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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 Bright Neutron Source Driven by a Short Pulse Laser

    NASA Astrophysics Data System (ADS)

    Roth, Markus

    2012-10-01

    Neutrons are a unique tool to alter and diagnose material properties, and to exciting nuclear reactions, for many applications. Accelerator based spallation sources provide high neutron fluxes for research, but there is a growing need for more compact sources with higher peak brightness, whether fast or moderated neutrons. Intense lasers promise such as source, readily linkable to other experimental facilities, or deployable outside a laboratory setting. We present experimental results on the first short-pulse laser-driven neutron source powerful enough for radiography. A novel laser-driven ion acceleration mechanism (Breakout Afterburner), operating in the relativistic transparency regime, is used. Based on the mechanism's advantages, a laser-driven deuteron beam is used to achieve a new record in laser-neutron production, in numbers, energy and directionality. This neutron beam is a highly directional pulse < 1 ns at ˜ 1 cm from the target, with a flux > 40/2̂, and thus suitable for imaging applications with high temporal resolution. The beam contained, for the first time, neutrons with energies of up to 150 MeV. Thus using short pulse lasers, it is now possible to use the resulting hard x-rays and neutrons of different energies to radiograph an unknown object and to determine its material composition. Our data matches the simulated data for our test samples.

  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. 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.

  5. A short pulse, high rep-rate microdischarge VUV source

    NASA Astrophysics Data System (ADS)

    Stephens, Jacob; Fierro, Andrew; Dickens, James; Neuber, Andreas; CenterPulsed Power; Power Electronics Team

    2013-09-01

    A MOSFET based high voltage pulser is utilized to excite a microdischarge (MD), or microdischarge array (MDA) with pulsed voltages of up to 1 kV, with risetime and FWHM on the order of 10 ns and 30 ns, respectively. Additionally, the pulser is capable of pulsing at rep-rates in excess of 35 MHz. However, for these experiments the rep-rate was set on the order of 1 MHz, so as to limit excess energy deposition into the background gas and optimize the energy efficiency of VUV generation. Using VUV capable spectral diagnostics, the VUV emission of the MDs for various pressures (50-800 + Torr) and gases, focused on argon, argon-hydrogen mixtures, and neon-hydrogen mixtures (all of which provide strong emission at λ < 130 nm) is studied, for pulsed, MHz rep-rated excitation. Using a photomultiplier tube the time dependent behavior of the VUV emission is characterized and compared to results from transient fluid modeling of the MDA. For instance, the MDA turn-on time is recorded to be about 15 ns, which matches the full plasma development time in the model, and the MDA self- capacitance largely determines the turn-off behavior. This research was supported by an AFOSR grant on the Physics of Distributed Plasma Discharges and fellowships from the National Physical Sciences Consortium, supported by Sandia National Laboratories.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Characteristics of long-pulse and short-pulse spallation-source targets

    SciTech Connect

    Ludewig, H.; Todosow, M.; Powell, J.

    1996-03-01

    Generation of sharp neutron pulses is the desired output of a pulsed spallation neutron source (PSNS). These pulses should be approximately 10 {mu}s. wide at half maximum, and preserve as much of the original flux as possible. A proposed PSNS has been designed to operate at an average proton beam power of 5 MW. The PSNS consists of a heavy metal target, surrounded by a reflector, and a selection of moderators. The moderators are connected to beam tubes in which the neutrons are transported to the experimental stations. Reflectors are generally made of good moderating material, in which neutrons leaking from the target are slowed down by elastic scattering, prior to moderation. It is proposed to investigate the possibility of using reflectors which slow neutrons down by inelastic scattering rather than elastic scattering. In a purely inelastic scattering medium neutron pulses leaking from the heavy metal target will tend to preserve their original shape in both energy and time. We will examine the effect of different reflectors and proton pulse lengths on the neutron pulses in the moderators. This study will be carried out using a simple target configuration. In this way effects introduced by complicated target arrangements can be avoided. All the analyses presented in this paper were carried out using the LAHET code system (LCS). This code system consists of two major modules: (1) LAHET, a modified version of the HETC intranuclear cascade code for evaluations above 20 MeV, and (2) HMCNP, a modified version of the well known MCNP transport code for calculations from 20 MeV down to thermal energies. Both modules employ a combinatorial surface/cell specification of the problem geometry which permits modeling of the target configurations with minimal approximations. In addition, HMCNP employs nuclear data from the ENDF/B files in essentially unapproximated point-wise form which avoid the complications associated with generation of group cross sections.

  12. 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.

  13. Planned Use of Pulsed Crab Cavities for Short X-Ray Pulse Generation at the Advanced Photon Source

    SciTech Connect

    Borland, Michael; Carwardine, J.; Chae, Y.; Emery, L.; Den Hartog, Patric; Harkay, K.C.; Lumpkin, A.H.; Nassiri, A.; Sajaev, V.; Sereno, Nicholas S.; Waldschmidt, G.; Yang, B.X.; Dolgashev, V.; /SLAC

    2007-11-06

    Recently, we have explored application to the Advanced Photon Source (APS) of Zholents'[1] crab cavity scheme for production of short x-ray pulses. We assumed use of superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made [2] for a pulsed system using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instabilities, and diagnostics plans.

  14. 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.

  15. 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}.

  16. Characteristics of High Energy Ka and Bremsstrahlung Sources Generated by Short Pulse Petawatt Lasers

    SciTech Connect

    Park, H; Izumi, N; Key, M H; Koch, J A; Landen, O L; Patel, P K; Phillips, T W; Zhang, B B

    2004-04-13

    We have measured the characteristics of high energy K{alpha} sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at LLNL. High energy x-ray backlighters will be essential for radiographing High-Energy-Density Experimental Science (HEDES) targets for NIF projects especially to probe implosions and high areal density planar samples. Hard K{alpha} x-ray photons are created through relativistic electron plasma interactions in the target material after irradiation by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator/CCD camera for imaging and a CCD camera for single photon counting. We measured the Ag K{alpha} source (22 keV) size using a pinhole array and the K{alpha} flux using a single photon counting method. We also radiographed a high Z target using the high energy broadband x-rays generated from these short pulse lasers. This paper will present results from these experiments.

  17. 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.

  18. 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.

  19. Design of the plasma grid for a short pulse negative ion source experimental setup at HUST

    NASA Astrophysics Data System (ADS)

    Zuo, C.; Li, D.; Chen, D.; Zhao, P.; Xu, Q.; Liao, Z.

    2017-08-01

    An experimental setup of a radio frequency (RF) driven negative hydrogen ion source has been developed at Huazhong University of Science and Technology (HUST). The setup without cesium oven and an extraction system had been completed and the plasma was ignited in the driver successfully in 2014. An extraction system with small area (5540 mm2) for short pulse (˜ 4 s) was designed to extract the negative hydrogen ions. Generally, the plasma grid temperature is controlled to reach 150 °C by the cooling channels inside the grid. But another method that we could use the PG current to raise the temperature is being considered only for the short pulse condition. An experiment was introduced to prove the feasibility of this method. A magnetic field produced by current flowing through the plasma grid is required to reduce the electron temperature and suppress the co-extraction electrons. The filter field homogeneity has been studied in detail by finite element method. There have been significant improvements regarding the field homogeneity by means of the grid geometry optimization.

  20. 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

  1. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

    DOE PAGES

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea; ...

    2016-10-17

    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 themore » 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 ~5x109 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 to 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. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  2. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

    SciTech Connect

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea; Merrill, Frank Edward; Falk, Katerina; Jung, D.; Tybo, Joshua L.; Wilde, Carl Huerstel; Croft, Stephen; Danly, Christopher R.; Deppert, O.; Devlin, Matthew James; Fernandez, Juan Carlos; Gautier, Donald Cort; Geissel, M; Haight, Robert Cameron; Hamilton, Christopher Eric; Hegelich, Bjorn Manuel; Henzlova, Daniela; Johnson, Randall Philip; Schaumann, G.; Schoenberg, Kurt Francis; Schollmeier, M.; Shimada, Tsutomu; Swinhoe, Martyn Thomas; Taddeucci, Terry Nicholas; Wender, Stephen Arthur; Wurden, Glen Anthony; Roth, Markus

    2016-10-17

    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 ~5x109 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 to 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. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  3. Characterization of a novel, short pulse laser-driven neutron source

    SciTech Connect

    Jung, D.; Falk, K.; Guler, N.; Devlin, M.; Favalli, A.; Fernandez, J. C.; Gautier, D. C.; Haight, R.; Hamilton, C. E.; Hegelich, B. M.; Johnson, R. P.; Merrill, F.; Schoenberg, K.; Shimada, T.; Taddeucci, T.; Tybo, J. L.; Wender, S. A.; Wilde, C. H.; Wurden, G. A.; Deppert, O.; and others

    2013-05-15

    We present a full characterization of a short pulse laser-driven neutron source. Neutrons are produced by nuclear reactions of laser-driven ions deposited in a secondary target. The emission of neutrons is a superposition of an isotropic component into 4π and a forward directed, jet-like contribution, with energies ranging up to 80 MeV. A maximum flux of 4.4 × 10{sup 9} neutrons/sr has been observed and used for fast neutron radiography. On-shot characterization of the ion driver and neutron beam has been done with a variety of different diagnostics, including particle detectors, nuclear reaction, and time-of-flight methods. The results are of great value for future optimization of this novel technique and implementation in advanced applications.

  4. 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.

  5. Characteristics of high energy Kα and Bremsstrahlung sources generated by short pulse petawatt lasers

    NASA Astrophysics Data System (ADS)

    Park, H.-S.; Izumi, N.; Key, M. H.; Koch, J. A.; Landen, O. L.; Patel, P. K.; Phillips, T. W.; Zhang, B. B.

    2004-10-01

    We have measured the characteristics of high energy Kα sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at Lawrence Livermore National Laboratory. High energy x-ray backlighters will be essential for radiographing high energy-density experimental science targets for NIF projects especially to probe implosions and high areal density planar samples. Hard Kα x-ray photons are created through relativistic electron plasma interactions in the target material after irradiated by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator charge coupled device (CCD) camera for imaging and a CCD camera for single photon counting. We have directly measured the 22 keV Ag Kα source size using the RAL petawatt laser and performed knife-edge measurements of a 40 keV Sm Kα source using the JanUSP laser. The measured source sizes are both ˜60 μm full width half maximum. We have also measured the Ag Kα conversion efficiencies. At laser intensities of 1×1018 W/cm2 range, the conversion efficiency at 22 keV is ˜1×10-4.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

    2016-06-15

    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 mm{sup 2} to 20 × 20 mm{sup 2}. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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)

  17. 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

  18. Neutronic studies on decoupled hydrogen moderator for a short-pulse spallation source

    NASA Astrophysics Data System (ADS)

    Harada, Masahide; Watanabe, Noboru; Teshigawara, Makoto; Kai, Tetsuya; Ikeda, Yujiro

    2005-02-01

    Neutronic studies of decoupled hydrogen moderators were performed by calculations taking into account para hydrogen content, decoupling energy, moderator dimensions/shapes and reflector material. Low-energy parts of calculated spectral intensities with different para hydrogen contents were analyzed by a modified Maxwell function to characterize neutron spectra. The result shows that a 100% para hydrogen moderator gives the highest pulse peak intensity together with the narrowest pulse width and the shortest decay times. Pulse broadening with a reflector was explained by time distributions of source neutrons entering into the moderator through a decoupler. Material dependence of time distribution was studied. A decoupling energy higher than 1 eV does not bring about a large improvement in pulse widths and decay times, even at a large penalty in the peak intensity. The optimal moderator thickness was also discussed for a rectangular parallelepipe-shaped and a canteen-shaped moderator.

  19. 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.

  20. 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.

  1. 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.

  2. 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}.

  3. Frequency entanglement characterization of short-pulse pumped SPDC biphoton source with a Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Zhai, Yiwei; Dong, Ruifang; Li, Baihong; Quan, Runai; Wang, Mengmeng; Hou, Feiyan; Liu, Tao; Zhang, Shougang

    2017-06-01

    Frequency entangled biphoton sources have played an important role in quantum information. There are two key characteristics which determine the extent of their applications: the spectral indistinguishability and the degree of frequency entanglement. Previously, the spectral indistinguishability of the biphoton state is measured by the Hong-Ou-Mandel (HOM) interference visibility, whereas the degree of frequency entanglement is normally characterized with independent spectral measurements. However, these two quantum features have not been successfully measured with a single experimental setup. In this paper, we deduce the temporal distribution of a short-pulse pumped type-II spontaneous parametric down converted (SPDC) biphoton source and its relevant temporal entanglement parameter R t for operationally quantifying the degree of frequency entanglement. Furthermore, we theoretically and experimentally demonstrate, due to the inherent group delay, the difference between the signal and idler photons at the exit of the type-II nonlinear crystal, resulting in a HOM-shape dip at both sides of the center fringed envelope of the MZ interferometric coincidence diagram. By measuring the HOM-shape dip depth, the separation between the two sideband dips as well as the MZ fringed envelope width, both the spectral indistinguishability and the temporal entanglement parameter can thus be simultaneously quantified. This implementation provides us a unified and convenient method to characterize the frequency entanglement of the short-pulse pumped biphotons.

  4. 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

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. A tunable continuous wave (CW) and short-pulse optical source for THz brain imaging applications

    NASA Astrophysics Data System (ADS)

    Bakopoulos, P.; Karanasiou, I.; Pleros, N.; Zakynthinos, P.; Uzunoglu, N.; Avramopoulos, H.

    2009-10-01

    We demonstrate recent advances toward the development of a novel 2D THz imaging system for brain imaging applications both at the macroscopic and at the bimolecular level. A frequency-synthesized THz source based on difference frequency generation between optical wavelengths is presented, utilizing supercontinuum generation in a highly nonlinear optical fiber with subsequent spectral carving by means of a fiber Fabry-Perot filter. Experimental results confirm the successful generation of THz radiation in the range of 0.2-2 THz, verifying the enhanced frequency tunability properties of the proposed system. Finally, the roadmap toward capturing functional brain information by exploiting THz imaging technologies is discussed, outlining the unique advantages offered by THz frequencies and their complementarity with existing brain imaging techniques.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. PULSED ION SOURCE

    DOEpatents

    Ford, F.C.; Ruff, J.W.; Zizzo, S.G.; Cook, B.

    1958-11-11

    An ion source is described adapted for pulsed operation and producing copious quantities of ions with a particular ion egress geometry. The particular source construction comprises a conical member having a conducting surface formed of a metal with a gas occladed therein and narrow non-conducting portions hereon dividing the conducting surface. A high voltage pulse is applied across the conducting surface or producing a discharge across the surface. After the gas ions have been produced by the discharge, the ions are drawn from the source in a diverging conical beam by a specially constructed accelerating electrode.

  1. 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.

  2. 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.

  3. Pulsed plasma electron sources

    SciTech Connect

    Krasik, Ya. E.; Yarmolich, D.; Gleizer, J. Z.; Vekselman, V.; Hadas, Y.; Gurovich, V. Tz.; Felsteiner, J.

    2009-05-15

    There is a continuous interest in research of electron sources which can be used for generation of uniform electron beams produced at E{<=}10{sup 5} V/cm and duration {<=}10{sup -5} s. In this review, several types of plasma electron sources will be considered, namely, passive (metal ceramic, velvet and carbon fiber with and without CsI coating, and multicapillary and multislot cathodes) and active (ferroelectric and hollow anodes) plasma sources. The operation of passive sources is governed by the formation of flashover plasma whose parameters depend on the amplitude and rise time of the accelerating electric field. In the case of ferroelectric and hollow-anode plasma sources the plasma parameters are controlled by the driving pulse and discharge current, respectively. Using different time- and space-resolved electrical, optical, spectroscopical, Thomson scattering and x-ray diagnostics, the parameters of the plasma and generated electron beam were characterized.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Pulsed welding plasma source

    NASA Astrophysics Data System (ADS)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Tyasto, A.

    2016-04-01

    It is shown that in order to form the current pulse of a near rectangular shape, which provides conversion of the welding arc into a dynamic mode, it is rational to connect a forming element made on the basis of an artificial forming line in series to the welding DC circuit. The paper presents a diagram of a pulsed device for welding with a non-consumable electrode in argon which was developed using the forming element. The conversion of the arc into the dynamic mode is illustrated by the current and voltage oscillograms of the arc gap and the dynamic characteristic of the arc within the interval of one pulse generation time in the arc gap. The background current travels in the interpulse interval.

  15. 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.

  16. Rapidly pulsed helium droplet source

    SciTech Connect

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin; Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  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. Short-pulse Laser Processing of CFRP

    NASA Astrophysics Data System (ADS)

    Weber, Rudolf; Freitag, Christian; Kononenko, Taras V.; Hafner, Margit; Onuseit, Volkher; Berger, Peter; Graf, Thomas

    Short-pulse lasers allow processing of carbon fiber reinforced plastics (CFRP) with very high quality, i.e. showing thermal damage in the range of only a few micrometers. Due to the usually high intensities and the short interaction times of such short pulses, only a small fraction of the incident laser energy is converted to residual heat which does not contribute to the ablation process. However, if the next pulse arrives before the material had time to cool down, i.e. this residual thermal energy did not sufficiently flow out of the interaction region, it encounters material which is still hot. This remaining energy and temperature is summing up during the sequence of pulses and is commonly referred to as "heat accumulation". Thermal damage in addition to the damage created by the process itself is induced, if the resulting temperature sum exceeds the damage temperatures of either the fibre or the plastic. The current paper presents the influence of the laser parameters such as pulse energy and repetition rate on this heat accumulation. An analytical model was used to describe the heat accumulation for different laser parameters. It describes the heat accumulation process and allows estimating the maximum number of pulses allowed at the same place before a detrimental temperature increase occurs.

  4. GSFC short pulse radar, JONSWAP-75

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Walton, W. T.; Eckerman, J.; Kutz, R. L.; Dombrowski, M.; Kalshoven, J. E., Jr.

    1977-01-01

    In September 1975, the Goddard Space Flight Center operated a short pulse radar during ocean wave measuring experiments off the coast of West Germany in the North Sea. The experiment was part of JONSWAP-75. The radar system and operations during the experiment are described along with examples of data.

  5. The Quest for Ultra-Short X-Ray Pulses

    SciTech Connect

    Zholents, Alexander

    2011-03-09

    Chemical bonds form, change, or break on a femtosecond timescale. Recording a 'molecular movie' with an atomic-scale spatial resolution at the timescale set by atomic motion is a critical step in understanding these processes that can be accomplished by using ultra-short x-ray pulses. In the first part of this talk I will discuss several ideas for a generation of femtosecond x-ray pulses using spontaneous emission of electrons. Some of them, like the laser 'slicing' technique, are now routinely used at several storage-ring-based synchrotron light sources; others, like an rf orbit deflection technique, is under construction at the Advanced Photon Source. Nowadays, the femtosecond x-ray pulses are also routinely produced by x-ray free electron lasers (FELs). In the second part of this talk I will discuss how one can use FELs to obtain even shorter x-ray pulses down to attosecond timescale.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Modeling of Ultra-Short-Pulse Reflectometry

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce I.

    1998-11-01

    Pulsed reflectometry offers the prospect of making space and time-resolved measurements of the radial profiles of both the electron density and the vector magnetic field in the midplane of a device, from which the current profile can be inferred if the device is toroidally symmetric and has a weak up-down asymmetry at the midplane. Detailed modeling of the use of ultra-short-pulse reflectometry to diagnose radial electron density and magnetic field strength profiles has been undertaken with a suite of one and two-dimensional, wave-equation-solving simulation codes and analytical calculations.(B. I. Cohen, L. L. LoDestro, E. B. Hooper, and T. A. Casper, Plasma Phys. Contr. Fusion 40), 75 (1998). The reflectometry simulations are coupled to the CORSICA equilibrium and transport code to allow realistic plasma density and magnetic profiles to be used. The simulations show that pulsed reflectometry is a relatively robust technique for inferring density and magnetic profiles. A new innovation is the demonstration that the linear mode conversion of extraordinary modes to ordinary modes induced by magnetic shear can be diagnosed with reflectometry from which the magnetic pitch angle can be inferred.(B. I. Cohen, E. B. Hooper, M. C. Spang, and C. W. Domier, "Theoretical Aspects of the Use of Pulsed Reflectometry in a Spheromak Plasma," (June, 1998), submitted to Rev. Sci. Instrum.) Some of the characteristics of fluctuations are also revealed by reflectometry. Simulation examples of applications of ultra-short-pulsed reflectometry to the SSPX spheromak experiment at Livermore are presented.

  12. 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.

  13. 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.

  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. 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.

  16. Short infrared laser pulses block action potentials in neurons

    NASA Astrophysics Data System (ADS)

    Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.

    2017-02-01

    Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

  17. Two concepts of short-period, pulse helical undulators

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexei V.

    2009-04-01

    Non-magnetic, pulse undulators are proposed for non-free-electron laser (FEL) applications. Both have a cm-sub-cm period and use a GW-sub-GW power level energy sources available within state-of-the-art technology. A two-beam undulator complements two-beam accelerator (TBA) scheme to generate polarized positrons using intense polarized gamma-photons radiated in a square waveguide powered by microwaves extractor-wakefield decelerator. Another concept revisits a bifilar pulse line carrying co-propagating non-sinusoidal wave driven by a high voltage, ns-pulse, commercial generator. It can be used as a short insertion device (ID) for synchrotron radiation facilities. Undulator factor approaching unity is achievable at substantial gap-to-period ratios exceeding 0.4 for both conceptual designs.

  18. 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.

  19. Table-top sources of ultrashort THz pulses

    NASA Astrophysics Data System (ADS)

    Reimann, Klaus

    2007-10-01

    In this paper techniques for the generation and measurement of ultrashort pulses in the frequency range from about 0.1 to 10 THz are reviewed. The methods for generation are restricted to table-top systems based on short-pulse lasers in the visible or in the near-infrared. Three techniques are dealt with in detail: photoconductive switches, difference frequency generation and plasma sources. Definitions and methods to measure the pulse width are given, among them cross-correlation and measurements of the electric field of these pulses as a function of time by photoconductive switches and electro-optic sampling.

  20. 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.

  1. Status of RF deflecting cavity design for the generation of short x-ray pulses in the Advanced Photon Source storage ring.

    SciTech Connect

    Waldschmidt, G.; Borland, M.; Chae, Y.C.; Harkay, K.; Horan, D.; Nassiri, A.; Accelerator Systems Division

    2006-01-01

    The Advanced Photon Source (APS) at Argonne National Laboratory is exploring the possibility of using radio frequency deflection to generate x-ray radiation pulses on the order of 1 pico-second (Delta t - 70%) or less. This scheme is based on a proposal by A. Zholents et al. that relies on manipulating the transverse momentum of the electrons in a bunch by using an rf deflecting cavity to induce a longitudinally dependent vertical deflection of the beam. The beam will then travel through a number of undulators before arriving at a second set of deflecting cavities where the deflection is reversed such that the remainder of the storage ring is largely unperturbed. Considerable effort has been expended on the design of a superconducting rf deflecting cavity operating in the S-band at 2.8 GHz to address fundamental design issues including cavity geometry, deflecting voltage, rf power coupling, tuning, and damping of higher-order and lower-order modes. In this paper we present simulation results and analysis of an optimized superconducting rf deflecting cavity design for the APS storage ring.

  2. 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.

  3. On Acceptable Exposures to Short Pulses of Electromagnetic Fields

    DTIC Science & Technology

    2015-09-01

    NAWCWD TP 8791 On Acceptable Exposures to Short Pulses of Electromagnetic Fields by Francis X. Canning, PhD Physics...prepared in response to a request to study the effects of exposure to short pulses of electromagnetic fields. The author is a physicist at the Naval... Exposures to Short Pulses of Electromagnetic Fields (U) 5a. CONTRACT NUMBER N/A 5b. GRANT NUMBER N/A 5c. PROGRAM ELEMENT NUMBER N/A 6. AUTHOR(S

  4. 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.

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. Application of Yb:YAG short pulse laser system

    DOEpatents

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Crane, John K.; Telford, Steve; Perry, Michael D.

    2004-07-06

    A diode pumped, high power (at least 20W), short pulse (up to 2 ps), chirped pulse amplified laser using Yb:YAG as the gain material is employed for material processing. Yb:YAG is used as the gain medium for both a regenerative amplifier and a high power 4-pass amplifier. A single common reflective grating optical device is used to both stretch pulses for amplification purposes and to recompress amplified pulses before being directed to a workpiece.

  10. 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)

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  19. Self-induced transparency of an extremely short pulse

    NASA Technical Reports Server (NTRS)

    Lee, C. T.

    1973-01-01

    An extremely short pulse propagation in a resonant medium is properly described by a closed form steady-state analytic solution. The usual slowly varying envelope approximation (SVEA) is not made. Instead, different assumptions with respect to pulse speed and pulse duration are used, and any possible nonresonant loss is ignored. This study indicates that the results obtained by the SVEA approach are much better than they have been intuitively expected to be.

  20. 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.

  1. Stabilization of CO2 laser short-pulse oscillation by tickle pulse for dot processing

    NASA Astrophysics Data System (ADS)

    Tokita, Daisaku; Sakurada, Noriyo; Ishii, Yoshio; Kubota, Yuzuru; Watanabe, Kazuhiro

    2005-03-01

    Image drawing using a laser system has been attempted by Segmented Pixel Drawing (SPD) method and Laser Plastic Coloring (LPC) method in our laboratory. Laser dot processing by a short pulse oscillation of a CO2 laser is used for these laser methods. Stable short pulse oscillation is required for an accurate image drawing. That oscillation has a tendency to be unstable because of its long oscillation interval. A tickle pulse is known as one of a technique which is conventionally used for a continuous pulse oscillation of a CO2 laser in order to make rising rate of laser oscillation quick. In this study, this tickle pulse has been improved and applied to the short pulse oscillation in order to stable short pulse oscillation and high accurate laser dot processing. In the result, processed dots are appeared bigger with less variation in their sizes with the improved tickle pulse case compared with the conventional case. Short pulse oscillation is stabilized by these improved tickle pulse. Reproducibility and accuracy ofthe SPD method and LPC method might be realized by this stabilized dot processing.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. The Advanced Photon Source pulsed deflecting cavity RF system.

    SciTech Connect

    Cours, A.; DiMonte, N. P.; Smith, T. L.; Waldschmidt, G.

    2008-01-01

    The Advanced Photon Source Deflecting Cavity System for producing short X-ray pulses uses two multi-cell, S-band cavities to apply a deflecting voltage to the stored electron beam ahead of an undulator that supports a beamline utilizing picosecond X-rays. Two additional multi-cell cavities are then used to cancel out the perturbation and restore the electron beam to its nominal orbit. The pulsed rf system driving the deflecting cavities is described. Design tradeoffs are discussed with emphasis on topology considerations and digital control loops making use of sampling technology in a manner consistent with the present state of the art.

  7. 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.

  8. Study of Non-LTE Spectra Dependence on Target Mass in Short Pulse Laser Experiments

    SciTech Connect

    Back, C. A.; Giraldez, E.; Phommarine, S.; Audbert, P.; Baton, S. D.; Bastiani-Ceccotti, S.; Guillou, P.; Barbrel, B.; Gauci, E.; Koenig, M.; Gremillet, L.; Lecherbourg, L.; Rousseaux, C.

    2007-08-02

    Backlight sources created from short pulse lasers are useful probes of high energy density plasmas because of their short duration and brightness. Recent work has shown that the production of K{alpha} radiation can be manipulated by the size and geometry of the targets. Empirical relationships suggest that the electron reflux in the target plays an important role in the heating of these targets to create x-ray backlight sources.

  9. Thermoelastic Response to a Short Laser Pulse.

    DTIC Science & Technology

    1982-11-01

    PULSE John C. Strikwerda and Andrew N. Scott* Technical Summary Report #2451 November 1982 ABSTRACT -W-Econsider a one-dimensional model of the...ka(t)0X .(ty)dy c + d x In a similar way one may derive expressione for T2 and u2 , however, for most applications the first two terms should suffice...Thermoelasti city, Perturbation Analysis S& ABSTRACT (Cin~ma at nve. side Nt .eem mE ti*.i by Week& am..) We consider a one-dimensional model of the

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Short pulse generation and high speed communication system

    NASA Astrophysics Data System (ADS)

    Fan, Honglei

    Ultrahigh-speed optical time-division-multiplexing (TDM) transmission technologies are essential to construct ultrahigh-speed all-optical networks needed in the multimedia era. In order to realize high-speed optical TDM systems, ultra-short pulses should be generated. In this dissertation, the gain switching and mode locking techniques have been analyzed and used to produce ultra- short pulses. Gain-switched pulses with a width of ~18ps have been obtained. The theoretical analysis on gain-switching phenomena has been carried out. A new approach for the simulation of the spectrum of a gain- switched laser has been developed. The principle of mode locking has been discussed. ~6.5ps, pulses have been obtained from a monolithic mode-locked distributed Bragg reflector (DBR) laser, which are the shortest pulses from the actively mode- locked DBR lasers as we know. ~1.1ps pulses have been achieved from a colliding-pulse mode-locked (CPM) laser. The operation principle of CPM lasers has been discussed. Pulse compression using dispersion-compensating fiber has been applied in order to get shorter pulses. The semiconductor optical amplifier (SOA) plays a very important role in TDM systems. The cross gain modulation (XGM) measurements on a 2-section SOA, using both cw and pulsed pump and probe beams, have been performed. A theoretical analysis has been carried out. Wavelength conversion and fiber transmission experiments have been achieved at different bit rates. The basic idea of TDM system has been discussed. Multiplexing has been achieved using fibers. Demulitplexing has been demonstrated using XGM in SOA, four-wave mixing (FWM) in SOA, and cascaded modulators. The operation principles have been discussed in detail. The FWM experiments between two optical pulses have been performed.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. Radiobiological response to ultra-short pulsed megavoltage electron beams of ultra-high pulse dose rate.

    PubMed

    Beyreuther, Elke; Karsch, Leonhard; Laschinsky, Lydia; Leßmann, Elisabeth; Naumburger, Doreen; Oppelt, Melanie; Richter, Christian; Schürer, Michael; Woithe, Julia; Pawelke, Jörg

    2015-08-01

    In line with the long-term aim of establishing the laser-based particle acceleration for future medical application, the radiobiological consequences of the typical ultra-short pulses and ultra-high pulse dose rate can be investigated with electron delivery. The radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) was used to mimic the quasi-continuous electron beam of a clinical linear accelerator (LINAC) for comparison with electron pulses at the ultra-high pulse dose rate of 10(10) Gy min(-1) either at the low frequency of a laser accelerator or at 13 MHz avoiding effects of prolonged dose delivery. The impact of pulse structure was analyzed by clonogenic survival assay and by the number of residual DNA double-strand breaks remaining 24 h after irradiation of two human squamous cell carcinoma lines of differing radiosensitivity. The radiation response of both cell lines was found to be independent from electron pulse structure for the two endpoints under investigation. The results reveal, that ultra-high pulse dose rates of 10(10) Gy min(-1) and the low repetition rate of laser accelerated electrons have no statistically significant influence (within the 95% confidence intervals) on the radiobiological effectiveness of megavoltage electrons.

  7. 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.

  8. 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.

  9. 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

  10. 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.

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

    SciTech Connect

    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.

  12. Status of the intense pulsed neutron source

    SciTech Connect

    Brown, B.S.; Carpenter, J.M.; Crawford, R.K.; Rauchas, A.V.; Schulke, A.W.; Worlton, T.G.

    1988-01-01

    IPNS is not unique in having concerns about the level of funding, and the future looks good despite these concerns. This report details the progress made at IPNS during the last two years. Other papers in these proceedings discuss in detail the status of the enriched uranium Booster target, the two instruments that are under construction, GLAD and POSY II, and a proposal for research on an Advanced Pulsed Neutron Source (ASPUN) that has been submitted to the Department of Energy (DOE). Further details on IPNS are available in the IPNS Progress Report 1987--1988, available by writing the IPNS Division Office. 9 refs., 3 tabs.

  13. 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.

  14. 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

  15. 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.

  16. Control of relativistic ionization by polarization of short laser pulses

    NASA Astrophysics Data System (ADS)

    Krajewska, K.; Cajiao Vélez, F.; Kamiński, J. Z.

    2017-07-01

    The Born approximation is applied to study the high-energy ionization that is driven by short, relativistically intense laser pulses. Assuming the fixed radiation flow through a surface of the laser focus, we investigate the optimal conditions for generating most energetic photoelectrons. We demonstrate that, under such constraint, one can control the photoelectron spectra using the polarization of the driving field. More precisely, the most energetic electrons are produced for a nearly linear polarization of the laser field. At the same time, the resulting electrons are detected in a narrow angular window which is of great importance for their potential applications; one of them being the generation of attosecond electron pulses.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Interaction of cold atoms with short laser pulses.

    NASA Astrophysics Data System (ADS)

    Chamberlin, Karen; Lilla, Derek; Taylor, Kyle; Zick, Kevin; Taft, Greg; Nguyen, Hai

    2006-05-01

    We present a powerful diagnostic system to observe the interaction of ultrafast laser pulses with trapped ^87Rb atoms. The ionization of cold atoms and the formation of cold molecules in an intense laser field in the μK temperature range open new branches of research in chemistry, metrology, and quantum physics. However, the interaction of cold atoms with short laser pulses and the subsequent ionization or molecule formation are processes which are not well understood and can be easily misinterpreted. In our proposed experimental setup, an existing ultrafast laser system at the University of Wisconsin-Stevens Point will be used in conjunction with Magneto Optical Trap Recoil Ion Momentum Spectroscopy (MOTRIMS) to directly measure the products formed by the interaction of ultrafast laser pulses with the cold trapped ^87Rb atoms.

  7. 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.

  8. 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

  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. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    SciTech Connect

    Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

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

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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").

  19. Development of ultra-short pulse VUV laser system for nanoscale processing

    NASA Astrophysics Data System (ADS)

    Katto, Masahito; Zushi, Hironari; Nagaya, Wataru; Harano, Shinya; Matsumoto, Ryota; Yokotani, Atushi; Kaku, Masanori; Kubodera, Shoichi; Miyanaga, Noriaki

    2010-11-01

    We have developed intense vacuum ultraviolet (VUV) radiation sources for advanced material processing, such as photochemical surface reactions and precise processing on a nanometer scale. We have constructed a new VUV laser system to generate sub-picosecond pulses at the wavelength of 126 nm. A seed VUV pulse was generated in Xe as the 7th harmonic of a 882-nm Ti:sapphire laser. The optimum conversion was achieved at the pressure of 1.2 Torr. The seed pulse will be amplified by the Ar2^{*} media generated by an optical-field-induced ionization Ar plasma produced by the Ti:sapphire laser. We have obtained a gain coefficient of g=0.16 cm-1. Our developing system will provide VUV ultra-short pulses with sub-μJ energy at a repetition rate of 1 kHz.

  20. 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.

  1. 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.}

  2. 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.

  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. An integrated CMOS detection system for optical short-pulse

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Gun; Hong, Nam-Pyo; Choi, Young-Wan

    2014-03-01

    We present design of a front-end readout system consisting of charge sensitive amplifier (CSA) and pulse shaper for detection of stochastic and ultra-small semiconductor scintillator signal. The semiconductor scintillator is double sided silicon detector (DSSD) or avalanche photo detector (APD) for high resolution and peak signal reliability of γ-ray or X-ray spectroscopy. Such system commonly uses low noise multichannel CSA. Each CSA in multichannel includes continuous reset system based on tens of MΩ and charge-integrating capacitor in feedback loop. The high value feedback resistor requires large area and huge power consumption for integrated circuits. In this paper, we analyze these problems and propose a CMOS short pulse detection system with a novel CSA. The novel CSA is composed of continuous reset system with combination of diode connected PMOS and 100 fF. This structure has linearity with increased input charge quantity from tens of femto-coulomb to pico-coulomb. Also, the front-end readout system includes both slow and fast shapers for detecting CSA output and preventing pile-up distortion. Shaping times of fast and slow shapers are 150 ns and 1.4 μs, respectively. Simulation results of the CMOS detection system for optical short-pulse implemented in 0.18 μm CMOS technology are presented.

  5. 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.

  6. The performance of neutron scattering spectrometers at a long-pulse spallation source

    SciTech Connect

    Pynn, R.

    1995-04-01

    The first conclusion the author wants to draw is that comparison of the performance of neutron scattering spectrometers at CW and pulsed sources is simpler for long-pulsed sources than it is for the short-pulse variety. Even though detailed instrument design and assessment will require Monte Carlo simulations (which have already been performed at Los Alamos for SANS and reflectometry), simple arguments are sufficient to assess the approximate performance of spectrometers at an LPSS and to support the contention that a 1 MW long-pulse source can provide attractive performance, especially for instrumentation designed for soft-condensed-matter science. Because coupled moderators can be exploited at such a source, its time average cold flux is equivalent to that of a research reactor with a power of about 15 MW, so only a factor of 4 gain from source pulsing is necessary to obtain performance that is comparable with the ILL. In favorable cases, the gain from pulsing can be even more than this, approaching the limit set by the peak flux, giving about 4 times the performance of the ILL. Because of its low duty factor, an LPSS provides the greatest performance gains for relatively low resolution experiments with cold neutrons. It should thus be considered complementary to short pulse sources which are most effective for high resolution experiments using thermal or epithermal neutrons.

  7. 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.

  8. 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.

  9. Modeling short pulse duration shock initiation of solid explosives

    SciTech Connect

    Tarver, C.M.; Hallquist, J.O.; Erickson, L.M.

    1985-06-27

    The chemical reaction rate law in the ignition and growth model of shock initiation and detonation of solid explosives is modified so that the model can accurately simulate short pulse duration shock initiation. The reaction rate law contains three terms to model the ignition of hot spots by shock compression, the slow growth of reaction from these isolated hot spots, and the rapid completion of reaction as the hot spots coalesce. Comparisons for PBX 9404 between calculated and experimental records are presented for the electric gun mylar flyer plate system, the minimum priming charge test, embedded manganin pressure and particle velocity gauges, and VISAR particle velocity measurements for a wide variety of input pressures, rise times and pulse durations. The ignition and growth model is now a fully developed phenomenological tool that can be applied with confidence to almost any hazard, vulnerability or explosive performance problem. 27 refs., 16 figs., 2 tabs.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Conservation laws of the generalized short pulse equation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Yong; Chen, Yu-Fu

    2015-02-01

    We show that the generalized short pulse equation is nonlinearly self-adjoint with differential substitution. Moreover, any adjoint symmetry is a differential substitution of nonlinear self-adjointness, and vice versa. Consequently, the general conservation law formula is constructed and new conservation laws for some special cases are found. Project supported by the National Natural Science Foundation of China (Grant Nos. 11301012 and 11271363), the Excellent Young Teachers Program of North China University of Technology (Grant No. 14058) and the Doctoral Fund of North China University of Technology (Grant No. 41).

  18. Ultra-short pulsed millimeter-wave laser

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas

    2000-10-01

    High peak power pulses of 1.22-mm wavelength radiation have recently been obtained from a novel cavity-dumped far-infrared optically-pumped laser^1. Smooth reproducible pulses with the following characteristics have been routinely obtained: peak power=25-kW, pulsewidth (FWHM)=5-ns, repetition rate=10 pps. (This compares favorably to typical far-infrared, cavity-dumped output - 11-kW, 30-ns, 1 pps - available from the University of California - Santa Barbara Free Electron Laser). The pumping laser is a grating-tuned, hybrid TEA CO2 laser providing 1J / pulse at the 9P32 transition. The far-infrared gain medium is isotopic (C^13) methyl flouride. Experiments are underway for using the novel source to resonantly excite coherent pulses of 250-GHz longitudinal acoustic phonons in silicon doping superlattices. ^1 Thomas E. Wilson, "Modeling the high-speed switching of far-infrared radiation by photoionization in a semiconductor", Phys. Rev. B 59 (20), 12996 (1999).

  19. 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.

  20. 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.

  1. Short-pulse high intensity laser thin foil interaction

    NASA Astrophysics Data System (ADS)

    Audebert, Patrick

    2003-10-01

    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  2. 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.

  3. Comparison of short pulse generation schemes for a soft x-ray free electron laser

    NASA Astrophysics Data System (ADS)

    Martin, I. P. S.; Bartolini, R.

    2011-03-01

    In this paper we study the performance of two complementary short pulse generation schemes as applied to a soft x-ray free electron laser. The first scheme, recently proposed by Saldin et al., makes use of a laser pulse consisting of only a few optical cycles to give an energy chirp to a short section of an electron bunch and tapers the main radiator undulator in order to compensate the chirped region. The second scheme investigated takes a low-charge, high brightness electron bunch and compresses it to ˜1fs in order to operate in the so-called “single-spike” regime. We perform start-to-end simulations of both these schemes, assess the sensitivity of each scheme to realistic jitter sources, and provide a direct comparison of the respective strengths and drawbacks.

  4. 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.

  5. The performance of neutron scattering spectrometers at a long-pulse spallation source

    SciTech Connect

    Pynn, R.

    1997-06-01

    In this document the author considers the performance of a long pulse spallation source for those neutron scattering experiments that are usually performed with a monochromatic beam at a continuous wave (CW) source such as a nuclear reactor. The first conclusion drawn is that comparison of the performance of neutron scattering spectrometers at CW and pulsed sources is simpler for long-pulsed sources than it is for the short-pulse variety. Even though detailed instrument design and assessment will require Monte Carlo simulations (which have already been performed at Los Alamos for SANS and reflectometry), simple arguments are sufficient to assess the approximate performance of spectrometers at an LPSS and to support the contention that a 1 MW long-pulse source can provide attractive performance, especially for instrumentation designed for soft-condensed-matter science. Because coupled moderators can be exploited at such a source, its time average cold flux is equivalent to that of a research reactor with a power of about 15 MW, so only a factor of 4 gain from source pulsing is necessary to obtain performance that is comparable with the ILL. In favorable cases, the gain from pulsing can be even more than this, approaching the limit set by the peak flux, giving about 4 times the performance of the ILL. Because of its low duty factor, an LPSS provides the greatest performance gains for relatively low resolution experiments with cold neutrons. It should thus be considered complementary to short pulse sources which are most effective for high resolution experiments using thermal or epithermal neutrons.

  6. Neodymium lasers as a source of synchronized high-power optical pulses

    NASA Astrophysics Data System (ADS)

    Sizer, Theodore, II; Duling, Irl N., III

    1988-02-01

    The recent considerable progress in the development of solid-state lasers, primarily neodymium-based lasers for use as sources of short, synchronized, high-power optical pulses, is reviewed. The amplification of femtosecond optical pulses using synchronous amplification techniques with these lasers has proved particularly applicable to experimentation. The authors also presents a laser design which combines several advantageous qualities into a single laser cavity.

  7. 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.

  8. 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

  9. 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.

  10. Distinguishing Raman from strongly coupled Brillouin amplification for short pulses

    SciTech Connect

    Jia, Qing; Barth, Ido; Edwards, Matthew R.; Mikhailova, Julia M.; Fisch, Nathaniel J.

    2016-05-15

    Plasma-based amplification by strongly coupled Brillouin scattering has recently been suggested for the compression of a short seed laser to ultrahigh intensities in sub-quarter-critical-density plasmas. However, by employing detailed spectral analysis of particle-in-cell simulations in the same parameter regime, we demonstrate that, in fact, Raman backscattering amplification is responsible for the growth and compression of the high-intensity, leading spike, where most of the energy compression occurs, while the ion mode only affects the low-intensity tail of the amplified pulse. The critical role of the initial seed shape is identified. A number of subtleties in the numerical simulations are also pointed out.

  11. Voyager Uranus encounter 0.2lbf T/VA short pulse test report

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The attitude control thrusters on the Voyager spacecraft were tested for operation at electrical pulse widths of less than the current 10-millisecond minimum to reduce impulse bit and, therefore, reduce image smear of pictures taken during the Uranus encounter. Thrusters with the identical configuration of the units on the spacecraft were fired in an altitude chamber to characterize impulse bit and impulse bit variations as a function of electrical pulse widths and to determine if the short pulses decreased thruster life. Pulse widths of 4.0 milliseconds provide approximately 45 percent of the impulse provided by a 10-ms pulse, and thruster-to-thruster and pulse-to-pulse variation is approximately plus or minus 10 percent. Pulse widths shorter than 4 ms showed wide variation, and no pulse was obtained at 3 ms. Three thrusters were each subjected to 75,000 short pulses of 4 ms or less without performance degradation. A fourth thruster exhibited partial flow blockage after 13,000 short pulses, but this was attributed to prevous test history and not short pulse exposure. The Voyager attitude control thrusters should be considered flight qualified for short pulse operation at pulse widths of 4.0 ms or more.

  12. All-Fiber, Directly Chirped Laser Source for Chirped-Pulse-Amplification

    NASA Astrophysics Data System (ADS)

    Xin, Ran

    Chirped-pulse-amplification (CPA) technology is widely used to produce ultra-short optical pulses (sub picosecond to femtoseconds) with high pulse energy. A chirped pulse laser source with flexible dispersion control is highly desirable as a CPA seed. This thesis presents an all-fiber, directly chirped laser source (DCLS) that produces nanosecond, linearly-chirped laser pulses at 1053 nm for seeding high energy CPA systems. DCLS produces a frequency chirp on an optical pulse through direct temporal phase modulation. DCLS provides programmable control for the temporal phase of the pulse, high pulse energy and diffraction-limited beam performance, which are beneficial for CPA systems. The DCLS concept is first described. Its key enabling technologies are identified and their experimental demonstration is presented. These include high-precision temporal phase control using an arbitrary waveform generator, multi-pass phase modulation to achieve high modulation depth, regenerative amplification in a fiber ring cavity and a negative feedback system that controls the amplifier cavity dynamics. A few technical challenges that arise from the multi-pass architecture are described and their solutions are presented, such as polarization management and gain-spectrum engineering in the DCLS fiber cavity. A DCLS has been built and its integration into a high energy OPCPA system is demonstrated. DCLS produces a 1-ns chirped pulse with a 3-nm bandwidth. The temporal phase and group delay dispersion on the DCLS output pulse is measured using temporal interferometry. The measured temporal phase has an ˜1000 rad amplitude and is close to a quadratic shape. The chirped pulse is amplified from 0.9 nJ to 76 mJ in an OPCPA system. The amplified pulse is compressed to close to its Fourier transform limit, producing an intensity autocorrelation trace with a 1.5-ps width. Direct compressed-pulse duration control by adjusting the phase modulation drive amplitude is demonstrated. Limitation

  13. 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.

  14. Short infrared laser pulses increase cell membrane fluidity

    NASA Astrophysics Data System (ADS)

    Walsh, Alex J.; Cantu, Jody C.; Ibey, Bennett L.; Beier, Hope T.

    2017-02-01

    Short infrared laser pulses induce a variety of effects in cells and tissues, including neural stimulation and inhibition. However, the mechanism behind these physiological effects is poorly understood. It is known that the fast thermal gradient induced by the infrared light is necessary for these biological effects. Therefore, this study tests the hypothesis that the fast thermal gradient induced in a cell by infrared light exposure causes a change in the membrane fluidity. To test this hypothesis, we used the membrane fluidity dye, di-4-ANEPPDHQ, to investigate membrane fluidity changes following infrared light exposure. Di-4-ANEPPDHQ fluorescence was imaged on a wide-field fluorescence imaging system with dual channel emission detection. The dual channel imaging allowed imaging of emitted fluorescence at wavelengths longer and shorter than 647 nm for ratiometric assessment and computation of a membrane generalized polarization (GP) value. Results in CHO cells show increased membrane fluidity with infrared light pulse exposure and this increased fluidity scales with infrared irradiance. Full recovery of pre-infrared exposure membrane fluidity was observed. Altogether, these results demonstrate that infrared light induces a thermal gradient in cells that changes membrane fluidity.

  15. 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%.

  16. 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.

  17. Short-pulse and short-wavelength ablation of semiconductor materials

    NASA Astrophysics Data System (ADS)

    Ostendorf, Andreas; Bauer, Thorsten; Temme, Thorsten; Wagner, Thilo

    2001-06-01

    Increasing miniaturization and integration of multiple functions into portable electronic devices and sensors ask for smaller electrical components. Conventional abrasive processes often reach their technological limit resulting in the demand for alternative technologies with increased precision and performance. Lasers have been proven to be a suitable tool for micromachining, but often suffering the disadvantage of heat or shock affected zones around the machined structures. To be feasible as an industrial solution, new approaches have to provide very high precision and process stability with minimal collateral damage. Presently, two different approaches for laser machining of semiconductor materials are being investigated. Although the interaction mechanism is completely different as described within this paper, both are regarded as promising technologies: ultrashort-pulse and short wavelength laser machining. Femtosecond laser machining has been used for a variety of applications, showing the advantage of non-thermal ablation of many kinds of materials. Due to the short pulse duration and the high intensities multi-photon absorption allows to overcome the bandgap of semiconductors while not affecting the bulk material. Due to the short wavelength excimer lasers as well as fluorine lasers provide the general ability to generate small spot sizes and emit photons with higher energies compared to the bandgap of the material, e.g. of silicon. Both technologies will be discussed and compared, and applications for micromachining of silicon will be presented.

  18. 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.

  19. 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

  20. Low-cost laser scanning photoacoustic microscopy system with a pulsed laser diode excitation source

    NASA Astrophysics Data System (ADS)

    Erfanzadeh, Mohsen; Zhu, Quing

    2017-03-01

    We present a low-cost laser scanning photoacoustic microscopy system with a pulsed laser diode as the excitation source. The system utilizes a 905 nm pulsed laser diode with 120 ns pulse width and 1 KHz repetition rate. No averaging is performed in data acquisition, resulting in a short image acquisition time. The maximum field of view is 4.6 mm × 3.7 mm and the lateral resolution is 71 μm. Images of human hairs and mouse ear are presented to demonstrate the feasibility of the system in imaging biological tissue.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Neutron Yield With a Pulsed Surface Flashover Deuterium Source

    SciTech Connect

    Guethlein, G.; Falabella, S.; Sampayan, S. E.; Meyer, G; Tang, V.; Kerr, P.

    2009-03-10

    As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact, low average power ion source is needed. Towards that end, we are testing a high current, pulsed surface flashover ion source, with deuterated titanium as the spark contacts. Neutron yield and source lifetime data will be presented using a low voltage (<100 kV) deuterated target. With 20 ns spark drive pulses we have shown >10{sup 6} neutrons/s with 1 kHz PRF.

  9. 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.

  10. 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.

  11. Proceedings of the workshop on neutron instrumentation for a long-pulse spallation source

    SciTech Connect

    Alonso, J.; Schroeder, L.; Pynn, R.

    1995-12-31

    This workshop was carried out under the auspices of the Lawrence Berkeley National Laboratory Pulsed Spallation Source activity and its Pulsed Spallation Source Committee (PSSC). One of our activities has been the sponsorship of workshops related to neutron production by pulsed sources. At the Crystal City PSSC meeting a decision was made to hold a workshop on the instrumentation opportunities at a long-pulse spallation source (LPSS). The enclosed material represents the results of deliberations of the three working groups into which the participants were divided, covering elastic scattering, inelastic scattering and fundamental physics, as well as contributions from individual participants. We hope that the material in this report will be useful to the neutron scattering community as it develops a road-map for future neutron sources. The workshop was held at LBNL in mid-April with about sixty very dedicated participants from the US and abroad. This report presents the charge for the workshop: Based on the bench mark source parameters provided by Gary Russell, determine how a suite of spectrometers in each of the three working group`s area of expertise would perform at an LPSS and compare this performance with that of similar spectrometers at a continuous source or a short-pulse source. Identify and discuss modifications to these spectrometers that would enhance their performance at an LPSS. Identify any uncertainties in the analysis of spectrometer performance that require further research. Describe what R & D is needed to resolve these issues. Discuss how the performance of instruments would be affected by changes in source parameters such as repetition rate, proton pulse length, and the characteristic time of pulse tails. Identify beneficial changes that could become goals for target/moderator designers. Identify novel methods that might be applied at an LPSS. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.

  12. Modulated Pulsed Laser Sources for Imaging Lidars

    DTIC Science & Technology

    2007-10-01

    manufactured by QPC. This C-mount device has a monolithic semiconductor amplifier allowing the package to output up to 1.5 Watts at 1064 nm with linewidths ɘ.1...pulsed driver based on the avalanche transistor circuit being used for gain switching, a 1064 nm DFB laser manufactured by QPC and a DBR -style laser...available now that may provide the needed power. An example of such a laser is the QPC C-mount monolithic oscillator/amplifier which can output 1.5

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Bremsstrahlung Dose Yield for High-Intensity Short-Pulse Laser–Solid Experiments

    DOE PAGES

    Liang, Taiee; Bauer, Johannes M.; Liu, James C.; ...

    2016-12-01

    A bremsstrahlung source term has been developed by the Radiation Protection (RP) group at SLAC National Accelerator Laboratory for high-intensity short-pulse laser–solid experiments between 1017 and 1022 W cm–2. This source term couples the particle-in-cell plasma code EPOCH and the radiation transport code FLUKA to estimate the bremsstrahlung dose yield from laser–solid interactions. EPOCH characterizes the energy distribution, angular distribution, and laser-to-electron conversion efficiency of the hot electrons from laser–solid interactions, and FLUKA utilizes this hot electron source term to calculate a bremsstrahlung dose yield (mSv per J of laser energy on target). The goal of this paper is tomore » provide RP guidelines and hazard analysis for high-intensity laser facilities. In conclusion, a comparison of the calculated bremsstrahlung dose yields to radiation measurement data is also made.« less

  19. Bremsstrahlung Dose Yield for High-Intensity Short-Pulse Laser–Solid Experiments

    SciTech Connect

    Liang, Taiee; Bauer, Johannes M.; Liu, James C.; Rokni, Sayed H.

    2016-12-01

    A bremsstrahlung source term has been developed by the Radiation Protection (RP) group at SLAC National Accelerator Laboratory for high-intensity short-pulse laser–solid experiments between 1017 and 1022 W cm–2. This source term couples the particle-in-cell plasma code EPOCH and the radiation transport code FLUKA to estimate the bremsstrahlung dose yield from laser–solid interactions. EPOCH characterizes the energy distribution, angular distribution, and laser-to-electron conversion efficiency of the hot electrons from laser–solid interactions, and FLUKA utilizes this hot electron source term to calculate a bremsstrahlung dose yield (mSv per J of laser energy on target). The goal of this paper is to provide RP guidelines and hazard analysis for high-intensity laser facilities. In conclusion, a comparison of the calculated bremsstrahlung dose yields to radiation measurement data is also made.

  20. 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.

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

    DOEpatents

    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.

  2. 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.

  3. 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

  4. Study of the excess noise associated with demodulation of ultra-short infrared pulses.

    PubMed

    Ivanov, Eugene N; Diddams, Scott A; Hollberg, Leo

    2005-07-01

    The demodulation of ultra-short light pulses with photodetectors is accompanied by excess phase noise at the pulse repetition rate and harmonics in the spectrum of the photocurrent. The major contribution to this noise is power fluctuations of the detected pulse train that, if not compensated for, can seriously limit the stability of frequency transfer from optical to microwave domain. By making use of an infrared femtosecond laser, we measured the spectral density of the excess phase noise, as well as power-to-phase conversion for different types of InGaAs photodetectors. Noise measurements were performed with a novel type of dual-channel readout system using a fiber coupled beam splitter. Strong suppression of the excess phase noise was observed in both channels of the measurement system when the average power of the femtosecond pulse train was stabilized. The results of this study are important for the development of low-noise microwave sources derived from optical "clocks" and optical frequency synthesis.

  5. 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.

  6. An optical fiber re-circulating loop for a single shot very short pulse or pulse train measurement

    NASA Astrophysics Data System (ADS)

    Yin, Yan

    1997-05-01

    A signle shot very short electrical pulse is converted into an optical pulse, then is injeted into a re-circulating optical fiber loop. It is tapped out at each turn to produce a pulse train. Each pulse in the train is a copy of the original one. This method generates a repetitive signals from a single shot signal. A sampling oscilloscope then can be used to perform the measurement. It uses the high bandwidth of modern optical fiber technique. The paper will describe the system and present the results of the bench tests. The work has bee done under DOE SBIR grant, DE-FG03-96ER82210/A000.

  7. 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.

  8. 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.

  9. The effect of short-term bed-rest on radial pulse in healthy subjects.

    PubMed

    Yim, Yun-Kyoung; Park, Kwang Suk

    2014-06-01

    The objective of this study is to investigate the effects of short-term bed rest on the radial pulse in healthy subjects. Twenty-one healthy volunteers participated in this study. Their radial pulse was measured at different measuring positions using a multi-step tonometry system. The participants took 30 minutes of bed rest and their radial pulse was measured before and after the bed rest. The effects of bed rest on the radial pulse were analyzed. The pulse area, the amplitudes of h4 and h5, the pulse period, and the diastolic pulse proportion increased with short-term bed rest, whereas the proportions of systolic and hightension pulse and the fundamental frequency of the pulse wave decreased with short-term bed rest. All the changes were in the same direction in both male and female participants at all measuring positions; however, some parameters changed more in women than in men, and some changed more at the distal position than at the proximal position. In shortly, Short-term bed rest induces significant changes in the radial pulse of healthy subjects. The results of this study could be used as a control reference for clinical acupuncture studies with participants lying on a bed for acupuncture treatment. Copyright © 2013. Published by Elsevier B.V.

  10. 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.

  11. Double and multi-pulsed operations of inductive plasma sources

    NASA Astrophysics Data System (ADS)

    Anderson, M.; Bystritskii, V.; Walters, J. K.

    2005-06-01

    This paper describes the study of double and multi-pulsed operations of two inductive plasma sources (IPS) for the generation of intense ion/plasma flows. Due to its simplicity and high efficiency, as compared to conventional coaxial J×B plasma sources, the IPS looks promising for a variety of applications that require a multi-pulse mode of operation, such as: intense plasma and ion beams [15th International Conference on High-Power Particle Beams, St. Petersburg, Russia, July 2004]; high current pulsed Hall accelerators [Plasma Phys. Rep. 29 (2003) 261]; spacecraft propulsion [AIP Conf. Proc. 608 (2002) 627] and the formation of field-reversed configurations by colliding current carrying plasma tori in magnetic fusion devices [Nucl. Fusion 39 (1999) 2001]. Design, projected parameters and initial test results for several modifications of the IPS, including characteristics of the generated plasma flows, are given. The density and temperature ranged between 10 12 and 10 15 cm -3 and 2 and 10 eV, respectively. Plasma transport velocities were measured between (1-5)×10 6 cm/s. The multi-pulse mode produced a train of pulses with frequencies up to 10 kHz for several milliseconds at power levels of (1-2)×10 7 W and several joules of deposited energy per pulse. The potential and limitations of double and multi-pulse modes of the IPS are also discussed.

  12. 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.

  13. 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.

  14. 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.

  15. High temperature, high density opacity measurements using short pulse lasers

    NASA Astrophysics Data System (ADS)

    Hoarty, D. J.; James, S. F.; Brown, C. R. D.; Williams, B. M.; Guymer, T.; Hill, M.; Morton, J.; Chapman, D.; Shepherd, R.; Dunn, J.; Brown, G.; Schneider, M.; Beiersdorfer, P.; Chung, H. K.; Harris, J. W. O.; Upcraft, L.; Smith, C. C.; Lee, R. W.

    2010-08-01

    Heating of thin foil targets by a high power laser at intensities of 1017 -1019W/cm2 has been studied as a method for producing high temperature, high density samples to investigate X-ray opacity and equation of state. The targets were plastic (parylene N) foils with a buried microdot of a sample material, which was either aluminium, germanium or a mixture of germanium and titanium mixture of germanium and titanium. L-shell and K-shell spectra were taken using crystal spectrometers recording onto film and an ultrafast X-ray streak camera coupled to a conical focussing crystal with a time resolution of 1ps. The conditions in the microdot were inferred by comparing the measured spectra to synthetic spectra produced by the time-dependent collisional-radiative (CR) models FLY and FLYCHK. The data were also compared to simulated spectra from a number of opacity codes assuming local thermodynamic equilibrium (LTE). Temperature and density gradients were taken into account in the comparisons. The sample conditions, inferred from the CR modelling using FLYCHK, were 800±100eV and 1.5±0.5g/cc, in the germanium/titanium samples and 600+50/-150eV, 3-4g/cc in the pure germanium or aluminium samples. The higher densities were achieved by using a combination of long and short pulses to compress and heat the foils respectively. The experimental results and comparisons to predicted spectra are presented and discussed.

  16. 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.

  17. Magnetization in ruby induced by a short laser pulse

    SciTech Connect

    Usmanov, R.G.; Khaimovich, E.P.

    1995-09-01

    Specific features of formation of nonequilibrium magnetization in ruby crystal excited by a laser pulse are experimentally studied. It is shown theoretically that the circularly polarized light pulse induces orientation of the medium and its magnetization. Changes of the magnetization direction induced by an external magnetic field are analyzed. 11 refs., 3 figs.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Short-pulse laser amplification and saturation using stimulated Raman scattering

    NASA Astrophysics Data System (ADS)

    Dodd, E. S.; Ren, J.; Kwan, T. J. T.; Schmitt, M. J.; Lundquist, P. B.; Sarkisyan, S.; Nelson-Melby, E.

    2010-11-01

    Recent theoretical and experimental work has focused on using backward-stimulated Raman scattering (BSRS) in plasmas as a means of laser pulse amplification and compression [1,2,3]. We present initial computational and experimental work on SRS amplification in a capillary-discharge generated Xe plasma. The experimental set-up uses a 200 ps pump pulse with an 800 nm wavelength seeded by a 100 fs pulse from a broadband source and counter-propagates the pulses through a plasma of length 1 cm and diameter 0.1 cm. Results from initial experiments characterizing the plasma and on short-pulse amplification will be presented. Additionally, we present results from calculations using pF3d [4], and discuss the role of SRS saturation and determine the possible significance of electron trapping with a model implemented in pF3d [5]. [1] G. Shvets, N. J. Fisch, A. Pukhov, and J. Meyer-ter-Vehn, Phys. Rev. Lett. 81 4879 (1998). [2] V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. 82 4448 (1999). [3] R. K. Kirkwood, E. Dewald, and C. Niemann, et al., Phys. Plasmas 14 113109 (2007). [4] R. L. Berger, B. F. Lasinski, T. B. Kaiser, et al., Phys. Fluids B 5 2243 (1993). [5] H. X. Vu, D. F. DuBois, and B. Bezzerides, Phys. Plasmas 14 012702 (2007). Supported by US DOE and LANS, LLC under contract DE-AC52-06NA25396. LA-UR-10-04787

  4. 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.

  5. 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.

  6. 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).

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Surface Characterization and Short-term Adhesion to Zirconia after Ultra-short Pulsed Laser Irradiation.

    PubMed

    Esteves-Oliveira, Marcella; Jansen, Patrick; Wehner, Martin; Dohrn, Andreas; Bello-Silva, Marina Stella; Eduardo, Carlos de Paula; Meyer-Lueckel, Hendrik

    To evaluate the suitability of an ultra-short pulsed laser (USPL) to treat zirconia ceramic surfaces and increase their adhesion to dual-curing resin cement. Twenty 10 × 10 × 5 mm³ blocks were prepared from a zirconia ceramic (Y-TZP). The specimens were polished and randomly assigned to four groups (n = 5) which received the following surface treatments: sandblasting (SB) with Al₂O₃ particles and silica coating (SC) with SiO₂ particles as positive controls; two groups received USPL irradiation, one with 10 scan repetitions (L10) and the other with 20 (L20). Laser irradiation was performed at 1030 nm, 2.3 J/cm², 6 ps pulse duration. The ceramic blocks were duplicated in composite resin and cemented with a dual-curing resin cement. Half of the blocks were then stored in water (37°C) for 24 h and the other half for 1 month. At each time, 40 to 60 sticks per group were subjected to microtensile bond strength testing. Data were analyzed statistically using the Kruskal-Wallis test (α = 0.05). Laser-treated zirconia presented statistically significantly higher roughness than did SB and SC. After 24 h, the highest bond strength means (MPa) were achieved by L10 (42.3 ± 10.8) and L20 (37.9 ± 14.4), and both of them were statistically significantly higher than SB (22.0 ± 5.3) and SC (20.8 ± 7.1) (p < 0.05). After 1 month of storage, L10- and L20-treated zirconia still showed significantly higher bond strengths than did SB- and SC-treated zirconia (p < 0.05). USPL irradiation significantly increases bond strength of zirconia ceramic to dual-curing resin cement and might be an alternative for improving adhesion to this material.

  12. 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.

  13. 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.

  14. 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)

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Comparison of the 585 nm pulse dye laser and the short pulsed CO2 laser in the treatment of striae distensae in skin types IV and VI.

    PubMed

    Nouri, K; Romagosa, R; Chartier, T; Bowes, L; Spencer, J M

    1999-05-01

    Striae distensae, or stretch marks, are a very common cosmetic problem. The successful management of stretch marks has long been a source of frustration and curiosity for both the clinician and the researcher. Recent studies suggest lasers may have a role in their management. As yet, no study has reported on the effects of either of these lasers in the treatment of stretch marks on persons with skin types 4 to 6. To assess the efficacy of short pulsed CO2 laser and pulsed dye laser for the treatment of stretch marks in skin types 4, 5, and 6. Four patients were initially enrolled in the study. All were female with abdominal stretch marks, present for a range of 8 to 19 years. The patients had skin types ranging from 4 to 6. The test area consisted of a stretch mark long enough to be divided into three contiguous 2 cm sections, labeled A, B, and C. Section A served as the short pulsed CO2 test site, section B served as a control, while section C served as the 585 nm pulsed dye site. Patients were seen for evaluation after 1 week, then every 4 weeks for a total of 20 weeks. Patients were evaluated subjectively by the investigators, and the patients' own self-evaluation was reported as well. Following the 585 nm pulse dye laser, at 20 week follow-up patients with type 4 skin showed no improvement, while type 6 skin showed hyperpigmentation. The short pulsed CO2 test site showed persistent erythema in type 4 skin and marked hyperpigmentation in type 6 skin. For patients with types 4, 5, and 6 skin, laser treatment of striae should be avoided or used with great caution.

  20. 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.

  1. A subnanosecond pulsed ion source for micrometer focused ion beams.

    PubMed

    Höhr, C; Fischer, D; Moshammer, R; Dorn, A; Ullrich, J

    2008-05-01

    A new, compact design of an ion source delivers nanosecond pulsed ion beams with low emittance, which can be focused to micrometer size. By using a high-power, 25 fs laser pulse focused into a gas region of 10(-6) mbar, ions at very low temperatures are produced in the small laser focal volume of 5 mum diameter by 20 mum length through multiphoton ionization. These ions are created in a cold environment, not in a hot plasma, and, since the ionization process itself does not significantly heat them, have as a result essentially room temperature. The generated ion pulse, up to several thousand ions per pulse, is extracted from the source volume with ion optical elements that have been carefully designed by simulation calculations. Externally triggered, its subnanosecond duration and even smaller time jitter allow it to be superimposed with other pulsed particle or laser beams. It therefore can be combined with any type of collision experiment where the size and the time structure of the projectile beam crucially affect the achievable experimental resolution.

  2. 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

  3. 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.

  4. Circular Dichroism in Laser-Assisted Short-Pulse Photoionization

    SciTech Connect

    Kazansky, A. K.; Grigorieva, A. V.; Kabachnik, N. M.

    2011-12-16

    A remarkable effect of circular dichroism, i.e., a difference in photoelectron spectra produced by right and left circularly polarized light in two-color multiphoton ionization of atoms, is predicted for the case when the atom is ionized by an extreme ultraviolet or x-ray femtosecond pulse in the field of a strong infrared laser pulse, both pulses being circularly polarized. We show that the sidebands formed in the spectra exhibit different circular dichroism often of different signs both in angle-resolved and angle-integrated experimental conditions. The effect can be used for detecting and measuring circular polarization of x rays in a spectral range where other methods are not effective.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Consideration of dynamic photothermal effect for evaluation of scanning light sources in optical devices using pulsed source criteria.

    PubMed

    Kim, Do-Hyun

    2014-04-01

    Quantitative evaluation of the potential radiation hazards of scanning light sources in medical optical devices is critical. Currently, point scanning light sources of continuous radiation are treated as pulsed sources, where the dwell time at each point is equal to the pulse duration. This study compares the photothermal effects from scanning light and pulsed sources using numerical calculation for scanning without restricting aperture and with various spot sizes. The calculation results show that the thermal damage threshold of scanning source not restricted by measurement aperture does not significantly differ from that of pulsed source. Temporal temperature response and size-dependent photothermal effect also confirm the similarity between scanning and pulsed sources.

  10. 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.

  11. 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.

  12. High power radiators of ultra-short electromagnetic quasi-unipolar pulses

    NASA Astrophysics Data System (ADS)

    Fedorov, V. M.; Ostashev, V. E.; Tarakanov, V. P.; Ul'yanov, A. V.

    2017-05-01

    Results of creation, operation, and diagnostics of the high power radiators for ultra-short length electromagnetic pulses (USEMPs) with a quasi-unipolar profile, which have been developed in our laboratory, are presented. The radiating module contains: the ultra-wideband (UWB) antenna array, the exciting high voltage pulse semiconductor generator (a pulser), the power source and the control unit. The principles of antenna array with a high efficiency aperture about 0.9 were developed using joint four TEM-horns with shielding electrodes in every TEM-horn. Sizes of the antenna apertures were (16-60) cm. The pulsers produced by “FID Technology” company had the following parameters: 50 Ohm connector impedance, unipolar pulses voltages (10-100) kV, the rise-time (0.04-0.15) ns, and the width (0.2-1) ns. The modules radiate the USEMPs of (0.1-10) GHz spectrum, their repetition rate is (1-100) kHz, and the effective potential is E*R = (20-400) kV, producing the peak E-field into the far-zone of R-distance. Parameters of the USEMP waves were measured by a calibrated sensor with the following characteristics: the sensitivity 0.32V/(kV/m), the rise-time 0.03 ns, the duration up to 7 ns. The measurements were in agreement with the simulation results, which were obtained using the 3-D code “KARAT”. The USEMP waves with amplitudes (1-10) kV/m and the pulse repetition rate (0.5-100) kHz were successfully used to examine various electronic devices for an electromagnetic immunity.

  13. 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.

  14. 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.

  15. 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.

  16. Short-pulse amplification by strongly coupled stimulated Brillouin scattering

    SciTech Connect

    Edwards, Matthew R. Mikhailova, Julia M.; Jia, Qing; Fisch, Nathaniel J.

    2016-08-15

    We examine the feasibility of strongly coupled stimulated Brillouin scattering as a mechanism for the plasma-based amplification of sub-picosecond pulses. In particular, we use fluid theory and particle-in-cell simulations to compare the relative advantages of Raman and Brillouin amplification over a broad range of achievable parameters.

  17. 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.

  18. 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.

  19. 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.

  20. Identification of vibration sources in pulse tube cryogenic refrigerator

    NASA Astrophysics Data System (ADS)

    Riabzev, S. V.; Veprik, A. M.; Vilenchik, H. S.; Pundak, N.

    2007-04-01

    As is known, a cold finger of a pulse tube cryogenic refrigerator does not contain moving mechanical components and, therefore, is traditionally thought of as producing low vibration and having extended lifespan. Because of these outstanding features, such cryogenic engines are especially attractive for use in a variety of vibration-sensitive instrumentation, such as infra-red imagers, scanning electron microscopes (SEM), superconductive quantum interference devices (SQUID), etc. However, even relatively low-level vibration produced by a cold tip of a pulse tube, resulting from oscillation of a gas pressure along with a vibration transmitted from a compressor through a metallic gas transfer tube, may sometimes appear to be excessive for the above vibration-sensitive applications. By making an extensive use of the finite element analysis supported by the full-scale experimentation, the authors are attempting to identify the sources of vibration occurring in a cold tip of a pulse tube.

  1. 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.

  2. 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

  3. Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

    PubMed

    Wang, Zhenzhen; Deguchi, Yoshihiro; Liu, Renwei; Ikutomo, Akihiro; Zhang, Zhenzhen; Chong, Daotong; Yan, Junjie; Liu, Jiping; Shiou, Fang-Jung

    2017-09-01

    Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

  4. 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.

  5. 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.

  6. 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.

  7. A high-current pulsed cathodic vacuum arc plasma source

    NASA Astrophysics Data System (ADS)

    Oates, T. W. H.; Pigott, J.; Mckenzie, D. R.; Bilek, M. M. M.

    2003-11-01

    Cathodic vacuum arcs (CVAs) are well established as a method for producing metal plasmas for thin film deposition and as a source of metal ions. Fundamental differences exist between direct current (dc) and pulsed CVAs. We present here results of our investigations into the design and construction of a high-current center-triggered pulsed CVA. Power supply design based on electrolytic capacitors is discussed and optimized based on obtaining the most effective utilization of the cathode material. Anode configuration is also discussed with respect to the optimization of the electron collection capability. Type I and II cathode spots are observed and discussed with respect to cathode surface contamination. An unfiltered deposition rate of 1.7 nm per pulse, at a distance of 100 mm from the source, has been demonstrated. Instantaneous plasma densities in excess of 1×1019 m-3 are observed after magnetic filtering. Time averaged densities an order of magnitude greater than common dc arc densities have been demonstrated, limited by pulse repetition rate and filter efficiency.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Dynamic properties of a pulse-pumped fiber laser with a short, high-gain cavity

    NASA Astrophysics Data System (ADS)

    Yang, Chaolin; Guo, Junhong; Wei, Pu; Wan, Hongdan; Xu, Ji; Wang, Jin

    2016-09-01

    We demonstrate a pulsed high-gain all-fiber laser without intracavity modulators, where a short and heavily Erbium-doped fiber is used as the gain medium in a ring cavity. By pulsed-pumping this short high gain cavity and tuning an intracavity variable optical coupler, the laser generates optical pulses with a pulse-width of μs at a repetition rate in the order of kHz down to one-shot operation. Furthermore, dynamic properties of this laser are investigated theoretically based on a traveling-wave-model, in which an adaptive-discrete-grid-finite-difference-method is applied. The simulation results validate the experimental results. The demonstrated pulsed laser is compact, flexible and cost-effective, which will have great potential for applications in all-optical sensing and communication systems.

  17. 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.

  18. 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.

  19. Absolute beam intensity measurements at the Intense Pulsed Neutron Source

    SciTech Connect

    Iverson, Erik B.; Carpenter, J. M.; Hill, E. J.

    1997-01-01

    The three moderators at the Intense Pulsed Neutron Source are of cryogenic methane (CH4): one of liquid methane at 100 K, and two of solid methane at 30 K. These moderators produce intense beams of both cold and thermal neutrons. The moderators are each of a different physical configuration in order to tailor their performance for the fourteen instruments and test facilities that operate on the twelve neutron beams. IPNS has started a program to enhance the effectiveness of its target/moderator/reflector system. This program involves both Monte Carlo computer modeling of the system and measuring the characteristics of the neutron beams. The measurements reported here provide absolute spectra using foil activation techniques joined with time-of-flight measurements performed with thin beam monitor detectors installed at the neutron scattering instruments. We also outline a codified procedure which we believe will be useful at other pulsed neutron sources to perform equivalent measurements. (auth)

  20. Characteristics of the WNR: a pulsed spallation neutron source

    SciTech Connect

    Russell, G.J.; Lisowski, P.W.; Howe, S.D.; King, N.S.P.; Meier, M.M.

    1982-01-01

    The Weapons Neutron Research facility (WNR) is a pulsed spallation neutron source in operation at the Los Alamos National Laboratory. The WNR uses part of the 800-MeV proton beam from the Clinton P. Anderson Meson Physics Facility accelerator. By choosing different target and moderator configurations and varying the proton pulse structure, the WNR can provide a white neutron source spanning the energy range from a few MeV to 800 MeV. The neutron spectrum from a bare target has been measured and is compared with predictions using an Intranuclear Cascade model coupled to a Monte Carlo transport code. Calculations and measurements of the neutronics of WNR target-moderator assemblies are presented.

  1. Probing Pulsar Emission on Short Timescales: Rotating Radio Transients, Cyclic Spectroscopy, and Single-Pulse Studies of Millisecond Pulsars

    NASA Astrophysics Data System (ADS)

    Palliyaguru, Nipuni Tharaka

    Rotating radio transients (RRATs) are neutron stars are that characterized by the emission of strong sporadic bursts. We have analysed the long- and short-term time dependence of the pulse arrival times and the pulse detection rates for eight RRAT sources from the Parkes Multi-beam Pulsar Survey (PMPS). We find significant periodicities in the individual pulse arrival times from six RRATs. These periodicities range from ˜30 minutes to 2100 days and from one to 16 independent (i.e. non-harmonically related) periodicities are detected for each RRAT. In addition, we find that pulse emission is a random process on short (hour-long) time scales but that most of the objects exhibit longer term (months-years) non-random behaviour. We find that PSRs J1819--1458 and J1317--5759 emit more doublets (two consecutive pulses) and triplets (three consecutive pulses) than is expected in random pulse distributions. No evidence for such an excess is found for the other RRATs. There are several different models for RRAT emission depending on both extrinsic and intrinsic factors which are consistent with these properties. Light travel time changes due to gravitational waves may be detected within the next decade through precision timing of an array of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups routinely correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a phase change in the signal that results in pulse broadening and arrival time delays. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover pulse broadening functions (PBFs), such as those that would be introduced

  2. Approaches to instrument design at pulsed neutron sources

    SciTech Connect

    Crawford, R.K.

    1997-04-14

    A number of tools are used in the design of scattering instruments for pulsed neutron sources. Initial design is based largely on simple analytical calculations. More complicated analytical calculations and Monte Carlo simulations come into play as the design is optimized to maximize the data rate and to improve the data quality. Examples are used to illustrate the relative roles of these different computational tools. Areas are also identified where appropriate computational tools are currently lacking.

  3. Absorption of the S-polarized short laser pulse in underdense plasma by considering the electrons ohmic heating and the laser pulse ponderomotive force effects

    NASA Astrophysics Data System (ADS)

    Panahi, Naser; Ettehadi-Abari, Mehdi; Hosseinnejad, Mohammad-Taghi

    2017-03-01

    With the advent of ultrashort high intensity laser pulses, laser absorption during laser-plasma interactions has received significant attention during the past two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Although some absorption mechanisms appear for short laser pulses with nanosecond duration time, they usually appear for some nonlinear phenomena as electron ohmic heating and laser pulse ponderomotive force are not considered. In this paper, the absorption of the S-polarized laser pulse through an interaction with an underdense plasma in attendance of electron ohmic heating and ponderomotive nonlinearities is analyzed. It is shown that, due to the effect of the ponderomotive force in both isothermal and non-isothermal plasmas, the increasing laser radiation angle leads to the increasing electric field wavelength. Also, since the ponderomotive force modifies the electron density and temperature distribution, it is shown that the decreasing radiation angle leads to the steepening of the electron density profile and the narrowing of electron bunching. Furthermore, by increasing the radiation angle, the absorption coefficient is decreased strongly. It is found that due to the heat of the plasma at the expanse of the wave energy in the case of a non-thermal plasma, the absorption coefficient is increased intensively in comparison to a collisional plasma.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Ultra-short pulse laser micro patterning with highest throughput by utilization of a novel multi-beam processing head

    NASA Astrophysics Data System (ADS)

    Homburg, Oliver; Jarczynski, Manfred; Mitra, Thomas; Brüning, Stephan

    2017-02-01

    In the last decade much improvement has been achieved for ultra-short pulse lasers with high repetition rates. This laser technology has vastly matured so that it entered a manifold of industrial applications recently compared to mainly scientific use in the past. Compared to ns-pulse ablation ultra-short pulses in the ps- or even fs regime lead to still colder ablation and further reduced heat-affected zones. This is crucial for micro patterning when structure sizes are getting smaller and requirements are getting stronger at the same time. An additional advantage of ultra-fast processing is its applicability to a large variety of materials, e.g. metals and several high bandgap materials like glass and ceramics. One challenge for ultra-fast micro machining is throughput. The operational capacity of these processes can be maximized by increasing the scan rate or the number of beams - parallel processing. This contribution focuses on process parallelism of ultra-short pulsed lasers with high repetition rate and individually addressable acousto-optical beam modulation. The core of the multi-beam generation is a smooth diffractive beam splitter component with high uniform spots and negligible loss, and a prismatic array compressor to match beam size and pitch. The optical design and the practical realization of an 8 beam processing head in combination with a high average power single mode ultra-short pulsed laser source are presented as well as the currently on-going and promising laboratory research and micro machining results. Finally, an outlook of scaling the processing head to several tens of beams is given.

  12. 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.

  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. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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).

  1. Pulsed Counter-Rotating Source of Slow, Cold Molecules

    NASA Astrophysics Data System (ADS)

    Lyuksyutov, Igor; Sheffield, Les; Hickey, Mark; Krasovitskiy, Vitaliy; Rathnayaka, Daya; Herschbach, Dudley

    2011-03-01

    We describe the performance of a new design of the counter-rotating source (CRS) of slow molecules introduced originally by Gupta and Herschbach. The CRS produces a supersonic expansion from a nozzle near the tip of a hollow rotor spun at high speed contrary to the exit beam velocity. Thereby the lab velocity can be markedly reduced. Introducing a pulsed feeding system, cryo-cooling, and shutter system has eliminated the main problem of the original CRS apparatus, in which continuous gas flow imposed high background pressure. The new version provides intense pulses, typically of duration 0.1 ms with lab speeds as low as 40 m/s and longitudinal temperature as low as 0.5 K. This device can, in principle, decelerate (or accelerate) any molecule available as a gas; we report experiments producing slow beams of krypton, oxygen, ammonia, and nitrogen dioxide.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Reduced Maxwell-Duffing description of extremely short pulses in nonresonant media.

    PubMed

    Kazantseva, Elena V; Maimistov, Andrei I; Caputo, Jean-Guy

    2005-05-01

    The propagation of extremely short pulses of an electromagnetic field (electromagnetic spikes) is considered in the framework of a model wherein the material medium is represented by anharmonic oscillators with cubic nonlinearities (Duffing model) and waves can propagate only in the right direction. The system of reduced Maxwell-Duffing equations admits two families of exact analytical solutions in the form of solitary waves. These are bright spikes propagating on a zero background, and bright and dark spikes propagating on a nonzero background. We find that these steady-state pulses are stable in terms of boundedness of the Hamiltonian. Direct simulations demonstrate that these pulses are very robust against perturbations. We find that a high-frequency modulated electromagnetic pulse evolves into a breather-like one. Conversely, a low frequency pulse transforms into a quasiharmonic wave.

  8. 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.

  9. 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.

  10. 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.

  11. Comparison between pulsed MIG and short-circuit MAG on economical aspects for structural building

    SciTech Connect

    Scotti, A.; Pereira, W.A.

    1996-12-01

    In this work is presented a comparison between Pulsed MIG and Short-circuit MAG processes concerning economical and operational aspects. A systematic experimental procedure was carried-out so that the response to variation of travel speed, mean current and contact tip-to-work distance could be assessed within the same range. The operational envelopes were built taking into account lack of fusion and lack of penetration. Deposition rate and deposition efficiency were raised to evaluate productivity. The results showed that short-circuit MAG has a broader operational envelop than Pulsed MIG, but the latter, despite the narrower range, provides more productivity.

  12. 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.

  13. Measurement of lake ice thickness with a short-pulse radar system

    NASA Technical Reports Server (NTRS)

    Cooper, D. W.; Mueller, R. A.; Schertler, R. J.

    1976-01-01

    Measurements of lake ice thickness were made during March 1975 at the Straits of Mackinac by using a short-pulse radar system aboard an all-terrain vehicle. These measurements were compared with ice thicknesses determined with an auger. Over 25 sites were explored which had ice thicknesses in the range 29 to 60 cm. The maximum difference between radar and auger measurements was less than 9.8 percent. The magnitude of the error was less than + or - 3.5 cm. The NASA operating short-pulse radar system used in monitoring lake ice thickness from an aircraft is also described.

  14. Short optical pulse generated by integrated MQW DBR laser/EA-modulator

    NASA Astrophysics Data System (ADS)

    Chen, Young-Kai; Tanbun-Ek, Tawee; Logan, Ralph A.; Tate, A. R.; Sergent, A. M.; Wecht, K. W.; Sciortino, Paul F., Jr.; Raybon, Gregory; Froberg, Nan M.; Johnson, Anthony M.

    1994-05-01

    We report on the generation of short optical pulses by utilizing the non-linear absorption characteristics of a multiple quantum well (MQW) electro-absorption modulator, which is monolithically integrated with a MQW wavelength-tunable distributed Bragg reflector (DBR) laser on a single chip. Optical pulses as short as 39 ps and 15 ps have been generated at a repetition rate of 3 GHz and 10 GHz, respectively, with a broad tuning range of 5.4 nm near 1554 nm lasing wavelength.

  15. A Simple Picaxe Microcontroller Pulse Source for Juxtacellular Neuronal Labelling.

    PubMed

    Verberne, Anthony J M

    2016-10-19

    Juxtacellular neuronal labelling is a method which allows neurophysiologists to fill physiologically-identified neurons with small positively-charged marker molecules. Labelled neurons are identified by histochemical processing of brain sections along with immunohistochemical identification of neuropeptides, neurotransmitters, neurotransmitter transporters or biosynthetic enzymes. A microcontroller-based pulser circuit and associated BASIC software script is described for incorporation into the design of a commercially-available intracellular electrometer for use in juxtacellular neuronal labelling. Printed circuit board construction has been used for reliability and reproducibility. The current design obviates the need for a separate digital pulse source and simplifies the juxtacellular neuronal labelling procedure.

  16. 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.

  17. Pulsed rotating supersonic source for merged molecular beams

    NASA Astrophysics Data System (ADS)

    Sheffield, L.; Hickey, M. S.; Krasovitskiy, V.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Herschbach, D. R.

    2012-06-01

    We describe a pulsed rotating supersonic beam source, evolved from an ancestral device [M. Gupta and D. Herschbach, J. Phys. Chem. A 105, 1626 (2001)]. The beam emerges from a nozzle near the tip of a hollow rotor which can be spun at high-speed to shift the molecular velocity distribution downward or upward over a wide range. Here we consider mostly the slowing mode. Introducing a pulsed gas inlet system, cryocooling, and a shutter gate eliminated the main handicap of the original device in which continuous gas flow imposed high background pressure. The new version provides intense pulses, of duration 0.1-0.6 ms (depending on rotor speed) and containing ˜1012 molecules at lab speeds as low as 35 m/s and ˜1015 molecules at 400 m/s. Beams of any molecule available as a gas can be slowed (or speeded); e.g., we have produced slow and fast beams of rare gases, O2, Cl2, NO2, NH3, and SF6. For collision experiments, the ability to scan the beam speed by merely adjusting the rotor is especially advantageous when using two merged beams. By closely matching the beam speeds, very low relative collision energies can be attained without making either beam very slow.

  18. Pulsed rotating supersonic source for merged molecular beams

    NASA Astrophysics Data System (ADS)

    Sheffield, Les; Hickey, Mark; Krasovitskiy, Vitaliy; Rathnayaka, Daya; Lyuksyutov, Igor; Herschbach, Dudley

    2012-10-01

    We continue the characterization of a pulsed rotating supersonic beam source. The original device was described by M. Gupta and D. Herschbach, J. Phys. Chem. A 105, 1626 (2001). The beam emerges from a nozzle near the tip of a hollow rotor which can be spun at high-speed to shift the molecular velocity distribution downward or upward over a wide range. Here we consider mostly the slowing mode. Introducing a pulsed gas inlet system, and a shutter gate eliminate the main handicap of the original device in which continuous gas flow imposed high background pressure. The new version provides intense pulses, of duration 0.1--0.6 ms (depending on rotor speed) and containing ˜10^12 molecules at lab speeds as low as 35 m/s and ˜10^15 molecules at 400 m/s. Beams of any molecule available as a gas can be slowed (or speeded); e.g., we have produced slow and fast beams of rare gases, O2, NO2, NH3, and SF6. For collision experiments, the ability to scan the beam speed by merely adjusting the rotor is especially advantageous when using two merged beams. By closely matching the beam speeds, very low relative collision energies can be attained without making either beam very slow.

  19. 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.

  20. Successful localization of the Broca area with short-train pulses instead of 'Penfield' stimulation.

    PubMed

    Axelson, Hans W; Hesselager, Göran; Flink, Roland

    2009-06-01

    Direct electrical stimulation of functional cortical areas is a standard procedure in epilepsy and glioma surgery. Many previous studies support that stimulation of the motor cortex with short-train pulses is a less epileptogenic alternative to the 50-60Hz 'Penfield' technique. However, whether the short-train stimulation is useful also in mapping of speech areas is unclear. In this case report we present a patient with oligodendroglioma near the Broca area. Extraoperative electrical stimulation via a subdural grid electrode was primarily performed to locate the speech area. The cortex was stimulated with short-train pulses (5 pulses, 0.5 pulse duration and 3ms interpulse interval) in addition to 1-3s 50Hz stimulation. The patient had speech arrest from both types of stimulation techniques during a naming task. It was however critical that the short (14.5ms) train stimulation was synchronized with the presentation of the naming objects. If not, there was no speech arrest. Despite this possible pitfall, this case has encouraged us to further try short-train stimulation in attempts to reduce stimulus-triggered seizures during mapping of eloquent areas.

  1. 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

  2. Fiber Laser Front Ends for High-Energy Short Pulse Lasers

    SciTech Connect

    Dawson, J W; Liao, Z M; Mitchell, S; Messerly, M; Beach, R; Jovanovic, I; Brown, C; Payne, S A; Barty, C J

    2005-01-18

    We are developing an all fiber laser system optimized for providing input pulses for short pulse (1-10ps), high energy ({approx}1kJ) glass laser systems. Fiber lasers are ideal solutions for these systems as they are highly reliable and once constructed they can be operated with ease. Furthermore, they offer an additional benefit of significantly reduced footprint. In most labs containing equivalent bulk laser systems, the system occupies two 4'x8' tables and would consist of 10's if not a 100 of optics which would need to be individually aligned and maintained. The design requirements for this application are very different those commonly seen in fiber lasers. High energy lasers often have low repetition rates (as low as one pulse every few hours) and thus high average power and efficiency are of little practical value. What is of high value is pulse energy, high signal to noise ratio (expressed as pre-pulse contrast), good beam quality, consistent output parameters and timing. Our system focuses on maximizing these parameters sometimes at the expense of efficient operation or average power. Our prototype system consists of a mode-locked fiber laser, a compressed pulse fiber amplifier, a ''pulse cleaner'', a chirped fiber Bragg grating, pulse selectors, a transport fiber system and a large flattened mode fiber amplifier. In our talk we will review the system in detail and present theoretical and experimental studies of critical components. We will also present experimental results from the integrated system.

  3. High speed ultra short pulse fiber ring laser using photonic crystal fiber nonlinear optical loop mirror

    NASA Astrophysics Data System (ADS)

    Ma, Shaozhen; Li, Wenbo; Hu, Hongyu; Dutta, Niloy K.

    2012-06-01

    A scheme to generate high speed optical pulse train with ultra short pulse width is proposed and experimentally studied. Two-step compression is used in the scheme: 20 GHz and 40 GHz pulse trains generated from a rational harmonic actively mode-locked fiber ring laser is compressed to a full width at half-maximum (FWHM) of ~ 1.5 ps using adiabatic soliton compression with dispersion shifted fibers (DSF). The pulse trains then undergo a pedestal removal process by transmission through a cascaded two photonic crystal fiber (PCF)-nonlinear optical loop mirrors (NOLM) realized using a double-ring structure. The shortest output pulse width obtained was ~ 610 fs for 20 GHz pulse train and ~ 570 fs for 40 GHz pulse train. The signal to noise ratio of the RF spectrum of the output pulse train is larger than 30 dB. Theoretical simulation of the NOLM transmission is conducted using split-step Fourier method. The results show that two cascaded NOLMs can improve the compression result compared to that for a single NOLM transmission.

  4. High-pressure dielectric barrier discharge Xenon lamps generating short pulses of high-peak-power VUV radiation (172nm) with high pulse-to-pulse reproducibility.

    NASA Astrophysics Data System (ADS)

    Carman, Robert; Ward, Barry; Mildren, Richard; Kane, Deborah

    2003-10-01

    Dielectric barrier discharges (DBDs) are used to efficiently generate radiation in the ultraviolet and vacuum-ultraviolet spectral regions (88nm-350nm) by forming rare-gas and rare-gas halide excimers in a transient plasma. Usually, DBD lamps generate the light output quasi-continuously or in bursts with a high degree of stochastic or random variability in the instantaneous UV/VUV intensity. However, regular pulses of high-peak-power UV/VUV, with high pulse-to-pulse reproducibility, are of interest for applications in biology, surface treatment and cleaning, and time-resolved fluorescence spectroscopy. Such pulses can be generated from spatially homogeneous plasmas in a Xe DBD when the discharge is driven by uni-polar voltage pulses of short duration ( 100ns)^1. In the present study, we will report Xe DBD lamp performance and VUV output pulse characteristics for gas pressures up to 2.5bar and excitation conditions tailored for high-peak-power output. The experimental results will be compared to theoretical results from a detailed 1-D computer model of the spatio-temporal evolution of the plasma kinetics and Xe species population densities. ^1R.P.Mildren and R.J.Carman, J.Phys.D, 34, L1-L6, (2001)

  5. Beam intensity increases at the intense pulsed neutron source accelerator

    SciTech Connect

    Potts, C.; Brumwell, F.; Norem, J.; Rauchas, A.; Stipp, V.; Volk, G.

    1985-01-01

    The Intense Pulsed Neutron Source (IPNS) accelerator system has managed a 40% increase in time average beam current over the last two years. Currents of up to 15.6..mu..A (3.25 x 10/sup 12/ protons at 30 Hz) have been successfully accelerated and cleanly extracted. Our high current operation demands low loss beam handling to permit hands-on maintenance. Synchrotron beam handling efficiencies of 90% are routine. A new H/sup -/ ion source which was installed in March of 1983 offered the opportunity to get above 8 ..mu..A but an instability caused unacceptable losses when attempting to operate at 10 ..mu..A and above. Simple techniques to control the instabilities were introduced and have worked well. These techniques are discussed below. Other improvements in the regulation of various power supplies have provided greatly improved low energy orbit stability and contributed substantially to the increased beam current.

  6. 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.

  7. 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.

  8. Electron dynamics from low-order harmonics generated by short laser pulses

    NASA Astrophysics Data System (ADS)

    Xiong, Wei-Hao; Gong, Qihuang; Peng, Liang-You

    2017-08-01

    Recently, low-order harmonics have gained much attention due to their applications as coherent light sources with a high repetition rate. In addition, the generation process is highly related to the bound electrons and can thus be applied to detect the dynamics of these electrons. In this work, we theoretically investigate the low-order harmonics below the first excited state, produced by a single-cycle optical pulse. We numerically solve the three-dimensional time-dependent Schrödinger equation (TDSE) to calculate the harmonic spectrum. With the help of a perturbation model, we can transparently understand the generation process of the spectrum. The results indicate that the harmonic spectrum can be sensitively influenced by the frequency component of the driving field. We find that the carrier envelope phase (CEP) dependence of low-order-harmonic generation originates from the interference of different harmonic orders. For these harmonics, the CEP effects can only be observed when the spectrum of the driving laser is extremely wide, which corresponds to the very short driving pulse. From the CEP-dependent interference structure, the phase relation of the third and the fifth harmonic can be extracted. The extracted information indicates that the atomic response induces a positive chirp for the emitted low-order harmonics. In addition, we investigated the harmonic phase calculated from the TDSE results. The harmonic phase is different from the phase predicted by the adiabatic model, and this phase difference can be related to the time delay of the electronic response. We extract the time delay from the harmonic phase and explore the CEP and intensity dependence of this time delay.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Frequency Conversion of Short Optical Pulses in Negatively Spatially Dispersive Metamaterials

    DTIC Science & Technology

    2015-10-22

    Short Optical Pulses inNegatively Spatially Dispersive Metamaterials We show that particular spatial distributions of nanoscopic plasmonic building...distributions of nanoscopic plasmonic building blocks in metamaterials may enable extraordinary nonlinear-optical frequency-shifted reflectivity and...particular spatial distributions of nanoscopic plasmonic building blocks in metamaterials may enable extraordinary nonlinear-optical frequency-shifted

  16. 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.

  17. Short energetic electron bunches from laser wakefield accelerator with orthogonally polarized perpendicularly crossed laser pulses

    NASA Astrophysics Data System (ADS)

    Horný, Vojtěch; Petržílka, Václav; Klimo, Ondřej; Krůs, Miroslav

    2017-05-01

    Electron acceleration with optical injection by a perpendicularly propagating and orthogonally polarized low intensity laser pulse into a nonlinear plasma wave driven by a short intense laser pulse was explored by particle- in-cell simulations. The scheme presented here provides an energetic electron bunch in the first ion cavity with a low energy spread. The electron bunch short and compact, with the mean energy about 400 MeV and a low energy spread about 10 MeV in time of 6 ps of acceleration. The injected charge is several tens of pC for the low intensity of the injection pulse. Initial positions of electrons forming the energetic bunch are shown and then these electrons are followed during the simulation in order to understand the injection process and determine electron bunch properties.

  18. Modelling K shell spectra from short pulse heated buried microdot targets

    NASA Astrophysics Data System (ADS)

    Hoarty, D. J.; Sircombe, N.; Beiersdorfer, P.; Brown, C. R. D.; Hill, M. P.; Hobbs, L. M. R.; James, S. F.; Morton, J.; Hill, E.; Jeffery, M.; Harris, J. W. O.; Shepherd, R.; Marley, E.; Magee, E.; Emig, J.; Nilsen, J.; Chung, H. K.; Lee, R. W.; Rose, S. J.

    2017-06-01

    K shell X-ray emission measurements have been used to diagnose plasma conditions in short-pulse heated buried microdot targets on the Orion high power laser. These experiments have been used to validate simulations of short pulse laser-solid interaction that combine hybrid PIC modelling of the laser absorption with radiation-hydrodynamics simulations including an electron transport model. Comparison of these simulations with streaked K shell spectroscopy show the importance of including radial gradients in fitting the spectra. An example is presented of the emission of sulphur from a 50 μm diameter microdot sample buried in a plastic foil. Previously agreement between simulation and experiment was obtained only by treating the absorbed energy, electron temperature and beam divergence as fitting parameters. The good agreement obtained in this work used the measured laser energy and laser pulse length and calculated the laser-solid target interaction from first principles.

  19. 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.

  20. All-reflective, highly accurate polarization rotator for high-power short-pulse laser systems.

    PubMed

    Keppler, S; Hornung, M; Bödefeld, R; Kahle, M; Hein, J; Kaluza, M C

    2012-08-27

    We present the setup of a polarization rotating device and its adaption for high-power short-pulse laser systems. Compared to conventional halfwave plates, the all-reflective principle using three zero-phase shift mirrors provides a higher accuracy and a higher damage threshold. Since plan-parallel plates, e.g. these halfwave plates, generate postpulses, which could lead to the generation of prepulses during the subsequent laser chain, the presented device avoids parasitic pulses and is therefore the preferable alternative for high-contrast applications. Moreover the device is easily scalable for large beam diameters and its spectral reflectivity can be adjusted by an appropriate mirror coating to be well suited for ultra-short laser pulses.

  1. [Long term outcome of treatment of diffuse proliferative glomerulonephritis with pulse steroids and short course pulse cyclophosphamide].

    PubMed

    Tani, C; Mosca, M; d'Ascanio, A; Neri, R; Tavoni, A; Carli, L; Bombardieri, S

    2010-01-01

    To evaluate the long- term outcome of a group of systemic lupus erythematosus (SLE) patients with diffuse proliferative glomerulonephritis (DPGN) treated with pulse steroids and a short course of pulse cyclophosphamide (Cyc) in order to find out baseline predictor variables of disease outcome at the end of the follow-up. Female SLE patients fulfilling ACR criteria with active DPGN treated with pulse steroids and pulse Cyc were enrolled in the study and retrospectively analyzed with particular interest to renal flares and poor renal outcome at the end of follow- up as outcome measures. 30 female patients with DPGN were included, of these 20 (66,7%) patients are actually in follow-up at our unit, 4 (13.3%) died and 6 (20%) were lost during the follow-up. Fourteen patients (46.6%) presented at least one renal flare (RF) during the follow up for a total of 21 flares. At our last observation, 18 (60%) presented a good renal outcome while 12 (40%) had a poor outcome. Lower age at kidney biopsy resulted an important prognostic factor for the occurrence of both RF and poor long- term renal outcome; additionally, a poor renal outcome resulted significantly correlated with an inadequate response at the end of the protocol and with the number of renal flares after remission. These data suggest that, in general, a short course therapy with Cyc might be effective in controlling disease activity but demonstrated high rate of RF and poor renal outcome over time; however, this protocol might represent an effective therapeutic strategy in a subgroup of patients with specific epidemiological and clinical characteristics and suggest the possibility of tailoring immunosuppressive therapy on the basis of prognostic factor at baseline.

  2. 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.

  3. 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.

  4. Particle-in-Cell Simulations of Gas Ionization by Short Intense Laser Pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Dimitre; Bruhwiler, David; Leemans, Wim; Esarey, Eric; Catravas, Palma; Toth, Csaba; Shadwick, Brad; Cary, John; Giacone, Rodolfo; Verboncoeur, John; Mardahl, Peter

    2001-10-01

    Laser wakefield accelerators (LWFA) can generate accelerating gradients orders of magnitude larger than those obtained in conventional metal structures. In many LWFA experiments, the leading edge of the short, intense laser pulse completely ionizes a background neutral gas. An important question is the effect of laser ionization on the evolution of the laser pulse. Dispersive effects can modify the length and shape of the pulse as it propagates through the gas/plasma. Pulse steepening or break-up can affect the growth of the plasma wake. We will present particle-in-cell simulations using the ADK [M.V. Ammosov et al., Sov. Phys. JETP 64, p. 1191 (1986)] tunneling ionization model in the XOOPIC [J.P. Verboncoeur et al., J. Comp. Phys. 104, p. 321 (1993)] code. These simulations will be compared with experimental LWFA results from the l'OASIS laboratory of LBNL [W.P. Leemans et al., Phys. Plasmas 8, p. 2510 (2001)].

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. A theory for optical wavelength control in short pulse free electron laser oscillators

    NASA Astrophysics Data System (ADS)

    Wilkenson, Wade F.

    1993-06-01

    The future safety of the U.S. Navy warship depends on the development of a directed energy self-defense system to keep pace with the ever-improving technology of anti-ship missiles. Two candidates are reviewed. The free electron laser (FEL) has the most advantages, but a chemical laser proposed by TRW is ready for installation on existing ships. Initial testing of issues related to directed energy use at sea can be conducted with the chemical laser. When the technology of the FEL matures, it can replace the chemical laser to provide the best possible defense in the shortest period of time. Continuous tunability is a key advantage of the FEL over the conventional laser. But since the output wavelength is dependent on electron energy, it is subject to random fluctuations originating from the beam source. At the Stanford University Superconducting (SCA) Free Electron Laser (FEL) Facility, the effects are minimized through negative feedback by changing the input electron energy proportional to the observed wavelength drift. The process is simulated by modifying a short pulse FEL numerical program to allow the resonant wavelength to vary over many passes. The physical effects behind optical wavelength control are explained. A theory for the preferential nature of the FEL to follow the resonant wavelength from longer to shorter wavelengths is presented. Finally, the response of the FEL to a rapidly changing resonant wavelength is displayed as a transfer function for the system.

  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. How short is short? Optimum source-detector distance for short-separation channels in functional near-infrared spectroscopy.

    PubMed

    Brigadoi, Sabrina; Cooper, Robert J

    2015-04-01

    In recent years, it has been demonstrated that using functional near-infrared spectroscopy (fNIRS) channels with short separations to explicitly sample extra-cerebral tissues can provide a significant improvement in the accuracy and reliability of fNIRS measurements. The aim of these short-separation channels is to measure the same superficial hemodynamics observed by standard fNIRS channels while also being insensitive to the brain. We use Monte Carlo simulations of photon transport in anatomically informed multilayer models to determine the optimum source-detector distance for short-separation channels in adult and newborn populations. We present a look-up plot that provides (for an acceptable value of short-separation channel brain sensitivity relative to standard channel brain sensitivity) the optimum short-separation distance. Though values vary across the scalp, when the acceptable ratio of the short-separation channel brain sensitivity to standard channel brain sensitivity is set at 5%, the optimum short-separation distance is 8.4 mm in the typical adult and 2.15 mm in the term-age infant.

  12. 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.

  13. Optical short pulse generation at high repetition rate over 80 GHz from a monolithic passively modelocked DBR laser diode

    NASA Astrophysics Data System (ADS)

    Arahira, S.; Matsui, Y.; Kunii, T.; Oshiba, S.; Ogawa, Y.

    1993-05-01

    Optical short pulses at high repetition rate over 80 GHz were successfully generated using a monolithically fabricated passively modelocked distributed Bragg reflector laser diode for the first time. By using linear fibre compression, a transform-limited optical pulse train with a duration of 2.7 ps was obtained. The pulse envelope closely matched a sech(sup 2) waveform.

  14. Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices.

    PubMed

    Di Sieno, Laura; Nissinen, Jan; Hallman, Lauri; Martinenghi, Edoardo; Contini, Davide; Pifferi, Antonio; Kostamovaara, Juha; Mora, Alberto Dalla

    2017-08-01

    We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12×6  mm2) has been previously developed for range finding applications and is able to provide short, high energy (∼100  ps, ∼0.5  nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  15. Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices

    NASA Astrophysics Data System (ADS)

    Di Sieno, Laura; Nissinen, Jan; Hallman, Lauri; Martinenghi, Edoardo; Contini, Davide; Pifferi, Antonio; Kostamovaara, Juha; Mora, Alberto Dalla

    2017-08-01

    We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12×6 mm2) has been previously developed for range finding applications and is able to provide short, high energy (˜100 ps, ˜0.5 nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

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

    SciTech Connect

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

    2016-04-14

    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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Numerical investigation of short-pulse laser radiation propagation in a turbulent atmosphere

    SciTech Connect

    Banakh, V A; Gerasimova, L O; Smalikho, I N

    2015-03-31

    An algorithm is presented for the numerical simulation of short-pulse optical radiation propagation in a turbulent atmosphere on the basis of the solution to the parabolic wave equation for the complex spectral amplitude of the wave field by the split-step method. We present examples of the use of this algorithm for simulating the propagation of a pulsed coherent spatially limited beam and a plane wave. It is shown that in the regime of strong optical turbulence the relative variance of fluctuations of energy density of femtosecond radiation becomes much smaller than the relative variance of the intensity of cw radiation. (laser radiation scattering)

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

    PubMed Central

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

    2012-01-01

    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 μJ and 90 fs pulses from a single-mode fiber amplifier illustrates the potential of the process. PMID:20634842

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Generation of short electron bunches by a laser pulse crossing a sharp boundary of inhomogeneous plasma

    SciTech Connect

    Kuznetsov, S. V.

    2016-08-15

    The formation of short electron bunches during the passage of a laser pulse of relativistic intensity through a sharp boundary of semi-bounded plasma has been analytically studied. It is shown in one-dimensional geometry that one physical mechanism that is responsible for the generation of electron bunches is their self-injection into the wake field of a laser pulse, which occurs due to the mixing of electrons during the action of the laser pulse on plasma. Simple analytic relationships are obtained that can be used for estimating the length and charge of an electron bunch and the spread of electron energies in the bunch. The results of the analytical investigation are confirmed by data from numerical simulations.

  19. A differential optical interferometer for measuring short pulses of surface acoustic waves.

    PubMed

    Shaw, Anurupa; Teyssieux, Damien; Laude, Vincent

    2017-09-01

    The measurement of the displacements caused by the propagation of a short pulse of surface acoustic waves on a solid substrate is investigated. A stabilized time-domain differential interferometer is proposed, with the surface acoustic wave (SAW) sample placed outside the interferometer. Experiments are conducted with surface acoustic waves excited by a chirped interdigital transducer on a piezoelectric lithium niobate substrate having an operational bandwidth covering the 200-400MHz frequency range and producing 10-ns pulses with 36nm maximum out-of-plane displacement. The interferometric response is compared with a direct electrical measurement obtained with a receiving wide bandwidth interdigital transducer and good correspondence is observed. The effects of varying the path difference of the interferometer and the measurement position on the surface are discussed. Pulse compression along the chirped interdigital transducer is observed experimentally. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. All-optical short pulse translation through cross-phase modulation in a VO₂ thin film.

    PubMed

    Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Breckenfeld, Eric; Kim, Heungsoo; Wu, Judy; Hui, Rongqing

    2016-01-15

    VO2 is a promising material for reconfigurable photonic devices due to the ultrafast changes in electronic and optical properties associated with its dielectric-to-metal phase transition. Based on a fiber-optic, pump-probe setup at 1550 nm wavelength window, and by varying the pump-pulse duration, we show that the material phase transition is primarily caused by the pump-pulse energy. For the first time, we demonstrate that the instantaneous optical phase modulation of probe during pump leading edge can be utilized to create short optical pulses at probe wavelength, through optical frequency discrimination. This circumvents the impact of long recovery time well known for the phase transition of VO2.

  3. 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.

  4. 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.

  5. 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.

  6. Comment on "Defocusing complex short-pulse equation and its multi-dark-soliton solution"

    NASA Astrophysics Data System (ADS)

    Youssoufa, Saliou; Kuetche, Victor K.; Kofane, Timoleon C.

    2017-08-01

    In their recent paper, Feng et al. [Phys. Rev. E 93, 052227 (2016), 10.1103/PhysRevE.93.052227] proposed a complex short-pulse equation of both focusing and defocusing types. They studied in detail the defocusing case and derived its multi-dark-soliton solutions. Nonetheless, from a physical viewpoint in order to better and deeply understand their genuine implications, we find it useful to provide a real and proper background for the derivation of the previous evolution system while showing that the expression of the nonlinear electric polarization the above authors used in their scheme is not suitable for getting the defocusing complex short-pulse equation.

  7. Multi-soliton solutions and the Cauchy problem for a two-component short pulse system

    NASA Astrophysics Data System (ADS)

    Zhaqilao, Z.; Hu, Qiaoyi; Qiao, Zhijun

    2017-10-01

    In this paper, we study multi-soliton solutions and the Cauchy problem for a two-component short pulse system. For the multi-soliton solutions, we first derive an N-fold Darboux transformation from the Lax pair of the two-component short pulse system, which is expressed in terms of the quasideterminant. Then by virtue of the N-fold Darboux transformation we obtain multi-loop and breather soliton solutions. In particular, one-, two-, three-loop soliton, and breather soliton solutions are discussed in detail with interesting dynamical interactions and shown through figures. For the Cauchy problem, we first prove the existence and uniqueness of a solution with an estimate of the analytic lifespan, and then investigate the continuity of the data-to-solution map in the space of an analytic function.

  8. 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.

  9. Ultra-short pulse laser deep drilling of C/SiC composites in air

    NASA Astrophysics Data System (ADS)

    Wang, Chunhui; Zhang, Litong; Liu, Yongsheng; Cheng, Guanghua; Zhang, Qing; Hua, Ke

    2013-06-01

    Ultra-short pulse laser machining is an important finishing technology for high hardness materials. In this study, it demonstrated that the ultra-short pulse laser can be used to drill the film cooling holes and square holes in aero-engine turbine blades made of C/SiC composites. Both the edges and bottoms of the drilling holes are covered with small particles. The following factors have a great effect on drilling holes according to this work: (1) circular holes can be processed only at a relative small helical lines spacing. (2) With the increase of laser scanning speed, the depth of holes reduces while the diameter rarely changes. (3) Through the holes of high aspect ratio can be obtained via high processing power.

  10. 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)].

  11. Two-color monochromatic x-ray imaging with a single short-pulse laser

    NASA Astrophysics Data System (ADS)

    Sawada, H.; Daykin, T.; McLean, H. S.; Chen, H.; Patel, P. K.; Ping, Y.; Pérez, F.

    2017-06-01

    Simultaneous monochromatic crystal imaging at 4.5 and 8.0 keV with x-rays produced by a single short-pulse laser is presented. A layered target consisting of thin foils of titanium and copper glued together is irradiated by the 50 TW Leopard short-pulse laser housed at the Nevada Terawatt Facility. Laser-accelerated MeV fast electrons transmitting through the target induce Kα fluorescence from both foils. Two energy-selective curved crystals in the imaging diagnostic form separate monochromatic images on a single imaging detector. The experiment demonstrates simultaneous two-color monochromatic imaging of the foils on a single detector as well as Kα x-ray production at two different photon energies with a single laser beam. Application of the diagnostic technique to x-ray radiography of a high density plasma is also presented.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Microwave short-pulse bed-level detector. Annual report, January 1-December 31, 1981

    SciTech Connect

    Balanis, C.A.; Delauder, D.M.

    1981-01-01

    A short-pulse microwave system for measuring the bed-level within a fluidized-bed combustor, has been designed, built, and laboratory tested on static beds. The system is a short-pulse radar which operates in the frequency region of 6.75 to 10.95 GHz as a time-domain measurement system. Laboratory measurements of static bed-levels, for smooth and corrugated surfaces of metal plates and limestone sand, agree to an average of 2.0% of the actual heights. Additionally, the system was tested with a dielectric thermal protector, which did not compromise the accuracy of the measurements. Analytical models have been formulated to provide insight into the operation of the system on a wide range of simulated targets without the necessity of performing expensive and difficult laboratory experiments. Two formulations have been used to describe electromagnetic scattering by a rough surface as a function of frequency: the space harmonic model and the physical optics model. A reconstruction technique has been devised which uses the scattering models and the spectrum of the transmitted pulse to synthesize the reflected pulse. The data generated by the models compare well to previously published data and to experimental results.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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".

  10. 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.

  11. 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.

  12. 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.

  13. New laser glass for short pulsed laser applications: the BLG80 (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    George, Simi A.

    2017-03-01

    For achieving highest peak powers in a solid state laser (SSL) system, significant energy output and short pulses are necessary. For mode-locked lasers, it is well-known from the Fourier theorem that the largest gain bandwidths produce the narrowest pulse-widths; thus are transform limited. For an inhomogeneously broadened line width of a laser medium, if the intensity of pulses follow a Gaussian function, then the resulting mode-locked pulse will have a Gaussian shape with the emission bandwidth/pulse duration relationship of pulse ≥ 0.44?02/c. Thus, for high peak power SSL systems, laser designers incorporate gain materials capable of broad emission bandwidths. Available energy outputs from a phosphate glass host doped with rare-earth ions are unparalleled. Unfortunately, the emission bandwidths achievable from glass based gain materials are typically many factors smaller when compared to the Ti:Sapphire crystal. In order to overcome this limitation, a hybrid "mixed" laser glass amplifier - OPCPA approach was developed. The Texas petawatt laser that is currently in operation at the University of Texas-Austin and producing high peak powers uses this hybrid architecture. In this mixed-glass laser design, a phosphate and a silicate glass is used in series to achieve a broader bandwidth required before compression. Though proven, this technology is still insufficient for the future compact petawatt and exawatt systems capable of producing high energies and shorter pulse durations. New glasses with bandwidths that are two and three times larger than what is now available from glass hosts is needed if there is to be an alternative to Ti:Sapphire for laser designers. In this paper, we present new materials that may meet the necessary characteristics and demonstrate the laser and emission characteristics these through the internal and external studies.

  14. Coherent diffractive imaging using short wavelength light sources

    NASA Astrophysics Data System (ADS)

    Quiney, H. M.

    2010-07-01

    Techniques that recover images from diffraction data obtained using coherent short-wavelength light sources are currently under active development for applications in nanotechnology and structural biology. In this review, an outline of paraxial optics is provided in a form that is sufficiently general to incorporate the coherence properties and frequency structure of illumination sources used in diffractive imaging applications. The Fourier phase problem is formulated in the context of imaging algorithms that are designed to obtain uniquely-determined phase distributions from measurements of diffraction data. The properties of several iterative phase retrieval algorithms for both coherent and partially-coherent diffractive imaging applications are presented in a unified formalism, together with a brief discussion of a non-iterative technique. Approaches to diffractive imaging based on Fraunhofer and Fresnel diffraction configurations are compared. Applications are described utilising quasi-monochromatic third-generation synchrotron X-ray sources and polychromatic high-harmonic generation table-top soft X-ray sources. The review concludes with a consideration of proposed applications of diffractive imaging approaches to the determination of biomolecular structures from isolated molecules using fourth-generation X-ray free-electron laser sources.

  15. 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

  16. 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.

  17. A 100 microsec, reliable, 10 Hz pulsed supersonic molecular beam source

    NASA Technical Reports Server (NTRS)

    Byer, R. L.; Duncan, M. D.

    1981-01-01

    A 10-Hz repetition rate, 100-microsec duration, reliable pulsed supersonic molecular beam source is described. Mechanical and electrical design of the pulsed valve are given in detail. Characteristics of the supersonic expansion obtained using coherent anti-Stokes Raman spectroscopy in acetylene are presented. They include pulse shape, gas rotational and translational cooling as a function of distance from the nozzle, clustering effects, and shock heating at the leading edge of the pulse.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Short pulse, high resolution, backlighters for point projection high-energy radiography at the National Ignition Facility

    DOE PAGES

    Tommasini, R.; Bailey, C.; Bradley, D. K.; ...

    2017-05-09

    High-resolution, high-energy X-ray backlighters are very active area of research for radiography experiments at the National Ignition Facility (NIF) [Miller et al., Nucl. Fusion 44, S228 (2004)], in particular those aiming at obtaining Compton-scattering produced radiographs from the cold, dense fuel surrounding the hot spot. We report on experiments to generate and characterize point-projection-geometry backlighters using short pulses from the advanced radiographic capability (ARC) [Crane et al., J. Phys. 244, 032003 (2010); Di Nicola et al., Proc. SPIE 2015, 93450I-12], at the NIF, focused on Au micro-wires. We show the first hard X-ray radiographs, at photon energies exceeding 60 keV,more » of static objects obtained with 30 ps-long ARC laser pulses, and the measurements of strength of the X-ray emission, the pulse duration and the source size of the Au micro-wire backlighters. For the latter, a novel technique has been developed and successfully applied.« less

  5. Short pulse, high resolution, backlighters for point projection high-energy radiography at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Tommasini, R.; Bailey, C.; Bradley, D. K.; Bowers, M.; Chen, H.; Di Nicola, J. M.; Di Nicola, P.; Gururangan, G.; Hall, G. N.; Hardy, C. M.; Hargrove, D.; Hermann, M.; Hohenberger, M.; Holder, J. P.; Hsing, W.; Izumi, N.; Kalantar, D.; Khan, S.; Kroll, J.; Landen, O. L.; Lawson, J.; Martinez, D.; Masters, N.; Nafziger, J. R.; Nagel, S. R.; Nikroo, A.; Okui, J.; Palmer, D.; Sigurdsson, R.; Vonhof, S.; Wallace, R. J.; Zobrist, T.

    2017-05-01

    High-resolution, high-energy X-ray backlighters are very active area of research for radiography experiments at the National Ignition Facility (NIF) [Miller et al., Nucl. Fusion 44, S228 (2004)], in particular those aiming at obtaining Compton-scattering produced radiographs from the cold, dense fuel surrounding the hot spot. We report on experiments to generate and characterize point-projection-geometry backlighters using short pulses from the advanced radiographic capability (ARC) [Crane et al., J. Phys. 244, 032003 (2010); Di Nicola et al., Proc. SPIE 2015, 93450I-12], at the NIF, focused on Au micro-wires. We show the first hard X-ray radiographs, at photon energies exceeding 60 keV, of static objects obtained with 30 ps-long ARC laser pulses, and the measurements of strength of the X-ray emission, the pulse duration and the source size of the Au micro-wire backlighters. For the latter, a novel technique has been developed and successfully applied.

  6. Optimization of interaction conditions for efficient short laser pulse amplification by stimulated Brillouin scattering in the strongly coupled regime

    SciTech Connect

    Chiaramello, M.; Riconda, C.; Amiranoff, F.; Fuchs, J.; Grech, M.; Marquès, J.-R.; Vinci, T.; Lancia, L.; Weber, S.

    2016-07-15

    Plasma amplification of low energy, a short (∼100–500 fs) laser pulse by an energetic long (∼10 ps) pulse via strong coupling Stimulated Brillouin Backscattering is investigated with an extensive analysis of one-dimensional particle-in-cell simulations. Parameters relevant to nowadays experimental conditions are investigated. The obtained seed pulse spectra are analyzed as a function of the interaction conditions such as plasma profile, pulses delay, and seed or pulse duration. The factors affecting the amount of energy transferred are determined, and the competition between Brillouin-based amplification and parasitic Raman backscattering is analyzed, leading to the optimization of the interaction conditions.

  7. 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.

  8. 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.

  9. Characterization of a heat flux sensor using short pulse laser calibration.

    PubMed

    Löhle, Stefan; Battaglia, Jean-Luc; Batsale, Jean-Christophe; Enouf, Olivier; Dubard, Jimmy; Filtz, Jean-Remy

    2007-05-01

    A method to calibrate classical heat flux sensors is presented. The classical approach to measure the temperature inside a known material by using a thermocouple fails when the measurement time is very short. In this work the surface heat flux is determined by solving the inverse heat conduction problem using a noninteger identified system as a direct model for the estimation process. Using short pulse laser calibration measurements the crucial design aspects of the sensor that play a significant role when assuming one-dimensional, semi-infinite heat transfer have been accounted for. The theoretical approach as well as the calibration results are presented and comparisons to the classical approach and results from finite element modeling are shown. It is concluded that the new method ameliorate the heat flux sensor significantly and extend its application to very short measurement times.

  10. In situ characterization of a cold and short pulsed molecular beam by femtosecond ion imaging.

    PubMed

    Irimia, Daniel; Kortekaas, Rob; Janssen, Maurice H M

    2009-05-28

    In this paper we report on the in situ characterization of the cold velocity distribution of a pulsed molecular beam produced by a novel cantilever piezo valve. The velocity distribution is measured at various temporal positions within the pulsed expansion using femtosecond velocity map ion imaging. It is shown that the universal detection of molecules by multi-photon femtosecond velocity map ion imaging can provide directly the velocity distribution with excellent velocity resolution. The novel cantilever piezo valve can operate both in continuous (DC) and pulsed mode without any modification using the same drive electronics. Pulsed operation was tested at repetition rates of 20 Hz, 1 kHz and 5 kHz and a conical nozzle 200 mum in diameter. The cantilever valve produces a pulsed molecular beam of translationally cold molecules at modest backing pressures of about 6 bar. At low to medium repetition rates (20-1000 Hz) the pulsed piezo valve produces pulses of 12-40 mus duration of translationally cold seeded beams of helium and neon with speed ratios up to S = 135 (20 Hz, 0.1% CD(3)I in neon) and S = 55 (1 kHz). At the highest tested repetition rate of 5 kHz, the speed ratio obtained for the same seeded beam is reduced to about S = 45. This is still more than a factor of two better than the speed ratio S = 21 measured for a continuous beam produced with the same nozzle at 0.5 bar backing pressure. The cold velocity distribution of the pulsed beam expansion as compared to a continuous beam expansion is beneficial for improved spatial resolution in velocity map ion imaging experiments at high repetition rates of 1-5 kHz. The cantilever piezo valve has a simple design and may find broad applicability in areas where short gas pulses are warranted because of limited pumping speed, the effective use of (expensive) samples or the production of translationally and internally cold molecular beams at high repetition rate. When operating the piezo valve at high backing

  11. 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.

  12. Response of LiTaO3 thin film to X-band short microwave pulse

    NASA Astrophysics Data System (ADS)

    Gao, Qiong; Wang, Honggang; Qu, Weidong; Jiao, Zhongke; Li, Guolin; Wang, Juanfeng; Zhang, Yanxiu

    2017-09-01

    The response of the LiTaO3 thin film detector to the X-band pulse with large power (of order 10 W/cm2) and short duration (of order 0.1 μs) is investigated experimentally and explained from the viewpoint of dielectric relaxation. With the output voltage signal of the detector, the current through the LiTaO3 thin film and its electric polarization are computed and used to examine the observation in a more fundamental manner. In contrast to the common step excitation, the short pulse can provide a delta-type excitation and the response is more appropriate for exploring the interaction mechanism. It is demonstrated from the viewpoint of energy that the response of the detector is not caused by the temperature change in the film, which is the core component in the traditional model of the pyroelectric detector. The polarizations under different pulse conditions show that the interaction is nonlinear, so the linear superposition assumption in the dielectric relaxation theory cannot be used any more. It is found that the polarization can be fitted quite well with a sine function and a time-dependent frequency can be defined. An empirical equation is derived for the dynamics of polarization, and the accelerating and damping effects in the relaxation process can be explained with the relative change in this frequency. The dynamics analysis indicates that the electromagnetic energy is mainly dissipated through driving the domain wall in the crystal.

  13. 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.

  14. 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.

  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. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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}.

  3. 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.

  4. Inertial displacement of a domain wall excited by ultra-short circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Janda, T.; Roy, P. E.; Otxoa, R. M.; Šobáň, Z.; Ramsay, A.; Irvine, A. C.; Trojanek, F.; Surýnek, M.; Campion, R. P.; Gallagher, B. L.; Němec, P.; Jungwirth, T.; Wunderlich, J.

    2017-05-01

    Domain wall motion driven by ultra-short laser pulses is a pre-requisite for envisaged low-power spintronics combining storage of information in magnetoelectronic devices with high speed and long distance transmission of information encoded in circularly polarized light. Here we demonstrate the conversion of the circular polarization of incident femtosecond laser pulses into inertial displacement of a domain wall in a ferromagnetic semiconductor. In our study, we combine electrical measurements and magneto-optical imaging of the domain wall displacement with micromagnetic simulations. The optical spin-transfer torque acts over a picosecond recombination time of the spin-polarized photo-carriers that only leads to a deformation of the initial domain wall structure. We show that subsequent depinning and micrometre-distance displacement without an applied magnetic field or any other external stimuli can only occur due to the inertia of the domain wall.

  5. 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.

  6. 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.

  7. Short-Term Effects of Pulsed Radiofrequency on Chronic Refractory Cervical Radicular Pain

    PubMed Central

    Choi, Gyu-Sik; Cho, Yun-Woo; Lee, Dong-Kyu

    2011-01-01

    Objective To evaluate the short-term effectiveness of pulsed radiofrequency on the dorsal root ganglion (DRG) in patients with chronic refractory cervical radicular pain. Method Fifteen patients (13 males, 2 females; mean age, 55.9 years) with chronic radicular pain due to cervical disc herniation or foraminal stenosis refractory to active rehabilitative management, including transforaminal cervical epidural steroid injection and exercise, were selected. All patients received pulsed radiofrequency on the symptomatic cervical dorsal root ganglion and were carefully evaluated for neurologic deficits and side effects. The clinical outcomes were measured using a visual analogue scale (VAS) and a neck disability index (NDI) before treatment, one and three months after treatment. Successful pain relief was defined as a 50% or greater reduction in the VAS score as compared with the pre-treatment score. After three months, we categorized the patients' satisfaction. Results The average VAS for radicular pain was reduced significantly from 5.3 at pretreatment to 2.5 at 3 months post-treatment (p<0.05). Eleven of 15 patients (77.3%) after cervical pulsed RF stimulation reported pain relief of 50% or more at the 3 month follow-up. The average NDI was significantly reduced from 44.0% at pretreatment to 35.8% 3 months post-treatment (p<0.05). At 3 months post-treatment, eleven of fifteen patients (73.3%) were satisfied with their status. No adverse effects were observed. Conclusion The results demonstrate that the application of pulsed radiofrequency on DRG might be an effective short-term intervention for chronic refractory cervical radicular pain. Further studies, including a randomized controlled trial with long-term follow-up, are now needed. PMID:22506211

  8. 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.

  9. 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.

  10. 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.

  11. Short-pulse cross-phase modulation in an electromagnetically-induced-transparency medium

    NASA Astrophysics Data System (ADS)

    Feizpour, Amir; Dmochowski, Greg; Steinberg, Aephraim M.

    2016-01-01

    Electromagnetically induced transparency (EIT) has been proposed as a way to greatly enhance cross-phase modulation, with the possibility of leading to few-photon-level optical nonlinearities [Schmidt and Imamoglu, Opt. Lett. 21, 1936 (1996), 10.1364/OL.21.001936]. This enhancement grows as the transparency window width, ΔEIT, is narrowed. Decreasing ΔEIT, however, has been shown to increase the response time of the nonlinear medium. This suggests that, for a given pulse duration, the nonlinearity would diminish once the window width became narrower than this pulse bandwidth. We show that this is not the case: the peak phase shift saturates but does not decrease. We show that in the regimes of most practical interest—narrow EIT windows perturbed by short signal pulses—the enhancement offered by EIT is not only in the magnitude of the nonlinear phase shift but also in its increased duration. That is, for the case of signal pulses much shorter (temporally) than the inverse EIT bandwidth, the narrow window serves to prolong the effect of the passing signal pulse, leading to an integrated phase shift that grows linearly with 1 /ΔEIT ; this continued growth of the integrated phase shift improves the detectability of the phase shift, in principle, without bound. For many purposes, it is this detectability which is of more interest than the absolute magnitude of the peak phase shift. We present analytical expressions based on a linear time-invariant model that accounts for the temporal behavior of the cross-phase modulation for several parameter ranges of interest. We conclude that in order to optimize the detectability of the EIT-based cross-phase shift, one should use the narrowest possible EIT window and a signal pulse that is as broadband as the excited-state linewidth and detuned by half a linewidth.

  12. On the limit of neutron fluxes in the fission-based pulsed neutron sources

    NASA Astrophysics Data System (ADS)

    Aksenov, V. L.; Ananiev, V. D.; Komyshev, G. G.; Rogov, A. D.; Shabalin, E. P.

    2017-09-01

    The upper limit of the density of the thermal neutron flux from pulsed sources based on the fission reaction is established. Three types of sources for research on ejected beams are considered: a multiplying target of the proton accelerator (a booster), a booster with the reactivity modulation (a superbooster), and a pulsing reactor. Comparison with other high-flux sources is carried out. The investigation has been performed at the Frank Laboratory of Neutron Physics of JINR.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.