More than 1500 hours of vacuum testing of this milli-Newton type system has been accumulated without any capacitor problems. Recommendations are made for future capacitor designs.

  11. SLIM, Short-pulse Technology for High Gradient Induction Accelerators

    SciTech Connect

    Krasnykh, A.; Kardo-Sysoev, A.; Arntz, F.; /Diversified Tech., Bedford

    2009-12-09

    The conclusions of this paper are: (1) The gradient of the SLIM-based technology is believed to be achievable in the same range as it is for the gradient of a modern rf-linac technology ({approx}100 MeV per meter). (2) The SLIM concept is based on the nsec TEM pulse mode operation with no laser or rf systems. (3) Main components of SLIM are not stressed while the energy is pumped into the induction system. Components can accept the hard environment conditions such as a radiation dose, mismatch, hard electromagnetic nose level, etc. Only for several nanoseconds the switch is OFF and produces a stress in the induction system. At that time, the delivery of energy to the beam takes place. (4) The energy in the induction system initially is storied in the magnetic field when the switch is ON. That fact makes another benefit: a low voltage power supplies can be used. The reliability of a lower voltage power supply is higher and they are cheaper. (5) The coreless SLIM concept offers to work in the MHz range of repetition rate. The induction system has the high electric efficiency (much higher than the DWA). (6) The array of lined up and activated SLIM cells is believed to be a solid state structure of novel accelerating technology. The electron-hole plasma in the high power solid state structure is precisely controlled by the electromagnetic process of a pulsed power supply.

  12. Computer simulation of short shock pulses propagation in ceramic materials

    NASA Astrophysics Data System (ADS)

    Skripnyak, Vladimir A.; Skripnyak, Evgenia G.; Zhukova, Tat'yana V.

    2001-06-01

    The propagation of shock impulses with duration from microsecond to several tens of nanoseconds and attenuation of their amplitude in single-phase polycrystalline ceramics, sapphire and ruby single crystals, nanocrystalline ceramic composites are investigated by numerical simulation method. The propagation of shock waves and unloading waves are determined by the mechanical behavior of ceramics depending from evolution of structure of ceramics. The relaxation of shear stress in constructional ceramics can be caused by set of physical mechanisms on meso- and micro-scale levels. The used model takes into account the kinetics of inelastic deformation caused by martensitic phase transformation, nucleation and motion of dislocation, nucleation of shear microcracks etc. The outcomes of simulation testify, that inelastic deformation can be negligible in the constructional elements from polycrystalline ceramics when the shock pulse amplitude is higher, than the Hugoniot Elastic Limit (HEL), if the impulses duration is comparable with time of relaxation corresponding to preferred physical mechanisms. In these conditions the actual spall strength of polycrystalline ceramics is comparable to the theoretical strength at tension of the single crystals. The Al2O3 ceramics is capable to be practically elastic-deformed and the shear stress is compared to the theoretical shear strength, if the duration of pulse loading is not more than some tens nanoseconds.

  13. All-solid-state repetitive semiconductor opening switch-based short pulse generator.

    PubMed

    Ding, Zhenjie; Hao, Qingsong; Hu, Long; Su, Jiancang; Liu, Guozhi

    2009-09-01

    The operating characteristics of a semiconductor opening switch (SOS) are determined by its pumping circuit parameters. SOS is still able to cut off the current when pumping current duration falls to the order of tens of nanoseconds and a short pulse forms simultaneously in the output load. An all-solid-state repetitive SOS-based short pulse generator (SPG100) with a three-level magnetic pulse compression unit was successfully constructed. The generator adopts magnetic pulse compression unit with metallic glass and ferrite cores, which compresses a 600 V, 10 mus primary pulse into short pulse with forward pumping current of 825 A, 60 ns and reverse pumping current of 1.3 kA, 30 ns. The current is sent to SOS in which the reverse pumping current is interrupted. The generator is capable of providing a pulse with the voltage of 120 kV and duration of 5-6 ns while output load being 125 Omega. The highest repetition rate is up to 1 kHz.

  14. Diode-pumped ultra-short-pulse solid-state lasers

    NASA Astrophysics Data System (ADS)

    Sorokin, E.; Sorokina, I. T.; Wintner, E.

    2001-01-01

    Many materials are good candidates for diode-pumped ultra-short-pulse lasers: several transition-metal-ion-doped crystals can or could support extremely short fs pulses. This goal, so far, has only been reached by Cr3+:LiSAF, but there are good chances for other crystals like Cr4+:YAG having its bandwidth within the third communication window, and the high-yield Cr2+:ZnSe with its impressive bandwidth in the near IR. Rare-earth-ion-doped media deliver only sub-ps pulses but allow unprecedented and scalable high average powers, like a SESAM mode-locked Yb:YAG thin-disk laser described recently. In all ranges of pulse durations there are fascinating applications ready for widespread employment as soon as compact, reliable and moderately priced ultra-short-pulse systems will be available for the non-laser-skilled user. The highest impact in the near future is attributed to microstructuring of materials and processing of biological samples, including dental enamel, by ps and sub-ps pulses, and optical coherence tomography needing pulses in the 10-fs regime at very modest average powers.

  15. Short Laser Pulse-Induced Irreversible Photothermal Effects in Red Blood Cells

    PubMed Central

    Lukianova-Hleb, Ekaterina Y.; Oginsky, Alexander O.; Olson, John S.; Lapotko, Dmitri O.

    2013-01-01

    Background and Objectives Photothermal (PT) responses of individual red blood cells (RBC) to short laser pulses may depend upon PT interactions at microscale. Study Design/Materials and Methods A sequence of identical short laser pulses (0.5 and 10 nanoseconds, 532 nm) was applied to individual RBCs, and their PT properties were analyzed at microscale in real time after each single pulse. Results PT interactions in RBC were found to be localized to sub-micrometer zones associated with Hb that may be responsible for overheating and evaporation at higher optical energies. At sub-ablative energies, a single short laser pulse induced irreversible changes in the optical properties of RBC that stimulated the transition from a heating-cooling response to ablative evaporation in individual erythrocytes during their exposure to subsequent, but identical pulses. Conclusion The PT response of RBCs to short laser pulses of specific energy includes localized irreversible modifications of cell structure, resulting in three different effects: thermal non-ablative response, ablative evaporation, and residual thermal response. PMID:21290393

  16. Effect of pulse to pulse interactions on ultra-short pulse laser drilling of steel with repetition rates up to 10 MHz.

    PubMed

    Finger, Johannes; Reininghaus, Martin

    2014-07-28

    We report on the effect of pulse to pulse interactions during percussion drilling of steel using high power ps-laser radiation with repetition rates of up to 10 MHz and high average powers up to 80 W. The ablation rate per pulse is measured as a function of the pulse repetition rate for four fluences ranging from 500 mJ/cm2 up to 1500 mJ/cm2. For every investigated fluence an abrupt increase of the ablation rate per pulse is observed at a distinctive repetition rate. The onset repetition rate for this effect is strongly dependent on the applied pulse fluence. The origin of the increase of the ablation rate is attributed to the emergence of a melt based ablation processes, as Laser Scanning Microscopy (LSM) images show the occurrence of melt ejected material surrounding the drilling holes. A semi empirical model based on classical heat conduction including heat accumulation as well as pulse-particle interactions is applied to enable quantitative conclusions on the origin of the observed data. In agreement with previous studies, the acquired data confirm the relevance of these two effects for the fundamental description of materials processing with ultra-short pulsed laser radiation at high repetition rates and high average power.

  17. Novel oral applications of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wieger, V.; Wernisch, J.; Wintner, E.

    2007-02-01

    In the past decades, many efforts have been made to replace mechanical tools in oral applications by various laser systems. The reasons therefore are manifold: i) Friction causes high temperatures damaging adjacent tissue. ii) Smear layers and rough surfaces are produced. iii) Size and shape of traditional tools are often unsuitable for geometrically complicated incisions and for minimum invasive treatment. iv) Mechanical damage of the remaining tissue occurs. v) Online diagnosis for feedback is not available. Different laser systems in the µs and sub-&mrgs-pulse regime, among them Erbium lasers, have been tested in the hope to overcome the mentioned drawbacks and, to some extent, they represent the current state of the art with respect to commercial and hence practical application. In the present work the applicability of scanned ultrashort pulse lasers (USPLs) for biological hard tissue as well as dental restoration material removal was tested. It is shown that cavities with features superior to mechanically treated or Erbium laser ablated cavities can be generated if appropriate scan algorithms and optimum laser parameters are matched. Smooth cavity rims, no microcracks, melting or carbonisation and precise geometry are the advantages of scanned USLP ablation. For bone treatment better healing conditions are expected as the natural structure remains unaffected by the preparation procedure. The novelty of this work is represented by a comprehensive compilation of various experimental results intended to assess the performance of USPLs. In this context, various pulse durations in the picosecond and femtosecond regime were applied to dental and bone tissue as well as dental restoration materials which is considered to be indispensable for a complete assessment. Parameters like ablation rates describing the efficiency of the ablation process, and ablation thresholds were determined - some of them for the first time - and compared to the corresponding Erbium

  18. Simple filtered repetitively pulsed vacuum arc plasma source

    NASA Astrophysics Data System (ADS)

    Chekh, Yu.; Zhirkov, I. S.; Delplancke-Ogletree, M. P.

    2010-02-01

    A very simple design of cathodic filtered vacuum arc plasma source is proposed. The source without filter has only four components and none of them require precise machining. The source operates in a repetitively pulsed regime, and for laboratory experiments it can be used without water cooling. Despite the simple construction, the source provides high ion current at the filter outlet reaching 2.5% of 400 A arc current, revealing stable operation in a wide pressure range from high vacuum to oxygen pressure up to more than 10-2 mbar. There is no need in complicated power supply system for this plasma source, only one power supply can be used to ignite the arc, to provide the current for the arc itself, to generate the magnetic field in the filter, and provide its positive electric biasing without any additional high power resistance.

  19. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  20. Development of a 1 J short pulse tunable TEA CO2 laser with high energy stability

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Reghu, T.; Biswas, A. K.; Bhargav, Pankaj; Pakhare, J. S.; Kumar, Shailesh; Verma, Abrat; Mandloi, Vagesh; Kukreja, L. M.

    2014-12-01

    The design, development and operational characteristics of a 1 J, repetitively pulsed, line tunable TEA CO2 laser producing nearly tail free short pulses (~170 ns) suitable for laser isotope separation is discussed. Tail free short laser pulses were generated by employing a nitrogen lean gaseous active medium. Use of an indigenously developed stable pulsed power supply, uniform and intense UV spark pre-ionization and optimum gas purging with catalytic regeneration to control the deleterious oxygen accumulation helps generate laser pulses with high energy stability. Integration of a sensitive arc detection system allows long term arc-free operation of the laser and protects it from catastrophic failure. Laser pulses in more than 90 lines in 10.6 μm and 9.6 μm bands of CO2 laser spectrum with energy about 1 J in as many as 50 lines could be generated with a typical efficiency of about 4%. A typical pulse to pulse energy stability of ±1.4% was obtained during one hour of continuous operation of the TEA CO2 laser at 75 Hz.

  1. Short Pulse Laser Production of Diamond Thin Films

    SciTech Connect

    Banks, P.S.; Stuart, B.C.; Dinh, L.; Feit, M.D.; Rubenchik, A.M.; McLean, W.; Perry, M.D.

    1998-03-20

    The use of diamond thin films has the potential for major impact in many industrial and scientific applications. These include heat sinks for electronics, broadband optical sensors, windows, cutting tools, optical coatings, laser diodes, cold cathodes, and field emission displays. Attractive properties of natural diamond consist of physical hardness, high tensile yield strength, chemical inertness, low coefficient of friction, high thermal conductivity, and low electrical conductivity. Unfortunately, these properties are not completely realized in currently produced diamond thin films. Chemical vapor deposition, in its many forms, has been the most successful to this point in producing crystalline diamond films microns to millimeters in thickness which are made up of closely packed diamond crystals microns in physical dimension. However, high purity films are difficult to realize due to the use of hydrogen in the growth process which becomes included in the film matrix. These impurities are manifest in film physical properties which are inferior to those of pure crystalline diamond. In addition, the large density of grain boundaries due to the polycrystalline nature of the films reduce the films' diamond-like character. Finally, substrates must be heated to several hundred degrees Celsius which is not suitable for many materials. Pulsed laser deposition is attractive due to its ability to produce high purity films-limited only by the purity of the target. For diamond film production, high purity carbon can be ablated directly by lasers and deposited as thin films at ambient temperatures. However, lasers currently in use generally deliver long (>10 ns) pulses, and the generally explosive nature of laser ablation, in addition to the desired single-atom or single-ion carbon, liberates significant amounts of carbon clusters (C{sub n} where n=2-30) and macroscopic particles (> 1-10 pm) of carbon. These carbon particles interrupt the ordered deposition of crystalline

  2. Flashover lithium ion source development for large pulsed power accelerators

    SciTech Connect

    Bieg, K.W.; Burns, E.J.T.; Gerber, R.A.; Olsen, J.N.; Lamppa, K.P.

    1985-01-01

    PBFA II, a light-ion pulsed power accelerator intended for inertial confinement fusion (ICF) applications, is currently under construction at Sandia National Laboratories. The accelerator will deliver a 30 MV, 5 MA lithium beam from an Applied-B diode to drive an ICF target. The ion source for this diode will require a thin (approx.1 mm), dense (10 W cm S) anode plasma layer of singly-ionized lithium over an anode area of 10T cmS. One type of source being investigated is the flashover ion source, which generates the anode plasma via vacuum flashover of a lithium-bearing dielectric material. Experiments with a LiF flashover source on the 0.03 TW Nereus accelerator have shown that contaminant ions account for as much as 70% of the extracted ion beam current. To overcome this, we have explored in-diode cleaning of the externally-prepared anode surface by glow discharge cleaning and vacuum baking as well as in-diode preparation of the anode surface by vacuum evaporation of the lithium dielectric. Lithium-bearing dielectric materials which have been investigated include LiF, LiI, LiNO3, and Li3N. These techniques have resulted in a two- to three-fold improvement in the extracted lithium ion purity. As a result, a glow-discharge cleaned LiF flashover source will be used for initial pulsed-power testing on PBFA II.

  3. Longitudinally excited CO2 laser with short laser pulse for hard tissue drilling

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Hayashi, Hiroyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2014-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with a circular beam and a low divergence angle. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse width of 103 ns and a pulse tail length of 32.6 μs. The beam cross-section was circular and the full-angle beam divergence was 1.7 mrad. The laser was used to drill ivory samples without carbonization at fluences of 2.3-7.1 J/cm2. The drilling depth of the dry ivory increased with the fluence. The drilling mechanism of the dry ivory was attributed to absorption of the laser light by the ivory.

  4. Forward voltage short-pulse technique for measuring high power laser array junction temperature

    NASA Technical Reports Server (NTRS)

    Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)

    2012-01-01

    The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

  5. Short-pulse, high-energy radiation generation from laser-wakefield accelerated electron beams

    NASA Astrophysics Data System (ADS)

    Schumaker, Will

    2013-10-01

    Recent experimental results of laser wakefield acceleration (LWFA) of ~GeV electrons driven by the 200TW HERCULES and the 400TW ASTRA-GEMINI laser systems and their subsequent generation of photons, positrons, and neutrons are presented. In LWFA, high-intensity (I >1019 W /cm2), ultra-short (τL < 1 / (2 πωpe)) laser pulses drive highly nonlinear plasma waves which can trap ~ nC of electrons and accelerate them to ~GeV energies over ~cm lengths. These electron beams can then be converted by a high-Z target via bremsstrahlung into low-divergence (< 20 mrad) beams of high-energy (<600 MeV) photons and subsequently into positrons via the Bethe-Heitler process. By increasing the material thickness and Z, the resulting Ne+ /Ne- ratio can approach unity, resulting in a near neutral density plasma jet. These quasi-neutral beams are presumed to retain the short-pulse (τL < 40 fs) characteristic of the electron beam, resulting in a high peak density of ne- /e+ ~ 1016 cm-3 , making the source an excellent candidate for laboratory study of astrophysical leptonic jets. Alternatively, the electron beam can be interacted with a counter-propagating, ultra-high intensity (I >1021 W /cm2) laser pulse to undergo inverse Compton scattering and emit a high-peak brightness beam of high-energy photons. Preliminary results and experimental sensitivities of the electron-laser beam overlap are presented. The high-energy photon beams can be spectrally resolved using a forward Compton scattering spectrometer. Moreover, the photon flux can be characterized by a pixelated scintillator array and by nuclear activation and (γ,n) neutron measurements from the photons interacting with a secondary solid target. Monte-Carlo simulations were performed using FLUKA to support the yield estimates. This research was supported by DOE/NSF-PHY 0810979, NSF CAREER 1054164, DARPA AXiS N66001-11-1-4208, SF/DNDO F021166, and the Leverhulme Trust ECF-2011-383.

  6. Ultra-short DBR fiber laser based sensor for arterial pulse monitoring

    NASA Astrophysics Data System (ADS)

    Sun, Qizhen; Wo, Jianghai; Wang, He; Liu, Deming

    2014-05-01

    An ultra-short DBR fiber laser based device for arterial pulse wave monitoring is proposed and demonstrated. As the sensing element, the 10mm length laser cavity is mounted onto a soft plastic plate and then embedded into textile. Deformation of the textile, involving the transverse force subjected by the laser cavity, is proportional to the vibration caused by the arterial pulse. The sensing principle is based on the linear relationship between the beat frequency of the laser and the transverse force. Laboratory studies demonstrate that the sensor could achieve real-time and accurate measurement of the weak and dynamical arterial pulse signal.

  7. Theoretical and experimental studies of ultra-short pulsed laser drilling of steel

    NASA Astrophysics Data System (ADS)

    Michalowski, Andreas; Qin, Yuan; Weber, Rudolf; Graf, Thomas

    2014-05-01

    Methods for the machining of metals based on the use of ultra-short pulsed laser radiation continue to gain importance in industrial production technology. Theoretical considerations and experimental studies on laser drilling of steel are discussed. The applicability of geometrical optics to calculate the absorbed energy distribution inside small blind holes is investigated theoretically. A model for melt transport during ultra-short pulsed drilling is proposed and verified experimentally. It confirms that helical drilling is advantageous for machining burr-free holes.

  8. High efficiency long pulse gigawatt sources of HPM radiation

    NASA Astrophysics Data System (ADS)

    Arman, M. Joseph

    1999-05-01

    The High Power Microwave (HPM) technology has advanced tremendously in the last five decades. What started out as a mere passive tool in the form of radar for detecting airborne objects during the second world war, has grown to be an active vehicle that can influence and impact its target. Progress has been made in all fronts. The peak radiated power has gone up several orders of magnitude to several gigawatts, the efficiency has grown by a wide margin, and the total energy radiated for pulsed sources has grown to several hundreds of Jules per pulse. Major obstacles still exist. The number of sources that have already achieved one gigawatt or higher is too great to cover here. In what follows, we will briefly describe the sources that have radiated one gigawatt or higher with a pulselength of 300 ns or longer, and an rms efficiency of 10% or higher. We also address the obstacles lying ahead and suggest possible means of overcoming them. The sources presented are the Relativistic Klystron Oscillator (RKO), the Magnetically Insulated Line Oscillator (MILO), and the Tapered Magnetically Insulated Line Oscillator (TMILO).

  9. Electroacoustic pulse source for high-resolution seismic explorations

    NASA Astrophysics Data System (ADS)

    Cannelli, G. B.; D'Ottavi, E.; Santoboni, S.

    1987-07-01

    We suggest an electroacoustic pulse source with frequency characteristics, directivity pattern, and energy suitable for high-resolution prospecting on land and underwater. The seismic wave is produced by a high-energy discharge, set in the focus of a parabolic aluminum reflector filled with insulating liquids. The acoustic pulse is transmitted to the soil via a neoprene diaphragm that couples the transducer to the earth. The discharge is primed by a low-energy preliminary spark, via a third electrode between the principal electrodes, which produces the liquid ionization. An important feature of the electroacoustic source is the variation of frequency spectrum of the impulse, by changing electrical parameters such as capacitance and inductance. The directivity pattern can be changed by inching the electrodes up or down with reference to the focus. First field measurements showed better penetration capacity of the seismic wave of the paraboloid in comparison with a traditional mechanical source. This electroacoustic source can be utilized on land, and even more successfully in underwater acoustic prospecting, by providing suitable electric insulation. In this latter application the frequency range is higher than that used for land prospecting.

  10. Pulsed, atmospheric pressure plasma source for emission spectrometry

    DOEpatents

    Duan, Yixiang; Jin, Zhe; Su, Yongxuan

    2004-05-11

    A low-power, plasma source-based, portable molecular light emission generator/detector employing an atmospheric pressure pulsed-plasma for molecular fragmentation and excitation is described. The average power required for the operation of the plasma is between 0.02 W and 5 W. The features of the optical emission spectra obtained with the pulsed plasma source are significantly different from those obtained with direct current (dc) discharge higher power; for example, strong CH emission at 431.2 nm which is only weakly observed with dc plasma sources was observed, and the intense CN emission observed at 383-388 nm using dc plasma sources was weak in most cases. Strong CN emission was only observed using the present apparatus when compounds containing nitrogen, such as aniline were employed as samples. The present apparatus detects dimethylsulfoxide at 200 ppb using helium as the plasma gas by observing the emission band of the CH radical. When coupled with a gas chromatograph for separating components present in a sample to be analyzed, the present invention provides an apparatus for detecting the arrival of a particular component in the sample at the end of the chromatographic column and the identity thereof.

  11. 3-D simulation of high-intensity ultra-short laser pulse propagation through atmospheric optical systems

    NASA Astrophysics Data System (ADS)

    Dodd, Evan S.; Schmitt, Mark J.

    2001-10-01

    The manipulation of ultra-short pulses (USPs) in the laboratory is affected by three main factors; (a) the layout of optical elements in the optical train, (b) the non-linear interaction of the pulse with the transmissive optical elements (including the intervening atmosphere) and (c) ionization effects near beam focal regions. These effects have been included in our simulation code in order to examine 3-D aspects of USP propagation through "real" optical systems. Our models for optical elements include the ability to examine the effects of element misalignments and asymmetric finite apertures. In the atmosphere, we have included the effect of the USP electric field intensity on the local index of refraction. A model to include the effects of ionization in the atmosphere has also been added. The collective behavior from these sources results in complex interactions within the laser pulse as it propagates. This is important since it reduces the distance the pulse may travel and the spatial and temporal energy distribution of the pulse after propagation. Simulation examples are presented.

  12. 5 MW pulsed spallation neutron source, Preconceptual design study

    SciTech Connect

    Not Available

    1994-06-01

    This report describes a self-consistent base line design for a 5 MW Pulsed Spallation Neutron Source (PSNS). It is intended to establish feasibility of design and as a basis for further expanded and detailed studies. It may also serve as a basis for establishing project cost (30% accuracy) in order to intercompare competing designs for a PSNS not only on the basis of technical feasibility and technical merit but also on the basis of projected total cost. The accelerator design considered here is based on the objective of a pulsed neutron source obtained by means of a pulsed proton beam with average beam power of 5 MW, in {approx} 1 {mu}sec pulses, operating at a repetition rate of 60 Hz. Two target stations are incorporated in the basic facility: one for operation at 10 Hz for long-wavelength instruments, and one operating at 50 Hz for instruments utilizing thermal neutrons. The design approach for the proton accelerator is to use a low energy linear accelerator (at 0.6 GeV), operating at 60 Hz, in tandem with two fast cycling booster synchrotrons (at 3.6 GeV), operating at 30 Hz. It is assumed here that considerations of cost and overall system reliability may favor the present design approach over the alternative approach pursued elsewhere, whereby use is made of a high energy linear accelerator in conjunction with a dc accumulation ring. With the knowledge that this alternative design is under active development, it was deliberately decided to favor here the low energy linac-fast cycling booster approach. Clearly, the present design, as developed here, must be carried to the full conceptual design stage in order to facilitate a meaningful technology and cost comparison with alternative designs.

  13. Brighter H/sup -/ source for the intense pulsed neutron source accelerator system

    SciTech Connect

    Stipp, V.; DeWitt, A.; Madsen, J.

    1983-01-01

    Further increases in the beam intensity of the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory required the replacement of the H/sup -/ source with a higher current source. A magnetron ion source of Fermi National Accelerator Laboratory (FNAL) design was adapted with a grooved cathode to provide a stable 40 to 50 mA of beam operating at 30 Hz for up to a 90 ..mu..s pulse duration. Problems of space charge blowup due to the lack of neutralization of the H/sup -/ beam were solved by injecting additional gs into the 20 keV transport system. The source has recently been installed in the machine and the available input to the accelerator has more than doubled.

  14. Generation of an ultra-short electrical pulse with width shorter than the excitation laser

    PubMed Central

    Shi, Wei; Wang, Shaoqiang; Ma, Cheng; Xu, Ming

    2016-01-01

    We demonstrate experimentally a rare phenomenon that the width of an electrical response is shorter than that of the excitation laser. In this work, generation of an ultrashort electrical pulse is by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) and the generated electrical pulse width is shorter than that of the excitation laser from diode laser. When the pulse width and energy of the excitation laser are fixed at 25.7 ns and 1.6 μJ respectively, the width of the generated electrical pulse width by 3-mm-gap GaAs PCSS at the bias voltage of 9 kV is only 7.3 ns. The model of photon-activated charge domain (PACD) is used to explain the peculiar phenomenon in our experiment. The ultrashort electrical pulse width is mainly relevant to the time interval of PACD from occurrence to disappearance in the mode. The shorter the time interval is, the narrower the electrical pulse width will become. In more general terms, our result suggests that in nonlinear regime a response signal can have a much short width than the excitation pulses. The result clearly indicates that generating ultrashort electrical pulses can be achieved without the need of ultrashort lasers. PMID:27273512

  15. Investigation of a high power electromagnetic pulse source.

    PubMed

    Wang, Yuwei; Chen, Dongqun; Zhang, Jiande; Cao, Shengguang; Li, Da; Liu, Chebo

    2012-09-01

    A high power electromagnetic pulse source with a resonant antenna driven by a compact power supply was investigated in this paper. To match the impedance of the resonant antenna and initial power source, a compact power conditioning circuit based on electro exploding opening switch (EEOS) and pulsed transformer was adopted. In the preliminary experiments, an impulse capacitor was used to drive the system. With the opening of the EEOS at the current of 15 kA flowing trough the primary of the transformer, the resonant antenna was rapidly charged to about -370 kV within a time of about 100 ns. When the switch in the resonant antenna closed at the charging voltage of about -202 kV, the peak intensity of the detected electric field at a distance of about 10 m from the center of the source was 7.2 kV∕m. The corresponding peak power of the radiated electromagnetic field reached 76 MW, while the total radiated electromagnetic energy was about 0.65 J. The total energy efficiency of the resonant antenna was about 22% which can be improved by increasing the closing rapidity of the switch in the antenna.

  16. Analysis of the stability of an active mode-locking pulsed laser for ultra-short pulses generation

    NASA Astrophysics Data System (ADS)

    Bracamontes Rodríguez, Y. E.; Beltrán Pérez, G.; Kuzin, Eugin; Castillo Mixcóatl, J.; Muñoz Aguirre, S.

    2013-11-01

    Pulsed lasers have become very important owing to the great amount of applications, from communications to diverse medicine areas. Many works have reported the development of these kinds of sources which uses quite complex cavity configurations and that present instabilities in the output signal. In this work the analysis of a pulsed laser that uses a ring cavity with a length of 16.5 m is presented. A phase modulator (LiNbO3) controlled by an RF generator operated at a frequency of 12.5108 MHz was used to perform the mode lock. The modulator input has a birrefringent fiber then the light polarization affects the mode lock. Therefore it was necessary to perform an analysis and characterization in the input and output signals of the modulator in order to obtain more stable output pulses without requiring a continuous adjustment. The laser implemented with 2 modes of operation, active mode-lock and passive mode-lock. The obtained pulses whit temporal width of 7 ns FWHM for the frequency fundamental 12.5108 MHz and 781 -261-120-116 ps for the harmonic 5-10-16-20 .The results for the passive mode-lock the obtained pulses whit temporal width 2 ps and average power 200 W.

  17. Bone tissue heating and ablation by short and ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Letfullin, Renat R.; Rice, Colin E. W.; George, Thomas F.

    2010-02-01

    Biological hard tissues, such as those found in bone and teeth, are complex tissues that build a strong mineral structure over an organic matrix framework. The laser-matter interaction for bone hard tissues holds great interest to laser surgery and laser dentistry; the use of short/ultrashort pulses, in particular, shows interesting behaviors not seen in continuous wave lasers. High laser energy densities in ultrashort pulses can be focused on a small irradiated surface (spot diameter is 10-50 μm) leading to rapid temperature rise and thermal ablation of the bone tissue. Ultrashort pulses, specifically those in the picosecond and femtosecond ranges, impose several challenges in modeling bone tissue response. In the present paper we perform time-dependent thermal simulations of short and ultrashort pulse laser-bone interactions in singlepulse and multipulse (set of ultrashort pulses) modes of laser heating. A comparative analysis for both radiation modes is discussed for laser heating of different types of the solid bone on the nanosecond, picosecond and femtosecond time scales. It is shown that ultrashort laser pulses with high energy densities can ablate bone tissue without heating tissues bordering the ablation creator. This reaction is particularly desirable as heat accumulation and thermal damage are the main factors affecting tissue regrowth rates, and thus patient recovery times.

  18. Incremental growth of short SWNT arrays by pulsed chemical vapor deposition.

    PubMed

    Puretzky, Alexander A; Geohegan, David B; Jackson, Jeremy J; Pannala, Sreekanth; Eres, Gyula; Rouleau, Christopher M; More, Karren L; Thonnard, Norbert; Readle, Jason D

    2012-05-21

    Very short arrays of continuous single-wall carbon nanotubes (SWNTs) are grown incrementally in steps as small as 25 nm using pulsed chemical vapor deposition (CVD). In-situ optical extinction measurements indicate that over 98% of the nanotubes reinitiate growth on successive gas pulses, and high-resolution transmission electron microscopy (HR-TEM) images show that the SWNTs do not exhibit segments, caps, or noticeable sidewall defects resulting from repeatedly stopping and restarting growth. Time-resolved laser reflectivity (3-ms temporal resolution) is used to record the nucleation and growth kinetics for each fast (0.2 s) gas pulse and to measure the height increase of the array in situ, providing a method to incrementally grow short nanotube arrays to precise heights. Derivatives of the optical reflectivity signal reveal distinct temporal signatures for both nucleation and growth kinetics, with their amplitude ratio on the first gas pulse serving as a good predictor for the evolution of the growth of the nanotube ensemble into a coordinated array. Incremental growth by pulsed CVD is interpreted in the context of autocatalytic kinetic models as a special processing window in which a sufficiently high flux of feedstock gas drives the nucleation and rapid growth phases of a catalyst nanoparticle ensemble to occur within the temporal period of the gas pulse, but without inducing growth termination.

  19. Towards pump-probe experiments of defect dynamics with short ion beam pulses

    NASA Astrophysics Data System (ADS)

    Schenkel, T.; Lidia, S. M.; Weis, C. D.; Waldron, W. L.; Schwartz, J.; Minor, A. M.; Hosemann, P.; Kwan, J. W.

    2013-11-01

    A novel, induction type linear accelerator, the Neutralized Drift Compression eXperiment (NDCX-II), is currently being commissioned at Berkeley Lab. This accelerator is designed to deliver intense (up to 3 × 1011 ions/pulse), 0.6 to ∼600 ns duration pulses of 0.05-1.2 MeV lithium ions at a rate of about 2 pulses per minute onto 1-10 mm scale target areas. When focused to mm-diameter spots, the beam is predicted to volumetrically heat micrometer thick foils to temperatures of ∼30,000 °K. At lower beam power densities, the short excitation pulse with tunable intensity and time profile enables pump-probe type studies of defect dynamics in a broad range of materials. We briefly describe the accelerator concept and design, present results from beam pulse shaping experiments and discuss examples of pump-probe type studies of defect dynamics following irradiation of materials with intense, short ion beam pulses from NDCX-II.

  20. Towards pump probe experiments of defect dynamics with short ion beam pulses

    SciTech Connect

    Schenkel, T.; Lidia, S.; Weis, C. D.; Waldron, W. L.; Schwartz, J.; Minor, Andrew; Hosemann, P; Kwan, J. W.

    2013-01-01

    A novel, induction type linear accelerator, the Neutralized Drift Compression eXperiment (NDCX-II), is currently being commissioned at Berkeley Lab. This accelerator is designed to deliver intense (up to 3 1011 ions/pulse), 0.6 to 600 ns duration pulses of 0.05 1.2 MeV lithium ions at a rate of about 2 pulses per minute onto 1 10 mm scale target areas. When focused to mm-diameter spots, the beam is predicted to volumetrically heat micrometer thick foils to temperatures of 30,000 K. At lower beam power densities, the short excitation pulse with tunable intensity and time profile enables pump probe type studies of defect dynamics in a broad range of materials. We briefly describe the accelerator concept and design, present results from beam pulse shaping experiments and discuss examples of pump probe type studies of defect dynamics following irradiation of materials with intense, short ion beam pulses from NDCX-II.

  1. Nonconstant ponderomotive energy in above-threshold ionization by intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Della Picca, R.; Gramajo, A. A.; Garibotti, C. R.; López, S. D.; Arbó, D. G.

    2016-02-01

    We analyze the contribution of the quiver kinetic energy acquired by an electron in an oscillating electric field of a short laser pulse to the energy balance in atomic ionization processes. Due to the time dependence of this additional kinetic energy, a temporal average is assumed to preserve a stationary energy conservation rule, which is used to predict the position of the energy peaks observed in the photoelectron (PE) spectra. For a plane wave and a flattop pulse, the mean value of the quiver energy over the whole pulse leads to the concept of ponderomotive energy Up. However, for a short pulse with a fast changing intensity, the stationary approximation loses its validity. We check these concepts by studying first the PE spectrum within the semiclassical model (SCM) for multiple-step pulses. The SCM offers the possibility to establish a connection between emission times and the PE spectrum in the energy domain. We show that PE substructures stem from ionization at different times mapping the pulse envelope. We also analyze the PE spectrum for a realistic sine-squared envelope within the Coulomb-Volkov and ab initio calculations solving the time-dependent Schrödinger equation. We found that the electron emission amplitudes produced at different times interfere with each other producing, in this way, a new additional pattern that modulates the above-threshold ionization (ATI) peaks.

  2. Streak camera measurements of laser pulse temporal dispersion in short graded-index optical fibers

    SciTech Connect

    Lerche, R.A.; Phillips, G.E.

    1981-08-28

    Streak camera measurements were used to determine temporal dispersion in short (5 to 30 meter) graded-index optical fibers. Results show that 50-ps, 1.06-..mu..m and 0.53-..mu..m laser pulses can be propagated without significant dispersion when care is taken to prevent propagation of energy in fiber cladding modes.

  3. Feasibility study on a short-pulsed IR wavelength for effective calculus fragmentation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2015-05-01

    Laser-induced lithotripsy has been used for a minimally-invasive surgery to treat kidney-stone disease associated with urinary obstruction. A short-pulsed Tm:YAG laser (λ = 2.01 µm) was developed to improve fragmentation efficiency and was evaluated with a Ho:YAG laser (λ = 2.12 μm) as to its ablation feature and mass removal rate. Application of a train of sub-microsecond pulses with a lower energy at a frequency of 500 Hz created multiple events of cavitation that accompanied strong acoustic transients. During Tm:YAG irradiation, both high light absorption and secondary photomechanical impacts readily fragmented the calculus into small pieces (< 3 mm) and removed them 130 times faster than photothermal Ho:YAG lithotripsy. The proposed short-pulsed Tm:YAG approach may be an effective lithotripter for treating calculus disease.

  4. K-(alpha) Radiography at 20-100 keV Using Short-Pulse Lasers

    SciTech Connect

    Park, H S; Chambers, D; Clarke, R; Eagleton, R; Giraldez, E; Goldsack, T; Heathcote, R; Izumi, N; Key, M; King, J; Koch, J; Landen, O L; Mackinnon, A; Nikroo, A; Patel, P; Pasley, J; Remington, B; Robey, H; Snavely, R; Steinman, D; Stephenson, R; Stoeckl, C; Storm, M; Tabak, M; Theobald, W; Town, R J

    2005-08-29

    X-ray radiography is an important tool for diagnosing and imaging planar and convergent hydrodynamics phenomena for laser experiments. Until now, hydrodynamics experiments at Omega and NIF utilize E{sub x-ray} < 9 keV backlighter x-rays emitted by thermal plasmas. However, future experiments will need to diagnose larger and denser targets and will require x-ray probes of energies from 20-100 keV and possibly up to 1 MeV. Hard K-{alpha} x-ray photons can be created through high-energy electron interactions in the target material after irradiation by petawatt-class high-intensity-short-pulse lasers with > 10{sup 17} W/cm{sup 2}. We have performed several experiments on the JanUSP, and the Vulcan 100TW, and Vulcan Petawatt lasers to understand K-{alpha} sources and to test radiography concepts. 1-D radiography using an edge-on foil and 2-D radiography using buried wires and cone-fiber targets were tested. We find that 1-D thin edge-on foils can have imaging resolution better than 10 {micro}m. Micro volume targets produce bright sources with measured conversion efficiency from laser energy to x-ray photons of {approx} 1 x 10{sup -5}. This level of conversion may not be enough for 2-D point projection radiography. A comparison of our experimental measurements of small volume sources with the LSP/PIC simulation show similar K-{alpha} creation profiles but discrepancy in absolute yields.

  5. Flashover lithium ion source development for large pulsed power accelerators

    SciTech Connect

    Bieg, K.W.; Burns, E.J.T.; Gerber, R.A.; Olsen, J.N.; Lamppa, K.P.

    1986-05-01

    The Particle Beam Fusion Accelerator II (PBFA II), a light-ion pulsed power accelerator intended for inertial confinement fusion (ICF) applications, is currently under construction at Sandia National Laboratories. The accelerator will deliver a 30 MV, 5 MA lithium beam from an Applied-B diode to drive an ICF target. The ion source for this diode will require a thin (approx.1 mm), dense (10/sup 16/ cm/sup -2/) anode plasma layer of singly ionized lithium over an anode area of 10/sup 3/ cm/sup 2/. One type of source being investigated is the flashover ion source, which generates the anode plasma via vacuum flashover of a lithium-bearing dielectric material. Experiments with a LiF flashover source on the 0.03 TW Nereus accelerator have shown that contaminant ions account for as much as 70% of the extracted ion beam current. To overcome this, we have explored in-diode cleaning of the externally prepared anode surface by glow discharge cleaning and vacuum baking as well as in-diode preparation of the anode surface by vacuum evaporation of the lithium dielectric. Lithium-bearing dielectric materials which have been investigated include LiF, LiI, LiNO/sub 3/, and Li/sub 3/N. These techniques have resulted in a two to threefold improvement in the extracted lithium ion purity. As a result, a glow-discharge cleaned LiF flashover source will be used for initial pulsed-power testing on PBFA II.

  6. Time of flight emission spectroscopy of laser produced nickel plasma: Short-pulse and ultrafast excitations

    SciTech Connect

    Smijesh, N.; Chandrasekharan, K.; Joshi, Jagdish C.; Philip, Reji

    2014-07-07

    We report the experimental investigation and comparison of the temporal features of short-pulse (7 ns) and ultrafast (100 fs) laser produced plasmas generated from a solid nickel target, expanding into a nitrogen background. When the ambient pressure is varied in a large range of 10⁻⁶Torr to 10²Torr, the plume intensity is found to increase rapidly as the pressure crosses 1 Torr. Time of flight (TOF) spectroscopy of emission from neutral nickel (Ni I) at 361.9 nm (3d⁹(²D) 4p → 3d⁹(²D) 4s transition) reveals two peaks (fast and slow species) in short-pulse excitation and a single peak in ultrafast excitation. The fast and slow peaks represent recombined neutrals and un-ionized neutrals, respectively. TOF emission from singly ionized nickel (Ni II) studied using the 428.5 nm (3p⁶3d⁸(³P) 4s→ 3p⁶3d⁹ 4s) transition shows only a single peak for either excitation. Velocities of the neutral and ionic species are determined from TOF measurements carried out at different positions (i.e., at distances of 2 mm and 4 mm, respectively, from the target surface) on the plume axis. Measured velocities indicate acceleration of neutrals and ions, which is caused by the Coulomb pull of the electrons enveloping the plume front in the case of ultrafast excitation. Both Coulomb pull and laser-plasma interaction contribute to the acceleration in the case of short-pulse excitation. These investigations provide new information on the pressure dependent temporal behavior of nickel plasmas produced by short-pulse and ultrafast laser pulses, which have potential uses in applications such as pulsed laser deposition and laser-induced nanoparticle generation.

  7. Fluctuations of energy density of short-pulse optical radiation in the turbulent atmosphere.

    PubMed

    Banakh, V A; Smalikho, I N

    2014-09-22

    Fluctuations of energy density of short-pulse optical radiation in the turbulent atmosphere have been studied based on numerical solution of the parabolic wave equation for the complex spectral amplitude of the wave field by the split-step method. It has been shown that under conditions of strong optical turbulence, the relative variance of energy density fluctuations of pulsed radiation of femtosecond duration becomes much less than the relative variance of intensity fluctuations of continuous-wave radiation. The spatial structure of fluctuations of the energy density with a decrease of the pulse duration becomes more large-scale and homogeneous. For shorter pulses the maximal value of the probability density distribution of energy density fluctuations tends to the mean value of the energy density.

  8. The evolution of ultra-intense, short-pulse lasers in underdense plasmas

    SciTech Connect

    Decker, C.D.; Mori, W.B.; Tzeng, K.C.

    1995-11-03

    The propagation of short-pulse lasers through underdense plasmas at ultra-high intensities (I {>=}10{sup 19}W/cm) is examined. The pulse evolution is found to be significantly different than it is for moderate intensities. Rather than beam breakup from self-modulation, Raman forward scattering and laser hose instabilities the behavior is dominated by leading edge erosion. A differential equation which describes local pump depletion is derived and used to analyze the formation and evolution of the erosion. This pulse erosion is demonstrated with one dimensional particle in cell (PIC) simulations. In addition, two dimensional simulations are presented which show pulse erosion along with other effects such as channeling and diffraction.

  9. Bremsstrahlung measurements for characterization of intense short-pulse, laser produced fast electrons with OMEGA EP

    NASA Astrophysics Data System (ADS)

    Daykin, Tyler; Sawada, Hiroshi; Sentoku, Yasuhiko; Pandit, Rishi; Chen, Cliff; Beg, Farhat; Chen, Hui; McLean, Harry; Patel, Pravesh; Tommasini, Riccardo

    2016-10-01

    Understanding relativistic fast electron generation and transport inside solids is important for applications such as generation of high energy x-ray sources and fast ignition. An experiment was carried out to study the scaling of the fast electron spectrum and bremsstrahlung generation in multi-pico second laser interactions using 1 ps and 10 ps OMEGA EP short-pulse beam to generate fast electrons at a similar peak intensity of 5x1018 W/cm2. The bremsstrahlung produced by collisions of the fast electrons with background ions was recorded using differential filter stacked spectrometers. A preliminary analysis with a Monte Carlo Code ITS shows that the electrons injection having an electron slope 1.8 MeV matched well with the high energy component of the 1 ps and 10 ps bremsstrahlung measurements. Details of the data analysis and modeling with Monte Carlo and a hybrid particle-in-cell codes will be presented at the conference. Work supported by the UNR Office of the Provost and by DOE/OFES under Contract No. DE-SC0008827. This collaborative work was partially supported under the auspices of the US DOE by LLNL under Contracts No. DE-AC52-07NA27344 and No. DE-FG-02-05ER54834.

  10. Lattice Boltzmann method for short-pulsed laser transport in a multi-layered medium

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

    2015-04-01

    We construct a lattice Boltzmann method (LBM) for transient radiative transfer in one-dimensional multi-layered medium with distinct refractive index in each layer. The left boundary is irradiated normally by a short-pulsed laser. The Fresnel interfaces conditions, which incorporate reflection and refraction, are used at the boundaries and the interfaces. Based on the Fresnel's law and Snell's law, the interfacial intensity formulas are introduced. The collimated and diffuse intensities are treated individually. At a transient time step, the collimated component is first solved by LBM and then embedded into the transient radiative transfer equation as a source term. To keep the consistency of the directions in all the layers, angular interpolation of the intensities at the interfaces is adopted. The transient radiative transfer in a two-layer medium is first investigated, and the time-resolved results are validated by comparing with those by the Monte Carlo method (MCM). Of particular interest, the angular intensities along the slab at different times are presented to illustrate a variety of interesting phenomena, and the discontinuous nature of the intensity at the interfaces is discussed. The effects of various parameters on the time-resolved signals are examined.

  11. Molecular dynamics induced by short and intense x-ray pulses from the LCLS

    NASA Astrophysics Data System (ADS)

    Berrah, Nora

    2016-12-01

    The past six years have led to a wealth of experimental and theoretical data revealing the nature of the interaction between gas-phase molecules and short and intense x-ray pulses, from the Linac coherent light source free electron laser (FEL). We present here a few highlights that describe some of the first photoabsorption measurements of gas-phase molecules. In particular, we report on a three decades long prediction of single-site double core holes (ss-DCH) and two-site double core holes (ts-DCH) in diatomic and triatomic molecules. We also describe recent measurements that validate a simple theory regarding femtosecond intense x-ray induced fragmentation dynamics of C60 as well as photoabsorption measurements of encapsulated fullerenes, Ho3N@C80. The latter investigation opens the way for even more complex molecular studies with FELs. In all of the described highlights, working in close collaboration with theorists enabled the interpretation of, or predicted our measurements, and in some cases our experiments guided the modeling. We conclude this article by describing the potential of new instrumentation for chemical and biological sciences especially in light of new or improved FELs.

  12. Portable radiation detection system for pulsed high energy photon sources

    SciTech Connect

    Harker, Y.D.; Lawrence, R.S.; Yoon, W.Y.

    1994-12-31

    Portable, battery-operated, radiation detection systems for measuring the intensity and energy characteristics of intense, pulsed photon sources (either high energy X-ray or gamma) have been developed at the Idaho National Engineering Laboratory. These field-deployable, suitcase-sized detection units are designed to measure and record the characteristics of a single radiation burst or multiple bursts from a pulsed ionizing radiation source. The recorded information can then be analyzed on a simple laptop computer at a location remote from the detection system and completely independent of the ongoing data acquisition process. Two detection unit designs are described. The first, called the MARK-1, has eight bismuth germanate (BGO) radiation detectors. Four of which are unshielded and have different thicknesses (diameters). The remaining four are the same size as the largest unshielded detector but have different thicknesses of lead shielding surrounding each detector. The second unit design, called the MARK-1 A, utilizes the same detection methodology as the MARK-1 but has ten BGO detectors instead of eight and utilizes a different method of amplifying detector signals enabling reduced overall size and weight of the detection unit. Both the detection system designs have sensitivity ranges from 3 x 10{sup {minus}9} cGy to 9 x 10{sup {minus}5} cGy per radiation burst. Experimental detection results will be presented and discussed along the systems` potential for commercial applications.

  13. Generating high-power short terahertz electromagnetic pulses with a multifoil radiator.

    PubMed

    Vinokurov, Nikolay A; Jeong, Young Uk

    2013-02-08

    We describe a multifoil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For transverse electromagnetic waves with a longitudinal (along the z axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawatt-level peak power can be generated with this device.

  14. Temporal resolution and temporal integration of short pulses at the auditory periphery of echolocating animals

    NASA Astrophysics Data System (ADS)

    Rimskaya-Korsakova, L. K.

    2004-05-01

    To explain the temporal integration and temporal resolution abilities revealed in echolocating animals by behavioral and electrophysiological experiments, the peripheral coding of sounds in the high-frequency auditory system of these animals is modeled. The stimuli are paired pulses similar to the echolocating signals of the animals. Their duration is comparable with or smaller than the time constants of the following processes: formation of the firing rate of the basilar membrane, formation of the receptor potentials of internal hair cells, and recovery of the excitability of spiral ganglion neurons. The models of auditory nerve fibers differ in spontaneous firing rate, response thresholds, and abilities to reproduce small variations of the stimulus level. The formation of the response to the second pulse of a pair of pulses in the multitude of synchronously excited high-frequency auditory nerve fibers may occur in only two ways. The first way defined as the stochastic mechanism implies the formation of the response to the second pulse as a result of the responses of the fibers that did not respond to the first pulse. This mechanism is based on the stochastic nature of the responses of auditory nerve fibers associated with the spontaneous firing rate. The second way, defined as the repeatition mechanism, implies the appearance of repeated responses in fibers that already responded to the first pulse but suffered a decrease in their response threshold after the first spike generation. This mechanism is based on the deterministic nature of the responses of fibers associated with refractoriness. The temporal resolution of pairs of short pulses, which, according to the data of behavioral experiments, is about 0.1 0.2 ms, is explained by the formation of the response to the second pulse through the stochastic mechanism. A complete recovery of the response to the second pulse, which, according to the data of electrophysiological studies of short-latency evoked brainstem

  15. Oral applications of ultra-short laser pulses: a new approach for gentle and painless treatment?

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Strassl, M.; Wieger, V.; Zoppel, S.; Wintner, E.

    2006-05-01

    In dental hard tissue ablation, ultra-short laser pulses have proven sufficiently their potential for material ablation with negligible collateral damage providing many advantages. The absence of microcracks and the possibility to avoid overheating of the pulp during dental cavity preparation may be among the most important issues, the latter opening up an avenue for potential painless treatment. Beside the evident short interaction time of laser radiation with the irradiated tissue, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of required quality and shape. Additionally, such a technique allows to treat larger areas like the ones dentists are used to work with, i.e. ~ 1 mm Ø.In this paper, an overview of different scanning methods together with the algorithms used and an assessment of their applicability is presented. A variety of pulse durations from ~100 fs up to several ps has been used by numerous authors over the last approximately ten years. Having employed 330 fs pulses, we present the corresponding ablation thresholds for dental hard tissue (enamel, dentine; human and bovine), for a number of dental restoration materials, as well as for different types of bovine bone. Dental implants frequently have to be cleaned from plaque being deposited around their necks in areas where the gums have already retreated. A preliminary investigation is presented on the applicability of ultra-short pulses with mentioned duration for the gentle cleaning of titanium implants focusing on the preservation of the special plasma-sprayed biocompatible implant surface.

  16. Numerical modeling of the intracavity stimulated Raman scattering as a source of subnanosecond optical pulses

    NASA Astrophysics Data System (ADS)

    Yashkir, Yuri M.; Yashkir, Yuriy Y.

    2004-09-01

    We present a computer numerical model (virtual sub-nanosecond laser) utilizing intracavity stimulated Raman scattering. The goal of this work is to shorten laser output pulses (for which the highly nonlinear frequency conversion process stimulated Raman scattering is used) and to obtain high efficiency (which is enhanced by placing a Raman-active crystal inside the cavity where the fundamental laser frequency intensity is maximal). The following laser components were modeled: a diodepumped solidstate laser active medium (a crystal of the Nd3+:YLF type), a closed cavity for a wave on its fundamental frequency with a Q-switching element and an internal subcavity with a Ramanactive crystal with controlled output coupler transmission at the Raman frequency. The model components are: a numerical integrator of a set of three rate equations (for an inverse population of the laser medium and for the number of fundamental and Stokes frequency photons), random number sources for radiation seeding, and an interactive data input interface and graphic output. A wide range of parameters was investigated and output pulses as short as 0.8 ns were found. The optimal conditions for the maximal peak power of Stokes pulses were determined and the conditions for generating pulse trains for burst laser machining were identified.

  17. A compact, short-pulse laser for near-field, range-gated imaging

    SciTech Connect

    Zutavern, F.J.; Helgeson, W.D.; Loubriel, G.M.; Yates, G.J.; Gallegos, R.A.; McDonald, T.E.

    1996-12-31

    This paper describes a compact laser, which produces high power, wide-angle emission for a near-field, range-gated, imaging system. The optical pulses are produced by a 100 element laser diode array (LDA) which is pulsed with a GaAs, photoconductive semiconductor switch (PCSS). The LDA generates 100 ps long, gain-switched, optical pulses at 904 nm when it is driven with 3 ns, 400 A, electrical pulses from a high gain PCSS. Gain switching is facilitated with this many lasers by using a low impedance circuit to drive an array of lasers, which are connected electrically in series. The total optical energy produced per pulse is 10 microjoules corresponding to a total peak power of 100 kW. The entire laser system, including prime power (a nine volt battery), pulse charging, PCSS, and LDA, is the size of a small, hand-held flashlight. System lifetime, which is presently limited by the high gain PCSS, is an active area of research and development. Present limitations and potential improvements will be discussed. The complete range-gated imaging system is based on complementary technologies: high speed optical gating with intensified charge coupled devices (ICCD) developed at Los Alamos National Laboratory (LANL) and high gain, PCSS-driven LDAs developed at Sandia National Laboratories (SNL). The system is designed for use in highly scattering media such as turbid water or extremely dense fog or smoke. The short optical pulses from the laser and high speed gating of the ICCD are synchronized to eliminate the back-scattered light from outside the depth of the field of view (FOV) which may be as short as a few centimeters. A high speed photodiode can be used to trigger the intensifier gate and set the range-gated FOV precisely on the target. The ICCD and other aspects of the imaging system are discussed in a separate paper.

  18. Interaction of ultra-short laser pulses with CIGS and CZTSe thin films

    NASA Astrophysics Data System (ADS)

    Gečys, P.; Markauskas, E.; Dudutis, J.; Račiukaitis, G.

    2014-01-01

    The thin-film solar cell technologies based on complex quaternary chalcopyrite and kesterite materials are becoming more attractive due to their potential for low production costs and optimal spectral performance. As in all thin-film technologies, high efficiency of small cells might be maintained with the transition to larger areas when small segments are interconnected in series to reduce photocurrent and related ohmic losses in thin films. Interconnect formation is based on the three scribing steps, and the use of a laser is here crucial for performance of the device. We present our simulation and experimental results on the ablation process investigations in complex CuIn1- x Ga x Se2 (CIGS) and Cu2ZnSn(S,Se)4 (CZTSe) cell's films using ultra-short pulsed infrared (~1 μm) lasers which can be applied to the damage-free front-side scribing processes. Two types of processes were investigated—direct laser ablation of ZnO:Al/CIGS films with a variable pulse duration of a femtosecond laser and the laser-induced material removal with a picosecond laser in the ZnO:Al/CZTSe structure. It has been found that the pulse energy and the number of laser pulses have a significantly stronger effect on the ablation quality in ZnO:Al/CIGS thin films rather than the laser pulse duration. For the thin-film scribing applications, it is very important to carefully select the processing parameters and use of ultra-short femtosecond pulses does not have a significant advantage compared to picosecond laser pulses. Investigations with the ZnO:Al/CZTSe thin films showed that process of the absorber layer removal was triggered by a micro-explosive effect induced by high pressure of sublimated material due to a rapid temperature increase at the molybdenum-CZTSe interface.

  19. Exploitation of stimulated Raman scattering in short-pulse fiber amplifiers.

    PubMed

    Zhou, Shian; Takamido, Tetsuji; Imai, Shinji; Wise, Frank

    2010-07-15

    Stimulated Raman scattering (SRS) generally limits the performance of short-pulse fiber amplifiers. We present the results of experiments that show that, under some conditions, SRS can extend the performance of amplifiers limited by nonlinear phase accumulation. The Stokes spectrum can be free of distortions arising from self-phase modulation and can circumvent the gain-narrowing limit of the amplifier. The generation of 1 microJ and 90 fs pulses from a single-mode fiber amplifier illustrates the potential of the process.

  20. Analytical model for interaction of short intense laser pulse with solid target

    SciTech Connect

    Luan, S. X.; Ma, G. J.; Yu, Wei; Yu, M. Y.; Zhang, Q. J.; Sheng, Z. M.; Murakami, M.

    2011-04-15

    A simple but comprehensive two-dimensional analytical model for the interaction of a normally incident short intense laser pulse with a solid-density plasma is proposed. Electron cavitation near the target surface by the laser ponderomotive force induces a strong local electrostatic charge-separation field. The cavitation makes possible mode conversion of the laser light into longitudinal electron oscillation at laser frequency, even for initial normal incidence of laser pulse. The intense charge-separation field in the cavity can significantly enhance the laser induced uxB electron oscillation at twice laser frequency to density levels even higher than that of the initial target.

  1. Plasma-based creation of short light pulses: analysis and simulation of amplification and focusing

    NASA Astrophysics Data System (ADS)

    Riconda, C.; Weber, S.; Lancia, L.; Marquès, J.-R.; Mourou, G.; Fuchs, J.

    2015-01-01

    Plasmas can serve as damage-less optics for amplifying and focusing light pulses to very high intensity. This provides a way to overcome the limitations of solid-state optical materials as a damage threshold in the classical sense is absent. The amplification process relies on parametric processes in plasmas exploiting the coupling of transverse electromagnetic waves to a longitudinal plasma wave. The plasma response can either be an electron plasma wave (stimulated Raman scattering), an ion-acoustic wave (stimulated Brillouin scattering) or a more complicated non-resonant feature in the case of very short pulses.

  2. Short time ion pulse extraction from the Dresden electron beam ion trapa)

    NASA Astrophysics Data System (ADS)

    Kentsch, U.; Zschornack, G.; Schwan, A.; Ullmann, F.

    2010-02-01

    We present measurements of the extraction of short time pulses of highly charged ions (4 keV, Ar16+) from the Dresden electron beam ion trap. Thereby the dependence of the extractable ionic charge on the extraction regime was investigated. The ion extraction time was varied between 20 ns and 1 μs. Furthermore the production of carbon ions and the influence of the extraction regime on the pulse widths was investigated to obtain information about the suitability of the Dresden EBIS-A in synchrotron based particle therapy facilities.

  3. Pulse-Shape Effects in Ionization of Atomic Hydrogen by Short-Pulse XUV Intense Laser Radiation

    NASA Astrophysics Data System (ADS)

    Bartschat, Klaus; Venzke, Joel; Grum Grzhimailo, Alexei N.

    2015-05-01

    In a recent publication, we investigated a displacement effect in strong-field atomic ionization by an XUV pulse. We found that the angular momentum of the ejected electron and, therefore, its angular distribution were strongly affected by the details in the short ramp-on/off characteristics of various pulses, all of which were otherwise identical with a plateau in the envelope function that was significantly longer than the ramp-on/off phase. In the present work, we studied the effect in more detail, especially regarding the role of the plateau, which is unlikely to occur in a realistic experimental setup. As expected, great care must be taken in setting up theoretical models to ensure that the pulses are, at least in principle, experimentally realizable. This work is supported by the United States National Science Foundation under grant No. PHY-1430245 and the XSEDE allocation PHY-090031, and by the Russian Foundation for Basic Research under Grant No. 12-02-01123.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. Phase engineered wavelength conversion of ultra-short optical pulses in TI:PPLN waveguides

    NASA Astrophysics Data System (ADS)

    Babazadeh, Amin; Nouroozi, Rahman; Sohler, Wolfgang

    2016-02-01

    A phase engineered all-optical wavelength converter for ultra-short pulses (down to 140 fs) in a Ti-diffused, periodically poled lithium niobate (Ti:PPLN) waveguide is proposed. The phase engineering, due to the phase conjugation between signal and idler (converted signal) pulses which takes place in the cascaded second harmonic generation and difference frequency generation (cSHG/DFG) based wavelength conversion, already leads to shorter idler pulses. The proposed device consists of an unpoled (passive) waveguide section beside of the PPLN waveguide section in order to compensate pulse broadening and phase distortion of the idler pulses induced by the wavelength conversion (in the PPLN section). For example numerical analysis shows that a 140 fs input signal pulse is only broadened by 1.6% in a device with a combination of 20 mm and 6 mm long periodically poled and unpoled waveguide sections. Thus, cSHG/DFG based wavelength converters of a bandwidth of several Tbits/s can be designed.

  6. Two-photon fluorescence bioimaging with an all-semiconductor laser picosecond pulse source.

    PubMed

    Kuramoto, Masaru; Kitajima, Nobuyoshi; Guo, Hengchang; Furushima, Yuji; Ikeda, Masao; Yokoyama, Hiroyuki

    2007-09-15

    We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.

  7. Methodology for the conception of speckle reduction elements in the case of short pulse illumination

    NASA Astrophysics Data System (ADS)

    Lutz, Yves; Poyet, Jean-Michel

    2015-10-01

    One of the most efficient ways to decrease the speckle contrast in the field of laser illumination is to increase the spatial diversity of coherent laser sources. For very short laser pulses such as those required for flash laser imaging, the spatial diversity should take place instantaneously and no time averaging effect can be used. The spatial diversity is realized by sampling the laser beam into m beamlets with increased optical path length. This path length has to be greater than or equal to the coherence length of the laser beam. In this case, the beamlets are no longer able to create interferences which each other. According to the Goodman's theory of speckle reduction, the speckle contrast is then reduced by a factor of 1/√m. Unfortunately, in the case of multimode lasers, the number of uncorrelated beamlets is not infinite but is limited by a periodicity function resulting from the laser resonator length itself. The speckle reduction possibility is therefore limited and is directly linked to each laser source where the coherence length and cavity length are defined. In this work we present a methodology to determine experimentally the optical path length difference as well as the number of beamlets for de-speckling a laser source. An experimental realization is presented where both, coherence length and periodicity function are measured with a Michelson interferometer where only the speckle contrast of the two beams from each arm is analyzed. For the validation of the method, the chosen laser source is a single emitter 660 nm laser diode. Two cylindrical steppers made with diamond turned PMMA have been realized. Both elements yield interesting results with close values and in accordance with the theory of spatial diversity. The speckle contrast could be reduced from about 10% to a value close to 4%. These values confirm and validate the methodology presented in this work. Steppers can also be a promising solution for the reduction of interference fringes

  8. Note: A pulsed laser ion source for linear induction accelerators

    SciTech Connect

    Zhang, H.; Zhang, K.; Shen, Y.; Jiang, X.; Dong, P.; Liu, Y.; Wang, Y.; Chen, D.; Pan, H.; Wang, W.; Jiang, W.; Long, J.; Xia, L.; Shi, J.; Zhang, L.; Deng, J.

    2015-01-15

    We have developed a high-current laser ion source for induction accelerators. A copper target was irradiated by a frequency-quadrupled Nd:YAG laser (266 nm) with relatively low intensities of 10{sup 8} W/cm{sup 2}. The laser-produced plasma supplied a large number of Cu{sup +} ions (∼10{sup 12} ions/pulse) during several microseconds. Emission spectra of the plasma were observed and the calculated electron temperature was about 1 eV. An induction voltage adder extracted high-current ion beams over 0.5 A/cm{sup 2} from a plasma-prefilled gap. The normalized beam emittance measured by a pepper-pot method was smaller than 1 π mm mrad.

  9. Note: A pulsed laser ion source for linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Zhang, K.; Shen, Y.; Jiang, X.; Dong, P.; Liu, Y.; Wang, Y.; Chen, D.; Pan, H.; Wang, W.; Jiang, W.; Long, J.; Xia, L.; Shi, J.; Zhang, L.; Deng, J.

    2015-01-01

    We have developed a high-current laser ion source for induction accelerators. A copper target was irradiated by a frequency-quadrupled Nd:YAG laser (266 nm) with relatively low intensities of 108 W/cm2. The laser-produced plasma supplied a large number of Cu+ ions (˜1012 ions/pulse) during several microseconds. Emission spectra of the plasma were observed and the calculated electron temperature was about 1 eV. An induction voltage adder extracted high-current ion beams over 0.5 A/cm2 from a plasma-prefilled gap. The normalized beam emittance measured by a pepper-pot method was smaller than 1 π mm mrad.

  10. Creating and Manipulating Vortices in Atomic Wave Functions with Short Electric Field Pulses

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. Yu; Sternberg, J. B.; Macek, J. H.; Lee, Teck-Ghee; Schultz, D. R.

    2010-11-01

    We demonstrate the creation of vortices in the electronic probability density of an atom subject to short electric field pulses, how these vortices evolve and can be manipulated by varying the applied pulses, and that they persist to macroscopic distances in the spectrum of ejected electrons. This opens the possibility to use practical femtosecond or shorter laser pulses to create and manipulate these vortex quasiparticles at the atomic scale and observe them in the laboratory. Within a hydrodynamic interpretation we also show, since the Schrödinger equation is a particular instance of the Navier-Stokes equations, that for compressible fluids vortices can appear spontaneously and with a certain time delay, which is not expected to occur from the conventional point of view, illustrating applicability of the present study to vortex formation more broadly.

  11. Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

    NASA Astrophysics Data System (ADS)

    Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

    2013-10-01

    We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

  12. Short-pulsed, electric-discharge degradation of toxic and sludge wastes

    SciTech Connect

    Rosocha, L.A.; Bystritskii, V.M.; Wessel, F.J.

    1998-12-01

    This is the final report of a three-year, Directed Research and Development (LDRD) project funded by the Los Alamos National Laboratory (LANL). The project was a collaborative effort with the University of California at Irvine (UCI), which was the lead project performer. Short-pulse, electric-discharge streamers were used to degrade aromatic and chlorinated compounds in water aerosols. An atomizer supplies 10--50 {micro}m aerosol droplets to a discharge chamber containing thin wires that are driven by electric pulses of 50--90 kV amplitude, 50--150 ns pulse duration, and 100 Hz repetition rate. The combination of a high electric field, large H{sub 2}O dielectric constant and atomization provide efficient degradation of organic molecules including: paranitrophenol, di-chlorophenol and perchloroethylene. The specific energy input for degradation of a pollutant molecule depends on the particular compound, its concentration, and the operational parameters of the discharge.

  13. Creating and Manipulating Vortices in Atomic Wavefunctions with Short Electric Field Pulses

    SciTech Connect

    Ovchinnikov, S. Yu.; Sternberg, J. B.; Macek, J. H.; Lee, Teck-Ghee; Schultz, David Robert

    2010-01-01

    We demonstrate the creation of vortices in the electronic probability density of an atom subject to short electric field pulses, how these vortices evolve and can be manipulated by varying the applied pulses, and that they persist to macroscopic distances in the spectrum of ejected electrons. This opens the possibility to use practical femtosecond or shorter laser pulses to create and manipulate these vortex quasiparticles at the atomic scale and observe them in the laboratory. Within a hydrodynamic interpretation we also show, since the Schr dinger equation is a particular instance of the Navier-Stokes equations, that for compressible fluids vortices can appear spontaneously and with a certain time delay, which is not expected to occur from the conventional point of view, illustrating applicability of the present study to vortex formation more broadly.

  14. A novel generation scheme of ultra-short pulse trains with multiple wavelengths

    NASA Astrophysics Data System (ADS)

    Su, Yulong; Hu, Hui; Feng, Huan; Li, Lu; Han, Biao; Wen, Yu; Wang, Yishan; Si, Jinhai; Xie, Xiaoping; Wang, Weiqiang

    2017-04-01

    We demonstrate a novel scheme based on active mode locking combined with four-wave mixing (FWM) to generate ultra-short pulse trains at high repetition rate with multiple wavelengths for applications in various fields. The obtained six wavelengths display high uniformity both in temporal and frequency domain. Pulses at each wavelength are mode locked with pulse duration of 44.37 ps, signal-to-noise ratio (SNR) of 47.89 dB, root-mean-square (RMS) timing jitter of 552.7 fs, and the time-bandwidth product of 0.68 at repetition rate of 1 GHz. The experimental results show this scheme has promising usage in optical communications, optical networks, and fiber sensing.

  15. Simulation studies of vapor bubble generation by short-pulse lasers

    SciTech Connect

    Amendt, P.; London, R.A.; Strauss, M.

    1997-10-26

    Formation of vapor bubbles is characteristic of many applications of short-pulse lasers in medicine. An understanding of the dynamics of vapor bubble generation is useful for developing and optimizing laser-based medical therapies. To this end, experiments in vapor bubble generation with laser light deposited in an aqueous dye solution near a fiber-optic tip have been performed. Numerical hydrodynamic simulations have been developed to understand and extrapolate results from these experiments. Comparison of two-dimensional simulations with the experiment shows excellent agreement in tracking the bubble evolution. Another regime of vapor bubble generation is short-pulse laser interactions with melanosomes. Strong shock generation and vapor bubble generation are common physical features of this interaction. A novel effect of discrete absorption by melanin granules within a melanosome is studied as a possible role in previously reported high Mach number shocks.

  16. Simulation studies of vapor bubble generation by short-pulse lasers

    NASA Astrophysics Data System (ADS)

    Amendt, Peter A.; London, Richard A.; Strauss, Moshe; Glinsky, Michael E.; Maitland, Duncan J.; Celliers, Peter M.; Visuri, Steven R.; Bailey, David S.; Young, David A.; Ho, Darwin; Lin, Charles P.; Kelly, Michael W.

    1998-01-01

    Formation of vapor bubbles is characteristic of many applications of short-pulse lasers in medicine. An understanding of the dynamics of vapor bubble generation is useful for developing and optimizing laser-based medical therapies. To this end, experiments in vapor bubble generation with laser light deposited in an aqueous dye solution near a fiber-optic tip have been performed. Numerical hydrodynamic simulations have been developed to understand and extrapolate results from these experiments. Comparison of two-dimensional simulations with the experiment shows excellent agreement in tracking the bubble evolution. Another regime of vapor bubble generation is short-pulse laser interactions with melanosomes. Strong shock generation and vapor bubble generation are common physical features of this interaction. A novel effect of discrete absorption by melanin granules within a melanosome is studied as a possible role in previously reported high Mach number shocks [Lin and Kelly, SPIE 2391, 294 (1995)].

  17. Electron acceleration in relativistic plasma waves generated by a single frequency short-pulse laser

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Decker, C.D.; Mori, W.B.; Tzeng, K.C., Clayton, C.E.; Marsh, K.A.; Joshi, C.

    1995-04-27

    Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 {mu}m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8{times}10{sup 17} W/cm{sup 2}. At a plasma density of 2{times}10{sup 19} cm{sup {minus}3}, 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultra-high gradient accelerators is explored.

  18. A novel multi-component generalization of the short pulse equation and its multisoliton solutions

    NASA Astrophysics Data System (ADS)

    Matsuno, Yoshimasa

    2011-12-01

    We propose a novel multi-component system of nonlinear equations that generalizes the short pulse (SP) equation describing the propagation of ultra-short pulses in optical fibers. By means of the bilinear formalism combined with a hodograph transformation, we obtain its multisoliton solutions in the form of a parametric representation. Notably, unlike the determinantal solutions of the SP equation, the proposed system is found to exhibit solutions expressed in terms of pfaffians. The proof of the solutions is performed within the framework of an elementary theory of determinants. The reduced 2-component system deserves a special consideration. In particular, we show by establishing a Lax pair that the system is completely integrable. The properties of solutions such as loop solitons and breathers are investigated in detail, confirming their solitonic behavior. A variant of the 2-component system is also discussed with its multisoliton solutions.

  19. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate

    NASA Astrophysics Data System (ADS)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-11-01

    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  20. A rapidly-tuned, short-pulse-length, high-repetition-rate CO{sub 2} laser for IR dial

    SciTech Connect

    Zaugg, T.; Thompson, D.; Leland, W.T.; Busch, G.

    1997-08-01

    Analysis of noise sources in Differential Absorption LIDAR (DIAL) in the infrared region of the spectrum indicates that the signal-to-noise ratio for direct detection can be improved if multiple-wavelength, short-pulse-length beams are transmitted and received at high repetition rates. Atmospheric effects can be minimized, albedo can be rapidly scanned, and uncorrelated speckle can be acquired at the maximum possible rate. A compact, rugged, RF-excited waveguide laser can produce 15 nanosecond pulses at a 100 kHz rate with sufficient energy per pulse to reach the speckle limit of the signal-to-noise ratio. A high-repetition-rate laser has been procured and will be used to verify these signal and noise scaling relationships at high repetition rates. Current line-tuning devices are mechanical and are capable of switching lines at a rate up to a few hundred Hertz. Acousto-optic modulators, deflectors or tunable filters can be substituted for these mechanical devices in the resonator of a CO{sub 2} laser and used to rapidly line-tune the laser across the 9 and 10 micron bands at a rate as high as 100 kHz. Several configurations for line tuning using acousto-optic and electro-optic devices with and without gratings are presented. The merits of and constraints on each design are also discussed. A pair of large aperture, acousto-optic deflectors has been purchased and the various line-tuning designs will be evaluated in a conventional, glass tube, CO{sub 2} laser, with a view to incorporation into the high-repetition-rate, waveguide laser. A computer model of the dynamics of an RF-excited, short-pulse-length, high-repetition-rate waveguide laser has been developed. The model will be used to test the consequences of various line-tuning designs.

  1. Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Mahalik, S. S.; Kundu, M.

    2016-12-01

    Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse >100 fs when Mie-plasma frequency ( ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse, the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω [ r ( t ) ] of an electron in the self-consistent anharmonic potential of the cluster satisfies Ω [ r ( t ) ] = ω . However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω [ r ( t ) ] in the self-generated anharmonic plasma potential, it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models, and MD calculations for the first time but also unequivocally prove that AHR process is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

  2. Distinctive features of photoionized plasma from short x-ray-pulse interaction with gaseous medium

    SciTech Connect

    Bychenkov, V.Yu.; Romanov, D.V.; Rozmus, W.; Capjack, C.E.; Fedosejevs, R.

    2006-01-15

    The study of a photoionized plasma created through the interaction of a short linearly polarized x-ray pulse with a gaseous medium is presented in the context of the future design of experiments involving femtosecond free-electron laser pulses. The dispersion properties and instabilities of such x-ray-produced plasma are studied. It is shown that a two-stream type of instability can be obtained with a growth rate comparable to the plasma frequency. This is expected to have a dramatic effect on the evolution of an x-ray laser-produced plasma. A model for describing electromagnetic-field generation and emission resulting from the interaction of a short x-ray laser pulse with a gas jet is proposed. Issues addressed include the effect of the thermal electromotive force at the edge of a plasma driven by the anisotropic electron energy distribution that arises from the photoionization of a gas. Terahertz pulse emission from these photoionized plasma is also predicted.

  3. Advanced concepts for high-power, short-pulse CO2 laser development

    NASA Astrophysics Data System (ADS)

    Gordon, Daniel F.; Hasson, Victor; von Bergmann, Hubertus; Chen, Yu-hsin; Schmitt-Sody, A.; Penano, Joseph R.

    2016-06-01

    Ultra-short pulse lasers are dominated by solid-state technology, which typically operates in the near-infrared. Efforts to extend this technology to longer wavelengths are meeting with some success, but the trend remains that longer wavelengths correlate with greatly reduced power. The carbon dioxide (CO2) laser is capable of delivering high energy, 10 micron wavelength pulses, but the gain structure makes operating in the ultra-short pulse regime difficult. The Naval Research Laboratory and Air Force Research Laboratory are developing a novel CO2 laser designed to deliver ~1 Joule, ~1 picosecond pulses, from a compact gain volume (~2x2x80 cm). The design is based on injection seeding an unstable resonator, in order to achieve high energy extraction efficiency, and to take advantage of power broadening. The unstable resonator is seeded by a solid state front end, pumped by a custom built titanium sapphire laser matched to the CO2 laser bandwidth. In order to access a broader range of mid infrared wavelengths using CO2 lasers, one must consider nonlinear frequency multiplication, which is non-trivial due to the bandwidth of the 10 micron radiation.

  4. Attenuation of short strongly nonlinear stress pulses in dissipative granular chains.

    PubMed

    Wang, S Y; Nesterenko, V F

    2015-06-01

    Attenuation of short, strongly nonlinear stress pulses in chains of spheres and cylinders was investigated experimentally and numerically for two ratios of their masses keeping their contacts identical. The chain with mass ratio 0.98 supports solitary waves and another one (with mass ratio 0.55) supports nonstationary pulses, which preserve their identity only on relatively short distances, but attenuate on longer distances because of radiation of small amplitude tails generated by oscillating small mass particles. Pulse attenuation in experiments in the chain with mass ratio 0.55 was faster at the same number of the particles from the entrance than in the chain with mass ratio 0.98. It is in quantitative agreement with results of numerical calculations with effective damping coefficient 6 kg/s. This level of damping was critical for eliminating the gap openings between particles in the system with mass ratio 0.55 present at lower or no damping. With increase of dissipation numerical results show that the chain with mass ratio 0.98 provides faster attenuation than the chain with mass ratio 0.55 due to the fact that the former system supports the narrower pulse with the larger difference between velocities of neighboring particles. The investigated chains demonstrated similar behavior at large damping coefficient 100 kg/s.

  5. Necessary and sufficient conditions for self-focusing of short ultraintense laser pulse in underdense plasma

    SciTech Connect

    Chen, X.L.; Sudan, R.N. )

    1993-04-05

    We analyze the propagation of a short intense laser pulse in underdense cold plasma. When no electron cavitation is present, a global invariant [ital H] is obtained, and its relation with self-focusing is studied. For relativistic self-focusing, [ital H][lt]0 is a sufficient and necessary condition. For relativistic and ponderomotive self-focusing, [ital H][lt]0 is sufficient but not necessary. Numerical simulations are performed to confirm the above points.

  6. Target Recognition Using Late-Time Returns from Ultra-Wideband, Short-Pulse Radar

    DTIC Science & Technology

    2004-06-01

    neglecting terms associated with surface resistance. The recognition sensor illuminates the target with a series of ultra-wideband, short radar pulses...the incident radar wave . Picture yourself looking into a mirror. If you can see your own face, you see the broadside of the mirror. Broadside is used...as an azimuth reference. Broadside illumination occurs when the incident wave approaches the object’s surface in a direction parallel to the surface

  7. Means and method for characterizing high power, ultra short laser pulses in a real time, on line manner

    DOEpatents

    Veligdan, James T.

    1994-01-01

    An ultra short (<10 ps), high power laser pulse is temporally characterized by a system that uses a physical measurement of a wavefront that has been altered in a known manner. The system includes a first reflection switch to remove a portion of a pulse from a beam of pulses, then includes a second reflection switch, operating in a mode that is opposite to the first reflection switch, to slice off a portion of that removed portion. The sliced portion is then directed to a measuring device for physical measurement. The two reflection switches are arranged with respect to each other and with respect to the beam of ultra short pulses such that physical measurement of the sliced portion is related to the temporal measurement of the ultra short pulse by a geometric or trigonometric relationship. The reflection switches are operated by a control pulse that is directed to impinge on each of the reflection switches at a 90.degree. angle of incidence.

  8. Workshop on scientific applications of short wavelength coherent light sources

    SciTech Connect

    Spicer, W.; Arthur, J.; Winick, H.

    1993-02-01

    This report contains paper on the following topics: A 2 to 4nm High Power FEL On the SLAC Linac; Atomic Physics with an X-ray Laser; High Resolution, Three Dimensional Soft X-ray Imaging; The Role of X-ray Induced Damage in Biological Micro-imaging; Prospects for X-ray Microscopy in Biology; Femtosecond Optical Pulses ; Research in Chemical Physics Surface Science, and Materials Science, with a Linear Accelerator Coherent Light Source; Application of 10 GeV Electron Driven X-ray Laser in Gamma-ray Laser Research; Non-Linear Optics, Fluorescence, Spectromicroscopy, Stimulated Desorption: We Need LCLS' Brightness and Time Scale; Application of High Intensity X-rays to Materials Synthesis and Processing; LCLS Optics: Selected Technological Issues and Scientific Opportunities; Possible Applications of an FEL for Materials Studies in the 60 eV to 200 eV Spectral Region.

  9. Workshop on scientific applications of short wavelength coherent light sources

    SciTech Connect

    Spicer, W.; Arthur, J.; Winick, H.

    1993-02-01

    This report contains paper on the following topics: A 2 to 4nm High Power FEL On the SLAC Linac; Atomic Physics with an X-ray Laser; High Resolution, Three Dimensional Soft X-ray Imaging; The Role of X-ray Induced Damage in Biological Micro-imaging; Prospects for X-ray Microscopy in Biology; Femtosecond Optical Pulses?; Research in Chemical Physics Surface Science, and Materials Science, with a Linear Accelerator Coherent Light Source; Application of 10 GeV Electron Driven X-ray Laser in Gamma-ray Laser Research; Non-Linear Optics, Fluorescence, Spectromicroscopy, Stimulated Desorption: We Need LCLS` Brightness and Time Scale; Application of High Intensity X-rays to Materials Synthesis and Processing; LCLS Optics: Selected Technological Issues and Scientific Opportunities; Possible Applications of an FEL for Materials Studies in the 60 eV to 200 eV Spectral Region.

  10. Effects of temporal laser profile on the emission spectra for underwater laser-induced breakdown spectroscopy: Study by short-interval double pulses with different pulse durations

    SciTech Connect

    Tamura, Ayaka Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo; Nakajima, Takashi; Ogata, Yukio H.; Fukami, Kazuhiro

    2015-01-14

    We investigate the effects of temporal laser profile on the emission spectra of laser ablation plasma in water. We use short-interval (76 ns) double pulses with different pulse durations of the composing two pulses for the irradiation of underwater target. Narrow atomic spectral lines in emission spectra are obtained by the irradiation, where the two pulses are wide enough to be merged into a single-pulse-like temporal profile, while deformed spectra are obtained when the two pulses are fully separated. The behavior of the atomic spectral lines for the different pulse durations is consistent with that of the temporal profiles of the optical emission intensities of the plasma. All these results suggest that continuous excitation of the plasma during the laser irradiation for ∼100 ns is a key to obtain narrow emission spectral lines.

  11. Short intense ion pulses for materials and warm dense matter research

    DOE PAGES

    Seidl, Peter A.; Persaud, Arun; Waldron, William L.; ...

    2015-11-11

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics tomore » be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Finally, we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.« less

  12. Short intense ion pulses for materials and warm dense matter research

    SciTech Connect

    Seidl, Peter A.; Persaud, Arun; Waldron, William L.; Barnard, John J.; Davidson, Ronald C.; Friedman, Alex; Gilson, Erik P.; Greenway, Wayne G.; Grote, David P.; Kaganovich, Igor D.; Lidia, Steven M.; Stettler, Matthew; Takakuwa, Jeffrey H.; Schenkel, Thomas

    2015-11-11

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Finally, we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

  13. Short Intense Ion Pulses for Materials and Warm Dense Matter Research

    NASA Astrophysics Data System (ADS)

    Seidl, Peter; Ji, Q.; Lidia, S. M.; Persaud, A.; Stettler, M.; Takakuwa, J. H.; Waldron, W. L.; Schenkel, T.; Barnard, J. J.; Friedman, A.; Grote, D. P.; Davidson, R. C.; Gilson, E. P.; Kaganovich, I. D.

    2015-11-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r <1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li + ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. We will describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminium perovskite using the fully integrated accelerator and neutralized drift compression components (arXiv:1506.05839). This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  14. Short intense ion pulses for materials and warm dense matter research

    NASA Astrophysics Data System (ADS)

    Seidl, Peter A.; Persaud, Arun; Waldron, William L.; Barnard, John J.; Davidson, Ronald C.; Friedman, Alex; Gilson, Erik P.; Greenway, Wayne G.; Grote, David P.; Kaganovich, Igor D.; Lidia, Steven M.; Stettler, Matthew; Takakuwa, Jeffrey H.; Schenkel, Thomas

    2015-11-01

    We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

  15. Ultra-short laser pulses in dentistry: a solution toward painless dental treatment?

    NASA Astrophysics Data System (ADS)

    Wieger, V.; Yousif, A.; Strassl, M.; Wintner, E.

    2006-06-01

    Within the last years, modern ultra-short pulse lasers have successfully proven their potential for application in medical tissue treatment in many respects. In dentistry, overheating of the pulp and induction of micro cracks are usually among the most problematic issues which can be solved in this way. An additional benefit can be seen in the possibility of plasma emission spectroscopy as a means of feedback. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the special physiological requirements. Beside the short interaction time with the irradiated biological matter, lateral scanning of ultra-short pulses following optimized algorithms turned out to be crucial for ablating cavities with the required quality and size, a finding which we also believe to be valid for dental restoration materials. Additionally, out of practical reasons, scanning is necessary to treat larger volumes than just the focal spots typically having dimensions on the order of more than 1 mm 3, thereby allowing to realize an "optical drill".

  16. Accurate modeling of antennas for radiating short pulses, FDTD analysis and experimental measurements

    NASA Astrophysics Data System (ADS)

    Maloney, James G.; Smith, Glenn S.

    1993-01-01

    Antennas used to radiate short pulses often require different design rules that those that are used to radiate essentially time-harmonic signals. The finite-difference time-domain (FDTD) method is a very flexible numerical approach that can be used to treat a variety of electromagnetic problems in the time domain. It is well suited to the analysis and design of antennas for radiating short pulses; however, several advances had to be made before the method could be applied to this problem. In this paper, we will illustrate the use of the FDTD method with two antennas designed for the radiation of short pulses. The first is a simple, two-dimensional geometry, and open-ended parallel-plate waveguide, while the second is a three-dimensional, rotationally symmetric geometry, a conical monopole fed through an image by a coaxial transmission line. Both antennas are 'optimized' according to given criteria by adjusting geometrical parameters and including resistive loading that varies continuously with position along the antenna. The predicted performance for the conical monopole antenna is compared with experimental measurements; this verifies the optimization and demonstrates the practicality of the design.

  17. Short-pulse CO2 laser with longitudinal tandem discharge tube

    NASA Astrophysics Data System (ADS)

    Uno, K.; Akitsu, T.; Jitsuno, T.

    2014-10-01

    We developed a longitudinally excited CO2 laser with a tandem discharge tube. The tandem scheme was constituted of two 30-cm long discharge tubes connected with an intermediate electrode. Two parts, each consisting of a charged capacitance and a 30-cm long discharge tube, were electrically connected in parallel and switched by a spark gap. The tandem scheme produced a short laser pulse like that of a TEA-CO2 laser with a charging voltage of -24.8 kV, which was smaller than the -40.0 kV charging voltage of our previous CO2 laser. At a gas pressure of 3.8 kPa, the spike pulse width was 145 ns, the pulse tail length was 58.8 μs, the output energy was 52.0 mJ, and the spike pulse energy was 2.4 mJ. We also investigated the dependence of the laser pulse and the discharge voltage on gas pressure.

  18. Spectral and dynamic properties of stimulated electromagnetic emission (SEE) generated by very short diagnostic pulses

    NASA Astrophysics Data System (ADS)

    Sergeev, Evgeny; Grach, Savely

    Results of the experimental investigations of the HF Upper Hybrid and LF ionospheric tur-bulence by the SEE diagnostic technique over the SURA heating facility are presented. For pumping of the ionosphere an alternation of two basic time modes was used: (1) high duty cycles, i.e. long pulses with a short pauses of 20-30 ms between them, in addition short (diag-nostic) pump pulses with a duration τ ≤ 200 µs were radiated in the middle of the pauses; (2) low-duty cycles consisting of short pulses τ ≤ 200 µs and interpulse period T = 20-200 ms. It is known that the SEE spectral shape and dynamics are determined mainly by the pump-induced UH plasma waves, while the LF turbulence (striations) is responsible for SEE intensity and interpulse dynamics. In previous experiments longer diagnostic pulses (τ 10-30 ms) and interpulse periods (T = 1-3 s) were used. The reduction of τ and T diminishes an influence of the pulses upon tested processes and improves a temporal resolution of the diagnostic SEE measurements. In case of well developed striations (during high duty cycle) diagnostic pulses excite the upper hybrid plasma waves, and, therefore, the SEE with frequencies close to diag-nostic pulse frequency fd practically without time delay. So far as the pulse duration τ was chosen to be much less than a period of their multiple ionospheric reflections (˜ 2 ms) we were able to analyze the decaying SEE spectra just after the ionospherically reflected pulse trailing edge during periods between multiple signal hops in a whole frequency bandwidth including the fd close vicinity. Observations have shown that the SEE spectral maximum is shifted towards lower frequencies from fd by 2-4 kHz during high duty cycle (well-developed striations), and by up to 4-6 kHz after the mode switching to low duty cycle. Then the SEE intensity decreases from pulse to pulse together with striation relaxation. The typical e-folding decay time of the total SEE intensity after the diagnostic

  19. Pulse compression below 40fs at 1μm: The first step towards a short-pulse, high-energy beam line at LULI

    NASA Astrophysics Data System (ADS)

    Chen, Xiaowei; Zou, Jiping; Martin, Luc; Simon, Francois; Lopez-Martens, Rodrigo; Audebert, Patrick

    2010-08-01

    We present the upgrading project ELFIE (Equipement Laser de Forte Intensité et Energie) based on the "100TW" mixed Nd:glass CPA laser system at 1μm at LULI, which includes an energy enhancement and the development of a short-pulse, high-energy, good temporal contrast beam line (50fs/5J). We report the first experimental step towards the short-pulse, high-energy beam line: spectral broadening above 60nm from 7nm and temporal pulse compression below 40fs from 300fs at 1μm through a Krypton-filled hollow fiber compressor.

  20. Cyclinac medical accelerators using pulsed C6+/H2+ ion sources

    NASA Astrophysics Data System (ADS)

    Garonna, A.; Amaldi, U.; Bonomi, R.; Campo, D.; Degiovanni, A.; Garlasché, M.; Mondino, I.; Rizzoglio, V.; Verdú Andrés, S.

    2010-09-01

    Charged particle therapy, or so-called hadrontherapy, is developing very rapidly. There is large pressure on the scientific community to deliver dedicated accelerators, providing the best possible treatment modalities at the lowest cost. In this context, the Italian research Foundation TERA is developing fast-cycling accelerators, dubbed `cyclinacs'. These are a combination of a cyclotron (accelerating ions to a fixed initial energy) followed by a high gradient linac boosting the ions energy up to the maximum needed for medical therapy. The linac is powered by many independently controlled klystrons to vary the beam energy from one pulse to the next. This accelerator is best suited to treat moving organs with a 4D multipainting spot scanning technique. A dual proton/carbon ion cyclinac is here presented. It consists of an Electron Beam Ion Source, a superconducting isochronous cyclotron and a high-gradient linac. All these machines are pulsed at high repetition rate (100-400 Hz). The source should deliver both C6+ and H2+ ions in short pulses (1.5 μs flat-top) and with sufficient intensity (at least 108 fully stripped carbon ions per pulse at 300 Hz). The cyclotron accelerates the ions to 120 MeV/u. It features a compact design (with superconducting coils) and a low power consumption. The linac has a novel C-band high-gradient structure and accelerates the ions to variable energies up to 400 MeV/u. High RF frequencies lead to power consumptions which are much lower than the ones of synchrotrons for the same ion extraction energy. This work is part of a collaboration with the CLIC group, which is working at CERN on high-gradient electron-positron colliders.

  1. Formation of silicon carbide and diamond nanoparticles in the surface layer of a silicon target during short-pulse carbon ion implantation

    NASA Astrophysics Data System (ADS)

    Remnev, G. E.; Ivanov, Yu. F.; Naiden, E. P.; Saltymakov, M. S.; Stepanov, A. V.; Shtan'ko, V. F.

    2009-04-01

    Synthesis of silicon carbide and diamond nanoparticles is studied during short-pulse implantation of carbon ions and protons into a silicon target. The experiments are carried out using a TEMP source of pulsed powerful ion beams based on a magnetically insulated diode with radial magnetic field B r . The beam parameters are as follows: the ion energy is 300 keV, the pulse duration is 80 ns, the beam consists of carbon ions and protons, and the ion current density is 30 A/cm2. Single-crystal silicon wafers serve as a target. SiC nanoparticles and nanodiamonds form in the surface layer of silicon subjected to more than 100 pulses. The average coherent domain sizes in the SiC particles and nanodiamonds are 12-16 and 8-9 nm, respectively.

  2. ELI-Beamlines: development of next generation short-pulse laser systems

    NASA Astrophysics Data System (ADS)

    Rus, B.; Bakule, P.; Kramer, D.; Naylon, J.; Thoma, J.; Green, J. T.; Antipenkov, R.; Fibrich, M.; Novák, J.; Batysta, F.; Mazanec, T.; Drouin, M. A.; Kasl, K.; Baše, R.; Peceli, D.; Koubíková, L.; Trojek, P.; Boge, R.; Lagron, J. C.; Vyhlídka, Å.; Weiss, J.; Cupal, J.,; Hřebíček, J.; Hříbek, P.; Durák, M.; Polan, J.; Košelja, M.; Korn, G.; Horáček, M.; Horáček, J.; Himmel, B.; Havlíček, T.; Honsa, A.; Korouš, P.; Laub, M.; Haefner, C.; Bayramian, A.; Spinka, T.; Marshall, C.; Johnson, G.; Telford, S.; Horner, J.; Deri, B.; Metzger, T.; Schultze, M.; Mason, P.; Ertel, K.; Lintern, A.; Greenhalgh, J.; Edwards, C.; Hernandez-Gomez, C.; Collier, J.; Ditmire, T.,; Gaul, E.; Martinez, M.; Frederickson, C.; Hammond, D.; Malato, C.; White, W.; Houžvička, J.

    2015-05-01

    Overview of the laser systems being built for ELI-Beamlines is presented. The facility will make available high-brightness multi-TW ultrashort laser pulses at kHz repetition rate, PW 10 Hz repetition rate pulses, and kilojoule nanosecond pulses for generation of 10 PW peak power. The lasers will extensively employ the emerging technology of diode-pumped solid-state lasers (DPSSL) to pump OPCPA and Ti:sapphire broadband amplifiers. These systems will provide the user community with cutting-edge laser resources for programmatic research in generation and applications of high-intensity X-ray sources, in particle acceleration, and in dense-plasma and high-field physics.

  3. Remote atmospheric breakdown for standoff detection by using an intense short laser pulse.

    PubMed

    Ting, Antonio; Alexeev, Ilya; Gordon, Daniel; Briscoe, Eldridge; Peñano, Joseph; Hubbard, Richard; Sprangle, Phillip; Rubel, Glenn

    2005-09-01

    A remote atmospheric breakdown is a very rich source of UV and broadband visible light that could provide an early warning of the presence of chemical-biological warfare agents at extended standoff distances. A negatively chirped laser pulse propagating in air compresses in time and focuses transversely, which results in a rapid laser intensity increase and ionization near the focal region that can be located kilometers away from the laser system. Proof-of-principle laboratory experiments are performed on the generation of remote atmospheric breakdown and the spectroscopic detection of mock biological warfare agents. We have generated third harmonics at 267 nm and UV broadband radiation in air from the compression and focusing of femtosecond laser pulses. Fluorescence emission from albumin aerosols as they were illuminated by the femtosecond laser pulse has been observed.

  4. Status of the pulsed magnetic field electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Mühle, C.; Ratzinger, U.; Bleuel, W.; Jöst, G.; Leible, K.; Schennach, S.; Wolf, B. H.

    1994-04-01

    Synchrotrons like the heavy-ion synchrotron SIS at GSI need an efficient low duty cycle injector (typical 1-pulse/s and 200-μs pulse length). To improve the peak current, an electron cyclotron resonance (ECR) ion source has been designed using a pulsed magnetic field (PuMa) to force ion extraction. We replaced the hexapole of a 10-GHz Minimafios ECR ion source by a vacuum chamber containing a water-cooled bilayered solenoid coil and a decapole permanent magnetic structure. A pulse line feeds the solenoid with a 250-μs pulse which increases the magnetic field in the minimum B region by 0.3 T. This process opens the magnetic bottle along the beam axis resulting in an extracted ion pulse. First tests of the PuMa ECR configuration in cw and pulsed operation are presented and analyzed.

  5. Micro drilling using deformable mirror for beam shaping of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Smarra, Marco; Strube, Anja; Dickmann, Klaus

    2016-03-01

    Using ultra-short laser pulses for micro structuring or drilling applications reduces the thermal influence to the surrounding material. The best achievable beam profile equals a Gaussian beam. Drilling with this beam profile results in cylindrical holes. To vary the shape of the holes, the beam can either be scanned or - for single pulse and percussion drilling - manipulated by masks or lenses. A high flexible method for beam shaping can be realized by using a deformable mirror. This mirror contains a piezo-electric ceramic, which can be deformed by an electric potential. By separating the ceramic into independent controllable segments, the shape of the surface can be varied individually. Due to the closed surface of the mirror, there is no loss of intensity due to diffraction. The mirror deformation is controlled by Zernike polynomials and results e.g. in a lens behavior. In this study a deformable mirror was used to generate e.g. slits in thin steel foils by percussion drilling using ultra-short laser pulses. The influence of the cylindrical deformation to the laser beam and the resulting geometry of the generated holes was studied. It was demonstrated that due to the high update rate up to 150 Hz the mirror surface can be varied in each scan cycle, which results in a high flexible drilling process.

  6. X-Ray Scattering Applications Using Pulsed X-Ray Sources

    SciTech Connect

    Larson, B.C.

    1999-05-23

    Pulsed x-ray sources have been used in transient structural phenomena investigations for over fifty years; however, until the advent of synchrotrons sources and the development of table-top picosecond lasers, general access to ligh temporal resolution x-ray diffraction was relatively limited. Advances in diffraction techniques, sample excitation schemes, and detector systems, in addition to IncEased access to pulsed sources, have ld tO what is now a diverse and growing array of pulsed-source measurement applications. A survey of time-resolved investigations using pulsed x-ray sources is presented and research opportunities using both present and planned pulsed x-ray sources are discussed.

  7. Short-Pulse Amplification by Strongly-Coupled Stimulated Brillouin Scattering

    NASA Astrophysics Data System (ADS)

    Edwards, Matthew; Jia, Qing; Mikhailova, Julia; Fisch, Nathaniel

    2016-10-01

    We examine the feasibility of strongly-coupled stimulated Brillouin scattering as a mechanism for the plasma-based amplification of sub-picosecond pulses. Fluid theory and particle-in-cell calculations are used to compare the relative advantages of Raman and Brillouin amplification over a broad range of parameters, with a focus on determining the maximum amplified pulse intensities and minimum durations that can be achieved. Amplification of short-wavelength pulses is considered in detail, with particular emphasis on the practical development of plasma-based x-ray amplifiers. Our results suggest that Brillouin scattering may allow amplification of shorter wavelength light than Raman scattering, but that at optical frequencies better performance is generally realized with Raman amplification, as strongly-coupled Brillouin scattering has limited capacity for amplifying sub-picosecond pulses. This work was supported by NNSA Grant No. DENA0002948 and AFOSR Grant No. FA9550-15-1-0391. M.R.E. gratefully acknowledges the support of the NSF through a Graduate Research Fellowship.

  8. Broadband short pulse measurement by autocorrelation with a sum-frequency generation set-up

    SciTech Connect

    Glotin, F.; Jaroszynski, D.; Marcouille, O.

    1995-12-31

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength {lambda}=8.5 {mu}m suggested that very short light pulses could be generated, about 500 fs wide (FWHM). For these measurements a Michelson interferometer with a Te crystal, as a non-linear detector, was used as a second order autocorrelation device. More recent measurements in similar conditions have confirmed that the laser pulses observed are indeed single: they are not followed by other pulses distant by the slippage length N{lambda}. As the single micropulse length is likely to depend on the slippage, more measurements at different wavelengths would be useful. This is not directly possible with our actual interferometer set-up, based on a phase-matched non-linear crystal. However, we can use the broadband non-linear medium provided by one of our users` experiments: Sum-Frequency Generation over surfaces. With such autocorrelation set-up, interference fringes are no more visible, but this is largely compensated by the frequency range provided. First tests at 8 {mu}m have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up.

  9. Photonic preprocessor for analog-to-digital-converter using a cavity-less pulse source.

    PubMed

    Wiberg, Andreas O J; Liu, Lan; Tong, Zhi; Myslivets, Evgeny; Ataie, Vahid; Kuo, Bill P-P; Alic, Nikola; Radic, Stojan

    2012-12-10

    A photonic preprocessor for analog to digital conversion is demonstrated and characterized using a cavity-less optical pulse source. The pulse source generates high fidelity pulses at 2 GHz repetition rate with temporal width of 3 ps. Chirped pulses are formed by cascaded amplitude and phase modulators, and subsequently compressed in dispersion compensating fiber. Sampling operation is performed with a dual-output Mach-Zehnder modulator, where the complimentary output enables a reduction of noise by 3 dB. Phase noise characterization shows that the phase noise of the generated pulses is fully dictated by the RF source. The high quality of the pulse source used in a sampling preprocessor experiment was verified by measuring 8 effective number of bits at 10 GHz and 7.0 effective number of bits at 40 GHz.

  10. A fast pulsed power source applied to treatment of conducting liquids and air

    SciTech Connect

    Heesch, E.J.M. van; Pemen, A.J.M.; Huijbrechts, P.A.H.J.; Laan, P.C.T. van der; Ptasinski, K.J.; Zanstra, G.J.; Jong, P. de

    2000-02-01

    Two pilot pulsed power sources were developed for fundamental investigations and industrial demonstrations of treatment of conducting liquids. The developed heavy-duty power sources have an output voltage of 100 kV (rise time 10 ns, pulse duration 150 ns, pulse repetition rate maximum 1,000 pps). A pulse energy of 0.5--3 J/pulse and an average pulse power of 1.5 kW have been achieved with an efficiency of about 80%. In addition, adequate electromagnetic compatibility is achieved between the high-voltage pulse sources and the surrounding equipment. Various applications, such as the use of pulsed electric fields (PEF's) or pulsed corona discharges for inactivation of microorganisms in liquids or air, have been tested in the laboratory. For PEF treatment, homogeneous electric fields in the liquid of up to 70 kV/cm at a pulse repetition rate of 10--400 pps could be achieved. The inactivation is found to be 85 kJ/L per log reduction for Pseudomonas fluorescens and 500 kJ/L per log reduction for spores of Bacillus cereus. Corona directly applied to the liquid is found to be more efficient than PEF. With direct corona they achieve 25 kJ/L per log reduction for both Gram positive and Gram negative bacteria. For air disinfection using their corona pulse source, the measured efficiencies are excellent: 2 J/L per log reduction.

  11. Spatial characterization of pulsed and continuous atom sources

    SciTech Connect

    Huie, C.W.

    1986-01-01

    A new concept for the determination of spatially resolved vibrational temperatures in atomic spectroscopic methods is demonstrated. A collimated laser beam is coupled to a vidicon camera to allow spatial mapping of absorption in flames. Vibrational temperature for each spatial location of the flame can be calculated by measuring the relative intensities of absorption from different vibrational levels in the ground states of the molecules. Temperature information generated by this system is very helpful to the understanding of dissociation and recombination of molecules in flames. The laser microprobe is a powerful technique for in situ elemental analysis of a small spot on the surfaces of any materials. Optimizations of the laser microprobe require the understanding of the fundamental processes that occur in the formation of the laser-generated plume. The availability of dynamic information such as spatial and temporal distribution of atoms and molecules is very important for the study of vaporization mechanisms. The spatial distribution of sodium dimers in a lower-generated plume is obtained for the first time in the laboratory. A new imaging instrument based on acousto-optic deflector has been developed for diagnostic studies of pulsed atoms sources. The device which has the capability of deflecting a laser beam across a spatial region of interest in the microsecond regime so that the transient events can be recorded in real-time is described. The instrument has been applied to the acquisition of spatially resolved scattering profiles of particles and absorption profiles of atoms in a laser microprobe.

  12. Mercury Cavitation Phenomenon in Pulsed Spallation Neutron Sources

    SciTech Connect

    Futakawa, Masatoshi; Naoe, Takashi; Kawai, Masayoshi

    2008-06-24

    Innovative researches will be performed at Materials and Life Science Experimental Facility in J-PARC, in which a mercury target system will be installed as MW-class pulse spallation neutron sources. Proton beams will be injected into mercury target to induce the spallation reaction. At the moment the intense proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. Localized impacts by micro-jets and/or shock waves which are caused by cavitation bubble collapse impose pitting damage on the vessel wall. The pitting damage which degrades the structural integrity of target vessels is a crucial issue for high power mercury targets. Micro-gas-bubbles injection into mercury may be useful to mitigate the pressure wave and the pitting damage. The visualization of cavitation-bubble and gas-bubble collapse behaviors was carried out by using a high-speed video camera. The differences between them are recognized.

  13. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

    SciTech Connect

    Shepherd, R; Chen, H; Ping, Y; Dyer, G; Wilks, S; Chung, H; Kemp, A; Hanson, S; Widmann, K; Fournier, K; Faenov, A; Pikuz, T; Niles, A; Beiersdorfer, P

    2007-02-27

    We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.

  14. Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M.; Neev, J.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  15. Atomic ionization by intense laser pulses of short duration: Photoelectron energy and angular distributions

    SciTech Connect

    Dondera, M.

    2010-11-15

    We introduce an adequate integral representation of the wave function in the asymptotic region, valid for the stage postinteraction between a one-electron atom and a laser pulse of short duration, as a superposition of divergent radial spherical waves. Starting with this representation, we derive analytic expressions for the energy and angular distributions of the photoelectrons and we show their connection with expressions used before in the literature. Using our results, we propose a method to extract the photoelectron distributions from the time dependence of the wave function at large distances. Numerical results illustrating the method are presented for the photoionization of hydrogenlike atoms from the ground state and several excited states by extreme ultraviolet pulses with a central wavelength of 13.3 nm and several intensities around the value I{sub 0}{approx_equal}3.51x10{sup 16} W/cm{sup 2}.

  16. Strong-field Breit-Wheeler pair production in short laser pulses: Relevance of spin effects

    NASA Astrophysics Data System (ADS)

    Jansen, M. J. A.; Kamiński, J. Z.; Krajewska, K.; Müller, C.

    2016-07-01

    Production of electron-positron pairs in the collision of a high-energy photon with a high-intensity few-cycle laser pulse is studied. By utilizing the frameworks of laser-dressed spinor and scalar quantum electrodynamics, a comparison between the production of pairs of Dirac and Klein-Gordon particles is drawn. Positron energy spectra and angular distributions are presented for various laser parameters. We identify conditions under which predictions from Klein-Gordon theory either closely resemble or largely differ from those of the proper Dirac theory. In particular, we address the question to which extent the relevance of spin effects is influenced by the short duration of the laser pulse.

  17. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    SciTech Connect

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.

    1989-04-01

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10/sup 12/ watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10/sup 9/ watts) and can be focussed to intensities of /approximately/10/sup 16/ W/cm/sup 2/. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs.

  18. Detection of Avalanche Victims Using Ultra-wideband Short-Pulse Radar

    NASA Astrophysics Data System (ADS)

    Chamma, Walid A.; Mende, Howard; Barrie, Greg; Robinson, Robert

    A short-pulse UWB radar system for search and rescue (SAR) operations of snow avalanche victims has been studied through numerical simulation and measurements. The FDTD method was used to model the radar system, the snow, and a realistic human phantom model buried in snow. A 0.5-ns UWB pulse with f0 = 2 GHz is used to illuminate the buried phantom from an array of nine transmitters. The reflected signals were received on a planer array and were processed using the time projection technique to generate ISAR images in the x-z and x-y planes. Farr impulse antennas were also used to measure reflected signals off buried targets, including a human phantom in snow. In both simulation and measurements, the removal of the background reflections (data with no buried targets) was a requirement to improve the dynamic range and toisolate the reflected signals due to buried targets.

  19. Circular polarization effects in ion acceleration from high intensity, short pulse laser interactions

    NASA Astrophysics Data System (ADS)

    Dollar, F.; Zulick, C.; Bulanov, S. S.; Chvykov, V.; Kalintchenko, G.; Matsuoka, T.; McGuffey, C.; Thomas, A. G. R.; Willingale, L.; Yanovsky, V.; Maksimchuk, A.; Krushelnick, K.; Petrov, G.; Davis, J.

    2011-10-01

    Experiments were performed to investigate ion acceleration effects from circular polarization from thin targets, using a high contrast, ultra-short laser pulse from the HERCULES laser facility at the Univ. of Michigan. Experiments were performed with 50 TW, 35 fs pulses at an intensity of >1021Wcm-2 on Si3N4 and Mylar targets of 30 nm to 1 μm thickness with contrast <10-13 . Protons with maximum energy 18 MeV and Carbon ions with energies of up to 10 MeV per nucleon were measured. Particle-in-cell simulations demonstrating the acceleration mechanism will be presented as well. Supported by NSF Physics Frontier Center FOCUS (Grant PHY-0114336), Defense Threat Reduction Agency, and Naval Research Laboratory. We acknowledge the OSIRIS consortium for the use of OSIRIS.

  20. Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height

    NASA Technical Reports Server (NTRS)

    Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

    1977-01-01

    A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

  1. Tamper to delay motion and decrease ionization of a sample during short pulse x-ray imaging

    DOEpatents

    London, Richard A.; Szoke; Abraham , Hau-Riege; Stefan P. , Chapman; Henry N.

    2007-06-26

    A system for x-ray imaging of a small sample comprising positioning a tamper so that it is operatively connected to the sample, directing short intense x-ray pulses onto the tamper and the sample, and detecting an image from the sample. The tamper delays the explosive motion of the sample during irradiation by the short intense x-ray pulses, thereby extending the time to obtain an x-ray image of the original structure of the sample.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  3. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    PubMed

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  4. High mode volume self filtering unstable resonator applied to a short pulse XeCl laser

    NASA Astrophysics Data System (ADS)

    Luches, A.; Nassisi, V.; Perrone, M. R.; Radiotis, E.

    1989-05-01

    A high mode volume non confocal self filtering unstable resonator has been applied to a short pulse XeCl laser. Such a resonator made up of a concave mirror (focal length is 25 cm) and a convex mirror (focal length is -25 cm), has a magnification | M|=34 and a cavity length of 151 cm. A nearly diffraction limited laser beam of 5.5 mJ, 10 ns duration and with a brightness of 2.5×10 13 W cm -2 sr -1 has been obtained. These results are compared to those obtained with another self-filtering unstable resonator having the same resonator length but | M|=10.

  5. Wakefield effects and solitary waves of an intense short laser pulse propagation in a plasma channel

    SciTech Connect

    Hong Xueren; Xie Baisong; Zhao Xueyan; Zhang Shan; Wu Haicheng

    2011-10-15

    In the presence of relativistic and channel-coupling nonlinearity and wakefield effects, the propagation characteristics and solitary waves of an intense short laser pulse in a preformed plasma channel are investigated. The evolution equation of the laser spot size is derived by using variational technique, the initial laser and plasma parameters for propagation with constant spot size, periodic defocusing and focusing oscillations, and solitary waves are identified. For illustration, some numerical results are also presented. It is found that the laser focusing is enhanced by the wakefield effects that result in a significant reduced focusing power.

  6. Modeling the absorption of intense, short laser pulses in steep density gradients

    SciTech Connect

    Alley, W.E.

    1991-01-28

    A subroutine which calculates the absorption of short pulse electromagnetic radiation in a material has been installed into the laser fusion modeling program called LASNEX. Calculational results show the necessity for NLTE physics to account for ionization, the development of non-exponential density profiles for the expanding plasma and movement of the critical point toward the surface which results in Doppler shifts of the reflected light. Comparison of calculations of local scale lengths with experiments shows not only good agreement but the correct scaling with intensity. 8 refs., 5 figs.

  7. Theory of suppressing avalanche process of carrier in short pulse laser irradiated dielectrics

    SciTech Connect

    Deng, H. X. E-mail: xtzu@uestc.edu.cn Zu, X. T. E-mail: xtzu@uestc.edu.cn Xiang, X.; Zheng, W. G.; Yuan, X. D.; Sun, K. E-mail: xtzu@uestc.edu.cn; Gao, F.

    2014-05-28

    A theory for controlling avalanche process of carrier during short pulse laser irradiation is proposed. We show that avalanche process of conduction band electrons (CBEs) is determined by the occupation number of phonons in dielectrics. The theory provides a way to suppress avalanche process and a direct judgment for the contribution of avalanche process and photon ionization process to the generation of CBEs. The obtained temperature dependent rate equation shows that the laser induced damage threshold of dielectrics, e.g., fused silica, increase nonlinearly with the decreases of temperature. Present theory predicts a new approach to improve the laser induced damage threshold of dielectrics.

  8. Ion acceleration in shell cylinders irradiated by a short intense laser pulse

    SciTech Connect

    Andreev, A.; Platonov, K.; Sharma, A.; Murakami, M.

    2015-09-15

    The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

  9. Atomic processes in plasmas created by an ultra-short laser pulse

    NASA Astrophysics Data System (ADS)

    Audebert, P.; Lecherbourg, L.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Blancard, C.; Cossé, P.; Faussurier, G.; Shepherd, R.; Renaudin, P.

    2008-05-01

    Point projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient aluminum plasma created by an ultra-short laser pulse. 1s-2p and 1s-3p absorption lines of weakly ionized aluminum were measured for an extended range of densities in a relatively low-temperature regime. Independent plasma characterization was obtained from frequency domain interferometry (FDI) diagnostic and allows the interpretation of the absorption spectra in terms of spectral opacities. The experimental spectra are compared with opacity calculations using the density and temperature inferred from the analysis of the FDI data.

  10. The RMT method for describing many-electron atoms in intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

    2012-11-01

    We describe how we have extended the underlying methods of the HELIUM code to describe multi-electron systems exposed to intense short-pulse laser light. We achieve this extension through exploiting the powerful R-matrix division-of-space concept to bring together a numerical method (basis set) most appropriate to the multi-electron finite inner region and a different numerical method (finite difference) most appropriate to the one-electron outer region. In order for the method to exploit massively parallel supercomputers efficiently, we time-propagate the wave function in both regions by employing schemes based on the Arnoldi method, long employed in HELIUM.

  11. The RMT method for describing many-electron atoms in intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

    2012-11-01

    We describe how we have developed an ab initio R-Matrix incorporating Time (RMT) method to provide an accurate description of the single ionization of a general many-electron atom exposed to short intense laser pulses. The new method implements the "division-of-space" concept central to R-matrix theory and takes over the sophisticated time-propagation algorithms of the HELIUM code. We have tested the accuracy of the new method by calculating multiphoton ionization rates of He and Ne and have found excellent agreement with other highly accurate and well-established methods.

  12. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    NASA Astrophysics Data System (ADS)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  13. Return current and proton emission from wire targets interacting with an intense short pulse laser

    NASA Astrophysics Data System (ADS)

    Beg, Farhat

    2004-05-01

    One of the important characteristics of short pulse high intensity laser-solid interactions is the generation of energetic charged particles, which result from the very efficient conversion of laser energy into hot electrons. Since the electrons in the electric field of the laser have relativistic quiver motions, the temperature of the hot electron distribution of the plasma produced at such extreme intensities can become very high. A large number of hot electrons (1013-1014) having an average energy of the order of 1-2 MeV can be generated as intensities exceed 1019 Wcm-2. Since the resulting beam current exceeds the Alfvén limit, a neutralizing return current of cold plasma electrons moving in the opposite direction is produced. Another source of return current is that due to the escape of very energetic electrons from the target, which then creates a large electrostatic potential due to charge separation. These return currents can cause significant ohmic heating. In addition escaping electrons establish the large electrostatic fields, accelerating a large number of protons from the target with energies of 10's of MeV. The experiments reported here were performed at the Rutherford Appleton Laboratory with the VULCAN laser facility at intensity greater than 5 x1019 Wcm-2 on wire targets. In some shots an additional wire or foil was placed nearby. The laser was blocked by the main wire target so that no laser light reached the additional wire or foil. Three main observations were made: (i) a Z-pinch was driven in the wire due to the return current, (ii) optical transition radiation (OTR) at 2w was generated and (iii) energetic proton emission was observed. The wire targets were observed to be ohmically heated and were m=0 unstable. The OTR emission is likely due to electron bunches accelerated by the ponderomotive force of the laser. The proton emission was in a form of thin disk perpendicular to the wire and centered on the wire at the laser focus. Proton

  14. Intense Pulsed Neutron Source progress report for 1991

    SciTech Connect

    Schriesheim, Alan

    1991-01-01

    The IPNS Progress Report 10th Anniversary Edition is being published in recognition of the first ten years of successful IPNS operation. To emphasize the significance of this milestone, we wanted this report to stand apart from the previous IPNS Progress Reports, and the best way to do this, we thought, was to make the design and organization of the report significantly different. In their articles, authors were asked to emphasize not only advances made since IPNS began operating but also the groundwork that was laid at its predecessor facilities - Argonne's ZING-P and ZING-P' prototype pulsed neutron sources and CP-5 reactor. Each article stands as a separate chapter in the report, since each represents a particular instrument or class of instruments, system, technique, or area of research. In some cases, contributions were similar to review articles in scientific journals, complete with extensive lists of references. Ten-year cumulative lists of members of IPNS committees and of scientists who have visited or done experiments at IPNS were assembled. A list of published and in press'' articles in journals, books, and conference proceedings, resulting from work done at IPNS during the past ten years, was compiled. And archival photographs of people and activities during the ten-year history of IPNS were located and were used liberally throughout the report. The titles of the chapters in this report are: accelerator; computer; radiation effects; powder; stress; single crystal; superconductivity; amorphous; small angle; reflection; quasielastic; inelastic; inelastic magnetic; deep inelastic; user program; the future; and publications.

  15. Intense Pulsed Neutron Source progress report for 1991

    SciTech Connect

    Not Available

    1991-12-31

    The IPNS Progress Report 10th Anniversary Edition is being published in recognition of the first ten years of successful IPNS operation. To emphasize the significance of this milestone, we wanted this report to stand apart from the previous IPNS Progress Reports, and the best way to do this, we thought, was to make the design and organization of the report significantly different. In their articles, authors were asked to emphasize not only advances made since IPNS began operating but also the groundwork that was laid at its predecessor facilities - Argonne`s ZING-P and ZING-P` prototype pulsed neutron sources and CP-5 reactor. Each article stands as a separate chapter in the report, since each represents a particular instrument or class of instruments, system, technique, or area of research. In some cases, contributions were similar to review articles in scientific journals, complete with extensive lists of references. Ten-year cumulative lists of members of IPNS committees and of scientists who have visited or done experiments at IPNS were assembled. A list of published and ``in press`` articles in journals, books, and conference proceedings, resulting from work done at IPNS during the past ten years, was compiled. And archival photographs of people and activities during the ten-year history of IPNS were located and were used liberally throughout the report. The titles of the chapters in this report are: accelerator; computer; radiation effects; powder; stress; single crystal; superconductivity; amorphous; small angle; reflection; quasielastic; inelastic; inelastic magnetic; deep inelastic; user program; the future; and publications.

  16. Properties of High-Frequency Sub-Wavelength Ripples on Stainless Steel 304L under Ultra Short Pulse Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Mitko, V. S.; Römer, G. R. B. E.; Veld, A. J. Huis in `t.; Skolski, J. Z. P.; Obona, J. V.; Ocelík, V.; De Hosson, J. T. M.

    The paper concentrates on surface texturing on sub-micro meter scale with ultra short laser pulses that has several applications, e.g. changing the hydrophilic/hydrophobic performance, optical or tribological properties of materials. In general, the formations of wavy structures, or ripples on a surface irradiated by short pulse lasers has been observed experimentally since 1965, and are usually referred to as Laser Induced Periodic Surface Structures (LIPSS). Generally Low Spatial Frequency LIPSS (LSFL) and High Spatial Frequency LIPSS (HSFL) are observed. The existing theoretical models do not describe the origin, nor growth of the ripples satisfactorily. That is why the experimental approach still plays a leading role in the investigation of ripple formation. In this paper we study the development of HSFL and LSFL as a result of picosecond laser pulses on a surface of stainless steel. Influences of number of pulses and pulse overlap on ripples growth were examined.

  17. Development and Applications of discharges generated in liquids with short high voltage pulses

    NASA Astrophysics Data System (ADS)

    Kolb, Juergen; Miron, Camelia; Kruth, Angela; Balcerak, Michal; Bonislawski, Michal; Holub, Marcin

    2016-09-01

    Discharges that are generated within a liquid have been of scientific interest for more than a century. The possibility for a breakdown development that is not mediated by an initial gaseous phase is still disputed. In this respect are especially discharges that are instigated with short high voltage pulses calling for attention. Associated with this specific excitation scheme is a change in plasma development, plasma parameters and reaction mechanisms in the liquid. We have compared discharges in a point-to-plane geometry that were generated with 50-us or 10-ns high voltage pulses. Time-resolved shadowgraphy and spectroscopy were performed to evaluate discharge structures, plasma parameter and reactive species that were formed in distilled water or ethanol. Different propagation modes, with velocities of 6.7 km/s for tree-like streamers and only 50 m/s for bush-like streamers, were observed. Optical emission spectroscopy has shown the formation of molecular bands of nitrogen, as well as strongly broadened atomic hydrogen and oxygen, which are likely to be responsible for the observed surface modifications of polymers. With nanosecond high voltage pulses we found an increase of unsaturated bondings for polyimide surfaces that were exposed in the discharge volume.

  18. The Radiation Dose Determination of the Pulsed X-ray Source

    NASA Astrophysics Data System (ADS)

    Miloichikova, I.; Stuchebrov, S.; Zhaksybayeva, G.; Wagner, A.

    2014-10-01

    In this paper the radiation dose measurement technique of the pulsed X-ray source RAP-160-5 is described. The dose rate measurement results from the pulsed X-ray beams at the different distance between the pulsed X-ray source focus and the detector obtained with the help of the thermoluminescent detectors DTL-02, the universal dosimeter UNIDOS E equipped with the plane-parallel ionization chamber type 23342, the dosimeter-radiometer DKS-96 and the radiation dosimeter AT 1123 are demonstrated. The recommendations for the dosimetry measurements of the pulsed X-ray generator RAP-160-5 under different radiation conditions are proposed.

  19. Channels of energy redistribution in short-pulse laser interactions with metal targets

    NASA Astrophysics Data System (ADS)

    Zhigilei, Leonid V.; Ivanov, Dmitriy S.

    2005-07-01

    The kinetics and channels of laser energy redistribution in a target irradiated by a short, 1 ps, laser pulse is investigated in computer simulations performed with a model that combines molecular dynamics (MD) simulations with a continuum description of the laser excitation and relaxation of the conduction band electrons, based on the two-temperature model (TTM). The energy transferred from the excited electrons to the lattice splits into several parts, namely the energy of the thermal motion of the atoms, the energy of collective atomic motions associated with the relaxation of laser-induced stresses, the energy carried away from the surface region of the target by a stress wave, the energy of quasi-static anisotropic stresses, and, at laser fluences above the melting threshold, the energy transferred to the latent heat of melting and then released upon recrystallization. The presence of the non-thermal channels of energy redistribution (stress wave and quasi-static stresses), not accounted for in the conventional TTM model, can have important implications for interpretation of experimental results on the kinetics of thermal and mechanical relaxation of a target irradiated by a short laser pulse as well as on the characteristics of laser-induced phase transformations. The fraction of the non-thermal energy in the total laser energy partitioning increases with increasing laser fluence.

  20. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    SciTech Connect

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-12-07

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  1. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    NASA Astrophysics Data System (ADS)

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-12-01

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  2. Short-pulse Calorimetric Load for High Power Millimeter-wave Beams

    NASA Astrophysics Data System (ADS)

    Gandini, F.; Bruschi, A.; Cirant, S.; Gittini, G.; Granucci, G.; Muzzini, V.; Sozzi, C.; Spinicchia, N.

    2007-02-01

    A spherical compact matched load, for high vacuum operation suited for short pulses (2 MW, 0.1 s) precise measurement has been designed to test high power gyrotrons Bruschi, Gandini, Muzzini, Spinicchia, Cirant, Gittini, Granucci, Mellera, Nardone, Simonetto, and Sozzi (Fusion Eng. Des. 56 57:649 654, 2001); Bruschi, Cirant, Gandini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, and Spinicchia (Nucl. Fusion 43:1513 1519, 2003); Bruschi, Cirant, Gandini, Gittini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, Spinicchia, Angella, and Signorelli (Development of CW and short-pulse calorimetric loads for high power millimeter-wave Beams, 23rd Symposium on Fusion Technology, September 20 24, 2004, Venice, Italy). In order to enhance the power handling capability of the load and to reduce the operation problems that may arise from an excessive reflection from the load, a ray tracing code has been written to model the power distribution on the inner surface and the pattern of the reflected radiation. The outcome of this code has been used to select a more convenient profile for the spreading mirror of the load and to optimize a pre-load specially conceived to minimize the power reflected fraction.

  3. On the nature of the sources of hard pulse X-ray radiation

    NASA Technical Reports Server (NTRS)

    Shklovskiy, I. S.

    1978-01-01

    Besides the identified sources of cosmic pulse X-ray radiation with globular clusters NGC 6624, NGC 1851 and MXB 1730-335 several new identifications were made. The source in Norma was probably identified with globular cluster NGC 5927, the source in Aquila with globular cluster NGC 6838 (M71), and the source in Puppis with globular cluster NGC 2298. Gamma pulses discovered by the Vela satellites and X-ray pulses thoroughly measured by the SAS-3, Ariel-5, and ANS satellites are thought to be the same phenomenon. The sources of such a radiation must be some kind of peculiarity at the central part of globular clusters; it is most probably a massive black hole. The sources of hard pulse radiation which cannot be identified with globular clusters are considered to be a new kind of galactic object, invisible globular clusters, which are naked nuclei of globular clusters.

  4. Reflectivity of plasmas created by high-intensity, ultra-short laser pulses

    SciTech Connect

    Gold, David Michael

    1994-06-01

    Experiments were performed to characterize the creation and evolution of high-temperature (T e~100eV), high-density (ne>1022cm-3) plasmas created with intense (~1012-1016W/cm2), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO2) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of ~3μm and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce ~3.5mJ, ~130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 1016W/cm2. In the insulator, SiO2, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities ~1016W/cm2, indicating a material-independent state insensitive to atomic or solid-state details.

  5. Development of a new pulsed source for photoacoustic imaging based on aperiodically poled lithium niobate

    PubMed Central

    Yankelevich, Diego; González, J. E.; Cudney, Roger S.; Ríos, Luis A.; Marcu, Laura

    2014-01-01

    We present the development of a source of deep-red radiation for photoacoustic imaging. This source, which is based on two cascaded wavelength conversion processes in aperiodically poled lithium niobate, emits 10 nanosecond pulses of over 500 µJ at 710 nm. Photoacoustic images were obtained from phantoms designed to mimic the optical and acoustic properties of oral tissue. Results indicate this device is a viable source of optical pulses for photoacoustic applications. PMID:24575341

  6. Manipulating mammalian cell by phase transformed titanium surface fabricated through ultra-short pulsed laser synthesis.

    PubMed

    Chinnakkannu Vijayakumar, Sivaprasad; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-15

    Developing cell sensitive indicators on interacting substrates that allows specific cell manipulation by a combination of physical, chemical or mechanical cues is a challenge for current biomaterials. Hence, various fabrication approaches have been created on a variety of substrates to mimic or create cell specific cues. However, to achieve cell specific cues a multistep process or a post-chemical treatment is often necessitated. So, a simple approach without any chemical or biological treatment would go a long way in developing bio-functionalized substrates to effectively modulate cell adhesion and interaction. The present investigation is aimed to study the manipulative activity induced by phase transformed titanium surface. An ultra-short laser is used to fabricate the phase transformed titanium surface where a polymorphic titanium oxide phases with titanium monoxide (TiO), tri-titanium oxide (Ti3O) and titanium dioxide (TiO2) have been synthesized on commercially pure titanium. Control over oxide phase transformed area was demonstrated via a combination of laser scanning time (laser pulse interaction time) and laser pulse widths (laser pulse to pulse separation time). The interaction of phase transformed titanium surface with NIH3T3 fibroblasts and MC3T3-E1 osteoblast cells developed a new bio-functionalized platforms on titanium based biomaterials to modulate cell migration and adhesion. The synthesized phase transformed titanium surface on the whole appeared to induce directional cues for cell migration with unique preferential cell adhesion unseen by other fabrication approaches. The precise bio-functionalization controllability exhibited during fabrication offers perceptible edge for developing a variety of smart bio-medical devices, implants and cardiovascular stents where the need in supressing specific cell adhesion and proliferation is of great demand.

  7. A 10-GeV, 5-MW proton source for a pulsed spallation source

    SciTech Connect

    Cho, Y.; Chae, Y.C.; Crosbie, E.

    1995-12-31

    A feasibility study for a pulsed spallation source based on a 5-MW, 10-GeV rapid proton synchrotron (RCS) is in progress. The integrated concept and performance parameters of the facility are discussed. The 10-GeV synchrotron uses as its injector the 2-GeV accelerator system of a 1-MW source described elsewhere. The 1-MW source accelerator system consists of a 400-MeV H{sup {minus}} linac with 2.5 MeV energy spread in the 75% chopped (25% removed) beam and a 30-Hz RCS that accelerates the 400-MeV beam to 2 GeV. The time averaged current of the accelerator system is 0.5 mA, equivalent to 1.04 {times} 10{sup 14} protons per pulse. The 10-GeV RCS accepts the 2 GeV beam and accelerates it to 10 GeV. Beam transfer from the 2-GeV synchrotron to the 10-GeV machine u highly efficient bunch-to-bucket injection, so that the transfer can be made without beam loss. The synchrotron lattice uses FODO cells of 90{degrees} phase advance. Dispersion-free straight sections are obtained using a missing magnet scheme. The synchrotron magnets are powered by dual-frequency resonant circuits. The magnets are excited at a 20-Hz rate and de-excited at 60-Hz. resulting in an effective 30-Hz rate. A key feature of the design of this accelerator system is that beam losses are minimized from injection to extraction, reducing activation to levels consistent with hands-on maintenance. Details of the study are presented.

  8. A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    NASA Astrophysics Data System (ADS)

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; van den Ende, Daan A.; Groen, Wilhelm A.; Janssen, Maurice H. M.

    2009-11-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10-6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv /v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever

  9. A short pulse (7 {mu}s FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    SciTech Connect

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; Janssen, Maurice H. M.; Ende, Daan A. van den; Groen, Wilhelm A.

    2009-11-15

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 {mu}s have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 {mu}m nozzle releases about 10{sup 16} particles/pulse and the beam brightness was estimated to be 4x10{sup 22} particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10{sup -6} Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow ({Delta}v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas

  10. Proceedings of the workshop on ion source issues relevant to a pulsed spallation neutron source: Part 2 workshop presentations

    SciTech Connect

    Schroeder, L.; Leung, Ka-Ngo; Alonso, J.

    1994-10-01

    As part of the Lawrence Berkeley Laboratory Pulsed Spallation Source study, this Workshop was convened to address ion-source technology`s present status with respect to the next-generation Pulsed Spallation Source in the 1-5 MW range for the neutron scattering community. Considerations of Low Energy Beam Transport (LEBT) parameters and designs were included in the discussions throughout the Workshop. Ion-source requirements and actually-achieved performances were assessed, resulting in a determination of research and development requirements to bridge the gap. Part 1 of these Proceedings summarizes the Workshop; Part 2 contains viewgraphs of Workshop presentations.

  11. Self-injection and acceleration of electrons during ionization of gas atoms by a short laser pulse

    SciTech Connect

    Singh, K.P.

    2006-04-15

    Using a relativistic three-dimensional single-particle code, acceleration of electrons created during the ionization of nitrogen and oxygen gas atoms by a laser pulse has been studied. Barrier suppression ionization model has been used to calculate ionization time of the bound electrons. The energy gained by the electrons peaks for an optimum value of laser spot size. The electrons created near the tail do not gain sufficient energy for a long duration laser pulse. The electrons created at the tail of pulse escape before fully interacting with the trailing part of the pulse for a short duration laser pulse, which causes electrons to retain sufficient energy. If a suitable frequency chirp is introduced then energy of the electrons created at the tail of the pulse further increases.

  12. Characterisation of a Surface-Flashover Ion Source with 10-250 ns Pulse Width

    SciTech Connect

    Falabella, S; Guethlein, G; Kerr, P L; Meyer, G A; Sampayan, S E; Tang, V; Morse, J D

    2008-08-05

    As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns. Thin film patterning techniques and deuteration parameters will be discussed.

  13. Using Adiabatic Inversion Pulses for Long-T2 Suppression in Ultra-short Echo Time (UTE) Imaging

    PubMed Central

    Larson, Peder E. Z.; Conolly, Steven M.; Pauly, John M.; Nishimura, Dwight G.

    2010-01-01

    Ultra-short echo time (UTE) imaging is a technique that can visualize tissues with sub-millisecond T2 values that have little or no signal in conventional MRI techniques. The short-T2 tissues, which include tendons, menisci, calcifications, and cortical bone, are often obscured by long-T2 tissues. This paper introduces a new method of long-T2 component suppression based on adiabatic inversion pulses that significantly improves the contrast of short-T2 tissues. Narrow bandwidth inversion pulses are used to selectively invert only long-T2 components. These components are then suppressed by combining images prepared with and without inversion pulses. Fat suppression can be incorporated by combining images with the pulses applied on the fat and water resonances. Scaling factors must be used in the combination to compensate for relaxation during the preparation pulses. The suppression is insensitive to RF inhomogeneities because it uses adiabatic inversion pulses. Simulations and phantom experiments demonstrate the adiabatic pulse contrast and how the scaling factors are chosen. In vivo 2D UTE images in the ankle and lower leg show excellent, robust long-T2 suppression for visualization of cortical bone and tendons. PMID:17969119

  14. Use of Proportional Counters for Yield Measurement in Extremely Short Pulses of Fast Neutrons: Counting Statistics and Absolute Calibration

    NASA Astrophysics Data System (ADS)

    Tarifeño-Saldivia, A.; Mayer, R. E.; Pavez, C.; Soto, L.

    2010-08-01

    A method for absolute calibration of proportional counters for pulsed fast neutrons is presented. The method is based on the use of an isotopic standard source and development of a model for counting detected events from area of a signal compounded by single piled up neutron pulses. Effects of detection counting statistics and electrical background noise are also considered.

  15. Heat Distribution in the Lower Leg from Pulsed Short-Wave Diathermy and Ultrasound Treatments

    PubMed Central

    Garrett, Candi L.; Draper, David O.; Knight, Kenneth L.

    2000-01-01

    Objective: To compare tissue temperature rise and decay after 20-minute diathermy and ultrasound treatments. Design and Setting: We inserted 3 26-gauge thermistor microprobes into the medial aspect of the anesthetized triceps surae muscle at a depth of 3 cm and spaced 5 cm apart. Eight subjects received the diathermy treatment first, followed by the ultrasound treatment. This sequence was reversed for the remaining 8 subjects. The diathermy was applied at a frequency of 27.12 MHz at the following settings: 800 bursts per second, 400-microsecond burst duration, 850-microsecond interburst interval, peak root mean square amplitude of 150 W per burst, and an average root mean square output of 48 W per burst. The ultrasound was delivered at a frequency of 1 MHz and an intensity of 1.5 W/cm2 in the continuous mode for 20 minutes over an area of 40 times the effective radiating area. The study was performed in a ventilated research laboratory. Subjects: Sixteen (11 men, 5 women) healthy subjects (mean age = 23.56 ± 4.73 years) volunteered to participate in this study. Measurements: We recorded baseline, final, and decay temperatures for each of the 3 sites. Results: The average temperature increases over baseline temperature after pulsed short-wave diathermy were 3.02°C ± 1.02°C in site 1, 4.58°C ± 0.87°C in site 2, and 3.28°C ± 1.64°C in site 3. The average temperature increases over baseline temperature after ultrasound were only 0.17°C ± 0.40°C, 0.09°C ± 0.56°C, and -0.43°C ± 0.41°C in sites 1, 2, and 3, respectively. The temperature dropped only 1°C in 7.65 ± 4.96 minutes after pulsed short-wave diathermy. Conclusions: We conclude that pulsed short-wave diathermy was more effective than 1-MHz ultrasound in heating a large muscle mass and resulted in the muscles' retaining heat longer. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5. PMID:16558608

  16. High intensity heat-pulse source operates without cooling system

    NASA Technical Reports Server (NTRS)

    Russell, L. D.

    1970-01-01

    Tungsten-iodine quartz lamp with on-off control is mounted at focus of ellipsoidal reflector and shutter is mounted at conjugate focus. Flux sensor monitors lamp and actuates shutter which emits a heat pulse when the radiant flux builds up to requisite level.

  17. Deposition of superhard amorphous carbon films by pulsed arc sources

    SciTech Connect

    Scheibe, H.J.; Schultrich, B.; Ziegele, H.; Siemroth, P.

    1996-12-31

    Hydrogen-free amorphous carbon films with hardness comparable to crystalline superhard materials have been deposited by special Pulsed arc techniques. By the combination of very high hardness, low adhesion and high smoothness, these films show superior behaviour in wear and glide applications. The influence of plasma and deposition conditions on these film properties and the choice of optimum conditions are discussed.

  18. Noise measurements in shunted, shorted, and fully electroded quartz gauges in the Saturn plasma radiation source x-ray simulator

    SciTech Connect

    Barrett, W.H.; Greenwoll, J.I.; Smith, C.W.; Johnson, D.E.; De La Cruz, C.F.

    1995-08-01

    This paper describes recent work to improve the measurement of the stress response of materials to intense, short pulses of radiation. When Saturn fires, large prompt electrical noise pulses are induced in stress measurement circuits. The conventional wisdom has been that the shorted guard ring quartz gauge was the only configuration with acceptable prompt signal-to-noise characteristics for stress measurements in this pulsed radiation environment. However, because of abnormal signal distortion, the shorted guard ring gauge is restricted to a maximum stress of about 8 kbars. Below this level, the normal, quantified signal distortion is correctable with analytical deconvolution techniques. The shunted guard ring gauge is acceptable for Egli fidelity measurements to about 25 kbars with negligible signal distortion. Experiments were conducted on the Saturn soft x-ray source which show that higher fidelity shunted guard ring gauges can successfully measure stress with acceptable induced noise. We also found that a 50-ohm impedance matching resistor at the gauge reduced the prompt noise amplitude and improved the baseline quality of the measurement prior to shock wave arrival.

  19. High-energy ion generation in interaction. of short laser pulse with high-density plasma

    NASA Astrophysics Data System (ADS)

    Sentoku, Y.; Bychenkov, V. Y.; Flippo, K.; Maksimchuk, A.; Mima, K.; Mourou, G.; Sheng, Z. M.; Umstadter, D.

    2002-03-01

    Multi-MeV ion production from the interaction of a short laser pulse with a high-density plasma, accompanied by an underdense preplasma, has been studied with a particle-in-cell simulation and good agreement is found with experiment. The mechanism primarily responsible for the acceleration of ions is identified. Comparison with experiments sheds light on the ion-energy dependence on laser intensity, preplasma scale length, and relative ion energies for a multi-species plasma. Two regimes of maximum ion-energy dependence on laser intensity, I, have been identified: subrelativistic, ∝I; and relativistic, ∝. Simulations show that the energy of the accelerated ions versus the preplasma scale length increases linearly and then saturates. In contrast, the ion energy decreases with the thickness of the solid-density plasma.

  20. Propagation of short stress pulses in discrete strongly nonlinear tunable metamaterials.

    PubMed

    Xu, Yichao; Nesterenko, Vitali F

    2014-08-28

    The propagation of short pulses with wavelength comparable to the size of a unit cell has been studied in a one-dimensional discrete metamaterial composed of steel discs alternating with toroidal nitrile O-rings under different levels of precompression using experiments, numerical simulations and theoretical analysis. This strongly nonlinear metamaterial is more tunable than granular chains composed of linear elastic spherical particles and has better potential for attenuation of dynamic loads. A double power-law relationship for compressed O-rings was found to describe adequately their quasi-static and dynamic behaviour with significantly different elastic moduli. It is demonstrated that the double power-law metamaterial investigated allows a dramatic increase in sound speed and acoustic impedance of three to four times using a moderate force.

  1. Integrable multi-component generalization of a modified short pulse equation

    NASA Astrophysics Data System (ADS)

    Matsuno, Yoshimasa

    2016-11-01

    We propose a multi-component generalization of the modified short pulse (SP) equation which was derived recently as a reduction of Feng's two-component SP equation. Above all, we address the two-component system in depth. We obtain the Lax pair, an infinite number of conservation laws and multisoliton solutions for the system, demonstrating its integrability. Subsequently, we show that the two-component system exhibits cusp solitons and breathers for which the detailed analysis is performed. Specifically, we explore the interaction process of two cusp solitons and derive the formula for the phase shift. While cusp solitons are singular solutions, smooth breather solutions are shown to exist, provided that the parameters characterizing the solutions satisfy certain conditions. Last, we discuss the relation between the proposed system and existing two-component SP equations.

  2. Multistage ion acceleration in the interaction of intense short laser pulse with ultrathin target

    NASA Astrophysics Data System (ADS)

    Mirzanejhad, Saeed; Joulaei, Atefeh; Babaei, Javad

    2016-12-01

    New analytical formalism is invented in the description of ion acceleration in the interaction of intense high-contrast short laser pulse with ultrathin target. The electrostatic shock wave acceleration is our fundamental point of view, but different criteria are obtained for description of various acceleration phenomenon. Acceleration condition for an ion with a definite charge to mass ratio ( z / m ) and initial velocity β0 is obtained in the electrostatic shock (ES) field in front side of the foil. According to this point of view, self organized multistage ion acceleration formalism is proposed and confirmed by the 1D3V particle in cell simulation results. In this formalism, ions may be re-accelerated repeatedly in the developing ES field.

  3. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    SciTech Connect

    Renaudin, P.; Blancard, C.; Cosse, P.; Faussurier, G.; Lecherbourg, L.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-02

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  4. Initial color development in radiochromic dye films after a short intense pulse of accelerated electrons

    NASA Astrophysics Data System (ADS)

    Uribe, R. M.; Barcelo, M.; McLaughlin, W. L.; Buenfil, A. E.; Rios, J.

    The radiation response of different dye precursors in several host plastics has been investigated after a single short-pulse irradiation with 2.5-MeV electrons. It was observed that in most films the radiation-initiated color development proceeds mainly during the first 300 seconds, after such high dose-rate irradiation (≈ 10 12 Gy/s). Absorption spectra show that the main absorption band increases at the expense of a shorter-wavelength precursor absorption band, showing an isosbestic point approximately midway between the two absorption bands. It was found that a certain combination of dye precursor and host plastic (namely a polyamide containing an aromatic group) constitutes a film which shows a very fast increase in optical density of the main absorption band, making it suitable for immediate dosimetric analysis in very high dose-rate installations.

  5. Modeling of Dense Plasma Effects in Short-Pulse Laser Experiments

    NASA Astrophysics Data System (ADS)

    Walton, Timothy; Golovkin, Igor; Macfarlane, Joseph; Prism Computational Sciences, Madison, WI Team

    2016-10-01

    Warm and Hot Dense Matter produced in short-pulse laser experiments can be studied with new high resolving power x-ray spectrometers. Data interpretation implies accurate modeling of the early-time heating dynamics and the radiation conditions that are generated. Producing synthetic spectra requires a model that describes the major physical processes that occur inside the target, including the hot-electron generation and relaxation phases and the effect of target heating. An important issue concerns the sensitivity of the predicted K-line shifts to the continuum lowering model that is used. We will present a set of PrismSPECT spectroscopic simulations using various continuum lowering models: Hummer/Mihalas, Stewart-Pyatt, and Ecker-Kroll and discuss their effect on the formation of K-shell features. We will also discuss recently implemented models for dense plasma shifts for H-like, He-like and neutral systems.

  6. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Renaudin, P.; Lecherbourg, L.; Blancard, C.; Cossé, P.; Faussurier, G.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  7. Monte Carlo simulation of wave sensing with a short pulse radar

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Davisson, L. D.; Kutz, R. L.

    1977-01-01

    A Monte Carlo simulation is used to study the ocean wave sensing potential of a radar which scatters short pulses at small off-nadir angles. In the simulation, realizations of a random surface are created commensurate with an assigned probability density and power spectrum. Then the signal scattered back to the radar is computed for each realization using a physical optics analysis which takes wavefront curvature and finite radar-to-surface distance into account. In the case of a Pierson-Moskowitz spectrum and a normally distributed surface, reasonable assumptions for a fully developed sea, it has been found that the cumulative distribution of time intervals between peaks in the scattered power provides a measure of surface roughness. This observation is supported by experiments.

  8. Two-dimensional electromagnetic Child-Langmuir law of a short-pulse electron flow

    SciTech Connect

    Chen, S. H.; Tai, L. C.; Liu, Y. L.; Ang, L. K.; Koh, W. S.

    2011-02-15

    Two-dimensional electromagnetic particle-in-cell simulations were performed to study the effect of the displacement current and the self-magnetic field on the space charge limited current density or the Child-Langmuir law of a short-pulse electron flow with a propagation distance of {zeta} and an emitting width of W from the classical regime to the relativistic regime. Numerical scaling of the two-dimensional electromagnetic Child-Langmuir law was constructed and it scales with ({zeta}/W) and ({zeta}/W){sup 2} at the classical and relativistic regimes, respectively. Our findings reveal that the displacement current can considerably enhance the space charge limited current density as compared to the well-known two-dimensional electrostatic Child-Langmuir law even at the classical regime.

  9. Pulse shape measurements using single shot-frequency resolved optical gating for high energy (80 J) short pulse (600 fs) laser

    SciTech Connect

    Palaniyappan, S.; Johnson, R.; Shimada, T.; Gautier, D. C.; Letzring, S.; Offermann, D. T.; Fernandez, J. C.; Shah, R. C.; Jung, D.; Hegelich, B. M.; Hoerlein, R.

    2010-10-15

    Relevant to laser based electron/ion accelerations, a single shot second harmonic generation frequency resolved optical gating (FROG) system has been developed to characterize laser pulses (80 J, {approx}600 fs) incident on and transmitted through nanofoil targets, employing relay imaging, spatial filter, and partially coated glass substrates to reduce spatial nonuniformity and B-integral. The device can be completely aligned without using a pulsed laser source. Variations of incident pulse shape were measured from durations of 613 fs (nearly symmetric shape) to 571 fs (asymmetric shape with pre- or postpulse). The FROG measurements are consistent with independent spectral and autocorrelation measurements.

  10. Large Area and Short-Pulse Shock Initiation of a Tatb/hmx Mixed Explosive

    NASA Astrophysics Data System (ADS)

    Guiji, Wang; Chengwei, Sun; Jun, Chen; Cangli, Liu; Jianheng, Zhao; Fuli, Tan; Ning, Zhang

    2007-12-01

    The large area and short-pulse shock initiation experiments on the plastic bonded mixed explosive of TATB(80%) and HMX(15%) have been performed with an electric gun where a Mylar flyer of 10-19 mm in diameter and 0.05˜0.30 mm in thickness was launched by an electrically exploding metallic bridge foil. The cylindrical explosive specimens (Φ16 mm×8 mm in size) were initiated by the Mylar flyers in thickness of 0.07˜0.20 mm, which induced shock pressure in specimen was of duration ranging from 0.029 to 0.109 μs. The experimental data were treated with the DRM(Delayed Robbins-Monro) procedure and to provide the initiation threshold of flyer velocities at 50% probability are 3.398˜1.713 km/s and that of shock pressure P 13.73˜5.23 GPa, respectively for different pulse durations. The shock initiation criteria of the explosive specimen at 50% and 100% probabilities are yielded. In addition, the 30° wedged sample was tested and the shock to detonation transition (SDT) process emerging on its inclined surface was diagnosed with a device consisting of multiple optical fiber probe, optoelectronic transducer and digital oscilloscope. The POP plot of the explosive has been gained from above SDT data.

  11. ePLAS examination of short-pulse laser- wire and foil interactions

    NASA Astrophysics Data System (ADS)

    Faehl, R.; Mason, R. J.; Wei, M.; Ma, T.; Beg, F. N.; Stephens, R.

    2009-11-01

    An enhanced 2D implicit hybrid simulation code ePLAS has been used to examine short-pulse laser interactions with cone-wire and foil targets. The code deposits picosecond pulses of 1 μm, ˜3x10^20 W/cm^2 laser light near critical, and tracks resultant megavolt ``hot'' particle-in-cell (PIC) electrons through an ionized copper or carbon background plasma. The background is modeled as collisional Van Leer ``cold electron'' and ion fluids. The code now elevates the returning fluid colds to hot particles, when their energy exceeds a specified threshold (e.g. 20 keV). It also uses real equations of state from analytic models or the Sesame Tables. Cylindrical and Cartesian results are compared. The emphasis will be on recent cone/nail-wire experimentsfootnotetextT. Ma et al., ``Transport of energy by ultra-intense laser-generated electrons in nail-wire targets,'' submitted to Physics of Plasmas with target heads of varying mass, and revisited foil studies.footnotetextR. J. Mason, et al. Phys. Rev. E 72, 01540 (R) (2005).

  12. Investigation of energy partitioning from Leopard short-pulse laser interactions in mass limited targets

    NASA Astrophysics Data System (ADS)

    Griffin, B.; Sawada, H.; Yabuuchi, T.; McLean, H.; Patel, P.; Beg, F.

    2013-10-01

    The energy distribution in the interaction of a high-intensity, short-pulse laser with a mass limited target was investigated by simultaneously collecting x-ray and particle data. The Leopard laser system at the Nevada Terawatt Facility delivered 15 J of energy in a 350 fs pulse duration. With a beam spot size limited to within 8 μm, the target interaction achieved a peak intensity of 1019 W/cm2 at 20° incidence. The size of the Cu foil targets was varied from 2-20 μm in thickness and from 50 by 50 μm to 2000 by 2000 μm in surface area. A Bragg crystal x-ray spectrometer and a spherical crystal imager were used to measure 7.5-9.5 keV x-rays and 8.05 keV monochromatic x-ray images respectively. The escaping electrons and protons in the rear were monitored with a magnet-based electron spectrometer and radiochromic film. Preliminary results show both a decrease of the K β/K α ratio and a stronger He α emission for smaller sized targets, less than 250 by 250 μm. The detailed analyses of the K α images and particle data will be presented.

  13. Short-pulse excimer laser performances and its applications: I. ophthamology

    NASA Astrophysics Data System (ADS)

    Przybylski, Marius; Simon, Gabriel

    1997-05-01

    A new very small powerful air-cooled excimer laser (193, 248, 308 nm) with metal-ceramic technology was developed by ATL Lasertechnik in Germany. The laser won 1995 Prize for the best innovation awarded by German federal states of Berlin & Brandenburg. The pulse energy of 10 - 20 mJ at high rep rates (200 - 500 Hz) from an active volume of only 1 cm3 are reached. The raw laser beam produces energy density of > 100 mJ/cm2 which is comparable to the performance of standard (large) excimer lasers. Its very short pulse length (3 ns), permits extremely high peak power density (30 MW/cm2). The ATLEX SP laser uses a new type of pre-ionization technique providing high beam homogeneity at low discharge voltages. Small footprint and weight, low operation costs opens up new industrial (micro-machining) and biomedical applications. Recently the ATLEX SP laser (193 nm) has been used for corneal refractive surgery. The setup consists of splitting a 193 nm laser beam into couples of beams which simultaneously ablates the corneal surface in a symmetrical scan-like fashion. Refractive changes up to 20 diopters were realized. Results of an analysis by corneal topography showed homogeneous ablation throughout the entire ablation zone.

  14. Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies.

    PubMed

    Ji, Q; Seidl, P A; Waldron, W L; Takakuwa, J H; Friedman, A; Grote, D P; Persaud, A; Barnard, J J; Schenkel, T

    2016-02-01

    The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ∼1 eV using intense, short pulses (∼1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He(+) ions leads to more uniform energy deposition of the target material than Li(+) ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li(+) ions from a hot plate type ion source. He(+) beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

  15. Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

    SciTech Connect

    Ji, Q. Seidl, P. A.; Waldron, W. L.; Takakuwa, J. H.; Persaud, A.; Schenkel, T.; Friedman, A.; Grote, D. P.; Barnard, J. J.

    2016-02-15

    The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ∼1 eV using intense, short pulses (∼1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He{sup +} ions leads to more uniform energy deposition of the target material than Li{sup +} ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li{sup +} ions from a hot plate type ion source. He{sup +} beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

  16. Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

    NASA Astrophysics Data System (ADS)

    Ji, Q.; Seidl, P. A.; Waldron, W. L.; Takakuwa, J. H.; Friedman, A.; Grote, D. P.; Persaud, A.; Barnard, J. J.; Schenkel, T.

    2016-02-01

    The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ˜1 eV using intense, short pulses (˜1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He+ ions leads to more uniform energy deposition of the target material than Li+ ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li+ ions from a hot plate type ion source. He+ beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

  17. Effect of pulse-modulated microwaves on fullerene ion production with electron cyclotron resonance ion source.

    PubMed

    Asaji, T; Uchida, T; Minezaki, H; Oshima, K; Racz, R; Muramatsu, M; Biri, S; Kitagawa, A; Kato, Y; Yoshida, Y

    2012-02-01

    Fullerene plasmas generated by pulse-modulated microwaves have been investigated under typical conditions at the Bio-Nano electron cyclotron resonance ion source. The effect of the pulse modulation is distinct from that of simply structured gases, and then the density of the fullerene plasmas increased as decreasing the duty ratio. The density for a pulse width of 10 μs at the period of 100 μs is 1.34 times higher than that for CW mode. We have studied the responses of fullerene and argon plasmas to pulsed microwaves. After the turnoff of microwave power, fullerene plasmas lasted ∼30 times longer than argon plasmas.

  18. Pulsed blue laser source based on frequency quadrupling of a thulium fiber laser

    NASA Astrophysics Data System (ADS)

    Honea, Eric; Savage-Leuchs, Matthias; Bowers, Mark S.; Yilmaz, Tolga; Mead, Roy

    2013-03-01

    We describe a pulsed blue (485 nm) laser source based on frequency quadrupling a pulsed Tm fiber laser. Up to 1.2 W at 485 nm was generated with an M2 of 1.3. At 10 kHz pulse repetition frequency, the output pulse at 485 nm was 65 ns FWHM resulting in an estimated peak power of 1.8 kW. We anticipate further improvements in power scaling with higher power Tm fiber lasers and improved conversion efficiency to the blue with optimized AR coatings and nonlinear optical crystals.

  19. Means and method for characterizing high power, ultra short laser pulses in a real time, on line manner

    DOEpatents

    Veligdan, J.T.

    1994-03-08

    An ultra short (<10 ps), high power laser pulse is temporally characterized by a system that uses a physical measurement of a wavefront that has been altered in a known manner. The system includes a first reflection switch to remove a portion of a pulse from a beam of pulses, then includes a second reflection switch, operating in a mode that is opposite to the first reflection switch, to slice off a portion of that removed portion. The sliced portion is then directed to a measuring device for physical measurement. The two reflection switches are arranged with respect to each other and with respect to the beam of ultra short pulses such that physical measurement of the sliced portion is related to the temporal measurement of the ultra short pulse by a geometric or trigonometric relationship. The reflection switches are operated by a control pulse that is directed to impinge on each of the reflection switches at a 90[degree] angle of incidence. 8 figures.

  20. FY05 LDRD Final ReportTime-Resolved Dynamic Studies using Short Pulse X-Ray Radiation

    SciTech Connect

    Nelson, A; Dunn, J; van Buuren, T; Budil, K; Sadigh, B; Gilmer, G; Falcone, R; Lee, R; Ng, A

    2006-02-10

    Established techniques must be extended down to the ps and sub-ps time domain to directly probe product states of materials under extreme conditions. We used short pulse ({le} 1 ps) x-ray radiation to track changes in the physical properties in tandem with measurements of the atomic and electronic structure of materials undergoing fast laser excitation and shock-related phenomena. The sources included those already available at LLNL, including the picosecond X-ray laser as well as the ALS Femtosecond Phenomena beamline and the SSRL based sub-picosecond photon source (SPPS). These allow the temporal resolution to be improved by 2 orders of magnitude over the current state-of-the-art, which is {approx} 100 ps. Thus, we observed the manifestations of dynamical processes with unprecedented time resolution. Time-resolved x-ray photoemission spectroscopy and x-ray scattering were used to study phase changes in materials with sub-picosecond time resolution. These experiments coupled to multiscale modeling allow us to explore the physics of materials in high laser fields and extreme non-equilibrium states of matter. The ability to characterize the physical and electronic structure of materials under extreme conditions together with state-of-the-art models and computational facilities will catapult LLNL's core competencies into the scientific world arena as well as support its missions of national security and stockpile stewardship.

  1. Propagation of the Ultra-Short Laser Pulses Through the Helical 1D Photonic Crystal Structure with Twist Defect

    NASA Astrophysics Data System (ADS)

    Antonov, Dmitrii V.; Iegorov, Roman

    2016-02-01

    The presence of the photonic band-gap is a featured property of the cholesteric liquid crystals (CLC). It can be practically realized for almost any reasonable wavelengths with very high degree of tunability. We have investigated theoretically the influence of the twist defect of the CLC helical structure onto the bandwidth-limited ultra-short laser pulse propagating inside the photonic band-gap. The changes of both pulse duration and peak power with defect angle were observed together with pulse acceleration and retardation for a case of normal incidence of the light.

  2. Simulations of High-Intensity Short-Pulse Lasers Incident on Reduced Mass Targets

    NASA Astrophysics Data System (ADS)

    King, Frank W.

    This thesis presents the results of a series of fully kinetic particle-in-cell (PIC) simulations of reduced mass targets with pre-plasma subjected to high-intensity short-pulse lasers. The simulations are performed in one, two, and three dimensions. The results of these simulations show that the creation of an electrostatic collisionless ion shock in the preplasma controls the creation of an above solid density ion perturbation in the target bulk, and this determines the reduced mass target heating and deformation. The ion perturbation is initiated by a population of high-energy electrons that rapidly spread throughout the target and reflux. The perturbation spreads longitudinally and transversely through the target and results in compression followed by the destruction of the target. This deformation requires a kinetic treatment due to the generation of non-equilibrium particle distributions and the role of ballistic electrons and ions. Kinetic and fluid simulations are compared and both exhibit the basic features of the above solid density ion perturbation, but the magnitude of the effect and the speed of propagation vary significantly between the two methods. Kinetic simulations do not naturally include equation-of-state physics and other aspects of the problem. Both approaches are complementary. The requirements on spatial resolution, particle count, and other numerical parameters are addressed in this work. From these simulations, the behavior of the reduced mass targets is found to vary significantly depending on the laser focal spot size or the intensity of the laser pulse. This occurs even if the energy and power of the laser pulses are held constant. The number of dimensions used in the particle-in-cell simulations has been observed to have a significant effect on late-time heating of the target, but not during or shortly after laser excitation. This is due to the representation of the equilibration process as the initial population of laser heated

  3. The Dosimetric Parameters Investigation of the Pulsed X-ray and Gamma Radiation Sources

    NASA Astrophysics Data System (ADS)

    Stuchebrov, S. G.; Miloichikova, I. A.; Shilova, X. O.

    2016-01-01

    The most common type of radiation used for diagnostic purposes are X-rays. However, X-rays methods have limitations related to the radiation dose for the biological objects. It is known that the use of the pulsed emitting source synchronized with the detection equipment for internal density visualization of objects significant reduces the radiation dose to the object. In the article the analysis of the suitability of the different dosimetric equipment for the radiation dose estimation of the pulsed emitting sources is carried out. The approbation results on the pulsed X-ray generator RAP-160-5 of the dosimetry systems workability with the pulse radiation and its operation range are presented. The results of the dose field investigation of the portable betatron OB-4 are demonstrated. The depth dose distribution in the air, lead and water of the pulsed bremsstrahlung generated by betatron are shown.

  4. Pulsed voltage electrospray ion source and method for preventing analyte electrolysis

    DOEpatents

    Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

    2011-12-27

    An electrospray ion source and method of operation includes the application of pulsed voltage to prevent electrolysis of analytes with a low electrochemical potential. The electrospray ion source can include an emitter, a counter electrode, and a power supply. The emitter can include a liquid conduit, a primary working electrode having a liquid contacting surface, and a spray tip, where the liquid conduit and the working electrode are in liquid communication. The counter electrode can be proximate to, but separated from, the spray tip. The power system can supply voltage to the working electrode in the form of a pulse wave, where the pulse wave oscillates between at least an energized voltage and a relaxation voltage. The relaxation duration of the relaxation voltage can range from 1 millisecond to 35 milliseconds. The pulse duration of the energized voltage can be less than 1 millisecond and the frequency of the pulse wave can range from 30 to 800 Hz.

  5. Pulsed discharge ionization source for miniature ion mobility spectrometers

    DOEpatents

    Xu, Jun; Ramsey, J. Michael; Whitten, William B.

    2004-11-23

    A method and apparatus is disclosed for flowing a sample gas and a reactant gas (38, 43) past a corona discharge electrode (26) situated at a first location in an ion drift chamber (24), applying a pulsed voltage waveform comprising a varying pulse component and a dc bias component to the corona discharge electrode (26) to cause a corona which in turn produces ions from the sample gas and the reactant gas, applying a dc bias to the ion drift chamber (24) to cause the ions to drift to a second location (25) in the ion drift chamber (24), detecting the ions at the second location (25) in the drift chamber (24), and timing the period for the ions to drift from the corona discharge electrode to the selected location in the drift chamber.

  6. Letter Report on 500 nA Pulsed Current from Field Ionization Source

    SciTech Connect

    Ellsworth, Jennifer L.

    2013-12-12

    We recently produced a milestone 500 nA of pulsed current using 40 Ir field ionizer electrodes in our ion source. In conclusion, we have produced the milestone pulsed current of 500 nA using 40 electrochemically etched iridium tips in a field ionization source. The pulsed current output is repeatable and scales as expected with gas fill pressure and bias voltage. We expect these current will be sufficient to produce neutral yields of 1∙107 DT n/s.

  7. INSTRUMENTS AND METHODS OF INVESTIGATION: Microstructure optical fibers for a new generation of fiber-optic sources and converters of light pulses

    NASA Astrophysics Data System (ADS)

    Zheltikov, Aleksei M.

    2007-07-01

    Breakthroughs in microstructure-fiber technologies are pushing the development of a new class of fiber-optic frequency converters, broadband light sources, and short-pulse lasers. The frequency profile of dispersion and the spatial profile of electromagnetic field distribution in waveguide modes of microstructure fibers can be tailored by modifying the core and cladding design on a micro- and nanoscale, suggesting ways of creating novel fiber-optic devices providing the highly efficient spectral and temporal transformation of laser pulses with pulse widths ranging from dozens of nanoseconds to a few optical cycles (several femtoseconds) within a broad range of peak powers from hundreds of watts to several gigawatts. In new fiber lasers, microstructure fibers provide a precise balance of dispersion within a broad spectral range, allowing the creation of compact all-fiber sources of high-power ultrashort light pulses.

  8. Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Xie, Xinglong; Zhu, Jianqiang; Zhu, Haidong; Yang, Qingwei; Kang, Jun; Guo, Ailin; Gao, Qi

    2014-11-01

    In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultra-short pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultra-short laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

  9. AGB stars as a source of short-lived radioactive nuclei in the solar nebula

    NASA Technical Reports Server (NTRS)

    Wasserburg, G. J.; Gallino, R.; Busso, M.; Raiteri, C. M.

    1993-01-01

    The purpose is to estimate the possible contribution of some short-lived nuclei to the early solar nebula from asymptotic giant branch (AGB) sources. Low mass (1 to 3 solar mass) AGB stars appear to provide a site for synthesis of the main s process component for solar system material with an exponential distribution of neutron irradiations varies as exp(-tau/tau(sub 0)) (where tau is the time integrated neutron flux with a mean neutron exposure tau(sub 0)) for solar abundances with tau(sub 0) = 0.28 mb(sup -1). Previous workers estimated the synthesis of key short-lived nuclei which might be produced in AGB stars. While these calculations exhibit the basic characteristics of nuclei production by neutron exposure, there is need for a self-consistent calculation that follows AGB evolution and takes into account the net production from a star and dilution with the cloud medium. Many of the general approaches and the conclusions arrived at were presented earlier by Cameron. The production of nuclei for a star of 1.5 solar mass during the thermal pulsing of the AGB phase was evaluated. Calculations were done for a series of thermal pulses with tau(sub 0) = 0.12 and 0.28 mb(sup -1). These pulses involve s nucleosynthesis in the burning shell at the base of the He zone followed by the ignition of the H burning shell at the top of the He zone. After about 10-15 cycles the abundances of the various nuclei in the He zone become constant. Computations of the abundances of all nuclei in the He zone were made following Gallino. The mass of the solar nebula was considered to consist of some initial material of approximately solar composition plus some contributions from AGB stars. The ratios of the masses required from the AGB He burning zone to the ISM necessary to produce the observed value of Pd-107/Pd-108 in the early solar system were calculated and this dilution factor was applied to all other relevant nuclei.

  10. Pulsed, Inductively Generated, Streaming Plasma Ion Source for Heavy Ion Fusion Linacs

    SciTech Connect

    Steven C. Glidden; Howard D Sanders; John B. Greenly; Daniel L. Dongwoo

    2006-04-28

    This report describes a compact, high current density, pulsed ion source, based on electrodeless, inductively driven gas breakdown, developed to meet the requirements on normalized emittance, current density, uniformity and pulse duration for an ion injector in a heavy-ion fusion driver. The plasma source produces >10 μs pulse of Argon plasma with ion current densities >100 mA/cm2 at 30 cm from the source and with strongly axially directed ion energy of about 80 eV, and sub-eV transverse temperature. The source has good reproducibility and spatial uniformity. Control of the current density during the pulse has been demonstrated with a novel modulator coil method which allows attenuation of the ion current density without significantly affecting the beam quality. This project was carried out in two phases. Phase 1 used source configurations adapted from light ion sources to demonstrate the feasibility of the concept. In Phase 2 the performance of the source was enhanced and quantified in greater detail, a modulator for controlling the pulse shape was developed, and experiments were conducted with the ions accelerated to >40 kV.

  11. Report on the international workshop on cold moderators for pulsed neutron sources.

    SciTech Connect

    Carpenter, J. M.

    1999-01-06

    The International Workshop on Cold Moderators for Pulsed Neutron Sources resulted from the coincidence of two forces. Our sponsors in the Materials Sciences Branch of DOE's Office of Energy Research and the community of moderator and neutron facility developers both realized that it was time. The Neutron Sources Working Group of the Megascience Forum of the Organization for Economic Cooperation and Development offered to contribute its support by publishing the proceedings, which with DOE and Argonne sponsorship cemented the initiative. The purposes of the workshop were: to recall and improve the theoretical groundwork of time-dependent neutron thermalization; to pose and examine the needs for and benefits of cold moderators for neutron scattering and other applications of pulsed neutron sources; to summarize experience with pulsed source, cold moderators, their performance, effectiveness, successes, problems and solutions, and the needs for operational data; to compile and evaluate new ideas for cold moderator materials and geometries; to review methods of measuring and characterizing pulsed source cold moderator performance; to appraise methods of calculating needed source characteristics and to evaluate the needs and prospects for improvements; to assess the state of knowledge of data needed for calculating the neutronic and engineering performance of cold moderators; and to outline the needs for facilities for testing various aspects of pulsed source cold moderator performance.

  12. Ipsilateral medial olivocochlear reflex adaptation of the primary-source DPOAE component measured with pulsed tones

    NASA Astrophysics Data System (ADS)

    Dalhoff, Ernst; Zelle, Dennis; Gummer, Anthony W.

    2015-12-01

    Measurement of contralateral suppression or ipsilateral adaptation of DPOAE due to the medial olivocochlear reflex (MOCR) in humans has so far been complicated by interference between the two major contributors to a DPOAE signal, namely, the nonlinear and the reflection-source components. For instance, while the MOCR has been shown to act inhibitory to the cochlear amplifier, a considerable share of the measured responses has been reported to be of the excitatory type (e.g. 22% for contralateral adaptation in [11]), and it has been shown that the magnitudes of ipsilateral adaptation as well as contralateral suppression depend on the precise frequency choice relative to the position of dips in the DPOAE fine structure [3, 8]. To separate MOCR effects on both source components, we developed a paradigm consisting of five short f2 pulses presented during a 0.35 s on-period of the f1 primary within blocks of 1.35 s length. The responses at f1 and f2 were cancelled using the primary-tone phase variation technique [13]. In 16 normal-hearing subjects, we measured MOCR-induced ipsilateral adaptation at three near-by frequencies in the DPOAE fine structure, corresponding roughly to characteristic interference states between the two major source components of a DPOAE, i.e. constructive, destructive and quadrature interference. Measurements were performed in the frequency range 1.7 ≤ f2 ≤ 2 kHz, f2/f1 = 1.2, and with moderate primary-tone levels (L2 = 45 dB SPL, L1 = 57 dB SPL). Analysis of the DPOAE time traces showed that the nonlinear component typically presents inhibitory adaptation between the 1st and the 5th pulses (median: 0.92 dB). Fitting a single exponential function to the pooled data yielded adaptation of 1.49 dB. From 26 statistically significant MOCR effects (P < 0.1) ranging between 0.29 and 2.81 dB, no excitatory response was detected. The separation of the DPOAE sources when analysing MOCR effects on ipsilateral DPOAE offers the potential of investigating

  13. Staged Inductive Pulse Generator with Capacitive Current Source.

    DTIC Science & Technology

    1986-10-24

    depends on the performance of the fuse opening switch and the vacuum flashover output switch. Sections III and IV briefly discuss the development of these...It was assumed that the vacuum flashover switch closed when 20 kV was across it, compared with the measured value of 25 kV. C. Late-Time Voltage ...up to 25 kV/cm when the voltage pulse generated by the second fuse is applied 1-2 us after the first fuse explodes. IV. VACUUM FLASHOVER SWITCH A

  14. Source-to-sensation level ratio of transmitted biosonar pulses in an echolocating false killer whale.

    PubMed

    Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

    2006-07-01

    Transmitted biosonar pulses, and the brain auditory evoked potentials (AEPs) associated with those pulses, were synchronously recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP amplitude was investigated as a function of the transmitted biosonar pulse source level. For that, a few thousand of the individual AEP records were sorted according to the spontaneously varied amplitude of synchronously recorded biosonar pulses. In each of the sorting bins (in 5-dB steps) AEP records were averaged to extract AEP from noise; AEP amplitude was plotted as a function of the biosonar pulse source level. For comparison, AEPs were recorded to external (in free field) sound pulses of a waveform and spectrum similar to those of the biosonar pulses; amplitude of these AEPs was plotted as a function of sound pressure level. A comparison of these two functions has shown that, depending on the presence or absence of a target, the sensitivity of the whale's hearing to its own transmitted biosonar pulses was 30 to 45 dB lower than might be expected in a free acoustic field.

  15. Effect of plasma density scale length on the properties of bremsstrahlung x-ray sources created by picosecond laser pulses

    SciTech Connect

    Courtois, C.; Compant La Fontaine, A.; Landoas, O.; Lidove, G.; Meot, V.; Morel, P.; Nuter, R.; Lefebvre, E.; Boscheron, A.; Grenier, J.; Aleonard, M. M.; Gerbaux, M.; Gobet, F.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.

    2009-01-15

    Results of an experimental study of multi-MeV bremsstrahlung x-ray sources created by picosecond laser pulses are presented. The x-ray source is created by focusing the short pulse in an expanding plasma obtained by heating a solid target with a time-delayed nanosecond laser beam. The high-energy part of the x-ray spectrum and emission lobe are inferred from photonuclear activation techniques. The x-ray dose is measured with silicon diodes. Two-dimensional images of the source are reconstructed from a penumbral imaging technique. These results indicate the creation of a relatively small source, below 200 {mu}m diameter, delivering doses up to 12 mrad in air at 1 m with x-ray temperature up to 2.8 MeV. The diagnostics used give access to a whole set of coherent experimental results on the x-ray source properties which are compared to extensive numerical simulations. X-ray intensity and temperature are found to increase with the size of the preplasma.

  16. Effect of plasma density scale length on the properties of bremsstrahlung x-ray sources created by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Courtois, C.; Compant La Fontaine, A.; Landoas, O.; Lidove, G.; Méot, V.; Morel, P.; Nuter, R.; Lefebvre, E.; Boscheron, A.; Grenier, J.; Aléonard, M. M.; Gerbaux, M.; Gobet, F.; Hannachi, F.; Malka, G.; Scheurer, J. N.; Tarisien, M.

    2009-01-01

    Results of an experimental study of multi-MeV bremsstrahlung x-ray sources created by picosecond laser pulses are presented. The x-ray source is created by focusing the short pulse in an expanding plasma obtained by heating a solid target with a time-delayed nanosecond laser beam. The high-energy part of the x-ray spectrum and emission lobe are inferred from photonuclear activation techniques. The x-ray dose is measured with silicon diodes. Two-dimensional images of the source are reconstructed from a penumbral imaging technique. These results indicate the creation of a relatively small source, below 200μm diameter, delivering doses up to 12mrad in air at 1m with x-ray temperature up to 2.8MeV. The diagnostics used give access to a whole set of coherent experimental results on the x-ray source properties which are compared to extensive numerical simulations. X-ray intensity and temperature are found to increase with the size of the preplasma.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  18. The physical response of soft musculoskeletal tissues to short-pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Dark, Marta Lyselle

    of the interaction of short laser pulses with cartilage tissue, and measured significant physical properties of knee meniscus with a minimally invasive laser technique. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  19. Compression of ultra-short pulses due to cascaded second order nonlinearities in photonic bandgap structures

    NASA Astrophysics Data System (ADS)

    Joseph, Shereena; Shahid Khan, Mohd.; Hafiz, Aurangzeb Khurram

    2016-03-01

    The cascaded second order nonlinearities in a 1-D photonic bandgap structure (1-D PBG) in the spectral domain have been explored. A weak signal pulse operating at frequency of interest is seeded with a strong pulse operating at its second harmonic (SH) frequency. The interaction of both pulses in the periodic structure takes place with a particular phase mismatch condition. The intensity of SH pulse controls the propagation of signal pulse and the signal pulse exhibits pulse compression at particular input SH intensity. Considering the parameter for GaInP/InAlP PBG structure we have demonstrated pulse compression from 290 fs to 155 fs. The dependency of pulse compression on the structural parameters, group velocity mismatch, group velocity dispersion and input intensity of pump has also been explored.

  20. Electrophysical and optophysical properties of air ionized by a short pulse of fast electrons

    NASA Astrophysics Data System (ADS)

    Vagin, Iu. P.; Stal', N. L.; Khokhlov, V. D.; Chernoiarskii, A. A.

    A method for solving the nonstationary kinetic equation of electron deceleration is developed which is based on the multigroup approximation. The electron distribution function in air ionized by nonstationary sources of primary electrons is determined, and the avalanche formation of secondary electrons is considered. Theoretical and experimental results are presented on the time dependence of the air luminescence intensity in two spectral intervals, one including the 391.4 nm N2(+) band and the other including the 337.1 nm N2 band, for different values of gas pressure under the effect of a short beam of electrons with energies of 100 keV.

  1. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    NASA Astrophysics Data System (ADS)

    Shakhmuratov, R. N.

    2017-03-01

    The resonant filtering method transforming the frequency-modulated radiation field into a train of short pulses is proposed to be applied in the optical domain. Effective frequency modulation can be achieved by using an electro-optic modulator. Due to frequency modulation, a narrow-spectrum cw radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning a narrow-bandwidth filter in resonance with the n th spectral component of the comb transforms the radiation field into bunches of pulses, with n pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in the formation of pulses, while destructive interference is seen as dark windows between pulses. It is indicated that the optimal thickness of the resonant filter is several orders of magnitude smaller than the necessary thickness of the dispersive filters used before in the optical domain to produce short pulses from the frequency-modulated field.

  2. A source of high-power pulses of elliptically polarized ultrawideband radiation

    SciTech Connect

    Andreev, Yu. A. Efremov, A. M.; Koshelev, V. I.; Kovalchuk, B. M.; Petkun, A. A.; Sukhushin, K. N.; Zorkaltseva, M. Yu.

    2014-10-01

    Here, we describe a source of high-power ultrawideband radiation with elliptical polarization. The source consisting of a monopolar pulse generator, a bipolar pulse former, and a helical antenna placed into a radioparent container may be used in tests for electromagnetic compatibility. In the source, the helical antenna with the number of turns N = 4 is excited with a high-voltage bipolar pulse. Preliminary, we examined helical antennas at a low-voltage source aiming to select an optimal N and to estimate a radiation center position and boundary of a far-field zone. Finally, characteristics of the source in the operating mode at a pulse repetition rate of 100 Hz are presented in the paper as well. Energy efficiency of the antenna is 0.75 at the axial ratio equal to 1.3. The effective potential of radiation of the source at the voltage amplitudes of the bipolar pulse generator equal to -175/+200 kV reaches 280 kV.

  3. Self-compression of intense short laser pulses in relativistic magnetized plasma

    SciTech Connect

    Olumi, M.; Maraghechi, B.

    2014-11-15

    The compression of a relativistic Gaussian laser pulse in a magnetized plasma is investigated. By considering relativistic nonlinearity and using non-linear Schrödinger equation with paraxial approximation, a second-order differential equation is obtained for the pulse width parameter (in time) to demonstrate the longitudinal pulse compression. The compression of laser pulse in a magnetized plasma can be observed by the numerical solution of the equation for the pulse width parameter. The effects of magnetic field and chirping are investigated. It is shown that in the presence of magnetic field and negative initial chirp, compression of pulse is significantly enhanced.

  4. Three-dimensional extremely-short optical pulses in carbon nanotube arrays in the presence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Zhukov, Alexander V.; Bouffanais, Roland; Belonenko, Mikhail B.; Galkina, Elena N.

    2016-12-01

    In this paper, we study the behavior of three-dimensional extremely-short optical pulses propagating in a system made of carbon nanotubes in the presence of an external magnetic field applied perpendicular both to the nanotube axis and to the direction of propagation of the pulse. The evolution of the electromagnetic field is classically derived on the basis of the Maxwell’s equations. The electronic system of carbon nanotubes is considered in the low-temperature approximation. Our analysis reveals the novel and unique ability of controlling the shape of propagating short optical pulses by tuning the intensity of the applied magnetic field. This effect paves the way for the possible development of innovative applications in optoelectronics.

  5. Proposal for a High-Brightness Pulsed Electron Source

    SciTech Connect

    Zolotorev, Max; Commins, Eugene D.; Heifets, Sam; Sannibale,Fernando

    2006-03-15

    We propose a novel scheme for a high-brightness pulsedelectron source, which has the potential for many useful applications inelectron microscopy, inverse photo-emission, low energy electronscattering experiments, and electron holography. A description of theproposed scheme is presented.

  6. Results of Research on Overcoming Pulse Shortening of GW Class HPM Sources

    DTIC Science & Technology

    2007-11-02

    The RPM sources basic research program of the Air Force has a major emphasis on the pulse shortening problem. This includes collaborative work in...universities and the Phillips Laboratory . We have demonstrated two fundamentally different RPM sources which radiate rf power in excess of 1 GW and are

  7. Characterization of a Surface-Flashover Ion Source with 10 - 250 ns Pulse Width

    SciTech Connect

    Falabella, S; Guethlein, G; Kerr, P L; Meyer, G A; Sampayan, S E; Tang, V; Morse, J D

    2008-08-05

    As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. An electrochemically-etched mask was used to define the electrode areas on the substrate during the sputtered deposition of the titanium films. Deuterium loading of the films was performed in an all metal-sealed vacuum chamber containing a heated stage. Deuterium ion current from the source was determined by measuring the neutrons produced when the ions impacted a deuterium-loaded target held at -90 kV. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns.

  8. Storm pulses and varying sources of hydrologic carbon export from a mountainous watershed

    NASA Astrophysics Data System (ADS)

    Jung, Byung-Joon; Lee, Hyun-Ju; Jeong, Jong-Jin; Owen, Jeffrey; Kim, Bomchul; Meusburger, Katrin; Alewell, Christine; Gebauer, Gerhard; Shope, Christopher; Park, Ji-Hyung

    2012-05-01

    SummaryAlthough soil erosion and leaching can transfer a substantial portion of the annual terrestrial carbon (C) increment to aquatic systems, little is known about rapid changes in the amount and characteristics of soil organic C exported from mountainous watersheds during storm events. To trace short-term changes in sources and characteristics of soil organic C exported during storm events, we investigated storm-induced changes in concentrations of particulate and dissolved organic C (POC and DOC) and the stable isotope composition of suspended sediment (SS) in a mountainous, mixed land-use watershed in northern South Korea. Biweekly stream sampling in a headwater forest stream and a watershed outlet receiving agricultural runoff showed that concentrations of SS and POC were higher in the watershed outlet. In both the forest stream and outlet, POC concentrations were lower than DOC concentrations during baseflow, but increased rapidly with rising discharge during intense storms, resulting in higher peak POC concentrations than peak DOC concentrations. When δ13C and δ15N were compared between SS and potential source soils during three storm events, SS δ13C and δ15N in the forest stream were similar to forest floor δ13C and δ15N. SS δ13C and δ15N in the watershed outlet reflected the contribution from forest and cropland mineral soils during peak flow, with sand-size SS displaying increasing δ13C and δ15N with rising rainfall intensity. The results suggest that storm pulses of POC can be a transient, but dominant pathway of hydrologic C export overwhelming DOC export and that POC sources and characteristics can rapidly change corresponding to varying rainfall intensity.

  9. Short-pulse generation at 10 μm in an active cw-injected ring laser cavity

    NASA Astrophysics Data System (ADS)

    Bourdet, Gilbert L.

    2003-09-01

    Continuous coherent light conversion in a train of short pulses with good efficiency is possible with a multipass interferometer in which the frequency is shifted at every pass with an acousto-optic frequency shifter. This technique allows one to generate a spectrum made of equidistant components, interferences of which build intense light pulses. Unfortunately, both the width and efficiency of the pulses are limited by the losses undergone by the waves traveling through the interferometer cavity. Improvement of the pulse duration, the peak intensity, and the contrast can be expected in such an experiment when an amplifier is set up inside the cavity. I report on theoretical computations related to this apparatus and apply this theoretical model to a high-pressure CO2 amplifier.

  10. Low dose short duration pulsed electromagnetic field effects on cultured human chondrocytes: An experimental study

    PubMed Central

    Anbarasan, Selvam; Baraneedharan, Ulaganathan; Paul, Solomon FD; Kaur, Harpreet; Rangaswami, Subramoniam; Bhaskar, Emmanuel

    2016-01-01

    Background: Pulsed electromagnetic field (PEMF) is used to treat bone and joint disorders for over 30 years. Recent studies demonstrate a significant effect of PEMF on bone and cartilage proliferation, differentiation, synthesis of extracellular matrix (ECM) and production of growth factors. The aim of this study is to assess if PEMF of low frequency, ultralow field strength and short time exposure have beneficial effects on in-vitro cultured human chondrocytes. Materials and Methods: Primary human chondrocytes cultures were established using articular cartilage obtained from knee joint during joint replacement surgery. Post characterization, the cells were exposed to PEMF at frequencies ranging from 0.1 to 10 Hz and field intensities ranging from 0.65 to 1.95 μT for 60 min/day for 3 consecutive days to analyze the viability, ECM component synthesis, proliferation and morphology related changes post exposure. Association between exposure doses and cellular effects were analyzed with paired't’ test. Results: In-vitro PEMF exposure of 0.1 Hz frequency, 1.95 μT and duration of 60 min/day for 3 consecutive days produced the most favorable response on chondrocytes viability (P < 0.001), ECM component production (P < 0.001) and multiplication. Exposure of identical chondrocyte cultures to PEMFs of 0.65 μT field intensity at 1 Hz frequency resulted in less significant response. Exposure to 1.3 μT PEMFs at 10 Hz frequency does not show any significant effects in different analytical parameters. Conclusions: Short duration PEMF exposure may represent a new therapy for patients with Osteoarthritis (OA). PMID:26955182

  11. Robust Short-Pulse, High-Peak-Power Laser Transmitter for Optical Communications

    NASA Technical Reports Server (NTRS)

    Wright, Malcolm W.

    2009-01-01

    We report on a pulsed fiber based master oscillator power amplifier laser at 1550 nm to support moderate data rates with high peak powers in a compact package suitable for interplanetary optical communications. To accommodate pulse position modulation, the polarization maintaining laser transmitter generates pulses from 0.1 to 1 ns with variable duty cycle over a pulse repetition frequency range of 10 to 100 MHz.

  12. 3D target array for pulsed multi-sourced radiography

    DOEpatents

    Le Galloudec, Nathalie Joelle

    2016-02-23

    The various technologies presented herein relate to the generation of x-rays and other charged particles. A plurality of disparate source materials can be combined on an array to facilitate fabrication of co-located mixed tips (point sources) which can be utilized to form a polychromatic cloud, e.g., a plurality of x-rays having a range of energies and or wavelengths, etc. The tips can be formed such that the x-rays are emitted in a direction different to other charged particles to facilitate clean x-ray sourcing. Particles, such as protons, can be directionally emitted to facilitate generation of neutrons at a secondary target. The various particles can be generated by interaction of a laser irradiating the array of tips. The tips can be incorporated into a plurality of 3D conical targets, the conical target sidewall(s) can be utilized to microfocus a portion of a laser beam onto the tip material.

  13. A compact picosecond pulsed laser source using a fully integrated CMOS driver circuit

    NASA Astrophysics Data System (ADS)

    He, Yuting; Li, Yuhua; Yadid-Pecht, Orly

    2016-03-01

    Picosecond pulsed laser source have applications in areas such as optical communications, biomedical imaging and supercontinuum generation. Direct modulation of a laser diode with ultrashort current pulses offers a compact and efficient approach to generate picosecond laser pulses. A fully integrated complementary metaloxide- semiconductor (CMOS) driver circuit is designed and applied to operate a 4 GHz distributed feedback laser (DFB). The CMOS driver circuit combines sub-circuits including a voltage-controlled ring oscillator, a voltagecontrolled delay line, an exclusive-or (XOR) circuit and a current source circuit. Ultrashort current pulses are generated by the XOR circuit when the delayed square wave is XOR'ed with the original square wave from the on-chip oscillator. Circuit post-layout simulation shows that output current pulses injected into an equivalent circuit load of the laser have a pulse full width at half maximum (FWHM) of 200 ps, a peak current of 80 mA and a repetition rate of 5.8 MHz. This driver circuit is designed in a 0.13 μm CMOS process and taped out on a 0.3 mm2 chip area. This CMOS chip is packaged and interconnected with the laser diode on a printed circuit board (PCB). The optical output waveform from the laser source is captured by a 5 GHz bandwidth photodiode and an 8 GHz bandwidth oscilloscope. Measured results show that the proposed laser source can output light pulses with a pulse FWHM of 151 ps, a peak power of 6.4 mW (55 mA laser peak forward current) and a repetition rate of 5.3 MHz.

  14. An all solid state pulse power source for high PRF induction accelerators

    SciTech Connect

    Kirbie, H., LLNL

    1998-06-01

    Researchers at the Lawrence Livermore National Laboratory (LLNL) are developing a flexible, all solid-state pulsed power source that will enable an induction accelerator to produce mulitkiloampere electron beams at a maximum pulse repetition frequency (prf) of 2 MHz. The prototype source consists of three, 15-kV, 4.8-kA solid-state modulators stacked in an induction adder configuration. Each modulator contains over 1300 field-effect transistors (FETs) that quickly connect and disconnect four banks of energy storage capacitors to a magnetic induction core. The FETs are commanded on and off by an optical signal that determines the duration of the accelerating pulse. Further electronic circuitry is provided that resets the magnetic cores in each modulator immediately after the accelerating pulse. The system produces bursts of five or more pulses with an adjustable pulse width that ranges from 200 ns to 2 {micro}s The pulse duty factor within a burst can be as high as 25% while still allowing time for the induction core to reset. The solid-state modulator described above is called ARM-II and is named for the Advanced Radiographic Machine (ARM)-a powerful radiographic accelerator that will be the principal diagnostic device for the future Advanced Hydrotest Facility (AHF).

  15. Matching a (sub)nanosecond pulse source to a corona plasma reactor

    NASA Astrophysics Data System (ADS)

    Huiskamp, T.; Beckers, F. J. C. M.; Hoeben, W. F. L. M.; van Heesch, E. J. M.; Pemen, A. J. M.

    2016-10-01

    In this paper we investigate the energy transfer from the pulses of a (sub)nanosecond pulse source to the plasma in a corona-plasma reactor. This energy transfer (or ‘matching’) should be as high as possible. We studied the effect of multiple parameters on matching, such as the reactor configuration, the pulse duration and amplitude and the energy density. The pulse reflection on the reactor interface has a significant influence on matching, and should be as low as possible to transfer the most energy into the reactor. We developed a multiple-wire inner conductor for the reactor which decreases the vacuum impedance of the reactor to decrease the pulse reflection on the reactor interface while maintaining a high electric field on the wire. The results were very encouraging and showed an energy transfer efficiency of over 90 percent. The matching results further show that there is only a small effect on the matching between different wire diameters. In addition, a long reactor and a long pulse result in the best matching due to the more intense plasma that is generated in these conditions. Finally, even without the multiple-wire reactor, we are able to achieve a very good matching (over 80 percent) between our pulse source and the reactor.

  16. Plasma processes in water under effect of short duration pulse discharges

    NASA Astrophysics Data System (ADS)

    Gurbanov, Elchin

    2013-09-01

    It is very important to get a clear water without any impurities and bacteria by methods, that don't change the physical and chemical indicators of water now. In this article the plasma processes during the water treatment by strong electric fields and short duration pulse discharges are considered. The crown discharge around an electrode with a small radius of curvature consists of plasma leader channels with a high conductivity, where the thermo ionization processes and UV-radiation are taken place. Simultaneously the partial discharges around potential electrode lead to formation of atomic oxygen and ozone. The spark discharge arises, when plasma leader channels cross the all interelectrode gap, where the temperature and pressure are strongly grown. As a result the shock waves and dispersing liquid streams in all discharge gap are formed. The plasma channels extend, pressure inside it becomes less than hydrostatic one and the collapse and UV-radiation processes are started. The considered physical processes can be successfully used as a basis for development of pilot-industrial installations for conditioning of drinking water and to disinfecting of sewage.

  17. Thermal interaction of short-pulsed laser focused beams with skin tissues

    NASA Astrophysics Data System (ADS)

    Jiao, Jian; Guo, Zhixiong

    2009-07-01

    Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.

  18. Detection of the Abraham force with a succession of short optical pulses

    NASA Astrophysics Data System (ADS)

    Brevik, Iver; Ellingsen, Simen Å.

    2012-08-01

    For over a century, two rival descriptions of electromagnetic field momentum in matter have coexisted, due to Abraham and Minkowski, respectively. We propose a setup for measuring the difference between Abraham's and Minkowski's predictions in optics. To wit, a setup is proposed in which the transient “Abraham force,” a consequence of the Abraham energy-momentum tensor of 1909, may be measured directly. We show that when a train of short laser pulses is sent through a fiber wound up on a cylindrical drum, the Abraham theory predicts a torque, which, by inserting realistic parameters, is found to be detectable. Indeed, the same torque when calculated with the Minkowski tensor takes the opposite sign. Numerical estimates show that with a typical torsion pendulum setup and standard laser parameters, the angular deflection is in the order of 10-3 rad, which is easily measurable and even visible to the naked eye. Although its prediction is a century old, the Abraham force has proven experimentally elusive, and to our knowledge no macroscopic experimental demonstration of the difference between the predictions of the two mentioned energy-momentum tensors exists at optical frequencies.

  19. Invited paper: Short pulse generation in mid-IR fiber lasers

    NASA Astrophysics Data System (ADS)

    Hudson, Darren D.

    2014-12-01

    Mode-locked fiber lasers emitting short pulses of light at wavelengths of 2 μm and longer are reviewed. Rare-earth doped silica and fluoride fiber lasers operating in the mode-locked regime in the mid-IR (2-5 μm) have attracted attention due to their usefulness to spectroscopy, nonlinear optics, laser surgery, remote sensing and ranging to name a few. While silica fiber lasers are fundamentally limited to emission wavelengths below 2.2 μm, fluoride fiber lasers can reach to nearly 4 μm. The relative infancy of fluoride fibers as compared to silica fibers means the field has work to do to translate the mode-locking techniques to systems beyond 2 μm. However, with the recent demonstration of a stable, mode-locked 3 μm fiber laser, the possibility of achieving high performance 3 μm class mode-locked fiber lasers looks promising.

  20. Large Area and Short Pulsed Shock Initiation of A TATB/HMX Mixed Explosive

    NASA Astrophysics Data System (ADS)

    Wang, Guiji; Sun, Chengwei; Chen, Jun; Liu, Cangli; Tan, Fuli; Zhang, Ning

    2007-06-01

    The large area and short pulsed shock initiation experiment on a plastic bonded mixed explosive of TATB(80%) and HMX(15%) has been performed with an electric gun where a mylar flyer of 19mm in diameter and 0.05˜0.30mm in thickness is launched by an electrically exploding metallic bridge foil. The cylindrical explosive specimens (φ16mm x 8mm in size) were initiated by the mylar flyers in thickness of 0.07˜0.20mm, which induced shock pressure in specimen was of duration ranging 0.029˜0.109μs. The experimental data were treated with the DRM(Delayed Robbins-Monro) procedure and to provide the threshold of shock pressure P 13.73˜5.23GPa. The shock initiation criterion of the explosive specimen is (P/GPa)^1.451(τ/μs) = 1.2. Meanwhile the criterion in 100% probability in the experiment is (P/GPa)^1.8(τ/μs) = 2.63. In addition, the 30^o wedged specimen was tested and the shock to detonation transition (SDT) process emerging on its inclined surface was diagnosed with a device consisting of multiple optical fiber probe, optoelectronic transducer and digital oscilloscope. The POP plot of the explosive has been gained from above SDT data.

  1. Theoretical analysis of saturation and limit cycles in short pulse FEL oscillators

    SciTech Connect

    Piovella, N.; Chaix, P.; Jaroszynski, D.

    1995-12-31

    We derive a model for the non linear evolution of a short pulse oscillator from low signal up to saturation in the small gain regime. This system is controlled by only two independent parameters: cavity detuning and losses. Using a closure relation, this model reduces to a closed set of 5 non linear partial differential equations for the EM field and moments of the electron distribution. An analysis of the linearised system allows to define and calculate the eigenmodes characterising the small signal regime. An arbitrary solution of the complete nonlinear system can then be expanded in terms of these eigenmodes. This allows interpreting various observed nonlinear behaviours, including steady state saturation, limit cycles, and transition to chaos. The single mode approximation reduces to a Landau-Ginzburg equation. It allows to obtain gain, nonlinear frequency shift, and efficiency as functions of cavity detuning and cavity losses. A generalisation to two modes allows to obtain a simple description of the limit cycle behaviour, as a competition between these two modes. An analysis of the transitions to more complex dynamics is also given. Finally, the analytical results are compared to the experimental data from the FELIX experiment.

  2. Annealing of SnO₂ thin films by ultra-short laser pulses.

    PubMed

    Scorticati, D; Illiberi, A; Bor, T; Eijt, S W H; Schut, H; Römer, G R B E; de Lange, D F; in 't Veld, A J Huis

    2014-05-05

    Post-deposition annealing by ultra-short laser pulses can modify the optical properties of SnO₂ thin films by means of thermal processing. Industrial grade SnO₂ films exhibited improved optical properties after picosecond laser irradiation, at the expense of a slightly increased sheet resistance [Proc. SPIE 8826, 88260I (2013)]. The figure of merit ϕ = T¹⁰ / R(sh) was increased up to 59% after laser processing. In this paper we study and discuss the causes of this improvement at the atomic scale, which explain the observed decrease of conductivity as well as the observed changes in the refractive index n and extinction coefficient k. It was concluded that the absorbed laser energy affected the optoelectronic properties preferentially in the top 100-200 nm region of the films by several mechanisms, including the modification of the stoichiometry, a slight desorption of dopant atoms (F), adsorption of hydrogen atoms from the atmosphere and the introduction of laser-induced defects, which affect the strain of the film.

  3. Creation of Pure Frozen Gas Targets for Ion Acceleration using Short Pulse Lasers

    NASA Astrophysics Data System (ADS)

    McCary, Edward; Stehr, Florian; Jiao, Xuejing; Quevedo, Hernan; Franke, Philip; Agustsson, Ronald; Oshea, Finn; Berry, Robert; Chao, Dennis; Woods, Kayley; Gautier, Donald; Letzring, Sam; Hegelich, Bjorn

    2015-11-01

    A system for shooting interchangeable frozen gas targets was developed at the University of Texas and will be tested at Los Alamos National Lab. A target holder which can hold up to five substrates used for target growing was cryogenically cooled to temperatures below 14 K. The target substrates consist of holes with diameters ranging from 15 μm-500 μm and TEM grids with micron scale spacing, across which films of ice are frozen by releasing small amounts of pure gas molecules directly into the vacuum target chamber. Frozen gas targets comprised of simple molecules like methane and single element gasses like hydrogen and deuterium will provide novel target configuations that will be compared with laser plasma interaction simulations. The targets will be shot with the ultra-intense short-pulse Trident laser. Accelerated ion spectra will be characterized using a Thomson Parabola with magnetic field strength of 0.92T and electric field strength of 30kV. Hydrogen targets will be additionally characterized using stacks of copper which become activated upon exposure to energetic protons resulting in a beta decay signal which be imaged on electron sensitive imaging plates to provide an energy spectrum and spacial profile of the proton beam. Details of target creation and pre-shot characterization will be presented.

  4. Exploring polygon scanner head capabilities for ultra-short pulse laser texturing

    NASA Astrophysics Data System (ADS)

    Mincuzzi, G.; Fleureau, M.; Faucon, M.; Kling, R.

    2016-03-01

    The combination of both, fast beam scanning systems and high repetition rate, high average power lasers, represents an interesting technological solution for surface texturing by Ultra-Short Pulses Laser to gain a foothold into industrial environment for commercial purposes. Nevertheless unwanted thermal effects are expected when the average power exceeds some tens of W. An interesting strategy for a reliable heat management would consists of texturing surfaces with a low fluence values (slightly higher than the ablation threshold) and utilising a polygon scanning head which is able to deflect the laser beam with unprecedented speed. Here we show that over stainless steel, it is possible to obtain different surface textures (in particular ripples, micro grooves and spikes) by utilising a 2 MHz femtosecond laser jointly with a fast and accurate polygonal scanner head at relatively low fluence (0.11 J·cm-2). The evolution of the Laser induced surface structures morphology is shown when varying the scan speed between 25 m·s-1 and 90 m·s-1. Two different wavelengths have been utilised for the process λ= 1030 nm and λ = 515 nm and the difference of the results obtained have been highlighted. Moreover, a full structures morphology characterization by SEM has been carried out for all the textured surfaces. Finally, by increasing the number of successive surface scans is possible to tailor the surface reflectivity. As a result an average reflectivity value of < 5% over the visible range has been extracted from a blackened stainless steel surface.

  5. Comments on the possibility of cavitation in liquid metal targets for pulsed spallation neutron sources

    SciTech Connect

    Carpenter J.M.

    1996-06-01

    When short pulses of protons strike the volume of a liquid target, the rapid heating produces a pressurized region which relaxes as the pressure wave propagates outward. Skala and Bauer have modeled the effects of the pressure wave impinging on the container walls of a liquid mercury target under ESS conditions. They find that high pressures and high wall stresses result if the medium is uniform, nearly incompressible liquid. The pressure and the stresses are much reduced if the liquid contains bubbles of helium, due to their high compressibility. However, according to the calculation, the pressure still reaches an atmosphere or so at the surface, which reflects the compressive wave as a rarefaction wave of the same magnitude. Even such modest underpressures can lead to the growth of bubbles (cavitation) at or near the surface, which can collapse violently and erode the container surface. It is necessary to avoid this. Leighton provides a wide ranging discussion of pressure waves in bubbly media, which may provide insights into the nature and control of cavitation phenomena. The paper surveys some of the relevant information from that source.

  6. Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source.

    PubMed

    Tiedtke, K; Sorokin, A A; Jastrow, U; Juranić, P; Kreis, S; Gerken, N; Richter, M; Arp, U; Feng, Y; Nordlund, D; Soufli, R; Fernández-Perea, M; Juha, L; Heimann, P; Nagler, B; Lee, H J; Mack, S; Cammarata, M; Krupin, O; Messerschmidt, M; Holmes, M; Rowen, M; Schlotter, W; Moeller, S; Turner, J J

    2014-09-08

    This paper reports novel measurements of x-ray optical radiation on an absolute scale from the intense and ultra-short radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the detection principle for radiation measurements which was specifically adapted for this photon energy range. We present data characterizing the soft x-ray instrument at the Linac Coherent Light Source (LCLS) with respect to the radiant power output and transmission by using an absolute detector temporarily placed at the downstream end of the instrument. This provides an estimation of the reflectivity of all x-ray optical elements in the beamline and provides the absolute photon number per bandwidth per pulse. This parameter is important for many experiments that need to understand the trade-offs between high energy resolution and high flux, such as experiments focused on studying materials via resonant processes. Furthermore, the results are compared with the LCLS diagnostic gas detectors to test the limits of linearity, and observations are reported on radiation contamination from spontaneous undulator radiation and higher harmonic content.

  7. Mechanism and influencing factors on critical pulse width of oil-immersed polymer insulators under short pulses

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Su, Jian Cang; Li, Rui; Zeng, Bo; Cheng, Jie; Zheng, Lei; Yu, Bin Xiong; Wu, Xiao Long; Zhang, Xi Bo; Pan, Ya Feng

    2015-04-01

    The critical pulse width (τc) is a pulse width at which the surface flashover threshold (Ef) is equal to the bulk breakdown threshold (EBD) for liquid-polymer composite insulation systems, which is discovered by Zhao et al. [Annual Report Conference on Electrical Insulation and Dielectric Phenomena (IEEE Dielectrics and Electrical Insulation Society, Shenzhen, China, 2013), Vol. 2, pp. 854-857]. In this paper, the mechanism of τc is interpreted in perspective of the threshold and the time delay (td) of surface flashover and bulk breakdown, respectively. It is found that two changes appear as the pulse width decreases which are responsible for the existence of τc: (1) EBD is lower than Ef; (2) td of bulk breakdown is shorter than td of surface flashover. In addition, factors which have influences on τc are investigated, such as the dielectric type, the insulation length, the dielectric thickness, the dielectrics configuration, the pulse number, and the liquid purity. These influences of factors are generalized as three types if τc is expected to increase: (1) factors causing EBD to decrease, such as increasing the pulse number or employing a dielectric of lower EBD; (2) factors causing Ef to increase, such as complicating the insulator's configuration or increasing the liquid purity; (3) factors causing EBD and Ef to increase together, but Ef increases faster than EBD, such as decreasing the dielectric thickness or the insulation length. With the data in references, all the three cases are verified experimentally. In the end, a general method based on τc for solid insulation design is presented and the significance of τc on solid insulation design and on solid demolition are discussed.

  8. Development and characterization of a high yield transportable pulsed neutron source with efficient and compact pulsed power system

    NASA Astrophysics Data System (ADS)

    Verma, Rishi; Mishra, Ekansh; Dhang, Prosenjit; Sagar, Karuna; Meena, Manraj; Shyam, Anurag

    2016-09-01

    The results of characterization experiments carried out on a newly developed dense plasma focus device based intense pulsed neutron source with efficient and compact pulsed power system are reported. Its high current sealed pseudospark switch based low inductance capacitor bank with maximum stored energy of ˜10 kJ is segregated into four modules of ˜2.5 kJ each and it cumulatively delivers peak current in the range of 400 kA-600 kA (corresponding to charging voltage range of 14 kV-18 kV) in a quarter time period of ˜2 μs. The neutron yield performance of this device has been optimized by discretely varying deuterium filling gas pressure in the range of 6 mbar-11 mbar at ˜17 kV/550 kA discharge. At ˜7 kJ/8.5 mbar operation, the average neutron yield has been measured to be in the order of ˜4 × 109 neutrons/pulse which is the highest ever reported neutron yield from a plasma focus device with the same stored energy. The average forward to radial anisotropy in neutron yield is found to be ˜2. The entire system is contained on a moveable trolley having dimensions 1.5 m × 1 m × 0.7 m and its operation and control (up to the distance of 25 m) are facilitated through optically isolated handheld remote console. The overall compactness of this system provides minimum proximity to small as well as large samples for irradiation. The major intended application objective of this high neutron yield dense plasma focus device development is to explore the feasibility of active neutron interrogation experiments by utilization of intense pulsed neutron sources.

  9. Development and characterization of a high yield transportable pulsed neutron source with efficient and compact pulsed power system.

    PubMed

    Verma, Rishi; Mishra, Ekansh; Dhang, Prosenjit; Sagar, Karuna; Meena, Manraj; Shyam, Anurag

    2016-09-01

    The results of characterization experiments carried out on a newly developed dense plasma focus device based intense pulsed neutron source with efficient and compact pulsed power system are reported. Its high current sealed pseudospark switch based low inductance capacitor bank with maximum stored energy of ∼10 kJ is segregated into four modules of ∼2.5 kJ each and it cumulatively delivers peak current in the range of 400 kA-600 kA (corresponding to charging voltage range of 14 kV-18 kV) in a quarter time period of ∼2 μs. The neutron yield performance of this device has been optimized by discretely varying deuterium filling gas pressure in the range of 6 mbar-11 mbar at ∼17 kV/550 kA discharge. At ∼7 kJ/8.5 mbar operation, the average neutron yield has been measured to be in the order of ∼4 × 10(9) neutrons/pulse which is the highest ever reported neutron yield from a plasma focus device with the same stored energy. The average forward to radial anisotropy in neutron yield is found to be ∼2. The entire system is contained on a moveable trolley having dimensions 1.5 m × 1 m × 0.7 m and its operation and control (up to the distance of 25 m) are facilitated through optically isolated handheld remote console. The overall compactness of this system provides minimum proximity to small as well as large samples for irradiation. The major intended application objective of this high neutron yield dense plasma focus device development is to explore the feasibility of active neutron interrogation experiments by utilization of intense pulsed neutron sources.

  10. Spiral Flux Compression Generator (FCG) Based Self-Contained Pulsed High Voltage Source

    DTIC Science & Technology

    2013-06-01

    electric There is an oltage source our view, th development diameter spira decreases in F output deterior energy source design with diameter 50 m...agnetic field. substantially or size, which e dimension implementa he electric str ally the spiral CG with a co D SELF- netic Resear e Enterpris...s d r h d d n B. FCG S Three m primary e high- volta The prim batteries DC volta across th pulsed ca surge in t connected explosive source

  11. Coherent excitation of a two-state system by a train of short pulses

    NASA Astrophysics Data System (ADS)

    Vitanov, Nikolay V.; Knight, Peter L.

    1995-09-01

    A theoretical nonperturbative study of the coherent excitation of a two-state system by N consecutive equally spaced identical pulses is presented. General relations between the evolution matrix elements in the cases of one and N pulses are obtained in a closed form. For pulse envelopes allowing analytical solutions, these relations enable analytical treatment of pulse-train excitation; for pulses that can only be treated numerically, they shorten the computations by a factor of N. The relations show that the multiple-pulse excitation of a two-state system can be considered as a quantum analog of the diffraction grating. The interaction dynamics substantially depends on the way the train is produced because the phase shift that is accumulated by the probability amplitudes due to the free evolution of the system during and between the pulses differs. In the limit of weak excitation, the results recover earlier conclusions based on perturbative treatments. Simple formulas are derived for the conditions for complete population inversion (CPI) and complete population return (CPR), which differ from the single-pulse ones. These general results are applied to four particular cases that allow analytical solutions: resonant, rectangular, Rosen-Zener, and Allen-Eberly pulses. A common feature in all these cases is that the number and the amplitude of oscillations in the state populations increase with the number of pulses, while their width decreases. For rectangular pulses, CPI is possible below a given value of the ratio between the detuning and the pulse area; this value increases nearly linearly with the number of pulses. For the Rosen-Zener model, CPI is found to be possible for two and more pulses, while it is impossible for a single non-resonant pulse. It is shown that for a given number of pulses there is an upper limit on the detuning for which CPI can be observed; this limit increases logarithmically with the number of pulses. For the Allen-Eberly model, CPR is

  12. Diffusion from a steady source of short duration

    NASA Astrophysics Data System (ADS)

    Palazzi, E.; De Faveri, M.; Fumarola, G.; Ferraiolo, G.

    Releases of short duration can result from safety valves, rupture disks, sudden failures of storage tanks, reactors, lines, etc. Models for atmospheric dispersion of continuous, constant flow rate or instantaneous emissions lack reliability in those instances, because they do not take into account certain indispensable parameters, such as release duration, release starting time and exposure time. This paper offers a mathematical model which has been developed and validated with field experiments, with the intention of supplying reference material for design purposes (relief valves, plant design and layout) or for predicting potential consequences of a leakage, such as fires, explosions, contaminations.

  13. Evidence of thermal additivity during short laser pulses in an in vitro retinal model

    NASA Astrophysics Data System (ADS)

    Denton, Michael L.; Tijerina, Amanda J.; Dyer, Phillip N.; Oian, Chad A.; Noojin, Gary D.; Rickman, John M.; Shingledecker, Aurora D.; Clark, Clifton D.; Castellanos, Cherry C.; Thomas, Robert J.; Rockwell, Benjamin A.

    2015-03-01

    Laser damage thresholds were determined for exposure to 2.5-ms 532-nm pulses in an established in vitro retinal model. Single and multiple pulses (10, 100, 1000) were delivered to the cultured cells at three different pulse repetition frequency (PRF) values, and overt damage (membrane breach) was scored 1 hr post laser exposure. Trends in the damage data within and across the PRF range identified significant thermal additivity as PRF was increased, as evidenced by drastically reduced threshold values (< 40% of single-pulse value). Microthermography data that were collected in real time during each exposure also provided evidence of thermal additivity between successive laser pulses. Using thermal profiles simulated at high temporal resolution, damage threshold values were predicted by an in-house computational model. Our simulated ED50 value for a single 2.5-ms pulse was in very good agreement with experimental results, but ED50 predictions for multiple-pulse trains will require more refinement.

  14. Vaporization and recondensation dynamics of indocyanine green-loaded perfluoropentane droplets irradiated by a short pulse laser

    NASA Astrophysics Data System (ADS)

    Yu, Jaesok; Chen, Xucai; Villanueva, Flordeliza S.; Kim, Kang

    2016-12-01

    Phase-transition droplets have been proposed as promising contrast agents for ultrasound and photoacoustic imaging. Short pulse laser activated perfluorocarbon-based droplets, especially when in a medium with a temperature below their boiling point, undergo phase changes of vaporization and recondensation in response to pulsed laser irradiation. Here, we report and discuss the vaporization and recondensation dynamics of perfluoropentane droplets containing indocyanine green in response to a short pulsed laser with optical and acoustic measurements. To investigate the effect of temperature on the vaporization process, an imaging chamber was mounted on a temperature-controlled water reservoir and then the vaporization event was recorded at 5 million frames per second via a high-speed camera. The high-speed movies show that most of the droplets within the laser beam area expanded rapidly as soon as they were exposed to the laser pulse and immediately recondensed within 1-2 μs. The vaporization/recondensation process was consistently reproduced in six consecutive laser pulses to the same area. As the temperature of the media was increased above the boiling point of the perfluoropentane, the droplets were less likely to recondense and remained in a gas phase after the first vaporization. These observations will help to clarify the underlying processes and eventually guide the design of repeatable phase-transition droplets as a photoacoustic imaging contrast agent.

  15. Determination of mean surface position and sea state from the radar return of a short-pulse satellite altimeter

    NASA Technical Reports Server (NTRS)

    Barrick, D. E.

    1972-01-01

    Using the specular point theory of scatter from a very rough surface, the average backscatter cross section per unit area per radar cell width is derived for a cell located at a given height above the mean sea surface. This result is then applied to predict the average radar cross section observed by a short-pulse altimeter as a function of time for two modes of operation: pulse-limited and beam-limited configurations. For a pulse-limited satellite altimeter, a family of curves is calculated showing the distortion of the leading edge of the receiver output signal as a function of sea state (i.e., wind speed). A signal processing scheme is discussed that permits an accurate determination of the mean surface position--even in high seas--and, as a by-product, the estimation of the significant seawave height (or wind speed above the surface). Comparison of these analytical results with experimental data for both pulse-limited and beam-limited operation lends credence to the model. Such a model should aid in the design of short-pulse altimeters for accurate determination of the geoid over the oceans, as well as for the use of such altimeters for orbital sea-state monitoring.

  16. Two-dimensional angular energy spectrum of electrons accelerated by the ultra-short relativistic laser pulse

    SciTech Connect

    Borovskiy, A. V.; Galkin, A. L.; Kalashnikov, M. P.

    2015-04-15

    The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.

  17. Mechanism and influencing factors on critical pulse width of oil-immersed polymer insulators under short pulses

    SciTech Connect

    Zhao, Liang Li, Rui; Zheng, Lei; Su, Jian Cang; Cheng, Jie; Yu, Bin Xiong; Wu, Xiao Long; Zhang, Xi Bo; Pan, Ya Feng; Zeng, Bo

    2015-04-15

    The critical pulse width (τ{sub c}) is a pulse width at which the surface flashover threshold (E{sub f}) is equal to the bulk breakdown threshold (E{sub BD}) for liquid-polymer composite insulation systems, which is discovered by Zhao et al. [Annual Report Conference on Electrical Insulation and Dielectric Phenomena (IEEE Dielectrics and Electrical Insulation Society, Shenzhen, China, 2013), Vol. 2, pp. 854–857]. In this paper, the mechanism of τ{sub c} is interpreted in perspective of the threshold and the time delay (t{sub d}) of surface flashover and bulk breakdown, respectively. It is found that two changes appear as the pulse width decreases which are responsible for the existence of τ{sub c}: (1) E{sub BD} is lower than E{sub f}; (2) t{sub d} of bulk breakdown is shorter than t{sub d} of surface flashover. In addition, factors which have influences on τ{sub c} are investigated, such as the dielectric type, the insulation length, the dielectric thickness, the dielectrics configuration, the pulse number, and the liquid purity. These influences of factors are generalized as three types if τ{sub c} is expected to increase: (1) factors causing E{sub BD} to decrease, such as increasing the pulse number or employing a dielectric of lower E{sub BD}; (2) factors causing E{sub f} to increase, such as complicating the insulator's configuration or increasing the liquid purity; (3) factors causing E{sub BD} and E{sub f} to increase together, but E{sub f} increases faster than E{sub BD}, such as decreasing the dielectric thickness or the insulation length. With the data in references, all the three cases are verified experimentally. In the end, a general method based on τ{sub c} for solid insulation design is presented and the significance of τ{sub c} on solid insulation design and on solid demolition are discussed.

  18. Urban air pollution by odor sources: Short time prediction

    NASA Astrophysics Data System (ADS)

    Pettarin, Nicola; Campolo, Marina; Soldati, Alfredo

    2015-12-01

    A numerical approach is proposed to predict the short time dispersion of odors in the urban environment. The model is based on (i) a three dimensional computational domain describing the urban topography at fine spatial scale (1 m) and on (ii) highly time resolved (1 min frequency) meteorological data used as inflow conditions. The time dependent, three dimensional wind velocity field is reconstructed in the Eulerian framework using a fast response finite volume solver of Navier-Stokes equations. Odor dispersion is calculated using a Lagrangian approach. An application of the model to the historic city of Verona (Italy) is presented. Results confirm that this type of odor dispersion simulations can be used (i) to assess the impact of odor emissions in urban areas and (ii) to evaluate the potential mitigation produced by odor abatement systems.

  19. A system for mapping sources of VHF and electric field pulses from in-cloud lightning at KSC

    NASA Technical Reports Server (NTRS)

    Thomson, Ewen M.; Medelius, Pedro J.

    1991-01-01

    The literature concerning VHF radiation and wideband electric fields from in-cloud lightning is reviewed. VHF location systems give impressive radio images of lightning in clouds with high spatial and temporal resolution. Using systems based on long and short baseline time-or-arrival and interferometry, workers have detected VHF sources that move at speeds of 10(exp 5) to 10(exp 8) m/s. The more slowly moving sources appear to be associated with channel formation but the physical basis for the higher speeds is not clear. In contrast, wideband electric fields are directly related to physical parameters such as current and tortuosity. A long baseline system is described to measure simultaneously VHF radiation and wideband electric fields at five stations at Kennedy Space Center. All signals are detected over remote, isolated ground planes with fiber optics for data transmission. The modification of this system to map rapidly varying dE/dt pulses is discussed.

  20. Whose Story Is This? Discrepancy Triggers Readers' Attention to Source Information in Short Narratives

    ERIC Educational Resources Information Center

    Rouet, Jean-François; Le Bigot, Ludovic; de Pereyra, Guillaume; Britt, M. Anne

    2016-01-01

    Three experiments investigated the role of source information (i.e., who said what) in readers' comprehension of short informational texts. Based on the Discrepancy-Induced Source Comprehension assumption (Braasch, Rouet, Vibert, & Britt, 2012), we hypothesized that readers would be more likely to make use of source information when…

  1. Evolution of hole shape and size during short and ultrashort pulse laser deep drilling.

    PubMed

    Döring, Sven; Szilagyi, John; Richter, Sören; Zimmermann, Felix; Richardson, Martin; Tünnermann, Andreas; Nolte, Stefan

    2012-11-19

    A detailed study of the influence of the pulse duration, from the femtosecond to the nanosecond regime, on the evolution of the hole shape and depth during percussion drilling in silicon is presented. Real-time backlight imaging of the hole development is obtained for holes up to 2 mm deep with aspect ratios extending to 25:1. For low pulse energies, the hole-shape and drilling characteristics are similar for femtosecond, picoseconds and nanosecond regimes. At higher pulse energies, ns-pulses exhibit slower average drilling rates but eventually reach greater final depths. The shape of these holes is however dominated by branching and large internal cavities. For ps-pulses, a cylindrical shape is maintained with frequent small bulges on the side-walls. In contrast, fs-pulses cause only a limited number of imperfections on a tapered hole shape.

  2. Electron Emission from Conductors Subjected to Intense, Short-Pulse Electric Fields

    DTIC Science & Technology

    1987-06-01

    showed that for 10-ns pulse lengths, anodized alumi- num surfaces could hold off more than twice the electric field strength of bare aluminum...shorter, 3-ns pulse lengths, anodizing was less effective at improving suppression of electron emission, while surface finish became the important...pulsewidth of 10 ns. The front end of the pulser, along with a typical output pulse , is shown in Fig. 1. The vacuum coaxial line is about 6-ns long, and

  3. Shock-wave ion acceleration by an ultra-relativistic short laser pulse

    NASA Astrophysics Data System (ADS)

    Zhidkov, A.; Batishchev, O.; Uesaka, M.

    2002-11-01

    Research on ion acceleration by intense short laser pulses grows in the last few years [1-9] because of various applications. However, the study is mainly focused on the forward ion acceleration. We study ion inward acceleration, which in contrast to other mechanisms has density of ions per unit energy not decreased with the laser intensity [8]. Magnetic field generated due to a finite size of laser spot can affect electron distribution. In the present work we study the effect of magnetic field on the shock wave formation and ion acceleration in a solid target via 2D PIC and Vlasov simulation. Though the PIC simulation can provide detailed information, in relativistic plasmas it may not calculate B correctly: (i) too many particles are needed to make B disappeared in thermal plasmas, (ii) local scheme [10] does not satisfy curl(Epl)=0. Therefore, two approaches are used in the present study. [1] S. P. Hatchett et al., Phys. Plas. 7, 2076 (2000); [2] A. Maksimchuk et al., Phys. Rev. Lett. 84, 4108 (2000); [3] E.L. Clark et al., Phys. Rev. Lett. 85, 1654 (2000); [4] A. Zhidkov et al., Phys. Rev. E60, 3273 (1999); E61, R2224 (2000); [5] Y. Murakami et al, Phys. Plasmas 8,4138 (2001); [6] T.Zh. Esirkepov et al, JETP Lett. 70, 82 (1999); [7] A. Pukhov, Phys. Rev. Lett. 86, 3562(2001); [8] A.A. Andreev et al., Plasma Phys. Contr. Fusion (2002); [9] O.V. Batishchev et al., Plasma Phys. Rep. 20, 587 (1994); [10] J. Villasenor et al., Comp. Phys. Comm. 69, 306 (1992).

  4. Measuring alpha eigenvalue of a subcritical system by a intense pulsed neutron source

    SciTech Connect

    Hu, Meng-chun; Gong, Jian; Peng, Tai-ping; Li, Zhong-bao; Zhang, Jian-hua; Tang, Deng-pan; Bai, Yun; Peng, Xian-jue; Zeng, Qing

    2015-07-01

    Intense-Pulsed-Neutron-Source (IPNS) technique is a new approach to measure the subcriticality of a reactor system, which has been theoretically analyzed by us while not been verified in experiment in other reference. In INPS technique the reactivity is derived via the system response to a prompt pulsed neutron source. The method utilizes very intense neutron pulses (about 1010 neutrons/pulse) with the duration ranging from 10 ns to 100 ns, which are generated by the dense plasma focus (DPF) device filled with pure DT mixture as the working gas. The neutron pulse in high intensity provides the opportunity to measure the signal using a scintillator and a photo-multiplier tube (PMT) (the intense pulse radiation measure method) with the flight distance of only twenty centimeters. The attenuation of the dense plasma focus device must be faster than the subcritical system so that the attenuation of the system can be researched. In this paper, after a neutron pulse is injected into the subcritical reactor, the subcriticality is determined by measuring the instantaneous characteristics of the leaking reactor neutron. The Monte Carlo analysis shows that, with the linear arrangement of the dense plasma focus, the subcritical system and the detector, the signal-to-noise ratio at the measure point meets the investigate requirement, in which the 14 MeV neutrons are attenuated by the subcritical system. The detector is close with the subcritical system to reduce the influence of the outer background and the spread of time-of-flight of the neutrons. The measure system utilizing gated detection technology is characterized with fast attenuation time and large linear current, the a value obtained with this method is 2.05 μs{sup -1} while the measurements using the {sup 252}Cf stochastic pulsed source method and the Rossi-a method were 2.18μs{sup -1} and 2.16μs{sup -1}.It showed that the measured result obtained with dense plasma focus instantaneous pulsed source is consistent

  5. Grating-based pulse compressor for applications to FEL sources

    NASA Astrophysics Data System (ADS)

    Poletto, Luca; Frassetto, Fabio; Miotti, Paolo; Gauthier, David; Fajardo, Marta; Mahieu, Benoit; Svetina, Cristian; Zangrando, Marco; Zeitoun, Philippe; De Ninno, Giovanni

    2015-05-01

    We present the optical layout of a reflective grating compressor specifically designed for extreme-ultraviolet FEL sources. The working principle is based on the use of a couple of constant-line-spaced gratings used at grazing incidence and illuminated in divergent light. The two possible grating configurations, namely the on-plane and off-plane, are analyzed and compared. The Group Delay Dispersion (GDD) introduced by the compressor is analytically analyzed and quantified. The spatial chirp also is considered, and its effect analyzed. The deviation from the ideal case in which the instrument is feed with a collimated beam is considered. The effect of the beam divergence on the compressor response is quantified and the attenuation of this effect by a "de-tuning" of the compressor is proposed. This solution avoids the use of a pre-collimating optics, therefore incrementing the total instrumental throughput. Finally, it is shown the optical design of an actual compressor for the FERMI FEL, that can be inserted in the optical path without any deviation or translation of the photon beam with respect to the nominal path.

  6. Energy-scalable pulsed mid-IR source using orientation-patterned GaAs.

    PubMed

    French, Douglas; Peterson, Rita; Jovanovic, Igor

    2011-02-15

    Coherent mid-IR sources based on orientation-patterned GaAs (OPGaAs) are of significant interest in diverse scientific, medical, and military applications. The generation of long-wavelength mid-IR beams in OPGaAs using optical parametric oscillation exhibits limitations in the obtainable pulse energy and peak power. The master oscillator power amplifier concept is demonstrated in OPGaAs, by which a mid-IR source based on optical parametric oscillation can be scaled to high energy by amplification of the output of the optical parametric oscillator in an optical parametric amplifier (OPA). A fivefold increase in the pulse energy is obtained using this method by amplifying 3.85μm pulses in an OPGaAs OPA pumped by a Th,Ho:YLF Q-switched laser.

  7. Subnanosecond pulsed X-ray source based on nanosecond discharge in air at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Kostyrya, I. D.; Tarasenko, V. F.

    2009-06-01

    We have studied the characteristics of an X-ray source based on a gas diode filled with air at atmospheric pressure. Driven by a SLEP-150 pulser with a maximum voltage amplitude of ˜140 kV, a pulse full width at half maximum (FWHM) of ˜1 ns, and a leading front width of ˜0.3 ns, a soft X-ray source produces subnanosecond pulses with an FWHM not exceeding 600 ps and an exposure dose of ˜3 mR per pulse. It is shown that the main contribution to the measured exposure dose is due to X-ray quanta with an effective energy of ˜7.5 keV.

  8. Low-noise pulsed current source for magnetic-field measurements of magnets for accelerators

    NASA Astrophysics Data System (ADS)

    Omelyanenko, M. M.; Borisov, V. V.; Donyagin, A. M.; Khodzhibagiyan, H. G.; Kostromin, S. A.; Makarov, A. A.; Shemchuk, A. V.

    2017-01-01

    The schematic diagram, design, and technical characteristics of the pulsed current source developed and produced for the magnetic-field measurement system of superconducting magnets for accelerators are described. The current source is based on the current regulator with pass transistor bank in the linear mode. Output current pulses (0-100 A) are produced by utilizing the energy of the preliminarily charged capacitor bank (5-40 V), which is additionally charged between pulses. The output current does not have the mains frequency and harmonics ripple. The relative noise level is less than-100 dB (or 10-5) of RMS value (it is defined as the ratio of output RMS noise current to a maximal output current of 100 A within the operating bandwidth, expressed in dB). The work was performed at the Veksler and Baldin Laboratory of High Energy Physics, Joint Institute for Nuclear Research (JINR).

  9. Short-Period RF Undulator for a SASE Nanometer source

    SciTech Connect

    Jay L. Hirshfield

    2001-12-21

    Analysis is described towards development of a RF undulator with a period < 1 cm, an undulator parameter K of the order of unity, and a gap greater than 2.25 mm. The application for the undulator is for a SASE source to produce 1 nm wavelength radiation using a low energy electron beam in the range 1-2 GeV. Particle orbit calculations in a conventional standing-wave resonator configuration show that the presence of a co-propagating component of RF field can cause deleterious motion for the undulating electrons that can seriously degrade their radiation spectrum. To obviate this problem, resonator designs were devised in which only the counter-propagating field components interact with the particles. Two resonator configurations with the same undulator parameter K = 0.4 have been devised and are described in this report.

  10. High-resolution VUV spectrometer/detector investigations of rare-earth pulsed plasma source (abstract)

    NASA Astrophysics Data System (ADS)

    Roberts, J. R.; Cromer, C. L.; Bridges, J. M.; Lucatorto, T. B.

    1985-05-01

    A 1.5-m grazing incidence spectrometer with a channel electron multiplier (CEMA) and electronic readout detector has been incorporated with a rare-earth target, pulsed plasma, continuum source. The spectrometer is compact and portable while maintaining high resolution. The CEMA detector consists of a single multichannel plate (MCP) with coned-shaped input pores which are cut at a 15-degree bias to improve efficiency at grazing angles. The source is a rare-earth plasma generated by a 10-J ruby laser producing intense continuum emission for wavelengths from 170 to 5 nm. This system will be used for both stationary and transient high-resolution atomic photoabsorption spectroscopy. The pulsed plasma source itself will be investigated for suitability as a radiometric transfer standard source. Preliminary results obtained with this integrated system will be discussed.

  11. Inelastic scattering research at a 1 MW long pulse spallation neutron source

    SciTech Connect

    Carlile, C.J.

    1995-12-31

    The brief was, with respect to the LPSS bench mark design supplied (60 Hz, 1 MW, Imsec proton pulse, with a split, non-fissile target and 4 moderators in a flux trap geometry design), to identify a set of instruments, and to assess their performance with respect to existing spectrometers on other sources. Any modifications to the existing instruments which would make them more effective on the bench-mark source, or conversely, any modifications to the source bench-mark required by the proposed instruments were to be identified, as were any uncertainties in the estimated performances, or any R & D needed to make the proposed instruments viable. Any new instrument concepts specifically matched to the long pulse itself were to be identified and assessed. This process was to result in an indicative list of instruments for the source. A figure of around 10 spectrometers was to be aimed for.

  12. Deuterium Gas-Puff Z-pinch as a Source of Fast Ions Producing Intensive Pulse of Neutrons

    NASA Astrophysics Data System (ADS)

    Rezac, K.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Kubes, P.; Sila, O.; Shishlov, A.; Cherdizov, R.; Fursov, F.; Kokshenev, V.; Kovalchuk, B.; Kurmaev, N.; Labetsky, A.; Ratakhin, N.; Turek, K.

    2015-11-01

    A deuterium gas-puff with outer plasma shell has been examined on GIT-12 generator (on the current level of 3 MA) since 2013. Such a configuration caused more stable implosion at final stage of z-pinch. The consequence of this was a production of intensive pulses of fast ions. During last 4 campaigns in 2013-2015, fast ions were examined by several in-chamber diagnostics such as: stack detector (ion energy), pinhole camera (location of ion source), multi-pinhole camera (asymmetry and anisotropy of ion emission), and ion beam detector (dynamics of ion pulses). A CR-39 track detectors and also GAFCHROMIC HD-V2 films from these diagnostics will be presented. On the basis of obtained results, the solid sample for increasing of neutron yield up to 1e13 could be placed below the cathode mesh. Except of neutron yield, other properties such as: neutron energies (up to 33 MeV), neutron emission time (about 20 ns), and emission anisotropy of neutrons were measured. Such a short and intensive neutron pulse provides various applications. This work was supported by the MSMT project LH13283.

  13. Feasibility of Thin Fresnel Lens Use in Multi-kj, Short Pulse Laser Systems

    SciTech Connect

    Jovanovic, I; Dixit, S N; Wattellier, B; Hermann, M R; Barty, C P J

    2002-11-18

    Recently-developed, thin-Fresnel-lens technology offers the potential for transmissive focusing of high-peak-power, ultrashort-duration laser pulses. Calculations of the transverse and longitudinal spectral blurring effects of thin Fresnel lenses when used to focus ultrashort, high-energy laser pulses are presented.

  14. Investigation of stimulated raman scattering using short-pulse diffraction limited laser beam near the instability threshold

    SciTech Connect

    Kline, John L; Montgomery, David S; Flippo, Kirk A; Rose, Harvey A; Yin, L; Albright, B J; Johnson, R P; Shimada, T; Bowers, K; Rousseaux, C; Tassin, V; Baton, S D; Amiranoff, F; Hardin, R A

    2008-01-01

    Short pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of Stimulated Raman Scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations ( > 1 kJ and> 1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the LULI (Laboratoire pour l'Utilisation des Lasers Intenses) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light respectively with 1.5-3.0 ps pulses. In both experiments, the interaction beam was focused into a pre-ionized He gas-jet plasma. Measurements of the reflectivity as a function of intensity and k{lambda}{sub D} were completed at the Trident laser facility. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC [K. J. Bowers, et at., Phys. Plasmas, 15 055703 (2008)] particle-in-cell code. Details of the experimental results are presented in this manuscript.

  15. Effect of plasma profile on ion acceleration in the interaction of a short laser pulse with a thin overdense target

    SciTech Connect

    Kwon, Duck-Hee; Rhee, Yong-Joo; Lee, Sungman; Cha, Hyungki

    2008-06-15

    Energetic ion generation from the interaction of a short laser pulse with a thin overdense plasma accompanied by a preplasma and a rear side plasma gradient is investigated by particle-in-cell simulations. The dynamics of ion acceleration depending on the maximum density of the preplasma in front of the overdense plasma slab with a smooth density gradient at the rear side are presented and discussed by comparing a sharp rear side boundary case.

  16. Short pulse laser stretcher-compressor using a single common reflective grating

    DOEpatents

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Telford, Steve

    2004-05-25

    The present invention provides an easily aligned, all-reflective, aberration-free pulse stretcher-compressor in a compact geometry. The stretcher-compressor device is a reflective multi-layer dielectric that can be utilized for high power chirped-pulse amplification material processing applications. A reflective grating element of the device is constructed: 1) to receive a beam for stretching of laser pulses in a beam stretcher beam path and 2) to also receive stretched amplified pulses to be compressed in a compressor beam path through the same (i.e., common) reflective multilayer dielectric diffraction grating. The stretched and compressed pulses are interleaved about the grating element to provide the desired number of passes in each respective beam path in order to achieve the desired results.

  17. A versatile, pulsed anion source utilizing plasma-entrainment: Characterization and applications

    NASA Astrophysics Data System (ADS)

    Lu, Yu-Ju; Lehman, Julia H.; Lineberger, W. Carl

    2015-01-01

    A novel pulsed anion source has been developed, using plasma entrainment into a supersonic expansion. A pulsed discharge source perpendicular to the main gas expansion greatly reduces unwanted "heating" of the main expansion, a major setback in many pulsed anion sources in use today. The design principles and construction information are described and several examples demonstrate the range of applicability of this anion source. Large OH-(Ar)n clusters can be generated, with over 40 Ar solvating OH-. The solvation energy of OH-(Ar)n, where n = 1-3, 7, 12, and 18, is derived from photoelectron spectroscopy and shows that by n = 12-18, each Ar is bound by about 10 meV. In addition, cis- and trans- HOCO- are generated through rational anion synthesis (OH- + CO + M → HOCO- + M) and the photoelectron spectra compared with previous results. These results, along with several further proof-of-principle experiments on solvation and transient anion synthesis, demonstrate the ability of this source to efficiently produce cold anions. With modifications to two standard General Valve assemblies and very little maintenance, this anion source provides a versatile and straightforward addition to a wide array of experiments.

  18. A versatile, pulsed anion source utilizing plasma-entrainment: Characterization and applications

    SciTech Connect

    Lu, Yu-Ju; Lehman, Julia H.; Lineberger, W. Carl

    2015-01-28

    A novel pulsed anion source has been developed, using plasma entrainment into a supersonic expansion. A pulsed discharge source perpendicular to the main gas expansion greatly reduces unwanted “heating” of the main expansion, a major setback in many pulsed anion sources in use today. The design principles and construction information are described and several examples demonstrate the range of applicability of this anion source. Large OH{sup −}(Ar){sub n} clusters can be generated, with over 40 Ar solvating OH{sup −}. The solvation energy of OH{sup −}(Ar){sub n}, where n = 1-3, 7, 12, and 18, is derived from photoelectron spectroscopy and shows that by n = 12-18, each Ar is bound by about 10 meV. In addition, cis– and trans– HOCO{sup −} are generated through rational anion synthesis (OH{sup −} + CO + M → HOCO{sup −} + M) and the photoelectron spectra compared with previous results. These results, along with several further proof-of-principle experiments on solvation and transient anion synthesis, demonstrate the ability of this source to efficiently produce cold anions. With modifications to two standard General Valve assemblies and very little maintenance, this anion source provides a versatile and straightforward addition to a wide array of experiments.

  19. Tunable WDM sampling pulse streams using a spatial phase modulator in a biased pulse shaper.

    PubMed

    Sinefeld, David; Shayovitz, Dror; Golani, Ori; Marom, Dan M

    2014-02-01

    We generate transform-limited WDM optical sampling pulse bursts by filtering ultrashort pulses from a mode-locked laser. A phase spatial light modulator (SLM) is used in a biased pulse shaper to circumvent the need to modulate with 2π phase wraps, which are known to limit the phase response. The arrangement compresses and retimes user-selectable bandwidths from the optical short pulse source with precise control of pulse bandwidth, pulse stream rates, and duty cycle.

  20. Transition from interpulse to afterglow plasmas driven by repetitive short-pulse microwaves in a multicusp magnetic field

    SciTech Connect

    Pandey, Shail; Sahu, Debaprasad; Bhattacharjee, Sudeep

    2012-08-15

    In the power-off phase, plasmas generated by repetitive short-pulse microwaves in a multicusp magnetic field show a transitive nature from interpulse to afterglow as a function of pulse duration t{sub w} = 20-200 {mu}s. The ionized medium can be driven from a highly non equilibrium to an equilibrium state inside the pulses, thereby dictating the behavior of the plasma in the power-off phase. Compared to afterglows, interpulse plasmas observed for t{sub w} < 50 {mu}s are characterized by a quasi-steady-state in electron density that persists for {approx} 20-40 {mu}s even after the end of the pulse and has a relatively slower decay rate ({approx} 4.3 Multiplication-Sign 10{sup 4} s{sup -1}) of the electron temperature, as corroborated by optical measurements. The associated electron energy probability function indicates depletion in low energy electrons which appear at higher energies just after the end of the pulse. The transition occurs at t{sub w} {approx} 50 {mu}s as confirmed by time evolution of integrated electron numbers densities obtained from the distribution function.